A collaborative optical transmission method and device based on multi-layer index modulation

Abstract

The present application discloses a collaborative optical transmission method and device based on multi-layer index modulation, which includes the following steps: obtaining a key and original data to be sent; generating a four-dimensional chaotic sequence based on the key using a four-dimensional chaotic model; constellation mapping the original data to obtain a 16QAM constellation signal; performing secondary scrambling of the subcarriers and symbols of the 16QAM constellation signal using the four-dimensional chaotic sequence to obtain a 16QAM scrambled signal; performing binary conversion on the key to separate it into a first set of keys and a second set of keys; performing a first-layer index modulation on the 16QAM scrambled signal using the first set of keys to obtain a first modulated signal, and performing a second-layer SIM index modulation on the first modulated signal using the second set of keys to obtain a second modulated signal; and performing OFDM modulation on the second modulated signal and then transmitting it through an optical fiber channel. By masking the transmission of the key using two index modulations and combining the multi-dimensional perturbation of the subcarriers and symbols, the security of the communication system is improved.

Description

Technical Field

[0001] The present application belongs to the field of optical communication technology, and specifically relates to a collaborative 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, while physical-layer security encryption mechanisms include quantum encryption, chaotic optical encryption, and digital domain chaotic encryption. With the rapid development of quantum computing technology, the former is more susceptible to brute-force attacks, while the latter effectively improves security by encrypting the optical signal itself, making it difficult to completely and unambiguously decrypt the information. Quantum key distribution (QKD) is currently widely used in quantum communications and its security has been proven. It can distribute keys even when there is an eavesdropper between two users. However, due to the imperfect device performance, channel losses and noise reduce the number of available photons. Furthermore, the key distribution rate is relatively low due to the limited decoding efficiency of the detector. Chaotic optical encryption technology uses diffraction and filtering techniques to transform plaintext images into ciphertext images that resemble noise, thereby providing a secure and reliable encryption solution. However, it also suffers from complex operation, limited distance, long processing time, and poor anti-interference capabilities. With the continuous development of digital signal processing technology and the upgrade and optimization of optoelectronic devices, it is possible to use sequences generated by chaotic systems through digital signal processing (DSP) to perturb the bit stream, subcarrier symbols, number of subcarriers, and constellation mapping during the DSP process. This solution not only ensures data security but also is compatible with existing fiber-optic communication network architectures, maintaining the powerful communication capabilities of high-speed optical transmission systems.

[0003] The properties of random sequences generated by chaotic systems depend on their dynamical characteristics. More complex chaotic systems tend to have richer dynamical characteristics, and therefore the random sequences they generate are generally more random. Comparisons show that digital domain chaotic encryption, compared to quantum encryption and chaotic optical encryption, can extend transmission distances, improve timeliness, and reduce losses. More importantly, it exhibits greater randomness and initial value sensitivity, resulting in higher security. However, most existing schemes suffer from a potential security vulnerability: the sender and receiver typically share a secret key in advance and use it for encryption and decryption. However, if the key is leaked and not promptly addressed, it can pose a long-term security risk. To improve system security and flexibility, how to transmit the key along with the data and support dynamic key updates has become a key research direction. Summary of the Invention

[0004] Purpose: 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, which simplifies key management, reduces the complexity of storing and updating keys, and improves the security of the communication system by masking the transmission of keys through multiple index modulations.

[0005] The technical solutions adopted in this application are:

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

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

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

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

[0010] 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.

[0011] 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;

[0012] Performing a first layer index modulation on the 16QAM scrambled signal using a first set of keys to obtain a first modulated signal, and performing a second layer SIM index modulation on the first modulated signal using a second set of keys to obtain a second modulated signal;

[0013] The second modulated signal is subjected to OFDM modulation and then enters the optical fiber channel for transmission.

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

[0015] The subcarriers of the 16QAM scrambled signal are grouped and arranged, with 16 columns of subcarriers forming a small group and 8 subcarrier groups forming a large group, to form a 16×8 subcarrier sequence matrix. Each symbol on each subcarrier contains 4 bits.

[0016] First-layer index modulation: Based on the first set 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;

[0017] Second-layer SIM index modulation: Based on the second group of keys and the second-layer SIM index modulation rules, the subcarrier muting sequence of the two subgroups with muting is determined, the specific positions of the two muted subcarriers are obtained, and the two muted subcarriers are silenced by setting them to zero.

