Patent Publication Number: US-2021166577-A1

Title: Artificial intelligent electroencephalography headband and learning system and method using the same

Description:
TECHNICAL FIELD 
     The present invention relates to an artificial intelligent electroencephalography headband and a learning system and method using the same. 
     BACKGROUND ART 
     Electronic learning (hereinafter, “e-learning”) is a system that offers personalized learning to anyone, anytime and anywhere using information and communication technology. In other words, e-learning is a learning system using cyberspace in face-to-face learning, that enhances students&#39; ability-based learning activities or self-directed learning activities as the place and time constraints become less stringent. 
     One problem with e-learning is that learning performance may decrease because, like traditional offline learning systems, information is unilaterally delivered to learners without consideration for learners&#39; concentration. 
     DISCLOSURE 
     Technical Problem 
     An aspect of the present invention is to solve the above-described needs and/or problems. 
     Another aspect of the present invention is to provide an artificial intelligent electroencephalography headband capable of accurately measuring a learner&#39;s brain waves. 
     Another aspect of the present invention is to provide a learning system and method that analyze a learner&#39;s concentration patterns on the basis of an artificial intelligent electroencephalography headband and give guidance on a learning method that fits these patterns. 
     Technical Solution 
     An exemplary embodiment of the present invention provides an artificial intelligent electroencephalography headband including: a sensor part that measures a learner&#39;s brain waves; a first algorithm processing part that comprises an artificial intelligence processor equipped with a neural network model and analyzes the measured brain waves; and a communication part that transmits learning guidance information created based on results of analysis of the brain waves to an external device, wherein the first algorithm processing part feeds the learner&#39;s left brain information and right brain information included in the brain waves and the learner&#39;s eye movement signals included in the brain waves into the neural network model and analyzes wave patterns in an EEG spectrum. 
     The learner&#39;s eye movement signals may comprise the number and frequency of the learner&#39;s eye blinks. 
     The learning guidance information may comprise a message urging the learner to increase concentration, a message urging the learner to take a rest, a message urging the learner to go over what he or she learned, and a learning content recommendation message. 
     The artificial intelligent electroencephalography headband may further comprise: a sound input part that picks up a sound source from the external device; and a sound output part that outputs the sound source to the learner. 
     The sound source may comprise audio learning content and relaxing sounds. 
     The artificial intelligent electroencephalography headband may further comprise a second algorithm processing part that removes noise components added into the sound source by producing a sound wave with an inverted phase to ambient noise picked up by the sound input part. 
     Another exemplary embodiment of the present invention provides a learning system using an artificial intelligent electroencephalography headband, the learning system comprising: an electroencephalography headband of claim  1 ; and a personal content providing medium that is connected to the electroencephalography headband over a first communication network and provides learning guidance information to a learner. 
     The first communication network may be implemented as a short-range communication network. 
     The personal content providing medium may comprise a home robot a first user terminal. 
     The personal content providing medium may provide the learning guidance information differently depending on the learner&#39;s state of concentration. 
     The personal content providing medium may further comprise an indication part shows the learner&#39;s concentration level in a visually distinct way. 
     The learning system may further comprise a learning server connected to the personal content providing medium over a second communication network and connected to a second user terminal of a learning content provider or of the learner&#39;s parent over a third communication network, wherein the learning server comprises: a data collector that collects the learning guidance information from the personal content providing medium over the second communication network; a data analyzer that comprises the AI processor equipped with the neural network model and analyzes the collected learning guidance information and outputs concentration-related information; and a data transmitter that transmits the concentration-related information to the personal content providing medium over the second communication network or transmits the concentration-related information to the second user terminal over the third communication network. 
     The concentration-related information transmitted to the personal content providing medium may comprise information on the average change in concentration among other learners, information on the positional distribution of records of how the learner&#39;s concentration has changed relative to the average, and information on decreased concentration spans. 
     The concentration-related information transmitted to the second user terminal may comprise information on records of how the learner&#39;s concentration has changed and learning achievement information. 
     The learning system may further comprise a learning server connected to the personal content providing medium over a second communication network and connected to a second user terminal of an instructor or parent corresponding to the leaner over a third communication network, wherein the learning server comprises: a data collector that collects the learning guidance information from a plurality of personal content providing media over the second communication network; a data analyzer that comprises the Al processor equipped with the neural network model and analyzes the collected learning guidance information and outputs concentration-related information; and a data transmitter that transmits the concentration-related information to the second user terminal over the third communication network. 
     The concentration-related information transmitted to the second user terminal may comprise information on the average change in concentration among other learners, information on the positional distribution of records of how the learner&#39;s concentration has changed relative to the average, information on decreased concentration spans, information on records of how the learner&#39;s concentration has changed, and learning achievement information. 
     The second communication network and the third communication network may be implemented as long-range communication networks. 
     A still another exemplary embodiment of the present invention provides a learning method using an artificial intelligent electroencephalography headband, the learning method comprising: measuring a learner&#39;s brain waves by a sensor part; analyzing the measured brain waves by a first algorithm processing part comprising an artificial intelligence processor equipped with a neural network model; transmitting learning guidance information created based on results of analysis of the brain waves to an external device by a communication part; and providing the learning guidance information to the learner through a personal content providing medium connected to a first communication network, wherein the analysis of the brain waves comprises feeding the learner&#39;s left brain information and right brain information included in the brain waves and the learner&#39;s eye movement signals included in the brain waves into the neural network model and analyzing wave patterns in an EEG spectrum. 
     Advantageous Effects 
     The present invention provides an artificial intelligent electroencephalography headband capable of accurately measuring a learner&#39;s brain waves. 
     Furthermore, the present invention can analyze a learner&#39;s concentration patterns on the basis of an artificial intelligent electroencephalography headband and give guidance on a learning method that fits these pattern. 
     The advantageous effects according to an embodiment of the present invention are not limited by what has been exemplified above, and more various advantageous effects are included in the present specification. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a wireless communication system to which the methods proposed herein may be applied. 
         FIG. 2  shows an example of a basic operation of an user equipment and a 5G network in a 5G communication system. 
         FIG. 3  illustrates an example of application operation of an user equipment and a 5G network in a 5G communication system. 
         FIGS. 4 to 7  show an example of an operation of an user equipment using 5G communication. 
         FIG. 8  is a diagram illustrating an example of a 3GPP signal transmission/reception method. 
         FIG. 9  illustrates an SSB structure and  FIG. 10  illustrates SSB transmission. 
         FIG. 11  illustrates an example of a random access procedure. 
         FIG. 12  shows an example of an uplink grant. 
         FIG. 13  shows an example of a conceptual diagram of uplink physical channel processing. 
         FIG. 14  shows an example of an NR slot in which a PUCCH is transmitted. 
         FIG. 15  is a block diagram of a transmitter and a receiver for hybrid beamforming. 
         FIG. 16  shows an example of beamforming using an SSB and a CSI-RS. 
         FIG. 17  is a flowchart illustrating an example of a DL BM process using an SSB. 
         FIG. 18  shows another example of DL BM process using a CSI-RS. 
         FIG. 19  is a flowchart illustrating an example of a process of determining a reception beam of a UE. 
         FIG. 20  is a flowchart illustrating an example of a transmission beam determining process of a BS. 
         FIG. 21  shows an example of resource allocation in time and frequency domains related to an operation of  FIG. 21 . 
         FIG. 22  shows an example of a UL BM process using an SRS. 
         FIG. 23  is a flowchart illustrating an example of a UL BM process using an SRS. 
         FIG. 24  is a diagram showing an example of a method of indicating a pre-emption. 
         FIG. 25  shows an example of a time/frequency set of pre-emption indication. 
         FIG. 26  shows an example of a narrowband operation and frequency diversity. 
         FIG. 27  is a diagram illustrating physical channels that may be used for MTC and a general signal transmission method using the same. 
         FIG. 28  is a diagram illustrating an example of scheduling for each of MTC and legacy LTE. 
         FIG. 29  shows an example of a frame structure when a subcarrier spacing is 15 kHz. 
         FIG. 30  shows an example of a frame structure when a subscriber spacing is 3.75 kHz. 
         FIG. 31  shows an example of a resource grid for NB-IoT uplink. 
         FIG. 32  shows an example of an NB-IoT operation mode. 
         FIG. 33  is a diagram illustrating an example of physical channels that may be used for NB-IoT and a general signal transmission method using the same. 
         FIG. 34  is a perspective view of an artificial intelligent electroencephalography headband according to an exemplary embodiment of the present invention. 
         FIG. 35  is a perspective view of an artificial intelligent electroencephalography headband according to another exemplary embodiment of the present invention. 
         FIG. 36  shows an internal configuration of the artificial intelligent electroencephalography headbands of  FIGS. 34 and 35 . 
         FIG. 37  shows a detailed configuration of a first algorithm processing part of  FIG. 36 . 
         FIG. 38  shows frequency bands, brain wave patterns, and brain states depending on the type of brain waves. 
         FIG. 39  shows an example of EEG modeling including both left/right EEG information and eye movement signals. 
         FIG. 40  shows an example of changes in brain waves associated with eye movements. 
         FIG. 41  shows an example of a learning system using an artificial intelligent electroencephalography band. 
         FIG. 42  shows another example of a learning system using an artificial intelligent electroencephalography headband. 
         FIG. 43  shows yet another example of a learning system using an artificial intelligent electroencephalography band. 
         FIG. 44  shows a further example of a learning system using an artificial intelligent electroencephalography band. 
         FIGS. 45 to 47  show a learning method using an artificial intelligent electroencephalography band according to an exemplary embodiment of the present invention when taking an online course. 
         FIGS. 48 and 49  show a learning method using an artificial intelligent electroencephalography band according to an exemplary embodiment of the present invention when taking an offline course. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, embodiments of the disclosure will be described in detail with reference to the attached drawings. The same or similar components are given the same reference numbers and redundant description thereof is omitted. The suffixes “module” and “unit” of elements herein are used for convenience of description and thus may be used interchangeably and do not have any distinguishable meanings or functions. Further, in the following description, if a detailed description of known techniques associated with the present invention would unnecessarily obscure the gist of the present invention, detailed description thereof will be omitted. In addition, the attached drawings are provided for easy understanding of embodiments of the disclosure and do not limit technical spirits of the disclosure, and the embodiments should be construed as including all modifications, equivalents, and alternatives falling within the spirit and scope of the embodiments. 
     While terms, such as “first”, “second”, etc., may be used to describe various components, such components must not be limited by the above terms. The above terms are used only to distinguish one component from another. 
     When an element is “coupled” or “connected” to another element, it should be understood that a third element may be present between the two elements although the element may be directly coupled or connected to the other element. When an element is “directly coupled” or “directly connected” to another element, it should be understood that no element is present between the two elements. 
     The singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     In addition, in the specification, it will be further understood that the terms “comprise” and “include” specify the presence of stated features, integers, steps, operations, elements, components, and/or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or combinations. 
     A. Example of Autonomous Vehicle and 5G Network 
       FIG. 1  is a block diagram of a wireless communication system to which methods proposed in the disclosure are applicable. 
     Referring to  FIG. 1 , a device including an autonomous driving module is defined as a first communication device ( 910  of  FIG. 1  and see paragraph N for detailed description), and a processor  911  may perform detailed autonomous driving operations. 
     Another vehicle or a 5G network communicating with the autonomous driving device is defined as a second communication device ( 920  of  FIG. 1 , and see paragraph N for details), and a processor  921  may perform detailed autonomous driving operations. 
     Details of a wireless communication system, which is defined as including a first communication device, which is an autonomous vehicle, and a second communication device, which is a 5G network, may refer to paragraph N. 
     B. AI operation Using 5G Communication 
       FIG. 2  shows an example of a basic operation of a user equipment and a 5G network in a 5G communication system. 
     The UE transmits the specific information transmission to the 5G network (SI). 
     Then, the 5G network performs 5G processing on the specific information (S 2 ). 
     In this connection, the 5G processing may include Al processing. 
     Then, the 5G network transmits a response including the AI processing result to the UE (S 3 ). 
       FIG. 3  shows an example of application operation of a user terminal and a 5G network in a 5G communication system. 
     The UE performs an initial access procedure with the 5G network (S 20 ). The initial connection procedure will be described in more detail in paragraph F. 
     Then, the UE performs a random access procedure with the 5G network (S 21 ). The random access procedure will be described in more detail in paragraph G. 
     The 5G network transmits an UL grant for scheduling transmission of specific information to the UE (S 22 ). The process of the UE receiving the UL grant will be described in more detail in the UL transmission/reception operation in paragraph H. 
     Then, the UE transmits specific information to the 5G network based on the UL grant (S 23 ). 
     Then, the 5G network performs 5G processing on the specific information (S 24 ). 
     In this connection, the 5G processing may include AI processing. 
     Then, the 5G network transmits a DL grant for scheduling transmission of the 5G processing result of the specific information to the UE (S 25 ). 
     Then, the 5G network transmits a response including the AI processing result to the UE based on the DL grant (S 26 ). 
     In  FIG. 3 , an example in which the AI operation and the initial connection process, or the random access process and the DL grant reception process are combined with each other has been exemplarily described using the S 20  to S 26 . However, the present invention is not limited thereto. 
     For example, the initial connection process and/or the random access process may be performed using the process of S 20 , S 22 , S 23 , S 24 , and S 24 . In addition, the initial connection process and/or the random access process may be performed using, for example, the process of S 21 , S 22 , S 23 , S 24 , and S 26 . Further, the Al operation and the downlink grant reception procedure may be combined with each other using the process of S 23 , S 24 , S 25 , and S 26 . 
     C. UE Operation Using 5G Communication 
       FIG. 4  to  FIG. 7  show an example of the operation of the UE using 5G communication. 
     Referring first to  FIG. 4 , the UE performs an initial access procedure with the 5G network based on SSB to obtain DL synchronization and system information (S 30 ). 
     Then, the UE performs a random access procedure with the 5G network for UL synchronization acquisition and/or UL transmission (S 31 ). 
     Then, the UE receives an UL grant to the 5G network to transmit specific information (S 32 ). 
     Then, the UE transmits the specific information to the 5G network based on the UL grant (S 33 ). 
     Then, the UE receives a DL grant for receiving a response to the specific information from the 5G network (S 34 ). 
     Then, the UE receives a response including the Al processing result from the 5G network based on the DL grant (S 35 ). 
     A beam management (BM) process may be added to S 30 . A beam failure recovery process may be added to S 31 . A quasi-co location relationship may be added to S 32  to S 35 . A more detailed description thereof will be described in more detail in paragraph I. 
     Next, referring to  FIG. 5 , the UE performs an initial access procedure with the 5G network based on SSB to obtain DL synchronization and system information (S 40 ). 
     Then, the UE performs a random access procedure with the 5G network for UL synchronization acquisition and/or UL transmission (S 41 ). 
     Then, the UE transmits the specific information to the 5G network based on a configured grant (S 42 ). A procedure for configuring the grant in place of receiving the UL grant from the 5G network will be described in more detail in paragraph H. 
     Then, the UE receives a DL grant for receiving a response to the specific information from the 5G network (S 43 ). 
     Then, the UE receives the response including the Al processing result from the 5G network based on the DL grant (S 44 ). 
     Next, referring to  FIG. 6 , the UE performs an initial access procedure with the 5G network based on the SSB to obtain DL synchronization and system information (S 50 ). 
     Then, the UE performs a random access procedure with the 5G network for UL synchronization acquisition and/or UL transmission (S 51 ). 
     Then, the UE receives a DownlinkPreemption IE from the 5G network (S 52 ). 
     The UE receives a DCI format 2_1 including a preamble indication from the 5G network based on the DownlinkPreemption IE (S 53 ). 
     Then, the UE does not perform (or expect or assume) the reception of the eMBB data using a resource (PRB and/or OFDM symbol) indicated by the pre-emption indication (S 54 ). 
     The operation related to the preemption indication is described in more detail in paragraph J. 
     Then, the UE receives an UL grant to the 5G network to transmit the specific information (S 55 ). 
     Then, the UE transmits the specific information to the 5G network based on the UL grant (S 56 ). 
     Then, the UE receives a DL grant for receiving a response to the specific information from the 5G network (S 57 ). 
     Then, the UE receives a response including the AI processing result from the 5G network based on the DL grant (S 58 ). 
     Next, referring to  FIG. 7 , the UE performs an initial access procedure with the 5G network based on SSB to obtain DL synchronization and system information (S 60 ). 
     Then, the UE performs a random access procedure with the 5G network for UL synchronization acquisition and/or UL transmission (S 61 ). 
     Then, the UE receives an UL grant to the 5G network to transmit the specific information (S 62 ). 
     The UL grant includes information on the number of repetitions of transmission of the specific information. The specific information is repeatedly transmitted based on the information on the repetition number (S 63 ). 
     The UE transmits the specific information to the 5G network based on the UL grant. 
     Then, the iterative transmission of the specific information is performed using the frequency hopping. The first transmission of the specific information may be done using a first frequency resource, and the second transmission of the specific information may be done using a second frequency resource. 
     The specific information may be transmitted over a narrow band of  6 RB (Resource Block) or  1 RB (Resource Block). 
     Then, the UE receives a DL grant for receiving a response to the specific information from the 5G network (S 64 ). 
     Then, the UE receives a response including the Al processing result from the 5G network based on the DL grant (S 65 ). 
     The mMTC described in  FIG. 7  will be described in more detail in the paragraph K. 
     D. Introduction 
     Hereinafter, downlink (DL) refers to communication from a base station (BS) to user equipment (UE), and uplink (UL) refers to communication from a UE to a BS. In the downlink, a transmitter may be part of the BS and a receiver may be part of the UE. In the uplink, a transmitter may be part of the UE and a receiver may be part of the BS. Herein, the UE may be represented as a first communication device and the BS may be represented as a second communication device. The BS may be replaced with a term such as a fixed station, a Node B, an evolved NodeB (eNB), a next generation nodeB (gNB), a base transceiver system (BTS), an access point (AP), a network or a 5G (5th generation), artificial intelligence (AI) system, a road side unit (RSU), robot, and the like. Also, the UE may be replaced with a terminal, a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), an advanced mobile station (AMS), a wireless terminal (WT), a machine-type communication (MTC) device, a machine-to-machine (M2M) device, a device-to-device (D2D) device, a vehicle, a robot, an Al module, and the like. 
     Techniques described herein may be used in a variety of wireless access systems such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), etc. CDMA may be implemented as a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented as a radio technology such as Global System for Mobile communications (GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a part of Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA. LTE-Advanced (LTE-A)/LTE-A pro is an evolution of 3GPP LTE. 3GPP NR NR(New Radio or New Radio Access Technology) is an evolution of 3GPP LTE/LTE-A/LTE-A pro. 
     For clarity, the following description focuses on a 3GPP communication system (e.g., LTE-A, NR), but technical features of the present invention is not limited thereto. LTE refers to technology after 3GPP TS 36.xxx Release 8. In detail, LTE technology after 3GPP TS 36.xxx Release 10 is referred to as LTE-A, and LTE technology after 3GPP TS 36.xxx Release 13 is referred to as LTE-A pro. 3GPP 5G (5th generation) technology refers to technology after TS 36.xxx Release 15 and technology after TS 38.XXX Release 15. The technology after TS 38.xxx Release 15 may be referred to as 3GPP NR, and technology after TS 36.xxx Release 15 may be referred to as enhanced LTE. “xxx” refers to a standard document detail number. LTE/NR may be collectively referred to as a 3GPP system. 
     In this disclosure, a node refers to a fixed point capable of transmitting/receiving a radio signal through communication with a UE. Various types of BSs may be used as nodes irrespective of the terms thereof. For example, a BS, a node B (NB), an e-node B (eNB), a pico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, etc. may be a node. In addition, the node may not be a BS. For example, the node may be a radio remote head (RRH) or a radio remote unit (RRU). The RRH or RRU generally has a power level lower than a power level of a BS. At least one antenna is installed per node. The antenna may refer to a physical antenna or refer to an antenna port, a virtual antenna, or an antenna group. A node may be referred to as a point. 
     In this specification, a cell refers to a prescribed geographical area to which one or more nodes provide a communication service. A “cell” of a geographic region may be understood as coverage within which a node can provide a service using a carrier and a “cell” of a radio resource is associated with bandwidth (BW) which is a frequency range configured by the carrier. Since DL coverage, which is a range within which the node is capable of transmitting a valid signal, and UL coverage, which is a range within which the node is capable of receiving the valid signal from the UE, depends upon a carrier carrying the signal, coverage of the node may be associated with coverage of “cell” of a radio resource used by the node. Accordingly, the term “cell” may be used to indicate service coverage by the node sometimes, a radio resource at other times, or a range that a signal using a radio resource can reach with valid strength at other times. 
     In this specification, communicating with a specific cell may refer to communicating with a BS or a node which provides a communication service to the specific cell. In addition, a DL/UL signal of a specific cell refers to a DL/UL signal from/to a BS or a node which provides a communication service to the specific cell. A node providing UL/DL communication services to a UE is called a serving node and a cell to which UL/DL communication services are provided by the serving node is especially called a serving cell. Furthermore, channel status/quality of a specific cell refers to channel status/quality of a channel or communication link formed between a BS or node which provides a communication service to the specific cell and a UE. 
     Meanwhile, a “cell” associated with radio resource may be defined as a combination of DL resources and UL resources, that is, a combination of a DL component carrier (CC) and a UL CC. A cell may be configured to be a DL resource alone or a combination of DL resources and UL resources. If carrier aggregation is supported, a linkage between a carrier frequency of a DL resource (or DL CC) and a carrier frequency of a UL resource (or UL CC) may be indicated by system information transmitted through a corresponding cell. Here, the carrier frequency may be the same as or different from a center frequency of each cell or CC. Hereinafter, a cell operating at a primary frequency will be referred to as a primary cell (Pcell) or a PCC, and a cell operating at a secondary frequency will be referred to as a secondary cell (Scell) Or SCC. The Scell may be configured after the UE performs a radio resource control (RRC) connection establishment with the BS to establish an RRC connection therebetween, that is, after the UE is RRC_ CONNECTED. Here, RRC connection may refer to a channel through which an RRC of the UE and an RRC of the BS may exchange RRC messages with each other. The Scell may be configured to provide additional radio resources to the UE. Depending on the capabilities of the UE, the Scell may form a set of serving cells for the UE together with the Pcell. In the case of a UE which is in the RRC_ CONNECTED state but is not configured in carrier aggregation or does not support carrier aggregation, there is only one serving cell that is only configured as the Pcell. 
     Cells support unique wireless access technologies. For example, transmission/reception according to LTE radio access technology (RAT) is performed on an LTE cell, and transmission/reception according to 5G RAT is performed on a 5G cell. 
     A carrier aggregation (CA) system refers to a system for supporting a wide bandwidth by aggregating a plurality of carriers each having a narrower bandwidth than a target bandwidth. A CA system is different from OFDMA technology in that DL or UL communication is performed using a plurality of carrier frequencies each of which forms a system bandwidth (or a channel bandwidth), whereas the OFDM system carries a base frequency band divided into a plurality of orthogonal subcarriers on a single carrier frequency to perform DL or UL communication. For example, in the case of OFDMA or orthogonal frequency division multiplexing (OFDM), one frequency band having a constant system bandwidth is divided into a plurality of subcarriers having a certain subscriber spacing, and information/data is mapped in the plurality of subcarriers, and the frequency band to which the information/data is mapped is unconverted and transmitted as a carrier frequency of the frequency band. In the case of wireless carrier aggregation, frequency bands having their own system bandwidth and carrier frequency may be simultaneously used for communication, and each frequency band used for carrier aggregation may be divided into a plurality of subcarriers having a predetermined subcarrier spacing. 
     The 3GPP-based communication standard defines DL physical channels corresponding to resource elements carrying information derived from a higher layer of a physical layer (e.g., a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) layer, a service data adaptation protocol (SDAP), and a non-access stratum (NAS) layer and DL physical signals corresponding to resource elements which are used by a physical layer but which do not carry information derived from a higher layer. For example, a physical downlink shared channel (PDSCH), a physical broadcast channel (PBCH), a physical multicast channel (PMCH), a physical control format indicator channel (PCFICH), and a physical downlink control channel (PDCCH) are defined as the DL physical channels, and a reference signal and a synchronization signal are defined as the DL physical signals. A reference signal (RS), also called a pilot, refers to a special waveform of a predefined signal known to both a BS and a UE. For example, a cell-specific RS (CRS), a UE-specific RS, a positioning RS (PRS), channel state information RS (CSI-RS), and a demodulation reference signal (DMRS) may be defined as DL RSs. Meanwhile, the 3GPP-based communication standards define UL physical channels corresponding to resource elements carrying information derived from a higher layer and UL physical signals corresponding to resource elements which are used by a physical layer but which do not carry information derived from a higher layer. For example, a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH) are defined as the UL physical channels, and a demodulation reference signal (DM RS) for a UL control/data signal and a sounding reference signal (SRS) used for UL channel measurement are defined as the UL physical signals. 
     In this specification, a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) may refer to a set of a time-frequency resources or a set of resource elements carrying downlink control information (DCI) and downlink data, respectively. In addition, a physical uplink control channel, a physical uplink shared channel (PUSCH), and a physical random access channel refer to a set of a time-frequency resources or a set of resource elements carrying uplink control information (UCI), uplink data and random access signals, respectively. Hereinafter, UE&#39;s transmitting an uplink physical channel (e.g., PUCCH, PUSCH, or PRACH) means transmitting UCI, uplink data, or a random access signal on the corresponding uplink physical channel or through then uplink physical channel. BS&#39;s receiving an uplink physical channel may refer to receiving DCI, uplink data, or random access signal on or through the uplink physical channel. BS&#39;s transmitting a downlink physical channel (e.g., PDCCH and PDSCH) has the same meaning as transmitting DCI or downlink data on or through the corresponding downlink physical channel. UE&#39;s receiving a downlink physical channel may refer to receiving DCI or downlink data on or through the corresponding downlink physical channel. 
     In this specification, a transport block is a payload for a physical layer. For example, data given to a physical layer from an upper layer or a medium access control (MAC) layer is basically referred to as a transport block. 
     In this specification, HARQ (Hybrid Automatic Repeat and reQuest) is a kind of error control method. HARQ-acknowledgement (HARQ-ACK) transmitted through the downlink is used for error control on uplink data, and HARQ-ACK transmitted on the uplink is used for error control on downlink data. A transmitter that performs the HARQ operation transmits data (e.g., a transport block, a codeword) and waits for an acknowledgment (ACK). A receiver that performs the HARQ operation sends an acknowledgment (ACK) only when data is properly received, and sends a negative acknowledgment (NACK) if an error occurs in the received data. The transmitter may transmit (new) data if ACK is received, and retransmit data if NACK is received. After the BS transmits scheduling information and data according to the scheduling information, a time delay occurs until the ACK/NACK is received from the UE and retransmission data is transmitted. This time delay occurs due to channel propagation delay and a time taken for data decoding/encoding. Therefore, when new data is sent after the current HARQ process is finished, a blank space occurs in the data transmission due to the time delay. Therefore, a plurality of independent HARQ processes are used to prevent generation of the blank space in data transmission during the time delay period. For example, if there are seven transmission occasions between an initial transmission and retransmission, the communication device may operate seven independent HARQ processes to perform data transmission without a blank space. Utilizing the plurality of parallel HARQ processes, UL/DL transmissions may be performed continuously while waiting for HARQ feedback for a previous UL/DL transmission. 
     In this specification, channel state information (CSI) refers to information indicating quality of a radio channel (or a link) formed between a UE and an antenna port. The CSI may include at least one of a channel quality indicator (CQI), a precoding matrix indicator (PMI), a CSI-RS resource indicator (CRI), an SSB resource indicator (SSBRI), a layer indicator (LI), a rank indicator (RI), or a reference signal received power (RSRP). 
     In this specification, frequency division multiplexing (FDM) may refer to transmission/reception of signals/channels/users at different frequency resources, and time division multiplexing (TDM) may refer to transmission/reception of signals/channels/users at different time resources. 
     In the present invention, a frequency division duplex (FDD) refers to a communication scheme in which uplink communication is performed on an uplink carrier and downlink communication is performed on a downlink carrier wave linked to the uplink carrier, and time division duplex (TDD) refers to a communication scheme in which uplink and downlink communications are performed by dividing time on the same carrier. 
     For background information, terms, abbreviations, etc. used in the present specification, may refer to those described in standard documents published before the present invention. For example, the following document may be referred: 
     3GPP LTE
         3GPP TS 36.211: Physical channels and modulation   3GPP TS 36.212: Multiplexing and channel coding   3GPP TS 36.213: Physical layer procedures   3GPP TS 36.214: Physical layer; Measurements   3GPP TS 36.300: Overall description   3GPP TS 36.304: User Equipment (UE) procedures in idle mode   3GPP TS 36.314: Layer 2—Measurements   3GPP TS 36.321: Medium Access Control (MAC) protocol   3GPP TS 36.322: Radio Link Control (RLC) protocol   3GPP TS 36.323: Packet Data Convergence Protocol (PDCP)   3GPP TS 36.331: Radio Resource Control (RRC) protocol   3GPP TS 23.303: Proximity-based services (Prose); Stage 2   3GPP TS 23.285: Architecture enhancements for V2X services   3GPP TS 23.401: General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access   3GPP TS 23.402: Architecture enhancements for non-3GPP accesses   3GPP TS 23.286: Application layer support for V2X services; Functional architecture and information flows   3GPP TS 24.301: Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3   3GPP TS 24.302: Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks; Stage 3   3GPP TS 24.334: Proximity-services (ProSe) User Equipment (UE) to ProSe function protocol aspects; Stage 3   3GPP TS 24.386: User Equipment (UE) to V2X control function; protocol aspects; Stage 3   3GPP NR   3GPP TS 38.211: Physical channels and modulation   3GPP TS 38.212: Multiplexing and channel coding   3GPP TS 38.213: Physical layer procedures for control   3GPP TS 38.214: Physical layer procedures for data   3GPP TS 38.215: Physical layer measurements   3GPP TS 38.300: NR and NG-RAN Overall Description   3GPP TS 38.304: User Equipment (UE) procedures in idle mode and in RRC inactive state   3GPP TS 38.321: Medium Access Control (MAC) protocol   3GPP TS 38.322: Radio Link Control (RLC) protocol   3GPP TS 38.323: Packet Data Convergence Protocol (PDCP)   3GPP TS 38.331: Radio Resource Control (RRC) protocol   3GPP TS 37.324: Service Data Adaptation Protocol (SDAP)   3GPP TS 37.340: Multi-connectivity; Overall description   3GPP TS 23.287: Application layer support for V2X services; Functional architecture and information flows   3GPP TS 23.501: System Architecture for the 5G System   3GPP TS 23.502: Procedures for the 5G System   3GPP TS 23.503: Policy and Charging Control Framework for the 5G System; Stage 2   3GPP TS 24.501: Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3   3GPP TS 24.502: Access to the 3GPP 5G Core Network (SGCN) via non-3GPP access networks   3GPP TS 24.526: User Equipment (UE) policies for 5G System (5GS); Stage 3       

