CN114760686A - Asset positioning method and system based on BLE Mesh network - Google Patents

Abstract

The invention belongs to the technical field of indoor positioning, and in particular relates to an asset positioning method and system based on a BLE Mesh network; the method includes: constructing an asset positioning system based on a BLE Mesh network; a gateway periodically sends a heartbeat packet to a node; the node scans the heartbeat packet to obtain the broadcast address and signal strength value of the neighbor node; when the number of signal strength samples reaches the threshold, filter all the signal strength samples; obtain the mean value of the signal strength corresponding to each neighbor node; the node periodically packs the neighbor node information; The packaged information is sent back to the background positioning server through the gateway; the background positioning server performs a relative positioning calculation on the asset according to the packaged information, and obtains the specific position of the asset; the invention greatly reduces the construction cost of the positioning system and reduces the preliminary construction at the same time. The complexity of the system improves the flexibility of system deployment.

Description

A method and system for asset location based on BLE Mesh network

technical field

The invention belongs to the technical field of indoor positioning, and in particular relates to an asset positioning method and system based on a BLE Mesh network.

Background technique

Because the early low-power Bluetooth can only achieve "point-to-point" communication, does not support Mesh networking, and cannot carry out "many-to-many" communication, the Bluetooth positioning methods commonly used in current commercial positioning products include range detection-based positioning, There are three types of positioning based on signal strength and positioning based on angle.

The positioning system based on range detection is realized by using the feature that the signal coverage range of Bluetooth devices of different power levels is different. The asset management tag is used to send signals with information such as its own MAC address, and the Bluetooth gateway is used to read and Parse the information sent by the asset management tag. If the information can be received, it means that the asset is in the room where the gateway is located. This method can only identify the existence of the asset in the space, but cannot detect the location of the asset.

The signal strength-based positioning system uses the received signal strength as a feature value for positioning. The positioning accuracy of this method is in the range of 1 to 10 m, which depends on the deployment density of anchor nodes and the optimization method used. Generally, it can be divided into two categories: signal model positioning method and field strength fingerprint matching method. The signal model positioning method converts the received RSSI value into a distance through a formula, and uses a ranging-based algorithm to locate the target. This kind of method usually needs to cooperate with a filtering algorithm or an iterative algorithm to improve the positioning accuracy. The field intensity fingerprint matching method is to directly compare the received RSSI value with the fingerprint database established in the previous stage to obtain the positioning coordinates. This kind of method does not need to solve, but the offline fingerprint collection in the early stage requires a lot of time and manpower cost.

The angle-based positioning system obtains the phase difference of the signal between different antennas through the antenna array in the anchor node, so as to obtain the angle information of the incoming wave direction, and then uses the triangulation positioning algorithm to realize the positioning. Compared with the positioning method based on signal strength, the positioning accuracy is greatly improved, and it can even reach the sub-meter level. However, this type of positioning method requires high hardware and needs to be equipped with an antenna array, which is not only costly but also complicated in data processing.

The asset positioning system based on range detection can only achieve "room-level" positioning, and its accuracy is not enough to meet the needs of current asset positioning. Although the positioning accuracy of the positioning system based on signal strength and angle has been improved, the angle-based positioning system even far exceeds the meter-level positioning requirements of asset positioning, but the current system structure of both requires the deployment of a large number of positioning base stations in the early stage of construction. As an anchor node, the failure of a single positioning base station will inevitably affect the asset positioning accuracy within its coverage area, and the data return needs to be solved by adding a WIFI module or laying a network cable, which further increases the construction cost of the system. The pre-engineering implementation is complicated.

To sum up, there is an urgent need for an asset positioning method that can meet the requirements of asset positioning accuracy, while greatly reducing the cost and making pre-construction more flexible and convenient.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention proposes a method and system for locating assets based on BLE Mesh network. The method includes:

S1: Use asset tags and gateways for networking, and obtain an asset positioning system that uses BLE Mesh network for communication;

S2: The gateway periodically sends heartbeat packets to all nodes in the Mesh network; wherein, different heartbeat packets have different sequence numbers;

