OTFS secure transmission method, system and device based on inductance integration and frequency domain power distribution, and medium

Abstract

The invention discloses an OTFS secure transmission method, system and device based on inductance integration and frequency domain power distribution, and a medium. The method comprises the following steps: generating an OTFS transmission frame XDD with signal-guide fusion, and obtaining a sent OTFS signal sRF (t) after OTFS modulation and up-conversion processing; a receiving user receives the OTFS signal sRF (t) and reflects the OTFS signal sRF (t) to generate an echo signal, and a transmitting end performs OTFS receiving and demodulation on the echo signal to obtain a DD domain echo frame # imgabs0 # estimated DD domain channel pulse response; deducing an optimal power distribution scheme of the TF domain under the condition of secure transmission; building a channel physical layer security analysis model; the system, the equipment and the medium are used for implementing the method. Through the OTFS modulation-based communication and inductance integrated system, DD domain channel pulse response estimation is carried out by using echo signals, optimal power distribution is carried out in a frequency domain through channel pulse response, the signal-to-noise ratio of received signals is improved, and the security of information transmission is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and in particular relates to an OTFS secure transmission method, system, device and medium based on synaesthesia integration and frequency domain power allocation. Background Art

[0002] With the continuous development of wireless communication technology, wireless spectrum resources are limited. The next generation of wireless communication systems needs to reuse radar frequency bands to realize communication and perception spectrum sharing to improve spectrum utilization. In high-mobility scenarios (such as high-speed rail and drones), Orthogonal Frequency Division Multiplexing (OFDM) technology destroys the orthogonality of subcarriers due to Doppler shift, resulting in serious inter-subcarrier interference. In order to solve this problem, the Orthogonal Time-Frequency-Space (OTFS) modulation technology is proposed. The OTFS modulation technology performs data modulation in the delayed Doppler domain and expands it over the entire time-frequency domain, so that the symbols in the transmission unit experience a slowly changing sparse channel, overcoming the problems caused by high Doppler shift.

[0003] The literature [Liu Dong. Research on communication-perception integrated power allocation based on OTFS [D]. China University of Mining and Technology, 2023.] proposes to jointly design the communication-perception integrated signal waveform in the Doppler domain-delay domain, and proposes a new ISAC power allocation method, which can serve the main radar purpose and the secondary communication purpose at the same time. However, due to the waveform design and power allocation in the Doppler domain-delay domain, problems such as complex structure and limited communication quality arise.

[0004] The patent application document with publication number CN202110553232 discloses a power allocation method based on the OTFS-NOMA cross-domain transmission system, which solves the power allocation problem of high-speed mobile users and low-speed mobile users during signal transmission by reusing the frequency band of high-speed users through low-speed users. However, due to the simultaneous design of low-speed users and high-speed users, power allocation is relatively complex and inefficient.

[0005] At the same time, the feasibility, signal detection and equalization of the 0TFS system have been studied sufficiently. However, considering the defect that wireless communication signals are easily eavesdropped, there is still a lack of work to achieve secure transmission of 0TFS signals. Summary of the invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide an OTFS secure transmission method, system, device and medium based on synaesthesia integration and frequency domain power allocation. Through a synaesthesia integration system based on OTFS modulation, the echo signal is used to estimate the DD domain channel impulse response, and the optimal power allocation is performed in the frequency domain through the channel impulse response, thereby improving the signal-to-noise ratio of the received signal and thus improving the security of information transmission.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] An OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation comprises the following steps:

[0009] Step 1: The OTFS transmitter generates a signal-guide fused OTFS transmission frame X DD , transmission frame X DD After OTFS modulation and up-conversion processing, the OTFS signal s sent by the transmitting antenna is obtained. RF (t);

[0010] Step 2: The receiving user receives the OTFS signal s sent in step 1 RF (t) and reflects to generate an echo signal. The transmitter performs OTFS reception and demodulation on the echo signal to obtain a DD domain echo frame.

[0011] Step 3: Use the OTFS transmission frame X generated in step 1 DD and the DD domain echo frame obtained in step 2 Estimate the DD domain channel impulse response;

[0012] Step 4: Based on the DD domain channel impulse response estimated in step 3, derive the optimal power allocation scheme in the TF domain under the condition of secure transmission;

[0013] Step 5: Based on the optimal power allocation scheme of the TF domain in step 4, build a channel physical layer security analysis model.

