Faster failure recovery based on candidate cell configurations

Abstract

A method and apparatus for a faster failure recovery based on candidate cell configurations is provided. A wireless device receives recovery information for failure recovery from a network. The recovery information includes access information which is to be used for accessing a candidate cell during the failure recovery. Upon detecting a failure, the wireless device initiates the failure recovery by applying a candidate cell configuration based on the recovery information. The wireless device determines whether to perform a random access procedure based on the access information, and accesses the candidate cell based on a determination related to the random access procedure.

Description

FASTER FAILURE RECOVERY BASED ON CANDIDATE CELL CONFIGURATIONS

[0001] The present disclosure relates to a faster failure recovery based on candidate cell configurations.

[0002] 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.

[0003] 3GPP New Radio (NR) targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced Mobile BroadBand (eMBB), massive Machine Type Communications (mMTC), Ultra-Reliable and Low Latency Communications (URLLC), etc. The NR shall be inherently forward compatible. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.

[0004] 6G is the successor to 5G cellular technology. 6G networks will be able to use higher frequencies than 5G networks and provide substantially higher capacity and much lower latency. The 6G technology market is expected to facilitate large improvements in the areas of imaging, presence technology and location awareness. Working in conjunction with Artificial Intelligence (AI), the 6G computational infrastructure will be able to identify the best place for computing to occur. This includes decisions about data storage, processing and sharing.

[0005] Layer 3 based mobility has evolved over several releases. Conditional Handover (CHO) and other conditional mobility procedures (Conditional PSCell Addition and Change (CPAC), Subsequent CPAC (SCPAC)) were developed to achieve high robustness by enabling the procedure to be executed without necessitating a signaling exchange with source cell beforehand. L1 / L2 Triggered Mobility (LTM) as introduced in Rel-18 offers short interruption time but not with the same level of robustness as the conditional L3 mobility procedures. In Rel-19, enhancements should be specified so that the system can benefit from both the high robustness and short interruption.

[0006] In an aspect, a method is provided. The method comprises receiving recovery information for failure recovery from a network. The recovery information includes access information which is to be used for accessing a candidate cell during the failure recovery. The method comprises, upon detecting a failure, initiating the failure recovery by applying a candidate cell configuration based on the recovery information. The method comprises determining whether to perform a random access procedure based on the access information, and accessing the candidate cell based on a determination related to the random access procedure.

[0007] In another aspect, an apparatus for implementing the above method is provided.

[0008] FIG. 1 shows an example of a communication system to which implementations of the present disclosure are applied.

[0009] FIG. 2 shows an example of wireless devices to which implementations of the present disclosure are applied.

[0010] FIG. 3 shows an example of UE to which implementations of the present disclosure are applied.

[0011] FIGS. 4 and 5 show an example of protocol stacks in a 3GPP based wireless communication system to which implementations of the present disclosure are applied.

[0012] FIG. 6 shows a frame structure in a 3GPP based wireless communication system to which implementations of the present disclosure are applied.

[0013] FIG. 7 shows a data flow example in the 3GPP NR system to which implementations of the present disclosure are applied.

[0014] FIG. 8 shows an example of inter-gNB handover procedures to which implementations of the present disclosure are applied.

[0015] FIG. 9 shows an example of signaling procedure for LTM to which implementations of the present disclosure are applied.

[0016] FIG. 10 shows an example of a method to which implementations of the present disclosure are applied.

[0017] FIG. 11 shows an example of another method to which implementations of the present disclosure are applied.

[0018] The following techniques, apparatuses, and systems may be applied to a variety of wireless multiple access systems. Examples of the multiple access systems include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, a Single Carrier Frequency Division Multiple Access (SC-FDMA) system, and a Multi Carrier Frequency Division Multiple Access (MC-FDMA) system. CDMA may be embodied through radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be embodied through radio technology such as Global System for Mobile communications (GSM), General Packet Radio Service (GPRS), or Enhanced Data rates for GSM Evolution (EDGE). OFDMA may be embodied through radio technology 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 a part of a Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA in Downlink (DL) and SC-FDMA in Uplink (UL). Evolution of 3GPP LTE includes LTE-Advanced (LTE-A), LTE-A Pro, 5G New Radio (NR) and / or 6G.

[0019] For convenience of description, implementations of the present disclosure are mainly described in regards 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 that are not limited to 3GPP based wireless communication system are applicable to other mobile communication systems.

[0020] For terms and technologies which are not specifically described among the terms of and technologies employed in the present disclosure, the wireless communication standard documents published before the present disclosure may be referenced.

[0021] 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".

[0022] In the present disclosure, slash ( / ) or comma (,) may mean "and / or". For example, "A / B" may mean "A and / or B". Accordingly, "A / B" may mean "only A", "only B", or "both A and B". For example, "A, B, C" may mean "A, B or C".

[0023] In the present disclosure, "at least one of A and B" may mean "only A", "only B" or "both A and B". In addition, the expression "at least one of A or B" or "at least one of A and / or B" in the present disclosure may be interpreted as same as "at least one of A and B".

[0024] In addition, in the present disclosure, "at least one of A, B and C" may mean "only A", "only B", "only C", or "any combination of A, B and C". In addition, "at least one of A, B or C" or "at least one of A, B and / or C" may mean "at least one of A, B and C".

[0025] Also, parentheses used in the present disclosure may mean "for example". In detail, when it is shown as "control information (PDCCH)", "PDCCH" may be proposed as an example of "control information". In other words, "control information" in the present disclosure is not limited to "PDCCH", and "PDCCH" may be proposed as an example of "control information". In addition, even when shown as "control information (i.e., PDCCH)", "PDCCH" may be proposed as an example of "control information".

[0026] Technical features that are separately described in one drawing in the present disclosure may be implemented separately or simultaneously.

[0027] Although not limited thereto, various descriptions, functions, procedures, suggestions, methods and / or operational flowcharts of the present disclosure disclosed herein can be applied to various fields requiring wireless communication and / or connection (e.g., 5G) between devices.

[0028] Hereinafter, the present disclosure will be described in more detail with reference to drawings. 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 unless otherwise indicated.

[0029] FIG. 1 shows an example of a communication system to which implementations of the present disclosure are applied.

[0030] The 5G usage scenarios shown in FIG. 1 are only exemplary, and the technical features of the present disclosure can be applied to other 5G usage scenarios which are not shown in FIG. 1.

[0031] Three main requirement categories for 5G include (1) a category of enhanced Mobile BroadBand (eMBB), (2) a category of massive Machine Type Communication (mMTC), and (3) a category of Ultra-Reliable and Low Latency Communications (URLLC).

[0032] Referring to FIG. 1, the communication system 1 includes wireless devices 100a to 100f, Base Stations (BSs) 200, and a network 300. Although FIG. 1 illustrates a 5G network as an example of the network of the communication system 1, the implementations of the present disclosure are not limited to the 5G system, and can be applied to the future communication system beyond the 5G system.

[0033] The BSs 200 and the network 300 may be implemented as wireless devices and a specific wireless device may operate as a BS / network node with respect to other wireless devices.

[0034] The wireless devices 100a to 100f represent devices performing communication using Radio Access Technology (RAT) (e.g., 5G NR or LTE) and may be referred to as communication / radio / 5G devices. The wireless devices 100a to 100f may include, without being limited to, a robot 100a, vehicles 100b-1 and 100b-2, an eXtended Reality (XR) device 100c, a hand-held device 100d, a home appliance 100e, an Internet-of-Things (IoT) device 100f, and an Artificial Intelligence (AI) device / server 400. For example, the vehicles may include a vehicle having a wireless communication function, an autonomous driving vehicle, and a vehicle capable of performing communication between vehicles. The vehicles 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 television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, etc. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), 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 a sensor and a smartmeter.

[0035] In the present disclosure, the wireless devices 100a to 100f may be called User Equipments (UEs). A UE may include, for example, a cellular phone, a smartphone, a laptop computer, a digital broadcast terminal, a Personal Digital Assistant (PDA), a Portable Multimedia Player (PMP), a navigation system, a slate Personal Computer (PC), a tablet PC, an ultrabook, a vehicle, a vehicle having an autonomous traveling function, a connected car, an 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 a financial device), a security device, a weather / environment device, a device related to a 5G service, or a device related to a fourth industrial revolution field.

[0036] The wireless devices 100a to 100f may be connected to the network 300 via the BSs 200. An AI technology may be applied to the wireless devices 100a to 100f and the wireless devices 100a to 100f may be connected to the AI server 400 via the network 300. The network 300 may be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, and a beyond-5G network. Although the wireless devices 100a to 100f may communicate with each other through the BSs 200 / network 300, the wireless devices 100a to 100f may perform direct communication (e.g., sidelink communication) with each other without passing through the BSs 200 / network 300. For example, the vehicles 100b-1 and 100b-2 may perform direct communication (e.g., Vehicle-to-Vehicle (V2V) / Vehicle-to-everything (V2X) communication). The IoT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100a to 100f.

