Beam indication for layer 1 / layer 2 triggered mobility (LTM)

Abstract

Apparatus and methods for beam indication for layer 1 / layer 2 triggered mobility (LTM) are disclosed. Advantages of the apparatus / methods include a reduction in cell switch latency. In an aspect, a user equipment apparatus (UE) receives, from a serving cell, a medium access control-control element (MAC-CE) including an indication of a candidate cell and an activation of one or more transmission configuration indicator (TCI) states for the candidate cell. The UE further receives, from the serving cell via lower layer signaling, a cell switch command indicating the candidate cell as a target cell. The UE further switches, in response to the cell switch command, communication with the serving cell to communication with the target cell, where the communication with the target cell includes communicating with the target cell by applying at least one of the one or more TCI states.

Description

This abstract discloses apparatus and method for beam indication in Layer 1 / Layer 2 triggered mobility (LTM). Advantages of this apparatus / method include reduced cell handover latency. In one aspect, a user equipment (UE) receives a Media Ingress Control (MAC-CE) from a serving cell, the MAC-CE including: a candidate cell and an indication of activation of one or more Transport Configuration Indicator (TCI) states for the candidate cell. The UE also receives a cell handover command from the serving cell via lower-layer signaling, the cell handover command indicating the candidate cell as the target cell. The UE further switches communication with the serving cell to communication with the target cell in response to the cell handover command, wherein communication with the target cell includes: communicating with the target cell by applying at least one of one or more TCI states.

Claims

CLAIMS:

1. A user equipment apparatus comprising: at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the user equipment apparatus at least to: receive, from a serving cell, a medium access control-control element (MAC-CE) including an indication of a candidate cell and an activation of one or more transmission configuration indicator (TCI) states for the candidate cell; receive, from the serving cell via lower layer signaling, a cell switch command indicating the candidate cell as a target cell; and switch, in response to the cell switch command, communication with the serving cell to communication with the target cell, wherein the communication with the target cell comprises communicating with the target cell by applying at least one of the one or more TCI states.

2. The user equipment apparatus of claim 1, wherein the MAC-CE includes: a first field; and a second field to indicate whether information in the first field is for the serving cell or the candidate cell.

3. The user equipment apparatus of claim 1, wherein the MAC-CE includes: a first value; and a second value to indicate that the first value identifies the candidate cell.

4. The user equipment apparatus of claim 1 , wherein the MAC-CE includes a candidate cell-specific TCI state list including the one or more TCI states.

5. The user equipment apparatus of claim 1, wherein the cell switch command further includes a reference to the at least one of the one or more TCI states.

6. The user equipment apparatus of claim 1, wherein the instructions when executed by the at least one processor, further cause the user equipment apparatus at least to receive the cell switch command by: receiving downlink control information (DCI) including an indication of the candidate cell and a TCI codepoint referencing the at least one of the one or more TCI states.

7. The user equipment apparatus of claim 1, wherein the instructions when executed by the at least one processor, further cause the user equipment apparatus at least to receive the cell switch command by: receiving downlink control information (DCI) including an indication of a candidate cell activated TCI list including the candidate cell and a TCI codepoint referencing the at least one of the one or more TCI states.

8. The user equipment apparatus of claim 1, wherein the instructions when executed by the at least one processor, further cause the user equipment apparatus at least to receive the cell switch command by: receiving downlink control information (DCI) including a reference to the at least one of the one or more TCI states and an indication that the at least one of the one or more TCI states is for the candidate cell.

9. The user equipment apparatus of claim 1, wherein the instructions when executed by the at least one processor, further cause the user equipment apparatus at least to: perform intra-cell beam management in the target cell based on the one or more TCI states.

10. The user equipment apparatus of claim 1, wherein the one or more TCI states are associated with more than one physical cell identifiers (PCIs), and wherein the instructions when executed by the at least one processor, further cause the user equipment apparatus at least to:perform at least one of intra-cell beam management or inter-cell beam management in the target cell based on the one or more TCI states.

