Cooperative light transmission method and device based on multi-layer index modulation

Abstract

The invention discloses a collaborative optical transmission method and device based on multi-layer index modulation. The method comprises the following steps: acquiring a key and to-be-sent original data; generating a four-dimensional chaotic sequence through a four-dimensional chaotic model according to the key; performing constellation mapping on the original data to obtain a 16QAM constellation signal; performing secondary scrambling on subcarriers and symbols of the 16QAM constellation signal by using the four-dimensional chaotic sequence to obtain a 16QAM scrambling signal; performing binary conversion on the secret key to divide the secret key into a first group of secret keys and a second group of secret keys; performing first-layer index modulation on the 16QAM scrambling signal by using the first group of keys to obtain a first modulation signal, and performing second-layer SIM index modulation on the first modulation signal by using the second group of keys to obtain a second modulation signal; and performing OFDM modulation on the second modulation signal, and transmitting the second modulation signal in an optical fiber channel. The security of a communication system is improved by means of the transmission of the index modulation masking key twice in combination with the multi-dimensional disturbance of subcarriers and symbols.

Description

Technical Field

[0001] This application belongs to the field of optical communication technology, and particularly relates to a cooperative optical transmission method and device based on multi-layer index modulation. Background Art

[0002] Currently, common upper-layer security encryption mechanisms include data security protocols and digital certificates, and physical-layer security encryption mechanisms include quantum encryption, chaotic optical encryption, and digital-domain chaotic encryption. In today's era of the rapid development of quantum computing technology, the former is more easily cracked by brute force, while the latter encrypts the optical signal itself, making it difficult to crack the information completely and clearly, thereby effectively improving security. Quantum key distribution (QKD) is currently widely used in the field of quantum communication, and its security has also been verified. It can distribute keys in the presence of eavesdroppers between two users. However, due to the fact that the devices cannot reach idealization, there are losses and noises in the channel, which reduces the number of available photons, and limited by the detector decoding efficiency, the key distribution rate is relatively low. Chaotic optical encryption technology transforms the plaintext image into a ciphertext image similar to noise through technologies such as diffraction and filtering, which plays a protective role by passing off the false as the real. However, there are also problems such as complex operations, limited distance, long time consumption, and poor anti-interference ability. With the continuous development of digital signal processing technology and the upgrade and optimization of optoelectronic devices, digital signal processing (DSP) can be used to perturb the bit stream, subcarrier symbols, number of subcarriers, and constellation mapping in the DSP process by using the sequence generated by the chaotic system. In this solution, not only can the security of the data be guaranteed, but it is also compatible with the existing optical fiber communication network architecture, maintaining the powerful communication ability of the high-speed optical transmission system.

[0003] The properties of the random sequence generated by the chaotic system depend on the dynamic characteristics of the system, and more complex chaotic systems often have more abundant dynamic characteristics. Therefore, the random sequence generated by them usually has higher randomness. Through comparison, it can be found that digital-domain chaotic encryption can increase the transmission distance, has high timeliness, and small losses compared with quantum encryption and chaotic optical encryption. More importantly, it has higher randomness and initial value sensitivity, so the security is higher. However, most existing solutions have a potential security vulnerability: that is, the transceiver parties usually share keys in advance and use these keys for encryption and decryption operations. However, once the key is leaked and not dealt with in time, it may lead to long-term security risks. In order to improve the security and flexibility of the system, how to transmit the key and data together and support the dynamic update of the key has become the key research direction at present. Summary of the Invention

[0004] Objective: In view of at least one of the above technical problems, the present application provides a collaborative optical transmission method and device based on multi-layer index modulation. By transmitting the masking key through multiple index modulations, the key management is simplified, the complexity of storing and updating keys is reduced, and the security of the communication system is improved.

[0005] The technical solution adopted in the present application is as follows:

[0006] In the first aspect, the present application provides a collaborative optical transmission method based on multi-layer index modulation, including:

[0007] Obtain a key and the original data to be sent;

[0008] Generate four-dimensional chaotic sequences X, Y, Z, and W according to the key through a four-dimensional chaotic model;

[0009] Perform constellation mapping on the original data to obtain a 16QAM constellation signal;

[0010] Use the four-dimensional chaotic sequences X, Y, Z, and W to perform secondary scrambling on the subcarriers and symbols of the 16QAM constellation signal to obtain a 16QAM scrambled signal;

[0011] Convert the key into binary to obtain four binary keys composed of 16 four-bit bits, and divide them into a first group of keys and a second group of keys;

[0012] Use the first group of keys to perform the first-layer index modulation on the 16QAM scrambled signal to obtain a first modulation signal, and use the second group of keys to perform the second-layer SIM index modulation on the first modulation signal to obtain a second modulation signal;

[0013] Perform OFDM modulation on the second modulation signal and then transmit it through an optical fiber channel.

