Energy, bandwidth and time efficiency in data gathering applications

Data gathering applications constitute the main class of applications supported by wireless sensor networks. However, these networks have resources of limited capacity. In this paper, we show how to use the resources more efficiently by reducing the energy required and improving both the throughput and end-to-end delays that can be provided to such applications. The proposed solution is based on graph coloring. It ensures parallel transmissions, taking advantage of spatial reuse. It allows data gathering in a single cycle, reducing the data gathering delays and ensuring a better time consistency of collected data. It considerably reduces energy consumption by allowing nodes to sleep. Unlike TDMA-ASAP, it allows an immediate acknowledgement of unicast transmissions. We compare the number of colors needed by TDMA-ASAP and our algorithm for different configurations of wireless sensor networks. We compute the benefits brought by our coloring algorithm, in terms of bandwidth, consumed energy and maximum end-to-end delays. We also apply our solution to a ZigBee network. With network calculus, we compute buffer dimensioning and end-to-end delays. We then show how the active period of ZigBee is reduced with our coloring algorithm and thus energy is more efficiently used.