Distributed satellite navigation simulation system

Abstract

The invention relates to the technical field of analogue simulation, in particular to a distributed satellite navigation simulation system which comprises a track step length coordination module, a node rhythm judgment module, a pseudo signal combination module, a rhythm synchronous modulation module and a simulation link verification module. According to the method, node visibility screening is completed by combining node space positions and satellite track states, a cross-node time synchronization mechanism is established based on rhythm states and local time precision, signal combination and navigation frame structure arrangement are performed in a frequency band division mode, and a multi-node collaborative output pseudo signal classification system is constructed. Performing synchronous modulation on the signal frame by combining with a unified time reference and marking a modulation state and a scheduling rhythm to realize time consistency control of the multi-source pseudo signal under a multi-frequency band condition, and verifying and sorting synchronous distribution characteristics in a signal transmission link through rhythm identification screening and a time sequence archiving mode; a simulation result has structure controllability, rhythm consistency and modulation time sequence normalization.

Description

Technical Field

[0001] The present invention relates to the field of simulation technology, and in particular to a distributed satellite navigation simulation system. Background Art

[0002] The field of simulation technology involves simulating physical processes, system behaviors, or operating mechanisms in the real world by establishing mathematical and physical models, including modeling methods, computational simulation, system response prediction, and the construction of virtual test environments. It is widely used in high-precision application scenarios such as aerospace, transportation, and military operations. Among them, the satellite navigation simulation system refers to the use of ground equipment to simulate the time, frequency, Doppler effect, and error characteristics of satellite navigation signals during space propagation to generate virtual navigation data. It is mainly aimed at the performance evaluation and algorithm verification of satellite navigation equipment in non-real space environments. It usually uses a physical signal generator combined with static scene parameter input to construct a pseudo-signal environment and performs simulation operations based on fixed orbit data or preset navigation information.

[0003] In the existing satellite navigation simulation process, static scene parameters and fixed orbit information are mainly used as the input basis. There is a lack of a real-time recognition mechanism for the spatial position changes of simulation nodes, and it is impossible to establish a visual mapping relationship between nodes and trajectories. At the same time, a unified signal source driving method is usually adopted for time control, which makes it difficult to deal with the rhythm offset problem caused by time scale differences between multiple simulation nodes. When constructing multi-band pseudo signals, it is often carried out in a centralized generation manner, resulting in inflexible structural organization between frequency bands and inconsistent modulation rhythm control. If concurrent simulation is performed in a multi-node environment, signal overlap, rhythm misalignment and modulation desynchronization are likely to occur, affecting the accuracy of signal synchronization and the authenticity of simulation verification. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a distributed satellite navigation simulation system.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: a distributed satellite navigation simulation system includes: The trajectory step coordination module obtains the initial parameters of each satellite trajectory, updates the satellite trajectory propulsion status in real time, and combines the spatial position parameters of each simulation node to determine the relationship between the trajectory propulsion status and the simulation node orientation, identifies the simulation nodes that meet the visibility criteria, and generates a trajectory visible node mapping list; The node rhythm determination module extracts the local time identifier of the simulation node according to the trajectory visual node mapping list, associates the local time of the simulation node with the system time scale, and classifies and marks the rhythm state to generate a synchronous response node state set; The pseudo signal combination module extracts the current frequency band label and signal generation status of each simulation node according to the synchronous response node state set, groups the pseudo signals according to the frequency band label, performs navigation frame structure combination sorting and frame index registration on the signals in the same group, and generates a multi-node pseudo signal classification sequence; The rhythm synchronization modulation module extracts the flag bits and time scheduling information of each signal frame according to the multi-node pseudo-signal classification sequence, synchronously modulates signal frames of different frequency bands according to a unified time reference, marks the modulation status and scheduling rhythm information corresponding to each group of signal frames, and generates a signal frame rhythm modulation mapping table.

[0006] As a further solution of the present invention, the trajectory visual node mapping list includes node identification identifier, trajectory status label, visibility criterion record, and node-trajectory correspondence; the synchronous response node status set includes a candidate node list, time synchronization label, rhythm classification status, and system time scale association result; the multi-node pseudo-signal classification sequence includes frequency band category index, signal source identifier, frame structure information, and navigation message index; the signal frame rhythm modulation mapping table includes modulation mode identifier, frequency band frame correspondence, time scheduling matrix, and synchronous rhythm mark.

[0007] As a further solution of the present invention, the trajectory step length coordination module includes: The trajectory initial parameter update submodule counts the initial parameters of each satellite trajectory, obtains the spatial position parameters and time step sequence of the simulation node, identifies the satellite trajectory point under the current time step, marks the position of the trajectory point in the trajectory advancement state, determines whether the advancement state needs to be updated, and replaces and advances the trajectory state under the premise of meeting the trajectory advancement range constraint, generating a trajectory advancement state sequence; The node visibility judgment submodule identifies all simulation nodes in the current propulsion state according to the trajectory propulsion state sequence, identifies the node set with spatial visibility attributes based on the spatial geometric position relationship between the nodes and the trajectory, and generates a visible node screening list; The trajectory node mapping generation submodule matches the node set with the trajectory path based on the visual node screening list, the spatial attributes of the visual nodes and the dynamic information of the propulsion trajectory state, and the time sequence. It marks the node numbers that match the trajectory propulsion direction and have an orientation correspondence, establishes a one-to-one correspondence between the trajectory points and the simulation nodes, and generates a trajectory visual node mapping list.

