共查询到20条相似文献,搜索用时 125 毫秒
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WCDMA系统STTD发送分集RAKE接收机的性能分析 总被引:4,自引:0,他引:4
第三代移动通信系统WCDMA的发送分集方式有两种:开环模式和闭环模式,其中开环模式采用基于空间-时间分组编码的STTD发送分集方式。本文针对WCDMA系统中的STTD发送方式,给出了利用公共导频信道进行信道估计,实现相干RAKE接收的模型算法、性能分析及仿真结果。仿真表明,在总发送比特能量相同的条件下,尤其是在接收机缓慢移动的情况下,采用STTD发送分集的RAKE接收性能优于单天线发送时的RAKE接收机的性能,而在高速移动情况下,STTD发送方式不能提供优于单天线发送时的接收性能。 相似文献
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多径环境中传统的DS-CDMA信号接收,一般采用RAKE接收技术.本文提出一种不使用RAKE接收机的DS-CDMA接收算法:基于时频二维扩频的思想,考虑DS-CDMA发射机发射的一个扩频符号对应时间内的信号,在接收机中先将接收到的信号做一个比扩频增益N小的DFT变换,联合对多个DFT变换后的信号进行扩频解扩处理,从而恢复出发射的原始信息比特.本文对比了DS-CDMA传统的RAKE接收算法、基于时频二维扩频的DS-CDMA接收算法(2DSS)、以及Wang等提出的具有信道选择的频域解扩算法的复杂度,并就性能进行了计算机仿真验证.结果表明,在根均方时延较小信道中的性能优于传统RAKE接收算法和具有信道选择的频域解扩算法的性能. 相似文献
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为研究不同接收机的架构、收发天线的角度和判决方式对穿戴式超宽带( UWB )信道RAKE接收机误码率( BER)的影响,利用数字抽样示波器获取时域接收信号,使用CLEAN算法去卷积,得到体表-体表和体表-体外环境下人体信道冲激响应;并采用不同结构不同分支数的RAKE接收机对含有加性高斯噪声的跳时信号进行接收,以分析其对BER的影响。仿真结果表明,包含所有分支的RAKE接收机BER最低但结构复杂;在相同分支数下,包含部分分支的RAKE接收机的BER损失要比选择性RAKE接收机高3 dB,但复杂度较低。对收发天线不同角度的研究表明,收发天线应避免垂直,否则体表反射作用带来的多径分量增多,容易出现码间干扰,从而增加BER。在重复编码情况下,软判决的BER性能要优于硬判决0.2~0.4 dB。该信道模型和误码率分析研究可对穿戴式UWB收发机的架构设计和性能研究提供参考。 相似文献
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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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Zi-Wei Zheng 《Wireless Personal Communications》2010,53(1):67-79
In this paper, we consider the receiver design problem for the uplink multiuser code division multiple access (CDMA) communication
system based on the neural network technique. The uplink multiuser CDMA communication system model is described in the form
of space–time domain through antenna array and multipath fading expression. Novel suitable neural network technique is proposed
as an effective signal processing method for the receiver of such an uplink multiuser CDMA system. By the appropriate choice
of the channel state information for the neural network parameters, the neural network can collectively resolve the effects
of both the inter-symbol interference due to the multipath fading channel and the multiple access interference in the receiver
of the uplink multiuser CDMA communication system. The dynamics of the proposed neural network receiver for the uplink multiuser
CDMA communication system is also studied. 相似文献
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为了在TD-SCDMA上行链路传输中获得更高的频谱利用率,提出了一种上行链路的发送和接收方案。发送端采用准同步CDMA加QAM调制,扩频序列采用优选相位的Gold序列,该序列在一定时延范围内具有良好的互相关性。接收端采用串行干扰抵消的方法去除或抑制很严重的多用户干扰,该方法实现简单,适合瑞利衰落信道。仿真结果说明采用这种发送和接收方案后,在应用智能天线抑制多径后,只要用户间的时延控制在3/8个chip之内,误符号率(SER)性能就几乎与单用户界(SUB)一致,频谱利用率可以达到4 bit/s/Hz。 相似文献
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作为5G多载波技术强有力的候选对象,通用滤波多载波利用子带滤波技术抑制带外功率泄露,进而降低同步要求和获得更高的频谱效率。本文首先针对通用滤波多载波在慢时变多径信道下的性能进行了分析和研究;其次为消除多径信道所带来的干扰,提出了适用于该多载波系统的信道估计方案,该方案设计了具有重复样式的导频结构进行信道估计,复杂度低;最后针对通用滤波多载波在多径信道下容易遭受符号间干扰的问题,提出了基于干扰消除的Zero-Forcing均衡算法和基于迭代干扰消除的均衡算法,两种算法均能够在消除ISI的基础上进一步地消除ICI和IBI。仿真结果表明,本文提出的信道估计和均衡算法能有效消除通用滤波多载波技术在多径信道下所经受的ISI、ICI和IBI。 相似文献
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The uplink and downlink performance of a digital cellular radio system that uses direct sequence code division multiple access is evaluated. Approximate expressions are derived for the area averaged bit error probability while accounting for the effects of path loss, log-normal shadowing, multipath-fading, multiple-access interference, and background noise. Three differentially coherent receivers are considered: a multipath rejection receiver, a RAKE receiver with predetection selective diversity combining, and a RAKE receiver with postdetection equal gain combining. The RAKE receivers are shown to improve the performance significantly, except when the channel consists of a single faded path. Error correction coding is also shown to substantially improve the performance, except for slowly fading channels 相似文献
