外文翻譯----一種新型的移動(dòng)ad hoc網(wǎng)絡(luò)跨層服務(wù)質(zhì)量模型

1、<p>　　A Novel Cross-layer Quality-of-service Model</p><p>　　For Mobile AD hoc Network</p><p>　　Leichun Wang, Shihong Chen, Kun Xiao, Ruimin Hu</p><p>　　National Engineering Res

2、arch Center of Multimedia Software, WuhanUniversity</p><p>　　Wuhan 430072, Hubei ,china</p><p>　　Email:wlc2345702@163.com</p><p><b>　　Abstract</b></p><p>　　

3、The divided-layer protocol architecture for Mobile 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 pa

4、per proposes Across-layers QoS Model for MANETs, CQMM. In CQMM ,a core component was added network status repository(NSR), which was the center of information exchange and share among different protocol layers in the sta

5、ck. At the same time,CQMM carried out all kinds of unified </p><p>　　Keyword Cross-layers QoS Model, Mobile Ad hoc Networks(MANETs);Network Status Repository(NSR) QoS Controls.</p><p>　　1 intro

6、duction</p><p>　　With the rapid development of multimedia technologies and the great increase of he bandwidth for personal communication,video and Video services begin to be deployed in MANETs. Different fro

7、m 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 in

8、tegrated services with different QoS requirements. These lead to great challenges in QoS g</p><p>　　At present, most researches on QoS based on traditional divided-layer protocol architecture for MANETs focu

9、s on MAC protocol supporting QoS[2],QoS routing protocol [3] and adaptive application layer protocol with QoS support[4], and so on. It is avoidless that there will be some redundancies on functions among the different p

10、rotocol layers in the stack. This will increase the complexity of QoS implementation and cause some difficulties in overall improvement on the network performances. Therefor</p><p>　　In recent years, the cro

11、ss-layers design based 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 communica

12、tion with QoS guarantee by exchange and cooperation of information among a few layers in MANETs. These can improve QoS in MANETs’ communication to some extent. However, MANETs is much more complex than wired system and s

13、tatic network, and improvements on Q</p><p>　　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 layer

14、s can exchange information fully and unified QoS managements and controls can be performed.</p><p>　　The rest of the paper is organized as follows. CQMM is described in section 2 in detail. In section 3,we a

15、nalyze CQMM by the comparison with DQMM..The section 4 concludes the paper.</p><p>　　2. A CROSS-LAYER QOS MODEL FOR MANETS-CQMM</p><p>　　2.1 Architecture of CQMM</p><p>　　In MANETs,

16、 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 proto

17、col supporting QoS in data link layer [9], routing protocol with QoS support in network layer[10.11],and so forth. It can be summarized as A Divided-layer QoS Model for MANETs, DQMM (see fig.1).</p><p>　　In

18、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 protocol layer has some QoS controls suc

19、h 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

20、, DQMM also has some shortcomings: ) due to the independe</p><p>　　Fig..1 </p><p>　　Therefore, it is necessary that more attention are focused on the cooperation among physical layer d

21、ata 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,

22、 CQMM, to improve the QoS guarantee and the overall network performances. The architecture of CQMM is provided in fig 2</p><p><b>　　Fig 2</b></p><p>　　From fig.2 ,it can be seen that

23、 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

24、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 perotoc

25、ol layer can read the status </p><p>　　All kinds of QoS controls in CQMM such as management and scheduling of network resources, network lifetime, error control, and congestion control and performance optimi

26、zation 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

27、MANETs is related to all layers in the protocol stack, and also constrained by all layers in the stack. The resu</p><p>　　2.2 protocol design in CQMM </p><p>　　In CQMM, the protocol designs aims

28、 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 th

29、e modular architecture.</p><p>　　Physical layer: Physical layer is responsible for modulation , transmission and receiving of data ,and also the key to the size, the cost and the energy consumption of each

30、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 complexity, big channel capability and so on, accordi

31、ng to the cost of implementation, energy constraint, and capability and QoS requirements from high layer.</p><p>　　Data link layer: The layer is low layer in the protocol stack and can be divided into two su

32、b-layers: logic link sub-layer and MAC sub-layer. Compared 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,

33、on the one hand data link layer can perform the basic QoS controls such as error control and management of communication channel. On the other one, the layer can be combined with high laye</p><p>　　Network l

