Patent Publication Number: US-11652575-B2

Title: Method and apparatus for transmitting and receiving data in wireless communication system

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based on and claims priority under 35 U.S.C. § 119(a) of a Korean patent application number 10-2018-0071617, filed on Jun. 21, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The disclosure relates to a method and apparatus for transmitting and receiving data in a wireless communication system. 
     2. Description of Related Art 
     To meet the increasing demand with respect to wireless data traffic after the commercialization of 4th generation (4G) communication systems, efforts have been made to develop 5th generation (5G) or pre-5G communication systems. For this reason, 5G or pre-5G communication systems are called ‘beyond 4G network’ communication systems or ‘post long term evolution (post-LTE)’ systems. To achieve high data rates, implementation of 5G communication systems in an ultra-high frequency or millimeter-wave (mmWave) band (e.g., a 60-GHz band) is being considered. To reduce path loss and increase a transmission distance in the ultra-high frequency band for 5G communication systems, various technologies such as beamforming, massive multiple-input and multiple-output (massive MIMO), full-dimension MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antennas are being studied. To improve system networks for 5G communication systems, various technologies such as evolved small cells, advanced small cells, cloud radio access networks (Cloud-RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, moving networks, cooperative communication, coordinated multi-points (CoMP), and interference cancellation have been developed. In addition, for 5G communication systems, advanced coding modulation (ACM) technologies such as hybrid frequency-shift keying (FSK) and quadrature amplitude modulation (QAM) (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), have been developed. 
     The Internet has evolved from a human-based connection network, where humans create and consume information, to the Internet of things (IoT), where distributed elements such as objects exchange information with each other to process the information. Internet of everything (IoE) technology has emerged, in which the IoT technology is combined with, for example, technology for processing big data through connection with a cloud server. To implement the IoT, various technological elements such as sensing technology, wired/wireless communication and network infrastructures, service interface technology, and security technology are required. In recent years, technologies related to sensor networks for connecting objects, machine-to-machine (M2M) communication, and machine-type communication (MTC) have been studied. In the IoT environment, intelligent Internet technology (IT) services may be provided to collect and analyze data obtained from connected objects to create new value in human life. As existing IT and various industries converge and combine with each other, the IoT may be applied to various fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart home appliances, and advanced medical services. 
     Various attempts are being made to apply 5G communication systems to the IoT network. For example, technologies related to sensor networks, M2M communication, and MTC are being implemented by using 5G communication technology including beamforming, MIMO, and array antennas. Application of Cloud-RAN as the above-described big data processing technology may be an example of convergence of 5G communication technology and IoT technology. 
     Because various services are providable due to the development of wireless communication systems, methods capable of appropriately providing these services are required. 
     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 an apparatus and method of effectively providing services in a mobile communication system. 
     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 of operating a terminal in a wireless communication system is provided. The method includes obtaining, from a radio link control (RLC) entity associated with a cell group of the terminal, information about a number of retransmissions of a packet, identifying whether packet duplication is activated, based on information indicating that the number of retransmissions of the packet reaches a maximum number of retransmissions of the packet, and transmitting, to a base station, a message indicating a failure of retransmission of the packet, based on a result of the identifying. 
     In accordance with another aspect of the disclosure, a terminal in a wireless communication system is provided. The terminal includes a transceiver, and at least one processor configured to obtain, from a RLC entity associated with a cell group of the terminal, information about a number of retransmissions of a packet, identify whether packet duplication is activated, based on information indicating that the number of retransmissions of the packet reaches a maximum number of retransmissions of the packet, and transmit, to a base station, a message indicating a failure of retransmission of the packet, based on a result of the identifying. 
     In accordance with another aspect of the disclosure, a computer program product is provided. The computer program product includes a non-transitory computer-readable recording medium having recorded thereon a computer-readable program to be executed on a computing device to cause the computing device to obtain, from a RLC entity associated with a cell group of a terminal, information about a number of retransmissions of a packet, identify whether packet duplication is activated, based on information indicating that the number of retransmissions of the packet reaches a maximum number of retransmissions of the packet, and transmit, to a base station, a message indicating a failure of retransmission of the packet, based on a result of the identifying. 
     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 A  is a schematic diagram of a wireless communication system according to an embodiment of the disclosure; 
         FIG.  1 B  is a block diagram of a base station in a wireless communication system according to an embodiment of the disclosure; 
         FIG.  1 C  is a block diagram of a user equipment (UE) in a wireless communication system according to an embodiment of the disclosure; 
         FIG.  1 DA  is block diagram of a communicator in a wireless communication system according to an embodiment of the disclosure; 
         FIG.  1 DB  is a circuit diagram of a communicator in a wireless communication system according to an embodiment of the disclosure; 
         FIG.  1 DC  is a circuit diagram of a communicator in a wireless communication system according to an embodiment of the disclosure; 
         FIG.  1 E  is a flowchart of a procedure, performed by a UE, of receiving channel status information-reference signal (CSI-RS) resource configuration information per bandwidth part (BWP) and performing measurement and reporting, according to an embodiment of the disclosure; 
         FIG.  1 F  is a flowchart of a procedure in a case in which an active BWP of a UE is switched in the procedure of  FIG.  1 E  according to an embodiment of the disclosure; 
         FIG.  1 GA  is a schematic diagram for describing a problem that a CSI-RS resource configuration information element (IE) needs to be repeatedly transmitted for BWPs according to an embodiment of the disclosure; 
         FIG.  1 GB  is a schematic diagram for describing a problem that a CSI-RS resource configuration IE needs to be repeatedly transmitted for BWPs according to an embodiment of the disclosure; 
         FIG.  1 GC  is a schematic diagram for describing a problem that a CSI-RS resource configuration IE needs to be repeatedly transmitted for BWPs according to an embodiment of the disclosure; 
         FIG.  1 GD  is a schematic diagram for describing a problem that a CSI-RS resource configuration IE needs to be repeatedly transmitted for BWPs according to an embodiment of the disclosure; 
         FIG.  1 H  is a schematic diagram for describing a problem that multiple CSI-RS resource configuration IEs need to be transmitted per BWP according to an embodiment of the disclosure; 
         FIG.  1 I  is a flowchart of a procedure in a case in which an active BWP of a UE is switched, according to an embodiment of the disclosure; 
         FIG.  1 J  is a flowchart of a procedure in a case in which an active BWP of a UE is switched, according to an embodiment of the disclosure; 
         FIG.  1 K  is a flowchart of a procedure in a case in which an active BWP of a UE is switched, according to an embodiment of the disclosure; 
         FIG.  2 A  is a schematic diagram of a structure for performing packet duplication transmission according to an embodiment of the disclosure; 
         FIG.  2 B  is a schematic diagram for describing a procedure in a case in which a maximum retransmission threshold of a radio link control (RLC) entity is reached in an environment in which packet duplication transmission is configured according to an embodiment of the disclosure; 
         FIG.  2 C  is a schematic diagram for describing a cell switching procedure in a case in which packet duplication transmission is deactivated according to an embodiment of the disclosure; 
         FIG.  2 D  is a flowchart of a UE procedure in a case in which a maximum retransmission threshold is reached, according to an embodiment of the disclosure; 
         FIG.  2 E  is a flowchart of a UE procedure in a case in which a maximum retransmission threshold is reached, according to an embodiment of the disclosure; 
         FIG.  2 F  is a flowchart of a UE procedure in a case in which a maximum retransmission threshold is reached, according to an embodiment of the disclosure; 
         FIG.  2 G  is a flowchart of a UE procedure in a case in which a maximum retransmission threshold is reached, according to an embodiment of the disclosure; 
         FIG.  2 H  is a flowchart of a UE procedure in a case in which a maximum retransmission threshold is reached, according to an embodiment of the disclosure; 
         FIG.  2 I  is a schematic diagram for describing a procedure of resetting a retransmission count at a timing at which packet duplication is activated according to an embodiment of the disclosure; 
         FIG.  3    is a block diagram of a UE according to an embodiment of the disclosure; and 
         FIG.  4    is a block diagram of a base station according to an embodiment of the disclosure. 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure 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 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     It will be understood that blocks in flowcharts or combinations of the flowcharts may be performed by computer program instructions. Because these computer program instructions may be loaded into a processor of a general-purpose computer, a special-purpose computer, or another programmable data processing apparatus, the instructions, which are performed by a processor of a computer or another programmable data processing apparatus, create units for performing functions described in the flowchart block(s). The computer program instructions may be stored in a computer-usable or computer-readable memory capable of directing a computer or another programmable data processing apparatus to implement a function in a particular manner, and thus the instructions stored in the computer-usable or computer-readable memory may also be capable of producing manufacturing items containing instruction units for performing the functions described in the flowchart block(s). The computer program instructions may also be loaded into a computer or another programmable data processing apparatus, and thus, instructions for operating the computer or the other programmable data processing apparatus by generating a computer-executed process when a series of operations are performed in the computer or the other programmable data processing apparatus may provide operations for performing the functions described in the flowchart block(s). 
     In addition, each block may represent a portion of a module, segment, or code that includes one or more executable instructions for executing specified logical function(s). It is also noted that, in some alternative implementations, functions mentioned in blocks may occur out of order. For example, two consecutive blocks may also be executed simultaneously or in reverse order depending on functions corresponding thereto. 
     As used herein, the term “unit” denotes a software element or a hardware element such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and performs a certain function. However, the term “unit” is not limited to software or hardware. The “unit” may be formed so as to be in an addressable storage medium, or may be formed so as to operate one or more processors. Thus, for example, the term “unit” may include elements (e.g., software elements, object-oriented software elements, class elements, and task elements), processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, micro-codes, circuits, data, a database, data structures, tables, arrays, or variables. Functions provided by the elements and “units” may be combined into the smaller number of elements and “units”, or may be divided into additional elements and “units”. Furthermore, the elements and “units” may be embodied to reproduce one or more central processing units (CPUs) in a device or security multimedia card. Also, the “unit” may include at least one processor. 
     As used herein, a downlink (DL) refers to a transmission path of a wireless signal from a base station to a user equipment (UE), and an uplink (UL) refers to a transmission path of a wireless signal from a UE to a base station. Although the following description may be provided about long term evolution (LTE) or LTE-advanced (LTE-A) systems as an example, the embodiments of the disclosure are also applicable to other communication systems having similar technical backgrounds or channel structures. For example, the embodiments of the disclosure are also applicable to 5th generation (5G) (or new radio (NR)) communication systems developed after LTE-A systems. In the following description, 5G may be understood as a concept including existing LTE and LTE-A, and other similar services. The disclosure is also applicable to other communication systems through modification at the discretion of one of ordinary skill in the art without greatly departing from the scope of the disclosure. 
     To achieve high data rates, implementation of 5G communication systems in an ultra-high frequency or millimeter-wave (mmWave) band (e.g., a 60-GHz band) is being considered. To reduce path loss and increase a transmission distance in the ultra-high frequency band for 5G communication systems, various technologies such as beamforming, massive multiple-input and multiple-output (massive MIMO), full-dimension MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antennas are being studied. 
     To improve system networks for 5G communication systems, various technologies such as evolved small cells, advanced small cells, cloud radio access networks (Cloud-RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, moving networks, cooperative communication, coordinated multi-points (COMP), and interference cancellation have been developed. 
     In addition, for 5G communication systems, advanced coding modulation (ACM) technologies such as hybrid frequency-shift keying (FSK) and quadrature amplitude modulation (QAM) (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), have been developed. 
     In communication systems, a UE requires initial cell selection and cell reselection to select the best accessible base station in an idle mode, and requires radio resource management (RRM) to hand over to a better cell in a connected mode. To select a cell and compare cell performances, each UE should be able to measure or calculate a representative measurement value of each cell or a value derived therefrom. To this end, in existing LTE systems, different base stations reserve orthogonal resources in a shared frequency band using an omni-beam to transmit cell-specific reference signals, and a UE measures the same to find out reference signal received power (RSRP) of each cell. 
     For next-generation communication systems considering beamforming, research has been conducted on various methods by which different base stations transmit cell- and beam-specific reference signals sequentially at different resources by using different beams, and a UE calculates a representative value corresponding each cell by using measurement values of multiple beams transmitted from the cell. 
     Although research on reference signal transmission using an omni-beam or reference signal transmission using multiple beams has been already conducted as described above, research has not been conducted on a method by which different base stations transmit two or more types of reference signals generated based on different signal generation rules, by using two or more types of beams having different beam areas, coverages, or transmission cycles. 
     The disclosure relates to a next-generation wireless communication system, and more particularly, to a system, method, and apparatus for configuring a reference signal for a UE in consideration of different bandwidth parts (BWPs) and for performing cell measurement and reporting by using the configured reference signal, in a beamforming-based system including one or more base stations and one or more UEs. 
     The disclosure also relates to a reference signal configuration method for beam measurement based on a condition, a reference signal measurement method based on a condition, and a reference signal measurement reporting procedure based on a condition, in a wireless system including a base station and a UE using multiple antennas. 
