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外文翻译----4G异构网络的切换-其他专业.doc

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外文翻译----4G异构网络的切换-其他专业.doc

Handoffs in Fourth Generation Heterogeneous Networks Nidal Nasser, University of Guelph Ahmed Hasswa and Hossam Hassanein, Queen’s University 4G异构网络的切换 加拿大安大略省圭尔夫大学 加拿大安大略省皇后大学 ABSTRACT As mobile wireless networks increase in popularity and pervasiveness, we are faced with the challenge of combining a diverse number of wireless networks. The fourth generation of wireless communications is expected to integrate a potentially large number of heterogeneous wireless technologies in what could be considered a huge step forward toward universal seamless access. One of the main challenges for seamless mobility is the availability of reliable horizontal intrasystem and vertical intersystem handoff schemes. Efficient handoff schemes enhance quality of service and provide flawless mobility. This article presents different and novel aspects of handoff and discusses handoff related issues of fourth generation systems.Desirable handoff features are presented. Handoff decisions, radio link transfer, and channel assignment are described as stages of the complete handoff process. A vertical handoff decision function, which enables devices to assign weights to different network parameters, is also presented. 摘要 移动无线网络日益盛行之?#20445;?#19981;同网络之间融合的挑战摆在面前。4G无线通信整合了大多数异构网络的无线技术,在走向通用的无缝接入方面迈向了一大步。无缝移动通信面临的主要挑战之?#30343;?#21487;靠的水平网间切换和垂直网内切换机制的有效性。有效的切换机制提高了服务质量提供?#23435;?#32541;移动通信。本文提出了新颖不同的切换并讨论了4G切换的相关问题。本为给出了令人满意的切换特性。切换判决,无线链路传输和信道分配在整个切换过程中分步描述。本文还给出了一种能够让终端去分配权重给不同网络?#38382;?#30340;垂直切换判决函数。 INTRODUCTION 1.介绍 First, second- and third-generation mobile systems depended on the employment of the radio spectrum that was either unlicensed available for public use or licensed for use by a very small number of service providers and network operators in each region. Differences in bandwidth and coverage areas have led to the necessity of developing multi-network interface devices terminals that are capable of using the variety of different network services provided. 首先,第二代第三代移动通信系统?#35272;?#20110;无线频谱的利用,这些频谱要么被公共使用要么被批准在各个地区由一些小数量的服务提供商和网络运营商使用。带宽?#36879;?#30422;范围的差异导?#36335;?#23637;多网络接口终端的必要性,多网络接口终端可以使用不同网络服务提供的多样性。 The fourth generation 4G of wireless communications is expected to integrate a potentially large number of different heterogeneous wireless technologies in what could be considered a huge step forward toward universal wireless access and omnipresent computing through seamless mobility [1]. Even though 4G is currently undefined,there are many current outlooks that delineate the vision of the new wireless technologies.Based on the emergent trends of mobile communication, 4G will have larger bandwidth, higher data rates, smoother and quicker handoff, and will focus on reducing faultless service and allowing seamless handoff across a multitude of wireless networks. The key concept is integrating the 4G capabilities with all of the existing mobile technologies. Network management will be necessary among different access systems in terms of horizontal intrasystemand vertical intersystem handoff as well as seamless mobility, quality of service, dependability,and security. 4G无线通信融合了大多数异构网络的无线技术,在通用的无缝接入方面和通过无缝移动通信进行泛在计算方面迈向了一大步[1]。即使4G当前没有明?#33539;?#20041;,仍然有很多当前的展望描述了新一代无线技术的景象。基于移动通信浮现的趋势,4G拥有更多的带宽和数率以?#26696;?#24179;滑快捷的切换,集中致力于减少差错服务和允许通过多种无线网络的无缝切换。关键概念是使用已存在的移动技术整合4G性能。网络管理,对于不同的接入系统如垂直和水平切换还有无缝移动性、服务质量、可靠性和安全性,很有必要。 The remainder of this article is organized as follows. We present a novel classification hierarchy for handoffs. A comprehensive study of various handoff decision factors in heterogeneous wireless networks is explained. We then explain and qualitatively evaluate the proposed vertical handoff decision function VHDF. We provide a performance evaluation of the described solution.Finally, an article summary is given. 