异步多径条件下空时CDMA多用户检测

本文利用最小均方误差准则,推导了异步多径条件下空时CDMA多用户检测算法,分析了多用户检测与单用户检测关系,提出空时CDMA多用户检测接收机结构。基于SAGE迭代算法进行空时多用户检测,并利用CDMA信号的有限字符特性和上行信道的导频信息对SAGE算法提出改进。仿真结果说明了本文提出的空时CDMA多用户检测算法性能。     

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。     

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。     

一种新颖的异步多径CDMA信号的 贝叶斯多用户检测方法

马尔可夫链蒙特卡罗(MCMC)方法有效地解决了贝叶斯计算的问题,但是不容易将它应用于有未知干扰用户的异步多径CDMA系统.为了克服这一困难,本文提出一种新颖的贝叶斯多用户检测方法,它首先用线性群盲解相关器对接收信号做预处理,然后再用Gibbs采样(一种典型的MCMC算法)做贝叶斯多用户检测.仿真结果表明,该方法的检测性能明显地优于线性群盲多用户检测,其计算复杂度的增加与小区内用户数目呈线性关系.为了进一步提高本文方法的性能,我们使用两级Gibbs采样,根据第一级Gibbs采样的输出得到更精确的参数估计,并把它用于第二级Gibbs采样中.仿真结果证明,与只使用一级Gibbs采样的方法相比,两级Gibbs采样的检测性能明显地改善了.     

CDMA系统粒子群多用户检测算法

Kennedy和Eberhart提出的粒子群优化算法(PSO),作为一种新的并行优化算法,在解决多维和非线性的复杂问题中,性能优良且算法简单易于实现。本文对二进制粒子群优化算法进行改进,并将其应用于DS-CDMA通信系统的多用户检测中,提出了基于矢量的二进制粒子群多用户检测器(V-BPSO-MUD),同时提出了两种高效实用的多用户检测器:基于矢量的串行二进制多用户检测器(VS-BPSO-MUD)及基于矩阵的二进制多用户检测器(M-BPSO-MUD)。仿真结果表明,PSO多用户检测器充分利用了粒子群优化算法的优良特性,性能明显优于传统的CDMA检测器,接近无多址干扰情况。     

蚁群算法多用户检测用于MC-CDMA系统

在MC-CDMA系统中检测技术是影响系统性能的关键技术之一。这里首先对最优多用户检测方法做出了简要的分析,然后引入蚁群算法多用户检测,使用最优多用户检测的判决准则作为蚁群算法中的目标函数,并对蚁群算法多用户检测和其他多用户检测性能做了仿真比较。结果表明蚁群算法多用户检测和其他次优多用户检测相比,具有较好的性能;和最优多用户检测相比具有很低的复杂度。在多用户检测的实际应用中表现出了很大的优势。     

Interference Identification and Blind Multiuser Detection for Asynchronous CDMA Systems With Multipath Fading

We propose a blind user identification detection (UID) scheme based on linear prediction algorithm for asynchronous direct-sequence code-division multiple-access systems over multipath fading channels. Numerical results show that both the false alarm rate and bit error rate of the proposed algorithm are better than those of the existing subspace-based UID algorithms.     

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。     

空时CDMA多用户信号检测

本文利用最小均方误差(MMSE)和最大似然(ML)准则,推导了空时CDMA多用户检测算法,分析了空时多用户检测与单用户检测的关系,并提出一种空时CDMA多用户检测接收机结构.计算机仿真结果说明了本文提出的空时CDMA多用户检测算法,与单用户检测方法相比其误码性能有相当的改进.     

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…     

CDMA移动通信中的判决反馈多用户信号检测器

本文推导了一种具有线性计算复杂度的同步ＤＳ—ＣＤＭＡ系统多用户检测算法，由此形成的判决反馈检测器在性能上优于解相关检测器，与两级多用户检测器的性能相当，而实现起来则更为简单。数值结果表明，当接收到的干扰信号能量比有用信号能量高４ｄＢ以上时，判决反馈检测器的性能将接近单用户系统的性能，因而该检测器可有效地克服ＣＤＭＡ移动通信中的远近影响。     

DS/CDMA系统中的多用户检测技术

多用户检测技术可抑制多址干扰（ＭＡＩ）,从而提高ＣＤＭＡ系统的容量和性能。介绍了多用户检测器的分类和自适应算法、盲算法在多用户检测中的应用。     

Multiuser Detection of Sparsely Spread CDMA

Code-division multiple access (CDMA) is the basis of a family of advanced air interfaces in current and future generation networks. The benefits promised by CDMA have not been fully realized partly due to the prohibitive complexity of optimal detection and decoding of many users communicating simultaneously using the same frequency band. From both theoretical and practical perspectives, this paper advocates a new paradigm of CDMA with sparse spreading sequences, which enables near-optimal multiuser detection using belief propagation (BP) with low-complexity. The scheme is in part inspired by capacity-approaching low-density parity-check (LDPC) codes and the success of iterative decoding techniques. Specifically, it is shown that BP-based detection is optimal in the large-system limit under many practical circumstances, which is a unique advantage of sparsely spread CDMA systems. Moreover, it is shown that, from the viewpoint of an individual user, the CDMA channel is asymptotically equivalent to a scalar Gaussian channel with some degradation in the signal-to-noise ratio (SNR). The degradation factor, known as the multiuser efficiency, can be determined from a fixed-point equation. The results in this paper apply to a broad class of sparse, semi-regular CDMA systems with arbitrary input and power distribution. Numerical results support the theoretical findings for systems of moderate size, which further demonstrate the appeal of sparse spreading in practical applications.     

异步DS-CDMA盲多用户检测

该文研究了频率选择性瑞利衰落信道中的异步DS-CDMA系统盲多用户检测。提出一种期望信号矢量估计方法,该方法同时利用了多径传播和接收机同步失调的特性,以利于把盲线性滤波优化技术应用于稳健的干扰抑制。为了抑制多址干扰(MAI),提出一种基于投影的辅助矢量(PAV)算法。该算法计算复杂度低,特别适用于短数据采样时滤波矢量的快速优化,仿真结果表明在低输入信号干扰噪声比(SINR)时能提供有效的干扰抑制,在高输入SINR时具有稳健的性能。     

Optimum Multiuser Detector for Multipath Slow Fading Asynchronous CDMA Channels

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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.     

码分多址（CDMA）系统MMSE-MUD算法研究

CDMA系统由于用户容量大、频谱利用率高等特点而优于其他多址方式,近年来在通信系统中得到越来越多的重视,如何克服多址干扰问题已成为提高CDMA系统容量的关键。而作为3G的关键技术之一的多用户检测技术,近年来取得了多个方面的发展。本文就TD—SCDMA系统的多用户检测技术（MUD）之一的最小均方误差（MMSE）技术进行了详细分析,并给出仿真结果。     

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.     

Kurtosis-Based Blind Multiuser Detection in Multipath CDMA Channels

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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。