Today, satellite communications are the result of research in the field of communications, space and new technologies in shipping and trade, aiming to increase the coverage and manage the spectrum and the quality of services (QoS) with the lowest possible costs of implementation and maintenance. Apart from the research, satellite communications have also been part of the everyday life, as many applications that contribute to people’s everyday lives would be impossible to operate without them (e.g. positioning services that contribute to facilitating transport and navigation, or the weather forecast for emergency measures in adverse weather conditions). Satellite communications has also great contribution to telecommunication applications by providing global coverage and communication to anywhere on Earth, where there is no terrestrial network support.
Our research is focused to study, analysis and design of new efficient cooperative and resource management techniques for terrestrial mobile terminals, participating in an efficient hybrid terrestrial (5G) / satellite network, while making use of network coding schemes, proactive caching, multicast precoding techniques, as well as localization schemes.
The efficient combination of such competent communication schemes, will provide:
- increased coverage by one satellite
- reduction of the overall transmissions from the satellite, thus resulting in energy efficiency
- satellite and terrestrial network off-loading
- simultaneous transmission of different data types to multiple users with appropriate spectrum management techniques
- identification of external interference signals targeting to avoid intentional and unintentional interferers
We also deal with the following fields of research for satellite and terrestrial mobile communications:
- Narrowband Satellite IoT
- Hybrid Terrestrial/Satellite IoT Networks
- Cooperative satellite and terrestrial networks, relays, route diversity protocols, MIMO capacity evaluation, throughput and goodput calculations
- Radio Planning and Propagation Modeling: Static and long-term design (radio planning and dimensioning) of mobile, wireless and satellite networks, Cross-layer algorithms, Interference avoidance and mitigation techniques, Synergy of satellite and terrestrial wired and wireless networks, Quality of Service modeling and measurements
- Multiple access techniques such NOMA. Cooperation NOMA and Network Coding (NCMA scheme) in order to minimize latency/energy consumption and simultaneous provision of high throughput and QoS in hybrid Terrestrial/Satellite Networks
- Study and Development of Handover Techniques in Satellite Constellations exploiting advanced network coding technique
Also, the research team had developed a fully custom made simulator (MATLAB/C++) in orbital mechanics and communication link level and continue until now to maintain and update for research and development purposes:
The developed simulator:
- Predicts and performs real-time tracking of any space object that is in orbit around the Earth using Simplified Perturbations Models (SGP4 / SDP4)
- Calculates the propagation losses that occur in a satellite link in the various atmospheric layers of Earth using the ITU models.
- Calculates the Land Mobile Satellite channel losses using empirical and stochastic / statistical models, such as Loo, Corazza-Vatalaro, Karasawa, Lutz and Perez Fontan.
- Simulates the motion of satellite constellations, such as Iridium and Globalstar, as well as the performance (throughput, Bit Error Rate – BER) of the satellite link, both at physical and network layer.
- Gives results of the performance metrics of the satellite link (uplink, downlink) of the constellation’s satellites at physical and network layer.
Satellite MAnagement Resources Tool (SMART), European Space Agency (ESA), ARTES strategic programme line Space Systems for Safety and Security (4S) (2021-2022)
GreeCom is the enabler of the Hellenic government satellite communications infrastructure that connects the country’s decision centres and authorities with voice and data services, with the goal of seamless and uninterrupted service even in times of crisis. In this context, there is a clear requirement for secure, resilient and reliable satellite communications.
The SMART project targets the design, development, integration and operational verification of a holistic user and resource communication service manager platform. The SMART solution is envisioned as a web application tool, which enhances GreeCom resilience, performance and security with the following functionalities:
- Data network management and provisioning.
The system provides the basic set of services of an application-specific customer management platform. The specific module provides the service provisioning choices and packages, handles the demand requests, retains service profiles and health status, keeps the analytical history of the user, or administrator requests and responses, keeps service/user statistics and finally has the ability to generate relevant reports.
- Bandwidth/Capacity resource planning and allocation.
The specific SMART module handles bandwidth requests, i.e., the user requests contiguous spectrum segments and provides information about the equipment and intended use. The SMART platform will have the exact view of the available and occupied resources. The overall managed bandwidth will be divided into two allocation pools: the fixed and the dynamic pool. The fixed pool includes long term leases – where the service provider has limited automated reconfiguration capabilities. On the other hand, the dynamic pool will be managed with real-time frequency planning and assignment, i.e., each request will be authenticated, examined and verified in respect to the available user equipment and based on usage history, and finally, a properly selected spectrum segment will be dynamically allocated to the user.
