A folding acquisition method for direct sequence spread spectrum long code

Abstract

The present invention discloses a folding capture method of a direct sequence spread spectrum long code, the method comprising: performing partial matching correlation with a local folding code after preprocessing and mixing a high frequency spread spectrum signal, storing the correlation result in a two-dimensional register, performing group FFT operation and accumulation on the correlation result, obtaining a power spectrum with the same code phase of the correlation result, performing square sum of the I / Q path power spectrum module to obtain a maximum peak value much larger than other power spectrum amplitudes, comparing the maximum peak value with a threshold value, if it is greater than the threshold value, then the local spread spectrum code phase offset corresponding to the peak value is consistent with the code offset of the input signal, and the Doppler frequency deviation estimation value of the input signal can be obtained through the corresponding local spread spectrum code. The local code is folded, multiple code phases can be searched for in one correlation, and the correlation results are grouped for FFT, which can reduce the difficulty of operation and reduce the calculation time.

Description

Technical Field

[0001] The invention relates to a folding capture method of a direct sequence spread spectrum long code, belonging to the technical field of spread spectrum communication. Background Art

[0002] Spread spectrum communication is widely used due to its many advantages such as good resistance to multipath effects, strong anti-interference ability and good confidentiality.

[0003] For a complete spread spectrum communication system, it can be mainly divided into a transmitter and a receiver. The transmitter mainly modulates the data information to be transmitted through a spread spectrum code sequence to achieve spectrum expansion of the data information, and then transmits it after shaping filtering; the receiver receives the signal after wireless propagation, and uses the same spread spectrum code sequence as the transmitter to perform correlation operations to achieve synchronous reception, despreading and recovery of the original data information to be transmitted. The ultimate goal of the entire wireless transmission system is to make the original data consistent with the data information after despreading and recovery, so as to achieve error-free data transmission.

[0004] However, after the entire signal is transmitted through the wireless channel, it will inevitably be affected by the transmission environment such as noise, obstacles, relative movement, etc., causing errors in the signal during transmission, making the effectiveness of the communication system lower. The capture of the spread spectrum communication system is the first processing module after the data is transmitted through the wireless channel, which directly determines the performance of subsequent synchronization and despreading, so the research on the capture system is particularly important. Summary of the invention

[0005] Synchronization in direct sequence spread spectrum communication systems can generally be divided into two stages: acquisition and tracking. Spread spectrum acquisition, also known as coarse synchronization, achieves initial synchronization of data and determines that the code phase of the data symbol is within a 1 / 2 symbol interval deviation range. Spread spectrum tracking, also known as fine synchronization, is the tracking stage after initial synchronization, using the autocorrelation of the PN code to control the phase deviation within a sampling interval.

[0006] The DSSS fast acquisition methods can be mainly divided into two categories: time domain acquisition and frequency domain acquisition. The time domain-based acquisition methods include serial / parallel acquisition using matched filters, and the frequency domain-based acquisition methods include parallel matching search using FFT for cyclic correlation. The combined search technology of time domain correlation and frequency domain parallel FFT search is called partial matching filter PMF-FFT, and a series of optimization algorithms derived from it. Among them, the time domain acquisition method matched filter method correlates each code phase with the local code. Its structure is simple to implement, but too many registers and operation units are required, so the acquisition time is too long. The frequency domain capture method parallel FFT method performs frequency domain conjugate convolution to capture quickly, but the implementation complexity is too high. The frequency deviation correction capability of the fast acquisition based on PMF-FFT is restricted by the number of FFT points, and may not meet the needs of large frequency deviation and limited resources.

[0007] The purpose of the present invention is to provide a folding acquisition method for direct sequence spread spectrum long code in view of the above problems existing in the existing acquisition technology.

[0008] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0009] In a first aspect, the present invention proposes a folding acquisition method of a direct sequence spread spectrum long code, comprising:

[0010] S1, obtaining a received high frequency spread spectrum signal transmitted through a wireless channel;

[0011] S2, performing down-conversion processing and A / D conversion on the high frequency spread spectrum signal to obtain a digital intermediate frequency signal;

[0012] S3, performing energy detection on the digital intermediate frequency signal;

[0013] S4, in response to detecting the packet signal energy, pre-processing and modulating the digital intermediate frequency signal into fixed-bit-width data to obtain pre-processed data; performing digital down-conversion processing on the pre-processed data using an orthogonal carrier to obtain I / Q two-way orthogonal data;

[0014] S5, obtaining M*L point local spread spectrum code data generated by the local spread spectrum code module; performing local code staggering N code chips on the local spread spectrum code data to obtain M*L folded codes;

[0015] S6, performing a partial matching correlation operation on the I / Q two-way orthogonal data and the folding code to obtain a partial matching correlation result between the folding code and the I / Q two-way orthogonal data;

[0016] S7, grouping the partial matching correlation results to obtain grouped matching correlation results, performing frequency domain FFT conversion on each group of the grouped matching correlation results to obtain frequency domain data; accumulating the frequency domain data of a set period to obtain M frequency domain energies K;

