Selection of mobility timer values in wireless communications

Abstract

The invention relates to selection of mobility timer values in wireless communications. According to an embodiment of the present disclosure, a method performed by a user equipment (UE) configured to operate in a wireless communication system comprises the steps of: receiving, from a network, a message including a configuration for a candidate cell for cell handover and a plurality of timer values of a timer for detecting a cell handover failure, each of the plurality of timer values is associated with a corresponding cell handover type; receiving a cell handover command for the candidate cell from the network; initiating a cell handover to the candidate cell based on the cell handover command, in which a timer having a timer value among a plurality of timer values is started when the UE initiates the cell handover, and the timer value is related to a cell handover type of the cell handover to be performed; and performing a cell handover to the candidate cell while the timer is running.

Description

Technical Field

[0001] The present disclosure relates to selection of mobility timer values ​​in wireless communications. Background Art

[0002] The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is a technology that enables high-speed packet communications. Many solutions have been proposed for LTE, including those aimed at reducing user and provider costs, improving service quality, and expanding and improving coverage and system capacity. As high-level requirements, 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of frequency bands, a simple structure, open interfaces, and appropriate power consumption of terminals.

[0003] The International Telecommunication Union (ITU) and 3GPP have begun developing requirements and specifications for New Radio (NR) systems. 3GPP must identify and develop the technical components necessary for successful standardization of the new RAT, which will meet both immediate market needs and the longer-term requirements outlined by the ITU Radiocommunication Sector (ITU-R) International Mobile Telecommunications (IMT)-2020 process. Furthermore, NR should be able to use any spectrum band available for wireless communications in the more distant future, at least up to 100 GHz.

[0004] The goal of NR is to be a single technology framework that addresses all use cases, requirements, and deployment scenarios, including enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), ultra-reliable and low-latency communications (URLLC), etc. NR should be inherently forward-compatible.

[0005] In wireless communications, when initiating mobility to a target cell, a user equipment (UE) may start a timer (e.g., T304 timer) and perform mobility to the target cell while the timer is running. If the mobility timer value is too small, a mobility failure may be detected too early. On the other hand, if the mobility timer value is too large, a mobility failure may be detected too late. Therefore, an appropriate mobility timer value is required. Summary of the Invention

[0006] Technical Solution

[0007] An aspect of the present disclosure is to provide a method and apparatus for selection of a mobility timer value in a wireless communication system.

[0008] According to one embodiment of the present disclosure, a method performed by a user equipment (UE) configured to operate in a wireless communication system includes the following steps: receiving a message from a network, the message including a configuration for a candidate cell for cell switching and multiple timer values ​​for a timer for detecting cell switching failure, wherein each of the multiple timer values ​​is associated with a corresponding cell switching type; receiving a cell switching command for the candidate cell from the network; initiating a cell switching to the candidate cell based on the cell switching command, wherein a timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell switching, and the timer value is associated with the cell switching type of the cell switching to be performed; and performing the cell switching to the candidate cell while the timer is running.

[0009] According to one embodiment of the present disclosure, a user equipment (UE) configured to operate in a wireless communication system includes: at least one transceiver; at least one processor; and at least one memory, wherein the at least one memory is operatively connected to the at least one processor and stores instructions, wherein the instructions perform operations based on being executed by the at least one processor, the operations including: receiving a message from a network, the message including a configuration for a candidate cell for cell switching and multiple timer values ​​for a timer for detecting cell switching failure, wherein each of the multiple timer values ​​is associated with a corresponding cell switching type; receiving a cell switching command for the candidate cell from the network; initiating a cell switching to the candidate cell based on the cell switching command, wherein a timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell switching, and the timer value is associated with the cell switching type of the cell switching to be performed; and performing the cell switching to the candidate cell while the timer is running.

[0010] According to one embodiment of the present disclosure, a network node configured to operate in a wireless communication system includes: at least one transceiver; at least one processor; and at least one memory, wherein the at least one memory is operatively connected to the at least one processor and stores instructions, wherein the instructions perform operations based on being executed by the at least one processor, the operations including: sending a message to a user equipment (UE), the message including a configuration for a candidate cell for cell switching and multiple timer values ​​for a timer for detecting cell switching failure, wherein each of the multiple timer values ​​is associated with a corresponding cell switching type; and sending a cell switching command for the candidate cell to the UE, wherein the cell switching to the candidate cell is initiated based on the cell switching command, wherein a timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell switching, and the timer value is associated with the cell switching type of the cell switching to be performed, and wherein the cell switching to the candidate cell is performed while the timer is running.

[0011] According to one embodiment of the present disclosure, a method performed by a network node configured to operate in a wireless communication system includes the following steps: sending a message to a user equipment (UE), the message including a configuration for a candidate cell for cell switching and multiple timer values ​​for a timer for detecting cell switching failure, wherein each of the multiple timer values ​​is related to a corresponding cell switching type; and sending a cell switching command for the candidate cell to the UE, wherein the cell switching to the candidate cell is initiated based on the cell switching command, wherein a timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell switching, and the timer value is related to the cell switching type of the cell switching to be performed, and wherein the cell switching to the candidate cell is performed while the timer is running.

[0012] According to one embodiment of the present disclosure, a device suitable for operating in a wireless communication system includes: at least a processor; and at least one memory, the at least one memory being operatively connected to the at least one processor and storing instructions, the instructions performing operations based on being executed by the at least one processor, the operations including: receiving a message from a network, the message including a configuration for a candidate cell for cell switching and multiple timer values ​​for a timer for detecting cell switching failure, wherein each of the multiple timer values ​​is associated with a corresponding cell switching type; receiving a cell switching command for the candidate cell from the network; initiating a cell switching to the candidate cell based on the cell switching command, wherein a timer having a timer value among the multiple timer values ​​is started when a UE initiates a cell switching, and the timer value is associated with the cell switching type of the cell switching to be performed; and performing a cell switching to the candidate cell while the timer is running.

[0013] According to one embodiment of the present disclosure, a non-transitory computer-readable medium (CRM) stores program code implementing instructions, wherein the instructions perform operations based on being executed by at least one processor, the operations including: receiving a message from a network, the message including a configuration for a candidate cell for cell switching and multiple timer values ​​for a timer for detecting cell switching failure, wherein each of the multiple timer values ​​is associated with a corresponding cell switching type; receiving a cell switching command for the candidate cell from the network; initiating a cell switching to the candidate cell based on the cell switching command, wherein a timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell switching, and the timer value is associated with the cell switching type of the cell switching to be performed; and performing the cell switching to the candidate cell while the timer is running.

[0014] The present disclosure may have various beneficial effects.

[0015] For example, according to the present disclosure, during a cell handover process, the UE can apply an appropriate failure detection timer value based on whether an RA process is performed. Thus, the problem of premature / late detection of LTM failure can be solved.

[0016] The beneficial effects that can be obtained by the specific embodiments of the present disclosure are not limited to the beneficial effects listed above. For example, there may be various technical effects that can be understood and / or derived from the present disclosure by a person of ordinary skill in the relevant art. Therefore, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that can be understood or derived from the technical features of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 An example of a communication system to which an implementation of the present disclosure is applied is shown.

[0018] Figure 2 An example of a wireless device to which an implementation of the present disclosure is applied is shown.

[0019] Figure 3 An example of a UE to which an implementation of the present disclosure is applied is shown.

[0020] Figure 4 and Figure 5 An example of a protocol stack in a 3GPP-based wireless communication system to which implementations of the present disclosure are applied is shown.

[0021] Figure 6 The frame structure in a 3GPP-based wireless communication system to which the implementation of the present disclosure is applied is shown.

[0022] Figure 7 An example of data flow in a 3GPP NR system to which an implementation of the present disclosure is applied is shown.

[0023] Figure 8 An example of a signaling procedure for LTM according to an embodiment of the present disclosure is shown.

[0024] Figure 9 An example of a CBRA process according to an embodiment of the present disclosure is shown.

[0025] Figure 10 An example of a CFRA process according to an embodiment of the present disclosure is shown.

[0026] Figure 11 An example of a method performed by a UE according to an embodiment of the present disclosure is shown.

[0027] Figure 12 An example of a signal flow between a UE and a network node according to an embodiment of the present disclosure is shown.

[0028] Figure 13 An example of a method for indicating a physical channel configuration in an LTM according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0029] The following techniques, devices, and systems can be applied to various wireless multiple access systems. Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and multi-carrier frequency division multiple access (MC-FDMA) systems. CDMA can be implemented using radio technologies such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented using radio technologies such as Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), or Enhanced Data Rates for GSM Evolution (EDGE). OFDMA can be implemented using radio technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of Evolved UMTS (E-UMTS) that uses E-UTRA. 3GPP LTE uses OFDMA in the downlink (DL) and SC-FDMA in the uplink (UL). Evolutions of 3GPP LTE include LTE-Advanced (LTE-A), LTE-A Pro, and / or 5G New Radio (NR).

[0030] For ease of description, the implementation of the present disclosure will be primarily described with respect to a 3GPP-based wireless communication system. However, the technical features of the present disclosure are not limited thereto. For example, although the following detailed description is given based on a mobile communication system corresponding to a 3GPP-based wireless communication system, various aspects of the present disclosure that are not limited to a 3GPP-based wireless communication system are applicable to other mobile communication systems.

[0031] For terms and techniques not specifically described among the terms and techniques employed in the present disclosure, reference may be made to wireless communication standard documents published prior to the present disclosure.

[0032] In the present disclosure, "A or B" may mean "only A", "only B", or "both A and B". In other words, in the present disclosure, "A or B" may be interpreted as "A and / or B". For example, in the present disclosure, "A, B, or C" may mean "only A", "only B", "only C", or "any combination of A, B, and C".

[0033] In this disclosure, a slash ( / ) or a comma (,) may mean "and / or". For example, "A / B" may mean "A and / or B". Thus, "A / B" may mean "only A", "only B", or "both A and B". For example, "A, B, C" may mean "A, B, or C".

[0034] In the present disclosure, “at least one of A and B” may mean “only A”, “only B”, or “both A and B”. In addition, the expression “at least one of A or B” or “at least one of A and / or B” in the present disclosure may be interpreted as being the same as “at least one of A and B”.

[0035] In addition, in the present disclosure, “at least one of A, B, and C” may mean “only A,” “only B,” “only C,” or “any combination of A, B, and C.” In addition, “at least one of A, B, or C” or “at least one of A, B, and / or C” may mean “at least one of A, B, and C.”

[0036] In addition, brackets used in this disclosure may mean "for example." Specifically, when "control information (PDCCH)" is shown, "PDCCH" may be cited as an example of "control information." In other words, in this disclosure, "control information" is not limited to "PDCCH," and "PDCCH" may be cited as an example of "control information." In addition, even when "control information (i.e., PDCCH)" is shown, "PDCCH" may be cited as an example of "control information."

[0037] The technical features described separately in one figure in this disclosure can be implemented separately or simultaneously.

[0038] Although not limited thereto, the various descriptions, functions, processes, suggestions, methods and / or operational flowcharts of the present disclosure disclosed herein may be applied to various fields requiring wireless communication and / or connectivity (e.g., 5G) between devices.

[0039] Hereinafter, the present disclosure will be described in more detail with reference to the accompanying drawings. Unless otherwise specified, the same reference numerals in the following drawings and / or descriptions may refer to the same and / or corresponding hardware blocks, software blocks and / or functional blocks.

[0040] Figure 1 An example of a communication system to which an implementation of the present disclosure is applied is shown.

[0041] Figure 1 The 5G usage scenarios shown are only exemplary, and the technical features of the present disclosure can be applied to Figure 1 Other 5G usage scenarios not shown.

[0042] The three main demand categories for 5G include: (1) enhanced mobile broadband (eMBB) category, (2) massive machine type communication (mMTC) category, and (3) ultra-reliable and low-latency communication (URLLC) category.

[0043] Reference Figure 1 , the communication system 1 includes wireless devices 100a to 100f, a base station (BS) 200, and a network 300. Figure 1 A 5G network is illustrated as an example of the network of the communication system 1 , but implementations of the present disclosure are not limited to the 5G system and may be applied to future communication systems other than the 5G system.

