A backward compatible low power bluetooth direction finding method and system

Abstract

The application relates to a backward-compatible low-power Bluetooth direction-finding positioning method and system, wherein the method comprises the following steps: establishing a communication connection among a trigger node, a target device and a locator through a Bluetooth signal; the trigger node simultaneously sends a nested data packet to the target device and the locator; the target device analyzes the nested data packet and sends a positioning signal; the locator analyzes the nested data packet, collects and pre-processes the positioning signal, obtains a first positioning signal, and sends the first positioning signal to a positioning server; the trigger node receives the positioning signal, obtains a second positioning signal, and forwards the second positioning signal to the positioning server; the positioning server receives the second positioning signal, demodulates an ideal reference signal, eliminates a phase offset of the first positioning signal based on the ideal reference signal, obtains a phase offset of each antenna, estimates an angle of arrival, and accurately positions the target device. Compared with the prior art, the application has the advantages of target device positioning without replacement of hardware devices, low cost, high accuracy and the like.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of Bluetooth direction finding positioning, and in particular to a backward-compatible low-power Bluetooth direction finding positioning method and system. BACKGROUND

[0002] With the rapid development of smart devices and the Internet of Things, indoor positioning technology has become one of the popular research directions in the field of modern technology. In many application scenarios, accurate indoor positioning technology can significantly improve the level of device automation, optimize resource allocation, and enhance user experience. For example, in large indoor environments such as shopping malls, museums, and hospitals, indoor positioning technology not only helps users quickly find their destinations, but also enables efficient space management and security monitoring. Despite the wide application prospects of indoor positioning technology, its implementation still faces various challenges. The main difficulties include the complex signal blocking and multipath effects in indoor environments, as well as the balance between accuracy and cost in existing technologies.

[0003] Currently, common indoor positioning technologies are mainly based on wireless signals such as Wi-Fi, Bluetooth, Ultra-Wideband (UWB), and Radio Frequency Identification (RFID). Among them, Wi-Fi and Bluetooth positioning technologies based on Received Signal Strength Indication (RSSI) are widely used due to their ease of deployment and relatively low cost. However, these technologies often only provide meter-level positioning accuracy, making it difficult to meet the needs of high-precision applications. In particular, Bluetooth positioning, although widely supported in smart devices, its traditional RSSI-based method has limited accuracy due to the susceptibility of signals to environmental interference. Although the update of Bluetooth technology standards in 2020 introduced a direction finding function, allowing the use of AoA (Angle of Arrival) technology to significantly improve positioning accuracy, the widespread application of this function faces significant challenges.

[0004] The AoA function requires that the device hardware have a specific antenna configuration and signal processing capability, and these technical details are not implemented in many existing Bluetooth devices. For example, a large number of Bluetooth devices on the market still use Bluetooth technology below version 5.1, and the hardware of these devices cannot handle the complex signal decoding and antenna switching operations necessary to implement AoA. These low-version devices lack support for the Constant Tone Extension (CTE) and related signal processing algorithms required for AoA signals, as these features were only introduced in the Bluetooth 5.1 and higher specifications. In addition, even some devices that support Bluetooth 5.1 or higher versions may not have implemented the direction finding function due to cost and energy consumption considerations, as implementing this function often requires additional hardware support such as enhanced antenna systems and more complex signal processing units, which increases the production cost of the device and affects the battery life of the device, resulting in these devices also being unable to use the direction finding function. Therefore, although the latest developments in Bluetooth technology have brought unprecedented precision potential for indoor positioning, hardware limitations and cost factors have severely hindered its widespread application in existing devices. This situation limits the deployment of high-precision indoor positioning solutions based on Bluetooth AoA technology, especially in environments where old Bluetooth devices have been widely deployed. SUMMARY

