OFDM transmission method and system based on two-dimensional chaotic mapping constellation encryption

Abstract

The present disclosure is about an OFDM transmission method and system based on two-dimensional chaotic mapping constellation encryption. The method comprises the following steps: the input signal is subjected to constellation mapping to obtain a modulation column vector; a first sequence and a second sequence are generated through two-dimensional chaotic mapping, and the modulation column vector is subjected to constellation encryption processing using the first sequence and the second sequence to generate an encrypted signal; the encrypted signal is subjected to IFFT transformation to generate a frequency domain signal, which is then transmitted to the receiving end through a channel; the received frequency domain signal is subjected to FFT transformation to generate a time domain signal; a decryption matrix is ​​generated according to the parameters of the two-dimensional chaotic mapping, and the encrypted signal is decrypted using the decryption matrix, thereby completing the demodulation process. The present disclosure enhances the physical layer security performance of the OFDM transmission system.

Description

Technical Field

[0001] The present disclosure relates to the field of secure communication technology, and in particular to an OFDM transmission method and system based on two-dimensional chaotic mapping constellation encryption. Background Art

[0002] Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier transmission (Multi Carrier Modulation, MCM) scheme that solves the problem of high receiver complexity of traditional single-carrier time-domain transmission technology. It can realize parallel transmission of high-speed serial data through frequency division multiplexing and has good resistance to multipath fading. It is an important modulation and demodulation technology commonly used in various wireless communication standards.

[0003] As we all know, the wireless channel is an open channel, and wireless transmission signals are subject to the risk of malicious eavesdropping and detection. At present, the research on OFDM transmission technology mainly focuses on aspects such as receiver processing algorithms, but there are still deficiencies in how to prevent eavesdropping activities by non-cooperative eavesdroppers and improve the physical layer security performance of OFDM systems. Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions to enhance the physical layer security performance of OFDM systems.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The purpose of the embodiments of the present disclosure is to provide an OFDM transmission method and system based on two-dimensional chaotic mapping constellation encryption to enhance the physical layer security performance of the OFDM system.

[0006] According to a first aspect of an embodiment of the present disclosure, an OFDM transmission method based on two-dimensional chaotic mapping constellation encryption is provided, the method comprising the following steps:

[0007] The input signal is mapped to a constellation to obtain a modulated column vector;

[0008] Generate a first sequence and a second sequence through a two-dimensional chaotic mapping, and perform constellation encryption processing on the modulated column vector using the first sequence and the second sequence to generate an encrypted signal;

[0009] The encrypted signal is transformed into a frequency domain signal by IFFT and then transmitted to the receiving end through the channel;

[0010] Performing FFT transformation on the received frequency domain signal to generate a time domain signal;

[0011] A decryption matrix is ​​generated according to the parameters of the two-dimensional chaotic map, and the encrypted signal is decrypted using the decryption matrix, thereby completing the demodulation process.

[0012] In an exemplary embodiment of the present disclosure, the step of performing constellation encryption processing on the modulation column vector using the first sequence and the second sequence further includes the following steps:

[0013] Using the first sequence to extend and encrypt the amplitude of the modulation symbol, and using the second sequence to rotate and encrypt the phase of the modulation symbol, to generate an encryption matrix of the amplitude and phase of the modulation symbol;

[0014] The modulation column vector is encrypted according to the encryption matrix.

[0015] In an exemplary embodiment of the present disclosure, in the step of using the first sequence to expand and encrypt the amplitude of the modulation symbol, the first sequence first obtains the amplitude expansion factor r by formula (1): n , and then generate the amplitude encryption matrix R of the modulation symbol through formula (2);

[0016]

[0017] R = diag(r) (2);

[0018] Among them, u is the first sequence, r=(r0,r1,…,r N-1 ) T .

[0019] In an exemplary embodiment of the present disclosure, in the step of rotating and encrypting the phase of the modulation symbol using the second sequence, the second sequence first obtains a phase rotation factor φ by formula (3): n , and then generate the phase encryption matrix Φ of the modulation symbol through formula (4);

[0020]

[0021]

[0022] Among them, v is the second sequence.

[0023] In an exemplary embodiment of the present disclosure, in the step of encrypting the modulated column vector according to the encryption matrix, encryption is performed by formula (5);

[0024] x0=RΦx (5);

[0025] Where x=(x0,x1,…x N-1 )T is the modulation column vector.

[0026] In an exemplary embodiment of the present disclosure, the decryption matrix and the encryption matrix are inverse matrices of each other.

