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  • 1.
    Chupisanyarote, Sanpetch
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kouyoumdjieva, Sylvia
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Helgason, Ólafur
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Caching in opportunistic networks with churn2012In: 2012 9th Annual Conference on Wireless On-Demand Network Systems and Services, WONS 2012, IEEE Communications Society, 2012, p. 39-42Conference paper (Refereed)
    Abstract [en]

    In this paper we examine opportunistic content distribution. We design and evaluate a caching strategy where a node will fetch and share contents on behalf of other nodes, although the contents are not of its own interest. We propose three caching options for improving the use of network resources: relay request on demand, hop-limit, and greedy relay request. The proposed strategies are implemented in the OMNeT++ simulator and evaluated on mobility traces from Legion Studio that have churn. We also compare our strategies with a strategy from the literature. The results are analyzed and they show that the use of opportunistic caching for a community of nodes may enhance the performance marginally while overhead increases significantly.

  • 2.
    Danielis, Peter
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kouyoumdjieva, Sylvia T.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    DiVote: A Distributed Voting Protocol for Mobile Device-to-Device Communication2016In: Proceedings of the 28th International Teletraffic Congress, ITC 2016, 2016, Vol. 1, p. 69-77Conference paper (Refereed)
    Abstract [en]

    Distributed aggregation algorithms have traditionally been applied to environments with no or rather low rates of node churn. The proliferation of mobile devices in recent years introduces high mobility and node churn to these environments, thus imposing a new dimension on the problem of distributed aggregation in terms of scalability and convergence speed. To address this, we present DiVote, a distributed voting protocol for mobile device-to-device communication. We investigate a particular use case, in which pedestrians equipped with mobile phones roam around in an urban area and participate in a distributed yes/no poll, which has both spatial and temporal relevance to the community. Each node casts a vote and collects votes from other participants in the system whenever in communication range; votes are immediately integrated into a local estimate. The objective of DiVote is to produce a precise mapping of the local estimate to the anticipated global voting result while preserving node privacy. Since mobile devices may have limited resources allocated for mobile sensing activities, DiVote utilizes D-GAP compression. We evaluate the proposed protocol via extensive trace-driven simulations of realistic pedestrian behavior, and demonstrate that it scales well with the number of nodes in the system. Furthermore, in densely populated areas the local estimate of participants does not deviate by more than 3% from the global result. Finally, in certain scenarios the achievable compression rate of DiVote is at least 19% for realistic vote distributions.

  • 3. Danielis, Peter
    et al.
    Kouyoumdjieva, Sylvia T.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    UrbanCount: Mobile Crowd Counting in Urban Environments2017In: 2017 8th IEEE Annual Information Technology, Electronics and Mobile Communication Conference (IEMCON) / [ed] Chakrabarti, S Saha, HN, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 640-648Conference paper (Refereed)
    Abstract [en]

    Surveillance, management and estimation of spontaneous crowd formations in urban environments, e.g., during open-air festivals or rush hours, are necessary measures for city administration. Most solutions that implement these measures however require additional costly hardware installations (e.g., installation of observation cameras) and infrastructure support, and often pose privacy concerns. In this work, we present UrbanCount, a fully distributed crowd counting protocol for cities with high crowd densities. UrbanCount relies on mobile device-to-device communication to perform crowd estimation. Each node collects crowd size estimates from other participants in the system whenever in communication range and immediately integrates these estimates into a local estimate. The objective of UrbanCount is to produce a precise mapping of the local estimate to the anticipated global result while preserving node privacy. We evaluate the proposed protocol via extensive tracedriven simulations of synthetic and realistic mobility models. Furthermore, we investigate the dependency between accuracy and density, and demonstrate that in dense environments the local estimate does not deviate by more than 2% for synthetic and 7% for realistic scenarios. Index Terms-Crowd counting,

  • 4.
    Helgason, Ólafur
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Kouyoumdjieva, Sylvia
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Enabling Multiple Controllable Radios in OMNeT nodes2011In: Proc. ICST SIMUTools 2011, OMNeT workshop, 2011Conference paper (Refereed)
    Abstract [en]

    This work describes our implementation of a framework that allows mobile nodes in OMNeT++ simulations to be equipped with multiple radio subsystems that can be dynamically suspended and woken up. Our framework enables the simulationof wireless architectures that exploit radio hierarchiesfor power-effecient neighbor and service discovery and connection setup. The design is implemented as an extension of the MiXiM framework and is maintained as a MiXiM branch.