下面的文章内容如下。给出了一?#20013;?#30340;用于切换的分类层次。对异构无线网络中各种切换判决因子的全面研究进行解释,解释和定量地评估本文提到垂直切换函数VHDF。提供所述解决方案的性能评估及文章概要。 CLASSIFICATION OF HANDOFFS 2.切换的分类 In principle, each mobile terminal node is, at all times, within range of at least one network access point, also known as a base station. The area serviced by each base station is identified as its cell. The dimensions and profile of every cell depend on the network type, size of the base stations,and transmission and reception power of each base station. Usually, cells of the same network type are adjacent to each other and overlap in such a way that, for the majority of time,any mobile device is within the coverage area of more than one base station. Cells of heterogeneous networks, on the other hand, are overlaid within each other. Therefore, the key issue for a mobile host is to reach a decision from time to time as to which base station of which network will handle the signal transmissions to and from a specific host and handoff the signal transmission if necessary. 大体上,每个移动终?#31169;?#28857;总是归类于至少一种网络接入点即基站。每一个基站的服务区定义为它的小区。每个小区的大小和外形?#35272;?#20110;网络类型、基站大小、基站的传输和?#37038;?#21151;?#30465;?#36890;常相同类型的小区以这样一种方式彼此相邻和重叠,大多数时间内任一移动终端所处的覆盖面积超过一个基站。另?#29615;?#38754;,异构网络的小区相互覆盖。因此,移动主机的关键问题是要时?#30343;?#22320;做出选择,哪个网络的哪个基站来处理具体移动主机的信号传输和?#37038;?#20197;及必要时切换信号的传输。 We classify handoffs based on several factors as shown in Fig. 1. No longer is the network type the only handoff classification factor. Many more factors constitute categorization of handoffs including the administrative domains involved, number of connections and frequencies engaged. The following are categorization factors along with the handoff classifications that are based on them. 如图1所示,基于?#38050;?#22240;素给出了切换的分类。网络类型不再是唯一的切换分类的因素。这个切换的分类因素有很多组成包含涉及的管理区域、连接和使用的频率数。下图是基于它们的切换类型的分类因素。 图1切换的分类树 FIRST FACTOR NETWORK TYPES INVOLVED This is the most common classification factor.Handoffs can be classified as either horizontal or vertical. This depends on whether a handoff takes place between a single type of network interface or a variety of different network interfaces. Horizontal handoff the handoff process of a mobile terminal between access points supporting the same network technology. For example,the changeover of signal transmission as themobile terminal moves around from an IEEE 802.11b base station to a geographically neighboring IEEE 802.11b base station is considered as a horizontal handoff process. Vertical handoff the handoff process of a mobile terminal among access points supporting different network technologies. For example, the changeover of signal transmission from an IEEE 802.11b base station to an overlaid cellular network is considered a vertical handoff process.Horizontal and vertical handoffs are discussed in more detail in the following sections. 2.1因素一 涉及的网络类型这是最普遍的分类因素。切换能被分为水平切换或者垂直切换。这主要看切换是发生在同种网络类型之间还是不同网络类型之间。 水平切换移动终端在支持相同网络技术的接入点之间的切换过程,例如,从802.11b基?#38236;?#22320;理上相邻802.11b基站的信号传输的转变就是水平切换过程。 垂直切换移动终端在支持不同网络技术的接入点之间的切换过程,例如,从802.11b基?#38236;?#37325;叠覆盖蜂窝网络的信号传输的转变就是垂直切换过程。水平和垂直切换在后面的章节中会详细讨论。 SECOND FACTOR FREQUENCIES ENGAGED Intrafrequency handoff the handoff process of a mobile terminal across access points operating on the same frequency. This type of handoff is present in code-division multiple access CDMA networks with frequency-division duplex FDD. Interfrequency handoff the handoff process of a mobile terminal across access points operating on different frequencies. This type of handoff is present in CDMA networks with time-division duplex TDD and is the only handoff type supported in GSM cellular systems. 2.2因素二使用的频率 ?#23548;?#20999;换移动终端穿越在相同频率上运行的接入点之间的切换过程。这种切换的典型例子就是FDD的CDMA网络。 ?#30340;?#20999;换移动终端穿越在不同频率上运行的接入点之间的切换过程。这种切换的典型例子就是TDD的CDMA网络和只支持GSM蜂窝系统的切换类型。 