Nicolai Viol

FootPath: Accurate map-based indoor navigation using smartphones

We present FootPath, a self-contained, map-based indoor navigation system. Using only the accelerometer and the compass readily available in modern smartphones we accurately localize a user on her route, and provide her with turn-by-turn instructions to her destination. To compensate for inaccuracies in step detection and heading estimation, we match the detected steps onto the expected route using sequence alignment algorithms from the field of bioinformatics. As our solution integrates well with OpenStreetMap, it allows painless and cost-efficient collaborative deployment, without the need for additional infrastructure.

SimBetAge: utilizing temporal changes in social networks for pocket switched networks

In this paper, we present SimBetAge, a delay and disruption tolerant routing protocol for highly dynamic socially structured mobile networks. We exploit the lightweight and ego-centric scheme of SimBet routing while at the same time taking the strength and the gradual aging of social relations into account and thereby increase the performance by one order of magnitude, especially in evolving network structures. We explore the model of similarity and betweenness over weighted graphs, and present a simulation on realistic traces from previous experiments, comparing our approach to the original SimBet, Epidemic Routing and Prophet.

Collaborative municipal Wi-Fi networks - challenges and opportunities

Municipal Wi-Fi networks aim at providing Internet access and selected mobile network services to citizens, travelers, and civil servants. The goals of these networks are to bridge the digital divide, stimulate innovation, support economic growth, and increase city operations efficiency. While establishing such urban networks is financially challenging for municipalities, Wi-Fi-sharing communities accomplish good coverage and ubiquitous Internet access by capitalizing on the dense deployment of private access points in urban residential areas. By combining Wi-Fi communities and municipal Wi-Fi, a collaborative municipal Wi-Fi system promises cheap and ubiquitous access to mobile city services. However, the differences in intent, philosophy, and technical realization between community and municipal Wi-Fi networks prevent a straight-forward combination of both approaches. In this paper, we highlight the conceptual and technical challenges that need to be solved to create collaborative municipal Wi-Fi networks.

Hidden Markov model-based 3D path-matching using raytracing-generated Wi-Fi models

We propose an efficient approach to probabilistic 3D indoor path-matching and localization based on Wi-Fi-signal measurements using Hidden Markov Model-based (HMM) algorithms. Given a 3D model of the building, we derive high-resolution emission probabilities and transition probabilities from raytracing-generated Wi-Fi signal propagations. Therefore we use both the generated signal-strength values and the geometric information of the 3D model. Based on the emission and transition probabilities and a sequence of Wi-Fi signal measurements provided by the client, the HMM-based algorithm computes the most probable path through the building.

Accurate map-based indoor navigation on the mobile

We present FootPath, a self-contained, map-based indoor navigation system. Using only the accelerometer and the compass readily available in modern smartphones, we accurately localise a user on her route and provide her with turn-by-turn instructions to her destination. To compensate for inaccuracies in step detection and heading estimation, we match the detected steps onto the expected route using sequence alignment algorithms from the field of bioinformatics. As our solution integrates well with OpenStreetMap, it allows painless and cost-efficient collaborative deployment, without the need for additional infrastructure.

SimBetAge: Utilizing temporal changes in social networks for delay/disconnection tolerant networking

In this paper, we present SimBetAge, an extension to Sim-Bet taking into account the gradual aging of connections in social networks which thereby increases the performance by an order of magnitude, especially in evolving network structures. For this purpose, we redefine similarity and betweenness to make use of weighted social network graphs.

POSTER: Privacy-preserving Indoor Localization.

Upcoming WiFi-based localization systems for indoor environments face a conflict of privacy interests: Server-side localization violates location privacy of the users, while localization on the users device forces the localization provider to disclose the details of the system, e.g., sophisticated classification models. We show how Secure Two-Party Computation can be used to reconcile privacy interests in a state-of-the-art localization system. Our approach provides strong privacy guarantees for all involved parties, while achieving room-level localization accuracy at reasonable overheads.

WiSec 2011 demo: PISA-SA - security and mobility in a collaborative muni-fi

Municipal Wi-Fi networks aim at city-wide wireless access to selected city services for a variety of users. Collaborative Muni-Fi approaches use existing private access points and provide controlled access to these services. However, the distributed and decentralized nature of a network comprised of strangers makes access control challenging. We present two design options for including mobile clients in such system: a client and a network centric design. For both designs we briefly discuss aspects of security and device mobility.