Low-power-consumption ranging and positioning system based on UWB

Abstract

The invention discloses a UWB-based low-power-consumption ranging and positioning system. The system comprises a plurality of beacons, a plurality of tags and a gateway, two wireless communication modes of UWB and Bluetooth BLE are built in the beacon, in a discovery state, the beacon closes all peripherals to enter a dormant state, Bluetooth BLE periodic broadcast is started, a data packet is sent periodically through the UWB, and a receiving waiting response is started; in a working state, a Poll packet is regularly and actively sent in a dormancy mode, receiving is started, whether correct response packet data is received or not is judged within set time, if yes, a Final packet is sent in a delayed mode to complete a distance measurement process, and if not, whether a discovery state is re-entered or not is judged according to receiving idle count; a three-axis sensor is arranged in the tag, and in a working state, distance measurement is completed through interaction of UWB signals and nearby beacons, and the distance is uploaded to a server. According to the invention, the beacon can be powered by the battery and can operate for a long time, stay wires deployed on site are omitted, and the installation complexity of the UWB positioning system is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultra-wideband (UWB) communication, in particular to a low-power ranging positioning system based on UWB. BACKGROUND

[0002] Ultra-wideband (UWB) technology has become one of the preferred technologies for high-precision indoor and outdoor positioning due to its inherent advantages such as high precision of centimeter level and strong anti-interference capability. Currently, the mainstream scheme for realizing UWB precise ranging and positioning is Two-Way Ranging (TWR) and its derivative protocols (such as DS-TWR). In this scheme, the positioning tag needs to complete multiple complex two-way communication handshake sequences with multiple fixed anchor nodes of known positions, so as to calculate a distance value, and then solve its own coordinates through a multilateration algorithm.

[0003] Although the TWR scheme has high precision, it has two inherent and difficult-to-overcome core defects in actual large-scale industrial environment deployment, especially in power-limited application scenarios:

[0004] (1) High installation cost and long installation period. The traditional TWR system requires base station networking to return data. This leads to two dilemmas: first, if wired power supply and communication are used, the on-site deployment has large engineering quantity, poor flexibility, high installation cost, and extremely difficult layout adjustment in the later period; second, if wireless anchor nodes are used, local power supply needs to be provided for the wireless nodes and the normal relay communication of the wireless nodes needs to be ensured, which increases the complexity of on-site deployment.

[0005] (2) Poor deployment flexibility and low scalability. The accuracy of the ranging positioning system based on TWR depends heavily on the density and geometry of the anchor nodes. Any expansion of the positioning area or adjustment of the anchor node position may require recalibration and configuration of the entire network system, which lacks the flexibility of "plug and play" and is difficult to adapt to rapidly changing application scenarios, such as personnel safety positioning system scenarios in a tunnel under excavation.

[0006] In order to reduce construction cost and deployment difficulty, the base station needs to be installed without wiring and powered by a built-in battery, which requires the base station to achieve low power consumption and be able to operate for at least 5 years on a limited battery capacity. Therefore, the applicant proposes a low-power ranging positioning system based on UWB. SUMMARY

[0007] The present application aims to provide a low-power ranging positioning system based on UWB, which aims to ensure that the positioning real-time performance meets the requirements of conventional personnel positioning, minimize the power consumption of the system, meet the requirements of battery-powered base stations, reduce the overall construction cost, and increase the flexibility of the system.

[0008] The application is achieved: a low-power ranging positioning system based on UWB, as shown in Figure 1 The gateway is an optional item.

[0009] The beacon has two wireless communication modes of UWB and Bluetooth BLE, and has a discovery state and a working state. In the discovery state, all peripherals are closed to enter a sleep state, Bluetooth BLE periodic broadcasting is opened, data packets are periodically sent through UWB, and reception is opened to wait for a response. In the working state, the device is normally in a sleep state, periodically sends a Poll packet, and opens reception.

[0010] The tag has a three-axis sensor built-in, and the current state is determined to be a static state or a motion state according to the three-axis sensor signal, so as to adjust the working frequency. The working frequency in the static state is lower than that in the motion state. In the working state, the ranging is completed through the interaction of UWB signals with nearby beacons, and is uploaded to the server.

