A ranging pseudo code design method and system

Abstract

The present invention relates to the field of digital communication and ranging technology, and in particular to a ranging pseudocode design method and system, the ranging pseudocode design method comprising: based on instructions and parameters, generating multiple pseudocode sequences, selecting the pseudocode sequence that meets a first preset condition to perform a chip flip operation to generate multiple bit-balanced pseudocode sequences, and sending the multiple bit-balanced pseudocode sequences into a first set, wherein the instruction represents the pseudocode type and the parameter represents the order; sequentially evaluating the performance index of the bit-balanced pseudocode sequence in the first set, selecting the bit-balanced pseudocode sequence whose performance index meets a second preset condition as the target pseudocode sequence; verifying whether the performance index of the target pseudocode sequence is better than a reference value, and if so, using it as a ranging pseudocode. The present invention is conducive to eliminating the main lobe noise generated during carrier modulation, and is conducive to increasing the capture and tracking accuracy of the ranging pseudocode.

Description

Technical Field

[0001] The invention belongs to the technical field of digital communication and ranging, and in particular relates to a ranging pseudo code design method and system. Background Art

[0002] Compared with microwaves, lasers have a smaller divergence angle and more concentrated energy. Therefore, lasers can achieve longer-distance communication transmission and can be applied to the integrated technology of ranging and communication. The integrated technology of ranging and communication has the characteristics of alleviating the shortage of spectrum resources, reducing power consumption, and reducing system volume. This technology is widely used in atmospheric science, satellite navigation and positioning, military, space gravitational wave detection and deep space exploration. With the deepening of scientific research, higher requirements have been put on the ranging accuracy, precision and bit error rate of the integrated technology of inter-satellite ranging and communication. Taking space gravitational wave detection as an example, it is necessary to achieve an absolute ranging accuracy of less than 1m under the conditions of a distance of millions of km and a receiving power of pW. At present, the integration of inter-satellite ranging and communication is based on the principle of spread spectrum communication. The ranging pseudo code sequence is XOR-combined with the communication data code, and modulated in the carrier for transmission to achieve ranging and communication.

[0003] The integration of intersatellite laser ranging and communication involves many technologies, and the ranging accuracy requirements are high. Taking space gravitational wave detection as an example, the intersatellite ranging communication distance under this background is relatively long. Therefore, the optical power at the receiving end is extremely low and the space transmission environment is complex. In order to reduce the influence of modulation on space gravitational wave detection, for the mixed code obtained by combining the ranging pseudocode sequence with the communication data code, the modulation depth of the mixed code in the laser phase is only 0.1rad. Therefore, if the ranging pseudocode sequence is not optimized, the detection results will be affected. For example, the ranging pseudocode sequence with poor correlation will have a high false alarm rate and cause multipath interference, affecting the capture and tracking of the ranging pseudocode sequence. Secondly, when the ranging pseudocode sequence is combined with the communication data code, it will cause the code chip to flip, and when modulated to the carrier, it will generate main lobe noise, affecting the ranging accuracy. Therefore, it is necessary to optimize the ranging pseudocode sequence to improve its overall robustness to adapt to intersatellite link transmission under complex noise background.

[0004] In response to the above needs, there are currently the following solutions at home and abroad:

[0005] Laser Interferometer Space Antenna (LISA) is a gravitational wave detection program jointly conducted by NASA and the European Space Agency. The program team studied the integration of ranging and communication technology in the context of space gravitational wave detection technology and obtained the following conclusions: the combination of ranging pseudocode sequence and communication data code will cause code chip flipping, which will generate main lobe noise after carrier modulation;

[0006] Deng Rujie et al. compared the auto / cross-correlation of m-sequence, Gold sequence and Weil sequence in the journal "Ground Electronics Verification of Intersatellite Laser Ranging in Taiji Project", selected Weil sequence as the ranging code, and conducted electronic and optical tests. This method can quickly obtain the pseudo-code sequence, but there are still some problems, such as: only considering the auto / cross-correlation of the pseudo-code sequence; not considering the chip flipping effect caused by the combination of the pseudo-code sequence and the communication data code;

[0007] A patent application with publication number CN117375697A and publication date January 9, 2024 proposes an inter-satellite ranging and communication modulation method and device, which can generate ranging communication codes with different code rates and modulation depths. This method can realize ground verification of inter-satellite communication transmission and absolute distance measurement, but there are still some problems such as: the pseudo code has not been optimized and designed.

[0008] In summary, the integrated technology of inter-satellite ranging and communication is different from the existing single inter-satellite communication technology or single ranging technology. The integrated technology of inter-satellite ranging and communication has higher requirements on the design of ranging pseudo code sequence. Although some existing literatures and patents have proposed certain solutions to these problems, the problems of noise and ranging accuracy have not been solved. Therefore, it is necessary to optimize the design of ranging pseudo code. Summary of the invention

[0009] In view of this, the present invention aims to provide a ranging pseudo code design method and system, which are conducive to eliminating the main lobe noise generated during carrier modulation and to increasing the capture and tracking accuracy of the ranging pseudo code.

[0010] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0011] On the one hand, an embodiment of the present invention provides a ranging pseudo code design method, comprising: generating multiple pseudo code sequences based on instructions and parameters, selecting a pseudo code sequence that meets a first preset condition to perform a chip flip operation to generate many bit-balanced pseudocode sequences, and send multiple bit-balanced pseudocode sequences into a first set, wherein the instruction represents the pseudocode type and the parameter represents the order; the performance indicators of the bit-balanced pseudocode sequences in the first set are evaluated in turn, and the bit-balanced pseudocode sequences whose performance indicators meet the second preset conditions are selected as target pseudocode sequences; verify whether the performance indicator of the target pseudocode sequence is better than the reference value, and if so, use it as the ranging pseudocode; wherein the performance indicators at least include: odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd mutual correlation and even mutual correlation.

