A New Rank-two Semidefinite Programming Relaxation Method for Multiuser Detection Problem

Based on the semidefinite programming relaxation model of the code division multiple access maximum likelihood multiuser detection problem, a detection strategy by the rank-two method is presented. The proposed method restricts the matrix variable in the semidefinite programming relaxation to be rank-two, and yields a quadratic objective function with simple quadratic constraints. A feasible direction method is used to solve the nonlinear programming. Coupled with randomized method, a suboptimal solution is obtained for the multiuser detection problem. Simulation results show that the bit error rate performances of a detection strategy based on the new rank-two method are almost similar to that of the detection strategy based on the semidefinite programming relaxation. Furthermore, average CPU time of the new rank-two method is at least 10 times lower than that of the semidefinite programming relaxation method, With the increasing of the users number, the average CPU time increasing rate of the new rank-two method is lower than that of the semidefinite programming relaxation method, especially for the large-scale detection problems. This approach provides good approximations to the optimal maximum likelihood performance.     

A Second-Order Cone Programming Method for Multiuser Detection Problem

Based on the binary quadratic programming model of the CDMA maximum likelihood multiuser detection problem, a detection strategy by the second-order cone programming method is presented. The proposed method relaxes the binary quadratic programming model as a second-order cone programming model. Coupled with the sign function, a suboptimal solution is obtained for the multiuser detection problem. Comparing with the reported semidefinite programming method, simulations demonstrate that the second-order cone programming method often yields the similar bit error rate (BER) performances for the multiuser detection problem, but the average CPU time of this method is significantly reduced.     

最优多用户检测问题研究

DS-CDMA无线通信中的最优多用户检测属于NP完备组合优化问题,启发式方法是求解这类问题的有效方法,通过分析最优多用户检测问题的适应值曲面特征,研究设计了系列低计算复杂度、接近最优多用户检测性能的启发式算法.仿真结果表明,基于演化策略的多用户检测算法能够在中等规模用户数情况下提供与最优多用户检测相当的性能,而快速迭代局域搜索算法能够以较低的计算复杂度得到比其他局域搜索算法更好的解.     

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系统解相关检测的一种新方法

借用有界算子的理论,提出了一种新的解相关的多用户检测的方法,该方法避免了矩阵求逆的复杂运算,有效地减少了计算复杂度。     

多径信道下一种线性空时多用户检测方法

给出了用于DS/CDMA系统的线性空时多用户接收机的数学模型,分析了在多用户空时接收机中空域处理和时域匹配滤波的作用,引入SOR算法,并将其改进应用到多径信道下的线性空时多用户检测中。通过迭代避免了直接求逆运算,显著降低了运算复杂度。仿真表明:线性空时多用户接收机能够明显提高接收机性能,并且随着接收机天线数的增加性能明显提高。     

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.     

基于径向基函数神经网络的CDMA多用户检测方法

径向基函数神经网络是一种三层前馈性神经网络,它具有较强函数逼近能力和分类能力,学习速度快等优点.本文根据径向基函数神经网络的这些优点提出了一种基于径向基函数网络的CDMA多用户检测方法(RMD).计算机模拟表明我们所提的算法具有能克服多址干扰,抑制噪声干扰和对"远-近"问题不敏感等优点,这为研究CDMA多用户检测器开辟了一条新的途径。     

一种多径衰落信道中的多用户检测算法

针对多径衰落CDMA信道,提出了一种基于信号子空间估计的联合盲特征波形估计与多用户检测方案,分析了两处线性多用户检测器（解相关检测器和线性MMSE检测器）在信号子空间参数下的闭式解及其抗远近效应能力,并讨论了用于联合盲特征波形估计与多用户检测实现的PASTd算法。最后给出了仿真结果。     

