Cognitive Multicarrier Spread Spectrum-Based Encrypted Communication System and Method

Abstract

This invention relates to an encrypted communication system and method based on cognitive multicarrier spread spectrum, belonging to the field of covert communication. The encrypted communication system includes a transmitting device and a receiving device. The transmitting device includes a data encryption module, a constellation encryption modulation module, a multicarrier spread spectrum module, a frequency hopping module, and a cognitive power allocation module. The receiving device includes a bandpass filtering module, a de-hopping module, a despreading module, a constellation decryption and demodulation module, a data decryption module, and a coherent merging module. The data encryption module is divided into two units: an interleaving coding unit and a dual-rule reversible cellular automaton encryption unit. The cognitive power allocation module continuously scans the radio electromagnetic environment and performs real-time spectrum analysis to provide the perceived power spectral density results for all frequency hopping frequency sets. This invention enables continuous detection and dynamic response to the spatial spectrum state, and by utilizing spectral holes, significantly improves communication covertness, anti-interference capabilities, and resource utilization efficiency in complex electromagnetic environments.

Description

Technical Field

[0001] This invention relates to an encrypted communication system and method based on cognitive multicarrier spread spectrum, belonging to the fields of spread spectrum communication, spectrum sensing and physical layer encryption technology. Background Technology

[0002] With the rapid development of information technology, wireless communication is increasingly being used in military, public safety, and emergency rescue fields. Especially in complex and high-risk confrontational environments such as peacekeeping and cross-border operations, communication systems not only need to ensure the effective transmission of information, but also face severe challenges in anti-jamming and low probability of detection / interception (LPD / LPI).

[0003] Traditional spread spectrum communication technologies, such as Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping (FHSS), gain processing gain by expanding the signal spectrum, thus improving anti-interference and anti-interception capabilities to some extent. However, these technologies have inherent limitations: DSSS systems are relatively vulnerable to broadband interference; and the security of FHSS systems is significantly compromised if the frequency hopping pattern is cracked or if they encounter follow-on jamming. Furthermore, traditional power allocation strategies are often fixed or semi-fixed, unable to intelligently adapt to rapidly changing electromagnetic environments.

[0004] In modern electronic warfare, the enemy possesses powerful spectrum sensing and jamming capabilities. When peacekeeping forces are carrying out critical missions, their communication links are highly vulnerable to detection, jamming, and attack. Therefore, there is an urgent need for an intelligent communication system capable of "sensing, recognizing, and adapting" to the environment. This system should be able to analyze the spectrum situation in real time and dynamically adjust transmission parameters (such as carrier frequency and transmit power) to maintain reliable communication in environments with strong interference (anti-jamming mode), or to perfectly "hide" the transmitted signal in background noise when covert penetration is required, greatly reducing the probability of detection and identification (covert mode).

[0005] In existing technologies, single encryption, spread spectrum, or frequency hopping techniques are insufficient to simultaneously and optimally meet the dual requirements of anti-interference and concealment. In particular, there is a lack of an integrated solution that deeply integrates physical layer signal modulation, spectrum sensing, and intelligent power allocation. Therefore, developing an encrypted communication system based on cognitive radio principles, integrating multi-layered encryption and dynamic resource allocation, is of great practical significance and urgent need for ensuring communication security and reliability in special scenarios. Summary of the Invention

[0006] To address the problems of limited spreading gain, insufficient cognitive spectrum sensing depth, and difficulty in achieving adaptive scheduling of multimodal resources and dynamic spectrum access in strong adversarial environments in existing spread spectrum communication systems, the present invention aims to provide an encrypted communication system and method based on cognitive multicarrier spread spectrum, which can achieve continuous detection and dynamic response to the spatial spectrum state, and significantly improve communication concealment, anti-interference and resource utilization efficiency in complex electromagnetic environments by utilizing spectrum holes.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] As a first aspect of the present invention, the present invention discloses an encrypted communication system based on cognitive multicarrier spread spectrum, comprising a transmitting device and a receiving device.

[0009] The transmitting device includes a data encryption module, a constellation encryption modulation module, a multi-carrier spread spectrum module, a frequency hopping module, and a cognitive power allocation module.

[0010] The receiving device includes a bandpass filter module, a frequency hopping de-hopping module, a despreading module, a constellation decryption and demodulation module, a data decryption module, and a coherent merging module.

[0011] The data encryption module consists of two units: an interleaving coding unit and a bi-rule reversible cellular automaton encryption unit. Data flows through the interleaving coding unit, scrambling the data. The scrambled data then enters the bi-rule reversible cellular automaton encryption unit, which selects the appropriate encryption rule combination based on the PN sequence 1. Through multiple encryption iterations, highly secure and resistant-to-cracking data is obtained.

