Secure communication method and system based on random frequency

Abstract

The invention provides a secure communication method and system based on random frequency. The secure communication method based on the random frequency comprises the following steps: according to a preset frequency range of a current environment, a communication initiator provides channels of a plurality of frequencies to a communication receiver; the communication receiver randomly selects a channel for communication from the channels of the plurality of frequencies at regular time in the communication process to communicate with a communication initiator; when a communication initiator transmits data information to a communication receiver, data to be transmitted are dispersed to frequency points of a randomly selected communication channel, and encrypted transmission is carried out. The system comprises modules corresponding to the steps of the method.

Description

Technical Field

[0001] The invention proposes a random frequency-based secure communication method and system, belonging to the technical field of secure communication. Background Art

[0002] With the development of intelligent transportation systems, real-time communication between vehicles has become increasingly important, especially in scenarios such as highways and urban intersections, where vehicles need to frequently exchange information to support functions such as collision avoidance warnings, road condition sharing, and collaborative driving. However, existing inter-vehicle communication technologies mostly rely on fixed frequency bands or preset communication protocols, which are susceptible to external interference and are at risk of being illegally monitored or tampered with. Especially when vehicles are traveling in opposite directions, the communication quality and security face greater challenges due to increased signal cross-interference.

[0003] Therefore, it is particularly important to develop a communication method that can adapt to environmental changes, effectively resist external interference and enhance data encryption capabilities. Based on this, the present invention proposes a secure communication method based on random frequency, which is particularly suitable for communication scenarios when vehicles are traveling in opposite directions. Summary of the invention

[0004] The present invention provides a random frequency-based secure communication method and system to solve the technical problem of poor vehicle communication security in the prior art. The technical solution adopted is as follows:

[0005] A secure communication method based on random frequency, the secure communication method based on random frequency comprising:

[0006] According to the preset frequency range of the current environment, the communication initiator provides a plurality of frequency channels to the communication receiver, and the communication receiver periodically randomly selects a channel for communication from the plurality of frequency channels during the communication process to communicate with the communication initiator;

[0007] When the communication initiator transmits data information to the communication receiver, the data to be transmitted is dispersed to the frequency points of the randomly selected communication channel and transmitted in encrypted form.

[0008] Further, according to a preset frequency range of the current environment, the communication initiator provides a plurality of frequency channels to the communication receiver, and the communication receiver periodically randomly selects a channel for communication from the plurality of frequency channels to communicate with the communication initiator during the communication process, including:

[0009] Determine the N candidate frequency sets that the current communication initiator can select Each set includes M frequencies, and the N×M frequencies are different from each other. Meanwhile, the frequencies of each frequency set are in the same frequency band, wherein the N frequency sets are as follows:

[0010] F 1 ={f 1，1 , f 1，2 , ..., f 1，M}F 2 ={f 2，1 , f 2，2 , ..., f 2，M},......,F N ={f N，1 , f N，2 , ..., f N，M}

[0011] Before a communication link is established between a communication initiator and a communication receiver, the communication initiator performs channel estimation on N×M frequencies and provides the N×M frequencies to the communication receiver;

[0012] After receiving N×M frequencies, the communication receiving party performs channel estimation on the received N×M frequencies to obtain the channel states of the N×M frequencies;

[0013] After the communication receiving party completes the channel estimation, the frequency diversity signal is demodulated;

[0014] Denote the nth channel state set as α n ={α n，1 , α n，2 , ..., α n，M};

[0015] After the communication link between the communication initiator and the communication receiver is established, the communication receiver selects a frequency from the candidate frequency set at each preset time interval. Randomly select multiple frequency points for communication;

[0016] Among them, the set F consisting of N(k) frequencies of the kth communication between the communication receiving party and the communication initiator is N(k) for:

[0017] F N(k) ={f 1 (k), f 2 (k), ..., f N(k) (k)|f i (k)∈F i , i = 1, 2, ..., N(k)}

[0018] k represents the kth communication; f i (k) indicates that in the kth communication, from the frequency set F i The frequency of random selection in .

[0019] Further, after receiving N×M frequencies, the communication receiving party performs channel estimation on the received N×M frequencies to obtain channel states of the N×M frequencies, including:

[0020] After receiving the N×M frequencies, the communication receiver uses the random resonance method to 1 To F N Conduct detection to determine whether there is stochastic resonance phenomenon;

[0021] When stochastic resonance occurs, the frequency set F 1 To F N Perform frequency estimation in sequence to obtain the frequency set F 1 To F N The corresponding communication frequency, wherein the frequency set F 1 To F N The frequency vector of the corresponding communication frequency is as follows:

[0022]

[0023] in, f 1 (k) is the estimated value.

[0024] Furthermore, after the communication receiving party completes the channel estimation, the frequency diversity signal is demodulated, including:

[0025] Retrieve frequency set F 1 To F N A frequency vector corresponding to the communication frequency;

[0026] Retrieving a set of N(k) frequencies for communication between a communication receiving party and the communication initiator;

[0027] Using frequency set F 1 The frequency vector of the communication frequency corresponding to FN and the set consisting of the N(k) frequencies obtain the frequency set F 1 The frequency difference between the frequency vector of the communication frequency corresponding to FN and the set consisting of the N(k) frequencies; wherein the frequency difference is in the following form:

[0028]

[0029] The demodulated signal is obtained by using the frequency difference, wherein the demodulated signal is as follows:

[0030]

[0031] Where c represents the attenuation constant after signal transmission; is the additive noise after demodulation; when the frequency estimation is accurate enough, ΔF N(k)The elements of are close to 0, and a more accurate signal demodulation result can be obtained. At this time, the demodulated signal can be simplified to:

[0032]

[0033] Furthermore, when the communication initiator transmits data information to the communication receiver, the data to be transmitted is dispersed to the frequency points of the randomly selected communication channel and encrypted for transmission, including:

[0034] When the communication initiator transmits data information to the communication receiver, the vector formed by the received signal of the communication initiator at all N(k) frequency points is as follows:

[0035] Y(t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =α(k) T s(t,k)+n(k)

[0036] Where α(k)=[α 1 (k), α 2 (k), ..., α N(k) (k)] T , α n (k)∈α n , 1≤n≤N(k), α(k) is the channel state vector corresponding to each frequency point between the communication receiving party and the communication sending party in the kth time period; n(k)=[n 1 (k), n 2 (k), ..., n N(k) (k)] T The encrypted channel noise is N(k) frequency points. Each noise element is independent and identically distributed and follows a Gaussian distribution. diag(·) represents a diagonal matrix, s(t, k) is the information baseband waveform sent at the kth moment;

[0037] During the data transmission between the communication receiving party and the communication sending party, the physical layer of the kth time period is encrypted, and the form of the received signal is changed into:

[0038] Y B (t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =C T s(t,k)+n(k)

[0039] in, is a constant vector.

[0040] A random frequency-based secure communication system, the random frequency-based secure communication system comprising:

[0041] A channel screening module, configured to provide a plurality of frequency channels to a communication receiving party according to a preset frequency range of the current environment, and the communication receiving party randomly selects a channel for communication from the plurality of frequency channels to communicate with the communication initiator during the communication process;

[0042] The encrypted transmission module is used for dispersing the data to be transmitted onto the frequency points of the randomly selected communication channel and encrypting the data when the communication initiator transmits data information to the communication receiver.

[0043] Furthermore, the channel screening module includes:

[0044] The candidate frequency set determination module is used to determine the N candidate frequency sets that the current communication initiator can select. Each set includes M frequencies, and the N×M frequencies are different from each other. Meanwhile, the frequencies of each frequency set are in the same frequency band, wherein the N frequency sets are as follows:

[0045] F 1 ={f 1，1 , f 1，2 , ..., f 1，M}F 2 ={f 2，1 , f 2，2 , ..., f 2，M},......,F N ={f N，1 , f N，2 , ..., f N，M}

[0046] A first channel estimation module, configured to, before a communication link is established between a communication initiator and a communication receiver, cause the communication initiator to perform channel estimation on N×M frequencies and provide the N×M frequencies to the communication receiver;

[0047] A second channel estimation module is used for, after receiving N×M frequencies, the communication receiving party to perform channel estimation on the received N×M frequencies to obtain channel states of the N×M frequencies;

[0048] A signal demodulation module, used to demodulate the frequency diversity signal after the communication receiving party completes the channel estimation;

[0049] The set representation module is used to represent the nth channel state set as α n ={αn，1 , α n，2 , .., α n，M};

[0050] The communication execution module is used for, after the communication link between the communication initiator and the communication receiver is established, at each preset time interval, the communication receiver selects a frequency from the candidate frequency set. Randomly select multiple frequency points for communication;

[0051] Among them, the set F consisting of N(k) frequencies of the kth communication between the communication receiving party and the communication initiator is N(k) for:

[0052] F N(k) ={f 1 (k), f 2 (k), ..., f N(k) (k)|f i (k)∈F i , i = 1, 2, ..., N(k)}

[0053] k represents the kth communication; f i (k) indicates that in the kth communication, from the frequency set F i The frequency of random selection in .

