Pushing the limits of Full-duplex: Design and Real-time Implementation
Authors: Achaleshwar Sahai, Gaurav Patel, and Ashutosh Sabharwal
Recent work has shown the feasibility of single-channel fullduplex wireless physical layer, allowing nodes to send and receive in the same frequency band at the same time. In this report, we first design and implement a real-time 64-subcarrier 10 MHz full-duplex OFDM physical layer, FDPHY. The proposed FD-PHY not only allows synchronous full-duplex transmissions but also selective asynchronous fullduplex modes. Further, we show that in over-the-air experiments using optimal antenna placement on actual devices, the self-interference can be suppressed upto 80dB, which is 10dB more than prior reported results. Then we propose a full-duplex MAC protocol, FD-MAC, which builds on IEEE 802.11 with three new mechanisms – shared random backoff, header snooping and virtual backoffs. The new mechanisms allow FD-MAC to discover and exploit fullduplex opportunities in a distributed manner. Our over-the air tests show over 70% throughput gains from using fullduplex over half-duplex in realistically used cases.