Downlink Precoding Design for Full-Duplex Enabled Massive MIMO Systems with Low Hardware Complexity

This paper aims to design a downlink precoding scheme for the base stations (BS) by concentration on both hardware complexity and interference mitigation capability in a cellular multi-user massive multiple input multiple output (MIMO) full-duplex (FD) enabled system. The presented precoder makes an effort to mitigate the power of three interference terms: the self-interference (SI) in the uplink, the multi-user interference in the downlink and the BS-to-BS interference of the uplink transmission. To reduce the implementation costs, a low hardware complexity (LHC) precoding design is utilized in which only a single radio frequency (RF) amplifier is required in each BS. However, since this structure requires full cellular collaboration, to reinforce the performance from the overhead point of view, a LHC precoding with small inter-cell collaboration is proposed. The precoding design is extended to a case where the channel state information (CSI) is imperfect due to pilot contamination, and it is attempted to combat this effect. Numerical results demonstrate the out-performance of the LHC schemes compared to the prior zero-forcing (ZF) based methods in the literature both in the uplink and in the downlink. The promising performance of the LHC-based pilot contamination cancellation design is also depicted in case imperfect CSI is at hand. Furthermore, it is shown that the overhead reduction is achieved with a minor performance degradation, which seems to be worth the cost.