Characterisation of a time-variant wireless propagation channel for outdoor short-range sensor networks

This study presents sample measurements and analysis characterising the radio channel for outdoor short-range sensor networks. A number of transmit and receive antennas are placed on the ground in an open area. The measured propagation channel is time varying because of the controlled motion of a person walking in the vicinity of the nodes. The statistics of both the line-of-sight (LOS) path and the scattered component of the measured channel are observed to be non-stationary. The channel (power) gains are found to be significantly influenced by the pedestrian movement, only when the LOS path is momentarily blocked. The authors present a generic approach to model receive signal fluctuations because of body blockage of the LOS path. Our approach, which is similar to the referenced work of Pagani and Pajusco, additionally models the time-variant Doppler spectrum of the residue (scattered) component of the measured channel, that is the remainder of the measured channel after the LOS path has been extracted. The proposed modelling approach is parameterised and validated from the measurements.