WO2025074334A1

WO2025074334A1 - Transmission control indicator (tci) state configuration signaling for layer 1/layer 2-triggered mobility (ltm)

Info

Publication number: WO2025074334A1
Application number: PCT/IB2024/059752
Authority: WO
Inventors: Icaro Leonardo DA SILVA; Antonino ORSINO; Ioanna Pappa
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-10-06
Filing date: 2024-10-04
Publication date: 2025-04-10
Anticipated expiration: 2026-04-06

Abstract

A method performed by a network node (QQ110) operating as a Central Unit (CU) serving a user equipment (UE)(QQ112) is provided. The CU is configured to communicate with a first Candidate-DU (C-DU) and a second C-DU. A Transmission Configuration Indication (TCI) state configuration of a L1/L2-Triggered Mobility (LTM) candidate cell of the second C-DU is obtained from the second C-DU. The TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C- DU.

Description

TRANSMISSION CONTROL INDICATOR (TCI) STATE CONFIGURATION SIGNALING FOR LAYER 1/LAYER 2-TRIGGERED MOBILITY (LTM)

FIELD

The present disclosure relates to wireless communications, and in particular to transmission control indicator (TCI) state configurations.

BACKGROUND

In Rel-18, Third Generation Partnership Project (3GPP) has agreed on a Work Item on Further New Radio (NR) mobility enhancements, in particular, in a technical area entitled L1/L2 based inter-cell mobility. See the Work Item Description (WID) in RP-213565 (Reference 1) for further details. According to the WID, when the user equipment (UE) moves from the coverage area of one cell to another cell, at some point a serving cell change needs to be performed. Currently serving cell change is triggered by L3 measurements and is done by Radio Resource Control (RRC) signaling triggered Reconfiguration with Synchronization for change of PCell and PSCell, as well as release add for SCells when applicable. All cases involve complete Layer 2 (L2) and Layer 1 (LI) resets, leading to longer latency, larger overhead and longer interruption time than beam switch mobility. The goal of L1/L2 mobility enhancements is to enable a serving cell change via L1/L2 signaling, in order to reduce the latency, overhead and interruption time.

According to the latest version of the running change request (CR) for 3GPP TS 38.330 (Reference 4), Ll/L2-Triggered Mobility (LTM) is a PCell (or PSCell) cell switch procedure that the network triggers via MAC CE based on LI measurements. The L1/L2- Triggered Mobility (LTM) cell switch may be a RACH-less LTM, where UE skips the RA procedure. Subsequent LTM(s) are also supposed, i.e., subsequent LTM cell switch procedures between candidate cells where the UE does not need to be reconfigured by the network in between.

The following has been so far assumed in terms of signaling for configuring LTM and for triggering an LTM cell switch execution, as captured in the running Change Request for 3GPP TS 38.401 in R3-234800 (Reference 2), e.g., for inter-Distributed Unit (DU):

Figure 1 illustrates LTM configuration and LTM cell switch in inter-DU scenarios.

Early Downlink (DL) synchronization (early Transmission Configuration Indication (TCI) state activation) According to Reference 4, when configured by the network, it is possible for a UE in RRC_CONNECTED to be Downlink (DL) synchronized with a cell which is different from the current serving cell. This is possible by activating in advance TCI state(s) that belongs to the cell to which the early DL sync is needed.

Figure 2 illustrates the early TCI state activation (early DL sync) procedures triggered by the network. In step 1, the Next Generation Node B (gNB) to which Cell A belongs provides a list of TCI states of Cell B to the UE within the RRCReconfiguration message. The (gNB to which Cell A belongs may provide a list of TCI state(s) for one or multiple cells to which the early TCI state activation procedure may be executed by the UE. In step 2, the UE replies with the RRCReconfigurationComplete message. In step 3, the gNB to which Cell A belongs sends an early TCI state activation MAC CE to the UE in order to initiate an early TCI state activation procedure with Cell B. The early TCI state activation MAC CE may also indicate TCI state(s) of other cells during the TCI state activation procedure. In step 4, the UE activates the TCI state(s) of Cell B indicated in the early TCI state activation MAC CE.

The UE is assumed to have early DL synchronization with the gNB to which Cell B belongs. With this, the gNB to which Cell A belongs may initiate cell switch procedure to Cell B by proving a cell switch command which indicates Cell B as target cell. The cell switch command can be e.g., the LTM cell switch command MAC CE.

There currently exist certain challenge(s) such as, for example, that a different LTM candidate DU is not able to interpret the lower layer measurements and the SSBRI and determine which TCI state ID to provide to the UE for a sub-sequent LTM cell switch. Thus, it is not able to create and generate an LTM cell switch command to the UE for sub-sequent LTM. The consequence is that LTM cells switch without random access (RACH-less LTM) may not be triggered, which degrade the LTM performance in terms of delay access times. Also, since the network will not be able to provide a TCI state index (or other information related to TCI states for an LTM candidate cell) within the LTM cell switch command, this may also impact the performance on when the UE needs to perform an LTM cell switch with random access (RACH-based LTM), as the network will not be allowed to provide a more fine beam to be used by the UE when sending the preamble to the network.

A second problem relates to the inability to trigger an early DL sync and/or an early TCI state activation of an LTM candidate, after a first LTM cell switch has occurred. SUMMARY

The disclosure includes the following embodiment Set A.

Al. This disclosure includes a method in a network node operating as a Central Unit (CU), serving a UE, the method comprising: transmitting to a first C-DU a TCI state configuration of an LTM candidate cell of a second C-DU.

A2. A method according to Al, wherein prior to transmitting to the first C-DU the TCI state configuration of the LTM candidate cell of the second C-DU, obtaining from the second C-DU the TCI state configuration of the LTM candidate cell.

A3. A method according to A2, wherein the CU obtains from the second C-DU the TCI state configuration of the LTM candidate cell during the LTM preparation or during an LTM cell switch procedure.

A4. A method according to Al, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is transmitted to the first C-DU in a message to the first C- DU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

A5. A method according to A4, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is transmitted to the first C-DU in a UE CONTEXT SETUP REQUEST message or a UE CONTEXT MODIFICATION REQUEST message, in which the first C-DU is requested to configure LTM.

A6. A method according to Al, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is transmitted to the first C-DU in a message during or after the LTM cell switch procedure to the first C-DU.

The disclosure includes the following embodiment Set B.

BL This disclosure also includes a method in a network node operating as a first Candidate DU (C-DU), the method comprising: receiving from a CU serving a UE a TCI state configuration of an LTM candidate cell of a second C-DU.

B2. A method according to B l, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

B3. A method according to Bl and B2, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received from the CU in a UE CONTEXT SETUP REQUEST message or a UE CONTEXT MODIFICATION REQUEST message, in which the first C-DU is requested to configure LTM. B4. A method according to Bl, B2 and/or B3, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received from the CU in a message during or after the LTM cell switch procedure to the first C-DU.

B5. A method according to B 1-B4, wherein the first C-DU, after having obtained the TCI state configuration of the LTM candidate cell of the second C-DU, and serving the UE, transmits to the UE one or more TCI state information of the LTM candidate cell (based on the TCI state configuration), included in one or more of the following commands: a LTM cell switch command indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU e.g. “LTM Cell Switch Command MAC CE”; or a TCI state activation/ deactivation command, indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU e.g. “Candidate Cell TCI States Activation/Deactivation MAC CE”.

The disclosure includes the following embodiment Set C.

CL This disclosure also includes a method in a User Equipment (UE), comprising: Receiving a TCI state configuration of an LTM candidate cell of a second C-DU, while being served by an S-DU which is different from the second C-DU and different from a first C-DU; Performing an LTM cell switch to the LTM candidate cell of the first C-DU and accessing the LTM candidate cell (cell A) of the first C-DU; After having accessed the LTM candidate cell (cell A) of the first C-DU; Receiving a command while connected to the first C-DU, wherein the command comprises: an indication of the LTM candidate cell of the second C-DU; and a TCI state information of the LTM candidate cell of the second C-DU

C2. A method according to Cl, wherein the TCI state information comprises one or more fields which are part of the TCI state configuration of the LTM candidate cell of the second C-DU.

C3. A method according to Cl, C2, wherein the TCI state information is based on the TCI State configuration of the LTM candidate cell of the second C-DU, wherein the TCI State configuration of the LTM candidate cell is received by the first C-DU from the CU during the LTM configuration or during an LTM cell switch procedure.

C4. A method according to Cl, C2, and C3, wherein the UE receives from the first C-DU one or more TCI state information of the LTM candidate cell (based on the TCI state configuration), included in one or more of the following commands: a LTM cell switch command indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU e.g. “LTM Cell Switch Command MAC CE”; and a TCI state activation/ deactivation command, indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU e.g. “Candidate Cell TCI States Activation/Deactivation MAC CE”.

The disclosure includes the following embodiment Set D.

DI. This disclosure includes a method in a network node operating as a source DU (S-DU), serving a UE, the method comprising: transmitting to a first C-DU a TCI state configuration of an LTM candidate cell of a second C-DU.

D2. A method according to DI, wherein the S-DU, prior to transmitting to the first C-DU the TCI state configuration of the LTM candidate cell of the second C-DU, obtains from the CU the TCI state configuration of the LTM candidate cell.

D3. A method according to DI and D2, wherein the S-DU obtains from the CU the TCI state configuration of the LTM candidate cell during the LTM preparation (LTM configuration).

D4. A method according to DI, D2, D3, and D4, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received by the S-DU in the same message in which also the TCI state configuration of the LTM candidate cell of the first C-DU is received.

D5. A method according to D4, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received by the S-DU in a UE CONTEXT SETUP REQUEST message or a UE CONTEXT MODIFICATION REQUEST message, in which the S-DU is requested to configure LTM.

D6. A method according to DI, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is transmitted by the S-DU to the first C-DU in a message during or after the LTM cell switch procedure to the first C-DU (e.g. LTM CELL CHANGE NOTIFICATION).

D7. A method according to DI, wherein the S-DU transmit the TCI state configuration of the LTM candidate cell of a second C-DU to the first C-DU via the CU (e.g., LTM CELL CHANGE NOTIFICATION to the CU) or via a direct interface between the S-DU and the first C-DU.

According to one aspect of the present disclosure, a method performed by a network node operating as a Central Unit (CU) serving a user equipment (UE) is provided. The CU is configured to communicate with a first Candidate-DU (C-DU) and a second C- DU. A Transmission Configuration Indication (TCI) state configuration of a L1/L2- Triggered Mobility (LTM) candidate cell of the second C-DU is obtained from the second C-DU. The TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU.

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in at least one of a UE Context Modification Request message or a UE Context Setup Request message.

According to one or more embodiments of this aspect, the UE Context Setup Request message comprises an Early Sync Information information element (IE) for an LTM candidate cell of the first C-DU.

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU and a second TCI state configuration of a corresponding LTM candidate cell of the first C-DU are transmitted to the Source-DU (S- DU).

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU based on an LTM cell switch being triggered toward the first C-DU.

According to one or more embodiments of this aspect, a TCI state configuration of an LTM candidate cell of the first C-DU is obtained from the first C-DU. The TCI state configuration of the LTM candidate cell of the first C-DU is transmitted to the second C- DU.

According to one or more embodiments of this aspect, the TCI state configuration comprises at least one of: an indication of a plurality of LTM downlink (DL) TCI states; an indication of a plurality of LTM uplink (UL) TCI states; an indication of a plurality of joint TCI states; an indication whether a TCI state is to be considered as an uplink TCI state, downlink TCI state, joint UL/DL TCI state or Unified TCI state; and a TCI related configuration for a cell group configuration.

According to another aspect of the present disclosure, a network node operating as a Central Unit (CU) serving a user equipment (UE) is provided. The CU is configured to communicate with a first Candidate-DU (C-DU) and a second C-DU. The network node is configured to: obtain, from the second C-DU, a Transmission Configuration Indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C-DU, and transmit, to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU.

According to one or more embodiments of this aspect, the network node is further configured to transmit, to a Source-DU (S-DU), the TCI state configuration of the LTM candidate cell of the second C-DU and a second TCI state configuration of a corresponding LTM candidate cell of the first C-DU.

According to one or more embodiments of this aspect, the network node is further configured to: obtain, from the first C-DU, a TCI state configuration of an LTM candidate cell of the first C-DU; and transmit, to the second C-DU, the TCI state configuration of the LTM candidate cell of the first C-DU.

According to another aspect of the present disclosure, a method performed by a network node operating as a first Candidate-DU (C-DU) is provided. A Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU is received from a Central Unit (CU) serving a UE. According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is received in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is received based on an LTM cell switch being triggered toward the first C-DU.

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

According to one or more embodiments of this aspect, layer 1 measurements are received from the UE where the layer 1 measurements are associated with the LTM candidate cell of the second C-DU. A TCI identifier (ID) associated with the layer 1 measurements is determined based at least in part on the TCI state configuration of the LTM candidate cell of the second C-DU. A command indicating that the LTM candidate cell of the second C-DU is a target cell is transmitted to the UE.

According to one or more embodiments of this aspect, an Early TCI Activation command indicating the LTM candidate cell of the second C-DU and a TCI state identifier (ID) is transmitted to the UE and before the LTM cell switch.

According to another aspect of the present disclosure, a network node operating as a first Candidate-DU (C-DU) is provided. The network node is configured to: receive, from a Central Unit (CU) serving a UE, a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C- DU.

