Handover failure recovery based on network indication

Abstract

Methods and apparatus for handover failure recovery based on network indication are provided. The wireless device receives one or more candidate cell configurations for one or more candidate cells. The one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells. The wireless device receives a cell handover command that triggers mobility to a primary candidate cell among the one or more primary candidate cells, and performs mobility to the primary candidate cell. The wireless device evaluates a failure of mobility, and performs mobility to a secondary candidate cell among the one or more secondary candidate cells when the failure of mobility is detected.

Description

Technical Field

[0001] The present disclosure relates to recovery from handover failures based on network indications. Background Art

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

[0003] The International Telecommunication Union (ITU) and 3GPP have started work to develop requirements and specifications for a New Radio (NR) system. 3GPP must identify and develop the technical components required to successfully standardize a new RAT that meets both urgent market needs in a timely manner and the longer-term requirements presented by the ITU Radiocommunication Sector (ITU-R) International Mobile Telecommunications (IMT)-2020 process. Additionally, even in the more distant future, NR should be able to use any spectrum band available for wireless communication up to at least 100 GHz.

[0004] NR aims at a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios, including enhanced mobile broadband (eMBB), massive machine type communication (mMTC), ultra-reliable low latency communication (URLLC), etc. NR should be inherently forward compatible.

[0005] When a User Equipment (UE) moves from the coverage area of one cell to another, at some point in time, a serving cell change needs to be performed. Currently, serving cell changes are triggered by L3 measurements and are completed by reconfiguration triggered by Radio Resource Control (RRC) signaling with synchronization for changes to the Primary Cell (PCell) and Primary Secondary Cell (PSCell), and release addition for SCell when applicable. All cases involve a complete L2 (and L1) reset, resulting in longer latency, greater overhead, and longer interruption times compared to beam switching mobility.

[0006] The goal of L1 / L2 mobility enhancement is to achieve serving cell changes via L1 / L2 signaling to reduce latency, overhead, and interruption times. Summary of the Invention

[0007] Technical Solution

[0008] The present disclosure is for providing a method and an apparatus for performing a recovery process for a Lower Layer Triggered Mobility (LTM) failure based on a network indication.

[0009] In one aspect, a method performed by a wireless device adapted to operate is provided. The method includes the steps of: receiving one or more candidate cell configurations for one or more candidate cells. The one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells. The method includes the steps of: receiving a cell handover command that triggers mobility to a primary candidate cell among the one or more primary candidate cells, and performing mobility to the primary candidate cell. The method includes the steps of: evaluating a failure of the mobility, and when a failure of the mobility is detected, performing mobility to a secondary candidate cell among the one or more secondary candidate cells.

[0010] In another aspect, a device for implementing the above method is provided.

[0011] Advantageous Effects

[0012] The present disclosure may have various advantageous effects.

[0013] For example, the UE may attempt to access a secondary candidate cell when a failure of the LTM of the primary candidate cell is detected.

[0014] For example, user data interruption may be reduced by performing a recovery faster than a conventional failure recovery based on an RRC reestablishment procedure.

[0015] The advantageous effects that can be obtained through the specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there are various technical effects that those of ordinary skill in the relevant art can understand and / or derive from the present disclosure. 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

[0016] Figure 1 An example of a communication system to which an implementation of the present disclosure is applied is shown.

[0017] Figure 2 An example of a wireless device to which an implementation of the present disclosure is applied is shown.

[0018] Figure 3 An example of a UE to which an implementation of the present disclosure is applied is shown.

[0019] Figure 4 and Figure 5 An example of a protocol stack in a 3GPP-based wireless communication system to which an implementation of the present disclosure is applied is shown.

[0020] Figure 6 An example of a frame structure in a 3GPP-based wireless communication system to which an implementation of the present disclosure is applied is shown.

[0021] Figure 7 Shows an example of a data flow in a 3GPP NR system that implements the present disclosure.

[0022] Figure 8 Shows an example of a method performed by a wireless device that implements the present disclosure.

[0023] Figure 9 Shows an example of a method performed by a base station that implements the present disclosure.

[0024] Figure 10 Shows an example of a process that implements Implementation 1 of the present disclosure.

[0025] Figure 11 Shows an example of a process that implements Implementation 2 of the present disclosure. Detailed implementation

[0026] The following technologies, devices, and systems can be applied to various wireless multi-access systems. Examples of these multi-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 by radio technologies such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented by 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 by 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 the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) is part of the Evolved UMTS (E-UMTS) that uses E-UTRA. 3GPP LTE employs OFDMA in the downlink (DL) and SC-FDMA in the uplink (UL). The evolution of 3GPP LTE includes LTE Advanced (LTE-A), LTE-A Pro, and / or 5G New Radio (NR).

[0027] For ease of description, embodiments of the present disclosure are mainly 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, aspects of the present disclosure not limited to 3GPP-based wireless communication systems are applicable to other mobile communication systems.

[0028] For terms and techniques not specifically described among the terms and techniques adopted in the present disclosure, reference may be made to wireless communication standard documents published prior to the present disclosure.

[0029] In the present disclosure, "A or B" may mean "only A", "only B", or "both A and B". In other words, "A or B" in the present disclosure may be interpreted as "A and / or B". For example, "A, B, or C" in the present disclosure may mean "only A", "only B", "only C", or "any combination of A, B, and C".

[0030] In the present 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".

[0031] In the present disclosure, "at least one of A and B" may mean "only A", "only B", or "both A and B". Additionally, the expressions "at least one of A or B" or "at least one of A and / or B" in the present disclosure may be interpreted in the same way as "at least one of A and B".

[0032] Additionally, 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". Additionally, "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".

[0033] Additionally, parentheses used in the present disclosure may mean "for example". Specifically, when shown as "control information (PDCCH)", "PDCCH" may be presented as an example of "control information". In other words, "control information" in the present disclosure is not limited to "PDCCH", and "PDDCH" may be presented as an example of "control information". Additionally, even when shown as "control information (i.e., PDCCH)", "PDCCH" may be presented as an example of "control information".

[0034] Technical features separately described in one figure in the present disclosure may be implemented separately or simultaneously.

[0035] Although not limited thereto, the various descriptions, functions, processes, suggestions, methods, and / or operation flowcharts of the present disclosure disclosed herein can be applied to various fields that require wireless communication and / or connection (e.g., 5G) between devices.

[0036] 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.

[0037] Figure 1 An example of a communication system to which an embodiment of the present disclosure is applied is shown.

[0038] In Figure 1 The 5G usage scenarios shown are merely exemplary, and the technical features of the present disclosure can be applied to other 5G usage scenarios not shown in Figure 1 Herein.

[0039] The three main requirement categories of 5G include: (1) the category of enhanced mobile broadband (eMBB), (2) the category of massive machine type communication (mMTC), and (3) the category of ultra-reliable and low-latency communication (URLLC).

[0040] Referring to Figure 1 , the communication system 1 includes wireless devices 100a to 100f, a base station (BS) 200, and a network 300. Although Figure 1 An example of a 5G network is illustrated as the network of the communication system 1, the embodiments of the present disclosure are not limited to 5G systems and can be applied to future communication systems other than 5G systems.

[0041] The BS 200 and the network 300 can be implemented as wireless devices, and a specific wireless device can operate as a BS / network node with respect to other wireless devices.

[0042] Wireless devices 100a to 100f represent devices that perform communication using a radio access technology (RAT) (e.g., 5G NR or LTE), and may be referred to as communication / wireless / 5G devices. Wireless devices 100a to 100f may include, but are not limited to, robot 100a, vehicles 100b-1 and 100b-2, extended reality (XR) device 100c, handheld device 100d, home appliance 100e, Internet of Things (IoT) device 100f, and artificial intelligence (AI) device / server 400. For example, a vehicle may include a vehicle with wireless communication capabilities, an autonomous driving vehicle, and a vehicle capable of performing communication between vehicles. The vehicle may include an unmanned aerial vehicle (UAV) (e.g., a drone). The XR device may include an augmented reality (AR) / virtual reality (VR) / mixed reality (MR) device, and may be implemented in the form of a head-mounted device (HMD), a head-up display (HUD) mounted in a vehicle, a TV, a smart phone, a computer, a wearable device, a home appliance device, a digital sign, a vehicle, a robot, etc. The handheld device may include a smart phone, a smart tablet, a wearable device (e.g., a smart watch or smart glasses), and a computer (e.g., a notebook). The home appliance may include a TV, a refrigerator, and a washing machine. The IoT device may include sensors and smart meters.

[0043] In the present disclosure, wireless devices 100a to 100f may be referred to as user equipment (UE). For example, the UE may include a cellular phone, a smart phone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate personal computer (PC), a tablet PC, a superbook, a vehicle, a vehicle with autonomous driving capabilities, a connected car, a 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 / environment device, a device related to 5G services, or a device related to the fourth industrial revolution field.

[0044] Wireless devices 100a to 100f can be connected to network 300 via BS200. 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 3G network, 4G (e.g., LTE) network, 5G (e.g., NR) network, and super 5G network. Although wireless devices 100a to 100f can communicate with each other via BS200 / network 300, wireless devices 100a to 100f can perform direct communication (e.g., sidelink communication) with each other 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.

[0045] Wireless communications / connections 150a, 150b, and 150c can be established between wireless devices 100a to 100f and / or between wireless devices 100a to 100f and BS200 and / or between BS 200s. Herein, wireless communications / connections can be established through 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 BS200 / wireless devices 100a to 100f can send / receive radio signals to / from each other through wireless communications / connections 150a, 150b, and 150c. For example, wireless communications / connections 150a, 150b, and 150c can send / receive signals through various physical channels. To this end, at least a part of various configuration information configuration processes, various signal processing processes (e.g., channel coding / decoding, modulation / demodulation, and resource mapping / demapping), and resource allocation processes for sending / receiving radio signals can be performed based on various proposals of the present disclosure.

[0046] NR supports multiple parameter sets (and / or multiple subcarrier spacings (SCSs)) to support various 5G services. For example, if the SCS is 15 kHz, wide area can be supported in traditional cellular bands, and if the SCS is 30 kHz / 60 kHz, dense cities, lower latency, and wider carrier bandwidth can be supported. If the SCS is 60 kHz or higher, bandwidth greater than 24.25 GHz can be supported to overcome phase noise.

