TETRA radio performance evaluated via the software package TETRASIM

TETRA (TErrestrial Trunked RAdio) is a digital mobile radio standard for voice and data transmission. It aims at satisfying the growing request of applications and facilities coming from professional users and emergency services. The system has been standardized by ETSI (European Telecommunications Standards Institute) and is provided with an European harmonized frequency band. The first TETRA networks appeared on the market in 1997. This paper reports TETRA radio performance evaluated via a simulation software package, named TETRASIM, entirely developed at CSELT according to TETRA specifications. The simulation results have been obtained for some of the traffic and control channels specified by the standard, in terms of BER (Bit Error Rate) and MER (Message Erasure Rate). As far as the simulated receiver scheme is concerned, the characteristics of the equivalent low-pass filters and the adopted synchronization technique are reported. The simulated demodulator uses a differential detection scheme with soft decision outputs in the case of coded channels. Performance analyses and results comparison are provided by taking into account the effects of signal-to-noise ratio, co-channel interference, adjacent channel interference, propagation models defined in the standard and mobile unit speed. The simulation results reported in this work have been included in the ETR (ETSI Technical Report) “TETRA Designers’ Guide Part 2: Radio and Traffic Performance”. This revised version was published online in June 2006 with corrections to the Cover Date.     

Understanding spaces as places: extending interaction design paradigms

This short paper focuses on some issues involved in the design of ubiquitous technologies and their integration within physical spaces. Current design methodologies and techniques do not explicitly consider the importance of gaining a full understanding of the human experience of space when designing technologies that will pervade and become an integral part of our physical environment. This paper is specifically focused on the importance of considering spaces as places, and of analysing those features of a place that are going to shape users interactions with technologically enhanced environments. It also examines the future implications that this approach may have on theoretical and methodological aspects of interaction design.

Saliva improves Streptococcus mitis protective effect on human gingival fibroblasts in presence of 2-hydroxyethyl-methacrylate

This study aimed to investigate the effect of saliva on Streptococcus mitis free cells and on S. mitis/human gingival fibroblasts (HGFs) co-culture model, in presence of 2-hydroxyethyl-methacrylate (HEMA). The bacterial aggregation both in the planktonic phase and on HGFs, as well as the apoptotic and necrotic eukaryotic cells amount were analyzed, in presence of saliva and/or HEMA. The aggregation test revealed a significant saliva aggregation effect on S. mitis strains compared to the untreated sample. No significant differences were recorded in the amount of culturable bacteria in all studied conditions; however, from microscopy images, the saliva/HEMA combining effect induced a significant bacterial aggregation and adhesion on HGFs. HEMA treatment decreased viable eukaryotic cell number with a parallel increment of necrotic cells, but when saliva was added to the co-culture, the viable cells percentage increased to a value comparable to the control sample.     

Visual acuity, lens flexure, and residual astigmatism of keratoconic eyes as a function of back optic zone radius of rigid lenses.

The purpose of this study was to determine whether the visual acuity of keratoconic eyes was affected by alteration of back optic zone radii (BOZRs) of rigid gas permeable lenses (RGP) contact lenses. Visual acuity, spherical and sphero-cylindrical over-refraction and keratometry of the front surface of the RGP lenses of nine keratoconic eyes were measured. The BOZR of the five lenses varied from steeper to flatter than that habitually worn by the subjects. The steepest lenses produced significantly greater lens flexure and residual astigmatism (P < 0.002) and worse high and low contrast visual acuity with the spherical over-refraction (P < 0.05). There was no statistical difference in visual acuity across the range of BOZR when a sphero-cylindrical over-refraction was applied. Thus reduced visual acuity in keratoconus with steep lenses is likely due to uncorrected residual astigmatism from a combination of several possible sources.     

Comparison of an objective method of measuring bulbar redness to the use of traditional grading scales.

PURPOSE: The primary objective was to compare measures of bulbar redness objectively using a photometric method with standard grading methods. Measures of redness were made on 24 participants wearing a silicone hydrogel contact lens in one eye for overnight wear. This report compares hyperaemia after 1 week of daily wear (baseline) with redness measured after 6 months of overnight wear. METHOD: A new method of objectively measuring bulbar conjunctival redness was performed using the Spectrascan650 Photometer by Photo Research under fixed illumination. Photometric measures in CIEu(*) chromaticity values involve the measurement of chromaticity, a physical analogue of redness, greenness and blueness in the image. This method was validated in Part 1 of the study using repeated measurements on the photographic CCLRU scale. In Part 2 of the study, the photographic grading scale (CCLRU) from 0 (none) to 100 (extreme) was used to make the comparison. RESULTS: Part 1 indicated that the photometer provides a repeatable and reliable measure of bulbar redness (CCC=0.989). A moderately strong and significant correlation was found between the CIEu(*) chromaticity values and the analogue data (R=0.795, p=0.000) at each measurement session (from baseline to 1 day, 1 week, and 1, 3 and 6 months of overnight wear). CONCLUSIONS: This new standardized and objective method of measuring bulbar redness has great potential to replace subjective grading scales, especially with multi-centre studies, where variability between investigators occurs. This method may also detect smaller changes between visits or between eyes.