阅读说明：本技术 用于在下一代无线通信系统中没有随机接入的情况下执行小区接入的方法和装置 (Method and apparatus for performing cell access without random access in next generation wireless communication system ) 是由 黄�俊 金成勋 H.范德韦尔德 于 2020-02-14 设计创作，主要内容包括：本公开涉及：一种用于将IoT技术与用于支持比4G系统更高的数据传输速率的5G通信系统融合的通信技术；及其系统。本公开可以应用于在5G通信技术和IoT相关技术的基础上的智能服务(例如,智能家庭、智能建筑、智能城市、智能汽车或联网汽车、卫生保健、数字教育、零售业务、安保和安全相关服务等)。本公开涉及无线通信系统中在没有随机接入的情况下执行的切换。(The present disclosure relates to: a communication technique for merging IoT technology with a 5G communication system for supporting higher data transmission rates than a 4G system; and a system thereof. The present disclosure may be applied to smart services (e.g., smart homes, smart buildings, smart cities, smart cars or networked cars, healthcare, digital education, retail business, security and security related services, etc.) on the basis of 5G communication technology and IoT related technology. The present disclosure relates to handover performed without random access in a wireless communication system.)

1. A method performed by a terminal in a wireless communication system, the method comprising:

receiving a first Radio Resource Control (RRC) message including first information for performing cell access without random access and second information on cell configuration information from a base station;

transmitting a second RRC message to the base station using an uplink grant configured in a specific bandwidth part BWP; and

receiving a medium access control, MAC, control element, CE, from the base station, the MAC CE indicating contention resolution by a cell radio network temporary identifier, C-RNTI, indicated in the first message,

wherein the specific BWP is determined by the second information.

2. The method of claim 1, wherein the first information comprises at least one of target Timing Advance (TA) information and information for releasing an uplink grant configured in a specific BWP.

3. The method of claim 2, further comprising, in case the first information includes information for releasing the uplink grant configured in the specific BWP, releasing the uplink grant configured in the specific BWP after transmitting the second RRC message.

4. The method of claim 2, wherein the TA information comprises at least one of TA-0, PTAG, and STAG-Id, where the first information comprises target TA information.

5. A method performed by a base station in a wireless communication system, the method comprising:

transmitting a first Radio Resource Control (RRC) message including first information for performing cell access without random access and second information on cell configuration information to a terminal;

receiving a second RRC message from the terminal using an uplink grant configured in a specific bandwidth part BWP; and

transmitting a medium access control, MAC, control element, CE, to the terminal, the MAC CE indicating contention resolution by a cell radio network temporary identifier, C-RNTI, indicated in the first message,

wherein the specific BWP is determined by the second information.

6. The method of claim 5, wherein the first information comprises at least one of target Timing Advance (TA) information and information for releasing an uplink grant configured in a specific BWP.

7. The method of claim 6, further comprising, in case the first information includes information for releasing the uplink grant configured in the specific BWP, releasing the uplink grant configured in the specific BWP after transmitting the second RRC message.

8. The method of claim 6, wherein the TA information comprises at least one of TA-0, PTAG, and STAG-Id, where the first information comprises target TA information.

9. A terminal, comprising:

a transceiver configured to transmit and receive at least one signal; and

a controller coupled to the transceiver and configured to control the transceiver,

wherein the controller is configured to:

receiving a first Radio Resource Control (RRC) message including first information for performing cell access without random access and second information on cell configuration information from a base station;

transmitting a second RRC message to the base station using an uplink grant configured in a specific bandwidth part BWP; and

receiving a medium access control, MAC, control element, CE, from the base station, the MAC CE indicating contention resolution by a cell radio network temporary identifier, C-RNTI, indicated in the first message, and

wherein the specific BWP is determined by the second information.

10. The terminal of claim 9, wherein 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.

11. The terminal of claim 10, wherein in case that the first information includes information for releasing the uplink grant configured in the specific BWP, the uplink grant configured in the specific BWP is released after transmitting the second RRC message.

12. The terminal of claim 10, wherein in the case that the first information includes target TA information, the TA information includes at least one of TA-0, PTAG, and STAG-Id.

13. A base station, comprising:

a transceiver configured to transmit and receive at least one signal; and

a controller coupled to the transceiver and configured to control the transceiver,

wherein the controller is configured to:

transmitting a first Radio Resource Control (RRC) message including first information for performing cell access without random access and second information on cell configuration information to a terminal;

receiving a second RRC message from the terminal using an uplink grant configured in a specific bandwidth part BWP; and

transmitting a medium access control, MAC, control element, CE, to the terminal, the MAC CE indicating contention resolution by a cell radio network temporary identifier, C-RNTI, indicated in the first message, and

wherein the specific BWP is determined by the second information.

14. The base station according to claim 13, wherein the first information comprises at least one of target timing advance, TA, information and information for releasing an uplink grant configured in a specific BWP.

15. The base station according to claim 14, wherein in case that the first information includes information for releasing the uplink grant configured in the specific BWP, the uplink grant configured in the specific BWP is released after transmitting the second RRC message, and

wherein, in a case where the first information includes target TA information, the TA information includes at least one of Ta-0, PTAG, and STAG-Id.

Technical Field

The present disclosure relates to handover performed without random access in a wireless communication system.

Background

In order to meet the increasing demand for wireless data traffic (traffic) since the deployment of 4G communication systems, efforts have been made to develop improved 5G or quasi-5G communication systems. Therefore, the 5G or quasi-5G communication system is also referred to as a "super 4G network" or a "post-LTE system". 5G communication systems are considered to be implemented in the higher frequency (mmWave) band, e.g., the 60GHz band, in order to achieve higher data rates. In order to reduce propagation loss of radio waves and increase transmission distance, beamforming, massive Multiple Input Multiple Output (MIMO), full-dimensional MIMO (FD-MIMO), array antenna, analog beamforming, massive antenna technology are discussed in the 5G communication system. Further, in the 5G communication system, research and development for system network improvement is being conducted based on advanced small cells, cloud Radio Access Network (RAN), ultra-dense network, device-to-device (D2D) communication, wireless backhaul, mobile network, cooperative communication, coordinated multipoint (CoMP), reception-side interference cancellation, and the like. In 5G systems, hybrid FSK and 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 techniques have been developed.

