Kostas Tsagkaris

WINGS ICT Solutions (Greece)

Author Statistics

Papers

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i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Panagiotis Demestichas

WINGS ICT Solutions (Greece)

142

Vera Stavroulaki

WINGS ICT Solutions (Greece)

ΑΓ

Ανδρέας Γεωργακόπουλος

WINGS ICT Solutions (Greece)

Dimitrios Karvounas

University of Piraeus

Nikos Koutsouris

National Technical University of Athens

Jens Gebert

Nokia (Germany)

Marios Logothetis

INTRASOFT International (Luxembourg)

Roussos Dimitrakopoulos

McGill University

Aimilia Bantouna

WINGS ICT Solutions (Greece)

Aristi Galani

University of Piraeus

Cooperative Institutions

National and Kapodistrian University of Athens

National Technical University of Athens

University of Piraeus

Orange (France)

Institute of Communication and Computer Systems

Universitat Politècnica de Catalunya

University of Surrey

Aristotle University of Thessaloniki

WINGS ICT Solutions (Greece)

Alcatel Lucent (Germany)

Author Statistics

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Research Field

Quality-of-Trust in 6G: Combining Emotional and Physical Trust through Explainable AI

2021 IEEE 94th Vehicular Technology Conference (VTC2021-Fall) (2023)

Chen Li Weijie Qi Bailu Jin Panagiotis Demestichas Kostas Tsagkaris

Wireless networks like many multi-user services have to balance limited resources in real-time. In 6G, increased network automation makes consumer trust crucial. Trust is reflect in both a personal emotional sentiment as well as a physical understanding of the transparency of AI decision making. Whilst there has been isolated studies of consumer sentiment to wireless services, this is not well linked to the decision making engineering. Likewise, limited recent research in explainable AI (XAI) has not established a link to consumer perception.Here, we develop a Quality-of-Trust (QoT) KPI that balances personal perception with the quality of decision explanation. That is to say, the QoT varies with both the time-varying sentiment of the consumer as well as the accuracy of XAI outcomes. We demonstrate this idea with an example in Neural Water-Filling (N-WF) power allocation, where the channel capacity is perceived by artificial consumers that communicate through Large Language Model (LLM) generated text feedback. Natural Language Processing (NLP) analysis of emotional feedback is combined with a physical understanding of N-WF decisions via meta-symbolic XAI. Combined they form the basis for QoT. Our results show that whilst the XAI interface can explain up to 98.9% of the neural network decisions, a small proportion of explanations can have large errors causing drops in QoT. These drops have immediate transient effects in the physical mistrust, but emotional perception of consumers are more persistent. As such, QoT tends to combine both instant physical mistrust and long-term emotional trends.

Sentiment Analysis

10.1109/vtc2023-fall60731.2023.10333364

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Opportunistic Network Creation Schemes for Capacity Extension in Wireless Access and Backhaul Segments

Mobile Networks and Management (2012)

Marios Logothetis Vera Stavroulaki Ανδρέας Γεωργακόπουλος Dimitrios Karvounas Nikos Koutsouris

It is expected that the wireless world will migrate towards an era that will comprise more local/temporary structures which, for instance, can be called Opportunistic Networks (ONs). Operator-governed ONs are dynamically created, temporary, coordinated extensions of the infrastructure. This paper presents an approach for exploiting such ONs in order to extend the capacity in wireless access and backhaul segments for efficient application provisioning, as well as an evaluation of an indicative test case as a proof of concept of the aforementioned approach.

Backhaul (telecommunications)

Provisioning

10.1007/978-3-642-30422-4_15

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Citations (1)

Results analysis and validation - D5.3

Oscar Moreno Jose Luis Martinez Gonzalez J. Pérez-Romero José Oriol Sallent Roig Alessandro Raschellà

Source

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5G PPP Architecture Working Group - View on 5G Architecture, Version 4.0

Zenodo (CERN European Organization for Nuclear Research) (2021)

Anastasius Gavras Ömer Bulakçı Marco Gramaglia Marius Iordache Mir Ghoraishi

10.5281/zenodo.5155657

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Citations (7)

