Une infrastructure flexible de collecte et de traitement de données d'un réseau de capteurs urbain mutualisé

Mathieu Vallérian 1, 2
2 SOCRATE - Software and Cognitive radio for telecommunications
CITI - CITI Centre of Innovation in Telecommunications and Integration of services, Inria Grenoble - Rhône-Alpes
Abstract : In this thesis, a receiver architecture for a gateway in a urban sensors network was designed. To embed the multiple protocols coexisting in this environment, the best approach seems to use a reconfigurable architecture, following the scheme of the Software-Defined Radio (SDR). All the received signals should be digitized at once by the Analog-to-Digital Converter (ADC) in order to sustain the reconfigurability of the architecture: then all the signal processing will be able to be digitally performed. The main complication comes from the heterogeneity of the propagation conditions: from the urban environment and from the diversity of the covered applications, the signals can be received on the gateway with widely varying powers. Then the gateway must be able to deal with the high dynamic range of these signals. This constraint applies strongly on the ADC whose resolution usually depends on the reachable digitized frequency band. A first study is led to evaluate the required ADC resolution to cope with the dynamic range. For this the dynamic range of the signals is first evaluated, then the required resolution to digitize the signals is found theoretically and with simulations. For a 100 dB power ratio between strong and weak signals, we showed that the ADC resolution needed 21 bits which is far too high to be reached with existing ADCs. Two different approaches are explored to reduce analogically the signals’ dynamic range. The first one uses the companding technique, this technique being commonly used in analog dynamic range reduction in practice (e.g. in audio signals acquisition), its relevance in multiple signal digitization is studied. Three existing compression laws are explored and two implementations are proposed for the most efficient of them. The feasibility of these implementations is also discussed. In the second approach we propose to use a two-antennas receiver architecture to decrease the dynamic range. In this architecture two digitization paths are employed: the first one digitizes only the strongest signal on the band. Using the information we get on this signal we reconfigure the second branch of the architecture in order to attenuate the strong signal. The dynamic range being reduced, the signals can be digitized with an ADC with a lower resolution. We show in this work that the ADC resolution can be decreased from 21 to 16 bits using this receiver architecture. Finally, the promising two-antennas architecture is tested in experimentation to demonstrate its efficiency with dynamic signals (i.e. with appearing and disappearing signals).
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Mathieu Vallérian. Une infrastructure flexible de collecte et de traitement de données d'un réseau de capteurs urbain mutualisé. Sciences de l'information et de la communication. UNIVERSITÉ DE LYON OPÉRÉE AU SEIN DE L’INSA LYON, 2016. Français. ⟨tel-01416750⟩

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