Method and apparatus for performing cell access without random access in a next generation wireless communication system

Abstract

The present disclosure relates to: a communication technology for integrating IoT technology with a 5G communication system for supporting a higher data transmission rate than a 4G system; and a system thereof. The present disclosure can be applied to smart services (e.g., smart homes, smart buildings, smart cities, smart cars or connected cars, health care, digital education, retail business, security and safety related services, etc.) based on 5G communication technology and IoT related technology. The present disclosure relates to handover performed without random access in a wireless communication system.

Description

Technical Field

[0001] The present disclosure relates to handover performed without random access in a wireless communication system. Background Art

[0002] In order to meet the growing demand for wireless data traffic since the deployment of 4G communication systems, efforts have been made to develop improved 5G or quasi-5G communication systems. Therefore, 5G or quasi-5G communication systems are also referred to as "super 4G networks" or "post-LTE systems". 5G communication systems are considered to be implemented in higher frequency (mmWave) bands, for example, in the 60GHz band, in order to achieve higher data rates. In order to reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple input multiple output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technology are discussed in 5G communication systems. In addition, in 5G communication systems, research and development for system network improvements are being carried out based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communications, wireless backhaul, mobile networks, cooperative communications, coordinated multi-point (CoMP), receiving end interference elimination, etc. In 5G systems, hybrid FSK with QAM modulation (FQAM) and sliding window superposition coding (SWSC) as advanced coding modulation (ACM), and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) as advanced access technologies have been developed.

[0003] The Internet, which is a human-centric connected network in which people generate and consume information, is evolving into the Internet of Things (IoT), in which distributed entities (such as things) exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of IoT technology and big data processing technology through connection with cloud servers, has emerged. Because technical elements such as "sensing technology", "wired / wireless communication and network infrastructure", "service interface technology", and "security technology" have been required for IoT implementation, sensor networks, machine-to-machine (M2M) communication, machine type communication (MTC), etc. have been studied recently. Such an IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing data generated among connected things. Through the integration and combination between existing information technology (IT) and various industrial applications, IoT can be applied in various fields, including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart appliances, and advanced medical services.

[0004] In accordance with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, machine type communications (MTC), and machine-to-machine (M2M) communications can be implemented through beamforming, MIMO, and array antennas. The application of cloud radio access networks (RANs) as the above-mentioned big data processing technology can also be considered as an example of the fusion between 5G technology and IoT technology.

[0005] Since various services can be provided according to the above description and the development of mobile communication systems, a method for efficiently providing these services is required. Summary of the invention

[0006] Technical issues

[0007] The present disclosure provides an apparatus and method for efficiently providing services in a mobile communication system. According to an embodiment of the present disclosure, there is a need for a method for a (user equipment) UE to receive resource allocation in a target cell to perform a random access channel (rachless) handover, and UL signal transmission required for access can be performed by using a configured granted UL configured in an existing bandwidth part.

[0008] Solution to the problem

[0009] Technical problems to be achieved in the embodiments of the present disclosure are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by ordinary technicians in the field to which the present disclosure belongs from the following description.

[0010] According to an embodiment of the present disclosure, a method performed by a UE in a wireless communication system includes: receiving a first radio resource control (RRC) message from a base station, the first radio resource control (RRC) message including first information for performing cell access without random access and second information about cell configuration information; sending a second RRC message to the base station using an uplink grant configured in a specific bandwidth part (BWP); and receiving a media access control (MAC) control element (CE) from the base station, the media access control (MAC) control element (CE) indicating contention resolution through a cell radio network temporary identifier (C-RNTI) indicated in the first message, wherein the specific BWP is determined by the second information.

[0011] In some embodiments, the first information includes at least one of target timing advance (TA) information and information for releasing an uplink grant configured in a specific BWP.

[0012] In some embodiments, when the first information includes information for releasing an uplink grant configured in a specific BWP, the method further includes: after sending the second RRC message, releasing the uplink grant configured in the specific BWP.

[0013] In some embodiments, when the first information includes target TA information, the TA information includes at least one of Ta-0, PTAG, and STAG-Id.

[0014] According to another embodiment of the present disclosure, a method performed by a base station in a wireless communication system includes: sending a first radio resource control (RRC) message to a UE, the first radio resource control (RRC) message including first information for performing cell access without random access and second information about cell configuration information; receiving a second RRC message from the UE using an uplink grant configured in a specific bandwidth part (BWP); and sending a media access control (MAC) control element (CE) to a terminal, the media access control (MAC) control element (CE) indicating contention resolution through a cell radio network temporary identifier (C-RNTI) indicated in the first message, wherein the specific BWP is determined by the second information.

[0015] According to another embodiment of the present disclosure, a UE includes: a transceiver configured to send and receive at least one signal; and a controller coupled to the transceiver, wherein the controller is configured to: receive a first radio resource control (RRC) message from a base station, the first radio resource control (RRC) message including first information for performing cell access without random access and second information about cell configuration information; send a second RRC message to the base station using an uplink grant configured in a specific bandwidth part (BWP); and receive a media access control (MAC) control element (CE) from the base station, the media access control (MAC) control element (CE) indicating contention resolution through a cell radio network temporary identifier (C-RNTI) indicated in the first message, and wherein the specific BWP is determined by the second information.

[0016] According to another embodiment of the present disclosure, a base station includes: a transceiver configured to send and receive at least one signal; and a controller coupled to the transceiver, wherein the controller is configured to: send a first radio resource control (RRC) message to a terminal, the first radio resource control (RRC) message including first information for performing cell access without random access and second information about cell configuration information; receive a second RRC message from a UE using an uplink grant configured in a specific bandwidth part (BWP); and send a media access control (MAC) control element (CE) to the terminal, the media access control (MAC) control element (CE) indicating contention resolution through a cell radio network temporary identifier (C-RNTI) indicated in the first message, and wherein the specific BWP is determined by the second information.

[0017] Advantageous Effects of the Invention

[0018] Embodiments disclosed in the present disclosure reduce data delays generated during handover by performing access using a predefined UL grant without sending a random access preamble for obtaining an uplink (UL) grant when attempting to access a target cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1a is a diagram showing the structure of an LTE system according to some embodiments of the present disclosure.

[0020] Figure 1b is a diagram showing a radio protocol structure of an LTE system according to some embodiments of the present disclosure.

[0021] Figure 1c is a diagram showing a structure of a next generation mobile communication system according to some embodiments of the present disclosure.

[0022] Figure 1d is a diagram illustrating a radio protocol structure of a next generation mobile communication system according to some embodiments of the present disclosure.

[0023] Figure 1e is a block diagram illustrating the internal structure of a UE according to some embodiments of the present disclosure.

[0024] Figure 1f is a block diagram showing the configuration of an NR base station according to some embodiments of the present disclosure.

