Applying wireless sensor networks (WSNs) in industrial applications usually requires cyclic and robust wireless communication of sensor data from the multiple sensor nodes deployed over an industrial plant to one or more base stations. These sensor values are typically processed by a central processing unit for data logging, control purposes, or for maintenance. In case the data are used in a control loop, low latency and highest reliability of the communication link are required. Additionally, the energy consumption of the sensor nodes determines if a WSN can be applied, because it should operate over months or years without maintenance from batteries or energy harvesting units.

We have developed a WSN operating in the 2.4 GHz ISM (industrial, scientific, medical) band for real-time monitoring of sensor data on a combustion engine test-bench. The demonstrator comprises 1XX sensor nodes, which are powered only by a solar cell in case of good ambient light conditions.
The sensor values are sampled at a rate of 10 Hz and a packet of 10 sensor samples is transmitted every second to the central processing unit, to minimize energy consumption. The TDMA (time division multiple access) protocol is designed in a way, that up to 4 retransmissions are possible to enhance the reliability of the wireless link, while keeping the 1 Hz update rate.