[0008] As a further solution of the present invention, the node rhythm determination module includes: The time mark extraction submodule extracts the corresponding numbers of the simulation nodes based on the trajectory visual node mapping list, classifies and organizes them according to the node numbers, records the local time mark of each node in the current advancement state of the system, and synchronously extracts the current unified system time of the system to generate a node local time tag set; The time difference judgment and screening submodule uses the system time as the reference time according to the local time tag set of the node , extract the local time identifier of each node, perform time difference judgment on the two, calculate the absolute difference between the node local time and the system time, calculate and obtain the status identifier of whether the synchronization criterion is met, filter all the node numbers that meet the requirements to form a candidate set, and obtain the synchronization candidate node number set; The response rhythm marking submodule reads the current simulation state record information for each candidate node according to the synchronization candidate node number set, classifies and marks the node state according to the response rhythm, archives all synchronization nodes according to the marking results, and generates a synchronization response node state set.

[0009] As a further solution of the present invention, the pseudo signal combination module includes: The frequency band state extraction submodule extracts the number of each node according to the synchronous response node state set, counts the communication frequency band label and signal generation state identifier of each node in the current advancement state, retains the valid signal nodes, groups the valid node numbers of the same frequency band together, organizes the grouping table of all simulation nodes by frequency band number, and generates a frequency band group number set; The navigation frame combination submodule extracts the node numbers under the same frequency band according to the frequency band group number set, reads the navigation subframes generated by each node, locates them according to the frame index number, performs field block-level splicing and combination of the navigation subframes of different nodes according to the navigation frame sequence specification, calculates and obtains the combination deviation coefficient, sorts the navigation frames based on the minimum combination deviation as the combination priority principle, and numbers the combination sequence according to the frame index to obtain the navigation frame structure index table; The signal sequence generation submodule synthesizes the simulation node output signal frames in sequence according to the frame index order based on the navigation frame structure index table, records the source node number, frequency band label and combined frame index position of each frame signal, establishes a three-layer mapping relationship table of frequency band → node → signal frame, and generates a multi-node pseudo signal classification sequence.

[0010] As a further solution of the present invention, the rhythm synchronization modulation module includes: The signal frame extraction submodule reads the node number and frequency band label according to the multi-node pseudo signal classification sequence, combines the node signal frame data and extracts the flag bit and scheduling time in each frame, parses the flag bit in sequence according to the byte structure, uses the scheduling time to represent the preset transmission time of the frame, and collects and organizes the signal frame content by number to obtain a frame structure field set; The modulation mode matching submodule sets the modulation type identifier of each signal frame based on the frequency band label and time information recorded in the frame structure field set and the frequency band mapping parameter, and performs an association operation between the flag bit and the scheduling time of all signal frames to obtain a modulation rhythm sorting set; The rhythm mapping construction submodule arranges the frame scheduling time in sequence according to the frame number and modulation identifier recorded in the modulation rhythm sorting set, groups the frame scheduling time according to the modulation identifier, associates and maps the grouping results with the node frequency band, and obtains the signal frame rhythm modulation mapping table.

[0011] As a further embodiment of the present invention, the system further comprises: The simulation link verification module screens and marks the distribution of each rhythm identifier in the signal transmission link between simulation nodes based on the signal frame rhythm modulation mapping table, archives the time sequence flow of all rhythm synchronization processes, and generates a distributed satellite navigation simulation synchronization record; The distributed satellite navigation simulation synchronization record includes rhythm synchronization process record, link rhythm distribution mark, signal frame timing archive record, and node interaction time mark.

[0012] As a further solution of the present invention, the simulation link verification module includes: The rhythm identification screening submodule extracts the rhythm sequence numbers, frequency bands and corresponding modulation type identifications of all signal frames according to the signal frame rhythm modulation mapping table, records and groups the arrangement of the signal frames in the rhythm distribution, determines whether there are rhythm segments with frequency band jumps or modulation type switches and marks them, and generates a rhythm distribution identification set; The synchronization timing archiving submodule compares the start and end scheduling time of each rhythm segment based on the rhythm number and the start and end corresponding frame number in the rhythm distribution identifier, summarizes the continuous change trajectory of the frequency band, modulation type and frame number, extracts the start and end time difference and frequency band label change sequence between adjacent rhythm segments, and constructs a logical mapping relationship between rhythms to obtain a rhythm synchronization timing set; The navigation record generation submodule extracts the starting node number, ending node number and modulation identifier in the rhythm segment according to the rhythm segment number and node number recorded in the rhythm synchronization timing set, combines the frequency band to which the node belongs and the frame number sequence, and arranges all path combinations in the rhythm number sequence to generate a distributed satellite navigation simulation synchronization record.

[0013] Compared with the prior art, the advantages and positive effects of the present invention are: In the present invention, node visibility screening is completed by combining the node spatial position and satellite trajectory status, and a cross-node time synchronization mechanism is established based on the rhythm status and local time accuracy. Signal combination and navigation frame structure are sorted in a frequency band division manner, and a pseudo-signal classification system for multi-node collaborative output is constructed. Then, the signal frame is synchronously modulated and the modulation status and scheduling rhythm are marked in combination with a unified time reference, so as to realize the time consistency control of multi-source pseudo-signals under multi-band conditions. The synchronization distribution characteristics in the signal transmission link are verified and sorted through rhythm identification screening and time sequence archiving, thereby realizing multi-dimensional coordination of spatial position, time rhythm and signal modulation in a multi-node environment, so that the simulation output results have structural controllability, rhythm consistency and modulation timing standardization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a system flow chart of the present invention; Figure 2 This is a flow chart of the trajectory step coordination module of the present invention; Figure 3 This is a flow chart of the node rhythm determination module of the present invention; Figure 4 This is a flow chart of the pseudo signal combination module of the present invention; Figure 5 This is a flow chart of the rhythm synchronization modulation module of the present invention; Figure 6 This is a flow chart of the simulation link verification module of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0016] In the description of the present invention, it should be understood that the terms "length," "width," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," and the like, indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, in the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

