一种基于模糊逻辑的预判决辅助垂直切换算法

针对全IP核心网络的不同无线接入技术,提出一种基于预判决模糊逻辑的垂直切换算法.引入预判决方法有效减少不必要的数据量和系统开销.采用前向差分预测能够较准确地预测出下一时刻的信号强度,提高了切换触发速度和切换判决精度.采用模糊逻辑的方法,以接收信号强度、预测信号强度及可用带宽作为网络参量设计模糊逻辑控制器,进而采用归一量化的方法改进模糊逻辑系统,得到网络的综合性能值进行垂直切换判决.仿真分析表明,本文提出的算法能够较准确做出切换判决,有效消除乒乓效应,提高系统性能.     

车联网中基于贝叶斯决策的垂直切换方法研究

车辆需要在车联网的异构无线网络环境下进行垂直切换,针对垂直切换技术普遍不能支持 WAVE, WiMAX和3G cellular间的垂直切换这一问题,提出了一种基于贝叶斯决策的垂直切换算法。首先,根据接入网络的信号强度、传输速率、误码率和网络阻塞率以及车辆终端的速度和运动趋势建立多条件相关的切换概率分布,计算出切换先验概率;然后通过贝叶斯决策算法计算后验概率并进行决策分类,从而选取最优网络接入。仿真实验结果表明,该算法不仅有效地实现WAVE,WiMAX和3G cellular无线接入技术之间的垂直切换,而且避免了乒乓效应,保证了网络及时更新。     

异构无线网络垂直切换技术综述

垂直切换是多网融合的基础,是实现异构网络互通、支持不同接入方式无缝衔接的核心技术,目前正在受到业界的重点关注,并成为学术界研究的热点问题。随着无线移动通信技术向接入多元化、网络一体化和应用综合化的方向发展,各种蜂窝移动接入、宽带无线接入和固定接入将共同接入基于IP的统一核心网络,通过网络间的垂直切换,支持用户的移动性和移动过程中业务的连续性。首先给出了垂直切换的定义和基本概念,介绍了垂直切换的分类和基本流程,随后详细论述垂直切换的切换判决和切换执行2个环节。针对切换判决,总结了现有判决算法,重点评述各代表算法工作原理并剖析论其特点和存在的不足。针对切换执行,详述了现有垂直切换执行机制的工作原理和适用场景,并分析其优缺点。最后,对未来垂直切换技术的研究方向进行了展望。     

多网络共存下基于贝叶斯的垂直切换算法

针对目前的垂直切换技术普遍不能满足多网络下的切换问题,提出了一种改进的基于贝叶斯决策的垂直切换算法。首先根据接入终端网络的信号强度、网络负载、误码率和网络阻塞率以及用户业务对网络的实际需求偏好建立多条件相关的切换概率分布,计算出先验切换概率;然后通过贝叶斯决策算法计算出后验概率来进行判决比较,从而选取最优的接入网络。仿真结果表明,该算法不仅能有效地实现不同接入技术之间的垂直切换,从而减少不必要的切换,提高了切换成功的概率,而且还能在维持各网络平均负载达到30%~40%时减轻通信热点的阻塞情况,为用户提供更优的服务质量。     

无线异构网络的垂直切换算法研究

以通用移动通信系统(UMTS)与无线局域网(WLAN)融合为例,研究无线异构网络的垂直切换算法。由于垂直切换算法应考虑因素的复杂性以及不同网络性能的各异性,有必要对现有算法作出归纳总结比较,并据此提出新的垂直切换算法。该算法以代价函数为基础,将稳定周期与切换目标网络和当前服务网络的效用函数联系起来,实现移动节点自适应的切换判决。提出的算法能有效减少不必要的切换,增强异构网络的适应性。     

基于区间二型模糊神经网络的垂直切换算法

在超密集异构无线网络中,针对传统垂直切换算法无法同时描述网络状态的模糊性和随机性,导致网络性能得不到有效提升的问题,提出一种基于区间二型模糊神经网络的垂直切换算法.重构了两阶段判决算法:在网络预筛选阶段,定义了历史接入率,结合当前候选网络集的数目设置阈值.根据接收信号强度和剩余可用带宽,对用户接收范围内的所有网络进行初步筛选;再在垂直切换判决阶段,将剩余候选网络的时延,丢包率以及误码率作为区间二型模糊神经网络的输入,利用前馈神经网络的结构完成模糊逻辑推理,经训练之后计算得到输出判决值,从而选择最佳接入网络.实验结果表明,该算法能在保证时间开销较低的同时,有效降低切换决策的错误概率,减少切换失败和切换次数,提升网络总吞吐量.     

