Throughput maximization under guaranteed dissemination coverage for VANET systems

Vehicular Ad Hoc Network (VANET) technology enables efficient inter-vehicular communications for the broad-casting of public-safety and other critical message flows among unmanned autonomous vehicles. A key challenge in VANET broadcasting is to achieve a high throughput rate while at the same time assure the delivery of packet flows to all the vehicles traveling over a targeted segment of the highway. We have proposed a Vehicular Backbone Network (VBN) protocol for dynamically synthesizing a networking scheme that supports message flows from a Road Side Unit (RSU) to vehicles traveling along a highway. Though proven to achieve significant throughput-rate improvements compared with existing protocols, a design of a VBN that maximizes the end-to-end throughput rate while guaranteeing the coverage scope of message flows has not been addressed. In this paper, we develop an analytical model that accurately characterizes the maximum throughput rate performance achievable under a prescribed outage probability constraint. We consider a spatial-reuse TDMA-based VBN. A joint optimization of inter-relay distances, transmission rates, and spatial-reuse factors, which has not yet been addressed in the existing literatures, is carried out. These results are confirmed by comparison with simulation results. They also serve as essential benchmark and performance upper bounds that characterize the behavior of robust distributed VBN protocols, applicable to VANET systems that provide vehicle-to-vehicle communications among stochastically roaming highway vehicles.