[0017] See also Figure 1 , a distributed satellite navigation simulation system includes: The trajectory step coordination module obtains the initial parameters of each satellite trajectory, updates the satellite trajectory advancement status in real time, and combines the spatial position parameters of each simulation node to determine the relationship between the trajectory advancement status and the simulation node orientation. It identifies simulation nodes that meet the visibility criteria (distance ≤ GPS orbit altitude 20200km and elevation angle ≥ 5° signal-to-noise ratio threshold), integrates the corresponding information between the node and trajectory status, and generates a trajectory visible node mapping list. The node rhythm determination module extracts the local time identifier of the simulation node based on the trajectory visual node mapping list, associates the local time of the simulation node with the system time scale (selecting nodes with a difference of ≤100ns precision clock synchronization tolerance as synchronization candidate nodes), and classifies and marks the rhythm status to generate a synchronization response node status set; The pseudo-signal combination module extracts the current frequency band label and signal generation status of each simulation node based on the synchronous response node status set, groups pseudo-signals according to the frequency band label, and performs navigation frame structure combination and frame index registration for the signals in the same group. It also organizes the organization and source identification of the simulation node output signal frames to generate a multi-node pseudo-signal classification sequence. The rhythm synchronization modulation module extracts the flag bits and time scheduling information of each signal frame based on the multi-node pseudo signal classification sequence, and synchronously modulates the signal frames of different frequency bands according to a unified time reference (BPSK is used for L1C / A code, and QPSK is used for L1C signal). It marks the modulation state and scheduling rhythm information corresponding to each group of signal frames, forms a sequence matrix, and generates a signal frame rhythm modulation mapping table. Based on the signal frame rhythm modulation mapping table, the simulation link verification module screens and marks the distribution of each rhythm identifier in the signal transmission link between simulation nodes, archives and organizes the timing flow of all rhythm synchronization processes, and generates distributed satellite navigation simulation synchronization records.

[0018] The trajectory visual node mapping list includes node identification, trajectory status label, visibility criterion record, and node-trajectory correspondence. The synchronous response node status set includes candidate node list, time synchronization label, rhythm classification status, and system time stamp association result. The multi-node pseudo-signal classification sequence includes frequency band category index, signal source identifier, frame structure information, and navigation message index. The signal frame rhythm modulation mapping table includes modulation mode identifier, frequency band frame correspondence, time scheduling matrix, and synchronization rhythm mark. The distributed satellite navigation simulation synchronization record includes rhythm synchronization process record, link rhythm distribution annotation, signal frame timing archive record, and node interaction time stamp.

[0019] See also Figure 2 , the trajectory step coordination module includes: The trajectory initial parameter update submodule counts the initial parameters of each satellite trajectory, obtains the spatial position parameters and time step sequence of the simulation node, identifies the satellite trajectory point under the current time step, marks the position of the trajectory point in the trajectory advancement state, determines whether the advancement state needs to be updated, and replaces and advances the trajectory state under the premise of meeting the trajectory advancement range constraint, generating a trajectory advancement state sequence; When obtaining the initial parameters of the satellite trajectory, it is necessary to extract the initial three-dimensional coordinates, initial velocity vector and initial orbit time label of each satellite from the satellite trajectory database one by one. For the time step sequence set by the current simulation system, for example, every 30 seconds is a propulsion unit, and the satellite propulsion state record value is read at each unit time point, including orbital inclination, perigee parameters and ascending node longitude, etc. Subsequently, the spatial position coordinates of the simulation node at the same time step are called and matched according to the number to determine whether the propulsion state is in the propulsion range. The propulsion range needs to be defined as the first 80% of the total simulation time. For example, if the total simulation time is 7200 seconds, the propulsion control range is 0 to 576 seconds. 0 seconds, match the propulsion state value of each satellite, and update the propulsion state with the time point as the index; in the implementation process, for example, a satellite numbered S1, its initial propulsion state time point is t0, the coordinates are X0 = (15600km, 0km, 0km), and the state value at t1 after step propulsion is X1 = (15580km, 25km, 5km), then the original state value is updated to X1 and stored in the trajectory propulsion state value sequence for subsequent node judgment analysis. To ensure the rationality of the propulsion state, each propulsion records the current propulsion time point and its previous state change value and updates the time index, see the data below: Table 1 Trajectory propulsion state value record table

[0020] As shown in Table 1, the state update value Δ can be used to track the trajectory change trend and verify the continuity and accuracy of orbital propulsion. Therefore, through the above steps, the final result obtained is the trajectory propulsion state sequence.

[0021] The node visibility judgment submodule identifies all simulation nodes in the current propulsion state according to the trajectory propulsion state sequence, identifies the node set with spatial visibility attributes based on the spatial geometric position relationship between the nodes and the trajectory, and generates a visible node screening list; According to the trajectory propulsion state value sequence, the time step value sequence corresponding to each propulsion state is first determined during the execution process, and the satellite space position coordinates corresponding to each time point in the trajectory propulsion state are extracted. , and then extract the spatial coordinates of all simulation nodes from the simulation node library ,The visibility relationship between the trajectory point and the node is judged according to the spatial geometric relationship. First, the spatial distance d between the two is calculated, which is expressed as follows using the three-dimensional Euclidean distance formula: ; when The distance condition is met when The calculation formula is: ; The judgment condition is , where the elevation angle is expressed in degrees converted from radians; if the satellite position in an example is , the node position is , then we can calculate: ; ; because and , so the node meets the visibility condition; in addition, to verify whether the signal-to-noise ratio threshold meets the condition, read the signal-to-noise ratio value corresponding to the node number , set the signal-to-noise ratio threshold to 32dB. If the node number is N4, the signal-to-noise ratio at t=60 seconds is 34dB, which satisfies , then node N4 is retained in the set of visible nodes at the current time step; finally, all time points and corresponding visible nodes are sorted to form a visible node screening list, such as time point The next visible node set is {N4, N7, N9}, which can be recorded as: ; The visible node sets at all time steps are summarized, and the final result is a filtered list of visible nodes.

