LTE Unlicensed and Wi-Fi: Moving Beyond Coexistence
The next major shift in mobile broadband – 5G – will enable innovative services through emerging wireless core technologies and a programmable infrastructure designed to meet new requirements. One of the emerging technologies from 5G is LAA-LTE. This report published by Senza Fili in collaboration with RCR Wireless focuses on the evolution of the role of LTE unlicensed, Wi-Fi and their coexistence.
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LTE unlicensed and Wi-Fi:
Moving beyond coexistence
By Monica Paolini, Senza Fili
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REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |3|
Table of contents
I. Market report 4
1. Introduction. Why LTE unlicensed? 5
2. Terminology. LTE unlicensed, LTE-U, LAA-LTE and more 7
3. LTE unlicensed integration with LTE licensed. A special case of
carrier aggregation 8
4. The 5 GHz unlicensed band. What?s so special about it? 10
5. Why do we need listen before talk (LBT)? Fair coexistence is a
requirement for success, not an option 11
6. LTE-U, ahead of inclusion of LBT in 3GPP standards. The solution for
operators ready to deploy 12
7. The LAA-LTE standardization process in 3GPP. Enshrining fairness
in the standards 14
8. Wi-Fi or LTE unlicensed in small-cell deployments? A look at the
9. Quantifying the LTE unlicensed performance benefits. The
challenges in generalizing simulation and trial results 18
10. One step further with LWA. Alternative or complement?23
11. Is LTE unlicensed worth the investment? A look at the business case
12. Summary. 27
II. Vendor profiles and interviews 28
Alcatel-Lucent: LTE unlicensed and Wi-Fi 29
A performance boost from combining Wi-Fi and LTE unlicensed 30
InterDigital: LTE unlicensed and Wi-Fi 36
Fairness to Wi-Fi is crucial to LTE unlicensed?s success 37
Qualcomm: LTE unlicensed and Wi-Fi 43
Improving spectrum efficiency with LTE unlicensed44
Ruckus Wireless: LTE unlicensed and Wi-Fi 50
Beyond LTE unlicensed, with LTE plus Wi-Fi link aggregation 51
Wi-Fi Alliance: LTE unlicensed and Wi-Fi 57
Learning from Wi-Fi, working toward coexistence with LTE in
unlicensed 5GHz 58
XCellAir: LTE unlicensed and Wi-Fi 63
A shared solution to manage Wi-Fi and LTE unlicensed traffic 64
III. Operator interview 71
Tele2: Maximizing the use of unlicensed spectrum withWi-Fi today, LTE
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I. Market report
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Why LTE unlicensed?
The increase in mobile traffic grabs most of the attention in the industry today, but even more remarkable is
themassive shift from wireline to wireless IP traffic over the last decade. Today, wireless traffic accounts for
more than half of IP traffic, and most of that is not cellular but Wi-Fi, as Cisco VNI?s data on the right shows ?
and transported over unlicensed spectrum, mostly still in the 2.4 GHz band.
In this context, it is difficult to overestimate the relevance and value of unlicensed spectrum. Initially allocated
for niche applications, it has become a key enabler of wireless consumption worldwide, driven by the success
Traditionallymobile operators have beenwary of using unlicensed spectrum. In the last few years, though,
they have started to warm to its use as they developed an appreciation of unlicensed spectrum?s versatility and
potential in serving their subscribers, especially indoors. While estimates vary across regions, in most markets
Wi-Fi accounts formore than half of traffic from mobile devices. Offloading cellular traffic into Wi-Fi networks ?
residential, enterprise or hotspot ? has been a vital approach for mobile operators under pressure to meet
subscriber demand and retain control over profit margins.
Mobile operators? recent interest in extending LTE to operations in the unlicensed 5 GHz band is the natural extension of those efforts. Wi-Fi offload was the first foray
into the unlicensed bands. It paid off handsomely, and now mobile operators want to expand their use of unlicensed spectrum and bring it closer to home ? using the
same technology they use for licensed access, LTE, so that licensed and unlicensed transmission can be natively integrated.
With LTE in the unlicensed 5 GHz band, mobile operators can expand their network capacity in a way that is at once cost effective and easy to implement. To be clear,
this is not an alternative to Wi-Fi, but a complement to it. Not even the most committed LTE unlicensed supporters question the dominance of Wi-Fi in residential and
enterprise settings, or the role it will continue to play for mobile operators. The reason to adopt LTE unlicensed is not to unseat Wi-Fi, but to increase the spectral
efficiency and capacity of the 5 GHz band, and to do so with a technology that is fully integrated within the mobile operators? networks.
The efficient use of unlicensed spectrum is all the more important because, although traffic load has been on the rise, ARPUs have been stagnant. That combination
forces operators to find cost-effective means to increase capacity ?which translates into improving per-bit economics by using available resources and assets more
intensively. The efficient use of unlicensed spectrum plays a crucial role in increasing resource utilization.
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But there is more to it. Mobile operators have moved away from a single service (e.g., voice) and a single air interface (e.g., GSM) for each subscriber. Instead, they are
embracing multi-RAT networks in which they can leverage the specific advantages of each technology for different services. Like Titian?s painting on the cover of this
report, mobile networks are multi-faceted, with older and more mature technologies coexisting with new ones. The key challenge is to seamlessly integratemultiple
network interfaces, technologies and bands to optimize resource utilization and improve subscriber experience.
Mobile operators are not the only ? nor the primary ? users of unlicensed spectrum. Most unlicensed use comes from Wi-Fi networks installed in residential and
enterprise environments. Service providers such as WISPs and cable operators also use Wi-Fi, to provide fixed or mobile broadband services to their customers.
Mobile operators may rely on this infrastructure for offload, but in most cases they do not own it or control it. The introduction of LTE unlicensed proposals has met
with deep concern from Wi-Fi vendors and service providers, which have used the 5 GHz band for a long time and want to continue to do so without being unfairly
penalized by the introduction of LTE.
The addition of LTE unlicensed in the 5 GHz band will unquestionably increase the traffic load in the band, the contention for spectrum resources, and, eventually, the
congestion. The 5 GHz band has hundreds of MHz of spectrum, and in most places it is not heavily congested today. But utilization of the band is growing quickly, and
it is only a matter of time before different Wi-Fi networks and different technologies will have to compete to transmit.
A fair coexistence of multiple technologies ? primarily, but not exclusively, Wi-Fi and LTE unlicensed ? is essential to preserving equilibrium in the 5 GHz band as new
tenants, namely mobile operators, join in with a new technology and as the traffic load increases. Wi-Fi was designed from the ground up to support fair coexistence
through listen-before-talk (LBT) mechanisms that restrict AP transmission to the times when no neighboring APs are transmitting. In contrast, LTE uses a scheduled-
transmission model designed to operate in licensed bands over which it has exclusive access. Extending this transmission approach to the 5 GHz band has a
detrimental impact on Wi-Fi, and virtually everybody agrees that this is not acceptable even if regulation allows it.
Modifications to LTE are necessary for coexistence with Wi-Fi and other technologies in the 5 GHz band.What these modifications should be and how they should be
incorporated into the 3GPP standards is at the center of the debate on LTE unlicensed today. As ofmid-2015, multiple proposals are under consideration and the 3GPP
standardization process is ongoing. This is a crucial moment: the standards specificationswill determine whether LTE unlicensed will provide guarantees of fair
coexistence with Wi-Fi and high spectral efficiency sufficient to garner the necessary support from both the Wi-Fi stakeholders and the LTE stakeholders.
With this report, we strive to present an overview of LTE unlicensed and how it can coexist with Wi-Fi. We discuss central issues such as performance, standardization,
business models, and deployment costs. The debate on LTE unlicensed is a heated one in which parties have often taken antagonistic views. In the interviews in this
report, we have tried to presentmultiple perspectives from players deeply involved in the Wi-Fi and LTE ecosystems, and discuss how to best develop a coexistence
regimen for LTE unlicensed that expands the overall use of the unlicensed spectrum in the 5 GHz band and benefits all the stakeholders.
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LTE unlicensed, LTE-U, LAA-LTE and more
There are different proposals on how to use LTE in unlicensed bands, and this has
created confusion in the terminology. In this report, we use ?LTE unlicensed? as the
umbrella term that covers all implementations of LTE in the 5 GHz unlicensed band
that use a licensed channel ? referred to as a primary channel or anchor ? for
signaling to coordinate transmission among different channels. Regardless of how
LTE unlicensed is implemented, it is fully integrated within LTE networks and it acts
as a secondary channel that relies on carrier aggregation (CA).
There are two types of LTE unlicensed: LTE-U and LAA-LTE.
LTE-U is the version of LTE unlicensed that was proposed in 2013 by Qualcomm and
Ericsson. LTE-U relies on 3GPP Release 10-12 functionality, with specifications
defined by the LTE-U Forum, an organization established by Verizon in collaboration
with Alcatel-Lucent, Ericsson, Qualcomm Technologies, Inc., a subsidiary of
Qualcomm Incorporated, and Samsung. Because it requires few modifications from
licensed LTE, LTE-U will be the first version of LTE unlicensed to be available in
commercial deployments. However, because it does not implement listen-before-
talk mechanisms, LTE-U can only be used in markets where regulation does not
require LBT, such as China, Korea, India and the USA.
LAA-LTE is the version of LTE unlicensed that 3GPP plans to standardize in Release 13
and that supports LBT in addition to CA. LAA-LTE is set to become a global standard
as it strives to meet regulatory requirements worldwide. However, because the
standardization work is not completed yet, commercialization will take longer than
for LTE-U. In the long term, we expect operators and vendors worldwide to support
LAA-LTE because it provides a globally harmonized solution that leads to better
scalability and choice among equipment and device vendors.
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3.LTE unlicensed integration with LTE licensed.
A special case of carrier aggregation
LTE unlicensed is fundamentally a special case of carrier aggregation in which the
primary carrier ? also referred to as the anchor ? uses licensed spectrum, and the
secondary carrier is in the 5 GHz band.
The primary carrier manages the control plane for both carriers, and hence is crucial
for the allocation of traffic between carriers. It is also used for data traffic in the
uplink and downlink. The secondary carrier is limited to the data plane, with
downlink required, but uplink optional in LTE-U. The secondary carrier uses TDD,
while the primary may use FDD or TDD.
To maximize the contribution of the combined carriers, the primary carrier is
preferred for voice and uplink traffic, while the secondary carrier transports more
downlink traffic. The primary carrier is better suited to supportingmobility. The
operator may choose to use the secondary channel on an opportunistic basis ? i.e.,
only when the primary carrier is at capacity or overloaded.
The secondary carrier operates in a high-capacity wide channel, but the capacity is
not guaranteed because the channel may be shared with other LTE unlicensed cells
or with Wi-Fi APs. For an efficient traffic allocation, the operator has to take into
account the traffic volume and real-time traffic condition in the second carrier and
use policy for load-balancing.
LTE unlicensed will be deployed mostly in small-cell topologies, often in indoor
locations. It can be co-located with macro cells, but this is an unlikely deployment
scenario because of the propagation characteristics of the 5 GHz spectrum. In a
small-cell deployment, multiple scenarios are possible.
The scenarios that 3GPP envisages are shown below, and all include an LAA-LTE
small cell. In the first scenario, the primary cell is the macro, and the LAA-LTE small-
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cell is not co-located, but linked to the macro cell with ideal backhaul (i.e., with less
than 2.5 ?s one-way latency and 10 Gbps throughput, most commonly fiber). In the
other three scenarios, the LTE unlicensed cell is always co-located with a licensed
small cell, with the small cell or the macro cell acting as the primary carrier. The
second scenario is most likely used in indoor environments. The choice of
deployment scenario depends on the operator?s strategy for small cells and the
availability of ideal backhaul.
A stand-alone version of LTE unlicensed that does not require aggregation with a
licensed band has also been proposed, but so far it has not gained industry-wide
support. It is a solution that may be attractive to cable operators, WISPs or hotspot
network operators that lack licensed spectrum. For an operator without licensed
spectrum, the cost and complexity of operating an LTE unlicensed only network is
likely to overshadow the performance advantages of LTE unlicensed over Wi-Fi.
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4.The 5 GHz unlicensed band.
What?s so special about it?
The 2.4 GHz band has for a long time carried most of the world?s unlicensed wireless
traffic the 100 MHz allocated to it. Initially established as an ISM band by the ITU in
1947, it has been an extremely powerful success story that has proved the benefits
of unlicensed spectrum ? in terms of high spectral efficiency, wide broadband access,
and low costs. No longer considered a harmless giveaway, unlicensed spectrum has
become a major driver of technical innovation, broadband connectivity and
As the use (and congestion) in the 2.4 GHz band has grown over the last decade, the
5 GHz band has become the new star in unlicensed spectrum. Wi-Fi traffic is rapidly
expanding in the 5 GHz band, with the latest version, Wi-Fi ac, working exclusively in
that band. Like the 2.4 GHz band, the 5 GHz band is available virtually worldwide,
even though regulation and band boundaries change country by country. The 5 GHz
band has a major advantage over the 2.4 GHz band: a wider spectrum allocation,
with at least 300 MHz in most markets. In the US, the 5 GHz band has 580MHz, in
Europe 455?605 MHz, and in China 325 MHz.
In the USA, the FCC allocated the first 300 MHz in the 5 GHz U-NII band in 1997; it
added spectrum in 2003 and 2014, along with the DFS
requirement to manage interference with radars that share
access to the band. The band is split into 20 and 40 MHz
TDD channels, and transmission is subject to power
limitations that restrict the coverage range and make the 5
GHz band well suited for Wi-Fi or small cells, mostly in
indoor environments. In addition to Wi-Fi and, in the future,
LTE unlicensed, the 5 GHz band is used by other wireless
technologies, including proprietary ones for point-to-point
and point-to-multipoint links, cordless phones, and medical,
scientific and other IoT devices.
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5.Why do we need listen before talk (LBT)?
Fair coexistence is a requirement for success, not an option
In many countries, transmission in the 5 GHz band requires that the equipment
implement a listen-before-talk mechanism that enables the peaceful coexistence of
multiple technologies and the adoption of dynamic frequency selection (DFS) to
protect radar transmissions in the band. Countries like China, India, South Korea and
the USA do not mandate the implementation of listen-before-talk mechanisms.
Coexistence with other technologies is required, but no specific mechanism to
support it is required.
LBT requirements in Europe and Japan have been instrumental in driving LAA-LTE
standardization, but the need to support LBT in LAA-LTE goes well beyond
regulation. The fair coexistence with Wi-Fi that LBT provides is so crucial to the
success of LTE unlicensed that most vendors and operators are keen to introduce it
across all markets, including those that do not require it, to address concerns from
With LBT enabled, each cell or access point operating at a location scans the
environment to detect activity, and transmits only when the channel is free. This
allows different technologies and devices to operate in the same spectrum channel.
There are different ways to implement LBT. For instance, how the backoff time ? i.e.,
the period between scans of network activity ? is defined in LAA-LTE plays an
important role in how the traffic will be split between Wi-Fi and LAA-LTE and, hence,
is a factor in how fair the coexistencewill be. For this reason, there is a growing
consensus that LAA-LTE specs may have to go beyond regulatory requirements to
meet the levels of fairness that stakeholders expect ? namely that the impact of an
LTE small cell is not greater than that of a Wi-Fi access point.
3GPP LAA-LTE study item take on LBT
?In some regions in the world, unlicensed technologies need to abide to
certain regulations, e.g. Listen-Before-Talk (LBT). Fair coexistence between
LTE and other technologies such asWi-Fi as well as between LTE operators
is seen necessary. Even in countries without LBT, regulatory requirements
exist to attempt to minimize interference with other users of the unlicensed
spectrum. However, it is not enough to minimize interference simply for
regulatory aspects. It is also essential to insure that a deployed system will
operate as a ?good neighbour?, and not significantly impact legacy systems.
Therefore a study is required to determine a single global solution which
enhances LTE to enable licensed-assisted access to unlicensed spectrum
while coexisting with other technologies and fulfilling the regulatory
requirements. When looking at such enhancements, current LTE physical-
layer design should be reused as much as possible. To ensure holistic
solutions are considered, in-device, co-channel, and adjacent channel intra
and inter RAT coexistence scenarios should be included in the study.? (3GPP
FCC on coexistence in the 5 GHz U-NII band
?Typically, unlicensed devices operate at very low power over relatively
short distances, and often employ various techniques, such as dynamic
spectrum access or listen-before-talk protocols, to reduce the interference
risk to others as well as themselves. The primary operating condition for
unlicensed devices is that the operator must accept whatever interference
is received and must not cause harmful interference. Should harmful
interference occur, the operator is required to immediately correct the
interference problem or to cease operation.? (FCC 14-30)
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6.LTE-U, ahead of inclusion of LBT in 3GPP standards.
The solution for operators ready to deploy
LTE-U is the first version of LTE unlicensed, initially proposed by Ericsson and
Qualcomm in 2013. It is the version that is easier to deploy, because it requires fewer
changes from LTE in licensed bands and does not require an ad-hoc standardization
effort. While LTE-U relies on 3GPP Release 10-12, it does not have to support
functionality such as LBT, which is not yet included in 3GPP standards. That means
LTE-U can be used only in countries such as China, India, South Korea and the USA,
where LBT is not required.
The advantage of LTE-U is that it can be deployed sooner than LAA-LTE, because all
the standardization work has been done and the specifications for the
implementation of LTE-U have been published by the LTE-U Forum. The availability is
attractive to operators that need to increase capacity in the short term, especially if
they plan to deploy LTE-U in environments where there are free channels and hence
fair coexistence with Wi-Fi is easy to achieve.
In such a setting, LTE-U can identify and use channels that co-locatedWi-Fi does not
use, as shown as the first step in the figure below. LTE-U and Wi-Fi coexist side by
side, and LTE-U does not impact Wi-Fi performance. Because LTE-U can transmit
continuously, the operator can expect performance comparable to licensed LTE in a
20MHz channel. Because the 5 GHz band is still not heavily used in many
environments, this is a solution that is especially attractive in the short term, as
operators wait for standardization and commercialization of LAA-LTE.
If there are no free channels in the 5 GHz band, the operator has to share the
channel with Wi-Fi. LAA-LTE will use LBT for coexistence. LTE-U uses adaptive duty
cycles. In the duty-cycle approach, LTE-U transmits only during part of the cycle,
leaving Wi-Fi to transmit for the rest of the cycle, as the figure on the right illustrates.
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Duty cycles can support fair coexistence with Wi-Fi when appropriately set up (e.g.,
when the duty-cycle duration is set in such a way that the existing Wi-Fi APs using
the same channel are affected in the same way they would be by a new Wi-Fi AP).
However, it is the LTE-U cell that decides how much fairness to allow ? and Wi-Fi
networks can only adapt to the rules set by LTE-U. In this context, it is easy to see
why some Wi-Fi players are nervous about the introduction of LTE-U, especially
because some (incorrectly) consider 5 GHz to be the ?Wi-Fi band.?
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7.The LAA-LTE standardization process in 3GPP.
Enshrining fairness in the standards
To be deployable worldwide, LTE unlicensed has to implement LBT, and this requires
the introduction of LBT in the 3GPP standards. 3GPP is working on this, having
created a study item in 2014; finalization is expected in Release 13, projected for
The main features of LAA-LTE have been largely defined and the commitment to fair
coexistence with Wi-Fi reiterated. The focus of the current work is to find an
industry-wide consensus as to what is required for fair coexistence. This is a difficult
process, because fairness does not come for free: the price is reduced performance.
Part of the reason Wi-Fi is less spectrally efficient than LTE in licensed bands is, in
fact, that it implements mechanisms like LBT to ensure fair coexistence with other
Wi-Fi networks.When adding LBT to LTE unlicensed, we should expect a degradation
in performance ? and that degradation will vary depending on how LBT is
As the standards body for LTE, 3GPP represents the mobile operator and vendor
ecosystem and only indirectly the Wi-Fi ecosystem (through operators and vendors
that have a presence in both). As a result, there have been concerns in the industry
that the LAA-LTE standardization process may be more favorable to LTE than to
An LAA-LTE standard that does not guarantee fair coexistence to Wi-Fi ? or does not
do so to the satisfaction of the main Wi-Fi stakeholders ? would be a destructive
outcome for the prospects of LTE unlicensed. Regardless of regulatory requirements,
if LAA-LTE does not gain a sufficient level of industry-wide support, it is unlikely to
succeed ? i.e., gain the scale it needs to motivate mobile device vendors to support
the technology in new devices. Wi-Fi is a technology so widely used ? it carries more
traffic than LTE ? and loved that it would be unwise to engage in an aggressive
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confrontation. These considerations are not lost on either vendors or operators, and
seem to be guiding the work being done at 3GPP. There is a growing commitment to
finding a robust solution to coexistence in environments where Wi-Fi will continue to
Progress in LTE unlicensed standardization
December 2013 Qualcomm and Ericsson presentation of the initial proposal for LTE-U at a 3GPP meeting in Busan, South Korea.
January 2014 A 3GPP unofficial meeting in Paris, with companies and operators presenting their perspectives on the use of LTE in unlicensed bands.
March 2014 Discussion at the 3GPP plenary meeting in Fukuoka, Japan.
June 2014 Workshop in Sophia Antipolis, France. Outcomes included
? A plan to set up a study item in September 2014
? Adoption of LAA-LTE designation
? Agreement to focus on the 5 GHz band
? Commitment to finding a global solution
? Establishment of fair coexistence with Wi-Fi and among LTE operators
September 2014 3GPP TSG-RAN approved LAA-LTE as a study item for Release 13. The main goal is to determine the changes needed for fair
coexistence of LAA-LTE andWi-Fi. Release 13 covers
? Regulatory requirements
? Deployment scenarios, including multiple operators, and coexistence with both Wi-Fi and other LAA-LTE networks
? Design targets and functionalities
? Coexistence evaluation and methodology
Required functionalities include
? LBT, with maximum transmission duration
? Dynamic frequency selection for radar avoidance in certain bands and regions
? Carrier selection
? Transmit power control
The primary focus is on the downlink, although uplink is also under consideration.
