Low-Complexity Optimization Algorithm for Irregular Low-Density Parity-Check Codes

A low-complexity algorithm is proposed in this paper in order to optimize irregular low-density parity-check （LDPC） codes.The algorithm proposed can calculate the noise threshold by means of a one-dimensional density evolution and search the optimal degree profiles with fast-convergence differential evolution,so that it has a lower complexity and a faster convergence speed.Simulation resuits show that the irregular LDPC codes optimized by the presented algorithm can also perform better than Turbo codes at moderate block length even with less computation cost.

Implementation of low-density parity-check codes decoder for CCSDS standard

The complexity/performance balanced decoder for low-density parity-check （LDPC） codes is preferred in practical wireless communication systems. A low complexity LDPC decoder for the Consultative Committee for Space Data Systems （CCSDS） standard is achieved in DSP. An ap- proximate decoding algorithm, normalized rain-sum algorithm, is used in the implementation for its low amounts of computation. To reduce the performance loss caused by the approximation, the pa- rameters of the normalized min-sum algorithm are determined by calculating and finding the mini- mum value of thresholds through density evolution. The minimum value which indicates the best per- formance of the decoding algorithm is corresponding with the optimized parameters. In implementa- tion, the memory cost is saved by decomposing the parity-check matrix into submatrices to store and the computation of passing message in decoding is accelerated by using the intrinsic function of DSP. The performance of the decoder with optimized factors is simulated and compared with the ideal BP decoder. The result shows they have about the same performance.

DESIGN OF LOW-DENSITY PARITY CHECK CODES FOR MIMO SYSTEMS WITH DOUBLY-ITERATIVE RECEIVERS

In this paper, the Multiple Input Multiple Output (MIMO) doubly-iterative receiver which consists of the Probabilistic Data Association detector (PDA) and Low-Density Parity-Check Code (LDPC) decoder is developed. The receiver performs two iterative decoding loops. In the outer loop, the soft information is exchanged between the PDA detector and the LDPC decoder. In the inner loop, it is exchanged between variable node and check node decoders inside the LDPC decoder. On the light of the Extrinsic Information Transfer (EXIT) chart technique, an LDPC code degree profile optimization algorithm is developed for the doubly-iterative receiver. Simulation results show the doubly-receiver with optimized irregular LDPC code can have a better performance than the one with the regular one.

Low-Density Parity-Check Codes: Research Status and Development Direction

In this paper, we conclude five kinds of methods for construction of the regular low-density parity matrix H and three kinds of methods for the construction of irregular low-density parity-check matrix H. Through the analysis of the code rate and parameters of these eight kinds of structures, we find that the construction of low-density parity-check matrix tends to be more flexible and the parameter variability is enhanced. We propose that the current development cost should be lower with the progress of electronic technology and we need research on more practical Low-Density Parity-Check Codes (LDPC). Combined with the application of the quantum distribution key, we urgently need to explore the research direction of relevant theories and technologies of LDPC codes in other fields of quantum information in the future.

Data Gathering in Wireless Sensor Networks Via Regular Low Density Parity Check Matrix

A great challenge faced by wireless sensor networks(WSNs) is to reduce energy consumption of sensor nodes. Fortunately, the data gathering via random sensing can save energy of sensor nodes. Nevertheless, its randomness and density usually result in difficult implementations, high computation complexity and large storage spaces in practical settings. So the deterministic sparse sensing matrices are desired in some situations. However,it is difficult to guarantee the performance of deterministic sensing matrix by the acknowledged metrics. In this paper, we construct a class of deterministic sparse sensing matrices with statistical versions of restricted isometry property(St RIP) via regular low density parity check(RLDPC) matrices. The key idea of our construction is to achieve small mutual coherence of the matrices by confining the column weights of RLDPC matrices such that St RIP is satisfied. Besides, we prove that the constructed sensing matrices have the same scale of measurement numbers as the dense measurements. We also propose a data gathering method based on RLDPC matrix. Experimental results verify that the constructed sensing matrices have better reconstruction performance, compared to the Gaussian, Bernoulli, and CSLDPC matrices. And we also verify that the data gathering via RLDPC matrix can reduce energy consumption of WSNs.

Design of Irregular QC-LDPC Code Based Multi-Level Coded Modulation Scheme for High Speed Optical Communication Systems

In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.

High Robust Broadcasting over DTMB-A with Low-rate LDPC Codes

As the 2nd generation digital terrestrial television broadcasting(DTTB)standard,digital terrestrial/television multimedia broadcasting-advanced(DTMB-A)can provide higher spectrum efficiency and transmission reliability by adopting flexible frame structure and advanced forward error correction coding compared with the 1 st generation DTTB systems.In order to increase the flexibility and robustness of the DTTB network,the frequency reuse scheme of factor one(reuse-1)is proposed,where the same RF channel is used by different stations covering the adjacent service areas.However,it demands a very low carrier-tonoise ratio(C/N)threshold below 0 dB at the DTTB physical layer.In this paper,a robust broadcasting technique is proposed based on DTMB-A with newly designed low-rate low density parity check(LDPC)codes.By adopting quasi-cyclic(QC)Raptor-like structure and progressive lifting method,the high performance low-rate LDPC codes are designed supporting multiple code lengths.Both density-evolution analyses and laboratory measurements demonstrate that DTMB-A with low-rate coding can complete the demodulation reliably with the C/N threshold below0 d B,which is one important necessary condition to support frequency reuse-1 scheme.