[0005] The purpose of the present application is to provide a backward compatible low-power Bluetooth direction finding positioning method and system, which solves the compatibility problem of the Bluetooth 5.1 version direction finding function and the inability of a large number of existing devices to support this function due to hardware limitations. The core innovation of the present application is to solve the popularization problem of the Bluetooth 5.1 direction finding function without relying on hardware upgrades of target devices, but through an additional trigger node that can work with existing Bluetooth locators. It simulates the communication behavior with the target device, so that all Bluetooth devices, including old devices that do not support AoA, can also be located. Specifically, the trigger node sends signals containing nested data packets, which are designed to both communicate with old devices and be correctly parsed by new locators, thereby achieving accurate positioning.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A backward compatible low-power Bluetooth direction finding positioning method, comprising the following steps:

[0008] Establishing communication connections between the trigger node and the target device, and between the trigger node and the locator through Bluetooth signals;

[0009] The trigger node sends a nested data packet containing predefined embedded instructions to the target device and the locator, the embedded instructions instructing the target device to send a positioning signal at a predetermined time;

[0010] The target device parses the received nested data packet and sends a positioning signal according to the embedded instructions;

[0011] The locator parses the received nested data packet, controls the collection of the positioning signal according to the embedded instructions, and obtains a first positioning signal after preprocessing and sends it to the positioning server;

[0012] The trigger node receives the positioning signal sent by the target device, obtains a second positioning signal, and forwards it to the positioning server;

[0013] The positioning server receives the second positioning signal and demodulates to obtain an ideal reference signal, eliminates the phase offset of the first positioning signal based on the ideal reference signal, obtains the phase offset of each antenna, estimates the angle of arrival based on the phase offset, and accurately locates the position of the target device.

[0014] The control of the collection of the positioning signal according to the embedded instructions is specifically: the locator determines the time window and signal length parameters of the upcoming direction-finding positioning sampling and antenna switching according to the decoded embedded instructions, and samples and analyzes the positioning signal at the specified time and channel according to the parameters according to the protocol standard, wherein the channel is the same as the channel of the target device sending the positioning signal.

[0015] The preprocessing is specifically: the locator processes the collected positioning signal, calculates the IQ value of the signal, and the IQ value includes amplitude and phase.

[0016] The positioning server performs the following steps to eliminate the phase offset of the first positioning signal:

[0017] Receive the second positioning signal and demodulate to obtain an ideal reference signal;

[0018] Perform preliminary amplitude judgment and screening on the first positioning signal;

[0019] Estimate the arrival time of the positioning signal based on the ideal reference signal and the screened first positioning signal using a differential phase correlation method;

[0020] Align the first positioning signal and the ideal reference signal based on the estimated arrival time, and estimate the reference frequency offset based on the aligned signals;

[0021] Estimate the carrier frequency offset based on the screened first positioning signal;

[0022] Subtract the reference frequency offset and the carrier frequency offset from the phase of the first positioning signal to eliminate the phase offset.

[0023] The preliminary amplitude judgment and screening of the first positioning signal collected by each antenna is specifically: analyzing the amplitude of the first positioning signal, and only retaining the first positioning signal with an amplitude higher than a preset threshold.

[0024] The preset threshold is set according to the environmental noise level and the expected strength of the signal.

[0025] The arrival time of the positioning signal is estimated by using a differential phase correlation method based on the ideal reference signal and the screened first positioning signal, including the following steps:

[0026] In the current antenna switching period, the phase of the ideal reference signal corresponding to a certain positioning signal is obtained, and the phase of the ideal reference signal in the last antenna switching period is differentiated to obtain an ideal differential phase signal;

[0027] In the current antenna switching period, the phase of the first positioning signal corresponding to the same positioning signal is obtained, and the first positioning signal in the last antenna switching period is differentiated to obtain a differential positioning phase signal;

[0028] The ideal differential phase signal and the differential positioning phase signal are convoluted to obtain time length information of the peak value;

[0029] The starting time of the current antenna switching period is added to the time length of the ideal differential phase signal and subtracted from the time length of the peak value to obtain the arrival time.

[0030] The estimation of the reference frequency offset is specifically: aligning the first positioning signal and the ideal reference signal based on the estimated arrival time, subtracting the phase of the ideal reference signal from the phase of the aligned first positioning signal to obtain the reference frequency offset.