[0014] In some embodiments, using the first group of keys to perform the first-layer index modulation on the 16QAM scrambled signal to obtain a first modulation signal, and using the second group of keys to perform the second-layer SIM index modulation on the first modulation signal to obtain a second modulation signal includes:

[0015] Arrange the subcarriers of the 16QAM scrambled signal in groups. Taking 16 columns of subcarriers as a small group and 8 small groups of subcarrier columns as a large group, construct a 16×8 subcarrier sequence matrix; where each symbol on each subcarrier contains 4 bits;

[0016] First-layer index modulation: According to the first group of keys and the first-layer index modulation rule, determine the subcarrier row orders of two groups with silent situations in the corresponding 16×8 subcarrier sequence matrix, and perform the first-layer index modulation on the subcarrier sequence matrix;

[0017] Second-layer SIM index modulation: According to the second set of keys and the second-layer SIM index modulation rules, respectively determine the column orders of subcarrier silencing for two groups with silencing situations to obtain the specific positions of the two silenced subcarriers, and perform zero silencing processing on these two silenced subcarriers;

[0018] Perform first-layer index modulation and second-layer SIM index modulation on all subcarrier sequence matrices in sequence to obtain a second modulated signal.

[0019] In a second aspect, the present application provides a collaborative optical transmission device based on multi-layer index modulation, including a processor and a storage medium;

[0020] The storage medium is used to store instructions;

[0021] The processor is used to operate according to the instructions to execute the method according to the first aspect.

[0022] In a third aspect, the present application provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the method according to the first aspect is implemented.

[0023] Advantageous effects: The collaborative optical transmission method and device based on multi-layer index modulation provided by the present application have the following advantages: Multi-layer encryption is used to perform multi-dimensional perturbation on the bits, subcarriers, and symbol points of the signal to improve the security performance. At the same time, through two-layer index modulation, according to the designed index modulation mapping rules, the group order of the subcarrier sequence matrix with silencing situations and the silencing positions of the subcarrier sequence are respectively used to represent the key information. With the help of different silencing position states for layer-by-layer indexing, the effect of masking the key during the signal transmission process can be effectively achieved. And the process of the two index modulations has a "double insurance" effect, and the key has better dynamics during the transmission process, reducing the key management complexity.

[0024] By superimposing a sequence group index modulation on top of the basic single-mode index modulation again, the collaborative transmission of the chaotic system keys and information with multi-layer encryption is effectively realized. The key has extremely high masking and flexibility, reducing the risk of leakage. In addition, in the solution of the present invention, only the legitimate receiving end can extract the correct key and decrypt and demodulate the signal through the two index modulation mapping rules involved. Under the protection of multi-layer encryption, the illegal receiving end cannot master the mapping rules involved and thus does not have the ability to extract the key, and finally cannot correctly demodulate the transmitted signal. This solution ensures the high security of the key and information during the collaborative transmission process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flowchart of a collaborative optical transmission method based on multi-layer index modulation according to an embodiment of the present application;

[0026] Figure 2 It is a schematic diagram of the phase diagram of the Rossler four-dimensional chaotic model according to an embodiment of the present application;

[0027] Figure 3 It is a schematic diagram of the binary conversion of the key according to an embodiment of the present application;

[0028] Figure 4 It is a schematic diagram of the principle of multi-layer index modulation key transmission according to an embodiment of the present application;

[0029] Figure 5 It is a schematic diagram of the 16QAM constellation integrating the SIM technology according to an embodiment of the present application. Detailed implementation manners

[0030] The present application will be further described below with reference to the drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0031] In the description of the present application, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, exceeding, etc. are understood as not including the present number, and above, below, within, etc. are understood as including the present number. If there is a description of first and second, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0032] In the description of the present application, the descriptions with reference to terms such as "an embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples" or "some examples" mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0033] The term "and / or" is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " generally represents an "or" relationship between the associated objects before and after.

[0034] Subcarrier Index Modulation (SIM) is a modulation method that transmits information through the position index of subcarriers. In this method, information is modulated by controlling the active (on) or silent (off) state of subcarriers, usually using On-Off Keying (OOK). Specifically, different subcarrier positions represent different information bits, and the on-off state of the subcarriers is used to further transmit information. This method utilizes the frequency-domain position of subcarriers, increasing the modulation method and information-carrying capacity during the transmission process.