[0017] S8, comparing the maximum value of the M frequency domain energies K with the adaptive threshold value;

[0018] In response to the maximum value of the M frequency domain energies K not exceeding the adaptive threshold value, the M*L point local spread spectrum code data generated by the local spread spectrum code module is updated, and steps S5 to S8 are repeated to perform the next round of capture;

[0019] S9. In response to the maximum value among the M frequency domain energy K values ​​exceeding the adaptive threshold value, it indicates that the capture is successful; the folded code corresponding to the maximum value among the M frequency domain energy K values ​​is restored to a set of unfolded N-segment local spread spectrum original codes, and the high-frequency spread spectrum signal and the N-segment local spread spectrum original codes are respectively correlated to determine the position information of the aligned local spread spectrum code data, thereby realizing the folded capture of the direct sequence spread spectrum long code.

[0020] In some embodiments, S3, performing energy detection on the digital intermediate frequency signal, comprises:

[0021] The digital intermediate frequency signal contains noise. n =s n +w n ,s n To receive the signal, w n is the noise component, so that the decision component m n is selected as the cumulative sum of the received signal energy under the window length L, expressed as Make the decision component equal to the predetermined threshold T h After comparison, determine the group detection situation:

[0022] H0:m n <T h No grouping occurs

[0023] H1:m n ≥T h Appearance Group

[0024] where r n-k is the value of the digital intermediate frequency signal after delay k, For r n-k The conjugate value of , n and k are variables ranging from 0 to L-1.

[0025] In some embodiments, preprocessing and modulating the digital intermediate frequency signal into fixed-bit-width data to obtain preprocessed data includes:

[0026] The digital intermediate frequency signal is modulated into fixed-bit-width data, and the data is divided into M data blocks, each of which contains L data points, denoted as x i (n), where i = 0, 1, ..., M-1, n = 0, 1, ..., L-1, and each segment of data is stored sequentially using a register.

[0027] In some embodiments, the pre-processed data is subjected to digital down-conversion processing using an orthogonal carrier to obtain I / Q two-way orthogonal data, including:

[0028] The preprocessed data x i (n) Using the orthogonal carrier wave for digital down-conversion, we get:

[0029] Ix i (n) = x i (n)*sin(2π*f I *m*t s ),i=0,1,...,M-1,n=0,1,...,L-1;

[0030] Qx i (n) = x i (n)*cos(2π*f I *m*t s ),i=0,1,...,M-1,n=0,1,...,L-1,

[0031] Among them, Ix i (n) is I-channel orthogonal data, Qx i (n) is the Q-path orthogonal data, f I is the intermediate frequency carrier frequency at the transmitting end, t s is the sampling time, m is the mth sampling point, and the window length is L.

[0032] In some embodiments, S5, obtaining M*L point local spread spectrum code data generated by the local spread spectrum code module; performing local code staggered N code chips superposition on the local spread spectrum code data to obtain M*L folded codes, including:

[0033] The local spread spectrum code data is divided into M segments, each segment is L code elements long. i (n), denoted as:

[0034] r i (n)i=0,1,...,M-1,n=0,1,...L-1;

[0035] The local spread spectrum code data is superimposed by staggering the local code by N code chips to obtain M*L folding codes r o (n), denoted as: r o (n) = r i(n)+r i (n+1)+...+r i (n+N-1)n=0,1,...,L-1.

[0036] In some embodiments, S6, performing a partial matching correlation operation on the I / Q two-way orthogonal data and the folding code to obtain a partial matching correlation result between the folding code and the I / Q two-way orthogonal data, includes:

[0037] The I-path and Q-path each have an L-bit matching correlation operator. The partial matching correlation results of the folded code and the I / Q orthogonal data are stored in a two-dimensional register with M rows and L columns. Taking the I-path data as an example, each partial matching correlation result is recorded as:

[0038]

[0039]

[0040] …

[0041]

[0042] Ix i (n) is the I-way orthogonal data, and the COR(0,0) correlation value is the first segment length L r o (n) and the first segment r of length L o (n) The incoherent accumulation value of each corresponding phase; Similarly:

[0043]

[0044]

[0045] …

[0046]

[0047] The partial match correlation result storage value of the two-dimensional register is (C i，j =COR(i,j)):

[0048]

[0049] In some embodiments, S7, grouping the partial matching correlation results to obtain grouped matching correlation results, and performing frequency domain FFT conversion on each group of the grouped matching correlation results to obtain frequency domain data, including:

[0050] The grouping rule is: each column of correlation values ​​is divided into W groups, each group has P = M / W correlation values, and the corresponding correlation values ​​of each group differ by W intervals; the first group of a column is: P 0,i :C 0,i ,Cw,i ,C 2w,i ,...,C w*(P-1),i ;P 0,i Represents the first grouping sequence in column i;

[0051] The matching correlation results after grouping have M*L data, of which M have the same phase difference; that is, the correlation values ​​obtained in the i-th column have the same phase;

