Article

# Design of low-density parity-check codes for modulation and detection

Bell Labs., Crawford, NJ, USA

IEEE Transactions on Communications (Impact Factor: 1.75). 05/2004; DOI: 10.1109/TCOMM.2004.826370 Source: DBLP

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**ABSTRACT:**The accuracy of the side information (SI) is critical in the performance of distributed video coding algorithms. The SI is typically built at a decoder based on the reconstructed data and on channel coding parity bits transmitted by the encoder. The optimal encoding rate is generally difficult to compute precisely due to the dynamics of video content with varying correlation. Effective methods for the refinement of imprecise SI are therefore important for improved decoding quality. In this paper, we propose to exploit the intrinsic property of channel coding algorithms in Wyner-Ziv video coding. The SI is refined via both the information-plane and the parity-plane bits, which rapidly increases the accuracy of refined SI. We use extrinsic information transfer chart analysis in order to estimate the variations of the mutual information in the iterative decoding. In particular, we characterize mutual information variations for punctured regular and irregular rate-compatible low-density parity-check codes. Tracking the mutual information changes permits to decrease the coding rate of the information and parity bitstreams, while preserving the decoding quality. Simulation results confirm that our method improves on the decoding quality of recent distributed video coding algorithms, especially for high-motion sequences or at high-coding rate regimes.IEEE Transactions on Circuits and Systems for Video Technology 01/2014; 24(1):141-156. · 1.82 Impact Factor -
##### Article: M-ary Detection and q-ary Decoding in Large-Scale MIMO: A Non-Binary Belief Propagation Approach

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**ABSTRACT:**In this paper, we propose a non-binary belief propagation approach (NB-BP) for detection of $M$-ary modulation symbols and decoding of $q$-ary LDPC codes in large-scale multiuser MIMO systems. We first propose a message passing based symbol detection algorithm which computes vector messages using a scalar Gaussian approximation of interference, which results in a total complexity of just $O(KN\sqrt{M})$, where $K$ is the number of uplink users and $N$ is the number of base station (BS) antennas. The proposed NB-BP detector does not need to do a matrix inversion, which gives a complexity advantage over MMSE detection. We then design optimized $q$-ary LDPC codes by matching the EXIT charts of the proposed detector and the LDPC decoder. Simulation results show that the proposed NB-BP detection-decoding approach using the optimized LDPC codes achieve significantly better performance (by about 1 dB to 7 dB at $10^{-5}$ coded BER for various system loading factors with number of users ranging from 16 to 128 and number of BS antennas fixed at 128) compared to using linear detectors (e.g., MMSE detector) and off-the-shelf $q$-ary irregular LDPC codes. Also, even with estimated channel knowledge (e.g., with MMSE channel estimate), the performance of the proposed NB-BP detector is better than that of the MMSE detector.10/2013; - [Show abstract] [Hide abstract]

**ABSTRACT:**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.IEEE Communications Letters 01/2014; 18(4):652-655. · 1.16 Impact Factor

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