同步CDMA系统中的迭代多用户检测技术

迭代多用户检测技术是Turbo译码算法中的精髓“迭代思想”的又一个应用 ,它结合了turbo码的译码和多用户检测的研究 ,成为目前通信领域研究的热点。结果表明 ,多次迭代后 ,系统性能将得到很大提高 ,接近单用户的性能。     

同步CDMA系统中多步迭代多用户检测技术

同时考虑系统性能和运算量，将多步联合检测和迭代多用户检测技术结合起来，提出了多步迭代多用户检测技术。相对于单纯的MSJD，系统性能将大大提高；相对于单纯的迭代多用户检测，运算量将大大减少。     

一种简化的线性空时多用户检测迭代算法

提出了一种简化的线性空时多用户检测迭代算法,仿真结果表明这种迭代算法具有较好的误码性能。     

一种新的盲多用户检测最大似然方法

线性受限最大似然盲多用户检测是盲多用户检测中的一类重要方法,现有的限制方法不能保证目标用户的最优解落在限制的搜索空间中,因此在理论上不能达到最优解。提出了一种新的限制方法,能保证目标用户的最优解落在限制的搜索空间中,因此保证算法收敛到目标用户。与现有方法相比,这里给出的算法结构简单,降低了运算复杂度。仿真试验表明其具有较低的误码率和较高的系统容量。     

异步编码CDMA系统中基于因子图的迭代多用户接收器

针对异步编码CDMA系统，本文提出了一种基于因子图的迭代多用户接收器，它是将用户信息比特对接收端噪声白化滤波器输出的条件后验概率分布用因子图表示，并采用和-积算法，经过有限次迭代获得用户信息比特的估计值．为降低计算复杂度，本文还提出一种简化算法．仿真结果表明，本文提出的迭代多用户接收器在经过几次迭代后的比特误码性能接近单用户系统；同时，简化算法的性能接近完全算法，但算法复杂度有明显改善．     

分层空时码检测算法的研究

分层空时码技术是提高无线信道传输速率的一种十分有效的方法.迫零检测算法和最小均方误差检测算法是分层空时码体制中经常使用的两种检测算法,它们都使用了通常的线性合并置零技术,因此要求接收天线数不小于发射天线数,即要求在接收机上安装较多的天线,从而限制了分层空时码在移动环境下的应用.本文引入分层空时码的最大似然检测算法,突破了前两种算法对接收天线数的限制,并分别针对单路径和多径衰落信道环境,对分层空时码的三种检测算法的性能进行了仿真比较和分析,从而提出了它们各自适合的应用环境.     

MIMO-OFDM系统中一种改进的V-BLAST检测算法

在V-BLAST MIMO-OFDM系统中,ML算法是检测信号的最佳方式,但是算法的复杂度随着天线数目呈指数增长,因此很难在实际中得到应用.OSIC算法可以降低算法的复杂度,但是其误码率性能也下降了,降低的原因是无法防止误码的扩散.本文提出的ML-OSIC算法,是ML与OSIC的结合,在减少ML算法搜索次数的同时,能有效地避免层间干扰和误码扩散.仿真结果表明,本算法在降低算法复杂度的同时,得到了与ML算法很接近的性能.     

交织多址与迭代多用户检测

介绍了一种新的多址方式IDMA，它采用不同的交织序列作为用户的标识特征。作为一种特殊的CDMA，IDMA继承了CDMA的很多优点，而且它以非常低的解码代价支持多用户，具有复杂度低、运算量小的特点。IDMA与迭代多用户检测技术相结合，在计算复杂度增加较少的情况下，有效提高了频谱利用率。     

基于免疫算法的多用户检测

本文提出了基于免疫算法的多用户检测方法，这种方法大大降低了最佳多用户检测器的计算复杂度，同时达到了次最佳的检测效果。     

FIR Zero-Forcing Multiuser Detection and Code Designs for Downlink MC-CDMA

This paper focuses on multiuser detection for multicarrier code-division multiple-access (MC-CDMA) systems, employing cyclic-prefixed (CP) or zero-padded (ZP) transmission techniques. For both systems, we consider either the classical linear finite-impulse response (L-FIR) receiving structures or, when the transmitted symbols are improper, the proposed widely linear FIR (WL-FIR) ones, which process both the received signal and its complex-conjugate version. With regard to both CP- and ZP-based downlink configurations, it is shown that, if the number of users does not exceed a given threshold and their codes are appropriately designed, L-FIR and WL-FIR universal zero-forcing (ZF) multiuser detectors can be synthesized, which, in the absence of noise, guarantee perfect symbol recovery for each user, regardless of the underlying frequency-selective channel. In particular, some spreading code examples are provided, which satisfy the design rules. Finally, numerical simulations are carried out to show that the theoretical considerations developed herein provide useful guidelines for practical MC-CDMA system designs.     

迫零准则下的V-BLAST检测算法比较

在采用分层空时编码V-BLAST的MIMO系统中,笔者对基于迫零准则的四种信号检测算法的性能进行了仿真分析。系统接收端分别使用迫零算法ZF、排序加干扰抵消的迫零算法ZF-OSIC、QR分解算法和排序的QR算法SQRD检测信号,通过仿真得到误码率曲线。对算法复杂度及相应误码率综合比较,得出了ZF-OSIC算法下系统接收端性能最好,SQRD算法为最可行的结论。     

