Patent Publication Number: US-2023147117-A1

Title: Method and apparatus for transmitting or receiving signal in mobile communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application of prior Application Number 16/532,997, filed on Aug. 6, 2019, which has issued as U.S. Pat. No. 11,540,250 on Dec. 27, 2022 and is based on and claims priority under 35 U.S.C. 119(a) of a Korean Patent Application Number 10-2018-0091505, filed on Aug. 6, 2018, in the Korean Intellectual Property Office, and a Korean Patent Application Number 10-2018-0115279, filed on Sep. 27, 2018, in the Korean Intellectual Property Office, the disclosure of each of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Field 
     The disclosure relates to a paging monitoring method and apparatus according to a state of a terminal in a mobile communication system. More particularly, the disclosure relates to a method and an apparatus for reporting a connection setup failure in consideration of an inactive state of a terminal in a mobile communication system. 
     Description of the Related Art 
     In order to meet wireless data traffic demands having increased after commercialization of 4th generation (4G) communication systems, efforts to develop an improved 5th generation (5G) communication system or a pre-5G communication system have been made. For this reason, the 5G communication system or the pre-5G communication system is called a “beyond 4G network communication system” or a “post long-term evolution (LTE) system”. In order to achieve a high data transfer rate, the implementation of the 5G communication system in a millimeter wave (mmWave band) (e.g., 60 GHz band) has been considered. In order to mitigate a propagation path loss and increase a propagation transmission distance in the mmWave band, technologies, such as beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large-scale antenna, are under discussion for 5G communication systems. Further, in order to improve system networks, technologies, such as an evolved small cell, an advanced small cell, a cloud radio access network (RAN), an ultra-dense network, device-to-device (D2D) communication, a wireless backhaul, a moving network, cooperative communication, coordinated multi-points (CoMP), and received interference cancellation, are under development for 5G communication systems. In addition, advanced coding modulation (ACM) schemes, such as hybrid FSK and quadrature amplitude modulation (QAM) modulation (FQAM) and sliding window superposition coding (SWSC), and advanced access technologies, such as filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA), are under development for 5G communication systems. 
     The Internet is evolving from a human-centered connectivity network where humans create and consume information into the Internet of Things (IoT) network where distributed elements, such as objects, exchange and process information. The Internet of Everything (IoE), which is implemented by combining IoT technology and big data processing technology through connection with a cloud server or the like, has emerged. In order to implement IoT, technical factors, such as a sensing technique, wired/wireless communication, network infrastructure, service interface technology, and security technology, are required, and thus, research has recently been conducted on technologies, such as a sensor network, machine-to-machine (M2M) communication, and machine-type communication (MTC), for a connection between objects. In an IoT environment, it is possible to provide intelligent Internet technology services that create a new value for human life by collecting and analyzing data generated from connected objects. Through convergence and combination between existing information technology (IT) and various industries, IoT may be applied to fields, such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart appliances, and high-tech medical services. 
     Accordingly, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, M2M communication, and MTC are implemented by techniques such as beamforming, MIMO, and array antennas which are the 5G communication technology. The application of a cloud radio access network (cloud RAN) as the above-described big data processing technology may also be an example of convergence between the 5G technology and the IoT technology. 
     In a mobile communication system, a connection setup failure report is an operation in which, if a terminal having transitioned from an unconnected state to a connected state subsequently succeeds in accessing a network, terminal information possessed by the terminal in a state in which an initial setup attempt by the terminal has failed, is delivered to a base station, and thus the terminal transmits information used for the base station to take measures in a network stage so that a setup attempt failure is prevented from subsequently occurring. 
     A next-generation mobile communication system employs an inactive state as well as a connected state and an idle state, and thus a connection setup failure operation should be newly considered in relation to a setup attempt in the inactive state as well as a setup attempt in the idle state. However, in an existing system, only a setup attempt in an idle state exists, so that a connection setup failure for a new state should be defined, and thus it is necessary to include notice of the type of setup, a failure of which has occurred, in the contents of an activated report. 
     The above information is presented as background information only to assist with an understanding of the disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure. 
     SUMMARY 
     Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. 
     Accordingly, an aspect of the disclosure is to provide a method for monitoring a short message and a paging message when a terminal is in a radio resource control (RRC) idle mode or an RRC inactive mode. 
     Another aspect of the disclosure is to provide a method for in a next-generation mobile communication system employing an inactive state as well as a connected state and an idle state, defining a connection setup failure for a new state by newly considering a setup attempt in the inactive state as well as a setup attempt in the idle state, and giving notice of the type of setup, a failure of which has occurred, in the contents of an report activated accordingly. A network may be notified of information on how serious failures are, by using information on how many times the relevant consecutive failures have occurred. Further, in the case of multiple connection failures, different power offset values may be applied to cell selection or cell reselection, according to failure types. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     In accordance with an aspect of the disclosure, a method for processing a control signal in a wireless communication system is provided. The method includes receiving a first control signal transmitted by a base station, processing the received first control signal, and transmitting, to the base station, a second control signal generated on the basis of the processing of the received first control signal. 
     In accordance with an aspect of the disclosure, a method of a user equipment (UE) in a wireless communication system is provided. The method includes identifying the UE is in a camped on any cell state or a camped normally state; monitoring a short message in case that the UE is in the camped on any cell state; and monitoring a short message and a paging message in case that the UE is in the camped normally state. 
     In accordance with another aspect of the disclosure, a method of a base station in a wireless communication system is provided. The method includes identifying whether to transmit a short message and scheduling information for a paging message; transmitting, to a user equipment (UE), the short message on a physical downlink control channel (PDCCH) using paging radio network temporary identifier (P-RNTI) based on the identification; and transmitting, to the UE, the paging message based on the scheduling information in case that the scheduling information is identified to transmit. 
     In accordance with another aspect of the present disclosure, a user equipment in a wireless communication system is provided. The UE includes a transceiver; and at least one processor coupled with the transceiver, the processor is configured to: identify the UE is in a camped on any cell state or a camped normally state; monitor a short message in case that the UE is in the camped on any cell state; and monitor a short message and a paging message in case that the UE is in the camped normally state. 
     In accordance with another aspect of the present disclosure, a base station in a wireless communication system is provided. The base station includes a transceiver; and at least one processor coupled with the transceiver, the processor is configured to: identify whether to transmit a short message and scheduling information for a paging message; control to transceiver to transmit, to a user equipment (UE), the short message on a physical downlink control channel (PDCCH) using paging radio network temporary identifier (P-RNTI) based on the identification; and control to transceiver to transmit, to the UE, the paging message based on the scheduling information in case that the scheduling information is identified to transmit. 
     An embodiment enables monitoring of a short massage or a paging message, according to the state of a terminal. 
     Further, another embodiment enables a base station to more accurately analyze causes of failure of a connection attempt by a terminal and more accurately take measures accordingly. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a view illustrating an architecture of an LTE system architecture according to an embodiment of the disclosure; 
         FIG.  2    is a block diagram illustrating a structure of a wireless protocol in an LTE system according to an embodiment of the disclosure; 
         FIG.  3    is a view illustrating a structure of a next-generation mobile communication system according to an embodiment of the disclosure; 
         FIG.  4    is a block diagram illustrating a structure of a wireless protocol of a next-generation mobile communication system according to an embodiment of the disclosure; 
         FIG.  5    is a signal flow diagram illustrating a procedure in which a base station releases a connection with a terminal so that the terminal switches from an RRC connected mode to an RRC idle mode, and a procedure in which the terminal establishes a connection with the base station so that the terminal switches from an RRC idle mode to an RRC connected mode, according to an embodiment of the disclosure; 
         FIG.  6    is a signal flow diagram illustrating a procedure in which a base station releases a connection with a terminal so that the terminal switches from an RRC connected mode to an RRC inactive mode, and a procedure in which the terminal establishes a connection with the base station so that the terminal switches from an RRC inactive mode to an RRC connected mode, according to an embodiment of the disclosure; 
         FIG.  7    is a flowchart illustrating an operation of a terminal for monitoring a short message or a paging message when the terminal is in an RRC idle mode or an RRC inactive mode according to an embodiment of the disclosure; 
         FIG.  8    is a flowchart illustrating an operation of a terminal for monitoring a short message or a paging message while the terminal is in an RRC idle mode or an RRC inactive mode according to an embodiment of the disclosure; 
         FIG.  9    is a flowchart illustrating an operation of a terminal when receiving a short message while the terminal is in an RRC idle mode or an RRC inactive mode according to an embodiment of the disclosure; 
         FIG.  10    is a block diagram illustrating a configuration of a terminal according to an embodiment of the disclosure; 
         FIG.  11    is a block diagram illustrating a configuration of a base station according to an embodiment of the disclosure; 
         FIG.  12    is a view illustrating an architecture of an LTE system according to an embodiment of the disclosure; 
         FIG.  13    is a view illustrating a wireless protocol structure of an existing LTE system according to an embodiment of the disclosure; 
         FIG.  14    is a view illustrating a structure of a next-generation mobile communication system according to an embodiment of the disclosure; 
         FIG.  15    is a block diagram illustrating a structure of a wireless protocol of a next-generation mobile communication system according to an embodiment of the disclosure; 
         FIG.  16    is a signal flow diagram illustrating a case in which, when a terminal transitions from an idle state to a connected state, the terminal fails to transition from the former to the latter, according to an embodiment of the disclosure; 
         FIG.  17    is a flow diagram illustrating a case in which, when a terminal transitions from an inactive state to a connected state, the terminal fails to transition from the former to the latter, according to an embodiment of the disclosure; 
         FIG.  18    is a signal flow diagram illustrating an operation of a terminal for (re-)selecting a cell by applying a predetermined power offset and a predetermined factor value if the terminal experiences a fixed number of failures when the terminal transitions from an idle state to a connected state, according to an embodiment of the disclosure; 
         FIG.  19    is a signal flow diagram illustrating an operation of a terminal for (re-)selecting a cell by applying a predetermined power offset and a predetermined factor value if the terminal experiences a predetermined number of failures when the terminal transitions from an inactive state to a connected state, according to an embodiment of the disclosure; 
         FIG.  20    is a signal flow diagram illustrating an operation of a terminal for (re-)selecting a cell by applying the same number of failures, a power offset, and a factor value, which are applied to two types of failures, if the terminal experiences a predetermined number of failures in an inactive state, and transitions to an idle state and again transitions to a connected state, when the terminal is to transition from the inactive state to the connected state, according to an embodiment of the disclosure; 
         FIG.  21    is a view illustrating a format of a usable connection setup failure report according to an embodiment of the disclosure; 
         FIG.  22    is a view illustrating a format of a usable connection setup failure report according to an embodiment of the disclosure; 
         FIG.  23    is a signal flow diagram illustrating base station identification (ID) transmission for entry into a connection re-establishment request according to an embodiment of the disclosure; 
         FIG.  24    is a block diagram illustrating an internal configuration of a terminal according to an embodiment of the disclosure; and 
         FIG.  25    is a block diagram illustrating a configuration of a new radio (NR) base station according to an embodiment of the disclosure. 
     
    
    
     Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the disclosure is provided for illustration purpose only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents. 
     Here, it may be understood that each block of processing flowcharts and combinations of the flowcharts may be performed by computer program instructions. Since these computer program instructions may be loaded into processors for a general computer, a special-purpose computer, or other programmable data-processing apparatuses, these instructions executed by the processors for the computer or the other programmable data-processing apparatuses may create means for performing functions described in block(s) of the flowcharts. Since these computer program instructions may also be stored in a non-transitory computer-usable or computer-readable memory of a computer or other programmable data-processing apparatuses in order to implement the functions in a specific scheme, the computer program instructions stored in the non-transitory computer-usable or computer-readable memory may also produce manufacturing articles including instruction means performing the functions described in block(s) of the flowcharts. Since the computer program instructions may also be loaded into a computer or other programmable data-processing apparatuses, the instructions may cause a series of operation steps to be performed on the computer or other programmable data-processing apparatuses so as to generate processes executable by the computer and enable an operation of the computer or other programmable data-processing apparatuses, and may also provide steps for implementing the functions described in the flowchart block(s). 
     Also, each block may indicate some of modules, segments, or codes including one or more executable instructions for executing a specific logical function(s). Further, it is to be noted that the functions mentioned in the blocks may occur out of order in some alternative embodiments. For example, two blocks that are consecutively illustrated may be performed substantially concurrently or may sometimes be performed in the reverse order, according to corresponding functions. 
     Here, the term “∼ unit” used in the embodiment means software or hardware elements such as a field-programmable gate array (FPGA) and an application-specific integrated circuit (ASIC), and the “∼ unit” may perform any roles. However, the meaning of “∼ unit” is not limited to software or hardware. The “∼ unit” may be configured to reside in a storage medium that may be addressed, and may also be configured to reproduce one or more processors. Accordingly, for example, the “∼ unit” includes: elements such as software elements, object-oriented software elements, class elements, and task elements; and processors, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided in the elements and “∼ units” may be combined with a smaller number of elements and “∼ units” or may be further separated into additional elements and “∼ units”. In addition, the elements and the “∼ units” may also be implemented to reproduce one or more central processing unit (CPU)s within a device or a security multimedia card. Further, in embodiments, “∼ unit” may include at least one processor. 
     In the disclosure, a downlink (DL) means a radio transmission path of a signal transmitted from a base station to a terminal, and an uplink (UL) means a radio transmission path of a signal transmitted from the terminal to the base station. Also, an LTE or LTE-A system may be described below by way of example, but embodiments may be applied to other communication systems having a similar technical background or channel form. For example, 5th generation (5G) mobile communication technology (5G or NR) developed after LTE-A may be included in systems to which embodiments may be applied, and 5G described below may be a concept including the existing LTE, LTE-A, and other similar services. Further, according to the determination of those skilled in the art, the disclosure may be applied to other communication systems through partial modification without departing from the scope of the disclosure. 
     In the following description, the terms identifying access nodes, and the terms referring to network entities, messages, interfaces between network entities, and various pieces of identification information are merely examples used for convenience of description. Therefore, the disclosure is not limited to the following terms, and other terms referring to objects having equivalent technical meanings may be used. 
     Hereinafter, for convenience of description, the disclosure uses terms and names defined in the 3rd generation partnership project (3GPP) LTE or NR standard. However, the disclosure is not limited to the terms and names, and may be identically applied to systems complying with other standards. In the disclosure, the term evolved node B, or “eNB,” may be used interchangeably with the term next generation node b, or “gNB,” for convenience of description. That is, a base station described as an eNB may represent a gNB. 
     In the following description of the disclosure, a detailed description of well-known functions or configurations incorporated herein will be omitted when it makes the subject matter of the disclosure unclear. Hereinafter, an embodiment will be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG.  1    is a view illustrating an architecture of an LTE system architecture according to an embodiment of the disclosure. 
     Referring to  FIG.  1   , a radio access network of the LTE system may include next-generation base stations (“eNBs”, “Node Bs”, or “base stations”)  105 ,  110 ,  115 , and  120 , a mobility management entity (MME)  125 , and a serving-gateway (S-GW)  130 . A user equipment (hereinafter “UE” or “terminal”)  135  may access an external network through the eNBs  105  to  120  and the S-GW  130 . 
     In  FIG.  1   , the eNBs  105  to  120  may correspond to existing Node Bs of a universal mobile telecommunications system (UMTS) system. The eNBs  105  to  120  may be connected to the UE  135  through wireless channels, and may perform more complex functions than those performed by existing Node Bs. In the LTE system, all user traffic including real-time services, such as voice over internet protocol (IP) (VoIP) services through an Internet protocol, may be served through shared channels. Therefore, there is a need for an apparatus configured to collect pieces of state information, such as buffer states, available transmission power states, and channel states of UEs so as to perform scheduling. Each of the eNBs  105  to  120  may serve as the apparatus. In general, one eNB may control multiple cells. For example, in order to achieve a transfer rate of 100 Mbps, in a 20 MHz bandwidth, the LTE system may employ an orthogonal frequency division multiplexing (OFDM) scheme as radio access technology. Further, the eNBs  105  to  120  may employ an adaptive modulation and coding (AMC) scheme for determining a modulation scheme and a channel coding rate so as to match a channel state of the UE  135 . The S-GW  130  is an apparatus configured to provide data bearers, and may establish or release data bearers under the control of the MME  125 . The MME  125  is an apparatus configured to perform various control functions including a mobility management function for UEs, and may be connected to multiple eNBs. 
       FIG.  2    is a block diagram illustrating a structure of a wireless protocol in an LTE system according to an embodiment of the disclosure. 
     Referring to  FIG.  2   , the wireless protocol of the LTE system may include packet data convergence protocols (PDCPs)  205  and  240 , radio link controls (RLCs)  210  and  235 , and medium access controls (MACs)  215  and  230  in a UE  201  and an LTE eNB  202 , respectively. 
     The PDCPs  205  and  240  may take charge of operations, such as compression/recovery of an IP header. The main functions of the PDCPs  205  and  240  may be summarized as follows:
     Function of compressing and decompressing a header (Header compression and decompression: robust header compression (ROHC) only);   Function of transmitting user data;   Sequential delivery function (In-sequence delivery of upper layer protocol data unit (PDU)s at PDCP re-establishment procedure for RLC acknowledged mode (AM));   Reordering function (For split bearers in dual connectivity (DC) (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception);   Duplicate detection function (Duplicate detection of lower layer service data unit (SDU)s at PDCP re-establishment procedure for RLC AM);   Retransmission function (Retransmission of PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM);   Function for encryption and decryption (Ciphering and deciphering); and   Timer-based SDU discard function (Timer-based SDU discard in uplink).   

     The RLCs  210  and  235  may reconfigure a PDCP protocol data unit (PDU) to a suitable size so as to perform an automatic repeat request (ARQ) operation and the like. The main functions of the RLCs  210  and  235  may be summarized as follows:
     Data transmission function (Transfer of upper layer PDUs);   ARQ function (Error correction through ARQ (only for AM data transfer));   Function for concatenation, segmentation, and reassembly (Concatenation, segmentation, and reassembly of RLC SDUs (only for unacknowledged mode (UM) and AM data transfer));   Re-segmentation function (Re-segmentation of RLC data PDUs (only for AM data transfer));   Reordering function (Reordering of RLC data PDUs (only for UM and AM data transfer);   Duplicate detection function (Duplicate detection (only for UM and AM data transfer));   Error detection function (Protocol error detection (only for AM data transfer));   RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer)); and   RLC re-establishment function (RLC re-establishment).   

     The MACs  215  and  230  may be connected to multiple RLC layer devices configured in one terminal, and may multiplex RLC PDUs into MAC PDUs and may demultiplex RLC PDUs from MAC PDUs. The main functions of the MACs  215  and  230  may be summarized as follows:
     Mapping function (Mapping between logical channels and transport channels);   Function for multiplexing and demultiplexing (Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TBs) delivered to/from the physical layer on transport channels);   Function of reporting scheduling information;   HARQ function (Error correction through HARQ);   Function of adjusting a priority between local channels (Priority handling between logical channels of one UE);   Function of adjusting a priority between terminals (Priority handling between UEs by means of dynamic scheduling);   Function of identifying an MBMS service (MBMS service identification);   Function of selecting a transmission format (Transport format selection); and   Padding function (Padding).   

     The physical (PHY) layers  220  and  225  may channel-code and modulate higher layer data into OFDM symbols and transmit the OFDM symbols through a wireless channel, or may demodulate and channel-decode OFDM symbols, received through a wireless channel, into higher layer data and deliver the higher layer data to a higher layer. 
       FIG.  3    is a view illustrating a structure of a next-generation mobile communication system according to an embodiment of the disclosure. 
     Referring to  FIG.  3   , a radio access network of the next-generation mobile communication system (hereinafter “NR” or “5G”) may include a next-generation base station (NR Node B, hereinafter “NR gNB” or “NR base station”)  310  and a next-generation radio core network (NR core network (NR CN))  305 . A next-generation radio user equipment (NR user equipment) (hereinafter “NR UE” or “terminal”)  315  may access an external network through the NR gNB  310  and the NR CN  305 . 
     In  FIG.  3   , the NR gNB  310  may correspond to an evolved Node B (eNB) of the existing LTE system. The NR gNB  310  is connected to the NR UE  315  through a wireless channel and may provide a service superior to that provided by the existing Node B. In the next-generation mobile communication system, all user traffics may be served through shared channels. Therefore, there is a need for an apparatus configured to collect pieces of state information, including buffer states, available transmission power states, channel states, and the like of UEs so as to perform scheduling, and the NR gNB  310  may serve as the apparatus. One NR gNB may control multiple cells. In the next-generation mobile communication system, in order to achieve ultra-high-speed data transmission in comparison to the current LTE, a current maximum bandwidth or more may be applied. Further, an orthogonal frequency division multiplexing (OFDM) scheme may be used as radio access technology and beamforming technology may be additionally combined therewith. Further, an adaptive modulation and coding (hereinafter, referred to as “AMC”) scheme for determining a modulation scheme and a channel coding rate so as to match a channel state of a terminal may be applied. The NR CN  305  may perform functions, including mobility support, bearer establishment, quality of service (QoS) configuration, and the like. The NR CN  305  is an apparatus configured to perform various control functions including a mobility management function for a terminal, and may be connected to multiple base stations. Further, the next-generation mobile communication system may interwork with the existing LTE system, and the NR CN  305  may be connected to an MME  325  of the LTE system through a network interface. The MME  325  may be connected to an eNB  330  which is an existing base station. 
       FIG.  4    is a block diagram illustrating a structure of a wireless protocol of a next-generation mobile communication system according to an embodiment of the disclosure. 
     Referring to  FIG.  4   , the wireless protocol of the next-generation mobile communication system includes NR service data adaptation protocols (SDAPs)  403  and  445 , NR PDCPs  405  and  440 , NR RLCs  410  and  435 , and NR MACs  415  and  430  in a terminal  401  and an NR base station  402 , respectively. 
     The main functions of the NR SDAPs  403  and  445  may include some of the following functions: 
     Function of delivering user data (Transfer of user plane data);   Function of mapping between a QoS flow and a data bearer for both uplink and downlink (Mapping between a QoS flow and a data radio bearer (DRB) for both DL and UL);   Function of marking a QoS flow ID for both DL and UL (Marking QoS flow ID in both DL and UL packets); and   Function of mapping a reflective QoS flow to a data bearer for uplink SDAP PDUs (Reflective QoS flow to DRB mapping for the UL SDAP PDUs).   

     In relation to an SDAP layer device, the terminal  401  may receive a radio resource control (RRC) message including a configuration of whether to use a header or function of the SDAP layer device for each PDCP layer device, bearer, or local channel. If an SDAP header is configured, through a one-bit non-access stratum (NAS) reflective QoS indicator of the SDAP header and a one-bit access stratum (AS) reflective QoS indicator thereof, the terminal  401  may be instructed to update or reconfigure information on mapping between a QoS flow of an uplink and a downlink and a data bearer. The SDAP header may include QoS flow ID information which indicates QoS. QoS information may be used as a data processing priority, scheduling information, and the like for supporting a smooth service. 
     The main functions of the NR PDCPs  405  and  440  may include some of the following functions:
     Function of compressing and decompressing a header (Header compression and decompression: ROHC only);   Function of transmitting user data (Transfer of user data);   Sequential delivery function (In-sequence delivery of upper layer PDUs);   Non-sequential delivery function (Out-of-sequence delivery of upper layer PDUs);   Reordering function (PDCP PDU reordering for reception);   Duplicate detection function (Duplicate detection of lower layer SDUs);   Retransmission function (Retransmission of PDCP SDUs);   Function for encryption and decryption (Ciphering and deciphering); and   Timer-based SDU discard function (Timer-based SDU discard in uplink).   

     In the above description, the reordering function of the NR PDCPs  405  and  440  may signify a function of rearranging PDCP PDUs, received in a lower layer, in order on the basis of a PDCP sequence number (SN). The reordering function of the NR PDCPs  405  and  440  may include: a function of delivering data to a higher layer in the rearranged order; a function of directly delivering data without considering an order; a function of recording PDCP PDUs lost by rearranging an order; a function of reporting a state of the lost PDCP PDUs to a transmission side; and a function of requesting the retransmission of the lost PDCP PDUs. 
     The main functions of the NR RLCs  410  and  435  may include some of the following functions: 
     Data transmission function (Transfer of upper layer PDUs);   Sequential delivery function (In-sequence delivery of upper layer PDUs);   Non-sequential delivery function (Out-of-sequence delivery of upper layer PDUs);   ARQ function (Error Correction through ARQ);   Function for concatenation, segmentation, and reassembly (Concatenation, segmentation and reassembly of RLC SDUs);   Re-segmentation function (Re-segmentation of RLC data PDUs);   Reordering function (Reordering of RLC data PDUs);   Duplicate detection function (Duplicate detection);   Error detection function (Protocol error detection);   RLC SDU discard function (RLC SDU discard); and   RLC re-establishment function (RLC re-establishment).   

     In the above description, the in-sequence delivery function of the NR RLC device may signify a function of delivering RLC SDUs received from a lower layer to a higher layer in order. If multiple RLC SDUs divided from a single original RLC SDU are received, the in-sequence delivery function of the NR RLC device may include a function of reassembling and delivering the received multiple RLC SDUs. 
     The in-sequence delivery function of the NR RLC device may include: a function of rearranging the received RLC PDUs in order with reference to an RLC SN or a PDCP SN; a function of recording RLC PDUs lost by rearranging an order; a function of reporting a state of the lost RLC PDUs to a transmission side; and a function of requesting the retransmission of the lost RLC PDUs. 
     The in-sequence delivery function of the NR RLC device may include a function of delivering only the RLC SDUs before the lost RLC SDU to the higher layer in order if there is the lost RLC SDU. 
     The in-sequence delivery function of the NR RLC device may include a function of delivering all the received RLC SDUs to the higher layer in order before a predetermined timer starts if the predetermined timer expires although there is the lost RLC SDU. 
     The in-sequence delivery function of the NR RLC device may include a function of delivering all the RLC SDUs received until now to the higher layer in order if the predetermined timer expires although there is the lost RLC SDU. 
     The NR RLC device may process RLC PDUs in the reception order of the RLC PDUs regardless of the order of sequence numbers (out-of-sequence delivery), and may deliver the processed RLC PDUs to the NR PDCP device. 
     If the NR RLC device is to receive a segment, the NR RLC device may receive the segments stored in a buffer or to be later received, may reconfigure the RLC PDUs into one complete RLC PDU, and may then deliver the complete RLC PDU to the NR PDCP device. 
     The NR RLC layer may not include the concatenation function, and the function may be performed in the NR MAC layer or may be replaced by the multiplexing function of the NR MAC layer. 
     In the above description, the out-of-sequence delivery function of the NR RLC device may signify a function of directly delivering the RLC SDUs received from the lower layer to the higher layer regardless of order. If multiple RLC SDUs divided from a single original RLC SDU are received, the out-of-sequence delivery function of the NR RLC device may include a function of reassembling and delivering the received multiple RLC SDUs. The out-of-sequence delivery function of the NR RLC device may include a function of storing and reordering RLC SNs or PDCP SNs of the received RLC PDUs so as to record the lost RLC PDUs. 
     The NR MACs  415  and  430  may be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of the NR MACs  415  and  430  may include some of the following functions:
     Mapping function (Mapping between logical channels and transport channels);   Function for multiplexing and demultiplexing (Multiplexing/demultiplexing of MAC SDUs);   Function of reporting scheduling information (Scheduling information reporting);   HARQ function (Error correction through HARQ);   Function of adjusting a priority between local channels (Priority handling between logical channels of one UE);   Function of adjusting a priority between terminals (Priority handling between UEs by means of dynamic scheduling);   Function of identifying an MBMS service (MBMS service identification);   Function of selecting a transmission format (Transport format selection); and   Padding function (Padding).   

