The Vault

Interference Coordination and Mitigation Techniques for LTE
Presentation / Feb 2014 / 3GPP, LTE, ICIC, HetNets

Learn more about tunable solutions and advanced recievers for multiband/multimode devices in this IWPC workshop presentation.

1 © 2013 InterDigital, Inc. All rights reserved. © 2013 InterDigital, Inc. All rights reserved. IWPC Workshop : Tunable Solutions and Advanced Receivers for Multiband/Multimode Devices INTERFERENCE COORDINATION AND MITIGATION TECHNIQUES FOR LTE 2 © 2013 InterDigital, Inc. All rights reserved. Outline About InterDigital Inter-Cell Interference Coordination (ICIC) for HetNets Interference Avoidance for In-Device Coexistence (IDC) Coordinated Multipoint Operation (CoMP) Advanced Receivers for LTE 3GPP Standardization Timeline 3 © 2013 InterDigital, Inc. All rights reserved. InterDigital Snapshot – Invention, Collaboration, Contribution InterDigital develops fundamental wireless technologies that are at the heart of mobile devices, networks, & services worldwide. Vision As a long time contributor to the wireless industry, we have solved many of the most critical mobile challenges for 30+ years Our technology is used in all 2G, 3G and LTE devices providing support for new mobile broadband & richer multimedia experience We offer our technologies to the market in IP blocks and full product solutions and have been key in high profile OEM offerings Technology Standards Solutions Four decades of discovery and innovation in wireless communications 4 © 2013 InterDigital, Inc. All rights reserved. 3GPP Standardization Timeline 2008 2009 2010 2011 2012 2013 2014 Release 8 Release 9 Release 10 Release 11 Release 12 LTE is fastest developing mobile technology*  474 operators investing in LTE (deployments and trials)  222 LTE networks commercially launched  1000+ LTE user devices launched *Based on Global mobile Suppliers Association (GSA) “Evolution to LTE Report” – October 2013 ICIC eICIC FeICIC CoMP IDC Advanced Rx Advanced Rx 5 © 2013 InterDigital, Inc. All rights reserved. Inter-Cell Interference Coordination for HetNets (1) Inter-Cell Interference Coordination (ICIC) enables frequency reuse 1 operation for LTE Frequency Tx Power Frequency Tx Power Frequency Tx Power Cell Edge Resource Blocks (RBs) Cell Centre RBs Cell Edge RBs Frequency Domain Coordination Frequency domain interference coordination over X2 interface:  Relative Narrowband Transmit Power (RNTP) indicator  High Interference Indicator (HII)  Interference Overload Indicator (OI) 3GPP Release 8 ICIC 6 © 2013 InterDigital, Inc. All rights reserved. Inter-Cell Interference Coordination for HetNets (2) Time Domain ICIC enhancements targeting two Heterogeneous Network scenarios Supporting Macro Cell UEs under heavy interference from CSG HeNBs Offloading Macro Cell UEs to Pico Cells using Cell Range Expansion (CRE) Macro – Aggressor Cell Pico – Victim Cell Macro – Victim Cell HeNB – Aggressor Cell  Bias applied to pico cell to “artificially” increase its footprint  Cell splitting gain achieved by offloading traffic to pico cells  Rebalancing UL and DL channel characteristics on cell association Cell Range Expansion Scenario 1: Scenario 2: Interference Interference Non CSG Member UE HeNB 7 © 2013 InterDigital, Inc. All rights reserved. Introduction of Almost Blank Subframes concept:  ABSs are subframes in aggressor cell with reduced or no transmit power on some physical channels.  ABSs protect resources in victim cell experiencing strong inter-cell interference  eNB ensures backwards compatibility by transmitting control channels and physical signals (e.g. CRS) required for legacy procedures during ABS  UEs in victim cell are provided a pattern (set of subframes) to perform RRM-related and CSI measurements 3GPP Release 10 Enhanced ICIC (eICIC) Inter-Cell Interference Coordination for HetNets (3)  CRS interference mitigation: CRS assistance information provided to UEs for CRS-based measurements and improved demodulation  Transfer of SIB1 via dedicated RRC signaling for UEs experiencing strong interference from neighboring cells 3GPP Release 11 Further Enhanced ICIC (FeICIC) Almost Blank Subframe (ABS) introduced to enable time domain coordination in HetNets 8 © 2013 InterDigital, Inc. All rights reserved. Coordinated Multipoint Operation – CoMP (1) Transmitting and/or receiving network nodes cooperate to improve cell-edge performance CoMP Transmission Techniques CoMP Deployment Scenarios Homogeneous Networks (Scenarios 1&2) Heterogeneous Networks Coordinated Scheduling/ Beamforming (CS/CB) Joint Transmission/ Processing (JT/JP) Scenario 3: Different Cell IDs Scenario 4: Same Cell IDs Coordination Area Optical Fiber 9 © 2013 InterDigital, Inc. All rights reserved. Coordinated Multipoint Operation – CoMP (2) CoMP introduced in 3GPP Release 11 for ideal backhaul between coordination points (eNB ↔ RRH)  Multiple transmission points coordinated for downlink data transmission  New approach to Channel State Information (CSI) reporting to enable DL CoMP scheduling  CSI-interference