Backward compatible low-power-consumption Bluetooth direction-finding positioning method and system

Abstract

The invention relates to a backward compatible low-power-consumption Bluetooth direction-finding positioning method and system. The method comprises the following steps: establishing communication connection between a trigger node and a target device and between the trigger node and a positioner through a Bluetooth signal; the trigger node sends a nested data packet to the target device and the locator at the same time; the target device analyzes the nested data packet and sends out a positioning signal; the locator analyzes the nested data packet, collects and preprocesses a positioning signal to obtain a first positioning signal, and sends the first positioning signal to a positioning server; the trigger node receives the positioning signal to obtain a second positioning signal and forwards the second positioning signal to the positioning server; and the positioning server receives the second positioning signal, demodulates the second positioning signal to obtain an ideal reference signal, performs phase offset elimination on the first positioning signal based on the ideal reference signal to obtain the phase offset of each antenna, estimates an angle of arrival, and accurately positions the position of the target equipment. Compared with the prior art, the method has the advantages that the target equipment can be positioned without replacing hardware equipment, the cost is low, and the accuracy is high.

Description

Technical Field

[0001] The present invention relates to the technical field of Bluetooth direction-finding and positioning technology, and in particular to a backward-compatible low-power Bluetooth direction-finding and positioning method and system. Background Art

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

[0003] At present, 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 easy deployment and low cost. However, these technologies can often only provide meter-level positioning accuracy, which is difficult to meet the needs of high-precision applications. In particular, Bluetooth positioning, although it is widely supported in smart devices, its traditional RSSI-based method has limited accuracy because the signal is susceptible to environmental interference. Although the update of the Bluetooth technology standard 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 major challenges.

[0004] The AoA feature requires the device hardware to have specific antenna configurations and signal processing capabilities, and these technical details are not implemented in many existing Bluetooth devices. For example, a large number of Bluetooth devices on the market are still using Bluetooth technology versions lower than 5.1, and the hardware of these devices cannot handle the complex signal decoding and antenna switching operations required to implement AoA. These low-version devices lack support for Constant Tone Extension (CTE) and related signal processing algorithms required for AoA signals, because these features are only introduced in the Bluetooth 5.1 and higher specifications. In addition, even some devices that support Bluetooth 5.1 or higher may not necessarily implement the direction finding function due to cost and energy consumption considerations, because implementing this function often requires additional hardware support, such as enhanced antenna systems and more complex signal processing units. Such hardware upgrades will increase the production cost of the device and affect the battery life of the device, resulting in these devices also being unable to use the direction finding function. Therefore, although the latest advances in Bluetooth technology have brought unprecedented accuracy potential to indoor positioning, hardware limitations and cost factors have seriously hindered its widespread use in existing devices. This situation limits the deployment of high-precision indoor positioning solutions based on Bluetooth AoA technology, especially in environments where older versions of Bluetooth devices are already widely deployed. Summary of the invention

[0005] The purpose of the present invention is to provide a backward compatible low-power Bluetooth direction-finding positioning method and system to solve the compatibility problem between the direction-finding function of Bluetooth 5.1 version and a large number of existing devices that cannot support this function due to hardware limitations. The core innovation of the present invention is that it does not rely on the hardware upgrade of the target device, but solves the popularization problem of the direction-finding function of Bluetooth 5.1 through an additional trigger node (Trigger). This trigger node can work in conjunction with the existing Bluetooth locator. 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 a signal containing nested data packets. These nested data packets are designed to communicate with old devices and be correctly parsed by new locators, thereby achieving precise positioning.

