Beidou short message and GPS / BDS positioning integrated communication method

Abstract

The invention relates to the technical field of satellite communication, and discloses a Beidou short message and GPS / BDS positioning integrated communication method, which comprises the following steps: acquiring an instantaneous carrier-to-noise ratio of a downlink signal, calculating a time change gradient, and locking a channel coding strategy; comparing the ground speed of the positioning data with a motion threshold value, and selecting to execute a trend priority truncation strategy or a precision priority retention strategy to generate a data packet; when the instantaneous carrier-to-noise ratio reaches the standard and the gradient is positive, emission is triggered, otherwise, emission is suspended until the gradient is positive or overtime fusing, the emission opportunity is locked through the instantaneous channel gradient, the load semantics are dynamically reconstructed based on the motion state, and on the premise that the radio frequency hardware cost is not increased, the transmission efficiency is improved. And the communication success rate and the information effectiveness in the periodic fast fading channel under the severe sea condition are improved.

Description

Technical Field

[0001] This invention relates to an integrated communication method of BeiDou short message service and GPS / BDS positioning, belonging to the field of satellite communication technology. Background Technology

[0002] Current satellite mobile communication systems possess wide-area coverage characteristics and are widely used in ocean shipping and emergency rescue scenarios. In existing integrated communication terminal designs, the common technique is to encapsulate high-precision positioning data output by the satellite positioning module, such as latitude, longitude, and time information in NMEA format, as application layer payloads into short message communication protocols for transmission. This positioning data pass-through mechanism can ensure accurate location acquisition for the terminal in static environments with good channel quality and sufficient bandwidth. However, in real-world scenarios where ocean-going vessels are subject to swaying from waves or the terminal is located in complex terrain, the communication link faces a contradiction between drastic fluctuations in channel capacity and the high entropy characteristics of positioning data. The physical layer channel is affected by multipath effects and antenna attitude changes, resulting in drastic dynamic changes in the instantaneous signal-to-noise ratio and frequent drops in modulation threshold. Under the existing pass-through mechanism, the terminal lacks a mechanism to adjust the application layer source coding structure according to the physical layer channel state, and continues to send long data packets containing full-precision coordinates even when channel conditions deteriorate.

[0003] While existing technologies have made progress in hardware integration and multi-mode collaboration, software control strategies for complex channel environments, especially the establishment of dynamic mapping between source coding and physical channel states, still suffer from rigid strategies and insensitivity to the environment. For example, the utility model patent with authorization announcement number CN204334968U discloses a Beidou short message communication and Beidou / GPS positioning terminal. It integrates the Beidou first-generation communication module and the dual-mode positioning module through an MCU to solve the communication link connectivity problem in areas without public network coverage at the hardware physical level. However, upon analyzing the control logic, this type of technology is still at the ready-to-go open-loop control stage. The data transmission strategy does not include a mechanism for sensing and feedback on the time-varying characteristics of channel quality, and it does not have the ability to dynamically adjust the data packet information entropy or coding redundancy according to the carrier's motion state. As a result, in actual applications, the terminal can only mechanically execute fixed-length data pass-through, and cannot achieve a balance between transmission reliability and data validity.

[0004] Therefore, the technical problem to be solved by this invention is how to establish a dynamic mapping between physical layer state and application layer coding logic in satellite mobile channels with limited signal-to-noise ratio and drastic fluctuations, so as to achieve positioning data transmission and ensure the accessibility of key information without increasing the terminal radio frequency transmission power. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: An integrated communication method for BeiDou short message service and GPS / BDS positioning, applied to a terminal including a processing unit and a communication unit, the method comprising the following steps:

[0006] Step S1: The processing unit continuously collects the instantaneous carrier-to-noise ratio of the downlink signal received by the communication unit at a preset sampling frequency, calculates the time change gradient of the instantaneous carrier-to-noise ratio, and compares the instantaneous carrier-to-noise ratio with a preset demodulation threshold set to determine the channel coding and modulation scheme that is allowed to be used at the current moment.

[0007] In step S2, the processing unit acquires the positioning data output by the satellite positioning unit, which includes latitude and longitude coordinates, ground speed, and heading parameters, and compares the ground speed with a preset motion threshold. If the ground speed is greater than the motion threshold, the processing unit executes a trend-first truncation strategy, which removes preset low-significant digits of the latitude and longitude coordinates to release payload space, and maps and fills the released payload space with the high-significant digits of the ground speed and heading parameters to generate a data packet to be sent. If the ground speed is not greater than the motion threshold, the processing unit executes a precision-first retention strategy, which retains the low-significant digits of the latitude and longitude coordinates and performs compression encoding on the ground speed and heading parameters to generate a data packet to be sent.