[0011] The gateway is connected in communication with the tag and the server, and is used for receiving the ranging information reported by the tag and uploading it to the server, and is also used for controlling the beacon or reading its state information. The gateway has one or more of a Bluetooth communication module, a UWB communication module, an RJ45 communication module, a 4G communication module, a 5G communication module, a WiFi communication module, and a LoRa communication module, and has at least one communication module connected in communication with the tag and at least one communication module connected in communication with the server.

[0012] The positioning system adopts a DS-TWR mode, and the position of the tag is calculated according to a corresponding positioning algorithm such as a trilateration algorithm according to the ranging values of the multiple beacons and tags.

[0013] (1) DS-TWR ranging principle

[0014] DS-TWR ranging is one of the most commonly used and most core ranging protocols in UWB positioning technology. Through three communication interactions of two devices, the clock frequency deviation of the two devices is eliminated according to the integration and operation of the receiving and sending time stamps of the process to finally calculate the signal flight time between the two devices, and the distance value is finally converted through the speed of light. As shown in Figure 2 The working process is as follows:

[0015] Step 1: Poll (inquiry)

[0016] Device A sends a Poll message to Device B at local time T_t1. Device B receives this Poll message at local time T_t2.

[0017] Step 2: Response

[0018] After processing the received Poll message, DeviceB sends a Response message to DeviceA at local time T_t3. DeviceA receives this Response message at local time T_t4.

[0019] Step 3: Final

[0020] After processing the received Response information, DeviceA sends a Final message to DeviceB at local time T_t5. DeviceB receives this Final message at local time T_t6.

[0021] Using the six timestamps T_t1 to T_t6, the flight time T_tof between Device A and B can be calculated using the following formula:

[0022]

[0023] Among them, T a =T_t4-T_t1,T b =T_t6-T_t3,T c =T_t3-T_t2,T d =T_t5-T_t4.

[0024] The speed at which UWB signals travel through the air is the speed of light, c, where c = 299792458 m / s. Therefore, the distance between the tag and the beacon is d = c * T_tof.

[0025] Subsequent ranging for beacons and tags will adopt the DS-TWR method, where Device A can be understood as the beacon and Device B as the tag. To reduce the number of air signal packet communications and lower power consumption, the ranging method used in this system has been modified from the basic DS-TWR method. This change is mainly reflected in the fact that the tag ID is not specified when sending the Poll packet, and the beacon is designed to increase the reception time when receiving the Response packet, accommodating more tag-reported Response packets.

[0026] (2) Beacon Implementation Scheme

[0027] The beacon integrates both UWB and Bluetooth BLE wireless communication. It operates in two states: discovery and active. In discovery mode, the beacon disables all peripherals and enters sleep mode, while enabling Bluetooth BLE broadcasting every 500ms and transmitting a data packet via UWB every 5 seconds, followed by a 10ms wait for a response. In this state, the beacon's power consumption is primarily due to the periodic transmission and reception of radio frequency signals, with overall power consumption reaching the microampere level. The beacon can be woken up and enter active mode in two ways:

[0028] 1) Connect via Bluetooth and send corresponding data to wake up the device.

[0029] 2) The beacon is actively woken up after successfully receiving the corresponding Response packet.

[0030] In operational mode, the beacon is in a normal sleep state, but it periodically sends a Poll packet every 500ms and initiates reception for 10ms. After 10ms, it checks if a correct Response packet has been received within that timeframe. If so, it delays before sending a final packet, completing one DS-TWR cycle. If not, it increments its internal receive idle count and checks if the count is greater than a set value. If it is, it re-enters the discovery state; otherwise, it returns to sleep and waits for the next cycle. The receive idle count is reset to zero after a successful Response packet reception. During the 10ms of reception, the beacon can accommodate up to 14 tags reporting Response data (one every 500ms), meaning it can perform ranging with 14 nearby tags at a time. A flowchart of the beacon's workflow is attached. Figure 3 .

[0031] (3) Tag Implementation Scheme

[0032] The tag has a built-in triaxial sensor. It can determine whether it is stationary or in motion by detecting the signal from the triaxial sensor. When stationary, it will reduce the operating frequency to reduce power consumption, generally working once every 10 seconds. When in motion, it needs to maintain a certain real-time performance, so it will work once every 1 second. The tag will be in sleep mode the rest of the time.

[0033] In operational mode, the tag primarily interacts with nearby beacons via UWB signals to complete ranging and uploads the data to the gateway or server. In operational mode, the triaxial sensor is enabled. This is triggered under static / dynamic operating conditions, such as... Figure 4 As shown, the labeling workflow is as follows:

[0034] 1. Initialize the ranging buffer and clear the buffer's ranging response beacon list. Start the timer and set the listening timeout to 1 second.

