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。     

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。     

一种可以高速传输数据的MTCM正交序列多码CDMA系统

为了有效地实现用户高速数据的传输本文提出了一种ＭＴＣＭ正交序列多码ＣＤＭＡ系统。这对此系统在ＡＷＧＮ信道的性能进行了计算,并和未编码系统的数值结果进行了分析和比较。     

多径CDMA信道下的一种改进的盲空时多用户检测

该文在多径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的基础上提出了一种改进的方法,该方法与原有的方法相比,运算量有所降低、对系统的要求降低,但通过仿真结果比较表明,该方法的检测性能与原有的方法大致相当,因而更加具有竞争力。     

CDMA通信系统中的多用户检测

ＣＤＭＡ由于其用户容量大,抗多径衰落能力强以及便于实现软切换等特点而优于其他多址方式,近年来在移动通信系统中越来越得到重视。但是ＣＤＭＡ通信系统由于存在着严重的多址干扰而限制了其容量的进一步提高。多用户检测利用每个用户的信息对接收信号进行相关处理作统计判决或是进行干扰对消从而恢复出各个用户的发送序列,多用户检测方法可以使用最优多用户检测器、线性多用户检测器及非纡性多用户检测器等几类。     

基于最小误码率准则的多载波CDMA系统多用户检测算法

本文介绍了一种将正交频分复用(OFDM)技术和码分多址(CDMA)技术相结合的多载波CDMA (MC-CDMA)系统,分析了MC-CDMA系统的发射端和接收端的结构,建立了MC-CDMA系统的信号模型,详细分析了MC-CDMA中的多址干扰形式,以及针对MC-CDMA系统的多用户检测原理,提出了一种基于最小误码率准则的多用户检测算法。理想的基于最小误码率准则的多用户检测算法在实际中难于实现,本文采用估计概率密度函数的方法,推导出了一种自适应实现的最小误码率多用户检测算法。仿真结果表明,该算法能够有效抑制多址干扰,降低误码率,同时,该算法还具有比基于最小均方误差准则的多用户检测器更低的误码率的优点。      

一种用于CDMA系统的正交序列调制方法

在宽带移动通信系统中，经常考虑采用通过ＦＦＴ实现的多载波调制，如ＯＦＤＭ。本文提出了一种利用ＦＨＴ实现的ＣＤＭＡ系统的正交序列调制方案。其基本思想为利用Ｗａｌｓｈ函数作为载波，将Ｗａｌｓｈ函数分组，从每组中选出一些作为载波，这样不同的载波组合方式本身将包含用户信息。这种方法实现简单，可提高传输效率，并容易与ＣＤＭＡ相结合，能有效地抑制多径干扰。仿真结果表明，该方案在多径衰落信道中能得到很好的性能。     

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。     

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.     

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。     

High spectral efficiency iterative multi-user detection for CDMA

An iterative multi-user detector for code-division multiple-access (CDMA) signals that is able to operate under highly loaded conditions with a non-binary modulation scheme is presented. The results presented demonstrate that the receiver is able to achieve near single-user bit error rate performance     

Quasi-orthogonal chaotic CDMA multi-user detection using optimal chaos synchronization

In this paper, a novel optimal chaos synchronization (CS)-based method is proposed to realize multi-user detection of quasi-orthogonal chaotic code-division multiple access (CDMA) system. Theoretical analysis and computer simulations show that the multi-user quasi-orthogonal chaotic signal used in the CDMA system can be detected successfully by using the optimal CS. . Computer simulations show that the proposed method achieves a lower bit-error-rate performance than the conventional decorrelating detector and the minimum mean-square-error detector, and its performance is closer to that of the single-user Rake detector.     

多用户检测CDMA系统的阻塞度量和控制

本文讨论了ＣＤＭＡ系统在多用户检测和单用户检测两种情况下系统的阻塞度量和控制问题,并给出了相应的用户功率平衡方程和小区干扰平衡方程。本文证明两种平衡方程有相同的阻塞因子,但干扰平衡方程和维数与系统内小区数相等,并远小于用户功率平衡方程的维数即系统用户数,因而降低了计算复杂度。理论和模拟结果表明多用户检测系统中平衡方程有更小的阻塞因子,因而相对应的迭代算法能很快收敛,并且系统的阻塞率得到降低。     

Asynchronous block-based minimum mean square error (B-MMSE) CDMA multi-user detection

This paper introduces a novel asynchronous CDMA multi-user detector, the block-based MMSE (B-MMSE) multi-user detector, in which the data stream is segmented into blocks by inserting zero bits and detection takes place block-by-block without compromising the MMSE detection efficiency. The BER performance of the B-MMSE detector is studied and the results are compared with those of the decorrelating detector. It is shown that the B-MMSE detector offers promising detection efficiency at a much lower implementation complexity, which is linear in the product of number of users and block size, than that of the traditional MMSE detector. © 1998 John Wiley & Sons, Ltd.     

