直扩卫星通信系统中多用户检测算法比较

实际在CDMA系统中,多址干扰(MAI)是主要的干扰来源,多用户检测技术完全可以抑制这种多址干扰。论文分析了几种典型的多用户检测技术,并在高斯信道环境下对解相关检测器、最小均方误差检测器和传统检测器进行了仿真和性能比较。     

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。     

码分多址系统中多用户检测算法的性能分析

多用户检测算法是码分多址系统中解决多址干扰的关键技术之一，近年来人们对此做了许多研究。现分析了几种典型的多用户检测算法的特性，给出了它们的性能特点。     

两类多用户检测技术

从技术角度比较了以美国和日本为研究重点的两类多用户检测技术,指出了它们的优缺点和当前国内外的研究状况,并给出了工程实现上的建议。     

异步DS-CDMA系统的等效同步多用户检测算法

第三代移动通信系统中，多用户检测技术是克服多址干扰(MAI)、增加系统容量的有效方法。本文针对多径衰落信道下的直扩码分多址(DS—CDMA)系统的上行链路，基于等效扩频码组Gram—Schmitz正交化与串行干扰消除(SIC)，提出了等效同步多用户检测(ESMUD)算法。分析最大比合并瑞克(RAKE)接收算法、传统的SIC算法以及本文算法的复杂度，并对三种算法的性能进行数值仿真。结果表明，本文提出的算法能有效抑制MAI，且计算复杂度与传统SIC算法在同一量级上。     

CDMA移动通信系统中的多用户检测技术

CDMA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，最彻底的关键技术之一，介绍了多用户检测的由来，一般结构，优缺点及其性能测度，分析了几种常用多用户检测器的原理及其性能。     

准同步DS-CDMA多用户检测算法

实际应用中的DS-CDMA系统,用户之间的传输时延控制在一定范围内。该文针对这一应用特点,着重研究准同步DS-CDMA多用户检测算法。通过降低部分相关矩阵的阶数,降低系统复杂度。然后对准同步DS-CDMA多用户检测算法进行分析,并仿真给出数值结果,证明其具有一定的抗频偏能力,以及误码性能优于传统CDMA系统性能。     

第三代移动通信系统中的关键技术多用户检测

多用户检测技术在传统检测技术的基础上,充分利用造成多址干扰(MAI)的所有用户信号信息对单个用户的信号进行检测,从而提高系统的容量和性能。本文研究了应用于第三代移动通信系统中的各种多用户检测技术的工作原理和优缺点;同时给出了多用户检测的性能分析;最后阐述了该技术发展前景。     

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。     

一种新的盲自适应多用户检测算法

多址干扰引发严重的远 /近问题。本文提出一种新的代价函数 :差分平均输出能量(DMOE) ,并设计了适用于DS/CDMA系统的盲多用户检测算法。理论分析和数值模拟表明该算法的收敛性能及误码性能均优于MOE检测器     

A Soft-Input Soft-Output Decorrelating Block Decision-Feedback Multiuser Detector for Turbo-Coded DS-CDMA Systems

Previously, a decorrelating decision-feedback multiuser detector for direct-sequence code-division multiple-access (DS-CDMA) systems normally produces only hard-decision outputs of users' data. In turbo-coded DS-CDMA systems, such a multiuser detector does not match well with the soft-input soft-output nature of a turbo-decoding algorithm, thereby resulting in some extent of performance loss. In this paper, a soft-input soft-output decorrelating block decision-feedback multiuser detector is proposed to perform joint multiuser detection and turbo decoding in an iterative manner. This multiuser detector partitions the received users' data into a number of blocks appropriately and then detects the users' data on a block-by-block basis, where the soft-decision outputs are generated based on the maximum a posteriori criterion and the decision outputs of a stronger block (with a higher energy) are fed back for use in making decisions of those weaker ones. Computer simulation results show that the proposed iterative multiuser detector with turbo decoding significantly improves the bit error rate performance of a DS-CDMA receiver.     

直扩码分多址个人通信系统在衰落信道中的多用户信号检测

本文在ＤＳ－ＣＤＭＡ ＰＣＮ系统抗干扰性能的分析中，首次提出了用户归一化扩频信号等效左半部分和等效右半部分的分析模型，并在此基础上有效地结合传统扩频通信ＲＡＫＥ接收机的抗多径性能和多用户信号检测器的抗多址干扰特性，得到了一种能同时消除同频干扰和对抗多径多用户信号检测新方法。     

