基于准正交空时分组码的高速率码字设计

为了适应通信系统对高速率大容量的需求,设计了码率为2及1.5的非正交空时分组码。在此基础上,采用简化了的条件最大似然译码方法,可以大大降低译码复杂度。仿真结果表明,该编码设计具有接近实际信道容量的特点,并且其误比特率性能优于正交及准正交编码设计。     

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.     

协作通信中一种分布式酉空时码

提出了一种基于三角函数酉星座的分布式酉空时码,主要介绍了编码矩阵结构及其低复杂度的译码算法。根据仿真结果可知:提出的酉空时性能差于正交设计、系统设计和循环酉群码的性能,但从译码复杂度看,所提出的译码算法计算复杂度相比其他3种简单很多,具有很大的优势。并且还证明了同样的码字采用最大似然译码算法与所提出的低复杂度算法性能相近,但是计算复杂度相差较大。总的来说,所提出的编码矩阵结构简单,易于构造,且具有较低的译码复杂度。     

一种低复杂度的部分干扰抵消群译码算法

本文研究了在MIMO系统的接收端,采用部分干扰抵消群译码算法对接收端信号进行译码的算法,在保证码字获得满分集的同时,降低接收端的译码复杂度.通过将一个空时分组码中所包含的符号进行群组划分,对于不同的符号群组,在对接收信号经过线性滤波处理之后分别独立地进行译码操作,从而达到降低译码复杂度的目的.仿真结果显示,该算法相对于传统的最大似然译码算法,译码复杂度明显降低.     

一种新的准正交空时分组码的设计

ABBA码是一种可用于3个以上发射天线系统的准正交空时分组码,该方案虽然可以实现全速率传输,但是其译码复杂度高。针对上述缺点提出了一种基于星座旋转的能够实现满分集增益、全速率传输的准正交空时分组码,给出了接收端最大似然译码的独立译码方案,简化了译码过程,降低了译码复杂度,仿真结果表明其误码性能与ABBA码相比得到了较大的改善。     

基于部分码字译码的MPA检测算法

稀疏码多址接入技术(SCMA)是一种新型非正交多址接入技术。针对SCMA中消息传递算法进行多用户检测复杂度较高的问题,提出基于部分码字球形译码多用户检测算法(PCSD-MPA)。该算法通过设置球型半径减少参与迭代的用户码字,并根据SCMA的非正交特性引入信道质量这一新的判决机制,从而进一步降低MPA算法的计算复杂度。同时采用部分码字初始概率均等分配策略,有效提升了算法的收敛速率。仿真结果表明,在球形半径设定合理的条件下,PCSD-MPA在几乎不改变系统误比特率性能的情况下降低了MPA的复杂度,且该算法的计算复杂度随着SNR的增大明显降低。     

异步OFDM空时协同分集方案

提出一种基于空时分组编码的异步正交频分复用（OFDM,Orthogonal Frequency Division Multiplexing）协同分集方案。提出的方案在中继节点实现OFDM调制及OFDM符号的时间反转和复共轭,信宿节点接收信号的每个OFDM子载波都具有Alamouti空时分组编码结构。信宿节点采用最大似然（ML,Maximum Likelihood）译码准则译码。仿真结果表明,提出的异步OFDM空时协同分集方案无需两个中继节点的同步可获得二阶分集增益,且与其它协同分集方案相比,该方案的误比特率和实现复杂度都更低。     

RIS辅助的LDPC乘积码编码中继协作系统构建与性能分析

为实现极其可靠信息传输,针对融合可重构智能表面（RIS）技术与编码中继协作技术系统展开研究,建立了RIS辅助的低密度奇偶校验（LDPC）乘积码编码中继协作系统模型;利用LDPC乘积码,信源节点对信息矩阵行编码,中继节点对信息矩阵列编码;提出了一种高效联合迭代译码算法,目的节点对接收的两路信号分别进行LDPC行译码与LDPC列译码,并迭代更新信息位的对数似然比,再判决输出。理论推导了所提系统的中断概率以及有限码长信道容量的闭合解。理论分析与仿真结果表明,所提系统性能明显优于传统编码中继协作系统,而且随着RIS反射单元数量增加,优势变得更明显;随着LDPC乘积码码长增加,所提系统的有限码长信道容量逐渐逼近理想信道容量。     

