Complex Behavior at Scale: An Experimental Study of Low-Power Wireless Sensor Networks

A new class of networked systems is emerging that involve very large numbers of small, low-power, wireless devices. We present findings from a large scale empirical study involving over 150 such nodes operated at various transmission power settings. The instrumentation in our experiments permits us to separate effects at the various layers of the protocol stack. At the link layer, we present statistics on packet reception, effective communication range and link asymmetry; at the MAC layer, we measure contention, collision and latency; and at the application layer, we analyze the structure of trees constructed using flooding. The study reveals that even a simple protocol, flooding, can exhibit surprising complexity at scale. The data and analysis lay a foundation for a much wider set of algorithmic studies in this space.