[0047] 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 as shown in Table 1 below. For ease of explanation, in the frequency ranges used in the NR system, FR1 can mean "the range below 6 GHz", and FR2 can mean "the range above 6 GHz", and can be referred to as millimeter wave (mmW).

[0048] [Table 1]

[0049] Frequency range specification Corresponding frequency range Subcarrier spacing FR1 450 MHz – 6000 MHz 15, 30, 60 kHz FR2 24250 MHz – 52600 MHz 60, 120, 240 kHz

[0050] As mentioned above, the numerical values of the frequency ranges of the NR system can be changed. For example, FR1 can include 410 MHz to 7125 MHz as shown in Table 2 below. That is, FR1 can include frequency bands of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or above. For example, the frequency bands of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or above included in FR1 can include unlicensed frequency bands. The unlicensed frequency bands can be used for various purposes, such as communication of vehicles (e.g., autonomous driving).

[0051] [Table 2]

[0052] Frequency range specification Corresponding frequency range Subcarrier spacing FR1 410 MHz – 7125 MHz 15, 30, 60 kHz FR2 24250 MHz – 52600 MHz 60, 120, 240 kHz

[0053] Here, the radio communication technologies implemented in the wireless devices in the present disclosure may include Narrowband IoT (NB-IoT) technology for low-power communication, as well as LTE, NR, and 6G. For example, the 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 names mentioned above. Additionally and / or alternatively, the radio communication technologies implemented in the wireless devices in the present disclosure may communicate based on LTE-M technology. For example, the LTE-M technology may be an example of an LPWAN technology and is known by various names such as enhanced MTC (eMTC). For example, the 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 technologies implemented in the wireless devices in 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 names mentioned above. For example, the ZigBee technology may 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 known by various names.

[0054] Figure 2 An example of a wireless device to which an embodiment of the present disclosure is applied is shown.

[0055] In Figure 2 the first wireless device 100 and / or the second wireless device 200 may be implemented in various forms according to usage / services. For example, {the first wireless device 100 and the second wireless device 200} may correspond to Figure 1 at least one of {wireless devices 100a to 100f and BS200}, {wireless devices 100a to 100f and wireless devices 100a to 100f}, and / or {BS200 and BS200}. The first wireless device 100 and / or the second wireless device 200 may be configured by various elements, devices / components, and / or modules.

[0056] The first wireless device 100 may include at least one transceiver, such as transceiver 106; at least one processing chip, such as processing chip 101; and / or one or more antennas 108.

[0057] The processing chip 101 may include at least one processor, such as processor 102, and at least one memory, such as memory 104. Additionally and / or alternatively, the memory 104 may be placed outside the processing chip 101.

[0058] 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 operation flowcharts described in the present disclosure. For example, the processor 102 may process the information within the memory 104 to generate a first information / signal, and then transmit a radio signal including the first information / signal via the transceiver 106. The processor 102 may receive a radio signal including a second information / signal via the transceiver 106 and then store the information obtained by processing the second information / signal in the memory 104.

[0059] The memory 104 may be operably connected to the processor 102. The memory 104 may store various types of information and / or instructions. The memory 104 may store firmware and / or software code 105 that implements a set of codes, commands, and / or commands, which, when executed by the processor 102, execute the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in the present disclosure. For example, the firmware and / or software code 105 may implement instructions that, when executed by the processor 102, execute the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in the present disclosure. For example, the firmware and / or software code 105 may control the processor 102 to execute one or more protocols. For example, the firmware and / or software code 105 may control the processor 102 to execute one or more layers of a radio interface protocol.

[0060] 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 of the transceivers 106 may include a transmitter and / or a receiver. The transceiver 106 may be used interchangeably with the radio frequency (RF) unit. In the present disclosure, the first wireless device 100 may represent a communication modem / circuit / chip.

[0061] The second wireless device 200 may include at least one transceiver, such as transceiver 206; at least one processing chip, such as processing chip 201; and / or one or more antennas 208.

[0062] The processing chip 201 may include at least one processor, such as processor 202, and at least one memory, such as memory 204. Additionally and / or alternatively, the memory 204 may be placed outside the processing chip 201.

[0063] 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 operation flowcharts described in the present disclosure. For example, the processor 202 may process the information within the memory 204 to generate a third information / signal, and then transmit a radio signal including the third information / signal via the transceiver 206. The processor 202 may receive a radio signal including a fourth information / signal via the transceiver 106, and then store the information obtained by processing the fourth information / signal in the memory 204.

[0064] The memory 204 may be operably connected to the processor 202. The memory 204 may store various types of information and / or instructions. The memory 204 may store firmware and / or software code 205 that implements codes, commands, and / or sets of commands, which, when executed by the processor 202, execute the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in the present disclosure. For example, the firmware and / or software code 205 may implement instructions that, when executed by the processor 202, execute the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in the present disclosure. For example, the firmware and / or software code 205 may control the processor 202 to execute one or more protocols. For example, the firmware and / or software code 205 may control the processor 202 to execute one or more layers of a radio interface protocol.

[0065] 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 the RF unit. In the present disclosure, the second wireless device 200 may represent a communication modem / circuit / chip.

[0066] In the following, the hardware elements of wireless devices 100 and 200 will be described in more detail. One or more protocol layers may be implemented by, but 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 the physical (PHY) layer, medium access control (MAC) layer, radio link control (RLC) layer, packet data convergence protocol (PDCP) layer, radio resource control (RRC) layer, and service data adaptation protocol (SDAP) layer). 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, procedures, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. One or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods, and / or operation flowcharts disclosed in this disclosure and provide the generated signals to one or more transceivers 106 and 206. One or more processors 102 and 202 may receive signals (e.g., baseband signals) from one or more transceivers 106 and 206 and obtain PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods, and / or operation flowcharts disclosed in this disclosure.

[0067] One or more processors 102 and 202 may be referred to as a controller, microcontroller, microprocessor, or 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 set of a communication control processor, an application processor (AP), an electronic control unit (ECU), a central processing unit (CPU), a graphics processing unit (GPU), and a memory control processor. One or more memories 104 and 204 may 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.

[0068] One or more memories 104 and 204 may be configured by random access memory (RAM), dynamic RAM (DRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EPROM), flash memory, volatile and non-volatile memories, hard disk drives, registers, cache memories, computer-readable storage media, and / or combinations thereof. One or more memories 104 and 204 may be located internal and / or external to one or more processors 102 and 202. One or more memories 104 and 204 may be connected to one or more processors 102 and 202 by various techniques such as wired or wireless connections.

[0069] One or more transceivers 106 and 206 may send user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, procedures, suggestions, methods, and / or flowcharts of operations disclosed in this disclosure to one or more other devices. One or more transceivers 106 and 206 may receive user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, procedures, suggestions, methods, and / or flowcharts of operations disclosed in this disclosure from one or more other devices. For example, one or more transceivers 106 and 206 may be connected to one or more processors 102 and 202 and send and receive radio signals. For example, one or more processors 102 and 202 may execute controls such that one or more transceivers 106 and 206 may send user data, control information, or radio signals to one or more other devices. One or more processors 102 and 202 may execute controls such that one or more transceivers 106 and 206 may receive user data, control information, or radio signals from one or more other devices.

[0070] One or more transceivers 106 and 206 may be connected to one or more antennas 108 and 208. Additionally and / 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 send and receive user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, procedures, suggestions, methods, and / or flowcharts of operations disclosed in this disclosure. In this disclosure, one or more antennas 108 and 208 may be multiple physical antennas or multiple logical antennas (e.g., antenna ports).

[0071] One or more transceivers 106 and 206 may convert received user data, control information, radio signals / channels, etc. from RF-band signals into baseband signals so as to process the received user data, control information, radio signals / channels, etc. using one or more processors 102 and 202. One or more transceivers 106 and 206 may convert user data, control information, radio signals / channels, etc. processed using one or more processors 102 and 202 from baseband signals into RF-band signals. To this end, one or more transceivers 106 and 206 may include (analog) oscillators and / or filters. For example, one or more transceivers 106 and 206 are capable of upconverting an OFDM baseband signal to an OFDM signal via their (analog) oscillators and / or filters under the control of one or more processors 102 and 202 and transmitting the upconverted OFDM signal at a carrier frequency. One or more transceivers 106 and 206 may receive an OFDM signal at a carrier frequency and downconvert the OFDM signal to an OFDM baseband signal via their (analog) oscillators and / or filters under the control of one or more processors 102 and 202.

[0072] Although not shown in Figure 2 the wireless devices 100 and 200 may further include additional components. The additional components 140 may be configured differently depending on the types of the wireless devices 100 and 200. For example, the additional components 140 may include at least one of a power unit / battery, input / output (I / O) devices (e.g., audio I / O ports, video I / O ports), a driving device, and a computing device. The additional components 140 may be coupled to one or more processors 102 and 202 via various techniques such as wired or wireless connections.

[0073] In an embodiment of the present disclosure, the UE may operate as a transmitting device in the UL and as a receiving device in the DL. In an embodiment of the present disclosure, the BS may operate as a receiving device in the UL and as a transmitting device in the DL. Hereinafter, for convenience of description, it is mainly assumed that the first wireless device 100 is the UE and the second wireless device 200 is the BS. For example, the processor 102 connected to, mounted on, or initiated in the first wireless device 100 may be adapted to execute UE behaviors according to embodiments of the present disclosure or control the transceiver 106 to execute UE behaviors according to embodiments of the present disclosure. The processor 202 connected to, mounted on, or initiated in the second wireless device 200 may be adapted to execute BS behaviors according to embodiments of the present disclosure or control the transceiver 206 to execute BS behaviors according to embodiments of the present disclosure.

[0074] In the present disclosure, the BS is also referred to as Node B (NB), eNode B (eNB), or gNB.

[0075] Figure 3 An example of a UE to which embodiments of the present disclosure are applied is shown.

[0076] Referring to Figure 3 , UE 100 may correspond to Figure 2 the first wireless device 100 of

[0077] UE 100 includes a processor 102, a memory 104, a transceiver 106, one or more antennas 108, a power management module 141, a battery 142, a display 143, a keyboard 144, a subscriber identification module (SIM) card 145, a speaker 146, and a microphone 147.