[0052] From each column, select P data for FFT in the first clock cycle, select P data for FFT in the second clock cycle, ..., select P data for FFT in the Wth clock cycle; (I0, I1, ..., I w-1 )=fft(P i,0 ,P i,1 ,...,P i,w-1 )、(Q0,Q1,...,Q w-1 )=fft(P i,0 ,P i,1 ,...,P i,w-1 );

[0053] After W clock cycles, the frequency domain data of each column of I / Q channels are non-coherently accumulated, and the accumulated value of the nth column of channel I is I n , the cumulative value of the nth column of Q path is Q n , add the square of the accumulated values ​​of the corresponding columns of the I / Q path to get the frequency domain energy K n , frequency domain energy K n =I n 2 +Q n 2 .

[0054] In some embodiments, the adaptive threshold value P=P max / P ave , where P max is the maximum peak energy of the I / Q two-way orthogonal data signal, P ave is the average energy of the I / Q two-channel orthogonal data.

[0055] In a second aspect, the present invention provides a folding capture device for a direct sequence spread spectrum long code, comprising a processor and a storage medium;

[0056] The storage medium is used to store instructions;

[0057] The processor is used to operate according to the instructions to execute the steps of the method according to the first aspect.

[0058] In a third aspect, the present invention provides a storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method described in the first aspect.

[0059] Beneficial effects: The present invention folds the local code and performs partial matching correlation with the received signal, which is equivalent to detecting multiple code phases at the same time in one correlation, greatly reducing the average capture time while the implementation structure will not become more complicated, effectively solving the contradiction between capture efficiency and implementation complexity. At the same time, in order to solve the problem that the more FFT points there are, the greater the amount of calculation and the longer the calculation time, a grouped FFT operation is performed, which reduces the complexity and greatly reduces resource consumption without affecting the signal envelope characteristics and the FFT spectrum resolution accuracy. The present invention has the advantages of high efficiency, short capture time, and large capture bandwidth, and has a better capture probability than traditional capture algorithms under high dynamic and low signal-to-noise ratio conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 The overall module diagram of the capture method proposed in the embodiment of the present invention;

[0061] Figure 2 A schematic diagram of the structure of an energy detection module in a capture method according to an embodiment of the present invention;

[0062] Figure 3 A schematic diagram of data folding in a capture method is provided for an embodiment of the present invention;

[0063] Figure 4 This is a diagram showing the operation sequence of the partial matching related modules in an embodiment of the present invention;

[0064] Figure 5 This is a schematic diagram of performing FFT in groups with partial matching related modules in an embodiment of the present invention;

[0065] Figure 6 A structural diagram of a capture method implemented in an embodiment of the present invention is provided;

[0066] Figure 7 This is a capture effect diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0067] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0068] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0069] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0070] Embodiment 1:

[0071] A folding acquisition method for a direct sequence spread spectrum long code, comprising:

[0072] S1, obtaining a received high frequency spread spectrum signal transmitted through a wireless channel;

[0073] S2, performing down-conversion processing and A / D conversion on the high frequency spread spectrum signal to obtain a digital intermediate frequency signal;

[0074] S3, performing energy detection on the digital intermediate frequency signal;

[0075] S4, in response to detecting the packet signal energy, pre-processing and modulating the digital intermediate frequency signal into fixed-bit-width data to obtain pre-processed data; performing digital down-conversion processing on the pre-processed data using an orthogonal carrier to obtain I / Q two-way orthogonal data;

[0076] S5, obtaining M*L point local spread spectrum code data generated by the local spread spectrum code module; performing local code staggering N code chips on the local spread spectrum code data to obtain M*L folded codes;

[0077] S6, performing a partial matching correlation operation on the I / Q two-way orthogonal data and the folding code to obtain a partial matching correlation result between the folding code and the I / Q two-way orthogonal data;

[0078] S7, grouping the partial matching correlation results to obtain grouped matching correlation results, performing frequency domain FFT conversion on each group of the grouped matching correlation results to obtain frequency domain data; accumulating the frequency domain data of a set period to obtain M frequency domain energies K;

[0079] S8, comparing the maximum value of the M frequency domain energies K with the adaptive threshold value;

[0080] In response to the maximum value of the M frequency domain energies K not exceeding the adaptive threshold value, the M*L point local spread spectrum code data generated by the local spread spectrum code module is updated, and steps S5 to S8 are repeated to perform the next round of capture;

[0081] S9. In response to the maximum value among the M frequency domain energy K values ​​exceeding the adaptive threshold value, it indicates that the capture is successful; the folded code corresponding to the maximum value among the M frequency domain energy K values ​​is restored to a set of unfolded N-segment local spread spectrum original codes, and the high-frequency spread spectrum signal and the N-segment local spread spectrum original codes are respectively correlated to determine the position information of the aligned local spread spectrum code data, thereby realizing the folded capture of the direct sequence spread spectrum long code.

