WOS5 – Wireless, Optical and Satellite Networks
Friday, 5 June 2026, 9:00-10:30, room Sala 5 (1st floor)
Session Chair: Delia Rico (Univ. Malaga, ES)
Unified Evaluation of Positioning Measurements in LEO-HAPS-BS Networks Under Doppler Effects
Lu Bai and Sharief Saleh (Chalmers University of Technology, Sweden); Hongzhao Zheng (Carleton University, Canada); Musa Furkan Keskin (Chalmers University of Technology, Sweden); Mohamed Atia (Carleton University & Queen’s University, Canada); Halim Yanikomeroglu (Carleton University, Canada); Henk Wymeersch (Chalmers University of Technology, Sweden)
Non-terrestrial 6G networks combining low earth orbit (LEO) satellites, high-altitude platform stations (HAPS), and terrestrial base stations (BS) promise high-precision positioning, but fair cross-tier benchmarking remains difficult under UE synchronization offsets and platform-dependent Doppler. We develop a unified discrete-time observation model for all three links, explicitly capturing both slow- and fast-time Doppler. To mitigate angle-of-departure (AoD)-Doppler coupling in multipath beam-sweeping, we apply a repetitive precoding phase profile that separates Doppler-induced frequency shifts from angular parameters. Using a common geometric environment with representative system settings, simulations quantify delay, Doppler, and AoD estimation accuracy. Results identify the excess transmit-power regime, precoding strategy, and Doppler prior quality as dominant performance drivers.
High-Performance Time-Modulated Array for User Terminal to LEO Satellite Communications
Gebrehiwet Gebrekrstos Lema, Eva Lagunas and Bhavani Shankar Mysore R (University of Luxembourg, Luxembourg); Joel Grotz (SES, Luxembourg)
Phased arrays offer high gain for User Terminals (UTs) in Non-Terrestrial Networks (NTNs), but they suffer from prohibitive costs and complexity. Recently, Time-Modulated Arrays (TMAs) have been proposed as a low-complexity alternative; however, they face challenges with harmonic control and limitations in gain and bandwidth. Motivated by the LEO satellite direct-to-UT scenario and the need for the mass deployment of low-cost UTs, this work presents a low-complexity, high-gain, wideband TMA for UTs. We study multilevel switching TMA, aiming to enhance both gain and effective bandwidth while minimizing complexity. We design a discrete sinusoidal multilevel switching integrated with a Quadrature Time-Delay (QTD) feeding network to maintain continuous element activation and focus power on the main beam. Further, we introduce an exponential multilevel switching and optimize it to enhance gain. The sinusoidal fit offers superior spectral purity, and the exponential fit provides better gain. The proposed TMA offers a low-cost, low-complexity antenna solution, with only a 1.5 dB gain deficit compared to an equivalent phased array, which is promising for emerging UTs.
Constellation Management for Inter-Satellite Link Scheduling in NB-IoT Non-Terrestrial Networks
Arnau Singla (i2CAT Foundation, Spain & Universitat Politècnica de Catalunya, Spain); Anna Calveras (Universidad Politecnica de Catalunya (UPC), Spain); Juan A. Fraire (Inria/INSA Lyon & CONICET, National University of Córdoba, France); Joan Adria Ruiz-de-Azua (Universitat Politècnica de Catalunya (UPC), Spain & Space Communications Research Group, i2CAT Foundation, Spain)
Inter-Satellite Links (ISL) can improve data delivery in Low Earth Orbit (LEO) constellations by enabling relay paths when direct satellite-to-ground contacts are unavailable. However, ISL transmissions are operational tasks that consume satellite resources and affect scheduling constraints, aspects typically abstracted away in network-centric routing approaches. This paper extends our previous work, the Constellation Management System (CMS) framework, to incorporate ISL as schedulable tasks within its multi-objective optimization, jointly considering satellite operational constraints and network service metrics. We present the mathematical formulation of two ISL task types for Mobile Originated and Mobile Terminated data relay, including constraint extensions for dual-satellite memory tracking, data availability enforcement across relay chains, and end-to-end latency computation through recursive path chasing. A configurable hop limit parameter enables operators to control the trade-off between scheduling flexibility and computational complexity. Validation with a 6-satellite polar constellation demonstrates throughput improvements of up to 23% with ISL enabled, while quantifying the associated reduction in optimization speed up to 70% at two-hop configurations.
