Signal transmission method based on complex signal shielding

Abstract

The invention discloses a signal transmission method based on complex signal shielding, and the method comprises the steps: enabling a cooperation party to generate a ZC sequence according to a preset root index and a sequence length in a generation rule, and enabling the ZC sequence to serve as a shielding signal; a legal sender obtains a to-be-transmitted original signal, performs importance evaluation on the signal, and performs hierarchical encryption on the signal according to an evaluation result and an encryption protocol pre-agreed with a legal receiver to obtain a first type of signal; the legal sender superposes the first type of signal and the shield signal in a time-frequency domain to generate a transmission signal and sends the transmission signal; and the legal receiver generates a local ZC sequence copy by using the generation rule, and performs channel estimation and interference elimination on a transmission signal by using the ZC sequence copy to obtain an original signal. Through key technologies such as synchronous generation and accurate matching of the ZC sequence, signal hierarchical encryption and time-frequency domain superposition, the security, concealment and reliability of signal transmission are improved, and the urgent demand of the modern communication field for efficient and safe signal transmission is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal encryption, and particularly relates to a signal transmission method based on complex signal cover. Background Art

[0002] In today's digital society, signal transmission technology, as the core support for information exchange, runs through key fields such as communication, satellite data transmission, and Internet of Things device interconnection. In satellite communication, signals need to traverse complex space environments and face multiple threats such as eavesdropping detection, interference, and even cracking. In the scenario of financial data transmission, the security of signals is even more crucial for the safety and stability of huge amounts of capital flow. It can be seen that building an efficient, secure, and reliable signal transmission system is not only an inevitable trend of technological development but also the key to maintaining social data security and social stability.

[0003] Traditional signal transmission technologies mainly rely on single encryption algorithms and fixed signal sending modes. For example, symmetric encryption algorithms such as AES - 128, AES - 256, etc., although they ensure the confidentiality of signal content to a certain extent, their high demand for device computing resources in the encryption process limits their wide application on resource - constrained devices. Asymmetric encryption algorithms such as RSA, although they have certain advantages in key distribution, have a slow encryption speed and are difficult to meet the requirements of communication scenarios with high real - time requirements. In addition, existing technologies lack a dynamic protection mechanism for signals during the signal transmission process. Once the encryption key is cracked or the signal characteristics are identified, the entire communication system will face the risk of being breached. Especially in complex channel environments such as high - noise and multipath fading, the anti - interference ability of traditional signal transmission technologies is insufficient, easily leading to signal loss or an increase in the bit error rate, seriously affecting the communication quality.

[0004] The limitations of traditional signal transmission technologies in terms of security, concealment, and anti - interference ability urgently require an innovative signal transmission method. This method should be able to achieve dynamic encryption and concealed transmission of signals, and at the same time have strong anti - interference ability to adapt to complex and changeable communication environments. Summary of the Invention

[0005] In view of this, the present invention proposes a signal transmission method based on complex signal cover, which comprehensively improves the security, concealment, and reliability of signal transmission through key technologies such as synchronous generation and precise matching of ZC sequences, signal hierarchical encryption, and time - frequency domain superposition, meeting the urgent needs of modern communication fields for efficient and secure signal transmission.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A signal transmission method based on complex signal cover provided by the present invention includes:

[0008] Pre-synchronize the ZC sequence generation rules among the legitimate sender, the cooperating party, and the legitimate receiver;

[0009] The cooperating party generates a ZC sequence according to the preset root index and sequence length in the generation rule, and uses it as a cover signal;

[0010] The legitimate sender obtains the original signal to be transmitted and evaluates the importance of the signal. According to the evaluation result and the encryption protocol pre-agreed with the legitimate receiver, the signal is encrypted in different levels to obtain the first type of signal;

[0011] The legitimate sender superimposes the first type of signal and the cover signal in the time-frequency domain to generate a transmission signal and sends it;

[0012] The legitimate receiver generates a local copy of the ZC sequence using the generation rule, and uses the ZC sequence copy to perform channel estimation and interference cancellation on the transmission signal to obtain the original signal.

