Service differentiation in multi-hop inter-vehicular communication using directional antenna

Inter-vehicular communication (IVC) on highways is one of the major application areas of ad hoc networks that enable multi-hop data exchange and forwarding between cars and between car and stationary gateways. In an IVC scenario, some emergency situations on highways may require an immediate communication with police, hospitals, highway assistance booth or with other cars. These messages should be forwarded on a top priority basis to the destination for immediate attention. So it is evident that, in an IVC scenario, some message flows are to be treated as high priority messages in order to ensure a timely and reliable delivery. We have proposed a priority-based communication scheme, which essentially selects shortest path for a high priority flow and reserves a zone known as high priority zone, along this path. Other low priority flows are forced to avoid this zone and take a longer diverse route to forward their messages to allow a contention-free communication to high priority flows. In this context, the use of directional antenna, having smaller transmission beam-width and larger transmission range compared to omni-directional antenna, helps to easily decouple interfering routes, and improves the overall utilization of the wireless medium through space division multiple access (SDMA).