异构无线网络中基于SINR和层次分析法的SAW垂直切换算法研究

B3G或者4G无线网络体系致力于集成各种异构无线接入网络,其中一个主要的设计课题是支持垂直切换的研究。该文将多属性QoS考虑在内,针对各业务特点,提出一种基于SINR(信干噪比)和层次分析法(AHP)的SAW(简单加权法)垂直切换算法(SASAW)。它综合考虑SINR的影响以及要获得同等数据速率情况下,目标网络需要的等效SINR数值、用户通信代价、网络可用带宽等来构造属性矩阵做切换判决。为了评估性能,考虑3GPP定义的4类业务,利用层次分析法中的特征向量法来决定各个QoS属性之间的权重关系,构造比较判决矩阵并检验其一致性;根据判决矩阵,利用特征根法获得权重向量;最后根据属性矩阵和权重向量,利用SAW垂直切换算法进行判决。通过对算法的通过率、丢话率、垂直切换次数、平均用户代价等的性能比较,结果表明该文提出的算法能够根据各业务特点综合考虑各属性间关系,获得优良的系统性能。     

一种基于业务切换的垂直切换判决算法

在下一代异构无线网络环境中,为满足在异构无线网络架构下采用不同切换方式的垂直切换请求,我们提出一种基于业务切换的垂直切换判决算法,并设计了一种基于业务切换的代价函数。通过数学分析和在UMTS,WLAN融合的网络环境下对该方案的切换失败率的仿真分析,证明了该方案在支持终端的移动性、保障用户业务请求满意度以及缓解网络负载压力上相比传统基于代价函数的垂直切换判决算法更具优势。     

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。     

基于模糊层次—熵权法的自适应垂直切换算法

针对当前异构网络中,采用多决策属性的垂直切换算法难以动态调整网络属性的权重值,从而无法满足用户服务质量(QoS)的需求问题,文章以接入最优的异构无线网络和保障用户QoS为目标,提出基于模糊层次—熵权法的自适应垂直切换算法.首先,根据用户对网络属性的不同要求,采用主观模糊层次赋权与客观熵权法结合的方式构建网络属性优化模型...     

异构无线网络中基于人工神经网络的自适应垂直切换算法

针对当前基于人工神经网络的垂直切换算法(ANN-VHO),存在业务自适应性差和计算复杂度高的问题,该文提出一种基于人工神经网络的自适应垂直切换算法。首先,根据终端获取到的接收信号强度(RSS),采用阈值判断的方法,遴选出候选网络集;其次,根据该文划分的不同业务类型,对参数进行自适应选择和归一化;再次,把选择的参数输入人工神经网络,判决出候选网络集中最佳的接入网络。最后,实验结果表明,该算法能根据用户的业务类型合理地选择切换网络,降低切换阻塞率,同时降低算法的时间复杂度。     

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。     

基于用户偏好的异构网络选择算法研究

针对当前大多数网络选择算法没有充分考虑用户基于业务的网络偏好这一问题,提出了一种基于用户偏好的异构网络选择算法。该算法充分考虑业务需求、用户偏好及网络性能差异,通过层次分析法和距离分析法分别计算用户对各候选网络的主观和客观偏好权重,根据用户策略动态确定综合权重,并由此结合各属性权重计算网络性能,选出最优网络。仿真结果表明该算法可以准确选择接入网络,并当用户在网络边缘做兵乓运动时有效减少切换次数。     

异构无线网络的自适应垂直切换判决算法

在未来的异构环境中,网络间的垂直切换将对QoS保证产生重要影响。针对移动终端在异构网络间切换不理想的问题,提出了一种自适应的垂直切换判决算法。采用基于用户多应用的代价函数对接入网络进行评估与选择,综合考虑移动终端当前的电池电量,判断当前业务是否需要进行网络切换,使移动终端能自适应地进行切换判决。仿真结果表明,该算法可以有效地延长移动终端的工作时间,减少乒乓效应,提高系统的切换性能,改善业务的QoS。     

联合资源管理的异构无线网络垂直切换算法

针对资源有限的无线异构网络,关键问题是如何管理稀缺的无线资源(如带宽)来满足服务提供者和享受服务的用户的需求。提出一种联合带宽动态分配,准入控制的垂直切换算法,旨在提高运营商的利益最大化的同时兼顾用户的服务质量。仿真结果表明,该算法可以有效地提高带宽资源的利用率,有效降低阻塞率和掉话率,能够满足不同业务的切换要求,适合异构无线网络的多业务传输。     