[0054] Furthermore, the second channel estimation module includes:

[0055] The stochastic resonance phenomenon detection module is used for the communication receiver to detect the received N×M frequencies by using the stochastic resonance method. 1 To F N Conduct detection to determine whether there is stochastic resonance phenomenon;

[0056] The communication frequency estimation module is used to estimate the frequency set F when stochastic resonance occurs. 1 To F N Perform frequency estimation in sequence to obtain the frequency set F 1 To F N The corresponding communication frequency, wherein the frequency set F 1 To F N The frequency vector of the corresponding communication frequency is as follows:

[0057]

[0058] in, f 1 (k) is the estimated value.

[0059] Furthermore, the signal demodulation module includes:

[0060] Frequency vector retrieval module, used to retrieve the frequency set F 1 To F N A frequency vector corresponding to the communication frequency;

[0061] A set retrieving module, used to retrieve a set consisting of N(k) frequencies for the communication receiving party to communicate with the communication initiator;

[0062] The frequency difference acquisition module is used to use the frequency set F 1 To F N The frequency vector of the corresponding communication frequency and the set consisting of the N(k) frequencies obtain the frequency set F 1 To F N The frequency difference between the frequency vector of the corresponding communication frequency and the set of N(k) frequencies; wherein the frequency difference is in the following form:

[0063]

[0064] The demodulated signal is obtained by using the frequency difference, wherein the demodulated signal is as follows:

[0065]

[0066] Where c represents the attenuation constant after signal transmission; is the additive noise after demodulation; when the frequency estimation is accurate enough, ΔF N(k) The elements of are close to 0, and a more accurate signal demodulation result can be obtained. At this time, the demodulated signal can be simplified to:

[0067]

[0068] Furthermore, the encryption transmission module includes:

[0069] The vector acquisition module is used when the communication initiator transmits data information to the communication receiver. The vector formed by the received signal of the communication initiator at all N(k) frequency points is as follows:

[0070] Y(t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =α(k) T S(t,k)+n(k)

[0071] Where α(k)=[α 1 (k), α 2 (k), ..., α N (k)(k)] T , α n (k)∈αn , 1≤n≤N(k), α(k) is the channel state vector corresponding to each frequency point between the communication receiving party and the communication sending party in the kth time period; n(k)=[n 1 (k), n 2 (k), ..., n N(k) (k)] T The encrypted channel noise is N(k) frequency points. Each noise element is independent and identically distributed and follows a Gaussian distribution. diag(·) represents a diagonal matrix, s(t, k) is the information baseband waveform sent at the kth moment;

[0072] The encryption processing module is used to perform encryption processing on the physical layer of the kth time period during the data transmission between the communication receiving party and the communication sending party, and in the encryption process, the form of the received signal is changed into:

[0073] Y B (t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =C T s(t,k)+n(k)

[0074] in, is a constant vector.

[0075] Beneficial effects of the present invention:

[0076] The random frequency-based secure communication method and system random frequency selection mechanism proposed in the present invention make the communication frequency difficult to predict, effectively reducing the risk of malicious monitoring or interference. The data decentralized encrypted transmission method increases the difficulty of data eavesdropping. Even if a data fragment is intercepted, it is difficult to restore the original information. The randomly selected communication channel can effectively avoid the multipath effect, Doppler frequency shift and other problems in fixed frequency communication, and improve the stability of communication. The data decentralized transmission method reduces the impact of data loss or errors on the overall communication quality and enhances the anti-interference ability of communication. The method can dynamically adjust the communication frequency range according to the electromagnetic spectrum conditions of the current environment to adapt to communication needs in different scenarios. The timing or random selection mechanism based on preset strategies allows the communicating parties to flexibly adjust the communication strategy according to actual conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 is a flow chart of the method of the present invention;

[0078] Figure 2 The figure is a flow chart of the system of the present invention. DETAILED DESCRIPTION

[0079] The preferred embodiments of the present invention are described below in conjunction with the accompanying 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.

[0080] The embodiment of the present invention proposes a secure communication method based on random frequency, such as Figure 1 As shown, the random frequency-based secure communication method includes:

[0081] S1. According to a preset frequency range of the current environment, the communication initiator provides a plurality of frequency channels to the communication receiver, and the communication receiver periodically randomly selects a channel for communication from the plurality of frequency channels to communicate with the communication initiator during the communication process;

[0082] S2. When the communication initiator transmits data information to the communication receiver, the data to be transmitted is dispersed to the frequency points of the randomly selected communication channel and encrypted for transmission.

[0083] The working principle of the above technical solution is as follows: the communication initiator first detects the electromagnetic spectrum status of the current environment, and determines an available frequency range based on preset safety and compliance standards. Within the determined frequency range, the communication initiator provides multiple alternative frequency channels to the communication receiver. During the communication process, the communication receiver randomly selects one of these alternative channels for the current communication session at regular intervals (or according to a preset strategy). This randomness makes the communication frequency difficult to predict, thereby reducing the risk of malicious monitoring or interference.

[0084] When the communication receiver transmits data information to the communication initiator, it first divides the data to be transmitted and randomly disperses the divided data fragments to multiple frequency points of the selected communication channel. This dispersion method increases the difficulty of data eavesdropping, because the attacker needs to capture data fragments on multiple frequency points at the same time and reassemble them to restore the original information. While the data is dispersed, the communication receiver encrypts each data fragment. The use of high-intensity encryption algorithms (such as AES, RSA, etc.) can ensure that even if the data fragments are intercepted, the attacker cannot easily obtain the useful information in them.

[0085] The effects of the above technical solutions are as follows: the random frequency selection mechanism makes the communication frequency difficult to predict, effectively reducing the risk of malicious monitoring or interference. The data decentralized encrypted transmission method increases the difficulty of data eavesdropping. Even if a data fragment is intercepted, it is difficult to restore the original information. The randomly selected communication channel can effectively avoid the multipath effect, Doppler frequency shift and other problems in fixed frequency communication, and improve the stability of communication. The data decentralized transmission method reduces the impact of data loss or errors on the overall communication quality and enhances the anti-interference ability of communication. The method can dynamically adjust the communication frequency range according to the electromagnetic spectrum conditions of the current environment to adapt to the communication needs in different scenarios. The timing or random selection mechanism based on preset strategies allows the communicating parties to flexibly adjust the communication strategy according to actual conditions.

[0086] In summary, this technical solution significantly improves the security and anti-interference capability of vehicle-to-vehicle communication through random frequency selection and data decentralized encrypted transmission, providing strong support for real-time and reliable communication between vehicles in intelligent transportation systems.