[0035] 2. If the timeout period has not yet expired, enable UWB listening and listen for poll packets sent by the beacon. Otherwise, disable UWB listening and proceed to step 6.

[0036] 3. Upon receiving the poll packet from the beacon, read the beacon ID from the data packet and check if the beacon exists in the response beacon list. If it exists, no further action is taken, and the process returns to step 2. If it does not exist, store the beacon information (including ID, poll packet reception timestamp T_t2, frame number, etc.) in the response beacon list and proceed to step 4.

[0037] 4. The tag sends a response packet to the beacon within 10ms based on a random number. Upon receiving the response packet, the beacon records the tag ID and the corresponding reception timestamp T_t4x. After transmission is complete, it is recorded as T_t3.

[0038] 5. After the tag sends the Response packet, it opens the receiver for a certain period of time to receive the Final packet returned by the beacon. The Final packet sent by the beacon includes the beacon ID, the communication frame number, the timestamp T_t4x of the Response packets received by each tag, and the timestamps T_t1 and T_t5 of the Poll and Final packets sent by the beacon. After the tag verifies that the communication frame number and the beacon ID are correct, it then checks whether its own ID timestamp exists in the communication packet. Finally, based on the timestamp T_t6 of the received Final packet, the six timestamps are substituted into the formula described in (1) to calculate the ranging value of the beacon and the tag. After the tag completes the ranging, it returns to step 2.

[0039] 6. Once a ranging cycle is completed, the tag broadcasts the ranging results for that cycle via UWB. The gateway receives this broadcast and uploads it to the backend server over the network. Alternatively, the ranging results can be directly uploaded to the backend server via 4G / Wi-Fi.

[0040] (4) Gateway Implementation Scheme

[0041] The gateway requires a stable power supply and has built-in communication capabilities via Bluetooth / UWB / RJ45 / 4G / Wi-Fi / LoRa. The gateway needs to continuously monitor Bluetooth and UWB to receive ranging information reported by the tags and then upload it to the backend server via other network communication methods. Additionally, the gateway can control the beacon or read its status information, such as its operational status and current battery level, via UWB or Bluetooth for system maintenance and management.

[0042] Compared with existing technologies, the advantages of this invention are: This invention enables beacons to be powered by batteries and operate for extended periods, eliminating the need for on-site wiring, reducing the complexity of UWB positioning system installation, and significantly reducing installation and maintenance costs. Ranging data can be transmitted back via a fixed gateway, and the installation locations of beacons can be changed as needed, improving system flexibility and serving as a solution for scenarios where positioning areas need to be varied. Attached Figure Description

[0043] Figure 1 This is the system architecture of the present invention;

[0044] Figure 2 This is a flowchart of the ranging process of the present invention;

[0045] Figure 3 This is a flowchart of the beacon operation process of the present invention;

[0046] Figure 4 This is a flowchart of the labeling process of the present invention. Detailed Implementation

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] The following description, in conjunction with the accompanying drawings and specific embodiments, provides further details:

[0049] A low-power ranging and positioning system based on UWB is disclosed, comprising hardware and software components. Figure 1 As shown, the hardware consists of: a beacon integrating UWB and BLE chips; a tag integrating UWB, BLE, and a triaxial sensor; and a gateway integrating BLE, UWB, an RJ45 interface, a 4G module, a Wi-Fi module, and a LoRa module. The UWB chip used is the DW3210, and the BLE chip is part of the MCU's built-in protocol stack. The MCU used is the nRF52832.

[0050] The following example illustrates a technical solution for using 4 beacons and a gateway network cable communication method to form a positioning system.

[0051] (1) Equipment installation

[0052] Typically, beacons are installed at the four corners of the positioning area, covering the entire area. The beacons can be screwed onto a bracket via screw holes on the bottom or mounted on a ceiling. The gateway, on the other hand, is installed in a location convenient for power and network connections. During installation, the ID of each beacon and its corresponding location must be recorded, as this location information will later be entered into the positioning system.

