CN114900888A

CN114900888A - Arrival angle positioning method and system of Bluetooth terminal

Info

Publication number: CN114900888A
Application number: CN202210536749.2A
Authority: CN
Inventors: 邓中亮; 华巍; 阳臻; 杨福兴; 代卫成; 雷彪; 刘京融; 胡恩文
Original assignee: Shenzhen Hezhong High Tech Co Ltd; Beijing University of Posts and Telecommunications
Current assignee: Shenzhen Hezhong High Tech Co Ltd; Beijing University of Posts and Telecommunications
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2022-08-12

Abstract

The invention provides an arrival angle positioning method and a system of a Bluetooth terminal, wherein the positioning method comprises the following steps: the master node Bluetooth base station establishes link connection with the Bluetooth terminal and instructs the Bluetooth terminal to send a Bluetooth broadcast signaling packet; the master node Bluetooth base station and the plurality of passive node Bluetooth base stations receive the Bluetooth broadcast signaling packet and calculate an arrival angle, and send the obtained arrival angle to the positioning platform; the positioning platform calculates the positioning result of the Bluetooth terminal at the current moment based on the geometric relationship between the multiple arrival angles and the position coordinates of the Bluetooth base station; determining whether the motion scene of the Bluetooth terminal is a dynamic scene or a static scene, and if the motion scene is determined to be the dynamic scene, optimizing a positioning result of the Bluetooth terminal at the current moment by a positioning platform based on an extended Kalman filtering algorithm; and if the static scene is determined, the positioning platform optimizes the positioning result of the Bluetooth terminal at the current moment based on a multipoint average filtering algorithm. The method and the system can realize the Bluetooth terminal positioning with low cost, low error and high real-time performance.

Description

Arrival angle positioning method and system of Bluetooth terminal

Technical Field

The invention relates to the technical field of Bluetooth positioning, in particular to a method and a system for positioning an arrival angle of a Bluetooth terminal.

Background

Research studies have shown that most people spend 70% of their time mostly in the home, and location-based services are becoming increasingly important, such as emergency rescue, traffic management, vehicle navigation and route planning, etc.

The 1 month bluetooth technical association in 2019 introduced a new technology in the published bluetooth 5.1 specification: the Bluetooth angle of Arrival (AoA) positioning technology is a two-base-station positioning method, and based on the Bluetooth Low energy (Bluetooth Low energy) characteristic, the Arrival direction of a transmitting node signal is sensed through some hardware devices such as an antenna array, the relative direction or angle between a positioned point and a sensing device is calculated, and then the position of the node is calculated by using a triangulation method. Compared with other existing indoor positioning technologies such as Wi-Fi positioning and UWB positioning, the Bluetooth arrival angle positioning technology has the outstanding advantages of remarkably reducing power consumption and cost while keeping the same communication range, being small in size, small in power consumption, long in working time, small in interference of the Bluetooth to the surrounding environment, having the sub-meter-level high-precision positioning advantage and having the technical characteristics of flexibility, high concurrency, low cost, low power consumption, high compatibility and the like. The problem of high cost caused by application of large-scale positioning labels of people, vehicles, objects, materials and the like in the smart industry can be effectively solved. Meanwhile, Bluetooth is used as a standard for intelligent terminals such as mobile phones and the like, an excellent technical port is provided for realizing rapid penetration of indoor high-precision positioning, and large-scale indoor positioning application ecological formation in public service fields such as intelligent business surpasses, transportation hubs, museums, exhibition centers, hospitals and the like is promoted.

However, the angle-of-arrival positioning method also has a plurality of problems, which results in that the accuracy and stability of the bluetooth angle-of-arrival positioning technology cannot be guaranteed, and the problems include: (1) signal interference caused by indoor multipath effects; (2) the arrival angle error caused by the phase error received by the Bluetooth antenna array element interferes the positioning result; (3) the limitation of the calculation method in the positioning result position calculation process causes the data with larger individual error to influence the overall result.

In the prior art, the positioning precision can be improved by increasing the number of array elements, increasing and accelerating the beat number, and suppressing noise by using various improved Kalman filtering algorithms and particle filtering algorithms. However, increasing the number of array elements increases the size of the positioning device, which is not favorable for miniaturization and increases the production cost. Increasing the number of beats increases the data collection amount, increases the data acquisition time, and consumes time for processing a large amount of data, which is not favorable for real-time positioning. In addition, unscented Kalman filtering is adopted to obtain second-order Taylor approximation precision by screening Sigma points which are approximate to Gaussian distribution statistics of a target state, but the calculation complexity is too high, the requirement on a processor is high, and the cost of the Bluetooth base station is increased.

Therefore, how to provide a method and a system for positioning the arrival angle of the bluetooth terminal, which have low cost, low error and high real-time performance, is a problem to be solved urgently.

Disclosure of Invention

In view of this, embodiments of the present invention provide a method and a system for positioning an angle of arrival of a bluetooth terminal, so as to eliminate or improve one or more defects existing in the prior art.

One aspect of the present invention provides an arrival angle positioning method for a bluetooth terminal, comprising the following steps:

and the master node Bluetooth base station establishes link connection with the Bluetooth terminal and instructs the Bluetooth terminal to send a Bluetooth broadcast signaling packet.

And the master node Bluetooth base station and the plurality of passive node Bluetooth base stations receive Bluetooth broadcast signaling packets sent by the Bluetooth terminal in a broadcast communication mode.

The master node Bluetooth base station and the plurality of passive node Bluetooth base stations calculate arrival angles based on phase differences between Bluetooth broadcast signaling packets received by different antennas in respective antenna arrays and the Bluetooth broadcast signaling packets, and send the obtained arrival angles to the positioning platform.

And the positioning platform receives a plurality of arrival angles and calculates the positioning result of the Bluetooth terminal at the current moment based on the geometric relationship between the arrival angles and the position coordinates of the Bluetooth base station.

Determining whether a motion scene of the Bluetooth terminal is a dynamic scene or a static scene based on a positioning result of the Bluetooth terminal at the current moment and a positioning result of a plurality of historical moments, and if the motion scene is determined to be the dynamic scene, optimizing the positioning result of the Bluetooth terminal at the current moment by the positioning platform based on an extended Kalman filtering algorithm; and if the static scene is determined, the positioning platform optimizes the positioning result of the Bluetooth terminal at the current moment based on a multipoint average filtering algorithm.

In some embodiments of the present invention, the arrival angles sent by the master node bluetooth base station and the plurality of passive node bluetooth base stations are collected to the positioning platform by a UART serial port and a switch.

In some embodiments of the present invention, the bluetooth broadcast signaling packet includes CTE location information.

In some embodiments of the present invention, adjacent antennas in the antenna array are spaced apart from each other by a predetermined distance, the predetermined distance being fixed and less than one-half of a communication carrier wavelength.

The angle of arrival is expressed by the formula

And calculating, wherein theta is an arrival angle, phi is a phase difference, lambda is the radio frequency signal wavelength of the Bluetooth broadcast signaling packet, and d is a preset distance between adjacent antennas.

