Patent Publication Number: US-2021192769-A1

Title: Methods and devices for providing content

Description:
This application claims the benefit of Korean Patent Application No. 10-2019-0171023, filed on Dec. 19, 2019, which is hereby incorporated by reference as if fully set forth herein. 
     TECHNICAL FIELD 
     This relates generally to an extended reality (XR) device for providing augmented reality (AR) mode and virtual reality (VR) mode and a method of controlling the same. More particularly, the present disclosure is applicable to all of the technical fields of 5th generation (5G) communication, robots, self-driving, and artificial intelligence (AI). 
     BACKGROUND 
     VR (Virtual Reality) technology creates a simulated environment by providing CG (Computer Graphic) image/video data that can be similar to or different from the real world. AR (Augmented Reality) technology provides CG image/video data generated by overlaying content on the real world. MR (Mixed Reality) technology (referred to as hybrid reality) is the merging of real and virtual worlds to provide new environments where physical and virtual objects co-exist and interact in real time. XR (Extended reality) technology refers to all real and virtual environments and can cover all the various forms of computer-altered reality, including: VR, AR, and MR. The development of XR devices providing XR content (hereinafter referred to as “XR content or content”) has increased significantly in recent years. The XR device for providing XR content (hereinafter referred to as “XR device or device”) may provide XR content that is generated by combining a real image representing real environment (e.g., real space, space, etc.) and image representing one or more virtual objects that are located in the space based on scanning operation. The user may check whether the virtual object may be placed in the space after the scanning operation is performed. The scanning operation generally takes a long time of about 10 minutes, and accordingly the user may recognize the possibility of locating the virtual object or executability of an application for providing content representing a space where a virtual object is located after waiting for a long time. Such a configuration may increase user inconvenience and provide only a low-quality user experience. 
     SUMMARY 
     Accordingly, there is a need for XR devices with improved methods for providing XR content for user-friendly XR content and enhanced user experience. Therefore, in some embodiments, the device may use one or more algorithms to quickly identify a space in which one or more real objects are located to determine whether one or more virtual objects can be correctly located. In addition, in some embodiments, the device may preferentially provide the user with information about whether an application for providing the content representing the space in which the one or more virtual objects are located is executable. Such methods and XR devices provide more realistic user experience. Such methods and XR devices provide more user-friendly XR content and various user experiences. 
     The above deficiencies and other problems associated with the device for providing the content are reduced or eliminated by the disclosed device and methods. In accordance with some embodiments, a method includes obtaining a real image, obtaining space information of space represented by the obtained real image, and determining whether an application is executed for providing content that represents the space in which one or more virtual objects are located and displaying information representing whether the application is executable based on the determination. 
     In accordance with some embodiments, a device includes an image/video receiver configured to obtain a real image, an image/video processor configured to obtain space information of space represented by the obtained real image, and determine whether an application is executed for providing content that represents the space in which one or more virtual objects are located and a display configured to display information representing whether the application is executable based on the determination. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the various described embodiments, reference should be made to the Description of Embodiments below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures. 
         FIG. 1  is a diagram illustrating an exemplary resource grid to which physical signals/channels are mapped in a 3rd generation partnership project (3GPP) system; 
         FIG. 2  is a diagram illustrating an exemplary method of transmitting and receiving 3GPP signals; 
         FIG. 3  is a diagram illustrating an exemplary structure of a synchronization signal block (SSB); 
         FIG. 4  is a diagram illustrating an exemplary random access procedure; 
         FIG. 5  is a diagram illustrating exemplary uplink (UL) transmission based on a UL grant; 
         FIG. 6  is a conceptual diagram illustrating exemplary physical channel processing; 
         FIG. 7  is a block diagram illustrating an exemplary transmitter and receiver for hybrid beamforming; 
         FIG. 8( a )  is a diagram illustrating an exemplary narrowband operation, and  FIG. 8( b )  is a diagram illustrating exemplary machine type communication (MTC) channel repetition with radio frequency (RF) retuning; 
         FIG. 9  is a block diagram illustrating an exemplary wireless communication system to which proposed methods according to the present disclosure are applicable; 
         FIG. 10  is a block diagram illustrating an artificial intelligence (AI) device  100  in accordance with some embodiments; 
         FIG. 11  is a block diagram illustrating an AI server  200  in accordance with some embodiments; 
         FIG. 12  is a diagram illustrating an AI system  1  in accordance with some embodiments; 
         FIG. 13  is a block diagram illustrating an extended reality (XR) device according to embodiments of the present disclosure; 
         FIG. 14  is a detailed block diagram illustrating a memory illustrated in  FIG. 13 ; 
         FIG. 15  is a block diagram illustrating a point cloud data processing system; 
         FIG. 16  is a block diagram illustrating a device including a learning processor; 
         FIG. 17  is a flowchart illustrating a process of providing an XR service by an XR device  1600  of the present disclosure, illustrated in  FIG. 16 ; 
         FIG. 18  is a diagram illustrating the outer appearances of an XR device and a robot; 
         FIG. 19  is a flowchart illustrating a process of controlling a robot by using an XR device; 
         FIG. 20  is a diagram illustrating a vehicle that provides a self-driving service; 
         FIG. 21  is a flowchart illustrating a process of providing an augmented reality/virtual reality (AR/VR) service during a self-driving service in progress; 
         FIG. 22  is a conceptual diagram illustrating an exemplary method for implementing an XR device using an HMD type in accordance with some embodiments; 
         FIG. 23  is a conceptual diagram illustrating an exemplary method for implementing an XR device using AR glasses in accordance with some embodiments; 
         FIG. 24  illustrates an example of a user using an application that provides XR content in accordance with some embodiments; 
         FIG. 25  is a block diagram illustrating a device in accordance with some embodiments; 
         FIG. 26  illustrates an example of a space recognition method in accordance with some embodiments; 
         FIG. 27  illustrates an example of a 3D map generated through a SLAM algorithm in accordance with some embodiments; 
         FIG. 28  illustrates an example of a space recognition method in accordance with some embodiments; 
         FIG. 29  illustrates an example of a real image to which a semantic segmentation algorithm is applied by a device in accordance with some embodiments; 
         FIG. 30  illustrates an example of information in accordance with some embodiments representing whether an application is executable; 
         FIG. 31  illustrates an example of information in accordance with some embodiments representing whether an application is executable; 
         FIG. 32  illustrates an example of information in accordance with some embodiments representing whether an application is executable; 
         FIG. 33  illustrates an example in which a device in accordance with some embodiments displays information to control the operation of a remote robot; 
         FIG. 34  illustrates operation of a device in accordance with some embodiments; and 
         FIG. 35  illustrates a flow diagram showing a method for providing content in accordance with some embodiments. 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts, and a redundant description will be avoided. The terms “module” and “unit” are interchangeably used only for easiness of description and thus they should not be considered as having distinctive meanings or roles. Further, a detailed description of well-known technology will not be given in describing embodiments of the present disclosure lest it should obscure the subject matter of the embodiments. The attached drawings are provided to help the understanding of the embodiments of the present disclosure, not limiting the scope of the present disclosure. It is to be understood that the present disclosure covers various modifications, equivalents, and/or alternatives falling within the scope and spirit of the present disclosure. 
     The following embodiments of the present disclosure are intended to embody the present disclosure, not limiting the scope of the present disclosure. What could easily be derived from the detailed description of the present disclosure and the embodiments by a person skilled in the art is interpreted as falling within the scope of the present disclosure. 
     The above embodiments are therefore to be construed in all aspects as illustrative and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. 
     INTRODUCTION 
     In the disclosure, downlink (DL) refers to communication from a base station (BS) to a user equipment (UE), and uplink (UL) refers to communication from the UE to the BS. On DL, a transmitter may be a part of the BS and a receiver may be a part of the UE, whereas on UL, a transmitter may be a part of the UE and a receiver may be a part of the BS. A UE may be referred to as a first communication device, and a BS may be referred to as a second communication device in the present disclosure. The term BS may be replaced with fixed station, Node B, evolved Node B (eNB), next generation Node B (gNB), base transceiver system (BTS), access point (AP), network or 5th generation (5G) network node, artificial intelligence (AI) system, road side unit (RSU), robot, augmented reality/virtual reality (AR/VR) system, and so on. The term UE may be replaced with terminal, mobile station (MS), user terminal (UT), mobile subscriber station (MSS), subscriber station (SS), advanced mobile station (AMS), wireless terminal (WT), device-to-device (D2D) device, vehicle, robot, AI device (or module), AR/VR device (or module), and so on. 
     The following technology may be used in various wireless access systems including code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier FDMA (SC-FDMA). 
     For the convenience of description, the present disclosure is described in the context of a 3 rd  generation partnership project (3GPP) communication system (e.g., long term evolution-advanced (LTE-A) and new radio or new radio access technology (NR)), which should not be construed as limiting the present disclosure. For reference, 3GPP LTE is part of evolved universal mobile telecommunications system (E-UMTS) using evolved UMTS terrestrial radio access (E-UTRA), and LTE-A/LTE-A pro is an evolution of 3GPP LTE. 3GPP NR is an evolution of 3GPP/LTE-A/LTE-A pro. 
     In the present disclosure, a node refers to a fixed point capable of transmitting/receiving wireless signals by communicating with a UE. Various types of BSs may be used as nodes irrespective of their names. For example, any of a BS, an NB, an eNB, a pico-cell eNB (PeNB), a home eNB (HeNB), a relay, and a repeater may be a node. At least one antenna is installed in one node. The antenna may refer to a physical antenna, an antenna port, a virtual antenna, or an antenna group. A node is also referred to as a point. 
     In the present disclosure, a cell may refer to a certain geographical area or radio resources, in which one or more nodes provide a communication service. A “cell” as a geographical area may be understood as coverage in which a service may be provided in a carrier, while a “cell” as radio resources is associated with the size of a frequency configured in the carrier, that is, a bandwidth (BW). Because a range in which a node may transmit a valid signal, that is, DL coverage and a range in which the node may receive a valid signal from a UE, that is, UL coverage depend on a carrier carrying the signals, and thus the coverage of the node is associated with the “cell” coverage of radio resources used by the node. Accordingly, the term “cell” may mean the service overage of a node, radio resources, or a range in which a signal reaches with a valid strength in the radio resources, under circumstances. 
     In the present disclosure, communication with a specific cell may amount to communication with a BS or node that provides a communication service to the specific cell. Further, a DL/UL signal of a specific cell means a DL/UL signal from/to a BS or node that provides a communication service to the specific cell. Particularly, a cell that provides a UL/DL communication service to a UE is called a serving cell for the UE. Further, the channel state/quality of a specific cell refers to the channel state/quality of a channel or a communication link established between a UE and a BS or node that provides a communication service to the specific cell. 
     A “cell” associated with radio resources 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 with DL resources alone or both DL resources and UL resources in combination. When carrier aggregation (CA) is supported, linkage between the carrier frequency of DL resources (or a DL CC) and the carrier frequency of UL resources (or a UL CC) may be indicated by system information transmitted in a corresponding cell. A carrier frequency may be identical to or different from the center frequency of each cell or CC. Hereinbelow, a cell operating in a primary frequency is referred to as a primary cell (Pcell) or PCC, and a cell operating in a secondary frequency is referred to as a secondary cell (Scell) or SCC. The Scell may be configured after a UE and a BS perform a radio resource control (RRC) connection establishment procedure and thus an RRC connection is established between the UE and the BS, that is, the UE is RRC_CONNECTED. The RRC connection may mean a path in which the RRC of the UE may exchange RRC messages with the RRC of the BS. The S cell may be configured to provide additional radio resources to the UE. The Scell and the Pcell may form a set of serving cells for the UE according to the capabilities of the UE. Only one serving cell configured with a Pcell exists for an RRC_CONNECTED UE which is not configured with CA or does not support CA. 
     A cell supports a unique radio access technology (RAT). For example, LTE RAT-based transmission/reception is performed in an LTE cell, and 5G RAT-based transmission/reception is performed in a 5G cell. 
     CA aggregates a plurality of carriers each having a smaller system BW than a target BW to support broadband. CA differs from OFDMA in that DL or UL communication is conducted in a plurality of carrier frequencies each forming a system BW (or channel BW) in the former, and DL or UL communication is conducted by loading a basic frequency band divided into a plurality of orthogonal subcarriers in one carrier frequency in the latter. In OFDMA or orthogonal frequency division multiplexing (OFDM), for example, one frequency band having a certain system BW is divided into a plurality of subcarriers with a predetermined subcarrier spacing, information/data is mapped to the plurality of subcarriers, and the frequency band in which the information/data has been mapped is transmitted in a carrier frequency of the frequency band through frequency upconversion. In wireless CA, frequency bands each having a system BW and a carrier frequency may be used simultaneously for communication, and each frequency band used in CA may be divided into a plurality of subcarriers with a predetermined subcarrier spacing. 
     The 3GPP communication standards define DL physical channels corresponding to resource elements (REs) conveying information originated from upper layers of the physical layer (e.g., the medium access control (MAC) layer, the radio link control (RLC) layer, the packet data convergence protocol (PDCP) layer, the radio resource control (RRC) layer, the service data adaptation protocol (SDAP) layer, and the non-access stratum (NAS) layer), and DL physical signals corresponding to REs which are used in the physical layer but do not deliver information originated from the upper layers. For example, physical downlink shared channel (PDSCH), physical broadcast channel (PBCH), physical multicast channel (PMCH), physical control format indicator channel (PCFICH), and physical downlink control channel (PDCCH) are defined as DL physical channels, and a reference signal (RS) and a synchronization signal are defined as DL physical signals. An RS, also called a pilot is a signal in a predefined special waveform known to both a BS and a UE. For example, cell specific RS (CRS), UE-specific RS (UE-RS), positioning RS (PRS), channel state information RS (CSI-RS), and demodulation RS (DMRS) are defined as DL RSs. The 3GPP communication standards also define UL physical channels corresponding to REs conveying information originated from upper layers, and UL physical signals corresponding to REs which are used in the physical layer but do not carry information originated from the upper layers. For example, physical uplink shared channel (PUSCH), physical uplink control channel (PUCCH), and physical random access channel (PRACH) are defined as UL physical channels, and DMRS for a UL control/data signal and sounding reference signal (SRS) used for UL channel measurement are defined. 
     In the present disclosure, physical shared channels (e.g., PUSCH and PDSCH) are used to deliver information originated from the upper layers of the physical layer (e.g., the MAC layer, the RLC layer, the PDCP layer, the RRC layer, the SDAP layer, and the NAS layer). 
     In the present disclosure, an RS is a signal in a predefined special waveform known to both a BS and a UE. In a 3GPP communication system, for example, the CRS being a cell common RS, the UE-RS for demodulation of a physical channel of a specific UE, the CSI-RS used to measure/estimate a DL channel state, and the DMRS used to demodulate a physical channel are defined as DL RSs, and the DMRS used for demodulation of a UL control/data signal and the SRS used for UL channel state measurement/estimation are defined as UL RSs. 
     In the present disclosure, a transport block (TB) is payload for the physical layer. For example, data provided to the physical layer by an upper layer or the MAC layer is basically referred to as a TB. A UE which is a device including an AR/VR module (i.e., an AR/VR device) may transmit a TB including AR/VR data to a wireless communication network (e.g., a 5G network) on a PUSCH. Further, the UE may receive a TB including AR/VR data of the 5G network or a TB including a response to AR/VR data transmitted by the UE from the wireless communication network. 
     In the present disclosure, hybrid automatic repeat and request (HARQ) is a kind of error control technique. An HARQ acknowledgement (HARQ-ACK) transmitted on DL is used for error control of UL data, and a HARQ-ACK transmitted on UL is used for error control of DL data. A transmitter performing an HARQ operation awaits reception of an ACK after transmitting data (e.g., a TB or a codeword). A receiver performing an HARQ operation transmits an ACK only when data has been successfully received, and a negative ACK (NACK) when the received data has an error. Upon receipt of the ACK, the transmitter may transmit (new) data, and upon receipt of the NACK, the transmitter may retransmit the data. 
     In the present disclosure, CSI generically refers to information representing the quality of a radio channel (or link) established 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), a synchronization signal block resource indicator (SSBRI), a layer indicator (LI), a rank indicator (RI), or a reference signal received power (RSRP). 
     In the present disclosure, frequency division multiplexing (FDM) is transmission/reception of signals/channels/users in different frequency resources, and time division multiplexing (TDM) is transmission/reception of signals/channels/users in different time resources. 
     In the present disclosure, frequency division duplex (FDD) is a communication scheme in which UL communication is performed in a UL carrier, and DL communication is performed in a DL carrier linked to the UL carrier, whereas time division duplex (TDD) is a communication scheme in which UL communication and DL communication are performed in time division in the same carrier. In the present disclosure, half-duplex is a scheme in which a communication device operates on UL or UL only in one frequency at one time point, and on DL or UL in another frequency at another time point. For example, when the communication device operates in half-duplex, the communication device communicates in UL and DL frequencies, wherein the communication device performs a UL transmission in the UL frequency for a predetermined time, and retunes to the DL frequency and performs a DL reception in the DL frequency for another predetermined time, in time division, without simultaneously using the UL and DL frequencies. 
       FIG. 1  is a diagram illustrating an exemplary resource grid to which physical signals/channels are mapped in a 3GPP system. 
     Referring to  FIG. 1 , for each subcarrier spacing configuration and carrier, a resource grid of N size,μ   grid *N RB   sc  subcarriers by 14·2 μ  OFDM symbols is defined. Herein, N size,μ   grid  is indicated by RRC signaling from a BS, and μ represents a subcarrier spacing Δf given by Δf=2μ*15 [kHz] where μϵ{0, 1, 2, 3, 4} in a 5G system. 
     may be different between UL and DL as well as a subcarrier spacing configuration μ. For the subcarrier spacing configuration an antenna port p, and a transmission direction (UL or DL), there is one resource grid. Each element of a resource grid for the subcarrier spacing configuration μ and the antenna port p is referred to as an RE, uniquely identified by an index pair (k,l) where k is a frequency-domain index and l is the position of a symbol in a relative time domain with respect to a reference point. A frequency unit used for mapping physical channels to REs, resource block (RB) is defined by 12 consecutive subcarriers (N RB   sc :=12) in the frequency domain. Considering that a UE may not support a wide BW supported by the 5G system at one time, the UE may be configured to operate in a part (referred to as a bandwidth part (BWP)) of the frequency BW of a cell. 
     For the background technology, terminology, and abbreviations used in the present disclosure, standard specifications published before the present disclosure may be referred to. For example, the following documents may be referred to. 
     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 (e.g. 5G)
         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 (5GCN) via non-3GPP access networks   3GPP TS 24.526: User Equipment (UE) policies for 5G System (5GS); Stage 3       