[0018] First-layer index modulation and second-layer SIM index modulation are performed on all subcarrier sequence matrices in sequence to obtain second modulated signals.

[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 configured 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 having a computer program stored thereon, which implements the method described in the first aspect when the computer program is executed by a processor.

[0023] Beneficial 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 perturbations on the bits, subcarriers, and symbol points of the signal to improve security performance. At the same time, through two-layer index modulation, according to the designed index modulation mapping rules, the subcarrier sequence matrix's silent group sequence and the silent position of the subcarrier sequence are used to represent the key information respectively. With the help of different silent position states, the effect of masking the key during the signal transmission process can be effectively achieved by indexing layer by layer. In addition, the process of two index modulations has the effect of "double insurance", and the key has better dynamics during the transmission process, which reduces the complexity of key management.

[0024] By superimposing a sequence group index modulation on top of the basic single-mode index modulation, the coordinated transmission of keys and information in a multi-layer encrypted chaotic system is effectively achieved. This provides extremely high concealment and flexibility for the keys, reducing the risk of leakage. Furthermore, in the scheme of the present invention, only legitimate receivers can extract the correct key and decrypt and demodulate the signal through the mapping rules involved in the two index modulations. Illegal receivers, protected by multi-layer encryption, are unable to grasp the mapping rules involved and thus lack the ability to extract the key, ultimately failing to correctly demodulate the transmitted signal. This scheme ensures the high security of the keys and information during the coordinated transmission process. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 Schematic diagram of a phase diagram of the Rossler four-dimensional chaos model according to an embodiment of the present application;

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

[0028] Figure 4 Schematic diagram of the principle of multi-layer index modulation key transmission according to one embodiment of the present application;

[0029] Figure 5 FIG. 1 is a schematic diagram of a 16QAM constellation incorporating SIM technology according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] The present application will be further described below in conjunction with the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application.

[0031] In the description of this application, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

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

[0033] The term "and / or" simply describes a relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. Additionally, the character " / " generally indicates an "or" relationship between the related objects.

[0034] Subcarrier Index Modulation (SIM) is a modulation method that transmits information by indexing the position of subcarriers. In this method, information is modulated by controlling the active (on) or silent (off) state of subcarriers, typically 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 convey information. This method utilizes the frequency domain position of subcarriers to increase the modulation options and information carrying capacity during transmission.

[0035] In traditional optical communication encryption transmission, key management is a potential security risk, which usually relies on pre-shared keys or the use of special key exchange protocols for key transmission. These methods have problems such as the risk of key leakage, complex key management, and security is limited by the static nature of the key. The key 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, which greatly reduces the risk of key leakage and effectively avoids man-in-the-middle attacks. This application proposes a collaborative transmission method based on multi-layer index modulation, which masks the transmission of keys through multiple index modulations, simplifies key management, reduces the complexity of storing and updating keys, and improves the security of the communication system.

[0036] This application is a collaborative optical transmission method based on multi-layer index modulation, the specific flow chart is as follows Figure 1 As shown, the process includes constellation mapping, subcarrier frequency and symbol scrambling. The first-level subcarrier sequence matrix is muted by group index modulation to mask the key, and the second-level subcarrier sequence is re-masked by group index modulation. The original data is first constellated. The chaotic sequence generated by the Rossler four-dimensional chaotic model is used to scramble and perturb the subcarriers and symbols, respectively, to achieve pre-encryption of the transmitted signal. Two different index modulations are then performed hierarchically. The index bits select the key of the four-dimensional chaotic system and are obtained by binary transformation. The subcarrier sequence matrix is first subjected to index modulation to map the subcarrier groups with muted subcarriers. The subcarrier sequence groups with muted positions after the initial modulation are then subjected to a second SIM modulation to map the specific muted positions. The four-dimensional hyperchaotic system, with the initial key input, generates four different chaotic sequences, corresponding to the scrambling of the subcarriers and symbol points during the two signal modulations. The signal passes through the OFDM system and reaches the receiver. At the receiving end, since the encryption process is reversible, two sets of corresponding keys are indexed for the silent position of a single subcarrier sequence and the position of a small group of silent subcarriers in the entire subcarrier matrix. After extracting the key, the chaotic sequence is obtained through the Rossler four-dimensional chaotic model, and decrypted through the inverse process to finally obtain the original data.