[0037] Wireless communication / connections 150a, 150b and 150c may be established between the wireless devices 100a to 100f and / or between wireless device 100a to 100f and BS 200 and / or between BSs 200. Herein, the wireless communication / connections may be established through various RATs (e.g., 5G NR) such as uplink / downlink communication 150a, sidelink communication (or Device-to-Device (D2D) communication) 150b, inter-base station communication 150c (e.g., relay, Integrated Access and Backhaul (IAB)), etc. The wireless devices 100a to 100f and the BSs 200 / the wireless devices 100a to 100f may transmit / receive radio signals to / from each other through the wireless communication / connections 150a, 150b and 150c. For example, the wireless communication / connections 150a, 150b and 150c may transmit / receive signals through various physical channels. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, and resource mapping / de-mapping), and resource allocating processes, for transmitting / receiving radio signals, may be performed based on the various proposals of the present disclosure.

[0038] NR supports multiples numerologies (and / or multiple Sub-Carrier Spacings (SCS)) to support various 5G services. For example, if SCS is 15 kHz, wide area can be supported in traditional cellular bands, and if SCS is 30 kHz / 60 kHz, dense-urban, lower latency, and wider carrier bandwidth can be supported. If SCS is 60 kHz or higher, bandwidths greater than 24.25 GHz can be supported to overcome phase noise.

[0039] The NR frequency band may be defined as two types of frequency range, i.e., Frequency Range 1 (FR1) and Frequency Range 2 (FR2). The numerical value of the frequency range may be changed. For example, the frequency ranges of the two types (FR1 and FR2) may be as shown in Table 1 below. For ease of explanation, in the frequency ranges used in the NR system, FR1 may mean "sub 6 GHz range", FR2 may mean "above 6 GHz range," and may be referred to as millimeter Wave (mmW).

[0040] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0041] As mentioned above, the numerical value of the frequency range of the NR system may be changed. For example, FR1 may include a frequency band of 410MHz to 7125MHz as shown in Table 2 below. That is, FR1 may include a frequency band of 6GHz (or 5850, 5900, 5925 MHz, etc.) or more. For example, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more included in FR1 may include an unlicensed band. Unlicensed bands may be used for a variety of purposes, for example for communication for vehicles (e.g., autonomous driving).

[0042] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0043] 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, NB-IoT technology may be an example of Low Power Wide Area Network (LPWAN) technology, may be implemented in specifications such as LTE Cat NB1 and / or LTE Cat NB2, and may not be limited to the above-mentioned names. 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, LTE-M technology may be an example of LPWAN technology and be called by various names such as enhanced MTC (eMTC). For example, LTE-M technology may be implemented in at least one of the 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-mentioned 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 which take into account low-power communication, and may not be limited to the above-mentioned names. For example, ZigBee technology may generate Personal Area Networks (PANs) associated with small / low-power digital communication based on various specifications such as IEEE 802.15.4 and may be called various names.

[0044] FIG. 2 shows an example of wireless devices to which implementations of the present disclosure are applied.

[0045] In FIG. 2, The first wireless device 100 and / or the second wireless device 200 may be implemented in various forms according to use cases / services. For example, {the first wireless device 100 and the second wireless device 200} may correspond to at least one of {the wireless device 100a to 100f and the BS 200}, {the wireless device 100a to 100f and the wireless device 100a to 100f} and / or {the BS 200 and the BS 200} of FIG. 1. The first wireless device 100 and / or the second wireless device 200 may be configured by various elements, devices / parts, and / or modules.

[0046] The first wireless device 100 may include at least one transceiver, such as a transceiver 106, at least one processing chip, such as a processing chip 101, and / or one or more antennas 108.

[0047] The processing chip 101 may include at least one processor, such a processor 102, and at least one memory, such as a memory 104. Additional and / or alternatively, the memory 104 may be placed outside of the processing chip 101.

[0048] The processor 102 may control the memory 104 and / or the transceiver 106 and may be adapted to implement the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts described in the present disclosure. For example, the processor 102 may process information within the memory 104 to generate first information / signals and then transmit radio signals including the first information / signals through the transceiver 106. The processor 102 may receive radio signals including second information / signals through the transceiver 106 and then store information obtained by processing the second information / signals in the memory 104.

[0049] The memory 104 may be operably connectable to the processor 102. The memory 104 may store various types of information and / or instructions. The memory 104 may store a firmware and / or a software code 105 which implements codes, commands, and / or a set of commands that, when executed by the processor 102, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 105 may implement instructions that, when executed by the processor 102, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 105 may control the processor 102 to perform one or more protocols. For example, the firmware and / or the software code 105 may control the processor 102 to perform one or more layers of the radio interface protocol.

[0050] Herein, the processor 102 and the memory 104 may be a part of a communication modem / circuit / chip designed to implement RAT (e.g., LTE or NR). The transceiver 106 may be connected to the processor 102 and transmit and / or receive radio signals through one or more antennas 108. Each of the transceiver 106 may include a transmitter and / or a receiver. The transceiver 106 may be interchangeably used with Radio Frequency (RF) unit(s). In the present disclosure, the first wireless device 100 may represent a communication modem / circuit / chip.

[0051] The second wireless device 200 may include at least one transceiver, such as a transceiver 206, at least one processing chip, such as a processing chip 201, and / or one or more antennas 208.

[0052] The processing chip 201 may include at least one processor, such a processor 202, and at least one memory, such as a memory 204. Additional and / or alternatively, the memory 204 may be placed outside of the processing chip 201.

[0053] The processor 202 may control the memory 204 and / or the transceiver 206 and may be adapted to implement the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts described in the present disclosure. For example, the processor 202 may process information within the memory 204 to generate third information / signals and then transmit radio signals including the third information / signals through the transceiver 206. The processor 202 may receive radio signals including fourth information / signals through the transceiver 106 and then store information obtained by processing the fourth information / signals in the memory 204.

[0054] The memory 204 may be operably connectable to the processor 202. The memory 204 may store various types of information and / or instructions. The memory 204 may store a firmware and / or a software code 205 which implements codes, commands, and / or a set of commands that, when executed by the processor 202, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 205 may implement instructions that, when executed by the processor 202, perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. For example, the firmware and / or the software code 205 may control the processor 202 to perform one or more protocols. For example, the firmware and / or the software code 205 may control the processor 202 to perform one or more layers of the radio interface protocol.

[0055] Herein, the processor 202 and the memory 204 may be a part of a communication modem / circuit / chip designed to implement RAT (e.g., LTE or NR). The transceiver 206 may be connected to the processor 202 and transmit and / or receive radio signals through one or more antennas 208. Each of the transceiver 206 may include a transmitter and / or a receiver. The transceiver 206 may be interchangeably used with RF unit. In the present disclosure, the second wireless device 200 may represent a communication modem / circuit / chip.

[0056] Hereinafter, hardware elements of the wireless devices 100 and 200 will be described more specifically. One or more protocol layers may be implemented by, without being limited to, one or more processors 102 and 202. For example, the one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as Physical (PHY) layer, Media 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). The one or more processors 102 and 202 may generate one or more Protocol Data Units (PDUs), one or more Service Data Unit (SDUs), messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. The 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 operational flowcharts disclosed in the present disclosure and provide the generated signals to the one or more transceivers 106 and 206. The one or more processors 102 and 202 may receive the signals (e.g., baseband signals) from the one or more transceivers 106 and 206 and acquire the PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure.

[0057] The one or more processors 102 and 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The 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 the one or more processors 102 and 202. For example, the 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 Graphic Processing Unit (GPU), and a memory control processor.

[0058] The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, code, instructions, and / or commands. The 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 memory, non-volatile memory, hard drive, register, cash memory, computer-readable storage medium, and / or combinations thereof. The one or more memories 104 and 204 may be located at the interior and / or exterior of the one or more processors 102 and 202. The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 through various technologies such as wired or wireless connection.

[0059] The one or more transceivers 106 and 206 may transmit user data, control information, and / or radio signals / channels, mentioned in the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure, to one or more other devices. The 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 operational flowcharts disclosed in the present disclosure, from one or more other devices. For example, the one or more transceivers 106 and 206 may be connected to the one or more processors 102 and 202 and transmit and receive radio signals. For example, the one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may transmit user data, control information, or radio signals to one or more other devices. The one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may receive user data, control information, or radio signals from one or more other devices.

[0060] The one or more transceivers 106 and 206 may be connected to the one or more antennas 108 and 208. Additionally and / or alternatively, the one or more transceivers 106 and 206 may include one or more antennas 108 and 208. The one or more transceivers 106 and 206 may be adapted to transmit and receive user data, control information, and / or radio signals / channels, mentioned in the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure, through the one or more antennas 108 and 208. In the present disclosure, the one or more antennas 108 and 208 may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).

[0061] The 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 in order to process received user data, control information, radio signals / channels, etc., using the one or more processors 102 and 202. The one or more transceivers 106 and 206 may convert the user data, control information, radio signals / channels, etc., processed using the one or more processors 102 and 202 from the base band signals into the RF band signals. To this end, the one or more transceivers 106 and 206 may include (analog) oscillators and / or filters. For example, the one or more transceivers 106 and 206 can up-convert OFDM baseband signals to OFDM signals by their (analog) oscillators and / or filters under the control of the one or more processors 102 and 202 and transmit the up-converted OFDM signals at the carrier frequency. The one or more transceivers 106 and 206 may receive OFDM signals at a carrier frequency and down-convert the OFDM signals into OFDM baseband signals by their (analog) oscillators and / or filters under the control of the one or more processors 102 and 202.

