WATER—FILLING SPACE—TIME GODE IN CORRELATED FLAT RAYLEIGH FADING MISO CHANNELS

In this paper,STC with water-filling transmit power distribution in MISO system is proposed when the partial channel information feedback is possible,for example,at slow fading scenarion.The performances of the water-filling STC including water-filling STTC and waterfilling STBC are analyzed.Performance comparison of the Ungerboeck‘s2/3 trellis coded 8PSK modulated 2-STBC and 2-STTCs with QPSK is given out different channel correlation.     

BER analysis of MPSK space-time block codes with differential detection

Closed-form expressions of the bit error rate (BER) are derived for space-time block codes based on Alamouti's (1998) scheme and utilizing M-ary phase shift keying modulation with noncoherent differential encoding/decoding. The analysis is carried out for the flat block-fading Rayleigh channel, and the BER expression is an approximation for high signal to noise ratio. Theoretical results are validated by simulations for BPSK and QPSK modulations.     

Nakagami衰落信道中差分空时分组码误比特率分析

研究差分空时分组码在Nakagami衰落信道下的性能.在介绍2发1收差分空时分组码编译码方案的基础上,得出Nakagami信道下差分空时分组码的误比特率.仿真结果与理论计算值一致,证明了所推导误比特率计算表达式的正确性.     

在频率选择性相关信道中的空频分组编码技术

本文提出了频率选择性瑞利衰落信道中的对角空频分组码(DSF)，研究了码的性能。分析表明，在各天线对间的信道相互独立，系统有NT个发射天线，NR个接收天线和信道冲击响应长度是L时，DSF码可实现分集增益NRNTL。此外，相关的发射天线阵列会使DSF码分集增益下降，但是对码的性能影响不大，特别是在较长的多路径信道上。因此，DSF码对于相关的衰落信道显示出优越的鲁棒性能。最终仿真结果证实了本文的分析。     

协作发射分集系统及其误码性能分析

协作分集（cooperative diversity）技术通过使网络中各单天线用户共享彼此天线，形成虚拟的多天线阵列来实现发射或接收分集，并结合一定的编码方式，可以有效地提高系统性能。多载波码分多址（MC-CDMA，multi．carder code division multiple access）技术将数据调制到各个子载波上发送，可以有效地抵抗信道频率选择性衰落的影响。由此提出了无线网络中频率选择性衰落信道环境下的一种基于分布式空时分组码（DSTBC，distributed space tim eblock code）和MC-CDMA的协作发射分集方案，建立了协作用户间的误码表示模型，基于该模型推导了在协作条件下整个系统误码性能的理论表达式。分析了协作用户间的平均解码差错概率对系统误码性能的影响，并给出了仿真结果。结果表明，本系统相对于未编码的MC-CDMA系统获得了明显的性能增益，同时仿真也较好地验证了理论结果。     

RS-MPSK编码调制在传输压缩图像的Rayleigh衰落信道中的性能

本文研究了两种结构的ＲＳ－ＭＰＳＫ编码调制方案在传输压缩图像的Ｒａｙｌｅｉｇｈ衰落信道中的性能。采用计算机仿真的方法得到了该方案在Ｒａｙｌｅｉｇｈ衰落信道中的误比特率,并与理论上限进行了比较,将方案用于传输压缩图像时,可大大提高系统的性能,具有较高的理论意义和衫价值。     

混沌DCSK抗噪和抗多径干扰的性能分析

目前各种混沌键控调制方案中，混沌差分键控（DCSK）有着最优的抗噪性能。主要研究混沌DCSK调制在加性高斯白噪声（AWGN）信道和两径瑞利衰落延时信道（two—ray Rayleigh fading channel with delay）的误码率公式，并对其误码率特性进行相应的仿真和分析，最后再与CSK系统的性能做比较。     

联合多幅多相差分制在衰落信道下的性能分析

本文研究了联合多幅多相差分调制方式－ARDPM在衰落信道下及不同多谱乐频移时的性能，并通过计算QAM系统和ARDPM系统在不同多谱勒频移时的误码率上界，对两个系统的性能进行了比较。在多谱勒频移较小时 ，ARDPM系统的性能优于QAM，但是随着多谱勒频移的增大，ARDPM系统的性能将迅速恶化，此时QAM系统的性能将优于ARDPM。最后本文给出计算机的理论计算曲线和实际的仿真结果。     

Performance analysis of ARQ schemes with code combining over Nakagami-m fading channel