[0027] In an exemplary embodiment of the present disclosure, in the step of generating a decryption matrix according to the parameters of the two-dimensional chaotic map and decrypting the encrypted signal using the decryption matrix, the decryption formula is:

[0028]

[0029] in, is the time domain signal;

[0030] R -1 is the amplitude decryption matrix of the modulation symbol, and

[0031] Φ -1 is the phase decryption matrix of the modulation symbol, and Φ -1 =Φ H .

[0032] In an exemplary embodiment of the present disclosure, the two-dimensional chaotic map is a Hénon chaotic map.

[0033] In an exemplary embodiment of the present disclosure, the modulation mode of the input signal after constellation mapping is PSK modulation, ASK modulation or QAM modulation.

[0034] According to a second aspect of an embodiment of the present disclosure, an OFDM transmission system based on two-dimensional chaotic mapping constellation encryption is provided, the system comprising:

[0035] A chaotic mapping constellation encryption unit, used to generate a first sequence and a second sequence through two-dimensional chaotic mapping, and perform constellation encryption processing on the modulation column vector generated by constellation mapping using the first sequence and the second sequence to generate an encrypted signal;

[0036] An IFFT transform unit, configured to transform the encrypted signal into a frequency domain signal through an IFFT transform, and then transmit the signal to a receiving end through a channel;

[0037] An FFT transform unit, used for performing FFT transform on the received frequency domain signal to generate a time domain signal;

[0038] A decryption unit is used to generate a decryption matrix based on the parameters of the two-dimensional chaotic map, and use the decryption matrix to decrypt the encrypted signal, thereby completing the demodulation process.

[0039] The technical solution provided by the present disclosure may have the following beneficial effects:

[0040] In the embodiment of the present disclosure, the transmitting end uses a two-dimensional chaotic sequence to generate amplitude and phase encryption matrices respectively, so that the original constellation diagram is expanded in amplitude and controllably rotated in phase, and then IFFT is performed to transform it to the frequency domain, and then a cyclic prefix is ​​added and transmitted to the receiving end. After removing the cyclic prefix, the receiving end performs FFT transformation on the received signal to the time domain, and then generates a decryption matrix using the same parameters as the transmitting end to complete the reconstruction process of the original constellation. Due to the initial value sensitivity of the two-dimensional chaotic sequence, the cooperative receiver and the transmitter have the same modulation parameters and chaotic initialization parameters, and the eavesdropping party cannot correctly process the received signal even if there is a very small parameter deviation, thereby enhancing the physical layer security performance of the OFDM transmission system.

[0041] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0043] Figure 1 A schematic diagram showing the steps of an OFDM transmission method based on two-dimensional chaotic mapping constellation encryption in an exemplary embodiment of the present disclosure is shown;

[0044] Figure 2 A schematic diagram of amplitude and phase encryption in an exemplary embodiment of the present disclosure is shown;

[0045] Figure 3 A block diagram showing a transmission method in an exemplary embodiment of the present disclosure;

[0046] Figure 4 The influence of the Hénon initial value on the chaotic sequence u in the exemplary embodiment of the present disclosure is shown;

[0047] Figure 5 A comparison diagram of the QPSK constellation diagram before and after encryption in an exemplary embodiment of the present disclosure is shown;

[0048] Figure 6 A diagram showing the anti-interception performance analysis in an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0049] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0050] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0051] In this example implementation, an OFDM transmission method based on two-dimensional chaotic mapping constellation encryption is first provided. Figure 1 As shown in , the method may include the following steps:

[0052] Step S101: The input signal is subjected to constellation mapping to obtain a modulation column vector;

[0053] Step S102: Generate a first sequence and a second sequence through a two-dimensional chaotic mapping, and perform constellation encryption processing on the modulated column vector using the first sequence and the second sequence to generate an encrypted signal;

[0054] Step S103: After the encrypted signal is transformed by IFFT to generate a frequency domain signal, it is transmitted to the receiving end through the channel;

[0055] Step S104: Performing FFT transformation on the received frequency domain signal to generate a time domain signal;

[0056] Step S105: Generate a decryption matrix according to the parameters of the two-dimensional chaotic map, and use the decryption matrix to decrypt the encrypted signal.

