| Mobile Ad hoc networks are collections of wireless mobile hosts forming a temporary, self-organized network without any existing wire line infrastructure. In such an environment, it may be necessary for one mobile host to enlist the aid of others in forwarding a packet to its target, due to the restricted propagation range of each mobile host's wireless transmission. It is not limited by the time and space to the built quickly and easily, so that it is applied to such positions as succor, conference, battlefield, exploration, dangerous situation and so on.There are most characters of wireless communication, including dynamic topology, multi-hop, and share channel, bandwidth-limited and energy-limited for Ad hoc networks. The routing protocols of Ad hoc networks are one of hottest issues in related research fields. Those traditional routing protocols cannot be applicable to new routing protocols and ad hoc networks must be designed, as the dynamic and variable topology. Recently, there are many routing protocol and for researching on ad hoc on-demand distance vector routing protocol, is a hotspot in ad hoc networks.Firstly, this thesis describes the basic introduces the existing routing protocols in detail and the characteristic of Ad hoc networks.Secondly, it stresses the principle and mechanism of AODV and analyzes the good aspects and a bad aspect of this routing protocol, moreover, gives the improvement on AODV. Combined with the bad aspects in the routing repair and power, this thesis suggests three ways for improving AODV protocol as follows:1) The thesis analyzes the most possible conditions, because the case of broken routing is very complex. So, in order to prevent the emerging of broken routing, a node builds up a backbone routing and overhears the RREQ data packet transmitted by its neighbor nodes. After that, the node sets up the process of backup routing according to the RREQ data packet, at the same time, the backup routing and the backbone routing should have different nodes. In the process of routing maintenance, the cases of routing-loop and infinite-counting aren't existent.2) We should consider the power element, meanwhile, ensuring the minimum of total power consumption and the lifetime of each node. Give respectively the quantity of energy necessary for the transmission or the reception of a packet. We should multiply the transmission power (txPower), to measure this amount of energy consumed during the transmission process (noted txEnergy) by the time needed to transmit a packet:txEnergy= txPower x (packetsize/bandwidth)And for a received packet:rxEnergy= rxPower x (packetsize/bandwidth)The algorithm is implemented in AODV protocol. The method can prolong the lifetime of the network to prevent the rupture of the network.3) This method is based on the power element and proposes the methods according to AODV protocol. The methods consider the main about the network lifetime in view of the energy consumption of each node, threshold, probability and the level of energy, so as to balance the energy consumption, enhance the lifetime of each node and reduce the dead numbers of the network.The methods mentioned above, all have been given the concrete implementation by the NS2 software. The studies show that the improved routing protocols can be implemented and available. The protocols can also be extended in other unticast and multicast protocols.This thesis has five chapters as below:Chapter 1 introduces the concept, the characteristic, research hotspot, application foreground, related work, key technology of Ad hoc networks and introduces the source and research meaning of this thesis.Chapter 2 describes the classification of routing protocols in Ad hoc networks, the mechanism of AODV protocol, the good aspects and flaws.Chapter 3 describes the simulation software of NS2.Chapter 4 introduces the Local Energy Aware of AODV (LEAP-AODV), moreover, we gave a compares of AODV and LEAP_AODV with simulation.Chapter 5 summarizes and gives the suggestions in the future work of this research topic.This thesis is supported by National Natural Science Foundation of China (No: 60773211,60970064), the National Science Foundation of HuBei Province under Grant No.2008CDB335, New Century Excellent Talents in university (No:NCET-08-0806), Open Fund of the State Key Laboratory of Software Development Environment (No:SKLSDE-2009KF-2-02), Fok Ying-Tong Education Foundation for Young Teachers in Higher Education Institutions of China (No:121067),NSF of Wuhan Municipality (No:201010621207)... |
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