| 1. |
- Chupisanyarote, Sanpetch, et al.
(författare)
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Caching in opportunistic networks with churn
- 2012
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Ingår i: 2012 9th Annual Conference on Wireless On-Demand Network Systems and Services, WONS 2012. - : IEEE Communications Society. - 9781457717222 ; , s. 39-42
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 2. |
- Danielis, Peter, et al.
(författare)
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DiVote : A Distributed Voting Protocol for Mobile Device-to-Device Communication
- 2016
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Ingår i: Proceedings of the 28th International Teletraffic Congress, ITC 2016. ; , s. 69-77
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 3. |
- Danielis, Peter, et al.
(författare)
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UrbanCount : Mobile Crowd Counting in Urban Environments
- 2017
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Ingår i: 2017 8th IEEE Annual Information Technology, Electronics and Mobile Communication Conference (IEMCON). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538633717 ; , s. 640-648
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Konferensbidrag (refereegranskat)abstract
- 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,
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| 4. |
- Helgason, Ólafur, et al.
(författare)
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A Middleware for Opportunistic Content Distribution
- 2016
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Ingår i: Computer Networks. - : Elsevier. - 1389-1286 .- 1872-7069. ; 107, s. 178-193
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Helgason, Ólafur, et al.
(författare)
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A mobile peer-to-peer system for opportunistic content-centric networking
- 2010
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Ingår i: Proceedings of the 2nd ACM SIGCOMM Workshop on Networking, Systems, and Applications on Mobile Handhelds, MobiHeld '10, Co-located with SIGCOMM 2010. - New York, NY, USA : ACM. - 9781450301978 ; , s. 21-26
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 6. |
- Helgason, Ólafur, et al.
(författare)
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Does Mobility Matter?
- 2010
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Ingår i: WONS 2010. - NEW YORK : IEEE. - 9781424460618 ; , s. 9-16
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 7. |
- Helgason, Ólafur, et al.
(författare)
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Enabling Multiple Controllable Radios in OMNeT nodes
- 2011
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Ingår i: Proc. ICST SIMUTools 2011, OMNeT workshop.
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 8. |
- Helgason, Ólafur, et al.
(författare)
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Opportunistic Communication and Human Mobility
- 2014
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Ingår i: IEEE Transactions on Mobile Computing. - 1536-1233 .- 1558-0660. ; 13:7, s. 1597-1610
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Kouyoumdjieva, Sylvia, et al.
(författare)
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Caching Strategies in Opportunistic Networks
- 2012
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Ingår i: 2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, WoWMoM 2012 - Digital Proceedings. - : IEEE. - 9781467312394 ; , s. 6263744-
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 10. |
- Kouyoumdjieva, Sylvia, et al.
(författare)
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Evaluating an Energy-efficient Radio Architecture for Opportunistic Communication
- 2012
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Ingår i: Communications (ICC), 2012 IEEE International Conference on. - : IEEE. - 9781457720529 ; , s. 5751-5756
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Konferensbidrag (refereegranskat)abstract
- 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.
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