Theofanis Orphanoudakis | Hellenic Open University (original) (raw)

Papers by Theofanis Orphanoudakis

Proceedings of SPIE, Nov 4, 1996

Demand for inter-activity drives the massive introduction of a return channel in CATV systems by ... more Demand for inter-activity drives the massive introduction of a return channel in CATV systems by means of the HFC architecture. Cost-effectiveness dictates sharing this return channel among many customers and the most suitable method is TDMA which can accommodate the high burstiness of the upstream traffic. The MAC protocol arbitrating the access to the time slots combines more than one access mechanisms but reservation ALOHA is the most promising method for the identification of busy stations. In this work a novel method allowing simultaneous reservations without previous symbol synchronization is presented. The simultaneous single symbol reservation (S3R) scheme greatly reduces the overhead for reservation sub-slots but also allows better and more predictable performance improving system utilization.

Journal of Optical Communications and Networking, Jun 21, 2016

The switchless elastic rate node (SERANO) is an elastic optical network block architecture facili... more The switchless elastic rate node (SERANO) is an elastic optical network block architecture facilitating reduction in network cost and blocking due to spectral fragmentation while extending the capacity-reach product in translucent optical networks. We present an analytical mathematical method for minimizing the number of transceivers that are solely used to construct this block, albeit a finite blocking probability. Moreover, based on a realistic traffic matrix and making use of a networking planning tool, we deduce a SERANO's block dimension for BT's national backbone network. Finally, we estimate the conditions under which the cost of a SERANO block is lower to the corresponding electronic switch for providing important networking functions like 3R regeneration, defragmentation, and network reoptimization.

IJCCS, Feb 23, 2023

Seiring dengan berkembangnya cryptocurrency, tidak dipungkiri bahwa harga dari crypto tidaklah st... more Seiring dengan berkembangnya cryptocurrency, tidak dipungkiri bahwa harga dari crypto tidaklah stabil. Salah satu faktor yang mempengaruhinya yaitu meningkatnya volume transaksi yang menarik minat peneliti untuk melakukan penelitian dalam mengembangkan metode prediksi harga koin dari cryptocurrency. Hasil prediksi dipengaruhi oleh penggunaan metode, algoritma hingga jumlah data. Pada penelitian ini akan dilakukan pemodelan prediksi dengan menggunakan metode LSTM dan data jangka pendek. Penelitian ini akan melakukan 2 percoba menggunakan metode LSTM sederhana dan memanfaatkan multivariate time series dengan LSTM. Hasilnya diperoleh nilai terkecil prediksi menggunakan skenario pembangian alokasi data 80/20, inputan layer LSTM = 360, Epoch = 500 yang dilakukan yaitu koin Solana dengan RMSE = 0.111, R2 = 0.9962. Dapat disimpulkan bahwa penggunaan data jangka pendek dapat digunakan dalam pembuatan pemodelan prediktif, namun perhatian khusus perlu diberikan pada karakteristik dataset yang digunakan dan metodologi pemodelan, dan diharapkan hasil penelitian ini dapat dapat dimanfaatkan dalam penelitian selanjutnya Kata kunci-Cryptocurrency, Prediksi, Long short-term memory (LSTM), Short-term data

MATEC web of conferences, 2016

We propose a novel optical cloud architecture where IT and Telecom resources are used interchange... more We propose a novel optical cloud architecture where IT and Telecom resources are used interchangeably as common infrastructure. Key assets are the MAC controlled passive networks for distributed multiplexing and grooming and a node architecture integrating transmission and switching.

2022 25th Euromicro Conference on Digital System Design (DSD)

