A signal transmission method and device based on joint index modulation

Abstract

The present invention discloses a signal transmission method and device based on joint index modulation, which belongs to the field of communication technology. The present invention not only realizes the accompanying transmission of the key of the multi-layer encrypted chaotic system through the joint index modulation rule, but also the rule has a certain constellation forming effect on the constellation diagram, and realizes the optimized distribution of the internal constellation points by optimizing the dual-mode index rule and the subcarrier index rule, thereby improving the transmission performance of the signal; in addition, only the legal receiving end can extract the correct key for decryption and demodulation through the joint index rule, while the illegal receiving end cannot realize the correct demodulation due to the effect of multi-layer encryption and the lack of the key, thereby ensuring the high security and high performance transmission of the key and the signal.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a signal transmission method based on joint index modulation. Background Art

[0002] The world's mobile communication network is in a stage of rapid development. In recent years, with the innovation of virtual reality, cloud computing, big data cloud and other technologies, new requirements have been put forward for the data capacity and transmission capacity of the current optical communication system. At the same time, with the increase in the number of users and the amount of data transmitted, the security of transmitted information will undoubtedly become a focus.

[0003] Passive optical network (PON) has many advantages such as wide bandwidth, low energy consumption and low cost. It is the main technology used in the access network field. PON technology has gone through time division multiplexing PON, wavelength division multiplexing PON and the currently popular orthogonal frequency division multiplexing PON, and is regarded as the development trend of future access. However, in the downlink of the PON system, there will be security risks due to the use of broadcasting. At present, due to factors such as cost, the security solutions of the communication system are mainly concentrated in the upper network layer and the physical layer. For the upper network layer encryption scheme, most of them are implemented through various security protocols. However, with the expansion of the number of users today, these schemes will have problems such as key management difficulties and cannot effectively guarantee digital security. For the physical layer encryption scheme, it provides higher security at a low cost, such as chaotic laser encryption, quantum key distribution, chaotic encryption and other schemes. Quantum key distribution is based on the principle of quantum mechanics to encrypt at the transceiver end. This technology uses quantum bits to distribute keys for encrypted communication. The security of key distribution is ensured by the non-cloning and unpredictability of quantum states. At the same time, due to the interference and non-locality of quantum states, illegal eavesdropping can be detected, and the security is extremely high. However, due to the slow key generation and the limited transmission cost and technology, its practical application has yet to be developed.

[0004] With the development of digital signal processing (DSP), digital domain encryption technology based on chaotic systems has been proposed, which has the characteristics of full data encryption at the physical layer, pseudo-randomness of chaotic systems, and sensitivity of key space to initial conditions and control parameters. Moreover, chaotic encryption technology is very suitable for PON systems, because signal generation, coding and modulation, and chaotic encryption are all implemented in the digital domain. At present, research on physical layer security focuses on using chaotic systems to encrypt various dimensions of signals. However, most solutions have a potential security risk: by default, both the sender and the receiver know the key and encrypt and decrypt the transmitted data. In the event of an attack and key leakage, they cannot respond in time, which will cause continuous losses. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a signal transmission method and device based on joint index modulation, which can ensure high-security and high-performance transmission of keys and signals.

[0006] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0007] On the one hand, the present invention provides a signal transmission method based on joint index modulation, comprising:

[0008] Obtaining a signal to be sent, an initial value of a first key, and an initial value of a second key;

[0009] The first initial key value is passed through a one-dimensional chaotic system to generate a one-dimensional chaotic sequence W, and the second initial key value is passed through a three-dimensional chaotic system to generate a three-dimensional chaotic sequence X, Y, Z;

[0010] Using X in the three-dimensional chaotic sequence to perform XOR processing on the signal to be sent to obtain a signal after XOR processing; dividing the signal after XOR processing into sub-blocks to obtain a sub-block matrix; using Y and Z in the three-dimensional chaotic sequence to perform scrambling processing on the sub-block matrix to obtain a scrambled signal;

[0011] The first initial key value and the second initial key value are respectively subjected to binary conversion and serial-to-parallel conversion to obtain a transformed first initial key value and a transformed second initial key value; the transformed first initial key value is up-sampled according to a first preset sampling number of times to obtain a sampled first initial key value, and the transformed second initial key value is up-sampled according to a second preset sampling number of times to obtain a sampled second initial key value; the sampled first initial key value and the sampled second initial key value are grouped to perform high-low bit interleaving and serial-to-parallel conversion to obtain a key matrix, wherein each unit in the key matrix includes a 4-bit mixed key;

