Multicast beamforming with LOS self‐interference cancellation in full‐duplex wireless communications

Abstract

SummaryIn this paper, we consider a full‐duplex system where the access point installed with multiple transmitting antennas and a single receiving antenna serves several single‐antenna remote users. In this case, there are 2 kinds of interferences. One is the near‐field self‐interference (SI) induced by the simultaneous transmitting and receiving over the same band, and the other is the cochannel interference caused by the multicast broadcasting in the same band. A problem of near‐field SI cancellation and the cochannel interference suppression using transmit beamforming is formulated at the access point. This problem of ensuring the near‐field line‐of‐sight SI suppression benchmark and maximizing the minimum received signal‐to‐interference‐plus‐noise ratio of remote receivers leads to a nonconvex NP‐hard optimization. Furthermore, we introduce a semidefinite relaxation technique coupled with linear program power adjustment and an outer bisection search loop to transform the problem into a convex optimization. This can be solved by the modern interior point methods. Simulations show that the proposed method is feasible even when the local receive antenna in near‐field and the remote receivers in far field are in the same direction.