[0014] The specific method of step 1 is:

[0015] The time and frequency axes are sampled to obtain a two-dimensional plane grid in the TF domain, which is defined as Λ=(nT,mΔf), where T and Δf represent the sampling intervals of the time and frequency axes respectively, and the corresponding number of sampling points is N and M, using n=0, 1, ..., N-1 and m=0, 1, ..., M-1 to represent the indexes of the time and frequency domains; similarly, the delay and Doppler axes are sampled to obtain a two-dimensional plane grid in the DD domain, which is defined as Γ=(k / (NT), l / (MΔf)), where k / (NT) and MΔf represent the sampling intervals along the delay and Doppler axes respectively, and l=0, 1, ..., M-1 and k=0, 1, ..., N-1 represent the indexes of the delay and Doppler domains; the total time length occupied by an OTFS data frame in the two-dimensional plane grid in the TF domain is T f =NT, the total bandwidth is B = MΔf, where N and M correspond to the number of OTFS symbols and the number of subcarriers, respectively, T and Δf represent the OTFS symbol period and the subcarrier spacing, respectively, and TΔf = 1 to maintain the orthogonality of the multicarriers;

[0016] At the OTFS transmitter, information symbols are used to transmit information, and pilot symbols are used for subsequent signal estimation; information symbols and pilot symbols are arranged into a two-dimensional matrix And placed on the DD domain two-dimensional plane grid Γ, X is the DD domain transmission modulation symbol matrix; the two-dimensional matrix After quadrature amplitude modulation (QAM), the OTFS transmission frame is obtained

[0017] Send OTFS transmission frame X DD The TF domain transmission modulation symbol matrix is ​​obtained by mapping the Inverse Symplectic FiniteFourier Transform (ISFFT) Transmit modulation symbol matrix The time-frequency grid points corresponding to the N symbols and M subcarriers occupying the two-dimensional plane grid Λ in the TF domain are as follows:

[0018]

[0019] Among them, X TF [n,m]∈X TF represents the transmitted modulation symbol at the nth time domain and mth frequency domain index grid point on the TF domain two-dimensional plane grid Λ;

[0020] Then for X TF [n, m] Apply Heisenberg Transform to obtain the OTFS synaesthesia integrated time domain baseband signal:

[0021]

[0022] Among them, g tx (t) represents the transmitted pulse, T and Δf represent the sampling interval of the time and frequency axes respectively;

[0023] The baseband signal s(t) is modulated by radio frequency to obtain the up-converted radio frequency signal, that is, the OTFS signal s sent by the transmitting antenna. RF (t);

[0024]

[0025] Where, the RF carrier frequency is f c .

[0026] The specific method of step 2 is:

[0027] The echo signal received by the transmitting antenna is After down-conversion processing, the time domain baseband received signal is obtained, namely:

[0028]

[0029] Where, the RF carrier frequency is f c , then Apply Wigner transform to get the received modulation symbol matrix in TF domain

[0030]

[0031] in, represents the received modulation symbol at the nth time domain index and the mth frequency domain index grid point on the two-dimensional plane grid Λ of the TF domain, and the receiving end uses the same rectangular pulse shaping filter, * represents the complex conjugate function, T and Δf represent the sampling intervals of the time and frequency axes respectively;

[0032] After Wigner transformation, the symplectic finite Fourier transform (SFFT) is used to transform De-mapping to obtain DD domain echo frame

[0033] in, represents the echo frame at the kth Doppler domain index and the lth delay domain index grid point on the DD domain two-dimensional plane grid Γ.

[0034] The specific method of step 3 is:

[0035] In the DD domain, the OTFS transmission frame X generated in step 1 DD The DD domain echo frame obtained in step 2 The relationship between and the channel impulse response hDD[k′, l′] is:

[0036]

[0037] Among them, h DD [k′, l′] is the DD domain channel impulse response, which describes the channel gain of the signal at a specific delay l′ and Doppler shift k′. v , l τ represents the maximum Doppler shift and delay, The term is the variance σ 2 Additive white noise;

[0038] Use Least Squares (LS) to estimate the channel:

[0039]

[0040] in, is the conjugate of the transmitted signal frame, |X DD [kk′,ll′]| 2 is the power of the transmitted signal frame;

[0041] The entire process of the transmission frame being reflected by the receiving user and receiving the echo signal at the transmitting end undergoes two round trips. The DD domain sensing channel will experience the influence of double delay spread and double Doppler frequency shift, and the channel complex gain is related to the gain of the transmitting and receiving antennas; that is, the estimated DD domain channel impulse response is:

