外文翻译一种新型的移动ADHOC网络跨层服务质量模型

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1、一种新型的移动AD HOC网络跨层服务质量模型 王磊春，陈实宏，肖坤，胡瑞敏 国家多媒体软件工程研究的中心，武汉大学 武汉430072 ，中国，湖北电子邮件： wlc2345702 摘要分层协议的体系结构只能为移动Ad Hoc网络（简称MANETs ）提供部分堆栈。这给移动Ad Hoc网络中的多媒体通信的质量保证带来了很大的困难。为了改进移动Ad Hoc网络中的多媒体信息传输的服务质量，本文将介绍一种针对移动Ad Hoc网络的跨层服务质量模型-CQMM。CQMM的一个核心组件是网络状态储存库(NSR)，它是信息交换的中心，而且能在堆栈中的不同协议层之间共享。同时，CQMM能够实现所有标准的Qo

2、S 控制。另外，CQMM还能消除堆栈中不同协议层之间的冗余功能，并有效的执行QoS控制和网络性能的全面改善。关键字 跨层QoS模型，移动Ad Hoc网络（MANETs） ，网络状态储存库（NSR），QoS控制。1、 引言随着多媒体技术的快速发展，和个人通信带宽的增加，音频和视频服务已开始在MANETs中出现。与静态网络和因特网不同的是，MANETs中的多媒体通信，如音频和视频服务，它们对QoS的保证有非常严的要求，特别是延迟的保证。此外，具有不同QoS要求用户之间的通信可以集成服务。这给MANETs.多媒体通信的QoS保证提出了很大的挑战。主要有两个原因：1 ）MANETs是在一种传统的无线环

3、境下运行的，即，该环境随时间而变化，具有不可靠的物理链接、广播频道和动态的有限的带宽，等等。因此，它只能为有严格QoS要求的被区分的服务提供有限的能力 1 . 2 ）由于MANETs的灵活性，多级跳以及自组性，因而，传 统 的流动项目和访问控制机制就非常难以实现。 目前，我国大部分基于MANETs传统的多层协议结构的QoS研究都侧重于支持QoS 2 的MAC协议， QoS路由协议 3 和与QoS支持 4 适应的应用层协议，等等。但，这无法避免堆栈中不同协议层之间会出现冗余。这会增加QoS实施的复杂性，并且给网络性能的整体改进造成困难。因此，MANETs必须具备较高的处理能力。近年来，基于MAN

4、ETs部份协议层的跨层设计得到了很大发展。 1 提出了网络层与MAC层交换信息而产生的异构流的机制，并有QoS保证。 5,6,7,8 主要是研究在保证QoS的前提下，在MANETs.中如何通过少层之间的信息交换与协作而实现视频通信。这些在某种程度上可以改进MANETs.通信的服务质量。然而MANETs.比有线系统和静态网络复杂得多，而且QoS保证的改善取决于协议栈中所有层的充分合作。因此，在MANETs.中很难设计一种能为通信与网络性能的改进提供有效的QoS保证的方案。为了充分的利用有限的资源和MANETs整体性能的最优化，本文将介绍一种新型的跨层QoS模型，CQMM，即不同层次可以充分交换信

5、息，还可以执行统一的QoS管理和控制。本文剩下内容将作如下安排： 第2部分仔细介绍CQMM。第3部分，我们将通过与DQMM的对比来分析CQMM。第4部分将对全文给与总结。.2. 移动AD HOC网络跨层服务质量模型-CQMM2.1 CQMM结构目前，在移动AD HOC网络中大部分的QoS研究都是基于传统的分层协议架构，支持QoS的信号和算法是在不同层次分别地设计和实施的。例如，在数据链路层 9 的支持QoS的MAC协议，在网络层 10.11 支持QoS路由协议，等等。它可以被归纳为一个移动AD HOC网络多层次的QoS模型， DQMM（见图1 ） 。 应用约束层次状态QoS 控制(QoS 应用