[0031] The estimation of the carrier frequency offset includes the following steps:

[0032] Coarse estimation: the target device continuously transmits a plurality of same positioning signals in a reference period of a preset time, and the locator receives the positioning signal with the first antenna in the reference period, and performs linear regression fitting on the first positioning signal sampled by the locator to obtain a preliminary carrier frequency offset per unit time;

[0033] Fine estimation: based on the preliminary carrier frequency offset, the period elapsed for a complete antenna switching round is determined, and for the first positioning signal sampled by the locator exceeding the reference period, a phase sequence is constructed using the phase information thereof, the phase sequence is composed of the phase information of the first positioning signal collected by m complete antenna switching rounds and N antennas, and is represented as: denotes the phase of the first positioning signal collected by the jth antenna in the ith antenna switching round; the phase sequence is subjected to differential processing, and a fine-grained carrier frequency offset is estimated based on the period of the complete antenna switching round:

[0034]

[0035] wherein, φ CFO denotes the carrier frequency offset, k is the period of the complete antenna switching round, φ CFO_c denotes the preliminary carrier frequency offset, denotes the floor operation.

[0036] A backward compatible low-power Bluetooth direction finding positioning system for implementing the above method, the system comprising:

[0037] The locator is used for parsing the received nested data packet, controlling the collection of the positioning signal according to the embedded instruction, and obtaining the first positioning signal after preprocessing, and sending the first positioning signal to the positioning server for further analysis and positioning calculation.

[0038] The target device is a Bluetooth device to be positioned, and is used for sending the positioning signal according to the nested data packet sent by the trigger node.

[0039] The trigger node has the bidirectional communication capability between the locator and the target device, is used for sending the nested data packet to the target device and the locator, the nested data packet contains the predefined embedded instruction, the embedded instruction is the instruction for triggering the target device to send the positioning signal within a predetermined time, and is used for receiving the positioning signal sent by the target device, obtaining the second positioning signal, and forwarding the second positioning signal to the positioning server.

[0040] The positioning server is used for receiving the second positioning signal and demodulating to obtain the ideal reference signal, eliminating the phase offset of the first positioning signal based on the ideal reference signal, obtaining the phase offset of each antenna, estimating the angle of arrival based on the phase offset, and accurately positioning the position of the target device.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] The present application solves the limitation of the Bluetooth 5.1 direction finding function through the trigger node technology, provides an economical and efficient indoor positioning solution for various types of facilities, and makes the accurate indoor positioning technology more popular and practical. The advantages are as follows:

[0043] 1) Universality: The invention can extend the direction finding function to old Bluetooth devices that do not support this function, without any hardware or firmware modification to the existing BLE5.1 Locator and positioning targets, thus providing direction finding function for all Bluetooth devices without the need to replace or upgrade existing Bluetooth devices, greatly expanding the application range of Bluetooth positioning technology and significantly increasing the flexibility of Bluetooth direction finding technology.

[0044] 2) Cost-effectiveness: The invention introduces the method of nested data packets and time overlap by using trigger nodes, allowing a single trigger node to communicate with both the locator and the target device at the same time, reducing the hardware requirements of the trigger node, avoiding the high cost of replacing or upgrading a large number of Bluetooth devices in large-scale facilities, and achieving an economic and efficient indoor positioning solution.

[0045] 3) Accuracy improvement: The invention improves the accuracy of angle estimation by combining multiple signal processing and estimation techniques, including fine estimation of carrier frequency offset (CFO) and reference cancellation. These techniques help the system work effectively in complex multipath and interference environments, providing more accurate positioning than traditional Bluetooth direction finding. Even devices without native direction finding capabilities can achieve high-precision AoA positioning through the trigger node, significantly improving positioning accuracy.

[0046] 4) Deployment flexibility: The system design allows for quick deployment in existing Bluetooth infrastructure without complex hardware modifications, making it easy to upgrade indoor positioning systems. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a flowchart of the method of the invention;

[0048] Figure 2 is a schematic diagram of the data exchange process between the trigger node, locator and target device of the invention;

[0049] Figure 3 is a schematic diagram of the data processing process by the positioning server of the invention. DETAILED DESCRIPTION

[0050] The invention will be described in detail below in conjunction with the drawings and specific embodiments. This embodiment is based on the technical solution of the invention and gives a detailed implementation and specific operation process, but the protection scope of the invention is not limited to the following examples.