[0087] In one embodiment of the present invention, according to a preset frequency range of the current environment, the communication initiator provides a plurality of frequency channels to the communication receiver, and the communication receiver periodically randomly selects a channel for communication from the plurality of frequency channels during the communication process to communicate with the communication initiator, including:

[0088] S101. Determine N candidate frequency sets that can be selected by the current communication initiator Each set includes M frequencies, and the N×M frequencies are different from each other. Meanwhile, the frequencies of each frequency set are in the same frequency band, wherein the N frequency sets are as follows:

[0089] F 1 ={f 1，1 , f 1,2 , ..., f 1，M}F 2 ={f 2，1 , f 2，2 , ..., f 2，M},......,F N ={f N，1 , f N，2 , ..., f N，M}

[0090] S102, before a communication link is established between a communication initiator and a communication receiver, the communication initiator performs channel estimation on N×M frequencies and provides the N×M frequencies to the communication receiver;

[0091] S103, after receiving N×M frequencies, the communication receiving party performs channel estimation on the received N×M frequencies to obtain channel states of the N×M frequencies;

[0092] S104, after the communication receiving party completes channel estimation, demodulating the frequency diversity signal;

[0093] S105: denote the nth channel state set as α n ={α n，1 , α n，2 , ..., α n，M};

[0094] S106. After the communication link between the communication initiator and the communication receiver is established, the communication receiver selects a candidate frequency from the candidate frequency set at each preset time interval. Randomly select multiple frequency points for communication;

[0095] Among them, the set F consisting of N(k) frequencies of the kth communication between the communication receiving party and the communication initiator is N(k) for:

[0096] F N(k) ={f 1 (k), f 2 (k), ..., f N(k) (k)|f i (k)∈F i， i=1,2,...,N(k)}

[0097] k represents the kth communication; f i (k) indicates that in the kth communication, from the frequency set F i The frequency of random selection in .

[0098] The working principle of the above technical solution is:

[0099] Let N frequency sets F 1 ={f 1，1 , f 1,2 , ..., f 1，M}、F 2 ={f 2，1 , f 2，2 , ..., f 2，M},......,F N ={f N，1 , f N，2 , ..., f N，M} is the candidate frequency set for communication Each set contains M frequencies, and the N*M frequencies are different. Usually, the frequencies of each frequency set are in the same frequency band. Before the communication link is established, the communication initiator Bob first initiates the channel estimation training process for N◇M frequencies. After receiving it, Alice performs channel estimation on the corresponding frequencies and obtains the channel states of N◇M frequencies. The nth channel state set is represented as α n ={α n，1 , α n，2 , ..., α n，M}, where each channel state element A m，n is the amplitude parameter of the channel state, is the phase parameter of the channel state. In formal communication, Alice selects a frequency from the frequency set F at every time Δt. 1 To F N Several frequencies are randomly selected for communication, and each frequency set selects at most one frequency. From time t+(k-1)·Δt to t+k·Δt, the set of N(k) frequencies (2≤N(k)≤N) selected is

[0100] f N(k) ={f 1 (k), f 2 (k), ..., f N(k) (k)|f i (k)∈F i , i=1,2,...,N(k)} (1)

[0101] The information is then modulated on these frequencies for communication. The difference here from frequency hopping communication is that the selected frequency is randomly selected by the signal sender, and the receiver Bob does not have a pre-agreed frequency hopping pattern to refer to. The signal frequency detection and subsequent signal demodulation process are achieved by blind signal detection technology.

[0102] The effect of the above technical solution is: by determining N candidate frequency sets, each set contains M different frequencies, and the N×M frequencies are different. This frequency diversity makes communication difficult to predict and intercept. Attackers need to monitor multiple frequencies at the same time to try to intercept the communication content, which greatly increases the difficulty of the attack. During the communication process, the communication receiver randomly selects multiple frequency points from the candidate frequency set for communication within each preset time interval. This randomness makes the communication frequency constantly changing, further reducing the risk of malicious monitoring.

[0103] The communication initiator and the communication receiver both perform channel estimation before and after the communication link is established to obtain the channel status of N×M frequencies. This helps both parties understand the transmission quality of each frequency, so that when selecting the communication frequency, they can avoid the frequency band with greater interference and improve the anti-interference ability of communication. By demodulating the frequency diversity signal, the signal redundancy on multiple frequencies can be used to improve the reliability of communication. Even if the signal on a certain frequency is interfered or lost, the signals on other frequencies can still be used to restore the original information.

[0104] The communication receiver can dynamically select the communication frequency from the candidate frequency set according to the current channel status and communication needs. This flexibility enables the communication system to adapt to the communication needs in different environments and scenarios, and improve the adaptability and efficiency of communication. By updating the communication frequency at preset time intervals, it can ensure the regular update of the communication frequency, further reducing the risk of long-term monitoring. At the same time, this regular update also enables the communication system to cope with rapidly changing communication environments. Through the channel estimation and frequency selection mechanism, the communicating parties can choose the frequency with better channel status for communication, thereby ensuring the quality of communication. This helps to reduce the bit error rate and packet loss rate during the communication process, and improve the reliability and stability of communication.

[0105] In summary, this technical solution effectively improves the security, anti-interference ability and flexibility of communication and ensures the communication quality by providing multiple candidate frequency sets, performing channel estimation, randomly selecting communication frequencies and demodulating frequency diversity signals. These technical effects are particularly important for vehicle-to-vehicle communication, especially for communication scenarios when vehicles are driving in opposite directions.

[0106] In one embodiment of the present invention, after receiving N×M frequencies, the communication receiving party performs channel estimation on the received N×M frequencies to obtain channel states of the N×M frequencies, including:

[0107] S1031, after receiving the N×M frequencies, the communication receiving party uses the random resonance method to 1 Go to FN for testing to determine whether there is stochastic resonance;

[0108] S1032. When stochastic resonance occurs, the frequency set F 1 To F N Perform frequency estimation in sequence to obtain the frequency set F 1 To F N The corresponding communication frequency, wherein the frequency set F 1 To F N The frequency vector of the corresponding communication frequency is as follows:

[0109]

[0110] in, is the estimated value of f1(k).

[0111] The working principle of the above technical solution is: since the transmitting end randomly selects the frequency point, the receiving end first needs to detect the current communication frequency. The stochastic resonance method has a good effect in weak signal detection, so the receiving end uses this method to first estimate the N(k) communication frequencies in formula (5). 1 To F N When testing, if there is a communication signal in the corresponding frequency band, random resonance will occur, causing the noise energy to be gradually converted into signal energy. As a result, obvious signal spectrum lines appear in the amplitude-frequency diagram on the corresponding frequency band. According to the existing theory, when the nth frequency is concentrated for signal detection, the bistable stochastic resonance system process is described as

[0112]

[0113] where y n (t, n) is a sinusoidal driving signal, corresponding to the communication signal to be detected; n n (t, n) is random noise, corresponding to additive channel noise; x n (t, k) is the output of the stochastic resonance system. In fact, the output of the first stochastic resonance system can be used as the input of the second stochastic resonance system. Through the cascade of multiple stochastic resonance systems, the energy of the signal to be detected can be continuously enhanced. For the nth frequency set in the k-time period, according to the first-order stochastic resonance process of formula (6), the multi-order stochastic resonance process containing the target frequency signal and the non-target frequency signal in the signal to be detected is defined as:

[0114]

[0115] RS (s) (·) is a function representing an s-order random process; n n (t, k) represents the channel noise of the nth frequency in the kth time period; is the output of the s-order random process. After performing random resonance detection on all frequency bands in sequence, the current communication frequency can be obtained through accurate frequency estimation. Since the estimated frequency has deviations, let the estimated frequency vector be

[0116]

[0117] In formula (8), f 1 (k) is the estimated value.

[0118] The effect of the above technical solution is: by using the stochastic resonance method to detect the frequency sets F1 to FN, it is possible to more accurately determine which frequency sets have stochastic resonance. Stochastic resonance is a phenomenon in which, in a nonlinear system, when the system is acted upon by noise and periodic signals, the system's response to periodic signals is enhanced. By using this characteristic, useful signals and noise interference in the channel can be more effectively identified, thereby improving the accuracy of channel detection.

[0119] When random resonance occurs, frequency estimation is performed on frequency sets F1 to FN in sequence to obtain the communication frequency corresponding to each frequency set. This process not only helps to understand the channel status of each frequency, but also can screen out frequencies that are more suitable for communication based on channel quality. By optimizing frequency selection, the bit error rate and packet loss rate during communication can be reduced, and the reliability and stability of communication can be improved.

[0120] By estimating the communication frequencies of frequency sets F1 to FN, the frequency vectors corresponding to each frequency set are obtained. These frequency vectors not only reflect the channel status of each frequency, but also provide important reference information for the subsequent communication process. Based on these frequency vectors, the communicating parties can formulate more reasonable communication strategies, such as dynamically adjusting the communication frequency, optimizing the modulation and coding method, etc., to further improve the communication performance.