[0044] BS 200 and network 300 may be implemented as wireless devices, and certain wireless devices may operate as BSs / network nodes relative to other wireless devices.

[0045] Wireless devices 100a to 100f represent devices that perform communication using a radio access technology (RAT) (e.g., 5GNR or LTE) and may be referred to as communication / radio / 5G devices. Wireless devices 100a to 100f may include, but are not limited to, a robot 100a, vehicles 100b-1 and 100b-2, an extended reality (XR) device 100c, a handheld device 100d, a home appliance 100e, an Internet of Things (IoT) device 100f, and an artificial intelligence (AI) device / server 400. For example, a vehicle may include a vehicle with wireless communication capabilities, an autonomous vehicle, and a vehicle capable of performing communication between vehicles. A vehicle may include an unmanned aerial vehicle (UAV) (e.g., a drone). XR devices may include augmented reality (AR) / virtual reality (VR) / mixed reality (MR) devices and may be implemented in the form of a head-mounted device (HMD), a head-up display (HUD) installed in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, and the like. Handheld devices can include smartphones, smart tablets, wearable devices (e.g., smart watches or smart glasses), and computers (e.g., laptops). Home appliances can include TVs, refrigerators, and washing machines. IoT devices can include sensors and smart meters.

[0046] In the present disclosure, wireless devices 100a to 100f may be referred to as user equipment (UE). UE may include, for example, a cellular phone, a smartphone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a tablet-shaped personal computer (PC), a tablet PC, an ultrabook, a vehicle, a vehicle with autonomous driving capabilities, a connected car, an unmanned aerial vehicle (UAV), an AI module, a robot, an AR device, a VR device, an MR device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a FinTech device (or financial device), a security device, a weather / environmental device, a device related to 5G services, or a device related to the Fourth Industrial Revolution.

[0047] Wireless devices 100a to 100f can be connected to network 300 via BS 200. AI technology can be applied to wireless devices 100a to 100f, and wireless devices 100a to 100f can be connected to AI server 400 via network 300. Network 300 can be configured using a 3G network, a 4G network (e.g., LTE), a 5G network (e.g., NR), and a beyond 5G network. While wireless devices 100a to 100f can communicate with each other via BS 200 / network 300, wireless devices 100a to 100f can perform direct communication with each other (e.g., sidelink communication) without going through BS 200 / network 300. For example, vehicles 100b-1 and 100b-2 can perform direct communication (e.g., vehicle-to-vehicle (V2V) / vehicle-to-everything (V2X) communication). IoT devices (e.g., sensors) can perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100a to 100f.

[0048] Wireless communications / connections 150a, 150b, and 150c may be established between wireless devices 100a to 100f and / or between wireless devices 100a to 100f and BS 200 and / or between BS 200. Wireless communications / connections may be established via various RATs (e.g., 5G NR), such as uplink / downlink communication 150a, sidelink communication (or device-to-device (D2D) communication) 150b, and inter-base station communication 150c (e.g., relay, integrated access and backhaul (IAB)). Wireless devices 100a to 100f and BS 200 / wireless devices 100a to 100f may transmit / receive radio signals to / from each other via wireless communications / connections 150a, 150b, and 150c. For example, wireless communications / connections 150a, 150b, and 150c may transmit / receive signals via various physical channels. To this end, various configuration information configuration processes for sending / receiving radio signals, various signal processing processes (e.g., channel coding / decoding, modulation / demodulation, and resource mapping / demapping), and at least a portion of the resource allocation process can be performed based on the various proposals of the present disclosure.

[0049] NR supports multiple numerologies (and / or multiple subcarrier spacings (SCS)) to support various 5G services. For example, if the SCS is 15kHz, wide areas can be supported in traditional cellular bands, while if the SCS is 30kHz / 60kHz, dense cities, lower latency, and wider carrier bandwidths can be supported. If the SCS is 60kHz or higher, bandwidths greater than 24.25GHz can be supported to overcome phase noise.

[0050] The NR frequency band can be defined as two types of frequency ranges, namely, frequency range 1 (FR1) and frequency range 2 (FR2). The numerical values ​​of the frequency ranges can be changed. For example, the two types of frequency ranges (FR1 and FR2) can be shown in Table 1 below. For ease of explanation, in the frequency range used in the NR system, FR1 can mean "a range below 6 GHz", FR2 can mean "a range above 6 GHz", and can be referred to as millimeter wave (mmW).

[0051] [Table 1]

[0052] Frequency range name Corresponding frequency range Subcarrier spacing FR1 450MHz-6000MHz 15, 30, 60kHz FR2 24250MH-52600MHz 60, 120, 240kHz

[0053] As described above, the numerical value of the frequency range of the NR system can be changed. For example, FR1 may include a frequency band of 410 MHz to 7125 MHz as shown in Table 2 below. That is, FR1 may include a frequency band of 6 GHz (or 5850 MHz, 5900 MHz, 5925 MHz, etc.) or higher. For example, the frequency band of 6 GHz (or 5850 MHz, 5900 MHz, 5925 MHz, etc.) or higher included in FR1 may include an unlicensed frequency band. The unlicensed frequency band can be used for various purposes, for example, for communication of vehicles (e.g., autonomous driving).

[0054] [Table 2]

[0055] Frequency range name Corresponding frequency range Subcarrier spacing FR1 410MHz-7125MHz 15, 30, 60kHz FR2 24250MHz-52600MHz 60, 120, 240kHz

[0056] Here, the radio communication technology implemented in the wireless device in the present disclosure may include narrowband Internet of Things (NB-IoT) technology for low-power communication as well as LTE, NR and 6G. For example, NB-IoT technology may be an example of a low-power wide area network (LPWAN) technology, may be implemented in specifications such as LTE Cat NB1 and / or LTE Cat NB2, and may not be limited to the above names. Additionally and / or alternatively, the radio communication technology implemented in the wireless device in the present disclosure may communicate based on LTE-M technology. For example, LTE-M technology may be an example of an LPWAN technology and may be referred to by various names such as enhanced machine type communication (eMTC). For example, LTE-M technology may be implemented in at least one of various specifications, such as 1) LTE Cat 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-bandwidth limited (non-BL), 5) LTE-MTC, 6) LTE machine type communication and / or 7) LTE M, and may not be limited to the above names. Additionally and / or alternatively, the radio communication technology implemented in the wireless device of the present disclosure may include at least one of ZigBee, Bluetooth, and / or LPWAN considering low-power communication, and may not be limited to the above names. For example, ZigBee technology can generate a personal area network (PAN) associated with small / low-power digital communication based on various specifications (such as IEEE 802.15.4) and may be referred to by various names. Figure 2 An example of a wireless device to which an implementation of the present disclosure is applied is shown.

[0057] exist Figure 2 In the embodiment, the first wireless device 100 and / or the second wireless device 200 may be implemented in various forms according to the use case / service. For example, {the first wireless device 100 and the second wireless device 200} may correspond to Figure 1At least one of {wireless devices 100a to 100f and BS 200}, {wireless devices 100a to 100f and wireless devices 100a to 100f} and / or {BS 200 and BS 200}. The first wireless device 100 and / or the second wireless device 200 may be configured by various elements, devices / components and / or modules.

[0058] The first wireless device 100 may include at least one transceiver (eg, transceiver 106 ), at least one processing chip (eg, processing chip 101 ), and / or one or more antennas 108 .

[0059] The processing chip 101 may include at least one processor (eg, processor 102 ) and at least one memory (eg, memory 104 ). Additionally and / or alternatively, the memory 104 may be located outside the processing chip 101 .

[0060] The processor 102 may control the memory 104 and / or the transceiver 106 and may be adapted to implement the descriptions, functions, processes, suggestions, methods, and / or operational flow charts described in the present disclosure. For example, the processor 102 may process information in the memory 104 to generate first information / signals, and then transmit a radio signal including the first information / signals through the transceiver 106. The processor 102 may receive a radio signal including second information / signals through the transceiver 106, and then store information obtained by processing the second information / signals in the memory 104.

[0061] Memory 104 may be operatively connected to processor 102. Memory 104 may store various types of information and / or instructions. Memory 104 may store firmware and / or software code 105 that implements codes, commands, and / or command sets that, when executed by processor 102, perform the descriptions, functions, procedures, suggestions, methods, and / or operational flow charts disclosed herein. For example, firmware and / or software code 105 may implement instructions that, when executed by processor 102, perform the descriptions, functions, procedures, suggestions, methods, and / or operational flow charts disclosed herein. For example, firmware and / or software code 105 may control processor 102 to execute one or more protocols. For example, firmware and / or software code 105 may control processor 102 to execute one or more layers of a wireless interface protocol.

[0062] In this document, the processor 102 and the memory 104 may be part of a communication modem / circuit / chip designed to implement a RAT (e.g., LTE or NR). The transceiver 106 may be connected to the processor 102 and transmit and / or receive radio signals via one or more antennas 108. Each transceiver 106 may include a transmitter and / or a receiver. The transceiver 106 may be used interchangeably with a radio frequency (RF) unit. In this disclosure, the first wireless device 100 may represent a communication modem / circuit / chip.

[0063] The second wireless device 200 may include at least one transceiver (eg, transceiver 206 ), at least one processing chip (eg, processing chip 201 ), and / or one or more antennas 208 .

[0064] The processing chip 201 may include at least one processor (eg, processor 202 ) and at least one memory (eg, memory 204 ). Additionally and / or alternatively, the memory 204 may be located outside the processing chip 201 .

[0065] The processor 202 may control the memory 204 and / or the transceiver 206 and may be adapted to implement the descriptions, functions, processes, suggestions, methods, and / or operational flow charts described in the present disclosure. For example, the processor 202 may process the information in the memory 204 to generate third information / signals, and then transmit a radio signal including the third information / signals through the transceiver 206. The processor 202 may receive a radio signal including fourth information / signals through the transceiver 106, and then store information obtained by processing the fourth information / signals in the memory 204.

[0066] Memory 204 may be operatively connected to processor 202. Memory 204 may store various types of information and / or instructions. Memory 204 may store firmware and / or software code 205 that implements code, commands, and / or command sets that, when executed by processor 202, perform the descriptions, functions, procedures, suggestions, methods, and / or operational flow charts disclosed herein. For example, firmware and / or software code 205 may implement instructions that, when executed by processor 202, perform the descriptions, functions, procedures, suggestions, methods, and / or operational flow charts disclosed herein. For example, firmware and / or software code 205 may control processor 202 to execute one or more protocols. For example, firmware and / or software code 205 may control processor 202 to execute one or more layers of a wireless interface protocol.

[0067] In this document, the processor 202 and the memory 204 may be part of a communication modem / circuit / chip designed to implement a RAT (e.g., LTE or NR). The transceiver 206 may be connected to the processor 202 and transmit and / or receive radio signals via one or more antennas 208. Each of the transceivers 206 may include a transmitter and / or a receiver. The transceiver 206 may be used interchangeably with an RF unit. In this disclosure, the second wireless device 200 may represent a communication modem / circuit / chip.

[0068] In the following, the hardware elements of the wireless devices 100 and 200 will be described in more detail. One or more protocol layers may be implemented by, but are not limited to, one or more processors 102 and 202. For example, one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) layer, and a service data adaptation protocol (SDAP) layer). The one or more processors 102 and 202 may generate one or more protocol data units (PDUs), one or more service data units (SDUs), messages, control information, data, or information according to the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts disclosed in the present disclosure. The one or more processors 102 and 202 may generate a signal (e.g., a baseband signal) including a PDU, SDU, message, control information, data, or information according to the description, functions, procedures, suggestions, methods, and / or operational flowcharts disclosed in the present disclosure and provide the generated signal to the one or more transceivers 106 and 206. The one or more processors 102 and 202 may receive a signal (e.g., a baseband signal) from the one or more transceivers 106 and 206 and obtain the PDU, SDU, message, control information, data, or information according to the description, functions, procedures, suggestions, methods, and / or operational flowcharts disclosed in the present disclosure.

