Diversity-multiplexing tradeoff in multiple-relay network-part I: Proposed scheme and single-antenna networks

This paper studies the setup of a multiple-relay network in which K half-duplex multiple-antenna relays assist in the transmission between a/several multiple-antenna source(s) and a multiple-antenna destination. Each two nodes are assumed to be either connected through a quasi-static Rayleigh fading channel, or disconnected. This paper is comprised of two parts. In this part of the paper, we propose a new scheme, which we call random sequential (RS), based on the amplify-and-forward relaying. We derive diversity-multiplexing tradeoff (DMT) of the proposed RS scheme for general single-antenna multiple-relay networks. As a result, we show that for single-antenna two-hop multiple-access multiple-relay (K > 1) networks (without direct link between the source(s) and the destination), the proposed RS scheme achieves the optimum DMT. However, for the case of multiple access single relay setup, we show that the RS scheme reduces to the naive amplify-and-forward relaying and is not optimum in terms of DMT, while the dynamic decode-and-forward scheme is shown to be optimum for this scenario.