March 2016 3GPP work item specs to be finalized. They will define the LBT coexistence mechanisms to be implemented, and the pairing of
unlicensed transmission with licensed bands.
Release 13 will also include LTE and Wi-Fi aggregation (LWA) and new functionality to improve mobility management and eNB
management in integrated LTE and Wi-Fi networks.
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8.Wi-Fi or LTE unlicensed in small-cell deployments?
A look at the tradeoffs
LTE unlicensed is squarely aimed at mobile operators because it requires an LTE
licensed spectrum allocation that can be used as a primary carrier. Residential and
enterprise Wi-Fi users, as well as WISPs, MSOs and other service providers using
Wi-Fi, may become involved by hosting or sharing access in LTE unlicensed
deployments, but we expect that these deployments will be driven (although not
necessarily funded) by mobile operators.
Mobile operators are assessing LTE unlicensed ? running trials, participating in the
3GPP standardization, or announcing deployment plans as Verizon and T-Mobile in
the USA have done. At the same time, mobile operators also rely on Wi-Fi for
residential and enterprise offload, hotspot access, or carrier Wi-Fi, and their use of
the technology is expanding as they become more comfortable using unlicensed
spectrum for opportunistic access.
The choice they face is not between Wi-Fi and LTE.Mobile operators will continue to
rely on Wi-Fi access for offload ? or, at a bare minimum if they do not want to
engage directly with Wi-Fi, they have to accept the fact that most of the data traffic
their subscribers generate goes through Wi-Fi. But even the operators that deploy
LTE unlicensed are likely to use Wi-Fi and, increasingly, carrier Wi-Fi in the same
types of locations where LTE unlicensed is used, and likely to step up their efforts to
integrate Wi-Fi within their LTE networks.
Instead, the place wheremobile operators face a complex decision of choosing
between Wi-Fi and LTE unlicensed ismostly in indoor environments where they plan
for a small-cell LTE deployment andmust decidewhether to invest inWi-Fi, in LTE
unlicensed, or in a mix of both.
Among all the factors we list in the graph, two have the heaviest weight:
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- LTE unlicensed has greater spectral efficiency and better performance than
Wi-Fi ? although it is unclear how much that differencewill be retained with
the introduction of LBT.
- Virtually all mobile devices have Wi-Fi, making the integration of Wi-Fi in LTE
networks possible today. The inclusion of LTE unlicensed in mobile devices
requires support from device vendors. Commercial availability will require a
couple of years, and thenwide adoption a few more years. At the same
time, the marginal cost of adding LTE unlicensed in mobile devices is not
high, and cost is not seen as a substantial challenge to adoption.
One additional advantage of Wi-Fi that is rarely mentioned is its wide AP footprint ?
in the enterprise and in public venues. This installed base can be used as a
springboard for small-cell deployments. In the deployment of small cells, acquiring
locations and backhaul connections to them for the equipment can be challenging
for mobile operators ?almost invariably time consuming and complex, and often
downright expensive. Being able to co-locate small cells where Wi-Fi APs already
exist can speed up deployments and reduce cost and complexity in enterprise
locations and public venues.
With a combined licensed and unlicensed LTE small-cell strategy, a mobile operator
may find it more complex to gain access to these premises, because enterprises, real
estate owners, city agencies, and public venue managers often have their own Wi-Fi
networks and, reasonably, they want to protect their investment, retain the
performance level of their networks, and be able to expand them as needed. An
operator wanting to install LTE unlicensed in the real estate they control might be
seen as an aggressive competitor, especially if those in charge of the property do not
trust the fair coexistence that LTE-U and LAA-LTE promise.
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9. Quantifying the LTE unlicensed performance benefits.
The challenges in generalizing simulation and trial results
If a key driver for LTE unlicensed adoption is its performance advantage over Wi-Fi,
we need to quantify the size of this advantage to assess whether mobile operators
stand to benefit from it, and whether there is a solid business case to support
Vendors and operators have run many simulations and trials, and we have listed
some in the references. It is difficult, however, to generalize the performance
differences that have been observed and how they will translate in commercial
deployments, because many factors (see table on the right) affect performance. The
assumptions made for the two technologies and the scenarios considered vary from
study to study to study, because the goal of each study is different. In addition, most
of the published data focus on throughput, but other metrics ? e.g., latency ? are
important to characterizing performance and quality of experience.
The high-level drivers of performance differences between the two technologies and
their directionality are, however, becoming established, even though the results
from individual trials and simulations are somewhat varied. The table below
summarizes the high-level findings to date, but interested readers should consult the
referenced documents for a detailed assessment of the results. As an example of the
results obtained in LTE unlicensed and Wi-Fi simulations, we show below the results
from NTT DOCOMO.
Multiple factors are responsible for the improved spectral efficiency of LTE
unlicensed over Wi-Fi:
? Robust FEC
? Hybrid ARQ
Factors affecting relative performance of Wi-Fi and LTE unlicensed
? LTE unlicensed specifications (3GPP LAA-LTE specifications are not
yet finalized, so current simulations and trials have to make
assumptions about what the specifications will be). Performance
differences should be expected between LTE-U and LAA-LTE
? LTE-U: CSAT implementation (e.g., duty cycle duration, percentage
of time LTE is active, and how they change as a function of Wi-Fi
activity) and parameters that operators can choose or that are fixed
? LAA-LTE: LBT implementation (e.g., fixed or exponential backoff,
defer period, CAA protocol)
? Physical environment and deployment topology (including indoor
versus indoor locations)
? Features and versions of the technologies
? Hardware vendor, equipment specifications
? Channel size; TDD or FDDmodulation; inclusion of uplink; frequency
? Spatial distribution of UEs and infrastructure nodes (macro and small
cells, Wi-Fi AP); co-located/non?co-located equipment
? Traffic model, including assumptions about traffic mix (e.g., voice
and video as a percentage of traffic)
? Other simulation parameters
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? Effective interference coordination and avoidance
? Better mobility support and device scheduling
? CA to manage traffic across licensed and unlicensed channels
? Inter-operator and intra-operator RAN synchronization.
In an environment in which LTE unlicensed has complete access to a channel
because there is no competing network (either Wi-Fi or LTE unlicensed), LTE
unlicensed performance reaps all these benefits to the maximum, and we can expect
it to be much better than Wi-Fi. This is because in unlicensed spectrum, LTE uses the
same scheduled transmission mechanisms that it uses in licensed bands, giving it a
higher spectral efficiency than Wi-Fi, which is subject to the overhead exacted by fair
coexistence mechanisms that are in place even if the channel is uncontended.
In contrast, when operating in a channel shared with Wi-Fi or another LTE unlicensed
network, LTE?s performance advantages are reduced by interference or by the
introduction of coexistence mechanisms.
In LTE-U, the duty cycle approach reduces the percentage of time the LTE-U cell
transmits and this affects the throughput. In a lightly loaded network, this may have
a limited impact on throughput, but as traffic load increases, so does the impact on
throughput. If the duty cycle is set as a function of the number of Wi-Fi or LTE-U
networks active in the same channel, we could expect a duty cycle of 50% for one
competing network, and 25% for three competing networks. So performance in this
case is tied to environmental constraints. If LTE-U were to use a duty cycle of 50%
regardless of the number of networks present, it would appropriate an unfair
portion of network resources.
The addition of LBT in LAA-LTE will degrade performance and hence reduce the
benefits of LTE unlicensed over Wi-Fi and, by improving coexistence with Wi-Fi (as
well as with other LTE unlicensed networks), it will improve Wi-Fi throughput.
However, the LBT penalty critically depends on the implementation. CableLabs
argued that an implementation of LBTmeant to only meet European regulation
would greatly penalizeWi-Fi, with the impact becomingmore severe as the number
of devices increases. An implementation of LBT according to the 3GPP target ? of not
LTE unlicensed versus Wi-Fi, stand-alone configuration
? LTE has better spectral efficiency:
? Interference management
? LTE performance is more robust than Wi-Fi with:
? Increased traffic load
? Increased number of users
How listen before talkworks
1. Listen for ongoing transmission in the selected channel.
2. If channel is idle, start transmission for a fixed amount of time, then
release traffic for a backoff period and start with step 1 again.
3. If the channel is busy, don?t transmit, and go back to step 1. If the
channel continues to be busy after multiple attempts, change
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degrading Wi-Fi performance any more than anotherWi-Fi access point would ? is
expected to degrade LAA-LTE performance more (simulations by Intel and Nokia
indicated a reduction in throughput by 30% or more ? but this is also associated with
an increase in Wi-Fi throughput of 50%) and reduce the combinedWi-Fi and LAA-LTE
channel throughput over the case in which LTE unlicensed does not use LBT. This is
to be expected because of the network resources needed by LBT?s overhead.
The impact on Wi-Fi, too, varies depending on how LBT is implemented. For instance,
3GPP is considering the use of a fixed backoff period, whereasWi-Fi uses a variable
backoff period. Because Wi-Fi performance benefits from a variable backoff period,
Wi-Fi players are increasingly requesting that LAA-LTE use a variable backoff period
as Wi-Fi does.
LBT allows for a distribution of spectrum resources that takes into account the traffic
load of each coexisting network. However, coexistence mechanisms that maximize
fairness in the allocation of network resources to competing networks necessarily
have a negative effect on performance, so the tradeoffs have to be assessed to avoid
a situation where fairness leads to a severe reduction in spectral efficiency in which
served users are collectively worse off ? i.e., there is a decrease in both channel
capacity and average per-device throughput.
One way to address this issue is to replicate within LAA-LTE a level of fairness that
closely mimics the one that is common in Wi-Fi networks. This approach makes
sense, because Wi-Fi is the prevalent technology using 5 GHz spectrum, and LAA-LTE
is the newcomer. There seems to be a growing consensus that this is the way to go,
but it is not clear yet what it takes to achieve this goal and how this will affect the
performance of LAA-LTE.
LTE unlicensed with Wi-Fi, coexistence
? Combined Wi-Fi and LTE capacity can be higher than Wi-Fi only.
? Stronger improvements in sparse deployments, with LAA-LTE
having a stronger impact on Wi-Fi performance in congested
environments (see NTT DOCOMO simulation results below).
? Wi-Fi performance may increase with LTE as neighbor (instead of
Wi-Fi) (see NTT DOCOMO simulation results below).
? LTE-U duty-cycle parameters affect Wi-Fi performance. For instance
longer periods increase Wi-Fi throughput stability but also latency
? LBT more onerous to implement that duty cycle, but leads to better
overall throughput for 50% duty cycle (Intel and InterDigital).
? Impact of LBT and fair coexistence mechanisms.
? Standardization still in progress, so it is difficult to assess impact.
? Degradation in LTE unlicensed performance due to LBT may
reduce throughput by 30% or more (Intel and Nokia). Wi-Fi
throughput may increase by 50% (Nokia).
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REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |22|
Beyond LTE unlicensed
What are the alternatives to LTE unlicensed ? or solutions complementary to it ? that give mobile operators a way to leverage spectrum assets beyond the
cellular bands they already use?
? Carrier Wi-Fi. Todaymobile operators mostly use Wi-Fi as an offload technology that enables them to reduce network congestion and give their subscribers
a better experience. Even when they own the Wi-Fi infrastructure, operators do not usually integrate it with their cellular networks, and Wi-Fi access is
managed as a separate access channel (and a special case of offload). With carrier Wi-Fi, operators can use their Wi-Fi infrastructure, and that of their
wholesale or roaming partners, as an integral part of their cellular network, and rely it on opportunistically ? when available, and when needed. Because
with carrier Wi-Fi, cellular and Wi-Fi are integrated in the core, mobile operators can present a consistent set of services, policy, and pricing across Wi-Fi and
cellular. This solution allows operators to use the 5 GHz band right away, using themobile devices already in the market, but they do have to integrate their
cellular and Wi-Fi networks. Many vendors and operators are working on Wi-Fi and cellular integration, but there is still work ahead before achieving full
? LTE and Wi-Fi aggregation (LWA). Complementary to carrier Wi-Fi and to LAA-LTE, LWA enables operators to integrate Wi-Fi and cellular traffic (see section
below). As carrier Wi-Fi does, LWA leverages the same 5 GHz band as LTE unlicensed, but, unlike LTE unlicensed, it does so without requiring new handsets.
3GPP is working on LWA standardization, and it is expected that the specs will be included in Release 13, along with LAA-LTU. In the meantime, interest in
LWA is rapidly expanding.
? LTE unlicensed in other bands. 3GPP has decided to focus initially on the 5 GHz band, but LTE unlicensed could easily expand to other unlicensed bands. An
obvious one is the 2.4 GHz band, but that is already congested, and hence unlikely to attract mobile operators because in such an environment, they cannot
protect their LTE unlicensed investment. The 60 GHz band is another possible target, but the range is too limited to be used in the enterprise or in public
venues, with few possible exceptions ? and there, operators will be able to use Wi-Fi instead, if they need to add capacity to their small cells.
? LTE in other (licensed) bands. LTE unlicensed?s attraction for mobile operators is that it gives them access to a new band. However, there are other bands
available that can be used to add capacity to cellular networks. The 3.5 GHz band is an attractive option, because it is underutilized in most markets. It is also
an excellent solution for small-cell deployments. Because of its short coverage radius, the 3.5 GHz band is well suited formacro deployments, but it works
well as an under-layer for small cells that, unlike co-channel deployments, does not create interference with the macro layers.
? LSA/ASA. Pending regulatory support, mobile operators will be able to use LSA/ASA in bands that can be shared with the primary spectrum holder (e.g.,
military entities). As in the LTE unlicensed case, LSA/ASA provides an opportunistic access channel that, where available, can provide a reliable capacity
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10. One step further with LWA.
Alternative or complement?
Alongside LTE unlicensed, LWA has started to gain traction, and it presents some
advantages over LTE unlicensed. Like the latter, LWA is being standardized by
3GPP and gives mobile operators a way to use unlicensed bands that is well
integrated within their network. Because LWA uses Wi-Fi and not LTE for
unlicensed access, it can use not only the 5 GHz band, but also the 2.4 GHz one.
Because the 2.4 GHz is already crowded, mobile operators? interest in it is
limited, but the marginal cost of adding 2.4 GHz in LWA is small.
With LWA, mobile operators use Wi-Fi for access, with Wi-Fi transmission
integrated in the cellular RAN. The RANmanages the traffic, and all signaling
goes through LTE in a licensed channel (as is the case in LTE unlicensed).
The main advantage of LWA is that it requires little intervention in existing
networks (only a software upgrade or a new Wi-Fi access point) and in devices
(an OS update should suffice; the existing Wi-Fi handsets do not have to be
replaced). Because it uses ubiquitous Wi-Fi and LTE wireless interfaces, it can
become commercially available in the short term. The downside of LWA is that it
lacks the performance benefits of LTE unlicensed (although, as discussed, we do
not yet have a way to quantify them, especially if we include the LBT
LWA delivers, however, important benefits over Wi-Fi offload and increases the
attractiveness of carrier Wi-Fi when the two are combined. In LWA, Wi-Fi is used
only for the downlink, with LTE carrying all the uplink traffic and, optionally,
downlink traffic as well. This combination can increase the spectral efficiency,
because Wi-Fi is well suited to carry downlink traffic, but less so for uplink traffic
? and on the opposite side, LTE uplink is better than Wi-Fi uplink.
In addition, RAN integration makes it possible to use real-time traffic conditions
and interference levels to allocate traffic to the most appropriate interface, and
to manage mobility more efficiently than in a Wi-Fi offload environment.
Because the RAN sends all traffic to the mobile core, all traffic ?Wi-Fi and LTE ?
is treated in the same way, and no further integration of Wi-Fi traffic in the core
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11. Is LTE unlicensed worth the investment?
A look at the business case
Ultimately, a new technology is adopted only if there is a business case that
supports it. For LTE unlicensed, a solid business case is not sufficient ? because
adoption will largely depend on the availability of new devices that support the
technology, but it is still nevertheless necessary. Assuming that lack of devices
will not be an obstacle to adoption, we need to understand whether there is a
business case that justifies LTE unlicensed adoption in small-cell deployments.
Mobile operators assessing the LTE unlicensed business case face two
? To increase capacity, is it cost effective to add LTE unlicensed to LTE
licensed small cells?
? To leverage the 5 GHz band, it is more cost effective to use LTE unlicensed
Depending on their strategy and environment, mobile operators are likely to
include in their assessment additional deployment scenarios ? e.g., stand-alone
LTE unlicensed deployments in which amacro cell that is not co-located is the
primary carrier for an LTE unlicensed small cell, or where the LTE licensed small
cell integrates LTE unlicensed and Wi-Fi (all co-located at one location).
In this section, we explore these two preliminary questions to understand the
basic economics behind LTE unlicensed adoption. We do so by looking at the
per-bit TCO (i.e., the 5-year TCO divided by capacity) of a small cell in three
? LTE lic: a small cell with only LTE licensed
? LTE lic + unlic: a small cell with both LTE licensed and unlicensed (we
assume the adoption of LAA-LTE)
? LTE lic + Wi-Fi: a small cell with both LTE licensed and Wi-Fi
To facilitate the comparison, our model assumes the same channel width for
each technology and reports the results as a percentage of the LTE lic
throughput. We chose this approach because the cost to deploy small cells
varies considerably across geographies, deployment locations (e.g., indoors vs.
outdoors), operators and other factors, but we expect that the marginal costs
to add LTE unlicensed or Wi-Fi ?measured as a percentage of the cost of the
small cell using only LTE licensed ? are comparable within each deployment.
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The cost of installing and operating a small cell in an airport in India may be very
different from that of an outdoor high-street small cell in the UK, but the
marginal cost of adding Wi-Fi or LTE unlicensed as a percentage of small-cell
costs is comparable.
The main obstacle in examining the business case for LTE unlicensed is that we
do not know yet how well LAA-LTE will perform and what impact LAA-LTE will
have on Wi-Fi. Furthermore, because the 5 GHz band is unlicensed, the
contention for spectrum resources from other networks is unknown and
cannot be controlled; hence, the impact of congestion and interference on
performance is variable.
So instead of looking at the per-bit TCO after making assumptions about
throughput, we look at the impact that performance has on the per-bit TCO.
This approach tells us at what performance thresholds LTE unlicensed is more
cost-effective than Wi-Fi, or Wi-Fi more cost effective than LTE unlicensed, as a
function of small-cell capacity.
The graph on the previous page shows our baseline 5-year TCO. We assume
that capex accounts for 34% of the TCO and equipment for about a third of the
capex. We estimate the incremental TCO contribution from the addition of
LAA-LTE to be limited to double the equipment costs, an increase of 15% in
operating costs, and an increase of 20% in backhaul. Overall the TCO for a small
cell with LAA-LTE is 113% of the TCO for an LTE licensed small cell alone. A small
cell withWi-Fi is less expensive (108% of the TCO for an LTE licensed small cell)
because of the lower equipment costs, but we assume that operating costs will
be the same as for a small cell with LAA-LTE.
The graph on this page shows the impact of adding LTE unlic to an LTE lic small
cell using the per-bit TCO (TCO divided by capacity, shown as a percentage of
the LTE lic base case) as the throughput of LTE unlic grows. The higher the LTE
unlic throughput, the lower the per-bit TCO, as expected. If LTE unlic has half
the capacity of LTE lic, the overall (lic and unlic) per-bit TCO is 25% lower than in
the LTE lic-only case. Because the incremental cost of adding LTE unlic is low, it
becomes cost-effective to add LTE unlic with an incremental throughput of only
To address the second question, we kept the Wi-Fi throughput fixed, and
looked at the impact on the business case from changes in throughput that
may be due to congestion or from the different overhead costs that specific
implementations of LBT have. To look at the sensitivity of this analysis, we show
the results from four cases that assume a fixed Wi-Fi throughput of 20%, 30%,
40% and 50% of LTE lic. Changes in Wi-Fi throughput may result from varying
congestion and interference levels, and from different LBT implementations.
We show the total throughput of the small cell (i.e., LTE lic +Wi-Fi, or LTE lic +
LTE unlic) as a percentage of the throughput for the LTE lic base case, and the
per-bit TCO as a percentage of the LTE lic per-bit TCO. In the graphs on the
right, LTE lic andWi-Fi throughput stay constant and hence the LTE lic andWi-Fi
per-bit TCO does not change. In the 10% to 20% range, the LTE unlic
throughput is lower than that ofWi-Fi, because in this graph, we assume a
Wi-Fi throughput of 20% of LTE lic or higher.
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The per-bit TCO for LTE lic + unlic decreases as the throughput grows, as
expected.Wi-Fi installed in LTE lic small cells has a lower per-bit TCO than LTE
lic + unlic if LTE unlic throughput is higher or comparable to LTE unlicensed. As
LTE unlicensed is expected to have a higher performance than Wi-Fi, the per-bit
TCO is better to LTE unlic than Wi-Fi in most environments. This is due to the
fact that the deployment and operation costs of the two solutions ? LTE unlic
and Wi-Fi ? are similar.
A better per-bit TCO for LTE unlic does not imply that LTE unlicensed should be
preferred to Wi-Fi, as there are many other considerations to take into account,
such as time-to-market, device availability and cost, business models,
integration options, alternative solutions and so on. The per-bit TCO spread
between Wi-Fi and LTE unlicensed should be assessedwithin the context of
these considerations. As it is always the case for financial analysis, a TCO
analysis does not give a go/no go answer, but it is a key took to assess the
tradeoffs between these two technologies.
The results of the per-bit TCO sensitivity analysis show that even in the face of
heavy use of the 5 GHz band, it is still cost-effective to add LTE unlicensed or
Wi-Fi to small cells using LTE in licensed bands, because their addition lowers
the per-bit TCO. At the same time, the cost tradeoffs between LTE unlicensed
andWi-Fi crucially depend on the relative performance of the two technologies
? and this is what gives the upcoming 3GPP specs a central role in determining
the breadth of LAA-LTE adoption and market success.