[0012] The constellation encryption modulation module is connected to the output of the data encryption module and is used to perform physical layer constellation diagram encryption modulation on the ciphertext data stream to obtain the encrypted modulated signal.

[0013] The multicarrier spread spectrum module is used to spread the data with N pseudocode sequences to obtain N sets of spread data streams.

[0014] The frequency hopping module is used to modulate different data streams onto different carrier frequencies, where the subcarrier frequencies are selected from a frequency set using PN sequence 2. The frequency hopping module uses pseudo-random codes to control the frequency hopping pattern, thereby controlling the carrier frequency to avoid interference from the interfering party.

[0015] The cognitive power allocation module continuously scans the radio electromagnetic environment and performs real-time spectrum analysis, providing the perceived power spectral density results for all frequency hopping frequencies. The module supports both anti-interference and covert communication modes. In anti-interference mode, facing interference, since each subcarrier channel is independent, the module detects the interference level of different channels separately and employs a power allocation method to achieve a capacity-maximizing power allocation scheme under fixed broadband interference. The power allocation principle references the "water-filling" method, minimizing the interference from subcarriers with high interference power. In covert communication mode, the transmitted signal is kept as consistent as possible with the spectrum of the radio electromagnetic environment. The power allocation principle adopts the "reverse water-filling" method, that is, reducing the transmit power of subcarriers with relatively low interference to compensate for subcarriers with relatively high interference.

[0016] The bandpass filter module receives radio frequency signals from the antenna and performs initial frequency selection. It sets the passband range according to the operating frequency band, filtering out out-of-band noise and strong interference to improve signal quality.

[0017] The frequency hopping de-hopping module works synchronously with the frequency hopping module of the transmitting device. Using the same pseudo-random code and frequency hopping pattern as the transmitting end, the de-hopping module generates a synchronized local carrier, performs de-hopping processing on the received frequency-hopping signal, down-converts the signals on each subcarrier to baseband or intermediate frequency, and recovers N parallel spread spectrum data streams. The same pseudo-random code as the transmitting end is PN sequence 2.

[0018] The despreading module corresponds to the multi-carrier spread spectrum module of the transmitting device. The despreading module uses N pseudo-random code sequences that are exactly the same as those at the transmitting end to perform correlation despreading processing on the N parallel data streams obtained after de-hopping, compress the signal spectrum, recover the N baseband constellation encrypted modulation symbol streams, and use the spreading gain to suppress noise and interference in the channel.

[0019] The constellation decryption and demodulation module is the reverse process of the constellation encryption modulation module in the transmitting device. It strictly and synchronously replicates the modulation scheme and phase angle selection logic of the transmitting end. Knowing the initial modulation scheme assignment, phase angle assignment, and decision rules, the module can deduce the modulation scheme and phase rotation angle used by the current symbol group based on the correct demodulation result of the previous group and the encoding information of the current group. It performs a reverse phase rotation on the received symbols to achieve phase restoration, demodulates the phase-restored signal using the modulation scheme used by the modulation module, and outputs the decrypted ciphertext data stream.

[0020] The data decryption module is connected to the output of the constellation decryption and demodulation module to complete the final decryption of the data. Internally, it includes a dual-rule reversible cellular automaton decryption unit and a deinterleaving unit. The dual-rule reversible cellular automaton decryption unit uses the inverse rule corresponding to the transmitting encryption unit to iteratively decrypt the received ciphertext data, restoring the interleaved data. The deinterleaving unit is connected to the output of the decryption unit, performing deinterleaving on the decrypted data to restore the bit order of the original data and output the correct original information sequence.

[0021] Since multiple subcarriers at the transmitting end transmit the same information, the coherent combining module is used to coherently combine the despread / demodulated multiple signals to obtain the original coherently combined signal, thereby obtaining diversity gain and improving the anti-interference and anti-fading capabilities of the received signal.

[0022] As a second aspect of the present invention, the encrypted communication method based on cognitive multicarrier spread spectrum disclosed herein is a working method of an encrypted communication system based on cognitive multicarrier spread spectrum, comprising the following steps:

[0023] Step 1: After the data is copied, it is processed in multiple parallel paths and then enters the data encryption module for interleaved reversible cellular automata encryption.

[0024] The specific implementation method of the interleaved reversible cellular automaton encryption method is as follows:

[0025] SA1. Perform interleaving encoding on the data according to the determined interleaving parameters;

[0026] SA2. The data read from the interleaved encoding is grouped into two groups of cells, namely R1 group and R2 group, and the data is encrypted according to the specified encryption method.