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。     

基于认知自选择决策树的垂直切换方法研究

在异构无线网络环境下高速移动的终端用户需要随时随地接入网络,然而,在垂直切换过程中,由于终端用户对网络选择的偏好不同以及切换之后网络连接时间和状态难以得到保障,无法满足用户的切换需求。因此,提出了一种支持终端用户高速移动的基于认知自选择决策树的垂直切换方法。该方法首先根据网络属性和终端运动趋势建立相应的切换概率分布,然后根据用户偏好选择相应的决策树进行决策,最后通过对切换后终端的业务类型和运动状态进行反馈分析,提出了反馈认知决策方法。仿真结果表明,所提的方法不仅能够保证高速移动终端在异构无线网络下的切换质量,而且减少了不必要的切换,保证了网络的及时更新。     

Vertical handoffs in fourth-generation multinetwork environments

Revolutionary drivers for 4G include a push toward universal wireless access and ubiquitous computing through seamless personal and terminal mobility. One of the major challenges for seamless mobility is the criterion of a vertical handoff protocol: a handoff protocol for users that move between different types of networks. Traditional operations for handoff detection policies, decision metrics, and radio link transfer are not able to adapt to dynamic handoff criteria or react to user inputs and changing network availabilities. Nor are they able to deliver context-aware services or ensure network interoperability. Thus, new techniques are needed to manage user mobility between different types of networks. This article presents a tutorial on the design and performance issues for vertical hand-off in an envisioned multinetwork fourth-generation environment. Various network architectures and technologies for 3G and beyond are described, including wireless LANs, cellular, satellite, and Mobile IP. Then the problem of vertical handoff is defined in the context of such a diverse network environment. Finally, research efforts to resolve the open problems are explored, including new techniques for dynamic handoff decision and detection algorithms and context-aware radio link transfer.     

On the Use of Ad Hoc Cooperation for Seamless Vertical Handoff and Its Performance Evaluation

In heterogeneous network environments, it is very important for users to provide seamless services while satisfying quality-of-service, regardless of the connected access network. In this paper, we apply a concept of ad hoc cooperation for the vertical handoff in the heterogeneous network. For the seamless vertical handoff of mobile nodes, a neighbor ad hoc node assists some parts of the handoff procedures requiring large latency, such as authentication and IP registration procedures. Details of the vertical handover operation using the ad hoc cooperation are presented and its performance is evaluated. Numerical results show that the proposed vertical handoff procedure decreases the service disruption time and the probability of packet loss, compared with the conventional handoff methods that do not consider the cooperation of ad hoc node.     

异构无线网络中新的成本感知网络切换方案

针对异构无线网络中用户希望通过较低的花费获取最满意的网络服务的需求,本文提出了一种以用户为中心的成本感知网络切换方案.首先,根据用户能够获取到的网络传输速率建立用户服务满足度模型,并结合归一化的网络费用,将网络切换问题转化为一个多目标优化问题.考虑到网络阻塞是由于大量用户同时选择同一个网络导致的,将这种背景下的用户决策行为转化为EI Farol酒吧问题,通过求解该问题纳什均衡状态下的用户获取网络服务的概率来得到用户服务满足度的期望值.最后,通过考虑用户服务满足度回报率将所构建的多目标优化问题转化为一个最大化问题.仿真结果表明本文算法能够提高网络总吞吐量,降低用户切换阻塞率,使网络负载更加均衡.     

A novel software‐defined networking approach for vertical handoff in heterogeneous wireless networks

We propose a novel vertical handoff scheme with the support of the software‐defined networking technique for heterogeneous wireless networks. The proposed scheme solves two important issues in vertical handoff: network selection and handoff timing. In this paper, the network selection is formulated as a 0‐1 integer programming problem, which maximizes the sum of channel capacities that handoff users can obtain from their new access points. After the network selection process is finished, a user will wait for a time period. Only if the new access point is consistently more appropriate than the current access point during this time period, will the user transfer its inter‐network connection to the new access point. Our proposed scheme ensures that a user will transfer to the most appropriate access point at the most appropriate time. Comprehensive simulation has been conducted. It is shown that the proposed scheme reduces the number of vertical handoffs, maximizes the total throughput, and user served ratio significantly. Copyright © 2016 John Wiley & Sons, Ltd.     

