WSN Team

                      DOCTORAT DE L'UNIVERSITE DE TOULOUSE

         Delivered by INSA


Doctoral School  : GEET

Research laboratory : LAAS-CNRS, groupe MINC

Option : Micro et Nano Systemes

Title:

Digital signal processing architecture for high data rate physical layer for WSN. Applications to metrology WSN for aerospace

by

Julien Henaut


Date : 26 Avril 2013 at 10h00

Jury :

Supervisers :

Daniela Dragomirescu, Associate Professor, INSA Toulouse

Robert PLANA, Professor, Université Paul Sabatier

Reviewers :

Patrick GARDA, Professor, Université Pierre et Marie Curie /LIP6

Olivier SENTIEYS, Professor, ENSSAT /INRIA

Members

Etienne SICARD, Professeur, INSA - President of the jury

Philippe CHEVALLEY, Research ingineer, ESA -ESTEC Pays Bas

Abstract :

To evaluate a system's compliance with its specified requirements, Hardware System Testing is conducted on the complete and integrated system. This phase is essential in all industry branches, especially in the very regulated and critical aerospace world. In the final phase of the development of an airplane, flight test equipment gathers and analyzes data during flight to evaluate the flight characteristics of the aircraft and validate its design, including safety aspects. One of the most cri! tical tests is the measure of the pressure around the wings during flight. All new aircrafts are computer designed with the use of virtual wind tunnels. So, very accurate measures have to be done on the aircraft to validate the model before the aircraft can be industrially produced. In the case of satellites, vibration and mechanical stress are two critical phenomena a satellite endures during launch. This is leading to the necessity for accurate ground tests using strain gauges or thermal sensors before allowing a launch. All such systems used by aircraft and satellite manufacturers today are wired systems. Sensors put around the wings or inside the satellite compartments are wired to a concentrator inside the cabin or the operator’s room. Although good performances are observed in terms of measurement accuracy, these systems have strong drawbacks. The two most important ones are the weight and the cost of both the systems and their installation. An additional drawba! ck concerning its use on aircrafts is due to the installation ! of a system that increases the weight of the aircraft and immobilizes it during many weeks due to the routing of every cable inside the wings. The cost and the complexity of such systems don’t allow a great number of measurement points.

The replacement of conventional measurement networks by wireless sensor networks is not an obvious solution. Despite the great interest in wireless sensor networks in the recent years, the technological barriers are still very numerous and there is currently no protocol to meet the expectations and needs of aviation professionals. The work presented in this thesis aims to meet the needs of a high-speed, low power consumption, low emission and reliable communication layer.

Measurements have been performed in real conditions using commercial devices based on the protocol MB-OFDM/Wimedia, the most common standard that approach the need expressed, and have served to define the basis of the study and have helped to select best development tracks. Measurements have demonstrated also the specificity of the propagation channel.

In order to reduce the time between the choice of algorithms and their testing in real conditions, it became necessary to use a design flow called Specification - Exploration – Improvement based on automatic synthesis tools. This development cycle has identified specific material needs for the design of the demonstrator.

The physical layer is based on an OFDM system and UWB to achieve a data rate of over 150 Mb/s. A fully functional demonstrator, implemented on FPGA and composed of four communicating nodes was presented and has been used to validate the physical layer. Finally first steps to develop a digital ASIC are presented to achieve the goal of low power consumption.