导频符号辅助干扰删除多用户检测器的研究

根据宽带码分多址（ ＷＣＤＭＡ） 系统的特点,提出并分析了一种导频符号辅助干扰删除多用户检测器（ＰＳＡＩＣ）,分析结果表明,该方法充分利用了ＷＣＤＭＡ系统中的帧结构,在不增加物理信道的情况下,实现接收信号的相干解调,并与多址干扰删除器相连,可以大大提高系统的性能,增加系统的容量,当干扰删除器的级数为２ 时,其性能有较大的改善,复杂度也不高     

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.     

Multi-Shot Approach to Multiuser Separation and Interference Suppression in Asynchronous CDMA

In this work, we present a new, computationally simple scheme (termed multi-shot approach) to separate and detect multiuser signals in an asynchronous code-division multiple-access (CDMA) communications system. By exploring the structure inherent in the matrix decomposition of properly arranged data, obtained from multi-shot matched filtering, we propose a near-far resistant multiuser detector. The proposed multiuser detector combines the multiple snapshots of matched filter outputs through a matrix filtering and de-biasing processing, revealed from the structure inherent in properly arranged data, prior to the final stage of decision making. Simulation results demonstrate the superior performance of the newly proposed computationally efficient detection scheme in comparison with other existing methods of comparable complexity.     

基于NLMS的CDMA盲自适应多用户检测算法研究

多用户检测是抑制DS-CDMA系统多址干扰最有效的技术之一。由于所需的先验知识仪有期望用户的地址码,盲多用户检测技术的研究尤受重视。最小输出能量(MOE)准则被广泛用于盲线性多用户检测。目前已提出的该类检测器多采用LMS或RLS算法。本文则研究基于NLMS算法的盲自适应检测技术,并进一步提出盲自适应变步长NLMS检测器和参数可变的盲自适应变步长NLMS检测器。它们具备很好的收敛速度和跟踪能力,以及较高的输出信干比,同时计算复杂度仅为O(3N)或O(4N),非常适合硬件实现。     

Selective partial PIC for wireless CDMA communications

This paper deals with a cancellation multiuser detector for CDMA communication systems. The proposed receiver, defined as selective partial parallel interference cancellation (SP‐PIC), is supposed to be used at the end of an up‐link channel characterized by multipath fading phenomena. The SP‐PIC main feature is to perform a weighted selective cancellation of the co‐channel interfering signals according to the received power level. With respect to other approaches, the proposed detector exhibits an improved bit error rate (BER) and a low computational complexity, linear with the number of users. Copyright © 2003 John Wiley & Sons, Ltd.     

Differentially Coherent Blind Adaptive Receiver for Rayleigh Fading CDMA Channels

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.     

自适应部分干扰抵消多用户接收机

在DS/CDMA系统中,采用多用户检测技术可以有效地克服多址干扰(MAI,MultipleaccessInterference)及远近效应。本文提出了一种自适应部分干扰抵消(APPIC,AdaptivePartialParallelInterferencecancellation)算法,根据匹配滤波器输出的判决统计对多址干扰进行选通抵消,以提高系统性能。同时本文给出了自适应部分干扰抵消接收机的非相干实现方案,并给出了仿真结果。     

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。     

CDMA多用户检测技术

首先分析了CDMA移动通信系统中采用多用户检测的必要性 ,然后介绍了各种多用户检测技术的工作原理 ,对各种多用户检测技术的特点进行了分析比较 ,最后提出了目前多用户检测技术的一些最新发展方向。     

Blind Multiuser Detection with Array Observations

Cochannel interference is usually a major limitation to the performance of mobile wireless systems. Examples of different forms of cochannel interference include multi-access interference in CDMA systems and cochannel interference resulting from frequency reuse in TDMA systems. In order to mitigate the interference from other users we present a blind multiuser receiver which utilizes array observations and performs both spatial and temporal processing of the received signal. The presented technique is completely blind in the sense that no signature sequences, channel state or spatial location needs to be known a priori, nor use of a training sequences, channel state or spatial location needs to be known a priori, nor use of a training sequence is required for the adaptation. The diversity introduced by the array observations can be efficiently combined with the use of CDMA signature sequences. After initial convergence, a reliable estimate of the combined temporal and spatial signature for each user is provided that can be employed by a multiuser receiver of lower complexity.     