JOINT ITERATIVE DECODING FOR SIMPLE-ENCODING SYSTEMATIC IRREGULAR-LDPC-BASED CODED COOPERATION IN NON-IDEAL RELAY CHANNEL

In this paper, a new kind of simple-encoding irregular systematic LDPC codes suitable for one-relay coded cooperation is designed, where the proposed joint iterative decoding is effectively performed in the destination which is in accordance with the corresponding joint Tanner graph characterizing two different component LDPC codes used by the source and relay in ideal and non-ideal relay cooperations. The theoretical analysis and simulations show that the coded cooperation scheme obviously outperforms the coded non-cooperation one under the same code rate and decoding complex. The significant performance improvement can be virtually credited to the additional mutual exchange of the extrinsic information resulted by the LDPC code employed by the source and its counterpart used by the relay in both ideal and non-ideal cooperations.

Irregular and regular LDPC codes with high spectrum efficiency modulation in image transmission over fading channel

If the degree distribution is chosen carefully, the irregular low-density parity-check (LDPC) codes can outperform the regular ones. An image transmission system is proposed by combining regular and irregular LDPC codes with 16QAM/64QAM modulation to improve both efficiency and reliability. Simulaton results show that LDPC codes are good coding schemes over fading channel in image communication with lower system complexity. More over, irregular codes can obtain a code gain of about 0.7 dB compared with regular ones when BER is 10 -4. So the irregular LDPC codes are more suitable for image transmission than the regular codes.

基于Golomb Ruler的QC-LDPC码构造方法

针对准循环低密度奇偶校验(QC-LDPC)码中短环结构会影响其纠错性能的问题,基于Golomb Ruler提出了一种新颖的围长为8的QC-LDPC码构造方法。该方法先根据码长码率的需求,从Golomb Ruler中选择部分元素构造一个集合,结合指数矩阵中元素所在位置的四六环特性,通过搜索算法,依次找出符合无四六环条件的元素得到另一个集合,然后构造相应的指数矩阵,最后得到其奇偶校验矩阵。仿真结果表明:在误码率为10^(-6)时,所构造的GR-QC-LDPC码与同码率码长的其他4种QC-LDPC码的码型相比,其净编码增益均有一定的提高,且无明显错误平层现象。

基于可靠度差值特征的自适应判决多元LDPC译码算法

利用变量节点符号可靠度在迭代过程中的分布特征,提出了一种基于可靠度差值特征的自适应判决多元低密度奇偶校验(Low Density Parity Check, LDPC)译码算法。整个迭代过程划分为两个阶段,针对不同阶段节点可靠度的差值特征分别采用不同的判决策略:前期阶段,采用传统的基于最大可靠度的判决策略;后期阶段,根据最大、次大可靠度之间的差值特征,设计自适应的码元符号判决策略。仿真结果表明,所提算法在相当的译码复杂度前提下,能获得0.15~0.4 dB的性能增益。同时,对于列重较小的LDPC码,具有更低的译码错误平层。

基于空中可重构智能表面的低轨卫星高通量通信

卫星通信凭借其全球覆盖、抗干扰能力强和稳定的通信质量,在通信领域展现出广阔的应用前景。针对新一代通信技术对于高速率、低时延和覆盖增强的需求,提出了一种低轨卫星、无人机和可重构智能表面协作的空天地一体化网络框架。从高通量卫星通信的角度出发,制订了一个通信容量最大化方案。该方案基于最大化-最小化算法和深度确定性策略梯度算法联合优化反射相移和无人机轨迹。仿真结果表明,所提方案能够显著提升通信容量。

基于帧交错的LDPC译码器流水结构设计

低密度奇偶校验码(LDPC)的译码器通常采用基于节点置信度更新迭代的算法,这种算法可以并行实现,具有非常高的吞吐量。在此提出了一种具有高硬件利用效率(HUE)的帧交错译码结构,并提供了一种用于层内节点重排序的动态规划方法,解决内存访问冲突问题。与现有的结构相比,该结构可以实现更高的硬件利用效率。