     E. 3GPP Signal Transmission/Reception Method 
       FIG. 8  is a diagram illustrating an example of a 3GPP signal transmission/reception method. 
     Referring to  FIG. 8 , when a UE is powered on or enters a new cell, the UE performs an initial cell search operation such as synchronization with a BS (S 201 ). For this operation, the UE can receive a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from the BS to synchronize with the BS and acquire information such as a cell ID. In LTE and NR systems, the P-SCH and S-SCH are respectively called a primary synchronization signal (PSS) and a secondary synchronization signal (SSS). The initial cell search procedure is described in detail in paragraph F. below. 
     After initial cell search, the UE can acquire broadcast information in the cell by receiving a physical broadcast channel (PBCH) from the BS. Further, the UE can receive a downlink reference signal (DL RS) in the initial cell search step to check a downlink channel state. 
     After initial cell search, the UE can acquire more detailed system information by receiving a physical downlink shared channel (PDSCH) according to a physical downlink control channel (PDCCH) and information included in the PDCCH (S 202 ). 
     Meanwhile, when the UE initially accesses the BS or has no radio resource for signal transmission, the UE can perform a random access procedure (RACH) for the BS (steps S 203  to S 206 ). To this end, the UE can transmit a specific sequence as a preamble through a physical random access channel (PRACH) (S 203  and S 205 ) and receive a random access response (RAR) message for the preamble through a PDCCH and a corresponding PDSCH (S 204  and S 206 ). In the case of a contention-based RACH, a contention resolution procedure may be additionally performed. The random access procedure is described in detail in paragraph G. below. 
     After the UE performs the above-described process, the UE can perform PDCCH/PDSCH reception (S 207 ) and physical uplink shared channel (PUSCH)/physical uplink control channel (PUCCH) transmission (S 208 ) as normal uplink/downlink signal transmission processes. Particularly, the UE receives downlink control information (DCI) through the PDCCH 
     The UE monitors a set of PDCCH candidates in monitoring occasions set for one or more control element sets (CORESET) on a serving cell according to corresponding search space configurations. A set of PDCCH candidates to be monitored by the UE is defined in terms of search space sets, and a search space set may be a common search space set or a UE-specific search space set. CORESET includes a set of (physical) resource blocks having a duration of one to three OFDM symbols. A network can configure the UE such that the UE has a plurality of CORESETs. The UE monitors PDCCH candidates in one or more search space sets. Here, monitoring means attempting decoding of PDCCH candidate(s) in a search space. When the UE has successfully decoded one of PDCCH candidates in a search space, the UE determines that a PDCCH has been detected from the PDCCH candidate and performs PDSCH reception or PUSCH transmission on the basis of DCI in the detected PDCCH. 
     The PDCCH can be used to schedule DL transmissions over a PDSCH and UL transmissions over a PUSCH. Here, the DCI in the PDCCH includes downlink assignment (i.e., downlink grant (DL grant)) related to a physical downlink shared channel and including at least a modulation and coding format and resource allocation information, or an uplink grant (UL grant) related to a physical uplink shared channel and including a modulation and coding format and resource allocation information. 
     F. Initial Access (IA) Process 
     Synchronization signal block (SSB) transmission and related operation 
       FIG. 9  illustrates an SSB structure. The UE can perform cell search, system information acquisition, beam alignment for initial access, and DL measurement on the basis of an SSB. The SSB is interchangeably used with a synchronization signal/physical broadcast channel (SS/PBCH) bloc. 
     Referring to  FIG. 9 , the SSB includes a PSS, an SSS and a PBCH. The SSB is configured in four consecutive OFDM symbols, and a PSS, a PBCH, an SSS/PBCH or a PBCH is transmitted for each OFDM symbol. Each of the PSS and the SSS includes one OFDM symbol and 127 subcarriers, and the PBCH includes 3 OFDM symbols and 576 subcarriers. The PBCH is encoded/decoded on the basis of a polar code and modulated/demodulated according to quadrature phase shift keying (QPSK). The PBCH in the OFDM symbol includes data resource elements (REs) to which a complex modulation value of a PBCH is mapped and DMRS REs to which a demodulation reference signal (DMRS) for the PBCH is mapped. There are three DMRS REs per resource block of the OFDM symbol, and there are three data REs between the DMRS REs. 
     Cell Search 
     Cell search refers to a process in which a UE acquires time/frequency synchronization of a cell and detects a cell identifier (ID) (e.g., physical layer cell ID (PCI)) of the cell. The PSS is used to detect a cell ID in a cell ID group and the SSS is used to detect a cell ID group. The PBCH is used to detect an SSB (time) index and a half-frame. 
     The cell search procedure of the UE may be summarized as shown in Table 1 below. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Type of Signals 
                 Operations 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 1st step 
                 PSS 
                 SS/PBCH block (SSB) symbol timing 
               
