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This paper proposes an extrinsic information transfer (EXIT) chart analysis and an asymptotic bit error rate (BER) prediction method to speed up the design of high rate RCM-LDGM hybrid codes over AWGN and fast Rayleigh channels. These codes are based on a parallel concatenation of a rate compatible modulation (RCM) code with a lowdensity generator matrix (LDGM) code. The decoder uses the iterative sum-product algorithm to exchange information between the variable nodes (VNs) and the two types of constituent check nodes: RCM-CN and LDGM-CN. The novelty of the proposed EXIT chart procedure lies on the fact that it mixes together the analog RCM check nodes with the digital LDGM check nodes, something not possible in previous multi-edge EXIT charts proposed in the literature.

In this paper, we look at the problem of implementing high-throughput Joint Source- Channel (JSC) coding schemes for the transmission of binary sources with memory over AWGN channels. The sources are modeled either by a Markov chain (MC) or a hidden Markov model (HMM). We propose a coding scheme based on the Burrows-Wheeler Transform (BWT) and the parallel concatenation of Rate-Compatible Modulation and Low-Density Generator Matrix (RCM-LDGM) codes. The proposed scheme uses the BWT to convert the original source with memory into a set of independent non-uniform Discrete Memoryless (DMS) binary sources, which are then separately encoded, with optimal rates, using RCM-LDGM codes.

In this paper we consider the problem of transmitting spatially Correlated Information Sources (CIS) over the Additive White Gaussian Noise (AWGN) Multiple Access Channel (MAC) with transmitted energy constraint. It is well known that the system performance is optimized if the codewords are designed to take advantage of the correlation among sources in the multiple access channel. To that end, we make use of Rate Compatible Modulation (RCM) codes, whose sparse nature is advantageous to preserve the source correlation in the MAC. In order to exploit the source correlation, the proposed RCM-CIS system is comprised of a set of RCM codes that share the same random structure but with each code having its own weight values that are jointly designed. At the receiver, non-binary decoding is applied to avoid short length cycles that arise in the factor graph, which is obtained by jointly considering the source correlation and the RCM codes. Simulation results show that for high throughput transmission rate RCM-CIS has good performance in terms of the BER vs SNR, attaining values below the Shannon limit if source-channel separation is assumed. As shown by the numerical results, the proposed RCM system inherits the high error floors encountered in point-to-point RCM codes. In order to lower the error floor, we propose the use of a Low Density Generation Matrix (LDGM) code in parallel with the proposed RCM structure. The LDGM system transmits a small fraction of the total coded sequence, and it is capable of correcting the residual errors produced by the RCM-CIS system.