Cooperative relay beamforming design for multi-cluster relay interference networks

Abstract

In this work, we consider a multi-cluster amplified-and-forward (AF) relay interference network and design relay beam matrix for each cluster to maximize the minimum signal-to-interference-and-noise ratio (SINR) at destinations subject to the relay power budget within each cluster. Both single and multiple source-destination (S-D) pair scenarios are considered. We propose a beam matrix structured as a weighted sum of two types of beam matrices: zero forcing (ZF) beam matrix for inter-cluster interference suppression, and another beam matrix for beamforming gain maximization within a cluster. Maximum ratio combing (MRC) and minimal mean square error (MMSE) are chosen to design the second beam matrix in single and multiple S-D pair scenarios, respectively. The optimal solution for each type of beam matrix is obtained in closed form. We then obtain the optimal weights to each type of beam matrix by transforming the max-min SINR problem and solving it via the SDR approach. Compared with applying the direct SDR approach to the original problem, our solution offers similar performance with significantly lower computational complexity. In addition, our proposed structured beam matrix clearly reveals the power shift between interference suppression among clusters and beamforming gain maximization within the cluster as the distance among clusters or the size of clusters changes.