Wireless energy autonomous sensor networks for automobile safety systems

Today modern cars are equipped with many electronic systems so that it is necessary to look at the quiescent current when the car is not in use and energy has to be delivered from the battery. One way to keep the quiescent current low is to replace conventional electronic systems like an intrusion detection system by an energy autonomous one. The approach within the research project ASYMOF (Energy Autonomous Microsystems with Mechanical Energy Harvester for Mobile (Safety-) Applications) is to use the example of a wireless glass break detection system. This paper presents a new wireless energy autonomous sensor network for automobile applications with built-in safety features like plausibility checks, encryption and radio channel monitoring. Special focus is laid on the MAC layer protocol design. Due to the fact that there are situations when a car is parked, e.g. in a parking garage, where not much energy can be harvested from ambient energy sources, the wireless sensor network has to be designed very energy efficient. Power consumption of the proposed wireless sensor network is computed and compared with other wireless networks employing different types of ALOHA MAC layer protocols for handling sporadic traffic without significant control overhead.