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Characterization of Wireless Propagation in Complex Indoor Scenarios

Leire Azpilicueta Fernández de las Heras

Electrical and Electronic Engineering Department, Public University of Navarre, 31006, Pamplona, Spain leyre.azpilicueta@unavarra.es

Abstract—In this work, the characteristics radiopropagation of wireless systems within complex indoor scenarios is presented. An analysis of the physical radio channel propagation inside different complex indoor scenarios is presented based on three-dimensional ray launching in house code. The influence of topology as well as morphology of complex indoor scenarios in the deployment of wireless sensor networks and wireless systems is analyzed. The use of adequate radioplanning strategies lead to optimal wireless network deployments in terms of capacity, quality of service, and reduced power consumption.

Index Terms—3D ray launching, channel modeling, wireless sensor networks.

I. INTRODUCTION The propagation study of complex wireless channels has

increased considerably in recent years because of the large amount of competition that exists in mobile communications systems. Channel performance directly determines the quality of the communication, in terms of sensitivity, capacity, and latency. Therefore, a very clear understanding of the channel must be pursued to get high-quality and high-capacity transmission of the useful information by using the more limited base stations and hot-spots to give an efficient service. It is highly important to consider the phenomena that affect radio propagation in complex indoor environments, being the most relevant fast fading [1-2] due to multipath propagation.

Traditionally, empirical methods were used (such as COST-231, Walfish-Bertoni, Okumura Hata, etc.) for initial coverage estimation. They give rapid results, but require calibration based on measurements in order to give an adequate fit of the results, based on initial regression methods. On the other hand, deterministic methods are based on numerical approaches to the resolution of Maxwell’s equations, such as ray launching and ray tracing (based on geometrical approximations) or full wave simulation techniques (MoM, FDTD, FITD, etc.) These methods are precise, but are time consuming to inherent computational complexity. As a mid-point, methods based on geometrical optics, for radio planning calculations with strong diffractive elements, offer a reasonable trade-off between precision and required calculation time [3].

The goal of this work is to assess the behavior of the radio channel in typical real indoor scenarios. The appearance of degradation effects fundamentally due multipath components

but also of phenomenon like reflection, refraction, diffraction, and scattering among others make the study of the associated radio channel a complex task. It is in this point where this work focuses its effort in order to optimize the wireless sensors deployment to achieve more efficient network coverage with the aid of an in-house 3D ray launching code.

II. SIMULATION TECHNIQUE AND RESULTS A 3D ray launching algorithm has been implemented in-

house, based on MatlabTM programming environment. Several transmitters can be placed within an indoor scenario, in which power is modeled as a finite number of rays launched within a solid angle. Parameters such as frequency of operation, radiation patterns of the antennas, number of multipath reflections, separation angle between rays and cuboid dimension are introduced. Phenomena such as reflection, refraction and diffraction are considered, as well as the material properties for all of the elements within the scenario, given the dielectric constant and the loss tangent at the frequency range of operation of the system under analysis. Fig. 1 shows a general indoor scenario (typical office of a department) that has been implemented in the simulator and the way in which rays impact with an object, storing the parameters in the different cuboids of the scenario.

Fig. 1. View of stored parameters of the ray in the indoor scenario.

Fig. 2. Bi-dimensional plane of estimated received power for a height of 1.36 meters in the indoor wagon train of Fig. 5.

Fig. 3. Bi-dimensional plane of estimated Delay spread for a height of 1.36 meters in the indoor wagon train of Fig. 5.

Fig. 4. Power-Delay Profile at a given cuboid located at the center in the

indoor scenario of Fig. 5.

Fig. 5. View of the schematic scenario of an indoor wagon passenger train. Fig. 2, Fig. 3 and Fig. 4 show simulation results of an

indoor wagon passenger train (depicted in Fig. 5). From the figures, it is shown the influence of morphology as well as topology of complex indoor scenarios in the deployment of a wireless system.

Fig. 6 and Fig. 7 show another complex indoor scenarios which corresponds with two different models of an aircraft. These scenarios have been analysed in terms of coverage and capacity with the aid of the 3D ray launching algorithm, leading to an optimization of wireless systems deployment inside them.

Fig. 6. View of the schematic scenario of two floors model of an aircraft.

Fig. 7. View of the schematic scenario of one floor model of an aircraft.

III. CONCLUSIONS In this work, the demands for modeling the radio channel in

complex indoor spaces are presented. The use of deterministic 3D ray launching algorithm implemented in-house allows the optimization in the placement of transceivers to improve system efficiency and obtain overall enhanced performance. The results show that by considering radio planning in complex indoor scenarios, the overall system performance can be strongly optimized.

REFERENCES [1] Hashemi, H., “The indoor radio propagation channel”, IEEE

Proceedings 81, pp. 943-968, 1993. [2] Hernández Rábanos, J. M., “Transmisión por radio”, Madrid: Ramón

Areces, 2008. [3] Iskander, M.F. and Yun, Z., “Propagation Prediction Models for

Wireless Communications Systems”, Microwave Theory and Techniques, IEEE Transaction on, vol. 50, nº3, pp. 662-673, March 2002.