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1、基于无线传感器网络的以数据为中心的数据分发路由协议,D3:Data-centric Data Dissemination in Wireless Sensor Networks,Maarten DitzelNetherlands Organisation for Applied Scientific ResearchP.O.Box 96864,2509 JG Den Haag,The NetherlandsEmail:maarten.ditzeltno.nl,摘要,Abstract：This paper presents a novel method to disseminate sensor
2、 data in a wireless sensor network,called D3(Data-centric Data Dissemination).The method combines the advantages of data-centric routing like SPIN and directed diffusion and energyefficient MAC protocols such as S-MAC and T-MAC.The protocols strengths are its energy-efficiency and its simplicity.Mes
3、sages are transmitted using broadcasting only,reaching as many nodes as possible with the least energy.Furthermore,D3 easily accommodates energy-dependent traffic balancing and data aggregation,crucial to prolong the lifetime of a sensor network.,本文提出了一种在无线传感器网络中用于散布传感器数据的新协议，这种协议叫做D3(Data-centric D
4、ata Dissemination)。这种协议结合了以数据为中心的路由协议（例如SPIN和directed diffusion）和低能耗MAC协议（例如S-MAC和T-MAC协议）两者的优点。这种协议的优势就在于它的低能耗性和简易性。它使用广播式来传输数据，使用最少的能量而传送数据到尽可能多的网络节点。更重要的是，D3协议能有效的调节传输路径来平衡节点的能耗，这样就能很好的延长整个传感器网络的寿命。,引言,Wireless sensor networks 1,2 have experienced increasing attention in academic,industrial and m
5、ilitary environments over the past few years.These networks promise an easy-todeploy,easy-to-use and moreover,low-cost means to remotelymonitor environments.Furthermore,sensing accuracy can beimproved significantly by processing and combining collected data within the network itself.Finally,the netw
6、ork can be made robust to the failure of individual nodes,which ensures that the lifetime and proper operation of the network is not limited to the lifetime of one node in particular 最近几年，无线传感器网络倍受学校、工业、军事等的高度关注。它主要应用于那些难以接近的区域或用于军事上的远程监控。例如，用于监测饮用水质量的监测系统，用于野生动物聚集地观察系统，用于监测冰河运动的网络监测系统。另外，无线传感器网络也能应
7、用在许多军事方面，例如战场数据采集网络，以便能及时发现敌军的行动。由于无线传感器网络的特殊性，其发展面临许多特有的问题。这些问题涵盖了网络组织、协议设计、网络运行维护等方面，目前的研究工作主要集中在媒体访问协议和路由协议等方面。传感器节点硬件资源受到了严格的限制，在这样的平台上实现通用的协议具有一定的难度，本人认为应该对潜在的应用分类，有针对性开发相应的协议，这样在带宽、延时、能量消耗等方面更容易取得平衡。,II.DATA-CENTRIC ROUTING以数据为中心的路由协议,To operate a wireless sensor network successfully,two close
8、ly related networking issues have to be addressed.The first is the media access protocol,i.e.,how the nodes access and share the radio channel.The second is routing,i.e.,how data is passed through the network.Dependent on the structure of the network different solutions may be found.In this paper we
9、 consider a homogeneous,randomly distributed wirelesssensor network.All nodes are identical and offer the same processing and communication capabilities.Several routing schemes and MAC protocols can be found in literature for an overview see 为了能有效地运转无线传感器网络，我们提出了两个有关其网络的协议。第一个是MAC协议，它主要研究网络节点间怎样才能接入
10、和共享无线信道。第二个就是路由协议，它主要研究整个传感器网络中的数据是怎样传输的。基于不用的网络结构我们有不同的解决方法。在本文中，我们采用了一种均匀的、随机的分布式无线传感器网络,所有的网络节点拥有相同的数据处理和通讯能力。,II.DATA-CENTRIC ROUTING以数据为中心的路由协议,由于数据处理和传输过程受到能量限制，传感器的数据必须尽快传输出去。基于这些限制，文献8的作者建议利用以数据为中心的路由协议和引入SPIN协议族（信息协商制的传感器协议）。这里，传感器节点若有新数据就向周围发布其有新数据信息，在发送实际新数据之前，必须等待附近对这信息感兴趣的节点发来的数据请求信息。文献
11、9中，作者提出了定向扩散数据分发机制，它定义了一个叫做SINK（接收器）的节点，这个节点向所有节点广播发送一个它要得到的数据的兴趣信号。接着，如果网络节点有SINK节点关心的数据的话，就使用梯度来传输数据。虽然directed diffusion和SPIN协议都是以数据为中心的路由协议，但是他们利用了以地址为中心的MAC协议，因为他们都是将数据发送给临近的节点。本文提出了一种完全以数据为中心的路由协议。,三、D3协议DATA-CENTRIC DATA DISSEMINATION,The D3 protocol is based on two basic assumptions.First,tr