This article investigates the performance of hybrid automatic repeat request (HARQ) with code combining over the ideally interleaved Nakagami-m fading channel. Two retransmission protocols with coherent equal gain code combining are adopted, where the entire frame and several selected portions of the frame are repeated in protocols Ⅰ and Ⅱ, respectively. Protocol Ⅱ could be viewed as a generalization of the recently proposed reliability-based HARQ. To facilitate performance analysis, an approximation of the product of two independent Nakagami-m distributed random variables is first developed. Then the approximate analysis is utilized to obtain exact frame error probability (FEP) for protocol Ⅰ, and the upper bound of the FEP for protocol Ⅱ. Furthermore, the throughput performance of both two protocols is presented. Simulation results show the reliability of the theoretical analysis, where protocol Ⅱ outperforms protocol Ⅰ in the throughput performance due to the reduced amount of transmitted information.     

慢变平坦衰落信道下空时码设计准则的改进

对用于慢变平坦瑞利衰落信道的空时码设计准则进行了研究。考察了不同长度的首事件差错概率，并基于这些概率推出误帧率的上界，进而提出一种使误帧率的上界最小化的新准则。另外，证明了空时码的几何一致性并使用该特性大大地减少了空时码搜索的复杂度。依据该准则搜索得到一些新码，并与现有好码进行性能比较。     

Performance of Hybrid ARQ Schemes with ML Code Combining over a Block-Fading Rayleigh Channel

This paper considers two well-known selective-repeat retransmission schemes, namely, hybrid type-I ARQ and hybrid type-II ARQ, using convolutional coding, in conjunction with maximum-likelihood code combining. Our theoretical analysis, based upon the concept of generalized weight distribution, shows that the use of code combining yields a significant throughput at very high channel error rates not only in constant AWGN channels but also in fading channels. To demonstrate this, we consider a widely-used block-fading Rayleigh channel model, in which the channel is assumed to be constant during each block of data and the fading is assumed to be independent from block to block. A key parameter in designing retransmission protocols for delay-limited applications in such channels is the minimum number of retransmissions, needed to achieve error-free decoding at almost all channel conditions (low outage probability). This number can be reduced significantly when code combining is employed.     

相关衰落信道上WCDMA系统的安全性能分析

对多输入多输出（MIMO）相关衰落信道上宽带码分多址接入（WCDMA）的安全性能进行评估,一种省时高效的解决方案是理论分析法。推导了相关 Nakagami 衰落信道上采用空时分组码和二维瑞克接收机（2D-Rake）的 WCDMA 系统的非零安全容量概率和安全中断概率的精确解析表达式。利用上述表达式,可以快速地评估收发天线数、天线相关系数、Nakagami衰落系数、平均路径衰减系数等参数对WCDMA系统安全性能造成的影响。数值计算和仿真结果相吻合,证明了以上理论分析的正确性。推导了WCDMA系统渐近安全中断概率的解析表达式。结果表明,WCDMA 系统的安全分集增益为主信道各个可分离路径上的分集增益之和,与窃听信道无关;对于恒定多径强度轮廓的同分布Nakagami衰落信道,WCDMA系统的安全分集增益为主信道的收/发天线数、多径个数以及Nakagami衰落系数四者之积。     

DS－SFH扩频多址系统在瑞利衰落信道中多径分集的性能研究

本文讨论了混合ＤＳ－ＳＦＨ扩频多址ＳＳＭＡ通信系统在瑞利衰落信道中多径分集接收的性能。基于多径干扰、多址干扰和信道噪声之和为一个高斯随机变量的分析，推导了在等增益组合（ＥＧＣ）和选择最大（ＳＭ）多径分集接收算法下，扩频系统的平均差错概率。理论分析和数值模拟指出：扩频多径分集接收可以明显地改善ＤＳ－ＳＦＨＳＳＭＡ系统的性能，在提高系统性能方面，等增益组合算法优于选择最大分集算法。     

Degrees of freedom of MIMO interference channel with distributed space-time interference alignment

In the context of K-user MIMO interference channel (IC),achievable degrees of freedom (DoF) were investigated with distributed space-time interference alignment (DSTIA).By precoding with distributed current and outdated channel state information at the transmitters (CSIT),new tradeoff regions between achievable DoF and CSI feedback delay/frequency were achieved for MISO system.The impact of the number of transmit antennas on achievable DoF in the MISO system was analyzed,revealing that DoF results approach to the outer bound as the number of transmit antennas increases.Further,the impact of the number of receive antennas on achievable DoF was characterized,deriving the range of CSI feedback delay that preserves achievable DoF in the MIMO system.Theoretical and numerical analyses show that,the proposed DSTIA scheme can achieve better sum-DoFs by eliminating inter-user interference perfectly,tighten the gap between achievable DoF and outer bound,as well as improve the achievable rate of the system.     

