A distributed satellite navigation simulation system

Abstract

This invention relates to the field of simulation technology, specifically a distributed satellite navigation simulation system. The system includes a trajectory step size coordination module, a node rhythm determination module, a pseudo-signal combination module, a rhythm synchronization modulation module, and a simulation link verification module. In this invention, node visibility is screened by combining node spatial location and satellite trajectory status. A cross-node time synchronization mechanism is established based on rhythm status and local time accuracy. Signal combination and navigation frame structure are organized using frequency band division, constructing a pseudo-signal classification system for multi-node collaborative output. Then, signal frames are synchronously modulated using a unified time reference, and modulation status and scheduling rhythm are labeled, achieving time consistency control of multi-source pseudo-signals under multi-frequency band conditions. The synchronization distribution characteristics in the signal transmission link are verified and organized through rhythm identification screening and time sequence archiving, ensuring that the simulation results possess structural controllability, rhythm consistency, and modulation timing standardization.

Description

Technical Field

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

[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. This includes modeling methods, computational simulation, system response prediction, and the construction of virtual testing environments. It is widely used in high-precision applications such as aerospace, transportation, and military operations. Among these, satellite navigation simulation systems utilize ground-based equipment to simulate the time, frequency, Doppler effect, and error characteristics of satellite navigation signals during their propagation in space to generate virtual navigation data. This primarily targets the performance evaluation and algorithm verification of satellite navigation equipment in non-real space environments. Typically, a pseudo-signal environment is constructed using a physical signal generator combined with static scene parameter input, and simulation operations are performed based on fixed orbit data or preset navigation information.

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

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a distributed satellite navigation simulation system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a distributed satellite navigation simulation system comprising:

[0006] The trajectory step size coordination module acquires 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 azimuth of the simulation node, identifies the simulation nodes that meet the visibility criteria, and generates a list of trajectory visible nodes.

[0007] The node rhythm determination module extracts the local time identifier of the simulation node according to the trajectory visual node mapping list, associates and judges the local time of the simulation node with the system time scale, classifies and marks the rhythm state, and generates a set of synchronous response node states.

[0008] The pseudo-signal combination module extracts the current frequency band label and signal generation status of each simulation node based on the synchronization response node state set, groups the pseudo-signals according to the frequency band labels, sorts and registers the navigation frame structure of the signals in the same group, and generates a multi-node pseudo-signal classification sequence.

[0009] 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, performs synchronous modulation on signal frames of different frequency bands according to a unified time reference, marks the modulation state and scheduling rhythm information corresponding to each group of signal frames, and generates a signal frame rhythm modulation mapping table.

[0010] As a further embodiment of the present invention, the trajectory visual node mapping list includes node identification identifiers, trajectory status labels, visibility criterion records, and node-trajectory correspondences; the synchronization response node status set includes a candidate node list, time synchronization labels, rhythm classification status, and system time stamp association results; the multi-node pseudo-signal classification sequence includes a frequency band category index, signal source identifier, frame structure information, and navigation message index; and the signal frame rhythm modulation mapping table includes a modulation method identifier, frequency band frame correspondences, a time scheduling matrix, and synchronization rhythm markers.

[0011] As a further aspect of the present invention, the trajectory step size coordination module includes:

[0012] 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 nodes, identifies the satellite trajectory points under the current time step, marks the position of the trajectory points 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 satisfying the trajectory advancement range constraints, generating a trajectory advancement state sequence;

[0013] The node visibility judgment submodule identifies all simulation nodes in the current advancement state based on the trajectory advancement state sequence, and identifies the set of nodes with spatial visibility attributes by combining the spatial geometric position relationship between the nodes and the trajectory, and generates a list of visible nodes for filtering.

[0014] The trajectory node mapping generation submodule, based on the visible node filtering list, matches the node set with the trajectory path according to the spatial attributes of the visible nodes and the dynamic information of the propulsion trajectory status, combined with the time sequence, marks the node numbers that conform to the trajectory propulsion direction and have directional correspondence, establishes a one-to-one correspondence between trajectory points and simulation nodes, and generates a trajectory visible node mapping list.

[0015] As a further aspect of the present invention, the node rhythm determination module includes:

[0016] The time stamp extraction submodule extracts the corresponding number of the simulation node based on the trajectory visual node mapping list, classifies and organizes them according to the node number, records the local time stamp of each node in the current system advancement state, and synchronously extracts the current unified system time to generate a node local time tag set.

[0017] The time difference determination and filtering submodule uses the local time stamp set of the node and the system time as the base time. Extract the local time identifier of each node, determine the time difference between the two, calculate the absolute difference between the node's local time and the system time, calculate the status identifier of whether the synchronization criterion is met, filter all the node numbers that meet the criteria to form a candidate set, and obtain the synchronization candidate node number set.

