CDMA系统中一种新的基于MMSE多用户检测的自适应功率控制算法

功率控制技术是CDMA通信系统中克服“远一近效应”，降低多址干扰、增大系统容量的一项关键技术。第三代移动通信系统对功率控制提出了新的研究课题。在本文提出CDMA系统中一种新的白适应功率控制和MMSE多用户检测的联合优化的算法，仿真结果表明，这种新的联合优化算法对提高系统容量，改善系统性能有很大的作用。     

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。     

多径CDMA信道下的一种改进的盲空时多用户检测

该文在多径CDMA信道下基于Rosen梯度投影实现的最小均方盲空时多用户检测方法的基础上提出了一种改进的方法,该方法与原有的方法相比,运算量有所降低、对系统的要求降低,但通过仿真结果比较表明,该方法的检测性能与原有的方法大致相当,因而更加具有竞争力。     

一种可以高速传输数据的MTCM正交序列多码CDMA系统

为了有效地实现用户高速数据的传输本文提出了一种ＭＴＣＭ正交序列多码ＣＤＭＡ系统。这对此系统在ＡＷＧＮ信道的性能进行了计算,并和未编码系统的数值结果进行了分析和比较。     

基于最小误码率准则的多载波CDMA系统多用户检测算法

本文介绍了一种将正交频分复用(OFDM)技术和码分多址(CDMA)技术相结合的多载波CDMA (MC-CDMA)系统,分析了MC-CDMA系统的发射端和接收端的结构,建立了MC-CDMA系统的信号模型,详细分析了MC-CDMA中的多址干扰形式,以及针对MC-CDMA系统的多用户检测原理,提出了一种基于最小误码率准则的多用户检测算法。理想的基于最小误码率准则的多用户检测算法在实际中难于实现,本文采用估计概率密度函数的方法,推导出了一种自适应实现的最小误码率多用户检测算法。仿真结果表明,该算法能够有效抑制多址干扰,降低误码率,同时,该算法还具有比基于最小均方误差准则的多用户检测器更低的误码率的优点。      

CDMA通信系统中的多用户检测

ＣＤＭＡ由于其用户容量大,抗多径衰落能力强以及便于实现软切换等特点而优于其他多址方式,近年来在移动通信系统中越来越得到重视。但是ＣＤＭＡ通信系统由于存在着严重的多址干扰而限制了其容量的进一步提高。多用户检测利用每个用户的信息对接收信号进行相关处理作统计判决或是进行干扰对消从而恢复出各个用户的发送序列,多用户检测方法可以使用最优多用户检测器、线性多用户检测器及非纡性多用户检测器等几类。     

一种用于CDMA系统的正交序列调制方法

在宽带移动通信系统中，经常考虑采用通过ＦＦＴ实现的多载波调制，如ＯＦＤＭ。本文提出了一种利用ＦＨＴ实现的ＣＤＭＡ系统的正交序列调制方案。其基本思想为利用Ｗａｌｓｈ函数作为载波，将Ｗａｌｓｈ函数分组，从每组中选出一些作为载波，这样不同的载波组合方式本身将包含用户信息。这种方法实现简单，可提高传输效率，并容易与ＣＤＭＡ相结合，能有效地抑制多径干扰。仿真结果表明，该方案在多径衰落信道中能得到很好的性能。     

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。     

多径CDMA信道下的盲空时多用户检测

本文提出了在多径CDMA信道下基于Rosen梯度投影实现的最小均方盲空时多用户检测方法,仿真结果表明,该方法具有良好的检测性能.     

MC-CDMA系统中一种预处理线性受限多用户检测算法

本文提出了MC-CDMA系统中一种预处理线性受限最小二乘恒模多用户检测算法(Pre-processed Linearly Con- strained Least Squares Constant Modulus Multi-user detection Algorithm),称为P-LCLSCMA。它是对MC-CDMA接收信号进行预处理,即在每次迭代中,用已估信道参数先消除信道在各个子载波上对期望用户信号的影响,然后对处理后的信号用P- LCLSCMA算法进行多用户检测,从而确保了算法收敛于期望信号,提高了系统的检测性能。我们对这种新算法分别在下行链路和上行链路进行了仿真,仿真结果表明,本文提出的P-LCLSCMA算法的误码率和信干比性能得到了提高。     

基于离散粒子群算法的CDMA多用户检测方法

研究了离散粒子群算法，并将其应用于CDMA多用户检测问题，提出一种基于离散粒子群优化算法的CDMA多用户检测的方法。该方法应用一种新的选择和分区搜索的策略，改进搜索的质量和效率。分析以及实验仿真表明该方法具有计算复杂度低且可以得到较好误码率性能的特点，为寻求新的多用户检测方法提供了思路。     