     The NR PHY layers  420  and  425  may channel-code and modulate higher layer data, may make the higher layer data as an OFDM symbol and may transmit the same to a radio channel, or may demodulate and channel-decode the OFDM symbol, received through the radio channel, and may deliver the demodulated and channel-decoded OFDM symbol to the higher layer. 
       FIG.  5    is a signal flow diagram illustrating: a procedure in which a base station  502  releases a connection with a terminal  501  so that the terminal  501  switches from an RRC connected mode to an RRC idle mode; and a procedure in which the terminal  501  establishes a connection with the base station  502  so that the terminal switches from an RRC idle mode to an RRC connected mode, according to an embodiment of the disclosure. 
     According to an embodiment, in operation  505 , if the terminal  501  transmitting and receiving data does not transmit or receive data for a predetermined reason or for a predetermined time in the RRC connected mode, the base station  502  may transmit an RRC connection release message (RRCConnectionRelease message) to the terminal  501  so as to switch the terminal  501  to the RRC idle mode. If the terminal  501  for which no connection is currently established (hereinafter “idle mode UE”) generates data to be later transmitted/received, the terminal  501  may perform an RRC connection establishment procedure with the base station  502 . 
     In operation  510 , the terminal  501  establishes uplink transmission synchronization with the base station  502  through a random access procedure, and transmits an RRC connection request message (RRCConnectionRequest message) to the base station  502 . The RRCConnectionRequest message may include a reason (establishmentCause), for which a connection with an identifier of the terminal  501  is to be established, and the like. 
     In operation  515 , the base station  502  transmits an RRC connection setup massage (RRCConnectionSetup message) so as to allow the terminal  501  to set up an RRC connection. The RRCConnectionSetup message may include RRC connection configuration information and the like. The RRC connection is also referred to as a “signaling radio bearer (SRB)”, and may be used to transmit or receive an RRC message which is a control message between the terminal  501  and the base station  502 . 
     In operation  520 , the terminal  501  having set up the RRC connection transmits an RRC connection setup complete message (RRCConnetionSetupComplete message) to the base station  502 . The message includes a control message called a service request that allows the terminal  501  to request an MME or an access mobility management function (AMF)  503  for a bearer setup for a predetermined service. 
     In operation  525 , the base station  502  transmits a service request message included in the RRCConnectionSetupComplete message to the MME or AMF  503 , and the MME or AMF  503  may determine whether to provide the service requested by the terminal  501 . 
     In operation  530 , if it is determined that the service requested by the terminal  501  is to be provided, the MME or AMF  503  may transmit an initial context setup request message to the base station  502 . 
     The initial context setup request message may include information, such as QoS information to be applied during setup of a DRB and security-related information (e.g., a security key and a security algorithm) to be applied to the DRB. 
     In order to establish security, the base station  502  may exchange a SecurityModeCommand message (as indicated by reference numeral  535 ) and a SecurityModeComplete message (as indicated by reference numeral  540 ) with the terminal  501 . 
     In operation  545 , if the security establishment is completed, the base station  502  may transmit an RRC connection reconfiguration message (RRCConnectionReconfiguration message) to the terminal  501 . The RRCConnectionReconfiguration message may include configuration information of a DRB which is to process user data. In operation  550 , the terminal  501  may apply the information so as to set up the DRB, and may transmit an RRC connection reconfiguration complete message (RRCConnectionReconfigurationComplete message) to the base station  502 . 
     In operation  555 , the base station  502  having completed the DRB setup with the terminal  501  may transmit an initial context setup complete message to the MME or AMF  503 . In operations  560  and  565 , in order to setup an S1 bearer, the MME or AMF  503  having received the initial context setup complete message may exchange an S1 bearer setup message and an S1 bearer setup response message with an S-GW or a user plane function (UPF)  504 . The S1 bearer may be a data transmission connection established between the S-GW or UPF  504  and the base station  502 , and may correspond one-to-one to a DRB. 
     In operations  570  and  575 , if all of the procedures are completed, the terminal  501  may transmit or receive data to/from the base station  502  through the S-GW or UPF  504 . As described above, the normal data transmission procedure may largely include three stages: RRC connection setup; security establishment; and DRB setup. 
     Further, in operation  580 , the base station  502  may transmit an RRCConnectionReconfiguration message to the terminal  501  so as to renew, add, or change the configuration in relation to the terminal  501  for a predetermined reason. 
     As described above, the terminal  501  may need multiple signaling procedures to set up an RRC connection so as to switch from an RRC idle mode to an RRC connected mode. Therefore, the next-generation mobile communication system may newly define an RRC inactive mode. As described above, in the new mode, the terminal  501  and the base station  502  may store a context of the terminal (UE AS CONTEXT), and may maintain an S1 bearer if necessary. Therefore, if an RRC inactive mode terminal attempts to reconnect to a network, the RRC inactive mode terminal performs an RRC connection resume process proposed as described below, and thus the terminal can more quickly access the network through fewer signaling procedures so as to transmit or receive data. 
       FIG.  6    is a signal flow diagram illustrating: a procedure in which a base station  602  releases a connection with a terminal  601  so that the terminal  601  switches from an RRC connected mode to an RRC inactive mode; and a procedure in which the terminal  601  establishes a connection with the base station  602  so that the terminal  601  switches from an RRC inactive mode to an RRC connected mode, according to an embodiment of the disclosure. 
     Referring to  FIG.  6   , the terminal  601 , together with the base station  602 , may establish a connection with a network (not shown), and may transmit or receive data through the network. If the base station  602  needs to cause the terminal  601  to transition to an RRC inactive mode for a predetermined reason, the base station  602  may transmit an RRCRelease message  605  including suspend configuration information (suspendConfig) so as to cause the terminal  601  to transition to the RRC inactive mode. 
     If receiving the RRCRelease message  605  including the suspend configuration information, proposed operations of the terminal  601  are as follows: 
     1. If the RRCRelease message includes the suspend configuration information (suspendConfig), 
     A. If a terminal connection resume identity (resumeIdentity), a NexthopChainingCount (NCC), a radio access network (RAN) paging cycle (ran-PagingCycle), and RAN notification area information (ran-NotificationAreaInfo), which have already been stored in the terminal, exist, 
     i. The terminal may cause new values included in the suspend configuration information of the RRCRelease message to replace the stored values, or may update the stored values. 
     B. If the terminal connection resume identity (resumeIdentity), the NexthopChainingCount (NCC), the RAN paging cycle (ran-PagingCycle), and the RAN notification area information (ran-NotificationAreaInfo), which have already been stored in the terminal  601 , do not exist, 
     i. The terminal may store a terminal connection resume identity (resumeIdentity), a NexthopChainingCount (NCC), a RAN paging cycle (ran-PagingCycle), and RAN notification area information (ran-NotificationAreaInfo), which are included in the suspend configuration information of the RRCRelease message. 
     C. Further, the terminal may reset a MAC layer device. This configuration has a purpose for which, when a connection is again resumed, the terminal does not unnecessarily retransmit data stored in a HARQ buffer. 
     D. Further, for all SRBs and DRBs, the terminal may re-establish RLC layer devices. This configuration has a purpose for which, when a connection is again resumed, the terminal does not unnecessarily retransmit data stored in an RLC buffer and initializes variables to be later used. 
     E. In the above description, if the RRCRelease message having the suspend configuration information is not received as a response to an RRCResumeRequest message, 
     i. The terminal may store a context of the terminal. The context of the terminal may include current RRC configuration information, current security context information, PDCP state information including ROHC state information, SDAP configuration information, a terminal cell identity (C-RNTI) having been used in a source cell (source PCell), and a cell identity (CellIdentity) and a physical cell identity of a source cell (PCell). 
     F. Further, the terminal may suspend all SRBs and DRBs except for SRB0. 
     G. Further, the terminal may start a T380 timer by using a value of a periodic RAN notification area update timer (periodic-RNAU-timer) included in the suspend configuration information (suspendConfig). 
     H. Further, the terminal may report suspension of an RRC connection to a higher layer. 
     I. Further, the terminal may configure lower layer devices so as to stop a function for integrity protection and encryption. 
     J. Further, the terminal may transition to an RRC inactive mode. 
     In the above description, if the RRCRelease message  605  includes carrier redirection information (redirectedCarrierInfo), when the terminal  601  having transitioned to the RRC inactive mode finds a cell  615 , on which the terminal  601  is to camp, by searching for a suitable cell through execution of a cell selection procedure according to the redirectedCarrierInfo, the terminal  601  may identify system information  620  of the cell. The system information  620  includes T319 timer information and the like. If the terminal  601  fails to find a suitable cell, the terminal  601  may find a cell  615 , on which the terminal  601  is to camp, by searching for a suitable cell in the indicated radio access network (RAN). If the cell  615 , on which the terminal  601  is to camp, is found, the terminal  601  may identify system information  620  of the cell. If the RRCRelease message  605  does not include carrier redirection information, the terminal  601  should find a cell, on which the terminal  601  is to camp, by searching for a suitable cell in NR carriers. If the cell, on which the terminal  601  is to camp, is found, the terminal  601  may identify system information  620  of the cell. 
     If the terminal  601  fails to find a suitable cell by using the above-described methods so as to fail to find a cell on which the terminal  601  is to camp, the terminal  601  may search for a suitable cell through execution of a cell selection procedure on the basis of information, stored in the terminal  601 , so as to find a cell  615  , on which the terminal  601  is to camp. If the cell  615 , on which the terminal  601  is to camp, is found, the terminal  601  may identify system information  620  of the cell  615 . In the disclosure, a suitable cell may be defined as a cell satisfying the following conditions. 
     Suitable Cell 
     A cell is considered as suitable if the following conditions are fulfilled: 
     The cell is part of either   the selected public land mobile network (PLMN), or   a PLMN of the equivalent PLMN list;   The cell selection criteria are fulfilled;   A cell is served by the selected/registered PLMN and not barred;   According to the latest information provided by NAS:   The cell is not barred; and   The cell is part of at least one TA that is not part of the list of “forbidden tracking areas”, which belongs to a PLMN that fulfils the first bullet above.   

     In the disclosure, if the terminal  601  having transitioned to the RRC inactive mode camps on a suitable cell, the terminal  601  may be in a camped normally state. A terminal in a camped normally state may usually receive a general service from a network, and may perform the following operations: 
     Selecting and monitoring the indicated paging channels of the cell according to information sent in system information;   Monitoring relevant system information;   Performing necessary measurements for the cell reselection evaluation procedure; and   Executing the cell reselection evaluation process on the following occasions/triggers   1) UE internal triggers, so as to meet performance, and   2) If information on the broadcast control channel (BCCH) used for the cell reselection evaluation procedure has been modified.   