[0025] Figure 1g A random access channel-less (RACHless) handover operation in conventional LTE is shown.

[0026] Figure 1h1 is a message flow diagram illustrating a use case where a random access channel skip (rach-skip) release configuration is included in a random access channel-free HO specific signal structure in NR according to some embodiments of the present disclosure.

[0027] Figure 1i is a message flow diagram illustrating a use case where a random access channel skip (rach-skip) does not include a release configuration in a random access channel-free HO specific signal structure in NR according to some embodiments of the present disclosure.

[0028] Figure 1j is a message flow diagram illustrating a switching case in which normal HO in NR and no random access channel HO signal are omitted according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0029] Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the accompanying drawings.

[0030] In the following description of the present disclosure, when it is determined that a detailed description of a known function or configuration related to the present disclosure may unnecessarily obscure the subject matter of the present disclosure, its detailed description will be omitted. In addition, the terms to be described later are terms defined in consideration of the functions in the present disclosure, which may vary according to the intentions or habits of users and operators. Therefore, they should be defined based on the contents in this specification. For ease of description, the terms used in the following description for identifying access nodes, terms for indicating network entities, terms for indicating messages, terms for indicating interfaces between network objects, terms for indicating various identification information, etc. are illustrated. Therefore, the present disclosure is not limited to the terms described below, and other terms referring to objects with equivalent technical meanings may be used.

[0031] Hereinafter, a base station is a subject that performs resource allocation of a UE, and may be at least one of a gNode B, an eNode B, a Node B, a base station (BS), a radio access unit, a base station controller, or a node on a network. A UE may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing a communication function. The present disclosure is not limited to the above examples.

[0032] In particular, the present disclosure may be applied to 3GPP NR (5th generation mobile communication standard). In addition, the present disclosure may be applied to smart services based on 5G communication technology and IoT-related technology (e.g., smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, and security and safety-related services). In the present disclosure, for ease of description, eNB may be used interchangeably with gNB. That is, a base station described as an eNB may represent a gNB. In addition, the term UE may refer to a mobile phone, an NB-IoT device, a sensor, and other wireless communication devices.

[0033] Wireless communication systems are evolving from initial voice-oriented services to broadband wireless communication systems that provide high-speed and high-quality packet data services, such as communication standards such as High Speed ​​Packet Access (HSPA), Long Term Evolution (LTE) or Evolved Universal Terrestrial Radio Access (E-UTRA), LTE Advanced (LTE-A), 3GPP's LTE-Pro, High Rate Packet Data (HRPD), 3GPP2's Ultra Mobile Broadband (UMB), and IEEE 802.16e.

[0034] As a representative example of a broadband wireless communication system, in the LTE system, an orthogonal frequency division multiplexing (OFDM) method is adopted in a downlink (DL), and a single carrier frequency division multiple access (SC-FDMA) method is adopted in an uplink (UL). UL refers to a radio link in which a user equipment (UE) or a mobile station (MS) sends data or a control signal to a base station (BS or eNode B), and DL refers to a radio link in which a base station sends data or a control signal to a UE. The multiple access method as described above divides the data or control information of each user by allocating and operating the time-frequency resources to which the data or control information will be sent for each user so that they do not overlap with each other, i.e., establishing orthogonality.

[0035] As a future communication system after LTE, that is, a 5G communication system should be able to freely reflect various needs such as users and service providers; therefore, services that simultaneously meet various needs should be supported. Services considered for the 5G communication system include enhanced mobile broadband (eMBB), massive machine type communication (mMTC), and ultra-reliable low latency communication (URLLC).

[0036] According to some embodiments, eMBB may be intended to provide an improved data transfer rate over that supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, from the perspective of a base station, eMBB should be able to provide a peak data rate of 20 Gbps in DL and a peak data rate of 10 Gbps in UL. In addition, a 5G communication system may have to provide a peak data rate while providing an increased user-perceived UE data rate. In order to meet these requirements, a 5G communication system may need to improve various transmission and reception technologies, including more advanced multiple-input multiple-output (MIMO) transmission technologies. In addition, the LTE system uses a maximum transmission bandwidth of 20 MHz to transmit signals in the 2 GHz band currently used by LTE, while the 5G communication system uses a frequency bandwidth wider than 20 MHz in a frequency band of 3 to 6 GHz or 6 GHz or higher, thereby meeting the required data rate.

[0037] At the same time, mMTC is being considered to support application services such as the Internet of Things (IoT) in 5G communication systems. In order to effectively provide the Internet of Things, mMTC may require large-scale terminal access support within the cell, improved terminal coverage, improved battery life time, and reduced terminal costs. Since the Internet of Things is attached to several sensors and various devices to provide communication functions, it should be able to support a large number of terminals within the cell (e.g., 1,000,000 terminals / square kilometer). In addition, because the terminal supporting mMTC is likely to be located in a shadow area that the cell cannot cover, such as the basement of a building, due to the characteristics of the service, wider coverage may be required compared to other services provided by the 5G communication system. Terminals supporting mMTC should be configured with low-cost terminals, and since it is difficult to frequently replace the battery of the UE, a very long battery life, such as 10 to 15 years, may be required.

[0038] Finally, URLLC is a cellular-based wireless communication service for mission-critical tasks and can be used for remote control of robots or machinery, as well as services used in services such as industrial automation, unmanned aerial vehicles, remote healthcare, emergency alerts, etc. Therefore, communications provided by URLLC may have to provide very low latency (ultra-low latency) and very high reliability (ultra-reliability). For example, services supporting URLLC should meet air interface delays of less than 0.5 milliseconds and may simultaneously have a packet error rate requirement of 10-5 or less. Therefore, for services supporting URLLC, the 5G system should provide a smaller transmission time interval (TTI) than other services, and at the same time, it may be necessary to allocate wide resources in the frequency band to ensure the reliability of the communication link.

[0039] The three services considered in the above-mentioned 5G communication system, namely eMBB, URLLC and mMTC, can be multiplexed and transmitted in one system. In this case, different transmission and reception technologies and transmission and reception parameters can be used between services to meet the different requirements of each service. However, the aforementioned mMTC, URLLC and eMBB are only examples of different service types, and the service types applied by the present disclosure are not limited to the above examples.

[0040] In addition, the following will use LTE, LTE-A, LTE Pro or 5G (or NR, next generation mobile communication) system as an example to describe the embodiments of the present disclosure, but the embodiments of the present disclosure can also be applied to other communication systems with similar technical backgrounds or channel types. In addition, the embodiments of the present disclosure can be applied to other communication systems by some modifications within the scope that does not significantly deviate from the scope of the present disclosure determined by a person with skilled technical knowledge.

[0041] Figure 1a is a diagram showing the structure of an LTE system according to some embodiments of the present disclosure.