[0018] The response rhythm marking submodule reads the current simulation state record information for each candidate node based on the set of synchronization candidate node numbers, classifies and marks the node state according to the response rhythm, archives all synchronization nodes according to the marking results, and generates a set of synchronization response node states.

[0019] As a further aspect of the present invention, the pseudo-signal combination module includes:

[0020] The frequency band status extraction submodule extracts the node number of each node according to the synchronization response node status set, counts the communication frequency band label and signal generation status identifier of each node in the current advancement state, retains the valid signal nodes, groups the valid node numbers of the same frequency band into a group, organizes the grouping table of all simulation nodes according to the frequency band number, and generates a frequency band group number set.

[0021] 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 navigation subframes of different nodes according to the navigation frame sequence specification, calculates and obtains the combination deviation coefficient, sorts each navigation frame according to the principle of minimum combination deviation, and numbers the combination order according to the frame index to obtain the navigation frame structure index table.

[0022] The signal sequence generation submodule synthesizes the simulated node output signal frames sequentially according to the navigation frame structure index table, and records the source node number, frequency band label and combined frame index position of each frame signal. It establishes a three-level mapping relationship table of frequency band → node → signal frame and generates a multi-node pseudo signal classification sequence.

[0023] As a further aspect of the present invention, the rhythm synchronization modulation module includes:

[0024] 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 byte order, 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 the frame structure field set.

[0025] 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, combined with the frequency band mapping parameters, and performs an association operation between the flag bit and the scheduling time for all signal frames to obtain the modulation rhythm sorting set.

[0026] The rhythm mapping construction submodule, based on the frame number and modulation identifier recorded in the modulation rhythm sorting set, groups the frames according to the 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 the signal frame rhythm modulation mapping table.

[0027] As a further aspect of the present invention, the system further includes:

[0028] 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 time sequence flow of all rhythm synchronization processes, and generates a distributed satellite navigation simulation synchronization record.

[0029] The distributed satellite navigation simulation synchronization record includes rhythm synchronization process record, link rhythm distribution label, signal frame timing archive record, and node interaction time stamp.

[0030] As a further aspect of the present invention, the simulation link verification module includes:

[0031] The rhythm identifier screening submodule extracts the rhythm sequence number, frequency band, and corresponding modulation type identifier 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 switching and marks them, and generates a rhythm distribution identifier set.

[0032] The synchronous timing archiving submodule, based on the rhythm number and the corresponding start and end frame number in the rhythm distribution identifier, compares the start and end scheduling times of each rhythm segment, 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 sequential logical mapping relationship between rhythms to obtain the rhythm synchronization timing set.

[0033] The navigation record generation submodule extracts the start node number, end node number and their modulation identifier from the rhythm segment based on the rhythm segment number and node number recorded in the rhythm synchronization timing set. Combining the frequency band to which the node belongs and the frame number order, it organizes all path combinations according to the rhythm number order to generate a distributed satellite navigation simulation synchronization record.

[0034] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0035] In this invention, node visibility screening is completed by combining node spatial location and satellite trajectory status, and a cross-node time synchronization mechanism is established based on rhythm status and local time accuracy. Signal combination and navigation frame structure are organized by frequency band division, and a pseudo-signal classification system for multi-node collaborative output is constructed. Then, the signal frames are synchronously modulated and the modulation status and scheduling rhythm are marked by combining a unified time reference, so as to achieve time consistency control of multi-source pseudo-signals under multi-frequency band conditions. The synchronization distribution characteristics in the signal transmission link are verified and organized by rhythm identification screening and time sequence archiving, thereby realizing multi-dimensional collaboration of spatial location, 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. Attached Figure Description

[0036] Figure 1 This is a system flowchart of the present invention;

[0037] Figure 2 This is a flowchart of the trajectory step size coordination module of the present invention;

[0038] Figure 3 This is a flowchart of the node rhythm determination module of the present invention;

[0039] Figure 4 This is a flowchart of the pseudo-signal combination module of the present invention;

[0040] Figure 5 This is a flowchart of the rhythm synchronization modulation module of the present invention;

[0041] Figure 6 This is a flowchart of the simulation link verification module of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0043] In the description of this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] Please see Figure 1 A distributed satellite navigation simulation system includes:

[0045] The trajectory step length coordination module acquires 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 azimuth of the simulation node. It identifies simulation nodes that meet the visibility criteria (distance ≤ GPS orbital altitude 20200km and elevation angle ≥ 5° signal-to-noise ratio threshold), integrates the node and trajectory status correspondence information, and generates a trajectory visible node mapping list.

[0046] The node rhythm determination module extracts the local time identifier of the simulation node based on the trajectory visible node mapping list, performs correlation judgment between the local time of the simulation node and the system time scale (selects nodes with a difference ≤100ns precision clock synchronization tolerance as synchronization candidate nodes), and classifies and marks the rhythm state to generate a synchronization response node state set.