[0012] Furthermore, the pseudocode types include: m-sequence, Gold sequence and Weil sequence, and the pseudocode sequence is a bipolar even sequence.

[0013] Further, selecting a pseudo code sequence that meets the first preset condition to perform a chip flipping operation includes: sequentially dividing each pseudo code sequence into N subsequences, each subsequence including n code chips, n code is: when the ranging pseudocode sequence is combined with the communication data code, the number of chips of the ranging pseudocode sequence corresponding to each chip of the communication data code; for any pseudocode sequence, if the sum of the chips of each subsequence of the pseudocode sequence is less than or equal to a preset value T0, then the first preset condition is met, and a chip flipping operation is performed on the pseudocode sequence that meets the first preset condition; if the sum of the chips of any subsequence of the pseudocode sequence is greater than the preset value T0, then the first preset condition is not met, and the pseudocode sequence that does not meet the first preset condition is eliminated.

[0014] Further, performing a chip flipping operation on a pseudocode sequence that satisfies the first preset condition includes: for each pseudocode sequence that satisfies the first preset condition, calculating the sum of the chips of each subsequence of the pseudocode sequence; if the sum of the chips of the subsequence is a positive number, the positive number is , then mark all positive chips in the subsequence as +1, and arbitrarily select The number of chips is flipped to make the sum of the chips of the subsequence 0, and the subsequences are combined in the order before segmentation to generate a bit-balanced pseudocode sequence; if the sum of the chips of the subsequence is a negative number, the negative number is - , then mark all negative chips in the subsequence as -1, and arbitrarily select a The number of chips are flipped so that the sum of the chips of the subsequence is 0, and the subsequences are combined in the order before segmentation to generate a bit-balanced pseudocode sequence.

[0015] Further, selecting a bit-balanced pseudocode sequence whose performance index meets the second preset condition as the target pseudocode sequence includes: for the bit-balanced pseudocode sequences in the first set, calculating the even autocorrelation value a, the odd autocorrelation value b and the maximum spectrum amplitude value c of each bit-balanced pseudocode sequence in turn, assigning a a first weight z1, assigning b a second weight z2, and assigning c a third weight z3, wherein z1+z2+z3=1, and obtaining the sum y of z1a, z2b and z3c 总 , calculate the y of each bit-balanced pseudocode sequence in the first set 总 The average value y 平均 , will be less than y 平均 of y 总 The corresponding bit-balanced pseudocode sequence is sent to the fourth set; the maximum clique model is used to evaluate the odd / even mutual correlation of the bit-balanced pseudocode sequence in the fourth set, and the target pseudocode sequence is obtained.

[0016] Further, using the maximum clique model to perform odd / even mutual correlation evaluation on the bit-balanced pseudocode sequences in the fourth set includes: calculating the even mutual correlation value e and the odd mutual correlation value f between different bit-balanced pseudocode sequences in the fourth set, and establishing the even mutual correlation matrix R based on e e , based on f, establish the odd correlation matrix R f The total number of bit-balanced pseudocode sequences in the fourth set is N3, and the search for R e The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial even cross-correlation threshold T e , using T e R e Make a judgment and get less than or equal to T e The maximum connected set A e And the corresponding pseudo code number M e ; Traverse and search R f The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial odd cross-correlation threshold T f , using T f R f Make a judgment and get less than or equal to T f The maximum connected set A f And the corresponding pseudo code number M f ; Judge M e and M f Are they all greater than or equal to the target code number M0? If so, then jump out of the iteration; if not, then T e Add 1, T f Add 1 and continue to use T e R e Make a decision and adopt T f R f Make a judgment and execute subsequent steps until M f ≥M0 and M e ≥M0, then jump out of iteration; get A e With A f The number of nodes with the same node number M ef , judge M ef Is it greater than or equal to the target code number M0? If so, then jump out of the iteration; if not, then T e Add 1, T f Add 1 and continue the loop until M ef ≥M0, then the iteration is jumped out; when the iteration is jumped out, A e or A f The corresponding bit-balanced pseudocode sequence is used as the target pseudocode sequence.

[0017] Furthermore, the even correlation matrix R is established based on e e And establish the odd correlation matrix R based on f fIncluding: Based on e, establish the even correlation matrix R according to formula 1 e , based on f, establish the odd correlation matrix R according to formula 1 f , Formula 1 is as follows:

[0018] ;

[0019] Among them, b n-1,n is the even mutual correlation value e or the odd mutual correlation value f between the n-1th bit balanced sequence and the nth bit balanced sequence, n=N3.

[0020] Furthermore, the reference value is: an average value of each evaluation index of the C / A code in the L1 frequency band in the global positioning system signal standard.

[0021] Furthermore, the method also includes: if the performance indicator of the target pseudo code sequence is worse than the reference value, returning to the step of generating a bit-balanced pseudo code sequence.

[0022] On the other hand, an embodiment of the present invention provides a ranging pseudocode design system, which is used to execute the above-mentioned ranging pseudocode design method. The system includes: a balanced code module, which generates multiple pseudocode sequences based on instructions and parameters, selects a pseudocode sequence that meets a first preset condition to perform a code chip flip operation to generate multiple bit balanced pseudocode sequences, and sends the multiple bit balanced pseudocode sequences into a first set, wherein the instruction represents the pseudocode type and the parameter represents the order; a preferred module, which is used to evaluate the performance indicators of the bit balanced pseudocode sequences in the first set in turn, and selects the bit balanced pseudocode sequence whose performance indicator meets the second preset condition as the target pseudocode sequence; a verification module, which is used to verify whether the performance indicator of the target pseudocode sequence is better than the reference value, and if so, it is used as the ranging pseudocode; wherein the performance indicators include: odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd mutual correlation and even mutual correlation.