               
                   
                   
                 acquisition 
               
               
                   
                   
                 Cell ID detection within a cell ID 
               
               
                   
                   
                 group(3 hypothesis) 
               
               
                 2nd Step 
                 SSS 
                 Cell ID group detection (336 hypothesis) 
               
               
                 3rd Step 
                 PBCH DMRS 
                 SSB index and Half frame (HF) index 
               
               
                   
                   
                 (Slot and frame boundary detection) 
               
               
                 4th Step 
                 PBCH 
                 Time information (80 ms, System 
               
               
                   
                   
                 Frame Number (SFN), SSB index, HF) 
               
               
                   
                   
                 Remaining Minimum System Information 
               
               
                   
                   
                 (RMSI) Control resource set (CORESET)/ 
               
               
                   
                   
                 Search space configuration 
               
               
                 5th Step 
                 PDCCH and 
                 Cell access information 
               
               
                   
                 PDSCH 
                 RACH configuration 
               
               
                   
               
            
           
         
       
     
     There are 336 cell ID groups and there are  3  cell IDs per cell ID group. A total of 1008 cell IDs are present. Information on a cell ID group to which a cell ID of a cell belongs is provided/acquired through an SSS of the cell, and information on the cell ID among 336 cell ID groups is provided/acquired through a PSS. 
       FIG. 10  illustrates SSB transmission. 
     The SSB is periodically transmitted in accordance with SSB periodicity. A default SSB periodicity assumed by a UE during initial cell search is defined as 20 ms. After cell access, the SSB periodicity can be set to one of {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms} by a network (e.g., a BS). An SSB burst set is configured at a start portion of the SSB period. The SSB burst set includes a 5 ms time window (i.e., half-frame), and the SSB may be transmitted up to N times within the SS burst set. The maximum transmission number L of the SSB may be given as follows according to a frequency band of a carrier wave. One slot includes a maximum of two SSBs.
         For frequency range up to 3 GHz, L=4   For frequency range from 3 GHz to 6 GHz, L=8   For frequency range from 6 GHz to 52.6 GHz, L=64       

     A time position of an SSB candidate in the SS burst set may be defined according to a subscriber spacing. The SSB candidate time position is indexed from 0 to L-1 (SSB index) in time order within the SSB burst set (i.e., half-frame). 
     A plurality of SSBs may be transmitted within a frequency span of a carrier wave. Physical layer cell identifiers of these SSBs need not be unique, and other SSBs may have different physical layer cell identifiers. 
     The UE may acquire the DL synchronization by detecting the SSB. The UE may identify a structure of the SSB burst set on the basis of the detected SSB (time) index and thus detect a symbol/slot/half-frame boundary. The number of the frame/half-frame to which the detected SSB belongs may be identified using system frame number (SFN) information and half-frame indication information. 
     Specifically, the UE may acquire a 10-bit SFN for a frame to which the PBCH belongs from the PBCH. Next, the UE may acquire 1-bit half-frame indication information. For example, if the UE detects a PBCH with a half-frame indication bit set to 0, it may determine that the SSB, to which the PBCH belongs, belongs to a first half-frame in the frame, and if the UE detects a PBCH with a half-frame indication bit set to 1, it may determine that the SSB, to which the PBCH belongs, belongs to a second half-frame in the frame. Finally, the UE may acquire an SSB index of the SSB to which the PBCH belongs on the basis of a DMRS sequence and PBCH payload carried by the PBCH. 
     Acquisition of System Information (SI) 
     SI is divided into a master information block (MIB) and a plurality of system information blocks (SIBs). The SI other than the MIB may be referred to as remaining minimum system information (RMSI). Details thereof may be referred to the following: 
     The MIB includes information/parameters for monitoring the PDCCH scheduling PDSCH carrying system information block 1  (SIB 1 ) and is transmitted by the BS through the PBCH of the SSB. For example, the UE may check whether a control resource set (CORESET) exists for the Type 0-PDCCH common search space on the basis of the MIB. The Type 0-PDCCH common search space is a kind of PDCCH search space and is used to transmit a PDCCH for scheduling an SI message. If the Type 0-PDCCH common search space is present, the UE may determine (i) a plurality of contiguous resource blocks and one or more consecutive resource blocks constituting a CORESET on the basis of information in the MIB (e.g., pdcch-ConfigSIB 1 ) and (ii) a PDCCH occasion (e.g., time domain position for PDCCH reception). If no Type 0-PDCCH common search space exists, pdcch-ConfigSIB 1  provides information on a frequency location where SSB/SIB 1  exists and information on a frequency range where SSB/SIB 1  does not exist. 
     SIB 1  includes information related to availability and scheduling (e.g., transmission periodicity and SI-window size) of the remaining SIBs (hereinafter, SIBx, x is an integer equal to or greater than 2). For example, SIB 1  may indicate whether the SIBx is periodically broadcast or provided according to a request from the UE on an on-demand basis. If SIBx is provided on the on-demand basis, SIB 1  may include information necessary for the UE to perform the SI request. The SIB 1  is transmitted through the PDSCH, the PDCCH for scheduling the SIB 1  is transmitted through the Type 0-PDCCH common search space, and the SIB 1  is transmitted through the PDSCH indicated by the PDCCH. 
     The SIBx is included in the SI message and transmitted via the PDSCH. Each SI message is transmitted within a time window (i.e., SI-window) that occurs periodically. 
     G. Random Access Procedure 
     The random access procedure of the UE may be summarized as shown in Table 2 and  FIG. 11 . 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Signal type 
                 Acquired operation/information 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 First 
                 PRACH preamble in UL 
                 Acquire initial beam 
               
               
                 step 
                   
                 Random selection of random 
               
               
                   
                   
                 access preamble ID 
               
               
                 Second 
                 Random access response on 
                 Timing advance information 
               
               
                 step 
                 PDSCH 
                 Random access preamble ID 
               
               
                   
                   
                 Initial UL grant, temporary 
               
               
                   
                   
                 C-RNTI 
               
               
                 Third 
                 UL transmission on PUSCH 
                 RRC connection request 
               
               
                 step 
                   
                 UE identifier 
               
               
                 Fourth 
                 Contention resolution on DL 
                 Temporary C-RNTI on PDCCH 
               
               
                 step 
                   
                 for initial access 
               
               
                   
                   
                 C-RNTI on PDCCH for 
               
               
                   
                   
                 RRC_CONNECTED UE 
               
               
                   
               
            
           
         
       
     
     The random access procedure is used for various purposes. For example, the random access procedure can be used for network initial access, handover, and UE-triggered UL data transmission. A UE can acquire UL synchronization and UL transmission resources through the random access procedure. The random access procedure is classified into a contention-based random access procedure and a contention-free random access procedure. 
       FIG. 11  illustrates an example of a random access procedure. In particular,  FIG. 11  illustrates a contention-based random access procedure. 
     First, a UE can transmit a random access preamble through a PRACH as Msg1 of a random access procedure in UL. 
     Random access preamble sequences having different two lengths are supported. A long sequence length  839  is applied to subcarrier spacings of 1.25 kHz and 5 kHz and a short sequence length  139  is applied to subcarrier spacings of 15 kHz, 30 kHz, 60 kHz and 120 kHz. 
     Multiple preamble formats are defined by one or more RACH OFDM symbols and different cyclic prefixes (and/or guard time). RACH configuration for a cell is included in the system information of the cell and is provided to the UE. The RACH configuration includes information on a subcarrier spacing of the PRACH, available preambles, preamble format, and the like. The RACH configuration includes association information between SSBs and RACH (time-frequency) resources. The UE transmits a random access preamble in the RACH time-frequency resource associated with the detected or selected SSB. 
     A threshold value of the SSB for the RACH resource association may be set by the network, and RACH preamble is transmitted or retransmitted on the basis of the SSB in which reference signal received power (RSRP) measured on the basis of the SSB satisfies the threshold value. For example, the UE may select one of the SSB (s) satisfying the threshold value and may transmit or retransmit the RACH preamble on the basis of the RACH resource associated with the selected SSB. 
     When a BS receives the random access preamble from the UE, the BS transmits a random access response (RAR) message (Msg2) to the UE. A PDCCH that schedules a PDSCH carrying a RAR is CRC masked by a random access (RA) radio network temporary identifier (RNTI) (RA-RNTI) and transmitted. Upon detection of the PDCCH masked by the RA-RNTI, the UE can receive a RAR from the PDSCH scheduled by DCI carried by the PDCCH. The UE checks whether the RAR includes random access response information with respect to the preamble transmitted by the UE, that is, Msg1. Presence or absence of random access information with respect to Msg1 transmitted by the UE can be determined according to presence or absence of a random access preamble ID with respect to the preamble transmitted by the UE. If there is no response to Msg1, the UE can retransmit the RACFI preamble less than a predetermined number of times while performing power ramping. The UE calculates PRACH transmission power for preamble retransmission on the basis of most recent pathloss and a power ramping counter. 
     When the random access response information includes timing advance information for UL synchronization and an UL grant, and when a temporary UE receives a random response information regarding the UE itself on the PDSCH, the UE may know timing advance information for UL synchronization, an initial UL grant, and a UE temporary cell RNTI (cell RNTI, C-RNTI). The timing advance information is used to control uplink signal transmission timing. In order to ensure that the PUSCH/PUCCH transmission by the UE is better aligned with the subfrarne timing at a network end, the network (e.g. BS) may measure a time difference between the PUSCH/PUCCH/SRS reception and subframes and send timing advance information on the basis of the time difference. The UE can perform UL transmission through Msg3 of the random access procedure over a physical uplink shared channel on the basis of the random access response information. Msg3 can include an RRC connection request and a UE ID. The network can transmit Msg4 as a response to Msg3, and Msg4 can be handled as a contention resolution message on DL. The UE can enter an RRC connected state by receiving Msg4. 
     Meanwhile, the contention-free random access procedure may be performed when the UE performs handover to another cell or BS or when the contention-free random access procedure is requested by a BS command. A basic process of the contention-free random access procedure is similar to the contention-based random access procedure. However, unlike the contention-based random access procedure in which the UE randomly selects a preamble to be used among a plurality of random access preambles, in the case of the contention-free random access procedure, a preamble (hereinafter referred to as a dedicated random access preamble) to be used by the UE is allocated by the BS to the UE. Information on the dedicated random access preamble may be included in an RRC message (e.g., a handover command) or may be provided to the UE via a PDCCH order. When the random access procedure is started, the UE transmits a dedicated random access preamble to the BS. When the UE receives the random access procedure from the BS, the random access procedure is completed. 
     As mentioned above, the UL grant in the RAR schedules PUSCH transmission to the UE. The PUSCH carrying initial UL transmission based on the UL grant in the RAR will be referred to as Msg3 PUSCH. The content of the RAR UL grant starts at an MSB and ends at a LSB and is given in Table 3. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 Number 
               
               
                   
                 RAR UL grant field 
                 of bits 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Frequency hopping flag 
                 1 
               
               
                   
                 Msg3 PUSCH frequency resource allocation 
                 12 
               
               
                   
                 Msg3 PUSCH time resource allocation 
                 4 
               
               
                   
                 Modulation and coding scheme (MCS) 
                 4 
               
               
                   
                 Transmit power control (TPC) for Msg3 PUSCH 
                 3 
               
               
                   
                 CSI request 
                 1 
               
               
                   
                   
               
            
           
         
       
     
     The TPC command is used to determine transmission power of the Msg3 PUSCH and is interpreted, for example, according to Table 4. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 TPC command 
                 value [dB] 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 −6 
               
               
                   
                 1 
                 −4 
               
               
                   
                 2 
                 −2 
               
               
                   
                 3 
                 0 
               
               
                   
                 4 
                 2 
               
               
                   
                 5 
                 4 
               
               
                   
                 6 
                 6 
               
               
                   
                 7 
                 8 
               
               
                   
                   
               
            
           
         
       
     
     In the contention-free random access procedure, the CSI request field in the RAR UL grant indicates whether the UE includes an aperiodic CSI report in the corresponding PUSCH transmission. A subcarrier spacing for the Msg3 PUSCH transmission is provided by an RRC parameter. The UE will transmit the PRACH and Msg3PUSCH on the same uplink carrier of the same service providing cell. A UL BWP for Msg3 PUSCH transmission is indicated by SIB 1  (SystemInformationBlock 1 ). 
     H. DL and UL Transmitting/Receiving Operations 
     DL Transmitting/Receiving Operation 
     A downlink grant (also referred to as a downlink assignment) may be divided into (1) dynamic grant and (2) configured grant. The dynamic grant, which is intended to maximize resource utilization, refers to a method of data transmission/reception on the basis of dynamic scheduling by the BS. 
     The BS schedules downlink transmission through a DCI. The UE receives on the PDCCH the DCI for downlink scheduling (i.e., including scheduling information of the PDSCH) from the BS. DCI format 1_0 or 1_1 may be used for downlink scheduling. The DCI format 1_1 for downlink scheduling may include, for example, the following information: an identifier for DCI format, a bandwidth part indicator, a frequency domain resource assignment, time domain resource assignment, MCS. 
     The UE may determine a modulation order, a target code rate, and a transport block size for the PDSCH on the basis of the MCS field in the DCI. The UE may receive the PDSCH in time-frequency resource according to frequency domain resource allocation information and time domain resource allocation information. 
     The DL grant is also referred to as semi-persistent scheduling (SPS). The UE may receive an RRC message including a resource configuration for transmission of DL data from the BS. In the case of the DL SPS, an actual DL configured grant is provided by the PDCCH and is activated or deactivated by the PDCCH. If the DL SPS is configured, at least the following parameters are provided to the UE via RRC signaling from the BS: a configured scheduling RNTI (CS-RNTI) for activation, deactivation and retransmission; and cycle. The actual DL grant of the DL SPS is provided to the UE by the DCI in the PDCCH addressed to the CS-RNTI. The UE activates an SPS associated with the CS-RNTI if specific fields of the DCI in the PDCCH addressed to the CS-RNTI are set to specific values for scheduling activation. The UE may receive downlink data through the PDSCH on the basis of the SPS. 
     UL Transmitting/Receiving Operation 
     The BS transmits a DCI including uplink scheduling information to the UE. The UE receives on the PDCCH the DCI for uplink scheduling (i.e., including scheduling information of the PUSCH) from the BS. DCI format 0_0 or 0_1 may be used for uplink scheduling. The DCI format 0_1 for uplink scheduling may include the following information: an identifier for DCI format, a bandwidth part indicator, a frequency domain resource assignment, a time domain resource assignment, MCS. 
     The UE transmits uplink data on the PUSCH on the basis of the DCI. For example, when the UE detects the PDCCH including the DCI format 0_0 or 0_1, the UE transmits the PUSCH according to an instruction based on the DCI. Two transmission schemes are supported for PUSCH transmission: codebook-based transmission and non-codebook-based transmission. 
     When an RRC parameter ‘txConfig’ receives an RRC message set to ‘codebook’, the UE is configured to a codebook-based transmission. Meanwhile, when an RRC message in which the RRC parameter ‘txConfig’ is set to ‘nonCodebook’ is received, the UE is configured to a non-codebook-based transmission. The PUSCH may be semi-statically scheduled by the DCI format 0_0, by the DCI format 0_1, or by RRC signaling. 
     The uplink grant may be divided into (1) a dynamic grant and (2) a configured grant. 
       FIG. 12  shows an example of an uplink grant.  FIG. 12( a )  illustrates an UL transmission process based on the dynamic grant, and  FIG. 12( b )  illustrates an UL, transmission process based on the configured grant. 
     A dynamic grant, which is to maximize utilization of resources, refers to a data transmission/reception method based on dynamic scheduling by a BS. This means that when the UE has data to be transmitted, the UE requests uplink resource allocation from the BS and transmits the data using only uplink resource allocated by the BS. In order to use the uplink radio resource efficiently, the BS must know how much data each UE transmits on the uplink. Therefore, the UE may directly transmit information on uplink data to be transmitted to the BS, and the BS may allocate uplink resources to the UE on the basis of the information. In this case, the information on the uplink data transmitted from the UE to the BS is referred to as a buffer status report (BSR), and the BSR relates to the amount of uplink data stored in a buffer of the UE. 
     Referring to  FIG. 12( a ) , an uplink resource allocation process for actual data when the UE does not have an uplink radio resource available for transmission of the BSR is illustrated. For example, since the UE which does not have a UL grant cannot available for UL data transmission cannot transmit the BSR through a PUSCH, the UE must request resource for uplink data must by starting transmission of a scheduling request via a PUCCH, and in this case, an uplink resource allocation process of five steps is used. 
     Referring to  FIG. 12( a ) , if there is no PUSCH resource for transmitting a BSR, the UE first transmits a scheduling request (SR) to the BS in order to be allocated a PUSCH resource. The SR is used by the UE to request the BS for PUSCH resources for uplink transmission when a reporting event occurs but there is no PUSCH resource available to the UE. Depending on whether there is a valid PUCCH resource for the SR, the UE transmits the SR via the PUCCH or initiates a random access procedure. When the UE receives the UL grant from the BS, it transmits the BSR to the BS via the PUSCH resource allocated by the UL grant. The BS checks the amount of data to be transmitted by the UE on the uplink on the basis of the BSR and transmits a UL grant to the UE. The UE receiving the UL grant transmits actual uplink data to the BS through the PUSCH on the basis of the UL grant. 
     Referring to  FIG. 12( b ) , the UE receives an RRC message including a resource configuration for transmission of UL data from the BS. There are two types of UL-configured grants in the NR system: Type 1 and Type 2. In the case of UL-configured grant type 1, an actual UL grant (e.g., time resource, frequency resource) is provided by RRC signaling, and in the case of Type 2, an actual UL grant is provided by the PDCCH and is activated or deactivated by the PDCCH. If the grant type 1 is configured, at least the following parameters are provided to the UE via RRC signaling from the BS: CS-RNTI for retransmission; periodicity of the configured grant type 1; information about a start symbol index S and a symbol length L for an intra-slot PUSCH; time domain offset representing an offset of the resource for SFN=0 in the time domain; MCS index indicating modulation order, target code rate, and transport block size. If the grant type 2 is configured, at least the following parameters are provided to the UE via RRC signaling from the BS: CS-RNTI for activation, deactivation and retransmission; periodicity of configured grant type 2. The actual UL grant of the configured grant type 2 is provided to the UE by the DCI in the PDCCH addressed to the CS-RNTI. If the specific fields of the DCI in the PDCCH addressed to the CS-RNTI are set to a specific value for scheduling activation, the UE activates the configured grant type 2 associated with the CS-RNTI. 
     The UE may perform uplink transmission via the PUSCH on the basis of the configured grant according to the type 1 or type 2. 
     Resources for initial transmission by the configured grant may or may not be shared by one or more UEs. 
       FIG. 13  shows an example of a conceptual diagram of uplink physical channel processing. 
     Each of the blocks shown in  FIG. 13  may be performed in each module in the physical layer block of a transmission device. More specifically, the uplink signal processing in  FIG. 13  may be performed in the processor of the UE/BS described in this specification. Referring to  FIG. 13 , the uplink physical channel processing may be performed through scrambling, modulation mapping, layer mapping, transform precoding, precoding, resource element mapping, and SC-FDMA signal generation (SC-FDMA signal generation). Each of the above processes may be performed separately or together in each module of the transmission device. The transform precoding is spreading UL data in a special way to reduce a peak-to-average power ratio (PAPR) of a waveform, and is a kind of discrete Fourier transform (DFT). OFDM using a CP together with the transform precoding that performs DFT spreading is called DFT-s-OFDM, and OFDM using a CP without DFT spreading is called CP-OFDM. Transform precoding may optionally be applied if it is enabled for the UL in an NR system. That is, the NR system supports two options for UL waveforms, one of which is CP-OFDM and the other is DFT-s-OFDM. Whether the UE must use the CP-OFDM as a UL transmit waveform or the DFT-s-OFDM as a UL transmit waveform is provided from the BS to the UE via RRC parameters.  FIG. 13  is a conceptual diagram of uplink physical channel processing for DFT-s-OFDM. In the case of CP-OFDM, the transform precoding among the processes of  FIG. 13  is omitted. 
     More specifically, the transmission device scrambles coded bits in a codeword by a scrambling module, and then transmits the coded bits through a physical channel. Here, the codeword is acquired by encoding a transport block. The scrambled bits are modulated by a modulation mapping module into complex-valued modulation symbols. The modulation mapping module may modulate the scrambled bits according to a predetermined modulation scheme and arrange the modulated bits as complex-valued modulation symbols representing a position on a signal constellation. pi/2-BPSK (pi/2-Binary Phase Shift Keying), m-PSK (m-Phase Shift Keying) or m-QAM (m-Quadrature Amplitude Modulation) may be used for modulating the coded data. The complex-valued modulation symbols may be mapped to one or more transport layers by a layer mapping module. The complex-valued modulation symbols on each layer may be precoded by a precoding module for transmission on an antenna port. If the transform precoding is enabled, the precoding module may perform precoding after performing transform precoding on the complex-valued modulation symbols as shown in  FIG. 13 . The precoding module may process the complex-valued modulation symbols in a MIMO manner according to multiple transmission antennas to output antenna-specific symbols, and distribute the antenna-specific symbols to a corresponding resource element mapping module. An output z of the precoding module may be acquired by multiplying an output y of the layer mapping module by a precoding matrix W of N×M. Here, N is the number of antenna ports and M is the number of layers. The resource element mapping module maps the complex-valued modulation symbols for each antenna port to an appropriate resource element in the resource block allocated for transmission. The resource element mapping module may map the complex-valued modulation symbols to appropriate subcarriers and multiplex the same according to users. The SC-FDMA signal generation module (CP-OFDM signal generation module if the transform precoding is disabled) modulates the complex-valued modulation symbol according to a specific modulation scheme, for example, an OFDM scheme, to generate a complex-valued time domain OFDM (Orthogonal Frequency Division Multiplexing) symbol signal. The signal generation module may perform Inverse Fast Fourier Transform (IFFT) on the antenna specific symbol, and a CP may be inserted into the time domain symbol on which the IFFT has been performed. The OFDM symbol undergoes digital-to-analog conversion, upconverting, and the like, and transmitted to a reception device through each transmission antenna. The signal generation module may include an IFFT module and a CP inserter, a digital-to-analog converter (DAC), and a frequency uplink converter. 
     A signal processing procedure of a reception device may be the reverse of the signal processing procedure of the transmission device. Details thereof may be referred to the above contents and  FIG. 13 . 
     Next, the PUCCH will be described. 
     The PUCCH supports a plurality of formats, and the PUCCH formats may be classified according to symbol duration, payload size, multiplexing, and the like. Table 5 below illustrates PUCCH formats. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                 PUCCH length 
                   