[0042]

[0043] The specific method of step 4 is:

[0044] The DD domain channel impulse response estimated in step 3 is shown in equation (9). The DD domain channel impulse response is converted into the TF domain channel impulse response through the inverse symplectic finite Fourier transform (ISFFT):

[0045]

[0046] Among them, H TF [n, m] represents the channel gain at each sampling point (n, m) in the TF domain, using H f Represents the channel state in the TF domain, which is an N*M diagonal matrix, and the (nM+m+1)th element is H TF [n, m];

[0047] After the Wigner transform, zero-forcing equalization (ZF equalization) is applied to the OTFS frequency domain signal. The frequency domain signal after zero-forcing equalization (ZF equalization) is:

[0048]

[0049] Among them, Y′ TF is the frequency domain signal after Wigner transformation at the receiving signal end;

[0050] The quality of the received signal is expressed using the received signal-to-noise ratio:

[0051]

[0052] Among them, YD D It is the DD domain signal received by the receiving signal end after OTFS demodulation;

[0053] Power allocation is performed in the TF domain to achieve the purpose of safe transmission. Then:

[0054] Y TF =(E*H f ) -1 *Y′ TF (13)

[0055] Where E is the power allocation matrix, so in the case of frequency domain power allocation, the received signal noise ratio is:

[0056]

[0057] Without knowing the channel information of the eavesdropping user, the goal of securely transmitting the channel information is to maximize the difference in the received signal-to-noise ratio:

[0058] Max(SNR E -SNR X )(15)

[0059] exist Under the total power constraint, the noise expectation value is minimized. At this time, the optimal power allocation scheme in the TF domain calculated using the Lagrange multiplier is:

[0060]

[0061] Among them, H TF [n, m] represents the channel gain at each sampling point (n, m) in the TF domain.

[0062] The specific method of step 5 is:

[0063] The security rate is a key indicator to measure the security performance of the communication system, which is used to reflect the system's ability to resist eavesdropping attacks.

[0064] The safe rate is calculated as follows:

[0065] R s =[C m -C e ] + (17)

[0066] Where [x] + =max(x, 0), C is the channel capacity, which indicates the maximum rate at which the channel can carry information, usually calculated according to Shannon's theorem: Where C is the channel capacity, B is the bandwidth, S is the signal power, N is the noise power, and C m The main channel capacity is the channel capacity of the legitimate user when receiving information, which is obtained by calculating the channel capacity of the main channel. eEavesdropping channel capacity: It is the channel capacity when the eavesdropper receives information, which is obtained by calculating the channel capacity of the eavesdropping channel.

[0067] The present invention also provides an 0TFS secure transmission system based on synaesthesia integration and frequency domain power allocation, comprising:

[0068] OTFS modulation module, used for generating signal-guide fused OTFS transmission frame X at the OTFS transmitter DD , transmission frame X DD After OTFS modulation and up-conversion processing, the OTFS signal s sent by the transmitting antenna is obtained. RF (t);

[0069] OTFS demodulation module, used to receive the user received OTFS signal s RF (t) and reflects to generate an echo signal. The transmitter performs OTFS reception and demodulation on the echo signal to obtain a DD domain echo frame.

[0070] DD domain channel impulse response estimation module for transmitting frame X using OTFS DD and DD domain echo frame Estimate the DD domain channel impulse response;

[0071] The frequency domain power allocation module is used to implement the optimal power allocation scheme in the TF domain under the condition of secure transmission based on the estimated DD domain channel impulse response;

[0072] The channel physical layer security analysis module is used to implement the optimal power allocation solution based on the TF domain and build a channel physical layer security analysis model.

[0073] The present invention also provides an 0TFS secure transmission device based on synaesthesia integration and frequency domain power allocation, comprising:

[0074] Memory: a computer program storing the above-mentioned 0TFS secure transmission method based on synaesthesia integration and frequency domain power allocation, which is a computer-readable device;

[0075] Processor: used to implement the 0TFS secure transmission method based on synaesthesia integration and frequency domain power allocation when executing the computer program.

[0076] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it can implement the 0TFS secure transmission method based on synaesthesia integration and frequency domain power allocation.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] 1. The present invention considers an OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation. This method generates an echo signal while receiving the signal, which is used for DD domain channel impulse response estimation. The receiving user uses the relevant parameters of the channel estimation to perform OTFS demodulation and performs optimal power allocation in the frequency domain, thereby reducing the bit error rate of the receiving user and improving the security of information transmission.

