CDMA系统中联合功率控制、波束赋形与多用户检测

应用功率控制、波束赋形和多用户检测可以有效地消除和减少CDMA系统中的干扰。本文结合波束赋形和多用户检测的特性，提出一种应用波束赋形增益和多用户相关矩阵的解相关算法。基于算法的复杂性，提出一种区分聚集用户进行多用户检测的的算法。由于波束赋形能够消减主瓣波束之外的多用户干扰，对聚集移动台采用解相关检测达到减少运算量和消除多用户干扰的目的。对算法进行了仿真分析，证明了本算法的优越性。     

非正交多脉冲调制的QR分解多用户检测

针对加性高斯白噪声信道下的多用户非正交多脉冲调制系统,提出了基于QR分解的非相干判决反馈多用户检测器。该检测器通过QR分解矩阵变换,利用功率较强用户的判决信息来进行干扰抵消,可以有效消除用户间的多址干扰。而在各用户内,针对多脉冲调制技术,提出了一种线性解相关运算来进行非相干检测。同时,考虑解相关运算中矩阵求逆的复杂度比较高,进一步提出了一种软干扰抵消检测器。仿真结果表明所提的两种多用户检测算法可以有效消除非正交调制所造成的多址干扰,极大地提高功率较弱用户的性能,并且所提软干扰抵消检测器通过避免矩阵求逆降低了计算复杂度,同时检测性能没有损失。      

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。     

一种快速的在线SVM多用户检测算法

基于传统支持向量机的多用户检测算法运算量大、耗时久,无法满足实时性要求。该文提出了一种快速的在线支持向量机多用户检测算法。该算法利用KKT条件判别实时增加的训练序列并构造当前训练样本集,从而能够有效地减少训练样本大小,加快训练速度。仿真实验表明,该算法在不影响分类效果的情况下大大加快了训练速度,且用于分类的支持向量较少,同时性能与传统支持向量机算法相当且明显优于MMSE(RLS)多用户检测器。     

基于快速矩阵运算的TD-SCDMA联合检测算法

联合检测是TD-SCDMA的关键技术之一.传统的联合检测技术虽然得到很好的性能,但复杂度高.提出一种快速算法,将联合检测的系统矩阵扩展成块循环矩阵,利用块FFT和块循环矩阵进行快速矩阵求逆和简化矩阵运算.矩阵求逆的运算量最大可下降到O(nlogzn),且存储量成倍下降.仿真实验表明,该算法和直接计算得到的系统性能一致,但运算时间大大下降.     

多径CDMA信道下一种新的RLS空时接收机

针对多径CDMA信道下的多用户检测中出现的线性约束二次规划问题提出一种新的递归最小二乘算法，该算法可以完全避免因约束而引进的矩阵求逆运算(相对常规的递归最小二乘算法)，并将这种算法与CDMA多用户系统结合起来给出了一种新的自适应接收机，仿真结果表明了这种算法是有效的(无论在检测性能上还是在收敛性能上)。     

迭代迫零多用户检测算法研究与应用

最优的最大似然多用户接收机的复杂度随用户数成指数增长,传统的Rake接收机干扰受限且存在远近效应。次优的线性多用户检测是性能和复杂度的折衷,其中,迫零联合检测多用户接收机属于一种线性解相关接收机,虽然避免了对数据符号矢量的穷举搜索,大大减少了计算量,但是由于其基本运算中包含了随机矩阵的求逆运算,而矩阵求逆运算对于硬件定点实现的舍入误差非常敏感,有时会产生很大的误差甚至无解。考察比较了迫零检测接收机的四种迭代算法。对其复杂度进行了分析和仿真,结果表明Gauss-Siedel是一种收敛速度较快,时间复杂度较低的迭代算法。     

多径衰落信道下的一种盲多用户检测方法

多径衰落信道下的盲自适应多用户检测算法的运算复杂度通常都比较大,提出了一种基于MSWF和CMA的盲自适应多用户检测方法,该方法避免了矩阵求逆和信道估计运算,具有相对较小的运算复杂度。通过模拟实验比较了几种算法的误码率性能,结果表明,所提方法具有明显的优势。     

编码的多载波CDMA系统中Turbo时空多用户检测

联合MAP多用户检测和信道译码的迭代多用户检测技术可显著提高多载波CDMA系统的容量和性能,本文给出了结合智能天线和迭代MAP多用户检测的Turbo时空多用户检测算法,该方法进一步提高了系统的性能.Turbo时空多用户检测算法不仅极大减小了传统最优MAP多用户检测算法的运算量,而且,此算法性能在AWGN和频率选择性衰落信道中都能逼近单用户编码多载波CDMA系统多天线接收的性能.     