34、ayer: The design and implementation of network 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

35、. QoS requirements of services from high layer such as the bandwidth and the delay, and implementation strategies of error control in logic link sub-layer and the way of the channel management in MAC sub-layer.</p>

36、<p>　　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 m

37、eans to 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 ana

38、lyze all kinds of events from low layers such as the interrupt and change</p><p>　　Application layer: There are two different strategies in the design of the application layer:1)differentiated services. Acco

39、rding to the functions provided by the low layers applications are classed as the different ones with different priority levels. 2) Application-aware design. Analyze specific requirements of different applications such a

40、s 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 th</p><p>　　2.3 QoS Cooperation and Management in CQM

41、M</p><p>　　In 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 a

42、mong different protocol layers the management and scheduling of the network resources and the overall optimization of the network performances can be implemented effectively. The management and scheduling of the network

43、 resources, the cross-layer QoS cooperation and the overall optimization of the netw</p><p>　　Management and scheduling of network resources: Network resources include all kinds of resources such as the cach

44、e, 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 ne

45、twork resources and full utilization of limited resources in order to increase the QoS of all kinds of communication.</p><p>　　QoS cooperation and control: In CQMM, all kinds of QoS controls and cooperation

46、such as the rate adaptation, the delay guarantee and the congestion control and so on, are not implemented by each layer alone, but completed through the operation of all layers in the protocol stack. For example, the co

47、ngestion 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 package from</p><p>

48、;　　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” ways accordin

49、g to the model in order to improve the overall performances in MANETs.</p><p>　　3ANALYSIS OF CQMM</p><p>　　Present QoS models for MANETs can mainly be classed as a QoS model based on traditional

50、 divided-layer architecture DQMM and a cross-layer QoS model proposed by this paper CQMM. QoS model used by [1,5-8] is to some extent extended on the basis of DQMM in nature. Here,. We only compare CQMM with DQMM</p&g

51、t;<p>　　3.1 Information Exchange </p><p>　　Different protocol architecture and principle between CQMM lead to great differences in the means, the frequency, the time and the requirement of the informa

52、tion exchange,(see table 1)</p><p>　　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

53、between layers or NSR, and crossing layers may exchange information through NSR; 2) simpler transform in information format. Different layers can exchange information by NSR, so these layers only need to deal with the fo

54、rmat transform between the layers and NSR;3)lower requirements. The protocol layers can read them in proper ti</p><p>　　3.2 Protocol Design </p><p>　　In DQMM, it is inevitable that there are som

55、e redundancy functions among different protocol layers for implementing reliable information transmission because of the independence in function and protocol design. However, CQMM can perform unified function assignatio

56、n among different layers and implement communication with QoS support by the cooperation among the different layers.</p><p>　　Table 1. Comparisons of information exchange between CQMM and DQMM</p><

57、;p>　　3.3 management and scheduling of network resources and performances optimization </p><p>　　The lack in full information exchange among different protocol layers in the stack limits the overall impro

58、vements on the network performances in DQMM. In the protocol stack can exchange information freely and fully through NSR. Which benefits unified planning and scheduling of the network resources establishing performance o

59、ptimization model based on the whole network, and performing the overall improvements on the network performances.</p><p>　　3.4 cost and complexity of implementing protocols </p><p>　　Due to the

60、 independence of each protocol layer in the stack, there are less interfaces and information exchange among different layers protocol layers of the stack requires: add NSR in each node to store network status and provide

61、 replacing strategies to u date status information in time; increase interfaces where each protocol layer and NSR exchange information; establish more complex mathematics model and control mechanism to optimize network p

62、erformances. There lead to the increase of the imp</p><p>　　Compared with DQMM, CQMM can provide free and full information exchange for different layers in the protocol stack, eliminate redundancy functions

63、among the different layers, better realize the management and scheduling of the network resources, and optimize overall performances in MANETs. There advantages are at the cost of higher cost and complexity.</p>&

64、lt;p>　　4. conclusions and future work</p><p>　　This paper provides a new cross-layer QoS model for MANETs,, CQMM. Compared with DQMM, CQMM has the following advantages:1) different layers in the protocol

65、 stack can exchange information freely and fully through NSR:2) CQMM layers in the protocol stack, and better implement different unified management and scheduling of the network resources, and the overall improvements o

