RE: How send long message in Instaburst?

tesc — Tue, 19 May 2020 13:19:36 GMT

Hi,

Instaburst is a replacement for the Bearer layer in Bluetooth mesh, where multiple Network PDUs are sent each advertising interval. This way throughput increases (by the ability to send more Network packets per time interval.)

However, the rest of the stack is not changed by introducing the Instaburst bearer layer. This means Lower Transport layer PDUs are still the same size, which means segmentation and reassembly (SAR) will happen as normally. Changing PDU sizes throughout the stack requires changes in headers and in payload sizes throughout the stack and would require careful consideration regarding how many bytes are available at each layer and how many (additional) bits and bytes are needed for increased size ranges in header fields.

As is, when sending e.g. a maximum Access payload of 380 bytes, this is segmented into 32 packets. Those are sent down the stack, and on the Bearer layer they are either sent one packet in each advertisement (ADV bearer) or they are sent multiple packets in the same advertisement (Instaburst bearer).

For an overview of the stack and mesh network data flow, see Bluetooth Mesh stack architecture.

Regards,
Terje