Protocols and Performance Limits for Half-Duplex Relay Networks

TL;DR

This paper introduces and evaluates protocols for half-duplex relay channels, analyzing their performance limits and demonstrating the dominance of compress-and-forward strategies over decode-and-forward in practical Gaussian systems.

Contribution

It presents a new hybrid protocol combining compress-and-forward and decode-and-forward relays, and analyzes the performance limits of various protocols under realistic orthogonality constraints.

Findings

Compress-and-forward protocols outperform decode-and-forward in many scenarios.

A hybrid protocol with one compress-and-forward and one decode-and-forward relay is proposed.

Random channel access offers minimal performance improvements in practical systems.

Abstract

In this paper, protocols for the half-duplex relay channel are introduced and performance limits are analyzed. Relay nodes underly an orthogonality constraint, which prohibits simultaneous receiving and transmitting on the same time-frequency resource. Based upon this practical consideration, different protocols are discussed and evaluated using a Gaussian system model. For the considered scenarios compress-and-forward based protocols dominate for a wide range of parameters decode-and-forward protocols. In this paper, a protocol with one compress-and-forward and one decode-and-forward based relay is introduced. Just as the cut-set bound, which operates in a mode where relays transmit alternately, both relays support each other. Furthermore, it is shown that in practical systems a random channel access provides only marginal performance gains if any.