4G Cat.1 passive Internet of Things monitoring system and method based on Vsim

Abstract

The invention relates to the technical field of Internet of Things monitoring, in particular to a 4G Cat.1 passive Internet of Things monitoring system and method based on Vsim. The method comprises the following steps: pre-storing network authentication information of at least two operators through a VSim software unit; establishing low-power-consumption network connection between the 4G Cat.1 communication unit and a preset cloud management platform according to the network authentication information in a terminal dormant state; the method comprises the following steps: continuously monitoring heat radiation change in a target monitoring area through a passive infrared sensor, and when an effective moving event is detected, generating a hardware interruption wake-up signal; and waking up the terminal according to the hardware interrupt wakeup signal, and obtaining compressed audio and video data of the target monitoring area through the terminal. According to the method, millisecond-level wakeup and optimal link maintenance under permanent endurance of the passive camera are realized through a VSim multi-operator dynamic switching and electric quantity self-adaption strategy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Internet of Things monitoring, and in particular to a 4G Cat.1 passive Internet of Things monitoring system and method based on Vsim. BACKGROUND

[0002] In remote sites in mountainous areas, deserts and the like without city power and without operator-level Wi-Fi, perimeter monitoring generally uses solar panels + 4G all-network cameras. After installation, the device is fixed in position, while the wireless signal environment dynamically changes with natural factors such as mountain shadow, vegetation growth, and rain and snow weather: when the A operator base station is blocked, the adjacent B operator still maintains good coverage. However, due to the physical SIM card hardware form limitation, the existing all-network module can only be written with a single operator at the factory once, and cannot be actively switched to other operators during operation according to real-time signal quality. The network connection capability is anchored at the moment of card slot insertion. Once the on-site signal is long-term degraded, the only remedy is to manually replace the SIM card on site, which has a long response period and high labor cost.

[0003] On the other hand, the solar power supply scenario is extremely sensitive to power consumption. The traditional 4G Cat.4 module is designed for continuous online, and from sleep to data link establishment, it needs to go through multiple stages such as power-on, network search, and registration authentication, which takes several seconds to tens of seconds, and is accompanied by hundreds of milliamperes or even ampere-level transient current peaks. The connection establishment delay not only easily misses the key initial picture, but also forms a significant power consumption burr on the energy storage battery. If the on-site event is frequently triggered or continuous rain causes insufficient replenishment, the cumulative burr power consumption will quickly deplete the power, causing the device to fail at the most critical time, which deviates from the permanent endurance design goal. Therefore, remote passive monitoring urgently needs a super low power consumption communication scheme that can remotely and dynamically switch operators and complete network access in milliseconds after waking up. SUMMARY

[0004] Therefore, it is necessary to provide a 4G Cat.1 passive Internet of Things monitoring system and method based on Vsim to solve at least one of the above technical problems.

[0005] To achieve the above-mentioned purpose, a 4G Cat.1 passive Internet of Things monitoring method based on Vsim is applied to an intelligent camera terminal, the intelligent camera terminal includes at least a master control unit, an energy storage unit, a VSim software unit, and a 4G Cat.1 communication unit, and the power supply mode of the intelligent camera terminal is solar power supply. The method further comprises the following steps: Step S1: Pre-storing network authentication information of at least two operators through the VSim software unit; in the terminal sleep state, establishing a low-power network connection between the 4G Cat.1 communication unit and the preset cloud management platform according to the network authentication information; Step S2: continuously monitoring the change of heat radiation in the target monitoring area through the passive infrared sensor, generating a hardware interrupt wake-up signal when a valid moving event is detected; waking up the terminal according to the hardware interrupt wake-up signal, and obtaining compressed audio and video data of the target monitoring area through the terminal; Step S3: monitoring the communication signal strength of each operator in real time, and generating a dynamic network quality table based on the communication signal strength; Step S4: determining the target operator network according to the dynamic network quality table; uploading the compressed audio and video data to the preset cloud management platform based on the target operator network; Step S5: when the data transmission is completed, the main control unit controls the 4G Cat.1 communication unit to return to a low-power standby network connection state, and closes the image acquisition of the terminal; obtaining the remaining power of the energy storage unit; generating a remote strategy instruction based on the dynamic network quality table and the remaining power of the energy storage unit; the terminal updates the local strategy after receiving the remote strategy instruction and reenters the hibernation.

[0006] Preferably, the application also provides a 4G Cat.1 passive Internet of Things monitoring system based on Vsim, which is used to execute the 4G Cat.1 passive Internet of Things monitoring method based on Vsim as described above, and the 4G Cat.1 passive Internet of Things monitoring system based on Vsim comprises: The authentication module is used to pre-store the network authentication information of at least two operators through the VSim software unit; in the terminal hibernation state, the low-power network connection between the 4G Cat.1 communication unit and the preset cloud management platform is established according to the network authentication information; The wake-up module is used to continuously monitor the change of heat radiation in the target monitoring area through the passive infrared sensor, generate a hardware interrupt wake-up signal when a valid moving event is detected, wake up the terminal according to the hardware interrupt wake-up signal, and obtain compressed audio and video data of the target monitoring area through the terminal; The network measurement module is used to monitor the communication signal strength of each operator in real time, and generate a dynamic network quality table based on the communication signal strength; The transmission module is used to determine the target operator network according to the dynamic network quality table; upload the compressed audio and video data to the preset cloud management platform based on the target operator network; The hibernation module is used to, when the data transmission is completed, control the 4G Cat.1 communication unit to return to a low-power standby network connection state by the main control unit, and close the image acquisition of the terminal; obtain the remaining power of the energy storage unit; generate a remote strategy instruction based on the dynamic network quality table and the remaining power of the energy storage unit; the terminal updates the local strategy after receiving the remote strategy instruction and reenters the hibernation.

[0007] The application has the following beneficial effects: In one aspect, the multi-operator network authentication information is pre-stored locally in the terminal by the VSim software unit, breaking the traditional hardware binding of "one card one operator" of the physical SIM card, so that the terminal can still maintain low-power standby network connection in the sleep state, realize millisecond-level access to the target operator after wake-up, eliminate the several to several tens of seconds of latency caused by the traditional 4G Cat.4 module search-network-registration-authentication, avoid the loss of the key initial picture, and at the same time, compress the radio frequency power consumption to less than 5% of the normal working mode, and completely suppress the impact of power consumption spikes on the solar energy storage unit.

[0008] On the other hand, the original signal strength of each operator in each frequency band is calibrated in real time by adopting a three-factor joint correction model of terrain shielding parameters-vegetation density index-weather attenuation coefficient, and the signal fluctuation secondary quantization network stability is introduced to generate a dynamic network quality table; based on the table, the target operator is adaptively selected, which can switch to the optimal link when any base station is blocked due to mountain shadow, vegetation growth or rain and snow weather, without the need for manual on-site replacement of the SIM card, and the connectivity reliability of the remote node in the time-varying wireless environment is significantly improved.

