Emergency communication method based on intelligent switching of multi-mode antenna of Beidou and deployment without network

Abstract

This invention provides an emergency communication method based on intelligent switching and network-free deployment of BeiDou multi-mode antennas, relating to the field of positioning and communication technology. The method includes: initializing a multi-mode antenna, a BeiDou positioning module, a cellular communication module, and local storage; receiving BeiDou and GPS signals and evaluating and generating signal quality deviation values; switching the working antenna based on the deviation values ​​and a switching hysteresis threshold, receiving positioning data, and uploading it to the cloud; when cellular communication and cloud access are interrupted or there is no network, entering an emergency mode and obtaining the cache load rate; if the load rate is below a first threshold, storing all data; if it reaches or exceeds a second threshold, downsampling and storing, merging multiple positioning points exceeding the time window into representative points to release space for continued recording; when cellular communication is restored, re-uploading the locally unuploaded data packets to the cloud in timestamp order. This invention solves the problem of data interruption and loss caused by antenna performance degradation or network absence, achieving reliable storage without network access and efficient re-uploading after recovery.

Description

Technical Field

[0001] This invention relates to the field of positioning and communication technology, and in particular to an emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment. Background Technology

[0002] With the development of mobile positioning technology and Internet of Things (IoT) communication technology, satellite positioning-based vehicle monitoring systems have been widely used in mobile terminal management scenarios such as logistics distribution and installation and maintenance services. However, in practical applications, the environments in which mobile terminals operate are complex and ever-changing, often facing two prominent problems.

[0003] On the one hand, vehicles frequently pass through areas with severe signal obstruction, such as densely built-up areas, underpasses, tunnels, mountainous regions, or forests. The ability of a single antenna to receive satellite signals is highly susceptible to factors such as antenna installation location, metal obstructions from the vehicle body, and multipath effects, leading to drastic fluctuations in the received satellite signal strength and signal-to-noise ratio. When signal quality deteriorates, the positioning module may experience positioning interruptions, a sharp drop in positioning accuracy, or drift in positioning results, severely impacting the continuity and accuracy of the vehicle's trajectory. Existing multi-antenna solutions typically employ simple fixed selection or polling methods, lacking real-time, refined assessment of signal quality and intelligent switching mechanisms. This makes it difficult to consistently lock onto the optimal antenna when the signal environment dynamically changes, thus failing to guarantee stable reception of positioning data.

[0004] On the other hand, cellular network coverage is not ubiquitous. In remote rural areas, underground parking garages, tunnels, or mountainous regions without 4G or 5G signal coverage, the data link between terminal devices and the cloud platform will be completely interrupted. In this situation, location data cannot be uploaded in real time. If the terminal relies solely on real-time transmission without local caching and post-transmission capabilities, data loss will occur, resulting in gaps in the monitoring platform's trajectory and making it impossible to fully trace the vehicle's path. Even if some devices have local storage capabilities, their storage strategies are often fixed, stopping recording once the cache is full, making it impossible to continuously save data in long-term network-free environments. Furthermore, after network recovery, how to efficiently and reliably retransmit large amounts of historical data without affecting the normal reporting of real-time data, while avoiding duplicate transmissions, is also a problem that existing solutions have not adequately addressed.

[0005] Furthermore, mobile devices typically rely on vehicle batteries for power. When the battery is depleted or there is an unexpected power outage, the device will completely cease operation, and the positioning and monitoring functions will immediately fail. Existing devices lack a coordinated design for intelligent power management and low-power operating modes, making it impossible to maintain operation for extended periods after an external power outage, further exacerbating the risk of data loss.

[0006] In summary, ensuring continuous and stable satellite positioning in complex and ever-changing signal environments, recording and reliably transmitting positioning data when cellular networks are unavailable, and extending the autonomous operation capability of equipment in the event of external power supply anomalies are pressing challenges that current mobile terminal positioning and monitoring systems need to address. Summary of the Invention

[0007] To address the technical problem in existing technologies where mobile positioning terminals struggle to continuously and stably receive satellite signals and completely preserve and reliably transmit positioning data in complex signal environments and without cellular networks, this invention provides an emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment.

