Geographic routing has been widely studied over the years as an effective solution for Vehicular Ad Hoc Networks (VANETs), especially because of the availability of wireless devices and global positioning system services. Given the unpredictable behavior of VANETs, selecting the next relay node has been proved a very challenging task. Therefore, in order to maintain acceptable network performance, the routing algorithm needs to be carefully designed to adapt to the fast network changes. The Geographic Perimeter Stateless Routing (GPSR) protocol is a widely adopted position-based routing protocol for VANETs, which makes it a good benchmark candidate. In this paper, we analyze the shortcomings of GPSR and propose a new strategy named Path Aware GPSR (PA-GPSR), which includes additional extension tables in the Neighbors' Table to select the best path and bypass the nodes that have delivered such previous packets in recovery mode. Moreover, our proposed algorithm can eliminate packet routing loops avoiding the delivery of the same packet to the same neighbor node. These PA-GPSR features can, for instance, help to overcome link-breakage due to the unavoidable reasons, such as road accidents or dead-end roads. We used the Simulation of Urban MObility (SUMO) and Network Simulator-version 3 (NS-3) platform to compare our proposed algorithm to the traditional GPSR and Maxduration-Minangle GPSR (MM-GPSR) in scenarios varying the number of nodes as well as the number of source-destination pairs. Our results show that the proposed PA-GPSR strategy performed better than the traditional GPSR and MM-GPSR when packet loss rate, end-to-end delay, and network yield are considered as performance metrics.

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Vehicles on cooperative inter-vehicular applications establish a mutual awareness of their presence by periodically broadcasting beacon messages. However, high vehicle density and poorly controlled beaconing lead to congested channel and degradation of system performance. Periodic beaconing may also lower the delivery rate of beacons and other types of messages. In this paper, we describe a beaconing rate control approach considering the density of nodes during beacon forwarding and adjusting the successive beacon delay to mitigate the congestion and maximize the delivery efficiency of beaconing. Our strategy can be adopted for any beacon-based algorithms. Therefore, we selected the widely adopted position-based routing protocol for VANETs known as Geographic Perimeter Stateless Routing (GPSR) to apply the proposed algorithm and evaluate the impact in the performance metrics. Our proposed algorithm shows performance improvement over standard GPSR related to the number of drops caused by collision and beacon load reduction, which keeps the information accuracy.

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