Performance Analysis of Dual-Branch Selection Combining Over Correlated Rician Fading Channels for Desired Signal and Cochannel Interference

System performances of dual selection combining over fading channels are analyzed. Fading between the diversity branches and between interferences is correlated and Rician distributed. Infinite series expressions for the probability density function, and the cumulative distribution function of the output signal-to-interference ratio are derived, which is the main contribution of this paper. Outage probability and the average bit error probability for noncoherent modulation schemes are also presented. Numerical results, presented in this paper, point out the effects of fading severity and correlation on the system performances.     

Predetection Switched Combining in Correlated Rician Fading

The performance of dual-branch predetection switch-and-stay combining (SSC) in correlated Rician fading is considered in conjunction with several modulation formats. Analytical expressions are derived for the average symbol error rate (SER) of predetection SSC in correlated Rician fading. Switching thresholds that minimize the average SER are obtained. The impact of fading factor and the fading correlation on the performance of predetection SSC is studied. Analytical expressions for the output average signal-to-noise ratio (SNR) and the outage probability are derived. The validity of the analytical expressions are verified using Monte Carlo simulation.     

Performance of S + N Selection Diversity Receivers in Correlated Rician and Rayleigh Fading

The performances of two signal-/?/wi-noise (S + N) selection diversity receivers employing noncoherent M-ary frequency shift keying (MFSK) in slow, flat, correlated Rayleigh and Rician fading channels are examined. The branches are assumed to be equally correlated for Rician fading. The correlation model for Rayleigh fading is more general than the equally correlated scenario and includes it as a special case. Analytical expressions are derived for the average symbol error rate (SER) and the average bit error rate (BER) of each receiver structure. Extensive Monte Carlo simulation results are presented to validate the analytical expressions. The performances of the S + N SC receivers are compared to the performance of the classical SC receiver. The effects of correlation, average fading power imbalance and diversity order on the performances of the S + N SC receivers are examined.     

MIMO系统在空时二维相关莱斯快衰落信道下的性能

与准静态独立的瑞利衰落信道模型相比较,在MIMO(Multi-Input Multi-Output)系统中,实际信道更趋向于空时相关莱斯快衰落。考虑到MIMO系统的收发分集优势以及收发两端天线阵列的空时相关性,在简单论述了MIMO系统和信道模型的基础上,该文利用多变量统计学理论,推导出MIMO系统在空时相关莱斯快衰落信道下平均成对差错概率上界的闭合表达式,并探讨了信道特性对系统性能的影响,然后给出相应仿真结果。     

Asymptotic Error Rate Analysis of Dual-Branch Diversity over Correlated Rician Channels

Asymptotic error rate expressions are derived for equal gain combining and selection combining on dual-branch correlated Rician channels. The asymptotic error rate performances of three popular diversity combining techniques are compared and some insights are obtained. The impacts of various channel parameters on the asymptotic performances of these diversity combining techniques are studied comprehensively. Some previous observations on diversity performances on correlated Rician channels are unified and further extended.     

相关阴影Rician信道上广义矩形MQAM的性能

本文使用矩生成函数方法推导了相关视距(LOS)分量和独立散射分量条件下的多输入多输出阴影Rician衰落信道上采用正交空时分组编码(OSTBC)的广义矩形M进制正交幅度调制(MQAM)的平均误符号率(SEP)的精确闭合表达式.利用该表达式可计算信道衰落参数以及天线间的相关性对广义矩形MQAM平均SEP性能的影响.数值计算结果阐明,天线间的相关性恶化了广义矩形MQAM的平均SEP性能,广义矩形MQAM的平均SEP性能随着信道衰落参数的增大而得到改善.     

发射分集系统在空间相关莱斯快衰落信道下的性能

采用空时编码的发射分集系统的性能分析是当前移动通信研究领域的热点问题。相对准静态独立的瑞利衰落信道模型而言,空间相关莱斯快衰落信道更适用于实际情况。但由于在空间相关莱斯快衰落情况下,发射分集系统的性能分析比较复杂,因此关于这方面的论文较少。本文利用多变量统计学理论,得到发射分集系统在空间相关莱斯快衰落信道下平均成对差错概率上界的闭合表达式,并详细说明了信道特性对系统性能的影响。最后给出了仿真结果。     

Capacity of MRC on Correlated Rician Fading Channels

A new exact explicit expression is derived for the ergodic capacity of maximal ratio combining (MRC) schemes over arbitrarily correlated Rician fading channels. This is used to study the effects of channel correlation on the ergodic capacity. Numerical results reveal that both the phase and the magnitude of correlation have an impact on the ergodic capacity of Rician fading channels. This is in contrast to correlated Rayleigh fading, where the phase of the correlation has no effect on the ergodic capacity. It is also observed that negatively correlated branches in Rician fading may lead to an increase in ergodic capacity beyond that obtained by uncorrelated branches.     

