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

• OKUMURA Mamoru

  Department of Computer Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology

• ASANO Keisuke

  Department of Computer Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology

• ABE Takumi

  Department of Computer Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology

• OKAMOTO Eiji

  Department of Computer Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology

• YAMAMOTO Tetsuya

  Digital & AI Technology Center, Technology Division, Panasonic Corporation

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.

Journal

• IEICE Transactions on Communications

  IEICE Transactions on Communications E105.B (8), 931-943, 2022-08-01

  The Institute of Electronics, Information and Communication Engineers

Keywords

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

Details

• CRID: 1390574411905595264
• NII Article ID: 130008159875
• DOI: 10.1587/transcom.2021ebt0007
• ISSN: 17451345
• ISSN: 09168516
• Web Site: https://www.jstage.jst.go.jp/article/transcom/E105.B/8/E105.B_2021EBT0007/_pdf
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed