Power control for limited feedback precoding: Achievable SINRs and optimal capacity analysis

This paper analyzes the performance of MIMO downlink broadcast channel employing precoding techniques, with imperfect channel state information at the transmitter (CSIT) due to limited feedback. We focus on two optimization issues that related to power control (PC) in precoding. Firstly we employ a distributed and competitive PC scheme for the interference-limited network, and derive two sufficient conditions of Nash Equilibrium, which are the upper bounds for achievable SINRs. Secondly, maximum sum capacity (SC) is investigated to show the maximal ability of PC in precoding. From Monte-Carlo simulation, it reveals that the capacity boost of non-linear Tomlinson-Harashima precoding (THP) with PC is significant as compared to its alternatives. Specially, the more users are served, the higher capacity gain is achieved. Maximally about 0.9 bps/Hz capacity gain can be achieved for THP, which is about 10.8% better than equal power allocation (EP).