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Synthesizing context for a sports domain on a mobile device
KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01). Appear Networks, Sweden.
2008 (English)In: 3rd European Conference on Smart Sensing and Context, EuroSSC 2008, 2008, 206-219 p.Conference paper, Published paper (Refereed)
Abstract [en]

In ubiquitous computing environments there are an increasing number and variety of devices that can generate context data. The challenge is to timely acquire, process, and deliver these data to context-aware applications. The role of context synthesis is to generate new knowledge, as a result of a reasoning process applied to context information that is already present in the system. The success of this mechanism mainly depends on the response time that the end-user or an application must wait for the response to a context query. This paper describes and evaluates an approach to context synthesis on a mobile device to be used by a set of applications in a sports domain. A scenario based on a live race at the Super Prestige Cyclocross in Gieten, Netherlands demonstrates the use of context synthesis to dynamically compose gaps and groups of cyclists in order to provide a nearly real-time virtual ranking service.

Place, publisher, year, edition, pages
2008. 206-219 p.
Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 5279
Keyword [en]
Context modeling, Context operators, Context synthesis, Sport scenario, Computer systems, Mobile devices, Object recognition, Portable equipment, Telecommunication equipment, Ubiquitous computing, Context datums, Context informations, Context-aware, Do-mains, Netherlands, Reasoning processes, Response times, Ubiquitous Computing environments, Applications
National Category
Computer Science
Identifiers
URN: urn:nbn:se:kth:diva-154152ISI: 000260605300016Scopus ID: 2-s2.0-57049146372ISBN: 354088792X (print)ISBN: 9783540887928 (print)OAI: oai:DiVA.org:kth-154152DiVA: diva2:756430
Conference
29 October 2008 through 31 October 2008, Zurich
Note

QC 20141017

Available from: 2014-10-17 Created: 2014-10-14 Last updated: 2017-05-03Bibliographically approved
In thesis
1. On Optimization of Quality of User Experience and Wireless Network Bandwidth in Video Content Delivery
Open this publication in new window or tab >>On Optimization of Quality of User Experience and Wireless Network Bandwidth in Video Content Delivery
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mobile video content today generates more than half of the mobile data traffic.The increasing popularity of mobile video on demand services poses great challenges to mobile operators and content providers. Frontmost, how to reduce the mobile video traffic load, while delivering high quality video content to mobile users without perceived quality degradations for the same (or cheaper) price? Battery lifetime represents another key factor of a user’s Quality of Experience(QoE). A lot of device energy is consumed by mobile network signalling and data transmission over new generation mobile communication systems. This thesis focuses on: (1) reducing the size of the video that is delivered to the enduser in the maximum achievable video quality, thus optimizing the wireless network bandwidth and the user-perceived QoE, and (2) reducing the energy consumption of a mobile device that is associated to data transfer over the radio interface, thus increasing the device’s battery lifetime. The main contributions have been given in providing the Over-the-Top video optimization and delivery schemes and recommendations on tuning their parameters in order to minimize the bandwidth and energy consumption of mobile video delivery, while maximizing the predictable user-perceived QoE. By preventing the video to be prefetched on low data rates and tuning the datarate threshold according to statistical properties of available data rates, we show that 20-70% of energy cost can be reduced by opportunistic prefetching, depending on the user’s pattern of available data rates. The data rate values ordered in time that have a large amount of serial correlation and low noise variance, or low average valueand high peak-to-mean ratio, are likely to yield the highest energy gains from content prefetching. Moreover, we show that energy gains are the largest when the threshold data rate is set close to an average data rate, due to the highest availability of data rates around this value, and for longer sleep time between the prefetching periods, which increases the probability of moving away from the areas with low data rates. Next, we focus on QoE-aware mobile video delivery solutions that are more bandwidth efficient without compromising the user-perceived video quality. They deliver a video over a varying data rate channel that is optimized for viewing on a mobile device in the highest perceptual video quality that can be achieved in the given video and network conditions. An optimized video consists of short segments in the minimum resolutions that satisfy the target perceptual video quality and have up to 60% reduced size compared to the video in the corresponding fixed video resolution, without perceptible quality difference. The delivery is performed by on demand download, context-aware prefetching, or in real time using the QoE-aware adaptive video streaming that runs over Dynamic Adaptive video Streaming over HTTP (DASH). By limiting the maximum bitrates of the requested video segments and using the remaining throughput to prefetch optimized video segments in advance of playout, we show that QoE-aware adaptive video streaming maintains a more stable perceptual video quality than DASH despite the fluctuations of the channel bandwidth, while using fewer number of bits, which improves a user-perceived QoE. The results of this thesis can help operators and content providers to reduce their costs and provide more content to their users at the same (or cheaper) price.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xii, 174 p.
Series
TRITA-ICT, 2015:17
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-177011 (URN)978-91-7595-739-5 (ISBN)
Public defence
2015-12-04, Sal/hall B, Electrum , KTH-ICT, Kista, 13:00 (English)
Opponent
Supervisors
Note

QC 20151113

Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2015-11-13Bibliographically approved

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf