Wideband measurements at 1.8 GHz across a 72- to 90-MHz bandwidth were carried out in the urban environments of Dublin (Ireland) city center and Manchester (England) city center. The measurements were conducted using a programable chirp sounder, which employed a heterodyne detector at the receiver. The digitized raw data were subsequently analyzed off-line by dividing the 72- or 90-MHz bandwidth into sections of 18 MHz. The resulting multipath delay structure as a function of frequency gave a panoramic view of the frequency selective fading of the individual multipath components. The effects of the frequency selectivity on the channel time delay descriptors such as average delay, rms delay spread, and the −10-, −15-, and −20-dB widths of the power delay profile were subsequently analyzed. These parameters were estimated both at the small-scale and large-scale levels as a function of frequency. For the 18-MHz sections, significant deviations of the order of 11.9–51.4% and 7.9–42.7% were detected in the small-scale channel characterization in Dublin city center and Manchester city center, respectively. In the large-scale characterization, deviations were more pronounced in the Dublin measurements, which were of the order of 19.2–65%, whereas the measurements from Manchester had deviations on the order of 5.2–14.2%. The results also show the effect of the bandwidth of analysis of the computed parameters. These effects are for the first time presented from the same set of measurements.
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