CN118489270A

CN118489270A - Method and device for controlling cell change operation

Info

Publication number: CN118489270A
Application number: CN202380015992.2A
Authority: CN
Inventors: 洪成杓
Original assignee: KT Corp
Current assignee: KT Corp
Priority date: 2022-01-03
Filing date: 2023-01-03
Publication date: 2024-08-13

Abstract

The present disclosure relates to a method of controlling a cell change operation of a mobile communication terminal and an apparatus thereof. The embodiment can provide a method and a device for a terminal to execute cell change operation, wherein the method comprises the following steps: a step of receiving an upper layer message containing more than one candidate target cell configuration information for an LTM (L1/L2 TRIGGERED MOBILITY ) operation; a step of receiving a MAC CE (Medium Access Control Control Element, medium access control element) for instructing to perform the LTM operation to a target cell; and a step of performing a detach operation from a source cell based on the MAC CE, and performing a cell change operation by applying the candidate target cell configuration information for the target cell.

Description

Method and device for controlling cell change operation

Technical Field

The present disclosure relates to a method of controlling a cell change operation of a mobile communication terminal and an apparatus thereof. And more particularly to a technique for controlling radio bearers during cell change.

Background

Users have increased with the popularity of small wireless communication devices, such as smartphones. Wireless communication devices are installed not only in smart phones, but also in various mobile means such as vehicles and airplanes, so that communication can be performed while moving.

Movement from one cell coverage to another can occur when the wireless communication device moves. In addition, with the development of high-speed moving means such as vehicles, the necessity of changing cells has increased.

Such a cell change operation is called handover, and conventionally, an RRC connection state terminal performs handover through RRC signaling. As described above, when performing handover based on L3 signaling, there is a problem in that a handover procedure of a base station, a core network individual, a terminal, etc. is complicated and requires a long time.

This makes it difficult to meet the low-delay high-speed movement requirement required in 5G later communication and the like. In particular, as the technology of performing communication operations at the beam level is developed and high-speed movement is frequent, the user communication quality can be maintained. In view of these aspects, techniques are needed that can reduce latency, overhead, and interrupt time during handoff.

Disclosure of Invention

Problems to be solved by the invention

The embodiment aims to provide a method and a device for quickly executing mobility control operation of a terminal in a lower layer.

Solution for solving the problem

In one aspect, the present embodiment may provide a method for a terminal to perform a cell change operation, including: a step of receiving an upper layer message containing more than one candidate target cell configuration information for an LTM (L1/L2 TRIGGERED MOBILITY ) operation; a step of receiving a MAC CE (Medium Access Control Control Element, medium access control element) for instructing to perform an LTM operation to a target cell; and a step of performing a detach operation from the source cell based on the MAC CE, and performing a cell change operation by applying candidate target cell configuration information for the target cell.

On the other hand, the present embodiment may provide a method for controlling a cell change operation of a terminal by a base station, including: a step of transmitting an upper layer message including one or more candidate target cell configuration information for an LTM (L1/L2 TRIGGERED MOBILITY) operation to the terminal; a step of receiving an L1 measurement result of the candidate target cell from the terminal; and transmitting to the terminal a MAC CE (Medium Access Control Control Element) indicating to perform an LTM operation to the target cell based on the L1 measurement result.

On the other hand, the present embodiment may provide a terminal that performs a cell change operation, including: a reception unit that receives an upper layer message including one or more candidate target cell configuration information for LTM (L1/L2 TRIGGERED MOBILITY) operation, and that receives a MAC CE that instructs execution of the LTM operation to the target cell; and a control section that performs a detach operation from the source cell based on the MAC CE (Medium Access Control Control Element) and performs a cell change operation by applying candidate target cell configuration information for the target cell.

On the other hand, the present embodiment may provide a base station for controlling a cell change operation of a terminal, including: a transmitting unit for transmitting an upper layer message including one or more candidate target cell configuration information for LTM (L1/L2 TRIGGERED MOBILITY) operation to a terminal; and a receiving unit that receives an L1 measurement result for the candidate target cell from the terminal, wherein the transmitting unit transmits to the terminal a MAC CE (Medium Access Control Control Element) that instructs execution of the LTM operation to the target cell based on the L1 measurement result.

Effects of the invention

According to the embodiment, a method and a device for quickly executing mobility control operation of a terminal at a lower layer can be provided.

Drawings

Fig. 1 is a diagram simply showing the structure of an NR wireless communication system applicable to the present embodiment.

Fig. 2 is a diagram for explaining a frame structure in an NR system to which the present embodiment is applicable.

Fig. 3 is a diagram for explaining a resource grid supporting a radio access technology to which the present embodiment is applicable.

Fig. 4 is a diagram for explaining a bandwidth portion supporting a radio access technology to which the present embodiment is applicable.

Fig. 5 is a diagram exemplarily showing a synchronization signal block in a radio access technology to which the present embodiment is applicable.

Fig. 6 is a diagram for explaining a random access flow in a radio access technology to which the present embodiment is applicable.

Fig. 7 is a diagram for explaining CORESET.

Fig. 8 is a diagram for explaining an operation of a terminal according to an embodiment.

Fig. 9 is a diagram for explaining the operation of a base station according to one embodiment.

Fig. 10 is a diagram showing one example of a downlink L2 structure for an LTM radio bearer.

Fig. 11 is a diagram showing one example of an uplink L2 structure for an LTM radio bearer.

Fig. 12 is a diagram showing another example of a downlink L2 structure for an LTM radio bearer.

Fig. 13 is a diagram showing another example of an uplink L2 structure for an LTM radio bearer.

Fig. 14 is a diagram showing the composition of a terminal according to another embodiment.

Fig. 15 is a diagram showing the composition of a base station according to another embodiment.

Detailed Description

Some embodiments of the present disclosure are described in detail below with reference to the exemplary drawings. When reference is made to components of each drawing, the same reference numerals are given to the same components as much as possible even though they are shown in different drawings. In the description of the present embodiment, if it is considered that the detailed description of the related known structure or function will obscure the gist of the present technical idea, the detailed description thereof may be omitted. In the case of reference to "including", "having", "composing", and the like in this specification, unless "only" is used, it means that other parts may be added. Where a component is expressed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

In addition, in describing the components of the present disclosure, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish one element from another element, and the nature, order, sequence, or number of elements is not limited by the term.

In the description of the positional relationship of the components, if two or more components are described as "connected", "combined" or "connected", etc., the two or more components may be directly "connected", "combined" or "connected", but it should be understood that other components may also be "interposed" in the two or more components, so as to be "connected", "combined" or "connected". Wherein other components may also be included in more than one of two or more components "connected," "joined," or "accessed" to each other.

In the description of time flow relationships relating to components, operation methods, production methods, or the like, when time precedence relationships or precedence relationships of flows are described by, for example, "after", "subsequent", "next", "before", or the like, unless "immediate" or "direct" is used, a discontinuous case may also be included.

On the other hand, when referring to numerical values of components or their corresponding information (e.g., grades, etc.), even if not explicitly recited alone, numerical values or their corresponding information should be interpreted to include error ranges that may occur due to various factors (e.g., process factors, internal or external impacts, noise, etc.).

A wireless communication system in this specification refers to a system that provides various communication services such as voice, data packets, etc. using wireless resources, and may include: a terminal, a base station, or a core network, etc.

The present embodiment disclosed below is applicable to a wireless communication system using a plurality of wireless access technologies. For example, the present embodiment is applicable to various radio access technologies, such as: CDMA (code division multiple access ), FDMA (frequency division multiple access, frequency division multiple access), TDMA (timedivision multiple access ), OFDMA (orthogonal frequency division multiple access, Orthogonal frequency division multiple access), SC-FDMA (SINGLECARRIER FREQUENCY DIVISION MULTIPLE ACCESS ), or NOMA (non-orthogonal multiple access, non-orthogonal multiple access). Further, radio access technology means not only a specific access technology but also various generations of communication technologies specified by various communication protocol institutions, such as: 3GPP, 3GPP2, wiFi, bluetooth, IEEE, ITU, etc. For example, CDMA may be implemented by wireless technology such as UTRA (universal terrestrial radio access ) or CDMA 2000. TDMA may be implemented by wireless technologies such as GSM (global system for mobile communications )/GPRS (GENERAL PACKET radio service)/EDGE (ENHANCED DATARATES for GSM evolution ). OFDMA may be achieved by, for example: IEEE (institute of electrical andelectronics engineers ) 802.11 (Wi-Fi, wireless local area network), IEEE 802.16 (WiMAX, worldwide interoperability for microwave Access), IEEE 802-20, E-UTRA (evolved UTRA), and other wireless technologies are implemented. IEEE 802.16m, an evolution of IEEE 802.16e, provides backward compatibility with IEEE 802.16 e-based systems (backward compatibility). UTRA is a part of UMTS (universal mobile telecommunications system ). 3GPP (3 rd generation partnership project, third Generation partnership project) LTE (long term evolution ) is part of E-UMTS (evolved UMTS) employing E-UTRA (evolved-UMTSterrestrial radio access, evolved UMTS terrestrial radio Access), OFDMA is employed in the downlink, and SC-FDMA is employed in the uplink. As described above, the present embodiment can be applied to a currently disclosed or commercialized radio access technology, and can also be applied to a radio access technology currently being developed or developed in the future.

On the other hand, a Terminal in the present specification refers to a device including a wireless communication module for communicating with a base Station in a wireless communication system as a comprehensive concept, and should be interpreted to include not only UEs (User Equipment) in WCDMA (wideband code division multiple access), LTE, NR (New air interface), HSPA (high speed packet access), IMT-2020 (5G or New Radio) and the like, but also MSs (Mobile Station), UT (User Terminal), SS (Subscriber Station ), wireless devices (WIRELESS DEVICE) and the like in GSM. The terminal may be a user portable device such as a smart phone, and the V2X (vehicle to everything, internet-enabled car technology) communication system may mean a vehicle, a device including an in-vehicle wireless communication module, or the like, depending on the usage form. In addition, in a machine type Communication (MACHINE TYPE Communication) system, an MTC terminal, an M2M (Machine to machine ) terminal, a URLLC (Ultra-Reliable Low-Latency Communications) terminal, and the like equipped with a Communication module to perform machine type Communication can also be meant.

A Base station or a cell in this specification refers to a terminal that communicates with the terminal in terms of a network, and is meant to cover various coverage areas, such as a Node-B (Node-B), an eNB (evolved Node-B), a gNB (gNode-B), an LPN (Low Power Node), a Sector (Sector), a Site (Site), antennas of various forms, a BTS (Base TRANSCEIVER SYSTEM, a Base station transmitter/receiver), an Access Point (Access Point), a Point (e.g., a transmission Point, a reception Point, a transmission/reception Point), a Relay Node (Relay), a super-size cell, a macrocell, a microcell, a picocell, a femtocell, an RRH (Remote Radio Head, a remote Radio head), an RU (Radio Unit), a small cell (SMALL CELL), and the like. In addition, a cell may be meant to contain BWP (Bandwidth Part) in the frequency domain. For example, the serving cell may mean an Activation BWP (active BWP) of the terminal.

Since the various cells listed above have a base station controlling more than one cell, the base station can be interpreted in two senses. The following may be indicated: (1) The apparatus itself, which provides a very large cell, macro cell, micro cell, pico cell, femto cell or small cell (SMALL CELL) associated with the wireless area; (2) the wireless zone itself. In case (1), all devices that interact so that the device that provides the prescribed wireless area is controlled by the same object or that configure the wireless area through cooperation are indicated as base stations. According to the configuration mode of the wireless area, one embodiment of the base station is: a point, a transmission/reception point, a transmission point, a reception point, etc. In case (2), the wireless domain itself receiving or transmitting a signal may be indicated as a base station from the viewpoint of a user terminal or from the standpoint of a neighboring base station.

In this specification, a Cell (Cell) may refer to a coverage component carrier (component carrier) having a signal coverage transmitted from a transmission/reception point or a signal transmitted from a transmission/reception point (transmission point or transmission/reception point) or the transmission/reception point itself.

Uplink (UL, or Uplink) means a manner of transmitting/receiving data to/from a base station by a terminal, and Downlink (Downlink, DL, or Downlink) means a manner of transmitting/receiving data to/from a terminal by a base station. The downlink (downlink) may mean a communication or a communication path from a plurality of transmission/reception points to a terminal, and the uplink (uplink) may mean a communication or a communication path from a terminal to a plurality of transmission/reception points. At this time, in the downlink, the transmitter may be part of a multiple transmission/reception point and the receiver may be part of the terminal. Further, in the uplink, the transmitter may be a part of a terminal and the receiver may be a part of a multiple transmission/reception point.

Uplink and downlink transmit/receive control information through a control channel such as PDCCH (Physical Downlink Control CHannel ), PUCCH (Physical Uplink Control Channel, physical uplink control channel), etc.; data is transmitted and received by configuring data channels such as PDSCH (Physical Downlink SHARED CHANNEL ) and PUSCH (Physical Uplink SHARED CHANNEL). Hereinafter, the case where signals are transmitted/received through channels such as PUCCH, PUSCH, PDCCH and PDSCH is also denoted by the form of "transmission/reception PUCCH, PUSCH, PDCCH and PDSCH".

For the sake of clarity, the present technical idea is described below mainly in the 3GPP LTE/LTE-A/NR (New RAT) communication system, but the present technical features are not limited to this communication system.

In 3GPP, after a 4G (4 th-Generation, fourth Generation, mobile information system) communication technology is studied, a 5G (5 th-Generation, fifth Generation, mobile information system) communication technology is developed that meets the requirements of the next Generation radio access technology of ITU-R. In particular, 3GPP develops a new NR communication technology through a 5G communication technology, which is different from LTE-A pro and 4G communication technologies in which LTE-Advanced technology is improved in a manner conforming to the requirements of ITU-R. Both LTE-a pro and NR mean 5G communication technology, and in the following, the 5G communication technology will be described centering on NR, without specifying a specific communication technology.

The operation scene in NR adds satellite, automobile, new vertical (vertical) and other considerations in the existing 4G LTE scene, and defines various operation scenes, supports eMBB (Enhanced Mobile Broadband ) scenes in terms of service; mMTC (MASSIVE MACHINE Communication, large-scale machine Communication) scenario, which has high terminal density and spreads over a wide range and requires low data rate (data rate) and unsynchronized access; URLLC (Ultra Reliability and Low Latency, ultra-reliable low latency communication) scenario, which requires high responsiveness and reliability and is capable of supporting high speed mobility.

To meet these scenes, NR discloses a wireless communication system to which new waveform and frame structure techniques, low latency (Low latency) techniques, ultra-high band (mmWave) support techniques, and forward compatibility (Forward compatible) providing techniques are applied. Particularly in NR systems, various technical variations are proposed in terms of flexibility in order to provide forward (Forard) compatibility. The main technical features of NR will be described below with reference to the drawings.

< General NR System >

Fig. 1 is a diagram simply showing the structure of an NR system applicable to the present embodiment.

Referring to fig. 1, the NR system is divided into 5GC (5G Core Network) and NR-RAN (new radio access network) parts, NG-RAN (next generation radio access network) consisting of a gNB and a NG-eNB providing a user plane (SDAP (service data adaptation protocol)/PDCP (packet data diversity protocol)/RLC (radio link control)/MAC (medium access control)/PHY (physical layer)) and a control plane (RRC) protocol terminal for UE (User Equipment). The gNB is connected with each other or the gNB and the ng-eNB through an Xn interface. The gNB and the NG-eNB are connected with the 5GC through NG interfaces respectively. The 5GC may include: AMF (ACCESS AND Mobility Management Function ) responsible for control plane of terminal access and mobility control functions, etc.; and, a UPF (User Plane Function ) that is responsible for user data control functions. NR is supported for both the Frequency band below 6GHz (FR 1, frequency Range 1) and the Frequency band above 6GHz (FR 2, frequency Range 2).