[0008] The technical solution provided by this invention is as follows: The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment provided by this invention includes: S1: The system powers on and starts up, initializing the multi-mode antenna array, BeiDou positioning module, cellular communication module and local storage module; S2: The multi-mode antenna array receives BeiDou and GPS dual-mode satellite signals in real time, and evaluates the signal quality received by each antenna at the current moment, generating a corresponding signal quality deviation value. The signal quality deviation value is used to characterize the overall deviation of the antenna received signal strength and signal-to-noise ratio. S3: Based on the signal quality deviation value of each antenna and the preset switching hysteresis threshold, execute the antenna intelligent switching logic, select the antenna with the best signal quality as the main working antenna, and use it to continuously receive satellite positioning data; S4: Receive the real-time positioning data calculated by the Beidou positioning module through the main working antenna, and encapsulate it into a standard data packet using the cellular communication module and upload it to the cloud platform; S5: When the connection between the cellular communication module and the cloud platform is interrupted or no available cellular network signal is detected, the emergency communication mode is automatically entered to obtain the current cache load rate of the local storage module in real time. The cache load rate is used to characterize the percentage of used cache space to total cache capacity. S6: Dynamically adjust the local storage strategy based on the cache load rate. If the cache load rate is lower than the first preset threshold, execute full data storage. If the cache load rate reaches or exceeds the second preset threshold, trigger downsampling storage, merge multiple stored positioning points that have exceeded the preset time window into a representative point to release storage space and continue to record new positioning data. S7: When the cellular communication module is detected to have restored its connection with the cloud platform, the data retransmission process is automatically triggered. According to the timestamp of the location data, all data packets that were not successfully uploaded in the local storage module are sequentially retransmitted to the cloud platform.

[0009] Furthermore, step S2 further includes: S201: Measure the strength of the BeiDou satellite signal received by each antenna in the multimode antenna array. With signal-to-noise ratio and the strength of received GPS satellite signals. With signal-to-noise ratio ; S202: According to the formula

[0010] Calculate the overall signal quality reference value of a single antenna, where a and b are preset weighting coefficients, and a+b=1; S203: The difference between the comprehensive signal quality reference value calculated by the current antenna and a preset standard reference value is used as the signal quality deviation value of the antenna.

[0011] Furthermore, the intelligent antenna switching logic in step S3 further includes: S301: If the signal quality deviation of the current main working antenna is less than the preset first deviation tolerance threshold, then the current antenna remains the main working antenna. S302: If the signal quality deviation value of the current main working antenna exceeds the first deviation tolerance threshold, then traverse the other antennas in the multimode antenna array to find whether there is a target antenna with a signal quality deviation value less than the preset second deviation tolerance threshold, where the second deviation tolerance threshold is less than the first deviation tolerance threshold. S303: If the target antenna exists, perform antenna switching, set the target antenna as the new main working antenna, and record the switching event and switching timestamp.

[0012] Furthermore, the standard data packet encapsulated in step S4 includes at least: timestamp, latitude and longitude coordinates, altitude, direction angle, instantaneous speed, number of satellite positioning points, vehicle status indicator, battery voltage value, vibration acceleration value, and ambient temperature value.

[0013] Furthermore, the emergency communication mode in step S5 also includes: starting a local real-time data recording thread, and writing each location data record to be stored into the local storage module according to a predefined protocol format, wherein the protocol format includes, in sequence: unique identifier of data packet, timestamp, latitude and longitude, speed, number of satellites, voltage, temperature and vibration information.

[0014] Furthermore, the unique identifier of the data packet is a globally unique identifier, which is generated by the device ID, the lower 32 bits of the timestamp, and an incrementing sequence number.

[0015] Furthermore, the downsampling storage in step S6 further includes: S601: When the cache load rate reaches or exceeds the second preset threshold, scan the location data records in the local storage module whose timestamps are more than 30 minutes past the current time. S602: Group the data records exceeding 30 minutes into consecutive time windows, with each window containing N consecutive location points, where N is dynamically determined based on the current cache load rate, according to the following formula: ; S603: For N positioning points within each window, calculate the arithmetic mean of their latitude and longitude as the coordinates of the representative point, and select the midpoint of the window as the timestamp of the representative point. Replace the original N positioning points within the window with the generated single representative point.

