A codebook and chirp joint perturbation method based on SCMA-OCDM

Abstract

The present invention discloses a codebook and chirp joint perturbation method based on SCMA-OCDM, including a signal encryption method and a decryption method. The signal encryption method includes, at the transmitting end, iterating the Chua chaotic model to obtain a rotation matrix and a chaotic sequence; encrypting the mother codebook with the rotation matrix; converting the binary information to be transmitted into an SCMA signal using the encrypted mother codebook; using the OCDM modulated signal to convert the SCMA signal into a time-domain chirp signal, and encrypting the time-domain chirp signal with the chaotic sequence; at the receiving end, restoring the received signal into an unencrypted time-domain chirp signal using the chaotic sequence B, and then converting the signal into an SCMA signal through ODCM demodulation; and using the encrypted mother code to restore the SCMA signal into the required binary data. The present invention solves the problems of insufficient number of accessible users and low spectrum efficiency in existing OCDM optical communication systems, while improving the security of the system.

Description

Technical Field

[0001] The present invention relates to optical transmission technology in the field of communication technology, and in particular to a codebook and chirp joint perturbation method based on SCMA-OCDM. Background Art

[0002] Orthogonal chirp division multiplexing (OCDM) is a relatively new digital signal processor (DSP) technology. Compared with orthogonal frequency division multiplexing (OFDM), OCDM not only has better dispersion resistance but also has better anti-interference capabilities while achieving the same spectrum utilization.

[0003] In existing technologies, the available spectrum for optical communications is extremely limited. This limited spectrum bandwidth restricts the number of chirps. OCDM can modulate information onto different chirps, but it cannot effectively improve the utilization of chirps and thus the spectrum efficiency, thus limiting the increase in the transmission capacity of OCDM communication systems. Furthermore, when using OCMD to modulate information, a user can only use one chirp, which also limits the upper limit of the number of user accesses.

[0004] With the rapid development of optical communication systems and the continuous improvement of optical fiber transmission capacity, the security of communication systems has received increasing attention. However, the security of OCDM has rarely been considered in existing technologies, resulting in the problem of low security in OCDM systems. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a codebook and chirp joint perturbation method based on SCMA-OCDM with high spectrum efficiency and security and suitable for multi-user access.

[0006] Technical solution: To achieve the above objectives, the present invention provides a codebook and chirp joint perturbation method based on SCMA-OCDM, comprising the following steps:

[0007] Step S1: At the transmitting end, the rotation matrix and chaotic sequence are obtained by iterating the Chua chaos model;

[0008] Step S2: Encrypt the mother codebook using the rotation matrix;

[0009] Step S3: Convert the binary information to be transmitted into an SCMA signal using the encrypted mother codebook;

[0010] Step S4: using OCDM modulation signal to convert the SCMA signal into a time domain chirp signal, and encrypting the time domain chirp signal using a chaotic sequence;

[0011] Step S5: At the receiving end, the received signal is restored to an unencrypted time domain chirp signal through the chaotic sequence B, and then the signal is converted into an SCMA signal through ODCM demodulation;

[0012] Step S6: Use the encrypted mother code to restore the SCMA signal to the required binary data.

[0013] The step S1 of obtaining the rotation matrix and the chaotic sequence by iterating the Chua's chaotic model includes the following sub-steps:

[0014] Step S101: a series of x values ​​are obtained by iterating the Chua's chaos model, x=x1, x2, x3...,

[0015] Cai's chaos model is:

[0016]

[0017]

[0018]

[0019] f(x)=bx+0.5(ab)(|x+1|-|x-1|);

[0020] Among them, α, β, a, and b are four custom constants, x, y, and z are variables related to t, and t is the number of iterations;

[0021] Extract a number from every other value in the x value to generate a new sequence of rotation matrices A = A1, A2, A3...; A1 = x1, A2 = x3, A3 = x5...; and multiply the decimal part of the sequence A by 2π to obtain the rotation angle sequence θ:

[0022] θ=mod(A,1)*2π;

[0023] The resulting rotation matrix is:

[0024]

[0025] Step S102: The remaining values ​​of x are used as chaotic sequences B=B1, B2, B3, ...; B1=x2, B2=x4, B3=x6, ... for disturbing the time domain chirp signal.

[0026] The encryption of the codebook using the rotation matrix in step S2 is specifically as follows:

[0027] The rotation matrix R and the mother constellation coordinates of the mother codebook Multiply them together to get the encrypted codebook constellation

[0028] Where θ is the rotation angle sequence.

