Information security transmission method for cooperative interference shielding

Abstract

The invention discloses an information security transmission method for cooperative interference shielding, which comprises the following steps of: 1, mixing a command signal and a cooperative interference signal at a transmitter according to a power allocation weight alpha; 2, the mixed signals are transmitted through a block fading channel and received by a legal receiver, and the mixed signals are converted into baseband mixed signals after down-conversion; step 3, performing analog-to-digital conversion and time-frequency synchronization on the baseband mixed signal at a receiver to obtain a synchronous receiving signal; step 4, performing channel estimation on each L symbols, and reconstructing a self-interference signal according to a channel coefficient obtained by channel estimation; step 5, on the basis of the principle of maximizing the reachable secrecy rate, the value of an elimination factor lambda is taken, and the reconstructed self-interference signal is multiplied by the elimination factor lambda to obtain a corrected reconstructed self-interference signal; and step 6, subtracting the corrected reconstructed self-interference signal from the synchronous receiving signal to obtain a signal after interference cancellation. According to the invention, information security transmission under cooperative interference shielding is effectively realized.

Description

Technical Field

[0001] The present invention belongs to the field of physical layer security of wireless communication, and relates to an information security transmission method with cooperative interference cover. Background Art

[0002] In recent years, with the rapid development and wide application of information technology, the security problem of command and control systems has become increasingly prominent. Due to the openness and broadcast nature of wireless communication, command and control signals are easily eavesdropped by illegal receiving devices, which poses a huge challenge to the security of data transmission. Therefore, how to deal with information leakage and enhance security protection has become a key task in the development of command systems.

[0003] Different from traditional cryptographic technologies that rely on computational complexity, physical layer security technology stems from information theory and focuses on the secrecy ability of the transmission channel. By utilizing the inherent randomness of the wireless propagation channel, even if the eavesdropper does not degrade, legitimate users can achieve secure communication. On this basis, an independent transmitter can add additional random signals to the channel to prevent the eavesdropper from intercepting the source information, and this technology is called cooperative interference. In this case, both the eavesdropper and the legitimate receiver are interfered; the difference is that legitimate users can resolve the required signals through the prior information of cooperative interference.

[0004] Unfortunately, the impact of propagation delay on the system security performance is very significant. In practice, perfect time synchronization is difficult to achieve. The propagation delay between the transmitter and the receiver will cause incomplete cancellation of cooperative interference, reducing the communication performance of the legitimate receiver and thus affecting the system security performance. This paper presents a physical layer security model for aerospace communication based on cooperative interference, and proposes a transceiver joint optimization scheme to reduce the impact of residual interference introduced by propagation delay and channel estimation error on the system security performance: select appropriate power allocation weights at the transmitter, and use cancellation factors at the legitimate receiver to compensate for the reconstructed cooperative interference error. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an information security transmission method with cooperative interference cover, in which the command signal and cooperative interference are transmitted by different antennas and received by the antennas of the legitimate receiver, and then the cooperative interference is cancelled at the legitimate receiver, effectively realizing information security transmission under cooperative interference cover.

[0006] The purpose of the present invention is achieved by the following technical solutions: an information security transmission method with cooperative interference cover, comprising the following steps:

[0007] Step 1: At the transmitter, the command signal and the cooperative jamming signal are converted into continuous wave signals through a digital-to-analog converter, then converted into radio frequency signals after up-conversion, and the command signal and the cooperative jamming signal are mixed with a power distribution weight α;

[0008] Step 2: Both the command signal and the cooperative jamming signal are transmitted through a block fading channel, and the mixed signal is received by the legitimate receiver. After down-conversion, the mixed signal is converted into a baseband mixed signal;

[0009] Step 3: At the receiver, the baseband mixed signal is subjected to analog-to-digital conversion and time-frequency synchronization to obtain a synchronized received signal;

[0010] Step 4: Channel estimation is performed every L symbols, and the self-interference signal is reconstructed according to the channel coefficients obtained from the channel estimation;

[0011] Step 5: Based on the principle of maximizing the achievable secrecy rate, the cancellation factor λ is determined. The reconstructed self-interference signal is multiplied by the cancellation factor λ to obtain a corrected reconstructed self-interference signal;

[0012] Step 6: The mixed received signal is subtracted from the corrected reconstructed self-interference signal to obtain a signal after interference cancellation.