[0008] In step S3, the processing unit writes the generated data packet to be sent into the transmission buffer and executes the transmission gating judgment process. When the instantaneous carrier-to-noise ratio is higher than the minimum demodulation threshold corresponding to the channel coding modulation scheme and the time change gradient is positive, a transmission trigger signal is generated to control the communication unit to perform uplink transmission. If the time change gradient is negative, the processing unit controls the communication unit to suspend the transmission action and maintain a delayed waiting state until the time change gradient is detected to turn positive or the duration of the delayed waiting state reaches the preset timeliness circuit breaker threshold.

[0009] Preferably, in step S1, before calculating the time-varying gradient, the processing unit calculates the link quality index, which characterizes the current channel quality, based on the instantaneous carrier-to-noise ratio. The link quality index The computational logic satisfies: ,in, The instantaneous carrier-to-noise ratio collected at the current moment. The average carrier-to-noise ratio within the preset sliding time window. The weighted smoothing coefficient is preset; the processing unit is based on the link quality index. The preset hierarchical decision interval into which the target scheme is located is selected from multiple preset channel coding and modulation schemes.

[0010] Preferably, in step S2, the specific operations of the processing unit in executing the trend-first truncation strategy include: the processing unit extracts the latitude and longitude coordinate field from the positioning data, and removes the low-order binary data of the field after a preset number of decimal places through displacement operation; the processing unit extracts the ground speed and heading parameter fields, retains the high-order binary data of the field and removes the low-order binary data; the processing unit fills the free bit positions formed by removing the low-order binary data of the latitude and longitude coordinates with the retained high-order binary data of the ground speed and heading parameters, and sets a mask status bit indicating that the trend-first strategy is currently adopted in the header field of the data packet to be sent.

[0011] Preferably, the timeliness of the circuit breaker threshold in step S3 is associated with a deadlock release mechanism. The processing unit starts a timer when it enters the delayed waiting state. If the count value of the timer exceeds the timeliness of the circuit breaker threshold and the time change gradient is still negative, the processing unit forcibly generates a transmission trigger signal and simultaneously adjusts the forward error correction coding redundancy in the data packet to be sent to the maximum value allowed by the current channel coding and modulation scheme.

[0012] Preferably, before step S2, the method further includes a dual-mode integrity screening step, in which the processing unit parses the first location data from the GPS system and the second location data from the BDS system in the positioning data respectively; the processing unit calculates the spatial Euclidean distance between the first location data and the second location data; if the spatial Euclidean distance is greater than a preset consistency judgment threshold, the processing unit generates a positioning alarm flag and places it in the highest priority field of the data packet to be sent, and selects only the set of data with higher signal quality indicators from the first location data and the second location data as the input data for step S2.

[0013] Preferably, selecting a single target scheme from multiple preset channel coding and modulation schemes includes: when the link quality index is in the first interval, the processing unit selects the full-dimensional transparent mode, which retains the full-precision coordinates and complete timestamps of the positioning data; when the link quality index is in the second interval below the first interval, the processing unit selects the differential compression mode, which uses the coordinates of the BDS system as a reference to calculate and encode the differential increment vector of the GPS system coordinates relative to the BDS system coordinates.

[0014] Preferably, when the link quality index is in the third interval below the second interval, the processing unit selects the dimension reduction and minimum guarantee mode. This mode executes a trend-first truncation strategy or a precision-first retention strategy, and uses the payload space released by the truncation strategy or retention strategy to fill the forward error correction code. The length ratio of the forward error correction code is negatively correlated with the value of the link quality index.

[0015] Preferably, in step S2, before comparing the ground speed with the preset motion threshold, the processing unit performs a moving average filtering process on the ground speed to filter out the high-frequency speed fluctuation component caused by the instantaneous vibration of the carrier; the setting value of the motion threshold is related to the channel multipath environment in which the terminal is currently located, and the motion threshold in the marine scenario is set to be lower than the motion threshold in the land urban canyon scenario.

