Bilayer Protograph Codes for Half-Duplex Relay Channels

TL;DR

This paper introduces a novel protograph-based LDPC coding scheme for half-duplex relay channels that is adaptable, easy to design, low in complexity, and performs near capacity with reasonable block lengths.

Contribution

It proposes a structured LDPC coding scheme that addresses design flexibility, low encoding complexity, and near-capacity performance for relay channels and networks.

Findings

Performance close to capacity with reasonable block length

Easy to adapt to various channel conditions

Demonstrated application to multi-relay networks

Abstract

Despite encouraging advances in the design of relay codes, several important challenges remain. Many of the existing LDPC relay codes are tightly optimized for fixed channel conditions and not easily adapted without extensive re-optimization of the code. Some have high encoding complexity and some need long block lengths to approach capacity. This paper presents a high-performance protograph-based LDPC coding scheme for the half-duplex relay channel that addresses simultaneously several important issues: structured coding that permits easy design, low encoding complexity, embedded structure for convenient adaptation to various channel conditions, and performance close to capacity with a reasonable block length. The application of the coding structure to multi-relay networks is demonstrated. Finally, a simple new methodology for evaluating the end-to-end error performance of relay coding systems is developed and used to highlight the performance of the proposed codes.