[0035] In traditional optical communication encrypted transmission, key management is a potential security risk, usually relying on pre-shared keys or using specialized key exchange protocols for key transmission. These methods have problems such as the risk of key leakage, complex key management, and security being limited by the static nature of the keys. The key-with-transmission technology avoids these problems by dynamically generating keys. In each communication, the key is no longer statically stored or exchanged, but is dynamically generated based on the current communication content, greatly reducing the risk of key leakage and effectively avoiding man-in-the-middle attacks. This application proposes a collaborative transmission method based on multi-layer index modulation, which simplifies key management, reduces the complexity of storing and updating keys, and improves the security of the communication system by masking the key transmission through multiple index modulations.

[0036] This application is a collaborative optical transmission method based on multi-layer index modulation. The specific flowchart is as Figure 1 shown, including constellation mapping, subcarrier frequency and symbol scrambling. There is group-order index modulation masking the key in the silent situation of the first-layer subcarrier sequence matrix, and the second-layer subcarrier sequence group index modulation key masking and other processes. First, perform constellation mapping on the original data, and use the chaotic sequence generated by the Rossler four-dimensional chaotic model to scramble and perturb the subcarriers and symbols respectively to achieve pre-encryption of the transmitted signal. Then, perform two different index modulations hierarchically. The index bits are obtained after binary transformation of the key of the four-dimensional chaotic system. First, perform the first index modulation on the subcarrier sequence matrix to map out the group with silent subcarriers. Then, perform the second SIM modulation on the subcarrier sequence group with silent positions after the first modulation to map out the specific silent positions. The four-dimensional hyperchaotic system under the input of the key initial value will generate four different chaotic sequences, which are respectively used to scramble the subcarriers and symbol points corresponding to the two signal modulations. The signal reaches the receiving end after passing through the OFDM system. At the receiving end, since the encryption process is reversible, two groups of corresponding keys are indexed respectively for the silent position situation of the single subcarrier sequence and the position situation of the subcarrier group with silence in the entire subcarrier matrix. After extracting the keys, the chaotic sequence is obtained through the Rossler four-dimensional chaotic model, and decryption is performed through the inverse process to finally obtain the original data.

[0037] Embodiment 1: This embodiment provides a cooperative optical transmission method based on multi-layer index modulation. As Figure 1 shown, it includes:

[0038] S1. Obtain keys X0, Y0, Z0, W0 and the original data to be transmitted.

[0039] S2. Generate four-dimensional chaotic sequences X, Y, Z, W according to the keys through a four-dimensional chaotic model.

[0040] In some embodiments, in step S2, generating four-dimensional chaotic sequences X, Y, Z, W according to the keys through a four-dimensional chaotic model specifically includes:

[0041] The four-dimensional chaotic model adopts the Rossler four-dimensional chaotic model, expressed as:

[0042] ,

[0043] where X, Y, Z, W are state variables, , , , are the derivatives of X, Y, Z, W with respect to time t respectively, and a, b, c, d, e are system parameters.

[0044] a, b, c, d are the control parameters of the system. When a = 0.2, b = 0.2, c = 5.7, d = 0.1, the system is a chaotic system.

[0045] In this embodiment, the key initial values X0, Y0, Z0, W0 of the four-dimensional chaotic model are 1.001257452376201, 0.995274263515032, 0.011574611854415, 0.023846371520675 respectively. The Runge-Kutta method can be used to solve the partial differential equation to obtain the values of the four-dimensional chaotic sequences. The phase diagram of the obtained Rossler four-dimensional chaotic model is as Figure 2 shown. The value ranges of the four chaotic sequences X, Y, Z, W in the Rossler four-dimensional chaotic model are (-10, 10), (-10, 10), (-5, 5), (-7, 7) respectively. Through the Figure 2 performance in, it can be found that the Rossler four-dimensional chaotic model has a high sensitivity to the initial value. Even a small change in the initial conditions will cause a significant change in the behavior of the system. This initial value sensitivity provides a high level of security for the system and is suitable for encryption applications with high requirements for key security.

[0046] S3. Perform constellation mapping on the original data to obtain a 16QAM constellation signal.

[0047] S4. Use the four-dimensional chaotic sequences X, Y, Z, and W to perform a secondary scrambling of the subcarriers and symbols of the 16QAM constellation signal to obtain a scrambled 16QAM signal.