GNB means a base station providing NR user plane and control plane protocol terminals to a terminal, and ng-eNB means a base station providing E-UTRA user plane and control plane protocol terminals to a terminal. The base station described in the present specification is understood to cover the meanings of the gNB and the ng-eNB, and can be used by distinguishing the meanings of the gNB or the ng-eNB as required.

< Waveforms, parameter sets, and frame Structure in NR >

In NR, a CP-OFDM (Cyclic prefix orthogonal frequency division multiplexing) waveform of Cyclic prefix (Cyclic prefix) is used for downlink transmission, and CP-OFDM or DFT-s-OFDM (spread spectrum orthogonal frequency division multiplexing based on discrete fourier transform) is used for uplink transmission. OFDM technology is easily combined with MIMO (Multiple Input Multiple Output ) and has the advantage of high frequency efficiency and low complexity receivers can be used.

On the other hand, in NR, since the requirements for the data speed, delay speed, coverage, and the like of the above three scenes are different, it is necessary to effectively satisfy the requirements for each scene by the frequency bands constituting an arbitrary NR system. For this, a technique for efficiently multiplexing (multiplexing) radio resources based on different multiple parameter sets (numerology) is proposed.

Specifically, the NR transmission parameter set is determined based on subcarrier spacing (sub-CARRIER SPACING) and CP (Cyclic prefix), as shown in table 1 below, and μ value is used as an exponent value of 2 on the basis of 15kHz and varies exponentially.

[ Table 1]

As shown in table 1 above, the parameter set of NR can be divided into 5 kinds according to the subcarrier spacing. This is different from the LTE of one of the 4G communication technologies in that the subcarrier spacing is fixed at 15 kHz. Specifically, the subcarrier intervals for data transmission in NR are 15kHz, 30kHz, 60kHz and 120kHz, and the subcarrier intervals for synchronization signal transmission are 15kHz, 30kHz, 120kHz and 240kHz. Further, the extended CP is only applicable to 60kHz subcarrier spacing. On the other hand, a frame (frame) having a length of 10ms is defined in a frame structure (frame) in NR, and is composed of 10 subframes (subframes) having the same length of 1 ms. One frame may be divided into 5ms half frames, each half frame including 5 subframes. In the case of a 15kHz subcarrier spacing, one subframe consists of one slot (slot), each slot consisting of 14 OFDM symbols (symbols). Fig. 2 is a diagram for explaining a frame structure in an NR system to which the present embodiment is applicable.

Referring to fig. 2, in the case of the normal CP, a slot is fixedly composed of 14 OFDM symbols, but in the time domain of the slot, the length may vary according to subcarrier spacing. For example, in the case of a parameter set with a 15kHz subcarrier spacing, the length of the slot is 1ms, which is the same as the length of the subframe. In contrast, in the case of a parameter set having a subcarrier spacing of 30kHz, a slot is composed of 14 OFDM symbols, but the length is 0.5ms, and two slots may be included in one subframe. That is, subframes and frames are defined by a fixed time length, and slots are defined by the number of symbols, and the time length may vary according to subcarrier spacing.

In addition, in NR, a basic unit of scheduling is defined as a slot, and in order to reduce a transmission delay in a radio section, a mini slot (or a sub slot or non-slot based schedule (non-slot scheduling based)) is introduced. If a wide subcarrier spacing is used, the length of one slot becomes inversely proportional to the length of the other slot, and thus the transmission delay of the radio section can be reduced. Mini-slots (or sub-slots) are used to efficiently support URLLC scenarios, which can be scheduled in units of 2, 4, 7 symbols.

Further, NR is different from LTE in that uplink and downlink resource allocation is defined as symbol level within one slot. In order to reduce HARQ (hybrid automatic repeat request) delay, a slot structure in which HARQ ACK/NACK (hybrid automatic repeat request-acknowledgement/negative) can be directly transmitted within a transmission slot is defined, and this slot structure is named as a self-contained (self-contained) structure for explanation.

In NR is designed to support 256 slot formats total, 62 of which are used for 3GPP Rel-15. In addition, a common frame structure constituting an FDD or TDD frame is supported by a combination of various slots. For example, the symbols supporting the slots are all set to the downlink slot structure and the symbols are all set to the uplink slot structure, and the slot structure of the combination of the downlink and uplink symbols. In addition, NR supports scheduling where data transmissions are scattered over more than one time slot. Thus, the base station may inform the terminal of whether a slot is a downlink slot, an uplink slot, or a flexible slot using a slot format indicator (SFI, slot Format Indicator). The base station may indicate the slot format by using SFI indication through a table index formed by a terminal-specific (UE-specific) RRC signaling, or may perform dynamic indication through DCI (Downlink Control Information ) or static or quasi-static indication through RRC.

< Physical resources in NR >

Regarding physical resources (physical resource) in NR, antenna ports (antenna ports), resource grids (resource elements), resource blocks (resource blocks), bandwidth parts (bandwidth parts), etc. can be considered.

An antenna port is defined as a channel carrying symbols on an antenna port that can be deduced from channels carrying other symbols on the same antenna port. If the large-scale property (large-scale property) of a channel carrying symbols on one antenna port can be deduced from a channel carrying symbols on another antenna port, then the two antenna ports can be considered to have a QC/QCL (quasico-located or quasico-located) relationship. Wherein the large scale characteristics include one or more of the following: delay spread (DELAY SPREAD), doppler spread (Doppler spread), frequency offset (Frequency shift), average received power (AVERAGE RECEIVED power), and receive timing (RECEIVED TIMING).

Referring to fig. 3, a Resource Grid (NR) may exist according to each parameter set since it supports a plurality of parameter sets in the same carrier. Further, the resource grid may exist according to antenna ports, subcarrier spacing, and transmission direction.

A resource block (resource block) is composed of 12 subcarriers and is defined only in the frequency domain. Furthermore, a resource element (resource element) is composed of one OFDM symbol and one subcarrier. Thus, as shown in fig. 3, the size of one resource block may vary according to the subcarrier spacing. Further, NR defines "Point a" and common resource blocks, virtual resource blocks, etc. that function as a common reference Point for a resource block grid.

In NR, unlike LTE in which the carrier bandwidth is fixed to 20Mhz, the maximum carrier bandwidth per subcarrier spacing is set to 50Mhz to 400Mhz. Therefore, no assumption is made that all terminals use these carrier bandwidths. Thus, in NR, as shown in fig. 4, a bandwidth portion (BWP) may be specified within a carrier bandwidth for use by a terminal. Furthermore, the bandwidth part is associated with one parameter set and consists of a subset of consecutive common resource blocks and may be dynamically activated in accordance with time. The terminal is configured such that the uplink and the downlink each have a maximum of 4 bandwidth parts, and data is transmitted/received using the activated bandwidth parts for a prescribed time.

In the case of paired spectrum (unpaired spectrum), the uplink and downlink bandwidth portions are set independently, and in the case of unpaired spectrum (unpaired spectrum), in order to prevent unnecessary frequency retuning (re-tunning) between downlink and uplink operations, the downlink and uplink bandwidth portions are paired to be able to share the center frequency.

< Initial Access in NR >

In NR, a terminal performs a cell search and a random access procedure for communication with an access base station.

The cell search is a process of synchronizing a terminal with a cell of a base station using a synchronization signal block (SSB, synchronization Signal Block) transmitted from the base station, and obtaining a physical layer cell ID and system information.

Referring to fig. 5, ssb is composed of PSS (primary synchronization signal ) and SSS (secondary synchronization signal, secondary synchronization signal) occupying 1 symbol and 127 subcarriers, respectively, and PBCH spanning 3 OFDM symbols and 240 subcarriers.

The terminal receives the SSB by monitoring the SSB in time and frequency domains.

SSB can be transmitted a maximum of 64 times within 5 ms. Most SSBs are transmitted in different transmission beams in 5ms time, and if a terminal is referenced to a specific one of the beams for transmission, SSBs are assumed to be transmitted once every 20ms period and detection is performed. The number of beams available for SSB transmission increases with the frequency band in 5 ms. For example, up to 4 SSB beams may be transmitted below 3GHz, up to 8 SSB beams may be used in the 3GHz to 6GHz frequency band, and up to 64 different SSB beams may be used in the 6GHz frequency band.

The SSB includes two in one slot, and the start symbol and the number of repetitions in the slot are determined as follows according to the subcarrier spacing.

On the other hand, unlike the SS of the existing LTE, SSB is not transmitted on the center frequency of the carrier bandwidth. That is, SSBs may be transmitted in a non-system band center, and when broadband operation (broadband operation) is supported, multiple SSBs may be transmitted in the frequency domain. Thereby, the terminal monitors the SSB using the synchronization grid (synchronization raster) as a candidate frequency location for monitoring the SSB, the carrier grid (CARRIER RASTER) and the synchronization grid are redefined in the NR as a center frequency location of a channel for initial access, and the frequency interval is set wider than the carrier grid, so that it is possible to support fast SSB search of the terminal.

The terminal may obtain MIB (master information block) through PBCH of SSB. MIB (Master Information Block) includes minimum information of remaining minimum system information (RMSI, REMAINING MINIMUM SYSTEM INFORMATION) used by the terminal to receive network broadcasts. Further, the PBCH may include: for the location information of the first DM-RS symbol in the time domain, the terminal is configured to monitor SIB1 information (e.g., SIB1 parameter set information, SIB1 CORESET related information, search space information, PDCCH related parameter information, etc.), offset information between the common resource block and the SSB (absolute position of the SSB in the carrier is transmitted through SIB 1), and the like. The SIB1 parameter set information is also applicable to a part of messages used in a random access procedure of the access base station after the terminal completes a cell search procedure. For example, the parameter set information of SIB1 may be applicable to at least one of messages 1 to 4 for the random access procedure.

The RMSI above may mean SIB1 (System Information Block (system information block) 1), which is periodically (e.g., 160 ms) broadcast in the cell. SIB1 includes information required for the terminal to perform an initial random access procedure, and is periodically transmitted through the PDSCH. In order for the terminal to receive SIB1, it is necessary to receive parameter set information for SIB1 transmission and CORESET (Control Resource Set ) information for SIB1 scheduling through the PBCH. And the terminal confirms the scheduling information of the SIB1 by utilizing the SI-RNTI in CORESET, and acquires the SIB1 on the PDSCH according to the scheduling information. Other SIBs than SIB1 may be transmitted periodically or according to the requirements of the terminal.

Referring to fig. 6, when cell search is completed, a terminal transmits a random access preamble for random access to a base station. The PRACH transmission is conducted before random access. Specifically, the random access preamble is transmitted to the base station through PRACH consisting of consecutive radio resources in a specific time slot that is repeated periodically. In general, when a terminal initially accesses a cell, a contention-based random access procedure is performed, and when random access is performed for beam fault recovery (BFR, beam Failure Recovery), a non-contention-based random access procedure is performed.

The terminal receives a random access response to the transmitted random access preamble. The random access response may include: a random access preamble Identifier (ID), UL Grant (uplink radio resource), temporary C-RNTI (Temporary Cell-Radio Network Temporary Identifier, temporary cell radio network temporary identifier), TAC (TIME ALIGNMENT Command ). Since one random access response may include random access response information for more than one terminal, a random access preamble identifier may be included to inform which terminal the included UL Grant, temporary C-RNTI, and TAC are valid for. The random access preamble identifier may be an identifier of a random access preamble received for the base station. The TAC may be included as information for the terminal to adjust uplink synchronization. The Random Access response may be indicated by a Random Access identifier, i.e. RA-RNTI (Random Access-Radio Network Temporary Identifier, random Access radio network temporary identifier), on the PDCCH.

The terminal that receives the valid random access response processes the information contained in the random access response and performs scheduling transmission to the base station. For example, the terminal may be TAC-compliant and store temporary C-RNTI. In addition, data stored in a terminal buffer or newly generated data is transmitted to a base station using UL Grant. In this case, information capable of identifying the terminal should be included.

Finally, the terminal receives a downlink message for contention elimination.

CORESET in NR-

The downlink control channel in NR is transmitted by CORESET (Control Resource Set) having a symbol length of 1 to 3, and transmits uplink/downlink scheduling information and SFI (Slot format Index ), TPC (Transmit Power Control, transmission power control) information, etc.

As described above, the concept of CORESET is introduced in NR in order to ensure flexibility of the system. CORESET (Control Resource Set) refers to time-frequency resources (i.e., time-frequency resources) for the downlink control signals. The terminal may use more than one search space in CORESET time-frequency resources to decode the control channel candidates. A QCL (Quasi CoLocation) hypothesis is set for each CORESET, the purpose of which is, in addition to informing the characteristics based on the existing QCL hypothesis: in addition to delay spread, doppler shift, and average delay, characteristics for the analog beam direction are also notified.

Fig. 7 is a diagram for explaining CORESET (control resource set).

Referring to fig. 7, coreset may exist in various forms within a carrier bandwidth within one slot, and CORESET may consist of at most 3 OFDM symbols in the time domain. Further CORESET is defined as a multiple of six resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated by the MIB as part of the initial bandwidth portion to receive additional configuration information and system information from the network. After establishing a connection with the base station, the terminal may receive and configure one or more CORESET messages through RRC signaling.

In this specification, frequencies, frames, subframes, resources, resource blocks, regions (regions), frequency bands, subbands, control channels, data channels, synchronization signals, various reference signals, or various messages related to NR (New Radio) may be interpreted as past or present meanings or various meanings used in the future.

The disclosure provides a cell inter-cell mobility control method and device based on L1/L2 for a mobile communication terminal. In addition, a radio bearer control step and a user plane data processing method in a cell change process (data/signaling) based on L1/L2 are provided.

Mobility in NR (mobility)

In the existing NR technology, mobility control for cell change of a terminal in an RRC connected state exhibits handover by displaying RRC signaling. The cell change may be triggered by L3 measurement and perform handover through RRC message signaling containing one or more of information for accessing the target cell (e.g., reconfiguration with Sync (synchronization reconfiguration), TARGET CELL ID (target cell ID), the new C-RNTI (new C-RNTI), THE TARGET gNB security algorithm identifiers for THE SELECTED security algorithms (target gNB security algorithm identifier for selected security algorithm), a set of DEDICATED RACH resources, the association between RACH resources and SSB(s) (association between RACH resource and SSB), the association between RACH resources and UE-SPECIFIC CSI-RS configuration(s) (association between RACH resource and UE-specific CSI-RS configuration), common RACH resources (common RACH resource), and systeminformation of THE TARGET CELL (system information of the target cell). When a cell change is performed, the MAC entity of the cell group is reset. The terminal then uses the new C-RNTI value received by the C-RNTI of the cell group. Then, the terminal configures the PHY/MAC/RLC/PDCP/SDAP layer according to the received configuration information. This results in more delay, overhead, break time compared to beam changes (beam level mobility) within the same cell.

Beam level mobility does not require explicit RRC signaling to be triggered during beam changes. The base station (network) may provide SSB/CSI resources and resource sets to the terminal through RRC signaling, trigger status for trigger channels, measurement configuration including interferometry and reporting configuration, etc. Beam level mobility may be provided by control signaling (e.g., DCI, MAC CE) of the physical layer/MAC layer in the lower layers. The SSB-based beam level mobility is based on SSBs associated with the initial downlink BWP and may be configured only for the downlink BWPs including the initial downlink BWP and SSBs associated with the initial downlink BWP. For the other DL BWPs, beam-level mobility can only be performed based on CSI-RS. In the prior art, however, beam switching only supports mobility within the same cell (intra-cell).