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。     

A new hybrid heuristic multiuser detector for DS‐CDMA communication systems

In this work, we present a new multiuser detection (MUD) structure which results from incorporating the tabu search (TS) heuristic algorithm with the local search (LS) heuristic algorithm. The new proposed structure brings much improvement when compared to both the conventional (matched filter) detector and the decorrelating detector. Moreover, the new TS‐LS‐detector proposed here approximates well the performance of the optimal MUD detector but with a very low computational complexity. Copyright © 2008 John Wiley & Sons, Ltd.     

DS-CDMA系统的一种进化规划多用户检测算法

针对码分多址接入（CDMA）系统中最优多用户检测的指数计算复杂度问题，结合CDMA通信的实际特点，利用进化规划免去了交叉操作因而计算复杂度小的特点，提出了一种基于进化规划的多用户检测问题的优化处理方法。实验结果表明本方法可获得接近最佳检测的性能，但计算复杂度降低。     

一种简化的解相关检测器及其性能分析

基于矩阵求逆的一阶近似提出了一种简化的解相关检测器,当用户间的相关系数较小时,这种检测器可以相当准确地逼近解相关检测器,文中分析了这种检测器的误码率性能。数值结果表明该检测器的性能远优于传统的多用户检测器,具有较好的抗远近性能,与解相关检测器相比,它的复杂度大大降低,使其有可能用于实际的 Ｃ Ｄ Ｍ Ａ 通信系统中。     

A low complexity multiuser detector for synchronous CDMA system

In a code-division multiple-access (CDMA) system, multiuser detection (MUD) can exploit the information of signals from other interfering users to increase the system capacity. However, the optimum MUD for CDMA systems requires the solution of an NP-hard combinatorial optimization problem. It is well known that the computational complexity of the optimum multiuser detector is exponential with the number of active users in the system. In this paper, we apply a hybrid algorithm to develop a suboptimal MUD strategy. The result of symmetric successive overrelaxation (SSOR) preconditioned conjugate-gradient method is first used to initialize the reduced-complexity recursive (RCR) multiuser detector. Then, RCR algorithm is applied to detect the received data bit by optimizing an objective function in relation with the linear system of decorrelating detector. Simulation results for the synchronous case show that the performance of our proposed SSOR-RCR multiuser detector is promising and outperform the decorrelator and linear minimum mean squared error multiuser detector with lower computational complexity.     

WCDMA系统上行链路阵列接收及自适应并行干扰对消技术

本文提出了一种适于WCDMA系统上行链路阵列接收加PIC的联合处理方案.首先针对WCMA系统上行链路帧结构的特征,将Z.Rong等中提出的LS-DRMTA改进为导频位辅助LMS-DRMTA算法.这种新的阵列接收CDMA解调算法相对于LS-DRMTA算法大大降低了基站处理的运算量,提高了算法的实用性,仿真实验还表明该算法比原算法具有更低的误码率.然后在阵列处理之后加上PIC,可以进一步消除CCI,降低系统误码率.这种阵列接收加PIC方案具有运算量小,延时小,易于适时实现等特点.     

