Since the concept of Bluetooth technology was proposed by Ericsson in 1994, it has evolved from the initial version 1.0 to the latest version 5.3. Each generation has achieved breakthroughs in transmission rate, power consumption control, application scenarios, etc. The current Bluetooth technology is led by the Bluetooth SIG and is divided into two major branches: "Bluetooth Classic" and "Bluetooth Low Energy (BLE)". The former focuses on high-speed data transmission (such as audio and files), while the latter supports IoT devices with extremely low power consumption. In the iteration of each version, BLE has gradually become the mainstream and has been deeply integrated with classic Bluetooth.

1. Comparison of Bluetooth version core parameters

2.Technical features of key versions

(1) Classic Bluetooth era (1.0–3.0)

1.1–1.2: basic voice transmission, weak anti-interference; 1.2 introduced frequency hopping technology (AFH) to reduce WiFi interference16.

Ø2.0/2.1+EDR: transmission rate increased to 3 Mbps, support stereo music (A2DP protocol), and 2.1 introduced SSP to simplify pairing, no need to enter PIN code, and standby power consumption reduced by 50%.

(2) Transition period: Bluetooth 3.0+HS

Ø24 Mbps high-speed transmission is achieved by calling the 802.11 WiFi module (the device needs to support the "+HS" logo), but the power consumption is high and it is not popular.

(3) Revolutionary turning point: Bluetooth 4.0 (BLE low power consumption)

ØDual-mode design: supports both classic Bluetooth (BR/EDR) and BLE low power consumption modes, and the power consumption is reduced to one-tenth of the traditional version.

ØThe explosion of the Internet of Things: button battery devices (such as bracelets, blood glucose meters) can operate for months or even years.

(4) Leap of the 5.x series

Ø5.0: Transmission distance reaches 300 meters (outdoors), broadcast data volume increases 8 times, and supports indoor positioning.

Ø5.2: Introducing LE Audio core functions: achieving multi-device audio synchronization (such as TWS headset left and right ear synchronization) and supporting lossless sound quality (24bit/192kHz) transmission.

Ø5.3: Further optimize power consumption and anti-interference, and reduce interference in the 2.4GHz band (such as WiFi, microwave ovens).

3.Protocol stack and functional layering characteristics

Bluetooth technology achieves diversified functions through layered protocol stacks:

l Bottom-layer control: HCI (Host Controller Interface) connects hardware and software.

l Data transmission:

ØRFCOMM: simulates serial port, used for file transfer (such as Bluetooth image transmission of old mobile phones).

ØL2CAP: data multiplexing, management of logical channels.

l Application layer protocol:

ØA2DP: classic Bluetooth audio transmission, only supports single device.

ØLE Audio (5.2+): supports multi-device simultaneous broadcasting (such as sharing audio to multiple headphones).

Note: If users consider the version selection and compatibility, they can use high-version Bluetooth devices or chips. High-version Bluetooth devices can connect to low-version devices, but the functions are limited. For example, Bluetooth 5.0 mobile phones can connect to Bluetooth 2.1 headphones, but only support basic audio.

4.Conclusion

Through continuous iteration, Bluetooth technology has developed from early short-range audio transmission to a core connection technology that supports the Internet of Things, high-precision positioning, and high-definition audio. When choosing a device, you need to match the version according to the scenario requirements (such as power consumption, distance, audio quality), and pay attention.