[0053] (2) Device activation and startup

[0054] When the beacon is in shipment mode, it is in transport mode. At this time, the beacon remains in sleep mode, only periodically broadcasting via Bluetooth slave function once every 1 second. You can activate the beacon and exit transport mode by connecting to the relevant app via Bluetooth on your mobile phone. Alternatively, you can activate the beacon by communicating with it through the gateway's Bluetooth function. After successful activation, the beacon enters discovery mode. In discovery mode, it broadcasts via Bluetooth slave function every 500ms and sends a Poll packet via UWB every 5 seconds, while listening for 10ms. Listening during this time uses the DW3210's low-power sniffing function; the chip will start receiving at the set duty cycle. The Poll packet includes the beacon's ID, the frame number of this communication (0-255), the current beacon status indicator (0: discovery state, 1: working state), the beacon's version number, the time interval T_poll before the beacon sends the next Poll packet, and the time Qms to start receiving.

[0055] (3) Distance measurement work

[0056] The tag determines whether it is stationary or in motion based on its internal triaxial sensor. The stationary or in motion state affects the tag's operating frequency. When the tag is stationary, frequent operation is not considered necessary, and the operating frequency is typically set to 0.1Hz. However, when the tag is in motion, to ensure real-time performance, the operating frequency is generally set to 1Hz.

[0057] Once the tag enters the working state, it first initializes the ranging buffer and clears the ranging response beacon list in the buffer. A timer is started, setting the listening timeout to R and enabling UWB listening, with R set to 1 second. If a poll packet from a beacon is detected, the beacon ID in the data packet is read, and the beacon is checked in the response beacon list. If it exists, no further action is taken, and listening continues. If it does not exist, the beacon information (including ID, Poll packet reception timestamp T_t2, and frame number) is stored in the response beacon list, and a response packet is sent after a random delay of Nms (N ranges from 1 to 9ms). The response packet is sent with a specified delay and must include the tag ID, the responding beacon ID, the communication frame number, and a response function indication (0: TWR ranging, 1: other custom functions). After sending the response packet, the tag records the timestamp T_t3 and enables UWB receiving, listening for the final packet. Due to the uncertainty of communication, the Final packet may fail to be received or may fail to be received successfully due to channel collisions. Therefore, the tag's listening process for the Final packet requires a corresponding timeout mechanism. The received Poll packet contains the beacon's beacon opening time Qms. The tag is designed with a timeout P = Q - N + 1ms for receiving the Final packet. If the Final packet is not received after time P, the tag considers the ranging attempt a failure, removes the beacon's information from the response beacon list, and reverts to listening for Poll packets.

[0058] When the beacon receives a Response packet, it first reads the beacon ID and communication frame number in the data packet to see if they match those of the previously sent Poll packet. If not, the received Response packet may correspond to another device and needs to be discarded and reception resumed. Upon receiving a correct Response, the beacon records the responding tag ID and the corresponding reception timestamp T_t4. When the beacon's reception time Q expires, the beacon shuts down UWB reception. If a correct Response packet is received during this listening process, a Final packet is sent. Otherwise, it goes into sleep mode and waits for the next cycle before resuming operation. The Final packet is a broadcast packet containing the beacon ID, communication frame number, number of tags received, the ID and reception timestamp of each tag, the Poll packet sending time T_t1, and the estimated Final packet sending time T_t6. This system directly uses the unique ID of the UWB chip for identification, and the data is 8 bytes. In the DW3210, the smallest unit of timestamp is 4 bytes. Since each tag's information requires 12 bytes, the tag information portion needs to transmit a maximum of 14 * 12 = 168 bytes. The DW3210 communication frames have two formats: standard frames conforming to the IEEE 802.15.4-2015 standard and extended frames. The former has a maximum data size of 127 bytes, while the latter can reach 1023 bytes. To reduce power consumption, the transmitted data size should not be too long. In the tag ID information transmitted in the Final packet, only the last two bytes of each ID are extracted as a short ID, and 8 bytes are used for CRC-8 checksum calculation to obtain a 1-byte checksum. Therefore, the information portion of each tag only needs 1 + 2 + 4 = 7 bytes, with a maximum of 14 * 7 = 98 bytes, which meets the communication requirements.

[0059] After receiving the Final packet, the tag first compares the beacon ID and communication frame number. If they are correct, the tag's short ID and checksum must also match before it is considered to be the tag's received timestamp T_t4. Then, it obtains T_t1 and T_t6 from the data packet and can use T_t1 to T_t6 to calculate the ranging value d using the formula.

[0060] After the tag completes ranging, if the timeout period R has not expired, it continues listening and waits to continue ranging with the beacon. If the timeout has expired, the tag stops listening and prepares to send all the measured data back to the gateway or server.