The internet, which is a human-centric connected network in which people generate and consume information, is evolving into the internet of things (IoT), where distributed entities, such as things, exchange and process information without human intervention. Internet of everything (IoE) has emerged as a combination of IoT technology and big data processing technology through a connection with a cloud server. Because technical elements such as "sensing technology", "wired/wireless communication and network infrastructure", "service interface technology", and "security technology" have been required for IoT implementations, sensor networks, machine-to-machine (M2M) communication, Machine Type Communication (MTC), and the like have been recently studied. Such IoT environments can provide intelligent internet technology services that create new value for human life by collecting and analyzing data generated among connected things. Through the convergence 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 networked cars, smart grids, health care, smart home appliances, and advanced medical services.

In light of this, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as sensor networks, Machine Type Communication (MTC), and machine-to-machine (M2M) communication may be implemented through beamforming, MIMO, and array antennas. The application of cloud Radio Access Networks (RANs) as the big data processing technology described above can also be considered as an example of the convergence between 5G technology and IoT technology.

Since various services can be provided according to the above description and the development of mobile communication systems, a method for effectively providing these services is required.

Disclosure of Invention

Technical problem

The present disclosure provides an apparatus and method for efficiently providing a service 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 (rach) less handover, and UL signaling required for access can be performed by using a configured grant UL configured in an existing bandwidth part.

Solution to the problem

Technical problems to be achieved in the embodiments of the present disclosure are not limited to the above technical problems, and other technical problems not mentioned will be clearly understood from the following description by a person of ordinary skill in the art to which the present disclosure belongs.

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 including first information for performing cell access without random access and second information on cell configuration information from a base station; transmitting a second RRC message to the base station using an uplink grant configured in a specific bandwidth part (BWP); and receiving a Medium Access Control (MAC) Control Element (CE) indicating contention resolution through a cell radio network temporary identifier (C-RNTI) indicated in the first message from the base station, wherein the specific BWP is determined by the second information.

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.

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

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

According to another embodiment of the present disclosure, a method performed by a base station in a wireless communication system includes transmitting a first Radio Resource Control (RRC) message including first information for performing cell access without random access and second information on cell configuration information to a UE; receiving a second RRC message from the UE using an uplink grant configured in a specific bandwidth part (BWP); and transmitting a Medium Access Control (MAC) Control Element (CE) indicating contention resolution through a cell radio network temporary identifier (C-RNTI) indicated in the first message to the terminal, wherein the specific BWP is determined by the second information.

According to another embodiment of the present disclosure, a UE includes a transceiver configured to transmit 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 including first information for performing cell access without random access and second information on cell configuration information from a base station; transmitting a second RRC message to the base station using an uplink grant configured in a specific bandwidth part (BWP); and receiving a Medium Access Control (MAC) Control Element (CE) indicating contention resolution through a cell radio network temporary identifier (C-RNTI) indicated in the first message from the base station, and wherein the specific BWP is determined by the second information.

According to another embodiment of the present disclosure, a base station includes a transceiver configured to transmit and receive at least one signal; and a controller coupled to the transceiver, wherein the controller is configured to transmit a first Radio Resource Control (RRC) message including first information for performing cell access without random access and second information on cell configuration information to a terminal; receiving a second RRC message from the UE using an uplink grant configured in a specific bandwidth part (BWP); and transmitting a Medium Access Control (MAC) Control Element (CE) to the terminal, the Medium 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.

Advantageous effects of the invention

Embodiments disclosed in the present disclosure reduce data delay generated during handover by performing access using a predefined UL grant without transmitting a random access preamble for obtaining an Uplink (UL) grant when attempting to access a target cell.

Drawings

Fig. 1a is a diagram illustrating the structure of an LTE system according to some embodiments of the present disclosure.

Fig. 1b is a diagram illustrating a radio protocol structure of an LTE system according to some embodiments of the present disclosure.

Fig. 1c is a diagram illustrating the structure of a next generation mobile communication system according to some embodiments of the present disclosure.

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

Fig. 1e is a block diagram illustrating the internal structure of a UE according to some embodiments of the present disclosure.

Fig. 1f is a block diagram illustrating a configuration of an NR base station according to some embodiments of the present disclosure.

Fig. 1g shows a random access channel (RACHless) handover operation in conventional LTE.

Fig. 1h is a message flow diagram illustrating a use case for a case where random access channel skip (rach-skip) will release the configuration included in the no random access channel HO specific signal structure in the NR, according to some embodiments of the present disclosure.

Fig. 1i is a message flow diagram illustrating a use case for a case where random access channel skip (rach-skip) does not include a release configuration in the no random access channel HO specific signal structure in the NR, according to some embodiments of the present disclosure.

Fig. 1j is a message flow diagram illustrating a handover situation in which normal HO and no random access channel HO signals in NR are omitted, according to some embodiments of the present disclosure.

Detailed Description

Hereinafter, the operational principle of the present disclosure will be described in detail with reference to the accompanying drawings.

