Cooperative Multiplexing in a Half Duplex Relay Network: Performance and Constraints

TL;DR

This paper demonstrates that a half-duplex relay network can achieve multiplexing gains comparable to MIMO systems by employing successive relaying and space-time coding, balancing diversity and data rate improvements.

Contribution

It introduces a novel successive relaying protocol and distributed coding architecture that enable multiplexing gains in relay networks, expanding their performance capabilities.

Findings

Achieves a lower bound on diversity multiplexing tradeoff similar to 2x2 MIMO.

Develops a distributed D-BLAST architecture for relay networks.

Proposes a space-time coding strategy for higher multiplexing gains.

Abstract

Previous work on relay networks has concentrated primarily on the diversity benefits of such techniques. This paper explores the possibility of also obtaining multiplexing gain in a relay network, while retaining diversity gain. Specifically, consider a network in which a single source node is equipped with one antenna and a destination is equipped with two antennas. It is shown that, in certain scenarios, by adding a relay with two antennas and using a successive relaying protocol, the diversity multiplexing tradeoff performance of the network can be lower bounded by that of a 2 by 2 MIMO channel, when the decode-and-forward protocol is applied at the relay. A distributed D-BLAST architecture is developed, in which parallel channel coding is applied to achieve this tradeoff. A space-time coding strategy, which can bring a maximal multiplexing gain of more than one, is also derived for this scenario. As will be shown, while this space-time coding strategy exploits maximal diversity for a small multiplexing gain, the proposed successive relaying scheme offers a significant performance advantage for higher data rate transmission. In addition to the specific results shown here, these ideas open a new direction for exploiting the benefits of wireless relay networks.