flatulus: Thanks for the comments. They are spot on.

- It is true that there are benefits beyond full duplex, namely in reducing duplexer filter requirements for FDD. We have received commercial interest for this application as well. LTE provides support for 24 FDD bands, a lot more than 3G. Having 24 fixed-frequency duplexers in a handset is near impossible. So, there is interest in tunable duplexers that can cover multiple bands but inevitably have reduced isolation and greater insertion loss than conventional fixed-frequency duplexers. Self-interference cancellation can be used to enhance the isolation back to the 55dB levels seen in conventional fixed-frequency duplexers. In our ISSCC paper, which has not yet been uploaded to IEEExplore, we show measurements for the FDD use case as well.

- It is true that cellular base stations will require 20-30dB higher isolation. I think the higher-gain antennas do offer an isolation advantage but not as much as the increase in antenna gain because the antenna-to-antenna coupling is a near-field phenomenon. In base stations, where form factor is less of a concern, discrete-component based approaches can be used as a first line of defense, followed by IC-based fully-integrated cancellation. Also, WiFi base stations and cellular small cells have lower transmit power levels and so are more direct applications for this IC technology.

- I did not follow the MWC, but as far as I know, in the literature, SAW-less receivers for TDD have been reported and have made it into phones, but duplexer-less receivers for FDD have not yet been reported. The SAW-less receiver problem is easier because one has to deal with jammers picked up from the environment, which tend to be a lot weaker than transmitter self-interference.

Some more clarifications: 6. The chip has been fully tested, and is able to provide the required SI cancellation so that the desired signal can be received without distortion in the presence of the powerful transmitter echo. What remains to be tested are rate gains when several of these chips are networked. This is not that straightforward because today's networks are designed for half-duplex nodes, not full-duplex. So new scheduling concepts etc. need to be developed, which is a topic of research. 7. Echo cancellation is certainly not old technology. While echo cancellation techniques exist, they use techniques that cannot be integrated into an IC (e.g. cm-long transmission lines to replicate 10s of nanoseconds of delay spread, photonic techniques etc.). The innovation here is a technique that can replicate the delay spreads of the echo at RF frequencies on an IC.