In the following description of the present disclosure, a detailed description of known functions or configurations related to the present disclosure will be omitted when it is determined that the detailed description may unnecessarily obscure the subject matter of the present disclosure. Further, terms to be described later are terms defined in consideration of functions in the present disclosure, and may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the contents in the present specification. For convenience of description, terms for identifying an access node, terms for indicating a network entity, terms for indicating a message, terms for indicating an interface between network objects, terms for indicating various identification information, and the like used in the following description are exemplified. Accordingly, the present disclosure is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

Hereinafter, the base station is a main body performing resource allocation of the UE, and may be at least one of a eNode 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 telephone, a smart phone, a computer, or a multimedia system capable of performing communication functions. The present disclosure is not limited to the above examples.

In particular, the present disclosure may be applied to 3GPP NR (5 th generation mobile communication standard). Furthermore, the present disclosure may be applied to smart services based on 5G communication technologies and IoT related technologies (e.g., smart homes, smart buildings, smart cities, smart cars or networked cars, healthcare, digital education, retail businesses, and security related services). In this 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. Further, the term UE may refer to mobile phones, NB-IoT devices, sensors, and other wireless communication devices.

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, e.g., High Speed Packet Access (HSPA), Long Term Evolution (LTE) or evolved universal terrestrial radio access (E-UTRA), LTE-advanced (LTE-a), LTE-Pro of 3GPP, High Rate Packet Data (HRPD), Ultra Mobile Broadband (UMB) of 3GPP2, and IEEE 802.16E.

As representative examples of the broadband wireless communication system, in the LTE system, an Orthogonal Frequency Division Multiplexing (OFDM) method is employed in Downlink (DL), and a single carrier frequency division multiple access (SC-FDMA) method is employed in Uplink (UL). The UL refers to a radio link in which a User Equipment (UE) or a Mobile Station (MS) transmits data or control signals to a base station (BS or eNode B), and the DL refers to a radio link in which a base station transmits data or control signals to a UE. The multiple access method as described above divides data or control information of each user by allocating and operating time-frequency resources to which the data or control information is to be transmitted for each user so that they do not overlap each other, i.e., establishing orthogonality.

As a future communication system after LTE, that is, a 5G communication system should be able to freely reflect various demands such as users and service providers; therefore, services that simultaneously satisfy various demands should be supported. Services considered for 5G communication systems include enhanced mobile broadband (eMBB), large-scale machine type communication (mtc), and ultra-reliable low latency communication (URLLC).

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

Meanwhile, mtc is being considered to support application services such as internet of things (IoT) in a 5G communication system. To effectively provide the internet of things, mtc may require extensive terminal access support within a cell, improved terminal coverage, improved battery life time, and reduced terminal cost. 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 (e.g., 1000000 terminals per square kilometer) within a cell. Furthermore, because a terminal supporting mtc is likely to be located in a shadow area that a cell cannot cover, such as a basement of a building, wider coverage may be required compared to other services provided by a 5G communication system due to the characteristics of the service. The mtc-capable terminal should be configured with a low-cost terminal, and may require a very long battery life, such as 10 to 15 years, due to the difficulty in frequently replacing the battery of the UE.

Finally, URLLC is a cellular-based wireless communication service for critical tasks, and may be used for remote control of robots or machinery, as well as services used in the services of industrial automation, unmanned aerial vehicles, telemedicine, emergency alerts, and the like. Therefore, the communication provided by URLLC may have to provide very low latency (ultra-low latency) and very high reliability (ultra-reliability). For example, a URLLC capable service should meet air interface delay of less than 0.5 milliseconds and may also have a packet error rate requirement of 10-5 or less. Therefore, for services supporting URLLC, a 5G system should provide smaller Transmission Time Intervals (TTIs) than other services, and at the same time, a design may be required to allocate wide resources in the frequency band to ensure reliability of the communication link.

Three services considered in the above-described 5G communication system, namely, eMBB, URLLC, and mtc, can be multiplexed and transmitted in one system. In this case, different transmission and reception techniques and transmission and reception parameters may be used between services in order to meet different requirements of each service. However, the aforementioned mtc, URLLC, and eMBB are only examples of different service types, and the service types to which the present disclosure is applied are not limited to the above examples.

Further, the embodiments of the present disclosure will be described below using an LTE, LTE-a, LTE Pro, or 5G (or NR, next generation mobile communication) system as an example, but the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. Furthermore, embodiments of the present disclosure may be applied to other communication systems with some modifications within the scope not significantly departing from the scope of the present disclosure as determined by one of ordinary skill in the art.

Fig. 1a is a diagram illustrating the structure of an LTE system according to some embodiments of the present disclosure.

Referring to fig. 1a, as shown, a radio access network of an LTE system may be configured with evolved node bs (hereinafter, ENBs, node bs, or base stations) 1a-05, 1a-10, 1a-15, and 1a-20, Mobility Management Entities (MMEs) 1a-25, and serving gateways (S-GWs) 1 a-30. The user equipments (hereinafter, UEs or terminals) 1a-35 can access the external network through the ENBs 1a-05, 1a-10, 1a-15 and 1a-20 and the S-GWs 1 a-30.

In FIG. 1a, ENBs 1a-05, 1a-10, 1a-15, and 1a-20 may correspond to existing node Bs of a UMTS system. The ENB can be connected to the UEs 1a-35 through radio channels and plays a more complex role than the existing node B. In the LTE system, all user traffic including real-time services such as voice over IP (VoIP) through an internet protocol can be served through a shared channel. Therefore, a device for scheduling by collecting status information such as a buffer status, an available transmission power status, and a channel status of the UE may be required, and the ENBs 1a-05, 1a-10, 1a-15, and 1a-20 may be responsible for this. One ENB may generally control a plurality of cells. For example, 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. Also, the ENB may apply an Adaptive Modulation and Coding (AMC) method, which determines a modulation scheme and a channel coding rate according to a channel status of the UE. The S-GW 1a-30 is a device that provides data bearers and may generate or remove data bearers under the control of the MME 1 a-25. The MME is a device responsible for various control functions of the UE and mobility management functions, and may be connected to a plurality of base stations.

