DS—CDMA系统中的功率分配算法的研究

第三代移动通信系统设计要求支持多媒体通信。由于各个业务在接收端所要求的功率不同,这就要求系统必须进行有效的功率分配。文章提出了一种基于信道特征（如业务量）的功率分配算法,并通过系统分析验证了该算法能确保各种业务的业务质量的同时提高系统的容量。     

无线多媒体DS-CDMA系统中的功率分配

第三代移动通信系统设计要求支持多媒体通信,如声音、视频、图像和数据传输等业务。由于各个业务在接收端所要求的功率不同,这就要求系统必须进行有效的功率分配。本文提出一种基于信道特征(如业务量)的功率分配算法,并通过系统分析验证了该算法能很好的在保证各业务的业务质量同时提高系统的容量。     

DS—CDMA通信正在崛起

这篇论文介绍了ＣＤＭＡ的发展概况和相关的标准；论述了ＤＳ－ＣＤＭＡ的技术能力，直接序列扩系统的性能和码分多址的优点；举例说明了ＤＳ－ＣＤＭＡ在五种通信系统的应用可行性；最后分析比较了ＣＤＭＡ和ＧＳＭ系统的经济成本和运营收益。     

MULTICARRIER DS—CDMA WITH ADAPTIVE MODULATION AND POWER ALLOCATION

Adaptive modulation and power allocation is introduced into the multicarrier DSCDMA system to improve the system performance and bandwidth efficiency.First,the system design appropriate for adaptive modulation and power allocation is given,then the algorithm of adaptive modulation and power allocation is applied.Simulation results demonstrate great performance improvement compared with the fixed modulated one.     

DS—CDMA中的空时处理技术

随着移动通信的发展，空时处理技术越来越引起人们的重视．本文首先介绍了DS-CDMA的特点，并在此基础上引入空时处理技术．通过对信号处理的比较，可获得系统性能改善的结论。     

DS—CDMA系统混合业务无线容量研究

文章通过对Ds—cDMA系统前反向容量理论进行分析,给出了基于混合业务的系统容量计算方法,同时给出各种参数在系统容量计算中的影响,最后以CDMA20001X网络为例,给出了工程参考值。     

多媒体CDMA系统在功率约束条件下的业务容量分析

码分多址接入（CDMA）技术可以灵活地支持无线多媒体业务传输。该文分析了多小区环境下CDMA系统上行链路的多媒体业务容量，主要讨论了用户最大发射功率约束条件在不同用户激活因子情况下对系统容量的影响。分析和计算结果表明用户最大发射功率约束使系统的容量有所降低。     

CDMA系统中的功率控制

功率控制是CDMA移动通信系统中最为重要的核心技术之一。该文主要介绍CDMA系统反向链路和前向链路的各种功率控制技术。首先介绍功率控制对于CDMA系统的重要性及功率控制的分类，然后分别介绍CDMA系统反向链路和前向链路的功率控制算法。     

W—CDMA系统与Q—CDMA系统的比较

本文将Ｗ－ＣＤＭＡ系统和Ｑ－ＣＤＭＡ系统的技术特点进行了比较，包括系统容量、信道结构和业务承载能力等。     

RF滤波器对DS—CDMA系统性能的影响

在无线通信系统特别是扩频通信系统中，其发射信号必须限定在一定频段，并遵守一定的无线频率资源管理规定，以防干扰别人，因而发射机必须用滤波器；同样，接收机为了抑制镜像干扰和带外噪声也需采用镜像滤波器各频滤波器。这些滤波器都对相关器的输出产生了不同程度的影响。本文主要是分析一些滤波器参数在这些影响中所起的作用，以便选取适当参数的滤波器。     

随机码多业务直扩系统的RAKE接收机在Nakagami信道下的性能

本文提出用RAKE接收机的可变处理增益系统,通过高斯近似,得出了各种业务在不同的概率的情况下,可变处理增益系统在Nakagami信道下误码率的计算公式,研究了衰落因子对系统的影响,最后,给出了两种业务,三种业务可变处理增益系统数值计算结果。     

直扩系统GSC接收机的性能研究

提出了用GSC接收机的可变处理增益系统,并分析了各种可能业务在不同的概率的情况下,双速率及三速率可变处理增益系统在Nakagami信道下的性能。     

CDMA系统下行链路性能优化的递阶算法研究

不对称的多媒体传输是未来宽带无线通信的主要模式，本文基于目前下行链路多种传输技术的特点，提出了一种递阶优化算法进行下行链路性能的优化，用功率控制（PC）、波束成形（BF）和发射分集（TD）三种要素进行系统建模，并根据移动用户的接收服务质量（QoS）要求构建效用函数进而进行性能优化，从向达到一种效能最佳的传输目标。文后给出了仿真实验并与常规的BF和TD算法进行了性能比较。     

A New Improved First-Order Approximate Decorrelating Detector for DS-CDMA Communication Systems

An improved first-order approximate decorrelating detector for direct-sequencecode divisionmultiple access (DS-CDMA) communication systems is proposed. This detector isbased on theminimization of the multiple access interference (MAI) for each user. Throughanalysis andnumerical results, the detector is shown to perform better than the originalfirst-order approximatedetector in various conditions at the expense of an additional complexity onthe order of O(K²), whereK is the number of active users in the system.     

