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在实际环境中RAKE接收机在接收信号时都要进行信道系数估计,以便进行相干合并。文章研究了不采用导频信号与采用导频信号两种估计器,具有估计误差情况下,在相关Nakagami信道下的RAKE接收机的性能,并且通过特征函数法得到了误码率公式的闭合表达式。比较了两种估计器对系统性能的影响,最后给出了数值结果,可以看出,当导频信号能量与信号能量相等,且导频数目比较多时(大于5),采用导频信号的系统性能优于直接估计信道系数的系统。直接估计信道系数的系统性能在信噪比大于5dB后,其性能远远优于导频信号的估计系统。 相似文献
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Al-Hussaini Emad K. Al-Bassiouni Abdulaziz M. Mourad Hebatallah M. Al-Shennawy Hamed 《Wireless Personal Communications》2002,21(3):309-328
This paper presents a generalized model of binary phase shift keying (BPSK) direct sequence code division multiple access (DS/CDMA) macrocellular and microcellular sectorized mobile radio systems over Nakagami fading plus lognormal shadowing channels. RAKE receiver, perfect and imperfect sectorization, voice activity monitoring, microscopic and composite microscopic plus macroscopic diversity are considered. The interrelationships among the number of interfering cells, sectorization degree, sectorization imperfection, voice activity factor, fading parameter, microscopic diversity degree, microscopic plus macroscopic diversity degree and the number of users are considered. Numerical results show that voice activity monitoring and sectorization can reduce multiple access interference (MAI). Furthermore, composite microscopic plus macroscopic diversity system can counteract the fast and slow fading components simultaneously. 相似文献
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On the basis of CFO (carrier frequency offset) point of view, the system performance results from the analysis by adopting
the channel scenarios characterized as Weibull fading for an MC-DS-CDMA (multi-carrier direct-sequence coded-division multiple-access)
system is proposed in this article. Moreover, an approximate simple expression with the criterion of BER (bit error rate)
versus SNR (signal-to-noise ratio) method is derived for an MC-DS-CDMA system combining with RAKE receiver, which is a special
case of MRC (maximal ratio combining) diversity, based on the MGF (moment generating function) formula of Weibull statistics,
and it associates with an alternative expression of Gaussian Q-function. In addition, the other point of view on the BER performance
evaluation of an MC-DS-CDMA system is not only the assumption of both single-user and multi-user cases applied, but the phenomena
of PBI (partial band interference) is also included. Furthermore, with several of the system parameters, such as CFO values,
ε, Weibull fading parameter, β, user number, K, spreading chip number, N, branch number, L, and the PBI values, JSR etc., are compared with each other in the numerical results in order to validate the accuracy in the derived formulas. To
the best of author’s knowledge, it is a brain fresh idea proposed in this paper to evaluate the system performance for an
MC-DS-CDMA system on the point of the CFO view over Weibull fading. 相似文献
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In this paper, the analytical and simulation results of the bit error rate (BER) performance for a multiple-input multiple-output
(MIMO) system with an arbitrary number of transmit and receive antennas are developed for the uplink transmission. The fading
channel is assumed to follow Nakagami-m distribution with correlation among branches. The BER is expressed in terms of Lauricella’s
multivariate hypergeometric function for both independent and correlated antenna branches for BPSK system.
相似文献
Emad K. Al-Hussaini (Corresponding author)Email: |
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Results obtained from using a geometrically based, single-bounce propagation model are presented to characterize small-scale fading in indoor propagation channels when directional antennas are used. The model is verified by comparing simulated results to measured results. The model is then used to obtain, via simulation, fading statistics for an indoor, line-of-sight channel. The results show that when directive antennas are used, the parameters of the Nakagami- or Rician-distributed small-scale fading vary with separation between the transmit and receive antennas. Furthermore, the strength of the variation depends on antenna directivity. Some physical mechanisms for this effect are discussed 相似文献
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Al-Hussaini Emad K. Sayed Iman M. Saad El-Sayed M. 《Wireless Personal Communications》2001,16(2):115-133
Spatial diversity is an attractive technology for coping with the fadingchannels encountered in mobile communications.In this paper, the bit error rate (BER) is analyzed theoretically fordiversity reception with a RAKE receiver in aNakagami fading environment using either selection or maximal ratio combining.A coherent binary phase-shiftkeying (CBPSK) direct sequence code division multiple access (DS/CDMA) systemis considered. An arbitrary branchcorrelation is also considered for any diversity order in the case ofidentical fading severity on the branches. 相似文献
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The throughput enhancement of Space-Time Spreading (STS)-based Code Division Multiple Access (CDMA) system is investigated
in this paper. Adaptive Modulation is utilized to improve the data throughput of the system in multipath Rayleigh fading channel.
