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A Presence Server for Context-aware Applications
KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. (CCSlab)
2007 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This master’s thesis project “A Presence Server for Context-aware Applications” was carried out at KTH Center for Wireless Systems (Wireless@KTH). The overall goal of this thesis project is to implement a context aware infrastructure to serve as middleware for different kinds of context aware applications, such as a context-aware printing application, location based notifier application, etc. This thesis examines different types of context aware architectures and considers different forms of context modeling. Additionally the thesis also explores some of the related technology, in order to provide the reader with suitable background information to understand the rest of the thesis. By using the SIP Express Router (SER) and its presence module (pa) a context server has been designed, implemented, and evaluated. Evaluation reveals that the critical bottleneck is the increasing service time as the number of Publish messages for different events in the SER database increases, i.e. the time required for handling and sending the Notify messages when a new Publish message is received increases as a function of the number of earlier Publish messages. The evaluation also shows that the dependence of SER upon the MySQL database as incorrect database queries can cause SER to crash. Additionally the performance of the database limits the performance of the context server. A number of future improvements are necessary to address security issues (in particular the authentication of Watchers) and adding policy based control in order to send Notify messages only to the Watchers authorized to receive information for a specific event.

Abstract [sv]

Examensarbetet "A Presence Server for Context-aware Applications" genomfördes på Kungliga Tekniska Högskolan, KTH Center for Wireless Systems (Wireless@KTH). Det övergripande målet med detta examensarbetsprojekt är att implementera en kontextmedveten infrastruktur som fungerar som "middleware" för olika typer av kontextmedvetna applikationer. Exempel på dessa är kontextmedveten utskriftsapplikation och platsberoende meddelarapplikation osv. Rapporten undersöker olika typer av kontextmedvetna arkitekturer och betraktar olika former av kontextmodellering. Rapporten utforskar även vissa besläktade teknologier för att kunna tillhandahålla läsaren med en passande bakgrundsinformation och därmed öka förståelsen för resten av examensarbetet. Genom att använda Sip Express Routern (SER) och dess närvaromodul (presence module, PA) har en kontextserver designats, implementerats och utvärderats. Utvärderingen visar att den kritiska flaskhalsen är tiden det tar för SER servern att svara på nya Publish meddelanden, för olika händelser, i SER databasen. Svarstiden ökar allteftersom databasen fylls med mer data. Detta påverkar hantering och sänding av Notify meddelande när en ny Publish meddelande är mottagen. Uvärderingen visar också att en viktig fråga är relationen mellan SER servern och MySQL databasen, eftersom felaktiga förfrågningar till databasen kan krascha SER servern. De viktigaste framtida förbättringarna är säkerhetsaspekter (mer specifikt autenticering av Watchers) och tillägg av policybaserad sändning av Notify meddelanden endast till auktoriserade Watchers för specifika händelser.

Place, publisher, year, edition, pages
2007. , 160 p.
Series
Trita-ICT-COS, ISSN 1653-6347 ; COS/CCS 2007-27
Keyword [en]
Context, Context-aware, SIP, SIP-SIMPLE, XML, PIDF, SER, Presence Agent module, Subscribe message, Publish message, Notify message
National Category
Communication Systems
Identifiers
URN: urn:nbn:se:kth:diva-91937OAI: oai:DiVA.org:kth-91937DiVA: diva2:511675
Subject / course
Computer Communication
Educational program
Master of Science - Internetworking
Presentation
2007-12-17, Seminar room Grimeton, Isafjordsgatan 22, Kista, 10:00 (English)
Uppsok
Technology
Supervisors
Examiners
Available from: 2012-03-23 Created: 2012-03-22 Last updated: 2013-09-09Bibliographically approved

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