无线ATM越区切换中的路由重选

论文研究了目前无线ATM通信网越区切换中的路由重选问题,对目前主要的几种路由重选方案进行了详细的比较和分析。     

个人通信业务网的越区切换管理

在无线个人通信系统中,当便携台在通话期间从一个基站BS覆盖区移动到另一个BS覆盖区时,需要进行越区切换,以保证通话的连续性。文中主要讨论越区切换管理、越区切换检测、信道分配和无线链路转接等问题。     

服务质量（QoS）的分类学

当前分布式多媒体系统技术在飞速发展,其核心问题是多媒体流的服务质量(QoS)保证。对于由QoS控制来实现QoS保证,国际上不同组织和团体提出了不同的控制机制和策略。比较著名的有:1)ISO/OSI提出的基于ODP分布式环境的QoS控制,但至今仍停留在只给出了用户层的QoS参数说明和编程接口阶段,具体实现QoS控制策略并未提出;2)ATM论坛也提出了QoS控制的策略和实现[3],ATM控制是“连接预定”型(connection and reservation),其核心内     

蜂窝移动IP网络越区切换问题解决方案的分析研究

在有线网和无线网日益结合的今天，网络技术和便携式终端的不断发展使得移动性的支持在现有IP网络中的地位与日俱增，在以蜂窝移动网为应用平台的移动IP网络中如何保证较好的QoS，越区切换问题的解决至关重要，给出了蜂窝移动IP网络的构架，对其提出了相应的越区切换的解决方案。     

移动无线因特网中的一种基于QoS的切换支持机制*

研究了移动无线因特网中基于QoS的切换支持机制,该机制采用移动台辅助切换策略和基于底层信息的动态切换准则,软、硬切换有机结合,同时辅以重路由、频繁切换QoS控制与缓存等技术,为用户QoS保证提供支持。原型系统实现表明,该机制是可行和有效的。     

ATM与Ethernet互连转发系统的QoS设计及其实现

该文为ATM与Ethernet互连转发系统提出了一种基于区分业务模型的QoS保证方案,下行转发通过WRED管理算法实现拥塞控制,并通过5种ATM传输类型来提供QoS保证,上行转发通过WFQ调度来保证实时业务的优先传输。     

蜂窝网中基于位置预测的切换算法

为了满足未来移动网络蜂窝小、切换频繁、支持规模用户和多媒体应用的需求,对位置预测与越区切换进行深入分析,提出了基于位置预测的越区切换方案HDLP(Handover Decision based on Location Prediction),其基本思想是:(1)从移动用户的大量历史移动轨迹数据中挖掘频繁轨迹;(2)根据挖掘出的频繁轨迹集合生成运动规则;(3)将运动规则运用于判决蜂窝移动通信的越区切换中。对所提算法进行仿真的结果表明,与传统的切换方案相比较,本算法减少了不必要的越区切换次数,降低了错误切换率,提高了切换的准确率,进而在一定程度上降低了通信代价,提高了通信系统的容量以及QoS。     

基于GSM-R铁路无线通信系统的越区切换分析研究

列车和无线闭塞中心在多数情况下通信处于正常状态,但是在实际通信过程中可能出现以下几种引发故障因素:传输数据出错、连接丢失、越区切换、端到端传输延时.主要考虑了高速列车在移动闭塞区间条件下GSM-R无线通信系统的越区切换的可靠性,采用计算机仿真的方法得到GSM-R通信系统在通信故障情况下的越区切换成功概率.结合随机Petri网理论对于铁路无线通信系统GSM-R中的越区切换事件进行了建模和分析,给出了随机Petri网表示的列车与无线闭塞中心通信的越区切换模型,并使用TimeNET仿真工具分析了GSM-R越区切换的可靠性.     