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is received in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

According to one or more embodiments of this aspect, the TCI state configuration of the LTM candidate cell of the second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell. According to one or more embodiments of this aspect, the network node is further configured to: receive layer 1 measurements from the UE, the layer 1 measurements being associated with the LTM candidate cell of the second C-DU; determine a TCI identifier (ID) associated with the layer 1 measurements based at least in part on the TCI state configuration of the LTM candidate cell of the second C-DU; and transmit, to the UE, a command indicating that the LTM candidate cell of the second C-DU is a target cell.

According to one or more embodiments of this aspect, the network node is further configured to transmit, to the UE and before a LTM cell switch, an Early TCI Activation command indicating the LTM candidate cell of the second C-DU and a TCI state identifier (ID).

According to another aspect of the present disclosure, a method performed by a network node operating as a source-DU (S-DU) serving a UE is provided. The S-DU is different from a first candidate-DU (C-DU) and a second C-DU. A Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU is obtained. The TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU based on a LTM cell switch being triggered toward the first C-DU.

According to another aspect of the present disclosure, a network node operating as a source-DU (S-DU) serving a UE is provided. The S-DU is different from a first candidate-DU (C-DU) and a second C-DU. The network node is configured to: obtain a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU; and transmit, to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU based on a LTM cell switch being triggered toward the first C-DU.

According to another aspect of the present disclosure, a method performed by a user equipment (UE) that is in communication with a Source Distributed Unit (S-DU) serving the UE is provided. The S-DU is different from a first Candidate Distributed Unit (C-DU) and a second C-DU. A Transmission Configuration indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C-DU is received from the S-DU. An LTM cell switch to a LTM candidate cell of the first C-DU is performed. After accessing the first C-DU, a command from the first C-DU is received where the command comprising an indication of a LTM candidate cell of the second C- DU. According to another aspect of the present disclosure, a user equipment (UE) configured to communicate with a Source Distributed Unit (S-DU) serving the UE is provided. The S-DU is different from a first Candidate Distributed Unit (C-DU) and a second C-DU. The UE is configured to receive, from the S-DU, a Transmission Configuration indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C-DU, perform an LTM cell switch to a LTM candidate cell of the first C-DU, and after accessing the first C-DU, receive a command from the first C- DU, the command comprising an indication of a LTM candidate cell of the second C-DU.

BRIEF DESCRIPTION OF DRAWINGS

A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

Figure 1 is a diagram of an example LTM configuration and LTM cell switch in inter-DU scenarios;

Figure 2 is diagram of an example early TCI state activation (early DL sync) procedures triggered by the network;

Figure 3 is a diagram of an example of the lists associated to an LTM candidate cell and for a given LTM candidate ID in accordance with some embodiments;

Figure 4 is a diagram of an example network architecture in accordance with some embodiments;

Figure 5 is a signaling diagram of an example signaling flow of the LTM configuration for Solution 1;

Figure 6 is a signaling diagram of an example signaling flow of the sub-sequent LTM cell switches for Solution 1 in accordance with some embodiments;

Figure 7 is a diagram of an example MAC CE for early TCI state activation / deactivation including TCI information of an LTM candidate cell in accordance with some embodiments;

Figure 8 is a signaling diagram of an example signaling flow of the LTM configuration for Solution 2 in accordance with some embodiments;

Figure 9 is a signaling diagram of an example signaling flow of the LTM configuration for Solution 3 in accordance with some embodiments;

Figure 10 is a signaling diagram of an example signaling flow of the LTM cell switch for Solution 3 in accordance with some embodiments;

Figure 11 is a signaling diagram of another example signaling flow of the LTM cell switch for Solution 3 in accordance with some embodiments;

Figure 12 is a signaling diagram of another example signaling flow of the LTM cell switch for Solution 3 in accordance with some embodiments;

Figure 13 is a diagram of an example of a communication system in accordance with some embodiments;

Figure 14 is a diagram of an example UE in accordance with some embodiments;

Figure 15 is a diagram of an example network node in accordance with some embodiments;

Figure 16 is a block diagram of an example host in accordance with some embodiments;

Figure 17 is a block diagram illustrating an example virtualization environment in accordance with some embodiments;

Figure 18 is a communication diagram of a host communicating via a network node with a UE over a partially wireless connection in accordance with some embodiments;

Figure 19 is a flowchart of an example process implemented by network node that is operating as a CU serving a UE in accordance with some embodiments;

Figure 20 is a flowchart of another example process implemented by a network node that is configured to operate as a first Candidate-DU in accordance with some embodiments;

Figure 21 is a flowchart of another example process implemented by a network node that is configured to operate as an S-DU serving UE in accordance with some embodiments; and

Figure 22 is a flowchart of an example process implemented by UE according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

As discussed above, there exist various issues with LTM cell switch. The LTM cell switch command (MAC CE) received by the UE for executing LTM includes a TCI State ID (for a TCI state to be activated in the LTM candidate cell indicated) in the LTM cell switch command. As the LTM cell switch command is set by the Source Distributed Unit (S-DU), and the S-DU receives lower layer measurements including the measurement (e.g. LI RSRP, or differential RSRP) and an identifier associated to an SSB index for that measurement, such as an SSB Resource Identifier (SSBRI), for LTM candidate cells based on SSB indexes, the S-DU needs to know which SSB indexes are associated to which TCI state ID(s).

For example, when the S-DU receives a lower measurement report from the UE indicating that an SSBRI for SSB index=X of LTM candidate cell whose candidate ID = Y has the strongest RSRP, the S-DU needs to be able to send the LTM cell switch command for the LTM candidate cell whose candidate ID = Y, including a TCI ID associated to that SSB index =X. For that, the S-DU needs to know the TCI state configuration of LTM candidate cell(s) the UE is configured with (e.g., mapping between TCI state ID(s) and SSB indexes).

According to the signaling flow in the latest running CR for TS 38.401, shown in Figure 1, that is possible thanks to the inclusion of the TCI state configuration in Step 5 i.e., in the UE CONTEXT MODIFICATION REQUEST from the CU to the S-DU, after the CU has obtained the confirmation of which LTM candidate cells from the Candidate DU have been accepted or not, and the respective TCI state configuration per accepted LTM Candidate cell.

The gNB-CU sends a UE CONTEXT MODIFICATION REQUEST message to the source gNB-DU including the collected RS configuration, TCI state configuration and RACH configuration for the accepted target candidate cell(s) in other gNB-DUs.

However, a first problem is that while that makes the procedure works fine when a first LTM cell switch needs to be triggered by the S-DU it does not work in case of subsequent LTM, which is a procedure between LTM candidate cells in which the UE does not need to be reconfigured by the network in between. In other words, once the UE is configured with LTM and performs a first LTM cell switch from the S-DU to an LTM candidate cell of a C-DU (which is not the S-DU), that different LTM candidate DU is not able to interpret the lower layer measurements and the SSBRI and determine which TCI state ID to provide to the UE for a sub-sequent LTM cell switch. Thus, it is not able to create and generate an LTM cell switch command to the UE for sub- sequent LTM. The consequence is that LTM cells switch without random access (RACH-less LTM) may not be triggered, which degrade the LTM performance in terms of delay access times. Also, since the network will not be able to provide a TCI state index (or other information related to TCI states for an LTM candidate cell) within the LTM cell switch command, this may also impact the performance on when the UE needs to perform an LTM cell switch with random access (RACH-based LTM), as the network will not be allowed to provide a more fine beam to be used by the UE when sending the preamble to the network.

A second problem relates to the need to trigger an early DL sync and/or an early TCI state activation of an LTM candidate, after a first LTM cell switch has occurred. In that case we may not call a sub-sequent LTM cell switch, but it is a step which is performed before a sub-sequent cell LTM switch. In other words, once the UE is configured with LTM and performs a first LTM cell switch from the S-DU to an LTM candidate cell of a C-DU (which is not the S-DU), that different LTM candidate CU is not able to interpret the lower layer measurements and the SSBRI and determine which TCI state ID to provide to the UE for an early DL sync and/or an early TCI state activation of an LTM candidate cell. Thus, the C-DU is not able to create, generate, or transmit to the UE the MAC CE (or any other signaling that may be defined later) for an early DL sync and/or early TCI state activation. The consequence is that it would not be possible to speed up the LTM cell switches, since the UE would always first need to perform DL sync before it performs the LTM cell switch, at the moment of the LTM cell switch.

Since this second problem occurs after the first LTM cell switch and is related to the preparations for the sub-sequent LTM cell switch, it is still related to sub-sequent LTM cell switches.

Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. The TCI State configuration may correspond to a beam configuration.

Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to transmission control indicator (TCI) state configurations. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and/or wireless connections.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The term “network node” used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell/multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a user equipment (UE) such as a wireless device (WD) or a radio network node.

In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The UE herein can be any type of wireless device capable of communicating with a network node or another UE over radio signals, such as a wireless device (WD). The UE may also be a radio communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), low-cost and/or low-complexity UE, a sensor equipped with UE, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device etc.

Also, in some embodiments the generic term “radio network node” is used. It can be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH).

Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and/or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

The text refers to the term Ll/L2-triggered Mobility (LTM) or “L1/L2 based intercell mobility” as used in the Work Item Description in 3GPP, though it interchangeably also uses the terms L1/L2 mobility, Ll-mobility, LI based mobility, Ll/L2-centric inter-cell mobility, L1/L2 inter-cell mobility Ll/L2-Triggered Mobility, Lower-layer triggered Mobility or LTM. The basic principle is that the UE receives a lower layer signaling from the network indicating to the UE a change (or switch or activation) of its serving cell (e.g., change of PCell, from a source to a target Pcell), wherein a lower layer signaling is a message/ signaling of a lower layer protocol, which may be referred as a L1/L2 inter-cell mobility execution command or LTM cell switch command. The change of serving cell (e.g., change of PCell) may also lead to a change in Scell(s) for the same cell group e.g. in case the command triggers the UE to change to another cell group configuration of the same type (e.g. another MCG configuration). Before the UE receives the LTM cell switch command, the UE is configured by the network with one or more LTM candidate cell configurations (e.g., reception of an RRC Reconfiguration message, with at least one LTM candidate cell configuration). A LTM candidate cell configuration may include parameters in the IE CellGroupConfig for an LTM candidate cell and/or an embedded RRC Reconfiguration for an LTM candidate cell.

The fields in the MAC CE related to the TCI State configuration(s) for a given LTM candidate ID are shown since they are the fields which need to be set by a DU when the DU needs to send the LTM cell switch command to the UE. This disclosure is about how the DU obtains the TCI state configuration which enables the DU to receive lower layer measurements (e.g., SSRI) and determines which TCI State ID(s) corresponds to the reported SSB indexes for a given LTM candidate cell.

The term LTM cell switch procedure refers to the process of a UE switching (or changing) its cell from a source cell to a target cell (which may be called here an LTM candidate cell or a neighbour cell), using Ll/L2-triggered mobility (LTM). In the context of Ll/L2-triggered mobility (LTM), an LTM cell switch procedure may sometimes also be known as L1/L2 based inter-cell mobility execution, LTM execution, dynamic switch, LTM switch, (LTM) cell switch, (LTM) serving cell change or (LTM) cell change. In the context of the disclosure, switching to the LTM candidate cell configuration comprises the UE considering that an LTM candidate cell becomes its new special cell (SpCell) e.g. PCell in case of LTM being configured for a Master Cell Group (MCG) and/or PSCell in case of LTM being configured for a Secondary Cell Group (SCG); or, changing its SpCell from the current PCell to an LTM candidate cell. Even if the term switch or change of cells is used, that may comprise a switch or change of a whole cell group configuration, which includes a change in the SpCell (e.g. change of PCell, or change of PSCell), a change in SCells of the cell group (e.g., addition, modification and/or release of one or more SCells) or a swap between SpCell and SCell roles for two cells (e.g. as result of the switch or change, a first cell which was SpCell becomes an SCell and a second cell that was an SCell becomes the new SpCell).

The term “beam” may correspond to a spatial direction in which a signal is transmitted (e.g. by a network node) or received (e.g. by the UE), or a spatial filter applied to a signal which is transmitted or received. Thus, transmitting signals different beams could correspond to transmitting signals in different spatial directions. When the text refers to a “beam which is selected” it may refer to a beam index and/or a Reference Signal (RS) index or identifier, such as a Synchronization Signal block (SSB) index, or a CSI-RS resource identifier. Thus, selecting a beam may correspond to selecting an SSB, associated to an SSB index. Or, selecting a beam may correspond to selecting a CSI-RS, associated to a CSI-RS resource identifier.

A “beam configuration” may also be expressed as a TCI state configuration which may include an indication of a beam and/or reference signal, such as an SSB index.

A “TCI State Configuration” (or beam configuration) associated to an LTM candidate cell corresponds to one or more of the following parameters:

List of LTM Downlink (DL) TCI States: In one option, this corresponds to the configuration in “Itm-dl-OrJointTCI-StateToAddModList”, comprising one or more DL TCI States i.e. instances of the IE CandidateTCLState, defined as a group of one or more TCI states configurations which includes Quasi-Co-Location (QCL)-relationships between the DL Reference Signals (RSs) in one RS set and the Physical Downlink Shared Channel (PDSCH) Demodulation Reference Signal (DMRS) ports. Notice that for a given TCI state configuration e.g. CandidateTCLState, there is a mapping between an RS ID, like an SSB index, and a TCI state ID. This may be a list of one element i.e. one TCI state (one instance of the IE CandidateTCLState).

List of LTM Uplink (UL) TCI States: In one option, this corresponds to the configuration in “Itm-ul-TCLToAddModLisf ’, comprising one or more UL TCI States i.e. instances of the IE CandidateTCLUL-State defined as a group of one or more uplink TCI states configurations. This may be a list of one element i.e. one TCI state (one instance of the IE CandidateTCLUL-State).