[0062] Although not shown in FIG. 2, the wireless devices 100 and 200 may further include additional components. The additional components 140 may be variously configured according to types of the wireless devices 100 and 200. For example, the additional components 140 may include at least one of a power unit / battery, an Input / Output (I / O) device (e.g., audio I / O port, video I / O port), a driving device, and a computing device. The additional components 140 may be coupled to the one or more processors 102 and 202 via various technologies, such as a wired or wireless connection.

[0063] In the implementations of the present disclosure, a UE may operate as a transmitting device in UL and as a receiving device in DL. In the implementations of the present disclosure, a BS may operate as a receiving device in UL and as a transmitting device in DL. Hereinafter, for convenience of description, it is mainly assumed that the first wireless device 100 acts as the UE, and the second wireless device 200 acts as the BS. For example, the processor(s) 102 connected to, mounted on or launched in the first wireless device 100 may be adapted to perform the UE behavior according to an implementation of the present disclosure or control the transceiver(s) 106 to perform the UE behavior according to an implementation of the present disclosure. The processor(s) 202 connected to, mounted on or launched in the second wireless device 200 may be adapted to perform the BS behavior according to an implementation of the present disclosure or control the transceiver(s) 206 to perform the BS behavior according to an implementation of the present disclosure.

[0064] In the present disclosure, a BS is also referred to as a node B (NB), an eNode B (eNB), or a gNB.

[0065] FIG. 3 shows an example of UE to which implementations of the present disclosure are applied.

[0066] Referring to FIG. 3, a UE 100 may correspond to the first wireless device 100 of FIG. 2.

[0067] A 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 keypad 144, a Subscriber Identification Module (SIM) card 145, a speaker 146, and a microphone 147.

[0068] The processor 102 may be adapted to implement the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. The processor 102 may be adapted to control one or more other components of the UE 100 to implement the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. Layers of the radio interface protocol may be implemented in the processor 102. The processor 102 may include ASIC, other chipset, logic circuit and / or data processing device. The processor 102 may be an application processor. The processor 102 may include at least one of DSP, CPU, GPU, a modem (modulator and demodulator). An example of the processor 102 may be found in SNAPDRAGONTMseries of processors made by Qualcomm®, EXYNOSTMseries of processors made by Samsung®, A series of processors made by Apple®, HELIOTMseries of processors made by MediaTek®, ATOMTMseries of processors made by Intel®or a corresponding next generation processor.

[0069] The memory 104 is operatively coupled with the processor 102 and stores a variety of information to operate the processor 102. The memory 104 may include ROM, RAM, flash memory, memory card, storage medium and / or other storage device. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, etc.) that perform the descriptions, functions, procedures, suggestions, methods and / or operational flowcharts disclosed in the present disclosure. The modules can be stored in the memory 104 and executed by the processor 102. The memory 104 can be implemented within the processor 102 or external to the processor 102 in which case those can be communicatively coupled to the processor 102 via various means as is known in the art.

[0070] The transceiver 106 is operatively coupled with the processor 102, and transmits and / or receives a radio signal. The transceiver 106 includes a transmitter and a receiver. The transceiver 106 may include baseband circuitry to process radio frequency signals. The transceiver 106 controls the one or more antennas 108 to transmit and / or receive a radio signal.

[0071] The power management module 141 manages power for the processor 102 and / or the transceiver 106. The battery 142 supplies power to the power management module 141.

[0072] The display 143 outputs results processed by the processor 102. The keypad 144 receives inputs to be used by the processor 102. The keypad 144 may be shown on the display 143.

[0073] The SIM card 145 is an　integrated circuit　that is intended to　securely store the　International Mobile Subscriber Identity　(IMSI) number and its related　key, which are used to identify and authenticate subscribers on　mobile telephony　devices (such as　mobile phones　and　computers). It is also possible to store contact information on many SIM cards.

[0074] The speaker 146 outputs sound-related results processed by the processor 102. The microphone 147 receives sound-related inputs to be used by the processor 102.

[0075] FIGS. 4 and 5 show an example of protocol stacks in a 3GPP based wireless communication system to which implementations of the present disclosure are applied.

[0076] In particular, FIG. 4 illustrates an example of a radio interface user plane protocol stack between a UE and a BS and FIG. 5 illustrates an example of a radio interface control plane protocol stack between a UE and a BS. The control plane refers to a path through which control messages used to manage call by a UE and a network are transported. The user plane refers to a path through which data generated in an application layer, for example, voice data or Internet packet data are transported. Referring to FIG. 4, the user plane protocol stack may be divided into Layer 1 (i.e., a PHY layer) and Layer 2. Referring to FIG. 5, the control plane protocol stack may be divided into Layer 1 (i.e., a PHY layer), Layer 2, Layer 3 (e.g., an RRC layer), and a Non-Access Stratum (NAS) layer. Layer 1, Layer 2 and Layer 3 are referred to as an Access Stratum (AS).

[0077] In the 3GPP LTE system, the Layer 2 is split into the following sublayers: MAC, RLC, and PDCP. In the 3GPP NR system, the Layer 2 is split into the following sublayers: MAC, RLC, PDCP and SDAP. The PHY layer offers to the MAC sublayer transport channels, the MAC sublayer offers to the RLC sublayer logical channels, the RLC sublayer offers to the PDCP sublayer RLC channels, the PDCP sublayer offers to the SDAP sublayer radio bearers. The SDAP sublayer offers to 5G core network Quality of Service (QoS) flows.

[0078] In the 3GPP NR system, the main services and functions of the MAC sublayer include: mapping between logical channels and transport channels; multiplexing / de-multiplexing of MAC SDUs belonging to one or different logical channels into / from Transport Blocks (TB) delivered to / from the physical layer on transport channels; scheduling information reporting; error correction through Hybrid Automatic Repeat reQuest (HARQ) (one HARQ entity per cell in case of Carrier Aggregation (CA)); priority handling between UEs by means of dynamic scheduling; priority handling between logical channels of one UE by means of logical channel prioritization; padding. A single MAC entity may support multiple numerologies, transmission timings and cells. Mapping restrictions in logical channel prioritization control which numerology(ies), cell(s), and transmission timing(s) a logical channel can use.

[0079] Different kinds of data transfer services are offered by MAC. To accommodate different kinds of data transfer services, multiple types of logical channels are defined, i.e., each supporting transfer of a particular type of information. Each logical channel type is defined by what type of information is transferred. Logical channels are classified into two groups: control channels and traffic channels. Control channels are used for the transfer of control plane information only, and traffic channels are used for the transfer of user plane information only. Broadcast Control Channel (BCCH) is a downlink logical channel for broadcasting system control information, Paging Control Channel (PCCH) is a downlink logical channel that transfers paging information, system information change notifications and indications of ongoing Public Warning Service (PWS) broadcasts, Common Control Channel (CCCH) is a logical channel for transmitting control information between UEs and network and used for UEs having no RRC connection with the network, and Dedicated Control Channel (DCCH) is a point-to-point bi-directional logical channel that transmits dedicated control information between a UE and the network and used by UEs having an RRC connection. Dedicated Traffic Channel (DTCH) is a point-to-point logical channel, dedicated to one UE, for the transfer of user information. A DTCH can exist in both uplink and downlink. In downlink, the following connections between logical channels and transport channels exist: BCCH can be mapped to Broadcast Channel (BCH); BCCH can be mapped to Downlink Shared Channel (DL-SCH); PCCH can be mapped to 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 uplink, the following connections between logical channels and transport channels exist: CCCH can be mapped to Uplink Shared Channel (UL-SCH); DCCH can be mapped to UL-SCH; and DTCH can be mapped to UL-SCH.

[0080] The RLC sublayer supports three transmission modes: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). The RLC configuration is per logical channel with no dependency on numerologies and / or transmission durations. In the 3GPP NR system, the main services and functions of the RLC sublayer depend on the transmission mode and include: transfer of upper layer PDUs; sequence numbering independent of the one in PDCP (UM and AM); error correction through ARQ (AM only); segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs; reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDU discard (AM and UM); RLC re-establishment; protocol error detection (AM only).

[0081] 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-order delivery; PDCP PDU routing (in case of split bearers); retransmission of PDCP SDUs; ciphering, deciphering and integrity protection; PDCP SDU discard; PDCP re-establishment and data recovery for RLC AM; PDCP status reporting for RLC AM; duplication of PDCP PDUs and duplicate discard indication to lower layers. The main services and functions of the PDCP sublayer for the control plane include: sequence numbering; ciphering, deciphering and integrity protection; transfer of control plane data; reordering and duplicate detection; in-order delivery; duplication of PDCP PDUs and duplicate discard indication to lower layers.

