| Ad hoc network is a self-organized peer to peer multi-hop wireless network with-out any infrastructure, each node in the network should play the role of both the router and the client simultaneously. At the same time, it is responsible for finding neighbor nodes which could be communicated with directly. Due to restricts of objective condi-tion, Ad hoc network is characterized with narrow bandwidth, limited battery energy, frequent change of network topology etc.Main research domain of Ad hoc network consists of network scale, battery effi-ciency,Quality of Service, network security,node mobility etc. In consequence of the irregular mobile feature of wireless nodes, the links between nodes in Ad hoc network often break so data packets are lost. Routing algorithm is the key area of Ad hoc net-work research, most research on Ad hoc network aims at routing protocol. This paper worked on how to alleviate the negative effect of node mobility on network reliability by improving the route selection mechanism.Currently, many research aiming at the mobility of Ad hoc network takes ad-vantage of GPS data of mobile nodes to calculate the node velocity which is used to influence route decision. However, in many cases velocity of nodes can’t predict if the link is stable because that it is the relative displacement rather than the absolute dis-placement that causes link collapse. Most routing protocols use the shortest path or the best one among several routes which bear the least hops as the data channel.Sometimes this strategy is not advisable for that the shortest path could not always provide with the most reliable transmission service.This paper takes relative node speed as a crucial parameter of path selection mech-anism, relative speed is more meaningful and precise in predicting linking condition between nodes. Taking advantage of link relationship between nodes and their neigh-bors, we could figure out and update the relative speed of each node. We could also get the mobility average of the whole path based on the relative speed of nodes in this path. Route mobility average of each path will impact the destination node’s path selection.This paper proposed a new routing protocol AD-AODV which utilized a com-parison parameter M to select the path for transmission. M indicates the synthetical stability degree of different paths between source node and destination node and both the route hop and route mobility average have an effect on the value of M. The range of candidate routes is widened by introducing this comparison parameter M which means even paths with more hops are possible to be selected as the data channel. Differing with the default shortest path route selection mechanism of AODV, AD-AODV proto-col choose the path with the smallest M as the final data channel.We did a lot of protocol simulation experiments on Network Simulator-2(NS-2) platform. The wireless node movement scenarios were generated by setdest implement automatically. In order to lower the accidental factor in experiment, experiment in each scenario was carried out for30times and the results were averaged to obtain the final simulation data. We depicted the curves which illustrated the relationship between node number, node speed and packet delivery ratio. Through the comparison with routing mechanism of another two protocols, the superiority and effectiveness of AD-AODV was approved. |
PDF Full Text Request