measurement (CSI-IM) resource: set of REs on which the UE measures interference  CSI process concept: measurement associated with one CSI- RS resource (desired signal) and one CSI-IM resource (interference signal)  A CSI process can represent a CoMP transmission hypothesis Downlink CoMP Transmission  Multiple reception points coordinated for uplink data reception  UE configured with UE-specific parameters for PUSCH DMRS, PUCCH sequence and PUCCH region for hybrid-ARQ  Virtual Cell ID concept introduced to replace physical cell identity of the UE’s serving cell Uplink CoMP Reception Ongoing Study Item in 3GPP Release 12 for CoMP with non-ideal backhaul (eNB ↔ eNB) 10 © 2013 InterDigital, Inc. All rights reserved. LTE with GPS for navigation and/or location-based services LTE with WiFi for traffic offloading or tethering Interference Avoidance for In-Device Coexistence (1) Enabling coexistence of multiple radio transceivers (LTE, Bluetooth, WiFi and GNSS) within a UE Use Cases Problem Scenarios LTE with Bluetooth for hands-free operation (VoIP, multimedia) LTE Bands 7/13/14: LTE Tx radio interferes with GNSS receiver  LTE Band 7: LTE UL transmission (Tx radio) interferes ISM band Rx radios (BT and WiFi)  LTE Band 40 : Two way interference  Interference caused by LTE Tx radio to ISM band Rx radio (BT and WiFi)  Interference caused from ISM band Tx radio (BT and WiFi) to LTE Rx radio Extreme proximity of radio transceivers operating on adjacent or sub-harmonic frequencies  Interference from transmitter may be much higher than received power of desired signal 11 © 2013 InterDigital, Inc. All rights reserved. Interference Avoidance for In-Device Coexistence (2) Phase 3: Network- Controlled IDC Solution  eNB provides solution to IDC interference problem  Two approaches: (1) FDM: Move LTE signal away from ISM band (2) TDM: Provide TDM patterns (using LTE DRX) to ensure that transmission and reception of different radio signals do not coincide Phase 2: IDC Interference Notification Phase 1: IDC Interference Detection  UE initiates transmission of the IDC indication to eNB  IDC indication includes necessary assistance information for eNB to solve problem:  List is problematic LTE frequencies  Direction of interference  Interference pattern  UE detects the start of IDC interference  Detection may rely on (1) Existing LTE measurements (2) UE internal coordination to assess the interference  Coordination amongst RATs within same device is assumed  UE can autonomously deny LTE UL transmission to protect ISM if necessary  eNB configures long-term maximum denial rate through dedicated control signalling  UE should also autonomously deny ISM transmission to ensure LTE connectivity Signaling and Procedures for In-Device Coexistence (IDC) introduced in 3GPP Release 11 Autonomous Denials 12 © 2013 InterDigital, Inc. All rights reserved. Advanced Receivers for LTE: R8  R12 Increasing the role of UE receivers to improve spectral efficiency as LTE evolves Baseline receivers for R8:  MMSE – Minimum Mean-Square Error  MRC – Maximal Ratio Combining Introduction of new receiver requirements for R11:  MMSE- IRC (Interference Rejection Combining) : Practical linear interference suppression (IS) receiver that does not require any transmission coordination  CRS Cancellation: non-linear interference cancellation receivers mitigating strong CRS interference (R11 FeICIC) Studying more advanced receiver architectures for R12+:  CRS Cancellation: CRS interference mitigation (R11 FeICIC hetnet concept) for homogeneous networks  NAICS: Network-Assisted Interference Cancellation and Suppression 3GPP Release 8 3GPP Release 11 3GPP Release 12+ 13 © 2013 InterDigital, Inc. All rights reserved. Advanced Receivers for LTE: R12+ NAICS Network-Assisted Interference Cancellation and Suppression (NAICS) being studied for R12+ Mitigation of intra-cell and inter-cell interference from control and data channels Multiple candidate receiver types grouped into 3 categories: Interference Suppression (IS)  Applies linear filtering to received signal to suppress interference instead of explicitly cancelling interference  Interference parameters enabling interferer channel estimation are used Maximum Likelihood (ML)  Joint detection of desired and interference signals using ML criterion  Interference parameters enabling interferer channel estimation and interferer detection are used Interference Cancellation (IC)  Successive application of detection, decoding, re-encoding and cancellation  Interference parameters enabling interferer channel estimation and interferer detection are used eNB provides interference knowledge to UE:  Presence and characteristics of interference  Transmission schemes (incl. resource allocation)  Reference symbols to enable channel estimation  Modulation format and/or coding rate 14 © 2013 InterDigital, Inc. All rights reserved. Thank You! Christopher Cave Director, Innovation Labs InterDigital Communications Montreal , QC, Canada +1 514.904.6264 Christopher.Cave@InterDigital.com 23 October