Reliable robust data transmission for unreliable high mobility sensor-based VANETs

To achieve active safe driving and autonomous driverless vehicle have become a key trend in Sensor-based Intelligent Transport Systems (S-ITS) recently. However, in the high-mobility unreliable Sensor-based Vehicular Ad-hoc NETworks (S-VANETs), the emergency messages or the driving videos are difficult to be sent to the receivers, the platoon leader or the cloud server in time. The efficiency of the active safe driving is thus degraded significantly. The reliable end-to-end transmission protocol suffers from extremely unreliable links and high mobility, and hardly provides an accurate congestion window (cwnd) for data transmissions. This paper thus proposes a Cross-Layer-based reliable robust Transmission Control Protocol, namely CL-TCP, to forward real-time emergency messages in Sensor-based VANET. To overcome the unstable network topology in VANET, this work proposes several TCP states: normal, congestion, loss, unstable, frozen and disconnecting, to control TCP cwnd according to the underlying network status of the layer 2 (L2) and the layer 3 (L3) protocols. Numerical results demonstrate that CL-TCP outperforms others in goodput, the number of link-breaks, average packet delivery ratio, etc. Furthermore, CL-TCP yields a higher fairness among sensor-based VANET connections.