[0048] In some embodiments, in step S4, using X, Y, Z, and W to perform a secondary scrambling of the subcarriers and symbols of the 16QAM constellation signal to obtain a scrambled 16QAM signal includes:

[0049] S41. Use the four-dimensional chaotic sequences X, Y, Z, and W to generate a first scrambling sequence, a second scrambling sequence, a third scrambling sequence, and a fourth scrambling sequence respectively;

[0050] More specifically, in step S41, using X, Y, Z, and W in the four-dimensional chaotic sequence to generate a first scrambling sequence, a second scrambling sequence, a third scrambling sequence, and a fourth scrambling sequence respectively includes:

[0051] Generate a first scrambling square matrix X1, a second scrambling square matrix Y1, a third scrambling square matrix Z1, and a fourth scrambling square matrix W1 according to X, Y, Z, and W respectively;

[0052] ;

[0053] where mod(-) represents the remainder function, multiplying each chaotic sequence by 10 11 is to generate a scrambling sequence from the 11th digit after the decimal point of the chaotic sequence, aiming to enhance the randomness of subcarrier and symbol masking. sort(-) represents the ascending sorting function, and the sort(-) function is used to sort the array matrix in ascending order and return the sorted result; T represents the transpose of the matrix; multiply the remainder matrix by the sorted transposed matrix to generate four scrambling square matrices; the order of each scrambling square matrix corresponds to the number of subcarriers and symbols in the two scramblings respectively. In each scrambling square matrix, each row and each column contain only one 1, and the rest of the elements are 0.

[0054] Extract the positions of 1 in the first scrambling square matrix X1, the second scrambling square matrix Y1, the third scrambling square matrix Z1, and the fourth scrambling square matrix W1 respectively to generate a first scrambling sequence, a second scrambling sequence, a third scrambling sequence, and a fourth scrambling sequence.

[0055] S42. Use the first scrambling sequence and the second scrambling sequence to perform a first scrambling of the subcarriers and symbols of the 16QAM constellation signal to obtain a first scrambled signal;

[0056] S43. Use the third scrambling sequence and the fourth scrambling sequence to perform a second scrambling of the subcarriers and symbols of the first scrambled signal to obtain a scrambled 16QAM signal.

[0057] S5. Convert the keys X0, Y0, Z0, and W0 through binary conversion to obtain four binary keys each consisting of 16 four-bit bits, and divide them into a first group of keys and a second group of keys;

[0058] It should be noted that in traditional optical communication, the transmitting and receiving ends default to sharing keys, which are easily cracked by brute force to steal information. In the present invention, based on traditional SIM modulation, secondary index modulation is combined with a subcarrier sequence group, and the key is hidden in the information and transmitted to the receiving end together, increasing the difficulty of brute force cracking, thereby further improving the security of the system.

[0059] In this embodiment, the keys X0, Y0, Z0, and W0 are respectively set to 1.001257452376201, 0.995274263515032, 0.011574611854415, and 0.023846371520675. Each key has 16 digits. After being converted into corresponding 4-bit binary numbers, there are 256 bits in total. As Figure 3 shown, first convert the key from decimal to the corresponding binary number, loop it 20 times, extract the key, and then perform bit decision on each bit, and select the one that appears more frequently during the loop as the result, so that the accuracy of the key can be improved. When the receiving end demodulates, this kind of repetition and majority decision can effectively improve the recovery quality of the key, minimize the error propagation as much as possible, ensure that subsequent decryption or other processing processes can be carried out at a lower bit error rate, thereby enhancing the stability and reliability of the entire communication system.

[0060] S6. Use the first group of keys to perform the first-layer index modulation on the 16QAM scrambled signal to obtain a first modulation signal, and use the second group of keys to perform the second-layer SIM index modulation on the first modulation signal to obtain a second modulation signal.

[0061] It should be noted that in traditional SIM modulation technology, only some specific subcarriers are selected to be silent, and information is transmitted through the positions of these silent subcarriers. In this application, according to the set rules, the subcarriers are first grouped and arranged, and the subcarrier sequence group is modulated. During the first index modulation, we can only determine which two subcarrier groups are silent, but we cannot determine the specific positions of the silent subcarriers within the group. The group order of this silent state has been mapped to the first group of index bits. Subsequently, in the second index modulation, the SIM technology is used to further determine the specific positions of the silent subcarriers within the group to obtain the second group of index bits, thereby realizing two-level embedding. The index bits generated during the two modulation processes can all be used to transmit keys, achieving an effect of co-transmitting the masked key and information.

