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Dive into the research topics where Georgia E. Athanasiadou is active.

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Featured researches published by Georgia E. Athanasiadou.


vehicular technology conference | 2000

Investigation into the sensitivity of the power predictions of a microcellular ray tracing propagation model

Georgia E. Athanasiadou; Andrew R. Nix

This paper investigates the sensitivity of the three-dimensional (3-D) ray tracing microcellular model presented in Astanasiadou et al. (1995, 2000). The variation of the received power is examined for different ray permutations, wall characteristics, antenna position offsets and database inaccuracies. Predictions of the different configurations in line-of-sight (LOS), non-LOS (NLOS), and deep shadow areas are compared with each other and also with narrowband measurements. The analysis illustrates that although the model produces reliable results with five orders of reflection and one order of diffraction, higher orders of reflection and double diffracted rays enhance the models performance in deep shadow areas. It is also shown that good agreement with measured results can be obtained for wall conductivity in the order of 10/sup -3/ S/m and values of relative permittivity around five. The sensitivity analysis to the antenna positioning and database inaccuracies indicates that the receiver positions which suffer the highest power deviations are those at the boundaries of the LOS areas, as well as the positions in the deep shadow regions. In general, for antenna offsets up to 1 m, the predictions of the model are not significantly affected. Finally, the building databases with 1m maximum displacement do not have severe effects on the predictions, but databases with less accuracy can seriously degrade the performance of the model.


Journal of Network and Computer Applications | 2012

Mobile telemedicine for moving vehicle scenarios: Wireless technology options and challenges

Michael C. Batistatos; George V. Tsoulos; Georgia E. Athanasiadou

Recent studies conclude that patient survival during a health emergency situation depends on the effective pre-hospital healthcare. Mobile telemedicine exploits different wireless network technologies in order to tackle this problem. This paper looks into the case of mobile telemedicine service provision in a moving vehicle (ambulance). The special characteristics and requirements of this operational scenario are discussed in terms of benefits and limitations in conjunction with the application of existing wireless communication systems in this case. Moreover, emerging wireless broadband communication systems and spectrum access technology are considered in the same context, in an attempt to further improve service provision and face future challenges.


vehicular technology conference | 2000

Low-complexity smart antenna methods for third-generation W-CDMA systems

George V. Tsoulos; Georgia E. Athanasiadou; Robert J. Piechocki

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 to the third-generation W-CDMA air interface. Methods to achieve this goal include fixed multibeam architectures with different beam selection algorithms (maximum power criterion, combined beams) or adaptive solutions driven by relatively simple direction finding algorithms. After comparing these methods against each other for several representative scenarios, some issues related to the sensitivity of these methods are also studied, (e.g., robustness to environment, mismatches originating from implementation limitations, etc.). Results indicate that overall, conventional beamforming seems to be the best choice in terms of balancing the performance and complexity requirements, in particular when the problem with interfering high-bit-rate W-CDMA users is considered.


personal, indoor and mobile radio communications | 2007

Incorporating the Fresnel Zone Theory in Ray Tracing for Propagation Modelling of Fixed Wireless Access Channels

Georgia E. Athanasiadou

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 theory of the Fresnel zones, even when there is line-of-sight (LOS), the loss can be as much as 6 dB due to a single obstacle just below the LOS. In the model presented here, the path of each ray is found by a three-dimensional (3D) ray tracing algorithm and the electromagnetic field of each ray is calculated according to geometric optics (GO) and the uniform theory of diffraction (UTD). The first Fresnel zone of each ray is also found and examined and the losses due to its partial blockage are taken into account. Simulation results show significant differences in the power predictions when the blockage of the Fresnel zones is considered.


parallel computing | 2010

Parallel radio-wave propagation modeling with image-based ray tracing techniques

Theodoros E. Athanaileas; Georgia E. Athanasiadou; George V. Tsoulos; Dimitra I. Kaklamani

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 wireless network planning, as they take into account diverse physical phenomena such as reflection, diffraction and foliage attenuation and are considered critical for the analysis of long term evolution (LTE) systems, which requires a detailed description of the wireless channel. A major practical drawback of these models is that they can easily become very computationally expensive, as the required level of accuracy and the corresponding areas of study increase. In this paper, a parallel ray tracing algorithm for radio-wave propagation prediction based on the electromagnetic theory of images is presented. The implementation of the algorithm is based on the message passing interface (MPI). The decomposition of the problem is conducted by partitioning the image tree, while dynamic load balancing techniques are employed by means of the master-worker and the work-pool patterns. The performance of the parallel implementation is studied for different problems and task assignment schemes, showing that high speedups can be achieved.


vehicular technology conference | 2004

Deterministic propagation modelling and measurements for the broadband fixed wireless access channel

Georgia E. Athanasiadou; Ian J. Wassell; Chia Leong Hong

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 attenuation. Outputs include the received power and the impulse response of the wireless channel, and as such the tool permits a detailed and realistic assessment of the performance of a broadband system, including network planning and deployment issues. Field trial measurements carried out for different scenarios (propagation conditions, antenna heights, distance from the access point, etc.) in the city of Cambridge (UK) with a commercial BFWA operating system (3.5 GHz), are compared with ray tracing simulation results. The analysis studies the propagation characteristics of the BFWA radio channel and the accuracy of the presented deterministic propagation modelling approach.