What is peculiar in the LTE unlicensed and Wi-Fi comparison is the fact that the
performance of each technology is tied to that of the other: a stricter
implementation of LBT stands to degrade LAA-LTE performance more and
improveWi-Fi performance. Conversely, an implementation of LBT that is
friendlier to LAA-LTE may result in less degradation of LAA-LTE and worse Wi-Fi
performance. The per-bit TCO analysis shows that finding the right balance in
drawing the specs for LAA-LTE has implications that go beyond meeting
regulatory requirements or ensuring basic fairness in coexistence with Wi-Fi.
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Growing value and usage of unlicensed spectrum: LTE unlicensed expands utilization of the 5 GHz band, with high spectral efficiency.
Two versions of LTE unlicensed: LTE-U (3GPP Release 10-12; only for China, India, South Korea, and USA; shorter time to market) and LAA-LTE
(Release 13, a global standard that will include listen-before-talk mechanisms to meet regulatory requirements and ensure fair coexistence).
Commitment to fair coexistence:With Wi-Fi dominating in the 5 GHz band, LTE unlicensed proponents realize that fair coexistence mechanisms
must in place to ensure acceptance of the technology ? especially in the enterprise. Wireless ecosystem acceptance is necessary to LTE unlicensed
LTE unlicensed strengths:High throughput, full integration in LTE network (it is a special case of CA, with one band using unlicensed spectrum).
Wi-Fi strengths:Ubiquitous in devices, widely deployed, can be integrated in LTE networks today with fair coexistence with other networks.
LTE unlicensed orWi-Fi? LTE unlicensed requires new mobile devices. The deciding factor may be device availability within an acceptable timeline
and at an acceptable price.
LBT does not come for free: There is a growing consensus that listen before talk is necessary and an overall positive, but it will degrade LTE
unlicensed performance ? and the impact on performance is still uncertain, because it depends on the LBT implementation that 3GPP selects.
LWA as an alternative: LTE and Wi-Fi aggregation is emerging as an alternative (and possibly a complement) to LAA-LTE. It gives mobile operators
another solution to leverage the 5 GHz band better than with Wi-Fi offload.
Business case: The choice between LTE unlicensed and Wi-Fi hinges on the relative performance of the two technologies, and this is dependent on
the ongoing 3GPP standardization process.
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II. Vendor profiles and interviews
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unlicensed and Wi-Fi
At Alcatel-Lucent, increasing wireless network
capacity goes hand in hand with an improvement
in the quality of experience. The goal is for wireless
networks? performance to match that of wireline
networks in terms of reliability, speed, and quality
of voice and video. Densification of the network
infrastructure with small cells and Wi-Fi is one path
that Alcatel-Lucent has pursued over recent years.
With the newly announced Wireless Unified
Networks, Alcatel-Lucent has moved two steps
further, by adding what it calls Cellular Boost with
LTE unlicensed, and adding Wi-Fi Boost by closely
tying Wi-Fi and cellular transmission.
The motivation to do so is that each technology
has different strengths. Alcatel-Lucent intends to
leverage these differences to optimize the
allocation of network resources. LTE provides good
uplink but can benefit from additional downlink
throughput, while Wi-Fi is strongest in the
downlink but can benefit from better scheduling
and uplink at the cell edge. Alcatel-Lucent
proposes that, where both technologies are
available, Wi-Fi provides the downlink, and LTE the
uplink as part of a blended service.
Wi-Fi Boost goes beyond Wi-Fi offload or solutions
like Passpoint and Hotspot 2.0, which improve
access of mobile devices to Wi-Fi with improved
authentication and network selection. In its
simplest implementation, best effort traffic is
transmitted down over Wi-Fi and up over LTE. In
advanced versions, it will use dual connectivity for
simultaneous Wi-Fi and LTE according to 3GPP?s
LWA. As an IP-layer solution, Wi-Fi Boost works
with 3G too, where the capacity gains of Wi-Fi over
3G are higher than those of Wi-Fi over 4G.
Alcatel-Lucent reports that the Wi-Fi Boost
approach provides a 20% to 30% increase in
downlink throughput to a single device, a tenfold
increase in the user?s uplink at cell edge, and a 2x
improvement in Wi-Fi range. With LWA, the
downlink is a summation of the available Wi-Fi and
LTE capacity. The link to the cellular network
improves performance reliability when Wi-Fi is
congested or not available. This is a solution that
can be deployed in the short term, because it does
not require new devices or new infrastructure.
Cellular Boost aims to improve the user experience
by increasing the capability of LTE through the
addition of unlicensed spectrum. With Cellular
Boost, devices transmit and receive LTE signals as
they do today, but aggregate carriers that operate
in unlicensed bands, and that coexist with other
traffic (e.g., Wi-Fi) within the same band. Cellular
Boost is complementary to Wi-Fi Boost; it enables
LTE to be added as an additional channel in the 5
GHz band to increase download capacity and
optimize end-user experience.
Alcatel-Lucent expects Wi-Fi Boost to be fully
commercial soon, as it builds on current Wi-Fi and
LTE deployments. Cellular Boost will take longer as
it requires new devices and new infrastructure.
Hence, Alcatel-Lucent sees Wi-Fi Boost as the
initial step for mobile operators, one that is
independent of the Cellular Boost. This gives
mobile operators a short-term path to increase
capacity by leveraging existing deployed network
components while the industry agrees on LTE
unlicensed standardization and gets ready for that
The joint connectivity across technologies raises
the issue of how mobile operators charge for the
traffic ? whether they want to treat traffic over LTE
differently from traffic over Wi-Fi, or over licensed
versus unlicensed bands (i.e., LTE licensed and LTE
unlicensed). From a technical viewpoint, the
operator has full visibility into all these networks,
so it can charge differently, and enable Wi-Fi Boost
and Cellular Boost as and when desired. From a
subscriber perspective, the difference may
eventually become irrelevant as subscribers learn
to trust interface selection to the network, so no
longer actively choose Wi-Fi or LTE.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |30|
boost from combining
A conversation with
Mike Schabel, VP of Small Cells,
Monica Paolini:Welcome to our conversation
today with Mike Schabel, the VP of Small Cells at
Alcatel-Lucent. This conversation is part of our
report on LTE unlicensed and its coexistence with
Wi-Fi from Senza Fili and in collaboration with RCR
Wireless news. Mike, thanks for taking the time to
talk to us today.
Mike Schabel: Thanks for having me, Monica.
Monica:Mike, can you tell us what you do on
small cells at Alcatel-Lucent?
Mike: I?m fortunate enough to run the small cell
business at Alcatel-Lucent, focusing on the over 70
operators that we do business with around the
world, in 53 countries, helping to commercially
deploy cellular in the home, in the indoor
enterprise, and in outdoor environments. Fifty-
three countries means I?m on a lot of airplanes.
Monica: A lot of flights and a lot of technologies.
The list of technologies keeps growing by the day.
Instead of getting smaller, it expands. This is what
is happening with LTE unlicensed. We had Wi-Fi.
We had LTE. LTE unlicensed is a little of Wi-Fi, a
little of LTE.
How does LTE unlicensed fit in this ecosystem of
Mike: It?s a great question, because it can get very
confusing when we?re talking about all of these
different technologies. To simplify it for myself, I
often think about what?s the problem we?re trying
I think you have to look no further than some of
the recent spectrum auctions to recognize that the
spectrum that we transmit wireless cellular signals
over is going to be challenged in a variety of ways.
First of all, when you have more users doing more
things on this spectrum, then you?re capacity
limited. People want to continue growing their
ability to send more traffic. You need more
When you try to go after more network capacity,
you need more spectrum. That spectrum is
limited. Therefore, operators have said, ?Why
don?t we go use some of the unlicensed spectrum
to complement what we do with our licensed
They can already do some pretty cool things ? such
as dual connectivity or carrier aggregation. Why
not aggregate that unlicensed traffic and
unlicensed spectrum? But there?s a small issue:
there are other technologies and devices that use
that unlicensed spectrum.
Wi-Fi is a great example, but not the only one. In
fact there are other technologies. In white spaces,
as an example, you have other technologies that
run and use some of that unlicensed spectrum.
The real challenge here is: if you?re going to go use
that unlicensed spectrum, how do you do it in a
way that?s 1) fair; 2) standardized in a way that
everybody can go use it; and 3) doesn?t really
change the nature or the behavior of the other
technologies that are already there? It requires a
tremendous amount of collaboration and careful
study to get that done properly.
Monica: This is a concern that some of the people
have with LTE unlicensed. Some see it as a
newcomer intruding in a territory that is already
occupied ? even though, obviously, the unlicensed
band is for everybody to use. There is a question of
fairness. How do you define fairness?
Mike:Unlicensed spectrum is unlicensed
spectrum. Anybody is allowed to use it for certain
purposes. ?Fair? is probably not a term I need to
try to define.
What I can say is it?s important to accommodate
the other technologies that are already there, and
existing and working in a particular way. There
may be a specific regulation or standard for which
they?re working and have agreed on. Or even
behaviorally, they may have agreed to work with
each other to use that space.
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I believe that you shouldn?t go confuse that or
mess that up. You should accommodate it. You
should recognize it. You should appreciate it and
work collaboratively with those other users in
order to become yet an additional user in their
space. These technologies have carved off their
space. You have to respect that.
LTE-U has to properly accommodate any other
technology, whether it?s Wi-Fi, white space, or
another one. It has to accommodate what?s there,
and do it in a collaborative way.
Monica: You can also make the argument that
using LTE unlicensed increases the spectrum
utilization, because the 5 GHz band is often not
used to maximum potential. Do you think that
with LTE unlicensed, we can get a better utilization
of the spectrum assets that are available?
Mike:Whenever you have your own slice of
spectrum, you can do some cool things within that
and get some very high performance schemes. But
then Wi-Fi says, ?You don?t have your own slice.?
Therefore, you have to spend more time in a
nonscheduled environment, because you have so
many different players. When you have so many
players, you can?t guarantee what anybody else
could do. You effectively have to listen before
somebody else engages.
What is really clever in LTE-U is to say, ?How can I
take the coding and spectrum efficiencies, and
blend them into the concept of being a good
partner and player in the use of that spectrum by
listening to everybody, and then speaking when
it?s an appropriate time to do so?? I?m using voice
analogies here, but it?s the same type of concept.
You have a conversation. Let?s not ruin it.
Monica: Today, Wi-Fi is in all smartphones, laptops
and tablets. And it?s relatively inexpensive. Do we
need another technology? What are the benefits
that an operator can gain from LTE unlicensed?
Mike:We?re thinking about LTE-U as a different
technology. It?s not. It?s cellular. It is LTE. It is LTE
running over a different piece of spectrum. If I look
in any operator?s LTE network today, generally
speaking, they?re operating over many different
pieces of spectrum down and up, as well as by
region ?multiple pieces of spectrum that they?re
aggregating together, so it?s unified.
Many consider this unlicensed piece something
new. It?s not new. It?s LTE carrier aggregation over
a piece of spectrum that we carved out. You need
to take one small step, technically, to figure out
when you can carve it out, when it?s not being
used ? and consume it when it?s not being used.
Or if everybody is using it, use it in a way that
respects what other people are doing.
LTE-U is the same technology, applied in another
piece of spectrum that?s also being used in other
ways. An operator who has access to more
spectrum can deliver a higher-capacity network.
As a consumer, why would I care? If my operator is
spending all of its capital on buying more spectrum
to give me what I want as a user experience,
ultimately it?s going to come back to me: I?ve got
to help them pay for that. If there is available
spectrum, the operator can go and deliver the type
of experience that I want. Because the operator
can lower its cost, that doesn?t come back to me
and I can (in theory) lower my cost as well.
Monica: At the same time, it?s not Wi-Fi versus LTE
unlicensed. Operators will not only use both
technologies in different places, but they might
also use them in the same place. So in the same
location, they may use LTE licensed, LTE
unlicensed, and Wi-Fi.
Mike:Wi-Fi is really interesting from a cellular
operator perspective because it has mobility
capabilities, but it was developed to serve nomadic
data usage. It?s well tuned for that.
Some operators have decided to roll out an
extension of their wireline network to provide a
wireless solution. I?ve seen cable operators and
wireline ISPs do that. I see a lot of that wireline or
wireless service provide that last meter?s access
and mobility with Wi-Fi. That?s going to continue.
It gets a little confusing when you see service
providers that actually have both, that they have
both carrier-grade Wi-Fi and cellular, and use load
balancing across the two networks.
They say, ?I?m going to put you on Wi-Fi or
cellular.? It?s an either-or technology. The cool
thing about Hotspot 2.0 and ANDSF was to enable
that type of switching capability. LTE-U absolutely
fits right into that paradigm. It?s not changing that
paradigm. I don?t know that it fundamentally
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |32|
enhances Wi-Fi or LTE-U. It?s just making LTE-U
available to use more spectrum. It?s as simple as
Monica: Alcatel-Lucent?s solution is interesting
because what you?re trying to do is to actually
increase the integration between the Wi-Fi and
LTE. By doing that, you can have a better utilization
of all the resources that are available.
Mike: LTE-U is a great technology, but let?s park it
for a minute. We?re introducing something that is
very different. We think that Wi-Fi is a great
technology. Wi-Fi in itself is a fantastic solution. It?s
in our homes, in our enterprises. It?s going to be a
very important part of the internet of things as
that moves forward in the wireless home and the
wireless enterprise. There?s no question about
What we recognized, though, is that as you put
more demands on Wi-Fi, you?re going to expose
the challenges that that technology has. It has a lot
of spectrum, and so a lot of capacity. But what we
also saw is that the uplink is challenged. That
network can be better served by using a cellular
solution. What we?ve come up with is a technology
called Wireless Unified Networks.
We?re saying it?s not Wi-Fi or cellular, but it?s Wi-Fi
and cellular operating at the same time using their
inherent strengths to deliver a unified experience
What?s the value? Who cares? Here?s yet another
technology that?s going to drive everybody crazy,
right? The value is now we can build a unified
wireless network, instead of Wi-Fi or cellular. And
it?s an extremely high-performance network.
With one of our partners, Qualcomm, we were
showing an instantiation of this by taking the
cellular and putting it together with Wi-Fi. At
Mobile World Congress, we were providing
download speeds of 450 Mbps down, using
standard, off-the-shelf gear that exists today. 450
Mbps down on wireless is pretty interesting. We
have 700 Mbps going in the labs, and we have a
pathway to greater than 1 Gbps down.
What we realize is that hitting those types of rates
with standalone technologies is going to get
harder over time. We just realized if we put the
two together, as simple as that, now all of a
sudden, you can get some extremely great
horsepower out of it. It changes our thinking about
what wireless networks actually should be on a go-
Monica: It?s not just putting them together, it?s
putting them together to leverage the relative
advantages of them. This is the first act, to get
Wi-Fi and cellular together. How does LTE
unlicensed come into that picture?
Mike:We?re blending Wi-Fi and cellular. I can do it
with standard cellular today and standard Wi-Fi
today. We blend those, and we end up with a very
For example, if I were trying to do a Wi-Fi video
uplink, that can put a lot of load on the Wi-Fi
network. But when I blend Wi-Fi and cellular, I can
more easily handle synchronous traffic and a lot of
that synchronous uplink traffic. This doesn?t
congest the Wi-Fi network as much as it otherwise
would, so the network can handle it well.
What about LTE-U? Remember, these are two
completely separate technologies. LTE-U is just
more spectrum for LTE. Wireless Unified Networks
are about blending technologies to get a better
overall user experience. We can actually take
LTE-U as the cellular piece. Remember, I?m just
taking Wi-Fi and cellular and I?m putting them
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |33|
together. I can also take Wi-Fi and LTE-U and put
them together. It?s exactly the same. These are
coexisting concepts, not competitive concepts in
Monica: A mobile operator can decide on which
interfaces the uplink/downlink traffic goes ? both
for the data plane. Do you expect that the
control-plane traffic to be over LTE?
Mike:Our first example of this is what we call
Wi-Fi Boost, because we?re just boosting the
performance of Wi-Fi. I take the Wi-Fi downlink
exactly as it is, no change. But instead of taking the
uplink on Wi-Fi, we can move the uplink over to
cellular. That?s the simplest form. When you do
that, you really free it.
You get two times more range out of the existing
Wi-Fi AP, you get about a 20% to 70%
improvement on the downlink, and you get 10X to
50X improvement on the uplink, depending on the
cellular technology you?re using. Great
horsepower out of existing technology, just by
doing these simple things.
From a control perspective, we?re still using the
typical WLAN access controller that?s in the loop.
Nothing gets changed. We do move the session,
though, to be handled by the mobile core.
When you do that, what?s really cool is that, when
you?re talking about having simultaneous Wi-Fi
and cellular, you can make a very quick and easy
decision on moving your voice traffic, for example,
from VoWi-Fi over to, let?s say, VoLTE ?where you
get to leverage the inherent spectrum advantages
of how LTE manages those voice packets.
You can use VoWi-Fi, but, if you have the option,
you can just flip it over to cellular because it?s an
efficient use of cellular spectrum, and you can
avoid to unnecessarily congest the Wi-Fi.
Monica: You mentioned the importance of
collaborating with the different players in the
industry to make sure that Wi-Fi keeps working
well and that LTE unlicensed doesn?t get disrupted.
Who are you working with to get the end-to-end
LTE unlicensed solution ready?
Mike:We have two major initiatives happening in
parallel. One is our LTE-U initiative, the Cellular
Boost. The other one is our Wi-Fi Boost. They?re
separate entities and they are both part of the
Wireless Unified Networks initiative.
Let me talk about Wireless Unified Networks first.
We introduced a great partner, Ruckus, that we?ll
go to market with on these Wi-Fi enhancement
technologies, where we bring cellular and
augment the Wi-Fi. We?ll do that very soon.
What?s great about that is that it?s a Wi-Fi
company who?s going to their Wi-Fi deployments
to say, ?Look, we can build a better wireless
network for you by using cellular.? That?s the key
aspect. Ruckus is a great commercial partner for
us, and we?re expanding to others.
We?re also working with Accenture with a joint go-
to-market business relationship. Accenture, of
course, serves many, many enterprises.
On the LTE-U side, we?re working with all the
players within standards bodies, with Wi-Fi
Alliance, with the handset providers and the silicon
In Wireless Unified Networks, it?s all pretty much
leveraging what exists, and now it?s about going to
On the LTE-U side, we?re talking about new
technology. It?s the same thing as LTE, but
repeated into new spectrum. New spectrum
means new handsets. New spectrum means new
eNBs ?whether they?re big or small, it?s still new.
We?ve got to spend a lot of time to make sure that
the silicon and the transceivers that go into the
devices are done really, really well and properly.
That?s all new.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |34|
Monica: As you said, we need infrastructure and
new devices. How long is it going to take to get to
Mike:We?ll have LTE-U prototypes and proofs of
concept for operators that are commercial grade
by the end of this year, in Q3 and Q4. From an
operator perspective, I see this potentially
happening in the first quarter of 2016, but there
are a lot of dependencies that I don?t control that
we?re counting on, such as standards finalization,
and deep collaboration and demonstration of the
technology between the Wi-Fi community and the
LTE-U requires new handsets and new silicon in
the baseband, before rolling all of that out. By the
end of this year, we?re going to be in a good proof-
of-concept phase. I?ll be prepared to go, but I think
we would have to work through the other
dependencies and make sure that everybody else
is ready for commercial adoption.
Monica: You work with many operators. What is it
you hear from them?
Mike:On LTE-U, operators are absolutely attracted
to it, in general. The planned use of unlicensed
spectrum is different for each operator, because it
depends on how much they have to pay for more
spectrum. They?re certainly interested in that
opportunity to augment their position, no
Operators are acutely aware of the dependencies
and the challenges, in particular with Wi-Fi Alliance
and in making sure that LTE-U works well with
Wi-Fi. If you?re making an investment in new
silicon, new handsets, new baseband and new
base stations, it?s really important that it?s done in
a way that has wide-scale deployment capabilities.
That?s why the standards are so important, and
the industry recognizes that.
Monica: In closing, what should we expect from
Alcatel-Lucent in the next two or three years on
Mike:On this front, we?re definitely going to
participate in LTE-U, there?s no question.
We?re really going to explore the segment of
converting the enterprise and the home to the
wireless enterprise and the wireless home.
I firmly believe that we?re going to move the
enterprise today from wires ? the huge body of
traffic on the wires in the enterprise ? onto the
wireless network. This transformation is going to
happen over the next couple of years.
We?re going to have to invent a lot of new
technology and services, and go to market with
partners in order to enable that, and we?ll
continue to do that. That?s a big industry shift that
I see happening. We?re going to be behind that,
trying tomake that big shift happen and work well.
Watch the video of the interview.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |35|
Alcatel-Lucent is the leading IP networking, ultra-broadband access and cloud technology specialist. We are dedicated to making global
communications more innovative, sustainable and accessible for people, businesses and governments worldwide. Our mission is to
invent and deliver trusted networks to help our customers unleash their value. Every success has its network. For more information,
visit Alcatel-Lucent on http://www.alcatel-lucent.com, read the latest posts on the Alcatel-Lucent blog http://www.alcatel-
lucent.com/blog and follow the Company on Twitter: http://twitter.com/Alcatel_Lucent.
About Mike Schabel
As the vice president in charge of Alcatel-Lucent?s Small Cells Division, Mike Schabel is responsible for establishing a leadership position
in this new market, from articulating a compelling industry vision, to working with partners to build small cell networks for wireless
operators, to creating an industrialized product portfolio and solution. Mike earned his doctorate in chemical engineering at the
University of Arizona, specializing in plasma chemistry, and also received degrees in materials science and aerospace engineering.
Starting his career with Alcatel-Lucent as a Bell Labs researcher in 2000, Mike soon recognized that he enjoyed commercializing
technology as well as trying to invent it. Mike quickly established a track record of successfully creating and scaling new businesses,
cutting his teeth on the Alcatel-Lucent 9900 Wireless Network Guardian.