MC-CDMA系统PIC多用户检测策略

主要研究了MC-CDMA系统下行链路上各种均衡策略，采用并行干扰消除技术进行多用户检测。计算机性能模拟结果表明：基于MMSE的PIC两级检测是兼顾系统性能和运算复杂度的一种较好的多用户检测方案。     

信道估计误差对Rayleigh衰落下多天线CDMA系统信道容量影响

目前对多天线信道容量的研究几乎都是集中在具有精确信道估计的假设上,但是它实现起来有一定的难度.在Walsh扩频地址码、多码检测和最大似然接收机的基础上,研究了Rayleigh衰落情况下信道估计误差对MIMO CDMA系统的影响.分析及仿真结果均表明:信道容量随着信道估计误差的增加迅速下降;对于N×N系统,在固定的信道估计误差和信噪比下容量和天线的数目呈线性关系,容量增加的斜率随信道估计误差的增大而减小.     

Coded asynchronous CDMA and its efficient detection

In this paper, receiver design and performance analysis for coded asynchronous code-division multiple access (CDMA) systems is considered. The receiver front-end consists of the near-far resistant multiuser detector known as the projection receiver (PR). The PR performs multiple-access interference resolution and is followed by error-control decoding. The output of the projection receiver yields the appropriate metric (i.e., soft information) for decoding of the coded sequences. An expression for the metric is derived that allows the use of a standard sequence decoder (e.g., Viterbi algorithm, M-algorithm) for the error-control code. It is then shown that the metric computer has an elegant adaptive implementation based on an extension of the familiar recursive least squares (RLS) algorithm. The adaptive PR operates on a single sample per chip and achieves a performance virtually identical to the algebraic PR, but with significantly less complexity. The receiver performance is studied for CDMA systems with fixed and random spreading sequences, and theoretical performance degradations with regard to the single-user bound are derived. The near-far resistance of the PR is also proven, and demonstrated by simulation     

基于多目标检测系统的盲多用户检测算法的改进

针对多目标检测系统中自适应盲多用户恒模算法存在多个局部收敛点,且依赖于初始向量和收敛步长参数选择的缺点,提出了折中小数据量与收敛步长所需窗口间的矛盾,使用扩展部分数据的方法,提高小数据量的多用户检测性能。仿真结果表明,该改进算法提高了恒模算法的窗口利用率且收敛精度高于等同数据长度的窗的恒模算法,能够对突发的小数据量信号进行检测。     

Dual-threshold sequential detection code synchronization for anoptical CDMA network in the presence of multi-user interference

The paper examines the acquisition performance of a synchronization system for an optical fiber-based code-division multiple-access (CDMA) network that employs a dual-threshold sequential detector. The noncoherent optical CDMA network operates asynchronously and optical orthogonal codes (OOCs) are used for the spreading sequences. The performance measure of the synchronizer, the mean acquisition time, is derived via the Markov flow-graph method and Monte Carlo simulations are used to obtain the statistical parameters of the synchronizer when used within the system. The model takes into account the number of active users, the multi-user interference (MUI), the receiver noise and the coupler losses within the network. The results show that by adjusting both the acceptance and rejection thresholds of the sequential detector, the mean acquisition time ran be optimized. The degradation in the synchronizer performance, when the number of active users is changed from the number the synchronizer is designed for, is also assessed     

一种新颖的CDMA移动通信系统无源定位算法

针对CDMA移动通信系统的特点,提出信号直放无源定位方法.为提高多直放设备无源定位成功率和定位效率,提出使用Levenberg-Marquardt(LM)算法.论文建立了多直放环境下CDMA无源定位模型和观测方程,详细描述了算法的基本原理.对算法进行仿真,结果表明同三边测量最小二乘算法相比,在保证水平方向定位精度的前提下该算法可以有效的提高定位成功率和定位效率.