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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2510.04744 |
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| _version_ | 1866914077419241472 |
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| author | Khan, Wali Ullah Sheemar, Chandan Kumar Lagunas, Eva Li, Xingwang Chatzinotas, Symeon Popovski, Petar Han, Zhu |
| author_facet | Khan, Wali Ullah Sheemar, Chandan Kumar Lagunas, Eva Li, Xingwang Chatzinotas, Symeon Popovski, Petar Han, Zhu |
| contents | In this work, we study a multi-user NTN in which a satellite serves as the primary network and a high-altitude platform station (HAPS) operates as the secondary network, acting as a cognitive radio. To reduce the cost, complexity, and power consumption of conventional antenna arrays, we equip the HAPS with a transmissive BD-RIS antenna front end. We then formulate a joint optimization problem for the BD-RIS phase response and the HAPS transmit power allocation under strict per-user interference temperature constraints. To tackle the resulting highly nonconvex problem, we propose an alternating-optimization framework: the power-allocation subproblem admits a closed-form, water-filling-type solution derived from the Karush-Kuhn-Tucker (KKT) conditions, while the BD-RIS configuration is refined via Riemannian manifold optimization. Simulation results show significant gains in data rate and interference suppression over diagonal RIS-assisted benchmarks, establishing BD-RIS as a promising enabler for future multilayer NTNs. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_04744 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Multilayer Non-Terrestrial Networks with Spectrum Access aided by Beyond-Diagonal RIS Khan, Wali Ullah Sheemar, Chandan Kumar Lagunas, Eva Li, Xingwang Chatzinotas, Symeon Popovski, Petar Han, Zhu Signal Processing In this work, we study a multi-user NTN in which a satellite serves as the primary network and a high-altitude platform station (HAPS) operates as the secondary network, acting as a cognitive radio. To reduce the cost, complexity, and power consumption of conventional antenna arrays, we equip the HAPS with a transmissive BD-RIS antenna front end. We then formulate a joint optimization problem for the BD-RIS phase response and the HAPS transmit power allocation under strict per-user interference temperature constraints. To tackle the resulting highly nonconvex problem, we propose an alternating-optimization framework: the power-allocation subproblem admits a closed-form, water-filling-type solution derived from the Karush-Kuhn-Tucker (KKT) conditions, while the BD-RIS configuration is refined via Riemannian manifold optimization. Simulation results show significant gains in data rate and interference suppression over diagonal RIS-assisted benchmarks, establishing BD-RIS as a promising enabler for future multilayer NTNs. |
| title | Multilayer Non-Terrestrial Networks with Spectrum Access aided by Beyond-Diagonal RIS |
| topic | Signal Processing |
| url | https://arxiv.org/abs/2510.04744 |