Introduction
When it comes to RTLS (Real-Time Location Systems) and IPS (Indoor Positioning Systems) solutions, one of the standout technologies is the Bluetooth Angle of Arrival (AoA). Now, bluetooth channel sounding has been introduced to offer centimeter-level accuracy for true distance awareness between devices. AoA’s direction-finding capability significantly enhances indoor positioning and navigation solutions, making it ideal for real-time location services and proximity solutions. On the other hand, bluetooth channel sounding takes precision to the next level with centimeter-level accuracy utilizing Phase-Based Ranging and Round-Trip Time. What exactly are the differences between them? Understanding the strengths of both Bluetooth AoA and Channel Sounding will help you choose the best solution for your specific needs.
Understanding Angle of Arrival (AoA)
Working Principle of Angle of Arrival (AoA)
In the AoA (Angle of Arrival) method, the device that needed to be determined direction with a single antenna sends a special direction finding radio signal to a receiving device. With multiple antennas arranged in an array, the receiving device can calculate the angle of arrival of the signal by measuring the slight time difference of arrival (TDoA) or phase difference of the signal at each antenna. If there is a system covering multiple locators, it can combine the AoA data from different locators to triangulate the position of the signal transmitter exactly.
The Benefits of Angle of Arrival (AoA)
Before the Bluetooth AoA and AoD capability was introduced, RSSI (Received Signal Strength Indicator) stood out as the solution for device distance calculation. RSSI determines the distance between the signal source and the receiving device by the strength of the wireless signal. Thus, positioning is not accurate in highly obstructed areas where the signal strength can easily be weakened. Adding the AoA and AoD method to Bluetooth enhances positioning accuracy.
Precise Positioning: The AoA method can achieve sub-meter accuracy by calculating the angle at which signals arrive at the receiving device with multiple arrayed antennas.
Real-Time Tracking: By providing the precise direction of objects, the AoA method, when working with RTLS, allows for real-time updates of their direction and location.
The Limitations of Angle of Arrival (AoA)
An unavoidable problem in RF (radio frequency) wireless technology is signal attenuation during transmission. The AoA method faces the same issue as RSSI (Received Signal Strength Indicator), where accuracy can be affected by obstacles, reflections, and interference. Buildings, walls, and other structures can cause multipath effects, leading to errors in angle calculation. However, technologies and methods such as bluetooth channel sounding have been developed to address this challenge. Additionally, calculating the angle of arrival involves complex signal processing and algorithms, which require powerful computing resources. That’s why the AoA typically requires a network-centric infrastructure.
The Applications of Angle of Arrival (AoA)
1.RTLS Solutions
AoA-supported solutions provide a sub-meter accuracy and real-time updates of location and direction, making them ideal for logistics and manufacturing, where they can accurately locate and track packages and materials.
2.IPS Solutions
The direction-finding capability of AoA greatly assists with indoor navigation. It can help navigate customers to the store and even to a specific shelf, providing a more seamless shopping experience.
3.Proximity Marketing
Imagine customers pointing their AoA-supported smartphone at a product and promptly seeing specific details on the screen. It offers a more convenient and efficient way to shop and market products.
AoA vs. AoD
Both the AoA and AoD methods have direction-finding capabilities. AoA measures the angle at which a signal reaches a receiver to determine the direction of a transmitting device, making it ideal for object tracking and real-time location systems. AoD measures the angle at which a signal leaves a transmitter, enabling a receiving device to calculate its own location. Compared to AoD, AoA is less complex and more widely used.
Understanding Bluetooth Channel Sounding
How Does Bluetooth Channel Sounding Work?
Bluetooth channel sounding utilizes PBR (Phase-Based Ranging) and RTT (Round-Trip Time) to determine the distances between Bluetooth-connected devices with unmatched centimeter-level accuracy. Combining the use of PBR and RTT enhances security by cross-checking.