[0037] Example 1: This embodiment provides a collaborative optical transmission method based on multi-layer index modulation, such as Figure 1 Shown, including:

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

[0039] S2. Generate a four-dimensional chaotic sequence X, Y, Z, and W using a four-dimensional chaotic model according to the key.

[0040] In some embodiments, step S2, generating a four-dimensional chaotic sequence X, Y, Z, and W using a four-dimensional chaotic model according to the key, specifically includes:

[0041] The four-dimensional chaos model adopts the Rossler four-dimensional chaos model, which is expressed as:

[0042] ,

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

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

[0045] In this embodiment, the initial values of the keys X0, Y0, Z0, and W0 of the four-dimensional chaotic model are 1.001257452376201, 0.995274263515032, 0.011574611854415, and 0.023846371520675, respectively. The partial differential equation can be solved by the Runge-Kutta method to obtain the value of the four-dimensional chaotic sequence. The phase diagram of the Rossler four-dimensional chaotic model is shown in FIG. Figure 2 As shown in the figure. The value ranges of the four chaotic sequences X, Y, Z, and W in the Rossler four-dimensional chaos model are (-10, 10), (-10, 10), (-5, 5), and (-7, 7). Figure 2 As can be seen from the performance in

[15] , the Rossler four-dimensional chaos model is highly sensitive to initial values. Even small changes in initial conditions can lead to significant changes in the system's behavior. This initial value sensitivity provides the system with high security, making it suitable for encryption applications that require high key security.

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

[0047] S4. Use the four-dimensional chaotic sequence 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.

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

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

[0050] More specifically, in step S41, 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:

[0051] 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;

[0052] ;

[0053] Among them, mod(-) represents the remainder function, and each chaotic sequence is multiplied by 10 11 The purpose is to generate a scrambled sequence from the 11th decimal place of the chaotic sequence, enhancing the randomness of the subcarrier and symbol masking. sort(-) represents an ascending sorting function, which sorts an array matrix in ascending order and returns the sorted result. T represents the transpose of the matrix. The remainder matrix is multiplied by the sorted transpose matrix to generate four scrambled matrices. The order of each scrambled matrix corresponds to the number of subcarriers and symbols in the two scrambles, respectively. In each scrambled matrix, each row and column contains only one 1, and the remaining elements are 0.

[0054] 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.

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

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

[0057] S5. Convert the keys X0, Y0, Z0, and W0 into binary form 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.

[0058] It should be noted that in traditional optical communications, the sender and receiver share a key by default, making it vulnerable to brute force attacks. This invention combines traditional SIM modulation with subcarrier sequence groups for secondary index modulation, embedding the key within the information and transmitting it to the receiver. This makes brute force attacks more difficult, further improving system security.

[0059] In this embodiment, the keys X0, Y0, Z0, and W0 are set to 1.001257452376201, 0.995274263515032, 0.011574611854415, and 0.023846371520675, respectively. Each key has 16 digits, which is 256 bits after being converted into the corresponding 4-bit binary number. Figure 3 As shown, the key is first converted from decimal to its corresponding binary number, which is then looped 20 times. After extracting the key, a bit decision is performed on each bit, and the result is selected based on the number that appears most frequently in the loop. This improves the key's accuracy. This repetition and majority decision-making during demodulation at the receiving end effectively improves key recovery quality, minimizes error propagation, and ensures that subsequent decryption or other processing can be performed with a lower bit error rate, thereby enhancing the stability and reliability of the entire communication system.

[0060] S6. Perform first-layer index modulation on the 16QAM scrambled signal using the first set of keys to obtain a first modulated signal, and perform second-layer SIM index modulation on the first modulated signal using the second set of keys to obtain a second modulated signal.

[0061] It should be noted that in traditional SIM modulation technology, only certain specific subcarriers are selected for silence, and information is transmitted through the position 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 position of the silent subcarriers in the group. The group sequence of the silent state has been mapped to the first group of index bits. Subsequently, in the second index modulation, SIM technology is used to further determine the specific position of the silent subcarrier in the group, and the second group of index bits is obtained, thereby realizing two-level embedding. The index bits generated in the two modulation processes can be used to transmit keys, achieving the effect of masking the key and collaborative transmission of information.