6、层要求)传送约束层次状态网络约束层次状态数据传输约束层次状态物理约束层次状态QoS 控制 (传输控制和比率控制)QoS 控制（队列与缓冲器管理, 拥塞控制）QoS控制(错误控制和信道管理)QoS控制(媒体调频选择)在DQMM中 ，协议栈里的不同层设计是独立设计与工作的。在逻辑上相邻的不同层之间只有静态的接触;每个协议层有一定的QoS的，如在逻辑链路层误差控制，网络中的拥塞控制等。一方面， DQMM可以极大简化MANETs设计，并增加了高可靠性和扩展性的协议。另一方面， DQMM也有一些不足之处： 1） 由于不同的协议层间独立设计，因此堆栈中不同协议层会存在功能上的冗余。2 ） 由于逻辑上不相邻

7、的层与层之间信息交换十分困难，从而引起了在统一的管理，QoS控制，网络性能的改善方面的许多问题。Fig 2因此，当试图最优化MANETs.各层的性能时，有必要把更多地注意力集中物理层、数据链路层、网络层和较高的层之间的协作。为此，我们结合分散在不同层次参数，设计了一种新型的跨层QoS模型， CQMM，以改善QoS保证和网络的整体性能。CQMM的结构如图2 图2从图2 ，我们可以看出CQMM保持了堆栈中每个协议层的核心功能和相关独立性，为保持模块机构的优势，它还允许逻辑上相邻的两个层之间的直接信息交换。在这些基础上，CQMM还增加了一个核心组件，网络状态储存库(简称 NSR)。NSR是核心，通过

8、它，不同层之间可以充分地交换和共享信息。一方面，通过NSR,每个协议层能够知道其它协议层的状态信息，并决定自己的功能与执行机制。另一方面，每个协议层在NSR上注明自己的状态信息以供协议栈的其它层查询。在CQMM，逻辑上相邻的协议层之间通过NSR可以直接或间接的交换信息，而那些逻辑上不相邻的协议层之间通过NSR用跨层的方法也可以交换信息。因此，在CQMM中，信息交换是非常灵活的。CQMM的各种QoS控制都不是独立的进行的，如网络资源管理和调度、网络寿命、差错控制、拥塞控制和性能优化等。与此相反， 通过堆栈中各协议层之间的协作，CQMM负责统一管理和所有QoS控制。MANETs中的每个QoS控制与

9、协议栈的所有层都相关，同时也受到它们的限制。QoS操作和管理的所有结果都要反馈给所有的层，并写进NSR成为MANETs.所有QoS控制的参数。2.2的协议设计CQMM协议设计着眼于各协议层之间信息的自由、充分交换和协作不会出现功能上的冗余，同时又能保持各协议层之间的相关独立性和模结构的优势。物理层：物理层负责数据的调制，传输与接收，同时也决定MANETs各节点大小、成本和能源消耗。在CQMM ，物理层的设计是根据执行成本，能量的大小和限制，以及高层的QoS要求，选择低成本，低耗能，低复杂度和大信道能力的传输介质、频率范围、调制算法。数据链路层：该层处于协议栈是低层，可分为两个子层：逻辑连接子层

10、和MAC子层。相对于高层，数据链路层可以较早感知MANETs中的网络状态，如频道质量更改，网络拥塞等。因此，一方面是数据链路层能够执行基本QoS的控制，如误差控制和交流频道管理。另一方面，可以与高层次相互结合，建立、选择和维护更快速度的路由，较早预防网络阻塞，并为传输层选择适当的传输机制和控制战略。网络层：CQMM网络层协议的设计和实施是为了建立，选择，维持适当的路由，同时考虑路由中每个节点的耗能，高速缓存和可靠性。QoS需要较高层的服务，如带宽、延迟，较低层次的实施策略，如逻辑连接子层的错误控制机制，物理层子层的频道管理的方法。传输层：CQMM传输层协议的设计需要同时考虑低层的功能与执行机制

11、，如数据链路层的错误控制方法，网络层路由的建立、选择、维持的方法，决定相应传输策略的来至应用层的QoS要求。应用层：有两种不同的应用层设计策略： 1 ）区分服务：按照各低层次所提供的职能划分为不同的优先等级。2 ）应用智能设计：分析不同应用程序的具体要求，如带宽，时延和twitter时延等，然后根据协议栈各层的要求分配和执行相应的功能。2.3 CQMM 的QoS合作与管理QoS合作和管理的核心是作为协议栈里信息状态交流和共享中心的NSR，通过不同协议层之间网络状态的充分交流与共享，网络资源的管理和调度，以及网络性能的整体优化都能够有效地实现。其中包括网络资源的管理与调度，跨层QoS 协作和网络

