Energy-Efficent TDMA Design Under Real-Time Constraints in Wireless Sensor Networks

Many wireless sensor networks (WSNs) are used to collect and aggregate data from potentially hostile environments. Catering to this, early application scenarios did not put tight constraints on performance properties like delay, but rather focused on ruggedness and energy conservation. Yet, there is a growing number of sceanarios like e.g. production monitoring, intrusion detection, or health care systems which depend on the sensor network to provide performance guarantees in order to be able to act upon the phenomena being sensed in a timely fashion. Nevertheless, these applications still face the traditional issue of energy-efficiency. In this paper, we present means to find energy-efficient medium assignments in time-slotted multi-hop networks that satisfy given real-time constraints. Specifically, we present a way to find the optimal length of time slots and periods in TDMA schemes. We also present a software to compute those values for typical sink-tree WSNs. Index Terms--Wireless Sensor Networks, Energy-Efficiency, Real-time guarantees, Optimal TDMA, Network calculus.