基于残差分层的归一化最小和LDPC译码算法

为了进一步缩小最小和(min-sum, MS)算法和置信传播(belief propagation, BP)算法译码性能的差距,提高归一化最小和(normalized min-sum, NMS)算法的译码性能,提出了一种基于残差分层的改进归一化最小和低密度奇偶校验(low density parity check,LDPC)译码算法。首先定量分析MS算法存在的高估问题,利用BP算法和MS算法检验节点LLR消息的比值特性,求其归一化因子。为了降低译码的复杂度,根据最优归一化因子的变化特征,对其采用加权平均处理;为了降低平均迭代次数,加快译码的收敛速度,所提算法利用校验节点信息的残差特性进行分层处理,优先更新残差值较大的一层,在不同迭代之间动态地重新排列层。仿真结果表明,提出的RB_LINMS译码算法,在误比特率为10-5时,相比于传统的NMS算法,其译码性能可获得0.26 d B的增益,平均迭代次数最多能够降低33.20%。因此,在复杂度略有增加的情况下,能够实现更快的收敛速度和出色的译码性能。

空间耦合低密度奇偶校验码残差滑窗译码算法

针对空间耦合低密度奇偶校验(SC-LDPC)码滑窗译码(SWD)算法中错误传播导致的高误码率问题,该文提出基于动态残差的滑窗译码(RSWD)算法。通过在窗口内计算边信息更新前后的残差值,动态选择可靠度最低(残差值最大)的边信息优先更新,降低边信息无效更新的频率,提高窗内译码收敛速度。仿真结果表明:相比于传统SWD算法,RSWD算法在窗口中各位置的误比特数明显降低,抑制错误传播效果明显;在高信噪比(SNR)区域或者低迭代次数的情况下,RSWD算法的误码率性能优于SWD算法;此外,将动态残差应用到消息复用(MR)和窗口扩展(WE)两种窗译码算法中,亦能得到类似结论,提升窗译码性能。

基于阿贝尔群上的差分集构造LDPC码

本文给出了区组长度为3、4和5的平衡不完全区组设计,将设计的关联矩阵作为校验矩阵,从而构造出3种低密度奇偶校验码(LDPC,low-density parity-check code)。由于这些校验矩阵是准循环矩阵,所以构造的码是拟循环LDPC码(QC-LDPC,quasi-cyclic LDPC)。计算码的相关参数,并针对具体的例子通过与类随机码的译码性能进行分析比较,结果显示,所构造的码具有较好的性能。

Minimum distances of three families of low-density parity-check codes based on finite geometries

Three families of low-density parity-check （LDPC） codes are constructed based on the totally isotropic subspaces of symplectic, unitary, and orthogonal spaces over finite fields, respectively. The minimum distances of the three families of LDPC codes in some special cases are settled.

高阶调制下物理层网络编码与OFDM联合设计

物理层网络编码(Physical-layer Network Coding,PNC)因其可以在中继通信中大幅提高吞吐量而备受关注。为了进一步提高传输效率,减少多径的影响,在三节点双向无线PNC系统中引入16QAM-OFDM高阶调制技术,设计了16QAMOFDM-PNC通信系统。由于采用16QAM-OFDM高阶调制的PNC系统存在中继映射模糊的问题,对16QAM信号的星座点重新布局,设计出相应的中继解调映射规则。为了进一步提高系统性能,在该设计中引入低密度奇偶校验码(Low Density Parity Check Code,LDPC),设计了相应的译码映射算法。最后实验表明,上述设计相较于16QAM-PNC系统具有更好的系统性能,同时联合LDPC编码的设计能提高系统增益约2dB。

Construction of Rate-Compatible(RC) Low-Density Parity-Check(LDPC) Convolutional Codes Based on RC-LDPC Block Codes

In this paper,a family of rate-compatible(RC) low-density parity-check(LDPC) convolutional codes can be obtained from RC-LDPC block codes by graph extension method.The resulted RC-LDPC convolutional codes,which are derived by permuting the matrices of the corresponding RC-LDPC block codes,are systematic and have maximum encoding memory.Simulation results show that the proposed RC-LDPC convolutional codes with belief propagation(BP) decoding collectively offer a steady improvement on performance compared with the block counterparts over the binary-input additive white Gaussian noise channels(BI-AWGNCs).

Area-efficient analog decoder design for low density parity check codes in deep-space applications

Area-efficient design methodology is proposed for the analog decoding implementations of the rate-l/2 accumulate repeat-4 jagged-accumulate （AR4JA） low density parity check （LDPC） code. The proposed approach is designed using optimized decoding architecture and regularized routing network, in such a way that the overall wiring overhead is minimized and the silicon area utilization is significantly improved. The prototyping chip used to verily the approach is tully integrated in a four-metal double-poly 0.35 lam complementary metal oxide semiconductor （CMOS） technology, and includes an input-output interface that maximizes the decoder throughput. The decoding core area is 2.02 mm2 with a post-layout area utilization of 80%. The decoder was successfully tested at the maximum data rate of 10 Mbit/s, with a core power consumption of 6.78 mW at 3.3 V, which corresponds to an energy per decoded bit of 0.677 nJ. The proposed analog LDPC decoder with low processing power and high-reliability is suitable lbr space- and power-constrained spacecraft system.