Georgia E. Athanasiadou

• PhD
• Professor (Associate) at University of Peloponnese

Despite the promising benefits, the integration of 5G, particularly through Non-Standalone (NSA) architectures that rely on existing 4G infrastructures, introduces challenges in maintaining optimal radio network performance and service quality. This study evaluates 4G and 5G radio network performance through empirical field trials across highway op...

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Η δημοτικότητα των κινητών επικοινωνιών και η έλευση των ασύρματων συστημάτων 5G έχει πυροδοτήσει ένα νέο κύμα συζητήσεων και ανησυχιών σχετικά με τις επιπτώσεις στην υγεία από την έκθεση στην ηλεκτρομαγνητική ενέργεια (HMΕ). Το έργο PANDORA ξεκίνησε τον Μάιο του 2021 και χρηματοδοτείται από την Περιφέρεια Πελοποννήσου, με στόχο την δημιουργία ενός...

This paper presents the design and implementation of a versatile IoT testbed utilizing the openHAB platform, along with various wireless interfaces, including Z-Wave, ZigBee, Wi-Fi, 4G-LTE (Long-Term Evolution), and IR (Infrared Radiation), and an array of sensors for motion, temperature, luminance, humidity, vibration, UV (ultraviolet), and energy...

The usage of unmanned aerial vehicles (UAVs) as flying base stations (FBSs) for expanding coverage and assisting the terrestrial cellular networks constitutes a promising technology for 5G and beyond. A crucial parameter affecting cellular network design is path loss prediction. An alternative to the accurate, though time-consuming, propagation pre...

This paper presents the design and implementation of a versatile IoT testbed utilizing the openHab platform along with various wireless interfaces, including Z-Wave, ZigBee, WiFi, 4G-LTE, and IR, and an array of sensors for motion, temperature, luminance, humidity, vibration, UV, and energy consumption. First, the testbed architecture, setup, basic...

Building Information Modeling (BIM) is a critical element for the “digitalization” of the construction industry and can be exploited for energy-driven renovation procedures of existing residences. Advancing beyond a BIM with data-capturing capabilities that are limited to building static information only requires sensor data streams related to indo...

Electric cars sales have been rising almost steadily over the past decade. Uncontrolled charging has recently emerged as the main detrimental factor to this otherwise environmentally friendly and paradigm shifting technology due to the incurred impact on the energy grid. In addition, people are usually hesitant in allowing their vehicles to be cont...

During the last few decades, electric vehicles (EVs) have emerged as a promising sustainable alternative to traditional fuel cars. The work presented here is carried out in the context of the Horizon 2020 project MERLON and targets the impact of EVs on electrical grid load profiles, while considering both grid-to-vehicle (G2V) and vehicle-to-grid (...

The GHG emissions caused by transport sector and especially by road transport is a major problem for our society since it is associated to the climate change. Electric vehicles (EVs), may be a sustainable alternative to traditional internal combustion engine vehicles and prossibly part of the solution. The aim of this work is to investigate the im...

The 5G radio networks have introduced major changes in terms of service requirements and bandwidth allocation compared to cellular networks to date and hence, they have made the fundamental radio planning problem even more complex. In this work, the focus is on providing a generic analysis for this problem with the help of a proper multi-objective...

In this paper, we apply ensemble learning methods for the prediction of the ground (cellular basestation) to air (flying node) received signal strength (RSS) at different heights, for future mobile communications.The training set is obtained by experimental data measurements taken from an unmanned aerial vehicle (UAV). We model the RSS using differ...

Service demand in cellular radio networks is generally heterogeneous and non uniform, leading to asymmetrical topologies. This complexity along with the multiple radio access technologies, the radio channel and practical constraints, make the radio network planning process a challenging task that leaves little room for intuitive solutions. In this...

Channel modelling of wireless communications from unmanned aerial vehicles (UAVs) is an emerging research challenge. In this paper, we propose a solution to this issue by applying a new framework for the prediction of received signal strength (RSS) in mobile communications based on Artificial Neural Networks (ANN). The experimental data measurement...

As future mobile networks move rapidly to 5G, ubiquitous network coverage (even in remote areas), temporary capacity enhancement, and network failure backup are still open issues. The recent advances in unmanned aerial vehicles technology have turned the attention of researchers and the industry toward utilizing flying nodes in 5G cellular. One or...

In this Letter, the use of the effective radiation pattern (ERP) concept for wireless systems analysis is proposed, in order to account for multipath angular spread effects upon ideal antenna radiation patterns. The method for producing the ERP that optimally models any real antenna radiation pattern is presented and the proof of concept is demonst...

