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1.
Khoa N. Le 《International Journal of Communication Systems》2014,27(10):2289-2308
This paper studies four aspects of multipath propagation with randomly distributed scatterers: (i) Gaussian and hyperbolic time‐of‐arrival (ToA) probability density functions (pdfs); (ii) theoretical bounds on the ToA pdfs; (iii) geometric pdfs in multipath propagation via Gaussian and hyperbolic scattering channels; and (iv) implementation of selective combining diversity as a method to decrease propagation delay, thus improving transmission performance. The Gaussian and hyperbolic scattering channels are employed to model random scatterers between a base station and a user equipment. One‐dimensional and three‐dimensional results of Gaussian and hyperbolic ToA pdfs are reported. Detailed discussions are given. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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This paper derives the capacity of a fading channel with orthogonal frequency division multiplexing transmission employing diversity techniques and adaptive policies in Rayleigh fading environments. The effects of Doppler shift fd on channel capacity are analysed. The main contribution of this work is to model intercarrier interference as a function of fd and symbol duration Ts. Two diversity techniques are considered (i) maximal ratio combining (MRC) and (ii) selective combining (SC). Three adaptive policies are combined with MRC and SC to estimate the following channel capacity: (i) optimal rate adaptive; (ii) optimal power and rate adaptive; and (iii) channel inversion with fixed rate adaptive. Closed‐form expressions and bounds on channel capacity employing different diversity techniques are derived. Simulation results are given. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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This paper derives capacity of a fading channel with orthogonal frequency division multiplexing (OFDM) transmission employing diversity techniques and adaptive policies involving (i) power and rate, (ii) optimal rate and (iii) channel inversion with fixed rate. Two major diversity techniques are considered (i) maximal ratio combining (MRC) and (ii) selective combining (SC). Closed‐form expressions and/or bounds on various channel capacity with OFDM transmission under different scenarios are derived. Simulation results are given. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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采用两条支路分集接收的相关瑞利衰落信道容量 总被引：5，自引：0，他引：5
本文研究采用两条支路最大比合并(MRC)或选择合并(SC)分集接收的相关瑞利衰落信道理论容量推导恒定发射功率自适应M进制正交幅度调制(M-QAM)的频谱效率,并将它们与独立同分布瑞利信道理论容量进行比较,其结果对收发信机之间无视距分量路径、接收机上分集天线之间的距离小于半个波长的无线通信系统设计具有指导作用. 相似文献
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Muhammad Asshad Adnan Kavak Kerem Küük Sajjad Ahmad Khan 《International Journal of Communication Systems》2020,33(15)
In this paper, we analyzed and compared the performance of cooperative diversity systems such as cooperative and multi dual‐hop networks with non‐regenerative relay nodes. The contributions of this study are twofolds. Firstly, analytical expressions of outage probability Pout and average symbol error rate ASER are derived using moment generating function (MGF) analysis of the received SNR with the assumption that the channel experiences Weibull fading and the best relay selection is used. Then, using the analytical results, comparative performance evaluation of cooperative and multi dual‐hop relay networks is done for varying number of relay nodes and different receive diversity schemes such as maximal ratio combining (MRC) and selection combining (SC). The results show that the cooperative relay network has better performance than a multi dual‐hop relay network in terms of Pout and ASER. The results also show that the multi dual‐hop network can achieve the same performance as the cooperative network with the requirement that it needs the deployment of three times more relay nodes. 相似文献
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Yongxu Hu Kwok Hung Li Kah Chan Teh 《Wireless Communications and Mobile Computing》2011,11(6):742-749
In this paper, we derive the upper bound of bit‐error rate (BER) performance and diversity gain for a decode‐and‐forward (DF) cooperative system. Either maximal‐ratio combining (MRC) or cooperative MRC (C‐MRC) is employed at the receiver in the presence of independent, non‐identical Nakagami‐m fading. Both analytical and simulation results show that C‐MRC takes advantage of spatial diversity more efficiently and thus achieves the same or better performance and diversity order as compared to MRC. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Tharith Sriv Chirasil Chayawan Wuttipong Kumwilaisak 《Wireless Communications and Mobile Computing》2008,8(2):231-244