[0082] In the 3GPP NR system, the main services and functions of SDAP include: mapping between a QoS flow and a data radio bearer; marking QoS Flow ID (QFI) in both DL and UL packets. A single protocol entity of SDAP is configured for each individual PDU session.

[0083] In the 3GPP NR system, the main services and functions of the RRC sublayer include: broadcast of system information related to AS and NAS; paging initiated by 5G Core network (5GC) or Next-Generation Radio Access Network (NG-RAN); establishment, maintenance and release of an RRC connection between the UE and NG-RAN; security functions including key management; establishment, configuration, maintenance and release of Signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs); mobility functions (including: handover and context transfer, UE cell selection and reselection and control of cell selection and reselection, inter-RAT mobility); QoS management functions; UE measurement reporting and control of the reporting; detection of and recovery from radio link failure; NAS message transfer to / from NAS from / to UE.

[0084] FIG. 6 shows a frame structure in a 3GPP based wireless communication system to which implementations of the present disclosure are applied.

[0085] The frame structure shown in FIG. 6 is purely exemplary and the number of subframes, the number of slots, and / or the number of symbols in a frame may be variously changed. In the 3GPP based wireless communication system, OFDM numerologies (e.g., SCS, Transmission Time Interval (TTI) duration) may be differently configured between a plurality of cells aggregated for one UE. For example, if a UE is configured with different SCSs for cells aggregated for the cell, an (absolute time) duration of a time resource (e.g., a subframe, a slot, or a TTI) including the same number of symbols may be different among the aggregated cells. Herein, symbols may include OFDM symbols (or Cyclic Prefix (CP)-OFDM symbols), SC-FDMA symbols (or Discrete Fourier Transform-spread-OFDM (DFT-s-OFDM) symbols).

[0086] Referring to FIG. 6, downlink and uplink transmissions are organized into frames. Each frame has Tf= 10ms duration. Each frame is divided into two half-frames, where each of the half-frames has 5ms duration. Each half-frame consists of 5 subframes, where the duration Tsfper subframe is 1ms. Each subframe is divided into slots and the number of slots in a subframe depends on a subcarrier spacing. Each slot includes 14 or 12 OFDM symbols based on a CP. In a normal CP, each slot includes 14 OFDM symbols and, in an extended CP, each slot includes 12 OFDM symbols. The numerology is based on exponentially scalable subcarrier spacing Δf = 2u*15 kHz.

[0087] Table 3 shows the number of OFDM symbols per slot Nslotsymb, the number of slots per frameNframe,uslot, and the number of slots per subframe Nsubframe,uslotfor the normal CP, according to the subcarrier spacing Δf = 2u*15 kHz.

[0088] uNslotsymbNframe,uslotNsubframe,uslot01410111420221440431480841416016

[0089] Table 4 shows the number of OFDM symbols per slot Nslotsymb, the number of slots per frameNframe,uslot, and the number of slots per subframe Nsubframe,uslotfor the extended CP, according to the subcarrier spacing Δf = 2u*15 kHz.

[0090] uNslotsymbNframe,uslotNsubframe,uslot212404

[0091] A slot includes plural symbols (e.g., 14 or 12 symbols) in the time domain. For each numerology (e.g., subcarrier spacing) and carrier, a resource grid ofNsize,ugrid,x*NRBscsubcarriers andNsubframe,usymbOFDM symbols is defined, starting at Common Resource Block (CRB)Nstart,ugridindicated by higher-layer signaling (e.g., RRC signaling), whereNsize,ugrid,xis the number of Resource Blocks (RBs) in the resource grid and the subscript x is DL for downlink and UL for uplink.NRBscis the number of subcarriers per RB. In the 3GPP based wireless communication system,NRBscis 12 generally. There is one resource grid for a given antenna portp, subcarrier spacing configurationu, and transmission direction (DL or UL). The carrier bandwidthNsize,ugridfor subcarrier spacing configurationuis given by the higher-layer parameter (e.g., RRC parameter). Each element in the resource grid for the antenna portpand the subcarrier spacing configurationuis referred to as a Resource Element (RE) and one complex symbol may be mapped to each RE. Each RE in the resource grid is uniquely identified by an indexkin the frequency domain and an indexlrepresenting a symbol location relative to a reference point in the time domain. In the 3GPP based wireless communication system, an RB is defined by 12 consecutive subcarriers in the frequency domain.

[0092] In the 3GPP NR system, RBs are classified into CRBs and Physical Resource Blocks (PRBs). CRBs are numbered from 0 and upwards in the frequency domain for subcarrier spacing configurationu. The center of subcarrier 0 of CRB 0 for subcarrier spacing configurationucoincides with 'point A' which serves as a common reference point for resource block grids. In the 3GPP NR system, PRBs are defined within a BandWidth Part (BWP) and numbered from 0 toNsizeBWP,i-1, where i is the number of the bandwidth part. The relation between the physical resource block nPRBin the bandwidth part i and the common resource block nCRBis as follows: nPRB= nCRB+NsizeBWP,i, whereNsizeBWP,iis the common resource block where bandwidth part starts relative to CRB 0. The BWP includes a plurality of consecutive RBs. A carrier may include a maximum of N (e.g., 5) BWPs. A UE may be configured with one or more BWPs on a given component carrier. Only one BWP among BWPs configured to the UE can active at a time. The active BWP defines the UE's operating bandwidth within the cell's operating bandwidth.

[0093] In the present disclosure, the term "cell" may refer to a geographic area to which one or more nodes provide a communication system, or refer to radio resources. A "cell" as a geographic area may be understood as coverage within which a node can provide service using a carrier and a "cell" as radio resources (e.g., time-frequency resources) is associated with bandwidth which is a frequency range configured by the carrier. The "cell" associated with the radio resources is defined by a combination of downlink resources and uplink resources, for example, a combination of a DL Component Carrier (CC) and a UL CC. The cell may be configured by downlink resources only, or may be configured by downlink resources and uplink resources. Since DL coverage, which is a range within which the node is capable of transmitting a valid signal, and UL coverage, which is a range within which the node is capable of receiving the valid signal from the UE, depends upon a carrier carrying the signal, the coverage of the node may be associated with coverage of the "cell" of radio resources used by the node. Accordingly, the term "cell" may be used to represent service coverage of the node sometimes, radio resources at other times, or a range that signals using the radio resources can reach with valid strength at other times.

[0094] In CA, two or more CCs are aggregated. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities. CA is supported for both contiguous and non-contiguous CCs. When CA is configured, the UE only has one RRC connection with the network. At RRC connection establishment / re-establishment / handover, one serving cell provides the NAS mobility information, and at RRC connection re-establishment / handover, one serving cell provides the security input. This cell is referred to as the Primary Cell (PCell). The PCell is a cell, operating on the primary frequency, in which the UE either performs the initial connection establishment procedure or initiates the connection re-establishment procedure. Depending on UE capabilities, Secondary Cells (SCells) can be configured to form together with the PCell a set of serving cells. An SCell is a cell providing additional radio resources on top of Special Cell (SpCell). The configured set of serving cells for a UE therefore always consists of one PCell and one or more SCells. For Dual Connectivity (DC) operation, the term SpCell refers to the PCell of the Master Cell Group (MCG) or the Primary SCell (PSCell) of the Secondary Cell Group (SCG). An SpCell supports Physical Uplink Control Channel (PUCCH) transmission and contention-based random access, and is always activated. The MCG is a group of serving cells associated with a master node, comprised of the SpCell (PCell) and optionally one or more SCells. The SCG is the subset of serving cells associated with a secondary node, comprised of the PSCell and zero or more SCells, for a UE configured with DC. For a UE in RRC_CONNECTED not configured with CA / DC, there is only one serving cell comprised of the PCell. For a UE in RRC_CONNECTED configured with CA / DC, the term "serving cells" is used to denote the set of cells comprised of the SpCell(s) and all SCells. In DC, two MAC entities are configured in a UE: one for the MCG and one for the SCG.

[0095] FIG. 7 shows a data flow example in the 3GPP NR system to which implementations of the present disclosure are applied.

[0096] Referring to FIG. 7, "RB" denotes a radio bearer, and "H" denotes a header. Radio bearers are categorized into two groups: DRBs for user plane data and SRBs for control plane data. The MAC PDU is transmitted / received using radio resources through the PHY layer to / from an external device. The MAC PDU arrives to the PHY layer in the form of a transport block.

[0097] In the PHY layer, the uplink transport 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 transport 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, Uplink Control Information (UCI) is mapped to PUCCH, and Downlink Control Information (DCI) is mapped to Physical Downlink Control Channel (PDCCH). A MAC PDU related to UL-SCH is transmitted by a UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCH is transmitted by a BS via a PDSCH based on a DL assignment.

[0098] Network controlled mobility applies to UEs in RRC_CONNECTED and is categorized 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.

[0099] Cell level mobility requires explicit RRC signaling to be triggered, i.e., handover.

[0100] FIG. 8 shows an example of inter-gNB handover procedures to which implementations of the present disclosure are applied.

[0101] For inter-gNB handover, the signaling procedures consist of at least the following elemental components described in FIG. 8.

[0102] 1. Step 1: The source gNB initiates handover and issues a HANDOVER REQUEST over the Xn interface.