- Spectrum and resource analysis using the Software Defined Radio (SDR) paradigm.
An SDR is a radio system that uses generic and simplified RF hardware, while the communication components that synthesize or analyse in the waveform are implemented exclusively on software – executed on embedded system and/or a conventional computer. In the SMART, SDR is used to implement a radio resource monitoring tool, in a time-frequency grid, that uses detection algorithms in order to: identify transmissions; classify them as licensed or unlicensed transmissions and estimate some signal features; and finally identify bandwidth segmentation, as well as monitor the resource utilization.
- Optimized resource scheduling and allocation.
This component evolves the SMART platform from a management software to an automated and optimized resource allocation engine. In this context, the user requests dedicated throughput instead of specific spectrum segment. The system, in real-time will estimate the performance and select the optimal bandwidth allocation strategy that covers the user requirements and optimizes the overall system spectrum efficiency.
- Automated ground segment control and monitoring
This element of SMART project will close the loop of automation and hereby create an agile and resilient system. The results of the optimized resource scheduling and allocation will be translated into a setting of the according ground station equipment. The equipment will be monitored and remotely controlled in order to adjust the device settings as it is required for a dynamic reallocation of resources.
- A study on the definition of use cases addressed by a future Greecom network expansion and the technical requirements for the expansion will run in parallel to the SMART project objectives.
Following the increasing demand for satellite communication and earth observation capabilities the interest in Low Earth Orbit solutions has increased. Being able to utilize its own constellation of LEO satellites Greece can acquire a significant advantage, as it becomes independent of acquiring such data from third party providers, as well as enabling the ability of using a specialized payload, designed from the ground up to serve the type of observations needed in the needed satellite overpass frequency.
The SMART platform will provide proper interfaces towards users as well as third party applications – in order to provide extendable and scalable features.
The SMART platform is expected to have major impact into the GreeCom ecosystem since:
- It develops new capabilities: With the use of efficient management, satellite resource allocation, monitoring and control of satellite communication capabilities, the achievement rate of the Governmental objectives will also increase. The efficient and reliable allocation of satellite resources at a national level is welcome by both military and civilian authorities – especially since it can effectively coordinate their co-existence. Furthermore, it will lead all the involved governmental stakeholders to consider new solutions to exploit the dynamically available satellite resources.
- It eliminates distrust by governmental authorities. The reluctance of the different Governmental entities to cooperate in shared efforts/resources programs could be overcome through a centralized architecture which will implement joint plans for investment, exploitation and allocation of resources. In this way the fragmentation of efforts could be minimized and goals could be more efficiently be achieved.
- It plays the role of the driver for future needs. The efficient monitoring of the allocated resources would be the driver of any future needs. The limitations that the current allocations impose to entities’ missions can help identify the requirements for furtherly expanding the current capabilities mitigating the current availability risks
- It provides an accurate record guiding and harmonizing new investments in the domain. The system keeps accurate history and records of requests, allocations, system exploitation and resource utilization. These reports could guide the actions for any new expenditure for satellite related equipment, either on the ground or in orbit, aligning any capital expenditure with the current national strategy.
- It creates new opportunities for beyond the national border’s cooperation. At an international level, a resilient, dynamic and, where possible, automated management framework allows two or more countries to use their allocation systems to jointly coordinate and share satellite resources, supporting each other in emergency (or not) situations. Joint resource management could be carried out with the exploitation of the SMART system that utilizes appropriate parameters and criteria based upon the situation in need.
- It supports the satellite communications as field and solution. Based on the GreeCom experience, the use of satellite resources can be enhanced through efforts mutually conducted by the various Governmental entities. In order to achieve that level of cooperation, technical means are required which will efficiently manage and monitor the satellite resources among the various stakeholders.
The final objective of SMART is the definition of use cases addressed by a future GreeCom expansion and the definition of the related technical requirements. The use case definition will be performed through the determination of users and stakeholders’ needs. The definition of scenarios of the high-level system architecture, the trade-off of satellite configuration, the spectrum requirements analysis within the limits imposed by the Radio Regulations and the identification of regulatory challenges are the main objectives to be reached towards the future GreeCom expansion design.
Development and Evolution of the GREEk Governmental Satcom (DEGREES), European Space Agency (ESA), ARTES strategic programme line Space Systems for Safety and Security (4S) (2021-2022)
The project aims at the development of a new service, a cyber-physical platform that enhances the security over satellite public safety networks utilizing intelligent algorithms for anomaly detection, timely incident identification/notification, and efficient data routing. DEGREES will introduce new services to support crisis management through a communication framework with reinforced security and increased reliability.
