Beacons and the Bluetooth Mesh

Traditional beacons transmit to other devices such as smartphones and gateways but not to other beacons. This limits the range of the communication to typically 50m although this can extend to 300m or even 4Km for specialist beacons with output power amplifiers.

Mesh beacons solve the problem of the limited range by connecting together to form a mesh. The mesh can include tens of thousands of beacons. Only devices at the edge of the mesh need to act on or pass information to, for example, servers. The mesh also provides for new scenarios that need many devices that are all inter-connected.

The Bluetooth Mesh was announced in July 2017. It's produced by the Bluetooth SIG who created all the other Bluetooth specifications. Industry organisations such as ourselves are members of the Bluetooth SIG. The Bluetooth mesh specifications run to about 1000 pages and took over three years to create. Special care has been taken to ensure the mesh is scalable, secure, reliable and flexible for many uses.

Bluetooth mesh relies on devices scanning and advertising in the same way as traditional beacons. Received packets are re-broadcasted by relays until the packet is received by other nodes. This provides a way of spreading information across the mesh network with no single point of failure.

It's expected that the Bluetooth mesh will be used for applications beyond just advertising information. They are already being used in lighting and are expected to be used in building automation, asset tracking and the general case of IoT sensing for many industries.

The Bluetooth SIG only produce the specifications and it's for 3rd parties to produce actual code that implements the mesh. This is fairly complex so it mainly falls to the System on a Chip (SoC) manufacturers to produce SDKs for their devices. So far, only Nordic Semiconductor has released an SDK for the nRF51 and nRF52 chips used in the majority of beacons.

The software is much more complex than in current beacons and hence requires more capable SoCs than are found in the majority of current beacons. Higher memory size variants of the nRF51 or the newer nRF52 need to be used. This means existing beacons can't be retro-fitted with new mesh firmware.

Mesh nodes are continually listening and re-transmitting and hence consume more power than traditional beacons. This means that mesh devices can't use coin-cell batteries for extended periods of time. Devices tend to be permanently connected to the mains or via USB. However, there is a facility to connect traditional beacons via a 'store and forward' mechanism that's called mesh friendship.

Mesh software providers can provide added facilities on top of the Mesh in order to differentiate their offering. For example, Nordic provide an API to allow for traditional beacon advertising alongside mesh advertising and also provide remote provisioning where unprovisoned devices can be added that are well away from the device adding nodes to the network.

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Tags: mesh, bluetooth