[0029] Among them, the conversion of the binary information to be transmitted by the encrypted mother codebook into an SCMA signal in step S3 is specifically: performing SCMA codebook mapping on the binary information to be transmitted by the encrypted mother codebook, converting the binary information into a form that is more conducive to transmission, and superimposing the information of different users by SCMA codebook mapping to obtain an overloaded SCMA signal.

[0030] The OCDM modulation signal is used in step S4 to convert the SCMA signal into a time domain chirp signal, and the chaotic sequence is used to encrypt the time domain chirp signal, specifically:

[0031] In the OCDM modulation process, the SCMA signal is converted into a time-domain chirp signal after inverse discrete Fresnel transform, and then the time-domain chirp signal is encrypted using a chaotic sequence:

[0032] Sn*=Sn×(0.5+(mod(Bn,1))),

[0033] Among them, n=1,2,3..., Sn is the time domain chirp signal symbol before encryption, and Sn* is the time domain chirp signal symbol after encryption, which realizes the time domain perturbation of the chirp signal.

[0034] Beneficial effects: The present invention has the following advantages: 1. The joint perturbation method of the present invention belongs to the chaotic security communication scheme in physical layer encryption. It uses the Chua chaos model to generate a chaotic sequence, and then generates a rotation matrix and a new sequence to change the constellation and chirp time domain signal of the mother codebook, encrypt the information, and improve the system security.

[0035] 2. The chirp signal of the present invention can be overlapped twice on a spectrum, and has the advantages of high anti-interference ability, wide bandwidth, pulse compression, strong robustness, and can resist adverse factors such as noise, multipath fading, and Doppler effect;

[0036] 3. The SCMA described in the present invention has higher spectrum utilization and more user access. Applying it to the method proposed in the present invention can increase spectrum efficiency and the number of access users. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of the signal encryption method of the present invention;

[0038] Figure 2 Schematic diagram of the signal decryption method of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail below with reference to the embodiments and drawings.

[0040] like Figure 1 and Figure 2 As shown, the codebook and chirp joint perturbation method based on SCMA-OCDM described in the present invention includes the following steps:

[0041] Step S1: At the transmitting end, the rotation matrix and chaotic sequence are obtained by iterating the Chua chaos model;

[0042] Step S2: Encrypt the mother codebook using the rotation matrix;

[0043] Step S3: Convert the binary information to be transmitted into an SCMA signal using the encrypted mother codebook;

[0044] Step S4: using OCDM modulation signal to convert the SCMA signal into a time domain chirp signal, and encrypting the time domain chirp signal using a chaotic sequence;

[0045] Step S5: At the receiving end, the received signal is restored to an unencrypted time domain chirp signal through the chaotic sequence B, and then the signal is converted into an SCMA signal through ODCM demodulation;

[0046] Step S6: Use the encrypted mother code to restore the SCMA signal to the required binary data.

[0047] The step S1 of obtaining the rotation matrix and the chaotic sequence by iterating the Chua's chaotic model includes the following sub-steps:

[0048] Step S101: a series of x values ​​are obtained by iterating the Chua's chaos model, x=x1, x2, x3...,

[0049] Cai's chaos model is:

[0050]

[0051]

[0052]

[0053] f(x)=bx+0.5(ab)(|x+1|-|x-1|);

[0054] Among them, α, β, a, and b are four custom constants, x, y, and z are variables related to t, and t is the number of iterations;

[0055] Extract a number from every other value in the x value to generate a new sequence of rotation matrices A = A1, A2, A3...; A1 = x1, A2 = x3, A3 = x5...; and multiply the decimal part of the sequence A by 2π to obtain the rotation angle sequence θ:

[0056] θ=mod(A,1)*2π;

[0057] The resulting rotation matrix is:

[0058]

[0059] Step S102: The remaining values ​​of x are used as chaotic sequences B=B1, B2, B3, ...; B1=x2, B2=x4, B3=x6, ... for disturbing the time domain chirp signal.

[0060] The encryption of the codebook using the rotation matrix in step S2 is specifically as follows:

[0061] The rotation matrix R and the mother constellation coordinates of the mother codebook Multiply them together to get the encrypted codebook constellation

[0062]

[0063] Among them, the binary information to be transmitted is converted into an SCMA signal through the encrypted mother codebook in step S3, specifically: the binary information to be transmitted is mapped by the encrypted mother codebook to the SCMA codebook, and the binary information is converted into a form that is more conducive to transmission. The SCMA codebook mapping can superimpose the information of different users to obtain an overloaded SCMA signal.

