Evaluation of wireless sensor network monitoring for indoor spaces

Small-scale, medium-term deployments are an important tool when planning to install a wireless sensor network (WSN) monitoring system. It is vital to assess the software and hardware reliability of the desired solution in a well specified scenario. Also, it allows the system designer to evaluate beforehand the radio environment, a critical task in crowded environments such as buildings. The multitude of walls and large metal objects can produce unwanted effects such as fading and multi-path reflections while high powered radio devices produce interference when operating in the same band as the sensor nodes. This leads to a high packet loss rate and affect battery life through increased number of packet retransmissions. In this paper we report our results from a week long continues monitoring of an indoor space. Our focus is on sampling data for temperature, humidity, barometric pressure and ambient light. We analyze the results and provide experience regarding future real systems aimed at high spatial resolution measurements of environmental parameters indoors. Our study concerns sensor data, energy consumption of sensor nodes and radio channel characterization. A network sniffer is also employed to provide insight into the behaviour of the wireless mesh networking protocol. We consider that the relevance of our work can be highlighted in saved costs associated with maintenance operations and man-hours after a final, large-scale deployment of WSN instrumentation has already taken place.