BLE Mesh up to 3500 devices

[gcb]

Hi

I'm wondering if I can build a Bluetooth Mesh network for up to 3500 devices. I researched the BLE Mesh standard and theoretically the protocol can create a mesh with up to 32,767 devices on a network, with a maximum network diameter of 126 hops. So far I've only seen use cases with up to 30 devices using nRF52x SoC, so from what I noticed the biggest limitation is the flash memory on the SoC to store the LUT with the routing keys, am I right?

If the limitation on the number of devices is the amount of flash memory available to store the LUT with the routing keys, can I solve this problem by adding a large external QSPI flash memory to my nRF52x SoC?

At Nordic, has anyone ever done a test case with a huge number of devices on the same BLE mesh network? If so, how many devices could you reach?

Best regards

[AHaug]

Hi,

with up to 32,767 devices on a network

Up to 32767 (int 16) number of unicast addresses, yes.

So far I've only seen use cases with up to 30 devices using nRF52x SoC, so from what I noticed the biggest limitation is the flash memory on the SoC to store the LUT with the routing keys, am I right?

Yes, this is the biggest limitation. You will have to make sure that your RPL (Replay protection list) is large enough to be able to store all the sender addresses you can receive messages from (sender addresses + sequence number + more). I'm not 100% sure how large this is, as it will vary depending on the features you intend to add, so some computations will have to be done from your end based on experimentation for such a large number.

Regarding the keys, this will only be an issue for the provisioner, as the provisioner will also have an overview over all of the nodes. If you're aiming to use an nRF for the Provisioner role, it could be wise to use an external flash to store the configuration database

At Nordic, has anyone ever done a test case with a huge number of devices on the same BLE mesh network? If so, how many devices could you reach?

Unfortunately we've not done any tests with such a large number of devices. 

Kind regards,
Andreas

[AHaug]

Hi,

I got some more information from the Mesh developers to get some more information regarding examples of how large networks we know of, and I got to know that there are at least one commercial setup running with over 6000 devices.

The network topology and device relationships within a network can give rise to flash limitations. For most normal usecases, RPL list size of 255 for light bulbs and upto 32 for buttons is more than enough. The gateway or provisioner embedded device would need large amount of flash if it wants to talk to all nodes in the network, however this is not an issue if provisioner/configurator is mobile phone.

PS: Also see  Large scale Bluetooth mesh testing  

Kind regards,
Andreas

[gcb]

This article seems quite interesting. I will definitely read it.

Thanks