     The disclosure provides a system, method, and apparatus for configuring a reference signal for a UE in consideration of different BWPs and for performing cell measurement and reporting by using the configured reference signal, in a beamforming-based system including one or more base stations and one or more UEs. 
     The disclosure also provides a reference signal configuration method for beam measurement based on a condition, a reference signal measurement method based on a condition, and a reference signal measurement reporting procedure based on a condition, in a wireless system including a base station and a UE using multiple antennas. 
     A UE may measure reference signals transmitted from base stations by using different antennas based on beam sweeping. The reference signals to be considered include a synchronization signal and a channel status information-reference signal (CSI-RS), but is not limited thereto. 
       FIG.  1 A  is a schematic diagram of a wireless communication system according to various embodiments of the disclosure.  FIG.  1 A  illustrates a base station  110 , a UE  120 , and a UE  130  as some of nodes using wireless channels in the wireless communication system. Although only one base station is illustrated in  FIG.  1 A , other base stations the same as or similar to the base station  110  may be further included. 
     The base station  110  is a network infrastructure for providing wireless access to the UEs  120  and  130 . The base station  110  may have a coverage defined as a certain geographical region based on a signal transmittable distance. The base station  110  may also be called an ‘access point (AP)’, an ‘evolved NodeB (eNB)’, a next-generation NodeB (gNB), a ‘5 th  generation (5G) node’, a ‘wireless point’, a ‘transmission/reception point (TRP)’, or another technically equivalent name. 
     Each of the UEs  120  and  130  is a device used by a user and may communicate with the base station  110  through a wireless channel. In some cases, at least one of the UE  120  or the UE  130  may operate without manipulation of the user. That is, at least one of the UE  120  or the UE  130  may be a machine type communication (MTC) device not carried by the user. Each of the UEs  120  and  130  may also be called a ‘terminal’, a ‘mobile station’, a ‘subscriber station’, a ‘remote terminal’, a ‘wireless terminal’, a ‘user device’, or another technically equivalent name. 
     The base station  110  and the UEs  120  and  130  may transmit and receive wireless signals in a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, or 60 GHz). In this case, to increase channel gain, the base station  110  and the UEs  120  and  130  may perform beamforming. Herein, beamforming may include transmit beamforming and receive beamforming. That is, the base station  110  and the UEs  120  and  130  may give directivity to a transmit signal or a received signal. To this end, the base station  110  and the UEs  120  and  130  may select serving beams  112 ,  113 ,  121 , and  131  through a beam search procedure or a beam management procedure. After the serving beams  112 ,  113 ,  121 , and  131  are selected, subsequent communication may be performed using quasi co-located (QCL) resources of resources used to transmit the serving beams  112 ,  113 ,  121 , and  131 . 
     When large-scale characteristics of a channel used to transmit symbols on a first antenna port may be inferred based on a channel used to transmit symbols on a second antenna port, the first and second antenna ports may be determined as QCL antenna ports. For example, the large-scale characteristics may include at least one of a delay spread, a Doppler spread, a Doppler shift, an average gain, an average delay, or a spatial receiver parameter. 
       FIG.  1 B  is a block diagram of a base station  110  in a wireless communication system according to various embodiments of the disclosure. Elements illustrated in  FIG.  1 B  may be understood as elements of the base station  110 . As used herein, a suffix such as ‘ . . . er’ or ‘ . . . or’ indicates a unit for performing at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software. 
     Referring to  FIG.  1 B , the base station  110  may include a wireless communicator  210 , a backhaul communicator  220 , a storage  230 , and a controller  240 . 
     The wireless communicator  210  may perform functions for transmitting and receiving signals through wireless channels. For example, the wireless communicator  210  may convert a baseband signal into a bitstream or vice versa according to physical layer specifications of the system. For example, for data transmission, the wireless communicator  210  may generate complex symbols by encoding and modulating a transmit bitstream. For data reception, the wireless communicator  210  may reconstruct a received bitstream by demodulating and decoding a baseband signal. 
     The wireless communicator  210  up-converts a baseband signal into a radio frequency (RF) band signal and transmits the RF band signal through an antenna, and down-converts an RF band signal received through an antenna, into a baseband signal. To this end, for example, the wireless communicator  210  may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), and an analog to digital convertor (ADC). The wireless communicator  210  may include a plurality of transmission/reception paths. Furthermore, the wireless communicator  210  may include at least one antenna array including a plurality of antenna elements. 
     In terms of hardware, the wireless communicator  210  may include a digital unit and an analog unit, and the analog unit may include a plurality of sub-units based on, for example, operating power or an operating frequency. The digital unit may be implemented as at least one processor (e.g., a digital signal processor (DSP)). 
     The wireless communicator  210  transmits and receives signals as described above. As such, a part or the entirety of the wireless communicator  210  may be called a ‘transmitter’, a ‘receiver’, or a ‘transceiver’. In the following description, transmission and reception through wireless channels may include the above-described process performed by the wireless communicator  210 . 
     The backhaul communicator  220  may provide an interface for communicating with another node in a network. That is, the backhaul communicator  220  may convert a bitstream to be transmitted from the base station  110  to another node, e.g., another access node, another base station, an upper node, or a core network, into a physical signal, or convert a physical signal received from another node, into a bitstream. 
     The storage  230  may store data such as basic programs, application programs, and configuration information for operating the base station  110 . The storage  230  may include volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. The storage  230  may provide the stored data upon a request of the controller  240 . 
     The controller  240  may control overall operations of the base station  110 . For example, the controller  240  may transmit and receive signals through the wireless communicator  210  or the backhaul communicator  220 . The controller  240  write and read data in and from the storage  230 . The controller  240  may perform functions of a protocol stack required by communication standards. According to another embodiment of the disclosure, the protocol stack may be included in the wireless communicator  210 . To this end, the controller  240  may include at least one processor. According to other embodiments of the disclosure, the controller  240  may control the base station  110  to perform operations described below according to various embodiments of the disclosure. 
       FIG.  1 C  is a block diagram of a UE  120  in a wireless communication system according to various embodiments of the disclosure. Elements illustrated in  FIG.  1 C  may be understood as elements of the UE  120 . As used herein, a suffix such as ‘ . . . er’ or ‘ . . . or’ indicates a unit for performing at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software. 
     Referring to  FIG.  1 C , the UE  120  may include a communicator  310 , a storage  320 , and a controller  330 . 
     The communicator  310  may perform functions for transmitting and receiving signals through wireless channels. For example, the communicator  310  may convert a baseband signal into a bitstream or vice versa according to physical layer specifications of the system. For example, for data transmission, the communicator  310  may generate complex symbols by encoding and modulating a transmit bitstream. For data reception, the communicator  310  may reconstruct a received bitstream by demodulating and decoding a baseband signal. The communicator  310  may up-convert a baseband signal into an RF band signal and transmit the RF band signal through an antenna, and down-convert an RF band signal received through an antenna, into a baseband signal. For example, the communicator  310  may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC. 
     The communicator  310  may include a plurality of transmission/reception paths. Furthermore, the communicator  310  may include at least one antenna array including a plurality of antenna elements. In terms of hardware, the communicator  310  may include a digital unit and an analog unit (e.g., a radio frequency integrated circuit (RFIC)). Herein, the digital circuit and the analog circuit may be implemented as a single package. The communicator  310  may include a plurality of RF chains. Furthermore, the communicator  310  may perform beamforming. 
     The communicator  310  may transmit and receive signals as described above. As such, a part or the entirety of the communicator  310  may be called a ‘transmitter’, a ‘receiver’, or a ‘transceiver’. In the following description, transmission and reception through wireless channels may include the above-described process performed by the communicator  310 . 
     The storage  320  may store data such as basic programs, application programs, and configuration information for operating the UE  120 . The storage  320  may include volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. The storage  320  may provide the stored data upon a request of the controller  330 . 
     The controller  330  may control overall operations of the UE  120 . For example, the controller  330  may transmit and receive signals through the communicator  310 . The controller  330  write and read data in and from the storage  320 . The controller  330  may perform functions of a protocol stack required by communication standards. To this end, the controller  330  may include at least one processor or microprocessor, or the controller  330  may be a part of the processor. A part of the communicator  310  and the controller  330  may be called a communication processor (CP). According to various embodiments of the disclosure, the controller  330  may control the UE  120  to perform operations described below according to various embodiments of the disclosure. 
     The controller  330  according to an embodiment of the disclosure may perform a series of operations described below. 
     The controller  330  according to an embodiment of the disclosure may configure reference signals for the UE  120  in consideration of different frequency bands, and perform cell measurement and reporting by using the configured reference signals. 
       FIGS.  1 DA to  1 DC  are block and circuit diagrams of a communicator in a wireless communication system according to various embodiments of the disclosure.  FIGS.  1 DA to  1 DC  illustrate elements of the wireless communicator  210  of  FIG.  1 B  or the communicator  310  of  FIG.  1 C . Specifically,  FIGS.  1 DA to  1 DC  illustrate elements for performing beamforming as a part of the wireless communicator  210  of  FIG.  1 B  or the communicator  310  of  FIG.  1 C . 
       FIG.  1 DA  is a block diagram of a communicator in a wireless communication system according to various embodiments of the disclosure. 
     Referring to  FIG.  1 DA , the wireless communicator  210  or the communicator  310  may include an encoder and modulator  402 , a digital beamformer  404 , a plurality of transmission paths  406 - 1  to  406 -N, and an analog beamformer  408 . 
     The encoder and modulator  402  may perform channel encoding. For channel encoding, at least one of low-density parity-check (LDPC) code, convolution code, or polar code may be used. The encoder and modulator  402  may generate modulated symbols by performing constellation mapping. 
     The digital beamformer  404  may perform beamforming on digital signals (e.g., the modulated symbols). To this end, the digital beamformer  404  may multiply the modulated symbols by beamforming weights. Herein, the beamforming weights may be used to change intensities and phases of signals and be called, for example, a ‘precoding matrix’ or a ‘precoder’. The digital beamformer  404  may output the digital-beamformed modulated symbols to the plurality of transmission paths  406 - 1  to  406 -N. In this case, based on a multiple-input multiple-output (MIMO) scheme, the modulated symbols may be multiplexed or the same modulated symbols may be provided to the plurality of transmission paths  406 - 1  to  406 -N. 
     The plurality of transmission paths  406 - 1  to  406 -N may convert the digital-beamformed digital signals into analog signals. To this end, each of the plurality of transmission paths  406 - 1  to  406 -N may include an inverse fast Fourier transform (IFFT) calculator, a cyclic prefix (CP) inserter, a DAC, and an upconverter. The CP inserter is used for an orthogonal frequency division multiplexing (OFDM) scheme and may be omitted for another physical layer scheme (e.g., a FBMC scheme). That is, the plurality of transmission paths  406 - 1  to  406 -N may provide independent signal processes for a plurality of streams generated through digital beamforming. However, depending on implementation, some elements of the plurality of transmission paths  406 - 1  to  406 -N may be shared. 
     The analog beamformer  408  may perform beamforming on analog signals. To this end, the digital beamformer  404  may multiply the analog signals by beamforming weights. Herein, the beamforming weights may be used to change intensities and phases of signals. Specifically, based on a connection structure between the plurality of transmission paths  406 - 1  to  406 -N and antennas, the analog beamformer  408  may be configured as illustrated in  FIG.  1 DB or  1 DC . 
       FIG.  1 DB  is a circuit diagram of a communicator in a wireless communication system according to various embodiments of the disclosure. 
     Referring to  FIG.  1 DB , the signals input to the analog beamformer  408  may be converted in phase/intensity, be amplified, and then be transmitted through antennas. In this case, the signals of different paths may be transmitted through different antenna sets, i.e., different antenna arrays. To process the signal input through a first path, the signal may be converted into signal sequences having different or equal phases/intensities by phase/intensity converters  412 - 1 - 1  to  412 - 1 -M, be amplified by amplifiers  414 - 1 - 1  to  414 - 1 -M, and then be transmitted through antennas. There may be up to N paths. To process the signal input through an N th  path, the signal may be converted into signal sequences having different or equal phases/intensities by phase/intensity converters  412 -N- 1  to  412 -N-M, be amplified by amplifiers  414 -N- 1  to  414 -N-M, and then be transmitted through antennas. 
       FIG.  1 DC  is a circuit diagram of a communicator in a wireless communication system according to various embodiments of the disclosure. 
     Referring to  FIG.  1 DC , the signals input to the analog beamformer  408  may be converted in phase/intensity, be amplified, and then be transmitted through antennas. In this case, the signals of different paths may be transmitted through the same antenna set, i.e., the same antenna array. To process the signal input through a first path, the signal may be converted into signal sequences having different or equal phases/intensities by phase/intensity converters  412 - 1 - 1  to  412 - 1 -M and be amplified by amplifiers  414 - 1 - 1  to  414 - 1 -M. To process the signal input through an N th  path, the signal may be converted into signal sequences having different or equal phases/intensities by phase/intensity converters  412 -N- 1  to  412 -N-M and be amplified by amplifiers  414 -N- 1  to  414 -N-M. Amplified signals of different paths may be added by adders  416 - 1  to  416 -M and be transmitted through one antenna array. 
       FIG.  1 DB  illustrates an example in which different transmission paths use independent antenna arrays, and  FIG.  1 DC  illustrates an example in which different transmission paths share one antenna array. However, according to another embodiment of the disclosure, some transmission paths may use independent antenna arrays and the other transmission paths may share one antenna array. According to another embodiment of the disclosure, by applying a switchable structure between transmission paths and antenna arrays, an adaptively variable structure may be used. 
     Embodiment 1: Method of Configuring, Measuring, and Reporting Reference Signal Per Bandwidth Part (BWP) 
     A base station may configure a certain reference signal for channel status measurement, e.g., a CSI-RS, for UEs belonging to the coverage of the base station and UEs belonging to the coverages of neighboring base stations. In this case, the CSI-RS may be configured to be subordinate to a specific BWP such that CSI-RS configuration information is included in DL BWP configuration information as shown in Table 1. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 BWP-Downlink ::= 
                 SEQUENCE { 
               
