空时分组码的多径译码方法

为有效地将空时分组码应用到多径衰落环境下的码分多址系统，以充分利用多个路径的信号能量，提出了一种多径环境下空时分组码译码的新方法。由于空时分组码译码与信道估计紧密相关，本文亦讨论了多径信道估计以及信道估计误差对本方法的影响。仿真结果表明，采用多路径译码方法可明显提高系统的误码率性能。     

频率选择性衰落信道下的空时分组码技术

空时分组码是一种有效抗衰落的发射分集技术,但是现有的研究大都集中在平坦衰落信道下进行。文章详细分析了频率选择性衰落信道下的空时分组码技术——OFDM-STBC(Orthogonal Frequency Division Multiplexing-Space TimeBlock Coding)的系统结构和编译码方法。仿真结果表明OFDM-STBC的性能可达到甚至优于STBC在非频率选择性信道下的性能。     

瑞利快衰落信道下STBC的译码器设计

Alamouti提出的空时分组码(STBC)发射分集技术,其优良性能及低复杂性的译码方案是限制在准静态衰落信道的情况下的,通过研究发现此系统在时变快衰落信道时性能会有严重的损失。为了改善系统在快衰落信道下的性能,提出一种最小均方误差(MMSE)线性译码器,该译码器能够同时抑制噪声和干扰。理论及计算机仿真证明,MMSE译码器用于空时分组码发射分集系统中可以有效地改善无线信道的时变快衰落对系统性能的影响。     

MISO-CDMA多径系统中空时分组码的译码方法

空时编码是实现宽带无线数据通信和下一代移动通信系统的一种极有潜力的技术。为有效的将空时分组码应用到多径衰落环境下的码分多址系统，以充分利用多个路径的信号能量，现提出了一种多径环境下空时分组译码的新方法。由于空时分组码译码与信道估计紧密相关，为此本文对多径信道估计以及信道估计误差对本方法产生的影响作研究。仿真结果表明，采用多路径译码方法可以明显提高系统的误码性能。     

频域均衡空时分组码技术研究

采用翻转矩阵定义了频域均衡空时分组码的编码方式,分析了它的系统结构和编译码过程,并且给出了信道分解的矩阵表达形式,得到了频域均衡空时分组码的一种简明的分析方法。仿真实验表明:与多载波的正交频分复用空时分组码相比,频域均衡空时分组码在频率选择性衰落信道下具有较好的性能。     

基于DSTBC的多级接收器

差分空时分组码（DSTBC）由于具有全空间分集且译码过程无需信参估计而备受青睐。在准静态衰落信道下,差分空时相干检测和传统相干检测有3 dB的衰减;在快衰落信道高信噪比下,DSTBC性能衰减更甚。一种基于Chiavaccini E和Vitetta G M文章所提的多级DSTBC架构应运而生,该架构适用于当信噪比从中等强度过渡到高等强度且衰减率从0.02到0.07的情况,仿真结果表明,运用该架构的DSTBC在快衰落信道高信噪比下性能优异。     

MIMO系统中的空时分组码(STBC)的性能分析

通过对MIMO系统的信道模型和分集技术的分析,详细讨论了基于发送分集的空时分组码(STBC,Space-time block coding).对STBC的编码、译码以及传输性能进行了详细的研究;并对它在RayMgh衰落信道上的性能进行了仿真分析.     

基于Turbo-TCM与时空分组码的级联系统的次优译码算法

针对瑞利信道中存在的严重的多径衰落,本文实现了Turbo-TCM方案与时空分组码的级联系统,以期利用空间分集改善系统的误码率性能。针对级联系统的译码,本文给出了一种具有低译码时延的次优译码算法,该算法的特点是各模块独立译码,先算比特对数似然比再进行二进制Turbo码译码。最后通过计算机仿真给出了使用该次优译码算法的Turbo－TCM方案与时空分组码的级联系统的译码性能。仿真结果说明,当发射天线数目一定时,随着接收天线数目的增加,译码性能的增益随之增加而帧长对译码性能的影响则随之减小。     

频率选择性衰落信道中一种低复杂度的正交空时分组码译码算法

针对正交空时分组码在频率选择性衰落信道中正交性被破坏的问题,该文提出了一种基于干扰对消的译码方案。该方案借鉴D-BLAST系统的检测方法,采用干扰抵消和干扰置零方法消除多径干扰,从而有效地检测出期望信号。理论分析和系统仿真表明,与迭代干扰抵消算法相比,该译码方案在有效地改善系统误码性能的同时,降低了译码复杂度,尤其适用于信道阶数较小的环境。     

STBC-OFDM系统的译码简化和性能分析

文章根据空时分组码的正交特性,提出了一种频率选择性衰落信道下STBC-OFDM系统的简化译码算法。对STBC-OFDM系统传统的译码方法与论文的简化译码算法的仿真结果和计算复杂度进行了比较,并进一步对STBC-OFDM系统的性能进行了分析。研究结果表明:论文的简化译码算法只是降低了计算复杂度,没有影响STBC-OFDM系统最大限度地利用系统所有可用的分集资源。     

Selective trellis pruning for block codes: theory and application to iterative decoding

In this paper we present a new method to simplify trellis‐based decoding of linear block codes. Our method is based on removing (pruning) some edges and states from the trellis representation of the code; the trellis is pruned through some hard‐decisions that are made on received bits whose likelihood exceeds a predefined threshold. We show in this paper how this simplification can be accounted for by a new generator matrix (and sometimes a coset leader) that totally parametrize the new trellis, or, equivalently, the set of allowed codewords after simplification. Extensive simulations show that significant computational savings can be achieved, at a very small loss in coding performance, as long as the operating point and threshold are carefully chosen. Moreover, the application of this technique to iterative decoding of product codes is outlined, and our results show that the simplifications do not hinder the convergence, again, as long as proper parameters are chosen. Copyright © 2007 John Wiley & Sons, Ltd.     

