EADS Innovation Works, Germany
Many Media Access Control (MAC) protocols for Wireless Sensor Networks (WSN) use variations of the popular Carrier Sense Multiple Access (CSMA) protocol due to its simplicity and its high performance in low traffic scenarios. However, CSMA does not always represent a good choice for WSNs since typical low power transceivers require a significant time to switch between receiving and transmitting and vice versa. Sensor nodes are not able to detect a busy channel during the switching. Thus, the collision probability in WSNs is very high in case of correlated event-driven traffic. In this paper we introduce the BPMAC protocol that uses a backoff preamble with variable length in order to mitigate the effect of Clear Channel Assessment (CCA) delay.