High spectral efficiency iterative multi-user detection for CDMA

An iterative multi-user detector for code-division multiple-access (CDMA) signals that is able to operate under highly loaded conditions with a non-binary modulation scheme is presented. The results presented demonstrate that the receiver is able to achieve near single-user bit error rate performance     

Quasi-orthogonal chaotic CDMA multi-user detection using optimal chaos synchronization

In this paper, a novel optimal chaos synchronization (CS)-based method is proposed to realize multi-user detection of quasi-orthogonal chaotic code-division multiple access (CDMA) system. Theoretical analysis and computer simulations show that the multi-user quasi-orthogonal chaotic signal used in the CDMA system can be detected successfully by using the optimal CS. . Computer simulations show that the proposed method achieves a lower bit-error-rate performance than the conventional decorrelating detector and the minimum mean-square-error detector, and its performance is closer to that of the single-user Rake detector.     

多用户检测CDMA系统的阻塞度量和控制

本文讨论了ＣＤＭＡ系统在多用户检测和单用户检测两种情况下系统的阻塞度量和控制问题,并给出了相应的用户功率平衡方程和小区干扰平衡方程。本文证明两种平衡方程有相同的阻塞因子,但干扰平衡方程和维数与系统内小区数相等,并远小于用户功率平衡方程的维数即系统用户数,因而降低了计算复杂度。理论和模拟结果表明多用户检测系统中平衡方程有更小的阻塞因子,因而相对应的迭代算法能很快收敛,并且系统的阻塞率得到降低。     

Asynchronous block-based minimum mean square error (B-MMSE) CDMA multi-user detection

This paper introduces a novel asynchronous CDMA multi-user detector, the block-based MMSE (B-MMSE) multi-user detector, in which the data stream is segmented into blocks by inserting zero bits and detection takes place block-by-block without compromising the MMSE detection efficiency. The BER performance of the B-MMSE detector is studied and the results are compared with those of the decorrelating detector. It is shown that the B-MMSE detector offers promising detection efficiency at a much lower implementation complexity, which is linear in the product of number of users and block size, than that of the traditional MMSE detector. © 1998 John Wiley & Sons, Ltd.     

MC-CDMA系统PIC多用户检测策略

主要研究了MC-CDMA系统下行链路上各种均衡策略，采用并行干扰消除技术进行多用户检测。计算机性能模拟结果表明：基于MMSE的PIC两级检测是兼顾系统性能和运算复杂度的一种较好的多用户检测方案。     

信道估计误差对Rayleigh衰落下多天线CDMA系统信道容量影响

目前对多天线信道容量的研究几乎都是集中在具有精确信道估计的假设上,但是它实现起来有一定的难度.在Walsh扩频地址码、多码检测和最大似然接收机的基础上,研究了Rayleigh衰落情况下信道估计误差对MIMO CDMA系统的影响.分析及仿真结果均表明:信道容量随着信道估计误差的增加迅速下降;对于N×N系统,在固定的信道估计误差和信噪比下容量和天线的数目呈线性关系,容量增加的斜率随信道估计误差的增大而减小.     

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.     

A new symbol-alphabet-aware multi-user detection scheme

In this letter, a new multi-user detection scheme is proposed. It employs a novel nonlinear minimum mean square error (MMSE) estimator that exploits the knowledge of symbol alphabet to estimate the interfering signals. After cancelling the estimated interference, a conventional linear multi-user detector such as the MMSE detector or, simply, the matched-filter receiver (MFR) is then used to detect the desired user signal. Simulation results demonstrate that the proposed detector significantly outperforms the conventional linear MMSE detector.     

Coded asynchronous CDMA and its efficient detection

In this paper, receiver design and performance analysis for coded asynchronous code-division multiple access (CDMA) systems is considered. The receiver front-end consists of the near-far resistant multiuser detector known as the projection receiver (PR). The PR performs multiple-access interference resolution and is followed by error-control decoding. The output of the projection receiver yields the appropriate metric (i.e., soft information) for decoding of the coded sequences. An expression for the metric is derived that allows the use of a standard sequence decoder (e.g., Viterbi algorithm, M-algorithm) for the error-control code. It is then shown that the metric computer has an elegant adaptive implementation based on an extension of the familiar recursive least squares (RLS) algorithm. The adaptive PR operates on a single sample per chip and achieves a performance virtually identical to the algebraic PR, but with significantly less complexity. The receiver performance is studied for CDMA systems with fixed and random spreading sequences, and theoretical performance degradations with regard to the single-user bound are derived. The near-far resistance of the PR is also proven, and demonstrated by simulation