Chapter 17: Artificial Materials for Protected Communications

Fr d rique de Fornel, OCP/LPUB Dijon,

France

Rabia Moussa, OCP/LPUB Dijon,

France

Laurent Salomon, OCP/LPUB Dijon,

France

Christian Boisrobert, LPIO Nantes,

France

Herv Sizun, FT R&D Belfort,

France

Philippe Guignard, France T l com R&D, Lannion,

France

1 Introduction

Infra-red technologies in open space constitute an interesting solution for communicating objects and in particular for indoor communications: the introduction of optics gives rise to the solution to the problem related to high data transmission. Its use in open space contributes , by mean its flexibility, to the quality of the service offered [Prunnot 02]. As for other types of information transfer, it is essential to ensure the transmission confidentiality of the exchanges, which is more difficult due to the "not guided" nature of these communications.

The securisation has in fact two different goals:

1. Guarantee of the confidentiality of the transmitted information.

2. Minimisation of the disturbances brought to the external environment of the room within which the exchanges of information take place.

Before giving the physical details of the problem, the question of the confidentiality level must be clarified. Thus, the different kinds of applications dictate the lower or higher level of confidentiality. A typical case where the confidentiality must be very high is for banking data transmission. Of course one will have to find a compromise between the desired level of confidentiality and the cost of the corresponding technical solutions. We have not yet completely defined the criteria of confidentiality; this will constitute one of the objectives of this study, namely: for an given establishment receiving-transmitter, which are the parameters to be respected for the materials constituting the walls and the glazing so that the intensity transmitted outside the room will be lower than a threshold level?. This threshold level will correspond to our criterion of confidentiality. So, let us consider a simple case to illustrate these remarks.