共查询到19条相似文献,搜索用时 78 毫秒
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在采用传统信号检验方式的CDMA无线通信网中,多址干扰限制了系统的容量和性能。多用户信号检测利用扩频码互相关信息在高斯信道中可以减小或消除多址干扰,缓解远近效应,增加系统容量。 相似文献
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提出采用量子神经网络(QNN)方法在平坦瑞利环境下进行多用户检测的方法。量子神经网络是量子计算与人工神经网络(ANN)相结合的产物,由于利用量子并行计算和量子纠缠等特性从而克服了传统人工神经网络的固有缺点。研究结果表明:该算法具有较强的鲁棒性;能有效地抑制噪声干扰,克服远近效应,在平坦瑞利衰减下具有较好地误码性能。 相似文献
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瑞利衰落信道中MC-CDMA系统的载波频率偏移性能 总被引:1,自引:0,他引:1
多载波CDMA(MC-CDMA)技术结合了OFDM和CDMA技术的优点,在无线衰落信道中传输高速数据时具有突出的性能。但由于MC-CDMA采用了多载波技术,载波频率偏移对系统性能的影响非常大。本文对瑞利衰落信道下存在载波频率偏移的MC-CDMA系统性能进行了理论分析并对误码率进行了详细讨论。 相似文献
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本文主要介绍了在平坦瑞利衰落信道下,MDPSK的判决反馈差分检测DF—DD(decision—feedback differential detection)。通过对多符号距离量度的计算,得出了DF—DD的距离量度,通过分析得出,DF—DD算法等效于是接收端采用了反馈FIR滤波器。最后通过仿真得出.在理想带宽受限的衰落条件下,传统差分解调中存在的误差平底是可以消除的,并仿真了在两种不同的量度系数的条件下,系统的性能变化趋势。 相似文献
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本文针对频率选择性Rayleigh衰落信道,设计了一种CDMA多用户检测器分集结构,通过该结构,高斯信道多用户检测算法可以有效地应用到Rayleigh衰落信道中,仿真结果表明,分集合并实现的多用户中以显著改善衰落信道的误码性能,其处理多址干扰能力并不因分集而受到影响,另外,本文还对不同的合并以及不同的检测地作了性能上的比较。 相似文献
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本文给出了在Rician衰落信道中一种抗多址干扰单用户检测接收机[1]的比特误码率特性。结果表明,当系统实际正使用用户数不大于系统的最大设计用户数时,这种接收机的误码率与系统内正使用用户数的相关性不大 相似文献
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本文提出一种适合于瑞利衰落信道多进制差分相移键控系统相位比较解调的性能分析方法,推导出符号错误率解析表示式,考虑了瑞利衰落、时间选择性衰落和高斯白噪声对体制性能的影响,并针对衰落功率谱为高斯型和矩形分别对二进制、四进制和八进制情形进行了数值计算。 相似文献
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Since the conventional detector performs poorly in bandwidth-efficient Code Division Multiple Access (CDMA) systems, several multiuser detectors were proposed recently. In this paper, we compare performance of the decorrelator, the two-stage detector (2S), and the decision-feedback detector (DF) for the Rayleigh flat fading synchronous CDMA channel. First, assuming perfect channel estimation, we show that the 2S and the DF have much lower bit error rate (BER) than the decorrelator, and prove that the ideal DF has unity Asymptotic Multiuser Efficiency (AME). Furthermore, we evaluate the performance of these detectors in the presence of channel mismatch. We model the Rayleigh flat fading channel as the second order Auto Regressive (AR) process, and use the Kalman filter as the channel estimator. The lower bounds on the BER of the 2S and the DF are derived. The analytical results and the simulations show that the estimation error accumulated due to cancellation of other users limits the performance of the 2S and the DF. Therefore, in the presence of channel mismatch, the decorrelator offers comparable or even better performance than more complex decision-feedback and two-stage detectors. 相似文献
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SONGLi-xin HUANGTian-shu DINGYao-ming 《半导体光子学与技术》2005,11(2):129-134
Based on the theory of multicarrier (MC) technique and the Rake receiver, a multicarrier DS-CDMA Rake system is proposed, where a data sequence multiplied by a spreading sequence modulates multiple carriers. The receiver provides a Rake for each subcarrier, and the outputs of the Rakes are combined by a maximal-ratio combiner. The average probability of error of the system is derived from an uncorrelated subcarrier and frequency-selective fading channel model. The system performances are evaluated over Rayleigh fading channel with an exponential multipath intensity profile(MIP) and with a rectangular MIP, respectively, when multipath interference is present. It is found that this kind of model has larger superiority in an exponential MIP than in a rectangular MIP. 相似文献
