Minimum real-time chunk delay for active safe driving in vehicular ad-hoc networks

The active safe driving application offers real-time video streaming services and real-time emergency messages (EMs) to improve the driving safety in intelligent transportation systems (ITS). As the required (or shared) video and EM quality increasing, the constraints of packet delay, packet loss rate and the required bandwidth of packet transmissions become critically in Vehicular Ad-hoc NETwork (VANET). Multicasting is thus adopted to reduce the bandwidth waste rate while a sender wants to send real-time videos to a group of receivers. Although the multicasting VANET can adopt the retransmissions of lost chunks, it yields a long multicasting delay and wastes bandwidth for re-sending video chunks to the receivers that have successfully received chunks. This paper thus proposes a Peer-to-Peer (P2P) overlay network to cooperate with the multicast VANET, namely the minimum Delay-Guarantee chunk Reloading approach (DGR), to reload the lost or unconfirmed chunks timely. In DGR, a chunk with the least delay to the lost-chunk node is selected as the optimal compensating chunk. Numerical results demonstrate that DGR outperforms the compared approaches in successful chunk reload rate, average chunk delay, and chunk delivery ratio. Clearly, the retransmission-based multicasting and the random chunk-selection mechanism lead to obvious long delay and large bandwidth waste rate.