66、n the network performances. On the basis of CQMM framework, future work will focus on the design of the cross—layer protocol</p><p>　　一種新型的移動(dòng)AD HOC網(wǎng)絡(luò)跨層服務(wù)質(zhì)量模型 王磊春，陳實(shí)宏，肖坤，胡瑞敏 &

67、#160;       國(guó)家多媒體軟件工程研究的中心，，武漢大學(xué)                       武漢430072

68、 ，中國(guó)，湖北                      電子郵件： wlc2345702@163.com 摘要</p><p>　　分層協(xié)議的體系結(jié)構(gòu)只能為移動(dòng)Ad Hoc網(wǎng)絡(luò)（簡(jiǎn)稱MANE

69、Ts ）提供部分堆棧。這給移動(dòng)Ad Hoc網(wǎng)絡(luò)中的多媒體通信的質(zhì)量保證帶來(lái)了很大的困難。為了改進(jìn)移動(dòng)Ad Hoc網(wǎng)絡(luò)中的多媒體信息傳輸?shù)姆?wù)質(zhì)量，本文將介紹一種針對(duì)移動(dòng)Ad Hoc網(wǎng)絡(luò)的跨層服務(wù)質(zhì)量模型—-CQMM。CQMM的一個(gè)核心組件是網(wǎng)絡(luò)狀態(tài)儲(chǔ)存庫(kù)(NSR)，它是信息交換的中心，而且能在堆棧中的不同協(xié)議層之間共享。同時(shí)，CQMM能夠?qū)崿F(xiàn)所有標(biāo)準(zhǔn)的QoS 控制。另外，CQMM還能消除堆棧中不同協(xié)議層之間的冗余功能，并有效的執(zhí)行QoS

70、控制和網(wǎng)絡(luò)性能的全面改善。</p><p>　　關(guān)鍵字 跨層QoS模型，移動(dòng)Ad Hoc網(wǎng)絡(luò)（MANETs） ，網(wǎng)絡(luò)狀態(tài)儲(chǔ)存庫(kù)（NSR），QoS控制。</p><p>　　1、 引言隨著多媒體技術(shù)的快速發(fā)展，和個(gè)人通信帶寬的增加，音頻和視頻服務(wù)已開(kāi)始在MANETs中出現(xiàn)。與靜態(tài)網(wǎng)絡(luò)和因特網(wǎng)不同的是，MANETs中的多媒體通信，如音頻和視頻服務(wù)，它們對(duì)QoS的保證有非常嚴(yán)的要求，特別是延

71、遲的保證。此外，具有不同QoS要求用戶之間的通信可以集成服務(wù)。這給MANETs.多媒體通信的QoS保證提出了很大的挑戰(zhàn)。主要有兩個(gè)原因：1 ）MANETs是在一種傳統(tǒng)的無(wú)線環(huán)境下運(yùn)行的，即，該環(huán)境隨時(shí)間而變化，具有不可靠的物理鏈接、廣播頻道和動(dòng)態(tài)的有限的帶寬，等等。因此，它只能為有嚴(yán)格QoS要求的被區(qū)分的服務(wù)提供有限的能力 [ 1 ]. 2 ）由于MANETs的靈活性，多級(jí)跳以及自組性，因而，傳 統(tǒng) 的流動(dòng)項(xiàng)目和訪問(wèn)控制機(jī)制就非常難以

72、實(shí)現(xiàn)。</p><p>　　目前，我國(guó)大部分基于MANETs傳統(tǒng)的多層協(xié)議結(jié)構(gòu)的QoS研究都側(cè)重于支持QoS [ 2 ]的MAC協(xié)議， QoS路由協(xié)議[ 3 ]和與QoS支持[ 4 ]適應(yīng)的應(yīng)用層協(xié)議，等等。但，這無(wú)法避免堆棧中不同協(xié)議層之間會(huì)出現(xiàn)冗余。這會(huì)增加QoS實(shí)施的復(fù)雜性，并且給網(wǎng)絡(luò)性能的整體改進(jìn)造成困難。因此，MANETs必須具備較高的處理能力。</p><p>　　近年來(lái)，基于