Turbo Multiuser Detection for TD-CDMA

In this paper the novel detection scheme multi-step joint detection for TD-CDMA mobile radio systems is presented. Multi-step joint detection uses the turbo principle for iteratively improving data detection. Extrinsic information obtained by FEC-decoding in a previous step is used for a joint reduction of interference and improvement of asymptotic efficiency of the linear multiuser detector. Multi-step joint detection helps to overcome the problems of small asymptotic efficiencies present in linear multiuser detectors like the zero forcing equalizer in TD-CDMA mobile radio systems in the case of high system loads. Simultaneously complexity is much lower than that of optimum nonlinear multiuser detectors based on the Viterbi algorithm. As an alternative to simulations the performance of multi-step joint detection can be theoretically determined under certain not too restrictive assumptions. Both approximate and simulative performance results are presented in the paper. It is shown that in typical mobile radio systems the required SNR at the receiver input can be reduced by approximately 10 dB compared to linear multiuser detection. Thus, multi-step joint detection helps to increase the permissible number of mobile stations per cell or to decrease the required cluster size in TD-CDMA mobile radio systems and thus improves spectrum efficiency and capacity.     

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。     

Space-Time Blind Multiuser Detection for Multiuser DS-CDMA and Oversampled Systems

Novel space-time blind multiuser detection method for multiuser DS-CDMA and oversampled systems is presented. To achieve signal recovery, Khatri-Rao product structure of the space-time channel matrix of received signals and rank-1 projection strategy are exploited. Two blind signal detection algorithms based on Khatri-Rao product decomposition are proposed. Uniqueness of the Khatri-Rao decomposition is discussed. Simulation results show that the proposed algorithms have performance close to the non-blind Zero Forcing algorithm and still work well in the case of only few antennae in the receiving end.     

一种低复杂度多用户MIMO预编码方法

针对多用户多输入多输出(MIMO,Multiple Input Multiple Output)系统下行链路,提出了一种基于特定矩阵结构的低复杂度线性预编码方法。该方法利用规则块对角化(RBD,Regularized Block Diagonalization)方法的预编码矩阵具有的内在结构设计预编码矩阵,通过最小化总的干扰与噪声功率之和得到预编码矩阵的最终形式。等效性证明和复杂度分析表明,该方法能够获得与规则块对角化方法相同的"和速率"性能,同时大幅度降低了运算复杂度。仿真实验结果验证了这一结论。     

A Novel Multiuser Detection Algorithm for CDMA-Based MIMO-OFDM System

1Introduction Recently,MultipleInputMultipleOutput(MIMO)wirelesstechnologieshavecapturedalotofresearchin terest,giventhatthecapacityincreaseturnsouttobe achievable[1-2].OrthogonalFrequencyDivisionMulti plexing(OFDM)techniquehastheremarkablecharac teristic…     

多用户检测的串行干扰抵消器算法

CDMA由于其独特的性能成为第三代移动通信中标准多址方式,传统的CDMA信号解调方法是求信号与本用户PN码的相关运算,而此时其它用户的CDMA信号就成为干扰信号.本文提出了一种串行干扰相减式抵消器法,实验表明,这种方法在对功率不相等的多用户进行信号检测时性能优于传统方法.     

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.     

一种盲自适应空时多用户检测技术

空时多用户检测技术是一种有效消除CDMA系统中多址干扰和码间干扰的方法。目前很多此类方法都需要知道一些系统参数,其自适应实现需要训练序列。提出了一种结合恒模算法(CMA)和解扩重扩算法(DRA)的盲自适应空时恒模解扩重扩算法(STCMDRA),他能够有效利用信号的恒模特性以及用户已知的扩频信号信息来较好地抑制多址干扰及码间干扰。仿真结果进一步验证了该方法的性能。     

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。     

用于DS/CDMA系统多用户检测的变步长符号算法

提出了一种新颖的变步长符号算法用于DS/CDMA系统的多用户检测。这种算法对盲平均符号算法的步长又一次采用二次最小均方误差算法,克服了盲平均符号算法受步长影响的缺点,并利用符号算法计算复杂度低的特点,加快了算法的收敛速度。仿真表明,这种算法能够自动迅速地适应环境的变化并且不受初始步长和学习率的影响,在性能上优于与其类似的自适应接收机。     

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。