[0016] Furthermore, the data retransmission process in step S7 further includes: S701: After receiving the retransmitted data packet, the cloud platform parses its unique identifier and returns an acknowledgment command to the terminal device; S702: After receiving the confirmation instruction, the terminal device marks the local storage corresponding to the data packet as uploaded; S703: If the terminal device does not receive an acknowledgment instruction within the preset timeout period, it will add the data packet back to the end of the retransmission queue and wait for the next retransmission opportunity to resend it.

[0017] Furthermore, the total cache capacity of the local storage module is 1 megabyte, a single location data record occupies 44 bytes, the first preset threshold corresponds to a cache occupancy rate of 80%, the second preset threshold corresponds to a cache occupancy rate of 80%, and the preset time window is 30 minutes.

[0018] Furthermore, the feature is that it also includes a power management step: monitoring the power supply status of the external electric vehicle battery, and automatically switching to the built-in lithium battery to power the system when the external battery voltage is lower than a preset undervoltage threshold, while simultaneously reducing the frequency of satellite positioning data collection from once per second to once every five seconds.

[0019] The beneficial effects of the technical solution provided by this invention include at least the following: (1) In this invention, a multi-mode antenna array is set up, and a comprehensive signal quality reference value is calculated based on the signal strength and signal-to-noise ratio of each antenna. This generates a signal quality deviation value, and intelligent antenna switching logic is executed based on this deviation value and a switching hysteresis threshold. This enables the system to select the antenna with the best signal quality as the main working antenna in real time when the signal environment changes dynamically. Compared to a fixed single antenna or simple polling method, this method effectively overcomes the positioning interruption and drift problems caused by antenna obstruction or multipath effects, significantly improving the positioning availability and trajectory continuity in complex urban environments.

[0020] (2) In this invention, the local storage strategy is dynamically adjusted based on the real-time monitoring of the cache load rate: full storage is performed when the cache is sufficient, and downsampling storage is triggered when the cache reaches a preset threshold. Multiple location points exceeding the preset time window are merged into representative points, thereby recording location data for as long as possible within a limited storage space. This mechanism solves the problem of traditional solutions stopping recording when the cache is full when there is no network signal, enabling the terminal to continuously save complete trajectory information even in areas without cellular coverage for a long time, providing a data foundation for post-event tracing.

[0021] (3) In this invention, by generating a globally unique identifier for each location data record and initiating the data retransmission process in the order of timestamps after network recovery, combined with the cloud platform's confirmation instructions and timeout retransmission mechanism, it is ensured that the cached data can be uploaded to the cloud completely, orderly, and without duplication. Simultaneously, the retransmission process employs breakpoint resumption and dynamic rate adjustment strategies to avoid interference between the retransmitted data and real-time location reporting. This solution overcomes the shortcomings of traditional solutions, such as chaotic data transmission, packet loss, or duplicate uploads after network recovery, and achieves reliable historical data retransmission.

[0022] (4) In this invention, the external battery voltage is monitored through a power management step. When the voltage is lower than the undervoltage threshold, the system automatically switches to the built-in lithium battery for power supply and simultaneously reduces the frequency of satellite positioning data acquisition. This design solves the problem of immediate device failure after an external power outage, extending the battery life of the built-in lithium battery several times over and ensuring that the vehicle's location and status can still be recorded for a long time without external power supply. Furthermore, when the vehicle is turned off and there is no vibration, it enters a deep sleep mode, reducing power consumption to the milliwatt level, further extending the standby time and providing strong support for post-event tracking and device recovery.

[0023] (5) In this invention, by explicitly defining multi-dimensional fields such as unique identifiers, timestamps, latitude and longitude, speed, voltage, temperature, and vibration information in the protocol format, and combining this with the generation method of globally unique identifiers, each location record is made independently identifiable. This design not only facilitates accurate filtering of duplicate packets by the cloud platform, but also supports synchronous monitoring of multi-dimensional states during vehicle operation, providing complete data support for subsequent big data analysis, operation and maintenance efficiency evaluation, and fault early warning. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the antenna signal quality assessment and switching process of the emergency communication method based on intelligent switching and network-free deployment of Beidou multi-mode antennas, provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the downsampling storage process of the emergency communication method based on intelligent switching of Beidou multi-mode antennas and network-free deployment provided in an embodiment of the present invention. Figure 4 This is a schematic diagram of the data retransmission process of the emergency communication method based on intelligent switching of Beidou multi-mode antenna and network-free deployment provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of the power management process of the emergency communication method based on intelligent switching of Beidou multi-mode antenna and network-free deployment, provided in an embodiment of the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to specific embodiments. Those skilled in the art should understand that these embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0026] This invention provides an emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment. This method can be applied to the positioning and monitoring systems of mobile terminals such as installation and maintenance vehicles, logistics delivery vehicles, or shared mobility tools. The method aims to solve the problems of positioning data interruption, loss, or untimely transmission caused by single-antenna performance degradation or lack of cellular network coverage in complex signal environments, thereby ensuring the continuous traceability and data integrity of mobile terminals under various operating conditions.