Reduced-Complexity Iterative Multiuser Detection for DS-CDMA

A reduced-complexity iterative multiuser detection scheme is proposed. The scheme involves a simple way of choosing only K + 1 user bit vectors instead of the full-complexity 2^K for the likelihood computation, thus reducing the complexity to O(K). An alternative, reduced computation method of increasing this list of vectors after each iteration is also presented. Simulations over AWGN, imperfect power control and multipath conditions demonstrate that the performance of the proposed reduced-complexity method is close to that of the full-complexity.Ju Yan Pan received the B.S.E.E. degree from Mississippi State University, U.S.A., in 1998 and the M.Eng. degree from Nanyang Technological University, Singapore, in 2002. He is currently working as a system design engineer at the wireless communication technology department of Oki Techno Centre Pte. Ltd. in Singapore Science Park II. His current reserach interests include third-generation WCDMA systems, turbo decoding and multiuser detection.Cheong Boon Soh received the Bachelor of Engineering in Electrical and Computer Systems Engineering (Hons I) and Ph.D. degrees from Monash University, Victoria, Australia, in 1983 and 1987, respectively. He is an Associate Professor in the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore. He has published more than one hundred international journal papers. His current research interests are robust control, system theory, nonlinear systems, coding theory, mobile communication systems and intelligent systems.Gunawan Erry received his B.Sc degree in Electrical and Electronic Engineering from the University of Leeds, U.K., in 1983. He then received his MBA and Ph.D. in total technology from Bradford University in 1984 and 1988 respectively. From 1984 to 1988, he worked for Communication Systems Research Ltd, U.K. as a satellite communication systems engineer. In 1988, he moved to Space Communications (SAT-TEL) Ltd, U.K. He joined the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore in 1989. Currently, he is an Associate Professor in the School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore. His current research interests are in digital communications, mobile and satellite communications, error coding and spread-spectrum. He has published over sixty international research papers and has been a consultant to a local company on the study of DECT system and Bluetooth.     

低复杂度的QR解相关多用户检测算法

针对常规解相关多用户检测算法因对相关矩阵求逆的运算量随用户数增加呈指数增加而失去了实用价值,提出了不需对相关阵求逆的计算复杂度低的快速QR解相关多用户检测算法。该快速算法运算量与常规解相关算法相比,运算量减少了70％,而检测性能丝毫没有降低。显然,该算法优于常规算法,具有实用意义。     

Iterative Frequency Domain Joint-over-Antenna Detection in Multiuser MIMO

Multiuser multiple-input-multiple-output (MIMO) wireless systems have great potential in improving information rate, diversity and resistance to against interference. The primary objective of this paper is to derive for broadband signaling a new iterative frequency domain (FD) multiuser MIMO signal detection technique for joint-over-antenna (JA) detection. The proposed detector is based on soft-cancellation and minimum mean square error (MMSE) filtering, followed by maximum a posteriori probability (MAP) detector to detect several of each users transmit antennas. The purpose of jointly detecting several transmit antennas is to preserve the degrees of freedom (DoF) for MMSE. Computational complexities with FD and its time domain (TD) counterpart are evaluated in this paper, and it is shown that FD requires significantly lower complexity than TD. Numerical results show that JA significantly outperforms the receiver that detects transmit antenna signals antenna-by- antenna (AA). The proposed iterative FD JA technique achieves larger performance gains compared to AA when the total number of transmit antennas is larger than the number of receiver antennas, as well as in the presence of spatial correlation.     

基于解相关判决反馈检测的迭代多用户接收器

提出了一种基于解相关判决反馈检测的迭代多用户接收器,它同时实现多用户检测,信道译码和信道参数估计,数据检测、译码与参数估计相辅相成。随着迭代次数的增加,比特误码率减低;同时,参数估计值也趋于最优值。     

下行链路通信中的迫零多用户发射预处理机制

在这篇文章中,一种多用户发射预处理(MUTP)方法被用来作为下行链路无线通信的机制,比如在空分多址系统中.所建议的MUTP预处理矩阵是通过构造一个和干扰子空间正交的子空间,而不依靠本征函数分析法.MUTP完全的消除了下行链路的多用户干扰,导致了迫零(ZF)解决方法.它可以取得和传统的以迫零为基础的MUTP(ZF-MUTP)相同的比特差错率的性能.     

Iterative Multiuser Detection for Single-Carrier Modulation with Frequency-Domain Equalization

In this letter, we propose a new multiuser detection scheme for single-carrier modulation with frequency-domain equalization (SC-FDE). We first present mathematical formulations of multiuser detection for the SC-FDE system with user- specific interleaving. The proposed structure employs spreader and different interleaver for each user at the transmitter, and re moves multiuser interference with an iterative detection method in the frequency domain at the receiver. Simulation results show that the proposed scheme outperforms the interleave- division multiple-access (IDMA) scheme in the block error rate even for severely frequency-selective channel, while providing considerably lower computational complexity.     

部分并行软干扰消除迭代多用户检测算法研究

本文提出了一种基于部分并行干扰消除(PPIC)结构的迭代多用户检测算法,并对基于PPIC的迭代多用户检测器的迭代结构进行了改进.由于PPIC多用户检测器前一级输出的信息的准确度会影响到后一级的检测,所以为了提高基于PPIC的迭代多用户检测器的性能,对PPIC每一级的输出信息结合最大后验概率(MAP)信道译码器单独进行迭代处理,这样就提高了PPIC每一级输出的信息的准确性.该迭代结构可用于其他基于PIC型的迭代多用户检测算法.     

一种基于检测信息可靠度的部分软干扰消除迭代多用户检测算法

该文提出了一种基于检测信息可靠度的部分软干扰消除迭代多用户检测算法。如果由从信道译码器所获得的发送字符的先验信息大于某一预定阈值,则认为对其检测具有较高的可靠度,因而可以考虑将其对应的多址干扰成分从匹配滤波器输出向量中直接消除,相当于减小了干扰用户的数目,从而可以减小迭代多用户检测算法的复杂度。该算法的计算复杂度能够随着多址干扰的减小和信道信噪比的增大而降低。