Method and apparatus for optimizing handover in a wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The disclosure relates to a method performed by a terminal of a wireless communication system, and can include the steps of: transmitting, to a source cell, L1 measurement information for candidate cells; receiving, from the source cell, a cell handover command; and performing lower tier triggered mobility (LTM) handover based on the cell handover command.

Description

Technical Field

[0001] This disclosure relates to methods and apparatus for optimizing handover in wireless communication systems or mobile communication systems. Background Technology

[0002] 5G mobile communication technology defines a wide frequency band, enabling high transmission rates and new services. It can be implemented not only in "sub-6GHz" bands such as 3.5GHz, but also in "above 6GHz" bands, including 28GHz and 39GHz, known as mmWave. Furthermore, 6G mobile communication technology (referred to as "super 5G systems") is being considered in terahertz (THz) bands (e.g., the 95GHz to 3THz band) to achieve transmission rates fifty times faster than 5G and ultra-low latency one-tenth that of 5G.

[0003] At the outset of 5G mobile communication technology development, standardization was underway for the following technologies to support services and meet performance requirements associated with enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC): beamforming and massive MIMO for mitigating radio wave path loss and increasing radio wave transmission distance in millimeter waves; dynamic operation supporting parameter sets (e.g., operating multiple subcarrier spacings) and time slot formats for efficient utilization of millimeter wave resources; initial access technologies supporting multi-beam transmission and broadband; definition and operation of BWP (bandwidth portion); new channel coding methods (such as LDPC (low-density parity-check) codes for large data transmissions and polar codes for highly reliable transmission of control information); L2 preprocessing; and network slicing for providing dedicated networks for specific services.

[0004] Currently, given the services that 5G mobile communication technology needs to support, discussions are underway regarding improvements and performance enhancements to the initial 5G mobile communication technology, and physical layer standardization already exists for technologies such as: V2X (Vehicle-to-Everything) for assisting autonomous vehicles in determining driving based on information about the vehicle's location and status transmitted by the vehicle and for enhancing user convenience; NR-U (New Radio Unlicensed) designed to make system operation in unlicensed bands comply with various regulatory requirements; NR UE power saving; non-terrestrial networks (NTNs) for UE-satellite direct communication to provide coverage in areas where communication with terrestrial networks is unavailable; and positioning.

[0005] Furthermore, standardization is underway in the wireless interface architecture / protocol domain for technologies such as: Industrial Internet of Things (IIoT) to support new services through interoperability and convergence with other industries; IAB (Integrated Access and Backhaul) for nodes to provide network service area extension by supporting wireless backhaul and access links in an integrated manner; mobility enhancements including conditional handover and DAPS (Dual Active Stack) handover; and two-step random access (2-step RACH for NR) to simplify the random access process. In terms of system architecture / services, standardization is also underway for: 5G baseline architectures (e.g., service-based architectures or service-based interfaces) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies; and Mobile Edge Computing (MEC) for UE location-based reception services.

[0006] With the commercialization of 5G mobile communication systems, the number of connected devices will increase exponentially, necessitating enhanced functionality and performance of 5G mobile communication systems, as well as integrated operation of connected devices. To this end, new research is planned related to: Extended Reality (XR) for effectively supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), etc.; improving 5G performance and reducing 5G complexity by leveraging Artificial Intelligence (AI) and Machine Learning (ML); AI service support; Metaverse service support; and drone communication.

[0007] Furthermore, this development of 5G mobile communication systems will serve as a foundation for: not only developing new waveforms for providing terahertz band coverage for 6G mobile communication technologies, multi-antenna transmission technologies (such as full-dimensional MIMO (FD-MIMO), array antennas, and massive MIMO), metamaterial-based lenses and antennas for improving terahertz band signal coverage, high-dimensional spatial multiplexing technologies using OAM (orbital angular momentum), and RIS (reconfigurable smart surfaces), but also developing full-duplex technologies to improve the frequency efficiency of 6G mobile communication technologies and enhance system networks, AI-based communication technologies to achieve system optimization by leveraging satellites and AI (artificial intelligence) from the design phase and internalizing end-to-end AI support capabilities, and next-generation distributed computing technologies to achieve services at a complexity level exceeding the operational capabilities of UEs by utilizing ultra-high-performance communication and computing resources. Summary of the Invention

[0008] [Technical Issues]

[0009] One aspect of the embodiments of this disclosure is to provide a method and apparatus capable of reducing handover time.

[0010] Solution to the problem

[0011] According to this disclosure, a method for processing control signals in a wireless communication system may include receiving a first control signal transmitted from a network entity, processing the received first control signal, and transmitting a second control signal generated based on the processing to the network entity.

[0012] [Beneficial effects of the invention]

[0013] The methods and apparatus according to embodiments of this disclosure can reduce the time required for random access for uplink synchronization during handover, thereby reducing the handover time of the UE. Attached Figure Description

[0014] Figure 1 The structure of a wireless communication system according to an embodiment of the present disclosure is shown.

[0015] Figure 2 Radio access state transitions in a wireless communication system according to an embodiment of the present disclosure are illustrated.

[0016] Figure 3 This is a flowchart illustrating the RA report reporting process according to an embodiment of the present disclosure.

[0017] Figure 4 This is a flowchart illustrating an LTM handover process based on early TA acquisition according to an embodiment of the present disclosure.

[0018] Figure 5 This is a flowchart illustrating UE operation of storing random access information according to an embodiment of the present disclosure.

[0019] Figure 6 This is a flowchart illustrating UE operation of storing random access information according to an embodiment of the present disclosure.

[0020] Figure 7 This is a flowchart illustrating UE operation of storing random access information according to an embodiment of the present disclosure.

[0021] Figure 8 This is a flowchart illustrating UE operation without storing random access information according to an embodiment of the present disclosure.

[0022] Figure 9 This is a flowchart illustrating the operation of a base station storing random access information according to an embodiment of the present disclosure.

[0023] Figure 10 This is a block diagram illustrating the structure of a UE according to an embodiment of the present disclosure.

[0024] Figure 11 This is a block diagram illustrating the structure of a base station according to an embodiment of the present disclosure.

[0025] Figure 12Components of a UE according to an embodiment of the present disclosure are shown.

[0026] Figure 13 Components of a base station according to an embodiment of the present disclosure are shown. Detailed Implementation

[0027] To meet the increased demand for wireless data services since the deployment of 4G communication systems, efforts have been made to develop improved 5G or near-5G communication systems. Therefore, 5G or near-5G communication systems are also referred to as "beyond 4G network" communication systems or "post-LTE" systems. The 5G communication system specified by 3GPP is called a "New Radio (NR) system."

[0028] 5G communication systems are considered to be implemented in ultra-high frequency (mmWave) bands (e.g., the 60 GHz band) to achieve higher data rates. To reduce radio wave propagation loss and increase transmission distance in the mmWave band, beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive MIMO technologies are being discussed in 5G communication systems.

[0029] In addition, in 5G communication systems, technologies for improving system networks are being developed based on evolved small cells, advanced small cells, cloud radio access networks (cloud RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, coordinated multipoint (CoMP), and receiver interference cancellation.

[0030] In 5G systems, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) have also been developed as advanced coding and modulation (ACM) schemes, as well as filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) as advanced access technologies.