In existing NR technology, cell-level mobility (cell change) is provided based on L3 signaling, thus resulting in more delay, overhead, and interruption time than beam-level mobility.

In order to solve the above-mentioned problems, the present embodiment proposes a method and steps for providing L1/L2-based cell change (inter-cell mobility) including a radio bearer control step and a user plane data processing method in the L1/L2-based cell change procedure (data/signaling).

The following describes a cell-level mobility providing method based on the 5G NR radio access technology. This is for ease of illustration only and the method is equally applicable to cell change/handover based on any radio access technology (e.g. 6G). Embodiments described in this disclosure include information elements, flows, operational content specified in any NR specification (e.g., NR MAC specification: TS 38.321, NR RRC specification: TS 38.331). Even if the definition of the corresponding information element, the related flow, the related terminal operation content are not described in the present specification, the related content specified in the standard specification as a known technology may be contained in the embodiment.

For ease of explanation, the scenario to which the present disclosure relates will first be explained. However, this is for convenience of explanation, and the present embodiment may be applied to any network deployment scenario, instead of the following scenario.

Cell change based on L1/L2 (signaling) may be performed in the following scenario: in an NR individual network (stand-alone) structure, a scenario of serving cell change (PCell change, SCell change) within one cell group; in the dual connectivity structure, a scenario of serving cell change (SpCell (PCell/PSCell) change, SCell change) within one cell group (e.g., MCG, SCG).

Within an intra-CU (intra CU), and within an intra-DU (intra DU) connected to the CU, intra-CU intra-DU L1/L2 based cell change may be performed between different cells associated with the DU. For example, the cells may have different PCIs (PHYSICAL CELL ID, physical cell identities), and the cells may be synchronized. For different DUs that are connected to the above-mentioned CUs within an intra-CU, intra-CU inter-DU L1/L2 based cell change may be performed between cells associated with each DU. As an example, there may be a case where the cells have different PCIs and there is no synchronization between the cells. For another example, the cells may have different PCIs, and the cells may be synchronized. The embodiments described below may be implemented alone/independently, or in any combination/combination, and are obviously included in the scope of the present disclosure.

For convenience of explanation, a Beam/BG (Beam group) (through a corresponding TRP) of a serving cell/Spcell/Scell providing configuration/activation of a terminal is labeled as a first TRP (Transmit/Receive Point). This is for ease of illustration, but may be replaced by any other name (e.g., primary/main/basic/SpCell associated/SERVING CELL associated TRP/beam/BG). The Transmit/Receive points/TRP/(through the corresponding TRP) Beam/Beams/BG (Beam group) providing PCI (Physical Cell Id) different from the serving cell/Spcell/Scell, or the Transmit/TRP/(through the corresponding TRP) Beam/Beams/BG (Beam group) associated with PCI (Physical Cell Id) different from the serving cell/Spcell/Scell, are labeled as the second TRP (Transmit/Receive Point). This is for convenience of explanation, and may be replaced by any other name (e.g., second/additional/assisting/non-SERVING CELL associated TRP/beam/BG). The second TRP or a cell associated with the second TRP may be configured/released in the terminal. The second TRP or a cell associated with the second TRP may be activated/deactivated at the terminal. For one terminal, one first TRP and one or more second TRPs may provide/support/configure/contact/activate/deactivate.

For ease of illustration, the cell change that provides low latency and low interruption time based on L1/L2 is labeled as LTM (L1/L2-TRIGGERED MOBILITY) operation. This is for ease of explanation, but may be replaced by any other name (e.g., low latency handover, HIGH SPEED HO, fast HO, low latency HO, L1/L2SIGNALING BASED HO, low LAYER SIGNALING based HO). Wherein L1/L2 may represent one or more of arbitrary L1/L2signaling (e.g., MAC-CE/DCI), L1/L2 execution indication information, QCL (Quasi Co Location)/TCI (Transmission Configuration Indication, transport configuration indication) status activation/update/indication, L1/L2 execution conditions (based on L1 measurement), L1/L2 events (based on L1 measurement), L1/L2 flows, and terminal operations in the L1/L2 layers.

For LTM operation, any of the functions described below are defined as individual terminal capabilities and may be transmitted by the terminal to the base station. Or any combination/combination of functions, defined as the terminal capabilities described above, and may be transmitted by the terminal to the base station.

Referring to fig. 8, in the method of performing a cell change operation, the terminal may perform a step of receiving an upper layer message containing one or more candidate target cell configuration information for an LTM (L1/L2 TRIGGERED MOBILITY) operation (S810).

For example, the terminal may receive an RRC message containing more than one candidate target cell configuration information from a base station or TRP. The RRC message may contain more than one candidate target cell configuration information, each of which may be differentiated according to each candidate target cell and contained therein.

For example, the upper layer message may include at least one of cell group configuration information, identification information for candidate target cell configuration information, bandwidth part identification information, and TCI (Transmission Configuration Indication) state configuration information. The cell group configuration information includes information for configuring a cell group using two or more cells. The identification information for the candidate target cell configuration information may include ID or index information. Thus, the terminal can distinguish each candidate target cell configuration information. The bandwidth part identification information may include an ID or index for distinguishing a bandwidth part (BWP). The TCI state configuration information may include at least one of TCI state ID, cell index, cell ID, and PCI (PHYSICAL CELL IDENTITY ). Further, detailed descriptions of various information will be described in more detail below.

Additionally, cell group configuration information may include candidate object PCell (Primary Cell) and candidate object SCell (Sencodary Cell) information. For example, the candidate target cell configuration information may be configured per each candidate target cell, and the candidate target cells may be divided into candidate target PCell and candidate target SCell. Accordingly, candidate target cell configuration information for the candidate target PCell and candidate target cell configuration information for the candidate target SCell may be included in the candidate target cell configuration information.

For example, the cell group configuration information includes the cell group configuration information of the candidate target cells described above, and the candidate target cell configuration information of the candidate target cells composed of one cell group can be distinguished by bundling into the same cell group.

The candidate target PCell included in the candidate target cell configuration information for the LTM operation may be set to one of: a cell of a non-serving cell configured in the terminal, or an SCell configured in the terminal. That is, the candidate target PCell is set to one of: a non-serving cell, or an SCell already configured in the terminal. Or the candidate target SCell may be set to one of: a cell of a non-serving cell configured in the terminal, or a PCell configured in the terminal. That is, the candidate target SCell is set to one of: a non-serving cell, or a PCell configured in a terminal.

On the other hand, the candidate target cell configuration information includes information for performing L1 measurement on the serving cell or the candidate target cell and transmitting the above L1 measurement result. For example, the terminal measures the channel state of the serving cell or the candidate target cell using the candidate target cell configuration information. The terminal transmits channel state or channel quality information measured based on information for transmitting a measurement result included in the candidate target cell configuration information to the base station. To this end, information for measurement reporting may be included in candidate target cell configuration information. For example, information of a measurement period, a measurement object, a measurement report period, a measurement report resource, a value related to a measurement report trigger condition, and the like may be included in the candidate target cell configuration information.

In addition, when an upper layer message including candidate target cell configuration information for LTM operation is received, the terminal may classify and store according to identification information for the candidate target cell configuration information and perform an addition or modification operation.

The terminal may perform the step of receiving a MAC CE (Medium Access Control Control Element) indicating to perform an LTM operation to the target cell (S820).

For example, the terminal may measure the channel state of the serving cell or the candidate target cell using information for measuring or transmitting the measurement result included in the above-described candidate target cell configuration information. Thereafter, the terminal transmits a measurement result including the L1 measurement result to the base station. As an example, the terminal may transmit the measurement result of the corresponding serving cell or candidate target cell to the base station when the transmission of the measurement result satisfies the trigger condition. As another example, the transmission of the L1 measurement is triggered when the measurement quality of the candidate target cell is higher than the measurement of the source PSCell minus the offset value. That is, when comparing the measurement result of the source PSCell and the measurement result of the candidate target cell, the comparison is performed by adding or subtracting a preset offset or an offset included in the candidate target cell configuration information from the measurement result of the source PSCell. Reporting of the measurement results may be triggered when the comparison results show that the channel state of the candidate target cell is better.

For example, the base station may determine whether to perform an LTM operation based on L1 measurement result information of the terminal. As another example, the base station may determine a target cell changed by the LTM operation based on the L1 measurement result information of the terminal.

For example, when the base station determines a cell change of a terminal based on L1 measurement result information received from the terminal, the instruction may be made through the MAC CE.

As one example, the terminal may receive indication information included in the MAC CE for indicating to perform the LTM operation. As another example, information of a target cell included in the MAC CE may be confirmed and an LTM operation execution instruction to the target cell may be received.

The terminal needs to obtain an execution instruction of the LTM operation and information for a target cell to perform a cell change through the MAC CE. To this end, the MAC CE may include at least one of identification information for candidate target cell configuration information, TCI state ID, bandwidth part identification information, and timing advance command. For example, the MAC CE may include identification information for distinguishing configuration information for candidate target cells configured in the terminal through an upper layer message. The identification information may consist of candidate target cell configuration information ID or index information. In addition, the MAC CE may further include at least one of a TCI status ID, a bandwidth part ID, and a TAG.

The terminal may perform the step (S830): a detach (detach) operation is performed from the source cell based on the MAC CE, and a cell change operation is performed by applying candidate target cell configuration information for the target cell.

The terminal may perform a cell change operation without reconfiguring RRC based on the MAC CE and applying candidate target cell configuration information for the target cell. In addition, the terminal performs an operation of separating (detach) from the source cell for cell change. For example, the terminal, after receiving the MAC CE, may confirm a target cell on which to perform cell change based on the MAC CE. As an example, the terminal confirms identification information for candidate target cell configuration information contained in the MAC CE and confirms candidate target cell configuration information allocated as corresponding identification information and received through an upper layer message.

After confirming the target cell, the terminal applies the candidate target cell configuration information applied to the target cell to the terminal. In addition, the terminal uses the candidate target cell configuration information of the target cell to perform a cell change operation to the target cell without performing an RRC reconfiguration operation. On the other hand, more than one candidate target cell configuration information may be stored and applied to the terminal until upper layer signaling for releasing the candidate target cell configuration information is received.

For example, the terminal may distinguish and perform a cell change operation according to whether the target cell and the source cell indicated by the MAC CE are included in the same cell group.

As an example, when the target cell and the source cell indicated by the MAC CE belong to the same cell group within DU (Distributed Unit), the terminal may perform a cell change operation by maintaining the user plane without performing at least one of a MAC reset operation, an RLC reset operation, and a PDCP data recovery operation. That is, when the target cell and the source cell are the same cell group in the intra-DU, the terminal does not perform a MAC reset operation, or does not perform an RLC reset operation, or does not perform a PDCP data recovery operation, thereby maintaining a user plane and performing a fast mobility control operation.

As another example, when the target cell and the source cell indicated by the MAC CE belong to different cell groups in DU (Distributed Unit), the terminal may perform a cell change operation by performing a MAC reset operation, an RLC reset operation, and a PDCP data recovery operation. That is, the terminal may perform a MAC reset operation, an RLC reset operation, and a PDCP data recovery operation in case of intra-DU cell change.

As yet another example, a cell change according to an LTM operation performed by a terminal may not support a security key update operation.

Through the above operation, the terminal can quickly execute the L1/L2 level cell change operation. More specific details are set forth below in more detail in the individual embodiments.

Referring to fig. 9, in the method of controlling a cell change operation of a terminal, the base station may perform a step of transmitting an upper layer message to the terminal (S910), the upper layer message including one or more candidate target cell configuration information for an LTM (L1/L2 TRIGGERED MOBILITY) operation.

For example, the base station or TRP may transmit an RRC message containing more than one candidate target cell configuration information to the terminal. The RRC message may contain more than one candidate target cell configuration information, each of which may be differentiated according to each candidate target cell and contained therein.

For example, the upper layer message may include: at least one of cell group configuration information, identification information for candidate target cell configuration information, bandwidth part identification information, and TCI (Transmission Configuration Indication) state configuration information. The cell group configuration information includes information for configuring a cell group using two or more cells. The identification information for the candidate target cell configuration information may include ID or index information. Thus, the terminal can distinguish each candidate target cell configuration information. The bandwidth part identification information may include an ID or index for distinguishing a bandwidth part (BWP). The TCI state configuration information may include at least one of TCI state ID, cell index, cell ID, and PCI (PHYSICAL CELL IDENTITY ).

Additionally, cell group configuration information may include candidate object PCell (Primary Cell) and candidate object SCell (Sencodary Cell) information. For example, the candidate target cell configuration information may be configured per each candidate target cell, and the candidate target cells may be divided into candidate target PCell and candidate target SCell. Accordingly, candidate target cell configuration information for the candidate target PCell and candidate target cell configuration information for the candidate target SCell may be included in the candidate target cell configuration information. For example, the cell group configuration information includes the cell group configuration information of the candidate target cells described above, and the candidate target cell configuration information of the candidate target cells composed of one cell group can be distinguished by bundling into the same cell group.

On the other hand, the candidate target cell configuration information includes information for performing L1 measurement on the serving cell or the candidate target cell and transmitting the above L1 measurement result. For example, the terminal measures the channel state of the serving cell or the candidate target cell using the candidate target cell configuration information. The terminal transmits the measured channel state or channel quality information to the base station based on information for transmitting the measurement result included in the candidate target cell configuration information. To this end, information for measurement reporting may be included in candidate target cell configuration information. For example, information of a measurement period, a measurement object, a measurement report period, a measurement report resource, a value related to a measurement report trigger condition, and the like may be included in the candidate target cell configuration information.

The base station may perform a step of receiving an L1 measurement result for the candidate target cell from the terminal (S920).

For example, the terminal may measure the channel state of the serving cell or the candidate target cell using information for measuring or transmitting the measurement result included in the above-described candidate target cell configuration information. As an example, the terminal may measure L1-RSRP. As another example, the terminal may measure L1-RSRQ. In addition, the terminal may also measure the channel state of the serving cell or candidate target cell using various measurement techniques capable of measuring the channel quality or channel state.

Thereafter, the base station receives a measurement result report including the L1 measurement result transmitted by the terminal. For example, the terminal may transmit the measurement result to the base station based on information for transmitting the measurement result included in the candidate target cell configuration information. As an example, the terminal may transmit the measurement result of the corresponding serving cell or candidate target cell to the base station when the transmission of the measurement result satisfies the trigger condition. As another example, the transmission of the L1 measurement is triggered when the measurement quality of the candidate target cell is higher than the measurement of the source PSCell minus the offset value. That is, when comparing the measurement result of the source PSCell and the measurement result of the candidate target cell, the comparison is performed by adding or subtracting a preset offset or an offset included in the candidate target cell configuration information from the measurement result of the source PSCell. Reporting of the measurement results may be triggered when the comparison results show that the channel state of the candidate target cell is better.

The base station may perform a step of transmitting a MAC CE (Medium Access Control Control Element) to the terminal (S930), the MAC CE indicating to perform an LTM operation to the target cell based on the L1 measurement result.

For example, the base station may determine whether to perform an LTM operation based on L1 measurement result information of the terminal. As another example, the base station may determine the target cell to be changed through the LTM operation based on the L1 measurement result information of the terminal. As described above, the base station may determine the execution of the LTM operation for the terminal and the target cell to be changed by the terminal based on the L1 measurement result received from the terminal.

