Waveform design and transmission method based on FDA and random code combination

Abstract

The waveform design and transmission method based on FDA and random code combination belong to the physical layer security transmission technical field of wireless communication.The present application solves the problems of the lack of physical layer waveform diversification characteristics and poor physical layer security performance of the existing method.The receiver of the waveform design based on FDA has the diversification of the amplitude and phase of the signals received at different angles, different distances and different times, and on this basis, the dimension of random code is introduced to increase the waveform degree of freedom and enhance the diversification of the waveform.The amplitude and phase of the signals received by the legal receiver are almost not distorted and do not change with time, while the eavesdropping receivers at other positions will receive different signal waveforms with serious amplitude and phase distortion, and cannot obtain useful information.The present application realizes the physical waveform diversification through the combination of FDA and random code, and enhances the physical layer security performance of communication.The method can be applied to the physical layer security transmission technical field of wireless communication.

Description

Technical Field

[0001] This invention belongs to the field of physical layer secure transmission technology in wireless communication, specifically relating to a waveform design and transmission method based on the combination of FDA and random code. Background Technology

[0002] Phased array-based secure communication is a classic physical layer security technology. While it offers a certain level of security, communication security is compromised when the eavesdropping receiver and the target receiver are at the same angle. In recent years, frequency diversity arrays (FDAs) have been introduced into physical layer security. Small frequency offsets between FDA elements can generate beam patterns that are dependent on both distance and angle. However, with increasingly sophisticated eavesdropping techniques, signal security characteristics still have certain shortcomings. While physical layer security methods such as artificial noise have improved security capacity, they lack the diverse waveform characteristics of physical layer communication, resulting in insufficient security capabilities in practical applications and room for improvement in security system design. Therefore, to better combat eavesdroppers, there is an urgent need for communication technologies that meet diverse secure communication requirements.

[0003] In summary, due to the continuous improvement of eavesdroppers' interception capabilities and the lack of diverse physical layer waveform characteristics, it is difficult to guarantee the secure communication requirements of the physical layer using existing signal transmission methods. The physical layer security performance of existing signal transmission methods remains poor. Summary of the Invention

[0004] The purpose of this invention is to address the problems of lack of diverse physical layer waveform features and poor physical layer security performance in existing methods, and to propose a waveform design and transmission method based on the combination of FDA and random code.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] A waveform design and transmission method based on the combination of FDA and random code, the method specifically includes the following steps:

[0007] Step 1: Perform baseband constellation mapping on the bit data (0, 1) to be transmitted to obtain the modulation result after constellation mapping;

[0008] The modulation result is a serial signal with a length of 2. U U is a positive integer, and the i-th complex digital modulation symbol in the serial signal is denoted as S. i i = 1, 2, ..., 2 U ;

[0009] Step 2: Generate a random code sequence, and then standardize the random codes in the random code sequence to obtain the standardized random code sequence {x0, x1, x2, ..., x...}. N-1},x0,x1,x2,...,,x N-1 These are the 0th, 1st, 2nd, ..., N-1th random codes in the standardized random code sequence;

[0010] Step 3: For the i-th complex digital modulation symbol S in the serial signal i Using the standardized random code sequence to test S i By expanding, we get S i The corresponding extended sequence [S] i x0,S i x1,...,S i x N-1 ];

[0011] Step 4: N transmitting antennas are uniformly and linearly arranged to form a linear array antenna structure. Each element in the extended sequence is multiplied by the corresponding baseband weighting factor, and the multiplication result is then converted from digital to analog. The result after digital-to-analog conversion is then transmitted to the channel through the transmitting antenna.