Fig. 1b is a diagram illustrating a radio protocol structure of an LTE system according to some embodiments of the present disclosure.

Referring to FIG. 1b, the radio protocols of the LTE system may include Packet Data Convergence Protocols (PDCP)1b-05 and 1b-40, Radio Link Controls (RLC)1b-10 and 1b-35, and Medium Access Controls (MAC)1b-15 and 1b-30 in a terminal and an ENB, respectively. The PDCP may be responsible for operations such as IP header compression/recovery. The main functions of the PDCP can be summarized as follows. The main function of PDCP is not limited to the following example.

Header compression and decompression ROHC only

-transfer of user data

-in order delivery of upper layer PDUs in RLC AM PDCP re-establishment procedure

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

Duplicate detection of lower layer SDUs during PDCP re-establishment procedure for RLC AM

-for RLC AM, PDCP SDU is retransmitted at handover and for split bearer in DC, PDCP PDU is retransmitted in PDCP data recovery procedure

-encryption and decryption

Timer based SDU discard in uplink.

According to some embodiments, Radio Link Control (RLC)1b-10 and 1b-35 may reconfigure PDCP Packet Data Units (PDUs) to appropriate sizes to perform ARQ operations or the like. The main functions of the RLC can be summarized as follows. The main function of the RLC is not limited to the following example.

-transmission of upper layer PDU

Error correction by ARQ (for AM data transfer only)

Concatenation, segmentation and reassembly of RLC SDUs (for UM and AM data transfer only)

Re-segmentation of RLC data PDUs (for AM data transfer only)

Reordering of RLC data PDUs (for UM and AM data transfer only)

Duplicate detection (for UM and AM data transfer only)

Protocol error detection (for AM data transfer only)

RLC SDU discard (for UM and AM data transfer only)

RLC re-establishment

According to some embodiments, the MACs 1b-15 and 1b-30 may be connected to several RLC layer devices configured in one terminal and perform operations of multiplexing RLC PDUs into MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of the MAC can be summarized as follows. The main function of the MAC is not limited to the following examples.

Mapping between logical channels and transport channels

-multiplexing/demultiplexing MAC SDUs belonging to one or different logical channels into/from Transport Blocks (TBs) delivered to/from the physical layer on/from transport channels

-scheduling information reporting

Error correction by HARQ

-priority handling between logical channels of one UE

-prioritization among UEs by dynamic scheduling

-MBMS service identification

-transport format selection

-patches

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 radio channel, or demodulating OFDM symbols received through the radio channel, channel-decoding the OFDM symbols, and transmitting the OFDM symbols to higher layers. The present disclosure is not limited to the following examples.

Fig. 1c is a diagram illustrating the structure of a next generation mobile communication system according to some embodiments of the present disclosure.

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

In fig. 1c, NR gNB 1c-10 may correspond to an evolved node b (enb) of an existing LTE system. The NR gNB may be connected to the NR UEs 1c-15 through radio channels and provide services superior to those of existing node bs. In the next generation mobile communication system, all user traffic can be served through a shared channel. Therefore, a device for scheduling by collecting status information such as a buffer status, an available transmission power status, and a channel status of the UE may be required, and the NR gNB 1c-10 may be responsible for this. One NR gbb may control a plurality of cells. In the next generation mobile communication system, a bandwidth greater than or equal to the current maximum bandwidth can be applied to realize ultra-high speed data transmission, compared to the current LTE. In addition, an Orthogonal Frequency Division Multiplexing (OFDM) technique may be used as the radio access technique, and a beamforming technique is additionally used.

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

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

Referring to fig. 1d, the radio protocols of the next generation mobile communication system may include NR Service Data Adaptation Protocols (SDAP)1d-01 and 1d-45, NR PDCP 1d-05 and 1d-40, NR RLC 1d-10 and 1d-35, and NR MACs 1d-15 and 1d-30 in the terminal and NR base station, respectively.

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

-transfer of user plane data

Mapping between QoS flows and DRBs for both DL and UL

Marking QoS flow IDs in both DL and UL packets

-reflected QoS flow to DRB mapping for ULSDAP PDU.

For the SDAP layer device, the terminal may receive a configuration as to 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. Further, in the SDAP layer device, when the SDAP header is set, the UE may instruct to update or reconfigure mapping information for uplink and downlink QoS flows and data bearers with 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 embodiments, the QoS information may be used as data processing priority, scheduling information, etc. for supporting a smooth service.

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

Header compression and decompression ROHC only

-transfer of user data

-sequential transfer of upper layer PDU

-out of order delivery upper layer PDU

-PDCP PDU reordering for reception

Duplicate detection of lower layer SDU

-retransmission of PDCP SDU

-encryption and decryption

Timer based SDU discard in uplink.

In the above description, the reordering of the NR PDCP device may mean a function of reordering PDCP PDUs received from a lower layer in order based on a 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 missing PDCP PDUs by reordering the order, a function of reporting a status on the missing PDCP PDUs to a transmitting side, and a function of requesting retransmission of the missing PDCP PDUs.

According to some embodiments, the primary 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.

-transmission of upper layer PDU

-sequential delivery of upper layer PDUs

Out-of-order delivery of upper layer PDUs

Error correction by ARQ

Concatenation, segmentation and reassembly of RLC SDUs

-re-segmentation of RLC data PDUs

Reordering of RLC data PDUs

-duplicate detection

-protocol error detection

RLC SDU discard

RLC re-establishment

In the above description, the sequential delivery of the NR RLC apparatus may mean a function of delivering RLC SDUs received from a lower layer to a higher layer in order. 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 recombining and delivering several RLC SDUs.