Thereafter, when the base station determines a cell change of the terminal based on the L1 measurement result information received from the terminal, an instruction may be made through the MAC CE.

As an example, the base station may include indication information for indicating the execution of the LTM operation in the MAC CE and transmit. As another example, the base station may include information of the target cell in the MAC CE and transmit.

The terminal may obtain an execution instruction of the LTM operation and information of a target cell to perform a cell change through the MAC CE. As one example, the MAC CE may include at least one of identification information for candidate target cell configuration information, TCI state ID, bandwidth part identification information, and timing advance command. For example, the MAC CE may include identification information for distinguishing configuration information for candidate target cells configured in the terminal through an upper layer message. The identification information may consist of candidate target cell configuration information ID or index information. Further, the MAC CE may include at least one of a TCI status ID, a bandwidth part ID, and a TAG.

For example, the terminal, after receiving the MAC CE, may confirm a target cell on which to perform cell change based on the MAC CE. As an example, the terminal confirms the identification information for the candidate target cell configuration information included in the MAC CE, and confirms the candidate target cell configuration information allocated as the identification information and received through the upper layer message. The candidate target cell to which the candidate target cell configuration information is applied may be a target cell to be a cell change object. That is, the identification information allocated to the one or more candidate target cell configuration information received through the upper layer message and the identification information allocated to the candidate target cell configuration information received through the MAC CE may be the same. Thus, the terminal can confirm the target cell through the MAC CE.

After confirming the target cell, the terminal applies the candidate target cell configuration information applied to the target cell to the terminal. In addition, the terminal uses the candidate target cell configuration information of the target cell to perform a cell change operation to the target cell without performing an RRC reconfiguration operation.

On the other hand, the terminal may distinguish and perform a cell change operation according to whether the target cell and the source cell indicated by the MAC CE are included in the same cell group.

Radio bearer for L1/L2 based cell change

When cell change/handover is triggered/started/executed/applied based on L1/L2 signaling/execution indication information/TCI status/execution condition/event/related procedure/operation (operation), or when an execution condition/event configured in a terminal is evaluated and an execution condition is satisfied, or when a specific procedure/operation (e.g., measurement, event detection, condition satisfaction, TCI status update application, etc.) is executed in the terminal according to L1/L2 signaling reception and corresponding configuration, a part or all of the configuration (or candidate/target cell configuration stored/previously configured in the terminal) included in the corresponding RRC reconfiguration message may be applied.

When cell change/handover is triggered/started/executed/applied based on L1/L2 signaling/execution indication information/TCI status/execution condition/event/related procedure/operation (operation), or when an execution condition/event configured in a terminal is evaluated and an execution condition is satisfied, or when a specific procedure/operation (e.g., measurement, event detection, condition satisfaction, TCI status update application, etc.) is executed in the terminal according to L1/L2 signaling reception and corresponding configuration, data can be transceived through a radio bearer for a corresponding LTM operation. As an example, the terminal may switch uplink/downlink data from the source cell to the candidate/target cell for transmission/reception. As another example, uplink/downlink data may be handed over from an L2 entity associated with the source cell to an L2 entity associated with the candidate/target cell for transmission/reception.

When the base station indicates LTM configuration to the terminal through RRC signaling, radio bearers for LTM operation may be applied/configured/stored at the terminal. Or the radio bearer for LTM operation (according to the stored configuration) may be applied/configured to the terminal when the corresponding L1/L2 signaling is received.

As an example, the radio bearer for LTM operation may use the same radio bearer structure as a general Data Radio Bearer (DRB) or a Signaling Radio Bearer (SRB) associated with one PDCP entity, one RLC entity, and one MAC entity. As another example, the radio bearers for LTM operations may be configured by adding a highly functional in L1/L2 entities included/associated in the normal data radio bearer/signaling radio bearer structure. For example, for a radio bearer used by a terminal in a source cell and L1/L2 entities (one PDCP entity, one RLC entity, one MAC entity) associated with the radio bearer, more than one parameter (or the entire parameter) may be reconfigured/set/maintained for use in the target cell with the same configured and/or sustained/maintained PDCP/RLC/MAC state variables (state variables)/buffer/timer/parameter values. For example, for the corresponding radio bearer, 0 is not set as an initial value for the corresponding state variables (e.g., tx_next, rx_next, rx_deliv, rx_ REOR), but a value stored in the corresponding PDCP entity in the source cell may be used as an initial value. For ease of illustration, only PDCP state variables are described, but this is for ease of illustration only, and it is apparent that any RLC state variable, any MAC parameter, is also included within the scope of the present disclosure.

As another example, to enable fast handover, the radio bearers for LTM operations may include one or more of the radio bearers (e.g., DRBs, SRBs) described below. For ease of illustration, any radio bearer used during LTM operation included in this disclosure is labeled LTM radio bearer. This is for convenience of explanation, and may represent any radio bearer configured in the terminal when performing the LTM operation. The radio bearer may be provided by one type/L2 structure, or more than one type/L2 structure may be defined and provided according to the corresponding scenario.

Referring to fig. 10, the ltm radio bearer may have a split structure in which one PDCP entity has two RLC entities (AM/UM), one PDCP entity being associated with two RLC entities. Each RLC entity may be associated with one MAC entity. For example, within an intra-CU/gNB (intra-CU/gNB-CU), within an intra-DU/gNB-DU connected to the CU, L1/L2 based cell change may be performed between cells associated with the DU.

Referring to fig. 11, within one cell group (e.g., MCG), one PDCP entity has a split structure of two RLC entities (AM/UM), one PDCP entity being associated with two RLC entities, LTM radio bearers may be configured at a terminal. Each RLC entity may be associated with a single MAC entity.

Referring to fig. 12, the ltm radio bearer may have a split structure in which one PDCP entity has two RLC entities (AM/UM), one PDCP entity being associated with two RLC entities. Each RLC entity may be associated with each MAC entity. For example, within an intra-CU, for different DUs connected to the CU, intra-CU intra-DU L1/L2 based cell changes may be performed between cells associated with each DU.

Referring to fig. 13, within one cell group (e.g., MCG), one PDCP entity has a split structure of two RLC entities (AM/UM), one PDCP entity being associated with two RLC entities, LTM radio bearers may be configured at a terminal. Each RLC entity may be associated with each MAC entity, where each MAC entity is associated with each cell group (e.g., MCG, SCG).

The LTM operation configuration by RRC signaling may include more than one candidate/target cell configuration. If more than one candidate cell is provided, additional L2 entities for supporting the candidate cells may be configured in association.

As an example, when two candidate cells are provided in the structure of fig. 10 and/or 11, RLC entities associated with one PDCP entity may be three. The remaining RLC entities may be released if the handover of a particular candidate/target cell is successfully completed. Or may maintain the remaining RLC entities if handover of a particular candidate/target cell is successfully completed. Thus, L1/L2 based cell change may be triggered/initiated/applied/performed before the release of the corresponding candidate cell is indicated later by RRC signaling. As another example, when two candidate cells are provided in the structure of fig. 12 and/or 13, RLC entities associated with one PDCP entity may be three. Each RLC entity may be associated with each MAC entity. If the handover of a particular candidate/target cell is successfully completed, the remaining RLC entities and MAC entities may be released. Or may maintain the remaining RLC entities and MAC entities if handover of a particular candidate/target cell is successfully completed. Thus, L1/L2 based cell change may be triggered/initiated/applied/performed before the release of the corresponding candidate cell is indicated later by RRC signaling.

As another example, when two candidate cells are provided in the structures of fig. 10 to 13, the active RLC entities (for LTM operation) associated with one PDCP entity may be limited to two. The number of PCIs associated with the active TCI state that are different from the serving cell may be limited to one. The RLC entity (or RLC entity/MAC entity) associated therewith may be limited to two. When the corresponding L1/L2 signaling is received, the corresponding L2 entity may be activated/configured/applied/used/set/added.

As another example, an RLC entity (or RLC entity/MAC entity) associated with a cell having a PCI different from the serving cell may be configured in a deactivated state, wherein the cell having a PCI different from the serving cell is associated with a deactivated TCI state. When the corresponding L1/L2 signaling is received, the corresponding L2 entity may be activated/configured/applied/used/set/added.

As described above, the LTM operation configuration indicated through the RRC signaling may include information of more than one of LTM candidate/target cell configuration, LTM radio bearer configuration, L1/L2 signaling configuration for LTM operation, execution indication information configuration for LTM operation, TCI status configuration for LTM operation, and execution condition/event configuration for LTM operation.

The above information may represent information of L1/L2 signaling configuration for LTM operation, execution indication information configuration for LTM operation, TCI status configuration for LTM operation, execution condition/event configuration for LTM operation, and trigger/start/execute/apply LTM operation. The configuration may include information for associating the configuration with an LTM candidate/target cell configuration and/or an LTM radio bearer configuration. One LTM candidate/target cell configuration may be configured as a one-to-one mapping with a corresponding configuration. Or one LTM candidate/target cell configuration may be configured to map one-to-many with more than one corresponding configuration.

Before cell change/handover based on L1/L2 signaling/execution indication information/TCI status/execution condition/event/related procedure/operation (operation) is triggered/started/executed/applied, if the terminal receives a handover command (RRC reconfiguration with sync) that does not contain LTM operation configuration (or is not for LTM operation but for general handover), the terminal may perform a handover procedure according to the received handover configuration (according to the standard specification described in section TS 38.331) without being affected by any LTM operation configuration received previously. When the terminal receives the corresponding command, when the terminal successfully completes the random access procedure to the corresponding cell, when the terminal successfully completes the handover, when the terminal sends an RRC reconfiguration complete message to the target cell, the terminal may release/remove the stored LTM operation configuration/terminal variables.

Before cell change/handover based on L1/L2 signaling/execution indication information/TCI status/execution condition/event/related procedure/operation (operation) is triggered/started/executed/applied, if the terminal receives an RRC reconfiguration message containing LTM operation configuration, a part or all of the configurations included in the corresponding configuration may be replaced/modified/changed/reconfigured/stored/applied. For example, by the information for identifying the corresponding LTM operation configuration (or detailed configuration included in the corresponding configuration), more than one of the LTM candidate/target cell configuration, LTM radio bearer configuration, L1/L2 signaling configuration for LTM operation, execution indication information configuration for LTM operation, TCI status configuration for LTM operation, execution condition/event configuration for LTM operation may be changed/modified.

When a handover command (RRC reconfiguration with sync) is received before a cell change/handover based on L1/L2 signaling/execution indication information/TCI status/execution condition/event/related procedure/operation (operation) is triggered/started/executed/applied, the handover command (or the RRC reconfiguration message) may contain an LTM configuration for LTM operation in the corresponding target cell. The terminal may perform the handover procedure according to the received handover configuration (according to the standard specification set forth in section TS 38.331). The terminal may release/remove LTM configuration/terminal variables configured/stored in the source cell. The terminal may store/apply LTM operation configuration using a target cell performing handover as a source cell/first TRP/cell/serving cell associated with the first TRP and using any cell having a PCI different from that of the cell as a target cell/candidate cell/second TRP/cell associated with the second TRP/non-serving cell. The storing/applying of LTM operation configuration in cell change and in changed cell can be performed through one RRC signaling message.

User plane processing based on L1/L2 cell change (e.g., spCell change, handover) procedures

As described above, when the L1/L2-based LTM operation is performed within an Intra CU (Intra DU), data can be transceived in a target cell by using/maintaining/reconfiguring a source cell configuration (or a part of the configuration). As an example, the terminal may continue to receive downlink user data in the source cell until a certain point in time according to the LTM radio bearer type. The point in time may be an L1/L2 signaling reception/event detection/program start/operation application for LTM operation (e.g., TCI state application time, base station indication/configured time/offset, LTM operation start decision, LTM operation application condition met, cell change trigger/start/execution/application), LTM operation indication information received from the lower layer, first uplink grant indication occasion to the target cell, downlink synchronization (or after synchronization) to the target cell, PDCCH/uplink grant received from the target cell, random access procedure (or MSG1/MSGA transmission) initiated to the target cell, successful completion of random access procedure to the target cell, RRC reconfiguration complete message transmitted to the target cell, acknowledgement/response information received from the target cell for RRC reconfiguration complete message, indication information received from the base station for releasing the source cell configuration, (via a signaling message/MAC-CE/MAC) radio bearer release entity/deactivation entity associated with the source cell and/or source cell, radio bearer entity/application entity associated with the source cell and any of the current specification and any of the release of the application, and any of the specifications of the release of the radio bearers and the application in order of the random access application, and any of the specifications.

As another example, the terminal may continue to transmit uplink user data to the source cell before a certain point in time. The point in time may be an L1/L2 signaling reception/event detection/program start/operation application for LTM operation (e.g., TCI state application time, base station indication/configured time/offset, LTM operation start decision, LTM operation application condition met, cell change trigger/start/execution/application), LTM operation indication information received from the lower layer, first uplink grant indication occasion to the target cell, downlink synchronization (or after synchronization) to the target cell, PDCCH/uplink grant received from the target cell, random access procedure (or MSG1/MSGA transmission) initiated to the target cell, successful completion of random access procedure to the target cell, RRC reconfiguration complete message transmitted to the target cell, acknowledgement/response information received from the target cell for RRC reconfiguration complete message, indication information received from the base station for releasing the source cell configuration, (via a signaling message/MAC-CE/MAC) radio bearer release entity/deactivation entity associated with the source cell and/or source cell, radio bearer entity/application entity associated with the source cell and any of the current specification and any of the release of the application, and any of the specifications of the release of the radio bearers and the application in order of the random access application, and any of the specifications.

As another example, the terminal may detach (detach) from the source cell at a specific point in time. The time point may be one or more of the time points described above.

As another example, the terminal may configure the target cell as a PCell at a specific point in time. The terminal may update the security key in the cell. The time point may be one or more of the time points described above. Or the target cell may be configured as a PCell when the terminal is detached from the source cell.

As another example, the terminal may request handover/restoration of uplink data/paths to the PDCP entity for radio bearers configured by the LTM radio bearer. The time point may be one or more of the time points described above.

As another example, for a fast and simple LTM operation, a terminal may perform the LTM operation using only a source PCell and a target PCell during the LTM operation. Or during the LTM operation, the terminal may perform LTM cell change using only the source SCell and the target SCell. Or during the LTM operation, the terminal may perform the LTM operation using only cells that can be composed of one cell group (e.g., MCG). As an example, when indicating an RRC configuration for LTM operation, the base station may instruct the terminal to release more than one of CA, DC, SUL, CHO, DAPS, NR SIDELINK, and V2X sidelink configurations. The terminal may avoid applying the corresponding configuration before the corresponding handover is completed. As another example, when L1/L2 signaling is received for LTM operations, one or more of the configurations CA, DC, SUL, CHO, DAPS, NR SIDELINK, and V2X sidelink may be released/suspended (suspend). As another example, the configuration of one or more of CA, DC, SUL, CHO, DAPS, NR SIDELINK, and V2X sidelink may be released/suspended when cell change is triggered/initiated/executed or applied based on L1/L2 signaling/execution indication information/TCI status/execution conditions/events/related procedures/operations for LTM operation.

Depending on the LTM radio bearer type, the terminal may perform one or more of the following operations when the terminal receives an LTM operation configuration through RRC, or when the terminal triggers/initiates/performs a cell change based on L1/L2 signaling/execution indication information/TCI state/execution condition/event/related procedure/operation.

The terminal may not detach (detach) from the source cell. The terminal may release the source resources when explicit release is received from the base station/target cell/source cell.

