MBR: A Map-Based Relaying Algorithm for Reliable Data Transmission through Intersection in VANETs

In recent years, a number of routing protocols have been proposed for urban vehicular ad-hoc networks (VANETs). Yet, a common issue in these protocols is that the building shadow effect at intersections is not carefully considered. As a result, the performance of these routing protocols may degrade as the data transmission at the intersections can be severely affected by the building shadowing. To solve this problem, in this paper, we propose MBR, a map-based relaying algorithm in the MAC layer, to enhance the performance of the routing protocols in urban VANETs. To improve the reliability of data transmission at intersections, MBR novelly utilizes the digital map and the Geohash coding system to relay the packets (frames) in the MAC layer, and selects the optimal relay node based on the relative position of the nodes and the intersection. In this paper, we propose two versions of the algorithm: MBR-S utilizes a single IEEE 802.11p radio; and MBR utilizes a collaboration of the IEEE 802.11p channel and the Sub-1GHz channel, which has border communication range in the intersections than that of MBR-S. Both our real world experiments and extensive simulations demonstrate that MBR-S can significantly improve the performance of the state-of-the-art VANET routing protocols, which can be further enhanced with the collaboration of two channels.