The sequential delivery of the NR RLC device may include a function of reordering received RLC PDUs based on an RLC Sequence Number (SN) or a PDCP Sequence Number (SN), and may include a function of recording missing RLC PDUs by reordering the order, a function of reporting a status about the missing RLC PDUs to a transmitting side, and a function of requesting retransmission of the missing RLC PDUs.

The sequential delivery of the NR RLC device may include a function of delivering only RLC SDUs preceding a missing RLC SDU to a higher layer in order when there is the missing RLC SDU.

The sequential delivery of the NR RLC device may include a function of delivering all RLC SDUs received before the start of the timer to a higher layer in order if a predetermined timer expires even if there is a missing RLC SDU.

The sequential delivery of the NR RLC device may include a function of delivering all RLC SDUs received so far to a higher layer in order even if there is a missing RLC SDU if a predetermined timer expires.

The NR RLC device may process 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 sequence numbers (out-of-order delivery).

When the NR RLC device receives the segmentation, the NR RLC device may receive the segmentation stored in the buffer or to be received later, reconfigure the segmentation into one complete RLC PDU, and then deliver the one complete RLC PDU to the NR PDCP device.

The NR RLC layer may not include a concatenation function, and the concatenation function may be performed in the NR MAC layer, or may be replaced with a multiplexing function of the NR MAC layer.

In the above description, out-of-order delivery of the NR RLC device may mean the following functions: RLC SDUs received from a lower layer are delivered directly to a higher layer regardless of order. The out-of-order delivery of the NR RLC device may include a function of reassembling and delivering several RLC SDUs when one RLC SDU is initially divided into several RLC SDUs and received. Out-of-order delivery of the NR RLC device may include functions of storing RLC SNs or PDCP SNs of received RLC PDUs, ordering the order thereof, and recording missing RLC PDUs.

According to some embodiments, NR MACs 1d-15 and 1d-30 may be connected to several NR RLC layer devices configured in one terminal, and the main functions of the NR MACs may include some of the following functions. However, the main function of the NR MAC is not limited to the following example.

Mapping between logical channels and transport channels

-multiplexing/demultiplexing of MAC SDUs

-scheduling information reporting

Error correction by HARQ

-priority handling between logical channels of one UE

-prioritization among UEs by dynamic scheduling

-MBMS service identification

-transport format selection

-patches

The NR PHY layers 1d-20 and 1d-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 to a radio channel, or demodulating and channel-decoding OFDM symbols received through the radio channel to deliver the OFDM symbols to the upper layer.

Fig. 1e is a block diagram showing an internal structure of a terminal to which the present disclosure is applied.

Referring to FIG. 1e, the terminal may include Radio Frequency (RF) processors 1e-10, baseband processors 1e-20, memory units 1e-30, and controllers 1 e-40. The present disclosure is not limited to the above examples and the terminal may comprise fewer or more configurations than shown in fig. 1 e.

The RF processors 1e-10 may perform functions for transmitting and receiving signals through a wireless channel, such as band conversion and amplification of the signals. That is, the RF processors 1e-10 may up-convert baseband signals provided from the baseband processors 1e-20 into RF band signals, transmit the RF band signals through an antenna, and down-convert RF band signals received through the antenna into baseband signals. For example, the RF processors 1e-10 may include transmit filters, receive filters, amplifiers, mixers, oscillators, digital-to-analog converters (DACs), analog-to-digital converters (ADCs), and so forth. The present disclosure is not limited to the above examples. Although only one antenna is shown in fig. 1e, the terminal may include multiple antennas. Further, the RF processors 1e-10 may include a plurality of RF chains. In addition, the RF processors 1e-10 may perform beamforming. For beamforming, the RF processors 1e-10 may adjust the phase and amplitude of each signal transmitted and received through multiple antennas or antenna elements. Further, the RF processors 1e-10 may perform multiple-input multiple-output (MIMO) and receive several layers while performing MIMO operation.

The baseband processors 1e-20 perform a function of converting between a baseband signal and a bit string in accordance with the physical layer standard of the system. For example, when transmitting data, the baseband processors 1e to 20 may encode and modulate the transmitted bit string to generate complex symbols. Further, when receiving data, the baseband processors 1e to 20 can restore the received bit string by demodulating and decoding the baseband signal supplied from the RF processors 1e to 10. For example, in the case of an Orthogonal Frequency Division Multiplexing (OFDM) scheme, when transmitting data, the baseband processors 1e-20 encode and modulate a transmission bit string to generate a complex symbol, map the complex symbol to subcarriers, and then configure the OFDM symbol by an Inverse Fast Fourier Transform (IFFT) operation and Cyclic Prefix (CP) insertion. Further, when receiving data, the baseband processors 1e-20 may divide the baseband signal provided from the RF processors 1e-10 into OFDM symbol units, recover the signal mapped to the subcarriers through Fast Fourier Transform (FFT), and then recover the received bit string through demodulation and decoding.

As described above, the baseband processors 1e-20 and the RF processors 1e-10 transmit and receive signals. The baseband processors 1e-20 and the RF processors 1e-10 may be referred to as transmitters, receivers, transceivers or communication units. Further, at least one of the baseband processors 1e-20 and the RF processors 1e-10 may include a plurality of communication modules in order to support a plurality of different radio access technologies. Further, at least one of the baseband processors 1e-20 and the RF processors 1e-10 may include different communication modules in order to process signals of different frequency bands. For example, the different radio access technologies may include wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), and the like. Further, the different frequency bands may include an ultra high frequency (SHF) (e.g., 2.NRHz, NRHz) band and a millimeter wave (e.g., 60GHz) band. The terminal can transmit and receive signals to and from the base station using the baseband processors 1e-20 and the RF processors 1e-10, and the signals can include control information and data.

