Mobile Computing Activity

    New paradigms in wireless access and spectrum markets are being formed. This is accelerated even further by the advances in the dynamic spectrum access. The cognitive radio network (CRN) technology empowers devices with new degrees of flexibility, enabling new network architectures, access methods, and services, enriching the roles of service providers, and opening new opportunities for businesses cases. Unlike the traditional cellular-based markets, these spectrum markets have larger sizes, are more heterogeneous, and can offer an improved set of services. As wireless access and use increase, users are differentiated even more by their usage and data-rate requirement profile. The main objective of this research is the development of a /modular multi-level modeling framework and simulation platform/, that enables the business-driven comparative analysis of various spectrum and access markets and services. The analysis will consider a diverse set of customer populations and QoE-based performance metrics from the perspective of providers, customers, and regulators.

Representative publications:

• Georgios Fortetsanakis, Maria Papadopouli, Gunnar Karlsson, Manos Dramitinos, Emre A. Yavuz . To subscribe, or not to subscribe: Modeling and analysis of service paradigms in cellular markets. IEEE DySPAN, Bellevue, Washington, USA, October 16-19, 2012 [PDF]

    The u-map is a novel user-centric geo-database that supports wireless access markets. It enables clients to upload information about their profile, their quality-of-experience (QoE) feedback for a service, traffic demand, network/spectrum conditions (e.g., interference, coverage), providers, and their position (e.g., GPS-based measurements) in a spatio-temporal geo-database. To evaluate the impact of the u-map on wireless access markets and study the evolution of such markets, we have developed an economic-driven modeling framework. The framework integrates models of the channel, clients and network operators, wireless infrastructures, types of interaction, and price adaptation in a modular manner. The u-map was analyzed by simulating the evolution of a cellular-based duopoly, with various cellular users. The analysis demonstrates that the u-map can be beneficial to users in their network operator selection process.In addition, a proof-of-concept implementation of the u-map has been developed. Evaluation studies using this testbed is an on-going activity.

Representative publications:

• Georgios Fortetsanakis, Michalis Katsarakis, Maria Plakia, Nick Syntychakis, and Maria Papadopouli. "Supporting Wireless Access Markets with a User-centric QoE-based Geo-database", ACM MobiArch 2012, Istanbul, Turkey, August 22, 2012.[PDF] [video]

    Current wireless networks are extremely complex. The interaction of different layers and technologies creates many situations that cannot be foreseen during the design and testing stages of technology development. Empirical studies in production environments enable researchers and engineers to uncover deficiencies and identify possible optimizations and extensions. Furthermore, accurate and scalable models are critical aspects in performance analysis studies. The objective of this research is to provide methodologies for efficient, accurate and scalable measurement, analysis and modeling. The main focus is on wireless traffic demand, access and roaming patterns.

Our research work uses real measurement data collected from large-scale wireless networks. A significant part of the measured data is available to the research community via the joint UNC/FORTH repository of traces and models for wireless networks.

Representative publications:

• Francisco Chinchilla, Mark Lindsey, and Maria Papadopouli. Analysis of wireless information locality and association patterns in a campus. IEEE INFOCOM 2004, Hong Kong, March 7-11, 2004 [PDF, PS, BIBTEX] (Acceptance percentage 18%)

    To enhance the data availability, the mobile peer-to-peer computing may empower the wireless devices to share resources. The focus is on three facets of cooperation, namely information sharing, network connection sharing and message forwarding. Peers communicate via a wireless LAN and may have (intermittent) connection to the Internet e.g., via a Bluetooth, IEEE802.11 AP, 3G. In information sharing, peers query, discover and disseminate information. When the network connection sharing is enabled, the system allows a host to act as an application-based gateway and share its connection to the Internet. This activity designed, prototyped and evaluated an architecture, set of protocols, and services that enable this resource sharing in a self-organizing fashion without the need of an infrastructure.

Representative publications:

• Maria Papadopouli and Henning Schulzrinne "Peer-to-Peer Computing for Mobile Networks: Information Discovery and Dissemination"
  
  

    Positioning is a critical component of the mobile and pervasive, computing. This research involves the design and evaluation of the Cooperative Location-Sensing (CLS) system. CLS positions wireless devices using the available infrastructure of wireless APs, without the need of specialized hardware. It also employs the peer-to-peer paradigm, enabling hosts to share positioning information and measurements. It also allows the easy incorporation of external information (e.g., maps and spatial information, mobility patterns) to improve its accuracy in an adaptive manner.

    In addition, this research has focused on RSSI-based statistical fingerprinting algorithms applying sophisticated signal processing techniques. For example, it developed algorithms based on multi-variate Gaussian distributions and compressive sensing. The algorithms have been evaluated in real-world environments, such as FORTH and Crete Aquarium.

Representative publications:

• Dimitris Milioris, George Tzagkarakis, Artemis Papakonstantinou, Maria Papadopouli, Panagiotis Tsakalides. Low-dimensional Signal-Strength Fingerprint-based Positioning in Wireless LANs. Elsevier Ad Hoc Networks (special issue), November/December 2011. (35 pages)[PDF]
• Charalampos Fretzagias and Maria Papadopouli. "Cooperative location-sensing for wireless networks", Second IEEE International conference on Pervasive Computing and Communications 2004, Orlando, Florida, March 14-17, 2004. [PDF, PS, BIBTEX, DEMO] (Acceptance percentage 15%)