Low-complexity maximum-likelihood decoder for four-transmit-antenna quasi-orthogonal space-time block code

This letter proposes a very low-complexity maximum-likelihood (ML) detection algorithm based on QR decomposition for the quasi-orthogonal space-time block code (QSTBC) with four transmit antennas, called the LC-ML decoder. The proposed algorithm enables the QSTBC to achieve ML performance with significant reduction in computational load for any high-level modulation scheme.     

Adaptive Channel‐Matched Extended Alamouti Space‐Time Code Exploiting Partial Feedback

Since the publication of Alamouti's famous space‐time block code, various quasi‐orthogonal space‐time block codes (QSTBC) for multi‐input multi‐output (MIMO) fading channels for more than two transmit antennas have been proposed. It has been shown that these codes cannot achieve full diversity at full rate. In this paper, we present a simple feedback scheme for rich scattering (flat Rayleigh fading) MIMO channels that improves the coding gain and diversity of a QSTBC for 2ⁿ (n = 3, 4,…) transmit antennas. The relevant channel state information is sent back from the receiver to the transmitter quantized to one or two bits per code block. In this way, signal transmission with an improved coding gain and diversity near to the maximum diversity order is achieved. Such high diversity can be exploited with either a maximum‐likelihood receiver or low‐complexity zero‐forcing receiver.     

适于匙孔信道的准正交极化空时分组码及性能分析

构建了一种适于匙孔信道的满码率极化准正交空时分组码以改善其误比特率性能,采用快速最大似然译码算法进行译码,并与匙孔信道的传统准正交空时分组码、单中继瑞利信道和单中继匙孔信道的极化准正交空时分组码分别进行误比特率的仿真和比较.结果表明:在相同SNR条件下,本文构建的分组码比传统准正交分组码具有更低的误比特率;与两种单中继极化准正交空时分组码相比,在SNR较高情况下本文分组码具有更好的性能.     

基于MIMO系统的准正交空时分组码的容量分析

应用于MIMO系统的准正交空时分组码可以获得较大的容量,同时能够提供较低的误码率。文中比较了MIMO系统的准正交空时分组码的容量与SIMO系统的容量。结果显示,在低SNR和接收天线数少的情况下,应用于MIMO系统的准正交空时分组码会产生较大的容量增益,但随着SNR和天线数目的增加,容量增益越来越不明显。另外,文中比较了MIMO系统中准正交空时分组码和正交空时分组码的容量,仿真结果表明前者的容量明显高于后者。     

一种面向长期演进的空时分组传输方案

移动基站MS（Mobile Station）在LTE-A（Long Term Evolution-Advanced长期演进）协议中要求上行链路的数据要在双天线和三个时隙中传输,这就使得针对LTE的空时分组码有了一个新的应用点.本文在传统的STBC（Space-Time Block Coding空时分组码）的基础上,通过改进,提出一种新的传输方案,使得数据实现在三个时隙使用双发射天线的传输.该方案特点：（1）它可以实现传输的全速率和全分集;（2）它的最大似然译码（Maximum Likelihood,ML）需要联合三个实信号;（3）它的最小行列式值并没有通过信号星座图的改变而变化;（4）它与单天线传输的模式相兼容.仿真结果显示提出的方案比传统的准正交空时分组码QSTBC方案和Alamouti方案在相同信噪比（SNR）的情况下有着更好的误比特率（BER）.     

Tight Upper Bound on the Outage Probability of QSTBC

Recently, the statistical properties of the equivalent channel representation of a multiple-input-multiple output (MIMO) system employing rate one quasi-orthogonal space-time block codes (QSTBC) for n _T=2ⁿ, nges2 transmit antennas was characterized. It was shown, that these QSTBC were capable of achieving a significant fraction of the outage mutual information of a MIMO system. In this letter, based on the Minkowski's determinant inequality and the Meijer's G-function we derive an upper bound for the fraction of outage probability achieved with QSTBC for the general case of n_T=2 ⁿ, nges2 transmit antennas. Simulations results show that this bound gets tight for all signal-to-noise-ratios (SNR) values by increasing the number of receive antennas     

Application of quasi-orthogonal space-time block codes in beamforming

It is well known that when channel information is available at the transmitter, transmit beamforming scheme can be employed to enhance the performance of a multiple-antenna system. Recently, Jongren et al. and Zhou-Giannakis proposed a new performance criterion based on partial channel side information at the transmitter. With this criterion, an optimal beamforming matrix was constructed for the orthogonal space-time block codes. However, the same method has not been applied to the recently proposed quasi-orthogonal space-time block codes (QSTBCs) due to the nonorthogonal nature of the quasi-orthogonal designs. In this paper, the issue of combining beamforming with QSTBCs is addressed. Based on our asymptotic analysis, we extend the beamforming scheme from Jongren et al. and construct the beamforming matrices for the quasi-orthogonal designs. The proposed beamforming scheme accomplishes high transmission rate as well as high-order spatial diversity. The new QSTBC beamformer can be presented as a novel four-directional or eight-directional eigen-beamformer that works for systems with four or more transmit antennas. Simulations for systems with multiple transmit antennas demonstrate significant performance improvement over several other widely used beamforming methods at various SNRs and for channels with different quality of feedback.     

