Some preliminary short-range transmission loss measurements for wireless sensors deployed on indoor walls

Antenna characteristics and propagation are of fundamental importance to the coverage, capacity and service quality of all wireless communication systems. This paper presents short-range narrowband propagation measurements at 2.445 GHz for sensor network applications in an indoor environment. The effect of sensor node location on a wall has been determined for a pair of linearly polarised rectaxial antennas and a pair of ceramic patch antennas. Propagation loss has been measured as a function of (i) node separation (i.e. link length), (ii) node drop (i.e. vertical displacement of nodes below the ceiling) and (iii) node height (i.e. the perpendicular displacement of the nodes from the wall surface). It is observed that there is no significant effect of wall offset. In addition, the path loss exponent n generally increases with decreasing node drop.