       FIG. 2  is a diagram illustrating an exemplary method of transmitting/receiving 3GPP signals. 
     Referring to  FIG. 2 , when a UE is powered on or enters a new cell, the UE performs an initial cell search involving acquisition of synchronization with a BS (S 201 ). For the initial cell search, the UE receives a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH), acquires synchronization with the BS, and obtains information such as a cell identifier (ID) from the P-SCH and the S-SCH. In the LTE system and the NR system, the P-SCH and the S-SCH are referred to as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), respectively. The initial cell search procedure will be described below in greater detail. 
     After the initial cell search, the UE may receive a PBCH from the BS and acquire broadcast information within a cell from the PBCH. During the initial cell search, the UE may check a DL channel state by receiving a DL RS. 
     Upon completion of the initial cell search, the UE may acquire more specific system information by receiving a PDCCH and receiving a PDSCH according to information carried on the PDCCH (S 202 ). 
     When the UE initially accesses the BS or has no radio resources for signal transmission, the UE may perform a random access procedure with the BS (S 203  to S 206 ). For this purpose, the UE may transmit a predetermined sequence as a preamble on a PRACH (S 203  and S 205 ) and receive a PDCCH, and a random access response (RAR) message in response to the preamble on a PDSCH corresponding to the PDCCH (S 204  and S 206 ). If the random access procedure is contention-based, the UE may additionally perform a contention resolution procedure. The random access procedure will be described below in greater detail. 
     After the above procedure, the UE may then perform PDCCH/PDSCH reception (S 207 ) and PUSCH/PUCCH transmission (S 208 ) in a general UL/DL signal transmission procedure. Particularly, the UE receives DCI on a PDCCH. 
     The UE monitors a set of PDCCH candidates in monitoring occasions configured for one or more control element sets (CORESETs) in a serving cell according to a corresponding search space configuration. The set of PDCCH candidates to be monitored by the UE is defined from the perspective of search space sets. A search space set may be a common search space set or a UE-specific search space set. A CORESET includes a set of (physical) RBs that last for a time duration of one to three OFDM symbols. The network may configure a plurality of CORESETs for the UE. The UE monitors PDCCH candidates in one or more search space sets. Herein, monitoring is attempting to decode PDCCH candidate(s) in a search space. When the UE succeeds in decoding one of the PDCCH candidates in the search space, the UE determines that a PDCCH has been detected from among the PDCCH candidates and performs PDSCH reception or PUSCH transmission based on DCI included in the detected PDCCH. 
     The PDCCH may be used to schedule DL transmissions on a PDSCH and UL transmissions on a PUSCH. DCI in the PDCCH includes a DL assignment (i.e., a DL grant) including at least a modulation and coding format and resource allocation information for a DL shared channel, and a UL grant including a modulation and coding format and resource allocation information for a UL shared channel. 
     Initial Access (IA) Procedure 
     Synchronization Signal Block (SSB) Transmission and Related Operation 
       FIG. 3  is a diagram illustrating an exemplary SSB structure. The UE may perform cell search, system information acquisition, beam alignment for initial access, DL measurement, and so on, based on an SSB. The term SSB is interchangeably used with synchronization signal/physical broadcast channel (SS/PBCH). 
     Referring to  FIG. 3 , an SSB includes a PSS, an SSS, and a PBCH. The SSB includes four consecutive OFDM symbols, and the PSS, the PBCH, the SSS/PBCH, or the PBCH is transmitted in each of the OFDM symbols. The PBCH is encoded/decoded based on a polar code and modulated/demodulated in quadrature phase shift keying (QPSK). The PBCH in an OFDM symbol includes data REs to which a complex modulated value of the PBCH is mapped and DMRS REs to which a DMRS for the PBCH is mapped. There are three DMRS REs per RB in an OFDM symbol and three data REs between every two of the DMRS REs. 
     Cell Search 
     Cell search is a process of acquiring the time/frequency synchronization of a cell and detecting the cell ID (e.g., physical cell ID (PCI)) of the cell by a UE. The PSS is used to detect a cell ID in a cell ID group, and the SSS is used to detect the cell ID group. The PBCH is used for SSB (time) index detection and half-frame detection. 
     In the 5G system, there are 336 cell ID groups each including 3 cell IDs. Therefore, a total of 1008 cell IDs are available. Information about a cell ID group to which the cell ID of a cell belongs is provided/acquired by/from the SSS of the cell, and information about the cell ID among 336 cells within the cell ID is provided/acquired by/from the PSS. 
     The SSB is periodically transmitted with an SSB periodicity. The UE assumes a default SSB periodicity of 20 ms during initial cell search. After cell access, the SSB periodicity may be set to one of {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms} by the network (e.g., a BS). An SSB burst set is configured at the start of an SSB period. The SSB burst set is composed of a 5-ms time window (i.e., half-frame), and the SSB may be transmitted up to L times within the SSB burst set. The maximum number L of SSB transmissions may be given as follows according to the frequency band of a carrier.
         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       

     The possible time positions of SSBs in a half-frame are determined by a subcarrier spacing, and the periodicity of half-frames carrying SSBs is configured by the network. The time positions of SSB candidates are indexed as 0 to L−1 (SSB indexes) in a time order in an SSB burst set (i.e., half-frame). Other SSBs may be transmitted in different spatial directions (by different beams spanning the coverage area of the cell) during the duration of a half-frame. Accordingly, an SSB index (SSBI) may be associated with a BS transmission (Tx) beam in the 5G system. 
     The UE may acquire DL synchronization by detecting an SSB. The UE may identify the structure of an SSB burst set based on a detected (time) SSBI and hence a symbol/slot/half-frame boundary. The number of a frame/half-frame to which the detected SSB belongs may be identified by using system frame number (SFN) information and half-frame indication information. 
     Specifically, the UE may acquire the 10-bit SFN of a frame carrying the PBCH from the PBCH. Subsequently, the UE may acquire 1-bit half-frame indication information. For example, when the UE detects a PBCH with a half-frame indication bit set to 0, the UE may determine that an SSB to which the PBCH belongs is in the first half-frame of the frame. When the UE detects a PBCH with a half-frame indication bit set to 1, the UE may determine that an SSB to which the PBCH belongs is in the second half-frame of the frame. Finally, the UE may acquire the SSBI of the SSB to which the PBCH belongs based on a DMRS sequence and PBCH payload delivered on the PBCH. 
     System Information (SI) Acquisition 
     SI is divided into a master information block (MIB) and a plurality of system information blocks (SIBs). The SI except for the MIB may be referred to as remaining minimum system information (RMSI). For details, the following may be referred to.
         The MIB includes information/parameters for monitoring a PDCCH that schedules a PDSCH carrying systemInformationBlock1 (SIB1), and transmitted on a PBCH of an SSB by a BS. For example, a UE may determine from the MIB whether there is any CORESET for a Type0-PDCCH common search space. The Type0-PDCCH common search space is a kind of PDCCH search space and used to transmit a PDCCH that schedules an SI message. In the presence of a Type0-PDCCH common search space, the UE may determine (1) a plurality of contiguous RBs and one or more consecutive symbols included in a CORESET, and (ii) a PDCCH occasion (e.g., a time-domain position at which a PDCCH is to be received), based on information (e.g., pdcch-ConfigSIB1) included in the MIB.   SIB1 includes information related to availability and scheduling (e.g., a transmission period and an SI-window size) of the remaining SIBs (hereinafter, referred to SIBx where x is an integer equal to or larger than 2). For example, SIB1 may indicate whether SIBx is broadcast periodically or in an on-demand manner upon user request. If SIBx is provided in the on-demand manner, SIB1 may include information required for the UE to transmit an SI request. A PDCCH that schedules SIB1 is transmitted in the Type0-PDCCH common search space, and SIB1 is transmitted on a PDSCH indicated by the PDCCH.   SIBx is included in an SI message and transmitted on a PDSCH. Each SI message is transmitted within a periodic time window (i.e., SI-window).       