12、性能的整体优化。网络资源的管理和调度：网络资源包括各种资源，例如高速缓存，每一个节点能力和队列，节点之间的通信频道，等等。在CQMM中，为了增加各种通信QoS，网络资源的管理和调度并不是统一的，有限的资源也不是完全利用的。QoS的合作和控制：在CQMM中 ，各种QoS的控制和合作，例如，比率调整，延迟保证和拥塞控制等，都并不是由各层单独实现的，而是协议栈各层相互协作完成的。举例来说，通过个协议层的协作，如物理子层的ACK，网络层的路由信息、包的丢失率和延时，传输层的比率调整信息等等，MANETs的拥塞可以较早地被预防和控制。性能优化：在CQMM中 ，网络性能的优化主要目的是建立一个由协议结构所

13、有层制约的网络优化模型，并根据这个模型找到一种能够改进MANETs整体新能的方法。3 CQMM分析 目前MANETs 的QoS模型可被归为两类，一类是基于传统层划分结构的DQMM，另一类是本文介绍的跨层QoS模型CQMM。 1,5-8 所使用的QoS模型本质上只是在DQMM基础上一定程度的拓宽。在这里，我们只是比较CQMM与DQMM。 3.1信息交流CQMM 与DQMM协议体系和原则的不同在信息交流的方式，频率，时间，需求也存在很大的区别。（见表1 ） 从表1中可以看出，与DQMM比较 ，CQMM有许多优点： 1 ）更灵活的信息交流 。相邻层可以通过层或NSR之间的接触交换信息，交叉层也可以通

14、过NSR交换信息。2 ）更简单的信息格式变换。不同层之间通过NSR可以交换信息，因此这些层只需要处理层与NSR之间的格式转换问题。3 ）更低的要求。协议层可以从临时存在NSR中的不同协议层适时信息读取它们，因此信息改变的层不必要及时保持同步4 ）更精确地控制。在CQMM中，NSR存储了不同层某些时候的信息，这样更利于准确地掌握网络状态和管理网络。3.2 Protocol Design .3.2协议设计在DQMM 中，由于功能和协议设计上的相互独立性，各层之间在执行可靠的信息传输时不可避免的会出现一些功能上的荣誉。不过，CQMM可以在不同的层之间执行统一的功能分配，并且能通过各层协作支持的QoS

15、实现通信。表1.CQMM与DQMM之间信息交换的对比信息交换对比DQMMCQMM方式临域层:静态交叉层层次接口:中间层临域层:静态 交叉层: NSR频率临域层: 高频交叉层: 低频临域层: 高频交叉层: 高频转换格式临域层: 一次交叉层: 多次各层与NSR之间的转换格式共享层所有的共享层和中间层NSR 和共享层时间需求特殊“有时”同步需求严格同步异步性时间交换稍微大量信息量临域层: 大交叉层: 小临域层大交叉层: 大3.3网络资源和性能优化的管理和调度不同协议层之间缺乏充分的信息交流限制了DQMM网络性能的整体改进。在DQMM中，通过NSR,协议栈里不同层之间能够自由、充分地交换信息，有利于网

16、络资源统一的规划和调度，在整个网络的基础上建立性能优化模型，并做好网络性能整体改善。3.4执行议定成本和复杂性由于栈里每个协议层的相互独立性，不同协议层之间只有较少的接触与信息的交流，因此DQMM需要较低的层本于复杂度。在CQMM中，栈中不同协议层之间自由、充分地交换信息需要：每个节点上上必须增加一个网络状态存储器，并提供替代策略以及时更新状态信息；在每个协议层和NSR交换信息的地方增加接口；建立更复杂的数学模型和控制机制以优化网络性能。这些都会导致CQMM中执行成本和复杂度的增加。相比DQMM ，CQMM能够为协议栈里的不同层提供自由和充分的信息交流，消除不同层之间的功能冗余，更好的实现网络

