多径信道下的盲群多用户检测

本文提出一种自适应盲群多用户检测算法,它可以在直扩CDMA下行链路中有效地抑制多址干扰(MAI)和符号间干扰(ISI).通过在子空间内对接收符号的相关矩阵进行预处理,可以得到一个具有盲群约束条件的GSC(广义旁瓣消除)算法.通过理论分析可以看出:这种满足新的约束条件的GSC算法不仅可以有效地抑制多址干扰和符号间干扰,而...     

The multi-user detection under fading channel

This paper proposes a method of blind multi-user detection algorithm based on signal sub-space estimation under the fading channels in the present of impulse noise. This algorithm adapts recursive least square (RLS) filter that can estimate the coefficients using only the signature waveform. In addition, to strengthen the ability of resisting the impulse noise, a new suppressive factor is induced, which can suppress the amplitude of the impulse, and improve the ability of convergence speed. Simulation results show that new RLS algorithm is more robust against consecutive impulse noise and have better convergence ability than conventional RLS. In addition, Compared to the least mean square (LMS) detector, the new robust RLS sub-space based method has better multi-address-inference (MAI) suppressing performance, especially, when channel degrades.     

多径信道下的软序列检测

本文提出一种基于软信息的序列检测算法,建立了状态转移条件下软信息的递推方程,并给出了计算不同时刻符号软信息的关系表达式.这种软序列检测算法与多径信道估计器配合,可以有效地解调发送符号序列.与传统的MLSE解调算法相比,软信息检测需要两个级连解调器,通过前后迭代来为每个发送符号计算边信息,因此误码率会得到很大的改善.此外,前端的信道估计可以由RLS算法及Kalman滤波器联合实时估计.仿真结果显示:软序列检测算法尽管在复杂度上增加了,但是误码性能远优于ML最佳准则下的解调算法.     

Optimization for faster-than-Nyquist signaling based combining under multi-path channel

We propose a faster-than-Nyquist (FTN) signaling based combining scheme to increase the achievable rate for the single-input-single-output (SISO) system and the single-carrier system under the multi-path channel, where the combining scheme aims to combine the signals received at all symbol periods during the channel length for each transmitted symbol. An important feature of the FTN signaling based combining scheme is that the transmitter ceases the transmission for b symbol periods after transmitting each symbol. By proposing the optimization algorithm for finding the optimum b that maximizes the achievable (information) rate, we propose in this paper the optimal FTN signaling based combining scheme. We first establish the optimization problem and then present a theorem for proving the existence of the optimum b that maximizes the lower bound of the average achievable (information) rate. On the basis of this theorem, we present the steps of the proposed optimization algorithm. Numerical results are provided, and they confirm that the proposed optimization algorithm can find the optimum b.     

多径衰落信道下基于子空间的RLS盲多用户检测

本文在RLS盲检测算法的基础上,利用子空间的概念,构建了基于子空间的RLS多用户盲检测算法,在仅仅需要知道目标用户的特征序列和定时的条件下,自适应地估计检测向量,通过理论分析表明,改进的检测算法在运算复杂度上低于满秩RLS算法[7].仿真结果表明,改进的检测算法收敛性能优于满秩RLS算法,同时在特征序列畸变条件下表现出健壮件也远优于满秩RLS检测算法.     

盲多用户检测技术中的恒模算法分析

恒模算法（CMA）是一种广泛应用于阵列处理、均衡和多用户检测中的盲算法。现对恒模算法及其在盲多用户检测技术中的应用进行了分析,并指出其研究方向。     

基于Gibbs采样的群盲多用户检测技术

多用户检测是第三代移动通信系统中的一项关键技术。研究存在邻近小区干扰时异步多径DS-CDMA信号的多用户检测问题。提出一种新颖的基于Gibbs采样的群盲多用户检测技术，它根据线性群盲解相关器的输出，利用Gibbs采样进行Bayes多用户检测。存在信道编码时，提出的检测器非常适合做Turbo多用户检测，仍然能够找到Bayes解。该方法具有简单易实现、检测性能好、应用范围广泛的优点。仿真实验证实了这一点。     

Activity detection in a multi-user environment

The detection of a weak stochastic signal in multi-variate impulsive noise is investigated. The signal is that of a new user in a Code-Division Multiple-Access multi-user system. A particular type of transformation noise is considered: the trasmitted signal vector is modified by a linear transformation prior to signal detection thereby yielding a signal process and noise process that are dependent from component to component of the recieved vector. The linear operator is designed to combat multiple-access interference. The effect of such a transformation is studied by deriving the efficacies and asymptotic relative efficiencies of several detectors. Both linear and non-linear cross-correlator detector structures are examined. The performance of the detectors is determined for two types of non-Gaussian noise: additive channel noise and residual multiple-access interference noise. The numerical results are consistent with previous findings and motivate the investigation of a hybrid detector which is composed of a combination of the linear correlator and the polarity coincidence correlator. The asymptotic normality of the test statistics under study is also investigated.This research was supported by the U.S. Army Research Office under Grant DAAH04-93-G-0219.     

