Evangelia Tzifa

Enhancing the TINA Architectural Framework for Personal Mobility Support

In this paper, extensions to the Telecommunications Information Networking Architecture (TINA) derived from personal mobility requirements are presented. The paper reflects the vision of the EC/ACTS research project DOLMEN that is developing OSAM, an Open Service Architecture for fixed and Mobile environments. The paper takes into account requirements to support personal mobility in a multi-provider environment, as well as requirements to distinguish user information from terminal information according to the basic principle that, in a personal mobility support environment, a user can dynamically be associated to different terminals for different services. According to these requirements, an enhanced TINA Business Model, and the impact on and extensions to the computational model of the TINA Service Architecture are elaborated.

Issues in service creation for future open distributed processing environments

The success of service providers in the competitive communications market of the future will be determined by the efficiency with which the services will be developed, and the quality levels at which the services will be provided. A service creation environment (SCE) should provide the service developer with solutions to these problems. In this paper we present an SCE focusing on the service creation practice, the software technologies applied for the development of the service logic, the support of standardised service architectures, through libraries of service components, and the provision of QoS handling related facilities.

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.

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

Interference-oriented carrier assignment in wireless communications

A carrier assignment problem, suitable for engineering the complex interference conditions of 2.5G and broadband fixed wireless access wireless environments, is addressed. The objective function minimizes the interference levels imposed by the carrier allocation, while the constraints assign the carriers required per cell and prevent unacceptable interference situations. The problem is formally stated and mathematically formulated. Solutions, adhering to the genetic algorithm and the simulated annealing paradigms, are discussed and indicative results are presented.

Design of the Access Network Segment of Future Mobile Communications Systems

An important component of future mobile communications systems is their access network segment that enables interworking between the mobile unit and the fixed network. In this paper we define and solve two important problems, related to the design of this segment. First, the efficient utilisation of the available radio spectrum. In this context we present a scheme that may be used for reconfiguring the frequency allocation, therefore, improving the spectrum utilisation. The second problem that we address is that of deploying Cell Site Switches (CSSs), and Local Exchanges (LEs). Our aim in this paper is the following. First, to formally define and optimally formulate these problems. Second, to solve them resorting also to computationally efficient heuristic algorithms. Finally, to provide results and draw subsequent conclusions.

Retailer selection in future open competitive communications environments

The highly competitive communications markets of the future should encompass mechanisms for enabling users to find and associate with the most appropriate retailers, i.e. those offering at a certain time period adequate quality services in a cost efficient manner. This paper presents such mechanisms. Our starting point is the definition of a business case, through which the role of the best candidate-retailer selection problem is explained. In the sequel, the problem is analysed and the identified sub-problems are concisely defined, mathematically formulated and solved. The identified components of the best candidate-retailer selection problem involve the evaluation of the quality of a retailer offer and the reduction of the set of candidate retailers by exploiting learning from experience notions. In the final sections, results are provided and concluding remarks are made.