共查询到20条相似文献,搜索用时 140 毫秒
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文章提出一种二重空间分集接收技术的计算机仿真方法,并研究了在不同副载波调制,不同车速的Rayleigh衰落信道中,仅用二重空间分集收技术以及同时采用分集与纠错码技术抗落的性能。仿真结果表明:综合应用分集,纠错编码技术可使信道误比特率大大降低。 相似文献
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异步CDMA移动通信系统采用分集接收的多用户检测器 总被引:1,自引:0,他引:1
在CDMA移动通信系统中,多址接入干扰可以通过多用户检测技术来消除,而分集接收可以减小信道衰落的影响,本文给出了一类应用解相关检测,天线分集,RAKE多径分集技术的接收机,并对这一类接收机的性能做了分析,结果表明,在上行链路中,应用多用户检测和分集接收能够极大提高接收机的性能。 相似文献
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异步CDMA移动通信系统中采用分集接收的多用户检测器 总被引:1,自引:0,他引:1
在CDMA移动通信系统中,多址接入干扰可以通过多用户检测技术来消除,而分集接收可以减小信道衰落的影响。本文给出了一类应用解相关检测、天线分集、RAKE多径分集技术的接收机,并对这一类接收机的性能做了分析。结果表明,在上行链路中,应用多用户检测和分集接收能够极大地提高接收机的性能。 相似文献
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相关衰落信道Turbo乘积编码MDPSK的分集接收 总被引:1,自引:1,他引:0
由于无线衰落信道中差分检测Turbo乘积编码调制具有良好的性能,文中研究了相关平坦Rayleigh衰落信道中差分检测Turbo乘积编码MDPSK信号的等增益分集,这种等增益分集接收无需任何信道状态信息.研究结果表明,等增益合并可以改善快衰落信道中TPC-MDPSK的错误平底效应,等增益分集合并的Turbo乘积编码的MDPSK信号在相关系数为0.5的平坦Rayleigh衰落信道中的性能和独立衰落信道中的系统性能相差仅1 dB. 相似文献
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码分多址系统中结合分集和多用户盲均衡的接收方案 总被引:2,自引:0,他引:2
符号间干扰和多用户干扰是影响码分多址系统性能的两个主要因素。本文中,我们提出用分集和多用户盲均衡方案相结合来克服它们。对中心判决反馈均衡器结构,我们证明了代价函数的全局收敛性,并用多径瑞利衰落信道的数值模拟作了验证。 相似文献
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An adaptive multipath decorrelating multiuser receiver is considered for application in Rayleigh fading multipath channels with significant Doppler spread. Coherent diversity combining is performed using adaptively obtained channel estimates in a manner that minimizes the impact of estimation errors on data detection. The bit-error rate of the receiver is evaluated analytically, showing dependence on the fading rate of the channel and tracking capabilities of adaptive least mean square and recursive least square algorithms, in addition to the order of multipath diversity and the number of active code-division multiple-access users 相似文献
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Nie Jingnan Cheng Shixin You Xiaohu 《电子科学学刊(英文版)》1997,14(3):285-288
In a CDMA communication network using conventional signal detection, system capacity is limited and its performance is degraded by the multi-access interference (MAI). Multiuser detection, which makes use of cross-correlation information between spread spectrum codes, can reduce or eliminate the MAI in a Gaussian channel so as to mitigate the near-far effects and increase the system capacity. This paper extends the multiuser detector to a flat Rayleigh fading CDMA environment, and discusses the bit error rate of typical multiuser detection algorithms in such a environment by combining theoretical analysis and computer simulation. It is shown that multiuser detection is superior to conventional detections in the flat Rayleigh fading channels. 相似文献
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空时分组码MC-CDMA系统多用户检测 总被引:2,自引:2,他引:2
本文研究了在频率选择性瑞利衰落信道中工作于时分双工(TDD)模式的多载波码分多址(MC-CDMA)系统上行链路,在用户终端处使用两个发射天线,采用基于空时分组码的发射分集。考虑对应于子载波的衰落系数是信道冲激响应的离散傅里叶变换,给出了基于空时分组码的MC-CDMA系统上行链路信号模型。采用适用于同步CDMA系统的低代价Steiner估计器来进行基于空时分组码的MC-CDMA系统的信道估计,每个用户终端的两个发射天线各分配一个midamble。研究了基于空时分组码的MC-CDMA系统的解相关多用户检测、最小均方误差(MMSE)多用户检测,进行联合的多用户检测和空时码解码。仿真结果验证了上述模型及算法的有效性。 相似文献
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Expressions for the average channel capacity of a multiuser diversity system combined with transmit diversity at each link are presented under the assumption of independent Rayleigh fading. The analysis results exactly agree with the simulation results and definitely show the impact of transmit diversity on multiuser diversity. 相似文献
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Proposes a suboptimal low-complexity multiuser receiver for synchronous CDMA frequency-selective Rayleigh fading channels. In contrast to the conventional RAKE receiver, which suffers from near-far effects due to channel fading, the proposed multiuser receiver is shown to alleviate the near-far problem while preserving multipath diversity gain. This is demonstrated by comparing the symbol error probability and asymptotic multiuser efficiency of the proposed multiuser detector and RAKE receiver 相似文献
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On the generation of correlated Rayleigh fading envelopes for accurate simulation of diversity channels 总被引:2,自引:0,他引:2