A seamless context-aware architecture for fourth generation wireless networks

The integration of a multitude of wireless networks is expected to lead to the emergence of the fourth generation (4G) of wireless technologies. Under the motivation of increasing the levels of user satisfaction while maintaining seamless connectivity and a satisfactory level of QoS, we design a novel cross-layer architecture that provides context-awareness, smart handoff and mobility control in heterogeneous wireless IP networks. We develop a Transport and Application Layer Architecture for vertical Mobility with Context-awareness (Tramcar). Tramcar presents a new approach to vertical handoff decisions, which is not exclusively based on network characteristics but also on higher level parameters which fall in the application and transport layers. Tramcar is tailored for a variety of different network technologies with different characteristics and has the ability of adapting to changing environment conditions and unpredictable background traffic. Furthermore, Tramcar allows users to identify and prioritize their preferences. Tramcar is a smart and practical system, which is more capable of dealing with 4G challenges. Simulation results demonstrate that Tramcar increases user satisfaction levels and network throughput under rough network conditions and reduces overall handoff latencies.     

Handoff prioritization and decision schemes in wireless cellular networks: a survey

Handoff is a key element in wireless cellular networks in order to provide Quality of Service (QoS) to the users and to support users? mobility. Handoff failure will result in the forced termination of an ongoing call. From the user?s point of view, the service of a handoff request is more important, as the forced termination of an ongoing call is more annoying than the blocking of new calls. Therefore, in order to support QoS to the users and to provide ubiquitous coverage, the handoff procedure ought to be further investigated. This paper provides a comprehensive survey of the basic elements, the different types and phases of the handoff procedure. Moreover, particular interest has been given in the horizontal handoff execution phase by discussing and classifying the most recent handoff prioritization schemes into categories based on the concepts that these schemes adopt, e.g. Channel Reservation, Handoff Queueing, Channel Transferred, SubRating, Genetic and Hybrid Schemes and in the vertical handoff decision phase by presenting different decision algorithms.     

一种适合于第四代公网集群系统的切换算法

提出了一种适合于公网集群系统的小区切换算法.在公网集群系统中,多个群组用户同时进行越区切换,可能造成信令风暴,导致更高的切换时延,降低了小区切换成功率.通过引入桥梁群组用户这一概念,通过桥梁群组用户同时连接2个网络,利用2次垂直切换代替一次水平切换的方法,避免了大量群组用户同时发起切换测量.仿真结果表明,利用移动自组织网络为准备切换的集群用户组成一个小网络,桥梁群组用户带领其他群组用户切换的方法比传统切换算法的切换成功率高,切换时延更短.     

集成Ad Hoc和移动蜂窝网络系统的切换算法

传统切换算法不能适应多准则切换的要求,基于多准则切换算法的实现越来越重要,必须发展新的技术来提高切换算法的有效性,在用户满意度和网络效率间形成平衡。智能和优化切换算法对像集成自组网(Ad hoc)和蜂窝网络结构的混合网络具有很好的适应性和鲁棒性,能够根据未来混合网络中的各种业务类型的服务质量需求、网络状态以及移动节点条件等多种因素的变化进行自适应切换,可以运用这些智能优化算法来进行更加有效的切换判决,从而提高系统的性能。更进一步的研究方向是在集成Ad hoc和蜂窝网络的环境下,使用智能或优化技术设计垂直切换算法来提高系统整体性能。     

Perceived Quality Measurement Model Supporting Full Session Mobility in Multimedia Service Delivery

Context-awareness is associated with the concept of machines being able to both recognize and react to the surrounding environment, which has accelerated multimedia computing technology to provide user-oriented intelligent services. The goal of this research focuses on the modeling of video quality measurement in seamless video service delivery process considering the mobility patterns of users. Mobility supporting schemes providing seamless multimedia services are classified into host mobility and user mobility. The former refers to a host-level handoff while the latter indicates a user-level handoff. In host-level handoff, the decisive factors affecting the quality of video contents consumption are the total distance between hosts, the distance to resume streaming while the user is in mobility mode as well as the screen size of the end host. The influential parameters affecting the degree of video quality and seamlessness are evaluated by a subjective quality assessment and then a perceived video quality model was developed, accordingly. In addition, the optimal video delivery switching point to enable user mobility based video service is studied through the quality analysis of host mobility services at varying distances among the hosts. Experimental results show that the proposed quality model has high correlation with assessed quality and is useful to enable an adequate seamless mobility for multimedia service delivery.