12、ansmitting information about data is cheaper in terms of energy than transmitting the actual data itself.1 Second,if a node has new data available,at least one of its neighbors is always interested.2 Hence,the data must always betransmitted.Therefore,a node does not require a confirmation that a nei
13、ghbor is interested and it can use broadcasting to communicate the data.The neighbors can decide individually whether to listen to the broadcast or not.Of course,these assumptions have to be verified.D3协议基于几个基本假设。第一假设是：传输数据的信息比传输实际数据所消耗的能量少。第二，当一个节点监测到有效的新数据时，它至少要有一个临近节点对其感兴趣，以保证数据总是能被输送出去。一个节点并不一定要
14、得到附近节点对其感兴趣的批准才能传送数据，因为它可以通过广播来传送其数据。其附近的节点能自己决定它是否应该接收其广播数据，当然，这些假设必须被证明。根据T-MAC协议的基本原理，节点处于周期性的激活和睡眠交替机制。每隔一定时间，节点从睡眠状态转为激活状态,三、D3协议DATA-CENTRIC DATA DISSEMINATION,D3协议使用了三种信息类型来散布数据：1.INTinterest。兴趣包，一个节点广播兴趣包给传感器网络中的其他节点。它包含了一个唯一的标示符和一个描述源节点（sink节点）所感兴趣的数据的任务描述符。每一个节点存储源节点发出的兴趣信息并把此节点到SINK节点的跳数传
15、送给sink节点。2.ADV data advertisement.消息广播包。当一个节点有符合源节点感兴趣的新节点时，就向它的邻居节点广播其有准备好了的带兴趣标示符和梯度的新数据。无论这个数据是其自己检测到的也还是接收其他节点的，都必须向前传送直到源节点。3.DATA数据包。就是实际的传感器检测的数据。,图一描述了D3协议的具体操作过程The basic operation of the D3 protocol is depicted in Fig.1.Node A starts with sending a data interest to all nodes using flooding
16、(Fig.1(a).When node E has new data available(Fig.1(b)it advertises the data to its neighbors C,D,F,and 2Sensor data is only collected after receiving an interest(similar to directeddiffusion).Therefore,at least the neighbor the interest originated from mustbe interested.G,and claims a time slot for
17、transmitting the data message.Subsequently,it sends the actual data(Fig.1(c)at the reserved time to all interested neighbors:C and D.Nodes F and G are not interested in the data and simply ignore the transmission by switching off their radios.This sequence of advertisement and data transmission(Fig.
18、1(d)and Fig.1(e)is repeated to forward the data until it reaches the sink where the interest originated from.Forwarded ADV messages are also used asvirtual acknowledgements(vACK)(see section III-B).Finally,the sink acknowledges the reception of the data(Fig.1(f)using a further unused advertisement a
19、s acknowledgement.,A.Detailed Operation-D3协议操作细节,The sensor network starts at rest.No data is collected by the nodes and no messages are communicated.To activate particular nodes and sensors an interest is injected into the network via a node,henceforth known as the sink.The interest is propagated t
20、o all the nodes in the network using flooding.Each node registers the interests identifier and its corresponding depth.Once a node has received and registered an interest,it inspects the task descriptor and activates the corresponding sensors if necessary.初始时传感器网络处于睡眠状态，节点不检测任何数据也没有任何消息传送。通过一个节点广播一个
21、兴趣消息给整个网络来激活其他的节点，我们管这个节点叫sink节点。Sink节点使用泛洪的方式来广播兴趣信息给传感器网络的所有节点。每一个节点存储兴趣消息标示符和其对应的梯度，一旦节点接收到或已经存储了兴趣消息，就检测其任务标示符并且激活响应的传感器。只要节点激活了传感器，这些传感器就能开始收集数据了。如果一个节点收集到了与已经存储的兴趣信息相同的数据时，就给其邻居节点发送信息以通知邻居节点它有源节点感兴趣的有效数据.当邻居节点接收到数据信息时，它们自动检测它们是否离SINK节点比较近，如果近的话，它们就准备接收数据信息。如果不近的话，它们就对这数据信息不理睬。由于数据传送是向梯度低的节点逐层传
22、送的，这样数据总能保证传送到SINK节点。,B、Virtual Acknowledgements 虚拟应答请求,Apart from announcing that sensor data is available for transmission,the ADV message serves another purpose,namely as a virtual acknowledgement.In Fig.1(d)node D broadcasts an advertisement in order to forward data originally coming from node E