[0069] One or more processors 102 and 202 may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. One or more processors 102 and 202 may be implemented by hardware, firmware, software, or a combination thereof. As an example, one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in one or more processors 102 and 202. For example, one or more processors 102 and 202 may be configured by a group of communication control processors, application processors (APs), electronic control units (ECUs), central processing units (CPUs), graphics processing units (GPUs), and memory control processors.

[0070] One or more memories 104 and 204 can be connected to one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, codes, instructions and / or commands. One or more memories 104 and 204 can be configured by random access memory (RAM), dynamic RAM (DRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EPROM), flash memory, volatile memory, non-volatile memory, hard drive, registers, cache memory, computer-readable storage media and / or combinations thereof. One or more memories 104 and 204 can be located inside and / or outside of one or more processors 102 and 202. One or more memories 104 and 204 can be connected to one or more processors 102 and 202 via various technologies such as wired connections or wireless connections.

[0071] One or more transceivers 106 and 206 can transmit user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts disclosed in this disclosure to one or more other devices. One or more transceivers 106 and 206 can receive user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts disclosed in this disclosure from one or more other devices. For example, one or more transceivers 106 and 206 can be connected to one or more processors 102 and 202 and transmit and receive radio signals. For example, one or more processors 102 and 202 can execute control so that one or more transceivers 106 and 206 can transmit user data, control information, or radio signals to one or more other devices. One or more processors 102 and 202 can execute control so that one or more transceivers 106 and 206 can receive user data, control information, or radio signals from one or more other devices.

[0072] One or more transceivers 106 and 206 may be connected to one or more antennas 108 and 208. Additionally or alternatively, one or more transceivers 106 and 206 may include one or more antennas 108 and 208. One or more transceivers 106 and 206 may be adapted to transmit and receive user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, processes, suggestions, methods, and / or operational flow charts disclosed in the present disclosure through one or more antennas 108 and 208. In the present disclosure, one or more antennas 108 and 208 may be multiple physical antennas or multiple logical antennas (e.g., antenna ports).

[0073] The one or more transceivers 106 and 206 may convert received user data, control information, radio signals / channels, etc. from RF band signals to baseband signals so that the received user data, control information, radio signals / channels, etc. may be processed by the one or more processors 102 and 202. The one or more transceivers 106 and 206 may convert user data, control information, radio signals / channels, etc. processed by the one or more processors 102 and 202 from baseband signals to RF band signals. To this end, the one or more transceivers 106 and 206 may include (analog) oscillators and / or filters. For example, under the control of the one or more processors 102 and 202, the one or more transceivers 106 and 206 may up-convert an OFDM baseband signal into an OFDM signal through their (analog) oscillators and / or filters and transmit the up-converted OFDM signal at the carrier frequency. One or more transceivers 106 and 206 may receive an OFDM signal at a carrier frequency and down-convert the OFDM signal to an OFDM baseband signal through their (analog) oscillators and / or filters under the control of one or more processors 102 and 202 .

[0074] although Figure 2 Although not shown in the figures, the wireless devices 100 and 200 may further include additional components. The additional components 140 may be configured differently depending on the type of the wireless devices 100 and 200. For example, the additional components 140 may include at least one of a power supply unit / battery, an input / output (I / O) device (e.g., an audio I / O port, a video I / O port), a drive device, and a computing device. The additional components 140 may be coupled to one or more processors 102 and 202 via various technologies, such as a wired or wireless connection.

[0075] In implementations of the present disclosure, a UE may function as a transmitting device in the uplink (UL) and a receiving device in the downlink (DL). In implementations of the present disclosure, a base station (BS) may function as a receiving device in the UL and a transmitting device in the DL. Hereinafter, for ease of description, it is primarily assumed that a first wireless device 100 functions as a UE and a second wireless device 200 functions as a base station (BS). For example, a processor 102 connected to, installed on, or activated in the first wireless device 100 may be adapted to perform UE behavior according to implementations of the present disclosure or to control a transceiver 106 to perform UE behavior according to implementations of the present disclosure. A processor 202 connected to, installed on, or activated in the second wireless device 200 may be adapted to perform BS behavior according to implementations of the present disclosure or to control a transceiver 206 to perform BS behavior according to implementations of the present disclosure.

[0076] In this disclosure, a BS is also referred to as a Node B (NB), an eNode B (eNB), or a gNB.

[0077] Figure 3 An example of a UE to which an implementation of the present disclosure is applied is shown.

[0078] Reference Figure 3 , UE 100 may correspond to Figure 2 The first wireless device 100 is configured to:

[0079] UE 100 includes a processor 102 , memory 104 , a transceiver 106 , one or more antennas 108 , a power management module 141 , a battery 142 , a display 143 , a keypad 144 , a subscriber identity module (SIM) card 145 , a speaker 146 , and a microphone 147 .

[0080] The processor 102 may be adapted to implement the descriptions, functions, processes, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. The processor 102 may be adapted to control one or more other components of the UE 100 to implement the descriptions, functions, processes, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. The radio interface protocol layer may be implemented in the processor 102. The processor 102 may include an ASIC, other chipsets, logic circuits and / or data processing devices. The processor 102 may be an application processor. The processor 102 may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). Examples of the processor 102 may be SNAPDRAGON MANUFACTURED TM series processors, Manufactured by EXYNOS TM series processors, A series of processors manufactured by HELIO manufactured TM series processors, ATOM manufactured TM series processors or the corresponding next-generation processors.

[0081] The memory 104 is coupled to the processor 102 during operation and stores various information to operate the processor 102. The memory 104 may include ROM, RAM, flash memory, a memory card, a storage medium, and / or other storage devices. When the embodiment is implemented in software, the technology described herein may be implemented using modules (e.g., processes, functions, etc.) that execute the descriptions, functions, processes, suggestions, methods, and / or operational flowcharts disclosed in this disclosure. The modules may be stored in the memory 104 and implemented by the processor 102. The memory 104 may be implemented within the processor 102 or external to the processor 102 (in which case, the memory may be communicatively coupled to the processor 102 via various means known in the art).

[0082] The transceiver 106 is coupled to the processor 102 during operation and transmits and / or receives radio signals. The transceiver 106 includes a transmitter and a receiver. The transceiver 106 may include baseband circuitry to process radio frequency signals. The transceiver 106 controls one or more antennas 108 to transmit and / or receive radio signals.

[0083] The power management module 141 manages the power of the processor 102 and / or the transceiver 106. The battery 142 provides power to the power management module 141.

[0084] The display 143 outputs a result processed by the processor 102. The keypad 144 receives an input to be used by the processor 102. The keypad 144 may be displayed on the display 143.

[0085] The SIM card 145 is an integrated circuit designed to securely store an International Mobile Subscriber Identity (IMSI) number and its associated keys, which are used to identify and authenticate subscribers on mobile telephony devices such as mobile phones and computers. Contact information can also be stored on many SIM cards.

[0086] The speaker 146 outputs sound-related results processed by the processor 102. The microphone 147 receives sound-related input to be used by the processor 102.

[0087] Figure 4 and Figure 5 An example of a protocol stack in a 3GPP-based wireless communication system to which implementations of the present disclosure are applied is shown.

[0088] Specifically, Figure 4 An example of a radio interface user plane protocol stack between a UE and a BS is illustrated, and Figure 5An example of a radio interface control plane protocol stack between a UE and a BS is illustrated. The control plane refers to a path through which control messages for managing calls by the UE and the network are transmitted. The user plane refers to a path through which data generated in the application layer (for example, voice data or Internet packet data) is transmitted. Figure 4 , the user plane protocol stack can be divided into layer 1 (L1, for example, PHY layer) and layer 2 (L2, for example, MAC / RLC / PDCP layer). Figure 5 The control plane protocol stack can be divided into Layer 1 (L1, e.g., PHY layer), Layer 2 (L2, e.g., MAC / RLC / PDCP layer), Layer 3 (L3, e.g., RRC layer), and Non-Access Stratum (NAS) layer. Layer 1, Layer 2, and Layer 3 are called Access Stratum (AS).

[0089] In 3GPP LTE systems, Layer 2 is separated into the following sublayers: MAC, RLC, and PDCP. In 3GPP NR systems, Layer 2 is separated into the following sublayers: MAC, RLC, PDCP, and SDAP. The PHY layer provides transport channels to the MAC sublayer, the MAC sublayer provides logical channels to the RLC sublayer, the RLC sublayer provides RLC channels to the PDCP sublayer, and the PDCP sublayer provides radio bearers to the SDAP sublayer. The SDAP sublayer provides Quality of Service (QoS) flows to the 5G core network.

[0090] In 3GPP NR systems, the main services and functions of the MAC sublayer include: mapping between logical channels and transport channels; multiplexing MAC SDUs belonging to one or different logical channels to / demultiplexing transport blocks (TBs) delivered to / from the physical layer on the transport channel; scheduling information reporting; error correction through hybrid automatic repeat request (HARQ) (one HARQ entity per cell in the case of carrier aggregation (CA); priority handling between UEs with dynamic scheduling; priority handling between logical channels of a UE with logical channel prioritization; and padding. A single MAC entity can support multiple parameter sets, transmission timings, and cells. Mapping restrictions in logical channel prioritization control which parameter set(s), cell, and transmission timing can be used by a logical channel.

[0091] MAC provides different types of data transmission services. In order to accommodate different types of data transmission services, multiple types of logical channels are defined, that is, each logical channel supports the transmission of a specific type of information. Each logical channel type is defined by what type of information is transmitted. Logical channels are divided into two groups: control channels and traffic channels. Control channels are only used for the transmission of control plane information, and traffic channels are only used for the transmission of user plane information. The Broadcast Control Channel (BCCH) is a downlink logical channel used to broadcast system control information, the Paging Control Channel (PCCH) is a downlink logical channel that transmits paging information, system information change notifications, and indications of ongoing Public Warning Service (PWS) broadcasts, the Common Control Channel (CCCH) is a logical channel used to send control information between the UE and the network and is used for UEs that do not have an RRC connection with the network, and the Dedicated Control Channel (DCCH) is a point-to-point bidirectional logical channel that sends dedicated control information between the UE and the network and is used by UEs with an RRC connection. The Dedicated Traffic Channel (DTCH) is a point-to-point logical channel dedicated to one UE, which is used to transmit user information. The DTCH can exist in both the uplink and downlink. In the downlink, the following connections exist between logical channels and transport channels: BCCH can be mapped to the broadcast channel (BCH); BCCH can be mapped to the downlink shared channel (DL-SCH); PCCH can be mapped to the paging channel (PCH); CCCH can be mapped to DL-SCH; DCCH can be mapped to DL-SCH; and DTCH can be mapped to DL-SCH. In the uplink, the following connections exist between logical channels and transport channels: CCCH can be mapped to the uplink shared channel (UL-SCH); DCCH can be mapped to UL-SCH; and DTCH can be mapped to UL-SCH.

[0092] The RLC sublayer supports three transmission modes: transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). RLC configuration is specific to each logical channel and is independent of the parameter set and / or transmission duration. In 3GPP NR systems, the main services and functions of the RLC sublayer depend on the transmission mode and include: delivery of upper layer PDUs; sequence numbering independent of either PDCP (UM and AM); error correction through ARQ (AM only); segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs; reassembly of SDUs (AM and UM); duplicate detection (AM only); RLC SDU discard (AM and UM); RLC re-establishment; and protocol error detection (AM only).

[0093] In the 3GPP NR system, the main services and functions of the PDCP sublayer for the user plane include: sequence numbering; header compression and decompression using Robust Header Compression (ROHC); delivery of user data; reordering and duplicate detection; in-sequence delivery; PDCP PDU routing (in the case of split bearers); retransmission of PDCP SDUs; ciphering, deciphering and integrity protection; PDCP SDU discard; PDCP re-establishment and data recovery for RLC AM; PDCP status reporting for RLC AM; PDCP PDU duplication and duplicate discard indication to lower layers. The main services and functions of the PDCP sublayer for the control plane include: sequence numbering; ciphering, deciphering and integrity protection; delivery of control plane data; reordering and duplicate detection; in-sequence delivery; PDCP PDU duplication and duplicate discard indication to lower layers.

