RR-ALOHA, a Reliable R-ALOHA broadcast channel for ad-hoc inter-vehicle communication networks

Ad-hoc networking is under evaluation for inter-vehicle communication architectures. In spite of the large existing literature, many problems generated by the peculiarity of this specific scenario are still unsolved. In this paper we present a novel MAC protocol, RR-ALOHA, able to guarantee a reliable single-hop broadcast communication in an ad-hoc network environment where the hidden terminals problem exists. This protocol is designed for the inter-vehicle communication architecture based on UTRA-TDD slotted physical channel, but can be easily modified to operate on other standard physical layers. According to this protocol any active terminal can reserve a channel by capturing a slot in the frame. Reliable communication is guaranteed, after access, even in presence of hidden terminals thanks to the information exchanged by the active terminals. The operation of the protocol is completely distributed and enables also to install channels of different speeds to satisfy QoS of different services. The protocol feasibility and some basic performance figures are discussed to prove the effectiveness of the protocol itself in the inter-vehicle communication scenario.