| 1. |
- Wennerström, Hjalmar, 1984-
(författare)
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A Node-Link Perspective on the Impact of Local Conditions in Sensor Networks
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sensor networks are made up of small battery-powered sensing devices with wireless communication capabilities, enabling the network to monitor the environment in which it is deployed. Through their flexible and cable-free design these networks open up for new deployment scenarios that were previously not plausible such as during a natural disaster. Motivated by scenarios where centralized oversight is not possible the focus of this thesis is to equip nodes with further adaptability to changes in the links it has with other nodes. This is achieved through contributions in three areas focusing on observations from a node-link perspective.First, the impact the local environment has on the nodes is explored by deploying a sensor network outdoors next to a meteorological station to correlate the variations in link quality to the changes in the environment. The work identifies temperature as the main factor, where through further investigations in a controlled setting, a linear relationship between the decrease in signal quality and the increase in temperature is described.Secondly, the thesis address how nodes in a sensor network can be motivated to exchange data by modeling it as a game. The game theoretic design is motivated by the absence of any centralized control and focus on the nodes as individual users in the network. The presented design motivates the selfish nodes to participate in the exchange of sensor data, showing that it is the best strategy.Lastly, by exploring and understanding how connections in a mobile sensor network occur, nodes are given more flexibility to determine how to send and sample sensor data. This adaptability to contact occurrences is shown to provide better ways of sending data by selecting higher quality links as well as making sampling more energy preserving by reducing the rate in the vicinity of other nodes.
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| 2. |
- Berti, Valentino, et al.
(författare)
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Datakommunikation
- 2012. - 7
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Denna bok ger en bred introduktion till datakommunikation i allmänhet och internetteknologi i synnerhet. Vad Internet är beror helt på vem du frågar, och detsamma gäller ämnet datakommunikation. Från att ha varit ett specialämne som studenter möjligtvis läste i årskurs 3 eller 4 på datatekniska universitetsutbildningar så kan man idag lära sig grunderna i datakommunikation på flera gymnasieprogram. Författarna till denna bok har alla personlig erfarenhet av att undervisa i ämnet datakommunikation på olika nivåer. Bokens struktur möjliggör olika sätt att tillgodogöra sig materialet beroende på vad som är mest tilltalande för respektive målgrupp.
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| 3. |
- Boano, Carlo Alberto, et al.
(författare)
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Hot Packets : A systematic evaluation of the effect of temperature on low power wireless transceivers
- 2013
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Ingår i: Proc. 5th Extreme Conference on Communication. - New York : ACM Press. - 9781450321716 ; , s. 7-12
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Konferensbidrag (refereegranskat)abstract
- Temperature is known to have a significant effect on the performance of radio transceivers: the higher the temperature, the lower the quality of links. Analysing this effect is particularly important in sensor networks because several applications are exposed to harsh environmental conditions. Daily or hourly changes in temperature can dramatically reduce the throughput, increase the delay, or even lead to network partitions. A few studies have quantified the impact of temperature on low-power wireless links, but only for a limited temperature range and on a single radio transceiver. Building on top of these preliminary observations, we design a low-cost experimental infrastructure to vary the onboard temperature of sensor nodes in a repeatable fashion, and we study systematically the impact of temperature on various sensornet platforms. We show that temperature affects transmitting and receiving nodes differently, and that all platforms follow a similar trend that can be captured in a simple first-order model. This work represents an initial stepping stone aimed at predicting the performance of a network considering the particular temperature profile of a given environment.
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| 4. |
- Girons Lopez, Marc, 1986-, et al.
(författare)
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Location and Density of Rain Gauges for the Estimation of Spatial Varying Precipitation
- 2015
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 97:1, s. 167-179
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Tidskriftsartikel (refereegranskat)abstract
- Accurate estimation of precipitation and its spatial variability is crucial for reliable discharge simulations. Although radar and satellite based techniques are becoming increasingly widespread, quantitative precipitation estimates based on point rain gauge measurement interpolation are, and will continue to be in the foreseeable future, widely used. However, the ability to infer spatially distributed data from point measurements is strongly dependent on the number, location and reliability of measurement stations.In this study we quantitatively investigated the effect of rain gauge network configurations on the spatial interpolation by using the operational hydrometeorological sensor network in the Thur river basin in north-eastern Switzerland as a test case. Spatial precipitation based on a combination of radar and rain gauge data provided by MeteoSwiss was assumed to represent the true precipitation values against which the precipitation interpolation from the sensor network was evaluated. The performance using scenarios with both increased and decreased station density were explored. The catchment-average interpolation error indices significantly improve up to a density of 24 rain gauges per 1000 km2, beyond which improvements were negligible. However, a reduced rain gauge density in the higher parts of the catchment resulted in a noticeable decline of the performance indices. An evaluation based on precipitation intensity thresholds indicated a decreasing performance for higher precipitation intensities. The results of this study emphasise the benefits of dense and adequately distributed rain gauge networks.
