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EP-4740589-A1 - SELECTING A CONFIGURATION FOR COMMUNICATION UPON A LOWER LAYER TRIGGERED CELL SWITCH

EP4740589A1EP 4740589 A1EP4740589 A1EP 4740589A1EP-4740589-A1

Abstract

A central unit (CU) of a distributed base station provides, to a user equipment (UE), a plurality of low-layer triggered mobility (LTM) distributed unit (DU) configurations for a plurality of respective candidate cells; receives a DU-to-CU message indicating an LTM switch of the UE to a target cell included in the plurality of candidate cells, the DU-to-CU message including an indication of the target cell; and identifies, based on the DU-to-CU message, one of the plurality of LTM DU configurations.

Inventors

  • WU, CHIH-HSIANG
  • HSIEH, CHING-JUNG

Assignees

  • GOOGLE LLC

Dates

Publication Date
20260513
Application Date
20240722

Claims (15)

  1. 1. A method implemented in a central unit (CU) of a distributed base station, the method comprising: providing, to a user equipment (UE), a plurality of low-layer triggered mobility (LTM) distributed unit (DU) configurations for a plurality of respective candidate cells; receiving a DU-to-CU message indicating an LTM switch of the UE to a target cell included in the plurality of candidate cells, the DU-to-CU message including an indication of the target cell; and identifying, based on the DU-to-CU message, one of the plurality of LTM DU configurations.
  2. 2. The method of claim 1, further comprising: prior to the providing of the plurality of LTM DU configurations to the UE, communicating with the UE via a serving DU of the distributed base station.
  3. 3. The method of claim 1 or 2, further comprising: receiving the plurality of LTM DU configurations from one or more DUs of the distributed base station.
  4. 4. The method any of claims 1-3, wherein the indication of the target cell includes a physical cell id (PCI).
  5. 5. The method any of claims 1-3, wherein the indication of the target cell includes a global cell id (GO).
  6. 6. The method any of claims 1-3, wherein: a reference to the target cell includes an LTM ID identifying a respective one of the plurality of LTM DU configurations, and each of the plurality of LTM DU configurations corresponds to a respective one of the plurality of candidate cells.
  7. 7. The method of claim 6, further comprising: assigning, at the CU, the LTM IDs to the plurality of LTM DU configurations.
  8. 8. The method of any of the preceding claims, further comprising: receiving, in the DU-to-CU message indicating the LTM switch, an identity of the UE.
  9. 9. The method of claim 8, wherein the identity of the UE includes a Cell Radio Network Temporary Identifier (C-RNTI).
  10. 10. The method of any of the preceding claims, wherein: the DU-to-CU message includes a first DU-to-CU message indicating that the UE successfully completed the LTM switch; the method further comprising: receiving, prior to the receiving the first DU-to-CU message, a second DU-to-CU message indicating that the UE initiated the LTM switch.
  11. 11. The method of claim 9 or 10, further comprising: receiving, from the UE and subsequently to the identifying of the one of the plurality of LTM DU configurations, a Radio Resource Control (RRC) reestablishment message including the identity of the UE.
  12. 12. The method of any of claims 9-11, further comprising: authenticating the UE based on the identity of the UE.
  13. 13. The method of any of the preceding claims, further comprising: transmitting the identified LTM DU configuration to a DU of the distributed base station.
  14. 14. The method of any of the preceding claim, wherein the providing of the plurality of LTM DU configurations includes: providing a reconfiguration with sync configuration.
  15. 15. A central unit (CU) of a distributed base station, the CU comprising processing hardware and configured to implement a method of any of the preceding claims

Description

SELECTING A CONFIGURATION FOR COMMUNICATION UPON A LOWER LAYER TRIGGERED CELL SWITCH CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to and the benefit of the filing date of provisional U.S. Patent Application No 63/515,088, entitled “Selecting a Configuration upon a Lower Layer Triggered Cell Switch,” filed on July 21, 2023. The entire contents of the provisional application are hereby expressly incorporated herein by reference. FIELD OF THE DISCLOSURE [0002] This disclosure relates to wireless communications and, more particularly, to selecting a configuration for communication upon a lower layer triggered cell switch. BACKGROUND [0003] This background description is provided for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. [0004] In telecommunication systems, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as transfer of user-plane data, ciphering, integrity protection, etc. For example, the PDCP layer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) radio interface (see the 3rd Generation Partnership Project (3GPP) specification TS 36.323) and New Radio (NR) (see 3GPP specification TS 38.323) provides sequencing of protocol data units (PDUs) in the uplink direction (from a user device, also known as a user equipment (UE), to a base station) as well as in the downlink direction (from the base station to the UE). Further, the PDCP sublayer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the Radio Resource Control (RRC) sublayer. Generally speaking, the UE and a base station can use SRBs to exchange RRC messages as well as non-access stratum (NAS) messages, and can use DRBs to transport data on a user plane. [0005] UEs can use several types of SRBs and DRBs. When operating in dual connectivity (DC), the cells associated with the base station operating the master node (MN) define a master cell group (MCG), and the cells associated with the base station operating as the secondary node (SN) define the secondary cell group (SCG). So-called SRB1 resources carry RRC messages, which in some cases include NAS messages over the dedicated control channel (DCCH), and SRB2 resources support RRC messages that include logged measurement information or NAS messages, also over the DCCH but with lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and the MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and also can be referred to as MCG SRBs. SRB3 resources allow the UE and the SN to exchange RRC messages related to the SN, and can be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via lower layer resources of the MN and the SN. Further, DRBs using the lower-layer resources of only the MN can be referred as MCG DRBs, DRBs using the lower-layer resources of only the SN can be referred as SCG DRBs, and DRBs using the lower-layer resources of both the MCG and the SCG can be referred to as split DRBs. [0006] The UE in some scenarios can concurrently utilize resources of multiple radio access network (RAN) nodes (e.g., base stations or components of a distributed base station), interconnected by a backhaul. When these network nodes support different radio access technologies (RATs), this type of connectivity is referred to as Multi-Radio Dual Connectivity (MR-DC). When a UE operates in MR-DC, one base station operates as a master node (MN) that covers a primary cell (PCell), and the other base station operates as a secondary node (SN) that covers a primary secondary cell (PSCell). The UE communicates with the MN (via the PCell) and the SN (via the PSCell). In other scenarios, the UE utilizes resources of one base station at a time. One base station and/or the UE determines that the UE should establish a radio connection with another base station. For example, one base station can determine to hand the UE over to the second base station, and initiate a handover procedure. [0007] When the UE moves from the coverage area of one cell to the coverage area of another cell in a RAN, the UE and the RAN at some point must perform a serving cell change. To this end, the RAN configures the UE to transmit Layer 3 (L3) measurement results. Using the L3 measurement results from the UE, the RAN transmits an RRC reconfiguration message configuring Reconfiguration with Synchronization (e.g., the RRC reconfiguration message includes a ReconfigurationWithSync IE) for a change of the serving cell (e.g., PCell or PSCell). When the UE operates in carrier aggregation (CA) of at least one seco