The DEGREES platform consists of four main high-level components:
- The GreeCom Security Information and Event Management (SIEM)
- The GreeCom Cloud
- The GreeCom Network orchestrator
- Satellite Network
The value of DEGREES solution is highlighted by considering a use case, where a set of satellite-enabled services is offered, i.e.:
- Static or mobile (UAV-supported) data/streams from conventional cameras,
- Static or mobile (UAV-supported) data/streams from hyperspectral cameras,
- Static or mobile (UAV-supported) data/streams from thermal cameras,
- Data/measurements from crossing sensors and detectors.
- Voice-video communication with the backend.
The set of services is offered for provision of enhanced situational awareness at a challenging and/or remote environment, more specifically for border monitoring and control, management of refugee flows, and respective rescue operations.
The data are gathered from the sources through wired or wireless connections at multiple portable satellite terminals deployed in the region of interest (the area of the incident) and forwarded to the system backend.
However, the described setup exposes a large attack surface to potential malicious users with the objective to undermine its operation or intercept data and communication. It should also be noted that the platform may operate in a hostile environment with many possible enemy actors in its proximity. More specifically, the cyber-attacks may compromise:
- Availability of the communication paths
- Integrity of transmitted data
- Integrity of processed data
- Confidentiality of transmitted data
- Assault system non-repudiation
DEGREES has the objective to introduce a service able to support the satellite platform in satisfying the aforementioned security requirements. The DEGREES platform treats three of the call objectives on the GreeCom Ground Segment, namely (and in priority order):
- Data routing and communication interface
- Public safety center for disaster management
National Strategic Reference Framework (NSRF), Education and Lifelong Learning
The success story of MIMO spans now for over a decade and has revolutionized all the aspects of wireless networks leading to its rapid embrace by the research community, standardization institutes and the industry. Application of MIMO technology to satellite and stratospheric communication systems have only recently begun to be investigated by academia and space agencies. The proposed research activity aims at shaping and enhancing the next generation fixed, mobile and hybrid satellite and stratospheric communication systems through MIMO techniques by contributing to both the theoretical and practical aspects of satellite technology. Another significant goal of the proposed activity is to create a Satellite Communications Network of Excellence in order to strengthen scientific and technological excellence on Satellite Communications (satcom) Technologies in Greece through the durable integration of the research capacities of the participants and having in view setting up in the long term a Hellenic Space Agency.
The research areas of the proposal are: a) Physical-Layer MIMO Techniques for next generation satcom and stratospheric systems, b) Multi-antenna terminal design for next generation satcom and stratospheric systems, c) Satellite and stratospheric MIMO radiochannel measurement campaign, d) Satellite and stratospheric MIMO radiochannel modeling, e) Satellite Communications and Stratospheric MIMO end-to-end system simulator and f) Various scenario applications including deep space communications and earth observation links. The expected results are: numerous contributions to standardization institutes (European Telecommunication Standardization Institute (ETSI), International Telecommunication Union-Radio (ITU-R), Digital Video Broadcasting (DVB)), scientific actions (COST), cooperation with European Space agencies (European Space Agency (ESA), German Aerospace Research Center (DLR), French Space Agency (CNES), French Aerospace Laboratory (ONERA), Italian Space Agency (ASI) etc) and numerous publications in the most prestigious Journals (IEEE) and Conferences relevant to Satellite and Wireless Communications and generally to Digital Communications.
- Derivation of a plethora of valuable results for the design of next generation fixed, mobile and hybrid satellite and stratospheric communication systems.
- Novel physical layer techniques for increasing capacity (multiplexing gain) and performance (coding and diversity gain).
- Development of efficient multiantenna terminal design methods.
- Conduct a state-of-the art MIMO radiochannel measurement campaign for various propagation scenarios.
- Novel realistic end-to-end system simulators with reference to recent satellite and industrial standards (e.g. DVB-S2, DVB-SH, DVB-RCS, DVB-NGH).
- A bulk of contributions to standardization institutes (ETSI, ITU-R, DVB), scientific actions (COST) is envisaged. International cooperation with European space agencies (ESA, DLR, CNES, ONERA etc).
- A series of research articles published in the most prestigious Journals and Conferences relevant to Satellite Communications and Digital Communications.
