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1.
Low-Density Parity-Check (LDPC) code is one of the most exciting topics among the coding theory community.It is of great importance in both theory and practical communications over noisy channels.The most advantage of LDPC codes is their relatively lower decoding complexity compared with turbo codes,while the disadvantage is its higher encoding complexity.In this paper,a new ap- proach is first proposed to construct high performance irregular systematic LDPC codes based on sparse generator matrix,which can significantly reduce the encoding complexity under the same de- coding complexity as that of regular or irregular LDPC codes defined by traditional sparse parity-check matrix.Then,the proposed generator-based systematic irregular LDPC codes are adopted as con- stituent block codes in rows and columns to design a new kind of product codes family,which also can be interpreted as irregular LDPC codes characterized by graph and thus decoded iteratively.Finally, the performance of the generator-based LDPC codes and the resultant product codes is investigated over an Additive White Gaussian Noise (AWGN) and also compared with the conventional LDPC codes under the same conditions of decoding complexity and channel noise.  相似文献   

2.
Two algebraic methods for systematic construction of structured regular and irregular low-density parity-check (LDPC) codes with girth of at least six and good minimum distances are presented. These two methods are based on geometry decomposition and a masking technique. Numerical results show that the codes constructed by these methods perform close to the Shannon limit and as well as random-like LDPC codes. Furthermore, they have low error floors and their iterative decoding converges very fast. The masking technique greatly simplifies the random-like construction of irregular LDPC codes designed on the basis of the degree distributions of their code graphs  相似文献   

3.
非规则LDPC码的不等错误保护性能研究   总被引:4,自引:1,他引:3  
马丕明  袁东风  杨秀梅 《通信学报》2005,26(11):132-140
提出了一种具有不等错误保护性能的非规则低密度校验(LDPC,low-density parity-check)码信道编码方案, 构造了重量递增校验(weight-increasing parity-check)矩阵,系统编码时,重要信息比特映射到LDPC码的“精华”比特上。AWGN和Rayliegh衰落信道的仿真结果表明,与随机构造的非规则LDPC码相比,WICP-LDPC码具有好的UEP性能。  相似文献   

4.
首先简单介绍了非正则LDPC码的结构,给出了一种基于IEEE802.16e直接编码法生成的(576,288)非正则LDPC码的编译码原理。然后详细论述了其在TI定点DSP(TMS320C5510)上的定点化算法实现方式,并在经过C和部分汇编优化后将算法效率提高了70%以上,达到了实时系统要求。最后给出了该LDPC码与(2,1,7)卷积码在AWGN信道下的性能对比,表明这种中短码长的非正则LDPC码较卷积码有较大的纠错性能优势。  相似文献   

5.
陈婧文  仰枫帆 《电子学报》2010,38(7):1535-1540
 本文构造了一种适用于中继协作通信的非正规LDPC系统码,并将双非正规LDPC系统码应用于中继协作系统中. 提出了目的点接收机基于双LDPC码联合Tanner图的对多路接收信号进行联合迭代译码的新算法. 理论分析和数值模拟表明本文所提出的新方法将高效信道编码和协作技术有机地结合起来以充分实现编码协作所具有的潜在分集和编码增益,与非协作系统相比可显著地提高系统性能.  相似文献   

6.
Rice信道下LDPC码密度进化的研究   总被引:1,自引:0,他引:1  
徐华  徐澄圻 《电子与信息学报》2006,28(10):1831-1836
应用低密度奇偶校验(LDPC)码译码消息的密度进化可以得到码集的噪声门限,依此评价不同译码算法的性能,并可以用来优化非正则LDPC码的次数分布对。该文首先以Rice信道下正则LDPC码为例,讨论了不同量化阶数及步长时BP,BP-based 和offset BP-based 3种译码算法的DDE(Discrete Density Evolution)分析,接着在offset BP-based译码算法的DDE分析基础上,采用差分进化方法对Rice信道下非正则LDPC码的次数分布对进行了优化,得出了相应的噪声门限。最后,给出了Rice信道下码率为1/2的优化非正则LDPC码的概率聚集函数(PMF)进化曲线。  相似文献   

7.
Using nonbinary low-density parity-check (LDPC) codes with random-coset mapping, Bennatan and Burshtein constructed bandwidth-efficient modulation codes with remarkable performance under belief propagation (BP) decoding. However, due to the random nature of LDPC codes, most of the good LDPC codes found in the literature do not have a simple encoding structure. Thus, the encoding complexity of those LDPC codes can be as high as O(N 2), where N is the codeword length. To reduce the encoding complexity, in this paper, nonbinary irregular repeat-accumulate (IRA) codes with time-varying characteristic and random-coset mapping are proposed for bandwidth-efficient modulation schemes. The time-varying characteristic and random-coset mapping result in both permutation-invariance and symmetry properties, respectively, in the densities of decoder messages. The permutation-invariance and symmetry properties of the proposed codes enable the approximations of densities of decoder messages using Gaussian distributions. Under the Gaussian approximation, extrinsic information transfer (EXIT) charts for nonbinary IRA codes are developed and several codes of different spectral efficiencies are designed based on EXIT charts. In addition, by proper selection of nonuniform signal constellations, the constructed codes are inherently capable of obtaining shaping gains, even without separate shaping codes. Simulation results indicate that the proposed codes not only have simple encoding schemes, but also have remarkable performance that is even better than that constructed using nonbinary LDPC codes.  相似文献   