[0031] The internet, a human-centric network for generating and consuming information, is now evolving into the Internet of Things (IoT), where distributed entities (such as things) exchange and process information without human intervention. The Internet of Everything (IoE) has emerged, combining IoT technologies with cloud servers and other big data processing technologies. Because IoT implementation requires technological elements such as sensing technology, wired / wireless communication and network infrastructure, service interface technology, and security technology, sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) have recently been studied. Such an IoT environment can provide intelligent internet of things (IT) services, creating new value for human life by collecting and analyzing data generated between connected things. Through the integration and combination of existing information technology (IT) with various industrial applications, IoT can be applied to a wide range of fields, including smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart appliances, and advanced medical services.

[0032] Consistent with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, 5G technologies such as sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) are implemented through beamforming, MIMO, and array antenna technologies, which are 5G communication technologies. Cloud radio access networks (cloud RAN), as an application of the aforementioned big data processing technologies, can also be considered an example of the integration of 5G and IoT technologies.

[0033] In the following, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that in the drawings, the same or similar elements are represented by the same or similar reference numerals wherever possible. Furthermore, it should be noted that the following drawings are provided to aid in understanding the present disclosure, and the present disclosure is not limited to the configurations or arrangements shown in the drawings. Additionally, detailed descriptions of known functions or configurations that may obscure the subject matter of the present disclosure will be omitted. It should be noted that in the following description of the present disclosure, only the parts necessary for understanding the operation of the various embodiments according to the present disclosure will be described, and descriptions of other parts will be omitted so as not to obscure the subject matter of the present disclosure. Furthermore, various embodiments of the present disclosure will be described using terminology adopted in some communication standards (e.g., the 3rd Generation Partnership Project (3GPP)), but these are for illustrative purposes only. The various embodiments of the present disclosure can be readily applied to other communication systems with modifications.

[0034] In describing this disclosure below, detailed descriptions of known functions or configurations will be omitted where it is determined that the description may unnecessarily obscure the subject matter of the disclosure. Embodiments of the disclosure will be described below with reference to the accompanying drawings.

[0035] Figure 1 The structure of a wireless communication system is shown.

[0036] refer to Figure 1 As shown, the radio access network of the wireless communication system (New Radio, NR) includes a next-generation base station (New Radio Node B, hereinafter referred to as gNB) 110 and an Access and Mobility Management Function (AMF) (New Radio core network) 105. User terminals (New Radio User Equipment, hereinafter referred to as NR UE or terminal) 115 can access external networks via gNB 110 and AMF 105.

[0037] exist Figure 1 In this context, the gNB can correspond to the evolved Node B (eNB) of a traditional LTE system. The gNB connects to the NR UE via radio channels and provides superior service compared to the traditional Node B (120). In wireless communication systems, since all user services are served through a shared channel, a device is needed to collect state information (such as the UE's buffer state, available transmit power state, and channel state) and perform scheduling accordingly; the gNB 110 serves as this device. Typically, one gNB can control multiple cells. To achieve ultra-high-speed data transmission exceeding current LTE, the wireless mobile communication system can provide a wider bandwidth than the current maximum bandwidth, employing Orthogonal Frequency Division Multiplexing (OFDM) as the radio access technology, and further integrating beamforming technology. Furthermore, the gNB can employ an Adaptive Modulation and Coding (AMC) scheme to determine the modulation scheme and channel coding rate based on the UE's channel state. The AMF 105 can perform functions such as mobility support, bearer configuration, and QoS configuration. The AMF is responsible for various control functions and UE mobility management functions and can connect to multiple base stations. Additionally, the wireless communication system can interoperate with the traditional LTE system, and the AMF can connect to the Mobility Management Entity (MME) 125 via a network interface. The MME connects to the eNB 130, which acts as a traditional base station. UEs supporting LTE-NR dual connectivity can send / receive data (135) while maintaining connections to both the gNB and the eNB.

[0038] Figure 2 This illustrates the radio access state transition in a wireless communication system.

[0039] Wireless communication systems can have three types of radio access states (RRC states). Connected mode (RRC_CONNECTED) 205 refers to a radio access state where the UE can send / receive data. Idle mode (RRC_IDLE) 230 refers to a radio access state where the UE monitors whether to send a paging message to the UE. These two modes are also applied to radio access states in conventional LTE systems, and the technical details can be the same as those in conventional LTE systems. In a wireless communication system according to embodiments of this disclosure, an inactive radio access state (RRC_INACTIVE) 215 can be defined. In the inactive radio access state, the UE context is maintained for the base station and the UE, and RAN-based paging is supported. The characteristics of the inactive radio access state are listed below.

[0040] -Cell reselection mobility;

[0041] - A CN-NR RAN connection (C / U plane) has been established for the UE;

[0042] - The UE AS context is stored in at least one gNB and UE;

[0043] - Paging is initiated by NR RAN;

[0044] - RAN-based notification areas are managed by NR RAN;

[0045] -NR RAN knows the RAN-based notification area to which the UE belongs;

[0046] The inactive radio access state can be transitioned to connected mode or idle mode using a specific procedure. The UE can transition from inactive mode to connected mode according to a recovery procedure, and can also transition from connected mode to inactive mode using a release procedure that includes pause configuration information (210). In procedure 210, one or more RRC messages can be sent / received between the UE and the base station, and the procedure may include one or more steps. Furthermore, the UE can transition from inactive mode to idle mode (220) through a release procedure following the recovery procedure. The transition between connected mode and idle mode can follow conventional LTE technology. That is, the transition between modes can be achieved through an establishment or release procedure (225).

[0047] Figure 3 This is a flowchart illustrating the process of reporting a Report RA according to an embodiment of this disclosure.

[0048] In wireless communication systems (NR), RA reports can record and report information about various types of random access, such as 4-step RA and 2-step RA.

[0049] UE 305 can perform a random access procedure with base station 310. The UE stores predetermined information (315) associated with the last successfully completed random access procedure. Subsequently, when another random access procedure is executed and successfully completed, UE 305 can delete the previously stored information and store predetermined information associated with the new random access procedure. All random access procedures executed within a predetermined time or the last N random access procedures can be considered. Additionally, depending on the purpose of the random access, information about failed random access procedures can be stored in addition to successful ones. This information can be stored according to the following ASN.1 structure and reported to the base station. A single successfully completed random access procedure is stored and reported in the RA-Report IE, and up to eight RA reports can be included in the RA-ReportList IE.

[0050] A single RA-Report IE includes information about multiple random access attempts in chronological order (Per-RAInfoList IE).

[0051] The PerRAInfo IE included in the Per-RAInfoList can include the aforementioned information for each SSB or CSI-RS used for random access attempts.

[0052] The PerRAAttemptInfo IE in PerRAAttemptInfoList can include information about each random access attempt, contentionDetected, and dlRSRPAboveThreshold.