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

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

[0008] Establishing communication connection between trigger node and target device, and between trigger node and locator through Bluetooth signal;

[0009] The trigger node sends a nested data packet to the target device and the locator at the same time, wherein the nested data packet contains a predefined embedded instruction, and the embedded instruction is an instruction to trigger the target device to send a positioning signal within a predetermined time;

[0010] The target device parses the received nested data packets and sends out positioning signals according to the embedded instructions;

[0011] The locator parses the received nested data packet, collects the positioning signal according to the embedded instruction control, obtains the 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 it to obtain an ideal reference signal, eliminates the phase offset of the first positioning signal based on the ideal reference signal to obtain the phase offset of each antenna, estimates the arrival angle based on the phase offset, and accurately locates the position of the target device.

[0014] The acquisition of positioning signals according to the embedded instruction control is specifically as follows: 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 instruction, and performs sampling and analysis of the positioning signal at the specified time and channel according to the parameters and the protocol standard, wherein the channel is the same channel as the channel through which the target device sends the positioning signal.

[0015] The preprocessing specifically includes: the locator processes the collected positioning signal and calculates the IQ value of the signal, where 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] receiving a second positioning signal and demodulating the signal to obtain an ideal reference signal;

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

[0019] Based on the ideal reference signal and the filtered first positioning signal, the arrival time of the positioning signal is estimated by using the differential phase correlation method;

[0020] aligning the first positioning signal with an ideal reference signal based on the estimated arrival time, and estimating a reference frequency offset based on the aligned signals;

[0021] estimating a carrier frequency offset based on the filtered first positioning signal;

[0022] The reference frequency offset and the carrier frequency offset are subtracted 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 first positioning signal according to its amplitude, and only retaining the first positioning signal with an amplitude higher than a preset threshold.

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

[0025] The method of estimating the arrival time of the positioning signal by using a differential phase correlation method based on the ideal reference signal and the filtered first positioning signal comprises the following steps:

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

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

[0028] Perform convolution processing on the ideal differential phase signal and the differential positioning phase signal to obtain the time length information of the peak appearance;

[0029] The arrival time is obtained by adding the time length of the ideal differential phase signal to the start time of the current antenna switching cycle and subtracting the time length of the peak.

[0030] The estimation of the reference frequency offset is specifically as follows: aligning the first positioning signal and the ideal reference signal based on the estimated arrival time, and 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 estimating carrier frequency offset comprises the following steps:

[0032] Rough estimation: The target device continuously sends multiple identical positioning signals within a reference period of a preset time. The locator receives the positioning signal with the first antenna within the reference period. A linear regression fit is performed on the first positioning signal sampled by the locator to obtain the preliminary carrier frequency offset per unit time.

[0033] Precise estimation: Based on the preliminary carrier frequency offset, determine the period of a complete antenna switching round. For the first positioning signal sampled by the locator beyond the reference period, use its phase information to construct a phase sequence. The phase sequence is composed of m complete antenna switching rounds and the phase information of the first positioning signal collected by N antennas, which is expressed as: represents the phase of the first positioning signal collected by the jth antenna in the i-th antenna switching round; differential processing is performed based on the phase sequence, and the fine-grained carrier frequency offset is estimated in combination with the cycle of the complete antenna switching round:

[0034]

[0035] Among them, φ CFO represents the carrier frequency offset, k is the period of a complete antenna switching round, φ CFO_c represents the preliminary carrier frequency offset, Indicates rounding down.

[0036] A backward compatible low-power Bluetooth direction-finding and positioning system, used to implement the above method, the system comprising:

[0037] Positioner: used to parse the received nested data packets, collect positioning signals according to the embedded instruction control, obtain the first positioning signal after preprocessing, and send it to the positioning server for further analysis and positioning calculation;

[0038] Target device: the Bluetooth device to be located, used to send out positioning signals according to the nested data packets sent by the triggering node;

[0039] Trigger node: having bidirectional communication capability with the locator and the target device, used to send a nested data packet to the target device and the locator at the same time, wherein the nested data packet contains a predefined embedded instruction, and the embedded instruction is an instruction to trigger the target device to send a positioning signal within a predetermined time; and, used to receive the positioning signal sent by the target device, obtain a second positioning signal, and forward it to the positioning server;

[0040] Positioning server: used to receive the second positioning signal and demodulate it to obtain an ideal reference signal, eliminate the phase offset of the first positioning signal based on the ideal reference signal, obtain the phase offset of each antenna, estimate the arrival angle based on the phase offset, and accurately locate the position of the target device.

