多用户分段移位差分混沌键控通信方案

为了满足现代通信的需求,多用户接入技术是近年来混沌通信的一个重要发展趋势。为了进一步改善现有多用户混沌通信方案的误码性能,该文提出一种多用户分段移位差分混沌键控(MultiUser Segment Shift Differential Chaos Shift Keying, MU-SSDCSK)通信方案。该方案根据传输的用户数,将MU-SSDCSK中的参考信号等分成m个信号段,再将这m个信号段进行移位,并配以不同的Walsh码,形成相互正交的信息携带信号。文中推导了该系统在加性高斯白噪声信道中的理论误码率公式并进行了仿真。仿真结果表明,该文提出的MU-SSDCSK方案能有效改善系统误码性能,在混沌通信领域具有一定的应用前景。     

MU-MIMO下行链路基于关联干扰的先验式用户调度

该文针对MU-MIMO下行(广播)信道提出一种基于空间子信道关联干扰的先验式调度算法。该方法将用户调度转换为子信道的选择问题,通过综合考虑候选子信道的传输增益,以及候选者与已选的和潜在的、将来可能被选中的子信道间的相互干扰,获得一组相互干扰较小的子信道。仿真结果表明,合理地选取关联干扰参数,该算法能够获得计算复杂度与传输性能的良好折中,有效改善系统和速率。     

多用户MIMO系统中一种基于一位反馈信息的调度算法

针对多用户MIMO(Multiple-Input Multiple-Output)无线通信系统潜在的多用户分集增益,该文提出了一种基于一位反馈信息的多用户调度算法.理论分析表明,设置合理的门限可以从统计意义上最大化系统平均频谱效率.同时,该文从理论上对最优门限的选择进行了分析.仿真结果表明所提算法可有效利用多用户分集来提高系统的频谱性能.     

Joint Optimization of User Set Selection and Transmit Power Allocation for Orthogonal Random Beamforming in Multiuser MIMO Systems

When the number of users is finite, the performance improvement of the orthogonal random beamforming (ORBF) scheme is limited in high signal‐to‐noise ratio regions. In this paper, to improve the performance of the ORBF scheme, the user set and transmit power allocation are jointly determined to maximize sum rate under the total transmit power constraint. First, the transmit power allocation problem is expressed as a function of a given user set. Based on this expression, the optimal user set with the maximum sum rate is determined. The suboptimal procedure is also presented to reduce the computational complexity, which separates the user set selection procedure and transmit power allocation procedure.     

Modified SMC method of blind multiuser detection for DS-CDMA systems over fading channels

This paper presents the application of sequential Monte Carlo (SMC) methodology for blind detection in wireless direct sequence code division multiple access (DS-CDMA) systems over fading channels. It is known that the conventional SMC method requires a high-computational complexity that grows exponentially with the number of active users. This paper proposes a solution to this problem by employing Cholesky factorization to decompose the observed data into separate components for each user and then the parameters of each user are estimated with the SMC inference method under the decision feedback framework. Based on these concepts, an efficient blind decision feedback SMC (DF-SMC) receiver is developed for differentially encoded DS-CDMA systems. Simulation results demonstrate the promising performance of the proposed receiver for both flat fading and frequency-selective fading channels.     

基于卡尔曼滤波的盲空时检测器

文章提出了一种基于卡尔曼滤波的盲空时多用户检测方法。卡尔曼滤波是一种线性最小方差状态估计,把它有效地结合阵列天线与多用户检测。该自适应多用户检测方法不需要发送训练序列。在多径衰落信道下,仿真结果表明该方法收敛速度比LMS算法更快,有较强的抗多径和多址干扰能力。     

Performance Analysis of Multiuser Detectors for Uplink Quasi-synchronous MC-CDMA Systems

This paper analyses and compares the average bit error rate (BER) of different multiuser detectors (MUD) in the uplink of a multicarrier code- division multiple access (MC-CDMA) system. In particular, maximum likelihood, zero-forcing, minimum mean-square error and interference cancellation-based multiuser detectors have been analysed for the special case of uncorrelated subcarriers. The derived BER expressions are based upon previous results on diversity combining and also on recent findings on multiple input multiple output (MIMO) architectures. The subcarrier correlation is considered in the context of physical parameters currently under discussion for future wireless systems to give an indication up to what extent the assumption of uncorrelated subcarrier fading is plausible.     

MIMO MRC Systems with and without Multiuser Diversity

In this paper, we consider the multiple-input multiple-output (MIMO) wireless systems employing maximal ratio combining (MRC) in the absence and presence of multiuser diversity. First, using the well-known moment generating function-based analysis approach, we derive the error performance of the MIMO MRC systems without multiuser diversity over spatially correlated fading channels. Second, we present the average capacity of MIMO MRC systems with multiuser diversity. Numerical results demonstrate the accuracy of our analytical expressions.     

PERFORMANCE OF MULTIUSER DETECTION FOR CDMA SYSTEM IN A FLAT RAYLEIGH FADING ENVIRONMENT

In a CDMA communication network using conventional signal detection, system capacity is limited and its performance is degraded by the multi-access interference (MAI). Multiuser detection, which makes use of cross-correlation information between spread spectrum codes, can reduce or eliminate the MAI in a Gaussian channel so as to mitigate the near-far effects and increase the system capacity. This paper extends the multiuser detector to a flat Rayleigh fading CDMA environment, and discusses the bit error rate of typical multiuser detection algorithms in such a environment by combining theoretical analysis and computer simulation. It is shown that multiuser detection is superior to conventional detections in the flat Rayleigh fading channels.     

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。