[0061] (4) Data return

[0062] After completing a ranging cycle, the tag needs to send a Result packet (UWB packet) back to the gateway to display the ranging result data from the beacon. The Result packet includes the tag's ID, the communication frame number of this ranging operation, the number of beacons successfully rangingd, and their corresponding beacon IDs and ranging values. Due to the communication length limitations of the DW3210, the beacon ID and ranging value information are processed in the same way as the beacon Final packet. The three bytes obtained by performing a CRC8 checksum on the beacon ID (taking the lowest two bytes and the entire ID data) replace the original eight-byte ID. Upon receiving the Result packet from the tag, the gateway uploads the data to the backend server via an RJ45 Ethernet cable. This example uses the TCP protocol.

[0063] (5) Position calculation

[0064] After receiving the beacon ranging results uploaded by the gateway, the backend server uses an algorithm to calculate the tag's location based on the pre-entered location information of the beacon.

[0065] (6) Beacon Conflict Avoidance

[0066] Because the beacons switch to their working state at different times, their clocks are independent, and they are unaware of each other's transmission status. In this invention, the beacons are configured to send a Poll packet every 500ms and listen for a Response for 10ms as a ranging action. Assuming a 90% time utilization rate, theoretically, stable ranging data from 500 * 0.9 / 10 = 45 beacons can be accommodated. The beacon's radiation range is approximately 40m. Within a 40*40m positioning area, it is generally unnecessary to install 45 beacons for positioning, as the probability of collisions is very low. Therefore, this invention uses a simple random delay mechanism. After a beacon fails to receive a Response packet multiple times, the ranging period is randomly changed to a number between 475 and 525ms to avoid potential ranging collisions.

[0067] In summary, this invention enables beacons to be powered by batteries and operate for extended periods, eliminating the need for on-site wiring, reducing the complexity of UWB positioning system installation, and significantly decreasing installation and maintenance costs. Ranging data can be transmitted back via a fixed gateway, and the installation locations of beacons can be changed as needed, improving system flexibility and providing a solution for scenarios requiring varying positioning areas.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-power ranging and positioning system based on UWB, characterized in that, include: Multiple beacons, each beacon having built-in UWB and Bluetooth BLE wireless communication modes, and having discovery and working states; In the discovery state, all peripherals are turned off and put into sleep mode. Bluetooth BLE periodic broadcasting and periodic sending of data packets via UWB are enabled and reception is turned on to wait for a response. In the working state, it is in normal sleep mode, periodically actively sending Poll packets and turning on reception. Within a set time, it determines whether the correct response packet data has been received. If so, it delays and sends a Final packet to complete one ranging process. Otherwise, it determines whether to re-enter the discovery state based on the idle count of reception. Multiple tags, each with a built-in triaxial sensor, determine whether the device is stationary or in motion based on the triaxial sensor signal, and adjust the operating frequency accordingly. The operating frequency is lower when the device is stationary than when it is in motion. In operation, the device interacts with nearby beacons via UWB signals to complete distance measurement and uploads the data to the server.

2. The low-power ranging and positioning system based on UWB according to claim 1, characterized in that, It also includes a gateway, which communicates with the tag and the server to receive ranging information reported by the tag and upload it to the server, and to control the beacon or read its status information.

3. A low-power ranging and positioning system based on UWB according to claim 2, characterized in that, The gateway has one or more of the following built-in communication modules: Bluetooth, UWB, RJ45, 4G, 5G, Wi-Fi, and LoRa. It also has at least one communication module that communicates with the tag and at least one communication module that communicates with the server.

4. A low-power ranging and positioning system based on UWB according to claim 1, characterized in that, The beacon integrates a UWB chip and a BLE chip, and the tag, in addition to a triaxial sensor, also integrates a UWB chip and a BLE chip.

5. A low-power ranging and positioning system based on UWB according to claim 4, characterized in that, The UWB chip uses the DW3210 chip, the BLE chip is the protocol stack that comes with the MCU main controller, and the MCU uses the nRF52832 chip.

