最大比合并分集接收性能的新的分析方法

对Rayleigh衰落信道中最大比合并分集系统的性能进行了分析.基于泊松分布,提出了一种新的误比特率计算式,并提出了一个新的性能上界,去除了级数和运算,进一步简化了性能分析.数值分析表明,提出的误码率计算式与原分析式一致,且性能上界与误码率的准确值近乎重合.运用仿真对理论分析进行了验证,数值和仿真结果表明,提出的性能分析式简单准确有效,可更为迅速的评估最大比分集合并系统的性能.     

双分集最大比合并相关瑞利衰落的误码性能

给出MPSK与CFSK在双分集最大比合并相关瑞利衰落信号下的误比特率的解析结果,无需冗长的模拟,易于研究分集合并与信道相关性对系统性能的影响,其数值结果与先前的研究结果一致.     

莱斯信道中Polar码的构造及性能分析

Polar码是由Arikan提出的一种新的编码方式。它是基于信道极化理论,被证明在二进制离散无记忆信道下能够获得信道对称容量。本文给出了polar码在莱斯信道下的构造及性能分析,针对莱斯信道已知信道边信息（CSI）和未知信道边信息（NCSI）两种情况分别进行polar码的构造。仿真结果表明:相比于LDPC码,polar码的性能更加优良。此外,莱斯因子K越大,polar码的误比特率就越小。polar码在信道边信息已知的情况下性能比信道边信息未知时的好。因此Polar码在莱斯衰落信道中具有很好的性能,非常适合未来移动通信技术。      

线性正交分集变换（LDRT）在莱斯衰落信道中的性能分析

线性正交分集变换（ＬＤＲＴ）是近来提出的一种有效的抗衰落技术,本文对线性分集变换在莱斯衰落信道中的性能进行了分析研究,当信号调制选用ＱＰＳＫ时,计算机仿真结果：在误码率为１０＾－４条件下,信道参数Ｋ等于０ｄＢ时,ＬＤＲＴ处理增中达２１ｄＢ;随着Ｋ的增大,相应的处理增益减小,当Ｋ＝１０ｄＢ时,经过ＬＤＲＴ后的性能对高斯信道的性能只相关１ｄＢ,另外对分集矩阵的阶数Ｌ对系统误比特性能的影响进行了分析讨论     

最大比合并接收系统在n-Rayleigh信道下的性能分析

在n-Rayleigh信道下,研究了MRC(Maximal Ratio Combining)合并接收系统的平均码字错误率(ASEP)性能。基于矩生成函数(MGF)的方法,推导了MRC接收系统在n-Rayleigh衰落信道上采用M进制相移键控(MPSK),M进制正交幅度调制(MQAM)和M进制脉冲幅度调制(MPAM)等几种M进制数字调制方式的ASEP的计算式。然后在不同条件下,仿真了系统的ASEP性能,仿真值与理论值相一致,理论分析的正确性得到了证明。分析结果表明:分集支路数和衰弱因子对系统的ASEP性能有重要影响。     

压缩频谱的差分跳频信号在莱斯衰落信道下的性能分析

差分跳频(DFH)信号具有良好的抗多径衰落、抗干扰及高速数据传输能力,在短波和水声军事通信领域得到广泛应用。但是,在有限的传输带宽内差分跳频信号编码增益受限,特别是每跳携带多个比特时,该文提出一种压缩频谱DFH(CS-DFH)方法,可以在相同的比特每跳(BPH)和带宽下提高DFH信号的编码增益。对CS-DFH信号在莱斯(Rice)衰落信道下的误比特率(BER)理论上界进行了推导,并通过仿真验证。结果表明,莱斯信道中,在相同BPH、带宽条件下,与常规DFH相比,CS-DFH是一种可以获得更高BER增益的方法,特别是当莱斯因子K很小的时候。     

双瑞利衰落信道下最大比合并性能研究

基于接收信噪比的统计特性,研究了双瑞利衰落条件下各分集支路衰落幅度不平衡时最大比合并MRC接收系统的差错和分集性能。采用基于矩生成函数的方法导出了涵盖多种调制方式的平均误符号率ASER的通用公式,并得到了其Chernoff一致界。仿真结果表明:双瑞利衰落下采用MRC接收技术可以大大减小传输系统的ASER且能获得与瑞利衰落时相同的渐进分集增益,但在实际可接收到的信噪比范围内可获得的分集增益与满分集增益具有明显的差距;相对于单支路接收系统,双瑞利衰落下的MRC系统可近似得到满的相对分集增益。     

