Abstract
The rapidly growing demand for accident-free driving in intelligent transportation makes reliable broadcast a critical factor for vehicular ad hoc networks. Existing solutions always try to improve the broadcast reliability by retransmitting lost packets. However, the excessive retransmissions can easily cause unpredictable time delay and even broadcast storms, rendering the reliable broadcast problem unsolved. In this paper, a novel reliable broadcast scheme is proposed by exploring the advantages of lost data piggybacking. Our scheme allows all the vehicles to piggyback some received packets cooperatively to help other vehicles to recover the lost packets. We formulate the cooperative piggybacking problem as a cooperative offloading game and present a decentralized solution to compute the optimal data piggybacking solutions based on only partial network information. A reward-penalty scheme is designed for the offloading process to impel all the vehicles' decisions that converge to the Nash equilibrium, which is proved to be the global optimal solution to the decentralized offloading scheme. Simulation results show that the proposed cooperative offloading scheme can achieve much higher broadcast reliability and lower propagation delay, in comparison with existing solutions. In a small vehicle network, all lost cooperative awareness messages can be successfully recovered within 25 ms after the initial broadcast by using the data traces generated by GEMV(2). Copyright (C) 2016 John Wiley & Sons, Ltd.