The generation of correlated Rayleigh fading envelopes based on mobile radio channel characteristics for realistic simulation of diversity systems was documented in 1974 by Jakes. In this letter, a survey of recent algorithms which draw upon Jakes' work will be given, as well as an illustration of their shortcomings. Subsequently, a procedure is presented for the generation of multiple equal-power correlated Rayleigh fading envelopes, with desired cross-correlations and autocorrelation functions specified so as to model channel conditions under the general assumption of isotropic scattering. The algorithm presented will enable accurate simulation and investigation of the effect of correlated fading on diversity schemes. 相似文献
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The performance of antenna diversity coherent and differentially coherent linear multiuser receivers is analyzed in frequency-nonselective Rayleigh fading CDMA channels with memory. The estimates of the complex fading processes are utilized for maximal-ratio combining and carrier recovery of the coherent multiuser receiver. To analyze the impact of channel estimation errors on the receiver performance, error probability is assessed directly in terms of the fading rate and the number of active users, showing the penalty imposed by imperfect channel estimation as well as the fading-induced error probability floor. The impact of fading dynamics on the differentially coherent decorrelating receiver with equal-gain combining is quantified. While performance of multiuser receivers at lower SNR is determined by both the fading dynamics and the number of active CDMA users, performance at higher SNR is given by an error probability floor which is due to fading only and has the same value as in a single-user case. The comparison of the two receiver structures indicates that the coherent decorrelating receiver with diversity reception may be preferable to the differentially coherent one in nonselective fading CDMA channels with memory. 相似文献
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Laura Cottatellucci Ralf R. Muller 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2007,53(3):1116-1136
This correspondence analyzes the behavior of code-division multiple-access (CDMA) systems with correlated spatial diversity. The users transmit to one or more antenna arrays. The centralized receiver employs a linear multiuser detector. We derive the performance of a large system with random spreading sequences and weak assumptions on the flat-fading channel gains-the fading may be correlated and contain line-of-sight components. We show that, as the number of users and the spreading factor grow large with fixed ratio, the performance of the system is fully characterized by a square matrix with size equal to the number of receiving antennas and multiuser efficiencies are not identical for all users. Our general result includes the analysis of CDMA systems with spatial diversity discussed by Hanly and Tse ('01) for independent channel gains in case of both micro-diversity and macro-diversity and provides a rigorous proof for the macro-diversity case missing in their work. We also show that to any scenario with correlated Rayleigh fading, there exists a macro-diversity scenario with independent Rayleigh fading which is characterized by the same signal-to-interference-and-noise ratio (SINR). Furthermore, sufficient conditions are given which force the multiuser efficiencies of all users to become identical also in case of statistically dependent channel gains 相似文献
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Multiuser detection in fast-fading multipath environments 总被引:2,自引:0,他引:2
Sayeed A.M. Sendonaris A. Aazhang B. 《Selected Areas in Communications, IEEE Journal on》1998,16(9):1691-1701
We propose a new framework for multiuser detection in fast-fading channels that are encountered in many mobile communication scenarios. Existing multiuser RAKE receivers, developed to combat multipath fading and multiuser interference in slow fading, suffer substantial degradation in performance under fast fading due to errors in channel state estimation. The detectors proposed in this paper employ a novel receiver structure based on time-frequency (TF) processing that is dictated by a canonical representation of the wide-sense stationary uncorrelated scatterer (WSSUS) channel model. The workhorse of the framework is a TF generalization of the RAKE receiver that exploits joint multipath-Doppler diversity. Analytical and simulated results based on realistic fast-fading assumptions demonstrate that the proposed multiuser detectors promise substantially improved performance compared to existing systems due to the inherently higher level of diversity afforded by multipath-Doppler processing 相似文献