Relay Selection Technology In Vanet

The Vehicular Ad Hoc Network(VANET)is a key component of the future intelligent transportation system.It can realize the communication between vehicles and vehicles and between a vehicle and a roadside station.It can transmit traffic information to each vehicle in real time and the traffic command center,which is of great significance for solving current road congestion and traffic safety issues.In addition,with the continuous development of collaborative communications,cooperative relay technology is gaining more and more attention.VANET has characteristics of fast-changing network topology,unstable communication channels,and limited network capacity.Thus,relay selection technology in VANET is the focus of this theses.Firstly,we introduce the research background and research status of cooperative relay and VANET.We theoretically deduce the system model and channel capacity as well as outage probability of cooperative communication systems.The VANET model,802.11 p standard and OFDM are also clarified.Secondly,this theses studies central relay selection algorithms in cooperative communication systems,which include the global relay selection algorithm----max-min relay selection method,the local relay selection algorithm----max-max relay selection method,and the hybrid algorithm of max-max & max-min counterparts.In addition,we have made some improvements to the hybrid algorithm and put forward the max-both algorithm,which makes the system performance achieve the upper bound under the condition of low delay requirement.Thirdly,this theses discusses the distributed relay selection algorithm in cooperative communication system.Based on the algorithm proposed by the previous one-hop Rayleigh channel selection,this theses proposes an adaptive threshold selection algorithm for the twohop channel from the source node to the relay node,and from the relay node to the destination node.Finally,proper relay selection algorithms are applied in VANET.We perform simulations based on the 802.11 p standard under the Jakes model,and analyze influences of feedback delay,vehicle moving speed and other factors on system outage probability,bit error rate,and 10% outage capacity,and prove the practicability of these methods.