Joint MSE-based hybrid precoder and equalizer design for full-duplex massive MIMO systems

In this paper, we study joint design of linear hybrid precoding and equalization for full-duplex (FD) massive multiple-input multiple-output (MIMO) systems such that the sum mean squared error is minimized across all mobile stations. To better resolve practical issues such as hardware complexity, power consumption, and overhead of channel estimation, hybrid processing, which consists of digital processing in the baseband and radio frequency (RF) analog processing, is employed at the base station for simultaneous transmission and reception. In particular, baseband processing is adjusted according to instantaneous channel variation while RF processing is only updated based on such long-term channel statistics as transmit and receive correlation. In the presence of self-interference (SI) and co-channel interference, joint power optimization is carried out in order to achieve balanced performance for both the uplink and the downlink. As demonstrated by numerical results, FD is able to outperform half-duplex under realistic SI. Furthermore, the employment of the proposed hybrid processing structure is justified by its near optimal performance when equipped with even only a small number of RF chains.