[0051] Before introducing the invention in detail, the following key devices are first defined:

[0052] 1、BLE5.1 Locator (Bluetooth 5.1 Locator): The locator supports the Bluetooth 5.1 Direction-finding method, receives and processes signals from target devices, and transmits data to the localization server for further analysis and positioning calculation.

[0053] 2、Target (Target Device): The target device refers to a Bluetooth device that needs to be located, which may cover various Bluetooth versions. These devices are included in the positioning process through direct communication with the trigger node, even if they do not originally support the Bluetooth 5.1 Direction-finding method.

[0054] 3、Trigger (Trigger Node): The trigger node is the core device of the invention, with bidirectional communication capability, capable of communicating with the Bluetooth 5.1 locator and target device simultaneously. The trigger node not only simulates the signal of the target device for the locator to analyze, but also receives signals from the target device and transmits these data to the localization server to complete accurate positioning.

[0055] 4、Localization Server (Localization Server): The localization server is the data processing center of the system, receiving signal data from the BLE5.1 Locator and Trigger. The server analyzes these data to calculate the position of the target device, using the algorithm proposed in this patent to process and analyze signal data from different sources, ensuring the accuracy of the positioning result.

[0056] Example 1

[0057] This embodiment provides a backward-compatible low-power Bluetooth direction-finding positioning method, as shown in Figure 1 , which includes the following steps:

[0058] S1, establish communication connection between the trigger node and the target device, and between the trigger node and the locator through Bluetooth signals.

[0059] As shown in Figure 2 , the process of establishing communication connection between the trigger node and the target device is as follows:

[0060] Trigger node requires to establish connection with target device: when a target device needs to be located, the trigger first establishes a standard Bluetooth communication connection with the target device through Bluetooth signals. In this process, the trigger simulates the behavior of a normal Bluetooth central device, sending pairing and connection requests, including control fields for specified time and communication channels, so that the target device can follow the subsequent data communication process according to the requirements of the trigger node.

[0061] The process of establishing communication connection between the trigger node and the localization server is as follows:

[0062] The trigger node first communicates with the BLE5.1 Locator using the Direction-finding protocol of Bluetooth 5.1, synchronizes the channel to be used for the subsequent positioning signal and specifies the positioning time and packet structure. This step ensures that the Trigger and the BLE5.1 Locator exchange data on the same channel, laying the foundation for accurate measurement of the Angle of Arrival (AoA).

[0063] S2, the trigger node sends a nested packet to the target device and the locator at the same time.

[0064] As shown in Figure 2 After the connection is established, in order to ensure data synchronization, the Trigger uses the Nesting Packet technology, which allows different data for multiple destinations to be contained in a single Bluetooth packet, ensuring that the Trigger can send different information to the target device and the BLE5.1 Locator at the same time. Specifically, the Trigger uses the Nesting Packet technology to send a nested packet to the target device and the locator at the same time, which contains a predefined embedded instruction that instructs the target device to send a positioning signal at a predetermined time. This nested packet design allows the Trigger to transmit signals with the same waveform but different decoded information to different receivers at the same time, ensuring the synchronization and precise control of the time of signal transmission. Therefore, after receiving the Nesting Packet from the trigger node, the target device will send a specific packet back on the communication channel at a specific time according to the requirements of the Bluetooth protocol standard, i.e., send a specific positioning signal. After the Nesting Packet from the trigger node is received by the locator, the locator decodes the instruction that instructs the target device to send a positioning signal at a predetermined time, preparing for the subsequent reception of the positioning signal from the target device.

[0065] S3, the target device parses the received nested packet and sends a positioning signal according to the embedded instruction.

[0066] After receiving the Nesting Packet from the trigger node, the target device sends a specific positioning signal according to the embedded instruction. This step is a standard Bluetooth communication and does not require any modification to the target device.