[0094] In 3GPP NR systems, the main services and functions of SDAP include: mapping between QoS flows and data radio bearers; marking QoS flow IDs (QFIs) in both DL and UL packets; and configuring a single SDAP protocol entity for each individual PDU session.

[0095] In the 3GPP NR system, the main services and functions of the RRC sublayer include: broadcast of system information related to AS and NAS; paging initiated by 5GC or NG-RAN; establishment, maintenance and release of RRC connection between UE and NG-RAN; security functions including key management; establishment, configuration, maintenance and release of signaling radio bearers (SRBs) and data radio bearers (DRBs); mobility functions (including: handover and context transfer; UE cell selection and reselection and control of cell selection and reselection; inter-RAT mobility); QoS management functions; UE measurement reporting and control of reporting; detection and repair of radio link failure; transmission of NAS messages from UE to NAS / from NAS to UE.

[0096] Figure 6 The frame structure in a 3GPP-based wireless communication system to which the implementation of the present disclosure is applied is shown.

[0097] Figure 6The frame structure shown is only exemplary, and the number of subframes, the number of time slots and / or the number of symbols in a frame may vary. In a 3GPP-based wireless communication system, OFDM parameter sets (e.g., subcarrier spacing (SCS), transmission time interval (TTI) duration) may be configured differently between multiple cells aggregated for one UE. For example, if a UE is configured with different SCSs for cells aggregated for a cell, the (absolute time) duration of time resources (e.g., subframes, time slots, or TTIs) comprising the same number of symbols may be different among the aggregated cells. In this document, symbols may include OFDM symbols (or CP-OFDM symbols), SC-FDMA symbols (or discrete Fourier transform-spread-OFDM (DFT-s-OFDM) symbols).

[0098] Reference Figure 6 , downlink and uplink transmissions are organized into frames. Each frame has T f =10ms duration. Each frame is divided into two half-frames, where each half-frame has a duration of 5ms. Each half-frame includes 5 sub-frames, where the duration of each sub-frame is T sf is 1 ms. Each subframe is divided into slots, and the number of slots in a subframe depends on the subcarrier spacing. Each slot includes 14 or 12 OFDM symbols based on the cyclic prefix (CP). In normal CP, each slot includes 14 OFDM symbols, and in extended CP, each slot includes 12 OFDM symbols. The parameter set is based on an exponentially scalable subcarrier spacing βf=2 u *15kHz.

[0099] Table 3 shows the subcarrier spacing βf=2 u *N number of OFDM symbols per slot for normal CP of 15 kHz slot symb , the number of time slots per frame N frame，u slot and the number of time slots per subframe N subframe，u slot .

[0100] [Table 3]

[0101] u <![CDATA[N slot symb ]]> <![CDATA[N frame，u slot ]]> <![CDATA[N subframe,u slot ]]> 0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

[0102] Table 4 shows the subcarrier spacing βf=2 u *N number of OFDM symbols per slot for extended CP of 15 kHz slot symb , the number of time slots per frame N frame，u slot and the number of time slots per subframe Nsubframe，u slot .

[0103] [Table 4]

[0104] u <![CDATA[N slot symb ]]> <![CDATA[N frame,u slot ]]> <![CDATA[N subframe,u slot ]]> 2 12 40 4

[0105] A slot includes a plurality of symbols (e.g., 14 or 12 symbols) in the time domain. For each parameter set (e.g., subcarrier spacing) and carrier, a common resource block (CRB) N indicated by higher layer signaling (e.g., RRC signaling) is defined. start,u grid Starting N size,u grid，x *N RB sc subcarriers and N subframe，u symb OFDM symbol resource grid, where N Size,u grid,x is the number of resource blocks (RBs) in the resource grid, and the subscript x is DL for the downlink and UL for the uplink. N RB sc is the number of subcarriers per RB. In 3GPP-based wireless communication systems, N RB sc Typically 12. For a given antenna port p, subcarrier spacing configuration u, and transmission direction (DL or UL), there is one resource grid. The carrier bandwidth N for subcarrier spacing configuration u size,u grid Given by high-level parameters (e.g., RRC parameters). Each element in the resource grid for antenna port p and subcarrier spacing configuration u is called a resource element (RE), and one complex symbol can be mapped to each RE. Each RE in the resource grid is uniquely identified by an index k in the frequency domain and an index 1 in the time domain that represents the symbol position relative to a reference point. In a 3GPP-based wireless communication system, an RB is defined by 12 consecutive subcarriers in the frequency domain. Figure 6As shown in the figure, as the SCS is doubled, the slot length and symbol length are halved. For example, when the SCS is 15kHz, the slot length is 1ms, which is the same as the subframe length. When the SCS is 30kHz, the slot length is 0.5ms (=500us), and the symbol length is half of the symbol length when the SCS is 15kHz. When the SCS is 60kHz, the slot length is 0.25ms (=250us), and the symbol length is half of the symbol length when the SCS is 30kHz. When the SCS is 120kHz, the slot length is 0.125ms (=125us), and the symbol length is half of the symbol length when the SCS is 60kHz. When the SCS is 240kHz, the slot length is 0.0625ms (=62.5us), and the symbol length is half of the symbol length when the SCS is 120kHz.

[0106] In the 3GPP NR system, RBs are classified into CRBs and physical resource blocks (PRBs). For subcarrier spacing configuration u, CRBs are numbered from 0 upwards in the frequency domain. The center of subcarrier 0 of CRB0 for subcarrier spacing configuration u coincides with "point A" used as a common reference point for the resource block grid. In the 3GPP NR system, PRBs are defined within a bandwidth part (BWP) and are numbered from 0 to N. size BWP,i -1 numbering, where i is the number of bandwidth parts. Physical resource blocks n in bandwidth part i PRB With public resource block n CRB The relationship between them is as follows: PRB =n CRB +N size BWP,i , where N size BWP，i A BWP is a common resource block where the bandwidth portion begins relative to CRB0. A BWP consists of multiple contiguous RBs. A carrier can include up to N (e.g., 5) BWPs. A UE can be configured with one or more BWPs on a given component carrier. Only one BWP configured for a UE can be active at a time. The active BWP defines the UE's operating bandwidth within the cell's operating bandwidth.

[0107] In the present disclosure, the term "cell" may refer to a geographical area in which one or more nodes provide a communication system or to a radio resource. A "cell" as a geographical area may be understood as a coverage area within which a node can provide services using a carrier, and a "cell" as a radio resource (e.g., a time-frequency resource) is associated with a bandwidth that is a frequency range configured by a carrier. A "cell" associated with a radio resource is defined by a combination of downlink resources and uplink resources (e.g., a combination of a DL component carrier (CC) and a ULCC). A cell may be configured only by downlink resources, or may be configured by downlink resources and uplink resources. Since the DL coverage (which is the range within which a node can send a valid signal) and the UL coverage (which is the range within which a node can receive a valid signal from a UE) depend on the carrier that carries the signal, the coverage of a node may be associated with the coverage of a "cell" of the radio resource used by the node. Therefore, the term "cell" may sometimes be used to refer to the service coverage of a node, at other times to refer to a radio resource, or at other times to refer to a range within which a signal using a radio resource can reach with effective strength.

[0108] In CA, two or more CCs are aggregated. The UE can receive or transmit on one or more CCs simultaneously depending on its capabilities. CA is supported for both contiguous CCs and non-contiguous CCs. When CA is configured, the UE has only one RRC connection with the network. During RRC connection establishment / reestablishment / handover, one serving cell provides NAS mobility information, and during RRC connection reestablishment / handover, one serving cell provides security input. This cell is called a primary cell (PCell). A PCell is a cell operating on the primary frequency, where the UE performs an initial connection establishment procedure or initiates a connection reestablishment procedure. Depending on the UE capabilities, a secondary cell (SCell) can be configured to form a set of serving cells together with the PCell. An SCell is a cell that provides additional radio resources on top of a special cell (SpCell). Therefore, the set of serving cells configured for a UE always consists of one PCell and one or more SCells. For dual connectivity (DC) operation, the term SpCell refers to the PCell of a primary cell group (MCG) or the primary SCell (PSCell) of a secondary cell group (SCG). SpCell supports PUCCH transmission and contention-based random access and is always activated. MCG is a group of serving cells associated with a master node, which includes SpCell (PCell) and optionally one or more SCells. For UEs configured with DC, SCG is a subset of serving cells associated with a secondary node, which includes PSCell and zero or more SCells. For RRCCONNECTED UEs not configured with CA / DC, there is only one serving cell consisting of PCell. For RRCCONNECTED UEs configured with CA / DC, the term "serving cell" is used to refer to a set of cells consisting of SpCell and all SCells. In DC, two MAC entities are configured in the UE: one for MCG and one for SCG.

[0109] Figure 7 An example of data flow in a 3GPP NR system to which an implementation of the present disclosure is applied is shown.

[0110] Reference Figure 7 "RB" stands for radio bearer, and "H" stands for header. Radio bearers are categorized into two groups: DRBs for user plane data and SRBs for control plane data. MAC PDUs are transmitted and received to and from external devices via the PHY layer using radio resources. MAC PDUs arrive at the PHY layer in the form of transport blocks.

[0111] In the PHY layer, the uplink transport channel UL-SCH and the random access channel (RACH) are mapped to their physical channels (physical uplink shared channel (PUSCH) and physical random access channel (PRACH)), and the downlink transport channels DL-SCH, BCH and PCH are mapped to the physical downlink shared channel (PDSCH), physical broadcast channel (PBCH) and PDSCH, respectively. In the PHY layer, uplink control information (UCI) is mapped to the physical uplink control channel (PUCCH), and downlink control information (DCI) is mapped to the physical downlink control channel (PDCCH). The UE transmits MAC PDUs related to the UL-SCH via the PUSCH based on the UL grant, and the BS transmits MAC PDUs related to the DL-SCH via the PDSCH based on the DL assignment.

[0112] Hereinafter, contents regarding mobility are described.

[0113] Mobility may include PCell change, PSCell change (or Secondary Node (SN) change) and / or PSCell addition (or SN addition).

[0114] There may be at least two types of mobility: network-controlled mobility (or, legacy mobility) and UE-based mobility (or, conditional mobility).

[0115] Network-controlled mobility (or legacy mobility) is when the network determines a target cell for mobility and configures the UE with mobility for the target cell. The network may send an RRCReconfiguration message to the UE including the configuration for the target cell. Upon receiving the cell configuration for the target cell, the UE may perform mobility to the target cell / apply the configuration for the target cell.

[0116] UE-based mobility (or conditional mobility) is a mobility in which the network configures multiple candidate cells for the UE and the UE determines a target cell that meets the mobility execution condition among the multiple candidate cells. The network may send an RRCReconfiguration message including a ConditionalReconfiguration information element (IE) with a conditional reconfiguration list for multiple candidate cells to the UE. The conditional reconfiguration for the candidate cell may include an identifier of the conditional reconfiguration, a mobility execution condition for the candidate cell, and a configuration for the candidate cell. The UE may evaluate the mobility execution condition for the multiple candidate cells, and when the mobility execution condition for the candidate cell is met, the UE may regard the candidate cell as the target cell and perform mobility to the target cell / apply the configuration for the target cell.

[0117] In the present disclosure, the term "handover (HO)" may mean a PCell change, or may be a broad concept including not only a PCell change but also a PSCell change / addition.

[0118] In this disclosure, the terms "handover", "mobility" and "cell handover" may be used interchangeably.

[0119] In the present disclosure, the description about handover may also be applied to other mobility procedures (eg, PSCell change / addition).

[0120] Hereinafter, L1 / L2-Triggered Mobility (LTM) is described.

[0121] LTM is the process by which the gNB receives L1 measurement reports from the UE and, based on these reports, changes the UE's serving cell via MAC CE. The gNB prepares one or more candidate cells and provides the candidate cell configurations to the UE via RRC messages. LTM cell handover is then triggered by the gNB selecting one of the candidate configurations as the target configuration for LTM. Candidate cell configurations can only be added, modified, and released by the network via RRC signaling.