[0022] The trajectory node mapping generation submodule is based on the visual node screening list. It matches the node set with the trajectory path according to the spatial attributes of the visual nodes and the dynamic information of the propulsion trajectory state, combined with the time sequence. It marks the node numbers that match the trajectory propulsion direction and have a corresponding position, establishes a one-to-one correspondence between the trajectory points and the simulation nodes, and generates a trajectory visual node mapping list. According to the visible node screening list, it is necessary to read each item according to the time point in the advancement state sequence, and make a one-to-one correspondence between the trajectory number and the node number for all visible nodes in each advancement state time point. During the correspondence process, it is necessary to read the time label, number and trajectory spatial coordinates of the current trajectory point from the trajectory advancement state, match the node number and its spatial position at the same time point, and judge whether the spatial direction relationship between the two is reasonable. The comparison is performed by calculating the consistency of their azimuth vector angle and the advancement direction. If the trajectory advancement direction is 30° east of north and the node spatial direction angle is 35°, it is considered that there is a corresponding relationship. A mapping item record is generated according to the trajectory number and node number, and all trajectory points and their corresponding visual nodes are organized in array form. For example, trajectory point T3 corresponds to nodes N4 and N5, trajectory point T4 corresponds to nodes N5 and N6, etc., generating a mapping relationship set with the structure {T3: [N4, N5], T4: [N5, N6]}, which is the trajectory visible node mapping list.

[0023] See also Figure 3 , the node rhythm determination module includes: The time stamp extraction submodule extracts the corresponding numbers of simulation nodes based on the trajectory visual node mapping list, classifies and organizes them according to the node numbers, records the local time stamp of each node in the current advancement state of the system, and synchronously extracts the current unified system time of the system to generate the node local time tag set; Extract the corresponding number of the simulation node based on the trajectory visual node mapping list. It is necessary to index the visual node number set associated with each time step from the mapping list according to the advancement state, obtain the local time identification item in the node storage record, and collect the time identification items one by one with the node number as the index, and record the corresponding time label. Each node in the simulation system will generate a local time scale with GPS synchronization reference time as the reference in each time step. The identification unit is nanoseconds. For example, when the node number N03 is in the advancement state t=120s, the local time scale is recorded as T=1 20000000200ns. At the same time, the simulation system main control module provides a unified system time scale. The system time corresponding to the propulsion state t=120s is T=120000000000ns. The correspondence between node numbers and time stamps needs to be organized into a mapping record table according to the propulsion state. The node time stamp mapping dataset adopts a two-dimensional mapping structure. Each row records the node number and corresponding local time stamp under a certain propulsion state. The calling format is {propulsion state: {node number: local time stamp}}. To verify the standardization of the record, the following sample dataset can be constructed: Table 2 Simulation node local time identification table

[0024] As shown in Table 2, the node local time has an independent record at the advancing state time point, which can be used to perform time difference judgment operations later. The final result is the node local time label set.

[0025] The time difference judgment and screening submodule uses the system time as the reference time according to the node local time tag set , extract the local time stamp of each node , judge the time difference between the two, and calculate the absolute difference between the node local time and the system time , using the formula: ; The status flag of whether the operation obtains the synchronization criteria , all satisfied The node numbers of are filtered to form a candidate set, and a synchronization candidate node number set is obtained, where represents the local time of node i, is the system time identifier, is the time difference between the node and the system, It is a synchronization judgment flag, with a value of 1 indicating a synchronization candidate and a value of 0 indicating that the synchronization tolerance is not met; According to the node local time tag set, the time difference of each node is extracted from it with the system time as the reference value. First, read the system time stamp under the advancing state time. For example, when the advancing state is t=120s, the system time stamp is T=120000000000ns. Extract the local time stamp of each node at this time point, such as T_i(N03)=120000000200ns, T_i(N04)=120000000080ns, etc., and calculate the absolute value of the time difference item by item. The calculation formula is , for node N03, the difference is , the 100ns threshold is compared to determine whether the precision synchronization tolerance is met. Node N03 does not meet the condition due to a time difference of 200ns, so its status is marked as 0. Node N04 has a time difference of 80ns, which is less than the threshold, so its status is marked as 1. The threshold of 100ns is the upper limit of the tolerance for precision synchronization. This value is determined by the stability of the system clock hardware and the simulation accuracy requirements. The reference setting is the standard deviation of clock drift in the system, σ≤10ns. At a 99.7% confidence level, the upper limit of the system's cumulative synchronization error is set to 3σ≈30ns. To improve the fault tolerance retention coefficient, the final threshold is determined to be 100ns. This value can support the relative synchronization accuracy error between nodes to be controlled within ±0.1μs under multiple rounds of actual measurements. The node number and its status are combined and counted according to the advancement state. For example, at t=120s, the node marked as 1 is N04, and the node marked as 0 is N03, forming a state record array {N03:0, N04:1}. All nodes marked as 1 are selected as synchronization candidate nodes, forming the synchronization candidate node number set.

[0026] The response rhythm marking submodule reads the current simulation state record information for each candidate node according to the synchronization candidate node number set, classifies and marks the node state according to the response rhythm, archives all synchronization nodes according to the marking results, and generates a synchronization response node state set; According to the synchronization candidate node number set, the simulation operation status records of the candidate nodes are read one by one at each advancement state time point, including the current task processing state (such as whether it is in data collection, forwarding, or sleep), the communication link state (whether there is downlink, relay or interruption), and the feedback rate value (in bit / ms). The multi-parameter feature vector of the current advancement state is established with the node number as the index. The vector structure is a triplet {state identifier, link identifier, feedback rate}. For example, the node N04 is recorded as {1, 1, 256} at t=120s, where state identifier 1 indicates active state, link identifier 1 indicates normal communication, and feedback rate 2 indicates normal communication. The rate is 256bit / ms. The feature vector is input into the preset response rhythm standard, and the feature vector is classified and judged. The nodes with status identification 1, link identification 1 and feedback rate ≥128bit / ms are classified as "high-speed response type", the nodes with status identification 1 but feedback rate <128bit / ms are classified as "low-speed response type", and the nodes with link identification 0 are classified as "non-response type". For example, N04 is classified as high-speed response type because it meets all the criteria. Finally, the response rhythm types of all synchronization candidate nodes are archived and marked, and a rhythm label dictionary indexed by node number is established to generate a synchronization response node state set.