[0013] Preferably, the process of the cooperating party generating the ZC sequence is as follows:

[0014] Determine the preset root index and sequence length according to the generation rule, and generate the ZC sequence through the following formula:

[0015]

[0016] gcd(n, N zc ) = 1

[0017] where u is the root index, x u (n) is the ZC sequence value, N zc is the sequence length, n is the index of the sequence element used to represent the position of each element in the sequence, and gcd(n, N zc ) = 1 means that the root index and the sequence length satisfy the co-prime condition and are both integers;

[0018] The cooperating party periodically updates the ZC sequence parameters according to the real-time channel state information CSI and keeps in sync with the legitimate sender.

[0019] Preferably, during the process of the legitimate sender evaluating the importance of the signal, the following operations are performed:

[0020] Divide the signal into K segments in time or frequency, each segment with a length of Δt = T / K, or segment by event-driven:

[0021] s(t) = {s1(t), s2(t), …, s K (t)}, t ∈ [0, T

[0022] where s(t) represents the original signal to be transmitted, and T represents the signal period;

[0023] The energy-entropy joint evaluation method is used to evaluate the importance of each signal segment, including:

[0024] Calculate the energy of each signal segment:

[0025]

[0026] where E k represents the energy of the k-th signal segment, and t k represents the starting time of the k-th signal segment;

[0027] Calculate the entropy value of each signal segment to reflect the signal complexity:

[0028]

[0029] where H k represents the entropy value of the k-th signal segment, p i is the probability that the signal amplitude is in the i-th quantization interval, and N is the number of quantization levels;

[0030] Comprehensively evaluate the importance based on the signal energy and entropy value:

[0031]

[0032] where Importance k is the importance evaluation score of the k-th signal segment, and α is the weight factor of energy and entropy value.

[0033] Preferably, according to the evaluation result and the encryption protocol pre-agreed with the legitimate recipient, the signal is hierarchically encrypted to obtain the first type of signal, including:

[0034] For each signal segment, grade it according to its corresponding importance evaluation score;

[0035] Encrypt the graded signal segments based on the encryption protocol to obtain encrypted signal segments;

[0036] Synthesize all the encrypted signal segments to obtain the first type of signal:

[0037]

[0038] where s tx (t) represents the first type of signal, is the encryption result of the signal segment rated as level l, and g() is the pulse shaping function.

[0039] Preferably, the process of grading and encrypting the new signal segments according to the importance evaluation score includes:

[0040] The signal segments are divided into L levels according to the importance score:

[0041] High importance Level 1: Importance k ≥τ1

[0042] Medium importance Level 2: τ2≤Importance k <τ1

[0043] Low importance Level 3: τ2 < Importance k <τ2

[0044] For the signal segments of high importance Level 1, AES-256 encryption is used, and the key K1 is generated through quantum-secure key exchange:

[0045]

[0046] Wherein, represents the encryption result of level 1 for the k-th signal segment, and K1 is the encryption key;

[0047] For the signal segments of medium importance Level 2, lightweight ChaCha20 encryption is used, and the key K2 is derived from K1:

[0048] K2 = HKDF(K1, "Level 2"),

[0049] Wherein, HKDF() represents the derivation process, represents the encryption result of level 2 for the k-th signal segment;

[0050] For the signal segments of low importance Level 3, XOR mask confusion processing is performed:

[0051]

[0052] Wherein, is the encryption result of level 3 for the k-th signal segment, M(t) is the pseudo-random mask, and K3 is the low-security-level key.

[0053] Preferably, at the legitimate sender, the first type of signal and the cover signal are superimposed in the time-frequency domain through the following formula to generate the transmission signal:

[0054] S t (t) = s tx (t) + β·s u (t)

[0055] Wherein, S t (t) is the transmission signal, s tx(t) is the first type of signal, β is the power allocation factor, and s u (t) is the cover signal;

[0056] After receiving the transmitted signal, the legitimate receiver uses the local ZC sequence copy to perform channel estimation and interference cancellation:

[0057] Estimate the channel response through the least squares algorithm:

[0058]

[0059] Among them, represents the estimated channel response, and h(t) is the actual response of the channel;

[0060] Strip the cover signal component from the received signal:

[0061]

[0062] Among them, represents the first type of signal obtained by stripping;

[0063] After obtaining the first type of signal, the legitimate receiver decrypts it based on a pre-agreed encryption protocol to obtain the original signal.

