Dimitrios J. Vergados

Dr. Dimitrios J. Vergados

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Research Focus & Metrics

Academic Career Length

19Years (2008-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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24 February 2015 in IEEE Transactions on Information Theory
Verified
Journal Article
Closed access
NANatalia Amelina
Natalia Amelina
AFAlexander Fradkov
Alexander Fradkov
YJYuming Jiang
Yuming Jiang
DVDimitrios J. Vergados
Dimitrios J. Vergados
This paper is devoted to the approximate consensus problem for stochastic networks of nonlinear agents with switching topology, noisy, and delayed information about agent states. A local voting protocol with nonvanishing (e.g., constant) step size is examined under time-varying environments of agents. To analyze dynamics of the closed-loop system, the so-called method of averaged models is used. It allows us to reduce analysis complexity of the closed-loop stochastic system. We derive the upper bounds for mean square distance between states of the initial stochastic system and its approximate averaged model. These upper bounds are used to obtain conditions for approximate consensus achievement. An application of general theoretical results to the load balancing problem in stochastic dynamic networks with incomplete information about the current states of agents and with changing set of communication links is considered. The conditions to achieve the optimal level of load balancing are established. The performance of the system is evaluated both analytically and by simulation.

1 September 2016 in Sustainable Energy, Grids and Networks
Verified
Journal Article
Closed access
DVDimitrios J. Vergados
Dimitrios J. Vergados
IMIoannis Mamounakis
Ioannis Mamounakis
PMProdromos Makris
Prodromos Makris
EVEmmanouel Varvarigos
Emmanouel Varvarigos

2 January 2010 in Information Sciences
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Journal Article
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ILIoanna Lykourentzou
Ioanna Lykourentzou
KPKaterina Papadaki
Katerina Papadaki
DVDimitrios J. Vergados
Dimitrios J. Vergados
NPNineta Polemi
Nineta Polemi
VLVassili Loumos
Vassili Loumos

27 June 2021 in Sensors
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Journal Article
Open access
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Emmanouel T. MichailidisEmmanouel T. Michailidis
Emmanouel T. Michailidis
NMNikolaos I. Miridakis
Nikolaos I. Miridakis
AMAngelos Michalas
Angelos Michalas
ESEmmanouil Skondras
Emmanouil Skondras
DVDimitrios J. Vergados
Dimitrios J. Vergados
Mobile edge computing (MEC) represents an enabling technology for prospective Internet of Vehicles (IoV) networks. However, the complex vehicular propagation environment may hinder computation offloading. To this end, this paper proposes a novel computation offloading framework for IoV and presents an unmanned aerial vehicle (UAV)-aided network architecture. It is considered that the connected vehicles in a IoV ecosystem should fully offload latency-critical computation-intensive tasks to road side units (RSUs) that integrate MEC functionalities. In this regard, a UAV is deployed to serve as an aerial RSU (ARSU) and also operate as an aerial relay to offload part of the tasks to a ground RSU (GRSU). In order to further enhance the end-to-end communication during data offloading, the proposed architecture relies on reconfigurable intelligent surface (RIS) units consisting of arrays of reflecting elements. In particular, a dual-RIS configuration is presented, where each RIS unit serves its nearby network nodes. Since perfect phase estimation or high-precision configuration of the reflection phases is impractical in highly mobile IoV environments, data offloading via RIS units with phase errors is considered. As the efficient energy management of resource-constrained electric vehicles and battery-enabled RSUs is of outmost importance, this paper proposes an optimization approach that intends to minimize the weighted total energy consumption (WTEC) of the vehicles and ARSU subject to transmit power constraints, timeslot scheduling, and task allocation. Extensive numerical calculations are carried out to verify the efficacy of the optimized dual-RIS-assisted wireless transmission.

11 April 2024 in Sensors
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Journal Article
Open access
PDF file
GGGeorgios Gkagkas
Georgios Gkagkas
DVDimitrios J. Vergados
Dimitrios J. Vergados
AMAngelos Michalas
Angelos Michalas
MDMichael Dossis
Michael Dossis
The Internet of Things (IoT) is what we have as a great breakthrough in the 5G network. Although the 5G network can support several Internet of Everything (IoE) services, 6G is the network to fully support that. This paper is a survey research presenting the 5G and IoT technology and the challenges coming, with the 6G network being the new alternative network coming to solve these issues and limitations we are facing with 5G. A reference to the Control Plane and User Plane Separation (CUPS) is made with IPv4 and IPv6, addressing which is the foundation of the network slicing for the 5G core network. In comparison to other related papers, we provide in-depth information on how the IoT is going to affect our lives and how this technology is handled as the IoE in the 6G network. Finally, a full reference is made to the 6G network, with its challenges compared to the 5G network.

31 October 2017 in IEEE Transactions on Wireless Communications
Verified
Journal Article
Closed access
DVDimitrios J. Vergados
Dimitrios J. Vergados
NANatalia Amelina
Natalia Amelina
YJYuming Jiang
Yuming Jiang
KKKatina Kralevska
Katina Kralevska
OGOleg Granichin
Oleg Granichin
In a multihop wireless network, it is crucial but challenging to schedule transmissions in an efficient and fair manner. In this paper, a novel distributed node scheduling algorithm, called Local Voting, is proposed. This algorithm tries to semi-equalize the load (defined as the ratio of the queue length over the number of allocated slots) through slot reallocation based on local information exchange. The algorithm stems from the finding that the shortest delivery time or delay is obtained when the load is semi-equalized throughout the network. In addition, we prove that, with Local Voting, the network system converges asymptotically toward the optimal scheduling. Moreover, through extensive simulations, the performance of Local Voting is further investigated in comparison with several representative scheduling algorithms from the literature. Simulation results show that the proposed algorithm achieves better performance than the other distributed algorithms in terms of average delay, maximum delay, and fairness. Despite being distributed, the performance of Local Voting is also found to be very close to a centralized algorithm that is deemed to have the optimal performance.