Search results for "Computer network"
showing 10 items of 1634 documents
How COVID-19 kick-started online learning in medical education-The DigiMed study.
2021
Background The coronavirus disease 2019 (COVID-19) pandemic led to far-reaching restrictions of social and professional life, affecting societies all over the world. To contain the virus, medical schools had to restructure their curriculum by switching to online learning. However, only few medical schools had implemented such novel learning concepts. We aimed to evaluate students’ attitudes to online learning to provide a broad scientific basis to guide future development of medical education. Methods Overall, 3286 medical students from 12 different countries participated in this cross-sectional, web-based study investigating various aspects of online learning in medical education. On a 7-…
Active queue management stability in multiple bottleneck networks
2004
In this paper, we show that the active queue management (AQM) controllers, usually configured on a single bottleneck basis, may not prevent instability in the presence of multiple bottlenecks. We justify this result through a multiple bottleneck model.
Measurement and Modeling of the Origins of Starvation in Congestion Controlled Mesh Networks
2008
Significant progress has been made in understanding the behavior of TCP and congestion-controlled traffic over multi- hop wireless networks. Despite these advances, however, no prior work identified severe throughput imbalances in the basic scenario of mesh networks, in which one-hop flows contend with two-hop flows for gateway access. In this paper, we demonstrate via real network measurements, test-bed experiments, and an analytical model that starvation exists in such a scenario, i.e., the one-hop flow receives most of the bandwidth while the two- hop flow starves. Our analytical model yields a solution consisting of a simple contention window policy that can be implemented via mechanism…
Comparison and analysis of the revenue-based adaptive queuing models
2006
This paper presents several adaptive resource sharing models that use a revenue criterion to allocate bandwidth in an optimal way. The models ensure QoS requirements of data flows and, at the same time, maximize the total revenue by adjusting parameters of the underlying schedulers. Besides, the adaptive models eliminate the need to find the optimal static weight values because they are calculated dynamically. The simulation consists of several cases that analyse the models and the way they provide the required QoS guarantees. The simulation reveals that the installation of the adaptive model increases the total revenue and ensures the QoS requirements for all service classes. The paper als…
Providing QOS in 3G-WLAN environment with RSVP and DIFFSERV
2006
Here we present the end-to-end QoS mechanism in 3G-multiaccess network environment. As multi-access wireless WLAN and wired xDSL wideband multi-access technologies has emerge and become more popular a need for interoperability with different technologies and domains has become necessity. There is also a need for end-to-end QoS management. We show a scenario where the UE-GGSN connection is covered by RSVP and RAN network part uses partial over dimensioning and real-time controlled ATM queuing. DiffServ covers WLAN-Core QoS and radio interface between WLAN AP and WLAN UE uses IEEE's 802.11e. Our interest is to find out how well 3G traffic classes can survive in different traffic conditions in…
RSS-eye: Human-assisted Indoor Localization without Radio Maps
2015
The pervasive diffusion of smartphones is boosting indoor positioning solutions and location-based services. We propose a novel methodology to perform indoor positioning of mobile users by the estimation of angles of arrival from access points whose locations are known. Angles of arrival are estimated by correlating WiFi RSSI measurements with data coming from a digital compass, which is provided by most current handsets. Our system has minimal requirements in terms of infrastructure and mobile hardware. The system neither needs calibration, nor radio maps but requires the user to perform a gesture when an estimation is needed. The resulting on-demand localization has advantages in terms of…
A Dynamic Reasoning Architecture for Computer Network Management
2005
This paper focuses on improving network management and monitoring by the adoption of Artificial Intelli- gence techniques. In order to allow automated reasoning on networking concepts, we defined an accurate ontologi- cal model capable of describing as better as possible the networking domain. The thorough representation of the do- main knowledge is used by a Logical Reasoner, which is an expert system capable of performing high-level manage- ment tasks.
Optimizing H.264/AVC interprediction on a GPU-based framework
2011
H.264/MPEG-4 part 10 is the latest standard for video compression and promises a significant advance in terms of quality and distortion compared with the commercial standards currently most in use such as MPEG-2 or MPEG-4. To achieve this better performance, H.264 adopts a large number of new/improved compression techniques compared with previous standards, albeit at the expense of higher computational complexity. In addition, in recent years new hardware accelerators have emerged, such as graphics processing units (GPUs), which provide a new opportunity to reduce complexity for a large variety of algorithms. However, current GPUs suffer from higher power consumption requirements because of…
Guaranteed access mode for downlink traffic over IEEE 802.11 WLANs
2011
IEEE 802.11 networks present an unfairness problem between the downlink and uplink traffic, using the default settings of the Enhanced Distributed Channel Access (EDCA). In order to reduce this unfairness, the Access Point (AP) can adapt the standard parameters, but this is not enough. In this paper, we propose simple and efficient solutions, which are implemented at the AP, thus they are standard compatible and no modifications to the current hardware and protocol stacks are needed. These solutions aim at providing guaranteed access to the downlink traffic when the AP perceives the unfairness problem. Our simulation results show a reduction in the unfairness and an enhancement in network p…
A system-level power saving approach for cellular networks with microcells/picocells
2011
Network power consumption reduction has recently become an active research topic. In this paper, we propose a novel approach to save power consumption of a three-cell microcellular network. When the traffic load in the middle cell is low, it can be switched-off and its users are covered. This is enabled by increasing the transmission power of one sector antenna in the two neighboring cells. Numerical results show that by increasing antenna transmission power of the two sectors, the overall network power consumption can be reduced.