SUCCESSIVE BEAMFORMING, MULTIUSER DETECTION AND DIVERSITY RECEPTION FOR MULTICARRIER DS-CDMA SYSTEM WITH ANTENNA ARRAY

Code-Division Multiple-Access (CDMA) systems are interference limited,and therefore efficient interference management is necessary to enhance the performance of a CDMA system.In this paper,a successive beamforming (spatial filtering),linear decorrelating MultiUser Detection (MUD, temporal filtering) and diversity reception structure for uplink multicarrier Direct Sequence CDMA (DS-CDMA) system with antenna array are proposed.By beamforming,the antenna array suppresses interference according to the distinct array signature.Subsequently,linear decorrelating MUD is ap- plied to separate the signals of different users and eliminate Multiple Access Interference (MAI).Finally, the decorrelated signals at different subcarriers that belong to the same user are combined to achieve frequency diversity.Simulation results show that the proposed structure offers significant Bit Error Rate (BER) performance improvement by successively exploiting the space-time-frequency processing.     

Research of Fast Satellite Selection Algorithm for Multi-constellation

We propose a fast satellite selection algorithm for multi-constellation,which is based on both Newton's identities for Geometric dilution of precision (GDOP)fast computation and optimal satellite geometric distribution for less cycle participation.An effective closed-form formula is proposed for GDOP approximation,avoiding conventional matrix inversion and complexity.We reduce computational cycles with auxiliary optimal satellite geometric distribution,which improves the efficiency of realtime positioning under the combined action of both.Simulation results indicate that we can save more than 44％ and 99％ computational complexity when selecting 7 satellites from 10 and 30 visible satellites respectively.The GDOP of proposed method is very close to optimal result,better than that of Quasi-Optimal algorithm.     

A joint swarm intelligence algorithm for multi-user detection in MIMO-OFDM system

In the multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system, traditional multi-user detection (MUD) algorithms that usually used to suppress multiple access interference are difficult to balance system detection performance and the complexity of the algorithm. To solve this problem, this paper proposes a joint swarm intelligence algorithm called Ant Colony and Particle Swarm Optimisation (AC-PSO) by integrating particle swarm optimisation (PSO) and ant colony optimisation (ACO) algorithms. According to simulation results, it has been shown that, with low computational complexity, the MUD for the MIMO-OFDM system based on AC-PSO algorithm gains comparable MUD performance with maximum likelihood algorithm. Thus, the proposed AC-PSO algorithm provides a satisfactory trade-off between computational complexity and detection performance.     

Fuzzy step size least mean square algorithm tuned linearly constrained constant modulus algorithm for multi‐carrier code division multiple access blind multiuser detector

Adaptive fuzzy logic step size least mean square algorithm (FLCLMS) tuning unit is designed to adjust the step size of the linear constrained constant modulus algorithm for blind multiuser detection (MUD) in multi‐carrier code division multiple access (MC‐CDMA) systems is presented. In wireless communications system, the conventional constant modulus algorithm for blind MUD has some disadvantages such as slow convergence speed and phase rotation. To overcome these shortages, a modified constant modulus algorithm was developed for blind multiuser detector. On the basis of the deterministic behavior of the FLCLMS algorithm, it has also proposed simplification over the cost function calculation, obtaining more efficient algorithm and creating new perspective for the MUD implementation. The proposed algorithm ensures the algorithm convergence to the desired user and suppresses the multiple access interference in this cost function. Thus, the performance of the system is improved. The computational experiments show that the proposed FLCLMS not only can find optimal or closed‐to‐optimal solutions but also can obtain the low computation complexity both better and more robust results than existing algorithm reported recently in the literature. Copyright © 2013 John Wiley & Sons, Ltd.     

MIMO-OFDM系统的低复杂度递推信道跟踪算法

该文针对时变多径信道下的MIMO-OFDM系统,基于变分贝叶斯原理,提出了一种新的联合信号检测和信道跟踪的低复杂度半盲贝叶斯迭代接收机。针对该接收机,基于递推变分期望最大化(RVBEM)算法,提出了一种RVBEM信道跟踪算法。由于RVBEM算法需要进行矩阵求逆,因此以该算法为基础推导得到了一种时频域联合递推的低复杂度信道跟踪(TF-LCRVBEM)算法。TF-LCRVBEM算法不仅完全避免了矩阵求逆运算,还通过合理的近似使得算法只具有线性复杂度。分析和仿真表明,在时变多径信道下,所提迭代接收机具有远优于传统接收机和接近理想接收机的性能。