[0082] In some embodiments, S3, performing energy detection on the digital intermediate frequency signal, comprises:

[0083] The digital intermediate frequency signal contains noise. n =s n +w n ,s n To receive the signal, w n is the noise component, so that the decision component m n is selected as the cumulative sum of the received signal energy under the window length L, expressed as Make the decision component equal to the predetermined threshold T h After comparison, determine the group detection situation:

[0084] H0:m n <T h No grouping occurs

[0085] H1:m n ≥T h Appearance Group

[0086] where r n-k is the value of the digital intermediate frequency signal after delay k, For r n-k The conjugate value of , n and k are variables ranging from 0 to L-1.

[0087] In some embodiments, preprocessing and modulating the digital intermediate frequency signal into fixed-bit-width data to obtain preprocessed data includes:

[0088] The digital intermediate frequency signal is modulated into fixed-bit-width data, and the data is divided into M data blocks, each of which contains L data points, denoted as x i (n), where i = 0, 1, ..., M-1, n = 0, 1, ..., L-1, and each segment of data is stored sequentially using a register.

[0089] In some embodiments, the pre-processed data is subjected to digital down-conversion processing using an orthogonal carrier to obtain I / Q two-way orthogonal data, including:

[0090] The preprocessed data x i (n) Using the orthogonal carrier wave for digital down-conversion, we get:

[0091] Ix i (n) = x i (n)*sin(2π*f I *m*t s ),i=0,1,...,M-1,n=0,1,...,L-1;

[0092] Qx i (n) = x i (n)*cos(2π*f I *m*t s ),i=0,1,...,M-1,n=0,1,...,L-1,

[0093] Among them, Ix i (n) is I-channel orthogonal data, Qx i (n) is the Q-path orthogonal data, f I is the intermediate frequency carrier frequency at the transmitting end, t s is the sampling time, m is the mth sampling point, and the window length is L.

[0094] In some embodiments, S5, obtaining M*L point local spread spectrum code data generated by the local spread spectrum code module; performing local code staggered N code chips superposition on the local spread spectrum code data to obtain M*L folded codes, including:

[0095] The local spread spectrum code data is divided into M segments, each segment is L code elements long. i (n), denoted as:

[0096] r i (n)i=0,1,...,M-1,n=0,1,...L-1;

[0097] The local spread spectrum code data is superimposed by staggering the local code by N code chips to obtain M*L folding codes r o (n), denoted as: r o (n) = r i (n)+r i (n+1)+...+r i (n+N-1)n=0,1,...,L-1.

[0098] In some embodiments, S6, performing a partial matching correlation operation on the I / Q two-way orthogonal data and the folding code to obtain a partial matching correlation result between the folding code and the I / Q two-way orthogonal data, includes:

[0099] The I-path and Q-path each have an L-bit matching correlation operator. The partial matching correlation results of the folded code and the I / Q orthogonal data are stored in a two-dimensional register with M rows and L columns. Taking the I-path data as an example, each partial matching correlation result is recorded as:

[0100]

[0101]

[0102] …

[0103]

[0104] Ix i (n) is the I-way orthogonal data, and the COR(0,0) correlation value is the first segment length L r o (n) and the first segment r of length L o (n) The incoherent accumulation value of each corresponding phase; Similarly:

[0105]

[0106]

[0107] …

[0108]

[0109] The partial match correlation result storage value of the two-dimensional register is (C i，j =COR(i,j)):

[0110]

[0111] In some embodiments, S7, grouping the partial matching correlation results to obtain grouped matching correlation results, and performing frequency domain FFT conversion on each group of the grouped matching correlation results to obtain frequency domain data, including:

[0112] The grouping rule is: each column of correlation values ​​is divided into W groups, each group has P = M / W correlation values, and the corresponding correlation values ​​of each group differ by W intervals; the first group of a column is: P 0,i :C 0,i ,C w,i ,C 2w,i ,...,C w*(P-1),i ;P 0,i Represents the first grouping sequence in column i;

[0113] The matching correlation results after grouping have M*L data, of which M have the same phase difference; that is, the correlation values ​​obtained in the i-th column have the same phase;

[0114] From each column, select P data for FFT in the first clock cycle, select P data for FFT in the second clock cycle, ..., select P data for FFT in the Wth clock cycle; (I0, I1, ..., I w-1 )=fft(Pi,0 ,P i,1 ,...,P i,w-1 )、(Q0,Q1,...,Q w-1 )=fft(P i,0 ,P i,1 ,...,P i,w-1 );

[0115] After W clock cycles, the frequency domain data of each column of I / Q channels are non-coherently accumulated, and the accumulated value of the nth column of channel I is I n , the cumulative value of the nth column of Q path is Q n , add the square of the accumulated values ​​of the corresponding columns of the I / Q path to get the frequency domain energy K n , frequency domain energy K n =I n 2 +Q n 2 .

[0116] In some embodiments, the adaptive threshold value P=P max / P ave , where P max is the maximum peak energy of the I / Q two-way orthogonal data signal, P ave is the average energy of the I / Q two-channel orthogonal data.