[0053]

[0054]

[0055] A UE in idle or inactive mode sends an RRCSetupRequest or RRCResumeRequest message to base station 310 to switch to connected mode (320). Base station 310 sends an RRCSetup or RRCResume message to UE 305 (325), and UE 305, having received the message, switches to connected mode. UE 305 may send an RRCSetupComplete or RRCResumeComplete message to base station 310 (330). Base station 310 may request UE 305 to report information (e.g., RA report) using a pre-defined RRC message (UEInformationRequest) (335). UE 305, having received the request, may send a pre-defined RRC response message (UEInformationRequest) including the stored information (340). The RA report information reported to base station 310 may be discarded. Even if not reported to base station 310, the stored RA report may be discarded by UE 305 after a certain period of time.

[0056] Figure 4 This is a flowchart illustrating the process of performing LTM handover through early TA acquisition according to an embodiment of the present disclosure.

[0057] In contrast to traditional RRC-based handover, L1 / L2-triggered mobility (LTM) technology enables L1 / L2-based handover. The source cell can indicate handover via L2 signaling (MAC CE) based on L1 measurement results reported from the UE.

[0058] In addition to LTM handover technology, RACH-free technology involving early TA acquisition is also being applied. When performing a handover, the UE needs to synchronize its uplink with the target cell, and this synchronization is performed via random access associated with the handover operation. However, this random access operation can increase the time required for the UE to complete the handover. Therefore, if uplink transmission timing information (e.g., timing advance (TA)) is provided to the UE before handover, random access can be omitted during the handover, thus saving time. The technique of providing uplink transmission timing information to the UE before handover is called early TA acquisition.

[0059] UE 405 sends a MeasurementReport message (420) to source cell 410. The MeasurementReport message may include Layer 3 (L3) cell measurement results measured by the UE based on cell measurement configuration information previously provided by source cell 410. The L3 cell measurement results may refer to cell measurement results that are ultimately processed and derived by the UE's RRC based on cell measurement results provided by the UE's lower layer (PHY).

[0060] Source cell 410 may negotiate with candidate target cell 415, based on L3 cell measurement results, for operations related to LTM and / or early TA acquisition (425). Through negotiation with the candidate target cell, source cell 410 provides UE 405 with derived LTM configuration information and early TA acquisition configuration information (EarlyUL-SyncConfig IE) (430). The early TA acquisition configuration information may include radio resource information necessary to send Msg1 (preamble) to the candidate target cell.

[0061] Source cell 410 instructs the UE to transmit Msg1 to the candidate target cell via a PDCCH command (L1 signaling) (435). UE 405, having received the PDCCH command, sends Msg1 to candidate target cell 415 (440). Upon receiving Msg1, candidate target cell 415 can derive the TA value to be applied to UE 405, taking into account the reception timing of Msg1. Candidate target cell 415 can then provide the derived TA value to source cell 410 (445).

[0062] UE 405 may periodically or semi-persistently report L1 cell measurement results (e.g., L1-RSRP) to source cell 410, depending on the configuration of source cell 410 (450). Source cell 410 determines whether to trigger LTM handover based on the L1 cell measurement results. When it is determined that LTM handover should be triggered, source cell 410 may determine whether the TA value provided from candidate target cell 415 is suitable for LTM handover (455). For example, when a TA value is received from candidate target cell 415, source cell 410 may start a predetermined timer and may consider the elapsed time of the timer until the time point at which LTM handover is determined. If the elapsed time exceeds a predetermined threshold or expires, source cell 410 may not apply the TA value to LTM handover. If the elapsed time is less than the predetermined threshold, source cell 410 may apply the TA value to LTM handover. The timer value and threshold may be configured directly by source cell 410, or alternatively, provided by candidate target cell 415 to source cell 410. Since the TA value is applied when UE 405 transmits data to target cell 415 during handover, target cell 415 can participate in the determination of the application of the TA value by providing a timer value and a threshold. The TA value provided from candidate target cell 415 can be processed by source cell 410 and then provided to the UE. For example, source cell 410 receives the TA value from candidate target cell 415, adds a predetermined compensation value to the TA value or subtracts a predetermined compensation value from the TA value based on the elapsed time, and then sends the resulting value to UE 405. This process can be performed to compensate for errors that may occur after the TA value is derived, and in practice, the compensation value can be derived by source cell 410. For example, source cell 410 can decrease the existing TA value as the signal strength value of candidate target cell 415 reported by the UE increases.

[0063] The source cell 410, which has been determined to trigger LTM handover by applying the TA value provided from the candidate target cell 415, can send a predetermined MAC CE, namely the LTM cell handover command MAC CE (460), to the UE 405. The LTM cell handover command MAC CE may include the following information.

[0064] - Target Configuration ID: An index indicating the configuration information of the candidate target cell.

[0065] - Pre-time command: TA value of the candidate target cell. This field can be included in the MAC CE when triggering LTM handover without RACH. This field can be configured to indicate an FFF value for which no valid TA value exists when triggering RA-based LTM handover.

[0066] -TCI State ID: An index that indicates the active TCI state in the candidate target cell.

[0067] -UL TCI Status ID: An index that indicates the active uplink TCI status in the candidate target cell.

[0068] - Random access related information (e.g., random access preamble index, NUL / SUL indicator, SS / PBCH index, and PRACH mask index): This indicates configuration information related to the RA to be performed during the handover in an RA-based LTM handover. This information may be unnecessary in an LTM without RACH.

[0069] Upon receiving an LTM cell handover command MAC CE including the TA value, UE 405 can perform LTM handover, skipping the random access procedure (465). In other words, UE 405 can send an RRCReconfigurationComplete message to the candidate target cell 415 via PUSCH.

[0070] Upon receiving an LTM cell handover command MAC CE that does not include a TA value, UE 405 performs an LTM handover (470) involving a random access procedure. That is, UE 405 can send Msg1 to the target cell and can send Msg3, including an RRCReconfigurationComplete message, to the candidate target cell based on the information included in the Random Access Response (RAR) message received from the target cell.

[0071] In this embodiment, for early TA acquisition, UE 405 can store predetermined information related to Msg1 sent to candidate target cell 415, and can report the collected information to the network using RA reports (or RLF reports and Successful Handover Reports (SHR)). Furthermore, in this embodiment, a scenario where Msg1 for early TA acquisition is sent to the candidate target cell multiple times can be considered. Upon receiving this information, the network can use it to optimize early TA acquisition operations and LTM handover without RACH.

[0072] Figure 5 This is a flowchart illustrating UE operations according to an embodiment of the present disclosure, which store information about random access triggered in response to an early TA acquisition.

[0073] UE 505 sends a MeasurementReport message (520) to source cell 510. The MeasurementReport message may include Layer 3 (L3) cell measurement results measured by UE 505 based on cell measurement configuration information previously provided by source cell 510. L3 cell measurement results may refer to cell measurement results that are ultimately processed and derived by the UE's RRC based on cell measurement results provided by the UE's lower layer (PHY).

[0074] Source cell 510 can negotiate with candidate target cell 515 for LTM and early TA acquisition operations based on L3 cell measurement results (525). Through negotiation with candidate target cell 515, source cell 510 can provide UE 505 with derived LTM configuration information and early TA acquisition configuration information (EarlyUL-SyncConfig IE) (530). The early TA acquisition configuration information includes the radio resource information necessary to send Msg1 (preamble) to candidate target cell 515.

