Research On Vehicular Ad Hoc Networks

VANET(Vehicular Ad Hoc Networks) is a kind of wireless network which iscomposed of cars as it's nodes, it doesn't rely on other infrastructure when it does datecommunication, so it's a kind of MANET(Mobile Ad Hoc Netwoks), and it's animportant direction in the erea of wireless sensor network. Routing protocol is a veryimportant part of networks, and it decides the performance of network to some extent.For the speciality of VANET: rapid movement of nodes rapidly change of thetopology structure of networks, the affection of the structure of the road in the city tothe movement of the nodes, most of the routing protocols in Ad Hoc aren't verysuitable if they are carried to the environment of VANET.We introduce Ad Hoc and it's protocol in the article at first, and tell the researchcondition home and abroad, then we introduce a special network in Vehicular Ad HocNetworks, and analyse the differences between VANET and common Ad Hoc, andintroduce several protocols which are suitble to VANET, then we describe GPSRwhich is one of such protocols in detail, we analyse the shortcomings in GPSR, thenwe put forward a improved GPSR named GPSR-WPP to deal with one of theshortcomings. GPSR doesn't think of the movement of the nodes during the periodbetween the time when the last packet of "HELLO" broadcasted and the time whenthe packet is sending, we pose position forecast algorithm to improve thisshortcoming. We describe the algorithm in detail and draw the algorithm flow chartthen.GPSR protocol is one of the most fitable protocols that are used in VANET, somany people study the protocol to improve it. Now lots of improved protocols forGPSR are appearing, and many of them are proved to be better in theory. And somescholars improve GPSR protocol to solve the specific problem in realities whichresults in making GPSR protocol more fitable to VANET.We describe the common emulations that are used in net work emulations in part5.We choose NS2as our emulation, and we explain the operating principle, the structureand the procedure of NS2. We creat the NS2model for GPSR-WPP. And make thesimulation in NS2-2.30for the improved protocol first. We compare the performance between GPSR and improved GPSR in two aspects, and analyse the different packetloss rates and time delays between them in different velocities which prove thatGPSR-WPP is valid. We conclude the whole article in part6, make some forecastingfor GPSR protocol, and give some own ideas. There are lots of improved GPSRprotocols, the two points below may be hot these years.1. In city environment, we can put the map information of the city into GPSRprotocol,that means to put path information, the blocks on the way, the density of thevehiculars into GPSR protocol which can improve the efficiency of GPSRprotocol, it can also improve GPSR protocol that used in city environment.2. The other way is to put fixed nodes in VANET to help data transmissionbetween mobile nodes. GPSR protocol need to deal with not only the transmissionbetween mobile nodes but also the transmission between vehicular and fixed nodes.Then with the help of the fixed nodes, more information with gets to the destination,such kinds of improvement s for GPSR will also improve the efficiency of GPSR.Many people start such kinds of research already.Because of the adaption of GPSR to VANET, and the problems of GPSR itself,more and more people with pay attention to the protocol, and it will be improvedbetter.