[0121] In actual communication environments, channel status may change due to a variety of factors. By performing channel estimation and frequency detection periodically or as needed, the communication receiver can promptly understand changes in channel status and take appropriate measures to adjust. This dynamic adaptability enables the communication system to better cope with complex and changing communication environments and ensure the continuity and stability of communication.

[0122] In summary, this technical solution not only improves the accuracy of channel detection and the optimization of frequency selection by using the stochastic resonance method for channel estimation and frequency detection, but also further improves the communication performance and system adaptability. These technical effects are of great significance for improving the reliability, stability and security of inter-vehicle communication.

[0123] In one embodiment of the present invention, after the communication receiving party completes channel estimation, the frequency diversity signal is demodulated, including:

[0124] S1041, retrieve frequency set F 1 To F N A frequency vector corresponding to the communication frequency;

[0125] S1042, retrieving a set consisting of N(k) frequencies used by the communication receiving party to communicate with the communication initiating party;

[0126] S1043, using frequency set F1 To F N The frequency vector of the corresponding communication frequency and the set consisting of the N(k) frequencies obtain the frequency set F 1 The frequency difference between the frequency vector of the communication frequency corresponding to FN and the set consisting of the N(k) frequencies; wherein the frequency difference is in the following form:

[0127]

[0128] The demodulated signal is obtained by using the frequency difference, wherein the demodulated signal is as follows:

[0129]

[0130] Where c represents the attenuation constant after signal transmission; is the additive noise after demodulation; when the frequency estimation is accurate enough, ΔF N(k) The elements of are close to 0, and a more accurate signal demodulation result can be obtained. At this time, the demodulated signal can be simplified to:

[0131]

[0132] The working principle of the above technical solution is: after the receiving end obtains the frequency estimation value of the signal in each frequency band, it combines the signals of each frequency point with equal gain, thereby realizing the signal demodulation process. If the frequency difference between the frequency estimation value shown in formula (8) and the standard frequency shown in formula (1) is

[0133]

[0134] The final demodulated signal is

[0135]

[0136] Where c is the constant of signal attenuation after transmission; is the additive noise after demodulation. When the frequency estimation is accurate enough, ΔF N(k) The elements of are close to 0, and a more accurate signal demodulation result can be obtained. At this time, formula (10) can be simplified to

[0137]

[0138] The effect of the above technical solution is: by calling the frequency vector of the communication frequency corresponding to the frequency set F1 to FN, and comparing it with the set consisting of N(k) frequencies used in the current communication, the frequency difference is calculated. This step uses accurate frequency vector information to ensure the accuracy of the frequency difference. The accurate calculation of the frequency difference is the basis for the accuracy of the subsequent demodulation signal. When the frequency estimate is accurate enough, the elements in the frequency difference vector approach 0, which means that the frequency offset in the demodulation process is effectively suppressed, thereby reducing the demodulation error caused by the frequency offset. This makes the demodulated signal closer to the original signal and improves the demodulation accuracy. In the demodulation process, the attenuation constant c after signal transmission and the additive noise after demodulation are considered. This processing method makes the demodulation algorithm more comprehensive and practical, and can cope with signal attenuation and noise interference in actual communication environments, and enhance the stability of the demodulation signal. Since the channel state changes with time and environmental changes, the demodulation algorithm needs to be able to adapt to different channel conditions. By using frequency vectors and frequency differences for demodulation, the algorithm can more flexibly respond to channel changes and ensure that a stable demodulation signal can be obtained under different channel conditions.

[0139] Through frequency diversity and dynamic frequency selection, the communication system can make more effective use of limited frequency resources. In the demodulation process, the use of accurate frequency vectors and frequency differences for demodulation helps to reduce the waste and interference of frequency resources and improve the overall performance of the communication system. As one of the key links in the communication process, the accuracy and stability of demodulation directly affect the reliability of the communication system. The above-mentioned demodulation technical solution enhances the reliability of the communication system by improving the demodulation accuracy and stability, and ensures the accurate transmission and reception of communication data. When the frequency estimation is accurate enough, the demodulation algorithm can be simplified to a form that only considers signal attenuation and additive noise. This simplification not only reduces the complexity of the algorithm, but also reduces the amount of calculation and improves the demodulation efficiency.

[0140] In summary, this technical solution improves the demodulation accuracy, enhances the stability of the demodulated signal, improves the overall performance of the communication system, and simplifies the demodulation algorithm under certain conditions by accurately calculating the frequency difference, considering signal attenuation and noise, optimizing the use of frequency resources, and simplifying the demodulation process (under certain conditions). These technical effects are of great significance for improving the reliability and performance of systems such as inter-vehicle communication and wireless communication.

[0141] In one embodiment of the present invention, when a communication initiator transmits data information to a communication receiver, the communication initiator disperses the data to be transmitted to the frequency points of a randomly selected communication channel and performs encrypted transmission, including:

[0142] S201, when the communication initiator transmits data information to the communication receiver, the vector formed by the received signals of the communication initiator at all N(k) frequency points is as follows:

[0143] Y(t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =α(k) T s(t,k)+n(k)

[0144] Where α(k)=[α 1 (k), α 2 (k), ..., α N(k) (k)] T , α n (k)∈α n , 1≤n≤N(k), α(k) is the channel state vector corresponding to each frequency point between the communication receiving party and the communication sending party in the kth time period; n(k)=[n 1 (k), n 2 (k), ..., n N(k) (k)] T The encrypted channel noise is N(k) frequency points. Each noise element is independent and identically distributed and follows a Gaussian distribution. diag(·) represents a diagonal matrix, s(t, k) is the information baseband waveform sent at the kth moment;

[0145] S202, during the data transmission between the communication receiving party and the communication sending party, the physical layer of the kth time period is encrypted, and the form of the received signal is changed into:

[0146] Y B (t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =C T s(t,k)+n(k)

[0147] in, is a constant vector.

[0148] The working principle of the above technical solution is: in the kth time period, for the frequency randomly selected in the set of formula (1), when Alice sends the signal using frequency diversity, the signal received by Bob at the N(k)th frequency is

[0149]

[0150] Then the vector formed by the received signals on all N(k) frequencies is

[0151] Y(t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =α(k) T S(t,k)+n(k) (2)

[0152] (2) In the formula, α(k)=[α 1 (k), α 2 (k), ..., α N(k) (k)] T , α n (k)∈α n , 1≤n≤N(k),

[0153] α(k) is the channel state vector corresponding to the N(k) frequency points between Alice and Bob in the kth time period (according to the channel reciprocity principle, the channel states of the sender and receiver are the same at the same time); n(k) = [n 1 (k), n 2 (k), ..., n N(k) (k)] T is the additive channel noise vector of N(k) frequency points, each noise element is independent and identically distributed and obeys Gaussian distribution

[0154] diag(·) represents a diagonal matrix, and s(t, k) is the information baseband waveform sent at the kth moment.

[0155] If the channel state vector between Alice and Bob is represented as α B (k), for α B (k) is a parallel vector and an orthogonal vector, let the channel state vector α B The normalized vector of (k) is α || (k), which satisfies α B (k) T α || =C, C is a constant; let α B The space spanned by the orthogonal vectors of (k) is For any element α ⊥ (k), satisfying α B (k) T α ⊥ (k) = 0. To achieve physical layer secure communication, it is necessary to ensure that the signal sent by Alice reaches Bob with good signal quality, while the signal reaching Eve with poor signal quality. Therefore, the physical layer encryption process H(k) for the kth period is designed, which is composed of α B The parallel vector and orthogonal vector of (k) together constitute

[0156]

[0157] Where (3) They are all matrices composed of N(k) vectors; And vector The elements of are randomly time-varying. The power of the two parts is and Power distribution meets η P is the power allocation threshold, and its value has a great impact on the security of physical layer information, which will be analyzed in depth later. After adding the encryption process, the form of the received signal in (2) becomes

[0158] Y(t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =α(k) T H(k)s(t,k)+n(k) (4)

[0159] For Bob, the received signal is consistent with the channel state α B (k) T The orthogonal part is eliminated and the received signal is

[0160] Y B (t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =C T s(t,k)+n(k) (5)

[0161] (4) is a constant vector.