[0117] Example 2

[0118] In a second aspect, this embodiment provides a folding capture device for a direct sequence spread spectrum long code, including a processor and a storage medium;

[0119] The storage medium is used to store instructions;

[0120] The processor is used to operate according to the instructions to execute the steps of the method according to embodiment 1.

[0121] In some embodiments, Figure 1As shown, a folding capture device for high dynamic direct sequence spread spectrum long code includes: A / D analog-to-digital conversion unit, energy detection module, data preprocessing module, mixing module, sampling clock control module, local spread spectrum code generation module, folding control module, partial matching correlation module, shift control module, grouping control module, FFT operation module, data accumulation buffer module, feedback control module, threshold judgment module, and code position determination module. After the input signal is processed by each module and correlated with the local code to obtain the power spectrum, a maximum peak value far greater than other power spectrum amplitudes will be obtained. The maximum peak value is compared with the threshold value. If it is greater than the threshold value, the received signal corresponding to the peak value is aligned with the local code phase at this time, and then the received signal is correlated with the corresponding local code involved in the folding, and then the peak value is calculated. The two-dimensional coordinates corresponding to the peak value can determine the input code phase and Doppler frequency deviation.

[0122] The sampling clock control module includes a local code and a received signal sent to a partial matching correlation module control clock, and a group extraction related data value FFT operation control clock. The clock for group extraction of related data is W times the clock of the partial matching correlation module, where W is the number of data groups.

[0123] The code phase determination module determines the accurate code phase of the received signal after successful capture. Since it has been determined that the correlation energy between the received signal and the local code obtained after overlapping is the largest, it is determined that the received signal must be aligned with a code phase of the multiple local codes participating in the overlap, so that the received signal and the local code before overlapping addition are correlated respectively to find the code phase with the largest correlation energy, that is, the code phase of the received signal is determined.

[0124] This embodiment folds the local spread spectrum code and performs partial matching correlation with the received signal, which is equivalent to detecting multiple code phases at the same time in one correlation, greatly reducing the average capture time while the implementation structure does not become more complicated, effectively solving the contradiction between capture efficiency and implementation complexity. At the same time, in order to solve the problem that the more FFT points, the greater the calculation amount and the longer the calculation time, the group FFT operation is performed, which reduces the complexity and greatly reduces resource consumption without affecting the signal envelope characteristics and FFT spectrum resolution accuracy.

[0125] The process of acquiring the spread spectrum signal in this embodiment includes the following steps:

[0126] 1) The folded capture method receives a high-frequency spread spectrum signal transmitted through a wireless channel, and transmits the received high-frequency spread spectrum signal to a radio frequency unit for down-conversion processing. After the down-conversion processing, the signal is converted into a digital intermediate frequency signal through an A / D conversion unit.

[0127] 2) By Figure 2The figure shows the structure of the energy detection module. The energy detection module includes a data cache module, a main control module, a delay window energy calculation module, a correlation window energy calculation module, and a symbol search module. The data cache module caches the input data waiting for detection, and outputs and stops the cached data when the start and end positions of the data packet are found; the main control module outputs corresponding control instructions (packet detection is valid, packet detection processing is completed, etc.) to the data cache module according to the current state of the system (such as the packet detection process, the packet detection process has been completed, etc.) and the output results of the symbol search module; the three modules of delay window energy calculation, correlation window energy calculation and symbol search constitute the main body of the delay correlation algorithm, complete the packet detection, and feed back to the main control module.

[0128] The digital intermediate frequency signal enters the energy detection module, which detects whether there is new data arriving on the burst transmission channel. Because the received signal contains noise, that is, r n =s n +w n ,s n To receive the signal, w n is the noise component, so that the decision component m n is selected as the cumulative sum of the received signal energy under the window length L, which can be expressed as Make the decision component equal to the predetermined threshold T h After comparison, determine the group detection situation:

[0129] H0:m n <T h No grouping occurs

[0130] H1:m n ≥T h Grouping appears.

[0131] 3) After the energy of the packet signal is detected, the digital intermediate frequency signal is sent to the data preprocessing module, which modulates the digital intermediate frequency signal into fixed-bit width data. At the same time, the data is divided into M data blocks, each of which contains L data points, denoted as x i (n), where i = 0, 1, ..., M-1, n = 0, 1, ..., L-1, and each segment of data is stored sequentially using a register.

[0132] 4) The pre-processed data is sent to the mixing module for digital down-conversion, the intermediate frequency signal is down-converted using an orthogonal carrier, and two channels of orthogonal data, I / Q, are generated.

[0133] Ix i (n) = x i (n)*sin(2π*f I *m*t s),i=0,1,...,M-1,n=0,1,...,L-1;

[0134] Qx i (n) = x i (n)*cos(2π*f I *m*t s ),i=0,1,...,M-1,n=0,1,...,L-1,

[0135] Among them, f I is the intermediate frequency carrier frequency at the transmitting end, t s is the sampling time, and m is the mth sampling point.