[0067] S4, the locator parses the received nested packet and controls the collection of the positioning signal according to the embedded instruction, and obtains the first positioning signal after preprocessing, and sends it to the positioning server.

[0068] After the Trigger sends data to the target device and the locator simultaneously using the Nesting Packet technology, the locator will perform sampling analysis of the positioning signal at the specified time and channel. At this time, the target device will send a data communication reply packet to the trigger node at the same channel, and this specific Bluetooth packet (i.e. the positioning signal) will be received and sampled by the locator according to the specified direction positioning process of the protocol.

[0069] Specifically, the locator determines the time window and signal length of the upcoming direction positioning sampling and antenna switching according to the decoded embedded instructions, and performs sampling analysis of the positioning signal at the specified time and channel according to the protocol standard. Different parameters will affect the antenna selection, switching time slot, and signal length during signal collection.

[0070] The locator pre-processes the collected positioning signal, calculates the IQ value (i.e. the amplitude and phase of the signal), and then sends it to the positioning server.

[0071] S5, the trigger node receives the positioning signal sent by the target device, obtains the second positioning signal, and forwards it to the positioning server.

[0072] S6, the positioning server receives the second positioning signal and demodulates to obtain the ideal reference signal, eliminates the phase offset of the first positioning signal based on the ideal reference signal, obtains the phase offset of each antenna, estimates the angle of arrival based on the phase offset, and accurately locates the position of the target device.

[0073] As shown in Figure 3 , the positioning server performs the following steps to achieve accurate positioning:

[0074] S61, the positioning server first aggregates the first positioning signal collected by the locator and the second positioning signal collected by the trigger node. Such data aggregation ensures that the server has signal data collected from different sources, providing input for subsequent positioning calculations.

[0075] S62, Arrival Time Estimation.

[0076] Due to the hardware limitations of existing BLE5.1 Locators on the market, although the device has multiple antennas, due to the presence of only one analog-to-digital converter (ADC), the Locator reads the data on each antenna one by one through polling. This mode of operation is determined by the hardware design, mainly to achieve the acquisition of multi-antenna data without changing the existing hardware. Although Trigger uses the Nesting Packet technology to synchronize the Locator and Target, it still needs to confirm which antenna is sampling when the Target signal reaches the Locator. Therefore, after receiving the IQ values from the Locator, the positioning server processes them through the following steps to estimate the time of arrival:

[0077] S621, the positioning server demodulates the second positioning signal to obtain the ideal reference signal.

[0078] S622, Preliminary Amplitude Judgment: Preliminary amplitude judgment and screening of the first positioning signal.

[0079] In this step, the amplitude of the received IQ values is first analyzed to determine the validity of the signal and the signal strength level for further processing. When the signal reaches each antenna, the amplitude of each signal is measured and compared with a pre-set threshold. Only signals with amplitudes above a certain threshold are considered valid and worthy of further analysis. This threshold is usually set according to the environmental noise level and the expected strength of the signal. The purpose of this step is to filter out signals that are not strong enough, thus avoiding errors caused by processing weak signals or noise. Amplitude judgment helps ensure that only potentially valid signals enter the subsequent processing steps, thus improving the overall performance and positioning accuracy of the system.

[0080] S623, Differential Phase Correlation: Based on the ideal reference signal and the screened first positioning signal, the differential phase correlation method is used to estimate the time of arrival of the positioning signal.

[0081] After the preliminary amplitude judgment is completed, the phase of the screened effective first positioning signal is analyzed to determine the time of arrival of the signal. This technique takes advantage of the phase differences of the signal at different antennas to estimate the time of arrival of the signal. By measuring the phases of the same signal received at each antenna and calculating the difference between them, the propagation path of the signal and the time of arrival relative to each antenna can be inferred by analyzing these phase differences. By comparing the ideal phase value of the original data packet signal, the differential phase correlation analysis can accurately measure the time of arrival of the signal, even in an environment with severe multipath and reflection. This method is particularly suitable for complex indoor environments and can significantly reduce errors caused by signal reflection and scattering.