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Sanguinetti L. Cosovic I. Morelli M. 《Selected Areas in Communications, IEEE Journal on》2006,24(6):1167-1178
Combined equalization has recently been proposed to enhance the error rate performance of conventional multicarrier code-division multiple-access (MC-CDMA) systems. This technique applies pre-equalization at the transmitter in conjunction with post-equalization at the receiver, thereby splitting the overall equalization process into two separate parts. In this way, efficient power allocation over the available subcarriers is possible at the transmitter, while leaving the interference cancellation task at the receiver. In this paper, we consider the uplink of an MC-CDMA system employing combined equalization. As the users transmit from different locations, the uplink signals arrive at the base station after passing through different multipath channels and the goal is to estimate the pre-equalized channel frequency response of each user. This is pursued following two different approaches. The first operates in the frequency-domain and treats the channel gains over adjacent subcarriers as independent unknown parameters. The second operates in the time-domain and achieves better performance by reducing the number of unknown parameters. Both schemes are based on maximum-likelihood reasoning and require knowledge of the transmitted symbols. Numerical examples are given to highlight the effectiveness of the proposed methods. 相似文献
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The main targets of any direct-sequence code division multiple-access (DS/CDMA) mobile communication system are to overcome the multipath fading influences as well as the near/far effect and to increase the capacity. Many optimal and suboptimal detection approaches have been proposed and analyzed in the literature. Unfortunately, most of them share the drawback of requiring a complex implementation and do not represent a practical solution. This paper proposes a simple interference cancellation receiver for applications in DS/CDMA uplink communications. This receiver allows users to overcome the near/far effect and to enhance the system capacity. Differently from previous methods, the interference cancellation is performed on a one-shot basis. The performance of the proposed interference cancellation receiver is derived through computer simulations. However, a suitable analytical approach is also presented in the appendix in order to evaluate the bit error rate (BER) performance in the particular case of synchronous users and the transmission channel being affected only by additive white Gaussian noise (AWGN). The good behavior of the proposed approach is demonstrated by means of comparisons in terms of the BER performance and implementation complexity with the classical RAKE receiver and different multiuser receivers previously proposed in the literature on this subject 相似文献
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The performance of a digital enhanced cordless telecommunications (DECT) receiver in a multipath channel is studied. The following issues were investigated: irreducible bit-error rate (BER) performance of the differentially coherent detector in Rayleigh and Rician channels; BER performance in the presence of both the noise in the receiver and a multipath interference. The theoretical estimates of the irreducible error rate developed in the paper showed reasonable agreement with the data obtained from computer-based simulation of the DECT link through a Rayleigh multipath channel. The combined effect from receiver noise and multipath interference has been studied, and asymptotic formulas for the total error probability have been developed. The results of calculating the error probabilities using these asymptotics demonstrate good agreement with measured data 相似文献