[0009] On the other hand, after each data transmission, the cloud management platform generates a remote strategy instruction by comprehensively considering the dynamic network quality table and the remaining power of the energy storage unit, dynamically adjusts the subsequent wake-up period, transmission bit rate and operator priority, and realizes two-dimensional adaptive management of power and communication; when the power is lower than the threshold and the packet loss rate or delay is abnormal, it is automatically degraded to a sub-optimal operator and the service code rate is reduced, so as to maximize the off-line endurance time under the premise of ensuring the integrity of the service, and avoid permanent endurance failure caused by continuous rain or frequent triggering events. BRIEF DESCRIPTION OF DRAWINGS

[0010] Other features, objects and advantages of the present application will become more apparent from the following detailed description, made with reference to the accompanying drawings: Fig. 1 A step flowchart of a Vsim-based 4G Cat.1 passive Internet of Things monitoring method of an embodiment is shown.

[0011] Fig. 2 A detailed step flowchart of an embodiment of acquiring compressed audio and video data of a target monitoring area by a terminal is shown.

[0012] Fig. 3 An elevation angle difference calculation schematic diagram of an embodiment is shown. DETAILED DESCRIPTION

[0013] The technical method of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0014] In addition, the drawings are only schematic illustrations of the present application and are not necessarily drawn to scale. Identical reference numerals in the drawings represent identical or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities, which do not necessarily have to correspond to physically or logically independent entities. The functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different network and / or processor methods and / or microcontroller methods.

[0015] It should be understood that although the terms "first", "second" and the like can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, a first element can be referred to as a second element, and similarly a second element can be referred to as a first element. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0016] To achieve the above-mentioned purpose, please refer to Figs. 1 to 3 The present application provides a 4G Cat.1 passive Internet of Things monitoring method based on Vsim, applied to a smart camera terminal. The smart camera terminal includes at least a master control unit, an energy storage unit, a VSim software unit, and a 4G Cat.1 communication unit. The power supply mode of the smart camera terminal is solar power supply. The method further includes the following steps: Step S1: Pre-storing network authentication information of at least two operators through the VSim software unit; in the terminal sleep state, establishing a low-power network connection between the 4G Cat.1 communication unit and the preset cloud management platform according to the network authentication information; Step S2: Continuously monitoring the thermal radiation change in the target monitoring area through a passive infrared sensor, generating a hardware interrupt wake-up signal when detecting an effective moving event; waking up the terminal according to the hardware interrupt wake-up signal, and obtaining compressed audio and video data of the target monitoring area through the terminal; Step S3: Real-time monitoring of the communication signal strength of each operator, and generating a dynamic network quality table based on the communication signal strength; Step S4: determining a target operator network according to the dynamic network quality table; uploading the compressed audio and video data to a preset cloud management platform based on the target operator network; Step S5: when the data transmission is completed, the master control unit controls the 4G Cat.1 communication unit to return to a low-power standby network connection state, and closes the image acquisition of the terminal; the residual power of the energy storage unit is obtained; a remote strategy instruction is generated based on the dynamic network quality table and the residual power of the energy storage unit; after the terminal receives the remote strategy instruction, the local strategy is updated and the terminal reenters the hibernation.

[0017] Preferably, step S3 comprises: scanning the communication frequency bands supported by the operators, performing at least 5 times of continuous signal strength sampling for each communication frequency band, the sampling interval is 200 milliseconds, and the median value after eliminating the maximum value and the minimum value is taken as the original signal strength of the corresponding communication frequency band; In the embodiment of the application, after the terminal is woken up, the 4G Cat.1 communication unit polls and scans the pre-stored frequency band list supported by each operator; taking operator A as an example, it supports Band 3, Band 5 and Band 8. For each frequency band, the radio frequency driver completes 5 times of RSSI (Received Signal Strength Indicator) sampling within 1s, the sampling interval is 200ms, 5 original RSSI values are obtained, the median value of the remaining 3 values is written into the original signal strength register of the frequency band after eliminating the maximum value and the minimum value, and is recorded as If the five sampling results of Band 3 are {-92dBm, -88dBm, -90dBm, -87dBm, -93dBm}, then -87dBm and -93dBm are eliminated, and the median value -90dBm is taken as the At the same time, the next round of 5-point sampling process of Band 5 is started, and the original strength collection of all frequency bands of all operators is completed.

[0018] Obtaining the terrain shielding parameter, the vegetation density index and the meteorological attenuation coefficient of the target monitoring area, and calculating the comprehensive signal attenuation coefficient according to the terrain shielding parameter, the vegetation density index and the meteorological attenuation coefficient; In the case, the comprehensive signal attenuation coefficient calculation formula is: ; Wherein, K is the comprehensive signal attenuation coefficient, is the terrain shielding parameter, is the vegetation density index, is the meteorological attenuation coefficient; If the comprehensive signal attenuation coefficient is less than a preset first threshold value, the comprehensive signal attenuation coefficient is forcibly set to the preset first threshold value; If the comprehensive signal attenuation coefficient is greater than a preset second threshold, the comprehensive signal attenuation coefficient is forced to be set as the preset second threshold; wherein the preset first threshold is less than the preset second threshold; The modified signal intensity is calculated according to the original signal intensity and the comprehensive signal attenuation coefficient; In the case, the modified signal intensity calculation formula is: ; Wherein, is the modified signal intensity, is the original signal intensity; In the embodiment of the application, after the terminal completes the original signal intensity collection, the current values of the terrain shielding parameter, the vegetation density index and the meteorological attenuation coefficient are read from the local attenuation parameter register ; ; The three are multiplied to obtain the comprehensive signal attenuation coefficient K, and it is judged whether K falls between the preset first threshold and the preset second threshold : if it is lower than , K is forced to be set as , if it is higher than , K is forced to be set as ; the K value after the limiting is substituted into the formula , and the original signal intensity of the current frequency band is attenuated and corrected, and the obtained modified signal intensity is the final signal intensity result of the frequency band.

[0019] In one implementation manner of the embodiment of the application, assuming that the read product , , is 0.85, which is lower than 1.10, K is forced to be set as 1.10, and the corresponding correction amount is-0.41dB; if the product is 3.45, which is higher than 3.00, K is forced to be set as 3.00, and the correction amount is fixed as-4.77dB; through the upper and lower limit truncation strategy, the terminal can still limit the signal attenuation estimation in a reasonable range in the extreme environment, avoid false weak field or false strong field due to excessive correction, and thus ensure the consistency and reliability of the subsequent network selection decision.

[0020] The maximum value of the modified signal intensity is selected as the final signal quality score of the corresponding operator for the signal correction result of all communication frequency bands of each operator; In the embodiment of the application, after the completion of the correction of Band 3, 5 and 8 of the operator A, the final signal quality scores of the operator A are obtained -94.6dBm, -92.3dBm, -89.8dBm; the maximum value -89.8dBm is selected as the final signal quality score of the operator.

[0021] Collecting the communication signal strength data of the operator in a preset time period, and counting the signal fluctuation times of the network of the operator according to the communication signal strength data; Calculating the network stability score of the corresponding operator based on the signal fluctuation times; In the case, the network stability score calculation formula is: ; Among them, is the network stability score, is the signal fluctuation times; Based on the final signal quality score and the signal fluctuation times, a dynamic network quality table is constructed.