Mike regularly runs marathons and frequently trains around the world while travelling to meet with customers.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |36|
unlicensed and Wi-Fi
With its focus on enhancing wireless technologies
and expanding wireless access and usage,
InterDigital has had a keen interest in the
development of LTE unlicensed from the
beginning, because the technology naturally fits
within InterDigital?s core areas of expertise ?
including cellular infrastructure, Wi-Fi and small
cells. One of the major areas of work at InterDigital
today is 5G, and there LAA-LTE is one of the
Like much of the work on 5G today, most of the
activities on LTE unlicensed still revolve around
standardization. InterDigital regards LAA-LTE
standardization as a prerequisite to commercial
rollouts and product availability. As a result, its
main efforts today are to ensure a robust LAA-LTE
standardization, with good coexistence with Wi-Fi
and a wide industry consensus that spans both the
Wi-Fi and the LTE vendors and service providers.
The standardization efforts at InterDigital are
focused on 3GPP and, specifically, on proposed
standards for LAA-LTE that require a listen-before-
talk foundation to ensure coexistence. According
to InterDigital, not only does this approach allow
for an LAA-LTE standard that can be deployed
globally, it is required to establish a fair
coexistence with existing and new Wi-Fi networks.
We can expect LAA-LTE solutions from InterDigital
to be available after the 3GPP standardization
process is completed.
In the meantime, InterDigital offers solutions that
optimize the use and performance of network
resources in existing networks while aiming at
improving the user experience and operators?
revenues. Within this area, InterDigital has worked
extensively on the integration and coexistence of
Wi-Fi and cellular networks. This gives InterDigital
a good vantage point to assess the potential of
LAA-LTE, and a good platform to develop solutions
to manage the joint transmission in the LTE
licensed and unlicensed bands, and in Wi-Fi.
InterDigital?s Smart Access Manager
product is designed to improve users?
QoE, and improve traffic management
across cellular and Wi-Fi. Because
most operators have limited or no
visibility into the real-time traffic load
and resource availability of the Wi-Fi
infrastructure, the Smart Access
Manager works from the mobile
device end to select the network that
provides the best connectivity
seamlessly. It bases the selection on
multiple factors, such as traffic load of
the network, link quality and capacity,
battery level, location, and time of
day. Network selection can be tied to
a policy server (based on ANDSF) to
implement the operator?s policy and
enable revenue-generating services.
Specifications like Hotspot 2.0 use real-time load
metrics to provide QoS and address the current
needs of operators to improve traffic management
in Wi-Fi networks. However, many network
equipment providers have not yet implemented
these features. Mobile operators prefer to manage
traffic from the network, using mechanisms that
supports resource management for both licensed
and unlicensed spectrum. LAA-LTE can address this
need, because it gives operators ability to jointly
manage both licensed and unlicensed spectrum.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |37|
Fairness to Wi-Fi is
crucial to LTE
A conversation with
Director, Radio Standards,
Monica Paolini:Good afternoon, and welcome to
our conversation on LTE unlicensed systems with
Wi-Fi. Today, I am talking to Jim Miller, Director of
Radio Standards at InterDigital. Jim, welcome and
thanks for talking to us today.
Jim Miller: Yes, thanks for having me to discuss
this important topic.
Monica: Can you tell us, what is your role at
Jim: I coordinate all of our 3GPP RAN activities,
and am heavily involved in our IEEE activities as
well. My goal is to develop a coherent strategy for
all of our radio work in both IEEE and 3GPP.
Monica: That?s excellent, because you?re seeing
both the Wi-Fi side and the LTE unlicensed side.
How do you approach both technologies at
Jim:We take a technology-agnostic position,
because we feel that, even though unlicensed
spectrum is free to use, we want LAA-LTE to use it
fairly. If it is not fair to Wi-Fi, LAA-LTE will end up
occupying a niche market, where it can only be
used in certain spectrum whereWi-Fi isn?t. That
would not be good for it, and would make it a
fringe technology that we wouldn?t necessarily
need to be further involved in.
We?re working strongly in that direction, to
progress both on the Wi-Fi side and the LAA-LTE
side for some cooperation, and in particular on the
LAA-LTE side, making sure it?s defined so it treats
Wi-Fi and anything else in the spectrum fairly.
Monica: There has been a lot of debate back and
forth, and a lot of changes over the last year or so,
in terms of the evolution of the role of LTE
unlicensed, Wi-Fi and how they coexist.
Can you provide some background about how we
are moving forward?
Jim: I?ll start briefly at the beginning of this, when it
came into the picture on the 3GPP side in
December 2013, within some initial proposals.
Though we were interested in LTE unlicensed, we
could not support those proposals at that time,
because they were not addressing fairness. These
proposals were more or less trying to put Wi-Fi in
one of the spectrum blocks still to be allocated.
We were not alone in that aspect. It took LAA-LTE
the following 9 to 12 months before it became
agreeable to everybody in 3GPP to go forward,
and fairness was a large part of that, and a large
addition to that.
Monica:How do you define ?fair? and ?nice??
They are appealing terms, but they?re not trivial to
define, are they?
Jim: That?s going to be the sticking point going
forward, as we try to come to a solution on the LTE
Coming to that solution is to define fairness. At
InterDigital, we define fairness as an LAA-LTE node
being brought into an existing system not causing
any more interference or degradation to a Wi-Fi
cell than adding another Wi-Fi cell.
Right now, anybody can come in and add a Wi-Fi
cell anywhere, and that?s part of the appeal of
Wi-Fi to begin with. So there?s no reason why an
LAA-LTE cell couldn?t go in there and have the
same basic effect on the existing Wi-Fi cell, and
that?s what we?re striving to get to. In certain
environments, that?s easier to define than in
Monica:Do you think the existing regulation good
is enough or sufficient to ensure this kind of
Jim: At InterDigital we look at some of the
regulations worldwide ? for instance, at DFS
requirements here in the US, LBT in Europe and
other places, and the various power control
requirements. They?re all different.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |38|
The 5 GHz spectrum is splintered, with radar and
other things in some of the blocks. We were
looking for a solution that is a superset to all of
those. We didn?t want a solution that would work,
for instance, in certain bands only in the US, or
that would not be allowed in Europe, or that
would need some different features to work in
We wanted, basically, a worldwide standard that
could be deployed in any unlicensed spectrum
band. The initial targets, of course, and the initial
studies are in the 5 GHz range.
Monica: You need to have a solution that meets
the requirements of all the regulations in major
countries worldwide so that you can have a global
product. Do you think that?s achievable?
Jim: I think it?s achievable. Fairness is probably
going to be the biggest sticking point, because
there are varying views on that, but I see a great
deal of similarity, and fundamentally the issue is
For LAA-LTE to be deployed in an area, for
example, and have the potential to bring down
somebody?s home Wi-Fi, or a company?s Wi-Fi or a
conference center?s Wi-Fi, based on conflicts or
hogging the spectrum ? that is going to attract
attention, and thus, trigger the regulators to get
I would anticipate that we will be able to have an
industry consensus on this, hopefully get to a point
where the number of issues in front of regulators
is small and they can rule in those particular areas.
I?ve talked to people on both sides. Neither side is
interested in having a big fistfight in front of
regulators. The idea is to define this, and get some
initial indications of how each side feels about it,
try to come to some consensus, and then bring it
out to the regulators. And hopefully, get to a point
where they?re answering a small number of
questions, and they handle a small number of
And thus, the regulators should not have to be put
in their referee perspective of saying you can?t be
here, or you can be here. We?ve have witnessed in
the past ? for instance in the 3GPP world, with
satellite conflicts, and it gets very messy.
That?s something that everybody I work with on
both the LTE side and the Wi-Fi side wants to
avoid, even though they?re in positions to possibly
have a good argument. The regulators are the
court of last resort, and we want to try to avoid
that as much as possible.
Monica: This is something that?s emerging in the
last few months. No matter where the operators
and the vendors are coming from, they all agree
that coexistence with Wi-Fi is crucial for LTE
unlicensed to succeed.
Everybody is willing to cooperate, and I think that
this cooperation within the industry is crucial to
success. Do you think this a foundation for the
Jim: Yes. In our perspective, definitely. We are
pushing strongly to have everybody involved, and
have an open discussion and an open forum as
much as possible, because right now, the
discussions go on both in the Wi-Fi and 3GPP camp
in separate meetings.
While there?s overlap in the company positions, in
each paradigm (3GPP/Wi-Fi), the differences in
how each standards body looks at the same issue
cause more disconnects between Wi-Fi and 3GPP
than is actually present.
Everybody has some strategy here on this. A
strong discussion is going on in both realms, each
using a different perspective, because the Wi-Fi
world is different than the LTE world. The
difference between the two technologies is at
work continuously in the unlicensed spectrum
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |39|
versus working in licensed spectrum: two different
viewpoints, and two different ways of even doing
The whole point of the effort right now, and what
we?re trying to contribute to it, is to get the 3GPP
design decisions? initially for instance, the 3GPP
models of the channels ? to a point where we can
judge fairness for both Wi-Fi and LTE.
People can point to certain aspects of Wi-Fi that
could cause more damage to LTE than the other
way around. And vice versa: LTE has a potential, if
the fairness algorithm is not written correctly, to
take over the whole band.
We?re working that battle from both ends to try to
get to a point where we have some intergroup
agreement on a system as being relatively fair. But
there may still be some sticking points, and we
may have to get some regulatory ruling on them.
But if that?s necessary, we hope that?s minimal, as
opposed to saying, ?Here?s the whole mess? and
throwing it in the regulators? lap.
Monica: There?s a lot of work being done, and
hopefully over the next few months, we will get to
some good standardization approach that satisfies
the industry. The question at that point, though, is,
how do we make sure the adopted standard is
followed in practice?
For instance, for Wi-Fi you do have a certification
program, and that ensures coexistence of different
Wi-Fi systems with each other. But here, we have
a different problem. Here you have two different
technologies and they both have to be fair to each
Right now, there is no way to ensure that. Do we
need to, or don?t we even need to do that? How
can we know that the vendors and operators are
complying with the standards?
Jim: Yes, that comes into play, and that will be a
further discussion. We anticipate that LAA-LTE
terminals will go through a rigorous conformance
testing, also. In fact, one could argue it?s even
stronger than the Wi-Fi one, because it?s normally
used in licensed networks.
But LAA-LTE will be, at the very least, on par with
Wi-Fi. The struggle once it?s defined will be to find
ways to test the terminal, to ensure that it is not
transmitting when it?s not supposed to be and that
it?s acting like it should be so it does not interrupt
Monica: You work with a lot of mobile operators,
obviously, and I?m sure this is a topic that comes
up all the time these days. What do you hear from
Jim:We get a large range of inputs from operators.
The issue is, right now Wi-Fi is used to offload
traffic. A lot of operators do have separate Wi-Fi
networks, or somewhat interrelated, where if you
subscribe to a carrier, you can get on their Wi-Fi
The same thing with cable companies: they have
their own Wi-Fi, and if you use their internet, you
can use their Wi-Fi.
There are multiple ways that the operators can do
offload right now.
The problem is, the Wi-Fi operations system is
completely separate from the 3G one, and it
requires a whole different set of tools for
operations, maintenance, etc.
Another problem is that, right now, the control of
the Wi-Fi offload is more in the terminal, not in the
networks. The operator has less control over Wi-Fi
offload from the network side.
At InterDigital, we have many operators looking at
our Smart Access Manager product, which is a
UE-based application that allows the selection of
the network that provides the best-quality service
Our solution works very well in environments
where the operator owns or has ready access to a
Wi-Fi network ? it is an obvious solution in those
environments. This type of solution isn?t as
effective in environments where an operator
doesn?t have access to a Wi-Fi network to offload
traffic. LAA-LTE would be a solution in those cases.
LAA-LTE will allow the 5 GHz band to be treated as
the licensed spectrum already is ? to be controlled
from the licensed side, and getting a better
guarantee of quality of service than with the Wi-Fi
When people go to Wi-Fi it is because there is a
good Wi-Fi signal there but the Wi-Fi network may
be or become congested. Thus they get worse
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |40|
service if they stay on Wi-Fi than they would in the
3G or LTE systems.
There are various operators that have existing
Wi-Fi, so they are moving at a different speed than
some of the other operators that just want to
utilize the spectrum and deploy it separately. Once
an operator has a large Wi-Fi deployment, it isn?t
necessarily looking to run out and replace the Wi-
Fi network with LAA-LTE.
The current version of LAA-LTE involves all the
signal scheduling from the macro ? the LTE station
? with the Wi-Fi being part of the macro and
connected directly to the macro with no real
LTE base stations in the unlicensed spectrum are
either co-located with a macro cell or at very short
distances away from one, so that can they be
controlled, more or less simultaneously? this is
called ?no latency backhaul.? Scheduling can be
done at a single location, which is the macro at the
Monica: This is quite interesting, because LTE
unlicensed gives operators more control from the
network side overWi-Fi.
At the same time, there is a lot of work being done
also on the Wi-Fi side that will make it easier to
integrate Wi-Fi with LTE. Does that reduce the
appeal of LTE unlicensed?
Jim: The LTE unlicensed is a somewhat separate
use case than the typicalWi-Fi offload.
If you?re traveling in a car, for example, you?re
probably not doing Wi-Fi offload that much. Even
if it?s tightly controlled ? and there is work going
on in LTE to make Wi-Fi even more tightly
controlled and somewhat network based ?Wi-Fi
offload still involves a connection with 3G or LTE.
To add Wi-Fi to it, you have to attach to a Wi-Fi
base station. But Wi-Fi was not necessarily built for
mobility. So if you?re moving fast, by the time you
associate with the Wi-Fi station and start
transmitting, you could need to be at the next
Wi-Fi station, and have to start the process over
In LAA-LTE, you?re going to be registered in the LTE
spectrum, and all the control signaling is on the
LTE licensed band. You?re just using it to transmit
data on the spare parts of the unlicensed 5 GHz
band, because of fairness mechanisms. You just
transmit there in that spectrum when the Wi-Fi is
not using it. But then you can come back and still
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |41|
have your connection through your macro cell
that?s based on LTE.
Monica:Do you envisage operators having both
Wi-Fi and LTE unlicensed in the same location, as
Jim: Potentially that could be done, and it is
dependent on the use cases and how much focus
an operator is putting on a particular use case. For
example, right now certain operators have
complete Wi-Fi networks and others don?t.
If you talked to five different operators, you are
going to have five different levels of Wi-Fi support
in a particular area. So Wi-Fi and LAA-LTE could be
used, at the same time.
Thus, if you have fairness with LAA-LTE, it?s just like
another Wi-Fi base station. It creates interference
in the spectrum that they share, but it?s still part of
the normal management that Wi-Fi networks have
for that, and thus, doesn?t create anymore
It still allows the operator to control their LAA-LTE
transmission in the unlicensed band, in the same
way they do with the licensed band, as far as the
quality of service and similar things. But even in
networks with LAA-LTE, LTE allows stationary users
to offload most or even all of the air traffic to a
Wi-Fi hotspot using Wi-Fi that?s nearby, as it does
today. It could theoretically be in the same area.
Monica:What are your plans at InterDigital in
terms of helping operators with LAA-LTE?
Jim:We have our Smart Access Manager to work
with the current UE-based offload. To enhance
that, we?re working with operators, and on the
standards, for improving that Wi-Fi offload even
more in the current release.
Simultaneously we are working on LAA-LTE to
make it as easy as possible for them to use their
licensed spectrum and the unlicensed spectrum.
For instance, they want to be able to come in and
out of LAA-LTE and at the same time retain the
guaranteed quality of service. Additionally we
work with the operators to help them use our
gateway products and expertise to leverage that
even more in the access to unlicensed spectrum.
But a lot of our work will be to enable the
operators to expand what they currently have with
LTE in licensed bands into the unlicensed band
and, thus, to have a single point of management
that includes an enhanced quality of service for
handling the traffic that goes over the unlicensed
Monica: In closing, when do you think we will be
able to see the first commercial deployments of
Jim: That?s a tricky question, because some
operators have already publicly announced plans
to do some pre-standard trials. That?s going to
happen pretty shortly.
That?s similar to what happens in the Wi-Fi
environment. Whenever a new standard comes
out, there?s always pre-standard equipment out
there to try to enhance performance.
They are doing initial LTE-U trials which utilize pre-
standards concepts which are being discussed
while standardizing LAA-LTE. These trials are in
particular spectrum blocks to minimize the effect
on Wi-Fi, because they?ll pick a spectrum channel
that?s outside of current Wi-Fi usage. And thus,
they will be able to test and see how the
The standardization of LAA-LTE through the first
couple of evolutions will probably take place over
the next couple years. The first version of this will
probably be finished at the end of the year or early
next year, thus fully standards-compliant LAA-LTE
will probably be available at the end of next year,
or the year after. But pre-standardization versions
of LAA-LTE will be available earlier.
Watch the video of this interview.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |42|
InterDigital develops technologies that are at the core of mobile devices, networks, and services worldwide. We solve many of the
industry's most critical and complex technical challenges, inventing solutions for more efficient broadband networks and a richer
multimedia experience years ahead of market deployment. InterDigital has licenses and strategic relationships with many of the world's
leading wireless companies. Founded in 1972, InterDigital is listed on NASDAQ and is included in the S&P MidCap 400? index.
About Jim Miller
As a Director in InterDigital?s Standards department, Jim Miller has been an active participant in the development of wireless
technology related standards. Currently, he leads the InterDigital 3GPP RAN delegation and participates in the standardization of the
IEEE 802. Prior to this, Jim spent 8 years as the Vice Chair of 3GPP TSG RAN WG3 (the organization that standardizes Radio Network
Architecture) from 2001 to 2009. Jim has been with InterDigital for 19 years, and holds a Bachelor?s degree in computer science from
Rensselaer Polytechnic Institute.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |43|
unlicensed and Wi-Fi
Qualcomm Incorporated?s wholly owned
subsidiary, QualcommTechnologies, Inc. (QTI) was
one of the initial proponents of LTE unlicensed,
along with vendors such as Ericsson and operators
such as Verizon. LTE unlicensed fits well within QTI?
1000x vision ? preparing for a thousand-fold
increase in mobile data usage. LTE-U complements
parallel efforts to increase wireless capacity with
small cells, shared access, and the multiple flavors
of Wi-Fi ? residential, community, hotspot,
enterprise, and carrier.
From QTI? perspective, LTE unlicensed is a tool to
maximize the use of the 5 GHz band, and to
increase the attractiveness of unlicensed spectrum
to mobile operators. It complements the ongoing
work to expand and improve carrier Wi-Fi. For
example, QTI has contributed to the development
of LTE and Wi-Fi link aggregation feature, which
enables devices to transmit concurrently over
Wi-Fi and LTE links. The dual connectivity enables
the operator to provide robust mobility and uplink
performance with the LTE anchor (i.e., a licensed
channel for LTE), and high downlink capacity with
Wi-Fi in the 2.4 GHz and 5 GHz bands. LWA is part
of an industry-wide effort to integrate Wi-Fi and
LTE, with 3GPP working on its standardization.
On the LTE unlicensed side, QTI is working on two
development tracks. The first addresses the LTE-U
opportunity in countries, such as the US, South
Korea, India and China, where the restrictive the
regulation regime does not require the adoption
listen-before-talk mechanisms, and LTE-U can use
existing LTE 3GPP standards (Release 10, 11 and
12) along with CSAT based co-existence
mechanisms in 5GHz.
These countries are likely to see the first LTE
unlicensed deployments, using dynamic channel
selection and CSAT to ensure fair coexistence with
The second LTE unlicensed solution is for markets
where LBT is required, and this is tied to the
ongoing LAA-LTE standardization efforts at 3GPP
to be included in Release 13. Because the
standardization process is not yet complete,
LAA-LTE will become commercial after LTE-U
LAA-LTE not only will meet the power, emission
levels and LBT requirements set by regulators, it
will go beyond the regulations to ensure
coexistence with Wi-Fi and to optimize LAA-LTE?s
performance. This includes conformance testing to
ensure that LTE unlicensed is implemented
according to the published specs.
QTI has announced products to support LTE-U, to
be available in the second half of 2015, with plans
to introduce LAA-LTE products after the 3GPP
specs are finalized. QTI has announced the
integration of LTE-U in its FSM99xx SoC, and the
availability of the FTR8950 RF transceiver for small
cells. On the UE side, QTI has announced the
WTR3950 RF transceiver, which supports LTE
Advanced CA with support for up to 40 MHz
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |44|
efficiency with LTE
A conversation with
Qualcomm Atheros Inc.
Monica Paolini:Good afternoon, and welcome to
our conversation on LTE unlicensed and Wi-Fi,
which is part of a report from Senza Fili in
collaboration with RCR Wireless News.
Today, our guest is Puneet Sethi, the Director of
Product Management at Qualcomm Atheros Inc.
Puneet, thank you for taking the time to talk to us
Puneet Sethi: Thank you, Monica.
Monica: To get started, can you tell us what
prompted QTI to get into this business, exploring
the use of LTE technology that was only used for
licensed spectrum and moving into the unlicensed
Puneet:Monica, you know about the 1000x
Challenge. That?s something that began almost
three years back. LTE-U came out of that initiative,
as did several other things.
You go back three years, we started this initiative
to drive solutions from within QTI and also across
the industry, to meet the challenges of exponential
growth in data demand, which was almost
doubling every year.
You really needed some innovative solutions to
meet that kind of challenge. Several solutions
under the 1000x Challenge initiative were brought
from conception to commercialization, and they
include hyper-dense mobile networks, UltraSON
solutions for LTE inside to out coverage, and
licensed shared access.
Now, LTE unlicensed is part of that tool set, as well,
which allows operators to pair unlicensed
spectrum with their licensed anchor, and deliver
higher throughput and better user experience to
Monica:What is the advantage that specifically
LTE unlicensed brings, when you can already use
Wi-Fi in the 5 GHz band? What is the value
proposition for a mobile operator?
Puneet: Yes, you?re correct: Wi-Fi has been there
in 5 GHz, and also, previous to that in 2.4 GHz.
Before we get into that, let me just say that both
LTE and Wi-Fi are technologies that have been
there for quite some time, and have seen multiple
layers of evolution. They will continue to evolve
and will be there to meet the different sets of use
cases we see out there in the real world, which
include diverse sets of devices, diverse sets of
applications, and diverse sets of QoS
LTE-U brings a certain set of unique advantages to
operators that have already deployed an LTE
network, to provide additional capacity by
leveraging unlicensed spectrum paired with a
licensed anchor, and delivering higher throughput,
as I mentioned earlier.