In some embodiments of the present invention, the step of calculating a positioning result of the current time of the bluetooth terminal based on the geometric relationship between the multiple angles of arrival and the position coordinates of the bluetooth base station includes: and the positioning platform gives a weight to each arrival angle, and the positioning platform performs Taylor expansion and least square iteration on the basis of a plurality of arrival angles, the position coordinates of the Bluetooth base station and the weights of the arrival angles to obtain a positioning result with least square optimization, wherein the weight of each arrival angle is inversely proportional to the distance between the corresponding Bluetooth base station and the Bluetooth terminal.

In some embodiments of the present invention, the step of calculating a positioning result of the current time of the bluetooth terminal based on the geometric relationship between the multiple angles of arrival and the position coordinates of the bluetooth base station further includes: and executing an arrival angle abnormity determination step based on the geometric relationship among the arrival angles, the positioning results and the position coordinates of the Bluetooth base stations, determining that the arrival angle is abnormal if the calculated Bluetooth terminal is positioned on a connecting line of the two Bluetooth base stations, removing the arrival angle corresponding to any one of the two Bluetooth base stations, and calculating the positioning result of the Bluetooth terminal at the current moment based on the geometric relationship among the arrival angles and the position coordinates of the Bluetooth base stations.

In some embodiments of the present invention, the determining whether the motion scene of the bluetooth terminal is a dynamic scene or a static scene based on the positioning result at the current time and the plurality of historical times includes: calculating Euclidean distances between the positioning result at the current moment and the positioning results at a plurality of historical moments, and comparing the Euclidean distances with the positioning error acceptance values; if the Euclidean distance between the positioning result at the current moment and the positioning results at a plurality of historical moments is larger than the positioning error acceptance value, determining that the scene is a dynamic scene; if the root mean square error is smaller than the positioning error admission value, judging as a static scene; the positioning error acceptance value is a root mean square error measured by a positioning system experiment or an initial value directly set manually.

In some embodiments of the present invention, the step of optimizing the positioning result based on the multi-point average filtering algorithm by the positioning platform comprises: and calculating the average value of the positioning result at the current moment and the positioning results at a plurality of historical moments.

Another aspect of the present invention provides a system for implementing the method for positioning an angle of arrival of any one of the bluetooth terminals, where the system includes a bluetooth terminal, a positioning platform, and a plurality of bluetooth base stations, where the bluetooth base stations include a master node bluetooth base station and a passive node bluetooth base station, where:

the main node Bluetooth base station is used for establishing link connection with a Bluetooth terminal, indicating the Bluetooth terminal to send a Bluetooth broadcast signaling packet and receiving the Bluetooth broadcast signaling packet sent by the Bluetooth terminal in a broadcast communication mode.

And the plurality of passive node Bluetooth base stations also receive Bluetooth broadcast signaling packets sent by the Bluetooth terminal in a broadcast communication mode under the condition of not establishing link connection with the Bluetooth terminal.

The master node Bluetooth base station and the plurality of passive node Bluetooth base stations respectively comprise antenna arrays, phase differences exist among Bluetooth broadcast signaling packets received by different antennas in the antenna arrays, the master node Bluetooth base station and the plurality of passive node Bluetooth base stations calculate arrival angles based on the phase differences and the Bluetooth broadcast signaling packets, and the obtained arrival angles are forwarded to the positioning platform.

The positioning platform receives a plurality of arrival angles, calculates a positioning result of the Bluetooth terminal at the current moment based on a geometric relation between the arrival angles and position coordinates of the Bluetooth base station, determines a motion scene of the Bluetooth terminal to be a dynamic scene or a static scene based on the positioning result of the Bluetooth terminal at the current moment and the positioning results of a plurality of historical moments, and optimizes the positioning result of the Bluetooth terminal at the current moment based on an extended Kalman filtering algorithm if the motion scene is determined to be the dynamic scene; and if the static scene is determined, the positioning platform optimizes the positioning result of the Bluetooth terminal at the current moment based on a multipoint average filtering algorithm.

In some embodiments of the invention, the bluetooth base station comprises an antenna array, a radio frequency switch, a BLE controller and a bluetooth protocol stack, wherein: the type of the antenna array is one or more of a uniform linear array, a uniform linear rectangular array or a uniform linear circular array; the radio frequency switch is used for switching an antenna mode; the BLE controller is used for controlling signal transmission and reception of the Bluetooth module, and firmware operated by the BLE controller supports an over-the-air transmission protocol; the bluetooth protocol stack contains supported profiles and a set of communications or events that interact with the bluetooth controller.

The method and the system for positioning the arrival angle of the Bluetooth terminal can reduce the error of the positioning of the arrival angle without increasing the cost, ensure the high real-time performance of a positioning system and realize good positioning effect.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

fig. 1 is an overall framework diagram of a positioning system according to an embodiment of the invention.

Fig. 2 is a schematic diagram of a positioning system according to an embodiment of the invention.

Fig. 3 is a schematic structural diagram of positioning hardware according to an embodiment of the present invention.

Fig. 4 is a schematic view of the angle of arrival principle.

FIG. 5 is a schematic diagram illustrating detection of arrival angles according to phase differences according to an embodiment of the present invention.

Fig. 6 is an IQ sampling schematic in an embodiment of the invention.

FIG. 7 is a diagram of a CTE data format in accordance with an embodiment of the present invention.

Figure 8 is a CTE switching slot diagram in accordance with an embodiment of the present invention.

FIG. 9 is a block diagram of the underlying architecture in an embodiment of the invention.

Figure 10 is a block diagram of a transmitter, a wireless channel model and a receiver in the BLE standard according to an embodiment of the present invention.

Fig. 11 is a schematic diagram illustrating an arrival angle positioning method in an embodiment of the present invention.

Fig. 12 is a schematic diagram illustrating an angle error correction method according to an embodiment of the invention.

Fig. 13 is a flow chart of a positioning process according to an embodiment of the invention.

FIG. 14 is a diagram of a static multi-measurement average filtering algorithm according to an embodiment of the invention.

Fig. 15 is a schematic diagram illustrating a method for determining an abnormal position of a bluetooth terminal according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.

It is also noted herein that the term "coupled," if not specifically stated, may refer herein to not only a direct connection, but also an indirect connection in which an intermediate is present.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar components, or the same or similar steps.

In order to solve the problems existing in the existing arrival angle positioning method and to add new problems in the process of reducing the positioning error as far as possible, the invention provides an arrival angle positioning method and a system of a Bluetooth terminal. The system is mainly used for indoor positioning requirements, can provide accurate positioning for the label, tracks the indoor activity track of personnel, supports real-time display of the indoor accurate position of the personnel, can be used for monitoring indoor fixed assets and controlling access, and can also prevent escort personnel from escaping or provide indoor navigation service for a market.

Fig. 1 is an overall framework diagram of a positioning system in an embodiment of the present invention, and the present invention provides a method for positioning an angle of arrival of a bluetooth terminal, including the following steps:

step 1: and the master node Bluetooth base station establishes link connection with the Bluetooth terminal and instructs the Bluetooth terminal to send a Bluetooth broadcast signaling packet.

Step 2: the master node Bluetooth base station and the plurality of passive node Bluetooth base stations receive Bluetooth broadcast signaling packets sent by the Bluetooth terminal in a broadcast communication mode.