[0075] Source cell 510 instructs UE 505 via a PDCCH command (L1 signaling) to transmit Msg1 to candidate target cell 515 (535). UE 505, having received the PDCCH command, sends Msg1 to candidate target cell 515 (540). Upon receiving Msg1, candidate target cell 515 can consider the reception timing of Msg1 to derive the TA value to be applied to UE 505. Candidate target cell 515 can then provide the derived TA value to source cell 510 (545).

[0076] UE 505 may periodically or semi-persistently report L1 cell measurement results (e.g., L1-RSRP) of candidate target cells to source cell 510, depending on the configuration of source cell 510 (550). Source cell 510 may determine whether to trigger LTM handover based on the L1 cell measurement results. When it is determined that LTM handover should be triggered, source cell 510 may determine whether the TA value provided from candidate target cell 515 is suitable for LTM handover (555). For example, when a TA value is received from candidate target cell 515, source cell 510 may start a predetermined timer and may consider the elapsed time of the timer until the time point at which LTM handover is determined. If the elapsed time exceeds a predetermined threshold or expires, source cell 510 may not apply the TA value to LTM handover. If the elapsed time is less than the predetermined threshold, source cell 510 may apply the TA value to LTM handover. The timer value and threshold may be configured directly by source cell 510, or alternatively, provided by candidate target cell 515 to source cell 510. Since the TA value is applied when the UE 505 sends data to the target cell 515 during handover, the target cell 515 can participate in the determination of the application of the TA value by providing a timer value and a threshold.

[0077] The source cell 510 that triggers LTM handover by applying the TA value provided from the candidate target cell 515 can send a predetermined MAC CE, namely the LTM cell handover command MAC CE (560), to the UE 505.

[0078] UE 505 can store predetermined information related to early TA acquisition as RA report content at predetermined time points (e.g., after sending Msg1 or upon receiving an LTM cell handover command MAC CE). Information related to early TA acquisition for a single candidate target cell can be recorded in a single RA report IE. Alternatively, all information related to early TA acquisition for one or more candidate target cells configured in the same RRCReconfiguration message can be recorded in a single RA report IE. Here, the RA report IE needs to include identification information about multiple candidate target cells and needs to have an ASN.1 format to distinguish the information corresponding to each candidate target cell. The predetermined information related to early TA acquisition that can be stored as RA report content is as follows.

[0079] - The new reason value in the raPurpose field, namely earlyUlSynchronized: This reason value can be used to indicate that random access related information included in the corresponding RA report IE is Msg1 and / or information related to early TA acquisition sent for early TA acquisition. (See ASN.1 below)

[0080]

[0081] - New time information, namely, the following information, can be included in the reservation information related to early TA acquisition.

[0082] timeMsg1-Reconfig: The time between receiving EarlyUL-SyncConfig (or LTM configuration) and sending the corresponding Msg1.

[0083] timeMsg1-PDCCHOrder: The time between the receipt of the PDCCH command and the corresponding Msg1 transmission.

[0084] timeSinceMsg1Transmission: The time elapsed from the time Msg1 is transmitted until the RA report is submitted.

[0085] timeCellSwitch-Reconfig: The time between the reception of EarlyUL-SyncConfig (or LTM configuration) and the reception of the corresponding LTM cell handover command MAC CE.

[0086] timeCellSwitch-PDCCHOrder: The time between the reception of the PDCCH command and the reception of the corresponding LTM cell handover command MAC CE.

[0087] timeCellSwitch-Msg1: The time between the transmission of Msg1 and the reception of the corresponding LTM cell handover command MAC CE.

[0088] - An indicator that shows whether the LTM cell handover command MAC CE received by the UE includes a valid TA value.

[0089] - An indicator that the UE has sent Msg1 to a specific candidate target cell but failed to receive an LTM cell handover command MAC CE in response.

[0090] -Includes the TA value in the LTM cell handover command MAC CE received by the UE.

[0091] - C-RNTI values ​​assigned by the source and target cells. C-RNTI information can be used to assess the relevance between the RA report including this information and the RLF report or SHR corresponding to the LTM handover without RACH associated with the RA report.

[0092] Upon receiving an LTM cell handover command MAC CE including the TA value, UE 505 can perform LTM handover, skipping the random access procedure (570). That is, UE 505 can send an RRCReconfigurationComplete message to the candidate target cell 515 via PUSCH.

[0093] Upon receiving an LTM cell handover command MAC CE that does not include a valid TA value (i.e., the TA command field value configured as FFF), UE 505 performs an LTM handover involving a random access procedure (575). Specifically, UE 505 sends Msg1 to target cell 515 based on the information included in the Random Access Response (RAR) message received from target cell 515, and sends Msg3, including an RRCReconfigurationComplete message, to candidate target cell 515. Having received the LTM cell handover command MAC CE, UE 505 performs a random access procedure and can therefore store information related to random access as RA report content. In this case, UE 505 can additionally store the following information as well as existing information.

[0094] - Indicates the indicator information associated with the corresponding random access and LTM handover.

[0095] - Indicator information indicating whether to perform a 1-step RA based on the configuration obtained from the early TA (target cell to be handed over to LTM) before executing the corresponding random access (or before receiving the LTM cell handover command MAC CE excluding the TA value).

[0096] - New time information can be stored separately, namely the following information.

[0097] timeMsg1-Reconfig: The time between the LTM-configured receive and the corresponding Msg1 transmission.

[0098] timeMsg1-PDCCHOrder: The time between the reception of the PDCCH command and the corresponding Msg1 transmission.

[0099] timeSinceMsg1Transmission: The time elapsed from the time Msg1 is transmitted until the RA report is submitted.

[0100] timeCellSwitch-Reconfig: The time between receiving the LTM configuration and receiving the corresponding LTM cell handover command MAC CE.

[0101] timeCellSwitch-PDCCHOrder: The time between the reception of the PDCCH command and the reception of the corresponding LTM cell handover command MAC CE.

[0102] timeCellSwitch-Msg1: The time between the transmission of Msg1 and the reception of the corresponding LTM cell handover command MAC CE.

[0103] The collected RA reports can be reported to the network through the UE information process.

[0104] In an embodiment, the UE can autonomously derive the TA value of a candidate cell based on the timing advance (TA) value of the current serving cell and the Rx timing difference between the serving cell and the candidate cell, regardless of the earlier TA acquisition operation. This operation can be referred to as UE-based TA measurement. The UE can perform LTM handover without RACH or RRC-based handover without RACH by applying the TA value of the candidate target cell derived through UE-based TA measurement. For example, when the UE receives an LTM cell handover command MAC CE that does not include a valid TA value through a pre-configured UE-based TA measurement operation and has the TA value of the candidate target cell, the UE can perform LTM handover or RRC-based handover without the random access operation of the candidate target cell by applying the TA value of the candidate target cell. When the UE performs LTM handover without RACH or RRC-based handover without RACH by using the TA value of the candidate target cell derived through UE-based TA measurement, the UE can also store the following information as the content of the RA report, RLF report, or SHR at existing or new time points where the contents of the RA report, RLF report, or SHR are stored.

[0105] -Indicator information indicating whether the UE has performed LTM without RACH or normal handover, based on the TA value of the candidate target cell derived from UE-based TA measurement.