[0162] The effect of the above technical solution is that the communication receiver disperses the data to be transmitted to the randomly selected communication channel frequency points. This decentralized transmission method makes it difficult for attackers to centrally intercept the complete data information, which increases the difficulty of data theft or tampering. In the data transmission process, the physical layer is encrypted to further enhance the confidentiality of the data. Even if the encrypted signal is intercepted, it is difficult for an unauthorized third party to decrypt and restore the original data. Using multiple frequency points for data transmission, even if a certain frequency point is interfered or blocked, the data on other frequency points can still be transmitted normally, thereby improving the anti-interference ability of the communication system. Each noise element is independent and identically distributed and obeys the Gaussian distribution. This noise characteristic helps to conceal the true signal characteristics, making it more difficult for attackers to extract useful signal information from the noise. In the representation of the received signal vector, the channel state vector corresponding to each frequency point is taken into account, which helps the communication receiver to perform corresponding processing according to the channel state when receiving the signal, such as channel equalization, error correction, etc., thereby improving the reliability of data transmission. s(t, k) is the information baseband waveform sent at the kth moment. By sending the baseband waveform instead of directly sending the data bit stream, the channel bandwidth can be used more effectively and the bit error rate can be reduced. The communication system can dynamically select the communication frequency according to the current channel status to adapt to different communication environments and requirements.

[0163] In summary, this technical solution effectively improves the security of communication, anti-interference capability and reliability of data transmission through data dispersion, random frequency selection, encrypted transmission and consideration of channel state vector. These technical effects are of great significance for data security transmission in scenarios such as vehicle-to-vehicle communication and wireless communication.

[0164] The embodiment of the present invention proposes a secure communication system based on random frequency, such as Figure 2 As shown, the random frequency-based secure communication system includes:

[0165] A channel screening module, configured to provide a plurality of frequency channels to a communication receiving party according to a preset frequency range of the current environment, and the communication receiving party randomly selects a channel for communication from the plurality of frequency channels to communicate with the communication initiator during the communication process;

[0166] The encrypted transmission module is used for dispersing the data to be transmitted onto the frequency points of the randomly selected communication channel and encrypting the data when the communication initiator transmits data information to the communication receiver.

[0167] The working principle of the above technical solution is as follows: the communication initiator first detects the electromagnetic spectrum status of the current environment, and determines an available frequency range based on preset safety and compliance standards. Within the determined frequency range, the communication initiator provides multiple alternative frequency channels to the communication receiver. During the communication process, the communication receiver randomly selects one of these alternative channels for the current communication session at regular intervals (or according to a preset strategy). This randomness makes the communication frequency difficult to predict, thereby reducing the risk of malicious monitoring or interference.

[0168] When the communication receiver transmits data information to the communication initiator, it first divides the data to be transmitted and randomly disperses the divided data fragments to multiple frequency points of the selected communication channel. This dispersion method increases the difficulty of data eavesdropping, because the attacker needs to capture data fragments on multiple frequency points at the same time and reassemble them to restore the original information. While the data is dispersed, the communication receiver encrypts each data fragment. The use of high-intensity encryption algorithms (such as AES, RSA, etc.) can ensure that even if the data fragments are intercepted, the attacker cannot easily obtain the useful information in them.

[0169] The effects of the above technical solutions are as follows: the random frequency selection mechanism makes the communication frequency difficult to predict, effectively reducing the risk of malicious monitoring or interference. The data decentralized encrypted transmission method increases the difficulty of data eavesdropping. Even if a data fragment is intercepted, it is difficult to restore the original information. The randomly selected communication channel can effectively avoid the multipath effect, Doppler frequency shift and other problems in fixed frequency communication, and improve the stability of communication. The data decentralized transmission method reduces the impact of data loss or errors on the overall communication quality and enhances the anti-interference ability of communication. The method can dynamically adjust the communication frequency range according to the electromagnetic spectrum conditions of the current environment to adapt to the communication needs in different scenarios. The timing or random selection mechanism based on preset strategies allows the communicating parties to flexibly adjust the communication strategy according to actual conditions.

[0170] In summary, this technical solution significantly improves the security and anti-interference capability of vehicle-to-vehicle communication through random frequency selection and data decentralized encrypted transmission, providing strong support for real-time and reliable communication between vehicles in intelligent transportation systems.

[0171] In one embodiment of the present invention, the channel screening module includes:

[0172] The candidate frequency set determination module is used to determine the N candidate frequency sets that the current communication initiator can select. Each set includes M frequencies, and the N×M frequencies are different from each other. Meanwhile, the frequencies of each frequency set are in the same frequency band, wherein the N frequency sets are as follows:

[0173] F1 ={f 1，1 , f 1，2 , ..., f 1，M}F 2 ={f 2，1 , f 2,2 , ..., f 2，M},......,F N ={f N，1 , f N，2 , ..., f N，M}

[0174] A first channel estimation module, configured to, before a communication link is established between a communication initiator and a communication receiver, cause the communication initiator to perform channel estimation on N×M frequencies and provide the N×M frequencies to the communication receiver;

[0175] A second channel estimation module is used for, after receiving N×M frequencies, the communication receiving party to perform channel estimation on the received N×M frequencies to obtain channel states of the N×M frequencies;

[0176] A signal demodulation module, used to demodulate the frequency diversity signal after the communication receiving party completes the channel estimation;

[0177] The set representation module is used to represent the nth channel state set as α n ={α n，1 , α n，2 , ..., α n，M};

[0178] The communication execution module is used for, after the communication link between the communication initiator and the communication receiver is established, at each preset time interval, the communication receiver selects a frequency from the candidate frequency set. Randomly select multiple frequency points for communication;

[0179] Among them, the set F consisting of N(k) frequencies of the kth communication between the communication receiving party and the communication initiator is N(k) for:

[0180] F N(k) ={f 1 (k), f 2 (k), ..., f N(k) (k)|f i (k)∈F i , i = 1, 2, ..., N(k)}

[0181] k represents the kth communication; f i (k) indicates that in the kth communication, from the frequency set F i The frequency of random selection in .

[0182] The working principle of the above technical solution is:

[0183] Let N frequency sets F 1 ={f 1，1 , f 1,2 , ..., f 1，M}、F 2 ={f 2，1 , f 2，2 , ..., f 2，M},......,F N ={f N，1 , f N，2 , ..., f N，M} is the candidate frequency set for communication Each set contains M frequencies, and the N*M frequencies are different. Usually, the frequencies of each frequency set are in the same frequency band. Before the communication link is established, the communication initiator Bob first initiates the channel estimation training process for N◇M frequencies. After receiving it, Alice performs channel estimation on the corresponding frequencies and obtains the channel states of N◇M frequencies. The nth channel state set is represented as α n ={α n，1 , α n，2 , ..., α n，M}, where each channel state element A m，n is the amplitude parameter of the channel state, is the phase parameter of the channel state. In formal communication, Alice selects a frequency from the frequency set F at every time Δt. 1 To F N Several frequencies are randomly selected for communication, and each frequency set selects at most one frequency. From time t+(k-1)·Δt to t+k·Δt, the set of N(k) frequencies (2≤N(k)≤N) selected is

[0184] F N(k) ={f 1 (k), f 2 (k), ..., f N(k) (k)|f i (k)∈F i ,i=1,2,...,N(k)} (1)

[0185] The information is then modulated on these frequencies for communication. The difference here from frequency hopping communication is that the selected frequency is randomly selected by the signal sender, and the receiver Bob does not have a pre-agreed frequency hopping pattern to refer to. The signal frequency detection and subsequent signal demodulation process are achieved by blind signal detection technology.

[0186] The effect of the above technical solution is: by determining N candidate frequency sets, each set contains M different frequencies, and the N×M frequencies are different. This frequency diversity makes communication difficult to predict and intercept. Attackers need to monitor multiple frequencies at the same time to try to intercept the communication content, which greatly increases the difficulty of the attack. During the communication process, the communication receiver randomly selects multiple frequency points from the candidate frequency set for communication within each preset time interval. This randomness makes the communication frequency constantly changing, further reducing the risk of malicious monitoring.

