Apparatus and methods for secondary cell (SCell) enhancements in wireless communications
A method and apparatus for triggering activation of a secondary cell (SCell) and activating the SCell is provided. A user equipment (UE) may receive, from a gNB, a SCell activation command indicating the UE to activate a SCell for communications between the UE and the gNB on the SCell, and receive a reference signal (RS) on the SCell. The RS is configured for activation of the SCell. The UE may perform, upon receiving the SCell activation command, SCell activation for activating the SCell based at least on the RS, and send, to the gNB, a report indicating that the SCell is activated for the UE.
1 . A method comprising:
receiving, by a user equipment (UE) from a gNB, a secondary cell (SCell) activation command indicating the UE to activate a SCell for communications between the UE and the gNB on the SCell;
receiving, by the UE, a reference signal (RS) on the SCell, wherein the RS is configured for fast activation of the SCell;
performing, by the UE upon receiving the SCell activation command, SCell activation for activating the SCell based at least on the RS; and
sending, by the UE to the gNB, a report indicating that the SCell is activated for the UE.
2 . The method of claim 1 , wherein the SCell activation command is received in an enhanced medium access control control element (MAC CE) on a first cell that was activated for serving the UE.
3 . The method of claim 2 , further comprising:
receiving, by the UE, a command sent on the first cell, the command triggering the UE to receive the RS, and the command being included in the enhanced MAC CE.
4 . The method of claim 3 , wherein the RS is one of a set of RSs configured for fast activation of the SCell, and is indicated by the command.
5 . The method of claim 1 , wherein the RS is an aperiodic RS, and is triggered for receiving or received during activation of the SCell, and a slot in which the RS is sent is based on a slot in which the SCell activation command is sent and a slot offset value, the slot offset value configured for the RS and being in terms of a number of slots.
6 . The method of claim 1 , further comprising:
performing, by the UE based on the RS, at least one of automatic gain control (AGC) settling, frequency tracking, time tracking, or fine timing.
7 . The method of claim 1 , wherein the RS comprises at least a channel state information (CSI)-RS for tracking, which is a tracking reference signal (TRS) configured for the SCell.
8 . The method of claim 7 , wherein transmission of the RS comprises one or more transmissions of the TRS on one or more slots.
9 . The method of claim 1 , further comprising:
receiving, by the UE after receiving the RS, a channel state information-reference signal (CSI-RS) configured for the SCell.
10 . The method of claim 9 , wherein the CSI-RS is quasi co-located (QCLed) with the RS.
11 . The method of claim 1 , wherein the report comprises a CSI report based on a CSI measurement of a CSI-RS, the CSI report comprising a valid channel quality indicator (CQI) indicating that the SCell is activated.
12 . The method of claim 1 , further comprising:
sending, by the UE to the gNB, a message acknowledging receipt of the SCell activation command.
13 . The method of claim 1 , further comprising:
activating, by the UE, a bandwidth part (BWP) of the SCell associated with the RS.
14 . The method of claim 1 , wherein the report indicates that a BWP of the SCell associated with the RS is active.
15 . A method comprising:
sending, by a gNB to a user equipment (UE), a secondary cell (SCell) activation command indicating the UE to activate an SCell for communications between the UE and the gNB on the SCell;
sending, by the gNB to the UE, a reference signal (RS) on the SCell to be activated by the UE, the RS configured for fast activation of the SCell; and
receiving, by the gNB from the UE in response to sending the SCell activation command and the RS, a report indicating that the SCell is activated for the UE.
16 . The method of claim 15 , wherein the SCell activation command is sent in an enhanced medium access control control element (MAC CE) on a first cell that was activated for serving the UE.
17 . The method of claim 16 , further comprising:
sending, by the gNB, a command on the first cell triggering the UE to receive the RS, the command being included in the enhanced MAC CE.
18 . The method of claim 17 , wherein the RS is one of a set of RSs configured for fast activation of the SCell, and is indicated by the command.
19 . The method of claim 15 , wherein the RS is an aperiodic RS and triggered/sent during activation of the SCell, and a slot in which the RS is sent is determined based on a slot in which the SCell activation command is sent and a slot offset value, the slot offset value configured for the RS and being in terms of a number of slots.
20 . An apparatus comprising:
a non-transitory memory storage comprising instructions; and
one or more processors in communication with the non-transitory memory storage, wherein the instructions, when executed by the one or more processors, cause the apparatus to perform:
receiving, from a gNB, a secondary cell (SCell) activation command indicating to activate a SCell for communications between the apparatus and the gNB on the SCell;
receiving a reference signal (RS) on the SCell, wherein the RS is configured for fast activation of the SCell;
performing, upon receiving the SCell activation command, SCell activation for activating the SCell based at least on the RS; and
sending, to the gNB, a report indicating that the SCell is activated for the apparatus.