BLE Central & Mesh Coexistence

[jkaye-du]

Dear Nordic,

I've integrated a BLE central device with an existing BLE mesh product to create a device that would scan & pair with a monitoring device, collect the data, and then transmit that data across the mesh. I've followed the coexistence guidelines and I've read that BLE central and mesh can coexist. Can you please confirm that is true. If true, are there examples?

I'm having difficulties sharing the softdevice between the central and mesh sides of the device. What are the softdevice sharing strategies for maintaining a connection to a peer while participating as a node on the mesh?

Thanks,

-John

[tesc]

Hi,

Since it is an existing product, I assume that it is built on nRF5 SDK and nRF5 SDK for Mesh, and not nRF Connect SDK. You can combine Bluetooth mesh and BLE based on both SDKs, but the approach is a bit different.

Combining Bluetooth mesh and BLE does need some consideration, since both need access to the same radio. This will be a constraint regardless of which protocols you combine, but for Bluetooth mesh and BLE one advantage is that since they both use the same type of advertising packet, combining Bluetooth mesh with a BLE scanner comes with virtually no overhead. When combining with BLE connections, on the other hand, time spent for the connections will impact the mesh performance.

For optimal Bluetooth mesh operation, the mesh stack needs access to the radio as much of the time as possible. This is because incoming mesh packets over the advertiser bearer may come in at any time. The larger the fraction of time used in RX, the higher chance of packet reception. When a node is spending less time in RX, you may experience that you need to configure the other nodes in the network to a higher retransmission count, to compensate.

On the BLE side you can increase the connection interval and slave latency for the connection, in order to use less radio time for BLE. Also, a high supervision timeout will allow for more connection events to be lost without losing the connection.

For an example of Bluetooth mesh combined with a BLE connection, see the SDK UART coexistence example. While we do not have an nRF5 SDK for Mesh example of coexistence with a BLE central, that example has a BLE peripheral which for the purposes of Bluetooth mesh coexistence with BLE is very similar. The main difference is that with central you are in control of the connection parameters, so you are in a better position to choose parameters that puts a smaller burden on the mesh communication.

Regards,
Terje

[jkaye-du]

Hi Terje,

Thank you for your response and I apologize for my late reply -- was out enjoying the August sun away from my desk. I did sort out the coexistence issues that I was having.

Thanks again,

-John