     Random Access Procedure 
     The random access procedure serves various purposes. For example, the random access procedure may be used for network initial access, handover, and UE-triggered UL data transmission. The UE may acquire UL synchronization and UL transmission resources in the random access procedure. The random access procedure may be contention-based or contention-free. 
       FIG. 4  is a diagram illustrating an exemplary random access procedure. Particularly,  FIG. 4  illustrates a contention-based random access procedure. 
     First, a UE may transmit a random access preamble as a first message (Msg1) of the random access procedure on a PRACH. In the present disclosure, a random access procedure and a random access preamble are also referred to as a RACH procedure and a RACH preamble, respectively. 
     A plurality of preamble formats are defined by one or more RACH OFDM symbols and different cyclic prefixes (CPs) (and/or guard times). A RACH configuration for a cell is included in system information of the cell and provided to the UE. The RACH configuration includes information about a subcarrier spacing, available preambles, a preamble format, and so on for a PRACH. The RACH configuration includes association information between SSBs and RACH (time-frequency) resources, that is, association information between SSBIs and RACH (time-frequency) resources. The SSBIs are associated with Tx beams of a BS, respectively. The UE transmits a RACH preamble in RACH time-frequency resources associated with a detected or selected SSB. The BS may identify a preferred BS Tx beam of the UE based on time-frequency resources in which the RACH preamble has been detected. 
     An SSB threshold for RACH resource association may be configured by the network, and a RACH preamble transmission (i.e., PRACH transmission) or retransmission is performed based on an SSB in which an RSRP satisfying the threshold has been measured. For example, the UE may select one of SSB(s) satisfying the threshold and transmit or retransmit the RACH preamble in RACH resources associated with the selected SSB. 
     Upon receipt of the RACH preamble from the UE, the BS transmits an RAR message (a second message (Msg2)) to the UE. A PDCCH that schedules a PDSCH carrying the RAR message is cyclic redundancy check (CRC)-masked by an RA radio network temporary identifier (RNTI) (RA-RNTI) and transmitted. When the UE detects the PDCCH masked by the RA-RNTI, the UE may receive the RAR message on the PDSCH scheduled by DCI delivered on the PDCCH. The UE determines whether RAR information for the transmitted preamble, that is, Msg1 is included in the RAR message. The UE may determine whether random access information for the transmitted Msg1 is included by checking the presence or absence of the RACH preamble ID of the transmitted preamble. If the UE fails to receive a response to Msg1, the UE may transmit the RACH preamble a predetermined number of or fewer times, while performing power ramping. The UE calculates the PRACH transmission power of a preamble retransmission based on the latest pathloss and a power ramping counter. 
     Upon receipt of the RAR information for the UE on the PDSCH, the UE may acquire timing advance information for UL synchronization, an initial UL grant, and a UE temporary cell RNTI (C-RNTI). The timing advance information is used to control a UL signal transmission timing. To enable better alignment between PUSCH/PUCCH transmission of the UE and a subframe timing at a network end, the network (e.g., BS) may measure the time difference between PUSCH/PUCCH/SRS reception and a subframe and transmit the timing advance information based on the measured time difference. The UE may perform a UL transmission as a third message (Msg3) of the RACH procedure on a PUSCH. Msg3 may include an RRC connection request and a UE ID. The network may transmit a fourth message (Msg4) in response to Msg3, and Msg4 may be treated as a contention solution message on DL. As the UE receives Msg4, the UE may enter an RRC_CONNECTED state. 
     The contention-free RACH procedure may be used for handover of the UE to another cell or BS or performed when requested by a BS command. The contention-free RACH procedure is basically similar to the contention-based RACH procedure. However, compared to the contention-based RACH procedure in which a preamble to be used is randomly selected among a plurality of RACH preambles, a preamble to be used by the UE (referred to as a dedicated RACH preamble) is allocated to the UE by the BS in the contention-free RACH procedure. Information about the dedicated RACH preamble may be included in an RRC message (e.g., a handover command) or provided to the UE by a PDCCH order. When the RACH procedure starts, the UE transmits the dedicated RACH preamble to the BS. When the UE receives the RACH procedure from the BS, the RACH procedure is completed. 
     DL and UL Transmission/Reception Operations 
     DL Transmission/Reception Operation 
     DL grants (also called DL assignments) may be classified into (1) dynamic grant and (2) configured grant. A dynamic grant is a data transmission/reception method based on dynamic scheduling of a BS, aiming to maximize resource utilization. 
     The BS schedules a DL transmission by DCI. The UE receives the DCI for DL scheduling (i.e., including scheduling information for a PDSCH) (referred to as DL grant DCI) from the BS. The DCI for DL scheduling may include, for example, the following information: a BWP indicator, a frequency-domain resource assignment, a time-domain resource assignment, and a modulation and coding scheme (MCS). 
     The UE may determine a modulation order, a target code rate, and a TB size (TBS) for the PDSCH based on an MCS field in the DCI. The UE may receive the PDSCH in time-frequency resources according to the frequency-domain resource assignment and the time-domain resource assignment. 
     The DL configured grant is also called semi-persistent scheduling (SPS). The UE may receive an RRC message including a resource configuration for DL data transmission from the BS. In the case of DL SPS, an actual DL configured grant is provided by a PDCCH, and the DL SPS is activated or deactivated by the PDCCH. When DL SPS is configured, the BS provides the UE with at least the following parameters by RRC signaling: a configured scheduling RNTI (CS-RNTI) for activation, deactivation, and retransmission; and a periodicity. An actual DL grant (e.g., a frequency resource assignment) for DL SPS is provided to the UE by DCI in a PDCCH addressed to the CS-RNTI. If a specific field in the DCI of the PDCCH addressed to the CS-RNTI is set to a specific value for scheduling activation, SPS associated with the CS-RNTI is activated. The DCI of the PDCCH addressed to the CS-RNTI includes actual frequency resource allocation information, an MCS index, and so on. The UE may receive DL data on a PDSCH based on the SPS. 
     UL Transmission/Reception Operation 
     UL grants may be classified into (1) dynamic grant that schedules a PUSCH dynamically by UL grant DCI and (2) configured grant that schedules a PUSCH semi-statically by RRC signaling. 
       FIG. 5  is a diagram illustrating exemplary UL transmissions according to UL grants. Particularly,  FIG. 5( a )  illustrates a UL transmission procedure based on a dynamic grant, and  FIG. 5( b )  illustrates a UL transmission procedure based on a configured grant. 
     In the case of a UL dynamic grant, the BS transmits DCI including UL scheduling information to the UE. The UE receives DCI for UL scheduling (i.e., including scheduling information for a PUSCH) (referred to as UL grant DCI) on a PDCCH. The DCI for UL scheduling may include, for example, the following information: a BWP indicator, a frequency-domain resource assignment, a time-domain resource assignment, and an MCS. For efficient allocation of UL radio resources by the BS, the UE may transmit information about UL data to be transmitted to the BS, and the BS may allocate UL resources to the UE based on the information. The information about the UL data to be transmitted is referred to as a buffer status report (BSR), and the BSR is related to the amount of UL data stored in a buffer of the UE. 
     Referring to  FIG. 5( a ) , the illustrated UL transmission procedure is for a UE which does not have UL radio resources available for BSR transmission. In the absence of a UL grant available for UL data transmission, the UE is not capable of transmitting a BSR on a PUSCH. Therefore, the UE should request resources for UL data, starting with transmission of an SR on a PUCCH. In this case, a 5-step UL resource allocation procedure is used. 
     Referring to  FIG. 5( a ) , in the absence of PUSCH resources for BSR transmission, the UE first transmits an SR to the BS, for PUSCH resource allocation. The SR is used for the UE to request PUSCH resources for UL transmission to the BS, when no PUSCH resources are available to the UE in spite of occurrence of a buffer status reporting event. In the presence of valid PUCCH resources for the SR, the UE transmits the SR on a PUCCH, whereas in the absence of valid PUCCH resources for the SR, the UE starts the afore-described (contention-based) RACH procedure. Upon receipt of a UL grant in UL grant DCI from the BS, the UE transmits a BSR to the BS in PUSCH resources allocated by the UL grant. The BS checks the amount of UL data to be transmitted by the UE based on the BSR and transmits a UL grant in UL grant DCI to the UE. Upon detection of a PDCCH including the UL grant DCI, the UE transmits actual UL data to the BS on a PUSCH based on the UL grant included in the UL grant DCI. 
     Referring to  FIG. 5( b ) , in the case of a configured grant, the UE receives an RRC message including a resource configuration for UL data transmission from the BS. In the NR system, two types of UL configured grants are defined: type 1 and type 2. In the case of UL configured grant type 1, an actual UL grant (e.g., time resources and frequency resources) is provided by RRC signaling, whereas in the case of UL configured grant type 2, an actual UL grant is provided by a PDCCH, and activated or deactivated by the PDCCH. If configured grant type 1 is configured, the BS provides the UE with at least the following parameters by RRC signaling: a CS-RNTI for retransmission; a periodicity of configured grant type 1; information about a starting symbol index S and the number L of symbols for a PUSCH in a slot; a time-domain offset representing a resource offset with respect to SFN=0 in the time domain; and an MCS index representing a modulation order, a target code rate, and a TB size. If configured grant type 2 is configured, the BS provides the UE with at least the following parameters by RRC signaling: a CS-RNTI for activation, deactivation, and retransmission; and a periodicity of configured grant type 2. An actual UL grant of configured grant type 2 is provided to the UE by DCI of a PDCCH addressed to a CS-RNTI. If a specific field in the DCI of the PDCCH addressed to the CS-RNTI is set to a specific value for scheduling activation, configured grant type 2 associated with the CS-RNTI is activated. The DCI set to a specific value for scheduling activation in the PDCCH includes actual frequency resource allocation information, an MCS index, and so on. The UE may perform a UL transmission on a PUSCH based on a configured grant of type 1 or type 2. 
       FIG. 6  is a conceptual diagram illustrating exemplary physical channel processing. 
     Each of the blocks illustrated in  FIG. 6  may be performed in a corresponding module of a physical layer block in a transmission device. More specifically, the signal processing depicted in  FIG. 6  may be performed for UL transmission by a processor of a UE described in the present disclosure. Signal processing of  FIG. 6  except for transform precoding, with CP-OFDM signal generation instead of SC-FDMA signal generation may be performed for DL transmission in a processor of a BS described in the present disclosure. Referring to  FIG. 6 , UL physical channel processing may include scrambling, modulation mapping, layer mapping, transform precoding, precoding, RE mapping, and SC-FDMA signal generation. The above processes may be performed separately or together in the modules of the transmission device. The transform precoding, a kind of discrete Fourier transform (DFT), is to spread UL data in a special manner that reduces the peak-to-average power ratio (PAPR) of a waveform. OFDM which uses a CP together with transform precoding for DFT spreading is referred to as DFT-s-OFDM, and OFDM using a CP without DFT spreading is referred to as CP-OFDM. An SC-FDMA signal is generated by DFT-s-OFDM. In the NR system, if transform precoding is enabled for UL, transform precoding may be applied optionally. That is, the NR system supports two options for a UL waveform: one is CP-OFDM and the other is DFT-s-OFDM. The BS provides RRC parameters to the UE such that the UE determines whether to use CP-OFDM or DFT-s-OFDM for a UL transmission waveform.  FIG. 6  is a conceptual view illustrating UL physical channel processing for DFT-s-OFDM. For CP-OFDM, transform precoding is omitted from the processes of  FIG. 6 . For DL transmission, CP-OFDM is used for DL waveform transmission. 
     Each of the above processes will be described in greater detail. For one codeword, the transmission device may scramble coded bits of the codeword by a scrambler and then transmit the scrambled bits on a physical channel. The codeword is obtained by encoding a TB. The scrambled bits are modulated to complex-valued modulation symbols by a modulation mapper. The modulation mapper may modulate the scrambled bits in a predetermined modulation scheme and arrange the modulated bits as complex-valued modulation symbols representing positions on a signal constellation. Pi/2-binay phase shift keying (pi/2-BPSK), m-phase shift keying (m-PSK), m-quadrature amplitude modulation (m-QAM), or the like is available for modulation of the coded data. The complex-valued modulation symbols may be mapped to one or more transmission layers by a layer mapper. A complexed-value modulation symbol on each layer may be precoded by a precoder, for transmission through an antenna port. If transform precoding is possible for UL transmission, the precoder may perform precoding after the complex-valued modulation symbols are subjected to transform precoding, as illustrated in  FIG. 6 . The precoder may output antenna-specific symbols by processing the complex-valued modulation symbols in a multiple input multiple output (MIMO) scheme according to multiple Tx antennas, and distribute the antenna-specific symbols to corresponding RE mappers. An output z of the precoder may be obtained by multiplying an output y of the layer mapper by an N×M precoding matrix, W where N is the number of antenna ports and M is the number of layers. The RE mappers map the complex-valued modulation symbols for the respective antenna ports to appropriate REs in an RB allocated for transmission. The RE mappers may map the complex-valued modulation symbols to appropriate subcarriers, and multiplex the mapped symbols according to users. SC-FDMA signal generators (CP-OFDM signal generators, when transform precoding is disabled in DL transmission or UL transmission) may generate complex-valued time domain OFDM symbol signals by modulating the complex-valued modulation symbols in a specific modulations scheme, for example, in OFDM. The SC-FDMA signal generators may perform inverse fast Fourier transform (IFFT) on the antenna-specific symbols and insert CPs into the time-domain IFFT-processed symbols. The OFDM symbols are subjected to digital-to-analog conversion, frequency upconversion, and so on, and then transmitted to a reception device through the respective Tx antennas. Each of the SC-FDMA signal generators may include an IFFT module, a CP inserter, a digital-to-analog converter (DAC), a frequency upconverter, and so on. 
     A signal processing procedure of the reception device is performed in a reverse order of the signal processing procedure of the transmission device. For details, refer to the above description and  FIG. 6 . 
     Now, a description will be given of the PUCCH. 
     The PUCCH is used for UCI transmission. UCI includes an SR requesting UL transmission resources, CSI representing a UE-measured DL channel state based on a DL RS, and/or an HARQ-ACK indicating whether a UE has successfully received DL data. 
     The PUCCH supports multiple formats, and the PUCCH formats are classified according to symbol durations, payload sizes, and multiplexing or non-multiplexing. [Table 1] below lists exemplary PUCCH formats. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 PUCCH length in 
                   
                   
               
               
                 Format 
                 OFDM symbols 
                 Number of bits 
                 Etc. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 0 
                 1-2  
                 ≤2 
                 Sequence selection 
               
               
                 1 
                 4-14 
                 ≤2 
                 Sequence modulation 
               
               
                 2 
                 1-2  
                 &gt;2 
                 CP-OFDM 
               
               
                 3 
                 4-14 
                 &gt;2 
                 DFT-s-OFDM 
               
               
                   
                   
                   
                 (no UE multiplexing) 
               
               
                 4 
                 4-14 
                 &gt;2 
                 DFT-s-OFDM 
               
               
                   
                   
                   
                 (Pre DFT orthogonal 
               
               
                   
                   
                   
                 cover code(OCC)) 
               
               
                   
               
            
           
         
       
     
