Multi-frequency radiowave propagation measurements in the portable radio environment

Time-delay-spread and signal-level measurements were made in two dissimilar office buildings at 850 MHz, 1.7 GHz, and 4.0 GHz. No significant statistical difference in time-delay spread was found. The maximum RMS time-delay spread at the three frequencies did not exceed 270 ns at the larger building and 100 ns at the smaller building. Attenuation, although very nearly the same, decreased slightly with increasing frequency, within the limits of the experiment´s accuracy. The variation of the received signal level with distance could be characterized by free-space propagation, together with attenuation per unit distance. This attenuation coefficient decreased slightly with increasing frequency. The fractional error was found to be a useful measure of the spread of the data