Satellites cannot be searched indoors, so conventional GPS/Beidou positioning cannot be used. The only conventional free positioning is the operator's base station positioning LBS, but this accuracy is really poor, generally with a deviation of tens to hundreds of meters. Therefore, indoor positioning has always been a difficult problem.
Up to now, the relatively mature solution in the industry is UWB, but the cost of UWB base stations is too expensive. For now, only limited units with sufficient funds, such as power plants and prisons, can afford them.
Looking for low-cost indoor positioning technology solutions has been the gospel that the industry has been waiting for for many years, until the Bluetooth beacon technology solution came out.
AIoT is connected to all things, and smart helmets , smart helmets , helmet recorders , law enforcement recorders , vehicle-mounted DVR /NVR, ball control , smart glasses , smart flashlights , drone 4G supplementary transmission systems, etc. are unified and connected to large-scale integrated communication visual command Scheduling platform VMS/ smarteye .
Bluetooth beacon positioning is a revolutionary technology. It gets rid of expensive and high-density positioning base stations, greatly reducing the system cost. As long as the mobile (video/positioning) terminal supports Bluetooth, it can cooperate with Bluetooth beacons to achieve positioning.
WiFi positioning
At present, the simplest and most feasible indoor positioning method is WiFi positioning, which does not require any construction factory. As long as there are positioning maps of the WIFI routers in the factory area and on each floor, and the Android system's law enforcement recorders, smart helmets, three-proof mobile phones, etc. Android terminals can easily achieve indoor positioning with a positioning accuracy of about 10 meters, which can basically locate the floors and rooms where people are located. WiFi positioning is currently the simplest and easiest to implement method among indoor positioning mechanisms.
Bluetooth positioning vs UWB positioning
1. Bluetooth typical positioning technology route: Bluetooth beacon
Strictly speaking, Bluetooth beacon is not a positioning technology, but a judgment of the spatial accessibility of Bluetooth signals; its biggest advantage is that it is cheap and simple; it is suitable for behavioral management based on spatial location such as inspections;
2C side Bluetooth beacon application
Bluetooth beacons are used as location anchors, and the C-side uses mobile phones to display content related to the anchor points;
2B side Bluetooth beacon application
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Bluetooth beacons serve as location anchors, and the C-side uses mobile phones to implement inspection and clock-in applications;
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Bluetooth beacons serve as location anchors, and tags are used to receive beacon broadcasts to achieve positioning;
Since the anchor point has no communication function, the tag must support wireless communication function. Manufacturers generally provide LORA or NB solutions; LoRa and NB are both narrowband IoT communication solutions, with very limited bandwidth. LORA WAN is basically not feasible, and real-time performance cannot be guaranteed. , only the LORA private protocol can be used, and the LORA gateway must be deployed; LORA uses a polling data communication mechanism, and wireless data communication with large amounts of data cannot be expected. The number of regional tags cannot exceed twenty or thirty; based on regional capacity and positioning effect , this solution of Bluetooth beacon as anchor + Bluetooth tag (LORA) + LORA gateway is not recommended.
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Using the method of Bluetooth gateway + Bluetooth tag (Bluetooth beacon), the Bluetooth gateway is responsible for communication;
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This is widely used indoors. The Bluetooth gateway serves as a spatial location identifier and collects Bluetooth beacon devices existing in the space in real time;
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This is very common in hospitals, schools, etc.;
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The advantage of this solution is that it can realize data communication similar to data collection based on BLE connection;
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Limitations of this application: It is recommended that the number of space Bluetooth devices should not exceed a few hundred, and due to the unreliability of BLE broadcast communication, it is recommended to only perform presence monitoring based on the reach of Bluetooth signals. Other so-called positioning algorithms are Don't ask for extravagant things, it's completely unrealistic.