[0062] In some embodiments, step S6 specifically includes:

[0063] S61. Group and arrange the subcarriers of the 16QAM scrambled signal. Take 16 columns of subcarriers as a small group, and 8 small groups of subcarrier columns as a large group to construct a 16×8 subcarrier sequence matrix;

[0064] S62. According to the first group of keys and the first-layer index modulation rule, determine the subcarrier row orders of the two small groups with silent situations in the corresponding 16×8 subcarrier sequence matrix, and perform the first-layer index modulation on the subcarrier sequence matrix;

[0065] S63. According to the second group of keys and the second-layer SIM index modulation rule, respectively determine the column orders of the subcarrier silences in the two small groups with silent situations to obtain the specific positions of the two silent subcarriers, and perform zero silent processing on these two silent subcarriers;

[0066] S64. Sequentially perform the first-layer index modulation and the second-layer SIM index modulation on all subcarrier sequence matrices to obtain the second modulation signal.

[0067] In this embodiment, the modulation format of 16QAM is adopted, each symbol on each subcarrier contains 4 bits, and there are a total of 512 bits of data. In the rules designed in the present invention, there will be 2 small groups with subcarrier silent situations in the first-layer index modulation, with a total of possibilities; there is a position where 1 column of subcarriers is silent in the second-layer SIM index modulation, and possibilities will occur, and 2 4 = 16 < 28. Therefore, in order to represent various combinations in the bit information, at most 4 bits can be used to represent the key. Therefore, during the above key conversion process, the 16-bit key is converted into a 4-bit binary number.

[0068] The bit mapping relationship rules for the two index modulations need to be set by ourselves. The first layer is two choices for the row dimension, and the second layer is to determine the specific positions in the column dimension. The first-layer index modulation rule is shown in Table 1, and the second-layer SIM index modulation rule is shown in Table 2.

[0069] Table 1: First-layer index modulation rule

[0070]

[0071] Table 2: Second-layer SIM index modulation rule

[0072]

[0073] More specifically, the first-layer index modulation rule includes: If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0000", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 1" and "Row 2"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0001", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 1" and "Row 3"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0010", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 1" and "Row 4"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0011", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 1" and "Row 5"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0100", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 2" and "Row 3"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0101", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 2" and "Row 4"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0110", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 2" and "Row 5"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0111", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 2" and "Row 6"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1000", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 3" and "Row 4"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1001", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 3" and "Row 5"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1010", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 3" and "Row 6"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1011", the row orders of the subcarriers of the two groups with silent situations in the subcarrier sequence matrix are "Row 3" and "Row 7"; If the index bits of the first set of keys corresponding to the subcarrier sequence matrix are "1100", the row orders of the subcarriers in the two groups with silent situations in the subcarrier sequence matrix are "Row 4" and "Row 5"; If the index bits of the first set of keys corresponding to the subcarrier sequence matrix are "1101", the row orders of the subcarriers in the two groups with silent situations in the subcarrier sequence matrix are "Row 4" and "Row 6"; If the index bits of the first set of keys corresponding to the subcarrier sequence matrix are "1110", the row orders of the subcarriers in the two groups with silent situations in the subcarrier sequence matrix are "Row 4" and "Row 7"; If the index bits of the first set of keys corresponding to the subcarrier sequence matrix are "1111", the row orders of the subcarriers in the two groups with silent situations in the subcarrier sequence matrix are "Row 4" and "Row 8".

[0074] More specifically, the second-layer SIM index modulation rule includes:

[0075] If the index bits of the second set of keys corresponding to the subcarrier group with a silent situation are "0000", the column order of the silent subcarriers in this subcarrier group is "Column 1";

[0076] If the index bits of the second set of keys corresponding to the subcarrier group with a silent situation are "0001", the column order of the silent subcarriers in this subcarrier group is "Column 2";

[0077] If the index bits of the second set of keys corresponding to the subcarrier group with a silent situation are "0010", the column order of the silent subcarriers in this subcarrier group is "Column 3";

[0078] If the index bits of the second set of keys corresponding to the subcarrier group with a silent situation are "0011", the column order of the silent subcarriers in this subcarrier group is "Column 4";

[0079] If the index bits of the second set of keys corresponding to the subcarrier group with a silent situation are "0100", the column order of the silent subcarriers in this subcarrier group is "Column 5";

[0080] If the index bits of the second set of keys corresponding to the subcarrier group with a silent situation are "0101", the column order of the silent subcarriers in this subcarrier group is "Column 6";

[0081] If the index bits of the second set of keys corresponding to the subcarrier group with a silent situation are "0110", the column order of the silent subcarriers in this subcarrier group is "Column 7";

[0082] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "0111", the column order of the silent subcarriers in this subcarrier group is "Column 8";

[0083] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1000", the column order of the silent subcarriers in this subcarrier group is "Column 9";

[0084] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1001", the column order of the silent subcarriers in this subcarrier group is "Column 10";

[0085] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1010", the column order of the silent subcarriers in this subcarrier group is "Column 11";

[0086] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1011", the column order of the silent subcarriers in this subcarrier group is "Column 12";

[0087] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1100", the column order of the silent subcarriers in this subcarrier group is "Column 13";

[0088] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1101", the column order of the silent subcarriers in this subcarrier group is "Column 14";

[0089] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1110", the column order of the silent subcarriers in this subcarrier group is "Column 15";

[0090] If the index bit of the second group of keys corresponding to the subcarrier group with a silent situation is "1111", the column order of the silent subcarriers in this subcarrier group is "Column 16".

