Concurrent Measurements of the Vehicular Channel Transfer Function and the 802.11 Received Signal Strength Index

This paper describes experiments which study the effects of both a stationary and a moving vehicle on the 22 MHz 802.11b and the 20 MHz 802.11a channel transfer functions. Our setup enables concurrent measurements of: (1) the complex channel transfer function with a Vector Network Analyzer (VNA), and (2) the Received Signal Strength Index (RSSI) obtained using off-the-shelf 802.11 cards. Our results show that, for the case of the stationary channel, the average RSSI is a several dBs away from the channel loss measured by the VNA, even with meticulous calibration of the 802.11 cards. The VNA measurements show that a vehicle moving in an environment resembling a multi-lane highway can cause a change in the magnitude of the transfer function on the order of tens of dB. The results of the RSSI measurements show that changes in RSSI caused by the passing vehicle are in the order of magnitude of the ones measured with the VNA.