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

[0063] S61. Arrange the subcarriers of the 16QAM scrambled signal in groups, with 16 columns of subcarriers forming a small group and 8 small groups of subcarriers forming a large group, to construct a 16×8 subcarrier sequence matrix.

[0064] S62. Determine the subcarrier row sequence of the two subgroups with silence in the corresponding 16×8 subcarrier sequence matrix according to the first group of keys and the first-layer index modulation rule, and perform first-layer index modulation on the subcarrier sequence matrix.

[0065] S63. Determine, based on the second group of keys and the second layer SIM index modulation rule, the column order of the subcarriers in the two groups where silence occurs, obtain the specific positions of the two silent subcarriers, and perform a silence process on the two silent subcarriers by setting them to zero.

[0066] S64 . Perform first-layer index modulation and second-layer SIM index modulation on all subcarrier sequence matrices in sequence to obtain a second modulated signal.

[0067] In this embodiment, the modulation format of 16QAM is adopted. Each symbol on each subcarrier contains 4 bits, with a total of 512 bits of data. In the rules designed by the present invention, there will be 2 groups of subcarriers with silent conditions in the first layer index modulation, with a total of There are two possibilities: there is a column of subcarrier silence in the second layer SIM index modulation, which will appear Possible, and 2 4 =16<28, so in order to represent various combinations in bit information, at most 4 bits can be used to represent the key. Therefore, in the key conversion process above, the 16-bit key is converted into a 4-bit binary number.

[0068] The bit mapping rules for the two index modulations must be defined by us. The first level defines two options for the row dimension, and the second level determines the specific position of the column dimension. The first level index modulation rules are shown in Table 1, and the second level SIM index modulation rules are shown in Table 2.

[0069] Table 1: First layer index modulation rules

[0070]

[0071] Table 2: Second layer SIM index modulation rules

[0072]

[0073] More specifically, the first-layer index modulation rule includes:

[0074] If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0000", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is "row 1" and "row 2";

[0075] 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 silence in the subcarrier sequence matrix are "row 1" and "row 3";

[0076] 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 silence in the subcarrier sequence matrix are "row 1" and "row 4";

[0077] 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 silence in the subcarrier sequence matrix are "row 1" and "row 5";

[0078] If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "0100", the row order of the subcarriers of the two groups with silence in the subcarrier sequence matrix is "row 2" and "row 3";

[0079] 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 silence in the subcarrier sequence matrix are "row 2" and "row 4";

[0080] 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";

[0081] 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 silence in the subcarrier sequence matrix are "row 2" and "row 6";

[0082] 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 silence in the subcarrier sequence matrix are "row 3" and "row 4";

[0083] 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 silence in the subcarrier sequence matrix are "row 3" and "row 5";

[0084] 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 silence in the subcarrier sequence matrix are "row 3" and "row 6";

[0085] 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 silence in the subcarrier sequence matrix are "row 3" and "row 7";

[0086] If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1100", the row orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 4" and "row 5";

[0087] If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1101", the row orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 4" and "row 6";

[0088] If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1110", the row orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 4" and "row 7";

[0089] If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1111", the row orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 4" and "row 8".

[0090] More specifically, the second layer SIM index modulation rule includes:

[0091] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0000", the column order of the silent subcarriers in the subcarrier group is "column 1";

[0092] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0001", the column order of the silent subcarriers in the subcarrier group is "column 2";

[0093] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0010", the column order of the silent subcarriers in the subcarrier group is "column 3";

[0094] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0011", the column order of the silent subcarriers in the subcarrier group is "column 4";

[0095] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0100", the column order of the silent subcarriers in the subcarrier group is "column 5";

[0096] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0101", the column order of the silent subcarriers in the subcarrier group is "column 6";

[0097] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0110", the column order of the silent subcarriers in the subcarrier group is "column 7";

[0098] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "0111", the column order of the silent subcarriers in the subcarrier group is "column 8";

[0099] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1000", the column order of the silent subcarriers in the subcarrier group is "column 9";

[0100] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1001", the column order of the silent subcarriers in the subcarrier group is "column 10";

[0101] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1010", the column order of the silent subcarriers in the subcarrier group is "column 11";

[0102] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1011", the column order of the silent subcarriers in the subcarrier group is "column 12";

[0103] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1100", the column order of the silent subcarriers in the subcarrier group is "column 13";

[0104] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1101", the column order of the silent subcarriers in the subcarrier group is "column 14";

[0105] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1110", the column order of the silent subcarriers in the subcarrier group is "column 15";

[0106] If the index bits of the second group of keys corresponding to the subcarrier group in which silence occurs are "1111", the column order of the silent subcarriers in the subcarrier group is "column 16".