[0136] 5) The local spread spectrum code module generates M*L point data spread spectrum code data and stores them in the local spread spectrum code register in sequence. The spread spectrum code can be divided into M segments, each segment is L code elements long, which can be recorded as:

[0137] r i (n)i=0,1,...,M-1,n=0,1,...L-1;

[0138] 6) Send the generated local spread spectrum code data to the folding control module, and perform local code staggered N code chips superposition. The superimposed data can be recorded as: o (n) = r i (n)+r i (n+1)+...+r i (n+N-1)n=0,1,...,L-1. After the local spread spectrum code passes through the folding control module, M*L folding codes can be obtained. Figure 3 Schematic diagram of local spreading code folding operation.

[0139] 7) The I / Q two-way orthogonal data and the local code are transmitted to the partial matching correlation module for correlation operation. The I and Q paths each have an L-bit matching correlation operator. The partial matching correlation results of each code bit of the folded code can be stored in a two-dimensional register with M rows and L columns. Figure 4 This is a schematic diagram of partial matching related operations. Each result expression is recorded as:

[0140]

[0141] From COR(0,0), we can see that its correlation value is the first segment of length L r o (n) and the first segment x of length L i (n) The incoherent accumulation value of each corresponding phase.

[0142]

[0143]

[0144] …

[0145]

[0146] Then, the other storage values ​​of this two-dimensional register can be obtained in sequence as follows: i，j =COR(i,j)):

[0147]

[0148] 8) Send the COR register to the group control module, and divide the correlation values ​​of each column into W groups, each group has P = M / W correlation values, and the corresponding bit correlation values ​​of each group differ by W intervals. Take the first group of a column as an example: P i,0 :C i,0 ,C i,w ,C i,2w ,...,C i,w*(P-1) .

[0149] 9) After matching correlation, there are M*L data, of which M have the same phase difference. That is, the correlation values ​​obtained in the i-th column have the same phase. From each column, select P data for FFT in the first clock cycle, select P data for FFT in the second clock cycle, ..., select P data for FFT in the W-th clock cycle. (I0,I1,...,I w-1 )=fft(P i,0 ,P i,1 ,...,P i,w-1 )、(Q0,Q1,...,Q w-1 )=fft(P i,0 ,P i,1 ,...,P i,w-1 ). Figure 5 Schematic diagram of group FFT operation.

[0150] 10) After W clock cycles, the W groups of frequency domain data of each column of the I / Q channels are non-coherently accumulated, and the accumulated value of the nth column of the I channel is I n , the cumulative value of the nth column of Q path is Q n , add the square of the accumulated values ​​of the corresponding columns of the I / Q path to get the frequency domain energy K n , frequency domain energy K n =I n 2 +Q n 2 .

[0151] 11) The I / Q two-way orthogonal data passes through the threshold adaptive module to solve the calculation of the adaptive threshold value. The maximum value of the M accumulated K values ​​obtained in the maximum step 9 is compared with the threshold value. If it is found that the maximum value exceeds the threshold, it indicates that the code is successfully captured. Otherwise, the local spread spectrum code module is adjusted, the next round of spread spectrum code value is replaced, and steps (5) to (10) are repeated for the next round of capture until the capture is successful.

[0152] 12) After the code is captured successfully, the spread spectrum code corresponding to the maximum value is restored to the local unfolded code and correlated with the received signal to find the exact code element position.

[0153] The local folding code is sent to the I and Q paths respectively, and is partially matched and correlated with the in-phase received signal and the orthogonal received signal respectively.

[0154] The local code generated by the local spread spectrum code generation module is stored in a register, and the register can perform operations such as simultaneous reading and writing, reading first and then writing, or writing first and then reading.

[0155] The processing clock of selecting correlation values ​​by the grouped FFT is W times faster than the clock of directly processing the correlation values ​​by FFT.

[0156] After successful capture, the corresponding folded local pseudo code sequence is found for the highest peak, and the folded code is restored to N segments of unfolded local spread spectrum original code. The received signal is correlated with the N segments of local spread spectrum code to find the local spread spectrum code corresponding to the maximum value, thereby determining the code offset.

[0157] The above spread spectrum signal acquisition method is described below through a specific example.

[0158] like Figure 6 The example capture implementation structure diagram is shown in FIG. 1. After the module receives the signal through the A / D conversion unit 1001, it is sent to the energy detection unit 1002. When new data arrives on the burst transmission channel, it can be observed that the received energy signal will jump significantly.

[0159] The detected signal reception model can be expressed as: P s is the received signal power, d(t) represents data modulation, ω0 is the data carrier frequency, ω d represents the carrier Doppler frequency shift during the propagation process, and n(t) is Gaussian white noise. The received signal is divided into I / Q paths and sent to the mixing module 1003. The mixing uses an orthogonal signal with the same frequency as the data carrier. I (n) = r I (t)cos(ω0t),x Q (n) = r Q(t)sin(ω0t). The mixed signal is stored in the register, and 2048 signal code elements are stored in sequence. The 2048 signal code elements are divided into 64 groups of data, each with 64 data, that is, the length of the received signal sent to the partial matching correlation 1004 each time is 64 code elements.

