Variable non-uniform quantized belief propagation algorithm for LDPC decoding

Non-uniform quantization for messages in Low-Density Parity-Check（LDPC）decoding can reduce implementation complexity and mitigate performance loss.But the distribution of messages varies in the iterative decoding.This letter proposes a variable non-uniform quantized Belief Propagation（BP）algorithm.The BP decoding is analyzed by density evolution with Gaussian approximation.Since the probability density of messages can be well approximated by Gaussian distribution,by the unbiased estimation of variance,the distribution of messages can be tracked during the iteration.Thus the non-uniform quantization scheme can be optimized to minimize the distortion.Simulation results show that the variable non-uniform quantization scheme can achieve better error rate performance and faster decoding convergence than the conventional non-uniform quantization and uniform quantization schemes.     

High efficient multipacket decoding approach for network coding in wireless networks

To improve the performance of transmission by reducing the number of transmission and network overhead of wireless single-hop networks, this paper presents a high efficient multipacket decoding approach for network coding (EMDNC) in wireless networks according to the idea of encoding packets which cannot be decoded and are stored in buffer by receiving nodes, the lost packets can be recovered from these encoded packets. Compared with the network coding wireless broadcasting retransmission (NCWBR), EMDNC can improve the efficiency of decoding and reduce the number of retransmission and transmission delay. Simulation results reveal that EMDNC can effectively reduce the number of retransmission and network overhead.     

A new class of linear codes with two-level structure

The binary extended Golay code has a two-level structure, which can be used in the decoding of the code. However, such structure is not limited to the Golay code, in fact, several binary linear codes can be constructed by a projective method which is related to the structure. In this correspondence, the binary (4n,n 2k, ≥min(8, n,2d)) linear codes are resulted from quaternary (n,k,d) linear block codes. Based on the structure, the efficient maximum likelihood decoding algorithms can be presented correspondingly for the derived codes.     

USERS’ TWO-DIMENSIONAL INTEREST AND ITS STORAGE METHOD

The users‘ interest can be mined from the web cache and can be used widely.The interest can be specialized by the two-tuple(term,weight) in the simple interest model,in which the association relations are not mined.and then interest cannot be associated in expressing the users‘interest.Based on analyzing the WWW cache model,this letter brings forward a twodimensional interest model and gives the interrelated methods on how to store the two-dimensional interest model effectively.     

THE PHASE—OFSET OVERLAPPED WAVE TECHNIQUE

A new digital communication technology based on the Phase-Offset Overlapped Waves (POOW) has been introduced in this letter.The waves can be considered as a special multicarrier different from traditional ones.The sud-waves in a coded word‘s period of the POOW are sine waves and have the same frequencies,but different starting phases.The most important characteristic is that these sub-waves are the piecewise functions and not orthogonal in a code word period.The decoding can be implemented by solving a linear equation group.This code has very high efficiency and thus the data transmissin rate is increased greatly.     

USERS' TWO-DIMENSIONAL INTEREST AND ITS STORAGE METHOD

The users' interest can be mined from the web cache and can be used widely. The interest can be specialized by the two-tuple (term, weight) in the simple interest model, in which the association relations are not mined, and then the interest cannot be associated in expressing the users' interest. Based on analyzing the WWW cache model, this letter brings forward a two-dimensional interest model and gives the interrelated methods on how to store the two-dimensional interest model effectively.     

An MMSE Decoding Algorithm without Matrix Inversion in QSTBC

The matrix inversion operation is needed in the MMSE decoding algorithm of orthogonal space-time block coding （OSTBC） proposed by Papadias and Foschini. In this paper, an minimum mean square error （MMSE） decoding algorithm without matrix inversion is proposed, by which the computational complexity can be reduced directly but the decoding performance is not affected.     

A novel BTC decoding algorithm based on the genetic algorithm in optical communication systems

Combining the advantages of both the genetic algorithm （GA） and the chase decoding algorithm, a novel improved decoding algorithm of the block turbo code （BTC） with lower computation complexity and more rapid decoding speed is proposed in order to meet the developing demands of optical communication systems. Compared with the traditional chase decoding algorithm, the computation complexity can be reduced and the decoding speed can be accelerated by applying the novel algorithm. The simulation results show that the net coding gain （NCG） of the novel BTC decoding algorithm is 1.1 dB more than that of the traditional chase decoding algorithm at the bit error rate （BER） of 10^-6. Therefore, the novel decoding algorithm has better decoding correction-error performance and is suitable for the BTC in optical communication systems.     

