Are BLE Multiple roles or sequential roles preferable?

[RSA]

Hi,

Im working on a configuration where role switching is neccessary. 

The following is expected:

- all nodes will be advertising when "idle"

- nodes only need to be central when ready to send data to a node of choice

- an arbitrary number of advertising peripherals (maybe even up to 20 or more)

My question is whether there is a cost for using the multiple roles found in the softdevice,  compared to switching manually when needed?

My fears are:

1: if the peripheral role adverting uptime will be influenced by the Central role scanning?

i expect this not to be the case because of the word "parallel" being used https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsds_s140%2FSDS%2Fs1xx%2Fmultilink_scheduling%2Fpriorities_and_events_intro.html

2: What if two nodes end up being synchronised, meaning that they scan and advertise on the same time, and therefore consistantly miss each others advertisments ?

3: Will using the concurrent roles affect throughput between a connected  central and  peripheral?

I hope than my worries and questions were explained adequately!

[Sigurd]

Hi,

1) There is 1 radio peripheral, so if you have a scanner that tries to take all the radio time(scan window == scan interval), then the advertiser will be influenced. If you see an issue with not enough advertisements being sent, you could e.g. decrease the scan window to reduce the amount of scheduling conflicts.

2) Advertising events have a random delay in the range of 0 - 10 ms, so they will not stay synchronized.

3) Yes. See this link.

You might find this image helpful:

[RSA]

Thanks for the answers. Another quick question:

From this page https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsds_s140%2FSDS%2Fs1xx%2Fs140.html&cp=4_5_3_0 i gather:

"

Bluetooth 5.1 compliant single-mode Bluetooth Low Energy protocol stack

• Concurrent central, observer, peripheral, and broadcaster roles with up to 20 concurrent connections along with one Observer and one Broadcaster

"

Does this mean that all three cases are possible?:

Case 1: a node  (Node B) being both central and peripheral.

Case 2: a central (Node A) with multiple peripheral connections.

Case 3: a peripheral (Node A) with multiple centrals connected.

with all of them broadcasting simultaneously.

[Sigurd]

Hi,

RSA said:

Does this mean that all three cases are possible?:

Yes, all these use-cases are possible and supported. 

[RSA]

okay thanks!