[0027] The encryption rule is as follows: based on the selection of PN sequence 1, two combinations of reversible elementary cellular automata (ECA) iterative rules are used to iterate and encrypt the two sets of cells n times. After each iteration, the cell state values ​​at the left and right ends of the current cell sequence are XORed, and the result is used as the new state value of the right-end cell. The entire sequence is inverted, and the inverted sequence is used as the initial cell state value for the next iteration. The evolution of the dual-rule reversible elementary cellular automata (DRECA) is expressed by the following formula.

[0028]

[0029]

[0030] in, Let be the state of the cell at time t. Let i represent the evolution of the cell at the next time step, and i denote the sequence position. This indicates the iteration rule. and It consists of two parts of a cell group of length L, namely group R1 and group R2. The state of this cell group at the next moment. This indicates a reversal.

[0031] Step 2: The encrypted data stream enters the constellation encryption and modulation module, where the data undergoes physical layer constellation diagram encryption and modulation.

[0032] Step 3: Spread the modulated data with N pseudo-code sequences to obtain N sets of spread data streams.

[0033] Step 4: Modulate each data stream onto a different carrier frequency, where the subcarrier frequency is selected from the frequency set using PN sequence 2. The frequency hopping system uses pseudo-random codes to control the frequency hopping pattern, thereby controlling the carrier frequency.

[0034] Step 5: Continuously scan the radio electromagnetic environment and perform real-time spectrum analysis, providing the perceived power spectral density results for all frequency hopping frequency sets. The cognitive power allocation module selects either anti-interference communication mode or covert communication mode as needed. In anti-interference communication mode, facing interference, since each subcarrier channel is independent, the degree of interference on different channels is detected separately. A power allocation method is adopted to achieve a power allocation scheme that maximizes capacity under fixed broadband interference. The allocation principle is similar to the "water-filling" method, avoiding subcarriers with high interference power as much as possible. In covert communication mode, the transmitted signal is kept as consistent as possible with the spectrum of the radio electromagnetic environment, that is, the transmission power of subcarriers with less interference is reduced to compensate for subcarriers with relatively higher interference. The allocation principle is similar to the "reverse water-filling" method.

[0035] Step Six: The data received by the receiver enters the bandpass filter module. The bandpass filter module receives the radio frequency signal from the antenna and performs preliminary frequency selection. The bandpass filter module sets the passband range according to the operating frequency band, filtering out out-of-band noise and strong interference to improve signal quality.

[0036] Step 7: The frequency hopping de-hopping module works synchronously with the frequency hopping module of the transmitting device. Using the same pseudo-random code and frequency hopping pattern as the transmitting end, it generates a synchronized local carrier, performs de-hopping processing on the received frequency hopping signal, down-converts the signal on each subcarrier to baseband or intermediate frequency, and recovers N parallel spread spectrum data streams.

[0037] Step 8: The despreading module performs relevant despreading processing on the N parallel data streams obtained after de-hopping, compresses the signal spectrum, recovers the N baseband constellation encrypted modulation symbol streams, and uses the spreading gain to suppress noise and interference in the channel.

[0038] Step Nine: The constellation decryption and demodulation module first performs a reverse phase rotation on the received symbols, demodulates them using the correct modulation method, and outputs the decrypted ciphertext data stream.

[0039] Step 10: The dual-rule reversible cellular automaton decryption unit uses the inverse rule corresponding to the transmitting encryption unit to iteratively decrypt the received ciphertext data, restoring the interleaved data. The deinterleaving unit performs deinterleaving on the decrypted data, restoring the bit order of the original data and outputting the correct original information sequence.

[0040] Step 11: Coherently combine the despread / demodulated multiple signals to obtain the recovered data, thereby obtaining diversity gain, further improving the anti-interference and anti-fading capabilities of the received signal, and thus realizing encrypted communication based on cognitive multicarrier spread spectrum.

[0041] Beneficial effects:

[0042] 1. Strong anti-interference and anti-detection capabilities: The encrypted communication system and method based on cognitive multi-carrier spread spectrum disclosed in this invention adopts a frequency hopping method with multi-carrier spread spectrum and pseudo-random code control, combined with dual-rule reversible cellular automaton encryption and constellation diagram dynamic encryption modulation, to achieve multi-dimensional signal spread and masking in the time domain, frequency domain and code domain, significantly reducing the signal power spectral density, giving the signal noise characteristics, and greatly improving the anti-interference and low-probability interception performance of the encrypted communication system based on cognitive multi-carrier spread spectrum.