[0082] Specifically includes the following steps:

[0083] (1) In the current antenna switching period, the phase of the ideal reference signal corresponding to a certain positioning signal is obtained, and the phase of the ideal reference signal in the last antenna switching period is subtracted to obtain an ideal differential phase signal;

[0084] (2) In the current antenna switching period, the phase of the first positioning signal corresponding to the same positioning signal is obtained, and the first positioning signal in the last antenna switching period is subtracted to obtain a differential positioning phase signal;

[0085] (3) The ideal differential phase signal and the differential positioning phase signal are convolved to obtain the time length information of the peak value;

[0086] (4) The starting time of the current antenna switching period is added to the time length of the ideal differential phase signal and subtracted from the time length of the peak value to obtain the time of arrival.

[0087] S63, positioning target reference frequency offset estimation (Reference Estimation): Align the first positioning signal and the ideal reference signal based on the estimated time of arrival, and estimate the reference frequency offset based on the aligned signal.

[0088] The reference frequency offset refers to the signal emitted by the positioning target being uncertain (related to the device and Bluetooth version), so the signal received by each antenna of the Locator will be offset in phase due to the difference in the signal, so the reference frequency offset caused thereby needs to be estimated. The estimation method is as follows: align the first positioning signal and the ideal reference signal based on the estimated time of arrival, subtract the phase of the ideal reference signal from the phase of the aligned first positioning signal to obtain the reference frequency offset.

[0089] S64, carrier frequency offset estimation (CFO Estimation): Estimate the carrier frequency offset based on the screened first positioning signal.

[0090] Carrier Frequency Offset (CFO) estimation is an important signal processing technique in wireless communication, which is used to correct the signal frequency deviation caused by the incomplete frequency synchronization between the transmitter and the receiver. In the positioning system, especially in the system using high frequency signals, accurate CFO estimation is crucial to ensure accurate demodulation of signals and subsequent signal processing.

[0091] The carrier frequency offset estimation specifically includes the following steps:

[0092] S641, coarse estimation: the target device continuously transmits a plurality of same positioning signals in a reference period of a preset time, and the locator receives the positioning signals with the first antenna in the reference period, and performs linear regression fitting on the first positioning signal obtained by sampling the locator to obtain a preliminary carrier frequency offset per unit time.

[0093] In an embodiment, in the Bluetooth 5.1 Direction-finding protocol, the target continuously transmits 8 same signals in a reference period of 8 μs, and the locator receives the signals with the first antenna in the reference period, so that the preliminary carrier frequency offset per unit time can be obtained by linear regression fitting of the 8 samples. However, due to synchronization problems, the locator may not receive all 8 samples, so the CFO estimated by using 8 or fewer samples has a large error and can only be used as a rough estimate, which needs to be further optimized by using samples outside the reference period.

[0094] S642, fine estimation: based on the preliminary carrier frequency offset, the period of a complete antenna switching round is determined, and for the first positioning signal obtained by sampling the locator beyond the reference period, a phase sequence is constructed using the phase information of the first positioning signal, the phase sequence being composed of the phase information of the first positioning signal collected by m complete antenna switching rounds and N antennas, and being represented as: φ i,j represents the phase of the first positioning signal collected by the jth antenna in the ith antenna switching round; based on the phase sequence, differential processing is performed, and the fine-grained carrier frequency offset is estimated by combining the period of the complete antenna switching round:

[0095]

[0096] wherein, φ CFO represents the carrier frequency offset, and k is the period of the complete antenna switching round.

[0097] It should be noted that the remaining phase difference It is possible that more than one cycle (2π) is exceeded in the case of a large number of antennas. Therefore, the preliminary carrier frequency offset will be used to determine the cumulative phase difference of completing a complete antenna switching cycle, and to determine whether one or more phase cycles are exceeded, i.e. φ CFO-c represents the preliminary carrier frequency offset, represents rounding down, and finally calculating the fine-grained CFO estimate.

[0098] S65, subtract the phase of the first positioning signal from the reference frequency offset and the carrier frequency offset to eliminate the phase offset.

[0099] S66, estimate the angle of arrival based on the phase offset.