[0103] 2. Step 2: The target gNB performs admission control and provides the new RRC configuration as part of the HANDOVER REQUEST ACKNOWLEDGE.

[0104] 3. Step 3: The source gNB provides the RRC configuration to the UE by forwarding theRRCReconfigurationmessage received in the HANDOVER REQUEST ACKNOWLEDGE. TheRRCReconfigurationmessage includes at least cell ID and all information required to access the target cell so that the UE can access the target cell without reading system information. For some cases, the information required for contention-based and contention-free random access can be included in theRRCReconfigurationmessage. The access information to the target cell may include beam specific information, if any.

[0105] 4. Step 4: The UE moves the RRC connection to the target gNB and replies with theRRCReconfigurationComplete.

[0106] User data may also be sent in step 4 if the grant allows.

[0107] Beam level mobility does not require explicit RRC signaling to be triggered. Beam level mobility can be within a cell, or between cells, the latter is referred to as Inter-Cell Beam Management (ICBM). For ICBM, a UE can receive or transmit UE dedicated channels / signals via a Transmission / Reception Point (TRP) associated with a Physical Cell ID (PCI) different from the PCI of a serving cell, while non-UE-dedicated channels / signals can only be received via a TRP associated with a PCI of the serving cell. The gNB provides via RRC signaling the UE with measurement configuration containing configurations of Synchronization Signal Block (SSB) / Channel State Information (CSI) resources and resource sets, reports and trigger states for triggering channel and interference measurements and reports. In case of ICBM, a measurement configuration includes SSB resources associated with PCIs different from the PCI of a serving cell. Beam level mobility is then dealt with at lower layers by means of physical layer and MAC layer control signaling, and RRC is not required to know which beam is being used at a given point in time.

[0108] SSB-based beam level mobility is based on　the SSB associated to the initial DL BWP and can only be　configured for　the initial DL BWPs and for　DL BWPs　containing the SSB associated to the initial DL BWP. For　other DL BWPs, beam level mobility can only be performed based on CSI-Reference Signal (RS).

[0109] A Conditional Handover (CHO) is defined as a handover that is executed by the UE when one or more handover execution conditions are met. The UE starts evaluating the execution condition(s) upon receiving the CHO configuration, and stops evaluating the execution condition(s) once a handover is executed.

[0110] The following principles apply to CHO:

[0111] - The CHO configuration contains the configuration of CHO candidate cell(s) generated by the candidate gNB(s) and execution condition(s) generated by the source gNB.

[0112] - An execution condition may consist of one or two trigger condition(s) (CHO events A3 / ). Only single 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 CHO execution condition of a single candidate cell.

[0113] - Before any CHO execution condition is satisfied, upon reception of HO command (without CHO configuration), the UE executes the HO procedure, regardless of any previously received CHO configuration.

[0114] - While executing CHO, i.e., from the time when the UE starts synchronization with target cell, the UE does not monitor source cell.

[0115] L1 / L2 Triggered Mobility (LTM) is a procedure in which a gNB receives L1 measurement report(s) from a UE, and on their basis the gNB changes UE's serving cell by a cell switch command signaled via a MAC CE. The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through RRC signaling. Then the UE switches to the target cell according to the cell switch command. The LTM procedure can be used to reduce the mobility latency.

[0116] When configured by the network, it is possible to activate Transmission Configuration Index (TCI) states of one or multiple cells that are different from the current serving cell. For instance, the TCI states of the LTM candidate cells can be activated in advance before any of those cells become the serving cell. This allows the UE to be DL synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when cell switch is triggered.

[0117] When configured by the network, it is possible to initiate UL Timing Advance (TA) acquisition procedure to one or multiple cells that are different from the current serving cell. For instance, the network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition is triggered by PDCCH order or realized through UE-based TA measurement. In the former case, the gNB to which the candidate cell belongs calculates the TA value and sends it to the gNB to which the serving cell belongs. The serving cell sends the TA value in the LTM cell switch command MAC CE when triggering LTM cell switch. In the latter case, the UE applies the TA value measured by itself and performs RACH-less LTM upon receiving the cell switch command.

[0118] If UE-based TA measurement is configured, the UE performs RACH-less LTM upon receiving the cell switch command. Otherwise, the UE determines whether to access the target cell with the RA procedure depending on whether a TA value is provided in the cell switch command. For RACH-less LTM, the UE accesses the target cell via a configured grant provided in the LTM candidate cell configuration and selects the configured grant occasion associated with the beam indicated in the cell switch command. If the LTM candidate cell configuration does not include a configured grant, the UE may monitor PDCCH for dynamic scheduling from the target cell upon LTM cell switch. Before RACH-less LTM procedure completion, the UE may not trigger random access procedure if it does not have a valid PUCCH resource for triggered Scheduling Requests (SRs).

[0119] The following principles apply to LTM:

[0120] - The UE does not update its security key after an intra-gNB LTM cell switch.

[0121] - Subsequent LTM is supported.

[0122] LTM supports both intra-gNB-Distributed Unit (DU) and intra-gNB-Centralized Unit (CU) inter-gNB-DU mobility. LTM supports both intra-frequency and inter-frequency mobility, including mobility to inter-frequency cell that is not a current serving cell. The following scenarios are supported:

[0123] - PCell change in non-CA scenario and non-DC scenario,

[0124] - PCell change in CA scenario,

[0125] - DC scenario, MCG PCell change and SCG PSCell change without MN involvement case (i.e., intra-SN PSCell change).

[0126] While the UE has stored LTM candidate cell configurations, the UE can also execute any L3 handover command sent by the network.

[0127] FIG. 9 shows an example of signaling procedure for LTM to which implementations of the present disclosure are applied.

[0128] Cell switch command is conveyed in a MAC Control Element (CE), which contains the necessary information to perform the LTM cell switch.

[0129] Subsequent LTM is done by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate cell configurations after each LTM cell switch completion.

[0130] The signaling procedure for LTM is as follows.

[0131] 1. Step 1: The UE sends aMeasurementReportmessage to the gNB. The gNB decides to configure LTM and initiates candidate cell(s) preparation.

[0132] 2. Step 2: The gNB transmits anRRCReconfigurationmessage to the UE including the LTM candidate cell configurations of one or multiple candidate cells.

[0133] 3. Step 3: The UE stores the LTM candidate cell configurations and transmits anRRCReconfigurationCompletemessage to the gNB.

[0134] 4a. Step 4a: The UE may perform DL synchronization with the candidate cell(s) before receiving the cell switch command.

[0135] 4b. Step 4b: When UE-based TA measurement is configured, the UE may acquire the TA value(s) of the candidate cell(s) by measurement. Otherwise, the UE may perform early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command. This may be done via Contention-Free Random Access (CFRA) triggered by a PDCCH order from the source cell, following which the UE may send preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE may not receive random access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. The UE may not maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

[0136] 5. Step 5: The UE performs L1 measurements on the configured candidate cell(s) and transmits L1 measurement reports to the gNB. L1 measurement should be performed as long as RRC reconfiguration (step 2) is applicable.

[0137] 6. Step 6: The gNB decides to execute cell switch to a target cell and transmits a MAC CE triggering cell switch by including the candidate configuration index of the target cell. The UE switches to the target cell and applies the configuration indicated by candidate configuration index.

[0138] 7. Step 7: The UE may perform the random access procedure towards the target cell, if the UE does not have valid TA of the target cell. The UE may perform CFRA if the LTM cell switch command MAC CE contains information for CFRA.

[0139] 8. Step 8: The UE completes the LTM cell switch procedure by sendingRRCReconfigurationCompletemessage to target cell. If the UE has performed a random access procedure in step 7, the UE considers that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE considers that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data. The UE determines successful reception of its first UL data by receiving a PDCCH addressing the UE's Cell Radio Network Temporary Identity (C-RNTI) in the target cell, which schedules a new transmission following the first UL data. The PDCCH carries either a DL assignment or an UL grant addressing the same HARQ process as the first UL data.

[0140] The steps 4-8 can be performed multiple times for subsequent LTM using the LTM candidate cell configuration(s) provided in step 2.

[0141] The UE may initiate the RRC re-establishment procedure when a failure condition occurs (e.g., radio link failure, handover failure, reconfiguration failure, etc.). If the UE initiates RRC re-establishment procedure, it may cause not only a large interruption but also unnecessary reconfiguration after the re-establishment.

[0142] For a fast failure recovery, the UE may utilize a configuration of candidate cells. When a candidate cell is (pre-)configured for either CHO or LTM for MCG, or a candidate cell is (pre-)configured for either CPAC or LTM for SCG, the UE may use the (pre-)configured candidate cell configuration for fast failure recovery, rather than proceeding the whole RRC re-establishment procedure. For example, upon detecting failure, UE may perform CHO (or LTM) if the selected cell according to the RRC re-establishment procedure is configured for CHO (or LTM).

[0143] However, even though using the (pre-)configured candidate cell configuration for fast failure recovery, the UE may perform a random access procedure to the selected cell as the first step of fast failure recovery. The random access procedure may lead to large interruption and latency.

