BLE AoA Positioning: How it Works

In today's rapidly evolving Internet of Things (IoT) era, location technology plays a critical role. Especially in indoor environments, where precise location information becomes essential, Bluetooth Low Energy's (BLE) Angle of Arrival (AoA) technology provides a highly accurate solution for precisely tracking the location of objects, leading to innovative applications in multiple industries.

How AoA technology works

BLE AoA technology focuses on precise positioning by measuring the angle of arrival (AoA) of a signal. The technology requires a receiver equipped with multiple antennas to receive the same signal from different directions. When a signal is emitted from a transmitting source and reaches the receiver, due to the differences in the positions of the different antennas at the receiver, the same signal causes small differences in timing at different antennas, which can be converted to phase differences and used to meter the
Calculate the arrival angle of the signal.

Principles of positioning methods and calculation examples

Phase difference is the central concept in the AoA technique and the measurement process involves the following steps:

1. Signal reception:

Multiple antennas of a receiver simultaneously receive signals from the same transmitting source. Due to the fixed spatial distribution between the antennas, the same signal will exhibit time differences across these antennas.

2. Measurement time differences:

These time differences, i.e., the difference in arrival times of the signals between the different antennas, can be directly measured by means of sophisticated timing techniques. These time differences are directly converted into phase differences of the signals.

3. Phase Difference Calculator, Inc:

• Δϕ: phase difference (radians)
• f is the frequency of the signal, the signal frequency is 2.45 GHz
• Δt is the time difference measured between the different antennas in ns.

4. Angle calculation:

Once the phase difference is obtained, a trigonometric function can be used to calculate the angle of arrival of the signal, this is done using the following formula:

• θ: angle at which the signal reaches the receiver
• d: distance between neighboring antennas

5. Data correction:

Due to the non-ideal characteristics of the hardware and external environmental factors, the measured phase differences may require further calibration. This typically involves the use of calibration data and algorithms to adjust and optimize the phase difference data.

Calculation example: determining the location of the emission source

In order to show how to calculate the transmitter source position starting from the angle measurements of receiver stations A and B, it is assumed that we know the exact locations of these receiver stations and their respective measured angles of arrival. This will help the reader to understand the entire flow of the application of AoA technology.

Receiving station and transmitting source setup

• Receiving station A position: (xA,yA)=(0,0)
• Receiving station B position: (xB,yB) = (10,0) (in meters)

Assume that receiving stations A and B are each configured with multiple antennas and are able to measure the angle of arrival of signals from the same transmitting source.

angular measurement

In order to perform the calculations, we first need to determine the angles of arrival measured from the receiving stations A and B. The angles of arrival are determined by the following steps. These angles are measured by the following steps:

1. Signal reception:The antenna array at receiving station A receives signals from the transmitting source.
2. Phase Difference Measurement:Based on the difference in arrival time of the signal at different antennas of the receiving station A, the phase
   Bit Difference.
3. Angle calculation: Use of formulas

where λ is the signal wavelength, Δϕ is the measured phase difference, and d is the distance between the antennas.

4. Calculation of the positioning of the emitting source
   The angle of arrival measured at receiving stations A and B is used to determine the location of the transmitting source:

● The angle of arrival measured by receiver station A:

● The angle of arrival measured by receiving station B:

These angles are converted to radians:

Use this angular information to create linear equations pointing from the receiving station to the transmitting source, and then solve these equations to find their point of intersection:

● From receiving station A:

● From receiving station B:

Solving these equations yields the emission source position:

reach a verdict

With this computational example, we show how the whole process starts from the angular measurement of the receiving station, through the calculation of the phase difference, to the final determination of the location of the transmitting source. The accuracy of this approach makes BLE AoA technology a powerful tool for indoor positioning and tracking applications.

Application Areas

BLE AoA technology has a wide range of applications in several areas, including:

• Indoor Navigation:Large indoor locations such as shopping malls, airports and museums provide users with real-time navigation.
• Asset tracking:Track the location of equipment and valuables in hospitals and manufacturing.
• Smart Home:Precisely control smart home devices to enhance the home automation experience.
• Personal safety:Tracking an individual's location for increased safety and security in child or elder care.

Challenges and constraints

While BLE AoA technology offers many possibilities, it also faces some challenges such as multipath interference and hardware costs. In addition, accurate angle measurements require complex algorithms and high-performance hardware support.

concluding remarks

With the continuous advancement of technology, BLE AoA positioning technology is gradually overcoming these challenges and opening a new chapter in high-precision indoor positioning technology. Whether it is to improve operational efficiency, enhance user experience or create new business opportunities, BLE AoA technology shows great potential and broad prospects.