[0042] refer to Figure 1a As shown in the figure, the radio access network of the LTE system can be configured with evolved Node Bs (hereinafter, ENBs, Node Bs or base stations) 1a-05, 1a-10, 1a-15 and 1a-20, a mobility management entity (MME) 1a-25 and a serving gateway (S-GW) 1a-30. User equipment (hereinafter, UE or terminal) 1a-35 can access external networks through ENBs 1a-05, 1a-10, 1a-15 and 1a-20 and S-GW 1a-30.

[0043] exist Figure 1aIn the LTE system, ENB 1a-05, 1a-10, 1a-15 and 1a-20 may correspond to the existing Node B of the UMTS system. The ENB may be connected to the UE 1a-35 via a radio channel and play a more complex role than the existing Node B. In the LTE system, all user services including real-time services such as Voice over IP (VoIP) over Internet Protocol may be served through a shared channel. Therefore, a device for scheduling by collecting status information such as the buffer status, available transmission power status and channel status of the UE may be required, and the ENB 1a-05, 1a-10, 1a-15 and 1a-20 may be responsible for this. One ENB may generally control multiple cells. For example, in order to achieve a transmission rate of 100Mbps, the LTE system may use, for example, Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in a 20MHz bandwidth. In addition, the ENB may apply an adaptive modulation and coding (AMC) method, which determines the modulation scheme and channel coding rate according to the channel status of the UE. The S-GW 1a-30 is a device that provides a data bearer, and can generate or remove a data bearer under the control of the MME 1a-25. The MME is a device responsible for various control functions of the UE and a mobility management function, and can be connected to a plurality of base stations.

[0044] Figure 1b is a diagram showing a radio protocol structure of an LTE system according to some embodiments of the present disclosure.

[0045] refer to Figure 1b , the radio protocols of the LTE system may include packet data convergence protocol (PDCP) 1b-05 and 1b-40, radio link control (RLC) 1b-10 and 1b-35, and medium access control (MAC) 1b-15 and 1b-30 in the terminal and ENB, respectively. PDCP may be responsible for operations such as IP header compression / recovery. The main functions of PDCP can be summarized as follows. The main functions of PDCP are not limited to the following examples.

[0046] -Header compression and decompression: ROHC only

[0047] -Transmission of user data

[0048] - Sequential delivery of upper layer PDUs during PDCP re-establishment in RLC AM

[0049] - For split bearers in DC (supported only for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception

[0050] - Duplicate detection of lower layer SDUs during PDCP re-establishment for RLC AM

[0051] - For RLC AM, retransmit PDCP SDUs at handover, and for split bearers in DC, retransmit PDCP PDUs during PDCP data recovery procedure

[0052] -Encryption and decryption

[0053] - Timer based SDU discard in uplink.

[0054] According to some embodiments, radio link control (RLC) 1b-10 and 1b-35 may reconfigure PDCP packet data units (PDUs) to an appropriate size to perform ARQ operations, etc. The main functions of RLC can be summarized as follows. The main functions of RLC are not limited to the following examples.

[0055] -Transmission of upper layer PDU

[0056] - Error correction via ARQ (for AM data transmission only)

[0057] -RLC SDU concatenation, segmentation and reassembly (only for UM and AM data transmission)

[0058] - Re-segmentation of RLC data PDU (only for AM data transmission)

[0059] - Reordering of RLC data PDUs (only for UM and AM data transmission)

[0060] - Duplicate detection (for UM and AM data transmission only)

[0061] -Protocol error detection (for AM data transmission only)

[0062] -RLC SDU discard (only for UM and AM data transmission)

[0063] -RLC reconstruction

[0064] According to some embodiments, MAC 1b-15 and 1b-30 can be connected to several RLC layer devices configured in one terminal and perform operations of multiplexing RLC PDU to MAC PDU and demultiplexing RLC PDU from MAC PDU. The main functions of MAC can be summarized as follows. The main functions of MAC are not limited to the following examples.

[0065] - Mapping between logical channels and transport channels

[0066] - Multiplexing / demultiplexing MAC SDUs belonging to one or different logical channels into / from a transport block (TB) delivered to / from the physical layer on a transport channel

[0067] -Dispatch information report

[0068] - Error correction through HARQ

[0069] - Priority handling between logical channels of a UE

[0070] - Prioritization between UEs through dynamic scheduling

[0071] -MBMS service identification

[0072] -Transmission format selection

[0073] -patch

[0074] According to some embodiments, the physical layers 1b-20 and 1b-25 may perform operations of channel coding and modulating upper layer data, making the upper layer data into OFDM symbols and transmitting the OFDM symbols using a wireless channel, or demodulating OFDM symbols received through a wireless channel, channel decoding the OFDM symbols, and transmitting the OFDM symbols to a higher layer. The present disclosure is not limited to the following examples.

[0075] Figure 1c is a diagram showing a structure of a next generation mobile communication system according to some embodiments of the present disclosure.

[0076] refer to Figure 1c , the radio access network of the next generation mobile communication system (hereinafter, NR or 5g) can be configured with a new radio node B (hereinafter, NR gNB or NR base station) 1c-10 and a new radio core network (NR CN) 1c-15. The new radio user equipment (NR UE or terminal) 1c-15 can access the external network through the NR gNB 1c-10 and the NR CN 1c-05.

[0077] exist Figure 1c In the present invention, the NR gNB 1c-10 may correspond to the evolved Node B (eNB) of the existing LTE system. The NR gNB may be connected to the NR UE 1c-15 through a radio channel and provide services superior to the existing Node B. In the next generation mobile communication system, all user services may be served through a shared channel. Therefore, a device for scheduling by collecting status information such as the buffer status, available transmission power status, and channel status of the UE may be required, and the NR gNB 1c-10 may be responsible for this. One NR gNB may control multiple cells. In the next generation mobile communication system, a bandwidth greater than or equal to the current maximum bandwidth may be applied to achieve ultra-high-speed data transmission compared to the current LTE. In addition, orthogonal frequency division multiplexing (OFDM) technology may be used as a radio access technology, and beamforming technology may be additionally used.

[0078] In addition, according to some embodiments, the NR gNB can apply an adaptive modulation and coding (hereinafter referred to as AMC) scheme, which determines the modulation scheme and channel coding rate according to the channel state of the terminal. NR CN 1c-05 can perform functions such as mobility support, bearer configuration, QoS configuration, etc. NR CN 1c-05 is a device responsible for various control functions of the terminal and mobility management functions, and can be connected to multiple base stations. In addition, the next-generation mobile communication system can be linked to the existing LTE system, and the NR CN can be connected to the MME 1c-25 through a network interface. The MME can be connected to the base station 1c-30 which is an existing base station.

[0079] Figure 1d is a diagram illustrating a radio protocol structure of a next generation mobile communication system according to some embodiments of the present disclosure.

