A time-recordable cross-layer communication protocol for the positioning of Vehicular Cyber-Physical Systems

Vehicular Cyber-Physical Systems are a rapidly growing research field that has applications in a variety of locations that include urban centers, underground parking lots, as well as tunnels environments. These systems require real-time or constant location information, but the traditional satellite signal-based positioning systems do not work well in tunnels or urban centers with dense skyscraper due to satellite signal Non-Line-Of-Sight (NLOS) problem. The One-Sided Synchronous Two-Way Ranging (OSS-TWR) algorithm can remedy the imprecise positioning of satellite signal-based positioning systems by using a Dedicated Short Range Communications (DSRC) link between the vehicle and Road Side Units (RSUs). However, the unavoidable network collisions in these wireless communication systems will severely influence the measurement of the signal flight of time, thus significantly degrading positioning estimation accuracy of OSS-TWR. In this paper, a cross-layer communication protocol is proposed to enhance OSS-TWR by compensating for the impact of network collision. Firstly, OSS-TWR positioning algorithm is analyzed and the reasons for the poor precision location estimation are further explored. Secondly, a time-recordable back-off algorithm is proposed that can record the total back-off time for a frame resend resulting from a network collision. Following this, the experimental ranging results show that the proposed algorithm is practically feasible and is superior to OSS-TWR.