[0027] In one specific embodiment, the terminal device implementing the method of the present invention includes a multi-mode antenna array, a BeiDou positioning module, a cellular communication module, and a local storage module. The multi-mode antenna array consists of at least two independent antenna elements, each capable of simultaneously receiving signals from both the BeiDou Navigation Satellite System and the Global Positioning System. The cellular communication module establishes a data link with the cloud platform using fourth-generation or fifth-generation mobile communication technology. The local storage module is a non-volatile memory.

[0028] After the system powers on and starts up, it first executes an initialization procedure: performing a self-test on each antenna in the multi-mode antenna array and calibrating its receive gain; performing a cold or warm start on the BeiDou positioning module to obtain the initial ephemeris; performing network attachment and protocol stack initialization on the cellular communication module; and mounting the file system and detecting bad blocks on the local storage module. After completing the above initialization, the system enters normal operating mode.

[0029] To eliminate the signal fading caused by a single antenna due to installation location, obstruction, multipath effect, or hardware aging, this invention proposes a dynamic antenna switching mechanism based on signal quality deviation value.

[0030] During each evaluation cycle, the system receives dual-mode satellite signals from BeiDou and Global Positioning System in real time through the multi-mode antenna array, and evaluates the signal quality received by each antenna at the current moment, generating a corresponding signal quality deviation value. This signal quality deviation value characterizes the combined deviation of the antenna's received signal strength and signal-to-noise ratio, i.e., the magnitude of the difference in the antenna's current performance relative to an ideal reference state.

[0031] In a first specific embodiment, the following sub-steps are performed on each antenna: First, the signal strength and signal-to-noise ratio (SNR) of the received BeiDou satellite signal and the signal strength and SNR of the received Global Positioning System (GPS) satellite signal are measured respectively. All the above measurements are directly read from the RF front-end chip at the antenna's rear end. Then, the overall signal quality reference value for a single antenna is calculated according to the following formula:

[0032] The parameters have the following meanings: This represents the strength of the BeiDou satellite signal received by the antenna, measured in dBm. This represents the strength of the GPS satellite signals received by the antenna, measured in dBm. The signal-to-noise ratio (SNR) of the antenna receiving BeiDou satellite signals is expressed in dB. The signal-to-noise ratio (SNR) of the received GPS satellite signals is expressed in dB; 'a' and 'b' are preset weighting coefficients, satisfying a + b = 1. In a preferred embodiment, considering that signal strength has a slightly greater impact on positioning continuity than SNR, a = 0.6 and b = 0.4 are chosen. The larger this comprehensive signal quality reference value 'q' is, the better the overall quality of the satellite signals received by the current antenna.

[0033] Finally, the calculated composite signal quality reference value q from the antenna is compared with a preset standard reference value. The difference is taken as the signal quality deviation value Δq of the antenna, i.e. .in The typical q value of this antenna model was measured in an open laboratory environment. Δq can be negative, indicating that the current quality is below standard.

[0034] In the second specific embodiment, to avoid dependence on standard reference values, the switching can be determined directly by relative comparison between antennas: calculate the q-values ​​of all antennas, select the antenna with the maximum value as a candidate, and compare it with the q-value of the currently operating antenna. If the difference exceeds a fixed threshold, the switching is performed. This method simplifies the calibration process and is suitable for large-scale deployment scenarios.

[0035] Based on the signal quality deviation value Δq of each antenna and a preset switching hysteresis threshold, the system executes intelligent antenna switching logic, selecting the antenna with the best signal quality as the main working antenna for continuous reception of satellite positioning data. The switching hysteresis threshold includes a first deviation tolerance threshold TH1 and a second deviation tolerance threshold TH2, where TH2...