[0027] See also Figure 4 , the pseudo signal combination module includes: The frequency band state extraction submodule extracts the node number according to the synchronous response node state set, counts the communication frequency band label and signal generation state identifier of each node in the current propulsion state, retains the valid signal nodes, groups the valid node numbers of the same frequency band together, organizes the grouping table of all simulation nodes by frequency band number, and generates a frequency band group number set; Extract the simulation node number according to the synchronous response node state set. It is necessary to extract the response attribute corresponding to each node under the advancement state index, and obtain its frequency band label value and current signal generation state value. The frequency band label is the node working frequency band identification code, which is represented by standard string labels L1, L2, and L5. The signal generation state is recorded in Boolean form, with a value of 1 indicating signal output and 0 indicating no output. After traversing all node records, remove the nodes with a state of 0 from the records, and only retain the node numbers that are currently in a valid signal output state. Classify and aggregate the remaining nodes according to the frequency band label, and establish a node grouping table with the frequency band as the primary key. The example is as follows: Table 3 Node frequency band and signal status table

[0028] As shown in Table 3, node N02 is eliminated because its status is 0, N01 and N03 are classified into group L1, and N04 is classified into group L5. Finally, the group set classified by frequency band is obtained, such as {L1: [N01, N03], L5: [N04]}, and the result is a frequency band group number set.

[0029] The navigation frame combination submodule extracts the node numbers under the same frequency band according to the frequency band group number set, and reads the navigation subframes generated by each. The navigation subframe structure refers to the GPS interface control file format. Each frame contains 1500 bits of data and is divided into 10 field blocks. Each field block is located according to the frame index number. The navigation subframes of different nodes are spliced ​​and combined at the field block level according to the navigation frame sequence specification. The formula is: ; The combination deviation coefficient is obtained by calculation, and the navigation frames are sorted with the minimum combination deviation as the combination priority principle. The combination sequence is numbered according to the frame index to obtain the navigation frame structure index table, where: Represents the deviation coefficient between node p and node q in the frame combination structure, Indicates the navigation frame bit value of node p in the kth field, the unit is bit, and the value is 0 or 1. Indicates the target bit structure reference value of node q in the kth field, in bits, with a value of 0 or 1. n indicates the upper limit of the bit number index of the field block in the navigation frame structure; Frequency band group number set, traverse its node number set in each frequency band, extract the navigation frame data content of each node and split it into field blocks according to the GPS protocol. Each navigation frame is 1500 bits, divided into 10 field blocks, each field block is 150 bits, align the field blocks between different nodes according to the index number, and extract the bit string value of the kth field block for any node p and node q 、 , the difference between the two represents the combined offset. The absolute value of the difference is used as input, all fields are summed, and the sum of squares of the two node field blocks is used as the denominator to construct the combined normalization coefficient. Suppose the node N01 field is {1, 0, 1, 1, 0, 1, 1, 0, 0, 1}, and the N03 field is {1, 1, 1, 0, 0, 1, 0, 0, 1, 1}. The sum of the absolute values ​​of the corresponding field block differences is 4, and the sum of the squares of the field blocks is , after rooting ,have to: ; The results show that the two-node navigation frame structure has a medium degree of combination deviation. The smallest item is the sorting priority item, and a navigation frame field block reorganization sequence is established. The final result is a navigation frame structure index table.

[0030] The combination deviation coefficient is used to measure the degree of difference in the navigation frame field structure between two simulation nodes. Its specific significance lies in characterizing the matching tightness of the navigation frame content generated by each node in the same frequency band at the bit level. The smaller the value, the closer the bit content of the two nodes at the corresponding field position is, the fewer frame structure reconstruction adjustments generated during the combination, and the higher the frame structure consistency. Therefore, it can be used for signal synthesis and frame output sorting first; on the contrary, a larger value indicates that there are a large number of structural conflicts or different fields between the navigation frames of the two nodes, the higher the reconstruction cost, and the lower the combination priority. This coefficient is the core indicator for judging the coupling of navigation frame reconstruction sorting and node structure.

[0031] The operational logic of the formula is to measure the degree of combination matching deviation of two simulation nodes in the navigation frame field structure, where the numerator part It represents the item-by-item difference in the bit values ​​of node p and node q at each corresponding field block position. The sum of the absolute values ​​can reflect the cumulative degree of difference in the overall structure, which has statistical significance of error. It is the square root of the sum of the squares of the corresponding bit values ​​of the two node field blocks, which is used to measure the combination strength or structural overlap. This normalization process can avoid the interference of different field numbers or inconsistent total bit amounts on the deviation value, thereby forming a relative deviation ratio coefficient between bit structures. This structure makes the combined deviation value It is always in the positive range, is comparable, and can be used as a ranking priority indicator for frame reordering.

[0032] The signal sequence generation submodule synthesizes the simulation node output signal frames in sequence according to the frame index order based on the navigation frame structure index table, records the source node number, frequency band label and combined frame index position of each frame signal, organizes the output structure index information corresponding to all simulation nodes, establishes a three-layer mapping relationship table of frequency band → node → signal frame, and generates a multi-node pseudo signal classification sequence; According to the navigation frame structure index table, each combination sorting structure is called, and the field block reorganization structure is read in the frame index order. For each field block, its source node number, frequency band and frame index position are recorded. All field information is assembled into a triple structure such as {field index, source node, frequency band label}, and sorted into a node output frame sequence in the navigation frame order. For example: the combination sequence is [field 1: N03@L1, field 2: N01@L1, field 3: N01@L1...], and the sorting result is written into a multi-layer dictionary. The first layer of the dictionary uses the frequency band as the primary key, the second layer is the node number, and the third layer is the signal frame index mapping. The structure is as follows: {L1: {N01: [2, 3], N03: [1]}}. The frequency band classification, node association and frame index matching relationship are established in this order, and the final result is a multi-node pseudo signal classification sequence.