Nakagami-m衰落信道下空时分组码的性能估计

基于等效单输入单输出SISO (Single-input Single-output) 模型,利用矩量母函数 (MGF) 分析法,空时分组码STBC (Space-Time Block Coding) 的误符号率是可以得到其准确闭式表达式的.对于独立同分布Nakagami-m衰落信道下的空时分组码的性能进行了研究,给出了采用M-PSK 和M-QAM调制方案的不同空时分组编码矩阵误符号率的闭式解以及基于闭式解的解析性能结果,通过蒙特卡洛仿真验证了闭式解的准确性.还从调制方案的角度对于几种新的空时分组码的性能进行了一些新的讨论.     

Performance analysis of cooperative diversity for two-way multi-relay system with channel estimation error

In this work, we consider an amplify-and-forward two-way multi-relay system for wireless communication and investigate the effect of channel estimation error on the error rate performance. With the derivation of effective signal-to-noise ratio at the transceiver and its probability density function, we can get approximate expression for average bit error rate. Simulation results are performed to verify the analytical results.     

短波差分跳频系统抗部分频带干扰性能分析

对接收端采用非相干平方律能量检测器及维特比译码器的短波差分跳频通信系统,在无衰落信道和频率非选择性慢衰落信道下抗部分频带干扰的性能进行了理论分析.若信道存在衰落,则假设每跳所经历的衰落过程是相互独立的,且服从瑞利分布.部分频带干扰被模拟为加性高斯噪声,分析中考虑了背景热噪声.结果表明:差分跳频相邻两跳频率之间的相关性为系统提供了良好的抗部分频带干扰的能力.若忽略背景热噪声,则当信干比为20dB时,在无衰落信道下最坏情况比特误码率可达10-5,而在频率非选择性瑞利慢衰落信道下最坏情况比特误码率可达10-3.     

OFDM-MQAM在相关Nakagami-m衰落信道上的性能分析

本文研究频率选择性相关Nakagami衰落信道上采用最大比合并(MRC)分集接收的正交频分多路复用M进制正交幅度调制(OFDM-MQAM)系统.使用矩生成函数(MGF)方法和高斯超几何函数、Appell超几何函数或Lauricella函数,推导任意衰落参数频率选择性相关Nakagami衰落信道上MRC分集接收的OFDM-MQAM系统的误符号率(SER)性能,获得了OFDM-MQAM误符号率的一个新的解析表达式.数值计算结果阐明了多径路径数、Nakagami衰落参数和信道脉冲响应抽头间的相关系数对OFDM-MQAM误符号率性能的影响.     

Analysis of K-Transmit Dual-Receive Diversity with Cochannel Interferers over a Rayleigh Fading Channel

The need to combat the severe effects of fading and interferencein the rapidly increasing number of communication systemsproviding wireless services has motivated the study of diversityin the presence of interference.Hence the analysis of wireless systems with both transmit andreceive diversity and subject to cochannel interference is animportant tool for system design.We consider here a K-transmit dual-receive diversitycommunication systememploying K antennas for transmission and two antennasfor reception. The desired signal is corruptedby N interfering sources apart from additive whiteGaussian noise. The channel is Rayleigh fading.As a result, the channel matrix for the desired signaland the propagation vectors of the interferers havezero-mean complexGaussian entries; the entries are assumedto be independent and identically distributed.The complex receive weight vectorused for combining the received signalsis chosen so as to maximize the outputsignal-to-interference-plus-noiseratio (SINR).From the statistics of the channel matrix and thepropagation vectors of the interferers,we derive a closed-form expressionfor the probability density function (p.d.f.)of the maximum outputSINR. This p.d.f. can be used to obtainthe symbol errorprobability for different digital modulation schemes.     

Effects of LDPC Code on the BER Performance of MPSK System with Imperfect Receiver Components over Rician Channels

In this letter, we study the influence of receiver imperfections on bit error rate (BER) degradations in detecting low‐density parity‐check coded multilevel phase‐shift keying signals transmitted over a Rician fading channel. Based on the analytical system model which we previously developed using Monte Carlo simulations, we determine the BER degradations caused by the simultaneous influences of stochastic phase error, quadrature error, in‐phase‐quadrature mismatch, and the fading severity.