            
           
           
               
            
               
                   -- An identifier for this bandwidth part. Other parts of the RRC 
               
               
                 configuration use the BWP-Id to associate themselves with a particular 
               
               
                   -- bandwidth part. The BWP ID=0 is always associated with the 
               
               
                 initial BWP and may hence not be used here. (in other bandwidth parts). 
               
               
                   -- The NW may trigger the UE to switch UL or DL BWP using a DCI 
               
               
                 field. The four code points in that DCI field map to the RRC-configured 
               
               
                   -- BWP-ID as follows: For up to 3 configured BWPs (in addition to 
               
               
                 the initial BWP) the DCI code point is equivalent to the BWP ID 
               
               
                   -- (initial = 0, first dedicated = 1, ...). If the NW configures 4 
               
               
                 dedicated bandwidth parts, they are identified by DCI code 
               
               
                   -- points 0 to 3. In this case it is not possible to switch to the initial 
               
               
                 BWP using the DCI field. 
               
               
                   -- Corresponds to L1 parameter ‘DL-BWP-index’. (see 38.211, 
               
               
                 38.213, section 12) 
               
            
           
           
               
               
            
               
                   bwp-Id 
                       BWP-Id, 
               
               
                   bwp-Common 
                       BWP- 
               
               
                 DownlinkCommon 
               
               
                       OPTIONAL, -- Need M 
               
               
                   bwp-Dedicated 
                     BWP- 
               
               
                 DownlinkDedicated 
               
               
                       OPTIONAL, -- Need M 
               
               
                   csi-ResourceConfigId 
                   CSI-ResourceConfigId 
               
               
                     OPTIONAL, 
               
               
                   nzp-CSI-RS-ResourceSetId 
                 NZP-CSI-RS-ResourceSetId 
               
               
                     OPTIONAL, 
               
               
                   zp-CSI-RS-ResourceSetId 
                   ZP-CSI-RS- 
               
               
                 ResourceSetId 
               
               
                     OPTIONAL, 
               
               
                   nzp-CSI-RS-ResourceId 
               
               
                     OPTIONAL, 
               
               
                   zp-CSI-RS-ResourceId 
               
               
                     OPTIONAL, 
               
               
                   ... 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     Alternatively, each CSI-RS configuration information element (IE) may include a BWP-Id to which a corresponding CSI-RS belongs. 
       FIG.  1 E  is a flowchart of a procedure, performed by a UE, of receiving CSI-RS resource configuration information per BWP and performing measurement and reporting, according to an embodiment of the disclosure. 
     In operation  1   e - 1 , the UE may receive CSI-RS resource configuration information per BWP from a network and check correlations between BWPs and CSI-RS resources. 
     In operation  1   e - 2 , the UE may specify a current active BWP of the UE. 
     In operation  1   e - 3 , the UE may specify a CSI-RS resource belonging to the active BWP specified in operation  1   e - 2 . 
     In operation  1   e - 4 , the UE may measure the CSI-RS resource specified in operation  1   e - 3 . 
     In operation  1   e - 5 , the UE may determine whether the CSI-RS resource measured in operation  1   e - 4  satisfies a preset measurement reporting condition, and transmit a measurement report upon determining that the CSI-RS resource satisfies the condition. 
     Although the flowchart of  FIG.  1 E  is illustrated on the assumption of one active BWP, according to another embodiment of the disclosure, when two or more active BWPs are simultaneously usable, the UE may perform the procedure of  FIG.  1 E  simultaneously on the two or more active BWPs. 
     The CSI-RS resource may be configured per BWP in such a manner that each CSI-RS resource configuration IE (CSI-ResourceConfig, non-zero power (NZP)-CSI-RS-ResourceSet, NZP-CSI-RS-Resource, CSI-interference measurement (IM)-ResourceSet, CSI-IM-Resource, zero power (ZP)-CSI-RS-ResourceSet, ZP-CSI-RS-Resource, . . . ) includes a BWP Id to which the CSI-RS resource belongs. 
       FIG.  1 F  is a flowchart of a procedure in a case in which an active BWP of a UE is switched in the procedure of  FIG.  1 E . In operation  1   f - 1 , the UE may receive CSI-RS resource configuration information per BWP from a network and check correlations between BWPs and CSI-RS resources. 
     In operation  1   f - 2 , the UE determines whether a current active BWP of the UE is switched. Upon determining that the active BWP is not switched, the UE may perform operations  1   f - 11  and  1   f - 12  to continuously measure a CSI-RS resource belonging to the current active BWP and transmit a measurement report when a specific reporting condition is satisfied. 
     Upon determining, in operation  1   f - 2 , that the active BWP is switched, in operation  1   f - 3 , the UE may discard and reset the entirety or a part of information related to a previous active BWP. The information to be discarded or reset may be as described below.
         CSI-RS measurement information in the BWP (e.g., memory storing a filter value and a sample value) is discarded.   Timer, counter, and measurement value information related to beam failure detection in the BWP is discarded.   Timer, counter, and measurement value information related to radio link monitoring in the BWP is discarded.   Stored information related to a hybrid automatic repeat request (HARQ) in the BWP is discarded.   Timer and counter information related to discontinuous reception (DRX) (or connected mode discontinuous reception (C-DRX)) in the BWP is discarded.       