[0057] In the embodiment of the present disclosure, the transmitting end uses a two-dimensional chaotic sequence to generate amplitude and phase encryption matrices respectively, so that the original constellation diagram is expanded in amplitude and controllably rotated in phase, and then IFFT is performed to transform it to the frequency domain, and then a cyclic prefix is ​​added and transmitted to the receiving end. After removing the cyclic prefix, the receiving end performs an FFT transform on the received signal to the time domain, and then uses the same parameters as the transmitting end to generate the amplitude and phase encryption inverse matrices respectively, completing the reconstruction process of the original constellation. Due to the initial value sensitivity of the two-dimensional chaotic sequence, the cooperative receiver and the transmitter have the same modulation parameters and chaos initialization parameters, and the eavesdropping party cannot correctly process the received signal even if there is a very small parameter deviation, thereby enhancing the physical layer security performance of the OFDM transmission system.

[0058] Below, each step of the above method in this example implementation will be described in more detail.

[0059] In step S101, the modulation mode of the input signal after constellation mapping is PSK modulation, ASK modulation or QAM modulation.

[0060] In this example, Figure 2 As shown, using The phase mapping QPSK constellation diagram is used as an example to illustrate. The marked point A is the original constellation mapping point, which corresponds to the current symbol x n , the corresponding phase is θ n In this example, Marked point B is the encrypted constellation mapping coordinate point obtained by using two-dimensional chaotic mapping to simultaneously generate two sets of chaotic sequences and use them to encrypt the amplitude and phase of the QPSK modulation symbol. Its radius is r n , at the same time, the phase is φ n The rotation of the angle, that is, the phase after rotation is φ n +θ n .

[0061] Chaos embodies the inherent randomness of a certain system. It is extremely sensitive to initial values, and very small disturbances can produce huge deviations, that is, the phenomenon of "a slight error leads to a huge difference". In step S102, the two-dimensional chaotic map used in this example is the Hénon chaotic map. The Hénon chaotic map is a typical two-dimensional chaotic map that can generate two sets of chaotic sequences at the same time, which is conducive to controlling multiple system parameters at the same time. In this example, it is used to encrypt the amplitude and phase of the QPSK modulation symbol at the same time. Of course, the present disclosure does not limit this. In other examples, other chaotic maps can also be used.

[0062] The step of encrypting the symbol column vector of the modulated signal using the first sequence and the second sequence in step S102 further includes the following steps:

[0063] Step S1021: using the first sequence to perform extension encryption on the amplitude of the modulation symbol, and using the second sequence to perform rotation encryption on the phase of the modulation symbol, to generate an encryption matrix of the amplitude and phase of the modulation symbol;

[0064] Step S1022: encrypt the modulated column vector according to the encryption matrix.

[0065] In the specific example, the radius r of the encrypted constellation mapping coordinate point B is n and the rotation angle φ n Can be generated in the following ways:

[0066] The first sequence u=[u0,u1,…,u N-1 ] T and the second sequence v=[v0,v1,…,v N-1 ] T , which is used to encrypt the amplitude and phase of the modulated column vector after serial-to-parallel conversion. The generation formula is as follows:

[0067]

[0068] v n+1 =bu n

[0069] In the above formula, when the parameter values ​​a=1.4 and b=0.3, chaotic phenomenon occurs.

[0070] Then, using the first sequence u=[u0,u1,…,u N-1 ] T and the second sequence v=[v0,v1,…,v N-1 ] T The amplitude and phase of the original constellation mapping point A are expanded and encrypted respectively to obtain the encrypted matrices of the amplitude and phase of the modulation symbol.

[0071] Specifically, the first sequence u first obtains the amplitude expansion factor through formula (1), that is, the radius r of the coordinate point B is obtained: n In formula (1), max(|u|) means taking the absolute value of each element in the sequence u and then taking the maximum value. Then, the elements in formula (1) are converted into a diagonal matrix to obtain formula (2), which is used to expand and encrypt the amplitude information of the modulation symbol and obtain the amplitude encryption matrix R. In formula (2), r = (r0, r1, ..., r N-1 ) T To generate a column vector of elements using formula (1), diag(·) is a diagonal matrix operation.

[0072]

[0073] R = diag(r) (2).

[0074] The second sequence v first obtains the phase rotation factor through formula (3), that is, the rotation angle φ of the coordinate point B is obtained n , and then use formula (4) to expand and encrypt the phase information of the modulation symbol to obtain the phase encryption matrix Φ.

[0075]

[0076]

[0077] Finally, according to the amplitude encryption matrix R and the phase encryption matrix Φ of the modulation symbol, the modulation column vector is encrypted using formula (5) to obtain the encrypted signal x0, where x = (x0, x1, ... x N-1 ) T It is the modulation column vector obtained after symbol mapping and serial-to-parallel conversion in the above QPSK modulation process.

[0078] x0=RΦx (5).