The terminal may stop/suspend downlink/uplink reception/transmission by the source cell.

The terminal may maintain the SRB through the source cell. The terminal may receive the RRC message through the corresponding signaling radio bearer before triggering/starting/performing the LTM operation based on L1/L2 signaling/event/procedure/operation (operation) and/or before receiving explicit release from the base station/target cell/source cell. As another example, the terminal may reconfigure/set an L2 structure/radio bearer type SRB (L2 entity for the corresponding SRB) as shown in fig. 10 to 13. The terminal may receive the RRC message through the corresponding signaling radio bearer before triggering/starting/executing/applying the LTM operation based on the L1/L2 signaling/event/procedure/operation (operation) and/or before receiving the explicit release from the base station/target cell/source cell.

As another example, the terminal may suspend SRB by the source cell. The terminal may stop transmitting/receiving RRC messages through the source cell. The terminal may set SRB for the target cell. For LTM operation, the terminal may set the RLC entity for the target cell group by the same configuration as the RLC entity for the source cell group. The terminal may release the source cell SRB when the terminal receives a source cell release indication from the target cell after successfully performing the LTM operation. When a cell change to the target cell according to the LTM operation fails, the terminal may return to the source cell configuration if a source cell link is available (UEreverts back to the source cell configuration). The terminal may recover the source cell SRB.

As another example, the terminal may suspend SRB by the source cell when triggering/starting/executing/applying LTM operation based on L1/L2 signaling/event/procedure/operation (operation). The terminal may stop transmitting/receiving RRC messages through the source cell. The terminal may set SRB for the target cell. For LTM operation, the terminal may set the RLC entity for the target cell group by the same configuration as the RLC entity for the source cell group. The terminal may set the logical channels for the target cell group through the same configuration as the logical channels for the source cell group. The terminal may transmit/receive an RRC message through the target cell. The terminal may release the source cell SRB when the terminal receives a source cell release indication from the target cell after successfully performing the LTM operation. When the LTM operation to the target cell fails, the terminal may return to the source cell configuration if a source cell link is available (UEreverts back to the source cell configuration). The terminal may recover the source cell SRB.

As another example, the terminal may suspend SRB through the source cell at the corresponding point in time described above. The terminal may stop transmitting/receiving RRC messages through the source cell. The terminal may set SRB for the target cell. For LTM operation, the terminal may set the RLC entity for the target cell group by the same configuration as the RLC entity for the source cell group. The terminal may set the logical channels for the target cell group through the same configuration as the logical channels for the source cell group. The terminal may transmit/receive an RRC message through the target cell. The terminal may release the source cell SRB when the terminal receives a source cell release indication from the target cell after successfully performing the LTM operation. When the LTM operation to the target cell fails, the terminal may return to the source cell configuration if a source cell link is available (UEreverts back to the source cell configuration). The terminal may recover the source cell SRB.

The terminal may generate/set a MAC entity for the target. For example, in the L2 structure/radio bearer type as shown in fig. 12 and 13, the terminal may generate/set a MAC entity for the target cell. The terminal may generate the MAC entity for the target cell group through the same configuration as the MAC entity for the source cell group. For each radio bearer (e.g., DRB, SRB) configured by the structure/type, the terminal may set a DTCH/DCCH logical channel associated with the RLC entity for the target cell. The terminal may set the RLC entity for the target cell group by the same configuration as the RLC entity for the source cell group. The terminal may set the logical channels for the target cell group through the same configuration as the logical channels for the source cell group. As another example, in the L2 structure/radio bearer type as shown in fig. 10 and 11, the terminal may maintain/reconfigure the MAC entity. For each radio bearer (e.g., DRB, SRB) configured by the structure/type, the terminal may set a DTCH/DCCH logical channel associated with the RLC entity for the target cell. In the MAC entity, the logical channel of the target cell of the radio bearer may be configured by a logical channel identifier that is different from the logical channel of the source cell. The logical channel identifier may have a general LCID value of 6 bits. Or the Logical channel identifier may have a eLCID (extended Logical CHANNEL ID) value of 8 bits/16 bits. In the MAC entity, logical channel mapping restrictions (logical CHANNEL MAPPING reservations) may be used to enable the logical channels of the radio bearer to distinguish between source and target cells for transmission. The configuration for the source cell group may be set by the same configuration as that for the target cell group except for LCID.

The remaining configuration of the source cell (e.g., more than one of PDCP entity configuration included in the radio bearer configuration of the corresponding radio bearer, special cell configuration (spCellConfig) included in the source cell group configuration, RCL bearer configuration (rl-BearerToAddModList), MAC cell group configuration (MAC-CellGroupConfig)) may be maintained (keep/retain) until the source cell is released.

The terminal may reset the source MAC when it receives indication information for releasing the source cell configuration (through RRC signaling message/MAC-CE/DCI) from the base station (or target cell). The terminal may release the source MAC configuration. The terminal may release the RLC entity and associated logical channels for the source cell for the LTM radio bearer. The terminal may release the PDCP entity, RLC entity, and associated logical channels for the source cell for the signaling radio bearer. The terminal may release the physical channel configuration for the source cell.

For the PDCP entity, the corresponding base station (CU) can continue downlink PDCP SNs allocation without requiring data forwarding between the base stations. In addition, since the base station does not need a security key refresh, a cell change can be performed without the security key refresh. But depending on the radio bearer structure of the application, the PDCP entity pit may need to additionally perform one or more actions of data/path handover/restoration, duplicate transmission, PDCP reset, PDCP data restoration, PDCP status report transmission, and data amount calculation on user data (uplink in case of terminal) during cell change. To indicate this, the PDCP entity may be reconfigured.

For convenience of explanation, during the LTM operation, the operation of the terminal for determining/changing/switching the path/route of uplink data is marked as switching/restoration of uplink data/path. This is for ease of description only and may be replaced by any other name. For a radio bearer configured by the LTM radio bearer, if handover/restoration of uplink data/path is requested to the PDCP entity, the transmitting PDCP entity may operate as follows.

As an example, for an AM radio bearer, a transmitting PDCP entity performs retransmission/transmission to an RLC entity associated with a target cell from a first PDCP SDU for which successful delivery of the PDCP data PDU was not acknowledged by an RLC entity associated with a source cell, all PDCP SDUs already associated with PDCP SNs, in ascending order of COUNT value associated with the PDCP SDU (for AM DRBs,from the first PDCP SDU for which the successful delivery of the corresponding PDCP Data PDU has not been confirmed by the RLC entity associated with the source cell,perform retransmission or transmission of all the PDCP SDUs already associated with PDCP SNs in ascending order of the COUNT values associated to the PDCP SDU to the RLC entity associated with the target cell).

As another example, for UM radio bearers, the transmitting PDCP entity performs transmission to RLC entities associated with the target cell in ascending order of COUNT value for all PDCP SDUs that have been processed by PDCP but have not yet been submitted to the lower layer (for UM DRBs,for all PDCP SDUs which have been processed by PDCP but which have not yet been submitted to lower layers,perform transmission of the PDCP SDUs in ascending order of the COUNT values to the RLC entity associated with the target cell).

As another example, for an AM radio bearer, the transmitting PDCP entity performs retransmission/transmission to the RLC entity associated with the target cell in ascending order of the photo-associated COUNT value for all PDCP data PDUs for which successful delivery of the PDCP data PDU was not acknowledged by the RLC entity associated with the source cell.

As another example, for an AM radio bearer, the transmitting PDCP entity performs retransmission/transmission in ascending order of the associated COUNT value for all PDCP data PDUs for which successful delivery (stopped/suspended/reset/released in the source cell according to LTM operation) is not acknowledged by the RLC entity.

As another example, for an AM radio bearer, a transmitting PDCP entity performs retransmission/transmission to a RLC entity of all PDCP SDUs that have been associated with the PDCP SDUs in ascending order of COUNT value associated with the PDCP SDUs from a first PDCP data PDU for which successful delivery (according to LTM operation) of the PDCP data PDU has not been acknowledged by a lower layer (e.g., RLC entity).

As another example, for an AM/UM radio bearer configured to transmit a PDCP status report in the uplink, if an upper layer requests handover/restoration of an uplink data/path, a receiving PDCP entity may trigger the PDCP status report.

As another example, for an AM/UM radio bearer configured to transmit a PDCP status report in the uplink, if an upper layer reconfigures PDCP in such a way as to release the LTM radio bearer, the receiving PDCP entity may trigger the PDCP status report.

As another example, for an AM/UM radio bearer configured to send PDCP status reports in the uplink, the receiving PDCP entity may trigger PDCP status reports if it receives (via RRC signaling message/MAC-CE/DCI) indication information for releasing the source cell configuration, radio bearer/L2 entity release/deactivation indication information associated with the source cell and/or source cell from the base station, radio bearer/L2 entity release/deactivation application associated with the source cell and/or source cell, the PDCP entity receives the corresponding indication/request information.

As another example, the terminal may configure/reconfigure the PDCP entity according to received PDCP configuration information (PDCP-config). The PDCP entity of the terminal configured with the LTM operation may continue to maintain the corresponding PDCP functions (e.g., security, ROHC header compression/decompression (decompression), reordering, duplicate detection, and sequentially discarding PDCP SDUs (PDCP SDUs in-sequence delivery to upper layers) PDCP SN continuity, PDCP state variables (e.g., tx_next, rx_next, rx_deliv, rx_ REOR)) delivered to the upper layer before the LTM operation is successfully completed or during the execution of the LTM operation.

As another example, when a normal radio bearer is configured in the terminal, the terminal may perform MAC reset, RLC reset, PDCP reset/data recovery. During LTM operation triggering/starting/executing/applying based on L1/L2 signaling/event/procedure/operation (operation), the terminal can suspend/stop data transmission/reception of the corresponding radio bearer in the source cell. When data transmission/reception through the target cell is available, the terminal may start/perform/resume data transmission/reception through the corresponding radio bearer for the target cell.

Embodiments of L1/L2-based cell change procedures, L1/L2 signaling, and the like according to the present disclosure are further described below.

L1/L2-based cell change procedure

The process for providing LTM (L1/L2-TRIGGERED MOBILITY) operations may include the steps of: for the candidate cell, the base station indicates configuration for LTM operation to the terminal through RRC signaling; terminal stores/applies configuration for LTM operation; cell change based on L1/L2 signaling is performed/applied. This will be described below.

The configuration for LTM operation indicated through RRC signaling may include information of more than one of LTM candidate/target cell configuration, LTM radio bearer configuration, L1/L2 signaling configuration for LTM operation, execution indication information configuration for LTM operation, TCI status configuration for LTM operation, execution condition/event configuration for LTM operation.

The terminal, upon receiving a configuration for LTM operation, may store some or all of the configuration included in the configuration. When the terminal receives a configuration for LTM operation, some or all of the configurations included in the configuration may be applied. For example, a terminal may define a terminal variable (UE variable) for storing the configuration, and may store part/all of the configuration for LTM operation in the terminal variable.

The terminal may transmit an RRC reconfiguration complete (RRC Reconfiguration Complet) message to the base station (through the source cell). The terminal may maintain the source cell connection after receiving the configuration for LTM operation. The terminal may monitor/evaluate L1/L2 signaling/execution indication information/TCI status/execution conditions/events for LTM operation for configured/stored candidate/target cells. Or the terminal may start monitoring/evaluating L1/L2 signaling/execution indication information/TCI status/execution conditions/events.

The LTM operation may trigger/start/execute/apply the terminal configured/stored in advance through the RRC based on the L1/L2 signaling/execution indication information/TCI status/execution condition/event/related procedure/operation (operation). The L1/L2 signaling/execution indication information/TCI state of the terminal may be indicated by the base station, the execution condition/event configured by the base station to the terminal, and one or more triggers/starts/executions/applications defined in the terminal. For example, the terminal may store/apply the configuration for execution/application in the selected/indicated/triggered candidate/target cell.

As an example, when the corresponding L1/L2 signaling is received, a part or all of the candidate/target cell configuration (or candidate/target cell configuration stored/previously configured in the terminal) included in the corresponding RRC reconfiguration message may be applied/executed. Upon receiving the corresponding L1/L2 signaling, the terminal may apply/perform the stored corresponding configuration to the selected candidate/target cell.

As another example, the candidate/target cell configuration may include more than one of a cell group configuration (CellGroupConfig), a special cell configuration (SpCellConfig), information for identifying the cell (e.g., PCI index, serving cell index, arbitrary cell identifier, ID, configuration identification information, TCI status ID associated with the cell), handover information (reconfigurationWithSync), candidate/target cell terminal identifier (newUE-Identity/C-RNTI), a timer for limiting/controlling LTM time (e.g., t304 or new timer), and SMTC(SSB-based measurement timing configuration,the SSB periodicity/offset/duration configuration of target cell) for synchronization/measurement of candidate/target cells.

As another example, when the corresponding L1/L2 signaling is received, data may be transceived through a radio bearer for the corresponding LTM operation.

As another example, the LTM operation may be triggered/started/executed when the execution condition is satisfied by evaluating the execution condition of the base station configuration in the terminal. And/or when receiving the corresponding L1/L2 signaling, may trigger/initiate/execute if the corresponding execution condition is satisfied. For example, the corresponding execution conditions may include: at least one of reaching a threshold based on L1 measurements, detecting an event based on L1 measurements (e.g., L1-RSRP), meeting an L1 report/CSI report trigger condition, detecting an event based on L3 measurements, presence of a valid candidate/target cell configuration (or stored configuration/pre-configuration), presence of an active TCI state (candidate/target cell), and configuration of a corresponding set of resources. The respective execution conditions/events may be configured to be associated with one or more of (L3) measurement identifiers, L1 measurement identifiers (e.g., measID), L1 report identifiers (e.g., L1/CSI-ReportConfigId), L1 event identifiers (e.g., eventID), and L3 event identifiers. The corresponding execution conditions/events may be configured as more than one of the following events: when the measurement associated with the source cell/source RS/target cell/target RS has a better value than the threshold; when the measurement associated with the source cell/source RS/target cell/target RS has a worse value than the threshold; when the measurement associated with the target cell/target RS is better than the measurement associated with the source cell/source RS; when the measurement associated with the target cell/target RS is better than the measurement associated with the source cell/source RS by adding or subtracting the offset value; and when the measurement associated with the source cell/source RS has a worse value than the threshold and the measurement associated with the target cell/target RS has a better value than the threshold.

L1/L2 signaling/procedure for L1/L2 based cell change

When a terminal is located in an overlapping coverage area of a source cell/first TRP/a cell/serving cell associated with the first TRP and a target cell/candidate cell/second TRP/a cell/non-serving cell associated with the second TRP, the terminal may be in a state where uplink/downlink data transmission can be sufficiently performed not only through the source cell/first TRP/the cell/serving cell associated with the first TRP but also through the target cell/candidate cell/second TRP/the cell/non-serving cell associated with the second TRP. L1/L2 signaling/events/procedures/operations (operations) for indicating/triggering/starting/executing/applying/supporting LTM operations may be defined. Or to indicate/trigger/initiate/execute/apply/support LTM operations, existing L1/L2 signaling (or L1/L2 signaling that improves existing L1/L2 signaling) may be associated to the LTM configuration for use. When the terminal receives the corresponding signaling (or according to the relevant configuration, a specific procedure/operation (e.g., measurement, event detection, condition satisfaction, TCI status update application, etc.) in the terminal triggers/starts/executes/applies), the terminal may indicate the corresponding information to the upper layer (e.g., MAC/RLC/RRC). The terminal may indicate to the upper layer more than one information contained/associated in the corresponding signaling/event/procedure/operation. The terminal may trigger/start/execute/apply LTM operations at an upper layer. The terminal may trigger/initiate/execute/apply cell change according to the stored/pre-configured configuration. The terminal may switch uplink/downlink data from the source cell to the candidate/target cell for transmission/reception according to the stored/pre-configured configuration.