[0012] Divide the scrambled signal into N groups, each group includes a 9-bit signal, and divide the 9-bit signal into 3 blocks, each block includes a 3-bit signal; use a preset joint index modulation rule table, according to a 4-bit mixed key, determine the position of each block of 3-bit signals inserted into the empty subcarrier, and perform silent processing on the silent position of the empty subcarrier to obtain the indexed subcarrier, wherein the empty subcarrier is four columns; perform two constellation mode mapping on the indexed subcarrier to obtain a three-dimensional constellation diagram;

[0013] Using a one-dimensional chaotic sequence W to perform constellation rotation encryption on the three-dimensional constellation diagram to obtain an encrypted signal;

[0014] The encrypted signal is subjected to OFDM modulation to obtain a modulated signal, and the modulated signal is transmitted to a receiving end through an optical fiber channel.

[0015] Optionally, the one-dimensional chaotic system is expressed as:

[0016] ;

[0017] In the formula, represents the nth term of the one-dimensional chaotic sequence W; represents the bifurcation parameter; represents a hyperparameter.

[0018] Optionally, the three-dimensional chaotic system is expressed as:

[0019] ;

[0020] In the formula, X, Y, and Z represent three-dimensional state variables; , , represents the derivatives of X, Y, and Z with respect to time t respectively; a, b, c, d, and e are system parameters.

[0021] Optionally, performing XOR processing on the signal to be sent by using X in the three-dimensional chaotic sequence includes:

[0022] ;

[0023] In the formula, Represents the signal after XOR processing; Indicates a signal to be sent; Indicates XOR processing; Indicates the value of the eighth decimal place of the three-dimensional chaotic sequence X; represents the remainder function; represents the floor function; Represents a three-dimensional chaotic sequence.

[0024] Optionally, using Y and Z in the three-dimensional chaotic sequence to perform scrambling processing on the sub-block matrix to obtain a scrambled signal includes:

[0025] The value Y1 of the sixth decimal place of Y in the three-dimensional chaotic sequence is sorted in ascending order and then counted down to generate a matrix, and then multiplied with Y1 to generate a first scrambled matrix Y2; the value Z1 of the sixth decimal place of Z is sorted in ascending order and then counted down to generate a matrix, and then multiplied with Z1 to generate a second scrambled matrix Y2. The first scrambled matrix Y2 and the second scrambled matrix Z2 are expressed as:

[0026] ;

[0027] in, Represents ascending sort function; represents the remainder function;

[0028] Extract the positions of 1 in the first scrambled matrix Y2 and the second scrambled matrix Z2 respectively to generate a first scrambled sequence and a second scrambled sequence;

[0029] The row and column dimensions of the sub-block matrix are scrambled using the first scrambling sequence and the second scrambling sequence respectively to obtain a scrambled signal.

[0030] Optionally, the 2 high bits of the mixed key come from the sampled first key initial value, and the 2 low bits of the mixed key come from the sampled second key initial value.

[0031] Optionally, using a preset joint index modulation rule table, according to a 4-bit mixed key, determining the position of each 3-bit signal inserted into the empty subcarrier, and performing silent processing on the silent position of the empty subcarrier to obtain the indexed subcarrier, including:

[0032] When the 4-bit mixed key is 0000, the subcarriers after the four columns of indexes are ; Where 0 represents a silent subcarrier, S A Indicates the subcarrier corresponding to constellation mode A, S B Indicates the subcarrier corresponding to constellation mode B;

[0033] When the 4-bit mixed key is 0001, the subcarriers after the four columns of indexes are ;

[0034] When the 4-bit mixed key is 0010, the subcarriers after the four columns of indexes are ;

[0035] When the 4-bit mixed key is 0011, the subcarriers after the four columns of indexes are ;

[0036] When the 4-bit mixed key is 0100, the subcarriers after the four columns of indexes are ;

[0037] When the 4-bit mixed key is 0101, the subcarriers after the four columns of indexes are ;

[0038] When the 4-bit mixed key is 0110, the subcarriers after the four columns of indexes are ;

[0039] When the 4-bit mixed key is 0111, the subcarriers after the four columns of indexes are ;

[0040] When the 4-bit mixed key is 1000, the subcarriers after the four columns of indexes are ;

[0041] When the 4-bit mixed key is 1001, the subcarriers after the four columns of indexes are ;

[0042] When the 4-bit mixed key is 1010, the subcarriers after the four columns of indexes are ;

[0043] When the 4-bit mixed key is 1011, the subcarriers after the four columns of indexes are ;

[0044] When the 4-bit mixed key is 1100, the subcarriers after the four columns of indexes are ;

[0045] When the 4-bit mixed key is 1101, the subcarriers after the four columns of indexes are ;

[0046] When the 4-bit mixed key is 1110, the subcarriers after the four columns of indexes are ;

[0047] When the 4-bit mixed key is 1111, the subcarriers after the four columns of indexes are .