[0079] 2. The present invention builds a channel physical layer security analysis model, and the eavesdropping user steals the signal at the signal receiving end and performs relevant demodulation. According to the simulation results, compared with the legitimate user, the legitimate user's received signal bit error rate is significantly lower than that of the eavesdropping user, and the security rate is stably higher than that of the eavesdropping user. In the comparison between the legitimate user performing frequency domain power allocation and the user not performing frequency domain power allocation, it is shown that the user performing power allocation has a higher security rate and stronger communication security.

[0080] In summary, the present invention adopts an OTFS secure transmission method, system, device and medium based on synaesthesia integration and frequency domain power allocation, uses echo signals to estimate the DD domain channel impulse response, and performs frequency optimal power allocation at the transmitting end, which has the advantages of reducing the bit error rate and improving the safety rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 It is a flow chart of the present invention.

[0082] Figure 2 It is a modulation flow chart of the OTFS signal transmission frame of the present invention.

[0083] Figure 3 It is a distribution diagram of arranging pilot, protection and data symbols in the delay Doppler grid of the OTFS signal transmission frame of the present invention.

[0084] Figure 4 It is a distribution diagram of data and channel estimation symbols of the echo signal in the delay Doppler grid of the present invention.

[0085] Figure 5 This is the process of the present invention for receiving an echo signal generated by a user after receiving an OTFS signal.

[0086] Figure 6 It is a flow chart of demodulating received signals by a legitimate user and an eavesdropping user of the present invention.

[0087] Figure 7 It is a simulation result diagram of the bit error rate (BER) of the received signal of the legitimate user and the eavesdropping user under different signal-to-noise ratios (SNR).

[0088] Figure 8 is the safe rate of legitimate users and eavesdropping users (R s) and the simulation results of the transmitted signal signal-to-noise ratio (SNR). DETAILED DESCRIPTION

[0089] The technical solution adopted by the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0090] The present invention provides an OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation. The method first maps the signal to the delay-Doppler domain (DD domain) through OTFS modulation, combines communication and perception functions, and uses the echo signal to estimate the DD domain channel impulse response. Subsequently, based on the channel impulse response, optimal power allocation is performed at the transmitting end, which effectively improves the signal-to-noise ratio of the received signal, thereby enhancing the security of communication. By further verifying the security of the physical layer, the simulation results show that with the increase of the signal-to-noise ratio (SNR) of the transmitted signal, the secure rate of the legitimate user is always higher than that of the eavesdropping user, which significantly improves the system's anti-eavesdropping ability and secure transmission performance.

[0091] See also Figure 1 , which is a flowchart of an OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation provided by an embodiment of the present invention, wherein the embodiment of the present invention utilizes echo signals for channel estimation and utilizes frequency domain power allocation at the receiving signal end to improve the security of information transmission. It includes at least the following steps:

[0092] OTFS modulation involves processing and transformation in the time-frequency domain (TF domain) and delay-Doppler domain (DD domain).

[0093] Step 1: At the OTFS transmitter, information symbols are generated by the information source. In order to reduce the estimation error, the present invention places two pilots in the signal pilot frame and selects the grid position [k p1 , l p1 ] and [k p2 , l p2 ] put 1, where 0≤k p1 , k p2 ≤N-1,0≤l p1 , l p2 ≤M-1. p1 -l τ ≤l≤l p1 +l τ , k p1 -2k v ≤k≤k p1 +2k v The other positions of are set to 0 as protection symbols. The protection symbols ensure that the received symbols used for channel estimation and data detection will not interfere with each other and are used to estimate the DD domain impulse response of the wireless channel. τ and k vDenotes the taps corresponding to the maximum delay and Doppler values. The information symbols and pilot symbols are arranged into a two-dimensional matrix And placed on the DD domain two-dimensional plane grid Γ, X is the DD domain transmission modulation symbol matrix. Two-dimensional matrix After quadrature amplitude modulation (QAM), the OTFS transmission frame is obtained Distribution diagram Figure 3 The OTFS signal frame is generated by using information symbols and pilot symbols, and the generated flow chart is as follows: Figure 2 First, the OTFS signal frame is transformed from the DD domain to the TF domain through the Inverse Symplectic Finite Fourier Transform (ISFFT) of formula (1) and the Heisenberg Transform of formula (2), and then converted into a transmission signal through the up-conversion transformation of formula (3).

