(1) State where the Carrier is not Added as Scell (“not Configured” State):

Here the UE may be configured to perform inter-frequency measurements on the carrier frequency layer using measurement gaps. No additional power consumption is necessary due to Scell receiver. The Scell receiver need not be turned on and measurements can be performed using the Pcell receiver.

(2) State where the Carrier is Added as Scell but not Activated (“Deactivated State”):

Here the UE receives relevant system information for the Scell from the Pcell. The UE may be configured to perform measurements on the Scell without measurement gaps. There will be minimal additional power consumption due to Scell receiver. The Scell receiver needs to be occasionally turned on (e.g., for 5 ms every 160 ms) for RRM measurements using either CRS or Discovery signals

(3) State where the Carrier is Added as Scell and Activated (“Activated State”):

Here the UE is expected to receive PDSCH on the Scell in all activated subframes. There is high additional power consumption due to the Scell receiver. Scell receiver should perform PDCCH monitoring in every subframe (for self scheduling case). The Scell receiver needs to buffer every subframe for potential PDSCH processing (for both self and cross-carrier scheduling cases)

For Scell operation on unlicensed carriers, it is desirable to retain the above states so that UE power consumption for unlicensed carrier operation is similar to that of licensed carrier operation.