[0048] Optionally, the three-dimensional constellation diagram includes constellation points corresponding to two constellation modes and constellation points generated at the origin;

[0049] The silent processed empty subcarriers are subjected to inverse fast Fourier transform to obtain the constellation points generated at the origin.

[0050] Optionally, the encrypted signal is expressed as:

[0051] ;

[0052] ;

[0053] ;

[0054] ;

[0055] In the formula, Represents the coordinates of the constellation points in the constellation diagram after rotation around the x-axis; Represents the coordinates of the constellation points in the constellation diagram after rotation around the y-axis; Represents the coordinates of the constellation points in the constellation diagram after rotation around the z-axis; Represents the coordinates of the constellation points in the constellation diagram; express The horizontal axis of express The vertical coordinate of express The vertical coordinate of express The horizontal axis of express The vertical coordinate of express The vertical coordinate of express The horizontal axis of express The vertical coordinate of express The vertical coordinate of Indicates the rotation angle of the constellation point around the x-axis in the constellation diagram; Indicates the rotation angle of the constellation point around the y-axis in the constellation diagram; Indicates the rotation angle of the constellation point around the z-axis in the constellation diagram; represents the floor function; Represents the remainder function.

[0056] In a second aspect, the present invention provides a signal transmission device based on joint index modulation, including a processor and a storage medium;

[0057] The storage medium is used to store instructions;

[0058] The processor is used to operate according to the instructions to execute the method described in the first aspect.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The present invention not only realizes the concomitant transmission of the key of the chaotic system with multi-layer encryption through the joint index modulation rule, but also the rule has a certain constellation forming effect on the constellation diagram. By optimizing the dual-mode index rule and the subcarrier index rule, the optimized distribution of the internal constellation points is realized, and the transmission performance of the signal is improved. In addition, only the legal receiving end can extract the correct key for decryption and demodulation through the joint index rule, while the illegal receiving end cannot achieve correct demodulation due to the effect of multi-layer encryption and the lack of the key, thereby ensuring the high security and high performance transmission of the key and the signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 FIG. 1 is a schematic diagram of a flow chart of a signal transmission method of the present invention in an embodiment;

[0062] Figure 2 Shown is a phase diagram of a three-dimensional chaotic system in one embodiment of the present invention;

[0063] Figure 3 FIG. 1 is a schematic diagram of mapping bifurcation of a one-dimensional chaotic system in an embodiment of the present invention;

[0064] Figure 4 Shown is a schematic diagram of the process of obtaining a hybrid key in an embodiment of the present invention;

[0065] Figure 5 The figure is a schematic diagram of the structure of the index rule of the present invention in one embodiment;

[0066] Figure 6 It is a schematic diagram of the process of mapping two constellation modes in an embodiment of the present invention;

[0067] Figure 7 The figure shows a schematic diagram of the structure of a three-dimensional constellation diagram in one embodiment of the present invention;

[0068] Figure 8 Shown is a schematic diagram of the structure of an encrypted signal in an embodiment of the present invention;

[0069] Fig. 9 Shown is a schematic structural diagram of a modulated signal in an embodiment of the present invention;

[0070] Fig.10 FIG. 1 is a schematic diagram of the structure of a signal after being recovered by a receiving end in an embodiment of the present invention. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. The embodiments of the present invention and the technical features in the embodiments may be combined with each other unless there is a conflict.

[0072] The term "and / or" is only a description of the association relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " generally indicates that the related objects are in an "or" relationship.

[0073] Embodiment 1:

[0074] like Figure 1As shown, this embodiment introduces a signal transmission method based on joint index modulation, which uses multi-layer encryption to perform multi-dimensional perturbations on the bits, subcarriers, symbol points and constellation points of the signal to improve security performance, and at the same time improves the dual-constellation mode index and subcarrier index rules, and performs mapping according to the designed index rules, and uses the position information of the silent subcarriers and the combination information of the two constellation modes to represent the key, and masks the key in the transmission signal, and realizes the loading and transmission of the key by controlling the silence of the subcarriers and the constellation mode state; at the same time, the index rule increases the distribution of the constellation points at the center of the constellation diagram, achieving an effect similar to constellation forming.

