Relay Selection for Heterogeneous Transmission Powers in VANETs

The main challenge in the vehicular ad hoc network vehicle-to-vehicle (V2V) multi-hop dissemination is to control the number of vehicles, that relay the broadcast message. Proper selection of relay nodes governs high delivery ratio, acceptable overall end-to-end delay, and efficient bandwidth usage. To date, several protocols have been proposed to identify appropriate relay vehicles. However, such approaches neglect the fact that vehicle transmission ranges are typically heterogeneous due to different transmission power values or dynamic adjustment of power to alleviate congestion and/or control energy consumption. In this paper, we introduce area-based dissemination protocols that work in heterogeneous transmission powers. The transmissions between relay vehicles are ordered in way that ensures that the node with high potential new coverage area transmits first. This eliminates useless transmission and retransmission that could be contained by other transmission. The new potential coverage area is computed as a function of the common overlap areas. In addition, we propose more reliable approaches by relaying duplicate received message. Thus, we introduce a geometric taxonomy for all possible overlap patterns in wireless environment, which is an apparently hitherto unsolved geometrical problem. Accordingly, we deduce the criteria used to define each pattern and relevant algebraic expression to compute the potential additional coverage area.