17、资源的管理域调度，使MANETs.的整体性能最优化。但这些优势都是高成本和高复杂度为代价的4 .结论和未来工作 本文为MANETs.提供了一种新的跨层QoS模型，CQMM。相比DQMM ， CQMM有以下优点： 1 ）通过NSR，协议栈中不同层可以自由、充分地交换信息。 2 ） CQMM.可以消除协议栈中不同层之间的功能冗余层协议栈，并更好地执行网络资源统一管理和调度和网络性能的整体改善。基于CQMM的框架，今后的工作将侧重于跨层协议的设计，跨层控制与QoS合作，用跨层的方法对MANETs性能的整体改善。5. 参考文献【1】L.Wei，X.Chen 等等，“内涵：支持区分在Ad Hoc网络中的

18、多次反射移动”，移动计算，IEEE事物处理，2004.3（4）：380-393.【2】G.Ahn，A.T. 坎贝尔等等，“本地多级无线网络确认支持服务”，美国电气及电子工程师学会全球电讯会议2003，洛杉矶，CA,USA,Dec.2003。【3】GMohsen,无线通讯系统和网络，2004【4】G.Andrea, 无线通讯，剑桥大学出版社，2004【5】W.Kumwilaisak , Y.T.Hou, 等等，一个跨层的品质服务映射架构的视频在无线网络中的传输。【6】Eric Setton,T.Yoo,等等, 跨层设计的Ad Hoc网络实时视频流，无线通讯，美国电气及电子工程师学会，2005,1

19、2(4):59-65.A Novel Cross-layer Quality-of-service ModelFor Mobile AD hoc NetworkLeichun Wang, Shihong Chen, Kun Xiao, Ruimin Hu National Engineering Resarch Center of Multimedia Software, WuhanUniversity Wuhan 430072, Hubei ,china Email:wlc2345702AbstractThe divided-layer protocol architecture for M

20、obile ad hoc Networks(simply MANETs)can only provide partial stack. This leads to treat difficulties in QoS guarantee of multimedia information transmission in MANETs, this paper proposes Across-layers QoS Model for MANETs, CQMM. In CQMM ,a core component was added network status repository(NSR), wh

21、ich was the center of information exchange and share among different protocol layers in the stack. At the same time,CQMM carried out all kinds of unified QoS controls. It is advantageous that CQMM avoids redundancy functions among the different protocol layers in the stack and performs effective QoS

22、 controls and overall improvements on the network performances.Keyword Cross-layers QoS Model, Mobile Ad hoc Networks(MANETs);Network Status Repository(NSR) QoS Controls.1 introductionWith the rapid development of multimedia technologies and the great increase of he bandwidth for personal communicat

23、ion,video and Video services begin to be deployed in MANETs. Different from static networks and Internet,multimedia communications in MANETs such as Voice and Video services require strict QoS guarantee, especially the delay guarantee. In addition, communication among different users can be integrat

24、ed services with different QoS requirements. These lead to great challenges in QoS guarantee of multimedia communication in MANETs. There are two main reasons in these: 1)MANETs runs in atypical wireless environment with time-varying and unreliable physical link, broadcast channel, and dynamic and l

25、imited bandwidth and so forth. Therefore, it can only provide limited capability for differentiated services with strict QoS requirements 1.2) It is difficult that traditional flow project and access control mechanism are implemented because of mobility, multiple hops and self-organization of MANETs

26、. At present, most researches on QoS based on traditional divided-layer protocol architecture for MANETs focus on MAC protocol supporting QoS2,QoS routing protocol 3 and adaptive application layer protocol with QoS support4, and so on. It is avoidless that there will be some redundancies on function

27、s among the different protocol layers in the stack. This will increase the complexity of QoS implementation and cause some difficulties in overall improvement on the network performances. Therefore, it is not suitable for MANETs with low processing ability In recent years, the cross-layers design ba

28、sed on the partial protocol layers in MANETs was put forward.1 proposed the mechanism with QoS guarantee for heterogeneous flow MAC layer.5,6,7,8 did some researches on implementing video communication with QoS guarantee by exchange and cooperation of information among a few layers in MANETs. These

29、can improve QoS in MANETs communication to some extent. However, MANETs is much more complex than wired system and static network, and improvements on QoS guarantee depend on full cooperation among all layers in the protocol stack. Therefore, it is difficult for the design to provide efficient QoS g

