Optimal roadside units placement along highways

Roadside units (RSUs) are a critical component of Vehicular ad hoc network (VANET). Ideally, RSUs should be deployed pervasively to provide continuous coverage or connectivity. However, during the initial stages of VANET, it will not be possible to ensure such a pervasive RSU deployment due to the huge cost and/or the lack of market penetration of VANET enabled vehicles. Given a limited number of RSUs, in this paper, we address the issue of optimal placement of these RSUs along highways with the goal of minimizing the average time taken for a vehicle to report an event of interest to a nearby RSU. We present a so-called balloon optimization method - the optimal solution is found by using a dynamic process similar to the natural expansion of multiple balloons in a two-dimensional space where each balloon corresponds to the coverage area of one RSU. Our preliminary evaluation shows that the balloon method performs optimal or near optimal compared with the exhaustive method and it can be used for the optimal placement of RSUs along highways.