[0106] - TA values ​​of candidate target cells derived from UE-based TA measurements

[0107] - TA value of the serving cell used to derive the TA value of the candidate target cell through UE-based TA measurement.

[0108] -Rx timing difference between the serving cell and the candidate target cell used to derive the TA value of the candidate target cell through UE-based TA measurement.

[0109] In an embodiment, RRC-based handover can refer to handover based on Layer 3 (L3) filtering measurement results derived from RRC to determine the handover configuration time, and the network configures the handover for the UE through a predetermined RRC message.

[0110] The embodiments disclosed herein can be applied not only to LTM handovers, but also to RRC-based handovers.

[0111] Figure 6 This is a flowchart illustrating the operation of a UE for early TA acquisition according to an embodiment of the present disclosure.

[0112] UE 605 sends a MeasurementReport message (620) to source cell 610. The measurementReport message may include Layer 3 (L3) cell measurement results measured by UE 605 based on cell measurement configuration information previously provided by source cell 610. L3 cell measurement results may refer to cell measurement results that are ultimately processed and derived by the UE's RRC based on cell measurement results provided by the UE's lower layer (PHY).

[0113] Source cell 610 can negotiate with candidate target cell 615 for LTM and early TA acquisition operations based on L3 cell measurement results (625). Through negotiation with candidate target cell 615, source cell 610 can provide UE 605 with derived LTM configuration information and early TA acquisition configuration information (EarlyUL-SyncConfig IE) (630). The early TA acquisition configuration information includes information about the number of repeated Msg1 transmissions and the radio resource information necessary to send Msg1 (preamble) to candidate target cell 615. If only one transmission of Msg1 to candidate target cell 615 is allowed, subsequent LTM handover without RACH can be avoided if candidate target cell 615 fails to successfully receive Msg1. Therefore, when UE 605 repeatedly transmits Msg1 to candidate target cell 615, the probability of candidate target cell 615 successfully receiving Msg1 can be increased. When a predetermined 1-bit indicator is included in the advance TA acquisition configuration information, UE 605 can perform a predefined repeated Msg1 transmission.

[0114] Source cell 610 instructs UE 605 to transmit Msg1 to candidate target cell 615 via a PDCCH command (L1 signaling) (635). The PDCCH command may include information about the number of repeated Msg1 transmissions. The advantage of providing information about the number of repeated Msg1 transmissions along with the PDCCH command is that source cell 610 can consider the latest channel state to determine the most appropriate number of repeated Msg1 transmissions. In another approach, UE 605 can perform predefined repeated Msg1 transmissions when a predetermined 1-bit indicator is included in the PDCCH command. Upon receiving the PDCCH command, UE 605 can repeatedly transmit Msg1 to candidate target cell 615 according to its configuration (640). In this case, repeated Msg1 transmissions can be performed at a series of Msg1 transmission times, regardless of any feedback received from the network. UE 605 can use a predetermined available transmission power in all Msg1 transmissions. In other words, since predetermined feedback information for subsequent transmissions is not considered after each Msg1 transmission, no mechanism is needed to change the transmission power of each Msg1, such as power ramping. Upon receiving a Msg1, candidate target cell 615 derives the TA value to be applied to UE 605, taking into account the reception timing of Msg1. Since UE 605 repeatedly transmits Msg1, candidate target cell 615 can receive multiple Msg1s from a single UE 605. In this case, candidate target cell 615 can derive a single TA value corresponding to each received Msg1. When the derived TA value is provided to source cell 610 (645), candidate target cell 615 can determine which of the multiple derived TA values ​​to transmit. The following options may be considered in the embodiments.

[0115] - Option 1: TA for the last successfully received Msg1

[0116] - Option 2: A list of TAs for all successfully received Msg1s. Here, the TA values ​​included in the list can be stored in the order in which the corresponding Msg1s were received.

[0117] Option 3: TA for the strongest successful reception of Msg1

[0118] - Option 4: Average TA for all successfully received Msg1s

[0119] Option 5: Shortest TA

[0120] UE 605 may periodically or semi-persistently report L1 cell measurement results (e.g., L1-RSRP) of candidate target cells to source cell 610, depending on the configuration of source cell 610 (650). Source cell 610 may determine whether to trigger LTM handover based on the L1 cell measurement results. When it is determined that LTM handover should be triggered, source cell 610 may determine whether the TA value provided from candidate target cell 615 is suitable for LTM handover (655). When candidate target cell 615 sends all TA values ​​to source cell 610 as in Option 2, source cell 610 may determine one of the TA values ​​in terms of implementation. For example, source cell 610 may select the last value in the list of TA values ​​received from candidate target cell 615, or it may select the minimum TA value. In another approach, source cell 610 may use the average of the values ​​included in the list of TA values.

[0121] The source cell 610, which has been determined to trigger LTM handover by applying the TA value provided by the candidate target cell 615, sends a predetermined MAC CE, namely the LTM cell handover command MAC CE (660), to UE 605.

[0122] UE 605 may store predetermined information related to early TA acquisition as RA report content (665) at predetermined time points (e.g., after transmitting Msg1 or upon receiving an LTM cell handover command MAC CE). The predetermined information has been mentioned above, and additional information exemplified below may be stored when Msg1 is transmitted again.

[0123] -Information regarding the number of repeated Msg1 transmissions performed by UE 605

[0124] The aforementioned time information includes information related to the timing of Msg1 transmission. Since Msg1 is transmitted repeatedly, the time information needs to be differentiated accordingly. Therefore, the following options can be considered in the embodiment.

[0125] Option 1: You can store only the transmission timing information of the last Msg1 transmission of the application.

[0126] Option 2: A list of time information associated with all Msg1 transmissions. In other words, it can store the time information for the transmission timing of each Msg1 transmission.

[0127] Option 3: You can store the average transmission timing information for all Msg1 transmissions.

[0128] In addition to the RA report, the above information can also be included in different reporting mechanisms, namely, a Radio Link Failure (RLF) report or a Successful Handover (SHR) report. UE 605, having received the LTM cell handover command MAC CE, can perform LTM handover. In this case, UE 605 can store the RLF report content in the event of an LTM handover failure and can store the SHR content in the event of a successful LTM handover. In an embodiment, UE 605 can store information related to early TA acquisition and LTM handover, and can report this information via an RLF report or SHR. Here, UE 605 can store the following additional information as RLF report content or SHR content.

[0129] - Indicate whether the information included in the RLF report corresponds to the indicator information for LTM handover.

[0130] - Indicate whether the information included in the SHR corresponds to the indicator information for LTM handover.

[0131] - Indicates whether a valid TA value is included in the indicator information of the received LTM cell handover command MAC CE that has triggered an LTM handover executed by UE 605.

[0132] - Prior to the LTM cell handover command MAC CE, L1 cell measurement information (CSI information, such as L1-RSRP) about the nearest candidate target cell 615.

[0133] -The information described in the foregoing embodiments (new indicator and time information)

[0134] Figure 7 This is a flowchart illustrating UE operations according to an embodiment of the present disclosure, which store information about random access triggered in response to an early TA acquisition.

[0135] In operation 705, the UE sends capability information about the UE to the base station. The capability information may include indicator information indicating whether the UE supports RA reporting enhancement operations.

