A novel automated site survey system

Evaluating the propagation of wireless signals in and indoor environment has become important for the design of wireless local area networks (WLANs) and for predicting cell phone coverage within buildings. This paper describes a robot used to measure the field strength as a function of position along a path in an indoor scenario. The robot is a platform that follows tape applied to the floor, and carries a battery-operated transmitter. The signal is received by a sleeve dipole antenna on a tripod and fed to a spectrum analyzer. A computer running a LabVIEW program reads the signal strength at each point and then commands the robot to move to the next point, using a 900-MHz wireless link. There are no cables interconnecting the robot and the receiving system. Because the system is fully automated, it can measure 1000 data points along a path relatively quickly. Sample results are presented for the field along a hallway centerline at 2.361 GHz, with a point spacing of 2 cm.