Space-frequency joint anti-interference signal sending method suitable for TDMA (Time Division Multiple Access) network

Abstract

The invention discloses a space-frequency joint anti-interference signal sending method suitable for a TDMA network, and relates to the technical field of ad hoc network transmission and wireless communication. According to the method, a transmission time slot format in the TDMA network is specified, and each time slot comprises a synchronous frequency hopping pulse and a data frequency hopping pulse. The method comprises the following steps: firstly, performing data framing according to network time slot control information, performing scrambling, channel coding, channel interleaving and data blocking on information source data, inserting synchronous pulse data, and then performing GMSK modulation; generating frequency hopping pulses from the modulated data according to the frequency hopping pulse control information, and generating time slot frames according to the time slot control information; and finally, a radio frequency signal is generated after DA conversion, and the radio frequency generates a frequency hopping signal according to the frequency hopping frequency control information and is finally sent out through an antenna. According to the method, an anti-interference transmission method is designed by combining spatial domain and frequency domain two-dimensional information in a directional network, reliable and stable transmission of signals can be ensured, and the anti-interference transmission requirement of node information in a TDMA (Time Division Multiple Access) network can be met.

Description

Technical Field

[0001] This invention relates to the field of ad hoc network transmission and wireless communication technology, and in particular to a space-frequency joint anti-interference signal transmission method suitable for TDMA networks. Background Technology

[0002] Aerial unmanned swarms typically interconnect using ad hoc networks. These networks often face complex interference environments, necessitating anti-interference transmission strategies in their signal transmission design. Ad hoc network systems typically employ TDMA access, allocating different transmission time slots to each network node, which then polls and transmits service data within its respective time slot. Therefore, burst communication transmission is required. Based on this, designing a high-speed frequency-hopping burst communication transmission method can effectively resist interference.

[0003] In addition, aerial platforms are often equipped with array antennas, achieving full airspace coverage by installing multiple array antennas around the platform. By adjusting the weights of each antenna element, nulls can be created in the direction of airspace interference, thereby achieving anti-interference purposes.

[0004] Currently, in the design of signal transmission systems in traditional TDMA networks, only the spatial or frequency domain is considered for anti-interference design, resulting in weak anti-interference capabilities. It is necessary to comprehensively consider both spatial and frequency information for anti-interference signal transmission design. Summary of the Invention

[0005] In view of this, the present invention proposes a space-frequency joint anti-interference signal transmission method suitable for TDMA networks. This method combines spatial and frequency domain two-dimensional information in directional networks to design an anti-interference transmission method, which can ensure reliable and stable signal transmission and meet the anti-interference transmission requirements of node information in TDMA networks.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A space-frequency joint anti-interference signal transmission method suitable for TDMA networks includes the following steps:

[0008] Step 1: Generate a timeslot table and count timeslot numbers. The counting period within the time slot is ;

[0009] Step 2: Calculate the frequency hopping pattern based on the current timeslot number;

[0010] Step 3: Buffer the input data and count it within the time slot. The length read out at time is Source data;

[0011] Step 4: Perform source scrambling on the source data to obtain scrambled data;

[0012] Step 5: Perform channel coding on the scrambled data to obtain channel-coded data;

[0013] Step 6: Interleave the channel-coded data to obtain interleaved data, and input it into the buffer;

[0014] Step 7: Count the next time slot as follows When modulation and framing begin, a synchronization pulse sequence is first generated. ;

[0015] Step 8: After generating the synchronization pulse, start generating the data pulse, read the data from the buffer, and synchronize it with the UW sequence. Composed of data pulses;

[0016] Step 9: Perform GMSK precoding on each pulse data;

[0017] Step 10: Modulate the precoded data using GMSK and output it sequentially according to the pulses;

[0018] Step 11: The modulated signal undergoes digital-to-analog conversion and is frequency-converted according to a frequency-hopping pattern at the baseband output, while retaining the frequency-cutting interval between pulses. This yields a simulated burst signal;

[0019] Step 12: The radio frequency channel module generates a frequency hopping signal based on the simulated burst signal and frequency hopping pattern information, selects a specific antenna to transmit the signal to the wireless link, and completes the transmission of a space-frequency joint anti-interference signal suitable for TDMA networks.

[0020] Furthermore, the time slot table structure in step 1 is a configurable periodic time slot structure, with a basic time slot period of 1 / 2. The time slot table period is , The periodic parameter is configurable; the transmission time slot is in the set. The selected time slot number.

