A Unified Geolocation Channel Model--Part I (Path Loss)

Abstract

Indoor geolocation systems have emerged and have attracted a wide audience recently. There are three important components that constitute an indoor geolocation system: (1) transmitter, (2) receiver, and (3) indoor channel model. To some extent the primary transmitter design requirements are transmit power and a frequency or a set of frequencies of operation. The receiver is designed to operate at a certain distance from the transmitter and at the same frequency or set of frequencies of operation. Hence, any indoor channel model must take into account these two important design requirements. The indoor channel is perhaps very intriguing because multipath is ubiquitous due to high signal scattering, reflection, and refraction. It is been widely accepted in the literature that the two primary channel effects are (1) path loss and (2) multipath distribution. First, the path loss model is currently accepted to be a function of the transmitter and receiver geometry and frequency of operation. Second, the most widely used and accepted indoor channel multipath distribution models are Raleigh, Rician, and lognormal. As indicated in the second paper (or part II) the Rayleigh distribution is wider than Rician and Rician is wider than lognormal. This implies that the Rayleigh fading channel is the most severe and Rician fading is more severe than lognormal and lognormal is the least severe channel. Unfortunately, the dependency of the path factor on the frequency of operation in the context of a unified channel model is overlooked in the literature. Furthermore, there is no agreement on an indoor multipath distribution channel model. Although a unified channel model has not yet been found, in this paper we make a first attempt to present a unified channel model which consists of a unified path loss model and a unified multipath distribution model. The unified path loss model consists of an approach for linking together the path loss models of the three geolocation systems (macro-outdoor, micro-outdoor, and indoor) with the distance between the transmitter and receiver, R, and the frequency of operation, f. Although there are several parameters that affect the power loss factor, we consider R and f as the most important parameters for two reasons. Most of the geolocation systems presented in the literature are based on a direct measure of the time of travel; i.e., distance between the transmitter and receiver. The frequency of these systems varies; hence, the path loss factor varies as well. While unifying the path loss model was to some extent initiated in the literature, unifying the multipath distribution model is currently a silent quest in the literature. It appears that the tendency is to come up with newer and more sophisticated models that would explain the characteristics of the old models. The approach that we present in part II (on in a separate paper in the future) to unify the multipath distribution models is rather simple. The theoretical performance results are validated from the measurements currently reported in the literature.