[0023] Compared with the prior art, the invention can achieve the following beneficial effects:

[0024] In the integrated ranging and communication technology, unbalanced ranging pseudocodes will provide narrowband interference, increase the internal interference of the system, and generate main lobe noise, affecting the phase extraction accuracy. The pseudocode sequence design method provided by the present invention can achieve balance within the specified ranging pseudocode code number; the balanced code module provided by the present invention is based on the pseudocode generation principle and can generate three commonly used types of pseudocode sequences, that is, various types of pseudocode sequences can be flexibly generated, and the order of the pseudocode sequence can be flexibly controlled, and the generated multiple pseudocode sequences provide a candidate basis for subsequent optimal design.

[0025] The bit-balanced pseudocode sequence obtained by screening the pseudocode sequence has the following advantages: based on the spread spectrum communication principle, it ensures that the subsequences of the ranging pseudocode combined with each communication data code are bit-balanced subsequences, so that the noise and error caused by code chip flipping can be effectively eliminated.

[0026] In addition, by evaluating the performance indicators of the bit-balanced pseudocode sequence, such as the odd / even autocorrelation, odd / even cross-correlation, and maximum spectrum range, a bit-balanced pseudocode sequence with better comprehensive performance can be obtained as the target pseudocode sequence. The comprehensive performance specifically refers to the capture performance, tracking performance, anti-interference performance, and compatibility. When evaluating the various performance indicators of the bit-balanced pseudocode sequence, the target code number can be flexibly changed, as well as the weight of the even autocorrelation, the weight of the odd autocorrelation, and the weight of the maximum spectrum amplitude can be flexibly changed, and then the corresponding target pseudocode sequence can be obtained according to the needs.

[0027] When evaluating various performance indicators of bit-balanced pseudocode sequences, a path optimization strategy is adopted, which can effectively reduce the complexity and number of calculations of various indicators in the performance indicator evaluation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0029] Figure 1 A flow chart of the ranging pseudo code design method according to an embodiment of the present invention;

[0030] Figure 2 A graph showing the computational complexity and number of calculations of various performance indicators involved in creating embodiments of the present invention;

[0031] Figure 3 A schematic diagram of a connection relationship of a mutual correlation threshold decision in an example of an embodiment of the present invention;

[0032] Figure 4 A schematic flow chart of the steps of generating a bit-balanced pseudocode sequence according to an embodiment of the present invention;

[0033] Figure 5 A flow chart of the preferred steps described in the embodiments of the present invention;

[0034] Figure 6 A schematic diagram of the structure of the ranging pseudo code design system described in an embodiment of the present invention.

[0035] Explanation of the reference numerals: 10, balancing code module; 20, optimization module; 30, verification module. DETAILED DESCRIPTION

[0036] The problem that the ranging pseudocode sequence will cause chip flipping when combined with the communication data code is analyzed as follows: the ranging pseudocode sequence and the communication data code are both binary codes, which can be -1 or 1, and the two are combined as an XOR combination. For example, in the first case, the ranging pseudocode is -1, the communication data code is -1, and the XOR is -1; in the second case, the ranging pseudocode is -1, the communication data code is 1, and the XOR is 1; in the second case, the ranging pseudocode is 1, the communication data code is 1, and the XOR is -1. Among them, the ranging pseudocode flips in the second and third cases. If the bit balance design is carried out, although the ranging pseudocode will also flip when the XOR is combined, it can be guaranteed that the number of flips from 1 to -1 and the number of flips from -1 to 1 are equal, then the overall balance can alleviate the noise and error caused by chip flipping.

[0037] It should be noted that bit balance means that the number of chips that are 1 is the same as the number of chips that are -1.

[0038] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0039] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0040] In the description of the invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0041] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0042] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0043] refer to Figure 1 On the one hand, an embodiment of the present invention provides a ranging pseudo code design method, comprising: generating multiple pseudo code sequences based on instructions and parameters, selecting a pseudo code sequence that meets a first preset condition to perform a chip flip operation to generate many bit-balanced pseudocode sequences, and send multiple bit-balanced pseudocode sequences into a first set, wherein the instruction represents the pseudocode type and the parameter represents the order; the performance indicators of the bit-balanced pseudocode sequences in the first set are evaluated in turn, and the bit-balanced pseudocode sequences whose performance indicators meet the second preset conditions are selected as target pseudocode sequences; verify whether the performance indicator of the target pseudocode sequence is better than the reference value, and if so, use it as the ranging pseudocode; wherein the performance indicators at least include: odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd mutual correlation and even mutual correlation.

[0044] It should be noted that the ranging pseudo code design method provided in the embodiment of the present invention can be implemented by a ranging pseudo code design system. Specifically, refer to Figure 1 and Figure 6 The ranging pseudo code design system includes a balanced code module 10, a preferred module 20 and a verification module 30. The balanced code module 10 is used to generate a bit-balanced pseudo code sequence of a specific pseudo code type and a specific order. The preferred module 20 is used to evaluate the performance index of the bit-balanced pseudo code sequence to obtain a target pseudo code sequence with better performance index. The verification module 30 is used to further verify the performance index of the target pseudo code sequence generated in the previous step, and the verified target pseudo code sequence is used as the ranging pseudo code.

[0045] Furthermore, the pseudocode types include: m-sequence, Gold sequence and Weil sequence, and the pseudocode sequence is a bipolar even sequence. M-sequence, Gold sequence and Weil sequence are all common pseudocode types. The design of pseudocode sequence based on the three pseudocode types can provide more selection basis for subsequent optimization and evaluation.

[0046] Among them, the m sequence is generated by the i-level feedback shift register, that is, i is the order of the m sequence, and the feedback characteristic polynomial corresponding to the m sequence can be as follows: ,in, , , … is the feedback coefficient, where and are all 1, and the remaining feedback coefficients are 0 or 1 according to the feedback polynomial, where 0 does not participate in feedback and 1 participates in feedback. By determining the feedback coefficient, the m sequence can be determined. The period of the m sequence is .

