Adaptive EDCF: Enhanced service differentiation for IEEE 802.11 wireless ad-hoc networks

This paper describes an adaptive service differentiation scheme for QoS enhancement in IEEE 802.11 wireless ad-hoc networks. Our approach, called adaptive enhanced distributed coordination function (AEDCF), is derived from the new EDCF introduced in the upcoming IEEE 802.11e standard. Our scheme aims to share the transmission channel efficiently. Relative priorities are provisioned by adjusting the size of the contention window (CW) of each traffic class taking into account both applications requirements and network conditions. We evaluate through simulations the performance of AEDCF and compare it with the EDCF scheme proposed in the 802.11e. Results show that AEDCF outperforms the basic EDCF, especially at high traffic load conditions. Indeed, our scheme increases the medium utilization ratio and reduces for more than 50% the collision rate. While achieving delay differentiation, the overall goodput obtained is up to 25% higher than EDCF. Moreover, the complexity of AEDCF remains similar to the EDCF scheme, enabling the design of cheap implementations

New Fisheries-related data from the Mediterranean Sea (April 2015)

In this second Collective Article with fisheries-related data from the Mediterranean Sea we present the evaluation of bony structures in aging of Barbus tauricus, otolith dimensions-body length relationships for two species (Trachinus draco and Synchiropus phaeton), information on the growth of juvenile Thunnus thynnus and of Ruvettus pretiosus, weight-length relationships for three species (Aulopus fiamentosus, Thunnus thynnus and Tylosurus acus imperialis) and data on feeding habits and reproduction of Aulopus fiamentosus

Sleep Quality and Physical Activity as Predictors of Mental Wellbeing Variance in Older Adults during COVID-19 Lockdown:ECLB COVID-19 International Online Survey

Background. The COVID-19 lockdown could engender disruption to lifestyle behaviors, thus impairing mental wellbeing in the general population. This study investigated whether sociodemographic variables, changes in physical activity, and sleep quality from pre- to during lockdown were predictors of change in mental wellbeing in quarantined older adults. Methods. A 12-week international online survey was launched in 14 languages on 6 April 2020. Forty-one research institutions from Europe, Western-Asia, North-Africa, and the Americas, promoted the survey. The survey was presented in a differential format with questions related to responses "pre" and "during" the lockdown period. Participants responded to the Short Warwick-Edinburgh Mental Wellbeing Scale, the Pittsburgh Sleep Quality Index (PSQI) questionnaire, and the short form of the International Physical Activity Questionnaire. Results. Replies from older adults (aged &gt;55 years, n = 517), mainly from Europe (50.1%), Western-Asia (6.8%), America (30%), and North-Africa (9.3%) were analyzed. The COVID-19 lockdown led to significantly decreased mental wellbeing, sleep quality, and total physical activity energy expenditure levels (all p &lt; 0.001). Regression analysis showed that the change in total PSQI score and total physical activity energy expenditure (F-(2,F- 514) = 66.41 p &lt; 0.001) were significant predictors of the decrease in mental wellbeing from pre- to during lockdown (p &lt; 0.001, R-2: 0.20). Conclusion. COVID-19 lockdown deleteriously affected physical activity and sleep patterns. Furthermore, change in the total PSQI score and total physical activity energy expenditure were significant predictors for the decrease in mental wellbeing.</p

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

A survey of QoS enhancements for IEEE 802.11 wireless LAN

Quality-of-service (QoS) is a key problem of today's IP networks. Many frameworks (ImServ, DiffServ, MPLS etc.) have been proposed to provide service differentiation in the Internet. At the same time, the Internet is becoming more and more heterogeneous due to the recent explosion of wireless networks. In wireless environments, bandwidth is scarce and channel conditions are time-varying and sometimes highly lossy. Many previous research works show that what works well in a wired network cannot be directly applied in the wireless environment. Although IEEE 802.11 wireless LAN (WLAN) is the most widely used IEEE 802.11 wireless LAN (WLAN) standard today, it cannot provide QoS support for the increasing number of multimedia applications. Thus. a large number of 802.11 QoS enhancement schemes have been proposed, each one focusing on a particular mode. This paper summarizes all these schemes and presents a survey of current research activities. First, we analyze the QoS limitations of IEEE 802.11 wireless MAC layers. Then, different QoS enhancement techniques proposed for 802.11 WLAN are described and classified along with their advantages/drawbacks. Finally, the upcoming IEEE 802.1 le QoS enhancement standard is introduced and studied in detail

QUMESH: Wireless mesh network deployment and configuration in harsh environment

The link delivery probability in a wireless mesh network is most accurately determined only by experiment, as it depends on many factors, including environment characteristics, transmission power, distance between transmitter and receiver, channel fading, and background noise. This paper provides an insightful framework for characterizing link performance results produced at Qatar University (QU) wireless mesh test-bed under harsh environmental conditions, including heavy buildings structure, mixed indoor/outdoor architecture, weather conditions, and coexistence with high interfering wireless transmission. Indeed, we are interested in looking at the link quality behavior for indoor and outdoor environments. In the outdoor environment, the effect of different weather conditions such as high humidity and sandstorms, which are typical in the Qatari weather, will be analyzed. Regarding the indoor environment, we investigate the effect of unique cell structure, and heavy lab machinery of the engineering building on the link performance. Furthermore, we study different wireless mesh node configurations and equipments' effect on performance and network connectivity. The causes behind link instability and performance shortcoming of the QU wireless mesh network (QUMESH) are identified. Thus, the content of this paper provides an input for developing the criteria for the test-bed and performing the evaluation of new proposed adaptive mechanisms. 2012 IEEE.Qatar National Research FundScopu

Growth and age estimation of the greater forkbeard, Phycis blennoides (Actinopterygii: Gadiformes: Phycidae), from the Gulf of Tunis (central Mediterranean)

Background. The greater forkbeard, Phycis blennoides (Brünnich, 1768), is a gadiform species, which has economical value and its population is dwelling in a 60–800 m depth range throughout the Atlantic and the Mediterranean. Along African north coast, there is a lack of information about the biology (age, growth, sex-ratio) of this species. This study provides the first data on population parameters of P. blennoides in Tunisia. Materials and methods. Specimens of Phycis blennoides were collected from the landings of the artisanal fisheries between September 2007 and June 2010. The length–weight relations were determined according to the allometric equation: W = aTLb. Growth parameters were estimated using the von Bertalanffy growth equation. Results. Length (TL)–Weight (W) relations were allometrically positive for the females (W = 22.10–4TL3.409), males (W  = 13.10–4TL3.674), and both sexes (W  = 19.10–4TL3.460), without significant differences between males and females. The relation between otolith weight and age showed a significant difference between males and females. The growth parameters were calculated as TL∞ = 57.17 cm, K = 0.193 · year–1, t0 = –1.578 · year for the females, and 44.74 cm, 0.313 · year–1, and –1.210 · year for the males, respectively. The females grew faster than the males which did not exceed 45 cm. The growth performance index Ф' calculated for the females (2.80 cm· year –1) and males (2.79 cm· year –1) yielded similar results. Conclusion. Results reported in this work will contribute to the knowledge on the biology of P. blennoides in Tunisia, with the aim of generating sufficient information to improve future stock management and sustainable fisheries