[0160] The local spread spectrum code is generated by the linear feedback shift register 1005. The local spread spectrum pseudo code period is L=2 23 -1. Each time the generated local code is sequentially taken from 64*256 local codes for 4-fold folding, the generated accumulated folding code length is 64, a total of 256 folding codes, there will be three code element losses, but the capture results are sequentially sent to the partial matching correlator 1004 for correlation operation with the received signal.

[0161] The two input ends of the partial matching correlator 1004 are from the local folding code and the received signal, respectively, and the length is 64. When performing the correlation operation, the first segment x(0), x(1), ..., x(63) received signal and r(0), r(1), ..., r(63) local folding code are first input into the partial matching correlator at the same time, and then the local folding code is shifted by one code element in sequence. For example, the second correlation moment is x(0), x(1), ..., x(63) and r(1), r(2), ..., r(64) are correlated. When the local folding code r(64), r(65), ..., r(127) is shifted into the partial matching correlator, the received signal input x(64), x(64), ..., x(127) enters the corresponding position. The correlation result of each time is stored in the two-dimensional (64, 64) register 1006.

[0162] The two-dimensional register has 64 rows and 64 columns in total. Taking the first column as an example, when it is sent to the grouped FFT module 1007 for calculation, it is grouped into four groups, that is, (C 0,0 ,C 0,4 ,...,C 0,60 )、(C 0,1 ,C 0,5 ,...,C 0,61 )、(C 0,2 ,C 0,6 ,...,C 0,62 )、(C 0,3 ,C 0,7 ,...,C 0,63 ) perform 16-point FFT operations respectively, and accumulate the results. The FFT operation method for each column is the same.

[0163] A two-dimensional register can calculate 64 energy values. There is one two-dimensional register for each I / Q path, which can be recorded as: I0, I1, ..., I 63 ; Q0, Q1, ..., Q63 .

[0164] make The maximum peak value K is obtained by comparison, and the peak value K is compared with the decision threshold module 1008. If it is larger than the threshold, the capture is successful and the next pseudo code phase determination is carried out. If it is smaller than the threshold, the next round of local pseudo code search is carried out and the above operation is repeated.

[0165] The pseudo code phase determination module 1009 finds the corresponding local spread spectrum folding code through the maximum peak value, restores the local spread spectrum folding code to the local spread spectrum original code, and then performs correlation operations on the local spread spectrum original code and the received signal to find the maximum correlation peak value. At this time, the received signal is aligned with the local spread spectrum code phase, and then the Doppler frequency deviation and code phase value are determined. Figure 7 As shown, the determined Doppler frequency offset and code phase value are then tracked to achieve fine synchronization.

[0166] Example 3

[0167] In a third aspect, this embodiment provides a storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described in Example 1 are implemented.

[0168] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0169] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0170] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0171] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0172] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A folding acquisition method for direct sequence spread spectrum long code, characterized in that: include: S1, obtaining a received high frequency spread spectrum signal transmitted through a wireless channel; S2, performing down-conversion processing and A / D conversion on the high frequency spread spectrum signal to obtain a digital intermediate frequency signal; S3, performing energy detection on the digital intermediate frequency signal; S4, in response to detecting the packet signal energy, preprocessing and modulating the digital intermediate frequency signal into fixed bit width data to obtain preprocessed data; Performing digital down-conversion processing on the pre-processed data using an orthogonal carrier to obtain I / Q two-channel orthogonal data; S5, obtaining the M*L point local spread spectrum code data generated by the local spread spectrum code module; Perform local code staggering N code chips on the local spread spectrum code data to obtain M*L folded codes; S6, performing a partial matching correlation operation on the I / Q two-way orthogonal data and the folding code to obtain a partial matching correlation result between the folding code and the I / Q two-way orthogonal data, specifically including: The I path and Q path each have an L-bit matching correlation operator. The partial matching correlation results of the folded code and the I / Q orthogonal data are stored in a two-dimensional register with M rows and L columns. Each partial matching correlation result is recorded as: Ix i (n) is the I-channel orthogonal data, and the COR(0,0) correlation value is the first segment length L Ix i (n) and the first segment r of length L o (n) The incoherent accumulation value of each corresponding phase; Similarly: The partial match correlation result storage value of the two-dimensional register is (C i，j =COR(i,j)): S7, grouping the partial matching correlation results to obtain grouped matching correlation results, performing frequency domain FFT conversion on each group of the grouped matching correlation results to obtain frequency domain data; accumulating the frequency domain data of a set period to obtain M frequency domain energies K; S8, comparing the maximum value of the M frequency domain energies K with the adaptive threshold value; In response to the maximum value of the M frequency domain energies K not exceeding the adaptive threshold value, the M*L point local spread spectrum code data generated by the local spread spectrum code module is updated, and steps S5 to S8 are repeated to perform the next round of capture; S9. In response to the maximum value among the M frequency domain energy K values ​​exceeding the adaptive threshold value, it indicates that the capture is successful; the folded code corresponding to the maximum value among the M frequency domain energy K values ​​is restored to a set of unfolded N-segment local spread spectrum original codes, and the high-frequency spread spectrum signal and the N-segment local spread spectrum original codes are respectively correlated to determine the position information of the aligned local spread spectrum code data, thereby realizing the folded capture of the direct sequence spread spectrum long code.

