I. What are Bluetooth and Bluetooth Mesh?

Bluetooth: Bluetooth is a short-range wireless communication technology, standardized by the Bluetooth Special Interest Group (SIG). It operates in the 2.4GHz unlicensed ISM band and uses frequency-hopping spread spectrum technology to combat interference. Traditional Bluetooth (such as versions prior to Bluetooth 4.0) is primarily designed for point-to-point or point-to-multipoint short-range data transmission, with a maximum transmission rate of 3Mbps and a communication distance generally within 10 meters. It is suitable for connecting mobile phones to peripherals such as headsets, keyboards, and mice. With the introduction of BLE (Bluetooth Low Energy) technology in Bluetooth 4.0, power consumption has been significantly reduced, and the transmission distance has increased to 50 meters, opening up applications in the field of IoT sensors.

Bluetooth Mesh: Bluetooth Mesh is a mesh networking protocol based on Bluetooth BLE technology, released by the Bluetooth SIG in 2017. It solves the problem of traditional Bluetooth's inability to form large-scale networks. It uses multi-hop forwarding technology, where each node in the network can act as a router, forwarding data to other nodes, thereby achieving long-range signal coverage. Bluetooth Mesh supports various topologies such as star, tree, and mesh. A single network can accommodate tens of thousands of nodes, and the communication distance can be extended to hundreds of meters through multi-hop networking, perfectly adapting to scenarios requiring large-scale device interconnection, such as smart homes, smart lighting, and building automation.

II. Protocol Features of Bluetooth Mesh

1. Large-scale networking: Breaking through the traditional Bluetooth "one master, many slaves" connection limitation, it supports large-scale network deployments of tens of thousands of nodes, enabling interconnection between nodes without a central device.

2. Multi-hop transmission: Nodes have relay forwarding capabilities, allowing signals to cover long distances through relay transmission from multiple nodes, ensuring stable signal even in complex indoor environments.

3. Low-power design: Inheriting the low-power characteristics of Bluetooth BLE, nodes support sleep/wake-up mechanisms, and battery life can reach several years, suitable for battery-powered sensors and switching devices.

4. High reliability: Employing broadcast communication and message acknowledgment mechanisms, it supports message retransmission to avoid data loss; it also supports AES-128 encryption to ensure data transmission security.

5. Strong Compatibility: Bluetooth Mesh devices are compatible with traditional Bluetooth BLE devices, allowing network configuration and device control via Bluetooth terminals such as mobile phones and tablets, without the need for a dedicated gateway.

6. Flexible Topology: Supports dynamic topology; nodes can freely join or leave the network. The network possesses self-organizing and self-healing capabilities; a failure in one node will not affect the operation of the entire network.

III. Bluetooth Mesh Network Architecture

The Bluetooth Mesh network adopts a distributed architecture with no central node. The complete network system includes terminal nodes, relay nodes, configuration nodes, and gateway nodes.

1. Terminal Nodes: Include sensor nodes (such as temperature and humidity sensors, human body sensors) and actuator nodes (such as smart light bulbs, smart switches), responsible for data acquisition or executing control commands. Some terminal nodes do not have relay capabilities.

2. Relay Nodes: Nodes with data forwarding capabilities, capable of receiving messages from other nodes and forwarding them to target nodes, extending network coverage. Examples include smart sockets and smart gateways.

3. Configuration Node: Responsible for initial network configuration, including network creation, node addition, address and key allocation, etc., typically handled by a mobile phone, tablet, or dedicated configurator.

4. Gateway Node: Enables interconnection between the Bluetooth Mesh network and other networks (such as WiFi, Ethernet), forwards Mesh network data to the cloud or local area network, and receives control commands from the cloud and sends them to the Mesh nodes.

Common Development and Deployment Tools

1. nRF Mesh SDK: A Bluetooth Mesh development kit from Nordic Semiconductor, providing rich API interfaces and sample code to support rapid development of Bluetooth Mesh node devices.

2. Bluetooth Mesh Studio: An official configuration tool from the Bluetooth SIG, used to create Mesh networks, configure node parameters, and test network communication performance.

3. Alibaba Cloud IoT Bluetooth Mesh Gateway: Supports the integration of Bluetooth Mesh networks with the Alibaba Cloud IoT platform, enabling cloud storage and remote control of device data.