[0187] The communication initiator and the communication receiver both perform channel estimation before and after the communication link is established to obtain the channel status of N×M frequencies. This helps both parties understand the transmission quality of each frequency, so that when selecting the communication frequency, they can avoid the frequency band with greater interference and improve the anti-interference ability of communication. By demodulating the frequency diversity signal, the signal redundancy on multiple frequencies can be used to improve the reliability of communication. Even if the signal on a certain frequency is interfered or lost, the signals on other frequencies can still be used to restore the original information.

[0188] The communication receiver can dynamically select the communication frequency from the candidate frequency set according to the current channel status and communication needs. This flexibility enables the communication system to adapt to the communication needs in different environments and scenarios, and improve the adaptability and efficiency of communication. By updating the communication frequency at preset time intervals, it can ensure the regular update of the communication frequency, further reducing the risk of long-term monitoring. At the same time, this regular update also enables the communication system to cope with rapidly changing communication environments. Through the channel estimation and frequency selection mechanism, the communicating parties can choose the frequency with better channel status for communication, thereby ensuring the quality of communication. This helps to reduce the bit error rate and packet loss rate during the communication process, and improve the reliability and stability of communication.

[0189] In summary, this technical solution effectively improves the security, anti-interference ability and flexibility of communication and ensures the communication quality by providing multiple candidate frequency sets, performing channel estimation, randomly selecting communication frequencies and demodulating frequency diversity signals. These technical effects are particularly important for vehicle-to-vehicle communication, especially for communication scenarios when vehicles are driving in opposite directions.

[0190] In one embodiment of the present invention, the second channel estimation module includes:

[0191] The stochastic resonance phenomenon detection module is used for the communication receiver to detect the received N×M frequencies by using the stochastic resonance method. 1 To F N Conduct detection to determine whether there is stochastic resonance phenomenon;

[0192] The communication frequency estimation module is used to estimate the frequency set F when stochastic resonance occurs. 1To F N Perform frequency estimation in sequence to obtain the frequency set F 1 To F N The corresponding communication frequency, wherein the frequency set F 1 The frequency vector of the communication frequency corresponding to FN is as follows:

[0193]

[0194] in, f 1 (k) is the estimated value.

[0195] The working principle of the above technical solution is: since the transmitting end randomly selects the frequency point, the receiving end first needs to detect the current communication frequency. The stochastic resonance method has a good effect in weak signal detection, so the receiving end uses this method to first estimate the N(k) communication frequencies in formula (5). 1 To F N When testing, if there is a communication signal in the corresponding frequency band, random resonance will occur, causing the noise energy to be gradually converted into signal energy. As a result, obvious signal spectrum lines appear in the amplitude-frequency diagram on the corresponding frequency band. According to the existing theory, when the nth frequency is concentrated for signal detection, the bistable stochastic resonance system process is described as

[0196]

[0197] where y n (t, n) is a sinusoidal driving signal, corresponding to the communication signal to be detected; n n (t, n) is random noise, corresponding to additive channel noise; x n (t, k) is the output of the stochastic resonance system. In fact, the output of the first stochastic resonance system can be used as the input of the second stochastic resonance system. Through the cascade of multiple stochastic resonance systems, the energy of the signal to be detected can be continuously enhanced. For the nth frequency set in the k-time period, according to the first-order stochastic resonance process of formula (6), the multi-order stochastic resonance process containing the target frequency signal and the non-target frequency signal in the signal to be detected is defined as:

[0198]

[0199] RS (s) (·) is a function representing an s-order random process; n n (t, k) represents the channel noise of the nth frequency in the kth time period; is the output of the s-order random process. After performing random resonance detection on all frequency bands in sequence, the current communication frequency can be obtained through accurate frequency estimation. Since the estimated frequency has deviations, let the estimated frequency vector be

[0200]

[0201] In formula (8), f 1 (k) is the estimated value.

[0202] The effect of the above technical solution is: by using the stochastic resonance method to detect the frequency sets F1 to FN, it is possible to more accurately determine which frequency sets have stochastic resonance. Stochastic resonance is a phenomenon in which, in a nonlinear system, when the system is acted upon by noise and periodic signals, the system's response to periodic signals is enhanced. By using this characteristic, useful signals and noise interference in the channel can be more effectively identified, thereby improving the accuracy of channel detection.

[0203] When random resonance occurs, frequency estimation is performed on frequency sets F1 to FN in sequence to obtain the communication frequency corresponding to each frequency set. This process not only helps to understand the channel status of each frequency, but also can screen out frequencies that are more suitable for communication based on channel quality. By optimizing frequency selection, the bit error rate and packet loss rate during communication can be reduced, and the reliability and stability of communication can be improved.

[0204] By estimating the communication frequencies of frequency sets F1 to FN, the frequency vectors corresponding to each frequency set are obtained. These frequency vectors not only reflect the channel status of each frequency, but also provide important reference information for the subsequent communication process. Based on these frequency vectors, the communicating parties can formulate more reasonable communication strategies, such as dynamically adjusting the communication frequency, optimizing the modulation and coding method, etc., to further improve the communication performance.

[0205] In actual communication environments, channel status may change due to a variety of factors. By performing channel estimation and frequency detection periodically or as needed, the communication receiver can promptly understand changes in channel status and take appropriate measures to adjust. This dynamic adaptability enables the communication system to better cope with complex and changing communication environments and ensure the continuity and stability of communication.

[0206] In summary, this technical solution not only improves the accuracy of channel detection and the optimization of frequency selection by using the stochastic resonance method for channel estimation and frequency detection, but also further improves the communication performance and system adaptability. These technical effects are of great significance for improving the reliability, stability and security of inter-vehicle communication.

[0207] In one embodiment of the present invention, the signal demodulation module includes:

[0208] Frequency vector retrieval module, used to retrieve the frequency set F 1 To F NA frequency vector corresponding to the communication frequency;

[0209] A set retrieving module, used to retrieve a set consisting of N(k) frequencies for the communication receiving party to communicate with the communication initiator;

[0210] The frequency difference acquisition module is used to use the frequency set F 1 To F N The frequency vector of the corresponding communication frequency and the set consisting of the N(k) frequencies obtain the frequency set F 1 To F N The frequency difference between the frequency vector of the corresponding communication frequency and the set of N(k) frequencies; wherein the frequency difference is in the following form:

[0211]

[0212] The demodulated signal is obtained by using the frequency difference, wherein the demodulated signal is as follows:

[0213]

[0214] Where c represents the attenuation constant after signal transmission; is the additive noise after demodulation; when the frequency estimation is accurate enough, ΔF N(k) The elements of are close to 0, and a more accurate signal demodulation result can be obtained. At this time, the demodulated signal can be simplified to:

[0215]

[0216] The working principle of the above technical solution is: after the receiving end obtains the frequency estimation value of the signal in each frequency band, it combines the signals of each frequency point with equal gain, thereby realizing the signal demodulation process. If the frequency difference between the frequency estimation value shown in formula (8) and the standard frequency shown in formula (1) is

[0217]

[0218] The final demodulated signal is

[0219]

[0220] Where c is the constant of signal attenuation after transmission; is the additive noise after demodulation. When the frequency estimation is accurate enough, ΔF N(k) The elements of are close to 0, and a more accurate signal demodulation result can be obtained. At this time, formula (10) can be simplified to

[0221]

[0222] The effect of the above technical solution is: by calling the frequency vector of the communication frequency corresponding to the frequency set F1 to FN, and comparing it with the set consisting of N(k) frequencies used in the current communication, the frequency difference is calculated. This step uses accurate frequency vector information to ensure the accuracy of the frequency difference. The accurate calculation of the frequency difference is the basis for the accuracy of the subsequent demodulation signal. When the frequency estimate is accurate enough, the elements in the frequency difference vector approach 0, which means that the frequency offset in the demodulation process is effectively suppressed, thereby reducing the demodulation error caused by the frequency offset. This makes the demodulated signal closer to the original signal and improves the demodulation accuracy. In the demodulation process, the attenuation constant c after signal transmission and the additive noise after demodulation are considered. This processing method makes the demodulation algorithm more comprehensive and practical, and can cope with signal attenuation and noise interference in actual communication environments, and enhance the stability of the demodulation signal. Since the channel state changes with time and environmental changes, the demodulation algorithm needs to be able to adapt to different channel conditions. By using frequency vectors and frequency differences for demodulation, the algorithm can more flexibly respond to channel changes and ensure that a stable demodulation signal can be obtained under different channel conditions.