窃听信道相关条件下最大比传输技术安全分析

在无线通信系统的实际传输中,当窃听用户距离合法接受者足够近,或者位于合法接收机信号的无线电波路径上时,就会出现主信道与窃听信道相关的场景。为此我们考虑一个多输入单输出,并且存在单天线被动窃听者的无线通信系统,研究了当基站采用最大比技术发射技术发送信号时,相关对系统性能的影响。推导了安全中断概率与平均安全容量的闭合表达式。数值仿真结果表明:（1）当主信道的信道质量高于窃听信道时,较低的相关对系统安全中断概率性能影响不大,然而强相关却能够带来更低的安全中断概率;（2）该相关对系统平均安全容量始终是有害的,且随着相关程度的增强,最大比发射技术相对于天线选择的优势逐渐变小。      

DS-CDMA系统中最大比合并的性能分析

该文推导了存在信道估计误差的DS-CDMA系统在多径Rayleigh衰落信道中的误码率。数值计算结果表明当实际系统中的信道估计存在误差并且信道多径功率不等时,在假设相等噪声功率和理想信道估计下得到的传统最大比合并方法因无法输出最大的信噪比而性能明显下降。     

MPSK与CFSK在相关瑞利衰落信号下的误比特性能

给出MPSK与CFSK在采用最大比合并双分集接收相关瑞利衰落信号下的误比特率的解析式,便于研究分集合并与信道相关性对系统性能的影响,无需冗长的模拟,其数值结果与先前的研究一致。     

Capacity and Error Probability for Maximal Ratio Combining Reception over Correlated Nakagami Fading Channels

In this paper, the capacity and error probability of maximal ratio combining (MRC) reception are considered for different modulation schemes over correlated Nakagami fading channels. Based on an equivalent scalar additive white Gaussian noise (AWGN) channel, we derive the characteristic function (CF) and the probability density function (PDF) of the signal to noise ratio for MRC reception over Nakagami fading channels. Using these CF and PDF results, closed form error probability and capacity expressions are obtained for PSK, PAM and QAM modulation. Wei Li received his Ph.D. degree in Electrical and Computer Engineering from the University of Victoria in 2004. He is now a Post-doctoral Research Fellow in the Department of Electrical and Computer Engineering at the University of Victoria. He is a Member of the IEEE. His research interests include ultra-wideband system, spread spectrum communications, diversity for wireless communications, and cellular communication systems. Hao Zhang was born in Jiangsu, China, in 1975. He received his Bachelor Degree in Telecom Engineering and Industrial Management from Shanghai Jiaotong University, China in 1994, his MBA from New York Institute of Technology, USA in 2001, and his Ph.D. in Electrical and Computer Engineering from the University of Victoria, Canada in 2004. His research interests include ultra-wideband radio systems, MIMO wireless systems, and spectrum communications. From 1994 to 1997, he was the Assistant President of ICO(China) Global Communication Company. He was the Founder and CEO of Beijing Parco Co., Ltd. from 1998 to 2000. In 2000, he joined Microsoft Canada as a Software Engineer, and was Chief Engineer at Dream Access Information Technology, Canada from 2001 to 2002. He is currently an Adjunct Assistant Professor in the Department of Electrical and Computer Engineering at the University of Victoria. T. Aaron Gulliver received the Ph.D. degree in Electrical and Computer Engineering from the University of Victoria, Victoria, BC, Canada in 1989. From 1989 to 1991 he was employed as a Defence Scientist at Defence Research Establishment Ottawa, Ottawa, ON, Canada. He has held academic positions at Carleton University, Ottawa, and the University of Canterbury, Christchurch, New Zealand. He joined the University of Victoria in 1999 and is a Professor in the Department of Electrical and Computer Engineering. He is a Senior Member of the IEEE and a member of the Association of Professional Engineers of Ontario, Canada. In 2002, he became a Fellow of the Engineering Institute of Canada. His research interests include information theory and communication theory, algebraic coding theory, cryptography, construction of optimal codes, turbo codes, spread spectrum communications, space-time coding and ultra wideband communications.     

Improved Performance Analysis for Maximal Ratio Combining in Asynchronous CDMA Channels

Direct Sequence Code Division Multiple Access (DS-CDMA) receivers typically use Maximal Ratio Combining (MRC) to favorably combine the energies of distinct multipath components from diversity branches. In previous research, compromising assumptions have been made to simplify the analysis, including a Gaussian approximation for interference or constant equal cross correlations. However, these assumptions corrupt the analysis especially in certain operating conditions such as a relatively small number of users, which is particularly relevant for modern CDMA systems that carry data. The contribution of this paper is to provide a general framework for accurately analyzing the performance of the diversity receiver in CDMA systems without these compromising approximations. From the analytical and numerical results, it is: shown that the developed framework provides higher accuracy than previous approaches.     