S3: All Mesh nodes in the Mesh network scan the heartbeat packet to obtain the broadcast address and signal strength value of the neighbor node; the Mesh node judges whether it has received the heartbeat packet of the sequence number for the first time, and if it is the first time, according to the heartbeat packet Obtain the shortest hop distance value from the node to the gateway and forward the heartbeat packet to the neighbor node, otherwise, discard the heartbeat packet;

S4: Set the threshold of the number of signal strength samples, and the node counts the number of scanned signal strength samples; if the number of signal strength samples reaches the threshold, all signal strength samples are processed to obtain the mean value of signal strength corresponding to each neighbor node;

S5: All Mesh nodes in the Mesh network regularly package the broadcast address and average signal strength of their neighbor nodes and the node's own power information; the packaged information is sent back to the background positioning server through the gateway;

S6: The background positioning server performs a relative positioning solution on the asset according to the packaged information to obtain the specific position of the asset.

Preferably, the process of obtaining the broadcast address and signal strength value of the neighbor node includes: the Mesh node scans the broadcast heartbeat packet, and extracts the broadcast address of the neighbor node and the signal strength value of the packet from the metadata of the broadcast packet.

Preferably, judging whether the node has received the heartbeat packet of the sequence number for the first time includes: if there is no information identical to the sequence number and source address of the heartbeat packet in the cache of the Mesh node, then judging that the heartbeat packet is received for the first time The source address and sequence number of the heartbeat packet are stored in the cache; if there is information matching the sequence number and source address of the heartbeat packet in the cache of the Mesh node, it is determined that the heartbeat packet is not received for the first time.

Preferably, the process of processing all signal strength samples includes: performing Gaussian filtering on all signal strength samples to obtain signal strength samples after removing outliers; averaging the signal strength samples after removing outliers to obtain each neighbor node The corresponding mean signal strength.

Preferably, the process of sending the packaged information back to the background location server includes: each Mesh node sets a TTL value, and forwards the packaged information to a neighbor node; the neighbor node determines whether it is the destination address of the information, and if so, receives and processes it The packaged information, otherwise, determine whether the shortest hop distance from itself to the gateway is less than or equal to the TTL value; if the shortest hop distance from itself to the gateway is less than or equal to the TTL value, the TTL value is subtracted by 1 and then relayed and forwarded. Otherwise, the packed information is discarded.

Preferably, the TTL value set by each Mesh node is the shortest hop distance value from itself to the gateway or the shortest hop distance value from itself to the gateway plus 1.

Preferably, performing the relative positioning solution on the asset includes: performing the relative positioning solution on the asset by using a combination of MDS and a trilateral positioning algorithm.

Further, using the combination of MDS and trilateral positioning algorithm to solve the relative positioning of assets includes: setting a threshold for the maximum number of fully connected nodes according to the number of asset tags and the actual deployment environment; when the returned data cannot be When the threshold of the maximum number of fully connected nodes is met, the Euclidean ranging method is used to complete the distance information between the missing nodes within two hops outside the current maximum fully connected node.

An asset positioning system based on BLE Mesh network, including: monitoring terminal, background positioning server, gateway, Mesh node;

Described Mesh node is used for obtaining the broadcast address and signal strength mean value of neighbor node and packing neighbor node information;

The gateway is used to periodically send heartbeat packets, receive the neighbor node information returned by the Mesh node, and send the neighbor node information to the background server;

The background positioning server is used to calculate the position of the Mesh node according to the neighbor node information, and obtain the specific position of the Mesh node;

The monitoring terminal is used to display the specific location of the Mesh node.

The beneficial effects of the present invention are as follows: the present invention aims to solve the problems of the current asset positioning system, such as low positioning accuracy, high cost, and inflexible deployment. The present invention cancels the positioning base station, uses asset tags and gateways to build a BLE Mesh network, and uses BLE Mesh to build a BLE Mesh network. The characteristics of mutual communication between nodes in the network, combined with its heartbeat mechanism to achieve the information acquisition of the mutual distance between nodes, and the use of TTL processing mechanism to improve the reliability of data backhaul, and finally through the centralized positioning algorithm for assets. The positioning solution is obtained to obtain the positioning information. Compared with the existing positioning system based on signal strength/angle, the present invention eliminates the deployment of the positioning base station and transmits data through the BLE Mesh network, so that the positioning accuracy is higher, and the meter-level requirements for asset positioning can be reduced. The complexity of pre-construction improves the flexibility of system deployment. It has lower cost, convenient construction, good flexibility and certain engineering.

