Modèles de télétrafic pour le réseau à intégration de services du satellite TELECOM 1

The author discusses models of multiservice circuit switched communications systems where, in particular, the amount of transmission capacity (e.g. bit rate) depends on the call type. Two modes of call set up are considered: «on demand» with blocked calls cleared and «reservation» where capacity is previously reserved for planned calls. The latter mode is described generally and, for particular cases, we suggest interpretations leading to birth process and multiservice queue models. The models have been studied for evaluating the performance of the telecom 1business communication network but derived exact and approximate results should be useful in other applications.     

Administration électronique, interopérabilité et sécurité: les risques de l’ambivalence

The notion of security and safety is eminently present when one considers the setting up of an e-administration and the concept of interoperablility which is assumed to be established. Hence it is revealed in two ways. Firstly, as the objective which is intended: interoperability becoming the means to gurantee security by combatting, or improving the struggle, against different perils : terrorism, immigration fraud, forgery and theft of documents, etc. Secondly, as the condition of its establishment : security thus being the duty owed to citizens and users to protect their rights, private life and the conditions for the use of such new e-administration instuments as electronic identity cards, biometrie passports, shared medical files, public serviceId cards, etc. These two dimensions of the notion of security, one of which comes within the framework of national security and the other of system reliability, are very obviously connected, yet they may result in contradictory dimensions which need to be controlled. The lack of strict regulations must not be overshadowed by the urgent need for public security. In this work we touch on several projects under way which may give rise to new fields of reflection.     

Étude des fluctuations relatives de fréquence de deux klystrons reflex stabilisés par divers procédés

Annals of Telecommunications -     

Étude statistique de la dépolarisation « anormale »

The importance of the anomalous depolarization has been checked on the slant path Ats-6 Gometz-la-Ville. Statistical analysis of the data shows that ice depolarization occurs as frequently as rain depolarization and is very important. Statistics of the ice crystal canting angles have been computed together with differential phase shift. From the results obtained, the effect of ice crosspolarization on a dualpolarized microwave link with M-ary Psk is investigated and emphasizes the necessity of implementing crosspolarization cancellation devices.     

Étude de la précision de l’estimation de la densité spectrale de puissance croisée,obtenue par transformation de fourier de la fonction de corrélation

The authors compare two different estimators of the crosscorrelation function and show that they give equivalent estimators in the frequency domain. They calculate the first and second order moments of the estimator of the cross-spectral-density (DSPC)due to the statistical errors and the quantification of inputs. From these general formulas, they perform numerical calculations for a particular case and they compare them to practical measurements. They show the interesting fact, that the variance of the statistical errors on the dspc is inferior by estimating its phase than by estimating its module. Furthermore, the quantification of the inputs may influence the variance of the phase of the DSPC estimated.     

Caractéristiques électriques de transistors à mobilité électronique élevée utilisant des superréseaux AlAs-GaAs de type N et fabriqués á I’aide de procédés laser

In-site laser desorption of GaAs semi-insulating substrate surfaces prior to moleculor beam epitaxy (Mbe) growth and laser processing of ohmic contacts have been used for the fabrication ofHemts with superlattice donor layers. The improvements made lead to high performance devices.