Turbo码在最大比合并分集接收系统中的性能分析

该文提出了turbo码在最大比合并分集接收无线通信系统中纠错性能的联合上界。基于误差积分函数的简化计算式,推导了分集接收的多路信道分别具有不同衰落特性时,成对差错概率的精确表达式。以瑞利衰落信道为例,对采用turbo码的分集接收无线系统的性能进行了数值计算和仿真。结果表明：turbo码纠错性能联合上界数值计算式与仿真结果一致,可普遍用于信道衰落统计特性各不相同的分集接收系统。     

相关Nakagami衰落信道上DE-QPSK性能分析

推导m为整数的任意相关Nakagami-m衰落信道上采用最大比合并(MRC)分集接收和相干检测的差分编码四相相移键控(DE-QPSK)调制的平均误符号率(SER)精确表达式,并利用高斯Q函数指数形式的近似表达式推导相关Nakagami-m衰落信道上采用MRC分集接收的DE-QPSK调制的平均SER近似表达式。计算机仿真结果验证了精确理论分析的正确性和近似分析的准确性。     

空间相关信道下大规模MIMO两跳系统性能分析

针对多对用户大规模MIMO两跳中继系统,考虑空间相关信道,在迫零(Zero-Forcing,ZF)准则下进行中继转发传输,利用确定性等价原理,推导得出遍历可达速率解析表达式,定量给出遍历速率与信道空间相关阵及系统参数间数学关系。基于此,分析了信道空间相关性对遍历速率的影响,并在发射功率缩放率模型下,分析了信源和中继发射功率随天线数增长时可获得的缩放增益。分析发现,中继节点天线阵列引起的信道空间相关性对遍历速率的渐进极限性能无任何影响,且不会影响发射功率缩放率,大大放宽了在中继节点部署大规模天线阵列时的天线间隔要求,有益于大规模天线阵列在中继节点部署实现。利用Matlab仿真验证了遍历速率解析表达式的有效性以及理论分析结果的正确性。     

Bit Error Rate Analysis of Maximal-Ratio Combining over Correlated Gaussian Vector Channels

Analytical results are derived for the performance of maximal-ratio combining (MRC) over correlated Gaussian vector channels. Generality is maintained by assuming arbitrary- power users and no specific form for the covariance matrices of the received faded signals. The scenarios of Rayleigh fading and statistical independence among diversity branches are considered as special cases of the general analysis. The analysis is presented within the context of a system with receive diversity and cochannel interference. The results obtained are applicable to antipodal signaling over a multiuser single-input multiple-output (SIMO) channel.     

Performance Analysis of Soft-Bit Maximal Ratio Combining in Cooperative Relay Networks

In digital cooperative relaying, signals from the source-destination and relay-destination links are combined at the destination to achieve spatial diversity. These signals may not necessarily belong to the same modulation scheme due to the varying channel qualities of the two links. Recently, we have proposed the "soft-bit maximum ratio combiner" (SBMRC) as a low complexity diversity combining scheme for signals with different modulation levels. SBMRC exhibits BER performance that is very close to the optimal maximum likelihood detector (MLD), but with much reduced complexity. In this paper, we revisit SBMRC and provide tight lower bound for the BER performance. Since SBMRC has BER performance slightly inferior to MLD, the derived lower bound can also be used as a good approximation for the BER performance of MLD.     

Negatively Correlated Diversity Branches Using Various Modulation Methods and Maximal Ratio Combining

A diversity system using maximal ratio combining, and in which the diversity branches are negatively correlated, is considered. The performance of some digital systems, namely PSK, DPSK, CFSK, and NFSK, are compared. The error probability as a function of frequency differences between the branches is given. Also, error probability averaged over time delay difference τ is given as a function of direct as well as indirect signal-to-noise ratio. The sensitivity of the error probability to the form of the density function of τ is investigated.Mth order of diversity is considered, but second- and third-order diversity are specifically analyzed.     

A Hybrid Selection/Equal-Gain Combining over Correlated Nakagami-m Fading Channels

A new type of hybrid selection/equal-gain combining (HS/EGC) scheme is proposed and analyzed. This scheme dynamically selects the best combination of branches by a simple test and combines them in equal-gain combining (EGC) manner. As a result, the scheme always shows better performance than conventional EGC and selection diversity (SD), and close to maximal-ratio combining (MRC). As an exemplary performance indicator, its average output SNR for dual correlated Nakagami-m fading channels is calculated and demonstrated in comparison with other diversity schemes