Bluetooth physical layer and mesh network

Question

I was wondering in order to have mesh in the Bluetooth, should it be supported by the physical layer or it is related to the higher layers? in particular, what factors should be considered for the physical layer in order that It supports mesh topology?

Answer 1

Bluetooth Mesh uses the same Bluetooth Low Energy Advertisement packets. It uses the same 2.4 GHz Spectrum and GFSK Modulation scheme. Only the higher level layers may change depending on the software architecture. On the Physical layer, it uses the same Bluetooth Low Energy PHY. So, it uses the ADV channels 37, 38 and 39 for communication between nodes.

If a chip or device has Bluetooth v4.0 and above, it can support Bluetooth Mesh. It needs one of the PHY to be supported (i.e) LE 1M, LE 2M, LE Coded PHY. Some chip vendors may not fully support all the PHYs. Bluetooth Mesh was introduced prior to Bluetooth v5.0 and hence some devices which support Bluetooth Mesh might not support all the Bluetooth v5.0 features. But Bluetooth Specifications does not restrict in using specific PHY. The Bluetooth Mesh Specifications says it supports GAP AD Types and Mesh Beacon AD Types specified in the Core Specifications. So, If the device supports secondary advertising(BLE v5.0 and above), then most likely, the device is able to support all the AD Types.