[0013] The beneficial effects of the present invention are as follows: In the present invention, the command signal and the cooperative jamming are transmitted by different antennas and received by the antenna of the legitimate receiver, and then the cooperative jamming is cancelled at the legitimate receiver, effectively realizing information secure transmission under the cover of cooperative jamming. Description of the Drawings

[0014] Figure 1 is a flowchart of the method of the present invention;

[0015] Figure 2 is a model diagram of a space communication system based on cooperative jamming;

[0016] Figure 3 is a secrecy performance diagram of a transmit-receive joint optimization scheme. Detailed Embodiment

[0017] The technical solution of the present invention will be further described in detail below with reference to the drawings, but the protection scope of the present invention is not limited to the following.

[0018] As Figures 1 - 2 shown, an information secure transmission method under the cover of cooperative jamming includes the following steps:

[0019] Step 1: At the transmitter, the command signal and the cooperative jamming signal are converted into continuous wave signals through a digital-to-analog converter, then converted into radio frequency signals after up-conversion, and the command signal and the cooperative jamming signal are mixed with a power distribution weight α;

[0020] At the transmitter, the command signal is modulated to s(t), the coordinated interference signal is j(t), and the command signal and the coordinated interference signal are added according to a set ratio to obtain a mixed signal y(t):

[0021] y(t) = s(t) + j(t) (1)

[0022] Among them, the sum of the powers of the command signal and the coordinated interference signal is P, and it satisfies:

[0023]

[0024] Among them, P s 、P j respectively represent the powers of the command signal and the coordinated interference signal.

[0025] Step 2: Both the command signal and the coordinated interference signal are transmitted through a block fading channel. The mixed signal is received by a legitimate receiver. After downconversion, the mixed signal is converted into a baseband mixed signal;

[0026] The mixed signal undergoes digital-to-analog conversion and radio frequency modulation to transmit the signal

[0027]

[0028] Among them, f t is the carrier frequency of the transmitter;

[0029] The mixed signal is received by a legitimate receiver. After downconversion, it is converted into a baseband signal, and the baseband signal is expressed as:

[0030]

[0031] Among them, f r is the carrier frequency of the legitimate receiver, h s and h j respectively represent the channel coefficients of the command signal and the coordinated interference signal; w(t) is additive white Gaussian noise and follows a zero-mean Gaussian distribution τ s and τ j respectively represent the propagation delays of s(t) and j(t).

[0032] Step 3: At the receiver, the baseband mixed signal is subjected to analog-to-digital conversion and time-frequency synchronization to obtain a synchronized received signal;

[0033] Assume that the time-frequency synchronization is perfect. Then, after analog-to-digital conversion and time-frequency synchronization, the synchronized received signal y s (t) is:

[0034] y s (t) = h s s(t - Ds ) + h j j(t - D j ) + w(t) (5)

[0035] where D s = τ s / T and D j = τ j / T are the normalized propagation delays of the command signal and the coordinated interference, respectively.