- Create and making of a critical mass of resources and expertise in order to set up a Network of Excellence and in Satellite Communications in Greece and, in the long term, creating a Hellenic Space Agency.
High Altitude Platforms for Communications and Other Services
COST297 – ‘HAPCOS’ was a European Action – now completed – dealing with HAPs and their applications. Representing an active group of researchers from academia, industry and governments, it has aimed to catalyse research activity, and to provide cohesion among the community. We included members from 20 European countries, and engaged active participation from across the world
Broadband Access Satellite Enabled Education
The overall objective of the BASE2 (Broadband Access Satellite Enabled Education) project is the implementation of an end-to-end system for tele-education applications, integrating broadband terrestrial networks with satellite broadband technologies. Aim of the project is to facilitate the sustainable provision of integrated tele- education services and applications to a large number of distributed interconnected sites over a variety of telecommunication infrastructures and the investigation of the seamless integration of low-cost satellite telecommunications infrastructures with broadband terrestrial systems. The project will integrate satellite communication technologies with various terrestrial network infrastructures. An integrated end-to-end system will be implemented in order to provide tele-education services to remote, distributed and isolated rural areas and maritime userswhere satellitecommunication technologieshave apotential edgeoverterrestrial infrastructures. Both oftheseuser groupsaretypical examplesof economicsectorsand activitiesthatcan benefitgreatlyby a wider deployment and use of satellite communications essentially due to the usually large distances which separate them from broadband terrestrial telecom infrastructures.
Mobile Application and Services based on Terrestrial and Satellite Interworking
The European satellite community is proceeding with great thrust towards the development of the innovative Satellite Digital Multimedia Broadcast (SDMB) concept, which will pave the way for an effective Satellite and Terrestrial network convergence. The SDMB system aims at complementing mobile networks with broadcast and multicast capabilities for a spectrum effective delivery of multimedia services on mobile devices. Taking advantage of the natural assets of satellite systems and of the full interoperability with terrestrial standards, the SDMB system will facilitate the successful deployment of UMTS, minimise geographical discrimination and foster multimedia usage adoption inEurope, effectively bridging the digital divide. Numerous studies, lead by the European Commission (e.g. MODIS, SATIN and RELY IST FP5 projects), the European Space Agency and National space agencies have contributed to the emergence of the SDMB concept, to secure the overall feasibility of the proposed innovations, to improve regulatory opportunities and to assess the market benefits.
Starting from this strong European knowledge base, the MAESTRO Integrated Project will proceed to specify, implement and validate the critical features of an SDMB system architecture. It aims at the highest possible degree of interoperability with terrestrial infrastructures with the objective to maximise its competitive assets and the underlying business rationale. Based on a solid consortium that achieves a balanced participation of terrestrial and satellite actors, the MAESTRO project will contribute to ensure wider adoption, broader availability of 3G and beyond 3G applications and services. In this perspective, MAESTRO is a unique opportunity for satellite communications to assure their role in the Generalised Access Network infrastructure, to foster the growth of the eEconomy and to improve European citizens welfare and safety.
Satellite UMTS IP Based Network
Project SATIN aims to investigate several new Satellite UMTS architectures that provide a range of new and complimentary packet based services to the terrestrial component of the UMTS. SATIN provides a fresh view as to the role of satellites within the overall UMTS design by focusing attention of using the satellite component as an effective and efficient access network for delivery of a wide range of packet-based and point-to-multipoint services. Based on the above architecture, SATIN will produce an optimised layer-1 and layer-2 design with full integration into the terrestrial UMTS core network in mind.
Integrated Satellite UMTS Real Environment Demonstrator
The main objective of the Integrated Satellite UMTS Real Environment Demonstrator (INSURED) project is to demonstrate Satellite-UMTS (S-UMTS) services and functionality in the context of a S-UMTS system demonstrator involving real first generation mobile Low Earth Orbit (LEO) satellites and Personal Communication Systems (PCS).
Collaboration with Laboratory of Informatics and New Technologies in Shipping, Transport and Insular Development (LINTSTID) of the Department Shipping Trade and Transport of the University of the Aegean. Study and Development of pico/nano/cube satellite. Advanced Space Systems Design and Management with the cooperation of the Lamdasat group.