     In operation  1   f - 4 , the UE may specify a new active BWP. 
     In operation if- 5 , the UE may specify a CSI-RS resource belonging to the new active BWP specified in operation if- 4 . 
     In operation if- 6 , the UE may measure the CSI-RS resource specified in operation if- 5 . 
     In operation  1   f - 7 , the UE may determine whether the CSI-RS resource measured in operation  1   f - 6  satisfies a preset measurement reporting condition, and transmit a measurement report upon determining that the CSI-RS resource satisfies the condition. 
     Although the flowchart of  FIG.  1 F  is illustrated on the assumption of one active BWP, when two or more active BWPs are simultaneously usable, the UE may perform the procedure of  FIG.  1 F  simultaneously on the two or more active BWPs. That is, the UE may perform the procedure of  FIG.  1 F  simultaneously or sequentially on a plurality of active BWPs. 
     According to an embodiment of the disclosure, the CSI-RS resource may be configured per BWP in such a manner that each CSI-RS resource configuration IE (CSI-ResourceConfig, NZP-CSI-RS-ResourceSet, NZP-CSI-RS-Resource, CSI-IM-ResourceSet, CSI-IM-Resource, ZP-CSI-RS-ResourceSet, ZP-CSI-RS-Resource, . . . ) includes a BWP Id to which the CSI-RS resource belongs. 
     Embodiment 2: Method of Including Multi-BWP Information in Reference Signal Configuration Information 
     A base station may configure a certain reference signal for channel status measurement, e.g., a CSI-RS, for UEs belonging to the coverage of the base station and UEs belonging to the coverages of neighboring base stations. In this case, when the configured CSI-RS is associated with only one BWP, the following problems may occur. 
     Problem 1: Multiple CSI-ResourceConjig IEs Need to be Configured when Measurement of the Same CSI-RS is Required by Overlapping BWPs. 
       FIGS.  1 GA to  1 GD  are schematic diagrams for describing a problem that, when overlapping BWPs include the same CSI-RS and one CSI-RS is configurable for only one BWP, a CSI-RS resource configuration IE for CSI-RS measurement needs to be repeatedly transmitted for the BWPs. As illustrated in  FIGS.  1 GA and  1 GB , a network may configure only one CSI-RS and want a UE to adaptively measure the CSI-RS based on bandwidths of overlapping BWPs. However, because one CSI-RS is configurable for only one BWP, as illustrated in  FIGS.  1 GC and  1 GD , the network repeatedly transmits a configuration IE as if three different CSI-RSs are configured. The UE may determine the configured CSI-RSs as different CSI-RSs and thus unnecessarily repeat the same filtering, condition comparing, and reporting operation even though resources thereof are the same. In addition, memory capacity may be additionally used. 
     Problem 2: Multiple CSI-RSs Need to be Configured Per BWP 
       FIG.  1 H  is a schematic diagram for describing a problem that, when overlapping BWPs and individual BWPs are present and one CSI-RS is configurable for only one BWP, multiple CSI-RS resource configuration IEs need to be transmitted per BWP. Because multiple CSI-RS resources having equal or different resource element regions are configurable in an overlapping manner based on the number of BWPs, the number of CSI-RS resource sets, and the number of CSI-RS configuration IEs, the number of CSI-RS resources to be transmitted by a network and to be received and managed by a UE may be exponentially increased. 
     To solve the above-described problem, the network may configure and transmit CSI-RSs over a wide frequency band. The frequency band for which the CSI-RSs are transmitted may include one or more BWPs. Information about the one or more BWPs may be included in CSI-RS configuration information which may be configured as shown in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 -- ASN1START 
               
               
                 -- TAG-CSI-RESOURCECONFIG-START 
               
               
                 -- One CSI resource configuration comprising of one or more resource sets 
               
               
                 CSI-ResourceConfig ::=    SEQUENCE { 
               
               
                   -- Used in CSI-ReportConfig to refer to an instance of CSI- 
               
               
                 ResourceConfig 
               
            
           
           
               
               
            
               
                   csi-ResourceConfigId 
                 CSI-ResourceConfigId, 
               
            
           
           
               
            
               
                   -- Contains up to maxNrofNZP-CSI-RS-ResourceSetsPerConfig 
               
               
                 resource sets if ResourceConfigType is ‘aperiodic’ and 1 otherwise. 
               
               
                   -- Corresponds to L1 parameter ‘ResourceSetConfigList’ (see 38.214, 
               
               
                 section 5.2.1.3.1) 
               
            
           
           
               
               
            
               
                   csi-RS-ResourceSetList 
                 CHOICE { 
               
            
           
           
               
            
               
                     nzp-CSI-RS-SSB 
               
               
                   SEQUENCE { 
               
               
                       nzp-CSI-RS-ResourceSetList 
               
               
                   SEQUENCE (SIZE (1..maxNrofNZP-CSI-RS- 
               
               
                 ResourceSetsPerConfig)) OF NZP-CSI-RS-ResourceSetId OPTIONAL, 
               
               
                       -- List of SSB resources used for beam measurement and 
               
               
                 reporting in a resource set 
               
               
                       -- Corresponds to L1 parameter ‘resource-config-SS-list’ 
               
               
                 (see 38,214, section FFS_Section) 
               
               
                       csi-SSB-ResourceSetList 
               
               
                   SEQUENCE (SIZE (1..maxNrofCSI-SSB-ResourceSetsPerConfig)) 
               
               
                 OF CSI-SSB-ResourceSetId OPTIONAL 
               
               
                     }, 
               
            
           
           
               
               
            
               
                     csi-IM-ResourceSetList 
                   SEQUENCE (SIZE 
               
            
           
           
               
            
               
                 (1..maxNrofCSI-IM-ResourceSetsPerConfig)) OF CSI-IM-ResourceSetId 
               
               
                   }, 
               
               
                   -- The DL BWPs which the CSI-RS associated with this CSI- 
               
               
                 ResourceConfig. 
               
               
                   -- Corresponds to L1 parameter ‘BWP-Info’ (see 38.214, section 
               
               
                   5.2.1.2 
               
            
           
           
               
               
            
               
                   bwp-IdList 
                 SEQUENCE 
               
            
           
           
               
            
               
                 (SIZE(1..maxBWP-Id)) OF BWP-Id OPTIONAL, 
               
               
                   -- Time domain behavior of resource configuration. Corresponds to 
               
               
                 L1 parameter ‘ResourceConfigType’ (see 38.214, section 5.2.2.3.5) 
               
            
           
           
               
               
            
               
                   resourceType 
                 ENUMERATED 
               
            
           
           
               
            
               
                 { aperiodic, semiPersistent, periodic }, 
               
               
                   ... 
               
               
                 } 
               
               
                 -- TAG-CSI-RESOURCECONFIGTOADDMOD-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     Although a current active BWP usable by the UE is switched, the UE having received CSI-RS configuration information including multi-BWP information may specify whether a CSI-RS configured over a previous active BWP and the current active BWP is present. When the CSI-RS is present, the UE may continuously measure the CSI-RS and transmit a measurement report thereof without discarding a measurement value of or a counter or timer related to the CSI-RS. 
       FIG.  1 I  is a flowchart of a procedure in a case in which an active BWP of a UE is switched, according to another embodiment of the disclosure. 
     In operation  1   i - 1 , the UE may receive CSI-RS resource configuration information including multi-BWP configuration information from a network and check correlations between CSI-RS resources and BWPs associated with the CSI-RS resources. In embodiments of the disclosure, the multi-BWP configuration information may be included in the multi-BWP information. 
     In operation  1   i - 2 , the UE may determine whether a current active BWP of the UE is switched. 
     Upon determining that the active BWP is not switched, the UE may perform operations  1   i - 12  and  1   i - 13  to continuously measure a CSI-RS resource belonging to the current active BWP and transmit a measurement report when a specific reporting condition is satisfied. 
     Upon determining, in operation  1   i - 2 , that the active BWP is switched, in operation  1   i - 3 , the UE may specify a new active BWP. The specification of the new active BWP refers to an operation, performed by the UE, of checking information corresponding to a BWP Id included in a DL signal previously received from a base station to switch a BWP, from BWP information previously received from the base station, and specifying an RF end, e.g., a center frequency, a frequency band, and a reception resource element, of the UE based on the BWP information. 
     In operation  1   i - 4 , the UE may specify a CSI-RS resource(s) associated with the new active BWP specified in operation  1   i - 3 , i.e., including a new active BWP ID in corresponding CSI-RS resource configuration information. 
     In operation  1   i - 5 , the UE may determine whether the CSI-RS resource specified in operation  1   i - 4  is the same as a preset CSI-RS resource measured in a previous active BWP. The determination may be made based on the following cases.
         A case in which both of an Id of the previous active BWP and an Id of the new active BWP specified in operation  1   i - 3  are included in an associated BWP-Id list included in corresponding CSI-RS ResourceConfig, NZP, ZP, or IM CSI-RS-ResourceSet, or NZP, ZP, or IM CSI-RS-Resource.   A case in which both of an Id of the previous active BWP and an Id of the new active BWP specified in operation  1   i - 3 , which are included in a table received by the UE from the base station and specifying correlations between BWPs and CSI-RSs, include a ResourceConfig Id, a NZP, ZP or IM CSI-RS-ResourceSet Id, or a NZP, ZP or IM CSI-RS-Resource Id of the CSI-RS resource specified in operation  1   i - 4 .   A case in which, when a certain CSI-RS including a measurement frequency bandwidth or a resource element of the previous active BWP of the UE is present, a measurement frequency bandwidth of the new active BWP of the UE is included in a transmission frequency bandwidth or a resource element region of the CSI-RS.       

     Upon determining that the CSI-RS resource specified in operation  1   i - 4  is not the same as the preset CSI-RS resource measured in the previous active BWP, in operation  1   i - 11 , the UE may discard and reset the entirety or a part of information related to the previous active BWP. The information to be discarded or reset may be as described below.
         CSI-RS measurement information in the BWP (e.g., memory storing a filter value and a sample value) is discarded.   Timer, counter, and measurement value information related to beam failure detection in the BWP is discarded.   Timer, counter, and measurement value information related to radio link monitoring in the BWP is discarded.   Stored information related to a HARQ in the BWP is discarded.   Timer and counter information related to DRX (or C-DRX) in the BWP is discarded.       

     After operation  1   i - 11 , the UE may perform operations  1   i - 12  and  1   i - 13  to continuously measure a CSI-RS resource belonging to the current active BWP and transmit a measurement report when a specific reporting condition is satisfied. 
     Upon determining, in operation  1   i - 5 , that the CSI-RS resource specified in operation  1   i - 4  is the same as the preset CSI-RS resource measured in the previous active BWP, in operation  1   i - 6 , the UE may continuously measure the CSI-RS resource specified in operation  1   i - 4 . The UE may input the CSI-RS measurement value measured in the new active BWP, to an L1/L3 measurement filter to which the CSI-RS measurement value in the previous active BWP has been input, to obtain a result thereof, and maintain a timer triggered by the CSI-RS or related to beam failure detection, radio link monitoring, radio link failure, and DRX, to perform a related operation. 
     In operation  1   i - 7 , the UE determines whether the CSI-RS resource measured in operation  1   i - 6  satisfies a preset measurement reporting condition, and transmit a measurement report upon determining that the CSI-RS resource satisfies the condition. The measurement report may include BWP-Id information indicating a certain BWP in which the CSI-RS resource is measured, or include a 1-bit indicator indicating that the CSI-RS resource is measured in two or more BWPs, and/or one or more BWP Ids. 
     Although the flowchart of  FIG.  1 I  is illustrated on the assumption of one active BWP, according to another embodiment of the disclosure, when two or more active BWPs are simultaneously usable, the UE may perform the procedure of  FIG.  1 I  simultaneously on the two or more active BWPs. 
     The CSI-RS resource may be configured per BWP in such a manner that each CSI-RS resource configuration IE (CSI-ResourceConfig, NZP-CSI-RS-ResourceSet, NZP-CSI-RS-Resource, CSI-IM-ResourceSet, CSI-IM-Resource, ZP-CSI-RS-ResourceSet, ZP-CSI-RS-Resource, . . . ) includes a BWP Id to which the CSI-RS resource belongs. 
     In the active BWP specification operation and the CSI-RS specification operation, the UE may specify one or more BWPs and CSI-RSs and perform subsequent operations on each of the BWPs and the CSI-RSs. 
     Embodiment 3: Method of Including Multi-BWP Information in Other Reference Signal Correlation Configuration Information 
     According to another embodiment of the disclosure, a UE may use correlations between reference signals and BWPs, which are included in information other than CSI-RS configuration information. 
     The UE may receive, from a base station, information including correlations between one or more BWPs and one or more CSI-RSs as described below. In this case, CSI-RS configuration information transmitted from a network to the UE may not include a specific BWP-Id. To this end, the network may configure a BWP-Id in a CSI-ResourceConfig IE, as optional information, and configure a condition shown in Table 3. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Conditional Presence 
                 Explanation 
               
               
                   
                   
               
             
            
               
                   
                 CSI-over-multiple-BWPs 
                 If the CSI-RS resource config is 
               
               
                   
                   
                 configured over multiple BWPs, this 
               
               
                   
                   
                 field is absent, otherwise, it is 
               
               
                   
                   
                 mandatory present. 
               