[0223] Through frequency diversity and dynamic frequency selection, the communication system can make more effective use of limited frequency resources. In the demodulation process, the use of accurate frequency vectors and frequency differences for demodulation helps to reduce the waste and interference of frequency resources and improve the overall performance of the communication system. As one of the key links in the communication process, the accuracy and stability of demodulation directly affect the reliability of the communication system. The above-mentioned demodulation technical solution enhances the reliability of the communication system by improving the demodulation accuracy and stability, and ensures the accurate transmission and reception of communication data. When the frequency estimation is accurate enough, the demodulation algorithm can be simplified to a form that only considers signal attenuation and additive noise. This simplification not only reduces the complexity of the algorithm, but also reduces the amount of calculation and improves the demodulation efficiency.

[0224] In summary, this technical solution improves the demodulation accuracy, enhances the stability of the demodulated signal, improves the overall performance of the communication system, and simplifies the demodulation algorithm under certain conditions by accurately calculating the frequency difference, considering signal attenuation and noise, optimizing the use of frequency resources, and simplifying the demodulation process (under certain conditions). These technical effects are of great significance for improving the reliability and performance of systems such as inter-vehicle communication and wireless communication.

[0225] In one embodiment of the invention, the encrypted transmission module comprises:

[0226] The vector acquisition module is used when the communication initiator transmits data information to the communication receiver. The vector formed by the received signal of the communication initiator at all N(k) frequency points is as follows:

[0227] Y(t, k) = [y 1(t,k),y 2 (t, k), ..., y N(k) (t, k)] T =α(k) T s(t,k)+n(k)

[0228] Where α(k)=[α 1 (k), α 2 (k), ..., α N(k) (k)] T , α n (k)∈α n , 1≤n≤N(k), α(k) is the channel state vector corresponding to each frequency point between the communication receiving party and the communication sending party in the kth time period; n(k)=[n 1 (k), n 2 (k), ..., n N(k) (k)] T The encrypted channel noise is N(k) frequency points. Each noise element is independent and identically distributed and follows a Gaussian distribution. diag(·) represents a diagonal matrix, s(t, k) is the information baseband waveform sent at the kth moment;

[0229] The encryption processing module is used to perform encryption processing on the physical layer of the kth time period during the data transmission between the communication receiving party and the communication sending party, and in the encryption process, the form of the received signal is changed into:

[0230] Y B (t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =C T s(t,k)+n(k)

[0231] in, is a constant vector.

[0232] The working principle of the above technical solution is: in the kth time period, for the frequency randomly selected in the set of formula (1), when Alice sends the signal using frequency diversity, the signal received by Bob at the N(k)th frequency is

[0233]

[0234] Then the vector formed by the received signals on all N(k) frequencies is

[0235] Y(t, k) = [y 1 (t,k),y 2(t, k), ..., y N(k) (t, k)] T =α(k) T S(t,k)+n(k) (2)

[0236] (2) In the formula, α(k)=[α 1 (k), α 2 (k), ..., α N(k) (k)] T , α n (k)∈α n , 1≤n≤N(k),

[0237] α(k) is the channel state vector corresponding to the N(k) frequency points between Alice and Bob in the kth time period (according to the channel reciprocity principle, the channel states of the sender and receiver are the same at the same time); n(k) = [n 1 (k), n 2 (k), ..., n N(k) (k)] T is the additive channel noise vector of N(k) frequency points, each noise element is independent and identically distributed and obeys Gaussian distribution

[0238] diag(·) represents a diagonal matrix, and s(t, k) is the information baseband waveform sent at the kth moment.

[0239] If the channel state vector between Alice and Bob is represented as α B (k), for α B (k) is a parallel vector and an orthogonal vector, let the channel state vector α B The normalized vector of (k) is α || (k), which satisfies α B (k) T α || =c, C is a constant; let α B The space spanned by the orthogonal vectors of (k) is For any element α ⊥ (k), satisfying α B (k) T α ⊥ (k) = 0. To achieve physical layer secure communication, it is necessary to ensure that the signal sent by Alice reaches Bob with good signal quality, while the signal reaching Eve with poor signal quality. Therefore, the physical layer encryption process H(k) for the kth period is designed, which is composed of α B The parallel vector and orthogonal vector of (k) together constitute

[0240]

[0241] Where (3) They are all matrices composed of N(k) vectors; And vector The elements of are randomly time-varying. The power of the two parts is and Power distribution meets η P is the power allocation threshold, and its value has a great impact on the security of physical layer information, which will be analyzed in depth later. After adding the encryption process, the form of the received signal in (2) becomes

[0242] Y(t, k) = [y 1 (t,k),y 2 (t, k), ..., y N(k) (t, k)] T =α(k) T H(k)S(t,k)+n(k) (4)

[0243] For Bob, the received signal is consistent with the channel state α B (k) T The orthogonal part is eliminated and the received signal is

[0244] Y B (t, k) = [y 1 (t,k),y 2 (t, k), ..., y N (k)(t, k)] T =C T S(t,k)+n(k) (5)

[0245] (4) is a constant vector.

[0246] The effect of the above technical solution is that the communication receiver disperses the data to be transmitted to the randomly selected communication channel frequency points. This decentralized transmission method makes it difficult for attackers to centrally intercept the complete data information, which increases the difficulty of data theft or tampering. In the data transmission process, the physical layer is encrypted to further enhance the confidentiality of the data. Even if the encrypted signal is intercepted, it is difficult for an unauthorized third party to decrypt and restore the original data. Using multiple frequency points for data transmission, even if a certain frequency point is interfered or blocked, the data on other frequency points can still be transmitted normally, thereby improving the anti-interference ability of the communication system. Each noise element is independent and identically distributed and obeys the Gaussian distribution. This noise characteristic helps to conceal the true signal characteristics, making it more difficult for attackers to extract useful signal information from the noise. In the representation of the received signal vector, the channel state vector corresponding to each frequency point is taken into account, which helps the communication receiver to perform corresponding processing according to the channel state when receiving the signal, such as channel equalization, error correction, etc., thereby improving the reliability of data transmission. s(t, k) is the information baseband waveform sent at the kth moment. By sending the baseband waveform instead of directly sending the data bit stream, the channel bandwidth can be used more effectively and the bit error rate can be reduced. The communication system can dynamically select the communication frequency according to the current channel status to adapt to different communication environments and requirements.

[0247] In summary, this technical solution effectively improves the security of communication, anti-interference capability and reliability of data transmission through data dispersion, random frequency selection, encrypted transmission and consideration of channel state vector. These technical effects are of great significance for data security transmission in scenarios such as vehicle-to-vehicle communication and wireless communication.

[0248] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A secure communication method based on random frequency, characterized in that: The random frequency-based secure communication method comprises: According to the preset frequency range of the current environment, the communication initiator provides a plurality of frequency channels to the communication receiver, and the communication receiver periodically randomly selects a channel for communication from the plurality of frequency channels during the communication process to communicate with the communication initiator; When the communication initiator transmits data information to the communication receiver, the data to be transmitted is dispersed to the frequency points of the randomly selected communication channel and transmitted in encrypted form.

2. The random frequency-based secure communication method according to claim 1, characterized in that: According to a preset frequency range of the current environment, the communication initiator provides a plurality of frequency channels to the communication receiver, and the communication receiver periodically randomly selects a channel for communication from the plurality of frequency channels during the communication process to communicate with the communication initiator, including: Determine N candidate frequency sets that can be selected by the current communication initiator, wherein the N frequency sets are as follows: F1={f 1，1 ,f 1，2 ,...,f 1，M } F2={f 2，1 ,f 2，2 ,...,f 2，M }、......、F N ={f N，1 ,f N，2 ,...,f N，M } Before a communication link is established between a communication initiator and a communication receiver, the communication initiator performs channel estimation on N×M frequencies and provides the N×M frequencies to the communication receiver; After receiving N×M frequencies, the communication receiving party performs channel estimation on the received N×M frequencies to obtain the channel states of the N×M frequencies; After the communication receiving party completes the channel estimation, the frequency diversity signal is demodulated; Denote the nth channel state set as α n ={α n，1 , α n，2 , ..., α n，M }; After the communication link between the communication initiator and the communication receiver is established, the communication receiver randomly selects multiple frequency points from the candidate frequency set for communication at each preset time interval; Among them, the set F consisting of N(k) frequencies of the kth communication between the communication receiving party and the communication initiator is N(k) for: F N(k) ={f1(k),f2(k),...,f N(k) (k)|f i (k)∈F i ,i=1,2,...,N(k)} k represents the kth communication; f i (k) indicates that in the kth communication, from the frequency set F i The frequency of random selection in .