The storage units 1e-30 store data for the operation of the UE, such as basic programs, application programs, and configuration information. In particular, the storage unit 1e-30 may store information related to a second access node performing wireless communication using a second radio access technology. The storage unit 1e-30 provides the stored data according to the request of the controller 1 e-40. The storage units 1e-30 may be configured with storage media such as Read Only Memory (ROM), Random Access Memory (RAM), a hard disk, a compact disc read only memory (CD-ROM), and a Digital Versatile Disc (DVD), or a combination of storage media. Further, the storage units 1e to 30 may include a plurality of memories.

The controllers 1e to 40 control the overall operation of the terminal. For example, the controller 1e-40 transmits and receives signals through the baseband processor 1e-20 and the RF processor 1 e-10. Further, the controllers 1e to 40 write and read data in the memory units 1e to 40. To this end, the controllers 1e-40 may include at least one processor. For example, the controllers 1e-40 may include a Communication Processor (CP) that controls communication and an Application Processor (AP) that controls an upper layer such as an application program. Further, at least one component in the terminal may be implemented in one chip.

Fig. 1f is a block diagram illustrating a configuration of an NR base station according to some embodiments of the present disclosure.

Referring to fig. 1f, the base station may include RF processors 1f-10, baseband processors 1f-20, backhaul communication units 1f-30, memory units 1f-40, and controllers 1 f-50. The present disclosure is not limited to this example and the base station may comprise fewer or more configurations than shown in fig. 1 f.

The RF processors 1f-10 may perform functions for transmitting and receiving signals through a wireless channel, such as band conversion and amplification of the signals. That is, the RF processors 1f-10 up-convert baseband signals supplied from the baseband processors 1f-20 into RF band signals, transmit the RF band signals through an antenna, and down-convert RF band signals received through the antenna into baseband signals. For example, the RF processors 1f-10 may include transmit filters, receive filters, amplifiers, mixers, oscillators, digital-to-analog converters (DACs), analog-to-digital converters (ADCs), and so forth. Although only one antenna is shown in FIG. 1f, the RF processors 1f-10 may include multiple antennas. Further, the RF processors 1f-10 may include a plurality of RF chains. In addition, the RF processors 1f-10 may perform beamforming. For beamforming, the RF processors 1f-10 may adjust the phase and amplitude of each signal transmitted and received through multiple antennas or antenna elements. The RF processor may transmit one or more layers to perform downlink MIMO operations.

The baseband processors 1f-20 may perform the function of converting between baseband signals and bit strings according to the physical layer standard of the first radio access technology. For example, when transmitting data, the baseband processors 1f-20 may encode and modulate the transmitted bit string to generate complex symbols. Further, when receiving data, the baseband processor 1f-20 can restore the received bit string by demodulating and decoding the baseband signal supplied from the RF processor 1 f-10. For example, in the OFDM scheme, when transmitting data, the baseband processors 1f to 20 encode and modulate a transmission bit string to generate complex symbols, map the complex symbols to subcarriers, and configure the OFDM symbols through IFFT operation and CP insertion. Further, when receiving data, the baseband processor 1f-20 may divide the baseband signal provided from the RF processor 1f-10 into OFDM symbol units, recover the signal mapped to the subcarriers through an FFT operation, and then recover the received bit string through demodulation and decoding. As described above, the baseband processors 1f-20 and the RF processors 1f-10 may transmit and receive signals. Thus, the baseband processors 1f-20 and the RF processors 1f-10 may be referred to as transmitters, receivers, transceivers, communication units or RF units. The base station may transmit and receive signals to and from the terminal using the baseband processors 1f-20 and the RF processors 1f-10, and the signals may include control information and data.

The backhaul communication units 1f-30 provide interfaces for communicating with other nodes in the network. That is, the backhaul communication units 1f-30 can convert a bit string transmitted from the master station to another node, e.g., a secondary 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 units 1f-30 may be included in a communication unit.

The storage units 1f to 40 store data such as basic programs, application programs, and configuration information for the operation of the base station. The memory units 1f-40 may store information about bearers assigned to the accessed terminal, measurement results reported from the accessed terminal, and the like. Further, the storage units 1f-40 may store information as a criterion for determining whether to provide or stop a plurality of connections to the terminal. The storage units 1f-40 provide stored data according to the requests of the controllers 1 f-50. The storage units 1f to 40 may be configured with storage media such as ROM, RAM, hard disk, CD-ROM, and DVD, or a combination of storage media. In addition, the memory units 1f-40 may include a plurality of memories. According to some embodiments, the storage units 1f-40 may store programs for performing the buffer status reporting method according to the present disclosure.

The controllers 1f-50 control the overall operation of the base station. For example, the controller 1f-50 transmits and receives signals through the baseband processor 1f-20 and the RF processor 1f-10 or through the backhaul communication unit 1 f-30. In addition, the controllers 1f to 50 write and read data in the memory cells 1f to 40. To this end, the controllers 1f-50 may include at least one processor. Further, at least one configuration of the base station may be implemented with one chip.

Fig. 1g illustrates a handover operation without random access channel in conventional LTE.

The UE 1g-10 receives an RRC reconfiguration message (RRC reconfiguration) including mobile control information (mobility control info) from the base station 1g-20 (step 1 g-01). The message may include a random access channel 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.

The UE 1g-10 having received the message may perform the following operation (step 1 g-02).

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

UE 1g-10 may configure the TA value with the TA information configured in the received RRC reconfiguration message.

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

The UE RRC may send a radio resource control reconfiguration complete (rrcreeconfigurationccomplete) message to the UE MAC.

UE MAC may trigger regular BSR.

The terminal 1g-10 may transmit a MAC PDU including rrcreeconfigurationcomplete delivered in this manner by applying a pre-allocated UL grant, which uses UL-ConfigInfo configured in a rach-skip, to the target cell (step 1 g-03).

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 1 g-04).