               
                   
                   
               
            
           
         
       
     
     An example of the other information is shown in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
             
            
               
                 -- ASN1START 
               
               
                 -- TAG-TCI-STATE-START 
               
            
           
           
               
               
            
               
                 TCI-State ::= 
                 SEQUENCE { 
               
            
           
           
               
               
            
               
                   tci-StateId 
                 TCI-StateId, 
               
               
                   qcl-Type1 
                 QCL-Info, 
               
               
                   qcl-Type2 
                 QCL-Info 
               
               
                   
                 OPTIONAL, -- Need R 
               
               
                   nrofPTRS-Ports 
                 ENUMERATED {n1, n2} 
               
               
                   
                 OPTIONAL, -- Need R 
               
               
                   ... 
               
               
                 } 
               
            
           
           
               
               
            
               
                 QCL-Info ::= 
                 SEQUENCE { 
               
            
           
           
               
            
               
                   -- The carrier which the RS is located in. If the field is absent, it 
               
               
                 applies to the serving cell in which the TCI-State is configured 
               
            
           
           
               
               
            
               
                   cell 
                 ServCellIndex 
               
               
                   
                 OPTIONAL, -- Need R 
               
            
           
           
               
            
               
                   -- The DL BWP which the RS is located in. 
               
            
           
           
               
               
            
               
                   bwp-IdList 
                 SEQUENCE 
               
            
           
           
               
            
               
                 (SIZE(1..maxBWP-Id)) OF BWP-Id OPTIONAL, -- Cond CSI-RS- 
               
               
                 Indicated 
               
               
                   -- Cond NZP-CSI-RS-Indicated: mandatory if csi-rs or csi-RS-for- 
               
               
                 tracking is included, absent otherwise 
               
            
           
           
               
               
            
               
                   referenceSignal 
                 CHOICE { 
               
            
           
           
               
               
            
               
                     csi-rs 
                 NZP-CSI-RS-ResourceId, 
               
            
           
           
               
               
            
               
                     ssb 
                 SSB-Index, 
               
            
           
           
               
            
               
                     -- A set of CSI-RS resources for tracking 
               
            
           
           
               
               
            
               
                     csi-RS-for-tracking 
                 NZP-CSI-RS-ResourceSetId 
               
               
                   }, 
               
               
                   qcl-Type 
                 ENUMERATED {typeA, typeB, 
               
            
           
           
               
            
               
                 typeC, typeD}, 
               
               
                   ... 
               
               
                 } 
               
               
                 -- TAG-TCI-STATE-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     The UE having received QCL information may check correlations between certain BWP Ids belonging to a certain cell, and certain reference signals, and more specifically, CSI-RSs. When such information about all BWPs in a specific cell, and all CSI-RSs is received, the UE may check correlations between all BWPs in the cell, and CSI-RSs. Although a current active BWP usable by the UE is switched, the UE having received such information may specify whether a CSI-RS configured over a previous active BWP and the current active BWP is present. As such, when the CSI-RS is present, the UE may continuously measure the CSI-RS and transmit a measurement report thereof without discarding a measurement value of or a counter or timer related to the CSI-RS. 
       FIG.  1 J  is a flowchart of a procedure in a case in which an active BWP of a UE is switched, according to another embodiment of the disclosure. 
     In operation  1   j - 0 , the UE may receive CSI-RS resource configuration information and report configuration information from a network. 
     In operation  1   j - 1 , the UE may receive, from the network, information indicating correlations between CSI-RSs configured by the CSI-RS resource configuration information, and multiple BWPs in a cell, and check correlations between CSI-RS resources and BWPs associated with the CSI-RS resources. 
     In operation  1   j - 2 , the UE may determine whether a current active BWP of the UE is switched. 
     Upon determining that the active BWP is not switched, the UE may perform operations  1   j - 12  and  1   j - 13  to continuously measure a CSI-RS resource belonging to the current active BWP and transmit a measurement report when a specific reporting condition is satisfied. 
     Upon determining, in operation  1   j - 2 , that the active BWP is switched, in operation  1   j - 3 , the UE may specify a new active BWP. The specification of the new active BWP refers to an operation, performed by the UE, of checking information corresponding to a BWP Id included in a DL signal previously received from a base station to switch a BWP, from BWP information previously received from the base station, and specifying an RF end, e.g., a center frequency, a frequency band, and a reception resource element, of the UE based on the BWP information. 
     In operation  1   j - 4 , the UE may specify a CSI-RS resource associated with the new active BWP specified in operation  1   j - 3 , i.e., including a new active BWP ID in corresponding CSI-RS resource configuration information. 
     In operation  1   j - 5 , the UE may determine whether the CSI-RS resource specified in operation  1   j - 4  is the same as a preset CSI-RS resource measured in a previous active BWP. The determination may be made based on the following cases.
         A case in which both of an Id of the previous active BWP and an Id of the new active BWP specified in operation  1   j - 3  are included in an associated BWP-Id list included in corresponding CSI-RS ResourceConfig, NZP, ZP, or IM CSI-RS-ResourceSet, or NZP, ZP, or IM CSI-RS-Resource.   A case in which both of an Id of the previous active BWP and an Id of the new active BWP specified in operation  1   j - 3 , which are included in a table received by the UE from the base station and specifying correlations between BWPs and CSI-RSs, include a ResourceConfig  1   d , a NZP, ZP or IM CSI-RS-ResourceSet Id, or a NZP, ZP or IM CSI-RS-Resource Id of the CSI-RS resource specified in operation  1   j - 4 .   A case in which, when a certain CSI-RS including a measurement frequency bandwidth or a resource element of the previous active BWP of the UE is present, a measurement frequency bandwidth of the new active BWP of the UE is included in a transmission frequency bandwidth or a resource element region of the CSI-RS.       

     Upon determining that the CSI-RS resource specified in operation  1   j - 4  is not the same as the preset CSI-RS resource measured in the previous active BWP, in operation  1   j - 11 , the UE may discard and reset the entirety or a part of information related to the previous active BWP. The information to be discarded or reset may be as described below, but is not limited thereto. 
     CSI-RS measurement information in the BWP (e.g., memory storing a filter value and a sample value) is discarded. 
     Timer, counter, and measurement value information related to beam failure detection in the BWP is discarded. 
     Timer, counter, and measurement value information related to radio link monitoring in the BWP is discarded.
         Stored information related to a HARQ in the BWP is discarded.   Timer and counter information related to DRX (or C-DRX) in the BWP is discarded.       

     After operation  1   j - 11 , the UE may perform operations  1   j - 12  and  1   j - 13  to continuously measure a CSI-RS resource belonging to the current active BWP and transmit a measurement report when a specific reporting condition is satisfied. 
     Upon determining, in operation  1   j - 5 , that the CSI-RS resource specified in operation  1   j - 4  is the same as the preset CSI-RS resource measured in the previous active BWP, in operation  1   j - 6 , the UE may continuously measure the CSI-RS resource specified in operation  1   j - 4 . The UE may input the CSI-RS measurement value measured in the new active BWP, to an L1/L3 measurement filter to which the CSI-RS measurement value in the previous active BWP has been input, to obtain a result thereof, and maintain a timer triggered by the CSI-RS or related to beam failure detection, radio link monitoring, radio link failure, and DRX, to perform a related operation. 
     In operation  1   j - 7 , the UE determines whether the CSI-RS resource measured in operation  1   j - 6  satisfies a preset measurement reporting condition, and transmit a measurement report upon determining that the CSI-RS resource satisfies the condition. The measurement report may include BWP-Id information indicating a certain BWP in which the CSI-RS resource is measured, or include a 1-bit indicator indicating that the CSI-RS resource is measured in two or more BWPs, and/or one or more BWP Ids. 
     Although the flowchart of  FIG.  1 J  is illustrated on the assumption of one active BWP, according to another embodiment of the disclosure, when two or more active BWPs are simultaneously usable, the UE may perform the procedure of  FIG.  1 J  simultaneously on the two or more active BWPs. 
     The CSI-RS resource may be configured per BWP in such a manner that each CSI-RS resource configuration IE (CSI-ResourceConfig, NZP-CSI-RS-ResourceSet, NZP-CSI-RS-Resource, CSI-IM-ResourceSet, CSI-IM-Resource, ZP-CSI-RS-ResourceSet, ZP-CSI-RS-Resource, . . . ) includes a BWP Id to which the CSI-RS resource belongs. 
     In the active BWP specification operation and the CSI-RS specification operation, the UE may specify one or more BWPs and CSI-RSs and perform subsequent operations on each of the BWPs and the CSI-RSs. 
     Embodiment 4: Method of Including, in Reference Signal Configuration Information, Multi-BWP Information Including Other Reference Signal Configuration Information Referred by the Reference Signal Configuration Information 
     According to another embodiment of the disclosure, a network may configure the same CSI-RS for different BWPs and transmit CSI-RS configuration information. In this regard, CSI-RS resource configuration is omitted (e.g., csi-RS-ResourceSetList is not omitted) in a certain configuration signal from among signals transmitted to a UE, and CSI-RS configuration information may be configured to include a CSI-RS configuration ID or a BWP Id using the same resource configuration, as shown in Tables 5 and 6. 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
             
            
               
                 -- ASN1START 
               
               
                 -- TAG-CSI-RESOURCECONFIG-START 
               
               
                 -- One CSI resource configuration comprising of one or more resource sets 
               
            
           
           
               
               
            
               
                 CSI-ResourceConfig ::= 
                 SEQUENCE { 
               
            
           
           
               
            
               
                   -- Used in CSI-ReportConfig to refer to an instance of CSI- 
               
               
                 ResourceConfig 
               
            
           
           
               
               
            
               
                   csi-ResourceConfigId 
                 CSI-ResourceConfigId, 
               
            
           
           
               
            
               
                   -- Contains up to maxNrofNZP-CSI-RS-ResourceSetsPerConfig 
               
               
                 resource sets if ResourceConfigType is ‘aperiodic’ and 1 otherwise. 
               