[0033] See also Figure 5 , the rhythm-synchronized modulation module includes: The signal frame extraction submodule reads the node number and frequency band label according to the multi-node pseudo-signal classification sequence, combines the node signal frame data and extracts the flag bit and scheduling time in each frame, parses the flag bit in sequence according to the byte structure, and uses the scheduling time to represent the preset transmission time of the frame. The signal frame content is grouped and organized by number to obtain the frame structure field set; Read the node number and frequency band label according to the multi-node pseudo-signal classification sequence, read the corresponding signal frame content one by one, parse the content of each frame bit by bit, extract the first 20 bits as the frame flag, which contains the node number, frame index value and frame generation cycle number, where the node number is converted from the preset field of the frame header to an 8-bit unsigned integer, the frame index value is a 3-bit binary, and the cycle number is a 9-bit integer value. Decode the content of the 21st to 40th bits to extract the scheduling time field, which represents the millisecond timestamp in decimal integer. The whole process is completed by sequential extraction. After the data of all signal frames are registered, a correspondence table between the frame number and its flag bit and scheduling time field is constructed. In this process, the frequency band label and node number are mapped and recorded in the sequence table. All frames are sorted by number and organized into a frame flag bit dictionary data structure with the format of {frame number: {node number: N03, frequency band label: L1C / A, flag bit: 001001..., scheduling time: 5023}}. By extracting the data of 5 frames of signal samples under each of the 20 nodes, a total of 100 frames of identification table structure is formed, see Table 4.

[0034] Table 4 Example of signal frame flag and scheduling time

[0035] As shown in Table 4, the node number and the frequency band label correspond to the extracted flag bit and the scheduling time and are uniformly registered, and the obtained result is a frame structure field set.

[0036] The modulation mode matching submodule sets the modulation type identifier of each signal frame based on the frequency band label and time information recorded in the frame structure field set and the frequency band mapping parameters. It then associates the flag bits and the scheduling time of all signal frames to obtain the modulation rhythm sorting set. Based on the frequency band label and frame scheduling time information recorded in the frame structure field set, first read the frequency band label value corresponding to each frame. In the process of processing the frequency band labels of frames 001 to 100, set the modulation identification value corresponding to the frequency band L1C / A to 1, L1C to 2, and L5 to 3. In the frequency band parsing process, the numerical identification value is directly mapped to the frequency band string, and a comparison relationship is established with the original frame number; then extract the millisecond timestamp in the scheduling time field, and establish a frame modulation sequence structure sequence with the frame scheduling time as the main key. After identifying the difference in frame scheduling time between frequency bands, the frames of the same modulation type are They are grouped into the same group, and the frames within the group are sorted by scheduling time and the sequence position values ​​are recorded. At the same time, the flag byte sequence of each frame is extracted as the synchronization comparison content. A mapping structure is established between the frame number, scheduling time, and modulation identification value, which is represented by a triple structure as {frame number, modulation identification value, scheduling time} and organized into a modulation rhythm sequence dictionary. In the actual test sample, frame number 002 corresponds to frequency band L1C, the modulation identification value is 2, and the scheduling time is 5023 milliseconds. Its rhythm sequence is located in the third position of the L1C group, and the corresponding frame number index is stored in the structure. The final result is the modulation rhythm sorting set.

[0037] The rhythm mapping construction submodule sorts the frame numbers and modulation identifiers recorded in the modulation rhythm, groups them by modulation identifier, and arranges the frame scheduling time in sequence. It then associates and maps the grouping results with the node frequency band to obtain a signal frame rhythm modulation mapping table. According to the frame number, modulation identification value and scheduling time numerical information recorded in the modulation rhythm sorting set, the initial grouping is performed according to the modulation identification value. After merging the modulation types corresponding to the frequency bands, the scheduling time of each frame is extracted from each group one by one, and a time sequence list is constructed based on milliseconds. The row vectors of the modulation frame rhythm sequence matrix are obtained by arranging them in ascending order according to the scheduling time. The column vectors are divided into dimensions according to the modulation identification value to construct a two-dimensional matrix structure, in which the matrix elements are filled with frame number, node number and scheduling time, generating a combination structure with the format M[i][j]={frame number, node number, scheduling time}. After the scheduling matrix is ​​established, the rhythm sequence number is written according to the row vector index. The matrix is ​​used to express the modulation rhythm synchronization structure, and the frequency band label is recorded and mapped to the node number. An example of the final matrix summary result is shown in Table 5.

[0038] Table 5 Signal frame rhythm modulation mapping matrix

[0039] Table 5 lists the rhythm modulation matrix structure established according to the modulation type and scheduling time sequence, and the result is a signal frame rhythm modulation mapping table.

[0040] See also Figure 6 , the simulation link verification module includes: The rhythm identification screening submodule extracts the rhythm sequence number, frequency band and corresponding modulation type identification of all signal frames according to the signal frame rhythm modulation mapping table, records and groups the arrangement of signal frames in the rhythm distribution, determines whether there are rhythm segments with frequency band jumps or modulation type switches and marks them, and generates a rhythm distribution identification set; According to the signal frame rhythm modulation mapping table, the frame number, frequency band type and modulation mode code in each frame data are extracted, the rhythm position number of each frame is read one by one in the frame order, and classified according to the frequency band mark to which it belongs. The continuous frame numbers under the same frequency band are combined into a rhythm segment structure, and the combination of adjacent frames with the same frequency band label and a rhythm number interval of 1 is detected, and the rhythm segments that meet the combination conditions are marked; then the modulation mode codes corresponding to the frames are compared. If the modulation mode codes between adjacent frames change, the jump node is recorded, and the segments with different modulation modes are grouped separately. In the whole process, it is necessary to ensure that each frame corresponds to The rhythm segments have unique rhythm numbers and clear frequency band labels. For the three frequency band types of L1C, L2C, and L5, the first five groups of rhythm segments are extracted as test samples. In the samples, the rhythm segments composed of frame numbers 013 to 018 belong to the L1C frequency band, and the modulation mode is 2 (representing QPSK). The numbers are continuous and meet the screening requirements. The frame numbers 031 to 033 have the same frequency band but the modulation mode number is 1 (BPSK), so they are included in another segment. Finally, a four-bit data structure of rhythm segment number, start and end frame number, frequency band label and modulation type is established based on all screening results and summarized by rhythm segment number to generate a rhythm distribution identification set.