[0080] refer to Figure 1d The radio protocols of the next generation mobile communication system can include NR Service Data Adaptation Protocol (SDAP) 1d-01 and 1d-45, NR PDCP 1d-05 and 1d-40, NR RLC 1d-10 and 1d-35, and NR MAC 1d-15 and 1d-30 in the terminal and NR base station, respectively.

[0081] According to some embodiments, the main functions of NR SDAP 1d-01 and 1d-45 may include some of the following functions. However, the main functions of NR SDAP 1d-01 and 1d-45 are not limited to the following examples.

[0082] -Transmission of user plane data

[0083] - Mapping between QoS flows and DRBs for both DL and UL

[0084] - Marking of QoS Flow ID in both DL and UL packets

[0085] - Reflective QoS Flow to DRB mapping for UL S DAP PDU.

[0086] For an SDAP layer device, the terminal may receive a configuration regarding whether to use a header of the SDAP layer device for each PDCP layer device, for each bearer, or for each logical channel, or whether to use a function of the SDAP layer device for a radio resource control (RRC) message. In addition, in an SDAP layer device, when the SDAP header is set, the UE may indicate that the mapping information for uplink and downlink QoS flows and data bearers is updated or reconfigured using a non-access stratum (NAS) quality of service (QoS) reflection 1-bit indicator (NAS reflection QoS) and an access stratum (AS) QoS reflection 1-bit indicator (AS reflection QoS) of the SDAP header. According to some embodiments, the SDAP header may include QoS flow ID information indicating QoS. According to some implementation methods, QoS information may be used as data processing priority, scheduling information, etc., to support smooth services.

[0087] According to some embodiments, the main functions of NR PDCP 1d-05 and 1d-40 may include some of the following functions. However, the main functions of NR PDCP 1d-05 and 1d-40 are not limited to the following examples.

[0088] -Header compression and decompression: ROHC only

[0089] -Transmission of user data

[0090] - Sequential delivery of upper layer PDUs

[0091] - Out-of-order delivery of upper layer PDUs

[0092] - Reordering of received PDCP PDUs

[0093] - Duplicate detection of lower layer SDU

[0094] -Retransmission of PDCP SDU

[0095] -Encryption and decryption

[0096] - Timer based SDU discard in uplink.

[0097] In the above description, the reordering of the NR PDCP device may mean a function of reordering the PDCP PDUs received from the lower layer in order based on the PDCP sequence number (SN). The reordering of the NR PDCP device may include a function of delivering data to a higher layer in a reordered order, or may include a function of directly delivering data regardless of the order, a function of recording lost PDCP PDUs by reordering the order, a function of reporting the status of lost PDCP PDUs to the transmitting side, and a function of requesting retransmission of lost PDCP PDUs.

[0098] According to some embodiments, the main functions of NR RLC 1d-10 and 1d-35 may include some of the following functions. However, the main functions of NR RLC 1d-10 and 1d-35 are not limited to the following examples.

[0099] -Transmission of upper layer PDU

[0100] - Sequential delivery of upper layer PDUs

[0101] - Out-of-order delivery of upper layer PDUs

[0102] - Error correction via ARQ

[0103] - Concatenation, segmentation and reassembly of RLC SDU

[0104] - Re-segmentation of RLC data PDUs

[0105] - Reordering of RLC data PDUs

[0106] - Duplicate detection

[0107] -Protocol error detection

[0108] -RLC SDU discarded

[0109] -RLC reconstruction

[0110] In the above description, the sequential delivery of the NR RLC device may mean a function of delivering the RLC SDU received from the lower layer to the higher layer in sequence. When one RLC SDU is initially divided into several RLC SDUs and received, the sequential delivery of the NR RLC device may include a function of reassembling and delivering several RLC SDUs.

[0111] The sequential delivery of the NR RLC device may include a function of reordering the received RLC PDU based on the RLC sequence number (SN) or the PDCP sequence number (SN), and may include a function of recording the lost RLC PDU by reordering the order, a function of reporting the status of the lost RLC PDU to the transmitting side, and a function of requesting retransmission of the lost RLC PDU.

[0112] The sequential delivery of the NR RLC device may include the function of delivering only the RLC SDUs preceding the lost RLC SDU to the higher layer in sequence when there is a lost RLC SDU.

[0113] The in-sequence delivery of the NR RLC device may include the function of delivering all RLC SDUs received before the start of the timer to the higher layer in sequence if a predetermined timer expires, even if there are lost RLC SDUs.

[0114] The in-sequence delivery of the NR RLC device may include the function of delivering all RLC SDUs received so far to the higher layer in sequence if a predetermined timer expires, even if there are lost RLC SDUs.

[0115] The NR RLC device can process the RLC PDUs in the order in which they are received and deliver the RLC PDUs to the NR PDCP device regardless of the order of the sequence numbers (out-of-order delivery).

[0116] When the NR RLC device receives the segment, the NR RLC device can receive the segment stored in the buffer or to be received later, reconfigure the segment into one complete RLC PDU, and then pass the one complete RLC PDU to the NR PDCP device.

[0117] The NR RLC layer may not include the cascading function, and the cascading function may be performed in the NR MAC layer, or the cascading function may be replaced by a multiplexing function of the NR MAC layer.

[0118] In the above description, the out-of-order delivery of the NR RLC device may mean the following function: directly delivering the RLC SDU received from the lower layer to the higher layer regardless of the order. The out-of-order delivery of the NR RLC device may include the function of reassembling and delivering several RLC SDUs when one RLC SDU is initially divided into several RLC SDUs and received. The out-of-order delivery of the NR RLC device may include the function of storing the RLC SN or PDCP SN of the received RLC PDU, sorting their order, and recording the lost RLC PDU.

[0119] According to some embodiments, NR MAC 1d-15 and 1d-30 can be connected to several NRRLC layer devices configured in one terminal, and the main functions of NR MAC may include some of the following functions. However, the main functions of NR MAC are not limited to the following examples.

[0120] - Mapping between logical channels and transport channels

[0121] -Multiplexing / demultiplexing of MAC SDU

[0122] -Dispatch information report

[0123] - Error correction through HARQ

[0124] - Priority handling between logical channels of a UE

[0125] - Prioritization between UEs through dynamic scheduling

[0126] -MBMS service identification

[0127] -Transmission format selection

[0128] -patch

[0129] NR PHY layers 1d-20 and 1d-25 can perform operations of channel coding and modulating upper layer data, making upper layer data into OFDM symbols, and sending OFDM symbols to a radio channel, or demodulating and channel decoding OFDM symbols received through a radio channel to pass the OFDM symbols to an upper layer.

[0130] Figure 1e is a block diagram showing an internal structure of a terminal to which the present disclosure is applied.