LTM Joint UL/ DL list: In one option, this corresponds to the configuration in “Itm- dl-OrJointTCLStateToAddModLis ’, comprising one or more joint TCI States i.e. instances of the IE CandidateTCLState, defined as a group of one or more TCI states configurations which includes Quasi-Co-Location (QCL)-relationships between the DL Reference Signals (RSs) in one RS set and the Physical Downlink Shared Channel (PDSCH) Demodulation Reference Signal (DMRS) ports. Notice that for a given TCI state configuration e.g. CandidateTCLState, there is a mapping between an RS ID, like an SSB index, and a TCI state ID. This may be a list of one element i.e. one TCI state (one instance of the IE CandidateTCLState).

One or more indications on whether a TCI state is to be considered as an UL TCI state, and/or a DL TCI state and/or a joint UL/DL TCI state and/or a Unified TCI State. Any other TCI related configuration within the IE CellGroupConfig (e.g. in the IE ServingCellConfig) of the LTM candidate cell configuration, for example: o enableTwoDefaultTCI-States-rl6 ENUMERATED {enabled} o enableDefaultTCI-StatePerCoresetPoolIndex-rl6 ENUMERATED {enabled} o TCI-ActivatedConfig-rl7

■ pdcch-TCI-rl7 SEQUENCE (SIZE (1..5)) OF TCI-Stateld,

• Indicates the TCI state for PDCCH for each configured CORESET of the DL BWP to be activated at SCell activation, to be activated for the PSCell at SCG activation and/or to be used for BFD, RLM and measurements while the SCG is deactivated. The list includes exactly as many entries as CORESETs configured in this BWP, ordered by increasing values of ControlResourceSet-Id, i.e. the first entry indicates the TCI state for the configured CORESET with the lowest ControlResourceset-Id value, the second value indicates the TCI states for the configured CORESET with the second lowest ControlResourceset-Id value, and so on

■ pdsch-TCI-rl7 BIT STRING (SIZE (L.maxNrofTCI- States))

• Indicates TCI states for PDSCH reception at SCell addition/activation or of the PSCell at SCG activation. This field indicates activated TCI state(s) for this BWP ordered by increasing values of TCI-Stateld, i.e. the first bit indicates the activation state of the TCI state with the lowest TCI- Stateld value, the second value indicates the activation status of the TCI state with the second lowest TC State-Id value, and so on. A bit set to 0 indicates that the corresponding TCI state is deactivated, a bit set to 1 indicates that the TCI state is activated. o unifiedTCI-StateType-rl7 ENUMERATED {separate, joint}

Note further, that functions described herein as being performed by a user equipment or a network node may be distributed over a plurality of user equipments and/or network nodes. In other words, it is contemplated that the functions of the network node and user equipment described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

This disclosure includes a method in a network node operating as a Central Unit (CU), serving a UE, in which the CU transmits to a first Candidate DU (first C-DU) a Transmission Configuration Indication (TCI) state configuration of an LTM candidate cell of a second C- DU. In one set of solutions (Solution 1 and Solution 2), the CU transmits to the first C-DU the TCI state configuration of the LTM candidate cell of the second C-DU when the CU requests the first C-DU to configure at least one of its cells as an LTM candidate cell. In another solution (Solution 3), the CU transmits to the first C-DU the TCI state configuration of the LTM candidate cell of the second C-DU when an LTM cell switch is triggered towards the first C-DU.

This disclosure also includes a method in a network node operating as a first Candidate DU (first C-DU), receiving from a CU serving a UE a TCI state configuration of an LTM candidate cell of a second C-DU. In one set of solutions (Solution 1 and Solution 2), the first C-DU receives from the CU the TCI state configuration of the LTM candidate cell of the second C-DU when the first C-DU is requested to configure at least one of its cells as an LTM candidate cell. In another solution (Solution 3), the first C-DU receives from the CU the TCI state configuration of the LTM candidate cell of the second C-DU when an LTM cell switch is triggered towards the first C-DU.

This disclosure also includes a method in a network node operating as a source DU (S-DU), in which the S-DU transmits to a CU and/or to a first Candidate DU (first C-DU) a Transmission Configuration Indication (TCI) state configuration of an LTM candidate cell of a second C-DU, when an LTM cell switch is triggered towards the first C-DU. In one solution, the S-DU sends the TCI state configuration to the CU, which forwards to the first C-DU e.g. in a transparent manner. In one solution, the S-DU sends the TCI state configuration directly to the first C-DU e.g., via a direct interface between DU(s). This disclosure also includes a method in a User Equipment (UE), comprising: Receiving a TCI state configuration of an LTM candidate cell of a second C-DU, while being served by an S-DU which is different from the second C-DU and different from a first C-DU; Receiving an LTM cell switch command and performing an LTM cell switch to the LTM candidate cell of the first C-DU and accessing the LTM candidate cell (cell A) of the first C-DU; After having accessed the LTM candidate cell (cell A) of the first C-DU; Receiving another LTM cell switch command while connected to the first C-DU, wherein the command comprises an indication of the LTM candidate cell of the second C-DU and a TCI state information of the LTM candidate cell of the second C-DU.

The TCI state information of the LTM candidate cell (based on the TCI state configuration) which the UE receives, includes in one or more of the following commands: A LTM cell switch command indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU e.g., “LTM Cell Switch Command MAC CE”; A TCI state activation/ deactivation command, indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU e.g. “Candidate Cell TCI States Activation/Deactivation MAC CE”.

Certain embodiments may provide one or more of the following technical advantage(s). The advantage is that this allows sub-sequent LTM cell switch to also work without the need of a random-access procedure, i.e., in a RACH-less manner, which reduces the interruption time, and the UE power consumption during LTM cell switch procedure in sub- sequent LTM, i.e., without the need of an RRC reconfiguration from the network.

In addition, it is possible to enable the pre- activation of TCI states of an LTM candidate cell after a first LTM cell switch, in preparation to a sub-sequent LTM cell switch.

Both the sub-sequent LTM cell switch and the early activation of TCI states of a candidates after a first LTM cell switch are possible thanks to the fact that the Candidate DU, which becomes a new S-DU in a first LTM cell switch, obtains the TCI state configuration of future LTM candidate cells for a second LTM cell switch, and, when it receives lower layer measurements associated to an SSB index and an LTM candidate cell (e.g. by receiving a reporting including an SSBRI and an RSRP measurement) it may determine which TCI ID is associated to a reported SSB index, so it may include a right TCI ID in the LTM cell switch command or the early TCI state activation/ deactivation command. Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

Initial description

Figure 3 illustrates an example of the lists disclosed above, associated to an LTM candidate cell (in the same IE LTM-Candidate) and for a given LTM candidate ID (Itm- Candidateld-rl8 of LTM-CandidateId-rl8). CandidateTCLStates field descriptions are listed in the table below.

Table 1

Network architecture, CU/DU split

Figure 4 illustrates a network architecture. This disclosure is applicable at least to scenarios in which the UE and network nodes are part of a Radio Access Network, such as a 5G RAN, a Next Generation RAN (NG-RAN), a 6G RAN, wherein, the RAN may comprise a set of RAN nodes (e.g., gNBs, gNB-DU(s) connected to the same CU) connected to a Core Network (e.g. a 5GC) through a RAN/CN interface (e.g. NG interface). In the case of NG-RAN, that may comprise one or more ng-eNBs, wherein an ng-eNB may consist of an ng-eNB-CU and one or more ng-eNB-DU(s). A gNB may consist of a gNB-CU and one or more gNB-DU(s). A gNB-CU and a gNB-DU is connected via Fl interface. A gNB-DU may be connected to multiple gNB-CUs by appropriate implementation. The method is presented as applicable to the NG-RAN as an example, however, the method is also applicable to any RAN architecture, such as a 6G RAN or any future RANs.

NG, Xn and Fl are logical interfaces. And, in case of the NG-RAN, the NG and Xn- C interfaces for a gNB consisting of a gNB-CU and gNB-DUs, terminate in the gNB-CU. For EN-DC, the Sl-U and X2-C interfaces for a gNB consisting of a gNB-CU and gNB- DUs, terminate in the gNB-CU. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB. A possible deployment scenario is shown below. The Protocol terminations of the NG and Xn interfaces are depicted as ellipses and, the terms "Central Entity" and "Distributed Entity" shown below refer to physical network nodes.

This disclosure mentions a Serving DU or Source DU (which is the Serving DU operating as a Source DU in the context of LTM), whose acronym is used interchangeably as S-DU. That may correspond to a gNode-DU (gNB-DU) which is responsible for one or more serving cell(s) the UE is configured with (being the reason it may be called a Serving DU).

This disclosure mentions a Centralized Unit (CU) to refer to the CU the UE is connected with, i.e., the CU wherein the higher layer protocols (e.g., RRC) for communication with the UE are terminated and where a UE Access Stratum context is stored.

This disclosure also mentions a Candidate DU (C-DU) to refer to the DU (which may correspond to a gNodeB-DU) which is responsible for an LTM candidate cell the UE is configured with. As part of the LTM configuration, the CU sends a request to the C-DU for configuring the LTM candidate cell for the UE. In response, it receives at least an LTM candidate cell configuration which is the configuration based on which the UE determines the configuration it needs to use when it switches to that LTM candidate cell in an LTM execution (also called LTM cell switch).

Solution 1

Figure 5 illustrates signaling flow of the LTM configuration for Solution 1. In a set of embodiments, a Central Unit (CU) which decides to configure LTM transmits to a first C-DU a first message including a request to setup LTM (e.g., UE CONTEXT SETUP REQUEST including the IE LTM Information to be Setup possibly with an LTM indicator set to ‘true’). In that message it is indicated at least an LTM candidate cell (e.g., by including a cell identifier, cell A) of that C-DU (which is to be configured as LTM candidate cell for a UE served by the CU, if accepted by the C-DU). In response to the first message, the CU receives from the C-DU a first response message (e.g., UE CONTEXT SETUP RESPONSE) including a TCI State Configuration of the requested LTM candidate cell (cell A). These steps are equivalent to steps 3a and 4a in Figure 5. Note: there may be other options for the CU to obtain TCI state configuration(s) of the LTM candidate cell(s) associated to the first C-DU e.g. the CU may have received the TCI State Configuration of a cell of the first C-DU (that may possibly become an LTM candidate cell) during the setup of an interface such as an F1AP.

In one option, the first message includes an explicit indication for a request of the TCI State configuration of the LTM candidate cell of the first C-DU being requested. Thus, the first C-DU includes the TCI state configuration of the requested LTM candidate cell (cell A) only when that explicit indication is included. In one option, the first message does not need to include an explicit indication for a request of the TCI State configuration of the LTM candidate cell of the first C-DU being requested. Thus, the first C-DU includes the TCI state configuration of the requested LTM candidate cell (cell A) simply when LTM is being requested for an LTM candidate cell (cell A) of the first C-DU.

The CU may repeat these steps for a second Candidate DU (C-DU), by transmitting to a second C-DU another first message including another request to setup LTM (e.g., UE CONTEXT SETUP REQUEST including the IE LTM Information to be Setup possibly with an LTM indicator set to ‘true’). In that message it is indicated at least another LTM candidate cell (e.g., by including a cell identifier, cell B) of that second C-DU (which is to be configured as LTM candidate cell for a UE served by the CU, if accepted by the second C-DU). In response to the another first message, the CU receives from the second C-DU another first response message (e.g. UE CONTEXT SETUP RESPONSE) including a TCI State Configuration of the requested LTM candidate cell (cell B). These steps are equivalent to steps 3b and 4b in Figure 5. Note: there may be other options for the CU to obtain TCI state configuration(s) of the LTM candidate cell(s) associated to the second C-DU e.g. the CU may have received the TCI State Configuration of a cell of the second C-DU (that may possibly become an LTM candidate cell) during the setup of an interface such as an F1AP.

After the CU receives the TCI state configuration of an LTM candidate cell (cell A) of a first C-DU (e.g. in step 4a), the CU transmits the TCI state configuration of an LTM candidate cell to a second C-DU (e.g. in a UE CONTEXT MODIFICATION REQUEST), so that the second C-DU becomes aware of the TCI state configuration of the LTM candidate cell of the first C-DU, being prepared for a sub-sequent LTM cell switch in case the UE comes to the second C-DU. This is equivalent to step 7b in Figure 5.

Similarly, after the CU receives the TCI state configuration of an LTM candidate cell (cell B) of a second C-DU (e.g., in step 4b) the CU may transmit the TCI state configuration of the LTM candidate cell (cell B) to a first C-DU (e.g., in a UE CONTEXT MODIFICATION REQUEST), so that the first C-DU becomes aware of the TCI state configuration of the LTM candidate cell of the second C-DU, being prepared for a subsequent LTM cell switch in case the UE comes to the first C-DU. This is equivalent to step 7a in Figure 5.

Notice that in solution 1, for each C-DU the CU triggers two procedures: one procedure to obtain the TCI state configuration of a requested LTM candidate cell of that C-DU, and another procedure to provide a TCI state configuration of another LTM candidate cell of another C-DU. For example, for the first C-DU, these two procedures would be the steps 3a/ 4a, to obtain the TCI State configuration of LTM candidate cell A of the first C-DU, and a second procedure to provide to the first C-DU the TCI state configuration of a second C-DU, in step 7a.

At that point, the network node(s) operating as C-DU(s) are aware of the TCI state configuration(s) of potential LTM candidate cell(s), which is needed in case there is an incoming UE to one of these C-DU(s) via LTM cell switch. Similarly, the S-DU is also aware of the TCI State configuration of the LTM candidate cell of the first C-DU, and the TCI State configuration of the LTM candidate cell of the second C-DU (thanks to step 5).

