Bluetooth Mesh: Advantages and Disadvantages

This page explores the advantages and disadvantages of Bluetooth mesh technology, including its architecture. It outlines the benefits and drawbacks of Bluetooth mesh.

Introduction:

Classic Bluetooth technology was first introduced in 1999. Managed by the Bluetooth SIG (Special Interest Group), it operates on radio frequencies from 2402 MHz to 2480 MHz. The primary function of Bluetooth is to transmit data over short distances. The initial version supported 79 channels spaced 1 MHz apart.

Bluetooth Low Energy (BLE), version 4.0, was launched in 2010 with a focus on extremely low power consumption. BLE supports approximately 40 channels at 2MHz spacing. It enables connections between devices using a master-slave concept and employs the GATT (Generic Attribute Profile) protocol for data transmission.

Bluetooth 5.0 was later developed to support a coverage range of up to 240 meters and a speed of 2 Mbps.

What is Bluetooth Mesh Technology?

Earlier versions of Bluetooth supported one-to-one and one-to-many topologies. The Bluetooth mesh specification, launched in 2017, allows devices to operate in a many-to-many topology. Bluetooth mesh is built upon BLE.

The main goals in developing Bluetooth mesh were to extend the range of existing Bluetooth networks and to support more industrial applications of BLE technology. BLE mesh utilizes the advertising and scanning states of nodes to relay messages. Devices that are part of a mesh network are referred to as “nodes.” Other Bluetooth-enabled devices, such as smartphones, tablets, or boards, are called “unprovisioned devices.” Once these devices are provisioned, they become “nodes.”

According to BLE mesh version 1.0, it supports about 32767 nodes and 127 hops. It doesn’t use IP (Internet Protocol) as it’s built on top of the BLE stack.

The figure above depicts a Bluetooth mesh architecture with different types of nodes.

It uses managed flooding instead of routing techniques employed by other mesh technologies. The functions of Bluetooth mesh nodes are as follows:

Node

Any device that has joined a Bluetooth mesh network is called a “node.” A node contains multiple parts, known as “elements,” which are controlled independently. Elements of a node can be in various conditions or “STATES,” e.g., ON and OFF for a light bulb. Properties, such as manufacturer or admin properties, can be added to the states.

Relay Node

This node relays or retransmits messages to other nodes, functioning as an intermediary for other nodes. This helps the message traverse the network to distant nodes, extending the coverage of the mesh network.

Low Power Nodes

These are power-constrained nodes that remain asleep most of the time and wake up according to a programmed schedule. They are primarily used to transmit messages.

Friend Nodes

These nodes are not power-constrained and keep their radio on all the time to listen for broadcast messages. A friend node maintains a “friendship” relationship with low-power nodes. It stores messages for low-power nodes when they are asleep. When a low-power node becomes active, the related friend node delivers the stored messages.

Proxy Node

This node facilitates communication between mesh nodes and BLE-enabled devices that lack mesh capabilities. It implements both mesh and BLE stack functionalities.

Bluetooth mesh supports three types of messages: GET, SET, and STATUS. Each of these messages is assigned a unique “opcode.” Messages in Bluetooth mesh contain source and destination addresses, which are used to identify the message’s termination node. The types of addresses used are unicast, group address, and virtual address. Messages in a mesh network are exchanged using a publish and subscribe pattern.

The following three features of BLE ensure the reliability of message delivery:

• Heartbeat message: Each BLE node transmits heartbeat messages periodically to inform other nodes in the network about its active state.
• TTL (Time to Live): This controls how far a message can traverse through the network. The TTL value restricts the number of times a message can be relayed within the network. Each time a message is received and relayed, the TTL value is decremented by 1. The heartbeat message can be used by the source node to set the correct TTL value.
• Message Cache: Each node maintains a cache of received messages. Whenever a node receives a new message, it checks its list of cached messages and ignores it if it’s already present.

Benefits or Advantages of Bluetooth Mesh Technology

The following are the benefits or advantages of Bluetooth Mesh Technology:

• Extended Range: It offers an extended range as nodes can relay messages to nodes that are far away.
• Self-Healing Capabilities: Bluetooth mesh nodes have self-healing capabilities. If a node drops or fails within the network, other nodes take over the transmission of messages to the other nodes.
• Global Interoperability: Products from one vendor will work seamlessly with products from other vendors.
• Backward Compatibility: BLE mesh is backward compatible with other BLE devices that don’t have mesh protocol.
• Cost-Effective: Bluetooth mesh runs on top of BLE. Most smartphones support BLE 4.0 and BLE 5.0 versions. Bluetooth mesh technology utilizes existing smartphones and doesn’t require external hardware devices, making it cost-effective.
• End-to-End Security: BLE mesh nodes support end-to-end security for messages exchanged between them.
• Power Efficient: It’s more power-efficient compared to other mesh technologies due to its friendship node concept.
• Offline Configuration: No internet connection is required once the configuration is downloaded from the cloud server to the smartphone. The smartphone can then be used to recover and configure the status of nodes in a Bluetooth mesh topology.

Drawbacks or Disadvantages of Bluetooth Mesh Technology

The following are the drawbacks or disadvantages of Bluetooth Mesh Technology:

• Complexity: Like wireless mesh, Bluetooth mesh topology is more complex, making it difficult to build and maintain.
• Not Suitable for Audio/Video: Bluetooth mesh is not suitable for transmitting audio and video data.
• Lower Bandwidth: Bluetooth mesh supports lower bandwidth compared to WiFi. Therefore, it’s primarily used for transmitting small-size commands for simple on/off functionalities, such as turning a light on or off.