IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 54, NO. 4, JULY 2005 1225 Deterministic Wideband Modeling of Satellite Propagation Channel With Buildings Blockage Zoran Blazevic, Igor Zanchi, Member, IEEE, and Ivan Marinovic Abstract—The article presents an example of satellite propaga- tion modeling, applying the radio channel transfer function analy- sis as described and experimentally verified in scientific literature. The simulation of a satellite radio channel is executed by employ- ing "ray tracing" and the uniform geometric theory of diffraction- based method for an assumed urban and suburban environment and different polarizations. Derived results regarding the channel transfer function are analyzed via a simulation of the wideband propagation measurement system and the Fourier transform pro- cedures. It has been concluded that, contrary to ground cell radio system situations, where two-ray models usually suffice, a more de- tailed calculation should be considered for wideband satellite radio systems. Moreover, it is shown that the conclusions derived for the path loss and the delay spread depend not only on the specific propagation scenario, but also on the building permittivity. Index Terms—Doppler spectrum, impulse response, “ray- tracing”, satellite channel. I. INTRODUCTION M OBILE radio systems of today, like satellite ones, play an important role in various fields of human activities such as communications, positioning, telemetry, and meteorol- ogy. Despite the commercial failure of IRIDIUM and Globalstar, partly due to the rapid spread of ground cellular systems around the globe, the role of satellite systems is likely to be emphasized in future radio communications. Not only due to global cover- age, but also because of developing of broadband services such as digital video, precise positioning, and many others that are ideally suited for satellite transmission, they represent very suit- able devices to ensure the efficient global connectivity. However, regardless of the type of service, different propagation phenom- ena strongly affecting the receiving signal shape and quality are the unavoidable problems. For services like mobile telephone and low bit rate data transfer, which could be said to require nar- row channel bandwidths, fading characteristics of the channel obtained at the carrier frequency represent the basic data for a radio system design. Such a signal could then only be subjected to the time-selective fading caused by the system mobility. In contrast, signals used for a high-speed data transfer or precise positioning occupy much larger bandwidths. Hence, they are more likely to be exposed to both frequency and time-selective fading. To exploit the allocated spectrum with a high efficiency Manuscript received June 23, 2003; revised February 5, 2004, August 2, 2004, and November 8, 2004. The review of this paper was coordinated by Prof. A. Abdi. The authors are with the Department of Electronics, University of Split, Rudera Boskovica b.b, 21 000 Split, Croatia (e-mail: zblaz@fesb.hr; izanchi@ unist.hr; imarin@fesb.hr). Digital Object Identifier 10.1109/TVT.2005.851297 and to combat the channel selectivity, it is necessary to determine some basic channel parameters that define those fading terms. In this article, the possibility of their theoretical predictions, which relies on the propagationpath- loss models from [1]–[4], is presented. The corresponding measurements of various radio systems and propagation conditions have been analyzed in [3]–[9]. In [1], the low-earth orbiting (LEO) satellite prop- agation path loss curves in narrow band, at carrier frequency 1625 MHz, have been obtained using "ray tracing" and the uniform theory of diffraction (UTD) [13], [14] in conditions of the standard atmosphere [15], [16] with the constant k—factor of 4/3 and the smooth Earth surface. Wideband path loss models for ground radio systems, followed by their analysis and comparison with measurements or with other models, have been introduced in [3] and [4]. In [3], a simple two-path model for the ground cellular radio system at 2154 MHz, with the receiver in the shadow of a row of buildings, has been developed. Characteristics such as the delay domain path loss, the narrow- and wideband path loss, has been calculated and compared for the example. The analysis has been performed by the inverse Fourier transform (FT)—[12] based simulation of the wideband propagation measurement system (WPMS) [3], [4]. The transmitter was at fixed positions in both [3] and [4]. Contrary to those scenarios with a fixed transmitter, the fol- lowing analysis deals with a time-varying radio propagation channel, caused by a transmitter traveling in fixed orbit around the Earth. Thus, the characteristics of the radio channel such as path loss are varying with time even in the case of both the receiver and the scatterers being fixed. In addition, a time- varying satellite channel caused by the receiver’s mobility is introduced, with the assumption of a fixed satellite. The analy- sis of a simulated propagation channel is explained in Section II. In Section III, the example of a satellite channel geometry that involves a receiver settled on the street between two buildings is modeled by the ray tracing method. The simulation results for various positions of the receiver and the building characteristics are commented on and compared in Section IV. II. PROPAGATION CHANNEL ANALYSIS In opposition to ground radio systems, satellite transceivers are generally in different positions regarding their examined ra- dio environment and at much longer distances. Thus, the propa- gation conditions are quite different. In both cases, however, the received signal has a multipath nature caused by the same phe- nomena of diffraction, reflection, and the like. The field strength U Rx at a receiving point is the sum of all complex contributions U Rx,i , collected by the receiver from all N possible radio paths, a direct path and those caused by single or multiple reflection, 0018-9545/$20.00 © 2005 IEEE