Space-Time Communication Protocols for N-Way Relay Networks

We address communication protocols for N-way relay networks with M antennas at the relay and a single antenna at the N source terminals. In particular, amplify-and-forward (AF), decode-and-forward (DF), and compress-and-forward (CF) strategies are extended to these networks, and in addition, two new relaying protocols, denoise-and-forward and estimate-and-forward, are proposed. In the first part of the paper, the performance of these schemes is analyzed in terms of the achievable rate region. Also, the optimal diversity-multiplexing tradeoff is derived for both AF and DF. The second part of the paper is devoted to practical space-time transmission strategies. Linear dispersion codes are used, which are optimized by maximizing the sum rate. For AF a diversity order of close to M can be achieved by using a specific space-time code construction.