CDMA移动通信中的判决反馈多用户信号检测器

本文推导了一种具有线性计算复杂度的同步ＤＳ—ＣＤＭＡ系统多用户检测算法，由此形成的判决反馈检测器在性能上优于解相关检测器，与两级多用户检测器的性能相当，而实现起来则更为简单。数值结果表明，当接收到的干扰信号能量比有用信号能量高４ｄＢ以上时，判决反馈检测器的性能将接近单用户系统的性能，因而该检测器可有效地克服ＣＤＭＡ移动通信中的远近影响。     

CDMA系统中的多用户检测技术

传统的直接序列扩频－码分多址（ＤＳ－ＣＤＭＡ）通信系统中,多址干扰（ＭＡＩ）的存在制约了系统的性能和容量。一个较好的解决办法是多用户检测。集中讨论了次佳多用户检测（包括各种线性方案和非线性方案）,给出了它们的结构,分析和比较了它们的性能。最后带提出了一种结合最小均方误差（ＭＭＳＥ）检测的连续干扰扰抵消（ＳＩＣ）方案,其性能好于单一的ＳＩＣ和ＭＭＳＥ检测器。     

DS/CDMA系统中的多用户检测技术

多用户检测技术可抑制多址干扰（ＭＡＩ）,从而提高ＣＤＭＡ系统的容量和性能。介绍了多用户检测器的分类和自适应算法、盲算法在多用户检测中的应用。     

Gram—Schmidt正交化算法在简化CDMA多用户检测算法中的应用

本文介绍了Ｇｒａｍ－Ｓｃｈｍｉｄｔ正交化算法在ＣＤＭＡ判决反馈多用户检测器中的应用。新的多用户判决反馈检测算法基于对ＣＤＭＡ扩频序列族采用Ｇｒａｍ－Ｓｃｈｍｉｄｔ正交化算法得到的一组正交归一化序列。引入了Ｇｒａｍ－Ｓｃｈｍｉｄｔ正交化算法得到的系统性能与原系统完全相同,但大大简化了检测器的结构。     

空间—时间预RAKE系统

本文提出了一种适用于ＴＤＤ／ＤＳ－ＣＤＭＡ下行链路的空间－时间预ＲＡＫＥ系统。该系统能实现空间的选择性发送和时间的ＲＡＫＥ发送。然后给出了单用户和多用户情况下的该系统性能分析,并讨论不同信道参数（角度扩散,Ｄｏｐｐｌｅｒ频率和突发帧长等）对系统性能的影响。     

业界风云

ＡＤＩ　ＤＳＰ使３Ｇ基础设备成本降低５０％美国模拟器件公司（ＡＤＩ）发布一种新型的安装第一层软件的ＴｉｇｅｒＳＨＡＲＣ数字信号处理器,它可使３Ｇ电信基础设备的系统成本降低到５０％。ＡＤＩ表示,只有这种ＤＳＰ解决方案才能通过“全软件”方法满足性能要求,所以ＡＤＩ公司的ＴｉｇｅｒＳＨＡＲＣ　ＡＤＳＰ－ＴＳ１０１Ｓ要比完全依赖于ＤＳＰ外加ＡＳＩＣ和ＦＰＧＡ的传统硬件方法能更好地满足制造商在增强灵活性、提高性能、降低原材料成本、增加功能方面的要求。ＴｉｇｅｒＳＨＡＲＣ除了提高性能和显著节省原材料之外,它…     

用ADSP—21060芯片构建多处理器DSP系统

采用多处理器数字信号处理（ＤＳＰ）系统是现代数字信号处理技术发展的客观要求,这里介绍了用ＡＤＳＰ—２１０６０芯片作为ＣＰＵ来构建多处理器ＤＳＰ系统的设计实现方案。     

SPVP/PVP技术在ATM ADSL业务中的应用

１ＳＰＶＰ／ＰＶＰ技术简介ＡＴＭ网络可以为用户提供永久虚电路（ＰＶＣ／ＰＶＰ）、软永久虚电路（ＳＰＶＣ／ＰＶＣ）和交换虚电路（ＳＶＣ／ＳＶＰ）用于数据高速传输。目前在基于ＡＴＭ信元的ＡＤＳＬ接入系统中 ,ＡＤＳＬＭｏｄｅｍ至ＤＳＬＡＭ主要采用ＰＶＣ（个别厂家虽然支持ＳＶＣ ,但由于技术、成本等原因应用实例较少）。而从ＤＳＬＡＭ至宽带接入服务器(包括中间经过一个或者多个ＡＴＭ交换机 ) ,可一个用户独占一条ＰＶＣ ,也可多个用户共享一条ＰＶＰ。前者虽性能较佳但配置复杂 ,因此 ,在ＡＤＳＬ业务开放中推荐使用ＰＶ…     