A policy based framework for governing Future networks

Aristi Galani Nikos Koutsouris Kostas Tsagkaris Panagiotis Demestichas Blanca Fuentes

Future Internet will constitute a complex and dynamic environment, the requirements of which cannot be handled by traditional management schemes. The alternative is the approach of autonomic service and network management, which targets at guidance and orchestration of the behavior of autonomic and contemporary network entities based on specific service requirements and business goals. In this context, policies can constitute a means for accomplishing the desired high level control in autonomic management. In order to achieve this objective, an advanced policy framework, confronting the challenges of the highly miscellaneous, decentralized and dynamic Future Internet, is needed. To this effect, this paper presents the main challenges of policy-based management in the context of governing the autonomic Future Internet, and based on their elaboration, the focus is placed on existing concepts that can constitute the basis for the design of a proper policy management framework. The paper also describes the functional specification of the policy management framework, deriving from the presented challenges, and instantiation of the policy framework on an illustrative scenario.

Orchestration

Autonomic Computing

10.1109/glocomw.2012.6477678

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Citations (6)

Intelligent 5G Networks: Managing 5G Wireless\/Mobile Broadband

IEEE Vehicular Technology Magazine (2015)

Panagiotis Demestichas Ανδρέας Γεωργακόπουλος Kostas Tsagkaris Serafim Kotrotsos

Today there are forceful work streams that aim at realizing the fifth generation of wireless/mobile broadband (5G WMB). The work is driven by a framework that consists of three main requirements and two main sets of technology trends. This article presents the framework with the aim of contributing to the solidification of the technological foundations and longevity of 5G WMB systems. The requirements call for the proper provisioning of a large and rap-idly expanding set of applications/services, the higher valorization of the infrastructure, and a drastic improvement of the energy efficiency. As will be explained, these requirements fulfill the need for fast and reliable ser-vice deployment, offering all types of relevant quality of ser-vice (QoS)/quality of experience (QoE), handling demanding and changing contexts of operation (exploding user-data/signaling trafflc volumes and diverse mobility/radio conditions), providing means for the higher monetization of service provision, and drastically improving the cost efficiency. In parallel, the first set of technology trends includes the expansion of the WMB infrastructure features in terms of a new multiservice radio interface, networking options, and ways of architecting the system due to the introduction of the software-defined networking (SDN) and network function virtualization (NFV) concepts. There is also the trend of becoming more of a cloud platform instead of being a mere communication system. The importance of advanced management intelligence is also stressed in this article.

Mobile broadband

Provisioning

10.1109/mvt.2015.2446419

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Citations (41)

Cognitive control channels for the cooperation of opportunistic and composite wireless networks

European Signal Processing Conference (2011)

Jens Gebert Ανδρέας Γεωργακόπουλος Vera Stavroulaki Kostas Tsagkaris R. Ferrús

Opportunistic networks (ONs) are considered as coordinated extensions of a radio access network infrastructure, which are dynamically and temporarily created in an infrastructure-less manner in order to increase service reachability, improve resource utilization efficiency and facilitate localised service provisioning. The realization of the ON concept relies on the existence of control channels which will provide necessary signalling for the coordination of the ON nodes. Proposed control channels are conceived as an evolution of the already established cognitive pilot channel concept. As a result, new interfaces are discussed in order to convey information from the infrastructure to the terminals and vice versa or between terminals. Finally, the business benefits of the aforementioned approach are provided in order to strengthen the notion of the proposed control channels and consider future expansions.

Control channel

Provisioning

Cognitive network

Signalling

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End-to-End Real-Time Service Provisioning Over a SDN-Controllable Analog mmWave Fiber -Wireless 5G X-Haul Network

Journal of Lightwave Technology (2023)

Christos Vagionas Ronis Maximidis Ioannis Stratakos A. Margaris Agapi Mesοdiakaki

