Hi Experts.
After an SCELL is added and activated in 5G through MAC CE, does a timer start for its deactivation?
On what basis will the SCELL be deactivated and removed?
SCELL can be deactivated based on the SCELL deactivation timer.
This timer starts when no data is scheduled for the SCELL and resets upon any scheduling activity. The timer is generally set to 1280 slots or ms.
Some vendors configure this timer in the UE, allowing the UE to implicitly deactivate the SCELL if no scheduling occurs before the timer expires.
Other vendors manage it in the gNB, which deactivates the SCELL through MAC CE when the timer expires.
Secondary cell deactivation timer.
The UE (and the network) can deactivate the activated SCell without explicit signaling which is based on sCellDeactivationTimer.
This is the amount of time (in radio frames) the UE has not received any data on the SCell.
SCell Activation is done via MAC Control Element whereas the deactivation mechanism is either by using MAC control element or by the expiry of the sCellDeactivationTimer.
RRC will configure the UE with sCellDeactivationTimer which is located in the IE mac-MainConfig. It is configured only if the UE is configured with one or more SCells.
sCellDeactivationTimer can take values starting from 20ms to 1280ms (20, 40, 80, 160, 320, 640, and 1280ms); configured in ServingCellConfig.
If the field is absent, the UE shall delete any existing value for this field and assume the value to be set to infinity.
UE maintains a sCellDeactivationTimer (as configured by the RRC) timer per configured SCell and deactivates the associated SCell upon its expiry.
If the UE receives an Activation/Deactivation MAC CE in subframe n activating the SCell, the UE shall start (SCell Activation) or restart (SCell Reactivation) the sCellDeactivationTimer associated with the SCell in subframe n+8.