Time dispersion measurements in urban microcellular environments

Time dispersion measurements have been conducted in the urban city centre of Liverpool at 1800 MHz. The measurement setup is based on the swept time-delay cross-correlation technique and has a time-delay resolution of 33 ns. The use of automatic gain control (AGC) circuitry in the RF stage permitted the observation of the spatial variation of the multipath power delay profile and RMS delay spread. The experimental work investigated the dependence of RMS delay spread on base antenna height, gain, downtilt and distance in the LOS and non-LOS regions of the microcell. The results obtained indicate that (a) the RMS delay spread is less than or equal to 520ns/280ns in the LOS/non-LOS regions, (b) that the delay spread increases with antenna height and with the use of a directional antenna but decreases with downtilt. Furthermore, the RMS delay spread results are compared with theoretical results obtained using geometrical optics (GO) and the uniform theory of diffraction (UTD).<>