Resource allocation for MIMO multi-relay systems with zero-forcing relaying

In this paper, we consider a two-hop multiple-input multiple-output (MIMO) multiple relays communication networks, where each relay employs the zero-forcing (ZF) relaying scheme, we assume that the perfect channel state information (CSI) is available at the source, the destination and the relays. We propose a total relays power allocation (PA) scheme with the sum relays transmit power constraint to maximize the average system capacity. Since the original PA optimization problem is not convex, it is difficult to derive an analytical solution, so we propose to simplify the problem by employing the relaxed power constraint which is slightly higher than the actual sum relays power, then we derive the closed-form solution. The Monte Carlo simulation results shown that our proposed joint PA scheme significantly improves the system capacity compared with the conventional ZF relaying scheme.