WCDMA系统中的差分最小均方误差多用户检测算法研究

针对现有自适应多用户检测算法需要训练比特、不能适应快衰落信道的问题,提出适用于WCDMA系统的基于差分最小均方误差（DMMSE）准则的自适应多用户检测算法。该算法结合二级扩频体制的特点,根据具有相同综合扩频码的相邻接收符号幅度变化的比率变化自适应调整横向滤波器的权系数,由于该方法更能刻画多址干扰的变化规律,因此可有效地抑制多址干扰。仿真结果表明,在多普勒频移的传播环境下,DMMSE算法的误码性能优于现有自适应MMSE算法。     

一种基于改进自适应遗传算法的多用户检测器

针对自适应遗传算法在多用户检测应用中容易早熟收敛和速度慢的问题,将非线性Sigmoid函数应用于自适应遗传算法并结合解相关算法的抗多址干扰能力,提出了一种基于改进自适应遗传算法和解相关算法的多用户检测器。实验仿真结果表明：该多用户检测器的检测性能,不论在抗多址干扰和远近效应方面还是在系统用户容量方面,都明显优于自适应遗传算法多用户检测器和简单遗传算法多用户检测器。     

一种用于DS/CDMA系统的联合信道估计与多用户检测方案

在DS/CDMA系统中,多用户检测技术可以减小多址干扰和远近效应,但一般情况下,多用户检测总是假设接收机对信道特性已知。本文提出一种慢衰落信道中的有效的联合信道估计和干扰抵消方法,这种方法需要很少的导频符号来进行信道估计,而且实现简单,可以用在快衰落信道中。     

一种用于CDMA系统的信道估计与检测方案

在DS/CDMA系统中,多用户检测技术可以减小多址干扰和远近效应,但一般情况下,多用户检测总是假设接收机对信道特性已知。本文提出一种慢衰落信道中的有效的联合信道估计和干扰抵消方法,这种方法需要很少的导频符号来进行信道估计,而且实现简单,可以用在较快衰落信道中。     

基于自适应卡尔曼滤波的盲多用户检测算法

对强多址干扰情况下码分多址系统的盲多用户检测算法进行研究,针对多径信道的码分多址系统,提出一种基于自适应卡尔曼滤波的盲多用户检测算法。该算法可在进行状态滤波的同时对未知噪声的统计特性进行在线估计,确保算法收敛于期望用户,提高检测器在动态环境下的跟踪性能。仿真结果表明,与最小均方算法及递推最小二乘算法相比,该算法具有更好的收敛性和动态性能。     

MC-CDMA系统中的自适应半盲多用户检测算法

研究多载波CDMA(MC-CDMA)上行半盲多用户检测技术,对基于Chebyshev逼近算法实现的最小输出能量(MOE)盲多用户检测进行改进,提出MC-CDMA系统下一种基于子空间跟踪和Chebyshev逼近的自适应半盲多用户检测算法。该算法基于MOE线性检测器原理,充分利用小区内所有用户的扩频码,设计了一种基于MOE准则的半盲检测器,很好地消除了多址干扰。为了减少计算复杂度,将修正的PASTd算法应用于Chebyshev逼近算法估计MOE半盲检测器的最优权向量。该算法计算复杂度低,具有较好的抗多址干扰性能和检测性能。仿真结果验证了该算法的可行性和优越性。     

一种基于隐训练序列的DS-UWB多用户检测算法研究

多用户检测技术目的是在传统检测技术的基础上,充分利用造成多址干扰的所有用户信号信息对多用户做联合检测,以有效地消除多址干扰和远近效应问题。基于隐训练序列的最小均方误差（MMSE）多用户检测算法是在基于完全训练序列的MMSE多用户检测算法基础上,通过对算法进行改进,将训练序列嵌入到用户信息序列中发送。该检测算法提高了频谱资源的利用率,仿真结果表明其性能接近于完全训练序列的MMSE多用户检测算法,并且算法复杂度较低,适于工程应用。     