[0144] Although many technologies have been introduced to reduce mobility interruptions, such as skipping random access procedure due to recent mobility enhancements, the above-mentioned fast failure recovery does not have such technologies, so interruptions due to fast failure recovery still exist significantly due to the need to perform random access procedure.

[0145] According to implementations of the present disclosure, the network may provide recovery information for faster failure recovery. The recovery information may be configured for some of candidate cells for fast failure recovery. The recovery information may provide access information for the configured candidate cells for fast failure recovery. Upon detecting failure, the UE may select a recovery target based on the recovery information and accesses the recovery target based on the access information.

[0146] More specifically, the UE may receive a configuration related to one or more candidate cells from the network. Then, the UE may receive recovery information for fast failure recovery from the network. The recovery information may include access information required for access to a subset of the one or more candidate cells. Upon detecting the failure, the UE may initiate a mobility to access one of the one or more candidate cells for fast failure recovery based on the recovery information.

[0147] If the recovery information includes access information required for RACH-less access, the UE may perform the mobility without random access. If the recovery information includes access information required for CFRA, the UE may perform the mobility with CFRA. Alternatively, if the recovery information does not include any access information required for RACH-less access or CFRA, the UE may perform the mobility with contention-based random access.

[0148] The following drawings are created to explain specific embodiments of the present disclosure. The names of the specific devices or the names of the specific signals / messages / fields shown in the drawings are provided by way of example, and thus the technical features of the present disclosure are not limited to the specific names used in the following drawings.

[0149] FIG. 10 shows an example of a method to which implementations of the present disclosure are applied.

[0150] In step S1000, the method comprises receiving a candidate cell configuration for a candidate cell from a network.

[0151] In step S1010, the method comprises receiving recovery information for failure recovery from the network. The recovery information includes access information which is to be used for accessing the candidate cell during the failure recovery.

[0152] In step S1020, the method comprises detecting a failure.

[0153] In step S1030, the method comprises upon detecting the failure, initiating the failure recovery by applying the candidate cell configuration based on the recovery information.

[0154] In step S1040, the method comprises determining whether to perform a random access procedure based on the access information.

[0155] In step S1050, the method comprises accessing the candidate cell based on a determination related to the random access procedure.

[0156] In some implementations, it may be determined to perform the random access procedure based on the access information being related to CFRA. In this case, the access information being related to CFRA may include at least one of i) information informing that a CFRA resource included in the candidate cell configuration is used for the failure recovery or ii) CFRA resource information.

[0157] In some implementations, it may be determined to not perform the random access procedure based on the access information being related to RACH-less access. In this case, the access information being related to RACH-less access may include at least one of i) beam related information or ii) uplink timing information.

[0158] In some implementations, the failure may include at least one of a radio link failure (RLF) or a mobility failure. The recovery information may be received via a separate DL control message based on the failure being the RLF (e.g., when the failure is RLF). Additionally and / or alternatively, the recovery information may be received via a mobility command or a separate DL control message based on the failure being the mobility failure (e.g., when the failure is mobility failure).

[0159] In some implementations, the recovery information may further include information related to a subset of candidate cells. The recovery information may further include information related to cell selection during the failure recovery.

[0160] In some implementations, initiating of the failure recovery may comprise performing cell selection towards the candidate cell based on the recovery information.

[0161] In some implementations, the method may be performed by a wireless device. The wireless device may be in communication with at least one of a mobile device, a network, and / or autonomous vehicles other than the wireless device.

[0162] Furthermore, the method described above in FIG. 10 may be performed by a wireless device. The wireless device may be implemented by the first wireless device 100 shown in FIG. 2 and / or the UE 100 shown in FIG. 3.

[0163] The wireless device comprises at least one transceiver, at least one processor, and at least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method described in FIG. 10.

[0164] More specifically, the wireless device receives, via the at least one transceiver, a candidate cell configuration for a candidate cell from a network.

[0165] The wireless device receives, via the at least one transceiver, recovery information for failure recovery from the network. The recovery information includes access information which is to be used for accessing the candidate cell during the failure recovery.

[0166] The wireless device detects a failure.

[0167] Upon detecting the failure, the wireless device initiates the failure recovery by applying the candidate cell configuration based on the recovery information.

[0168] The wireless device determines whether to perform a random access procedure based on the access information.

[0169] The wireless device accesses the candidate cell based on a determination related to the random access procedure.

[0170] In some implementations, it may be determined to perform the random access procedure based on the access information being related to CFRA. In this case, the access information being related to CFRA may include at least one of i) information informing that a CFRA resource included in the candidate cell configuration is used for the failure recovery or ii) CFRA resource information.

[0171] In some implementations, it may be determined to not perform the random access procedure based on the access information being related to RACH-less access. In this case, the access information being related to RACH-less access may include at least one of i) beam related information or ii) uplink timing information.

[0172] In some implementations, the failure may include at least one of a radio link failure (RLF) or a mobility failure. The recovery information may be received via a separate DL control message based on the failure being the RLF (e.g., when the failure is RLF). Additionally and / or alternatively, the recovery information may be received via a mobility command or a separate DL control message based on the failure being the mobility failure (e.g., when the failure is mobility failure).

[0173] In some implementations, the recovery information may further include information related to a subset of candidate cells. The recovery information may further include information related to cell selection during the failure recovery.

[0174] In some implementations, initiating of the failure recovery may comprise performing cell selection towards the candidate cell based on the recovery information.

[0175] Furthermore, the method described above in FIG. 10 may be performed by control of a processing apparatus adapted to control a wireless device. The processing apparatus may be implemented by the processor 102 included in the first wireless device 100 shown in FIG. 2 and / or the processor 102 included in the UE 100 shown in FIG. 3.

[0176] The processing apparatus adapted to control the wireless device comprises at least one processor, and at least one memory operably connectable to the at least one processor. The at least one processor is adapted to perform the method described in FIG. 10.

[0177] Furthermore, the method described above in FIG. 10 may be performed by a software code 105 stored in the memory 104 included in the first wireless device 100 shown in FIG. 2.

[0178] The technical features of the present disclosure may be embodied directly in hardware, in a software executed by a processor, or in a combination of the two. For example, a method performed by a wireless device in a wireless communication may be implemented in hardware, software, firmware, or any combination thereof. For example, a software may reside in RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disk, a removable disk, a CD-ROM, or any other storage medium.

[0179] Some example of storage medium may be coupled to the processor such that the processor can read information from the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. For other example, the processor and the storage medium may reside as discrete components.

[0180] The computer-readable medium may include a tangible and non-transitory computer-readable storage medium.

[0181] For example, non-transitory computer-readable media may 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 may also include combinations of the above.

[0182] In addition, the method described herein may be realized at least in part by a computer-readable communication medium that carries or communicates code in the form of instructions or data structures and that can be accessed, read, and / or executed by a computer.

[0183] According to some implementations of the present disclosure, a non-transitory Computer-Readable Medium (CRM) stores instructions that, based on being executed by at least one processor, perform the method described in FIG. 10.

[0184] FIG. 11 shows an example of another method to which implementations of the present disclosure are applied.

[0185] In step S1100, the method comprises transmitting a candidate cell configuration for a candidate cell to a wireless device.

[0186] In step S1110, the method comprises transmitting recovery information for failure recovery to the wireless device. The recovery information includes access information which is to be used for accessing the candidate cell during the failure recovery.

[0187] In step S1120, upon detecting a failure, the failure recovery is initiated by applying the candidate cell configuration based on the recovery information. Whether to perform a random access procedure is determined based on the access information. The candidate cell is accessed based on a determination related to the random access procedure.

[0188] Furthermore, the method described above in FIG. 11 may be performed by a base station. The base station may be implemented by the second wireless device 200 shown in FIG. 2.

[0189] The base station comprises at least one transceiver, at least one processor, and at least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method described in FIG. 11.

[0190] More specifically, the base station transmits, via the at least one transceiver, a candidate cell configuration for a candidate cell to a wireless device.

[0191] The base station transmits, via the at least one transceiver, recovery information for failure recovery to the wireless device. The recovery information includes access information which is to be used for accessing the candidate cell during the failure recovery.

[0192] Upon detecting a failure, the failure recovery is initiated by applying the candidate cell configuration based on the recovery information. Whether to perform a random access procedure is determined based on the access information. The candidate cell is accessed based on a determination related to the random access procedure.

[0193] More specific details related to implementations of the present disclosure described above are described.

[0194] The network may provide the UE with a conditional configuration related to one or more candidate cells for mobility, e.g., CHO, LTM, conditional LTM, etc. The conditional configuration may include at least one of the followings.

[0195] - One or more candidate cell configurations: A candidate cell configuration may be separately provided as reference and delta configurations

[0196] - Indicator indicating whether to perform fast recovery based on the candidate cell configuration or not: e.g.,attemptLTM-Switchfor LTM or conditional LTM configuration, orattemptCondReconfigfor CHO configuration

[0197] For each candidate cell, at least one of followings can be provided for candidate cell configuration.

