GPS based wireless communication protocols for vehicular ad-hoc networks.

摘要

In this dissertation, GPS based wireless communication protocols for two important problems in VANETs, namely broadcasting and Internet access, are proposed. The common feature of the new protocols is using the position information of vehicles in the MAC layer. Inter-Vehicle Communication Systems rely on multi-hop broadcast to disseminate information to locations beyond the transmission range of individual nodes. Our multi-hop broadcast protocols are proposed to address the broadcast storm, hidden node, and reliability problems of multi-hop broadcast in vehicular networks. In these proposed protocols, the functions of forwarding and acknowledging a broadcast packet are assigned to only one vehicle by dividing the road portion inside the transmission range into segments and choosing the vehicle in the furthest non-empty segment without a priori topology information. Assigning the forwarding function to only one vehicle is sufficient for successful broadcast in vehicular ad-hoc networks (VANETs) because of their special topology constrained by roads.; For the Internet access problem, a new cross-layer communication protocol for vehicular Internet access along highways is introduced. The objective of the new Controlled Vehicular Internet Access (CVIA) protocol is to increase the end-to-end throughput while achieving fairness in bandwidth usage between road segments. To achieve this goal, the CVIA protocol eliminates contention in relaying packets over long distances. CVIA creates single-hop vehicle clusters and mitigates the hidden node problem by dividing the road into segments and controlling the active time of each segment. Using an analytical throughput estimation model, the protocol parameters are fine-tuned to provide fairness among road segments. Finally, extentions to support QoS under the CVIA protocol are introduced. The new protocol, CVIA-QoS, uses admission control for soft-real time traffic to provide delay bounded throughput guarantees.