               
                   -- Corresponds to L1 parameter ‘ResourceSetConfigList’ (see 38.214, 
               
               
                 section 5.2.1.3.1) 
               
            
           
           
               
               
            
               
                   csi-RS-ResourceSetList 
                 CHOICE { 
               
            
           
           
               
            
               
                     nzp-CSI-RS-SSB 
               
               
                   SEQUENCE { 
               
               
                       nzp-CSI-RS-ResourceSetList 
               
               
                   SEQUENCE (SIZE (1..maxNrofNZP-CSI-RS- 
               
               
                 ResourceSetsPerConfig)) OF NZP-CSI-RS-ResourceSetId 
               
               
                 OPTIONAL, 
               
               
                       -- List of SSB resources used for beam measurement and 
               
               
                 reporting in a resource set 
               
               
                       -- Corresponds to L1 parameter ‘resource-config-SS-list’ 
               
               
                 (see 38,214, section FFS_Section) 
               
               
                       csi-SSB-ResourceSetList 
               
               
                 SEQUENCE (SIZE (1..maxNrofCSI-SSB-ResourceSetsPerConfig)) OF 
               
               
                 CSI-SSB-ResourceSetId  OPTIONAL 
               
               
                     }, 
               
            
           
           
               
               
            
               
                     csi-IM-ResourceSetList 
                 SEQUENCE (SIZE 
               
            
           
           
               
            
               
                 (1..maxNrofCSI-IM-ResourceSetsPerConfig)) OF CSI-IM-ResourceSetId 
               
               
                   } OPTIONAL, 
               
               
                   -- The DL BWPs which the CSI-RS associated with this CSI- 
               
               
                 ResourceConfig. 
               
               
                   -- Corresponds to L1 parameter ‘BWP-Info’ (see 38.214, 
               
               
                   section 5.2.1.2 
               
            
           
           
               
               
            
               
                   bwp-IdList 
                 SEQUENCE 
               
            
           
           
               
            
               
                 (SIZE(1..maxBWP-Id)) OF BWP-Id OPTIONAL, 
               
            
           
           
               
               
            
               
                   ref-csi-ResourceConfigId 
                 CSI-ResourceConfigId 
               
            
           
           
               
            
               
                     OPTIONAL, -- Cond Duplicated-CSI-RS-ResourceSetList 
               
               
                   -- Time domain behavior of resource configuration. Corresponds 
               
               
                 to L1 parameter ‘ResourceConfigType’ (see 38.214, section 5.2.2.3.5) 
               
            
           
           
               
               
            
               
                   resourceType 
                 ENUMERATED 
               
            
           
           
               
            
               
                 { aperiodic, semiPersistent, periodic }, 
               
               
                   ... 
               
               
                 } 
               
               
                 -- TAG-CSI-RESOURCECONFIGTOADDMOD-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 Conditional Presence 
                 Explanation 
               
               
                   
               
             
            
               
                 Duplicated-CSI-RS-ResourceSetList 
                 If csi-RS-ResourceSetList is 
               
               
                   
                 absent, this field is optionally 
               
               
                   
                 present, otherwise, it is absent. 
               
               
                   
               
            
           
         
       
     
     Although a current active BWP to which the UE belongs is switched, the UE having received CSI-RS configuration information including multi-BWP information may specify whether a CSI-RS configured over a previous active BWP and the current active BWP is present. As such, when the CSI-RS is present, the UE may continuously measure the CSI-RS and transmit a measurement report thereof without discarding a measurement value of or a counter or timer related to the CSI-RS. 
       FIG.  1 K  is a flowchart of a procedure in a case in which an active BWP of a UE is switched, according to another embodiment of the disclosure. 
     In operation  1   k - 1 , the UE may receive CSI-RS resource configuration information including multi-BWP configuration information from a network and check correlations between CSI-RS resources and BWPs associated with the CSI-RS resources. In embodiments of the disclosure, the multi-BWP configuration information may be included in the multi-BWP information. 
     In operation  1   k - 2 , the UE may determine whether a current active BWP of the UE is switched. 
     Upon determining that the active BWP is not switched, the UE may perform operations  1   k - 12  and  1   k - 13  to continuously measure a CSI-RS resource belonging to the current active BWP and transmit a measurement report when a specific reporting condition is satisfied. 
     Upon determining, in operation  1   k - 2 , that the active BWP is switched, in operation  1   k - 3 , the UE may specify a new active BWP. The specification of the new active BWP refers to an operation, performed by the UE, of checking information corresponding to a BWP Id included in a DL signal previously received from a base station to switch a BWP, from BWP information previously received from the base station, and specifying an RF end, e.g., a center frequency, a frequency band, and a reception resource element, of the UE based on the BWP information. 
     In operation  1   k - 4 , the UE may specify a CSI-RS resource associated with the new active BWP specified in operation  1   k - 3 , i.e., including a new active BWP ID in corresponding CSI-RS resource configuration information. 
     In operation  1   k - 5 , the UE may determine whether the CSI-RS resource specified in operation  1   k - 4  is the same as a preset CSI-RS resource measured in a previous active BWP. The determination may be made based on the following cases.
         A case in which both of an Id of the previous active BWP and an Id of the new active BWP specified in operation  1   k - 3  are included in an associated BWP-Id list included in corresponding CSI-RS ResourceConfig, NZP, ZP, or IM CSI-RS-ResourceSet, or NZP, ZP, or IM CSI-RS-Resource.   A case in which both of an Id of the previous active BWP and an Id of the new active BWP specified in operation  1   k - 3 , which are included in a table received by the UE from the base station and specifying correlations between BWPs and CSI-RSs, include a ResourceConfig Id, a NZP, ZP or IM CSI-RS-ResourceSet Id, or a NZP, ZP or IM CSI-RS-Resource Id of the CSI-RS resource specified in operation  1   k - 4 .   A case in which, when a certain CSI-RS including a measurement frequency bandwidth or a resource element of the previous active BWP of the UE is present, a measurement frequency bandwidth of the new active BWP of the UE is included in a transmission frequency bandwidth or a resource element region of the CSI-RS.   A case in which it is determined that different CSI-ResourceConfig IEs configured in two different BWPs have the same CSI-RS resource configuration information, based on a CSI-RS set or CSI-RS resource configuration information included in CSI-RS ResourceConfig associated with the previous active BWP or the new active BWP (configured in each active BWP), and a reference ID (e.g., a CSI-ResourceConfigId or a BWP-Id) referring to the CSI-RS set or the CSI-RS resource configuration information.       

     Upon determining that the CSI-RS resource specified in operation  1   k - 4  is not the same as the preset CSI-RS resource measured in the previous active BWP, in operation  1   k - 11 , the UE may discard and reset the entirety or a part of information related to the previous active BWP. The information to be discarded or reset may be as described below.
         CSI-RS measurement information in the BWP (e.g., memory storing a filter value and a sample value) is discarded.   Timer, counter, and measurement value information related to beam failure detection in the BWP is discarded.   Timer, counter, and measurement value information related to radio link monitoring in the BWP is discarded.   Stored information related to a HARQ in the BWP is discarded.   Timer and counter information related to DRX (or C-DRX) in the BWP is discarded.       