     The BS configures PUCCH resources for the UE by RRC signaling. For example, to allocate PUCCH resources, the BS may configure a plurality of PUCCH resource sets for the UE, and the UE may select a specific PUCCH resource set corresponding to a UCI (payload) size (e.g., the number of UCI bits). For example, the UE may select one of the following PUCCH resource sets according to the number of UCI bits, N UCI .
         PUCCH resource set #0, if the number of UCI bits ≤2   PUCCH resource set #1, if 2&lt;the number of UCI bits ≤N 1      . . .   PUCCH resource set #(K−1), if NK−2&lt;the number of UCI bits ≤N K-1          

     Herein, K represents the number of PUCCH resource sets (K&gt;1), and Ni represents the maximum number of UCI bits supported by PUCCH resource set #i. For example, PUCCH resource set #1 may include resources of PUCCH format 0 to PUCCH format 1, and the other PUCCH resource sets may include resources of PUCCH format 2 to PUCCH format 4. 
     Subsequently, the BS may transmit DCI to the UE on a PDCCH, indicating a PUCCH resource to be used for UCI transmission among the PUCCH resources of a specific PUCCH resource set by an ACK/NACK resource indicator (ARI) in the DCI. The ARI may be used to indicate a PUCCH resource for HARQ-ACK transmission, also called a PUCCH resource indicator (PRI). 
     Enhanced Mobile Broadband Communication (eMBB) 
     In the NR system, a massive MIMO environment in which the number of Tx/Rx antennas is significantly increased is under consideration. On the other hand, in an NR system operating at or above 6 GHz, beamforming is considered, in which a signal is transmitted with concentrated energy in a specific direction, not omni-directionally, to compensate for rapid propagation attenuation. Accordingly, there is a need for hybrid beamforming with analog beamforming and digital beamforming in combination according to a position to which a beamforming weight vector/precoding vector is applied, for the purpose of increased performance, flexible resource allocation, and easiness of frequency-wise beam control. 
     Hybrid Beamforming 
       FIG. 7  is a block diagram illustrating an exemplary transmitter and receiver for hybrid beamforming. 
     In hybrid beamforming, a BS or a UE may form a narrow beam by transmitting the same signal through multiple antennas, using an appropriate phase difference and thus increasing energy only in a specific direction. 
     Beam Management (BM) 
     BM is a series of processes for acquiring and maintaining a set of BS (or transmission and reception point (TRP)) beams and/or UE beams available for DL and UL transmissions/receptions. BM may include the following processes and terminology.
         Beam measurement: the BS or the UE measures the characteristics of a received beamformed signal.   Beam determination: the BS or the UE selects its Tx beam/Rx beam.   Beam sweeping: a spatial domain is covered by using a Tx beam and/or an Rx beam in a predetermined method for a predetermined time interval.   Beam report: the UE reports information about a signal beamformed based on a beam measurement.       

     The BM procedure may be divided into (1) a DL BM procedure using an SSB or CSI-RS and (2) a UL BM procedure using an SRS. Further, each BM procedure may include Tx beam sweeping for determining a Tx beam and Rx beam sweeping for determining an Rx beam. The following description will focus on the DL BM procedure using an SSB. 
     The DL BM procedure using an SSB may include (1) transmission of a beamformed SSB from the BS and (2) beam reporting of the UE. An SSB may be used for both of Tx beam sweeping and Rx beam sweeping. SSB-based Rx beam sweeping may be performed by attempting SSB reception while changing Rx beams at the UE. 
     SSB-based beam reporting may be configured, when CSI/beam is configured in the RRC_CONNECTED state.
         The UE receives information about an SSB resource set used for BM from the BS. The SSB resource set may be configured with one or more SSBIs. For each SSB resource set, SSBI 0 to SSBI 63 may be defined.   The UE receives signals in SSB resources from the BS based on the information about the SSB resource set.   When the BS configures the UE with an SSBRI and RSRP reporting, the UE reports a (best) SSBRI and an RSRP corresponding to the SSBRI to the BS.       

     The BS may determine a BS Tx beam for use in DL transmission to the UE based on a beam report received from the UE. 
     Beam Failure Recovery (BFR) Procedure 
     In a beamforming system, radio link failure (RLF) may often occur due to rotation or movement of a UE or beamforming blockage. Therefore, BFR is supported to prevent frequent occurrence of RLF in NR. 
     For beam failure detection, the BS configures beam failure detection RSs for the UE. If the number of beam failure indications from the physical layer of the UE reaches a threshold configured by RRC signaling within a period configured by RRC signaling of the BS, the UE declares beam failure. 
     After the beam failure is detected, the UE triggers BFR by initiating a RACH procedure on a Pcell, and performs BFR by selecting a suitable beam (if the BS provides dedicated RACH resources for certain beams, the UE performs the RACH procedure for BFR by using the dedicated RACH resources first of all). Upon completion of the RACH procedure, the UE considers that the BFR has been completed. 
     Ultra-Reliable and Low Latency Communication (URLLC) 
     A URLLC transmission defined in NR may mean a transmission with (1) a relatively small traffic size, (2) a relatively low arrival rate, (3) an extremely low latency requirement (e.g., 0.5 ms or 1 ms), (4) a relatively short transmission duration (e.g., 2 OFDM symbols), and (5) an emergency service/message. 
     Pre-Emption Indication 
     Although eMBB and URLLC services may be scheduled in non-overlapped time/frequency resources, a URLLC transmission may take place in resources scheduled for on-going eMBB traffic. To enable a UE receiving a PDSCH to determine that the PDSCH has been partially punctured due to URLLC transmission of another UE, a preemption indication may be used. The preemption indication may also be referred to as an interrupted transmission indication. 
     In relation to a preemption indication, the UE receives DL preemption RRC information (e.g., a DownlinkPreemption IE) from the BS by RRC signaling. 
     The UE receives DCI format 2_1 based on the DL preemption RRC information from the BS. For example, the UE attempts to detect a PDCCH conveying preemption indication-related DCI, DCI format 2_1 by using an int-RNTI configured by the DL preemption RRC information. 
     Upon detection of DCI format 2_1 for serving cell(s) configured by the DL preemption RRC information, the UE may assume that there is no transmission directed to the UE in RBs and symbols indicated by DCI format 2_1 in a set of RBs and a set of symbols during a monitoring interval shortly previous to a monitoring interval to which DCI format 2_1 belongs. For example, the UE decodes data based on signals received in the remaining resource areas, considering that a signal in a time-frequency resource indicated by a preemption indication is not a DL transmission scheduled for the UE. 
     Massive MTC (mMTC) 
     mMTC is one of 5G scenarios for supporting a hyper-connectivity service in which communication is conducted with multiple UEs at the same time. In this environment, a UE intermittently communicates at a very low transmission rate with low mobility. Accordingly, mMTC mainly seeks long operation of a UE with low cost. In this regard, MTC and narrow band-Internet of things (NB-IoT) handled in the 3GPP will be described below. 
     The following description is given with the appreciation that a transmission time interval (TTI) of a physical channel is a subframe. For example, a minimum time interval between the start of transmission of a physical channel and the start of transmission of the next physical channel is one subframe. However, a subframe may be replaced with a slot, a mini-slot, or multiple slots in the following description. 
     Machine Type Communication (MTC) 
     MTC is an application that does not require high throughput, applicable to machine-to-machine (M2M) or IoT. MTC is a communication technology which the 3GPP has adopted to satisfy the requirements of the IoT service. 
     While the following description is given mainly of features related to enhanced MTC (eMTC), the same thing is applicable to MTC, eMTC, and MTC to be applied to 5G (or NR), unless otherwise mentioned. The term MTC as used herein may be interchangeable with eMTC, LTE-M1/M2, bandwidth reduced low complexity (BL)/coverage enhanced (CE), non-BL UE (in enhanced coverage), NR MTC, enhanced BL/CE, and so on. 
     MTC General 
     (1) MTC operates only in a specific system BW (or channel BW). 
     MTC may use a predetermined number of RBs among the RBs of a system band in the legacy LTE system or the NR system. The operating frequency BW of MTC may be defined in consideration of a frequency range and a subcarrier spacing in NR. A specific system or frequency BW in which MTC operates is referred to as an MTC narrowband (NB) or MTC subband. In NR, MTC may operate in at least one BWP or a specific band of a BWP. 
     While MTC is supported by a cell having a much larger BW (e.g., 10 MHz) than 1.08 MHz, a physical channel and signal transmitted/received in MTC is always limited to 1.08 MHz or 6 (LTE) RBs. For example, a narrowband is defined as 6 non-overlapped consecutive physical resource blocks (PRBs) in the frequency domain in the LTE system. 
     In MTC, some DL and UL channels are allocated restrictively within a narrowband, and one channel does not occupy a plurality of narrowbands in one time unit.  FIG. 8( a )  is a diagram illustrating an exemplary narrowband operation, and  FIG. 8( b )  is a diagram illustrating exemplary MTC channel repetition with RF retuning. 
     An MTC narrowband may be configured for a UE by system information or DCI transmitted by a BS. 
     (2) MTC does not use a channel (defined in legacy LTE or NR) which is to be distributed across the total system BW of the legacy LTE or NR. For example, because a legacy LTE PDCCH is distributed across the total system BW, the legacy PDCCH is not used in MTC. Instead, a new control channel, MTC PDCCH (MPDCCH) is used in MTC. The MPDCCH is transmitted/received in up to 6 RBs in the frequency domain. In the time domain, the MPDCCH may be transmitted in one or more OFDM symbols starting with an OFDM symbol of a starting OFDM symbol index indicated by an RRC parameter from the BS among the OFDM symbols of a subframe. 
     (3) In MTC, PBCH, PRACH, MPDCCH, PDSCH, PUCCH, and PUSCH may be transmitted repeatedly. The MTC repeated transmissions may make these channels decodable even when signal quality or power is very poor as in a harsh condition like basement, thereby leading to the effect of an increased cell radius and signal penetration. 
     MTC Operation Modes and Levels 
     For CE, two operation modes, CE Mode A and CE Mode B and four different CE levels are used in MTC, as listed in [Table 2] below. 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 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 
               
               
                   
               
            
           
         
       
     