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

[0042] This invention solves the limitation of Bluetooth 5.1 direction finding function by triggering node technology, and provides an economical and efficient indoor positioning solution for various types of facilities, making accurate indoor positioning technology more popular and practical. Its advantages are reflected in the following aspects:

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

[0044] 2) Cost-effectiveness: The present invention introduces a method of nested data packets and time overlap by using trigger nodes, allowing a single trigger node to communicate with 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 realizing a cost-effective indoor positioning solution.

[0045] 3) Improved accuracy: The present 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 elimination. These techniques help the system work effectively in complex multipath and interference environments, providing more accurate positioning than traditional Bluetooth direction finding. Even for devices that do not have native direction finding capabilities, the present invention can achieve high-precision AoA positioning by triggering nodes, significantly improving positioning accuracy.

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

[0047] Figure 1 is a flow chart of the method of the present invention;

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

[0049] Figure 3 A schematic diagram of the data processing flow performed by the positioning server of the present invention. DETAILED DESCRIPTION

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

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

[0052] 1. BLE5.1 Locator: The locator supports the direction-finding method of Bluetooth 5.1, receives and processes signals from the target device, and transmits the data to the positioning server for further analysis and positioning calculation.

[0053] 2. Target: The target device refers to the 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 natively support the direction-finding method of Bluetooth 5.1.

[0054] 3. Trigger: The trigger node is the core device of the present invention. It has two-way communication capabilities and can communicate with the Bluetooth 5.1 locator and the target device at the same time. The trigger node not only simulates the signal of the target device for the locator to analyze, but also receives the signal from the target device and transmits the data to the positioning server to complete accurate positioning.

[0055] 4. Localization Server: The positioning server is the data processing center of the system, receiving signal data from BLE5.1 Locator and Trigger. The server analyzes this data to calculate the location of the target device, and uses the algorithm proposed in this patent to process and parse signal data from different sources to ensure the accuracy of the positioning results.

[0056] Example 1

[0057] This embodiment provides a backward compatible low-power Bluetooth direction finding and positioning method, such as Figure 1 As shown, the following steps are included:

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

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

[0060] The trigger node requires a connection with the 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 and sends a pairing and connection request, which includes a control field for the specified time and communication channel, so that the target device can perform subsequent data communication processes according to the requirements of the trigger node.

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

[0062] The trigger node first uses the Bluetooth 5.1 Direction-finding protocol to communicate with the BLE5.1 Locator, synchronously determines the channel to be used by the subsequent positioning signal and standardizes the positioning time and data packet structure. This step ensures that the Trigger and 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 nested packets to the target device and the locator simultaneously.

[0064] like Figure 2 As shown, after the connection is established, in order to ensure data synchronization, Trigger uses Nesting Packet technology, which allows different data for multiple destinations to be included in a single Bluetooth packet, ensuring that Trigger can send different information to the target device and BLE5.1 Locator at the same time. Specifically, Trigger uses Nesting Packet technology to send nested data packets to the target device and locator at the same time. The nested data packets contain predefined embedded instructions, which are instructions for triggering the target device to send a positioning signal within a predetermined time. This nested data packet design allows Trigger to transmit signals with the same waveform but different information after decoding to different recipients at the same time, ensuring the synchronization of signal transmission and precise control of time. Therefore, after receiving the Nesting Packet of the trigger node, the target device will send back data packets on a specific time and communication channel in accordance with the Bluetooth protocol standard, that is, send a specific positioning signal. After the Nesting Packet of the trigger node is received by the locator, the locator decodes the instruction that triggers the target device to send a positioning signal within a predetermined time, and prepares for the subsequent reception of the positioning signal of the target device.