[0064] The OCDM modulation signal is used in step S4 to convert the SCMA signal into a time domain chirp signal, and the chaotic sequence is used to encrypt the time domain chirp signal, specifically:

[0065] In the OCDM modulation process, the SCMA signal is converted into a time-domain chirp signal after inverse discrete Fresnel transform, and then the time-domain chirp signal is encrypted using a chaotic sequence:

[0066] Sn*=Sn×(0.5+(mod(Bn,1))),

[0067] Wherein, n=1, 2, 3, ..., Sn is the time domain chirp signal symbol before encryption, and Sn* is the time domain chirp signal symbol after encryption, thus realizing the time domain perturbation of the chirp signal.

[0068] The joint perturbation method proposed in the present invention belongs to a chaotic security communication scheme in physical layer encryption. It uses the Cai chaos model to generate a chaotic sequence, and then generates a rotation matrix and a new sequence to change the constellation and chirp time domain signal of the mother codebook, encrypt the information, and improve the system security. The chirp signal can be overlapped twice on a spectrum, has the advantages of high anti-interference ability, wide bandwidth, pulse compression, strong robustness, etc., and can resist adverse factors such as noise, multipath fading, and Doppler effect. The SCMA has higher spectrum utilization and more user access. Applying it to the method proposed in the present invention can improve spectrum efficiency and the number of access users.

Claims

1. A codebook and chirp joint perturbation method based on SCMA-OCDM, characterized by: The following steps are involved: Step S1: At the transmitting end, the rotation matrix and chaotic sequence B are obtained by iterating the Chua's chaotic model; the steps include the following: Step S101: a series of x values ​​are obtained by iterating the Chua chaos model, x=x1, x2, x3..., Cai's chaos model is: Among them, α, β, a, and b are four custom constants, x, y, and z are variables related to t, and t is the number of iterations; Extract a number from every other value in the x value to generate a new sequence of rotation matrices A=A1,A2,A3...;A1=x1,A2=x3,A3=x5...; and multiply the decimal part of the sequence A by 2π to obtain the rotation angle sequence θ: θ=mod(A,1)*2π; The resulting rotation matrix is: R = ； Step S102: using the remaining values ​​of x as a chaotic sequence B=B1, B2, B3...; B1=x2, B2=x4, B3=x6... for disturbing the time domain chirp signal; Step S2: Encrypt the mother codebook using the rotation matrix; Step S3: Convert the binary information to be transmitted into an SCMA signal using the encrypted mother codebook; Step S4: Use OCDM modulation signal to convert the SCMA signal into a time domain chirp signal, and encrypt the time domain chirp signal using chaotic sequence B; Step S5: At the receiving end, the received signal is restored to an unencrypted time-domain chirp signal through the chaotic sequence B, and then converted into an SCMA signal through OCDM demodulation; Step S6: Use the encrypted mother code to restore the SCMA signal to the required binary data.

2. The codebook and chirp joint perturbation method based on SCMA-OCDM according to claim 1 is characterized in that: The codebook is encrypted using the rotation matrix in step S2, specifically: The rotation matrix R and the mother constellation coordinates of the mother codebook Multiply them together to get the encrypted codebook constellation : = ; where θ is the rotation angle sequence.

3. The codebook and chirp joint perturbation method based on SCMA-OCDM according to claim 1, characterized in that: Step S3 converts the binary information to be transmitted into an SCMA signal through the encrypted mother codebook, specifically: performing SCMA codebook mapping on the binary information to be transmitted through the encrypted mother codebook, converting the binary information into a form that is more conducive to transmission, and superimposing the information of different users on the SCMA codebook to obtain an overloaded SCMA signal.

4. The codebook and chirp joint perturbation method based on SCMA-OCDM according to claim 1, characterized in that: In step S4, the OCDM modulation signal is used to convert the SCMA signal into a time domain chirp signal, and the chaotic sequence B is used to encrypt the time domain chirp signal. Specifically, In the OCDM modulation process, the SCMA signal is converted into a time-domain chirp signal after inverse discrete Fresnel transform, and then the time-domain chirp signal is encrypted using the chaotic sequence B: Sn*=Sn×(0.5+(mod(Bn,1))), Among them, n=1,2,3..., Sn is the time domain chirp signal symbol before encryption, and Sn* is the time domain chirp signal symbol after encryption, realizing the time domain perturbation of the chirp signal.

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