Once the UE is configured with LTM candidate cell A (of the first C-DU) and LTM candidate cell B (of the second C-DU), while the UE is connected with a S-DU, the UE may transmit lower measurement reports and receive in response an LTM cell switch command (e.g. MAC CE indicating one of the LTM candidate cell(s) the UE is configured with), for example, indicating cell A and a TCI state ID of cell A, so the UE performs the LTM cell switch to cell A of the first C-DU. This is equivalent to Step 17 in Figure 6. Figure 6 illustrates signaling flow of the sub-sequent LTM cell switches for Solution 1.

Thus, the UE accesses cell A of the first C-DU (which is now the S-DU for that UE) and transmits lower layer measurements. In other words, after the UE has accessed the first C-DU, the first C-DU receives one or more lower layer measurements from the UE, possibly including Received Signal Received Power (RSRP) measurements (e.g., Ll-RSRP or differential RSRP) associated to an LTM candidate cell, like cell B, and a beam, e.g., SSB index. The measurement report may include associate to the measurement an SSB Resource Index, which identifies the LTM candidate cell B (by an LTM candidate ID) and an SSB index of cell B.

Thus, when the first C-DU (which is a new S-DU) receives the lower layer measurement it knows which SSB indexes of the LTM candidate cell B maps to which TCI State ID, or, in more general, it may determine TCI state information of the LTM candidate cell B based on the TCI State configuration which it has obtained.

The first C-DU may transmit to the UE an LTM cell switch command including an indication of the LTM candidate cell of the second C-DU and a TCI state ID (based on the TCI state configuration of the LTM candidate cell of the second C-DU). That LTM cell switch from cell A to cell B is considered a sub-sequent LTM cell switch because the UE moves to B from A, which was also an LTM candidate the UE moved to with a previous LTM cell switch. This is shown in Figure 6. The first C-DU may also transmit to the UE, before an LTM cell switch, an Early DL pre sync (Early TCI Activation command), including an indication of the LTM candidate cell of the second C-DU and a TCI state ID (based on the TCI state configuration of the LTM candidate cell of the second C-DU), or other information related to the TCI state configuration. That early TCI state activation command for cell B may be considered as a preparation for a sub-sequent LTM cell switch because later, the UE may receive an LTM cell switch command indicating the UE to move to cell B from A, and the UE would be DL pre-sync with B, i.e., it would have a pre-activated TCI state with B.

In other words, the first C-DU, having obtained the TCI state configuration of the LTM candidate cell of the second C-DU, and serving the UE, transmits to the UE TCI state information of the LTM candidate cell (based on the TCI state configuration) i.e. the UE receives the TCI state information of the LTM candidate cell of the second C-DU included in one or more of the following commands:

A LTM cell switch command indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU.

In one option, the command corresponds to a “LTM Cell Switch Command MAC CE”, containing one or more of the following fields:

• R: Reserved bit, set to 0;

• Target Configuration ID: This field indicates the index of candidate target configuration to apply for LTM cell switch, corresponding to [Itm-Candidateld] as specified in 3GPP TS 38.331 V17.6.0. The length of the field is 3 bits;

• Timing Advance Command: This field indicates whether the TA is valid for the LTM target cell (i.e., the SpCell corresponding to the target configuration indicated by Target Configuration ID field). If the value of this field is set to FFF, this field indicates that no valid timing adjustment is available for the PTAG of the LTM target cell (and UE shall perform Random Access to the LTM target cell); Otherwise, this field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in 3GPP TS 38.213 V17.7.0, and that the UE can skip the Random Access procedure for this LTM cell switch. The length of the field is 12 bits;

• TCI state ID: This field indicates and activates the TCI state for the LTM target cell (i.e., the SpCell of the target configuration indicated by the Target Configuration ID field). The TCI state is identified by TCI-Stateld as specified in 3GPP TS 38.331 V17.6.0. If the value of unifiedTCI-StateType in the SpCell of the target configuration indicated by Target Configuration ID field is joint, this field is for joint TCI state, otherwise, this field is for downlink TCI state. The length of the field is 7 bits;

• UL TCI state ID: This field indicates and activates the uplink TCI state for the LTM target cell (i.e., the SpCell of the target configuration indicated by the Target Configuration ID field). The most significant bits of UL TCI state ID are considered as reserved bits and the remainder 6 bits indicate the TCI-UL-Stateld as specified in 3GPP TS 38.331 V17.6.0. This field is included if the value of unifiedTCI-StateType in the SpCell corresponding to the target configuration indicated by Target Configuration ID field is separate. The length of the field is [8] bits;

A TCI state activation/ deactivation command, indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU;

In one option, the command corresponds to a “Candidate Cell TCI States Activation/Deactivation MAC CE”, containing one or more of the following fields:

• Candidate Cell ID: This field indicates the identity of an LTM candidate Cell for which the MAC CE applies, corresponding to the Itm-Candidateld minus 1 as specified in TS 38.331. The length of the field is X e.g. 3 bits;

• Pi: This field indicates whether each TCI codepoint has multiple TCI states or a single TCI state. If the Pi field is set to 1, the i^lh TCI codepoint includes the DL TCI state and the UL TCI state. If the Pi field is set to 0, the i^lh TCI codepoint includes only the DL/joint TCI state or the UL TCI state. The codepoint to which a TCI state is mapped is determined by its ordinal position among all the TCI state ID fields;

• D/U: This field indicates whether the TCI state ID in the same octet is for a joint/downlink or an uplink TCI state. If this field is set to 1, the TCI state ID in the same octet is for joint/downlink. If this field is set to 0, the TCI state ID in the same octet is for uplink;

• TCI state ID: This field indicates the TCI state identified by TCI-Stateld or TCI-UL-Stateld as specified in TS 38.331. If D/U is set to 1, 7 -bits length TCI state ID i.e. TCI-Stateld as specified in TS 38.331 is used. If D/U is set to 0, the most significant bit of TCI state ID is considered as the reserved bit and remaining 6 bits indicate the TCI-UL-Stateld as specified in TS 38.331. The maximum number of activated TCI states is 16; • R: Reserved bit, set to 0.

Figure 7 illustrates MAC CE for early TCI state activation / deactivation including TCI information of an LTM candidate cell.

The method comprises the CU updating the first C-DU with a TCI state configuration of an LTM candidate cell of a third C-DU. For example, when the CU receives from the UE an RRC measurement reports indicating a new cell C, from the third C-DU, for a UE configured with LTM candidate cells A and B being served by the S-DU, the CU may determine to configure that cell C as an LTM candidate cell. Thus, that cell C would also be a possible future candidate in the first C-DU and the second C-DU, so that the CU needs to transmit to the first C-DU and the second C-DU the TCI state configuration of cell C of the third C-DU to the first C-DU and to the second C-DU.

The method comprises the CU removing (or requesting to remove) in the first C-DU a TCI state configuration of an LTM candidate cell which is to be removed in the UE’ s LTM configuration. For example, when the CU receives from the UE an RRC measurement reports indicating that an LTM candidate cell e.g. cell B, of the second C-DU, would have a too low RSRP value, the CU may determine to remove that in the UE’s LTM candidate cells. And, the CU also transmits to the first C-DU, an indication that the TCI state configuration of the LTM candidate cell B is to be removed. In one option, the first C-DU receives a message indicating the request to remove the LTM candidate cell B for subsequent LTM, so in response to it the first C-DU also removes the TCI state configuration of cell B. In another option, despite the request for removal, the first C-DU keeps the TCI state configuration of the LTM candidate cell being removed, because that may be useful later when that cell is to be requested as an LTM candidate cell again.

The method also comprises the C-DU, which had initially provided a first TCI state configuration of at least one of its LTM candidate cell(s) to a CU, determining that the TCI state configuration of at least one of its LTM candidate cell(s) has changed to a second TCI state configuration, and in response to that, indicating the second TCI state configuration to the CU. In response to that, the CU indicates the second TCI state configuration to the other C-DU(s) in which that LTM candidate cell has been configured for sub-sequent LTM and/or to the other C-DU(s) which had received that first TCI state configuration. This may be performed with a release followed by an addition, and/or an updating / modification procedure.

Solution 2 Figure 8 illustrates signaling flow of the LTM configuration for Solution 2. In a set of embodiments, a Central Unit (CU) obtains from a second C-DU a TCI state configuration of an LTM candidate cell (cell B) of the second C-DU. The CU may obtain TCI state configuration(s) of the LTM candidate cell(s) associated to the second C-DU in different ways e.g. the CU may have received the TCI State Configuration of a cell of the second C- DU (that may possibly become an LTM candidate cell) during the setup of an interface such as an F1AP.

Then, the CU decides to configure LTM and transmits to a first C-DU a first message including a request to setup LTM (e.g., UE CONTEXT SETUP REQUEST including the IE LTM Information to be Setup possibly with an LTM indicator set to ‘true’). In that message it is indicated at least an LTM candidate cell (e.g. by including a cell identifier, cell A) of that C-DU (which is to be configured as LTM candidate cell for a UE served by the CU, if accepted by the C-DU) and, in addition, that message also includes the TCI state configuration of the LTM candidate cell (cell B) of the second C-DU. This step is equivalent to step 3a in Figure 7 for Solution 2. At least in part because of that step, the first C-DU becomes prepared to perform sub-sequent LTM cell switches in case the UE comes to the first C-DU (e.g., by an LTM cell switch triggered by the S-DU).

In response to the first message, the CU receives from the C-DU a first response message (e.g. UE CONTEXT SETUP RESPONSE) including the lower layer configuration for the LTM candidate cell A (e.g., CellGroupConfig), so that the CU is able to generate the overall LTM candidate cell configuration for cell A (RRC Reconfiguration), to be provided to the UE in the LTM configuration (step 9).

The CU may repeat these steps for other C-DU(s), such as a second Candidate DU (second C-DU), by transmitting to a second C-DU another first message including another request to setup LTM (e.g., UE CONTEXT SETUP REQUEST including the IE LTM Information to be Setup possibly with an LTM indicator set to ‘true’). In that message it is indicated at least another LTM candidate cell (e.g., by including a cell identifier, cell B) of that second C-DU (which is to be configured as LTM candidate cell for a UE served by the CU, if accepted by the second C-DU), and, in addition, that message also includes the TCI state configuration of the LTM candidate cell (cell B) of the first C-DU. This step is equivalent to step 3b in Figure 7 for Solution 2. Thanks to that step the second C-DU also becomes prepared to perform sub-sequent LTM cell switches in case the UE comes to the second C-DU (e.g., by an LTM cell switch triggered by the S-DU, or afterwards by the first C-DU). In response to the first message, the CU receives from the second C-DU a first response message (e.g., UE CONTEXT SETUP RESPONSE) including the lower layer configuration for the LTM candidate cell B (e.g., CellGroupConfig), so that the CU is able to generate the overall LTM candidate cell configuration for cell B (RRC Reconfiguration), to be provided to the UE in the LTM configuration (step 9).

Notice that in solution 2, for each C-DU the CU triggers a single procedure for requesting an LTM candidate cell to a C-DU and to provide a TCI state configuration of another LTM candidate cell of another C-DU (assuming the CU has already obtained that TCI state configuration). For example, for the first C-DU, this single procedure would be the steps 3a/ 4a.

At that point, after LTM configuration, the network node(s) operating as C-DU(s) are aware of the TCI state configuration(s) of potential LTM candidate cell(s), which is needed in case there is an incoming UE to one of these C-DU(s) via LTM cell switch. Similarly, the S-DU is also aware of the TCI State configuration of the LTM candidate cell of the first C-DU, and the TCI State configuration of the LTM candidate cell of the second C-DU (thanks to step 5).

Similar to the previous case, shown for Solution 1, once the UE is configured with LTM candidate cell A (of the first C-DU) and LTM candidate cell B (of the second C-DU), while the UE is connected with a S-DU, the UE may transmit lower measurement reports and receive in response an LTM cell switch command (e.g. MAC CE indicating one of the LTM candidate cell(s) the UE is configured with), for example, indicating cell A and a TCI state ID of cell A, so the UE performs the LTM cell switch to cell A of the first C-DU. This is equivalent to Step 17 in the Figure 6.

Thus, the UE accesses cell A of the first C-DU (which is now the S-DU for that UE) and transmits lower layer measurements. In other words, after the UE has accessed the first C-DU, the first C-DU receives one or more lower layer measurements from the UE, possibly including Received Signal Received Power (RSRP) measurements (e.g., Ll-RSRP or differential RSRP) associated to an LTM candidate cell, like cell B, and a beam e.g., SSB index. The measurement report may include, associated to the measurement, an SSB Resource Index, which identifies the LTM candidate cell B (by an LTM candidate ID) and an SSB index of cell B. Thus, when the first C-DU (which is a new S-DU) receives the lower layer measurement it knows which SSB indexes of the LTM candidate cell B maps to which TCI State ID. Thanks to that, the first C-DU may transmit to the UE an LTM cell switch command including an indication of the LTM candidate cell of the second C-DU and a TCI state ID (based on the TCI state configuration of the LTM candidate cell of the second C-DU). That LTM cell switch from cell A to cell B is considered a sub-sequent LTM cell switch because the UE moves to B from A, which was also an LTM candidate the UE moved to with a previous LTM cell switch.