30、uarantee for communication and overall improvements on the network performances in MANETs.To make good use of limited resources and optimize overall performances in MANETs, this paper proposes a novel cross-layer QoS model, CQMM, where different layers can exchange information fully and unified QoS

31、managements and controls can be performed. The rest of the paper is organized as follows. CQMM is described in section 2 in detail. In section 3,we analyze CQMM by the comparison with DQMM.The section 4 concludes the paper.2. A CROSS-LAYER QOS MODEL FOR MANETS-CQMM2.1 Architecture of CQMMIn MANETs,

32、present researches on QoS are mostly based on traditional divided-layer protocol architecture, where signals and algorithms supporting QsS are designed and implemented in different layers respectively, such as MAC protocol supporting QoS in data link layer 9, routing protocol with QoS support in net

33、work layer10.11,and so forth. It can be summarized as A Divided-layer QoS Model for MANETs, DQMM (see fig.1). In DQMM, different layers in the protocol stack are designed and work independently; there are only static interfaces between different layers that are neighboring in logic; and each protoco

34、l layer has some QoS controls such as error control in logic link layer, congestion control in network, etc. On the one hand, DQMM can simplify the design of MANETs greatly and gain the protocols with high reliability and extensibility. On the other one, DQMM also has some shortcomings: ) due to the

35、 independent design among he different protocol layers, there are some redundancy functions among the different protocol layers in the stack, 2) it is difficult that information is exchanged among different layers that are not neighboring in logic, which leads to some problems in unified managements

36、, QoS controls and overall improvements on the network performances. Fig.1 Application ConstraintLayer StatusQoS controls (QoS requirements formApplication layer)Transport ConstraintLayer StatusNetwork ConstraintLayer StatusData Link ConstraintLayer StatusPhysical ConstraintLayer StatusQoS controls

37、(transport control and rate control)QoS controls（queue and cache management, congestion control）QoS controls (error control and channel management)QoS controls (selection of media frequency and modulation) Therefore, it is necessary that more attention are focused on the cooperation among physical l

38、ayer data link layer, network layer and higher when attempting to optimize performances of each of layer in MANETs. For this reason, we combine parameters dispersed in different layers and design a novel cross-layer QoS model, CQMM, to improve the QoS guarantee and the overall network performances.

39、The architecture of CQMM is provided in fig 2Fig 2From fig.2 ,it can be seen that CQMM keeps the core functions and relative independence of each protocol layer in the stack and allows direct information exchange between two neighboring layers in logics to maintain advantages of the modular architec

40、ture .On the basic of these , a core component is added in CQMM, Network Status Repository (simply NSR).NSR is the center, by which different layers can exchange and share information fully. On the one hand, each perotocol layer can read the status information of other protocol layers from NSR to de

41、termine its functions and implementation mechanisms. On the other one , each protocol layer can write its status information to NSR that can be provided with other layers in the protocol stack. In CQMM, the protocol layers that are neighboring in logics can exchange information directly or indirectl

42、y by NSR, and the protocol layers that are not neighboring in logics can exchange information using cross-layer ways via NSR. Therefore, information exchange is flexible in CQMM.All kinds of QoS controls in CQMM such as management and scheduling of network resources, network lifetime, error control,

43、 and congestion control and performance optimization and so on, are not carried out independently. On the contrary, CQMM is in charge of the unified management and all QoS controls by the cooperation among different protocol layers in the stack. Each QoS control in MANETs is related to all layers in

44、 the protocol stack, and also constrained by all layers in the stack. The results of all QoS operations and managements are fed back to the different layers and written back to NSR, which will become the parameters of all kinds of QoS controls in MANETs.2.2 protocol design in CQMM In CQMM, the proto

45、col designs aims at the full and free information exchange and cooperation among different protocol layers to avoid possible redundancy functions when maintaining the relative independence among different layers and the advantages of the modular architecture.Physical layer: Physical layer is respons

46、ible for modulation , transmission and receiving of data ,and also the key to the size, the cost and the energy consumption of each node in MANETs. In CQMM,the design of physical layer is to choose the transmission media, the frequency range and the modulation algorithm wit the low cost, power and c