THIRD FACTOR NUMBER OF CONNECTIONS INVOLVED Handoffs can be classified as hard, soft, or softer. Hard handoff In a hard handoff the radio link to the old base station is released at the same time a radio link to the new base station is established. In other words, using hard handoff,a mobile node is allowed to maintain a connection with only one base station at any given time. Soft handoff Contrary to hard handoffs, in a soft handoff a mobile node maintains a radio connection with no less than two base stations in an overlapping handoff region and does not release any of the signals until it drops below a specified threshold value. Soft handoffs are possible in situations where the mobile node is moving between cells operating on the same frequency. Softer handoff A softer handoff is very similar to a soft handoff, except the mobile terminal switches connections over radio links that belong to the same access point. 2.3因素三涉及连接数 切换被分为硬切换,软切换?#36879;?#36719;切换。 硬切换在硬切换中,目标基站无线链路建立的同时释放原基站的无线链路。也就是说,使用硬切换?#20445;?#22312;任?#38382;?#38388;,移动节点只能同一个基站保持连?#21360;?软切换与硬切换相比,在软切换中,移动节点在重叠覆盖的切换区内和不少于2个基站保持连接,并?#20063;换?#37322;放任何信号直到某信号低于给定的阀门值。当移动节点在相同频率上运行的小区间移动时可能会发生软切换。 更软切换除了移动终端在同一个接入节点的无线链路上?#25442;?#36830;接这点特性之外,更软切换同软切换很类似。 FOURTH FACTOR ADMINISTRATIVE DOMAINS INVOLVED An administrative domain is a group of systems and networks operated by a single organization of administrative authority. Administrative domains play a significant role in 4G wireless networks as different networks, each controlled by different administrative authorities, become available. Consequently, the classification of handoffs in terms of administrative domains is a crucial issue. Intra-administrative handoff a handoff process where the mobile terminal transfers between different networks supporting the same or different types of network interfaces managed by the same administrative domain. Inter-administrative handoff a handoff process where the mobile terminal transfers between different networks supporting the same or different types of network interfaces managed by different administrative domains. 2.4因素四涉及的管理区域 管理区域是由同一个管理者管理的一组系统和网络。管理区域在4G无线网络如不同的网络中扮演重要的角色,不同的网络?#21152;?#19981;同的管理者。因此,根据管理区域划分的切换类型是一个很重要的研究问题。 管理域之内的切换移动节点在相同管理域管理的不同网络支持相同或不同类型网络接口之间切换过程。 管理域之间的切换移动节点在不同管理域管理的不同网络支持相同或不同类型网络接口之间切换过程。 FIFTH FACTOR NECESSITY OF HANDOFF Handoffs can be classified based on need. Obligatory handoff In some situations it is necessary for the mobile terminal to transfer the connection to another access point in order to avoid disconnection. Voluntary handoff In other situations transfer of connection is optional and may or may not improve the quality of service.Voluntary and obligatory handoffs are discussed in more details later on. 2.5因素五切换的必要性 基于需要而划分的切换 强制切换在有些情况下,为了避免掉线,有必要将移动终端的连?#24188;?#31227;到另一个接入点。 自愿切换在其他情况下,连接的转移是可选择的,对于提高服务质量不?#33539;ā?#33258;愿切换和强制切换在以后的章节中详细讨论。 SIXTH FACTOR USER CONTROL ALLOWANCE Handoffs can be classified as proactive or passive. Proactive handoff In a proactive handoff the mobile terminal’s user is allowed to decide when to handoff. The handoff decision can be based on a set of preferences specified by the user.Proactive handoff is expected to be one of the radical features of 4G wireless systems. Passive handoff The user has no control over the handoff process. This type of handoff is the most common in first-, second-, and third-generation wireless systems. 2.6因素六用户控制允许 切换可分为主动的和?#27426;?#30340;。 主动切换在主动切换中,移动终端用户可以选择?#38382;?#20999;换。这种切换判决基于用户事先设定好的?#38382;?#20027;动切换是4G无线网络系统的基本特点之一。 ?#27426;?#20999;换用户不控制切换过程。这种类型的切换在前3代无线通信系?#25345;?#26368;为普遍。 HANDOFFS IN 4G HETEROGENEOUS NETWORKS 3. 