ICERI proceedings, Nov 1, 2022

Technology rapidly changed our everyday lives and shifted modern societies towards a new digital ... more Technology rapidly changed our everyday lives and shifted modern societies towards a new digital era. These changes are seen everywhere-in our homes, jobs, and cars. However, even with this technological advance, we are still solving problems as we did several years ago. Inevitably, the question arises: "Why don't we use new specialized tools for problem-solving to fight the complexity of the arising new problems?". We tend to think about solving problems as we have always done because this is what we have learned to do from a young age. Since a significantly higher degree of complexity has emerged in our century, the contribution of citizens, especially the young generation and communities, in problem-solving is of utmost importance to be supported by educational institutions, especially schools, promoting and leading students and educators to take action and encouraging each other to change their mindsets. Following the above, six European organizations from Spain, Portugal, Greece, Croatia, and Cyprus designed and implemented the project" Plan for Green Opportunities: Be A Digital scientific changemaker" (PARADIGM), a European-funded collective project under the framework of the Erasmus+ program. The partnership has identified the need for raising environmental awareness and decided to develop a project targeting the school community. PARADIGM aims to use the appropriate technological infrastructure (devices, data platforms and tools) to empower the active engagement of citizens in taking action against climate change and for sustainable development through better monitoring and observing the environment and its environmental impacts. The project's activities focus on designing and developing an E-learning course for ecological awareness, an IoT-STEM-based environmental observatories framework, and designing and developing a citizen science platform serving as the PARADIGM Virtual Maker Space and Repository. The Internet of Things (IoT) framework is designed to comprise of Do it Yourself (D.I.Y.) like experimental platforms (embedded microcontrollers like the well-known Arduino, sensors, connectors and packaging kits etc.) interoperable with cloud-based IoT data aggregation platforms to set up the necessary dashboards for data analysis and visualizations, supported by a complete set of technical datasheets as well as detailed lesson plans for teachers to introduce relevant challenges in their classrooms. The specific study presents the pedagogical approach of PARADIGM, focusing on the training curricula for environmental awareness designed on the problem-based learning (P.B.L.) approach. Furthermore, by introducing environmental observatories, educators are taught to coordinate with students to manage and collect data on natural resources via an environmental data monitoring process (selection, analysis, and interpretation of data on the PARADIGM platform). Finally, PARADIGM develops a set of plausible interactions for a given ecosystem via a scenario planning process, enabling learners to participate in fundamental cutting-edge research across environmental issues, increasing its visibility within the European public and discourse. Through the latter, the learners will acquire additional competencies that will make them competitive in the labour market and advance their skills through novel educational methodologies promoting STEM-oriented activities and raising awareness concerning environmental issues.

2018 21st Euromicro Conference on Digital System Design (DSD)

The present paper proposes a SIP-based emergency embedded framework, named SEEK, that enables emb... more The present paper proposes a SIP-based emergency embedded framework, named SEEK, that enables embedded devices to trigger calls to emergency centers and support IP-based real time communication. SEEK framework is consisted of body sensors and a haptic device enabling elderly and disabled people who live independent to perform emergency calls. Sensors embedded in SEEK, aggregate environmental data and vital signs that monitor user's current health status and automatically trigger emergency calls when an emergency occurs, providing continuous real-time sensor data. The haptic device enhances further the communication among the end user (disabled person or elderly), first responders and healthcare providers at emergency centers. A prototype implementation and initial results are presented as a proof of concept for deaf and speech impaired people. The results depict that the proposed framework seems to be an auspicious solution for a wide range of disabled people enabling them to report emergency events and establish real time communication with first responders regardless of their disabilities.

Sensors

In this paper, we present the results of a performance evaluation and optimization process of an ... more In this paper, we present the results of a performance evaluation and optimization process of an indoor positioning system (IPS) designed to operate on portable as well as miniaturized embedded systems. The proposed method uses the Received Signal Strength Indicator (RSSI) values from multiple Bluetooth Low-Energy (BLE) beacons scattered around interior spaces. The beacon signals were received from the user devices and processed through an RSSI filter and a group of machine learning (ML) models, in an arrangement of one model per detected node. Finally, a multilateration problem was solved using as an input the inferred distances from the advertising nodes and returning the final position approximation. In this work, we first presented the evaluation of different ML models for inferring the distance between the devices and the installed beacons by applying different optimization algorithms. Then, we presented model reduction methods to implement the optimized algorithm on the embedd...

