Projekte

Routing in opportunistic networks heavily relies on past behavior of the mobile devices it is formed of to predict their future and thus making routing decisions. While almost every protocol relies on this history, its prediction quality has never been studied in a realistic setting. Using extensive simulations on real traces, we are able to describe for the first time how well predictions can be. Unlike oracle-based prediction comparisons, we do not try to predict a contact, but compare the expected user result, namely message delivery probabilities. The analysis also provides guidance on the importance of multi-path routing and the path diversity required, as well as on the impact on forward error correction on the delivery probability. Our results show that the repetitive nature of path is directly proportional to the mobility extent of the devices and, consequently, history obtained from dense opportunistic networks is reliable.

Routing in Opportunistic Networks, as a relatively young discipline, still lacks coherent, simple and valid benchmarks. It is customary to use epidemic routing as performance benchmark for Opportunistic Networks. We identify and describe the current simulation practices that do not expose the shortcomings of flooding as an upper bound. In this paper to provide a step towards a routing benchmark, which is flexible, provides results close to an upper bound, is simple to implement, and thus might be a candidate for a common benchmark. This new method called EPO, does not suffer from bottlenecks that limit the performance of epidemic flooding, even when bandwidth is scarce. Our analysis shows that networks are not suffering from that much severe congestion as suggested by flooding and thus giving a better insight to the underlying network.

The big challenge of routing in opportunistic mobile networks, overlooked by most researchers, is to not only find any path to the destination, but a path that is stable and powerful enough to actually carry the message. Few attempts addressed this problem, all of them under controlled scenarios, avoiding the complexity of real-world connectivity. As a result of our comparison of selected networks under a wide variety of realistic scenarios, we have not only been able to identify and describe favorable traits of protocols, but also necessary relationship of successful MON protocols with QoS routing in wired networks. We present a novel protocol, Nile, that performs both in dense as well as sparse networks. Nile is the first autonomous “controlled Hooding” protocol that keeps the link loads in check, to push replicas only on those paths that are both promising and may sustain more load. It is a multi path protocol that deploys replication based on heuristic for disjoint path calculation. Other protocols' performance, when simulated in real-world traces, highly depends on parameter choice. Nile, however, consistently performs among the top protocols without any external tuning and exerts far less overhead than other replication protocols.

New social networks are born each day, at a formal conference, at informal social gathering, at family reunions etc. Internet has already been playing an important role in modern way of socialising. But it is still not the optimal way of interaction as one has to be very active updating profiles. With the easy access to mobile devices, modern technologies have now started to adopt to new ways of socialising. mobile devices accompany their users almost all the time, they can record and observe their users behavior as well as gather information about their social circle. Therefore, they can help users to get information from contacts, that they probably not even know. In this paper we put our efforts towards the initial design of an architecture that will sniff for information around the user's surrounding, leveraging useful answers on their demand.

Many applications of ad-hoc networks include intermittent connectivity. Anyone wishing to implement routing into her delay-tolerant network can select from a wide variation of options, but the choice is hard, as there is no strong comparative evidence to the relative performance of the algorithms. Every paper uses a different setting, mostly far from realistic. In our desire to improve the basis for decisions, we simulated a promising selection of DTN routing algorithms in three vastly different scenarios, all based on publicly available real-world traces. Using our open-source DTN simulator, we compare and analyse 11 routing techniques, then provide explanations for the behaviour and give advice for choosing a suitable mechanism. To our own surprise, the results challenge the conventional wisdom gained from synthetic simulations and poses the question whether the world is ready for DTNs.