基于混沌序列的DS-CDMA相关解调系统

本文从截断混沌序列的相关特性入手,直接推导出混沌序列为地址码的异步DS-CDMA通信系统的相关解调结果,仿真研究不同的混沌序列在异步DS CDMA条件下的多址特性,说明混沌序列优化的必要性并指出了优化的途径.     

cdma2000 1x前向功率分配分析

本文提出了一种在多径传输约束条件及不同的移动台运动速度条件下对前向信道链路进行功率分配的方法,这是根据导频信道和业务信道之间各自信号强度的相关性合理地分配前向链路中的信道发射功率.通过实验测试及理论推导,本文给出了这种相关性曲线,从而发现了最佳的导频信道功率,它能够在满足1%FER时使总发射功率最小.     

Power Allocation and Control in Multimedia CDMA Wireless Systems

This paper proposes an analysis of outage performance of a Direct Sequence-Code Division Multiple Access (DS-CDMA) wireless system with heterogeneous traffic. Imperfections in closed-loop power control and the activity characteristics of any traffic source in the system are taken into account. For given requirements of signal-to-(noise + interference) ratio and outage probability of every user in the system, the system capacity is derived in terms of the maximum number of users of each class that can be accomodated. The optimization problem is explicitly solved for a system consisting of a single cell and an approach is outlined for solving the optimization problem in a multi-cell system. The analysis is carried out by resorting to various approximations of Multiple Access Interference (MAI), that require different methods for solving the optimization problem and yield different degrees of accuracy. From numerical results it is seen that optimal power allocation is essential to limit the effects of power control imperfections, mainly in the case of non uniform amplitudes of residual power fluctuations. In the second part of the paper, a performance study of fixed step closed-loop power control algorithms is presented. A detailed simulation of the power control loop evidences that fast fading phenomena can not be easily tracked, even at moderate Doppler spread. Statistics of residual power fluctuations are estimated and can be used to support the assumptions in the first part of the paper. Furthermore, second order statistics of the controlled channel are estimated, and second order outage statistics (average rate and duration of outage events) are derived as a quantitative measure of residual channel burstiness.     

Near-Optimum Iterative Multiuser Receiver for FEC Encoded DS-CDMA

The powerful iterative algorithm of Turbo code is employed in the proposed iterative multiuser receiver for the downlink of a forward error correction (FEC) coded direct-sequence code-division multiple access (DS-CDMA) environment. The receiver iterates between the 2 coding dimensions, namely the spreading codes and the FEC codes. The optimum iterative multiuser receiver uses the optimum decentralised single-user detector to generate the single-user extrinsic information for the single-user decoders. This paper suggests a near-optimum detector using a folded trellis preselection stage for the multiuser signal detection, in order to reduce the dominating complexity of the optimum decentralised detector. Simulation results show that performance is close to optimum. The effect of the single-user decoders' extrinsic information on the signal detection stage is also investigated and it is found that extrinsic information improves performance.     

The Applicative Investigation of Adaptive BP Networks for Multi-user Detection in Asynchronous DS-CDMA Mobile Communications

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Constrained Power Control to Enhance the Capacity of Slotted DS-CDMA Cellular Systems

We propose and study the constrained power control scheme for direct sequence code division multiple access (DS-CDMA) systems supporting voice and data services. In the proposed scheme, the voice users are subject to the conventional power control, while the data users are subject to distance dependent transmit power constraint. Several power control profiles for data users are suggested to reduce interference within its own and neighboring cells. For given delay and outage probability requirements, we present an analytical framework to analyze the number of users that can be supported by the proposed scheme. The results are compared to the conventional power control scheme, where no such constraint is imposed. We derive new closed form expression for the interference correction factor for the constrained power control scheme. In addition, we show that the total interference power can be approximated by the log-normal distribution, and we evaluate the mean and variance of the log-normal distribution analytically. We also derive the distribution of the signal-to-noise ratios for voice and data users, which is useful in evaluating the user capacity for slotted DS-CDMA cellular systems with both delay and power constraints.