Decentralised Data Piggybacking and Link Scheduling for Reliable Broadcast in VANETs

Unstable channel links in Vehicular Ad hoc Net- works (VANETs) make the design of reliable broadcast schemes challenging. Existing solutions fail to balance the requirements in Packet Delivery Ratio (PDR), latency and communication overhead, rendering the vehicular broadcast either severe packet losses, long time delay or excessive duplication. In this paper, we propose a Decentralized Cooperative Broadcast (DCB) scheme to provide reliable broadcast in VANETs with short latency and lightweight overhead, where all vehicles jointly piggyback some received data to help other neighbors recover the lost packet, and the broadcast links are also flexibly scheduled to enhance the broadcast efficiency. DCB requires no global information but has comparable performance with those solutions holding hypothetical global network information. We prove that DCB is an optimal solution to enhance the PDR when the broadcast is interference-free, and such potential interference can also be solved in DCB with little cost of a bounded time delay. Simulation results show that DCB can achieve an average PDR of 99.6% in less than 100 ms within a 50-vehicle network, which is far more efficient than existing solutions, even very close to the hypothetical centralized broadcast scheme.