WOS1 – Advancements in Satellite-Aided Communications and Integrated Network Architectures for Next-Generation Telecommunications

Tuesday, 4 June 2024, 11:00-13:00, room Galapagos

Session Chair: Vasilis Maglogiannis (Ghent University – imec & IDLab Research Group, BE)

Feasibility Study of Function Splits in RAN Architectures with LEO Satellites
Siva Satya Sri Ganesh Seeram (KTH Royal Institute of Technology, Sweden); Luca Feltrin (Ericsson Research, Sweden); Mustafa Ozger, Shuai Zhang and Cicek Cavdar (KTH Royal Institute of Technology, Sweden)
This paper explores the evolution of Radio Access Network (RAN) architectures and their integration into Non-Terrestrial Networks (NTN) to address escalating mobile traffic demands. Focusing on Low Earth Orbit (LEO) satellites as key components of NTN, we examine the feasibility of RAN function splits (FSs) in terms of fronthaul (FH) latency, elevation angle, and bandwidth (BW) across LEO satellites and ground stations (GS), alongside evaluating performance of Conditional Handover (CHO) procedures under diverse scenarios. By assessing performance metrics such as handover duration, disconnection time, and control traffic volume, we provide insights on several aspects such as stringent constraints for Low Layer Splits (LLSs), leading to longer delays during mobility procedures and increased control traffic across the feeder link in comparison with the case when gNodeB is onboard satellite. Despite challenges, LLSs demonstrate minimal onboard satellite computational requirements, promising reduced power consumption and payload weight. These findings underscore the architectural possibilities and challenges within the telecommunications industry, paving the way for future advancements in NTN RAN design and operation.

Measuring Service Continuity in Integrated TN/NTN for 5G-Advanced and 6G
Fanny Parzysz (Orange Labs, France); Alessandro Guidotti and Alessandro Vanelli-Coralli (University of Bologna, Italy)
Service continuity has been defined in 3GPP TS 22.261 as the “uninterrupted user experience of a service that is using an active communication when a UE undergoes an access change without, as far as possible, the user noticing the change”. Such definition remains open and cannot be used to compare the many architecture and business options that can be envisaged to deploy and operate 3D networks. In this paper, we propose a generic three-phased approach, with KPIs, to quantify the seamless performance of TN / NTN switching. We also discuss the purpose, applicability and order of magnitude of each KPI, based on concrete architecture examples.

Deep Learning-Based Forward-Aware Quantization for Satellite-Aided Communications via Information Bottleneck Method
Matthias Hummert, Shayan Hassanpour, Dirk Wübben and Armin Dekorsy (University of Bremen, Germany)
We consider a two-hop transmission setup in the context of Non-Terrestrial Networks (NTNs). Explicitly, a noisy source signal should be compressed at an on-ground relay node before getting forwarded over an error-prone and rate-limited channel to a satellite transponder. The impacts of this imperfect forwarding should be integrated into the compressor’s design formulation. In full harmony with the Information Bottleneck (IB) principle, we choose the Mutual Information (MI) as the fidelity criterion and devise a data-driven algorithm, the Deep Forward-Aware Vector Information Bottleneck (Deep FAVIB), to tackle the design problem, when solely a finite sample set is available. To this end, first we derive a tractable objective function and, later on, utilize it to train the encoder and decoder Deep Neural Networks (DNNs) in the introduced learning architecture. Our approach here, that is based on (generative) latent variable models, extends the well-known concepts of Variational Auto-Encoders (VAEs) and Deep Variational Information Bottleneck (Deep VIB) from remote source coding to joint source-channel coding. To corroborate the effectiveness of our data-driven approach, we also present several numerical results over a typical transmission scenario for NTNs.

A Case Study of an Hybrid RF and Optical Inter-Satellite Link Terminal to Enhance Optical Pointing
Elena Fernández Niño (I2CAT Foundation, Spain); Juan Fraire (Inria/INSA Lyon & CONICET, National University of Córdoba, Argentina); Sergi Figuerola (Chief Technology and Innovation Officer, i2CAT Foundationi, Spain); Adriano Camps (UPC BarcelonaTech, Spain); Joan Adria Ruiz-de-Azua (i2CAT Foundation, Spain)
The attitude determination and control system of a satellite plays a crucial role, especially in optical communication systems due to the narrow field-of-view of the laser. In the last years, the space ecosystem has shown a large interest in optical technology due to its high speed, reduced size, weight, and power, and reliable communications link. However, its narrow field-of-view puts some challenges in terms of connectivity. For this reason, an optical terminal requires a pointing, acquisition, and tracking system to establish the link. This work proposes the use of a dual-plane communications system in which optics and low throughput radiofrequency technologies are combined in a single module. This hybrid system leverages on the quasi-omnidirectional ability of the radiofrequency antennas to enhance the optical pointing system. The improvement is evaluated by means of a simulator that includes the dynamic pointing between two spacecrafts. Results demonstrate that the designed hybrid system can heavily reduce the pointing error.