结合信道编码的两用户协作分集方案及其性能研究

基于一种分布式空时码的非正交协作分集（DSTC-NOCD）系统,并且结合信道编码,在译码转发（DF）中继信道模型下对两用户协作分集的方案性能进行了研究。通过将turbo码和空时码引入到协作分集中,在准静态的瑞利衰落信道下对此方案的误比特率进行了系统仿真。仿真结果表明：即使协作用户间的信道存在噪声,该文所采用的方案仍优于未加信道编码的分布式空时码的非正交协作分集系统,使得误比特率进一步降低。     

一种重叠Alamouti码的最大似然检测优化算法

针对准正交重叠Alamouti码(Overlapped Alamouti Code,OAC)采用最大似然(maximum likelihood,ML)接收机检测时译码复杂度高的缺点,提出了一种ML译码优化算法。利用等价信道矩阵具有部分正交性的特点,将等价信道矩阵拆分成2个相互正交的子等价信道矩阵,使得在检测每个符号分组时可分别检测2个较短分组,从而降低了ML接收机的译码复杂度。改进算法保持了与ML译码相近的误码率性能,而运算量大幅度降低,从而克服了ML译码复杂度高的缺点。     

旋转星座下极化准正交空时分组码及性能分析

设计了发射天线数分别为8和6、码率为3/4的极化准正交空时分组码,对星座图进行最佳角度旋转,接收机采用成对译码算法,并对未旋转-极化、旋转-极化、未旋转-传统、旋转-传统这4种准正交空时分组码进行了仿真比较.结果表明,在相同条件下,当采用双极化天线时,星座图旋转对系统误码率性能改善不明显;当采用单极化天线时,旋转对系统误码率性能改善明显.     

基于旋转因子的差分酉空时分组码

基于TBH和Jafarkhan编码方案的两组准正交空时分组码,引入自适应旋转因子构造出四种差分调制酉矩阵,该方法不仅没有带来星座扩展,还使新的码字具有较大的欧氏距离。同时在接收端基于角度算子,形成了简化的成对译码方法。仿真结果表明：尽管此设计方法增加了一定的复杂度,但它比没有加入旋转因子的差分酉空时分组码具有更好的误码性能。     

A Kind of Quasi-Orthogonal Space-Time Block Codes and its Decoding Methods

1IntroductionSpace-Ti me Coding(STC)technology has been stud-ied extensively in recent years as a method to combatdetri mental effects in wireless fading channel and in-crease the transmission capacity in an open-loop way.Therein,a special class of space-…     

A Kind of Quasi-Orthogonal Space-Time Block Code and its Decoding Methods

It is well known that it is impossible for complex orthogonal space-time block codes with full diversity and full rate to have more than two transmit antennas while non-orthogonal designs will lose the simplicity of maximum likelihood decoding at receivers. In this paper, we propose a new quasi-orthogonal space-time block code. The code is quasi-orthogonal and can reduce the decoding complexity significantly by employing zero-forced and minimum mean squared error criteria. This paper also presents simulation results of two examples with three and four transmit antennas respectively.     

Signal constellations for quasi-orthogonal space-time block codes with full diversity

Space-time block codes (STBCs) from orthogonal designs proposed by Alamouti, and Tarokh-Jafarkhani-Calderbank have attracted considerable attention lately due to their fast maximum-likelihood (ML) decoding and full diversity. However, the maximum symbol transmission rate of an STBC from complex orthogonal designs for complex signals is only 3/4 for three and four transmit antennas, and it is difficult to construct complex orthogonal designs with rate higher than 1/2 for more than four transmit antennas. Recently, Jafarkhani, Tirkkonen-Boariu-Hottinen, and Papadias-Foschini proposed STBCs from quasi-orthogonal designs, where the orthogonality is relaxed to provide higher symbol transmission rates. With the quasi-orthogonal structure, the quasi-orthogonal STBCs still have a fast ML decoding, but do not have the full diversity. The performance of these codes is better than that of the codes from orthogonal designs at low signal-to-noise ratio (SNR), but worse at high SNR. This is due to the fact that the slope of the performance curve depends on the diversity. It is desired to have the quasi-orthogonal STBCs with full diversity to ensure good performance at high SNR. In this paper, we achieve this goal by properly choosing the signal constellations. Specifically, we propose that half of the symbols in a quasi-orthogonal design are chosen from a signal constellation set A and the other half of them are chosen from a rotated constellation e/sup j/spl phi// A. The resulting STBCs can guarantee both full diversity and fast ML decoding. Moreover, we obtain the optimum selections of the rotation angles /spl phi/ for some commonly used signal constellations. Simulation results show that the proposed codes outperform the codes from orthogonal designs at both low and high SNRs.     