相干接收随机多码CDMA在多径衰落信道中的容量性能研究

本文研究采用ＢＰＳＫ调制、相干ＰＡＫＥ接收的随机访问多码ＣＤＭＡ）ＲＡＭＣ＿ＣＤＭＡ）在频率选择性Ｎａｋａｇａｍｉ多径衰落、噪声信道（ＭＦＮＣ）中的容量性能,建立系统模型后,推导出了多用户条件下接收机输出的条件概率分布及判决平均比特误码率,并以Ｒａｙｌｉｇｈ多径衰落、噪声信道为例,计算了系统容量的数值解,分析表明：ＲＡＭＣ－ＣＤＭＡ解决了普通ＤＳ－ＣＤＭＡ系统存在的用户可传信息速率受限的问题,能在     

基于Hopfield神经网络的多用户信号检测器

用连续Ｈｏｐｆｉｅｌｄ神经网络实现ＣＤＭＡ通信系统中多用户信号检测的设想，并针对同步ＣＤＭＡ系统构造了基于连续Ｈｏｐｆｉｅｌｄ神经网络的用户信号检测器。计算机仿真结果表明：这种检测器的性能远远优于传统检测器的性能，它的性能可与最佳多用户信号检测相比拟。     

A CORBA-based quality of service management framework fordistributed multimedia services and applications

For distributed multimedia services, it is essential that quality of service be guaranteed system-wide, including end systems, communication systems, and networks. Although many researchers have addressed issues of QoS management, little attention has so far been paid to the QoS management services in distributed multimedia services and applications. To address this deficiency, we have designed a layered model for end-to-end QoS management called the QoS management framework. Our framework, which is CORBA-based, includes a generic QoS MIB for the QoS parameterization of various multimedia services and the services needed to perform various QoS functions. A key component of this framework is the QoS management service object (QMSO), which orchestrates resources at endpoints, coordinating resource management across layer boundaries. Services such as translation, monitoring, admission, and negotiation are provided by the QMSO. To validate this concept, we have developed a QoS management system for managing and controlling the QoS of a distributed multimedia system called MAESTRO. The QoS management system has been implemented through CORBA objects and provides an interface to multimedia applications, which can be dynamic negotiation and renegotiation of QoS by users. Some performance results in QoS negotiation and renegotiation are also presented     

Wireless Access Method to Ensure Each User's QoS in Unpredictable and Various QoS Requirements

With the fast growth of Internet services, the demand for wireless high speed and advanced multimedia communications is rapidly increasing. Initial multimedia services have already been offered in the second generation systems (2-G). Currently, the third generation systems (3-G) are being deployed and it will support up to 2 Mbps packet oriented data services. But it is expected that the demand for higher data rate and large variety of high quality services will increase further more. Therefore, it is mandatory for the fourth generation systems (4-G) to take each user's quality of service (QoS) control into account.In this paper, we firstly describe an overview on requirements and technical issues for the 4-G systems, and wireless QoS control issues considering End-to-End QoS control in the IP network. Next, we propose broadband wireless access method for the fourth generation mobile communication systems. The proposed method for downlink is based on MC-CDMA (Multi-Carrier Code Division Multiple Access) with Multi-Timeslot, in which total downlink resources are split into three aggregates according to the QoS classes in time domain. It is considered that one of the typical advantages for the MC-CDMA is the effect of frequency diversity. We evaluated the effect by computer simulation using ray-traced propagation model. Simulation results show that short-term fading can be relaxed. Furthermore, we propose Multi-Level (ML) ARQ as one of the link adaptation methods. Simulation results show that the proposed scheme has a good performance with throughput and average retransmission power.     

基于Web Services的QoS本体研究

QoS本体为描述不同系统的QoS参数提供了一种有效、可重用的模型,已经应用于Web Services选择、QoS监控和QoS参数调整等方面。通过比较和分析几种典型的QoS本体的特点,可以得出大多数QoS本体考虑如度量、协议和网络属性等概念,这些特征应用于Web Service发现,特别是Web Service选择,对进一步开发QoS本体、选择最优的服务质量有着重要意义。     

第三代移动通信中的服务质量及技术挑战

第三代移动通信(3G)系统将Internet和移动通信相结合，使得移动通信中业务的数量和种类得到前所未有的增长。各种实时和多媒体业务的不断涌现，要求提供端到端的服务质量(QoS)保证。与Internet相比，3G系统中的QoS具有自身的特点，给3G系统QoS的实现带来更大的技术挑战。本文总结了这一领域近年来众多的研究成果，对实现3G系统中的QoS所面临的挑战进行分析，指出了几种技术解决途径，提出了无线接口的QoS实现框架，最后展望了3G的未来及支持QoS的技术发展方向。     

Resource Allocation in OFDMA Wireless Communications Systems Supporting Multimedia Services