Within the Fifth Generation framework of dynamic network topology and moving cells, the nomadic node (NN) concept is seen as a promising paradigm to provide coverage extension and capacity improvement on demand as well as to attain reduced capital expenditure and operational expenditure when compared with fixed-node deployment, such as microcells....

The need for 5G to adapt the radio access network to the spatial and temporal traffic variations makes the paradigm of moving networks essential. Dynamic network topology and moving cells through vehicular nomadic nodes (NN) will provide coverage extension and capacity improvement on demand as well as achieve reduced capital and operational expendi...

Long distance and beyond sight of view communication between a ground control station and an Unmanned Aerial Vehicle (UAV) is mainly achieved using high-gain antennas, antenna trackers or satellites. These implementations demand expensive, heavy and not easily deployed equipment, while in many cases cannot provide a sufficient communication range....

Carrier frequencies beyond 300 GHz have recently received attention primarily due to the potential for impressive capacity for future multi-gigabit wireless communication systems. In this context, this paper considers the different attenuation factors at the THz band and estimates the available bandwidth and the corresponding maximum data rate in t...

Energy-efficient planning is a current challenge for heterogeneous 4g wireless networks, since ‘greener’ strate- gies typically act against the always growing traffic require- ments. However, network-wide optimization of base station an- tenna patterns can be exploited to that end, leading the total transmit power of the network to a global minimum...

This work exploits the algorithm for the “rate-optimum beamformer” in spatially correlated MIMO Rician fading channels and proposes a probabilistic analysis for the “optimality of transmit beamforming condition”, (the necessary and sufficient condition when beamforming achieves ergodic capacity). The proposed analysis allows now for simulations to...

Optimization of base-station antenna patterns in the framework of heterogeneous LTE networks with geographically inhomogeneous throughput requirements is not an easy problem to tackle, and therefore, frequently omitted. Moreover, the initial phase of network dimensioning and planning often fails to meet growing throughput demands, and as a result,...

The optimum location of base-stations that meet certain coverage and capacity constraints is a major step in dimensioning a cellular network. The increasing capacity demand and mixed cell scenarios (relay nodes, microcells) make base-station location in LTE systems non trivial and call for sophisticated optimization methods. This paper proposes the...

This paper considers a broadband multicell system with key characteristics that base-stations and relays employ beamforming via large antenna arrays, as well as in-band full duplex relay operation. The signal to interference plus noise ratio gain (which is in excess of the maximum required for such a system) could be exploited either for reducing s...

Optimization of basestation antenna patterns and transmitted powers in heterogeneous 4g networks with geographically inhomogeneous throughput requirements is not an easy problem to tackle, and hence, frequently omitted. Moreover, the initial phase of network dimensioning and planning often fails to meet growing throughput demands, and hence, networ...

The problem of optimum base station positioning started with the deployment of the first cellular wireless systems, initially with coverage and traffic criteria. Nowadays, the increased demand for geographically inhomogeneous capacity leads to mixed cell structures as well as relay nodes, while the cost of the different deployments varies significa...

In-band full-duplex operation has recently attracted a lot of attention as a possible solution for increasing the spectral efficiency of wireless communication systems. This paper considers a 4G multicell system where base-stations and relays employ beamforming, while relays also operate in in-band full duplex mode. In the context of LTE, the exces...

This paper considers a 4G multicell system where base-stations and relays employ typical or large size antenna arrays with beamforming capabilities, as well as in-band full duplex relays. The achieved signal to interference ratio (SIR) gain in excess of the maximum required for such systems can be exploited either for reducing the major problem of...

The optimization of base station locations started with coverage and traffic criteria. Nowadays, the increased demand for geographically inhomogeneous capacity leads to mixed cell structures as well as relay nodes, while the cost of the different deployments varies significantly. Furthermore, MIMO technology offers solutions to the ever increasing...

Minimizing the cost of a cellular network usually includes the optimum selection and location of base-stations, that meet certain coverage and capacity constraints. In the framework of LTE wireless networks, coverage and capacity planning are interrelated in terms of interference. Moreover, the ever increasing capacity demand for non-uniformly dist...

Optimum basestation positioning in the framework of LTE wireless networks is not an easy task since there are several factors that need to be taken into account. The ever increasing demand for geographically inhomogeneous capacity, which has become the limiting factor in the network planning process, as well as the presence of relay nodes and ixed...

This paper presents approximate formulas for the signal to interference ratio (SIR) gain and the corresponding bit error rate (BER) performance, when the simple concept of an effective radiation pattern of the produced ‘real world’ Multiple-Input-Multiple-Output (MIMO) beamforming radiation pattern, is considered for CDMA multi-cell/tier deployment...

