Adaptive self-interference cancellation in wideband full-duplex decode-and-forward MIMO relays

Full-duplex relays suffer from self-interference due to simultaneous reception and transmission in the same frequency. This relay-induced interference signal can be of significant power and considerably distort the information-bearing signal, leading to unacceptable performance degradation. In this paper we present a method to solve the problem of self-interference mitigation for full-duplex decode-and-forward multiple-input multiple-output (MIMO) relays that is based on an adaptive gradient-descent algorithm. The method makes use of signals available at the relay to estimate the self-interference channel in order to cancel it. We analyze the behavior of the algorithm in terms of its stationary points and mean convergence. Under a low SNR scenario case and convergence time constraints, simulations show that the proposed method can provide several tens of dBs of mitigation.