Performance of Joint Channel and Physical Network Coding Based on Alamouti STBC

This work considers the protograph-coded physical network coding (PNC) based on Alamouti space-time block coding (STBC) over Nakagami-fading two-way relay channels, in which both the two sources and relay possess two antennas. We first propose a novel precoding scheme at the two sources so as to implement the iterative decoder efficiently at the relay. We further address a simplified updating rule of the log-likelihood-ratio (LLR) in such a decoder. Based on the simplified LLR-updating rule and Gaussian approximation, we analyze the theoretical bit-error-rate (BER) of the system, which is shown to be consistent with the decoding thresholds and simulated results. Moreover, the theoretical analysis has lower computational complexity than the protograph extrinsic information transfer (PEXIT) algorithm. Consequently, the analysis not only provides a simple way to evaluate the error performance but also facilitates the design of the joint channel-and-PNC (JCNC) in wireless communication scenarios.Comment: 6 pages, 4 figures, accpete

Design and Analysis of Protograph-based LDPC Codes in Shallow Water Acoustic Channels

原模图低密度奇偶校验码相较于传统LDPC码,具有结构简单、迭代译码门限低、易于扩展及线性编译码复杂度等优点。针对强多途、长时延、窄带宽的浅海水声信道,该文研究了PG-LDPC码的设计及性能特征,提出一种码型设计方案,并采用基于原模图度分布的外部信息转移图算法,对所设计PG-LDPC码的纠错性能进行分析及预测。仿真与实验结果表明,与(3,6)随机规则LDPC码相比,所提的PG-LDPC码在低、高信噪比区域均有良好的纠错性能。Proto Graph-based Low Density Parity Check(PG-LDPC) codes have many advantages over the conventional LDPC codes, such as simple structure, low iterative decoding threshold, easy extension and linear encoding/decoding complexity. After investigating the characteristics of PG-LDPC codes over the Shallow Water Acoustic(SWA) channels, which have the features of strong multipath interference, long delay spreading and limited bandwidth, a new design scheme to search for good codes is proposed. Furthermore, protographdegree-distribution-based EXtrinsic Information Transfer(EXIT) chart algorithm is used to predict and analyze the error performances of protograph-based LDPC codes. The simulation and experiment results show that the proposed code outperforms the(3, 6) randomly regular LDPC code in both low and high SNR region, over the SWA channels.国家自然科学基金(41176032;41376040;41476026);; 教育部高等学校博士学科点专项科研基金(20130121120033);; 中央高校基本科研业务费专项资金/厦门大学基础创新科研基金(20720140506)~

Near-capacity fixed-rate and rateless channel code constructions

Fixed-rate and rateless channel code constructions are designed for satisfying conflicting design tradeoffs, leading to codes that benefit from practical implementations, whilst offering a good bit error ratio (BER) and block error ratio (BLER) performance. More explicitly, two novel low-density parity-check code (LDPC) constructions are proposed; the first construction constitutes a family of quasi-cyclic protograph LDPC codes, which has a Vandermonde-like parity-check matrix (PCM). The second construction constitutes a specific class of protograph LDPC codes, which are termed as multilevel structured (MLS) LDPC codes. These codes possess a PCM construction that allows the coexistence of both pseudo-randomness as well as a structure requiring a reduced memory. More importantly, it is also demonstrated that these benefits accrue without any compromise in the attainable BER/BLER performance. We also present the novel concept of separating multiple users by means of user-specific channel codes, which is referred to as channel code division multiple access (CCDMA), and provide an example based on MLS LDPC codes. In particular, we circumvent the difficulty of having potentially high memory requirements, while ensuring that each user’s bits in the CCDMA system are equally protected. With regards to rateless channel coding, we propose a novel family of codes, which we refer to as reconfigurable rateless codes, that are capable of not only varying their code-rate but also to adaptively modify their encoding/decoding strategy according to the near-instantaneous channel conditions. We demonstrate that the proposed reconfigurable rateless codes are capable of shaping their own degree distribution according to the nearinstantaneous requirements imposed by the channel, but without any explicit channel knowledge at the transmitter. Additionally, a generalised transmit preprocessing aided closed-loop downlink multiple-input multiple-output (MIMO) system is presented, in which both the channel coding components as well as the linear transmit precoder exploit the knowledge of the channel state information (CSI). More explicitly, we embed a rateless code in a MIMO transmit preprocessing scheme, in order to attain near-capacity performance across a wide range of channel signal-to-ratios (SNRs), rather than only at a specific SNR. The performance of our scheme is further enhanced with the aid of a technique, referred to as pilot symbol assisted rateless (PSAR) coding, whereby a predetermined fraction of pilot bits is appropriately interspersed with the original information bits at the channel coding stage, instead of multiplexing pilots at the modulation stage, as in classic pilot symbol assisted modulation (PSAM). We subsequently demonstrate that the PSAR code-aided transmit preprocessing scheme succeeds in gleaning more information from the inserted pilots than the classic PSAM technique, because the pilot bits are not only useful for sounding the channel at the receiver but also beneficial for significantly reducing the computational complexity of the rateless channel decoder

Design and Performance Analysis of Protograph LDPC Codes

1963年，R.Gallager首次提出了一种性能优秀的纠错码—低密度奇偶校验(Low-Density-Parity-Check,LDPC)码。这种码型在信度传播(BeliefPropagation,BP)译码算法下的纠错性能非常接近香农限，并已被广泛应用在各种通信标准之中。然而，传统LDPC码存在一些固有的缺陷，如编译码复杂度高、存在错误地板及码率不可扩展等。最近，美国空气动力实验室(JetPropulsionLaboratory,JPL)提出了一类新型LDPC码—原模图LDPC码。原模图LDPC码克服了传统LDPC码的诸多缺点，不仅具有优秀的纠错性能，而且能够实现线性编译码。基于以上优点，...As a superior error-correction code, low-density-parity-check (LDPC) code was first proposed by R. Gallager in 1963. Exploiting the belief propagation (BP) decoding algorithm, LDPC codes can perform very close to the Shannon limit and hence have been widely used in many communication standards. However, the conventional LDPC codes possess some drawbacks, e.g., relatively high encoding/decoding com...学位：工学博士院系专业：信息科学与技术学院_通信与信息系统学号：2332010015404