Maria Chantzara

Context management for the provision of adaptive services to roaming users

Various types of sophisticated networks and terminals are used for the provision of thirdgeneration services, and even more complicated ones are designed for 4G systems. Roaming users will rely on new kinds of wireless networks and terminals to offer mobility and make multimedia services available everywhere. They will, of course, expect continuous access to personalized services from any place, transparently and independent of the underlying network technology and the terminal or point of access. Virtual home environment features were specified and implemented in order to satisfy these requirements in 3G systems. The enhanced role of IP in 4G systems and the assimilation of WLAN technology will enable further advances toward pervasive computing and the pursuit of corn-, plete context awareness in state-of-the-art applications and services. 4G services can he smarter and more adaptive by taking advantage of all types of context available to them within a well defined context management framework. This article presents results from work carried out over the last few years at NTUA,’ bringing us closer to the definition of such a flexible framework for cfficient management of content, which will he able to support the development of advanced telecommunications services and integrated real-time information provision and processing systems.

Designing a quality-aware discovery mechanism for acquiring context information

The alignment of the context information with the service objectives facilitates the successful provisioning of context-aware services. Moreover, the fact that context may come from transient and/or unreliable sources needs consideration. False or stale context can dramatically affect the decisions and the actions taken by context-aware services. This paper presents an approach for evaluating and selecting the information to be used by context-aware services that takes into account the quality of information, and automatically adapts to any source changes and failures. The proposed quality-aware discovery of context information sources allows services to be ported easily to environments with different sets of sources.

Context-Aware Services Provisioning on Top of Active Technologies

With respect to the pervasive computing vision, the paper deals with the efficient provisioning of context-aware services making use of Active Networks (ANs) on top of fixed and mobile infrastructure. This represents a starting point for studying on the utilization of Active Technologies in order to provide context-aware services. In these terms, Mobile Agent (MA) Technology comprises a type of Active Technology and the exploitation of its utilization in the field of context-awareness is analyzed. Following, an evaluation comparison of ANs and MAs paradigms is given, identifying the drawbacks and the advantages of each paradigm. Finally, some concluding remarks regarding the combined usage of them are presented.

MVRC heuristic for solving the multi-choice multi-constraint knapsack problem

This paper presents the heuristic algorithm Maximizing Value per Resources Consumption (MVRC) that solves the Multi-Choice Multi-Constraint Knapsack Problem, a variant of the known NP-hard optimization problem called Knapsack problem. Starting with an initial solution, the MVRC performs iterative improvements through exchanging the already picked items in order to conclude to the optimal solution. Following a three step procedure, it tries to pick the items with the maximum Value per Aggregate Resources Consumption. The proposed algorithm has been evaluated in terms of the quality of the final solution and its run-time performance.

Enabling distributed QoS management utilizing active network technology

This paper deals with the QoS management issue utilizing the active network technology. The disadvantages of the centralized network management are presented and the current solutions for distributed network management are discussed. The proposed architecture focuses on the QoS management for DiffServ architecture. The improvements that our architecture offers are presented through a service example, which involves QoS configurations.

The virtual home environment roaming perspective

The virtual home environment (VHE) is an important portability concept of the 3rd generation mobile systems as it promises personalized services for roaming users across network and terminal boundaries. This paper examines the roaming issues involved in the provision of VHE services. It aims to present an overview of the service portability mechanisms proposed and tested within 3G systems, while it introduces an efficient VHE roaming approach and exposes the features of the core entities that realize it.

Provision of VHE services to roaming users

Towards the deployment of 3rd generation systems, Virtual Home Environment (VHE), stemming from 3GPP, appears to be a powerful concept advocating the provision and delivery of personalized services to roaming users across network and terminal boundaries. This paper aims to expose the pathway for materializing the VHE concept, via the specification, implementation and evaluation of a prototype. Core aspects for realizing the concept such as the business and roaming models are presented, while a VHE enabling architecture utilizing key technologies (OSA/Parlay, MExE, and USAT) is introduced. The proposed architecture has already been evaluated by performing an initial trial demonstration. Currently it is being extended to support VHE service provision to roaming users, an aspect to be addressed by the final trial.

User‐sensitive and quality‐driven discovery of context information for the successful delivery of context‐aware services

The successful provision of context‐awareness in pervasive environments requires the support of autonomic management facilities that provide ways to efficiently acquire and use contextual information. This paper claims that in order to offer viable context‐aware services, the issue of context imperfection and aging as well as the alignment of the context information that is used by a service with the customized service objectives should be taken into account. It presents an approach for managing the selection of context sources considering the freshness and actuality of the available information, and dynamically adapting to any source change and failure. Accordingly, there is no need to know beforehand the context sources to obtain the required information, but a quality‐aware discovery of the sources is envisioned. Finally, the proposed approach allows services to be ported easily to an environment with a different set of context sources.