Bluetooth mesh/time synchronization

[TinoMK]

Dear all,

I am interested in a BT mesh modules that support precise time synchronization between the modules (microseconds). This is required for sensors application that uses accelerometers distributed along a building. Each sensor needs to transmit payload of ~1.5KB each second. BT modules needs to be integrated under embedded device with STM32 MCU. 

Also what type of gateways/interfaces you offer for integrating the MQTT protocol for communication of the sensor modules with Cloud application?

Thank you,

[Hung Bui]

Hi Tino, 

Time synchronization was not covered in current Bluetooth Mesh spec. Meaning for now you would need to do it proprietary way. 

We have an example on time synchronization described here: https://devzone.nordicsemi.com/nordic/short-range-guides/b/bluetooth-low-energy/posts/wireless-timer-synchronization-among-nrf5-devices

The challenge would be how to define a timing master and how the time synchronization be propagandize in the mesh network.  

The throughput for Bluetooth mesh is roughly about 3.5kbs, so it's not easy to achieve 1.5kB per second as your requirement. 

Bluetooth Mesh is defined as a closed network, so there is no definition on how it should be connected to cloud and how it to be used with MQTT. It's up to you to define that. We have no gateway example that work with Bluetooth Mesh. 

[TinoMK]

Hi Hung,

Thank you so much for your answers.

The throughput of the BT mesh you say it is ~3.5kbs. Why is this limitation when Bluetooth 5.0 protocol defines speed of up to 2Mbps. Can you please explain?

Thank you,

[Hung Bui]

Hi Tino,

There is something need to be clarified here. Bluetooth 5.0 protocol doesn't cover Bluetooth mesh. Bluetooth mesh is a independent protocol that only use the Link layer and MAC layer of the Bluetooth Low Energy. Speed of 2Mbps is only for Bluetooth Low Energy when in connection. Bluetooth Mesh doesn't do any connection and only use Advertising packets. Please read more about mesh network here: https://www.bluetooth.com/blog/introducing-bluetooth-mesh-networking/