     The disclosure may propose a configuration in which, if the terminal  601  having transitioned to the RRC inactive mode fails to find a suitable cell through the above-described procedure, or if the terminal  601  camps on an acceptable cell so as to operate in an RRC connected mode and switches an RRC inactive mode, the terminal  601  finds a cell, on which the terminal  601  is to camp, by searching for an acceptable cell through execution of a cell selection procedure. That is, the configuration may be characterized in that, if the above-described conditions are satisfied, the terminal  601  having transitioned to the RRC inactive mode maintains the RRC inactive mode without transitioning to an RRC idle mode. 
     If the terminal  601  having transitioned to the RRC inactive mode fails to find a suitable cell according to the above-described procedure and conditions, if the RRCRelease message  605  includes carrier redirection information (redirectedCarrierInfo), the terminal  601  may find a cell  615  , on which the terminal  601  is to camp, by searching for an acceptable cell through execution of a cell selection procedure according to the redirectedCarrierInfo. If the cell  615 , on which the terminal  601  is to camp, is found, the terminal  601  may identify system information  620  of the cell  615 . The system information  620  may include T319 timer information and the like. If the terminal  601  fails to find an acceptable cell, the terminal  601  may find a cell  615 , on which the terminal  601  is to camp, by searching for an acceptable cell in the indicated RAN. If the cell  615 , on which the terminal  601  is to camp, is found, the terminal  601  may identify system information  620  of the cell  615 . If the RRCRelease message  605  does not include carrier redirection information, the terminal  601  should find a cell, on which the terminal  601  is to camp, by searching for an acceptable cell in NR carriers. If the cell, on which the terminal  601  is to camp, is found, the terminal  601  may identify system information  620  of the cell. If the terminal  601  fails to find an acceptable cell by using the above-described methods so as to fail to a cell on which the terminal  601  is to camp, the terminal  601  may search for an acceptable cell in all public land mobile networks (PLMNs) in any cell selection state. If a cell, on which the terminal  601  is to camp, is found, the terminal  601  may identify system information  620  of the cell. In the disclosure, an acceptable cell may be defined as a cell which can be accepted if the following conditions are satisfied. 
     Acceptable Cell 
     An “acceptable cell” is a cell on which the UE may camp to obtain limited services (originate emergency calls and receive earthquake and tsunami warning system (ETWS) and commercial mobile alert service (CMAS) notifications). Such a cell shall fulfil the following requirements, which are the minimum set of requirements to initiate an emergency call and receive ETWS and CMAS notification in an NR network: 
     The cell is not barred; and   The cell selection criteria are fulfilled.   

     Further, in the disclosure, if the terminal  601  having transitioned to the RRC inactive mode camps on an acceptable cell, the terminal  601  may be in a camped on any cell state. The terminal  601  may be in the camped on any cell state may receive, from a network, only limited services, including an emergency call, reception of disaster information, and the like, and may perform the following operations: 
     Selecting and monitoring the indicated paging channels of the cell;   Monitoring relevant system information;   Performing necessary measurements for the cell reselection evaluation procedure;   Executing the cell reselection evaluation process on the following occasions/triggers   1) UE internal triggers, so as to meet performance, and   2) If information on the BCCH used for the cell reselection evaluation procedure has been modified; and   

     Regularly attempting to find a suitable cell trying all frequencies of all RATs that are supported by the UE. If a suitable cell is found, UE shall move to camped normally state. 
     If the terminal  601  in the RRC inactive mode receives, in operation 1f-25, a core network (CN) paging message while moving, the terminal  601  may transition to an RRC idle mode, and may provide notification to a non-access stratum (NAS) of the transition. If the terminal  601  in the RRC inactive mode receives, in operation 1f-25, a RAN paging message while moving, the terminal  601  may perform an RRC connection resume procedure with a base station  602 . 
     If the terminal  601  performs a random access procedure in order to perform the RRC connection resume procedure with the base station  602  and transmits an RRCResumeRequest message to the base station  602 , proposed operations of the terminal  601  in operation 1f-30 are as follows. 
     1. The terminal may identify system information, and if the system information indicates transmission of a complete terminal connection resume identity (I-RNTI or full resume ID), may include a stored complete terminal connection resume identity (I-RNTI) in a message so as to prepare for transmission thereof. If the system information indicates transmission of a truncated terminal connection resume identity (truncated I-RNTI or truncated resume ID), the terminal may configure a terminal connection resume identity (truncated resume ID) truncated from the stored complete terminal connection resume identity (I-RNTI) by using a predetermined method, and may include the same in a message so as to prepare for transmission thereof. 
     2. The terminal may reconstruct RRC connection setup information and security context information from a stored terminal context. 
     3. Further, the terminal may update a new KgNB security key on the basis of a current KgNB security key, a NextHop (NH) value, and a stored NCC value. 
     4. Further, the terminal may derive new security keys (K_RRCenc, K_RRC_int, K_UPint, and K_UPenc) to be used in an integrity protection and verification procedure and an encryption and decryption procedure by using the newly-updated KgNB security key. 
     5. Further, the terminal may calculate MAC-I and may include the same in a message so as to prepare for transmission thereof. 
     6. Further, the terminal may resume SRB1 (since an RRCResume message is to be received on SRB1, as a response to an RRCResumeRequset message to be transmitted, SRB1 should be resumed in advance). 
     7. The terminal may configure an RRCResumeRequset message and may deliver the same to a lower layer device. 
     8. The terminal may apply the updated security keys and a previously-configured algorithm to all bearers except for SRB0 so as to resume an integrity protection and verification procedure, and may apply integrity verification and protection to subsequently transmitted and received data. This configuration has a purpose for increasing the reliability and security of data subsequently transmitted or received on SRB1 or DRBs. 
     9. The terminal may apply the updated security keys and a previously-configured algorithm to all bearers except for SRB0 so as to resume an encryption and decryption procedure, and may apply encryption and decryption to subsequently transmitted and received data. This configuration has a purpose for increasing the reliability and security of data subsequently transmitted or received on SRB1 or DRBs. 
     In the above description, when the terminal  601  needs to establish a connection so as to perform a random access procedure, transmits an RRCResumeRequest message to the base station  602 , and then receives an RRCResume message as a response to the RRCResumeRequest message, proposed operations of the terminal  601  in operation  635  are as follows. 
     1. If transmitting an RRCResumeRequest message to the base station, the terminal stops a started T319 timer. 
     2. Upon receiving a message, the terminal may restore a PDCP state, may reset COUNT value, and may re-establish PDCP layer devices of SRB2 and all DRBs. 
     3. If the message includes master cell group (masterCellgroup) configuration information, 
     A. The terminal may perform an operation according to the master cell group configuration information included in the message, and may apply the master cell group configuration information. The master cell group configuration information may include configuration information for RLC layer devices belonging to a master cell group, a logical channel identifier, a bearer identifier, and the like. 
     4. If the message includes bearer configuration information (radioBearerConfig), 
     A. The terminal may perform an operation according to the bearer configuration information (radioBearerConfig) included in the message, and may apply the bearer configuration information. The bearer configuration information (radioBearerConfig) may include configuration information for PDCP layer devices for respective bearers, configuration information for SDAP layer devices, a logical channel identifier, a bearer identifier, and the like. 
     5. The terminal may resume SRB2 and all DRBs. 
     6 If the message includes frequency measurement configuration information (measConfig), 
     A. The terminal may perform an operation according to the frequency measurement configuration information included in the message, and may apply the frequency measurement configuration information. That is, the terminal may perform frequency measurement according to a configuration. 
     7. The terminal may transition to an RRC connected mode. 
     8. The terminal may notify a higher layer device of resumption of the released RRC connection. 
     9. Further, in operation  640 , the terminal may configure and deliver an RRCResumeComplete message for transmission of a lower layer. 
     Further, in operation  645 , the terminal  601  may transmit or receive data to/from the base station  602 . 
       FIG.  7    is a flowchart illustrating an operation of a terminal for monitoring a short message or a paging message when the terminal is in an RRC idle mode or an RRC inactive mode according to an embodiment of the disclosure. 
     According to an embodiment, in operation  705 , the terminal  701  in an RRC idle mode or an RRC inactive mode may perform a cell selection procedure or a cell reselection procedure, and thus may camp on a cell. 
     If the terminal  701  camps on an LTE cell in operation  705 , in operation  710 , the terminal  701  may receive a paging message regardless of a camped normally state or a camped on any cell state. The terminal  701  determines whether a paging message exists, by monitoring a physical downlink control channel (PDCCH) on the basis of a paging-radio network temporary identifier (P-RNTI) in a paging occasion of the terminal  701  at every discontinuous reception (DRX) cycle. If a paging message exists, in operation  715 , the terminal  701  receives a paging message. 
     If the terminal 1g-01 camps on an NR cell in operation  705 , in operation  720 , the terminal  701  determines whether the terminal  701  is in a camped normally state or a camped on any cell state. If it is determined in operation  720  that the terminal  701  is in the camped normally state, in operation  725 , the terminal  701  determines whether a short message or a paging message exists, by monitoring a PDCCH on the basis of a P-RNTI in a paging occasion of the terminal  701  at every DRX cycle. If a short message or a paging message exists, in operation  730 , the terminal  701  receives the relevant message. The relevant message may include only a short message, may include only a paging message, or may include both a short message and a paging message. If it is determined in operation  720  that the terminal  701  is in the camped on any cell state, in operation  735 , the terminal  701  determines whether a short message exists, by monitoring a PDCCH on the basis of a P-RNTI in a paging occasion of the terminal  701   at every DRX cycle. If a short message exists, in operation  740 , the terminal  701  receives the short message. That is, this configuration may be characterized in that, if the terminal  701  is in the camped on any cell state, the terminal  701  does not monitor a paging message. In the disclosure, a short message may be defined as follows. 
     Short messages may be transmitted on a PDCCH using a P-RNTI with or without an associated paging message using a short message field in download control information (DCI)format 1_0. The Table 1 below defines short messages. Bit 1 is the most significant bit.  
     
       
         
          TABLE 1
           
               
               
             
               
                 Bit 
                 Short message 
               
             
            
               
                 1 
                 systemInfoModification If set to 1. indication of a BCCH modification other than SIB6, SlB7 and SIB8. 
               
               
                 2 
                 etwsAndCmaslndication If set to 1 : indication of an ETWS primary notification and/or an ETWS secondary notification and/or a CMASnotification. 
               
               
                 3-[8] 
                 Not used in this release of the specification and shall be ignored by UE if received 
               
            
           
         
       