8.
周华  李文杰  马凌峻 《电讯技术》2024,64(6):952-959
广义低密度奇偶校验(Generalized Low睤ensity Parity睠heck,GLDPC)码把低密度奇偶校验(Low睤ensity Parity睠heck,LDPC)码中的单奇偶校验(Single Parity睠heck,SPC)节点替换为校验能力更强的广义约束(Generalized Constraint,GC)节点,使其在中短码和低码率的条件下具有更低的误码率。传统GLDPC码要求基矩阵的行重等于分量码的码长,这限制了GLDPC码构造的灵活性。另外,相比于传统GLDPC码中GC节点位置的随机选取,GC节点的位置选择在GLDPC码的误码率性能上有一定的优化空间。针对以上两点,提出了一种基于渐进边增长(Progressive Edge-rowth,PEG)算法的非规则GLDPC码构造方法和一种基于Tanner图边数的GC节点位置选择算法。使用PEG算法生成的非规则LDPC码作为本地码,根据本地码的校验节点度使用多种分量码,结合GC节点位置选择算法构造非规则GLDPC码。仿真结果表明,与传统方法构造的GLDPC码相比,基于Tanner图边数的GC节点位置选择算法构造的非规则PEG-LDPC码在误码率和译码复杂度上均得到明显改善。  相似文献   

9.
一种非规则卷积低密度校验码的构造和短环去除方法   总被引:1,自引:0,他引:1  
该文研究了使用为分组低密度校验(Low-Density Parity-Check,LDPC)码优化的度序列分布来构造卷积低密度(Low-Density Convolutional,LDC)码的方法,详细讨论了LDC码的编码、译码和短环的消除算法,实验结果说明用为分组LDPC码优化的非规则度序列分布所构造的LDC码,其性能要优于目前文献上提出的规则(homogeneous)LDC码。  相似文献   

10.
On construction of rate-compatible low-density Parity-check codes   总被引:1,自引:0,他引:1  
In this letter, we present a framework for constructing rate-compatible low-density parity-check (LDPC) codes. The codes are linear-time encodable and are constructed from a mother code using puncturing and extending. Application of the proposed construction to a type-II hybrid automatic repeat request (ARQ) scheme with information block length k=1024 and code rates 8/19 to 8/10, using an optimized irregular mother code of rate 8/13, results in a throughput which is only about 0.7 dB away from Shannon limit. This outperforms existing similar schemes based on turbo codes and LDPC codes by up to 0.5 dB.  相似文献   

11.
This paper presents a new class of irregular low-density parity-check (LDPC) codes of moderate length (10/sup 3//spl les/n/spl les/10/sup 4/) and high rate (R/spl ges/3/4). Codes in this class admit low-complexity encoding and have lower error-rate floors than other irregular LDPC code-design approaches. It is also shown that this class of LDPC codes is equivalent to a class of systematic serial turbo codes and is an extension of irregular repeat-accumulate codes. A code design algorithm based on the combination of density evolution and differential evolution optimization with a modified cost function is presented. Moderate-length, high-rate codes with no error-rate floors down to a bit-error rate of 10/sup -9/ are presented. Although our focus is on moderate-length, high-rate codes, the proposed coding scheme is applicable to irregular LDPC codes with other lengths and rates.  相似文献   

12.
A numerical method has been presented to determine the noise thresholds of low density parity-check (LDPC) codes that employ the message passing decoding algorithm on the additive white Gaussian noise (AWGN) channel. In this paper, we apply the technique to the uncorrelated flat Rayleigh fading channel. Using a nonlinear code optimization technique, we optimize irregular LDPC codes for such a channel. The thresholds of the optimized irregular LDPC codes are very close to the Shannon limit for this channel. For example, at rate one-half, the optimized irregular LDPC code has a threshold only 0.07 dB away from the capacity of the channel. Furthermore, we compare simulated performance of the optimized irregular LDPC codes and turbo codes on a land mobile channel, and the results indicate that at a block size of 3072, irregular LDPC codes can outperform turbo codes over a wide range of mobile speeds  相似文献   

