Research On Multicast Routing Protocol Of Wireless Sensor Networks

Wireless sensor network is composed with a large number of low-costmicro-sensor nodes in monitored region, and it is a kind of multi-hop selforganizingnetworks through wireless communications formation. Thepurpose is to sense collaboratively, collect, process the perception objectinformation in the network coverage region, and send it to the observer. Itcombines sensor technology, embedded computing technology, modernnetworking, wireless communications technology and so on. Wirelesssensor networks can be widely used in the areas such as national defenseand military, national security, environmental monitoring, trafficmanagement, health care, manufacturing and combating terrorism.A sensor node uses limited non-replacement power, and its capacity ofcomputing, communications and storage is limited. Usually, there are alarge number of high density nodes in a wireless sensor network and theinformation that the nodes collect is great redundancy. As a result of thesenew features, the traditional network routing protocol is not suitable forapplications in wireless sensor network, even traditional wireless ad hocnetwork routing protocols can not be directly used for wireless sensornetworks. There have been many new wireless sensor network routingprotocols. The wireless sensor network routing protocol has become a hotresearch on wireless sensor networks.Wireless sensor networks restriction on energy consumption is verystrict. It can be said that excessive consumption of energy node wirelesssensor networks is a fatal factor. But multicast routing data transmitted bythe high efficiency can reduce energy consumption, so as to further expandthe wireless sensor network applications. In practical applications, from theenergy consumption of sensor nodes can be seen that in the nodes for communication overhead is much larger than the energy used to calculateenergy costs. Thus, multicast in "one-to-many" scenes of sensor networkcan significantly reduce the number of packets, and it can be significantlysaved in energy consumption of nodes, thereby the life time of sensor nodescan be extended.This paper has studied on the existing wireless sensor networksmulticast routing protocols, and designed and implemented a statelessmulticast routing protocol of wireless sensor networks and a soft statemulticast routing protocol of wireless sensor networks.This paper designed and implemented a stateless multicast routingprotocol of wireless sensor networks in Chapter 3. The multicast routingprotocol is based on the unicast routing protocols to achieve. This routingprotocol is no forwarding structure, and multicast source nodes can fullcontrol distributing multicast packets.In the routing table, it is stored in number of the jump to the destinationnode and address of the next jump. In the operation of the network, it is inthe process of routing only when it needs to establish routing, and try to findthe shortest route. When running multicast routing, the node according withthe unicast routing table has been established, forwards multicast data. Amulticast packet contains a payload and a multicast header. Each multicastheader is composed of receiving addresses, and neighbors that are selectedto relay the packet. When a node relays a multicast packet, it accords itsrouting table and information of the packet to distribute the multicast packet.This stateless multicast routing protocol accords current routing tableand information of a multicast packet to relay multicast packets. Theprotocol does not know overall network topology. Its algorithm complexityis low, not manage a multicast tree, and not send routing control packets.Thus this protocol can significantly increase the efficiency of a network. Inmulticast addresses that receive multicast packets frequently changing scenes, this protocol will continue to be good.This stateless multicast routing protocol only accords local routingtable to determine how to relay multicast packets, and it restricts by thelocal information, so its multicast routing may be not optimal. A multicastpacket carries all of the destination address, but the address number of thepacket carrying is limited, so it limits the scale of multicast in wirelesssensor networks. Therefore this stateless multicast routing protocol is notsuitable for running in large-scale multicast scenes. Chapter 4 designed andimplemented a soft state multicast routing protocol of wireless sensornetworks, and the soft state protocol can solve above problem to a certainextent.Both the soft state multicast routing protocol of wireless sensornetworks in Chapter 4 and the stateless multicast routing protocol in Chapter4 are based on a unicast routing protocol to achieve. This soft state multicastrouting protocol is different from the stateless multicast routing protocol,and each node accords control information in receiving multicast packets tomanage a forward state of a multicast group in running this soft statemulticast routing protocol networks. This state is called soft state.There is a group identifier in a multicast group. This group identifieruses to distinguish among different multicast groups. Multicast groups usetree structure. There are three types nodes in the tree structure: group leadernode, receiving multicast packets nodes and relaying multicast packetsnodes.Each node in a multicast group is not only to manage a unicast routingtable but also a multicast routing table. Each multicast packet is retainedsmall space for storage destination address, and a node uses this informationto manage its multicast routing table.Each node in a multicast group, in this soft state multicast routingprotocol, accords control information of multicast packets to manage its multicast routing table. There are not control packets in networks, so thisprotocol can improve network performance. This protocol only uses smallspace of multicast packets to manage the whole multicast group, and it cansolve the problem in Chapter 3 to a certain extent. This protocol can beapplied in larger scale multicast scenes.To manage multicast routing table, nodes have to use more storagespace comparing with stateless multicast routing protocol in Chapter 3.When multicast addresses that receive multicast packets frequently change,the efficiency of the soft state multicast routing protocol will be affected,but the stateless multicast routing protocol in Chapter 3 will not be affected.In the initial establishment of the multicast tree, when the multicastreceiving nodes are too many in the group, due to addresses in a multicastpacket is limited, group leader needs to send the same multicast packetsmany times, to builds the multicast group. This will waste some networkresources. After Multicast tree having been established, it will not be subjectto restrictions on the number of recipient address. Because to managemulticast routing table, and each sensor node storage space is limited, soeach node's routing table is not too big. Storage space is limited multicastscale and each node can not have too many neighbors.This paper has developed these two multicast routing protocols in theNS2 simulator, carried out some experiments in a specific networkenvironment and compared their performance.