How to set TX power for BIS ISO streams alone

[Benno Trutmann]

Hi.

I would like to set the TX power level for broadcast streams to a higher level then the other radio packets (especially the packets on the primary ADV channels). First I tried to set the TX level with the pseudo connection handle from the ISO streams themself returned by bt_hci_get_conn_handle(bap_ep_info.iso_chan->iso, &conn_handle), but these handles were not accepted by the BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL command. Then I set the TX level on the advertisement set belonging to the streams, this works, but sets the TX level not only for the BIS streams but also for the primary and extended advertising packets.

Is there a way to only set the TX power level for the packets belonging to BIS streams?

Regards,

Benno

[Maria Gilje]

Hi Benno,

Is there a way to only set the TX power level for the packets belonging to BIS streams?

I will investigate if this is possible and/or supported in nRF Connect SDK (NCS).

Please let me know which NCS version you are using so we can give you the most relevant information.

Best regards,

Maria

[Benno Trutmann]

I am using NCS 2.7.0.

[Maria Gilje]

Hi again Benno,

My apologies for the wait.

I have found some relevant information internally which I will prepare and share with you tomorrow. The gist of it is that we have functionality to configure the transmit power on individual channels, but I need some more time to find the specifics.

but these handles were not accepted by the BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL command.

The reason for this is that BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL was created for the now deprecated LE Audio-specific Controller subsystem. It is not valid for the SoftDevice Controller which supports LE Audio from NCS v2.6.0.

I'll be back tomorrow with more!

Best regards,

Maria

[Maria Gilje]

I return with some more resources.

You can set the TX power for individual channels by using the TX power part of  the Multiprotocol Service Layer (MPSL). Populate a mpsl_tx_power_envelope_t struct and pass it to mpsl_tx_power_channel_map_set().

BR,

Maria

[Benno Trutmann]

This is not workable for me. I want to set a fixed TX power level for a whole BIS ISO stream and not for a fixed BLE channel. The BIS ISO stream frequency hops over all available channels, so setting the TX power level for all these channels via mpsl_tx_power_channel_map_set() would set the TX power level for any communication and not only the BIS ISO stream.

[Maria Gilje]

Hello,

I appreciate your patience.

Sorry to hear that setting the TX powers for channels is not a feasible solution. Unfortunately it is not possible to set the TX power for individual BISes.

A possible future solution is to set the TX power for BIGs. This is a feature request which we are tracking internally. If this is a good option for you I will let you know when there are any relevant updates.

Best regards,

Maria