[0122] The LTM candidate cells may be configured via an RRCReconfiguration message for the candidate target cells and / or a CellGroupConfig IE for each candidate target cell.

[0123] The following principles can be applied to LTM:

[0124] -Candidate cell configurations may be provided as delta configurations on a reference configuration. The reference configuration is managed separately, and the UE stores the reference configuration as a separate configuration.

[0125] - Whenever possible (eg within a distributed unit DU), continue the user plane without a reset, where the goal is to avoid data loss and additional delays in data recovery.

[0126] - Security is not updated in LTM.

[0127] - Subsequent LTM between candidates can be performed without RRC reconfiguration (ie after triggering LTM, the UE does not release other candidate cell configurations).

[0128] LTM supports intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. LTM also supports inter-frequency mobility, including mobility to an inter-frequency cell that is not the current serving cell. The following scenarios are supported:

[0129] - PCell changes in non-CA scenarios,

[0130] - PCell change without SCell change in CA scenario,

[0131] - PCell change with SCell change in CA scenario, including the following cases:

[0132] a) The target PCell / target SCell is not the current serving cell (CA to CA scenario with PCell change)

[0133] b) The target PCell is the current SCell

[0134] c) The target SCell is the current PCell.

[0135] - Dual connectivity scenarios, at least for PSCell changes without MN participation (ie, intra-SN).

[0136] Inter-cell beam management is also supported but is not considered a prerequisite for using LTM.

[0137] The design of L1 / L2-based mobility within and between DUs should share commonality as much as possible.

[0138] In some implementations, upon receiving a candidate cell configuration, a validity / compliance check of the candidate cell configuration is performed.

[0139] The cell handover trigger information is transmitted in a MAC CE containing at least a candidate configuration index. Cell-specific radio bearer and measurement configurations may be part of the LTM candidate cell configuration.

[0140] In some implementations, the MAC CE may indicate the TCI state (or other beam information) to be activated for the target cell.

[0141] In some implementations, SCell activation / deactivation may be performed concurrently with LTM triggering MAC CE (among SCells associated with the candidate configuration).

[0142] The UE can perform contention-based random access (CBRA) or contention-free random access (CFRA) during cell handover. If the UE does not need to acquire the timing advance (TA) for the target cell during cell handover, the UE can also skip the random access procedure. RACH resources for CFRA are provided in the RRC configuration.

[0143] In some implementations, CFRA resources may be provided via a MAC CE.

[0144] The whole process for LTM is as follows Figure 8Subsequent LTMs are completed by repeating the early synchronization, LTM execution, and LTM completion steps without releasing other candidates after each LTM is completed.

[0145] Figure 8 An example of a signaling procedure for LTM according to an embodiment of the present disclosure is shown.

[0146] Reference Figure 8 In step S801, the UE may send a MeasurementReport message to the gNB.

[0147] In step S803, the gNB may decide to use LTM and initiate LTM candidate preparation.

[0148] In step S805, the gNB may send an RRCReconfiguration message including the configuration of one or more LTM candidate target cells to the UE.

[0149] In step S807, the UE may store the configuration of the LTM candidate target cell and send an RRCReconfigurationComplete message to the gNB.

[0150] In some implementations, the UE may optionally perform early synchronization. In this case, the UE may perform DL synchronization and / or TA acquisition with the candidate target cell before receiving the LTM cell handover command.

[0151] For example, DL synchronization for candidate cells prior to a cell handover command may be supported based at least on SSB.

[0152] For example, TA acquisition of candidate cells before an LTM cell handover command may be supported at least based on RACH of a PDCCH command, wherein the PDCCH command is triggered only by the source cell.

[0153] In step S809, the UE may perform L1 measurement on the configured LTM candidate target cell and send a lower layer measurement report to the gNB. The lower layer measurement report may be carried on L1 or MAC.

[0154] In step S811, the gNB may decide to perform LTM cell handover to the target cell.

[0155] In step S813, the gNB may send a MAC CE triggering LTM cell handover by including the candidate configuration index of the target cell. The UE may switch to the configuration of the LTM candidate target cell.

[0156] At step S815, the UE may detach from the source cell and apply the target cell configuration. If the TA is not available, the UE may perform a random access procedure (or RACH procedure) toward the target cell.

[0157] At step S817 , the UE may indicate successful completion of the LTM cell handover towards the target cell.

[0158] In some implementations, an uplink signal or message after the UE has switched to the target cell may be used to indicate successful completion of the LTM cell handover.

[0159] exist Figure 8 In the RACH-skip condition, when the RACH-skip condition is met, the RACH procedure can be skipped (i.e., the UE can perform RACH-free mobility to the target cell). The RACH-skip condition may include one or more of the following conditions:

[0160] - The TA information of the target cell is available to the UE and / or the TA of the target cell is valid;

[0161] - a beam indication of the target cell is available to the UE and / or no beam failure is detected on the target cell; or

[0162] - An uplink (UL) grant for sending an uplink signal indicating successful completion of LTM cell handover is available to the UE.

[0163] When performing a random access procedure / RACH procedure: i) if CFRA resources / dedicated RACH configuration are available for the UE, the UE may perform contention-free random access (CFRA); and ii) if CFRA resources / dedicated RACH configuration are not available for the UE, the UE may perform contention-based random access (CBRA). The specific CBRA procedure and CFRA procedure are described in Figure 9 and 10 Shown in.

[0164] Figure 9 An example of a CBRA process according to an embodiment of the present disclosure is shown.

[0165] Reference Figure 9 In step S901, the UE may send a random access preamble to the RAN node in the uplink. The UE may send a message 1 (MSG1) including the random access preamble to the RAN node. The random access preamble may be associated with a random access-radio resource temporary identifier (RA-RNTI). The random access preamble may be selected based on a selected RACH resource and sent via a time / frequency resource identified by the selected RACH resource.

[0166] In step S903, the UE may receive a random access response (RAR) generated by the MAC from the RAN node on a downlink shared channel (DL-SCH). The UE may receive a message 2 (MSG2) including the RAR from the RAN node. The UE may monitor the PDCCH with the corresponding RA-RNTI within the RAR window. When a PDCCH with the corresponding RA-RNTI is detected within the RAR window, the UE may read the corresponding downlink control information (DCI) scheduling the RARPDSCH and receive the RAR in the PDSCH. The RAR may include timing advance (TA) information for time synchronization in the uplink, UL grant, and / or temporary cell-RNTI (TC-RNTI).

[0167] At step S905, the UE may send a device identification message to the RAN node. The UE may send a message 3 (MSG3) including the device identification message via a PUSCH corresponding to the UL grant in the RAR. The device identification message may include a TC-RNTI.

[0168] At step S907, the UE may receive a contention resolution message from the RAN node. The UE may receive Message 4 (MSG4) including the contention resolution message. The UE may monitor the PDCCH with the TC-RNTI. Upon detecting the PDCCH with the TC-RNTI, the UE may read the corresponding DCI scheduling the PDSCH, receive the contention resolution message in the PDSCH, and set the C-RNTI to the TC-RNTI.

[0169] Figure 10 An example of a CFRA process according to an embodiment of the present disclosure is shown.

[0170] Reference Figure 10 In step S1001, the UE may send a dedicated random access preamble to the RAN node in the uplink. The UE may send a message 1 (MSG1) including the dedicated random access preamble to the RAN node. The dedicated random access preamble may be associated with a random access-radio resource temporary identifier (RA-RNTI). The dedicated random access preamble may be selected based on a CFRA resource / dedicated RACH configuration and sent via the time / frequency resources identified by the CFRA resource / dedicated RACH configuration.

[0171] In step S1003, the UE may receive a random access response (RAR) generated by the MAC from the RAN node on the downlink shared channel (DL-SCH). The UE may receive a message 2 (MSG2) including the RAR from the RAN node. The UE may monitor the PDCCH with the corresponding RA-RNTI within the RAR window. When the PDCCH with the corresponding RA-RNTI is detected within the RAR window, the UE may read the corresponding downlink control information (DCI) scheduling the RARPDSCH and receive the RAR in the PDSCH. The RAR may include timing advance (TA) information for time synchronization in the uplink, UL grant, and / or cell-RNTI (C-RNTI). Upon receiving the RAR from the RAN node, the UE may terminate the CFRA procedure.

[0172] In addition, L1 / L2 triggered mobility (LTM) is introduced to reduce latency, overhead and interruption time. For LTM, the network can provide the UE with the configuration of candidate cells in advance (i.e., pre-configuration of candidate cells for LTM). The UE can then perform L1 measurement of the candidate cell and perform L1 measurement reporting (i.e., report the measurement results for the candidate cell to the network). The network can determine that the UE performs LTM to the candidate cell based on the L1 measurement report. The network can send an LTM command (or a cell switching command) to the UE via L1 / L2 signaling to trigger the UE to perform LTM toward the candidate cell. Upon receiving the LTM command, the UE can initiate a cell switching process (i.e., LTM execution to the candidate cell), wherein the cell switching process is supervised by a timer. The specific cell switching process supervised by the timer can be as follows: i) when the UE initiates the LTM execution process, the timer starts; ii) when the LTM execution is successfully completed, the timer stops; and iii) when the timer expires, the UE detects the failure of the LTM execution.

[0173] LTM can be performed in two types: i) Random Access Channel (RACH)-based LTM execution, in which a random access (RA) procedure is performed during LTM execution; and ii) RACH-free LTM execution, in which no RA procedure is performed during LTM execution. RACH-based LTM execution can be further divided into two types: contention-based random access (CBRA) and contention-free random access (CFRA).

[0174] If the network configures an incorrect timer value for the LTM execution procedure for the UE, the UE may detect the LTM failure too early or too late (i.e., the LTM failure early / late detection problem). The LTM failure early detection problem may cause false failure detections, while the LTM failure late detection may increase mobility interruption time. If a timer value that assumes RACH-free LTM execution (i.e., a small timer value) is configured, when RACH-based LTM execution is performed, LTM failure may be detected too early because the timer value is too small to wait for RA completion even if a normal RACH procedure is in progress. When RACH-free LTM execution is performed using a timer value that assumes RACH-based LTM execution (i.e., a large timer value), LTM failure may be detected too late because the timer is still running even though the LTM execution has failed.

[0175] In this disclosure, "cell handover" and "LTM execution" may be used interchangeably.

[0176] In this disclosure, "cell handover failure" and "LTM failure" may be used interchangeably.

[0177] In this disclosure, "cell switching command" and "LTM command" may be used interchangeably.

[0178] In this disclosure, "LTM timer" and "failure detection timer" may be used interchangeably.

[0179] In the present disclosure, "mobility execution type", "cell handover type", "type of cell handover" and "LTM execution type" may be used interchangeably.

[0180] Figure 11 An example of a method performed by a UE according to an embodiment of the present disclosure is shown. The method may also be performed by a wireless device.

[0181] Reference Figure 11 In step S1101, the UE may receive a message from the network, the message including a configuration of candidate cells for cell handover and multiple timer values ​​for detecting cell handover failure. Each of the multiple timer values ​​may be associated with a corresponding cell handover type.

[0182] In step S1103 , the UE may receive a cell handover command for a candidate cell from the network.

[0183] In step S1105 , the UE may initiate a cell handover to a candidate cell based on the cell handover command.

[0184] In step S1107 , when the UE initiates a cell handover, the UE may start a timer having a timer value related to a cell handover type of the cell handover to be performed among a plurality of timer values.

[0185] In step S1109 , the UE may perform cell handover to the candidate cell while the timer is running.

[0186] According to various embodiments, the message may include multiple configurations for candidate cells for cell handover, the multiple configurations including a configuration for the candidate cell. Each of the multiple configurations may be associated with a corresponding candidate cell and include a candidate configuration index for the configuration of the corresponding candidate cell. The cell handover command may include a candidate configuration index for the configuration of the candidate cell. The UE may identify a configuration for the candidate cell having a matching candidate configuration index in the cell handover command among the multiple configurations for the candidate cell. The UE may apply the identified configuration for the candidate cell to perform cell handover to the candidate cell.

