Cooperative Algorithms for MIMO Amplify-and-Forward Relay Networks

Abstract

Interference alignment is a signaling technique that provides high\nmultiplexing gain in the interference channel. It can be extended to multi-hop\ninterference channels, where relays aid transmission between sources and\ndestinations. In addition to coverage extension and capacity enhancement,\nrelays increase the multiplexing gain in the interference channel. In this\npaper, three cooperative algorithms are proposed for a multiple-antenna\namplify-and-forward (AF) relay interference channel. The algorithms design the\ntransmitters and relays so that interference at the receivers can be aligned\nand canceled. The first algorithm minimizes the sum power of enhanced noise\nfrom the relays and interference at the receivers. The second and third\nalgorithms rely on a connection between mean square error and mutual\ninformation to solve the end-to-end sum-rate maximization problem with either\nequality or inequality power constraints via matrix-weighted sum mean square\nerror minimization. The resulting iterative algorithms converge to stationary\npoints of the corresponding optimization problems. Simulations show that the\nproposed algorithms achieve higher end-to-end sum-rates and multiplexing gains\nthat existing strategies for AF relays, decode-and-forward relays, and direct\ntransmission. The first algorithm outperforms the other algorithms at high\nsignal-to-noise ratio (SNR) but performs worse than them at low SNR. Thanks to\npower control, the third algorithm outperforms the second algorithm at the cost\nof overhead.\n