Fast Converging Adaptive MMSE Multiuser Detector for DS-CDMA System

A fast converging adaptive minimum-mean-squared-error (MMSE) multiuser detector is proposed for direct-sequence code-division multiple-access (DS-CDMA) systems with severe near-far problem where the convergence rate of adaptive MMSE detectors for distinct users can be very different. It is shown that by successively cancelling the interference signals of strong power users, the convergence rate of the proposed detectors for weak power users can be significantly increased, which helps to reduce the length of training sequence for tracking. It is also shown that the order of cancellation and several important parameters required for interference cancellation can be determined from the convergence behavior of the proposed detector. Numerical results are presented to show that the proposed detector offers improved performance in various DS-CDMA environments.Zhiwei Mao received the B.Sc. degrees from Beijing University of Posts and Telecommunications (BUPT), Beijing, China in 1996 and 1999, respectively. Since 2000, she had been a Research Assistant and graduate student in the Department of Electrical and Coumputer Engineering, University of Victoria, Victoria, BC, Canada. She received the Ph.D. degree in electrical engineering in 2003. Currently, she is an Assistant Professor at Lakehead University, Thunder Bay, Ontario, Canada.Her research interests include wireless communications, multiuser detection, digital communications and digital singal processing.Vijay K. Bhargava received the B.Sc., M.Sc., and Ph.D. degree from Queens University, Kingston, ON, Canada in 1970, 1972 and 1974 respectively.Currently, he is a Professor and Head of the Department of Electrical and Computer Engineering at the University of British Columbia, Vancouver, Canada. Previously he was with the Univeristy of Victoria (1984–2003) and with Concordia University in Montréal (1976–1984). He is a co-author of the book Digital Communications by Satellite (New York: Wiley, 1981), co-editor of Reed-Solomon Codes and Their Applications (New York: IEEE, 1994) and co-editor of Communications, Information and Network Security (Boston: Kluwer, 2002). His research interest are in wireless communications.Dr. Bhargava is a Fellow of the B.C. Advanced Systems Institute, Engineering Institute of Canada (EIC), the IEEE, the Canadian Academy of Engineering and the Royal Society of Canada. He is a recipient of the IEEE Centennial Medal (1984), IEEE Canadas McNaughton Gold Medal (1995), the IEEE Haraden Pratt Award (1999), the IEEE Third Millennium Medal (2000), IEEE Graduate Teaching Award (2002), and the Eadie Medal of the Royal Society of Canada (2004).Dr. Bhargava is very active in the IEEE and was nominated by the IEEE Board of Director for the Office of IEEE President-Elect. Currently he serves on the Board of Communications Society. He is an Editor for the IEEE Transactions on Wireless Communications. He is a Past President of the IEEE Information Theory Society.     

Performance of Multiuser Detection in Multirate CDMA Systems

Multiuser detectors for asynchronous multirate code-division multiple-access (CDMA) systems are considered. A multirate CDMA system model able to fit several system concepts in the same framework is presented. The performance of the multi-code (MC) system with one processing gain and the multiple processing gain (MPG) system is compared. Upper bounds for the expected value of the asymptotic multiuser efficiency of the decorrelating detector for a synchronous multirate CDMA system with three effective users are derived for a system with one and two processing gains. The numerical results show that the performance of the decorrelating detector for MC and MPG systems do not differ significantly. The bit error rates (BER) of the decorrelating, parallel interference canceler (PIC) and groupwise serial interference canceler (GSIC) with either PIC or decorrelator within the group are compared. The results show that the decorrelating and the GSIC detectors yield the best performance. For all interference cancellation schemes the BER saturates at high SNRs due to decision errors degrading the multiple-access interference (MAI) estimates.     

DS-CDMA移动通信系统中的数据检测技术

在第3代DS-CDMA移动通信系统研究中,先进的数据检测技术是解决码分多址通信中多址干扰、多径干扰和信道噪声干扰的手段之一。文章讨论了单用户和多用户信号检测问题,重点介绍干扰抑制和联合检测。     

Multiuser Detection in MC-CDMA Communication Systems Using MPEM Algorithm

In this paper, we propose a sub-optimum multiuser detection technique in multicarrier code division multiple access (MC-CDMA) communication systems based on missing parameter expectation maximization (MPEM) algorithm. In the proposed detection procedure, first initial values for the bits of all users are estimated from received signal. Then, the proposed MPEM based algorithm uses outputs of carries’ demodulators to improve the accuracy of the initial estimates of the bits. In this paper, the expectation and maximization steps’ functions of the MPEM algorithm for MC-CDMA multiuser detection are derived and the performance of the proposed algorithm is analyzed. Our presented numerical results demonstrate the efficiency of the proposed detection algorithm both in bit error rate performance and computational complexity points of view. Paeiz Azmi was born in Tehran, Iran, on April 17, 1974. He received the B.Sc., M.Sc., and Ph.D. degrees in electrical engineering from Sharif University of Technology (SUT), Tehran, Iran, in 1996, 1998, and 2002, respectively. Since September 2002, he has been with the Electrical and Computers Engineering Department of Tarbiat Modarres University, Tehran, Iran. From 1999 to 2001, he was with Advanced Communication Science Research Laboratory at Iran Telecommunication Research Center (ITRC), Tehran, Iran. From 2002 to 2005, he was with Signal Processing Research Group at ITRC. His current research interests include modulation and coding techniques, digital signal processing, and optical CDMA communications.     

Relative Performance of BPSK and QPSK in the Presence of Complex Multiuser CDMA Interference

In a typical mobile communications channel, the multiple accessinterference (MAI) experienced by any user in a multiuser CDMA systemwill be complex-valued due to independent phase offsets betweensignals received from different users. In addition, complex spreadingcodes may also be employed, in which case MAI is complex-valued evenwithout phase offsets. This paper shows that complex MAI substantiallyalters the single-user relationship between BPSK and QPSK modulation,in which QPSK offers twice the bandwidth efficiency of BPSK withoutsacrificing BER versus E _b /N ₀ performance. Itis shown bothanalytically and through simulations that it is possible to adjustsystem parameters to achieve identical system bandwidth efficiency andBER performance in BPSK and QPSK systems using the conventionaldetector. The performance of the well-known successive interferencecanceller and decorrelating detector are also examined.     

Asynchronous QR-RLS-CMOE Blind Multiuser Detection

DS/CDMA communication systems are widelyused because of their obvious advantages, such as softcapacity, soft handover, higher spectral efficiency andthe ability to mitigate the effects of multi-path fading.However, the multiple access interference (MAI) andnear-far problem in DS/CDMA limit the furtherapplications of this technique. The structure of the conventional single-userdetector (CD), which neglects the presence of MAI, issimple, but its performance is limited, and the receiversuf…