And step 3: the master node Bluetooth base station and the plurality of passive node Bluetooth base stations calculate arrival angles based on phase differences between Bluetooth broadcast signaling packets received by different antennas in respective antenna arrays and the Bluetooth broadcast signaling packets, and send the obtained arrival angles to the positioning platform.

And 4, step 4: and the positioning platform receives the multiple arrival angles and calculates the positioning result of the Bluetooth terminal at the current moment based on the geometric relationship between the multiple arrival angles and the position coordinates of the Bluetooth base station.

And 5: determining whether a motion scene of the Bluetooth terminal is a dynamic scene or a static scene based on a positioning result of the Bluetooth terminal at the current moment and a positioning result of a plurality of historical moments, and if the motion scene is determined to be the dynamic scene, optimizing the positioning result of the Bluetooth terminal at the current moment by the positioning platform based on an extended Kalman filtering algorithm; and if the static scene is determined, the positioning platform optimizes the positioning result of the Bluetooth terminal at the current moment based on a multipoint average filtering algorithm.

Fig. 2 is a schematic diagram of a positioning system in an embodiment of the present invention, and the present invention provides a system for implementing an angle of arrival positioning method of a bluetooth terminal in any embodiment of the present invention, where the system includes a bluetooth terminal, a positioning platform, and a plurality of bluetooth base stations, where the bluetooth base stations include a master node bluetooth base station and a passive node bluetooth base station, where:

the main node Bluetooth base station is used for establishing link connection with a Bluetooth terminal, indicating the Bluetooth terminal to send a Bluetooth broadcast signaling packet and receiving the Bluetooth broadcast signaling packet sent by the Bluetooth terminal in a broadcast communication mode. And the plurality of passive node Bluetooth base stations also receive Bluetooth broadcast signaling packets sent by the Bluetooth terminal in a broadcast communication mode under the condition of not establishing link connection with the Bluetooth terminal. The master node Bluetooth base station and the plurality of passive node Bluetooth base stations respectively comprise antenna arrays, phase differences exist among Bluetooth broadcast signaling packets received by different antennas in the antenna arrays, the master node Bluetooth base station and the plurality of passive node Bluetooth base stations calculate arrival angles based on the phase differences and the Bluetooth broadcast signaling packets, and the obtained arrival angles are forwarded to the positioning platform. The positioning platform receives a plurality of arrival angles, calculates a positioning result of the Bluetooth terminal at the current moment based on a geometric relation between the arrival angles and position coordinates of the Bluetooth base station, determines a motion scene of the Bluetooth terminal to be a dynamic scene or a static scene based on the positioning result of the Bluetooth terminal at the current moment and the positioning results of a plurality of historical moments, and optimizes the positioning result of the Bluetooth terminal at the current moment based on an extended Kalman filtering algorithm if the motion scene is determined to be the dynamic scene; and if the static scene is determined, the positioning platform optimizes the positioning result of the Bluetooth terminal at the current moment based on a multipoint average filtering algorithm.

In an embodiment of the present invention, the bluetooth base station includes a master node bluetooth base station and a passive node bluetooth base station, and both the bluetooth base station and the bluetooth terminal can be used by a development board through different settings and extensions, and an arrival angle is obtained through common measurement and calculation. The positioning platform calculates to obtain the position coordinates of the Bluetooth terminal based on the received arrival angle information from the plurality of Bluetooth base stations through an internal preset algorithm, executes the correction step of the arrival angle and the judgment step of the angle abnormity mentioned in the following, performs Bluetooth hardware control, and manages the Bluetooth terminal.

In an embodiment of the present invention, the Bluetooth terminal hardware platform of the present invention is developed based on the LAUNCHXL-CC26X2 series multi-standard wireless MCU of the company TI, and the platform includes Wi-Fi, low power consumption Bluetooth, Sub 1GHz, Thread, Zigbee, 802.15.4, and host MCU, which share a common development environment easy to use, and includes a single-core Software Development Kit (SDK) and a rich tool set, wherein an integrated module implementing the functions specified by the Bluetooth 5.1 protocol can support a long-distance mode, a high-speed mode, broadcast extension, and up to 32 connections.

In an embodiment of the present invention, the physical entity of the positioning platform is a computer.

In the embodiment of the invention, the main node Bluetooth base station establishes link connection with the Bluetooth terminal, and sends link parameters (including address information, clock precision, Cyclic Redundancy Code (CRC) and the like) to the positioning platform, wherein the link connection establishment process comprises an identity verification process. Because the bluetooth terminal sends the bluetooth broadcast signaling packet in a broadcast mode, the passive node bluetooth base station can monitor the bluetooth broadcast signaling packet without establishing link connection with the bluetooth terminal.

Fig. 3 is a schematic diagram of a positioning hardware structure in an embodiment of the present invention, where arrival angles sent by a master node bluetooth base station and a plurality of passive node bluetooth base stations are summarized to the positioning platform by a UART serial port and a switch.

Fig. 4 is a schematic diagram of the angle of arrival principle, where the transmitter and the receiver are bluetooth modules located at a bluetooth base station or a bluetooth terminal, the bluetooth base station includes an antenna array, the antenna array includes a plurality of antennas, the antennas in the antenna array are separated from each other by a predetermined distance, the predetermined distance is fixed and less than one-half of the carrier wavelength, when the radio frequency signals received by them have a phase difference proportional to the difference between their respective distances from the transmitter, and when the phase differences are close enough, the position of the transmitter (i.e., the bluetooth terminal) can be determined. A transmitter when its antenna array is used to transmit signals and a receiver when its antenna array is used to receive signals. The Bluetooth base station and the Bluetooth terminal are built based on the single-chip microcomputer module and both comprise radio-frequency transmitting and receiving modules, the Bluetooth terminal sends a Bluetooth broadcast signaling packet through a broadcast format, the connected master node Bluetooth base station and the passive node Bluetooth base station which does not build a connection relation can both receive the Bluetooth broadcast signaling packet, the Bluetooth broadcast signaling packets which are received by adjacent antennas of an antenna array on the Bluetooth base station which receives the Bluetooth broadcast signaling packet and are in a radio-frequency signal form have phase differences, and the Bluetooth base station calculates an arrival angle based on the phase differences.

Fig. 5 is a schematic diagram of detecting an arrival angle according to a phase difference according to an embodiment of the present invention, in which a bluetooth terminal includes a single antenna, the bluetooth terminal uses the single antenna to transmit a bluetooth broadcast signaling packet, the transmission and reception of the bluetooth broadcast signaling packet are both in a radio frequency signal form in a physical layer, and the radio frequency signal form itself belongs to a direction-finding signal type, so that an array antenna located on a bluetooth base station receives the bluetooth broadcast signaling packet in the radio frequency signal form, and since a certain interval exists between each antenna of the array antenna, the received bluetooth broadcast signaling packet in the radio frequency signal form has a certain phase difference Φ, and an arrival angle of the bluetooth broadcast signaling packet signal can be calculated based on the phase difference Φ.