无线Mesh网在城市轨道交通车地通信系统中的研究

无线Mesh网因组网灵活、支持范围大和移动性强等特点,使其在城市轨道交通(城轨)中具有很好的应用前景。尝试将无线Mesh网技术应用于城轨车地通信系统中,针对车地通信存在的越区切换问题,提出了一种基于车载MMS(mobile Mesh station)位置触发的越区切换方案,利用OPNET对组网方案和切换方案进行了仿真。仿真结果表明,无线Mesh组网方案性能优于传统WLAN组网方案性能,切换方案能有效降低时延并避免了假切换和乒乓切换的发生。     

基于RBF神经网络的LTE-R切换算法优化

在LTE-R越区切换中,基于A3事件的越区切换算法在列车高速运行时容易出现乒乓效应和无线链路连接失败的问题。为此,提出基于RBF神经网络的越区切换优化算法。采集列车运行在特定环境中不同速度时切换效果较好的hys和ttt参数,并将其发送到RBF神经网络进行训练,得到不同速度下hys和ttt的非线性表达式,根据列车接收到的参考信号质量,加入自矫正项对hys和ttt进行二次调整和优化。在Matlab上进行的仿真实验结果表明,该算法能够降低掉话率和乒乓切换率,提高列车在高速运行环境下的切换成功率及鲁棒性。     

ATM网络中的服务质量问题

文章基于ATM论坛及ITU的推荐协议,对ATM网络中关于服务质量(QoS)方面的一些概念如业务合同、业务参数、一致性校验、服务质量参数等做了解释说明,同时也涉及到了ATM网络服务质量的保证机制,最后简要介绍了服务质量问题的研究情况。     

Quality of service estimation for soft handoff region ratio and call admission control in CDMA cellular systems

In the operational stage of code division multiple access (CDMA) systems, the soft handoff region ratio (SHRR) is among the important parameters that guarantee the quality of service (QoS) and resource allocation. This paper analytically investigates the effects of the SHRR on QoS. In doing so, we simultaneously take into account the capacity increasing factor and traffic load variation. For this purpose, we propose a new traffic load estimation model using a semi-Markov chain in order to consider the call arrivals influenced by the SHRR under general resident time condition. We also present the calculation algorithm of the QoS measures such as the new call blocking probability (NBP) and forced termination probability (FTP) by applying the proposed model to the prioritized call admission control (CAC). The numerical result illustrates the effects of various soft handoff system parameters. Likewise, it shows that the value of SHRR has a significant impact of the QoS under the normal propagation conditions. Sensitivity analysis is also performed to show the effect of exponential cell resident time assumption. The proposed modeling is expected to provide a practical guide to improve the QoS of CDMA soft handoff systems.     

基于位置服务信息的动态速率切换算法

提出了一种新的无线网络中的基于位置服务信息的动态速率切换算法,根据LBS信息和信号变化矢量判断即将来临的数据切换呼叫并为其预留信道,兼顾数据业务的VBR特性而自适应动态改变其服务带宽。仿真的结果表明,与其他切换算法相比,新算法的呼叫强拆率和呼叫阻塞率均有下降,信道利用率得到提高,提高了无线呼叫接入控制系统的QoS。     

一种无线异构网络的自适应垂直切换算法

针对移动节点在异构网络间切换性能不理想的问题,提出了一种自适应主动预测的垂直切换算法。采用一种面向当前应用程序的代价函数对可接入网络进行评估与选择;根据稳定周期、移动节点的运动速度及所处位置来自动调整切换执行时间,使移动节点能自适应地进行切换判决。仿真结果表明,该算法可以有效地减少切换延迟、分组丢失及切换次数,提高系统的切换性能,改善业务的QoS。     

ATM congestion control using Minimal Resource Allocation Networks (MRAN)

This paper presents a congestion control scheme for ATM traffic using a minimal radial basis function neural network referred to as Minimal Resource Allocation Network (MRAN). Earlier studies have shown that MRAN is well suited for online adaptive control of nonlinear time varying systems as it can adjust its size by adding and pruning the hidden neurons based on the input data. Since ATM traffic is nonlinear and time varying performance of MRAN as a congestion controller is investigated here. These studies are carried out using OPNET to model the ATM traffic. The ATM traffic model consists of bursty, Variable Bit-Rate (VBR) and custom traffic in a multiplexed form so as to generate a heavily congested traffic situation. For this scenario, the controller has to minimize the congestion episodes and maintain the Quality of Service (QoS) requirements. This paper compares the performance of the MRAN congestion controller with that of a modified Explicit Rate Indication with Congestion Avoidance (ERICA) scheme and a Back-Propagation (BP) neural controller. Simulation results indicate that MRAN controller performs better than the modified ERICA and BP controller in reducing the congestion episodes and maintaining the desirable QoS.     