[0047] The pseudo-signal combination module extracts the current frequency band label and signal generation status of each simulation node based on the state set of the synchronization response node, groups the pseudo-signals according to the frequency band label, sorts and registers the navigation frame (1500 bits / subframe navigation message structure defined by the GPS interface control file) structure of the signals in the same group, organizes the organization method and source identifier of the output signal frames of the simulation nodes, and generates a multi-node pseudo-signal classification sequence.

[0048] 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, performs synchronous modulation on signal frames of different frequency bands according to a unified time reference (Binary Phase Shift Keying (BPSK) is used for L1C / A code, and Quadrature Phase Shift Keying (QPSK) is used for L1C signal), 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.

[0049] The simulation link verification module, based on the signal frame rhythm modulation mapping table, screens and marks the distribution of rhythm identifiers in the signal transmission link between simulation nodes, archives and organizes the time sequence flow of all rhythm synchronization processes, and generates a distributed satellite navigation simulation synchronization record.

[0050] The trajectory visual node mapping list includes node identification identifiers, trajectory status labels, visibility criterion records, and node-trajectory correspondences. The synchronization response node status set includes a candidate node list, time synchronization labels, rhythm classification status, and system time stamp association results. 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 identifiers, frequency band frame correspondences, time scheduling matrix, and synchronization rhythm markers. The distributed satellite navigation simulation synchronization record includes rhythm synchronization process records, link rhythm distribution annotations, signal frame time sequence archiving records, and node interaction time stamps.

[0051] Please see Figure 2 The trajectory step size coordination module includes:

[0052] 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 nodes, identifies the satellite trajectory points under the current time step, marks the position of the trajectory points 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 satisfying the trajectory advancement range constraints, generating a trajectory advancement state sequence;

[0053] When obtaining initial satellite trajectory parameters, it is necessary to extract the initial three-dimensional coordinates, initial velocity vector, and initial orbital time label for each satellite from the satellite trajectory database. For the time step sequence set by the current simulation system, for example, every 30 seconds as a propulsion unit, the satellite propulsion status record values ​​are read at each unit time point, including orbital inclination, perigee parameters, and ascending node longitude. Subsequently, the spatial position coordinates of the simulation nodes at the same time step are retrieved and matched according to their numbers. It is then determined whether the propulsion status is within 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. At 0 seconds, the propulsion status value of each satellite is matched, and the propulsion status is updated by indexing the time point. During implementation, if a satellite is numbered S1, its initial propulsion status time point is t0, and its coordinates are X0 = (15600km, 0km, 0km). After step-wise propulsion, its status value at t1 is X1 = (15580km, 25km, 5km). Then, the original status value is updated to X1 and stored in the trajectory propulsion status value sequence for subsequent node judgment and analysis. To ensure the rationality of the propulsion status, each propulsion records the current propulsion time point and its previous status change value and updates the time index. See the data below:

[0054] Table 1. Trajectory Advancement Status Value Record Table

[0055]

[0056] 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 the track advancement. Therefore, through the above steps, the final result is the trajectory advancement state sequence.

[0057] The node visibility judgment submodule identifies all simulation nodes in the current advancement state based on the trajectory advancement state sequence, and combines the spatial geometric position relationship between the nodes and the trajectory to identify the set of nodes with spatial visibility attributes and generate a list of visible nodes for filtering.

[0058] Based on the trajectory advancement state value sequence, the time step value sequence corresponding to each advancement state is first determined during execution, and the satellite spatial position coordinates corresponding to each time point in the trajectory advancement state are extracted. Then, extract the spatial coordinates of all simulation nodes from the simulation node library. To determine the visibility relationship between trajectory points and nodes based on spatial geometric relationships, first calculate the spatial distance d between them, which is expressed using the three-dimensional Euclidean distance formula:

[0059] ;

[0060] when The distance condition is met at the same time; at the same time, the elevation angle is... The calculation formula is:

[0061] ;

[0062] The judgment condition is The elevation angle is expressed in radians converted to degrees; if the satellite position in a certain instance is... The node position is Then the calculation yields:

[0063] ;

[0064] ;

[0065] because and Therefore, this node meets the visibility requirement; furthermore, to verify whether the signal-to-noise ratio threshold is met, the signal-to-noise ratio value corresponding to the node number is read. If the signal-to-noise ratio (SNR) threshold is set to 32 dB, and the node number is N4, the SNR at t = 60 seconds is 34 dB, which satisfies the condition... Node N4 is then retained in the set of visible nodes at the current time step; finally, all time points and their corresponding visible nodes are compiled to form a list of visible nodes for filtering, such as time points. If the set of visible nodes is {N4, N7, N9}, then it is denoted as:

[0066] ;

[0067] The set of visible nodes at all time steps is summarized to obtain the final result as a list of visible nodes to be filtered.

