The Vault

Advanced Waveforms Demo Interview with Doug Castor
Video / Dec 2012 / 5G

Doug Castor: Under the advanced waveforms in [RF] project we’re looking at some of the limitations of OFDM and searching for new waveforms for 5G and future system architectures. Some of the future system architectures are built on assumptions which are a lot different than 4G and prior system architectures. We’re now looking at small cells, heterogeneous networks, TV white space, and shared spectrum situations where we have to be more conscious of the interference that we’re causing to neighboring spectrum. So, it forces us to rethink OFDM and whether that’s an appropriate waveform for systems going forward. We’re looking at providing advantages and energy efficiency and spectral agility.

Spectral agility is the ability to support noncontiguous waveforms in flexible bandwidth. On this platform we have the advanced waveforms evaluation platform which allows us to load on baseband waveforms under the class of filter bank multicarrier and look at energy efficiency, spectral agility solutions, and ways that we can reduce the side loads of modulations so that they have less interference to neighboring systems. The baseband waveforms are able to be played out through two different radios. The first one is our LTE 1.9 GHz radio and the second one is the wireless LAN 5.5 GHz radio. The evaluation [board] also has the capabilities for press factor reduction, envelope tracking, and digital pre-distortion.

When I turn on each of these technologies, with press factor reduction we see an increase in average power of roughly 1.5dB for a total average output power of 20.5dB and we also have digital pre-distortion capabilities in this platform. With digital pre-distortion we’ll see a decrease in the adjacent channel interference from -40dB to roughly -50dB. So, we have a 10dB decrease on adjacent channel interference. So, in this platform we’re able to take our baseband waveforms and evaluate those in a combined manner with the envelope tracking, digital pre-distortion, and press factor reduction techniques. And this is a platform that [we’re] going to be used to continue to evaluate future, 5G [air] interface waveforms.