基于非高斯度量的多用户DS-CDMA系统多干扰消除与用户检测

非同步的直接序列扩频码分复用(DS-CDMA)系统可能同时存在符号间串扰、多址干扰以及外部干扰。将扩频系统普遍存在的外部窄带干扰作为讨论重点,依据函数空间理论,对干扰进行有限维函数空间上的分解,并将基函数作为混合向量,基函数下的坐标作为待恢复源,通过过采样处理,结合DS-CDMA系统多用户检测模型,提出一种基于盲分离的算法。该算法在未知扩频序列以及信道多径的情况下完成盲多用户检测与盲均衡处理,同时实现外部窄带干扰消除,提高系统的干扰容限。仿真结果表明,在不同的信噪比以及信干比条件下,该算法普遍优于带理想均衡器的RAKE接收机,尤其在干扰显著的情况下,能获得更高的增益。     

消除噪声的ICA盲多用户检测

针对已有的基于独立分量分析（Independent Component Analysis,ICA）的盲多用户检测中为了便于分析经常将噪声信号忽略,从而造成系统检测性能下降的问题。提出了基于ICA的盲多用户检测的改进算法,该算法不仅能抑制远近效应和多址干扰,而且利用信号子空间和有效无偏估计原理可最大限度地消除被忽略的噪声,提高了系统的容量。通过Matlab实验仿真,验证了该算法的有效性和实用性。     

STC-OFDM系统改进的消除串行干扰算法

STC-OFDM系统有效弥补了正交频分复用多址系统中符号间干扰和频率选择性衰落等不足,但存在如何有效抑制因多天线传输产生的相互干扰问题.为此,提出了一种结合信道频率响应恢复和串行干扰消除来抑制干扰的改进算法,该算法在串行干扰消除之前先对导频进行信道频率响应恢复,减小估计对信道频率响应的影响.仿真实验表明,该算法能进一步改善STC-OFDM系统比特误码率并进而抑制相互干扰.     

Performance improvement in detection and estimation of MC-CDMA systems over MIMO channels

Multiple-input Multiple-output (MIMO) multi-carrier code division multiple access (MC-CDMA) is a strong candidate for the downlink of future mobile communications to obtain high data rates. Nevertheless, during any transmission over fading channel, performance of MC-CDMA systems are highly degraded due to the presence of multiple access interference (MAI). Multi-user detection (MUD) and channel estimation play a major role in overcoming MAI and characterising the channel, respectively. In this paper, space time serial interference cancellation (STSIC) detection using random and Gold codes and turbo aided iterative channel estimation (ICE) techniques are extended for MC-CDMA system MIMO channels to overcome MAI. Simulation results show STSIC outperforms optimal MUD and linear MUD techniques in mitigating MAI and turbo aided ICE surpasses ICE in characterising the channel with reduced error rates.     

基于前导干扰消除的FBMC系统加权信道估计算法

针对FBMC系统信道估计时存在虚部干扰问题,提出一种新的信道估计算法。首先,该算法采用了基于虚部干扰消除的新导频结构;然后,利用两列导频分别作粗信道估计;最后,对粗信道估计采用加权方式进行精信道估计,进一步提高信道估计性能。仿真结果表明,与传统虚部干扰消除算法（IIE）相比,新导频结构算法在误码率为1%时,可获得1~2 dB的性能提升。     

基于粒子群算法的盲多用户检测器

在信道参数未知的多径环境下,盲多用户检测算法性能存在诸如收敛速度慢和估计精度低等问题。将粒子群算法运用到基于恒模算法的盲多用户检测中。仿真结果显示,粒子群算法能够更精确地估计出信道的参数,且其收敛速度非常快,在估计出信道参数之后再进行盲多用户检测,检测性能优良。     

引入加权系数消除ICI的二次快时变信道估计算法

针对高速移动环境下由多普勒频移引起的子载波间干扰（inter-carrier interference,ICI）,提出一种引入加权系数消除ICI的二次快时变信道估计算法。该算法进行两次信道估计,第一次估计用于提供信道状态信息,在保证符号率的前提下消除ICI,第二次估计在ICI消除的情况下进行,可以提高信道估计精度;并对简化的并行干扰消除（parallel interference cancellation,PIC）算法进行改进,基于最小均方误差准则引入加权系数,使得ICI消除后的残余误差最小。仿真结果和理论分析达到很好的一致性,当信道信噪比为0 dB时,归一化均方误差（normalized mean square error,NMSE）性能增益最大约为0.0714,提高了快时变信道估计的精度。     

