GPS based vehicular collision warning system using IEEE 802.15.4 MAC/PHY standard

Detection of other vehicles in the vicinity of a moving vehicle is of primary importance to help the driver safely negotiate acceleration, deceleration and parking. In these situations the vehicle must acquire its positional knowledge with respect to others and be able to identify a possible collision. This paper introduces an active alarming system for predicting a collision between two or more vehicles using GPS and IEEE 802.15.4 MAC/PHY specification compatible system on chip (SOC). We develop a generic estimation mechanism for the safety coordinates of a vehicle based on its orientation, size, current speed, acceleration and its braking potential. Such safety coordinates are communicated among all vehicles in proximity and is used to determine overlaps thus detecting a possible collision. The IEEE 802.15.4 standard is designed for low rate wireless personal area networks and we investigate its applicability in a VANET through two series of tests. Firstly, we simulate a scenario of upto 10 vehicles in proximity and test the practically achievable throughput using commercially available SOCs. This gives an estimate of the best average latency the standard can support. We also simulate our system in NS2 and study the packet loss as a function of periodicity of packet transmission, the number of nodes and the mode of data transmission.