Introduction#

This section gives an overview of Bluetooth mesh topology concepts.

Bluetooth Mesh Topology#

Although the Bluetooth mesh technology uses Bluetooth Low Energy (Bluetooth LE) for message transport, when it comes to data flow, there are significant differences.

Bluetooth mesh does not use a point-to-point communication scheme. Rather, it relies on advertising packets being sent and relayed through the mesh network. A node can identify if a network packet is addressed to itself via its destination mesh address (unicast, group or virtual address) which is different from a regular public or private Bluetooth LE address. For more information, please refer to the Bluetooth mesh profile specification.

The following example illustrates a Bluetooth mesh network with the various roles and bearers (taken from the Bluetooth mesh profile specification 1.0.1):

As opposed to Bluetooth LE, Bluetooth mesh nodes have a “many-to-many” relationship with mesh devices within their radio range. In the case where two nodes are not within radio range, the data is relayed by nodes supporting that feature from the emitter to the receiver.

Additionally, nodes in a network have different energy consumption requirements. This impacts the network design, as a node taking part would constantly need to scan for incoming advertising packets and transmit, if necessary, which requires a relatively large amount of power. To mitigate that, nodes can be put to sleep and rely on other nodes within radio range and with fewer power constraints, to store the messages addressed to them.

Finally, Bluetooth mesh relies on the advertising/scanning state of the Bluetooth LE Link Layer. As a result, no low-level collision control exists. If a device does not support the advertising bearer, the GATT bearer can be used (relying on connection). This allows a device to communicate with nodes of a mesh network that support both bearers and that can operate as a proxy between the advertising and GATT bearer.

When building a Bluetooth mesh network, it is important to consider aspects such as these to ensure maximum efficiency.

This document lays out the basic principles and discusses the main parameters that influence network operation.