[0131] refer to Figure 1e The terminal may include a radio frequency (RF) processor 1e-10, a baseband processor 1e-20, a storage unit 1e-30, and a controller 1e-40. The present disclosure is not limited to the above examples, and the terminal may include more Figure 1e Fewer or more configurations are shown.

[0132] The RF processor 1e-10 can perform functions for sending and receiving signals through wireless channels, such as frequency band conversion and amplification of signals. That is, the RF processor 1e-10 can up-convert the baseband signal provided by the baseband processor 1e-20 into an RF band signal, send the RF band signal through an antenna, and down-convert the RF band signal received through the antenna into a baseband signal. For example, the RF processor 1e-10 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and the like. The present disclosure is not limited to the above examples. Although in Figure 1e Only one antenna is shown in the figure, but the terminal may include multiple antennas. In addition, the RF processor 1e-10 may include multiple RF chains. In addition, the RF processor 1e-10 can perform beamforming. For beamforming, the RF processor 1e-10 can adjust the phase and amplitude of each signal sent and received through multiple antennas or antenna elements. In addition, the RF processor 1e-10 can perform multiple-input multiple-output (MIMO) and receive several layers when performing MIMO operation.

[0133] The baseband processor 1e-20 performs the function of converting between the baseband signal and the bit string according to the physical layer standard of the system. For example, when sending data, the baseband processor 1e-20 can encode and modulate the transmitted bit string to generate complex symbols. In addition, when receiving data, the baseband processor 1e-20 can recover the received bit string by demodulating and decoding the baseband signal provided from the RF processor 1e-10. For example, in the case of an orthogonal frequency division multiplexing (OFDM) scheme, when sending data, the baseband processor 1e-20 encodes and modulates the transmitted bit string to generate complex symbols, maps the complex symbols to subcarriers, and then configures OFDM symbols by inverse fast Fourier transform (IFFT) operation and cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processor 1e-20 can divide the baseband signal provided from the RF processor 1e-10 into OFDM symbol units, recover the signal mapped to the subcarrier by fast Fourier transform (FFT), and then recover the received bit string by demodulation and decoding.

[0134] As described above, the baseband processor 1e-20 and the RF processor 1e-10 send and receive signals. The baseband processor 1e-20 and the RF processor 1e-10 may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. In addition, at least one of the baseband processor 1e-20 and the RF processor 1e-10 may include multiple communication modules to support a variety of different wireless access technologies. In addition, at least one of the baseband processor 1e-20 and the RF processor 1e-10 may include different communication modules to process signals of different frequency bands. For example, different wireless access technologies may include wireless LANs (e.g., IEEE 802.11), cellular networks (e.g., LTE), and the like. In addition, different frequency bands may include ultra-high frequency (SHF) (e.g., 2.NRHz, NRhz) bands and millimeter wave (e.g., 60GHz) bands. The terminal may use the baseband processor 1e-20 and the RF processor 1e-10 to send and receive signals to and from a base station, and the signal may include control information and data.

[0135] The storage unit 1e-30 stores data for the operation of the UE, such as basic programs, applications, and configuration information. In particular, the storage unit 1e-30 can store information related to a second access node that performs wireless communication using a second radio access technology. The storage unit 1e-30 provides the stored data according to a request of the controller 1e-40. The storage unit 1e-30 can be configured with a storage medium, such as a read-only memory (ROM), a random access memory (RAM), a hard disk, a compact disk read-only memory (CD-ROM), and a digital versatile disk (DVD), or a combination of storage media. In addition, the storage unit 1e-30 may include multiple memories.

[0136] The controller 1e-40 controls the overall operation of the terminal. For example, the controller 1e-40 sends and receives signals through the baseband processor 1e-20 and the RF processor 1e-10. In addition, the controller 1e-40 writes and reads data in the storage unit 1e-40. To this end, the controller 1e-40 may include at least one processor. For example, the controller 1e-40 may include a communication processor (CP) that controls communication and an application processor (AP) that controls the upper layer such as an application. In addition, at least one component in the terminal may be implemented in one chip.

[0137] Figure 1f is a block diagram showing the configuration of an NR base station according to some embodiments of the present disclosure.

[0138] refer to Figure 1f , the base station may include an RF processor 1f-10, a baseband processor 1f-20, a backhaul communication unit 1f-30, a storage unit 1f-40, and a controller 1f-50. The present disclosure is not limited to this example, and the base station may include more Figure 1f Fewer or more configurations are shown.

[0139] The RF processor 1f-10 can perform functions for sending and receiving signals through wireless channels, such as frequency band conversion and amplification of signals. That is, the RF processor 1f-10 up-converts the baseband signal provided by the baseband processor 1f-20 into an RF band signal, transmits the RF band signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processor 1f-10 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and the like. Although in Figure 1f Only one antenna is shown in the figure, but the RF processor 1f-10 may include multiple antennas. In addition, the RF processor 1f-10 may include multiple RF chains. In addition, the RF processor 1f-10 can perform beamforming. For beamforming, the RF processor 1f-10 can adjust the phase and amplitude of each signal sent and received through multiple antennas or antenna elements. The RF processor can send one or more layers to perform downlink MIMO operations.

[0140] The baseband processor 1f-20 can perform the function of converting between the baseband signal and the bit string according to the physical layer standard of the first radio access technology. For example, when sending data, the baseband processor 1f-20 can encode and modulate the transmitted bit string to generate complex symbols. In addition, when receiving data, the baseband processor 1f-20 can recover the received bit string by demodulating and decoding the baseband signal provided from the RF processor 1f-10. For example, in the OFDM scheme, when sending data, the baseband processor 1f-20 encodes and modulates the transmission bit string to generate complex symbols, maps the complex symbols to subcarriers, and configures OFDM symbols through IFFT operations and CP insertion. In addition, when receiving data, the baseband processor 1f-20 can divide the baseband signal provided from the RF processor 1f-10 into OFDM symbol units, recover the signal mapped to the subcarrier through FFT operations, and then recover the received bit string through demodulation and decoding. As described above, the baseband processor 1f-20 and the RF processor 1f-10 can send and receive signals. Therefore, the baseband processor 1f-20 and the RF processor 1f-10 can be referred to as a transmitter, a receiver, a transceiver, a communication unit, or an RF unit. The base station can use the baseband processor 1f-20 and the RF processor 1f-10 to send and receive signals to and from the terminal, and the signals may include control information and data.

[0141] The backhaul communication unit 1f-30 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 1f-30 can convert a bit string sent from the master station to another node, for example, an auxiliary base station, and a core network into a physical signal, and convert a physical signal received from another node into a bit string. The backhaul communication unit 1f-30 can be included in the communication unit.