[0016] Preferably, the communication unit performs the uplink transmission action by: receiving a transmission trigger signal and detecting the timing second pulse signal of the BeiDou satellite navigation system; after detecting the rising edge of the timing second pulse signal, the communication unit modulates the data packet to be transmitted onto the carrier and transmits it to the satellite network within a preset short message communication time slot protection interval.

[0017] Preferably, in step S2, if the processing unit determines that the ground speed is less than a preset stationary threshold and the change in the positioning data relative to the last successfully transmitted position is less than a preset drift threshold, the processing unit generates a simplified data packet containing only the heartbeat status word and the incremental change in positioning data, and controls the communication unit to perform uplink transmission at a power value lower than the standard transmission power.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. In the integrated communication of BeiDou short message and GPS / BDS positioning, a dynamic mapping mechanism between physical channel state and source coding structure is established. When the downlink quality index decreases and the channel capacity is limited, the positioning data is lossily truncated and the forward error correction code is filled using the released payload space. The fixed-length positioning data stream in traditional communication is transformed into a dynamic game variable between source accuracy and channel redundancy. Without increasing the terminal radio frequency transmission power and antenna gain, the information entropy is reduced to obtain additional coding gain. This solves the problem of demodulation failure and spectrum resource loss caused by repeated retransmission of long data packets due to excessively high bit error rate in low signal-to-noise ratio or obstructed environments.

[0020] 2. By using the instantaneous carrier-to-noise ratio time gradient as the transmission gating trigger condition, the uplink data transmission action is forcibly locked to the rising edge window of the channel quality improvement trend. Based on the time-varying characteristics of the channel, the phase-locked transmission logic avoids the physical risk of signal energy falling into the periodic deep fading trough due to random access or ready-to-transmit. Statistically, the transmission timing is automatically aligned with the channel gain peak. In scenarios where periodic fast fading is caused by ocean waves or violent carrier swaying, the time diversity principle is used to improve the physical layer reachability of single pulse signals.

[0021] 3. Construct an adaptive adaptation mechanism based on semantic masking of carrier motion state. Dynamically adjust the weight of static coordinate accuracy and dynamic vector information bit allocation in the data payload according to ground speed parameters. Break the traditional fixed truncation strategy that indiscriminately discards motion trend information. Establish the coding rule of prioritizing the retention of high-value vector data such as speed and heading in high-speed motion scenarios. Ensure that the payload space of extremely limited short messages always carries the most business-value information component for trajectory estimation at the receiving end. Solve the technical contradiction of loss of target motion trend due to insufficient communication bandwidth in high dynamic scenarios. Attached Figure Description

[0022] Figure 1 This is a flowchart of the integrated communication method of channel gradient and motion semantics of the present invention;

[0023] Figure 2 This is a comparison diagram of payload bit resource allocation for the trend-first and precision-first strategies of this invention;

[0024] Figure 3 This is a schematic diagram of the hardware architecture and data interaction of the integrated communication terminal device of the present invention. Detailed Implementation

[0025] 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.

[0026] This invention discloses an integrated communication method for BeiDou short message service and GPS / BDS positioning. The method's execution flow begins with the processing unit initiating a channel state awareness process. The processing unit continuously reads the physical layer parameters of the downlink pilot signal received by the communication unit at a preset sampling frequency, such as 20Hz to 100Hz. Specifically, this is achieved by acquiring the instantaneous carrier-to-noise ratio. And combined with the average carrier-to-noise ratio within the preset sliding time window Using the linear weighting formula Calculate the link quality index, which characterizes the current channel quality. ,in To characterize the weighted smoothing coefficient of the channel's time-varying sensitivity, the link quality index is compared with a preset hierarchical decision interval to determine the channel coding and modulation scheme allowed by the system at the current moment. This covers multiple levels from full-dimensional transparent mode to dimensionality-reduced baseline mode, achieving adaptive matching between source data volume and channel capacity. This method introduces a payload reconstruction mechanism based on kinematic semantics. After acquiring the positioning data output by the satellite positioning unit, which includes latitude and longitude coordinates, ground speed, and heading parameters, the processing unit performs a dual-mode integrity screening, i.e., calculating the spatial Euclidean distance between the GPS location data and the BDS location data. If this distance exceeds the consistency judgment threshold, an alarm is triggered, and a set of data with high signal quality is retained. The ground speed of the positioning data is compared with a preset motion threshold. When the system is in dimensionality-reduced baseline mode and the ground speed is greater than the motion threshold, the processing unit executes a trend-first truncation strategy, removing a preset number of decimal places after the latitude and longitude coordinates through displacement operations, such as removing the lower 12 binary bits. The data is compressed to release the payload space, and the high-order significant digits of the ground speed and heading parameters, which characterize the target's motion trend, are mapped and filled into the released space, thus prioritizing the transmission of dynamic vector information in high-speed motion scenarios. Conversely, if the ground speed is not greater than the motion threshold, a precision-priority retention strategy is implemented, retaining the low-order precision of the coordinates and compressing the speed parameters, ultimately generating a data packet to be transmitted that is adapted to the current channel and motion state. Finally, this method completes uplink transmission through phase-locked gating logic. After the processing unit writes the data packet into the transmission buffer, it does not immediately trigger the transmission, but continuously calculates the time change gradient of the instantaneous carrier-to-noise ratio. When the instantaneous carrier-to-noise ratio is higher than the minimum demodulation threshold and the time change gradient is positive, i.e., the channel is on the rising edge, a transmission trigger signal is generated to control the communication unit to perform the transmission action within the protection interval of the BeiDou timing second pulse. If the gradient is negative, it is suspended and waited until the gradient turns positive or the time-sensitive fuse threshold is triggered, thus achieving statistical alignment between the transmission energy and the channel gain peak.