[0036] Through the aforementioned dynamic switching, even when the vehicle passes through areas with strong signal attenuation such as underpasses, densely populated areas with tall buildings, or forests, the system can automatically select the optimal antenna to ensure that the positioning module continuously obtains a sufficient number of visible satellites and a stable carrier-to-noise ratio, thereby avoiding positioning interruption or drift. Compared with fixed single-antenna solutions, the antenna switching method of this invention can significantly improve positioning availability in complex urban environments.

[0037] After selecting the main working antenna, the BeiDou positioning module continuously receives satellite signals through this antenna and calculates real-time positioning data. The real-time positioning data includes timestamp, longitude, latitude, altitude, azimuth angle, instantaneous velocity, number of satellites participating in the positioning, and the status of the positioning solution.

[0038] In one specific implementation, the system encapsulates the aforementioned positioning data along with the vehicle's own status data into a standard data packet. The vehicle's status data includes a vehicle status identifier (driving or off), battery voltage in volts, vibration acceleration in meters per second squared, and ambient temperature in degrees Celsius. The data packet format uses a compact binary protocol or a JavaScript object representation text protocol for easy parsing by the cloud platform. After encapsulation, the packet is uploaded to the cloud platform using a cellular communication module.

[0039] When the cellular communication module detects an interruption in the connection with the cloud platform or fails to scan for any available cellular network signals, the system automatically enters emergency communication mode.

[0040] First, the current cache load rate L of the local storage module is obtained in real time. The cache load rate is defined as the percentage of used cache space to total cache capacity, that is, L equals the number of used bytes divided by the total number of bytes and then multiplied by 100%.

[0041] In the first specific implementation, the total cache capacity of the local storage module is 1 megabyte. Actual testing showed that a single complete location data record occupies 44 bytes, and this record includes a unique data packet identifier, timestamp, latitude and longitude, speed, number of satellites, voltage, temperature, and vibration information. Therefore, in the absence of a network, the local storage module can cache a maximum of approximately 23,800 records.

[0042] The system dynamically adjusts its local storage strategy based on the cache load rate L. If L is below a first preset threshold, full data storage is executed: each received location data is written to the local storage module in its original format. If L reaches or exceeds a second preset threshold, downsampling storage is triggered. Downsampling storage refers to merging multiple stored location points that have exceeded a preset time window into a single representative point to free up storage space and continue recording new location data. Both the first and second preset thresholds are set to 80%, and the preset time window is 30 minutes.

[0043] In a specific embodiment of downsampling storage, when L reaches or exceeds 80%, the system scans all location data records in the local storage module whose timestamps are earlier than the current time minus 30 minutes. For example... Figure 3 As shown, these old records are grouped into consecutive time windows, with each window containing N consecutive location points. N is dynamically determined based on the current cache load rate, using the following formula:

[0044] The load factor is a decimal between 0 and 1. When the load factor is 80%, N equals 4; when the load factor is 90%, N equals 5; and when the load factor is 100%, N equals 5. The higher the load factor, the larger the merged window, and the more space is freed up. Then, for the N positioning points within each window, the arithmetic mean of their longitudes is calculated as the longitude of the representative point, and the arithmetic mean of their latitudes is calculated as the latitude of the representative point. The midpoint of the time within the window is selected as the timestamp of the representative point. Finally, the N positioning points in the original window are replaced with the generated single representative point. This downsampling operation can compress the space occupied by the old data to one-Nth of the original without losing the key trajectory trend, thereby freeing up enough buffer to record the newly generated positioning data.

[0045] In the second specific embodiment, a non-uniform downsampling method is adopted: more positioning points are retained during periods of drastic speed changes, while uniform linear motion segments are more aggressively merged. Specifically, this is achieved by calculating the rate of change of heading for every three consecutive points: if the rate of change of heading exceeds 10 degrees per second, the number of merged points N in that window is halved, and vice versa. However, given that the core of this invention is to solve the capacity problem of network-free storage, the above-mentioned uniform window merging can already meet the needs of most scenarios.

[0046] With this dynamic storage strategy, the system will not stop recording even when there is no network signal for a long time because the cache is full, effectively ensuring the integrity of the location data.