[0142] The storage unit 1f-40 stores data such as basic programs, applications, and configuration information for the operation of the base station. The storage unit 1f-40 may store information about the bearer assigned to the accessed terminal, measurement results reported from the accessed terminal, and the like. In addition, the storage unit 1f-40 may store information as a criterion for determining whether to provide or stop multiple connections to the terminal. The storage unit 1f-40 provides the stored data according to a request of the controller 1f-50. The storage unit 1f-40 may be configured with a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media. In addition, the storage unit 1f-40 may include a plurality of memories. According to some embodiments, the storage unit 1f-40 may store a program for executing the buffer status reporting method according to the present disclosure.

[0143] The controller 1f-50 controls the overall operation of the base station. For example, the controller 1f-50 sends and receives signals through the baseband processor 1f-20 and the RF processor 1f-10 or through the backhaul communication unit 1f-30. In addition, the controller 1f-50 writes and reads data in the storage unit 1f-40. To this end, the controller 1f-50 may include at least one processor. In addition, at least one configuration of the base station may be implemented with one chip.

[0144] Figure 1g A random access-free channel switching operation in conventional LTE is shown.

[0145] UE 1g-10 receives an RRC reconfiguration message including mobility control information from base station 1g-20 (step 1g-01). The message may include a random access channel skip IE (rach-skip IE). The rach-skip IE (information element) may include TA information to be used in the target cell 1g-30 and pre-allocated UL grant information.

[0146] The UE 1g-10 having received the message may perform the following operations (step 1g-02).

[0147] -UE 1g-10 may perform synchronization with the target PCell.

[0148] -UE 1g-10 may configure the TA value using the TA information configured in the received RRC reconfiguration message.

[0149] -UE 1g-10 may use the pre-allocated UL grant using the uplink configuration information (ul-ConfigInfo) configured in rach-skip.

[0150] -UE RRC may send a radio resource control reconfiguration complete (RRCReconfigurationcComplete) message to UE MAC.

[0151] -UE MAC may trigger a regular BSR.

[0152] By applying the pre-allocated UL grant (which uses ul-ConfigInfo configured in rach-skip) to the target cell, the terminal 1g-10 can send a MAC PDU including RRCReconfigurationComplete delivered in this manner (step 1g-03).

[0153] The UE MAC may receive a contention resolution MAC CE indicated by the C-RNTI. Accordingly, the UE MAC may report successful reception of the PDCCH transmission addressed by the C-RNTI (step 1g-04).

[0154] UE RRC may stop timer T304 and release ul-ConfigInfo (step 1g-05).

[0155] Figure 1h 2 is a diagram illustrating a use case where a rach-skip includes a configuredUplinkGrantrelease configuration in a RACHless HO specific signal structure in NR according to some embodiments of the present disclosure.

[0156] The base station 1h-20 may send a radio resource control reconfiguration (RRCReconfiguration) message including synchronization reconfiguration (reconfigurationWithSync) to the terminal 1h-10 (step 1h-01). In this case, the message may include the following information.

[0157] -The message may include Rach-Skip IE and SpCellConfig IE.

[0158] - Rach-Skip IE includes a target TA field, and this field may specify a TA value used in the target cell. This field may indicate one of three of TA-0, PTAG, or STAG id.

[0159] -In addition, the Rach-Skip IE may include a configuredUplinkGrantrelease field, and this field may include a value for determining whether to release the configured uplink grant used after performing a random access channel-less (rach less) HO successfully. This field may have a Boolean value (yes or no) or an enumeration {true} data type.

[0160] - The SpCellConfig field includes N BWP configuration information and also includes first Active BWP (firstActiveBWP) id information. The BWP configuration information may include ConfiguredGrantConfig information.

[0161] When the terminal 1h-10 receives a message from the base station 1h-20 (step 1h-01), the terminal 1h-10 can perform the following operations in sequence (step 1h-02).

[0162] UE 1h-10 may be synchronized with the target PCell.

[0163] In addition, according to the value in the target TA field, the N_{ta} value used in the target Pcell can be applied as follows. If the field value is TA-0, N_{TA}=0, and if the target TA field value is PTAG, and if the SpCellConfig received in step 1h-01 is included in the master cell group (MasterCellGroup) information, the NTA of the PTAG of the MCG is applied, and if the SpCellConfig is included in the secondary cell group (SecondaryCellGroup) information, the NTA of the PTAG of the SCG can be applied. In addition, if the target TA value is STAG id, and if the SpCellConfig received in step 1h-01 is included in the MasterCellGroup information, the NTA of the STAG specified by the STAG id is applied, and if the SpCellConfig is included in the SecondaryCellGroup information, the NTA of the STAG specified by the STAG id can be applied.

[0164] Thereafter, the RRC of the terminal may send an RRCReconfigurationcComplete RRC PDU to the UE MAC. Thereafter, the UE MAC may trigger a regular BSR. In addition, the terminal 1h-10 may send a MAC PDU including an RRCReconfigurationComplete message to a specific ULBWP using the configured uplink grant (step 1h-03). In this case, the specific ULBWP may be the BWP specified by the first activated BWP id.

[0165] Thereafter, UE 1h-10 may receive a confirmation MAC CE (which may include only a separate LCID) or a contention resolution MAC CE in the first activated DLBWP through C-RNTI (C-RNTI indicated in the RRCReconfiguration message of reconfigurationWithSync received in step 1h-01) (step 1h-04). Here, the confirmation MAC CE is a MAC CE separate from the contention resolution MAC CE and has a separate LCID. When the terminal receives the MAC CE, the terminal may perform the following operations (step 1h-05).

[0166] The MAC of the UE that has received the MAC CE can report to the RRC that the PDCCH transmission addressed by the C-RNTI has been successfully received. In addition, the RRC of the terminal stops the T304 timer. In addition, when ConfiguredUplinkGrantRelease is configured to mean the release in the rach-skip IE included in the RRCReconfiguration message including reconfigurationWithSync received in step 1h-01, for example, when it has a Boolean data type, it is configured to be yes or true, or when ConfiguredUplinkGrantRelease has an enumeration {true} data type, if ConfiguredUplinkGrantRelease itself has been set, it is possible to release the configured uplink grant of a specific BWP. In this case, the specific BWP can be the BWP specified by the first activated BWP id.

[0167] Information included in ConfiguredGrantConfig in the configuration information for each BWP included in SpcellConfig included in the RRCReconfiguration message including reconfigurationWithSync received by the UE 1h-10 in step 1h-01 may have the following values.

