LDPC编码的MIMO大气激光通信系统研究

通过将信道编码LDPC与分集技术相结合,分析了级联空时码在对抗大气湍流效应的作用。首先建立了Gamma-Gamma大气湍流信道模型,并且设计了LDPC编码的MIMO自由空间光通信系统,仿真了弱湍流和强湍流两种情况下,未编码和已编码的MIMO系统的性能。结果表明,在弱湍流和强湍流情况下,LDPC编码的MIMO系统较未编码的MIMO系统的误码率得到了很好的改善,性能得到了极大的提升。     

面向自由空间光通信的PC-STBC方法研究

针对大气湍流对自由空间光通信系统误码率影响较大的问题,提出了一种在多输入多输出系统中将极化编码与空时编码直接级联的方案。在弱湍流信道中,使用高斯近似的方式构造出编码序列并进行极化编码,并使用二进制相移键控对编码序列进行调制,再与空时编码进行直接级联。仿真结果表明:在多输入多输出系统中,码字长度N=1 024时,系统的误码率可下降至10-6级以下;若码字长度N=2 048时,信噪比高于2 dB时,误码率可趋近于0。接收天线数越多,系统的分集阶数越高,系统误码率下降速度变慢,系统整体性能变差。因而该级联方案能够更好地改善系统误码率性能。并且在不同的湍流强度下,表现出对强湍流具有更好的抑制效果,误码率下降更明显。     

Rice衰落下RS码级联空时分组码系统的性能分析

从理论上给出一种Rice衰落条件下Reed-Solomon码级联空时分组码系统的差错性能分析方法,并推导给出级联码误比特率上界的数学表达式。理论分析和仿真结果表明,随着信噪比的增加,级联码系统的性能曲线迅速变好,获得了很高的编码增益。在误比特率为10-4时,与Reed-Solomon码的级联可以使衰落条件下空时分组码的性能提高大约5 dB。     

无线光通信中的空时编码研究进展(三)

空时编码利用多天线阵列提供的并行信道传输信息,可以在保证通信质量的前提下进一步提高信息传输速率。介绍了笔者在正交空时码、空时网格码、酉空时码、差分空时码、混合空时码等方面的工作。采用类脉冲位置调制定义了负数、共轭、求补等运算,将编码矩阵转化为一个用脉冲位置表示的实数矩阵。分析了不同发射天线/接收天线数目、大气湍流强度与系统误码率之间的关系。讨论了差分空时码、酉空时码在不同大气湍流条件下的误码率特性;将分层空时码和空时分组码相结合,对复用增益和分集增益进行合理的折中,提出了一种适合于IM/DD式光通信的混合空时编码方案。     

改进Turbo码与MIMO-OFDM级联的系统性能分析

丈中研究了MIMO-OFDM系统中的空时分组编码,并在此系统的基础上与Turbo码进行级联,从而使系统具有分集和抗多径衰落的性能.为了更进一步的减少系统误码率,文中对Turbo码的译码算法进行改进后,与MIMO-OFDM再进行级联.仿真结果表明,改进的Turbo码译码算法与其他译码算法相比,减少了误码率.这种级联后的系统比传统的MIMO系统的性能有较好的改善.     

基于LDPC码和MIMO的无线光通信系统性能

针对大气湍流严重影响无线光通信系统性能的问题,研究了基于低密度奇偶校验(LDPC)码和多输入多输出(MIMO)无线光通信系统性能,给出了基于LDPC码的空时编码MIMO(ST MIMO)和重复编码MIMO(rep MIMO)系统的解码算法,最后在对数正态模型和K分布模型下进行了仿真分析。仿真结果表明rep MIMO系统性能优于ST MIMO和单输入单输出(SISO)系统,ST MIMO在强湍流情况下性能明显优于SISO系统,基于LDPC码的ST MIMO和rep MIMO能取得10 dB以上的编码增益,并且编码增益随着湍流强度的增大而增加,基于LDPC码和rep MIMO的无线光通信系统差错性能更加优异,可以有效提高系统抗干扰能力。     

