Panagiotis Demestichas

Use of agent technology in service and retailer selection in a personal mobility context

This paper reports on work and key results of the ACTS Project MONTAGE that aims to exploit agent technology in support of personal mobility. In particular, agents are implemented to enable selection on behalf of users of the most beneficial service offer among those by multiple retailers, on the basis of user preferences encoded in the user profile, and market offerings made by retailers. A framework for agent intelligence to support service and retailer selection is proposed and justified. Enterprise, analysis and computational models of the envisaged personal mobility context that offers the capability of agent supported service and retailer selection, are provided.

Formulation and Computationally Efficient Algorithms for an Interference-Oriented Version of the Frequency Assignment Problem

The frequency assignment problem will maintain its importance for several years, since future versions of legacy cellular systems, e.g., those of GSM, will continue to exist. This paper elaborates on an interference-oriented version of the frequency assignment problem. The objective function is associated with the interference levels that are imposed by the frequency allocation, while the constraints are related to the allocation of the frequencies required in each cell and the prevention of some unacceptable interference situations. The problem is formally stated, mathematically formulated and solved by means of computationally efficient heuristics. Finally, results are obtained and concluding remarks are made.

Efficient Location and Paging Area Planning in Future Cellular Systems

Efficient resource utilisation in future cellular systems is partly related to the location update and paging operations, which rely on “proper” planning of location and paging areas, and the application of efficient paging schemes. Important is the design of low complexity planning algorithms that may enable the system to dynamically adapt to new traffic and mobility conditions. In this paper we define and solve versions of the location and paging area planning problems focusing also on algorithms that are applicable in real-time. Thus, they can be used to adapt location and paging areas to traffic and mobility conditions. Starting from a formal definition and an optimal formulation, we solve efficiently by means of a low complexity heuristic, a general version of the location area planning problem. Regarding paging area planning, we provide a low complexity algorithm, under the assumption that the scheme applied falls within the last interaction based paging (LIBP) category. The results presented, and the low cost and complexity induced by the proposed schemes, indicates that the real-time application of the schemes is feasible.

Distributed traffic adaptive channel allocation

Dynamic channel allocation (DCA) schemes adapt to the time variant demand for channels in cellular mobile telephony systems. In this paper we propose a DCA scheme that smoothly changes the channel allocation by solving the following problem. Given a cell structure, a collection of channels, the frequency reuse distance, an allocation of channels to cells, and the number of active connections per cell, accommodate a new call or a new handover by minimally reconfiguring the established allocation of channels to cells. First, this problem is formulated as 0–1 quadratic programming problem. Next, we present a distributed, heuristic solution to the problem, which is based on the observed behaviour of the optimal algorithm. Finally, we present some simulation results on the performance and the feasibility of the distributed algorithm.

Radio resource management schemes for combined GSM/GPRS mobile systems

Data services like Web browsing, e-mail and file transfer are becoming more and more popular in cellular systems. In contemporary systems like Global System for Mobile communications (GSM), data transfer has been circuit-switched, that is, physical resources are allocated to a user for the entire call/session duration. However, this is inefficient in case of bursty traffic, where bursts are separated by long intervals of inactivity. This has been the main reason for the introduction of General Packet Radio Service (GPRS), which on the one hand acts as a mobile access network to the Internet, while on the other hand it enables the operator to offer a wide variety of value-added services [Wireless Access Protocol (WAP) over GPRS, e/m-banking, e/m-commerce, push services, etc.] efficiently. However, in contemporary commercial implementations of GPRS the radio resource allocation algorithm does not take into account the Quality of Service (QoS)-related service characteristics—although such information is exchanged between the terminal and the network—and consequently all service requests are treated the same way (‘best effort’). In this paper, we propose and evaluate via a simulation platform various Radio Resource Management (RRM) schemes capable of differentiating the handling of ‘service requests’ (in uplink and downlink), taking into account the GPRS-related QoS parameters (precedence, reliability, delay, mean and peak throughput). The evaluation is performed for a range of voice (circuit-switched) traffic loads, number of Transmit Receive eXchange (TRXs), offered data (packet-switched) services characteristics, number of dedicated Packet Data Channels (PDCHs), and so on, taking into account the respective QoS requirements for both service types (circuit- and packet-switched). Copyright