[0022] In the embodiment of the application, the Band 3 modified intensity of the operator A is sampled at 1Hz in a 10-minute window, and there are 600 samples; the fluctuation threshold is set to ±3dB, the total number of rising edges and falling edges that cross the threshold is 46, and = 46; substituting , S = 0.178 is obtained, which is written into the stability field of the dynamic network quality table together with the signal quality score.

[0023] In one implementation mode of the embodiment of the application, if the sample fluctuation in the same window is very small, = 5, then S = 1 / (1+0.5) = 0.667; accordingly, the stability level of the operator A is marked as high, and a 0.35 coefficient is given in the subsequent network selection weight, and the comprehensive optimization index is obtained after weighting the signal quality score.

[0024] Preferably, the acquisition of the terrain shielding parameter comprises: Acquiring a digital elevation model of a target monitoring area; In the embodiment of the application, after the terminal is powered on and initialized, the digital elevation model file of the target monitoring area is downloaded through a local SPI-Flash or a remote low-power consumption link, and is parsed into a two-dimensional elevation matrix; the matrix takes longitude and latitude as indexes, and stores the elevation value of each grid point. After parsing, the elevation matrix is cached in RAM, and the southwest corner origin coordinates and the grid resolution of the matrix are recorded.

[0025] In one implementation manner of the embodiment of the application, the file size read by the terminal from the Flash is 1MB, the corresponding area is 0.01°*0.01°, the grid resolution is 30m, and the origin coordinate is (28.30°N, 112.50°E); after analysis, a 600*600 pixel elevation matrix is obtained, each pixel occupies 2 bytes, and the range of the elevation is from-50m to 3000m, and the terminal stores the first address pointer of the matrix into the terrain calculation module.

[0026] The terminal coordinate and the base station coordinate are collected, and the terminal coordinate and the base station coordinate are mapped into the digital elevation model, and the terminal coordinate and the base station coordinate are connected into a straight line in the digital elevation model. In the embodiment of the application, the terminal obtains the longitude and latitude of itself through the GNSS module, and extracts the longitude and latitude of the service base station from the pre-stored base station information table; after the two sets of longitude and latitude are converted into radians, the geographic coordinate is mapped into the row and column indexes of the digital elevation matrix by using the projection formula, so that the corresponding positions of the terminal pixel point and the base station pixel point in the matrix are obtained. After the mapping is completed, the terrain calculation module takes the two pixel points as the end points and prepares to sample the straight line path.

[0027] It should be noted that the projection formula in the case includes but is not limited to Mercator projection, equidistant cylindrical projection and UTM projection (Universal Transverse Mercator Projection).

[0028] In one implementation manner of the embodiment of the application, the terminal coordinate (28.305°N, 112.505°E) is converted to correspond to the matrix row and column (300, 300), and the base station coordinate (28.310°N, 112.510°E) corresponds to (400, 400); the projection formula adopts equidistant grid approximation, and the row and column numbers are rounded and written into the structure.

[0029] The elevations of the sampling points are collected along the straight line according to the preset sampling interval, and a sampling point elevation set is generated; In the embodiment of the application, the terminal pixel and the base station pixel are connected on the matrix to form a discrete straight line; the gray value of each pixel through which the straight line passes is read in turn according to the preset sampling interval (pixel step), so that the corresponding sampling point elevation is obtained, and the sampling point elevation set array is stored in order. If the straight line crosses the matrix boundary, it is automatically truncated to the boundary to prevent memory overflow.

[0030] In one implementation manner of the embodiment of the application, the step length is 1 pixel, and a total of 501 sampling points are obtained, and the first 10 points of the elevation sequence are {120m, 122m, 125m,...}; the array length is written into a variable.

[0031] determining the highest point on the straight line according to the sampling point altitude set, and calculating the elevation angle difference of the highest point relative to the line connecting the device and the base station; In the embodiment of the application, the altitudes of each point are compared by traversing the sampling point altitude set, and the maximum value and its index position on the straight line are recorded; the elevation angle difference of the highest point relative to the line connecting the terminal and the base station is calculated according to the horizontal distance and the height difference between the point and the terminal and base station pixels by using the trigonometric function formula.

[0032] In one implementation manner of the embodiment of the application, the highest point altitude 150 m is located at the index 250, the horizontal distance between the terminal and the base station pixels is about 3000 m, the height difference is 30 m, and the elevation angle difference arctan(30 / 3000)=0.57°; the function returns angle_diff=0.57°.

[0033] If the elevation angle difference is greater than a preset threshold, a preset first coefficient is set as the terrain shielding parameter, otherwise, a preset second coefficient is set as the terrain shielding parameter; wherein the preset first coefficient is greater than the preset second coefficient.

[0034] In the embodiment of the application, the calculated elevation angle difference is compared with the preset threshold: if the elevation angle difference is greater than the preset threshold, it is indicated that the terrain has obvious shielding effect on the wave propagation, and the preset first coefficient is assigned to the terrain shielding parameter ; otherwise, it is considered that the shielding is slight, and the preset second coefficient is assigned; the parameter is then stored in the attenuation parameter register.

[0035] In one implementation manner of the embodiment of the application, the preset threshold=0.5°, the current angle_diff=0.57°>0.5°, and therefore =1.8; if the angle_diff of another area is 0.3°, then =1.2.

[0036] Preferably, the vegetation density index is obtained by: obtaining, by a satellite remote sensing platform, normalized vegetation index images of a target monitoring area in two adjacent months, and the image spatial resolution is not less than 10 meters; In the embodiment of the application, the terminal receives the normalized vegetation index (NDVI) image file issued by the satellite remote sensing platform through the low-power Beidou short message channel on the first day of each month, the file is a single-band Geo TIFF format, and the spatial resolution is 10 meters; after the reception is completed, the image is written into a fixed partition of the SPI-Flash, and an image date tag is recorded to ensure that the latest data of two adjacent months is always saved.

[0037] In one implementation manner of the embodiment of the present application, the terminal receives a file with size=1.2MB, row and column number 1000*1000, pixel depth 8bit, NDVI value range 0-255, corresponding to actual NDVI=-1~1 on June 1, 03:00; and receives a second image in the same way on July 1.

[0038] A circular region with a radius of 100 meters is drawn on the normalized vegetation index image with the GPS coordinates of the terminal device as the center, and the pixels with the normalized vegetation index values in the effective interval [0.05, 0.95] are recorded as limited pixels. In the embodiment of the present application, the terminal reads the current latitude and longitude given by the GNSS module, and generates a circular mask on the NDVI image with the latitude and longitude as the center and a radius of 100 meters; the pixels within the circle are retained, and the pixels outside the circle are set to invalid values; the mask array has the same width and height as the image, and 1 represents validity and 0 represents invalidity. All pixels within the circular mask are traversed, the NDVI values are linearly stretched from 0-255 to the interval -1~1, and it is judged whether each pixel falls within [0.05, 0.95]; the pixels meeting the condition are marked as limited pixels, and the counter is accumulated, and the remaining pixels are discarded as water or buildings.

[0039] In one implementation manner of the embodiment of the present application, the center coordinates (28.305°N, 112.505°E) are converted into image row and column (500, 500), and the radius corresponds to 10 pixels; in the mask array mask

[1000]

[1000] , the pixels within the circle are set to 1, and there are 317 valid pixels, and the remaining pixels are set to 0.