2019 4th South-East Europe Design Automation, Computer Engineering, Computer Networks and Social Media Conference (SEEDA-CECNSM), 2019

The objective of this work is to develop an indoor location system with high precision and contin... more The objective of this work is to develop an indoor location system with high precision and continuous position monitoring in real time with the use of a mobile phone without any special hardware using only commercially available low-cost sensors. Finding the location is done using the measured Received Signal Strength Indicator (RSSI) value of Bluetooth beacons received from mobile phones combined with measurements from other phone sensors. For the development of our model, we collected measurements for the RSSI values from Beacons which we placed in a space of 30.75 sqm and the values from the mobile accelerometer in motion. We divided the space into 16 subareas of 1.45m x 1.35m and used our measurements to develop a machine learning model using the open source TensorFlow framework to predict the correct subarea of the user. Through experiments, we show that our model can reach an accuracy of 0.7209 which means that our system can predict the correct user location in 72% of the cases with accuracy less than 1 meter.

2015 European Conference on Optical Communication (ECOC), 2015

We report a Datacentre system architecture and its performance, that is exploiting PON configurat... more We report a Datacentre system architecture and its performance, that is exploiting PON configurations in the interconnection fabric to play down the role of switching. Advanced transceiver technology is considered that is optimised for balancing performance with cost/power consumption.

The Institute of Electrical and Electronics Engineers, 2010

Microprocessors and Microsystems, 2019

Being able to perform promptly and accurate emergency calls is crucial for every human life. Howe... more Being able to perform promptly and accurate emergency calls is crucial for every human life. However, people with impairments feel precluded when there is need to have access to emergency centers. The main reason is the absence of IP-based emergency systems triggered by assistive devices and body area networks. To guarantee that anyone can benefit from emergency systems, it is essential to enable embedded devices to trigger calls to emergency centers and support IP-based real time communication. To achieve this, the present paper extends SEEK framework (Andriopoulou et al., 2018), an embedded framework consisting of environmental, body sensors and a haptic device. SEEK framework enables elderly and disabled people who live independent to perform emergency calls. Sensors embedded in SEEK, aggregate environmental data and vital signs that monitor user's current health status 7and automatically trigger emergency calls when an emergency occurs, providing continuous real-time sensor data. The haptic device provides further modalities to the end user (disabled person or elderly) supporting audio, media and text communication with first responders and healthcare providers at emergency centers. A prototype implementation and initial results are presented as a proof of concept for deaf and speech impaired people enabling them to report emergency events and establish real time communication with first responders. The results depict that even lower capability hardware platforms may be used in order to minimize the cost and increase usability by minimizing power consumption of such an embedded framework.

IEEE Wireless Communications, 2016

With vehicle-to-vehicle and vehicle-to-infrastructure communications gaining momentum, immense op... more With vehicle-to-vehicle and vehicle-to-infrastructure communications gaining momentum, immense opportunities for developing a new application gamut open up. These range from applications targeting security/safety and efficient transportation to in-car entertainment enjoying multi-player mixed-reality games. The potential of VANETs has been recognized by standardization bodies and other stakeholders, including car manufacturers, that have established multiple consortia and initiatives to explore the capabilities of VANET technologies. From the communication technology perspective, the high speed at which nodes move in VANETs together with the adverse environmental conditions (rapidly changing surroundings, weather, etc.) present great challenges. These have attracted the interest of researchers who have sought to evaluate the performance of these systems, mostly paying attention to the lower layers of the protocol stack (physical and MAC). In this article, we explore the network architecture and protocol stack for supporting a broad range of infotainment applications in VANETs based on IEEE 802.11p and assess VANETs' capabilities to support networked multimedia. To this end, our evaluation focuses on application-layer performance for video streaming over a prototype system based on NEC's Linkbird-MX devices.

2015 European Conference on Networks and Communications (EuCNC), 2015

ABSTRACT The elastic optical networks paradigm offers a competitive solution in terms of resource... more ABSTRACT The elastic optical networks paradigm offers a competitive solution in terms of resource utilization to cope with the ever-increasing traffic demand. Specifically, the ability to make a number of previously fixed transmission parameters tunable, for example the data rate or channel spacing, requires an evolution of the node architecture. To fully benefit from elasticity, the data plane should evolve towards a software-defined architecture. In this paper, we report the work carried out in the ICT IDEALIST project and in particular the data plane solutions towards 1Tb/s optical networks with flexgrid and flex-rate technology. Flexibility requires changes in optical cross-connect, transponder as well as in the digital layer. The consortium builds pre-commercial experimental testbeds to validate the proposed building blocks and to analyze candidate applications.

