Dimitris Kouis

Resource management of IP-enabled DVB-T networks in the context of wireless B3G systems

The wireless beyond 3G systems or the so called Composite Radio Environments (CRE) (or even 4G systems), consist of multiple type radio access technologies, collaborating with each other, providing both diverse access alternatives and QoS improvement, especially as far as concerns protection against traffic congestion and loss of radio coverage situations. The merits deriving from beyond 3G systems interest not only network and service providers but also the mobile users. Additionally, the need of broadband wireless access is directly associated with the intense demand for IP multimedia services (e.g. video streaming or high speed web browsing), mainly inside hot-spot areas. Taking into consideration the above described tendency in the area of wireless network systems, the IP-enabled DVB-T (the terrestrial specification of the Digital Video Broadcasting family) systems appear as an attractive alternative network access in the CRE context. Along this direction, this paper presents the most important aspects of a CRE network management system (NMS), focusing on the component responsible for the DVB-T resource management (RM). Finally, we implement and investigate through simulation a greedy algorithm suitable for DVB-T networks that performs fast resource management and configuration. We also provide some indicative results which prove that the algorithm demonstrates a close to optimal performance at the RM functionality.

NGL03-3: Provision of Active Services through Next Generation Networking Middleware

The evolution of next generation networking middleware (NGNM) yields to the provision of personalized next-generation active services, each one with different traffic characteristics and networking requirements for security, billing, QoS (Quality of Service), mobility, etc. in an efficient and economical usage of network resources. The introduction and well establishment of the active services concept, which will be services capable of dynamically adapting themselves to various underlying networking environment conditions according to the instructions of NGNM and the requirements posed by the end user, constitutes the major goal of this paper. In order to avoid proprietary and custom implementation solutions, an initial and generic active services reference architecture that can be followed by potential active services developers is presented. Finally, an implemented prototype that follows the proposed reference architecture provides a first quick validation of the discussed active service concept.

A rate adaptation scheme for media streaming over heterogeneous networks

In this paper, a Rate Adaptation Scheme (RAS) for media streaming applications, appropriate for future heterogeneous networks is presented. In such environments, vertical handovers across networks with highly diverse characteristics are likely to occur. In these cases, RASs should cope with abrupt network resources variations. Existing rate adaptations mechanisms would fail to adjust, in a timely manner, to the characteristics of the new network or recognise a vertical handover event. The proposed scheme enhances an existing rate adaptation algorithm towards providing uninterrupted streaming sessions to mobile terminals, when moving across networks with diverse characteristics. Applications can adapt their rate, based not only on application level feedback (e.g. packet and frame loss rate), but also on feedback received from a terminal management entity. The proposed scheme is evaluated using extensive simulations, is implemented over an open end-to-end MPEG-4 streaming suite and it is experimentally validated.