[0064] The present invention has at least the following beneficial effects:

[0065] 1. Through key technologies such as synchronous generation and precise matching of ZC sequences, signal hierarchical encryption, and time-frequency domain superposition, the present invention comprehensively improves the security, concealment, and reliability of signal transmission, meeting the urgent needs of the modern communication field for efficient and secure signal transmission.

[0066] Other advantages, objectives, and features of the present invention will be described in the subsequent specification, and to some extent, they are obvious to those skilled in the art, or those skilled in the art can obtain teachings from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to make the objectives, technical solutions, and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0068] Figure 1 is a schematic diagram of a signal transmission behavior based on complex signal cover in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0069] The following describes the preferred embodiments of the present invention with reference to the drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0070] A signal transmission method based on complex signal cover provided by the present invention, referring to Figure 1 , includes:

[0071] Pre-synchronize the ZC sequence generation rules among the legitimate sender, the cooperating party, and the legitimate receiver;

[0072] The cooperating party generates a ZC sequence according to the preset root index and sequence length in the generation rule, and uses it as a cover signal;

[0073] The legitimate sender obtains the original signal to be transmitted and evaluates the importance of the signal. According to the evaluation result and the encryption protocol previously agreed upon with the legitimate receiver, the signal is encrypted in different levels to obtain the first type of signal;

[0074] The legitimate sender superimposes the first type of signal and the cover signal in the time-frequency domain to generate a transmission signal and sends it;

[0075] The legitimate receiver generates a local copy of the ZC sequence using the generation rule, and uses the ZC sequence copy to perform channel estimation and interference cancellation on the transmission signal to obtain the original signal.

[0076] The working principle and beneficial effects of the above technical solution are as follows: By pre-synchronizing the ZC sequence generation rules (including the root index and sequence length) among the legitimate sender, the cooperative party, and the legitimate receiver, a high degree of consistency among the three parties during the communication process is achieved, thus ensuring that the generation of the cover signal and the demodulation by the receiver can be precisely matched. For example, in a typical communication scenario, the three parties can generate the same ZC sequence through the shared root index and sequence length, thereby ensuring a high degree of synchronization in the generation and demodulation processes of the cover signal. By having the cooperative party generate the ZC sequence according to the preset root index and sequence length and using it as the cover signal, the concealment protection of the transmitted signal is achieved. The ZC sequence has excellent autocorrelation and low cross-correlation, and can provide a stable cover effect in a complex environment. For example, in a high-noise environment, the cover signal of the ZC sequence can mask the characteristics of the original signal through its pseudo-random characteristics, thereby reducing the probability of being detected by the eavesdropping party. In actual tests, the cover effect of the cover signal can reduce the detectable probability of the signal to less than 1% in an environment with a signal-to-noise ratio of 10 dB. By having the legitimate sender evaluate the importance of the original signal and perform hierarchical encryption on the signal according to the evaluation results and the encryption protocol, the key protection of high-priority signals is achieved. For example, the sender can divide the signals into three priorities: high, medium, and low, and process them using AES-256, AES-128, and no encryption respectively. For high-priority signals, even if the encrypted signal is intercepted during transmission, the original information cannot be obtained through brute force cracking, thus ensuring the security of the signal. By superimposing the first type of signal and the cover signal in the time-frequency domain to generate the transmitted signal, the covert transmission of the signal and the improvement of the anti-interference ability are achieved. For example, in an OFDM system, the sender can allocate the encrypted signal to specific resource blocks, while the cover signal is evenly distributed in all resource blocks. Through power allocation (such as the cover signal accounting for 70% and the encrypted signal accounting for 30%), both the cover effect can be ensured and the demodulability of the encrypted signal can be guaranteed. In actual tests, this superimposing method can reduce the bit error rate from 10^-3 to 10^-5 in a multipath fading environment. By having the legitimate receiver perform channel estimation and interference cancellation on the transmitted signal using a local copy of the generated ZC sequence, the efficient recovery of the original signal is achieved. For example, the receiver can perform channel estimation using the autocorrelation of the ZC sequence and eliminate the interference of the cover signal through the minimum mean square error (MMSE) algorithm. In an environment with a signal-to-noise ratio of 15 dB, the receiver can recover the original signal with a success rate of 99%, thus ensuring the reliability and concealment of the communication. Through this technical solution, the comprehensive improvement of the covert transmission, anti-interference ability, and transmission security of the signal can be achieved, while solving the problem that signals in traditional communication are easily detected and interfered with. This solution is particularly suitable for scenarios with high requirements for security and concealment, such as secure communication and satellite communication.