[0091] Such as Figure 4As shown, taking a set of 512-bit data as an example, first perform the first index modulation on the subcarrier sequence matrix, that is: after corresponding 4-bit keys to the positions of the subcarrier sequences with silent situations, perform the first-layer index modulation, and fill part of the data into the subcarrier groups without silent situations in order, realizing the first co-transmission of keys and data. Then perform the second-layer SIM index modulation on the subcarriers of two groups with silent situations (such as the first row and the third row), process the data according to the SIM principle, each group of data generates 16 columns of subcarriers, according to the second-layer SIM index modulation rule, map the 4-bit key information to the positions of each column of subcarriers in the group and then perform traditional SIM modulation, fill the remaining data into the remaining subcarriers of the group in order, and perform the same processing on the other group, finally skillfully completing the process of key co-transmission, and carrying a higher data rate under the same bandwidth.

[0092] The index bits of the whole process are determined by the subcarrier silent positions and are not directly reflected in the traditional amplitude / phase constellation diagram, making it difficult for eavesdroppers to easily detect. Through two-layer index modulation, the difficulty for attackers to guess the index pattern is further increased. If there is a bit error in binary during demodulation due to misalignment, the original data cannot be restored, and the two-layer index rules are designed differently. Even if the index key embedding rule of the first layer is cracked, it is difficult to break through the second layer. The double-insurance effect can greatly improve the security of the system.

[0093] S7. After performing OFDM modulation on the second modulation signal, it enters the optical fiber channel for transmission.

[0094] In the OFDM system of this application, first divide the broadband signal into multiple orthogonal subcarriers and perform 16QAM modulation on these subcarriers according to a predetermined grouping structure; then within each subcarrier group, by controlling the active or silent states of some subcarriers, realize the first-stage index modulation - that is, judge whether there is a silent phenomenon in a group and embed the corresponding key information. Then for the subcarrier groups detected to have a silent state, further utilize the OFDM frequency-domain characteristics to realize the second-stage index modulation through the specific positions of the silent subcarriers, thereby embedding additional index bits (key information) again. Finally, at the transmitter, convert the frequency-domain signal into a time-domain signal through IFFT and add a cyclic prefix to resist multipath interference.

[0095] At the receiving end, the cyclic prefix is removed, FFT is performed, and channel equalization is carried out. The frequency-domain signals after OFDM demodulation are utilized to recover the active and silent subcarriers, thereby completing the joint demodulation of the regular data and the two-level index bits. First, the received OFDM signal is synchronized, the cyclic prefix is removed, and FFT transformation is performed to obtain the frequency-domain complex samples of each subcarrier. Then, each subcarrier is equalized using the channel estimation result to counteract the channel effect. Subsequently, each small group (16 columns of subcarriers) is processed according to a predetermined subcarrier grouping method. By comparing the received power of each subcarrier with a set threshold, it is determined whether there are silent subcarriers in this group, thereby generating the first group of index bits. If a silent phenomenon is detected, the specific positions of the silent subcarriers are further determined in this group by using minimum power decision or maximum likelihood detection, and these positions are mapped to the second group of index bits. If there are no silent subcarriers in this subcarrier group, the second-layer index modulation is directly skipped, and conventional 16QAM demodulation is performed to recover the data bits. Among them, the index bits of the first group and the second group are used to transmit the key by identifying the positions. The receiving end integrates the index bits extracted by the two index modulations with the regular data bits to completely recover the transmitted data containing the original data and the embedded key information. As Figure 5 shown, since SIM is used to hide the key, signals will be generated at the silent subcarriers after passing through the OFDM system. Compared with the ordinary 16QAM constellation diagram, there will be an additional constellation point at the origin to represent the information of the silent position situation.