Description of drawings

Fig. 1 is the flow chart of the asset location method based on BLE Mesh network in the present invention;

2 is a schematic structural diagram of an existing positioning system based on range detection;

3 is a schematic structural diagram of an existing signal strength/angle-based positioning system;

FIG. 4 is a schematic structural diagram of an asset positioning system in the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The present invention proposes a method and system for locating assets based on BLE Mesh network, and the method includes:

The Mesh node obtains the broadcast address and the average signal strength of the neighbor nodes, and the Mesh node is the Bluetooth asset tag, which corresponds to the fixed assets one-to-one;

The Mesh node regularly packages neighbor node information and sends the packaged information back to the background positioning server; wherein, the neighbor node information includes the neighbor node's broadcast address and average signal strength, as well as the Mesh node's own power information;

The Mesh node determines the specific location according to the solution information of the background positioning server.

The structure of the existing positioning system based on range detection is shown in Figure 2. The Bluetooth tag in the figure is used to send signals with information such as its own MAC address, and the gateway is used to read and parse the information sent by the Bluetooth tag. The arrival information indicates that the asset is in the room where the gateway is located. This method can only identify the existence of the asset in the space, but cannot detect the location of the asset. The structure of the positioning system based on signal strength/angle is shown in Figure 3. The positioning system using this structure needs to deploy a large number of positioning base stations on the ceiling as anchor nodes in the early stage of construction. The failure of a single positioning base station will inevitably affect the coverage of the The accuracy of asset positioning and the return of data need to be solved by adding a WIFI module or laying a network cable, which further increases the construction cost of the system and complicated the implementation of the preliminary project.

The present invention also provides an asset positioning system based on the BLE Mesh network, comprising: a monitoring terminal, a background positioning server, a gateway, and a Mesh node;

Described Mesh node is used for obtaining the broadcast address and signal strength mean value of neighbor node and packing neighbor node information;

The gateway is used to periodically send heartbeat packets, receive the neighbor node information returned by the Mesh node, and send the neighbor node information to the background server;

The background positioning server is used to calculate the position of the Mesh node according to the neighbor node information, and obtain the specific position of the Mesh node;

The monitoring terminal is used to display the specific location of the Mesh node.

The process of a BLE Mesh network-based asset positioning method of the present invention is shown in Figure 1, and the specific process of asset positioning is as follows:

Build an asset location system based on BLE Mesh network. Specifically, use asset tags and gateways for networking to obtain an asset location system that utilizes BLE Mesh network for communication; the asset location system of the present invention is shown in Figure 4, which consists of Mesh nodes, The gateway, the positioning server and the monitoring terminal are composed. The Mesh node is the asset tag (Bluetooth tag). The positioning system realizes that each device in the positioning system can communicate with each other by building a BLE Mesh network with the Bluetooth tag and the gateway. Both Bluetooth tags and gateways after forming a mesh network can collect the signal strength value and broadcast address of adjacent nodes, and both have the relay function. The difference is that Bluetooth tags are battery-powered, and each tag corresponds to a unique asset information, while the gateway It is connected to the mains, and can communicate with the positioning server through the serial line; the positioning server can parse the information returned by the gateway and perform positioning calculation, and the monitoring terminal matches the positioning information calculated by the positioning server with the map, and intuitively render.

The gateway periodically sends a heartbeat packet with a TTL value of 127 to all nodes in the mesh network. The heartbeat packet can be relayed to any node in the network through other nodes. Among them, in order to prevent replay attacks, according to the BLE Mesh protocol , the heartbeat packet sent by the gateway each time has a different sequence number SEQ. SEQ is a field defined by the Mesh network. To prevent replay attacks, each message published is set to a unique sequence number.

