Effects of Bandwidth on Observable Multipath Clustering in Outdoor/Indoor Environments for Broadband and Ultrawideband Wireless Systems

摘要

A multipath-clustering phenomenon, which is caused by the fact that scatterers tend to group together in realistic environments, has a significant impact on the channel capacity. For a band-limited system, due to the limitation of the signal time resolution, observable multipath-clustering is affected not only by propagation environments but also by the signal bandwidth. Since a larger bandwidth gives better time resolution, it is possible to observe more multipath components and, therefore, stronger clustering effects. In this paper, a new method based on the Delta-K model for multipath times of arrival (TOAs) is proposed to investigate and quantify the effect of signal bandwidth on observable multipath clustering. Furthermore, to completely characterize the time dispersion characteristics of the channel, a statistical model using a power ratio, a decay constant, and the Rician factor to describe multipath averaged power decay and amplitude fading is proposed. Newly derived formulas are given to relate the model parameters of a wideband signal, including those of the multipath TOA, averaged power decay, and amplitude fading, to those of a narrowband signal. The channel parameter estimation methods have been extensively validated by comparing the computed channel parameters with the ones extracted from the measured channel responses of 1.95 and 2.44 GHz broadband radios in metropolitan and suburban areas, and of 3-5 GHz ultrawideband signals in indoors.