[0078] The processor 102 may be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in the present disclosure. The processor 102 may be configured to control one or more other components of the UE 100 to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in the present disclosure. The layers of the radio interface protocol may be implemented in the processor 102. The processor 102 may include an ASIC, other chip sets, 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 DSP, a CPU, a GPU, and a modem (modulator and demodulator). Examples of the processor 102 can be found in the SNAPDRAGON TM series processors manufactured by the EXYNOS TM series processors manufactured by the A series processors manufactured by the HELIO TM series processors manufactured by the ATOM TM series processors or corresponding next-generation processors.

[0079] Memory 104 is operably coupled to processor 102 and stores various information for operating processor 102. Memory 104 may include ROM, RAM, flash memory, memory cards, storage media, and / or other storage devices. When an implementation is implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, etc.) that execute the descriptions, functions, procedures, suggestions, methods, and / or operation flowcharts disclosed in the present disclosure. The modules can be stored in memory 104 and executed by processor 102. Memory 104 can be implemented within or external to processor 102, in which case memory 104 can be communicatively coupled to processor 102 via various means known in the art.

[0080] Transceiver 106 is operably coupled to processor 102 and transmits and / or receives radio signals. Transceiver 106 includes a transmitter and a receiver. Transceiver 106 may include baseband circuitry for processing radio frequency signals. Transceiver 106 controls one or more antennas 108 to transmit and / or receive radio signals.

[0081] Power management module 141 manages the power of processor 102 and / or transceiver 106. Battery 142 supplies power to power management module 141.

[0082] Display 143 outputs the results processed by processor 102. Keyboard 144 receives inputs to be used by processor 102. Keyboard 144 may be shown on display 143.

[0083] SIM card 145 is an integrated circuit designed to securely store the International Mobile Subscriber Identity (IMSI) number and its associated keys, which are used to identify and authenticate subscribers on mobile phone devices such as mobile phones and computers. Contact information can also be stored on many SIM cards.

[0084] Speaker 146 outputs sound-related results processed by processor 102. Microphone 147 receives sound-related inputs to be used by processor 102.

[0085] Figure 4 and Figure 5 An example of a protocol stack in a 3GPP-based wireless communication system implementing the present disclosure is shown.

[0086] 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 the radio interface control plane protocol stack between a UE and a BS is illustrated. The control plane refers to the path through which control messages for managing calls made by the UE and the network are transmitted. The user plane refers to the path through which data generated in the application layer (e.g., voice data or Internet packet data) is transmitted. Refer to Figure 4 , the user plane protocol stack can be divided into Layer 1 (i.e., the PHY layer) and Layer 2. Refer to Figure 5 , the control plane protocol stack can be divided into Layer 1 (i.e., the PHY layer), Layer 2, Layer 3 (e.g., the RRC layer), and the non-access stratum (NAS) layer. Layer 1, Layer 2, and Layer 3 are referred to as the access stratum (AS).

[0087] In the 3GPP LTE system, Layer 2 is separated into the following sub-layers: MAC, RLC, and PDCP. In the 3GPP NR system, Layer 2 is separated into the following sub-layers: MAC, RLC, PDCP, and SDAP. The PHY layer provides a transport channel to the MAC sub-layer, the MAC sub-layer provides a logical channel to the RLC sub-layer, the RLC sub-layer provides an RLC channel to the PDCP sub-layer, and the PDCP sub-layer provides a radio bearer to the SDAP sub-layer. The SDAP sub-layer provides a quality of service (QoS) flow to the 5G core network.

[0088] In the 3GPP NR system, the main services and functions of the MAC sub-layer include: mapping between logical channels and transport channels; multiplexing / demultiplexing MAC SDUs belonging to one or different logical channels into / from transport blocks (TBs) transmitted to / from the physical layer on the transport channel; scheduling information reporting; error correction via hybrid automatic repeat request (HARQ) (one HARQ entity per cell in the case of carrier aggregation (CA)); priority handling between UEs via dynamic scheduling; priority handling between the logical channels of one UE via logical channel prioritization; padding. A single MAC entity can support multiple parameter sets, transmission timings, and cells. The mapping restriction in logical channel prioritization controls which parameter sets, cells, and transmission timings a logical channel can use.

[0089] The MAC provides different types of data transfer services. To accommodate different types of data transfer services, multiple types of logical channels are defined, i.e., each logical channel supports the transfer of a specific type of information. Each logical channel type is defined by what type of information is transferred. Logical channels are divided into two groups: control channels and traffic channels. Control channels are only used for the transfer of control plane information, and traffic channels are only used for the transfer of user plane information. The Broadcast Control Channel (BCCH) is a downlink logical channel for broadcasting system control information, the Paging Control Channel (PCCH) is a downlink logical channel for transmitting paging information, system information change notifications, and indications of ongoing Public Warning Service (PWS) broadcasts, the Common Control Channel (CCCH) is a logical channel for sending control information between the UE and the network and is used by UEs that do not have an RRC connection to the network, and the Dedicated Control Channel (DCCH) is a point-to-point two-way logical channel for sending 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 a single UE and is used to transfer user information. DTCH can exist in both the uplink and the downlink. In the downlink, there are the following connections 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, there are the following connections 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.

[0090] The RLC sublayer supports three transfer modes: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). The RLC configuration is per logical channel, without dependence on the parameter set and / or transfer duration. In the 3GPP NR system, the main services and functions of the RLC sublayer depend on the transfer mode and include: transfer of upper layer PDUs; sequence numbering (UM and AM) independent of the sequence numbering in PDCP; error correction via ARQ (only AM); segmentation (AM and UM) and re-segmentation (only AM) of RLC SDUs; reassembly of SDUs (AM and UM); duplicate detection (only AM); RLC SDU discard (AM and UM); RLC re-establishment; protocol error detection (AM).

[0091] 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); transfer of user data; reordering and duplicate detection; in-sequence delivery; PDCP PDU routing (in the case of split bearers); retransmission of PDCP SDUs; encryption, decryption, and integrity protection; PDCP SDU discard; PDCP reconstruction and data recovery for RLC AM; PDCP status reporting for RLC AM; duplicate and duplicate discard indication of PDCP PDUs to the lower layer. The main services and functions of the PDCP sublayer for the control plane include: sequence numbering; encryption, decryption, and integrity protection; transfer of control plane data; reordering and duplicate detection; in-sequence delivery; duplicate and duplicate discard indication of PDCP PDUs to the lower layer.

[0092] In the 3GPP NR system, the main services and functions of SDAP include: mapping between QoS flows and data radio bearers; marking the QoS flow ID (QFI) in both DL packets and UL packets. A single protocol entity of SDAP is configured for each individual PDU session.

[0093] In the 3GPP NR system, the main services and functions of the RRC sublayer include: broadcasting of system information related to the AS and NAS; paging initiated by the 5G core network (5GC) or the next-generation radio access network (NG-RAN); establishment, maintenance, and release of the RRC connection between the UE and the 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 recovery of radio link failures; NAS message transfer from the UE to the NAS / from the NAS to the UE.

[0094] Figure 6 The frame structure in a 3GPP-based wireless communication system implementing the present disclosure is shown.

[0095] Figure 6The frame structure shown is merely exemplary, and the number of sub-frames, the number of time slots, and / or the number of symbols in a frame can be changed differently. In a 3GPP-based wireless communication system, the OFDM parameter set (e.g., SCS, transmission time interval (TTI) duration) can be configured differently between multiple cells aggregated for one UE. For example, if a UE is configured with different SCSs for the cells targeted for cell aggregation, the (absolute time) duration of a time resource (e.g., sub-frame, time slot, or TTI) including the same number of symbols can be different among the aggregated cells. In this document, a symbol can include an OFDM symbol (or a cyclic prefix (CP)-OFDM symbol), an SC-FDMA symbol (or a discrete Fourier transform-spread-OFDM (DFT-s-OFDM) symbol).

[0096] Referring to Figure 6 , downlink and uplink transmissions are organized into frames. Each frame has a duration of T f = 10 ms. Each frame is divided into two half-frames, where each half-frame has a duration of 5 ms. Each half-frame includes 5 sub-frames, where the duration T sf of each sub-frame is 1 ms. Each sub-frame is divided into time slots, and the number of time slots in a sub-frame depends on the subcarrier spacing. Each time slot includes 14 or 12 OFDM symbols based on the CP. In normal CP, each time slot includes 14 OFDM symbols, and in extended CP, each time slot includes 12 OFDM symbols. The parameter set is based on the exponentially scalable subcarrier spacing Δf = 2 u * 15 kHz.

[0097] Table 3 shows the number of OFDM symbols N u of each time slot according to the subcarrier spacing Δf = 2 slot symb , the number of time slots N frame,u slot of each frame, and the number of time slots N subframe,u slot of each sub-frame for normal CP.

[0098] [Table 3]

[0099] 4 <![CDATA[N slot symb > <![CDATA[N frame，u sloot > <![CDATA[N subframe slot > 0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

[0100] Table 4 shows the number of OFDM symbols N u of each time slot according to the subcarrier spacing Δf = 2 slot symb , the number of time slots N frame,u slot of each frame, and the number of time slots Nsubframe,u slot .

[0101] [Table 4]

[0102] u <![CDATA[N slot symb > <![CDATA[N frame，u slot > <![CDATA[N subframe，u slot > 2 12 40 4

[0103] A time slot includes a plurality of symbols in the time domain (e.g., 14 or 12 symbols). For each parameter set (e.g., subcarrier spacing) and carrier, starting from a common resource block (CRB) N indicated by higher layer signaling (e.g., RRC signaling), a resource grid of N subcarriers and N OFDM symbols is defined, where N is the number of resource blocks (RBs) in the resource grid, and the subscript x is DL for downlink and UL for uplink. N is the number of subcarriers per RB. In a 3GPP-based wireless communication system, N is typically 12. For a given antenna port p, subcarrier spacing configuration u, and transmission direction (DL or UL), there is a resource grid. The carrier bandwidth N for subcarrier spacing configuration u is given by higher layer 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 a 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 l representing the symbol position relative to a reference point in the time domain. start,u grid starting size,u grid,x *N RB sc subcarriers and N subframe,u symb OFDM symbols, where N size,u grid,x is the number of resource blocks (RBs) in the resource grid, and the subscript x is DL for downlink and UL for uplink. N RB sc is the number of subcarriers per RB. In a 3GPP-based wireless communication system, N RB sc is typically 12. For a given antenna port p, subcarrier spacing configuration u, and transmission direction (DL or UL), there is a resource grid. The carrier bandwidth N for subcarrier spacing configuration u is given by higher layer 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 a 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 l representing the symbol position relative to a reference point in the time domain. size,u grid is given by higher layer 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 a 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 l representing the symbol position relative to a reference point in the time domain.