级联纠错编码DS/BPSK系统性能分析与仿真

为了研究级联编码对DS/BPSK系统性能的影响,设计了一种基于RS与卷积码级联编码的DS/BPSK系统,分析了该级联编码直扩系统的性能,仿真了在纠错编码参数发生改变时的系统性能。仿真结果表明,级联编码的DS/BPSK系统性能比单码编码的DS/BPSK系统性能要好。在RS码参数保持不变时,降低卷积码的码率,采用软判决方式译码以及多比特软判决,能有效提升系统性能;同时,交织在一定程度上能改善系统的性能。     

基于Turbo乘积码的MIMO-OFDM系统在IMT2000信道下的性能研究

为了提高无线通信系统的可靠性,采用极具纠错性能的Turbo乘积码与空时分组码级联,构成Turbo乘积码编码的MIMO-OFDM系统。测试了采用三种Turbo乘积码的两发两收MIMO-OFDM系统在通过IMT2000信道后的性能。仿真结果表明采用Turbo乘积码后的MIMO-OFDM系统性能有明显改善。     

级联LDPC的空时分组码性能研究

阐述了空时分组码的编译码算法并进行性能分析,就其编码能提供分集增益但不能提供编码增益的特点,给出空时分组码级联LDPC(low density parity check code,低密度奇偶校验码)的系统模型。最后利用Matlab对级联LDPC的空时分组码进行仿真,结果表明:级联LDPC码的空时分组码能有效提高编码性能。     

级联 Turbo-空时格码 OFDM 系统的性能分析

在研究传统的空时编码 OFDM 系统模型及误码率性能的基础上,提出了 Turbo 码级联空时格码的 OFDM 系统方案；并给出了该系统在无线瑞利衰落信道中的性能上界和误码率仿真结果,仿真结果表明：该系统能最大限度地利用所有的分集资源,获得相当大的分集增益和编码增益。     

一种新的两用户协作分集方案及其性能研究

该文提出了一种基于信道编码和分布式空时分组码级联下的两用户协作分集方案,并且在准静态的瑞利衰落信道下对此方案的系统容量,中断概率以及误比特率进行了理论推导和系统仿真,分别给出了解析表达式和数值结果。通过将信道编码和空时码引入到协作分集中,系统容量得到显著改善,同时中断概率也明显降低。在协作用户间信道存在噪声的情况下,对卷积码与分布式空时分组码级联下的发射方案进行了性能分析和仿真。仿真结果表明:即使协作用户间的信道存在噪声,该文所提方案在各方面都优于传统协作分集,系统容量明显增大,中断概率及误比特率大大降低。     

Enhanced space-time block coded systems by concatenating turbo product codes

The BER performance of a turbo product code (TPC) based space-time block coding (STBC) wireless system has been investigated. With the proposed system, both the good error correcting capability of TPC and the concurrent large diversity gain characteristic of STBC can be achieved. The BER upper bound has been derived taking BPSK modulation as an example. The simulation results show that the proposed system with the concatenated codes outperforms the one with only TPC or STBC and other reported schemes that concatenate STBC with convolutional Turbo codes or trellis codes.     

Analysis of Serial and Hybrid Concatenated Space-Time Codes Applying Iterative Decoding

In this letter, we investigate serial and hybrid concatenated space-time (SC-ST and HC-ST) codes applying iterative decoding topologies. The coding operations are based on the concatenation of convolutional coding, interleaving, and space-time coding along with a multiple-transmitter/multiple-receiver diversity system. Through the analysis of the SC-ST and HC-ST coding systems, improved design specifications can be selected for the component encoders with considerations of the wireless channel characteristics. Based on the iterative decoding process and the optimum parameter selection operations, a considerable improvement in the error rate performance is obtained. For the applied specs, the results indicate that at the frame error rate (FER) 10⁻² level the SC-ST coding system provides a coding gain of approximately 3 dB in comparison to the Tarokh, Seshadri, Calderbank (TSC) space-time (ST) code [1], where the HC-ST coding system provides an additional coding gain of approximately 1 dB beyond the SC-ST code.     