                   
                   
               
               
                   
                 in OFDM 
                 Number 
               
               
                 Format 
                 symbols 
                 of bits 
                 Usage 
                 Etc. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 0 
                 1-2  
                 ≤2 
                 1 
                 Sequence selection 
               
               
                 1 
                 4-14 
                 ≤2 
                 2 
                 Sequence modulation 
               
               
                 2 
                 1-2  
                 &gt;2 
                 4 
                 CP-OFDM 
               
               
                 3 
                 4-14 
                 &gt;2 
                 8 
                 DFT-s-OFDM(no UE 
               
               
                   
                   
                   
                   
                 multiplexing) 
               
               
                 4 
                 4-14 
                 &gt;2 
                 16 
                 DFT-s-OFDM(Pre 
               
               
                   
                   
                   
                   
                 DFT orthogonal 
               
               
                   
                   
                   
                   
                 cover code(OCC)) 
               
               
                   
               
            
           
         
       
     
     The PUCCH formats shown in Table 5 may be divided into (1) a short PUCCH and (2) a long PUCCH. PUCCH formats 0 and 2 may be included in the short PUCCH, and PUCCH formats 1, 3 and 4 may be included in the long PUCCH. 
       FIG. 14  shows an example of an NR slot in which a PUCCH is transmitted. 
     The UE transmits one or two PUCCHs through serving cells in different symbols in one slot. When the UE transmits two PUCCHs in one slot, at least one of the two PUCCI-Is has a structure of the short PUCCH. 
     I. eMBB (Enhanced Mobile Broadband Communication) 
     In the case of the NR system, a massive multiple input multiple output (MIMO) environment in which the transmit/receive antennas are significantly increased may be considered. That is, as the large MIMO environment is considered, the number of transmit/receive antennas may increase to several tens or hundreds or more. Meanwhile, the NR system supports communication in above 6 GHz band, that is, the millimeter frequency band. However, the millimeter frequency band has a frequency characteristic in which signal attenuation according to a distance is very sharp due to the use of a frequency band which is too high. Therefore, an NR system using the band of 6 GHz or higher uses a beamforming technique in which energy is collected and transmitted in a specific direction, not in all directions, in order to compensate for sudden propagation attenuation characteristics. In the massive MIMO environment, a hybrid type beam forming technique combining an analog beamforming technique and a digital beamforming technique is required depending on a position to which a beamforming weight vector/precoding vector is applied, to reduce complexity of hardware implementation, increase performance using multiple antennas, obtain flexibility of resource allocation, and facilitate beam control for each frequency. 
     Hybrid Beamforming 
       FIG. 15  illustrates an example of a block diagram of a transmitter and a receiver for hybrid beamforming. 
     As a method for forming a narrow beam in a millimeter frequency band, a beam forming scheme in which energy is increased only in a specific direction by transmitting the same signal using a phase difference suitable for a large number of antennas in a BS or a UE is mainly considered. Such beamforming scheme includes digital beamforming to create a phase difference in a digital baseband signal, analog beamforming to create a phase difference in a modulated analog signal using time delay (i.e., cyclic shift), and hybrid beamforming using both digital beamforming and analog beamforming, or the like. If each antenna element has an RF unit (or transceiver unit (TXRU)) to adjust transmission power and phase, independent beamforming is possible for each frequency resource. However, it is not effective in terms of price to install an RF unit in all 100 antenna elements. That is, since the millimeter frequency band requires a large number of antennas to compensate for the sudden attenuation characteristics and digital beamforming requires an RF component (e.g., a digital-to-analog converter (DAC), a mixer, a power amplifier, a linear amplifier, and the like), implementation of digital beamforming in the millimeter frequency band causes the price of the communication device to increase. Therefore, when a large number of antennas are required such as in the millimeter frequency band, the use of analog beamforming or hybrid beamforming is considered. In the analog beamforming scheme, a plurality of antenna elements are mapped to one TXRU and a direction of a beam is adjusted by an analog phase shifter. Such an analog beamforming scheme may generate only one beam direction in the entire band, and thus, it cannot perform frequency selective beamforming (BF). Hybrid BF is an intermediate form of digital BF and analog BF and has B RF units fewer than Q antenna elements. In the case of the hybrid BF, directions of beams that may be transmitted at the same time is limited to B or less, although there is a difference depending on a method of connecting the B RF units and Q antenna elements. 
     Beam Management (BM) 
     The BM process includes processes for acquiring and maintaining a set of BS (or a transmission and reception point (TRP)) and/or UE beams that may be used for downlink (DL) and uplink (UL) transmission/reception and may include the following processes and terms.
         beam measurement: operation for BS or UE to measure characteristic of received beamforming signal.   beam determination: operation for BS or UE to select its own Tx beam/Rx beam.   beam sweeping: an operation to cover spatial domain using transmission and/or reception beam during a predetermined time interval in a predetermined manner.   beam report: an operation for UE to report information of beamformed signal on the basis of beam measurement.       

     The BM process may be classified into (1) DL BM process using SSB or CSI-RS and (2) UL BM process using SRS (sounding reference signal). Also, each BM process may include Tx beam sweeping to determine Tx beam and Rx beam sweeping to determine Rx beam. 
     DL BM Process 
     The DL BM process may include (1) transmission of beamformed DL RSs (e.g., CSI-RS or SSB) by the BS, and (2) beam reporting by the UE. 
     Here, the beam report may include a preferred DL RS ID(s) and a corresponding reference signal received power (RSRP). The DL RS ID may be an SSBRI (SSB Resource Indicator) or a CRI (CSI-RS Resource Indicator). 
       FIG. 16  shows an example of beamforming using SSB and CSI-RS. 
     As shown in  FIG. 16 , the SSB beam and the CSI-RS beam may be used for beam measurement. The measurement metric is an RSRP per resource/block. The SSB may be used for coarse beam measurement, and the CSI-RS may be used for fine beam measurement. SSB may be used for both Tx beam sweeping and Rx beam sweeping. Rx beam sweeping using the SSB may be performed by attempting to receive the SSB while the UE changes the Rx beam for the same SSBRI across multiple SSB bursts. Here, one SS burst may include one or more SSBs, and one SS burst set includes one or more SSB bursts. 
     1. DL BM Using SSB 
       FIG. 17  is a flowchart illustrating an example of a DL BM process using SSB. 
     A configuration for beam report using the SSB is performed at the time of channel state information (CSI)/beam configuration in RRC_CONNECTED.
         The UE receives from the BS a CSI-ResourceConfig IE including a CSI-SSB-ResourceSetList for the SSB resources used for the BM (S 410 ). The RRC parameter csi-SSB-ResourceSetList represents a list of SSB resources used for beam management and reporting in one resource set. Here, the SSB resource set may be configured to {SSBx 1 , SSBx 2 , SSBx 3 , SSBx 4 }. The SSB index may be defined from 0 to 63.   The UE receives signals on the SSB resources from the BS on the basis of the CSI-SSB-ResourceSetList (S 420 ).   If the CSI-RS reportConfig associated with reporting on the SSBRI and reference signal received power (RSRP) is configured, the UE reports the best SSBRI and its corresponding RSRP to the BS S 430 ). For example, if the reportQuantity of the CSI-RS reportConfig IE is set to ‘ssb-Index-RSRP’, the UE reports the best SSBRI and a corresponding RSRP to the BS.       

     When the CSI-RS resource is configured in the same OFDM symbol (s) as the SSB and ‘QCL-Type D’ is applicable, the UE may assume that the CSI-RS and the SSB are quasi co-located (QCL-ed) in terms of ‘QCL-TypeD’. Here, QCL-TypeD may refer to QCL-ed between antenna ports in terms of spatial Rx parameter. The same receive beam may be applied when the UE receives signals of a plurality of DL antenna ports in the QCL-TypeD relationship. Details of QCL may refer to a section 4. QCL below. 
     2. DL BM Using CSI-RS 
     Referring to the use of CSI-RS, i) if a repetition parameter is set for a specific CSI-RS resource set and TRS_ info is not configured, CSI-RS is used for beam management. ii) If the repetition parameter is not set and TRS_ info is set, the CSI-RS is used for a tracking reference signal (TRS). Iii) If the repetition parameter is not set and TRS_ info is not set, the CSI-RS is used for CSI acquisition. 
     (RRC Parameter) If the repetition is set to ‘ON’, it relates to a Rx beam sweeping process of the UE. If the repetition is set to ‘ON’, the UE may assume that if NZP-CSI-RS-ResourceSet is configured, signals of at least one CSI-RS resource in the NZP-CSI-RS-ResourceSet are transmitted in the same downlink space domain filter. That is, at least one CSI-RS resource in the NZP-CSI-RS-ResourceSet is transmitted through the same Tx beam. Here, signals of at least one CSI-RS resource in the NZP-CSI-RS-ResourceSet may be transmitted in different OFDM symbols. 
     Meanwhile, if the repetition is set to ‘OFF’, it relates to a Tx beam sweeping process of the BS. If the repetition is set to ‘OFF’, the UE does not assume that signals of at least one CSI-RS resource in the NZP-CSI-RS-ResourceSet are transmitted in the same downlink spatial domain transmission filter. That is, the signals of at least one CSI-RS resource in the NZP-CSI-RS-ResourceSet are transmitted through different Tx beams.  FIG. 18  shows another example of the DL BM process using CSI-RS. 
       FIG. 18( a )  shows a process of Rx beam determination (or refinement) of the UE, and  FIG. 18( b )  shows a Tx beam sweeping process of the BS.  FIG. 18( a )  shows a case where the repetition parameter is set to ‘ON’, and  FIG. 18( b )  shows a case where the repetition parameter is set to ‘OFF’. 
     A process of determining the Rx beam of the UE will be described with reference to  FIGS. 18( a )  and  19 . 
       FIG. 19  is a flowchart illustrating an example of a process of determining a reception beam of a UE.
         The UE receives an NZP CSI-RS resource set IE including the RRC parameter regarding ‘repetition’ from the BS through RRC signaling (S 610 ). Here, the RRC parameter ‘repetition’ is set to ‘ON’.   The UE repeatedly receives signals on the resource(s) in the CSI-RS resource in which the RRC parameter ‘repetition’ is set to ‘ON’ in different OFDM (s) through the same Tx beam (or DL space domain transmission filter) of the BS (S 620 ).   The UE determines its own Rx beam (S 630 ).   The UE omits the CSI reporting (S 640 ). That is, the UE may omit CSI reporting when the uplink RRC parameter ‘repetition’ is set to ‘ON’.       

     A Tx beam determining process of the BS will be described with reference to  FIGS. 18( b )  and  20 . 
       FIG. 20  is a flowchart illustrating an example of a transmission beam determining process of the BS.
         The UE receives an NZP CSI-RS resource set IF including an RRC parameter regarding ‘repetition’ from the BS through RRC signaling (S 710 ). Here, the RRC parameter ‘repetition’ is set to ‘OFF’ and is related to the Tx beam sweeping process of the BS.   The UE receives signals on the resources in the CSI-RS resource in which the RRC parameter ‘repetition’ is set to ‘OFF’ through different Tx beams (DL spatial domain transmission filters) of the BS (S 720 ).   The UE selects (or determines) the best beam (S 730 )   The UE reports an ID (e.g., CRI) for the selected beam and related quality information (e.g., RSRP) to the BS (S 740 ). That is, the UE reports the CRI and the RSRP to the BS when the CSI-RS is transmitted for the BM.       

       FIG. 21  shows an example of resource allocation in time and frequency domains related to the operation of  FIG. 18 . 
     When repetition ‘ON’ is set in the CSI-RS resource set, a plurality of CSI-RS resources are repeatedly used by applying the same transmission beam, and when repetition ‘OFF’ is set in the CSI-RS resource set, different CSI-RS resources may be transmitted in different transmission beams. 
     3. DL BM-Related Beam Indication 
     The UE may receive a list of up to M candidate transmission configuration indication (TCI) states for at least a quasi co-location (QCL) indication via RRC signaling. Here, M depends on UE capability and may be 64. 
     Each TCI state may be configured with one reference signal (RS) set. Table 6 shows an example of a TCI-State IE. The TCl-State IE is associated with a quasi co-location (QCL) type corresponding to one or two DL reference signals (RSs). 
     
       
         
           
               
               
             
               
                   
                 TABLE 6 
               
               
                   
                   
               
             
            
               
                   
                 -- ASN1 START 
               
               
                   
                 -- TAG-TCI-STATE-START 
               
            
           
           
               
               
               
            
               
                   
                 TCI-State ::= 
                  SEQUENCE { 
               
            
           
           
               
               
               
            
               
                   
                 tci-StateId 
                 TCI-StateId, 
               
               
                   
                 qcl-Type1 
                 QCL-Info, 
               
               
                   
                 qcl-Type2 
                 QCL-Info 
               
            
           
           
               
               
               
            
               
                   
                 OPTIONAL, 
                 -- Need R 
               
            
           
           
               
               
            
               
                   
                 ... 
               
