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Paper Abstract and Keywords
Presentation 2025-12-04 10:20
A Study on the Statistical Properties of Post-detection LLRs Based on Expectation Propagation in Coded MIMO Systems
Fuga Kobayashi, Takumi Takahashi, Hideki Ochiai (UOsaka) WBS2025-48 ITS2025-27 RCC2025-47
Abstract (in Japanese) (See Japanese page) 
(in English) This paper investigates the statistical properties of the log-likelihood ratios (LLRs) at the output of an iterative signal detector based on expectation propagation (EP), highlighting the role of moment matching (MM)-based extrinsic value exchange in coded systems. Prior studies have mainly examined the convergence behavior in asymptotic regimes; however, EP’s advantage is not always evident in practical finite-size uncoded multi-input multi-output (MIMO) detection, where probabilistic data association (PDA), which lacks extrinsic value exchange, can perform comparably to or even better than EP. In contrast, when channel coding is applied, EP consistently outperforms PDA. To clarify this difference, we analyze the statistical characteristics of the detector outputs in both the symbol and LLR domains. In particular, we show that the extrinsic value exchange through MM plays a key role not only in ensuring inter-iteration independence but also in enhancing the Gaussianity of the demodulator output LLRs. We quantify this effect using negentropy and demonstrate its benefit in improving the decoder’s error-correcting capability, thereby establishing the superiority of EP in coded systems.
Keyword (in Japanese) (See Japanese page) 
(in English) Expectation propagation / LLRs / Negentropy / Channel decoder / Coded MIMO systems / / /  
Reference Info. IEICE Tech. Rep., vol. 125, no. 264, WBS2025-48, pp. 73-78, Dec. 2025.
Paper # WBS2025-48 
Date of Issue 2025-11-26 (WBS, ITS, RCC) 
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 WBS2025-48 ITS2025-27 RCC2025-47

Conference Information
Committee RCC ITS WBS  
Conference Date 2025-12-03 - 2025-12-04 
Place (in Japanese) (See Japanese page) 
Place (in English) B-Con Plaza (Beppu) 
Topics (in Japanese) (See Japanese page) 
Topics (in English)  
Paper Information
Registration To WBS 
Conference Code 2025-12-RCC-ITS-WBS 
Language Japanese 
Title (in Japanese) (See Japanese page) 
Sub Title (in Japanese) (See Japanese page) 
Title (in English) A Study on the Statistical Properties of Post-detection LLRs Based on Expectation Propagation in Coded MIMO Systems 
Sub Title (in English)  
Keyword(1) Expectation propagation  
Keyword(2) LLRs  
Keyword(3) Negentropy  
Keyword(4) Channel decoder  
Keyword(5) Coded MIMO systems  
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Keyword(7)  
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1st Author's Name Fuga Kobayashi  
1st Author's Affiliation Osaka University (UOsaka)
2nd Author's Name Takumi Takahashi  
2nd Author's Affiliation Osaka University (UOsaka)
3rd Author's Name Hideki Ochiai  
3rd Author's Affiliation Osaka University (UOsaka)
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Speaker Author-1 
Date Time 2025-12-04 10:20:00 
Presentation Time 25 minutes 
Registration for WBS 
Paper # WBS2025-48, ITS2025-27, RCC2025-47 
Volume (vol) vol.125 
Number (no) no.264(WBS), no.265(ITS), no.266(RCC) 
Page pp.73-78 
#Pages 6 
Date of Issue 2025-11-26 (WBS, ITS, RCC) 

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