Unicast routing on VANETs

Greedy routing in VANETs requires some geographical informations, such as the source location and the destination location. The first one could be obtained using some localization devices like GPS receiver. However, the second one is provided by a location service. This later has a high overhead especially if it is implemented over V2V (vehicle to vehicle) communications. Many location services are well known as HLS, RLS, GLS. This paper is interested in reducing this overhead by using some Road Side Units (RSU) already deployed along the roads. We propose here a location service called "improved Reactive Location Service (iRLS)", which is an extension of the RLS service. The major difference is that RLS assumes only V2V communications and iRLS takes profit of a wireless backbone based on RSUs to catch the destination's position. This allows to reduce the overhead instead of flooding requests and also makes the communication faster since we will not have to wait to the request to reach the destination before receiving the response and then starting sending data. In our proposal, the closest RSU will reply with the actual location. In order to show the contribution of our approach, we have conducted some simulations that prove that iRLS outperforms any geographic protocol by using the V2I communications in terms of end-to-end delay which is one of the most important parameter. We considered also the ratio of packet received correctly by the destination vehicle (PDR), our protocol improves significantly this second parameter, and ensures more than 20% of packets received correctly.