[0100] After obtaining the phase offset of each antenna, the distance between the antennas is known, and the AoA can be obtained by using the existing AoA estimation algorithm. This step is implemented by using the existing algorithm and does not belong to the protection scope of the patent. Possible implementation methods include but are not limited to MUSIC (Multiple Signal Classification), ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques), beamforming, etc.

[0101] S67, accurately positioning the position of the target device.

[0102] The positioning server calculates the accurate position of the target device by combining the position coordinates of multiple Locators and the AoA measured by each of them. This step is implemented by using the existing algorithm and does not belong to the protection scope of the patent. Possible implementation methods include but are not limited to geometric position solving.

[0103] Embodiment 2

[0104] This embodiment provides a backward compatible low-power Bluetooth direction finding positioning system for implementing the method of embodiment 1, which comprises:

[0105] Locator: for parsing the received nested data packet, controlling the collection of positioning signals according to the embedded instructions, and obtaining the first positioning signal after preprocessing, and sending it to the positioning server for further analysis and positioning calculation;

[0106] Target device: i.e. the Bluetooth device to be positioned, for sending positioning signals according to the nested data packet sent by the trigger node;

[0107] Trigger node: It has bidirectional communication capability with the locator and the target device, and is used to send nested data packets to the target device and the locator at the same time. The nested data packets contain predefined embedded instructions, which are instructions to trigger the target device to send a positioning signal within a predetermined time. It is also used to receive the positioning signal sent by the target device, obtain a second positioning signal, and forward it to the positioning server.

[0108] Positioning server: used to receive the second positioning signal and demodulate it to obtain an ideal reference signal, perform phase offset cancellation on the first positioning signal based on the ideal reference signal to obtain the phase offset of each antenna, estimate the angle of arrival based on the phase offset, and accurately locate the position of the target device.

[0109] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of each module can be referred to the corresponding process in the aforementioned method embodiments, and will not be repeated here.

[0110] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A backward-compatible low-power Bluetooth direction finding and positioning method, characterized in that, Includes the following steps: Communication connections are established between the trigger node and the target device, and between the trigger node and the locator, via Bluetooth signals. The triggering node simultaneously sends nested data packets to the target device and the locator. The nested data packets contain predefined embedded instructions, which are instructions to trigger the target device to send a positioning signal within a predetermined time. The target device parses the received nested data packets and sends a positioning signal according to the embedded instructions; The locator parses the received nested data packets, controls the acquisition of positioning signals according to the embedded instructions, and obtains the first positioning signal after preprocessing, which is then sent to the positioning server. The triggering node receives the positioning signal sent by the target device, obtains the second positioning signal, and forwards it to the positioning server; The positioning server receives the second positioning signal and demodulates it to obtain an ideal reference signal. Based on the ideal reference signal, it performs phase offset cancellation on the first positioning signal to obtain the phase offset of each antenna. Based on the phase offset, it estimates the angle of arrival and accurately locates the position of the target device. The positioning server performs the following steps to eliminate the phase offset of the first positioning signal: Receive the second positioning signal and demodulate it to obtain the ideal reference signal; Perform preliminary amplitude judgment and screening on the first positioning signal; Based on the ideal reference signal and the filtered first positioning signal, the arrival time of the positioning signal is estimated using the differential phase correlation method. Align the first positioning signal and the ideal reference signal based on the estimated time of arrival, and estimate the reference frequency offset based on the aligned signal; Estimate the carrier frequency offset based on the filtered first positioning signal; Subtract the reference frequency offset and carrier frequency offset from the phase of the first positioning signal to eliminate the phase offset; The estimated carrier frequency offset includes the following steps: Coarse estimation: The target device continuously sends multiple identical positioning signals within a reference period of a pre-set time. The locator receives the positioning signal with the first antenna within the reference period. Linear regression fitting is performed on the first positioning signal sampled by the locator to obtain the preliminary carrier frequency offset per unit time. Precise estimation: Based on the initial carrier frequency offset, the period of a complete antenna switching cycle is determined. For the first positioning signal sampled by the locator that exceeds the reference period, its phase information is used to construct a phase sequence. The phase sequence consists of the phase information of m complete antenna switching cycles and N antenna-acquired first positioning signals, expressed as: , Indicates the first i In the antenna switching round, the first... j The phase of the first positioning signal acquired by each antenna; differential processing based on the phase sequence, and estimation of fine-grained carrier frequency offset by combining the period elapsed during a complete antenna switching cycle: in, Indicates carrier frequency offset. k The number of cycles elapsed during a complete antenna switching cycle. , Indicates the initial carrier frequency offset. This indicates rounding down to the nearest integer.