73、MANETs部份協(xié)議層的跨層設(shè)計(jì)得到了很大發(fā)展。 [ 1 ]提出了網(wǎng)絡(luò)層與MAC層交換信息而產(chǎn)生的異構(gòu)流的機(jī)制，并有QoS保證。 [ 5,6,7,8 ]主要是研究在保證QoS的前提下，在MANETs.中如何通過(guò)少層之間的信息交換與協(xié)作而實(shí)現(xiàn)視頻通信。這些在某種程度上可以改進(jìn)MANETs.通信的服務(wù)質(zhì)量。然而MANETs.比有線系統(tǒng)和靜態(tài)網(wǎng)絡(luò)復(fù)雜得多，而且QoS保證的改善取決于協(xié)議棧中所有層的充分合作。因此，在MANETs.中很難設(shè)計(jì)一種

74、能為通信與網(wǎng)絡(luò)性能的改進(jìn)提供有效的QoS保證的方案。</p><p>　　為了充分的利用有限的資源和MANETs整體性能的最優(yōu)化，本文將介紹一種新型的跨層QoS模型，CQMM，即不同層次可以充分交換信息，還可以執(zhí)行統(tǒng)一的QoS管理和控制。 </p><p>　　本文剩下內(nèi)容將作如下安排： 第2部分仔細(xì)介紹CQMM。第3部分，我們將通過(guò)與DQMM的對(duì)比來(lái)分析CQMM。第4部分將對(duì)

75、全文給與總結(jié)。</p><p><b>　　.</b></p><p>　　移動(dòng)AD HOC網(wǎng)絡(luò)跨層服務(wù)質(zhì)量模型--CQMM2.1 CQMM結(jié)構(gòu)目前，在移動(dòng)AD HOC網(wǎng)絡(luò)中大部分的QoS研究都是基于傳統(tǒng)的分層協(xié)議架構(gòu)，支持QoS的信號(hào)和算法是在不同層次分別地設(shè)計(jì)和實(shí)施的。例如，在數(shù)據(jù)鏈路層[ 9 ]的支持QoS的MAC協(xié)議，在網(wǎng)絡(luò)層[ 10.11 ] 支持QoS

76、路由協(xié)議，等等。它可以被歸納為一個(gè)移動(dòng)AD HOC網(wǎng)絡(luò)多層次的QoS模型， DQMM（見(jiàn)圖1 ） 。 </p><p>　　在DQMM中 ，協(xié)議棧里的不同層設(shè)計(jì)是獨(dú)立設(shè)計(jì)與工作的。在邏輯上相鄰的不同層之間只有靜態(tài)的接觸;每個(gè)協(xié)議層有一定的QoS的，如在邏輯鏈路層誤差控制，網(wǎng)絡(luò)中的擁塞控制等。一方面， DQMM可以極大簡(jiǎn)化MANETs設(shè)計(jì)，并增加了高可靠性和擴(kuò)展性的協(xié)議。另一方面， DQMM也有一些不足之處： 1）

77、 由于不同的協(xié)議層間獨(dú)立設(shè)計(jì)，因此堆棧中不同協(xié)議層會(huì)存在功能上的冗余。2 ） 由于邏輯上不相鄰的層與層之間信息交換十分困難，從而引起了在統(tǒng)一的管理，QoS控制，網(wǎng)絡(luò)性能的改善方面的許多問(wèn)題。</p><p><b>　　Fig 2</b></p><p>　　因此，當(dāng)試圖最優(yōu)化MANETs.各層的性能時(shí)，有必要把更多地注意力集中物理層、數(shù)據(jù)鏈路層、網(wǎng)絡(luò)層和較高的層之

78、間的協(xié)作。為此，我們結(jié)合分散在不同層次參數(shù)，設(shè)計(jì)了一種新型的跨層QoS模型， CQMM，以改善QoS保證和網(wǎng)絡(luò)的整體性能。CQMM的結(jié)構(gòu)如圖2 圖2</p><p>　　從圖2 ，我們可以看出CQMM保持了堆棧中每個(gè)協(xié)議層的核心功能和相關(guān)獨(dú)立性，為保持模塊機(jī)構(gòu)的優(yōu)勢(shì)，它還允許邏輯上相鄰的兩個(gè)層之間的直接信息交換。在這些基礎(chǔ)上，CQMM還增加了一個(gè)核心組件，網(wǎng)絡(luò)狀態(tài)儲(chǔ)存庫(kù)(簡(jiǎn)稱 NSR)。NSR是核心，通過(guò)它，