     An MTC operation mode is determined by a BS and a CE level is determined by an MTC UE. 
     MTC Guard Period 
     The position of a narrowband used for MTC may change in each specific time unit (e.g., subframe or slot). An MTC UE may tune to different frequencies in different time units. A certain time may be required for frequency retuning and thus used as a guard period for MTC. No transmission and reception take place during the guard period. 
     MTC Signal Transmission/Reception Method 
     Apart from features inherent to MTC, an MTC signal transmission/reception procedure is similar to the procedure illustrated in  FIG. 2 . The operation of S 201  in  FIG. 2  may also be performed for MTC. A PSS/SSS used in an initial cell search operation in MTC may be the legacy LTE PSS/SSS. 
     After acquiring synchronization with a BS by using the PSS/SSS, an MTC UE may acquire broadcast information within a cell by receiving a PBCH signal from the BS. The broadcast information transmitted on the PBCH is an MIB. In MTC, reserved bits among the bits of the legacy LTE MIB are used to transmit scheduling information for a new system information block 1 bandwidth reduced (SIB1-BR). The scheduling information for the SIB1-BR may include information about a repetition number and a TBS for a PDSCH conveying SIB1-BR. A frequency resource assignment for the PDSCH conveying SIB-BR may be a set of 6 consecutive RBs within a narrowband. The SIB-BR is transmitted directly on the PDSCH without a control channel (e.g., PDCCH or MPDCCH) associated with SIB-BR. 
     After completing the initial cell search, the MTC UE may acquire more specific system information by receiving an MPDCCH and a PDSCH based on information of the MPDCCH (S 202 ). 
     Subsequently, the MTC UE may perform a RACH procedure to complete connection to the BS (S 203  to S 206 ). A basic configuration for the RACH procedure of the MTC UE may be transmitted in SIB2. Further, SIB2 includes paging-related parameters. In the 3GPP system, a paging occasion (PO) means a time unit in which a UE may attempt to receive paging. Paging refers to the network&#39;s indication of the presence of data to be transmitted to the UE. The MTC UE attempts to receive an MPDCCH based on a P-RNTI in a time unit corresponding to its PO in a narrowband configured for paging, paging narrowband (PNB). When the UE succeeds in decoding the MPDCCH based on the P-RNTI, the UE may check its paging message by receiving a PDSCH scheduled by the MPDCCH. In the presence of its paging message, the UE accesses the network by performing the RACH procedure. 
     In MTC, signals and/or messages (Msg1, Msg2, Msg3, and Msg4) may be transmitted repeatedly in the RACH procedure, and a different repetition pattern may be set according to a CE level. 
     For random access, PRACH resources for different CE levels are signaled by the BS. Different PRACH resources for up to 4 respective CE levels may be signaled to the MTC UE. The MTC UE measures an RSRP using a DL RS (e.g., CRS, CSI-RS, or TRS) and determines one of the CE levels signaled by the BS based on the measurement. The UE selects one of different PRACH resources (e.g., frequency, time, and preamble resources for a PARCH) for random access based on the determined CE level and transmits a PRACH. The BS may determine the CE level of the UE based on the PRACH resources that the UE has used for the PRACH transmission. The BS may determine a CE mode for the UE based on the CE level that the UE indicates by the PRACH transmission. The BS may transmit DCI to the UE in the CE mode. 
     Search spaces for an RAR for the PRACH and contention resolution messages are signaled in system information by the BS. 
     After the above procedure, the MTC UE may receive an MPDCCH signal and/or a PDSCH signal (S 207 ) and transmit a PUSCH signal and/or a PUCCH signal (S 208 ) in a general UL/DL signal transmission procedure. The MTC UE may transmit UCI on a PUCCH or a PUSCH to the BS. 
     Once an RRC connection for the MTC UE is established, the MTC UE attempts to receive an MDCCH by monitoring an MPDCCH in a configured search space in order to acquire UL and DL data allocations. 
     In legacy LTE, a PDSCH is scheduled by a PDCCH. Specifically, the PDCCH may be transmitted in the first N (N=1, 2 or 3) OFDM symbols of a subframe, and the PDSCH scheduled by the PDCCH is transmitted in the same subframe. 
     Compared to legacy LTE, an MPDCCH and a PDSCH scheduled by the MPDCCH are transmitted/received in different subframes in MTC. For example, an MPDCCH with a last repetition in subframe #n schedules a PDSCH starting in subframe #n+2. The MPDCCH may be transmitted only once or repeatedly. A maximum repetition number of the MPDCCH is configured for the UE by RRC signaling from the BS. DCI carried on the MPDCCH provides information on how many times the MPDCCH is repeated so that the UE may determine when the PDSCH transmission starts. For example, if DCI in an MPDCCH starting in subframe #n includes information indicating that the MPDCCH is repeated 10 times, the MPDCCH may end in subframe #n+9 and the PDSCH may start in subframe #n+11. The DCI carried on the MPDCCH may include information about a repetition number for a physical data channel (e.g., PUSCH or PDSCH) scheduled by the DCI. The UE may transmit/receive the physical data channel repeatedly in the time domain according to the information about the repetition number of the physical data channel scheduled by the DCI. The PDSCH may be scheduled in the same or different narrowband as or from a narrowband in which the MPDCCH scheduling the PDSCH is transmitted. When the MPDCCH and the PDSCH are in different narrowbands, the MTC UE needs to retune to the frequency of the narrowband carrying the PDSCH before decoding the PDSCH. For UL scheduling, the same timing as in legacy LTE may be followed. For example, an MPDCCH ending in subframe #n may schedule a PUSCH transmission starting in subframe #n+4. If a physical channel is repeatedly transmitted, frequency hopping is supported between different MTC subbands by RF retuning. For example, if a PDSCH is repeatedly transmitted in 32 subframes, the PDSCH is transmitted in the first 16 subframes in a first MTC subband, and in the remaining 16 subframes in a second MTC subband. MTC may operate in half-duplex mode. 
     Narrowband-Internet of Things (NB-IoT) 
     NB-IoT may refer to a system for supporting low complexity, low power consumption, and efficient use of frequency resources by a system BW corresponding to one RB of a wireless communication system (e.g., the LTE system or the NR system). NB-IoT may operate in half-duplex mode. NB-IoT may be used as a communication scheme for implementing IoT by supporting, for example, an MTC device (or UE) in a cellular system. 
     In NB-IoT, each UE perceives one RB as one carrier. Therefore, an RB and a carrier as mentioned in relation to NB-IoT may be interpreted as the same meaning. 
     While a frame structure, physical channels, multi-carrier operations, and general signal transmission/reception in relation to NB-IoT will be described below in the context of the legacy LTE system, the description is also applicable to the next generation system (e.g., the NR system). Further, the description of NB-IoT may also be applied to MTC serving similar technical purposes (e.g., low power, low cost, and coverage enhancement). 
     NB-IoT Frame Structure and Physical Resources 
     A different NB-IoT frame structure may be configured according to a subcarrier spacing. For example, for a subcarrier spacing of 15 kHz, the NB-IoT frame structure may be identical to that of a legacy system (e.g., the LTE system). For example, a 10-ms NB-IoT frame may include 10 1-ms NB-IoT subframes each including two 0.5-ms slots. Each 0.5-ms NB-IoT slot may include 7 OFDM symbols. In another example, for a BWP or cell/carrier having a subcarrier spacing of 3.75 kHz, a 10-ms NB-IoT frame may include five 2-ms NB-IoT subframes each including 7 OFDM symbols and one guard period (GP). Further, a 2-ms NB-IoT subframe may be represented in NB-IoT slots or NB-IoT resource units (RUs). The NB-IoT frame structures are not limited to the subcarrier spacings of 15 kHz and 3.75 kHz, and NB-IoT for other subcarrier spacings (e.g., 30 kHz) may also be considered by changing time/frequency units. 
     NB-IoT DL physical resources may be configured based on physical resources of other wireless communication systems (e.g., the LTE system or the NR system) except that a system BW is limited to a predetermined number of RBs (e.g., one RB, that is, 180 kHz). For example, if the NB-IoT DL supports only the 15-kHz subcarrier spacing as described before, the NB-IoT DL physical resources may be configured as a resource area in which the resource grid illustrated in  FIG. 1  is limited to one RB in the frequency domain. 
     Like the NB-IoT DL physical resources, NB-IoT UL resources may also be configured by limiting a system BW to one RB. In NB-IoT, the number of UL subcarriers N UL   sc , and a slot duration T slot  may be given as illustrated in [Table 3] below. In NB-IoT of the LTE system, the duration of one slot, T slot  is defined by 7 SC-FDMA symbols in the time domain. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Subcarrier 
                   
                   
               
               
                   
                 Spacing 
                 N UL   SC   
                 T slot   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Δf = 3.75 
                 kHz 
                 48 
                  6144 · T s   
               
               
                 Δf = 15 
                 kHz 
                 12 
                 15360 · T s   
               
               
                   
               
            
           
         
       
     
     In NB-IoT, RUs are used for mapping to REs of a PUSCH for NB-IoT (referred to as an NPUSCH). An RU may be defined by N UL   symb *N UL   slot  SC-FDMA symbols in the time domain by N RU   sc  consecutive subcarriers in the frequency domain. For example, N RU   sc  and N UL   symb  are listed in [Table 4] for a cell/carrier having an FDD frame structure and in [Table 5] for a cell/carrier having a TDD frame structure. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 NPUSCH 
                   
                   
                   
                   
                   
               
               
                   
                 format 
                   
                 Δf 
                 N RU   SC   
                 N UL   SC   
                 N UL   Symb   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 1 
                 3.75 
                 kHz 
                 1 
                 16 
                 7 
               
               
                   
                   
                 15 
                 kHz 
                 1 
                 16 
               
               
                   
                   
                   
                   
                 3 
                 8 
               
               
                   
                   
                   
                   
                 6 
                 4 
               
               
                   
                   
                   
                   
                 12 
                 7 
               
               
                   
                 2 
                 3.75 
                 kHz 
                 1 
                 4 
               
               
                   
                   
                 15 
                 kHz 
                 1 
                 4 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 Supported 
                   
                   
                   
               
               
                   
                   
                 uplink- 
               
               
                 NPUSCH 
                   
                 downlink 
               
               
                 format 
                 Δf 
                 configurations 
                 N RU   SC   
                 N UL   SC   
                 N UL   Symb   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 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 
               
               
                   
               
            
           
         
       
     
