The Latest Version and Features of the Bluetooth Protocol

Amidst the rapid advancement of wireless communication technology, the Bluetooth protocol continues to play a crucial role. As of August 2025, the Bluetooth Special Interest Group (Bluetooth SIG) has introduced numerous revolutionary features in Bluetooth 6.0 and released Bluetooth Core Specification 6.1. This article will systematically review the technological breakthroughs and application scenarios of the latest version, revealing how Bluetooth is redefining the possibilities of wireless connectivity.

Bluetooth 6.0

As a key version of Bluetooth technology on its journey toward the "Intelligent Connection of Everything," Bluetooth 6.0's core goal is to address the pain points of low-power devices in secure ranging, large-scale networking, and intelligent interaction through two key features: Channel Sounding and Extended Advertising.

Channel Sounding

Traditional Bluetooth positioning relies on RSSI (signal strength) or path loss calculations, which are susceptible to environmental interference and present security vulnerabilities. The Channel Sounding feature introduced in Bluetooth 6.0 achieves breakthroughs through the following technologies:

Dual-mode ranging: Combining a hybrid algorithm based on phase difference (PBR) and round-trip time (RTT), it achieves centimeter-level accuracy in a 1:1 device topology. For example, digital car keys can accurately identify the owner's location within 1 meter, preventing relay attacks.

Security Mechanism: An integrated FIPS 140-2 standard random number generator ensures encrypted transmission of ranging data, defending against distance spoofing attacks. Tests show that its anti-interference capability is 80% higher than path loss methods.

Multi-antenna Support: Antenna arrays reduce multipath propagation errors, making it suitable for complex scenarios such as industrial robot collaboration and drone formations.

Extended Broadcast

Bluetooth 6.0 optimizes the broadcast communication mechanism, significantly improving the efficiency of large-scale device connections:

Secondary Channel Filtering: The primary broadcast channel (Primary ADV) carries metadata, allowing scanning devices to decide whether to receive complete packets on the secondary channel (Secondary ADV), reducing energy consumption from ineffective scanning. For example, smart shelf tags can transmit inventory data only to management terminals to avoid interference from other devices.

Duplicate Packet Suppression: The host can instruct the controller to filter duplicate broadcast packets, reducing the host's processing load. However, this comes with a trade-off in real-time performance, as the host cannot detect whether a device is offline. Monitoring broadcast events: Notifying the host device of device entry and exit range through HCI events, optimizing the wake-up strategy for low-power sensors.

 

Bluetooth 6.1

Released in April 2025, Bluetooth 6.1 focuses on privacy and security, addressing the risk of long-term device tracking through a randomized resolvable private address (RPA) update mechanism.

Dynamic RPA Update Cycle

Traditional solution: In Bluetooth 5.x, the RPA update cycle is controlled by a single timeout value (default 15 minutes), making it vulnerable to predictable attacks.

Bluetooth 6.1 Improvement: The RPA_Timeout_Min and RPA_Timeout_Max parameters are introduced, allowing the controller to randomly select an update cycle between the two. For example, if the minimum value is set to 8 minutes and the maximum value is set to 15 minutes, the actual update time may be 10 or 12 minutes, increasing the difficulty of attacks.

Security Standards: Random number generation must comply with FIPS SP800-22 testing to ensure unpredictability.

Application Scenarios

Wearable devices: Smartwatches change their MAC addresses every 8-15 minutes to prevent advertisers from tracking users' locations through Bluetooth signals. Smart home: Smart door locks update the RPA after each unlock to prevent pairing key cracking.

 

Bluetooth 5.x Series

Although Bluetooth 6.x is leading the technology, the Bluetooth 5.x series remains the mainstream choice for IoT devices. Its core versions (5.0-5.4) support connecting hundreds of millions of devices through the following features:

Bluetooth 5.0: long distance and high-speed transmission

LE Long Range mode: Extends the transmission range to 400 meters (outdoors) through coded PHY (e.g., S=2), making it suitable for smart agricultural sensor networks.

2Mbps High Data Rate: Using a 2MHz symbol rate, data transmission speeds double that of Bluetooth 4.2, meeting the low-latency requirements of AR/VR headsets.

Advertisement Data Extension: Supports 255-byte advertisement packets, enabling Beacon devices to simultaneously transmit multi-dimensional data such as temperature, humidity, and light intensity.

Bluetooth 5.1: Centimeter-Level Indoor Positioning

AOA/AOD Direction Finding: Calculates the angle of arrival/departure of signals using an antenna array, achieving positioning accuracy within 1 meter. For example, shopping mall navigation can guide customers directly to their desired store. Broadcast Codec Selection: Optimizes broadcast channel coding to improve interference resistance in dense environments.

Bluetooth 5.2: LE Audio and Multi-Device Synchronization

LE Audio Architecture: Introduces LC3 audio codecs, achieving higher sound quality at a lower bitrate and supporting simultaneous playback for both left and right earbuds in TWS earbuds.

Multi-Master-Multi-Slave Connection: A single device can simultaneously connect to up to seven slave devices and be connected as a slave by other masters, making it ideal for multi-screen interaction in industrial HMIs (human-machine interfaces).

Bluetooth 5.3: Interference Mitigation and Low Power Optimization

LE Channel Classification: Dynamically assesses channel quality in the 2.4GHz band to avoid interference sources such as WiFi and microwave ovens. Tests show a 60% reduction in packet loss in complex electromagnetic environments.

Periodic Broadcast ADI: Adds a unique identifier to broadcast data, improving communication efficiency. For example, electronic shelf labels can quickly update price information to avoid broadcast conflicts.

 

The evolution of the Bluetooth protocol is a story of wireless communication technology constantly pushing the limits of physics and reshaping application scenarios. From the channel detection of Bluetooth 6.0 to the privacy protection of 6.1, and then to the support of the 5.x series for the Internet of Things, Bluetooth technology is upgrading from a "connection tool" to an "intelligent interaction platform."