  • 5.
    Helgason, Ólafur
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Kouyoumdjieva, Sylvia T.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Does Mobility Matter?2010In: WONS 2010: SEVENTH INTERNATIONAL CONFERENCE ON WIRELESS ON-DEMAND NETWORK SYSTEMS AND SERVICES, NEW YORK: IEEE , 2010, p. 9-16Conference paper (Refereed)
    Abstract [en]

    In modern society, wireless devices are commonly carried by humans. The wireless communication is therefore affected by pedestrian mobility in urban outdoor and indoor spaces which is the scenario we consider in this work. Many of the mobility models currently used for evaluating wireless communication systems have poor resemblance to reality. Although advances have recently been made, there is still a lack of understanding on which elements of mobility affect system performance. In the civil-engineering field of transport and urban planning there exist advanced pedestrian mobility models, used for designing and dimensioning public spaces for pedestrian crowds and emergency evacuation. These models capture micro-mobility of pedestrians better than most mobility models used in mobile networking since the application domain requires that they realistically capture node interactions with its physical environment as well as other nodes. In this work we use Legion Studio, a commercial simulator, to explore which elements of pedestrian mobility are important with respect to system performance and how sensitive the connectivity metrics of nodes are to input mobility parameters. These studies give insight into whether relatively simple mobility models suffice for evaluating wireless systems. Furthermore, they contribute to our understanding of which parameters are important for modelling mobility and the accuracy in which these parameters need to be estimated to give dependable results.

  • 6.
    Helgason, Ólafur
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kouyoumdjieva, Sylvia T.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Opportunistic Communication and Human Mobility2014In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 13, no 7, p. 1597-1610Article in journal (Refereed)
    Abstract [en]

    Many mobility models currently used for evaluating wireless communication systems have weak resemblance to reality and there is a lack of understanding on which characteristics of human mobility affect system performance. In particular, most current mobility models assume a free flow of nodes and do not consider how mobility is affected by interactions with other persons and with the physical environment. They also assume a closed system, not considering the effect of node arrival and departure. The structure of space in which the mobility occurs is either not considered at all, or only in a limited way. In this work, we address human pedestrian mobility for evaluation of wireless communication to determine which of the aforementioned aspects need to be captured and to what level of detail. We focus on opportunistic communication in the form of ad-hoc and delay-tolerant networks. For the evaluation, we use mobility models from the field of transportation and urban planning that are used for designing and dimensioning public spaces for comfort and safety of pedestrians in rush hour and emergency evacuation. The models capture micro-mobility of pedestrians better than most mobility models used in mobile networking since the application domain requires realistic representation of node interactions with the physical environment and with other nodes. Our results show that the free flow assumption used in most models does not have a significant performance impact. We also conclude that performance is not very sensitive to accurate estimation of the probability distributions of mobility parameters such as speed and arrival process. Our results, however, suggest that it is important to capture the scenario and space in which mobility occurs since these may affect performance significantly.

  • 7.
    Helgason, Ólafur
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kouyoumdjieva, Sylvia T.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pajevic, Ljubica
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Yavuz, Emre A.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A Middleware for Opportunistic Content Distribution2016In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069Article in journal (Refereed)
    Abstract [en]

    In this work we present a middleware architecture for a mobile peer-to-peer content distribution system. Our architecture allows wireless content dissemination between mobile nodes without relying on infrastructure support. In addition, it supports the dissemination of contents between the wireless ad-hoc domain and the wired Internet. In the ad-hoc domain, contents are exchanged opportunistically when nodes are within communication range. Applications access the service of our platform through a publish/subscribe interface and therefore do not have to deal with low-level opportunistic networking issues or matching and soliciting of contents. Our middleware consists of three key components. A content structure that facilitates dividing contents into logical topics and allows efficient matching of content lookups and downloading under sporadic node connectivity. A solicitation protocol that allows nodes to solicit content meta-information in order to discover contents available at a neighboring node and to download content entries disjointedly from different nodes. An API that allows applications to access the system services through a publish/subscribe interface. In this work we present the design and implementation of our middleware and describe a set of applications that use the services provided by our middleware. We also assess the performance of the system using our Android implementation as well as a simulation implementation for large-scale evaluation.

