Performance Improvement of Radio-Wave Encrypted MIMO Communications Using Average LLR Clipping

Mamoru OKUMURA; Keisuke ASANO; Takumi ABE; Eiji OKAMOTO; Tetsuya YAMAMOTO

doi:10.1587/transcom.2021EBT0007

IEICE TRANSACTIONS on Communications

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Performance Improvement of Radio-Wave Encrypted MIMO Communications Using Average LLR Clipping

Mamoru OKUMURA, Keisuke ASANO, Takumi ABE, Eiji OKAMOTO, Tetsuya YAMAMOTO

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Summary :

In recent years, there has been significant interest in information-theoretic security techniques that encrypt physical layer signals. We have proposed chaos modulation, which has both physical layer security and channel coding gain, as one such technique. In the chaos modulation method, the channel coding gain can be increased using a turbo mechanism that exchanges the log-likelihood ratio (LLR) with an external concatenated code using the max-log approximation. However, chaos modulation, which is a type of Gaussian modulation, does not use fixed mapping, and the distance between signal points is not constant; therefore, the accuracy of the max-log approximated LLR degrades under poor channel conditions. As a result, conventional methods suffer from performance degradation owing to error propagation in turbo decoding. Therefore, in this paper, we propose a new LLR clipping method that can be optimally applied to chaos modulation by limiting the confidence level of LLR and suppressing error propagation. For effective clipping on chaos modulation that does not have fixed mappings, the average confidence value is obtained from the extrinsic LLR calculated from the demodulator and decoder, and clipping is performed based on this value, either in the demodulator or the decoder. Numerical results indicated that the proposed method achieves the same performance as the one using the exact LLR, which requires complicated calculations. Furthermore, the security feature of the proposed system is evaluated, and we observe that sufficient security is provided.

Publication: IEICE TRANSACTIONS on Communications Vol.E105-B No.8 pp.931-943

Publication Date: 2022/08/01

Publicized: 2022/02/15

Online ISSN: 1745-1345

DOI: 10.1587/transcom.2021EBT0007

Type of Manuscript: PAPER

Category: Wireless Communication Technologies

Authors

Mamoru OKUMURA
  Nagoya Institute of Technology
Keisuke ASANO
  Nagoya Institute of Technology
Takumi ABE
  Nagoya Institute of Technology
Eiji OKAMOTO
  Nagoya Institute of Technology
Tetsuya YAMAMOTO
  Panasonic Corporation

Keyword

radio-wave encryption, chaos modulation, physical layer security, LLR clipping, multiple-input multiple-output

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Mamoru OKUMURA, Keisuke ASANO, Takumi ABE, Eiji OKAMOTO, Tetsuya YAMAMOTO, "Performance Improvement of Radio-Wave Encrypted MIMO Communications Using Average LLR Clipping" in IEICE TRANSACTIONS on Communications, vol. E105-B, no. 8, pp. 931-943, August 2022, doi: 10.1587/transcom.2021EBT0007.
Abstract: In recent years, there has been significant interest in information-theoretic security techniques that encrypt physical layer signals. We have proposed chaos modulation, which has both physical layer security and channel coding gain, as one such technique. In the chaos modulation method, the channel coding gain can be increased using a turbo mechanism that exchanges the log-likelihood ratio (LLR) with an external concatenated code using the max-log approximation. However, chaos modulation, which is a type of Gaussian modulation, does not use fixed mapping, and the distance between signal points is not constant; therefore, the accuracy of the max-log approximated LLR degrades under poor channel conditions. As a result, conventional methods suffer from performance degradation owing to error propagation in turbo decoding. Therefore, in this paper, we propose a new LLR clipping method that can be optimally applied to chaos modulation by limiting the confidence level of LLR and suppressing error propagation. For effective clipping on chaos modulation that does not have fixed mappings, the average confidence value is obtained from the extrinsic LLR calculated from the demodulator and decoder, and clipping is performed based on this value, either in the demodulator or the decoder. Numerical results indicated that the proposed method achieves the same performance as the one using the exact LLR, which requires complicated calculations. Furthermore, the security feature of the proposed system is evaluated, and we observe that sufficient security is provided.
URL: https://global.ieice.org/en_transactions/communications/10.1587/transcom.2021EBT0007/_p