[0198] - ID of candidate cell configuration;

[0199] - physical ID of candidate cell;

[0200] - Configuration for early synchronization;

[0201] - Information related to reference signals (e.g., SSB, CSI-RS);

[0202] - Information related to beam indication (e.g., UL / DL or joint Transmission Configuration Index (TCI) state configuration);

[0203] - UL resource configuration for mobility: e.g., configured grant, or CFRA resource information

[0204] The UE may transmit acknowledgement to the network as a response of receiving the conditional configuration.

[0205] The network may provide the UE with recovery information for failure recovery. The recovery information may include at least one of the followings.

[0206] - Indicator indicating a subset of the candidate cells: e.g., list of candidate cell configuration IDs, or list of physical cell IDs of candidate cells

[0207] - Information for cell selection during fast recovery: e.g., priority of each candidate cell, or radio quality (e.g. RSRP, RSRQ, SINR) threshold

[0208] - Access information required for RACH-less access for one or more indicated candidate cells

[0209] - access information required for CFRA for one or more indicated candidate cells

[0210] The access information required for RACH-less access for an indicated cell may include at least one of the followings.

[0211] - Beam related information: e.g., DL TCI state ID, UL TCI state ID, or joint TCI state ID

[0212] - Uplink timing information: e.g., Timing Advance (TA) command, or UE-based TA measurement indication (e.g.., the UE may perform UE-based TA measurement of the corresponding candidate cell if indicated)

[0213] The access information required for CFRA for an indicated cell may include at least one of the followings.

[0214] - Indicator indicating that the CFRA resource included in the candidate cell configuration is used for failure recovery.

[0215] - CFRA resource information: e.g., RA preamble, SSB index, PRACH mask index, Supplementary UL SUL) indicator, or MSG1 repetition number

[0216] The recovery information may be transmitted via at least one of the followings:

[0217] - A separate DL control message, e.g., recovery Information MAC CE orRRCReconfigurationmessage

[0218] -A mobility command, e.g., Cell Switch Command MAC CE, LTM Cell Switch Command MAC CE orRRCReconfigurationmessage

[0219] The UE may detect a failure. The failure may be a radio link failure or a mobility failure. UE may detect a radio link failure based on lower layer reporting of estimated link quality, counter, and / or timer. The UE may consider that a radio link fails based on detecting security failure, number of retransmissions exceeding a threshold, number of PRACH retransmission exceeding a threshold. The UE may detect a mobility failure based on mobility timer.

[0220] For example, for detection of physical layer problems in RRC_CONNECTED, the UE may:

[0221] 1> if any Dual Application Stack Protocol (DAPS) bearer is configured, upon receiving N310 consecutive "out-of-sync" indications for the source SpCell from lower layers and T304 is running:

[0222] 2> start timer T310 for the source SpCell.

[0223] 1> upon receiving N310 consecutive "out-of-sync" indications for the SpCell from lower layers while neither T300, T301, T304, T311, T316 nor T319 are running:

[0224] 2> start timer T310 for the corresponding SpCell.

[0225] For detection of radio link failure, the UE may:

[0226] 1> if any DAPS bearer is configured and T304 is running:

[0227] 2> upon T310 expiry in source SpCell; or

[0228] 2> upon random access problem indication from source MCG MAC; or

[0229] 2> upon indication from source MCG RLC that the maximum number of retransmissions has been reached; or

[0230] 2> upon consistent uplink Listen-Before-Talk (LBT) failure indication from source MCG MAC:

[0231] 3> consider radio link failure to be detected for the source MCG, i.e., source RLF;

[0232] 3> suspend the transmission and reception of all DRBs and multicast Multicast Radio Bearers (MRBs) in the source MCG;

[0233] 3> reset MAC for the source MCG;

[0234] 3> release the source connection.

[0235] 1> else:

[0236] 2> during a DAPS handover: the following only applies for the target PCell;

[0237] 2> upon T310 expiry in PCell; or

[0238] 2> upon T312 expiry in PCell; or

[0239] 2> upon random access problem indication from MCG MAC while neither T300, T301, T304, T311 nor T319 are running and Small Data Transmission (SDT) procedure is not ongoing; or

[0240] 2> upon indication from MCG RLC that the maximum number of retransmissions has been reached while SDT procedure is not ongoing; or

[0241] 2> if connected as an IAB-node, upon Backhaul (BH) RLF indication received on Backhaul Adaptation Protocol (BAP) entity from the MCG; or

[0242] 2> upon consistent uplink LBT failure indication from MCG MAC while T304 is not running:

[0243] 3> if the indication is from MCG RLC and CA duplication is configured and activated for MCG, and for the corresponding logical channelallowedServingCellsonly includes SCell(s):

[0244] 4> initiate the failure information procedure to report RLC failure.

[0245] 3> else:

[0246] 4> consider radio link failure to be detected for the MCG, i.e., MCG RLF;

[0247] 4> discard any segments of segmented RRC messages;

[0248] 4> if AS security has not been activated:

[0249] 5> perform the actions upon going to RRC_IDLE, with release cause 'other';

[0250] 4> else if AS security has been activated but SRB2 and at least one DRB or multicast MRB or, for IAB and Network-Controlled Repeater (NCR), SRB2, have not been setup:

[0251] 5> store the radio link failure information in theVarRLF-Report;

[0252] 5> perform the actions upon going to RRC_IDLE, with release cause 'RRC connection failure';

[0253] 4> else:

[0254] 5> store the radio link failure information in theVarRLF-Report;

[0255] 5> if Multi-Path (MP) is configured:

[0256] 6> if T316 is configured, and MP indirect path transmission is not suspended; and

[0257] 6> if neither MP indirect path change nor MP indirect path addition is ongoing:

[0258] 7> initiate the MCG failure information procedure to report MCG radio link failure.

[0259] 6> else:

[0260] 7> initiate the connection re-establishment procedure.

[0261] The UE may initiate a mobility to access one of the candidate cells for failure recovery based on the recovery information. The failure recovery may be comprised of two phases: 1) cell selection based on the recovery information, and 2) access to the selected cell.

[0262] (1) The UE selects a recovery target cell based on the recovery information.

[0263] For example, if priority of each candidate cell and radio quality threshold are included in the recovery information, among the candidate cells whose radio quality exceeds the threshold, the candidate cell with the highest priority may be selected.

[0264] For example, if priority of each candidate cell is included in the recovery information and if radio quality threshold is not included in the recovery information, the candidate cell with the highest priority may be selected.

[0265] For example, if priority of each candidate cell is not included in the recovery information and if radio quality threshold is included in the recovery information, among the candidate cells whose radio quality exceeds the threshold, the candidate cell with the highest radio quality may be selected.

[0266] When selecting a recovery target cell, the UE may prioritize a cell to which RACH-less access is possible over other cell to which RACH-less access is not possible based on the recovery information. When selecting a recovery target cell, the UE may prioritize a cell to which CFRA-based access is possible over other cell to which CBRA-based access is only possible.

[0267] (2) The UE attempts to access the selected cell.

[0268] If the recovery information includes access information required for RACH-less access, the UE may perform the mobility without random access.

[0269] If the recovery information includes access information required for contention-free random access, the UE may perform the mobility with contention-free random access.

[0270] If the recovery information does not include any access information required for RACH-less access or contention-free random access, the UE may perform the mobility with contention-based random access.

[0271] For example, the UE may initiate the re-establishment procedure when one of the following conditions is met:

[0272] 1> upon detecting radio link failure of the MCG andt316is not configured; or

[0273] 1> upon detecting radio link failure of the MCG while SCG transmission is suspended; or

[0274] 1> upon detecting radio link failure of the MCG while PSCell change or PSCell addition is ongoing; or

[0275] 1> upon detecting radio link failure of the MCG while the SCG is deactivated; or

[0276] 1> upon re-configuration with sync failure of the MCG; or

[0277] 1> upon mobility from NR failure; or

[0278] 1> upon integrity check failure indication from lower layers concerning SRB1 or SRB2, except if the integrity check failure is detected on theRRCReestablishmentmessage; or

[0279] 1> upon an RRC connection reconfiguration failure; or

[0280] 1> upon detecting radio link failure for the SCG while MCG transmission is suspended; or

[0281] 1> upon reconfiguration with sync failure of the SCG while MCG transmission is suspended; or

[0282] 1> upon SCG change failure while MCG transmission is suspended; or

[0283] 1> upon SCG configuration failure while MCG transmission is suspended; or

[0284] 1> upon integrity check failure indication from SCG lower layers concerning SRB3 while MCG is suspended; or

[0285] 1> upon T316 expiry.