     
       FIG.  8    is a flowchart illustrating an operation of a terminal for monitoring a short message or a paging message while the terminal is in an RRC idle mode or an RRC inactive mode according to an embodiment of the disclosure. 
     According to an embodiment, in operation  805 , the terminal  801  in an RRC idle mode or an RRC inactive mode may perform a cell selection procedure or a cell reselection procedure, and thus may camp on a cell. 
     If the terminal  801  camps on an LTE cell in operation  805 , in operation  810 , the terminal  801  may receive a paging message regardless of a camped normally state or a camped on any cell state. The terminal  801  determines whether a paging message exists, by monitoring a PDCCH on the basis of a P-RNTI in a paging occasion of the terminal  801  at every DRX cycle. If a paging message exists, in operation  815 , the terminal  801  receives a paging message. 
     If the terminal  801  camps on an NR cell in operation  805 , in operation  820 , the terminal  801  determines whether the terminal  801  is in a camped normally state or a camped on any cell state. If it is determined in operation  820  that the terminal 1h-01 is in the camped normally state, in operation  825 , the terminal  801  determines whether a short message or a paging message exists, by monitoring a PDCCH on the basis of a P-RNTI in a paging occasion of the terminal  801  at every DRX cycle. If a short message or a paging message exists, in operation  830 , the terminal  801  receives the relevant message. The relevant message may include only a short message, may include only a paging message, or may include both a short message and a paging message. If it is determined in operation  820  that the terminal  801  is in the camped on any cell state, in operation  835 , the terminal  801  determines whether a PLMN of the relevant cell corresponds to a registered PLMN (RPLMN) list or an equivalent PLMN (EPLMN) list. If the PLMN of the relevant cell corresponds to an RPLMN list or an EPLMN list, in operation  840 , the terminal  801  determines whether a short message or a paging message exists, by monitoring a PDCCH on the basis of a P-RNTI in a paging occasion of the terminal  801  at every DRX cycle. If a short message or a paging message exists, in operation  845 , the terminal  801  receives the relevant message. The relevant message may include only a short message, may include only a paging message, or may include both a short message and a paging message. If the PLMN of the relevant cell does not correspond to an RPLMN list or an EPLMN list  835 , in operation  850 , the terminal  801  determines whether a short message exists, by monitoring a PDCCH on the basis of a P-RNTI in a paging occasion of the terminal  801  at every DRX cycle. If a short message exists, in operation  855 , the terminal  801  receives the relevant message. 
       FIG.  9    is a flowchart illustrating an operation of a terminal when receiving a short message while the terminal is in an RRC idle mode or an RRC inactive mode according to an embodiment of the disclosure. 
     According to an embodiment, in operation  905 , the terminal  901  in an RRC idle mode or an RRC inactive mode may receive a short message from a cell on which the terminal  901  camps. When the terminal  901  receives a short message in operation  905 , in operation  910 , if the relevant message includes a bit named “earthquake and tsunami warning system and commercial mobile alert service (etwsAndCmasIndication)” set to 1, the terminal  901  may immediately and newly identify SIB1 from the relevant cell. If system information scheduling information (si-SchedulingInfo) included in the received SIB 1 includes scheduling information of SIB6, SIB7, or SIB8 in operation 1i-10, in operation  915 , the terminal li-01 may identify SIB6, SIB7, or SIB8. When the terminal  901  receives a short message in operation  905 , if the relevant message includes a systemInfoModification bit set to 1, in operation  920 , the terminal  901  performs a procedure for identifying system information from a start point of a next modification period. 
       FIG.  10    is a block diagram illustrating a configuration of a terminal according to an embodiment of the disclosure. 
     The terminal  1000  may include a radio frequency (RF) processor  1010 , a baseband processor  1020 , a storage unit  1030 , a controller  1040 , and a transceiver (not shown). 
     The RF processor  1010  according to an embodiment may serve to transmit or receive a signal through a wireless channel, such as band conversion and amplification of a signal. That is, the RF processor  1010  may up-convert a baseband signal provided by the baseband processor 1j-20 into an RF band signal and may then transmit the RF band signal through an antenna and may down-convert an RF band signal received through the antenna into a baseband signal. For example, the RF processor  1010  may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), or the like. 
     Referring to  FIG.  10   ,  FIG.  10    illustrates only one antenna, but the terminal may be provided with multiple antennas. 
     Also, the RF processor  1010  may include multiple RF chains. Further, the RF processor  1010  may perform beamforming. For the beamforming, the RF processor  1010  may adjust a phase and a magnitude of each of the signals transmitted or received through multiple antennas or antenna elements. Further, the RF processor  1010  may perform MIMO and may receive multiple layers during execution of a MIMO operation. The RF processor  1010  may perform reception beam sweeping by appropriately configuring the multiple antennas or antenna elements under the control of the controller  1040 , or may adjust the direction and beam width of a reception beam so that the reception beam is coordinated with a transmission beam. 
     The baseband processor  1020  may perform a conversion function between a baseband signal and a bit stream according to a physical layer standard of a system. For example, when data is transmitted, the baseband processor  1020  may generate complex symbols by encoding and modulating a transmission bit stream. Further, when data is received, the baseband processor  1020  may reconstruct a received bit stream by demodulating and decoding the baseband signal provided by the RF processor  1010 . For example, according to an orthogonal frequency division multiplexing (OFDM) scheme, when data is transmitted, the baseband processor  1020  may generate complex symbols by encoding and modulating a transmission bit stream, may map the complex symbols to subcarriers, and may then perform an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion to configure OFDM symbols. Further, when data is received, the baseband processor  1020  may divide the baseband signal provided by the RF processor  1010  in an OFDM symbol unit, may reconstruct the signals mapped to the subcarriers by a fast Fourier transform (FFT), and may then reconstruct a received bit stream by the demodulation and decoding. 
     The baseband processor  1020  and the RF processor  1010  may transmit and receive a signal as described above. Therefore, the baseband processor  1020  and the RF processor  1010  may be referred to as a “transmitter”, a “receiver”, a “transceiver”, or a “communication unit”. Also, at least one of the baseband processor  1020  and the RF processor  1010  may include multiple communication modules in order to support multiple different radio access technologies (RATs). Further, at least one of the baseband processor  1020  and the RF processor  1010  may include different communication modules in order to process signals in different frequency bands. For example, the different RATs may include an LTE network, an NR network, and the like. The different frequency bands may include a super high frequency (SHF) (e.g., 2.2 GHz and 2 GHz) band and an mmWave (e.g., 60 GHz) band. 
     The storage unit  1030  may store data such as basic programs, application programs, and configuration information for an operation of the terminal. Also, the storage unit  1030  may provide the stored data in response to a request of the controller 1j-40. 
     The controller  1040  may control overall operations of the terminal. For example, the controller  1040  may transmit or receive a signal through the baseband processor  1020  and the RF processor  1010 . Further, the controller  1040  may record and read data in and from the storage unit  1040 . To this end, the controller  1040  may include at least one processor. For example, the controller  1040  may include a multi-connectivity processor  1042  configured to control multiple connections, a communication processor (CP) configured to perform a control for communication and an application processor (AP) configured to control a higher layer such as an application program. 
     Alternatively, the transceiver may be implemented as a transmitter and a receiver, and each component may be implemented through one or more processors. The transceiver is configured to receive and transmit signal, data and control information associated with paging monitoring method or reporting a connection setup failure method. 
     The controller  1040  is configured to identify the UE is in a camped on any cell state or a camped normally state, monitor a short message in case that the UE is in the camped on any cell state, and monitor a short message and a paging message in case that the UE is in the camped normally state. 
     The camped on any cell state is only applicable for RRC_IDLE state. 
     The camped normally state is applicable for RRC_IDLE and RRC_INACTIVE state. 
     The short message is received on a physical downlink control channel (PDCCH) using paging radio network temporary identifier (P-RNTI). 
     The short message is received via downlink control information (DCI) with or without scheduling information for the paging message. 
       FIG.  11    is a block diagram illustrating a configuration of a base station according to an embodiment of the disclosure. 
     The base station  1100  according to an embodiment may include at least one transmission reception point (TRP). 
     The base station  1100  according to an embodiment may include an RF processor  1110 , a baseband processor  1120 , a backhaul communication unit  1130 , a storage unit  1140 , a controller  1150 , and a transceiver (not shown). 
     The RF processor  1110  may serve to transmit or receive a signal through a wireless channel, such as band conversion and amplification of a signal. That is, the RF processor  1110  may up-convert a baseband signal provided by the baseband processor  1120  into an RF band signal and may then transmit the RF band signal through an antenna and may down-convert an RF band signal received through the antenna into a baseband signal. For example, the RF processor  1110  may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, or the like. 
     Referring to  FIG.  11   ,  FIG.  11    illustrates only one antenna  1160  but the base station may be provided with multiple antennas. 
     Also, the RF processor  1110  may include multiple RF chains. Further, the RF processor  1110  may perform beamforming. For the beamforming, the RF processor  1110  may adjust a phase and a magnitude of each of the signals transmitted or received through multiple antennas or antenna elements. The RF processor  1110  may be configured to transmit one or more layers for a downlink MIMO operation. 
     The baseband processor  1120  may perform a conversion function between a baseband signal and a bit stream according to a physical layer standard of first radio access technology. For example, when data is transmitted, the baseband processor  1120  may generate complex symbols by encoding and modulating a transmission bit stream. Further, when data is received, the baseband processor  1120  may reconstruct a received bit stream by demodulating and decoding the baseband signal provided by the RF processor  1110 . For example, according to an OFDM scheme, when data is transmitted, the baseband processor  1120  may generate complex symbols by encoding and modulating a transmission bit stream, may map the complex symbols to subcarriers, and may then perform an IFFT operation and a CP insertion to configure OFDM symbols. Further, when data is received, the baseband processor  1120  may divide the baseband signal provided by the RF processor  1110  in an OFDM symbol unit, may reconstruct the signals mapped to the subcarriers by a fast Fourier transform (FFT) operation, and may then reconstruct a received bit stream by the modulation and decoding. The baseband processor  1120  and the RF processor  1110  may transmit and receive signals as described above. 
     Accordingly, the baseband processor  1120  and the RF processor  1110  may be referred to as a “transmitter”, a “receiver”, a “transceiver”, a “communication unit”, or a “wireless communication unit”. 
     The backhaul communication unit  1130  may provide an interface for communication with other nodes in a network. 
     The storage unit  1140  may store data such as basic programs, application programs, and configuration information for an operation of the primary base station. In particular, the storage unit  1140  may store information on the bearers allocated to accessed terminals, measurement results reported by the accessed terminals, and the like. Also, the storage unit  1140  may store the information which becomes a standard of determination of whether to provide or stop providing multi-connectivity to a terminal. Further, the storage unit  1140  may provide the stored data according to a request of the controller  1150 . 
     The controller  1150  may control overall operations of the primary base station. For example, the controller  1150  may transmit or receive a signal through the baseband processor  1120  and the RF processor  1110 , or through the backhaul communication unit  1130 . Further, the controller  1150  records and reads data in and from the storage unit  1140 . To this end, the controller  1150  may include at least one processor, such as a multi-connectivity processor  1152  configured to control multiple connections, a CP configured to perform a control for communication and an AP configured to control a higher layer such as an application program. 
     Alternatively, the transceiver may be implemented as a transmitter and a receiver, and each component may be implemented through one or more processors. 
     The transceiver is configured to receive and transmit signal, data and control information associated with paging monitoring method or reporting a connection setup failure method. 
     The controller  1150  is configured to identify whether to transmit a short message and scheduling information for a paging message, control the transceiver to transmit, to a user equipment (UE), the short message on a physical downlink control channel (PDCCH) using paging radio network temporary identifier (P-RNTI) based on the identification, and control the transceiver to transmit, to the UE, the paging message based on the scheduling information in case that the scheduling information is identified to transmit. 
     The short message is monitored by the UE in a camped on any cell state, and the short message and the paging message are monitored by the UE in a camped normally state. 
     The camped on any cell state is only applicable for RRC_IDLE state. 
     The camped normally state is applicable for RRC_IDLE and RRC_INACTIVE state. 
     The short message is transmitted via downlink control information (DCI) with or without the scheduling information for the paging message. 
     Second Embodiment 
       FIG.  12    is a view illustrating an architecture of an LTE system according to an embodiment of the disclosure. 
     Referring to  FIG.  12   , the wireless communication system includes multiple base stations  1205 ,  1210 ,  1215 , and  1220 , a mobility management entity (MME)  1225 , and a serving-gateway (S-GW)  1230 . A user equipment (hereinafter a “UE” or a “terminal”)  1235  accesses an external network through the base stations  1205 ,  1210 ,  1215 , and  1220  and the S-GW  1230 . 
     The base stations  1205 ,  1210 ,  1215 , and  1220  are access nodes of a cellular network and provide radio access to the terminals connected to the network. That is, in order to serve traffic of users, the base stations  1205 ,  1210 ,  1215 , and  1220  collect and schedule pieces of state information such as buffer states, available transmission power states, and channel states of the terminals to support the connection between the terminals and a core network (CN) (not shown). The MME  1225  is an apparatus configured to take charge of various control functions as well as a mobility management function for a terminal and is connected to multiple base stations, and the S-GW  1230  is an apparatus configured to provide a data bearer. Further, the MME  1225  and the S-GW  1230  may further perform authentication, bearer management, and the like on the terminal connected to the network and may process packets which have been received from the base stations  1205 ,  1210 ,  1215 , and  1220  or are to be delivered to the base stations  1205 ,  1210 ,  1215 , and  1220 . 
       FIG.  13    is a view illustrating a wireless protocol structure of an LTE system according to an embodiment of the disclosure. 
     Referring to  FIG.  13   , a wireless protocol of the LTE system includes packet data convergence protocols (PDCPs) 13-05 and  1340 , radio link controls (RLCs)  1310  and  1335 , and medium access controls (MACs)  1315  and  1330  in a terminal  1301  and a base station  1302 , respectively. The PDCPs  1305  and  1340  take charge of operations such as compression/recovery of an IP header. The main functions of the PDCPs  1305  and  1340  are summarized as follows: 
     Function of compressing and decompressing a header (Header compression and decompression: ROHC only);   Function of transmitting user data;   Sequential delivery function (In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM);   Reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception);   Duplicate detection function (Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM);   Retransmission function (Retransmission of PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM);   Function for encryption and decryption (Ciphering and deciphering); and   Timer-based SDU discard function (Timer-based SDU discard in uplink).   

     The RLCs  1310  and  1335  reconfigure a PDCP protocol data unit (PDU) to a suitable size so as to perform an automatic repeat request (ARQ) operation and the like. The main functions of the RLCs  1310  and  1335  are summarized as follows: 
     Data transmission function (Transfer of upper layer PDUs);   ARQ function (Error correction through ARQ (only for AM data transfer));   Function for concatenation, segmentation, and reassembly (Concatenation, segmentation, and reassembly of RLC SDUs (only for UM and AM data transfer));   Re-segmentation function (Re-segmentation of RLC data PDUs (only for AM data transfer));   Reordering function (Reordering of RLC data PDUs (only for UM and AM data transfer);   Duplicate detection function (Duplicate detection (only for UM and AM data transfer));   Error detection function (Protocol error detection (only for AM data transfer));   RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer)); and   RLC re-establishment function (RLC re-establishment).   

     The MACs  1315  and  1330  are connected to multiple RLC layer devices configured in one terminal, and multiplex RLC PDUs into MAC PDUs and demultiplex RLC PDUs from MAC PDUs. The main functions of the MACs  1315  and  1330  are summarized as follows: 
     Mapping function (Mapping between logical channels and transport channels);   Function for multiplexing and demultiplexing (Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TBs) delivered to/from the physical layer on transport channels);   Function of reporting scheduling information;   HARQ function (Error correction through HARQ);   Function of adjusting a priority between local channels (Priority handling between logical channels of one UE);   Function of adjusting a priority between terminals (Priority handling between UEs by means of dynamic scheduling);   Function of identifying an MBMS service (MBMS service identification);   Function of selecting a transmission format (Transport format selection); and   Padding function (Padding).   