As in Solution 1, the first C-DU may also transmit to the UE, before an LTM cell switch, an Early DL pre sync (Early TCI Activation command), including an indication of the LTM candidate cell of the second C-DU and a TCI state ID (based on the TCI state configuration of the LTM candidate cell of the second C-DU), or other information related to the TCI state configuration. That early TCI state activation command for cell B may be considered as a preparation for a sub- sequent LTM cell switch because later, the UE may receive an LTM cell switch command indicating the UE to move to cell B from A, and the UE would be DL pre-sync with B, i.e., it would have a pre-activated TCI state with B.

In other words, the first C-DU, having obtained the TCI state configuration of the LTM candidate cell of the second C-DU, and serving the UE, transmits to the UE TCI state information of the LTM candidate cell (based on the TCI state configuration), i.e., the UE receives the TCI state information of the LTM candidate cell of the second C-DU included in one or more of the following commands:

• R: Reserved bit, set to 0;

A TCI state activation/ deactivation command, indicating an identifier of the LTM candidate cell and TCI state information of the LTM candidate cell of the second C-DU.

• TCI state ID: This field indicates the TCI state identified by TCI-Stateld or TCI- UL-Stateld as specified in TS 38.331. If D/U is set to 1, 7-bits length TCI state ID i.e. TCI-Stateld as specified in TS 38.331 is used. If D/U is set to 0, the most significant bit of TCI state ID is considered as the reserved bit and remaining 6 bits indicate the TCI-UL-Stateld as specified in TS 38.331. The maximum number of activated TCI states is 16; • R: Reserved bit, set to 0.

The method comprises the CU removing (or requesting to remove) in the first C-DU a TCI state configuration of an LTM candidate cell which is to be removed in the UE’ s LTM configuration. For example, when the CU receives from the UE an RRC measurement reports indicating that an LTM candidate cell e.g. cell B, of the second C-DU, would have a too low RSRP value, the CU may determine to remove that in the UE’s LTM candidate cells. And, the CU also transmits to the first C-DU, an indication that the TCI state configuration of the LTM candidate cell B is to be removed. In one option, the first C-DU receives a message indicating the request to remove the LTM candidate cell B for subsequent LTM, so in response to it the first C-DU also removes the TCI state configuration of cell B. In another option, despite the request for removal, the first C-DU keeps the TCI state configuration of the LTM candidate cell being removed, because that may be useful later when that cell is to be requested as an LTM candidate cell again. It can also be the case that during the LTM procedure some cells got inactivated for some reason. The CU will not need to send the TCI Info for these cells.

Solution 3 Figure 9 illustrates signaling flow of the LTM configuration for Solution 3. In a set of embodiments, a Central Unit (CU) obtains from a second C-DU a TCI state configuration of an LTM candidate cell (cell B) of the second C-DU. The CU may obtain TCI state configuration(s) of the LTM candidate cell(s) associated to the second C-DU in different ways e.g. the CU may have received the TCI State Configuration of a cell of the second C- DU (that may possibly become an LTM candidate cell) during the setup of an interface such as an F1AP, or in a UE context setup procedure e.g. upon reception of a UE CONTEXT SETUP RESPONSE from a C-DU.

Similarly, the CU obtains from a first C-DU a TCI state configuration of an LTM candidate cell (cell B) of the first C-DU. The CU may obtain TCI state configuration(s) of the LTM candidate cell(s) associated to the first C-DU in different ways, e.g., the CU may have received the TCI State Configuration of a cell of the first C-DU (that may possibly become an LTM candidate cell) during the setup of an interface such as an F1AP, or in a UE context setup procedure e.g. upon reception of a UE CONTEXT SETUP RESPONSE from a C-DU.

During LTM configuration (or LTM preparation), the CU and the second C-DU may perform the actions as defined in the steps from 1 to 12, as defined in R3-234800, (BLCR to 38.401). When LTM is configured, the S-DU and the CU has obtained the TCI state configuration(s) of the LTM candidates from different C-D(s). Thus, it is possible that the S-DU properly triggers the first LTM cell switch to one of the other C-DU(s). However, at that point, different from what is disclosed for Solution 2 and Solution 1, the C-DU(s) are not aware of the TCI State configuration(s) of LTM candidate cell(s) of other C-DU(s). this is shown in Figure 9.

In a set of embodiments, according to Solution 3, a CU transmits to a first C-DU a TCI state configuration of an LTM candidate cell of a second C-DU, during and/or after an LTM cell switch procedure for the UE to the first C-DU.

When the CU configures the UE with LTM, the UE is configured with LTM candidate cell A (of the first C-DU) and LTM candidate cell B (of the second C-DU). While the UE is connected with a S-DU, the UE may transmit lower measurement reports and receive in response an LTM cell switch command (e.g., MAC CE indicating one of the LTM candidate cell(s) the UE is configured with), for example, indicating cell A and a TCI state ID of cell A, so the UE performs the LTM cell switch to cell A of the first C-DU. This is equivalent to Step 17 in Figure 10. Figure 10 illustrates signaling flow of the LTM cell switch for Solution 3 in which the CU transmits to the C-DU(s) the TCI state configuration(s) of LTM candidate cell(s) of other C-DU(s) in response to the LTM CELL CHANGE NOTIFICATION.

When LTM cell switch is triggered, the CU receives from the S-DU a message indicating an LTM cell change (e.g., LTM CELL CHANGE NOTIFICATION) including e.g. a Target Cell ID of the LTM candidate cell, in this example cell A, and a selected beam information, such as the TCI State ID of cell A (which is a cell of the first C-DU) indicated in the LTM cell switch command to the UE (e.g., and/or an SSB index based on which the S-DU has selected the TCI ID provided to the UE in the LTM Cell Switch Command). This is step 18a in Figure 10 for Solution 3.

In one option, in response to the message indicating the LTM Cell, the CU transmits a message (e.g., the same or a different message) to the first C-DU, which is the C-DU of cell A, including the TCI state configuration of LTM candidate cell(s) of other candidate DU(s), such as the TCI State configuration of the LTM candidate cell (cell B) of the second C-DU, since cell B is now an LTM candidate for the incoming UE to be served by that first C-DU. That message may also be an LTM CELL CHANGE NOTIFICATION, but from the CU to the first C-DU. At this point, the first C-DU becomes aware of the TCI state configurations of LTM candidate cells of other C-DU and is able to trigger commands (e.g. sub-sequent LTM cell switch commands and/or Early TCI state activation/ deactivation commands) including TCI state information, such as TCI State ID(s) of the candidate(s), according to the TCI state configuration(s). This is equivalent to step 19a in Figure 10 for solution 3.

For example, the UE accesses cell A of the first C-DU (which is now the S-DU for that UE) and transmits lower layer measurements. In other words, after the UE has accessed the first C-DU, the first C-DU receives one or more lower layer measurements from the UE, possibly including Received Signal Received Power (RSRP) measurements (e.g., Ll-RSRP or differential RSRP) associated to an LTM candidate cell, like cell B, and a beam e.g. SSB index. The measurement report may include associate to the measurement an SSB Resource Index, which identifies the LTM candidate cell B (by an LTM candidate ID) and an SSB index of cell B. Thus, when the first C-DU (which is a new S-DU) receives the lower layer measurement it knows which SSB indexes of the LTM candidate cell B maps to which TCI State ID, thanks to the TCI state configuration for LTM candidate cell B of the second C- DU, received in the previous LTM cell switch. Thanks to that, the first C-DU may transmit to the UE an LTM cell switch command including an indication of the LTM candidate cell of the second C-DU and a TCI state ID (based on the TCI state configuration of the LTM candidate cell of the second C-DU). That LTM cell switch from cell A to cell B is considered a sub-sequent LTM cell switch because the UE moves to B from A, which was also an LTM candidate the UE moved to with a previous LTM cell switch.

In another option, in response to the reception of the ACCESS SUCCESS message from the first C-DU, the CU transmits a message to the candidate DU(s) including the TCI state configuration of LTM candidate cell(s) of other candidate DU(s). In one sub-option this message could be a UE CONTEXT MODIFICATION REQUEST message or a LTM CELL CHANGE NOTIFICATION message. On advantage one of this option is that the CU at this point is aware that the LTM cell switch procedure for that UE has been successful. This is shown in Figure 11. Figure 11 illustrates signaling flow of the LTM cell switch for Solution 3 in which the CU transmits to the C-DU(s) the TCI state configuration(s) of LTM candidate cell(s) of other C-DU(s) in response to the ACCESS SUCCESS.

In a set of embodiments, the network node which sends the TCI State configuration of the LTM candidate cell (cell B) of the second C-DU is the S-DU, during or after an LTM cell switch procedure. The CU, when configuring LTM, provides the S-DU with a TCI State configuration of the LTM candidate cell (cell B) of the second C-DU and with a TCI state configuration of the LTM candidate cell (cell A) of the first C-DU (see step 5 in Figure 9).

In one option, when the S-DU triggers an LTM cell switch to the UE, after sending the LTM Cell Switch Command to the UE, the S-DU informs the first C-DU (e.g., via the CU) that an LTM cell switch has been triggered.

In one sub-option the S-DU sends to the CU a message (e.g., LTM CELL CHANGE NOTIFICATION) to the CU, which includes the LTM candidate cell ID, the selected beam information (e.g., TCI ID indicated to the UE in the LTM cell Switch command), and the TCI State configuration of the LTM candidate cell (cell B) of the second C-DU. Upon reception, the CU forwards it to the first C-DU. In one sub-option the TCI State configuration of the LTM candidate cell (cell B) of the second C-DU is included in an RRC container.

In one sub-option the S-DU sends a direct message to the first C-DU which includes the LTM candidate cell ID, the selected beam information (e.g. TCI ID indicated to the UE in the LTM cell Switch command), and the TCI State configuration of the LTM candidate cell (cell B) of the second C-DU e.g. in an RRC container.

In one sub-option, the S-DU sends to the CU a message (e.g., LTM CELL CHANGE NOTIFICATION) to the CU, which includes the LTM candidate cell ID, the selected beam information (e.g. TCI ID indicated to the UE in the LTM cell Switch command), and the TCI State configuration of the LTM candidate cell (cell B) of the second C-DU. Upon reception, the CU waits until the first C-DU sends a confirmation that the UE has accessed the first C-DU successfully, e.g., by receiving an ACCESS SUCCESS message. In response to that the CU transmits to the first C-DU the TCI State configuration of the LTM candidate cell (cell B) of the second C-DU, e.g., in a UE CONTEXT MODIFICATION REQUEST.

The first C-DU may also transmit to the UE, before an LTM cell switch, an Early DL pre sync (Early TCI Activation command), including an indication of the LTM candidate cell of the second C-DU and a TCI state ID (based on the TCI state configuration of the LTM candidate cell of the second C-DU), or other information related to the TCI state configuration. That early TCI state activation command for cell B may be considered as a preparation for a sub-sequent LTM cell switch because later, the UE may receive an LTM cell switch command indicating the UE to move to cell B from A, and the UE would be DL pre-sync with B, i.e., it would have a pre-activated TCI state with B.

In other words, the first C-DU, having obtained the TCI state configuration of the LTM candidate cell of the second C-DU (after or during the LTM cell switch execution) and serving the UE, transmits to the UE TCI state information of the LTM candidate cell (based on the TCI state configuration), i.e., the UE receives the TCI state information of the LTM candidate cell of the second C-DU included in one or more of the following commands:

• R: Reserved bit, set to 0;

• Timing Advance Command: This field indicates whether the TA is valid for the

LTM target cell (i.e., the SpCell corresponding to the target configuration indicated by Target Configuration ID field). If the value of this field is set to FFF, this field indicates that no valid timing adjustment is available for the PTAG of the LTM target cell (and UE shall perform Random Access to the LTM target cell);

Otherwise, this field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in 3GPP TS 38.213 V17.7.0, and that the UE can skip the Random Access procedure for this LTM cell switch. The length of the field is 12 bits;

• Candidate Cell ID: This field indicates the identity of an LTM candidate Cell for which the MAC CE applies, corresponding to the Itm-Candidateld minus 1 as specified in TS 38.331. The length of the field is X, e.g., 3 bits;

• D/U: This field indicates whether the TCI state ID in the same octet is for a joint/downlink or an uplink TCI state. If this field is set to 1, the TCI state ID in the same octet is for joint/downlink. If this field is set to 0, the TCI state ID in the same octet is for uplink; • TCI state ID: This field indicates the TCI state identified by TCI-Stateld or TCI-UL-Stateld as specified in TS 38.331. If D/U is set to 1, 7 -bits length TCI state ID, i.e., TCI-Stateld as specified in TS 38.331 is used. If D/U is set to 0, the most significant bit of TCI state ID is considered as the reserved bit and remaining 6 bits indicate the TCI-UL-Stateld as specified in TS 38.331. The maximum number of activated TCI states is 16;

• R: Reserved bit, set to 0.

The method comprises the CU determining to add and/or remove an LTM candidate cell of the first/ second C-DU, and/or add an LTM candidate cell of the third C-DU. When that occurs, the CU would trigger the remove and/or adding of LTM candidate cells in the UE, and, release LTM candidate cells of the first C-DU and/or second C-DU. In response to that, the first and/or second C-DU would not need to remove TCI state configuration(s) of an LTM candidate of another C-DU which has been removed at the UE, since these are not yet there.

Figure 12 illustrates signaling flow of the LTM cell switch for Solution 3 in which the CU transmits to the C-DU(s) the TCI state configuration(s) of LTM candidate cell(s) of other C-DU(s) in response to the LTM CELL CHANGE NOTIFICATION.

Figure 13 shows an example of a communication system QQ100 in accordance with some embodiments.