79、不同層之間可以充分地交換和共享信息。一方面，通過(guò)NSR,每個(gè)協(xié)議層能夠知道其它協(xié)議層的狀態(tài)信息，并決定自己的功能與執(zhí)行機(jī)制。另一方面，每個(gè)協(xié)議層在NSR上注明自己的狀態(tài)信息以供協(xié)議棧的其它層查詢。在CQMM，邏輯上相鄰的協(xié)議層之間通過(guò)NSR可以直接或間接的交換信息，而那些邏輯上不相鄰的協(xié)議層之間通過(guò)NSR用跨層的方法也可以交換信息。因此，在CQMM中，信息交換是非常靈活的。</p><p>　　CQMM的各種Qo

80、S控制都不是獨(dú)立的進(jìn)行的，如網(wǎng)絡(luò)資源管理和調(diào)度、網(wǎng)絡(luò)壽命、差錯(cuò)控制、擁塞控制和性能優(yōu)化等。與此相反， 通過(guò)堆棧中各協(xié)議層之間的協(xié)作，CQMM負(fù)責(zé)統(tǒng)一管理和所有QoS控制。MANETs中的每個(gè)QoS控制與協(xié)議棧的所有層都相關(guān)，同時(shí)也受到它們的限制。QoS操作和管理的所有結(jié)果都要反饋給所有的層，并寫(xiě)進(jìn)NSR成為MANETs.所有QoS控制的參數(shù)。</p><p><b>　　2.2的協(xié)議設(shè)計(jì)</b&g

81、t;</p><p>　　CQMM協(xié)議設(shè)計(jì)著眼于各協(xié)議層之間信息的自由、充分交換和協(xié)作不會(huì)出現(xiàn)功能上的冗余，同時(shí)又能保持各協(xié)議層之間的相關(guān)獨(dú)立性和模結(jié)構(gòu)的優(yōu)勢(shì)。</p><p>　　物理層：物理層負(fù)責(zé)數(shù)據(jù)的調(diào)制，傳輸與接收，同時(shí)也決定MANETs各節(jié)點(diǎn)大小、成本和能源消耗。在CQMM ，物理層的設(shè)計(jì)是根據(jù)執(zhí)行成本，能量的大小和限制，以及高層的QoS要求，選擇低成本，低耗能，低復(fù)雜度和大信道

82、能力的傳輸介質(zhì)、頻率范圍、調(diào)制算法。</p><p>　　數(shù)據(jù)鏈路層：該層處于協(xié)議棧是低層，可分為兩個(gè)子層：邏輯連接子層和MAC子層。相對(duì)于高層，數(shù)據(jù)鏈路層可以較早感知MANETs中的網(wǎng)絡(luò)狀態(tài)，如頻道質(zhì)量更改，網(wǎng)絡(luò)擁塞等。因此，一方面是數(shù)據(jù)鏈路層能夠執(zhí)行基本QoS的控制，如誤差控制和交流頻道管理。另一方面，可以與高層次相互結(jié)合，建立、選擇和維護(hù)更快速度的路由，較早預(yù)防網(wǎng)絡(luò)阻塞，并為傳輸層選擇適當(dāng)?shù)膫鬏敊C(jī)制和控制戰(zhàn)

83、略。</p><p>　　網(wǎng)絡(luò)層：CQMM網(wǎng)絡(luò)層協(xié)議的設(shè)計(jì)和實(shí)施是為了建立，選擇，維持適當(dāng)?shù)穆酚?，同時(shí)考慮路由中每個(gè)節(jié)點(diǎn)的耗能，高速緩存和可靠性。QoS需要較高層的服務(wù)，如帶寬、延遲，較低層次的實(shí)施策略，如邏輯連接子層的錯(cuò)誤控制機(jī)制，物理層子層的頻道管理的方法。</p><p>　　傳輸層：CQMM傳輸層協(xié)議的設(shè)計(jì)需要同時(shí)考慮低層的功能與執(zhí)行機(jī)制，如數(shù)據(jù)鏈路層的錯(cuò)誤控制方法，網(wǎng)絡(luò)層路由的建