PBR: In Phase-Based Ranging (PBR), an initiator device sends a signal to a reflector device, which receives and reflects the signal back to the initiator. The initiator device then measures the phase offset or difference between the transmitted and received signals, allowing for accurate distance calculation between the two devices by estimating this phase difference.
RTT: In the Round-Trip Time (RTT) method, the initiator device sends signals to the reflector device, which returns the signals. The distance between the two devices is estimated by assessing the time of flight (ToF), which is the time it takes for the packets to travel back and forth. RTT is regarded as a highly secure method.
The Benefits of Bluetooth Channel Sounding
Accuracy
Bluetooth channel sounding uses PBR (Phase-Based Ranging) to measure distances up to about 150 meters before encountering distance ambiguity. By combining RTT (Round-Trip Timing) with PBR, applications can detect and resolve this ambiguity, allowing for more accurate distance measurements over greater ranges.
Security
Security concerns specific to distance measurement solutions typically involve the risk of an untrusted device deceiving a trusted device into believing that another trusted device is close enough to allow certain actions to be taken or authorized.
The combined use of PBR and RTT is one of bluetooth channel sounding’s strategies to counter this threat. Since these two methods work completely differently, the likelihood of both being simultaneously attacked or manipulated to produce misleading results is extremely low. The high security offered by cross-checking PBR and RTT provides developers with greater possibilities.
The Limitations of Bluetooth Channel Sounding
1.Complexity
The process of channel estimation and signal processing can be computationally demanding, especially for devices with limited processing capabilities.
2.Power Consumption
The accuracy of channel sounding depends on the transmission power of the Bluetooth devices involved. Higher power consumption can be a concern for battery-powered devices.
3.Environmental Impact
In complex environments with obstacles and reflections, the accuracy of channel sounding can also be affected.
The Applications of Bluetooth Channel Sounding
1.’Find My’ Solution
For the end-user of Bluetooth ‘Find My’ solutions, which is the most ubiquitous low-power wireless technology, it is easier and faster to locate lost items, whether by direction or distance.
2.Digital Key
In digital key solutions, bluetooth channel sounding can enhance security and user experience by ensuring that a lock only opens when the authorized device is within a certain distance.
3.Indoor Positioning with Centimeter-Level Accuracy
Channel Sounding offers fine ranging that may transform RTLS solutions, such as more precise package tracking in logistics and supply chain, and quicker responses to patient calls or emergencies in healthcare and hospitals.
Bluetooth channel sounding offers exceptional technical flexibility in terms of security, accuracy, and latency. This gives developers maximum freedom to innovate, enabling the creation of endless possibilities between Bluetooth devices and paving the way for a more wireless and connected world.
The Differences Between Angle of Arrival and Bluetooth Channel Sounding
| AoA/ AoD | Bluetooth Channel Sounding | |
|---|---|---|
| Measurements | Estimates the angle of incoming (AoA) and outgoing (AoD) signals | Uses PBR and RTT for fine ranging |
| Complexity | AoA is simpler; AoD is more complex and less frequently used | Less complex, simpler implementation |
| Accuracy | Capable of sub-meter accuracy but can be hindered by multipath propagation | Centimeter-level accuracy even in multipath environments |
| Antenna Requirements | Requires multiple antennas to capture phase shifts | Multi-antenna not required, but can be used to enhance accuracy |
| Power Consumption | Low power consumption | Slightly higher power consumption |
| Applications | Direction finding capability for IPS and RTLS solutions | For fine ranging projects requiring high security |
Which is Good for You: Angle of Arrival and Bluetooth Channel Sounding?
Both Bluetooth AoA (Angle of Arrival) positioning and channel sounding offer ultra-high accuracy in location services. If you’re looking for a project that’s easy to scale, AoA is a better choice due to its maturity and widespread application. Additionally, AoA’s direction-finding capability is very beneficial for indoor positioning, navigation, and proximity solutions. However, if your project demands extremely high precision in location services or places a high emphasis on security, bluetooth channel sounding is more suitable.
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