On the Achievable Rates of the Diamond Relay Channel with Conferencing Links

TL;DR

This paper analyzes the achievable communication rates in a half-duplex diamond relay channel with rate-limited conferencing links, exploring decode-and-forward, compress-and-forward, and amplify-and-forward schemes, and identifying conditions for capacity achievement.

Contribution

It introduces and compares three relaying schemes with conferencing, deriving achievable rates and capacity conditions for the diamond relay channel.

Findings

Decode-and-forward achieves capacity with common and private messages.

Compress-and-forward benefits from conferencing for better compression and cooperation.

Amplify-and-forward's optimal combining enhances relay performance.

Abstract

We consider a half-duplex diamond relay channel, which consists of one source-destination pair and two relay nodes connected with two-way rate-limited out-of-band conferencing links. Three basic schemes and their achievable rates are studied: For the decode-and-forward (DF) scheme, we obtain the achievable rate by letting the source send a common message and two private messages; for the compress-and-forward (CF) scheme, we exploit the conferencing links to help with the compression of the received signals, or to exchange messages intended for the second hop to introduce certain cooperation; for the amplify-and-forward (AF) scheme, we study the optimal combining strategy between the received signals from the source and the conferencing link. Moreover, we show that these schemes could achieve the capacity upper bound under certain conditions. Finally, we evaluate the various rates for the Gaussian case with numerical results.