[0104] In a 3GPP-based wireless communication system, an RB is defined by 12 consecutive subcarriers in the frequency domain. In a 3GPP NR system, RBs are classified into CRBs and physical resource blocks (PRBs). CRBs are numbered upwards from 0 in the frequency domain for subcarrier spacing configuration u. The center of subcarrier 0 of CRB 0 for subcarrier spacing configuration u coincides with "Point A" which serves as a common reference point for the resource block grid. In a 3GPP NR system, PRBs are defined within a bandwidth part (BWP) and are numbered from 0 to N size BWP,i - 1, where i is the number of the bandwidth part. The relationship between physical resource block n in bandwidth part i PRB and common resource block n CRB is as follows: nPRB = n CRB + N size BWP,i , where N size BWP,i is the common resource block where the bandwidth part starts relative to CRB 0. A BWP includes a plurality of consecutive RBs. A carrier may include up to N (e.g., 5) BWPs. A UE may be configured with one or more BWPs on a given component carrier. Among the BWPs configured for a UE, only one BWP can be active at a time. The active BWP defines the operating bandwidth of the UE within the operating bandwidth of the cell.

[0105] In the present disclosure, the term "cell" may refer to a geographical area provided by one or more nodes for a communication system or may refer to radio resources. The "cell" as a geographical area can be understood as the coverage area within which a node can provide services using a carrier, and the "cell" as radio resources (e.g., time-frequency resources) is associated with a bandwidth, which is the frequency range configured by the carrier. The "cell" associated with radio resources is defined by a combination of downlink resources and uplink resources (e.g., a combination of a DL component carrier (CC) and a UL CC). 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 transmit 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 carrying the signal, the coverage of a node can be associated with the coverage of the "cell" of the radio resources used by the node. Therefore, the term "cell" can be used to sometimes represent the service coverage of a node, at other times represent radio resources, or at other times represent the range within which a signal using radio resources can reach with an effective intensity.

[0106] In CA, two or more CCs are aggregated. The UE can receive or transmit on one or more CCs simultaneously according to 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. At RRC connection establishment / re - establishment / handoff, one serving cell provides NAS mobility information, and at RRC connection re - establishment / handoff, one serving cell provides security input. This cell is called the primary cell (PCell). The PCell is the cell operating on the primary frequency where the UE performs the initial connection establishment process or initiates the connection re - establishment process. Depending on the UE capabilities, secondary cells (SCells) 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 the special cell (PCell). Thus, the set of configured serving cells for the UE always consists of one PCell and one or more SCells. For dual - connectivity (DC) operation, the term "PCell" refers to the PCell of the master cell group (MCG) or the primary SCell (PSCell) of the secondary cell group (SCG). The SpCell supports physical uplink control channel (PUCCH) transmission and contention - based random access and is always active. The MCG is the set of serving cells associated with the master node, which includes the SpCell (PCell) and optionally one or more SCells. For a UE configured with DC, the SCG is a subset of the serving cells associated with the secondary node, which includes the PSCell and zero or more SCells. For a UE in RRC_CONNECTED not configured with CA / DC, there is only one serving cell consisting of the PCell. For a UE in RRC_CONNECTED configured with CA / DC, the term "serving cell" is used to denote the set of cells consisting of the SpCell and all SCells. In DC, two MAC entities are configured in the UE: one for the MCG and one for the SCG.

[0107] Figure 7 An example of data flow in a 3GPP NR system implementing the present disclosure is shown.

[0108] Refer to Figure 7 ,"RB" represents radio bearer, and "H" represents header. Radio bearers are classified into two groups: DRBs for user - plane data and SRBs for control - plane data. MAC PDUs are sent / received to / from external devices through the PHY layer using radio resources. The MAC PDU arrives at the PHY layer in the form of a transport block.

[0109] In the PHY layer, the uplink transmission channels UL-SCH and random access channel (RACH) are mapped to their physical channels physical uplink shared channel (PUSCH) and physical random access channel (PRACH) respectively, and the downlink transmission channels DL-SCH, BCH, and PCH are mapped to physical downlink shared channel (PDSCH), physical broadcast channel (PBCH), and PDSCH respectively. In the PHY layer, the uplink control information (UCI) is mapped to physical PUCCH, and the downlink control information (DCI) is mapped to physical downlink control channel (PDCCH). The MAC PDU associated with UL-SCH is sent by the UE via PUSCH based on UL grant, and the MAC PDU associated with DL-SCH is sent by the BS via PDSCH based on DL assignment.

[0110] Network-controlled mobility applies to UEs under RRC_CONNECTED and is classified into two types of mobility: cell-level mobility and beam-level mobility. Beam-level mobility includes intra-cell beam-level mobility and inter-cell beam-level mobility.

[0111] Cell-level mobility requires triggering explicit RRC signaling, i.e., handover. For handover between gNBs, the signaling procedure consists of at least the following operations.

[0112] 1. The source gNB initiates the handover and sends a handover request (HANDOVER REQUEST) message via the Xn interface.

[0113] 2. The target gNB performs admission control and provides a new RRC configuration as part of the handover request acknowledgement (HANDOVER REQUEST ACKNOWLEDGE) message.

[0114] 3. The source gNB provides the RRC configuration to the UE by forwarding the RRCReconfiguration message received in the HANDOVER REQUEST ACKNOWLEDGE message. The RRCReconfiguration message includes at least the cell identifier (ID) and all the information required to access the target cell, so that the UE can access the target cell without reading the system information. For some cases, the information required for contention-based and contention-free random access can be included in the RRCReconfiguration message. The access information for the target cell can include beam-specific information (if any).

[0115] 4. The UE moves the RRC connection to the target gNB and replies with an RRCReconfigurationComplete message.

[0116] In the case of Dual Active Protocol Stack (DAPS) handover, the UE continues to receive DL user data from the source gNB until the source cell is released, and continues to send UL user data to the source gNB until the random access procedure to the target gNB is successful.

[0117] During DAPS handover, only the source PCell and the target PCell are used. CA, DC, Supplementary UL (SUL), Multi-Transmit / Receive Point (TRP), Ethernet Header Compression (EHC), Conditional Handover (CHO), User Data Convergence (UDC), NR Sidelink Configuration, and V2X Sidelink Configuration are released by the source gNB before the handover command is sent to the UE and are configured by the target gNB only until the DAPS handover is completed (i.e., earliest in the same message that releases the source PCell).

[0118] The handover mechanism triggered by RRC requires the UE to at least reset the MAC entity and re-establish the RLC, except for DAPS handover, where upon receiving the handover command, the UE:

[0119] - Creates a MAC entity for the target;

[0120] - For each DRB configured with DAPS, establishes an RLC entity for the target and the associated DTCH logical channel;

[0121] - For each DRB configured with DAPS, reconfigures the PDCP entity with separate security and ROHC functions for the source and the target and associates these PDCP entities with the RLC entities configured by the source and the target respectively;

[0122] - Retains the remaining source configuration until the source is released.

[0123] Both RRC-managed handovers with and without PDCP entity re-establishment are supported. For DRBs using RLC AM mode, PDCP can be re-established together with a security key change or initiate a data recovery process without a key change. For DRBs using RLC UM mode, PDCP can be re-established together with a security key change or remain as it is without a key change. For SRBs, PDCP can remain as it is, discard its stored PDCP PDU / SDU without a key change, or be re-established together with a security key change.

[0124] When the target gNB uses the same DRB configuration as the source gNB, data forwarding, in-sequence delivery, and duplicate avoidance during handover can be guaranteed.

[0125] Timer-based handover failure procedures are supported in NR. The RRC connection reestablishment procedure is used to recover from handover failures, except in certain CHO or DAPS handover scenarios:

[0126] - When a DAPS handover fails, the UE reverts to the source cell configuration, restores the connection to the source cell, and if the source link has not been released, reports the DAPS handover failure via the source without triggering RRC connection reestablishment.

[0127] - When an initial CHO execution attempt fails or an HO fails, the UE performs cell selection, and if the selected cell is a CHO candidate and if the network configures the UE to attempt CHO after a handover / CHO failure, the UE attempts one CHO execution, otherwise performs reestablishment.

[0128] Beam-level mobility does not require triggering explicit RRC signaling. Beam-level mobility can be within a cell or between cells, the latter being referred to as inter-cell beam management (ICBM). For ICBM, the UE can receive or transmit UE-specific channels / signals via a TRP associated with a physical cell ID (PCI) different from that of the serving cell, whereas UE-specific channels / signals can only be received via the TRP associated with the PCI of the serving cell. The gNB provides the UE with a measurement configuration via RRC signaling, which includes synchronization signal block (SSB) / channel state information (CSI) resources and resource sets, reports, and configurations for triggering channel and interference measurements and reporting trigger states. In the case of ICBM, the measurement configuration includes SSB resources associated with a PCI different from that of the serving cell. Beam-level mobility is then handled at the lower layers by means of physical layer and MAC layer control signaling, and RRC does not need to know which beam is being used at a given point in time.

[0129] SSB-based beam-level mobility is based on the SSB associated with the initial DL BWP and can only be configured for the initial DL BWP and DL BWPs that contain the SSB associated with the initial DL BWP. For other DL BWPs, beam-level mobility can only be performed based on CSI-RS.

[0130] CHO is defined as a handover performed by the UE when one or more handover execution conditions are met. The UE starts evaluating the execution conditions upon receiving the CHO configuration and stops evaluating the execution conditions once the handover is executed.

[0131] The following principles apply to CHO:

[0132] - The CHO configuration includes the configuration of CHO candidate cells generated by the candidate gNB and the execution conditions generated by the source gNB.

