LAUSR

In low-power Internet of Things (IoT) devices, designed for harsh environments, radio duty cycle (RDC) at the MAC layer provides energy efficiency to achieve network longevity. RDC can be either static or dynamic. In a static RDC (SRDC) mechanism, all nodes possess the same but fixed RDC value. In a dynamic RDC (DRDC) mechanism, nodes possess different RDC values due to indigenous conditions, for example, traffic load and battery status. To synchronize, IoT nodes use a phase-lock mechanism, where the sender estimates the wake-up time of the receiver in order to awake with it. Phase lock works well in SRDC because all nodes have the same RDC value, but it is affected in the DRDC mechanism because a sender does not know the wake-up time of the receiver that has changed the RDC value. This creates a problem. Although ContikiMAC is the most wide SRDC mechanism, it does not perform well in DRDC environments. State-of-the-art DRDC mechanisms, which predominantly work based on the RDC mechanism of ContikiMAC, do not share their RDC with neighbors and, therefore, work poorly in dynamic environments. This article proposes a novel adaptive dynamic RDC (AD-RDC) mechanism based on the extended phase lock, where nodes dynamically adjust their RDC based on traffic load and residual energy and share it with neighbors to remain synchronized. Simulations, performed in the Cooja emulator, reveal that the proposed AD-RDC has improved the packet delivery ratio, network lifetime, end-to-end delay, and broadcast reachability in DRDC environments.