Fig. 6 is an IQ sampling schematic diagram in an embodiment of the present invention, where IQ sampling is a specific way for an antenna array located on a bluetooth base station to receive a bluetooth broadcast signaling packet, where the reception of the bluetooth broadcast signaling packet is actually to receive a radio frequency signal, and both the CTE specified by the bluetooth 5.1 standard protocol and the related technical requirements of the IQ signal are supported in the present invention. The phase difference is measured by at least two (or more) array antennas connected to the same bluetooth base station, the antennas being in a straight line and spaced apart by a fixed distance, and the phase difference between adjacent antennas is kept constant. Arrow 1 is the signal vector from antenna 1 of the array antenna of the bluetooth base station, arrow 2 is the signal vector from antenna 2 on the array antenna of the same bluetooth base station, there is a phase difference phi between them, and the purpose of IQ sampling is to obtain this phase difference phi.

In an embodiment of the present invention, the arrival angle is calculated by formula (1), where θ is the arrival angle, Φ is the phase difference, λ is the wavelength of the radio frequency signal of the bluetooth broadcast signaling packet, and d is the preset distance between adjacent antennas.

In the embodiment of the present invention, the bluetooth broadcast signaling packet includes CTE (constant Tone extension) positioning information, fig. 7 is a CTE data format diagram in the embodiment of the present invention, where the CTE data carries information related to angle of arrival transmission, including angle of arrival reception: 1 microsecond switch and sample slot and 2 microsecond switch and sample slot. With reference to fig. 6 and fig. 7, the detailed flow of IQ sampling is as follows:

step 1: the bluetooth terminal calculates its angular position relative to the bluetooth base station by sending direction-finding enabled packets to the bluetooth base station using a single antenna. After receiving the signals, the bluetooth base station performs amplitude modulation and phase measurement at fixed intervals in a process called IQ sampling;

step 2: when performing IQ sampling in a system of a bluetooth base station with an antenna array, each sample has to be attributed to a different antenna. For the angle of arrival, IQ sampling must be performed for each antenna in the correct order. Whenever requested by the host, the bluetooth base station shall perform IQ sampling when receiving a valid data packet containing the CTE. It may also perform IQ sampling when a data packet with a valid CTE but invalid Cyclic Redundancy Check (CRC) is received.

And step 3: when receiving a packet with an angle of arrival CTE, antenna switching is required on the bluetooth base station side, and the rate is determined according to the host-configured switching pattern. The bluetooth base station should collect IQ samples at each millisecond and each sampling slot in the reference period, and the IQ samples are phase differences. Therefore, we have 8 reference IQ samples and 2 to 74 IQ samples with 1 μ s slots, or 1 to 37 IQ samples with 2 μ s slots.

And 4, step 4: the controller then reports these IQ samples to the host.

Fig. 7 is a CTE data format diagram of an embodiment of the present invention, and contents and format of CTE (constant Tone extension) positioning information, that is, the CTE data format includes: preamble frame (Preamble), Access address (Access address), Protocol Data Unit (Protocol Data Unit), Cyclic Redundancy Check (Cyclic Redundancy Check), and Constant Tone Extension (microsecond level). The pdu further includes a Header (Header), a Payload (Payload), and a Message authentication code (Message authentication code). The header in turn includes CTE information (8 bits) and 16 bits of other information. The CTE information includes CTE duration (CTEtime, 8 bits), Reserved word (Reserved for Future Use), CTE type (CTEType).

Fig. 8 is a CTE switching slot diagram in an embodiment of the present invention, where the CTE switching slot is a specific gap of sampling selected by the bluetooth base station in the IQ sampling process, and the diagram shows a 1-microsecond switching and sampling slot for angle-of-arrival reception and a 2-microsecond switching and sampling slot for angle-of-arrival reception. In the transmission of the angle of arrival, signals sent by the bluetooth terminal are continuous, but the process of executing IQ sampling by the bluetooth base station is intermittent, because IQ sampling obtains a phase difference and then obtains the angle of arrival from the phase difference, the switch summarizes the angle of arrival to the positioning platform, and then the positioning platform resolves the angle of arrival to obtain positioning information, which needs time.

In the embodiment of the invention, for the convenience of phase difference detection, the Bluetooth 5.1 uses a fixed frequency (250kHz) unmodulated Bluetooth broadcast signal, namely a Bluetooth broadcast signaling packet carrying CTE information, the time length is 16us to 160us, no CRC (cyclic redundancy check) is carried out, and a broadcast mode and a connection mode are supported, so that both a master node Bluetooth base station and a passive Bluetooth base station can receive the Bluetooth broadcast signaling packet. The CTE signal is a signal added after the CRC check and does not affect the original data content.

Wherein the CTE switching time slots are divided into: guard slot (4 μ s), Reference slot (8 μ s), switch slot (switch slot), Sample slot (Sample slot). The switching time slot and the sampling time slot are a series of time slices for adopting and switching, and the Bluetooth controller sets an antenna switching mode through an HCI command. In the 2 microsecond switch and sample slot received in the arrival angle, the switch slot and the sample slot can be combined into one to be treated.

Fig. 9 is a block diagram of a bottom layer architecture in an embodiment of the present invention, and the architecture flow is as follows:

(1) the antenna array is positioned on the Bluetooth base station and plays a crucial role in the process of receiving the CTE data packet, wherein the design of the antenna array can adopt a uniform linear array or a uniform linear rectangular array or a uniform linear circular array. In the embodiment of the invention, the adopted antenna array is a uniform linear array.

(2) Array element switching is realized through a radio frequency switch and a BLE controller, and the radio frequency switch is used for switching an antenna mode when needed; the BLE controller is used for controlling signal transmission and reception of the Bluetooth module, firmware operated by the BLE controller supports an over-the-air transmission protocol and is used for communicating with peer-to-peer/remote equipment, and the BLE controller is responsible for interacting with the antenna array and the radio frequency switch; the array element switching is the action of switching the array antenna according to the specified time slot shown in fig. 7, and is the hardware basis for the execution of IQ sampling.

(3) A Bluetooth protocol stack containing supported profiles and a set of communications or events that interact with the Bluetooth controller.

(4) And the radio frequency core is responsible for sending and receiving the Bluetooth broadcast signaling packet in the form of radio frequency signals of the physical layer.

(5) IQ sampling, wherein an antenna array positioned in a Bluetooth base station is responsible for execution and is realized under the coordination of a radio frequency switch and a BLE controller.

(6) And calculating an angle, wherein a storage unit of the Bluetooth base station stores the phase difference and the calculated arrival angle, an operation unit calculates the arrival angle based on the phase difference information, and a correlation algorithm for calculating the arrival angle is also stored in the storage unit.

(7) And filtering processing, namely a filtering processing structure carried by the Bluetooth base station and positioned on a physical layer.

(8) And displaying the GUI, wherein the GUI is a Graphical User Interface (GUI) and is used for displaying the positioning result and displaying the measurement angle by taking the degree as a unit.

In an embodiment of the present invention, a bluetooth base station structurally includes an antenna array, a radio frequency switch, a BLE controller, and a bluetooth protocol stack, wherein: the type of the antenna array is one or more of a uniform linear array, a uniform linear rectangular array or a uniform linear circular array; the radio frequency switch is used for switching the antenna mode; the BLE controller is used for controlling signal transmission and reception of the Bluetooth module, and firmware operated by the BLE controller supports an air transmission protocol; the bluetooth protocol stack contains supported profiles and a set of communications or events that interact with the bluetooth controller.