[0047] In emergency communication mode, the system initiates a local real-time data recording thread. Each location data record to be stored is written to the local storage module according to a predefined protocol format. In one specific implementation, the protocol format includes the following fields in sequence: a unique identifier for the data packet (16 bytes), a timestamp (4 bytes), a longitude (4 bytes, floating-point number), a latitude (4 bytes, floating-point number), a speed (2 bytes, integer, in units of 0.1 km / h), the number of satellites (1 byte), a voltage (2 bytes, integer, in units of 0.1 volts), a temperature (1 byte, signed integer, in units of degrees Celsius), and vibration information (2 bytes, integer representing the root mean square value of the combined triaxial acceleration). These fields total approximately 44 bytes.

[0048] To ensure accurate identification and prevent duplicate uploads during subsequent retransmissions, the data packet unique identifier is designed to be globally unique. This globally unique identifier is generated by combining three parts: a 40-bit device ID, a 32-bit lower 32-bit timestamp, and a 16-bit sequence number that automatically increments with each data transmission. The device ID is either the terminal's International Mobile Equipment Identity (IMEI) or a custom hardware serial number. The sequence number is reset after each power-on, but since the probability of the lower 32 bits of the timestamp and the sequence number being the same is extremely low, and collisions do not occur within a normal retransmission cycle, this globally unique identifier can be considered globally unique. Each data packet carries this globally unique identifier, and the cloud platform can accurately filter duplicate packets by maintaining a list of received identifiers.

[0049] Once the system detects that the cellular communication module has restored its connection with the cloud platform, it automatically triggers the data retransmission process. For example... Figure 4 As shown, the process sequentially uploads all unmarked data packets from the local storage module to the cloud platform according to the timestamp of the location data.

[0050] To ensure the reliability of retransmission, this invention employs a confirmation-based reliable transmission mechanism. Upon receiving a retransmitted data packet, the cloud platform parses its unique identifier and returns a confirmation command to the terminal device. This confirmation command contains the same globally unique identifier. Upon receiving the confirmation command, the terminal device marks the corresponding local storage record as uploaded. Subsequently, the system periodically cleans up all uploaded records with timestamps exceeding 7 days to free up space. If the terminal device does not receive a confirmation command within a preset timeout period, the data packet transmission is deemed to have failed, and the packet is re-added to the tail of the retransmission queue, awaiting the next retransmission opportunity for resending. The maximum number of retransmissions is set to 5; exceeding this limit results in the packet being marked as an upload failure and retained locally for manual export.

[0051] In a preferred embodiment, the retransmission process also supports resume transmission: if the network is interrupted again during retransmission, the system records the last globally unique identifier that has been successfully uploaded, and resumes retransmission from the next record after that identifier when the connection is restored, avoiding duplicate transmissions. Furthermore, the retransmission rate can be dynamically adjusted: when the vehicle is in motion and real-time positioning has a higher priority, the system limits the retransmission bandwidth to a maximum of 5 historical packets per second to avoid affecting the reporting of current positioning data; when the vehicle is off or idle, it retransmits at full speed at 20 packets per second.

[0052] As a further supplement to the above solution, the present invention also includes a power management step to extend the battery life of the terminal device in the absence of external power supply.

[0053] The system continuously monitors the power supply status of the external electric vehicle battery. This external battery is typically a 48-volt or 60-volt lead-acid or lithium battery pack, which is stepped down to 3.7 volts via a DC-DC converter to power the device and simultaneously float-charge the internal lithium battery. When the external battery voltage is detected to be below a preset undervoltage threshold, the system determines that the external power supply is abnormal and automatically switches to the internal lithium battery to power the system. The undervoltage threshold is 85% of the nominal voltage, i.e., a 48-volt battery dropping to 40.8 volts.

[0054] Meanwhile, to reduce overall power consumption, the system automatically reduces the frequency of satellite positioning data acquisition from once per second in normal operating mode to once every five seconds. Correspondingly, the data upload cycle is also extended. This frequency reduction strategy reduces the overall power consumption from approximately 50 milliwatts to approximately 15 milliwatts, thereby extending the battery life of the built-in lithium battery from approximately 3 days to more than 10 days. This ensures that the system can record vehicle location and status for extended periods without external power, facilitating post-event tracking.

