27. Design of Real-Time MAC Protocol for Road Traffic Status Provision Using Sensor Networks

In ubiquitous environment, sensor networks that sense and transmit sensing data without human intervention will become more important. If sensors are installed for detecting vehicles and measuring their speed on the road and that information is given to drivers in real-time, it will be very effective for enhancing safety and controlling traffic on the road. In this paper, we proposed a new reliable and real-time sensor MAC protocol between AP and sensor nodes in order to provide real-time traffic information using ubiquitous sensor networks. The proposed MAC allocates one TDMA slot to each sensor node on the IEEE 802.15.4 based channel structure, introduces indirect communication via a relay for distant sensors, and adopts a frame structure that supports retransmission in case of errors. In addition, the proposed MAC protocol synchronizes with AP by using beacon and adopts a hybrid tracking mode that supports economic power consumption in various traffic situations. We implemented a simulator of the proposed MAC by using sim++ [1] and evaluated various performances. The simulation results show that the proposed MAC protocol reduces the power consumption and reveals excellent performance in real-time application systems.