[0047] Gold sequences are generated by two m sequences of the same length. The two m sequences used to generate the Gold sequence usually have different initial states or different feedback polynomials to ensure good cross-correlation between the two. A series of new Gold sequences can be generated by performing an XOR operation on the two m sequences. Specifically, for any given two m sequences, multiple Gold sequences can be generated by performing an XOR operation on each possible phase offset of the two m sequences. Multiple Gold sequences include the two original m sequences and their XOR results. Two m sequences of the same length can generate a total of Gold sequence.

[0048] The Weil sequence is based on the XOR addition of two sets of Legendre sequences of the same length. The two sets of Legendre sequences have the same characteristic expression, with only a certain phase difference. By changing the size of the phase difference, different Weil sequences can be combined. The characteristic expression of the Weil sequence is as follows:

[0049] ;

[0050] Where, mod is the modulo operation; w is the phase difference between two Legendre sequences; L(k) and L(k+w) are two Legendre sequences with a phase difference of w;

[0051] The characteristic expression of Legendre sequence L(k) is:

[0052] .

[0053] It can be understood that multiple pseudocode sequences can be generated according to different parameters and different instructions, and each pseudocode sequence can enter the subsequent optimization and evaluation steps in turn.

[0054] After generating multiple pseudo code sequences, further, a pseudo code sequence that meets the first preset condition is selected to perform a chip flipping operation, specifically including: dividing each pseudo code sequence into N subsequences in turn, each subsequence includes n code chips, n codeis: when the ranging pseudocode sequence is combined with the communication data code, the number of chips of the ranging pseudocode sequence corresponding to each chip of the communication data code; for any pseudocode sequence, if the sum of the chips of each subsequence of the pseudocode sequence is less than or equal to a preset value T0, then the first preset condition is met, and a chip flipping operation is performed on the pseudocode sequence that meets the first preset condition; if the sum of the chips of any subsequence of the pseudocode sequence is greater than the preset value T0, then the first preset condition is not met, and the pseudocode sequence that does not meet the first preset condition is eliminated.

[0055] Further, performing a chip flipping operation on a pseudocode sequence that satisfies the first preset condition includes: for each pseudocode sequence that satisfies the first preset condition, calculating the sum of the chips of each subsequence of the pseudocode sequence; if the sum of the chips of the subsequence is a positive number, the positive number is , then mark all positive chips in the subsequence as +1, and arbitrarily select The number of chips is flipped to make the sum of the chips of the subsequence 0, and the subsequences are combined in the order before segmentation to generate a bit-balanced pseudocode sequence; if the sum of the chips of the subsequence is a negative number, the negative number is - , then mark all negative chips in the subsequence as -1, and arbitrarily select a The number of chips are flipped so that the sum of the chips of the subsequence is 0, and the subsequences are combined in the order before segmentation to generate a bit-balanced pseudocode sequence.

[0056] In the design method provided by the invention, the acquisition performance, tracking performance, anti-interference performance and compatibility of the bit-balanced pseudocode sequence are comprehensively considered, an evaluation standard is established, and the best bit-balanced pseudocode sequence in the first set is selected. Figure 2 , Figure 2 In the calculation complexity corresponding to different performance indicators, the specific value of N is the same, O represents the big O sign function, the specific value of M in the number of calculations corresponding to different performance indicators is the same, and the performance indicators may include five indicators: odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd mutual correlation, and even mutual correlation. It can be seen that when the number of sequences to be selected in the candidate code family is large, the number of calculations of odd mutual correlation and even mutual correlation is very large. In order to reduce the difficulty of optimization and the number of calculations, the optimization module 20 provided in the embodiment of the present invention adopts a "divide and conquer" optimization strategy, that is, the three indicators of odd autocorrelation, even autocorrelation and maximum spectrum amplitude are used as the first step of evaluation, and preliminary screening is performed to reduce the number of sequences in the candidate code family, and then the second step of odd mutual correlation and even mutual correlation is evaluated. This is conducive to reducing the amount of calculation and reducing the difficulty of optimization.

[0057] The specific steps of the first and second evaluation steps are explained below.

[0058] In some embodiments of the present invention, a bit-balanced pseudocode sequence whose performance index meets the second preset condition is selected as a target pseudocode sequence, specifically comprising: for the bit-balanced pseudocode sequences in the first set, the even autocorrelation value a, the odd autocorrelation value b and the maximum spectrum amplitude value c of each bit-balanced pseudocode sequence are calculated in turn, a is assigned a first weight z1, b is assigned a second weight z2, and c is assigned a third weight z3, wherein z1+z2+z3=1, and the sum y of z1a, z2b and z3c is obtained. 总 , calculate the y of each bit-balanced pseudocode sequence in the first set 总 The average value y 平均 , will be less than y 平均 of y 总 The corresponding bit-balanced pseudocode sequence is sent to the fourth set, thus completing the first step of evaluation; the maximum clique model is used to evaluate the odd / even mutual correlation of the bit-balanced pseudocode sequence in the fourth set, that is, the second step of evaluation is performed, and the target pseudocode sequence is obtained.

[0059] The specific method of the second step evaluation is described in detail below.

[0060] Further, using the maximum clique model to perform odd / even mutual correlation evaluation on the bit-balanced pseudocode sequences in the fourth set includes: calculating the even mutual correlation value e and the odd mutual correlation value f between different bit-balanced pseudocode sequences in the fourth set, and establishing the even mutual correlation matrix R based on e e , based on f, establish the odd correlation matrix R f The total number of bit-balanced pseudocode sequences in the fourth set is N3, and the search for R e The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial even cross-correlation threshold T e , using T e R e Make a judgment and get less than or equal to T e The maximum connected set A e And the corresponding pseudo code number M e ; Traverse and search R f The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial odd cross-correlation threshold T f , using T f R f Make a judgment and get less than or equal to T f The maximum connected set A f And the corresponding pseudo code number M f ; Judge M e and M f Are they all greater than or equal to the target code number M0? If so, then jump out of the iteration; if not, then T e Add 1, Tf Add 1 and continue to use T e R e Make a decision and adopt T f R f Make a judgment and execute subsequent steps until M f ≥M0 and M e ≥M0, then jump out of iteration; get A e With A f The number of nodes with the same node number M ef , judge M ef Is it greater than or equal to the target code number M0? If so, then jump out of the iteration; if not, then T e Add 1, T f Add 1 and continue the loop until M ef ≥M0, then the iteration is jumped out; when the iteration is jumped out, A e or A f The corresponding bit-balanced pseudocode sequence is used as the target pseudocode sequence.

