Bit-interleaved coded modulation with iterative decoding (BICM-ID) is a key technology enabling communication systems to realize high-throughput and high-reliability. In contrast to previous studies focused exclusively on uniformly distributed sources, this work investigates irregular mapping (IM)-based BICM-ID systems for sources with non-uniform distributions. First, a density evolution (DE) algorithm based on Gaussian weighted mixture approximation (GWMA) is put forward to estimate the convergence performance of the IM-BICM-ID systems with non-uniform sources, where the probability density function of the log-likelihood ratio messages output from the bit-level channels in this system is neither Gaussian nor symmetric. Then, by employing the GWMA-DE algorithm and the achievable system rates analysis, a design strategy for optimal IM labelings is established, which utilizes the inherent redundancy in non-uniform sources to achieve shaping gains. Furthermore, channel codes tailored to the proposed IM labelings are designed to further improve the bit error rate performance. Both analytical results and simulations indicate that the proposed labelings and codes outperform existing counterparts in IM-BICM-ID systems with non-uniform sources.

Recent studies have shown that analog joint source-channel coding (AJSCC) is capable of approaching the optimum performance theoretically attainable (OPTA). However, it would be costly to transmit the continuous output of AJSCC. This paper proposes a two-dimensional (2D) quantization-based modulation scheme to map the discrete-time real-valued source encoder output into a finite set of 2D constellation points for modulated transmission. To minimize the resultant quantization distortion, the constellation is optimized by constructing a centroidal Voronoi diagram that can best match the distribution of the source encoder output under power transformation. Based on a comprehensive analysis of effects of encoder configuration and power transformation in connection with the channel condition, an algorithm is presented for jointly optimizing the source encoder and the constellation, with the objective of maximizing the system performance in terms of the end-to-end signal-to-distortion ratio (SDR) with respect to the channel condition in terms of signal-to-noise ratio (SNR). Simulation results show that under joint optimization, the modulated AJSCC system improves as the modulation order increases, and it tends to approach the benchmark performance of the unmodulated system that is close to the OPTA. More practically, the modulated AJSCC system is robust to tolerate imperfect channel estimation to some extent. This work provides a promising way of enabling a source-oriented AJSCC system to access digital communication networks.

In this paper, we propose a polarization-aided polar coding scheme over non-orthogonal multiple access channels operated with physical-layer network coding (PN-NOMA), where M users adopt polar coding for transmission. By exploiting the characteristic of PNC and polar encoding, we found that the polar code at the users can be seen as nested codes and sub-codeword of a larger polar code. It enables us to construct a single (virtual) polar code at the receiver, which has the length M times longer than that of the original user codes. In this way, we can decode all the user messages within this single polar code. The channel polarization effect as well as the decoding performance can be improved. We further propose a Monte Carlo-based code construction for the virtual polar code with user channel coefficients, and short nested user codes can be individually derived from this code. Simulation results show that the proposed PN-NOMA can achieve significant performance gains of more than 0.5 dB as compared to conventional polar-coded NOMA (PC-NOMA) over power-imbalanced channels, and this gain is more than 2 dB over Rayleigh fading channels.

This paper investigates the possibilities of optimizing existing protograph low-density parity-check (PLDPC) codes and designing optimal PLDPC codes on both AWGN and Rayleigh channels under binary modulation with unequal power allocation (UPA) for nonuniform sources. While the binary UPA modulation achieves a power gain, it also results in unequal error protection on the coded bits in systematic codewords during transmission. For irregular codes, it is possible to best protect the information bits by optimizing the classification of variable nodes (VNs). Those VNs represent the coded bits in protograph that allows exploiting jointly the degree irregularity and the power differentiation. An algorithm for UPA-based protograph extrinsic information transfer (UPA-PEXIT) analysis on the Rayleigh channel is proposed with the concept of surrogate channel which circumvents the channel asymmetry problem with UPA. With the RJA code as example, it is shown that classification optimization does improve the decoding threshold when the source entropy is small. To design optimal codes, a UPA-based differential evolution (UPA-DE) algorithm is proposed in conjunction with the UPA-PEXIT analysis. A family of optimized codes are illustrated for three typical nonuniform source distributions and compared with the RJA and NND codes by simulations in error rate performance.

Probabilistic amplitude shaping (PAS) has proved to be a promising way to achieve the shaping gain for an additive white Gaussian noise channel with a distribution matcher (DM). However, the DM schemes may suffer a rate loss and increase both complexity and latency, when they are not suited for the input bit stream with redundancy. In this paper, a novel PAS strategy is proposed for a joint source and channel coded modulation system, where the residual source redundancy after source coding can be exploited to obtain both shaping and coding gains. It is shown that the residual source redundancy can be controlled by choosing the row weight distribution for source code, thus making the probability distribution of the modulated symbols be optimized under an appropriate interleaver design. To guarantee the error-floor performance, the source code is constrained by predicting the probability distribution of source bits within target finite-length frames. By jointly designing source and channel codes, the residual source redundancy can also be exploited to achieve the coding gain. Compared with the state-of-the-art code pairs, the proposed code pairs have better error-floor performance, and achieve higher coding and shaping gains without suffering from the rate-loss and the latency caused by DM.

In this paper, we propose a constellation-based differential chaotic bit-interleaved coded modulation system with iterative receiver (DC-BICM-IR) over power line channels (PLCs) and then design a new protograph-based low density parity check (P-LDPC) code for the system.

In this study, two generalised carrier index M ‐ary differential chaos shift keying (CI‐MDCSK) schemes are proposed, which combine index modulation with multicarrier M ‐ary DCSK (MC‐MDCSK). At the transmitter, two different index selectors based on two different mapping rulers are employed to select active carriers, where the modulated bits are transmitted by the active carriers through M ‐ary DCSK modulation, which is based on the Hilbert transform and constellation theory. At receiver, maximum or minimum energy detection is employed to determine the active carriers, where the bits carried on these active carriers are demodulated. The analytical bit error rate (BER) expressions over additive white Gaussian noise as well as multipath Rayleigh fading channels are derived. Simulations are performed with different numbers of carriers and different constellation sizes. Both analytical and simulation results show the superiority of the new schemes in BER performance or spectral efficiency (SE) compared with the MC‐MDCSK scheme. Moreover, compared with conventional DCSK, CI‐MDCSK schemes owns both better BER performance and SE in some cases, where the constellation is not greater than 8.

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.