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Interest in code division multiple access (CDMA) has increased dramaticallyin boththe industry and academia. This is due to the potential increase in usercapacity andinterference, multipath fading, and jam-resistant capabilities. Differentapproaches ofmultiuser detection schemes have shown improvement over the conventionalreceiver.However, multiuser detectors require system parameters and adaptive multiuserreceivers require training sequences. These parameters are difficult toobtain inmultipath fading channels with a degradation in performance. A blind adaptivemultiuser receiver for flat fading and frequency-selective fading environments isstudied in this paper. This receiver alleviates the problem of multiuser detectors and adaptivemultiuser receivers by using a blind adaptive equalization method. The structure of the receiveris similar to that of the adaptive MMSE receiver which consists of an adaptive equalizer and an adaptivemechanism that uses a standard least mean-squared (LMS) algorithm, but uses a matched filterto generate a reference signal. The receiver is shown to be effective in different fadingchannels with perfect power control and a near-far effect. Furthermore, the simulationresults show that the blind MMSE receiver outperforms the conventional receiver and theRAKE receiver. 相似文献
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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. 相似文献
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OptimumMultiuserDetectorforMultipathSlowFadingAsynchronousCDMAChannelsWangZhaocheng;YangZhixing;YaoYan(TsinghuaUniversity,Bei... 相似文献
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CDMA移动通信中的判决反馈多用户信号检测器 总被引:4,自引:0,他引:4
本文推导了一种具有线性计算复杂度的同步DS—CDMA系统多用户检测算法,由此形成的判决反馈检测器在性能上优于解相关检测器,与两级多用户检测器的性能相当,而实现起来则更为简单。数值结果表明,当接收到的干扰信号能量比有用信号能量高4dB以上时,判决反馈检测器的性能将接近单用户系统的性能,因而该检测器可有效地克服CDMA移动通信中的远近影响。 相似文献
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In this paper, blind adaptive multiuser detection (MUD) technique is developed for uplink transmission in multiuser space
diversity DS-CDMA system to overcome multipath fading effect and multiple access interference. The system consists of a space
diversity, a precombining blind adaptive detector (PBAD), and a weight adaptation technique based on the minimization of the
mean output energy (MOE). The bit error rate (BER) performance of this receiver for asynchronous DS-CDMA signals with independent
and correlated antenna branches under Nakagami fading channel for BPSK system is evaluated. It has been seen that the use
of antenna diversity can yield substantial improvement in performance even if the correlation between the antenna elements
is relatively large (up to 0.795). However, the large correlation values pose a significant reduction in the diversity gain
in comparison with the zero correlation situation. It has also been confirmed by simulations that the PBAD provides a significant
receiver performance in comparison with the RAKE receiver employing antenna diversity.
Khodr A. Saaifan Born in lebanon 1978, received B.S.c. degree in electrical and electronics engineering (with honors) from Benha higher institute
of technology, Benha, Egypt, in 2001, and the M.S.c. degree in communications from Cairo University, Giza, Egypt, in 2005.
He is currently pursuing for the Ph.D. degree at the Cairo University. His current research interest includes space–time-coded
transmission, multiple-input multiple-output (MIMO) systems, fading channels, equalization, turbo (iterative) processing,
and wideband code division multiple access (WCDMA).
Emad K. Al-Hussaini received his B.Sc degree in Electrical Communication Engineering from Ain-Shams University, Cairo, Egypt, in 1964 and his
M.Sc and Ph.D. degrees from Cairo University, Giza, Egypt, in 1974 and 1977, respectively. From 1964 to 1970, he was with
the General Egyptian Aeroorganization. Since 1970, he has been with the Department of Electronics and Communications, Faculty
of Engineering, Cairo University, and is currently professor there. He was a research fellow at Imperial College, London,
UK, and at the Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA, in the academic
years 1976/1977 and 1981/1982, respectively. In 1990, he received the Egyptian national encouragement award for outstanding
engineering research. He has written several papers for technical international journals and conferences. His research interests
include signal processing, fading channel communication, modulation, and cellular mobile radio systems. Dr Al-Hussaini is
a senior member of IEEE. He is listed in Marquis Who's Who in the World and in the IBC (International Biographical Center,
Cambridge) for outstanding people of the 20th century. 相似文献