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Paper Abstract and Keywords
Presentation 2025-11-14 11:40
SVD-Based Optimization of Steered Null Directions for Aerial-Terrestrial Spectrum Sharing
Tsutomu Ishikawa, Koji Tashiro, Koichi Maki, Kenji Hoshino (SoftBank) RCS2025-177
Abstract (in Japanese) (See Japanese page) 
(in English) Aerial communication using platforms (PFs) such as balloons and aircraft has attracted attention as a means to provide connectivity in regions where terrestrial infrastructure deployment is difficult or during disaster recovery. An aerial PF can cover a wide area with a single station owing to its line-of-sight advantage and is expected to complement and extend terrestrial networks. However, when an aerial PF shares the same frequency band with terrestrial base stations (BSs), interference suppression becomes essential. Conventional nullforming consumes the antenna degrees of freedom in the directions for suppressing interference from the aerial PF to the ground. As a result, the beamforming gain for aerial PF users decreases, causing coverage degradation in densely deployed terrestrial BS environments. This paper proposes an optimization method that performs nullforming only toward dominant interference directions based on the singular value decomposition (SVD) of the channel matrix between the aerial PF and terrestrial base stations (BSs). Simulation results demonstrate that the proposed method maintains the total capacity of aerial--terrestrial networks while expanding aerial coverage by approximately 16% compared with the conventional method.
Keyword (in Japanese) (See Japanese page) 
(in English) aerial platform / HAPS / spectrum sharing / MU-MIMO / nullforming / / /  
Reference Info. IEICE Tech. Rep., vol. 125, no. 242, RCS2025-177, pp. 169-174, Nov. 2025.
Paper # RCS2025-177 
Date of Issue 2025-11-05 (RCS) 
ISSN Online edition: ISSN 2432-6380
Copyright
and
reproduction		 All rights are reserved and no part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Notwithstanding, instructors are permitted to photocopy isolated articles for noncommercial classroom use without fee. (License No.: 10GA0019/12GB0052/13GB0056/17GB0034/18GB0034)
Download PDF RCS2025-177

Conference Information
Committee AP RCS  
Conference Date 2025-11-12 - 2025-11-14 
Place (in Japanese) (See Japanese page) 
Place (in English) Ehime Prefectural Convention Hall 
Topics (in Japanese) (See Japanese page) 
Topics (in English) Adaptive Antenna, Equalization, Interference Canceler, MIMO, Wireless Communications, etc. 
Paper Information
Registration To RCS 
Conference Code 2025-11-AP-RCS 
Language Japanese 
Title (in Japanese) (See Japanese page) 
Sub Title (in Japanese) (See Japanese page) 
Title (in English) SVD-Based Optimization of Steered Null Directions for Aerial-Terrestrial Spectrum Sharing 
Sub Title (in English)  
Keyword(1) aerial platform  
Keyword(2) HAPS  
Keyword(3) spectrum sharing  
Keyword(4) MU-MIMO  
Keyword(5) nullforming  
Keyword(6)  
Keyword(7)  
Keyword(8)  
1st Author's Name Tsutomu Ishikawa  
1st Author's Affiliation SoftBank Corp. (SoftBank)
2nd Author's Name Koji Tashiro  
2nd Author's Affiliation SoftBank Corp. (SoftBank)
3rd Author's Name Koichi Maki  
3rd Author's Affiliation SoftBank Corp. (SoftBank)
4th Author's Name Kenji Hoshino  
4th Author's Affiliation SoftBank Corp. (SoftBank)
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Speaker Author-1 
Date Time 2025-11-14 11:40:00 
Presentation Time 20 minutes 
Registration for RCS 
Paper # RCS2025-177 
Volume (vol) vol.125 
Number (no) no.242 
Page pp.169-174 
#Pages 6 
Date of Issue 2025-11-05 (RCS) 

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