Fig. 10 is a block diagram of a transmitter, a wireless channel model and a receiver in the BLE standard according to an embodiment of the present invention, where a left dotted frame is a transmitter portion, a right dotted frame is a receiver portion, and the middle h (t, τ) and n (t) are wireless channel models. In the embodiment of the present invention, as shown in fig. 9, the BLE bluetooth module selected by the bluetooth terminal and the bluetooth base station supports 40 channels with an interval of 2MHz, including 37 data channels for data transmission and 3 advertisement channels, for the device to publish its presence before initiating a connection. To prevent interference within BLE channels, BLE uses a Frequency Hopping (FH) transmission method to switch carrier frequencies between all data channels.

Fig. 11 is a schematic diagram of an arrival angle positioning method in an embodiment of the present invention, where the step of calculating a positioning result of a bluetooth terminal at a current time based on a geometric relationship between multiple arrival angles and a bluetooth base station position coordinate includes: and assigning weights to each arrival angle by a positioning platform, carrying out Taylor expansion and least square iteration on the positioning platform based on the arrival angles, the position coordinates of the Bluetooth base station and the weights of the arrival angles, and linking the positioning results at different historical moments (especially in a dynamic scene) to obtain an optimal positioning result with least squares, wherein the weights of the arrival angles are inversely proportional to the distances between the corresponding Bluetooth base station and the Bluetooth terminal. The actual calculation process is explained below in conjunction with the formula.

In the embodiment of the present invention, the arrival angles (also called incident angles) of two base stations are θ ₁ And theta ₂ The incident angle direction forms the intersection of straight lines with each base station as a starting point, i.e.Is the location of the bluetooth terminal (MS). Let X be (X, y) as the position coordinate of the bluetooth terminal, and S be the position coordinate of n bluetooth Base Stations (BS) _i ＝(x _i ,y _i ) I is 1,2, … n. According to geometric knowledge

Deformation y-xtan θ _i ＝y _i -x _i tanθ _i ，θ _i Writing the arrival angle of the ith Bluetooth base station and the Bluetooth terminal into a matrix form

CX＝Y (2)

Wherein the content of the first and second substances,

and (3) obtaining rough Bluetooth terminal position coordinates according to Taylor expansion and least square iterative calculation:

X＝(C ^T C) ^-1 C ^T Y (6)

it should be noted that, the position coordinate is obtained by solving based on the geometric relationship based on the position coordinate and the arrival angle of the bluetooth base station, the position coordinate can be obtained by solving together two angles, multiple angles, or multiple data to perform taylor expansion and least square iteration together, so as to obtain the least square optimum of multiple groups of data, and theoretically, the larger the angle is, the more stable the angle is, and the more accurate the angle is.

Fig. 12 is a schematic diagram of an angle error correction method in an embodiment of the present invention, which is used to remove some arrival angles that have a large influence on the positioning result error, so as to optimize the positioning result. In an embodiment of the present invention, after the step of calculating the positioning result of the bluetooth terminal at the current time based on the geometric relationship between the multiple angles of arrival and the position coordinates of the bluetooth base station, the method further includes the steps of: and executing an arrival angle abnormity determination step based on the geometric relationship among the arrival angles, the positioning results and the position coordinates of the Bluetooth base stations, determining that the arrival angle is abnormal if the calculated Bluetooth terminal is positioned on the connecting line of the two Bluetooth base stations, removing the arrival angle corresponding to any one of the two Bluetooth base stations, and calculating the positioning results of the Bluetooth terminal at the current moment based on the geometric relationship among the multiple arrival angles and the position coordinates of the Bluetooth base stations.

As the distance between the terminal and the base station increases, the smaller angle jitter causes larger jitter of the positioning position, and larger errors are brought, so that the angle errors are corrected by introducing weight values related to the distance. Wherein bs (base station) represents a bluetooth base station, MS represents a real position of a bluetooth terminal assuming that a measurement value of an angle of arrival has an angle deviation of Δ θ, wherein MS1 and MS2 are real positions of a first bluetooth terminal and a second bluetooth terminal, respectively, and MS 'represents a positioning result, wherein MS' ₁ And MS' ₂ The positioning results of the first Bluetooth terminal and the second Bluetooth terminal are respectively, and r represents the real distance between the terminal and the base station, wherein r ₁ And r ₂ The actual distances between the first bluetooth terminal and the base station and the actual distances between the second bluetooth terminal and the base station are respectively. r 'represents the distance between the base station and the positioning result, wherein r' ₁ And r' ₂ The distance between the Bluetooth base station and the positioning results of the first Bluetooth terminal and the second Bluetooth terminal is shown, delta r represents the positioning error, and delta r represents the positioning error ₁ And Δ r ₂ The positioning error of the first Bluetooth terminal and the second Bluetooth terminal from the Bluetooth base station.

As shown in fig. 12, it can be seen that as the distance increases, Δ r increases, so for measurement angles with longer distances, less weight should be given, and the positioning error is linearly proportional to the distance, expressed as the following equation:

first based on the common min in FIG. 10Two-multiplication is used for solving rough Bluetooth terminal position coordinate X ═ X, y] ^T Then, the rough distance r from the terminal to each base station is obtained _n ＝||X-X _n If the distance w of the nth Bluetooth base station of the corresponding Bluetooth terminal is less than the weight w of the distance of the nth Bluetooth base station of the corresponding Bluetooth terminal _n Comprises the following steps:

wherein σ _n Weight w as standard deviation of angle of arrival _n As standard deviation sigma of angle of arrival _n The reciprocal of (c).

In another embodiment of the present invention, the weight may also take the following values:

the value of the weight does not consider the influence of the distance between the Bluetooth terminal and the Bluetooth base station on the weight.

Based on the introduced distance-dependent weights, a more accurate taylor least squares iteration is again performed using taylor expansion and the weights found above, based on the coarse bluetooth coordinates given by the general least squares method shown in fig. 10. The specific process is as follows:

(1) the N base station measurements are:

wherein S _i ＝(x _i ,y _i ) Where i is 1,2, … n is the ith bluetooth base station position coordinate, and X is the rough bluetooth terminal position coordinate X obtained as [ X, y ═ X] ^T ，Δθ ₁ ,Δθ ₂ ,…，Δθ _n The angle deviations are respectively contained in the measured values of the arrival angles of the n Bluetooth base stations and the Bluetooth terminal.

(2) According to Taylor least square iteration, in the j iteration, the solution of the j iteration is (X, y), and the solution of the j-1 iteration is X _j ＝(x _j-1 ,y _j-1 ) In (x) _j-1 ,y _j-1 ) And (4) performing Taylor expansion in the step (1) to reserve a first-order term, omitting other high-order terms and obtaining linearization treatment. Take the nth term in (1) as an example:

(3) the final equation (11) can be converted into an approximate linear equation set G Δ X ═ B, and G, Δ X, B are the n equations in step (2) written in matrix form, where:

(4) introducing weight to obtain delta X ═ G ^T W ^T WG) ^-1 G ^T W ^T WB，

(5) The result of the jth iteration is X _j ＝X _j-1 + Δ X, checking whether Δ X meets the precision requirement, if so, stopping iteration, and the final result is X _j Otherwise, is X _j And (4) repeatedly executing the steps (3) and (4) as a starting value of the j +1 th iteration until the precision of the delta X is reached.