[0055] In the second implementation, when the system detects that the vehicle has been off and without vibration for more than 15 minutes, it further enters a deep sleep mode, retaining only the real-time clock and vibration wake-up function. At this point, power consumption can be as low as below 1 milliwatt. Figure 5 As shown.

[0056] The following is a complete application example to illustrate the collaborative working process of the above modules.

[0057] Assume a certain electric vehicle used for vehicle maintenance is equipped with the terminal device of this invention. After the vehicle starts, the system initializes. Antenna A and antenna B measure signal strength and signal-to-noise ratio respectively, calculating their respective comprehensive signal quality reference values ​​and signal quality deviation values. The deviation value of antenna A is -15 dB, lower than the first deviation tolerance threshold of -3 dB, while the deviation value of antenna B is only -2 dB. The system performs antenna switching, setting antenna B as the primary working antenna. The vehicle enters an urban area with good cellular network signal, and location data is uploaded to the cloud platform every second in real time.

[0058] The vehicle then entered a mountain tunnel, and the cellular communication module detected a network connection interruption. The system entered emergency communication mode. At this time, the cache load rate was 20%, lower than the first preset threshold of 80%, so the system performed full storage, recording one location data record to the local storage module every 5 seconds. Approximately 120 records were generated during the tunnel journey, occupying approximately 5.3 kilobytes of storage space.

[0059] After the vehicle exited the tunnel, the cellular network was restored. The system automatically initiated a retransmission process, uploading the 120 data entries cached in the tunnel to the cloud platform in chronological order of their timestamps. During the retransmission, real-time location data continued to be reported normally at a frequency of once per second, utilizing the remaining bandwidth for the retransmission. Upon receiving each data entry, the cloud platform returned a confirmation command, and the terminal device marked the corresponding data as uploaded.

[0060] During subsequent driving, the external battery voltage dropped below the undervoltage threshold, triggering power management procedures. The system automatically switched to internal lithium battery power and reduced the satellite positioning data collection frequency from once per second to once every five seconds. The vehicle continued driving to a remote area without cellular network coverage, but due to the reduced collection frequency, the cache growth rate slowed significantly. Approximately 2000 records were generated for the remainder of the day, with cache occupancy remaining below 60%, and downsampling storage was not triggered. In the evening, the vehicle returned to the charging point, external power was restored, and the system automatically switched back to external power mode, resuming the collection frequency of once per second, while simultaneously re-transmitting all cached data from the daytime.

[0061] Through the above description of specific embodiments, those skilled in the art can understand that the emergency communication method based on intelligent switching of Beidou multi-mode antennas and network-free deployment proposed in this invention significantly improves the communication reliability and data integrity of mobile positioning terminals in complex environments through dynamic antenna selection, adaptive downsampling storage with buffer load, reliable retransmission mechanism and intelligent power management.

[0062] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment, characterized in that, include: S1: The system powers on and starts up, initializing the multi-mode antenna array, BeiDou positioning module, cellular communication module and local storage module; S2: The multi-mode antenna array receives BeiDou and GPS dual-mode satellite signals in real time, and evaluates the signal quality received by each antenna at the current moment, generating a corresponding signal quality deviation value. The signal quality deviation value is used to characterize the overall deviation of the antenna received signal strength and signal-to-noise ratio. S3: Based on the signal quality deviation value of each antenna and the preset switching hysteresis threshold, execute the antenna intelligent switching logic, select the antenna with the best signal quality as the main working antenna, and use it to continuously receive satellite positioning data; S4: Receive the real-time positioning data calculated by the Beidou positioning module through the main working antenna, and encapsulate it into a standard data packet using the cellular communication module and upload it to the cloud platform; S5: When the connection between the cellular communication module and the cloud platform is interrupted or no available cellular network signal is detected, the emergency communication mode is automatically entered to obtain the current cache load rate of the local storage module in real time. The cache load rate is used to characterize the percentage of used cache space to total cache capacity. S6: Dynamically adjust the local storage strategy based on the cache load rate. If the cache load rate is lower than the first preset threshold, execute full data storage. If the cache load rate reaches or exceeds the second preset threshold, trigger downsampling storage, merge multiple stored positioning points that have exceeded the preset time window into a representative point to release storage space and continue to record new positioning data. S7: When the cellular communication module is detected to have restored its connection with the cloud platform, the data retransmission process is automatically triggered. According to the timestamp of the location data, all data packets that were not successfully uploaded in the local storage module are sequentially retransmitted to the cloud platform.