We design a resource allocation algorithm for downlink of orthogonal frequency division multiple access (OFDMA) systems supporting real-time (RT) and best-effort (BE) services simultaneously over a time-varying wireless channel. The proposed algorithm aims at maximizing system throughput while satisfying quality of service (QoS) requirements of the RT and BE services. We take two kinds of QoS requirements into account. One is the required average transmission rate for both RT and BE services. The other is the tolerable average absolute deviation of transmission rate (AADTR) just for the RT services, which is used to control the fluctuation in transmission rates and to limit the RT packet delay to a moderate level. We formulate the optimization problem representing the resource allocation under consideration and solve it by using the dual optimization technique and the projection stochastic subgradient method. Simulation results show that the proposed algorithm well meets the QoS requirements with the high throughput and outperforms the modified largest weighted delay first (M-LWDF) algorithm that supports similar QoS requirements.     

Analysis of effective capacity for free-space optical communication systems over gamma-gamma turbulence channels with pointing errors

To facilitate the efficient support of quality-of-service (QoS) for promising free-space optical (FSO) communication systems, it is essential to model and analyze FSO channels in terms of delay QoS. However, most existing works focus on the average capacity and outage capacity for FSO, which are not enough to characterize the effective transmission data rate when delay-sensitive service is applied. In this paper, the effective capacity of FSO communication systems under statistical QoS provisioning constraints is investigated to meet heterogeneous traffic demands. A novel closed-form expression for effective capacity is derived under the combined effects of atmospheric turbulence conditions, pointing errors, beam widths, detector sizes and QoS exponents. The obtained results reveal the effects of some significant parameters on effective capacity, which can be used for the design of FSO systems carrying a wide range of services with diverse QoS requirements.     

Quality of service in telecommunications. I. Proposition of a QoSframework and its application to B-ISDN

The the quality of service (QoS) concept is becoming an ever more important issue in telecommunication and computer communication. The article focuses on the QoS notion and concept. The definition of QoS in the International Telecommunications Union-Telecommunications Sector (ITU-T) recommendations and the International Standards Organization (ISO) standards is analysed. Little is known about the asynchronous transfer mode (ATM) performance requirements of the broadband integrated services digital network (B-ISDN) services, especially for multimedia applications. This is because the ATM performance requirements of multimedia applications depend not only on the diverse QoS requirements from application and user, but also on the protocol stacks and scheduling in end systems. Therefore, in order to guarantee QoS to the user, it is necessary to introduce a set of QoS parameters whose properties indicate the nature and requirements of the layered protocol stack. We describe how a proposed QoS framework can be applied to B-ISDN as a specific network. The QoS aspects related to B-ISDN signaling (the control plane) and the QoS aspects related to layer and plane management (the management plane) are described. We also describe how the QoS framework resides in a protocol stack and works together with the B-ISDN network management and signaling     

多业务类分层结构CDMA系统功率控制研究

针对不同QoS要求的多业务类提供支持的分层结构CDMA系统的功率控制进行了研究，给出了该系统的一种功率控制算法。通过对反向链路运用HMRC方法，得到了一种支持多业务类的分层结构CDMA系统中反向链路CIR的简单分析方案和系统容量分析方法。     

基于双层分级的无线城域网资源分配方案

未来移动通信系统,诸如IEEE802.16旨在能够传送多种具有不同QoS要求的多媒体业务。为了保证业务的QoS,需合理设计调度器的结构和相应的调度算法。针对IEEE802.16宽带无线接入系统中的双层分级带宽分配体系结构,结合总调度器分配算法优点,采用了更适用于分类调度器且不同于参考文献的分配算法,旨在能够针对不同QoS等级的业务提供不同的调度方案,更好地满足用户的QoS要求。     

Admission control scheme for soft handoff in DS-CDMA cellular systems supporting voice and stream-type data services

The soft handoff call requests of real-time services in third-generation (3G) direct-sequence code-division multiple access (DS-CDMA) and first- and second-generation cellular systems are more important than new call requests from the viewpoint of quality of service (QoS). Rejection of soft handoff requests causes forced termination of an ongoing real-time call, which is a severer problem than blocking of new call attempts. An admission control scheme that can guarantee a higher QoS for the soft handoff requests of real-time services in 3G DS-CDMA systems is proposed for delay-sensitive voice and delay-tolerant stream-type data services. The proposed scheme (P-Scheme) accommodates both voice and data services by utilizing the full bandwidth. However, voice soft handoff call requests are given priority over new voice call and stream-type data packet requests by suppressing interference from stream-type data services according to voice soft handoff requests, and by varying interference levels. Performance of the P-Scheme is evaluated using a Markovian model. Results are compared with a conventional reservation scheme (C-Scheme) that reserves resources exclusively for voice soft handoff requests. Numerical results show that system performance can be significantly improved using the proposed P-Scheme, compared with the conventional C-Scheme, when various types of service are supported in third-generation DS-CDMA systems.