The UE RRC may stop the timer T304 and release the ul-ConfigInfo (steps 1 g-05).

Fig. 1h is a diagram illustrating a use case of a case where a rach-skip includes a configured uplink grant release (configuredpulinkgrantlease) configuration in a random access channel-free (RACHless) HO specific signal structure in the NR according to some embodiments of the present disclosure.

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

The message may include a Rach-Skip IE and a SpCellConfig IE.

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

Furthermore, the Rach-Skip IE may include a configured uplink grant release (configuredjulinkgrantlease) field, and the field may include a value for determining whether to release the configured uplink grant used after the success of performing a random-access-channel-less (Rach) HO. This field may have a boolean value (yes or no) or a data type enumerating true.

The SpCellConfig field includes N number of BWP configuration information and also includes first active BWP (firstactivebwp) id information. The BWP configuration information may include configured authorization configuration (ConfiguredGrantConfig) information.

When the terminal 1h-10 receives a message from the base station 1h-20 (step 1h-01), the terminal 1h-10 may sequentially perform the following operations (step 1 h-02).

The UE 1h-10 may be synchronized with the target PCell.

Further, depending on the value in the target TA field, the N _ { TA } value used in the target Pcell may 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 master cell group (MasterCellGroup) information, NTA of PTAG of MCG is applied, and if the SpCellConfig is included in secondary cell group (SecondaryCellGroup) information, NTA of PTAG of SCG may be applied. Further, if the target TA value is STAG id, and if the SpCellConfig received in step 1h-01 is included in 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 may be applied.

Thereafter, the RRC of the terminal may transmit rrcreeconfigurationccomplete RRC PDU to the UE MAC. Thereafter, the UE MAC may trigger a regular BSR. Further, the terminal 1h-10 may transmit a MAC PDU including a rrcreeconfigurationcomplete message to a specific ul bwp using the configured uplink grant (step 1 h-03). In this case, the specific ul BWP may be the BWP specified by the first active BWP id.

Thereafter, the UE 1h-10 may receive an acknowledgement MAC CE (which may include only a separate LCID) or a contention resolution MAC CE in the first active DLBWP through a C-RNTI (C-RNTI indicated in the RRCREConfiguration message including the reconfigurationWithSync received in step 1h-01) (step 1 h-04). Here, the acknowledgement 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 (steps 1 h-05).

The MAC of the UE that has received the MAC CE may report to the RRC that the PDCCH transmission addressed by the C-RNTI has been successfully received. Further, the RRC of the terminal stops the T304 timer. Furthermore, when configuredjurringprintrelease is configured to mean a release in the rach-skip IE included in the rrcconfiguration message including recordingwithsync received in step 1h-01, for example, when it has a boolean data type, it is configured to be yes or true, or when configuredjurringgradntrelease has an enumerationtrue data type, if configuredjurringgradntrelease itself has been set, it is possible to release the configured uplink grant for a specific BWP. In this case, the specific BWP may be the BWP specified by the first active BWP id.

The configuration information included in the configuration information for each BWP may have a value in which the configuration information for each BWP is included in the spcellconfiguration included in the rrcrecconfiguration message including reconfigurationWithSync received by the UE 1h-10 in step 1 h-01.

nrofHARQ-Processes the number of configured HARQ,

periodicity-the period that can be sent with a configured grant UL;

-a time domain offset (timeDomainOffset) offset value based on SFN ═ 0,

time domain allocation (timesdomainAllocation) displaying the starting symbol, length and PUSCH mapping type,

frequency domain allocation (frequency domain allocation) frequency domain allocation information,

mcs and TBS value information for configured UL grants

Furthermore, the validity time information of the configured UL grant to be used for the specific time of the rach-skip HO purpose may additionally 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 information of a specific BWP in units of the maximum valid possible period. When expressed in absolute time units, the UE starts a 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. Further, the terminal may stop the timer when the HO is successful and the contention resolution MAC CE is successfully received. In case of setting the maximum valid possible period unit of a specific BWP, when the UE starts counting after synchronizing with the corresponding target PCell and does not receive a contention resolution MAC CE from the target PCell while passing the corresponding period, it may be considered as a HO failure.

Fig. 1i is a diagram illustrating a use case of a case where the rach-skip does not include a configuredjurringonclinkgrantlease configuration in a random access channel (RACHless) -free HO-specific signal structure in the NR, according to some embodiments of the present disclosure.

The base station 1i-20 may transmit a rrcelecoxonfiguration message including a reconfigurationWithSync to the terminal 1i-10 (step 1 i-01). In this case, the message may include the following information.

The message may include a Rach-Skip IE and a SpCellConfig IE.

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

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

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

The UE 1i-10 may be synchronized with the target PCell.

Also, the value of N _ { TA } used in the target Pcell is applied as follows, depending on the value in the target TA field. 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 master cell group (MasterCellGroup) information, NTA of PTAG of MCG is applied, and if the SpCellConfig is included in secondary cell group (SecondaryCellGroup) information, NTA of PTAG of SCG may be applied. Further, when the target TA value is STAG id, if the SpCellConfig received in step 1i-01 is included in MasterCellGroup information, NTA of the STAG designated by the STAG id may be applied, and if the SpCellConfig is included in SecondaryCellGroup information, NTA of the STAG designated by the STAG id may be applied.

Thereafter, the RRC of the terminal may transmit rrcreeconfigurationccomplete RRC PDU to the UE MAC. Thereafter, the MAC of the terminal may trigger a regular BSR. Further, the UE 1i-10 may transmit a MAC PDU including a rrcreeconfigurationcomplete message using a configured uplink grant of a specific UL BWP (step 1 i-03). In this case, the UE 1i-10 may transmit the MAC PDU through the configured uplink grant for the BWP specified by the first active BWP id.