[0040] The vegetation index values of all valid pixels within the circular region in the last month are extracted, and the arithmetic mean value is calculated as the vegetation index mean value of the last month; In the embodiment of the present application, the valid pixel array of the last month is accumulated and summed, and then divided by the number of valid pixels to obtain the vegetation index mean of the last month.

[0041] In one implementation manner of the embodiment of the present application, the cumulative sum of 289 valid NDVI values in June is 86.7, and the mean value is 86.7 / 289=0.300.

[0042] The vegetation index values of all valid pixels within the circular region in the last month are extracted, and the arithmetic mean value is calculated as the vegetation index mean value of the last month; In the embodiment of the present application, the same method as that of the last month is used to average the valid pixels within the image circle of the current month to obtain the vegetation index mean value of the current month.

[0043] In one implementation manner of the embodiment of the present application, the cumulative sum of 295 valid NDVI values in July is 97.6, and the mean value is 97.6 / 295=0.331.

[0044] The monthly average coverage growth rate is calculated based on the average vegetation index of the last month and the average vegetation index of the current month. In the embodiment of the application, the monthly average coverage growth rate is obtained by subtracting the average of the last month from the average of the current month and then dividing the average of the last month. The result is saved in the form of percentage. If the average of the last month is zero or negative, the growth rate is forced to be 0 to prevent division by zero exception and ensure stable subsequent scaling calculation.

[0045] In an implementation manner of the embodiment of the application, the growth rate=(0.331-0.300) / 0.300=10.3%.

[0046] The vegetation density index is obtained by multiplying the monthly average coverage growth rate by a preset scaling coefficient and adding a reference value.

[0047] In an implementation manner of the embodiment of the application, the scaling coefficient=0.5 and the reference value=1.0, so the vegetation density index =0.103×0.5+1.0=1.051.

[0048] Preferably, the acquisition of the meteorological attenuation coefficient comprises: acquiring real-time meteorological observation data of the target monitoring area; In the embodiment of the application, the terminal automatically pulls the real-time meteorological observation data of the target monitoring area once an hour through the on-board meteorological sensor or the low-power wide-area network interface. The data packet contains the current hour cumulative rainfall, relative humidity and temperature fields. After the terminal parses, the rainfall is stored in the meteorological buffer as the primary criterion.

[0049] In an implementation manner of the embodiment of the application, the terminal receives the meteorological platform downlink data packet through NB-IoT at 08:55, and parses to obtain the cumulative rainfall of 1.2 mm, the relative humidity of 85%, and the temperature of 6°C. The data is written into the weather structure body, and the field rainfall=1.2.

[0050] determining the current weather condition of the target monitoring area according to the real-time meteorological observation data; In the embodiment of the application, the current hour cumulative rainfall is compared with the preset threshold based on the rainfall threshold. If the current hour cumulative rainfall is greater than the preset threshold, the weather is marked as rain or snow, otherwise, the weather is considered as normal. The state result is stored in the weather flag bit in the form of Boolean quantity. The weather flag bit is updated once every whole point to ensure that the meteorological attenuation coefficient is switched in time and stably, and frequent jitter is avoided.

[0051] In an implementation manner of the embodiment of the application, the preset threshold is 1.0 mm, the current rainfall is 1.2 mm>1.0 mm, the weather flag bit is is_rain=1, indicating rain or snow weather. If the next hour rainfall is 0.3 mm, then is_rain=0, indicating normal weather.

[0052] If the current weather condition is rain and snow, a preset first attenuation coefficient is set as the meteorological attenuation coefficient; If the current weather condition is normal weather, a preset second attenuation coefficient is set as the meteorological attenuation coefficient; Wherein, the preset first attenuation coefficient is greater than the preset second attenuation coefficient.

[0053] In the embodiment of the application, the attenuation coefficient is selected according to the weather flag bit: if the flag bit is rain and snow, the preset first attenuation coefficient is assigned to the meteorological attenuation coefficient; if the flag bit is normal, the preset second attenuation coefficient is assigned.

[0054] In one implementation of the embodiment of the application, when is_rain=1, the meteorological attenuation coefficient =1.50; when is_rain=0, the meteorological attenuation coefficient =1.00.

[0055] Preferably, the low-power network connection between the 4G Cat.1 communication unit and the preset cloud management platform in step S1 is established according to network authentication information, comprising: In the terminal sleep state, the default operator is loaded from the network configuration file of the VSim software unit as the standby operator; In the embodiment of the application, after the terminal enters sleep, the main control unit closes all peripherals except the RTC (Radio Resource Control) and the VSim software unit; the VSim reads the default operator configuration file from the specified partition of the Flash, the file contains the PLMN (Public Land Mobile Network), IMSI (International Mobile Subscriber Identity), authentication key and APN (Access Point Name), and after the parsing is completed, it is written into the baseband NV (Non-Volatile) area as the basis for subsequent standby network camping.

[0056] In one implementation of the embodiment of the application, the default configuration file size is 512 bytes, PLMN=46001, APN=cmnbiot, the parsing time is 2ms, after loading, the register flag_default=1, indicating that the default operator is ready.

[0057] Based on the network authentication information of the standby operator, an initial standby network connection between the 4G Cat.1 communication unit and the cloud management platform is established; In the embodiment of the present application, after the baseband loading configuration, an attachment request is initiated to the network in a manner of not establishing a packet data network (PDN) and only registering attachment; an Attach Accept returned by the cloud management platform is considered as that the initial standby network connection is successful, and the terminal subsequently enters an RRC (Radio Resource Control) suspended state, keeps downlink paging monitoring, and temporarily does not activate the uplink data channel to save power consumption.

[0058] In one implementation manner of the embodiment of the present application, the attachment request is sent out 120 ms after the terminal is woken up, the network side returns an Accept at 180 ms, the T3412 extended period is set to 54 min, and the RRC suspended current is reduced to 0.6 mA.

[0059] It should be noted that T3412 is a timer in the LTE network, which is used to control the periodic tracking area update (TAU) process of a user equipment (UE) in an idle mode. When the terminal enters the idle mode, the T3412 timer starts timing, and when the timer expires, the terminal needs to send a tracking area update request to the network to inform the network of its current location information.

[0060] The basic radio frequency unit of the 4G Cat.1 communication unit is activated at a preset period; In the embodiment of the present application, the RTC generates a timing interrupt at a preset period, and only the radio frequency PLL (Phase-Locked Loop) and the receiver are turned on after the interrupt arrives to complete a paging channel monitoring; after the monitoring is completed, the radio frequency is turned off to keep a sleep state, so that the average current in the monitoring process is lower than the standby budget, and the terminal can receive a wake-up short message or a control instruction issued by the platform in time.

[0061] In one implementation manner of the embodiment of the present application, the period is set to 2.56 s, the single monitoring duration is 6 ms, the peak value of the radio frequency current is 14 mA, and the average current increment is only 0.03 mA, which has almost no impact on the solar energy storage.