Additionally, it enables them to spread the capital
expenditure on the core network across both
licensed and unlicensed spectrum. It?s a more
efficient use of the investment that they made in
the core network.
It also enables them to use the same security,
mobility and signaling framework that is core to
the LTE protocol itself across both licensed and
unlicensed spectrum, thereby enabling seamless
mobility to their subscribers.
Monica: LTE unlicensed fits better with the mobile
operator network, but if you look at it from the
point of view of the users, will they notice the
difference? Does it make any difference to them if
they connect to Wi-Fi or LTE unlicensed?
Puneet: It really depends on the use case and the
requirements, and there are different sets of users
out there, including enterprise and residential
For a local area use case, I think Wi-Fi has been
there and has been serving that market well.
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For use cases that require increased mobility and
where you have a licensed anchor that you can
rely on for control and signaling, that?s where I
think LTE unlicensed provides certain benefits.
LTE also is inherently spectrally more efficient. For
the same amount of spectrum, it can deliver 2x
more capacity than Wi-Fi.
It also works better alongside Wi-Fi. What we say
is it?s a better neighbor to Wi-Fi than Wi-Fi is to
itself. If you have two Wi-Fi nodes right next to
each other and you replace one of them with LTE
unlicensed, not only would you see the gains from
the LTE unlicensed node, but also you will see the
improvement on the neighboring Wi-Fi?s
Again, the two technologies are very
complementary, and, depending on the use case
and the requirements, either one or the other
would meet the subscriber needs.
Monica: If you can pack more throughput, more
capacity and demand, that?s to the collective
advantage of everybody involved ? service
providers, enterprises and subscribers.
Another important stakeholder here is the
enterprise. Many Wi-Fi networks are managed and
owned by the enterprise ? including public venues.
There, the owners of the Wi-Fi networks are going
to be very protective about their Wi-Fi networks,
and they want to control the unlicensed spectrum
as much as they can. What are you seeing in terms
of the reaction of the enterprise to LTE
Puneet: Enterprise, again, represents a very
unique set of subscribers with their unique
In today?s enterprise, mobility is a key
requirement. Enterprises are becoming
increasingly mobile, with employees moving
across the enterprise, in and out of buildings, and
within the enterprise building itself.
LTE unlicensed satisfies those requirements,
because mobility, as I said, is inherent to the LTE
technology itself. If you pair unlicensed spectrum
with the licensed anchor, you get the mobility
that?s needed, and you are also able to meet the
coverage and capacity needs of enterprises.
The challenge there is typically around indoor
coverage, which is where LTE unlicensed is more
relevant. This technology is more applicable to
small cells because of the higher-frequency band
that?s used in the LTE-U product. You?re able to
deploy those small cells inside the building for
indoor coverage and capacity.
Monica: You mentioned the fact that these
technologies have to coexist, but there is just so
much spectrum out there. You need to find a good
way to allocate spectrum resources to support
A term frequently used is ?nice.? What does ?nice?
mean? What does it mean for technologies to be
nice to each other?
Puneet: At the basic level, it really means that the
radio technology is able to detect the presence of
other users of the transmission medium, and
thereby adapt its own behavior and share the
transmission medium with the other users.
There are ways to ensure that technologies are
nice to each other. There are different layers to
The first layer is the regulatory side. There are
regulations in every country as to how to utilize
the unlicensed spectrum; those regulations may
define a spectrum mask, transmit power and other
requirements. Every radio technology has to
comply with that.
There are certain differences as you go from one
country to another in terms of regulations that
apply to the unlicensed spectrum. For example, if
you look at Europe and Japan, and some of the
other markets that have what we call a listen
before talk, or LBT, requirement, that forces
changes on the waveform in order to meet those
regulatory requirements of listen before talk. Then
there are other countries ? the US, South Korea
and China ?where you don?t have those
requirements, and those are the non-LBT regions.
Regardless of whether it is an LBT region or not,
the first layer is that radio technology has comply
with the regulatory requirements.
That is not enough from the perspective of being
nice, or standardizing coexistence procedures. You
have to go beyond regulatory requirements, and
actually define and standardize coexistence
procedures that define how technologies coexist.
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That requires industry consensus. For LTE
unlicensed in the LBT regions, that work is
happening in 3GPP, as a Release 13 study item
supported by various operators and vendors.
For non-LBT regions, you have the opportunity to
use the existing Release 10, Release 11, Release 12
LTE waveform with an adaptive duty-cycle
mechanism, which we call CSAT, to ensure
That has also been standardized. LTE-U Forum, as
you know, has published specs that are publicly
available for everybody to review and see what
coexistence procedures and aspects are defined
for that space.
Monica: Right. There is a lot of ongoing work right
now. There is a lot of activity on the organization
As you say, we need to have industry consensus.
How close are we to getting that consensus?
Knowing that not everybody has the same goals,
how close are we to finding a solution that makes
everybody reasonably happy?
Puneet: I think we are pretty close. Fortunately
LTE unlicensed has seen a lot of industry support.
There?s a lot of ecosystem support building for this
For LBT regions, that work is ongoing in 3GPP. That
work is supported by the major operators and
vendors, and is going to be part of Release 13
discussions as they play out within 3GPP.
For non-LBT regions such as the US, LTE-U Forum
published the specs. That work was done over the
past several months by leading operators,
including Verizon, and infrastructure vendors such
as Ericsson. QTI was also a founding member of
the Forum. That work has resulted in these
coexistence specs that are available for anybody to
If somebody wants to create an LTE-U product,
they can look at the specs and see what
coexistence procedures they have to implement,
and what test they would have to pass.
The work ahead in those regions is to take those
specs and drive those products ? solutions for LTE
unlicensed products ? into those markets. I think,
in short, we?re pretty close. There?s a lot of
ecosystem momentum behind LTE unlicensed.
Monica: For most vendors, there is both a Wi-Fi
component and an LTE component within their
own business, and they have to manage both;
there is no choice between the two of them.
QTI is one such vendor, because at QTI you have
both the Wi-Fi business and the LTE business.
Puneet: Both technologies have been around for
some time. We?ve participated in the evolution of
both these technologies.
A few weeks back, I was at an event in the Bay
Area with our team that is responsible for the
Wi-Fi infrastructure. Organizationally, small cells fit
closely with the Wi-Fi infrastructure team, as well.
We were all in the same room, brainstorming
future-generation products for both LTE
unlicensed and Wi-Fi. As you?ve seen, even on the
Wi-Fi side, we have driven the leadership in Wi-Fi
11ac and multiuser wave 2 MIMO.
We are the leader in that space and we are driving
that evolution further with 11ax and however
Wi-Fi technology will evolve going forward.
Similarly, for LTE unlicensed, we?re working for the
LBT regions, supporting the industry and the 3GPP
discussions. For non-LBT regions, we?re now
working on our productization plans based on the
LTE-U Forum spec.
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In short, both technologies are here to stay.
They?re going to be required to meet a diverse set
of use cases, and devices and applications.
We just want to make sure we drive both
technologies really hard, and have best-in-class
solutions on both sides. Whatever our customers
end up selecting based on their own requirements,
we would have something to offer to them.
Monica: There is a lot of work that you are doing,
moving forward in terms of technology and
If a mobile operator comes to you and says,
?We?re interested in LTE unlicensed,? how can you
specifically help them? How can you help them
move to where they?re deploying the technology?
Puneet: Earlier this year, we announced support
for LTE-U in non-LBT regions for both small-cell
and UE products.
We?re driving those products towards
commercialization and early trials later this year.
That?s the way we?re going to help mobile
operators in the non-LBT regions to get to
products in the field faster. North American mobile
operators have already expressed support for LTE
unlicensed trials, and we?re working with them.
For the LBT regions, we will continue to work with
the industry and within the 3GPP forum to drive
that technology through the standards. And then,
when the standards firm up, we?re going to drive
technology through our product plans, both on the
small cells and on the UE side.
Monica: If a mobile operator wants to deploy LTE
unlicensed today, say in a non-LBT region, what
upgrade do they need to then move to LAA-LTE, if
they decide to do that?
Puneet: The answer depends on several factors,
including what sort of investment the mobile
operator would have already made in LTE
unlicensed, or is going to make.
There?re a lot of architectural details that would
have to get into there. In short, the platforms that
we?re looking at have features that would enable
software upgradability from along the LTE
That is designed to enable operators to upgrade
from one phase of LTE unlicensed to another
phase, depending on the product architecture, of
course, and also, depending on the core network
architecture, as well.
Monica: And I guess it depends on what the
standards will be.
Puneet: Yes, there are some moving parts there,
too, as the standards are not set. A lot will depend
on what actually comes out of 3GPP.
Monica:One crucial element to determine the
success of LTE unlicensed is the handset, because
you need to have handsets that support it, you
need to have the device vendors that will make
those handsets and subscribers that will buy them.
What are you doing in that area, specifically?
Puneet:On the handset, we announced our
WTR 3950, which is a companion chip that
supports the 5 GHz band. It will be commercially
available later this year; that?s part of the LTE
unlicensed support on the handset side.
For the LBT regions, we will have productization
plans to meet the 3GPP specs for LAA-LTE.
There is work being done both on the handset and
on the small-cell side to drive the solutions to
market, both for LBT and non-LBT regions.
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Monica:What do you have specifically on the
small-cell side for LTE access?
Puneet:On the small-cell side, we already have
commercially available the FSM9955 solution.
We?re able to software-upgrade that solution to
support LTE unlicensed. We then pair that
baseband solution with our new RFIC FTR8950,
and that will support the 5 GHz band with
FTR8950. Both of those solutions will line up with
the UE availability in the latter half of 2015.
Monica: Can you give a bit of a sense of how
difficult it is and how expensive it is to add LTE
unlicensed to the current devices and small cells?
Puneet: There are different aspects of that,
One aspect is the product cost. You really need to
add 5 GHz band support to the product, and that
would be the additional cost.
And then additionally, depending on how the
operator decides to deploy this, LTE unlicensed
may require some software upgrades to the other
elements of the network, as well.
Monica:When will the devices be available?
Puneet:We?re targeting our chipset solutions for
both small cells and handsets to the latter half of
this year, and expect commercial solutions three
to six months after that, depending on the OEM
trials and schedules.
Monica:Within the 1000x vision, Qualcomm
Technologies has been very vocal on the use of the
3.5 GHz band as a spectrum resource that can be
used to increase capacity.
How does the availability of the 3.5 GHz relate to
LTE unlicensed? Is it in addition to that, or an
Puneet: I think it complements very well the LTE
unlicensed model. The LTE unlicensed initial focus
is on the 5 GHz band, which is sort of a global
band. The 3.5 GHz band is different, because there
are different regulations depending on the
country. Outside of the US, in some markets ?
Europe and Japan ? it?s mainly a licensed band.
For those markets, it really becomes licensed LTE
in 3.5 GHz. In the US, the FCC is still working on
how to regulate this. There are proposals on the
table about a tiered approach. Depending on what
finally comes out of that, we can potentially see
LTE unlicensed deployment in the 3.5 GHz band, as
Monica: Let me ask you a final question. What
should we expect in the next year or two in terms
of the priorities of what needs to be done to make
sure that LTE unlicensed succeeds, and of what
other major challenges are there?
Puneet: The work ahead of us is for the LBT
regions. I think the big chunk of work that?s ahead
of the industry is to drive the item through the
There?s a lot of support there. A lot of operators,
equipment manufacturers, mobile manufacturers,
silicon manufacturers are working on this
together. We?ve got to make sure that this gets
standardized through 3GPP Release 13.
For the non-LBT regions, the specs are already out
there for everybody?s review and feedback. Now
we have to take those specs and implement
products, and drive those products through early
trials, and then launch in the early part of next
Qualcomm is a trademark of Qualcomm
Incorporated, registered in the United States and
other countries. FSM is a product of Qualcomm
Atheros, Inc. UltraSON and Qualcomm Small Cells
are products of Qualcomm Technologies, Inc.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |49|
About Qualcomm, Inc.
Qualcomm Incorporated is a world leader in 3G, 4G and next-generation wireless technologies. Qualcomm Incorporated includes
Qualcomm?s licensing business, QTL, and the vast majority of its patent portfolio. Qualcomm Technologies, Inc., a wholly-owned
subsidiary of Qualcomm Incorporated, operates, along with its subsidiaries, substantially all of Qualcomm?s engineering, research and
development functions, and substantially all of its products and services businesses, including its semiconductor business, QCT. For
more than 25 years, Qualcomm ideas and inventions have driven the evolution of digital communications, linking people everywhere
more closely to information, entertainment and each other.
About Puneet Sethi
Puneet Sethi is a Director of Product Management at Qualcomm Atheros. At Qualcomm Atheros, he drives roadmap and strategy for
small cell SoC solutions, UltraSON and other related products. He is instrumental in defining software strategies and managing
relationships with various eco-system partners including software providers. He works with QualcommAtheros?s `global sales
organization to market QualcommAtheros?s portfolio of small cell solutions to operators and OEMs around the world. Puneet also
drove the LTE PHY enhancements for the LTE-Advanced project at QualcommAtheros. Prior to that, Puneet provided consulting
services to Ixonos for its entry in to the US market and, before that, he held engineering positions at Radioframe Networks, Comneon
and Ubinetics. Puneet earned his MBA with concentrations in Finance and Marketing from the Anderson School of Management at
UCLA and has a B.S. in computer science and engineering from the Indian Institute of Technology at Guwahati.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |50|
Ruckus Wireless: LTE
unlicensed and Wi-Fi
There are two dimensions that are crucial to the
deployment and success of LTE in the 5 GHz
unlicensed band: spectrum and site acquisition.
Spectrum in the 5 GHz band is license-exempt
virtually everywhere, but LTE unlicensed can
realistically use that band only if it coexists with
Site acquisition is equally crucial as LTE unlicensed
is going to be tied to small-cell deployments, which
will mostly occur in indoor locations. Operators
will need easy and affordable access to these
indoor venues to be able to successfully deploy
Through its background in Wi-Fi, Ruckus Wireless
is very familiar with both unlicensed spectrum and
the needs of businesses and venues and intends to
leverage this expertise to ensure that spectrum
utilization in the 5 GHz band is fair to current and
As a provider of high-performance Wi-Fi
equipment for operator and enterprises, Ruckus
understands the challenges that come from having
large numbers of collocated Wi-Fi networks
contending for access to spectrum.
A robust listen-before-talk mechanism is required
to ensure coexistence. To retain a similarly fair
environment in the 5 GHz band, Ruckus believes
that LTE unlicensed has to adopt listen before talk
as well, even though this represents a departure
from the way LTE normally operates.
The listen-before-talk approach is required to
ensure fairness but is also crucial for operators to
gain access to venues -- especially indoor venues.
Operators need to get consent and support of the
entities that control these venues. That consent
may be hard to come by if the venues? managers
worry that LTE unlicensed may affect the
performance of existing Wi-Fi networks, which are
often mission critical to their operations.
Ruckus has experience in working with public
venues and private enterprise in developing a
wireless strategy that helps them meet their
Wi-Fi has a crucial role to play here as do LTE small
cells. Increasing the performance of LTE small cells
by using the unlicensed bands can make for an
even better user experience in venues or
businesses, provided it is done properly. In most
cases this means supporting listen before talk to
ensure fair access the spectrum.
This flexible approach makes it possible to support
a variety of business models, which may be driven
by capex commitments from the service providers,
enterprises, or neutral-host parties.
While much of the debate today revolves around
the role of LBT in deployments of LTE unlicensed,
LTE Wi-Fi Link Aggregation, or LWA, has emerged
as a new option. With this approach LTE traffic is
simultaneously sent over both LTE and Wi-Fi
radios. A separate SSID is configured on the Wi-Fi
access point for this purpose.
LWA gives Ruckus an opportunity to expand its
solution portfolio by allowing traffic that currently
uses LTE to transit its commercially deployed Wi-Fi
LWA?s objective is similar to that of LTE unlicensed,
but its focus is on leveraging the advantages of
Wi-Fi in the 5 GHz band and of LTE in the licensed
Ruckus believes this approach leads to a more
efficient use of the 5 GHz band, because Wi-Fi is
designed for this environment, and LTE is
optimized for licensed bands. Each will be allowed
to do what they do best.
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unlicensed, with LTE
plus Wi-Fi link
A conversation with
Service Provider Marketing,
Monica Paolini:Good afternoon, and welcome to
our conversation on LTE unlicensed and its
coexistence with Wi-Fi. Today, we are talking to
Steve Hratko, the director of service provider
marketing at Ruckus Wireless.
Steve, thanks for talking to us today.
Steve Hratko: It?s always a pleasure, Monica.
Monica: Steve, how do you rationalize your
involvement with both Wi-Fi and LTE unlicensed?
Steve: Ruckus Wireless has been in the Wi-Fi
business for more than a decade, and we
specialize in two primary markets.
We have a pretty significant enterprise business
that focuses on venues like airports, train stations,
hotels, et cetera. We also have a large service
provider business, and the service provider
business focuses on the needs of both mobile
operators and cable operators, along with wireless
ISPs and managed service providers.
As part of our focus on service providers, we?ve
been taking a long, hard look at LTE in the
unlicensed band. At Ruckus, we use these bands
for Wi-Fi, which has been an enormously
successful business, largely because of its ability to
share unlicensed spectrum. The unlicensed bands
are free for anyone to use, for any purpose.
Now, with the arrival of LTE-U, we?ve been taking a
look at what impact this will have on the
unlicensed bands. We certainly understand the
driver for LTE-U, which is how best to use this
spectrum to provide a more compelling, higher-
performance LTE service. At Ruckus, we want to
understand how LTE-U is going to impact Wi-Fi
services, which are broadly deployed and very
Monica: As you said, Wi-Fi has been very
successful. It has also taught us a lot about how
different networks can coexist in the same
frequency band. Can we expand to other
technologies, like LTE unlicensed, what we learned
with Wi-Fi? What is necessary for the two
technologies to coexist?
Steve: There?s an established mechanism for Wi-Fi
networks to share spectrum, called listen before
talk. With listen before talk, the Wi-Fi device waits
for the channel to be clear, and when it is, it
transmits. Typically, an AP would transmit for up to
10 milliseconds, then it would release the channel
and the process repeats. This works extremely well
for the sharing of the unlicensed bands.
This isn?t terribly efficient ? and certainly not as
efficient as LTE, which uses a scheduled MAC
process ? but it works extremely well for sharing
The big debate within 3GPP right now about LTE-U
is just exactly how LTE might implement listen
before talk, or will it implement something
different? A lot of the early work around LTE-U is
not focused on using listen before talk per the
IEEE, but is instead focused on looking at other
approaches that might be a better fit for LTE.
We?re advocating, along with the whole Wi-Fi
industry, that 3GPP come forward in Release 13
with an approach that supports listen before talk.
This is going to make LTE-U and, more specifically,
LAA-LTE much more successful.
Monica:Do you think there is enough consensus
in the industry ? not just from the Wi-Fi side, but
from all the LTE players ? to support listen before
Steve: I think the consensus in the industry is to
move towards implementing listen before talk for
LTE-U. We think this will be done by 3GPP in
Release 13 as LAA-LTE.
There are a number of reasons for this.
The first reason is that in some jurisdictions,
specifically in the European Union, it?s required by
regulation. It?s not required by regulation in the US
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and some other markets, but in the interest of
having a solution that works worldwide, it makes
sense to implement listen before talk. I think it?s
going to make everything run a lot smoother.
The second reason is that there is a huge installed
base of Wi-Fi equipment, and it is in everyone?s
best interest for LTE-U to work with that installed
base and to share spectrum fairly.
A third factor, which doesn?t get enough attention
in the listen-before-talk debate, is that LTE-U and
LAA-LTE are small-cell technologies. LTE-U and
LAA-LTE operate on the unlicensed band, so you
have the same power limitations that Wi-Fi has
and they are ideally suited to high-capacity-density
Those are locations where Ruckus has a lot of
expertise. Stadiums, train stations, convention
centers, airports, downtown city centers, areas
where you have huge numbers of people
aggregating in close proximity, and they are all
using data. One of the challenges with addressing
this opportunity is that in almost all cases, to
deploy any radio technology will require the
permission of the venue.
If it?s a downtown city center, you?ve got to go
through a large number of municipal commissions
and committees. It?s going to be easier to get
permission to deploy LTE small cells if they don?t
impact the Wi-Fi networks already deployed.
An operator proposing to install LAA-LTE-enabled
small cells with listen before talk will have a much
easier time passing muster with that stadium, with
that convention center, with that airport.
In many cases, these venues have people whose
job it is to keep an eye on how the unlicensed
bands are being used, because Wi-Fi services are
so important to the venue -- in many cases are
mission critical. Any solution that?s not IEEE
compatible is going to get a lot of scrutiny.
Monica: Is the enterprise going to allow somebody
else to come and use the same spectrum?
Steve: At these very high-capacity-density venues,
it?s very important to make sure that you meet the
needs of the venue. This applies whether you?re
deploying Wi-Fi in that venue, or LTE small cells, or
LTE small cells using LTE-U. In all cases you have to
understand the needs of the venue.
Many of us pick venues based on how good the
Wi-Fi is. People who enter these venues expect
high-quality Wi-Fi, so anything that potentially
impacts the Wi-Fi networks is going to get looked
at very closely by the venue.
Now, it?s possible that even if you implement
LAA-LTE with listen before talk, the venue still may
not like that. They still may prefer that the LTE stay
in the licensed band, and the Wi-Fi stay in the
It?s going to be their choice, because they control
access to the facility. Again, they are an important
constituent in this debate, and I think we need to
hear more from them going forward.
This convergence of service providers and public
venues is the sweet spot for Ruckus, in that we
build very high-end Wi-Fi gear that?s designed for
these sorts of installations, and so we have a good
sense of what venues are looking for, what?s
important to them, what the industry needs to do.
Monica:Now, from a mobile operator point of
view, there is the opportunity not only to use LTE
unlicensed, but also LTE unlicensed and Wi-Fi in a
much more tightly integrated way.