[0079] In step S103, the encrypted signal x0 obtained by formula (5) is transformed into a frequency domain signal by IFFT. The specific transformation formula is:

[0080] X=F H x0 (7)

[0081] Where F is the normalized DFT matrix, which can be expressed as:

[0082]

[0083] In formula (8), W N =e -2πj / N .

[0084] Then, after inserting the cyclic prefix (CP), it is transmitted to the receiving end through the channel.

[0085] In step S104, the signal after the CP is removed at the receiving end can be expressed as

[0086] Y=F H x0+n (9)

[0087] Where n is the noise vector.

[0088] For the received N-dimensional vector Y=[y0,y1,…,y N-1 ] T Perform FFT transformation, which can be expressed as

[0089]

[0090] Then, the obtained time domain signal is subjected to amplitude and phase decryption processing.

[0091] In step S105, due to the cooperation between the receiver and the transmitter, the initial value of the Hénon two-dimensional chaotic sequence and the two-dimensional chaotic mapping parameters such as a and b can be accurately obtained. Therefore, the above parameters can be used to generate a decryption matrix, wherein the decryption matrix and the encryption matrix are inverse matrices of each other.

[0092] The specific decryption formula is:

[0093]

[0094] in, is the above time domain signal.

[0095] Furthermore, since the amplitude encryption matrix R is a real diagonal matrix, its amplitude inverse matrix, i.e., the amplitude decryption matrix formula is:

[0096]

[0097] The phase inverse matrix, i.e. the phase decryption matrix formula is:

[0098] Φ -1 =Φ H (12)

[0099] Then the decryption formula can be written as:

[0100]

[0101] Then, the amplitude and phase decoded data are processed for decision making. The entire signal transmission process can be found in Figure 3 .

[0102] A computer simulation test was conducted on the above encrypted information to prove its encryption effect:

[0103] Experiment 1. Key sensitivity - initial value impact

[0104] Figure 4 The amplitude value change of the first sequence u generated by the Hénon two-dimensional chaotic map under different initial values. Obviously, in the sequence generation process, the amplitude values ​​of the first few chaotic sequences are relatively close, but as the number of iterations increases, the amplitude values ​​of the generated chaotic sequences change greatly and have less correlation.

[0105] Experiment 2: The impact of amplitude and phase encryption module on signal constellation diagram

[0106] from Figure 5It can be seen that after the amplitude phase encryption processing of the QPSK constellation using the Hénon two-dimensional chaotic mapping modulation signal, the phase constellation has obvious phase rotation and confusion. Around the four mapping points of the original QPSK modulation constellation, the amplitude value varies between 1-2, while the phase is scattered around the original constellation, with significant random characteristics. Obviously, compared with the original four constellation mapping points, the confidentiality performance of the encrypted constellation has been significantly improved. For the eavesdropper, it is impossible to determine the modulation method used by the sender from the constellation.

[0107] Test 3: Analysis of anti-interception performance

[0108] from Figure 6 As can be seen from the above, since the legitimate user can accurately obtain various parameters of the system, its system performance has a significant advantage over the eavesdropping user. Even if we assume that the receiver can obtain all information except the initial value of the Hénon two-dimensional chaotic map, and the initial value of the chaotic sequence obtained by the eavesdropper is only 1e different from the correct value, -10 Although there is a difference of orders of magnitude, the interception performance of the eavesdropper is still very poor, and the bit error rate (BER) is always close to 0.5, which shows that the key sensitivity of the proposed algorithm is high and can meet the requirements of confidential communication.

[0109] In summary, the OFDM transmission method based on two-dimensional chaotic mapping constellation encryption provided by the present disclosure enhances the physical layer security performance of the OFDM transmission system.

[0110] It should be noted that, although the steps of the method in the present disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in this specific order, or that all the steps shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may be decomposed into multiple steps for execution, etc. In addition, it is also easy to understand that these steps may be, for example, executed synchronously or asynchronously in multiple modules / processes / threads.

[0111] Furthermore, in this example implementation, an OFDM transmission system based on two-dimensional chaotic mapping constellation encryption is also provided, which may include a chaotic mapping constellation encryption unit, an IFFT transformation unit, an FFT transformation unit, and a decryption unit. Among them, the chaotic mapping constellation encryption unit is used to generate a first sequence and a second sequence through a two-dimensional chaotic mapping, and use the first sequence and the second sequence to perform constellation encryption processing on the modulation column vector generated by the constellation mapping to generate an encrypted signal. The IFFT transformation unit is used to transform the encrypted signal into a frequency domain signal through an IFFT transformation, and then transmit it to the receiving end through a channel. The FFT transformation unit is used to perform an FFT transformation on the received frequency domain signal to generate a time domain signal. The decryption unit is used to generate a decryption matrix according to the parameters of the two-dimensional chaotic mapping, and use the decryption matrix to decrypt the encrypted signal, thereby completing demodulation.