[0021] Furthermore, the frequency hopping pattern in step 2 is generated by a 32nd-order pseudo-random sequence, with the initial phase being the reverse of the current time slot number. The frequency hopping points in each time slot are not repeated and the adjacent intervals are greater than 100MHz.

[0022] Furthermore, the number of synchronization pulses in step 7 is One, using A length of pseudo-random sequence constitute.

[0023] Furthermore, the number of data pulses in step 8 is Each data pulse is divided into five parts, the first part being the UW field, with a length of [missing information]. pseudo-random sequence The second part is the data field, with a length of The data segment, the third part is the UW field, with a length of pseudo-random sequence The fourth part is the data field, with a length of The fifth part of the data segment is the UW field, with a length of [length missing]. pseudo-random sequence .

[0024] Furthermore, in step 9, the GMSK precoding format is as follows.

[0025]

[0026] For the pre-coded bits, These are the pre-coded bits.

[0027] Furthermore, in step 11, the intermediate frequency point is output. In bandwidth Inside, This refers to the frequency hopping point in the frequency hopping pattern output; the space frequency sensing interval is preserved between pulses. The length meets the requirements for demodulation end spectrum interference detection and processing time.

[0028] Due to the adoption of the above technical solution, the beneficial effects of this invention compared with the prior art are as follows:

[0029] 1. This invention designs a signal transmission format by combining two-dimensional information in the spatial and frequency domains, and has the characteristic of simultaneously employing spatial and frequency domain anti-interference algorithms in signal transmission.

[0030] 2. This invention adopts the GSMK frequency hopping burst communication method, with random frequency distribution, strong signal concealment, and anti-interception characteristics.

[0031] 3. The present invention has flexible time slot configuration, is suitable for TDMA networks, and supports large-scale aerial unmanned cluster network transmission. Attached Figure Description

[0032] Figure 1 This is a structural diagram of the transmitting end in an embodiment of the present invention.

[0033] Figure 2 This is a time frame and time slot structure diagram in an embodiment of the present invention.

[0034] Figure 3 This is a structural diagram of the receiving end in an embodiment of the present invention. Detailed Implementation

[0035] The invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] A space-frequency joint anti-interference signal transmission method suitable for TDMA networks, such as Figure 1 As shown, it includes the following steps:

[0037] Step 1: Generate a timeslot table and count timeslot numbers. The counting period within the time slot is The specific steps are as follows: the basic time slot period is... The time slot table period is , The periodic parameter is configurable; the transmission time slot is in the set. The selected time slot number.

[0038] Step 2: Calculate the frequency hopping pattern based on the current timeslot number. Specifically, the frequency hopping pattern is generated from a 32nd-order pseudo-random sequence, with the initial phase being the current timeslot number. Within each timeslot, the frequency hopping points are non-repeating and the adjacent intervals are greater than 100MHz. Before the synchronization pulse is acquired, the frequency hopping controller performs frequency hopping according to the search pattern; after the synchronization pulse is acquired, the frequency hopping controller performs frequency hopping according to the tracking pattern.

[0039] (1) Each time slot is determined by the time slot number. Using the reverse order of the first phase as the initial phase, a pseudo-random sequence is calculated based on the initial phase, with each 32 bits forming a binary number. , where i represents the pulse frequency index. Calculate

[0040]

[0041] floor is rounded down to the nearest integer. That is The result mapped to 792 frequency points, The range is [0, 791]. The meaning is that the frequency difference between adjacent subnets is 40MHz at the same time. First, calculate... Value and output frequency hopping point ,make This refers to the frequency hopping point.

[0042] (2) Continue calculation .like and Between, there exists Then perform iterative calculations. .

[0043] (3) Judgment and all the center frequencies that have been generated Are there any duplicates? If there are no duplicates, then... If there is a duplicate, return to step (302).

[0044] (4) After calculating all frequency point values, P represents the total number of pulses.

[0045] Step 3: Buffer the input data and count it within the time slot. The length read out at time is Source data;

[0046] Step 4: Perform source scrambling on the source data to obtain scrambled data;

[0047] Step 5: Perform channel coding on the scrambled data to obtain channel-coded data;

[0048] Step 6: Interleave the channel-coded data to obtain interleaved data, and input it into the buffer;

[0049] Step 7: As Figure 2 As shown, the count in the next time slot is When modulation and framing begin, a synchronization pulse sequence is first generated. The specific steps are as follows: the number of synchronization pulses is... One, using A length of pseudo-random sequence constitute

[0050] Step 8: After generating the synchronization pulse, start generating the data pulse, read the data from the buffer, and synchronize it with the UW sequence. Composed of data pulses; such as Figure 2 As shown, the specific steps are as follows: the number of data pulses is... Each data pulse is divided into five parts, the first part being the UW field, with a length of [missing information]. pseudo-random sequence The second part is the data field, with a length of The data segment, the third part is the UW field, with a length of pseudo-random sequence The fourth part is the data field, with a length of The fifth part of the data segment is the UW field, with a length of [length missing]. pseudo-random sequence .