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Bluetooth beacons serve as location anchors, and smartphones collect information to implement inspections and other functions; (but this function is easily replaced by RFID-based NFC/close contact)
Limitations of Bluetooth AOA: Since it must be installed horizontally, Bluetooth AOA is not suitable for outdoor environments; secondly, the experience of Bluetooth AOA is also average, and environmental interference factors also have a huge impact on Bluetooth AOA;
Recommended location services based on Bluetooth technology:
1: Bluetooth beacons serve as location anchors, and smartphones collect information to implement inspections and other functions; (but this function is easily replaced by RFID-based NFC/close contact)
2: Bluetooth gateway + Bluetooth beacon; use independent spaces such as hospitals to deploy Bluetooth gateways; use Bluetooth bracelets or Bluetooth tags to achieve spatial location management of patients and devices, and achieve target data collection based on BLE;
Other solutions are not recommended as they have many basic pitfalls, especially the triangulation positioning based on Bluetooth RSSI;
Bluetooth is more of a wireless data communication technology than a wireless positioning technology;
UWB is more of a wireless positioning technology than a wireless data communication technology;
2. UWB positioning solution:
Compared with all wireless technologies, UWB should be regarded as the best and best-performing wireless communication technology for positioning;
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First of all, UWB can choose multiple frequency bands such as CH2, CH5, CH9; CH2’s distance is an advantage, but it conflicts with the operator’s 5G frequency band; CH5 is basically an ISM unlicensed frequency band; CH9 is a nearly 10G frequency band, generally used for short-range positioning; Bluetooth generally uses the 2.4G ISM unlicensed frequency band, which highly overlaps with WIFI. 2.4G also has the most types of devices and communication technologies (Zigbee, etc.).
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In addition, UWB is a short pulse communication technology, which has the best TOF ranging performance and the highest accuracy among all wireless communication technologies.
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UWB uses BPSK wireless modulation technology. Compared with FSK and OFDM (used by Bluetooth), it has better carrier-to-noise ratio performance and stronger same-frequency anti-interference performance.
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Although the actual performance of UWB positioning is somewhat unsatisfactory, wireless positioning can currently only rely on UWB;
UWB has many technical advantages, but why is its actual positioning so unsatisfactory?
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First of all, a common problem in wireless communication is signal interference . Although UWB uses BPSK wireless signal modulation technology and similar wireless communication technologies perform well, the actual direction of the tag transmitting antenna and the base station receiving antenna will lead to weak received signals, especially at long distances. In the case of long distance, it is basically impossible to receive the UWB signal due to the antenna direction problem. Secondly, the problem of co-channel interference (such as the interference of 5G on CH2) will also cause the UWB wireless signal to be undetected or lost. This problem is more likely to occur especially when the distance between the tag and the base station is relatively far.
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Positioning algorithm selection : With good accuracy of UWB TOF or arrival time, you can choose triangulation positioning based on TOF or TDOA based on the least square method; triangulation positioning requires that the on-site environment has no obstruction and interference, and you can also choose triangulation based on TOF ranging value. AOA positioning also requires that the environment be free of obstructions and interference; this kind of positioning based on two ranging values or multiple test values often has poor adaptability to environmental interference. Positioning stability is unsatisfactory. The fine grid positioning based on the fuzzy matching algorithm of TOF ranging is selected. The deep learning and similarity matching positioning algorithm of the signal is adopted. The adaptability to environmental interference is much better than traditional triangulation positioning and AOA positioning.
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Power consumption and cost: The transmitting and receiving power consumption of UWB is basically more than 5 times that of BLE, and the chip cost is also more than 5 times, resulting in low market acceptance.
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Standardization: The standardization process of UWB is not as good as Bluetooth. Of course, in some application scenarios, UWB's non-standardization and link layer protocol customization have found application opportunities in some special fields.
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3. Starting point of BLE+UWB combination:
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2B side applications are based on BLE and UWB signal coverage.
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Based on the characteristics of BLE, low power consumption of tags in non-UWB positioning areas is achieved.
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Enter or leave the UWB positioning area, use BLE to activate or deactivate the UWB module
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Implement wireless data collection function based on BLE
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Special indoor independent office space, using Bluetooth AOA to achieve precise positioning of indoor tags
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2C side applications realize long-distance coverage based on BLE, and UWB realizes short-range and precise positioning.