This paper presents approximate formulas for the signal to interference ratio (SIR) gain and the corresponding bit error rate (BER) performance, when the simple concept of an effective radiation pattern of the produced 'real world' Multiple-Input-Multiple-Output (MIMO) beamforming radiation pattern, is considered for CDMA multi-cell/tier deploy-men...

This work investigates the theoretical SIR gain of MISO beamforming multicarrier systems when the antenna beamwidth and side lobe level are considered in the system parameters via the concept of a simple effective radiation pattern. The effective radiation pattern models the result of the convo-lution of the power azimuth spectrum with the ideal an...

This work investigates the theoretical SIR gain of MISO beamforming for multicarrier systems when the antenna beamwidth and side lobe level are considered in the system parameters via the concept of the effective radiation pattern. In order to solve this problem a fully loaded one-tier network with realistic adaptive arrays at each base station was...

Radio channels induce distortions to the radiation pattern of beamforming systems such as beam broadening as well as sidelobe level and null rising. If these effects are ignored, the system performance is overestimated. This paper proposes the simple concept of an effective radiation pattern (ERP) calculated by optimally fitting the “real-world” ra...

The opportunistic beamforming (OB) technique in multicellular OFDMA networks is investigated in this paper. Three cross-layer radio resource management (RRM) algorithms for OFDMA operational scenarios are considered. These algorithms build upon typical network planning practices for OFDMA systems. The first two implement an OFDMA network with oppor...

This work examines the technique of fractional frequency reuse for the downlink of multi-cellular WiMAX networks. Different frequency-reuse deployment scenarios are presented. Three schemes for the reuse zone selection are evaluated, namely, the distance-based and SINR-based approaches, as well as a new scheme, which is based on load-balancing betw...

The goal of the study presented in this paper is the accurate performance evaluation of adaptive beam-centric admission control (AC) for wideband code-division multiple access (WCDMA) multicell networks with non-uniform traffic requirements. Each NodeB employs antenna arrays (AAs), used either to form fixed grids of beams (FGoBs), or to steer and s...

The issue of fairness and throughput trade-off in universal mobile telecommunications system network planning based on wideband code division multiple access is discussed in this paper. The employed radio resource management (RRM) fully supports rate adaptation and hence, new potentials arise in terms of system throughput and fairness. The authors...

Ray tracing is a technique based on the numerical simulation of geometrical optics and the uniform theory of diffraction, two well-known approximate methods for estimating a high-frequency electromagnetic field, based on the ray theory of field propagation. Radio-wave propagation prediction models based on ray tracing play an important role in wire...

The opportunistic beamforming (OB) technique in multicellular OFDMA networks is investigated in this paper. For this reason, three cross#layer radio resource management (RRM) algorithms for OFDMA operational scenarios that are based on typical resource allocation targets such as minimization of transmit power, maximization of throughput and interfe...

The opportunistic beamforming (OB) technique in multicellular OFDMA networks is investigated in this paper. For this reason, three cross-layer radio resource management (RRM) algorithms for OFDMA operational scenarios that are based on typical resource allocation targets such as minimization of transmit power, maximization of throughput and interfe...

Field trial results for different scenarios (propagation conditions, antenna heights, distance from the access point, etc.) in the city of Cambridge (UK) with a broadband FWA operating system (3.5 GHz) are used to evaluate the predictions of a 3D ray tracing propagation model. The model is optimised for FWA operational scenarios and combines the de...

Orthogonal frequency division multiple access (OFDMA) techniques are investigated in this paper. Five subchannel allocation algorithms are analysed and their performance in a multicellular environment is evaluated with simulations. Four schemes of lower complexity, suitable for the early deployment of wireless systems, are compared with a more comp...

Orthogonal Frequency Division Multiple Access (OFDMA) techniques are investigated in this paper. Five sub-channel allocation algorithms are analysed and their performance in a multicellular environment is evaluated with simulations. Four schemes of lower complexity, suitable for the early deployment of wireless systems, are compared with a more com...

This paper investigates the performance of an adaptive beam-shaping (ABS) strategy for wideband code division multiple access (WCDMA) multicellular networks with antenna arrays (AAs) at the base station (BS). The purpose of this ABS strategy is to form beams in directions of increased traffic distribution while at the same time minimize the total d...

Until now deterministic models only considered the power loss of a ray due to its total path length or its interactions with the environment (i.e. reflections, diffractions). However, in the fixed wireless access scenarios the radio waves propagate close to roof tops and according to the theory of the Fresnel zones, even when for LOS conditions, th...

A propagation model which combines the Fresnel zone theory and the ray tracing techniques is presented in this paper. The aim of this novel approach is a more accurate representation of the fixed wireless access channel. Deterministic models do not consider power loss when the radio waves propagate close to roof tops. However, according to the theo...

