Near-field self-interference suppression with subscriber beamforming in full-duplex communications

With a wide range of spatial domain self-interference (SI) suppression techniques in full-duplex (FD) systems, the available literatures focus on verifying the feasibility of the types of technologies used in the experiments. The current literatures overlook the principle that the local receive antennas are always in the near-field of the local transmit antennas when the antennas are separate and omnidirectional. If near-field assumption of the SI channels is considered, more degrees of freedom are achieved. This may reduce the impact on the remote users while adopting spatial domain SI suppression. Thus, a minimization of the near-field spatial SI with the remote user beamforming is stated. First, it is reformulated and solved by least square (LS) method. Second, the problem can be relaxed by l1 norm and solved by linear programming. The simulation results are used to analyze the impact of the near-field spatial SI suppression on the remote user. The SI suppression is feasible even when the local receive antenna in the near-field and the users in the far-field are in the same direction.