相关瑞利衰落信道下空时分组编码性能分析

目前对空时编码的研究大都是基于信道是独立的假设下进行的,然而在实际系统中独立性假设是不成立的。基于此,研究了信道的相关性对空时编码性能的影响。计算机仿真结果表明：由于衰落信道的相关性,系统性能有所下降,且系统性能关于相关系数存在“地板效应”,即相关系数小于某一数值时,对系统性能的影响较小;当大于此值时,系统性能就会急剧下降。     

Exact Performance Analysis of Dual-Branch Coherent Equal-Gain Combining in Nakagami- $m$, Rician, and Hoyt Fading

The exact symbol error rates (SERs) of several M-ary modulation schemes are obtained in a unified manner for mobile radio receivers employing dual-branch coherent equal-gain combining (EGC), where the received signals on each branch follow either similar or different fading distributions. Specifically, the cases considered are Nakagami-m, Rice, and Hoyt fading on both branches, but with not necessarily identical parameters, and mixed Nakagami-m/Rice and Nakagami-m/Hoyt fading; only the integer or half-integer values of the Nakagami-parameter are considered. While the previous exact expressions for the SERs of general M-ary modulations with L-branch EGC contained double integrals, the error probability expressions derived in this paper for the case of L=2 contain only a single integral. In addition, the derived probability distributions also allow the direct obtaining of other useful performance measures, such as the exact level crossing rates, average fade durations, and outage probabilities.     

Chaos-Coded Modulations Over Rician and Rayleigh Flat Fading Channels

In this brief, we analyze a kind of chaos-coded modulations over both Rician and Rayleigh frequency non-selective uncorrelated fading in the presence of additive white Gaussian noise. We provide bounds both for the case when perfect channel-state information (CSI) is available at the decoder and when there is no CSI. We show that the bounds proposed can be tight enough to give reason of the behavior of these systems in a flat fading channel. We compare the results with a related trellis-coded modulation and show that the degradation in performance can be at least as low as with conventional coded modulation systems.     

The Performance of Multicarrier CDMA for the Correlated Rayleigh Fading Channel

We present an new method for the analytical calculation of the error probability in a Rayleigh fading channel with correlated fading amplitudes. Even though the method can be applied for more general problems, we restrict ourselves on the investigation of a multicarrier CDMA transmission. The frequency correlation between the fading amplitudes of the carriers is given by the delay power spectrum of the channel. We generalize the well-known analytical expressions for the pairwise error probability of the uncorrelated Rayleigh channel to this case of correlated fading. This probability can be expressed in a closed form by an integral over a finite interval which can be easily evaluated numerically. We present some examples to show how much of the diversity of a code remains useful if the transmission channel does not provide an arbitrary degree of diversity.     

相关瑞利衰落下的2D-RAKE接收机

本文针对单蜂窝直扩码分多址(DS-CDMA)通信系统，研究了在相关瑞利衰落下使输出信号与干扰加噪声功率比(SINR)最大的2D-RAKE接收机，推导出误比特率(BER)的解析表示式，证明了只要具有足够大的信噪比(SNR)和适当的权值矢量，这种接收机也能获得独立多径信号所能贡献的最大空时分集增益，其用户容量增益也远优于普通的RAKE或多天线接收机，且更适于宽带CDMA系统的应用.     