[0112] Regarding the system in the above embodiment, the specific manner in which each unit performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0113] It should be noted that although several units of the system for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiment of the present disclosure, the features and functions of two or more units described above can be concretized in one unit. Conversely, the features and functions of a unit described above can be further divided into multiple units for concretization. Some or all of the units can be selected according to actual needs to achieve the purpose of the disclosed solution. Those of ordinary skill in the art can understand and implement it without paying creative work.

[0114] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. An OFDM transmission method based on two-dimensional chaotic mapping constellation encryption, characterized in that: The following steps are involved: The input signal is mapped to a constellation to obtain a modulated column vector; Generate a first sequence and a second sequence through a two-dimensional chaotic mapping, and perform constellation encryption processing on the modulated column vector using the first sequence and the second sequence to generate an encrypted signal; The encrypted signal is transformed into a frequency domain signal by IFFT and then transmitted to the receiving end through the channel; Performing FFT transformation on the received frequency domain signal to generate a time domain signal; Generate a decryption matrix according to the parameters of the two-dimensional chaotic map, and use the decryption matrix to decrypt the encrypted signal, thereby completing the demodulation process; The step of performing constellation encryption processing on the modulation column vector using the first sequence and the second sequence further includes the following steps: Using the first sequence to extend and encrypt the amplitude of the modulation symbol, and using the second sequence to rotate and encrypt the phase of the modulation symbol, to generate an encryption matrix of the amplitude and phase of the modulation symbol; The modulation column vector is encrypted according to the encryption matrix.

2. The transmission method according to claim 1, characterized in that: In the step of using the first sequence to expand and encrypt the amplitude of the modulation symbol, the first sequence first obtains the amplitude expansion factor r by formula (1): n , and then generate the amplitude encryption matrix R of the modulation symbol through formula (2); R = diag(r)(2); Among them, u is the first sequence, r=(r0,r1,…,r N-1 ) T .

3. The transmission method according to claim 2, characterized in that: In the step of rotating and encrypting the phase of the modulation symbol using the second sequence, the second sequence first obtains a phase rotation factor φ by formula (3): n , and then generate the phase encryption matrix Φ of the modulation symbol through formula (4); Among them, v is the second sequence.

4. The transmission method according to claim 3, characterized in that: In the step of encrypting the modulated column vector according to the encryption matrix, encryption is performed using formula (5); x0=RxΦ (5); Where x=(x0,x1,…x N-1 ) T is the modulation column vector.

5. The transmission method according to claim 4, characterized in that: The decryption matrix and the encryption matrix are inverse matrices of each other.

6. The transmission method according to claim 5, characterized in that: In the step of generating a decryption matrix according to the parameters of the two-dimensional chaotic map and decrypting the encrypted signal using the decryption matrix, the decryption formula is: in, is the time domain signal; R -1 is the amplitude decryption matrix of the modulation symbol, and Φ -1 is the phase decryption matrix of the modulation symbol, and Φ -1 =Φ / .

7. The transmission method according to claim 1, characterized in that: The two-dimensional chaotic map is a Hénon chaotic map.

8. The transmission method according to claim 1, characterized in that: The modulation mode of the input signal after constellation mapping is PSK modulation, ASK modulation or QAM modulation.

9. An OFDM transmission system based on two-dimensional chaotic mapping constellation encryption, characterized in that: include: A chaotic mapping constellation encryption unit, used to generate a first sequence and a second sequence through two-dimensional chaotic mapping, and perform constellation encryption processing on the modulation column vector generated by constellation mapping using the first sequence and the second sequence to generate an encrypted signal; An IFFT transform unit, configured to transform the encrypted signal into a frequency domain signal through an IFFT transform, and then transmit the signal to a receiving end through a channel; An FFT transform unit, used for performing FFT transform on the received frequency domain signal to generate a time domain signal; A decryption unit, used to generate a decryption matrix according to the parameters of the two-dimensional chaotic map, and use the decryption matrix to decrypt the encrypted signal, thereby completing the demodulation process; The process of performing constellation encryption processing on the modulation column vector by using the first sequence and the second sequence includes: Using the first sequence to extend and encrypt the amplitude of the modulation symbol, and using the second sequence to rotate and encrypt the phase of the modulation symbol, to generate an encryption matrix of the amplitude and phase of the modulation symbol; The modulation column vector is encrypted according to the encryption matrix.

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