13.
Performance analysis and design optimization of LDPC-coded MIMO OFDM systems   总被引:11,自引:0,他引:11  
We consider the performance analysis and design optimization of low-density parity check (LDPC) coded multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems for high data rate wireless transmission. The tools of density evolution with mixture Gaussian approximations are used to optimize irregular LDPC codes and to compute minimum operational signal-to-noise ratios (SNRs) for ergodic MIMO OFDM channels. In particular, the optimization is done for various MIMO OFDM system configurations, which include a different number of antennas, different channel models, and different demodulation schemes; the optimized performance is compared with the corresponding channel capacity. It is shown that along with the optimized irregular LDPC codes, a turbo iterative receiver that consists of a soft maximum a posteriori (MAP) demodulator and a belief-propagation LDPC decoder can perform within 1 dB from the ergodic capacity of the MIMO OFDM systems under consideration. It is also shown that compared with the optimal MAP demodulator-based receivers, the receivers employing a low-complexity linear minimum mean-square-error soft-interference-cancellation (LMMSE-SIC) demodulator have a small performance loss (< 1dB) in spatially uncorrelated MIMO channels but suffer extra performance loss in MIMO channels with spatial correlation. Finally, from the LDPC profiles that already are optimized for ergodic channels, we heuristically construct small block-size irregular LDPC codes for outage MIMO OFDM channels; as shown from simulation results, the irregular LDPC codes constructed here are helpful in expediting the convergence of the iterative receivers.  相似文献   

14.
该文提出了一种非规则LDPC码字基于度分布HARQ技术的改进方案。该方案在选择重传信息的过程中,不仅考虑了节点度分布的影响,而且考虑了非规则LDPC码字自身的不均等错误保护特性。与原始的基于度分布的HARQ方案相比,该方案使系统的误比特率和吞吐量指标得到了明显改善。  相似文献   

15.
本文提出了一种基于围长约束的非规则短码长LDPC编码的改进算法。在每次生成的列向量有多个最大平均围长的情况下,通过选择其中局部短环个数最少,及最小渐进环外消息度(ACE)最大的列向量,依次放入当前校验矩阵完成编码构造,能有效改善影响编码性能的环特性。其中,计算短环数和最小ACE值的方法,采用基于图论的深度优先算法。仿真结果表明:该算法构造的非规则短码长LDPC码的性能优于原基于围长约束的算法及PEG算法所构造的码字。  相似文献   

16.
改进型多元QC-LDPC码的构造及其在PDM-CO-OFDM系统中的应用   总被引:3,自引:3,他引:0  
位长度相同的多元LDPC(NB-LDPC)码优于相应的二 元LDPC(B-LDPC)码,但是它的实现复杂度相对较高。为了降低NB- LDPC码的实现复杂度,提高系统的编码增益,利用置换多项式的方法对一般多元准循 环LDPC(NB-QC-LDPC)码进行改进,并将改进后的NB-QC-LDPC码应用于基于偏振复用的 相干光正交频分复用(PDM-CO-OFDM)系统中,详细研究了其传输性能。仿真结果表明:基于GF(4) QC-LDPC 编码的系统性能 明显优于相应的B-QC-LDPC编码的系统性能,而且基于改进型GF(4) QC-LDPC编码的 系统与 一般GF(4) QC-LDPC编码的系统相比,其误码性能可改善0.65dB, 频谱效率提高了2.16bit/s/Hz,抑制信道色散能力和运转复杂度也 均得到了改善。  相似文献   

17.
基于PEG算法的准循环LDPC码构造方法研究   总被引:1,自引:0,他引:1  
PEG算法,即逐步边增长算法,是一种基于Tanner图构造LDPC码的方法,研究表明该方法构造的LDPC码具有优 异的纠错性能.在PEG算法的基础上,本文提出了一种准循环LDPC码的构造方法.仿真结果表明,所提出的方法构造的LDPC码与用原始PEG算法构造的随机LDPC码具有几乎相同的优异性能,而且由于准循环特性,用本文提出的方法编译码更简单,可以通过反馈移位寄存器来实现.此外,码率更易于调整.  相似文献   

18.
非规则LDPC(low-density parity-check)码具有不等误差保护性能,但是随机编码过程却使这一特性很难实现.现将PEG(Progressive Edge-Growth)算法与信道编码的UEP(Unequal Error Protection)性能相结合,用于构造具有不等误差保护性能的校验矩阵H.AWGN和Rayleigh信道的仿真结果表明,采用PEG算法构造的具有UEP性能的非规则LDPC码能够有效提高系统性能.  相似文献   

19.
本文构造了两类部分平衡不完全区组设计.并利用它们构造了一类低密度校验码(LDPC码),其最小环长至少为6,码率的选取具有很大的灵活性,而且可以具有拟循环结构.计算机仿真结果表明这种方法构造的LDPC码,在加性高斯白噪声信道中BPSK调制下用和积迭代译码性能很好.  相似文献   

20.
This paper deals with the irregular binary low-density parity-check (LDPC) codes and two iterative low-complexity decoding algorithms. The first one is the majority error-correcting decoding algorithm, and the second one is iterative erasure-correcting decoding algorithm. The lower bounds on correcting capabilities (the guaranteed corrected error and erasure fraction respectively) of irregular LDPC code under decoding (error and erasure correcting respectively) algorithms with low-complexity were represented. These lower bounds were obtained as a result of analysis of Tanner graph representation of irregular LDPC code. The numerical results, obtained at the end of the paper for proposed lower-bounds achieved similar results for the previously known best lower-bounds for regular LDPC codes and were represented for the first time for the irregular LDPC codes.  相似文献   

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