[0187] According to various embodiments, the plurality of configurations for the candidate cells may be received via radio resource control (RRC) signaling.The cell handover command may be received via medium access control (MAC) control element (CE) signaling.

[0188] According to various embodiments, a UE may obtain a list of candidate cell configurations for failure recovery from among multiple configurations of candidate cells for cell handover. Upon expiration of a timer, the UE may detect a cell handover failure. Based on the candidate cell configurations in the list of candidate cell configurations, the UE may perform a failure recovery procedure on the candidate cell associated with the candidate cell configuration.

[0189] According to various embodiments, the list of candidate cell configurations may be included in at least one of a message, a configuration for a candidate cell, or a cell handover command.

[0190] According to various embodiments, the configuration for the candidate cell may include multiple timer values ​​for a timer used to detect cell handover failure.

[0191] According to various embodiments, the cell handover type includes at least one of a random access channel (RACH)-free cell handover or a RACH-based cell handover. The multiple timer values ​​may include at least one of: a first timer value associated with a RACH-free cell handover; or a second timer value associated with a RACH-based cell handover. The RACH-free cell handover may include skipping random access to a candidate cell while a timer with the first timer value is running. The RACH-based cell handover may include performing contention-free random access (CFRA) or contention-based random access (CBRA) on the candidate cell while a timer with the second timer value is running.

[0192] According to various embodiments, the cell handover type may include at least one of the following: random access channel (RACH)-free cell handover, contention-free random access (CFRA)-based cell handover, or contention-based random access (CBRA)-based cell handover. The multiple timer values ​​may include at least one of the following: a first timer value associated with RACH-free cell handover; a second timer value associated with CFRA-based cell handover; or a third timer value associated with CBRA-based cell handover. The RACH-free cell handover may include skipping random access to a candidate cell while a timer with the first timer value is running. The CFRA-based cell handover may include performing CFRA on the candidate cell while a timer with the second timer value is running. The CBRA-based cell handover may include performing CBRA on the candidate cell while a timer with the third timer value is running.

[0193] According to various embodiments, a UE may determine a cell handover type based on at least one of a random access channel (RACH) skip condition or whether contention-free random access (CFRA) resources are available to the UE. The UE may determine a timer value associated with the determined cell handover type. The RACH skip condition includes at least one of the following: a condition that timing advance (TA) information for a candidate cell and a beam indication for the candidate cell are included in a cell handover command; a condition that the TA for the candidate cell is valid; or a condition that no beam failure is detected on the candidate cell.

[0194] According to various embodiments, the cell handover type may include at least one of a random access channel (RACH)-free cell handover or a RACH-based cell handover. Based on satisfying a RACH skipping condition, the cell handover type may be determined as a RACH-free cell handover. Based on not satisfying the RACH skipping condition, the cell handover type may be determined as a RACH-based cell handover.

[0195] According to various embodiments, the cell handover type may include at least one of the following: random access channel (RACH)-free cell handover, contention-free random access (CFRA)-based cell handover, or contention-based random access (CBRA)-based cell handover. Based on satisfying a RACH-skipping condition, the cell handover type may be determined as RACH-free cell handover. Based on not satisfying the RACH-skipping condition and CFRA resources being available for the UE, the cell handover type may be determined as CFRA-based cell handover. Based on not satisfying the RACH-skipping condition and CFRA resources being unavailable for the UE, the cell handover type may be determined as CBRA-based cell handover.

[0196] According to various embodiments, the cell handover may include Layer 1 (L1) / Layer 2 (L2) Triggered Mobility (LTM).The cell handover command may include an LTM command.

[0197] Figure 12 An example of a signal flow between a UE and a network node according to an embodiment of the present disclosure is shown. The network node may include a base station (BS) and may be associated with a source cell in a cell handover.

[0198] Reference Figure 12 In step S1201, the network node may send a message to the UE, the message including configurations of candidate cells including candidate cell 1 and candidate cell 2 and timer values ​​of a timer for cell handover failure detection. Each timer value may be associated with a corresponding cell handover type.

[0199] At step S1203 , the network node may send a cell handover command including a candidate configuration index 1 for candidate cell 1 to the UE.

[0200] In step S1205 , the UE may initiate a cell handover to the candidate cell 1 based on the cell handover command.

[0201] In step S1207 , when the UE initiates a cell handover, the UE may start a timer having a timer value related to a cell handover type of the cell handover to be performed among a plurality of timer values.

[0202] In step S1209 , the UE may perform cell handover to the candidate cell 1 while the timer is running.

[0203] According to an implementation of the present disclosure, a network (NW) may configure two or more LTM timer values ​​to a UE before transmitting an LTM command to the UE or through an LTM command, wherein each timer value corresponds to an LTM execution type. The LTM execution type may be LTM execution based on RACH (i.e., CBRA or CFRA) or LTM execution without RACH. Upon receiving the LTM command, the UE may check one or more conditions to determine the LTM execution type, then initiate an LTM execution process, and start a failure detection timer (i.e., an LTM timer) whose value corresponds to the LTM execution type. That is, for the timer value, a configuration value corresponding to the LTM execution type of the LTM execution process to be executed is applied. If the cell switching process is unsuccessful until the failure detection timer expires, the UE may perform a failure recovery process.

[0204] Figure 13 An example of a method for indicating a physical channel configuration in LTM according to an embodiment of the present disclosure is shown. The method may be performed by a UE and / or a wireless device.

[0205] Reference Figure 13 In step S1301, the UE may receive a message (i.e., an RRC message / configuration, such as an RRC reconfiguration message) including one or more candidate cell configurations (i.e., one or more configurations for candidate cells). In other words, one or more candidate serving cells may be configured. The (pre-)configuration of the candidate cells may include at least one of the following: a portion that the UE directly applies when LTM is executed; or another portion that the UE selectively applies based on an indication included in an LTM command when LTM is executed.

[0206] The candidate cell configuration (or configuration for a candidate cell) may include at least one of the following:

[0207] - Configuration for special cells, such as servingCellConfigCommon, servingCellConfig, reconfigurationWithSync, and RLF-related configurations;

[0208] - SCell-specific configuration, such as servingCellConfigCommon, servingCellConfig, smtc, DRX configuration; or

[0209] -MAC / RLC related configurations.

[0210] The candidate cell configuration may include a set of BWP configurations. For each BWP configuration, a flag may be included to indicate whether the UE should first apply the corresponding BWP configuration when executing LTM. Each BWP configuration may include a set of resource configurations, such as configurations for physical channels (i.e., a physical channel configuration set). For example, each BWP configuration may include at least one of a PUCCH configuration set, a PUSCH configuration set, a PDCCH configuration set, a PDSCH configuration set, or a PRACH configuration set. For each physical channel configuration in the set, a flag may be included to indicate whether the UE should first apply the corresponding physical channel configuration when executing LTM.

[0211] According to various embodiments, there may be one or more timer values ​​and / or one or more timer configurations. Each timer configuration (i.e., a configuration for a timer value) may include an identifier or index of the corresponding timer configuration and a corresponding timer value. During the cell handover process, the timer value may be used for a failure detection timer.

[0212] The timer value may correspond to which type of mobility to be performed / implemented during the cell handover procedure (i.e., the mobility execution type). For example, the mobility execution type may be divided into the following two types: i) RACH-based execution (i.e., performing an RA procedure during the cell handover procedure); and / or ii) RACH-free execution (i.e., not performing an RA procedure during the cell handover procedure). For another example, the mobility execution type may be divided into the following three types: i) CBRA-based execution (i.e., performing a CBRA procedure during the cell handover procedure); ii) CFRA-based execution (i.e., performing a CFRA procedure during the cell handover procedure); or iii) RACH-free execution (i.e., not performing an RA (i.e., CBRA or CFRA) procedure during the cell handover procedure).

[0213] In some implementations, one or more timer values ​​and / or one or more timer configurations may be included in a message including one or more candidate cell configurations (i.e., one or more configurations for a candidate cell). In this case, the one or more timer values ​​and / or one or more timer configurations may be common to the one or more candidate cell configurations / candidate cells.

[0214] In some implementations, one or more timer values ​​and / or one or more timer configurations may be included in each candidate cell configuration (i.e., a configuration for a candidate cell). In this case, the one or more timer values ​​and / or one or more timer configurations may be specific to the corresponding candidate cell configuration / candidate cell.

[0215] According to various embodiments, there may be a list of cells to be used for cell handover failure recovery. The list may contain indices of candidate cell configurations to be used for cell handover failure recovery. For example, upon cell handover failure detection, the cells in the list may be considered as new target cells for cell handover.

[0216] In some implementations, the cell list to be used for cell handover failure recovery may be included in a message including one or more candidate cell configurations (i.e., one or more configurations for candidate cells). In this case, the cell list to be used for cell handover failure recovery may be common to the one or more candidate cell configurations / candidate cells.

[0217] In some implementations, a list of cells to be used for cell handover failure recovery may be included in each candidate cell configuration (i.e., a configuration for a candidate cell). In this case, the list of cells to be used for cell handover failure recovery may be specific to the corresponding candidate cell configuration / candidate cell.

[0218] In step S1303, the UE may receive a cell handover command (i.e., an LTM command) indicating a candidate cell configuration (i.e., a configuration of a candidate cell). The cell handover command may be sent via L1 / L2 / L3 signaling. The cell handover command may be associated with a network-controlled serving cell change or a UE-autonomous serving cell change (e.g., conditional mobility).

[0219] The cell switching command may include at least one of the following:

[0220] - Target cell information: If the target cell is one of the pre-configured candidate serving cells for the UE, the target cell information may be the identifier of the candidate serving cell / candidate cell configuration indicated by the LTM command. Otherwise (i.e., the target cell is not one of the pre-configured candidate serving cells for the UE), the target cell information may be the configuration for the target cell / candidate cell configuration (e.g., RRCReconfiguration including reconfigurationWithSync).

[0221] -ConditionalReconfiguration, in case of conditional mobility.

[0222] - Indicator indicating that the source cell has been changed to a candidate serving cell: For example, this indicator may be a 1-bit indication in a DCI or MAC CE. For example, an LTM command via L1 / L2 signaling may implicitly indicate that the source cell has been changed to a candidate serving cell. For example, the target cell may be included in a list, where the list may indicate that the source cell has been changed to a candidate serving cell. For example, the indicator may be an explicit RRC Information Element (IE).

[0223] -Cell handover parameters (i.e., configurations applied by the UE when LTM is executed): For example, the cell handover parameters may include a physical channel configuration index indicating a PRACH configuration, a PUCCH configuration, a PUSCH configuration, a PDCCH configuration, and / or a PDSCH configuration. The cell handover parameters may include a DL / UL BWP index, SCell state, TA information, TCI state, an indication for L2 operation (e.g., PDCP resumption / RLC re-establishment / MAC (full or partial) reset), SSB / CSI-RS, and / or an indication of whether the UE performs random access when LTM is executed.

[0224] The cell handover command may include a timer value to be used for the failure detection timer during the cell handover procedure. The cell handover command may include one or more identifiers (or indexes) indicating the configuration for the timer value. Alternatively, the cell handover command may include one or more timer values ​​to be used for the failure detection timer during the cell handover procedure.

[0225] The timer value may correspond to which type of mobility is executed / implemented during the cell handover procedure (i.e., the mobility execution type). For example, the mobility execution type may be divided into the following two types: RACH-based execution (i.e., performing an RA procedure during the cell handover procedure); and ii) RACH-free execution (i.e., not performing an RA procedure during the cell handover procedure). For another example, the mobility execution type may be divided into the following three types: i) CBRA-based execution (i.e., performing a CBRA procedure during the cell handover procedure); ii) CFRA-based execution (i.e., performing a CFRA procedure during the cell handover procedure); and iii) RACH-free execution (i.e., not performing an RA (i.e., CBRA or CFRA) procedure during the cell handover procedure).

[0226] The cell handover command may include a list of cells to be used for cell handover failure recovery. The list may contain indices of candidate cell configurations to be used for cell handover failure recovery. The cell handover command may need to include the cell handover parameters of the cell in the list. Upon cell handover failure detection, one of the cells in the list may be considered as the new target cell for cell handover.