[0036] Step 4: Perform channel estimation for every L symbols, and reconstruct the self - interference signal according to the channel coefficients obtained from the channel estimation;

[0037] Assume that the channel estimation length is L, and convert the self - interference signal into a vector form j[k]:

[0038] j[k] = [j(0) j(1) … j(kL + L - 1)], k = 0, 1, 2… (6)

[0039] Similarly, convert the synchronized received signal y s (t) into a vector form y[k]:

[0040] y[k] = [y s (0) y s (1) … y s (kL + L - 1)], k = 0, 1, 2… (7)

[0041] The estimated value of the channel coefficient is:

[0042]

[0043] The variance of the channel coefficient error is:

[0044]

[0045] where are the variances of the useful signal, the self - interference signal, and the Gaussian white noise, respectively;

[0046] Reconstruct the self - interference signal according to the estimated channel coefficients

[0047]

[0048] Step 5: Determine the value of the cancellation factor λ based on the principle of maximizing the achievable secrecy rate, and multiply the reconstructed self - interference signal by the cancellation factor λ to obtain the corrected reconstructed self - interference signal;

[0049] Based on the principle of maximizing the achievable secrecy rate, study the value of the cancellation factor λ:

[0050] For a bug, assume that its thermal noise follows a Gaussian distribution with zero mean is the variance of the thermal noise. The signal-to-jamming-noise ratio (SJNR) of the eavesdropping machine is expressed as:

[0051]

[0052] where h se and h je represent the channel coefficients of the command signal and the coordinated jammer to the eavesdropping machine, respectively;

[0053] The SJNR of the legitimate receiver is expressed as:

[0054]

[0055] The achievable secrecy rate is the difference between the achievable rates of the legitimate receiver and the eavesdropping machine, and is expressed as:

[0056]

[0057] To calculate the influence of the cancellation factor on the monotonicity of R s The problem of the cancellation factor weight is mathematically characterized as follows:

[0058]

[0059] where:

[0060]

[0061] In the above formula, represents the total power budget, and p, q, r, s, t are intermediate mathematical variables;

[0062] The optimal solution λ* of the cancellation factor:

[0063]

[0064] The reconstructed self-interference signal is multiplied by the cancellation factor λ * to compensate for the influence of imperfect time-frequency synchronization in channel estimation on interference reconstruction:

[0065]

[0066] Step 6: Subtract the corrected reconstructed self-interference signal from the mixed received signal to obtain the interference-cancelled signal.

[0067] Subtract the corrected reconstructed self-interference signal from the mixed received signal, and then the interference-cancelled signal is obtained.

[0068]

[0069] The signal after interference cancellation is used for signal demodulation processing.

[0070] Next, the transceiver joint optimization scheme proposed in this paper is simulated and analyzed. It is assumed that the command signal node and the cooperative interference node are 100 m and 200 m away from the receiver respectively. According to the free space propagation loss formula, the simulation parameters are shown in Table 1.

[0071] Table 1. Simulation parameter settings of the self-interference transceiver joint suppression algorithm

[0072]

[0073] Appendix Figure 3 The transceiver joint optimization scheme considering propagation delay and channel estimation error is compared with the ideal power allocation scheme without considering non-ideal factors. The simulation results show that when the error is small, as the error increases, the gain of joint optimization is greater. However, when the error is large, the gain brought by joint optimization gradually decreases. The simulation results show that when the propagation delay D j <10°, compared with the traditional power allocation scheme without considering propagation delay and channel estimation error, the transceiver joint optimization scheme has a significant secrecy performance gain and improves the system's secure transmission performance.

[0074] The above are the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in other combinations, modifications, and environments, and can be changed within the scope of the concept described herein through the above teachings or the techniques or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for secure information transmission with coordinated interference protection, characterized in that: The following steps are involved: Step 1: At the transmitter, the command signal and the coordinated interference signal are converted into continuous wave signals through a digital-to-analog converter, and then converted into radio frequency signals after up-conversion, and the command signal and the coordinated interference signal are mixed with a power allocation weight α; Step 2: The mixed signal is transmitted through a block fading channel, received by a legitimate receiver, and converted into a baseband mixed signal after down-conversion; Step 3: The receiver performs analog-to-digital conversion and time-frequency synchronization on the baseband mixed signal to obtain a synchronous received signal; Step 4: Perform channel estimation for every L symbols, and reconstruct the self-interference signal according to the channel coefficients obtained by the channel estimation; Step 5: based on the principle of maximizing the achievable confidentiality rate, the elimination factor λ is selected, and the reconstructed self-interference signal is multiplied by the elimination factor λ to obtain a corrected reconstructed self-interference signal; Step 6: Subtract the corrected reconstructed self-interference signal from the synchronous received signal to obtain a signal after interference cancellation.