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

[0066] After receiving the Nesting Packet from the trigger node, the target device sends a specific positioning signal according to the embedded command. This step is standard Bluetooth communication and no modification is required to the target device.

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

[0068] After the Trigger uses the Nesting Packet technology to send data to the target device and the locator at the same time, the locator will sample and analyze 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 on the same channel. This specific Bluetooth packet (i.e., positioning signal) will be received and sampled by the locator according to the direction-finding and positioning process specified by the protocol.

[0069] Specifically, the locator determines the parameters such as the time window and signal length for the upcoming direction-finding positioning sampling and antenna switching according to the decoded embedded instructions, and performs sampling and 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 acquisition signal length during the signal collection process.

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

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

[0072] S6, the positioning server receives the second positioning signal and demodulates it 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 arrival angle based on the phase offset, and accurately locates the position of the target device.

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

[0074] S61, the positioning server first summarizes 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 to provide input for subsequent positioning calculations.

[0075] S62, Arrival Time Estimation.

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

[0077] S621: The positioning server demodulates the second positioning signal to obtain an ideal reference signal.

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

[0079] In this step, the received IQ value is first analyzed for amplitude 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 the preset threshold. Only signals with an amplitude above a certain threshold are considered valid signals and worthy of further analysis. This threshold is usually set based on the ambient noise level and the expected strength of the signal. The purpose of this step is to screen out sufficiently strong signals to avoid errors introduced by processing weak signals or noise. Amplitude judgment helps ensure that only potentially valid signals enter subsequent processing steps, thereby improving the overall performance of the system and positioning accuracy.

[0080] S623, Differential Phase Correlation: 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.

[0081] After completing the preliminary amplitude judgment, the phase analysis of the screened valid first positioning signal is performed to determine the arrival time of the signal. This technology uses the phase difference of the signal on different antennas to estimate the arrival time of the signal. By measuring the phase of the same signal received on each antenna and calculating the difference between them. By analyzing these phase differences, the propagation path of the signal and the arrival time relative to each antenna can be inferred. By comparing the ideal phase value of the original data packet signal, differential phase correlation analysis can accurately measure the arrival time of the signal, maintaining a high degree of accuracy even in environments 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] The specific steps include:

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

[0084] (2) in the current antenna switching cycle, obtaining the phase of the first positioning signal corresponding to the same positioning signal, and performing differentiation with the first positioning signal of the previous antenna switching cycle to obtain a differential positioning phase signal;

[0085] (3) Perform convolution processing on the ideal differential phase signal and the differential positioning phase signal to obtain the time length information of the peak appearance;

[0086] (4) Add the time length of the ideal differential phase signal to the start time of the current antenna switching cycle and subtract the time length of the peak to obtain the arrival time.

[0087] S63, positioning target reference frequency offset estimation (Reference Estimation): 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.

[0088] Reference frequency offset means that the signal sent by the positioning target is uncertain (related to the device and Bluetooth version), so the signal received by each antenna of the Locator will be affected by the different signals, causing its phase to shift, so it is necessary to estimate the reference frequency offset caused by it. The specific estimation method is: align the first positioning signal and the ideal reference signal based on the estimated arrival time, subtract the phase of the ideal reference signal from the phase of the aligned first positioning signal, and obtain the reference frequency offset.

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

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

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

[0092] S641, rough estimation: the target device continuously sends multiple identical positioning signals within a reference period of a preset time. The locator receives the positioning signal with the first antenna within the reference period. A linear regression fit is performed on the first positioning signal sampled by the locator to obtain a preliminary carrier frequency offset per unit time.

[0093] In one embodiment, in the Bluetooth 5.1 Direction-finding protocol, the Target will continuously send 8 identical signals in the first 8μs reference period, and the Locator will use the first antenna to receive in this reference period. Therefore, by fitting these 8 samples with linear regression, the preliminary carrier frequency offset per unit time can be obtained. However, due to synchronization issues, the Locator may not receive all 8 samples, so the CFO error estimated using 8 or less samples is large and can only be used as a rough estimate. It is necessary to further use samples outside the reference period to further optimize the CFO estimate.