Concatenated Coding Systems Employing a Unit-Memory Convolutional Code and a Byte-Oriented Decoding Algorithm

Concatenated coding systems utilizing a convolutional code as the inner code and a Reed-Solomon code as the outer code are considered. In order to obtain very reliable communications over a very noisy channel with relatively modest coding complexity, it is proposed to concatenate a byte-oriented unit-memory convolutional code with an RS outer code whose symbol size is one byte. It is further proposed to utilize a real-time minimal-byte-error probability decoding algorithm, together with feedback from the outer decoder, in the decoder for the inner convolutional code. The performance of the proposed concatenated coding system is studied, and the improvement over conventional concatenated systems due to each additional feature is isolated.     

Multipulse-Per-Row Codes for High-Speed Optical Wavelength/Time CDMA Networks

New wavelength/time code families constructed with short code lengths are proposed for optical code-division multiple- access networks. Since the code matrices inherit correlation properties from the underlined one-dimensional codes, much effort for codeword searching and code property validation is saved. In addition, since the proposed code matrices with multipulse-per-row (MPR) property have optimal cardinalities, the total number of supported users in the network is increased. Performance analysis shows that the proposed MPR matrix codes have bit-error rates comparable to other wavelength/time codes proposed previously.     

An optimal two transmit antenna space-time code and its stacked extensions

A space-time code is proposed that exhibits the highest coding gain among competing full-rate full transmit diversity space-time codes for the two transmit and receive antenna coherent quasi-static fading channel. The proposed code is derived from a layered architecture with real rotation of quadrature amplitude modulation (QAM) information symbols in two dimensions. The existing codes of similar architecture concentrate on application of complex full modulation diversity rotations or asymmetric real rotations. An analytic evaluation illustrates the significant improvement in coding gain achieved with the proposed code. Moreover, the coding gain of the proposed code is independent of its rate. This implies that the proposed code achieves the optimal diversity-multiplexing tradeoff curve for the two transmit antenna system. A stacked extension of the proposed code offers a reduced complexity capacity optimal alternative to the full diversity codes for larger number of transmit antennas. Performance enhancement in several scenarios is verified through simulations.     

结合Turbo码的多级编码调制研究介绍

论文作者在对已有的多级编码调制方案深入研究的基础上 ,进一步研究了Turbo码编码技术 ,并把Turbo码作为分量码结合多级编码调制方案进行了理论研究 .符合当今移动通信的大容量、高可靠性的要求 .论文的主要创新点有 ,通过理论研究 ,证明了以Turbo码为分量码的多级编码方案比以往的以分组码及卷积码为分量码的方案具有一定的优越性     

一种串行级联空时频分组编码方法

为了提高MIMO-OFDM系统中的空时频分组编码(STFBC)性能,本文提出了一种串行级联空时频分组编码(SCSTFBC)方法,该方法把卷积码作为外码、空时频分组码作为内码,通过交织器,连接内码和外码。仿真结果表明,本文建议的方法随着发收天线数的增加,其性能不断得到改善,在误比特率(BER)为10-3时,本文建议方法与空时频分组编码(STFBC)、空时频网格编码(STFTC)相比,其性能增益分别提高了6dB和8dB。     

基于循环中国剩余定理和改进的PEG算法的IRA码

为了避免交织器产生的时延,通过改进的渐进边增长(PEG)算法和循环中国剩余定理构造了一种不规则重复累积(IRA)码.与常规的IRA码相比,提出的码字具有半随机半结构化形式,不需要设计交织器,且码长选择更加灵活.仿真结果显示,在码率为1/2的条件下,当误码率为10-6时,构造的IRA(1 000,500)码与PEG-IRA(1 000,500)码和基于剩余类数对的IRA(1 000,500)码相比,在对应的相同条件下分别取得了0.2 dB和0.1 dB左右的净编码增益提升;且在码率为3/4时,所构造的IRA(16 200,11 880)码比相同码长和码率的DVB-S2标准LDPC码净编码增益提高了约0.1 dB左右.     