Steve: There is a focus in the industry on
combining LTE small cells with Wi-Fi access points
? putting both radios into the same box. We?re
already working with major RAN vendors that are
looking to add Wi-Fi to their small-cell products.
Part of the challenge is that site acquisition is
difficult when deploying any kind of a small radio
in a high-density venue. Once you get permission
to deploy, you might as well deploy a box that
does more things. If you have Wi-Fi in the box, add
an LTE small cell. It makes a lot of sense to
combine them, and we expect to see a lot of that
But it introduces some interesting problems that
have not gotten enough attention in the industry.
If you have a single node with both a Wi-Fi access
point and an LTE-U small cell, you end up in a
situation where that node has two 5 GHz radios
operating at the same time. Running the Wi-Fi and
LTE-U radios together in the same box with
antennas in very close proximity requires very
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People haven?t been spending enough time
figuring out how that?s going to work. And these
challenges bring us to LWA. I have a feeling we?re
heading in this direction.
Monica:What?s happening with LWA?
Steve: LWA is LTE plus Wi-Fi link aggregation. It is
another proposal coming from our friends at
Qualcomm. It builds on the original LTE-U concept.
As with all things, with each iteration the
technology gets better and the solutions get
better. At Ruckus, we?re big fans of LWA. In the
end, it will prove to be a stronger solution than
running LTE directly over the unlicensed band.
The theory here is that rather than try to put a
5 GHz unlicensed radio inside an LTE small cell,
you?ll have Wi-Fi access points running in the
unlicensed band, and you?ll have LTE small cells
running in the licensed band. You let each of them
do what they do best.
The smartphone would turn on both of its radios
and send some of the data natively over LTE, and
the rest as a tunnel over Wi-Fi.
You?re running LTE in the unlicensed band, but
you?re using the Wi-Fi MAC and PHY. You don?t
have any of the issues with listen before talk and
fair sharing that come with LTE-U. When the LWA
signal arrives at the Wi-Fi access point, it is peeled
off and tunneled back to the eNB, where the Wi-Fi
and LTE signals are combined and sent back to the
This is a really nice solution, because it gets us out
of that debate over running LTE in an unlicensed
band, something it was never designed to do.
By recombining the Wi-Fi data at the eNB, you can
bring it all back into the mobile core without
having to go through any 3GPP S2A, S2B, or S2C
interfaces, which are normally used to bring Wi-Fi
data into the mobile core. It?s just going to be a
straight S1 interface through a Serving Gateway
There?s a lot of value in this approach. It is the right
way to give cellular service a boost, by letting it tap
into that enormous pool of bandwidth we have in
the unlicensed bands. In the US, there is close to
700 MHz. This varies by geography, but there is a
significant amount of unlicensed bandwidth, and it
can be shared.
Monica: LWA is also something that 3GPP is
working on ? it?s not a proprietary solution.
Steve: The industry has been trying to understand
how to do Wi-Fi and cellular convergence now for
close to a decade. There have been a number of
different approaches that have been queued up,
and I think everybody agrees that Wi-Fi and
cellular technologies can be combined to offer a
truly compelling user experience.
We have to figure out how to make them
converge so that the user is always best
connected. Sometimes cellular is the better
connection. Sometimes Wi-Fi is the better
connection. But regardless of which one?s better,
how do we combine them?
Monica: From the operational and business model
point of view, how will the LTE-U and LWA models
work? That?s an even a bigger challenge than
working out the technology issues, How will this
get deployed in venues and who will pay?
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Steve: I think that?s a fascinating question, and I
think we are well-positioned to answer it.
Many of the technical issues around deploying LTE
small cells have been worked out by the RAN
industry. Now we?re going down the path of trying
to understand how to use LTE in the unlicensed
As we start looking to deploy small cells, whether
it?s just a straight LTE small cell or an LTE small cell
using the unlicensed band, what does the business
model look like?
In a convention center or an airport, mobile
operators are going to want to deploy LTE small-
cell networks. Each operator will negotiate with
the venue, put in its own network, and pay the
venue whatever site rental fee is required.
But once you get past the high-capacity-density
venues, you?re looking at smaller venues, like the
tens of thousands of hotel chains in the United
States and around the world. You?re also looking at
hospitals, shopping malls and universities.
We?ve learned a couple of lessons from deploying
Wi-Fi in public venues of various types.
Number one, once you?re past the high-capacity-
density venues, the enterprise or venue has to
pay. For almost any radio deployment, whether it?s
Wi-Fi or LTE, you?ve got to come up with a model
where the venue will pay to deploy the
Number two, it should be deployable by a value-
added reseller, or VAR. If radio engineers are
required, things can get really expensive.
Obviously, you need to make the deployment as
easy as possible, and have that equipment be as
cost effective as possible.
We?ve seen a lot of projections from analysts
talking about the LTE small-cell market being
worth upwards of $10 billion in five years. But to
get there, we?ve got some business model
challenges we need to address.
Monica: As you move to smaller venues, you still
want multiple operators, but it becomes
increasingly difficult to have multiple operators
deployed side by side. So you need a DAS-like
neutral-host model. Do you think it will work for
indoor LTE-U or LTE licensed small cells?
Steve: To get the venue to pay for the
deployment, it has to be a neutral-host model.
Everyone who walks into that venue has to be able
to access that network. Venues don?t want to put
in three or four networks, they want just one.
That?s why Wi-Fi has been so successful. A single
Wi-Fi network is a perfect neutral-host solution,
because everybody who walks into the venue can
We need to do the same with LTE. We need to find
a way to make the neutral-host model work with
LTE. The venue will pay to deploy the network, and
anyone who walks into the building will be able to
use that small-cell network. Venues won?t pay for
two, three or even four networks, but they will pay
To make the small-cell LTE market really explode,
we?ve got to solve the neutral-host problem.
Monica: Is there a difference in terms of
geography? In the US, there is much less of an
infrastructure-sharing mentality than in places like
Europe, for instance.
Steve: Yeah, RAN sharing tends to be much more
The neutral-host model is now becoming a top-of-
mind issue for the LTE small-cell industry,
especially, as we start looking at potentially
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |55|
running LTE in the unlicensed band. The industry
needs to better understand the business model
and better understand how to neutral-host the
Monica:What do you see in the short- to
mid-term for the coexistence of Wi-Fi and LTE
Steve: I think the key right now is what?s going to
happen at 3GPP. They?ve taken on the challenge of
looking at LTE-U and trying to understand how to
I think everybody wants to see a standard come
out of 3GPP, and that?s targeted for Release 13 in
the summer of 2016. We believe that at that time,
3GPP will come up with a mechanism that
supports listen before talk per the IEEE. There are
so many reasons to go down that path that we
expect that to happen.
Separately, we also have LWA, and that?s being
worked by 3GPP, also, for Release 13. We should
see something big coming out in the summer of
2016. There?s going to be a great deal of interest in
terms of understanding what 3GPP is doing there.
Certainly, a lot of the Wi-Fi standards organizations
are also plugging themselves in to the 3GPP
process. I think we?ll come out with a solution
that?s going to be a win-win for the entire industry.
Monica: Is this going to make the small-cell market
bigger, or is it just going to have a larger benefit for
Steve: These approaches accelerate the
convergence, which is good for everyone. We?ve
been working to converge Wi-Fi and cellular for
some time now, and approaches like LTE-U and
especially LWA accelerate that convergence, as do
things like Hotspot 2.0 and Wi-Fi Calling.
Anything that helps to accelerate this convergence
makes a more compelling user experience for
people using wireless services, and I think it?s going
to be a plus for the entire industry.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |56|
About Ruckus Wireless
Headquartered in Sunnyvale, CA, Ruckus Wireless, Inc. (NYSE: RKUS) is a global supplier of advanced wireless systems for the rapidly
expanding mobile Internet infrastructure market. The company offers a wide range of indoor and outdoor ?Smart Wi-Fi? products to
mobile carriers, broadband service providers, and corporate enterprises, and has over 40,000 end-customers worldwide. Ruckus
technology addresses Wi-Fi capacity and coverage challenges caused by the ever-increasing amount of traffic on wireless networks due
to accelerated adoption of mobile devices such as smartphones and tablets. Ruckus invented and has patented state-of-the-art wireless
voice, video, and data technology innovations, such as adaptive antenna arrays that extend signal range, increase client data rates, and
avoid interference, providing consistent and reliable distribution of delay-sensitive multimedia content and services over standard
802.11 Wi-Fi. For more information, visit http://www.ruckuswireless.com.
About Steve Hratko
Steve Hratko is the Director of Service Provider Marketing at Ruckus Wireless. Steve is responsible for the marketing of all service
provider class products worldwide. The primary markets for Ruckus solutions include MNOs, MSOs, WISPs, managed services providers
and wireline providers. Steve?s specific areas of expertise include Wi-Fi technology, licensed radio technology (specifically small cells),
mobile packet core and related systems. Steve has worked with service providers of all types and in all geographies. He has also been
quoted extensively in industry press, written extensively on the wireless market, and spoken at a wide variety of wireless industry
events. Prior to joining Ruckus in the spring of 2012, Steve served in a variety of product marketing positions at Juniper Networks and
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |57|
Wi-Fi Alliance: LTE
unlicensed and Wi-Fi
Managing the coexistence of multiple networks in
unlicensed spectrum is something with which Wi-
Fi Alliance has unmatched experience, gained
through its certification programs. Certification
ensures that multiple Wi-Fi devices meet
standards requirements and behave nicely toward
each other. Wi-Fi Alliance is eager to use this
experience to ensure a successful coexistence of
Wi-Fi and LTE in the 5 GHz band, through a
consensus-based process that includes all the
stakeholders ? service providers, users and
In parallel with the standardization efforts for
LAA-LTE, Wi-Fi Alliance continues its work on the
integration of Wi-Fi and cellular networks. Many
programs have already been established to
improve the performance of Wi-Fi in mobile
devices and to facilitate its integration with cellular
interfaces. The growing adoption of VoWi-Fi is the
latest example of how Wi-Fi and cellular, each with
its own strengths, complement each other to
improve the end-user experience.
More work lies ahead at Wi-Fi Alliance to promote
carrier Wi-Fi, which will require increasingly tight
coordination of Wi-Fi and cellular to enable
operators to flexibly allocate traffic between the
Wi-Fi Alliance recognizes that LTE in 5GHz requires
the industry to collaborate to find a satisfactory
solution for sharing the 5 GHz band. Currently
Wi-Fi Alliance is tracking both the LTE-U and
LAA-LTE closely, and actively trying to facilitate
strong collaboration between the Wi-Fi and
Certification and testing programs that facilitate Wi-Fi and cellular integration
Providing seamless authentication and government-grade security in public Wi-Fi networks, with users no longer required to
repeatedly enter credentials. Based onWi-Fi Alliance Hotspot 2.0 Technical Specification, Passpoint enables SIM and non-SIM
mobile devices to discover, select and connect to Wi-Fi networks without user intervention. Passpoint devices ?see behind?
the SSID that designates the network identity, tomake a network selection based on ownership, services and performance
characteristics. The technology behind Passpoint is foundational to Wi-Fi roaming and has been specified by both Wireless
Broadband Alliance and the GSMA Terminal Steering Group.
Wi-Fi CERTIFIED? ac, Wi-Fi
CERTIFIED? n Encouraging use of the 5 GHz band via high-performance Wi-Fi networking. With ac, Wi-Fi can reach Gbps throughput rates.
WPA2? Personal and Enterprise, EAP SupportingWi-Fi wireless network security in both personal and enterprise environments.
WMM? Providing support for multimedia traffic by enabling QoS to improve real-time traffic (e.g., voice and video streaming).
WMM Power Save Extending battery life of mobile devices by managing the time the devices spend in sleep mode.
Voice Personal, Voice Enterprise Testing the performance of Wi-Fi devices in a network loaded with both voice and data traffic streams, in multiple networkconfigurations, to support good voice call quality over a Wi-Fi link, with VoWi-Fi technologies, including Wi-Fi Calling.
Testing forWi-Fi and cellular devices that provides detailed information about theWi-Fi performance in the mobile device,
and about the interaction between Wi-Fi and cellular. Although this test program ? developed with CTIA ? is not an element
of Wi-Fi certification, completion of the testing is mandatory for Wi-Fi handsets seeking CTIA certification.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |58|
Learning from Wi-Fi,
coexistence with LTE
in unlicensed 5GHz
A conversation with
President and CEO, Wi-Fi Alliance
Monica Paolini:Good afternoon and welcome to
our conversation today. This is part of a Senza Fili
report, in collaboration with RCR Wireless News,
on LTE unlicensed and its coexistence with Wi-Fi.
Today I am talking to Edgar Figueroa, the CEO and
president of the Wi-Fi Alliance.
Edgar, thanks for taking the time to talk with us.
Edgar Figueroa: Thanks for having me, Monica. It
is nice to be here.
Monica:Wi-Fi has been using the 5 GHz band that
LTE unlicensed is planning to use for a long time. In
the 5 GHz band, Wi-Fi is the incumbent. At the
same time, there are many other technologies that
use the 5 GHz band and the 2.4 GHz unlicensed
In a way, it?s nothing new but there is a lot of
discussion going on with LTE unlicensed.
Edgar:We shouldn?t be surprised that there is
interest in doing more with 5 GHz, because Wi-Fi
has been so successful there. Last year we shipped
over a billion devices that operate in 5 GHz. We?ve
been absolutely successful with that. Wi-Fi
CERTIFIED ac is the first version of Wi-Fi that
delivers gigabit per second speed.
We have been tremendously successful operating
in unlicensed. I would say we are the model of
success in unlicensed. The conversation is shifting
quickly toward how to ensure that whatever
happens in 5 GHz does not unduly impair the
current tenants in that band.
Monica: This is a major issue because the 5 GHz
band is unlicensed, so everybody can use it. How
can all the different tenants with the different
technologies in that band coexist nicely?
Edgar: At a very high level, coexistence will require
extreme collaboration. Wi-Fi Alliance stands ready
to collaborate on this front. We have a history of
being able to collaborate successfully, particularly
with operators. You probably know that one of our
early programs, which ushered in the era of
equipment that has both Wi-Fi and cellular, came
about through collaboration between Wi-Fi
Alliance and CTIA. Together we made sure devices
that have Wi-Fi and cellular can operate radios
concurrently without one unduly impacting the
other. That has been terrifically successful. We can
do that again in this area. That is our hope.
Monica: This is really an important precedent,
because it made technologies collaborate. With
mobile devices, each device works with multiple
technologies and networks. Integration across
technologies becomes important because you
can?t really mandate something on a unilateral
basis. How do you see the willingness in the
industry to collaborate on technology coexistence?
Edgar: Collaboration is hard work, there is
absolutely no doubt. We know a lot about
collaboration. And even within Wi-Fi, the solutions
we have brought about have required a lot of
I would say that the complexity in unlicensed LTE is
one order of magnitude bigger than what we?ve
ever had up to now in dealing with licensed LTE. A
good solution will require collaboration, etiquette
across different spectrum domains, across
different technologies, across licensed and
unlicensed bands, and across equipment that
supports primarily one technology or another.
It will definitely require a lot of collaboration. That
is something that we are eager to get involved
Monica:Nice coexistence among networks started
within Wi-Fi because you often have multiple
networks sharing the same band. These networks
have to be nice to each other. How is Wi-Fi nice to
Edgar: I would say probably the testaments to our
success with Wi-Fi etiquette protocols, the good-
neighbor protocols that we have in all versions of
Wi-Fi, are that the density of the networks has
continued to increase, the speed of the data
transfer has continued to increase, and Wi-Fi
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networks continue to work well with other Wi-Fi
There are a number of parameters that need to be
considered in assessing how well a technology
shares the medium. Probably the ultimate
testament is, as I said, that the technology
continues to advance, gain popularity, and
increase in density. Wi-Fi has been able to do that.
We have mechanisms in the protocol that address
With unlicensed LTE, the challenge is going to be
to make sure the medium is shared so that all
tenants in unlicensed operate in a way that
doesn?t unduly impair the operation of other
Monica:What is the status of LTE unlicensed right
now? There?s a lot of work in terms of
standardization, and a lot of discussion.
Edgar:Weare far from a solution for sharing the
band that is broadly accepted as addressing the
issues of coexistence and fair sharing. It is still very
early. The standardization work has just started.
Only a handful of solutions have been
demonstrated, and no commercial solutions exist
that we can go pull off the shelf today and test.
A solution that is harmonized, that is broadly
understood, and that is recognized for having all
these proper etiquette techniques within it
requires peer evaluations. It requires
implementation across different bands. It requires
collaboration across industry segments.
A lot of that is nascent. We are just starting with all
of this. The good news is that it could be a seminal
moment for unlicensed in general. It might require
a very close working collaboration across the
different segments to make sure we continue to
evolve on this terrific path of innovation that
we?ve been on.
Monica: In addition to the standardization work,
there?s also regulation to take into account.
Unlicensed bands are regulated in a very different
way in different countries.
Do you think we need stronger regulation to
enforce nice behaviors of different technologies?
Edgar:Our philosophy that less regulation is better
has served us well up to now. That, of course, is a
philosophy that can only be upheld if there is
proper self-policing, if we are all operating from
the principle of sharing the spectrum in the best
possible way ? in a way that is respectful toward
other tenants in unlicensed.
When you have lighter regulation, you leave the
door open for even more innovation. Our hope is
that we can continue to cooperate with those
basic principles set in place. These are principles
that have allowed unlicensed to continue to be the
model of innovation in the last 15 years or so.
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I hope that, in working with the stakeholders in
unlicensed LTE we can continue on that path, and
that we will not need heavy-handed regulation,
and certainly no more regulation than we
Now, there is also the possibility that we will not
be able to continue to operate in that mode. So
long as devices and solutions are operating within
current regulations, then they?re operating legally,
but they may do so in ways that impair current
I?ll give you a very quick example. Within Wi-Fi
Alliance, we have policies just for Wi-Fi operation
with other Wi-Fi gear, to ensure that devices do
not operate in a way that impairs other Wi-Fi gear.
When that doesn?t happen, we recognize that it
hurts everybody. We operate in a very open and
transparent way based on self-policing. We have
policies like that in place to ensure no undue
With unlicensed LTE we need to take that to the
next level and ensure that these self-policing rules
are taken into account in this new era of,
potentially, many different technologies operating
in licensed and unlicensed.
Monica: You have a good model to ensure the
implementation of self-policing rules in your
certification program. You can test the ability of
Wi-Fi gear to coexist. When it comes to LTE
unlicensed, however, there is no obvious way to
do that yet.
The standards are excellent in providing a
framework. But within a standard, multiple things
are allowed; different vendors interpret standards
differently. At some point, somebody needs to
make sure that the implementation of the
standard follows the specs. It could be the
operators, it could be vendors, it could be an
association similar to the Wi-Fi Alliance.
Edgar: Ideally there could be some third-party
validation ensuring that the gear is properly
configured or developed, not only within the
standards and within the regulations, but beyond
that. We need a higher bar in unlicensed.
That higher bar is to ensure proper coexistence, so
that the medium is not impaired and end users are
not unduly harmed. My hope is that that will
eventually be put in place.
The good news is we are ready to participate in
that if there is interest inWi-Fi Alliance
participating. If it is needed, we will take on the
work. Beyond that, there are enough of our
members interested in this. We already have a
task group that is focused on looking at
coexistence. We will have to monitor this space.
Monica: You brought up the issue of the users.
Oftentimes in our discussions about LTE
unlicensed, we focus on the mobile operators. But
actually the enterprises and residential consumers
are the major users of Wi-Fi.
What is the best way to protect their access to the
band? How do we maximize it for everybody
involved ? not just the Wi-Fi users, not just the LTE
users, but everybody out there?
Edgar: You?re absolutely right that you have to
start with a focus on the end user. And you have to
start with a focus on getting it right, instead of
getting it right now.
This is terrifically important in order to come out
with the best possible solution that continues not
only to honor that legacy of making sure that we
are getting the most value out of unlicensed.
It requires an awful lot of collaboration and
discussion among the different stakeholders.
The key thing here is that now the interest in
5 GHz is expanding beyond just Wi-Fi and other
tenants of the 5 GHz spectrum that we have had
up to now. The stakeholders now include new use
cases with an operator focus and new bands.
Monica: Right now, often the 5 GHz band is not
used heavily, so it is possible to split up the
channels across technologies. Each technology
could take a different channel, and that?s fine.
That?s a very simple solution.
But when you have to share a channel, how do
you go about it? Because you can allocate more or
less capacity to different technologies depending
on the usage. What do you think is a fair
framework to do that?
Edgar: A framework is fair when it is not self-
centered. When it takes into account all the
different energy that is being emitted by all the
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |61|
folks using that spectrum at that time. There is a
lot of discussion that needs to happen about how
we take into account the different sharing
mechanisms that are going to be employed by
It is not necessarily the case that one size is going
to fit all here, but what we need are solutions that
take into account everyone else. In the case of
Wi-Fi, it has been mechanisms like listen before
talk, and algorithmic back-off that have been used
and proven effective.
That may need to evolve, but certainly Wi-Fi would
need to be taken into account when new solutions
come into the 5 GHz and other unlicensed
spectrum domains, because Wi-Fi has been very
successful. You can be sure the solutions with
Wi-Fi using 5 GHz today will be there for a very
long time. It is something that you do not do in a
vacuum, I suppose is the short answer.
Monica:We?ve been talking about LTE unlicensed,
but Wi-Fi is also evolving in a direction that will
make it easier for Wi-Fi to be integrated with the
mobile cellular networks and help mobile
operators to leverage unlicensed spectrum.
Can you tell us what plans Wi-Fi Alliance has for
the future in this area? What should we expect in
terms of commitment to get Wi-Fi to work more
extensively with the cellular?
Edgar: This is very much aligned with our
commitment to continue to make Wi-Fi better for
all stakeholders. But, certainly, operators have
been making their interest known within Wi-Fi
We are working on things such as multiband
operations to ensure that there is a similar way to
go from one spectrum band to the other ? for
instance, between the 2.4 GHz and 5 GHz bands?
and to make that seamless to the end user and
easy to manage for the operator.
We are working to continue to improve power
efficiency and manage the network layer by
improving Passpoint, with its third generation
being developed right now.