[0136] In operation 710, the UE receives LTM configuration information from the base station. The configuration information may include configuration information related to early TA acquisition, such as EarlyUL-SysncConfig. The configuration information may also include information about the number of times Msg1 transmissions are repeated.

[0137] In operation 715, the UE can receive a PDCCH command from the base station corresponding to the early TA acquisition operation. The PDCCH command may include information about the candidate target cells to which Msg1 needs to be sent, and may additionally include information about the number of repeated Msg1 transmissions.

[0138] In operation 720, the UE sends Msg1 to the candidate target cell. When repeated Msg1 transmissions are configured, the UE can send Msg1 a pre-configured or pre-defined number of times.

[0139] In operation 725, the UE determines whether Msg1 transmission has been performed by applying the previously received EarlyUL-SyncConfig configuration information.

[0140] When the previously received EarlyUL-SyncConfig configuration information has not yet been applied to Msg1 transmission, in operation 730, the UE can store the existing predefined information as RA report content.

[0141] When the previously received EarlyUL-SyncConfig configuration information has been applied to Msg1 transmission, in operation 735, the UE can store the information defined in the embodiments of this disclosure together with existing predefined information as RA report content.

[0142] Figure 8 This is a flowchart illustrating UE operation according to an embodiment of the present disclosure without storing information about random access triggered for early TA acquisition.

[0143] In operation 805, the UE sends capability information about the UE to the base station. The capability information may include indicator information indicating whether the UE supports RA reporting enhancement operations.

[0144] In operation 810, the UE receives LTM configuration information from the base station. The configuration information may include configuration information related to early TA acquisition, such as EarlyUL-SysncConfig. The configuration information may include an indicator indicating whether to skip storing 1-step RA-related information for early TA acquisition in the RA report. Alternatively, 1-step RA-related information for early TA acquisition may be considered to never be stored in the RA report.

[0145] In operation 815, the UE receives a PDCCH command from the base station corresponding to the early TA acquisition operation. The PDCCH command includes information about the candidate target cells to which Msg1 needs to be sent.

[0146] In operation 820, the UE sends Msg1 to the candidate target cell. When repeated Msg1 transmissions are configured, the UE can send Msg1 a pre-configured or pre-defined number of times.

[0147] In operation 825, the UE determines whether Msg1 transmission has been performed by applying the previously received EarlyUL-SyncConfig configuration information.

[0148] When the previously received EarlyUL-SyncConfig configuration information has not yet been applied to Msg1 transmission, in operation 830, the UE can store the existing predefined information as RA report content.

[0149] In operation 835, when previously received EarlyUL-SyncConfig configuration information has been applied to the Msg1 transmission and includes an indicator indicating whether to skip storing 1-step RA-related information for early TA acquisition in the RA report, the UE skips storing the 1-step RA-related information for early TA acquisition in the RA report. The UE may include pre-defined information about the previous 1-step RA in the RA report of the next random access. This pre-defined information may include an indicator indicating that the previous random access was a 1-step RA for early TA acquisition.

[0150] The 1-step RA information used for early TA acquisition can be considered to never be stored in the RA report. In this case, when the UE has already applied the previously received EarlyUL-SyncConfig configuration information for Msg1 transmission, the operation of storing the 1-step RA information used for early TA acquisition from the RA report can always be skipped.

[0151] Figure 9 This is a flowchart illustrating base station operations according to an embodiment of the present disclosure, which store information about random access triggered for an early TA acquisition.

[0152] In operation 905, the base station receives capability information about an individual UE from the UE. The capability information may include indicator information indicating whether the proposed RA report enhancement operation is supported.

[0153] In Operation 910, the base station receives L3 cell measurement results from the UE.

[0154] In Operation 915, the base station can negotiate with candidate target cells to operate LTM and acquire early TA based on L3 cell measurement results.

[0155] In Operation 920, the base station provides the UE with exported LTM configuration information and early TA acquisition configuration information (EarlyUL-SyncConfig IE) through negotiation with the candidate target cell.

[0156] In operation 925, the base station sends a PDCCH command to the UE corresponding to the early TA acquisition operation. The PDCCH command may include information about the candidate target cells to which Msg1 needs to be transmitted, and may additionally include information about the number of times Msg1 transmissions are repeated.

[0157] In Operation 930, the base station can receive TA values ​​from candidate target cells.

[0158] In Operation 935, the base station can receive L1 cell measurement results from the UE and determine whether to trigger LTM handover based on the results.

[0159] In Operation 940, the base station can send an LTM cell handover command MAC CE, which includes the TA value, to the UE.

[0160] Figure 10 This is a block diagram illustrating the internal structure of a UE that applies this disclosure.

[0161] Referring to the accompanying drawings, the UE may include a radio frequency (RF) processor 1010, a baseband processor 1020, a memory 1030, and a controller 1040.

[0162] The RF processor 1010 can perform functions for transmitting and receiving signals via a wireless channel, such as signal band conversion and amplification. That is, the RF processor 1010 can up-convert a baseband signal provided by the baseband processor 1020 into an RF band signal, which can be transmitted via an antenna, and can down-convert an RF band signal received via an antenna back to a baseband signal. For example, the RF processor 1010 may include transmit filters, receive filters, amplifiers, mixers, oscillators, digital-to-analog converters (DACs), analog-to-digital converters (ADCs), etc. Although only one antenna is shown in the figures, the UE may include multiple antennas. Furthermore, the RF processor 1010 may include multiple RF chains. Additionally, the RF processor 1010 can perform beamforming. For beamforming, the RF processor 1010 can adjust the phase and amplitude of each signal transmitted and received via multiple antennas or antenna elements. Furthermore, the RF processor can perform MIMO and can receive multiple layers when performing MIMO operation.

[0163] The baseband processor 1020 can perform conversion functions between baseband signals and bit strings according to the system's physical layer specifications. For example, during data transmission, the baseband processor 1020 can encode and modulate the transmitted bit string to generate complex symbols. Additionally, during data reception, the baseband processor 1020 can demodulate and decode the baseband signal provided from the RF processor 1010 to recover the received bit string. For example, when following an Orthogonal Frequency Division Multiplexing (OFDM) scheme, during data transmission, the baseband processor 1020 can encode and modulate the transmitted bit string to generate complex symbols, map the complex symbols to subcarriers, and configure the OFDM symbols through inverse Fast Fourier Transform (IFFT) operations and cyclic prefix (CP) insertion. Furthermore, during data reception, the baseband processor 1020 can separate the baseband signal provided from the RF processor 1010 at the OFDM symbol level, recover the signal mapped to the subcarriers through Fast Fourier Transform (FFT) operations, and recover the received bit string through demodulation and decoding.

[0164] The baseband processor 1020 and RF processor 1010 can transmit and receive signals as described above. Therefore, the baseband processor 1020 and RF processor 1010 can be referred to as a transmitter, receiver, transceiver, or communication unit. Furthermore, at least one of the baseband processor 1020 and RF processor 1010 may include multiple communication modules to support various different radio access technologies. Additionally, at least one of the baseband processor 1020 and RF processor 1010 may include different communication modules to process signals in different frequency bands. For example, different radio access technologies may include wireless LAN (e.g., IEEE 802.11), cellular networks (e.g., LTE), etc. Furthermore, different frequency bands may include the ultra-high frequency (SHF) band (e.g., 2NRHz) and the millimeter wave (mmWave) band (e.g., 60GHz).