The current work presents the first experimental demonstration of real-time Ethernet (ETH) trial services and 4K-Ultra High Definition (UHD) video application transmission over a 2λ Wavelength Division Multiplexing (WDM) analog Fiber-Wireless (FiWi) mmWave X-haul network, supporting dynamic flexible capacity allocation through an integrated silicon photonic Si ₃ N ₄ Reconfigurable Optical Add Drop Multiplexer (ROADM) and 60 GHz wireless transmission across a 7 m V-band link distance, while controlled by a Software Defined Network (SDN) controller based on Open Daylight. Analog X-haul transport of the radio signals is based on an Intermediate Frequency over Fiber (IFoF) scheme centered at 1.5 GHz using an Orthogonal Frequency Division Multiplexing (OFDM) radio-waveform with a bandwidth of 204 MHz, generated by a Field Programmable Gated Array (FPGA)-based RF System-on-Chip (SoC) processor that converts on-the-fly the real-time ETH downlink traffic to analog radio and vice-versa for the uplink. Dynamic allocation of the X-haul traffic capacity is handled through the use of the 802.1Q Virtual Local Area Network (VLAN) tag-mechanism, which controls the forwarding operation to the proper DAC and InP EML for optical modulation using Intensity Modulation/Direct Detection (IM/DD) schemes, while the wavelength routing operation is handled by the low-loss four-port Si ₃ N ₄ ROADM featuring only 2.5 dB fiber-to-fiber losses based on a cascaded MZI-interleaver design on the TriPleX platform, routing the real-time traffic to a second mmWave antenna site. Detailed measurements and traffic statistics indicate end-to-end latency of less than 260 μs and a packet loss less than 0.0054% across a dynamic range of at least 6.5 dB in the optical domain, while the high user bandwidth and signal quality are validated by an uninterrupted 4K-UHD video transmission across the FiWi X-haul mmWave transport network. The current work aims to shape a complete technology roadmap for Point-to-Multipoint FiWi transport network architectures with high spectral efficiency X-haul transport for dense areas and 5G/6G hotspots of future mmWave Centralized Radio Access Networks (C-RANs).

Optical networking

10.1109/jlt.2023.3234365

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Citations (26)

Saturation Throughput Performance Analysis of a Medium Transparent MAC Protocol for 60 GHz Radio-Over-Fiber Networks

Journal of Lightwave Technology (2011)

George Kalfas Nikos Pleros Kostas Tsagkaris Luis Alonso Christos Verikoukis

We demonstrate an analytical model for calculating the saturation throughput performance of a medium transparent medium access control (MAC) protocol in 60 GHz radio-over-fiber (RoF) networks. The proposed model incorporates effectively the medium transparent MAC mechanism, assuming a finite number of terminals and ideal channel conditions. It takes into account contention both at the optical and wireless layer, ensuring seamless and dynamic capacity allocation over both transmission media. This model enables extensive saturation throughput performance analysis for the medium transparent MAC and has been applied to 60 GHz RoF network scenarios considering variable numbers of available optical wavelengths, wireless nodes and serving antenna elements and for two different data rate values, namely 155 Mbps and 1 Gbps. Comparison between the model-based throughput results and respective simulation-based outcomes reveals that our model is extremely accurate in predicting the system throughput. Moreover, it confirms that the proposed medium transparent MAC protocol can effectively operate in high-speed 60 GHz RoF LAN environments.

Media access control

10.1109/jlt.2011.2172392

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Citations (23)

Introducing Energy Awareness in the Cognitive Management of Future Networks

Journal of Green Engineering (2011)

Kostas Tsagkaris George Athanasiou Marios Logothetis Yiouli Kritikou Dimitrios Karvounas

The current circumstances on a worldwide level urgently impose to exploit technology in order to reduce environmental pollution, CO2. emissions and waste. The current technologies and the provisioned evolution steps take into consideration these facts and contribute to achieve greener footprint. This paper describes technologies as important elements in the design of Energy-aware Future Networks. They comprise Energy-aware Opportunistic Networks and Traffic Engineering schemes that can be seen as two major extensions towards future networks in the wireless infrastructure-less and wired backhaul/core segments, respectively. In parallel, the role of Cognitive Management Systems for enhancing these technologies with intelligent features that can assist in the optimization of network performance goals, including green targets, is also pointed out. Several simulation results evince how the proposed schemes can contribute in achieving greener footprint in the context of Future Networks.

Provisioning

Backhaul (telecommunications)

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