DFU over BLE mesh - reliability and speed

[mr_jj]

I understand that Nordic provides a proprietary DFU via the BLE mesh. What mechanisms are in place to ensure that all packets reach their destination, e.g. acknowledgements or retransmissions.

What is the payload size and average speed used for the DFU assuming a maximum of 4 hops?

[Hung Bui]

Hi John, 

 

Actually there is no acknowledgements when the new image is populating through the network. The distributor distribute image packets one by one, each six times using trickle algorithm.

A node that missing a packet (base on packet ID) will send a request beacon to its neighbors to have the neighbors to help retransmit the missing packet or forward that request if they don't have). After 64 newer packets it still haven't received the missing packet, it will terminate and start requesting from the beginning (ready beacon). 

You can have a look at the DFU packet format here

 

We haven't run a performance test for DFU with Mesh. But in our test here we updating 150kB of flash took about 60 minutes.

 

[Igor]

Hung Bui 60 minutes to upload firmware via UART or to propagate it through a Mesh network?

[Hung Bui]

It's 60 minutes to propagate the image through Mesh network.