Future R&D Directions
- Cooperative satellite and terrestrial networks, relays, route diversity protocols, MIMO capacity evaluation, throughput and goodput calculations
- Channel characterization, propagation models and performance modeling of wireless systems
- Static and long-term design (radio planning and dimensioning) of mobile, wireless and satellite networks, Cross-layer algorithms, Interference avoidance and mitigation techniques, Synergy of satellite and terrestrial wired and wireless networks, Quality of Service modeling and measurements
- Satellite communication systems and localization
- Study and Development of pico/nano/cube satellite. Advanced Space Systems Design and Management with the cooperation of the Lamdasat group http://lambdasat.com
- Study and Development of Handover Techniques in Satellite Constellations exploiting advanced network coding technique
- Orbital Mechanics: Simulator development using SGP4/SDP4 perturbations models to predict the orbit of a near earth or deep space satellite. Research based on C++/Matlab Simulator
- Satellite Channel Modeling and Propagation Impairments: study and analysis of new channel models in E-Band (mmWave)
- L. Tsipi, M. Karavolos, D. Vouyioukas, An Unsupervised Machine Learning Approach for UAV-Aided Offloading of 5G Cellular Networks, Telecom, Vol. 3, pp. 86-102, 2022, MDPI, https://doi.org/10.3390/telecom3010005.
- M. Karavolos, N. Nomikos, D. Vouyioukas, P. Mathiopoulos, HST-NNC: A Novel Hybrid Satellite-Terrestrial Communication with NOMA and Network Coding Systems, Open Journal of the Communications Society, Vol. 2, pp. 887-898, 2021, IEEE, https://doi.org/10.1109/OJCOMS.2021.3072110.
- M. Karavolos, N. Nomikos, D. Vouyioukas, Enhanced Integrated Satellite–Terrestrial NOMA with Cooperative Device-to-Device Communication, Telecom, 2020, MDPI, https://doi.org/10.3390/telecom1020010.
DIRECTOR – PROFESSOR
Mobile and Satellite Communication Systems
Dr Demosthenes Vouyioukas received the five-year Diploma in Electrical and Computer Engineering from the National Technical University of Athens (NTUA), and the Ph.D. degree in Electrical and Computer Engineering from NTUA, in 1996 and 2003 respectively. He has also received a Joint Engineering-Economics M.Sc. from NTUA. From 1996 to 2003 he has been a scientific researcher, and from 2003 to 2005 he was a senior researcher at the Mobile Radiocommunications Laboratory of NTUA, where he has been engaged to several European and National Projects. From 2005 to 2006, he was with the Hellenic Aerospace Industry at the Department of Satellite Communications. Ηe is currently Professor and Director of the Computer and Communication Systems Laboratory in the Department of Information and Communication Systems Engineering, University of the Aegean, Greece, where he served as an adjunct lecturer (2004-2010), an Assistant Professor (2010-2016) and an Associate Professor (2016-2020). He also serves as a scientific coordinator in several R&D projects.
Mobile and Wireless Communications
Nikolaos Nomikos received the Diploma in Electrical Engineering and Computer Technology from the University of Patras in 2009 and the MSc and Ph.D. from the Information and Communication Systems Engineering Department (ICSΕD) of the University of the Aegean in 2011 and 2014, respectively. Currently, he is a post-doctoral researcher at ICSED and a member of ICSΕD’s Computer and Communication Systems Laboratory (CCSL). He is a member of the Technical Chamber of Greece, IEEE and IEEE Communications Society (ComSoc). His research interest is focused on 5G opportunistic mobile networks, cooperative communications, buffer-aided networks and non-orthogonal multiple access.
Terrestrial/Satellite 5G Networks
Michail Karavolos was born in Athens, Greece in 1993. He received his Diploma from the Department of Information and Communication Systems Engineering, Technical School of the University of the Aegean in 2017. As an undergraduate student, he received awards for excellent grades, by the State Scholarships Foundation of Greece. Also, he involved in Robotics, Algorithms, Network Security, Software Design and Digital Systems Design with special emphasis on Mobile and Satellite Communications during his undergraduate studies. He was a member of the Robotics team of the University of the Aegean and he has participated in the International Robotics Competition held in Istanbul, Turkey in April 2014, 8th ITU Robot Olympics (ITURO2014). In addition, he participated in the research program Thales of the University of Patras entitled “Algorithmic Game Theory”. He has also worked in projects like website construction (Web Development) and Database Design on behalf of International Society. Furthermore, he has been involved in the design and construction of the UOA/Mythpelsat satellite and is still an active member of the UOA/Mythpelsat team. Currently, he is a PhD Candidate at the Computer and Communication Systems Laboratory (CCSL) of the Department of Information and Communication Systems Engineering of the University of the Aegean. His research interests are in the field of Satellite and Mobile Communications (5G, LTE).