6. A low-power ranging and positioning system based on UWB according to claim 1, characterized in that, In the discovery state, the beacon enables Bluetooth BLE broadcasting every 500ms and sends a data packet via UWB every 5s, while simultaneously receiving data for 10ms and waiting for a response. In the discovery state, the beacon wakes up to enter the working state in two ways: first, by connecting via Bluetooth and sending corresponding data; second, by actively waking up after successfully receiving the corresponding response packet. In the working state, the beacon actively sends a poll packet every 500ms and opens reception for 10ms. After 10ms, it checks whether a correct response packet has been received within those 10ms. If so, it delays before sending a final packet, completing one DS-TWR process. If not, it increments the internal receive idle count and checks if the current receive idle count is greater than a set value. If it is, it re-enters the discovery state; otherwise, it goes back to sleep and waits for the next cycle. The receive idle count is reset to zero after successfully receiving a response packet.

7. A low-power ranging and positioning system based on UWB according to claim 1, characterized in that, The ranging of the beacons and tags is performed using DS-TWR ranging. The location of the tags is calculated based on the ranging values ​​of multiple beacons and tags according to the positioning algorithm. The specific steps are as follows: Step 1: Poll; DeviceA sends a Poll message to DeviceB at local time T_t1, and DeviceB receives the Poll message at local time T_t2. Step 2: Response; After DeviceB processes the received Poll message, it sends a Response message to DeviceA at local time T_t3. DeviceA receives this Response message at local time T_t4. Step 3: Final After DeviceA processes the received Response information, it sends a Final message to DeviceB at local time T_t5. DeviceB receives this Final message at local time T_t6. Using the six timestamps T_t1 to T_t6, calculate the flight time T_tof between Device A and B according to the following formula: Among them, T a =T_t4-T_t1,T b =T_t6-T_t3,T c =T_t3-T_t2,T d =T_t5-T_t4; The speed at which UWB signals travel through the air is the speed of light c, and the ranging value between the tag and the beacon d = c*T_tof.

8. A low-power ranging and positioning system based on UWB according to claim 7, characterized in that, The specific workflow of the tag in its working state is as follows: Step 1: Initialize the ranging buffer, clear the buffer's ranging response beacon list, and start the timer with a listening timeout of 1 second; Step 2: If the current time has not expired, open the UWB listener and listen for Poll packets sent by the beacon; otherwise, close the UWB listener and proceed to step 6. Step 3: After receiving the poll packet from the beacon, read the beacon ID in the data packet and check if the beacon exists in the response beacon list. If it exists, no further action is taken, and the process returns to Step 2. If it does not exist, the beacon information is stored in the response beacon list, and the process proceeds to Step 4. Step 4: The tag sends a response packet to the beacon within 10ms based on a random number. After receiving the response packet, the beacon records the tag ID and the corresponding receiving timestamp T_t4x. After sending is completed, it is recorded as T_t3. Step 5: After the tag sends the Response packet, it opens the receiver for a certain period of time to receive the Final packet returned by the beacon. After the tag compares the communication frame number and the beacon ID and finds that they are correct, it looks for the timestamp of its own ID in the communication packet. Finally, based on the timestamp T_t6 of the received Final packet, it substitutes the 6 timestamps into the formula to calculate the ranging value of the beacon and the tag, and then returns to step 2. Step 6: Once a ranging cycle is completed, the tag broadcasts the ranging results of this cycle via uwb. After receiving the broadcast, the gateway uploads the results to the server via the network, or directly uploads the ranging results to the server via 4G / WIFI.

9. A low-power ranging and positioning system based on UWB according to claim 8, characterized in that, After receiving a Poll packet, the tag sends a Response packet after a random delay of 1-9ms. The Final packet reception timeout is set to P = Q - N + 1ms, where Q is the beacon reception time and N is the delay time. If the packet is not received within the timeout period, the ranging is considered a failure, the beacon information is removed from the response beacon list, and the beacon returns to the state of listening for Poll packets. When the beacon is in working condition and there are multiple instances of no Response packets, the ranging period is randomly changed to avoid possible ranging conflicts.

10. A low-power ranging and positioning system based on UWB according to claim 8, characterized in that, The final packet sent by the beacon is a broadcast packet, which includes the beacon ID, frame number, number of tags and each tag ID and check value, and a receiving timestamp. It also includes the poll packet sending time and the estimated final packet sending time. After receiving the Final packet, the tag compares the short ID with the checksum and if they are correct, it calculates the ranging value using the timestamp. The Result sent by the tag includes the tag ID, frame number, number of successfully ranging beacons, short ID and checksum of each beacon, and ranging value. After receiving the Result, the gateway uploads it to the server. The server calculates the tag position using a positioning algorithm based on the preset beacon position.

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