Is BT Mesh still not compatible with coded PHY

[Fridtjof]

Hi

I'm looking into using the nrf52833 and/or nrf52843 for a long range mesh network. Since I require long range, but not high bandwidths, using a coded PHY seems appropriate. However, I read in a previous answer (linked below) from 3 years ago that coded PHYs are not supported for BT Mesh, because coded PHYs are Bluetooth 5, and mesh is Bluetooth 4. Is it possible that this has changed over the last three years? Can we now use coded PHY to extend the range of our Bluetooth Meshes?

 Bluetooth Mesh options for increasing or changing radio range 

-Fridtjof

[Fridtjof]

I read the official Bluetooth Mesh FAQ, and it says that BT Mesh is available for Bluetooth 5, so I would think it can handle coded PHYs. Is this something that has been tried on the nrf528XX?

[Amanda Hsieh]

Hi, 

Please see my colleague's explanation in this post. 

Regards,
Amanda H.

[Fridtjof]

Thank you for the answer, Amanda

It seems coded PHYs cannot be used with BT Mesh IF we need qualification. I'm trying to figure out whether we would need it. If we use Bluetooth Mesh but do not advertise that we use Bluetooth, use the Bluetooth logo, or wish to be compatible with any other Bluetooth devices (just our own mesh); would we need to get qualified?

[Amanda Hsieh]

If you want to use the Bluetooth logo, it needs to be qualified. 

[Fridtjof]

If and only if?

[Fridtjof]

I will assume the answer is something like "most probably yes, but we do not wish to take on any possible legal liability." This is understandable. Thank you for the guidance!

[Amanda Hsieh]

Hi,

I got an update from the team:

It is a bit incorrect to say coded PHYs cannot be used with BT Mesh. 

BT Mesh specification does not define transporting mesh packets over coded PHY. However, it also does not prevent anyone from doing so. If you can develop your coded-phy bearer module (like adv_ext.c module which sends mesh packets using 1M PHY), and activate this functionality using a 'Vendor model', this wouldn't cause any issues. So, as long as the node works like a normal BT Mesh node without activating codes-PHY using the vendor model ... I don't see a problem with doing this and using Bluetooth TM (since Code-PHY by itself is a Bluetooth functionality). Of course, such a device may not be marketed as a "true interoperable mesh device", but there is no issue when using the Bluetooth logo by itself as long as you qualify and list your design in the Bluetooth qualification database. 

Bluetooth qualification for a particular product grants customers a license to use parts of Bluetooth technology (that you claim to qualify in your listing) in that commercial product. How customers combine various Bluetooth features and mix and match is up to your creativity and technical feasibility. If interoperability is not a goal, I don't see any blocker in transporting mesh packets over coded-phy. 

Making such a thing won't be trivial and the dev team may not be able to support it fully, but you are free to experiment on your own.

Regards,
Amanda H.

[Fridtjof]

Thank you for the excellent answer, Amanda!