[0068] The trajectory node mapping generation submodule is based on the visible node filtering list. According to the spatial attributes of the visible nodes and the dynamic information of the propulsion trajectory status, it matches the node set with the trajectory path in combination with the time sequence, marks the node number that conforms to the trajectory propulsion direction and has an azimuth correspondence, establishes a one-to-one correspondence between trajectory points and simulation nodes, and generates a trajectory visible node mapping list.

[0069] Based on the visible node filtering list, each item in the advancement state sequence needs to be read one by one. For each advancement state time point, all visible nodes need to be matched one-to-one with the trajectory number and node number. In the matching process, the time tag, number, and trajectory spatial coordinates of the current trajectory point need to be read from the trajectory advancement state. The node number and its spatial position at the same time point need to be matched to determine whether the spatial direction relationship between the two is reasonable. The comparison is made by calculating the angle between their azimuth vectors 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. All trajectory points and their corresponding visible 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. A mapping relationship set with the structure {T3: [N4, N5], T4: [N5, N6]} is generated, which is the trajectory visible node mapping list.

[0070] Please see Figure 3 The node rhythm determination module includes:

[0071] 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 system advancement state, and synchronously extracts the current unified system time to generate a set of local time stamps for nodes.

[0072] To extract the corresponding simulation node numbers based on the trajectory visual node mapping list, it is necessary to index the set of visual node numbers associated with each time step from the mapping list according to the advancement state, obtain the local time stamp items in the node storage records, and collect the time stamp items one by one using the node number as the index, and record their corresponding time tags. In the simulation system, each node will generate a local time stamp with GPS synchronization reference time as the reference at each time step. The unit of this stamp is nanoseconds. For example, node number N03 records a local time stamp of T=1 at the advancement state t=120s. 20000000200ns. Simultaneously, the simulation system's main control module provides a unified system timescale. 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 timescale mapping dataset adopts a two-dimensional mapping structure. Each row records the node number and corresponding local timescale in a certain propulsion state. The calling format is {propulsion state: {node number: local timescale}}. To verify the standardization of the records, the following sample dataset can be constructed:

[0073] Table 2 Simulation Node Local Time Identification Table

[0074]

[0075] As shown in Table 2, the local time of a node is recorded independently at the time point of the advancement state. This can be used to perform time difference judgment operations, and the final result is the node local time tag set.

[0076] The time difference determination and filtering submodule uses the local time stamp set of the node and the system time as the base time. Extract the local time identifier of each node. The time difference between the two is determined by calculating the absolute difference between the node's local time and the system time. The formula used is:

[0077] ;

[0078] The operation retrieves the status flag indicating whether the synchronization criterion is met. To satisfy all The node IDs are filtered to form a candidate set, resulting in a synchronization candidate node ID set, where... Represents the local time of node i. For system time identification, This represents the time difference between the node and the system. This is a synchronization judgment flag; a value of 1 indicates a synchronization candidate, and a value of 0 indicates that the synchronization tolerance is not met.

[0079] Based on the local time stamp set of each node, the time difference between each node is extracted using the system time as the base value. First, the system time stamp under the propulsion state is read. For example, in the propulsion state, t=120s, the system time stamp is T=120000000000ns. The local time stamps of each node at that time point are extracted, such as T_i(N03)=120000000200ns, T_i(N04)=120000000080ns, etc. The absolute value of the time difference is calculated for each item using the following formula: For node N03, the difference is The system compares the time difference with the 100ns threshold to determine if 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. Here, the 100ns threshold is the tolerable upper limit for precision synchronization. This value is jointly set by the system clock hardware stability and simulation accuracy requirements. The reference is that the standard deviation of clock drift in the system is σ≤10ns. At a 99.7% confidence level, the upper limit for the cumulative synchronization error of the system 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 tests. The node number and its status are merged and counted according to the progress status. For example, at t=120s, the node marked as 1 is N04, and the node marked as 0 is N03, forming a status record array {N03:0, N04:1}. All nodes marked as 1 are selected as synchronization candidate nodes, forming a synchronization candidate node number set.

[0080] The response rhythm marking submodule reads the current simulation state record information for each candidate node based on the set of synchronization candidate node numbers, performs response rhythm classification judgment and marking on the node state, archives all synchronization nodes according to the marking results, and generates a set of synchronization response node states.

[0081] Based on the set of candidate node numbers, the simulation running status records of each candidate node are read one by one at each advancement state time point, including the current task processing status (e.g., whether it is in data acquisition, forwarding, or sleep mode), communication link status (whether there is downlink, relay, or interruption), and feedback rate value (unit: bit / ms). A multi-parameter feature vector is established for the current advancement state using the node number as an index. The vector structure is a triple {state identifier, link identifier, feedback rate}. For example, node N04 is recorded as {1, 1, 256} at t=120s. State identifier 1 indicates an active state, link identifier 1 indicates normal communication, and feedback rate 1 indicates a positive feedback rate. With a rate of 256 bits / ms, the feature vector is input into a preset response rhythm standard. The feature vector is then classified and judged. Nodes with a state identifier of 1, a link identifier of 1, and a feedback rate ≥ 128 bits / ms are classified as "high-speed response type". Nodes with a state identifier of 1 but a feedback rate < 128 bits / ms are classified as "low-speed response type". Nodes with a link identifier of 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 type of all synchronization candidate nodes is archived and marked, and a rhythm label dictionary indexed by node number is established to generate a synchronization response node state set.