Performance Analysis of Linear Modulation Schemes With Generalized Diversity Combining on Rayleigh Fading Channels With Noisy Channel Estimates

Generalized diversity combining (GDC), also known as hybrid selection/maximal ratio combining or generalized selection combining, is a low-complexity diversity combining technique by which a fixed subset of a large number of available diversity channels is chosen and then combined using the rules of maximal ratio combining. In this paper, we analyze the performance of GDC on time-correlated Rayleigh fading channels with noisy channel estimates. We derive expressions for the probability of error for various linear modulation schemes with coherent detection, and discuss the conditions under which the analysis can be extended to noncoherent and differentially coherent receiver structures. Throughout the paper, using a fundamental approach to obtain the decision statistic at the combiner output, a number of new expressions for the error probabilities are obtained in a rigorous way, along with a presentation of their performance with channel estimation errors. The final expressions have roughly the same complexity of evaluation as that for the channel with only additive Gaussian noise. Our results correct various inaccuracies in the literature, and show that coherent receivers based on imperfectly estimated channel knowledge incur a significant performance loss.      

Performance Analysis of System with Micro- and Macrodiversity Reception in Correlated Gamma Shadowed Rician Fading Channels

In this paper, the performance of wireless system employing microdiversity to mitigate the effects of short-term fading and macrodiversity to reduce long-term fading (shadowing) effects is studied. The system model assumes implementation of maximal-ratio combining (MRC) at the microlevel and selection combining (SC) at the macrolevel. The received signal envelope follows a Rician distribution and it also suffers gamma shadowing. Novel expressions for the probability density function (PDF), cumulative distribution function (CDF), and moment-generating function (MGF) of the output signal-to-noise ratio (SNR) are obtained. Several useful performance criteria, such as the moments of the output SNR and outage probability are analytically derived. Moreover, the average bit error probability (ABEP) for noncoherent binary differential phase-shift keying (BDPSK) is calculated using the MGF based approach while the ABEP for coherent binary phase-shift keying (BPSK) is studied by averaging the conditional bit error probability over the PDF. Numerical results are graphically presented to show the effects of various system parameters to the system performance, as well as the enhancement due to use of the combination of micro- and macrodiversity. Some of numerical results are complemented by equivalent computer simulated results which validate the accuracy of the proposed analysis. The agreement between the Rician-gamma and Rician-lognormal fading model is also established.     

Performance Analysis of Generalized Selection Combining in Generalized Correlated Nakagami- m Fading

The exact performance of selection combining, hybrid selection/maximal-ratio combining (H-S/MRC), and threshold-based H-S/MRC in correlated Nakagami-m fading for positive integer values of fading parameter m, is analyzed for a particular correlation structure. This correlation model, though not general, is much more general than the equal-correlation case, and includes equal correlation as a special case. The symbol-error rate and outage probability of the three combining schemes are obtained by transforming the correlated branch gains into a set of conditionally independent branch gains. Numerical and simulation results show excellent agreement with theoretical results     

Diversity Cutoff Rate Evaluation of the Rayleigh and Rician Fading Channels

This paper presents expressions for the cutoff rate R0diversity transmission over the Rayleigh and Rician fading channels withM-ary orthogonal signaling. These expressions include the unquantized R0forD-fold diversity, which upper bounds the channel performance, and hard decision and four- and eight-level soft decision quantized R0expressions. Tradeoffs betweenDand the number of quantization levels for equivalent performance are presented for the unquantized and quantized channels. These tradeoffs illustrate the reduction in signal energy, system bandwidth, and system complexity by increasing the number of quantization levels, thereby allowing a reduction inD.     

相关瑞利分集系统容量的研究

一般来说,充分利用无线信道的特性能够极大地提高通信系统的容量,但是对于相关瑞利信道的平均容量讨论的不多。文章借助于一种线性变换的方法,得出了一种相关瑞利分集情况下容量的近似表达式,简化了在通常情况下的复杂的表达式。数值计算的结果也形象地说明了相关系数对分集容量的影响,以及分集能够有效的提高系统的容量。     

Error Probability and SINR Analysis of Optimum Combining in Rician Fading

This paper considers the analysis of optimum combining systems in the presence of both co-channel interference and thermal noise. We address the cases where either the desired-user or the interferers undergo Rician fading. Exact expressions are derived for the moment generating function of the SINR which apply for arbitrary numbers of antennas and interferers. Based on these, we obtain expressions for the symbol error probability with M-PSK. For the case where the desireduser undergoes Rician fading, we also derive exact closed-form expressions for the moments of the SINR. We show that these moments are directly related to the corresponding moments of a Rayleigh system via a simple scaling parameter, which is investigated in detail. Numerical results are presented to validate the analysis and to examine the impact of Rician fading on performance.