[0043] 2. Automatic Spectrum Sensing and Dynamic Power Adaptation Capabilities: The encrypted communication system and method based on cognitive multi-carrier spread spectrum disclosed in this invention uses a cognitive power allocation module to scan and analyze the electromagnetic environment in real time. This module can identify interference distribution and dynamically adjust the transmission strategy. In anti-interference mode, power is allocated using a "water-filling" principle to prioritize high-quality subcarriers and maximize system capacity. In covert mode, a "reverse water-filling" strategy is used to ensure that the transmitted signal highly matches the environmental noise spectrum, effectively avoiding detection by interfering parties.

[0044] 3. Dual-mode flexible configuration to adapt to multiple scenario requirements: The encrypted communication system and method based on cognitive multi-carrier spread spectrum disclosed in this invention supports two communication modes: anti-interference and covert. It can be dynamically switched according to the actual electromagnetic countermeasure intensity and environmental threat level. It can maintain smooth communication under strong interference and achieve covert transmission in high-risk detection environment, with high tactical flexibility and environmental adaptability.

[0045] 4. The spectrum hole sensing system and method disclosed in this invention, based on deep spread spectrum and cognitive radio, utilizes a frequency hopping method controlled by multi-carrier spread spectrum and pseudo-random codes, cellular automata encryption and constellation diagram dynamic encryption modulation, electromagnetic environment scanning, and "water-filling" and "anti-water-filling" methods. This enables continuous detection and dynamic response to the spatial spectrum state, significantly improving communication concealment, anti-interference capabilities, and resource utilization efficiency in complex electromagnetic environments by utilizing spectrum holes. Attached Figure Description

[0046] Figure 1 This is a schematic diagram showing the composition and connection of the transmitter portion of the encrypted communication system based on cognitive multicarrier spread spectrum according to the present invention;

[0047] Figure 2 This is a schematic diagram showing the composition and connection of the receiver portion of the encrypted communication system based on cognitive multicarrier spread spectrum according to the present invention;

[0048] Figure 3 This is a block diagram of the transmitter structure of the encrypted communication system based on cognitive multicarrier spread spectrum according to the present invention;

[0049] Figure 4 This is a block diagram of the receiver structure of the encrypted communication system based on cognitive multicarrier spread spectrum of the present invention;

[0050] Figure 5 This is a schematic diagram of a power allocation principle—the "anti-water injection" method—used by the cognitive power allocation module in the cognitive multicarrier spread spectrum encrypted communication system of the present invention.

[0051] Figure 6 This is a diagram illustrating the anti-detection effect of the cognitive power allocation module in the cognitive multicarrier spread spectrum encrypted communication system of the present invention under the covert communication mode.

[0052] Figure 7 This is a diagram illustrating the anti-interference effect of the cognitive power allocation module in the cognitive multicarrier spread spectrum encrypted communication system of the present invention under the anti-interference mode.

[0053] Figure 8 This diagram illustrates the algorithm of the interleaved reversible cellular automaton encryption method in the cognitive multicarrier spread spectrum encrypted communication system of this invention. Detailed Implementation

[0054] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0055] Example 1:

[0056] like Figure 1 and Figure 2As shown, this embodiment discloses an encrypted communication system based on cognitive multicarrier spread spectrum, including a transmitting device and a receiving device.

[0057] The transmitting device includes a data encryption module, a constellation encryption modulation module, a multi-carrier spread spectrum module, a frequency hopping module, and a cognitive power allocation module.

[0058] The receiving device includes a bandpass filter module, a frequency hopping de-hopping module, a despreading module, a constellation decryption and demodulation module, a data decryption module, and a coherent merging module.

[0059] The data encryption module consists of two units: an interleaving coding unit and a dual-rule reversible cellular automaton encryption unit. 255 bits of data flow through a 15×17 interleaving coding unit, scrambling the data. The scrambled data then enters the dual-rule reversible cellular automaton encryption unit. Based on the PN sequence 1, iteration rules No. 85 and No. 51 from the periodic elementary cellular automaton are selected, and the data divided into two groups is encrypted iterated 100 times each. With 255 cells and 12 possible combinations of reversible rules, the system key space size is calculated to be 2^35. 255 × 12 ≈ 2 258 Clearly exceeding 2 128 This is sufficient to withstand brute-force attacks. Furthermore, the data is masked by the interleaving encoding and subsequent spreading code scrambling, resulting in highly secure and resistant encrypted data.

[0060] The constellation encryption modulation module is connected to the output of the data encryption module and is used to perform physical layer constellation diagram encryption modulation on the ciphertext data stream to obtain the encrypted modulated signal.

[0061] The multicarrier spread spectrum module is used to spread the data with N pseudocode sequences to obtain N sets of spread data streams.

