LTE: Carrier Aggregation - SCell Activation and Deactivation Timings

Use the below calculator for understanding the timing of several actions upon SCell Activation or Deactivation

SCell Activation/Deactivation Details

Activation or Deactivation Activation Deactivation by MAC CE sCellDeactivationTimerExpiry         SFN         subframe 0 1 2 3 4 5 6 7 8 9   

    

If the UE receives an Activation/Deactivation MAC CE in subframe #n activating the SCell, the UE shall apply the below defined actions no earlier than subframe #n+8 and no later than subframe #n+24 or subframe #n+34 (as defined in section 7.7.2 of 36.133)

    ― Transmit SRS on the SCell in case if UL CA and SRS on the SCell is configured;

    ― PDCCH monitoring on the SCell;

    ― PDCCH monitoring for the SCell (Cross Carrier Scheduling);

    ― Start or restart the sCellDeactivationTimer associated with the SCell;

    ― Trigger PHR

    ― CSI reporting for the SCell: The UE should start transmitting valid CSI report no later than subframe #n+24 or #n+34 (as defined in section 7.7.2 of 36.133) but it can report out of range (CQI index = 0) values from subframe #n+8, otherwise the eNodeB has to do blind decoding of PUSCH (if scheduled) from subframe #n+8 till subframe #n+24 or #n+34

If the UE receives an Activation/Deactivation MAC CE in subframe #n deactivating the SCell or if the sCellDeactivationTimer associated with the activated SCell expires in subframe #n, the UE shall deactivate the SCell no later than subframe #n+8.

If the SCell is deactivated, the UE shall apply the following actions:

    ― SRS shall not be transmitted in case if UL CA and SRS on the SCell is configured

    ― The UE shall not transmit UL-SCH on the SCell (UL CA)

    ― PDCCH on/for the SCell shall not be monitored.

    ― The UE shall flush all HARQ buffers associated with the SCell.

    ― The UE shall not transmit RACH on the SCell

    ― Stop the sCellDeactivationTimer associated with the SCell (if running);

    ― The UE shall stop reporting CSI from subframe #n+8 if the sCellDeactivationTimer associated with the SCell expires in subframe #n or if the UE receives an Activation/Deactivation MAC CE in subframe #n deactivating the SCell

Reference: 3GPP TS 36.321, 36.213, 36.331, 36.133, and 36.300