码分多址通信系统中的多用户信号检测

文中叙述了码分多址通信系统中多用户信号检测的概念、一些研究结果以及需要进一步研究的内容。     

一种多径衰落信道中的多用户检测算法

针对多径衰落CDMA信道,提出了一种基于信号子空间估计的联合盲特征波形估计与多用户检测方案,分析了两处线性多用户检测器（解相关检测器和线性MMSE检测器）在信号子空间参数下的闭式解及其抗远近效应能力,并讨论了用于联合盲特征波形估计与多用户检测实现的PASTd算法。最后给出了仿真结果。     

差异性QoS条件下CDMA系统在衰落信道中的性能分析

未来B3GCDMA系统采取不同误码率和带宽要求的业务分配不同功率和传输速率的方法。分析了在变速率、多功率级别条件下CDMA系统在衰落信道下的性能，给出了系统接收机信号噪声比的解析表达式和不同业务所需功率之间的关系，并对数值结果进行了讨论。     

Rayleigh衰落信道中的CDMA多用户分集接收性能

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。     

码分多址通信系统中线性多用户信号检测器研究

提出了通过非线性优化求解线性多用户检测器中性变换矩阵的一种方法，并分析了其性能。     

平坦瑞利衰落环境下CDMA系统的多用户检测性能

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。     

降低码分多址移动通信系统中的衰落

降低码分多址移动通信系统中的衰落（金健青译，张洪达、王忆校）未来的移动通信系统将采用复杂的压缩技术，以在有限的带宽中传送更多的数据。近来，扩展频谱码分多址（ＣＤＭＡ）技术已引起人们的广泛重视。日本ＫＤＤ公司已采用分集技术来抑制多径衰落─－ＣＤＭＡ移动...     

码分多址系统中的多用户检测

CDMA通信系统是一个自干扰受限系统，如何克服CDMA系统中的多址干扰问题已成为提高CDMA系统容量的关键。多用户检测是克服CDMA多址干扰最有潜力的关键技术之一。本文研究了CDMA移动通信系统中几种常见的多用户检测技术，分析了他们的原理，并对各种多用户检测的优缺点进行了比较。     

码分多址系统中的线性多用户检测

本文分析了直接序列分多址系统中针对消除多址干扰的线性多用户检测技术，这种方法与会相比可大大提高系统的性能和容量，降低了对功率控制的要求及系统的复杂性。     

多载波码分多址系统在瑞利衰落信道中的性能分析

多载波码分多址(MC-CDMA)是一种把多载波和CDMA相结合的技术方案。在MC-CDMA中,每个数据符号通过N个子载波传输,且根据扩频码对每个子载波以0或π相位偏移进行编码。分别研究了MC-CDMA系统上行链路和下行链路的瑞利衰落信道模型以及采用等增益组合和最大比组合的接收机模型,并对上行链路和下行链路的系统误码率性能进行了分析和计算。数值结果表明,MRC在上行链路中的性能要优于EGC,但在下行链路中的抗干扰性能不如EGC。     

Optimum Multiuser Detector for Multipath Slow Fading Asynchronous CDMA Channels

ＯｐｔｉｍｕｍＭｕｌｔｉｕｓｅｒＤｅｔｅｃｔｏｒｆｏｒＭｕｌｔｉｐａｔｈＳｌｏｗＦａｄｉｎｇＡｓｙｎｃｈｒｏｎｏｕｓＣＤＭＡＣｈａｎｎｅｌｓＷａｎｇＺｈａｏｃｈｅｎｇ；ＹａｎｇＺｈｉｘｉｎｇ；ＹａｏＹａｎ（ＴｓｉｎｇｈｕａＵｎｉｖｅｒｓｉｔｙ，Ｂｅｉ...     

Implementation of the Decorrelating Receiver for Asynchronous DS-CDMA Systems over Multipath Fading Channels

This paper presents a decorrelating detector for DS-CDMAasynchronous systems over multipath fading channels. The decorrelatingreceiver applies the inverse correlation matrix of signature waveformsto detect the received signal. A procedure for finding such an inversematrix is developed. This procedure employs the reciprocal basis,derived from the basis of normalized user signatures, to cancelsimultaneously both the multiuser and the intersymbolinterference. The proposed multiuser detector operates over a finitedetection window, and the only restriction imposed on the set of signaturesis that the signatures must be independent at the receiver end. If the channelis slowly variant, the detectorcan be very efficient for high bit rate transmissions. Theoreticalbounds for the multiuser interference are obtained. Simulationresults, in which both binary and non-binary sequences are used,reveal that the behaviour of the detector approaches the single userbound when an adequate set of signatures is employed. The reducedcomplexity of this detector indicates that it could be a good candidatefor practical implementation.     