  • 8.
    Helgason, Ólafur
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Yavuz, Emre A.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kouyoumdjieva, Sylvia
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Pajevic, Ljubica
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    A mobile peer-to-peer system for opportunistic content-centric networking2010In: Proceedings of the 2nd ACM SIGCOMM Workshop on Networking, Systems, and Applications on Mobile Handhelds, MobiHeld '10, Co-located with SIGCOMM 2010, 2010, p. 21-26Conference paper (Refereed)
    Abstract [en]

    In this work we present a middleware architecture for a mobile peer-to-peer content distribution system. Our architecture allows wireless content dissemination between mobile nodes without relying on infrastructure support. Contents are exchanged opportunistically when nodes are within communication range. Applications access the service of our platform through a publish/subscribe interface and therefore do not have to deal with low-level opportunistic networking issues or matching and soliciting of contents. Our architecture consists of three key components. A content structure that facilitates dividing contents into logical topics and allows for efficient matching of content lookups and downloading under sporadic node connectivity. A solicitation protocol that allows nodes to solicit content meta-information in order to discover contents available at a neighboring node and to download content entries disjointedly from different nodes. An API that allows applications to access the system services through a publish/subscribe interface. In this work we describe the design and implementation of our architecture. We also discuss potential applications and present evaluation results from profiling of our system.

  • 9.
    Kouyoumdjieva, Sylvia
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Chupisanyarote, Sanpetch
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Helgason, Ólafur
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Caching Strategies in Opportunistic Networks2012In: 2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, WoWMoM 2012 - Digital Proceedings, IEEE , 2012, p. 6263744-Conference paper (Refereed)
    Abstract [en]

    In this paper we examine content distribution in opportunistic networks. We design and evaluate strategies by which a node fetches and shares contents on behalf of other nodes, even when the contents are not of its own interest. We propose four relaying/caching options for improving the use of network resources: relay request on demand, hop-limit, greedy relay request, and weighted relay request with allocated caching positions. We also compare our strategies with a strategy from the literature. The proposed strategies are implemented in the OMNeT++ simulator, and evaluated on mobility traces with different churn levels. The results show that the performance of opportunistic caching is strongly dependent on the level of churn in the network. However, we find a strategy that outperforms the rest in all of the explored network settings.

  • 10.
    Kouyoumdjieva, Sylvia
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Helgason, Ólafur
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Yavuz, Emre A.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Evaluating an Energy-efficient Radio Architecture for Opportunistic Communication2012In: Communications (ICC), 2012 IEEE International Conference on, IEEE , 2012, p. 5751-5756Conference paper (Refereed)
    Abstract [en]

    A major challenge for wireless networks is to minimize the energy consumption in the mobile devices. This work evaluates potential performance gains of a dual-radio architecture in which a low power radio is used to wake up the primary high power radio. Our targeted domain is opportunistic communication directly between devices. We show that it can significantly reduce the energy consumption at a price of slightly decreased goodput. We also examine the effect of the MAC protocol on the performance of the dual-radio system and we point out that in dense scenarios MAC layer protocols, such as of 802.15.4, do not perform well. We observe that information on device density of an environment can be used to address this shortcoming.

  • 11.
    Kouyoumdjieva, Sylvia T.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    System Design for Opportunistic Networks2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Device-to-device communication has been suggested as a complement to traditional cellular networks as a means of offloading cellular traffic. In this thesis we explore a solution for device-to-device communication based on opportunistic content distribution in a content-centric network. Communication opportunities arise as mobile nodes roam around in an area and occasionally enter in direct communication range with one another. We consider a node to be a pedestrian equipped with a mobile device and explore the properties of opportunistic communication in the context of content dissemination in urban areas.

