Research On The Channelaccess Control For Vehicle Ad-hoc Network

Vehicular Ad hoc network has been an important application of wireless self-organizingad hoc network in vehicular environment. The VAENT uses multi-channel operation model toprovide open security services and safe effective driving experience, thus multi-channelaccess scheme plays an important role in VANET. There are two important indexs--Throughput and delay. As one of the key technology in vehicular Ad hoc network, themedium access control also supports Quality of Service(QoS). IEEE802.11p, which employsin the Dedicated Short Range Communication (DSRC), and uses access protocol to provideQoS guarantee through Enhanced distributedAccess control (EDCA) and prioritization.This paper first analyzes the state of the art and development of vehiclar self-organizingnetworks, and introduces the MAC protocol standards. As one of its key technology, channelaccess mechanism plays an irreplaceable role. Aiming at the problems existing in the IEEE802.11p and1609.4, we analyze its principle of access and make the simulation analysis onits performance. Based on IEEE802.11p MAC, a novel multichannel access scheme, MCAS,is put forward, which considers the communication channel between the load balancing andvehicle channel adaptive multi channel access mechanism of collaboration according to thecharacteristics of vehicle ad-hoc network and the characteristics of vehicles of oppositedirection driving, aiming at the existing defects of service channel access. Firstly the systemmodel of the MCAS is presented, and a detailed analysis of the markov model is made bytheoretically analyzing various properties of MCAS, and then the throughput, packet delayand packet loss rate and other performance are presented through MATLAB simulation. Theresults show that the new algorithm of time delay, packet loss rate and throughput are betterthan the WAVE and VeMAC. This mechanism can make full use of control channel andcollaborative relationship among service channels effectively to make it better to the vehiclead hoc network environment.Furthermore, we also try to use a hibrid method, namely combine CSMA scheme andMCAS mechanism to get better use in vehicular ad hoc networks. Our straterge divides theframes into transmission period and reserve period, which uses TDMA scheme in the trasmission period and CSMA scheme in the reservation period respectively to access thechannel. The simulation results show that MCAS mechanism can improve networkperformance in a large extent, which can be able to solve channel competition and allocation,transmission delay, channel utilization, throughput and other issues in the existing MACprotocols, making it well satisfy the application of actual network.The project proposed in this paper plays a very important role in vehicle ad hoc network,and is also of great help of research on MAC protocols.