     After operation  1   k - 11 , the UE may perform operations  1   k - 12  and  1   k - 13  to continuously measure a CSI-RS resource belonging to the current active BWP and transmit a measurement report when a specific reporting condition is satisfied. 
     Upon determining, in operation  1   k - 5 , that the CSI-RS resource specified in operation  1   k - 4  is the same as the preset CSI-RS resource measured in the previous active BWP, in operation  1   k - 6 , the UE may continuously measure the CSI-RS resource specified in operation  1   k - 4 . The UE may input the CSI-RS measurement value measured in the new active BWP, to an L1/L3 measurement filter to which the CSI-RS measurement value in the previous active BWP has been input, to obtain a result thereof, and maintain a timer triggered by the CSI-RS or related to beam failure detection, radio link monitoring, radio link failure, and DRX, to perform a related operation. 
     In operation  1   k - 7 , the UE determines whether the CSI-RS resource measured in operation  1   k - 6  satisfies a preset measurement reporting condition, and transmit a measurement report upon determining that the CSI-RS resource satisfies the condition. The measurement report may include BWP-Id information indicating a certain BWP in which the CSI-RS resource is measured, or include a 1-bit indicator indicating that the CSI-RS resource is measured in two or more BWPs, and/or one or more BWP Ids. 
     Although the flowchart of  FIG.  1 K  is illustrated on the assumption of one active BWP, when two or more active BWPs are simultaneously usable, the UE may perform the procedure of  FIG.  1 K  simultaneously on the two or more active BWPs. 
     The CSI-RS resource may be configured per BWP in such a manner that each CSI-RS resource configuration IE (CSI-ResourceConfig, NZP-CSI-RS-ResourceSet, NZP-CSI-RS-Resource, CSI-IM-ResourceSet, CSI-IM-Resource, ZP-CSI-RS-ResourceSet, ZP-CSI-RS-Resource, . . . ) includes a BWP Id to which the CSI-RS resource belongs. 
     In the active BWP specification operation and the CSI-RS specification operation, the UE may specify one or more BWPs and CSI-RSs and perform subsequent operations on each of the BWPs and the CSI-RSs. 
       FIG.  2 A  is a schematic diagram of a structure for performing packet duplication transmission in a carrier aggregation (CA) environment. Packet duplication transmission refers to a technology by which one packet data convergence protocol (PDCP) entity (e.g. a PDCP entity  2   a - 10 ) duplicates a packet (i.e., a PDCP protocol data unit (PDU)) and sends the packets to two or more radio link control (RLC) entities (e.g. an RLC 1   2   a - 20  and an RLC 2   2   a - 30 ) to independently transmit the packets. RLC entities connected to a PDCP entity may be defined as a primary RLC entity and a secondary RLC entity. A PDCP layer (also referred to as entity) of a transmitter may send a packet to the primary RLC entity regardless of whether packet duplication is activated. The PDCP layer of the transmitter may send a packet to the secondary RLC entity only when packet duplication is activated. In this case, one RLC entity may correspond to one logical channel. Mapping between logical channels and cells may be required to effectively performing packet duplication transmission in a CA environment. In other words, cells to which logical channels may send data need to be restricted. According to an embodiment of the disclosure, as illustrated in  FIG.  2 A , the PDCP entity  2   a - 10  may send packets to the RLC 1   2   a - 20  and the RLC 2   2   a - 30 , which may use one or more of a primary cell (PCell)  2   a - 60 , a secondary cell (SCell)  1   2   a - 70 , a SCell  2   2   a - 80 , a SCell  3   2   a - 90 , a SCell  4   2   a - 100 , and a SCell  5   2   a - 110  to transmit packets. When packet duplication is activated, a logical channel  1   2   a - 40  may send data to the SCell  1   2   a - 70  and the SCell  2   2   a - 80 , and a logical channel  2   2   a - 50  may send data to the SCell  3   2   a - 90  and the SCell  4   2   a - 100 . Herein, a cell may also be called a component carrier (CC). 
     Based on packet duplication, the same packet is transmitted using two or more RLC entities and thus radio resource consumption may be increased. Performing of packet duplication all the time may cause inefficient use of radio resources and thus is not appropriate. Therefore, packet duplication may be controlled to be performed only when necessary. Controlling of packet duplication to be performed in a radio bearer for which packet duplication is configured is called activation of packet duplication. On the contrary, controlling of packet duplication not to be performed in a radio bearer for which packet duplication is configured is called deactivation of packet duplication. Activation and deactivation of packet duplication may be directed by a base station (also referred to as a next-generation NodeB (gNB)) and be performed by a UE. Alternatively, activation and deactivation of packet duplication may be performed based on a preset condition of the UE. 
     When packet duplication is deactivated, cells to which a logical channel corresponding to each RLC entity may send data may not need to be restricted. As shown in  FIG.  2 A , a PDCP entity  2   a - 15  may send packets to an RLC 1   2   a - 25  and an RLC 2   2   a - 35 , which may use one or more of a PCell  2   a - 65 , a SCell  1   2   a - 75 , a SCell  2   2   a - 85 , a SCell  3   2   a - 95 , a SCell  4   2   a - 105 , and a SCell  5   2   a - 115  to transmit packets. Therefore, when packet duplication is deactivated, a logical channel  1   2   a - 45  and a logical channel  2   2   a - 55  may use all of the PCell  2   a - 65 , the SCell  1   2   a - 75 , the SCell  2   2   a - 85 , the SCell  3   2   a - 95 , the SCell  4   2   a - 105 , and the SCell  5   2   a - 115  to transmit packets. That is, packets may be transmitted to all activated cells. However, when packet duplication is deactivated, the PDCP entity  2   a - 15  does not send a packet to the secondary RLC entity  2   a - 35  and thus the secondary RLC entity  2   a - 35  may not transmit much data. 
       FIG.  2 B  is a schematic diagram for describing a procedure in a case in which an RLC maximum retransmission threshold is reached in an environment in which packet duplication is configured. The procedure is performed in an RLC acknowledged mode (AM) and, when a negative acknowledgement (NACK) message is received in response to an initially transmitted packet, a UE sets a RETX_COUNT to be 0 and performs retransmission. Thereafter, the RETX_COUNT is increased by 1 whenever a NACK message is received in response to the same packet and, when a preset maximum retransmission threshold maxRetxThreshold is reached, the UE may notify a gNB of the event. When an RLC entity having reached the maximum retransmission threshold may not use a PCell or a primary secondary cell (PSCell) and may use only SCells like RLC 1   2   a - 20  or RLC 2   2   a - 30  of  FIG.  2 A , the UE may simply notify the gNB that the maximum retransmission threshold is reached  2   b - 100 . In this case, to notify the RLC entity having an error, the UE transmits a logical channel identifier (LCID) and cell group information of the RLC entity to the gNB. Thereafter, the gNB may, for example, reset the RLC entity or reconfigure a radio bearer to solve the error. When cells usable by the logical channel are not restricted or the logical channel may use a PCell or a PSCell, the UE performs a radio link failure (RLF) procedure. 
     Although the RLC entity having reached the maximum retransmission threshold may not use a PCell or a PSCell and may use only SCells like RLC 1   2   a - 20  or RLC 2   2   a - 30  of  FIG.  2 A , when packet duplication is deactivated, the RLC entity may transmit a packet by using a PCell or a PSCell. Activation or deactivation of packet duplication may be flexibly switched based on an indication of the gNB or a preset condition. The embodiment of the disclosure illustrated in  FIG.  2 B  assumes that packet duplication is deactivated  2   b - 10  until second retransmission  2   b - 32  and is activated  2   b - 15  after the second retransmission  2   b - 32 . In this case, initial transmission  2   b - 30 , first retransmission  2   b - 31 , second retransmission  2   b - 32 , third retransmission  2   b - 33 , and fourth retransmission  2   b - 34  may be performed to a PCell or a PSCell. At this time, when only the LCID and the cell group information of the RLC entity having reached the maximum retransmission threshold  2   b - 50  are transmitted  2   b - 100  from the UE  2   b - 25  to the gNB  2   b - 20 , the gNB  2   b - 20  may not accurately determine the error. 
       FIG.  2 C  is a schematic diagram for describing a cell switching procedure in a case in which packet duplication is deactivated, according to an embodiment of the disclosure. As illustrated in  FIG.  2 C , a PDCP entity  2   c - 10  may send packets to an RLC 1   2   c - 20  and an RLC 2   2   c - 30 , which may use one or more of a PCell  2   c - 60 , a SCell  1   2   c - 70 , a SCell  2   2   c - 80 , a SCell  3   2   c - 90 , a SCell  4   2   c - 100 , and a SCell  5   2   c - 110  to transmit packets. A list of cells usable by each logical channel when packet duplication is activated is the same as that of  FIG.  2 A . In other words, a logical channel  1   2   c - 40  may use the SCell  1   2   c - 70  and the SCell  2   2   c - 80 , and a logical channel  2   2   c - 50  may use the SCell  3   2   c - 90  and the SCell  4   2   c - 100 . 
     When packet duplication of a corresponding radio bearer is deactivated, cells usable by each logical channel may be increased. As shown in  FIG.  2 C , a PDCP entity  2   c - 15  may send packets to an RLC 1   2   c - 25  and an RLC 2   2   c - 35 , which may use one or more of a PCell  2   c - 65 , a SCell  1   2   c - 75 , a SCell  2   2   c - 85 , a SCell  3   2   c - 95 , a SCell  4   2   c - 105 , and a SCell  5   2   c - 115  to transmit packets. According to the embodiment of the disclosure illustrated in  FIG.  2 C , when packet duplication is deactivated, each logical channel of the radio bearer may use all cells usable by logical channels connected to the radio bearer. That is, each of a logical channel  1   2   c - 45  and a logical channel  2   2   c - 35  may use all of the SCell  1   2   c - 75 , the SCell  2   2   c - 85 , the SCell  3   2   c - 95 , and the SCell  4   2   c - 105  usable by the logical channels. However, the PCell  2   c - 65  and the SCell  5   2   c - 115  unusable by the logical channel  1   2   c - 45  or the logical channel  2   2   c - 55  may not be used even when packet duplication is deactivated. According to the embodiment of the disclosure illustrated in  FIG.  2 C , a PDCP layer of a transmitter may send a packet to a primary RLC entity regardless of whether packet duplication is activated. The PDCP layer of the transmitter may send a packet to a secondary RLC entity only when packet duplication is activated. 
       FIG.  2 D  is a flowchart of a UE procedure in a case in which a specific packet reaches an RLC maximum retransmission threshold, according to an embodiment of the disclosure. When the specific packet reaches the RLC maximum retransmission threshold and a list of cells usable by a logical channel corresponding to an RLC entity does not include a PCell or a PSCell in operation  2   d -10, a UE may perform a RLF procedure of a master cell group (MCG) or a secondary cell group (SCG) in operation  2   d -40 or simply notify a gNB that the maximum retransmission threshold is reached in operation  2   d - 30  or  2   b - 100  of  FIG.  2 B , based on whether packet duplication has been continuously activated after the packet is initially transmitted in operation  2   d -20. In this regard, the UE may compare an initial transmission timing of every packet (e.g., an RLC PDU) and the latest packet duplication activation timing. When packet duplication has been continuously activated up to now after the packet having reached the maximum retransmission threshold is initially transmitted, the UE may notify the gNB that the maximum retransmission threshold is reached in operation  2   d -30. The RLC entity of the UE may inform a radio resource control (RRC) entity of the UE, and the RRC entity of the UE may report to the gNB. In this case, the RRC entity of the UE may provide a report indicating the RLC entity having an error, to the gNB, and the report provided to the gNB may include an LCID and cell group information. When packet duplication has been deactivated after the packet having reached the maximum retransmission threshold is initially transmitted, the UE may perform the RLF procedure of the MCG or the SCG in operation  2   d -40. 
       FIG.  2 E  is a flowchart of a UE procedure in a case in which a specific packet reaches an RLC maximum retransmission threshold, according to another embodiment of the disclosure. When the specific packet reaches the RLC maximum retransmission threshold and a list of cells usable by a logical channel corresponding to an RLC entity does not include a PCell or a PSCell in operation  2   e - 10 , a UE may perform a RLF procedure of a MCG or a SCG in operation  2   e - 40  or simply notify a gNB that the maximum retransmission threshold is reached in operation  2   e - 30  or  2   b - 100  of  FIG.  2 B , based on whether packet duplication is activated at a timing at which the maximum retransmission threshold is reached in operation  2   e - 20 . According to an embodiment of the disclosure, the UE does not need to check an initial transmission timing of every packet (e.g., an RLC PDU) and may merely determine whether packet duplication is activated at the timing at which the maximum retransmission threshold is reached. When packet duplication is activated at the timing at which the maximum retransmission threshold is reached, the UE may notify the gNB that the maximum retransmission threshold is reached in operation  2   e - 30 . The RLC entity of the UE may inform a RRC entity of the UE, and the RRC entity of the UE may report to the gNB. The RRC entity of the UE may provide a report indicating the RLC entity having an error, to the gNB, and the report provided to the gNB may include an LCID and cell group information. When packet duplication is deactivated at the timing at which the maximum retransmission threshold is reached, the UE may perform the RLF procedure of the MCG or the SCG in operation  2   e - 40 . 