3. The random frequency-based secure communication method according to claim 2, characterized in that: After the communication receiving party receives the N×M frequencies, the communication receiving party performs channel estimation on the received N×M frequencies to obtain the channel states of the N×M frequencies, including: After receiving the N×M frequencies, the communication receiver uses the random resonance method to reconstruct the frequency set F1 to F N Conduct detection to determine whether there is stochastic resonance phenomenon; When stochastic resonance occurs, the frequency set F1 to F N Perform frequency estimation in sequence to obtain frequency sets F1 to F N The corresponding communication frequencies, wherein the frequency set F1 to F N The frequency vector of the corresponding communication frequency is as follows: in, is the estimated value of f1(k).

4. The random frequency-based secure communication method according to claim 2, characterized in that: After the communication receiving party completes the channel estimation, the frequency diversity signal is demodulated, including: Retrieve frequency set F1 to F N A frequency vector corresponding to the communication frequency; Retrieving a set of N(k) frequencies for communication between a communication receiving party and the communication initiator; Using frequency set F1 to F N The frequency vector of the corresponding communication frequency and the set consisting of the N(k) frequencies obtain the frequency set F1 to F N The frequency difference between the frequency vector of the corresponding communication frequency and the set of N(k) frequencies; wherein the frequency difference is in the following form: The demodulated signal is obtained by using the frequency difference, wherein the demodulated signal is as follows: Where c represents the attenuation constant after signal transmission; is the additive noise after demodulation; when the frequency estimation is accurate enough, ΔF N(k) The elements of are close to 0, and a more accurate signal demodulation result can be obtained. At this time, the demodulated signal can be simplified to:

5. The random frequency-based secure communication method according to claim 1, characterized in that: When the communication initiator transmits data information to the communication receiver, the data to be transmitted is dispersed to the frequency points of the randomly selected communication channel and encrypted for transmission, including: When the communication initiator transmits data information to the communication receiver, the vector formed by the received signal of the communication initiator at all N(k) frequency points is as follows: Y(t,k)=[y1(t,k),y2(t,k),...,y N(k) (t,k)] T =α(k) T s(t,k)+n(k) Among them, α(k)=[α1(k), α2(k),...,α N(k) (k)] T , α n (k)∈α n , 1≤n≤N(k), α(k) is the channel state vector corresponding to each frequency point between the communication receiver and the communication sender in the kth time period; n(k)=[n1(k), n2(k), ..., n N(k) (k)] T The encrypted channel noise is N(k) frequency points. Each noise element is independent and identically distributed and follows a Gaussian distribution. diag(·) represents a diagonal matrix, s(t, k) is the information baseband waveform sent at the kth moment; During the data transmission between the communication receiving party and the communication sending party, the physical layer of the kth time period is encrypted, and the form of the received signal is changed into: Y B (t,k)=[y1(t,k),y2(t,k),...,y N(k) (t,k)] T =C T S(t,k)+n(k) in, is a constant vector.

6. A secure communication system based on random frequency, characterized in that: The random frequency based secure communication system comprises: A channel screening module, configured to provide a plurality of frequency channels to a communication receiving party according to a preset frequency range of the current environment, and the communication receiving party randomly selects a channel for communication from the plurality of frequency channels to communicate with the communication initiator during the communication process; The encrypted transmission module is used for dispersing the data to be transmitted onto the frequency points of the randomly selected communication channel and encrypting the data when the communication initiator transmits data information to the communication receiver.

7. The random frequency based secure communication system according to claim 6, characterized in that: The channel screening module comprises: The candidate frequency set determination module is used to determine the N candidate frequency sets that the current communication initiator can select. The N frequency sets are as follows: F1={f 1，1 ,f 1，2 ,...,f 1，M } F2={f 2，1 ,f 2，2 ,...,f 2，M }、......、F N ={f N，1 ,f N，2 ,...,f N，M } A first channel estimation module, configured to, before a communication link is established between a communication initiator and a communication receiver, cause the communication initiator to perform channel estimation on N×M frequencies and provide the N×M frequencies to the communication receiver; A second channel estimation module is used for, after receiving N×M frequencies, the communication receiving party to perform channel estimation on the received N×M frequencies to obtain channel states of the N×M frequencies; A signal demodulation module, used to demodulate the frequency diversity signal after the communication receiving party completes the channel estimation; The set representation module is used to represent the nth channel state set as α n ={α n，1 , α n，2 , ..., α n，M }; The communication execution module is used for, after the communication link between the communication initiator and the communication receiver is established, at each preset time interval, the communication receiver selects a candidate frequency from the candidate frequency set. Randomly select multiple frequency points for communication; Among them, the set F consisting of N(k) frequencies of the kth communication between the communication receiving party and the communication initiator is N(k) for: F N(k) ={f1(k),f2(k),...,f N(k) (k)|f i (k)∈F i ,i=1,2,...,N(k)} k represents the kth communication; f i (k) indicates that in the kth communication, from the frequency set F i The frequency of random selection in .

8. The random frequency based secure communication system according to claim 7, characterized in that: The second channel estimation module comprises: The stochastic resonance phenomenon detection module is used for the communication receiving party to detect the received N×M frequencies by using the stochastic resonance method. N Conduct detection to determine whether there is stochastic resonance phenomenon; The communication frequency estimation module is used to estimate the frequency set F1 to F when stochastic resonance occurs. N Perform frequency estimation in sequence to obtain frequency sets F1 to F N The corresponding communication frequencies, wherein the frequency set F1 to F N The frequency vector of the corresponding communication frequency is as follows: in, is the estimated value of f1(k).

9. The random frequency based secure communication system according to claim 7, characterized in that: The signal demodulation module comprises: Frequency vector call module, used to call the frequency set F1 to F N A frequency vector corresponding to the communication frequency; A set retrieving module, used to retrieve a set consisting of N(k) frequencies for the communication receiving party to communicate with the communication initiator; A frequency difference acquisition module is used to obtain the frequency difference between the frequency vector of the communication frequency corresponding to the frequency set F1 to FN and the set consisting of the N(k) frequencies by using the frequency vector of the communication frequency corresponding to the frequency set F1 to FN and the set consisting of the N(k) frequencies; wherein the frequency difference is in the following form: The demodulated signal is obtained by using the frequency difference, wherein the demodulated signal is as follows: Where c represents the attenuation constant after signal transmission; is the additive noise after demodulation; when the frequency estimation is accurate enough, ΔF N The elements of (k) are close to 0, and a more accurate signal demodulation result can be obtained. At this time, the demodulated signal can be simplified to:

10. The random frequency based secure communication system according to claim 6, characterized in that: The encryption transmission module comprises: The vector acquisition module is used when the communication initiator transmits data information to the communication receiver. The vector formed by the received signal of the communication initiator at all N(k) frequency points is as follows: Y(t,k)=[y1(t,k),y2(t,k),...,y N(k) (t,k)] T =α(k) T s(t,k)+n(k) Among them, α(k)=[α1(k), α2(k),...,α N(k) (k)] T , α n (k)∈α n , 1≤n≤N(k), α(k) is the channel state vector corresponding to each frequency point between the communication receiver and the communication sender in the kth time period; n(k)=[n1(k), n2(k), ..., n N(k) (k)] T The encrypted channel noise is N(k) frequency points. Each noise element is independent and identically distributed and follows a Gaussian distribution. diag(·) represents a diagonal matrix, s(t, k) is the information baseband waveform sent at the kth moment; The encryption processing module is used to perform encryption processing on the physical layer of the kth time period during the data transmission between the communication receiving party and the communication sending party, and in the encryption process, the form of the received signal is changed into: Y B (t,k)=[y1(t,k),y2(t,k),...,y N(k) (t,k)] T =C T s(t,k)+n(k) in, is a constant vector.

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