Proceedings of the 19th Panhellenic Conference on Informatics, 2015

Sensors

Computing has undergone a significant transformation over the past two decades, shifting from a m... more Computing has undergone a significant transformation over the past two decades, shifting from a machine-based approach to a human-centric, virtually invisible service known as ubiquitous or pervasive computing. This change has been achieved by incorporating small embedded devices into a larger computational system, connected through networking and referred to as edge devices. When these devices are also connected to the Internet, they are generally named Internet-of-Thing (IoT) devices. Developing Machine Learning (ML) algorithms on these types of devices allows them to provide Artificial Intelligence (AI) inference functions such as computer vision, pattern recognition, etc. However, this capability is severely limited by the device’s resource scarcity. Embedded devices have limited computational and power resources available while they must maintain a high degree of autonomy. While there are several published studies that address the computational weakness of these small systems-m...

2022 IEEE Global Engineering Education Conference (EDUCON)

Lecture Notes in Computer Science, 2020

This paper presents a fuzzy logic model for Real-time Stress Detection (RSD) that allows continuo... more This paper presents a fuzzy logic model for Real-time Stress Detection (RSD) that allows continuous and in-depth evaluation of user’s stress in a straightforward and systematic way by using physiological data. The RSD model takes as input signals’ values (galvanic skin response, heart rate) and then generates the corresponding level for user’s stress (low, mid-low, mid-high and high). To this end, skin conductance and heart rate signals were used to determine the stress levels classes. Results showed that the proposed tool-based stress detection mechanism can support a systematic evaluation of user’s stress in real time. Given that stress is highly subjective and may largely depend both on context and user characteristics, such results are rather encouraging for such a challenging problem. From a UX evaluators’ perspective, a preliminary study, involving three HCI experts, investigated the usefulness of the proposed RSD mechanism and revealed that it can substantially decrease time and effort required to make sense of user testing data. Furthermore, practitioners reported that using RSD they could conduct a more in-depth analysis compared to their current practices.

Proceedings of SPIE, Nov 4, 1996

Demand for inter-activity drives the massive introduction of a return channel in CATV systems by ... more Demand for inter-activity drives the massive introduction of a return channel in CATV systems by means of the HFC architecture. Cost-effectiveness dictates sharing this return channel among many customers and the most suitable method is TDMA which can accommodate the high burstiness of the upstream traffic. The MAC protocol arbitrating the access to the time slots combines more than one access mechanisms but reservation ALOHA is the most promising method for the identification of busy stations. In this work a novel method allowing simultaneous reservations without previous symbol synchronization is presented. The simultaneous single symbol reservation (S3R) scheme greatly reduces the overhead for reservation sub-slots but also allows better and more predictable performance improving system utilization.

Journal of Optical Communications and Networking, Jun 21, 2016

The switchless elastic rate node (SERANO) is an elastic optical network block architecture facili... more The switchless elastic rate node (SERANO) is an elastic optical network block architecture facilitating reduction in network cost and blocking due to spectral fragmentation while extending the capacity-reach product in translucent optical networks. We present an analytical mathematical method for minimizing the number of transceivers that are solely used to construct this block, albeit a finite blocking probability. Moreover, based on a realistic traffic matrix and making use of a networking planning tool, we deduce a SERANO's block dimension for BT's national backbone network. Finally, we estimate the conditions under which the cost of a SERANO block is lower to the corresponding electronic switch for providing important networking functions like 3R regeneration, defragmentation, and network reoptimization.