基于运动趋势的模糊逻辑垂直切换算法

随着无线异构网络的融合,移动性管理技术成为其关键问题,而切换管理又是移动性管理的重要部分。针对垂直切换管理提出了一种基于运动趋势的模糊逻辑垂直切换算法。算法分为预判定、模糊逻辑控制及切换判决3个过程。首先,在预判定阶段根据MN的运动趋势及接收信号强度滤除掉不适宜接入WLAN的网络信息,从而有效减少不必要的数据量和系统开销;其次,将接收信号强度、网络的可用带宽和网络开销送入模糊逻辑控制器,通过参数的归一量化最终得到网络综合性能值(VCPN);最后,通过综合考虑VCPN和驻留时间来进行网络切换判决。仿真结果显示,该算法能够有针对性地做出切换判决,有效消除乒乓效应,提高网络切换性能。     

一种LTE与WLAN间垂直切换新算法

为提高用户在异构网络中的服务质量(QoS),减少切换产生的乒乓效应,文中提出了一种LTE和WLAN网络垂直切换新算法。该算法考虑了衰落对接收信号强度(RSS)的影响,基于RSS选出目标网络,根据用户移动速度并结合代价函数选出最佳网络,代价函数中采用了层次分析法来确定时延、资费和用户偏好等参数的权重。仿真结果表明,文中所提的垂直切换算法有效降低了“乒乓效应”,并提高了通信网络的服务质量。     

一种基于上下文感知的垂直切换技术研究

未来网络的发展趋势是各种无线接入网络共存的异构网络环境,而垂直切换技术是融合多个异构接入网络的关键技术之一,垂直切换包括三个阶段,即系统发现、切换决策和切换执行。文中主要研究了基于上下文感知的垂直切换判决策略,并与移动垂直切换技术相结合,实现了WLAN/UMTS网络间的垂直切换,通过仿真表明该方法在吞吐量和切换时延方面都得到改善。     

改善用户体验的垂直切换算法

针对由超密集异构无线网络的超高动态性而引起掉话率不断增长的问题,并考虑到以往基于模糊逻辑相关垂直切换算法的较大时间开销,该文提出一种改善用户体验的垂直切换算法。首先利用5G核心访问和移动管理功能发现终端附近的所有候选网络,同时,利用自组织网络技术的环境感知能力,随时监测网络的运行状况,主动维护网络之间的邻居关系表。然后,引入动态模糊神经网络(DFNN)算法来执行切换判决,将获取到的网络参数数据作为该系统的输入,动态生成对垂直切换有效的规则库,经学习之后,计算得到输出判决值,从而为终端选择最佳接入网络。最后,仿真结果表明,该算法能够明显改善垂直切换过程中的掉话情况,降低切换失败概率。同时,与其他同类算法的时间消耗相比,该算法能够维持在一个较低的水平。     

基于分段式PPP协商的快速网络接入算法

多网融合是当今无线通信网络发展的必然趋势,垂直切换是网络融合的关键技术之一。对现有3G网络的终端接入信令流程进行分析,提出了一种基于分段式PPP协商的快速接入算法。通过在现网环境中测试,证明该算法有效地缩短了切换执行时延,对垂直切换过程中"切换执行"阶段的研究做出了贡献。     

无线异构网络的垂直切换判决算法

传统上的水平切换处理方法已经应用在同一接入技术的网络中（如无线蜂窝网络）。随着多种异构无线网络的出现,下一代网络必须支持垂直切换技术以保证用户从一个网络切换到内一个网络时仍然保持连接,垂直切换作为多网融合的基础,受到了学术界和工业界的广泛关注。对使用层次分析法进行垂直切换技术的工作原理及应用环境进行了分析,提出同时使用多种切换技术以解决不同环境下的切换问题。     

Design,Implementation and Evaluation of Programmable Handoff in Mobile Networks

We describe the design, implementation and evaluation of a programmable architecture for profiling, composing and deploying handoff services. We argue that future wireless access networks should be built on a foundation of open programmable networking allowing for the dynamic deployment of new mobile and wireless services. Customizing handoff control and mobility management in this manner calls for advances in software and networking technologies in order to respond to specific radio, mobility and service quality requirements of future wireless Internet service providers. Two new handoff services are deployed using programmable mobile networking techniques. First, we describe a multi-handoff access network service, which is capable of simultaneously supporting multiple styles of handoff control over the same physical wireless infrastructure. Second, we discuss a reflective handoff service, which allows programmable mobile devices to freely roam between heterogeneous wireless access networks that support different signaling systems. Evaluation results indicate that programmable handoff architectures are capable of scaling to support a large number of mobile devices while achieving similar performance to that of native signaling systems.     