Each Mesh node scans the heartbeat packet, specifically, the Mesh node scans the metadata in the broadcast packet, extracts the broadcast address of the neighbor node and the signal strength value RSSI of the packet from the metadata China; judges whether the node receives the sequence number for the first time. If the heartbeat packet is the first time, the shortest hop value from itself to the gateway is obtained according to the content of the TTL field in the heartbeat packet, and then the TTL value of the heartbeat packet is decremented by 1 and relayed and forwarded, otherwise, the heartbeat packet throw away. The Mesh node judges whether it receives the heartbeat packet of the sequence number for the first time, including: if the cache of the Mesh node does not have the same information as the sequence number and source address of the heartbeat packet, it is judged that it is the first time that the heartbeat packet is received and will be sent to the Mesh node. The source address and sequence number of the heartbeat packet are stored in the cache; if there is information matching the sequence number and source address of the heartbeat packet in the cache of the mesh node, it is determined that the heartbeat packet is not received for the first time.

Set the threshold of the number of signal strength samples, and the Mesh node counts the number of scanned signal strength samples; the threshold of the number of samples is set before the code is burned to the node. However, it is also necessary to comprehensively consider the memory size of the chip. Preferably, the threshold of the number of signal strength samples is set to 100; if the number of signal strength samples reaches the threshold, all signal strength samples are processed. The process of processing all signal strength samples is as follows: After receiving the RSSI samples that meet the threshold of the number of signal strength samples, Gaussian filtering is performed on these RSSI sample values at the node, and the data outliers caused by signal fluctuations are eliminated, and the signal strength samples after the outliers are eliminated are obtained. The signal strength samples of neighbor nodes after removing outliers are averaged to obtain the mean value of signal strength corresponding to each neighbor node.

All Mesh nodes in the Mesh network regularly package the broadcast address of each neighbor node collected in the previous stage, the average signal strength after filtering and the power information of the node itself; the packaged information is sent back to the background positioning server through the gateway; During the return process, each Mesh node sets the TTL value of the returned data (packaged information), and sets the destination address of the returned data as the unicast address of the gateway; preferably, the TTL value set by each Mesh node is itself. The shortest hop distance value to the gateway or the shortest hop distance value from itself to the gateway is increased by 1, and by setting the TTL to the shortest hop distance value from itself to the gateway plus 1, a certain margin is generated, thereby increasing the reliability of the returned data; The other nodes first determine whether they are the destination address of the information before relaying and forwarding the return data. If so, that is, when the node is a gateway, it will receive the return data and send the return data to the background location server through the serial line; Otherwise, judge whether the shortest hop distance from itself to the gateway is less than or equal to the TTL value set in the data to be relayed; if the shortest hop distance from itself to the gateway is less than or equal to the TTL value, then reduce the TTL value by 1 before relaying Forward, otherwise, discard the packaged information.

The above process ensures that the data is sent back toward the gateway, so as to avoid flooding the entire Mesh network with a large amount of redundant data, reduce message conflict and implosion, and improve the reliability of data reaching the location server.

The positioning server receives and calculates the relative positioning of the asset according to the packaged information. The specific process is as follows:

The positioning server can obtain the mutual distance information between the nodes according to the data sent back by each node; the relative positioning solution of the assets is carried out by the combination of MDS and the trilateral positioning algorithm; among them, the MDS positioning algorithm is implemented. The premise is that the nodes need to form a fully connected structure, that is, the distance between any two nodes is known. In order to ensure the final positioning accuracy, the present invention sets a threshold for the maximum number of fully connected nodes in combination with the number of asset tags and the actual deployment environment, so as to ensure that there are enough nodes that can pass the high-precision centralized positioning such as MDS. The algorithm realizes the initial positioning, and uses these nodes as the reference anchor nodes of the subsequent three-sided positioning algorithm; when the returned data itself cannot meet the threshold of the maximum number of fully connected nodes, the Euclidean ranging method is used to measure the peripheral nodes of the current maximum fully connected node. The distance information between the missing nodes within the two-hop range is completed. When the maximum number of fully connected nodes after completion reaches the set threshold, the above positioning algorithm can be solved. This method can improve the final asset. positioning accuracy.

Through the positioning solution, the specific location information of the asset can be obtained.

Compared with the existing positioning system based on range detection, the present invention realizes mutual communication by building a BLEMesh network between a Bluetooth tag and a gateway, and improves the positioning accuracy by means of the mutual distance information between nodes obtained thereby; In the existing positioning system based on signal strength/angle, the present invention greatly reduces the construction cost of the positioning system by canceling the deployment of the positioning base station and returning data through the BLE Mesh network, while reducing the complexity of the preliminary construction and improving the performance of the positioning system. flexibility in system deployment.

