The Bluetooth 5.1 specification adds accurate positioning capabilities, a basic use case for many of the industry's desired IoT (IoT) applications. Bluetooth 5 burst flying, and brought a lot of related functions, people may think that this time it is difficult to improve.
However, although the new version of the number is only 5.1, and 5 seems to be not far apart, but Bluetooth 5.1 is actually very important.
Find the way forward via Bluetooth
Direction finding is a major feature of Bluetooth 5.1, which brings the absolute positioning of products and items in three-dimensional space into a world of low-power wireless connectivity. This is a very important addition to the low-power Bluetooth feature library. We think the impact it has on indoor positioning applications is as great as the impact of GPS on outdoor positioning production.
GPS technology has fundamentally changed the travel and tracking of cars, people and goods on a macroscopic scale, and the Bluetooth direction finding function can have a similar effect on the micro-scale applications in buildings and properties.
The Bluetooth Technology Alliance (SIG) predicts that 400 million Bluetooth location service products will be launched each year by 2022. Built on the success of Bluetooth beacons Real-time Location services (RTLS) using Bluetooth technology have been on the market for several years. This is achieved by introducing a Bluetooth beacon, which can give an approximate value of the distance or proximity between the targets.
For example, this could be the distance the customer is close to the airline check-in counter. The Beacon method is based on the receiving signal strength Indication (RSSI) to monitor the strength of the radio signal from the source. The RSSI method is useful, however, it is more careless.
In addition to the distance-only information traditionally brought by RSSI, the arrival angle (AoA) and the departure angle (AoD) data can give people a precise direction.
Methods of using angles to locate
The two concepts of arrival angle (AoA) and departure angle (AoD) are the core of Bluetooth 5.1 direction finding function. Using AoA, a device or label uses only one antenna to send specific geodetic packet data, the receiving device or locator has multiple antennas, and the input signal from the label will be moved to these antennas at a very small difference from each other. The phase change of the signal received by these antennas is sampled as the IQ component of the signal.
Then, by using the relevant algorithm at the locator, the sample data will generate accurate coordinate information.
This method is ideal for specific item lookup and point of Interest (PoI) applications. In contrast, the AoD method has an antenna array for key devices that determine direction, such as the positioning beacon in the indoor positioning System (IPS), which sends packet data through the antenna array.
In this case, the receiving device (most likely the phone) will take IQ samples on its antenna and perform coordinate calculations. Design complexity There are pros and cons to the different designs of Bluetooth measurement products.
If you use a Nordic device that supports Bluetooth 5.1 direction, the design of the locator label is not significantly different from the regular Bluetooth hardware layout, so this is simple and, in fact, will be the majority of the products used in bluetooth direction measurement. In the locator hub, antenna arrays need to be designed and multiplexed to the Bluetooth SoC, because the Bluetooth SoC does not have multiple antenna ports to avoid becoming very expensive. There are a number of devices on the market that can complement the Nordic SoC to achieve this functionality.
In addition, the antenna array may require a 360-degree coverage to capture the signal, or, if it is a wall-mounted unit, a 180-degree coverage may be required. Realistic expectations Most people will agree that accurate indoor positioning is a great feature. But there should also be a bit of cautious guidance. All of this is related to the transmission of radio waves, and we have no direct control over their transmission path between the transmitter and receiver. The less obstacles, the less crowded, the more open the sight (LoS) scene of the technology, the higher the positioning accuracy will be. As signals bounce back from walls, cabinets, windows, and human bodies, phase and signal strength are affected and smaller or larger errors are introduced.
In any case, this is an advanced direction finding solution, and even in very challenging situations, the test results are very stable and accurate.
In short, the technology needs to be actually tested for use cases so that you can get a good idea of whether it's right for your product. Typical use Cases As mentioned above, the more open and uncrowded the scene is, the better accuracy may be. First, we can look at the positioning system inside the stadium. Since the positioning hub may be located above the course or stage area, this can receive transmission data from the device being worn.
This scene is very open, the seat is vertically layered and provides a good LoS property, and this application should be very effective. Another good use case is to look for items at home or in the workplace, so let's use the key as the most common "where did I put it?" Examples of this. Through the locator hub in the room, this can work well.
However, it is reasonable that the locator hub at another level is unlikely to provide an accurate location, taking into account physical challenges. Finally, it is a valuable use case to position people in emergency situations. Such as a large shopping mall or office building, and equipped with sufficient locator hubs to cover all areas. For example, this can provide very accurate information for emergency services to obtain information about anyone who may still be in a building in the event of a fire. This will help emergency workers find people in trouble directly without having to conduct a systematic search across the complex (when rescuers don't see if anyone is trapped inside), saving valuable time for better liaison and rescue or life-saving care on site.