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Paper Abstract and Keywords
Presentation 2026-06-18 10:15
Investigation of PAPR Reduction Using Null Space in MIMO Channel for Beamforming-Aided Multi-Antenna AF Relay Transmission
Shunta Okuno (Tokyo Univ. of Science), Satoshi Suyama, Satoshi Nagata (NTT DOCOMO), Kenichi Higuchi (Tokyo Univ. of Science) RCS2026-52
Abstract (in Japanese) (See Japanese page) 
(in English) In multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) relay transmission, the high peak-to-average power ratio (PAPR) of OFDM signals increases the required input backoff at the power amplifiers of the base station (BS) and relay station (RS), resulting in degradation of power efficiency. In particular, when receive and transmit beamforming (BF) are applied at the RS, the RS transmit signal is transformed not only by the BS-RS channel but also by the RS BF matrices. Assuming the BF-aided AF relaying, we propose a PAPR reduction method for both the BS and RS transmitters based on signal processing at the BS, where data-signal BF space and PAPR-reduction-signal BF space are separately introduced at the RS. In the proposed method, the BS utilizes the null space of the extended channel to transmit the PAPR reduction signal in a direction that does not appear in the received BF output for the RS data signal or in the user reception via the direct link. This achieves PAPR reduction at the RS transmitter while minimizing interference with the data signal. Computer simulation results show that the proposed method reduces the PAPR at both the BS and RS transmitters and improves the SNR versus packet error rate (PER) performance, considering the input backoff of the power amplifiers.
Keyword (in Japanese) (See Japanese page) 
(in English) PAPR / OFDM / MIMO / AF relay transmission / beamforming / null space / /  
Reference Info. IEICE Tech. Rep., vol. 126, no. 72, RCS2026-52, pp. 154-160, June 2026.
Paper # RCS2026-52 
Date of Issue 2026-06-10 (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 RCS2026-52

Conference Information
Committee RCS  
Conference Date 2026-06-17 - 2026-06-19 
Place (in Japanese) (See Japanese page) 
Place (in English) The Ohama Nobumoto Memorial Hall 
Topics (in Japanese) (See Japanese page) 
Topics (in English) First Presentation in IEICE Technical Committee, Resource Control, Scheduling, Wireless Communications, etc. 
Paper Information
Registration To RCS 
Conference Code 2026-06-RCS 
Language Japanese 
Title (in Japanese) (See Japanese page) 
Sub Title (in Japanese) (See Japanese page) 
Title (in English) Investigation of PAPR Reduction Using Null Space in MIMO Channel for Beamforming-Aided Multi-Antenna AF Relay Transmission 
Sub Title (in English)  
Keyword(1) PAPR  
Keyword(2) OFDM  
Keyword(3) MIMO  
Keyword(4) AF relay transmission  
Keyword(5) beamforming  
Keyword(6) null space  
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Keyword(8)  
1st Author's Name Shunta Okuno  
1st Author's Affiliation Tokyo University of Science (Tokyo Univ. of Science)
2nd Author's Name Satoshi Suyama  
2nd Author's Affiliation NTT DOCOMO,INC. (NTT DOCOMO)
3rd Author's Name Satoshi Nagata  
3rd Author's Affiliation NTT DOCOMO,INC. (NTT DOCOMO)
4th Author's Name Kenichi Higuchi  
4th Author's Affiliation Tokyo University of Science (Tokyo Univ. of Science)
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Speaker Author-1 
Date Time 2026-06-18 10:15:00 
Presentation Time 10 minutes 
Registration for RCS 
Paper # RCS2026-52 
Volume (vol) vol.126 
Number (no) no.72 
Page pp.154-160 
#Pages 7 
Date of Issue 2026-06-10 (RCS) 

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