Integrated Cooperative Localization in VANETs for GPS Denied Environments
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Accurate and ubiquitous localization is the driving force for location based services in Vehicular Ad-hoc NETworks (VANETs). In urban areas, Global Positioning System (GPS) and in-vehicle navigation sensors (e.g. odometers) suffer from prolonged outages and unsustainable error accumulation, respectively. The need for precise vehicle localization remains paramount, and cooperative vehicle localization based on ranging techniques are being exploited to this end. This research presents a novel Cooperative Localization (CL) scheme called CL KF-RISS that utilizes Round Trip Time (RTT) for inter-vehicle distance calculation, integrated with Reduced Inertial Sensor System (RISS) measurements to update the position of not only the vehicle to be localized, but its neighbors as well. We adopted the Extended Kalman Filter (EKF), to limit the effect of errors in both the sensors and the neighbors' positions, in computing the new location. In comparison to the existing cooperative localization techniques, our proposed cooperative scheme does not depend on GPS updates for the neighbors’ positions thus making it far more suitable in urban canyons and tunnels. In addition, our scheme considers updating the neighbors' positions using their current inertial sensor measurements resulting in improved position estimation. The scheme is implemented and tested using the standard compliant network simulator 3 (ns-3), vehicle traces were generated using Simulation of Urban MObility (SUMO) and error models were introduced to the sensors, the initial and the updated positions. Different scenarios using different velocities and neighbors' densities were implemented. GPS updates with different percentages and error variances were introduced to test the robustness of the proposed scheme. Results show that our scheme outperforms the non-cooperative GPS and the non-cooperative RISS typically used in challenging GPS environments. Moreover, we compare our proposed scheme to a cooperative scheme based on GPS positions and demonstrate the reliability of a reduced inertial sensor system (RISS)-based cooperative scheme for relatively long time duration.