IJCCS, Feb 23, 2023

Seiring dengan berkembangnya cryptocurrency, tidak dipungkiri bahwa harga dari crypto tidaklah st... more Seiring dengan berkembangnya cryptocurrency, tidak dipungkiri bahwa harga dari crypto tidaklah stabil. Salah satu faktor yang mempengaruhinya yaitu meningkatnya volume transaksi yang menarik minat peneliti untuk melakukan penelitian dalam mengembangkan metode prediksi harga koin dari cryptocurrency. Hasil prediksi dipengaruhi oleh penggunaan metode, algoritma hingga jumlah data. Pada penelitian ini akan dilakukan pemodelan prediksi dengan menggunakan metode LSTM dan data jangka pendek. Penelitian ini akan melakukan 2 percoba menggunakan metode LSTM sederhana dan memanfaatkan multivariate time series dengan LSTM. Hasilnya diperoleh nilai terkecil prediksi menggunakan skenario pembangian alokasi data 80/20, inputan layer LSTM = 360, Epoch = 500 yang dilakukan yaitu koin Solana dengan RMSE = 0.111, R2 = 0.9962. Dapat disimpulkan bahwa penggunaan data jangka pendek dapat digunakan dalam pembuatan pemodelan prediktif, namun perhatian khusus perlu diberikan pada karakteristik dataset yang digunakan dan metodologi pemodelan, dan diharapkan hasil penelitian ini dapat dapat dimanfaatkan dalam penelitian selanjutnya Kata kunci-Cryptocurrency, Prediksi, Long short-term memory (LSTM), Short-term data

MATEC web of conferences, 2016

We propose a novel optical cloud architecture where IT and Telecom resources are used interchange... more We propose a novel optical cloud architecture where IT and Telecom resources are used interchangeably as common infrastructure. Key assets are the MAC controlled passive networks for distributed multiplexing and grooming and a node architecture integrating transmission and switching.

2022 25th Euromicro Conference on Digital System Design (DSD)

ICERI proceedings, Nov 1, 2022

Technology rapidly changed our everyday lives and shifted modern societies towards a new digital ... more Technology rapidly changed our everyday lives and shifted modern societies towards a new digital era. These changes are seen everywhere-in our homes, jobs, and cars. However, even with this technological advance, we are still solving problems as we did several years ago. Inevitably, the question arises: "Why don't we use new specialized tools for problem-solving to fight the complexity of the arising new problems?". We tend to think about solving problems as we have always done because this is what we have learned to do from a young age. Since a significantly higher degree of complexity has emerged in our century, the contribution of citizens, especially the young generation and communities, in problem-solving is of utmost importance to be supported by educational institutions, especially schools, promoting and leading students and educators to take action and encouraging each other to change their mindsets. Following the above, six European organizations from Spain, Portugal, Greece, Croatia, and Cyprus designed and implemented the project" Plan for Green Opportunities: Be A Digital scientific changemaker" (PARADIGM), a European-funded collective project under the framework of the Erasmus+ program. The partnership has identified the need for raising environmental awareness and decided to develop a project targeting the school community. PARADIGM aims to use the appropriate technological infrastructure (devices, data platforms and tools) to empower the active engagement of citizens in taking action against climate change and for sustainable development through better monitoring and observing the environment and its environmental impacts. The project's activities focus on designing and developing an E-learning course for ecological awareness, an IoT-STEM-based environmental observatories framework, and designing and developing a citizen science platform serving as the PARADIGM Virtual Maker Space and Repository. The Internet of Things (IoT) framework is designed to comprise of Do it Yourself (D.I.Y.) like experimental platforms (embedded microcontrollers like the well-known Arduino, sensors, connectors and packaging kits etc.) interoperable with cloud-based IoT data aggregation platforms to set up the necessary dashboards for data analysis and visualizations, supported by a complete set of technical datasheets as well as detailed lesson plans for teachers to introduce relevant challenges in their classrooms. The specific study presents the pedagogical approach of PARADIGM, focusing on the training curricula for environmental awareness designed on the problem-based learning (P.B.L.) approach. Furthermore, by introducing environmental observatories, educators are taught to coordinate with students to manage and collect data on natural resources via an environmental data monitoring process (selection, analysis, and interpretation of data on the PARADIGM platform). Finally, PARADIGM develops a set of plausible interactions for a given ecosystem via a scenario planning process, enabling learners to participate in fundamental cutting-edge research across environmental issues, increasing its visibility within the European public and discourse. Through the latter, the learners will acquire additional competencies that will make them competitive in the labour market and advance their skills through novel educational methodologies promoting STEM-oriented activities and raising awareness concerning environmental issues.

