Design of Low-Density Parity-Check Codes for Modulation and Detection

Abstract-In this paper, we propose a multiple-input multiple-output (MIMO) receiver algorithm that exploits channel hardening that occurs in large MIMO channels. Channel hardening refers to the phenomenon where the off-diagonal terms of the matrix become increasingly weaker compared to the diagonal terms as the size of the channel gain matrix increases. Specifically, we propose a message passing detection (MPD) algorithm which works with the real-valued matched filtered received vector (whose signal term becomes , where is the transmitted vector), and uses a Gaussian approximation on the off-diagonal terms of the matrix. We also propose a simple estimation scheme which directly obtains an estimate of (instead of an estimate of ), which is used as an effective channel estimate in the MPD algorithm. We refer to this receiver as the channel hardening-exploiting message passing (CHEMP) receiver. The proposed CHEMP receiver achieves very good performance in large-scale MIMO systems (e.g., in systems with 16 to 128 uplink users and 128 base station antennas). For the considered large MIMO settings, the complexity of the proposed MPD algorithm is almost the same as or less than that of the minimum mean square error (MMSE) detection. This is because the MPD algorithm does not need a matrix inversion. It also achieves a significantly better performance compared to MMSE and other message passing detection algorithms using MMSE estimate of . Further, we design optimized irregular low density parity check (LDPC) codes specific to the considered large MIMO channel and the CHEMP receiver through EXIT chart matching. The LDPC codes thus obtained achieve improved coded bit error rate performance compared to off-the-shelf irregular LDPC codes.

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“…We combine the CHEMP receiver's EXIT curves with those of the LDPC decoder, whose EXIT curves have known closed-form expressions [33]. Fig.…”

Section: B Design Of Ldpc Codes For the Joint Detector-decodermentioning

confidence: 99%

Channel hardening-exploiting message passing (CHEMP) receiver in large MIMO systems

Narasimhan

Chockalingam

2014

2014 IEEE Wireless Communications and Networking Conference (WCNC)

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“…Recall that the function F i is constituted by the sum and boxplus operations, when genarating the extrinsic LLRs. According to [9], the MI after the sum and boxplus operations between the extrinsic LLRs A and B are derived by (22) where I A and I B represent the MI for the LLRs A and B, respectively 3 . Substituting these MI calculations into (16) and (17), I β S and I β R are expressed in (23) and (24).…”

Section: B Exit Chart Analysismentioning

confidence: 99%

“…In sophisticated JCN coded systems, extrinsic information transfer (EXIT) chart analysis may be involved for visualizing the convergence behavior of the iterative detection scheme [8], [9]. Against this background, the novel contribution of this treatise is that an EXIT-chart-aided relay activation scheme is proposed for a low-complexity XOR assisted JCN code.…”

Section: Introductionmentioning

confidence: 99%

Joint channel-and-network coding using EXIT chart aided relay activation

Ibi

Sampei

Hanzo

2011

2011 IEEE Wireless Communications and Networking Conference

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Abstract-This paper presents a relay activation scheme designed for joint channel-and-network (JCN) coded systems relying on an iterative decoding. A primary focus is on proposing criteria of the relay activation to find the best user combination for cooperative relaying, which exploits extrinsic information transfer (EXIT) chart analysis. We will demonstrate that the EXIT chart aided relay activation scheme is capable of reducing the probability of outages, despite increasing the effective throughput of network.Index Terms-User cooperation, network coding, channel coding, iterative decoding, multi-hop, cooperative relaying, EXIT chart analysis. I. INTRODUCTIONUser cooperation has attracted significant research attention owing to its spatial diversity benefits [1], [2]. Relaying or multi-hop transmissions constitute the simplest form of user cooperation. However, due to the creation of the broadcast and cooperation phases, they achieve a high diversity gain at the cost of a factor two multiplexing loss. To overcome this deficiency, the adoption of network coding has been studied, where we multiplex several users' information by their algebraic superposition over a finite field [3], [4]. As a benefit of the network coding, the above-mentioned half duplex multiplexing loss is mitigated without sacrificing the diversity gain. The designs of joint channel-and-network (JCN) codes and their iterative detection have been investigated in [5]-[7]. In [5], a simple triangular topology conceived for two-user cooperation was combined with beneficial channel codes. As further advances, two-way relay channels (TWRC) and multiple-access relay channels (MARC) were investigated in [6] and [7], respectively, where a turbo-like code was constituted for transmissions over the TWRC and MARC in order to achieve a high diversity gain.The primary focus of this paper is on finding beneficial relay activation criteria for a simple triangular topology. In sophisticated JCN coded systems, extrinsic information transfer (EXIT) chart analysis may be involved for visualizing the convergence behavior of the iterative detection scheme [8], [9]. Against this background, the novel contribution of this treatise is that an EXIT-chart-aided relay activation scheme is proposed for a low-complexity XOR assisted JCN code.

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“…Extrinsic information transfer (EXIT) charts [9] are employed to optimize the degree distributions that are associated with each code rate. However, the general EXIT charts cannot be applied to compute the decoding thresholds of QC-LDPC codes with the same degree distribution.…”

Section: Introductionmentioning

confidence: 99%

Construction of Multiple-Rate QC-LDPC Codes Using Hierarchical Row-Splitting

Zhao

Wang

2016

IEEE Commun. Lett.

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Abstract-In this letter, we propose an improved method called hierarchical row-splitting with edge variation for designing multiple-rate quasi-cyclic low-density parity-check (QC-LDPC) codes, which constructs lower-rate codes from a high-rate mother code by row-splitting operations. Consequently, the obtained QC-LDPC codes with various code rates have the same blocklength and can share common hardware resources to reduce the implementation complexity. Compared with the conventional row-combining-based algorithms, a wider range of code rates are supported. Moreover, each individual rate code could be separately optimized, making it easier to find a set of multiplerate QC-LDPC codes with good performance for all different rates. Simulation results demonstrate that the obtained codes outperform the counterparts from digital video broadcastingsecond generation terrestrial.

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Design of Low-Density Parity-Check Codes for Modulation and Detection

Cited by 981 publications

References 31 publications

Channel hardening-exploiting message passing (CHEMP) receiver in large MIMO systems

Channel hardening-exploiting message passing (CHEMP) receiver in large MIMO systems

Joint channel-and-network coding using EXIT chart aided relay activation

Construction of Multiple-Rate QC-LDPC Codes Using Hierarchical Row-Splitting

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