异构分层无线网络中基于业务QoS保证的切换策略研究

针对异构分层无线网络提出了一种保证业务QoS的切换策略。该策略在层间呼叫双向溢出基础上,为实时业务切换设置了保护信道,为非实时业务切换设置了缓冲队列。为了进一步降低实时业务切换的掉线率,还使用了信道侵占技术,原理是实时业务切换呼叫可以侵占数据业务正在使用的信道资源。仿真结果表明,提出的切换方法能够显著降低各类切换业务的掉线率,同时整个异构分层系统的信道利用率也略有提高。     

基于NS2的校园网服务质量控制模型设计及实现

ATM(AsynchronousTransferMode)在多媒体应用中的服务质量QOS(QualityofService)的优势使其成为综合业务模型中的一种新的技术。文章首先介绍了QOS定义和VINT项目(VirtualInter-NetworkTestbed)及其网络模拟环境NS2(NetworkSimulation2),重点阐述了基于NS2的CIPOA(ClassicalIPoverATM)的具体模型的实现,并在此基础上实现了校园网络的一种用户优先级的QOS策略,通过控制ATM交换虚通道(SVCs)获得更好的服务质量。     

A new MAC protocol design based on TDMA/FDD for QoS support in WATM networks

Several wireless networking solutions have been developed to provide different types of services for various end user applications. Currently, wireless networking infrastructures are not suitable for multimedia applications each requiring a different QoS support with various traffic parameters. Due to the success of ATM technology in the wired network, WATM concept and related researches are of importance in the information technology area. Main objective of WATM, which promises seamless transmission of different traffics such as voice, data and video over wireless medium, is to implement high bit rate and QoS guaranteed data transfer, already well achieved by ATM technology over wired medium. To support QoS guaranteed data transfer over error-prone and low bandwidth wireless medium, an effective MAC protocol must be designed and utilized. In this paper, a new TDMA/FDD based MAC protocol, maintaining QoS requirements of real-time wireless multimedia applications, is proposed. The main contribution of this study is the new guarantee-based scheduling algorithm used in the proposed MAC to support required level of QoS guarantee for all multimedia traffic types in wireless medium. Computer modeling and simulation of the new approach providing CBR, VBR, ABR and UBR ATM services are realized using OPNET Modeler. Simulation results are also presented together with comparisons those of a WATM counterpart which uses PRMA/DA MAC protocol.     

异构无线网络域内动态资源优化管理研究

针对异构无线网络中域内资源管理优化方案进行了研究,提出了部分可观察马尔科夫调制泊松过程的业务模型对异构无线网络单一域内突发性事件——溢出呼叫进行了分析,提出了针对异构无线网络结构特点和实际业务需求的优化接纳控制模型。建立了最小化网络能耗的优化目标,综合考虑网络状态和拒绝呼叫产生的网络开销,构建了优化决策模型,获得的优化策略能平衡溢出呼叫引起的网络开销和业务服务质量需求之间的矛盾,进一步推导和验证了业务服务请求到达网络的到达率、呼叫连接时间和呼叫逗留时间之间的关系,采用部分可观察马尔科夫调制泊松过程进行性能分析,根据获得的性能参数进行接纳控制决策,验证了异构无线网络域内优化管理模型的合理性和适用性。与资源完全共享算法相比,所提模型降低了网络能耗,在优化策略适应网络状态变化的同时,保证了业务的服务质量需求。     

An integrated traffic model for multimedia wireless networks

Multimedia wireless networks are seen today as one of the key factors for the success of the global communication infrastructure in the near future. Such networks will have to handle a range of heterogeneous traffic classes with different QoS requirements. Their design, planning and control must be supported by suitable traffic models capable of dealing with a new set of constraints where QoS management and mobility play an important role.This paper proposes a traffic model for a cellular multimedia wireless network characterized by the integration of mobility and traffic management aspects. User mobility is modeled through a Markov renewal process, which allows for non-exponential cell residence times and may restrict the user mobility to existent paths in the system. A Markov-modulated fluid process is used to describe the changes in the bandwidth requirements of each mobile over the duration of its calls, including the periods where the mobile is inactive (without call).Based on the proposed model, the number of mobiles per class of traffic in a cell and the handoff processes are characterized. System performance results, such as new and handoff call blocking probabilities, for network planning are derived. Also, the distribution of the required capacity in a short time interval for network control is obtained. Simulations were carried out to validate the analytical results. The comparisons have shown that the integrated model may be regarded as a good basis to build useful teletraffic engineering tools for multimedia wireless networks.