A Location-Aware Middleware Framework for Collaborative Visual Information Discovery and Retrieval

This work addresses the problem of scalable location-aware distributed indexing to enable the leveraging of collaborative effort for the construction and maintenance of world-scale visual maps and models which could support numerous activities including navigation, visual localization, persistent surveillance, structure from motion, and hazard or disaster detection. Current distributed approaches to mapping and modeling fail to incorporate global geospatial addressing and are limited in their functionality to customize search. Our solution is a peer-to-peer middleware framework based on XOR distance routing which employs a Hilbert Space curve addressing scheme in a novel distributed geographic index. This allows for a universal addressing scheme supporting publish and search in dynamic environments while ensuring global availability of the model and scalability with respect to geographic size and number of users. The framework is evaluated using large-scale network simulations and a search application that supports visual navigation in real-world experiments

Evaluating the Robustness of the DGT Approach for Smartphone-based Vehicular Networks

To cope with millions users becoming increasingly connected to Internet on the move, location-based services may be better supported by decentralized infrastructures enabling improved scalability, access rate and resiliency. In this context, our previous work introduced the Distributed Geographical Table (DGT), an overlay scheme that builds and maintains virtual neighborhood relationships between peers with heterogeneous connections. In this paper we illustrate a smartphone-based vehicular network that uses the DGT, and we show its robustness against disconnections caused by the unavailability of connectivity/ coverage (mostly occurring in rural areas), as well as overlay reconnections due to vertical handovers (mostly occurring in highly serviced urban areas). The simulative analysis of sample scenarios based on experimental measurements of coverage and connection throughput, carried out across/around Parma urban area, gives us valuable insights for defining an integrated model that will combine the DGT, user/vehicle mobility and connectivity/ coverage types

Distributed Algorithms for Location Based Services

Real-time localization services are some of the most challenging and interesting mobile broadband applications in the Location Based Services (LBS) world. They are gaining more and more importance for a broad range of applications, such as road/highway monitoring, emergency management, social networking, and advertising. This Ph.D. thesis focuses on the problem of defining a new category of decentralized peer-to-peer (P2P) algorithms for LBS. We aim at defining a P2P overlay where each participant can efficiently retrieve node and resource information (data or services) located near any chosen geographic position. The idea is that the responsibility and the required resources for maintaining information about position of active users are properly distributed among nodes, for which a change in the set of participants causes only a minimal amount of disruption without reducing the quality of provided services. In this thesis we will assess the validity of the proposed model through a formal analysis of the routing protocol and a detailed simulative investigation of the designed overlay. We will depict a complete picture of involved parameters, how they affect the performance and how they can be configured to adapt the protocol to the requirements of several location based applications. Furthermore we will present two application scenarios (a smartphone based Traffic Information System and a large information management system for a SmartCity) where the designed protocol has been simulated and evaluated, as well as the first prototype of a real implementation of the overlay using both traditional PC nodes and Android mobile devices