[0051] Step 9: Perform GMSK precoding on each pulse data. The specific steps of GMSK precoding are as follows:

[0052]

[0053] For the pre-coded bits, For precoded bits

[0054] Step 10: Modulate the precoded data using GMSK and output it sequentially according to the pulses;

[0055] Step 11: The modulated signal undergoes digital-to-analog conversion, and the synchronization pulse is frequency-converted according to the frequency hopping pattern at the baseband output, resulting in an output intermediate frequency of... Preserving the frequency cut interval between pulses The specific steps are as follows: Output the intermediate frequency point. In bandwidth Within, the space frequency sensing interval is preserved between pulses. The length meets the requirements for demodulation end spectrum interference detection and processing time. , This represents the number of sampling points for spectrum detection. To reduce the computational delay in spectrum processing, a simulated burst signal is obtained;

[0056] Step 12: The radio frequency channel module generates a frequency hopping signal based on the simulated burst signal and frequency hopping pattern information, and selects a specific antenna to transmit it to the wireless link.

[0057] Reference Figure 3 Corresponding to the above receiving method, the transmitting end adopts the following transmitting method:

[0058] Step 1: Radio waves are received by the antenna, generating an analog radio frequency signal, which is then output to the radio frequency channel module;

[0059] Step 2: Working principle of the frequency hopping controller: A frequency hopping pattern is generated by a random sequence generator and a frequency hopping seed sequence. The frequency of the frequency hopping pattern at a certain moment is called the frequency hopping code, which is placed into the RF front-end phase-locked source to realize frequency hopping.

[0060] Step 3: The RF channel module receives the synchronization pulse frequency according to the frequency hopping pattern, generates an intermediate frequency analog signal, and outputs it to the A / D analog-to-digital converter; the total bandwidth of the frequency hopping pattern is 800MHz, and the range of the frequency hopping center frequency is [4, 795]MHz. The frequency step is 1MHz, and there are a total of 792 frequency points, with frequency point numbers from 0 to 791.

[0061] Generated from a 32nd-order pseudo-random sequence, with the initial phase being the current time slot number. Within each time slot, the frequency hopping points are not repeated and the adjacent intervals are greater than 100MHz. The specific method is as follows:

[0062] (1) Each time slot is determined by the time slot number. Using the reverse order of the first phase as the initial phase, a pseudo-random sequence is calculated based on the initial phase, with each 32 bits forming a binary number. ,calculate

[0063]

[0064] floor is the floor function; mod(x,y) is the function where x is the dividend and y is the remainder after division. That is The result mapped to 792 frequency points, The range is [0, 791]. The meaning is that the frequency difference between adjacent subnets is 40MHz at the same time. Let This is the frequency hopping point. First, calculate... Value and output frequency hopping point .

[0065] (2) Continue calculation .like and Between, there exists Then perform iterative calculations. .

[0066] (3) Judgment and all the center frequencies that have been generated Are there any duplicates? If there are no duplicates, then... If there is a duplicate, return to step (302).

[0067] (4) After calculating all frequency point values, P represents the total number of pulses.

[0068] Step 4: After the intermediate frequency analog signal undergoes A / D conversion, digital down-conversion, and filtering, a baseband digital signal is generated; the synchronous pulse down-conversion frequency is... In bandwidth Inside.

[0069] Step 5: Perform spatial domain anti-interference processing on the baseband digital signal from Step 3 to generate a spatially anti-interference digital signal; such as... Figure 2 As shown, the specific steps are as follows:

[0070] (1) Minimize the variance of the output signal by adaptively adjusting the weights of the space-time filter. ; in for A dimensional vector representing the weighted values ​​of the matrix elements. This represents the number of elements in the array antenna. express The received signal sampling covariance matrix of dimension . This represents the constraint matrix, and its size is... , The constraint response vector dimension is... ,in This indicates the number of constraints, which is typically selected in anti-interference systems. The constraint matrix and constraint response vector have no independent physical meaning; they are used together to characterize the constraint conditions, such as the desired signal being distortion-free or the interference direction being nulled. In this patent, It is related to the frequency output of the frequency hopping controller. Different frequencies should have different... .