       FIG.  2 F  is a flowchart of a UE procedure in a case in which a specific packet reaches an RLC maximum retransmission threshold, according to another embodiment of the disclosure. When the specific packet reaches the RLC maximum retransmission threshold and a list of cells usable by a logical channel corresponding to an RLC entity does not include a PCell or a PSCell in operation  2   f - 10 , a UE may perform a RLF procedure of a MCG or a SCG in operation  2   f - 40  or simply notify a gNB that the maximum retransmission threshold is reached in operation  2   f - 30  or  2   b - 100  of  FIG.  2 B , based on whether initial transmission and all retransmissions of the packet having reached the maximum retransmission threshold are performed to a cell included in a list of cells usable by a corresponding logical channel in operation  2   f - 20 . In this regard, the UE needs to record cells to which initial transmission and retransmissions of every packet (e.g., an RLC PDU) are performed, and may compare the cells at a timing at which the maximum retransmission threshold is reached. When the initial transmission and all the retransmissions of the packet having reached the maximum retransmission threshold are performed to a cell included in the list of cells usable by the logical channel, the UE may notify the gNB that the maximum retransmission threshold is reached in operation  2   f - 30 . The RLC entity of the UE may inform a RRC entity of the UE, and the RRC entity of the UE may report to the gNB. In this case, the RRC entity of the UE may provide a report indicating the RLC entity having an error, to the gNB, and the report provided to the gNB may include an LCID and cell group information. When at least one of the initial transmission or all the retransmissions of the packet having reached the maximum retransmission threshold is performed to a cell not included in the list of cells usable by the logical channel, the UE may perform the RLF procedure of the MCG or the SCG in operation  2   f - 40 . 
     In another embodiment of the disclosure, the UE may perform the RLF procedure or simply notify the gNB, based on whether the initial transmission and all the retransmissions of the packet having reached the maximum retransmission threshold are performed to a SCell. In this case, when the initial transmission and all the retransmissions of the packet having reached the maximum retransmission threshold are performed to a SCell, the UE may report the maximum retransmission threshold. Otherwise, the UE may perform the RLF procedure of the MCG or the SCG. In operation  2   f - 20 , it may be additionally considered whether packet duplication is activated at the timing. 
       FIG.  2 G  is a flowchart of a UE procedure in a case in which a specific packet reaches an RLC maximum retransmission threshold, according to another embodiment of the disclosure. When the specific packet reaches the RLC maximum retransmission threshold and a list of cells usable by a logical channel corresponding to an RLC entity does not include a PCell or a PSCell in operation  2   g - 10 , a UE may perform a RLF procedure of a MCG or a SCG in operation  2   g - 40  or simply notify a gNB that the maximum retransmission threshold is reached in operation  2   g - 30  or  2   b - 100  of  FIG.  2 B , based on whether initial transmission and all retransmissions of the packet having reached the maximum retransmission threshold are performed while packet duplication is being activated in operation  2   g - 20 . In this regard, the UE needs to record activation statuses of packet duplication when initial transmission and retransmissions of every packet (e.g., an RLC PDU) are performed, and may compare the activation statuses at a timing at which the maximum retransmission threshold is reached. When the initial transmission and all the retransmissions of the packet having reached the maximum retransmission threshold are performed while packet duplication is being activated, the UE may notify the gNB that the maximum retransmission threshold is reached in operation  2   g - 30 . The RLC entity of the UE may inform a RRC entity of the UE, and the RRC entity of the UE may report to the gNB. In this case, the RRC entity of the UE may provide a report indicating the RLC entity having an error, to the gNB, and the report provided to the gNB may include an LCID and cell group information. When at least one of the initial transmission or all the retransmissions of the packet having reached the maximum retransmission threshold is performed while packet duplication is being deactivated, the UE may perform the RLF procedure of the MCG or the SCG in operation  2   g - 40 . In operation  2   g - 20 , it may be additionally considered whether packet duplication is activated at the timing. 
       FIG.  2 H  is a flowchart of a UE procedure in a case in which a specific packet reaches an RLC maximum retransmission threshold, according to another embodiment of the disclosure. When the specific packet reaches the RLC maximum retransmission threshold and a list of cells usable by a logical channel corresponding to an RLC entity does not include a PCell or a PSCell in operation  2   h - 10 , a UE may perform a RLF procedure of a MCG or a SCG in operation  2   h - 40  or simply notify a gNB that the maximum retransmission threshold is reached in operation  2   h - 30  or  2   b - 100  of  FIG.  2 B , based on whether packet duplication has been continuously activated during a preset period of time until a timing at which the maximum retransmission threshold is reached in operation  2   h - 20 . For example, when the preset period of time is 1 sec., the UE may determine whether packet duplication has been continuously activated within, for example, the last 1 sec. before the timing at which the maximum retransmission threshold is reached. In this regard, the UE may record the latest packet duplication activation timing of every packet (e.g., an RLC PDU) and compare the same with the timing at which the maximum retransmission threshold is reached. When packet duplication has been continuously activated during the latest preset period of time until the timing at which the maximum retransmission threshold is reached, the UE may notify the gNB that the maximum retransmission threshold is reached in operation  2   h - 30 . The RLC entity of the UE may inform a RRC entity of the UE, and the RRC entity of the UE may report to the gNB. In this case, the RRC entity of the UE may provide a report indicating the RLC entity having an error, to the gNB, and the report provided to the gNB may include an LCID and cell group information. When packet duplication has been deactivated during the preset period of time until the timing at which the maximum retransmission threshold is reached, the UE may perform the RLF procedure of the MCG or the SCG in operation  2   h - 40 . 
     According to an embodiment of the disclosure, criteria used when the UE determines whether to perform a RLF operation or to simply notify a gNB that a maximum retransmission threshold is reached are not limited to the examples described above in relation to  FIGS.  2 D to  2 H . The UE may determine whether to perform the RLF operation or to simply notify the gNB that the maximum retransmission threshold is reached, by simultaneously or sequentially applying two or more of the embodiments of the disclosure described above in relation to  FIGS.  2 D to  2 H . 
       FIG.  2 I  is a schematic diagram for describing a procedure, performed by a UE, of updating a retransmission count, according to an embodiment of the disclosure. According to the embodiment of the disclosure illustrated in  FIG.  2 B , when a NACK message corresponding to an initially transmitted packet is received, a UE may reset a retransmission count RETX_COUNT. Whenever a NACK message is received after retransmission, the UE may increase the RETX_COUNT by 1. However, according to the previous embodiment of the disclosure, a packet may be transmitted to a cell other than cells usable by a logical channel while packet duplication is being deactivated, which may not be considered for a maximum retransmission threshold. 
     Therefore, as illustrated in  FIG.  2 I , according to an embodiment of the disclosure, the UE  2   i - 25  may reset the RETX_COUNT  2   i - 40  at a timing at which packet duplication is activated. According to an embodiment of the disclosure, it is assumed that initial transmission  2   i - 30  and first retransmission  2   i - 31  to gNB  2   i - 20  fail and second retransmission  2   i - 32  is performed while packet duplication is deactivated  2   i - 10 , and then packet duplication is activated  2   i - 15 . As packet duplication is activated, the UE  2   i - 25  may reset the RETX_COUNT. Thereafter, a NACK message is received in response to the second retransmission  2   i - 62 . In this case, the UE  2   i - 25  may regard the NACK message as failure of initial transmission of the packet and update the RETX_COUNT to 0. When a maximum retransmission threshold is reached thereafter, because all transmissions of the packet are performed while packet duplication is being activated, the UE  2   i - 25  may not declare RLF and may report to the gNB  2   i - 20  that the maximum retransmission threshold is reached. 
     According to another embodiment of the disclosure, after the RETX_COUNT is reset, the UE may ignore previous retransmissions and perform initial transmission again. 
     According to another embodiment of the disclosure, after the RETX_COUNT is reset, retransmission may be regarded as first transmission  2   i - 33 . When a NACK message is received in response to the first transmission, the UE  2   i - 25  may regard the NACK message as failure of the first transmission and may perform a second transmission  2   i - 34 . 
       FIG.  3    is a block diagram of a UE according to an embodiment of the disclosure. 
     Referring to  FIG.  3   , the UE may include a processor  301 , a transceiver  302 , and a memory  303 . Herein, the processor  301  may be defined as a circuit- or ASIC or at least one processor. 
     The processor  301  illustrated in  FIG.  3    may correspond to the controller  330  described above in relation to  FIG.  1 C , the transceiver  302  illustrated in  FIG.  3    may correspond to the communicator  310  described above in relation to  FIG.  1 C , and the memory  303  illustrated in  FIG.  3    may correspond to the storage  320  described above in relation to  FIG.  1 C . 
     The processor  301  according to an embodiment of the disclosure may control overall operations of the UE. For example, the processor  301  may control the flow of signals between blocks to perform the operations described above in the previous embodiments of the disclosure. 
     The transceiver  302  according to an embodiment of the disclosure may transmit and receive signals to and from other network entities. For example, the transceiver  302  may receive system information and a synchronization signal or a reference signal from a base station. 
     The memory  303  according to an embodiment of the disclosure may store at least one of information to be transmitted or received through the transceiver  302  or information generated by the processor  301 . 
     The processor  301  according to an embodiment of the disclosure may perform a series of operations described above in relation to FIG. H. 
     The processor  301  according to an embodiment of the disclosure may configure a reference signal for the UE in consideration of different frequency bands, and perform cell measurement and reporting by using the configured reference signal. 
     The processor  301  according to another embodiment of the disclosure may perform a series of operations described above in relation to  FIGS.  2 D to  2 H . When a specific packet reaches an RLC maximum retransmission threshold and a list of cells usable by a logical channel corresponding to an RLC entity does not include a PCell or a PSCell, the processor  301  according to another embodiment of the disclosure may determine whether to perform a RLF procedure of a MCG or a SCG or to simply notify a base station that the maximum retransmission threshold is reached, for the UE based on whether the packet has been transmitted to a cell included in a list of cells usable by the logical channel, or information about activation of packet duplication. 
     That is, the processor  301  may control the other elements of the UE to implement all of the previous embodiments of the disclosure. 
       FIG.  4    is a block diagram of a base station according to an embodiment of the disclosure. 
     Referring to  FIG.  4   , the base station may include a processor  410 , a transceiver  420 , and a memory  430 . 
     The processor  410  illustrated in  FIG.  4    may correspond to the controller  240  described above in relation to  FIG.  1 B , the transceiver  420  illustrated in  FIG.  4    may correspond to the wireless communicator  210  described above in relation to  FIG.  1 B , and the memory  430  illustrated in  FIG.  4    may correspond to the storage  230  described above in relation to  FIG.  1 B . 
     Herein, the processor  410  may be defined as a circuit- or application-specific IC or at least one processor. 
     The processor  410  according to an embodiment of the disclosure may control overall operations of the base station according to an embodiment of the disclosure. For example, the processor  410  may control the flow of signals between blocks to perform the operations described above in the previous embodiments of the disclosure. 
     The transceiver  420  according to an embodiment of the disclosure may transmit and receive signals to and from other network entities. For example, the transceiver  420  may transmit system information and a synchronization signal or a reference signal to a UE. 
     The memory  430  may store at least one of information to be transmitted or received through the transceiver  420  or information generated by the processor  410 . 
     The methods according to the embodiments of the disclosure as described herein or in the following claims may be implemented as hardware, software, or a combination of hardware and software. 
     When implemented as software, a computer-readable storage medium storing one or more programs (e.g., software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors in an electronic device. The one or more programs include instructions directing the electronic device to execute the methods according to the embodiments of the disclosure as described herein or in the following claims. 
     The programs (e.g., software modules or software) may be stored in non-transitory non-volatile memory including random access memory (RAM) or flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), a magnetic disc storage device, a compact disc (CD)-ROM, a digital versatile disc (DVD), another optical storage device, or a magnetic cassette. Alternatively, the programs may be stored in memory including a combination of some or all of the above-mentioned storage media. A plurality of such memories may be included. 
     In addition, the programs may be stored in an attachable storage device accessible through any or a combination of communication networks such as the Internet, an intranet, a local area network (LAN), a wide LAN (WLAN), and a storage area network (SAN). Such a storage device may access the electronic device via an external port. Furthermore, an additional storage device on the communication network may access the electronic device. 
     In the afore-described embodiments of the disclosure, an element or elements included in the disclosure are expressed in a singular or plural form depending on the described embodiments of the disclosure. However, the singular or plural form is selected appropriately for a situation assumed for convenience of description and the disclosure is not limited to the singular or plural form. An element expressed in a singular form may include a plurality of elements, and elements expressed in a plural form may include a single element. 
     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.