Experimental Investigation of Electromagnetic Reverberation Characteristics as a Function of UWB Frequencies

Abstract

Abstract-The electromagnetic reverberation time characteristics of indoor environments are experimentally investigated from 2 to 10 GHz with bandwidths up to 900 MHz. At a given frequency, the reverberation time is observed to be approximately constant up to 900 MHz. Moreover, the reverberation time decreases for increasing frequencies. Based on the theory of electromagnetic fields in cavities, a model to predict the room quality factor, reverberation time value, and average absorption coefficient is developed for the first time in indoor environments for the investigated frequency range. The validity and robustness of the model is investigated with data obtained for various environments, central frequencies, and bandwidths. The model is applied to another room over the whole 2-10 GHz frequency band and a maximum and average relative error of 22.30% and 8.80% were obtained, respectively, with an rms error of 1.90 ns. Furthermore, good agreement is obtained with measurements reported in the literature with settings falling into the model range; scenarios for which relative errors smaller than 10% were computed. The results demonstrate that this approach is not only an accurate alternative to the reverberation time measurements and computations of indoor environments in the 2-10 GHz frequency range but also a viable route to link propagation mechanisms in indoor scenarios with reverberation chambers.

Reverberation Time and Power Model in Indoor Wireless Scenarios

“…The PDP is time-averaged [19] and subsequently spatial-averaged [4] to provide more insightful understandings on characteristics of the channel. Reverberation time can thus be determined from the slope of the quasi-linear tail of Spatial-averaged PDP (SPDP) [5]:…”

“…Over the last decade, studies based on room electromagnetics manage to provide more insightful physical understanding for indoor wireless channels [1][2][3][4][5][6][7]. The room electromagnetics theory [1] points out that the electromagnetic waves in indoor wireless scenarios and the acoustic waves in room acoustics share similar behaviors in various aspects.…”

“…The index describes the decaying of primary component in reverberation models, and it can get closer to 2 than in traditional models [4]. Reverberation time is a key parameter in reverberation models [5][6][7], [9], [10]. It originates from room acoustics, where it is defined as the time in which the total energy falls to one millionth of its initial value [11][12][13].…”

“…Hence, the modeling of reverberation time is of great importance, as it is a basis of reverberation models. Most reported electromagnetic reverberation time models are based on either Sabine's or Eyring's equation [1], [4][5][6][7], [11], [12]. In analogy with acoustics, it is proposed in the two equations that electromagnetic reverberation time in an indoor wireless scenario is solely dependent on three parameters that are fixed by propagation geometry and materials: volume, surface and average absorption coefficient of the environment [11][12][13][14].…”

“…Also, the small scale fading characteristics including the modeling of PDP are rarely investigated. Meanwhile, most of these studies are limited in enclosed environments like conference rooms and classrooms [1][2][3][4][5][6][7], but semi-enclosed scenarios are rarely studied. Therefore, it is highly desired to develop a novel, accurate and more general reverberation model for indoor wireless scenarios.…”