Research And Optimization Of OLSR Protocol For Flying Ad Hoc Network

With the popularization of unmanned aerial vehicle in the civilian field,the FANET(Flying Ad Hoc Network,FANET)composed of clustered micro UAVs has also been used widely in various fields because of its efficiency and flexibility in performing tasks.As the expansion of the mobile ad hoc network in the air field,the difficulty of data transmission between UAVs has also increased.Therefore,the research of routing protocols in FANET is particularly important.Due to the characteristics of high node mobility,unstable link connection between nodes and limited node energy in FANET,the traditional routing protocols in mobile ad hoc networks can no longer be applied to FANET.In this paper,combined with the network characteristics of FANET,the OLSR(optimized link state routing,OLSR)protocol is researched and improved,so that the improved OLSR protocol can show good protocol performance in FANET with frequent network topology changes.The main works of this paper are as follows:Firstly,in view of the shortcomings of the traditional MPR(Multi Point Relay,MPR)selection algorithm applied to FANET,a routing protocol based on multi-metric selection(LECOLSR)is proposed.Considering that the link survival time between nodes,node remaining energy and node coverage can affect the selection of MPR nodes,the MPR selection algorithm of this protocol comprehensively considers three influencing factors and uses the analytic hierarchy process to accurately calculate the weight factors of each influencing factor,and then use their weighted sum as a comprehensive measure to select an appropriate MPR node.At the same time,in order to successfully apply the improved MPR selection algorithm to the LECOLSR protocol,the formats of HELLO message,TC message and neighbor table are also modified.Secondly,in order to solve the problems of increased routing overhead and untimely update of topology information caused by fixed control message sending interval in LEC-OLSR protocol,a LEC-OLSR routing protocol based on dynamic adjustment of control message sending interval(DLEC-OLSR)is proposed.The protocol predicts the stability of the network topology according to the changes of the information table maintained by the node to determine the sending interval of the control message.On the one hand,the sending interval of HELLO messages is dynamically adjusted;on the other hand,the sending interval and forwarding range of TC messages are dynamically adjusted.The further improved DLEC-OLSR protocol can effectively reduce the number of redundant control messages in the network and improve network communication performance.Finally,use OMNe T++ to build a simulation scenario to verify the effectiveness of the improved routing protocol in the two scenarios of increasing the number of nodes and increasing node speed.Compared with the traditional OLSR protocol,LEC-OLSR protocol has a certain degree of improvement in node survival rate,packet delivery rate and average end-toend delay,but the network routing overhead is increased.In the scenario of increasing node speed,DLEC-OLSR protocol effectively improves the network routing overhead and node survival rate when the node speed is low.Although DLEC-OLSR protocol brings a larger average end-to-end delay than LEC-OLSR protocol,it is still better than OLSR protocol,and the optimization of the packet delivery rate becomes more and more obvious when the node speed increases.