[0096] The entire receiving and demodulating process is based on the traditional OFDM framework, and on this basis, the detection steps of index modulation are added, which can effectively extract index information and data from the mixed signal. For an illegal receiving end, since it does not know the two-layer index rules and the key embedding method, it is impossible to brute-force crack and extract the correct information. The proposed solution of the present invention can not only ensure the security of the signal through multiple encryptions, but also dynamically and collaboratively transmit the key and data with high security and high accuracy, effectively improving the security, concealment, and data transmission efficiency of the system. And it can create possibilities for more levels and more data collaborative transmissions.

[0097] This application proposes a collaborative transmission method based on multi-layer index modulation. By masking the transmission of the key through multiple index modulations, it simplifies the key management, reduces the complexity of storing and updating the key, and improves the security of the communication system. Compared with the situation where both the transmitting and receiving ends know the key in the traditional transmission method, relying on two index modulations, the activation state of the key-controlled signal subcarriers is used for masking, and combined with the use of a four-dimensional chaotic system to achieve multi-dimensional perturbations of bits, subcarriers, and symbol points, ultimately realizing the collaborative transmission of signals and keys. For a legitimate receiving end, the key can be correctly extracted and restored for demodulation, while an illegal receiving end cannot crack the information without knowing the key and the encryption method.

[0098] Example 2: Based on Example 1, this example provides a collaborative optical transmission device based on multi-layer index modulation, including a processor and a storage medium;

[0099] The storage medium is used to store instructions;

[0100] The processor is used to operate according to the instructions to execute the method described in Example 1.

[0101] Example 3: Based on Example 1, this example provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the method described in Example 1 is implemented.

[0102] Example 4: Based on Example 1, this example provides a computer device, including a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the method described in Example 1 is implemented.

[0103] Example 5: Based on Example 1, this example provides a computer program product, including a computer program, and when the computer program is executed by a processor, the method described in Example 1 is implemented.

[0104] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take 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 code.

[0105] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the processes and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0106] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the function specified in one or more of the processes and / or blocks Figure 1 one or more of the processes and / or blocks Figure 1 specified in the block or blocks.

[0107] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable apparatus provide steps for implementing the function specified in one or more of the processes and / or blocks Figure 1 one or more of the processes and / or blocks Figure 1 specified in the block or blocks.

[0108] The foregoing is only a preferred embodiment of the present application, and it should be noted that: for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A collaborative optical transmission method based on multi-layer index modulation, characterized in that: include: Get the key and the original data to be sent; Generate four-dimensional chaotic sequences X, Y, Z, and W through a four-dimensional chaotic model according to the key; Perform constellation mapping on the original data to obtain a 16QAM constellation signal; The 16QAM constellation signal is scrambled twice using the four-dimensional chaotic sequence X, Y, Z, and W to perform subcarrier and symbol scrambling on the 16QAM constellation signal to obtain a 16QAM scrambled signal. The key is converted into binary to obtain four binary keys consisting of 16 four-bit bits, which are divided into a first group of keys and a second group of keys; Using the first group of keys to perform first layer index modulation on the 16QAM scrambled signal to obtain a first modulated signal, and using the second group of keys to perform second layer SIM index modulation on the first modulated signal to obtain a second modulated signal; The second modulated signal is OFDM modulated and then enters the optical fiber channel for transmission.

2. The method according to claim 1, characterized in that Using a first group of keys to perform a first layer index modulation on the 16QAM scrambled signal to obtain a first modulated signal, and using a second group of keys to perform a second layer SIM index modulation on the first modulated signal to obtain a second modulated signal, including: The subcarriers of the 16QAM scrambled signal are grouped and arranged, with 16 columns of subcarriers as a small group and 8 small groups of subcarriers as a large group, to construct a 16×8 subcarrier sequence matrix; each symbol on each subcarrier contains 4 bits; First-layer index modulation: According to the first group of keys and the first-layer index modulation rule, the subcarrier row sequence of the two groups with silence in the corresponding 16×8 subcarrier sequence matrix is ​​determined, and the first-layer index modulation is performed on the subcarrier sequence matrix; Second layer SIM index modulation: According to the second group of keys and the second layer SIM index modulation rule, the column order of the subcarriers in the two groups with silence is determined respectively, the specific positions of the two silent subcarriers are obtained, and the two silent subcarriers are set to zero for silence processing; The first layer index modulation and the second layer SIM index modulation are performed on all subcarrier sequence matrices in sequence to obtain a second modulated signal.