Alamouti Code with Quadrature Partial Response Signaling

In this letter, the Alamouti code combined with partial response signaling (PRS) is proposed. The bit error rate of the proposed quadrature PRS (QPRS) Alamouti code is derived for the quasi-static Rayleigh fading and additive white Gaussian noise channel. Furthermore, its performance in a severely bandlimited channel is simulated by using chopping filter and compared with the conventional Alamouti code. The numerical results show that the proposed QPRS Alamouti code outperforms the conventional Alamouti code under the chopping environment.     

Nonlinear network coding based on multiplication and exponentiation in GF（2^m）

This article proposes a novel nonlinear network code in the GF(2m) finite field. Different from previous linear network codes that linearly mix multiple input flows, the proposed nonlinear network code mixes input flows through both multiplication and exponentiation in the GF(2m). Three relevant rules for selecting proper parameters for the proposed nonlinear network code are discussed, and the relationship between the power parameter and the coding coefficient K is explored. Further analysis shows that the proposed nonlinear network code is equivalent to a linear network code with deterministic coefficients.     

基于EXIT Chart的码率兼容LDPC码的构造

提出了一种码率兼容LDPC(Rate-Compatible LDPC,以下简称RC-LDPC)码的构造方法.通过该方法构造所得到的一个高码率LDPC码的校验矩阵(H矩阵)中所包含的其它低码率LDPC码的度分布对都是通过码率兼容约束EXIT Chart优化得到.仿真结果表明这样优化得到的各个码率的LDPC码性能与采用普通的最优约束EXIT Chart优化所得到的LDPC码的性能接近.     

基于跳频扩时光正交码的光码分多址系统性能分析

提出了一种基于光正交码（OOC）的跳频方案，与OOC系统相比，采用该跳频码字的光码分多址（OCDMA）系统的可容纳用户数目得到了极大提高，并且多用户干扰（MAI）大大降低，从而系统整体性能得到提高。同时提出了使用该跳频码的多比特传输光码分多址系统方案，该方案利用了跳频码字数目的充裕性，使得系统传输速率成倍提高。     

一种改进的DSSS系统的码捕获技术

针对低信噪比条件下直接序列扩频(DSSS)系统的码捕获问题,提出了差分非相干累加的PN码捕获技术。研究了差分相干与差分非相干码捕获技术的工作性能,仿真结果表明,差分非相干码捕获技术具有更强的抗载波频偏能力。在此基础上,克服调制数据对码捕获的影响,提出了一种改进的差分非相干码捕获技术,即差分非相干累加的码捕获技术。仿真研究证明了差分非相干累加码捕获技术比差分非相干码捕获技术有4 dB的改善,其更能适应低信噪比条件工作。     

A new full-rate full-diversity orthogonal space-time block coding scheme

In this work, we present a new space-time orthogonal coding scheme with full-rate and full-diversity. The proposed space-time coding scheme can be used on quaternary phase-shift keyed (QPSK) transceiver systems with four transmit antennas and any number of receivers. An additional feature is that the coded signals transmitted through all four transmit antennas do not experience any constellation expansion. The performance of the proposed coding scheme is studied in comparison with that of 1/2-rate full-diversity orthogonal space-time code, quasi-orthogonal code, as well as constellation-rotated quasi-orthogonal code. Our study shows that the proposed coding scheme offers full rate and outperforms the 1/2-rate orthogonal codes as well as full-rate quasi-orthogonal codes when the signal-to-noise increases. Compared to the constellation-rotated quasi-orthogonal codes (the improved QO scheme), the newly proposed code has the advantage of not expanding the signal constellation at each transmit antenna. The performance of the newly proposed code is comparable to that of the improved QO scheme.     

一种利用完备差集构造原模图QC-LDPC码的方法

利用组合数学中的完备差集,对原模图提出了一种新颖的准循环低密度奇偶校验码(Quasi-Cyclic Low-Density Parity-Check,QC-LDPC)扩展方法。该方法能大幅降低编译码的复杂度,所得到的校验矩阵中不存在四环。仿真结果表明:利用该方法构造出的P-CDS-QC-LDPC(798,399)码,在BER为10-4时,对比基于完备差集构造的同码率CDS-QC-LDPC(1092,546)码,其净编码增益提高约0.24dB。在BER为10-5时,对比基于渐近边增长(Progressive EdgeGrowth,PEG)算法构造的同码率PEG-LDPC(900,450)码,其净编码增益提高约0.15dB。