11. The user equipment apparatus of claim 1, wherein the instructions when executed by the at least one processor, further cause the user equipment apparatus at least to: retain, while operating in the target cell, a TCI state list activated by the serving cell.

12. The user equipment apparatus of claim 1, wherein the instructions when executed by the at least one processor, further cause the user equipment apparatus at least to: transmit an indication of a user equipment capability, wherein at least one of a number of the one or more TCI states activated in the MAC-CE for the candidate cell or a number of TCI states activated across multiple cells at the user equipment apparatus is based on the user equipment capability.

13. A method performed by a user equipment apparatus, the method comprising: receiving, from a serving cell, a medium access control-control element (MAC-CE) including an indication of a candidate cell and an activation of one or more transmission configuration indicator (TCI) states for the candidate cell; receiving, from the serving cell via lower layer signaling, a cell switch command indicating the candidate cell as a target cell; and switching, in response to the cell switch command, communication with the serving cell to communication with the target cell, wherein the communication with the target cell comprises communicating with the target cell by applying at least one of the one or more TCI states.

14. The method of claim 13, wherein the MAC-CE includes: a first field; and a second field to indicate whether information in the first field is for the serving cell or the candidate cell.

15. The method of claim 13, wherein the MAC-CE includes: a first value; and a second value to indicate that the first value identifies the candidate cell.

16. The method of claim 13, wherein the MAC-CE includes a candidate cell-specific TCI state list including the one or more TCI states.

17. The method of claim 13, wherein the cell switch command further includes a reference to the at least one of the one or more TCI states.

18. The method of claim 13, wherein the receiving the cell switch command comprises: receiving downlink control information (DCI) including an indication of the candidate cell and a TCI codepoint referencing the at least one of the one or more TCI states.

19. The method of claim 13, wherein the receiving the cell switch command comprises: receiving downlink control information (DCI) including an indication of a candidate cell activated TCI state list including the candidate cell and a TCI codepoint referencing the at least one of the one or more TCI states.

20. The method of claim 13, wherein the receiving the cell switch command comprises: receiving downlink control information (DCI) including a reference to the at least one of the one or more TCI states and an indication that the at least one of the one or more TCI states is for the candidate cell.

21. The method of claim 13, further comprising: wherein the one or more TCI states are associated with more than one physical cell identifiers (PCIs), performing intra-cell beam management in the target cell based on the one or more TCI states.

22. The method of claim 13,wherein the one or more TCI states are associated with more than one physical cell identifiers (PCIs), and wherein the method further comprises: performing at least one of intra-cell management or inter-cell management in the target cell based on the one or more TCI states.

23. The method of claim 13, further comprising: retaining, while operating in the target cell, a TCI state list activated by the serving cell.

24. The method of claim 13, further comprising: transmitting an indication of a UE capability, wherein at least one of a number of the one or more TCI states activated in the MAC-CE for the candidate cell or a number of TCI states activated across multiple cells at the user equipment apparatus is based on the UE capability.

25. A network apparatus comprising: at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the network apparatus at least to: transmit, to a user equipment apparatus, a medium access control-control element (MAC-CE) including an indication of a candidate cell and an activation of one or more transmission configuration indicator (TCI) states for the candidate cell; transmit, to the user equipment apparatus via lower layer signaling, a cell switch command indicating the candidate cell as a target cell; and perform a handover of the user equipment apparatus to target cell responsive to the cell switch command.

26. A method performed by a network apparatus, the method comprising: transmitting, to a user equipment apparatus, a medium access control-control element(MAC-CE) including an indication of a candidate cell and an activation of one or more transmission configuration indicator (TCI) states for the candidate cell; andtransmitting, to the user equipment apparatus via lower layer signaling, a cell switch command indicating the candidate cell as a target cell; and performing a handover of the user equipment apparatus to target cell responsive to the cell switch command.

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