[0027] Example 1: This example aims to explain how the present invention solves the communication interruption problem through cross-layer collaboration between the physical layer and the application layer by reviewing a long-range search and rescue communication process under severe sea conditions. In this scenario, the rescued target was a life raft that had lost power and was violently rocking with the swells in sea state 4. The equipped terminal not only faced periodic rapid fading of the channel due to wave obstruction, but was also in a dynamic state of high-speed drift. This caused continuous packet loss of short messages under the traditional fixed-length transparent transmission mechanism due to excessively high bit error rate, and the command center could not obtain an effective location. After the intervention of the present invention, the terminal's processing unit identified that the current channel was in a low-quality range by calculating the link quality index and automatically switched to the dimension reduction and minimum guarantee mode. This only solves the static channel capacity matching problem. The key breakthrough lies in the synergistic effect of phase-locked transmission and semantic mask reconstruction. The terminal detected that the instantaneous carrier-to-noise ratio showed a sinusoidal fluctuation with an amplitude exceeding 10dB. The processing unit did not use the traditional random signal transmission method. Instead of using a competitive launch strategy, this approach utilizes gradient gating logic to lock the launch action within a window of several hundred milliseconds as the signal-to-noise ratio (SNR) rises from a trough to a peak. This adaptive scheduling strategy, without increasing RF power, leverages the time-varying characteristics of the channel itself to avoid deep fading points, successfully delivering a physical layer signal frame to the satellite. Because the life raft was in a rapid drifting state, the ground speed detection module triggered a trend-priority truncation strategy. The terminal intelligently discarded the now meaningless sub-meter-level static coordinate accuracy and used valuable payload bits to encode the drift speed and heading vector with high fidelity. This strategy adjustment enabled the command center to perform accurate dead reckoning based on the high-confidence motion trend vector contained in this data packet, even though the coordinate accuracy was only at the hundred-meter level. This allowed for rapid convergence of the search and rescue radius and successful guidance of rescue vessels to intercept the target, verifying the core technological value that fuzzy correctness is far superior to precise loss under extremely limited conditions.

[0028] Example 2: This example quantitatively verifies the performance advantages of the method of the present invention in periodic fast fading channels by constructing a reproducible comparative test environment. The test builds a closed-loop test system including a Beidou satellite signal simulator, a channel fading simulator and the terminal under test. The channel model is set as a Ricean fading channel, and dynamic fading with a period of 4 seconds and a depth of 15dB is superimposed to simulate a moderate sea wave environment. The test indicators mainly focus on the uplink success rate of data packets and the effective service value of the demodulated information. The test data recorded in the table below are under the same average signal-to-noise ratio (C / N0=36dBHz), see Table 1.

[0029] Table 1: Performance Comparison of Traditional Transparent Transmission Method and Integrated Communication Method of the Present Invention

[0030]

[0031] Data analysis shows that the experimental group reduced the packet loss rate from 68.4% in the control group A to 12.3% by introducing a gradient phase-locking mechanism, proving the effectiveness of avoiding channel fading troughs in the time domain. At the same time, under the same low signal-to-noise ratio and bandwidth limitation, the experimental group used a motion semantic adaptive strategy. Although the single-point position accuracy was lower than that of the control group A, the single-point accuracy was meaningless under the large number of packet losses in the control group A. By retaining the velocity vector, the trajectory prediction error of the receiver was greatly reduced to within 200 meters. This confirms that the present invention improves the actual service efficiency of the communication link by optimizing the semantic allocation of bits without increasing the physical bandwidth.

