Jointly optimized rate-compatible UEP-LDPC codes for half-duplex co-operative relay networks

Abstract

This paper addresses the design of low-density parity-check (LDPC) codes for half-duplex co-operative relay networks. Structured rate-compatible codes with unequal error protection (UEP) are designed through joint optimization of the codes for the channels between source and relay and source and destination. The proposed codes clearly outperform simpler LDPC codes which are not optimized for relay channels and puncturing-based rate-compatible LDPC codes, and they show a significant performance improvement over the direct link communication depending on the position of relay. The optimization algorithm for the proposed codes is based on density evolution using the Gaussian approximation and optimal variable node degree distributions are found through iterative linear programming. Interestingly, they anyhow show performance which is almost comparable to the performance of codes optimized through a more complex non-linear optimization algorithm. We analyze the performance of our proposed codes with short, medium and long block lengths, and with low and high rates under realistic assumptions, i.e., imperfect decoding of the codeword at relay and variant signal-to-noise ratio within a single codeword.

A Hybrid Statistical and Prioritised Unequal Error Protection Scheme for IEEE 802.11n LDPC Codes

“…At the BER of 10 -5 , the scheme achieved a gain between 0.1 and 0.5 dB [13]. Furthermore, in [14], structured rate-compatible codes with UEP were designed. The codes for the source-relay and source destination were optimized together.…”

“…The codes for the source-relay and source destination were optimized together. A significant gain was obtained over conventional LDPC codes and punctured rate compatible LDPC codes [14]. Finally, in [15], a statistical QAM based modulation scheme for low complexity video transmission was proposed.…”

Coding scheme based on multi‐dimensional constellations for relay‐assisted multi‐user system

“…Khattak et al . [2] also used RC‐LDPC to design the optimised code for source, relay and destination. Differently, unequal error protection is added in the code structure.…”

Performance assessment and design of finite length LDPC codes for the Gaussian wiretap channel

“…We also propose a twofold code optimization tool which allows to design optimal codes in terms of the considered metrics. Similar twofold code optimizations have been proposed for the relay channel [7]- [9], but no solution has been presented for the wiretap channel, at our best knowledge. We show that our approach allows to achieve great flexibility in the choice of the system parameters, as well as higher security levels with respect to previous solutions based on punctured LDPC codes [6].…”