[0082] Please see Figure 4 The pseudo-signal combination module includes:

[0083] The frequency band status extraction submodule extracts the node number of each node based on the synchronization response node status set, counts the communication frequency band label and signal generation status identifier of each node in the current advancement state, retains the valid signal nodes, groups the valid node numbers of the same frequency band into a group, organizes the grouping table of all simulation nodes according to the frequency band number, and generates a frequency band group number set.

[0084] To extract simulation node numbers from the synchronous response node state set, the response attributes corresponding to each node need to be extracted under the advancement state index, and their frequency band label values ​​and current signal generation state values ​​need to be obtained. The frequency band label is the node's working frequency band identification code, 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, nodes with a state of 0 are removed from the records, retaining only the node numbers currently in a valid signal output state. The remaining nodes are then categorized and aggregated according to their frequency band labels, and a node grouping table is established using the frequency band as the primary key, as shown in the example below:

[0085] Table 3 Node Frequency Bands and Signal Status Table

[0086]

[0087] As shown in Table 3, node N02 is removed because its state is 0. N01 and N03 are assigned to group L1, and N04 is assigned to group L5. Finally, the group set classified by frequency band is obtained as {L1: [N01, N03], L5: [N04]}. The result is the frequency band group number set.

[0088] The navigation frame assembly submodule extracts the node numbers for each node within the same frequency band based on the frequency band grouping number set, and reads the navigation subframes generated by each node. The navigation subframe structure follows the GPS interface control file format, with each frame containing 1500 bits of data divided into 10 field blocks. Each field block is located according to its frame index number. The subframes from different nodes are then assembled at the field block level according to the navigation frame sequence specification, using the following formula:

[0089] ;

[0090] The combination deviation coefficient is calculated, and the navigation frames are sorted according to the principle of minimum combination deviation. The combination order is then numbered according to the frame index to obtain the navigation frame structure index table. This represents the deviation coefficient between node p and node q in the frame assembly structure. This represents the navigation frame bit value of node p in the k-th field, in bits, and can be either 0 or 1. This represents the target bit structure reference value of node q in the k-th field, in bits, with a value of 0 or 1, and n represents the upper limit of the bit index of the field block in the navigation frame structure;

[0091] The frequency band grouping and numbering set is used. Within each frequency band group, its node number set is traversed. The navigation frame data content of each node is extracted and split into field blocks according to the GPS protocol. Each navigation frame is 1500 bits, divided into 10 field blocks, each field block being 150 bits. The field blocks between different nodes are aligned according to their index numbers. For any node p and node q, the bit string value of its k-th field block is extracted. , The difference between the two values ​​represents the combined offset. Using the absolute value of this difference as input, all fields are summed, and the combined normalization coefficient is constructed using the sum of squares of the field blocks of the two nodes as the denominator. Let the field of node N01 be {1, 0, 1, 1, 0, 1, 1, 0, 0, 1}, and the field of N03 be {1, 1, 1, 0, 0, 1, 0, 0, 1, 1}. The sum of the absolute values ​​of the differences in the corresponding field blocks is 4, and the sum of squares of the field blocks is... After the roots are opened, ,have to:

[0092] ;

[0093] This result indicates that the two-node navigation frame structure has a moderate degree of combinational bias, and subsequent... The minimum item is the sorting priority item. A navigation frame field block reorganization sequence is established, and the final result is the navigation frame structure index table.

[0094] The combination deviation coefficient is used to measure the degree of difference between two simulation nodes in the field structure of navigation frames. Specifically, it characterizes 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 is at the corresponding field position. The less frame structure reconstruction adjustment is required during combination, the higher the frame structure consistency. Therefore, it can be given priority for signal synthesis and frame output sorting. Conversely, a larger value indicates that there are a lot of structural conflicts or differences in fields between the navigation frames of the two nodes. The recombination cost is higher and the combination priority is lower. This coefficient is the core indicator for navigation frame reconstruction sorting and node structure coupling judgment.