     NB-IoT Physical Channels 
     OFDMA may be adopted for NB-IoT DL based on the 15-kHz subcarrier spacing. Because OFDMA provides orthogonality between subcarriers, co-existence with other systems (e.g., the LTE system or the NR system) may be supported efficiently. The names of DL physical channels/signals of the NB-IoT system may be prefixed with “N (narrowband)” to be distinguished from their counterparts in the legacy system. For example, DL physical channels may be named NPBCH, NPDCCH, NPDSCH, and so on, and DL physical signals may be named NPSS, NSSS, narrowband reference signal (NRS), narrowband positioning reference signal (NPRS), narrowband wake up signal (NWUS), and so on. The DL channels, NPBCH, NPDCCH, NPDSCH, and so on may be repeatedly transmitted to enhance coverage in the NB-IoT system. Further, new defined DCI formats may be used in NB-IoT, such as DCI format NO, DCI format N1, and DCI format N2. 
     SC-FDMA may be applied with the 15-kHz or 3.75-kHz subcarrier spacing to NB-IoT UL. As described in relation to DL, the names of physical channels of the NB-IoT system may be prefixed with “N (narrowband)” to be distinguished from their counterparts in the legacy system. For example, UL channels may be named NPRACH, NPUSCH, and so on, and UL physical signals may be named NDMRS and so on. NPUSCHs may be classified into NPUSCH format 1 and NPUSCH format 2. For example, NPUSCH format 1 may be used to transmit (or deliver) an uplink shared channel (UL-SCH), and NPUSCH format 2 may be used for UCI transmission such as HARQ ACK signaling. A UL channel, NPRACH in the NB-IoT system may be repeatedly transmitted to enhance coverage. In this case, the repeated transmissions may be subjected to frequency hopping. 
     Multi-Carrier Operation in NB-IoT 
     NB-IoT may be implemented in multi-carrier mode. A multi-carrier operation may refer to using multiple carriers configured for different usages (i.e., multiple carriers of different types) in transmitting/receiving channels and/or signals between a BS and a UE. 
     In the multi-carrier mode in NB-IoT, carriers may be divided into anchor type carrier (i.e., anchor carrier or anchor PRB) and non-anchor type carrier (i.e., non-anchor carrier or non-anchor PRB). 
     The anchor carrier may refer to a carrier carrying an NPSS, an NSSS, and an NPBCH for initial access, and an NPDSCH for a system information block, N-SIB from the perspective of a BS. That is, a carrier for initial access is referred to as an anchor carrier, and the other carrier(s) is referred to as a non-anchor carrier in NB-IoT. 
     NB-IoT Signal Transmission/Reception Process 
     In NB-IoT, a signal is transmitted/received in a similar manner to the procedure illustrated in  FIG. 2 , except for features inherent to NB-IoT. Referring to  FIG. 2 , when an NB-IoT UE is powered on or enters a new cell, the NB-IoT UE may perform an initial cell search (S 201 ). For the initial cell search, the NB-IoT UE may acquire synchronization with a BS and obtain information such as a cell ID by receiving an NPSS and an NSSS from the BS. Further, the NB-IoT UE may acquire broadcast information within a cell by receiving an NPBCH from the BS. 
     Upon completion of the initial cell search, the NB-IoT UE may acquire more specific system information by receiving an NPDCCH and receiving an NPDSCH corresponding to the NPDCCH (S 202 ). In other words, the BS may transmit more specific system information to the NB-IoT UE which has completed the initial call search by transmitting an NPDCCH and an NPDSCH corresponding to the NPDCCH. 
     The NB-IoT UE may then perform a RACH procedure to complete a connection setup with the BS (S 203  to S 206 ). For this purpose, the NB-IoT UE may transmit a preamble on an NPRACH to the BS (S 203 ). As described before, it may be configured that the NPRACH is repeatedly transmitted based on frequency hopping, for coverage enhancement. In other words, the BS may (repeatedly) receive the preamble on the NPRACH from the NB-IoT UE. The NB-IoT UE may then receive an NPDCCH, and a RAR in response to the preamble on an NPDSCH corresponding to the NPDCCH from the BS (S 204 ). In other words, the BS may transmit the NPDCCH, and the RAR in response to the preamble on the NPDSCH corresponding to the NPDCCH to the NB-IoT UE. Subsequently, the NB-IoT UE may transmit an NPUSCH to the BS, using scheduling information in the RAR (S 205 ) and perform a contention resolution procedure by receiving an NPDCCH and an NPDSCH corresponding to the NPDCCH (S 206 ). 
     After the above process, the NB-IoT UE may perform an NPDCCH/NPDSCH reception (S 207 ) and an NPUSCH transmission (S 208 ) in a general UL/DL signal transmission procedure. In other words, after the above process, the BS may perform an NPDCCH/NPDSCH transmission and an NPUSCH reception with the NB-IoT UE in the general UL/DL signal transmission procedure. 
     In NB-IoT, the NPBCH, the NPDCCH, and the NPDSCH may be transmitted repeatedly, for coverage enhancement. A UL-SCH (i.e., general UL data) and UCI may be delivered on the PUSCH in NB-IoT. It may be configured that the UL-SCH and the UCI are transmitted in different NPUSCH formats (e.g., NPUSCH format 1 and NPUSCH format 2). 
     In NB-IoT, UCI may generally be transmitted on an NPUSCH. Further, the UE may transmit the NPUSCH periodically, aperiodically, or semi-persistently according to request/indication of the network (e.g., BS). 
     Wireless Communication Apparatus 
       FIG. 9  is a block diagram of an exemplary wireless communication system to which proposed methods of the present disclosure are applicable. 
     Referring to  FIG. 9 , the wireless communication system includes a first communication device  910  and/or a second communication device  920 . The phrases “A and/or B” and “at least one of A or B” are may be interpreted as the same meaning. The first communication device  910  may be a BS, and the second communication device  920  may be a UE (or the first communication device  910  may be a UE, and the second communication device  920  may be a BS). 
     Each of the first communication device  910  and the second communication device  920  includes a processor  911  or  921 , a memory  914  or  924 , one or more Tx/Rx RF modules  915  or  925 , a Tx processor  912  or  922 , an Rx processor  913  or  923 , and antennas  916  or  926 . A Tx/Rx module may also be called a transceiver. The processor performs the afore-described functions, processes, and/or methods. More specifically, on DL (communication from the first communication device  910  to the second communication device  920 ), a higher-layer packet from a core network is provided to the processor  911 . The processor  911  implements Layer 2 (i.e., L2) functionalities. On DL, the processor  911  is responsible for multiplexing between a logical channel and a transport channel, provisioning of a radio resource assignment to the second communication device  920 , and signaling to the second communication device  920 . The Tx processor  912  executes various signal processing functions of L1 (i.e., the physical layer). The signal processing functions facilitate forward error correction (FEC) of the second communication device  920 , including coding and interleaving. An encoded and interleaved signal is modulated to complex-valued modulation symbols after scrambling and modulation. For the modulation, BPSK, QPSK, 16QAM, 64QAM, 246QAM, and so on are available according to channels. The complex-valued modulation symbols (hereinafter, referred to as modulation symbols) are divided into parallel streams. Each stream is mapped to OFDM subcarriers and multiplexed with an RS in the time and/or frequency domain. A physical channel is generated to carry a time-domain OFDM symbol stream by subjecting the mapped signals to IFFT. The OFDM symbol stream is spatially precoded to multiple spatial streams. Each spatial stream may be provided to a different antenna  916  through an individual Tx/Rx module (or transceiver)  915 . Each Tx/Rx module  915  may upconvert the frequency of each spatial stream to an RF carrier, for transmission. In the second communication device  920 , each Tx/Rx module (or transceiver)  925  receives a signal of the RF carrier through each antenna  926 . Each Tx/Rx module  925  recovers the signal of the RF carrier to a baseband signal and provides the baseband signal to the Rx processor  923 . The Rx processor  923  executes various signal processing functions of L1 (i.e., the physical layer). The Rx processor  923  may perform spatial processing on information to recover any spatial stream directed to the second communication device  920 . If multiple spatial streams are directed to the second communication device  920 , multiple Rx processors may combine the multiple spatial streams into a single OFDMA symbol stream. The Rx processor  923  converts an OFDM symbol stream being a time-domain signal to a frequency-domain signal by FFT. The frequency-domain signal includes an individual OFDM symbol stream on each subcarrier of an OFDM signal. Modulation symbols and an RS on each subcarrier are recovered and demodulated by determining most likely signal constellation points transmitted by the first communication device  910 . These soft decisions may be based on channel estimates. The soft decisions are decoded and deinterleaved to recover the original data and control signal transmitted on physical channels by the first communication device  910 . The data and control signal are provided to the processor  921 . 
     On UL (communication from the second communication device  920  to the first communication device  910 ), the first communication device  910  operates in a similar manner as described in relation to the receiver function of the second communication device  920 . Each Tx/Rx module  925  receives a signal through an antenna  926 . Each Tx/Rx module  925  provides an RF carrier and information to the Rx processor  923 . The processor  921  may be related to the memory  924  storing a program code and data. The memory  924  may be referred to as a computer-readable medium. 
     Artificial Intelligence (AI) 
     Artificial intelligence is a field of studying AI or methodologies for creating AI, and machine learning is a field of defining various issues dealt with in the AI field and studying methodologies for addressing the various issues. Machine learning is defined as an algorithm that increases the performance of a certain operation through steady experiences for the operation. 
     An artificial neural network (ANN) is a model used in machine learning and may generically refer to a model having a problem-solving ability, which is composed of artificial neurons (nodes) forming a network via synaptic connections. The ANN may be defined by a connection pattern between neurons in different layers, a learning process for updating model parameters, and an activation function for generating an output value. 
     The ANN may include an input layer, an output layer, and optionally, one or more hidden layers. Each layer includes one or more neurons, and the ANN may include a synapse that links between neurons. In the ANN, each neuron may output the function value of the activation function, for the input of signals, weights, and deflections through the synapse. 
     Model parameters refer to parameters determined through learning and include a weight value of a synaptic connection and deflection of neurons. A hyperparameter means a parameter to be set in the machine learning algorithm before learning, and includes a learning rate, a repetition number, a mini batch size, and an initialization function. 
     The purpose of learning of the ANN may be to determine model parameters that minimize a loss function. The loss function may be used as an index to determine optimal model parameters in the learning process of the ANN. 
     Machine learning may be classified into supervised learning, unsupervised learning, and reinforcement learning according to learning methods. 
     Supervised learning may be a method of training an ANN in a state in which a label for training data is given, and the label may mean a correct answer (or result value) that the ANN should infer with respect to the input of training data to the ANN. Unsupervised learning may be a method of training an ANN in a state in which a label for training data is not given. Reinforcement learning may be a learning method in which an agent defined in a certain environment is trained to select a behavior or a behavior sequence that maximizes cumulative compensation in each state. 
     Machine learning, which is implemented by a deep neural network (DNN) including a plurality of hidden layers among ANNs, is also referred to as deep learning, and deep learning is part of machine learning. The following description is given with the appreciation that machine learning includes deep learning. 
     &lt;Robot&gt; 
     A robot may refer to a machine that automatically processes or executes a given task by its own capabilities. Particularly, a robot equipped with a function of recognizing an environment and performing an operation based on its decision may be referred to as an intelligent robot. 
     Robots may be classified into industrial robots, medical robots, consumer robots, military robots, and so on according to their usages or application fields. 
     A robot may be provided with a driving unit including an actuator or a motor, and thus perform various physical operations such as moving robot joints. Further, a movable robot may include a wheel, a brake, a propeller, and the like in a driving unit, and thus travel on the ground or fly in the air through the driving unit. 
     &lt;Self-Driving&gt; 
     Self-driving refers to autonomous driving, and a self-driving vehicle refers to a vehicle that travels with no user manipulation or minimum user manipulation. 
     For example, self-driving may include a technology of maintaining a lane while driving, a technology of automatically adjusting a speed, such as adaptive cruise control, a technology of automatically traveling along a predetermined route, and a technology of automatically setting a route and traveling along the route when a destination is set. 
     Vehicles may include a vehicle having only an internal combustion engine, a hybrid vehicle having both an internal combustion engine and an electric motor, and an electric vehicle having only an electric motor, and may include not only an automobile but also a train, a motorcycle, and the like. 
     Herein, a self-driving vehicle may be regarded as a robot having a self-driving function. 
     &lt;eXtended Reality (XR)&gt; 
     Extended reality is a generical term covering virtual reality (VR), augmented reality (AR), and mixed reality (MR). VR provides a real-world object and background only as a computer graphic (CG) image, AR provides a virtual CG image on a real object image, and MR is a computer graphic technology that mixes and combines virtual objects into the real world. 
     MR is similar to AR in that the real object and the virtual object are shown together. However, in AR, the virtual object is used as a complement to the real object, whereas in MR, the virtual object and the real object are handled equally. 
     XR may be applied to a head-mounted display (HMD), a head-up display (HUD), a portable phone, a tablet PC, a laptop computer, a desktop computer, a TV, a digital signage, and so on. A device to which XR is applied may be referred to as an XR device. 
       FIG. 10  illustrates an AI device  1000  in accordance with some embodiments. 
     The AI device  1000  illustrated in  FIG. 10  may be configured as a stationary device or a mobile device, such as a TV, a projector, a portable phone, a smartphone, a desktop computer, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation device, a tablet PC, a wearable device, a set-top box (STB), a digital multimedia broadcasting (DMB) receiver, a radio, a washing machine, a refrigerator, a digital signage, a robot, or a vehicle. 
     Referring to  FIG. 10 , the AI device  1000  may include a communication unit  1010 , an input unit  1020 , a learning processor  1030 , a sensing unit  1040 , an output unit  1050 , a memory  1070 , and a processor  1080 . 
     The communication unit  1010  may transmit and receive data to and from an external device such as another AI device or an AI server by wired or wireless communication. For example, the communication unit  1010  may transmit and receive sensor information, a user input, a learning model, and a control signal to and from the external device. 
     Communication schemes used by the communication unit  1010  include global system for mobile communication (GSM), CDMA, LTE, 5G; wireless local area network (WLAN), wireless fidelity (Wi-Fi), Bluetooth™, radio frequency identification (RFID), infrared data association (IrDA), ZigBee, near field communication (NFC), and so on. Particularly, the 5G technology described before with reference to  FIGS. 1 to 9  may also be applied. 
     The input unit  1020  may acquire various types of data. The input unit  1020  may include a camera for inputting a video signal, a microphone for receiving an audio signal, and a user input unit for receiving information from a user. The camera or the microphone may be treated as a sensor, and thus a signal acquired from the camera or the microphone may be referred to as sensing data or sensor information. 
     The input unit  1020  may acquire training data for model training and input data to be used to acquire an output by using a learning model. The input unit  1020  may acquire raw input data. In this case, the processor  1080  or the learning processor  1030  may extract an input feature by preprocessing the input data. 
     The learning processor  1030  may train a model composed of an ANN by using training data. The trained ANN may be referred to as a learning model. The learning model may be used to infer a result value for new input data, not training data, and the inferred value may be used as a basis for determination to perform a certain operation. 
     The learning processor  1030  may perform AI processing together with a learning processor of an AI server. 
     The learning processor  1030  may include a memory integrated or implemented in the AI device  1000 . Alternatively, the learning processor  1030  may be implemented by using the memory  1070 , an external memory directly connected to the AI device  1000 , or a memory maintained in an external device. 
     The sensing unit  1040  may acquire at least one of internal information about the AI device  1000 , ambient environment information about the AI device  1000 , and user information by using various sensors. 
     The sensors included in the sensing unit  1040  may include a proximity sensor, an illumination sensor, an accelerator sensor, a magnetic sensor, a gyro sensor, an inertial sensor, a red, green, blue (RGB) sensor, an IR sensor, a fingerprint recognition sensor, an ultrasonic sensor, an optical sensor, a microphone, a light detection and ranging (LiDAR), and a radar. 
     The output unit  1050  may generate a visual, auditory, or haptic output. 
     Accordingly, the output unit  1050  may include a display unit for outputting visual information, a speaker for outputting auditory information, and a haptic module for outputting haptic information. 
     The memory  1070  may store data that supports various functions of the AI device  1000 . For example, the memory  1070  may store input data acquired by the input unit  1020 , training data, a learning model, a learning history, and so on. 
     The processor  1080  may determine at least one executable operation of the AI device  100  based on information determined or generated by a data analysis algorithm or a machine learning algorithm. The processor  1080  may control the components of the AI device  1000  to execute the determined operation. 
     To this end, the processor  1080  may request, search, receive, or utilize data of the learning processor  1030  or the memory  1070 . The processor  1080  may control the components of the AI device  1000  to execute a predicted operation or an operation determined to be desirable among the at least one executable operation. 
     When the determined operation needs to be performed in conjunction with an external device, the processor  1080  may generate a control signal for controlling the external device and transmit the generated control signal to the external device. 
     The processor  1080  may acquire intention information with respect to a user input and determine the user&#39;s requirements based on the acquired intention information. 
     The processor  1080  may acquire the intention information corresponding to the user input by using at least one of a speech to text (STT) engine for converting a speech input into a text string or a natural language processing (NLP) engine for acquiring intention information of a natural language. 