    The contributions of this thesis lie in three areas. We first study human mobility as one of the main enablers of opportunistic communication. We introduce traces collected from a realistic pedestrian mobility simulator and demonstrate that the performance of opportunistic networks is not very sensitive to the accurate estimation of the probability distributions of mobility parameters. However, capturing the space in which mobility occurs may be of high importance. Secondly, we design and implement a middleware for opportunistic content-centric networking, and we evaluate it via a small-scale testbed, as well as through extensive simulations. We conclude that energy-saving mechanisms should be part of the middleware design, while caching should be considered only as an add-on feature. Thirdly, we present and evaluate three different energy-saving mechanisms in the context of opportunistic networking: a dual-radio architecture, an asynchronous duty-cycling scheme, and an energy-aware algorithm which takes into account node selfishness. We evaluate our proposals analytically and via simulations. We demonstrate that when a critical mass of participants is available, the performance of the opportunistic network is comparable to downloading contents directly via the cellular network in terms of energy consumption while offloading large traffic volumes from the operator.

  • 12.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Device-to-Device Mobile Data Offloading for Music Streaming2016In: 2016 IFIP Networking Conference (IFIP Networking) and Workshops, IFIP Networking 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 377-385, article id 7497219Conference paper (Refereed)
    Abstract [en]

    Device-to-device communication (also referred to as opportunistic networking) is considered a feasible means for offloading mobile data traffic. Due to the sporadic nature of contact opportunities, applications in the domain of device-todevice communication are assumed to be delay-tolerant, with content delivery deadlines being in the order of hours. However, predictions suggest that by 2020 more than 75% of the traffic volumes at mobile operators will be generated by multimedia contents which is often seen as data served in real-time. In this paper we explore how the concept of opportunistic networking can be used for dissemination of real-time streaming contents for users in urban environments without degrading quality of experience. We first present a general framework for offloading multimedia data that is organized in terms of playlists, and we then investigate the performance of the framework in realistic urban environments using the music streaming service Spotify as a use-case. Our results show that it is feasible to use opportunistic device-to-device communication in the context of music streaming. We demonstrate that the system performance is insensitive to a number of parameters such as playlist length distribution, and initial content availability distribution, however it exhibits sensitivity towards the amount of requested data and the node density.

  • 13.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Energy-Aware Opportunistic Mobile Data Offloading for Users in Urban Environments2015In: IFIP Networking Conference (IFIP Networking), 2015, IEEE conference proceedings, 2015, p. 1-9Conference paper (Refereed)
    Abstract [en]

    Opportunistic networking (a.k.a. device-to-device communication) is considered a feasible means for offloading mobile data traffic. Since mobile nodes are battery-powered, opportunistic networks must be expected to satisfy the user demand without greatly affecting battery lifetime. To address this requirement, this work introduces progressive selfishness, an adaptive and scalable energy-aware algorithm for opportunistic networks used in the context of mobile data offloading. The paper evaluates the performance of progressive selfishness in terms of both application throughput and energy consumption via extensive trace-driven simulations of realistic pedestrian behavior, and demonstrates that the proposed algorithm is robust against the distributions of node density and initial content availability. The results show that in certain scenarios progressive selfishness achieves up to 85% energy savings during opportunistic downloads while sacrificing less than 1% in application throughput. Furthermore, the study demonstrates that in terms of total energy consumption (by both cellular and opportunistic downloads) in dense environments the performance of progressive selfishness is comparable to downloading contents directly from a mobile network.