[0095] The formula's operational logic aims to measure the degree of mismatch in the combined matching of two simulation nodes in the navigation frame field structure, where the numerator part... This represents the word-by-word difference in bit values ​​between node p and node q at their corresponding field block positions. Summing the absolute values ​​reflects the cumulative degree of difference in the overall structure and has statistical significance for error. The denominator part... This is the square root of the sum of the squares of the corresponding bit values ​​in two node field blocks, used to measure the combination strength or structural overlap. This normalization process avoids interference from differences in the number of fields or the total number of bits affecting the deviation value, thus forming a relative deviation ratio coefficient between bit structures. This structure ensures that the combination deviation value... It is always in the positive range, has comparability, and can be used as a priority index for frame reordering.

[0096] The signal sequence generation submodule synthesizes the output signal frames of the simulation nodes in the order of the frame index according to the navigation frame structure index table. It 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-level mapping relationship table of frequency band → node → signal frame, and generates a multi-node pseudo signal classification sequence.

[0097] According to the navigation frame structure index table, each combined sorting structure is called, and the field blocks are read and reorganized according to the frame index order. For each field block, the source node number, the frequency band and its frame index position are recorded. All field information is assembled into a triplet structure such as {field index, source node, frequency band label}, and arranged into a node output frame sequence according to the navigation frame order. For example, the combined sequence is [field 1: N03@L1, field 2: N01@L1, field 3: N01@L1...]. The sorting result is written into a multi-level dictionary. The first level of the dictionary is based on the frequency band as the primary key, the second level is the node number, and the third level 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. The final result is a multi-node pseudo signal classification sequence.

[0098] Please see Figure 5 The rhythm synchronization modulation module includes:

[0099] 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 bits and scheduling time in each frame, parses the flag bits in byte order, 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 the frame structure field set.

[0100] Based on the multi-node pseudo-signal classification sequence, node numbers and frequency band labels are read. The corresponding signal frame content is read one by one for each node number. Each frame content is parsed bit by bit, and the first 20 bits are extracted as frame flag bits. These flag bits contain the node number, frame index value, and frame generation cycle number. The node number is converted from a preset field in the frame header to an 8-bit unsigned integer, the frame index value is a 3-bit binary value, and the cycle number is a 9-bit integer value. Bits 21 to 40 are decoded to extract the scheduling time field, which represents a millisecond timestamp as a decimal integer. The entire process is completed sequentially. After the data of each signal frame is registered, a correspondence table is constructed between the frame number and its flag bit and scheduling time field. During 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, using the format {frame number: {node number: N03, frequency band label: L1C / A, flag bit: 001001..., scheduling time: 5023}}. By extracting data from 5 frames of signal samples under each of the 20 nodes, a total of 100 frames of identifier table structure is formed, as shown in Table 4.

[0101] Table 4. Example of Signal Frame Flag Bits and Scheduling Time

[0102]

[0103] As shown in Table 4, the node number and frequency band label correspond to the extracted flag bits and scheduling time, which are then uniformly registered, and the result is a set of frame structure fields.

[0104] The modulation 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, combined with the frequency band mapping parameters, and performs an association operation between the flag bit and the scheduling time for all signal frames to obtain the modulation rhythm sorting set.

[0105] Based on the frequency band labels and frame scheduling time information recorded in the frame structure field, the frequency band label value corresponding to each frame is first read. During the processing of frequency band labels for frames 001 to 100, the modulation identifier value corresponding to frequency band L1C / A is set to 1, L1C to 2, and L5 to 3. During frequency band parsing, the frequency band string is directly mapped to the numerical identifier value, and a correspondence is established with the original frame number. Next, the millisecond timestamp in the scheduling time field is extracted, and a frame modulation order structure sequence is established using the frame scheduling time as the primary key. After identifying differences in frame scheduling times between frequency bands, frames with the same modulation type are grouped together. Frames are grouped together, sorted by scheduling time, and their sequence position values ​​are recorded. Simultaneously, the flag byte sequence of each frame is extracted as synchronization comparison content. A mapping structure is established between frame number, scheduling time, and modulation identifier value, represented as a triplet structure: {frame number, modulation identifier value, scheduling time}. This is then organized into a modulation rhythm order dictionary. In the actual test example, frame number 002 corresponds to frequency band L1C, modulation identifier value is 2, and scheduling time is 5023 milliseconds. Its rhythm order is located in the 3rd position of the L1C group, and the corresponding frame number index is stored in the structure. The final result is the modulation rhythm sort set.

[0106] The rhythm mapping construction submodule sorts the frame numbers and modulation identifiers recorded in the modulation rhythm sorting set, groups them by modulation identifiers, arranges the frame scheduling time in order, and associates the grouping results with the node frequency bands to obtain the signal frame rhythm modulation mapping table.

[0107] Based on the frame number, modulation identifier value, and scheduling time information recorded in the modulation rhythm sorting set, the frame is initially grouped according to the modulation identifier value. After merging the modulation types corresponding to the frequency bands, the scheduling time of each frame is extracted within each group, and a time sequence list is constructed based on milliseconds. The row vectors of the modulation frame rhythm sequence matrix are obtained by arranging the scheduling time in ascending order. The column vectors are divided according to the modulation identifier value to construct a two-dimensional matrix structure. The matrix elements are filled with the frame number, node number, and scheduling time, generating a combined structure in 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 records the frequency band label and maps it to the node number. The final summary result of the matrix is ​​shown in Table 5.