To enable association between L1/L2 signaling for indicating/supporting LTM operation and an RRC message including LTM configuration, one or more information of RRC information elements included in the RRC message may be included in the L1/L2 signaling for indication. For example, the base station may indicate that more than one information element included in the LTM configuration is included in the L1/L2 signaling. Or L1/L2 signaling/event/procedure/operation (operation) and one or more information of RRC information elements included in the RRC message for LTM operation are configured by default association so that the terminal can recognize it. For example, by including information for associating between the configurations in each detailed configuration (LTM candidate/target cell configuration, LTM radio bearer configuration, L1/L2 signaling configuration for LTM operation, execution instruction information configuration for LTM operation, execution CI status configuration for LTM operation, execution condition/event configuration for LTM operation) included in the LTM configuration, LTM operation can be associated by the L1/L2 signaling/event/procedure/operation (operation).

As one example, any detailed configuration included in the LTM configuration (e.g., LTM candidate/target cell configuration, LTM radio bearer configuration, L1/L2 signaling configuration for LTM operation, execution indication information configuration for LTM operation, execution TCI status configuration for LTM operation, execution condition/event configuration for LTM operation) may include a TCI status ID for triggering/starting/applying/executing. When a terminal configured with this function receives the TCI state ID through L1/L2 signaling (e.g., MAC-CE/DCI), an LTM operation is triggered/started/applied/performed.

As another example, PCI (physical cell identity)/PCI index/serving cell index/arbitrary cell identifier/ID/configuration identification information/TCI status ID contained in the received LTM configuration (e.g., candidate/target cell configuration information) may be contained in association with L1/L2 signaling/event/operation.

As another example, the LTM operation previously configured/existing in the terminal may be triggered/started/applied/executed by including PCI (physical cell identity)/PCI index/arbitrary cell identifier/ID/configuration identification information/TCI state ID included in the LTM candidate/target cell configuration in one or more of L1/L2 signaling configuration for the LTM operation, execution instruction information configuration for the LTM operation, execution TCI state configuration for the LTM operation, execution condition/event configuration for the LTM operation, upon receiving/detecting the corresponding signaling/execution instruction information/TCI state/execution condition/event.

As another example, more than one of the following events/procedures/operations may be used alone or in any combination through the corresponding L1/L2 signaling/events/procedures/operations: activation/update/indication by MAC CE and/or DCI status; TCI state activation/update/indication of a reference signal (or associated with) of a source cell/first TRP/cell associated with the first TRP configured for a target cell/candidate cell/second TRP/cell associated with the second TRP is used; TCI state activation/update/indication of a reference signal (or associated with the reference signal) of a target cell/candidate cell/second TRP/cell associated with the second TRP configured for the source cell/first PTR/cell associated with the first TRP is used; TCI state activation/update/indication of a reference signal (or associated with) of a target cell/candidate cell/second TRP/cell associated with the second TRP configured for LTM operation is used; an L1 measurement result associated with the reference signal; event/execution condition detection based on L1 measurement; L1/CSI reporting; meets the L1/CSI reporting criteria/threshold; in timer operation for limiting/controlling LTM operation time (e.g., before expiration of the timer); l3 measurements (from/received from upper layers); and event/execution conditions based on L3 measurement are satisfied.

For example, when the corresponding L1/L2 signaling is received, a cell change may be triggered/initiated/performed when all corresponding events/execution conditions/references/thresholds previously defined/configured/stored in the terminal are met/detected. For another example, a cell change may be triggered/initiated/performed when an active TCI state indicated by a MAC CE and/or DCI is associated with one target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP. For another example, a cell change may be triggered/initiated/performed when all active TCI states indicated by the MAC CE and/or DCI are associated with one target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP.

To activate/update/indicate TCI status based on source/serving cell reference signals (and/or activate/update/indicate TCI status based on target/candidate cell reference signals) (for cells with different PCIs), the base station may configure the TCI status of the cell (S)/CC (S) in the terminal (for LTM operations associated with the Intra CU). For example, the corresponding cell/CC may be configured as a second cell in the serving cell configuration and distinguished by the serving cell index. Or the corresponding cell/CC may be differentiated by defining/allocating a cell index/identifier/ID/TCI status ID for distinguishing it in the serving cell configuration (configured as target cell/candidate cell/second TRP/cell associated with the second TRP/non-serving cell). Or the corresponding cell/CC may be configured as a serving cell in a target cell configuration (e.g., LTM configuration or LTM RRC message containing reconfiguration with sync) and distinguished by a serving cell index used to distinguish it. Or the corresponding cell/CC may be differentiated by defining/allocating a cell index/identifier/ID/TCI status ID for distinguishing it in the target cell configuration (e.g., LTM configuration or LTM RRC message containing reconfiguration with sync). Or the corresponding cell/CC is distinguished in the corresponding terminal by a PCI/PCI index for distinguishing the corresponding cell. Or the source/serving cell and the target/candidate cell for LTM operation in the corresponding terminal may be included in one cell group. Or the source/serving cell and the target/candidate cell for LTM operation in the respective terminals may be included in different cell groups. For example (Intra CU, inter DU scenario), the source/serving cell may be contained in the MCG and the target/candidate cell may be contained in the SCG.

To update the TCI state (at the time of LTM operation start/execution/application/completion) within a corresponding one of the target cells based on the reference signal (intra-cell) of the corresponding cell, the base station may configure the corresponding TCI state in the terminal. To update the TCI state (at the time of LTM operation start/execution/application/completion) in the neighbor cell/CC of the target cell (for LTM operation associated with Intra CU) based on the reference signal (Intra-cell) of the corresponding cell, the base station may configure the corresponding TCI state in the terminal. To update the TCI state (at LTM operation start/execution/application/completion) based on the reference signal (intra-cell) of the (previous) source cell, the base station may configure the corresponding TCI state in the terminal. The TCI state of the cell/non-serving cell associated with the target cell/candidate cell/second TRP may be configured in the terminal. The TCI state that the terminal needs to use in the corresponding cell (target cell/candidate cell/second TRP/cell associated with second TRP) where the LTM operation is completed and associated with the serving cell before handover (or a cell different from the corresponding cell, the source cell/first TRP/cell associated with first TRP before handover) may be configured at the time of (LTM operation start/execution/application/completion). The TCI state associated with the respective cell (target cell/candidate cell/second TRP/cell associated with the second TRP) in which the terminal completes the LTM operation may be configured at the time of (LTM operation start/execution/application/completion) the terminal.

The L1/CSI reporting configuration of the reference signal of the source cell/first TRP/cell/serving cell associated with the first TRP, the TCI status associated with the reference signal may be indicated to the terminal. The L1/CSI reporting configuration of the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP, the TCI status associated with the reference signal may be indicated to the terminal. The TCI may include PCI (physical cell identity)/PCI (Physical Cell Id)/PCI index/associated TRP identification information/TCI status ID.

The SSBs of the source cell/first TRP/cell/serving cell associated with the first TRP may be used as QCL sources of the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP. The CSI-RS resource of the source cell/first TRP/cell/serving cell associated with the first TRP may be allowed to serve as a QCL source for the attachment of one SSB and the corresponding CSI-RS may serve as a QCL source for the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP. The SSB of the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP may be used as a QCL source of the source cell/first TRP/cell/serving cell associated with the first TRP. The CSI-RS resource of the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP may be allowed to be used as a QCL source for the attachment of one SSB and the CSI-RS may be used as a QCL source for the source cell/first TRP/cell/serving cell associated with the first TRP. For a cell, the TCI state included in the corresponding configuration may be associated by QCL information/QCL source to a cell having a different PCI than the cell.

For measuring the target cell/candidate cell/second TRP/cell/non-serving cell (L1) associated with the second TRP, a reference resource set configuration (e.g., CSI-MeasConfig/CSI-SSB-resource set) and/or an associated trigger/report configuration (e.g., CSI-AperiodicTriggerState, CSI-AssociatedReportConfigInfo) for distinguishing the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP/PCI index/serving cell index/arbitrary cell identifier/ID/configuration identification information/TCI status ID/associated TRP identification information may be included in the serving cell configuration (ServingCellConfig). Thus, the L1-RSRP measurement/L1 reporting/CSI reporting for the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP may be instructed/configured to be performed. Or may indicate to the terminal a configuration for the target cell/candidate cell/second TRP/cell/non-serving cell associated with the second TRP, the reference resource set for the respective cell and the L1 measurement/report associated with the reference resource set for the respective cell. The configuration may include a PCI/PCI index/serving cell index/any cell identifier/ID/configuration identification information/TCI status ID/associated TRP identification information for distinguishing the respective cells in the respective reference resource set configuration (e.g., CSI-MeasConfig/CSI-SSB-resource set) and/or associated trigger/report configuration (e.g., CSI-AperiodicTriggerState, CSI-AssociatedReportConfigInfo).

To update the TCI state for indicating/triggering/initiating/associating/supporting LTM operation, a TCI state/state pool (TCI state pool) may be configured per cell or BWP through RRC. Or to update the TCI state for indicating/triggering/initiating/associating/supporting LTM operation, a TCI state/state pool (TCI state pool) may be configured per cell (per configuration information associated with the cell) by RRC. Or to update the TCI state for indicating/triggering/initiating/associating/supporting LTM operation, the TCI state/state pool (TCI state pool) may be configured by RRC per cell group (serving as common information shared in all cells s/CCs/BWPs within the cell group of the terminal, or one base/reference/TCI state/state pool of a different cell/CC/BWP within the cell group of the terminal). Or to update the TCI state for indicating/triggering/initiating/associating/supporting LTM operation, the TCI state/state pool (TCI state pool) may be configured to be used as common information shared among all cells s/CCs/BWPs within the terminal (or cells s/CCs/BWPs configured in a specific group at the terminal), or one base/reference/TCI state/state pool of different cells/CCs/BWP within the terminal.

Here, a cell group may represent a subset of serving cells consisting of PCell/PSCell and 0 or more second cells, such as MCG/SCG. Or a cell group may represent a PCell/PSCell, 0 or more than one second cell, a subset of cells consisting of 0 or more than one second cell. Or a cell group may represent a subset of cells consisting of the source cell and the target/candidate cell. Or a group of cells may represent a subset of cells associated with a first TRP, cells associated with a second TRP. Or a cell group may represent a subset of PCell/PSCell, 0 or more second cells, cells that may consist of 0 or more second cells, 0 or more cells associated with a serving cell/first TRP, one or more cells including 0 or more cells associated with a non-serving cell/second TRP. Or small +

A granule may represent a group of more than one cell indicated by a base station and configured at one terminal.

The TCI state may be configured by SEPARATE DL/UL TCI. One downlink TCI state and one uplink TCI state may be indicated by separate state IDs. A downlink TCI state may be indicated by a downlink TCI state ID. An uplink TCI state may be indicated by an uplink TCI state ID. A differentiated TCI status ID may be configured for the downlink and uplink, respectively. Or a downlink TCI status ID may be associated with a common/join TCI status ID. An uplink TCI status ID may be associated with a common/join TCI status ID. A downlink TCI state ID and an uplink TCI state ID pair may be associated with a common/join TCI state ID.

The TCI state may be configured by joint DL/UL TCI. A downlink TCI status configuration and an uplink TCI status configuration may be combined and indicated by a (public/join) TCI status ID. A downlink TCI state and an uplink TCI state pair may be combined and indicated/configured by a (public/join) TCI state ID. A downlink TCI state ID and an uplink TCI state ID pair may be individually associated with a common TCI state ID. Information for distinguishing whether the corresponding TCI status ID is DL or UL or join may be configured. Or MAC CE and/or DCI signaling for indicating/triggering/initiating/associating LTM operations may be limited to the case of including a join TCI status ID. SEPARATE DL/UL TCI can share a TCI status pool (pool) with joint DL/UL TCI. Each TCI state may be associated with PCI (Physical Cell Id)/PCI index/TRP (first TRP) of the corresponding serving cell or may be associated with a PCI/PCI index/TRP (second TRP) that is not the corresponding serving cell. The PCI index may represent an index/identifier for identifying the PCI within the terminal configured PCI set for LTM operation (or inter-cell beam management). The PCI index may consist of a bit value below PCI. For example, in RRC, PCI may have an integer value from 0 to 1007, for which 10 bits may be required. If the maximum number of cells configured in advance for LTM operation is 4 or 8, the cells may be indicated by a 2-bit or 3-bit PCI index.

The RRC configuration of a TCI state/state pool (TCI state pool) for updating the TCI state for indicating/triggering/starting/associating/supporting LTM operation may be indicated to the terminal by taking the source cell/first TRP/cell associated with the first TRP as PCell/SpCell. The configuration may include information for distinguishing the target cell/candidate cell/second TRP/cell associated with the second TRP. The terminal may trigger/initiate/execute/apply the LTM operation when the terminal is instructed to make a cell change to the target cell/candidate cell/second TRP/cell associated with the second TRP according to L1/L2 signaling/event/procedure/operation (operation) in the source cell/first TRP/cell associated with the first TRP.

Or regarding RRC configuration of a TCI state/state pool (TCI state pool) used for updating TCI state for indicating/triggering/starting/associating/supporting LTM operation, may be indicated to the terminal by regarding a target cell/candidate cell/second TRP/cell associated with the second TRP as PCell/SpCell. When the terminal is instructed to make a cell change to the target cell/candidate cell/second TRP/cell associated with the second TRP according to L1/L2 signaling/event/procedure/operation (operation) in the source cell/first TRP/cell associated with the first TRP, the LTM operation may be triggered/initiated/executed/applied.

The TCI state/state pool configuration of the source cell/first TRP/cell associated with the first TRP (configured by RRC) and the TCI state/state pool configuration of the target cell/candidate cell/second TRP/cell associated with the second TRP (or partial configuration) may have the same configuration/configuration parameter values and be indicated/applied/configured on the terminal. Or the TCI state/state pool configuration of the source cell/first TRP/cell associated with the first TRP may use/replace/reference the TCI state/state pool configuration indicated as target cell/candidate cell/second TRP/cell associated with the second TRP. For example, when there is no TCI state/state pool configuration of the target cell/candidate cell/second TRP/cell associated with the second TRP, the corresponding configuration may be replaced by the TCI state/state pool configuration of the target cell/candidate cell/second TRP/cell associated with the second TRP by taking the TCI state/state pool configuration of the source cell/first TRP/cell associated with the first TRP as a base/reference.

Or the TCI state/state pool configuration of the target cell/candidate cell/second TRP/cell associated with the second TRP may be indicated as the TCI state/state pool configuration of the source cell/first TRP/cell associated with the first TRP using/replacing/referencing. For example, when there is no TCI state/state pool configuration of the source cell/first TRP/cell associated with the first TRP, the corresponding configuration may be replaced by the TCI state/state pool configuration of the source cell/first TRP/cell associated with the first TRP by taking the TCI state/state pool configuration of the target cell/candidate cell/second TRP/cell associated with the second TRP as a reference.

Or the TCI state/state pool configuration of a particular serving cell may be indicated as a TCI state/state pool configuration of a cell having a different PCI than the corresponding cell, using/replacing/referencing. For example, when there is no TCI state/state pool configuration of one cell, the corresponding configuration may be replaced by the TCI state/state pool configuration of the cell having a different PCI from the corresponding cell by taking the TCI state/state pool configuration of the cell as a base/reference.