多径CDMA信道下的盲空时多用户检测

本文提出了在多径CDMA信道下基于Rosen梯度投影实现的最小均方盲空时多用户检测方法,仿真结果表明,该方法具有良好的检测性能.     

The Least Square Constant Modulus Algorithm for Blind Adaptive Multiuser Detection

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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…     

Interference cancellation for a multicellular CDMA environment

This paper considers the performance of adaptive interference cancellation applied to a CDMA microcellular environment, by employing a circular cell geometry and a closed form expression for the Bit Error Rate of a CDMA system with interference cancellation to analyze the effect of out-of-cell interference. Results are presented which indicate that out-of-cell interference will severely limit the benefits of interference cancellation in a multicellular system. Attempts to cancel all out-of-cell interference will further degrade performance. However, the use of selective interference cancellation in which only the strongest out-of-cell interferers are cancelled may result in significant performance enhancement. These results agree closely with those obtained using a hexagonal geometry.Portions of this paper have been presented at the PIMRC'95 conference in Toronto, Canada.     

多径CDMA信道下最小均方盲空时多用户检测

本文首先在码片匹配滤波的基础上为多径CDMA信道环境的接收机提出四种数据选择方案,分析了各种数据方案对多址干扰与码间干扰的影响;接着提出了基于Rosen梯度投影实现的最小均方盲空时多用户检测方法并分析了四种数据选择方案对其运算复杂度的影响;最后通过仿真实验结果的分析比较给出较合理的实现方法,该方法在降低运算量具有一定的优势,因而更加具有实用意义.     

一种新的盲自适应多用户检测技术

基于对传统RAKE接收机和自适应技术的研究,提出了一种新的盲自适应多用户检测技术方案,给出了这种盲自适应多用户检测接收机的模型,并对其进行计算机仿真。结果表明这种新的盲自适应多用户接收机具有优良的抗干扰性能。     

CDMA系统中一种新的基于MMSE多用户检测的自适应功率控制算法

功率控制技术是CDMA通信系统中克服“远一近效应”，降低多址干扰、增大系统容量的一项关键技术。第三代移动通信系统对功率控制提出了新的研究课题。在本文提出CDMA系统中一种新的白适应功率控制和MMSE多用户检测的联合优化的算法，仿真结果表明，这种新的联合优化算法对提高系统容量，改善系统性能有很大的作用。     

DS/CDMA多用户检测盲自适应梯度算法的改进

本文在直接序列/码分多址(DS/CDMA)系统盲检测自适应梯度算法(BAG)的基础上,提出了一种多用户检测盲自适应梯度算法的改进算法(IBAG).BAG算法包括自适应梯度算法(TBAG)和时变自适应梯度算法(TIBAG),TBAG算法的跟踪特性较好,但起始收敛特性不好;TIBAG算法的收敛特性较好,但跟踪特性较差,几乎不具备跟踪能力.本改进算法结合了这两种自适应梯度算法的优点,在不增加算法复杂度的前提下,使其收敛性和跟踪特性较BAG算法有所提高.     

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.     

一种空时CDMA系统的多用户检测算法

多用户检测技术在实际应用中,难以解决的问题是在减少计算复杂度的同时又提高系统性能。本文针对空时CDMA系统设计了一种多用户检测算法,即附带噪声梯度的最速下降算法。此算法利用变步长迭代的思想实现多用户检测,避免了最小均方误差(MMSE)多用户检测庞大而复杂的求逆运算和固定步长收敛速度较慢的问题。计算机仿真结果表明,在空时CDMA系统中使用本文算法,收敛速度大大增加,同时在保持系统性能的前提下能够容纳较多的用户。