[0041] The synchronization timing archiving submodule compares the start and end scheduling time of each rhythm segment based on the rhythm number and the corresponding start and end frame number in the rhythm distribution identifier, summarizes the continuous change trajectory of frequency band, modulation type and frame number, extracts the start and end time difference and frequency band label change sequence between adjacent rhythm segments, and constructs the logical mapping relationship between rhythms to obtain the rhythm synchronization timing set; Based on the rhythm segment number and its start and end frame number information in the rhythm distribution identification center, the scheduling time field value is extracted from the start frame and end frame of each segment, and they are arranged in ascending order according to the timestamp, and the order between the rhythm segments is sorted out. For rhythm segments that are continuous in time but have different frequency bands or modulation types, their time offset values ​​and rhythm numbers are extracted, and whether there is frequency hopping switching between these rhythm segments is identified and marked; then, the rhythm number, corresponding start and end time, modulation code and frequency band type of each pair of continuous rhythm segments are combined and registered, and the combined structure is classified into the synchronous timing sequence. Table, forming a logical sequence data chain between rhythm segments. In the sample test, rhythm segment numbers 003 and 004 correspond to frame numbers 019 to 025 and 026 to 029 respectively, with different modulation codes, timestamps between 13782 milliseconds and 13897 milliseconds, and an interval value of 115 milliseconds. The rhythm switching node is recorded and included in the sequence structure. After processing all adjacent rhythm segments in this way, the timing comparison table is converted into a two-dimensional timing matrix, in which the horizontal direction is the rhythm segment number and the vertical direction is the time sequence. An offset comparison relationship is established by column to generate a rhythm synchronization timing set.

[0042] The navigation record generation submodule extracts the start node number, end node number and modulation identifier in the rhythm segment according to the rhythm segment number and node number recorded in the rhythm synchronization time sequence set, combines the frequency band to which the node belongs and the frame number sequence, and arranges all path combinations in the rhythm number sequence to generate a distributed satellite navigation simulation synchronization record; According to the rhythm segment number, node number and scheduling time structure recorded in the rhythm synchronization timing set, all rhythm segments are sequentially traversed and node frame sequences are extracted. The node number, modulation type code and scheduling time are extracted from each frame sequence respectively. The node number change, frequency band label change and time interval between adjacent frames are used as the basis for path structure judgment. The path combination within the rhythm segment is constructed, and the frame flow direction and frame number sequence are marked. After sorting out all frame combination paths, a frame pair sequence mapping table is generated, which records the starting frame number, ending frame number, starting node number, ending node number, frequency band type , scheduling time sequence and other fields. In the sample data, the frame numbers in rhythm segment number 005 are 033 to 036, and its node numbers are N01, N01, N03, N03, the frequency band labels are L1C / L1C / L2C / L2C, and the scheduling times are 14213, 14240, 14270, 14295 milliseconds. After extracting the above data, a multi-layer nested structure is established in sequence according to the rhythm number, node pair and frequency band label combination order, and all frame paths, node combinations and rhythm segment number mappings are integrated into a structural dictionary to finally generate a distributed satellite navigation simulation synchronization record.

[0043] The above are merely preferred embodiments of the present invention and do not limit the present invention in any other form. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A distributed satellite navigation simulation system, characterized in that: The system comprises: The trajectory step coordination module obtains the initial parameters of each satellite trajectory, updates the satellite trajectory propulsion status in real time, and combines the spatial position parameters of each simulation node to determine the relationship between the trajectory propulsion status and the simulation node orientation, identifies the simulation nodes that meet the visibility criteria, and generates a trajectory visible node mapping list; The node rhythm determination module extracts the local time identifier of the simulation node according to the trajectory visual node mapping list, associates the local time of the simulation node with the system time scale, and classifies and marks the rhythm state to generate a synchronous response node state set; The pseudo signal combination module extracts the current frequency band label and signal generation status of each simulation node according to the synchronous response node state set, groups the pseudo signals according to the frequency band label, performs navigation frame structure combination sorting and frame index registration on the signals in the same group, and generates a multi-node pseudo signal classification sequence; The rhythm synchronization modulation module extracts the flag bits and time scheduling information of each signal frame according to the multi-node pseudo-signal classification sequence, synchronously modulates signal frames of different frequency bands according to a unified time reference, marks the modulation status and scheduling rhythm information corresponding to each group of signal frames, and generates a signal frame rhythm modulation mapping table.

2. The distributed satellite navigation simulation system according to claim 1, characterized in that: The trajectory visible node mapping list includes node identification identifier, trajectory status label, visibility criterion record, and node-trajectory correspondence; the synchronous response node status set includes a candidate node list, time synchronization label, rhythm classification status, and system time scale association result; the multi-node pseudo-signal classification sequence includes frequency band category index, signal source identifier, frame structure information, and navigation message index; the signal frame rhythm modulation mapping table includes modulation mode identifier, frequency band frame correspondence, time scheduling matrix, and synchronous rhythm mark.