[0227] In step S1305 , the UE may apply the candidate cell configuration indicated by the LTM command.

[0228] For example, if the received LTM command has ConditionalReconfiguration (ie, in case of conditional mobility), the UE may apply the stored configuration (eg, condRRCReconfig) of the cell that meets the execution condition.

[0229] For example, if the received LTM command does not have ConditionalReconfiguration (i.e., in the case of legacy mobility), the UE may apply the stored candidate cell configuration / candidate cell configuration indicated in the LTM command. If the LTM command includes cell handover parameters / configuration for the UE to apply when LTM is executed, the UE may selectively apply the preconfiguration indicated by the LTM command. For example, if the preconfiguration has a first PRACH configuration and a second PRACH configuration for the BWP, and if the LTM command indicates the first PRACH configuration, the UE applies the first PRACH configuration instead of the second PRACH configuration for the PRACH configuration. Otherwise, if the LTM command does not include a configuration for the UE to apply when LTM is executed, the UE may directly apply the preconfiguration of the candidate cell.

[0230] In step S1307, the UE may check one or more conditions to determine the LTM execution type. For example, the LTM execution type may be determined as follows:

[0231] If the beam indication and / or TA information of the candidate cell is included in the cell handover command, the LTM execution type may be determined as LTM execution without RACH.

[0232] -Otherwise, if the TA of the candidate cell is valid and there is no beam failure on the candidate cell (assuming that the TA of the candidate cell has been maintained based on the TA adjustment process and the beam failure detection process has been performed / monitored for the candidate cell), the LTM execution type can be determined as LTM execution without RACH.

[0233] Otherwise (i.e., if the cell handover command does not include the TA information and beam indication of the candidate cell, and if the TA of the candidate cell has not been maintained based on the TA adjustment process or the beam failure detection process has not been performed / monitored for the candidate cell or a beam failure has been detected on the candidate cell), the LTM execution type may be determined to be RACH-based LTM execution. If CFRA resources are indicated in the cell handover command or the configuration of the candidate cell, the LTM execution type may be determined to be CFRA-based LTM execution. Otherwise (i.e., CFRA resources are not indicated), the LTM execution type may be determined to be CBRA-based LTM execution.

[0234] In step S1309 , the UE may perform mobility by transmitting a UL signal to a candidate cell (ie, a target cell) and / or starting a failure detection timer having a timer value related to the LTM execution type.

[0235] In some implementations, the UE may send an UL signal / message to the candidate cell via L1 signaling (e.g., PUCCH, PUSCH, PRACH). If the UE is configured by (pre-) configuration of the candidate cell with a dedicated PRACH configuration (i.e., LTM execution based on CFRA), the UE may send an RA preamble to the candidate cell based on the (pre-) configured dedicated PRACH configuration. Otherwise, if the dedicated PRACH configuration of the candidate cell is indicated to the UE by an LTM command (i.e., LTM execution based on CFRA), the UE may send an RA preamble to the candidate cell based on the dedicated PRACH configuration indicated by the LTM command. Otherwise (i.e., the UE does not have a dedicated PRACH configuration), the UE may send an RA preamble to the candidate cell based on the (pre-) configured common PRACH configuration.

[0236] For example, in case of RACH-based LTM execution, the UE may send a random access (RA) preamble to the candidate cell.

[0237] For example, in case of LTM execution without RACH, the UE may send a scheduling request to the candidate cells.

[0238] In some implementations, the UE may send an UL signal to the candidate cell via L2 signaling (eg, MAC CE). For example, in the case of LTM execution without RACH, the UE may send an LTM complete MAC CE to the candidate cell indicating the UE's arrival.

[0239] In some implementations, the UE may send an UL signal to the candidate cell via L3 signaling (eg, RRCReconfigurationComplete).

[0240] The first UL signal may be transmitted on UL resources corresponding to the indicated physical channel configuration. For example, if the LTM command indicates a specific PRACH configuration, the UE may transmit an RA preamble corresponding to the indicated PRACH configuration. For example, if the LTM command does not include information about the physical channel configuration, and if the BWP configuration applied by the UE during LTM execution has a physical channel configuration, the UE may transmit the first UL signal on UL resources corresponding to the physical channel configuration in the BWP configuration.

[0241] In some implementations:

[0242] -If the mobility message (i.e., LTM command / cell handover command) is sent via L1 / L2 signaling, the UE can maintain the source resources and configuration, and / or perform TA maintenance and beam failure detection (BFD) / radio link monitoring (RLM) on the source cell / target cell.

[0243] If the mobility message includes an indicator indicating that the source cell is changed to a candidate serving cell, the UE may maintain the source resources and configuration, and / or perform TA maintenance and BFD / RLM on the source cell / target cell.

[0244] - Otherwise, the UE may release the source resources and configuration and / or stop DL / UL reception / transmission with the source cell.

[0245] If a cell list to be used for cell handover failure recovery is configured, the UE may start measuring the cells in the list. The measurement may include at least one of L1 measurement or L2 measurement.

[0246] When initiating execution of mobility, the UE may start a failure detection timer with a timer value.

[0247] For example, the cell handover command may include a single instruction for setting a timer value. In this case, the timer value for expiration may be set to the value indicated by the cell handover command.

[0248] For example, the cell handover command may include two instructions for setting a timer value, one of which indicates an instruction for RACH-free LTM execution and the other indicates an instruction for RACH-based LTM execution. If the LTM execution type is determined to be RACH-free LTM execution, the timer value for expiration may be set to a value corresponding to the RACH-free LTM execution indicated by the cell handover command. Otherwise, if the LTM execution type is determined to be RACH-based (i.e., CFRA or CBRA) LTM execution, the timer value for expiration may be set to a value corresponding to the RACH-based LTM execution indicated by the cell handover command.

[0249] For example, the cell handover command may include three instructions for setting a timer value, one of which indicates LTM execution without RACH, another indicates LTM execution based on CFRA, and another indicates LTM execution based on CBRA. If the LTM execution type is determined to be LTM execution without RACH, the timer value for expiration may be set to a value corresponding to the LTM execution without RACH indicated by the cell handover command. Otherwise, if the LTM execution type is determined to be LTM execution based on CFRA, the timer value for expiration may be set to a value corresponding to the LTM execution based on CFRA indicated by the cell handover command. Otherwise, if the LTM execution type is determined to be LTM execution based on CBRA, the timer value for expiration may be set to a value corresponding to the LTM execution based on CBRA indicated by the cell handover command.

[0250] For example, the cell handover command may not include any indication for setting a timer value, and the configuration of the candidate cell may include two indications for setting a timer value, one of which indicates for RACH-free LTM execution and the other indicates for RACH-based LTM execution. In this case, if the LTM execution type is determined to be RACH-free LTM execution, the timer value for expiration is set to a value corresponding to the RACH-free LTM execution indicated by the configuration of the candidate cell, and if the LTM execution type is determined to be RACH-based (i.e., CFRA or CBRA) LTM execution, the timer value for expiration is set to a value corresponding to the RACH-based LTM execution indicated by the configuration of the candidate cell.

[0251] For example, the cell handover command may not include any instructions for setting a timer value, and the configuration of the candidate cell may include three instructions for setting timer values, one of which indicates LTM execution without RACH, another indicates LTM execution based on CFRA, and another indicates LTM execution based on CBRA. In this case, if the LTM execution type is determined to be LTM execution without RACH, the timer value for expiration may be set to a value corresponding to LTM execution without RACH indicated by the configuration of the candidate cell. Otherwise, if the LTM execution type is determined to be LTM execution based on CFRA, the timer value for expiration may be set to a value corresponding to LTM execution based on CFRA indicated by the configuration of the candidate cell. Otherwise, if the LTM execution type is determined to be LTM execution based on CBRA, the timer value for expiration may be set to a value corresponding to LTM execution based on CBRA indicated by the configuration of the candidate cell.

[0252] In step S1311, the UE may perform a failure recovery procedure when the failure detection timer expires. That is, if the cell handover procedure is unsuccessful (ie, cell handover failure detection) until the failure detection timer expires, the UE may perform a failure recovery procedure.

[0253] Upon cell handover failure detection, one of the cells in the cell list to be used for cell handover failure recovery given / configured by the candidate cell configuration and / or the cell handover command may be considered as a new target cell for cell handover.

[0254] For example, if the UE has valid measurement results for the cells in the list, the UE may consider the cell with the best performance as the new target cell and initiate a cell handover procedure by applying the configuration of the new target cell, which may be provided by the configuration for the candidate cells and / or the cell handover command.

[0255] For example, if the UE does not have valid measurement results for a cell in the list, the UE may consider one of the cells in the list as a new target cell and initiate a cell handover procedure by applying the configuration of the new target cell, which may be provided by the configuration for the candidate cell and / or the cell handover command.

[0256] If the cell list to be used for cell handover failure recovery is not configured for the UE, the UE may initiate an RRC connection reestablishment procedure.

[0257] In the present disclosure, a UE may receive an RRC configuration for a candidate cell. The RRC configuration may include two or more timer values ​​for a cell handover failure detection timer. The UE may receive a cell handover command for a target cell. The UE may perform a cell handover procedure to the target cell. The UE may start a cell handover failure detection timer. The value of the cell handover failure detection timer may be set to one of the configured timer values ​​based on whether random access to the target cell can be skipped or should be performed. If the cell handover procedure is successful, the UE may stop the cell handover failure detection timer. If the cell handover failure detection timer expires, the UE may perform a failure recovery procedure.

[0258] The RRC configuration may include a list of cells to be used for failure recovery.

[0259] If two timer values ​​for RACH-free cell switching and RACH-based cell switching, respectively, are received / configured, the value of the cell switching failure detection timer may be set to one of the two timer values ​​based on whether an RA procedure is performed during the cell switching procedure.

[0260] If three timer values ​​for CBRA-based cell handover, CFRA-based cell handover, and RACH-free cell handover, respectively, are received, the value of the cell handover failure detection timer may be set to one of the three timer values ​​based on whether a CBRA procedure is performed, a CFRA procedure is performed, or RA is skipped during the cell handover procedure;

[0261] If the TA information and / or beam indication of the candidate cell is included in the cell handover command, RACH-free cell handover can be performed.

[0262] If the candidate TA has been maintained based on the TA adjustment procedure and / or the beam failure detection procedure has been performed / monitored for the candidate cell, RACH-free cell switching can be performed.

[0263] If the TA information and beam indication of the candidate cell are not included in the cell switching command, and if the TA of the candidate cell has not been maintained based on the TA adjustment process or the beam failure detection process has not been performed / monitored for the candidate cell or beam failure has been detected on the candidate cell, RACH-based cell switching can be performed.

[0264] If RACH-based cell switching is determined and if a dedicated RACH configuration is available, CFRA-based cell switching may be performed.

[0265] If RACH-based cell switching is determined and if a dedicated RACH configuration is not available, CBRA-based cell switching may be performed.

[0266] The cell handover command may include a list of cells to be used for failure recovery.

[0267] When cell handover is performed according to a cell handover command, the candidate cell may become a new serving cell.

[0268] If a list of cells to be used for failure recovery is received, one of the cells in the list may be considered as a new target cell for failure recovery.

[0269] If a new target cell is selected from the list of cells to be used for failure recovery, a cell handover procedure towards the new target cell may be initiated.

[0270] If a cell list to be used for failure recovery is not received, an RRC connection re-establishment procedure may be initiated.

[0271] In addition, in this disclosure (for example, Figure 11 The method described from the perspective of UE can be Figure 2 The first wireless device 100 and / or Figure 3 The UE 100 shown in FIG.

[0272] More specifically, the UE includes at least one transceiver, at least one processor, and at least one computer memory operatively connected to the at least one processor and storing instructions that perform operations upon execution by the at least one processor.

