Modeling of ZigBee (IEEE 802.15.4) channel in rail environment for Intelligent Transport

To deploy Wireless Sensor Networks (WSNs) in the railway transport, knowledge of signal propagation in this environment is required for the safety and the reliability of whole system. This calls to two domains of research. Firstly, the study of the propagation characteristics is necessary to predict the propagation law that rules attenuation of the signal in the train environment along with the multipath characteristics. Secondly, the effects of external disturbance and interferences onto wireless signal must also be investigated. In this paper, we present first-ever measurements (to our knowledge) of propagation channel along railway track for WSNs. Extensive real hardware measurements of RSSI: Received Signal Strength Indication are presented and compared to the theoretical models, to investigate the IEEE 802.15.4 ZigBee propagation channel characteristics. Results of extensive measurement campaigns that validate Log-normal and shadowing path-loss model with accurate loss parameters at 2.4 GHz in outdoor environments are presented. A comparison of this model and extensive real hardware measurement in two selected scenarios is discussed.