[0168] -nrofHARQ-Processes: the number of configured HARQs,

[0169] - Periodicity: The period of UL transmission can be configured through the authorization;

[0170] -Time Domain Offset (timeDomainOffset): offset value based on SFN=0,

[0171] -Time Domain Allocation: Displays the start symbol, length and PUSCH mapping type,

[0172] - Frequency Domain Allocation: frequency domain allocation information,

[0173] -mcsAndTBS: mcs and TBS value information for UL authorization configured

[0174] In addition, the valid time information of the configured UL grant to be used for the rach-skip HO purpose for a specific time may be additionally included. For example, the valid time may be included in an absolute time unit, and in this case, the information may be included in the rach-skip IE. Alternatively, the valid time information may be represented in the ConfiguredGrantConfig configuration information of a specific BWP in units of the maximum valid possible period. When represented in absolute time units, the UE starts the timer from the moment the terminal receives the message received in step 1i-01, and when the timer expires, it is considered to be a HO failure. In addition, when the HO is successful and the contention resolution MAC CE is successfully received, the terminal may stop the timer. In the case of setting the maximum valid possible period unit for a specific BWP, when the UE starts counting after synchronizing with the corresponding target PCell, and does not receive the contention resolution MAC CE from the target PCell when the corresponding period passes, it may be considered to be a HO failure.

[0175] Figure 1i is a diagram illustrating a use case where rach-skip does not include the ConfiguredUplinkGrantrelease configuration in a random access channel-less (RACHless) HO specific signal structure in NR according to some embodiments of the present disclosure.

[0176] The base station 1i-20 may send an RRCReconfiguration message including reconfigurationWithSync to the terminal 1i-10 (step 1i-01). In this case, the message may include the following information.

[0177] -The message may include Rach-Skip IE and SpCellConfig IE.

[0178] - Rach-Skip IE may include a Target Timing Advance (TA) field, and this field may specify the TA value used in the target cell. This field may indicate one of three of TA-0, PTAG, or STAG id.

[0179] - The SpCellConfig field includes N number of BWP configuration information and also includes firstActiveBWP id information. The BWP configuration information may include ConfiguredGrantConfig information.

[0180] When UE 1i-10 receives a message from base station 1i-20 (step 1i-01), terminal 1i-10 may perform the following operations (step 1i-02).

[0181] UE 1i-10 may be synchronized with the target PCell.

[0182] In addition, according to the value in the target TA field, the N_{ta} value used in the target Pcell is applied as follows. When the field value is TA-0, N_{TA}=0, and when the target TA field value is PTAG, if the SpCellConfig received in step 1i-01 is included in the master cell group (MasterCellGroup) information, the NTA of the PTAG of the MCG is applied, and if the SpCellConfig is included in the secondary cell group (SecondaryCellGroup) information, the NTA of the PTAG of the SCG can be applied. In addition, when the target TA value is STAG id, if the SpCellConfig received in step 1i-01 is included in the MasterCellGroup information, the NTA of the STAG specified by the STAG id can be applied, and if the SpCellConfig is included in the SecondaryCellGroup information, the NTA of the STAG specified by the STAG id can be applied.

[0183] Thereafter, the RRC of the terminal may send an RRCReconfigurationcComplete RRC PDU to the UE MAC. Thereafter, the MAC of the terminal may trigger a regular BSR. In addition, the UE 1i-10 may send a MAC PDU including an RRCReconfigurationComplete message using the configured uplink grant of a specific UL BWP (step 1i-03). In this case, the UE 1i-10 may send a MAC PDU using the configured uplink grant of the BWP specified by the first activated BWP id.

[0184] After the transmission, UE 1i-10 may receive a confirmation MAC CE (which may include only a separate LCID) or a contention resolution MAC CE in the first activated DLBWP by means of the C-RNTI (the C-RNTI indicated in the RRCReconfiguration message including the reconfigurationWithSync received in the first step) (step 1i-04). Here, the confirmation MAC CE is a MAC CE separate from the contention resolution MAC CE and has a separate LCID. When the terminal receives the MAC CE (step 1i-04), the terminal may perform the following operations (step 1i-05).

[0185] The UE may first stop T304. In addition, the MAC of the terminal that has received the MAC CE may report to the RRC that the PDCCH transmission addressed to the C-RNTI has been successfully received. In addition, the MAC of the UE may release the RACH-skip configuration and release the configured uplink grant of the first activated BWP. Thereafter, portions of the CQI report configuration, scheduling request configuration, and sounding RS configuration that can be configured even if the UE does not know the relative system frame number (SFN) information of the target spcell are applied. When the SFN information of the target spcell is obtained later, the measurement and radio resource configuration portions may be applied.

[0186] Information included in ConfiguredGrantConfig in the configuration information for each BWP, which is included in SpcellConfig included in the RRCReconfiguration message including reconfigurationWithSync received by the terminal in step 1i-01, may have the following values.

[0187] -nrofHARQ-Processes: the number of configured HARQs,

[0188] - Periodicity: The period of UL transmission can be configured through the authorization;

[0189] -Time Domain Offset (timeDomainOffset): offset value based on SFN=0,

[0190] -Time Domain Allocation: Displays the start symbol, length and PUSCH mapping type,

[0191] - Frequency Domain Allocation: frequency domain allocation information,

[0192] -mcsAndTBS: mcs and TBS value information for UL authorization configured

[0193] In addition, the valid time information of the configured UL grant to be used for the rach-skip HO purpose for a specific time may be additionally included. For example, the valid time may be included in an absolute time unit, and in this case, the information may be included in the rach-skip IE. Alternatively, the valid time information may be represented in the ConfiguredGrantConfig configuration information of a specific BWP in units of the maximum valid possible period. When represented in absolute time units, the terminal starts the timer from the moment the terminal receives the message received in step 1i-01, and when the timer expires, it is considered to be a HO failure. In addition, when the HO is successful and the contention resolution MAC CE or confirmation MAC CE is successfully received, the terminal may stop the timer. In the case of setting the maximum valid possible period unit for a specific BWP, the terminal starts counting after synchronizing with the corresponding target PCell, and when the terminal does not receive the contention resolution MAC CE from the target PCell when the corresponding period passes, it is considered to be a HO failure.

[0194] Figure 1j is a diagram illustrating a handover scenario in which a random access channel-less (RACHless) HO signal is omitted in an RRCRconfiguration message including reconfigurationWithSync in NR according to some embodiments of the present disclosure.

[0195] In this embodiment, Figure 1h and Figure 1g rach-skip is optional, and includes the case where the configuration is omitted.

[0196] The base station 1j-20 can send an RRC reconfiguration (RRCReconfiguration) including reconfigurationWithSync to the terminal 1j-10 (step 1j-01). When there is no rach-skip IE, the terminal 1j-10 that has received the message can perform the following operations (step 1j-02).

[0197] UE 1j-10 may perform synchronization with the target PCell. In addition, terminal 1j-10 may send a random access preamble configured in RRCReconfiguration including reconfigurationWithSync to the RACH resource of the target cell.