  • 14.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Energy-Aware Opportunistic Mobile Data Offloading Under Full and Limited Cooperation2016In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 84, p. 84-95Article in journal (Refereed)
    Abstract [en]

    Opportunistic networking (a.k.a. device-to-device communication) is considered a feasible means for offloading mobile data traffic. Since mobile nodes are battery-powered, opportunistic networks must be expected to satisfy the user demand without greatly affecting battery lifetime. To address this requirement, this work introduces progressive selfishness, an adaptive and scalable energy-aware algorithm for opportunistic networks used in the context of mobile data offloading. The paper evaluates the performance of progressive selfishness in terms of both application throughput and energy consumption via extensive trace-driven simulations of realistic pedestrian behavior. The evaluation considers two modes of nodal cooperation: full and limited, with respect to the percentage of nodes in the system that adopt progressive selfishness. The paper demonstrates that under full cooperation the proposed algorithm is robust against the distributions of node density and initial content availability. The results show that in certain scenarios progressive selfishness achieves up to 85% energy savings during opportunistic downloads while sacrificing less than 1% in application throughput. Furthermore, the study demonstrates that in terms of total energy consumption (by both cellular and opportunistic downloads) in dense environments the performance of progressive selfishness is comparable to downloading contents directly from a mobile network. Finally, the paper shows that progressive selfishness is robust against the presence of non-cooperative nodes in the system, and that in certain scenarios the system-level performance does not deteriorate significantly under limited cooperation even when 50% of the nodes in the system do not adhere to the specifics of the algorithm.

  • 15.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Experimental Evaluation of Precision of a Proximity-based Indoor Positioning System2019In: 2019 15th Annual Conference on Wireless On-demand Network Systems and Services, WONS 2019 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 130-137, article id 8795488Conference paper (Refereed)
    Abstract [en]

    Bluetooth Low Energy beacons are small transmitters with long battery life that are considered for providing proximity-based services. In this work we evaluate experimentally the performance of a proximity-based indoor positioning system built with off-the-shelf beacons in a realistic environment. We demonstrate that the performance of the system depends on a number of factors, such as the distance between the beacon and the mobile device, the positioning of the beacon as well as the presence and positioning of obstacles such as human bodies. We further propose an online algorithm based on moving average forecasting and evaluate the algorithm in the presence of human mobility. We conclude that algorithms for proximity-based indoor positioning must be evaluated in realistic scenarios, for instance considering people and traffic on the used radio bands. The uncertainty in positioning is high in our experiments and hence the success of commercial context-aware solutions based on BLE beacons is highly dependent on the accuracy required by each application.

  • 16.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    From Opportunistic Networks to 3GPP Network-Independent Device-to-Device Communication2016In: GetMobile: Mobile Computing and Communications, Vol. 20, no 2, p. 22-26Article, review/survey (Other academic)
    Abstract [en]

    Device-to-device (D2D) communication may be able to complement traditional cellular network communication. D2D communication establishes a direct link between nearby mobile devices instead of relaying traffic through the cellular infrastructure. While D2D is currently a popular research topic in telecommunications, allowing co-located devices to communicate directly has been studied for more than a decade under the name “opportunistic communication.” By comparing 3GPP’s networkindependent D2D communication to opportunistic communication, we demonstrate that they share a number of common characteristics. We identify best practices from opportunistic networking that can be applied to network-independent D2D, and discuss open questions in D2D communication that have not been addressed.

  • 17.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    From Opportunistic Networks to 3GPP Network-Independent Device-to-Device Communication2015Report (Other academic)
    Abstract [en]

    Device-to-device (D2D) communication is being proposed as a complement to traditional communication via cellular networks. D2D establishes a direct communication link between mobile devices instead of relaying traffic through the cellular infrastructure. While D2D is currently one of the popular research topics in telecommunications, the concept of allowing devices in proximity to communicate directly with one another has been extensively studied for more than a decade under the name opportunistic communication. We here compare 3GPP’s network-independent D2D communication to opportunistic communication and demonstrate that they share a number of common characteristics. We discuss which best practices from the opportunistic networking domain may be applied to networkindependent D2D, and outline open questions in the D2D design that have not been answered by previous research efforts.

