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。     

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。     

多媒体CDMA蜂窝网络中联合退避缓存及速率自适应的呼叫接纳控制策略

资源管理和呼叫接纳控制作为未来蜂窝网络的核心管理模块,能为移动用户提供具有QoS保证的多媒体应用并实现无线资源的有效利用.针对多业务CDMA蜂窝网络,结合非理想功率控制下的容量定义,提出退避缓存与自适应速率调控相结合的呼叫接纳控制策略.其中退避缓策略采用请求呼叫主动退避的思想,有效降低阻塞率;自适应速率调控策略则采用业务用户双重分级的思想,确保用户公平性的同时实现平稳的QoS.仿真结果表明,该策略可以自适应地保证各类业务的QoS要求,提高业务间的公平性和系统资源的利用率.     

一种基于移动IPv6的自适应主动预测邻居切换机制

现有的移动IPv6切换机制依然存在切换时延在,分组丢失等问题。移动IPv6切换的关键问题是移动检测,本文提出了一种自适应主动预测邻居切换移动IPv6切换机制,采用主动自适应预测算法,根据网络和移动主机的运动状态智能的预测主机的切换,实现快速平滑切换。实验结果表明,该机制大大减少了切换时延和切换次数,提高了系统的切换性能,保证了网络的QoS。     

基于切换的MIPv6 over MPLS的QoS机制研究*

为了缩短移动节点切换引起的通信中断时间,减少切换对服务质量（QoS）的影响,以MIPv6 over MPLS的框架结构为基础,给出了一种基于切换的QoS方案,为移动节点切换提供有效的QoS保证。     

适合于移动多媒体网络的呼叫接纳控制算法

移动多媒体网络应该能够同时支持传统的数据业务和实时交互式多媒体业务,并能够为用户提供QoS保证.在无线移动网中提供QoS保证,呼叫接纳控制扮演着重要的角色.通过对呼叫接纳算法中资源预留方案进行了分析总结,提出了一种适合于移动多媒体网络的自适应呼叫接纳控制算法.     

一种有效的移动IP自适应主动预测邻居切换机制

现有的移动IP切换机制存在切换时延大,分组易丢失,安全性差等问题。该文从移动IP切换的关键问题移动检测出发,提出并实现了一种有效的自适应主动预测邻居移动IP切换机制,运用主动自适应预测算法,根据网络和移动主机的运动状态动态智能地预测移动主机的切换,实现快速平滑切换。仿真结果表明,该策略与现有机制相比,极大地减少了切换时延和切换次数,保证分组按时到达,提高了系统的切换性能,保证了系统的QoS。      

移动环境下的QoS保证技术

1 引言各种Internet业务在全世界范围内的广泛应用推动了Internet技术的发展,IP协议原有的“尽力发送“机制已经不能很好地适应业务的需求,因此,IETF提出了资源预留协议和实时传输协议等来保证传输业务流的服务质量。同时,越来越多的移动用户要求能够连续无缝地接入Internet,为此I-ETF设计了移动IP协议以满足移动用户的需求。但是,由于移动环境中通信链路质量经常变化,可用的系统资源较少,通信过程中的多次切换可能导致连接中断,因此在移动环境下提供QoS保证需要新的机制。本文第2部分简述了基于固定网络的QoS保证机制,探讨了移动性对QoS的影响,第3部分介绍了几种在移动环境下提供QoS保证的技术,着重介绍了移动资源预留协议,并给出了移动QoS保证技术的研究方向,第4部分提出了一个新的移动QoS框架,最后给出了下一步要做的主要工作。     

IEEE802.16中基于自适应信道预留的呼叫接入策略

呼叫接入控制(CAC)在宽带无线接入(BWA)服务质量(QoS)中起着非常重要的作用。对无线城域网中IEEE802.16复杂的QoS定义,该文提出了一种在IEEE802.16中基于自适应资源预留的呼叫接入控制策略(AR-CAC)。该策略根据UGS负载和信道利用率为其自适应预留信道,同时考虑了IEEE802.16业务的带宽特性。仿真结果表明,该策略在硬切换呼叫切换失败概率不变的情况下降低了高优先级服务的呼叫阻塞率,同时增大了系统的吞吐量。     

