Journal of Jilin University(Engineering and Technology Edition) ›› 2026, Vol. 56 ›› Issue (8): 2240-2248.doi: 10.13229/j.cnki.jdxbgxb.20250031

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Variable time width OCDM-IM communication system design and performance analysis

Xiao-yan NING(),Yu-hao SHAO,Shuai YE,Zhen-duo WANG()   

  1. College of Information and Communication Engineering,Harbin Engineering University,Harbin 150001,China
  • Received:2025-01-09 Online:2026-08-01 Published:2026-09-02
  • Contact: Zhen-duo WANG E-mail:ningxiaoyan@hrbeu.edu.cn;zhenduowang@hrbeu.edu.cn

Abstract:

To enhance the covertness of the Orthogonal Chirp Division Multiplexing with Index Modulation (OCDM-IM), a variable time-width and index mapping scheme is proposed to construct the corresponding VT-OCDM-IM system. By selecting time-width and index mapping methods using the same pseudorandom sequences, the system disrupts signal periodicity and enhances covert performance in scenarios where detecting signal periodicity features is critical. Simulation and experimental results show that altering the number of subcarriers alongside variable time-width improves reliability under certain conditions while enhancing covert performance without compromising the system's transmission rate advantage.

Key words: communication and information systems, covert communication, orthogonal chirp division multiplexing, index modulation, variable time width

CLC Number: 

  • TN914

Fig.1

Principle block diagram of VT-OCDM-IM system"

Table 1

AICs and mapped bits"

IiAICsZIgPI
I11,20110010
I21,31101011
I32,320110-
I41,431001-
I52,44010100
I63,45001101

Fig.2

Mapping relationship of partial subcarriers (L=4,K=2,PI=100?001)"

Fig.3

Performance comparison between VT-OCDM-IM and OFDM-IM"

Table 2

System parameter settings"

方法基信号时宽个数

DFT/DFnT

大小

星座映射

激活子

载波/N

带宽/kHzT/sTcp/s比特速率/(kbit·s-1
OFDM-IM正弦信号1256BPSK646.40.040.013.84
OCDMChirp1256BPSK64/1286.40.040.011.92/3.84
OCDM-IMChirp1256BPSK646.40.040.013.84
VT-OCDM-IMChirp4128/256/384/512BPSK

32/64/96/

128

6.4

0.02/0.04/

0.06/0.08

0.005/0.01/

0.015/0.02

3.84

Fig.4

Performance comparison between VT-OCDM-IM and OCDM"

Fig.5

Performance comparison between VT-OCDM-IM and OCDM-IM"

Fig.6

Cepstrum comparison between VT-OCDM-IM and OCDM-IM"

Fig.7

Cepstrum detection probability"

Fig.8

Cyclic spectrum comparison between VT-OCDM-IM and OCDM-IM"

Fig.9

Cyclic spectrum comparison at f=f0"

Fig.10

Cyclic spectrum comparison at f=f0 that with AWGN"

Fig.11

Cyclic spectrum detection probability"

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