Fig. 13 is a flow chart of positioning processing in an embodiment of the present invention, where the bluetooth angle of arrival positioning system mainly includes a bluetooth base station with an antenna array, a bluetooth terminal, a switch, and a positioning platform (i.e., a server, a PC). The Bluetooth base station is divided into a main node Bluetooth base station and a passive node Bluetooth base station, and angle measurement data, namely the angle of arrival, are concentrated to the switch through UART serial ports respectively. The switch then aggregates all the positioning data logs such as angle information to the same server (PC). The bluetooth terminal is the slave node in the notion of node management, is the equipment that needs to be fixed a position, only needs through portable power source power supply alright normal operating, and specific flow is as follows:

(1) when the Bluetooth arrival angle positioning system starts to work, a Bluetooth base station main node in a base station firstly scans a Bluetooth terminal and automatically establishes connection with the Bluetooth terminal through a Bluetooth protocol stack, and the Bluetooth terminal starts to send a Bluetooth broadcast signaling packet containing CTE positioning information to the Bluetooth base station main node at the moment.

(2) And the Bluetooth base station master node and the Bluetooth base station passive node receive a Bluetooth broadcast signaling packet containing CTE positioning information sent by a Bluetooth terminal.

(3) The Bluetooth base station main node and the Bluetooth base station passive node execute IQ sampling: carrying out IQ sampling by switching different array elements in the antenna array through a radio frequency switch according to a time slot which is in line with the Bluetooth 5.1 protocol after the data packet, and storing the result in a radio frequency memory of a main node chip; meanwhile, a Bluetooth base station passive node in the base station runs a Bluetooth protocol stack which is the same as that of a Bluetooth base station main node, but can monitor a link between the Bluetooth base station main node and a Bluetooth terminal under the condition of not establishing connection with the Bluetooth terminal, and IQ sampling is carried out through switching of an antenna array.

(4) The content of IQ sampling is phase difference, and the Bluetooth base station converts the phase into an arrival angle: the singlechip programs of the main node and the passive node of the Bluetooth base station comprise an algorithm for converting IQ samples into angles, and the finally calculated angles are collected into the same server (PC) through a UART serial port and a switch.

(5) And running a filtering and scene judging algorithm on the PC, if the static scene is judged, executing a multipoint average filtering algorithm to perform positioning settlement, if the dynamic scene is judged, executing an extended Kalman filtering algorithm to perform positioning settlement, and displaying a final positioning result through a GUI program. By aiming at different static and dynamic filtering modes, a smoother and low-error base station measurement angle is obtained, and then positioning settlement is carried out to obtain a more accurate positioning result.

In an embodiment of the present invention, the step of determining whether the motion scene of the bluetooth terminal is a dynamic scene or a static scene based on the positioning results of the current time and the plurality of historical times includes: calculating Euclidean distances between the positioning result at the current moment and the positioning results at a plurality of historical moments, and comparing the Euclidean distances with the positioning error acceptance values; if the Euclidean distances between the positioning result at the current moment and the positioning results at the multiple historical moments are larger than the positioning error acceptance value, determining that the scene is a dynamic scene; if the root mean square error is smaller than the positioning error acceptance value, judging as a static scene; the positioning error acceptance value is a root mean square error measured by a positioning system experiment or an initial value directly set by people. Here, the concept of the positioning error tolerance value is equivalent to the concept of the positioning error threshold, and when the root mean square error is greater than the positioning error threshold, it is determined as a dynamic scene, and when the root mean square error is less than the positioning error threshold, it is determined as a static scene.

Further, in an embodiment of the present invention, the initial value and the later period of the positioning error tolerance value that are manually and directly set can be corrected and updated according to the positioning result, and the scene where the positioning system is located and the moving target where the bluetooth terminal is located are combined.

The step of judging whether the motion scene of the Bluetooth terminal is a dynamic scene or a static scene specifically comprises the following steps: and (3) solving the Euclidean distance between the current position and the positions at the first two moments, comparing the Euclidean distance with Root Mean Square Error (RMSE) measured by equipment experiments, judging that the Bluetooth terminal moves when the absolute value of X (k) and X (k-2) is larger than the Root Mean Square Error, and judging that the Bluetooth terminal is static when the absolute value of X (k) and X (k-2) are the coordinates of the position of the Bluetooth terminal at the kth moment and the kth-2 moment. For example: when a person is still, the device with the Bluetooth terminal is within 10 meters of the Bluetooth base station, and under the condition of no non-line-of-sight interference, the positioning root mean square error is within 1m under the condition of 96%. And the normal adult walking speed is 1m/s to 1.5m/s, and if a person holding the arrival angle positioning Bluetooth terminal moves, the person can obviously move within two seconds.

For the different positioning settlement strategies respectively adopted in the static and dynamic scenarios, fig. 14 is a schematic diagram of a static multi-measurement average filtering algorithm in an embodiment of the present invention, where M is the total number of measurements, and since it is determined that a static scenario is present, multiple measurements may be averaged at different times of the same base station to obtain a more stable result. X (k), X (k-1), …, X (k-M +1) is the static coordinate of each measurement, and based on the results of M measurements, the static multi-measurement average filtering calculation formula is:

in the embodiment of the present invention, for a multipoint average filtering algorithm in a static scene, the step of optimizing a positioning result by a positioning platform based on the multipoint average filtering algorithm includes: and calculating the average value of the positioning result at the current moment and the positioning results at a plurality of historical moments. Considering that too much data storage will occupy too much memory, the upper storage limit may be set to M1000. The whole static average filtering is equivalent to sliding window filtering of 1000 measured angle sample values. And substituting the angle measurement value subjected to the moving average filtering into a least square method for solving. Specifically, assuming that the total number of arrival angles of the bluetooth terminal from the bluetooth base station determined to be in the static scene to a certain base station at the current time is m, then:

when the static time is long, the obtained multiple least square solutions are subjected to average filtering shown in fig. 14, the centroid coordinates of the multiple least square solutions are obtained, and the static Bluetooth positioning accuracy can reach the decimeter level.