In the example, the communication system QQ100 includes a telecommunication network QQ102 that includes an access network QQ104, such as a radio access network (RAN), and a core network QQ106, which includes one or more core network nodes QQ108. The access network QQ104 includes one or more access network nodes, such as network nodes QQ110a and QQ110b (one or more of which may be generally referred to as network nodes QQ110), or any other similar 3^rd Generation Partnership Project (3GPP) access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network QQ102 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network QQ102 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network QQ102, including one or more network nodes QQ110 and/or core network nodes QQ108.

Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O- CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an 0-2 interface defined by the O- RAN Alliance or comparable technologies. The network nodes QQ110 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs QQ112a, QQ112b, QQ112c, and QQ112d (one or more of which may be generally referred to as UEs QQ112) to the core network QQ106 over one or more wireless connections.

Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system QQ100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system QQ100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

The UEs QQ112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes QQ110 and other communication devices. Similarly, the network nodes QQ110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs QQ112 and/or with other network nodes or equipment in the telecommunication network QQ102 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network QQ102.

In the depicted example, the core network QQ106 connects the network nodes QQ110 to one or more hosts, such as host QQ116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network QQ106 includes one more core network nodes (e.g., core network node QQ108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node QQ108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).

The host QQ116 may be under the ownership or control of a service provider other than an operator or provider of the access network QQ104 and/or the telecommunication network QQ102, and may be operated by the service provider or on behalf of the service provider. The host QQ116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

As a whole, the communication system QQ100 of Figure 13 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

In some examples, the telecommunication network QQ102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network QQ102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network QQ102. For example, the telecommunications network QQ102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive loT services to yet further UEs.

In some examples, the UEs QQ112 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network QQ104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network QQ104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of WiFi, NR (New Radio) and LTE, i.e., being configured for multi-radio dual connectivity (MR- DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

In the example, the hub QQ114 communicates with the access network QQ104 to facilitate indirect communication between one or more UEs (e.g., UE QQ112c and/or QQ112d) and network nodes (e.g., network node QQl lOb). In some examples, the hub QQ114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub QQ114 may be a broadband router enabling access to the core network QQ106 for the UEs. As another example, the hub QQ114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes QQ110, or by executable code, script, process, or other instructions in the hub QQ114. As another example, the hub QQ114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub QQ114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub QQ114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub QQ114 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub QQ114 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

The hub QQ114 may have a constant/persistent or intermittent connection to the network node QQl lOb. The hub QQ114 may also allow for a different communication scheme and/or schedule between the hub QQ114 and UEs (e.g., UE QQ112c and/or QQ112d), and between the hub QQ114 and the core network QQ106. In other examples, the hub QQ114 is connected to the core network QQ106 and/or one or more UEs via a wired connection. Moreover, the hub QQ114 may be configured to connect to an M2M service provider over the access network QQ104 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes QQ110 while still connected via the hub QQ114 via a wired or wireless connection. In some embodiments, the hub QQ114 may be a dedicated hub - that is, a hub whose primary function is to route communications to/from the UEs from/to the network node QQ110b. In other embodiments, the hub QQ114 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node QQ110b, but which is additionally capable of operating as a communication start and/or end point for certain data channels.

Figure 14 shows a UE QQ200 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customerpremise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE. A UE may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

The UE QQ200 includes processing circuitry QQ202 that is operatively coupled via a bus QQ204 to an input/output interface QQ206, a power source QQ208, a memory QQ210, a communication interface QQ212, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 14. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

The processing circuitry QQ202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory QQ210. The processing circuitry QQ202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry QQ202 may include multiple central processing units (CPUs).

In the example, the input/output interface QQ206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE QQ200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

In some embodiments, the power source QQ208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source QQ208 may further include power circuitry for delivering power from the power source QQ208 itself, and/or an external power source, to the various parts of the UE QQ200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source QQ208. Power circuitry may perform any formatting, converting, or other modification to the power from the power source QQ208 to make the power suitable for the respective components of the UE QQ200 to which power is supplied.

The memory QQ210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory QQ210 includes one or more application programs QQ214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data QQ216. The memory QQ210 may store, for use by the UE QQ200, any of a variety of various operating systems or combinations of operating systems.

The memory QQ210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory QQ210 may allow the UE QQ200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory QQ210, which may be or comprise a device-readable storage medium.

The processing circuitry QQ202 may be configured to communicate with an access network or other network using the communication interface QQ212. The communication interface QQ212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna QQ222. The communication interface QQ212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter QQ218 and/or a receiver QQ220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter QQ218 and receiver QQ220 may be coupled to one or more antennas (e.g., antenna QQ222) and may share circuit components, software or firmware, or alternatively be implemented separately.

In the illustrated embodiment, communication functions of the communication interface QQ212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol/intemet protocol (TCP/IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface QQ212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and/or software in dependence of the intended application of the loT device in addition to other components as described in relation to the UE QQ200 shown in Figure 14.

As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3 GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

Figure 15 shows a network node QQ300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)), O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU).

Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi- cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).

The network node QQ300 includes a processing circuitry QQ302, a memory QQ304, a communication interface QQ306, and a power source QQ3O8. The network node QQ300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node QQ300 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeB s. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node QQ300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory QQ304 for different RATs) and some components may be reused (e.g., a same antenna QQ310 may be shared by different RATs). The network node QQ300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node QQ300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node QQ300.

The processing circuitry QQ302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node QQ300 components, such as the memory QQ304, to provide network node QQ300 functionality.

In some embodiments, the processing circuitry QQ302 includes a system on a chip (SOC). In some embodiments, the processing circuitry QQ302 includes one or more of radio frequency (RF) transceiver circuitry QQ312 and baseband processing circuitry QQ314. In some embodiments, the radio frequency (RF) transceiver circuitry QQ312 and the baseband processing circuitry QQ314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry QQ312 and baseband processing circuitry QQ314 may be on the same chip or set of chips, boards, or units. The memory QQ3O4 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device- readable and/or computer- executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry QQ302. The memory QQ304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry QQ302 and utilized by the network node QQ300. The memory QQ304 may be used to store any calculations made by the processing circuitry QQ302 and/or any data received via the communication interface QQ306. In some embodiments, the processing circuitry QQ302 and memory QQ304 is integrated.

The communication interface QQ306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface QQ306 comprises port(s)/terminal(s) QQ316 to send and receive data, for example to and from a network over a wired connection. The communication interface QQ306 also includes radio front-end circuitry QQ318 that may be coupled to, or in certain embodiments a part of, the antenna QQ310. Radio front-end circuitry QQ318 comprises filters QQ320 and amplifiers QQ322. The radio front-end circuitry QQ318 may be connected to an antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry may be configured to condition signals communicated between antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry QQ318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry QQ318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters QQ320 and/or amplifiers QQ322. The radio signal may then be transmitted via the antenna QQ310. Similarly, when receiving data, the antenna QQ310 may collect radio signals which are then converted into digital data by the radio front-end circuitry QQ318. The digital data may be passed to the processing circuitry QQ302. In other embodiments, the communication interface may comprise different components and/or different combinations of components. In certain alternative embodiments, the network node QQ300 does not include separate radio front-end circuitry QQ318, instead, the processing circuitry QQ302 includes radio front-end circuitry and is connected to the antenna QQ310. Similarly, in some embodiments, all or some of the RF transceiver circuitry QQ312 is part of the communication interface QQ306. In still other embodiments, the communication interface QQ306 includes one or more ports or terminals QQ316, the radio front-end circuitry QQ318, and the RF transceiver circuitry QQ312, as part of a radio unit (not shown), and the communication interface QQ306 communicates with the baseband processing circuitry QQ314, which is part of a digital unit (not shown).

The antenna QQ310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna QQ310 may be coupled to the radio front-end circuitry QQ318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna QQ310 is separate from the network node QQ300 and connectable to the network node QQ300 through an interface or port.

The antenna QQ310, communication interface QQ306, and/or the processing circuitry QQ302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna QQ310, the communication interface QQ306, and/or the processing circuitry QQ302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

The power source QQ3O8 provides power to the various components of network node QQ300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source QQ3O8 may further comprise, or be coupled to, power management circuitry to supply the components of the network node QQ300 with power for performing the functionality described herein. For example, the network node QQ300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source QQ3O8. As a further example, the power source QQ3O8 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

Embodiments of the network node QQ300 may include additional components beyond those shown in Figure 15 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, the network node QQ300 may include user interface equipment to allow input of information into the network node QQ300 and to allow output of information from the network node QQ300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node QQ300.

Figure 16 is a block diagram of a host QQ400, which may be an embodiment of the host QQ116 of Figure 16, in accordance with various aspects described herein. As used herein, the host QQ400 may be or comprise various combinations hardware and/or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host QQ400 may provide one or more services to one or more UEs.

The host QQ400 includes processing circuitry QQ402 that is operatively coupled via a bus QQ404 to an input/output interface QQ406, a network interface QQ408, a power source QQ410, and a memory QQ412. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures 14 and 15, such that the descriptions thereof are generally applicable to the corresponding components of host QQ400.

The memory QQ412 may include one or more computer programs including one or more host application programs QQ414 and data QQ416, which may include user data, e.g., data generated by a UE for the host QQ400 or data generated by the host QQ400 for a UE. Embodiments of the host QQ400 may utilize only a subset or all of the components shown. The host application programs QQ414 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). The host application programs QQ414 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host QQ400 may select and/or indicate a different host for over-the-top services for a UE. The host application programs QQ414 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc.

Figure 17 is a block diagram illustrating a virtualization environment QQ500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments QQ500 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment QQ500 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an 0-2 interface.

Applications QQ502 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment Q400 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

Hardware QQ504 includes processing circuitry, memory that stores software and/or instructions executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers QQ506 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs QQ508a and QQ508b (one or more of which may be generally referred to as VMs QQ508), and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer QQ506 may present a virtual operating platform that appears like networking hardware to the VMs QQ508. The VMs QQ508 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer QQ506. Different embodiments of the instance of a virtual appliance QQ502 may be implemented on one or more of VMs QQ508, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

In the context of NFV, a VM QQ508 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs QQ508, and that part of hardware QQ504 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs QQ508 on top of the hardware QQ504 and corresponds to the application QQ502.

Hardware QQ504 may be implemented in a standalone network node with generic or specific components. Hardware QQ504 may implement some functions via virtualization. Alternatively, hardware QQ504 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration QQ510, which, among others, oversees lifecycle management of applications QQ502. In some embodiments, hardware QQ504 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system QQ512 which may alternatively be used for communication between hardware nodes and radio units.

Figure 18 shows a communication diagram of a host QQ602 communicating via a network node QQ604 with a UE QQ606 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as a UE QQ112a of Figure 13 and/or UE QQ200 of Figure 14), network node (such as network node QQl lOa of Figure 13 and/or network node QQ300 of Figure 15), and host (such as host QQ116 of Figure 13 and/or host QQ400 of Figure 16 discussed in the preceding paragraphs will now be described with reference to Figure 18.

Like host QQ400, embodiments of host QQ602 include hardware, such as a communication interface, processing circuitry, and memory. The host QQ602 also includes software, which is stored in or accessible by the host QQ602 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE QQ606 connecting via an over-the-top (OTT) connection QQ650 extending between the UE QQ606 and host QQ602. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection QQ650.

The network node QQ604 includes hardware enabling it to communicate with the host QQ602 and UE QQ606. The connection QQ660 may be direct or pass through a core network (like core network QQ106 of Figure 13) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

The UE QQ606 includes hardware and software, which is stored in or accessible by UE QQ606 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator- specific “app” that may be operable to provide a service to a human or non-human user via UE QQ606 with the support of the host QQ602. In the host QQ602, an executing host application may communicate with the executing client application via the OTT connection QQ650 terminating at the UE QQ606 and host QQ602. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection QQ650 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection QQ650.

The OTT connection QQ650 may extend via a connection QQ660 between the host QQ602 and the network node QQ604 and via a wireless connection QQ670 between the network node QQ604 and the UE QQ606 to provide the connection between the host QQ602 and the UE QQ606. The connection QQ660 and wireless connection QQ670, over which the OTT connection QQ650 may be provided, have been drawn abstractly to illustrate the communication between the host QQ602 and the UE QQ606 via the network node QQ604, without explicit reference to any intermediary devices and the precise routing of messages via these devices. As an example of transmitting data via the OTT connection QQ650, in step QQ608, the host QQ602 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE QQ606. In other embodiments, the user data is associated with a UE QQ606 that shares data with the host QQ602 without explicit human interaction. In step QQ610, the host QQ602 initiates a transmission carrying the user data towards the UE QQ606. The host QQ602 may initiate the transmission responsive to a request transmitted by the UE QQ606. The request may be caused by human interaction with the UE QQ606 or by operation of the client application executing on the UE QQ606. The transmission may pass via the network node QQ604, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step QQ612, the network node QQ604 transmits to the UE QQ606 the user data that was carried in the transmission that the host QQ602 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step QQ614, the UE QQ606 receives the user data carried in the transmission, which may be performed by a client application executed on the UE QQ606 associated with the host application executed by the host QQ602.

In some examples, the UE QQ606 executes a client application which provides user data to the host QQ602. The user data may be provided in reaction or response to the data received from the host QQ602. Accordingly, in step QQ616, the UE QQ606 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE QQ606. Regardless of the specific manner in which the user data was provided, the UE QQ606 initiates, in step QQ618, transmission of the user data towards the host QQ602 via the network node QQ604. In step QQ620, in accordance with the teachings of the embodiments described throughout this disclosure, the network node QQ604 receives user data from the UE QQ606 and initiates transmission of the received user data towards the host QQ602. In step QQ622, the host QQ602 receives the user data carried in the transmission initiated by the UE QQ606.