2. The backward-compatible low-power Bluetooth direction finding and positioning method according to claim 1, characterized in that, The acquisition of positioning signals according to the embedded instructions specifically involves the locator determining the time window and signal length parameters for the upcoming direction-finding positioning sampling and antenna switching based on the decoded embedded instructions. According to the parameters, the locator performs sampling and analysis of the positioning signals at a specified time and on a specified channel in accordance with the protocol standard. The channel is the same as the channel through which the target device emits positioning signals.

3. The backward-compatible low-power Bluetooth direction finding and positioning method according to claim 1, characterized in that, The preprocessing specifically involves the locator processing the acquired positioning signal and calculating the IQ value of the signal, which includes amplitude and phase.

4. The backward-compatible low-power Bluetooth direction finding and positioning method according to claim 1, characterized in that, The preliminary amplitude judgment and screening of the first positioning signal collected by each antenna is specifically as follows: based on the amplitude of the first positioning signal, only the first positioning signal with an amplitude higher than a preset threshold is retained.

5. A backward-compatible low-power Bluetooth direction finding and positioning method according to claim 4, characterized in that, The preset threshold is set based on the ambient noise level and the expected signal strength.

6. The backward-compatible low-power Bluetooth direction finding and positioning method according to claim 1, characterized in that, The method of estimating the arrival time of the positioning signal based on the ideal reference signal and the filtered first positioning signal using the differential phase correlation method includes the following steps: Within the current antenna switching cycle, the phase of the ideal reference signal corresponding to a certain positioning signal is obtained, and the phase of the ideal reference signal in the previous antenna switching cycle is differentially divided to obtain the ideal differential phase signal. Within the current antenna switching cycle, the phase of the first positioning signal corresponding to the same positioning signal is acquired, and differentially divided with the first positioning signal of the previous antenna switching cycle to obtain the differential positioning phase signal; The ideal differential phase signal and the differential positioning phase signal are convolved to obtain the time length information of the peak occurrence. The arrival time is obtained by adding the duration of the ideal differential phase signal to the start time of the current antenna switching cycle and subtracting the duration of the peak occurrence.

7. A backward-compatible low-power Bluetooth direction finding and positioning method according to claim 1, characterized in that, The estimation of the reference frequency offset is specifically as follows: based on the estimated arrival time, align the first positioning signal and the ideal reference signal, and subtract the phase of the ideal reference signal from the phase of the aligned first positioning signal to obtain the reference frequency offset.

8. A backward-compatible low-power Bluetooth direction-finding positioning system, characterized in that, For implementing the method as described in any one of claims 1-7, the system comprises: Locator: Used to parse the received nested data packets, control the acquisition of positioning signals according to the embedded instructions, and obtain the first positioning signal after preprocessing, and send it to the positioning server for further analysis and positioning calculation; Target device: The Bluetooth device to be located, used to send a location signal based on the nested data packets sent by the triggering node; Trigger node: It has bidirectional communication capability with the locator and the target device, and is used to send nested data packets to the target device and the locator at the same time. The nested data packets contain predefined embedded instructions, which are instructions to trigger the target device to send a positioning signal within a predetermined time. It is also used to receive the positioning signal sent by the target device, obtain a second positioning signal, and forward it to the positioning server. Positioning server: used to receive the second positioning signal and demodulate it to obtain an ideal reference signal, perform phase offset cancellation on the first positioning signal based on the ideal reference signal to obtain the phase offset of each antenna, estimate the angle of arrival based on the phase offset, and accurately locate the position of the target device.

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