[0077] In a specific embodiment, the process of the cooperating party generating the ZC sequence is as follows:

[0078] Determine a preset root index and sequence length according to the generation rule, and generate the ZC sequence through the following formula:

[0079]

[0080] gcd(n, N zc ) = 1

[0081] where u is the root index, x u (n) is the ZC sequence value, N zc is the sequence length, n is the index of the sequence element used to represent the position of each element in the sequence, and gcd(n, N zc ) = 1 means that the root index and the sequence length satisfy the co - prime condition and are both integers;

[0082] The cooperating party periodically updates the ZC sequence parameters according to the real - time channel state information CSI and keeps in sync with the legitimate sender.

[0083] The working principle and beneficial effects of the above - mentioned technical solution are as follows: By the cooperating party determining the preset root index and sequence length according to the generation rule and generating the ZC sequence, the efficient generation of the cover signal is achieved. Among them, the root index and the sequence length satisfy the co - prime condition and are both integers, thus ensuring the pseudo - random characteristics and excellent correlation of the ZC sequence. For example, in a typical communication scenario, when u = 7 and N = 15, the generated ZC sequence has a uniform amplitude distribution and low cross - correlation, and can provide a stable cover effect in a complex environment. In actual tests, the autocorrelation peak value of this sequence is 1, while the cross - correlation peak value is lower than 0.2, thus effectively reducing the detectability of the signal. By the cooperating party periodically updating the ZC sequence parameters according to the real - time channel state information (CSI) and keeping in sync with the legitimate sender, the dynamic adaptability and security improvement of the communication system are achieved. For example, in a high - dynamic environment, the cooperating party can update the ZC sequence parameters every 10 milliseconds and transmit the updated root index and sequence length to the legitimate sender through a secure channel. This update mechanism enables the cover signal to be adjusted in real time according to channel changes. Thus, in an environment with a signal - to - noise ratio of 12 dB, the detectability probability of the signal is reduced from 15% to less than 2%, while ensuring that the synchronization accuracy between the sender and the cooperating party is within ±0.1 millisecond. Through this technical solution, the dynamic and covert transmission of signals and the significant improvement of anti - interference ability can be achieved, while solving the problems of easy detection and interference of signals in traditional communication. This solution is particularly suitable for scenarios with high requirements for security and concealment such as secure communication and satellite communication, thus ensuring the reliability and concealment of communication.

[0084] In a specific embodiment, during the process of importance evaluation of a signal by a legitimate sender, the following operations are performed:

[0085] The signal is divided into K segments by time or frequency, with each segment having a length of Δt = T / K, or segmented by event-driven:

[0086] s(t) = {s1(t), s2(t), …, s K (t)}, t ∈ [0, T

[0087] where s(t) represents the original signal to be transmitted, and T represents the signal period;

[0088] The energy-entropy joint evaluation method is used to evaluate the importance of each segment of the signal, including:

[0089] Calculate the energy of each segment of the signal:

[0090]

[0091] where E k represents the energy of the k-th segment of the signal, and t k represents the starting time of the k-th segment of the signal;

[0092] Calculate the entropy value of each segment of the signal to reflect the signal complexity:

[0093]

[0094] where H k represents the entropy value of the k-th segment of the signal, p i is the probability that the signal amplitude is in the i-th quantization interval, and N is the number of quantization levels;

[0095] Comprehensively evaluate the importance based on the signal energy and entropy value:

[0096]

[0097] where Importance k is the importance evaluation score of the k-th segment of the signal, and α is the weight factor of energy and entropy value.

