Summary of new features in Bluetooth 6.0

Previous versions of the technology had several issues. For example, distance measurement between devices was easily affected by the environment, and communication efficiency decreased in environments with multiple devices. Furthermore, even slight delays could become a problem in applications that require real-time performance.
In particular, it has been difficult to ensure accuracy with distance measurement technology, and it has sometimes been difficult to achieve in noisy real-world environments. However, with this update, the distance measurement technology has been improved, which is likely to lead to further consideration in applications that require accurate distance measurement, such as keyless entry for vehicles.
In the next chapter, we'll take a look at the specific technologies that have been added.

• [Previous version]
  The signal information changes
  → Misperception of distance information
  → The key cannot be opened or closed properly.

  

• [Bluetooth 6.0]
  The signal information remains unchanged
  →Accurate recognition of distance information
  → The lock can be opened and closed correctly

  

Bluetooth 6.0 is the next-generation standard scheduled for release in August 2024, and will significantly improve communication efficiency, accuracy, and security. It adds a variety of new features, including Bluetooth channel sounding for improved ranging accuracy, optional advertising FILTERS for improved scanning efficiency, and improved ISOAL for enhanced real-time performance.
These advancements will make connections between IoT and smart devices even smoother, and are expected to be used in a wider range of applications. Let's take a look at the innovative new features of Bluetooth 6.0.

Bluetooth Channel Sounding

The new feature "Bluetooth Channel Sounding" is

• Phase-Based Ranging (PBR)
• Round-Trip Timing (RTT) ranging

By using the above two distance measurement methods alone or in combination, we can achieve more accurate and reliable distance measurements than traditional path loss methods.
This technology is resistant to interference and environmental factors, and has many security mechanisms to prevent man-in-the-middle and relay attacks. It is expected to be used in a wide range of applications to improve convenience and safety, such as improving the accuracy of locating lost tags, smart locks, and keyless entry for vehicles.

This time we will discuss distance measurement methods.

Conventional path loss methods estimate the distance between a transmitter and a receiver based on the strength of the signal (Received Signal Strength Indicator, RSSI). The distance from the transmitter is estimated by the attenuation of RSSI depending on the distance, but if there are obstacles in the path of the signal, such as absorption or diffraction, the amount of attenuation changes. This can result in an error of several meters.

In contrast, with this channel sounding technology, the two devices are defined as the "initiator (signal transmitter)" and the "reflector (signal return)," and distance is measured through communication between the two.
First, PBR measures the phase of the signal transmitted by the initiator and the signal received from the reflector, and then compares the phases of these signals to calculate the relative distance between them.

RTT also uses the Time of Flight (ToF) to calculate the distance between the initiator and reflector. The Time of Arrival (ToA) and Time of Departure (ToD) are recorded for both the initiator → reflector and reflector → initiator, and the distance is calculated from the difference between them. The processing time from receiving the reflector's message to replying is also included in the calculation.

By combining the above PBR and RTT, the channel sounding error is approaching 20cm.

The AoA (Angle of Arrival) and AoD (Angle of Departure) technologies specified in Bluetooth 5.1 measure distance from the angles of received and transmitted radio signals. While this method can achieve an accuracy of less than one meter, it depends on the accuracy of the signal reaching ANTENNAS, making it unreliable in situations with many obstacles or reflections.
ANTENNAS design also needs to be considered.
To address these issues, a new channel sounding standard has been established.

Optional advertising FILTERS

An advertising channel FILTERS function has been added, which the Bluetooth SIG describes as "DBAF: Decision-Based Advertising Filtering."
BLE originally discovered peripheral devices using the advertisement channel. The DBAF feature adds this functionality, allowing a scanning device to use the content of packets received on the primary advertisement channel to determine whether to scan for related packets on the secondary channel next. This eliminates the need to scan FRAMES containing unnecessary Protocol Data Units (PDUs), improving scanning efficiency.

Advertiser Monitoring

Previous versions required frequent scanning to see if any Bluetooth devices were nearby, which could waste energy.
The newly added feature uses HCI (Host Controller Interface) events to notify the host whenever the target device moves in or out of range, reducing energy consumption when detecting whether a Bluetooth device is in range or out.

ISOAL Enhancements

ISOAL: Isochronous Adaptation Layer allows large data FRAMES to be split into smaller packets for transmission, but there can be delays in reassembling the data, which can be a concern for some applications.
This new feature defines a new framing mode that reduces this delay, improving real-time performance.

Link Layer Extensions

The link layer contains a variety of functions, and a Bluetooth device will only use those functions that it supports.
When two Bluetooth devices start communicating with each other, they exchange information about the link layer functions they support and can select the optimal communication method.
As Bluetooth LE becomes more advanced and multi-functional, the link layer has been enhanced to support more features. This update also brings further enhancements, allowing devices to exchange more information about the features they support, enabling future Bluetooth feature expansion.

FRAMES interval update

In previous versions, the time interval separating the transmission of adjacent packets was defined as a fixed value of 150us. With this update, this interval can now be changed to any value (0-10,000us).
This makes it possible to flexibly respond to the throughput and other requirements of each application.

Bluetooth 6.0 adds six major new features, but the improvement in ranging accuracy through channel sounding is particularly noteworthy. This improvement in ranging accuracy is expected to lead to applications such as the following:

• Pet tracking, asset tracking
• Vehicle keyless entry
• Smart Lock
• Geofencing