[0012] Step 5: The receiving end receives the signal transmitted in Step 4 from the channel;

[0013] Step 6: The receiving end puts the received signal into N channels, and performs down-conversion processing on the signals of N channels respectively to obtain the down-conversion results of the received signal in each channel;

[0014] Step 7: Perform low-pass filtering on the signal obtained in Step 6 to obtain the low-pass filtered signal y′. m (θ,r,t);

[0015] Step 8: Convert the output signal y′ from step 7... m (θ,r,t) is converted into signal data y″ by an analog-to-digital converter. m Using random codes to pair y″ m Data recovery is performed, the recovered data is summed to obtain signal data y″, and y″ is normalized to obtain signal data Y. i ;

[0016] Step 9: For each complex digital modulation symbol in the serial signal, perform the process from Step 3 to Step 8 until all data signals have been received.

[0017] The signal received by the legitimate receiver is represented as a single serial digital signal. Again Demodulate the signal to recover the 0 and 1 bits of data.

[0018] The beneficial effects of this invention are:

[0019] This invention proposes a waveform design and transmission method based on a combination of FDA (Discretionary Detection and Randomization) and random codes. The receiver based on the FDA waveform design receives signals with diverse amplitude and phase at different angles, distances, and times. Furthermore, the introduction of random codes increases the waveform's degrees of freedom and enhances its diversity. Legitimate receivers receive signals with virtually no amplitude and phase distortion that do not change over time. Conversely, eavesdropping receivers in other locations will receive inconsistent signal waveforms with severely distorted amplitude and phase, making it impossible to obtain useful information. This invention achieves physical waveform diversity through the combination of FDA and random codes, thereby enhancing the physical layer security of communication. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the workflow of the method of the present invention at the transmitting end;

[0021] Figure 2 This is a flowchart of the workflow of the method of the present invention at the receiving end. Detailed Implementation

[0022] The present application will now be described in further detail with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are all within the scope of protection of the present invention.

[0023] Specific Implementation Method 1: Combination Figure 1 and Figure 2 This embodiment describes a waveform design and transmission method based on a combination of FDA and random codes. The method specifically includes the following steps:

[0024] Step 1: Perform baseband constellation mapping on the bit data (0, 1) to be transmitted to obtain the modulation result after constellation mapping;

[0025] This implementation method uses BPSK as an example, but it is compatible with other modulation methods.

[0026] The modulation result is a serial signal with a length of 2. U U is a positive integer, and the i-th complex digital modulation symbol in the serial signal is denoted as S. i i = 1, 2, ..., 2 U ;

[0027] Step 2: Generate a random code sequence, and then standardize the random codes in the random code sequence to obtain the standardized random code sequence {x0, x1, x2, ..., x...}. N-1},x0,x1,x2,...,,x N-1 These are the 0th, 1st, 2nd, ..., N-1th random codes in the standardized random code sequence;

[0028] Taking the μ-order Chebyshev mapping as an example, the method for generating random code sequences is as follows:

[0029] Step 2: 1. Initialize the value of the first random code to x′0, and initialize the total number of random codes in the random code sequence to N, and let k = 0;

[0030] Step 22: Based on the random code x′ k Generate the next random code x′ k+1 :

[0031] x′ k+1 =f(x′) k )=cos(μarccosx′ k ),|x′ k |≤1

[0032] Steps two and three: Determine if k is less than N-2;

[0033] If k is less than N-2, then let k = k+1 and return to step two.

[0034] Otherwise, if k equals N-2, then the output random code sequence is {x0′,x1′,...,x′}. k ,...,x′ N-1}

[0035] Alternatively, other methods can be chosen to generate spreading codes or random codes;

[0036] Step 3: For the i-th complex digital modulation symbol S in the serial signal i Using the standardized random code sequence to test S i By expanding, we get S i The corresponding extended sequence [S] i x0,S i x1,...,S i x N-1 ];

[0037] Step 4: N transmitting antennas are uniformly and linearly arranged to form a linear array antenna structure. Each element in the extended sequence is multiplied by the corresponding baseband weighting factor, and the multiplication result is then converted from digital to analog. The result after digital-to-analog conversion is then transmitted to the channel through the transmitting antenna.

[0038] Step 5: The receiving end receives the signal transmitted in Step 4 from the channel;

[0039] Step 6: In order to achieve secure point-to-point communication with coordinated transmission and reception, the receiving end puts the received signal into N channels, and performs down-conversion processing on the signals of N channels respectively to obtain the down-conversion results of the received signal in each channel.

