Cross-Layer Link Adaptation Design for Relay Channels with Cooperative ARQ Protocol

TL;DR

This paper proposes a cross-layer adaptive modulation, coding, and power control scheme for relay channels with cooperative ARQ, improving spectral efficiency while maintaining packet loss constraints.

Contribution

It introduces a novel cross-layer adaptation method for C-ARQ relay channels with closed-form efficiency expressions and an iterative optimization algorithm.

Findings

Enhanced spectral efficiency compared to existing schemes

Guarantees of packet loss rate constraints

Reduced average power consumption

Abstract

The cooperative automatic repeat request (C-ARQ) is a link layer relaying protocol which exploits the spatial diversity and allows the relay node to retransmit the source data packet to the destination, when the latter is unable to decode the source data correctly. This paper presents a cross-layer link adaptation design for C-ARQ based relay channels in which both source and relay nodes employ adaptive modulation coding and power adaptation at the physical layer. For this scenario, we first derive closed-form expressions for the system spectral efficiency and average power consumption. We then present a low complexity iterative algorithm to find the optimized adaptation solution by maximizing the spectral efficiency subject to a packet loss rate (PLR) and an average power consumption constraint. The results indicate that the proposed adaptation scheme enhances the spectral efficiency noticeably when compared to other adaptive schemes, while guaranteeing the required PLR performance.