Computer Communications | 2009

OFDMA techniques in multicellular networks with total frequency reuse

Dimitra Zarbouti; Ioannis N. Stiakogiannakis; George V. Tsoulos; Georgia E. Athanasiadou; Dimitra I. Kaklamani

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 computationally demanding scheme with respect to their blocking probability, loading factor and offered bit rate. The channel condition of each carrier is calculated and its knowledge is used for power controlled adaptive modulation, as an essential feature of the OFDMA technique. The general radio resource management process is divided into two steps: in the first step a base station allocates carriers to users while in the second step the modulation and power levels for each allocated carrier are defined. The simulation results demonstrate that a wireless system in its early deployment phase (up to 15-30% blocking probability) can employ simple OFDMA techniques capable of achieving high throughput. Furthermore, it is demonstrated that two of the proposed lower complexity schemes, (those based on cell coordination), offer good performance gain for higher data rate services. Nevertheless, these schemes achieve relatively lower gains with adaptive modulation, when compared with the techniques which exploit interference averaging or adaptive interference mitigation.


IEEE Antennas and Propagation Magazine | 2008

Implementation and Evaluation of a Web- Based Grid-Enabled Environment for WCDMA Multibeam System Simulations [Wireless Corner]

Theodoros E. Athanaileas; Panagiotis K. Gkonis; Georgia E. Athanasiadou; George V. Tsoulos; D.L. Kaklamani

In the work presented in this paper, a Web-based, grid-enabled environment for wideband code-division multiple-access (WCDMA) system simulations has been implemented and evaluated. The increasing demands for computation times as the complexity of the simulation increases (e.g., increased sectorization order, smart antennas, etc., or combining system with link-level simulations) soon become prohibitively high. A WCDMA simulation is essentially a Monte Carlo simulation, consisting of a large number of identical and independent processes, which are viable for efficient and cost-effective distributed processing on a grid infrastructure. In the work presented herein, a problem-solving environment (PSE) has been implemented for grid-enabled execution of WCDMA simulations on the production grid infrastructure deployed by the Enabling Grids for E-sciencE (EGEE) project. The problem-solving environment provides a secure, Web-based portal for interacting with the grid middleware (e.g., job submission and monitoring, result retrieval, etc.). The grid-enabled simulator is presented, and implementation details are discussed. Simulation results and grid execution statistics are also shown, in order to demonstrate the validity of the approach.


International Journal of Antennas and Propagation | 2013

The Effective Radiation Pattern Concept for Realistic Performance Estimation of LTE Wireless Systems

Dimitra Zarbouti; George V. Tsoulos; Georgia E. Athanasiadou; Constantinos A. Valagiannopoulos

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” radiation pattern to the ERP. The proposed ERP method is incorporated into a multicell bad urban 4G LTE operational scenario which employs beamforming for both the BSs and the RNs. The performed simulations provide evidence that the ideal instead of the real radiation pattern overestimates the SIR and capacity by almost 3 dB and 13 Mbps, respectively, for the reference scenario without RNs. It also proves that the ERP method produces almost identical performance results with the real radiation pattern, and hence it is a simple and viable option for realistic performance analysis. Finally, the network performance is studied as a function of the number of RNs with the help of the ERP method. Results show that a beamforming LTE network with RNs that also employ beamforming provides 3 dB SIR gain with the addition of 1 RN per cell and 15 dB gain with 4 RNs per cell.


Wireless Personal Communications | 1998

Adaptive Antennas for Microcellular and Mixed Cell Environments withDS-CDMA

George V. Tsoulos; Georgia E. Athanasiadou; Mark A Beach; Sc Swales

Adaptive antenna technology is now regarded as one of the key system components in future generation cellular networks. This paper considers the performance of a DS-CDMA system which employs adaptive antennas at the base station sites of both microcell and mixed micro/umbrella cell operational environments. A microcellular ray tracing propagation tool has been employed in order to ascertain site specific propagation data. Results for a typical small cell environment highlight both the propagation characteristics and the behaviour of the adaptive antenna, as well as the sensitivity of the system upon parameters such as the mutual coupling effect. This work does not assume idealised propagation conditions or antenna radiation patterns for the small cell analysis.In summary, the results indicate that microcellular base stations employing adaptive antenna signal processing can offer a significant capacity enhancement and improved channel characteristics when compared with their omnidirectional counterparts. In addition, it is shown that umbrella cells overlaying microcells within the same RF bandwidth allocation, do not impact upon system capacity providing that adaptive antenna technology is employed at the umbrella cell site.

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Dimitra I. Kaklamani

National Technical University of Athens

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I. K. Valavanis

University of Peloponnese

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Ioannis N. Stiakogiannakis

National Technical University of Athens

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Panagiotis K. Gkonis

National Technical University of Athens

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Theodoros E. Athanaileas

National Technical University of Athens

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D. C. Tsilimantos

National Technical University of Athens

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