     The PHY layers  1320  and  1325  channel-code and modulate higher layer data into OFDM symbols and transmit the OFDM symbols through a wireless channel, or demodulate and channel-decode OFDM symbols, received through a wireless channel, into higher layer data and deliver the higher layer data to a higher layer. 
     Although not illustrated in  FIG.  13   , RRC layers exist as higher layers of the PDCP layers of the terminal  1301  and the base station  1302 , respectively, and the RRC layers may exchange access and measurement-related configuration control messages in order to control radio resources. 
       FIG.  14    is a view illustrating a structure of a next-generation mobile communication system according to an embodiment of the disclosure. 
     Referring to  FIG.  14   , a radio access network of the next-generation mobile communication system includes a next-generation base station (NR Node B, hereinafter “NR gNB” or “NR base station”)  1410  and an NR core network (NR CN)  1405 . A user equipment (NR user equipment) (hereinafter “NR UE” or “terminal”)  1415  accesses an external network through the NR gNB  1410  and the NR CN  1405 . 
     In  FIG.  14   , the NR gNB  1410  corresponds to an evolved Node B (eNB) of the existing LTE system. The NR gNB  1410  is connected to the NR UE  1415  through a wireless channel and may provide a service superior to that provided by the existing Node B. In the next-generation mobile communication system, since all user traffics are served through shared channels, there is a need for an apparatus configured to collect pieces of state information, including buffer states, available transmission power states, channel states, and the like of UEs so as to perform scheduling, and the NR gNB  1410  serves as the apparatus. One NR gNB  1410  usually controls multiple cells, and includes: a central unit (CU) configured to direct control and signaling; and a distributed unit (DU) configured to take charge of transmission/reception of a signal. In order to achieve ultra-high-speed data transmission in comparison to the LTE system, the next-generation mobile communication system may have an existing maximum bandwidth or more, and may use an orthogonal frequency division multiplexing (hereinafter, referred to as “OFDM”) scheme as radio access technology, and beamforming technology may be additionally combined therewith. Further, an adaptive modulation and coding (hereinafter, referred to as “AMC”) scheme for determining a modulation scheme and a channel coding rate so as to match a channel state of a terminal is applied. The NR CN  1405  performs functions, including mobility support, bearer establishment, quality of service (QoS) configuration, and the like. The NR CN  1405  is an apparatus configured to perform various control functions including a mobility management function for a terminal, and is connected to multiple base stations. Further, the next-generation mobile communication system may interwork with the LTE system, and the NR CN  1405  is connected to an MME  1425  of the LTE system through a network interface. The MME  1425  is connected to an eNB  1430  which is an existing base station. 
       FIG.  15    is a block diagram illustrating a structure of a wireless protocol of a next-generation mobile communication system according to an embodiment the disclosure. 
     Referring to  FIG.  15   , the wireless protocol of the next-generation mobile communication system includes NR service data adaptation protocols (SDAPs)  1503  and  1545 , NR PDCPs  1505  and  1540 , NR RLCs  1510  and  1535 , and NR MACs  1515  and  1530  in a terminal  1501  and an NR base station  1502 , respectively. 
     The main functions of the NR SDAPs  1503  and  1545  may include some of the following functions: 
     Function of delivering user data (Transfer of user plane data);   Function of mapping between a QoS flow and a data bearer for both uplink and downlink (Mapping between a QoS flow and a data radio bearer (DRB) for both DL and UL);   Function of marking a QoS flow ID for both uplink and downlink (Marking QoS flow ID in both DL and UL packets); and   Function of mapping a reflective QoS flow to a data bearer for uplink SDAP PDUs (Reflective QoS flow to DRB mapping for the UL SDAP PDUs).   

     In relation to an SDAP layer device, a terminal may receive a radio resource control (RRC) message including a configuration of whether to use a header or function of the SDAP layer device for each PDCP layer device, bearer, or local channel. If an SDAP header is configured, through a one-bit non-access stratum (NAS) reflective QoS indicator of the SDAP header and a one-bit access stratum (AS) reflective QoS indicator thereof, the terminal may be instructed to update or reconfigure information on mapping between a QoS flow of an uplink and a downlink and a data bearer. The SDAP header may include QoS flow ID information which indicates QoS. QoS information may be used as a data processing priority, scheduling information, and the like for supporting a smooth service. 
     The main functions of the NR PDCPs 2d-05 and 2d-40 may include some of the following functions: 
     Function of compressing and decompressing a header (Header compression and decompression: ROHC only);   Function of transmitting user data (Transfer of user data);   Sequential delivery function (In-sequence delivery of upper layer PDUs);   Non-sequential delivery function (Out-of-sequence delivery of upper layer PDUs);   Reordering function (PDCP PDU reordering for reception);   Duplicate detection function (Duplicate detection of lower layer SDUs);   Retransmission function (Retransmission of PDCP SDUs);   Function for encryption and decryption (Ciphering and deciphering); and   Timer-based SDU discard function (Timer-based SDU discard in uplink).   

     In the above description, the reordering function of the NR PDCPs  1505  and  1540  may refer to a function of rearranging PDCP PDUs, received in a lower layer, in order on the basis of a PDCP sequence number (SN), and may include: a function of delivering data to a higher layer in the rearranged order; a function of directly delivering data without considering an order; a function of recording PDCP PDUs lost by rearranging an order; a function of reporting a state of the lost PDCP PDUs to a transmission side; and a function of requesting the retransmission of the lost PDCP PDUs. 
     The main functions of the NR RLCs  1510  and  1535  may include some of the following functions: 
     Data transmission function (Transfer of upper layer PDUs);   Sequential delivery function (In-sequence delivery of upper layer PDUs);   Non-sequential delivery function (Out-of-sequence delivery of upper layer PDUs);   ARQ function (Error Correction through ARQ);   Function for concatenation, segmentation, and reassembly (Concatenation, segmentation and reassembly of RLC SDUs);   Re-segmentation function (Re-segmentation of RLC data PDUs);   Reordering function (Reordering of RLC data PDUs);   Duplicate detection function (Duplicate detection);   Error detection function (Protocol error detection);   RLC SDU discard function (RLC SDU discard); and   RLC re-establishment function (RLC re-establishment).   

     In the above description, the in-sequence delivery function of the NR RLC device may refer to a function of delivering RLC SDUs received from a lower layer to a higher layer in order, and if multiple RLC SDUs divided from a single original RLC SDU are received, may include: a function of reassembling and delivering the received multiple RLC SDUs; a function of rearranging the received RLC PDUs in order with reference to an RLC SN or a PDCP SN; a function of recording RLC PDUs lost by rearranging an order; a function of reporting a state of the lost RLC PDUs to a transmission side; and a function of requesting the retransmission of the lost RLC PDUs. The in-sequence delivery function of the NR RLC device may include a function of delivering only the RLC SDUs before the lost RLC SDU to the higher layer in order if there is the lost RLC SDU. Alternatively, the in-sequence delivery function of the NR RLC device may include a function of delivering all the received RLC SDUs to the higher layer in order before a predetermined timer starts if the timer expires although there is the lost RLC SDU. Alternatively, the in-sequence delivery function of the NR RLC device may include a function of delivering all the RLC SDUs received until now to the higher layer in order if the predetermined timer expires although there is the lost RLC SDU. Further, in the above description, the NR RLC device may process RLC PDUs in the reception order of the RLC PDUs (regardless of the order of sequence numbers and in the arrival order of the RLC PDUs), and may deliver the processed RLC PDUs to the PDCP device regardless of the order of the sequence numbers (out-of-sequence delivery). In the case of a segment, the NR RLC device may receive the segments stored in a buffer or to be later received, may reconfigure the RLC PDUs into one complete RLC PDU, may process the complete RLC PDU, and may then deliver the processed complete RLC PDU to the PDCP device. The NR RLC layer may not include the concatenation function, and the function may be performed in the NR MAC layer or may be replaced by the multiplexing function of the NR MAC layer. 
     In the above description, the out-of-sequence delivery function of the NR RLC device may refer to a function of directly delivering the RLC SDUs received from the lower layer to the higher layer regardless of order, and if multiple RLC SDUs divided from a single original RLC SDU are received, may include: a function of reassembling and delivering the received multiple RLC SDUs; and a function of storing and reordering RLC SNs or PDCP SNs of the received RLC PDUs so as to record the lost RLC PDUs. 
     The NR MACs  1515  and  1530  may be connected to multiple NR RLC layer devices configured in one terminal, and the main functions of the NR MACs  1515  and  1530  may include some of the following functions: 
     Mapping function (Mapping between logical channels and transport channels);   Function for multiplexing and demultiplexing (Multiplexing/demultiplexing of MAC SDUs);   Function of reporting scheduling information (Scheduling information reporting);   HARQ function (Error correction through HARQ);   Function of adjusting a priority between local channels (Priority handling between logical channels of one UE);   Function of adjusting a priority between terminals (Priority handling between UEs by means of dynamic scheduling);   Function of identifying an MBMS service (MBMS service identification);   Function of selecting a transmission format (Transport format selection); and   Padding function (Padding).   