[0133] - The execution condition can consist of one or two trigger conditions (CHO event A3 / A5). Only a single reference signal (RS) type is supported, and at most two different trigger quantities (e.g., reference signal received power (RSRP) and reference signal received quality (RSRQ), RSRP and signal-to-interference-plus-noise ratio (SINR), etc.) can be configured simultaneously for the evaluation of the CHO execution condition of a single candidate cell.

[0134] - Before any CHO execution condition is met, when a HO command (without CHO configuration) is received, the UE performs the HO procedure regardless of any previously received CHO configuration.

[0135] - When performing CHO, i.e., from the time the UE starts synchronizing with the target cell, the UE does not monitor the source cell.

[0136] In Rel-18, L1L2-triggered mobility (LTM) is introduced to reduce latency, overhead, and interruption time. For LTM, the network can pre-provide the UE with the configuration of candidate serving cells (i.e., pre-configuration of candidate cells for LTM). After receiving the pre-configuration of candidate cells for LTM, if the UE receives a corresponding cell handover command from the network via L1 / L2 signaling (i.e., LTM command), the UE applies the configuration of the candidate serving cell indicated by the L1 / L2 signaling. The UE can perform LTM only through an indication from the network. That is, without a network indication, the UE may not perform LTM by itself.

[0137] An example of UE operation for LTM can be as follows.

[0138] The network can configure the UE with one or more LTM candidate configurations within the LTM-Config IE.

[0139] An LTM candidate configuration is a configuration associated with an LTM candidate cell. An LTM candidate configuration can be a complete LTM candidate configuration or an increment (difference) configuration relative to the LTM reference configuration.

[0140] The LTM reference configuration is a configuration provided by the network to the UE, which is common for all configured non-complete LTM candidate configurations within the same cell group. The UE uses this LTM reference configuration to generate a complete LTM candidate configuration by applying the LTM candidate configuration on top of the LTM reference configuration.

[0141] Table 5 shows an example of LTM-Config. The information element (IE) LTM-Config is used to provide the LTM candidate cell configuration (i.e., pre-configuration of candidate cells for LTM).

[0142] [Table 5]

[0143]

[0144] According to Table 5, a reference configuration (i.e., ltm-ReferenceConfiguration) can be configured. The UE can store the reference configuration as a separate configuration. The reference configuration can be managed separately.

[0145] Table 6 shows an example of LTM-CandidateToAddModList, which can be included in the LTM-Config shown in Table 5. The IE LTM-CandidateToAddModList relates to a list of LTM candidate cell configurations to be added or modified.

[0146] [Table 6]

[0147]

[0148]

[0149] According to Table 5 and Table 6, an RRCReconfiguration message can be configured for each candidate target configuration RRCReconfiguration to configure the target candidate cell.

[0150] In NR-DC, the UE can receive two independent ltm-Configs:

[0151] - The ltm-Config associated with the MCG, which is included in the RRCReconfiguration message received via SRB1; and

[0152] - The ltm-Config associated with the SCG, which is included in the RRCReconfiguration message received via SRB3, or alternatively embedded in the RRCReconfiguration message received via SRB1.

[0153] In this case:

[0154] - The UE maintains two independent VarLTM-Configs, one VarLTM-Config associated with each ltm-Config;

[0155] - The UE maintains two independent VarLTM-ServingCellNoResetIDs, one VarLTM-ServingCellNoResetID associated with each ltm-Config;

[0156] - The UE maintains two independent VarLTM-ServingCellUE-MeasuredTA-IDs, with one VarLTM-ServingCellUE-MeasuredTA-ID associated with each ltm-Config;

[0157] - Unless otherwise explicitly stated, the UE independently performs all the following procedures for each ltm-Config and the associated VarLTM-Config.

[0158] The UE may perform the following actions based on the received LTM-Config IE:

[0159] 1> If the received LTM-Config includes ltm-ReferenceConfiguration, then:

[0160] 2> If the current VarLTM-Config includes ltm-ReferenceConfiguration, then:

[0161] 3> Replace the ltm-ReferenceConfiguration value within the VarLTM-Config with the received ltm-ReferenceConfiguration;

[0162] 2> Otherwise:

[0163] 3> Store the received ltm-ReferenceConfiguration into the VarLTM-Config;

[0164] 1> If the received LTM-Config includes ltm-ServingCellNoResetID, then:

[0165] 2> If the current VarLTM-ServingCellNoResetID includes ltm-ServingCellNoResetID, then:

[0166] 3> Replace the ltm-ServingCellNoResetID value within the VarLTM-ServingCellNoResetID with the received ltm-ServingCellNoResetID;

[0167] 2> Otherwise:

[0168] 3> Store the received ltm-ServingCellNoResetID into the VarLTM-ServingCellNoResetID;

[0169] 1> If the received LTM-Config includes ltm-ServingCellUE-MeasuredTA-ID, then:

[0170] 2> If the current VarLTM-ServingCellUE-MeasuredTA-ID includes ltm-ServingCellUE-MeasuredTA-ID:

[0171] 3> Replace the ltm-ServingCellUE-MeasuredTA-ID value within VarLTM-ServingCellUE-MeasuredTA-ID with the received ltm-ServingCellUE-MeasuredTA-ID;

[0172] 2> Otherwise:

[0173] 3> Store the received ltm-ServingCellUE-MeasuredTA-ID into VarLTM-ServingCellUE-MeasuredTA-ID;

[0174] 1> If the received LTM-Config includes ltm-CSI-ResourceConfigToAddModList, then:

[0175] 2> If the current VarLTM-Config includes ltm-CSI-ResourceConfigToAddModList, then:

[0176] 3> Replace the ltm-CSI-ResourceConfigToAddModList value within VarLTM-Config with the received ltm-CSI-ResourceConfigToAddModList;

[0177] 2> Otherwise:

[0178] 3> Store the received ltm-CSI-ResourceConfigToAddModList into VarLTM-Config;

[0179] 1> Otherwise, if the received LTM-Config includes ltm-CandidateToAddModList, then:

[0180] 2> Perform LTM candidate cell addition or reconfiguration.

[0181] For the addition / modification of LTM candidate cells, the UE may:

[0182] 1> For each ltm-CandidateId value in ltm-CandidateToAddModList:

[0183] 2> If the current VarLTM-Config includes an LTM-Candidate with the given ltm-CandidateId value, then:

[0184] 3> Replace the LTM-Candidate within VarLTM-Config according to the received LTM-Candidate;

[0185] 2> Otherwise:

[0186] 3> Add the received LTM-Candidate to VarLTM-Config.

[0187] That is to say, during the RRC procedure, when the UE receives the LTM configuration (before the LTM cell handover), it can apply the candidate incremental configuration on top of the reference configuration to form a complete candidate configuration. During the RRC procedure, the complete candidate configuration can be applied and replace the current UE configuration (when the reconfiguration is executed / cell handover) through the RRC reconfiguration procedure, which replaces the configuration but does not necessarily reset MAC, RLC, or PDCP.

[0188] When the lower layer indicates to trigger the LTM cell handover procedure, or when performing LTM cell handover after cell selection while the timer T311 is running, the UE may:

[0189] 1> Release / clear all current dedicated radio configurations associated with the cell group that triggers the LTM cell handover procedure, except for the following:

[0190] 2> If the LTM cell handover is triggered on the MCG, then:

[0191] - MCG C-RNTI;

[0192] - AS security configuration associated with the master key;

[0193] 2> Otherwise, if the LTM cell handover is triggered on the SCG, then:

[0194] - AS security configuration associated with the secondary key;

[0195] 2> For each SRB / DRB in the current UE configuration:

[0196] - Maintain associated PDCP and SDAP entities, their status variables, buffers, and timers;

[0197] - Release all fields related to SRB / DRB configuration except srb-Identity and drb-Identity;

[0198] 2> For each RLC bearer in the current UE configuration for the cell group that triggers LTM:

[0199] - Maintain the associated RLC entity, its status variables, buffers, and timers;

[0200] - Release all fields related to RLC-BearerConfig except logicalChannelIdentity and logicalChannelIdentityExt.

[0201] - UE variables VarLTM-Config and VarLTM-ServingCellNoResetID.

[0202] 1> Release / clear all current common radio configurations associated with the cell group that triggers the LTM cell handover procedure;

[0203] 1> Use the default values for timers T310, T311 and constants N310, N311 associated with the cell group that triggers the LTM cell handover procedure;

[0204] 1> Apply the default L1 parameter values specified in the corresponding physical layer specification;

[0205] 1> If the value of the ltm-NoResetID field within the LTM-Candidate IE included in VarLTM-Config indicated by the lower layer or for the selected cell is equal to the value of ltm-ServingCellNoResetID within VarLTM-ServingCellNoResetID, then:

[0206] 2> Continue to use the current RLC entity in the LTM candidate configuration indicated by the lower layer;

[0207] 2> Replace the value of ltm-ServingCellNoResetID in VarLTM-ServingCellNoResetID with the value received within ltm-NoResetID;

[0208] 1> Otherwise:

[0209] 2> For each RLC-BearerConfig within rlc-BearerToAddModList that is part of the current UE configuration:

[0210] 3> Reconstruct the RLC entity;

[0211] 2> For each drb-Identity value included in drb-ToAddModList that is part of the current UE configuration:

[0212] 3> Trigger the PDCP entity of the DRB to perform data recovery;

[0213] 2> Replace the value of ltm-ServingCellNoResetID in VarLTM-ServingCellNoResetID with the value of ltm-NoResetID in LTM-Candidate within VarLTM-Config indicated by the lower layer or for the selected cell;

[0214] 1> If the value of the field ltm-UE-MeasuredTA-ID within the LTM-Candidate IE included in VarLTM-Config indicated by the lower layer or for the selected cell is equal to the value of ltm-ServingCellUE-MeasuredTA-ID within VarLTM-ServingCellUE-MeasuredTA-ID, then:

[0215] 2> Notify the lower layer that the UE should perform UE-based TA measurement;

[0216] 2> Replace the value of ltm-ServingCellUE-MeasuredTA-ID in VarLTM-ServingCellUE-MeasuredTA-ID with the value received within ltm-UE-MeasuredTA-ID;

[0217] 1> Otherwise:

[0218] 2> Replace the value of ltm-ServingCellUE-MeasuredTA-ID in VarLTM-ServingCellUE-MeasuredTA-ID with the value of ltm-UE-MeasuredTA-ID within the LTM-Candidate in VarLTM-Config indicated by the lower layer or for the selected cell;

[0219] 1> Continue to use the current PDCP entity in the LTM candidate configuration indicated by the lower layer; 1> If ltm-ConfigComplete is not included in the LTM-Candidate IE in VarLTM-Config indicated by the lower layer or for the selected cell:

[0220] 2> Consider ltm-ReferenceConfiguration in VarLTM-Config as the current UE configuration.