[0032] Example 3: This example combines Figures 1 to 3 This document describes an integrated communication method combining BeiDou short message service and GPS / BDS positioning, such as... Figure 1 As shown, the process involves acquiring positioning data and collecting downlink signals. On one hand, the processing unit acquires raw GPS and BDS data and performs dual-mode integrity screening based on spatial Euclidean distance consistency. On the other hand, the communication unit continuously samples downlink signals for the processing unit to calculate the link quality index based on instantaneous carrier-to-noise ratio and gradient, and thereby lock the channel coding scheme of full-dimensional, differential, or reduced-dimensional mode. The process then enters the branch determination stage, comparing the ground speed with the motion threshold. If it is determined to be a high-speed state, a trend-first truncation strategy is executed, i.e., removing the low coordinate bits and filling the high vector bits. If it is determined to be a low-speed state, a precision-first retention strategy is executed, retaining the coordinate precision and compressing the speed parameters. The data packets to be sent generated by the above strategies must contain mask status bits and error correction codes. Finally, the process enters the transmission gating determination process. When the gradient is detected to be positive and higher than the demodulation threshold or the gradient turning positive and triggering the circuit breaker condition are met, the uplink transmission action is performed using the timing second pulse protection interval. Otherwise, the process remains in a suspended waiting state.

[0033] like Figure 2 As shown in the figure, the horizontal axis lists four key data fields: latitude and longitude coordinates, ground speed parameters, heading parameters, and forward error correction codes. The vertical axis represents the number of bits occupied by each field. The horizontal striped bar chart represents the trend-first truncation strategy. Under this strategy, the number of bits for latitude and longitude coordinates is reduced, and the saved space is used to significantly increase the bit allocation for ground speed and heading parameters to ensure high-precision expression of dynamic vectors. The horizontal striped bar chart represents the precision-first preservation strategy. A very high proportion of bits is allocated to maintain the complete accuracy of latitude and longitude coordinates, while only a very small number of bits are reserved for ground speed and heading parameters. Both strategies reserve a corresponding proportion of forward error correction code space according to the channel conditions.

[0034] like Figure 3As shown, the space segment consists of a hybrid satellite network composed of the GPS / BDS system providing global positioning services and the BeiDou satellite system providing short message / positioning services. The user end is an integrated communication terminal device, whose core components include a dual-mode satellite positioning module, a main control processing unit (MCU), and a BeiDou communication radio frequency module. The dual-mode satellite positioning module has a built-in BeiDou positioning receiver and a GPS positioning receiver, and is responsible for transmitting positioning and speed data streams to the MCU through the raw data output interface. The main control processing unit integrates four functional modules: dual-mode integrity screening logic, channel state awareness logic, payload adaptive reconstruction logic, and phase-locked transmission gating. It is responsible for receiving downlink channel parameters from the radio frequency module and outputting transmission trigger signals. The BeiDou communication radio frequency module includes a radio frequency transceiver front-end, a timing second pulse detection, and a power amplifier. It is responsible for executing short message uplink under the control of the MCU and interacting bidirectionally with the satellite network.

