Multibeam satellite networks in Ka band have been designed to accommodate the increasing traffic demands of the coming years. However, these systems are spectrum limited due to the current spectrum allocation policies. This paper investigates the potentials of applying cognitive radio techniques in satellite communications in order to increase the spectrum opportunities for future generation of satellite networks without interfering operation of incumbent services. These extra spectrum

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... ties can potentially amount to 2.4 GHz of bandwidth in downlink, and to 2 GHz of bandwidth in uplink for high density fixed satellite services (HDFSS). 1-Introduction The Ka band is mainly considered by the SatCom industry for deployment of satellite high speed broadband networks in un-served and under-served areas. To determine the market demand for Ka band, recent R&D studies in Europe [1], [2], show the potential demand for satellite broadband services in rural areas in order to meet the objectives of the Digital Agenda for Europe, i.e. universal availability of broadband speeds of at least 30 Mb/s throughout Europe, with at least 50% of households having access to data rates above 100 Mb/s. Moreover, some studies conclude that the average number of total European households which choose a satellite broadband connection in 2020 is expected to be between 5 to 10 Million [2]. This represents a market potential for several satellite systems and creates the need to access extra spectrum, including the frequency bands shared with other services, in order to accommodate the increasing bandwidth and data rate demand [3] . It is foreseeable that spectrum congestions can make future Ka band deployments more difficult. High Throughput Satellites (HTS) already suffer from spectrum scarcity in Ka band in order to deliver meaningful performance. Only 500 MHz of exclusive Geostationary Satellite Orbit (GSO) incumbent spectrum is available in all ITU Regions for downlink. The access to a further 2.4 GHz of spectrum in Ka band as discussed in this paper, potentially allows satellite operators to meet the demand for HDFSS without prior individual frequency coordination. This in turn justifies the need to investigate cognitive radio (CR) techniques in the SatCom context, in order to allow exploitation of the shared frequency bands while guaranteeing acceptable interference to the incumbent users [3] . Another important aspect to be taken into account is the long-term and persistent interference from the terrestrial services which affects the core business of satellite operators. In this context, CR based solutions can provide relief as well as a measurable utilization and revenue increase to the SatCom business. Sina Maleki received his PhD from Delft University of Technology, Netherlands in 2013. He is currently a research associate in SnT, University of Luxembourg working on several national and international projects related to interference processing and cognitive radio for satellite communications. Symeon Chatzinotas is a Research Scientist in SnT, University of Luxembourg, managing H2020, ESA and FNR projects. He has authored more than 120 technical papers in international journals, conferences and scientific books. He is the co-recipient of the 2014 Distinguished Contributions to Satellite Communications Award by IEEE ComSoc. Barry Evans was until recently Director of the Centre for communications Research at Surrey and VP for research and Enterprise for the University. He has been involved in satellite communications for over 30 years and is Editor of the International Journal of Satellite communications and networks and author of the IET Press book on satellite communication systems. He has been involved in many recent EU and ESA funded satellite programmes and is on the steering Board of the European Engineering Technology platform and the European Network of satellite experts. Konstantinos Liolis holds the PhD and Dipl.-Eng. degrees from the National Technical University of Athens, Greece, and the MSc degree from the University of California at San Diego, USA. He is currently with SES TechCom SA, Luxembourg, working as Space Systems Engineer mainly on R&D projects. He has more than 40 publications in international journals, conferences and book chapters mainly in the Satellite Communications area. Joel Grotz currently works as senior engineer within the Technology Labs at Newtec Cy, Belgium. He graduated from the University of Karlsruhe and the Grenoble Institute of Technology in electrical engineering and holds a Ph.D. from the Royal Institute of Technology (KTH), Stockholm. He has previously worked at SES on projects related to satellite based internet access and broadcast systems as well as payload specification and testing.. Alessandro Vanelli-Coralli received the Dr. Ing. Degree and the Ph.D. from the University of Bologna (Italy) in 1991 and 1996, respectively. In 1996, he joined the University of Bologna, where he is currently an Associate Professor. He is an elected member of the Steering Board of the Networld European Technology Platforms, representing the SatCom R&D domain. He has been involved in several EU and ESA projects. Nicolas Chuberre works with Thales Alenia Space, Toulouse, France.