[0061] Furthermore, the even correlation matrix R is established based on the even correlation value e e And establish the odd correlation matrix R based on the odd correlation value f f Including: Based on e, establish the even correlation matrix R according to formula 1 e , based on f, establish the odd correlation matrix R according to formula 1 f , Formula 1 is as follows:

[0062] ;

[0063] Among them, b n-1,n is the even mutual correlation value e or the odd mutual correlation value f between the n-1th bit balanced sequence and the nth bit balanced sequence, n=N3.

[0064] It should be noted that the odd mutual correlation and the even mutual correlation are used as the second step of evaluation, and the maximum clique model is used for evaluation, and the bit-balanced pseudocode sequence with the best performance is obtained as the target pseudocode sequence, and the target pseudocode sequence can be sent to the second set. Finally, the performance of the bit-balanced pseudocode sequence in the second set is verified. Specifically, the five performance index values ​​of the bit-balanced pseudocode sequence in the second set are compared with the reference values ​​saved by the computer to verify whether the performance of the bit-balanced pseudocode sequence in the second set is qualified.

[0065] The preferred module 20 uses the maximum clique model in graph theory to screen the bit-balanced pseudocode sequences in the fourth set to obtain the required ranging pseudocode, and in the preferred module 20, the weights of the evaluation indicators and the target number of codes can be flexibly changed to obtain the required ranging pseudocode according to needs. The "divide and conquer" path optimization strategy can effectively reduce the computational complexity and number of calculations of each evaluation indicator.

[0066] Furthermore, the reference value is: an average value of each evaluation index of the C / A code in the L1 frequency band in the global positioning system signal standard.

[0067] Furthermore, the method also includes: if the performance indicator of the target pseudo code sequence is worse than the reference value, returning to the step of generating a bit-balanced pseudo code sequence.

[0068] The performance indicators such as odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd cross-correlation and even cross-correlation are introduced as follows:

[0069] The autocorrelation of the ranging pseudocode sequence is a statistic that measures the similarity of a sequence at different time points. A ranging pseudocode sequence with excellent performance needs to have good autocorrelation. Non-zero sidelobes of the autocorrelation function will lead to false alarm events, affecting the capture performance, tracking performance and multipath interference performance of the ranging pseudocode sequence. Secondly, the autocorrelation includes odd autocorrelation, because in gravitational wave detection, the ranging pseudocode will flip after the ranging pseudocode sequence is XORed with the communication data code, increasing the first sidelobe and causing ranging deviation. Specifically, the expressions of odd autocorrelation and even autocorrelation of the ranging pseudocode sequence are as follows:

[0070] ;

[0071] Among them, a represents the ranging pseudo code sequence, N is the sequence length of the ranging pseudo code sequence, τ is the code chip shift value, i=0~N or i=(N-τ)~(N-1).

[0072] The maximum spectrum amplitude is the maximum absolute value obtained after Fourier transform of the ranging pseudo code sequence. The maximum spectrum amplitude can reflect the robustness of the ranging pseudo code sequence to narrowband interference. The larger the maximum spectrum amplitude, the weaker the robustness of the ranging pseudo code sequence against narrowband interference. On the contrary, the stronger the robustness of the ranging pseudo code sequence against narrowband interference. The expression of the maximum spectrum amplitude is:

[0073] ;

[0074] Wherein, a(n) represents a pseudo code sequence of length n, and FT is Fourier transform.

[0075] The cross-correlation of the ranging pseudo code sequence is a statistic that measures the similarity between two sequences and is used to compare the similarity between different ranging pseudo code sequences. Like the autocorrelation, a code family with excellent performance needs to have good cross-correlation. Non-zero cross-correlation function sidelobes will also lead to false alarm events, affecting the acquisition performance, tracking performance, and multipath interference performance of the ranging pseudo code sequence and resulting in poor compatibility. The expression of the odd / even cross-correlation of the ranging pseudo code sequence is:

[0076] ;

[0077] Where a and b represent two different ranging pseudo code sequences, N is the sequence length, and τ is the chip shift value.

[0078] The maximum clique model is introduced as follows: Based on graph theory, the ranging pseudocode sequence and its cross-correlation function are described. By iteratively searching for the maximum clique, the global optimal solution can be obtained in theory, and the required optimal bit-balanced pseudocode sequence can be obtained. For example, in a pseudocode family C, each pseudocode a is regarded as a node in the graph. There are n pseudocodes in total, which can be recorded as a1, a2, ...an, respectively. The cross-correlation performance value of a1 and a2 is b 1、2 It can be regarded as the distance between node a1 and node a2, and then the following cross-correlation performance matrix can be established:

[0079] ;

[0080] On the basis of the mutual correlation performance matrix, a threshold is set to judge whether two nodes are connected, so as to obtain the corresponding ranging pseudo code sequence.