  • 18.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Impact of Duty Cycling on Opportunistic Communication2016In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 15, no 7, p. 1686-1698Article in journal (Refereed)
    Abstract [en]

    A major challenge in mobile wireless devices for opportunistic networks is to decrease the energy consumption. The decrease should not come at a cost of reduced application throughput (i.e. goodput). This work evaluates the potential performance gains for mobile nodes that adopt duty cycling in an opportunistic context. The paper presents an analytical framework for evaluating goodput and energy consumption of nodes based on a probabilistic estimation of effective contact durations, and it validates this framework on a mobility scenario. The study shows that both goodput and energy consumption depend strongly on the distribution of listening durations, and that goodput is independent of the contact rate among nodes. This work also includes extensive trace-driven simulations and demonstrates that duty cycling considerably improves the performance of opportunistic networks by decreasing the energy consumption without significantly affecting the goodput.

  • 19.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Precision of a Proximity-based Indoor Positioning System with Bluetooth Low Energy Beacons2017Conference paper (Refereed)
    Abstract [en]

    Bluetooth Low Energy beacons are small transmitters with long battery life that are considered appropriate for providing proximity-based services for businesses. In this work we evaluate experimentally the performance of a proximity-based indoor positioning system built with off-the-shelf beacons in a realistic environment. We demonstrate that the performance of the system depends on a number of factors, such as the displacement between the beacon and the mobile device, the positioning of the beacon as well as the presence and positioning of obstacles such as human bodies. We conclude that algorithms for improving proximity-based indoor positioning need always to be evaluated in realistic scenarios. We believe that the success of commercial context-aware solutions based on BLE beacons is highly dependent on the accuracy required by each application.

  • 20.
    Kouyoumdjieva, Sylvia T.
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    The Virtue of Selfishness: Device Perspective on Mobile Data Offloading2015In: Wireless Communications and Networking Conference (WCNC), 2015 IEEE, IEEE conference proceedings, 2015, p. 2067-2072Conference paper (Refereed)
    Abstract [en]

    Direct device-to-device communication based on the ’store-carry-forward’ paradigm is considered a feasible means for offloading mobile data traffic. Employing device-to-device communication however should satisfy user demand without greatly affecting battery lifetime. In order to provide satisfactory application throughput it is often assumed that nodes behave altruistic, and are willing to share contents for an infinite amount of time. In the context of energy savings, this assumption is overly optimistic. This work evaluates the performance of a publish/subscribe opportunistic content dissemination application that uses duty cycling for energy saving and allows nodes to behave in a selfish manner. Two types of selfishness are introduced: strict and mild. The paper presents the impact of selfishness on both application throughput and energy consumption via extensive trace-driven simulations, and demonstrates that introducing strictly selfish behavior on top of duty cycling leads to great decrease in energy consumption (up to 90% in certain cases) without causing significant loss in application throughput. Moreover, when the duration of the mild selfishness interval is chosen appropriately, mild selfishness can lead to even further decrease in energy consumption while at the same time increasing the application throughput.

  • 21.
    Kouyoumdjieva, Sylvia Todorova
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Opportunistic Content Distribution: A System Design Approach2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The penetration of smart pocket-size devices that provide constant Internet connectivity, such as mobile phones, has significantly changed the way people obtain, view and share information. Content provision is not anymore a prerogative to professionals; individuals are not solely customers, but also act as content generators and distributors. This shift in social behavior requires changes in the way information is delivered to target audiences in an efficient, interest-based and location-aware manner.

    This thesis explores a solution for opportunistic content distribution in a content-centric network that primarily targets content dissemination among mobile users in urban areas. The term ’opportunistic’ here refers to a concept which rejects the assumption of always-connected user devices and instead allows nodes to leverage sporadic contacts which occur when two neighbors come into direct radio communication range. Such communication mode allows data exchanges to occur in areas with little or no infrastructure; moreover, it is a potential solution for offloading the increasing traffic volumes observed by mobile operators.

    The contributions of this thesis lie in three areas. We first outline a general architecture and design for opportunistic content-centric networking. We implement our proposal on the Google Android platform, and provide application scenarios which illustrate the potential of mobile peer-to-peer communication. Our tests however show that energy consumption turns out to be a major issue for opportunistic networks. Therefore, our second effort is in the area of energy-efficiency. We propose a dual-radio architecture for opportunistic communication, and evaluate it through extensive simulations on realistic human mobility traces. Our final study lies in the area of content dissemination when nodes in the network act altruistically and are willing to solicit data on behalf of other participants. We propose a number of relaying and caching strategies, and evaluate them through simulations in environments that exhibit different churn levels.

