L. Valle

CINDOOR: an engineering tool for planning and design of wireless systems in enclosed spaces

This paper presents the program CINDOOR. This program is an engineering tool for aiding in the design, planning, and effective implementation of wireless systems in general enclosed spaces. The method underlying CINDOOR is a flexible approach to the propagation process, allowing analysis of indoor and outdoor environments and the interaction between them. The method is based on a full three-dimensional implementation of GO/UTD. Ray tracing is efficiently carried out by combining image theory with binary space partitioning algorithms. The space-time distribution of the electromagnetic field is processed to obtain a set of magnitudes that form a basis for planning a wireless system: coverage (mean power), fading statistics, power delay profile and associated parameters, such as the rms delay spread and the coherent bandwidth.

An accurate and efficient method based on ray-tracing for the prediction of local flat-fading statistics in picocell radio channels

Ray-tracing techniques have proven to be very useful for the analysis and design of wireless systems both in urban microcells and in indoor picocells. At present, the optimization of these techniques enables not only the signal mean level but also the local statistics to be estimated accurately, which is of great practical importance. A wide range of comparisons between measurements and simulations confirming this have been carried out by the authors, and some examples are presented. The most interesting contribution of this paper is that starting from the signal information at one single point, obtained using ray-tracing techniques, it is possible to estimate the signal statistics in a local area of that point. This possibility substantially reduces the local statistics calculation time, confirming the idea that an efficient site specific channel model might be feasible. Finally, it is also shown that ray-tracing techniques are able to accurately estimate the first- and second-order statistics in those environments where the Clarke (1968) or isotropic scattering model is not applicable.

An efficient ray-tracing method for radiopropagation based on the modified BSP algorithm

A new and efficient ray-tracing method based on a combination of image theory and the binary space partitioning (BSP) algorithm is presented. The efficiency of the method allows a full three-dimensional implementation of the Geometrical Optics and the Uniform Theory of Diffraction (GO/UTD). The optimization of ray-tracing makes it possible to take into account a great number of rays: reflected, diffracted and multiple combinations of these effects. This degree of precision in the calculation of the signal levels permits an accurate estimation not only of the signal mean level but also its statistics. The main feature of the method is the possibility of analyzing the radio channel in general enclosed spaces, including indoor, outdoor and mixed indoor/urban environments.

Coverage optimization and power reduction in SFN using simulated annealing

An approach that predicts the propagation, models the terrestrial receivers and optimizes the performance of single frequency networks (SFN) for digital video broadcasting in terms of the final coverage achieved over any geographical region, enhancing the most populated areas, is proposed in this paper. The effective coverage improvement and thus, the self-interference reduction in the SFN is accomplished by optimizing the internal static delays, sector antenna gain, and both azimuth and elevation orientation for every transmitter within the network using the heuristic simulated annealing (SA) algorithm. Decimation and elevation filtering techniques have been considered and applied to reduce the computational cost of the SA-based approach, including results that demonstrate the improvements achieved. Further representative results for two SFN in different scenarios considering the effect on the final coverage of optimizing any of the transmitter parameters previously outlined or a combination of some of them are reported and discussed in order to show both, the performance of the method and how increasing gradually the complexity of the model for the transmitters leads to more realistic and accurate results.

Characterization and Modeling of BFWA Channels in Outdoor--Indoor Environments

This letter presents the experimental characterization and modeling of the radio channel for outdoor-indoor communications, within the framework of broadband fixed wireless access (BFWA) systems. Five models based on tapped delay lines have been proposed. These models provide a good fit of the measured rms delay spread. The time delay values are considerably lower than the typical values for outdoor channels in urban and suburban environments. In quasi-line-of-sight (LOS) situations, it is not necessary to distinguish between open and closed environments, while this is necessary in the case of NLOS and hard-NLOS situations

Site-specific BER simulation for indoor wireless communications

A new method for simulating site-specific BER performance of digital communications in indoor environments is presented, including those environments where the channel presents arbitrary statistics that are difficult to fit to an analytic expression. The method is based on importance sampling in conjunction with a site-specific channel model obtained by ray-tracing.

Computer tool to analyze radio channel in arbitrary enclosed spaces using ray tracing

This article presents a flexible approach to the propagation process allowing analysis of indoor and outdoor environments, and of the interaction between them. The method is based on a full 3D implementation of geometrical optics and the uniform theory of diffraction (GO/UTD). Ray tracing is efficiently carried out by combining image theory with binary space partitioning algorithms.

Multilayer FSS Optimizer based on PSO and CG-FFT

Traditionally, Frequency Selective Surfaces (FSS) are designed to produce a certain spectral response, in one or more frequency bands, using a methodology that manually tunes and simulates the behavior of the structure. In some cases, due to the high filtering requirements of an application, it could be necessary make FSS with several periodic surfaces, in order to improve the frequency response of the final prototype. This process is difficult to be carried out if the filtering response to synthesize cannot be directly obtained with a combination of classical FSS unit cell geometries. To overcome this problem, in this paper a methodology of optimization that automates the hard and costly search is introduced, combining the PSO and an analysis methodology of structures with several periodic surfaces that act as the cost function: the Conjugate Gradient Fast Fourier Transform (CG-FFT). This approximation uses a multilayer Green function calculated applying the transmission line model that considers the mutual coupling effects by translating the field from the source FSS to the other periodic surfaces. Representative results including the optimization of a three layer FSS with two planar periodic surfaces are reported and discussed in order to show the usefulness of the approach proposed.

Coverage optimization in single frequency Networks using simulated annealing

In the last years, the migration from analog to digital terrestrial television systems has favored the deployment of Single Frequency Networks (SFN), more efficient from a spectrum point of view, to provide DVB-T services in larger geographical areas through the reuse of frequencies. However, the planning of a SFN is not a trivial task, since the designer must find a trade-off between the quality of service (QoS) required in a geographical area and the overall cost involving the deployment and maintenance of such a network, which depends primarily on the number of transmitters needed and their power. In this work, a simulated annealing (SA) based approach applied to improve the overall coverage in a SFN by optimizing transmitters parameters such as the static delay or the gain and orientation to be applied to the sector antennas, is presented. For this purpose, the approach is divided into three blocks that work as a whole: A) A propagation prediction tool, B) A receiver behavior modeling, including different methods for the FFT window positioning and echoes combination, and C) SA, used to improve the coverage over the desired area according to certain QoS requirements. Results for two SFN are included in order to demonstrate the usefulness of the method.

Accuracy analysis of GO/UTD radio channel modelling in indoor scenarios including cross-polarisation

The accuracy of a ray-tracing technique based on a full 3D implementation of GO/UTD is investigated by comparison between measurements and simulations carried out at several indoor wireless environments and at two different frequency bands: 1.8 and 2.4 GHz. The narrow-band analysis shows that both the mean level of the received signal and the statistical behaviour of its variations about the mean can be accurately estimated The capability of simulating cross-polarisation is also analysed, showing comparisons of measured versus simulated data. In the wide-band analysis, the comparison between measured and predicted power delay profiles shows that both the amplitude and the arrival time of the main multipath components can be well predicted. The statistical distributions of the measured and simulated wide-band parameters are also compared.