[0062] The frequency hopping module is used to modulate different data streams onto different carrier frequencies, where the subcarrier frequencies are selected from a frequency set using PN sequence 2. The frequency hopping module uses pseudo-random codes to control the frequency hopping pattern, thereby controlling the carrier frequency to avoid interference from the interfering party.

[0063] The cognitive power allocation module continuously scans the radio electromagnetic environment and performs real-time spectrum analysis, providing the perceived power spectral density results for all frequency hopping sets. The cognitive power allocation module supports both anti-interference and covert communication modes. When subjected to interference signals covering 20% ​​of the bandwidth, single-carrier, five-subcarrier, and seven-subcarrier signals are transmitted in anti-interference communication mode to avoid interference, using an Eb / N0 of 4.7dB and an interference-to-signal ratio ranging from 30dB to 56dB. Faced with this interference, because each subcarrier channel is independent, the degree of interference on different channels is detected separately, and a power allocation method is adopted to achieve a power allocation scheme that maximizes capacity under fixed broadband interference. The power allocation principle is based on the "water-filling" method, aiming to avoid subcarriers with high interference power as much as possible. When the JSR exceeds approximately 45dB, the bit error rate of the multi-carrier system without interference avoidance deteriorates rapidly, while the interference avoidance scheme maintains a lower bit error rate. Finally, a comparison chart of transmission for each carrier under interference avoidance conditions is obtained, as shown below. Figure 7 As shown. In covert communication mode, the transmitted signal is kept as consistent as possible with the spectrum of the radio electromagnetic environment, and the power allocation principle adopts the "reverse water injection" method, such as... Figure 5 As shown, this means reducing the transmit power for subcarriers with relatively less interference to compensate for subcarriers with relatively more interference. A comparison of the bit error rates for the three receiving methods is shown in the figure below. Figure 6 As shown.

[0064] The bandpass filter module receives radio frequency signals from the antenna and performs initial frequency selection. It sets the passband range according to the operating frequency band, filtering out out-of-band noise and strong interference to improve signal quality.

[0065] The frequency hopping de-hopping module works synchronously with the frequency hopping module of the transmitting device. Using the same pseudo-random code and frequency hopping pattern as the transmitting end, the de-hopping module generates a synchronized local carrier, performs de-hopping processing on the received frequency-hopping signal, down-converts the signals on each subcarrier to baseband or intermediate frequency, and recovers N parallel spread spectrum data streams. The same pseudo-random code as the transmitting end is PN sequence 2.

[0066] The despreading module corresponds to the multi-carrier spread spectrum module of the transmitting device. The despreading module uses N pseudo-random code sequences that are exactly the same as those at the transmitting end to perform correlation despreading processing on the N parallel data streams obtained after de-hopping, compress the signal spectrum, recover the N baseband constellation encrypted modulation symbol streams, and use the spreading gain to suppress noise and interference in the channel.

[0067] The constellation decryption and demodulation module is the reverse process of the constellation encryption modulation module in the transmitting device. It strictly and synchronously replicates the modulation scheme and phase angle selection logic of the transmitting end. Knowing the initial modulation scheme assignment, phase angle assignment, and decision rules, the module can deduce the modulation scheme and phase rotation angle used by the current symbol group based on the correct demodulation result of the previous group and the encoding information of the current group. It performs a reverse phase rotation on the received symbols to achieve phase restoration, demodulates the phase-restored signal using the modulation scheme used by the modulation module, and outputs the decrypted ciphertext data stream.

[0068] The data decryption module is connected to the output of the constellation decryption and demodulation module to complete the final decryption of the data. Internally, it includes a dual-rule reversible cellular automaton decryption unit and a deinterleaving unit. The dual-rule reversible cellular automaton decryption unit uses the inverse rule corresponding to the transmitting encryption unit to iteratively decrypt the received ciphertext data, restoring the interleaved data. The deinterleaving unit is connected to the output of the decryption unit, performing deinterleaving on the decrypted data to restore the bit order of the original data and output the correct original information sequence.

[0069] Since multiple subcarriers at the transmitting end transmit the same information, the coherent combining module is used to coherently combine the despread / demodulated multiple signals to obtain the original coherently combined signal, thereby obtaining diversity gain and improving the anti-interference and anti-fading capabilities of the received signal.

[0070] like Figure 3 and Figure 4 As shown, the encrypted communication method based on cognitive multi-carrier spread spectrum disclosed in this embodiment is a working method of an encrypted communication system based on cognitive multi-carrier spread spectrum, including the following steps:

[0071] Step 1: After the data is copied, it is processed in multiple parallel paths and then enters the data encryption module for interleaved reversible cellular automata encryption.

