Protograph Extrinsic Information Transfer Research Articles

Image Transmission Based on QC-LDPC Codes with Simple Recursive Encoding Form

Low encoding delay and complexity is very important for image transmission. This paper proposes a novel image transmission scheme with low encoding complexity. The proposed scheme is based on quasi-cyclic low density parity check (QC-LDPC) codes with a simple recursive encoding form (SREF QC-LDPC code) which results in low encoding complexity and delay. Constructing the SREF QC-LDPC codes in this scheme composes of two main steps, construction of the base matrix and the exponent matrix. We combine the differential evolution and protograph extrinsic information transfer (PEXIT) method to optimize the base matrix of QC-LDPC code. Consequently, the exponent matrix and the parity check matrix are constructed. Simulation results show that the proposed scheme based on SREF QC-LDPC code can provide a good tradeoff between the performance and complexity.

Performance of Joint Source-Channel Coding Based on Protograph LDPC Codes over Rayleigh Fading Channels

This letter presents a joint protograph extrinsic information transfer (PEXIT) analysis for joint source and channel coding (JSCC) with double protograph-based low-density parity-check (DP_LDPC) codes over single-input multiple-output (SIMO) Rayleigh fading channels. The impacts of source statistics and receive antenna diversity on convergence performance for the JSCC are investigated, and we find that source sparsity plays a more vital role than diversity orders in improving both convergence and error performances under fading environments.

Optimization of Protograph-Based LDPC Coded BICM-ID for the Poisson PPM Channel

Protograph-based LDPC coded bit-interleaved coded modulation (BICM) schemes are able to achieve near Shannon-limit performance over the additive white Gaussian noise (AWGN) channel. However, the performance of protograph-based BICM and BICM with iterative decoding (BICM-ID) schemes over the Poisson pulse-position modulation (PPM) channel has not been adequately studied. In this work, we investigate and optimize the performance of protograph-based BICM-ID schemes for the Poisson PPM channel. We propose a modified protograph extrinsic information transfer (PEXIT) algorithm and construct an optimized protograph code for the BICM-ID schemes. Threshold analysis and simulation results demonstrate that, for the case of BICM-ID, our proposed code is superior to existing protograph codes, achieving a threshold within a gap of 0.6 dB to the capacity.

Performance analysis of protograph-based low-density parity-check codes with spatial diversity

In wireless communications, spatial diversity techniques, such as space-time block code and single-input multiple-output (SIMO), are employed to strengthen the robustness of the transmitted signal against channel fading. This article studies the performance of protograph-based low-density parity-check (LDPC) codes with receive antenna diversity. The authors first propose a modified version of the protograph extrinsic information transfer algorithm and use it for deriving the threshold of the protograph codes in a SIMO system. The authors then calculate the decoding threshold and simulate the bit-error rate (BER) of two protograph codes (accumulate-repeat-by-3-accumulate (AR3A) code and accumulate-repeat-by-4-jagged-accumulate (AR4JA) code), a regular (3,6) LDPC code and two optimised irregular LDPC codes. The results reveal that the irregular codes achieve the best error performance in the low signal-to-noise-ratio (SNR) region and the AR3A code outperforms all other codes in the high-SNR region. Utilising the theoretical analyses and the simulated results, the authors further discuss the effect of the diversity order on the performance of the protograph codes. Accordingly, the AR3A code stands out as a good candidate for wireless communication systems with multiple receive antennas.

Construction of quasi‐cyclic low‐density parity‐check codes with low encoding complexity

SUMMARYLow encoding complexity is very important for quasi‐cyclic low‐density parity‐check (QC‐LDPC) codes used in wireless communication systems. In this paper, a new scheme is presented to construct QC‐LDPC codes with low encoding complexity. This scheme is called two‐stage particle swarm optimization (TS‐PSO) algorithm, in which both the threshold and girth distribution of QC‐LDPC codes are considered. The proposed scheme is composed of two stages. In the first stage, we construct a binary base matrix of QC‐LDPC code with the best threshold. The matrix is constructed by combining a binary PSO algorithm and the protograph extrinsic information transfer (PEXIT) method. In the second stage, we search an exponent matrix of the QC‐LDPC code with the best girth distribution. This exponent matrix is based on the base matrix obtained in the first stage. Consequently, the parity‐check matrix of the QC‐LDPC code with the best threshold and best girth distribution are constructed. Furthermore, bit error rate performances are compared for the QC‐LDPC codes constructed by proposed scheme, the QC‐LDPC code in 802.16e standard, and the QC‐LDPC code in Tam's study. Simulation results show that the QC‐LDPC codes proposed in this study are superior to both the 802.16e code and the Tam code on the additive white Gaussian noise (AWGN) and Rayleigh channels. Moreover, proposed scheme is easily implemented, and is flexible and effective for constructing QC‐LDPC codes with low encoding complexity. Copyright © 2012 John Wiley & Sons, Ltd.

Optimizing Protograph Coded BICM for Half-Duplex DF Relay

In this letter, we use the the protograph low-density parity check (LDPC) codes to create bit-interleaved coded modulation (BICM) for the half-duplex decode-and-forward (DF) relay network. The DF relay BICM design problem can be transformed into a problem of rate-compatible BICM design, where the different segments of modulated symbols experience different signal-to-noise ratios (SNRs). To optimize the BICM based on the protograph structure, we use the protograph extrinsic information transfer (EXIT) to evaluate the thresholds of different mapping patterns between the variable nodes and the modulated bits. With this tool, we search for the most efficient mapping pattern of BICM for the half-duplex DF relay network. Our work can achieve significant gains over the existing work.