  • 22.
    Kouyoumdjieva, Sylvia Todorova
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Energy savings in opportunistic networks2014In: 11th Annual Conference on Wireless On-Demand Network Systems and Services, IEEE/IFIP WONS 2014 - Proceedings, IEEE Computer Society, 2014, p. 57-64Conference paper (Refereed)
    Abstract [en]

    A major challenge in mobile wireless devices for opportunistic networks is to minimize the energy consumption. The minimization however should not come at a cost of reduced application throughput (i.e. goodput). This work evaluates the potential performance gains for mobile nodes that adopt a duty-cycling scheme in an opportunistic context. We present an analytical framework for evaluating the energy consumption of nodes based on a probabilistic estimation of effective contact durations, and we validate this framework on a mobility sce-nario. We further perform extensive trace-driven simulations and demonstrate that a duty-cycling scheme considerably improves the performance of opportunistic content distribution systems by decreasing the energy consumption without significantly affecting the goodput.

  • 23.
    Kouyoumdjieva, Sylvia
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Yavuz, Emre A.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Helgason, Olafur
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Pajevic, Ljubica
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Opportunistic Content-Centric Networking: The Conference Case Demo2011In: Proceedings of the IEEE International Conference on Computer Communications, INFOCOM’11, 2011Conference paper (Refereed)
    Abstract [en]

    We present a demonstration scenario to evaluate a middleware architecture that we designed and implemented for distributing content over mobile ad hoc networks. The peer to-peer networking architecture allows content dissemination between mobile devices without relying on any infrastructure support. Content is exchanged opportunistically when nodes are in proximity. We developed a mobile application utilizing the services provided by the implemented middleware. The application facilitates opportunistic content distribution in both one-to-one and one-to-many dissemination modes.

  • 24.
    Pajevic, Ljubica
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Yavuz, Emre A.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Helgason, Olafur
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Kouyoumdjieva, Sylvia
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Demo: Opportunistic Mobile Social Networking2011In: Proc. ACM Annual International Conference on Mobile Systems, Applications and Services, MobiSys’11, 2011Conference paper (Refereed)
    Abstract [en]

    We present a demonstration scenario to validate a middleware architecture that we designed and implemented for distributing content between mobile users in an opportunistic manner. The peer-to-peer networking architecture allows content dissemination between mobile devices without relying on any infrastructure support. We developed a mobile application utilizing the services provided by the implemented middleware. The application facilitates opportunistic content distribution in both one-to-one and one-to-many dissemination modes.

  • 25.
    Trifunovic, Sacha
    et al.
    ETH Zurich.
    Kouyoumdjieva, Sylvia T.
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distl, Bernhard
    ETH Zurich.
    Pajevic, Ljubica
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Plattner, Bernhard
    ETH Zurich.
    A Decade of Research in Opportunistic Networks: Challenges, Relevance, and Future Directions2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 1, p. 168-173, article id 7823357Article in journal (Refereed)
    Abstract [en]

    Opportunistic networks are envisioned to complement traditional infrastructure-based communication by allowing mobile devices to communicate directly with each other when in communication range instead of via the cellular network. Due to their design, opportunistic networks are considered to be an appropriate communication means in both urban scenarios where the cellular network is overloaded, as well as in scenarios where infrastructure is not available, such as in sparsely populated areas and during disasters. However, after a decade of research, opportunistic networks have not yet been ubiquitously deployed. In this article we explore the reasons for their absence. We take a step back, and first question whether the use cases that are traditionally conjured to motivate opportunistic networking research are still relevant. We also discuss emerging applications that leverage the presence of opportunistic connectivity. Further, we look at past and current technical issues, and we investigate how upcoming technologies would influence the opportunistic networking paradigm. Finally, we outline some future directions for researchers in the field of opportunistic networking.

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