[0108] Table 5 Signal Frame Rhythm Modulation Mapping Matrix

[0109]

[0110] Table 5 lists the rhythm modulation matrix structure established according to the modulation type and scheduling time order, and the result is a signal frame rhythm modulation mapping table.

[0111] Please see Figure 6The simulation link verification module includes:

[0112] The rhythm identifier screening submodule extracts the rhythm sequence number, frequency band, and corresponding modulation type identifier 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 switching and marks them, and generates a rhythm distribution identifier set.

[0113] The frame number, frequency band type, and modulation scheme code are extracted from each frame of data according to the signal frame rhythm modulation mapping table. The rhythm position number of each frame is read sequentially, and the frames are classified according to their frequency band labels. Consecutive frame numbers within the same frequency band are grouped into rhythm segment structures. It is checked whether adjacent frames have the same frequency band label and a rhythm number interval of 1; rhythm segments that meet this condition are marked. Subsequently, the modulation scheme codes corresponding to the frames are compared. If the modulation scheme codes change between adjacent frames, the jump node is recorded, and segments with different modulation schemes are grouped separately. Throughout the process, it is necessary to ensure that each frame corresponds to... With a unique rhythm number and a clear frequency band label, the first 5 rhythm segments were extracted as test samples for the three frequency band types: L1C, L2C, and L5. In the samples, the rhythm segment consisting of frames 013 to 018 belongs to the L1C frequency band, and the modulation mode is 2 (representing QPSK). The numbers are consecutive and meet the screening requirements. The frequency bands of frames 031 to 033 are the same, but the modulation mode number is 1 (BPSK), so they are assigned to another segment. Finally, based on all screening results, a four-bit data structure of rhythm segment number, start and end frame number, frequency band label and modulation type is established and summarized according to the rhythm segment number to generate a rhythm distribution identifier set.

[0114] The synchronous timing archive submodule compares the start and end scheduling times of each rhythm segment with 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 sequential logical mapping relationship between rhythms to obtain the rhythm synchronization timing set.

[0115] Based on the rhythm distribution identifier, the rhythm segment number and its start and end frame number information are collected. The scheduling time field value is extracted from the start and end frames of each segment and arranged in ascending order of timestamps to organize the sequence of rhythm segments. For rhythm segments that are continuous in time but different in frequency band or modulation type, their time offset value and rhythm number are extracted to identify and mark whether there is frequency hopping switching between these rhythm segments. 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 included in the synchronization timing sequence. The table forms 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. Their modulation codes are different, and their timestamps are between 13782 milliseconds and 13897 milliseconds, with an interval 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 time sequence lookup table is converted into a two-dimensional time sequence matrix, where the horizontal axis represents the rhythm segment number and the vertical axis represents the chronological order. An offset comparison relationship is established by column to generate a rhythm synchronization time sequence set.

[0116] The navigation record generation submodule extracts the start node number, end node number and their modulation identifier from the rhythm segment number and node number recorded in the rhythm synchronization timing set. Combining the frequency band to which the node belongs and the frame number order, it organizes all path combinations according to the rhythm number order to generate a distributed satellite navigation simulation synchronization record.

[0117] Based on the rhythm segment numbers, node numbers, and scheduling time structure recorded in the rhythm synchronization timing set, all rhythm segments are sequentially traversed and node frame sequences are extracted. Node numbers, modulation type codes, and scheduling times are extracted from each frame sequence. Changes in node numbers, frequency band labels, and time intervals between adjacent frames are used as criteria for path structure determination. Path combinations within rhythm segments are constructed, and frame flow directions and frame number sequences are marked. After organizing all frame combination paths, a frame pair sequence mapping table is generated, recording the start frame number, end frame number, start node number, end node number, and frequency band type. Fields such as scheduling time order are extracted. In the sample data, the frame numbers within rhythm segment 005 are 033 to 036, and their node numbers are N01, N01, N03, and N03. The frequency band labels are L1C / L1C / L2C / L2C, and the scheduling times are 14213, 14240, 14270, and 14295 milliseconds. After extracting the above data, a multi-level nested structure is established in sequence according to the combination order of rhythm number, node pair, and frequency band label. All frame paths, node combinations, and rhythm segment numbers are mapped and integrated into a structure dictionary, and finally, a distributed satellite navigation simulation synchronization record is generated.