One or more of the various embodiments improve the performance of OTT services provided to the UE QQ606 using the OTT connection QQ650, in which the wireless connection QQ670 forms the last segment. More precisely, the teachings of these embodiments may improve the data rate, latency, power consumption and thereby provide benefits such as better responsiveness, reduced user waiting time. In an example scenario, factory status information may be collected and analyzed by the host QQ602. As another example, the host QQ602 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host QQ602 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host QQ602 may store surveillance video uploaded by a UE. As another example, the host QQ602 may store or control access to media content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host QQ602 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing and/or transmitting data.

In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection QQ650 between the host QQ602 and UE QQ606, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host QQ602 and/or UE QQ606. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection QQ650 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection QQ650 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node QQ604. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host QQ602. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection QQ650 while monitoring propagation times, errors, etc.

Figure 19 is a flowchart of an example process implemented by network node QQ110 that is operating as a CU serving a UE QQ112. For example, network node QQ110 operates as a Central Unit (CU) serving UE QQ112 where the CU is configured to communicate with a first Candidate-DU (C-DU) and a second C-DU, network node QQ110 is configured to: obtain (Block S 100), from the second C-DU, a Transmission Configuration Indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C-DU, as described herein. Network node QQ110 is configured to transmit (Block S102), to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU, as described herein.

According to one or more embodiments, the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in at least one of a UE Context Modification Request message or a UE Context Setup Request message.

According to one or more embodiments, the UE Context Setup Request message comprises an Early Sync Information information element (IE) for an LTM candidate cell of the first C-DU.

According to one or more embodiments, the network node QQ110 is further configured to transmit, to a Source-DU (S-DU), the TCI state configuration of the LTM candidate cell of the second C-DU and a second TCI state configuration of a corresponding LTM candidate cell of the first C-DU.

According to one or more embodiments, the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

According to one or more embodiments, the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU based on an LTM cell switch being triggered toward the first C-DU.

According to one or more embodiments, the network node QQ110 is further configured to: obtain, from the first C-DU, a TCI state configuration of an LTM candidate cell of the first C-DU; and transmit, to the second C-DU, the TCI state configuration of the LTM candidate cell of the first C-DU.

According to one or more embodiments, the TCI state configuration comprises at least one of: an indication of a plurality of LTM downlink (DL) TCI states; an indication of a plurality of LTM uplink (UL) TCI states; an indication of a plurality of joint TCI states; an indication whether a TCI state is to be considered as an uplink TCI state, downlink TCI state, joint UL/DL TCI state or Unified TCI state; and a TCI related configuration for a cell group configuration.

Figure 20 is a flowchart of another example process implemented by a network node QQ110 that is configured to operate as a first Candidate-DU (C-DU). Network node QQ110 is configured to receive (Block S106), from a Central Unit (CU) serving a UE, a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU.

According to one or more embodiments, the TCI state configuration of the LTM candidate cell of the second C-DU is received in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

According to one or more embodiments, the TCI state configuration of the LTM candidate cell of the second C-DU is received based on an LTM cell switch being triggered toward the first C-DU.

According to one or more embodiments, the TCI state configuration of the LTM candidate cell of the second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

According to one or more embodiments, network node QQ110 is further configured to: receive layer 1 measurements from the UE QQ112, the layer 1 measurements being associated with the LTM candidate cell of the second C-DU; determine a TCI identifier (ID) associated with the layer 1 measurements based at least in part on the TCI state configuration of the LTM candidate cell of the second C-DU; and transmit, to the UE QQ112, a command indicating that the LTM candidate cell of the second C-DU is a target cell. According to one or more embodiments, the network node QQ110 is further configured to transmit, to the UE QQ112 and before a LTM cell switch, an Early TCI Activation command indicating the LTM candidate cell of the second C-DU and a TCI state identifier (ID).

Figure 21 is a flowchart of another example process implemented by a network node QQ110 that is configured to operate as an S-DU serving UE QQ112, according to some embodiments of the present disclosure. The S-DU is different from a first C-DU and a second C-DU. Network node QQ110 is configured to obtain (Block S108) a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU, as described herein. Network node QQ110 is configured to transmit (Block SI 10), to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU based on a LTM cell switch being triggered toward the first C-DU, as described herein.

Figure 22 is a flowchart of an example process implemented by UE QQ112 according to some embodiments of the present disclosure. UE QQ112 is configured to communicate with an S-DU serving the UE QQ112 where the S-DU is different from a first Candidate Distributed Unit (C-DU) and a second C-DU. UE QQ112 is configured to: receive (Block SI 12), from the S-DU, a Transmission Configuration indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C-DU, as described herein. UE QQ112 is configured to perform (Block S 114) an LTM cell switch to a LTM candidate cell of the first C-DU, as described herein. UE QQ112 is configured to, after accessing the first C-DU, receive (Block S 116) a command from the first C-DU where the command comprises an indication of a LTM candidate cell of the second C-DU, as described herein.

Some Examples

Group A Examples

1. A method performed by a user equipment (UE) for Transmission Configuration Indication (TCI) state configuration signaling, the method comprising: receiving a TCI state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of a second Candidate Distributed Unit (C-DU) from a Source Distributed Unit (S-DU), wherein the S-DU is different from the second C-DU and a first C-DU; performing an LTM cell switch to a LTM candidate cell of the first C-DU; receiving a command from the first C-DU, wherein the command comprises an indication of a LTM candidate cell of the second C-DU, and a TCI state information of the LTM candidate cell of the second C-DU.

2. The method of Example 1, wherein the TCI state information comprises one or more fields which are part of the TCI state configuration of the LTM candidate cell of the second C-DU.

3. The method of any of Examples 1 and 2, wherein the TCI state information is based on the TCI state configuration of the LTM candidate cell of the second C-DU, wherein the TCI state configuration of the LTM candidate cell is received by the first C-DU from the CU during an LTM configuration or during an LTM cell switch procedure.

4. The method of any of Examples 1-3, wherein the UE receives from the first C- DU one or more commands comprising one or more TCI state information of the LTM candidate cell.

5. The method of Example 4, wherein the one or more commands comprise an LTM cell switch command or a TCI state activation or deactivation command.

6. The method of any of Examples 1-5, further comprising: providing user data; and forwarding the user data to a host via transmission to a network node.

Group B Examples

7. A method performed by a network node operating as a Central Unit (CU) serving a UE, the method comprising: transmitting, to a first C-DU, a TCI state configuration of an LTM candidate cell of a second C-DU.

8. The method of Example 7, wherein prior to transmitting to the first C-DU the TCI state configuration of the LTM candidate cell of the second C-DU, obtaining from the second C-DU the TCI state configuration of the LTM candidate cell.

9. The method of Example 8, wherein obtaining from the second C-DU the TCI state configuration of the LTM candidate cell is performed during an LTM preparation or during an LTM cell switch procedure.

10. The method of any of Examples 7-9, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in a message to the first C-DU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

11. The method of Example 10, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in a UE CONTEXT SETUP REQUEST message or a UE CONTEXT MODIFICATION REQUEST message.

12. The method of any of Examples 7-11, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in a message during or after an LTM cell switch procedure to the first C-DU.

13. A method performed by a network node operating as a first Candidate DU (C- DU), the method comprising: receiving from a CU serving a UE a TCI state configuration of an LTM candidate cell of a second C-DU.

14. The method of Example 13, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

15. The method of any of Examples 13-14, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received from the CU in a UE CONTEXT SETUP REQUEST message or a UE CONTEXT MODIFICATION REQUEST message, in which the first C-DU is requested to configure LTM. 16. The method of any of Examples 13-15, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received from the CU in a message during or after an LTM cell switch procedure to the first C-DU.

17. The method of any of Examples 13-16, further comprising, serving the UE, and transmitting to the UE one or more commands comprising one or more TCI state information of the LTM candidate cell.

18. The method of Example 17, wherein the one or more commands comprise a LTM cell switch command or a TCI state activation or deactivation command.

19. A method performed by a network node operating as a source DU (S-DU) serving a UE, the method comprising: receiving a TCI state configuration of an LTM candidate cell of a second C-DU, while being served by an S-DU which is different from the second C-DU and a first C- DU; performing an LTM cell switch to an LTM candidate cell of the first C-DU and accessing the LTM candidate cell of the first C-DU, and receiving a command while connected to the first C-DU, wherein the command comprises an indication of an LTM candidate cell of the second C-DU, and a TCI state information of the LTM candidate cell of the second C-DU.

20. The method of Example 19, wherein the TCI state information comprises one or more fields which are part of the TCI state configuration of the LTM candidate cell of the second C-DU.

21. The method of any of Examples 19-20, wherein the TCI state information is based on the TCI state configuration of the LTM candidate cell of the second C-DU, wherein the TCI state configuration of the LTM candidate cell is received by the first C-DU from the CU during an LTM configuration or during an LTM cell switch procedure.

22. The method of any of Examples 19-21, wherein the UE receives from the first C-DU one or more commands comprising one or more TCI state information of the LTM candidate cell.

23. The method of Example 22, wherein the one or more commands comprise an LTM cell switch command or a TCI state activation or deactivation command.

24. The method of any of Examples 7-22, further comprising: obtaining user data; and forwarding the user data to a host or a user equipment. Group C Examples

25. A user equipment for TCI state configuration signaling, comprising: processing circuitry configured to perform any of the steps of any of the Group A Examples; and power supply circuitry configured to supply power to the processing circuitry.

26. A network node for TCI state configuration signaling, the network node comprising: processing circuitry configured to perform any of the steps of any of the Group B Examples; power supply circuitry configured to supply power to the processing circuitry.

27. A user equipment (UE) for TCI state configuration signaling, the UE comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of the Group A Examples; an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE.

28. A host configured to operate in a communication system to provide an over-the- top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a network node in a cellular network for transmission to a user equipment (UE), the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B Examples to transmit the user data from the host to the UE.

29. The host of the previous Example, wherein: the processing circuitry of the host is configured to execute a host application that provides the user data; and the UE comprises processing circuitry configured to execute a client application associated with the host application to receive the transmission of user data from the host.

30. A method implemented in a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular network comprising the network node, wherein the network node performs any of the operations of any of the Group B Examples to transmit the user data from the host to the UE.

31. The method of the previous Example, further comprising, at the network node, transmitting the user data provided by the host for the UE.

32. The method of any of the previous 2 Examples, wherein the user data is provided at the host by executing a host application that interacts with a client application executing on the UE, the client application being associated with the host application.

33. A communication system configured to provide an over-the-top (OTT) service, the communication system comprising: a host comprising: processing circuitry configured to provide user data for a user equipment (UE), the user data being associated with the over-the-top service; and a network interface configured to initiate transmission of the user data toward a cellular network node for transmission to the UE, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B Examples to transmit the user data from the host to the UE.

34. The communication system of the previous Example, further comprising: the network node; and/or the UE.

35. A host configured to operate in a communication system to provide an over-the- top (OTT) service, the host comprising: processing circuitry configured to initiate receipt of user data; and a network interface configured to receive the user data from a network node in a cellular network, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B Examples to receive the user data from a user equipment (UE) for the host.

36. The host of the previous 2 Examples, wherein: the processing circuitry of the host is configured to execute a host application that receives the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.

37. The host of the any of the previous 2 Examples, wherein the initiating receipt of the user data comprises requesting the user data.

38. A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: at the host, initiating receipt of user data from the UE, the user data originating from a transmission which the network node has received from the UE, wherein the network node performs any of the steps of any of the Group B Examples to receive the user data from the UE for the host.

39. The method of the previous Example, further comprising at the network node, transmitting the received user data to the host.

40. A host configured to operate in a communication system to provide an over-the- top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the operations of any of the Group A Examples to receive the user data from the host.

41. The host of the previous Example, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data to the UE from the host.

42. The host of the previous 2 Examples, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.

43. A method implemented by a host operating in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular network comprising the network node, wherein the UE performs any of the operations of any of the Group A Examples to receive the user data from the host.

44. The method of the previous Example, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the host application.

45. The method of the previous Example, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application.

46. A host configured to operate in a communication system to provide an over-the- top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the steps of any of the Group A Examples to transmit the user data to the host.

47. The host of the previous Example, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data from the UE to the host.

48. The host of the previous 2 Examples, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application. 49. A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: at the host, receiving user data transmitted to the host via the network node by the UE, wherein the UE performs any of the steps of any of the Group A Examples to transmit the user data to the host.

50. The method of the previous Example, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the UE.

51. The method of the previous 2 Examples, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application.

Some Additional Examples

1A. A method performed by a network node operating as a Central Unit (CU) serving a user equipment (UE), the method comprising: transmitting, to a first Candidate Distributed Unit (C-DU), a Transmission Configuration Indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU.

2A. The method of Example 1A, wherein prior to transmitting to the first C-DU the TCI state configuration of the LTM candidate cell of the second C-DU, obtaining from the second C-DU the TCI state configuration of the LTM candidate cell.

3A. A method performed by a network node operating as a first Candidate DU (C- DU), the method comprising: receiving from a CU serving a UE a TCI state configuration of an LTM candidate cell of a second C-DU.

4A. The method of Example 3A, wherein the TCI state configuration of the LTM candidate cell of a second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

5A. A method performed by a network node operating as a source DU (S-DU) serving a UE, the method comprising: receiving a TCI state configuration of an LTM candidate cell of a second C-DU, while being served by an S-DU which is different from the second C-DU and a first C- DU; performing an LTM cell switch to an LTM candidate cell of the first C-DU and accessing the LTM candidate cell of the first C-DU, and receiving a command while connected to the first C-DU, wherein the command comprises an indication of an LTM candidate cell of the second C-DU, and a TCI state information of the LTM candidate cell of the second C-DU.