[0198] The RRC of the terminal may deliver an RRCReconfigurationComplete message to the MAC of the UE. The MAC of the terminal may send a MAC PDU including RRCReconfigurationComplete to Mg3 (step 1j-03). In this case, the transmission may be performed using the UL grant indicated by the RAR. In this case, when the preamble transmitted during the RA is a common preamble, a contention resolution MAC CE may be received via the TC-RNTI (C-RNTI indicated in the RAR) in the first activated DLBWP (step 1j-04). Thereafter, T304 may be stopped (step 1j-05).

[0199] In addition, the CQI report configuration, scheduling request configuration and sounding RS configuration parts that can be configured even when the UE does not know the relative SFN information of the target spcell are applied. When the SFN information of the target spcell is obtained later, the measurement and radio resource configuration parts can be applied.

[0200] Information included in ConfiguredGrantConfig in the configuration information for each BWP may have the following values, where the configuration information for each BWP is included in SpcellConfig included in the RRCReconfiguration message including reconfigurationWithSync received by the UE in step 1j-01.

[0201] -nrofHARQ-Processes: the number of configured HARQs,

[0202] - Periodicity: The period of UL transmission can be configured through the authorization;

[0203] -Time Domain Offset (timeDomainOffset): offset value based on SFN=0,

[0204] -Time Domain Allocation: Displays the start symbol, length and PUSCH mapping type,

[0205] - Frequency Domain Allocation: frequency domain allocation information,

[0206] -mcsAndTBS: mcs and TBS value information for UL authorization configured

[0207] In addition, the valid time information of the configured UL grant to be used for the purpose of rach-skip HO for a specific time may be included. For example, the valid time may be included in an absolute time unit, and in this case, the information may be included in the rach-skip IE. Alternatively, the valid time information may be represented in the ConfiguredGrantConfig configuration information of a specific BWP in units of the maximum valid possible cycle. When represented in absolute time units, the terminal starts the timer from the moment the terminal receives the message received in step 1i-01, and when the timer expires, it is considered to be a HO failure. In addition, when the HO is successful and the contention resolution MAC CE or confirmation MAC CE is successfully received, the terminal may stop the timer. In the case of setting the maximum valid possible cycle unit for a specific BWP, the terminal starts counting after synchronizing with the corresponding target PCell, and when the terminal does not receive the contention resolution MAC CE from the target PCell when the corresponding cycle passes, it is considered to be a HO failure.

[0208] exist Figure 1g and Figure 1h The confirmation MAC CE used in the embodiments may be classified into a MAC PDU subheader with an LCID having a specific value and has a fixed size of 0 bits.

[0209] The embodiments of the present disclosure disclosed in this specification and the accompanying drawings only present specific examples in order to easily describe the technical content of the present disclosure and help understand the present disclosure, and they are not intended to limit the scope of the present disclosure. That is, it is obvious to those of ordinary skill in the art to which the present disclosure belongs that other modifications can be implemented based on the technical spirit of the present disclosure. In addition, as required, each of the above embodiments can be combined with each other to operate. For example, a base station and a terminal can be operated by combining parts of the embodiments of the present disclosure.

[0210] In addition, in this specification and the accompanying drawings, preferred embodiments of the present disclosure have been disclosed. Although specific terms are used, these terms are only used in a general sense to easily describe the technical content of the present disclosure and help understand the present disclosure, and they are not intended to limit the scope of the present disclosure. For ordinary technicians in the field to which the present disclosure belongs, it is obvious that in addition to the embodiments disclosed herein, other modifications based on the technical spirit of the present disclosure can also be implemented.

Claims

1. A method performed by a terminal in a wireless communication system, the method comprising: A radio resource control (RRC) message for a random access channel-less (RACHless) handover (HO) is received from a source base station, wherein: The RRC message includes information for RACHless HO and at least one bandwidth part (BWP) configuration information; performing uplink transmission for RACHless HO using a configured uplink grant for RACHless HO for a specific BWP identified based on a configuration associated with at least one of the at least one BWP; In case the information is included in the RRC message and the lower layer reports that the RACHless HO is successfully completed, stopping the timer; as well as Based on stopping the timer, releasing the configured uplink grant for the RACHless HO for the specific BWP if the information is included in the RRC message and the configuration associated with at least one BWP is configured, The information includes target timing advance (TA) information.

2. The method according to claim 1, wherein: The TA information includes Ta-0.

3. A method performed by a base station in a wireless communication system, the method comprising: A radio resource control RRC message for a random access channel-less (RACHless) handover (HO) is sent to a terminal, wherein: The RRC message includes information for RACHless HO and at least one bandwidth part (BWP) configuration information, wherein uplink transmission for RACHless HO is performed using a configured uplink grant for RACHless HO for a specific BWP, wherein the specific BWP is identified based on a configuration associated with at least one of the at least one BWP, Wherein, the information includes target timing advance (TA) information, wherein, in the case where the information is included in the RRC message and the lower layer reports that the RACHless HO is successfully completed, stopping the timer, and Wherein, in a case where the information is included in the RRC message and the configuration associated with at least one BWP is configured, releasing the configured uplink grant for the RACHless HO of the specific BWP.

4. The method according to claim 3, wherein: The TA information includes Ta-0.

5. A terminal comprising: a transceiver configured to transmit and receive at least one signal; and a controller coupled to the transceiver, in, The controller is configured to: receiving a radio resource control (RRC) message for a random access channel-less (RACHless) handover (HO) from a source base station, wherein the RRC message includes information for the RACHless HO and at least one bandwidth part (BWP) configuration information, performing uplink transmission for the RACHless HO using a configured uplink grant for the RACHless HO for a specific BWP identified based on a configuration associated with the at least one BWP, In case the information is included in the RRC message and the lower layer reports that the RACHless HO is successfully completed, stop the timer, and Based on stopping the timer, releasing the configured uplink grant for the RACHless HO for the specific BWP if the information is included in the RRC message and the configuration associated with at least one of the at least one BWP is configured, The information includes target timing advance (TA) information. The terminal according to claim 5, wherein: The TA information includes Ta-0.

7. A base station, comprising: a transceiver configured to transmit and receive at least one signal; and a controller coupled to the transceiver, in, The controller is configured to: sending a radio resource control RRC message for a random access channel-less (RACHless) handover (HO) to a terminal, wherein the RRC message includes information for the RACHless HO and at least one bandwidth part (BWP) configuration information, wherein uplink transmission for RACHless HO is performed using a configured uplink grant for RACHless HO for a specific BWP, wherein the specific BWP is identified based on a configuration associated with at least one of the at least one BWP, Wherein, the information includes target timing advance (TA) information, wherein, in the case where the information is included in the RRC message and the lower layer reports that the RACHless HO is successfully completed, stopping the timer, and Wherein, in a case where the information is included in the RRC message and the configuration associated with at least one BWP is configured, releasing the configured uplink grant for the RACHless HO of the specific BWP.

8. The base station according to claim 7, wherein: The TA information includes Ta-0.

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