4G异构网络的切换 As discussed above, handoffs can be defined as the transition of signal transmission between different cells. A handoff scheme is required to preserve connectivity as devices move about, and at the same time curtail disturbance to ongoing transfers. Therefore, handoffs must exhibit low latency, sustain minimal amounts of data loss, as well as scale to large networks. Handoff schemes have been thoroughly researched and deployed in cellular systems, also known as wireless wide area networks WWANs, and are escalating in importance in other networks, such as wireless LANs WLANs, as research in 4G wireless communications increases in popularity. Handoffs can be classified as either horizontal or vertical,as depicted in Fig. 2. 如上面讨论的,切换可以定义为不同小区之间传输信号的转移。切换机制要求当设备移动时保持连?#26377;裕?#21516;时对正在进行的转移减少干扰。因此,切换必须表现出低的反应时间,保持最小的数据丢失和测量大的网络。切换机制在蜂窝网络中已经彻底地研究和配置过,?#28909;?#26080;线广域网WWANs,在无线局域网WLANs中的重要性也逐渐提高。如图2,切换可划分为水平切换和垂直切换。 Horizontal handoff is the changeover of signal communication from one base station to a geographically neighboring base station supporting the same technology, as the user roams about. Horizontal handoff is also referred to as intra-technology handoff. Every time a mobile cellular host crosses from one cell into a neighboring cell supporting the same technology,the network routinely and automatically exchanges the coverage responsibility from one base station to another. Each base station change, as well as the exchange procedure or method is known as horizontal handoff. In a properly operating network, handoff takes place smoothly and efficiently, without gaps in communications and without uncertainty as to which base station should be dealing with the mobile node. Mobile users need not get involved in order for horizontal handoff to take place nor do they have to sense the handoff process or identify which base station is managing the signals at any certain time. 水平切换是从一个基?#38236;?#22320;理上相邻且支持相同技术基站的信号传输的转变,如用户漫?#38382;薄?#27700;平切换也被当作技术内切换提及。每当一个移动蜂窝主机从一个小区穿越相邻小区支持相同技术,网络通常会自动地从一个基?#38236;?#21478;一个基站?#25442;?#35206;盖责任。每一次基站的改变,还有?#25442;皇中?#21644;方法都认为是水平切换。在一个运行良好的网络中,切换会平滑而有效的发生,没有通信上的不通畅,也没有不?#33539;?#24615;,即不知道哪个基站应该接管这个移动节点。移动用户不需要涉及水平切换的发生,对切换过程也没有感觉,在任?#38382;?#38388;也不涉及识别到底哪个基站正在处理信号。 Horizontal handoff is the most widespread definition of handoff due to the extensive research that has taken place in this field in the last several years. Vertical handoff, on the other hand is a more recent and exciting scheme that promises to transfigure the way we communicate.While horizontal handoff is a handover among base stations in service by the same wireless network interface, vertical handoff takes place between different network interfaces that usually represent different technologies [2]. Vertical handoff architectures and schemes will play a major role in the IEEE 802.21 standard and shall pave the road for emergence of 4G overlay multinetwork environments. 水平切换是范围最为广泛的切换定义,是由于其在这个领域里的广泛研究在最近很多年一直在进?#23567;?#21478;?#29615;?#38754;,垂直切换更多的是最近提出而令人振奋的切换机制,让大家感觉将来的通信方式会很美好。水平切换是处于相同无线网络接口服务的基站之间的切换,而垂直切换发生在不同网络接口之间,这些接口通常代表了不同的技术[2]。垂直切换体系和机制在IEEE 802.21标准中将扮演主要角色,并为4G重叠多网络环境的融合铺平道路。 There are two types of vertical handoffsupward and downward. An upward vertical handoff [3] is roaming to an overlay with a larger cell size and lower bandwidth such asWANs cellular networks, and a downward vertical handoff is roaming to an overlay with a smaller cell size and larger bandwidth. Downward vertical handoffs are less time critical, since a mobile device can always remain connected to the upper overlay and not handoff at all. 有两种垂直切换类型向上和向下。向上垂直切换[3]是漫游到一个覆盖更大带宽?#31995;?#30340;区域如蜂窝网络,向下垂直切换是漫游到一个覆盖更小带宽较大的区域。向下垂直切换的时间急迫性较小,因为移动设备能总是保持同更大覆盖网络的连接而可以不切换。 SEAMLESS HANDOFF In one of the revolutionary drivers for 4G, technologies will complement each other to provide ubiquitous high-speed wireless connectivity to mobile terminals [4]. In such an environment, it will be necessary to support seamless handoffs of mobile terminals without causing disruption to their ongoing sessions. As a result, the need for seamless handoff across the different wireless networks is becoming increasingly

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