[0107] like Figure 4 As shown, taking a 512-bit data block as an example, the subcarrier sequence matrix undergoes a first-level index modulation. This involves mapping the 4-bit key to the position of the subcarrier sequence with silence, followed by a first-level index modulation. Partial data is then sequentially inserted into the subcarrier groups without silence, achieving the initial coordinated transmission of key and data. Next, a second-level SIM index modulation is performed on the subcarriers in two subcarrier groups with silence (e.g., rows 1 and 3). Data processing is performed according to the SIM principle, generating 16 columns of subcarriers for each subcarrier group. Following the second-level SIM index modulation rules, the 4-bit key information is mapped to the position of each subcarrier column within the group, followed by traditional SIM modulation. The remaining data is sequentially inserted into the remaining subcarriers in that group. The same process is repeated for the other subcarrier group, ultimately completing the key transmission process and enabling higher data rates within the same bandwidth.

[0108] The index bits in this entire process are determined by the subcarrier's silent position and are not directly reflected in traditional amplitude / phase constellation diagrams, making them difficult for eavesdroppers to detect. The two-layer index modulation further increases the difficulty for attackers to guess the index pattern. If a misalignment during demodulation causes a binary bit error, the original data cannot be recovered. Furthermore, the two layers of indexing rules are designed differently, so even if the index key embedding rules of the first layer are cracked, it is difficult to break through the second layer. This double insurance effect greatly improves system security.

[0109] S7. Perform OFDM modulation on the second modulated signal and then transmit it into the optical fiber channel for transmission.

[0110] In the OFDM system of this application, the broadband signal is first divided into multiple orthogonal subcarriers, and these subcarriers are modulated with 16QAM according to a predetermined grouping structure. Then, within each subcarrier group, the first stage of index modulation is implemented by controlling the activation or silence state of some subcarriers. That is, it is determined whether there is silence in a certain group and the corresponding key information is embedded. Then, for the subcarrier group detected to be in a silent state, the OFDM frequency domain characteristics are further utilized to implement the second stage of index modulation through the specific location of the silent subcarrier, thereby embedding additional index bits (key information) again. Finally, at the transmitter, the frequency domain signal is converted into a time domain signal through IFFT, and a cyclic prefix is added to resist multipath interference.

[0111] At the receiving end, the cyclic prefix is removed, FFT and channel equalization are performed, and the frequency-domain signal after OFDM demodulation is used to recover the active and silent subcarriers, thereby completing the joint demodulation of regular data and two-level index bits. The received OFDM signal is first synchronized, the cyclic prefix is removed, and an FFT is performed to obtain frequency-domain complex samples of each subcarrier. Each subcarrier is then equalized using the channel estimation results to offset channel effects. Each subcarrier group (16 columns of subcarriers) is then processed according to a predetermined subcarrier grouping scheme. The presence of silent subcarriers in the group is determined by comparing the received power of each subcarrier with a set threshold, thereby generating the first set of index bits. If silence is detected, minimum power decision or maximum likelihood detection is used within the group to determine the specific silent subcarrier locations, which are mapped to the second set of index bits. If there are no silent subcarriers in the subcarrier group, the second-level index modulation is skipped and regular 16QAM demodulation is performed to recover the data bits. The index bits of the first and second groups are used to transmit the key by identifying their positions. The receiving end integrates the index bits extracted from the two index modulations with the regular data bits to completely restore the transmitted data containing the original data and the embedded key information. Figure 5 As shown in the figure, since SIM is used to hide the key, the subcarriers in the silent position will generate signals after passing through the OFDM system. Compared with the ordinary 16QAM constellation diagram, there will be an additional constellation point at the origin to indicate the information of the silent position.