23、.When node E receives the broadcasted ADV message,it will ignore the upcoming transmission as usual,because the depth included in the advertisement is lower than its own depth.However,it also checks the advertisements identifier to see where the data originated from.If the node can find this identif
24、ier in its own history of sent ADV messages,it implicitly knows the data package has been properly received.ADV信息包除了通知节点其检测到了兴趣数据外，它还有一个作用，我们管这个作用叫虚拟应答请求。在图1（d）中节点D向邻居节点发送广播信息包以进一步向前传送。一般，当节点E接收到D节点发送的广播信息包时，E节点将接收节点D即将要发来的数据。因为ADV信息包的梯度比节点E的梯度低。虽然如此，它还是会检测ADV信息包的标示符以查看这是数据是从哪个节点发出来的。如果这个节点在自己发送ADV信
25、息包的历史记录里找到了与接收到的ADV信息包相同的标示符，那么它就知道自己发出的数据包已经被成功的接收到了。因此，ADV信息包也能起到通知节点其发送的数据已经被成功发送出去了。如果这个节点在发送数据信息包后一定的时间里还没有接收到虚拟请求应答信号时，那么此节点就认为其数据丢失并采取相应的措施。,IV.RESULTS 仿真结果,To verify the ideas and concepts introduced in this paper,simulations have been carried out using the OMNet+simulation environment 13(se
26、e Fig.2).Moreover,the D3 protocol is implemented on a small scale experimental sensornetwork(see Fig.3).Preliminary results show the proper operation of the protocol and,especially,its scalability.Apart from verifying the proper operation of the protocol,the first experiments focused on possible red
27、undant paths from thesource node to the sink,which may reduce the efficiency of the protocol.为了证实本文提出的观点，这里给出了在OMNet+仿真环境下的仿真结果（图2）。图三描述了D3协议运用在小规模试验传感器网络的情形。初步结果显示本文提出的D3协议是可行的。另外本试验集中于对从源节点到sink节点多余路径的研究，此研究能减少本协议的功耗。,IV.RESULTS 仿真结果,IV.RESULTS 仿真结果,当节点没有从邻居节点接收到虚拟请求应答信号时，就会引起多余路径的产生。此时，一个信息包将沿着不同
28、的路径传送到sink节点。图4描述了最坏的情况，整个网络里传输的数据包都有重叠复制。,IV.RESULTS 仿真结果,理想情况下，sink节点只要接收源节点的一个信息包，也就是冗余度为1.。如果源节点到SINK节点有多条传输路径的话，那么它的数据冗余度R可用下式来表示：式中，ni表示第i个节点，n1为源节点，s(ni)表示节点i发送的数据信息包的总数，d(n1)表示源节点的梯度（图四例子中d(n1)为4）。在本试验中，冗余度是在大规模的随机产生且连通度不断增加的传感器网络中计算的。网络的连通度就是指每个节点的邻居节点的数量。本实验中，每个传感器网络都至少有250个节点，在图5中，描绘了冗余度随
29、网络连通度的变化的关系图。在这个图中的每一个点，都有100个仿真器在运行。每一个仿真器都有100个信息包从源节点发送给sink节点。图5显示了随着连通度越来越大，冗余度只有微少的增加。,V.CONCLUSION,In this paper,the shift in paradigm towards data-centric routing is followed and incorporated into energy-efficient MAC protocols.This leads to a novel data dissemination protocol,called D3.The
30、D3 protocol uses advertisement messages to announce that new data is available.Interested nodes listen to the subsequent transmission of the actual data,while uninterested nodes simply ignore the data message.Allcommunication follows an active-sleep regime,alleviating the problem of idle-listening.本
31、文中，结合了以数据为中心的路由协议和低功耗的MAC协议的优点，从而提出了一种叫做D3的数据分发协议。D3协议源节点使用广播信息以通知邻居节点其检测到了新有用数据，对新数据感兴趣的节点就监听并接收这个数据，且对新数据不感兴趣的节点就不监听此数据。所有的通信都遵循激活-睡眠机制，以便减少功耗。,V.CONCLUSION,The protocol combines the advantages of data-centric routing like SPIN and directed diffusion and energy-efficient MAC protocols such as S-MA
32、C and T-MAC.Its strength is its energy-efficiency and its simplicity.Nodes only need to process local data and control messages are kept to an absolute minimum,both in number and in length.Furthermore,D3 can be easily extended to accommodate energy-dependent traffic balancing and data aggregation,vital for prolonging the lifetime of a battery-powered network.本协议综合了以数据为中心的路由协议（如SPIN）、数据分发协议和低功耗MAC协议（如S-MAC和T-MAC）的优点。它的优点是：低功耗、简易性。节点只需要处理局部数据，无论是数量还是长度，控制消息都保持绝对小。还有，D3协议能够方便地调节整个网络的通信功耗平衡和数据聚合，以便能延长整个网络的寿命。,Thank You!,