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| 5. |
- Heintz, Fredrik, 1975-, et al.
(författare)
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Introducing Programming and Digital Competence in Swedish K-9 Education
- 2017
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Ingår i: Informatics in Schools. - Cham : Springer. - 1611-3349 .- 0302-9743. - 9783319714820 - 9783319714837 ; , s. 117-128
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Konferensbidrag (refereegranskat)abstract
- The role of computer science and IT in Swedish schools has varied throughout the years. In fall 2014, the Swedish government gave the National Agency for Education (Skolverket) the task of preparing a proposal for K–9 education on how to better address the competences required in a digitalized society. In June 2016, Skolverket handed over a proposal introducing digital competence and programming as interdisciplinary traits, also providing explicit formulations in subjects such as mathematics (programming, algorithms and problem-solving), technology (controlling physical artifacts) and social sciences (fostering aware and critical citizens in a digital society). In March 2017, the government approved the new curriculum, which needs to be implemented by fall 2018 at the latest. We present the new K–9 curriculum and put it in a historical context. We also describe and analyze the process of developing the revised curriculum, and discuss some initiatives for how to implement the changes.
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| 6. |
- Hermans, Frederik, et al.
(författare)
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SoNIC: Classifying Interference in 802.15.4 Sensor Networks
- 2013. - 11
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Ingår i: Proc. 12th International Conference on Information Processing in Sensor Networks. - New York, NY, USA : ACM. - 9781450319591 ; , s. 55-66
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Konferensbidrag (refereegranskat)abstract
- Sensor networks that operate in the unlicensed 2.4 GHz frequency band suffer cross-technology radio interference from a variety of devices, e.g., Bluetooth headsets, laptops using WiFi, or microwave ovens. Such interference has been shown to significantly degrade network performance. We present SoNIC, a system that enables resource-limited sensor nodes to detect the type of interference they are exposed to and select an appropriate mitigation strategy. The key insight underlying SoNIC is that different interferers disrupt individual 802.15.4 packets in characteristic ways that can be detected by sensor nodes. In contrast to existing approaches to interference detection, SoNIC does not rely on active spectrum sampling or additional hardware, making it lightweight and energy-efficient. In an office environment with multiple interferers, a sensor node running SoNIC correctly detects the predominant interferer 87% of the time. To show how sensor networks can benefit from SoNIC, we add it to a mobile sink application to improve the application's packet reception ratio under interference.
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| 7. |
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| 8. |
- Mannila, Linda, et al.
(författare)
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Digital Competence, Teacher Self-Efficacy and Training Needs
- 2018
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Ingår i: ICER'18. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450356282 ; , s. 78-85
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Konferensbidrag (refereegranskat)abstract
- Computing related content is introduced in school curricula all over the world, placing new requirements on school teachers and their knowledge. Little attention has been paid to fostering the skills and attitudes required to teach the new content. This involves not only traditional computing topics, such as algorithms or programming, but also the role of technology in society as well as questions related to ethics, safety and integrity. As technology develops at a fast rate, so does the content to be taught. Learning computing content through isolated in-service training initiatives is by no means enough, but rather, teachers need to develop confidence to independently and continuously explore what is new, what is relevant and how to include digital competence in their teaching. Teachers' self-efficacy is hence of crucial importance. In a previous article [13] we described the development of a self-efficacy scale for teachers, focusing on digital competence as described in EU's framework DigComp 2.0. In this paper, we extend that work by analysing 530 teachers' responses collected in Autumn 2017 during a series of workshops and other professional development events. Our goal was to collect baseline data, painting a picture of teachers' current self-efficacy levels in order to facilitate follow-up studies. In addition, our results also point out challenging areas, consequently providing important insight into what topics and themes should be emphasized in professional development initiatives.
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| 9. |
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| 10. |
- Nordén, Lars-Åke, et al.
(författare)
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Development of a self-efficacy scale for digital competences in schools
- 2017
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Ingår i: 2017 IEEE Frontiers in Education Conference (FIE). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509059195 - 9781509059201
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Konferensbidrag (refereegranskat)abstract
- As computer science enters the school curricula in an increasing number of countries, teachers must prepare to integrate digital competences into their teaching. This integration is a moving target where new methods, tools and applications appear and disappear at such rates that teachers must have confidence to independently and continuously explore what is new, what is relevant and how to plan their pedagogic activities to include digital competences. In this context approaches which can be used to study self-efficacy in digital competences among school teachers are desperately needed. With such a tool in place, we can make a baseline study and then follow teachers over time to measure changes in their self-efficacy, the cause of these changes and learn how to build their digital competence self-efficacy in different ways. The same tool can also be used to measure the self-efficacy in other populations, e.g., students in teacher training programs to ensure that they obtain an adequate self-efficacy in digital competences during their studies. This paper describes the development of a self-efficacy scale in digital competences, based on the DigiComp 2.0 framework definition of digital competence. The tool focuses predominantly on digital competences relevant for teachers in school years K-9.
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