Diversity-multiplexing tradeoff in multiple-relay network-part II: Multiple-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 study multiple-antenna multiple-relay network. We prove that the Random Sequential (RS) scheme proposed in achieves the maximum diversity gain in a general multiple-antenna multiple-relay network. Moreover, we show that utilizing independent random unitary matrix multiplication at the relay nodes enables the RS scheme to achieve better diversity-multiplexing tradeoff (DMT) results comparing with the traditional amplify-and-forward relaying. Indeed, using the RS scheme, we derive a new achievable DMT for the MIMO parallel relay network. Interestingly, it turns out that the DMT of the RS scheme is optimum for the MIMO half-duplex parallel 2-relay (K = 2) setup. Finally, we show that utilizing random unitary matrix multiplication also improves the DMT of the Non-Orthogonal amplify-and-forward relaying scheme of in the MIMO single relay channel.