[0062] The data transmission rate of the initial standby network is set to a preset transmission rate, and the radio frequency power consumption of the basic radio frequency unit is controlled to be less than k times of the normal working mode, wherein k is greater than 0 and less than 0.05; In the embodiment of the present application, the transmission rate of the initial standby network is set to a preset low rate level, the maximum radio frequency transmission power is reduced to the lowest grade, and narrowband transmission filtering is enabled; the digital pre-distortion module of the power amplifier is automatically turned off by the baseband, so that the radio frequency power consumption is compressed to less than k times of the normal working mode, and the permanent endurance requirement is met.

[0063] In one implementation manner of the embodiment of the present application, the rate level is selected as Cat.1 UL 1Mbps / DL 1Mbps, the PA output power is set as +5dBm, k=0.04, the actual measured radio frequency power consumption is reduced from 200mW to 8mW, and the requirement of k<0.05 is met.

[0064] The registration state scanning is performed on all the operator networks stored in the VSim software unit, the registration success / failure state of each operator network is recorded, and the number of consecutive registration failures of each operator network is counted. In the embodiment of the present application, at each periodic wake-up monitoring, the VSim sequentially injects other operator configurations, and the baseband performs a fast registration scanning; the scanning result is written into a state bitmap with a success or failure flag, and a failure counter is accumulated, and the success is cleared, so as to form the real-time statistics of the number of consecutive registration failures of each operator.

[0065] In one implementation manner of the embodiment of the present application, the time consumption of each scanning is 80ms, the state bitmap is 8bit, the consecutive failure count of the operator A is 3, the count of the operator B is 0, and the counter variable is stored in the Flash backup, and is not lost in power failure.

[0066] When the consecutive registration failure of any operator network is detected for N times, the automatic switching to the backup network configuration file is performed for re-registration, wherein N is a positive integer less than 5.

[0067] In the embodiment of the present application, when the consecutive registration failure number of any operator reaches N times, the VSim automatically marks the configuration as "short-term invalid", and loads the backup network configuration file; the baseband uses the new configuration to re-initiate the registration, and the original configuration is not attempted within 24 hours, so as to avoid the energy waste caused by invalid retries, and improve the network staying success rate.

[0068] In one implementation manner of the embodiment of the present application, N=3, after the failure count of the operator A reaches 3, the VSim reads the backup configuration PLMN=46000, and the re-registration time consumption is 150ms; after the registration is successful, the flag_default=0 and the flag_backup=1 are updated, and the smooth switching of the low-power standby network is completed.

[0069] Preferably, after the target operator network is determined according to the dynamic network quality table in step S4, the method further comprises: determining a suboptimal operator network according to the dynamic network quality table; In the embodiment of the present application, after the target operator selection is completed, the second-ranked operator is marked as a suboptimal operator in the descending order of the signal quality score in the dynamic network quality table; the difference between the scores of the target operator and the suboptimal operator is temporarily stored, and is used for priority comparison in subsequent switching, so as to ensure that the switching decision always faces the optimal available alternative link.

[0070] In one implementation of the embodiment of the application, the target operator scores -87dBm, and the suboptimal operator scores -89dBm, with a difference of 2dB.

[0071] The preset test data packet is sent to the preset cloud management platform based on the target operator network, signal fluctuation variance, packet loss rate and delay in the transmission process are recorded synchronously, and the remaining power of the energy storage unit is obtained; if any of the following conditions is met, switching to the suboptimal operator network is triggered: the packet loss rate is greater than a preset packet loss threshold or the delay is greater than a preset delay threshold; the signal fluctuation variance is greater than a preset fluctuation variance; the remaining power of the energy storage unit is less than a preset power threshold and the packet loss rate is greater than the preset packet loss threshold.

[0072] In the embodiment of the application, after the target operator is determined, a preset test data packet with a fixed length is sent to the cloud management platform through the attached bearer, the baseband automatically records the time stamp, sequence number and ACK state in the transmission process, and the MCU (Microcontroller Unit) calculates the packet loss rate, average delay and signal strength sample variance based on the foregoing, reads the remaining power of the energy storage unit, and all indexes are collected into a temporary link quality structure body; whether the packet loss rate or the delay exceeds the preset threshold, whether the signal fluctuation variance is too large, and whether the power is lower than the threshold and the packet loss rate is still excessive are judged in sequence, any condition meeting the preset condition sets the link degradation flag, triggers switching to the suboptimal operator, and the business code rate can be reduced synchronously when the power is insufficient, so as to avoid continuing transmission in a poor link or extreme power.

[0073] In one implementation of the embodiment of the application, the test packet length is 512 bytes, the sending interval is 1 second, a total of 20 packets, the actual measured packet loss is 1 packet, the packet loss rate is 5%, the average delay is 220 milliseconds, the signal variance is 4.2 decibels, and the power remaining is 42%; the packet loss threshold is set to 3%, the delay threshold is 200 milliseconds, the fluctuation variance threshold is 3.0 decibels, and the power threshold is 40%. The current packet loss rate and variance are both excessive, the target operator bearer is suspended, and the suboptimal operator configuration is loaded immediately; if the power further decreases to 38% and the packet loss rate remains 5%, the video code rate will be automatically reduced from 512kbps to 256kbps after switching is completed.

[0074] Preferably, step S2 comprises: sampling the thermal radiation intensity of the target monitoring area at a preset sampling period through the passive infrared sensor, and recording the intensity change rate of each sampling period; In the embodiment of the application, the thermal radiation intensity of the monitoring area is continuously collected at a fixed sampling period through the passive infrared sensor; after each sampling, the current intensity value is differentiated from the last period value to obtain the intensity change rate, and the signed integer is stored in the ring buffer.

[0075] In one implementation manner of the embodiment of the present application, the sampling period is set to 250 ms, the sensor output is 12-bit ADC value, the current intensity is 1200 LSB, the last period is 1180 LSB, the difference is the change rate +20 LSB, and the change rate is stored in the buffer.

[0076] When the intensity change rates of three consecutive sampling periods all exceed the preset change rate threshold, it is determined that the current monitoring event is a valid moving event, and a hardware interrupt wake-up signal is generated; In the embodiment of the present application, after calculating the change rate each time, the value is compared with the preset change rate threshold; if the change rates of three consecutive sampling periods all exceed the threshold, it is determined that it is a valid moving event, the MCU generates a hardware interrupt wake-up signal, and the event time stamp is latched.

[0077] In one implementation manner of the embodiment of the present application, the change rate threshold is set to 15 LSB, the change rates of three consecutive periods are +18, +22 and +20 LSB respectively, all of which are greater than the threshold, the valid event flag is triggered, and an interrupt signal is generated.

[0078] The sleep state of the terminal is woken up according to the hardware interrupt wake-up signal; In the embodiment of the present application, the hardware interrupt signal is directly connected to the low-power wake-up pin of the main control unit; after the interrupt arrives, the main control exits the deep sleep mode, opens the necessary power supply domain, and reads the event latching register to confirm the wake-up source; after confirming that it is a valid moving event, the subsequent image acquisition task is started, and other peripherals remain closed, so as to shorten the duration of the wake-up current spike.

[0079] In one implementation manner of the embodiment of the present application, the rising edge of the interrupt pin PA0 is received, the wake-up time is 120 µs, the main control reads the register, confirms that the event is valid, opens the power supply of the camera and the encoder, and the remaining domains remain closed, so that the wake-up peak current is controlled within 60 mA.