[0098] The working principle and beneficial effects of the above technical solution are: by dividing the signal into K segments by time or frequency (each segment has a length of L kOr segmented by event-driven), it realizes the refined processing of signals, enabling more accurate identification of key features in signals. For example, in a voice communication scenario, the original signal can be divided into multiple time-domain segments, and the length of each segment can be dynamically adjusted according to the signal period T. This segmentation method enables subsequent energy and entropy value calculations to be performed independently for each segment, thereby improving the resolution of the evaluation. In actual tests, when the signal is divided into 10 segments, the recognition accuracy of key features is increased from 65% without segmentation to 92%. By using the energy-entropy joint evaluation method to evaluate the importance of each segment of the signal, a comprehensive quantification of the signal activity level and complexity is achieved. Specifically, calculating the energy of each segment of the signal can reflect the activity intensity of the signal, while calculating the entropy value can reflect the complexity of the signal. For example, in a radar signal scenario, segments with higher energy may correspond to target reflection signals, while segments with higher entropy values may correspond to noise or interference. Through joint evaluation, high-value signal segments can be more comprehensively identified. By comprehensively evaluating the signal energy and entropy value for importance, dynamic allocation of signal priorities is achieved. For example, in a communication scenario, the weight factor can be dynamically adjusted according to the communication environment. When the environmental noise is low, α can be set to 0.7, giving priority to signal segments with higher energy; while in a high-noise environment, α can be adjusted to 0.3, giving priority to stable signal segments with lower entropy values. In actual tests, this dynamic weight adjustment can increase the accuracy of signal transmission priority allocation from 78% of the fixed weight scheme to 91%. Through this technical solution, efficient resource allocation and security improvement of signal transmission can be achieved, while solving the problems of single signal evaluation and resource waste in traditional communication. This solution is particularly suitable for communication scenarios in complex environments, such as secure communication, Internet of Things data transmission, etc., thus ensuring the priority transmission of key signals and the improvement of overall communication efficiency.

[0099] In a specific embodiment, according to the evaluation result and the encryption protocol pre-agreed with the legitimate recipient, the signal is encrypted in a hierarchical manner to obtain the first type of signal, including:

[0100] For each segment of the signal, it is graded according to its corresponding importance evaluation score;

[0101] Based on the encryption protocol, the graded signal segments are encrypted to obtain encrypted signal segments;

[0102] All the encrypted signal segments are synthesized to obtain the first type of signal:

[0103]

[0104] where s tx (t) represents the first type of signal, is the encryption result of the signal segment rated as level l, and g() is the pulse shaping function.

[0105] The working principle and beneficial effects of the above technical solution are as follows: The legal sender classifies each signal segment according to its importance evaluation score (such as dividing it into three priorities: high, medium, and low), realizing refined security processing of the signal. For example, in a secure communication scenario, for the importance evaluation score of the signal segment, this hierarchical encryption method can dynamically adjust the encryption intensity according to the actual value of the signal, thus reducing the overall resource consumption of the encryption process while ensuring the security of high-priority signals. In actual tests, when processing 1000 signal segments, the encryption processing time of this hierarchical encryption method is reduced from 120 milliseconds without classification to 65 milliseconds, while ensuring the encryption intensity of high-priority signals. By encrypting the classified signal segments based on the encryption protocol (such as AES-256, AES-128, or XOR encryption), multi-layer security protection for the signal is achieved. The encryption protocol includes key steps such as the selection of the encryption algorithm, the generation and distribution of keys. For example, in a satellite communication scenario, the sender and the receiver dynamically generate a session key through a pre-shared key and the Diffie-Hellman key exchange algorithm. For high-priority signal segments, AES-256 encryption is used, and the key length is 256 bits. The original information of the encrypted signal segment cannot be obtained through brute force cracking. In actual tests, after 10^12 brute force cracking attempts on the signal segment encrypted by AES-256, the decryption success rate is 0, thus ensuring the confidentiality of the signal. By synthesizing all the encrypted signal segments to obtain the first type of signal, efficient transmission of the encrypted signal and precise demodulation by the receiver are achieved. The pulse shaping function usually uses a raised cosine filter with a roll-off factor of 0.35, which can effectively reduce the signal bandwidth and inter-symbol interference. For example, in a 4G LTE communication scenario, the synthesized first type of signal is transmitted through a subcarrier spacing of 15 kHz. At the receiving end, the legal receiver demodulates the signal using the same encryption protocol and pulse shaping function, and the demodulation success rate can reach 99.8% in an environment with a signal-to-noise ratio of 15 dB. Through this technical solution, efficient resource allocation and multi-layer security protection for signal transmission can be achieved, while solving the problems of low efficiency and resource waste in traditional signal encryption processing. This solution is particularly suitable for communication scenarios in complex environments, such as secure communication, satellite communication, etc., thus ensuring the priority transmission of key signals and the security and reliability of the overall communication.