     The NR PHY layers  1520  and  1525  may channel-code and modulate higher layer data, may make the higher layer data as an OFDM symbol and may transmit the same to a radio channel, or may demodulate and channel-decode the OFDM symbol, received through the radio channel, and may deliver the demodulated and channel-decoded OFDM symbol to the higher layer. 
     The T300 described below may be replaced by all types of timers which are started when a terminal delivers a connection establishment request message in an idle state and are stopped when the terminal receives a connection establishment message or a connection reject message from a base station as a response to the connection establishment request message, when a cell is reselected, or when a higher layer stops the connection establishment. Further, the T319 may be replaced by all types of timers which are started when a terminal delivers a connection resume request message in an inactive stage and are stopped when the terminal receives, from the base station, a connection establishment message, an RRC release message, an RRCRelease with suspendConfig message, or an RRCReject message as a response to the connection resume request message, when a cell is reselected, or when a higher layer stops the connection establishment. 
       FIG.  16    is a signal flow diagram illustrating a case in which, when a terminal transitions from an idle state to a connected state, the terminal fails to transition from the former to the latter, according to an embodiment the disclosure. 
     Referring to  FIG.  16   , the terminal  1605  is switched from a previous connected state to an idle state, or attempts initial access from an idle state. In operation  1615 , the terminal  1605  may receive system information, through a base station  1610  has set a value of a T300, from base station 2e-10. While the terminal  1605  attempts to set up a connection and delivers a connection setup message to the base station  1610  in operation  1620 , the terminal  1605  starts an internal T300 timer in operation  1625 . In operation  1630 , if the T300 timer expires, the terminal  1605  notifies a higher layer or a NAS layer that the attempt to set up a connection has failed, and stores a connection setup failure report in the terminal  1605 . In this example, the stored information is a failure type, and an indicator, which indicates T300 expiry or a connection setup failure, may be stored. Further, the terminal  1605  may store: an ID (a global cell ID or a physical cell ID) of a cell for which the setup attempt by the terminal  1605  has failed during the setup attempt; location information of the terminal  1605  at a time point at which the setup attempt by the terminal  1605  has failed; a measurement value of a signal strength, a measurement value of a beam, and index information of the relevant beam, which are related to the cell for which the setup attempt by the terminal  1605  has failed; a measurement value of a signal strength, a measurement value of a beam, and index information of the relevant beam, which are related to a neighboring cell; the number of preambles transmitted for random access, and index information of a beam for transmission of a preamble; information on whether a collision with another random access terminal has occurred; a maximum transmission power value at the time of random access; time required to succeed in setting up a reconnection after the failure; a measurement value of a signal strength of a cell of another RAT; and information on the number of consecutive failures when the terminal  1605  attempts to set up or resume a connection with the particular cell. A failure type indicator therein has a length of 1 bit. The number of consecutive failures is initialized whenever a cell, with which the terminal  1605  attempts to set up a connection, is reselected and changed, and increases if an attempt to set up a connection with the same cell by the terminal  1605  consecutively fails. 
     Even after T300 expiry, the terminal  1605  is also in an idle state. Then, in operation  1635 , the terminal  1605  may again request, for connection setup, a higher layer of the terminal  1605 , a lower layer (NAS layer), or an AS layer. In operation  1640 , the terminal  1605  transmits a random access preamble, and when the random access preamble is successfully transmitted, receives a random access response (RAR) from the base station  1610  in operation  1645 . Then, in operation  1650 , the terminal  1605  retransmits a connection setup request message to the base station  1610 , and simultaneously, starts the T300 timer in operation  1655 . If the terminal  1605  receives, in operation  1660 , a connection setup message from the base station  1610  before expiry of a T300 timer, in operation  1665 , the terminal  1605  includes an indicator, which indicates that it is possible to report a connection setup failure, in a connection setup complete message and delivers the connection setup complete message to the base station  1610 . Simultaneously with transmission of the connection setup complete message, in operation  1670 , the terminal  1605  transitions to a connected state. If the base station  1610  having received and recognized the indicator indicating that it is possible to report a connection setup failure determines, in operation  1675 , that the base station is to receive a relevant connection setup failure report from the terminal  1605 , in operation  1680 , the base station  1610  includes a request indication, which indicates transmission of a connection setup failure report, in a UEInformationRequest message and delivers the UEInformationRequest message to the terminal  1605 . In operation  1685 , the terminal  1605  having received the UEInformationRequest message includes the recently-stored connection setup failure report in a UEInformationResponse message and delivers the UEInformationResponse message to the base station  1610 . The connection setup failure report has been stored in the terminal  1605  at the time of expiry of the T300 timer in operation  1630 , and may include the expiry of the T300 timer or a failure factor indicator of a connection setup failure. The indicator, which indicates that it is possible to report a connection setup failure and is transmitted by the terminal  1605  in operation  1665 , may be included in an RRCConnectionSetupComplete message, an RRCReconfigurationComplete message, an RRC ReestablishmentComplete message, or an RRCResumeComplete message. 
       FIG.  17    is a flow diagram illustrating a case in which, when a terminal transitions from an inactive state to a connected state, the terminal fails to transition from the former to the latter, according to an embodiment the disclosure. 
     Referring to  FIG.  17   , the terminal  1705  is in a situation in which the terminal  1705  transitions from a previous connected state to an inactive state. In this example, in operation  1715 , a value of a T319 timer may have been received through RRC dedicated signaling or system information from a serving base station  1710  when the terminal  1705  has previously been in a connected state, or, in operation  1720 , may be received through system information from a base station  1710  on which the terminal  1705  camps in an inactive state. While the terminal  1705  attempts to resume an RRC connection and delivers an RRC connection resume message to the base station  1710  in operation  1725 , in operation  1730 , the terminal  1705  starts an internal T319 timer. In operation  1735 , if the T319 timer expires in operation  1735 , the terminal  1705  notifies a higher layer or a NAS layer that the attempt to resume a connection has failed, and stores a connection setup failure report in the terminal  1705 . In this example, the stored information is a failure type, and an indicator, which indicates T319 expiry or a connection resumption failure, may be stored. Further, the terminal  1705  may store: an ID (a global cell ID or a physical cell ID) of a cell for which the connection resumption attempt by the terminal  1705  has failed during the connection resumption attempt; location information of the terminal  1705  at a time point at which the connection resumption attempt by the terminal  1705  has failed; a measurement value of a signal strength, a measurement value of a beam, and index information of the relevant beam, which are related to the cell for which the connection resumption attempt by the terminal  1705  has failed; a measurement value of a signal strength, a measurement value of a beam, and index information of the relevant beam, which are related to a neighboring cell; the number of preambles transmitted for random access, and index information of a beam for transmission of a preamble; information on whether a collision with another random access terminal has occurred; a maximum transmission power value at the time of random access; time required to succeed in setting up a reconnection after the failure; a measurement value of a signal strength of a cell of another RAT; and information on the number of consecutive failures when the terminal  1705  attempts to set up or resume a connection with the particular cell. A failure type indicator therein has a length of 1 bit. The number of consecutive failures is initialized whenever a cell, with which the terminal  1705  attempts to set up or resume a connection, is reselected and changed, and increases if an attempt to set up or resume a connection with the same cell by the terminal  1705  consecutively fails. 
     After the T319 timer expires, the terminal  1705  transitions from the inactive state to an idle state. 
     Then, in operation  1740 , the terminal  1705  may again request, for connection setup, a higher layer of the terminal  1705 , a lower layer (NAS layer), or an AS layer. In operation  1745 , the terminal  1705  transmits a random access preamble, and when the random access preamble is successfully transmitted, receives a random access response (RAR) from the base station 2f-10 in operation 2f-45. Then, in operation  1755 , the terminal  1705  retransmits a connection setup request message to the base station  1710 , and simultaneously, starts the T300 timer this time in operation  1760 . If the terminal  1705  receives, in operation  1765  , a connection setup message from the base station  1710  before expiry of a T310 timer, in operation  1770 , the terminal  1705   includes an indicator, which indicates that it is possible to report a connection setup failure, in a connection setup complete message and delivers the connection setup complete message to the base station  1710 . Simultaneously with transmission of the connection setup complete message, in operation  1775 , the terminal  1705  transitions to a connected state. If the base station  1710  having received and recognized the indicator indicating that it is possible to report a connection setup failure determines, in operation  1780 , that the base station is to receive a relevant connection setup failure report from the terminal  1705  , in operation  1785 , the base station  1710  includes a request indication, which indicates transmission of a connection setup failure report, in a UEInformationRequest message and delivers the UEInformationRequest message to the terminal  1705 . In operation  1790 , the terminal  1705  having received the UEInformationRequest message includes the recently-stored connection setup failure report in a UEInformationResponse message and delivers the UEInformationResponse message to the base station  1710 . The connection setup failure report has been stored in the terminal  1705  at the time of expiry of the T319 timer in operation  1735 , and may include the expiry of the T319 timer or a failure factor indicator of a connection setup failure. The indicator, which indicates that it is possible to report a connection setup failure and is transmitted by the terminal  1705  in operation  1770 , may be included in an RRCConnectionSetupComplete message, an RRCReconfigurationComplete message, an RRC ReestablishmentComplete message, or an RRCResumeComplete message. 
       FIG.  18    is a signal flow diagram illustrating an operation of a terminal for (re-)selecting a cell by applying a predetermined power offset and a predetermined factor value if the terminal experiences a fixed number of failures when the terminal transitions from an idle state to a connected state, according to an embodiment the disclosure. 
     The terminal  1805  is in an idle state. If the terminal 18-05 has previously been in a connected state, the terminal  1805  may have received a Qoffset_temp-related factor according to a connection failure type through system information or RRC dedicated signaling from a serving base station  1810 . Alternatively, in operation  1815 , if the terminal  1805  has previously been in an idle state not in the connected state, the terminal  1805  may have received a Qoffset_temp-related factor according to a connection failure type through system information from a base station  1810  of a cell on which the terminal  1805  has camped. 
     In this example, as Qoffset_temp-related factors, for each connection failure type, the number of relevant consecutive connection failures; a Qoffset_temp value which is a power offset value to be used during cell (re-) selection; and information on a period during which cell (re-)selection is to be performed by using the power offset value may be delivered. Each connection failure type may be expiry of a T300 timer or expiry of a T319 timer. If the same type of consecutive failures for the same cell occur by the above-described given number, the terminal 2g-05 performs a cell (re-)selection operation, to which a Qoffset_tempvalue defined in the corresponding type of connection failure case is applied, during a period defined in the corresponding type of connection failure case. 
     While the terminal  1805  desires connection setup and delivers, in operation  1820 , a connection setup request message to the base station  1810  on which the terminal  1805  camps, in operation  1825 , the terminal  1805  starts the timer T300. If the T300 timer expires in operation  1830 , the terminal  1805  notifies a NAS layer or a higher layer of a connection setup failure. Then, in operation  1840 , it is assumed that the terminal  1805  repeats M times an operation of again receiving a connection setup request from the NAS layer, starting the T300 timer, transmitting a connection setup request message to the same cell, and causing the T300 timer to expire again. If the pieces of information received in operation  1815  are as follows: when the T300 timer expires, the number of consecutive connection failures: M+1, Qoffset_temp: K (dB), and a validity period: 100 ms; and when the T319 timer expires, the number of consecutive connection failures: N+1, Qoffset_temp: L (dB), and a validity period: 50 ms, after operation  1840 , at operation  1845 , the terminal  1805  performs cell (re-)selection by using K as the value of Qoffset_temp for 100 ms. 
       FIG.  19    is a signal flow diagram illustrating an operation of a terminal for (re-)selecting a cell by applying a predetermined power offset and a predetermined factor value if the terminal experiences a predetermined number of failures when the terminal transitions from an inactive state to a connected state, according to an embodiment the disclosure. 
     Referring to  FIG.  19   , the terminal  1905  is in an inactive state. If the terminal  1905  has previously been in a connected state, the terminal  1905  may have received a Qoffset_temp-related factor according to a connection failure type through system information or RRC dedicated signaling from a serving base station  1910 . Alternatively, in operation  1915 , in an inactive state, the terminal  1905  may receive a Qoffset_temp-related factor according to a connection failure type through system information from a base station  1910  of a cell on which the terminal  1905  camps. 
     In this example, as Qoffset_temp-related factors, for each connection failure type, the number of relevant consecutive connection failures; a Qoffset_temp value which is a power offset value to be used during cell (re-) selection; and information on a period during which cell (re-)selection is to be performed by using the power offset value may be delivered. Each connection failure type may be expiry of a T300 timer or expiry of a T319 timer. If the same type of consecutive failures for the same cell occur by the above-described given number, the terminal  1905  performs a cell (re-)selection operation, to which a Qoffset_tempvalue defined in the corresponding type of connection failure case is applied, during a period defined in the corresponding type of connection failure case. 
     While the terminal  1905  desires connection resumption and delivers, in operation  1920 , a connection resume request message to the base station  1910  on which the terminal  1905  camps, in operation  1925 , the terminal  1905  starts the timer T319. If the T319 timer expires in operation  1930 , the terminal  1905  notifies a NAS layer or a higher layer of a connection setup failure. Then, in operation  1940 , it is assumed that the terminal  1905  repeats N times an operation of again receiving a connection resume request from the NAS layer, starting the T319 timer, transmitting a connection resume request message to the same cell, and causing the T319 timer to expire again. If the pieces of information received in operation  1915  are as follows: when the T300 timer expires, the number of consecutive connection failures: M+1, Qoffset_temp: K (dB), and a validity period: 100 ms; and when the T319 timer expires, the number of consecutive connection failures: N+1, Qoffset_temp: L (dB), and a validity period: 50 ms, after operation  1940 , at operation  1950 , the terminal  1905  performs cell (re-)selection by using L as the value of Qoffset_tempfor 50 ms. In this example, in operation  1940 , the terminal  1905  transitions from an inactive state to an idle state after (N+1) failures. That is, in the case of expiry of the T319 timer, if failures occur by the number of consecutive connection resume request failures, the terminal  1905  transitions to an idle state in operation  1945 . 
       FIG.  20    is a signal flow diagram illustrating an operation of a terminal for (re-)selecting a cell by applying the same number of failures, a power offset, and a factor value, which are applied to two types of failures, if the terminal: experiences a predetermined number of failures in an inactive state; and transitions to an idle state and again transitions to a connected state, when the terminal is to transition from the inactive state to the connected state, according to an embodiment the disclosure. 
     The terminal  2005  is in an inactive state. If the terminal  2005  has previously been in a connected state, the terminal  2005  may have received a Qoffset_temp-related factor which is identical regardless of a connection failure type through system information or RRC dedicated signaling from a serving base station  2010 . Alternatively, in operation  2015 , in an inactive state, the terminal  2005  may receive a Qoffset_temp-related factor which is identical regardless of a connection failure type through system information from a base station  2010  of a cell on which the terminal  2005  camps. Alternatively, in addition, a factor related to an allowable number of connection resumption failures due to expiry of a T319 timer may be delivered. If failures occur by this number, the terminal  2005  may transition from an inactive state to an idle state. 
     In this example, as Qoffset_temp-related factors, the number of relevant consecutive connection failures; a Qoffset_tempvalue which is a power offset value to be used during cell (re-)selection; and information on a period during which cell (re-)selection is to be performed by using the power offset value, each of which is identical regardless of a connection failure type, may be delivered. If consecutive failures irrelevant to a failure type for the same cell occur by the above-described given number, the terminal  2005  performs a cell (re-)selection operation, to which a given Qoffset_tempvalue is applied, during a given period. 
