Research And Improvementof OLSR Protocol For MANET

The mobile Ad Hoc network (MANET) is a self-configuring and infrastructurelesswireless network, which is designed for mobile devices. Unlike thecellular mobilecommunication network,MANETwill bebuilt as a temporary wireless network anytimeand anywhere,and it doesn’t require any existing network infrastructure or any centralcontrol device. All nodes in MANET play the roles of both a user and a router.Optimized link-state routing protocol (OLSR) is a proactive table-driven routingprotocols designed for MANET, which optimizes the classic link state algorithm to meetthe requirements of the MANET. The keyof the protocol is using multipoint relay (MPR)to minimize flooding network control information. There are three kinds of messages inOLSR for network maintenance, namely, HELLO message,topology control (TC)message and multiple interface declaration (MID) message.OLSR protocol gets the linkstate by periodically exchangingHELLO and TCmessages with other nodes in the network. The fixed transmissionperiod does notmakethe protocol adapt to the changes of thenetwork topology.Whenthe networktopologychanges, the performance of the protocol will degrade sharply.When thenetwork topology remains stationary, it maywastenetwork resources.Aiming at this problem in the OLSR,this thesis proposes an adapting routingprotocol named AFE-OLSR, which is combined fisheye state routing (FSR)withenergyaware.Firstly,in order to adapt to network topology change, the node in AFE-OLSRautomatically adjusts the transmission intervals between HELLO and TC messages,according to the changes of link set and MPR selector set.Afterwards, in cooperationwith the fisheye state routing,the node automatically adjusts the forwarding times of TCmessagein order to reduce the forwarding times of TC message.Finally, the node caneasily choose a more stable and reliable routing according to theenergy-aware andmobile-aware results.Based on NS2tools, the simulation resultsshow that comparedwith OLSR, AFE-OLSR reduces end-to-end delay at about8%, improves packetarrivalrate at about13%saves12%routing achievingtime of whole network. When networktopology remains stationary,the transmission amount of HELLO message reduces at about19%and the forwarding times of TC message reduces at about15%.In addition, this thesis proposes a mobility prediction routing protocol namedEMP-OLSR which based on energyaware.Firstly, EMP-OLSR protocol recordsthesignal energy and time durationwhen receiving a HELLO message.Then according tosignal energyloss formulain two ray ground model, the relative distance between nodeswill be calculated.After that the node location will be estimatedwhen the node sendsnext HELLO messages bygeometric methods. Finally, according to the estimatedresults,the node chooses the more stable and reliable routing when calculating therouting.The simulation results show that compared with OLSR, EMP-OLSR improves4%packet arrival rate, while results in additional11%end-to-end delaywhen networktopology changes.