In this paper, the outage probability of maximum ratio combining (MRC) in the spherically invariant fading environment was analyzed. The study was done with and without consideration of the effect of noise. First, the probability density functions (pdf) of signal‐to‐interference plus noise ratio (SINR) and signal‐to‐interference ratio (SIR) were derived. In our derivation, the characteristic pdfs of spherically invariant random process (SIRP) corresponding to the interferences were assumed to be both different and identical. Moreover, both equal and different mean powers of interferences were considered. With the derived pdfs of SINR and SIR, the expressions of outage probability were computed. Numerical analysis was done using three numerical methods known as Gauss–Laguerre, Gauss–Hermite, and Gauss–Legendre integrations. It should be noted that SIRP, the generalization of Gaussian random process, is assumed to have K‐distribution, which is the generalization of Rayleigh. Our analysis was verified by comparing the outage probabilities of the considered environments with those of Rayleigh fading channel. From the numerical results, the derived outage probability converges to that of Rayleigh fading, when the shape parameter of characteristic pdf approaches infinity. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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In this work, we present a performance analysis of two‐phase‐based single‐channel radio‐frequency (RF) direction finding (DF) methods in two wireless environments: open field and an open parking lot. A wireless channel model is created for both environments, and a software receiver is used to process the incoming RF signal to estimate the angle of arrival (AOA). The channel and receiver models are compared against measurements from a hardware prototype. Results shows a 100% pass rate in the open field environment when the receiver is located at the exterior center roof of the car. The pass rate does not exceed 25% if the receiver module is placed inside the car or if the system is evaluated in the open parking lot environment. This paper shows that a phase‐based single‐channel DF approach will not perform reliably in a highly reflective wireless environment. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
Liang Yang 《Wireless Communications and Mobile Computing》2008,8(10):1247-1253
In this paper, we present a comprehensive performance analysis for multiple‐input multiple‐output (MIMO) systems with multiuser diversity over Rayleigh fading channels. We derive exact closed‐form expressions of the outage probability and the average bit error rate (BER) for different MIMO schemes, including the selective combining (SC), maximum ratio combining (MRC) and space‐time block codes (STBC). We also provide the explicit upper bounds on the BER performance. Finally, the mathematical formalism is verified by numeric results that study the interaction between the antenna diversity and the multiuser diversity. It is observed that the system performance is deteriorated as the number of transmit antennas increases in multiuser scenario, which is unlike the case in single‐user systems. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Yuzhen Huang Qihui Wu Jinlong Wang Yunpeng Cheng Yuming Zhang 《International Journal of Communication Systems》2015,28(2):201-212
A comprehensive analytical framework of a spectrum sharing system, in which secondary receiver (SR) is equipped with multiple antennas, is presented over Rayleigh fading channels. The impact of spatial fading correlation on the performance of spectrum sharing system with maximal‐ratio combining at the SR is investigated. In particular, we explicitly derive the CDF and moment generating function of the end‐to‐end signal‐to‐noise ratio by assuming a correlation model with arbitrary eigenvalue multiplicities at the SR. On the basis of these results, we conduct an evaluation of secondary system performance in terms of the outage probability, the average symbol error probability, and the ergodic capacity. All analytical results are verified by Monte Carlo simulations. Furthermore, to obtain an insight of system performance, the asymptotic analysis is studied to obtain the diversity gain and the coding gain in the peak transmit power dominated region. Our results show that the diversity gain is unaffected by antenna correlation whereas the coding gain is degraded. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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针对在非均匀散射体分布下信号到达角度、到达时间以及多普勒效应等信道参数估计的复杂性,提出一种合理的空间信道模型,并引入几何分割法导出基于散射体Inverted-Parabolic分布的空间统计信道模型。模型能方便地估计室外宏小区和微小区移动通信环境下各种重要的空时信道参数,如AOA、TOA概率分布密度函数和多普勒功率谱以及信号的空—时相关性。数值结果与均匀散射体圆模型和高斯散射体圆模型对比表明本模型的信道参数估计结果符合理论和经验,且与实测结果吻合较好。在基站设计采用指向性天线时研究了移动台MS的多普勒效应,修正了Clarke U-shaped经典模型,阐明了天线主瓣宽度 、空间模型参数D/R和MS移动参数影响信道参数的机理。 相似文献
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针对某些特殊的移动通信环境中信号的到达角度( TOA)、到达时间( AOA)等信道参数估计的复杂性,提出一种基于散射体均匀分布室外统计信道模型。该模型将树木中的树冠层作为散射体呈均匀分布在移动台与基站周围的椭圆形区域内,通过树冠层在雨雪环境中的相对介电常数来分析降雨降雪量对信号传输带来的影响,可以方便地估计出此室外微小区的空时信道参数,如AOA概率密度分布函数、TOA概率密度分布函数以及到达角度/到达时间( AOA/TOA )联合概率密度分布函数。仿真结果表明,信号的到达时间TOA以及到达角度AOA随着降雨降雪量的增大而增大,尤其当降雪量增大使得树冠层相对介电常数达到4.5时,信号的传输将被阻塞。该模型的信道参数估计结果符合理论与经验,扩展了移动无线通信信道模型的研究与应用。 相似文献
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近年来基于蜂窝网络对移动台进行定位估计的无线定位技术受到广泛的关注,目前的几种基于网络的定位方法在不同的信道和网络环境中表现出的性能各不相同,还没有一种技术能在各种不同信道和网络环境中都能表现出最佳性能,满足对蜂窝网络移动台定位的精度要求。数据融合是一种对不同类型数据进行融合,以取得比单一方法和技术更佳的数据输出的技术。论文将信息融合应用于无线定位之中,对无线定位的信息融合模型进行了深入的研究。 相似文献
