Four Types of Bluetooth Protocols

Since its inception, Bluetooth technology has evolved from a simple short-range communication tool to a core standard covering consumer electronics, industrial control, healthcare, and other fields. The diversity of its protocol stack is key to its success—the stable transmission of Classic Bluetooth, the extreme energy efficiency of Bluetooth Low Energy, the compatibility of dual-mode chipsets, and the scenario-specific innovation of smart protocols. Together, these four types form the foundation of the Bluetooth technology ecosystem, supporting a wide range of applications from personal devices to the Internet of Things.

Classic Bluetooth (BR/EDR): The cornerstone of high-speed data transmission

Classic Bluetooth (Bluetooth Basic Rate/Enhanced Data Rate) is the original form of Bluetooth technology, designed for high-speed, reliable data transmission. Its core features include:

Physical Layer Architecture: Utilizing Time Division Duplex (TDD) and Frequency Hopping Spread Spectrum (FHSS) technology, it divides the 2.4 GHz band into 79 1 MHz channels. Frequency hopping occurs 1600 times per second to avoid interference and ensure stability in complex electromagnetic environments.

Link Type: Supports both asynchronous connectionless (ACL) and synchronous connection-oriented (SCO) links. ACL links are used for non-real-time data services such as file transfer and audio streaming, providing high throughput. SCO links are optimized for voice communications, ensuring low latency through fixed time slot allocation to meet real-time requirements.

Protocol Stack Structure: From bottom to top, it includes modules such as the physical layer, link layer, L2CAP (Logical Link Control and Adaptation Protocol), and SDP (Service Discovery Protocol). L2CAP supports multiplexing and segment reassembly, and can carry upper-layer protocols such as A2DP (Advanced Audio Distribution) and AVRCP (Audio/Video Remote Control).

 

Bluetooth Low Energy (BLE): An Energy Revolution in the IoT Era

Bluetooth Low Energy (BLE) is a revolutionary technology introduced in Bluetooth 4.0. Designed specifically for battery-powered devices, it offers over 10 times the energy efficiency of Classic Bluetooth. Core innovations include:

Connection Mechanism: Utilizing a three-phase "advertisement-scan-connection" model, devices periodically broadcast data packets in low-power mode when not connected. This reduces connection establishment time from 100ms in Classic Bluetooth to 6ms, significantly reducing standby power consumption. Data Transmission Optimization: The GATT (Generic Attribute Protocol) architecture is introduced, abstracting data into a "service-characteristic" model. Services define device functions (such as temperature monitoring), while characteristics represent specific data items (such as the current temperature value). These services support operations such as read, write, and notification, simplifying application development.

Security Enhancement: Support for LE Secure Connections pairing mode uses AES-CMAC encryption and elliptic curve Diffie-Hellman key exchange to provide end-to-end security and prevent data eavesdropping and man-in-the-middle attacks.

 

Dual-Mode Bluetooth: A Compatible Bridging Technology

Dual-Mode Bluetooth chips integrate both Classic Bluetooth and BLE protocol stacks, becoming a hub connecting traditional devices with the IoT. Technical features include:

Hardware Architecture: A dual RF front-end design uses time-division multiplexing to share antenna resources, supporting the concurrent operation of Classic Bluetooth and BLE protocols. Internally, the chip uses the Host Control Interface (HCI) to enable interaction between the two protocol stacks and coordinate resource allocation. Application Scenarios: In the automotive sector, dual-mode modules can simultaneously connect to car audio (Classic Bluetooth A2DP) and tire pressure monitoring sensors (BLE GATT). In consumer electronics, smartphones use dual-mode Bluetooth to seamlessly switch between headset calls (Classic Bluetooth HFP) and health data synchronization (BLE).

Protocol Conversion: The HCI layer schedules packets between Classic Bluetooth and BLE. When a device handles requests from both protocols simultaneously, the HCI layer dynamically allocates channel resources based on priority to avoid conflicts and optimize transmission efficiency.

 

Smart Bluetooth Protocol: A Catalyst for Scenario-Based Innovation

With the release of Bluetooth 5.0 and subsequent versions, a series of smart protocols have emerged, driving the technology deeper into various verticals. Core areas include:

Bluetooth Mesh Networking: A flooding routing protocol based on BLE that supports multi-hop communication between devices and builds large-scale self-organizing networks. Using a publish-subscribe model for message forwarding, it is suitable for scenarios such as smart lighting and building automation, and a single network can accommodate tens of thousands of nodes. LE Audio: Introducing the LC3 audio codec, it delivers higher sound quality at the same bitrate, supporting multi-stream audio transmission and broadcast audio capabilities. Auracast technology allows a single device to simultaneously transmit independent audio streams to multiple headphones or speakers, reshaping the audio experience in public spaces.

Direction Finding: Bluetooth 5.1's new AOA (Angle of Arrival) and AOD (Angle of Departure) positioning technologies, combined with antenna arrays and phase difference calculations, improve device positioning accuracy to centimeter-level, enabling widespread application in areas such as asset tracking and indoor navigation.

 

Future Outlook: Protocol Convergence and Ecosystem Expansion

Bluetooth technology is breaking new frontiers through protocol convergence. The "Channel Sounding" technology introduced in the Bluetooth 6.0 standard improves positioning accuracy to millimeter-level, supporting industrial automation and robotic collaboration. Furthermore, pilot programs are underway to integrate Bluetooth with UWB (Ultra-Wideband) technologies, enabling seamless device discovery and spatial awareness through a hybrid model of "Bluetooth Fast Connect + UWB Precise Positioning." With the widespread adoption of the RISC-V architecture and the application of AI-assisted code generation technology, Bluetooth protocol stack development efficiency will be further improved, driving a wave of innovation in areas such as smart homes and smart cities.

 

From the 732kbps transmission rate of Bluetooth 1.0 to the 144Mbps high-speed mode of Bluetooth 6.0; from simple headphone pairing to whole-home smart control, the four types of Bluetooth protocols have always been the core driving force of technological evolution. In the future, with the continuous optimization of protocol standards and the flourishing of the open source ecosystem, Bluetooth technology will continue to reshape the wireless communication landscape, creating a smarter and more convenient connection experience for humanity.