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zephyrproject-rtos / zephyr

Primary Git Repository for the Zephyr Project. Zephyr is a new generation, scalable, optimized, secure RTOS for multiple hardware architectures.
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Bluetooth: controller: Possibility to have an active CIS and extended advertising at the same time #56201

Open ladivin opened 1 year ago

ladivin commented 1 year ago

Is your enhancement proposal related to a problem? Please describe. If an acceptor (peripheral) listens to a CIS from an initiator (central) and the acceptor starts extended advertising while the CIS is still active, the extended advertising may cause audio glitches (loss of ISO data).

Describe the solution you'd like Solution proposed by @cvinayak: currently primary channel ADV_EXT_IND PDU advertising nudges automatically around other radio events, the fix would do the same for auxiliary channel AUX_ADV_IND PDUs to nudge around any new peripheral ACL radio event (and not overlap).

Describe alternatives you've considered None

Additional context The motivation behind this request is to have the possibility for a peripheral to accept an audio stream from one central, then start extended advertising again and then based on certain criteria possibly to switch to a stream from a different central.

cvinayak commented 1 year ago

ISO implementation is still lacking feature completion and conformance testing, this enhancement will be delayed. The strategy would be to implement a Babblesim CI test for the said usecase as a test driven development.

Test:

  1. Develop a testcase with procedures to have two extended advertising sets active, one being connectable.
  2. Establish an ACL connection and Create CIS from a central device
  3. Verify that there is no lost ISO data reception on the peripheral

Implementation changes:

  1. Extended Advertising Primary channel radio event, in a low priority execution context evaluates relative drift between AUX_ADV_IND, any peripheral ACL and CIG radio event
  2. If the margin between is lower than a threshold, then use ticker_update interface on the AUX_ADV_IND to move it accordingly to a new position in timeline.
cvinayak commented 1 hour ago

@ladivin I have a draft implementation change in #75760 that can make the Extended Advertising to nudge around ACL connection events. Please give a try and let me know...

The feature gets enabled when using in the PR branch:

CONFIG_BT_CTLR_ADVANCED_FEATURES=y
CONFIG_BT_TICKER_EXT=y
CONFIG_BT_TICKER_EXT_SLOT_WINDOW_YIELD=y
CONFIG_BT_CTLR_ADV_AUX_SLOT_WINDOW=y