[0080] The thermal radiation fluctuation with a duration less than a preset minimum duration or an intensity change rate lower than a preset change rate threshold is marked as environmental noise and ignored; In the embodiment of the present application, before event determination, the fluctuation sequence with a duration lower than a preset minimum duration or an intensity change rate less than a threshold is marked as environmental noise and discarded; after marking, the corresponding buffer data is cleared.

[0081] In one implementation manner of the embodiment of the present application, the minimum duration is set to 500 ms, if the change rate sequence decreases to less than 10 LSB after 250 ms, and the total duration is only 375 ms, it is determined to be noise, the flag noise_flag=1, the buffer diff_buf is cleared, and the event counter is reset.

[0082] acquire compressed audio and video data of the target monitoring area through the terminal.

[0083] In the embodiment of the present application, after confirming the valid moving event, the terminal starts the camera and the hardware encoder, and records the audio and video of the target area according to the current data collection mode; after the encoding is completed, the data stream is packaged into an MP4 file and stored in the SDRAM queue, waiting for the 4G communication unit to upload.

[0084] In one implementation manner of the embodiment of the present application, the recording resolution is 1920x1080, the frame rate is 15fps, the time length is 5s, the generated file size is 625KB, and the file name contains a timestamp and an event number.

[0085] Preferably, the acquiring compressed audio and video data of the target monitoring area through the terminal comprises: Step S211: acquiring an azimuth angle of the monitoring target relative to the terminal lens through the passive infrared sensor; In the embodiment of the present application, after the passive infrared sensor is triggered, the multi-section pulse amplitude sequence output by the passive infrared sensor is read, the horizontal offset angle of the target relative to the optical axis of the lens is calculated by comparing the amplitude values of the sections, and the angle is converted into an azimuth angle, which is stored in the azimuth register in the form of an 8-bit signed number.

[0086] In one implementation manner of the embodiment of the present application, the number of sensor sections is 7, the amplitude value of the center section is 120mV, the amplitude value of the right section is 180mV, the offset angle obtained through differential operation is +12°, and the azimuth angle register value is +12.

[0087] Step S212: determining the percentage of the monitoring target to the center of the terminal lens according to the azimuth angle, and acquiring the remaining power of the energy storage unit; In the embodiment of the present application, the azimuth angle is divided by the maximum field of view angle of the lens to obtain a normalized offset, and then the absolute value is taken and multiplied by 100 to convert it into a percentage to the center of the lens; at the same time, the voltage of the energy storage unit is sampled through an ADC (Analog-to-Digital Converter), and the remaining power percentage is obtained by looking up the table.

[0088] In one implementation manner of the embodiment of the present application, the maximum field of view angle is 60°, the current azimuth angle is +12°, the normalized offset is 0.2, and the percentage to the center is 20%; the battery voltage measured by the ADC is 3.70V, the remaining power percentage obtained by looking up the table is 55%, and the two parameters are written into the structure body offset_pct and soc_pct.

[0089] Step S213: determining the data collection mode of the terminal according to the percentage to the center of the lens and the remaining power of the energy storage unit; In the embodiment of the present application, a two-dimensional lookup table strategy is adopted, taking percentage from the lens center as the horizontal axis and residual power as the vertical axis, to map the current allowed data acquisition mode; the mode is divided into three kinds of high-definition video recording, standard-definition video recording and static picture, the smaller the center percentage and the higher the power, the more the mode tends to high definition, and vice versa, and the lookup table is fixed in the Flash.

[0090] In one implementation of the embodiment of the present application, the lookup table defines: offset_pct≤25% and soc_pct≥50%→high-definition video recording; offset_pct≤25% and soc_pct<50%→standard-definition video recording; offset_pct>25%→static picture; the current offset_pct=20%, soc_pct=55%, the mode is high-definition video recording obtained by looking up the table, and the mode code 0x03 is written into the variable cap_mode.

[0091] Step S214: acquiring compressed audio and video data of the target monitoring area through the terminal according to the data acquisition mode.

[0092] In the embodiment of the present application, according to the data acquisition mode, the image sensor configuration of the corresponding resolution is started, and the H.264 hardware encoder is opened; after the acquisition is completed, the encoder outputs the compressed code stream directly through DMA to write into the SDRAM ring buffer, the MCU synchronously adds the time stamp and the azimuth angle information, and finally encapsulates into an MP4 or JPEG file, waiting for subsequent uploading.

[0093] In one implementation of the embodiment of the present application, the high-definition video recording mode has a resolution of 1920x1080, a frame rate of 15fps, a code rate of 1Mbps, an acquisition time length of 5s, and a generated file size of 625KB; after the encoding is completed, the file header writes the azimuth angle+12° and the UTC time stamp, and is stored in the uploading queue for calling and sending by the 4G Cat.1 communication unit.

[0094] Especially important is that between step S1 and step S3, it also includes: When the terrain shielding parameter is greater than the preset parameter threshold, the current service operator is added to the shielding list and marked as permanent shielding; When the rain and snow weather is detected, the high-frequency band operator is added to the temporary shielding list; In the dynamic network quality table generation process, the operators in the shielding list are automatically excluded; When the vegetation density index is greater than the preset index threshold, the low-frequency band is forcibly locked for data transmission; The signal strength score of the high-frequency band is reduced by 40% to avoid vegetation shielding attenuation.

[0095] In the embodiment of the present application, after the terminal completes the calculation of the terrain shielding parameter, if the terrain shielding parameter is greater than the preset parameter threshold, the current service operator is added to the shielding list and marked as permanent shielding; when detecting the rainy and snowy weather, the high frequency band operator (Band 38 / 40) is automatically added to the temporary shielding list; in the process of generating the dynamic network quality table, the operators in the shielding list are automatically excluded, and the network selection is optimized; when the vegetation density index is greater than the preset threshold, the low frequency band (Band 5 / 8 / 20) is forced to be locked for data transmission, and the signal strength score of the high frequency band is reduced by 40%, so as to avoid the attenuation caused by the vegetation shielding.

[0096] In one implementation manner of the embodiment of the present application, the preset terrain shielding parameter threshold is 1.5, the current terrain shielding parameter calculation result is 1.6, the current service operator A is added to the permanent shielding list; when detecting the rainy and snowy weather, Band 38 and Band 40 are added to the temporary shielding list; when generating the dynamic network quality table, the shielded operator A and the frequency band Band 38 / 40 are automatically excluded; the preset threshold of the vegetation density index is 1.2, the current index is 1.3, the low frequency band Band 5 / 8 / 20 is forced to be locked for data transmission, and the signal strength score of the high frequency band Band 38 / 40 is reduced by 40%, so as to ensure that the stable communication link can be maintained in the complex environment.

[0097] Especially important is that the network access process after the terminal is woken up in step S2 includes: In the low-power standby network state, the multi-operator network registration is completed in advance by the VSim software unit, and a connection pool is formed; When the event wakes up, the security context token of the target operator is directly extracted from the connection pool; The security context token is injected into the baseband processor of the 4G Cat.1 communication unit, and the network search and authentication process is skipped; Within the preset connection establishment delay, an available data link is established to transmit compressed audio and video data.