84、立、選擇、維持的方法，決定相應(yīng)傳輸策略的來(lái)至應(yīng)用層的QoS要求。。</p><p>　　應(yīng)用層：有兩種不同的應(yīng)用層設(shè)計(jì)策略： 1 ）區(qū)分服務(wù)：按照各低層次所提供的職能劃分為不同的優(yōu)先等級(jí)。2 ）應(yīng)用智能設(shè)計(jì)：分析不同應(yīng)用程序的具體要求，如帶寬，時(shí)延和twitter時(shí)延等，然后根據(jù)協(xié)議棧各層的要求分配和執(zhí)行相應(yīng)的功能。</p><p>　　2.3 CQMM 的QoS合作與管理</p&

85、gt;<p>　　QoS合作和管理的核心是作為協(xié)議棧里信息狀態(tài)交流和共享中心的NSR，通過(guò)不同協(xié)議層之間網(wǎng)絡(luò)狀態(tài)的充分交流與共享，網(wǎng)絡(luò)資源的管理和調(diào)度，以及網(wǎng)絡(luò)性能的整體優(yōu)化都能夠有效地實(shí)現(xiàn)。其中包括網(wǎng)絡(luò)資源的管理與調(diào)度，跨層QoS 協(xié)作和網(wǎng)絡(luò)性能的整體優(yōu)化。</p><p>　　網(wǎng)絡(luò)資源的管理和調(diào)度：網(wǎng)絡(luò)資源包括各種資源，例如高速緩存，每一個(gè)節(jié)點(diǎn)能力和隊(duì)列，節(jié)點(diǎn)之間的通信頻道，等等。在CQMM中，

86、為了增加各種通信QoS，網(wǎng)絡(luò)資源的管理和調(diào)度并不是統(tǒng)一的，有限的資源也不是完全利用的。</p><p>　　QoS的合作和控制：在CQMM中 ，各種QoS的控制和合作，例如，比率調(diào)整，延遲保證和擁塞控制等，都并不是由各層單獨(dú)實(shí)現(xiàn)的，而是協(xié)議棧各層相互協(xié)作完成的。舉例來(lái)說(shuō)，通過(guò)個(gè)協(xié)議層的協(xié)作，如物理子層的ACK，網(wǎng)絡(luò)層的路由信息、包的丟失率和延時(shí)，傳輸層的比率調(diào)整信息等等，MANETs的擁塞可以較早地被預(yù)防和控制。

87、</p><p>　　性能優(yōu)化：在CQMM中 ，網(wǎng)絡(luò)性能的優(yōu)化主要目的是建立一個(gè)由協(xié)議結(jié)構(gòu)所有層制約的網(wǎng)絡(luò)優(yōu)化模型，并根據(jù)這個(gè)模型找到一種能夠改進(jìn)MANETs整體新能的方法。</p><p>　　3 CQMM分析 目前MANETs 的QoS模型可被歸為兩類，一類是基于傳統(tǒng)層劃分結(jié)構(gòu)的DQMM，另一類是本文介紹的跨層QoS模型CQMM。[ 1,5-8 ] 所使用的QoS模型本質(zhì)上只是在DQ

88、MM基礎(chǔ)上一定程度的拓寬。在這里，我們只是比較CQMM與DQMM。 </p><p>　　3.1信息交流CQMM 與DQMM協(xié)議體系和原則的不同在信息交流的方式，頻率，時(shí)間，需求也存在很大的區(qū)別。（見(jiàn)表1 ） </p><p>　　從表1中可以看出，與DQMM比較 ，CQMM有許多優(yōu)點(diǎn)： 1 ）更靈活的信息交流 。相鄰層可以通過(guò)層或NSR之間的接觸交換信息，交叉層也可以通過(guò)NSR交換信

89、息。2 ）更簡(jiǎn)單的信息格式變換。不同層之間通過(guò)NSR可以交換信息，因此這些層只需要處理層與NSR之間的格式轉(zhuǎn)換問(wèn)題。3 ）更低的要求。協(xié)議層可以從臨時(shí)存在NSR中的不同協(xié)議層適時(shí)信息讀取它們，因此信息改變的層不必要及時(shí)保持同步4 ）更精確地控制。在CQMM中，NSR存儲(chǔ)了不同層某些時(shí)候的信息，這樣更利于準(zhǔn)確地掌握網(wǎng)絡(luò)狀態(tài)和管理網(wǎng)絡(luò)。3.2 Protocol Design </p><p><b>　　.