[0094] Step 2: The transmitter sends the OTFS signal and also receives the reflected echo signal. The process of receiving the echo signal is as follows: Figure 5 As shown. For the echo signal received by the transmitting antenna, it is first down-converted by equation (4) to obtain the time domain baseband received signal, and then the Wigner transform equation (5) is applied to obtain the TF domain received modulation symbol matrix, and then the symplectic finite Fourier transform (SFFT) is performed to obtain the DD domain echo frame by equation (6) The received echo frame distribution diagram is as follows: Figure 4 shown.

[0095] Step 3: Transmit frame X based on the OTFS generated in step 1 DD and the DD domain echo frame obtained in step 2 Use formula (7) to build the transmission frame X DD With echo frame and the channel impulse response h DD The relationship between [k′, l′], in actual cases, the DD domain channel impulse response h DD [k', l'] is usually sparse, which means that the channel only exists at a limited number of delays l' and Doppler shifts k'. In this case, the present invention uses the sparsity of the signal to further optimize the estimation process. Using equation (8) in the presence of noise, a more stable channel estimation is obtained.

[0096] At the same time, it should be pointed out that because the transmission frame undergoes two round trips from the receiving user to the transmitting end receiving the echo signal, compared with the one-way propagation from the transmitting end to the receiving user, the DD domain sensing channel will experience double delay spread and double Doppler frequency shift, and the channel complex gain is related to the gain of the transmitting and receiving antennas; that is, the estimated DD domain channel impulse response h[k, l] can be calculated by formula (9).

[0097] Since the present invention places two pilots in the signal pilot frame, the positions are [k p1 , l p1 ] and [k p2 , l p2 The channel estimates calculated by the two pilot signals at ] using equation (8) are and Then the final DD domain channel impulse response combined with equation (9) is:

[0098] Step 4: Based on the DD domain channel impulse response estimated in step 3, derive the optimal power allocation scheme in the TF domain under the condition of secure transmission;

[0099] The DD domain channel impulse response estimated in step 3 is converted into the TF domain channel impulse response through equation (10). TF [n, m] represents the channel gain at each sampling point (n, m) in the TF domain. In order to represent the channel state information of the entire TF grid and facilitate subsequent fast calculations, H is used. f Indicates the channel state of the TF domain. f is an N*M diagonal matrix, the (nM+m+1)th element is H TF [n, m]; Due to the inter-symbol interference (ISI) caused by the channel, after the Wigner transform, the zero-forcing equalization (ZF equalization) is applied to the OTFS frequency domain signal through equation (11). ZF equalization is a classic linear equalization method. The core idea is to completely eliminate the distortion of the signal after passing through the channel through the inverse channel matrix, thereby restoring the original transmitted signal. ZF equalization can completely eliminate the inter-symbol interference introduced by the channel, but it will also amplify the noise. In order to analyze and quantify the impact of noise on the system output, the received signal signal-to-noise ratio represented in equation (12) is used to represent the quality of the received signal.

[0100] In the OTFS scheme with FD-ZF equalizer, all symbols in the DD domain experience almost the same channel fading, so the benefit of power allocation in the DD domain can be ignored. Only power allocation needs to be performed in the TF domain. The optimal power allocation scheme in the TF domain of equation (16) is calculated using equations (13), (14), (15) and the total power constraint, and the optimal power allocation operation is completed at the transmitter. The specific implementation process is as follows: Figure 6 As shown in the figure, the signal received by the receiving user first undergoes time-frequency analysis (Wigner transform), then undergoes zero-forcing equalization (ZF equalization), then recovers the signal through SFFT transform, and then undergoes QAM demodulation before finally being received by the legitimate user.

[0101] Step 5: Based on the optimal power allocation scheme of the TF domain in step 4, build a channel physical layer security analysis model. In a communication system, the eavesdropping channel model usually describes the situation where an unauthorized user (i.e., an eavesdropper) attempts to intercept and decode communication information between legitimate users. In this model, the source (source information) is encoded by the encoder, transmitted to the decoder of the legitimate user through the main channel, and finally received and decoded by the legitimate user. The eavesdropping channel represents an unauthorized path through which the eavesdropper obtains the encoded information and attempts to restore the original information through its decoder.