[0094] S642, precise estimation: Determine the period of a complete antenna switching round based on the preliminary carrier frequency offset. For the first positioning signal sampled by the locator beyond the reference period, use its phase information to construct a phase sequence. The phase sequence is composed of m complete antenna switching rounds and the phase information of the first positioning signal collected by N antennas, which is expressed as: represents the phase of the first positioning signal collected by the jth antenna in the i-th antenna switching round; differential processing is performed based on the phase sequence, and the fine-grained carrier frequency offset is estimated in combination with the cycle of the complete antenna switching round:

[0095]

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

[0097] It should be noted that the remaining phase difference It may exceed one period (2π) in the case of a large number of antennas. Therefore, the preliminary carrier frequency offset will be used to determine the cumulative phase difference to complete a complete antenna switching cycle and determine whether it exceeds one or more phase periods, that is, φ CFO-c represents the preliminary carrier frequency offset, Indicates rounding down, and finally calculating the fine-grained CFO estimate.

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

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

[0100] After obtaining the phase offset of each antenna, the existing AoA estimation algorithm can be used to obtain the AoA if the antenna spacing is known. This step is implemented using an existing algorithm and is not within the scope of protection 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 locate the location of the target device.

[0102] Combining the position coordinates of multiple Locators and their respective measured AoAs, the positioning server calculates the precise position of the target device. This step is implemented using existing algorithms and is not within the scope of protection of the patent. Possible implementation methods include but are not limited to geometric position solution.

[0103] Example 2

[0104] This embodiment provides a backward compatible low-power Bluetooth direction-finding and positioning system, which is used to implement the method of Embodiment 1. The system includes:

[0105] Positioner: used to parse the received nested data packets, collect positioning signals according to the embedded instruction control, obtain the first positioning signal after preprocessing, and send it to the positioning server for further analysis and positioning calculation;

[0106] Target device: the Bluetooth device to be located, used to send out positioning signals according to the nested data packets sent by the triggering node;

[0107] Trigger node: having bidirectional communication capability with the locator and the target device, used to send a nested data packet to the target device and the locator at the same time, wherein the nested data packet contains a predefined embedded instruction, and the embedded instruction is an instruction to trigger the target device to send a positioning signal within a predetermined time; and, 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, eliminate the phase offset of the first positioning signal based on the ideal reference signal, obtain the phase offset of each antenna, estimate the arrival angle based on the phase offset, and accurately locate the position of the target device.

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

[0110] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A backward compatible low-power Bluetooth direction finding and positioning method, characterized in that: The following steps are involved: Establishing communication connection between trigger node and target device, and between trigger node and locator through Bluetooth signal; The trigger node sends a nested data packet to the target device and the locator at the same time, wherein the nested data packet contains a predefined embedded instruction, and the embedded instruction is an instruction 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 out positioning signals according to the embedded instructions; The locator parses the received nested data packet, collects the positioning signal according to the embedded instruction control, obtains the first positioning signal after preprocessing, and sends it to the positioning server; The trigger node receives the positioning signal sent by the target device, obtains a 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, eliminates the phase offset of the first positioning signal based on the ideal reference signal to obtain the phase offset of each antenna, estimates the arrival angle based on the phase offset, and accurately locates the position of the target device.

2. A 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 instruction control is specifically as follows: 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 instruction, and performs sampling and analysis of the positioning signal at the specified time and channel according to the parameters and the protocol standard, wherein the channel is the same channel as the channel through which the target device sends the positioning signal.

3. A backward compatible low power Bluetooth direction finding and positioning method according to claim 1, characterized in that: The preprocessing specifically includes: the locator processes the collected positioning signal and calculates the IQ value of the signal, where the IQ value includes amplitude and phase.

