RADIO CHANNEL CHARACTERIZATION FOR BLUETOOTH COMMUNICATION SYSTEMS ONBOARD COMMERCIAL AIRCRAFTS Leire Azpilicueta, Peio L opez Iturri, Erik Aguirre, and Francisco Falcone Department of Electrical and Electronic Engineering, Public University of Navarre, Pamplona, 31006, Spain; Corresponding author: leyre.azpilicueta@unavarra.es Received 1 April 2014 ABSTRACT: In this article, a model based on a three dimensional ray- launching algorithm is developed to analyze the behavior of a bluetooth system within a commercial aircraft. Results show that the use of deter- ministic techniques for radio planning purposes can aid to enhance the overall system efficiency. V C 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2660–2664, 2014; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.28669 Key words: 3D ray launching; channel modeling; bluetooth; wireless sensor networks 1. INTRODUCTION The airlines industry is increasingly requiring mobile communi- cations and Internet access that provide to passengers similar entertainment or business experience as their terrestrial counter- parts. Because of that, researchers as well as aircraft manufac- turers have shown strong interest in the development of wireless systems for on-board use. Focusing on applications within the cabin, there are a wide range of wireless technologies which are used for a broad range of applications, with different systems used depending on the final intended use, for example, wireless multimedia networks for in-flight entertainment [1, 2], deploy- ment of wireless local area network communication systems [3, 4], pilot health monitoring by means of wireless sensor networks [5], and sensing and monitoring. In the literature, the wireless channel for intravehicle com- munications has been studied within cars [6, 7], commercial air- crafts [8, 9], or trains [10]. This is an important task due to the occurrence of significant multipath propagation in this type of environment because of the major metallic mass of the vehicle. The implementation of a successful wireless communication sys- tem inside an aircraft is not a trivial task because it is a com- plex environment which cannot be compared with a typical indoor environment. The higher density of obstacles and the specific geometry make necessary an in-depth channel character- ization within the aircraft. Channel performance directly deter- mines the quality of the communication, in terms of coverage and capacity. Therefore, a very clear understanding of the chan- nel must be pursued to get enough quality and capacity trans- mission of the useful information using the more limited base stations and hot-spots to give an efficient service. Traditionally, analytical methods based on semiempirical approaches were used for radioplanning purposes. These meth- ods require low computational cost and provide limited accuracy [11, 12], whereas full wave techniques exhibit high precision results but also very high computational cost [13, 14]. As a mid- point, deterministic methods based on geometrical optics (GO) offer an adequate compromise between accuracy and calculation time [15]. Specifically, The Ray tracing method combined with uniform theory of diffraction is most frequently applied to radio coverage prediction [16–19]. This article aims characterizing the effect of radio wave propagation phenomena by means of an in-house developed 3D ray tracing method in on-board transceivers for a bluetooth com- munication system to assess the impact of the morphology of the aircraft as well as the topology of the wireless system. 2. SIMULATION TECHNIQUE AND MEASUREMENT RESULTS To assess the radio wave propagation within the aircraft, a three dimensional ray launching algorithm has been developed based on GO and geometrical theory of diffraction. Different applica- tions of this algorithm can be found in the literature, like the analysis of wireless propagation in closed environments [20–23], interference analysis [24] or electromagnetic dosimetry evaluation in wireless systems [25]. Ray launching techniques are based on identifying a single point on the wave front of the radiated wave with a ray that propagates along the space following a combina- tion of optic and electromagnetic theories. In the algorithm, power is modeled as a finite number of rays launched within a solid angle. Parameters such as frequency of operation, radiation patterns of the transceivers, number of multipath reflections, sepa- ration angle between rays and cuboid dimension are introduced. Phenomena such as reflection, refraction, and diffraction are con- sidered, as well as the material properties for all the elements within the considered scenario, given the dielectric constant and the loss tangent at the frequency range of operation. To validate the presented in-house ray-launching software which will be used for the simulations of the indoor environ- ment of the aircraft in next section, simulations and real meas- urements have been made in a typical office environment at the Public University of Navarra. Figure 1 shows the schematic rep- resentation of the scenario considered for simulation. This sce- nario has the inherent complexity of a typical office environment, with different types of walls (plywood and con- crete), interior columns and a variety of furniture as metallic and wooden boards, chairs, computers, tables, and so forth. This proposed scenario can emulate the behavior of complex indoor Figure 1 Schematic representation of the scenario used for validation of the 3D ray-launching code in an indoor environment. [Color figure can be viewed in the online issue, which is available at wileyonlineli- brary.com] 2660 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 56, No. 11, November 2014 DOI 10.1002/mop