Joint quantisation levels and power optimisation in uplink network multiple-input and multiple-output under constraint backhaul

This article studies the performance of the cooperative system where each base station (BS) is connected to a central processor (CP) via a noiseless and rate-limited backhaul link. The single-user compress-and-forward scheme is deployed at the BSs, and the problem for jointly setting the quantisation noise and the transmit power levels is left open. The authors formulate the weighted sum-rate (WSR) problem of optimising quantisation and transmit power levels for K-users and B-BSs situation. However, the problem is non-convex and difficult to be solved directly by conventional convex methods. In this work, an algorithm is proposed to solve the optimisation problem and achieve its global optimality. More importantly, the authors reveal the reason for the effect of the quantisation levels on the performance of cooperative system. Lower and upper bounds of quantisation levels are derived under the given signal to interference noise ratio (SINR) requirements. The lower and upper bounds are then demonstrated to be rather close to the numerical results. It is also numerically shown that the proposed algorithm can achieve the global optimality and is robust with respect to different multi-user situations.