[0075] The sending method specifically comprises the following steps:

[0076] Step 1: Obtain the signal to be sent, the initial value of the first key, and the initial value of the second key.

[0077] Step 2: Generate a one-dimensional chaotic sequence W by passing the first initial key value through a one-dimensional chaotic system, and generate a three-dimensional chaotic sequence X, Y, and Z by passing the second initial key value through a three-dimensional chaotic system, specifically:

[0078] The one-dimensional (1D) chaotic system is represented as:

[0079] ;

[0080] In the formula, represents the n+1th term of the one-dimensional chaotic sequence W; represents the nth term of the one-dimensional chaotic sequence W; represents the bifurcation parameter; represents a hyperparameter; Figure 3 is the mapping bifurcation diagram of the 1D chaotic system. In this embodiment, the value range of the one-dimensional chaotic sequence W is (0, 1), and the bifurcation parameter The value range is (1.132, ], the 1D chaotic system is in a chaotic state, and the hyperparameter Is a positive integer that affects the range of the chaotic state. In this embodiment, 2 is taken. The initial value of the second key of the 1D chaotic system is W0=0.372468420421673.

[0081] The three-dimensional (3D) chaotic system is represented as:

[0082] ;

[0083] In the formula, X, Y, and Z represent three-dimensional state variables; , , represents the derivatives of X, Y, and Z with respect to time t respectively; a, b, c, d, and e are system parameters. When a=2, b=4, c=2, d=1, and e=2, the system is a chaotic system. In this embodiment, the first key initial value (X0, Y0, Z0) of the 3D chaotic system is set to (0.971257028576201, 1.015274263515032, 1.011574611854415). The partial differential equation can be solved by the Runge-Kutta method, and the phase diagram of the 3D chaotic system is as follows: Figure 2 As shown in the figure, it can be found that the value ranges of the three three-dimensional chaotic sequences of the system are (-1.8, 1.7), (-1.8, 2.1), and (-2, 2) respectively.

[0084] Step 3: Using X in the three-dimensional chaotic sequence to perform XOR processing on the signal to be sent to obtain a signal after XOR processing, specifically:

[0085] The signal to be sent is a randomly generated binary data stream. In this embodiment, 51840 bits of information are generated, and then the original data is bit-exclusive-ored using the value X1 of the eighth digit after the decimal point of the three-dimensional chaotic sequence X, including:

[0086] ;

[0087] In the formula, Represents the signal after XOR processing; Indicates a signal to be sent; Indicates XOR processing; Indicates the value of the eighth decimal place of the three-dimensional chaotic sequence X; represents the remainder function; Represents the floor function.

[0088] Step 3: Divide the signal after XOR processing into sub-blocks. Each sub-block has 3 bits of information. After serial-to-parallel conversion, a 80×216 sub-block matrix is ​​obtained.

[0089] Step 4: Use Y and Z in the three-dimensional chaotic sequence to scramble the sub-block matrix to obtain a scrambled signal, specifically:

[0090] The value Y1 of the sixth decimal place of Y in the three-dimensional chaotic sequence is sorted in ascending order and then counted down to generate a matrix, and then multiplied with Y1 to generate a first scrambled matrix Y2; the value Z1 of the sixth decimal place of Z is sorted in ascending order and then counted down to generate a matrix, and then multiplied with Z1 to generate a second scrambled matrix Y2. The first scrambled matrix Y2 and the second scrambled matrix Z2 are expressed as:

[0091] ;

[0092] in, Represents ascending sort function;

[0093] Extract the positions of 1 in the first scrambled matrix Y2 and the second scrambled matrix Z2 respectively to generate a first scrambled sequence and a second scrambled sequence;

[0094] The row and column dimensions of the sub-block matrix are scrambled using the first scrambling sequence and the second scrambling sequence respectively to obtain a scrambled signal.