A novel adaptive V-BLAST algorithm based on subspace tracking and Hermitian matrix perturbation theorem

A novel vertical Bell laboratories layered space-time(V-BLAST)system with adaptive successive interference cancellation(SIC)detector based on subspace tracking(SST)and Hermitian matrix perturbation theorem is proposed in this paper,and the corresponding optimal symbol detection order operation is obtained.Moreover,asymptotic limit theorems for the detectors are established.The final simulation results verify that the symbol error probability(SEP)performance,the immunity to channel estimation errors and the algorithm convergence rate are superior to that of the conventional V-BLAST detection algorithm when channel estimation errors exist.     

多用户CDMA系统中Turbo-BLAST迭代检测算法

将V-BLAST结构和CDMA技术相结合,构造了多用户CDMA系统模型,提出了一种联合多用户检测和Turbo迭代思想的多用户检测算法.该方案首先利用解相关算法对接收信号进行空时多用户检测.以去除用户间干扰.然后再对期望用户的接收信号进行软干扰抵消迭代检测,以去除天线间干扰.解相关后数据检测仅和单个用户的天线数目有关,算法复杂度较低.仿真结果表明,构造的空时多用户模型可使各用户检测相对独立,有利于已有单用户Turbo-BLAST方案的应用.     

Efficient groupwise multiuser detection with iterative soft interference cancellation for multi-rate MC-CDMA

This paper presents an effective multiuser detector (MUD) for the uplink of multi-rate multi-carrier code division multiple access (MC-CDMA) systems. The MUD considered is an iterative receiver which utilizes the soft information to refine the estimation of the interference to enhance the interference cancellation capability. More specifically, users are first classified into separate groups according to their transmission rates. In each iteration, these groups of users are detected sequentially based on a set of group detectors with the removal of multiple access interferences (MAI) group by group, where the estimated interferences in each group, incurred from the users either in the same rate group or in the other rate groups, are refined successively with the assistance of the soft information in the symbol detection process. Moreover, for practical low-complexity implementations, the users in each group are further partitioned into smaller subgroups based on their effective channel correlations and then detected in parallel by a bank of minimum mean-squared error (MMSE) soft detectors to further reduce the computational load. Conducted simulations show that the proposed MUD can effectively suppress the MAI to render superior performance but with reduced computations compared to previous works.     

An adaptive least squares channel estimation based on conjugate gradient approach for multipath fading CDMA systems

Multiple access interference (MAI) is the main factor affecting the performance of channel estimation techniques for code division multiple access (CDMA) systems. Although, several multi-user channel estimation algorithms have been proposed to mitigate MAI, these algorithms require high computational complexities. In this paper, we address the problem of iterative least squares (LS) mobile channel estimation at high channel efficiency that requires a short training sequence along with the spreading sequences. We employ an efficient iterative method based on conjugate gradient (CG) algorithm to reduce the computational complexity of the estimation method. Computer simulations illustrate that the proposed method performs almost identical to the exact LS estimate for reasonable training lengths.     

A novel initial ranging algorithm for OFDMA systems using smart antenna

To improve the capacity of initial ranging （IR） users simultaneously accessing into network and enhance the performance of the IR, a novel IR algorithm is presented for the orthogonal frequency division multiple access systems with the smart antenna. The beamforming weight vectors provided by the antenna array are introduced for the IR users, and the procedures of the multiuser parameter estimation and the interference cancellation are designed. The proposed method can improve the accuracy of the channel estimation of active paths and efficiently reduce the residual multiple access interference. Simulation results show that the proposed method has a much better performance than the available successive multiuser detection and interference cancellation algorithm and accommodates more active ranging users simultaneously accessing into a cell.