Most of the solutions that we are working on
should be of keen interest to operators. The reality
is that Wi-Fi has become integral to operators in
their own services.
It should not be surprising that we are working
hard to continue to make Wi-Fi better for
operators, as we are continuing to make it better
for a number of the other vertical segments that
Monica: And VoWi-Fi has become a hot topic that
comes up the most when we talk about LTE
unlicensed. It?s also another direction in which
Wi-Fi becomes closer to LTE.
Edgar: It is the topic du jour, but the reality is that
Wi-Fi Alliance worked on enabling voice within
Wi-Fi many years ago. Again, it is a testament to
the efficacy of Wi-Fi, the reliability of Wi-Fi, the
confidence that operators have in Wi-Fi and in the
core services with Wi-Fi. It is here today. It is a
terrific testament now.
We are evolving toward a world where, as a part
of the operator HetNets, Wi-Fi would just fit in the
background. Users will just be connected the best
possible way, whether it is on cellular or
I am encouraged by this progression toward
bringing that about, because users want the best
experience. We are working to try to make that
Monica: In closing, can you tell me what you
expect over the next several years in terms of the
coexistence of Wi-Fi and LTE unlicensed?
Edgar: The biggest thing we need to do is to work
very closely together to make sure we come out
with the best solutions in 5 GHz ? solutions that do
not impair either the experiences that folks might
have with any 5 GHz solution today, but also that
set us on the path toward a positive future for
unlicensed well into the future.
This is a pivotal moment. It requires different
industries that have operated very independently
to get intensely close to each other and to work
very well together, because our interests are
joined. To the extent that we can evolve toward
successful solutions in sharing 5 GHz we will have a
bright future together.
Watch the video of this interview.
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Wi-Fi Alliance? is a global non-profit industry association ? our members are the worldwide network of companies that brings you
Wi-Fi?. The members of our collaboration forum come from across the Wi-Fi ecosystem and share a common vision of connecting
everyone and everything, everywhere. Since 2000, the Wi-Fi CERTIFIED? seal of approval designates products with proven
interoperability, industry-standard security protections, and the latest technology. Wi-Fi Alliance has certified more than 25,000
products, delivering the best user experience and encouraging the expanded use of Wi-Fi products and services in new and established
markets. Today, billions of Wi-Fi products carry a significant portion of the world?s data traffic in an ever-expanding variety of
About Edgar Figueroa
As president and CEO of Wi-Fi Alliance, Edgar has led an unprecedented period of growth for Wi-Fi?, with more than two and a half
billion devices shipped in 2014 alone. Under Edgar?s leadership, Wi-Fi Alliance has grown to more than 600 member companies,
maintained an aggressive development roadmap, and adopted a vision of ?Connecting everyone and everything, everywhere.? Edgar
forged numerous strategic partnerships to facilitate penetration of Wi-Fi into established and emerging markets. Edgar also defined the
Wi-Fi Alliance Wi-Fi CERTIFIED? program development framework, and guided the launch of several generations of interoperable Wi-Fi
programs that have proliferated Wi-Fi into mass markets such as mobile and consumer electronics.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |63|
unlicensed and Wi-Fi
XCellAir, a spinoff from InterDigital announced in
February 2015, provides a shared solution with
which operators can manage large-scale LTE and
Wi-Fi networks within a HetNet framework.
To address the surge in data traffic, mobile
operators have to move beyond the limited small-
cell deployments that dominate in their networks
today, to large-scale densification deployments
that will involve multiple access technologies (Wi-
Fi and LTE), multiple bands (licensed and
unlicensed), and multiple vendors. A denser and
more complex network infrastructure will increase
operators? need for scalability, reliability and
resiliency. At the core of the XCellAir solution is
SON functionality to address the requirements of
operators managing ? or preparing to manage ?
these multi-access, multivendor networks.
XCellAir aims to go beyond coexistence of network
elements, and to maximize resource utilization and
revenue generation. XCellAir?s is a shared platform
that takes into account real-time RAN
performance data, policy, and application and
The unified management system includes
? Radio resource management (RRM)
? Capacity optimization
Deploying and managing a network with multiple
access technologies makes it possible for an
operator to benefit from the specific strengths of
each technology ? e.g., using higher frequencies
for indoor coverage and lower, licensed
frequencies for outdoor hot spots and wide area
coverage. In turn, the improved network utilization
can reduce per-bit costs and improve coverage.
In line with the trend toward virtualization,
XCellAir takes a cloud-based approach designed to
provide the flexibility and scalability that operators
require as they build out and expand dense, large-
scale HetNets. The cloud-based architecture
supports SaaS business models geared toward a
shift from a capex-intensive business model to a
cost model more tightly linked to the pace of
The integrated LTE and Wi-Fi network
management solution leverages development
work previously done at InterDigital and
contributions from two ecosystem partners:
? GoNet, for the management of in outdoor and
indoor deployments, with high-performance Wi-
Fi access points with MIMO and beamforming
? AirHop, for SON functionality supporting LTE-A
features in LTE-TDD and LTE-FDD networks
In this context, LTE unlicensed is treated as
another air channel. Mobile operators can use
traffic steering and load balancing to decide how
to allocate traffic across technologies, depending
on network loading, user preferences, subscription
plans, location, time of day, and RAN conditions.
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A shared solution
to manage Wi-Fi and
LTE unlicensed traffic
A conversation with
CTO and EVP of Engineering,
Monica Paolini:Welcome to our conversation
with Narayan Menon. He is the CTO and EVP of
Engineering at XCellAir, and one of the company?s
founders. Today?s conversation is part of our
report on LTE unlicensed.
Narayan, thanks a lot for taking the time to talk to
Narayan Menon: It?s my pleasure to talk to you
about these topics.
Monica: XCellAir is a new company that just came
out of stealth mode. Can you tell us what is it you
do at XCellAir?
Narayan: At XCellAir, we are developing network
management and optimization solutions for
HetNets, and particularly for LTE small cells and
Wi-Fi networks. The company was formally
launched a few weeks ago. It?s a spin-out of
InterDigital and folks who were at InterDigital in its
early years, like I and the rest of the team were.
The technology was initially incubated and
developed starting in late 2013 in InterDigital.
A few weeks back, the team and the technology
were transitioned over to XCellAir, which was
launched just before the Mobile World Congress in
Barcelona. Our solution includes both
management and optimization of mobile traffic.
We cover things like provisioning, configuration
management, fault management, and
optimization techniques like SON, applied to both
Wi-Fi and cellular.
We also deal with optimization aspects ? like
traffic management, capacity management, and
traffic steering ? that apply to both Wi-Fi and
cellular. It?s a cloud-based, scalable, multivendor,
Monica: This is a brand new solution, but you have
a lot of experience and substantial work already
done. You start off in a very good position. It?s
really a very hot topic right now because all
operators are working with both Wi-Fi and cellular.
Obviously they face a big challenge in how to
combine the two.
To date, mobile operators have used a basic
offload type of environment in which, whenever
there is Wi-Fi, you use it. There is not much
coordinating and integrating of the two sources of
With LTE unlicensed, there will be an additional
layer of complexity, integration, and opportunity
at the same time. How will LTE unlicensed fit in
with both Wi-Fi, on one end, and licensed LTE on
the other end?
Narayan: LTE unlicensed, the way we see it, is
going to be a nice complement to LTE the way it is
today. It will help augment the capacity and
bandwidth available to LTE systems by being able
to take channels in the unlicensed band and
aggregate them with channels in the licensed
band. It serves as a bandwidth boost for the LTE
Most of the scenarios you?re talking about involve
both the macro cells and small cells, and aim to
give this bandwidth boost. They also segregate
traffic intelligently between licensed or unlicensed
spectrum, based on quality-of-service
Wi-Fi is a very key aspect to consider, because
when LTE operates in these bands, in the 5 GHz
band, it will need to coexist with Wi-Fi, as well as
with other LTE systems that are operating in the
same band, following the channel access
etiquette. This etiquette and the rules that apply
within the band become very important. It is
crucial that one network doesn?t trample on the
others. The LTE system should not trample on or
interfere with the Wi-Fi solutions.
The coexistence of the two systems, Wi-Fi and LTE
unlicensed, will become very, very critical. That?s
the way they would relate to each other. One
would not necessarily displace the other. Wi-Fi will
have its own place and continue to have its place
in the sun. What this enables is for the LTE
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solutions to expand and reach out on the
unlicensed spectrum and gain more bandwidth.
Monica: There are going to be locations where
there is only Wi-Fi or only LTE unlicensed. That?s
relatively easy to manage. The challenge for the
operator is to operate in locations with a
combination of Wi-Fi, LTE unlicensed, and LTE.
How can you help an operator steer different
types of traffic to the different interfaces?
Narayan: A very interesting, very relevant
question. There are multiple ways to do traffic
steering, or traffic segregation as we call it.
It could be done based upon policy ? policy as it
relates to the user?s SLA, as it relates to the user?s
quality-of-service requirements, as it relates to the
type of application. The policy could end up
placing some applications on one system and
other applications on the other system.
For example, the operator might prefer to keep
applications that require a high level of quality of
service and reliability on the licensed band ?
whereas best-effort traffic, for example, might be
placed on the unlicensed band. Or it could be the
other way around, depending on the scenario.
The operator could also leverage this to provide
wholesaling capabilities to in-house customers and
third parties. The bandwidth that is wholesaled to
the third party might come out of the unlicensed
band, or it could be the other way around. The
operator may prefer to place that on the licensed
band. LTE-U gives the operator the flexibility to
Network conditions are another angle. As
conditions change, the system has to be adroit
enough, nimble enough, to be able to move things
around. If a particular application is on the
unlicensed band and things start to get flaky
because there?s too much contention there, the
systemmight move that piece of traffic back to the
Those kinds of mechanisms ? based on awareness
of the network conditions, based on awareness of
latency, throughput, packet loss rates, etc. ? have
to come into play to make this work really well.
Monica: This level of complexity is difficult to
manage. But if you manage it correctly, it brings a
lot of value to the operator because it can use the
resources more efficiently. You?re combining the
real-time network information from the RAN with
Narayan: A third element that comes into play is
user preferences. On top of all of these
requirements, the user might have certain
preferences ? for example, not to use the
unlicensed band at all, or in certain scenarios or
Monica: Voice is a special case. How can an
operator manage voice where you have three
Narayan: Voice will be treated as one of the
applications. It?s obviously a key application.
Especially as we move more and more to VoIP and
away from the circuit switch world, network
quality, link quality and quality of service become
more and more important. In the case of voice, the
default preference is to keep that on the licensed
side. If you?re using VoIP, there?s no reason why
you couldn?t be on either side.
This would be subject to the actual network
conditions. If the voice call is on the unlicensed
band and the conditions start to get bad, the
operator needs to be able to hand the voice call
back over to the licensed band. That capability
becomes very important. In a sense, VoIP, video
and other applications could be associated to a
There would be a per-user, per-application policy
that really depends on what the user has signed up
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for and paid for. Based on that policy, the
application might be placed in one place or the
other. Then if network conditions change, the
application can be moved back and forth. If the
user has some preferences applied on top of that,
those preferences would need to be respected as
Monica: The same flexibility can be used when an
operator has to manage IoT applications, for which
you have different types of devices and different
Narayan: Absolutely. IoT is such a diverse world.
There are tons and tons of applications in the IoT
space. Some of them, such as health care
applications, will require higher reliability.
You may want to keep those on the band you
consider to be more secure, more safe ? perhaps
on the licensed side. Some applications within the
IoT space that may be best effort or may be
possible to do after hours have more flexibility in
terms of placing them on the unlicensed side.
Monica:Mobile operators today use unlicensed
spectrum through Wi-Fi offload, but they don?t
really manage it. With LTE unlicensed, they face a
new challenge because they have to manage
traffic both in licensed and unlicensed bands, using
the same air interface.
Narayan: The management of mobile traffic with
respect to LTE-U has to happen at two levels. At
one level, there have to be mechanisms in place to
make sure that the LTE system, when it operates
on the unlicensed band, is following the rules and
etiquette that apply on that channel and on that
spectrum, to ensure that it doesn?t cause any kind
of damage to Wi-Fi services.
LTE-U should not impact Wi-Fi any more than
another Wi-Fi system on the same branch of the
system. That?s where listen before talk and similar
mechanisms come into play. And on top of that is
the traffic steering, traffic management capability
we talked about: being able to place traffic
intelligently on one or the other band, based on
these factors that we outlined previously.
There?s a challenge in terms of how effectively that
gets done, but it?s also a huge opportunity for
It is two levels. One is fundamentally making sure
that the mobile traffic is not impacting or impeding
other types of traffic in the unlicensed band. The
second aspect is once you?ve conquered that, you
try to make best use of that bandwidth with the
right things in the right place.
Monica: Let?s go back a little bit. Wi-Fi is widely
available. Every handset has Wi-Fi. Why does an
operator need LTE unlicensed? What is he going to
gain from it that Wi-Fi cannot deliver?
Narayan: That?s a great question as well. Wi-Fi is
there today. As you mentioned earlier, it exists in a
somewhat disparate fashion. Today, when you go
home, the iPhone switches to Wi-Fi no matter
what. There?s no real control. Like you said,
Monica, there?s no real management, there?s no
control of that. There?s no ability to put certain
types of traffic on Wi-Fi, some types of traffic on
cellular. Those elements are missing now.
Cellular standards have tried to foster more
integration of Wi-Fi networks into the cellular core.
They haven?t yet come into play on a large scale in
the cellular network.
LTE-U provides another, and in some ways more
interesting, more tightly coupled way to combine
transmission in the two types of bands, without
forcing the integration of Wi-Fi with LTE.
You?re not trying to integrate your Wi-Fi solution
with LTE. LTE-U is another way of tapping into, or
leveraging, the unlicensed band without
necessarily trying to couple Wi-Fi with cellular or
integrate Wi-Fi with cellular in a very tight fashion.
That?s the opportunity here ? to be able to use
LTE-U to provide bandwidth aggregation and
It could be used either to segregate traffic, like we
discussed before, or to aggregate bandwidth, or to
provide more bandwidth to an application when it
needs it. When a single application needs more
bandwidth, you reach out on the unlicensed band,
grab a couple of channels, aggregate them, and
you get this boost.
This ties in nicely with the LTE architecture. Some
of these mechanisms, such as listen before talk
and radio resource management schemes, will get
built into the LTE architecture. It becomes a much
more holistic solution that happens to be on the
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Monica: For an operator, LTE unlicensed is a way
to leverage unlicensed spectrum in a more
efficient way, and that?s good.
But what about Wi-Fi? Is LTE unlicensed going to
be nice enough to the existing Wi-Fi infrastructure
there? Should we worry about it? There are a lot
of worries that it?s going to create a lot of
disruption in Wi-Fi networks. Do you think that
challenge is being addressed right now?
Narayan: That challenge is being addressed quite
adequately, in my opinion. There was a study item
that 3GPP started a while back to study LTE-U and
the impact on Wi-Fi, to come up with
requirements and recommendations for what
needs to be done to ensure that the LTE systems
don?t disrupt the Wi-Fi systems in place. The end
of that study item resulted in a technical report
which outlines several recommendations.
One of those recommendations, one of the key
ones, is listen before talk (LBT). That?s essentially
making the LTE system do a channel check to see if
there?s any activity on the channel, via energy
sensing or energy detection on the channel, before
trying to access and use that channel. It?s
essentially making LTE behave almost like Wi-Fi.
That?s what Wi-Fi does with the collision detection
in that band.
There are other things as well. They recommended
the use of dynamic frequency selection (DFS) to
prevent interference with radar and other systems
that operate on the 5 GHz band in some countries.
One other recommendation is to use
discontinuous transmission to ensure that you
don?t hog the channel and increase the probability
of collision due to an existing Wi-Fi system trying
to access the channel. In 3GPP, we?ve discussed
things like radio resource management schemes
that will come into play.
For Wi-Fi and LTE systems to coexist, we believe
that some of the SON schemes will have to evolve
to incorporate awareness of other systems.
Today?s SON solutions are LTE-specific. Or in some
cases, there?s limited SON functionality in some
Wi-Fi systems. One technology is not cognizant of
We believe SON has to evolve significantly to
create this multi cross-technology awareness.
That?s an area we can have at XCellAir. Our
solutions address the whole network management
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with multi-technology access designed into our
solution from the beginning. Extending our SON?s
schemes to provide this kind of multi-technology
coordination in the unlicensed band would not be
difficult at all for us to do.
Monica:What?s special about what you do at
XCellAir, in terms of how you help operators deal
with this challenge?
Narayan: A big part of our solution is network
management and optimization. We provide the
ability to configure, provision and fault-manage
small cells and Wi-Fi access points. Also, we
combine that with optimization and SON
capabilities, such as optimal channel allocation and
interference mitigation schemes.
The nice thing is that these are all tied into one
solution. Traditionally, network management and
SON tended to be uncoordinated. We combine
these into one end-to-end solution. To that, we
are adding other capabilities, like traffic
management, traffic steering, and bandwidth
management, into one holistic solution.
We help the operator accelerate the rollout of
small-cell networks. Today, one of the
impediments for small-cell network adoption is the
lack of plug-and-play automated procedures to
bring up small cells quickly. If you want to bring
these up in large numbers, you needmuch-more-
automated procedures than what the macro-cell
network procedures support today.
With our solution, we help operators to manage
millions of units in a hands-free, zero-touch
fashion. We enable the operator to get the small
cells up and running fast, and to be able to manage
them easily and scale the network easily. Then, we
enable the operator to extract value out of the
network by adding other aspects, such as capacity
band and the bandwidth optimization.
One aspect is acceleration of deployment. Other
ones are ease of management, and value
extraction from the access technology the
There are three key attributes that make our
One is that it is access technology independent.
From the outset, we have designed it to be unified
across LTE and Wi-Fi ? and LTE-U can be easily
added to that. We have developed the system
with reusable components that enable us to go
from Wi-Fi to LTE very quickly.
This enables us to support the two systems with a
unified visual interface, a common set of
algorithmic tools, a common set of database
components, etc. This is unique, because a lot of
systems start with one technology and then try to
move to the other. They?re breaking concrete to
The second key aspect is our multivendor
approach. One of the issues that operators will
have with large-scale small-cell deployments is
that they will inherently end up going multivendor.
Today, each vendor solution comes with its own
native management capability, its own EMS. What
we provide here is a multivendor solution that
easily works across multiple vendors? access
The way we do it is that the vendor specificities are
isolated or confined to a small part of our system.
Large parts of our system that deal, for instance,
with the algorithms, the databases and the
virtualized tools do not get impacted when we
move from one technology to the other. This
enables us to adapt to each vendor?s specifications
very quickly and flexibly.
The third piece is the scalability. Our solution is
virtualized today in the cloud. It makes the
network bandwidth solution very scalable for the
operator. As opposed to buying big controller
boxes upfront, the operator can scale the solution
very granularly as the network grows and as it
adds more access points. Resources on the cloud
side ? such as processing, memory and storage ?
can be scaled very gradually, very granularly.
Operators are able to scale as they grow. They pay
for those resources as they scale. That gives them
a lot of flexibility.
Monica: In closing, can you tell us what we should
expect next from XCellAir? This is all new ground.
What?s coming next?
Narayan:On one hand, we are working very
promisingly towards taking our technology to
market. We are dialoguing with operators, we are
dialoguing with vendors to integrate our solution
with different vendors? access points. In our near-
term roadmap, our goal is to get the ecosystem
dialogs going, get the IoTs, get to the lab trials,
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |69|
pretrials in the next few months, and get this to
market very quickly.
In the longer term, we will focus on the capacity
and bandwidth management capabilities and on
analytics. We collect, store and analyze a lot of
information from the access points within our
system ? attributes, metrics that relate to network
performance, subscriber data that we get from the
access points. All of that data can be analyzed and
made available to the carrier or service provider,
via either well-defined APIs or analytics capabilities
that we will provide in the future.
Of course, support of LTE-U is on our
roadmap, as well as supporting community
Wi-Fi networks and enabling coordinated
management of community Wi-Fi networks.
Watch the video of this interview.
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XCellAir enables wireless service providers to efficiently manage, optimize and monetize their wireless access networks. Heterogenous
Networks (HetNets) consisting ofWi-Fi and/or cellular small cells can deliver massive increases in capacity, extended coverage and a
lower cost-per-bit for wireless service providers, but ? to date ? their potential remains largely unrealized. This untapped potential is
why XCellAir exists. XCellAir provides the industry?s first cloud-based, multi-vendor, multi-technology mobile network management and
At XCellAir, Narayan develops and evangelizes the technology strategy and roadmap, and leads product development. Prior to XCellAir,
Narayan drove research and development for InterDigital, leading elite teams to innovate and implement next-generation wireless
solutions ? including the inception and early development of the XCellAir product. Narayan has over 25 years of experience in the
wireless field, holding leadership roles at Siemens Mobile Networks, Omnipoint Technologies and Hughes Network Systems in the
development of TDMA, GSM/GPRS and 3G systems. Narayan holds Engineering degrees from the Indian Institute of Technology, New
Delhi and an Executive MBA from Hofstra University.
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III. Operator interview
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Tele2: Maximizing the
use of unlicensed
today, LTE later
EVP andGroup CTO,
Monica Paolini:Goodmorning.Welcome to our
conversationwith JoachimHorn, at themobile
operator Tele2. He is its EVP and groupCTO. Today
we?re going to talk about LTEunlicensed, and the
role it playswithin theecosystem and services of a
Joachim, thanks for taking the time to talk to us
JoachimHorn: It?s a pleasure.
Monica: Joachim,what is your role at Tele2,
especiallywith respect to different radio interfaces
such asWi-Fi, 3G andLTE?
Joachim: Tele2 is anoperator in Scandinavia, based
in Sweden.Weareoperating in nine countries in
northeastern Europe, and also in Kazakhstan.We
are a low-cost operator.
Weare a fastmover and a challenger. Our tagline is
?Wedeliverwhat you need, but for less.?Weare
always looking for howcanwe getmoreefficient in
order to give our customers a better service. In this
context, you also need to seehowwe approach the
strategy for radio interfaces.