[0072] The specific implementation method of the interleaved reversible cellular automaton encryption method is as follows:

[0073] SA1. Perform interleaving encoding on 255 bits of data according to the determined interleaving parameters of 15×17.

[0074] SA2. The data read from the interleaved encoding is grouped into two groups of cells, namely R1 group and R2 group, and the data is encrypted according to the specified encryption method.

[0075] like Figure 8As shown, the encryption rule specifically involves using one of the twelve dual-rule combinations of the reversible elementary cellular automaton ECA iteration rule combination, namely iteration rule No. 85 and iteration rule No. 51, to iterate and encrypt these two sets of cells 100 times each, based on the selection of PN sequence 1. After each iteration, the cell state values ​​at the left and right ends of the current cell sequence are XORed, and the result is used as the new state value of the right-end cell. The entire sequence is then inverted, and the inverted sequence is used as the initial cell state value for the next iteration. The evolution of the dual-rule reversible elementary cellular automaton DRECA is expressed by the following formula.

[0076]

[0077]

[0078] in, Let be the state of the cell at time t. Let i represent the evolution of the cell at the next time step, and i denote the sequence position. This indicates the iteration rule. and It consists of two parts of a cell group of length L, namely group R1 and group R2. The state of this cell group at the next moment. This indicates a reversal.

[0079] Step 2: The encrypted data stream enters the constellation encryption and modulation module, where the data undergoes physical layer constellation diagram encryption and modulation.

[0080] Step 3: Spread the modulated data with N pseudo-code sequences to obtain N sets of spread data streams.

[0081] Step 4: Modulate each data stream onto a different carrier frequency, where the subcarrier frequency is selected from the frequency set using PN sequence 2. The frequency hopping system uses pseudo-random codes to control the frequency hopping pattern, thereby controlling the carrier frequency.

[0082] Step 5: Continuously scan the radio electromagnetic environment and perform real-time spectrum analysis, providing the perceived power spectral density results for all frequency hopping sets. The cognitive power allocation module selects either anti-interference communication mode or covert communication mode as needed. When subjected to interference signals with 20% bandwidth, single-carrier, five-subcarrier, and seven-subcarrier signals are transmitted in anti-interference communication mode to avoid interference. The signal uses Eb / N0 = 4.7dB, and the interference-to-signal ratio ranges from 30dB to 56dB. Faced with interference, because each subcarrier channel is independent, the degree of interference on different channels is detected separately. A power allocation method is adopted to achieve a power allocation scheme that maximizes capacity under fixed broadband interference. The power allocation principle refers to the "water-filling" method, avoiding subcarriers with high interference power as much as possible. When the JSR exceeds approximately 45dB, the bit error rate of the multi-carrier system without interference avoidance deteriorates rapidly, while the interference avoidance scheme maintains a lower bit error rate. In covert communication mode, the transmitted signal is kept as consistent as possible with the spectrum of the radio electromagnetic environment. That is, the transmission power of subcarriers with less interference is reduced to compensate for subcarriers with relatively greater interference. The allocation principle refers to the "anti-water injection" method.

[0083] Step Six: The data received by the receiver enters the bandpass filter module. The bandpass filter module receives the radio frequency signal from the antenna and performs preliminary frequency selection. The bandpass filter module sets the passband range according to the operating frequency band, filtering out out-of-band noise and strong interference to improve signal quality.

[0084] Step 7: The frequency hopping de-hopping module works synchronously with the frequency hopping module of the transmitting device. Using the same pseudo-random code and frequency hopping pattern as the transmitting end, it generates a synchronized local carrier, performs de-hopping processing on the received frequency hopping signal, down-converts the signal on each subcarrier to baseband or intermediate frequency, and recovers N parallel spread spectrum data streams.

[0085] Step 8: The despreading module performs relevant despreading processing on the N parallel data streams obtained after de-hopping, compresses the signal spectrum, recovers the N baseband constellation encrypted modulation symbol streams, and uses the spreading gain to suppress noise and interference in the channel.

[0086] Step Nine: The constellation decryption and demodulation module first performs a reverse phase rotation on the received symbols, demodulates them using the correct modulation method, and outputs the decrypted ciphertext data stream.

[0087] Step 10: The dual-rule reversible cellular automaton decryption unit uses the inverse rule corresponding to the transmitting encryption unit to iteratively decrypt the received ciphertext data, restoring the interleaved data. The deinterleaving unit performs deinterleaving on the decrypted data, restoring the bit order of the original data and outputting the correct original information sequence.

[0088] Step 11: Coherently combine the despread / demodulated multiple signals to obtain the recovered data, thereby obtaining diversity gain, further improving the anti-interference and anti-fading capabilities of the received signal, and thus realizing encrypted communication based on cognitive multicarrier spread spectrum.