[0221] 1> If the LTM cell handover is triggered by an indication from the lower layer, then:

[0222] 2> Apply the LTM configuration in ltm-CandidateConfig in the LTM-Candidate IE in VarLTM-Config related to the LTM candidate configuration identity received from the lower layer;

[0223] 1> Otherwise (when the LTM cell handover is triggered during cell selection while timer T311 is running):

[0224] 2> Apply the LTM configuration in ltm-CandidateConfig in the LTM-Candidate IE in VarLTM-Config related to the LTM candidate configuration identity corresponding to the cell selected while timer T311 is running;

[0225] 2> Perform the LTM configuration release procedure for MCG.

[0226] LTM may fail. When conventional mobility (e.g., handover) fails, the UE may perform / initiate an RRC reconstruction procedure. If the UE initiates an RRC reconstruction procedure due to LTM failure, it not only causes a large interruption but also leads to unnecessary reconfiguration after reconstruction.

[0227] For faster recovery, the UE can utilize the configured candidate cells. For example, when LTM fails, the UE can attempt to access one of the other candidate cells. In this case, if the UE arbitrarily selects a target cell from the configured candidate cells, the UE may select a target cell that is not preferred by the network for recovery. For example, some candidate cells may not be fully ready for quick recovery, while other candidate cells may be fully ready for quick recovery. If the UE attempts to access a candidate cell that is not fully ready for quick recovery, the recovery may be delayed and / or even fail.

[0228] According to an implementation of the present disclosure, pre-configured candidate cells for LTM can be classified into one or more primary candidate cells and one or more secondary candidate cells. When an LTM failure of a primary candidate cell among one or more primary candidate cells is detected, the UE can attempt to access a secondary candidate cell among one or more secondary candidate cells.

[0229] According to an implementation of the present disclosure, the network can indicate to the UE some of the pre-configured candidate cells for LTM. For example, the network can send an indication / information notifying one or more secondary candidate cells to the UE.

[0230] According to an implementation of the present disclosure, for the signaling of the indication / information, the indication / information can be included in the LTM command and / or the cell handover command. The indication / information can be configured as part of the candidate cell configuration. The indication / information can be pre-configured as part of the serving cell configuration. That is to say, the indication / information can be pre-configured per serving cell. When multiple serving cells are configured, the indication / information can be provided in each of the serving cell configurations. The indication / information can be pre-configured per target cell and source cell pair. In this case, the source cell configuration can be retained only when mobility causes the serving cell to change from the source cell to the target cell. The indication can be provided in the conditional mobility configuration.

[0231] According to an implementation of the present disclosure, the network can indicate the priority information of each of one or more secondary candidate cells. Then, after detecting an LTM failure, the UE can select the secondary candidate cell with the highest priority among one or more secondary candidate cells and access the secondary candidate cell for recovery.

[0232] The following drawings are created to explain specific embodiments of the present disclosure. The names of specific devices shown in the drawings or the names of specific signals / messages / fields are provided by way of example, so the technical features of the present disclosure are not limited to the specific names used in the following drawings.

[0233] Figure 8 An example of a method executed by a wireless device applying an implementation of the present disclosure is shown.

[0234] In step 800, the method includes: receiving a serving cell configuration for a serving cell.

[0235] In step 810, the method includes: receiving one or more candidate cell configurations for one or more candidate cells. The one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells.

[0236] In step 820, the method includes: receiving a cell handover command that triggers mobility to a primary candidate cell among one or more primary candidate cells.

[0237] In step 830, the method includes: performing mobility to the primary candidate cell, the mobility including applying a candidate cell configuration for the primary candidate cell among one or more candidate cell configurations.

[0238] In step 840, the method includes: evaluating a failure of the mobility.

[0239] In step 850, the method includes: when a failure of the mobility is detected, performing mobility to a secondary candidate cell among one or more secondary candidate cells, the mobility including applying a candidate cell configuration for the secondary candidate cell among one or more candidate cell configurations.

[0240] In some implementations, the method further includes: receiving information related to one or more secondary candidate cells.

[0241] In some implementations, the information related to one or more secondary candidate cells may be received via one or more candidate cell configurations. In this case, the information related to one or more secondary candidate cells may be included as a list separate from the list related to one or more primary candidate cells. Alternatively, the information related to one or more secondary candidate cells may be included as a flag in the candidate cell configuration for each of one or more primary candidate cells.

[0242] In some implementations, the information related to one or more secondary candidate cells may be received via the cell handover command.

[0243] In some implementations, the information related to one or more secondary candidate cells may include priority information for one or more secondary candidate cells. In this case, the secondary candidate cell may have the highest priority among one or more secondary candidate cells based on the priority information.

[0244] In some implementations, one or more secondary candidate cells may be a subset of one or more primary candidate cells.

[0245] In some implementations, one or more candidate cell configurations and / or cell handover commands may include information about the value of a timer for evaluating the failure of mobility. In such a case, the step of evaluating the failure of mobility may include: starting the timer and evaluating the expiration of the timer based on the value of the timer. The timer may be started when an uplink (UL) signal for performing mobility to the primary candidate cell is sent to the primary candidate cell. The timer may be stopped when an acknowledgement of the UL signal sent to the primary candidate cell is received from the primary candidate cell.

[0246] In some implementations, a wireless device may communicate with at least one of a mobile device, a network, and / or an autonomous vehicle other than the wireless device itself.

[0247] In addition, the methods described above from the perspective of the wireless device may be performed by Figure 8 the first wireless device 100 shown in Figure 2 and / or Figure 3 the UE 100 shown in

[0248] The wireless device includes at least one transceiver, at least one processor, and at least one memory that is operably connected to the at least one processor and stores instructions that, when executed by the at least one processor, perform the Figure 8 methods described in

[0249] More specifically, the wireless device receives a serving cell configuration for the serving cell.

[0250] The wireless device receives one or more candidate cell configurations for one or more candidate cells. The one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells.

[0251] The wireless device receives a cell handover command that triggers mobility to a primary candidate cell among the one or more primary candidate cells.

[0252] The wireless device performs mobility to the primary candidate cell, and the mobility includes applying the candidate cell configuration for the primary candidate cell among the one or more candidate cell configurations.

[0253] The wireless device evaluates the failure of mobility.

[0254] When a failure of mobility is detected, the wireless device performs mobility to a secondary candidate cell among the one or more secondary candidate cells, and the mobility includes applying the candidate cell configuration for the secondary candidate cell among the one or more candidate cell configurations.

[0255] In some implementations, a wireless device may receive information related to one or more secondary candidate cells.

[0256] In some implementations, information related to one or more secondary candidate cells may be received via one or more candidate cell configurations. In this case, the information related to one or more secondary candidate cells may be included as a list separate from the list related to one or more primary candidate cells. Alternatively, the information related to one or more secondary candidate cells may be included as a flag in the candidate cell configuration for each of the one or more primary candidate cells.

[0257] In some implementations, information related to one or more secondary candidate cells may be received via a cell handover command.

[0258] In some implementations, the information related to one or more secondary candidate cells may include priority information for one or more secondary candidate cells. In this case, the secondary candidate cell may have the highest priority among the one or more secondary candidate cells based on the priority information.

[0259] In some implementations, one or more secondary candidate cells may be a subset of one or more primary candidate cells.

[0260] In some implementations, one or more candidate cell configurations and / or cell handover commands may include information about the value of a timer for evaluating a failure in mobility. In this case, evaluating a failure in mobility may include: starting the timer, and evaluating the expiration of the timer based on the value of the timer. The timer may be started when transmitting an uplink (UL) signal for performing mobility to a primary candidate cell. The timer may be stopped when receiving an acknowledgement of the UL signal transmitted to the primary candidate cell from the primary candidate cell.

[0261] In addition, the methods described above from the perspective of a wireless device in Figure 8 may be performed by controlling a processor 102 included in a first wireless device 100 shown in Figure 2 and / or by controlling a processor 102 included in a UE 100 shown in Figure 3

[0262] A processing device adapted to control a wireless device includes at least one processor and at least one memory operatively connectable to the at least one processor. The at least one processor is adapted to execute the method described in Figure 8

[0263] In addition, the methods described above from the perspective of a wireless device in Figure 8 may be performed by being stored in a memory included inFigure 2 It is executed by the software code 105 in the memory 104 of the first wireless device 100 shown in

[0264] The technical features of the present disclosure can be implemented directly in hardware, in software executed by a processor, or in a combination of both. For example, a method executed by a wireless device in wireless communication can be implemented in hardware, software, firmware, or any combination thereof. For example, software can reside in RAM, flash memory, ROM, EPROM, EEPROM, registers, a hard disk, a removable disk, a CD-ROM, or any other storage medium.

[0265] Some examples of storage media can be coupled to the processor such that the processor can read information from the storage media. In an alternative, the storage media can be integrated into the processor. The processor and the storage media can reside in an ASIC. For other examples, the processor and the storage media can reside as discrete components.

[0266] A computer-readable medium can include tangible and non-transitory computer-readable storage media.

[0267] For example, non-transitory computer-readable media can include RAM, such as synchronous DRAM (SDRAM), ROM, non-volatile RAM (NVRAM), EEPROM, flash memory, magnetic or optical data storage media, or any other medium that can be used to store instructions or data structures. Non-transitory computer-readable media can also include combinations of the above.

[0268] In addition, the methods described herein can be implemented at least in part via a computer-readable communication medium that carries or transports code in the form of instructions or data structures and that can be accessed, read, and / or executed by a computer.