RF-Emulated TN-NTN Testbed for Service Continuity in Emergency Communications
Arnau Singla (i2CAT Foundation, Spain & Universitat Politècnica de Catalunya, Spain); Roger Pueyo Centelles (Fundació i2CAT, Spain); Anna Calveras (Universidad Politecnica de Catalunya (UPC), Spain); Juan A. Fraire (Inria/INSA Lyon & CONICET, National University of Córdoba, France); Joan Adria Ruiz-de-Azua (Universitat Politècnica de Catalunya (UPC), Spain & Space Communications Research Group, i2CAT Foundation, Spain)
The integration of non-terrestrial networks (NTN) with terrestrial infrastructure is fundamental to the sixth-generation (6G) vision of ubiquitous connectivity. However, validating hybrid terrestrial-NTN systems requires realistic testbeds that capture RF propagation effects and timing synchronization challenges beyond IP-level simulation capabilities. This paper presents a federated RF-emulated testbed for integrated network validation, using OpenAirInterface 5G NR, software-defined radios, and both open-source (GNU Radio) and commercial (Keysight PropSim) channel emulators. The geographically distributed architecture spans i2CAT Foundation and Gradiant research centers, enabling collaborative experimentation. We implement and validate two application-layer handover mechanisms for an emergency response use case in which a rescue vehicle transitions between terrestrial and geostationary satellite coverage. Experimental results demonstrate that GNU Radio achieves partial 5G NR attach while PropSim enables complete attach with bidirectional data transfer, identifying timing synchronization as the critical technical challenge. Results achieve 100% handover success with complete service continuity, confirming that position reporting services successfully operate with GEO satellite latency (300 ms approx.). This work provides a reference implementation and validation methodology for the NTN research community, demonstrating the feasibility of integrated terrestrial-satellite systems for emergency communications.
FLEXSCALE Flexible Multi-Band Optical Networking in Support of Distributed Re-Training of Generative AI Models
Matin Rafiei Forooshani (Amirkabir University of Technology (Tehran Polytechnic), Iran); Farhad Arpanaei and David Larrabeiti (Universidad Carlos III de Madrid, Spain); Hamzeh Beyranvand (Amirkabir University of Technology, Iran); José Manuel Rivas-Moscoso (Telefónica Innovación Digital, Spain); Juan Pedro Fernández-Palacios (Telefónica I+D, Spain); Varsha Lohani and Raul Muñoz (Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Spain); Ramon Casellas (Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Spain); Charalampos G Papapavlou, Christos Christofidis and Ioannis Tomkos (University of Patras, Greece)
The emergence of distributed Generative AI (GenAI) necessitates a paradigm shift in optical transport to accommodate periodic, massive “elephant flows” between edge GPU clusters and core “Giga-scale AI Super-factories”. Traditional ROADMs based on single-granular Wavelength Selective Switches (WSS) face significant scaling and SWaP-C limitations when handling such high-intensity workloads across Ultra-Wideband (UWB) and Space Division Multiplexing (SDM) layers. This work evaluates the performance of the FlexSCALE Multi-Granular Optical Node (MG-ON)-a three-layered hierarchical architecture capable of switching at fiber, flexible waveband, and wavelength granularities-specifically for distributed GenAI re-training. Utilizing Photonic Integrated Circuit (PIC)-based flexible WaveBand-Selective Switches (WBSS), the architecture targets a net node throughput of 10 Pb/s. Our simulation results demonstrate that the multi-granular approach significantly outperforms legacy single-granular WSS architectures by substantially reducing total network cost and the number of required switching components. By routing AI-driven data bursts as coarse-grained wavebands, we maintain the Generalized Signal-to-Noise Ratio (GSNR) required for high-capacity transmission while enabling the millisecond-level latency vital for AI model synchronization. These findings validate multi-granular, multi-band networking as a critical enabler for the 6G-era AI infrastructure.