     At least one of the STT engine or the NLP engine may be configured as an ANN, at least part of which is trained according to the machine learning algorithm. At least one of the STT engine or the NLP engine may be trained by the learning processor, a learning processor of the AI server, or distributed processing of the learning processors. For reference, specific components of the AI server are illustrated in  FIG. 11 . 
     The processor  1080  may collect history information including the operation contents of the AI device  1000  or the user&#39;s feedback on the operation and may store the collected history information in the memory  1070  or the learning processor  1030  or transmit the collected history information to the external device such as the AI server. The collected history information may be used to update the learning model. 
     The processor  1080  may control at least a part of the components of AI device  1000  so as to drive an application program stored in the memory  1070 . Furthermore, the processor  1080  may operate two or more of the components included in the AI device  1000  in combination so as to drive the application program. 
       FIG. 11  illustrates an AI server  1120  in accordance with some embodiments. 
     Referring to  FIG. 11 , the AI server  1120  may refer to a device that trains an ANN by a machine learning algorithm or uses a trained ANN. The AI server  1120  may include a plurality of servers to perform distributed processing, or may be defined as a 5G network. The AI server  1120  may be included as part of the AI device  1100 , and perform at least part of the AI processing. 
     The AI server  1120  may include a communication unit  1121 , a memory  1123 , a learning processor  1122 , a processor  1126 , and so on. 
     The communication unit  1121  may transmit and receive data to and from an external device such as the AI device  1100 . 
     The memory  1123  may include a model storage  1124 . The model storage  1124  may store a model (or an ANN  1125 ) which has been trained or is being trained through the learning processor  1122 . 
     The learning processor  1122  may train the ANN  1125  by training data. The learning model may be used, while being loaded on the AI server  1120  of the ANN, or on an external device such as the AI device  1110 . 
     The learning model may be implemented in hardware, software, or a combination of hardware and software. If all or part of the learning model is implemented in software, one or more instructions of the learning model may be stored in the memory  1123 . 
     The processor  1126  may infer a result value for new input data by using the learning model and may generate a response or a control command based on the inferred result value. 
       FIG. 12  illustrates an AI system in accordance with some embodiments. 
     Referring to  FIG. 12 , in the AI system, at least one of an AI server  1260 , a robot  1210 , a self-driving vehicle  1220 , an XR device  1230 , a smartphone  1240 , or a home appliance  1250  is connected to a cloud network  1200 . The robot  1210 , the self-driving vehicle  1220 , the XR device  1230 , the smartphone  1240 , or the home appliance  1250 , to which AI is applied, may be referred to as an AI device. 
     The cloud network  1200  may refer to a network that forms part of cloud computing infrastructure or exists in the cloud computing infrastructure. The cloud network  1200  may be configured by using a 3G network, a 4G or LTE network, or a 5G network. 
     That is, the devices  1210  to  1260  included in the AI system may be interconnected via the cloud network  1200 . In particular, each of the devices  1210  to  1260  may communicate with each other directly or through a BS. 
     The AI server  1260  may include a server that performs AI processing and a server that performs computation on big data. 
     The AI server  1260  may be connected to at least one of the AI devices included in the AI system, that is, at least one of the robot  1210 , the self-driving vehicle  1220 , the XR device  1230 , the smartphone  1240 , or the home appliance  1250  via the cloud network  1200 , and may assist at least part of AI processing of the connected AI devices  1210  to  1250 . 
     The AI server  1260  may train the ANN according to the machine learning algorithm on behalf of the AI devices  1210  to  1250 , and may directly store the learning model or transmit the learning model to the AI devices  1210  to  1250 . 
     The AI server  1260  may receive input data from the AI devices  1210  to  1250 , infer a result value for received input data by using the learning model, generate a response or a control command based on the inferred result value, and transmit the response or the control command to the AI devices  1210  to  1250 . 
     Alternatively, the AI devices  1210  to  1250  may infer the result value for the input data by directly using the learning model, and generate the response or the control command based on the inference result. 
     Hereinafter, various embodiments of the AI devices  1210  to  1250  to which the above-described technology is applied will be described. The AI devices  1210  to  1250  illustrated in  FIG. 12  may be regarded as a specific embodiment of the AI device  1000  illustrated in  FIG. 10 . 
     &lt;AI+XR&gt; 
     The XR device  1230 , to which AI is applied, may be configured as a HMD, a HUD provided in a vehicle, a TV, a portable phone, a smartphone, a computer, a wearable device, a home appliance, a digital signage, a vehicle, a fixed robot, a mobile robot, or the like. 
     The XR device  1230  may acquire information about a surrounding space or a real object by analyzing 3D point cloud data or image data acquired from various sensors or an external device and thus generating position data and attribute data for the 3D points, and may render an XR object to be output. For example, the XR device  1230  may output an XR object including additional information about a recognized object in correspondence with the recognized object. 
     The XR device  1230  may perform the above-described operations by using the learning model composed of at least one ANN. For example, the XR device  1230  may recognize a real object from 3D point cloud data or image data by using the learning model, and may provide information corresponding to the recognized real object. The learning model may be trained directly by the XR device  1230  or by the external device such as the AI server  1260 . 
     While the XR device  1230  may operate by generating a result by directly using the learning model, the XR device  1230  may operate by transmitting sensor information to the external device such as the AI server  1260  and receiving the result. 
     &lt;AI+Robot+XR&gt; 
     The robot  1210 , to which AI and XR are applied, may be implemented as a guide robot, a delivery robot, a cleaning robot, a wearable robot, an entertainment robot, a pet robot, an unmanned flying robot, a drone, or the like. 
     The robot  1210 , to which XR is applied, may refer to a robot to be controlled/interact within an XR image. In this case, the robot  1210  may be distinguished from the XR device  1230  and interwork with the XR device  1230 . 
     When the robot  1210  to be controlled/interact within an XR image acquires sensor information from sensors each including a camera, the robot  1210  or the XR device  1230  may generate an XR image based on the sensor information, and the XR device  1230  may output the generated XR image. The robot  1210  may operate based on the control signal received through the XR device  1230  or based on the user&#39;s interaction. 
     For example, the user may check an XR image corresponding to a view of the robot  1210  interworking remotely through an external device such as the XR device  1210 , adjust a self-driving route of the robot  1210  through interaction, control the operation or driving of the robot  1210 , or check information about an ambient object around the robot  1210 . 
     &lt;AI+Self-Driving+XR&gt; 
     The self-driving vehicle  1220 , to which AI and XR are applied, may be implemented as a mobile robot, a vehicle, an unmanned flying vehicle, or the like. 
     The self-driving driving vehicle  1220 , to which XR is applied, may refer to a self-driving vehicle provided with a means for providing an XR image or a self-driving vehicle to be controlled/interact within an XR image. Particularly, the self-driving vehicle  1220  to be controlled/interact within an XR image may be distinguished from the XR device  1230  and interwork with the XR device  1230 . 
     The self-driving vehicle  1220  provided with the means for providing an XR image may acquire sensor information from the sensors each including a camera and output the generated XR image based on the acquired sensor information. For example, the self-driving vehicle  1220  may include an HUD to output an XR image, thereby providing a passenger with an XR object corresponding to a real object or an object on the screen. 
     When the XR object is output to the HUD, at least part of the XR object may be output to be overlaid on an actual object to which the passenger&#39;s gaze is directed. When the XR object is output to a display provided in the self-driving vehicle  1220 , at least part of the XR object may be output to be overlaid on the object within the screen. For example, the self-driving vehicle  1220  may output XR objects corresponding to objects such as a lane, another vehicle, a traffic light, a traffic sign, a two-wheeled vehicle, a pedestrian, a building, and so on. 
     When the self-driving vehicle  1220  to be controlled/interact within an XR image acquires sensor information from the sensors each including a camera, the self-driving vehicle  1220  or the XR device  1230  may generate the XR image based on the sensor information, and the XR device  1230  may output the generated XR image. The self-driving vehicle  1220  may operate based on a control signal received through an external device such as the XR device  1230  or based on the user&#39;s interaction. 
     VR, AR, and MR technologies of the present disclosure are applicable to various devices, particularly, for example, a HMD, a HUD attached to a vehicle, a portable phone, a tablet PC, a laptop computer, a desktop computer, a TV, and a signage. The VR, AR, and MR technologies may also be applicable to a device equipped with a flexible or rollable display. 
     The above-described VR, AR, and MR technologies may be implemented based on CG and distinguished by the ratios of a CG image in an image viewed by the user. 
     That is, VR provides a real object or background only in a CG image, whereas AR overlays a virtual CG image on an image of a real object. 
     MR is similar to AR in that virtual objects are mixed and combined with a real world. However, a real object and a virtual object created as a CG image are distinctive from each other and the virtual object is used to complement the real object in AR, whereas a virtual object and a real object are handled equally in MR. More specifically, for example, a hologram service is an MR representation. 
     These days, VR, AR, and MR are collectively called XR without distinction among them. Therefore, embodiments of the present disclosure are applicable to all of VR, AR, MR, and XR. 
     For example, wired/wireless communication, input interfacing, output interfacing, and computing devices are available as hardware (HW)-related element techniques applied to VR, AR, MR, and XR. Further, tracking and matching, speech recognition, interaction and user interfacing, location-based service, search, and AI are available as software (SW)-related element techniques. 
     Particularly, the embodiments of the present disclosure are intended to address at least one of the issues of communication with another device, efficient memory use, data throughput decrease caused by inconvenient user experience/user interface (UX/UI), video, sound, motion sickness, or other issues. 
       FIG. 13  is a block diagram illustrating an XR device according to embodiments of the present disclosure. The XR device  1300  includes a camera  1310 , a display  1320 , a sensor  1330 , a processor  1340 , a memory  1350 , and a communication module  1360 . Obviously, one or more of the modules may be deleted or modified, and one or more modules may be added to the modules, when needed, without departing from the scope and spirit of the present disclosure. 
     The communication module  1360  may communicate with an external device or a server, wiredly or wirelessly. The communication module  1360  may use, for example, Wi-Fi, Bluetooth, or the like, for short-range wireless communication, and for example, a 3GPP communication standard for long-range wireless communication. LTE is a technology beyond 3GPP TS 36.xxx Release 8. Specifically, LTE beyond 3GPP TS 36.xxx Release 10 is referred to as LTE-A, and LTE beyond 3GPP TS 36.xxx Release 13 is referred to as LTE-A pro. 3GPP 5G refers to a technology beyond TS 36.xxx Release 15 and a technology beyond TS 38.XXX Release 15. Specifically, the technology beyond TS 38.xxx Release 15 is referred to as 3GPP NR, and the technology beyond TS 36.xxx Release 15 is referred to as enhanced LTE. “xxx” represents the number of a technical specification. LTE/NR may be collectively referred to as a 3GPP system. 
     The camera  1310  may capture an ambient environment of the XR device  1300  and convert the captured image to an electric signal. The image, which has been captured and converted to an electric signal by the camera  1310 , may be stored in the memory  1350  and then displayed on the display  1320  through the processor  1340 . Further, the image may be displayed on the display  1320  by the processor  1340 , without being stored in the memory  1350 . Further, the camera  110  may have a field of view (FoV). The FoV is, for example, an area in which a real object around the camera  1310  may be detected. The camera  1310  may detect only a real object within the FoV. When a real object is located within the FoV of the camera  1310 , the XR device  1300  may display an AR object corresponding to the real object. Further, the camera  1310  may detect an angle between the camera  1310  and the real object. 
     The sensor  1330  may include at least one sensor. For example, the sensor  1330  includes a sensing means such as a gravity sensor, a geomagnetic sensor, a motion sensor, a gyro sensor, an accelerator sensor, an inclination sensor, a brightness sensor, an altitude sensor, an olfactory sensor, a temperature sensor, a depth sensor, a pressure sensor, a bending sensor, an audio sensor, a video sensor, a global positioning system (GPS) sensor, and a touch sensor. Further, although the display  1320  may be of a fixed type, the display  1320  may be configured as a liquid crystal display (LCD), an organic light emitting diode (OLED) display, an electroluminescent display (ELD), or a micro LED (M-LED) display, to have flexibility. Herein, the sensor  1330  is designed to detect a bending degree of the display  1320  configured as the afore-described LCD, OLED display, ELD, or M-LED display. 
     The memory  1350  is equipped with a function of storing all or a part of result values obtained by wired/wireless communication with an external device or a service as well as a function of storing an image captured by the camera  1310 . Particularly, considering the trend toward increased communication data traffic (e.g., in a 5G communication environment), efficient memory management is required. In this regard, a description will be given below with reference to  FIG. 14 . 
       FIG. 14  is a detailed block diagram of the memory  1350  illustrated in  FIG. 13 . With reference to  FIG. 14 , a swap-out process between a random access memory (RAM) and a flash memory in accordance with some embodiments will be described. 
     When swapping out AR/VR page data from a RAM  1410  to a flash memory  1420 , a controller  1430  may swap out only one of two or more AR/VR page data of the same contents among AR/VR page data to be swapped out to the flash memory  1420 . 
     That is, the controller  1430  may calculate an identifier (e.g., a hash function) that identifies each of the contents of the AR/VR page data to be swapped out, and determine that two or more AR/VR page data having the same identifier among the calculated identifiers contain the same contents. Accordingly, the problem that the lifetime of an AR/VR device including the flash memory  1420  as well as the lifetime of the flash memory  1420  is reduced because unnecessary AR/VR page data is stored in the flash memory  1420  may be overcome. 
     The operations of the controller  1430  may be implemented in software or hardware without departing from the scope of the present disclosure. More specifically, the memory illustrated in  FIG. 14  is included in a HMD, a vehicle, a portable phone, a tablet PC, a laptop computer, a desktop computer, a TV, a signage, or the like, and executes a swap function. 
     A device according to embodiments of the present disclosure may process 3D point cloud data to provide various services such as VR, AR, MR, XR, and self-driving to a user. 
     A sensor collecting 3D point cloud data may be any of, for example, a LiDAR, a red, green, blue depth (RGB-D), and a 3D laser scanner. The sensor may be mounted inside or outside of a HMD, a vehicle, a portable phone, a tablet PC, a laptop computer, a desktop computer, a TV, a signage, or the like. 
       FIG. 15  illustrates a point cloud data processing system. 
     Referring to  FIG. 15 , a point cloud processing system  1500  includes a transmission device which acquires, encodes, and transmits point cloud data, and a reception device which acquires point cloud data by receiving and decoding video data. As illustrated in  FIG. 15 , point cloud data according to embodiments of the present disclosure may be acquired by capturing, synthesizing, or generating the point cloud data (S 1510 ). During the acquisition, data (e.g., a polygon file format or standard triangle format (PLY) file) of 3D positions (x, y, z)/attributes (color, reflectance, transparency, and so on) of points may be generated. For a video of multiple frames, one or more files may be acquired. Point cloud data-related metadata (e.g., metadata related to capturing) may be generated during the capturing. The transmission device or encoder according to embodiments of the present disclosure may encode the point cloud data by video-based point cloud compression (V-PCC) or geometry-based point cloud compression (G-PCC), and output one or more video streams (S 1520 ). V-PCC is a scheme of compressing point cloud data based on a 2D video codec such as high efficiency video coding (HEVC) or versatile video coding (VVC), G-PCC is a scheme of encoding point cloud data separately into two streams: geometry and attribute. The geometry stream may be generated by reconstructing and encoding position information about points, and the attribute stream may be generated by reconstructing and encoding attribute information (e.g., color) related to each point. In V-PCC, despite compatibility with a 2D video, much data is required to recover V-PCC-processed data (e.g., geometry video, attribute video, occupancy map video, and auxiliary information), compared to G-PCC, thereby causing a long latency in providing a service. One or more output bit streams may be encapsulated along with related metadata in the form of a file (e.g., a file format such as ISOBMFF) and transmitted over a network or through a digital storage medium (S 1530 ). 
     The device or processor according to embodiments of the present disclosure may acquire one or more bit streams and related metadata by decapsulating the received video data, and recover 3D point cloud data by decoding the acquired bit streams in V-PCC or G-PCC (S 1540 ). A renderer may render the decoded point cloud data and provide content suitable for VR/AR/MR/service to the user on a display (S 1550 ). 
     As illustrated in  FIG. 15 , the device or processor according to embodiments of the present disclosure may perform a feedback process of transmitting various pieces of feedback information acquired during the rendering/display to the transmission device or to the decoding process (S 1560 ). The feedback information according to embodiments of the present disclosure may include head orientation information, viewport information indicating an area that the user is viewing, and so on. Because the user interacts with a service (or content) provider through the feedback process, the device according to embodiments of the present disclosure may provide a higher data processing speed by using the afore-described V-PCC or G-PCC scheme or may enable clear video construction as well as provide various services in consideration of high user convenience. 
