Search results for " Network"
showing 10 items of 6428 documents
Significance of channel failures on network performance in CRNs with reserved spectrum
2016
It is well understood that in wireless networks, channel failures, which are typically caused by equipment or power failures as well as intrinsic features in radio transmissions, such as fading and shadowing, can easily result in network performance degradation. Therefore, fast recovery from channel failures is an important measure that should be incorporated with those networks. Consequently, in a cognitive radio network (CRN), channel failures can cause significant performance degradation in both primary and secondary networks. Instead, retainability, i.e., the capability of providing continuous connection for users must be guaranteed even if a significant network element is disrupted. In…
An analytical study of mixed backoff schemes for QoS differentiation in wireless LAN
2009
In this paper, we propose an analytical model to evaluate performances of a wireless network composed by two groups of nodes using two different backoff schemes for channel access. The two different backoff schemes are used for QoS differentiation in term of priority. Our analysis results show that the priority group can have its performances enhanced, in term of saturation throughput and delay, without significant degradation of normal group nodes performances. This enhancement is also noticed for throughput efficiency at system level.
Enabling Cognitive-Radio Paradigm on Commercial Off-The-Shelf 802.11 Hardware
2013
Cognitive Radio paradigm (CR) has been recognized as key enabler for next generation wireless networking: the pos- sibility to access the limited radio spectrum in an oppor- tunistic manner allows secondary users to boost their trans- mission performance without interfering with existing pri- mary networks. Full testing and experimenting with this paradigm, however, is still a tough task, given either the i) limited capabilities above the PHY layer of cheap SDR so- lutions, or the ii) heavy investment required for setting up multi-node testbeds powered by FPGAs. In this demo we show how we leveraged our Wireless MAC Processor archi- tecture to tackle the two issues at the same time, providi…
Making WiFi work in multi-hop topologies: Automatic negotiation and allocation of airtime
2015
We propose a solution for mitigating the performance impairments of CSMA/CA protocols in multi-hop topologies based on the dynamic adaptation of the contention process experienced by nodes in a wireless network. A distributed protocol is used to negotiate the channel airtime for a node as a function of the traffic requirements of its neighbourhood, taking into account bandwidth reserved for the control operations. A mechanism is provided for a node to tune its contention window depending on its allocated airtime. Different from previous schemes, a node's contention window is fixed in size unless the traffic requirements of its neighbourhood change. The scheme is implemented on legacy commer…
Power consumption analysis for mobile stations in hybrid relay-assisted wireless networks
2010
While Internet access using mobile or wireless technologies has become ubiquitous these days, the energy consumption aspect of such connections has not been studied in-depth yet. In this paper, a hybrid wireless network, which consists of a cellular component and a relay-assisted ad hoc component, is studied focusing on energy consumption by mobile stations with respect to the amount of data communicated and achieved battery lifetime. Four alternative paths are considered, including both pure cellular and hybrid ad hoc/cellular links for uplink and downlink traffic. The effects of each alternative connection on energy consumption of the involved mobile stations are analyzed in terms of the …
On building an infrastructure for mobile and wireless systems
2002
Over the last few years, there have been at least two dramatic changes in the way computers are used. The first has its origin in the fact that computers have become more and more connected to each other. The second was triggered by the increasing miniaturization and affordability of hardware components and power supplies, together with the development of wireless communication paths. These two trends combined have allowed the development of powerful, yet comparatively low-priced, portable computers. In spite of these changes, little attention has been given to reaching a common consensus and to the development of a strong infrastructure in this area.
Wittgenstein, Turing, and Neural Networks
2018
The main task of this paper is grounding the socio-anthropological “naturalization” of meaning operated by the later Wittgenstein in his remarks on rule-following in the Philosophical Investigations in considerations relating to models of low-level (biological) processes of imitation, training, and learning. If the operation suggested above is successful, two of its immediate consequences are that the social aspect of language can no longer be considered as a primitive notion, but needs to be placed upon, if not reduced to, a biological foundation; and that the study of thought, and, actually, of certain brain processes, becomes prior in the order of explanation to the study of language. Th…
Mobile information systems - executives' view
1997
The concepts of travelling executive and executives' mobile information system are first defined in this paper. The main findings are in the form of collected data and opinions concluded from our personal discussions with 49 executives in the United Kingdom, France, Italy and Finland concerning the nature of the work of executives and the usage of information technology (IT) to support their work today. The near future expectations of the executives are also analysed, especially concerning the mobile use of IT services in order to construct executives' holistic view of mobile computing. The use of IT services was found to be very widespread. Big differences were found: some of the executive…
The influence of the momentum coefficient and the number of the averaging points of the power spectrum density on the recognition effectiveness of th…
2006
The subject matter of this paper refers to the next stage of the research work connected with the improvement of the acoustic emission method (AE) used for the evaluation of partial discharges (PDs) generated in paper-oil insulation systems of high-voltage power appliances. The subject matter discussed here refers to one of the aspects of the analysis of the signals registered - a correct and effective recognition of the AE signals generated by basic PD forms. The paper presents research results of the application of the unidirectional artificial neuron networks (ANN) used for the recognition of basic PD forms that can occur in paper-oil insulation impaired by aging processes.
Viscoelasticity: an electrical point of view
2014
Time dependent hereditary properties of complex materials are well described by power-laws with real order exponent. This experimental observation and analogous electrical experiments, yield a description of these properties by using fractional-order operators. In this paper, elasto-viscous and visco-elastic behaviors of fractional order hereditary materials are firstly described by using fractional mathematical operators, based on recent work of some of the authors. Then, electrical analogous models are introduced. Viscoelastic models have elastic and viscous components which can be obtained by combining springs and dashpots: these models can be equivalently viewed as electrical circuits, …