[0089] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An encrypted communication system based on cognitive multicarrier spread spectrum, characterized in that: Includes a transmitting device and a receiving device; The transmitting device includes a data encryption module, a constellation encryption modulation module, a multi-carrier spread spectrum module, a frequency hopping module, and a cognitive power allocation module; The receiving device includes a bandpass filter module, a frequency hopping de-module, a despreading module, a constellation decryption and demodulation module, a data decryption module, and a coherent merging module; The data encryption module is divided into two units: an interleaving coding unit and a dual-rule reversible cellular automaton encryption unit. The data flows through the interleaving coding unit, which scrambles the data. The scrambled data enters the dual-rule reversible cellular automaton encryption unit, which selects the encryption rule combination according to the PN sequence 1. Through multiple encryption iterations, the encrypted data is obtained as highly secure and resistant to cracking. The constellation encryption modulation module is connected to the output of the data encryption module and is used to perform physical layer constellation diagram encryption modulation on the ciphertext data stream to obtain the encrypted modulated signal. The multi-carrier spread spectrum module is used to spread the modulated signal with N pseudo-code sequences to obtain N sets of spread data streams; The frequency hopping module is used to modulate each data stream onto a different carrier frequency, wherein the subcarrier frequency is selected on a frequency set by PN sequence 2; The frequency hopping module uses pseudo-random codes to control the frequency hopping pattern, and controls the carrier frequency to avoid interference from the interfering party. The cognitive power allocation module continuously scans the radio electromagnetic environment and performs real-time spectrum analysis, providing the perceived power spectral density results for all frequency hopping frequency sets. The module supports both anti-interference and covert communication modes. In anti-interference mode, facing interference, since each subcarrier channel is independent, the module detects the degree of interference on different channels and employs a power allocation method to achieve a power allocation scheme that maximizes capacity under fixed broadband interference. The power allocation principle references the "water-filling" method, minimizing the interference on subcarriers with high interference power. In covert communication mode, the transmitted signal is kept as consistent as possible with the spectrum of the radio electromagnetic environment. The power allocation principle adopts the "reverse water-filling" method, which reduces the transmission power of subcarriers with relatively low interference to compensate for subcarriers with relatively high interference. The frequency hopping de-hopping module works synchronously with the frequency hopping module of the transmitting device. The frequency hopping de-hopping module uses the same pseudo-random code and frequency hopping pattern as the transmitting end to generate a synchronous local carrier, performs de-hopping processing on the received frequency hopping signal, down-converts the signal on each subcarrier to baseband or intermediate frequency, and recovers N parallel spread spectrum data streams. The same pseudo-random code as the transmitter, namely PN sequence 2.

2. The encrypted communication system based on cognitive multicarrier spread spectrum as described in claim 1, characterized in that: The bandpass filter module is used to receive radio frequency signals from the antenna and perform preliminary frequency selection; the bandpass filter module sets the passband range according to the operating frequency band, filters out out-of-band noise and strong interference, and improves signal quality; The despreading module corresponds to the multi-carrier spread spectrum module of the transmitting device. The despreading module uses N pseudo-random code sequences that are exactly the same as those at the transmitting end to perform correlation despreading processing on the N parallel data streams obtained after de-hopping, compress the signal spectrum, recover the N baseband constellation encrypted modulation symbol streams, and use the spread spectrum gain to suppress noise and interference in the channel. The constellation decryption and demodulation module is the reverse process of the constellation encryption and modulation module in the transmitting device; The constellation decryption and demodulation module strictly and synchronously reproduces the modulation method and phase angle selection logic of the transmitter. Knowing the initial modulation method assignment, phase angle assignment, and decision rules, the constellation decryption and demodulation module derives the modulation method and phase rotation angle used by the current group of symbols based on the correct demodulation results of the previous group of symbols and the encoding information of the current group of symbols. Phase recovery is achieved by performing a reverse phase rotation on the received symbol. The phase-recovered signal is then demodulated using the modulation scheme employed by the modulation module, and the decrypted ciphertext data stream is output. The data decryption module is connected to the output of the constellation decryption and demodulation module to complete the final decryption of the data. It contains a dual-rule reversible cellular automaton decryption unit and a deinterleaving unit. The dual-rule reversible cellular automaton decryption unit uses the inverse rule corresponding to the encryption unit at the transmitting end to iteratively decrypt the received ciphertext data and restore the interleaved data. The deinterleaving unit is connected to the output of the decryption unit to perform deinterleaving operation on the decrypted data, restore the bit order of the original data, and output the correct original information sequence.