            
           
           
               
               
            
               
                   
                 } 
               
            
           
           
               
               
               
            
               
                   
                 QCL-Info ::= 
                 SEQUENCE { 
               
            
           
           
               
               
            
               
                   
                 cell 
               
               
                   
                 ServCellIndex 
               
            
           
           
               
               
               
            
               
                   
                 OPTIONAL, 
                 -- Need R 
               
            
           
           
               
               
               
            
               
                   
                 bwp-Id 
                 BWP-Id 
               
            
           
           
               
               
            
               
                   
                 OPTIONAL, -- Cond CSI-RS-Indicated 
               
            
           
           
               
               
               
            
               
                   
                 referenceSignal 
                 CHOICE { 
               
            
           
           
               
               
            
               
                   
                 csi-rs 
               
            
           
           
               
               
            
               
                   
                 NZP-CSI-RS-ResourceId, 
               
            
           
           
               
               
            
               
                   
                 ssb 
               
            
           
           
               
               
            
               
                   
                 SSB-Index 
               
               
                   
                 }, 
               
               
                   
                 qcl-Type 
               
               
                   
                 ENUMERATED {typeA, typeB, typeC, typeD}, 
               
               
                   
                 ... 
               
            
           
           
               
               
            
               
                   
                 } 
               
               
                   
                 -- TAG-TCI-STATE-STOP 
               
               
                   
                 -- ASN1STOP 
               
               
                   
                   
               
            
           
         
       
     
     In Table 6, ‘bwp-Id’ denotes a DL BWP where RS is located, ‘cell’ denotes a carrier where RS is located, ‘referencesignal’ denotes a reference antenna port(s) which is a QCL-ed source for target antenna port(s) or a reference signal including the same. The target antenna port(s) may be CSI-RS, PDCCH DMRS, or PDSCH DMRS. 
     4. QCL(Quasi-co Location) 
     The UE may receive a list including up to M TCI-state configurations to decode the PDSCH according to the detected PDCCH having an intended DCI for the UE and a given cell. Here, M depends on the UE capability. 
     As illustrated in Table 6, each TCI-State includes a parameter for establishing a QCL relationship between one or two DL RSs and the DM-RS port of the PDSCH. The QCL relationship is configured with a RRC parameter qcl-Type1 for the first DL RS and a qcl-Type2 (if set) for the second DL RS. 
     The QCL type corresponding to each DL RS is given by the parameter ‘qcl-Type’ in QCL-Info and may have one of the following values:
         ‘QCL-TypeA’: {Doppler shift, Doppler spread, average delay, delay spread}   ‘QCL-TypeB’: {Doppler shift, Doppler spread}   ‘QCL-TypeC’: {Doppler shift, average delay}   ‘QCL-TypeD’: {Spatial Rx parameter}       

     For example, when a target antenna port is a specific NZP CSI-RS, corresponding NZP CSI-RS antenna ports may be instructed/configured to be QCL-ed with a specific TRS in terms of QCL-Type A and QCL-ed with a specific SSB in terms of QCL-Type D. The thusly instructed/configured UE may receive the corresponding NZP CSI-RS using a Doppler and delay value measured by the QCL-TypeA TRS and apply a reception beam used for receiving the QCL-TypeD SSB to the corresponding NZP CSI-RS reception. 
     UL BM Process 
     In the UL BM, a Tx beam-Rx beam reciprocity (or beam correspondence) may be or may not be established depending on UE implementation. If the Tx beam-Rx beam reciprocity is established in both the BS and the UE, a UL beam pair may be matched through a DL beam pair. However, if the Tx beam-Rx beam reciprocity is not established in either the BS or the UE, a UL beam pair determining process is required, apart from DL beam pair determination. 
     In addition, even when the BS and the UE maintain beam correspondence, the BS may use the UL BM process for DL Tx beam determination without requesting the UE to report a preferred beam. 
     The UL BM may be performed through beamformed UL SRS transmission and whether to apply the UL BM of the SRS resource set is configured by the RRC parameter in a (RRC parameter) usage. If the usage is configured as ‘BeamManagement (BM)’, only one SRS resource may be transmitted for each of a plurality of SRS resource sets at a given time instant. 
     The UE may be configured with one or more sounding reference signal (SRS) resource sets (through RRC signaling, etc.) set by the (RRC parameter) SRS-ResourceSet. For each SRS resource set, K≥1 SRS resources may be set for the UE. Here, K is a natural number, and a maximum value of K is indicated by SRS_ capability. 
     Like the DL BM, the UL BM process may also be divided into Tx beam sweeping of the UE and Rx beam sweeping of the BS. 
       FIG. 22  shows an example of a UL BM process using SRS. 
       FIG. 22( a )  shows a process of determining Rx beamforming of a BS, and  FIG. 22( b )  shows a process of sweeping Tx beam of the UE. 
       FIG. 23  is a flowchart illustrating an example of a UL BM process using SRS.
         The UE receives RRC signaling (e.g., SRS-Config  1 E) including an (RRC parameter) usage parameter set to ‘beam management’ from the BS (S 1010 ). An SRS-Config IE is used for configuration of SRS transmission. The SRS-Config IE includes a list of SRS-Resources and a list of SRS-ResourceSets. Each SRS resource set refers to a set of SRS-resources.   The UE determines Tx beamforming for the SRS resource to be transmitted on the basis of SRS-SpatialRelation Info included in the SRS-Config IE (S 1020 ). Here, the SRS-SpatialRelation Info is configured for each SRS resource and indicates whether to apply the same beam forming as that used in SSB, CSI-RS, or SRS for each SRS resource.   If SRS-SpatialRelationInfo is configured in the SRS resource, the same beamforming as that used in SSB, CSI-RS, or SRS is applied and transmitted. However, if SRS-SpatialRelationInfo is not configured in the SRS resource, the UE randomly determines the Tx beamforming and transmits the SRS through the determined Tx beamforming (S 1030 ).       

     More specifically, regarding P-SRS in which ‘SRS-ResourceConfigType’ is set to ‘periodic’: 
     i) If the SRS-SpatialRelationInfo is set to ‘SSB/PBCH’, the UE transmits the corresponding SRS by applying the same spatial domain transmission filter (or generated from the corresponding filter) as the spatial domain Rx filter used for receiving SSB/PBCH; or 
     ii) If the SRS-SpatialRelationInfo is set to ‘CSI-RS’, the UE transmits the SRS by applying the same spatial domain transmission filter used for receiving the CSI-RS; or 
     iii) When SRS-SpatialRelationInfo is set to ‘SRS’, the UE transmits the corresponding SRS by applying the same spatial domain transmission filter used for transmitting the SRS.
         In addition, the UE may receive or may not receive a feedback on the SRS from the BS as in the following three cases (S 1040 ).       

     i) When Spatial_ Relation_ Info is set for all SRS resources in the SRS resource set, the UE transmits the SRS to the beam indicated by the BS. For example, if Spatial_ Relation_ Info indicates SSB, CRI, or SRI in which Spatial_ Relation_ Info is the same, the UE repeatedly transmits the SRS on the same beam. 
     ii) Spatial_ Relation_ Info may not be set for all SRS resources in the SRS resource set. In this case, the UE may freely transmit while changing the SRS beamforming. 
     iii) Spatial_ Relation_ Info may only be set for some SRS resources in the SRS resource set. In this case, the SRS is transmitted on the indicated beam for the set SRS resource, and for an SRS resource in which Spatial_ Relation_Info is not set, the UE may transit the SRS resource by randomly applying Tx beam forming. 
     A Beam Failure Recovery (BFR) Process 
     In a beamformed system, a radio link failure (RLF) may occur frequently due to rotation, movement, or beamforming blockage of the UE. Therefore, BFR is supported in NR to prevent frequent occurrence of the RLFs. The BFR is similar to the radio link failure recovery process and may be supported if the UE knows the new candidate beam(s). 
     For beam failure detection, the BS configures beam failure detection reference signals for the UE, and if the number of times of beam failure indications from the physical layer of the UE reaches a threshold set by the RRC signaling within a period set by the RRC signaling of the BS, the UE declares beam failure. 
     After the beam failure is detected, the UE triggers a beam failure recovery by initiating a random access procedure on the PCell; and performs beam failure recovery by selecting a suitable beam (If the BS provides dedicated random access resources for certain beams, they are prioritized by the UE). Upon completion of the random access procedure, beam failure recovery is considered to be completed. 
     J. URLLC (Ultra-Reliable and Low Latency Communication) 
     The URLLC transmission defined by the NR may refer to transmission for (1) a relatively low traffic size, (2) a relatively low arrival rate, (3) an extremely low latency requirement (e.g., 0.5, 1 ms), (4) relatively short transmission duration (e.g., 2 OFDM symbols), and (5) urgent service/message, etc. 
     In the case of UL, transmission for a particular type of traffic (e.g., URLLC) needs to be multiplexed with other previously scheduled transmissions (e.g., eMBB) to meet a more stringent latency requirement. In this regard, one method is to give information indicating that a scheduled UE will be preempted for a specific resource, and allow the URLLC UE to use the resource for UL transmission. 
     Pre-Emption Indication 
     In the case of NR, dynamic resource sharing between eMBB and URLLC is supported. eMBB and URLLC services may be scheduled on non-overlapping time/frequency resources and URLLC transmission may occur on scheduled resources for ongoing eMBB traffic. The eMBB UE may not know whether PDSCH transmission of the UE is partially punctured and the UE may not be able to decode the PDSCH due to corrupted coded bits. In consideration of this, NR provides a preemption indication. 
     The preemption indication may also be referred to as an interrupted transmission indication. 
     With respect to the preamble indication, the UE receives DownlinkPreemption IE through RRC signaling from the BS. Table 7 below shows an example of the DownlinkPreemption IE. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
             
            
               
                 -- ASN1 START 
               
               
                 -- TAG-DOWNLINKPREEMPTION-START 
               
            
           
           
               
               
            
               
                 DownlinkPreemption ::= 
                 SEQUENCE { 
               
            
           
           
               
               
               
            
               
                   
                  int-RNTI 
                  RNTI-Value, 
               
               
                   
                  timeFrequencySet 
                  ENUMERATED [set0, set1}, 
               
               
                   
                  dci-PayloadSize 
                 INTEGER (0..maxINT-DCI-PayloadSize), 
               
            
           
           
               
               
               
            
               
                   
                  int-ConfigurationPerServingCell 
                 SEQUENCE (SIZE (1..maxNrofServingCells)) 
               
            
           
           
               
            
               
                 OF INT-ConfigurationPerServingCell, 
               
            
           
           
               
               
            
               
                   
                 ... 
               
            
           
           
               
            
               
                 } 
               
               
                 INT-ConfigurationPerServingCell ::= SEQUENCE { 
               
            
           
           
               
               
               
            
               
                   
                  servingCellId 
                  ServCellIndex, 
               
            
           
           
               
               
               
            
               
                   
                  positionInDCI 
                 INTEGER (0..maxINT-DCI-PayloadSize-1) 
               
            
           
           
               
            
               
                 } 
               
               
                 -- TAG-DOWNLINKPREEMPTION-STOP 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     If the UE is provided with the DownlinkPreemption IE, the UE is configured with an INT-RNTI provided by a parameter int-RNTI in the DownlinkPreemption IE to monitor a PDCCH conveying the DCI format 2_1. The UE is further configured with a set of serving cells and a corresponding set of locations for fields in the DCI format 2_1 by positionInDCI by an INT-ConfigurationPerServing Cell including a set of serving cell indices provided by a servingCellID, is configured with an information payload size for DCI format 2_1 by dci-PayloadSize, and is configured with granularity of time-frequency resources by timeFrequencySect. 
     The UE receives the DCI format 2_1 from the BS on the basis of the DownlinkPreemption IE. 
     If the UE detects the DCI format 2_1 for a serving cell in the set of serving cells, the UE may assume there is no transmission to the UE in PRBs and symbols indicated by the DCI format 2_1 among sets of PRBs and sets of symbols in the last monitoring period before a monitoring period to which the DCI format 2_1 belongs. For example, referring to  FIG. 9A , the UE determines that a signal in the time-frequency resource indicated by pre-emption is not a DL transmission scheduled for the UE itself and decodes data on the basis of signals received in the remaining resource area. 
       FIG. 24  is a diagram showing an example of an preemption indication method. 
     A combination of {M,N} is set by the RRC parameter timeFrequencySet. {M, N}={ 14 , 1 }, { 7 , 2 }. 
       FIG. 25  shows an example of a time/frequency set of a preemption indication. 
     A 14-bit bitmap for a preemption indication indicates one or more frequency parts (N&gt;=1) and/or one or more time domain parts (M&gt;=1). In the case of {M, N}={ 14 , 1 }, as shown in  FIG. 25( a ) , 14 parts in the time domain correspond one-to-one to 14 bits of the 14-bit bit map, and a part corresponding to a bit set to 1, among the 14 bits, is part including pre-empted resources. In the case of {M, N}={ 7 , 2 }, as shown in  FIG. 25( b ) , the time-frequency resources of the monitoring period is divided into seven parts in the time domain and two parts in the frequency domain, so as to be divided into a total of 14 time-frequency parts. The total of 14 time-frequency parts correspond one-to-one to the 14 bits of the 14-bit bitmap, and the part corresponding to the bit set to 1 among the 14 bits includes the pre-empted resources. 
     K. MMTC (Massive MTC) 
     The massive machine type communication (mMTC) is one of the 5G scenarios for supporting a hyper-connection service that simultaneously communicates with a large number of UEs. In this environment, the UE intermittently performs communication with a very low transfer rate and mobility. Therefore, mMTC is aimed at how low cost and for how long the UE can be driven. In this regard, MTC and NB-IoT, which are dealt with in 3GPP will be described. 
     Hereinafter, a case where a transmission time interval of a physical channel is a subframe will be described as an example. For example, a case where a minimum time interval from a start of transmission of one physical channel (e.g., MPDCCH, PDSCH, PUCCH, PUSCH) to a start of transmission of a next physical channel is one subframe will be described as an example. In the following description, the subframe may be replaced by a slot, a mini-slot, or multiple slots. 
     MTC (Machine Type Communication) 
     MTC (Machine Type Communication), which is an application that does not require much throughput applicable to M2M (Machine-to-Machine) or IoT (Internet-of-Things), refers to a communication technology adopted to meet the requirements of the IoT service in 3GPP (3rd Generation Partnership Project). 
     The MTC may be implemented to meet the criteria of (1) low cost &amp; low complexity, (2) enhanced coverage, and (3) low power consumption. 
     In 3GPP, MTC has been applied since release 10 (3GPP standard document version 10.x.x.) and features of MTC added for each release of 3GPP will be briefly described. 
     First, the MTC described in 3GPP Release 10 and Release 11 relates to a load control method. The load control method is to prevent IoT (or M2M) devices from suddenly loading the BS. More specifically, 3GPP Release 10 relates to a method of controlling a load by disconnecting IoT devices when the load occurs, and Release 11 relates to a method of preventing connection of the UE in advance by informing the UE about connection to a cell later through system information of the cell. In Release 12, features for low cost MTC are added, for which UE category 0 is newly defined. The UE category is an indicator indicating how much data the UE may handle at a communication modem. A UE in UE category 0 is a UE with a reduced peak data rate and relaxed radio frequency (RF) requirements, thus reducing baseband and RF complexity. In Release 13, a technology called eMTC (enhanced MTC) was introduced, which allows the UE to operate only at 1.08 MHz, a minimum frequency bandwidth supported by legacy LTE, thereby lowering the price and power consumption of the UE. 
     The contents described hereinafter is features mainly related to eMTC but may also be equally applicable to the MTC, eMTC, 5G (or NR) unless otherwise mentioned. Hereinafter, for convenience of explanation, MTC will be collectively described. 
     Therefore, the MTC described below may referred to as the enhanced MTC (eMTC), the LTE-M 1 /M 2 , BL (bandwidth reduced low complexity/CE (coverage enhanced), non-BE UE (in enhanced coverage), NR MTC, enhanced BL/CE, and the like. That is, the term MTC may be replaced with terms to be defined in the 3GPP standard in the future. 
     MTC General Features 
     (1) MTC operates only within a specific system bandwidth (or channel bandwidth). 
     MTC may use six resource blocks (RBs) in the system band of the legacy LTE as shown in  FIG. 26  or use a specific number of RBs in the system band of the NR system. The frequency bandwidth in which the MTC operates may be defined in consideration of a frequency range of NR and subcarrier spacing. Hereinafter, a specific system or frequency bandwidth in which the MTC operates is referred to as an MTC narrowband (NB). In the NR, the MTC may operate in at least one bandwidth part (BWP) or in a specific band of BWP. 
     MTC follows a narrowband operation to transmit and receive physical channels and signals, and a maximum channel bandwidth in which the MTC UE is operable is reduced to 1.08 MHz or six (LTE) RBs. 
     The narrowband may be used as a reference unit in resource allocation units of some downlink and uplink channels, and a physical location of each narrowband in the frequency domain may be defined to be different depending on the system bandwidth. 
     The bandwidth of 1.08 MHz defined in MTC is defined for the MTC UE to follow the same cell search and random access procedure as the legacy UE. 
     MTC may be supported by cells having a bandwidth (e.g., 10 MHz) much larger than 1.08 MHz but the physical channels and signals transmitted and received by the MTC are always limited to 1.08 MHz. The system with having much larger bandwidth may be legacy LTE, NR systems, 5G systems, and the like. 
     A narrowband is defined as six non-overlapping consecutive physical resource blocks in the frequency domain. 
       FIG. 26( a )  is a diagram showing an example of a narrowband operation, and  FIG. 26( b )  is a diagram showing an example of repetition having RF returning. 
     Frequency diversity by RF returning will be described with reference to  FIG. 26( b ) . 
     Due to narrowband RF, single antenna and limited mobility, the MTC supports limited frequency, space and time diversity. In order to reduce fading and outage, frequency hopping is supported by MTC between different narrow bands by RF returning. 
     In MTC, frequency hopping is applied to different uplink and downlink physical channels when repetition is possible. For example, if 32 subframes are used for PDSCH transmission, first 16 subframes may be transmitted on a first narrowband. Here, the RF front end is returned to another narrow band, and the remaining 16 subframes are transmitted on the second narrow band. 
     The narrowband of MTC may be set to the UE via system information or DCI (downlink control information) transmitted by the BS. 
     (2) The MTC operates in a half duplex mode and uses a limited (or reduced) maximum transmit power. The half duplex mode refers to a mode in which a communication device operates only in an uplink or a downlink at one frequency at one time point and operates in a downlink or an uplink at another frequency at another time point. For example, when the communication device operates in the half-duplex mode, the communication device performs communication using the uplink frequency and the downlink frequency, and the communication device may not use the uplink frequency and the downlink frequency at the same time. The communication device divides time to perform uplink transmission through the uplink frequency and the downlink reception by re-tuning to the downlink frequency for another predetermined time. 
     (3) MTC does not use channels (defined in legacy LTE or NR) that must be distributed over the entire system bandwidth of the legacy LTE or NR. For example, in the MTC, the PDCCH of the legacy LTE is not used because the PDCCH is distributed over the entire system bandwidth. Instead, a new control channel, MPDCCH (MTC PDCCH), is defined in the MTC. The MPDCCH is transmitted/received within a maximum of  6  RBs in the frequency domain. 
     (4) MTC uses the newly defined DCI format. For example, DCI formats 6-0A, 6-0B, 6-1A , 6-1B, 6-2, etc., may be used as a DCI format for MTC (see 3GPP TS 36.212). 
     (5) In the case of MTC, a physical broadcast channel (PBCH), a physical random access channel (PRACH), an MTC physical downlink control channel (M-PDCCH), a physical downlink shared channel (PDSCH), a physical uplink control channel (PUCCH), and a physical uplink shared channel (PUSCH) may be repeatedly transmitted. Due to the MTC repeated transmission, an MTC channel may be decoded even when signal quality or power is very poor, such as in an inadequate environment such as a basement, thereby increasing a cell radius and increasing a penetration effect. 
     (6) In MTC, PDSCH transmission based on PDSCFI scheduling (DCI) and PDSCH scheduling may occur in different subframes (cross-subframe scheduling). 
     (7) In the LTE system, the PDSCH carrying a general SIB 1  is scheduled by the PDCCH, whereas all the resource allocation information (e.g., subframe, transport block size, narrowband index) for SIB 1  decoding is determined by a parameter of the MIB and no control channel is used for SIB 1  decoding of the MTC. 
     (8) All resource allocation information (subframe, TBS, subband index) for SIB 2  decoding is determined by several SIB 1  parameters and no control channel for SIB 2  decoding of MTC is used. 
     (9) The MTC supports an extended paging (DRX) cycle. Here, the paging period refers to a period during which the UE must be wake up to check whether there is a paging from a network even when the UE is in a discontinuous reception (DRX) mode in which it does not attempt to receive a downlink signal for power saving. 
     (10) MTC may use the same PSS (Primary Synchronization Signal)/SSS (Secondary Synchronization Signal)/CRS (Common Reference Signal) used in legacy LTE or NR. In the case of NR, the PSS/SSS is transmitted on an SSB basis, and a tracking RS (TRS) is a cell-specific RS and may be used for frequency/time tracking. 
     MTC Operation Mode and Level 
     Next, an MTC operation mode and level will be described. MTC is classified into two operation modes (first mode, second mode) and four different levels for coverage improvement as shown in Table 8 below. 
     The MTC operation mode is referred to as a CE (Coverage Enhancement) mode. In this case, the first mode may be referred to as a CE mode A, and the second mode may be referred to as a CE mode B. 
     
