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dc.contributor.advisorHelvik, Bjarne E.
dc.contributor.authorFølstad, Eirik Larsen
dc.date.accessioned2016-04-06T07:58:30Z
dc.date.available2016-04-06T07:58:30Z
dc.date.issued2016
dc.identifier.isbn978-82-326-1471-4
dc.identifier.issn1503-8181
dc.identifier.urihttp://hdl.handle.net/11250/2384138
dc.description.abstractThe Information and Communications Technology (ICT) industry has through the last decades changed and still continues to affect the way people interact with each other and how they access and share information, services and applications in a global market characterized by constant change and evolution. For a networked and highly dynamic society, with consumers and market actors providing infrastructure, networks, services and applications, the mutual dependencies of failure free operations are getting more and more complex. Service Level Agreements (SLAs) between the various actors and users may be used to describe the offerings along with price schemes and promises regarding the delivered quality. However, there is no guarantee for failure free operations whatever efforts and means deployed. A system fails for a number of reasons, but automatic fault handling mechanisms and operational procedures may be used to decrease the probability for service interruptions. The global number of mobile broadband Internet subscriptions surpassed the number of broadband subscriptions over fixed technologies in 2010. The User Equipment (UE) has become a powerful device supporting a number of wireless access technologies and the always best connected opportunities have become a reality. Some services, e.g. health care, smart power grid control, surveillance/monitoring etc. called critical services in this thesis, put high requirements on service dependability. A definition of dependability is the ability to deliver services that can justifiably be trusted. For critical services, the access networks become crucial factors for achieving high dependability. A major challenge in a multi operator, multi technology wireless environment is the mobility of the user that necessitates handovers according to the physical movement. In this thesis it is proposed an approach for how to optimize the dependability for critical services in multi operator, multi technology wireless environment. This approach allows predicting the service availability and continuity at real-time. Predictions of the optimal service availability and continuity are considered crucial for critical services. To increase the dependability for critical services dual homing is proposed where the use of combinations of access points, possibly owned by different operators and using different technologies, are optimized for the specific location and movement of the user. A central part of the thesis is how to ensure the disjointedness of physical and logical resources so important for utilizing the dependability increase potential with dual homing. To address the interdependency issues between physical and logical resources, a study of Operations, Administrations, and Maintenance (OA&M) processes related to the access network of a commercial Global System for Mobile Communications (GSM)/Universal Mobile Telecommunications System (UMTS) operator was performed. The insight obtained by the study provided valuable information of the inter woven dependencies between different actors in the delivery chain of services. Based on the insight gained from the study of OA&M processes a technological neutral information model of physical and logical resources in the access networks is proposed. The model is used for service availability and continuity prediction and to unveil interdependencies between resources for the infrastructure. The model is proposed as an extension of the Media Independent Handover (MIH) framework. A field trial in a commercial network was conducted to verify the feasibility in retrieving the model related information from the operators' Operational Support Systems (OSSs) and to emulate the extension and usage of the MIH framework. In the thesis it is proposed how measurement reports from UE and signaling in networks are used to define virtual cells as part of the proposed extension of the MIH framework. Virtual cells are limited geographical areas where the radio conditions are homogeneous. Virtual cells have radio coverage from a number of access points. A Markovian model is proposed for prediction of the service continuity of a dual homed critical service, where both the infrastructure and radio links are considered. A dependability gain is obtained by choosing a global optimal sequence of access points. Great emphasizes have been on developing computational e cient techniques and near-optimal solutions considered important for being able to predict service continuity at real-time for critical services. The proposed techniques to obtain the global optimal sequence of access points may be used by handover and multi homing mechanisms/protocols for timely handover decisions and access point selections. With the proposed extension of the MIH framework a global optimal sequence of access points providing the highest reliability may be predicted at real-time.nb_NO
dc.language.isoengnb_NO
dc.publisherNTNUnb_NO
dc.relation.ispartofseriesDoctoral thesis at NTNU;2016:66
dc.relation.haspartPaper 1: Følstad, Eirik Larsen; Helvik, Bjarne Emil. Managing availability in wireless inter domain access. I: Proceedings of the International Conference on Ultra Modern Telecommunications. IEEE Communications Society 2009. http://doi.org/10.1109/ICUMT.2009.5345550. © 2009 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
dc.relation.haspartPaper 2: Følstad, Eirik Larsen; Helvik, Bjarne Emil. Determining dependencies in multi technology inter domain wireless access; A case study. Globecom - Workshop on Mobile Computing and Emerging Communication Networks.; 2010. http://doi.org/10.1109/GLOCOMW.2010.5700114. © 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
dc.relation.haspartPaper 3: Følstad, Eirik Larsen; Helvik, Bjarne Emil. Failures and changes in cellular access networks; A study of field data. I: Proceedings of the 2011 8th International Workshop on the Design of Reliable Communication Networks. IEEE Press 2011, s. 132-139. http://doi.org/10.1109/DRCN.2011.6076895 © 2011 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
dc.relation.haspartPaper 4: Cholda, Piotr; Følstad, Eirik Larsen; Helvik, Bjarne Emil; Kuusela, Pirkko; Naldi, Maurizio; Norros, Ilkka. Towards risk-aware communications networking. Reliability Engineering & System Safety 2012 ; Volum 109. s. 160-174. http://doi.org/10.1016/j.ress.2012.08.009
dc.relation.haspartPaper 5: Følstad, Eirik Larsen; Helvik, Bjarne Emil. Reliability modelling of access point selection and handovers in heterogeneous wireless environments. I: Design of Reliable Communication Networks (DRCN), 2013 9th International Conference on the. IEEE Press 2013 ISBN 978-1-4799-0049-7. s. 103-110. © 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
dc.relation.haspartPaper 6: Følstad, Eirik Larsen; Helvik, Bjarne Emil. The cost for meeting SLA requirements; Implications for customers and providers. Reliability Engineering & System Safety 2016 ; Volum 145. s. 136-146. http://doi.org/10.1016/j.ress.2015.09.011.
dc.relation.haspartPaper 7: Følstad, Eirik Larsen; Helvik, Bjarne Emil. Optimizing service continuity in a multi operator multi technology wireless environment. I: Design of Reliable Communication Networks (DRCN), 2013 9th International Conference on the. IEEE Press 2013. s. 111-118. © 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
dc.relation.haspartPaper 8: Følstad, Eirik Larsen; Helvik, Bjarne Emil. Using genetic algorithms to improve the reliability of dual homed wireless critical services. 6th International Workshop on Reliable Networks Design and Modeling [RNDM'14]. http://doi.org/10.1109/RNDM.2014.7014946 © 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
dc.relation.haspartPaper 9: Følstad, Eirik Larsen; Helvik, Bjarne Emil. Maximizing the reliability of dual homed, critical services in wireless/cellular networks. Optical Switching and Networkning Journal 2016 ;Volum 19. s. 110-121. http://doi.org/10.1016/j.osn.2015.01.004
dc.titleManaged access dependability for critical services in wireless inter domain environmentnb_NO
dc.typeDoctoral thesisnb_NO
dc.subject.nsiVDP::Technology: 500::Information and communication technology: 550::Telecommunication: 552nb_NO


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