基于峰度的盲自适应多用户检测

基于四阶累积量,分析一种新的优化准则,即定向最小峰度(OMK:Oriented Minimum Kur-tosis)准则。理论分析表明:该准则函数具有全局最小值且极值点满足解相关条件。由此,通过求解该优化问题,能得到一种新的盲多用户接收方案。然后,利用最速下降法,给出盲多用户检测的自适应算法。仿真结果进一步验证了本文的结论。     

空时分组码OFDM系统的上行多用户检测

针对目前空时编码结构大多只研究单用户检测这一现状，研究了空时分组码OFDM系统的多用户结构，并提出了一种性能次优的基于均值的软判决多用户检测（SDMUD）算法。仿真表明，该检测算法性能要比MMSE线性检测算法提高约4dB，可获得较为满意的干扰消除效果，满足系统对多用户检测性能的现实期望。     

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。     

多径CDMA信道下一种改进的RLS空时接收机

该文首先在码片匹配滤波的基础上提出一种次优的数据选择方案,并分析了它对多址干扰与字符间干扰的影响;接着在此基础上提出了基于约束RLS的盲空时多用户检测算法,最后通过仿真实验验证了所提出的方法的有效性。     

SIMO-NOMA系统分步多用户检测策略

上行免调度非正交多址接入（NOMA）系统中,针对低信噪比情况下通过压缩感知技术联合检测活跃用户和数据的误码率性能比较差的问题,提出了分步多用户检测策略。该策略考虑信号的稀疏度对系统检测性能的影响,理论分析得出了检测成功概率的下界,以降低稀疏度来提高重构概率;结合压缩感知硬融合算法（CS-HFA）,对稀疏信号进行二次筛选,最终实现信号的精确检测。仿真结果表明,随着信噪比、活跃用户数或者过载率的改变,改进方案表现出较好的系统检测性能。     

多径衰落信道下的扩频码设计与联合检测

在多径衰落信道CDMA系统中，扩频码设计与联合检测为提高系统容量的两个重要手段。在扩频码设计中，通过构造零相关窗码可以消除MAI和ISI，从而提高系统容量。当扩频码相关特性不理想时，通过联合检测也可以消除干扰，提高系统容量。但二者都有一定局限性，对于零相关窗码来说，它的码字资源十分有限，对于联合检测来说，当用户数很大，它的复杂度不能容忍。该文将扩频码设计与联合检测结合起来，提出了一种具有组间零相关窗特性的新型扩频码。在扩频码设计时考虑联合检测，可以增加码字资源，在联合检测中考虑扩频设计，又可以降低联合检测的复杂度。     

Throughput enhancement with a modified 802.11 MAC protocol with multi-user detection support

A modification to the traditional CSMA-based media access control protocol, named 802.11-MUD, is proposed in this paper which differs from the IEEE 802.11 in its support of simultaneous transmissions/receptions with multi-user detection (MUD). A joint information and renewal theoretic analysis framework is introduced to study the performance of 802.11-MUD. While the information theoretic part is useful for modeling the increase in sum capacity attributed to MUD, the renewal theoretic part is good for modeling the impact of MUD on alleviating the collision probability and increasing the network throughput. In addition, this analytical framework helps us finetune the 802.11-MUD system (called 802.11-MUD^* after the optimal tuning) and achieve significantly enhanced network throughput especially in busy networks.     

Iterative multi-user detection and decoding for space-time block coding systems

1 Introduction Recently space–time coding (STC) techniques [1] are designed to combat fading in wireless links by utilizing multiple antenna systems, in which transmit diversity and coding gains can be exploited without sacrificing additional power and b…     

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.     

基于自调整步长的LMS盲多用户检测

提出了一种自调整步长的LMS盲多用户检测算法,该算法的收敛步长能跟踪系统的变化,克服了定步长LMS算法的收敛步长与输入信号的自相关特征值大小相关的缺点。仿真结果表明,该算法不仅加快了收敛,并且具有较好的抑制多址干扰和克服“远-近”效应的能力。     

变步长LMS盲多用户检测算法改进研究

针对CDMA系统中存在多址干扰的问题,提出了一种变步长LMS盲多用户检测算法。根据瞬时输出能量作为平均输出能量的这一准则,将步长因子μ定义为输入函数,灵活地更新检测器的权值,使步长自调整,前期μ较大值,方便算法收敛,待稳定后再减小μ的取值,以减少迭代误差,提高算法精度。该算法在继承了传统算法计算复杂度低的优点的前提下,性能有较大的提高。计算机仿真表明,该算法达到了加快收敛速率,提高抗干扰能力,减小稳态误差的效果。     

Full-diversity design criterion for multi-user STBC based on integer-forcing detection

Multi-user space time block code systems have the problem of high decoding complexity.To ensure good system performance with low decoding complexity at the same time,low complexity integer-forcing (IF) detection algorithm was applied to multi-user space time block code.Then the upper bound of error probability for IF detection was derived by minimizing the equivalent noise power.To obtain good multi-user space time block code when decoded with IF detection,a full-diversity design criterion was proposed.It was proved that full diversity could be achieved if every user’s space time block code had property of non-vanishing singular value.Simulation result shows that the code gain is found related to the minimum singular value.