Double Protograph Low-density Parity-check Codes Research Articles

Global Design of Double Protograph LDPC Codes for Joint Source-Channel Coding

In this letter, a global design of double protograph low-density parity-check (DP-LDPC) codes is proposed for joint source-channel coding (JSCC) system. The maximum number of degree-2 variable nodes (VNs), which is very important for the performance of the system, is determined from a global perspective that considers the joint protograph as a whole. Based on the allocation of degree-2 VNs, the new guidelines with this more comprehensive perspective are summarized and the global optimized DP-LDPC codes are designed. The simulation results that are in consistent with the joint protograph extrinsic information transfer (P-EXIT) analysis indicate that the optimized DP-LDPC codes have better performance compared with the existing re-designed DP-LDPC codes.

Joint Component Design for the JSCC System Based on DP-LDPC Codes

The joint base matrix ${{{{B}}_{{\mathrm{J}}}}}$ of the joint source-channel coding (JSCC) system based on double protograph low-density parity-check (DP-LDPC) codes consists of four components, namely, the source code ${{{{B}}_{{\mathrm{s}}}}}$ , the channel code ${{{{B}}_{{\mathrm{c}}}}}$ , the type-1 connection edge ${{{{B}}_{{ \textit {L1}}}}}$ and the type-2 connection edge ${{{{B}}_{{ \textit {L2}}}}}$ , each having a non-negligible influence on the system performance. Different from the traditional component-specific design approach, we propose a joint design and optimization algorithm based on the idea of multi-objective differential evolution (MODE). Specifically, we consider the optimization of the DP-LDPC JSCC system through joint design of three components ${{{{B}}_{{\mathrm{s}}}}}$ , ${{{{B}}_{{\mathrm{c}}}}}$ , ${{{{B}}_{{ \textit {L1}}}}}$ and all four components ${{{{B}}_{{\mathrm{s}}}}}$ , ${{{{B}}_{{\mathrm{c}}}}}$ , ${{{\mathbf{B}}_{{ \textit {L1}}}}}$ , ${{{{B}}_{{ \textit {L2}}}}}$ , respectively. The proposed algorithm has low search complexity due to the reduction in size and element value of base matrices. The joint protograph extrinsic information transfer (JPEXIT) analyses and the simulation results demonstrate that the resulting JSCC system is free from a high error floor, requires fewer number of iterations for reaching the same bit error rate (BER) and achieves significant coding gains as compared to the state-of-the-art. Our DP-LDPC JSCC system is also shown to outperform its separation-based counterpart by a wide margin.

Design and Analysis of Joint Source Channel Coding Schemes Over Non-Standard Coding Channels

Although a mountain of work on joint source-channel coding (JSCC) scheme over standard coding channels (a combination of BPSK modulation and AWGN channels) have been studied deeply, there has been no knowledge about JSCC over non-standard coding channels. In this paper, a JSCC scheme based on double protograph low-density parity-check (DP-LDPC) codes is proposed over non-standard coding channels which consists of M -ary differential chaos shift keying (DCSK) and Rayleigh fading channels is proposed, named as JSCC-DCSK system. A joint protograph extrinsic information transform (JPEXIT) algorithm is proposed to analyze the decoding threshold of DP-LDPC codes on the non-standard coding channels. Considering the effects from the source redundancy left by source coding and the non-linear property of non-standard coding channels, the design of DP-LDPC structure is discussed, and new design principles from a global perspective are proposed. Several DP-LDPC codes for different source statistic are designed by the aid of JPEXIT algorithm and verified by Monte Carlo simulation. The appropriate number of the turbo iteration is determined to keep the bit error rate (BER) of system performance and the complexity of the receiver at a low level.

Integrated Design of JSCC Scheme Based on Double Protograph LDPC Codes System

In this letter, an integrated design of joint source-channel coding scheme based on the double protograph low-density parity-check (DP-LDPC) codes is proposed. As degree-2 variable nodes (VNs) structure plays an important role in the performance of both water-fall and error-floor regions, the maximum number of degree-2 VNs for DP-LDPC codes is determined from a global perspective. By comparing different allocation schemes for degree-2 VNs, new design principles are proposed. Several DP-LDPC codes with different numbers of degree-2 VNs are proposed. The simulated results reveal the superiority of the optimized DP-LDPC codes, which are in line with the decoding threshold analysis by a joint protograph extrinsic information transfer algorithm.

Joint Coding and Adaptive Image Transmission Scheme Based on DP-LDPC Codes for IoT Scenarios

For wireless image communication in the Internet of Things (IoT) scenarios, fast and low error coding and transmission mechanisms are imperative. The joint source-channel coding scheme based on the double protograph low-density parity-check (DP-LDPC) codes would be a potential candidate due to the low complexity and good error performance. However, the error floor performance of DP-LDPC codes may deteriorate for source sequences with higher source probabilities or shorter block lengths. This paper aims to improve the traditional DP-LDPC image transmission system for the IoT scenarios from the following aspects. First, a joint optimization method of finite-length DP-LDPC codes is proposed to reduce the error floor while keeping satisfactory waterfall region performance. Second, an improved rate allocation strategy based on the fuzzy logic control is adopted to further improve the transmission reliability of the proposed short block length DP-LDPC codes. This scheme may offer some new solutions for the IoT image communication. The simulation results indicate the effectiveness of the proposed methods.

Design of Linking Matrix in JSCC Scheme Based on Double Protograph LDPC Codes

A joint source channel coding (JSCC) scheme based on source and channel low density parity check (LDPC) codes, which is named as the D-LDPC system, has attracted a lot of attention recently. However, it suffers from a high error-floor. By introducing a linking matrix connecting variable nodes of source LDPC and check nodes of channel LDPC, the error-floor can be lowered effectively. However, the water-fall performance was lost with the increasing of the size of linking matrix. In this paper, a detailed analysis about the impact of this linking matrix on the water-fall region is conducted. Some design principles for the linking matrix are proposed, by which several linking matrices for different source statistics will be designed to improve the water-fall performance from the perspective of both the source and channel LDPC codes. The extrinsic information transfer (EXIT) analysis and numerical simulations will be compared to verify the superiority of the proposed linking matrices.

Performance analysis and optimisation for edge connection of JSCC system based on double protograph LDPC codes

For a joint source-channel coding system based on double protograph low-density parity-check codes, the exchange of extrinsic information through edge connection between the source code and channel code is essential for good performance. In this study, the relationship between the performance and edge connection in the tanner graph is analysed and it has never been seen in the literature to the authors' knowledge. Both the joint protograph extrinsic information transfer and simulation results indicate that the edge connection should be optimised in practical applications since it plays an important role in the bit error rate performance and an optimisation scheme for the edge connection is put forward to enhance performance.

Matching Criterion Between Source Statistics and Source Coding Rate

Joint source-channel coding (JSCC) based on double protograph low-density parity-check (DP-LDPC) codes has been shown to be a good solution for wireless communications. However, the premature error floor region of the DP-LDPC codes usually does not meet the bit-error-rate requirements. In this letter, we provide a matching criterion between the source statistics and the source coding rate using a novel protograph extrinsic information transfer (PEXIT) algorithm with a new decoding threshold. The resulting matching criterion helps predict the error floor region performance and give directions for source coding rate designs.