Search results for "LESS"
showing 10 items of 2452 documents
Side Effects of Ambient Noise Immunity Techniques on Outdoor IEEE 802.11 Deployments
2008
A very common conclusion of many experimental studies about IEEE 802.11 outdoor network deployments is that their poor performance results derive from the unfavorable interference and multi-path signals in which the WLAN-cards are required to operate. Goal of this paper is to show that this condition does not always hold, and unexpected and inaccurated PHY layer implementations can be a primary cause of packet losses. With the support of extensive measurement campaigns led in our campus, we provide the performance evidence that IEEE 802.11 outdoor performance impairments are strongly affected by proprietary interference mitigation techniques that adaptively adjust the WLAN-card receiver sen…
TEACHER TEAMS AND SCHOOLS BECOME LEADERS TO DISSEMINATE INNOVATIVE PRACTICE
2016
We will introduce a study about teachers taking part in networking for personal development and becoming teacher leaders. In 2011 a multilevel national joint collaboration network of schools with innovative experience was created to foster dissemination of new teaching and learning experiences among teachers. In order to organize learning for teachers, a lesson based collaborative continuous teacher professional learning model was implemented. The research shows that conducting and analyzing lessons has helped participants become more competent professionals and develop skills that are crucial for a good leader. Categories characterizing teacher leaders and lead schools were identified. Fac…
Sensorless control of permanent magnet synchronous motors for wide speed range applications
2006
This paper deals with sensorless control of Interior Permanent Magnet Synchronous Motors (IPMS) based on the estimation of speed and rotor angular position. The above estimate is based on the injection of high frequency stator currents able to generate a signal similar to that generated by a resolver connected to the axis of the motor. A new digital algorithm has been designed to demodulate the above signal whose implementation can be carried out on the same DSP that processes the control algorithm. In this paper a new scheme of speed and angular position estimator is proposed and justified on the theoretic point of view. The experimental results here shown validate the effectiveness of the…
Stochastic Graph Filtering Under Asymmetric Links in Wireless Sensor Networks
2018
Wireless sensor networks (WSN s) are often characterized by random and asymmetric packet losses due to the wireless medium, leading to network topologies that can be modeled as random, time-varying and directed graphs. Most of existing works related to graph filtering in the context of WSNs assume that the probability of delivering an information from one node to a neighbor node is the same as in the reverse direction. This assumption is not realistic due to the typical link asymmetry in WSNs caused by interferences and background noise. In this work, we analyze the problem of applying stochastic graph filtering over random time-varying asymmetric network topologies. We show that it is poss…
New client puzzle approach for DoS resistance in ad hoc Networks
2010
In this paper we propose a new client puzzle approach to prevent Denial of Service (DoS) attacks in ad hoc networks. Each node in the network first solves a computational problem and with the solution has to create and solve a client puzzle. By combining computational problems with puzzles, we improve the efficiency and latency of the communicating nodes and resistance in DoS attacks. Experimental results show the effectiveness of our approach.
1 Hop or 2 hops: Topology analysis in Body Area Network
2014
Wireless Body Area Networks (WBANs) have recently received much attention due to the possibility to be used in healthcare applications. For these applications, link reliability and energy efficiency are critical issues, as in many cases, information carried can be vital for the patient and batteries cannot be easily replaced. The wireless on-body channel experiences significant temporal variation due to body movements and the use of relays is sometimes necessary in order to guarantee reliability or improve lifetime. In this paper, an experimental evaluation is used to give a better understanding about reliability, energy consumption and lifetime in a single hop or a two hops communication. …
The Critical Mass of Wireless Communications
2011
The aim of this chapter is to identify and analyze the timing and level of critical mass in the development of market penetration for wireless communications. The authors assume that critical mass is fulfilled at the point when the acceleration of the diffusion process is at its maximum. In practice, this point is determined by estimating the diffusion function and calculating the second derivative with respect to time. The diffusion of mobile subscription is modelled using the Bass diffusion model. The penetration levels and points of time of critical mass of 209 countries or areas of the world are identified and subsequently subjected to regression analysis against population and economic…
A Multi-Relay Cooperative Automatic Repeat Request Protocol in Wireless Networks
2010
This paper proposes a Multi-relay Cooperative Automatic Repeat ReQuest protocol (MC-ARQ) for IEEE 802.11 based wireless networks. The proposed distributed relay selection scheme not only selects the best relays but also solves the collision problem among multiple contending relays, by sorting the relays in the network according to their instantaneous channel quality with the destination node. No prior information or explicit signaling among relay nodes is required. Both analytical and simulation results show that significant benefits can be achieved with the MC-ARQ protocol, compared with both the recently proposed PRCSMA scheme and the original non-cooperative DCF scheme.
A particle based simulation model for glacier dynamics
2013
This publication is contribution number 22 of the Nordic Centre of Excellence SVALI, “Stability and Variations of Arctic Land Ice”, funded by the Nordic Top-level Research Initiative (TRI). The work has been supported by the SVALI project through the University of Lapland, Arctic Centre, and through the University Centre in Svalbard. Funding was also provided by the Conoco-Phillips and Lunding High North Research Program (CRIOS: Calving Rates and Impact on Society). A particle-based computer simulation model was developed for investigating the dynamics of glaciers. In the model, large ice bodies are made of discrete elastic particles which are bound together by massless elastic beams. These…
A novel traffic splitting policy for performance improvement in wireless mesh networks
2009
Wireless mesh networks are expected to play an important role in the next-generation wireless communication systems as it can provide wide coverage and scalable broadband Internet access services. However, as more traffic is injected into the network it may lead to throughput degradation, packet loss and longer transmission delay. In this paper, we argue that network performance can be improved by cross-layer design over multiple layers and load balancing based on service types. Correspondingly, a novel traffic splitting policy which can potentially utilize diverse paths for transmitting traffic flows of different service types from the same router has been proposed and investigated. Such a…