Search results for "Computer network"
showing 10 items of 1634 documents
Underlay Device-to-Device Communications on Multiple Channels
2018
Author´s accepted manuscript (postprint). © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Since the spectral efficiency of wireless communications is already close to its fundamental bounds, a significant increase in spatial efficiency is required to meet future traffic demands. Device-to-device (D2D) communications provide such an increase by allowing nearby u…
On the Performance of Channel Assembling and Fragmentation in Cognitive Radio Networks
2014
[EN] Flexible channel allocation may be applied to multi-channel cognitive radio networks (CRNs) through either channel assembling (CA) or channel fragmentation (CF). While CA allows one secondary user (SU) occupy multiple channels when primary users (PUs) are absent, CF provides finer granularity for channel occupancy by allocating a portion of one channel to an SU flow. In this paper, we investigate the impact of CF together with CA for SU flows by proposing a channel access strategy which activates both CF and CA and correspondingly evaluating its performance. In addition, we also consider a novel scenario where CA is enabled for PU flows. The performance evaluation is conducted based on…
Model and optimal Call Admission Policy in Cellular Mobile Networks
2000
For current cellular networks, two important Quality of Service (QoS) measures are the fractions of new and handoff calls that are blocked due to unavailability of channels. Based on these QoS measures, we propose a queuing network model with impatient users for handoff and new calls in cellular mobile networks. The number of simultaneous calls, that can be supported, is modeled by C identical servers with exponentially distributed session duration for each one of them. Priority is given to handoffs over new calls. We use for that a Guard Channel policy that reserves a set of CH channels for handoff calls, new calls being served at their arrival if there are more than CH available channels.…
<title>Statistical bandwidth allocation for multiservice networks</title>
2002
Multiservice networks will carry di erent kinds of applications in the near future. Bandwidth requirements change rapidly, and the network resource management will play an important role to guarantee the use of the limited resources in the most eAEcient way. We approach the channel capacity allocation problem by developing an SLA (Service Level Agreement) based channel allocation method. In our model, the channel may be wired or wireless, so this method can be adapted in multi-technique networks. The algorithm allocates resources to several di erent service classes via several di erent capacity routes. Service provider perfroms optimization by allocating data rate in such a way that the sat…
Childhood Adversities and Adult Headache in Poland and Germany.
2015
Objective Various childhood adversities have been found to be associated with chronic pain in adulthood. However, associations were moderate in most studies, i.e. odds ratios (OR) were between one and two. Method An internet survey was performed in 508 Polish and 500 German subjects. A total of 19 childhood adversities were selected and their associations with headaches explored. Age, gender and country were included as potential confounders, as well as their two-way interaction with the risk factors. Results Two strong risk factors were identified. (1) A combined score for physical and emotional neglect showed an odds ratio (OR) of 2.78 (p < .002) to the frequency of headache in adulthood …
Wireless MAC processors: programming MAC protocols on commodity hardware
2012
Programmable wireless platforms aim at responding to the quest for wireless access flexibility and adaptability. This paper introduces the notion of wireless MAC processors. Instead of implementing a specific MAC protocol stack, Wireless MAC processors do support a set of Medium Access Control “commands” which can be run-time composed (programmed) through software-defined state machines, thus providing the desired MAC protocol operation. We clearly distinguish from related work in this area as, unlike other works which rely on dedicated DSPs or programmable hardware platforms, we experimentally prove the feasibility of the wireless MAC processor concept over ultra-cheap commodity WLAN hardw…
VoiP performance analysis in IEEE802.16 networks
2012
WiMAX, as known as IEEE standard 802.16, is a wide range broadband wireless access network which has a significant good support for the quality of service. According to IEEE standard 802.16e WiMAX has support also for mobility. One of the key advantages of the WiMAX network is the possibility to assign QoS parameters as connection based. A good example of traffic type having strict QoS demands is VoIP. VoIP will probably be a killer application in the future's broadband wireless networks because of its cost efficiency compared to circuit switched networks. In this paper, we analyze by extensive simulations how QoS is applied per connection, especially for the VoIP connection.
Fotovoz como metodología innovadora en educación superior
2022
La adaptación al EEES ha exigido el surgimiento de metodologías activas adscritas a la educación, siendo fotovoz clave en diferentes niveles educativos. Sin embargo, la investigación en el contexto educativo, y en concreto en el de Educación Superior, es escaso. Por tanto, el objetivo de este trabajo es analizar el uso de fotovoz en educación superior, a través de una revisión sistemática basada en la Declaración PRISMA 2020 en tres bases de datos. Quince de los 408 estudios identificados cumplieron con los criterios de inclusión. Los resultados posicionan Fotovoz como una alternativa educativa con potencial en entornos de Educación Superior. The adaptation to the EHEA has demanded the emer…
Educating reflective Enterprise Systems practitioners: a design research study of the iterative building of a teaching framework
2013
This research paper reports on the iterative design of a teaching framework developed for teaching Enterprise Systems ES classes for Information Systems IS graduates. These systems embed technical complexity and create organizational challenges when implemented in organizations. Therefore, teaching good ES classes is pedagogically challenging for faculty, and ES curricula are difficult for students. We have gradually designed and rebuilt curricula and teaching frameworks over 8years. This has also resulted in a set of eight design principles. We report from our design and evaluation process and present our final artefact, the teaching framework. The aim is to educate reflective practitioner…
The effectiveness of office information systems: a social action perspective
1991
. The purpose of this paper is to show that a number of basic issues have not been adequately addressed in existing office information systems research. Prominent among these are the nature and role of offices, the goals of office information systems development, and the nature of its organizational and managerial consequences. It is proposed that office information systems should be analysed as social action systems the behaviour of which is strongly affected by socially determined forces and constraints such as the behaviour-channelling influences of authority, norms, customs, habits and precedence. Four types of social action are discussed: instrumental, strategic, communicative and disc…