[0095] That is, the value of the sixth digit after the decimal point of the three-dimensional chaotic sequences Y and Z is selected to generate the binary sequences Y1 and Z1, and then the binary sequences Y1 and Z1 are sorted in ascending order and then inversely generated matrices, and then multiplied with the original matrices Y1 and Z1 respectively to generate a scrambled square matrix, the orders of which are the number of subcarriers and the number of symbols, respectively. There is a 1 in each row and column of the square matrix, and the remaining elements are all marked as 0. The positions of 1 in the generated square matrices Y2 and Z2 are respectively extracted to generate two scrambled sequences, and the row and column dimensions of the sub-block matrix are scrambled using the first scrambled sequence and the second scrambled sequence respectively to obtain the scrambled signal.

[0096] Step 5: First, the first initial key value (Key1) and the second initial key value (Key2) are converted into binary and serial-to-parallel respectively to obtain a 64-bit first initial key value and a 192-bit second initial key value;

[0097] Then, the 64-bit first key initial value is up-sampled according to a first preset sampling number of times to obtain a sampled first key initial value, and the 192-bit second key initial value is up-sampled according to a second preset sampling number of times to obtain a sampled second key initial value;

[0098] In this embodiment, the first preset sampling number is 180 times, and the second preset sampling number is 60 times. This is done on the one hand to make the two key numbers match and facilitate signal embedding; on the other hand, after upsampling a certain number of times, the accuracy of key transmission can be ensured by bit-by-bit judgment during demodulation;

[0099] Finally, in order to ensure the security of the key during transmission, we choose to interleave the two keys. The operation process is as follows: Figure 4 As shown, the sampled first key initial value and the sampled second key initial value are grouped and interleaved with high and low bits and converted into serial and parallel bits to obtain a key matrix, wherein each unit in the key matrix includes a 4-bit mixed key, wherein the 2 high bits of the mixed key come from the sampled first key initial value, and the 2 low bits of the mixed key come from the sampled second key initial value;

[0100] In this embodiment, when the high and low bits of the key are interleaved, we divide the key into 5760 groups, each with 4 bits, where the high 2 bits come from the first initial value of the key after sampling, and the low 2 bits come from the first initial value of the key after sampling. After serial-to-parallel conversion, an 80×72 matrix is ​​obtained, and each unit contains a 4-bit mixed key.

[0101] Step 6: Divide the scrambled signal into N groups, each group includes 9-bit signals, and divide the 9-bit signal into 3 blocks, each block includes 3-bit signals; after obtaining the mixed key, select the 4-bit mixed key and the 9-bit data information as a group for indexing. The indexing rule is as follows: Figure 5 shown.

[0102] Using the preset joint index modulation rule table, according to the 4-bit mixed key, determine the position of each 3-bit signal inserted into the empty subcarrier, and perform silent processing on the silent position of the empty subcarrier to obtain the indexed subcarrier, wherein the empty subcarrier is four columns; the indexed subcarrier is mapped into two constellation modes to obtain a three-dimensional constellation diagram; the constellation mapping process is as follows Figure 6 As shown, the resulting constellation diagram is Figure 7 shown.

[0103] The two constellation modes are mapped according to the joint index modulation rule lookup table shown in Table 1, where 00×× indicates that the four items in the same row are high-order information of the mixed key, and ××00 indicates that the four items in the same column are low-order information of the mixed key, and 9 bits are allocated to the four columns of subcarriers through the mixed key.

[0104] In this embodiment, as shown in Table 1, when the 4-bit mixed key is 0000, the subcarriers after the four columns of indexes are ; Where 0 represents a silent subcarrier, S A Indicates the subcarrier corresponding to constellation mode A, S B Indicates the subcarrier corresponding to constellation mode B; when the 4-bit mixed key is 0001, the subcarrier after the four columns index is ; When the 4-bit mixed key is 0010, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0011, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0100, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0101, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0110, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0111, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1000, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1001, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1010, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1011, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1100, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1101, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1110, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1111, the subcarriers after the four columns of indexes are .

[0105] In a specific embodiment, when the 4-bit mixed key is 0101, the subcarriers after the four columns of indexes are , 0 means the second column of subcarriers is silent, no information is allocated, 9 bits are divided into 3 groups, each group of 3 bits uses 8QAM modulation format, and S A It means that the bit information on the corresponding subcarrier is mapped to the corresponding constellation point of constellation mode A, S B Corresponding to the constellation point mapped to constellation mode B, it can be found that compared with the normal situation where four columns of subcarriers can transmit 4×3=12 bits of information, under index modulation, 3×3+4=13 bits of transmission are achieved through subcarrier silence and constellation combination mode, completing the transmission of more information in the same spectrum space.

