Intelligent Transport Systems; Vehicular Communication; Channel Emulation
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Abstract:
The aim of this thesis is to describe the use of a communications channel emulator to assess the performance of modems installed in vehicles, in the field of Intelligent Transportation Systems applications. These vehicle nodes are responsible for exchanging safety and traffic efficiency information, using the amendment to the Wi-Fi protocol known as 802.11p. This enables the simulation of a realistic vehicular channel with reconfigurable parameters and without the need of field measurements. For that, it is essential to thoroughly model the non-stationary channel, characterized by dynamic environments, high node velocities and multipath. The channel is described by a tapped-delay line model, in which the taps are determined by an optimization algorithm, based on LASSO, on real-life measurements in Lund, Sweden. The algorithm aims at minimizing the mean square error between the approximated channel description and the original measurements, and limiting the number of taps in use. The emulator is part of a project developed in the Telecommunications Institute of the Technical University of Vienna. Its further development enables the emulation of several consecutive scenarios and the configuration of the delay parameters for each magnitude and phase. The performance of the channel emulator is evaluated through the packet error ratio, for the various scenarios and different attenuations, showing that stationary channel models do not emulate vehicular scenarios realistically and, for the non-stationary model, exchanged information is almost completely lost except when the vehicles are in close proximity.
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