[0286] Upon initiation of the re-establishment procedure, the UE may:

[0287] 1> stop timer T310, if running;

[0288] 1> stop timer T312, if running;

[0289] 1> stop timer T304, if running;

[0290] 1> start timer T311;

[0291] Regarding actions following cell selection while T311 is running, upon selecting a suitable NR cell, the UE may:

[0292] 1> ensure having valid and up to date essential system information;

[0293] 1> stop timer T311;

[0294] 1> if the cell selection is triggered by detecting radio link failure of the MCG or re-configuration with sync failure of the MCG, except for an LTM cell switch procedure following cell selection performed while timer T311 was running, or mobility from NR failure, and

[0295] 1> ifattemptCondReconfigis configured; and

[0296] 1> if the selected cell is not configured withCondEventT1, or the selected cell is configured withCondEventT1and leaving condition has not been fulfilled; and

[0297] 1> if the selected cell is one of the candidate cells for which thereconfigurationWithSyncis included in themasterCellGroupin the MCGVarConditionalReconfigand thecondExecutionCondPSCellis not configured for the correspondingcondReconfigIdin the MCGVarConditionalReconfig:

[0298] 2> if the UE supports RLF-Report for conditional handover, set thechoCellIdin theVarRLF-Reportto the global cell identity, if available, otherwise to the physical cell identity and carrier frequency of the selected cell;

[0299] 2> apply the storedcondRRCReconfigassociated to the selected cell;

[0300] 1> if the cell selection is triggered by detecting radio link failure of the MCG or re-configuration with sync failure of the MCG for an LTM cell switch procedure triggered upon the indication by lower layers; and

[0301] 1> ifattemptLTM-Switchis configured; and

[0302] 1> if the selected cell is one of the LTM candidate cells in theLTM-CandidateIE withinltm-Configassociated with the MCG:

[0303] 2> perform the LTM cell switch procedure for the selected LTM candidate cell;

[0304] In case bothattemptCondReconfigandattemptLTM-Switchare configured, it is left to the UE implementation which procedure to execute.

[0305] Various examples according to implementations of the present disclosure are described below.

[0306] 1. Example 1: RLF case

[0307] (1) Step 1. The network provides the UE with a configuration related to two candidate cells for mobility. That is, the configuration includes mobility configurations for candidate cell #1 and candidate cell #2.

[0308] (2) Step 2. The network provides the UE with recovery information for failure recovery. The recovery information includes the at least one of the followings: candidate cell configuration IDs for candidate cell #1 and candidate cell #2, priority between candidate cell #1 and candidate cell #2 (candidate cell #1 is prioritized over candidate cell #2), beam indication and TA command for candidate cell #1, or CFRA resource information for candidate cell #2.

[0309] (3) Step 3. The UE detects a radio link failure of the source cell.

[0310] (4) Step 4. The UE selects candidate cell #1 for fast failure recovery because candidate cell #1 is prioritized over candidate cell #2.

[0311] (5) Step 5. The UE performs RACH-less access to the candidate cell #1.

[0312] The UE applies the candidate cell configuration for candidate cell #1. If configured grant is included in the candidate cell configuration, the UE may transmit theRRCReconfigurationCompletemessage to candidate cell #1. Else if configured grant is not included in the candidate cell configuration, the UE may monitor PDCCH of candidate cell #1 in order to receive a dynamic grant, and transmit theRRCReconfigurationCompletemessage to candidate cell #1 if a dynamic grant is received.

[0313] 2. Example 2: Mobility failure case

[0314] (1) Step 1. The network provides the UE with a configuration related to two candidate cells for mobility. That is, the configuration includes mobility configurations for candidate cell #1 and candidate cell #2.

[0315] (2) Step 2. The network transmits to the UE an LTM Cell Switch Command MAC CE with recovery information for failure recovery. The LTM Cell Switch Command MAC CE indicates a cell switch to candidate cell #1. The recovery information includes at least one of the followings: candidate cell configuration IDs for candidate cell #1 and candidate cell #2, radio quality threshold, beam indication and TA command for candidate cell #1, or CFRA resource information for candidate cell #2.

[0316] (3) Step 3. The UE performs the LTM cell switch to candidate cell #1 based on the LTM Cell Switch Command MAC CE.

[0317] (4) Step 4. The UE detect a mobility failure.

[0318] (5) Step 5. The UE selects candidate cell #2 for fast failure recovery because the radio quality of candidate cell #2 is above the threshold and larger than that of candidate cell #1.

[0319] (6) Step 6. The UE performs CFRA-based access to candidate cell #2. That is, the UE applies the candidate cell configuration of candidate cell #2 and then the UE transmits the RA preamble indicated by the recovery information to candidate cell #2.

[0320] 3. Example 3: Mobility failure case

[0321] (1) Step 1. The network provides the UE with a configuration related to two candidate cells for mobility. That is, the configuration includes mobility configurations for candidate cell #1 and candidate cell #2.

[0322] (2) Step 2. The network provides the UE with recovery information for failure recovery. The recovery information includes the at least one of the followings: candidate cell configuration IDs for candidate cell #1 and candidate cell #2, priority between candidate cell #1 and candidate cell #2 (candidate cell #1 is prioritized over candidate cell #2), beam indication and TA command for candidate cell #1, or CFRA resource information for candidate cell #2.

[0323] (3) Step 3. The network transmits to the UE an LTM Cell Switch Command MAC CE with recovery information for failure recovery. The LTM Cell Switch Command MAC CE indicates a cell switch to candidate cell #1. The recovery information includes at least one of the followings: candidate cell configuration IDs for candidate cell #1 and candidate cell #2, radio quality threshold, beam indication and TA command for candidate cell #1, and CFRA resource information for candidate cell #2.

[0324] (4) Step 4. The UE performs the LTM cell switch to candidate cell #1 based on the LTM Cell Switch Command MAC CE.

[0325] (5) Step 5. The UE detect a mobility failure.

[0326] (6) Step 6. The UE selects candidate cell #2 for fast failure recovery because the radio quality of candidate cell #2 is above the threshold and larger than that of candidate cell #1.

[0327] (7) Step 7. The UE performs CFRA-based access to candidate cell #2. That is, the UE applies the candidate cell configuration of candidate cell #2 and then the UE transmits the RA preamble indicated by the recovery information to candidate cell #2.

[0328] The present disclosure may have various advantageous effects.

[0329] For example, the UE can initiate a mobility to access one of the candidate cells for fast failure recovery based on the recovery information upon detecting the failure.

[0330] For example, the UE can perform the mobility without random access if the recovery information includes access information required for RACH-less access.

[0331] For example, the interruption and latency due to failure recovery can be reduced.

[0332] Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and / or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

[0333] Claims in the present disclosure can be combined in a various way. For instance, technical features in method claims of the present disclosure can be combined to be implemented or performed in an apparatus, and technical features in apparatus claims can be combined to be implemented or performed in a method. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in an apparatus. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in a method. Other implementations are within the scope of the following claims.

Claims

1.A method comprising:receiving a candidate cell configuration for a candidate cell from a network;receiving recovery information for failure recovery from the network,wherein the recovery information includes access information which is to be used for accessing the candidate cell during the failure recovery;detecting a failure;upon detecting the failure, initiating the failure recovery by applying the candidate cell configuration based on the recovery information;determining whether to perform a random access procedure based on the access information; andaccessing the candidate cell based on a determination related to the random access procedure.2.The method of claim 1, wherein it is determined to perform the random access procedure based on the access information being related to contention-free random access (CFRA).3.The method of claim 2, wherein the access information being related to CFRA includes at least one of i) information informing that a CFRA resource included in the candidate cell configuration is used for the failure recovery or ii) CFRA resource information.4.The method of claim 1, wherein it is determined to not perform the random access procedure based on the access information being related to random access channel (RACH)-less access.5.The method of claim 4, wherein the access information being related to RACH-less access includes at least one of i) beam related information or ii) uplink timing information.6.The method of any claims 1 to 5, wherein the failure includes at least one of a radio link failure (RLF) or a mobility failure.7.The method of claim 6, wherein the recovery information is received via a separate downlink (DL) control message based on the failure being the RLF.8.The method of claim 6, wherein the recovery information is received via a mobility command or a separate DL control message based on the failure being the mobility failure.9.The method of any claims 1 to 8, wherein the recovery information further includes information related to a subset of candidate cells.10.The method of any claims 1 to 9, wherein the recovery information further includes information related to cell selection during the failure recovery.11.The method of any claims 1 to 10, wherein initiating of the failure recovery comprises performing cell selection towards the candidate cell based on the recovery information.12.The method of any claims 1 to 11, wherein the method is performed by a wireless device.13.The method of claim 12, wherein the wireless device is in communication with at least one of a mobile device, a network, and / or autonomous vehicles other than the wireless device.14.A wireless device comprising:at least one transceiver;at least one processor; andat least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method of any claims 1 to 13.15.A processing apparatus adapted to control a wireless device comprising:at least one processor; andat least one memory operably connectable to the at least one processor,wherein the at least one processor is adapted to perform the method of any claims 1 to 13.16.A non-transitory Computer Readable Medium (CRM) storing instructions that, based on being executed by at least one processor, perform the method of any claims 1 to 13.17.A method comprising:transmitting a candidate cell configuration for a candidate cell to a wireless device;transmitting recovery information for failure recovery to the wireless device,wherein the recovery information includes access information which is to be used for accessing the candidate cell during the failure recovery,wherein, upon detecting a failure, the failure recovery is initiated by applying the candidate cell configuration based on the recovery information,wherein whether to perform a random access procedure is determined based on the access information, andwherein the candidate cell is accessed based on a determination related to the random access procedure.18.A base station comprising:at least one transceiver;at least one processor; andat least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform the method of claim 17.

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