       
         
           
               
               
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 Mode 
                 Level 
                 Description 
               
               
                   
               
             
            
               
                 Mode A 
                 Level 1 
                 No repetition for PRACH 
               
               
                   
                 Level 2 
                 Small Number of Repetition for PRACH 
               
               
                 Mode B 
                 Level 3 
                 Medium Number of Repetition for PRACH 
               
               
                   
                 Level 4 
                 Large Number of Repetition for PRACH 
               
               
                   
               
            
           
         
       
     
     The first mode is defined for small coverage enhancement to support full mobility and CSI (channel state information, in which there is no repetition or fewer repetition times. The second mode is defined for UEs with extremely poor coverage conditions that support CSI feedback and limited mobility, in which a large number of repetitive transmissions is defined. The second mode provides a coverage improvement of up to 15 dB. Each level of MTC is defined differently in the random access procedure and the paging process. 
     The MTC operation mode is determined by the BS, and each level is determined by the MTC UE. Specifically, the BS transmits RRC signaling including information on the MTC operation mode to the UE. Here, the RRC signaling may be an RRC connection setup message, an RRC connection reconfiguration message or an RRC connection reestablishment message. 
     Thereafter, the MTC UE determines a level in each operation mode and transmits the determined level to the BS. Specifically, the MTC UE determines a level in an operation mode on the basis of measured channel quality (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), or signal to interference plus noise ratio (SINR), and transmits an RACH preamble using a PRACFI resource (e.g., frequency, time, preamble resource for PRACH) corresponding to the determined level, thereby informing the BS about the determined level. 
     MTC Guard Period 
     As discussed above, MTC operates in narrow band. The location of the narrow band used in the MTC may be different for each particular time unit (e.g., subframe or slot). The MTC UE may tune to different frequencies depending on the time units. A certain amount of time is required for frequency returning, and certain amount of time is defined as a guard period of MTC. That is, a guard period is required when frequency returning is performed while transitioning from one time unit to the next time unit, and transmission and reception do not occur during the guard period. 
     MTC Signal Transmission/Reception Method 
       FIG. 27  is a diagram illustrating physical channels that may be used for MTC and a general signal transmission method using the same. 
     In step S 1001 , the MTC UE, which is powered on again or enters a new cell, performs an initial cell search operation such as synchronizing with the BS. To this end, the MTC UE receives a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the BS, adjusts synchronization with the BS, and acquires information such as a cell ID. The PSS/SSS used in the initial cell search operation of the MTC may be a PSS/SSS, a resynchronization signal (RSS), or the like of an legacy LTE. 
     Thereafter, the MTC UE may receive a physical broadcast channel (PBCH) signal from the BS to acquire broadcast information in a cell. 
     Meanwhile, the MTC UE may receive a downlink reference signal (DL RS) in an initial cell search step to check a downlink channel state. The broadcast information transmitted through the PBCH is a master information block (MIB), and in the LTE, the MIB is repeated by every 10 ms. 
     Among the bits of the MIB of the legacy LTE, reserved bits are used in MTC to transmit scheduling for a new SIB 1 -BR (system information block for bandwidth reduced device) including a time/frequency location and a transport block size. The SIB-BR is transmitted directly on the PDSCH without any control channel (e.g., PDSCH, MPDDCH) associated with the SIB-BR. 
     Upon completion of the initial cell search, the MTC UE may receive an MPDCCH and a PDSCH according to the MPDCCFI information to acquire more specific system information in step S 1002 . The MPDCCH may be transmitted only once or repeatedly. The maximum number of repetitions of the MPDCCH is set to the UE by RRC signaling from the BS. 
     Thereafter, the MTC UE may perform a random access procedure such as steps S 1003  to S 1006  to complete the connection to the BS. A basic configuration related to the RACH process of the MTC UE is transmitted by SIB 2 . In addition, SIB 2  includes parameters related to paging. In the 3GPP system, a paging occasion (PO) refers to a time unit in which the UE may attempt to receive paging. The MTC UE attempts to receive the MPDCCH on the basis of a P-RNTI in the time unit corresponding to its PO on the narrowband (PNB) set for paging. The UE that has successfully decoded the MPDCCH on the basis of the P-RNTI may receive a PDSCH scheduled by the MPDCCH and check a paging message for itself. If there is a paging message for itself, the UE performs a random access procedure to access a network. 
     For the random access procedure, the MTC UE transmits a preamble through a physical random access channel (PRACH) (S 1003 ), and receives a response message (RAR) for the preamble through the MPDCCH and the corresponding PDSCH. (S 1004 ). In the case of a contention-based random access, the MTC UE may perform a contention resolution procedure such as transmission of an additional PRACH signal (S 1005 ) and reception of the MPDCCH signal and corresponding PDSCH signal (S 1006 ). The signals and/or messages Msg 1, Msg 2, Msg 3, and Msg 4transmitted in the RACH process in the MTC may be repeatedly transmitted, and the repeat pattern is set to be different according to the CE level. 
     Msg1 denotes a PRACH preamble, Msg2 denotes a random access response (RAR), Msg3 denotes UL transmission on the basis of a UL grant included in the RAR, and Msg4 denotes a DL transmission of the BS to Msg3. 
     For random access, PRACH resources for the different CE levels are signaled by the BS. This provides the same control of a near-far effect on the PRACH by grouping together UEs experiencing similar path loss. Up to four different PRACH resources may be signaled to the MTC UE. 
     The MTC UE estimates RSRP using a downlink RS (e.g., CRS, CSI-RS, TRS, and the like), and selects one of different PRACH resources (e.g., frequency, time, and preamble resources for PRACH) for the random access on the basis of the measurement result. The RAR for the PRACH and search spaces for the contention resolution messages for PRACH are also signaled at the BS via system information. 
     The MTC UE that has performed the above-described process may then receive an MPDCCH signal and/or a PDSCH signal (S 1007 ) and transmit a physical uplink shared channel (PUSCH) signal and/or a physical uplink control channel (PUCCH) (S 1108 ) as a general uplink/downlink signal transmission process. The MTC UE may transmit uplink control information (UCI) to the BS through the PUCCH or PUSCH. The UCI may include HARQ-ACK/NACK, scheduling request (SR), and/or CSI. 
     When RRC connection to the MTC UE is established, the MTC UE monitors the MPDCCH in a search space set to acquire uplink and downlink data allocation and attempts to receive the MDCCH. 
     In the case of MTC, the MPDCCH and the PDSCH scheduled by the MDCCH are transmitted/received in different subframes. For example, the MPDCCH having the last repetition in subframe #n schedules the PDSCH starting at subframe #n+2. The DCI transmitted by the MPDCCH provides information on how many times the MPDCCH is repeated so that the MTC UE may know when the PDSCI-I transmission is started. For example, when the DCI in the MPDCCH started to be transmitted from the subframe #n includes information that the MPDCCH is repeated 10 times, a last subframe in which the MPDCCH is transmitted is the subframe #n+9 and transmission of the PDSCH may start at subframe #n+11. 
     The PDSCH may be scheduled in the same as or different from a narrow band in which the MPDCCH scheduling the PDSCH is present. If the MPDCCH and the corresponding PDSCH are located in different narrow bands, the MTC UE needs to retune the frequency to the narrow band in which the PDSCH is present before decoding the PDSCH. 
     For uplink data transmission, scheduling may follow the same timing as legacy LTE. For example, the MPDCCH which is lastly transmitted at subframe #n may schedule PUSCH transmission starting at subframe #n+4. 
       FIG. 28  shows an example of scheduling for MTC and legacy LTE, respectively. 
     In the legacy LTE, the PDSCH is scheduled using the PDCCH, which uses the first OFDM symbol(s) in each subframe, and the PDSCH is scheduled in the same subframe as the subframe in which the PDCCH is received. 
     In contrast, the MTC PDSCH is cross-subframe scheduled, and one subframe between the MPDCCH and the PDSCH is used as a time period for MPDCCH decoding and RF returning. The MTC control channel and data channel may be repeated over a large number of subframes including up to 256 subframes for the MPDCCH and up to 2048 subframes for the PDSCH so that they may be decoded under extreme coverage conditions. 
     NB-IoT (Narrowband-Internet of Things) 
     The NB-IoT may refer to a system for supporting low complexity, low power consumption through a system bandwidth (system BW) corresponding to one resource block (RB) of a wireless communication system. 
     Here, NB-IoT may be referred to as other terms such as NB-LTE, NB-IoT enhancement, enhanced NB-IoT, further enhanced NB-IoT, NB-NR. That is, NB-IoT may be replaced with a term defined or to be defined in the 3GPP standard, and hereinafter, it will be collectively referred to as ‘NB-IoT’ for convenience of explanation. 
     The NB-IoT is a system for supporting a device (or UE) such as machine-type communication (MTC) in a cellular system so as to be used as a communication method for implementing IoT (i.e., Internet of Things). Here, one RB of the existing system band is allocated for the NB-IoT, so that the frequency may be efficiently used. Also, in the case of NB-IoT, each UE recognizes a single RB as a respective carrier, so that RB and carrier referred to in connection with NB-IoT in the present specification may be interpreted to have the same meaning. 
     Hereinafter, a frame structure, a physical channel, a multi-carrier operation, an operation mode, and general signal transmission/reception related to the NB-IoT in the present specification are described in consideration of the case of the legacy LTE system, but may also be extendedly applied to a next generation system (e.g., an NR system, etc.). In addition, the contents related to NB-IoT in this specification may be extendedly applied to MTC (Machine Type Communication) oriented for similar technical purposes (e.g., low-power, low-cost, coverage enhancement, etc.). 
     Hereinafter, a case where a transmission time interval of a physical channel is a subframe are described as an example. For example, a case where a minimum time interval from the start of transmission of one physical channel (e.g., NPDCCH, NPDSCH, NPUCCH, NPUSCH) to the start of transmission of a next physical channel is one subframe will be described, but in the following description, the subframe may be replaced by a slot, a mini-slot, or multiple slots. 
     Frame Structure and Physical Resource of NB-IoT 
     First, the NB-IoT frame structure may be configured to be different according to subcarrier spacing. Specifically,  FIG. 29  shows an example of a frame structure when a subscriber spacing is 15 kHz, and  FIG. 30  shows an example of a frame structure when a subscriber spacing is 3.75 kHz. However, the NB-IoT frame structure is not limited thereto, and NB-IoT for other subscriber spacings (e.g., 30 kHz) may be considered with different time/frequency units. 
     In addition, although the NB-IoT frame structure on the basis of the LIE system frame structure has been exemplified in the present specification, it is merely for the convenience of explanation and the present invention is not limited thereto. The method described in this disclosure may also be extendedly applied to NB-IoT based on a frame structure of a next-generation system (e.g., NR system). 
     Referring to  FIG. 29 , the NB-IoT frame structure for a 15 kHz subscriber spacing may be configured to be the same as the frame structure of the legacy system (e.g., LTE system) described above. For example, a 10 ms NB-IoT frame may include ten 1 ms NB-IoT subframes, and the 1 ms NB-IoT subframe may include two 0.5 ms NB-IoT slots. Further, each 0.5 ms NB-IoT may include 7 OFDM symbols. 
     Alternatively, referring to  FIG. 30 , the 10 ms NB-IoT frame may include five 2 ms NB-IoT subframes, the 2 ms NB-IoT subframe may include seven OFDM symbols and one guard period (GP). Also, the 2 ms NB-IoT subframe may be represented by an NB-IoT slot or an NB-IoT RU (resource unit). 
     Next, physical resources of the NB-IoT for each of downlink and uplink will be described. 
     First, the physical resources of the NB-IoT downlink may be configured by referring to physical resources of other wireless communication system (e.g., LTE system, NR system, etc.), except that a system bandwidth is limited to a certain number of RBs (e.g., one RB, i.e., 180 kHz). For example, when the NB-IoT downlink supports only the 15-kHz subscriber spacing as described above, the physical resources of the NB-IoT downlink may be configured as resource regions limiting a resource grid of the LTE system shown in  FIG. 31  to one RB in the frequency domain. 
     Next, in the case of the NB-IoT uplink physical resource, the system bandwidth may be limited to one RB as in the case of downlink. For example, if the NB-IoT uplink supports 15 kHz and 3.75 kHz subscriber spacings as described above, a resource grid for the NB-IoT uplink may be expressed as shown in  FIG. 31 . In this case, the number of subcarriers NULsc and the slot period Tslot in the uplink band in  FIG. 31  may be given as shown in Table 9 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 9 
               
               
                   
                   
               
               
                   
                 Subcarrier spacing 
                 NULsc 
                 Tslot 
               
               
                   
                   
               
             
            
               
                   
                 Δf = 3.75 kHz 
                 48 
                  6144 · Ts 
               
               
                   
                 Δf = 15 kHz 
                 12 
                 15360 · Ts 
               
               
                   
                   
               
            
           
         
       
     
     In NB-IoT, resource units (RUs) are used for mapping the PUSCH for NB-IoT (hereinafter referred to as NPUSCH) to resource elements. RU may include NULsymb*NULslot SC-FDMA symbols in the time domain and include NRUsc number of consecutive subcarriers in the frequency domain. For example, NRUsc and NULsymb may be given by Table 10 below for frame structure type 1, which is a frame structure for FDD, and may be given by Table 11 below for frame structure type 2, which is frame structure for TDD. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 10 
               
               
                   
               
               
                 NPUSCH 
                   
                   
                   
                   
               
               
                 format 
                 Δf 
                 NRUsc 
                 NULslots 
                 NULsymb 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 1 
                 3.75 kHz 
                 1 
                 16 
                 7 
               
               
                   
                     15 kHz 
                 1 
                 16 
               
               
                   
                   
                 3 
                 8 
               
               
                   
                   
                 6 
                 4 
               
               
                   
                   
                 12 
                 2 
               
               
                 2 
                 3.75 kHz 
                 1 
                 4 
               
               
                   
                     15 kHz 
                 1 
                 4 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 11 
               
               
                   
               
               
                   
                   
                 Supported 
                   
                   
                   
               
               
                   
                   
                 uplink- 
               
               
                 NPUSCH 
                   
                 downlink 
               
               
                 format 
                 Δf 
                 configurations 
                 NRUsc 
                 NULslots 
                 NULsymb 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 1 
                 3.75 kHz 
                 1, 4 
                 1 
                 16 
                 7 
               
               
                   
                     15 kHz 
                 1, 2, 3, 4, 5 
                 1 
                 16 
               
               
                   
