Mote Herding for Tiered Wireless Sensor Networks

We propose Mote Herding, a new system architecture for large scale, heterogeneous sensor networks. Mote herding uses a mix of many 8-bit sensor nodes (motes) and fewer but more powerful 32-bit sensor nodes (microservers). Mote herding groups motes into flocks that are connected via a multihop network to a microserver acting as a shepherd. Shepherds exploit their greater communications and compute power to form an overlay network, with many flocks joining to form a herd. By keeping each flock small and utilizing several shepherds, the herd can support many nodes with better latency, reliability, and energy efficiency than homogeneous architectures. Using the Mote Herding abstractions, we have implemented a set of services that run across both platforms, namely a mote routing service, a data reliability service and a resource discovery service that is based on three subservices. We evaluate the performance of our services using simulations and emulations of both sample scenarios and a habitat monitoring application. Our results show that the mote routing service is able to maintain better than than 99% connectivity at high network densities, while incurring 60% lower transmission overhead than two other routing protocols. We also show that the data reliability service is able to deliver 100% of the data even when more than 30% of the network exhibits failures. Finally, we show that the habitat monitoring application that uses Mote Herding is able to deliver all of the data with low control overhead and latency.