移动IP网络中基于策略的切换架构研究

提出了一种移动IP网络中基于策略的切换架构，并对其运行机制进行了描述。仿真分析表明，该架构能针对网络资源的动态变化、特定的业务类型和用户的定制服务要求，用抽象的策略对切换请求和过程进行自适应判定和动态控制，从而有效改善切换性能。     

A distributed-request-based CDMA CAC for DiffServ multimedia services in wireless cellular mobile networks

In this paper, a distributed-request-based CDMA DiffServ (differentiated service) call admission control (CAC) scheme is proposed to provide various multimedia services seamlessly in wireless mobile Internet. Conventional CDMA CAC schemes cannot fully support DiffServ QoS (Quality of Service) and seamless handoff due to lack of consideration on service priority and seamless mobility. Therefore, in order to achieve QoS guarantee for each service class, seamless fast-handoff, and high utilization of the scarce wireless resource, we define a code assignment policy and an adaptive access permission scheme taking each user’s service priority and mobility into consideration. For that purpose, in the proposed scheme, the DQRUMA/CDMA is combined with the new code assignment scheme and the adaptive access permission probability (APP). Numerical examples show that the forced termination ratio of handoff calls is guaranteed to be much less than the blocking ratio of new calls for a seamless fast-handoff while proposed scheme provides QoS guarantee for each service class efficiently.     

无线多媒体网络中一种基于测量网络状态的动态呼叫接纳控制算法

提出了一种无线多媒体网络中基于测量网络状态的动态呼叫接纳控制算法.它区分了实时和非实时业务,在网络带宽资源不足时可通过降低非实时业务带宽确保实时业务呼叫连接的可靠性;还可根据当前网络状况调整预留带宽大小,使小区实时业务切换呼叫掉线率低于设定的门限值.大量仿真结果显示该算法具有低实时业务切换呼叫掉线率和与固定预留方案相当的带宽利用率,而只以略高的新呼叫阻塞率为代价,适合各种不同概率发生时实际应用的情况.     

基于模糊多目标决策的两跳中继蜂窝网络切换算法

简要介绍了在集成两跳AdHoc和蜂窝网络的结构下,触发网络进行切换的一些因素和两种路由代理发现算法,并且提出了一种新的基于模糊多目标决策方法的切换决定算法。算法从层次分析和模糊综合评价理论的思想出发,结合用户、终端、业务和网络信息,对网络链路的性能进行综合评价,选择出最适合用户业务请求的路径。仿真显示在用户可感知业务QoS下降的情况下,算法可以通过增加QoS的权重而切换到更好的网络链路上,从而为用户提供了"总是最好连接"的服务。     

Markov-based vertical handoff decision algorithms in heterogeneous wireless networks

In this paper, we propose a received signal strength (RSS)-based single-attribute handoff decision algorithm at first, and investigate handoff decision model based on connection lifetime, which can keep mobile terminals (MTs) staying long enough in the preferred network. Since the preferred quality of service (QoS) parameters may be distinct among different MTs, we then formulate the vertical handoff decision problem as a Markov decision process, with the objectives of maximizing the expected total reward and minimizing average number of handoffs. A reward function is constructed to assess the QoS during each connection, and the G1 and entropy methods are applied in an iterative way, by which we can work out a stationary deterministic handoff decision policy. Numerical results demonstrate the superiority of our proposed schemes compared with other existing algorithms.     