Non-full rank space-time trellis codes for serially concatenated system

The feasibility of the non-full rank space-time trellis codes (NFR-STTCs) for the serially concatenated system is described carefully in this letter and a QPSK-based NFR-STTC suitable for the system is proposed. As the simulation results show, over the flat block Rayleigh fading channels, a concatenated system with the proposed NFR-STTC inner code can achieve full diversity, and improve the coding gains compared with other concatenated systems adopting full-rank space-time trellis codes (FR-STTCs) of the same complexity. The introduction of the NFR-STTC to serial concatenation space-time (SCST) system provides a new research community of SCST.     

Reliability and Throughput Analysis of a Concatenated Coding Scheme

In this paper, the performance of a concatenated coding scheme for error control in ARQ systems is analyzed for both randomerror and burst-error channels. In particular, the probability of undetected error and the system throughput are calculated. In this scheme, the inner code is used for both error correction and error detection, and the outer code is used for error detection only. Interleaving/deinterleaving of the outer code is assumed. A retransmission is requested if either the inner code or the outer code detects the Presence of errors. Various coding examples are considered. The results show that concatenated coding can provide extremely high system reliability (i.e., low probability of undetected error) and high system throughput.     

Concatenated space-time block coding with trellis coded modulation in fading channels

Trellis coded modulation (TCM) is a bandwidth efficient transmission scheme that can achieve high coding gain by integrating coding and modulation. This paper presents an analytical expression for the error event probability of concatenated space-time block coding with TCM which reveals some dominant factors affecting the system performance over slow fading channels when perfect interleavers are used. This leads to establishing the design criteria for constructing the optimal trellis codes of such a concatenated system over slow flat fading channels. Through simulation, significant performance improvement is shown to be obtained by concatenating the interleaved streams of these codes with space-time block codes over fading channels. Simulation results also demonstrate that these trellis codes have better error performance than traditional codes designed for single-antenna Gaussian or fading channels. Performance results over quasi-static fading channels without interleaving are also compared in this paper. Furthermore, it is shown that concatenated space-time block coding with TCM (with/without interleaving) outperforms space-time trellis codes under the same spectral efficiency, trellis complexity, and signal constellation.     

Forward error correction concatenated code in DWDM systems

The three concatenated coding schemes of the inner-outer type, the parallel type and the consecutive type to improve the current forward error correction (FEC)coding technologies are proposed for dense wavelengthdivision multiplexing (DWDM) systems, after introducing the development trend of DWDM optical communication systems. The concatenated code is theoretically analyzed.The theoretical analyses and simulation results show that inner-outer concatenated code has a greater redundancy and the decoding of parallel concatenated code is too complex. However, consecutive concatenated code is superior coding scheme with advantages such as better error correction performance, moderate redundancy and easy implementation, therefore it could be better used in high-speed and long-haul DWDM systems.     

空时编码在单天线UWB通信系统中的应用

超宽带(UWB)适用于基带多用户通信、战场无线通信和高数据率多媒体业务等通信系统,其数据传输速率高、功耗低、多径分辨能力强。但超宽带脉冲信号时域支撑区极窄,信道为密集多径,将空时编码技术引入超宽带通信系统,能够提升无线通信系统的信道容量与抗误比特率性能。在对UWB空时分组编码系统模型性能理论分析的基础上,对空时分组码在单天线UWB系统应用方案与UWB空时分层码方案进进行了简要介绍,利用Matlab对IEEEUWB信道模型进行仿真,提出了空时编码在UWB通讯技术中应用后提升短距高速率无线通信的性能的结论 。