Aiming at a dynamic scene, a Kalman filtering technology is used to obtain a more stable positioning result, and the Kalman system state equation is as follows:

L(k)＝AL(k-1)+W(k-1) (18)

wherein, L represents a state variable and comprises a terminal abscissa, an ordinate, a speed in the abscissa direction, a speed in the ordinate direction, k represents a time sequence, W represents a process noise vector, and A represents a state transition matrix. Δ T is the sampling period, and the process noise vector is zero-mean normal gaussian white noise, i.e.:

E(V)＝[0,0,0,0] ^T (22)

E(W)＝[0,0,0,0] ^T (23)

Cov(W)＝Cov(WW ^T )＝Q (24)

the system measurement equation:

Z(k)＝h(k,L(k))+V(k) (25)

wherein the content of the first and second substances,

z (k) is a column vector consisting of N incident angles measured by N base stations. h (l (k)) is a non-linear mapping of known base stations and unknown terminals to true angles of incidence. V (k) represents the measurement noise vector, which is also a normal white noise with a mean value of zero. Namely:

E(V)＝[0 ₁ … 0 _N ] ^T (28)

Cov(V)＝Cov(VV ^T )＝R (29)

the observation equation is nonlinear, so the observation equation needs to be linearized, and the linearized system observation matrix h (k) is replaced by a jacobian matrix of h (l (k)). The Jacobian matrix H (k) is obtained by the following process:

wherein the content of the first and second substances,

then

In the embodiment of the invention, a positioning resolving strategy under a dynamic scene, namely an extended Kalman filtering algorithm, is as follows:

initialization, initial state L (0), covariance matrix P (0)

State prediction L (k | k-1) ═ AL (k-1)

Observation prediction Z (k | k-1) ═ h (L (k | k-1))

Relational observation matrix

Covariance prediction P (k | k-1) ═ AP (k-1) a ^T +Q

Update kalman gain k (k) ═ P (k | k-1) H ^T (k)(H(k)P(k|k-1)H ^T (k)+R) ^-1

Obtaining a real-time measurement Z (k)

Update state L (k) ═ L (k | k-1) + L (k) ((Z) (k) — Z (k | k-1))

Updating covariance matrix p (k) ═ (I) _n -K(k)H(k))P(k|k-1)

The above is a calculation period of the system EKF, and the processing of the nonlinear system by the EKF at each time is a process of continuous loop iteration of the calculation period. Wherein, I _n Refers to an n-order identity matrix. n is equal to the number of state variables. k refers to the k-th time instant.

The invention provides an extended Kalman filtering for carrying out scene division according to prior information such as relative layout between base stations, relative positions of the base stations and a terminal, motion states of the terminal at historical moments, surrounding environments (such as a wall and other major reflecting surfaces) and the like, and effectively solves the problems of low positioning precision and poor stability in different environments, states and regions.

The complicated environmental factors around the above steps (1) to (8) may cause the radio waves to be scattered, refracted or reflected, and Non-Line-Of-Sight (NLOS) propagation occurs. The non-line-of-sight propagation causes a large deviation in the propagation direction of the electromagnetic waves, and causes a large deviation in the measured value (i.e., the arrival angle) received by the base station end, so that the actual angle between the transmitting end and the receiving end cannot be correctly reflected. If the abnormal angle values containing the non-line-of-sight errors are not processed, Kalman filtering has memory, and subsequent positioning values are subjected to accumulated deviation. If the effects of these measurements, including large errors, can be eliminated, the NLOS error can be largely eliminated.

The method is mainly applied to multi-base station Bluetooth arrival angle positioning, has enough base station arrival angle measurement values, and adds judgment sentences in iteration of the extended Kalman filter in order to not change the structure of the extended Kalman filter too much. And setting an extended Kalman gain through a judgment statement to discard an angle of arrival value containing an NLOS error.

In the extended kalman filter algorithm step (7), δ ═ z (k) — h (L (k | k-1)) is calculated, and if δ is greater than a threshold value, the kalman gain is set to 0, and then the state estimation value is made equal to the state prediction value. If delta is smaller than the threshold value, the error of the measurement value at the moment is indicated to be within an acceptable range, and the extended Kalman gain value is kept unchanged to obtain an estimated value. Namely:

the selection of the threshold value delta is the key of the algorithm, multiple times of experimental data acquisition are needed, overlarge NLOS errors cannot be effectively filtered, and too small threshold values can screen excessive measured values. Through a large number of experiments, 3 times of sample variance is generally selected as a threshold value, and the measured value of the arrival angle containing NLOS errors can be filtered well.

Fig. 15 is a schematic diagram of a method for determining an abnormal location of a bluetooth terminal according to an embodiment of the present invention, which determines whether the location of the terminal is in a special area according to map information and a base station layout after obtaining a positioning result. When the positioning terminal is located in the vicinity of the connection line between the two base stations, even a slight angular jump may cause a sharp jump in the final positioning position. When the terminal is far from the base station, a slight angle jump may also cause a drastic change in location. Therefore, the invention deletes the arrival angle of the corresponding Bluetooth base station under the condition that the Bluetooth terminal is positioned between the two base stations. BS1, BS2, BS3, and BS4 in fig. 15 are positions of four bluetooth base stations, where point B is a real position of the bluetooth terminal, and point A, C, D is a deviated position located after a deviation occurs in a measurement angle of the bluetooth base station BS1 (assuming that there is no deviation in other measurement angles). It can also be seen from the observation that point D is farther from the actual location point B of the bluetooth terminal than points a and C. Therefore, when the bluetooth terminal is located on the connection line of the two bluetooth base stations or in the area near the connection line, the two bluetooth base stations measure the arrival angles, which have a large influence on the positioning result, and the arrival angles of the two bluetooth base stations can be discarded when enough arrival angles are available.

The above is a schematic diagram of a method for judging the position abnormality of the bluetooth terminal, and the specific process is as follows: after obtaining a more refined positioning result based on the arrival angles of all available Bluetooth base stations, according to the positioning result and the Bluetooth base stationsAnd (4) judging whether the terminal is in a special area, if the terminal is in a gray area similar to the frame of the upper graph, discarding the measurement value with larger influence, and recalculating to obtain the discarded terminal position. And comparing the residual errors before and after discarding, and selecting the terminal position with small residual error. The judgment basis is the distance from the refined terminal positioning result to the connection line of any two base stations, and the threshold value is related to the connection line distance between the base stations and can be set according to the actual effect. Let two bluetooth base station coordinates be BS ₁ ＝(x ₁ ,y ₁ )，BS ₂ ＝(x ₂ ,y ₂ ) The coordinate of the positioning result after fine positioning is MS ═ x, y. Let vector r ₁ ＝(x-x ₁ ,y-y ₁ ) Sum vector r ₁₂ ＝(x ₂ -x ₁ ,y ₂ -y ₁ ). The connection distance d from the Bluetooth terminal to the two Bluetooth base stations is as follows:

d＝r ₁ sinΘ (34)

therefore, the vector r is calculated ₁ And r ₁₂ The included angle Θ is:

and judging whether the Bluetooth terminal is in a connecting line of the two Bluetooth base stations or a nearby area through the included angle theta, if the included angle is smaller than a preset angle value, discarding the included angle, and if the included angle is larger than the preset angle value, reserving the included angle. The setting of the included angle can be selected according to the actual situation, and is determined according to the precision required by positioning and the total number of the base stations.

Assuming that M base stations are provided, the number of the areas needing to be judged is

In practice M is generally not too large, so that when there are enough measured angles to allow rejection, a basic positioning must be guaranteed.

After the treatment, a positioning result with high precision and high stability is finally obtained.

Correspondingly to the above method, the present invention further provides a system for implementing the method for positioning the angle of arrival of a bluetooth terminal according to any embodiment of the present invention, the system is as shown in fig. 2, and includes a bluetooth terminal, a positioning platform, and a plurality of bluetooth base stations, where the bluetooth base stations include a master node bluetooth base station and a passive node bluetooth base station, where:

In an embodiment of the present invention, the positioning platform includes a computer device, the computer device includes a processor and a memory, the memory stores computer instructions, the processor is configured to execute the computer instructions stored in the memory, and when the computer instructions are executed by the processor, the steps of calculating the coordinates of the bluetooth terminal position, correcting the angle error, and determining the position anomaly of the bluetooth terminal based on the angle-of-arrival information in the present invention are implemented.