[0273] The operations include: receiving a message from a network, the message including a configuration for a candidate cell for cell handover and a plurality of timer values ​​for a timer for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; receiving a cell handover command for the candidate cell from the network; initiating a cell handover to the candidate cell based on the cell handover command, wherein a timer having a timer value among the plurality of timer values ​​is started when the UE initiates the cell handover, and the timer value is associated with the cell handover type of the cell handover to be performed; and performing the cell handover to the candidate cell while the timer is running.

[0274] In addition, in this disclosure (for example, Figure 11 The method described in the perspective of the UE can be stored in Figure 2 The software code 105 in the memory 104 in the first wireless device 100 is shown to be executed.

[0275] More specifically, at least one computer-readable medium (CRM) stores instructions that perform operations based on being executed by at least one processor, the operations including: receiving a message from a network, the message including a configuration for a candidate cell for cell switching and multiple timer values ​​for a timer for detecting cell switching failure, wherein each of the multiple timer values ​​is associated with a corresponding cell switching type; receiving a cell switching command for the candidate cell from the network; initiating a cell switching to the candidate cell based on the cell switching command, wherein a timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell switching, and the timer value is associated with the cell switching type of the cell switching to be performed; and performing the cell switching to the candidate cell while the timer is running.

[0276] In addition, in this disclosure (for example, Figure 11 The method described from the perspective of the UE can be achieved by including Figure 2 The processor 102 in the first wireless device 100 shown is controlled and / or includes Figure 3 The execution is performed under the control of the processor 102 in the UE 100 shown.

[0277] More specifically, an apparatus configured / adapted to operate in a wireless communication system (e.g., a wireless device / UE) includes at least one processor and at least one computer memory operatively connected to the at least one processor. The at least one processor is configured / adapted to perform operations, the operations including: receiving a message from a network, the message including a configuration for a candidate cell for cell handover and a plurality of timer values ​​for a timer for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; receiving a cell handover command for the candidate cell from the network; initiating a cell handover to the candidate cell based on the cell handover command, wherein a timer having a timer value among the plurality of timer values ​​is started when the UE initiates the cell handover, and the timer value is associated with the cell handover type of the cell handover to be performed; and performing the cell handover to the candidate cell while the timer is running.

[0278] In addition, in this disclosure (for example, Figure 12 The method described in the perspective of a network node associated with a source cell in a cell handover can be implemented by Figure 2 The second wireless device 200 shown in FIG.

[0279] More specifically, the network node includes at least one transceiver, at least one processor, and at least one computer memory operatively connected to the at least one processor and storing instructions that perform operations upon execution by the at least one processor.

[0280] The operations include: sending a message to a user equipment (UE), the message including a configuration for a candidate cell for cell handover and a plurality of timer values ​​for a timer for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; and sending a cell handover command for the candidate cell to the UE, wherein the cell handover to the candidate cell is initiated based on the cell handover command, wherein a timer having a timer value among the plurality of timer values ​​is started when the UE initiates the cell handover, and the timer value is associated with the cell handover type of the cell handover to be performed, and wherein the cell handover to the candidate cell is performed while the timer is running.

[0281] The present disclosure may have various beneficial effects.

[0282] For example, according to the present disclosure, during a cell handover process, the UE can apply an appropriate failure detection timer value based on whether an RA process is performed. Thus, the problem of premature / late detection of LTM failure can be solved.

[0283] The beneficial effects that can be obtained by the specific embodiments of the present disclosure are not limited to the beneficial effects listed above. For example, there may be various technical effects that can be understood and / or derived from the present disclosure by a person of ordinary skill in the relevant art. Therefore, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that can be understood or derived from the technical features of the present disclosure.

[0284] The claims in this disclosure may be combined in various ways. For example, the technical features in the method claims of this disclosure may be combined to be implemented or performed in a device, and the technical features in the device claims may be combined to be implemented or performed in a method. Furthermore, the technical features in the method claims and the device claims may be combined to be implemented or performed in a device. Furthermore, the technical features in the method claims and the device claims may be combined to be implemented or performed in a method. Other implementations are within the scope of the appended claims.

Claims

1. A method performed by a user equipment (UE) configured to operate in a wireless communication system, the method comprising the following steps: receiving a message from a network, the message including a configuration of a candidate cell for cell handover and a plurality of timer values ​​for a timer for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; receiving a cell handover command for the candidate cell from the network; initiating the cell handover to the candidate cell based on the cell handover command, wherein the timer having the timer value among the plurality of timer values ​​is started when the UE initiates the cell handover, and the timer value is related to a cell handover type of the cell handover to be performed; and The cell handover to the candidate cell is performed while the timer is running.

2. The method according to claim 1, wherein The message includes a plurality of configurations for candidate cells for the cell handover, the plurality of configurations including the configuration for the candidate cell, Each of the plurality of configurations is associated with a corresponding candidate cell and includes a candidate configuration index for the configuration of the corresponding candidate cell. The cell switching command includes a candidate configuration index for the configuration of the candidate cell, The method further comprises the following steps: identifying, among the multiple configurations for the candidate cell, the configuration for the candidate cell having a matching candidate configuration index in the cell handover command, and The step of performing the cell handover includes: applying the identified configuration for the candidate cell.

3. The method according to claim 2, wherein: The plurality of configurations for the candidate cells are received via radio resource control (RRC) signaling, and The cell switching command is received via medium access control MAC control element CE signaling.

4. The method according to claim 2, further comprising the steps of: obtaining a list of candidate cell configurations for failure recovery among the plurality of configurations of the candidate cells for the cell handover; detecting the cell handover failure when the timer expires; as well as Based on the candidate cell configurations in the list of candidate cell configurations, a failure recovery process is performed on the candidate cells associated with the candidate cell configurations.

5. The method according to claim 4, wherein The list of candidate cell configurations is included in at least one of the message, the configurations for the candidate cells, or the cell handover command.

6. The method according to claim 1, wherein The configuration for the candidate cell includes the multiple timer values ​​of the timer used to detect the cell handover failure.

7. The method according to claim 1, wherein The cell handover type includes at least one of a random access channel (RACH)-free cell handover and a RACH-based cell handover. The multiple timer values ​​include at least one of the following items: a first timer value associated with the RACH-free cell handover; or a second timer value associated with the RACH-based cell handover, The RACH-free cell switching includes: skipping random access to the candidate cell while the timer with the first timer value is running, and The RACH-based cell switching includes: performing contention-free random access (CFRA) or contention-based random access (CBRA) on the candidate cell while the timer with the second timer value is running.

8. The method according to claim 1, wherein The cell handover type includes at least one of a random access channel (RACH)-free cell handover, a contention-free random access (CFRA)-based cell handover, or a contention-based random access (CBRA)-based cell handover. The multiple timer values ​​include at least one of the following items: a first timer value associated with the RACH-free cell handover; a second timer value associated with the CFRA-based cell handover; or a third timer value associated with the CBRA-based cell handover, The RACH-free cell switching includes: while the timer with the first timer value is running, skipping random access to the candidate cell, The CFRA-based cell switching includes: performing CFRA on the candidate cell while the timer with the second timer value is running, and The CBRA-based cell switching includes: performing CBRA on the candidate cell while the timer with the third timer value is running.

9. The method according to claim 1, further comprising the steps of: determining the cell handover type based on whether a random access channel (RACH)-skip condition or a contention-free random access (CFRA) resource is available for at least one of the UEs; as well as determining the timer value associated with the determined cell handover type, The RACH-skip condition includes at least one of the following: A condition that the timing advance (TA) information for the candidate cell and the beam indication of the candidate cell are included in the cell handover command; Conditions for the TA of the candidate cell to be valid; or No beam failure condition is detected on the candidate cell.

10. The method according to claim 9, wherein: The cell handover type includes at least one of a random access channel (RACH)-free cell handover and a RACH-based cell handover. wherein, based on satisfying the RACH-skip condition, the cell handover type is determined to be the RACH-free cell handover, and Wherein, based on not satisfying the RACH-skip condition, the cell handover type is determined to be the RACH-based cell handover.

11. The method according to claim 9, wherein The cell handover type includes at least one of a random access channel (RACH)-free cell handover, a contention-free random access (CFRA)-based cell handover, or a contention-based random access (CBRA)-based cell handover. Wherein, based on satisfying the RACH-skip condition, the cell handover type is determined to be the RACH-free cell handover, wherein, based on the RACH-skipping condition not being satisfied and the CFRA resources being available for the UE, the cell handover type is determined to be the CFRA-based cell handover, and The cell handover type is determined to be the CBRA-based cell handover based on the fact that the RACH-skipping condition is not satisfied and the CFRA resources are not available for the UE.

12. The method according to claim 1, wherein The cell handover includes layer 1 L1 / layer 2 L2 triggering mobility LTM, and The cell switching command includes an LTM command.

13. The method according to claims 1 to 12, wherein: The UE communicates with at least one of a mobile device, a network, or an autonomous vehicle.

14. A user equipment (UE) configured to operate in a wireless communication system, the UE comprising: at least one transceiver; at least one processor; as well as at least one memory operatively coupled to the at least one processor and storing instructions that, upon execution by the at least one processor, perform operations comprising: receiving a message from a network, the message including a configuration of a candidate cell for cell handover and a plurality of timer values ​​for a timer for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; receiving a cell handover command for the candidate cell from the network; initiating the cell handover to the candidate cell based on the cell handover command, wherein the timer having the timer value among the plurality of timer values ​​is started when the UE initiates the cell handover, and the timer value is related to a cell handover type of the cell handover to be performed; and While the timer is running, the cell handover to the candidate cell is performed.

15. The UE according to claim 14, wherein: The UE is arranged to implement the method according to one of claims 2 to 13.

16. A network node configured to operate in a wireless communication system, the network node comprising: at least one transceiver; at least one processor; as well as at least one memory operatively coupled to the at least one processor and storing instructions that, upon execution by the at least one processor, perform operations comprising: Sending a message to a user equipment (UE), the message including a configuration of a candidate cell for cell handover and a plurality of timer values ​​for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; and sending a cell handover command for the candidate cell to the UE, wherein the cell handover to the candidate cell is initiated based on the cell handover command, wherein the timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell handover, and the timer value is related to the cell handover type of the cell handover to be performed, and The cell handover to the candidate cell is performed while the timer is running.

17. A method performed by a network node configured to operate in a wireless communication system, the method comprising the steps of: Sending a message to a user equipment (UE), the message including a configuration of a candidate cell for cell handover and a plurality of timer values ​​for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; and sending a cell handover command for the candidate cell to the UE, wherein the cell handover to the candidate cell is initiated based on the cell handover command, wherein the timer having a timer value among the multiple timer values ​​is started when the UE initiates the cell handover, and the timer value is related to the cell handover type of the cell handover to be performed, and The cell handover to the candidate cell is performed while the timer is running.

18. The method according to claim 17, wherein: The UE is arranged to implement the method according to one of claims 1 to 13.

19. A device adapted to operate in a wireless communication system, the device comprising: at least one processor; as well as at least one memory operatively coupled to the at least one processor and storing instructions that, upon execution by the at least one processor, perform operations comprising: receiving a message from a network, the message including a configuration of a candidate cell for cell handover and a plurality of timer values ​​for a timer for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; receiving a cell handover command for the candidate cell from the network; initiating the cell handover to the candidate cell based on the cell handover command, wherein the timer having the timer value among the plurality of timer values ​​is started when the UE initiates the cell handover, and the timer value is related to a cell handover type of the cell handover to be performed; and The cell handover to the candidate cell is performed while the timer is running.

20. A non-transitory computer readable medium (CRM) having program code stored thereon implementing instructions, wherein the instructions, upon execution by at least one processor, perform operations comprising: receiving a message from a network, the message including a configuration of a candidate cell for cell handover and a plurality of timer values ​​for a timer for detecting a cell handover failure, wherein each of the plurality of timer values ​​is associated with a corresponding cell handover type; receiving a cell handover command for the candidate cell from the network; initiating the cell handover to the candidate cell based on the cell handover command, wherein the timer having the timer value among the plurality of timer values ​​is started when the UE initiates the cell handover, and the timer value is related to a cell handover type of the cell handover to be performed; and The cell handover to the candidate cell is performed while the timer is running.

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