[0071] (2) Because it is impossible to directly address To find the optimal solution, we need to construct the Lagrange function: ,make The optimal weight is obtained This expression is a general expression for the optimal weights; its specific value does not need to be calculated until it is simplified in step 3. This indicates gradient calculation operation.

[0072] (3) Simplify the calculation in step 2. In order to solve the minimum variance distortionless response in the communication system, select the constraint response vector. The linearly constrained minimum variance criterion degenerates into the minimum variance distortionless response. ;in It is known that the wave direction can be solved by the shape of the antenna array and the signal. The spatial steering vector of the array antenna in dimension .

[0073] (4) Solve the minimum variance distortionless response equation to obtain the optimal weight of the spatial anti-interference array. ; in for A dimensional vector represents the optimal weighted vector for spatial anti-interference.

[0074] (5) Perform a weighted summation operation on the sampled data received by the multi-antenna channels and output the data after spatial anti-interference.

[0075] Step 6: Perform frequency domain anti-interference processing on the spatial domain anti-interference digital signal output from Step 4 to generate a frequency domain anti-interference digital signal; the specific steps are as follows:

[0076] (1) In the space-frequency sensing interval Add a bartlett window within the interface.

[0077]

[0078] in, Let n be the window function index. Then, after adding the window, perform... Point FFT operation .

[0079] (2) For each FFT operation result, The points are partially accumulated and smoothed to obtain... dot operation result .

[0080] (3) In dot operation result Select the smallest modulus value And calculate the adaptive threshold. Among them, relative threshold With fixed threshold These are all adjustable coefficients for adaptive thresholds, derived from actual debugging. 1 < <128, 0< <255;

[0081] (4) Based on the threshold As a threshold, it will be greater than The value determines the location of the interference, and the frequency domain notch window function is selected.

[0082]

[0083] in, For frequency domain notch window function, , , The frequency domain notch window adjustment coefficient is obtained through actual debugging, and its typical range is between 0 and 1, satisfying... , As the value increases, the main lobe energy increases and the stopband attenuation decreases; As the value increases, the main lobe energy narrows, and the side lobe level increases; Increasing the value increases the main lobe width and decreases the side lobe level. Adjusting the coefficients of the window function ensures its performance under different interference ratios and intensities. Aligning the frequency domain notch position with the interference position achieves anti-interference. N is the maximum value of the window length index.

[0084] (5) Based on the selected window function Windowing is applied to digital signals. Point FFT operation.

[0085] (6) In The threshold is calculated from the point operation result. ,in .in, and All are adjustable coefficients. 1 < <128, 0< <255;

[0086] (7) Based on the threshold Interference erasure is performed, and the FFT result at the corresponding position is trapped to zero.

[0087] (8) Perform IFFT operation and output the frequency domain anti-interference data.

[0088] Step 7: The acquisition module acquires the digital signal after frequency domain anti-interference in Step 5, outputs the acquisition position, completes frequency hopping synchronization, and controls the RF channel module to receive data pulses according to the frequency hopping pattern sequence; for example... Figure 3 As shown, the specific steps are as follows:

[0089] (1) Use local synchronization sequence With digital signals Performing sliding conjugate complex multiplication

[0090] ;

[0091] (2) Divide the result of conjugate complex multiplication by length Perform partial accumulation to obtain the accumulated signal:

[0092]

[0093] (3) Perform processing on the accumulated signal Point FFT operation, And by comparison Maximum energy value in the calculation results at each time step ;

[0094] (4) The maximum FFT energy of the synchronization pulse is delayed and accumulated, and the delay time is the pulse time. ,

[0095] (5) Perform peak search and threshold judgment on the accumulated signal, and output the capture position;

[0096] Step 8: Synchronize the symbols according to the capture position and output the synchronized data;

[0097] Step 9: Perform carrier recovery on the data after symbol synchronization and output the data after carrier recovery. The specific steps are as follows:

[0098] (1) After capture, read out the buffered synchronization pulse data in sequence. ; ;

[0099] (2) Multiply the data read from each pulse by the conjugate of the local synchronization sequence: and according to length Perform partial accumulation to obtain the accumulated signal. :

[0100] (3) The accumulated signal is padded with zeros. Point FFT operation

[0101] (4) All synchronous pulse FFT calculation results are incoherently accumulated, and the accumulated results are... Find the maximum value to obtain the peak value. Let i be the index corresponding to the peak value, and calculate the carrier error. The digital resolution of the FFT is [value missing]. .

