Interference Alignment for Transceiver Design in Multi-User MIMO Relay System

A multi-user multiple-input multiple-output (MU-MIMO) relay system using macrocell and femtocells has numerous advantages, such as optimal coverage, better fairness in the resource allocation and spectral efficiency. Despite these advantages, interference management remains an important challenge especially for the cell edge (CE) users. In this article, a linear transceiver design for CE macrocell user equipments (CE-MUEs) and amplify-and-forward (A-F) relay node (RN) dealing with the interference in perfect channel state information (CSI) case is proposed. The proposed scheme is based on the interference alignment (IA) technique, which is formulated as a sum mean square error (MSE) problem using the minimum MSE (MMSE) criterion. In comparison with the conventional solutions, the simulation results of the proposed IA scheme show a marked improvement of the system performance in terms of average sum-rate.