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Thessaloniki, Greece

The International Hellenic University was established in October 2005, in accordance to Law No. 3391. The University consists of three Schools: The School of Economics and Business Administration, the School of Humanities and the School of Science and Technology. All degrees in IHU are taught exclusively in English. The IHU is financed by the European Union and the Greek state, and aims at providing higher education particularly to foreigners who are interested in studying in Greece. Wikipedia.

Koutitas G.,International Hellenic University | Karousos A.,Aircom International | Tassiulas L.,University of Thessaly
IEEE Transactions on Wireless Communications

The energy efficiency of cellular networks is explored for different network deployment strategies and traffic conditions. The total network power consumption and the ratios Watts/kbps, Watts/user are used as metrics to quantify the performance and it is shown that efficiency depends on the deployment strategy and the state of operation of the network (underutilized-overutilized). As a general conclusion it is shown that a microcell based network, comprising a large number of low power stations, is the most efficient strategy but it does not present traffic proportional characteristics. For the purpose of the investigation, the paper presents a pre-processing of the database 3D ray tracing algorithm that is enhanced with an image test procedure and multiple slope diffraction mechanisms to achieve fast and accurate predictions. The algorithm is used for channel estimations over a real urban environment described in a vector format. In addition, a power control algorithm is developed that explicitly considers power levels of neighbor base stations and is used for the network power consumption estimation. Finally, network planning is achieved through an evolutionary optimization technique that combines the above mentioned algorithms. © 2012 IEEE. Source

Koutitas G.,International Hellenic University
IEEE Transactions on Broadcasting

This paper investigates the network deployment of single frequency networks (SFN) based on OFDM schemes that are standardized for terrestrial broadcasting systems, for digital audio broadcasting (DAB) and for digital video broadcasting (DVB) systems. The concept of green network planning is presented. The term green refers to low carbon, energy efficiency and low exposure to radiation, parameters important for the sustainable growth. For the purpose of our investigation a mountainous area of Northern Greece is examined, that is described by a digital terrain elevation model (DTEM) and field computations are based on multi shape slope uniform theory of diffraction (UTD) technique. A genetic algorithm (GA) optimization method is developed for the network planning purposes. A comparison between various planning strategies is presented. It is shown that great Co2 reductions, cost savings and low exposure to radiation can be achieved when the network planning considers a 'green' strategy. © 2006 IEEE. Source

Koutitas G.,International Hellenic University
IEEE Antennas and Wireless Propagation Letters

This letter investigates the channel variations in wireless body area networks (WBANs). For the purpose of the investigation, a ray solution for multiple closed surfaces is proposed that utilizes a modified slope uniform theory of diffraction (UTD) technique and can be applied to model scattering, radiation, coupling effects, or a combination of the three in a single formulation. The solution considers all possible ray paths and is valid at the transition boundaries of the scenario. The human bodies are represented as closed cylindrical surfaces with constitutive parameters based on the Muscle model. The proposed algorithm predicts channel variations in a ray format that requires less CPU and is characterized by lower complexity compared to full-wave techniques. Body-to-access point (BAP) and body-to-body networks are investigated. © 2010 IEEE. Source

Koutitas G.,International Hellenic University
2010 European Wireless Conference, EW 2010

This paper investigates the deployment of single frequency terrestrial DVB networks in terms of their carbon footprint. A network optimization tool is presented that is based on evolution optimisation method, the genetic algorithm. The target of the investigation is to design the network considering the minimization of its carbon emissions. For the purpose of the investigation a real mountainous area is examined. The field computations are based on accurate multiple slope uniform theory of diffraction (UTD) approximations. Simulation results show a great reduction of CO2 emissions when carbon footprint is included in the optimization process. © 2010 IEEE. Source

Koutitas G.,International Hellenic University | Koutitas G.,University of Thessaly
IEEE Transactions on Smart Grid

This paper investigates load control and demand response in a smart grid environment where a bidirectional communication link between the operator and the smart flexible devices supports command and data flow. Two control schemes are investigated that can provide energy management, taking into account user's comfort, via binary on-off policies of the smart flexible devices. A dynamic control algorithm is introduced that considers real time network characteristics and initiates command flow when critical parameters exceed predefined thresholds. To sustain fairness in the system, priority based and round robin scheduling algorithms are proposed. A continuous control algorithm is also explored to define the higher bounds of energy savings. To quantify the discomfort of users that participate in this type of services, a heuristic consumer utility metric is proposed and measurements with a flexible device (air conditioning unit) are performed to model empirically possible time intervals of the control scheme. Reciprocal fair energy management schemes are investigated being both operator and user centric. It is shown that great energy and cost savings can be achieved providing the required degrees of freedom to the smart grid to self-adapt during peak hours. © 2010-2012 IEEE. Source

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