Also,we are a fastmover onLTE.We?re already
rolling out LTE in six countries. In Sweden,we have
99%population coverage over the past year. The
experience is outstanding.
LTE brings together exactlywhatwewant ?
superior user experience and lowproduction cost.
This is the reasonwhy, strategically,we see LTE as
the future standard for cellular for the years to
come.We see customersmigrating from2Gand
3G, to LTE relatively quickly.
When it comes to spectrumon the unlicensed
band, it?smainlyWi-Fi.We are a big fanofWi-Fi.
Actually,we are selling hotspots that are LTEon the
one side andWi-Fi on theother, and it?s being used
in Sweden inmore than 100,000 cases. There are
manyWi-Fi hotspotsout therewhich use LTE from
Tele2 as a backup.
Wi-Fi is extremely important for our customers.
More than70%of data today goes overWi-Fi.We
are very interested inwhatever comes in the future
in this unlicensed band, andwewant tomake sure
it does not harmour customers, as they need to be
able to useWi-Fi.
There is a lot of spectrumout there, in particular in
the 5GHzband, for unlicensed use. Today it?s
mainly usedwithWi-Fi.With LTE unlicensedwe
have to answer the questionofwhetherwe should
use LTE also in the unlicensed band.
The benefit for thatwould be that LTE unlicensed
will bemuchmore efficient in termsof
coordinationwith the licensed bands, and generate
amuch better user experience.
Why doweneed that? Because 70% to 80%of
usage happens indoors, in particularwhen it comes
Now, indoor coverage, in particularwith high
capacity, is not easy to get. Todayoperators try to
do it fromoutside, building big base stations and
blast through thewall to reach inside, but it doesn?t
workwhen it comes to high capacities. Then there
is a need for indoor coveragewith indoor antenna
systems, or pico cells and so on, which is an
extremely costly game.
The question is, how canweapproach this in a
more cost-efficientway? Thenumber one step
would be actually tomakemore use ofWi-Fi, to
coordinate the use ofWi-Fiwith LTE in amuch
In the long run it?s very attractive to think about in
parallel toWi-Fi,without jeopardizing theWi-Fi
quality, to also put LTE into the unlicensed band
and combine itwith the licensed band, and by
doing that getmuchbetter coverage and also
capacity, deep indoors,whichwill lead to amuch
better user experience for our customers.
Monica:Weoften think about LTE unlicensed as a
competitor toWi-Fi, but at the same time it?s a fact
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of life that prettymuchallmobile operators rely on
Wi-Fi in oneway or another.
LTE unlicensed andWi-Fi can coexist in the same
location, so it?s not residentialWi-Fi and LTE
Joachim: Yes. Therewould not be any benefit for
operators ifwewouldmesswith theWi-Fi camp.
Wi-Fi is a consumer, noncellularwireless standard,
which has extremely high value toour customers
and also toour operators.We have no interest in
endangering that situationor even getting into a
political fight aboutwhat?s right.
I think an unlicensed LTE standardwill only have a
chance if it is ensured that it has no impact on Wi-
Fi. That?swhat?s happening currently in the
discussionswithoperators in the standardization
process.We look for technologies that are available
andmake sure that they can coexist.
The first performancemeasurements I?ve seen
fromdifferent companies showwe can get an
excellent LTE performancewithout amajor impact
on the existingWi-Fi. It?s using technologies that
we all knownow inWi-Fi ? for example, listen
before talk. It is using the same lowpower, so there
is not a strong LTE signal andweakWi-Fi signal.
They areworkingon the samepower levels.
There areothermethods, like dynamic frequency
selection, that help to avoid conflicts betweena
Wi-Fi transmission and LTE transmission.
Monica: You said the LTE unlicensed shouldn?t
create anymajor impacton theWi-Fi.What impact
do you consider to be acceptable?
Joachim: In the 5GHz band, there is 300 to 400
MHzof bandwidth. TheWi-Fi channel is typically 20
MHz to 40MHzwide,maybe80MHz. The LTE
channel is typically 20MHz,maybe 40MHz.
Wi-Fi and LTEwill competewith eachother over
this spectrum. But it?s not like LTE takes the
spectrum and holds it for all time. The spectrum is
only allocatedduring transmission. Then it?s being
It?s random access. It?s like Ethernet:many people
can use the same cable, and there aremethods to
avoid collisions, to detect if somebody else is
sending and receiving.
From aWi-Fi perspective, it?s as if anotherWi-Fi
stationwould enter the scene. Froman LTE
perspective, I have additional spectrum I can use
with the LTE technology and interface,which is a
little bitmore efficient thanWi-Fi.Weexpect 50%
more efficiency here.
Monica:As long as it behaves likeWi-Fi, that?s good
enough.Do you think the listen-before-talk
regulation,which is prevalent in Europe andAsia, is
sufficient to ensure this?
Joachim: I thinkwe have not dug down to all the
details of coexistence. I think this is still in the
research. I obviously cannot speak for the
regulator, but I think theremust be an intent to
make sure eachof the technologies and services
can coexistwithout endangering the other side.
I?m sure that the regulatorswill look to that. Listen
before talk is a good technology. It?s definitely a
good start to prevent LTE from taking it all and then
there?s nothing left forWi-Fi. The first trials have
shownus that this is a goodway to progress;
whether it?s sufficient or not, difficult to say.
Monica: You said thatwith LTE unlicensed you get
a better user experience.Where is the
improvement coming from?
Joachim:Wi-Fi is a relativelyold standard. It has
been developed further and further,withMIMO,
beamforming, andWi-Fi ac andWi-Fi ad coming in.
LTE ismuch younger. LTE ismore robust. It?s built
from a telco-grade perspective,whereasWi-Fi
comes from a totally other area,more a best-effort
I think also that the experience onLTE is related to
how to dealwith radio and spectrum. It?s very
sophisticated,was not built for consumers
originally. But now,with LTE unlicensed, there?s a
chance to gomore into that space for consumers.
Monica:Now,when youhave to allocate, you?re
going to have the same indoor locationvenue,
where youhave licensed andunlicensed LTE, and
Wi-Fi. Howdo you split the traffic? Howdo you
decidewhich subscriber orwhich application is
allocated towhich radio interface?
Joachim: First of all, if you are anoperator, that?s
the part of the designwhichneeds to happen still.
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But it?s all about the control plane and the control
mechanisms behind it.
Unlicensed LTEwill be just an extension to licensed
LTE. Youwill never leave the licensed LTE for
The phone detects there is an unlicensed band, and
itwill add that band. Thismeans increased
capacity, and probably also coverage, compared to
if you just stickwith the licensed band.
It is not intended to only roamon the unlicensed
band. Of course, a user can always decide to switch
to the phone to the normalWi-Fimode. That?s in
the user?s hands.
Monica:Do you have any plans tomanage traffic
depending on the applications ? for instance, to
keepvoice on licensed, or video onWi-Fi?
Joachim: The idea is to keep the real-time services
in the licensed band, because the conditionswill be
more predictable and reliable, andbecause the
unlicensedband has an undefined interference
situation. For video streaming, downloads and
internet access, youwouldmove to the unlicensed
LTE unlicensed is obviously a very interesting
technology. Itwill not be available any time soon.
We need to be realistic. Standardization just has
It will take two years to develop the equipment.
Then itwill take awhile until we have devices
supporting that.My estimation is that before three
to four, ormaybe five years, LTE unlicensedwill not
play amajor role.
As anoperator,weare looking at the question
?Howcanwemakemore useofWi-Fi?? Improving
the combinationofWi-Fi and LTE ? both existing
technologies ? does not needa new phoneor a
new chipset to be developed.
Oneof the first thingswe are looking at is,
obviously, VoWi-Fi. Today, at least in densely
populated areas, there isWi-Fi practically in all
buildings. Then, even if youhave a coverage issue
with yourmicro-network, you could continue a
voice call onWi-Fi.
We all have seen that the iPhone is now supporting
VoWi-Fi, giving the technology a new dynamic.We
are now starting a trial to see how wecan integrate
that, and howbig the value would be for us.
I see a big benefit, beforemoving even to use LTE
unlicensedwhen it?s available. Today it?s already a
big benefit to add the capacity ofWi-Fi towhat you
have in 3Gand4G for both voice and data, before
wemove to LTE unlicensed for data.
Monica: Youwere talking about the timeline, and
oneof the concerns that I hear is about the
availability of devices, because, as you say, you
cannot use your current phone to use LTE
unlicensed. Do you think that?s going to be an issue
down the line?
because the standardwas there but it took years
until themobile deviceswere there.Wehad the
With4G, itwas not so bad?we had the devices.
Now,when it comes to LTEAdvanced,with carrier
aggregation announcedoneor two years ago, still
there areonly a fewphones supporting it, although
CA is a very good feature.
I expect the same to happenwith LTE unlicensed.
We need to add to the phone another frequency
band, the 5GHzone,whichphones don?t have for
the cellular yet.
A new chipset is required.We need to be able to
run 5GHz in parallel to other bands, because LTE
unlicensedwill be used togetherwith LTE licensed.
That?s a numberof requirementswhich need to be
developed andalso put into the phone in a very
power-efficientmanner. At the same time, once
youneed to deploy base stations, is LTE unlicensed
built into themacro base station?
Itmakes not toomuch sense, because theoutput
power is a fractionof that in amacro cell. You need
separate base stations to deploy indoors, insteadof
Wi-Fi or in a combinationwithWi-Fi, so we are
talking about pico-, femto-cell technologies.
There is the question still about economics,
becausewhat LTE unlicenseddoes not do is change
the economics of small cells. It is only interesting if
this can be deployed in thewaywe deploy to the
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Actually,we don?t deployWi-Fi. In the consumer
case, typically, the end user deploys theWi-Fi
hotspot because he has a cable connectionwith
theWi-Fi there, and itworks.
That?s a very cost-efficientway to deployWi-Fi. If
we, asoperators, go to private houses, that?s very
unrealistic. Of course, in public buildings,wedo
indoor coverage anyway. Then it?s relatively easy to
add this kindof technology.
It is very interesting to expand the use also to the
private houses ? in particular, big houses ? and the
new buildings,with the thermal glazedwindows,
where it?s very difficult to cover fromoutside.
Monica: In the caseof residential, could youhave a
model like the one for femto cells,where the cost is
sufficiently low that subscribers buy the Wi-Fi
access points that support LTE unlicensed?
Joachim: Yeah, I think the economics and the
dynamics should be the same. The question is, why
did that notwork for femto cells?Whydid femto
cells not getmuch greater traction? Because the
price point of femto cells is now reasonably low.
I remember the first discussions, four of five years
ago,where the discussionwas ?Let?s put the femto
cells into the shop next to theWi-Fi router, or
integrate into theWi-Fi router, and just sell it to the
customer or give it away subsidized, and then by
thatmake surewe can improve coverage.?
It has beendone.We did it in some countries, on a
very small scale,more in theB2Benvironment, but
the big deployment never happened.
Oneof the reasonswas thatwe hada lot of
interference issueswith femto cells, because they
used the same bandasmicro cells.
With unlicensed LTE that could be better. Still, the
economics need to be solved. Howdowe
distribute that? Howdowemake the price point
lowenough in order tomake it attractive?
Monica:Howmuchwould residential users gain
fromhaving LTE unlicensed in their home,when
the bottleneck is the broadband connection?
Joachim: That?s a fair point.At the endof the day
what LTE unlicensedwould bring is definitely
much-more-reliable services, in termsof
robustness against interference.Wi-Fi ismuch
more sensitive against interference from the
Here inmy house, for example, if I checkWi-Fi ac, I
find 50Wi-Fi hotspots using the same band. It
makes it very difficult to get goodperformance.
The LTE unlicensed technology ismore robust
against this kindof interference.
With LTE unlicensed therewill better service for the
end user. But how tomake sure this is attractive to
users needs to be found. It is verymuch dependent
on the economics, andon the cost of such devices.
Monica:Can you tell us aboutwhat youhave done
so far in termsof testing the technology, looking at
how it performs, andwhat are your plans for the
Joachim:Wehave not yet started to test LTE
unlicensed; we are a low-cost operator andweare
relatively lean. Butwe engage in the discussion
with vendors and fellowoperators. Also,we think a
lot about how to solve the indoor coverage
problem, and also the potential capacity problem.
Everybody is talking about 1,000xmore data by
2020, andof course all of us need to think about
howwe get this done if we don?t getmore
spectrum.Then these technologies are very
attractive, because all youneed to deploy them is a
Youdon?t need to buildwide coverage, but
wherever youhave a high density of traffic you
could use that technology to offload.
I have no doubt that LTE unlicensedwill perform
well, because it is the same technologywe use in
the licensed band; it is just adifferent bandwith
someadjustments, lower power and compatibility
There is no reason to believe that itwouldn?twork.
The trial does not need to showwhether itworks or
not. It ismore about the economics.What are the
deployment scenarios?What?s the business case
Monica:Whendeploying it indoors, you are
dealingwith enterprise or real estateowners that
might have their ownWi-Fi network, and then are
going to be very protective of yourWi-Fi network.
Youexpect them to visit this and say, ?Holdon,
before you come in and youuse the same
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frequency that I use, Iwant to be really sure, or I
might notwant youbecauseyoumight create
interferencewithme.? Do you expect that to
become an issue?
Joachim: Itmay become an issue. Todaywehave
caseswhere some landlordsdo notwant anything
else to be deployed beyondwhat they have
deployed. Therefore, I?m coming back towhat I
said earlier: it?s very important thatwe are flexible,
This is amuch lower-hanging fruit. It is easier to get
a combinationof the normalWi-Fi consumers have
at home,with tighter integrationor collaboration
with the cellular standard.
There are a number of features coming on theWi-
Fi side with automatic sign-on, and much faster
registration procedures and so on, with Hotspot
2.0. There are a lot of things coming whichwill
make it more attractive to operate.
The benefit is that you don?t need new chipsets.
It?s not a new frequency. The things are there and
probably easier also to get around when the
landlord insists on deploying their old technology,
which is their right.
Monica: In closing, can you tellmewhat you think
are the challenges for LTE unlicensed to succeed?
Joachim: It?s very important to think about the use
cases, because we should not do LTE unlicensed
just because we can do it. We should be very
conscious about exactly some of the discussions
we?ve just had.
What are the deployment scenarios? What is the
business case behind them? Is the economic
model of such a technology better than any other
small-cell technology? If not, the likelihood that it
succeeds is as big as any other small-cell
technology we have seen today. It?s another
I believe there are goodopportunities in it, and by
working today alreadywithWi-Fi andVoWi-Fi, we
take a first step in this direction. The useof the
unlicensedbandwill probably play amuchbigger
role in the upcoming 5Gnetworks.
Watch the video of this interview.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |77|
Tele2 is one of Europe?s fastest growing telecomoperators, with 14million customers in 9 countries. Tele2 offersmobile communication
services, fixed broadbandand telephony, data network services and content services. Ever since Jan Stenbeck founded the company in
1993, Tele2 has been a tough challenger to former governmentmonopolies andother established providers. Tele2 has been listedon the
NASDAQOMX Stockholm since 1996. In 2014, Tele2 hadnet sales of SEK 26 billion and reported anoperating profit (EBITDA) of SEK 5.9
JoachimHorn is Executive Vice President and theGroupChief Technology and InformationOfficer of the Tele2 Group headquartered in
Stockholm, Sweden. He also serves as a chairmanof the boardof two affiliate companies to Tele2, ProcureItRight, a leading procurement
management consultancy in the Nordic region, andNet4Mobility, a joint venture betweenTelenor Sweden andTele2, operating the
world?s first shared2G/4G radio network in Sweden. Joachim hasover thirty years of global experience in the telecommunicationsmarket
both from an infrastructure vendor and telecomoperator perspective. He hasworked and lived in emerging aswell as developedmarkets.
JoachimHorn also served as aGSMAboardmember andwas the chairmanof theGSMA strategy committee.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |78|
3GPP (2013) Technical Specification Group Radio Access Network; Scenarios and
requirements for small cell enhancements for E-UTRA and E-UTRAN (Release
3GPP (2014) Study on Licensed-Assisted Access to Unlicensed Spectrum, 3GPP
Alcatel-Lucent (2015)Wireless Unified Networks blending Wi-Fi and cellular
technologies. NBED NEED TO CONFIRM IF CONFIDENTIAL
FCC (2014) Revision of Part 15 of the Commission?s Rules to Permit Unlicensed
National Information Infrastructure (U-NII) Devices in the 5 GHz Band, FCC 14-
FCC (2014) Revision of Part 15 of the Commission?s Rules to Permit Unlicensed
National Information Infrastructure (U-NII) Devices in the 5 GHz Band. First
Report and Order, ET Docket No. 13-49.
FCC (2015) Office of Engineering and Technology and Wireless
Telecommunications Bureau Seek Information on Current Trends in LTE-U and
LAA Technology, ET Docket No. 15-105.
Flore, Dino (2015) 3GPP and the unlicensed spectrum.
Hratko, Steve (2015) Getting engaged: LTE and Wi-Fi fall in love, The Ruckus
Huawei (2014) U-LTE: Unlicensed spectrum utilization of LTE.
Intel (2014) LTE System Deployment and Performance in Unlicensed Bands.
LTE-U Forum (2015) LTE-U SDL Coexistence Specifications.
LTE-U Forum (2015) LTE-U Technical Report. Coexistence Study for LTE-U SDL.
McKibben, Bernie; Kyung Mun; and Rob Alderfer (2014) LTE-Unlicensed:
Augmenting mobile data capacity, but coexistence needs consideration, Cable
Television Laboratories, Inc.
Murias, Ron (2014) LTE-U Coexistence Mechanisms, InterDigital.
Nguyen, Tho (2014) New Rules for Unlicensed National Information
Infrastructure (U-NII) Bands KDB 789033, KDB 644545, FCC.
Nielsen, Sari, and Antti Toskala (2014) LTE in unlicensed spectrum: European
regulation and co-existence considerations, Nokia.
Nokia (2014) LTE for unlicensed spectrum.
NTT DOCOMO (2014) NTT DOCOMO?s views on LAA for unlicensed spectrum:
scenarios and initial evaluation results.
NTT DOCOMO (2014) NTT DOCOMO?s views on LTE unlicensed.
Padden, Joey (2015)Wi-Fi vs. EU LBT: Houston, we have a problem, Cable
Television Laboratories, Inc.
Qualcomm (2013) Extending LTE Advanced to unlicensed spectrum.
Qualcomm (2013) Introducing LTE in unlicensed spectrum.
Qualcomm Research (2014) LTE in unlicensed spectrum: Harmonious
coexistence with Wi-Fi.
Ruckus Wireless (2015) Making sense of convergence: LTE-U, LAA-LTE, and LWA.
Wright, Dave (2015) When worlds collide, and When worlds collide: digging
deeper, The Ruckus Room.
REPORT LTE unlicensed and Wi-Fi: Moving beyond coexistence ? 2015 Senza Fili Consulting ? www.senzafiliconsulting.com |79|
3G Third generation
3GPP Third Generation Partnership Project
4G Fourth generation
ANDSF Access network discovery and
AP Access point
API Application programming interface
ARPU Average revenue per user
ARQ Automatic Repeat-reQuest
ASA Authorized Shared Access
BS Base station
CA Carrier aggregation
CCA Clear channel assessment
CG Coexistence gap
CPP Coexistence pattern period
CQI Channel quality information
CSAT Carrier Sensing and Adaptive
CWG-RF Converged Wireless Group?Radio
DAS Distributed antenna system
DFS Dynamic frequency selection
EAP Extensible Authentication Protocol
EMS Element management system
eNB Evolved NodeB
E-UTRA Evolved Universal Terrestrial Radio
FCC Federal Communications
FDD Frequency division duplex
FEC Forward error correction
GSM Global System for Mobile
HeNB Home eNodeB
HetNet Heterogeneous network
IEEE Institute of Electrical and Electronics
IOT Interoperability testing
IoT Internet of things
IP Internet Protocol
ISM Industrial, scientific and medical
ISP Internet service provider
ITU International Telecommunication
LAA Licensed-assisted access
LAA-LTE Licensed-assisted access Long Term
LBT Listen before talk
LSA Licensed Shared Access
LTE Long Term Evolution
LTE-FDD LTE frequency-division duplex
LTE-TDD LTE time-division duplex
LTE-U LTE Unlicensed (LTE-U Forum specs)
LWA LTE Wi-Fi Aggregation
MAC Media Access Control [layer]
MIMO Multiple input, multiple output
MNO Mobile network operator
MSO Multiple-system operator
OEM Original equipment manufacturer
PCRF Policy and charging rules function
PHY Physical (layer)
QoS Quality of service
RAN Radio access network
RAT Radio access technology
RF Radio frequency
RFIC Radio frequency integrated circuit
RRM Radio resource management
SaaS Software as a service
SCG Small-cell gateway
SDL Supplemental Downlink
SIM Subscriber Identity Module
SLA Service-level agreement
SoC System on a chip
SON Self-organizing network
SSID Service Set Identifier
SU Secondary user
TCO Total cost of ownership
TDD Time-division duplex
Toff Transmission off
Ton Transmission on
TPC Transmit power control
TSG-RAN Radio Access Network Technical
UE User equipment
U-NII Unlicensed National Information
VAR Value-added reseller
VoIP Voice over Internet Protocol
VoLTE Voice over LTE
VoWi-Fi Voice overWi-Fi
WISP Wireless internet service provider
WLAN Wireless local area network
WMM Wi-Fi Multimedia
WPA Wi-Fi Protected Access
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About the interviewer
Monica Paolini, PhD, is the founder and president of Senza Fili. She is an expert in wireless technologies and has helped clients
worldwide to understand technology and customer requirements, evaluate business plan opportunities, market their services
and products, and estimate the market size and revenue opportunity of new and established wireless technologies. She has
frequently been invited to give presentations at conferences and has written several reports and articles on wireless broadband
technologies. She has a PhD in cognitive science from the University of California, San Diego (US), an MBA from the University of
Oxford (UK), and a BA/MA in philosophy from the University of Bologna (Italy). She can be contacted at
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prudently, lest it spoil future actions.?