Impact of location data freshness on routing in VANETs

In this paper, we propose a combination of GPSR (Greedy Perimeter Stateless Routing) and Hierarchical Location Service (HLS). They used to be combined in the original work with a direct method, i.e. GPSR takes care of routing packets and HLS is called to get destination position when the target node position is unknown or is not fresh enough. When a destination is quite far away from the sender, the exact position of the target is first calculated. An extra overhead is generated from the sender to the receiver. Our aim in this paper, is to reduce this overhead. Then, when we send the packet to the former region where the destination was supposed to be. When the packet enters into the same region than the target, an HLS request is sent to determine the exact position of the destination. In order to implement this concept, we have proposed a patch over the NS-2 simulator which mixes both GPSR and HLS according to our proposal. We have conducted various simulations and we have varied the freshness of the destination location data. The obtained results are promising in terms of latency, packet delivery rate and overhead.