90、</b></p><p>　　3.2協(xié)議設(shè)計(jì)在DQMM 中，由于功能和協(xié)議設(shè)計(jì)上的相互獨(dú)立性，各層之間在執(zhí)行可靠的信息傳輸時(shí)不可避免的會(huì)出現(xiàn)一些功能上的榮譽(yù)。不過(guò)，CQMM可以在不同的層之間執(zhí)行統(tǒng)一的功能分配，并且能通過(guò)各層協(xié)作支持的QoS實(shí)現(xiàn)通信。</p><p>　　表1.CQMM與DQMM之間信息交換的對(duì)比</p><p>　　3.3網(wǎng)絡(luò)資源和性

91、能優(yōu)化的管理和調(diào)度</p><p>　　不同協(xié)議層之間缺乏充分的信息交流限制了DQMM網(wǎng)絡(luò)性能的整體改進(jìn)。在DQMM中，通過(guò)NSR,協(xié)議棧里不同層之間能夠自由、充分地交換信息，有利于網(wǎng)絡(luò)資源統(tǒng)一的規(guī)劃和調(diào)度，在整個(gè)網(wǎng)絡(luò)的基礎(chǔ)上建立性能優(yōu)化模型，并做好網(wǎng)絡(luò)性能整體改善。</p><p>　　3.4執(zhí)行議定成本和復(fù)雜性由于棧里每個(gè)協(xié)議層的相互獨(dú)立性，不同協(xié)議層之間只有較少的接觸與信息的交流，

92、因此DQMM需要較低的層本于復(fù)雜度。在CQMM中，棧中不同協(xié)議層之間自由、充分地交換信息需要：每個(gè)節(jié)點(diǎn)上上必須增加一個(gè)網(wǎng)絡(luò)狀態(tài)存儲(chǔ)器，并提供替代策略以及時(shí)更新?tīng)顟B(tài)信息；在每個(gè)協(xié)議層和NSR交換信息的地方增加接口；建立更復(fù)雜的數(shù)學(xué)模型和控制機(jī)制以優(yōu)化網(wǎng)絡(luò)性能。這些都會(huì)導(dǎo)致CQMM中執(zhí)行成本和復(fù)雜度的增加。</p><p>　　相比DQMM ，CQMM能夠?yàn)閰f(xié)議棧里的不同層提供自由和充分的信息交流，消除不同層之間的功

93、能冗余，更好的實(shí)現(xiàn)網(wǎng)絡(luò)資源的管理域調(diào)度，使MANETs.的整體性能最優(yōu)化。但這些優(yōu)勢(shì)都是高成本和高復(fù)雜度為代價(jià)的</p><p>　　4 .結(jié)論和未來(lái)工作  本文為MANETs.提供了一種新的跨層QoS模型，CQMM。相比DQMM ， CQMM有以下優(yōu)點(diǎn)： 1 ）通過(guò)NSR，協(xié)議棧中不同層可以自由、充分地交換信息。 2 ） CQMM.可以消除協(xié)議棧中不同層之間的功能冗余層協(xié)議棧，并更好地執(zhí)行網(wǎng)絡(luò)資源

94、統(tǒng)一管理和調(diào)度和網(wǎng)絡(luò)性能的整體改善?；贑QMM的框架，今后的工作將側(cè)重于跨層協(xié)議的設(shè)計(jì)，跨層控制與QoS合作，用跨層的方法對(duì)MANETs性能的整體改善。</p><p><b>　　5. 參考文獻(xiàn)</b></p><p>　　【1】L.Wei，X.Chen 等等，“內(nèi)涵：支持區(qū)分在Ad Hoc網(wǎng)絡(luò)中的多次反射移動(dòng)”，移動(dòng)計(jì)算，IEEE事物處理，2004.3（4）：3

95、80-393.</p><p>　　【2】G..Ahn，A.T. 坎貝爾等等，“本地多級(jí)無(wú)線網(wǎng)絡(luò)確認(rèn)支持服務(wù)”，美國(guó)電氣及電子工程師學(xué)會(huì)全球電訊會(huì)議2003，洛杉磯，CA,USA,Dec.2003。</p><p>　　【3】G．Mohsen,無(wú)線通訊系統(tǒng)和網(wǎng)絡(luò)，2004</p><p>　　【4】G..Andrea, 無(wú)線通訊，劍橋大學(xué)出版社，2004</p