Amélioration des performances et réduction de la puissance consommée des téléphones portables par l’égalisation conditionnelle

In TDMA systems, the autonomy of portable handsets is a major constraint. We propose a new method, conditional equalization, which minimises the power consumption due to equalization. The performance of our method is theoretically analysed for 2- path Rayleigh fading channels and simulated for the Cost 207 models. Conditional equalization enables the saving of at least 30 % of equalizations in urban environments with a loss in the SNR performance of less than 0.1 dB, and leads to a gain in the performance of 1.5 dB with 97 % of saved equalizations in rural area environment.     

L’union radio-scientifique internationale (URSI) Et les télécommunications mondiales

Au cours de sa dernière Assemblée générale (Lima, août 1975), I’ursi aporté à sa présidence M. J. Voge, Ingénieur général des télécommunications et Directeur de l’enseignement supérieur technique des Postes et Télécommunications. Le correspondant français de l’ursi est le cnfrs (Comité National Français de Radioélectricité Scientifique) auquel appartiennent plusieurs membres du Comité de rédaction des Annales desTélécommunications. M. Voge a pris une grande part dans la décision d’infléchir les activités et objectifs de l’ursi,de façon à en faire l’Union scientifique des télécommunications, et il préside actuellement à la mise en ?uvre de cette décision. Le texte qui suit, où M. Voge décrit l’ursi,son passé et ses nouvelles orientations, trouve donc naturellement sa place dans les Annales desTélécommunications.     

Présentation d’une technique 3D d’accélération de la recherche de rayons application aux télécommunications microcellulaires

Development of telecommunications using mobile phones requires the installation of many base stations (BTS) in order to cover the large number of cells which make up the network. Existing systems (GSM, DSC) use carrier frequencies within the microwave range. Ideally, operators should have simulation software to determine the position of BTS. This software would be used initially to determine the geometric configuration of the cells. The next step would be to optimise the radiation pattern of each BTS antenna. In this article we present a method for determining radioelectric coverage based on image theory adapted to the problem, which is more accurate and less time-consuming than conventional methods.     

Amélioration des performances des systèmes à haut débit par une méthode de réduction de la diaphonie dans les câbles multiconducteurs de télécommunications

dsl (Digital Subscriber Line) technology provides low cost access to the consumers and sources of information for any one subscribing to classical analogical telephony. Indeed xdsl services enable high-speed digital transmission on conventional telephone lines. For sixteen years that the internet has risen, a great number of offers proposing increasing bit rate have been developed. Considering this increasing demand of high bit rate access, telecommunication operators perpetually work on finding solutions to optimize the copper lines channel. In that way, we present here a new method of crosstalk reduction in a multiconductor telecommunication cable. Interests and limitations of this method are presented and some simulations on a frequency band extending to 30 MHz will picture those theoretical results.     

Quelques résultats théoriques et expérimentaux sur la modulation par déplacement de fréquence à deux états et à phase continue d’indice 0,5 (MSK)

Minimumshift keying modulation seems to be very attractive for digital transmission systems in particular because an only small degradation can be expected on non linear channels. In the first part of this paper, some general features of the signal are recalled. After a theoretical method for the calculation of the bit error rate in presence of inter symbol interference is described; the results are compared with experimental values, obtained with a modulator demodulator build incnet laboratories in Lannion.     

Étude de la génération d’impulsions brèves d’un laser DFB à trois contrôles de phases (3QWS-DFB)

The purpose of this paper is to study the generation of short pulses of the three quarter wave shift distributed feedback (3Qws-dfb) laser by using switching gain technique. We have used the temporal domain model (Tdm) which is a multimode spatio-temporal model that considers simultaneously all the modes of the overall intra-cavity field as well as the two following nonlinear effects, the spectral hole burning (Shb) and the gain saturation. Obtained results showed that a 3Qws-dfb laser can generate short pulses in accordance with Fourier criteria. These results show that 3Qws-dfb lasers are potential candidates as monomode optical sources for long distance high bit rate telecommunications.     

Compte rendu du 2e congrès international sur la planification des réseaux de télécommunications Networks 83 (Brighton : 21–25/03/1983)

During this second Telecommunication Network Planning Symposium, several hundreds of delegates from thirty countries met together. The discussed topics covered public and private, existing and future networks and important present problems : planning tools, digitalization, securization, integration of networks and services. After a presentation of Cnet participation, the authors describe the main contributions, classified in different topics.