Asynchronous energy-efficient MAC protocols for wireless sensor networks

In this paper, we propose two asynchronous energy-efficient MAC protocols: A-MAC and ASCEMAC, from contention- and schedule-based perspectives correspondingly. Through applying free-running method, novel rescheduling and time-slot allocation schemes, A-MAC and ASCEMAC do not require network time synchronization any more, which is necessary in existing energy-efficient MAC protocols. So, our algorithms are more suitable for the system which is difficult to ensure perfect network time synchronization. Moreover, we present a traffic-intensity- and network-density-based model to compute essential algorithm parameters: power on/off duration, interval of schedule broadcast, as well as super-time-slot size and sequence.