3. The method according to claim 2, characterized in that The first layer index modulation rule includes: If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0000", the row sequences of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 1" and "row 2"; If the index bit of the first group of keys corresponding to the subcarrier sequence matrix is ​​"0001", the row sequence of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 1" and "row 3"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0010", the row sequence of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 1" and "row 4"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0011", the row sequence of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 1" and "row 5"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0100", the row sequence of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 2" and "row 3"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0101", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 2" and "row 4"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0110", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 2" and "row 5"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0111", the row sequences of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 2" and "row 6"; If the index bit of the first group of keys corresponding to the subcarrier sequence matrix is ​​"1000", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 3" and "row 4"; If the index bit of the first group of keys corresponding to the subcarrier sequence matrix is ​​"1001", the row sequence of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 3" and "row 5"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1010", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 3" and "row 6"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1011", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 3" and "row 7"; If the index bit of the first group of keys corresponding to the subcarrier sequence matrix is ​​"1100", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 4" and "row 5"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1101", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 4" and "row 6"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1110", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is ​​"row 4" and "row 7"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1111", the row sequences of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 4" and "row 8".

4. The method according to claim 2, characterized in that: The second layer SIM index modulation rule includes: If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0000", the column order of the silent subcarriers in the subcarrier group is "column 1"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0001", the column order of the silent subcarriers in the subcarrier group is "column 2"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0010", the column order of the silent subcarriers in the subcarrier group is "column 3"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0011", the column order of the silent subcarriers in the subcarrier group is "column 4"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0100", the column order of the silent subcarriers in the subcarrier group is "column 5"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0101", the column order of the silent subcarriers in the subcarrier group is "column 6"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0110", the column order of the silent subcarriers in the subcarrier group is "column 7"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "0111", the column order of the silent subcarriers in the subcarrier group is "column 8"; If the index bit of the second group of keys corresponding to the subcarrier group with silence is "1000", the column order of the silent subcarriers in the subcarrier group is "column 9"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "1001", the column order of the silent subcarriers in the subcarrier group is "column 10"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "1010", the column order of the silent subcarriers in the subcarrier group is "column 11"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "1011", the column order of the silent subcarriers in the subcarrier group is "column 12"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "1100", the column order of the silent subcarriers in the subcarrier group is "column 13"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "1101", the column order of the silent subcarriers in the subcarrier group is "column 14"; If the index bits of the second group of keys corresponding to the subcarrier group with silence are "1110", the column order of the silent subcarriers in the subcarrier group is "column 15"; If the index bits of the second group of keys corresponding to the subcarrier group in which silence exists are "1111", the column order of the silent subcarriers in the subcarrier group is "column 16".

5. The method according to claim 1, characterized in that The four-dimensional chaos model adopts the Rossler four-dimensional chaos model, which is expressed as: ， Among them, X, Y, Z, and W are state variables. , , , are the derivatives of X, Y, Z, W with respect to time t respectively, and a, b, c, d, e are system parameters.

6. The method according to claim 1 or 5, characterized in that: The keys X0, Y0, Z0, and W0 are 1.001257452376201, 0.995274263515032, 0.011574611854415, and 0.023846371520675, respectively; And / or, the value ranges of the four-dimensional chaotic sequences X, Y, Z, and W are (-10, 10), (-10, 10), (-5, 5), and (-7, 7), respectively.

7. The method according to claim 1, characterized in that The 16QAM scrambled signal is obtained by performing secondary scrambling of subcarriers and symbols of the 16QAM constellation signal using the four-dimensional chaotic sequence X, Y, Z, and W, including: Using four-dimensional chaotic sequences X, Y, Z, and W, a first scrambled sequence, a second scrambled sequence, a third scrambled sequence, and a fourth scrambled sequence are generated respectively; Performing a first scrambling of subcarriers and symbols of a 16QAM constellation signal using a first scrambling sequence and a second scrambling sequence to obtain a first scrambled signal; The subcarriers and symbols of the first scrambled signal are scrambled for the second time using the third scrambled sequence and the fourth scrambled sequence to obtain a 16QAM scrambled signal.

8. The method according to claim 7, characterized in that Using X, Y, Z, and W in the four-dimensional chaotic sequence to generate a first scrambled sequence, a second scrambled sequence, a third scrambled sequence, and a fourth scrambled sequence, respectively, includes: Generate the first scrambled matrix X1, the second scrambled matrix Y1, the third scrambled matrix Z1, and the fourth scrambled matrix W1 according to X, Y, Z, and W respectively; ； Among them, mod(-) represents the remainder function, sort(-) represents the ascending sorting function; T represents the transpose of the matrix; The positions of 1 in the first scrambled matrix X1, the second scrambled matrix Y1, the third scrambled matrix Z1, and the fourth scrambled matrix W1 are extracted respectively to generate a first scrambled sequence, a second scrambled sequence, a third scrambled sequence, and a fourth scrambled sequence.

9. A collaborative optical transmission device based on multi-layer 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 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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