English abstract
A Vehicular Ad-hoc Network (VANET) uses cars as mobile nodes in a MANET to create a mobile network. A VANET turns every participating car into a wireless router or node, allowing cars approximately 100 to 300 meters of each other (transmission range) to connect and, in turn, create a network with a wide range. The study of VANETs is a developing area of research. Efforts have been taken to achieve efficient broadcasting in VANETs. Network broadcasting is the process in which one node sends a packet to all other nodes in the network. Various network algorithms are based on broadcasting including: routing, information dissemination and service/resource discovery. Since many systems have stringent end-to-end delay requirements, the design of lowlatency and low overhead broadcasting schemes is essential to many practical applications.
In this research work, an enhancement of one of the existing algorithms has been proposed along with a simulation model. The original algorithm is called Cell Broadcast for streets (CB-S) [1]. CB-S divides the streets into cells according to intersections and street blocks. The assumption is that all vehicles have a radio range sufficient to cover any three consecutive cells. One vehicle in these three consecutive cells will re-broadcast the message. CB-S gives the priority for the vehicles located in the far away downstream cell to re-broadcast. This will allow the re-broadcast to happen from every other cell.
The original algorithm gives the priority to re-broadcast the message from every other cell. However, some vehicles within the transmission range can be located in the fourth cell and will lose the opportunity to participate in the rebroadcast process and hence losing the opportunity to select the farthest vehicle to rebroadcast the message. Our enhancement is to give the vehicles within the transmission range the opportunity to participate in re-broadcasting the message. We claim that, by introducing this enhancement the total end-to-end delay will be reduced and the reachability will be increased. A simulation model based on Network Simulator (ns2) and VANET simulator SUMO has been developed and performance evaluation has been performed to compare both algorithms. Both end-to-end delay and reachability have been evaluated for different network conditions: vehicle mobility, network density, traffic load, and dissemination area. The simulation results show a good improvement in both end-to-end delay and reachability.
