Performance Study Of IEEE802.11 Based On Vehicular Ad Hoc Networks

VANET (Vehicular Ad Hoc Network) has attracted great attention of the world, and is an emerging researching area with multi-discipline interleaving. VANET integrates wireless communication technology, embedded computation technology, and distributed information processing through the collaboration of wireless communication module, sending and receiving the traffic safety information and multimedia information in real time. VANET has some special characteristics such as peer to peer status, self-organization, lack of infrastructure or control center, limited bandwidth, and dynamic topology, as a result, the research of VANET, especially in the field of its medium access control protocol, is full of challenge. Therefore, the research of VANET, in particular to its media access control protocol which has a huge challenge. The researchers have focused on studying how to deliver such information timely and reliably in VANET. However, it is difficult to implement a real network at the first stage of research. Generally, network simulation is one of the effective means to perform the research on the network technologies.This thesis, firstly, introduces the origin, characteristics, applications and current situations of the vehicular Ad Hoc network and the IEEE802.11 protocol which is widely used in vehicular networks. Secondly, with the consideration of the properties of VANET, a single direction with four lanes traffic flow generation algorithm is realized, which provides the topology of VANET needed by NS2. Thirdly, the fading channel model is added into the NS2, so that the wireless channel conditions in the simulation environment can be similar to that if a VANET. Then, with different parameters of the IEEE802.11 MAC layer, and simulate it by NS2 using chain topology and topology generated by the model. Finally, this thesis shows the simulation result to prove that the performance of single-hop communication is better than those of multi-hop in actual complex channel environment. It is obviously inadequate to apply the IEEE802.11 protocol in VANET directly. Therefore, the improvement of IEEE802.11 MAC protocol is of great significance to get better performance of the communication in VANET.As for simulation of protocol in the VANET, many a document simulates only with fixed topology or random one, fewer with the topology of VANET. Moreover, those documents not focus on the fading channels. This dissertation, however, concentrates on the topology of VANET under the TwoRayGround and fading channels. The facts show that this simulation measure approaches the reality.