| Wireless mobile Ad hoc network is a kind of movable,multihop,self-organized system.Each node in the network construction is a node of data source,and also can play a role as data forwarding route.But this structure can lead to partial congestion,even totally congestion easily,and also the bandwidth resource of Ad hoc is relatively limited,so it is necessary to research the Ad hoc network congestion control strategy.Existing solutions for Ad hoc network congestion control focus on Physical Layer,Network Layer and Transport Layer.In this paper,we focused on Network Layer.It is involved in below subject:First,we analyzed the factors leading to congestion and some existing congestion control mechanisms.According to the analysis,it was found out that currently a reliable and robust congestion control mechanism did not exist.Secondly,we analyzed the performance of traditional TCP congestion control mechanism in Ad hoc environment: TCP congestion control mechanism is designed for cable network which assume that packet loss problem is caused only by network congestion,but comparing with it,there are much more factors can lead to packet loss in Ad hoc circumstance,like congestion,node mobility,multihop,high bit error rate,etc.Second,effects of node mobility,multihop,high bit error rate on Ad hoc network are analyzed by simulation experiments in this paper.Thus we proposed a new Efficient Congestion Avoid Solution(ECAS),including congestion monitoring,building efficient,none-congestion routing.The congestion status is supervised by congestion monitoring module.Again,In the phase of building routing,this paper proposed a specific channel competition measurement based on data packets queue length,totally congestion standards,packet loss ratio and substitution rate.In the meanwhile,the purpose of building a none-congestion routing based on congestion standards is to reduce the packet lossratio,high resource costs and long delay.At last,The experimental results on NS2 simulation platform show that the proposed method can reach higher throughput rate,higher packets delivery rate,lower point-to-point delay and resource cost. |
