Study On LTE V2X Based Multi-hop Broadcast Algorithm For VANET

Vehicular Ad hoc Network(VANET)is a wireless communication network,in which vehicles communicate with other vehicles and communication units.Safety is the primary goal of intelligent transportation systems,in which safety messages are often sent to surrounding vehicles through broadcast communication.Vehicles make the decision based on the received message and take measures.In multi-hop broadcast for VANET,the source vehicle broadcasts safety messages,while forwarding vehicles rebroadcast the message.Through multi-hop broadcasts,as many vehicles as possible receive broadcast messages.One of the key issues of the multi-hop broadcast algorithm is which criterion is adopted to select the forwarding nodes.First of all,we introduce the structures,applications,Long Term Evolution-Vehicle to Everything(LTE-V2X)related protocol of VANET.Then we present typical broadcast algorithms in VANET.Current multi-hop broadcast algorithms often use local information to select forwarding vehicles,which may cause many problems.As a result,broadcast messages cannot reach all nodes in the range with high reliability and low latency.Then,to overcome the shortcomings of existing broadcast algorithms,we propose the dynamic topology based center broadcast algorithm.The broadcast algorithm constructs the global dynamic topology with the help of the base station.The base station employs the center selection algorithm to decide the set of forwarding vehicles in case of emergency situation.The center selection algorithm is a kind of greedy algorithm,in which the vehicle that is farthest from the current set of forwarding vehicles should be selected as the new forwarding vehicle in each iteration.The forwarding vehicles rebroadcast the message once receiving it.In addition,we build the simulation platform based on the LTE-V2X protocol,which includes highway scenario and urban scenario,and supports Vehicle-to-Vehicle(V2V),Vehicle-to-Infrastructure(V2I)and V2X communication schemes.Finally,we improve the dynamic topology based center broadcast algorithm and propose the semi-static center broadcast algorithm for multi-service.The broadcast algorithm employs semi-static center selection algorithm to decide the set of forwarding vehicles,and applies reserved resource selection scheme.The semi-static center broadcast algorithm meets the multiple service requirements via different periods and priorities of the broadcast events.Simulation results show the Packet Delivery Ratio(PDR)of the proposed algorithm has improvement in highway and urban scenarios.