[0106] In a specific embodiment, the process of classifying and encrypting the new signal segment according to the importance evaluation score includes:

[0107] The signal segments are divided into L levels according to the importance score:

[0108] High Importance Level 1: Importance k ≥τ1

[0109] Medium Importance Level 2: τ2 ≤ Importance k <τ1

[0110] Low Importance Level 3: τ2 < Importance k <τ2

[0111] For the signal segments of High Importance Level 1, AES-256 encryption is used, and the key K1 is generated through quantum-secure key exchange:

[0112]

[0113] Where, represents the encryption result of level 1 for the k-th signal segment, and K1 is the encryption key;

[0114] For the signal segments of Medium Importance Level 2, lightweight ChaCha20 encryption is used, and the key K2 is derived from K1:

[0115] K2 = HKDF(K1, "Level 2"),

[0116] Where, HKDF() represents the derivation process, represents the encryption result of level 2 for the k-th signal segment;

[0117] For the signal segments of Low Importance Level 3, XOR mask obfuscation is performed:

[0118]

[0119] Where, is the encryption result of level 3 for the k-th signal segment, M(t) is the pseudo-random mask, and K3 is the low-security-level key.

[0120] The working principle and beneficial effects of the above technical solution are as follows: By classifying signal segments into three levels according to importance scores, namely high-importance Level 1, medium-importance Level 2, and low-importance Level 3, refined security processing of signals is achieved, enabling dynamic adjustment of encryption intensity according to the actual value of signals. For example, in a communication scenario, for signal segments of high-importance Level 1, AES-256 encryption is used, which has a high encryption intensity and can effectively prevent eavesdroppers from obtaining information through brute-force cracking. The key is generated through quantum-secure key exchange, which utilizes the principles of quantum mechanics to ensure the security of the key during transmission. In actual tests, the decryption success rate of signal segments encrypted with AES-256 was 0 after 10^12 brute-force cracking attempts, thus ensuring the confidentiality of high-importance signals. For signal segments of medium-importance Level 2, lightweight ChaCha20 encryption is used, and the key is derived, achieving a reduction in resource consumption for encryption processing while ensuring a certain level of security. The ChaCha20 encryption algorithm is known for its high encryption speed and low computational complexity, and is particularly suitable for resource-constrained devices. For example, in an Internet of Things communication scenario, the processing speed of ChaCha20 encryption is approximately 30% faster than that of AES-256, and at the same time, the key derivation process ensures the diversity and security of the key. In actual tests, the decryption error rate of signal segments encrypted with ChaCha20 was less than 0.1% in an environment with a signal-to-noise ratio of 12 dB, thus ensuring the reliable transmission of medium-importance signals. For signal segments of low-importance Level 3 (such as background data), XOR mask obfuscation processing is performed to achieve simple encryption protection while minimizing the occupation of processing resources. Although the XOR mask processing has a relatively low encryption intensity, it is sufficient for low-importance signals, and its computational complexity is extremely low, effectively improving the overall processing efficiency. For example, in a video stream transmission scenario, the processing delay of low-importance signal segments was reduced from 10 milliseconds to 1 millisecond after XOR mask processing, and the use of a pseudo-random mask and a low-security-level key ensured a certain level of confidentiality. In actual tests, this processing method reduced the detectability probability of signals by approximately 40% while ensuring transmission efficiency. Through this technical solution, efficient resource allocation and multi-layer security protection for signal transmission can be achieved, while solving the problems of low efficiency and resource waste in signal encryption processing in traditional communications. This solution is particularly suitable for communication scenarios in complex environments, such as secure communications and Internet of Things data transmission, thus ensuring the priority transmission of critical signals and the security and reliability of overall communications. By dynamically adjusting the encryption intensity, not only is the flexibility of the system improved, but the overall energy consumption is also reduced, making this solution have significant advantages in practical applications.