Mobility management in ubiquitous environments

Ubiquitous computing is aiming at providing users with intelligent human-centric context-aware services at anytime anywhere. However, mobility increases dynamism and uncertainty conditions. This study therefore explores the management and uses of various contexts for automatically providing appropriate services to individual users. This issue is explored from an open framework perspective referred to as ubiquitous gate (U-gate). In this framework, a distributed context management architecture and a communication model based on standard protocols are proposed. To fit user requirements and to achieve complete mobility management, a context-aware path planning mechanism (UbiPaPaGo) and a context-aware handoff mechanism (UbiHandoff) are proposed based on context stored in an open and distributed context management server U-gate. Based on the path planning results of UbiPaPaGo, UbiHandoff derives a minimum access point (AP) handoff plan that satisfies multiple QoS requirements for individual users and services. The UbiHandoff mechanism includes multiple-attribute decision making method (MADM)–based handoff planning, referred to as MADM-based UbiHandoff, and genetic algorithm (GA)–based handoff planning, referred to as GA-based UbiHandoff. In the proposed MADM-based UbiHandoff, analytic hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS) provide efficient and seamless AP handoff to gain higher QoS performance. In GA-based UbiHandoff, genetic algorithm is employed to minimize handoff by finding appropriate APs along the path under QoS constraints. Finally, the effectiveness of the proposed mechanisms is evaluated through simulations. Numerical results demonstrate that both mechanisms minimize handoffs and ensure compliance with QoS requirements.     

QoS-aware radio resource management scheme for CDMA cellular networks based on dynamic interference guard margin (IGM)

Efficient radio resource management (RRM) for CDMA-based cellular communication systems using the interference guard margin (IGM) scheme is investigated in this work. Two important concepts, i.e., the guard channel (GC) and the load curve (LC), are integrated to derive IGM. The resulting call admission control (CAC) scheme gives preferential treatment to higher priority handoff calls by pre-reserving a certain amount of resource in terms of IGM. A radio resource estimation (RRE) function is implemented in each base station (BS) to assist RRM module to adjust the level of IGM dynamically. RRE in each BS estimates the amount of IGM by considering traffic load in its current cell as well as traffic conditions in neighboring cells. A service model is adopted to support quality of service (QoS) demand of multiple services, which includes mobile terminal’s data rate, different levels of priorities, mobility and rate adaptivity characteristics. Simulations are conducted by OPNET to study performance of the proposed IGM scheme in terms of a defined cost function, new call blocking probability, handoff dropping probability and system utilization, under different traffic conditions.     

CDMA网络中综合业务的呼叫接纳控制算法及性能分析

呼叫接纳控制(CAC)是CDMA系统无线资源管理中的重要组成部分,有效的CAC算法能在满足各类业务不同QoS要求的同时,提高资源的利用率。本文对于新呼叫和切换呼叫,提出了一种有效的呼叫接纳控制算法,给予了切换呼叫更高的优先级,并采用Markov链对算法的性能进行了分析。     

Service Adaptability in Multimedia Wireless Networks

Next-generation wireless communication systems aim at supporting wireless multimedia services with different quality-of-service (QoS) and bandwidth requirements. Therefore, effective management of the limited radio resources is important to enhance the network performance. In this paper, we propose a QoS adaptive multimedia service framework for controlling the traffic in multimedia wireless networks (MWN) that enhances the current methods used in cellular environments. The proposed framework is designed to take advantage of the adaptive bandwidth allocation (ABA) algorithm with new calls in order to enhance the system utilization and blocking probability of new calls. The performance of our framework is compared to existing framework in the literature. Simulation results show that our QoS adaptive multimedia service framework outperforms the existing framework in terms of new call blocking probability, handoff call dropping probability, and bandwidth utilization.      

Bandwidth Reservation Using Velocity and Handoff Statistics for Cellular Networks

The percentages of blocking and forced termination rates as parameters representing quality of services （QoS） requirements are presented. The relation between the connection statistics of mobile users in a cell and the handoff number and new call number in next duration in each cell is explored. Based on the relation, statistic reservation tactics are raised. The amount of bandwidth for new calls and handoffs of each cell in next period is determined by using the strategy. Using this method can guarantee the communication system suits mobile connection request dynamic. The QoS parameters： forced termination rate and blocking rate can be maintained steadily though they may change with the offered load, Some numerical experiments demonstrate this is a practical method with affordable overhead.