Increasing Reliability in Cable-Free Radio LANs Low Level Forwarding in HIPERLAN

Radio LANs are emerging in the computing world. They are supported by distinct configurations: on the one hand radio LANs with base stations and a wired backbone, on the other hand radio LANs implementing Intra-forwarding. Adding a new node in a radio LAN with Intra-forwarding, increases the reliability, while this reliability decreases with ad hoc or hub configurations. This advantage of Intra-forwarding is quantified. Intra-forwarding, as defined in the HIPERLAN standard, is based on a hop-by-hop policy and link check procedures. It is shown how point-to-point packets and broadcast packets are forwarded. The three basic components of Intra-forwarding needed to build and update the Intra-forwarding database are described. The originality of this approach is the use of multipoint relays which enable better scalability. The correctness of the Intra-forwarding protocol is proved and its cost is evaluated.     

Validation ďun modèle analytique de la pose par poussage des câbles à fibres optiques

The construction of an entire optical access networks for connected customers requires the mastery of optical fibre cable installation. We are interested in the pushing process in urban areas and the understanding of the global behaviour during this process and the estimation of the pushing force before laying are important. The work of Griffioen [5] and Buler [4] were used to develop software (taking into account friction and cable rigidity), including some improvements coming from a collaboration between France Télécom R&D Lannion and the LM2S. To go further in this process, in the first part of our work, we will work without buckling phenomena, that will be included in our modelisation in the second part of this paper. In order to validate our modelisation, comparison will be made between finite element simulations and experimental results obtained on a life-sized bench at France Télécom R&D Lannion.     

Data Transfer for HIPERLAN

HIPERLAN offers a high speed (23.5 Mbit/s) radio LAN and therefore HIPERLAN is likely to support various kinds of traffic requirements. A Data Transfer function is in charge of handling various traffics which can result in simultaneous services. HIPERLAN nodes are not necessarily within direct radio range; and in some cases packets are forwarded by intermediate stations from the source node to the destination node. Since HIPERLAN is more than a single hop network, the support of specific traffics like Time Bounded traffics require a dedicated architecture which can not be centralized. This paper describes the architecture of the Data Transfer in HIPERLAN which allows the support of various traffics. This approach is not based on a connection oriented protocol nor on a centralized architecture but on a connection-less mode where users provide quality of services parameters to indicate its requirements. HIPERLAN architecture for data transfer is based on a mix of two main mechanisms: hierarchically independent priority levels and an earliest dead line first algorithm. This paper describes and explains the architecture choices made in HIPERLAN. Results of simulation and analytical models are given.     

Source primaire multi-éléments et matrice de commutation associée pour satellite de télécommunication utilisé en mode AMRT

This paper describes a 12 GHz primary feed system designed for a scanning spot-beam transmitting antenna system operated in time-division multiple access (tdma) mode. The feed is made of three main parts: a radiating cluster consisting of seven horn elements, apin diode switch device which performs electronic scanning of the beam by successively activating the seven radiating elements, arf sensing waveguide network. The antenna system features are designed to optimize the gain throughout the coverage. A minimum directivity above 46 dB (without considering power losses due to the switch device) in a 1.35° coverage (corresponding to France) is expected from measured characteristics of the primary feed. This is corresponding at a 4 to 5 dB improvement upon a global beam system.     

Priority and Collision Detection with Active Signaling - The Channel Access Mechanism of HIPERLAN

HIPERLAN will provide a 23.5 Mbps data rate transmission to radio channel user. The medium access control is based on carrier sense (CSMA) and on active signaling. Active signaling is an original feature which makes it possible to merge priority contention and collision detection into an elegant and efficient channel access mechanism. In particular it is expected to boost the performance of HIPERLAN above the level of IEEE 8802.3 standard (Ethernet). It also gives the opportunity to mix time constraint traffics (like voice) with non-time constraint traffics (data) by making use of access priorities.     

Urinary infection in geriatric short stay: value of urinary strips

The blinded study of CBUE (cytobacteriological urine examination) test strips was carried out in 100 patients (65 women, 35 men), mean age 85.52 +/- 6.28 years, admitted for a short stay in a geriatrics department. Urinary infection was present in 19% of the cases. Typical clinical signs (pollakiuria, dysuria, hematuria, burning upon voiding) were rare, less than 10%. General signs, such as deterioration of general status (65% of the cases) and loss of autonomy (53% of the cases), on the other hand, were predominant and their relatively unspecific nature required a reliable screening test for urinary infection. Good results of sensitivity (89.5%), specificity (98.7%), and the leukocytes/nitrites values, confirmed the validity of the urine test strip in hospitalized elderly patients. In addition, the negative predictive value of the combination leukocytes and nitrites (90.8%) would have prevented 71 samples from being sent to the laboratory for CBUE, resulting in an obvious financial savings.