A Cooperative Positioning Method for VANETs using DSRC Carrier Frequency Offset

Vehicular positioning in urban canyons or covered areas such as car parks is a challenging issue due to the limited availability or lack of Global Navigation Satellite System (GNSS) signals. Tackling this problem, the concept of Cooperative Positioning (CP) has recently emerged for positioning or positioning enhancement in Vehicular Ad-Hoc Networks (VANETs). In the literature, CP techniques are generally based on vehicular communication and range estimates between the vehicle and some reference nodes with known position. The viability and performance of conventional radio ranging methods such as Received Signal Strength (RSS), Time of Arrival (TOA), and Time Difference of Arrival (TDOA) for vehicular environments is questionable. Avoiding the constraints and shortcomings of radio-ranging methods, a new CP technique is presented. This technique is based on range-rate estimates between the vehicle and reference nodes. Range-rate is estimated using Carrier Frequency Offset (CFO) of the vehicular communication signals. The performance of the proposed CP method is evaluated with regard to the speed of the vehicle and CFO noise. The possibility of CFO-based range-rating is verified experimentally. It is concluded that, range-rate-based CP is a potential method for CP where the GNSS signal is weak or not available.