[0106] Table 1 Joint index modulation rule lookup table

[0107] Index Bit 00×× 01×× 10×× 11×× ××00 #timg# #timg# #timg# #timg# ××01 #timg# #timg# #timg# #timg# ××10 #timg# #timg# #timg# #timg# ××11 #timg# #timg# #timg# #timg#

[0108] At the same time, the two constellations finally form a constellation diagram under joint index modulation, and the three-dimensional constellation diagram includes constellation points corresponding to the two constellation modes and the constellation points generated at the origin; wherein, the empty subcarriers processed by silence are subjected to inverse fast Fourier transform (IFFT) to obtain the constellation points generated at the origin.

[0109] In this embodiment, the eight outer points are defined as the constellation points of constellation mode B, and the eight inner points represent the constellation points of constellation mode A. The points generated at the origin are because after one column of four columns of subcarriers is silent, there is no information on the silent subcarrier, and the elements in the matrix are 0 after the inverse fast Fourier transform, that is, an additional constellation point is generated at the origin; due to the clever design of the index rule, we can see that when the constellation mode is selected, more information will be mapped to the constellation points of the internal constellation mode A, and because one column of silent subcarriers is generated in every four columns of subcarriers, the number of additional constellation points generated at the center will increase, so there are more internal constellation points, and the distribution is closer to the Gaussian channel, which has the effect of approximation and constellation forming, which will improve the transmission performance of the system to a certain extent.

[0110] Step 7: Use the one-dimensional chaotic sequence W to perform constellation rotation encryption on the three-dimensional constellation diagram to obtain an encrypted signal, specifically:

[0111] Since the transmission is carried out in three-dimensional space, each constellation point will be represented by 3×1. Therefore, after joint index modulation, we get a 240×288 signal matrix, that is, the three-dimensional constellation diagram of the signal. Next, the 1D chaotic system is used to perform constellation rotation encryption. The one-dimensional chaotic sequence W is used to generate the perturbation vector of the three-dimensional constellation point. The rotation angle of the constellation point in the three-dimensional constellation diagram in the three-dimensional space is expressed as:

[0112] ;

[0113] In the formula, Indicates the rotation angle of the constellation point around the x-axis in the constellation diagram; Indicates the rotation angle of the constellation point around the y-axis in the constellation diagram; Indicates the rotation angle of the constellation point around the z-axis in the constellation diagram; in three-dimensional space, the constellation point is represented by three-dimensional coordinates, .

[0114] Then the encrypted signal is expressed as:

[0115] ;

[0116] ;

[0117] ;

[0118] In the formula, Represents the coordinates of the constellation points in the constellation diagram after rotation around the x-axis; Represents the coordinates of the constellation points in the constellation diagram after rotation around the y-axis; Represents the coordinates of the constellation points in the constellation diagram after rotation around the z-axis; Represents the coordinates of the constellation points in the constellation diagram; express The horizontal axis of express The vertical coordinate of express The vertical coordinate of express The horizontal axis of express The vertical coordinate of express The vertical coordinate of express The horizontal axis of express The vertical coordinate of express The vertical coordinate of .

[0119] After three rotations, the original constellation points become a noise-like shape with two spherical shells, such as Figure 8 As shown in the figure, the position information of the subcarrier where the point at the center is located cleverly transmits the high-bit information of the mixed key, while the combined distribution of the two constellation modes transmits the low-bit information of the mixed key. If you want to demodulate, you must get the key, and the masked key is immersed in the noise-like spherical shell encryption signal after rotation, thereby realizing multi-layer encryption.

[0120] Step 8: Perform OFDM modulation on the encrypted signal to obtain a modulated signal, and transmit the modulated signal to a receiving end through an optical fiber channel, specifically:

[0121] For the transmission scheme of the three-dimensional constellation diagram, we choose to operate the rows and columns twice in succession when performing the inverse fast Fourier transform, and convert the frequency domain signal into the time domain signal after IFFT. In order to reduce the inter-symbol interference, we choose to add a cyclic prefix and suffix before and after. Then, the modulated parallel time domain signal is converted into a serial signal and sent to the optical fiber channel.

[0122] Step 9: Only the legal receiving end can extract the correct key for decryption and demodulation through the rules. The illegal receiving end cannot achieve correct demodulation due to the effect of multi-layer encryption and the lack of the key.

[0123] For the key transmission scheme, the key transmission performance is crucial. If the key cannot be accurately extracted after being transmitted to the receiving end, then due to the initial value sensitivity of the chaotic system, the wrong initial value will generate a completely different chaotic sequence, and decryption cannot be completed, which will result in a large bit error rate of the data.

