Enhancing connectivity for spectrum-agile Vehicular Ad hoc NETworks in fading channels

In Vehicular Ad hoc NETwork (VANET) safety applications, connectivity among vehicles is important to disseminate the upcoming traffic information (e.g., warning messages generated by a source vehicle that detects an accident) to other following vehicles to notify drivers in a timely manner. Because of the highly dynamic VANET topology and the short transmission range mandated for Dedicated Short Range Communication (DSRC) by Federal Communications Commission (FCC), communication links among vehicles are short-lived especially in sparse vehicular density, making the task of establishing (through connection setup process) and maintaining the communications for fast-moving vehicles difficult. Furthermore, when a fixed transmission range is used in dynamically changing VANET, network could be easily suffered by a “broadcast-storm” in dense vehicular density while vehicles in VANET could be disconnected frequently in sparse vehicular density. In addition, when communication channels are overcrowded in VANET, vehicles should be able to switch from one radio frequency (RF) bands to another to make robust communication using spectrum-agile wireless environment. In this paper, we study the connectivity for spectrum-agile VANET in fading channels. Specifically, connectivity enhancement for vehicle-to-vehicle communications for vehicles traveling in opposite directions and for vehicles traveling in same direction is investigated using mathematical analysis and simulation results. Performance of the proposed approach is evaluated using numerical and simulation results.