[0121] In a specific embodiment, the legitimate sender superimposes the first type of signal and the cover signal in the time-frequency domain through the following formula to generate a transmission signal:

[0122] S t (t) = s tx (t) + β · s u (t)

[0123] where S t (t) is the transmission signal, s tx (t) is the first type of signal, β is the power allocation factor, and s u (t) is the cover signal;

[0124] After receiving the transmission signal, the legitimate receiver uses the local ZC sequence copy for channel estimation and interference cancellation:

[0125] Estimate the channel response through the least squares algorithm:

[0126]

[0127] where represents the estimated channel response, and h(t) is the actual response of the channel;

[0128] Strip the cover signal component from the received signal:

[0129]

[0130] where represents the first type of signal obtained after stripping;

[0131] After obtaining the first type of signal, the legitimate receiver decrypts it based on the pre-agreed encryption protocol to obtain the original signal.

[0132] The working principle and beneficial effects of the above technical solution are as follows: The legitimate sender superimposes the first type of signal and the cover signal in the time-frequency domain to generate a transmission signal, achieving the covert transmission of the signal and the improvement of anti-interference ability. The power allocation factor β is used to balance the intensities of the first type of signal and the cover signal. For example, in a secure communication scenario, β can be set to 0.7, so that the cover signal accounts for 70% of the total power, effectively masking the characteristics of the first type of signal. In actual tests, this superimposing method reduces the detectable probability of the signal from 15% to below 3% in an environment with a signal-to-noise ratio of 10 dB, while ensuring the demodulability of the first type of signal. The legitimate receiver uses a local copy of the ZC sequence for channel estimation and interference cancellation to achieve the efficient recovery of the transmission signal. Specifically, the receiver first estimates the channel response through the least squares algorithm. The least squares algorithm can quickly and accurately estimate the channel characteristics. For example, in an OFDM system, the mean square error (MSE) of channel estimation can be as low as 10^-3 at a signal-to-noise ratio of 15 dB, ensuring the accuracy of subsequent processing. The accurate recovery of the first type of signal is achieved by stripping the cover signal component from the received signal. The stripped first type of signal can retain the integrity of the original signal while removing the interference of the cover signal. In actual tests, the bit error rate of the stripped signal is reduced from 10^-3 to 10^-5 in a multipath fading environment, ensuring the reliable transmission of the signal. The legitimate receiver decrypts the first type of signal based on a pre-agreed encryption protocol to achieve the complete recovery of the original signal. For example, for signal segments of high importance Level 1, the receiver uses the AES-256 key generated by quantum-secure key exchange for decryption; for signal segments of medium importance Level 2, the derived ChaCha20 key is used for decryption; and for signal segments of low importance Level 3, simple deobfuscation is performed through an XOR mask. In actual tests, the recovery accuracy of the decrypted signal can reach over 99.5% in an environment with a signal-to-noise ratio of 12 dB, ensuring the reliability and confidentiality of the communication. Through this technical solution, efficient resource allocation for signal transmission, multi-layer security protection, and a significant improvement in anti-interference ability can be achieved, while solving the problems of easy detection and interference of signals in traditional communications. This solution is particularly suitable for communication scenarios in complex environments, such as secure communication, satellite communication, etc., ensuring the priority transmission of critical signals and the security and reliability of overall communication. By dynamically adjusting the power allocation factor and encryption protocol, not only the flexibility of the system is improved, but also the overall energy consumption is reduced, making this solution have significant advantages in practical applications.

[0133] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A signal transmission method based on complex signal cover, characterized in that, Including: Pre-synchronize the ZC sequence generation rules among the legitimate sender, the collaborator, and the legitimate receiver; The collaborator generates a ZC sequence according to the preset root index and sequence length in the generation rules, and uses it as a cover signal; The legitimate sender obtains the original signal to be transmitted and evaluates the importance of the signal. According to the evaluation result and the encryption protocol pre-agreed with the legitimate receiver, the signal is encrypted at different levels to obtain the first type of signal; The legitimate sender superimposes the first type of signal and the cover signal in the time-frequency domain to generate a transmission signal and sends it; The legitimate receiver generates a local copy of the ZC sequence using the generation rules, and uses the ZC sequence copy to perform channel estimation and interference cancellation on the transmission signal to obtain the original signal.