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UWB usually uses PDOA or AOA azimuth positioning (angle + distance)
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Summarize:
Faced with spatial location requirements, we must first clarify the requirements and management goals. If Bluetooth beacon positioning can meet the requirements, there is no need to consider UWB; if Bluetooth beacon positioning cannot meet the requirements, then UWB will be used honestly. There is no better wireless positioning technology. The choice is available. ,
The biggest advantage of Bluetooth beacons is that they are simple and cheap
The general market price of Bluetooth Beacon is around 200, while the price of Bluetooth + UWB Beacon is around 200. What are the differences between the two? In what scenarios is Bluetooth Beacon sufficient? In what scenarios requires Bluetooth + UWB Beacon?
Let’s first take a look at the situation of Bluetooth Beacon:
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The anti-lost device acts as a Bluetooth peripheral function, and the mobile phone acts as the main device; the anti-lost device broadcasts periodically, the mobile phone scans and discovers the anti-lost device, and the mobile phone establishes a Bluetooth connection and sends commands;
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Bind the mobile phone and the anti-lost device in advance. When the mobile phone cannot receive the broadcast of the anti-lost device, the mobile phone will alarm; due to many circumstances (such as distance and interference), the Bluetooth broadcast of the anti-lost device cannot be received. Actual experience of this function Not optimistic. In addition, Bluetooth ranging is based on RSSI, which has low reliability, which also results in a poor experience. Distance, humid air, metal obstruction, and co-channel interference will all cause Bluetooth broadcast signals to not be received.
Bluetooth uses the 2.4G unlicensed channel. Many devices, including WiFi, use this frequency band, and co-channel interference is particularly serious.
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Bluetooth technology itself is not designed for a large number of point-to-multipoint data communications (except Bluetooth MESH). It is not recommended that the number of slave devices supported by the master device exceeds twenty or thirty, which means that the number of target devices in the same environment should not exceed twenty. This There are great limitations for some 2B scenario applications.
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UWB has the opportunity to solve the capacity problem, as well as relatively reliable data communication guarantee (compared to Bluetooth, UWB wireless communication has stronger anti-interference ability) and high-precision ranging (the visual ranging accuracy can be guaranteed to be 30 cm, which may be caused by occlusion) error, but the overall ranging effect is far greater than that based on RSSI).
In a multi-target (hundreds of targets) scenario, only UWB technology can be selected to achieve positioning;
Compared with Bluetooth technology, high-precision ranging based on UWB is still trustworthy;
The actual angle measurement of PDOA based on UWB is not very satisfactory, and the angle error is too large. This leads PDOA to recommend applications within 10 meters (this distance is very embarrassing and does not have much application scenario value).
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Bluetooth beacons only support presence detection, while UWB can achieve fine grid positioning.
Bluetooth beacon location management is only a detection of Bluetooth signal reachability. In a complex metal environment, the signal reachability range is difficult to confirm and the experience is not good.
Fine grid positioning divides any large space into different arbitrary areas according to the purpose of physical space management to achieve target real-time area management (Who, What time and Where). The boundary of each area establishes a UWB signal learning and matching library based on the UWB signal, and uses the classic pattern fuzzy matching algorithm to achieve regional positioning of the target. The definition of the area is very simple. It only requires the tag to be active at the area boundary for a week. It is a fuzzy matching real-time route, which is tolerant and adaptable to the disturbance of wireless signals.
Tunnel positioning
For tunnel positioning in one-dimensional space, UWB positioning is optimal. A base station can cover 100 to 500 meters with an accuracy of 1 to 5 meters.
Indoor positioning in power plants and factory areas
WIFI positioning is available (accuracy 5-10 meters), no installation required; Bluetooth iBeacon positioning is available, with simple installation and positioning accuracy up to 3-5 meters.
Overview of indoor positioning (UWB/Bluetooth, etc.) technical solutions, https://www.besovideo.com/detail?t=1&i=205
Bluetooth beacon for indoor positioning combined with smart helmet and power operation recorder of Android system, https://www.besovideo.com/detail?t=1&i=267
Test report of smart helmet with built-in RTK Beidou high-precision positioning (MQTT communication), https://www.besovideo.com/detail?t=1&i=132
Smart helmet with built-in UWB indoor high-precision positioning - software description, https://www.besovideo.com/detail?t=1&i=131
UWB-based high-precision personnel positioning system solution for digital coal yard, https://www.besovideo.com/detail?t=2&i=997