[0124] For a legitimate receiving end, the method further includes: after the receiving end receives the transmission signal, performing the following steps:

[0125] Receive the modulated signal in the optical fiber channel. Fig. 9 Shown is the modulated signal.

[0126] The modulated signal is subjected to OFDM demodulation to obtain a demodulated signal; the demodulated signal is obtained after serial-to-parallel conversion, removal of cyclic prefixes and suffixes, and Fourier transformation.

[0127] The four columns of subcarriers are divided into a group. Due to the design of the rules in Table 1, we can extract the high-order information of the mixed key by judging the position of the silent subcarrier. Due to multiple upsampling, we can compare the key information after extracting it, and take the information with the most occurrences of each bit in 180 times as the final high-order key. This can effectively ensure the accuracy of the key. When the key is accurate, we can restore the initial value of the first key.

[0128] According to the high-order key, the initial value of the first key is reintroduced into the 1D chaotic system to obtain a rotation angle, and the demodulated signal is subjected to reverse constellation rotation decryption to obtain a constellation diagram of the decrypted signal.

[0129] After rotation recovery, the constellation diagram of the decrypted signal is obtained, and then the initial value of the second key is extracted: keep four columns of subcarriers as a group, make a judgment based on the constellation mode corresponding to the signal on the non-silent subcarrier, and reversely index the low-order information of the mixed key according to Table 1, and then obtain the initial value of the second key in the same way as step 3.

[0130] After the initial value of the second key is brought back into the 3D chaotic system, the row and column dimensions of the sub-block matrix are scrambled and restored in turn, and then the signals in the two constellation modes are demapped and restored to the bit level, and then XOR recovery is performed to obtain the restored signal. Fig.10 Shown is the restored signal.

[0131] For illegal receivers, since they do not know the index rules and key embedding methods, they cannot extract the correct information. Our solution can not only ensure the security of the signal through multiple encryptions, but also dynamically transmit the key with high security and accuracy, and the transmission performance of the entire signal can be improved to a certain extent under the design of the index rules.

[0132] Embodiment 2:

[0133] This embodiment introduces a signal transmission device based on joint index modulation, including a processor and a storage medium;

[0134] The storage medium is used to store instructions;

[0135] The processor is used to operate according to the instructions to execute the method described in Example 1.

[0136] Embodiment 3:

[0137] A computer-readable storage medium having a computer program stored thereon, characterized in that the computer program implements the method described in Example 1 when executed by a processor.

[0138] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0139] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0140] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0141] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0142] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A signal transmission method based on joint index modulation, characterized in that: include: Obtaining a signal to be sent, an initial value of a first key, and an initial value of a second key; The first key initial value is passed through a one-dimensional chaotic system to generate a one-dimensional chaotic sequence W, and the second key initial value is passed through a three-dimensional chaotic system to generate a three-dimensional chaotic sequence X, Y, Z; Using X in the three-dimensional chaotic sequence to perform XOR processing on the signal to be sent to obtain a signal after XOR processing; dividing the signal after XOR processing into sub-blocks to obtain a sub-block matrix; using Y and Z in the three-dimensional chaotic sequence to perform scrambling processing on the sub-block matrix to obtain a scrambled signal; The first initial key value and the second initial key value are respectively subjected to binary conversion and serial-to-parallel conversion to obtain the transformed first initial key value and the transformed second initial key value; the transformed first initial key value is upsampled according to a first preset sampling number of times to obtain the sampled first initial key value, and the transformed second initial key value is upsampled according to a second preset sampling number of times to obtain the sampled second initial key value; the sampled first initial key value and the sampled second initial key value are grouped to perform high-low bit interleaving and serial-to-parallel conversion to obtain a key matrix, wherein each unit in the key matrix includes a 4-bit mixed key; the 2 high bits in the mixed key come from the sampled first initial key value, and the 2 low bits in the mixed key come from the sampled second initial key value; The scrambled signal is divided into N groups, each group includes a 9-bit signal, and the 9-bit signal is divided into 3 blocks, each block includes a 3-bit signal; using a preset joint index modulation rule table, according to a 4-bit mixed key, the position of each block of 3-bit signal inserted into the empty subcarrier is determined, and the silent position of the empty subcarrier is silently processed to obtain the indexed subcarrier, wherein the empty subcarrier is four columns; the indexed subcarrier is mapped to two constellation modes to obtain a three-dimensional constellation diagram; the three-dimensional constellation diagram includes constellation points corresponding to the two constellation modes and constellation points generated at the origin; wherein the silent empty subcarrier is subjected to an inverse fast Fourier transform to obtain the constellation point generated at the origin; Using a one-dimensional chaotic sequence W to perform constellation rotation encryption on the three-dimensional constellation diagram to obtain an encrypted signal; Perform OFDM modulation on the encrypted signal to obtain a modulated signal, and transmit the modulated signal to a receiving end through an optical fiber channel; Using the preset joint index modulation rule table, according to the 4-bit mixed key, determine the position of each 3-bit signal inserted into the empty subcarrier, and perform silent processing on the silent position of the empty subcarrier to obtain the indexed subcarrier, including: When the 4-bit mixed key is 0000, the subcarriers after the four columns of indexes are ; Where 0 represents a silent subcarrier, S A Indicates the subcarrier corresponding to constellation mode A, S B Indicates the subcarrier corresponding to constellation mode B; When the 4-bit mixed key is 0001, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0010, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0011, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0100, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0101, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0110, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 0111, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1000, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1001, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1010, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1011, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1100, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1101, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1110, the subcarriers after the four columns of indexes are ; When the 4-bit mixed key is 1111, the subcarriers after the four columns of indexes are .

