Integrated cooperative localization for Vehicular networks with partial GPS access in Urban Canyons

Accurate and ubiquitous localization is the driving force for location-based services in Vehicular Ad-hoc NETworks (VANETs). Most of present vehicle localization systems rely on Global Positioning Sytems (GPS). In urban canyons, GPS suffer from prolonged outages. Other vehicle motion sensors (e.g. gyroscopes, accelerometers and odometers) suffer from unsustainable error accumulation. This research presents a novel Cooperative Localization scheme 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. Our scheme is also extended to account for the scenarios where some of the vehicles might experience GPS availability for a short duration. The ultimate aim of this work is to efficiently manage and coordinate this heterogeneous set of sensors/technologies into a consistent, accurate, and robust navigation system. Different scenarios using different velocities and neighbors' densities were implemented. GPS updates with different percentages and error variances were also introduced to test the robustness of the proposed scheme. 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. Results show that our RISS-based scheme outperforms the non-cooperative RISS typically used in challenging GPS environments. GPS updates with low error variance can enhance the accuracy of the proposed cooperative scheme and share this enhancement among the network. Moreover, we compare our proposed scheme to a GPS cooperative scheme and demonstrate the reliability of a RISS-based cooperative scheme for relatively long time duration.