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EP-4740595-A1 - CONDITIONAL LAYER 1/LAYER 2 TRIGGERED MOBILITY IN WIRELESS SYSTEMS

EP4740595A1EP 4740595 A1EP4740595 A1EP 4740595A1EP-4740595-A1

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Techniques for performing a conditional low-layer triggered mobility (CLTM) are disclosed. A user equipment (UE), comprising: a transceiver configured to: receive, from a serving cell, for one or more candidate target cells, a cell configuration, a physical layer (L1) measurement configuration, and at least one execution condition; and a processor operably coupled to the transceiver and configured to: perform, based on the L1 measurement configuration, L1 measurement for the one or more candidate target cells; and evaluate, based on the L1 measurement, the at least one execution condition corresponding to the one or more candidate target cells; in case that the at least one execution condition corresponding to a candidate target cell is met, determine the candidate target cell as a new serving cell; select a beam for the new serving cell based on the L1 measurement; and detach from the serving cell and apply the cell configuration corresponding to the new serving cell; wherein the transceiver is further configured to transmit, to the new serving cell, an uplink (UL) message using the selected beam.

Inventors

  • LENG, Shiyang

Assignees

  • Samsung Electronics Co., Ltd.

Dates

Publication Date
20260513
Application Date
20240711

Claims (14)

  1. A user equipment (UE), comprising: a transceiver configured to: receive, from a serving cell, for one or more candidate target cells, a cell configuration, a physical layer (L1) measurement configuration, and at least one execution condition; and a processor operably coupled to the transceiver and configured to: perform, based on the L1 measurement configuration, L1 measurement for the one or more candidate target cells; and evaluate, based on the L1 measurement, the at least one execution condition corresponding to the one or more candidate target cells; in case that the at least one execution condition corresponding to a candidate target cell is met, determine the candidate target cell as a new serving cell; select a beam for the new serving cell based on the L1 measurement; and detach from the serving cell and apply the cell configuration corresponding to the new serving cell; wherein the transceiver is further configured to transmit, to the new serving cell, an uplink (UL) message using the selected beam.
  2. The UE of claim 1, wherein in case that a timing advance (TA) is not obtained for the new serving cell, the transceiver is further configured to transmit the message via a random access procedure.
  3. The UE of claim 1, wherein: in case that a timing advance (TA) is obtained for the new serving cell, the transceiver is further configured to transmit the message using the obtained TA via a random access channel (RACH)-less procedure, and the message is a first UL PUSCH.
  4. The UE of claim 1, wherein: the at least one execution condition comprises one or more events of: an identified beam of the one or more evaluated candidate target cells having a measured L1 metric higher by an offset value than a beam of the serving cell; an identified beam of the one or more evaluated candidate target cells having a measured L1 metric that exceeds a threshold; or an identified beam of one or more of the evaluated candidate target cells having a measured L1 metric higher than a first threshold and a beam of the serving cell having a measured L1 metric lower than a second threshold, and the measured L1 metric of the one or more evaluated candidate target cells for each of the one or more events corresponds to a value of the identified beam, or an average value of identified beams of the one or more evaluated candidate target cells.
  5. The UE of claim 1, wherein the transceiver is configured to apply the selected beam for the new serving cell based on the L1 measurement that correspond to the execution condition being met for the new serving cell.
  6. The UE of claim 1, wherein the transceiver is further configured to apply the selected beam for the new serving cell for use in a first downlink reception from the new serving cell.
  7. The UE of claim 1, wherein: the processor is further configured to apply one or more of a joint transmission configuration indicator (TCI) state, a downlink (DL) TCI state, or an UL TCI state; for each of the one or more states, the reference signal is quasi-collocated to the selected beam; and the transceiver is configured to perform one or both of (i) transmitting, to the new serving cell, the (UL) message based on the joint TCI state or the UL TCI state, or (ii) receiving, from the new serving cell, a first DL message based on the joint TCI state or the DL TCI state.
  8. A method performed by a user equipment, the method comprising: receiving, from a serving cell, one or more candidate target cells, a cell configuration, a physical layer (L1) measurement configuration, and at least one execution condition; performing, based on the L1 measurement configuration, L1 measurement for the one or more candidate target cells; evaluating, based on the L1 measurement, the at least one execution condition corresponding to the one or more candidate target cells; in case that the at least one execution condition corresponding to a candidate target cell is met, determining the candidate target cell as a new serving cell; selecting a beam for the new serving cell based on the L1 measurement; detaching from the serving cell and applying the cell configuration corresponding to the new serving cell; and transmitting, to the new serving cell, an uplink (UL) message using the selected beam.
  9. The method of claim 8, further comprising, in case that a timing advance (TA) is not obtained for the new serving cell, transmitting the message via a random access procedure.
  10. The method of claim 8, further comprising, in case that a timing advance (TA) is obtained for the new serving cell, transmitting the message using the obtained TA via a random access channel (RACH)-less procedure, wherein the message is a first UL PUSCH.
  11. The method of claim 8, wherein the at least one execution condition comprises one or more events of: an identified beam of the one or more evaluated candidate target cells having a measured L1 metric higher by an offset value than a beam of the serving cell; an identified beam of the one or more evaluated candidate target cells having a measured L1 metric that exceeds a threshold; or an identified beam of one or more of the evaluated candidate target cells having a measured L1 metric higher than a first threshold and a beam of the serving cell having a measured L1 metric lower than a second threshold, and the measured L1 metric of the one or more evaluated candidate target cells for each of the one or more events corresponds to a value of the identified beam, or an average value of identified beams of the one or more evaluated candidate target cells.
  12. The method of claim 8, further comprising applying the selected beam for the new serving cell based on the L1 measurement that correspond to the execution condition being met for the new serving cell.
  13. The method of claim 8, further comprising applying the selected beam for the new serving cell for use in a first downlink reception from the new serving cell.
  14. The method of claim 8, further comprising: applying one or more of a joint transmission configuration indicator (TCI) state, a downlink (DL) TCI state, or an UL TCI state, wherein for each of the one or more states, the reference signal is quasi-collocated to the selected beam; and performing one or both of (i) transmitting, to the new serving cell, the (UL) message based on the joint TCI state or the UL TCI state, or (ii) receiving, from the new serving cell, a first DL message based on the joint TCI state of the DL TCI state.