[0040] Step 7: Perform low-pass filtering on the signal obtained in Step 6 to obtain the low-pass filtered signal y′. m (θ,r,t);

[0041] Step 8: Convert the output signal y′ from step 7... m (θ,r,t) is converted into signal data y″ by an analog-to-digital converter. m Using random codes to pair y″ m Data recovery is performed, the recovered data is summed to obtain signal data y″, and y″ is normalized to obtain signal data Y. i ;

[0042] Step 9: For each complex digital modulation symbol in the serial signal, perform the process from Step 3 to Step 8 until all data signals have been received.

[0043] The signal received by the legitimate receiver is represented as a single serial digital signal. Again Demodulate the signal to recover the 0 and 1 bits of data.

[0044] This invention introduces random codes into waveform design based on the FDA (Focused Atmosphere Processing) method. The FDA-based waveform design method offers good spatial diversity. Building upon this, to further enhance waveform diversity, the invention utilizes the diverse characteristics of random codes to improve signal security. By leveraging the spatial, temporal, and random code dimensions of the signal to achieve waveform diversity, this invention counters traditional spatial eavesdropping techniques, increases the difficulty of joint eavesdropping, and enhances the security of communication systems.

[0045] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One or Two in that the spacing d between adjacent transmitting antennas in the linear array antenna structure is:

[0046]

[0047] Where c represents the speed of light, f0 represents the carrier frequency of the signal emitted by the reference array element, Δf is the frequency increment, and Δf << f0;

[0048] The transmitting antenna furthest from the valid receiver is used as the reference element and marked as element 0. Starting from element 0, the other transmitting antennas are marked as elements 1, 2, ..., N-1.

[0049] That is, each transmitting antenna is marked in sequence according to the distance between the transmitting antenna and the legitimate receiver, from farthest to closest.

[0050] The other steps and parameters are the same as in Specific Implementation Method 1.

[0051] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the transmitted signal of the transmitting antenna is:

[0052]

[0053] Where n = 0, 1, 2, ..., N-1, e n (t) is the transmitted signal of the transmitting antenna corresponding to the nth element, P n w is the power of the transmitting antenna corresponding to element n. n S represents the baseband weighting coefficient of the nth element. i x n It is the (n+1)th element in the extended sequence, j is the imaginary unit, e is the base of the natural logarithm, t is time, and f is the time interval. n It is the carrier frequency of array element n.

[0054] Other steps and parameters are the same as in specific implementation method one or two.

[0055] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the carrier frequency of the nth array element is:

[0056] f n =f0+nΔf

[0057] The other steps and parameters are the same as those in one of the specific implementation methods one to three.

[0058] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the baseband weighting coefficient of the nth array element is:

[0059]

[0060] Where, θ D The azimuth angle r represents the direction of the normal to the linear array relative to the legitimate receiver. D This indicates the distance between the legitimate receiver and the reference array element.

[0061] The other steps and parameters are the same as those in one of the specific implementation methods one to four.

[0062] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that, in step five, the received signal at the receiving end is:

[0063]

[0064] Where y(θ,r,t) is the received signal at the receiver, and ρ(R) is the received signal at the receiver. n ) represents the amplitude distance attenuation factor, λ is the channel coefficient, and P n ′ is the received power of the receiving antenna to the signal from the nth transmitting antenna, g(t) represents additive white Gaussian noise, and τ n τ represents the time delay of receiving the signal transmitted by array element n. n =R n / c, R n This represents the distance between the receiver and array element n.

[0065] The transmitting antenna is isotropic and transmits the signal into the channel. When the receiver's position satisfies the far-field condition, the beam transmitted by the array can be considered a parallel beam. Therefore, the distance R between the receiver and the nth array element is... n =r-ndsinθ,n=0,...,N-1.