2. The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment according to claim 1, characterized in that, Step S2 further includes: S201: Measure the strength of the BeiDou satellite signal received by each antenna in the multimode antenna array. With signal-to-noise ratio and the strength of received GPS satellite signals. With signal-to-noise ratio ; S202: According to the formula ； Calculate the overall signal quality reference value of a single antenna, where a and b are preset weighting coefficients, and a+b=1; S203: The difference between the comprehensive signal quality reference value calculated by the current antenna and a preset standard reference value is used as the signal quality deviation value of the antenna.

3. The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment according to claim 1, characterized in that, The intelligent antenna switching logic in step S3 further includes: S301: If the signal quality deviation of the current main working antenna is less than the preset first deviation tolerance threshold, then the current antenna is maintained as the main working antenna. S302: If the signal quality deviation value of the current main working antenna exceeds the first deviation tolerance threshold, then traverse the other antennas in the multimode antenna array to find whether there is a target antenna with a signal quality deviation value less than the preset second deviation tolerance threshold, where the second deviation tolerance threshold is less than the first deviation tolerance threshold. S303: If the target antenna exists, perform antenna switching, set the target antenna as the new main working antenna, and record the switching event and switching timestamp.

4. The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment according to claim 1, characterized in that, The standard data packet encapsulated in step S4 includes at least: timestamp, latitude and longitude coordinates, altitude, direction angle, instantaneous speed, number of satellite positioning points, vehicle status indicator, battery voltage value, vibration acceleration value, and ambient temperature value.

5. The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment according to claim 1, characterized in that, The emergency communication mode in step S5 further includes: starting a local real-time data recording thread, and writing each location data record to be stored into the local storage module according to a predefined protocol format. The protocol format includes, in sequence: unique identifier of data packet, timestamp, latitude and longitude, speed, number of satellites, voltage, temperature and vibration information.

6. The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment according to claim 5, characterized in that, The unique identifier of the data packet is a globally unique identifier, which is generated by the device ID, the lower 32 bits of the timestamp, and an incrementing sequence number.

7. The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment according to claim 1, characterized in that, The downsampling storage in step S6 further includes: S601: When the cache load rate reaches or exceeds the second preset threshold, scan the location data records in the local storage module whose timestamps are more than 30 minutes past the current time. S602: Group the data records exceeding 30 minutes into consecutive time windows, with each window containing N consecutive location points, where N is dynamically determined based on the current cache load rate, according to the following formula: ; S603: For N positioning points within each window, calculate the arithmetic mean of their latitude and longitude as the coordinates of the representative point, and select the midpoint of the window as the timestamp of the representative point. Replace the original N positioning points within the window with the generated single representative point.

8. The emergency communication method based on intelligent switching and network-free deployment of BeiDou multi-mode antennas according to claim 1, characterized in that, The data retransmission process in step S7 further includes: S701: After receiving the retransmitted data packet, the cloud platform parses its unique identifier and returns an acknowledgment command to the terminal device; S702: After receiving the confirmation instruction, the terminal device marks the local storage corresponding to the data packet as uploaded; S703: If the terminal device does not receive an acknowledgment instruction within the preset timeout period, it will add the data packet back to the end of the retransmission queue and wait for the next retransmission opportunity to resend it.

9. The emergency communication method based on intelligent switching and network-free deployment of BeiDou multi-mode antennas according to claim 1, characterized in that, The total cache capacity of the local storage module is 1 megabyte, a single location data record occupies 44 bytes, the first preset threshold corresponds to a cache occupancy rate of 80%, the second preset threshold corresponds to a cache occupancy rate of 80%, and the preset time window is 30 minutes.

10. The emergency communication method based on intelligent switching of BeiDou multi-mode antennas and network-free deployment according to claim 1, characterized in that, It also includes a power management step: monitoring the power supply status of the external electric vehicle battery, and automatically switching to the built-in lithium battery to power the system when the external battery voltage is lower than the preset undervoltage threshold, while at the same time reducing the frequency of satellite positioning data collection from once per second to once every five seconds.

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