Improved Reduced Latency Soft-Cancellation Algorithm for Polar Decoding

Soft-cancellation(SCAN) is a soft output iterative algorithm widely used in polar decoding. This algorithm has better decoding performance than reduced latency soft-cancellation(RLSC) algorithm, which can effectively reduce the decoding delay of SCAN algorithm by 50% but has obvious performance loss. A modified reduced latency soft-cancellation(MRLSC) algorithm is presented in the paper. Compared with RLSC algorithm, LLR information storage required in MRLSC algorithm can be reduced by about 50%, and better decoding performance can be achieved with only a small increase in decoding delay. The simulation results show that MRLSC algorithm can achieve a maximum block error rate(BLER) performance gain of about 0.4 dB compared with RLSC algorithm when code length is 2048. At the same time, compared with the performance of several other algorithms under(1024, 512) polar codes, the results show that the throughput of proposed MRLSC algorithm has the advantage at the low and medium signal-to-noise ratio(SNR) and better BLER performance at the high SNR.     

Bidirectional Viterbi Decoding Algorithm for OvTDM

Overlapped time domain multiplexing(OvTDM)is an innovative encoding scheme that can obtain high spectral efficiency.However,the intentional inter-symbol interference(ISI)caused by OvTDM will make the decoding process more complex.The computational complexity of maximum likelihood sequence detection increases exponentially with the growth of spectral efficiency in OvTDM.As a consequence of high complexity,the decoding effort for a given spectral efficiency may occasionally exceed the physical limitations of the decoder,leading inevitably to buffer overflows and information erasures.In this paper,we propose a bidirectional Viterbi algorithm(BVA)based on the bidirectional sequence decoding for OvTDM.With the BVA,the decoding operation starts simultaneously from the both ends of the corresponding trellis and stops at the middle of trellis.The simulation results show that compared with Viterbi algorithm(VA),the decoding time of BVA can be reduced by about half.And the memory space of two decoders in BVA are about half of that in VA,which means that the BVA has lower memory requirements for decoder.And the decoding performance of BVA is almost the same as VA.     

系统极化码的置信传播译码性能分析

置信传播( BP)算法可以为系统极化码提供软信息作为判决依据,也可以为系统极化码在级联迭代译码中提供交换软信息。在详细描述基于信道极化结构的置信传播算法基础上,比较了系统极化码在软信息判决方法和极化编码判决方法下错误率性能的差异。仿真结果表明,软信息判决方法可以提高系统极化码的误比特率,在高信噪比下误帧率方面也略有提高。     

基于改进罚函数的LDPC码分层调度ADMM惩罚译码

通过增加伪码字的代价,基于交替方向乘子法（Alternating Direction Method of Multipliers,ADMM）的惩罚译码方法可以改善低密度奇偶校验（Low-Density Parity-Check,LDPC）码低信噪比区域的译码性能,同时具有低的译码复杂度.而减少ADMM惩罚译码的欧几里德投影次数、选择合适的消息调度策略和设计有效的罚函数是提高ADMM惩罚译码速度的三种重要方法.为了进一步提高ADMM惩罚译码速度,通过利用Wei等人提出的方法来减少欧几里德投影的次数,本文设计了基于I-l₁-PF罚函数的水平分层调度与垂直分层调度策略的两种LDPC码ADMM惩罚译码方法.仿真实验表明,与现有ADMM惩罚译码方法相比较,所设计的译码方法不仅具有较好的译码性能,而且能够显著降低LDPC码译码的平均迭代次数和平均译码时间.     

Parallel Viterbi decoding methods for uncontrollable andcontrollable sources

The parallel Viterbi decoding is discussed for two different cases: uncontrollable sources and controllable sources. For general, uncontrollable Markov processes, a previously known parallel method is extended to a hierarchical parallel decoding approach, which achieves a lower latency. For controllable Markov sources in telecommunications applications, new parallel decoding methods are obtained by controlling the source processes in appropriate ways. The focus is on the parallel decoding methods for controllable sources because these methods have zero processing overhead. Because the methods modify the coding process, they bring positive changes to framing and negative changes to latency and code performance. However, one can adjust the parameters of the methods to make the degradation negligible. Because of their low overhead, the methods are most attractive for high-speed decoders for convolutional and trellis codes, and they are also applicable to other sequential algorithms for suboptimal decoding and estimation of complex Markov sources     

状态网格图的LDPC码在OFDM系统中的应用

介绍了LDPC码的编译码技术,提出了一种新颖的2状态网格图译码算法,研究了该码在OFDM系统中的性能,对不同的译码算法进行了比较.仿真结果表明,LDPC码在OFDM基带传输系统中用2状态网格图对其译码能够更好的对错误码进行纠错,提高码字性能,信息传输速率会大大提高.     