After the transmission, the UE 1i-10 may receive an acknowledgement MAC CE (which may include only a separate LCID) or a contention resolution MAC CE in the first active DLBWP through a C-RNTI (C-RNTI indicated in the rrcreeconfiguration message including the recorfigurationwithsync received in the first step) (step 1 i-04). Here, the acknowledgement 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 1 i-05).

The UE may first stop T304. Further, 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. Further, the MAC of the UE may release the RACH-skip configuration and release the uplink grant of the configuration of the first active BWP. Thereafter, the portions of the CQI report configuration, the scheduling request configuration, and the sounding RS configuration that can be configured even if the UE does not know the relative System Frame Number (SFN) information of the target scell are applied. The measurement and radio resource configuration part may be applied when SFN information of the target scell is obtained later.

The configuration information included in the configuration information for each BWP may have a value in which the configuration information for each BWP is included in the scellconfiguration included in the rrcrecconfiguration message including the reconfigurationWithSync received by the terminal in step 1 i-01.

nrofHARQ-Processes the number of configured HARQ,

periodicity-the period that can be sent with a configured grant UL;

-a time domain offset (timeDomainOffset) offset value based on SFN ═ 0,

time domain allocation (timesdomainAllocation) displaying the starting symbol, length and PUSCH mapping type,

frequency domain allocation (frequency domain allocation) frequency domain allocation information,

mcs and TBS value information for configured UL grants

Furthermore, the validity time information of the configured UL grant to be used for the specific time of the rach-skip HO purpose may additionally 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 information of a specific BWP in units of the maximum valid possible period. When expressed in absolute time units, the terminal starts a 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. Further, the terminal may stop the timer when the HO is successful and the contention resolution MAC CE or the acknowledgement MAC CE is successfully received. In case of setting the maximum valid possible period unit of a specific BWP, the terminal starts counting after synchronizing with the corresponding target PCell, and is considered to be a HO failure when the terminal does not receive a contention resolution MAC CE from the target PCell while passing through the corresponding period.

Fig. 1j is a diagram illustrating a handover case in which a random access channel (RACHless) HO signal is omitted in a RRCRconfiguration message including a reconfigurationWithSync in an NR according to some embodiments of the present disclosure.

In this embodiment, in the case of fig. 1h and 1g, the rach-skip is optional and includes the case of omitting the configuration.

The base station 1j-20 may transmit an RRC reconfiguration (rrcrconfiguration) including a reconfigurationWithSync to the terminal 1j-10 (step 1 j-01). When there is no rach-skip IE, the terminal 1j-10 that has received the message may perform the following operation (step 1 j-02).

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

The RRC of the terminal may deliver the rrcreeconfigurationcomplete message to the MAC of the UE. The MAC of the terminal may transmit a MAC PDU including rrcreconfigurable complete to Mg3 (step 1 j-03). In this case, transmission may be performed using the UL grant indicated by the RAR. In this case, when the preamble delivered during RA is a common preamble, the contention resolution MAC CE may be received through TC-RNTI (C-RNTI indicated in RAR) in the first active DLBWP (step 1 j-04). Thereafter, T304 may be stopped (steps 1 j-05).

In addition, the portions of the CQI report configuration, the scheduling request configuration, and the sounding RS configuration, which can be configured even when the UE does not know the relative SFN information of the target scell, are applied. The measurement and radio resource configuration part may be applied when SFN information of the target scell is obtained later.

The ConfiguredGrantConfig included in the configuration information for each BWP may have a value where the configuration information for each BWP is included in the scellconfigug included in the rrcrecconfiguration message including reconfigurationWithSync received by the UE in step 1 j-01.

nrofHARQ-Processes the number of configured HARQ,

periodicity-the period that can be sent with a configured grant UL;

-a time domain offset (timeDomainOffset) offset value based on SFN ═ 0,

time domain allocation (timesdomainAllocation) displaying the starting symbol, length and PUSCH mapping type,

frequency domain allocation (frequency domain allocation) frequency domain allocation information,

mcs and TBS value information for configured UL grants

Furthermore, validity time information of configured UL grants to be used for the purpose of a specific time of a rach-skip HO 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 validity time information may be represented in ConfiguredGrantConfig information of a specific BWP in the maximum valid possible period unit. When expressed in absolute time units, the terminal starts a 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. Further, the terminal may stop the timer when the HO is successful and the contention resolution MAC CE or the acknowledgement MAC CE is successfully received. In case of setting the maximum valid possible period unit of a specific BWP, the terminal starts counting after synchronizing with the corresponding target PCell, and when the terminal does not receive a contention resolution MAC CE from the target PCell while passing the corresponding period, it is considered as a HO failure.

The acknowledgement MAC CE used in the embodiments of fig. 1g and 1h may be classified into a MAC PDU subheader having a specific value of LCID and have a fixed size of 0 bits.

The embodiments of the present disclosure disclosed in the present specification and the drawings merely present specific examples in order to easily describe the technical content of the present disclosure and to assist understanding of the present disclosure, and they are not intended to limit the scope of the present disclosure. That is, it is apparent to those of ordinary skill in the art to which the present disclosure pertains that other modifications may be implemented based on the technical spirit of the present disclosure. Further, each of the above embodiments may operate in conjunction with each other as needed. For example, a base station and a terminal may operate by combining parts of the embodiments of the present disclosure.

Furthermore, in the present specification and the drawings, there have been disclosed preferred embodiments of the present disclosure, and although specific terms are used, they are used in a generic sense only to easily describe the technical content of the present disclosure and to aid understanding thereof, and they are not intended to limit the scope of the present disclosure. It is apparent to those of ordinary skill in the art to which the present disclosure pertains that other modifications based on the technical spirit of the present disclosure may be implemented in addition to the embodiments disclosed herein.