[0081] For example, a pseudo code family has 5 pseudo code sequences, the threshold can be set to 350, and its cross-correlation matrix is ​​as follows:

[0082] ;

[0083] refer to Figure 3 , Figure 3 The different circles in the above example represent different pseudo code sequences in the five pseudo code sequences. The circle with a value of 1 represents the first pseudo code sequence in the five pseudo code sequences, and the circle with a value of 2 represents the second pseudo code sequence in the five pseudo code sequences. By analogy, the numbers on the bidirectional arrows between two different pseudo code sequences represent the cross-correlation performance values ​​of the two pseudo code sequences. It should be noted that Figure 3 Only the cross-correlation performance values ​​less than the threshold value 350 are marked, that is, the cross-correlation performance values ​​that meet the requirements. According to the cross-correlation matrix provided in the above example and Figure 3It can be seen that among the five pseudocode sequences, the cross-correlation between the fifth pseudocode sequence and the other pseudocode sequences except the first pseudocode sequence does not meet the requirements. Therefore, the remaining four pseudocode sequences except the fifth pseudocode sequence meet the requirements. Except for the fifth pseudocode sequence, the rest are interconnected nodes, that is, they are pseudocode sequences that meet the cross-correlation requirements.

[0084] The following specific embodiments are provided for the ranging pseudo code design method provided by the present invention.

[0085] Example 1

[0086] refer to Figure 4 , the steps for generating a bit-balanced pseudocode sequence are as follows:

[0087] Step 1: Input instructions and parameters to select the type and order of pseudo code to design the pseudo code sequence;

[0088] Step 2: Generate the specified bipolar pseudocode sequence family according to the instructions and parameters. The bipolar pseudocode sequence family includes N1 pseudocode sequences, and each pseudocode sequence is a bipolar code. It should be noted that for the m sequence, it is an odd length. In order to achieve bit balance, each generated pseudocode sequence will be automatically traversed and inserted by -1 or traversed and inserted by 1 to ensure that the final generated pseudocode sequence is an even sequence. In the generation of the Gold sequence, the computer stores m sequences of various orders to generate the Gold sequence of the required order. Similar to the m sequence, after the Gold sequence is generated, it is traversed and inserted by -1 or traversed and inserted by 1 to ensure that the final generated pseudocode sequence is an even sequence. The Weil sequence generates the Legendre sequence closest to the target sequence length through the characteristic expression of the Weil sequence, and the Legendre sequence is a Legendre sequence of prime length, and the Weil sequence of the target length is obtained by interception. The target length is the length of the required ranging pseudocode sequence;

[0089] Step 3: Send all the pseudo code sequences in the bipolar pseudo code sequence family to the next step in sequence, that is, only one pseudo code sequence is segmented and the code chip is flipped at a time;

[0090] Step 4: Divide the pseudocode sequence into N subsequences, each subsequence includes n code chips, n code When the pseudo code sequence is combined with the communication data code, the number of chips of the pseudo code sequence corresponding to each chip of the communication data code. The value obtained by dividing the pseudo code rate by the communication data code rate is rounded to n. code For example, if the pseudo code rate is 1.6 Mbps and the communication data code rate is 25 Kbps, 1 Mbps = 1000 Kbps, then n codeThen it is 64, which means that one chip of the communication data code will be combined with 64 chips of the pseudo code sequence. If the pseudo code sequence length is 1024, the pseudo code sequence can be divided into 16 sub-sequences;

[0091] Step 5: To reduce the damage to the characteristics of the pseudocode sequence, the pseudocode sequence is preliminarily screened according to the subsequence. The preliminarily screening condition is: determine whether the absolute value of the sum of the code chips of each subsequence is less than or equal to T0. If so, the condition is met and sent to the next step. Otherwise, the pseudocode sequence is eliminated and returns to step 3 to segment and judge the next pseudocode sequence. T0 is an even number. In the above example, when T0 is set to 6, the absolute value of the sum of the 64 code chips of a subsequence is less than or equal to 6, which is considered to meet the condition. T0 is a variable, and T0 is based on n code Setting, specifically, T0 can be n code rounded to one tenth of;

[0092] Step 6: For the pseudo code sequence that meets the conditions, the reversible chips in each subsequence of the pseudo code sequence are numbered. For example, in 16 subsequences, if the sum of 64 chips in a subsequence is +T1, all positive chips in the subsequence are marked as +1. Conversely, if the sum of the chips is -T1, all negative chips are marked as -1.

[0093] Step 7: Randomly flip the marked chips in each subsequence. For example, if the sum of the 64 chips in a subsequence is 8, randomly select 4 chips from all the positive chips marked +1 for chip flipping, so that the sum of the chips in the flipped subsequence is 0.

[0094] Step 8: Reassemble the subsequences flipped in step 7 in their original order to obtain a bit-balanced pseudocode sequence, send the bit-balanced pseudocode sequence into the first set and return to step 3, split, judge and flip the next pseudocode sequence until all pseudocode sequences in step 2 are processed.

[0095] After the above steps of generating a bit-balanced pseudocode sequence, the following preferred steps are performed.

[0096] The preferred steps are as follows:

[0097] refer to Figure 5 , step 1: input a first set of N2-bit balanced pseudocode sequences;

[0098] Step 2: Process the bit-balanced pseudocode sequences in the first set in order, and calculate the even autocorrelation value a, odd autocorrelation value b and maximum spectrum amplitude value c of the bit-balanced pseudocode sequences;

[0099] Step 3: assign a a first weight z1, b a second weight z2, and c a third weight z3. , and The specific value of can be changed according to the needs, for example, z1 is 0.4, z2 is 0.4, z3 is 0.2, and their sum is 1. Get the sum y of z1a, z2b and z3c 总 Send to the third set until all bits in the first set are balanced pseudo code sequence y 总 All are sent to the third set and proceed to the next step;

[0100] Step 4: Calculate y for all bit-balanced pseudocode sequences in the third set 总 The average value y 平均 , will be less than y 平均 of y 总 The corresponding bit-balanced pseudo code sequence is sent to a fourth set, which includes N3 bit-balanced pseudo code sequences;

