Diversity-Multiplexing Tradeoff in Multi-Antenna Multi-Relay Networks: Improvements and Some Optimality Results

TL;DR

This paper demonstrates that using random unitary matrix multiplication at relay nodes enhances the diversity-multiplexing tradeoff in multi-antenna relay networks, achieving optimal or improved DMT in various configurations.

Contribution

It introduces a novel relay scheme employing random unitary matrices that improves DMT performance over traditional AF relaying in multi-antenna networks.

Findings

RS scheme achieves optimal DMT in single-relay two-hop networks.

New achievable DMT for multi-antenna half-duplex parallel relay networks.

Improved DMT bounds for multi-antenna full-duplex relay networks.

Abstract

This paper investigates the benefits of Amplify-and-Forward (AF) relaying in the setup of multi-antenna wireless networks. The concept of Random Sequential (RS) relaying is previously introduced in the literature and showed that it achieves the maximum diversity gain in a general multi-antenna network. Here, we show that random unitary matrix multiplication at the relay nodes empowers the RS scheme to achieve a better Diversity-Multiplexing Tradeoff (DMT) as compared to the traditional AF relaying. First, we study the case of a multi-antenna full-duplex single-relay two-hop network, for which we show that the RS achieves the optimum DMT. Applying this result, we derive a new achievable DMT for the case of multi-antenna half-duplex parallel relay network. Interestingly, it turns out that the DMT of the RS scheme is optimum for the case of multi-antenna two parallel non-interfering half-duplex relays. Next, we show that random unitary matrix multiplication also improves the DMT of the Non-Orthogonal AF relaying scheme in the case of a multi-antenna single relay channel. Finally, we study the general case of multi-antenna full-duplex relay networks and derive a new lower-bound on its DMT using the RS scheme.