Linear Differentially Coherent Multiuser Detection for Multipath Channels

By combining multipath processing, differential signal detection, and multiuser detection techniques, we develop a class of near-far resistant linear detectors for differentially coherent multipath signals. We derive and establish performance relationships among the following detectors: an optimally near-far resistant detector, a suboptimum detector which does not require knowledge of the signal coordinates, and a minimum mean square error (MMSE) detector which achieves near-optimum asymptotic efficiency. We present an adaptive multiuser detector which converges to the MMSE detector without training sequences and which requires less information than the conventional single user rake receiver.     

DS-CDMA卫星通信系统线性多用户检测算法性能比较

CDMA是新一代移动通信系统的关键技术,现代卫星移动通信也采用CDMA技术。多址干扰(MAI)的存在严重影响了CDMA系统的性能,需要采用多用户检测技术进行抑制。本文分析了卫星移动通信系统的模型,将线性多用户检测算法用于卫星移动通信系统,并对传统检测器、解相关检测器、MMSE检测器等线性检测器进行了性能比较。计算机仿真结果表明采用线性多用户检测技术使卫星移动通信系统的性能得到了明显的改善。     

相干接收随机访问多码CDMA在 多径衰落信道中的容量性能研究

本文研究采用BPSK调制、相干PAKE接收的随机访问多码CDMA(RAMC-CDMA)在频率选择性Nakagami多径衰落、噪声信道(MFNC)中的容量性能.建立系统模型后,推导出了多用户条件下接收机输出的条件概率分布及判决平均比特误码率,并以Rayleigh(Nakagami的特例)多径衰落、噪声信道为例,计算了系统容量的数值解.分析表明RAMC-CDMA解决了普通DS-CDMA系统存在的用户可传信息速率受限(过低)的问题,能在不增加射频带宽的前题下为用户提供高峰值速率信息传送,而且保证了容量没有明显下降.文中还对理论分析的关键结果进行了仿真.     

An adaptive multiuser detector for DS‐CDMA systems in multipath fading channels

In this paper, we investigate the performance of an adaptive multistage detection scheme for direct‐sequence code‐division multiple‐access (DS‐CDMA) systems. The first stage consists of an adaptive multiuser detector which is based on the linear constrained minimum variance (LCMV) criterion. The interference cancellation (IC) occurs in the second stage. The performance of the iterative receiver over both flat and frequency‐selective fading channels is investigated and compared to the single‐user bound. In all cases, and under heavy system loads with near‐far problems, the iterative receiver is shown to offer substantial performance improvement and large gain in user‐capacity relative to the standard LCMV. In flat‐fading channels, our results show that the performance of the iterative detector is very close to the single‐user bound. For the frequency‐selective channel, this performance is noted to be in the order of 1 dB far from the single‐user bound. Copyright © 2007 John Wiley & Sons, Ltd.     

Near-Optimum Iterative Multiuser Receiver for FEC Encoded DS-CDMA

The powerful iterative algorithm of Turbo code is employed in the proposed iterative multiuser receiver for the downlink of a forward error correction (FEC) coded direct-sequence code-division multiple access (DS-CDMA) environment. The receiver iterates between the 2 coding dimensions, namely the spreading codes and the FEC codes. The optimum iterative multiuser receiver uses the optimum decentralised single-user detector to generate the single-user extrinsic information for the single-user decoders. This paper suggests a near-optimum detector using a folded trellis preselection stage for the multiuser signal detection, in order to reduce the dominating complexity of the optimum decentralised detector. Simulation results show that performance is close to optimum. The effect of the single-user decoders' extrinsic information on the signal detection stage is also investigated and it is found that extrinsic information improves performance.     

多径信道下一种线性空时多用户检测方法

给出了用于DS/CDMA系统的线性空时多用户接收机的数学模型,分析了在多用户空时接收机中空域处理和时域匹配滤波的作用,引入SOR算法,并将其改进应用到多径信道下的线性空时多用户检测中。通过迭代避免了直接求逆运算,显著降低了运算复杂度。仿真表明:线性空时多用户接收机能够明显提高接收机性能,并且随着接收机天线数的增加性能明显提高。