3. The distributed satellite navigation simulation system according to claim 1, characterized in that: The trajectory step coordination module includes: The trajectory initial parameter update submodule counts the initial parameters of each satellite trajectory, obtains the spatial position parameters and time step sequence of the simulation node, identifies the satellite trajectory point under the current time step, marks the position of the trajectory point in the trajectory advancement state, determines whether the advancement state needs to be updated, and replaces and advances the trajectory state under the premise of meeting the trajectory advancement range constraint, generating a trajectory advancement state sequence; The node visibility judgment submodule identifies all simulation nodes in the current propulsion state according to the trajectory propulsion state sequence, identifies the node set with spatial visibility attributes based on the spatial geometric position relationship between the nodes and the trajectory, and generates a visible node screening list; The trajectory node mapping generation submodule matches the node set with the trajectory path based on the visual node screening list, the spatial attributes of the visual nodes and the dynamic information of the propulsion trajectory state, and the time sequence. It marks the node numbers that match the trajectory propulsion direction and have an orientation correspondence, establishes a one-to-one correspondence between the trajectory points and the simulation nodes, and generates a trajectory visual node mapping list.

4. The distributed satellite navigation simulation system according to claim 1, characterized in that: The node rhythm determination module includes: The time mark extraction submodule extracts the corresponding numbers of the simulation nodes based on the trajectory visual node mapping list, classifies and organizes them according to the node numbers, records the local time mark of each node in the current advancement state of the system, and synchronously extracts the current unified system time of the system to generate a node local time tag set; The time difference judgment and screening submodule uses the system time as the reference time according to the local time tag set of the node , extract the local time identifier of each node, perform time difference judgment on the two, calculate the absolute difference between the node local time and the system time, calculate and obtain the status identifier of whether the synchronization criterion is met, filter all the node numbers that meet the requirements to form a candidate set, and obtain the synchronization candidate node number set; The response rhythm marking submodule reads the current simulation state record information for each candidate node according to the synchronization candidate node number set, classifies and marks the node state according to the response rhythm, archives all synchronization nodes according to the marking results, and generates a synchronization response node state set.

5. The distributed satellite navigation simulation system according to claim 1, characterized in that: The pseudo signal combination module includes: The frequency band state extraction submodule extracts the number of each node according to the synchronous response node state set, counts the communication frequency band label and signal generation state identifier of each node in the current advancement state, retains the valid signal nodes, groups the valid node numbers of the same frequency band together, organizes the grouping table of all simulation nodes by frequency band number, and generates a frequency band group number set; The navigation frame combination submodule extracts the node numbers under the same frequency band according to the frequency band group number set, reads the navigation subframes generated by each node, locates them according to the frame index number, performs field block-level splicing and combination of the navigation subframes of different nodes according to the navigation frame sequence specification, calculates and obtains the combination deviation coefficient, sorts the navigation frames based on the minimum combination deviation as the combination priority principle, and numbers the combination sequence according to the frame index to obtain the navigation frame structure index table; The signal sequence generation submodule synthesizes the simulation node output signal frames in sequence according to the frame index order based on the navigation frame structure index table, records the source node number, frequency band label and combined frame index position of each frame signal, establishes a three-layer mapping relationship table of frequency band → node → signal frame, and generates a multi-node pseudo signal classification sequence.

6. The distributed satellite navigation simulation system according to claim 1, characterized in that: The rhythm synchronization modulation module includes: The signal frame extraction submodule reads the node number and frequency band label according to the multi-node pseudo signal classification sequence, combines the node signal frame data and extracts the flag bit and scheduling time in each frame, parses the flag bit in sequence according to the byte structure, uses the scheduling time to represent the preset transmission time of the frame, and collects and organizes the signal frame content by number to obtain a frame structure field set; The modulation mode matching submodule sets the modulation type identifier of each signal frame based on the frequency band label and time information recorded in the frame structure field set and the frequency band mapping parameter, and performs an association operation between the flag bit and the scheduling time of all signal frames to obtain a modulation rhythm sorting set; The rhythm mapping construction submodule arranges the frame scheduling time in sequence according to the frame number and modulation identifier recorded in the modulation rhythm sorting set, groups the frame scheduling time according to the modulation identifier, associates and maps the grouping results with the node frequency band, and obtains the signal frame rhythm modulation mapping table.

7. The distributed satellite navigation simulation system according to claim 1, characterized in that: The system further comprises: The simulation link verification module screens and marks the distribution of each rhythm identifier in the signal transmission link between simulation nodes based on the signal frame rhythm modulation mapping table, archives the time sequence flow of all rhythm synchronization processes, and generates a distributed satellite navigation simulation synchronization record; The distributed satellite navigation simulation synchronization record includes rhythm synchronization process record, link rhythm distribution mark, signal frame timing archive record, and node interaction time mark.

8. The distributed satellite navigation simulation system according to claim 7, characterized in that: The simulation link verification module includes: The rhythm identification screening submodule extracts the rhythm sequence numbers, frequency bands and corresponding modulation type identifications of all signal frames according to the signal frame rhythm modulation mapping table, records and groups the arrangement of the signal frames in the rhythm distribution, determines whether there are rhythm segments with frequency band jumps or modulation type switches and marks them, and generates a rhythm distribution identification set; The synchronization timing archiving submodule compares the start and end scheduling time of each rhythm segment based on the rhythm number and the start and end corresponding frame number in the rhythm distribution identifier, summarizes the continuous change trajectory of the frequency band, modulation type and frame number, extracts the start and end time difference and frequency band label change sequence between adjacent rhythm segments, and constructs a logical mapping relationship between rhythms to obtain a rhythm synchronization timing set; The navigation record generation submodule extracts the starting node number, ending node number and modulation identifier in the rhythm segment according to the rhythm segment number and node number recorded in the rhythm synchronization timing set, combines the frequency band to which the node belongs and the frame number sequence, and arranges all path combinations in the rhythm number sequence to generate a distributed satellite navigation simulation synchronization record.

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