JointNull : Combining Reconfigurable Analog Cancellation with Transmit Beamforming for Large-antenna Full-duplex Wireless

In this paper, we study the performance of a full-duplex architecture for large-antenna systems, where each receive antenna uses digital canceler but analog cancelers can be fewer in number than receive antennas. Analog cancelers are reconfigurable in the sense that they can be assigned to any antenna and convert it into a full-duplex antenna. We propose JointNull that jointly optimizes reconfigurable analog cancellation and transmit beamforming. JointNull assigns each antenna one of the three roles—fullduplex, half-duplex receive and half-duplex transmit antenna—and then designs a transmit precoder to suppress self-interference on receive antennas. We evaluate JointNull using channel measurements from an array with 72 antennas. We find that when combined with transmit beamforming, there is an optimal number of analog cancelers, less than total number of antennas, which achieve the maximum sum-rate. Further, JointNull achieves close to ideal full-duplex sum-rates using much fewer analog cancelers than the total number of antennas. For example, JointNull achieves 90% of ideal full-duplex sum-rate using only eight poor quality analog cancelers, each of which can cancel 20 dB of self-interference. Finally, rate region shows that when demand is highly biased towards downlink, JointNull achieves 90% of ideal sum-rate with even fewer or no analog cancelers.