[0102] (5) Generate a locally compensated sine wave based on the carrier error. Carrier recovery is achieved by multiplying the signal with the carrier signal. ;

[0103] Step 10: Perform phase recovery with the data after carrier recovery, and output the phase-recovered data; the specific steps are as follows:

[0104] (1) The data pulse synchronization sequence is multiplied by the conjugate of the local synchronization sequence. And sum the results. ,in UW1, UW2, and UW3 represent the pulse synchronization sequence used for phase recovery.

[0105] (2) Calculate the phase angle of the accumulated results, obtain the phase shift, and compensate for it. ,in To find the arctangent function, In order to seek the truth, To find the imaginary part.

[0106] Step 11: Perform GMSK demodulation on the phase-recovered data and output the demodulated data;

[0107] Step 12: Perform deinterleaving operation on the demodulated data and output the deinterleaved data;

[0108] Step 13: Perform channel decoding on the deinterleaved data and output the channel-decoded data;

[0109] Step 14: Perform descrambling on the data after channel decoding and output the descrambling data.

[0110] Those skilled in the art will recognize that the described embodiments are intended to help readers understand the principles of the invention and should be understood as not limiting the scope of protection of the invention to the described embodiments. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of the claims of the invention.

Claims

1. A space-frequency joint anti-jamming signal transmission method suitable for a TDMA network, characterized in that, The method comprises the following steps: Step 1: Generate a time slot table, time slot number count , intra-slot count period is ; Step 2: calculating the frequency hopping pattern according to the current time slot number; Step 3: Buffering the input data, counting in time slots Read out the source data with length in time Step 4: performing source scrambling on the source data to obtain scrambled data; Step 5: performing channel coding on the scrambled data to obtain channel coded data; Step 6: performing interleaving on the channel coded data to obtain interleaved data and inputting the interleaved data into a buffer; Step 7: When the count within the next time slot is the modulation framing begins, first producing a sequence of sync pulses ; Step 8: After the sync pulse is generated, the data pulse is generated and the data is read from the cache and combined with the UW sequence to form the data pulse; Step 9: performing GMSK pre-coding on the pulse data; Step 10: performing GMSK modulation on the pre-coded data and sequentially outputting the pulse data; Step 11: The modulated signal is converted into digital signal, and frequency conversion is performed according to the frequency hopping pattern to obtain an analog burst signal ; Step 12: the radio frequency channel module generates a frequency hopping signal according to the analog burst signal and the frequency hopping pattern information, selects a specific antenna to transmit to the wireless link, and completes a kind of space-frequency joint anti-interference signal transmission suitable for TDMA network.

2. The space-frequency joint anti-jamming signal transmission method for TDMA network according to claim 1, characterized in that, The time slot table structure in step 1 is a configurable period time slot structure, and the basic time slot period is , the time slot table period is , is a configurable period parameter; the sending time slot is the time slot number selected in the set .

3. The method according to claim 1, wherein the method is characterized by, The frequency hopping pattern in step 2 is generated by a 32-order pseudo-random sequence, and the initial phase is the reverse sequence of the current time slot number. The frequency hopping points in each time slot are not repeated and the adjacent interval is greater than 100MHz.

4. The method of claim 1, wherein the method is applied to a TDMA network. The number of synchronization pulses in step 7 is One, using A length of pseudo-random sequence constitute.

5. The method of claim 1, wherein the method is applied to a TDMA network. The number of data pulses in step 8 is , each of which is divided into five parts, the first part is a UW field with a length of a pseudo-random sequence , the second part is a data field with a length of a data segment, the third part is a UW field with a length of a pseudo-random sequence , the fourth part is a data field with a length of a data segment, and the fifth part is a UW field with a length of a pseudo-random sequence .

6. The method of claim 1, wherein the method is applied to a TDMA network. In step 9, the GMSK pre-coding format is: ； is a pre-encoding bit, is a post-encoding bit.

7. The method of claim 1, wherein the method is applied to a TDMA network. In step 11, the intermediate frequency point is output. In bandwidth Inside, This refers to the frequency hopping point in the frequency hopping pattern output; the space frequency sensing interval is preserved between pulses. The length meets the requirements for demodulation end spectrum interference detection and processing time.

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