[0165] The memory 1030 stores basic programs, application programs, and data, such as configuration information, for the operation of the UE. Specifically, the memory 1030 may store information related to a second access node that performs wireless communication using a second wireless access technology. Additionally, the memory 1030 provides stored data upon request from the controller 1040.

[0166] Controller 1040 controls the overall operation of the UE. For example, controller 1040 can send / receive signals via baseband processor 1020 and RF processor 1010. Additionally, controller 1040 records data in memory 1030 and reads data from memory 1030. For this purpose, controller 1040 may include at least one processor. For example, controller 1040 may include a communication processor (CP) configured to perform control for communication, and an application processor (AP) configured to control upper-layer applications such as applications.

[0167] Figure 11 This is a block diagram illustrating the structure of a base station according to the present disclosure.

[0168] As shown in the figure, the base station may include an RF processor 1110, a baseband processor 1120, a backhaul communication unit 1130, a memory 1140, and a controller 1150.

[0169] RF processor 1110 can perform functions for transmitting and receiving signals via a wireless channel, such as frequency band conversion and signal amplification. That is, RF processing unit 1110 up-converts baseband signals provided by baseband processing unit 1120 into RF band signals, transmits these signals through an antenna, and down-converts RF band signals received through the antenna back into baseband signals. For example, RF processor 1110 may include transmit filters, receive filters, amplifiers, mixers, oscillators, DACs, and ADCs. Although only one antenna is shown in the figures, the first access node may include multiple antennas. Furthermore, RF processor 1110 may include multiple RF chains. Additionally, RF processor 1110 can perform beamforming. For beamforming, RF processor 1110 can adjust the phase and amplitude of each signal transmitted and received through multiple antennas or antenna elements. The RF processor can perform downlink MIMO operation by transmitting one or more layers.

[0170] The baseband processor 1120 can perform conversion functions between baseband signals and bit strings according to the physical layer specifications of the first radio access technology. For example, during data transmission, the baseband processor 1120 can encode and modulate the transmitted bit string to generate complex symbols. Additionally, during data reception, the baseband processor 1120 can recover the received bit stream by demodulating and decoding the baseband signal provided from the RF processor 1110. For example, when following an OFDM scheme, during data transmission, the baseband processor 1120 can encode and modulate the transmitted bit string to generate complex symbols, map the complex symbols to subcarriers, and configure OFDM symbols through IFFT operations and CP insertion. Furthermore, during data reception, the baseband processor 1120 can separate the baseband signal provided from the RF processor 1110 at the OFDM symbol level, recover the signal mapped to the subcarriers through FFT operations, and recover the received bit string through demodulation and decoding. The baseband processor 1120 and the RF processor 1110 can transmit and receive signals as described above. Therefore, the baseband processor 1120 and the RF processor 1110 can be referred to as a transmitter, receiver, transceiver, communication unit, or wireless communication unit.

[0171] The backhaul communication unit 1130 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 1130 can convert bit strings sent from the main base station to other nodes (e.g., auxiliary base stations, core network) into physical signals, and can convert physical signals received from other nodes into bit strings.

[0172] The memory 1140 can store basic programs, applications, and data for the operation of the main base station, such as configuration information. Specifically, the memory 1140 can store information about bearers assigned to connected UEs, measurement results reported from connected UEs, etc. Additionally, the memory 1140 can store information used as criteria for determining whether to provide multiple connections to a UE or suspend multiple connections. Furthermore, the memory 1140 provides stored data upon request from the controller 1150.

[0173] The controller 1150 controls the overall operation of the main base station. For example, the controller 1150 can transmit / receive signals via the baseband processor 1120 and the RF processor 1110 or via the backhaul communication unit 1130. Additionally, the controller 1150 records data in and reads data from the memory 1140. For this purpose, the controller 1150 may include at least one processor.

[0174] Figure 12 Components of a UE according to an embodiment of the present disclosure are shown.

[0175] The UE according to embodiments of this disclosure may include a processor 1220 for controlling the overall operation of the UE, a transceiver 1200 including a transmitter and a receiver, and a memory 1210. Of course, the examples given above are not limiting, and the UE may include more than... Figure 12 The components shown are fewer or more components. Figure 12 The UE in the text can correspond to Figures 1 to 10 The UE described in the document.

[0176] According to embodiments of this disclosure, transceiver 1200 can send / receive signals with a network entity or other UEs. Signals sent / received via the network entity may include control information and data. Additionally, transceiver 1200 can receive signals via a radio channel, output them to processor 1220, and transmit signals output from processor 1220 via a radio channel.

[0177] According to embodiments of this disclosure, processor 1220 can control the UE to perform any of the operations described in the above embodiments. Processor 1220, memory 1210, and transceiver 1200 need not be implemented as separate modules, but can be implemented as a single component unit such as a single chip. Furthermore, processor 1220 and transceiver 1200 can be electrically connected to each other. Additionally, processor 1220 can be an application processor (AP), a communication processor (CP), a circuit, a dedicated circuit, or at least one processor.

[0178] According to embodiments of this disclosure, memory 1210 may store basic programs, application programs, and data such as configuration information for operation of the UE. Specifically, memory 1210 provides the stored data upon request from processor 1220. Memory 1210 may include storage media or combinations of storage media such as ROM, RAM, hard disk, CD-ROM, and DVD. Furthermore, memory 1210 may include multiple memories. Additionally, processor 820 may execute the above-described embodiments of this disclosure based on programs stored in memory 810 for executing embodiments.

[0179] Figure 13 Components of a base station according to an embodiment of the present disclosure are shown.

[0180] A base station according to embodiments of the present disclosure may include a processor 1320 for controlling the overall operation of the base station, a transceiver 1300 including a transmitter and a receiver, and a memory 1310. Of course, the examples given above are not limiting, and the base station may include more than... Figure 13 The components shown are fewer or more components. Figure 13 The base station in the middle can correspond to Figures 1 to 11 The base station described in the text.

[0181] According to embodiments of this disclosure, transceiver 1300 can transmit / receive signals with at least one of other network entities or UEs. Signals transmitted / received with at least one of other network entities or UEs may include control information and data.

[0182] According to embodiments of this disclosure, processor 1320 can control the base station to perform any of the operations described in the above embodiments. Of course, processor 1320, memory 1310, and transceiver 1300 are not necessarily implemented as separate modules, but can be implemented as a single component unit such as a single chip. Furthermore, processor 1320 and transceiver 1300 can be electrically connected to each other. Additionally, processor 1320 can be an application processor (AP), a communication processor (CP), a circuit, a dedicated circuit, or at least one processor.

[0183] According to embodiments of this disclosure, memory 1310 may store basic programs, application programs, and data such as configuration information for the operation of a base station. Specifically, memory 1310 provides the stored data upon request from processor 1320. Memory 1310 may include storage media or combinations of storage media such as ROM, RAM, hard disk, CD-ROM, and DVD. Furthermore, memory 1310 may include multiple memories. Additionally, processor 1320 may execute the above-described embodiments of this disclosure based on programs stored in memory 1310 for executing implementation methods.