[0066] Since (N-1)d << r and (N-1)Δf << f0, where "<<" represents much smaller than, therefore, n 2 Δfdsinθ / c≈0, ρ(R) n )=ρ(r), τ=r / c, where τ represents the time delay of the received reference array element radiated signal, after removing the fixed phase offset. The received signal y(θ,r,t) is simplified to:

[0067]

[0068] Where ρ(r) represents the amplitude distance attenuation factor, θ represents the azimuth angle between the receiver and the normal direction of the linear array, and r represents the distance between the receiver and the reference array element.

[0069] The other steps and parameters are the same as those in one of the specific implementation methods one to five.

[0070] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that the down-conversion result of the received signal in the m-th channel is:

[0071]

[0072] Among them, y m (θ,r,t) represents the downconversion result of the m-th channel, where m = 0, 1, ..., N-1, f m =f0+mΔf.

[0073] The other steps and parameters are the same as those in one of the specific implementation methods one to six.

[0074] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the low-pass filtered signal is:

[0075]

[0076] Where, y′ m (θ,r,t) represents the low-pass filtered signal of the m-th channel. Here, h(t) represents the convolution operator, h′(t) represents the response function of a low-pass filter with a cutoff frequency of Δf / 2, and g′(t) represents the Gaussian white noise in the baseband.

[0077] The other steps and parameters are the same as those in any of the specific implementation methods one to seven.

[0078] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the specific process of step eight is as follows:

[0079]

[0080] in, It is x m The conjugate of complex numbers.

[0081] The other steps and parameters are the same as those in one of the specific implementation methods one to eight.

[0082] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that, in the standardized random code sequence, the mean of all random codes is 0 and the variance is 1.

[0083] The other steps and parameters are the same as those in any of the specific implementation methods one to nine.

[0084] The above examples of the present invention are merely illustrative of the computational model and process of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is impossible to exhaustively list all possible implementations here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A waveform design and transmission method based on a combination of FDA and random code, characterized in that, The method specifically includes the following steps: Step 1: Perform baseband constellation mapping on the bit data (0, 1) to be transmitted to obtain the modulation result after constellation mapping; The modulation result is a serial signal with a length of 2. U U is a positive integer, and the i-th complex digital modulation symbol in the serial signal is denoted as S. i i = 1, 2, ..., 2 U ; Step 2: Generate a random code sequence, and then standardize the random codes in the random code sequence to obtain the standardized random code sequence {x0, x1, x2, ..., x...}. N-1 },x0,x1,x2,...,x N-1 These are the 0th, 1st, 2nd, ..., N-1th random codes in the standardized random code sequence; The random code sequence is generated as follows: Step 2:

1. Initialize the value of the first random code to x′0, and initialize the total number of random codes in the random code sequence to N, and let k = 0; Step 22: Based on the random code x′ k Generate the next random code x′ k+1 : x′ k+1 =f(x′ k )=cos(μarccos x′ k ),|x′ k |≤1 Steps two and three: Determine if k is less than N-2; If k is less than N-2, then let k = k+1 and return to step two. Otherwise, if k equals N-2, then the output random code sequence is {x′0,x′1,...,x′}. k ,...,x′ N-1 }; Step 3: For the i-th complex digital modulation symbol S in the serial signal i Using the standardized random code sequence to test S i By expanding, we get S i The corresponding extended sequence [S] i x0,S i x1,...,S i x N-1 ]; Step 4: N transmitting antennas are uniformly and linearly arranged to form a linear array antenna structure. Each element in the extended sequence is multiplied by the corresponding baseband weighting factor, and the multiplication result is then converted from digital to analog. The result after digital-to-analog conversion is then transmitted to the channel through the transmitting antenna. The transmitting signal of the transmitting antenna is: Where n = 0, 1, 2, ..., N-1, e n (t) is the transmitted signal of the transmitting antenna corresponding to the nth element, P n w is the power of the transmitting antenna corresponding to element n. n S represents the baseband weighting coefficient of the nth element. i x n It is the (n+1)th element in the extended sequence, j is the imaginary unit, e is the base of the natural logarithm, t is time, and f is the time interval. n It is the carrier frequency of the nth array element; The baseband weighting coefficient of the nth array element is: Where, θ D The azimuth angle r represents the direction of the normal to the linear array relative to the legitimate receiver. D This indicates the distance between the legitimate receiver and the reference array element; Step 5: The receiving end receives the signal transmitted in Step 4 from the channel; Step 6: The receiving end puts the received signal into N channels, and performs down-conversion processing on the signals of N channels respectively to obtain the down-conversion results of the received signal in each channel; Step 7: Perform low-pass filtering on the signal obtained in Step 6 to obtain the low-pass filtered signal y′. m (θ,r,t); Step 8: Convert the output signal y′ from step 7... m (θ,r,t) is converted into signal data y″ by an analog-to-digital converter. m Using random codes to pair y″ m Data recovery is performed, the recovered data is summed to obtain signal data y″, and y″ is normalized to obtain signal data Y. i ; Step 9: For each complex digital modulation symbol in the serial signal, perform the process from Step 3 to Step 8 until all data signals have been received. The signal received by the legitimate receiver is represented as a single serial digital signal. Again Demodulate the signal to recover the 0 and 1 bits of data.