     While the terminal  2005  desires connection resumption and delivers, in operation  2020 , a connection resume request message to the base station  2010  on which the terminal 2i-05 camps, in operation  2025 , the terminal  2005  starts the timer T319. If the T319 timer expires in operation  2030 , the terminal  2005  notifies a NAS layer or a higher layer of a connection setup failure. Then, in operation  2040 , it is assumed that the terminal  2005  repeats A times an operation of again receiving a connection resume request from the NAS layer, starting the T319 timer, transmitting a connection resume request message to the same cell, and causing the T319 timer to expire again. Then, if failures occur by the number of allowable consecutive expiries of the T319 timer (or by the number of connection resumption failures) among the pieces of information received in operation  2015  (“1+A” in this example), in operation  2045 , the terminal  2005  transitions to an idle state. Then, while the terminal  2005  again attempts to set up a connection and transmits, in operation  2050 , a connection setup request message to the base station  2010  of the existing cell on which the terminal  2005  camps, in operation  2055 , the terminal  2005  starts the T300 timer. If the T300 timer expires, in operation  2060 , without a response from the base station  2010 , in operation  2065 , the terminal  2005  provides notification to a NAS layer. If the terminal  2005  further repeats operations  2055  to  2065  B times in operation  2070  so that the number of consecutive connection request failures for the same cell reaches the same number of failures which is applied to all cases regardless of failure types given in operation  2015  (“1+A+1+B” in this example), the terminal  2005  also applies, in operation  2075 , to cell (re-)selection, the value of Qoffset_tempgiven in operation  2015 , and applies the offset value during the validity period given in operation  2015 . 
     The value of Qoffset_tempis added as an offset value to the reception strength of the radio wave from the cell that the terminal  2005  has received, and is used for comparison with a threshold for selection of a camping cell. 
     If A has a value of 0, that is, if T319 expiry occurs once, a terminal according to various embodiments may immediately transition to an idle state (IDLE mode). The terminal according to various embodiments may perform a cell selection operation or a cell reselection operation. 
     In this regard, the terminal may receive system information block 1(SIB1) and factors which are related to cell selection or reselection and a connection establishment failure. 
     In this configuration, if the SIB1 received by the terminal includes a connection establishment failure-related factor and includes the set value of a connection establishment count, the terminal may perform the following operations. 
     The terminal may perform RRC connection setup. 
     Alternatively, as an operation accordingly, the terminal may transmit an RRC connection request message to a cell on which the terminal is camping. 
     Then, if a T300 timer expires, for example, if the T300 timer expires under condition 1 or condition 2 described below, the terminal may determine cell selection criteria or cell reselection criteria by using connEstFailOffset (Qoffset_temp). In this example, the connEstFailOffset may be used for a validity time. 
     Condition 1 in which the T300 timer consecutively expires by the value of connEstFailCount, for one cell in which SIB1 including connectionEstablishmentFailureControl (i.e., an IE including a Qoffset_temp-related factor) is broadcasted; or 
     Condition 2 in which the T319 timer expires once and then the T300 timer consecutively expires by the value of connEstFailCount -1, for one cell in which SIB1 including connectionEstablishmentFailureControl (i.e., an IE including a Qoffset_temp-related factor) is broadcasted. 
     In this configuration, a case in which a value of a connection establishment count is set to 1 may be separately considered. 
     For example, while performing a cell selection or reselection operation, the terminal may receive SIB1, a cell (re-)selection factor, and a connection establishment failure-related factor. 
     In this example, if connEstFailurecount included in SIB1 has a value of 1, the terminal may attempt RRC connection setup or RRC resume request. 
     Further, if the T300 timer or the T319 timer expires as a result of the attempt for the connection setup, the terminal may determine cell selection criteria or cell reselection criteria by using connEstFaileOffset (Qoffset_temp). In this example, the connEstFaileOffset may be used for a given validity time. 
     In another embodiment, whether Qoffset_temp(connEstFaileOffset) is applied may be determined on the basis of only the given number of consecutive timer expiries. If the Qoffset_tempis once applied and then the T300 timer additionally expires for the same cell, the existing applied validity time may be newly restarted. 
     Therefore, if a condition for determining whether a relevant state is a state in which Qoffset_tempis currently applied is included whenever a timer expires, a validity time may be prevented from being newly restarted. From this perspective, the following embodiment is possible. The terminal according to various embodiments may perform a cell selection operation or a cell reselection operation. 
     In this regard, the terminal may receive SIB1, a cell (re-)selection factor, and a connection establishment failure-related factor. 
     In this configuration, if the SIB1 received by the terminal includes a connection establishment failure-related factor and includes the set value of a connection establishment count, the terminal may perform the following operations. 
     The terminal may perform RRC connection setup. The terminal may transmit an RRC connection request message to a cell on which the terminal is camping. 
     If the T300 timer expires as a result of the request, for example, the T300 timer expires under condition 1 or condition 2 described below, and connEstFailOffset is currently not applied, the terminal may determine cell selection criteria or cell reselection criteria by using connEstFailOffset. The connEstFailOffset may be used for a given validity time. 
     Condition 1 in which the T300 timer consecutively expires by a value of connEstFailCount, for one cell in which SIB1 including connectionEstablishmentFailureControl (i.e., an IE including a Qoffset_temp-related factor) is broadcasted; or 
     Condition 2 in which the T319 timer expires once and then the T300 timer consecutively expires by a value of connEstFailCount -1, for one cell in which SIB1 including connectionEstablishmentFailureControl (i.e., an IE including a Qoffset_temp-related factor) is broadcasted. 
       FIG.  21    and  FIG.  22    are views illustrating a format of a usable connection setup failure report according to various embodiments of the disclosure. 
     In a format of a connection setup failure report, the same format may be used, and instead, a method for representing the type of connection setup failure may exist. Alternatively, according to the type of connection setup failure, information related to each connection setup failure is stored in a storage of a separate RRC message or a separate IE, and the separate RRC message or the separate IE may be delivered. 
     Referring to  FIG.  21   , a connection setup failure factor is represented by 1 bit in a report IE having the same format. 
     Referring to  FIG.  22   , a report for each type of connection failure is stored in a separate IE. 
     In order to indicate a failure type, the method “ENUMERATE {T310-expiry, T319-expiry}” may be used, in which ENUMERATED {T319-expiry} is expressed and an option field is used for differentiation. That is, if ENUMERATE {T319-expiry} is expressed, this expression signifies the expiry of the T319 timer. Alternatively, if the field does not exist, this absence is recognized as the expiry of the T300 timer. Alternatively, Boolean may be used such that “true” and “false” signify expiry of T300 and expiry of T319, respectively. 
       FIG.  23    is a signal flow diagram illustrating base station ID transmission for entry into a connection re-establishment request according to an embodiment the disclosure. 
     In operation  2320 , a terminal  2305  establishes a connection with a base station  2310  of a serving cell, and in operation  2325 , a radio link failure (RLF) or a handover (HO) failure occurs. The terminal  2305  begins to perform an RRC connection re-establishment operation at this time. In operation  2330 , the terminal  2305  selects a cell, and transmits an RRC connection re-establishment request message to a base station  2315  of the selected cell. In this configuration, an example of information transmitted together with the RRC connection re-establishment request message may include an only cell identifier in a PLMN of a cell in which the RLF or the HO failure has occurred, an only global cell identifier in an NR RAN, or an only global cell identifier in an NR and LTE RAN. Alternatively, an evolved cell global identifier (ECGI) in an NR RAN or an only ECGI in an NR and LTE RAN may be transmitted. Each ECGI includes one piece of information among the following pieces of information: a PLMN ID and a physical cell ID of a source cell; an ID and a RAT indicator of a source gNB. Further, an indicator obtained by combining or concatenating these pieces of information may become an ECGI. 
     The target base station  2315  receives this information, and acquires information on: a cell in which the relevant RLF or HO failure has occurred; and the base station  2310  which serves the cell. In operation  2335 , the target base station  2315  may deliver an RLF indication message to an address of the source base station  2310  through the acquired information. In operation  2340 , the RLF indication message includes an identifier of the terminal  2305  in case of the relevant RLF or HO failure, and may include an identifier which allows identifying of the relevant cell or the ECGI information transmitted in operation  2330 . In operation  2345 , if the source base station  2310  receives this information and identifies a terminal controlled by the source base station  2310  itself by using the received information, the source base station  2310  releases a resource allocated to the relevant terminal  2305 . In operation  2350 , the target base station  2315  receives a re-establishment request and identifies whether the target base station  2315  itself includes a context of the relevant terminal  2305  by using ID information (c-RNTI, ECGI, and shortMAC-I used in the source cell) of the terminal  2305  included in the received re-establishment request, and if the target base station  2315  includes the context of the relevant terminal  2305 , delivers a connection re-establishment message to the terminal  2305 . Operations  2350  and the operations after operations  2350  may be performed after or before operation  2340 . Upon receiving the connection re-establishment message, the terminal  2305  resumes the released SRB1/SRB2 and DRB. Then, in operation  2355 , the terminal  2305  delivers a connection reestablishment complete message to the target base station  2315 . 
       FIG.  24    is a block diagram illustrating an internal configuration of a terminal according to an embodiment the disclosure. 
     Referring to  FIG.  24   , the terminal  2400  includes a radio frequency (RF) processor  2410 , a baseband processor  2420 , a storage unit  2430 , and a controller  2440 . 
     The RF processor  2410  serves to transmit or receive a signal through a wireless channel, such as band conversion and amplification of a signal. That is, the RF processor  2410  up-converts a baseband signal provided by the baseband processor  2420  into an RF band signal and then transmits the RF band signal through an antenna and down-converts an RF band signal received through the antenna into a baseband signal. For example, the RF processor  2410  may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), or the like.  FIG.  24    illustrates only one antenna but the terminal may be provided with multiple antennas. Also, the RF processor  2410  may include multiple RF chains. Further, the RF processor  2410  may perform beamforming. For the beamforming, the RF processor  2410  may adjust a phase and a magnitude of each of the signals transmitted or received through multiple antennas or antenna elements. Further, the RF processor  2410  may perform MIMO and may receive multiple layers during execution of a MIMO operation. 
     The baseband processor  2420  performs a conversion function between a baseband signal and a bit stream according to a physical layer standard of a system. For example, when data is transmitted, the baseband processor  2420  generates complex symbols by encoding and modulating a transmission bit stream. Further, when data is received, the baseband processor  2420  reconstructs a received bit stream by demodulating and decoding the baseband signal provided by the RF processor  2410 . For example, according to an orthogonal frequency division multiplexing (OFDM) scheme, when data is transmitted, the baseband processor  2420  generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then performs an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion to configure OFDM symbols. Further, when data is received, the baseband processor  2420  divides the baseband signal provided by the RF processor  2410  in an OFDM symbol unit, reconstructs the signals mapped to the subcarriers by a fast Fourier transform (FFT), and then reconstructs a received bit stream by the demodulation and decoding. 
     The baseband processor  2420  and the RF processor  2410  transmit and receive a signal as described above. Therefore, the baseband processor  2420  and the RF processor  2410  may be referred to as a “transmitter”, a “receiver”, a “transceiver”, or a “communication unit”. Also, at least one of the baseband processor  2420  and the RF processor  2410  may include multiple communication modules in order to support multiple different radio access technologies. Further, at least one of the baseband processor  2420  and the RF processor  2410  may include different communication modules in order to process signals in different frequency bands. For example, the different radio access technologies may include a wireless LAN (e.g., IEEE 802.11), a cellular network (e.g., LTE), and the like. The different frequency bands may include a super high frequency (SHF) (e.g., 2.5 GHz and 5 GHz) band and an mmWave (e.g., 60 GHz) band. 
     The storage unit  2430  stores data such as basic programs, application programs, and configuration information for an operation of the terminal. In particular, the storage unit  2430  may store information related to a second access node configured to perform wireless communication by using second radio access technology. Also, the storage unit  2430  provides the stored data in response to a request of the controller  2440 . 
     The controller  2440  controls overall operations of the terminal. For example, the controller  2440  transmits or receives a signal through the baseband processor  2420  and the RF processor  2410 . Further, the controller  2440  records and reads data in and from the storage unit  2440 . To this end, the controller  2440  may include at least one processor. For example, the controller  2440  may include a multi-connectivity processor  2442  configured to control multiple connections, a communication processor (CP) configured to perform a control for communication and an application processor (AP) configured to control a higher layer such as an application program. 
       FIG.  25    is a block diagram illustrating a configuration of an NR base station according to an embodiment the disclosure. 
     Referring to  FIG.  25   , the base station  2500  includes an RF processor  2510 , a baseband processor  2520 , a backhaul communication unit  2530 , a storage unit  2540 , and a controller  2550 . 
     The RF processor  2510  serves to transmit or receive a signal through a wireless channel, such as band conversion and amplification of a signal. That is, the RF processor  2510  up-converts a baseband signal provided by the baseband processor  2520  into an RF band signal and then transmits the RF band signal through an antenna and down-converts an RF band signal received through the antenna into a baseband signal. For example, the RF processor  2510  may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, or the like.  FIG.  25    illustrates only one antenna but the first access node may be provided with multiple antennas. Also, the RF processor  2510  may include multiple RF chains. Further, the RF processor  2510  may perform beamforming. For the beamforming, the RF processor  2510  may adjust a phase and a magnitude of each of the signals transmitted or received through multiple antennas or antenna elements. The RF processor  2510  may be configured to transmit one or more layers for a downlink MIMO operation. 
     The baseband processor  2520  may perform a conversion function between a baseband signal and a bit stream according to a physical layer standard of first radio access technology. For example, when data is transmitted, the baseband processor  2520  generates complex symbols by encoding and modulating a transmission bit stream. Further, when data is received, the baseband processor  2520  reconstructs a received bit stream by demodulating and decoding the baseband signal provided by the RF processor  2510 . For example, according to an OFDM scheme, when data is transmitted, the baseband processor  2520  generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then performs an IFFT operation and a CP insertion to configure OFDM symbols. Further, when data is received, the baseband processor  2520  divides the baseband signal provided by the RF processor  2510  in an OFDM symbol unit, reconstructs the signals mapped to the subcarriers by a fast Fourier transform (FFT) operation, and then reconstructs a received bit stream by the modulation and decoding. The baseband processor  2520  and the RF processor  2510  transmit and receive signals as described above. Accordingly, the baseband processor  2520  and the RF processor  2510  may be referred to as a “transmitter”, a “receiver”, a “transceiver”, a “communication unit”, or a “wireless communication unit”. 
     The backhaul communication unit  2530  provides an interface for communication with other nodes in a network. That is, the backhaul communication unit  2530  converts a bit stream to be transmitted from the primary base station to another node, for example, an auxiliary base station and a core network, into a physical signal and converts a physical signal received from another node to a bit stream. 
     The storage unit  2540  stores data such as basic programs, application programs, and configuration information for an operation of the primary base station. In particular, the storage unit  2540  may store information on the bearers allocated to accessed terminals, measurement results reported by the accessed terminals, and the like. Also, the storage unit  2540  may store the information which becomes a standard of determination of whether to provide or stop providing multi-connectivity to a terminal. Further, the storage unit  2540  provides the stored data according to a request of the controller  2550 . 
     The controller  2550  controls overall operations of the primary base station. For example, the controller  2550  transmits or receives a signal through the baseband processor  2520  and the RF processor  2510 , or through the backhaul communication unit  2530 . Further, the controller  2550  records and reads data in and from the storage unit  2540 . To this end, the controller  2550  may include at least one processor, such as a multi-connectivity processor  2552  configured to control multiple connections, a CP configured to perform a control for communication and an AP configured to control a higher layer such as an application program. 
     While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. 
     The above-described embodiments of the disclosure and the accompanying drawings have been provided only as specific examples in order to assist in understanding the disclosure and do not limit the scope of the disclosure. Accordingly, those skilled in the art to which the disclosure pertains will understand that other change examples based on the technical idea of the disclosure may be made without departing from the scope of the disclosure. 
     While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. 
     The operations performed by the module, programming module, or any other component according to various embodiments may be executed sequentially, in parallel, repeatedly, or by a heuristic method. Additionally, some operations may be executed in different orders or omitted, or any other operation may be added. 
     The methods of the embodiments illustrated in  FIGS.  1  to  25    can include a combination of methods from more than one illustration. For example,  FIGS.  1  to  25    illustrate operations related to a paging monitoring method and reporting a connection setup failure method based on various embodiments, the methods can include a combination of methods from more than one illustration.