[0184] It should be noted that the above configuration diagrams, illustrations of control / data signal transmission methods, illustrations of operation processes, and structural diagrams are not intended to limit the scope of this disclosure. That is, all components, entities, or operational steps described in the embodiments of this disclosure should not be construed as essential elements for implementing this disclosure, and this disclosure can be implemented without prejudice to its authenticity even when only some elements are included. Furthermore, the various embodiments described above can be combined as needed. For example, the methods proposed in this disclosure can be partially combined with each other to operate network entities and UEs.

[0185] The aforementioned operations of the base station or terminal can be achieved by providing any unit of the base station or terminal equipment with a memory device that stores the corresponding program code. In other words, the controller of the base station or terminal equipment can perform the aforementioned operations by reading and executing the program code stored in the memory device using a processor or central processing unit (CPU).

[0186] Various units or modules of network entities, base station equipment, or terminal equipment can be operated using hardware circuits such as logic circuits based on complementary metal-oxide-semiconductor (CMOS), firmware, or combinations of hardware circuits such as software and / or hardware, and firmware and / or software embedded in a machine-readable medium. For example, various electrical structures and methods can be implemented using transistors, logic gates, and circuits such as application-specific integrated circuits (ASICs).

[0187] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). The one or more programs stored in the computer-readable storage medium may be configured to be executed by one or more processors within an electronic device. The at least one program includes instructions to cause the electronic device to perform methods according to various embodiments of the present disclosure as defined by the appended claims and / or disclosed herein.

[0188] These programs (software modules or software) can be stored in non-volatile memory, including random access memory and flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), disk storage devices, optical disc ROM (CD-ROM), digital versatile optical disc (DVD), or other types of optical storage devices or magnetic tape cartridges. Alternatively, any combination of some or all of these can form the memory storing the programs. Additionally, multiple such memories may be included.

[0189] Furthermore, the program can be stored in an attachable storage device that can be accessed by the electronic device via a communication network such as the Internet, intranet, local area network (LAN), wide area network (WLAN), and storage area network (SAN), or a combination thereof. Such a storage device can be accessed by the electronic device via an external port. Additionally, a separate storage device on the communication network can be accessed by a device used to execute embodiments of this disclosure.

[0190] In the detailed embodiments described above, the elements included in this disclosure are represented in a singular or plural form according to the presented embodiments. However, for ease of description, the singular or plural form is suitably chosen for the presented situation, and this disclosure is not limited to elements represented in a singular or plural form. Therefore, an element represented in a plural form may also include a single element, or an element represented in a singular form may include multiple elements.

[0191] Although specific embodiments have been described in detail in this disclosure, it will be apparent that various modifications and changes can be made thereto without departing from the scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the embodiments set forth herein, but should be defined by the appended claims and their equivalents. That is, it will be apparent to those skilled in the art that other variations based on the technical ideas of this disclosure can be implemented. Furthermore, the various embodiments described above can be combined as needed. For example, the methods proposed in this disclosure can be partially combined with each other to operate network entities and terminals. Moreover, although the embodiments described above are based on 5G or NR systems, other variations based on the technical ideas of the embodiments can also be implemented in other communication systems such as LTE, LTE-A, and LTE-A-Pro systems.

[0192] Although specific embodiments have been described in the detailed description of this disclosure, it will be apparent that various modifications and changes can be made thereto without departing from the scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the embodiments set forth herein, but should be defined by the appended claims and their equivalents.

[0193] The embodiments of this disclosure described and illustrated in the specification and drawings are merely specific examples presented to facilitate the explanation of the technical content of this disclosure and to aid in understanding it, and are not intended to limit the scope of this disclosure. That is, it will be apparent to those skilled in the art that other variations based on the technical concepts of this disclosure can be implemented. Furthermore, the various embodiments described above can be combined as needed. As an example, a portion of one embodiment of this disclosure can be combined with a portion of another embodiment to operate a base station and a terminal. Moreover, other variations based on the technical concepts of the embodiments can also be implemented in various systems such as FDD LTE, TDD LTE, and 5G or NR systems.

Claims

1. A method performed by a terminal in a wireless communication system, the method comprising: Send L1 measurement information for candidate cells to the source cell; Receive cell handover command from the source cell; as well as Based on the cell handover command, perform the lower-layer triggered mobility (LTM) handover.

2. The method according to claim 1, further comprising: In the event of LTM handover failure, a Radio Link Failure (RLF) report is recorded based on the cell handover command. The RLF report includes indicators indicating whether the cell handover is based on random access (RA) or without RA.

3. The method according to claim 2, wherein, The RLF report also includes L1 measurement information for candidate cells.

4. The method according to claim 1, further comprising: Based on the received cell handover command, record the Random Access (RA) report. The RA report includes indicators indicating cell handover based on random access (RA) or cell handover without RA, or indicators indicating the reason for random access.

5. A method performed by a base station in a wireless communication system, the method comprising: Receive L1 measurement information for candidate cells from the terminal; Based on L1 measurement information, a cell handover command is sent to the terminal; Send a report request message to the terminal; as well as Receive reports from the terminal.

6. The method according to claim 5, wherein, Report request messages include Random Access (RA) Report Request messages or Radio Link Failure (RLF) Report Request messages, and The reports include RA reports or RLF reports.

7. The method according to claim 6, wherein, The RLF report includes L1 measurement information for candidate cells and indicators indicating cell handover based on random access (RA) or cell handover without RA.

8. The method according to claim 6, wherein, Random access reports include indicators indicating cell handover based on random access (RA) or cell handover without RA, or indicators indicating the reason for random access.

9. A terminal in a wireless communication system, the terminal comprising: transceiver; as well as The controller is connected to the transceiver. The controller is configured as follows: Send L1 measurement information for candidate cells to the source cell; Receive cell handover command from the source cell; and Based on the cell handover command, perform LTM handover.

10. The terminal according to claim 9, wherein, The controller is configured to: in the event of an LTM handover failure, based on a cell handover command, record a radio link failure (RLF) report, and The RLF report includes indicators indicating whether the cell handover is based on random access (RA) or without RA.

11. The terminal according to claim 10, wherein, The RLF report also includes L1 measurement information for candidate cells.

12. The terminal according to claim 9, wherein, The controller is configured to record random access (RA) reports based on received cell handover commands, and The RA report includes indicators indicating cell handover based on random access (RA) or cell handover without RA, or indicators indicating the reason for random access.

13. A base station in a wireless communication system, the base station comprising: transceiver; as well as The controller is connected to the transceiver. The controller is configured as follows: Receive L1 measurement information for candidate cells from the terminal; Based on L1 measurement information, a cell handover command is sent to the terminal; Send a report request message to the terminal; and Receive reports from the terminal.

14. The base station according to claim 13, wherein, Report request messages include Random Access (RA) Report Request messages or Radio Link Failure (RLF) Report Request messages, and The reports include RA reports or RLF reports.

15. The base station according to claim 14, wherein, The RLF report includes L1 measurement information for candidate cells and indicators indicating cell handover based on random access (RA) or cell handover without RA. The random access report includes indicators indicating cell handover based on random access (RA) or cell handover without RA, or indicators indicating the reason for random access.

Images