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@ARTICLE{e105-b_8_931,
author={Mamoru OKUMURA, Keisuke ASANO, Takumi ABE, Eiji OKAMOTO, Tetsuya YAMAMOTO, },
journal={IEICE TRANSACTIONS on Communications},
title={Performance Improvement of Radio-Wave Encrypted MIMO Communications Using Average LLR Clipping},
year={2022},
volume={E105-B},
number={8},
pages={931-943},
abstract={In recent years, there has been significant interest in information-theoretic security techniques that encrypt physical layer signals. We have proposed chaos modulation, which has both physical layer security and channel coding gain, as one such technique. In the chaos modulation method, the channel coding gain can be increased using a turbo mechanism that exchanges the log-likelihood ratio (LLR) with an external concatenated code using the max-log approximation. However, chaos modulation, which is a type of Gaussian modulation, does not use fixed mapping, and the distance between signal points is not constant; therefore, the accuracy of the max-log approximated LLR degrades under poor channel conditions. As a result, conventional methods suffer from performance degradation owing to error propagation in turbo decoding. Therefore, in this paper, we propose a new LLR clipping method that can be optimally applied to chaos modulation by limiting the confidence level of LLR and suppressing error propagation. For effective clipping on chaos modulation that does not have fixed mappings, the average confidence value is obtained from the extrinsic LLR calculated from the demodulator and decoder, and clipping is performed based on this value, either in the demodulator or the decoder. Numerical results indicated that the proposed method achieves the same performance as the one using the exact LLR, which requires complicated calculations. Furthermore, the security feature of the proposed system is evaluated, and we observe that sufficient security is provided.},
keywords={},
doi={10.1587/transcom.2021EBT0007},
ISSN={1745-1345},
month={August},}

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TY - JOUR
TI - Performance Improvement of Radio-Wave Encrypted MIMO Communications Using Average LLR Clipping
T2 - IEICE TRANSACTIONS on Communications
SP - 931
EP - 943
AU - Mamoru OKUMURA
AU - Keisuke ASANO
AU - Takumi ABE
AU - Eiji OKAMOTO
AU - Tetsuya YAMAMOTO
PY - 2022
DO - 10.1587/transcom.2021EBT0007
JO - IEICE TRANSACTIONS on Communications
SN - 1745-1345
VL - E105-B
IS - 8
JA - IEICE TRANSACTIONS on Communications
Y1 - August 2022
AB - In recent years, there has been significant interest in information-theoretic security techniques that encrypt physical layer signals. We have proposed chaos modulation, which has both physical layer security and channel coding gain, as one such technique. In the chaos modulation method, the channel coding gain can be increased using a turbo mechanism that exchanges the log-likelihood ratio (LLR) with an external concatenated code using the max-log approximation. However, chaos modulation, which is a type of Gaussian modulation, does not use fixed mapping, and the distance between signal points is not constant; therefore, the accuracy of the max-log approximated LLR degrades under poor channel conditions. As a result, conventional methods suffer from performance degradation owing to error propagation in turbo decoding. Therefore, in this paper, we propose a new LLR clipping method that can be optimally applied to chaos modulation by limiting the confidence level of LLR and suppressing error propagation. For effective clipping on chaos modulation that does not have fixed mappings, the average confidence value is obtained from the extrinsic LLR calculated from the demodulator and decoder, and clipping is performed based on this value, either in the demodulator or the decoder. Numerical results indicated that the proposed method achieves the same performance as the one using the exact LLR, which requires complicated calculations. Furthermore, the security feature of the proposed system is evaluated, and we observe that sufficient security is provided.
ER -

IEICE TRANSACTIONS on Communications