4. A backward compatible low power Bluetooth direction finding and positioning method according to claim 1, characterized in that: The positioning server performs the following steps to eliminate the phase offset of the first positioning signal: receiving a second positioning signal and demodulating the signal to obtain an ideal reference signal; Performing 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 by using the differential phase correlation method; aligning the first positioning signal with an ideal reference signal based on the estimated arrival time, and estimating a reference frequency offset based on the aligned signals; estimating a carrier frequency offset based on the filtered first positioning signal; The reference frequency offset and the carrier frequency offset are subtracted from the phase of the first positioning signal to eliminate the phase offset.

5. A backward compatible low power Bluetooth direction finding and positioning method according to claim 4, characterized in that: The preliminary amplitude judgment and screening of the first positioning signal collected by each antenna is specifically: analyzing the first positioning signal according to its amplitude, and only retaining the first positioning signal with an amplitude higher than a preset threshold.

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

7. A backward compatible low power Bluetooth direction finding and positioning method according to claim 4, characterized in that: The method of estimating the arrival time of the positioning signal by using a differential phase correlation method based on the ideal reference signal and the filtered first positioning signal comprises the following steps: In the current antenna switching cycle, the phase of the ideal reference signal corresponding to a certain positioning signal is obtained, and the phase is differentiated from the phase of the ideal reference signal in the previous antenna switching cycle to obtain an ideal differential phase signal; In the current antenna switching cycle, the phase of the first positioning signal corresponding to the same positioning signal is obtained, and the phase is differentiated from the first positioning signal of the previous antenna switching cycle to obtain a differential positioning phase signal; Perform convolution processing on the ideal differential phase signal and the differential positioning phase signal to obtain the time length information of the peak appearance; The arrival time is obtained by adding the time length of the ideal differential phase signal to the start time of the current antenna switching cycle and subtracting the time length of the peak.

8. A backward compatible low power Bluetooth direction finding and positioning method according to claim 4, characterized in that: The estimation of the reference frequency offset is specifically as follows: aligning the first positioning signal and the ideal reference signal based on the estimated arrival time, and subtracting the phase of the ideal reference signal from the phase of the aligned first positioning signal to obtain the reference frequency offset.

9. A backward compatible low power Bluetooth direction finding and positioning method according to claim 4, characterized in that: The estimating carrier frequency offset comprises the following steps: Rough estimation: The target device continuously sends multiple identical positioning signals within a reference period of a preset time. The locator receives the positioning signal with the first antenna within the reference period. A linear regression fit 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 preliminary carrier frequency offset, determine the period of a complete antenna switching round. For the first positioning signal sampled by the locator beyond the reference period, use its phase information to construct a phase sequence. The phase sequence is composed of m complete antenna switching rounds and the phase information of the first positioning signal collected by N antennas, which is expressed as: represents the phase of the first positioning signal collected by the jth antenna in the i-th antenna switching round; differential processing is performed based on the phase sequence, and the fine-grained carrier frequency offset is estimated in combination with the cycle of the complete antenna switching round: Among them, φ CFO represents the carrier frequency offset, k is the period of a complete antenna switching round, φ CFO_c represents the preliminary carrier frequency offset, Indicates rounding down.

10. A backward compatible low-power Bluetooth direction-finding and positioning system, characterized in that: For implementing the method according to any one of claims 1 to 9, the system comprises: Positioner: used to parse the received nested data packets, collect positioning signals according to the embedded instruction control, 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 out positioning signals according to the nested data packets sent by the triggering node; Trigger node: having bidirectional communication capability with the locator and the target device, used to send a nested data packet to the target device and the locator at the same time, wherein the nested data packet contains a predefined embedded instruction, and the embedded instruction is an instruction to trigger the target device to send a positioning signal within a predetermined time; and, 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, eliminate the phase offset of the first positioning signal based on the ideal reference signal, obtain the phase offset of each antenna, estimate the arrival angle based on the phase offset, and accurately locate the position of the target device.

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