[0269] According to some implementations of the present disclosure, a non-transitory computer-readable medium (CRM) stores instructions that, when executed by at least one processor, perform Figure 8 the methods described in

[0270] Figure 9 An example of a method executed by a base station applying an implementation of the present disclosure is shown.

[0271] In step S900, the method includes: sending a serving cell configuration for a serving cell.

[0272] In step S910, the method includes: sending one or more candidate cell configurations for one or more candidate cells. The one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells.

[0273] In step S920, the method includes: sending a cell handover command that triggers the mobility to a primary candidate cell among one or more primary candidate cells.

[0274] In step S930, perform the mobility to the primary candidate cell, where the mobility includes applying the candidate cell configuration for the primary candidate cell among one or more candidate cell configurations.

[0275] In step S940, evaluate the failure of the mobility, and when the failure of the mobility is detected, perform the mobility to a secondary candidate cell among one or more secondary candidate cells, where the mobility includes applying the candidate cell configuration for the secondary candidate cell among one or more candidate cell configurations.

[0276] In addition, the method described above from the perspective of the base station serving the second serving cell can be executed by Figure 9 the second wireless device 200 shown in Figure 2 .

[0277] The base station includes at least one transceiver, at least one processor, and at least one memory, and the at least one memory can be operatively connected to the at least one processor and store instructions that, when executed by the at least one processor, execute the Figure 9 method described in

[0278] More specifically, the base station sends the serving cell configuration for the serving cell.

[0279] The base station sends one or more candidate cell configurations for one or more candidate cells. The one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells.

[0280] The base station sends a cell handover command that triggers the mobility to a primary candidate cell among one or more primary candidate cells.

[0281] Perform the mobility to the primary candidate cell, where the mobility includes applying the candidate cell configuration for the primary candidate cell among one or more candidate cell configurations.

[0282] Evaluate the failure of the mobility, and when the failure of the mobility is detected, perform the mobility to a secondary candidate cell among one or more secondary candidate cells, where the mobility includes applying the candidate cell configuration for the secondary candidate cell among one or more candidate cell configurations.

[0283] Hereinafter, various embodiments of the present disclosure will be described.

[0284] (1) Implementation 1

[0285] Figure 10An example of the process implementing Implementation 1 of the present disclosure is shown.

[0286] According to Implementation 1 of the present disclosure, the indication / information is configured as part of the candidate cell configuration. The UE operations according to Implementation 1 of the present disclosure may include at least one of the steps described below.

[0287] (1) Step 1: The UE may receive one or more candidate cell configurations.

[0288] In one or more candidate cell configurations, one or more candidate serving cells may also be configured.

[0289] One or more candidate cell configurations may include at least one of the following items:

[0290] - Configuration of a special cell (SpCell), for example, servingCellConfigCommon, servingCellConfig, reconfigurationWithSync, radio link failure (RLF) related configuration, etc.

[0291] - Configuration of an SCell, for example, servingCellConfigCommon, servingCellConfig, smtc, discontinuous reception (DRX) configuration, etc.

[0292] - MAC / RLC related configuration

[0293] - A list of one or more primary candidate cells

[0294] - A list of one or more secondary candidate cells

[0295] - Configuration for detecting LTM failure: Timer values for evaluation expiration.

[0296] The list of one or more secondary candidate cells may be included as a list separate from the list of one or more primary candidate cells.

[0297] The list of one or more secondary candidate cells may be a subset of the list of one or more primary candidate cells.

[0298] Instead of the list of one or more secondary candidate cells, for each primary candidate cell from one or more primary candidate cells, a flag may be included to indicate whether the corresponding cell may be a secondary candidate cell.

[0299] (2) Step 2: The UE receives an LTM command (i.e., a cell handover command).

[0300] The LTM command can be received via one of the L1 / L2 / L3 signaling.

[0301] The LTM command can be used for network-controlled serving cell change (e.g., normal mobility) or UE autonomous serving cell change (e.g., conditional mobility such as CHO, CPA, CPC).

[0302] The LTM command can include at least one of the following items:

[0303] - Target cell information: If the target cell is one of the pre-configured candidate serving cells for the UE, the LTM command can include the identifier (ID) of the candidate serving cell indicated by the LTM command. Otherwise, if the target cell is not one of the pre-configured candidate serving cells, the LTM command can include the configuration of the target cell (e.g., RRCReconfiguration including reconfigurationWithSync).

[0304] - Conditional reconfiguration (e.g., ConditionalReconfiguration).

[0305] - Indicator indicating that the source cell is changed to a candidate serving cell: For example, the indicator can be an explicit 1-bit indication in DCI or MAC control element (CE). For example, the indicator can be an explicit RRC information element (IE). For example, the LTM command received via L1 / L2 signaling can implicitly indicate that the source cell is changed to a candidate serving cell. For example, the target cell can be included in a list, where the list can implicitly indicate that the source cell is changed to a candidate serving cell.

[0306] - Configuration for detecting LTM failure: Timer values for evaluating expiration.

[0307] (3) Step 3: The UE applies the candidate cell configuration of the primary candidate cell.

[0308] If the LTM command includes ConditionalReconfiguration and if the execution condition is met for the primary candidate cell, the UE can apply the stored candidate cell configuration (e.g., condRRCReconfig) of the primary candidate cell that meets the execution condition.

[0309] Otherwise, if the primary candidate cell is one of the pre-configured candidate serving cells for the UE, the UE can apply the stored candidate cell configuration of the primary candidate cell.

[0310] Otherwise, the UE can apply the candidate cell configuration of the primary candidate cell included in the LTM command.

[0311] (4) Step 4: The UE performs mobility to the primary candidate cell by sending a UL signal to the primary candidate cell.

[0312] The UE can send a UL signal to the primary candidate cell via at least one of L1 signaling (e.g., PUCCH, PUSCH, etc.), L2 signaling (e.g., MAC CE), or L3 signaling (e.g., RRCReconfigurationComplete).

[0313] When sending a UL signal to the primary candidate cell, the UE can start evaluating mobility failure based on timer-based failure detection. For example, the timer can be started after sending the UL signal to the primary candidate cell. For example, the timer can be stopped when receiving a message indicating the confirmation of the UL signal sent to the primary candidate cell. The value of the timer can be set to evaluate the expiration of the timer.

[0314] The UE can receive a message indicating the confirmation of the UL signal sent to the primary candidate cell. When receiving the message, the successful execution of mobility to the primary candidate cell can be considered.

[0315] If receiving an LTM command via one of L1 / L2 signaling, the UE can maintain the source resources and configurations and perform TA maintenance and beam failure detection (BFD) and / or radio link monitoring (RLM). Otherwise, if the LTM command includes an indicator indicating that the source cell is changed to a candidate serving cell, the UE can maintain the source resources and configurations and perform TA maintenance and BFD / RLM. Otherwise, the UE can release the source resources and configurations and stop DL / UL reception / transmission with the source cell.

[0316] (5) Step 5: If the UE detects the failure of LTM of the primary candidate cell, the UE applies the candidate cell configuration of the secondary candidate cell.

[0317] The failure can be detected after the expiration of the timer described in Step 4.

[0318] If the LTM command includes ConditionalReconfiguration, and if the execution condition is met for the secondary candidate cell, the UE can apply the stored candidate cell configuration (e.g., condRRCReconfig) of the secondary candidate cell that meets the execution condition.

[0319] Otherwise, if the secondary candidate cell is one of the pre-configured candidate serving cells for the UE, the UE can apply the stored candidate cell configuration of the secondary candidate cell.

[0320] Otherwise, the UE can apply the candidate cell configuration of the secondary candidate cell included in the LTM command.

[0321] The UE may need to restore the previous source cell (group) configuration before LTM, and may apply the candidate cell configuration of the secondary candidate cell when using the previous source cell (group) configuration and / or other reference cell configurations (if configured) as the baseline.

[0322] (6) Step 6: The UE performs mobility to the secondary candidate cell by sending a UL signal to the secondary candidate cell.

[0323] The UE may synchronize with the secondary candidate cell.

[0324] The UE may send a UL signal to the secondary candidate cell via at least one of L1 signaling (e.g., PUCCH, PUSCH, etc.), L2 signaling (e.g., MAC CE), or L3 signaling (e.g., RRCReconfigurationComplete).

[0325] The UE may receive a message indicating an acknowledgment of the UL signal sent to the secondary candidate cell. When this message is received, the mobility to the secondary candidate cell can be considered successfully performed.

[0326] If a LTM command is received via one of L1 / L2 signaling, the UE may maintain the source resources and configuration and perform TA maintenance and BFD / RLM. Otherwise, if the LTM command 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 perform TA maintenance and BFD / RLM. Otherwise, the UE may release the source resources and configuration and stop DL / UL reception / transmission with the source cell.

[0327] (1) Implementation 2

[0328] Figure 11 An example of the process of applying Implementation 2 of the present disclosure is shown.

[0329] According to Implementation 2 of the present disclosure, the indication / information is included in the LTM command. The UE operations according to Implementation 2 of the present disclosure may include at least one of the steps described below.

[0330] (1) Step 1: The UE may receive one or more candidate cell configurations.

[0331] In one or more candidate cell configurations, one or more candidate serving cells may also be configured.

[0332] One or more candidate cell configurations may include at least one of the following items:

[0333] - Configuration of SpCell, e.g., servingCellConfigCommon, servingCellConfig, reconfigurationWithSync, RLF-related configuration, etc.

[0334] - Configuration of SCell, e.g., servingCellConfigCommon, servingCellConfig, smtc, DRX configuration, etc.

[0335] - MAC / RLC-related configuration

[0336] - Configuration for detecting LTM failure: Timer values for evaluation of expiration.

[0337] A list of one or more secondary candidate cells may be included as a list separate from the list of one or more primary candidate cells.

[0338] A list of one or more secondary candidate cells may be a subset of the list of one or more primary candidate cells.

[0339] Instead of a list of one or more secondary candidate cells, for each primary candidate cell from one or more primary candidate cells, a flag may be included to indicate whether the corresponding cell can be a secondary candidate cell.

[0340] (2) Step 2: The UE receives an LTM command (i.e., a cell handover command).

[0341] The LTM command may be received via one of the L1 / L2 / L3 signaling.

[0342] The LTM command may be used for network-controlled serving cell change (e.g., normal mobility) or UE-initiated serving cell change (e.g., conditional mobility such as CHO, CPA, CPC).