Design and control of the interconnecting network of the access segment of mobile communications systems

In mobile communication systems, the network segment interconnecting the Base Station (BS) layout with the Base Station Controllers (BSCs) and the BSCs with the Fixed Network Switches (FNSs) should be carefully designed and controlled. This paper presents techniques for the efficient design and control (reconfiguration) of this network segment. The corresponding problems are formally defined and mathematically formulated. Two solutions are presented to the design problem, based on the genetic algorithm and the simulated annealing paradigms. Additionally, a third solution, based on neural networks, is proposed for the control (reconfiguration) problem. Results are provided indicating the efficiency of the proposed algorithms.

Power allocation in the context of dimensioning the air‐interface of third generation W‐CDMA‐based cellular systems

The adoption of W-CDMA as an essential component of the air-interface of third-generation cellular systems brings to the foreground the need for new planning methodologies and software tools. In this perspective, this paper addresses planning problems that are important to the dimensioning of W-CDMA-based cellular networks. The problems aim at finding the optimal feasible allocation of transmission power to the sets of uplink and downlink connections that should be supported by the system, so as to cope with a corresponding traffic load scenario. The problems are concisely defined, mathematically formulated and solved by means of two computationally efficient, novel algorithms. The solutions of the problems may be seen as operating points at which the system performance should be driven. Finally, numerical results are presented and concluding remarks are drawn. Copyright

QoS Management by Means of ApplicationControl

The complexity and sophistication of integratedbroadband networks call for a broad repertoire ofmanagement methods. Foreseen intensive competition ofthe communications market, and the upgrade ofend-customers satisfaction as the focal point of anymanagement policy, raise a very important problem: howto utilize efficiently the resources of the networkwhile maintaining the Quality of Service (QoS) provided to end-users within a pre-negotiated range. Inthis paper, a QoS management architecture for multimediaapplications based on an application control scheme isproposed. Adhering to the Total Quality Management (TQM) paradigm, we let management span over theentire communication stack, the entire network(end-to-end) and the entire call duration. Applicationcontrol scheme aims to meet pre-specified QoS goals by adjusting the traffic produced by theend-user applications. The adjustment technique is basedon the notion that each multimedia session is allowed tooperate on a set of discrete application quality levels. A method for monitoring and assessingthe end-user perceived quality is presented. Themathematical problem of optimal resources allocation andan associated heuristic are specified. Finally, a specific instantiation of the introduced QoSmanagement architecture on a real testbed is describedand experimentation results are presented andevaluated.

Management of wireless home networking technologies in the context of composite radio environments

BRAN/WLAN systems are seen as promising solutions for covering residential, business, etc., environments, and therefore realising the wireless home/office concept. This paper presents management functionality for augmenting the exploitation of these systems, by making feasible their integration in a composite radio (CR) context. In the followed approach the first point will be to revisit the main features of a HiperLAN2 system. Next, will be the presentation of a general Service and Network Management System (SNMS) architecture. The last point will be the functionality of the SNMS components that are tailored to the managed HiperLAN2 technology. A set of resource management problems will be addressed, for exploiting HiperLAN2 networks in a CR context.

A Framework to Service and Network Resource Management in Composite Radio Environments

This paper builds on the assumption that in the future, UMTS, HIPERLAN-2 and DVB-T can be three (co-operating) components of a composite radio infrastructure that offers wideband wireless access to broadband IP-based services. Managing the resources of this powerful, composite-radio infrastructure in an aggregate manner, and multioperator scenario, is a complex task. This paper presents an approach to the overall UMTS, HIPERLAN-2 and DVB-T network and service management problem, providing the internal operation of a system addressing this problem. Key points addressed are the development of an architecture that can jointly optimise the resources of the technologies in the composite radio environment, and the development of open interfaces with Service Provider mechanisms and the heterogeneous managed infrastructure.