[0102] The security rate is a key indicator for measuring the security performance of a communication system, and is used to reflect the system's ability to resist eavesdropping attacks. A higher security rate means that it is more difficult for an eavesdropper to successfully decode information, thereby enhancing the security of communications. In areas such as military communications and financial transactions that have extremely high requirements for information security, it is particularly important to ensure a high security rate, which can effectively prevent information leakage and data theft. The calculation method of the security rate is shown in formula (17). In the present invention, the signal bandwidth B is set to 1 MHz, and the channel impulse response of the eavesdropper is set to a random complex number, thereby simulating the security rate performance under different channel conditions.

[0103] So far, the OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation of this embodiment is completed from step 1 to step 5.

[0104] Figure 7 It is a result diagram of the bit error rate (BER) of the received signal under different signal-to-noise ratios (SNR) according to the invention scheme proposed in step 4, the scheme without frequency domain power allocation, and the scheme of eavesdropping users receiving and demodulating the sent information. Assume that the number of sender antennas is 2, the number of legitimate user antennas is 2, and the number of eavesdropping user antennas is 1. The number of OTFS modulation subcarriers N = 16, the number of time slots M = 16, and the maximum delay l τ is 2, the maximum Doppler k pis 2, the maximum speed is 300Km / h. Figure 7 It can be seen that the bit error rate (BER) of the legitimate user receiving information is significantly lower than that of the eavesdropping user, and the bit error rate of the power allocation method proposed in the present invention is lower than the bit error rate of not using the power allocation method.

[0105] Figure 8 The system shows the security rate (R) of the system when the legitimate user and the eavesdropping user receive and demodulate information based on the same transmission signal. s ) and the signal-to-noise ratio (SNR) of the transmitted signal, the signal bandwidth B is set to 1MHz. The simulation results are based on the physical layer security analysis and are mainly used to evaluate the anti-eavesdropping performance of the system. In the present invention, the channel impulse response of the eavesdropping user is set to a random complex number, which simulates the complex channel conditions that the eavesdropper may face in different scenarios. Figure 6 As shown, both the legitimate user and the eavesdropping user perform ZF equalization on the frequency domain signal after Wigner transformation, and then perform symplectic finite Fourier transform and constellation demapping to restore the 0 and 1 bit streams. Figure 8 The simulation results show that as the SNR of the transmitted signal increases, the physical layer security rate of the legitimate user is always higher than that of the eavesdropping user. This means that the legitimate user in the present invention can transmit data securely at a higher rate, while the eavesdropping user, even if it receives the signal, has difficulty in effectively decoding, thereby improving the security transmission performance of the system. In contrast, the channel quality of the eavesdropping user is further reduced. In this case, the decoding performance of the eavesdropping user is worse, but the decoding performance after the power allocation in the present invention is improved to a certain extent, further improving the security of the system.

[0106] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above 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 in the scope of protection of the present invention.

[0107] The present invention also provides an OTFS secure transmission system based on synaesthesia integration and frequency domain power allocation, comprising:

[0108] OTFS modulation module, used to realize the OTFS transmitter in step 1 to generate the OTFS transmission frame X with signal and guide fusion DD , transmission frame X DD After OTFS modulation and up-conversion processing, the OTFS signal s sent by the transmitting antenna is obtained. RF (t);

[0109] The OTFS demodulation module is used to implement the receiving user in step 2 to receive the OTFS signal s sent in step 1RF (t) and reflects to generate an echo signal. The transmitter performs OTFS reception and demodulation on the echo signal to obtain a DD domain echo frame.

[0110] DD domain channel impulse response estimation module, used to implement the OTFS transmission frame X generated in step 1 in step 3 DD and the DD domain echo frame obtained in step 2 Estimate the DD domain channel impulse response;

[0111] A frequency domain power allocation module, used to implement step 4, based on the DD domain channel impulse response estimated in step 3, to derive an optimal power allocation scheme in the TF domain under the condition of secure transmission;

[0112] The channel physical layer security analysis module is used to implement the optimal power allocation solution in the TF domain based on step 4 in step 5 and build a channel physical layer security analysis model.

[0113] The present invention also provides an OTFS secure transmission device based on synaesthesia integration and frequency domain power allocation, comprising:

[0114] Memory: a computer program storing the above-mentioned OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation, which is a computer-readable device;

[0115] Processor: used to implement the OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation when executing the computer program.

[0116] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it can implement the OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation.

