An Experimental Validation of Accurate and Precise GNSS Time Synchronization in Vehicular Networks

Vehicular Networks are one of the enabling technologies for cooperative Intelligent Transportation Systems. For accurate and precise time synchronization in vehicular networks, Global Navigation Satellite System (GNSS) is getting increasing attention for effective use of its time dissemination to vehicular networks. In urban road scenarios, the blockage of satellite signals affects precise positing due to erroneous geometry. However, for timing, it creates less deflection as long as a single satellite is visible. With the recent development of Multi-GNSS receivers, signal reception no longer relies on a single GNSS constellation but all the existing four GNSS systems. This increases the number of visible satellites in the sky, thus increasing the coverage of satellite signals. Developing a method of GNSS time synchronization, we have conducted a systematic field-based study in this paper to determine the attainable timing accuracy in vehicular networks using commercial-grade GNSS receivers and off-the-shelf communication devices. Our experimental results show that the attainable timing accuracy from GNSS services in consumer-grade on-board devices can be as good as 2 microseconds. A momentary outage of GNSS time solution due to signal blockage on the road can lead a clock error of up to sub-microseconds, which still meets the desired requirement for most vehicular applications.