Dimitris Nikitopoulos

Packet-switched network selection with the highest QoS in 4G networks

The evolution of telecommunications during the last decades has been enormous and as a result, nowadays, people find themselves before the challenge of 4G networks. Due to the fact that the latter constitute an environment of heterogeneous networks, their integration in terms of the Quality of Service (QoS) offered is of crucial importance. In general, the topic of this paper is to integrate the parameters that define QoS. Specifically, the main scope of this paper is the development of a process to evaluate three packet-switched networks (UMTS, WLAN and GPRS) in reference to the QoS offered and finally, the selection of the network that offers the highest standard for QoS. In order to achieve the above goal, there has been an attempt to distinguish the most important QoS indicators that characterize packet-switched networks and a few processes have been developed in order to either estimate the contribution of each parameter to the total QoS, or identify the weak points of a network. Apparently, each of these processes approaches the term of QoS in a different way and gives results of different usefulness.

Enhancing Quality of Experience in Next Generation Networks Through Network Selection Mechanisms

The evolution of telecommunications during the last decades has been enormous and as a result, nowadays, people find themselves before the challenge of 4G networks. Consequently, network selection techniques play a vital role in ensuring quality of experience (QoE) in heterogeneous networks. The main scope of this paper is the development of a process in order to compare packet-switched networks in terms of QoE offered and finally select the network that offers the highest standard of QoE. For this reason, main QoS parameters are identified and a scheme is proposed to identify each parameters importance based on network performance. The proposed methodology combines the analytical hierarchy process (AHP) to decide the relative weights of evaluative criteria set according to the networks performance, as well as the grey relational analysis (GRA) to rank the network alternatives. The proposed methodology is then applied for GPRS and WLAN.

ANN Prediction Models for Outdoor Environment

This paper presents the results of our studies concerning the applications of feedforward artificial neural networks to the propagation path loss prediction in outdoor environment. An error correction model is proposed, based on the combination between a theoretical model and a neural network. The performances of the proposed artificial neural network models are compared to the measured path loss values, based on the absolute mean error, standard deviation and root mean square error. Also, the proposed neural network models are compared to each other and to the COST 231-Walfisch-Ikegami

ANN Prediction Models for Indoor Environment

This work presents the results of the studies concerning the application of the feedforward neural networks to the prediction of propagation path loss in indoor environment. The proposed models consist of a multilayer perceptron and a generalized regression neural network trained with measurements. The results of the prediction made by the proposed neural models show a good agreement with the measurements

Authentication platform for seamless handover in heterogeneous environments

This work tackles the hot issue of user handover from one network to another, or generally from one radio access technology (RAT) to another, in a 4G heterogeneous mobile and wireless environment without the interruption of an ongoing service (seamless handover) with user authentication support. This paper proposes an authenticated seamless handover mechanism and describes the authentication platform for two network environments: an operator with both GPRS and WLAN networks (the user performs a vertical handover). Two different WLAN operators (the user performs a horizontal handover)

Real-Time WLAN Monitoring in a 4G Multiplatform Environment

Real-time monitoring in 4G networks is of prime importance for network operators of present and future generation. Nowadays operators utilize stored historical data from their data warehouses to improve networks and services, at the same time the number of mobile subscribers rapidly increases and additionally, the new data-technologies for wireless access add extra traffic to the already overloaded networks, often causing serious problems to their performance. A real-time monitoring tool is necessary to operators in order to guarantee high quality of service. In this paper a novel 4G multiplatform real-time monitoring system is presented and analyzed, giving emphasis to WLAN part. The main idea of this system is to collect reports from numerous network elements in such way that the system is compatible and operational in any kind of network of any manufacturer and operator. Additionally the system architecture discussed in this paper is capable of accommodating and supporting 4G networks effectively

Performance evaluation of GSM and GPRS systems based on measurement campaigns

A comprehensive study of the performance of GSM and GPRS is presented. The behavior of the network is classified into traffic load scenarios and key indicators are presented. Network response and logical channel occupation are discussed and the GPRS segment is evaluated according to a measurement campaign. Focus is given. on traffic overload and network congestion. This in-depth study can be used as a basis to evaluate the efficiency of resource management techniques in cellular systems.

Mobile Terminal Subarea Localisation Method in GSM Networks

In this paper, a novel method for mobile terminal (MT) subarea localisation in GSM networks is presented. No base stations position and additional hardware are required. It is a variation of the fingerprinting localisation method aiming to determine not the MT geographic position but the MT subarea and to reduce necessary initialisation measurements. Several GSM-based methods have been developed for MT localisation. The localisation method, proposed in this paper, is based on the fingerprinting method but is differentiated regarding the produced result. In this method the location server does not compare the MT collected radio network measurements with the stored radio map but with the subareas proprietary characteristics indicating the subarea where the MT is located and not the exact MT geographic position. Finally, if an LBS requires as input the subscriber subarea and not the geographic position then the novel method presented here reduces significantly the localisation initialisation requirements and computational cost in order to provide the service.

Comparison of ANN Based Models for Path Loss Prediction in Indoor Environment

This work presents the results of the studies concerning the application of the neural networks to the propagation path loss prediction in indoor environment. The proposed models consist of a multilayer perceptron and a generalized regression neural network trained with measurements. The results of the prediction made by the proposed neural models show a good agreement with the measurements.

Performance evaluation of GSM and GPRS systems based on measurement campaigns and statistical analysis

Today we are moving toward the deployment of new services, mainly based on high-speed data communication. The circuit-switched networks are about to come to the end of their lifecycle and the rapidly increased number of subscribers give a boost to development of new technologies. GPRS is the first step towards this milestone and most cellular GSM operators have already launched services based on GPRS. It is expected that both GSM and GPRS will continue to be operated in a diversified radio environment of the forthcoming years. In this paper we present an in-depth study performed in a cellular DCS system, both for the circuit- and the packet-switched part. We identify problems so that we can indirectly trigger further development of the systems.