Claims

1. An OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation, characterized in that: The following steps are involved: Step 1: The OTFS transmitter generates a signal-guide fused OTFS transmission frame X DD , transmission frame X DD After OTFS modulation and up-conversion processing, the OTFS signal s sent by the transmitting antenna is obtained. RF (t); Step 2: The receiving user receives the OTFS signal s sent in step 1 RF (t) and reflects to generate an echo signal. The transmitter performs OTFS reception and demodulation on the echo signal to obtain a DD domain echo frame. Step 3: Use the OTFS transmission frame X generated in step 1 DD and the DD domain echo frame obtained in step 2 Estimate DD domain channel impulse response; Step 4: Based on the DD domain channel impulse response estimated in step 3, derive the optimal power allocation scheme in the TF domain under the condition of secure transmission; Step 5: Based on the optimal power allocation scheme of the TF domain in step 4, build a channel physical layer security analysis model.

2. The OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation according to claim 1 is characterized in that: The specific method of step 1 is: The time and frequency axes are sampled to obtain a two-dimensional plane grid in the TF domain, which is defined as Λ=(nT,mΔf), where T and Δf represent the sampling intervals of the time and frequency axes respectively, and the corresponding number of sampling points is N and M, using n=0, 1, ..., N-1 and m=0, 1, ..., M-1 to represent the indexes of the time and frequency domains; similarly, the delay and Doppler axes are sampled to obtain a two-dimensional plane grid in the DD domain, which is defined as Γ=(k / (NT), l / (MΔf)), where k / (NT) and MAf represent the sampling intervals along the delay and Doppler axes respectively, and l=0, 1, ..., M-1 and k=0, 1, ..., N-1 represent the indexes of the delay and Doppler domains; the total time length occupied by an OTFS data frame in the two-dimensional plane grid in the TF domain is T f =NT, the total bandwidth is B = MΔf, where N and M correspond to the number of OTFS symbols and the number of subcarriers, respectively, T and Δf represent the OTFS symbol period and the subcarrier spacing, respectively, and TΔf = 1 to maintain the orthogonality of the multicarriers; At the OTFS transmitter, information symbols are used to transmit information, and pilot symbols are used for subsequent signal estimation; information symbols and pilot symbols are arranged into a two-dimensional matrix And placed on the DD domain two-dimensional plane grid Γ, X is the DD domain transmission modulation symbol matrix; the two-dimensional matrix After quadrature amplitude modulation (QAM), the OTFS transmission frame is obtained Send OTFS transmission frame X DD The TF domain transmission modulation symbol matrix is ​​obtained by mapping the Inverse Symplectic Finite Fourier Transform (ISFFT) Transmit modulation symbol matrix The time-frequency grid points corresponding to the N symbols and M subcarriers occupying the two-dimensional plane grid Λ in the TF domain are as follows: Among them, X TF [n,m]∈X TF represents the transmitted modulation symbol at the nth time domain and mth frequency domain index grid point on the TF domain two-dimensional plane grid Λ; Then for X TF [n, m] Apply Heisenberg Transform to obtain the OTFS synaesthesia integrated time domain baseband signal: Among them, g tx (t) represents the transmitted pulse, T and Δf represent the sampling interval of the time and frequency axes respectively; The baseband signal s(t) is modulated by radio frequency to obtain the up-converted radio frequency signal, that is, the OTFS signal s sent by the transmitting antenna. RF (t); Where, the RF carrier frequency is f c .

3. The OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation according to claim 1 is characterized in that: The specific method of step 2 is: The echo signal received by the transmitting antenna is After down-conversion processing, the time domain baseband received signal is obtained, namely: Where, the RF carrier frequency is f c , then Apply Wigner transform to get the received modulation symbol matrix in TF domain in, represents the received modulation symbol at the nth time domain index and the mth frequency domain index grid point on the two-dimensional plane grid Λ of the TF domain, and the receiving end uses the same rectangular pulse shaping filter, * represents the complex conjugate function, T and Δf represent the sampling intervals of the time and frequency axes respectively; After Wigner transformation, the symplectic finite Fourier transform (SFFT) is used to transform De-mapping to obtain DD domain echo frame in, represents the echo frame at the kth Doppler domain index and the lth delay domain index grid point on the DD domain two-dimensional plane grid Γ.