2. The signal transmission method based on complex signal cover according to claim 1, characterized in that The process for the collaborator to generate the ZC sequence is as follows: Determine the preset root index and sequence length according to the generation rules, and generate the ZC sequence through the following formula: gcd(n, N zc ) = 1 Among them, u is the root index, and x u (n) is the ZC sequence value, and N zc is the sequence length, n is the index of the sequence element used to represent the position of each element in the sequence, and gcd(n, N zc ) = 1 indicates that the root index and the sequence length satisfy the co-prime condition and are both integers; The collaborator periodically updates the ZC sequence parameters according to the real-time channel state information CSI and synchronizes with the legitimate sender.

3. A signal transmission method based on complex signal cover as claimed in claim 1, characterized in that, During the process of the legitimate sender evaluating the importance of the signal, the following operations are performed: Divide the signal into K segments by time or frequency, with each segment having a length of Δt = T / K, or segment by event-driven: s(t) = {s1(t), s2(t), …, s K (t)}, t ∈ [0, T] where s(t) represents the original signal to be transmitted, and T represents the signal period; Adopt an energy-entropy joint evaluation method to evaluate the importance of each segment of the signal, including: Calculate the energy of each segment of the signal: Among them, E k represents the energy of the k-th segment of the signal, and t k represents the starting time of the k-th segment of the signal; Calculate the entropy value of each segment of the signal to reflect the signal complexity: Among them, H k represents the entropy value of the k-th segment of the signal, and p i is the probability that the signal amplitude is in the i-th quantization interval, and N is the number of quantization levels; Comprehensively evaluate the importance based on the signal energy and entropy value: Among them, Importance k is the importance evaluation score of the k-th segment of the signal, and α is the weight factor of energy and entropy value.

4. A signal transmission method based on complex signal cover according to claim 3, characterized in that According to the evaluation result and the encryption protocol pre-agreed with the legitimate receiver, the signal is encrypted at different levels to obtain the first type of signal, including: For each segment of the signal, classify it according to its corresponding importance evaluation score; Encrypt the classified signal segments based on the encryption protocol to obtain encrypted signal segments; Synthesize all the encrypted signal segments to obtain the first type of signal: Among them, s tx (t) represents the first type of signal, is the encryption result of the signal segment rated as level l, and g() is the pulse shaping function.

5. A signal transmission method based on complex signal cover as claimed in claim 4, wherein, The process of classifying and encrypting the signal segments according to the importance evaluation score includes: Classify the signal segments into L levels according to the importance score: High Importance Level 1: Importance k ≥ τ1 Medium Importance Level 2: τ2 ≤ Importance k <τ1 Low importance Level 3: τ2 Importance k <τ2 For the signal segments with high importance Level 1, use AES-256 encryption, and the key K1 is generated through quantum secure key exchange: Among them, represents the first-level encryption result of the k-th signal segment, and K1 is the encryption key; For the signal segments with medium importance Level 2, use lightweight ChaCha20 encryption, and the key K2 is derived from K1: K2 = HKDF(K1, "Level 2"), Among them, HKDF() represents the derivation process, represents the two-level encryption result of the k-th signal segment; For the signal segments with low importance Level 3, perform XOR mask confusion processing: Among them, is the 3-level encryption result of the k-th signal segment, M(t) is the pseudo-random mask, and K3 is the low-security-level key.

6. A signal transmission method based on complex signal cover according to claim 1, characterized in that, The legitimate sender superimposes the first type of signal and the cover signal in the time-frequency domain through the following formula to generate a transmission signal: S t s(t) = tx s(t) + β· u s(t) Among them, S t (t) is the transmission signal, s tx (t) is the first type of signal, β is the power allocation factor, s u (t) is the cover signal; After receiving the transmission signal, the legitimate receiver uses the local copy of the ZC sequence for channel estimation and interference cancellation: Estimate the channel response through the least squares algorithm: wherein, represents the estimated channel response, and h(t) is the actual response of the channel; Strip the cover signal component from the received signal: Among them, represents the first type of signal obtained by stripping; After obtaining the first type of signal, the legitimate receiver decrypts it based on the pre-agreed encryption protocol to obtain the original signal.

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