In this paper, results from a three-dimensional (3D) ray-tracing propagation model are compared with field trial measurements. The ray tracing algorithm is optimised for Broadband Fixed Wireless Access (BFWA) operational scenarios. The model works with raster terrain as well as 3D vector building and foliage databases. It considers reflections off...

A 3D ray-tracing propagation model is presented in this paper. The algorithm is optimised for broadband fixed wireless access (BFWA) operational scenarios. The model works with raster terrain as well as 3D vector building and foliage databases. It also considers reflections off building walls, off-axis roof top and terrain diffractions and foliage...

A deterministic propagation model is used to simulate broadband radio propagation at 3.5 GHz for a fixed wireless access (FWA) network in a high-rise city environment, with linear antenna polarisation. It is shown that some rooftop locations are unsuitable positions for subscriber units (SUs), due to the existence of single- or multiple-bounce refl...

This paper presents the results of measurements made to characterise the 3.5GHz Broadband Fixed Wireless Access channel in a suburban environment, using a sectored base station antenna and a directional subscriber antenna. A tapped delay line channel impulse response model of the Single-Input Single-Output (SISO) channel is derived from the measure...

This paper presents the results of measurements made to characterise the 3.5 GHz broadband fixed wireless access channel in a suburban environment, using a sectored base station antenna and a directional subscriber antenna. A tapped delay line channel impulse response model of the single-input single-output (SISO) channel is derived from the measur...

A ray-tracing algorithm is used to simulate broadband radio propagation at 3.5 GHz for a FWA network in a high-rise city environment. Both coverage and uplink interference are investigated, with linear antenna polarisation. It is shown that some rooftop locations are unsuitable positions for SU's, due to the existence of single or multiple-bounce r...

This paper presents the results of propagation measurements at 3.5 GHz for a broadband fixed wireless access (BFWA) system with a directional subscriber antenna and a sectored base station antenna. First we describe the equipment and data processing methods used for extracting the channel impulse response. This is followed by the results of narrowb...

The possible application of adaptive antennas in microcellular operational environments is studied in this paper with the help of a site-specific ray-tracing propagation model. First are examined the statistics of propagation parameters that play an important role for the performance of adaptive antennas. Particular emphasis is put on the spatial c...

There is still an open debate within the research community regarding the likely performance enhancement of smart antennas versus their complexity for commercial wireless applications. The goal of the study presented in this paper is to investigate the performance improvement attainable using relatively simple smart antenna techniques when applied...

A novel three-dimensional (3-D) ray-tracing model capable of supporting detailed representation of the indoor environment, as well as external building structures, is presented in this paper. The developed algorithm uses a hybrid imaging technique where the two-dimensional (2-D) image generations in vertical and horizontal planes are combined to pr...

To support the seamless upgrading of current cellular networks and to fulfil the requirements of third generation systems, an optimised base-station location algorithm, referred to as the combination algorithm for total-optimisation (CAT), is presented. Results show that the CAT approach is well suited to constrained optimisation, providing results...

Due to the site specific nature of microcellular operational environments, propagation models are required to take into account the exact position, orientation and electrical properties of individual buildings, and hence, ray-tracing techniques have emerged as the dominant methods to predict propagation in such environments. A novel hybrid three-di...

The combination algorithm for total optimisation (CAT) is proposed to support smooth upgrading of third generation systems and to fulfil the requirements of current cellular networks. The CAT algorithm solves the problem of base-station location in different environments. Until now experiments were based on simple statistical propagation models suc...

The combination algorithm for total optimisation (CAT) is a new base-station placement optimisation tool for cellular network planning. The CAT algorithm operates with two external modules, a propagation module and a capacity module that provide the algorithm with the necessary information to solve the base-station placement problem. In this paper...

The combination algorithm for total optimisation (CAT) solves the problem of optimised base-station location and density for different cellular configurations and environments. The algorithm relies on two main user supplied databases for its operation. The first is an over specified list of possible base-station locations and the second is a databa...

The cost and complexity of a network is closely related to the number of base-stations (BSs) required to achieve the system operator's service objectives. The location of BSs is not an easy task and there are numerous factors that must be taken into account when deciding the optimum position of BSs. This paper discusses the performance of three dif...

In this paper, a ray tracing propagation tool which produces the full impulse response of the radio channel in microcellular environments is employed in order to study the effect of such an environment to the performance of some spatial and temporal reference algorithms, for adaptive antennas. Results show that with one user an adaptive version of...

The characteristics of indoor propagation at 60GHz have been investigated using an image-based ray-tracing prediction model. It has been demonstrated that 60GHz signals are heavily attenuated by transmission through walls, and consequently, operation is likely to be restricted to locations where there is either an LOS path between base station and...