On the Sum-Rate of Uplink MIMO Cellular Systems with Amplify-and-Forward Relaying and Collaborative Base Stations

Abstract

Cooperation and relaying are emerging technologies as flexible solutions for improving the capacity of cellular systems. Motivated by this, we investigate the asymptotic achievable sum-rate for multiple-input multiple-output (MIMO) multiple-access cellular systems in the uplink employing cooperative base stations (BSs) and amplify-and-forward (AF) relaying. In our model, the antennas at the user equipments (UEs), relay terminals, and BSs are correlated and there are direct links between UEs and BSs. Using the replica method, we derive the large-system sum-rate for the uplink system using joint optimal decoding (JOD) as well as separate detection and decoding (SDD) and show that each UE's performance can be characterized by a vector Gaussian channel with an appropriate vector input, an effective channel gain, and a vector Gaussian noise. Based on the asymptotic result, we also devise an efficient algorithm to determine the asymptotic optimum transmit matrices for the UEs and relays that can maximize the sum-rate of the MIMO multiple-access cellular network if the spatial channel covariance information (CCI) is available and exploited at the UEs and the relay terminals.