WOS1 – Non-terrestrial networks

Wednesday, 7 June 2023, 16:00-17:30, Room J2

Session Chair: Daniel Gaetano Riviello (University of Bologna, Italy)

Multi-Criteria Ground Segment Dimensioning for Non-Geostationary Satellite Constellations
Victor Monzon Baeza, Flor Ortiz, Eva Lagunas, Tedros Salih Abdu and Symeon Chatzinotas (University of Luxembourg, Luxembourg)
Non-Geostationary Orbit (NGSO) satellite constellations are becoming increasingly popular as an alternative to terrestrial networks to deliver ubiquitous broadband services. With satellites travelling at high speeds in low altitudes, a more complex ground segment composed of multiple ground stations is required. Determining the appropriate number and geographical location of such ground stations is a challenging problem. In this paper, we propose a ground segment dimensioning technique that takes into account multiple factors such as rain attenuation, elevation angle, visibility, and geographical constraints as well as user traffic demands. In particular, we propose a methodology to merge all constraints into a single map-grid, which is later used to determine both the number and the location of the ground stations. We present a detailed analysis for a particular constellation combining multiple criteria whose results can serve as benchmarks for future optimization algorithms.

Inter-Satellite Link Prediction for Non-Terrestrial Networks Using Supervised Learning
Estel Ferrer Torres (i2CAT Foundation, Spain); Josep Escrig (I2CAT Foundation, Spain); Joan Adria Ruiz-de-Azua (i2CAT Foundation, Spain)
Distributed Space Systems (DSS) are becoming increasingly popular in the space industry as they integrate advancements in 6G and Non-Terrestrial Networks concepts to offer innovative and efficient solutions for satellite communication and data transmission. In those DSS where communication between heterogeneous satellites is required, achieving autonomous cooperation while minimizing energy consumption is crucial (especially in sparse constellations with nano-satellites). This work proposes an autonomous and scalable solution based on a Supervised Learning model that enables heterogeneous satellites in circular polar Low Earth Orbits to predict their encounters with other satellites given the orbital elements and assuming isotropic antenna patterns. The proposed solution obtains an accuracy of around 90 % when evaluated with realistic data from real Celestrak satellites. This work could be considered the
first stage of a promising and alternative approach in the field of DSS.

O-RAN Based Non-Terrestrial Networks: Trends and Challenges
Riccardo Campana (University of Bologna, Italy); Carla Amatetti (Alma Mater Studiorum University of Bologna, Italy); Alessandro Vanelli-Coralli (University of Bologna, Italy)
While 5G networks are already being deployed for commercial applications, Academia and industry are focusing their effort on the development and standardization of the next generations of mobile networks, i.e., 5G-Advance and 6G. Beyond 5G networks will revolutionize communications systems providing seamless connectivity, both in time and in space, to a unique ecosystem consisting of the convergence of the digital, physical, and human domains. In this scenario, Non-Terrestrial Networks (NTN) will play a crucial role by providing ubiquitous, secure, and resilient infrastructure fully integrated into the overall system. The NTN nodes will be organized into a MultiLayer Multi-dimensional (ML-MD) architecture. This ML-MD network will rely on the interoperability of very different network elements, enabled by the disaggregation and virtualization of network components, their interconnection by open standard interfaces and orchestrated by data-driven network Artificial Intelligence. This paradigm, which has been standardized by the O-RAN Alliance, is now being implemented in Terrestrial Networks (TNs) but has not been fully addressed in NTN, yet. Therefore, this paper aims at exploring the possible implementation of an NTN infrastructure based on the O-RAN approach. By starting with the review of the State of the Art of O-RAN in TNs and flying platforms, we identify a possible architecture solution for an O-RAN-based NTN system and we foresee the ORAN implementation trends that will increase the NTN system efficiency.

Graph-Based User Scheduling Algorithms for LEO-MIMO Non-Terrestrial Networks
Bilal Ahmad, Daniel Gaetano Riviello, Alessandro Guidotti and Alessandro Vanelli-Coralli (University of Bologna, Italy)
In this paper, we study the user scheduling problem in a Low Earth Orbit (LEO) Multi-User Multiple-InputMultiple-Output (MIMO) system. We propose an iterative graphbased maximum clique scheduling approach, in which users are grouped together based on a dissimilarity measure and served by the satellite via space-division multiple access (SDMA) by means of Minimum Mean Square Error (MMSE) digital beamforming on a cluster basis. User groups are then served in different time slots via time-division multiple access (TDMA). As dissimilarity measure, we consider both the channel coefficient of correlation and the users’ great circle distance. A heuristic optimization of the optimal cluster size is performed in order to maximize the system capacity. To further validate our analysis, we compare our proposed graph-based schedulers with the wellestablished algorithm known as Multiple Antenna Downlink Orthogonal clustering (MADOC). Results are presented in terms of achievable per-user capacity and show the superiority in performance of the proposed schedulers w.r.t. MADOC.

Proof of Concept for Spectrum Sharing Between Terrestrial and Satellite Networks
Heikki Kokkinen (Fairspectrum, Finland); Amina Piemontese (University of Parma, Italy); Arto Kivinen (Fairspectrum Ltd., Finland); Łukasz Kułacz (Poznan University of Technology, Poland); Nathan Borios (Thales Alenia Space, France); Carla Amatetti (Alma Mater Studiorum University of Bologna, Italy)
Satellite communication systems are fundamental components to deploy the future smart and sustainable networks and to achieve the ambitious goal of bringing wireless connectivity anywhere, anytime, at any device. In this new role, one of the main challenges that satellite communication component has to face is the maximization of the spectrum usage. 3GPP communication technologies are extended from Terrestrial Networks (TNs) to Non-Terrestrial Networks (NTNs), but so far the standardisation efforts have been focused on systems where TNs and NTNs operate in their dedicated frequency bands. In this paper, a dynamic spectrum sharing model between NTN elements, in a Non Geostationary orbit, and TN is proposed. A Proof of Concept (PoC) is developed, in order to carry out the interference protection computation. We show that the developed spectrum sharing model can enable spectrum sharing between NTN and TN when their coverage areas do not have to overlap, that the sharing arrangement increases significantly the service coverage in the frequency band and slightly improves the spectrum utilization efficiency. It is also shown that the spectrum management system is able to manage the interference level and to keep the interference-to-noise ratio at the TN user equipment below the specified limit. In fact, the aggregate interference caused by the sharing arrangement does not decrease the capacity of the TN downlink.

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