On the other hand, the L1-RSRP report/CSI report/L1 report may be transmitted to the base station. L1-RSRP may be calculated and reported in terms of PCI/PCI index/TRP. For example, the (relative) difference value of the PCI/PCI index/TRP specific reference (7 bit) L1-RSRP value may be used to reduce the number of bits (e.g., 4 bit). For another example, the corresponding report may include PCI/PCI index/serving cell index/any cell ID/configuration identification information/TCI status ID. Or L1-RSRP may be calculated and reported without distinguishing PCI/PCI index/TRP. For example, the (relative) difference value of the reference (7 bit) L1-RSRP value can be used to reduce the number of bits (e.g., 4 bit). More than one L1-RSRP measurement may be indicated to the base station by one L1-RSRP report.

The set of resources (e.g., CSI-SSB-resource) for L1-RSRP measurement/reporting may be configured in the terminal. The resource set may contain SSB indexes (a set of SSB indices) for a set. The SSB may be associated with the PCI/PCI index/TRP of the corresponding serving cell or with the PCI/PCI index/TRP of the non-corresponding serving cell.

To support LTM operations, CSI reporting/L1-RSRP reporting/L1 reporting/LTM triggering operations may be performed based on execution conditions/events/references/thresholds. The events for which are defined and may be configured in the terminal by the base station. The corresponding report may contain more than one of event name, event identification information, event index, TCI status indication information, TCI status ID, PCI/PCI index/serving cell index/arbitrary cell ID/configuration identification information.

TCI status update/activation/indication for indicating/triggering/associating LTM operation may be provided through MAC CE and/or DCI. The MAC CE may indicate more than one TCI state in an active manner in a TCI state pool consisting of RRC. If multiple TCI states are activated, the DCI (via the code points/TCI fields associated with the TCI states) may select/indicate one of the activated TCI states. If one TCI state is activated, the activated TCI state may be selected by default without additional DCI indication. For another example, if multiple TCI states are activated and the respective TCI states are all associated with one target/candidate cell, then the TCI state corresponding to the order of the first/last/low/high/RRC indication may be selected.

The number of code points that are activated by the MAC CE-based TCI status update/activation/indication for indicating/triggering/associating/supporting LTM operations may be more than one (e.g., 8). The number of DCI-based code points (codepoints) for the beam indication/TCI state update/TCI state activation TCI field for indicating/triggering/associating/supporting LTM operations may be more than one. The number may be configured differently depending on the capabilities of the terminal.

The number of PCIs (different from the serving cell) associated with the TCI state for beam indication/TCI state update/TCI state activated for TCI state activation based on the TCI state indication based on the MAC CE for indicating/triggering/associating/supporting LTM operation and/or based on the DCI may be configured differently according to the performance of the terminal. The number of TCI status indications based on MAC CE and/or DCI based for beam indication/TCI status update/PCI (different from serving cell) associated with TCI status activated for TCI status activation may be more than one.

To indicate/trigger/associate/support LTM operations, a MAC CE may be defined. The MAC CE may include information on one or more of a serving cell ID, a serving cell BWP ID, a serving cell SUL, a candidate/target cell ID/PCI index, a target cell BWP ID, a target cell SUL, candidate/target cell configuration identification information, a serving/target cell or not, a beam/cell change application time (application time), a CSI-RS resource/resource set ID, an SRS resource/resource set ID, a TCI state, a PCI/PCI index, an extension field, CORESET Pool ID, CORESET ID, a PUCCH resource/resource set ID, a temporary RS trigger or not for LTM operation, a trigger time offset of a corresponding/associated RS, resources for a corresponding/associated RS, a QCL source of a corresponding/associated RS, a number of corresponding/associated RS bits, an index/identifier for identifying RRC configuration/configuration information including parameters (e.g., one or more of the above parameters) of a corresponding/associated RS, a C-RNTI, UL Grant, TIMING ADVANCE com d, and dedicated RACH configuration information.

Here, the serving cell ID represents a serving cell identifier of the application MAC CE (or any field included in the MAC CE). The candidate/target cell ID/PCI index may represent a cell identifier/PCI index of a target/handover cell performing a cell change according to the LTM operation. The BWP ID is a code point of DCI bandwidth part indicator field, and represents DL BWP to which the MAC CE (or any field included in the MAC CE) is applied. SUL indicates whether MAC CE (or any field contained in MACCE) is applied to NUL bearer or SUL bearer (This field is set to 1to indicate that it applies to the SUL carrier configuration,and it is set to 0to indicate that it applies to the NUL carrier configuration).

The candidate/target cell configuration identification information represents information for associating a configuration (or a corresponding detailed configuration, or candidate/target cell configuration) for LTM operation included in a corresponding RRC message. The serving/target cell or not may be indicated with 1 bit (1/0) by the following information: any information field contained in the MAC CE indicates whether it is associated with/contained in/corresponding to the serving cell or with/contained in/corresponding to the target cell. The beam application time (application time) is the time when the corresponding beam/TCI state is applied, and a value indicated/configured by the base station may be used. Or a cell change application time (application time) is a time when a corresponding cell change is applied, a value indicated/configured by the base station may be used. The CSI-RS resource/resource set ID represents an index of NZP-CSI-RS-resource set including SEMI PERSISTENT NZP CSI-RS resources, or a resource identifier for steering/associating a corresponding TCI state. The SRS resource/resource set ID represents the (SEMI PERSISTENT) SRS resource set identifier identified by the SRS resource set identifier, or a resource identifier for directing/associating the corresponding TCI state.

The TCI state may include a TCI state ID to be activated. Or the TCI state may include a TCI state ID (TCI-StateId) of the TCI state (to be activated) that is used (or applicable) as a QCL source of resources within the respective CSI-RS resource set/SRS resource set/control resource set. Or the TCI state may represent an active/inactive state of the TCI state with TCI state ID i. The TCI state may be composed of a bitmap representing the activation/deactivation states in terms of TCI state IDs for each configuration. For example, a TCI state having a TCI state identifier i may be activated/deactivated when the corresponding field is set to 1/0 (or 0/1). The activated TCI status identifier may be mapped to a code point on a field (e.g., transmission Configuration Indication) contained within the DCI. The code points of the TCI state map may be determined from sequential locations (ordinal position) in all TCI state/TCI state IDs with active TCI states in the corresponding bitmap. The TCI state may represent a common/joint DL/UL TCI state ID. Or the TCI state may be configured by a downlink TCI state ID field and an uplink TCI state ID field to indicate SEPARATE DL/UL TCI. Or the corresponding MAC CE may include a field for indicating whether the corresponding TCI state represents a joint DL/UL TCI state, or whether SEPARATE DL/UL TCI state is represented. Or the corresponding MAC CE may use only the joint DL/UL TCI status ID. Or may indicate to the terminal the TCI state/TCI state ID (e.g., joint DL/UL TCI state, SEPARATE DL/UL TCI state, both) for association to LTM operation through RRC. If the activation/deactivation status is indicated by the above-described bitmap, the above-described bitmap may be configured according to the order of the corresponding TCI status/TCI status IDs. One TCI state may be used as more than one QCL source in the PDSCH/PDCCH/PUCCH/PUSCH/CSI-RS resource set/SRS resource set. Each TCI state may include more than one parameter for configuring QCL (quasico-location) relation between DL/UL reference signals and DM-RS ports of PDCCH/PDSCH, CSI-RS ports of CSI-RS resources, PUCCH/PUSCH spatial relation, spatial correlation of SRS resources. The respective TCI state may include only the TCI state associated with the second TRP. Or the respective TCI state may include a TCI state associated with both the first TRP and the second TRP. Or a MAC CE (for indicating a TCI state associated with the second TRP) for LTM operation may be defined as a MAC CE with a separate LCID. The extension field may represent a flag indicating whether the corresponding TCI state is the last TCI state. Or the extension field may represent a flag for indicating whether there is 8 bits (octets) containing the corresponding TCI status ID. It can be distinguished and indicated using a 1/0 value.

The PCI/PCI index may represent the PCI/PCI index associated with the corresponding TCI status identifier. CORESET Pool ID denotes CORESET Pool ID/control resource set identifier specific to the corresponding TCI state (ControlResourceSetId)(This field set to 1indicates that this MAC CE shall be applied for the DL transmission scheduled by CORESET with the CORESET pool ID equal to 1,otherwise,this MAC CE shall be applied for the DL transmission scheduled by CORESET pool ID equal to 0.).

CORESET ID denotes a control resource set (In case the value of the field is 0,the field refers to the Control Resource Set configured by controlResourceSetZero).PUCCH resource/resource set ID applicable/usable to the corresponding TCI state identified by the control resource set identifier, denotes a PUCCH resource identifier identified by a PUCCH resource identifier, or a resource identifier for directing/associating the corresponding TCI state. The temporary RS for LTM operation represents Temporary RS burst for LTM operation, and the number of RS bursts, the candidate value of the trigger offset, may be configured by RRC. The C-RNTI indicates a terminal identifier (newUE-Identity/C-RNTI) to be used in the candidate/target cell. UL Grant indicates resources to be used by candidate/target cells in uplink. TIMING ADVANCE command indicates Index value (The Timing Advance Command field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in TS 38.213).RACH Dedicated configuration information (rach-Config-defined, e.g., RA occision, msgA-PUSCH-Resource-Index, RA-Preamble Index, SSB-Index, etc. for contention free random access) used for controlling the amount of timing adjustment that needs to be applied in the corresponding MAC entity, indicates random access configuration information for cell change.

Here, the information of one or more of the CSI-RS resource/resource set ID, SRS resource/resource set ID, DL/UL TCI status, PCI/PCI index, CORESET Pool ID, CORESET ID, PUCCH resource/resource set ID, temporary RS trigger or not for LTM operation, trigger time offset of the corresponding RS, resources for the corresponding RS, QCL source for the corresponding RS, the corresponding RS burst number, and parameters of the corresponding RS may be distinguished into information contained in the source cell configuration and information contained/associated in the target cell configuration, and included in each field. Or may include only information contained/associated in the source cell configuration. Or may include only information contained/associated in the target cell configuration.

The corresponding MAC CE may be defined as being divided into a MAC CE for indicating joint DL/UL TCI activation/deactivation and a MAC CE for indicating SEPARATE DL/UL TCI activation/deactivation, and having a separate LCID. Or the corresponding MAC CE may be defined as a MAC CE with one LCID that can support joint DL/UL TCI activation/deactivation and SEPARATE DL/UL TCI activation/deactivation simultaneously. The corresponding MAC CE may be defined as a MAC CE for indicating a temporary RS (for LTM operation) has a separate LCID, and may be indicated to the terminal together with any of the above-described MAC CEs.

Using MAC CE and/or DCI, TCI status ID update/activation may be provided/indicated via (across) source/first TRP/cell associated with the first TRP/serving cell and target/candidate/second TRP/cell associated with the second TRP/non-serving cell, wherein TCI status ID provides QCL information for terminal specific PDCCH/PDSCH/CSI-RS and/or uplink TX SPATIAL FILTER (S) for terminal specific PUSCH/PUCCH/SRS.

To indicate/trigger/enable/support LTM operation, the base station may transmit TCI status activation/deactivation MAC CE and/or DCI to the terminal. The base station may activate/deactivate a configured TCI state of (UE-specific/Non-UE-specific) PDSCH/PDCCH/PUCCH/PUSCH/CSI-RS resource set/SRS resource set (for receiving PDSCH/PDCCH) of a cell (or target cell) having a different PCI from that of the serving cell through the second TRP. The base station may activate/deactivate the TCI state of the configuration of the code point of DCI Transmission configuration indication field of PDSCH/PDCCH/PUCCH/PUSCH/CSI-RS resource set/SRS resource set (for receiving PDSCH/PDCCH) of a cell (or target cell) having a different PCI from that of the serving cell through the second TRP. The TCI for the configuration of PDSCH/PDCCH/PUCCH/PUSCH/CSI-RS resource set/SRS resource set is initially deactivated upon receiving the RRC reconfiguration message. In performing the LTM operation, the TCI for the configuration of PDSCH/PDCCH/PUCCH/PUSCH/CSI-RS resource set/SRS resource set may perform cell change/handover in an active state. Thus, the TCI for the configuration of PDSCH/PDCCH/PUCCH/PUSCH/CSI-RS resource set/SRS resource set may be in an active state after LTM operation. Or may remain active during handoff. Or the active state may be maintained during the indicated timer operation. Or the active state may be maintained until explicit signaling (e.g., L3/L2/L1 indication/acknowledgement information) defined by the base station is indicated/received. Or the activation state may be maintained until a specific point of time included in the present specification.

The base station may indicate TCI status ID update/activation through MAC CE and/or DCI. When a terminal (MAC entity) receives the MAC CE through a serving cell/first TRP, the terminal may indicate information about the MAC CE to a lower layer/physical layer. The terminal may update/activate the MAC CE/indication/command through the received TCI state, and map the received activated TCI state to a code point of a corresponding field (e.g., 'Transmission Configuration Indication', or any field defined for LTM action) included in the DCI. The terminal may apply TCI states corresponding to code points/values of respective fields included in the DCI. The terminal may apply the received TCI state ID. When the terminal transmits the PUCCH with HARQ ACK information corresponding to the PDSCH carrying the corresponding active MAC CE/indication/command to the slot n, the mapping between the TCI state and the code point of the corresponding field included in the DCI may be applied to a specific application time calculated after the slot n using the parameters indicated by the base station. The terminal may apply the corresponding TCI state to the corresponding application time.

The terminal may trigger/initiate/execute/apply LTM operations. For example, the LTM operation may be triggered/initiated/executed/applied at a corresponding application time (or after the application time, or after an additional time/offset indicated/configured by the base station). The terminal may indicate the LTM operation to an upper layer (e.g., RRC). The lower layer (PHY/MAC) of the terminal may pass corresponding information to MAC/RLC/PDCP/RRC. The upper layer of the terminal may trigger/initiate/execute/apply cell change.

In NR, in order to support efficient network construction, a base station (gNB) is divided into a separate structure of a centralized node (hereinafter referred to as gNB-CU for convenience of explanation) and a distributed node (hereinafter referred to as gNB-DU for convenience of explanation). A wireless network consists of a set of base stations connected to a 5GC (5G Core network) through an NG interface. The base stations are connected with each other through an Xn interface. A base station may consist of one gNB-CU and more than one gNB-DU. The gNB-CU and the gNB-DU are connected through an F1 interface. One gNB-DU can only connect one gNB-CU. The NG interface and Xn-C interface for one base station consisting of the gNB-CU and the gNB-DU terminate in the gNB-CU. The gNB-DU connected to gNB-CU is only one base station for other base stations and 5 GC. gNB-CU is a logical node hosting the RRC, SDAP and PDCP protocols of the base station. The gNB-DU is a logical node hosting the RLC, MAC and PHY layers of the base station. One gNB-DU supports more than one cell. One cell is supported by only one gNB-DU.

As an example, the LTM operation determination may be performed in the CU. For example, the CU may determine the LTM operation based on RRM measurements, etc. If the CU determines the LTM operation, the CU may transmit an F1AP message to the DU indicating the LTM operation. The information may include more than one information contained in the present specification. The DU may indicate L1/L2 signaling for LTM operation to the terminal. The DU may transmit reference signals associated with L1/L2 signaling.

