900 MHz multipath propagation measurements for US digital cellular radiotelephone

The results of multipath power delay profile measurements of 900-MHz mobile radio channels in Washington, DC, Greenbelt, MD, Oakland, CA, and San Francisco, CA, are presented. The measurements have focused on acquiring worst-case profiles for typical operating locations. The data reveal that at over 98% of the measured locations, RMS (root mean square) delay spreads are less than 12 μs. Urban areas typically have RMS delay spreads on the order of 2 to 3 μs and have continuous multipath power out to excess delays of 5 μs. In hilly residential areas and in open areas within a city, RMS delay spreads are slightly larger, typically having values of 5 to 7 μs. In very rare instances, reflections from city skylines and mountains can cause RMS delay spreads in excess of 20 μs. The worst-case profiles show resolvable components at excess delays of 100 μs which are 15 dB down from the first arriving signal. Depending on the precise symbol duration, unequalized 40-kb/s TDMA (time division multiple access) channels will be harmed by multipath at less than 1% to 4% of vehicle locations.