2. The folding acquisition method of direct sequence spread spectrum long code according to claim 1, characterized in that: S3, performing energy detection on the digital intermediate frequency signal, including: The digital intermediate frequency signal contains noise. n =s n +w n ,s n To receive the signal, w n is the noise component, so that the decision component m n is selected as the cumulative sum of the received signal energy under the window length L, expressed as Make the decision component equal to the predetermined threshold T h After comparison, determine the group detection situation: H0:m n <T h No grouping occurs H1:m n ≥T h Appearance Group where r n-k is the value of the digital intermediate frequency signal after delay k, For r n-k The conjugate value of , n and k are variables ranging from 0 to L-1.

3. The folding acquisition method of direct sequence spread spectrum long code according to claim 1, characterized in that: The digital intermediate frequency signal is pre-processed and modulated into fixed-bit-width data to obtain pre-processed data, including: The digital intermediate frequency signal is modulated into fixed-bit-width data, and the data is divided into M data blocks, each of which contains L data points, denoted as x i (n), where i = 0, 1, ..., M-1, n = 0, 1, ..., L-1, and each segment of data is stored sequentially using a register.

4. The folding acquisition method of direct sequence spread spectrum long code according to claim 1, characterized in that: The pre-processed data is subjected to digital down-conversion processing using an orthogonal carrier to obtain I / Q two-way orthogonal data, including: The preprocessed data x i (n) Using the orthogonal carrier wave for digital down-conversion, we get: Ix i (n)=x i (n)*sin(2π*f I *m*t s ),i=0,1,...,M-1,n=0,1,...,L-1; Qx i (n)=x i (n)*cos(2π*f I *m*t s ),i=0,1,...,M-1,n=0,1,...,L-1, Among them, Ix i (n) is the I-channel orthogonal data, Qx i (n) is the Q-path orthogonal data, f I is the intermediate frequency carrier frequency at the transmitting end, t s is the sampling time, m is the mth sampling point, and the window length is L.

5. The folding acquisition method of direct sequence spread spectrum long code according to claim 1, characterized in that: S5, obtaining the M*L point local spread spectrum code data generated by the local spread spectrum code module; The local spread spectrum code data is superimposed with local codes staggered by N chips to obtain M*L folding codes, including: The local spread spectrum code data is divided into M segments, each segment is L code elements long. i (n), denoted as: r i (n)i=0,1,...,M-1,n=0,1,...L-1; The local spread spectrum code data is superimposed by staggering the local code by N code chips to obtain M*L folding codes r o (n), denoted as: r o (n) = r i (n)+r i (n+1)+...+r i (n+N-1)n=0,1,...,L-1.

6. The folding acquisition method of direct sequence spread spectrum long code according to claim 1, characterized in that: S7, grouping the partial matching correlation results to obtain grouped matching correlation results, and performing frequency domain FFT conversion on each group of the grouped matching correlation results to obtain frequency domain data, including: The grouping rule is: each column of correlation values ​​is divided into W groups, each group has P = M / W correlation values, and the corresponding correlation values ​​of each group differ by W intervals; the first group of a column is: P 0,i :C 0,i ,C w,i ,C 2w,i ,...,C w*(P-1),i ;P 0,i Represents the first grouping sequence in column i; The matching correlation results after grouping have M*L data, of which M have the same phase difference; that is, the correlation values ​​obtained in the i-th column have the same phase; From each column, select P data for FFT in the first clock cycle, select P data for FFT in the second clock cycle, ..., select P data for FFT in the Wth clock cycle; (I0, I1, ..., I w-1 )=fft(P i,0 ,P i,1 ,...,P i,w-1 )、(Q0,Q1,...,Q w-1 )=fft(P i,0 ,P i,1 ,...,P i,w-1 ); After W clock cycles, the frequency domain data of each column of I / Q channels are non-coherently accumulated, and the accumulated value of the nth column of channel I is I n , the cumulative value of the nth column of Q path is Q n , add the square of the accumulated values ​​of the corresponding columns of the I / Q path to get the frequency domain energy K n , frequency domain energy K n =I n 2 +Q n 2 .

7. The folding acquisition method of direct sequence spread spectrum long code according to claim 1, characterized in that: The adaptive threshold value P=P max / P ave , where P max is the maximum peak energy of the I / Q two-way orthogonal data signal, P ave is the average energy of the I / Q two-channel orthogonal data.

8. A folding acquisition device for direct sequence spread spectrum long code, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 7.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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