[0098] In the embodiment of the present application, in the low-power standby network connection state of the terminal, the multi-operator network registration is completed in advance by the VSim software unit, all operator configuration files are loaded and the air interface authentication is performed, the network security context after the authentication is successfully stored in the FRAM memory, and a connection pool is formed; when the event wakes up, the security context token of the target operator is directly extracted from the connection pool, and is injected into the baseband processor of the 4G Cat.1 communication unit, the network search and authentication process is skipped, and within the preset connection establishment delay, an available data link is established to transmit compressed audio and video data, so as to ensure that the network is quickly accessed and data is transmitted.

[0099] In one implementation manner of the embodiment of the present application, the terminal loads 3 operator configuration files in the standby state, completes authentication in turn, and stores the context to the FRAM address 0x0000-0x0FFF after success, to form a connection pool; after being woken up by an event, the context token of the operator A is extracted from the connection pool, injected into the baseband processor within 100 milliseconds, the network search authentication is skipped, and the data link is established within 200 milliseconds to transmit compressed audio and video data.

[0100] Especially important is step S51: controlling the 4G Cat.1 communication unit to return to the standby network connection state within 30 seconds after the data transmission is completed, and simultaneously turning off the image acquisition unit; In the embodiment of the present application, after confirming that the uploaded data has received the platform ACK, a 30-second timer is started; during the running of the timer, the standby bearer is maintained to wait for potential retransmission requirements, and after the timeout, the baseband actively releases the RRC connection and loads the default VSim configuration, returns to the low-power paging state, and simultaneously turns off the image sensor power domain, to ensure that there is no additional milliamperes of leakage current.

[0101] In one implementation manner of the embodiment of the present application, the ACK arrival time is 14:03:10, the timer is triggered after 30 seconds, the baseband performs RRC Release at 14:03:40, the current is reduced from 80 mA to 6 mA, the image sensor power MOS tube is turned off, the leakage current is <5 µA, and the power saving switching is completed.

[0102] Step S52: real-time acquisition of the remaining power of the energy storage unit, and extraction of the comprehensive score of each operator network in the dynamic network quality table; In the embodiment of the present application, after the timeout of the timer, the MCU samples the voltage of the energy storage unit, obtains the remaining power percentage by table lookup, and reads the corrected signal strength and the latest delay of each operator in the dynamic network quality table, to calculate the comprehensive score according to the weight of 70% strength+30% delay.

[0103] In one implementation manner of the embodiment of the present application, the voltage measured by the ADC is 3.65 V, corresponding to the remaining power of 45%; the signal of the operator A is -88 dBm and the delay is 180 ms, the comprehensive score is 0.71, the signal of the operator B is -90 dBm and the delay is 150 ms, and the score is 0.68, and the difference is 0.03.

[0104] Step S53: the remote policy instruction is generated by the preset cloud management platform according to the following rules: When the remaining power is less than the preset remaining power threshold, an instruction package containing three adjustments is generated: extending the standby network activation period to a preset time length, reducing the sensitivity threshold of the passive infrared sensor, and limiting the image acquisition resolution to a preset resolution; When there is a sub-optimal operator network with a comprehensive score difference greater than 0.3, a network switching instruction is generated, and a VSim configuration file priority is updated; In the embodiment of the application, after the cloud management platform receives the power and score reported by the terminal, a strategy package is automatically generated according to a preset rule: if the power is lower than a threshold, a three-adjustment instruction is issued: the standby listening period is extended, the PIR (Passive Infrared) trigger threshold is reduced, and the video resolution is limited; if there is a sub-optimal network with a score difference greater than 0.3, a switching instruction is added, and the VSim priority is updated.

[0105] In one implementation manner of the embodiment of the application, the power threshold is 50%, the current is 45%, and the energy-saving strategy is triggered; the platform issues: the active period is 2.56s→5.12s, the PIR threshold is 15→10LSB, and the resolution is 1080→720p; the difference between the operators A and B is 0.03, which does not reach 0.3, so there is no switching instruction, the JSON length is 182 bytes, and it is transmitted to the terminal by MQTT (Message Queuing Telemetry Transport) downward.

[0106] Step S54: The terminal receives the remote strategy instruction through the standby network connection, writes the remote strategy instruction into the non-volatile FRAM memory, and controls the terminal to re-enter the sleep state according to the remote strategy instruction.

[0107] In the embodiment of the application, the terminal listens to the downlink Topic under the standby network, writes the original text into the non-volatile FRAM by using hardware after receiving the strategy package, reads and verifies after writing, and updates the RTC period, PIR threshold and camera resolution configuration according to the new parameters after verification, further, turns off the power of all peripherals, sets the wake-up source as RTC or PIR, and formally enters the deep sleep state, waiting for the next event or period wake-up.

[0108] Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the application file are intended to be included in the application.

[0109] The above description is only a specific implementation of the application, enabling those skilled in the art to understand or implement the application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A 4G Cat.1 passive IoT monitoring method based on Vsim, applied to a smart camera terminal, the smart camera terminal including at least a main control unit, an energy storage unit, a Vsim software unit, and a 4G Cat.1 communication unit, the smart camera terminal being powered by solar energy, characterized in that... The method further includes the following steps: Step S1: Pre-store network authentication information of at least two operators through the VSim software unit; in the terminal sleep state, establish a low-power network connection between the 4G Cat.1 communication unit and the preset cloud management platform based on the network authentication information; Step S2: Continuously monitor the thermal radiation changes within the target monitoring area using a passive infrared sensor. When a valid movement event is detected, generate a hardware interrupt wake-up signal. Wake up the terminal based on the hardware interrupt wake-up signal and obtain compressed audio and video data of the target monitoring area through the terminal. Step S3: Monitor the communication signal strength of each operator in real time and generate a dynamic network quality table based on the communication signal strength; Step S4: Determine the target operator's network based on the dynamic network quality table; upload the compressed audio and video data to the preset cloud management platform based on the target operator's network; Step S5: After data transmission is completed, the main control unit controls the 4G Cat.1 communication unit to return to the low-power standby network connection state and shuts down the terminal's image acquisition; obtains the remaining power of the energy storage unit; the preset cloud management platform generates remote policy instructions based on the dynamic network quality table and the remaining power of the energy storage unit; after receiving the remote policy instructions, the terminal updates the local policy and re-enters sleep mode.

2. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 1, characterized in that, Step S3 includes: Scan the communication frequency bands supported by the operator, perform at least 5 consecutive signal strength samples for each communication frequency band, with a sampling interval of 200 milliseconds, and take the median value after removing the maximum and minimum values ​​as the original signal strength of the corresponding communication frequency band; Obtain the terrain shading parameters, vegetation density index, and meteorological attenuation coefficient of the target monitoring area, and calculate the comprehensive signal attenuation coefficient based on the terrain shading parameters, vegetation density index, and meteorological attenuation coefficient; If the overall signal attenuation coefficient is less than the preset first threshold, then the overall signal attenuation coefficient will be forcibly set to the preset first threshold. If the overall signal attenuation coefficient is greater than the preset second threshold, then the overall signal attenuation coefficient is forcibly set to the preset second threshold; wherein, the preset first threshold is less than the preset second threshold; The corrected signal strength is calculated based on the original signal strength and the overall signal attenuation coefficient. For each operator, the maximum value of the corrected signal strength is selected as the final signal quality score for all communication frequency bands. Collect communication signal strength data of operators within a preset time period, and count the number of signal fluctuations in the operator's network based on the communication signal strength data; Calculate the network stability score of the corresponding operator based on the number of signal fluctuations; A dynamic network quality table is constructed based on the final signal quality score and the number of signal fluctuations.

3. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 2, characterized in that, Obtaining terrain shading parameters includes: Obtain a digital elevation model of the target monitoring area; Collect the coordinates of the terminal and the base station, and map the terminal and base station coordinates into the digital elevation model. In the digital elevation model, connect the terminal coordinates and the base station coordinates into a straight line. The altitude of sampling points is collected along a straight line according to a preset sampling interval, and a set of sampling point altitudes is generated. The highest point on the straight path is determined based on the elevation set of the sampling points, and the difference in elevation angle between the highest point and the line connecting the device and the base station is calculated. If the elevation angle difference is greater than the preset threshold, the preset first coefficient is set as the terrain occlusion parameter; otherwise, the preset second coefficient is set as the terrain occlusion parameter. The preset first coefficient is greater than the preset second coefficient.

4. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 2, characterized in that, Obtaining the vegetation density index includes: The normalized vegetation index images of the target monitoring area for two consecutive months are obtained through a satellite remote sensing platform, with a spatial resolution of no less than 10 meters. Using the GPS coordinates of the terminal device as the center, a circular area with a radius of 100 meters is delineated on the normalized vegetation index image, and pixels with normalized vegetation index values ​​within the effective range [0.05, 0.95] are recorded as finite pixels; Extract the vegetation index values ​​of all valid pixels within the circular area from the previous month, and calculate the arithmetic mean as the average vegetation index value for the previous month. Extract the vegetation index values ​​of all valid pixels within the circular area for this month, and calculate the arithmetic mean as the average vegetation index for this month; The average monthly coverage growth rate is calculated based on the average vegetation index of the previous month and the average vegetation index of this month. Multiply the average monthly coverage growth rate by a preset scaling factor, and then add the baseline value to obtain the vegetation density index.

5. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 2, characterized in that, The acquisition of the meteorological attenuation coefficient includes: Acquire real-time meteorological observation data for the target monitoring area; Determine the current weather conditions of the target monitoring area based on real-time meteorological observation data; If the current weather conditions are rain or snow, then the preset first attenuation coefficient will be set as the meteorological attenuation coefficient. If the current weather conditions are normal, then the preset attenuation coefficient will be set as the meteorological attenuation coefficient. Among them, the preset first attenuation coefficient is greater than the preset second attenuation coefficient.

6. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 1, characterized in that, Step S1 establishes a low-power network connection between the 4G Cat.1 communication unit and the preset cloud management platform based on network authentication information, including: When the terminal is in sleep mode, the default operator is loaded from the network configuration file of the VSim software unit as the standby operator; Based on the network authentication information of the standby operator, an initial standby network connection is established between the 4G Cat.1 communication unit and the cloud management platform; The basic radio frequency unit of the 4G Cat.1 communication unit is activated at a preset cycle; Set the data transmission rate of the initial standby network to the preset transmission rate, and control the RF power consumption of the basic RF unit to be less than k times that of the normal operating mode, where k is greater than 0 and less than 0.

05. Perform a registration status scan on all carrier networks stored in the VSim software unit, record the registration success / failure status of each carrier network, and count the number of consecutive registration failures for each carrier network. If any operator's network fails to register N times consecutively, the system will automatically switch to the backup network configuration file for re-registration, where N is a positive integer less than 5.

7. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 1, characterized in that, After determining the target operator's network based on the dynamic network quality table in step S4, the following steps are also included: The suboptimal operator network is determined based on the dynamic network quality table; Based on the target operator's network, a preset test data packet is sent to a preset cloud management platform. The signal fluctuation variance, packet loss rate, and latency during transmission are recorded simultaneously, and the remaining power of the energy storage unit is obtained. A switch to the suboptimal operator's network is triggered if any of the following conditions are met: The packet loss rate is greater than the preset packet loss threshold or the latency is greater than the preset latency threshold. The signal fluctuation variance is greater than the preset fluctuation variance; The remaining power of the energy storage unit is less than the preset power threshold and the packet loss rate is the preset packet loss threshold.

8. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 1, characterized in that, Step S2 includes: The thermal radiation intensity of the target monitoring area is sampled by a passive infrared sensor at a preset sampling period, and the rate of change of intensity in each sampling period is recorded. When the rate of change of intensity for three consecutive sampling periods exceeds the preset rate of change threshold, the current monitored event is determined to be a valid movement event, and a hardware interrupt wake-up signal is generated. The terminal is awakened from its sleep state by a hardware interrupt wake-up signal; Thermal radiation fluctuations whose duration is less than the preset minimum duration or whose intensity change rate is less than the preset change rate threshold are marked as environmental noise and ignored. Compressed audio and video data of the target monitoring area are obtained through the terminal.

9. The 4G Cat.1 passive IoT monitoring method based on Vsim according to claim 8, characterized in that, The step of acquiring compressed audio and video data of the target monitoring area through the terminal includes: Step S211: Obtain the azimuth angle of the monitored target relative to the terminal lens using a passive infrared sensor; Step S212: Determine the percentage of distance between the monitored target and the center of the terminal lens based on the azimuth angle, and obtain the remaining power of the energy storage unit; Step S213: Determine the terminal data acquisition mode based on the percentage of distance from the lens center and the remaining power of the energy storage unit; Step S214: Obtain compressed audio and video data of the target monitoring area through the terminal according to the data acquisition mode.

10. A 4G Cat.1 passive IoT monitoring system based on Vsim, characterized in that, For executing the Vsim-based 4G Cat.1 passive IoT monitoring method as described in claim 1, the Vsim-based 4G Cat.1 passive IoT monitoring system comprises: The authentication module is used to pre-store network authentication information of at least two operators through the VSIM software unit; in the terminal sleep state, it establishes a low-power network connection between the 4G Cat.1 communication unit and the preset cloud management platform based on the network authentication information. The wake-up module is used to continuously monitor changes in thermal radiation within the target monitoring area using a passive infrared sensor. When a valid movement event is detected, a hardware interrupt wake-up signal is generated. The terminal is then woken up based on the hardware interrupt wake-up signal, and compressed audio and video data of the target monitoring area is obtained through the terminal. The network testing module is used to monitor the communication signal strength of each operator in real time and generate a dynamic network quality table based on the communication signal strength. The transmission module is used to determine the target operator's network based on a dynamic network quality table; and to upload compressed audio and video data to a preset cloud management platform based on the target operator's network. The hibernation module is used to control the 4G Cat.1 communication unit to return to the low-power standby network connection state and turn off the terminal's image acquisition after data transmission is completed; obtain the remaining power of the energy storage unit; generate remote policy instructions based on the dynamic network quality table and the remaining power of the energy storage unit; and update the local policy and re-enter hibernation after the terminal receives the remote policy instructions.

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