[0101] Step 5: Calculate the even mutual correlation value e and the odd mutual correlation f between any two bit-balanced pseudocode sequences in the fourth set, and send them to the fifth set until the even mutual correlation value e and the odd mutual correlation f between the bit-balanced pseudocode sequences in the fourth set are calculated, and then proceed to the next step;

[0102] Step 6: Based on the e in the fifth set, establish the even correlation matrix R according to formula 1 e , based on f in the fifth set, establish the odd correlation matrix R according to formula 1 f ;

[0103] Step 7: Traverse and search R e The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial even cross-correlation threshold T e , traverse and search R f The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial odd cross-correlation threshold T f , T e and T f That is the threshold T h , if R e or R f As follows:

[0104] ;

[0105] T e or T f It is 277. It should be noted that the example is only used to show the specific calculation process and does not distinguish between odd / even correlations;

[0106] Step 8: Use T e Re Make a judgment and get less than or equal to T e The maximum connected set A e And the corresponding pseudo code sequence number M e , using T f R f Make a judgment and get less than or equal to T f The maximum connected set A f And the corresponding pseudo code sequence number M f , the example continues, when T e or T f When it is 277, connect set A e or A f is (2, 3), M e or M f is 2;

[0107] Step 9: Determine M separately e 、M f The relationship between the size of the target code number M0 is that if it is less than M0, the target requirement is not met, the corresponding threshold is increased by 1, and the optimization process is returned to step 8 for iteration until , go to the next step, the example continues: Set to 4, when T e or T f When M is 277, e or M f If it is 2, it does not meet the condition, T e or T f Add 1 and return to step 8 until the conditions are met and proceed to the next step;

[0108] Step 10: When M e and M f After meeting the conditions, judge A e With A f The number of nodes with the same sequence number Whether the target yardage is met , if less than If the target requirement is not met, the cross-correlation threshold is increased by 1, and the process returns to step 8 for iteration until Then the iteration is skipped and the result is sent to the second set. The example continues: when the threshold is 312, assuming that the odd / even correlation values ​​are the same, the connected set , All are (1, 2, 3), and The number of nodes with the same sequence number is 3. , then the condition is met, the iteration is skipped and the result is sent to the second set; otherwise, the threshold is increased by 1 and the process returns to step 8;

[0109] Step 11: After obtaining the second set, compare the various indicators of the target pseudocode sequence in the second set with the reference values ​​saved by the computer to verify whether the performance of the target pseudocode sequence meets the standard. The evaluation standard is that all indicators of the target pseudocode sequence must be better than the reference value. If they meet the standard, they are output as the ranging pseudocode. If they do not meet the standard, restart step 7 in the bit-balanced pseudocode sequence generation step to regenerate a new bit-balanced pseudocode sequence until a ranging pseudocode that meets the requirements is obtained.

[0110] It should be noted that the reason for restarting step 7 in the bit-balanced pseudocode sequence generation step is that the flipping in step 7 is random, and the flipped code chips selected for the re-random flipping may change, so different bit-balanced pseudocode sequences may be obtained.

[0111] The present invention starts from the robustness of the ranging pseudocode and takes into account the influence of the ranging pseudocode encoding method on the capture and tracking of the receiving end and the influence on the ranging accuracy, and provides a bit-balanced ranging pseudocode design method, which realizes bit balance in the application of the communication data code and the ranging pseudocode. And establishes an evaluation standard, adopts odd / even auto / cross-correlation function, maximum spectrum amplitude function, etc., through the divide-and-conquer strategy, and adopts the maximum clique model to select the bit-balanced ranging pseudocode sequence with good comprehensive performance. By optimizing the design of the ranging pseudocode, the overall robustness of the inter-satellite ranging communication is improved.

[0112] Another aspect of the present invention provides a ranging pseudo code design system, which is used to execute the ranging pseudo code design method as described above, referring to Figure 6 The system includes: a balanced code module 10, which generates multiple pseudocode sequences based on instructions and parameters, selects a pseudocode sequence that meets a first preset condition to perform a chip flip operation to generate multiple bit-balanced pseudocode sequences, and sends the multiple bit-balanced pseudocode sequences into a first set, wherein the instruction represents the pseudocode type and the parameter represents the order; a preferred module 20, which is used to evaluate the performance indicators of the bit-balanced pseudocode sequences in the first set in turn, and selects the bit-balanced pseudocode sequence whose performance indicator meets the second preset condition as the target pseudocode sequence; a verification module 30, which is used to verify whether the performance indicator of the target pseudocode sequence is better than the reference value, and if so, it is used as a ranging pseudocode; wherein the performance indicators include: odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd mutual correlation and even mutual correlation.

[0113] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0114] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A ranging pseudo code design method, It is characterized in that include: Based on the instruction and the parameter, a plurality of pseudo code sequences are generated, and the pseudo code sequence satisfying the first preset condition is selected to perform a chip flip operation to generate many bit balanced pseudocode sequences, and sending the plurality of bit balanced pseudocode sequences into a first set, wherein the instruction represents the pseudocode type and the parameter represents the order; Performing performance index evaluation on the bit-balanced pseudocode sequences in the first set in turn, and selecting a bit-balanced pseudocode sequence whose performance index meets a second preset condition as a target pseudocode sequence; Verify whether the performance index of the target pseudo code sequence is better than the reference value, and if so, use it as the ranging pseudo code; The performance indicators include at least odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd mutual correlation and even mutual correlation.

2. The ranging pseudo code design method according to claim 1, It is characterized in that The pseudocode types include: m-sequence, Gold sequence and Weil sequence, and the pseudocode sequence is a bipolar even sequence.

