Carrier Aggregation (CA) Activation/Deactivation

Hi Expert

Can you please help to provide the CA activation/deactivation full details bas per 3GPP specs.


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Hello @chandanamitab,

CA/Activation deactivation mainly depend upon buffer status for UE and channel conditions.
CA activated when RLC buffer for the UE exceeds some threshold.
And it’s kept activated until deactivation conditions are not satisfied.
Deactivation conditions are like, when there is no scheduling on SCell for configured number of frames (typically 128), scell is implicitly deacatived.
Also when there number consecutive NACKS by UE in uplonk or CQI is poor, eNB can explicitly deactivate SCell.
However, these conditions are totally vendor dependent.

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You can find a nice overview here:

Or a full explanation base on 3GPP here:

3GPP TS 36.321 V11.1.0 section "Activation/Deactivation MAC Control Element…
The eNodeB delivers a MAC CE to activate a configured SCell UL or DL traffic volume.
For DL the eNodeB determine that the CA UE has met the DL traffic:
*Data volume buffered at the RLC>,

  • Delay of the first RLC protocol data unit PDU>
    For UL:
  • The report UL buffer status is greater than the threshold specific;
  • Transmission time interval

For Deactivation

  • Traffic volume <
  • Channel quality
  • Residual block errors

Carrier management switch on I think can deactivate scell based on channel condition, otherwise it won’t.
Cqi is more than 9 for all carriers, then off will be good, otherwise on.
Cross carrier scheduling would help ease load of pdcch in scell, as only dci will be involved both in pcell and scell.
Pcfich and phich is only in pcell.
If cif is false then ca won’t work in ue which message we get this information even thou release supports is this info on ue capability info or rrc reconfiguration.

Sharetechnote, always a solid source :wink:

Thanks @sadanandk2 .

Any specific parameters to configure to make 2CA works well, like priority, Loadbalancing, thresholds and boundaries. Specifically Ericsson platform. I would appriciate your response.