一种基于八叉树的Huffman解码方法及其在MPEG-4中的应用

传统的二值Huffman解码方法的解码效率较低。为了提高解码速度,该文提出了一种基于八叉树的Huffman解码方法。该方法将Huffman码表示为八叉树结构,并根据各个节点在树中的位置将码表重建为一维数组。解码时,每次从码流中读取3 bit码元,并使用数值计算代替判断和跳转操作,从而提高了解码效率。将本文方法应用于MPEG-4 VLC和RVLC解码的实验结果表明,该方法在内存增加不大的情况下能大幅度提高Huffman解码效率,其性能优于其它方法。     

单片机定时器捕获模式解码红外遥控器的方法

以单片机作为核心控制器的电子产品日益广泛使用,它们的操作方式主要还是由外接的键盘来完成。若在此类产品中增加红外遥控功能,将使它们的操作更加人性化。用单片机进行软件解码最普遍的方法有查询法和外部中断法,在此详细介绍一种用AT89S52单片机定时器T2捕获功能实现接收解码的新方法,给出了解码的程序流程图和相应的子程序。实践证明,该解码方法占用单片机资源少,程序代码运行稳定可靠,效率高。该解码方法可为单片机产品开发者提供一个非常实用的参考,也可为学习者提供一个典型的应用范例。     

Construction of Quasi-Cyclic LDPC Codes for AWGN and Binary Erasure Channels: A Finite Field Approach

In the late 1950s and early 1960s, finite fields were successfully used to construct linear block codes, especially cyclic codes, with large minimum distances for hard-decision algebraic decoding, such as Bose-Chaudhuri-Hocquenghem (BCH) and Reed-Solomon (RS) codes. This paper shows that finite fields can also be successfully used to construct algebraic low-density parity-check (LDPC) codes for iterative soft-decision decoding. Methods of construction are presented. LDPC codes constructed by these methods are quasi-cyclic (QC) and they perform very well over the additive white Gaussian noise (AWGN), binary random, and burst erasure channels with iterative decoding in terms of bit-error probability, block-error probability, error-floor, and rate of decoding convergence, collectively. Particularly, they have low error floors. Since the codes are QC, they can be encoded using simple shift registers with linear complexity.     

光纤通信中序列估计与纠错译码的级联的研究

使用误码率仿真的方法,比较了基于Viterbi算法(VA)的最大似然序列估计(MLSE)电色散补偿技术和低密度奇偶校验(LDPC)纠错译码技术的VA+BF译码、VA+BP译码简单级联和VA+BP译码置信级联3种级联方法。仿真结果表明,本文提出的置信级联能够有效地判断出VA给出的序列估计值是否可信,并在此基础上进行LDPC译码需要的对数似然比(LLR)信息的初始化。与简单级联方式相比,置信级联的方法能够获得更好的LDPC软译码性能,而且随着光纤传输距离的增加和码间串扰(ISI)效应的恶化,置信级联比简单级联具有更高的性能增益。     

Performance of a new decoding method used in open-loop all-optical chaotic communication system

A new decoding method with decoder is used in open-loop all-optical chaotic communi-cation system under strong injection condition. The performance of the new decoding method is nu-merically investigated by comparing it with the common decoding method without decoder. For new decoding method, two cases are analyzed, including whether or not the output of the decoder is ad-justed by its input to receiver. The results indicate the decoding quality can be improved by adjusting for the new decoding method. Meanwhile, the injection strength of decoder can be restricted in a certain range. The adjusted new decoding method with decoder can achieve better decoding quality than decoding method without decoder when the bit rate of message is under 5 Gb/s. However, a stronger injection for receiver is needed. Moreover, the new decoding method can broaden the range of injection strength acceptable for good decoding quality. Different message encryption techniques are tested, and the result is similar to that of the common decoding method, indicative of the fact that the message encoded by using Chaotic Modulation (CM) can be best recovered by the new decoding method owning to the essence of this encryption technique.     

On the computation of the performance probabilities for block codeswith a bounded-distance decoding rule

When a block code is used on a discrete memoryless channel with an incomplete decoding rule that is based on a generalized distance, the probability of decoding failure, the probability of erroneous decoding, and the expected number of symbol decoding errors can be expressed in terms of the generalized weight enumerator polynomials of the code. For the symmetric erasure channel, numerically stable methods to compute these probabilities or expectations are proposed for binary codes whose distance distributions are known, and for linear maximum distance separable (MDS) codes. The method for linear MDS codes saves the computation of the weight distribution and yields upper bounds for the probability of erroneous decoding and for the symbol error rate by the cumulative binomial distribution. Numerical examples include a triple-error-correcting Bose-Chaudhuri-Hocquenghem (BCH) code of length 63 and a Reed-Solomon code of length 1023 and minimum distance 31