[0118] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A distributed satellite navigation simulation system, characterized in that, The system includes: The trajectory step size coordination module acquires 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 azimuth of the simulation node, identifies the simulation nodes that meet the visibility criteria, and generates a list of trajectory visible nodes. The node rhythm determination module extracts the local time identifier of the simulation node according to the trajectory visual node mapping list, associates and judges the local time of the simulation node with the system time scale, classifies and marks the rhythm state, and generates a set of synchronous response node states. The pseudo-signal combination module extracts the current frequency band label and signal generation status of each simulation node based on the synchronization response node state set, groups the pseudo-signals according to the frequency band labels, sorts and registers the navigation frame structure of 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, performs synchronous modulation on signal frames of different frequency bands according to a unified time reference, marks the modulation state 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 visual node mapping list includes node identification identifiers, trajectory status labels, visibility criterion records, and node-trajectory correspondence. The synchronization response node status set includes a candidate node list, time synchronization labels, rhythm classification status, and system time stamp association results. The multi-node pseudo-signal classification sequence includes a frequency band category index, signal source identifier, frame structure information, and navigation message index. The signal frame rhythm modulation mapping table includes a modulation method identifier, frequency band frame correspondence, time scheduling matrix, and synchronization rhythm marker.

3. The distributed satellite navigation simulation system according to claim 1, characterized in that, The trajectory step size 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 nodes, identifies the satellite trajectory points under the current time step, marks the position of the trajectory points 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 satisfying the trajectory advancement range constraints, generating a trajectory advancement state sequence; The node visibility judgment submodule identifies all simulation nodes in the current advancement state based on the trajectory advancement state sequence, and identifies the set of nodes with spatial visibility attributes by combining the spatial geometric position relationship between the nodes and the trajectory, and generates a list of visible nodes for filtering. The trajectory node mapping generation submodule, based on the visible node filtering list, matches the node set with the trajectory path according to the spatial attributes of the visible nodes and the dynamic information of the propulsion trajectory status, combined with the time sequence, marks the node numbers that conform to the trajectory propulsion direction and have directional correspondence, establishes a one-to-one correspondence between trajectory points and simulation nodes, and generates a trajectory visible 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 stamp extraction submodule extracts the corresponding number of the simulation node based on the trajectory visual node mapping list, classifies and organizes them according to the node number, records the local time stamp of each node in the current system advancement state, and synchronously extracts the current unified system time to generate a node local time tag set. The time difference determination and filtering submodule uses the local time stamp set of the node and the system time as the base time. Extract the local time identifier of each node, determine the time difference between the two, calculate the absolute difference between the node's local time and the system time, calculate the status identifier of whether the synchronization criterion is met, filter all the node numbers that meet the criteria 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 based on the set of synchronization candidate node numbers, classifies and marks the node state according to the response rhythm, archives all synchronization nodes according to the marking results, and generates a set of synchronization response node states.

5. The distributed satellite navigation simulation system according to claim 1, characterized in that, The pseudo-signal combination module includes: The frequency band status extraction submodule extracts the node number of each node according to the synchronization response node status set, counts the communication frequency band label and signal generation status identifier of each node in the current advancement state, retains the valid signal nodes, groups the valid node numbers of the same frequency band into a group, organizes the grouping table of all simulation nodes according to the 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 navigation subframes of different nodes according to the navigation frame sequence specification, calculates and obtains the combination deviation coefficient, sorts each navigation frame according to the principle of minimum combination deviation, and numbers the combination order according to the frame index to obtain the navigation frame structure index table. The signal sequence generation submodule synthesizes the simulated node output signal frames sequentially according to the navigation frame structure index table, and records the source node number, frequency band label and combined frame index position of each frame signal. It establishes a three-level 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 byte order, 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 the 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, combined with the frequency band mapping parameters, and performs an association operation between the flag bit and the scheduling time for all signal frames to obtain the modulation rhythm sorting set. The rhythm mapping construction submodule, based on the frame number and modulation identifier recorded in the modulation rhythm sorting set, groups the frames according to the 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 the signal frame rhythm modulation mapping table.

7. The distributed satellite navigation simulation system according to claim 1, characterized in that, The system also includes: 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 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 label, signal frame timing archive record, and node interaction time stamp.

8. The distributed satellite navigation simulation system according to claim 7, characterized in that, The simulation link verification module includes: The rhythm identifier screening submodule extracts the rhythm sequence number, frequency band, and corresponding modulation type identifier 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 switching and marks them, and generates a rhythm distribution identifier set. The synchronous timing archiving submodule, based on the rhythm number and the corresponding start and end frame number in the rhythm distribution identifier, compares the start and end scheduling times of each rhythm segment, 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 sequential logical mapping relationship between rhythms to obtain the rhythm synchronization timing set. The navigation record generation submodule extracts the start node number, end node number and their modulation identifier from the rhythm segment based on the rhythm segment number and node number recorded in the rhythm synchronization timing set. Combining the frequency band to which the node belongs and the frame number order, it organizes all path combinations according to the rhythm number order to generate a distributed satellite navigation simulation synchronization record.

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