[0035] Example 4: This example focuses on the parameter calibration method and deadlock release mechanism of the Link Quality Index (LRI) calculation logic in this invention to ensure the stability of the system under various boundary conditions. The LRI calculation formula is explained below. Medium weighted smoothing coefficient The selection of parameters and the system design of adaptive adjustment logic: when the terminal is in a rapidly changing channel environment such as vehicle-mounted or high sea state, the system monitors... The variance determination, the processing unit will The value is adjusted to the range of 0.7 to 0.9, setting a higher weight for instantaneous values ​​to quickly respond to sudden changes in the channel; conversely, in static or slow fading environments, the value is adjusted to... The value is lowered to 0.2 to 0.4, using historical averages to smooth noise interference and prevent frequent oscillations in the coding strategy. In addition, to address the risk of infinite waiting that may be caused by the transmission gating mentioned in step S3, namely the problem of data stagnation in the buffer due to a long-term negative gradient or a long-term carrier-to-noise ratio below the threshold under extremely poor channel conditions, this invention incorporates a dual deadlock release mechanism (i.e., time-sensitive circuit breaking): The first-level circuit breaking is based on data freshness. When the location data stays in the buffer for longer than the effective lifespan, such as the 1-second update cycle of GPS data, the old frame is directly discarded and new data is collected. The second-level circuit breaking is based on the maximum delay tolerance. When the timer reaches the preset 3-second threshold and the gradient has not yet turned positive, the system triggers a transmission action and simultaneously instructs the source coding module to adjust the redundancy of the forward error correction code (FEC) to the theoretical maximum value allowed by the current protocol, such as using convolutional coding with a 1 / 2 code rate or increasing the number of repeated transmissions. By sacrificing great spectral efficiency in exchange for the weak probability of success of this forced breakthrough, the system ensures that it has deterministic behavioral logic under any physical limits.

[0036] Example 5: This example details the dual-mode integrity screening and anti-interference defense mechanism under complex electromagnetic environments. Considering the risk of positioning drift caused by suppression or spoofing interference with a single satellite navigation system such as GPS in practical applications, this invention constructs a strict spatial consistency judgment fence at the source of the data link, before step S2. In each positioning cycle, the processing unit synchronously parses the NMEA data streams output by GPS and BDS, calculates the spatial Euclidean distance in the WGS-84 coordinate system, and sets a consistency judgment threshold. For example, 50 meters, this threshold is dynamically adjusted based on the geometrical factor of precision (GDOP) of the number of currently visible satellites; if the calculated distance difference Upon receiving the data, the processing unit immediately determines that an integrity fault exists. At this point, it not only sets a positioning alarm flag in the header field of the data packet to be sent, but also initiates signal quality arbitration logic, reads the carrier phase variance and satellite lock-in number of the two systems, automatically eliminates the data from the side with poor signal quality, and uses the set of data with higher credibility as the input source for subsequent compression encoding. This ensures that every bit of data transmitted through the precious narrowband satellite link is real information that has been cross-verified, preventing misleading command decisions caused by false positioning data occupying channel resources, thereby achieving defense against navigation layer deception attacks at the communication layer.

[0037] Example 6: This example specifically demonstrates how, in the dimension reduction and baseline protection mode, bitwise operations are used to implement the specific encoding operations of the trend-first truncation strategy and the precision-first retention strategy. When the processing unit determines that the trend-first truncation strategy needs to be executed, it extracts the 32-bit floating-point latitude and longitude data, converts it to fixed-point integers, and directly discards the lower 12 bits representing the fourth decimal place and lower precision through a right shift operation, retaining only the higher 20 bits representing the large range of positions. The processing unit reads the heading (0-360 degrees) and ground speed (0-100 knots) data that would normally be discarded in low-speed mode, performs 5-bit and 7-bit quantization encoding respectively, and fills the upper part with these two sets of dynamic vector data totaling 12 bits. The data packet header uses the empty bits left after latitude and longitude truncation. Finally, a 10-bit binary code is written into the control field to indicate that the current mask format is trend-first. Conversely, when the precision-first preservation strategy is executed, the processing unit maintains the full precision of the latitude and longitude data or truncates only a very small number of low bits, such as the lower 4 bits, and forces the velocity and heading fields to zero or uses only 1 bit to represent the stationary / moving state. At this time, a 01 binary code is written into the control field of the data packet header. The decoding server at the receiving end calls the corresponding inverse mapping logic according to the mask status bits in the header, so that the most valuable physical information in the current scene can be adaptively restored without increasing the total transmission bandwidth. The whole process is based entirely on basic bit operation instructions, reducing the computing power requirements of the terminal microcontroller.