Embodiments of the present invention further provide a computer-readable storage medium, on which a computer program is stored, where the computer program is executed by a processor to implement the steps performed by the foregoing edge positioning platform. The computer readable storage medium may be a tangible storage medium such as Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, floppy disks, hard disks, removable storage disks, CD-ROMs, or any other form of storage medium known in the art.

Those of ordinary skill in the art will appreciate that the various illustrative components, systems, and methods described in connection with the embodiments disclosed herein may be implemented as hardware, software, or combinations of both. Whether this is done in hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments may be stored in a machine-readable medium or transmitted by a data signal carried in a carrier wave over a transmission medium or a communication link.

It is to be understood that the invention is not limited to the specific arrangements and instrumentality described above and shown in the drawings. A detailed description of known methods is omitted herein for the sake of brevity. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present invention are not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications and additions or change the order between the steps after comprehending the spirit of the present invention.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments in the present invention.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made to the embodiment of the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An angle-of-arrival positioning method for a bluetooth terminal, the method comprising the steps of:

the master node Bluetooth base station establishes link connection with a Bluetooth terminal and instructs the Bluetooth terminal to send a Bluetooth broadcast signaling packet;

a master node Bluetooth base station and a plurality of passive node Bluetooth base stations receive Bluetooth broadcast signaling packets sent by the Bluetooth terminal in a broadcast communication mode;

the master node Bluetooth base station and the plurality of passive node Bluetooth base stations calculate arrival angles based on phase differences between Bluetooth broadcast signaling packets received by different antennas in respective antenna arrays and the Bluetooth broadcast signaling packets, and send the obtained arrival angles to a positioning platform;

the positioning platform receives a plurality of arrival angles, and calculates the positioning result of the Bluetooth terminal at the current moment based on the geometric relationship between the arrival angles and the position coordinates of the Bluetooth base station;

determining whether a motion scene of the Bluetooth terminal is a dynamic scene or a static scene based on a positioning result of the Bluetooth terminal at the current moment and a positioning result of a plurality of historical moments, and if the motion scene is determined to be the dynamic scene, optimizing the positioning result of the Bluetooth terminal at the current moment by the positioning platform based on an extended Kalman filtering algorithm; and if the situation is determined to be a static scene, the positioning platform optimizes the positioning result of the Bluetooth terminal at the current moment based on a multipoint average filtering algorithm.

2. The arrival angle positioning method of the bluetooth terminal as claimed in claim 1, wherein the arrival angles sent by the master node bluetooth base station and the plurality of passive node bluetooth base stations are summarized to the positioning platform by a UART serial port and a switch.

3. The method of claim 1, wherein the bluetooth broadcast signaling packet contains CTE location information.

4. The method of claim 1, wherein adjacent antennas in the antenna array are separated from each other by a predetermined distance, and the predetermined distance is fixed and less than one-half of the wavelength of the communication carrier;

the angle of arrival is expressed by the formula

5. The method of claim 1, wherein the step of calculating the positioning result of the current time of the bluetooth terminal based on the geometric relationship between the angles of arrival and the position coordinates of the bluetooth base station comprises:

and the positioning platform gives a weight to each arrival angle, and the positioning platform performs Taylor expansion and least square iteration on the basis of a plurality of arrival angles, the position coordinates of the Bluetooth base station and the weights of the arrival angles to obtain a positioning result with least square optimization, wherein the weight of each arrival angle is inversely proportional to the distance between the corresponding Bluetooth base station and the Bluetooth terminal.

6. The method of claim 1, wherein the step of calculating the positioning result of the current time of the bluetooth terminal based on the geometric relationship between the angles of arrival and the position coordinates of the bluetooth base station further comprises:

and executing an arrival angle abnormity judgment step based on the geometric relationship among the arrival angle, the positioning result and the position coordinates of the Bluetooth base station, judging that the arrival angle is abnormal if the calculated Bluetooth terminal is positioned on a connecting line of the two Bluetooth base stations, removing the arrival angle corresponding to any one of the two Bluetooth base stations, and calculating the positioning result of the Bluetooth terminal at the current moment based on the geometric relationship among the multiple arrival angles and the position coordinates of the Bluetooth base stations.

7. The method of claim 1, wherein the step of determining whether the motion scene of the bluetooth terminal is a dynamic scene or a static scene based on the positioning results at the current time and the plurality of historical times comprises:

calculating Euclidean distances between the positioning result at the current moment and the positioning results at a plurality of historical moments, and comparing the Euclidean distances with the positioning error acceptance values;

if the Euclidean distance between the positioning result at the current moment and the positioning results at a plurality of historical moments is larger than the positioning error acceptance value, determining that the scene is a dynamic scene;

if the root mean square error is smaller than the positioning error admission value, judging as a static scene;

the positioning error acceptance value is a root mean square error measured by a positioning system experiment or an initial value directly set manually.

8. The method of claim 1, wherein the step of optimizing the positioning result by the positioning platform based on a multi-point average filtering algorithm comprises: and calculating the average value of the positioning result at the current moment and the positioning results at a plurality of historical moments.

9. A system for implementing the angle-of-arrival positioning method for the bluetooth terminal as claimed in any one of claims 1 to 8, comprising a bluetooth terminal, a positioning platform and a plurality of bluetooth base stations, wherein the bluetooth base stations comprise a master node bluetooth base station and a passive node bluetooth base station, and wherein:

the master node Bluetooth base station is used for establishing link connection with a Bluetooth terminal, instructing the Bluetooth terminal to send a Bluetooth broadcast signaling packet and receiving the Bluetooth broadcast signaling packet sent by the Bluetooth terminal in a broadcast communication mode;

the plurality of passive node Bluetooth base stations also receive Bluetooth broadcast signaling packets sent by the Bluetooth terminal in a broadcast communication mode under the condition that link connection is not established between the plurality of passive node Bluetooth base stations and the Bluetooth terminal;

the master node Bluetooth base station and the plurality of passive node Bluetooth base stations respectively comprise antenna arrays, phase differences exist among Bluetooth broadcast signaling packets received by different antennas in the antenna arrays, the master node Bluetooth base station and the plurality of passive node Bluetooth base stations calculate arrival angles based on the phase differences and the Bluetooth broadcast signaling packets, and the obtained arrival angles are forwarded to the positioning platform;

10. The system according to claim 9, wherein the bluetooth base station comprises an antenna array, a radio frequency switch, a BLE controller, and a bluetooth protocol stack, wherein:

the type of the antenna array is one or more of a uniform linear array, a uniform linear rectangular array or a uniform linear circular array;

the radio frequency switch is used for switching an antenna mode;

the BLE controller is used for controlling signal transmission and reception of the Bluetooth module, and firmware operated by the BLE controller supports an over-the-air transmission protocol;

the bluetooth protocol stack contains supported profiles and a set of communications or events that interact with the bluetooth controller.