2018 21st Euromicro Conference on Digital System Design (DSD)

The present paper proposes a SIP-based emergency embedded framework, named SEEK, that enables emb... more The present paper proposes a SIP-based emergency embedded framework, named SEEK, that enables embedded devices to trigger calls to emergency centers and support IP-based real time communication. SEEK framework is consisted of body sensors and a haptic device enabling elderly and disabled people who live independent to perform emergency calls. Sensors embedded in SEEK, aggregate environmental data and vital signs that monitor user's current health status and automatically trigger emergency calls when an emergency occurs, providing continuous real-time sensor data. The haptic device enhances further the communication among the end user (disabled person or elderly), first responders and healthcare providers at emergency centers. A prototype implementation and initial results are presented as a proof of concept for deaf and speech impaired people. The results depict that the proposed framework seems to be an auspicious solution for a wide range of disabled people enabling them to report emergency events and establish real time communication with first responders regardless of their disabilities.

Sensors

In this paper, we present the results of a performance evaluation and optimization process of an ... more In this paper, we present the results of a performance evaluation and optimization process of an indoor positioning system (IPS) designed to operate on portable as well as miniaturized embedded systems. The proposed method uses the Received Signal Strength Indicator (RSSI) values from multiple Bluetooth Low-Energy (BLE) beacons scattered around interior spaces. The beacon signals were received from the user devices and processed through an RSSI filter and a group of machine learning (ML) models, in an arrangement of one model per detected node. Finally, a multilateration problem was solved using as an input the inferred distances from the advertising nodes and returning the final position approximation. In this work, we first presented the evaluation of different ML models for inferring the distance between the devices and the installed beacons by applying different optimization algorithms. Then, we presented model reduction methods to implement the optimized algorithm on the embedd...

2019 4th South-East Europe Design Automation, Computer Engineering, Computer Networks and Social Media Conference (SEEDA-CECNSM), 2019

The objective of this work is to develop an indoor location system with high precision and contin... more The objective of this work is to develop an indoor location system with high precision and continuous position monitoring in real time with the use of a mobile phone without any special hardware using only commercially available low-cost sensors. Finding the location is done using the measured Received Signal Strength Indicator (RSSI) value of Bluetooth beacons received from mobile phones combined with measurements from other phone sensors. For the development of our model, we collected measurements for the RSSI values from Beacons which we placed in a space of 30.75 sqm and the values from the mobile accelerometer in motion. We divided the space into 16 subareas of 1.45m x 1.35m and used our measurements to develop a machine learning model using the open source TensorFlow framework to predict the correct subarea of the user. Through experiments, we show that our model can reach an accuracy of 0.7209 which means that our system can predict the correct user location in 72% of the cases with accuracy less than 1 meter.

2015 European Conference on Optical Communication (ECOC), 2015

We report a Datacentre system architecture and its performance, that is exploiting PON configurat... more We report a Datacentre system architecture and its performance, that is exploiting PON configurations in the interconnection fabric to play down the role of switching. Advanced transceiver technology is considered that is optimised for balancing performance with cost/power consumption.

The Institute of Electrical and Electronics Engineers, 2010

Microprocessors and Microsystems, 2019

Being able to perform promptly and accurate emergency calls is crucial for every human life. Howe... more Being able to perform promptly and accurate emergency calls is crucial for every human life. However, people with impairments feel precluded when there is need to have access to emergency centers. The main reason is the absence of IP-based emergency systems triggered by assistive devices and body area networks. To guarantee that anyone can benefit from emergency systems, it is essential to enable embedded devices to trigger calls to emergency centers and support IP-based real time communication. To achieve this, the present paper extends SEEK framework (Andriopoulou et al., 2018), an embedded framework consisting of environmental, body sensors and a haptic device. SEEK framework enables elderly and disabled people who live independent to perform emergency calls. Sensors embedded in SEEK, aggregate environmental data and vital signs that monitor user's current health status 7and automatically trigger emergency calls when an emergency occurs, providing continuous real-time sensor data. The haptic device provides further modalities to the end user (disabled person or elderly) supporting audio, media and text communication with first responders and healthcare providers at emergency centers. A prototype implementation and initial results are presented as a proof of concept for deaf and speech impaired people enabling them to report emergency events and establish real time communication with first responders. The results depict that even lower capability hardware platforms may be used in order to minimize the cost and increase usability by minimizing power consumption of such an embedded framework.