4. The OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation according to claim 1 is characterized in that: The specific method of step 3 is: In the DD domain, the OTFS transmission frame X generated in step 1 DD The DD domain echo frame obtained in step 2 and the channel impulse response h DD The relationship between [k′, l′] is: Among them, h DD [k′, l′] is the DD domain channel impulse response, which describes the channel gain of the signal at a specific delay l′ and Doppler shift k′. v , l τ represents the maximum Doppler shift and delay, The term is the variance σ 2 Additive white noise; Use Least Squares (LS) to estimate the channel: in, is the conjugate of the transmitted signal frame, |X DD [kk′,ll′]| 2 is the power of the transmitted signal frame; The entire process of the transmission frame being reflected by the receiving user and receiving the echo signal at the transmitting end undergoes two round trips. The DD domain sensing channel will experience the influence of double delay spread and double Doppler frequency shift, and the channel complex gain is related to the gain of the transmitting and receiving antennas; that is, the estimated DD domain channel impulse response is:

5. The OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation according to claim 1 is characterized in that: The specific method of step 4 is: The DD domain channel impulse response estimated in step 3 is shown in equation (9). The DD domain channel impulse response is converted into the TF domain channel impulse response through the inverse symplectic finite Fourier transform (ISFFT): Among them, H TF [n, m] represents the channel gain at each sampling point (n, m) in the TF domain, using H f Represents the channel state in the TF domain, which is an N*M diagonal matrix, and the (nM+m+1)th element is H TF [n, m]; After the Wigner transform, zero-forcing equalization (ZF equalization) is applied to the OTFS frequency domain signal. The frequency domain signal after zero-forcing equalization (ZF equalization) is: Among them, Y' TF is the frequency domain signal after Wigner transformation at the receiving signal end; The quality of the received signal is expressed by the received signal-to-noise ratio: Among them, Y DD It is the DD domain signal received by the receiving signal end after OTFS demodulation; Power allocation is performed in the TF domain to achieve the purpose of safe transmission. Then: AND TF (E*H) f ) -1 *AND' TF (13) Where E is the power allocation matrix, so in the case of frequency domain power allocation, the received signal noise ratio is: Without knowing the channel information of the eavesdropping user, the goal of securely transmitting the channel information is to maximize the difference in the received signal-to-noise ratio: Max(SNR E -SNR X ) (15) exist Under the total power constraint, the noise expectation value is minimized. At this time, the optimal power allocation scheme in the TF domain calculated using the Lagrange multiplier is: Among them, H TF [n,m] represents the channel gain at each sampling point (n,m) in the TF domain.

6. The OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation according to claim 1 is characterized in that: The specific method of step 5 is: The security rate is a key indicator to measure the security performance of the communication system, which is used to reflect the system's ability to resist eavesdropping attacks. The safe rate is calculated as follows: R s =[C m -C e ] + (17) Where [x] + =max(x, 0), C is the channel capacity, which indicates the maximum rate at which the channel can carry information, usually calculated according to Shannon's theorem: Where C is the channel capacity, B is the bandwidth, S is the signal power, N is the noise power, and C m The main channel capacity is the channel capacity of the legitimate user when receiving information. It is obtained by calculating the channel capacity of the main channel. e Eavesdropping channel capacity: It is the channel capacity when the eavesdropper receives information, which is obtained by calculating the channel capacity of the eavesdropping channel.

7. An OTFS secure transmission system based on synaesthesia integration and frequency domain power allocation based on the method according to any one of claims 1 to 6, characterized in that: include: O TFS modulation module, used for OTFS transmitter to generate signal-guide fused OTFS transmission frame X DD , transmission frame X DD After OTFS modulation and up-conversion processing, the OTFS signal s sent by the transmitting antenna is obtained. RF (t); OTFS demodulation module, used to receive the user received OTFS signal s RF (t) and reflects to generate an echo signal. The transmitter performs OTFS reception and demodulation on the echo signal to obtain a DD domain echo frame. DD domain channel impulse response estimation module for transmitting frame X using OTFS DD and DD domain echo frame Estimate DD domain channel impulse response; The frequency domain power allocation module is used to implement the optimal power allocation scheme in the TF domain under the condition of secure transmission based on the estimated DD domain channel impulse response; The channel physical layer security analysis module is used to implement the optimal power allocation solution based on the TF domain and build a channel physical layer security analysis model.

8. An OTFS secure transmission device based on synaesthesia integration and frequency domain power allocation, characterized by: include: Memory: a computer program storing the OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation as described in any one of claims 1 to 6, which is a computer-readable device; Processor: used to implement the OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation as described in any one of claims 1 to 6 when executing the computer program.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it can implement an OTFS secure transmission method based on synaesthesia integration and frequency domain power allocation as described in any one of claims 1 to 6.

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