As peer‐to‐peer (P2P) applications become more mature and demanding, there is a need for the underlying technologies to provide more adaptive characteristics, according to the application's requirements. In this paper, we present K‐Umbrella, a K‐ary distributed hash table (DHT), which allows us to efficiently route through the use of a fixed‐size routing table. By controlling a number of parameters, our algorithm is able to trade‐off between efficiency, fault‐tolerance and decentralisation according to the application's requirements. Through a detailed analysis of our algorithms and an extensive set of simulations, we will show that our protocol is able to offer an improved alternative to current DHT algorithms. Copyright © 2007 John Wiley & Sons, Ltd.

This article presents the AVATON system. AVATON aims at providing citizens with ubiquitous user-friendly services, offering personalized, location-aware (GSM Association, 2003), tourism-oriented multimedia information related to the area of the Aegean Volcanic Arc. Towards this end, a uniform architecture is adopted in order to dynamically release the geographic and multimedia content to the end users through enhanced application and network interfaces, targeting different device technologies (mobile phones, PDAs, PCs, and TV sets). Advanced positioning techniques are applied for those mobile user terminals that support them.

This article presents a location-based multimedia content delivery system (LMCDS) for monitoring purposes, which incorporates media processing with a decision support system and positioning techniques for providing the appropriate content to the most suitable users, in respect to user profile and location, for monitoring purposes. This system is based on agent technology (Hagen & Magendanz, 1998) and aims to promote the social welfare, by increasing the overall situation awareness and efficiency in emergency cases and in areas of high importance. Such a system can be exploited in many operational (public or commercial) environments and offers increased security at a low cost.

This article presents the AVATON system. AVATON aims at providing citizens with ubiquitous user-friendly services, offering personalized, location-aware (GSM Association, 2003), tourism-oriented multimedia information related to the area of the Aegean Volcanic Arc. Towards this end, a uniform architecture is adopted in order to dynamically release the geographic and multimedia content to the end users through enhanced application and network interfaces, targeting different device technologies (mobile phones, PDAs, PCs, and TV sets). Advanced positioning techniques are applied for those mobile user terminals that support them.

In modern broadband mesh networks, communication between two end nodes is carried out not directly, but through a number of intermediate nodes. While these nodes’ only function may be to relay information from one point to another, they may also host computational elements which perform some service on behalf of other applications. We deal with the problem of optimally mapping multimedia content transcoding service elements onto network resources. There may be several places in the network where the required compression and decompression services could be performed. We would like to select the best locations that meet the application’s requirements. We propose a new approximation algorithm for constrained path optimization, which provides better scalability and simplicity than previous approaches. This is accomplished basically by partitioning the overall problem into smaller ones.