IEEE Wireless Communications, 2016

With vehicle-to-vehicle and vehicle-to-infrastructure communications gaining momentum, immense op... more With vehicle-to-vehicle and vehicle-to-infrastructure communications gaining momentum, immense opportunities for developing a new application gamut open up. These range from applications targeting security/safety and efficient transportation to in-car entertainment enjoying multi-player mixed-reality games. The potential of VANETs has been recognized by standardization bodies and other stakeholders, including car manufacturers, that have established multiple consortia and initiatives to explore the capabilities of VANET technologies. From the communication technology perspective, the high speed at which nodes move in VANETs together with the adverse environmental conditions (rapidly changing surroundings, weather, etc.) present great challenges. These have attracted the interest of researchers who have sought to evaluate the performance of these systems, mostly paying attention to the lower layers of the protocol stack (physical and MAC). In this article, we explore the network architecture and protocol stack for supporting a broad range of infotainment applications in VANETs based on IEEE 802.11p and assess VANETs' capabilities to support networked multimedia. To this end, our evaluation focuses on application-layer performance for video streaming over a prototype system based on NEC's Linkbird-MX devices.

2015 European Conference on Networks and Communications (EuCNC), 2015

ABSTRACT The elastic optical networks paradigm offers a competitive solution in terms of resource... more ABSTRACT The elastic optical networks paradigm offers a competitive solution in terms of resource utilization to cope with the ever-increasing traffic demand. Specifically, the ability to make a number of previously fixed transmission parameters tunable, for example the data rate or channel spacing, requires an evolution of the node architecture. To fully benefit from elasticity, the data plane should evolve towards a software-defined architecture. In this paper, we report the work carried out in the ICT IDEALIST project and in particular the data plane solutions towards 1Tb/s optical networks with flexgrid and flex-rate technology. Flexibility requires changes in optical cross-connect, transponder as well as in the digital layer. The consortium builds pre-commercial experimental testbeds to validate the proposed building blocks and to analyze candidate applications.

Proceedings of the 19th Panhellenic Conference on Informatics, 2015

Sensors

Computing has undergone a significant transformation over the past two decades, shifting from a m... more Computing has undergone a significant transformation over the past two decades, shifting from a machine-based approach to a human-centric, virtually invisible service known as ubiquitous or pervasive computing. This change has been achieved by incorporating small embedded devices into a larger computational system, connected through networking and referred to as edge devices. When these devices are also connected to the Internet, they are generally named Internet-of-Thing (IoT) devices. Developing Machine Learning (ML) algorithms on these types of devices allows them to provide Artificial Intelligence (AI) inference functions such as computer vision, pattern recognition, etc. However, this capability is severely limited by the device’s resource scarcity. Embedded devices have limited computational and power resources available while they must maintain a high degree of autonomy. While there are several published studies that address the computational weakness of these small systems-m...

2022 IEEE Global Engineering Education Conference (EDUCON)

Lecture Notes in Computer Science, 2020

This paper presents a fuzzy logic model for Real-time Stress Detection (RSD) that allows continuo... more This paper presents a fuzzy logic model for Real-time Stress Detection (RSD) that allows continuous and in-depth evaluation of user’s stress in a straightforward and systematic way by using physiological data. The RSD model takes as input signals’ values (galvanic skin response, heart rate) and then generates the corresponding level for user’s stress (low, mid-low, mid-high and high). To this end, skin conductance and heart rate signals were used to determine the stress levels classes. Results showed that the proposed tool-based stress detection mechanism can support a systematic evaluation of user’s stress in real time. Given that stress is highly subjective and may largely depend both on context and user characteristics, such results are rather encouraging for such a challenging problem. From a UX evaluators’ perspective, a preliminary study, involving three HCI experts, investigated the usefulness of the proposed RSD mechanism and revealed that it can substantially decrease time and effort required to make sense of user testing data. Furthermore, practitioners reported that using RSD they could conduct a more in-depth analysis compared to their current practices.