In this contribution, an analytical approach is proposed to compute a new expression for the Bit Error Rate (BER) performance
and the output Signal-to-Interference-and-Noise Ratio (SINR) of the RAKE receiver-assisted STS-based CDMA system for QAM data,
considering multipath and multiuser interferences. The other contribution of the paper is deriving a new closed form expression
for computing the throughput enhancement and the BER performance of the adaptive modulated STS-based CDMA system over multipath
fading channel. Simulation and analytical results demonstrate that using adaptive modulation method in this system improves
the average throughput by keeping the BER performance at a target level. The novel expressions presented in this paper bring
out the facility of evaluation of the proposed system with no need to more calculations and simulations.
相似文献
Hassan AghaeiniaEmail: |
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在理想多输入多输出(MIMO)系统容量的基础上,推导了衰落信道空间相关性对MIMO系统容量的影响,并通过MATLAB仿真进行了验证,最后给出了结论。 相似文献
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J. Zhang R. A. Kennedy T. D. Abhayapala 《International Journal of Wireless Information Networks》2003,10(4):193-200
In this paper, the conditions and performance of ideal RAKE reception for time hopping Ultra-Wideband (UWB) investigated. Owing to the complex propagation phenomena and specific structure of UWB signals, new problems relevant to the operation of RAKE receivers arise. This motivates us to reconsider the conditions under which a RAKE receiver can work effectively with negligible interference between fingers. Key findings are that the conditions not only relate to the property of time hopping codes, but also modulation methods. An analytical technique is introduced to derive explicit expressions of RAKE performance for various combining methods for a lognormal fading channel. Numerical results show that RAKE reception can largely improve the performance, and equal gain combining has comparable performance to maximum ratio combining. 相似文献
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为了提高空间相关信道估计的精度,提出了一种适用于空间相关信道的MIMO-OFDM系统的空域LMMSE信道估计算法及其改进算法,从理论上分析了MSE误差。仿真结果表明,空域LMMSE算法能有效地提高信道估计的精度,尤其是在低信噪比的情况下,所提出的算法获得的效果更为明显。 相似文献
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跳时超宽带无线通信系统中信道估计的准确度对系统接收性能具有重要影响,首先对超宽带系统收发模型进行介绍,然后对TH-UWB系统中基于训练序列的非结构化最大似然信道估计算法进行分析,最后在超宽带信道模型下对估计算法性能进行仿真.仿真结果表明基于训练序列的非结构化最大似然信道估计算法能够有效估计出信道参数. 相似文献
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Application of the EM (Expectation–Maximization) algorithm to sequence estimation in an unknown channel can in principle produce MLSE (maximum likelihood sequence estimates) that are not dependent on a particular channel estimate. The Expectation step of this algorithm cannot be directly performed for continuous phase modulated (CPM) signals transmitted in a time varying multipath channel. We therefore derive a simplification of the EM algorithm for CPM signals in this channel. Simulations applied to the Global System for Mobile Communications (GSM) show that the simplified EM algorithm significantly decreases the amount of training data needed for the channel model considered, and removes the majority of the bit errors that are due to imperfect knowledge of the channel. 相似文献
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HE Bo~ LI Jun~ LIN Jia-ru~ WU Wei-ling~ .School of Information Science Engineering Beijing University of Posts Telecommunications Beijing P.R. China .School of Information Science Engineering Shandong University 《中国邮电高校学报(英文版)》2005,12(2)
1IntroductionOFDM known as a multicarrier modulation schemehas recently received considerable attention for its ro-bustness to multipath selective fading,provided by onetap equalization in frequency domain. This technique isrecommendedin Europe bythe ITU-Ras atransmissionstandard for Digital Audio Broadcasting ( DAB) fromsatellite or terrestrial fixed stations to mobile users ;andit also being adopted by EBU for terrestrial DigitalVideo Broadcasting (DVB-T) .In wireless environments … 相似文献
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数据的高速率传输以及终端的高速移动,导致无线通信信道具有时间选择性与频率选择性两个特征。该文主要研究了数据分组传输方式下,基于导频符号辅助调制(PSAM)的多输入多输出(MIMO)时间-频率双选择性信道的信道估计问题。首先,将时间-频率双选择性MIMO信道,建模为一个随时间变化的多项式内插信道模型;然后,根据信道Doppler衰落速率、多项式模型中的误差项,确定出模型的阶数以及整个数据块的长度;最后,基于该多项式内插信道模型,提出了采用PSAM的MIMO双选择性信道估计方法。实验结果表明该算法在时间-频率双选择性衰落信道下具有较好的性能。 相似文献