For another example, LTM operation determination may be performed in DUs. For example, the DU may determine the LTM operation based on an L1 report (e.g., CSI report) or the like. The DU may transmit L1/L2 signaling for LTM operation to the terminal. The DU may transmit reference signals associated with L1/L2 signaling. The DU may transmit a F1AP message to the CU to inform the CU that L1/L2 signaling for LTM operation has been indicated to the terminal. The information may include more than one information contained in the present specification. The RRC/PDCP of a CU may perform more than one operation according to the present specification when the CU receives the corresponding message.

As described above, the present disclosure can effectively reduce delay of a cell change procedure by controlling mobility for a terminal and processing corresponding radio bearer data based on L1/L2 signaling.

The configurations of the terminal and the base station capable of performing all or a part of the embodiments of the present disclosure described above will be described below with reference to the drawings.

Referring to fig. 14, a terminal 1400 performing a cell change operation may include: a receiving section 1430 that receives an upper layer message containing one or more candidate target cell configuration information for LTM (L1/L2 TRIGGERED MOBILITY) operation, and that receives a MAC CE (Medium Access Control Control Element) that instructs execution of the LTM operation to the target cell; and a control part 1410 performing a detach operation from the source cell based on the MAC CE and performing a cell change operation by applying candidate target cell configuration information for the target cell.

For example, the receiving unit 1430 may receive an RRC message including one or more candidate target cell configuration information from a base station or TRP. The RRC message may contain more than one candidate target cell configuration information, each of which may be differentiated according to each candidate target cell and contained therein.

For example, the upper layer message may include at least one of cell group configuration information, identification information for candidate target cell configuration information, bandwidth part identification information, and TCI (Transmission Configuration Indication) state configuration information. The cell group configuration information includes information for configuring a cell group using two or more cells. The identification information for the candidate target cell configuration information may include ID or index information. Thus, the terminal can distinguish each candidate target cell configuration information. The bandwidth part identification information may include an ID or index for distinguishing a bandwidth part (BWP). The TCI state configuration information may include at least one of TCI state ID, cell index, cell ID, and PCI (PHYSICAL CELL IDENTITY ).

On the other hand, the candidate target cell configuration information includes information for performing L1 measurement on the serving cell or the candidate target cell and transmitting the above L1 measurement result. For example, the control part 1410 measures the channel state of the serving cell or the candidate target cell using the candidate target cell configuration information. The transmitting section 1420 transmits the measured channel state or channel quality information to the base station based on information for transmitting the measurement result included in the candidate target cell configuration information. As an example, the transmitting part 1420 may transmit the measurement result of the corresponding serving cell or candidate target cell to the base station when the transmission of the measurement result satisfies the condition of the trigger. As another example, the transmission of the L1 measurement is triggered when the measurement quality of the candidate target cell is higher than the measurement of the source PSCell minus the offset value.

In addition, when an upper layer message including candidate target cell configuration information for LTM operation is received, the control part 1410 may classify and store according to identification information for the candidate target cell configuration information and perform an addition or modification operation.

The reception section 1430 may receive instruction information included in the MAC CE to instruct to perform the LTM operation. As another example, the receiving part 1430 may confirm information of a target cell included in the MAC CE and receive an LTM operation execution instruction to the target cell. The control unit 1410 needs to obtain an instruction to perform LTM operation and information of a target cell to perform cell change through the MAC CE. To this end, the MAC CE may include at least one of identification information for candidate target cell configuration information, TCI state ID, bandwidth part identification information, and timing advance command. For example, the MAC CE may include identification information for distinguishing configuration information for candidate target cells configured in the terminal through an upper layer message. The identification information may consist of candidate target cell configuration information ID or index information. In addition, the MAC CE may further include at least one of a TCI status ID, a bandwidth part ID, and a TAG.

Further, the control unit 1410 may confirm the target cell performing the cell change based on the MAC CE after receiving the MAC CE. As an example, the control part 1410 confirms identification information for candidate target cell configuration information included in the MAC CE and confirms candidate target cell configuration information allocated as corresponding identification information and received through an upper layer message. After confirming the target cell, the control unit 1410 applies candidate target cell configuration information applied to the target cell to the terminal. In addition, the control part 1410 performs a cell change operation to the target cell using the candidate target cell configuration information of the target cell without performing an RRC reconfiguration operation. On the other hand, the control part 1410 may store and apply more than one candidate target cell configuration information to the terminal until upper layer signaling for releasing the candidate target cell configuration information is received.

In addition, the control part 1410 may distinguish and perform a cell change operation according to whether or not the target cell and the source cell indicated by the MAC CE are included in the same cell group.

As an example, when the target cell and the source cell indicated by the MAC CE belong to the same cell group within DU (Distributed Unit), the control part 1410 may perform the cell change operation by maintaining the user plane without performing at least one of the MAC reset operation, the RLC reset operation, and the PDCP data restoration operation. That is, when the target cell and the source cell are the same cell group in the intra-DU, the control part 1410 does not perform a MAC reset operation, or does not perform an RLC reset operation, or does not perform a PDCP data recovery operation, thereby maintaining the user plane and performing a fast mobility control operation.

As another example, when the target cell and the source cell indicated by the MAC CE belong to different cell groups in DU (Distributed Unit), the control part 1410 may perform a cell change operation by performing a MAC reset operation, an RLC reset operation, and a PDCP data recovery operation. That is, the control part 1410 may perform a MAC reset operation, an RLC reset operation, and a PDCP data recovery operation in case of intra-DU cell change.

As yet another example, a cell change according to an LTM operation performed by the control section 1410 may not support a security key update operation.

Further, the transmitting section 1420 and the receiving section 1430 are used to transmit and receive signals, messages, and data necessary for performing the above-described embodiment with the base station. In addition, the control section 1410 controls the operation of the overall terminal 1400 required to perform the above-described embodiment.

Referring to fig. 15, a base station 1500 controlling a cell change operation of a terminal may include: a transmitting part 1520 transmitting an upper layer message including one or more candidate target cell configuration information for an LTM (L1/L2 TRIGGERED MOBILITY) operation to the terminal; the reception unit 1530 receives an L1 measurement result for the candidate target cell from the terminal. The transmitting part 1520 may also transmit a MAC CE (Medium Access Control Control Element) indicating to perform an LTM operation to the target cell based on the L1 measurement result to the terminal.

The transmitting part 1520 may transmit an RRC message including one or more candidate target cell configuration information to the terminal. The RRC message may contain more than one candidate target cell configuration information, each of which may be differentiated according to each candidate target cell and contained therein. For example, the upper layer message may include at least one of cell group configuration information, identification information for candidate target cell configuration information, bandwidth part identification information, and TCI (Transmission Configuration Indication) state configuration information. The cell group configuration information includes information for configuring a cell group using two or more cells. The identification information for the candidate target cell configuration information may include ID or index information. Thus, the terminal can distinguish each candidate target cell configuration information. The bandwidth part identification information may include an ID or index for distinguishing a bandwidth part (BWP). The TCI state configuration information may include at least one of TCI state ID, cell index, cell ID, and PCI (PHYSICAL CELL IDENTITY ).

On the other hand, the candidate target cell configuration information includes information for performing L1 measurement on the serving cell or the candidate target cell and transmitting the above L1 measurement result. For example, the terminal measures the channel state of the serving cell or the candidate target cell using the candidate target cell configuration information. The terminal transmits channel state or channel quality information measured based on information for transmitting a measurement result included in the candidate target cell configuration information to the base station. To this end, information for measurement reporting may be included in candidate target cell configuration information.

The reception unit 1530 receives a measurement result report including L1 measurement results transmitted by the terminal. For example, the terminal may transmit the measurement result to the base station 1500 based on information for transmitting the measurement result included in the candidate target cell configuration information. As an example, the terminal may transmit the measurement result of the corresponding serving cell or candidate target cell to the base station when the transmission of the measurement result satisfies the trigger condition. As another example, the transmission of the L1 measurement is triggered when the measurement quality of the candidate target cell is higher than the measurement of the source PSCell minus the offset value.

The control section 1510 may determine whether to perform the LTM operation based on the L1 measurement result information of the terminal. As another example, the control part 1510 may determine a target cell to be changed through an LTM operation based on L1 measurement result information of the terminal. As described above, the control section 1510 may determine execution of an LTM operation for a terminal and a target cell to be changed by the terminal based on an L1 measurement result received from the terminal.

When the transmitting unit 1520 determines a cell change of the terminal based on the L1 measurement result information received from the terminal, the instruction may be made through the MAC CE.

As an example, the transmitting part 1520 may include instruction information for instructing the execution of the LTM operation in the MAC CE and transmit it. As another example, the transmitting section 1520 may include information of the target cell in the MAC CE and transmit.

The terminal may obtain an execution instruction of the LTM operation and information of the target cell performing the cell change through the MAC CE. As one example, the MAC CE may include at least one of identification information for candidate target cell configuration information, TCI state ID, bandwidth part identification information, and timing advance command. For example, the MAC CE may include identification information for distinguishing configuration information for candidate target cells configured in the terminal through an upper layer message. The identification information may consist of candidate target cell configuration information ID or index information. In addition, the MAC CE may further include at least one of a TCI status ID, a bandwidth part ID, and a TAG.

For example, the terminal, after receiving the MAC CE, may confirm a target cell on which to perform cell change based on the MAC CE. As an example, the terminal confirms the identification information for the candidate target cell configuration information included in the MAC CE, and confirms the candidate target cell configuration information allocated as the identification information and received through the upper layer message. The candidate target cell to which the candidate target cell configuration information is applied may be a target cell to be a cell change object. After confirming the target cell, the terminal applies the candidate target cell configuration information applied to the target cell to the terminal. In addition, the terminal uses the candidate target cell configuration information of the target cell to perform a cell change operation to the target cell without performing an RRC reconfiguration operation. On the other hand, more than one candidate target cell configuration information is stored and applied to the terminal until upper layer signaling for releasing the candidate target cell configuration information is received.

Further, the transmitting part 1520 and the receiving part 1530 are for transmitting and receiving signals, messages, and data necessary for performing the above-described embodiment with a base station. In addition, the control section 1510 controls the operation of the overall terminal 1500 required to execute the above-described embodiment.

The above-described embodiments may be supported by provision as a standard document disclosed in at least one of the wireless access systems IEEE 802, 3GPP, and 3GPP 2. That is, in the present embodiment, steps, components, parts, which are not explained in order to clearly disclose the present technical idea, may be supported by the above-described standard documents. In addition, all terms disclosed in the present specification can be interpreted by the above-disclosed standard documents.

The present embodiment described above can be implemented by various means. For example, the present embodiment may be implemented by hardware, firmware (firmware), software, or a combination thereof.

In the case of implementation by hardware, the method according to the present embodiment may be implemented by one or more ASICs (Application SPECIFIC INTEGRATED Circuits), DSPs (DIGITAL SIGNAL Processors ), DSPs (DIGITAL SIGNAL Processing Devices, digital signal processing devices), PLDs (Programmable Logic Devices ), FPGAs (Field Programmable GATE ARRAYS, programmable logic gate arrays), processors, controllers, microcontrollers, microprocessors, or the like.

In the case of implementation by firmware or software, the method according to the present embodiment may be implemented in the form of a device, flow, or function that performs the functions or operations described above. The software codes may be stored in a memory cell and driven by a processor. The memory cell is located inside or outside the processor and can exchange data with the processor through a variety of known devices.

In addition, the terms "system," "processor," "controller," "component," "module," "interface," "model," or "cell" as described above may generally refer to the physical hardware, a combination of hardware and software, or software in execution, in connection with a computer. For example, the foregoing components may be, but are not limited to being, processes driven by a processor, a controller, a control processor, an individual, a thread of execution, a program, and/or a computer. For example, an application running in a controller or processor and the controller or processor may both be a component. More than one component may be located within a process and/or thread of execution, and a component may be located in one device (e.g., a system, computing device, etc.) or distributed across more than two devices.

The above description is merely illustrative of the technical idea of the present disclosure, and various modifications and variations can be made by those skilled in the art to which the present disclosure pertains without departing from the essential characteristics of the present application. The present embodiment is for explaining the technical idea of the present disclosure, and is not limited to the embodiment, and therefore the scope of the technical idea is not limited to the embodiment. The scope of the present disclosure should be construed in accordance with the following claims, and all technical ideas within the equivalent scope thereof should be construed to be included in the scope of the claims of the present disclosure.

Claims

1. A method for a terminal to perform a cell change operation, comprising:

a step of receiving an upper layer message containing more than one candidate target cell configuration information for an L1/L2 triggered mobility operation;

A step of receiving a medium access control element for indicating to perform the L1/L2 triggered mobility operation to a target cell; and

A step of performing a detach operation from a source cell based on the medium access control element, and performing a cell change operation by applying the candidate target cell configuration information for the target cell.

2. The method of claim 1, wherein,

The upper layer message includes: cell group configuration information, identification information for candidate target cell configuration information, bandwidth part identification information, and transmission configuration indication state configuration information.

3. The method of claim 2, wherein,

The cell group configuration information includes: candidate target primary cell and candidate target secondary cell information,

The candidate target primary cell is set to one of: a cell other than a serving cell configured in a terminal, or a secondary cell configured in the terminal,

The candidate target secondary cell is set to one of: a cell of a non-serving cell configured in the terminal, or a primary cell configured in the terminal.

4. The method of claim 1, wherein,

The medium access control element includes: at least one of identification information for candidate target cell configuration information, a transmission configuration indication status identifier, bandwidth part identification information, and a timing advance command.

5. The method of claim 1, wherein,

In the performing of the cell change operation, when the target cell and the source cell indicated by the medium access control element are the same cell group within a distributed unit, the cell change is performed by maintaining a user plane without performing at least one of a medium access control reset operation, a radio link control reset operation, and a packet data convergence protocol data recovery operation.

6. The method of claim 1, wherein,

Cell change according to the L1/L2 triggered mobility operation does not support security key update operation.

7. A method of a base station controlling a cell change operation of a terminal, comprising:

a step of transmitting an upper layer message containing one or more candidate target cell configuration information for the L1/L2 triggered mobility operation to the terminal;

A step of receiving an L1 measurement result of a candidate target cell from the terminal; and

A step of transmitting a medium access control element indicating to perform the L1/L2 triggered mobility operation to the target cell based on the L1 measurement result to the terminal.

8. The method of claim 7, wherein,

9. The method of claim 8, wherein,

10. The method of claim 7, wherein,

11. The method of claim 7, wherein,

The terminal performs a detach operation from a source cell based on the medium access control element, and performs a cell change operation by applying the candidate target cell configuration information for the target cell,

When the target cell and the source cell indicated by the medium access control element are the same cell group within a distributed unit, the terminal performs a cell change operation by maintaining a user plane without performing at least one of a medium access control reset operation, a radio link control reset operation, and a packet data convergence protocol data recovery operation.

12. A terminal that performs a cell change operation, comprising:

a reception unit that receives an upper layer message including configuration information of one or more candidate target cells for an L1/L2-triggered mobility operation, and that receives a medium access control element indicating to perform the L1/L2-triggered mobility operation to a target cell; and

A control section that performs a detach operation from a source cell based on the medium access control element, and performs a cell change operation by applying the candidate target cell configuration information for the target cell.

13. The terminal of claim 12, wherein,

14. The terminal of claim 13, wherein,

15. The terminal of claim 12, wherein,

16. The terminal of claim 12, wherein,

When the target cell and the source cell indicated by the medium access control element are the same cell group within a distributed unit, the control section performs a cell change operation by maintaining a user plane without performing at least one of a medium access control reset operation, a radio link control reset operation, and a packet data convergence protocol data recovery operation.

17. The terminal of claim 12, wherein,