[0038] Example 7: In this example, based on the Doppler frequency shift feature environmental scene recognition and motion threshold setting procedure, the processing unit executes the motion threshold setting step, utilizing the physical principle of the correlation between carrier micro-motion characteristics and scene: In marine scenes, the carrier is affected by swells, and the received signal Doppler frequency shift exhibits periodic high-frequency jitter characteristics; in land scenes, the carrier characteristics are relatively convergent. The processing unit executes the recognition process to determine the current scene and the corresponding motion threshold: Data input: with The sampling rate reads the raw carrier phase observations output by the satellite positioning unit and extracts the most recent values. For example, a Doppler frequency shift data sequence within 3 seconds is preferred; feature calculation: calculate the variance of the data sequence. Characterizing the instantaneous micro-motion intensity of the carrier, scene determination and threshold mapping: pre-stored scene decision benchmark value Statistical calibrations derived from typical sea states, for example If calculation The current scene is determined to be a high-dynamic ocean scene, and the motion threshold is set accordingly. Set as For example A lower threshold setting increases the system's sensitivity to ocean current drift, ensuring that the trend-priority truncation strategy, triggered under low-speed drift conditions, preserves vector information. Determine if the current scene is land or stable, and set the motion threshold. Set as For example A higher threshold is set to filter out false displacements caused by positioning noise in land scenes.

[0039] Based on the dynamic calculation procedure for the integrity judgment threshold of the geometric accuracy factor, when performing the dual-mode integrity screening step, the processing unit dynamically adjusts the consistency judgment threshold according to the engineering law of the linear expansion of the positioning error boundary with the dilution of satellite geometric distribution. To ensure that the threshold setting strictly matches the current satellite observation conditions and avoid false alarms or missed alarms caused by fixed thresholds, the processing unit uses analytical formulas to calculate in real time. : K is the confidence level safety factor, with a dimensionless constant ranging from 3.0 to 5.0 according to the Radio Technical Committee on Aeronautics (RTCA) standard. Probability interval; The standard deviation of the system's basic ranging error, in meters, is determined by the nominal accuracy of the receiver hardware, for example, a value of 6.0m. The geometric precision factor output by the satellite positioning unit at the current moment is a dimensionless real number, and is only used when calculating the spatial Euclidean distance. Location alarm flags are generated in real time; based on the adaptive adjustment procedure of the link smoothing coefficient according to the signal-to-noise ratio variance, the weighted smoothing coefficient is used when the processing unit calculates the link quality index L. The signal processing principle is to select a filter whose bandwidth matches the dynamic characteristics of the signal. When the channel changes rapidly, the weights are increased to track the trend, and when the channel is stable, the weights are decreased to suppress noise. The processing unit determines the coefficients at the current time through a mapping function. Statistical calculation: Calculate the variance of the most recent N instantaneous carrier-to-noise ratio (CNR) samples (e.g., N = 50). Linear mapping: Based on the variance value within a preset static baseline variance With fast fading limit variance Calculation of position between : , The minimum smoothing coefficient under steady-state conditions is, for example, 0.2. The maximum smoothing coefficient under high dynamic conditions is, for example, 0.8. If the calculation result exceeds... to The interval is directly truncated to the boundary value, ensuring that the link quality index L adapts to various sea conditions and maintains the optimal balance between sensitivity and stability without human intervention.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. An integrated communication method for BeiDou short message service and GPS / BDS positioning, characterized in that, This method is applied to a terminal that includes a processing unit and a communication unit, and includes the following steps: Step S1: The processing unit continuously collects the instantaneous carrier-to-noise ratio of the downlink signal received by the communication unit at a preset sampling frequency, calculates the time change gradient of the instantaneous carrier-to-noise ratio, and compares the instantaneous carrier-to-noise ratio with a preset demodulation threshold set to determine the channel coding and modulation scheme that is allowed to be used at the current moment. Step S2: The processing unit acquires the positioning data output by the satellite positioning unit, which includes latitude and longitude coordinates, ground speed, and heading parameters, and compares the ground speed with a preset motion threshold. If the ground speed is greater than the motion threshold, the processing unit executes a trend-first truncation strategy, which removes preset low-order significant digits of the latitude and longitude coordinates to release payload space, and maps and fills the released payload space with the high-order significant digits of the ground speed and heading parameters to generate a data packet to be sent. If the ground speed is not greater than the motion threshold, the processing unit executes a precision-first retention strategy, which retains the low-order significant digits of the latitude and longitude coordinates and performs compression encoding on the ground speed and heading parameters to generate a data packet to be sent. In step S3, the processing unit writes the generated data packet to be sent into the transmission buffer and executes the transmission gating judgment process. When the instantaneous carrier-to-noise ratio is higher than the minimum demodulation threshold corresponding to the channel coding modulation scheme and the time change gradient is positive, a transmission trigger signal is generated to control the communication unit to perform uplink transmission. If the time change gradient is negative, the processing unit controls the communication unit to suspend the transmission action and maintain a delayed waiting state until the time change gradient is detected to turn positive or the duration of the delayed waiting state reaches the preset timeliness circuit breaker threshold.

2. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 1, characterized in that, In step S1, before calculating the time-varying gradient, the processing unit calculates the link quality index, which characterizes the current channel quality, based on the instantaneous carrier-to-noise ratio. The link quality index The computational logic satisfies: ,in, The instantaneous carrier-to-noise ratio collected at the current moment. The average carrier-to-noise ratio within the preset sliding time window. The weighted smoothing coefficient is preset; the processing unit is based on the link quality index. The preset hierarchical decision interval into which the target scheme is located is selected from multiple preset channel coding and modulation schemes.

3. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 1, characterized in that, In step S2, the specific operations of the processing unit in executing the trend-first truncation strategy include: the processing unit extracts the latitude and longitude coordinate field from the positioning data, and removes the binary low-order data with a preset number of decimal places from the latitude and longitude coordinate field through displacement operation; the processing unit extracts the ground speed and heading parameter fields, retains the binary high-order data of the fields and removes the binary low-order data; the processing unit fills the free bit positions formed by removing the binary low-order data of the latitude and longitude coordinates with the retained binary high-order data of the ground speed and heading parameters, and sets a mask status bit indicating that the trend-first strategy is currently adopted in the header field of the data packet to be sent.

4. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 1, characterized in that, The time-sensitive circuit breaker threshold in step S3 is associated with a deadlock release mechanism. The processing unit starts a timer when it enters the delayed waiting state. If the timer count exceeds the time-sensitive circuit breaker threshold and the time change gradient is still negative, the processing unit forcibly generates a transmission trigger signal and simultaneously adjusts the forward error correction coding redundancy in the data packet to be sent to the maximum value allowed by the current channel coding and modulation scheme.

5. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 1, characterized in that, Before step S2, the method further includes a dual-mode integrity screening step, in which the processing unit parses the first location data from the GPS system and the second location data from the BDS system in the positioning data respectively; the processing unit calculates the spatial Euclidean distance between the first location data and the second location data; If the spatial Euclidean distance is greater than the preset consistency judgment threshold, the processing unit generates a positioning alarm flag and places it into the highest priority field of the data packet to be sent. At the same time, it selects only the set of data with higher signal quality indicator from the first location data and the second location data as the input data for step S2.

6. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 2, characterized in that, Selecting a single target scheme from multiple preset channel coding and modulation schemes includes: when the link quality index is in the first interval, the processing unit selects the full-dimensional transparent mode, which retains the full-precision coordinates and complete timestamps of the positioning data; when the link quality index is in the second interval below the first interval, the processing unit selects the differential compression mode, which uses the coordinates of the BDS system as a reference to calculate and encode the differential increment vector of the GPS system coordinates relative to the BDS system coordinates.

7. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 6, characterized in that, When the link quality index is in the third interval below the second interval, the processing unit selects the dimension reduction and bottom-line mode. This dimension reduction and bottom-line mode executes the trend-first truncation strategy or the accuracy-first retention strategy, and uses the payload space released by the truncation strategy or retention strategy to fill the forward error correction code. The length ratio of the forward error correction code is negatively correlated with the value of the link quality index.

8. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 1, characterized in that, In step S2, before comparing the ground speed with the preset motion threshold, the processing unit performs a moving average filtering process on the ground speed to filter out the high-frequency speed fluctuation component caused by the instantaneous vibration of the carrier. The setting value of the motion threshold is related to the channel multipath environment in which the terminal is currently located. The motion threshold in the marine scenario is set to be lower than the motion threshold in the land urban canyon scenario.

9. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 1, characterized in that, The communication unit performs the uplink transmission action as follows: the communication unit receives the transmission trigger signal and detects the timing second pulse signal of the Beidou satellite navigation system; after detecting the rising edge of the timing second pulse signal, the communication unit modulates the data packet to be transmitted onto the carrier and transmits it to the satellite network within the preset short message communication time slot protection interval.

10. The integrated communication method of BeiDou short message service and GPS / BDS positioning according to claim 1, characterized in that, In step S2, if the processing unit determines that the ground speed is less than the preset stationary threshold and the change in the positioning data relative to the last successfully transmitted position is less than the preset drift threshold, the processing unit generates a simplified data packet containing only the heartbeat status word and the incremental change in positioning data, and controls the communication unit to perform uplink transmission at a power value lower than the standard transmission power.

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