                   
                   
                 3 
                 8 
               
               
                   
                   
                   
                 6 
                 4 
               
               
                   
                   
                   
                 12 
                 2 
               
               
                 2 
                 3.75 kHz 
                 1, 4 
                 1 
                 4 
               
               
                   
                     15 kHz 
                 1, 2, 3, 4, 5 
                 1 
                 4 
               
               
                   
               
            
           
         
       
     
     Physical Channel of NB-IoT 
     A BS and/or a UE supporting the NB-IoT may be configured to transmit/receive physical channels and/or physical signals configured separately from the legacy system. Hereinafter, specific contents related to physical channels and/or physical signals supported by the NB-IoT will be described. 
     An orthogonal frequency division multiple access (OFDMA) scheme may be applied to the NB-IoT downlink on the basis of a subscriber spacing of 15 kHz. Through this, co-existence with other systems (e.g., LTE system, NR system) may be efficiently supported by providing orthogonality between subcarriers. A downlink physical channel/signal of the NB-IoT system may be represented by adding ‘N (Narrowband)’ to distinguish it from the legacy system. For example, a downlink physical channel may be referred to as an NPBCH (narrowband physical broadcast channel), an NPDCCH (narrowband physical downlink control channel), or an NPDSCH (narrowband physical downlink shared channel), and a downlink physical signal may be referred to as an NPSS (narrowband primary synchronization signal), an NSSS (narrowband secondary synchronization signal), an NRS (narrowband reference signal), an NPRS (narrowband positioning reference signal), an NWUS (narrowband wake up signal), and the like. Generally, the downlink physical channels and physical signals of the NB-IoT may be configured to be transmitted on the basis of a time domain multiplexing scheme and/or a frequency domain multiplexing scheme. In the case of NPBCH, NPDCCFI, NPDSCH, etc., which are the downlink channels of the NB-IoT system, repetition transmission may be performed for coverage enhancement. In addition, the NB-IoT uses a newly defined DCI format. For example, the DCI format for NB-IoT may be defined as DCI format N 0 , DCI format N 1 , DCI format N 2 , and the like. 
     In the NB-IoT uplink, a single carrier frequency division multiple access (SC-FDMA) scheme may be applied on the basis of a subscriber spacing of 15 kHz or 3.75 kHz. As mentioned in the downlink section, the physical channel of the NB-IoT system may be expressed by adding ‘N (Narrowband)’ to distinguish it from the existing system. For example, the uplink physical channel may be represented by a narrowband physical random access channel (NPRACH) or a narrowband physical uplink shared channel (NPUSCH), and the uplink physical signal may be represented by a narrowband demodulation reference signal (NDMRS), or the like. NPUSCH may be divided into NPUSCH format 1 and NPUSCH format 2. In one example, NPUSCH Format 1 may be used for uplink shared channel (UL-SCH) transmission (or transport), and NPUSCH Format 2 may be used for uplink control information transmission such as HARQ ACK signaling. In the case of NPRACH, which is an uplink channel of the NB-IoT system, repetition transmission may be performed for coverage enhancement. In this case, repetition transmission may be performed by applying frequency hopping. 
     Multi-Carrier Operation of NB-IoT 
     Next, a multi-carrier operation of the NB-IoT will be described. The multicarrier operation may refer to that multiple carriers set for different uses (i.e., different types) are used for transmitting/receiving channels and/or signals between the BS and/or UE in the NB-lot. 
     The NB-IoT may operate in a multi-carrier mode. Here, in the NB-IoT, a carrier wave in the N-lot may be classified as an anchor type carrier (i.e., an anchor carrier, an anchor PRB) and a non-anchor type carrier a non-anchor type carrier (i.e., non-anchor carrier). 
     The anchor carrier may refer to a carrier that transmits NPSS, NSSS, NPBCH, and NPDSCH for a system information block (N-SIB) for initial access from a point of view of the BS. That is, in NB-IoT, the carrier for initial access may be referred to as an anchor carrier and the other(s) may be referred to as a non-anchor carrier. Here, only one anchor carrier wave may exist in the system, or there may be a plurality of anchor carrier waves. 
     Operation Mode of NB-IoT 
     Next, an operation mode of the NB-IoT will be described. In the NB-IoT system, three operation modes may be supported.  FIG. 32  shows an example of operation modes supported in the NB-IoT system. Although the operation mode of the NB-IoT is described herein on the basis of an LTE band, this is for convenience of explanation and may be extendedly applied to other system bands (e.g. NR system band). 
     Specifically,  FIG. 32( a )  shows an example of an in-band system,  FIG. 32( b )  shows an example of a guard-band system, and  FIG. 32( c )  Represents an example of a stand-alone system. In this case, the in-band system may be expressed as an in-band mode, the guard-band system may be expressed as a guard-band mode, and the stand-alone system may be expressed in a stand-alone mode. 
     The in-band system may refer to a system or mode that uses a specific RB in the (legacy) LTE band. The in-band system may be operated by allocating some resource blocks of the LTE system carrier. 
     A guard-band system may refer to a system or mode that uses NB-IoT in a space reserved for a guard-band of the legacy LTE band. The guard-band system may be operated by allocating a guard-band of an LTE carrier not used as a resource block in the LTE system. For example, the (legacy) LTE band may be configured to have a guard-band of at least 100 kHz at the end of each LTE band, and with two non-contiguous guard-bands for 200 kHz for NB-IoT may be used. 
     As described above, the in-band system and the guard-band system may be operated in a structure in which NB-IoT coexists in the (legacy) LTE band. 
     By contrast, the stand-alone system may refer to a system or mode that is configured independently of the legacy LTE band. The stand-alone system may be operated by separately allocating frequency bands (e.g., reassigned GSM carriers in the future) used in a GERAN (GSM EDGE radio access network). 
     The three operation modes described above may be operated independently of each other, or two or more operation modes may be operated in combination. 
     NB-IoT Signal Transmission/Reception Process 
       FIG. 33  is a diagram illustrating an example of physical channels that may be used for NB-IoT and a general signal transmission method using the same. In a wireless communication system, an NB-IoT UE may receive information from a BS through a downlink (DL) and the NB-IoT UE may transmit information to the BS through an uplink (UL). In other words, in the wireless communication system, the BS may transmit information to the NB-IoT UE through the downlink and the BS may receive information from the NB-IoT UE through the uplink. 
     The information transmitted/received by the BS and the NB-IoT UE includes data and various control information, and various physical channels may exist depending on the type/purpose of the information transmitted/received by the BS and NB-IoT UE. The signal transmission/reception method of the NB-IoT may be performed by the above-described wireless communication devices (e.g., BS and UE). 
     The NB-IoT UE, which is powered on again or enters a new cell, may perform an initial cell search operation such as adjusting synchronization with the BS, or the like (S 11 ). To this end, the NB-IoT UE receives NPSS and NSSS from the BS, performs synchronization with the BS, and acquires cell identity information. Also, the NB-IoT UE may receive the NPBCH from the BS and acquire the in-cell broadcast information. In addition, the NB-IoT UE may receive a DL RS (downlink reference signal) in the initial cell search step to check a downlink channel state. 
     After completion of the initial cell search, the NB-IoT UE may receive the NPDCCH and the corresponding NPDSCH to acquire more specific system information (S 12 ). In other words, the BS may transmit more specific system information by transmitting the NPDCCH and corresponding NPDSCH to the NB-IoT UE after completion of the initial cell search. 
     Thereafter, the NB-IoT UE may perform a random access procedure to complete connection to the BS (S 13  to S 16 ). 
     Specifically, the NB-IoT UE may transmit a preamble to the BS via the NPRACH (S 13 ). As described above, the NPRACH may be configured to be repeatedly transmitted on the basis of frequency hopping or the like to enhance coverage or the like. In other words, the BS may (repeatedly) receive a preamble through the NPRACH from the NB-IoT UE. 
     Thereafter, the NB-IoT UE may receive a random access response (RAR) for the preamble from the BS through the NPDCCH and the corresponding NPDSCH (S 14 ). In other words, the BS may transmit the RAR for the preamble to the NB-IoT UE through the NPDCCH and the corresponding NPDSCH. 
     Thereafter, the NB-IoT UE transmits the NPUSCH to the BS using scheduling information in the RAR (S 15 ), and may perform a contention resolution procedure such as the NPDCCH and the corresponding NPDSCH (S 16 ). In other words, the BS may receive the NPUSCH from the UE using the scheduling information in the NB-IoT RAR, and perform the contention resolution procedure. 
     The NB-IoT UE that has performed the above-described process may perform NPDCCH/NPDSCH reception (S 17 ) and NPUSCH transmission (S 18 ) as a general uplink/downlink signal transmission process. In other words, after performing the above-described processes, the BS may perform NPDCCH/NPDSCH transmission and NPUSCH reception as a general signal transmission/reception process to the NB-IoT UE. 
     In the case of NB-IoT, as mentioned above, NPBCH, NPDCCH, NPDSCH, and the like may be repeatedly transmitted for coverage improvement and the like. In the case of NB-IoT, UL-SCH (i.e., general uplink data) and uplink control information may be transmitted through the NPUSCH. Here, the UL-SCH and the uplink control information (UCI) may be configured to be transmitted through different NPUSCH formats (e.g., NPUSCH format 1, NPUSCH format 2, etc.). 
     Also, the UCI may include HARQ ACK/NACK (Hybrid Automatic Repeat and reQuest Acknowledgement/Negative-ACK), SR (Scheduling Request), CSI(Channel State Information), and the like. As described above, the UCI in the NB-IoT may generally be transmitted via the NPUSCH. Also, in response to a request/instruction from the network (e.g., BS), the UE may transmit the UCI via the NPUSCH in a periodic, aperiodic, or semi-persistent manner. 
     Hereinafter, the wireless communication system block diagram shown in  FIG. 1  will be described in detail. 
     N. Wireless Communication Device 
     Referring to  FIG. 1 , a wireless communication system includes a first communication device  910  and/or a second communication device  920 . ‘A and/or B’ may be interpreted to have the same meaning as ‘includes at least one of A or B.’ The first communication device may represent a BS and the second communication device may represent a UE (alternatively, the first communication device may represent a UE and the second communication device may represent a BS). 
     The first and second communication devices may include processors  911  and  921 , memories  914  and  924 , one or more Tx/Rx RF modules  915  and  925 , Tx processors  912  and  922 , Rx processors  913  and  923 , and antennas  916  and  926 , respectively. The Tx/Rx module is also called a transceiver. The processor implements the functions, procedures and/or methods discussed above. More specifically, in the DL (communication from the first communication device to the second communication device), a higher layer packet from the core network is provided to the processor  911 . The processor implements the function of a layer 2 (i.e., L2) layer. In the DL, the processor multiplexes a logical channel and a transport channel, provides radio resource allocation to the second communication device  920 , and is responsible for signaling to the second communication device. A transmission (TX) processor  912  implements various signal processing functions for the L1 layer (i.e., the physical layer). The signal processing function facilitates forward error correction (FEC) in the second communication device, and includes coding and interleaving. The encoded and interleaved signals are scrambled and modulated into complex-valued modulation symbols. For modulation, BPSK (Quadrature Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (quadrature amplitude modulation), 64QAM, 246QAM, and the like may be used. The complex-valued modulation symbols (hereinafter referred to as modulation symbols) are divided into parallel streams, each stream being mapped to an OFDM subcarrier and multiplexed with a reference signal (RS) in the time and/or frequency domain, and combined together using IFFT (Inverse Fast Fourier Transform) to create a physical channel carrying a time domain OFDM symbol stream. The OFDM symbol stream is spatially precoded to produce multiple spatial streams. Each spatial stream may be provided to a different antenna  916  via a separate Tx/Rx module (or transceiver,  915 ). Each Tx/Rx module may upconvert each spatial stream into an RF carrier for transmission. In the second communication device, each Tx/Rx module (or transceiver,  925 ) receives a signal of the RF carrier via each antenna  926  of each Tx/Rx module. Each Tx/Rx module restores the RF carrier signal to a baseband signal and provides it to the reception (RX) processor  923 . The RX processor implements various signal processing functions of the L1 (i.e., the physical layer). The RX processor may perform spatial processing on the information to recover any spatial stream directed to the second communication device. If multiple spatial streams are directed to the second communication device, they may be combined into a single OFDMA symbol stream by multiple RX processors. The RX processor transforms the OFDM symbol stream, which is a time domain signal, into a frequency domain signal using a fast Fourier transform (FFT). The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The modulation symbols and the reference signal on each subcarrier are recovered and demodulated by determining the most likely signal constellation points sent by the first communication device. These soft decisions may be based on channel estimate values. Soft decisions are decoded and deinterleaved to recover data and control signals originally transmitted by the first communication device on the physical channel. The corresponding data and control signals are provided to the processor  921 . 
     The UL (communication from the second communication device to the first communication device) is processed in the first communication device  910  in a manner similar to that described in connection with a receiver function in the second communication device  920 . Each Tx/Rx module  925  receives a signal via each antenna  926 . Each Tx/Rx module provides an RF carrier and information to RX processor  923 . The processor  921  may be related to the memory  924  that stores program code and data. The memory may be referred to as a computer-readable medium. 
     The 5G communication technology discussed above may be applied in combination with the methods proposed in the present disclosure to be described later with reference to  FIGS. 34 to 49 , or may be used as a supplement to embody or clarify the technical features of the methods proposed in the present disclosure. 
       FIG. 34  is a perspective view of an artificial intelligent electroencephalography headband according to an exemplary embodiment of the present invention.  FIG. 35  is a perspective view of an artificial intelligent electroencephalography headband according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 34 , an artificial intelligent electroencephalography headband  10  according to an exemplary embodiment of the present invention may include a main body  11 , electroencephalography electrodes  12 , a fixed bracket  13 , and a headset  14 . 
     The main body  11  is bent into a round shape so as to make contact with a learner&#39;s forehead. The electroencephalography electrodes  12  may be placed on a forehead contact surface of the main body  11 . The electroencephalography electrodes  12  also may be placed on a temple contact surface of the main body  11 , as well as on the forehead contact surface of the main body  1   1 . The electroencephalography electrodes  12  are for measuring a learner&#39;s brain waves (electroencephalography or EEG), and are included in a sensing part. Electroencephalography (EEG) refers to measuring signals generated in the brain by the electroencephalography electrodes  12 —that is, minute signals occurring at the surface of the brain as electrical signals produced by millions of neurons in the brain combine. Electroencephalography signals are changed spatially and temporally depending on the brain&#39;s activity, the state of the brain during measurement, and the brain&#39;s functions, and therefore the electroencephalography signals have characteristic frequency bands, time domain features, and spatial features associated with braining functioning. 
     The fixed bracket  13  is a component worn over the learner&#39;s ears, which serves to attach the artificial intelligent electroencephalography headband  10  to the head of the learner. Earpieces  13 A are connected to the ends of the fixed bracket  13 . The headset  14  serves to play to the learner audio learning content and relaxing sounds received through a communication part. 
     Referring to  FIG. 35 , an artificial intelligent electroencephalography headband  20  according to another exemplary embodiment of the present invention may include a main body  11 , electroencephalography electrodes  12 , a fixed bracket  13 , and a headset  14 . 
     The artificial intelligent electroencephalography headband  20  of  FIG. 35  is substantially identical to that  20  of  FIG. 34 , except that an elastic fixing band  15  is connected to both ends of the fixed bracket  13 . The elastic fixing band  15  serves to fix the artificial intelligent electroencephalography headband  20  securely to the head of the learner. 
       FIG. 36  shows an internal configuration of the artificial intelligent electroencephalography headbands of  FIGS. 34 and 35 .  FIG. 37  shows a detailed configuration of a first algorithm processing part of  FIG. 36 .  FIG. 38  shows frequency bands, brain wave patterns, and brain states depending on the type of brain waves.  FIG. 39  shows an example of EEG modeling including both left/right EEG information and eye movement signals.  FIG. 40  shows an example of changes in brain waves associated with eye movements. 
     Referring to  FIG. 36 , the artificial intelligent electroencephalography headband  20  may include a sensor part  101 , a controller  102 , a first algorithm processing part  103 , a second algorithm processing part  104 , a sound input part  105 , a sound output part  106 , and a communication part  107 . 
     The sensor part  101  includes electroencephalography electrodes, and measures the brain waves of a learner who is learning or resting. The brain waves are divided into frequency bands—delta, theta, alpha, SMR, beta, high beta, etc.  FIG. 38  depicts various physical states in different brain wave frequency bands. Delta ranges from0.5 to 4 Hz and is associated with deep sleep or brain disorders. Theta ranges from 4 to 7 Hz and is associated with drowsiness, distraction, or daydreaming. Alpha ranges from 8 to 12 Hz and is associated with relaxation, rest, or decreased attention. SMR ranges from 12 to 15 Hz and is associated with sustaining attention without moving. Beta ranges from 15 to 18 Hz and is associated with sustaining attention while moving. High beta is 18 Hz or above and is associated with intense states of stress such as nervousness, anxiousness, and feeling on edge. 
     The controller  102  may include the first algorithm processing part  103  and the second algorithm processing part  104 . The controller  102  may control the operations of the sensor part  101 , sound input part  105 , sound output part  106 , and communication part  107 . 
     The first algorithm processing part  103  creates learning guidance information by analyzing a learner&#39;s brain waves measured by the sensor part  101 . Conventional electroencephalogram analysis algorithms detect a learner&#39;s physical state based only on the frequency or voltage of his or her brain waves. That is, conventional electroencephalogram analysis algorithms analyze wave patterns in an EEG spectrum based only on the learner&#39;s left brain information and right brain information. By the way, the wave patterns in the EEG spectrum are affected by the learner&#39;s eye movement signals, as well as the learner&#39;s left brain information and right brain information included in the brain waves. The conventional electroencephalogram analysis algorithms had about 60% lower accuracy in EEG analysis because the learner&#39;s eye movements signals are removed as noise. 
     The first algorithm processing part  103  may improve the accuracy of EEG analysis by up to nearly 84% because it analyzes wave patterns in an EEG spectrum based on the learner&#39;s eye movement signals, as well as the learner&#39;s left brain information and right brain information included in the brain waves, as shown in  FIG. 39 . The learner&#39;s eye movement signals include the number and frequency of the learner&#39;s eye blinks as shown in  FIG. 40 . 
     The first algorithm processing part  103  may include an artificial intelligence processor (hereinafter, “AI processor”) equipped with a neural network model and analyze the learner&#39;s brain waves through AI processing. The first algorithm processing part  103  may detect the learner&#39;s physical state more accurately by feeding the learner&#39;s eye movement signals, as well as the learner&#39;s left brain information and right brain information included in the brain waves, into the neural network model and analyzing wave patterns in an EEG spectrum. 
     The first algorithm processing part  103  may further include a memory X 2 , along with the AI processor X 1 , and perform AI processing, as shown in  FIG. 37 . The AI processing may include all operations related to controlling the artificial intelligent electroencephalography headband  20 . The first algorithm processing part  103  is a computing device capable of training a neural network, and may be implemented as various electronic devices. 
