An empirical evaluation of the consumption of 802.15.4/ZigBee sensor motes in noisy environments

This paper presents an empirical study of the effects of the channel occupation on the consumption of actual IEEE 802.15.4/ZigBee motes. The study is focused on the current demanded by a sensor node in a simple beaconless star topology when the CSMA contention algorithm introduces idle times in the activity of the radio transceiver. For this purpose, the developed testbed permits to define the probability of failure of the CCA (Clear Channel Assessment) operation, which is executed by the 802.15.4 MAC layer to check the availability of the radio channel before any transmission. The obtained results evidence that the sensor lifetime can be seriously diminished for CCA failure rates higher than 30%, which can be a common situation in Wireless Sensor Networks with tens of nodes where data must be updated several times per second.