3. The encrypted communication system based on cognitive multicarrier spread spectrum as described in claim 2, characterized in that: Since multiple subcarriers at the transmitting end transmit the same information, the coherent combining module is used to coherently combine the despread / demodulated multiple signals to obtain the original coherently combined signal, thereby obtaining diversity gain and improving the anti-interference and anti-fading capabilities of the received signal.

4. A cognitive multi-carrier spread spectrum-based encrypted communication method, implemented according to the cognitive multi-carrier spread spectrum-based encrypted communication system as described in claim 3, characterized in that: Includes the following steps: Step 1: After the data is copied, it is processed in multiple parallel paths and then enters the data encryption module for interleaved reversible cellular automata encryption. Step 2: The encrypted data stream enters the constellation encryption and modulation module, where the data undergoes physical layer constellation diagram encryption and modulation; Step 3: Spread the modulated data with N pseudo-code sequences to obtain N sets of spread data streams; Step 4: Modulate each data stream onto a different carrier frequency, where the subcarrier frequency is selected from the frequency set using PN sequence 2; the frequency hopping system uses a pseudo-random code to control the frequency hopping pattern and control the carrier frequency; Step 5: Continuously scan the radio electromagnetic environment and perform real-time spectrum analysis, providing the perceived power spectral density results for all frequency hopping frequency sets; the cognitive power allocation module selects either anti-interference communication mode or covert communication mode as needed; in anti-interference communication mode, facing interference, since each subcarrier channel is independent, the degree of interference on different channels is detected separately, and a power allocation method is adopted to achieve a power allocation scheme that maximizes capacity under fixed broadband interference. The allocation principle refers to the "water injection" method, avoiding subcarriers with high interference power as much as possible; in covert communication mode, the transmitted signal is kept as consistent as possible with the spectrum of the radio electromagnetic environment, that is, the transmission power of subcarriers with less interference is reduced to compensate for subcarriers with relatively large interference. The allocation principle refers to the "anti-water injection" method; Step Six: The data received by the receiving device enters the bandpass filter module. The bandpass filter module is used to receive the radio frequency signal from the antenna and perform preliminary frequency selection. The bandpass filter module sets the passband range according to the operating frequency band and filters out out-of-band noise and strong interference. Step 7: The frequency hopping de-hopping module works synchronously with the frequency hopping module of the transmitting device. Using the same pseudo-random code and frequency hopping pattern as the transmitting end, it generates a synchronized local carrier, performs de-hopping processing on the received frequency hopping signal, down-converts the signal on each subcarrier to baseband or intermediate frequency, and recovers N parallel spread spectrum data streams. Step 8: The despreading module performs relevant despreading processing on the N parallel data streams obtained after de-hopping, compresses the signal spectrum, recovers the N baseband constellation encrypted modulation symbol streams, and uses the spreading gain to suppress noise and interference in the channel; Step Nine: The constellation decryption and demodulation module first performs a reverse phase rotation on the received symbols, demodulates them using the correct modulation method, and outputs the decrypted ciphertext data stream; Step 10: The dual-rule reversible cellular automaton decryption unit uses the inverse rule corresponding to the transmitting end encryption unit to iteratively decrypt the received ciphertext data and restore the interleaved data; the deinterleaving unit performs deinterleaving operation on the decrypted data to restore the bit order of the original data and output the correct original information sequence. Step 11: Coherently combine the despread / demodulated multiple signals to obtain the recovered data, thereby obtaining diversity gain, further improving the anti-interference and anti-fading capabilities of the received signal, and realizing encrypted communication based on cognitive multicarrier spread spectrum.

5. The encrypted communication method based on cognitive multicarrier spread spectrum as described in claim 4, characterized in that: The specific implementation method of the interleaved reversible cellular automaton encryption method is as follows: SA1. Perform interleaving encoding on the data according to the determined interleaving parameters; SA2. The data read from the interleaved encoding is grouped into two groups of cells, namely R1 group and R2 group, and the data is encrypted according to the specified encryption method. The encryption rules are as follows: based on the selection of PN sequence 1, two combinations of reversible elementary cellular automata (ECA) iterative rules are used to iterate and encrypt the two sets of cells n times respectively; after each iteration, the cell state values ​​of the left and right ends of the current cell sequence are XORed, and the result is used as the new state value of the right end cell; the entire sequence is inverted, and the inverted sequence is used as the initial value of the cell state for the next iteration. The evolution of the dual-rule reversible elementary cellular automata (DRECA) is expressed by the following formula. in, Let be the state of the cell at time t. Let i represent the evolution of the cell at the next time step, and i denote the sequence position. Indicates the iteration rule; and It consists of two parts of a cell group of length L, namely group R1 and group R2; The state of this cell group at the next moment. This indicates a reversal.

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