2. The information security transmission method of cooperative interference masking according to claim 1 is characterized by: The step 1 comprises: At the transmitter, the command signal is modulated to s(t), and the coordinated interference signal is j(t). The command signal and the coordinated interference signal are added according to the set ratio to obtain the mixed signal y(t): y(t)=s(t)+j(t) (1) Among them, the power sum of the command signal and the coordinated interference signal is P, and it satisfies: Among them, P s , P j Represent the power of command signal and cooperative interference signal respectively.

3. The information security transmission method of cooperative interference masking according to claim 1 is characterized by: The step 2 comprises: The mixed signal is converted into digital and analog signals and then modulated into radio frequency to transmit the signal. where f t is the carrier frequency of the transmitter; The mixed signal is received by a legal receiver and converted to a baseband signal after down-conversion. The baseband signal is expressed as: where f r is the carrier frequency of the legal receiver, h s and h j Represent the channel coefficients of command signal and cooperative interference respectively; w(t) is additive white Gaussian noise and obeys zero-mean Gaussian distribution τ s and τ j denote the propagation delays of s(t) and j(t) respectively.

4. The information security transmission method of cooperative interference masking according to claim 1 is characterized by: The step 3 comprises: Assuming that the time-frequency synchronization is perfect, after analog-to-digital conversion and time-frequency synchronization, the synchronously received signal y s (t) is: y s (t)=h s s(t-D s )+h j j(t-D j )+w(t) (5) Where D s =τ s / T and D j =τ j / T are the normalized propagation delays of the command signal and the cooperative interference, respectively.

5. The information security transmission method of cooperative interference masking according to claim 1 is characterized in that: The step 4 comprises: Assume that the channel estimation length is L, and convert the self-interference signal into a vector form j[k]: j[k]=[j(0) j(1) … j(kL+L-1)],k=0,1,2… (6) Similarly, the synchronous receiving signal y s (t) is converted into vector form y[k]: y[k]=[y s (0) y s (1) … y s (kL+L-1)],k=0,1,2… (7) The estimated value of the channel coefficient is: The variance of the channel coefficient error is: in, are the variances of useful signal, self-interference signal and Gaussian white noise respectively; Reconstruct the self-interference signal based on the estimated channel coefficients 6. The information security transmission method of cooperative interference masking according to claim 1 is characterized by: The step 5 comprises: Based on the principle of maximizing the achievable confidentiality rate, the value of the elimination factor λ is studied: For the eavesdropper, it is assumed that its thermal noise follows a zero-mean Gaussian distribution. is the variance of thermal noise, and the signal to noise ratio of the eavesdropping machine is expressed as: where h se and h je They represent the channel coefficients of command signal and cooperative interference to eavesdropping machine respectively; The signal-to-interference-to-noise ratio of a legitimate receiver is expressed as: The achievable confidentiality rate is the difference between the rates that can be achieved by the legitimate receiver and the eavesdropping machine, expressed as: To calculate the offset factor for R s The impact of monotonicity and the problem of offsetting factor weights can be mathematically represented as follows: in: In the above formula, represents the total power budget, p, q, r, s, t are intermediate mathematical variables; The optimal solution of the offset factor λ*: Reconstruct the self-interference signal multiplied by the cancellation factor λ * To compensate for the impact of imperfect time-frequency synchronization in channel estimation on interference reconstruction:

7. The information security transmission method of cooperative interference masking according to claim 1 is characterized by: The step 6 comprises: The mixed received signal minus the corrected reconstructed self-interference signal is used to obtain a signal after interference cancellation. The signal after interference cancellation is used for signal demodulation processing.

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