Wireless MIMO switching: Distributed zero-forcing relaying using network coding

In a switching problem, a multiple-input-multiple-output (MIMO) switch conducts a one-to-one mapping from the input links to the output links. This paper studies the cases that a set of single-antenna relay nodes act together as a MIMO switch to perform distributed precode-and-forward, where all users transmit simultaneously to the switch in the uplink and then the switch broadcasts the precoded received signal vector in the downlink. By the signals at the switch properly precoded, each user could receive its desired signal from one other user without interference from other users, where self-interference is allowed as it can be perfectly canceled when the equivalent channel gain information is available. We propose a distributed zero-forcing relaying scheme that nulls every interference from other users. We also provide a message passing approach with low overhead. Simulation results show that the proposed scheme achieves much larger throughput than the existing distributed schemes for multi-way relaying with little attendant overhead.