3. The ranging pseudo code design method according to claim 1 or 2, It is characterized in that Selecting the pseudo code sequence that meets the first preset condition to perform a chip flipping operation includes: Sequentially divide each of the pseudocode sequences into N subsequences, each of which includes n code Chips, n code is: when the ranging pseudo code sequence is combined with the communication data code, the number of chips of the ranging pseudo code sequence corresponding to each chip of the communication data code; For any of the pseudo code sequences, if the sum of the chips of each subsequence of the pseudo code sequence is less than or equal to the preset value T 0 , then to meet the first preset condition, a chip flipping operation is performed on the pseudo code sequence that meets the first preset condition. If the sum of the chips of any subsequence of the pseudo code sequence is greater than the preset value T 0 , then the first preset condition is not met, and the pseudo code sequence that does not meet the first preset condition is eliminated.

4. The ranging pseudo code design method according to claim 3, It is characterized in that Performing a chip flip operation on the pseudo code sequence that meets the first preset condition includes: For each of the pseudo code sequences that meets the first preset condition, calculating the sum of chips of each subsequence of the pseudo code sequence; If the sum of the chips of the subsequence is a positive number, the positive number is , then all positive chips in the subsequence are marked as +1, and any one of the multiple chips marked as +1 is selected flipping a number of chips so that the sum of the chips of the subsequence is 0, and combining the subsequences in the order before segmentation to generate the bit-balanced pseudocode sequence; If the sum of the chips of the subsequence is a negative number, the negative number is - , then mark all negative chips in the subsequence as -1, and arbitrarily select a The number of chips is flipped so that the sum of the chips of the subsequence is 0, and the subsequences are combined in the order before division to generate the bit-balanced pseudocode sequence.

5. The ranging pseudo code design method according to claim 1, It is characterized in that Selecting a bit-balanced pseudocode sequence whose performance index meets the second preset condition as a target pseudocode sequence includes: For the bit-balanced pseudocode sequences in the first set, the even autocorrelation value a, the odd autocorrelation value b and the maximum spectrum amplitude value c of each bit-balanced pseudocode sequence are calculated in sequence, and a is assigned a first weight z 1 , assign a second weight z to b 2 , assign the third weight z to c 3 , where z 1 +z 2 +z 3 =1, get z 1 a、z 2 b and z 3 The sum of c and y 总 , calculate the y of each bit-balanced pseudocode sequence in the first set 总 The average value y 平均 , will be less than y 平均 of y 总 The corresponding bit-balanced pseudo-code sequence is sent to the fourth set; The maximum clique model is used to evaluate the odd / even mutual correlation of the bit-balanced pseudocode sequences in the fourth set, and a target pseudocode sequence is obtained.

6. The ranging pseudo code design method according to claim 5, It is characterized in that Using the maximum clique model to perform odd / even mutual correlation evaluation on the bit-balanced pseudocode sequence in the fourth set includes: Calculate the even mutual correlation values ​​e and odd mutual correlation values ​​f between different bit-balanced pseudocode sequences in the fourth set, and establish an even mutual correlation matrix R based on e e , based on f, establish the odd correlation matrix R f ; The total number of bit-balanced pseudocode sequences in the fourth set is N3, and the search for R e The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial even cross-correlation threshold T e , using T e R e Make a judgment and get less than or equal to T e The maximum connected set A e And the corresponding pseudo code number M e ; Traversal Search R f The N3×N3 elements in the equation are selected, and the minimum non-zero value is selected as the initial odd cross-correlation threshold T f , using T f R f Make a judgment and get less than or equal to T f The maximum connected set A f And the corresponding pseudo code number M f ; Judge M e and M f Are they both greater than or equal to the target code number M? 0 If yes, then exit the iteration; if no, then e Add 1, the T f Add 1 and continue to use T e R e Make a decision and adopt T f R f Make a judgment and execute subsequent steps until M f ≥M 0 And M e ≥M 0 , then jump out of the iteration; Get A e With A f The number of nodes with the same node number M ef , judge M ef Is it greater than or equal to the target code number M? 0 If yes, then exit the iteration, if no, then the T e Add 1, the T f Add 1 and continue the loop until M ef ≥M 0 , then jump out of the iteration; When jumping out of the iteration, A e or A f The corresponding bit-balanced pseudo code sequence is used as the target pseudo code sequence.

7. The ranging pseudo code design method according to claim 6, It is characterized in that The pair-correlation matrix R is established based on e e And establish the odd correlation matrix R based on f f Including: Based on e, establish the even correlation matrix R according to formula 1 e , based on f, establish the odd correlation matrix R according to formula 1 f , Formula 1 is as follows: ； Among them, b n-1,n is the even mutual correlation value e or the odd mutual correlation value f between the n-1th bit balanced sequence and the nth bit balanced sequence, n=N3.

8. The ranging pseudo code design method according to claim 1, It is characterized in that The reference value is: the average value of each evaluation index of the C / A code in the L1 frequency band in the global positioning system signal standard.

9. The ranging pseudo code design method according to claim 1 or 8, It is characterized in that The method further includes: if the performance indicator of the target pseudo code sequence is worse than the reference value, returning to the step of generating the bit-balanced pseudo code sequence.

10. A ranging pseudo code design system, It is characterized in that The ranging pseudo code design system is used to execute the ranging pseudo code design method according to any one of claims 1 to 9, and the system comprises: A balanced code module, wherein the balanced code module generates a plurality of pseudo code sequences based on instructions and parameters, selects the pseudo code sequence that meets a first preset condition to perform a chip flip operation to generate a plurality of bit balanced pseudo code sequences, and sends the plurality of bit balanced pseudo code sequences into a first set, wherein the instruction represents a pseudo code type, and the parameter represents an order; A preferred module, the preferred module is used to evaluate the performance indicators of the bit-balanced pseudocode sequences in the first set in turn, and select the bit-balanced pseudocode sequence whose performance indicator meets the second preset condition as the target pseudocode sequence; A verification module, the verification module is used to verify whether the performance index of the target pseudo code sequence is better than the reference value, and if so, it is used as the ranging pseudo code; The performance indicators include odd autocorrelation, even autocorrelation, maximum spectrum amplitude, odd mutual correlation and even mutual correlation.

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