Difference Friend node and Relay nodes

[SamTheMan]

Hello everyone,

 

I have a Bluetooth Mesh network of Friend nodes that communicate with eachother and allow message to pash through them.

Currently only a few need to have Low Power Nodes attached to them and the rest is needed to extend my network.

But maybe far into the future this will change.

 

So I'm wondering; Would it be beneficial to disable the friend feature on some of the nodes?

Are there any negatives to just making all backbone nodes be friend nodes (for possible future changes / flexibility)?

What is the major difference between Friend nodes and relay nodes?

[Amanda Hsieh]

Hi, 

The Friend feature and the Low Power feature combines to provide low power message reception for the Low Power Node. (TX from the Low Power Node uses the standard protocol of sending normal ADV bearer packets.)

The relay feature makes the node retransmit messages over the advertising bearer. (Mostly affects the network / bearer layers.)

For the short story about layers and concepts, see Bluetooth mesh concepts.

For the full specification, see the Mesh Profile Specification from bluetooth.com, where the features are specified.

I suggest you go through these documentations:

Bluetooth Mesh Network: Friendship

Low Power node feature

Integrating Low Power node feature

Low Power node example

You will get a better understanding of Relay, LPNs and Friendship nodes and how things work between them.

Regards,
Amanda

[SamTheMan]

Hi Amanda,

The backbone of my Bluetooth Mesh network consists of Friend nodes loaded with the "Light Switch Server Example".

Some of these nodes however are only really used as extenders, but don't have any Low Power Nodes attached to them yet in my current topology.

Would there be a benefit to disabling the friend feature on them as it's unneeded for my current setup? (example: power consumption etc.).

Regards,

Sam

[Amanda Hsieh]

Hi Sam, 

When the project is built with the Friend feature in it, but the Friend feature is not enabled (or it has been disabled) runtime, then I would not expect any noticeable difference. If the project is not built with the Friendship feature at all, then I would expect some Flash and RAM savings. 

For any Low Power Nodes in a Friendship, that would mean some more TX (instead of RX) and packet handling (CPU usage).

Regards, 
Amanda