Concatenated multilevel block coded modulation

Encoding and decoding schemes for concatenated multilevel block codes are presented. By one of these structures, a real coding gain of 5.6-7.4 dB for the bit error range of 10^-6 to 10^-9 is achieved for transmission through the additive white Gaussian noise channel. Also, a rather large asymptotic coding gain is obtained. The new coding schemes have very low decoding complexity and increased coding gain in comparison with the conventional block and trellis coded modulation structures. A few design rules for concatenated (single and) multilevel block codes with large coding gain are also provided     

Erasure-free sequential decoding of trellis codes

An erasure-free sequential decoding algorithm for trellis codes, called the buffer looking algorithm (BLA), is introduced. Several versions of the algorithm can be obtained by choosing certain parameters and selecting a resynchronization scheme. These can be categorized as block decoding or continuous decoding, depending on the resynchronization scheme. Block decoding is guaranteed to resynchronize at the beginning of each block, but suffers some rate loss when the block length is relatively short. The performance of a typical block decoding scheme is analyzed, and we show that significant coding gains over Viterbi decoding can be achieved with much less computational effort. A resynchronization scheme is proposed for continuous sequential decoding. It is shown by analysis and simulation that continuous sequential decoding using this scheme has a high probability of resynchronizing successfully. This new resynchronization scheme solves the rate loss problem resulting from block decoding. The channel cutoff rate, demodulator quantization, and the tail's influence on performance are also discussed. Although this paper considers only the decoding of trellis codes, the algorithm can also be applied to the decoding of convolutional codes     

满速率串行级联空时分组MTCM编码方法研究

该文研究了级联空时编码系统在编码增益,分集增益和传输能量效率的限定下最大化传输速率的问题,提出了一种在保留TCM编码方法校验位冗余的同时,还可获得满速率串行级联空时分组TCM编码方法。新方法通过引入具有不同功率分集因子的正交发射码字矩阵,并给出新的译码算法,从而使得新的编码方法在获得满速率的同时还可以获得满分集增益。分析和MATLAB仿真结果表明,在相同的编码状态数下,新方法在编码增益上比现有的满速率超正交空时分组编码方法提高1dB左右。     

Scarce-state-transition error-trellis decoding of block codes withBPSK signals

A novel decoding technique for linear block codes with coherent BPSK signals is proposed. The new system has the same error performance as and similar complexity to the conventional trellis decoding of block codes. Like the scarce-state-transition Viterbi decoding of convolutional codes, the proposed system is also well suited for CMOS VLSI implementation and has a lower power consumption     

Time-invariant trellis encoding of ergodic discrete-time sources with a fidelity criterion

The theory of sliding-block codes (nonlinear, time-invariant, discrete-time filters) is employed to obtain general source coding theorems for ergodic sources using time-invariant trellis coding (time-invariant decoding filter and replicating trellis). The results are coupled with the theory of universal block source codes to obtain universal trellis source coding theorems for classes of sources. It is shown for a certain class of sources that the problem of designing good trellis codes is equivalent to that of simulating general random processes by filtering digital memoryless sources.     

Single-block coded modulation for MINO systems

This paper introduces a new class of space-time codes that achieve coding gain without a trellis or any form of inter-block dependency. The construction of the new codes starts from an existing (parent) space-time block code (STBC). Then by increasing the constellation size followed by expurgation of the expanded codebook, a better code is obtained at the original transmission rate. This method can be applied to a wide variety of space-time block codes, including orthogonal codes and quasi-orthogonal codes. A multi-stage design algorithm is presented, and for orthogonal parent codes, an efficient decoding algorithm is developed, and its decoding complexity is analyzed. Despite altering the regular structure of the orthogonal code, the decoding complexity is only affected by a constant factor.     

Robustly good trellis codes

The relationship between the distance properties of trellis codes and the computational effort and error performance of sequential decoding is studied and optimum distance profile (ODP) and optimum free distance (OFD) trellis codes are constructed for 8-PSK and 16 QAM modulation. A comparison of the performance of both the ODP and the OFD trellis codes reveals that neither class of codes results in the best trade-off between error performance and computational effort when sequential decoding is used. A new algorithm is then proposed to construct robustly good trellis codes for use with sequential decoding. New trellis codes with asymptotic coding gains up to 6.66 dB are obtained using this algorithm, and the new codes achieve nearly the same free distances as the OFD codes and nearly the same distance profiles as the ODP codes     

Efficient maximum likelihood decoding of linear block codes using a trellis

It is shown that soft decision maximum likelihood decoding of any(n,k)linear block code overGF(q)can be accomplished using the Viterbi algorithm applied to a trellis with no more thanq^{(n-k)}states. For cyclic codes, the trellis is periodic. When this technique is applied to the decoding of product codes, the number of states in the trellis can be much fewer thanq^{n-k}. For a binary(n,n - 1)single parity check code, the Viterbi algorithm is equivalent to the Wagner decoding algorithm.     

Iterative maximum-likelihood trellis decoding for block codes

An iterative trellis search technique is described for the maximum-likelihood (ML) soft decision decoding of block codes. The proposed technique derives its motivation from the fact that a given block code may be a subcode for a parent code whose associated trellis has substantially fewer edges. Through the use of list-Viterbi (1967) decoding and an iterative algorithm, the proposed technique allows for the use of a trellis for the parent code in the ML decoding of the desired subcode. Complexity and performance analyses, as well as details of potential implementations, indicate a substantial reduction in decoding complexity for linear block codes of practical length while achieving ML or near-ML soft decision performance