Joint Source and Relays Power Allocation for MIMO AF Multi-relay Networks

In this paper, we consider a two-hop multiple-input multiple-output amplify-and-forward multiple relays communication networks with the assumption that the perfect channel state information is available at the source, the destination and the relays. We propose a joint design of the precoding matrices at the source and relays to maximize the system capacity. Based on the joint precoding matrices design results, we derive the joint source and relays power allocation (PA) optimization problem with the total source and relays transmit power constraint. Since it is difficult to derive an analytical solution to the original joint PA optimization problem, we simplified the problem and derive the closed-form solution based on high SNR approximation. The Monte Carlo simulation results shown that our proposed joint PA scheme significantly improves the system capacity compared with that solely considering PA at the relays.