2. The signal transmission method based on joint index modulation according to claim 1, characterized in that: The one-dimensional chaotic system is expressed as: ； In the formula, represents the nth term of the one-dimensional chaotic sequence W; represents the bifurcation parameter; represents a hyperparameter.

3. The signal transmission method based on joint index modulation according to claim 1, characterized in that: The three-dimensional chaotic system is expressed as: ； In the formula, X, Y, and Z represent three-dimensional state variables; , , represents the derivatives of X, Y, and Z with respect to time t respectively; a, b, c, d, and e are system parameters.

4. The signal transmission method based on joint index modulation according to claim 1, characterized in that: Using X in the three-dimensional chaotic sequence to perform XOR processing on the signal to be sent includes: ； In the formula, Represents the signal after XOR processing; Indicates a signal to be sent; Indicates XOR processing; Indicates the value of the eighth decimal place of the three-dimensional chaotic sequence X; represents the remainder function; represents the floor function; Represents a three-dimensional chaotic sequence.

5. The signal transmission method based on joint index modulation according to claim 1, characterized in that: The sub-block matrix is ​​scrambled by using Y and Z in the three-dimensional chaotic sequence to obtain a scrambled signal, including: The value Y1 of the sixth decimal place of Y in the three-dimensional chaotic sequence is sorted in ascending order and then counted down to generate a matrix, and then multiplied with Y1 to generate a first scrambled matrix Y2; the value Z1 of the sixth decimal place of Z is sorted in ascending order and then counted down to generate a matrix, and then multiplied with Z1 to generate a second scrambled matrix Y2. The first scrambled matrix Y2 and the second scrambled matrix Z2 are expressed as: ； in, Represents ascending sort function; represents the remainder function; Extract the positions of 1 in the first scrambled matrix Y2 and the second scrambled matrix Z2 respectively to generate a first scrambled sequence and a second scrambled sequence; The row and column dimensions of the sub-block matrix are scrambled using the first scrambling sequence and the second scrambling sequence respectively to obtain a scrambled signal.

6. The signal transmission method based on joint index modulation according to claim 1 or 2, characterized in that: The encrypted signal is expressed as: ； ； ； ； In the formula, Represents the coordinates of the constellation points in the constellation diagram after rotation around the x-axis; Represents the coordinates of the constellation points in the constellation diagram after rotation around the y-axis; Represents the coordinates of the constellation points in the constellation diagram after rotation around the z-axis; Represents the coordinates of the constellation points in the constellation diagram; express The horizontal axis of express The vertical coordinate of express The vertical coordinate of express The horizontal axis of express The vertical coordinate of express The vertical coordinate of express The horizontal axis of express The vertical coordinate of express The vertical coordinate of Indicates the rotation angle of the constellation point around the x-axis in the constellation diagram; Indicates the rotation angle of the constellation point around the y-axis in the constellation diagram; Indicates the rotation angle of the constellation point around the z-axis in the constellation diagram; represents the floor function; Represents the remainder function.

7. A signal transmission device based on joint index modulation, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the method according to any one of claims 1 to 6.

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