FD2: A directional full duplex communication system for indoor wireless networks

We present the design and implementation of FD², a directional full-duplex (FD) communication system for indoor wireless networks. An FD² AP uses directional transmit and receive antennas to reduce self-interference, and to combat AP-AP and client-client interferences that arise due to FD operation in multi-cell networks. FD² addresses the joint problem of scheduling and beam selection by proposing efficient practical algorithms. FD² is implemented on the WARP platform, and its performance is compared against CSMA/CA and other FD and directional communication systems. Our experimental results reveal that: (i) Simple application of FD to multi-cell networks can result in significant loss of capacity due to high FD induced interference, while FD² can effectively overcome the problem and provide an average gain of ninefold; (ii) FD²´s performance depends on the hardware capture properties and the corresponding rate table, and increases when packets can be captured at lower SINR margins, or when dynamic range of the rate table is high; and (iii) FD²´s uplink and downlink performances are susceptible to channel dynamics, and are impacted differently due to mobility. However, we show that training FD²´s rates according to traffic direction, mobility, and feedback rate, increases its robustness to channel dynamics.