6A. The method of Example 5A, wherein the TCI state information comprises one or more fields which are part of the TCI state configuration of the LTM candidate cell of the second C-DU.

7A. A method performed by a user equipment (UE) for Transmission Configuration Indication (TCI) state configuration signaling, the method comprising: receiving a TCI state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of a second Candidate Distributed Unit (C-DU) from a Source Distributed Unit (S-DU), wherein the S-DU is different from the second C-DU and a first C-DU; performing an LTM cell switch to a LTM candidate cell of the first C-DU; receiving a command from the first C-DU, wherein the command comprises an indication of a LTM candidate cell of the second C-DU, and a TCI state information of the LTM candidate cell of the second C-DU.

8A. The method of Example 7A, wherein the TCI state information comprises one or more fields which are part of the TCI state configuration of the LTM candidate cell of the second C-DU.

ABBREVIATIONS

At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

Abbreviations Explanation

C-DU Candidate Distributed Unit

CU Central Unit

DU Distributed Unit

LTM Ll/L2-Triggered Mobility

S-DU Source Distributed Unit TCI Transmission Configuration Indication

Ix RTT CDMA2000 lx Radio Transmission Technology

3GPP 3rd Generation Partnership Project

5G 5th Generation

6G 6^th Generation

ABS Almost Blank Subframe

ARQ Automatic Repeat Request

AWGN Additive White Gaussian Noise

BCCH Broadcast Control Channel

BCH Broadcast Channel

CA Carrier Aggregation

CC Carrier Component

CCCH SDU Common Control Channel SDU

CDMA Code Division Multiplexing Access

CGI Cell Global Identifier

CIR Channel Impulse Response

CP Cyclic Prefix

CPICH Common Pilot Channel

CPICH Ec/No CPICH Received energy per chip divided by the power density in the band

CQI Channel Quality information

C-RNTI Cell RNTI

CSI Channel State Information

DCCH Dedicated Control Channel

DL Downlink

DM Demodulation

DMRS Demodulation Reference Signal

DRX Discontinuous Reception

DTX Discontinuous Transmission

DTCH Dedicated Traffic Channel

DUT Device Under Test

E-CID Enhanced Cell-ID (positioning method) eMBMS evolved Multimedia Broadcast Multicast Services

E-SMLC Evolved-Serving Mobile Location Centre ECGI Evolved CGI eNB E-UTRAN NodeB ePDCCH Enhanced Physical Downlink Control Channel

E-SMLC Evolved Serving Mobile Location Center

E-UTRA Evolved UTRA

E-UTRAN Evolved UTRAN

FDD Frequency Division Duplex

FFS For Further Study gNB Base station in NR

GNSS Global Navigation Satellite System

HARQ Hybrid Automatic Repeat Request

HO Handover

HSPA High Speed Packet Access

HRPD High Rate Packet Data

LOS Line of Sight

LPP LTE Positioning Protocol

LTE Long-Term Evolution

MAC Medium Access Control

MAC Message Authentication Code

MBSFN Multimedia Broadcast multicast service Single Frequency Network

MBSFN ABS MBSFN Almost Blank Subframe

MDT Minimization of Drive Tests

MIB Master Information Block

MME Mobility Management Entity

MSC Mobile Switching Center

NPDCCH Narrowband Physical Downlink Control Channel

NR New Radio

OCNG OFDMA Channel Noise Generator

OFDM Orthogonal Frequency Division Multiplexing

OFDMA Orthogonal Frequency Division Multiple Access

OSS Operations Support System

OTDOA Observed Time Difference of Arrival

O&M Operation and Maintenance

PBCH Physical Broadcast Channel P-CCPCH Primary Common Control Physical Channel PCell Primary Cell PCFICH Physical Control Format Indicator Channel PDCCH Physical Downlink Control Channel PDCP Packet Data Convergence Protocol PDP Profile Delay Profile PDSCH Physical Downlink Shared Channel PGW Packet Gateway PHICH Physical Hybrid- ARQ Indicator Channel PLMN Public Land Mobile Network PMI Precoder Matrix Indicator PRACH Physical Random Access Channel PRS Positioning Reference Signal PSS Primary Synchronization Signal PUCCH Physical Uplink Control Channel PUSCH Physical Uplink Shared Channel QAM Quadrature Amplitude Modulation RACH Random Access Channel RAN Radio Access Network RAT Radio Access Technology RLC Radio Link Control RLM Radio Link Management RNC Radio Network Controller RNTI Radio Network Temporary Identifier RRC Radio Resource Control RRM Radio Resource Management RS Reference Signal RSCP Received Signal Code Power RSRP Reference Symbol Received Power OR

Reference Signal Received Power

RSRQ Reference Signal Received Quality OR

Reference Symbol Received Quality

RSSI Received Signal Strength Indicator RSTD Reference Signal Time Difference SCH Synchronization Channel

SCell Secondary Cell

SDAP Service Data Adaptation Protocol

SDU Service Data Unit

SFN System Frame Number

SGW Serving Gateway

SI System Information

SIB System Information Block

SNR Signal to Noise Ratio

SON Self Optimized Network

SS Synchronization Signal

SSS Secondary Synchronization Signal

TDD Time Division Duplex

TDOA Time Difference of Arrival

TCI Transmission Configuration Indicator

TOA Time of Arrival

TSS Tertiary Synchronization Signal

TTI Transmission Time Interval

UE User Equipment

UL Uplink

USIM Universal Subscriber Identity Module

UTDOA Uplink Time Difference of Arrival

WCDMA Wide CDMA

WLAN Wide Local Area Network

Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and/or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and/or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and/or by end users and a wireless network generally.

It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

1. A method performed by a network node (QQ110) operating as a Central Unit (CU) serving a user equipment (UE)(QQ112), the CU configured to communicate with a first Candidate-DU (C-DU) and a second C-DU, the method comprising: obtaining (S100), from the second C-DU, a Transmission Configuration Indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C-DU; and transmitting (S102), to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU.

2. The method of Claim 1, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in at least one of a UE Context Modification Request message or a UE Context Setup Request message.

3. The method of Claim 2, wherein the UE Context Setup Request message comprises an Early Sync Information information element (IE) for an LTM candidate cell of the first C-DU.

4. The method of any one of Claims 1-3, further comprising transmitting, to a Source-DU (S-DU), the TCI state configuration of the LTM candidate cell of the second C-DU and a second TCI state configuration of a corresponding LTM candidate cell of the first C-DU.

5. The method of any one of Claims 1-4, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

6. The method of any one of Claims 1-5, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU based on an LTM cell switch being triggered toward the first C-DU.

7. The method of any one of Claims 1-6, further comprising: obtaining, from the first C-DU, a TCI state configuration of an LTM candidate cell of the first C-DU; and transmitting, to the second C-DU, the TCI state configuration of the LTM candidate cell of the first C-DU.

8. The method of any one of Claims 1-7, wherein the TCI state configuration comprises at least one of: an indication of a plurality of LTM downlink (DL) TCI states; an indication of a plurality of LTM uplink (UL) TCI states; an indication of a plurality of joint TCI states; an indication whether a TCI state is to be considered as an uplink TCI state, downlink TCI state, joint UL/DL TCI state or Unified TCI state; and a TCI related configuration for a cell group configuration.

9. A network node (QQ110) operating as a Central Unit (CU) serving a user equipment (UE)(QQ112), the CU being configured to communicate with a first Candidate- DU (C-DU) and a second C-DU, the network node (QQ110) configured to: obtain, from the second C-DU, a Transmission Configuration Indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C- DU; and transmit, to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU.

10. The network node (QQ110) of Claim 9, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C-DU in at least one of a UE Context Modification Request message or a UE Context Setup Request message.

11. The network node (QQ110) of Claim 10, wherein the UE Context Setup Request message comprises an Early Sync Information information element (IE) for an LTM candidate cell of the first C-DU.

12. The network node (QQ110) of any one of Claims 9-11, wherein the network node (QQ110) is further configured to transmit, to a Source-DU (S-DU), the TCI state configuration of the LTM candidate cell of the second C-DU and a second TCI state configuration of a corresponding LTM candidate cell of the first C-DU.

13. The network node (QQ110) of any one of Claims 9-12, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C- DU in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

14. The network node (QQ110) of any one of Claims 9-13, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is transmitted to the first C- DU based on an LTM cell switch being triggered toward the first C-DU.

15. The network node (QQ110) of any one of Claims 9-14, wherein the network node (QQ110) is further configured to: obtain, from the first C-DU, a TCI state configuration of an LTM candidate cell of the first C-DU; and transmit, to the second C-DU, the TCI state configuration of the LTM candidate cell of the first C-DU.

16. The network node (QQ110) of any one of Claims 9-15, wherein the TCI state configuration comprises at least one of: an indication of a plurality of LTM downlink (DL) TCI states; an indication of a plurality of LTM uplink (UL) TCI states; an indication of a plurality of joint TCI states; an indication whether a TCI state is to be considered as an uplink TCI state, downlink TCI state, joint UL/DL TCI state or Unified TCI state; and a TCI related configuration for a cell group configuration.

17. A method performed by a network node (QQ110) operating as a first Candidate-DU (C-DU), the method comprising: receiving (S106), from a Central Unit (CU) serving a user equipment (UE)(QQ112) , a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU.

18. The method of Claim 17, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is received in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

19. The method of any one of Claims 17-18, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is received based on an LTM cell switch being triggered toward the first C-DU.

20. The method of any one of Claims 17-19, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

21. The method of any one of Claims 17-20, further comprising: receiving layer 1 measurements from the UE (QQ112) , the layer 1 measurements being associated with the LTM candidate cell of the second C-DU; determining a TCI identifier (ID) associated with the layer 1 measurements based at least in part on the TCI state configuration of the LTM candidate cell of the second C- DU; and transmitting, to the UE (QQ112), a command indicating that the LTM candidate cell of the second C-DU is a target cell.

22. The method of any one of Claims 17-21, further comprising transmitting, to the UE (QQ112) and before a LTM cell switch, an Early TCI Activation command indicating the LTM candidate cell of the second C-DU and a TCI state identifier (ID).

23. A network node (QQ110) operating as a first Candidate-DU (C-DU), the network node (QQ110) configured to: receive, from a Central Unit (CU) serving a user equipment (UE)(QQ112), a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU.

24. The network node (QQ110) of Claim 23, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is received in a message that requests the first C-DU to configure a cell of the first C-DU as an LTM candidate cell.

25. The network node (QQ110) of any one of Claims 23-24, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is received based on an LTM cell switch being triggered toward the first C-DU.

26. The network node (QQ110) of any one of Claims 23-25, wherein the TCI state configuration of the LTM candidate cell of the second C-DU is received by the first C-DU in a message from the CU which requests the first C-DU to configure a cell of the first C- DU as an LTM candidate cell.

27. The network node (QQ110) of any one of Claims 23-25, wherein the network node (QQ110) is further configured to: receive layer 1 measurements from the UE (QQ112), the layer 1 measurements being associated with the LTM candidate cell of the second C-DU; determine a TCI identifier (ID) associated with the layer 1 measurements based at least in part on the TCI state configuration of the LTM candidate cell of the second C-DU; and transmit, to the UE (QQ112), a command indicating that the LTM candidate cell of the second C-DU is a target cell.

28. The network node (QQ110) of any one of Claims 23-27, wherein the network node (QQ110) is further configured to transmit, to the UE (QQ112) and before a LTM cell switch, an Early TCI Activation command indicating the LTM candidate cell of the second C-DU and a TCI state identifier (ID).

29. A method performed by a network node (QQ110) operating as a source-DU (S-DU) serving a user equipment (UE)(QQ112), the S-DU being different from a first candidate-DU (C-DU) and a second C-DU, the method comprising: obtaining (S108) a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU; and transmitting (SI 10), to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU based on a LTM cell switch being triggered toward the first C-DU.

30. A network node (QQ110) operating as a source-DU (S-DU) serving a user equipment (UE)(QQ112), the S-DU being different from a first candidate-DU (C-DU) and a second C-DU, the network node (QQ110) configured to: obtain a Transmission Configuration Indication (TCI) state configuration of an Ll/L2-Triggered Mobility (LTM) candidate cell of a second C-DU; and transmit, to the first C-DU, the TCI state configuration of the LTM candidate cell of the second C-DU based on a LTM cell switch being triggered toward the first C-DU.

31. A method performed by a user equipment (UE)(QQ112) that is in communication with a Source Distributed Unit (S-DU) serving the UE (QQ112), the S- DU being different from a first Candidate Distributed Unit (C-DU) and a second C-DU, the method comprising: receiving (SI 12), from the S-DU, a Transmission Configuration indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C- DU; performing (S 114) an LTM cell switch to a LTM candidate cell of the first C-DU; and after accessing the first C-DU, receiving (SI 16) a command from the first C-DU, the command comprising an indication of a LTM candidate cell of the second C-DU.

32. A user equipment (UE)(QQ112) configured to communicate with a Source Distributed Unit (S-DU) serving the UE (QQ112), the S-DU being different from a first Candidate Distributed Unit (C-DU) and a second C-DU, the UE (QQ112) configured to: receive, from the S-DU, a Transmission Configuration indication (TCI) state configuration of a Ll/L2-Triggered Mobility (LTM) candidate cell of the second C-DU; perform an LTM cell switch to a LTM candidate cell of the first C-DU; and after accessing the first C-DU, receive a command from the first C-DU, the command comprising an indication of a LTM candidate cell of the second C-DU.