Design of network-coding based multi-edge type LDPC codes for multi-source relaying systems

TL;DR

This paper introduces a novel network-coded multi-edge type LDPC scheme for multi-source relay systems, demonstrating improved thresholds and mutual information over existing schemes through EXIT analysis.

Contribution

It proposes a new NCMET-LDPC scheme that leverages network coding for multi-source relay systems, enhancing performance beyond direct extensions of single-source LDPC schemes.

Findings

NCMET-LDPC achieves higher extrinsic mutual information.

The scheme attains a higher decoding threshold.

EXIT analysis confirms performance improvements.

Abstract

In this paper we investigate a multi-source LDPC scheme for a Gaussian relay system, where M sources communicate with the destination under the help of a single relay (M-1-1 system). Since various distributed LDPC schemes in the cooperative single-source system, e.g. bilayer LDPC and bilayer multi-edge type LDPC (BMET-LDPC), have been designed to approach the Shannon limit, these schemes can be applied to the $M-1-1$ system by the relay serving each source in a round-robin fashion. However, such a direct application is not optimal due to the lack of potential joint processing gain. In this paper, we propose a network coded multi-edge type LDPC (NCMET-LDPC) scheme for the multi-source scenario. Through an EXIT analysis, we conclude that the NCMET-LDPC scheme achieves higher extrinsic mutual information, relative to a separate application of BMET-LDPC to each source. Our new NCMET-LDPC scheme thus achieves a higher threshold relative to existing schemes.