The above-mentioned embodiments further describe the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made to the present invention within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. an asset location method based on BLE Mesh network, is characterized in that, comprises: The gateway periodically sends heartbeat packets to all Mesh nodes, and the Mesh nodes forward the heartbeat packets to their neighbor nodes; The Mesh node receives the heartbeat packet forwarded by the neighbor node, and obtains the broadcast address and the average signal strength of the neighbor node; The Mesh node regularly packages neighbor node information and sends the packaged information back to the background positioning server; wherein, the neighbor node information includes the neighbor node's broadcast address and average signal strength, as well as the Mesh node's own power information; The Mesh node determines the specific location according to the solution information of the background positioning server; Mesh nodes are Bluetooth asset tags, which correspond one-to-one with fixed assets. 2. a kind of asset location method based on BLE Mesh network according to claim 1, is characterized in that, the signal strength mean value that Mesh node obtains neighbor node comprises: The Mesh node periodically scans the heartbeat packets sent from the gateway; wherein, in order to prevent replay attacks, according to the BLE mesh protocol, the heartbeat packets sent by the gateway each time have different sequence numbers; The Mesh node scans the heartbeat packet to obtain the broadcast address and signal strength value of the neighbor node; The Mesh node counts the number of signal strength samples, and when the number of signal strength samples reaches the threshold, the signal strength samples are processed to obtain the average signal strength. 3. a kind of asset location method based on BLE Mesh network according to claim 2, is characterized in that, the process of Mesh node scanning heartbeat packet comprises: The Mesh node scans the broadcast packet carrying the heartbeat data, and extracts the broadcast address of the neighbor node and the signal strength value of the heartbeat packet from the metadata of the broadcast packet; The Mesh node judges whether it is the first time to receive the heartbeat packet of the sequence number; If the judgment result is yes, obtain the shortest hop distance value from the Mesh node to the gateway according to the heartbeat packet and forward the heartbeat packet to the neighbor node; If the judgment result is no, the heartbeat packet is discarded. 4. a kind of asset location method based on BLE Mesh network according to claim 3, is characterized in that, the process that Mesh node judges whether to receive the heartbeat packet of this sequence number for the first time comprises: if there is no buffer in the cache of Mesh node. If the information is the same as the sequence number and source address of the heartbeat packet, it is judged that the heartbeat packet is received for the first time and the source address and sequence number of the heartbeat packet are stored in the cache; if there is a sequence of the heartbeat packet in the cache of the Mesh node If the number matches the source address, it is determined that the heartbeat packet is not received for the first time. 5. The method for locating assets based on BLE Mesh network according to claim 2, wherein the process of processing the signal strength samples comprises: performing Gaussian filtering on all the signal strength samples, and obtaining an abnormal value after removing the abnormal value. Signal strength samples; average the signal strength samples after removing outliers to obtain the mean value of signal strength corresponding to each neighbor node. 6. a kind of asset location method based on BLE Mesh network according to claim 1, is characterized in that, the process that the information after the package is sent back to the background location server comprises: each Mesh node is set TTL value, the information after the package is Forward to the neighbor node; the neighbor node judges whether it is the destination address of the information, and if so, receives and processes the packaged information, otherwise, the neighbor node judges whether the shortest hop distance from itself to the gateway is less than or equal to the TTL value; if it reaches the gateway If the shortest hop distance value is less than or equal to the TTL value, the TTL value is decremented by 1 and then relayed and forwarded; otherwise, the packaged information is discarded. 7. a kind of asset location method based on BLE Mesh network according to claim 6, is characterized in that, the TTL value that each Mesh node is set is the shortest hop distance value from itself to gateway or the shortest hop distance value from itself to gateway plus. 1. 8. An asset positioning system based on a BLE Mesh network, comprising: a monitoring terminal, a background positioning server, a gateway, and a Mesh node; Described Mesh node is used for obtaining the broadcast address and signal strength mean value of neighbor node and packing neighbor node information; The gateway is used to periodically send heartbeat packets, receive the neighbor node information returned by the Mesh node, and send the neighbor node information to the background server; The background positioning server is used to calculate the position of the Mesh node according to the neighbor node information, and obtain the specific position of the Mesh node; The monitoring terminal is used to display the specific location of the Mesh node.

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