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We propose an unbiased signal‐to‐interference ratio (SIR) estimator for the high speed downlink packet access (HSDPA) system. The proposed SIR estimator solves the problem of underestimation present in conventional SIR estimators and is suitable for channel quality measurement in the adaptive modulation and coding scheme of HSDPA, which requires accurate SIR estimation for optimum adaptive modulation and coding selection. Our analysis and simulation results demonstrate the improved estimation performance of the proposed SIR estimator. 相似文献
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准确地估计信号的到达角（Angle Of Arrival,AOA）为实现在室内高精度定位提供了可能,为了能够准确地估计室内多径信号的AOA,并提取出直射路径的AOA信息进行定位,本文提出一种利用信道频率响应信息（Channel Frequency Response,CFR）扩展阵列天线的亚米级室内定位系统.首先,采集CFR信息进行AOA和信号到达时间（Time Of Arrival,TOA）的联合估计;其次,提出了一种基于AOA和TOA二维聚类信息的直射路径识别算法;另外,还提出了可视环境（Line Of Sight,LOS）以及非可视环境（Non Line Of Sight,NLOS）的识别算法,可以准确的判断出当前接收机相对发射机是处于LOS还是NLOS环境;最后,利用现有的三天线Wi-Fi设备在室内进行了测角以及定位测试,实验结果表明本文提出的定位系统在室内LOS和NLOS环境下分别可以达到中值误差为0.8m,1.3m的定位精度,可用于室内高精度定位. 相似文献
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Shixun Wu Dengyuan Xu Jin Tan Kai Xu Honggang Wang 《International Journal of Communication Systems》2016,29(6):1073-1083
In circular scattering environments, novel location techniques with only two base stations (BSs) are proposed in this paper. The proposed techniques estimate the true or line‐of‐sight ranges and angle based on non‐line‐of‐sight range and angle measurements. Three new variables are introduced when range measurements and angle measurement are available from two BSs and the serving BS, respectively. Bounds and relationships between the three variables are extracted from the geometry of the cell layout with the unknown and known scattering radius conditions, respectively. Our aim is to obtain the estimation of three new variables and then the hybrid line of position technique with the adjusted ranges, and angle is utilized to obtain the position estimation of a mobile station. In order to obtain the estimation of three new variables, a new nonlinear objective function is built to form the constrained nonlinear optimization and solved by the existing optimization algorithms. However, because of the nonconvex objective function, the optimization algorithm may converge to the local optimum and lead to bad performance. Thus, a heuristic search algorithm is proposed by averaging all the potential point. Simulation results show that the proposed techniques outperform conventional hybrid techniques. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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在Kolmogorov湍流模型下,建立了到达角起伏对星地激光通信误码性能影响的理论模型。基于该模型,推导了星地激光通信系统误码率的闭合表达式。综合考虑光强闪烁、光束漂移和到达角起伏,推导出三者共同作用下,星地系统上行链路的接收光强概率密度解析式以及误码率的闭合表达式。文中采用的调试方式是适合星地激光通信的相干探测圆偏振调制。针对上行链路,仿真分析了弱、中、强湍流下,三者共同作用时,星地激光通信系统的误码率,并与不考虑到达角起伏条件下进行了比较。还分析了到达角起伏与误码率的变化关系,以及在考虑发射功率受限的条件下,三者共同作用对系统性能的影响。研究结果表明,除了光强闪烁和光束漂移以外,到达角起伏也是通信性能中不可或缺的因素。 相似文献
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Aniruddha Chandra Srinivasa Rao Poram Chayanika Bose 《International Journal of Communication Systems》2011,24(2):202-224
In this paper, the authors derive symbol error probability (SEP) expressions for coherent M‐ary frequency shift keying (MFSK) modulation schemes in multipath fading channels. The multipath or small‐scale fading process is assumed to be slow and frequency non‐selective. In addition, the channel is also subjected to the usual degradation caused by the additive white Gaussian noise (AWGN). Different small‐scale fading statistics such as Rayleigh, Rician (Nakagami‐n), Hoyt (Nakagami‐q), and Nakagami‐m have been considered to portray diverse wireless environments. Further, to mitigate fading effects through space diversity, the receiver front‐end is assumed to be equipped with multiple antennas. Independent and identically distributed (IID) as well as uncorrelated signal replicas received through all these antennas are combined with a linear combiner before successive demodulation. As the detection is coherent in nature and thus involves phase estimation, optimum phase‐coherent combining algorithms, such as predetection maximal ratio combining (MRC), may be used without any added complexity to the receiver. In the current text, utilizing the alternate expressions for integer powers (1≤n≤4) of Gaussian Q function, SEP values of coherent MFSK are obtained through moment generating function (MGF) approach for all the fading models (with or without MRC diversity) described above. The derived end expressions are composed of finite range integrals, which can be numerically computed with ease, dispenses with the need of individual expressions for different M, and gives exact values up to M=5. When the constellation size becomes bigger (M≥6), the same SEP expressions provide a quite realistic approximation, much tighter than the bounds found in previous literatures. Error probabilities are graphically displayed for each fading model with different values of constellation size M, diversity order L, and for corresponding fading parameters (K, q, or m). To validate the proposed approximation method extensive Monte‐Carlo simulations were also performed, which show a close match with the analytical results deduced in the paper. Both these theoretical and simulation results offer valuable insight to assess the efficacy of relatively less studied coherent MFSK in the context of the optimum modulation choice in wireless communication. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献