2. The waveform design and transmission method based on the combination of FDA and random code according to claim 1, characterized in that, In the linear array antenna structure, the spacing d between adjacent transmitting antennas is: Where c represents the speed of light, f0 represents the carrier frequency of the signal emitted by the reference array element, and Δf is the frequency increment; The transmitting antenna furthest from the valid receiver is used as the reference element and marked as element 0. Starting from element 0, the other transmitting antennas are marked as elements 1, 2, ..., N-1.

3. The waveform design and transmission method based on the combination of FDA and random code according to claim 2, characterized in that, The carrier frequency of the nth array element is: f n =f0+nΔf。 4. The waveform design and transmission method based on the combination of FDA and random code according to claim 3, characterized in that, In step five, the received signal at the receiving end is: Where y(θ,r,t) is the received signal at the receiver, and ρ(R) is the received signal at the receiver. n ) represents the amplitude distance attenuation factor, λ is the channel coefficient, and P′ n It is the received power of the receiving antenna to the signal from the nth transmitting antenna, g(t) represents additive white Gaussian noise, and τ n τ represents the time delay of receiving the signal transmitted by array element n. n =R n / c, R n This represents the distance between the receiver and array element n. Since (N - 1)d << r and (N - 1)Δf << f0, then, n 2 Δfdsinθ / c ≈ 0, ρ(R n ) = ρ(r), τ = r / c, τ represents the time delay of receiving the radiation signal of the reference array element, and the fixed phase offset is removed The received signal y(θ, r, t) is simplified to: Where ρ(r) represents the amplitude distance attenuation factor, θ represents the azimuth angle between the receiver and the normal direction of the linear array, and r represents the distance between the receiver and the reference array element.

5. The waveform design and transmission method based on the combination of FDA and random code according to claim 4, characterized in that, The down-conversion result of the received signal in the m-th channel is: Among them, y m (θ,r,t) represents the downconversion result of the m-th channel, where m = 0, 1, ..., N-1, f m =f0+mΔf.

6. The waveform design and transmission method based on the combination of FDA and random code according to claim 5, characterized in that, The low-pass filtered signal is: Where, y′ m (θ,r,t) represents the low-pass filtered signal of the m-th channel. Here, h(t) represents the convolution operator, h′(t) represents the response function of a low-pass filter with a cutoff frequency of Δf / 2, and g′(t) represents the Gaussian white noise in the baseband.

7. The waveform design and transmission method based on the combination of FDA and random code according to claim 6, characterized in that, The specific process of step eight is as follows: in, It is x m The conjugate of complex numbers.

8. The waveform design and transmission method based on the combination of FDA and random code according to claim 7, characterized in that, In the standardized random code sequence, the mean of all random codes is 0 and the variance is 1.

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