submitted to IEEE Transactions on Signal Processing, Dec., 2011.
Interference alignment is a signaling technique that provides high multiplexing gains in interference channels. It can be extended to multi-hop interference channels, where relays aid transmission between sources and destinations. In addition to coverage extension and capacity enhancement, relays enhance the multiplexing gain in the interference channel. In this paper, three cooperative algorithms are proposed for a multiple-antenna amplify-and-forward two-hop interference channel. The algorithms use the spatial dimensions at the transmitters and the relays to forward interference to the receivers so that interference can be aligned and canceled. The first algorithm minimizes the sum power of enhanced noise from the relays and interference at the receivers. The second and third algorithms rely on a connection between mean square error and mutual information to solve the end-to-end sum-rate maximization problems with either equality or inequality power constraints via matrix-weighted sum mean square error minimization. The resulting iterative algorithms converge to stationary points of the corresponding optimization problems. Our simulations show that amplify-and-forward relays achieve higher end-to-end sum-rates and multiplexing gains than decode-and-forward relays and direct transmission.
This paper is available on ArXiv.