SatNet SpaceSim: A Platform for Performance Analysis of Small Satellites Mega-Constellations
Hamzeh Abu Qamar, Khaled Mohammed, Ruhul Amin Khalil and Nasir Saeed (United Arab Emirates University, United Arab Emirates)
The emergence of small satellites is crucial in the dynamic domain of space networks, enabling cost-effective networks for diverse applications such as monitoring, surveillance, and data rely in space. The upcoming Emirati Interplanetary Mission in 2028 emphasizes the importance of well-designed mega-constellations of small satellites to ensure coverage in remote and challenging terrains. Nevertheless, establishing such localized systems involves substantial financial demands and intricate technical challenges. To tackle these obstacles, this paper introduces SatNet SpaceSim, a simulator developed to analyze the performance of communication links and coverage of small satellite constellations before deployment. This emulation aims to detect and address potential issues proactively, reducing the risk of costly satellite malfunctions. The proposed SatNet SpaceSim offers comprehensive performance analysis through diverse simulations. Moreover, a graphical user interface (GUI) has been devised for SatNet SpaceSim, integrating requisite calculations to assess links based on parameters such as received power and signal-to-noise ratio. Furthermore, we provide extensive simulations for various constellations to demonstrate dynamic orbital maneuverability and coverage analysis, presenting a cost-effective avenue for thorough performance evaluations. Our proposed SatNet SpaceSim platform has the potential to reduce production expenses and improve the efficiency of regional small satellite constellations.

Location-Based User Scheduling through Graph Coloring for Cell-Free MIMO NTN Systems
Daniel Gaetano Riviello (Politecnico di Torino & National Inter-University Consortium for Telecommunications (CNIT), Italy); Bruno De Filippo, Bilal Ahmad, Alessandro Guidotti and Alessandro Vanelli-Coralli (University of Bologna, Italy)
Non-Terrestrial Networks (NTN) have recently grown in popularity, with Low Earth Orbit (LEO) mega-constellations delivering broadband services to households worldwide. Under the cell-free MIMO paradigm in full frequency reuse systems, meeting the increasing traffic demand requires complex scheduling and digital beamforming algorithms to minimize the excessive co-channel interference. In this paper, we present a user scheduling algorithm for LEO-based B5G NTNs with reduced computational complexity that does not require knowledge of downlink (DL) Channel State Information (CSI). In our proposed method, we perform user grouping by first solving the Minimum Clique Cover (MCC) problem on an inter-user distance adjacency matrix, avoiding the need for DL pilots for CSI estimation. We approach MCC as a graph coloring task on the complementary graph, using the DSatur algorithm to minimize the computational complexity of the scheduler. Users within the same group are served via space-division multiplexing by means of feed space digital beamforming, inferring the users’ channel vectors from their position. System-level analysis show that the proposed algorithm, named Distance-based MCC DSatur (D-MCC-DSatur), achieves a per-cluster sum-rate capacity gain of up to 1.8% with respect to the distance-based Multiple Antenna Downlink User Scheduling (D-MADOC) algorithm.

Noise Analysis of Chirped Sinh-Gaussian Beams in Free Space Optical Links
Mert Bayraktar (University of Luxembourg, Luxembourg); Victor Monzon Baeza (University Oberta Catalunya – Sateliot, Spain); Juan Duncan and Symeon Chatzinotas (University of Luxembourg, Luxembourg)
Bandwidth requirements have been increasing daily since the number of users and the data size have increased rapidly. Due to this high demand, it is foreseen that optical wireless communication (OWC) systems will play a crucial role in 6G systems. Accordingly, we studied the scintillation of chirped beams in a turbulent atmosphere for the first time in literature. For this purpose, we selected chirped sinh-Gaussian (CSG) beam at the transmitter of the free space optics (FSO) system. We modeled the atmosphere using the split-step approach to generate atmospheric turbulence in the software environment and compute the received field in wave optics. We computed the most dominant noise in FSO systems and bit error rate (BER). We observed that chirped factor reduces scintillation noise and BER significantly. According to the results, the pointlike scintillation of chirped beams is significantly less than the beam without chirped factor. Considering the scintillation of CSG beam with a large Gaussian source size, chirped factor mitigates approximately half of the scintillation. This result reflects BER and it reduces by a significant amount. In light of our results, we expect that chirped beams could be a good alternative to increase FSO performance in 6G systems.

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