Rethinking the Importance of Accurately Simulating the Runtimes of Firmware used in Wireless Sensor Networks

Abstract

In a wireless sensor network, the energy consumption of the nodes continues to impose a tight constraint. Researchers have therefore proposed several MAC protocols to decrease the energy consumption of the radio transceiver, which has increased the complexity of the firmware running on the nodes. In this paper, we show the consequences of ignoring runtimes of state-of-the-art MAC protocols, as proposed by some simulators. The quantitative discussion is based on a comparison between hardware measurements and simulations. We ported the Contiki operating system to STEAM-Sim, a recently developed simulator. With this setup it is possible to omit runtimes of firmware in a stepwise manner. We further used STEAM-Sim to accurately evaluate the X-MAC, Low Power Probing, and ContikiMAC radio duty-cycling protocols. The energy consumption profiles of hardware modules thus generated give interesting insights into the protocols. Scalability comparisons to the state-of-the-art simulator COOJA/MSPSim show that scalable and time-accurate simulation of WSNs in the nanosecond range is possible.