[0343] The LTM command may include at least one of the following items:

[0344] - A list of one or more primary candidate cells

[0345] - A list of one or more secondary candidate cells

[0346] - Target cell information: If the target cell is one of the pre-configured candidate serving cells for the UE, the LTM command may include the ID of the candidate serving cell indicated by the LTM command. Otherwise, if the target cell is not one of the pre-configured candidate serving cells, the LTM command may include the configuration of the target cell (e.g., RRCReconfiguration including reconfigurationWithSync).

[0347] - Conditional reconfiguration (e.g., ConditionalReconfiguration).

[0348] - Indicator indicating that the source cell is changed to a candidate serving cell: For example, the indicator can be an explicit 1-bit indication in DCI or MAC CE. For example, the indicator can be an explicit RRC IE. For example, an LTM command received via L1 / L2 signaling can implicitly indicate that the source cell is changed to a candidate serving cell. For example, the target cell can be included in a list, where the list can implicitly indicate that the source cell is changed to a candidate serving cell.

[0349] - Configuration for detecting LTM failure: Timer values for evaluation of expiration.

[0350] (3) Step 3: The UE applies the candidate cell configuration of the primary candidate cell.

[0351] If the LTM command includes ConditionalReconfiguration and if the execution condition is met for the primary candidate cell, the UE may apply the stored candidate cell configuration (e.g., condRRCReconfig) of the primary candidate cell that meets the execution condition.

[0352] Otherwise, if the primary candidate cell is one of the pre-configured candidate serving cells for the UE, the UE may apply the stored candidate cell configuration of the primary candidate cell.

[0353] Otherwise, the UE may apply the candidate cell configuration of the primary candidate cell included in the LTM command.

[0354] (4) Step 4: The UE performs mobility to the primary candidate cell by sending a UL signal to the primary candidate cell.

[0355] The UE may send a UL signal to the primary candidate cell via at least one of L1 signaling (e.g., PUCCH, PUSCH, etc.), L2 signaling (e.g., MAC CE), or L3 signaling (e.g., RRCReconfigurationComplete).

[0356] When sending a UL signal to the primary candidate cell, the UE may start evaluating mobility failure based on timer-based failure detection. For example, the timer may be started when sending a UL signal to the primary candidate cell. For example, the timer may stop when receiving a message confirming the UL signal indicating being launched to the primary candidate cell. The value of the timer can be set to evaluate timer expiration.

[0357] The UE may receive a message indicating the confirmation of the UL signal sent to the primary candidate cell. When receiving this message, the mobility to the primary candidate cell can be considered to be successfully executed.

[0358] If the UE receives an LTM command via one of the L1 / L2 signaling, the UE may maintain the source resources and configurations and perform TA maintenance and beam failure detection (BFD) and / or radio link monitoring (RLM). Otherwise, if the LTM command includes an indicator that the source cell is changed to a candidate serving cell, the UE may maintain the source resources and configurations and perform TA maintenance and BFD / RLM. Otherwise, the UE may release the source resources and configurations and stop DL / UL reception / transmission with the source cell.

[0359] (5) Step 5: If the UE detects the failure of the LTM of the primary candidate cell, the UE applies the candidate cell configuration of the secondary candidate cell.

[0360] The failure can be detected at the expiration of the timer described in step 4.

[0361] If the LTM command includes ConditionalReconfiguration, and if the execution condition is satisfied for the secondary candidate cell, the UE may apply the stored candidate cell configuration (e.g., condRRCReconfig) of the secondary candidate cell that satisfies the execution condition.

[0362] Otherwise, if the secondary candidate cell is one of the pre-configured candidate serving cells for the UE, the UE may apply the stored candidate cell configuration of the secondary candidate cell.

[0363] Otherwise, the UE may apply the candidate cell configuration of the secondary candidate cell included in the LTM command.

[0364] The UE may need to restore to the previous source cell (group) configuration before LTM, and may apply the candidate cell configuration of the secondary candidate cell when using the previous source cell (group) configuration and / or other reference cell configurations (if configured) as the baseline.

[0365] (6) Step 6: The UE performs the mobility to the secondary candidate cell by sending a UL signal to the secondary candidate cell.

[0366] The UE may synchronize with the secondary candidate cell.

[0367] The UE may send a UL signal to the secondary candidate cell via at least one of L1 signaling (e.g., PUCCH, PUSCH, etc.), L2 signaling (e.g., MAC CE), or L3 signaling (e.g., RRCReconfigurationComplete).

[0368] The UE may receive a message indicating the confirmation of the UL signal sent to the secondary candidate cell. When receiving this message, it can be considered that the mobility to the secondary candidate cell has been successfully performed.

[0369] If the UE receives an LTM command via one of the L1 / L2 signaling, the UE may maintain the source resources and configurations and perform TA maintenance and BFD / RLM. Otherwise, if the LTM command includes an indicator indicating that the source cell is changed to a candidate serving cell, the UE may maintain the source resources and configurations and perform TA maintenance and BFD / RLM. Otherwise, the UE may release the source resources and configurations and stop DL / UL reception / transmission with the source cell.

[0370] The present disclosure may have various beneficial effects.

[0371] For example, the UE may attempt to access the secondary candidate cell when detecting the failure of the LTM of the primary candidate cell.

[0372] For example, the user data interruption can be reduced by performing a recovery faster than the conventional failure recovery based on the RRC reconstruction procedure.

[0373] The beneficial effects obtained through the specific examples of this specification are not limited to the effects listed above. For example, there may be various technical effects that those of ordinary skill in the art can understand or derive from this specification. 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.

[0374] The claims in the present disclosure can be combined in various ways. For example, the technical features in the method claims of the present disclosure can be combined to be implemented or executed in a device, and the technical features in the device claims can be combined to be implemented or executed in a method. In addition, the technical features in the method claims and the device claims can be combined to be implemented or executed in a device. In addition, the technical features in the method claims and the device claims can be combined to be implemented or executed in a method. Other embodiments are within the scope of the appended claims.

Claims

1. A method performed by a wireless device adapted to operate in a wireless communication system, the method comprising the steps of: receiving a serving cell configuration for a serving cell; receiving one or more candidate cell configurations for one or more candidate cells, wherein the one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells; receiving a cell handover command triggering mobility to a primary candidate cell among the one or more primary candidate cells; performing mobility to the primary candidate cell, the mobility including applying a candidate cell configuration for the primary candidate cell among the one or more candidate cell configurations; evaluating a failure of the mobility; and upon detecting the failure of the mobility, performing mobility to a secondary candidate cell among the one or more secondary candidate cells, the mobility including applying a candidate cell configuration for the secondary candidate cell among the one or more candidate cell configurations.

2. The method according to claim 1, wherein, the method further comprises the step of: receiving information related to the one or more secondary candidate cells.

3. The method according to claim 2, wherein, the information related to the one or more secondary candidate cells is received via the one or more candidate cell configurations.

4. The method according to claim 3, wherein, the information related to the one or more secondary candidate cells is included as a list separate from a list related to the one or more primary candidate cells.

5. The method according to claim 3, wherein, the information related to the one or more secondary candidate cells is included as a flag in the candidate cell configuration for each of the one or more primary candidate cells.

6. The method according to claim 2, wherein, the information related to the one or more secondary candidate cells is received via the cell handover command.

7. The method according to any one of claims 2 to 6, wherein, the information related to the one or more secondary candidate cells includes priority information for the one or more second candidate cells.

8. The method according to claim 7, wherein, the secondary candidate cell has the highest priority among the one or more secondary candidate cells based on the priority information.

9. The method according to any one of claims 1 to 8, wherein, the one or more secondary candidate cells are a subset of the one or more primary candidate cells.

10. The method according to any one of claims 1 to 9, wherein, the one or more candidate cell configurations and / or the cell handover command include information about a value of a timer for evaluating the failure of the mobility.

11. The method according to claim 10, wherein, the step of evaluating the failure of the mobility includes the steps of: starting the timer; and evaluating expiration of the timer based on the value of the timer.

12. The method according to claim 11, wherein, When transmitting an uplink (UL) signal for performing the mobility to the primary candidate cell to the primary candidate cell, the timer is started.

13. The method according to claim 11 or 12, wherein, when receiving an acknowledgement of the UL signal transmitted to the primary candidate cell from the primary candidate cell, the timer is stopped.

14. The method according to any one of claims 1 to 13, wherein, the wireless device communicates with at least one of a mobile device, a network, and / or an autonomous vehicle other than the wireless device.

15. A wireless device adapted to operate in a wireless communication system, the wireless device comprising: at least one transceiver; at least one processor; and at least one memory, the at least one memory being operatively connected to the at least one processor and storing instructions that, when executed by the at least one processor, perform the method according to any one of claims 1 to 14.

16. A processing device adapted to control a wireless device in a wireless communication system, the processing device comprising: at least one processor; and at least one memory, the at least one memory being operatively connected to the at least one processor, wherein the at least one processor is adapted to perform the method according to any one of claims 1 to 14.

17. A non-transitory computer-readable medium (CRM) storing instructions that, when executed by at least one processor, perform the method according to any one of claims 1 to 14.

18. A method performed by a base station adapted to operate in a wireless communication system, the method comprising the steps of: transmitting a serving cell configuration for a serving cell; transmitting one or more candidate cell configurations for one or more candidate cells, wherein the one or more candidate cells include one or more primary candidate cells and one or more secondary candidate cells; and transmitting a cell handover command triggering mobility to a primary candidate cell among the one or more primary candidate cells, wherein performing the mobility to the primary candidate cell, the mobility including applying the candidate cell configuration for the primary candidate cell among the one or more candidate cell configurations, and wherein evaluating a failure of the mobility and, when detecting the failure of the mobility, performing mobility to a secondary candidate cell among the one or more secondary candidate cells, the mobility including applying the candidate cell configuration for the secondary candidate cell among the one or more candidate cell configurations.

19. A base station serving a second serving cell and adapted to operate in a wireless communication system, the base station comprising: at least one transceiver; at least one processor; and at least one memory, the at least one memory being operatively connected to the at least one processor and storing instructions that, when executed by the at least one processor, perform the method according to claim 18.

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