Description

CONDITIONAL LAYER 1/LAYER 2 TRIGGERED MOBILITY IN WIRELESS SYSTEMS This disclosure relates generally to a wireless communication system, and more particularly to, for example, but not limited to, conditional handovers for use in wireless mobility. Mobility management operations including network handovers represent a pivotal aspect of any wireless communication system. These systems include, for example, LTE and 5G New Radio (NR), and upcoming technologies currently coined "6G". Mobility is presently controlled by the network with UE assistance to maintain optimal connection quality. The network may hand over the UE to a target cell with superior signal quality. The inclusion of enhanced broadband mechanisms requiring high speeds and low latencies has necessitated more sophisticated handover mechanisms. Accordingly, conditional handovers (CHOs) and separately, layer 1/layer triggered mobility (LTM) have been introduced to provide additional conditions for specific networks or slices thereof to increase handover speed. The use of these enhancements, however, introduces latencies of its own, at least because the network needs to conduct several data exchanges with the UE during the handover process. The initiation of a prospective handover triggered by the network consequently introduces latencies, signaling overhead, and interruption times of its of its own. The description set forth in the background section should not be assumed to be prior art merely because it is set forth in the background section. The background section may describe aspects or embodiments of the present disclosure. 5th generation (5G) or new radio (NR) mobile communications is recently gathering increased momentum with all the worldwide technical activities on the various candidate technologies from industry and academia. The candidate enablers for the 5G/NR mobile communications include massive antenna technologies, from legacy cellular frequency bands up to high frequencies, to provide beamforming gain and support increased capacity, new waveform (e.g., a new radio access technology (RAT)) to flexibly accommodate various services/applications with different requirements, new multiple access schemes to support massive connections, and so on. 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies. At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service. Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning. Moreover, there has been ongoing standardization in air interface architecture/protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interwo