[0112] The entire reception and demodulation process is based on the traditional OFDM framework, with the addition of an index modulation detection step, which effectively extracts index information and data from mixed signals. Unauthorized receivers, unaware of the two-layer indexing rules and key embedding methods, cannot brute-force the correct information. The solution not only ensures signal security through multiple encryptions but also dynamically and accurately transmits keys and data in a highly secure and accurate manner, effectively improving the system's security, confidentiality, and data transmission efficiency. It also enables the coordinated transmission of more layers and more data.

[0113] This application proposes a collaborative transmission method based on multi-layer index modulation. By masking the transmission of keys through multiple index modulations, key management is simplified, the complexity of storing and updating keys is reduced, and the security of the communication system is improved. Compared with the traditional transmission method in which both the sender and the receiver have the key, this scheme relies on two index modulations and masks the activation state of the key-keyed signal subcarrier. It is combined with the use of a four-dimensional chaotic system to achieve multi-dimensional perturbations of bits, subcarriers, and symbol points, ultimately achieving the coordinated transmission of signals and keys. For legitimate receiving ends, the key can be correctly extracted and restored and demodulated, while illegal receiving ends cannot decipher the information without knowing the key and encryption method.

[0114] Example 2: Based on Example 1, this embodiment provides a collaborative optical transmission device based on multi-layer index modulation, including a processor and a storage medium;

[0115] The storage medium is used to store instructions;

[0116] The processor is configured to operate according to the instructions to execute the method according to embodiment 1.

[0117] Example 3: Based on Example 1, this example provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described in Example 1 is implemented.

[0118] Example 4: Based on Example 1, this example provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the method described in Example 1 when executing the computer program.

[0119] Example 5: Based on Example 1, this example provides a computer program product, including a computer program, which implements the method described in Example 1 when executed by a processor.

[0120] 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 take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0121] 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 block in the flowchart and / or block diagram and the combination of processes and / or blocks 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 produce 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.

[0122] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work 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 The function specified in one or more boxes.

[0123] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0124] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection 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 a four-dimensional chaotic sequence 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 scrambled signal is obtained by performing secondary scrambling on the subcarriers and symbols of the 16QAM constellation signal using the four-dimensional chaotic sequence X, Y, Z, and W. 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; The 16QAM scrambled signal is subjected to first-layer index modulation using a first group of keys to obtain a first modulated signal, and the first modulated signal is subjected to second-layer SIM index modulation using a second group of keys to obtain a second modulated signal, including: grouping and arranging the subcarriers of the 16QAM scrambled signal, 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; wherein 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, determining the subcarrier row sequence of the two small groups with silence in the corresponding 16×8 subcarrier sequence matrix, and performing first-layer index modulation 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, respectively determining the column sequence of the subcarrier silence of the two small groups with silence, obtaining the specific positions of the two silent subcarriers, and silencing the two silent subcarriers by zeroing; performing first-layer index modulation and second-layer SIM index modulation on all subcarrier sequence matrices in turn to obtain the second modulated signal; The second modulated signal is subjected to OFDM modulation and then enters the optical fiber channel for transmission.

2. The method according to claim 1, 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 two subcarrier groups with silence 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 silence 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 two subcarrier groups with silence 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 two subcarrier groups with silence 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 order 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 orders of the subcarriers of the two groups with silence 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 silence 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 two subcarrier groups with silence 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 silence 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 silence 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 silence 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 silence in the subcarrier sequence matrix are "row 3" and "row 7"; If the index bits of the first group of keys corresponding to the subcarrier sequence matrix are "1100", the row orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "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 orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "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 orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "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 orders of the subcarriers of the two groups with silence in the subcarrier sequence matrix are "row 4" and "row 8".

3. The method according to claim 1, characterized in that The second layer SIM index modulation rules include: 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 bits of the second group of keys corresponding to the subcarrier group with silence are "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 occurs are "1111", the column order of the silent subcarriers in the subcarrier group is "column 16".

4. The method according to claim 1, wherein 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, and W with respect to time t, and a, b, c, and d are system parameters.

5. The method according to claim 1 or 4, characterized in that The keys X0, Y0, Z0, and W0 are 1.001257452376201, 0.995274263515032, 0.011574611854415, and 0.023846371520675, respectively.

6. The method according to claim 1 or 4, characterized in that The value ranges of the four-dimensional chaotic sequence 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 on the 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 scrambling sequence and the fourth scrambling 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 processors and storage media; 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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