异构网络垂直切换技术

下一代无线网络(Next Generation Wireless Networks,NGWN)将融合多种不同的网络体系结构与无线技术,NGWN的异构性要求向用户提供无缝切换。为此文章引入了异构无线网络垂直切换策略,并深入论述了其中的关键细节——网络发现、切换判决和切换信息交互流程等。     

Artificial Neural Network Based Vertical Handoff Algorithm for Reducing Handoff Latency

One of the most challenging topics for next generation wireless networks is vertical handoff concept since several wireless technologies are assumed to cooperate. Plenty of parameters related to user preferences, application requirements, and network conditions, such as; data rate, service cost, network latency, speed of mobile, battery level, interference ratio and etc. must be considered in vertical handoff process along with traditional RSSI information. In this study, a new artificial neural network based handoff decision algorithm is proposed in order to reduce the handoff latency of smart terminal deployed in aforementioned wireless heterogeneous infrastructures. The prominent parameters data rate, monetary cost and RSSI information are taken as inputs of the developed vertical handoff decision system. Performance results of the proposed system are also compared with those of classical Multiple Attribute Decision Making method Simple Additive Weighting, and of some other artificial intelligence based algorithms. According to the results obtained, the proposed neural network based vertical handoff decision algorithm is able to determine whether a handoff is necessary or not properly, and selects the best candidate access network considering the abovementioned parameters. The results also show that, the neural network based algorithm developed significantly reduces the handoff latency while the number of handoffs, which is another vital performance metric, is still reasonable.     

无线异构网络中带有动态权值的新型垂直切换算法

In order to enhance the quality of vertical handoff in an overlay wireless network, multiple attributes are taken into account when optimizing the vertical handoff decision including user-based and network-based QoS factors. In this paper, we develop a novel vertical handoff algorithm in an integrated 3G cellular and Wireless LAN networks. The proposed algorithm can adjust the weight of each QoS attribute dynamically as the networks change, trace the network condition and choose the optimal access point at transient regions. Simulation results show that this algorithm is able to provide accurate handoff decision, resulting in small unnecessary handoff numbers, good performance of throughput and handoff delay in heterogeneous environments.     

A Simple and Robust Vertical Handoff Algorithm for Heterogeneous Wireless Mobile Networks

Wireless networking is becoming an increasingly important and popular way of providing global information access to users on the move. One of the main challenges for seamless mobility is the availability of simple and robust vertical handoff algorithms, which allow a mobile node to roam among heterogeneous wireless networks. In this paper, motivated by the facts that vertical handoff procedure is done on mobile nodes and battery power may be one crucial parameter for certain mobile nodes, a simple and robust two-step vertical handoff decision algorithm is proposed for heterogeneous wireless mobile networks. To the best of our knowledge, this is the first vertical handoff algorithm that takes the classification of mobile nodes into consideration, one is resource-poor mobile nodes, and the other is resource-rich mobile nodes. This new feature makes it more applicable in the real world. In addition, dynamic new call blocking probability is firstly introduced by this paper to make handoff decision for wireless networks. The experiment results have shown that the proposed algorithm outperforms traditional algorithms in bandwidth utilization, handoff dropping rate and handoff rate.     

A new handoff management system for heterogeneous wireless access networks

In heterogeneous wireless access networks, each mobile terminal may frequently need to change its base station (BS); this change is called a ‘handoff’. BSs have static parameters, which are related to their radio access technologies (RATs); however, they also contain dynamic parameters such as load and signal quality. Therefore, the problem of handoff decision includes two subproblems of RAT selection and BS selection. In this paper, first a ‘heterogeneous handoff management system’ for gathering all different required parameters is proposed. Second, a RAT Selection algorithm based on analytic hierarchy process and a BS Selection algorithm based on data envelopment analysis are designed. Finally, by means of ‘weight restriction’ technique, we develop a method for studying the impact of RAT Selection parameters on the performance of the network. Simulation results indicate that RAT Selection parameters have significant impact on the bandwidth utilization, energy consumption and the whole satisfaction of the users in heterogeneous wireless access networks.Copyright © 2012 John Wiley & Sons, Ltd.