Beamforming Design and Power Allocation Aided by Relay Selection in Cooperative Massive MIMO Network

Abstract

Abstract In this paper, we study the relay selection and power allocation to maximize the achievable sum rate of all the users in the cooperative Massive Multiple Input-Multiple Output (mMIMO) system. Some users have direct paths to the base station (BS) to communicate in the considered system model. In contrast, there is no direct path for the rest users, and the relay helps transmit information signals from BS to these users (indirect users). Firstly, we design a beamforming matrix at BS and relay according to the block diagonalization (BD) and Zero-Forcing (ZF) methods, respectively. Then, relay selection and power allocation problems are analyzed. Generally, the joint power allocation and relay selection problem is a combinatorial problem, and it needs a global search algorithm to solve, which is complex and time-consuming. Therefore, we convert this joint problem into two sub-problems. The first sub-problem selects the suitable relay based on some criteria. The convex optimization method solves the power allocation problem in the second sub-problem based on the selection. The simulation results showed that the proposed algorithms are significantly close to the benchmark methods.