47、omplexity, big channel capability and so on, according to the cost of implementation, energy constraint, and capability and QoS requirements from high layer.Data link layer: The layer is low layer in the protocol stack and can be divided into two sub-layers: logic link sub-layer and MAC sub-layer. C

48、ompared with high layers, data link layer can sense network status in MANETs earlier such as the change of channel quality, the network congestion and so on. Therefore, on the one hand data link layer can perform the basic QoS controls such as error control and management of communication channel. O

49、n the other one, the layer can be combined with high layers to establish, choose and maintain the routing faster , prevent the congestion of the network earlier, and choose appropriate transport mechanisms and control strategies for transport layer.Network layer: The design and implementation of net

50、work layer protocol in CQMM is to establish, choose and maintain appropriate routings by taking into consideration the power, the cache, the reliability of each node in a routing. QoS requirements of services from high layer such as the bandwidth and the delay, and implementation strategies of error

51、 control in logic link sub-layer and the way of the channel management in MAC sub-layer.Transport layer: In CQMM , the protocol design of transport layer needs to be aware of both functions and implementation mechanism of lower layers such as the way of error control in data link layer , the means t

52、o establish, choose and maintain routing in the network layer, and QoS requirements from the application layer, to determine corresponding transmission strategies. In addition, the transport layer also needs to analyze all kinds of events from low layers such as the interrupt and change of the routi

53、ng and the network congestion, and then respond properly to avoid useless sending data.Application layer: There are two different strategies in the design of the application layer:1)differentiated services. According to the functions provided by the low layers applications are classed as the differe

54、nt ones with different priority levels. 2) Application-aware design. Analyze specific requirements of different applications such as the bandwidth, the delay and the delay twitter and so on, and then assign and implement the functions for each layer in the protocol stack according to the requirement

55、s.2.3 QoS Cooperation and Management in CQMMIn CQM, the core of QoS cooperation and management is that NSR acts as the exchange and share center of status information in protocol stack, and by the full exchange and share of network status among different protocol layers the management and scheduling

56、 of the network resources and the overall optimization of the network performances can be implemented effectively. The management and scheduling of the network resources, the cross-layer QoS cooperation and the overall optimization of the network performances.Management and scheduling of network res

57、ources: Network resources include all kinds of resources such as the cache, the energy and the queue in each node, and the communication channel among nodes and so froth. In CQMM, the management and scheduling of the network resources are not to the unified management and scheduling of the network r

58、esources and full utilization of limited resources in order to increase the QoS of all kinds of communication.QoS cooperation and control: In CQMM, all kinds of QoS controls and cooperation such as the rate adaptation, the delay guarantee and the congestion control and so on, are not implemented by

59、each layer alone, but completed through the operation of all layers in the protocol stack. For example, the congestion in MANETs can be earlier prevented and controlled by the cooperation among different layers such as ACK from MAC sub-layer, the routing information and the loss rate and delay of pa

60、ckage from network layer, and the information of rate adaptation in transport layer and so on. Performances Optimization: In CQMM, the optimization of the network performances aims to establish a network optimization model constrained by all layers in the protocol architecture and finds the “best” w

61、ays according to the model in order to improve the overall performances in MANETs.3ANALYSIS OF CQMMPresent QoS models for MANETs can mainly be classed as a QoS model based on traditional divided-layer architecture DQMM and a cross-layer QoS model proposed by this paper CQMM. QoS model used by 1,5-8

62、is to some extent extended on the basis of DQMM in nature. Here,. We only compare CQMM with DQMM3.1 Information Exchange Different protocol architecture and principle between CQMM lead to great differences in the means, the frequency, the time and the requirement of the information exchange,(see tab

63、le 1) From Table 1, it can be seen that compared wit DQMM CQMM has some advantages:1) more flexible information exchange,. Neighboring layers can information by the interfaces between layers or NSR, and crossing layers may exchange information through NSR; 2) simpler transform in information format.

64、 Different layers can exchange information by NSR, so these layers only need to deal with the format transform between the layers and NSR;3)lower requirements. The protocol layers can read them in proper time Information from different protocol layers temporarily stored in NSR, so the layers exchanging information are not required to be synchronous in time;4)