Using Orthogonal and Quasi-Orthogonal Designs in Wireless Relay Networks

Distributed space-time coding was proposed to achieve cooperative diversity in wireless relay networks without channel information at the relays. Using this scheme, antennas of the distributive relays work as transmit antennas of the sender and generate a space-time code at the receiver. It achieves the maximal diversity when the transmit power is infinitely large. This paper is on the design of practical distributed space-time codes (DSTCs). We use orthogonal and quasi-orthogonal designs which are originally used in the design of space-time codes for multiple-antenna systems. It is well known that orthogonal space-time codes have full diversity and linear decoding complexity. They are particularly suitable for transmissions in the network setting using distributed space-time coding since their ldquoscale-freerdquo property leads to good performance. Our simulations show that they achieve lower error rates than the random code. We also compare distributed space-time coding to selection decode-and-forward using the same orthogonal designs. Simulations show that distributed space-time coding achieves higher diversity than selection decode-and-forward (DF) when there is more than one relay. We also generalize the distributed space-time coding scheme to wireless relay networks with channel information at the relays. Although our analysis and simulations show that there is no improvement in the diversity, in some networks, having channel information at the relays saves both the transmission power and the transmission time.     

一种全速率准正交空时分组码

空时分组码是发射分集中的一项新技术。通常的空时分组码采用正交设计，虽可以提供全分集增益，却不能保证全速率传输，造成发射端数据的积压。改进的空时分组码采用准正交设计，能够保证数据以全速率传输，但是其性能在低信噪比时优于正交空时分组码，在高信噪比时反而不如前者。提出一种改进的基于准正交设计的空时分组码。通过仿真表明，在不增加译码复杂度的情况下，其性能不论在低信噪比还是高信噪比时都优于正交设计的空时分组码，从而改善了系统性能。     

Improved QO-STBC for three and four transmit antennas

A new quasi-orthogonal space-time block code (QO-STBC) based on ABBA code with lower decoding complexity and higher bit error statistics (BER) performance was proposed by U.Park recently,which can obtain full transmission rate and full diversity.In this article,the authors proposed an improved U.Park scheme based on rotational ABBA code.For eliminating the interference terms resulting from neighboring signals during signal detection,two different matrixes are used.And independent decoding can be realized when maximum-likelihood decoding at the receiver is used.Simulation results demonstrate that the BER performance is improved dramatically without increasing the decoding complexity compared with U.Park scheme.     

可快速迭代解码的非相干空时编码

提出了一种基于满分集准正交空时分组码构造非酉非相干空时码的方法,该编码能够最大限度地利用信道的相关时间来提高码率.根据代数分集的定义,证明了所构造的编码可获得满代数分集.为了能够充分利用编码的准正交结构简化解码,选用了基于期望最大化的迭代算法对所构造的编码进行解码,该算法能够极大地减小最优解码器的复杂度.仿真结果表明,迭代解码算法可快速收敛且其能够很好地对解码复杂度和误码性能进行折衷.     

Novel full-diversity high-rate STBC for 2 and 4 transmit antennas

We design a new rate-5/4 full-diversity orthogonal space-time block code (STBC) for QPSK and 2 transmit antennas (TX) by enlarging the signalling set from the set of quaternions used in the Alamouti code. Selective power scaling of information symbols is used to guarantee full-diversity while maximizing the coding gain (CG) and minimizing the transmitted signal peak-to-minimum power ratio (PMPR). The optimum power scaling factor is derived analytically and shown to outperform schemes based only on constellation rotation while still enjoying a low-complexity maximum likelihood (ML) decoding algorithm. Finally, we extend our designs to the case of 4 TX by enlarging the set of quasi-orthogonal STBC with power scaling. Extensions to general M-PSK constellations are straightforward.