GNSS time synchronization in vehicular ad-hoc networks: benefits and feasibility

Time synchronization is critical for operation of distributed systems in networked environments. It is also demanded in Vehicular Ad-hoc NETworks (VANETs), which, as a special type of wireless networks, are becoming increasingly important for emerging Cooperative Intelligent Transport Systems (C-ITSs). Global Navigation Satellite System (GNSS) is a proven technology to provide precise timing information in many distributed systems. It is well recognized to be the primary means for vehicle positioning and velocity determination in VANETs. However, GNSS-based time synchronization is not well understood for its role in coordination of various tasks in VANETs. To address this issue, this paper examines the requirements, potential benefits and feasibility of GNSS time synchronization in VANETs. The availability of GNSS time synchronization is characterized by almost 100\% in our experiments in high-rise urban streets, where the availability of GNSS positioning solutions is only 80\%. Experiments are also conducted to test the accuracy of time synchronization with 1 PPS signals output from consumer-grade GNSS receivers. They have shown 30 ns synchronization accuracy between two receivers of different models. All these experimental results demonstrate the feasibility of GNSS time synchronization for stringent VANET applications.