Optimum Duty Cycle Evaluation for Slotted IEEE 802.15.4 Mac for Real Time Applications

Wireless Sensor Networks (WSNs) have been attracting increasing interest for supporting a new generation of ubiquitous computing systems with great potential for many applications such as surveillance, environmental monitoring, health care monitoring or home automation. Sensors and wireless sensor networks are being deployed around the world, measuring local and global environmental conditions. Their advanced sensing functionalities enable context-aware ubiquitous platforms, middleware and applications to proliferate. Recent advances in micro-electro-mechanical systems technology, wireless communications, and digital electronics have enabled the development of low-cost, low-power, multi-functional sensor nodes that are small in size and communicate over short distances. Low-rate low-power consumption and low-cost communication are the key points which are associate with wireless sensor networks and that lead to the specification of the IEEE 802.15.4 standard for WSN. Nevertheless, when addressing applications with (soft/hard) timing requirements some inherent paradoxes emerge, such as power-efficiency versus timeliness. Consequently, there is the need of engineering solutions for an efficient deployment of IEEE 802.15.4 in such scenarios. The current specification of the IEEE 802.15.4 standard for beacon-enabled wireless sensor networks does not define how the fraction of the time that wireless nodes are active, known as the duty cycle, needs to be configured in order to achieve the optimal network performance in all traffic conditions. This paper proposed an optimal duty cycle decision mechanism that adapts the duty cycle during run time without the need of human intervention in order to minimize power consumption while balancing probability of successful data delivery and delay constraints of the application.