     The AI processor X 1  may train a neural network by using a program stored in the memory X 2 . Particularly, the AI processor X 1  may train a neural network for recognizing EEG-related data. Here, the neural network for recognizing EEG-related data may be designed to emulate a human brain&#39;s structure on a computer, and may include a plurality of network nodes having weights that emulate neurons in a human neural network. The plurality of network nodes may send and receive data through connections so that they emulate the synaptic activity of neurons sending and receiving signals through synapses. Such a neural network may include a deep learning model, which has evolved from a neural network model. In the deep learning model, the plurality of network nodes are arranged in different layers, and may send and receive data through convolutions. Examples of the neural network model include various deep learning techniques such as deep neural networks (DNN), convolutional deep neural networks (CNN), recurrent neural networks (RNN), restricted Boltzmann machines (RBM), deep belief networks (DBN), and deep Q-networks, and are applicable to fields including computer vision, speech recognition, natural language processing, and speech/signal processing. 
     The memory X 2  may store various programs and data required for the control operation of the controller  102 . The memory X 2  may be implemented as non-volatile memory, volatile memory, flash memory, hard disk drive (HDD), or solid state drive (SSD). The memory X 2  is accessed by the AI processor X 1 , and the AI processor X 1  may read, write, modify, delete, or update data. Also, the memory X 2  may store a neural network model (e.g., deep learning model X 21 ) created by a learning algorithm for EEG data classification/recognition according to an exemplary embodiment of the present invention. 
     Meanwhile, the AI processor X 1  may further include a data learning part X 11  for training a neural network for EEG data classification/recognition. The data learning part X 11  may learn criteria about which learning data it will use to determine on EEG data classification/recognition and how data is classified and recognized using learning data. The data learning part X 11  may train a deep learning model by acquiring learning data to be used in learning and applying the acquired learning data to the deep learning model. 
     The data learning part X 11  may be manufactured in the form of at least one hardware chip and mounted on the AI processor X 1 . For example, the data learning part XII may be manufactured in the form of a hardware chip dedicated to artificial intelligence (AI), or may be manufactured as part of a general-purpose processor (CPU) or dedicated graphics processor (GPU) and mounted on the AI processor X 1 . Also, the data learning part X 11  may be implemented as a software module. If it is implemented as a software module (or a program module including instructions), the software module may be stored in a non-transitory computer readable medium. In this case, at least one software module may be provided by an OS (operating system) or by an application. 
     The data learning part X 11  may include a learning data acquisition part X 12  and a model training part X 13 . 
     The learning data acquisition part X 12  may acquire learning data required for a neural network model for classifying and recognizing EEG data. For example, the learning data acquisition part X 12  may acquire EEG data and/or sample data as learning data to feed into the neural network model. 
     By using the acquired learning data, the model training part X 13  may train the neural network model to have criteria for determining how to classify certain data. In this instance, the model training part X 13  may train the neural network model through supervised learning which uses at least part of the learning data as the criteria for determination. Alternatively, the model training part X 13  may train the neural network model through unsupervised learning which helps find criteria for determination by allowing the neural network model to learn on its own without supervision using the learning data. Also, the model training part X 13  may train the neural network model through reinforcement learning by using feedback about whether a right decision is made on a situation by learning. Also, the model training part X 13  may train the neural network model by using a learning algorithm including error back-propagation or gradient descent. 
     Once the neural network model is trained, the model training part X 13  may store the trained neural network model in memory. The model training part X 13  may store the trained neural network model in a memory of a learning server connected to the AI processor X 1  over a wired or wireless network. 
     The data learning part X 11  may further include a learning data preprocessing part (not shown) and a learning data selection part (not shown), in order to improve analysis results from a recognition model or save the resources or time needed to create the recognition model. 
     The learning data preprocessing part may preprocess acquired data so that the acquired data is used in learning to decide on a situation. For example, the learning data preprocessing part may process acquired learning data into a preset format to enable the model training part X 13  to use the acquired data in learning to recognize images. 
     Moreover, the learning data selection part may select data required for learning from among the learning data acquired by the learning data acquisition part X 12  or the learning data preprocessed by the preprocessing part. The selected learning data may be provided to the model learning part X 13 . 
     In addition, the data learning part X 11  may further include a model evaluation part (not shown) for improving analysis results from the neural network model. 
     The model evaluation part may feed evaluation data into the neural network model, and, if analysis results produced from the evaluation data do not satisfy a predetermined criterion, may get the model training part X 13  to train the neural network model again. In this case, the evaluation data may be data that is defined for evaluating the recognition model. In an example, if the number or proportion of evaluation data from which inaccurate analysis results are produced by analyzing the recognition model trained on the evaluation data exceeds a preset threshold, the model evaluation part may evaluate the analysis results as not satisfying the predetermined criterion. 
     The first algorithm processing part  103  may create learning guidance information while the learner is learning or resting, based on AI processing results, that is, EEG analysis results. The learning guidance information may include a message related to learning or rest. 
     The communication part  107  may transmit the learning guidance information created by the first algorithm processing part  103  to an external electronic device. The learning guidance information may include a message urging the learner to increase concentration, a message urging the learner to take a rest, a message urging the learner to go over what he or she learned, and a learning content recommendation message. The external electronic device may include a personal content providing medium, a user terminal of a user (parent, instructor, content provider, etc.) related to the learner, and so on. 
     Although the first algorithm processing part  103  shown in  FIG. 37  has been described as being functionally divided into the AI processor X 1  the memory X 2 , etc., the above-described components may be integrated into one module and called an Al module. 
     The sound input part  105  is connected to an external device (user terminal (smartphone or the like) or PC) through the communication part  107 , and picks up a sound source from the external device. The sound source may include audio learning content (such as online courses) and relaxing sounds (such as meditation music). The sound input part  105  may be a microphone. 
     The sound output part  106  outputs the sound source to the learner. The sound output part  106  may be a speaker. 
     The second algorithm processing part  104  may include a logic for performing active noise cancellation (hereinafter, “ANC”). The ANC is the concept of cancelling sounds out by each other. The second algorithm processing part  104  collects the waveform of a specific noise and then adds noise with an inverted waveform to the specific noise. As a result, low-density air overlaps in a segment in which the existing air has a high density. Likewise, high-density air overlaps in a segment in which the existing air has a low density. This way, the air density becomes uniform, and the specific noise is not heard. 
     The second algorithm processing part  104  collects ambient noise picked up by the sound input part  105 , and produces a sound wave with an inverted phase to the ambient noise by the sound output part  106  to cancel out the ambient noise. That is, the second algorithm processing part  104  may improve the audio quality of a sound source by removing the ambient noise by performing the ANC function. 
       FIG. 41  shows an example of a learning system using an artificial intelligent electroencephalography band.  FIG. 42  shows another example of a learning system using an artificial intelligent electroencephalography headband. 
     Referring to  FIGS. 41 and 42 , a learning system using an artificial intelligent electroencephalography headband according to an exemplary embodiment of the present invention may include an artificial intelligent electroencephalography headband  30  and a personal content providing medium  35  and  45 . The artificial intelligent electroencephalography headband  30  worn on the learner may be connected to the personal content providing medium  35  and  45  over a first communication network  37 . 
     The first communication network  37  may be implemented as a short-range communication network such as Bluetooth, RFID (radio frequency identification), IrDA (infrared Data Association), UWB (ultra wideband), Zigbee, and WiFi (wireless fidelity). 
     The personal content providing medium  35  and  45  may show learning guidance information received from the artificial intelligent electroencephalography headband  30  to the learner through a screen, or may let the learner hear the learning guidance information through audio. 
     The personal content providing medium  35  and  45  may be a home robot  35  or a first user terminal  45 . The first user terminal  45  may be, but not limited to, a handheld device such as a smartphone, a tablet PC, or a smartwatch. 
     The personal content providing medium  35  and  45  may include a display and an audio output to provide learning guidance information to the learner. The personal content providing medium  35  and  45  may provide to the learner a message urging the learner to increase concentration, like “Stay more focused!”, a message urging the learner to take a rest, like “Get some rest and then continue”, a message urging the learner to go over what he or she learned, like “Will you go over on the page 2?”, and a learning state message, like “You&#39;ve worked hard and achieved your goal today”. Moreover, the personal content providing medium  35  and  45  may provide to the learner a message recommending content that suits the learner&#39;s concentration level. 
     The personal content providing medium  35  and  45  may further include an indication part  35 A and  45 A that is capable of receiving information on the learner&#39;s concentration level corresponding to the learning guidance information from the artificial intelligent electroencephalography headband  30  and show the learner&#39;s concentration level visually and intuitively. The indication part  35 A and  45 A may be implemented as a light-emitting part capable of displaying the learner&#39;s concentration level in a distinct color. The learner may know their current concentration level intuitively from the color shown on the indication part  35 A and  45 A. 
       FIG. 43  shows yet another example of a learning system using an artificial intelligent electroencephalography band. 
     Referring to  FIG. 43 , a learning system using an artificial intelligent electroencephalography headband according to another exemplary embodiment of the present invention may include an artificial intelligent electroencephalography headband  30 , a personal content providing medium  35  and  45 , a learning server  50 , and a second user terminal  60 . 
     The artificial intelligent electroencephalography headband  30  and the personal content providing medium  35  and  45  are identical to those described with reference to  FIGS. 41 and 42 . 
     The learning server  50  is connected to the personal content providing medium  35  and  45  over a second communication network  47 , and is connected to a second user terminal of a learning content provider (or the learner&#39;s parent) over a third communication network  57 . 
     The second communication network  47  and the third communication network  57  may be implemented as a long-range communication network such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), SCFDMA (single carrier frequency division multiple access), and 5G. 
     The learning server  50  may be a cloud server. The learning server  50  may include a data collector  51 , a data analyzer  52 , and a data transmitter  53 . 
     The data collector  51  may collect learning guidance information from the personal content providing medium  35  and  45  over the second communication network  47 . 
     The data analyzer  52  may include an AI processor equipped with a neural network model and a memory, and may analyze the collected learning guidance information and output concentration-related information. The AI processor and memory of the data analyzer  52  may be configured similarly to those shown in  FIG. 37 . 
     The data transmitter  53  may transmit the concentration-related information to the personal content providing medium  35  and  45  over the second communication network  47 , or may transmit the concentration-related information to the second user terminal  60  over the third communication network  57 . 
     The second user terminal  60  may be, but not limited to, a handheld device such as a smartphone, a tablet PC, or a smartwatch. 
     The concentration-related information transmitted to the personal content providing medium  35  and  45  may include information on the average change in concentration among other learners, information on the positional distribution of records of how the learner&#39;s concentration has changed relative to the average, and information on decreased concentration spans. Each learner is able to see how their or other learners&#39; concentration has changed during an online class through the personal content providing medium  35  and  45 . Each learner is also able to go over what corresponds to a decreased concentration span. 
     The concentration-related information transmitted to the second user terminal  60  may include information on records of how the learner&#39;s concentration has changed and learning achievement information. The concentration-related information may be provided to the second user terminal  60  of the content provider and give the content provider guidance for delivering the most suitable learning content. Also, the concentration-related information may be provided to the second user terminal  60  of a parent of the learner and allow the parent to see how their child&#39;s concentration has changed. 
       FIG. 44  shows a further example of a learning system using an artificial intelligent electroencephalography band. 
     Referring to  FIG. 44 , a learning system using an artificial intelligent electroencephalography headband according to yet another exemplary embodiment of the present invention is for offline learning, and may include a plurality of artificial intelligent electroencephalography headbands  30 , a plurality of personal content providing media  35  and  45 , a learning server  50 , and a plurality of second user terminals  70 . 
     The artificial intelligent electroencephalography headbands  30  and the personal content providing media  35  and  45  come in multiples so as to correspond to a plurality of learners X 1  to Xn. The artificial intelligent electroencephalography headbands  30  and the personal content providing media  35  and  45  corresponding respectively to the learners X 1  to Xn are identical to those described with reference to  FIGS. 41 and 42 . 
     The learning server  50  may include a data collector  51 , a data analyzer  52 , and a data transmitter  53 . The data collector  51  collects learning guidance information from the personal content providing media  35  and  45 . 
     The data analyzer  52  may include an AI processor equipped with a neural network model and a memory, and may analyze the collected learning guidance information and output concentration-related information. The Al processor and memory of the data analyzer  52  may be configured similarly to those shown in  FIG. 37 . 
     The data transmitter  53  may transmit the concentration-related information to the plurality of second user terminals  70  over a third communication network  57 . The concentration-related information transmitted to the second user terminals  70  may include information on the average change in concentration among other learners, information on the positional distribution of records of how the learner&#39;s concentration has changed relative to the average, information on decreased concentration spans, information on records of how the learner&#39;s concentration has changed, and learning achievement information. 
     The concentration-related information may be provided to the second user terminal  70  of an instructor and give the instructor guidance on changing the lecture&#39;s content or the duration of the lecture depending on the learners&#39; levels of concentration during the class. Also, the concentration-related information may be provided to the second user terminals  70  of parents Y 1  to Ym of the learners and allow the parents to see how their children&#39;s concentration has changed. 
       FIGS. 45 to 47  show a learning method using an artificial intelligent electroencephalography band according to an exemplary embodiment of the present invention when taking an online course. 
     Referring to  FIG. 45 , in the present invention, a learner&#39;s brain waves are measured and analyzed during online learning (S 451  and S 452 ). 
     In the present invention, the learner&#39;s concentration level during learning is derived based on results of analysis of the learner&#39;s brain waves, and, i f the concentration level is lower than a preset, first reference value, the learner may be urged to increase concentration through a personal content providing medium (S 453  and S 454 ). 
     In the present invention, if the concentration level is lower than a preset, second reference value (lower than the first reference value), the learner may be urged to take a rest through the personal content providing medium (S 455  and S 456 ). 
     In the present invention, the learner&#39;s brain waves are measured and analyzed during rest (S 457 ), and it is determined whether the learner has taken a good rest based on results of analysis of the learner&#39;s brain waves (S 458 ). In the present invention, if it is determined that the learner hasn&#39;t had a good rest, the learner may be urged again to take a rest through the personal content providing medium. 
     In the present invention, if the learner&#39;s concentration level during learning is equal to or higher than the first reference value, the learner may be informed through the personal content providing medium that he or she is maintaining good concentration (S 459 ). 
     Referring to  FIG. 46 , in the present invention, upon completion of learning, the learner may be presented with how their concentration has changed during the online class, through the personal content providing medium  35  and  45  (S 461  and S 462 ). In this instance, in the present invention, each learner is presented with the average change in concentration among other learners taking the same course. This enables each learner to compare how their concentration has changed relative to the average. In the present invention, the change in each learner&#39;s concentration may be presented in comparison to a graph of the concentration of high-achieving learners. 
     In the present invention, upon completion of learning, a parent may be presented with how the child&#39;s concentration has changed during the online class, through a second user terminal (S 461  and S 462 ). 
     In the present invention, each learner&#39;s decreased concentration span during the online class may be detected, and each learner may be urged through the personal content providing medium to go over what corresponds to the decreased concentration span (S 463  and S 464 ). 
     Referring to  FIG. 47 , in the present invention, upon completion of learning, the content provider may be presented with records of how the learners&#39; concentration has changed during the online class and the learner&#39;s learning achievements, through a second user terminal (S 471  and S 472 ). In the present invention, the content provider may be given guidance for delivering the most suitable learning content (S 473 ). 
       FIGS. 48 and 49  show a learning method using an artificial intelligent electroencephalography band according to an exemplary embodiment of the present invention when taking an offline course. 
     Referring to  FIG. 48 , in the present invention, each learner&#39;s brain waves are measured and analyzed during offline learning (S 481  and S 482 ). 
     In the present invention, each learner&#39;s concentration during learning is derived based on results of analysis of the learner&#39;s brain waves, and information on each learner&#39;s concentration may be provided to the instructor to give guidance for delivering the most suitable lecture content (S 483  and S 484 ). 
     Referring to  FIG. 49 , in the present invention, upon completion of offline learning, the changes in the learners&#39; concentration during learning may be analyzed, and then the instructor may be given guidance for delivering the most suitable class content through a second user terminal (S 491 ,  5492 , and S 493 ). 
     Moreover, in the present invention, upon completion of offline learning, the changes in the learners&#39; concentration during learning may be analyzed, and then their parents may be provided with their child&#39;s learning achievements and information on the change in concentration (S 491 , S 492 , and S 494 ). 
     As explained above, the present invention may provide an artificial intelligent electroencephalography headband capable of accurately measuring a learner&#39;s brain waves. 
     Furthermore, the present invention may analyze a learner&#39;s concentration patterns on the basis of an artificial intelligent electroencephalography headband and give guidance on a learning method that fits these patterns. 
     Accordingly, the foregoing detailed description should not be interpreted as restrictive in all aspects, and should be considered as illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.