       FIG. 16  is a block diagram of an XR device  1600  including a learning processor. Compared to  FIG. 13 , only a learning processor  1670  is added, and thus a redundant description is avoided because  FIG. 13  may be referred to for the other components. 
     Referring to  FIG. 16 , the XR device  1600  may be loaded with a learning model. The learning model may be implemented in hardware, software, or a combination of hardware and software. If the whole or part of the learning model is implemented in software, one or more instructions that form the learning model may be stored in a memory  1650 . 
     According to embodiments of the present disclosure, a learning processor  1670  may be coupled communicably to a processor  1640 , and repeatedly train a model including ANNs by using training data. An ANN is an information processing system in which multiple neurons are linked in layers, modeling an operation principle of biological neurons and links between neurons. An ANN is a statistical learning algorithm inspired by a neural network (particularly the brain in the central nervous system of an animal) in machine learning and cognitive science. Machine learning is one field of AI, in which the ability of learning without an explicit program is granted to a computer. Machine learning is a technology of studying and constructing a system for learning, predicting, and improving its capability based on empirical data, and an algorithm for the system. Therefore, according to embodiments of the present disclosure, the learning processor  1670  may infer a result value from new input data by determining optimized model parameters of an ANN. Therefore, the learning processor  1670  may analyze a device use pattern of a user based on device use history information about the user. Further, the learning processor  1670  may be configured to receive, classify, store, and output information to be used for data mining, data analysis, intelligent decision, and a machine learning algorithm and technique. 
     According to embodiments of the present disclosure, the processor  1640  may determine or predict at least one executable operation of the device based on data analyzed or generated by the learning processor  1670 . Further, the processor  1640  may request, search, receive, or use data of the learning processor  1670 , and control the XR device  1600  to perform a predicted operation or an operation determined to be desirable among the at least one executable operation. According to embodiments of the present disclosure, the processor  1640  may execute various functions of realizing intelligent emulation (i.e., knowledge-based system, reasoning system, and knowledge acquisition system). The various functions may be applied to an adaptation system, a machine learning system, and various types of systems including an ANN (e.g., a fuzzy logic system). That is, the processor  1640  may predict a user&#39;s device use pattern based on data of a use pattern analyzed by the learning processor  1670 , and control the XR device  1600  to provide a more suitable XR service to the UE. Herein, the XR service includes at least one of the AR service, the VR service, or the MR service. 
       FIG. 17  illustrates a process of providing an XR service by the XR service  1600  of the present disclosure illustrated in  FIG. 16 . 
     According to embodiments of the present disclosure, the processor  1670  may store device use history information about a user in the memory  1650  (S 1710 ). The device use history information may include information about the name, category, and contents of content provided to the user, information about a time at which a device has been used, information about a place in which the device has been used, time information, and information about use of an application installed in the device. 
     According to embodiments of the present disclosure, the learning processor  1670  may acquire device use pattern information about the user by analyzing the device use history information (S 1720 ). For example, when the XR device  1600  provides specific content A to the user, the learning processor  1670  may learn information about a pattern of the device used by the user using the corresponding terminal by combining specific information about content A (e.g., information about the ages of users that generally use content A, information about the contents of content A, and content information similar to content A), and information about the time points, places, and number of times in which the user using the corresponding terminal has consumed content A. 
     According to embodiments of the present disclosure, the processor  1640  may acquire the user device pattern information generated based on the information learned by the learning processor  1670 , and generate device use pattern prediction information (S 1730 ). Further, when the user is not using the device  1600 , if the processor  1640  determines that the user is located in a place where the user has frequently used the device  1600 , or it is almost time for the user to usually use the device  1600 , the processor  1640  may indicate the device  1600  to operate. In this case, the device according to embodiments of the present disclosure may provide AR content based on the user pattern prediction information (S 1740 ). 
     When the user is using the device  1600 , the processor  1640  may check information about content currently provided to the user, and generate device use pattern prediction information about the user in relation to the content (e.g., when the user requests other related content or additional data related to the current content). Further, the processor  1640  may provide AR content based on the device use pattern prediction information by indicating the device  1600  to operate (S 1740 ). The AR content according to embodiments of the present disclosure may include an advertisement, navigation information, danger information, and so on. 
       FIG. 18  illustrates the outer appearances of an XR device and a robot. 
     Component modules of an XR device  1800  in accordance with some embodiments have been described before with reference to the previous drawings, and thus a redundant description is not provided herein. 
     The outer appearance of a robot  1810  illustrated in  FIG. 18  is merely an example, and the robot  1810  may be implemented to have various outer appearances according to the present disclosure. For example, the robot  1810  illustrated in  FIG. 18  may be a drone, a cleaner, a cook root, a wearable robot, or the like. Particularly, each component of the robot  1810  may be disposed at a different position such as up, down, left, right, back, or forth according to the shape of the robot  1810 . 
     The robot  1810  may be provided, on the exterior thereof, with various sensors to identify ambient objects. Further, to provide specific information to a user, the robot  1810  may be provided with an interface unit  1811  on top or the rear surface  1812  thereof. 
     To sense movement of the robot  1810  and an ambient object, and control the robot  1810 , a robot control module  1850  is mounted inside the robot  1810 . The robot control module  1850  may be implemented as a software module or a hardware chip with the software module implemented therein. The robot control module  1850  may include a deep learner  1851 , a sensing information processor  1852 , a movement path generator  1853 , and a communication module  1854 . 
     The sensing information processor  1852  collects and processes information sensed by various types of sensors (e.g., a LiDAR sensor, an IR sensor, an ultrasonic sensor, a depth sensor, an image sensor, and a microphone) arranged in the robot  1810 . 
     The deep learner  1851  may receive information processed by the sensing information processor  1851  or accumulative information stored during movement of the robot  1810 , and output a result required for the robot  1810  to determine an ambient situation, process information, or generate a moving path. 
     The moving path generator  1852  may calculate a moving path of the robot  1810  by using the data calculated by the deep learner  8151  or the data processed by the sensing information processor  1852 . 
     Because each of the XR device  1800  and the robot  1810  is provided with a communication module, the XR device  1800  and the robot  1810  may transmit and receive data by short-range wireless communication such as Wi-Fi or Bluetooth, or 5G long-range wireless communication. A technique of controlling the robot  1810  by using the XR device  1800  will be described below with reference to  FIG. 19 . 
       FIG. 19  is a flowchart illustrating a process of controlling a robot by using an XR device. 
     The XR device and the robot are connected communicably to a 5G network (S 1901 ). Obviously, the XR device and the robot may transmit and receive data by any other short-range or long-range communication technology without departing from the scope of the present disclosure. 
     The robot captures an image/video of the surroundings of the robot by means of at least one camera installed on the interior or exterior of the robot (S 1902 ) and transmits the captured image/video to the XR device (S 1903 ). The XR device displays the captured image/video (S 1904 ) and transmits a command for controlling the robot to the robot (S 1905 ). The command may be input manually by a user of the XR device or automatically generated by AI without departing from the scope of the disclosure. 
     The robot executes a function corresponding to the command received in step S 1905  (S 1906 ) and transmits a result value to the XR device (S 1907 ). The result value may be a general indicator indicating whether data has been successfully processed or not, a current captured image, or specific data in which the XR device is considered. The specific data is designed to change, for example, according to the state of the XR device. If a display of the XR device is in an off state, a command for turning on the display of the XR device is included in the result value in step S 1907 . Therefore, when an emergency situation occurs around the robot, even though the display of the remote XR device is turned off, a notification message may be transmitted. 
     AR/VR content is displayed according to the result value received in step S 1907  (S 1908 ). 
     According to another embodiment of the present disclosure, the XR device may display position information about the robot by using a GPS module attached to the robot. 
     The XR device  1300  described with reference to  FIG. 13  may be connected to a vehicle that provides a self-driving service in a manner that allows wired/wireless communication, or may be mounted on the vehicle that provides the self-driving service. Accordingly, various services including AR/VR may be provided even in the vehicle that provides the self-driving service. 
       FIG. 20  illustrates a vehicle that provides a self-driving service. 
     According to embodiments of the present disclosure, a vehicle  2010  may include a car, a train, and a motor bike as transportation means traveling on a road or a railway. According to embodiments of the present disclosure, the vehicle  2010  may include all of an internal combustion engine vehicle provided with an engine as a power source, a hybrid vehicle provided with an engine and an electric motor as a power source, and an electric vehicle provided with an electric motor as a power source. 
     According to embodiments of the present disclosure, the vehicle  2010  may include the following components in order to control operations of the vehicle  2010 : a user interface device, an object detection device, a communication device, a driving maneuver device, a main electronic control unit (ECU), a drive control device, a self-driving device, a sensing unit, and a position data generation device. 
     Each of the user interface device, the object detection device, the communication device, the driving maneuver device, the main ECU, the drive control device, the self-driving device, the sensing unit, and the position data generation device may generate an electric signal, and be implemented as an electronic device that exchanges electric signals. 
     The user interface device may receive a user input and provide information generated from the vehicle  2010  to a user in the form of a UI or UX. The user interface device may include an input/output (I/O) device and a user monitoring device. The object detection device may detect the presence or absence of an object outside of the vehicle  2010 , and generate information about the object. The object detection device may include at least one of, for example, a camera, a LiDAR, an IR sensor, or an ultrasonic sensor. The camera may generate information about an object outside of the vehicle  2010 . The camera may include one or more lenses, one or more image sensors, and one or more processors for generating object information. The camera may acquire information about the position, distance, or relative speed of an object by various image processing algorithms. Further, the camera may be mounted at a position where the camera may secure an FoV in the vehicle  2010 , to capture an image of the surroundings of the vehicle  1020 , and may be used to provide an AR/VR-based service. The LiDAR may generate information about an object outside of the vehicle  2010 . The LiDAR may include a light transmitter, a light receiver, and at least one processor which is electrically coupled to the light transmitter and the light receiver, processes a received signal, and generates data about an object based on the processed signal. 
     The communication device may exchange signals with a device (e.g., infrastructure such as a server or a broadcasting station), another vehicle, or a terminal) outside of the vehicle  2010 . The driving maneuver device is a device that receives a user input for driving. In manual mode, the vehicle  2010  may travel based on a signal provided by the driving maneuver device. The driving maneuver device may include a steering input device (e.g., a steering wheel), an acceleration input device (e.g., an accelerator pedal), and a brake input device (e.g., a brake pedal). 
     The sensing unit may sense a state of the vehicle  2010  and generate state information. The position data generation device may generate position data of the vehicle  2010 . The position data generation device may include at least one of a GPS or a differential global positioning system (DGPS). The position data generation device may generate position data of the vehicle  2010  based on a signal generated from at least one of the GPS or the DGPS. The main ECU may provide overall control to at least one electronic device provided in the vehicle  2010 , and the drive control device may electrically control a vehicle drive device in the vehicle  2010 . 
     The self-driving device may generate a path for the self-driving service based on data acquired from the object detection device, the sensing unit, the position data generation device, and so on. The self-driving device may generate a driving plan for driving along the generated path, and generate a signal for controlling movement of the vehicle according to the driving plan. The signal generated from the self-driving device is transmitted to the drive control device, and thus the drive control device may control the vehicle drive device in the vehicle  2010 . 
     As illustrated in  FIG. 20 , the vehicle  2010  that provides the self-driving service is connected to an XR device  2000  in a manner that allows wired/wireless communication. The XR device  2000  may include a processor  2001  and a memory  2002 . While not shown, the XR device  2000  of  FIG. 20  may further include the components of the XR device  1300  described before with reference to  FIG. 13 . 
     If the XR device  2000  is connected to the vehicle  2010  in a manner that allows wired/wireless communication. The XR device  2000  may receive/process AR/VR service-related content data that may be provided along with the self-driving service, and transmit the received/processed AR/VR service-related content data to the vehicle  2010 . Further, when the XR device  2000  is mounted on the vehicle  2010 , the XR device  2000  may receive/process AR/VR service-related content data according to a user input signal received through the user interface device and provide the received/processed AR/VR service-related content data to the user. In this case, the processor  2001  may receive/process the AR/VR service-related content data based on data acquired from the object detection device, the sensing unit, the position data generation device, the self-driving device, and so on. According to embodiments of the present disclosure, the AR/VR service-related content data may include entertainment content, weather information, and so on which are not related to the self-driving service as well as information related to the self-driving service such as driving information, path information for the self-driving service, driving maneuver information, vehicle state information, and object information. 
       FIG. 21  illustrates a process of providing an AR/VR service during a self-driving service. 
     According to embodiments of the present disclosure, a vehicle or a user interface device may receive a user input signal (S 2110 ). According to embodiments of the present disclosure, the user input signal may include a signal indicating a self-driving service. According to embodiments of the present disclosure, the self-driving service may include a full self-driving service and a general self-driving service. The full self-driving service refers to perfect self-driving of a vehicle to a destination without a user&#39;s manual driving, whereas the general self-driving service refers to driving a vehicle to a destination through a user&#39;s manual driving and self-driving in combination. 
     It may be determined whether the user input signal according to embodiments of the present disclosure corresponds to the full self-driving service (S 2120 ). When it is determined that the user input signal corresponds to the full self-driving service, the vehicle according to embodiments of the present disclosure may provide the full self-driving service (S 2130 ). Because the full self-driving service does not need the user&#39;s manipulation, the vehicle according to embodiments of the present disclosure may provide VR service-related content to the user through a window of the vehicle, a side mirror of the vehicle, an HMD, or a smartphone (S 2130 ). The VR service-related content according to embodiments of the present disclosure may be content related to full self-driving (e.g., navigation information, driving information, and external object information), and may also be content which is not related to full self-driving according to user selection (e.g., weather information, a distance image, a nature image, and a voice call image). 
     If it is determined that the user input signal does not correspond to the full self-driving service, the vehicle according to embodiments of the present disclosure may provide the general self-driving service (S 2140 ). Because the FoV of the user should be secured for the user&#39;s manual driving in the general self-driving service, the vehicle according to embodiments of the present disclosure may provide AR service-related content to the user through a window of the vehicle, a side mirror of the vehicle, an HMD, or a smartphone (S 2140 ). 
     The AR service-related content according to embodiments of the present disclosure may be content related to full self-driving (e.g., navigation information, driving information, and external object information), and may also be content which is not related to self-driving according to user selection (e.g., weather information, a distance image, a nature image, and a voice call image). 
     While the present disclosure is applicable to all the fields of 5G communication, robot, self-driving, and AI as described before, the following description will be given mainly of the present disclosure applicable to an XR device with reference to following figures. 
       FIG. 22  is a conceptual diagram illustrating an exemplary method for implementing the XR device using an HMD type in accordance with some embodiments. The above-mentioned embodiments may also be implemented in HMD types shown in  FIG. 22 . 
     The HMD-type XR device  100   a  shown in  FIG. 22  may include a communication unit  110 , a control unit  120 , a memory unit  130 , an input/output (I/O) unit  140   a , a sensor unit  140   b , a power-supply unit  140   c , etc. Specifically, the communication unit  110  embedded in the XR device  10   a  may communicate with a mobile terminal  100   b  by wire or wirelessly. 
       FIG. 23  is a conceptual diagram illustrating an exemplary method for implementing an XR device using AR glasses in accordance with some embodiments. The above-mentioned embodiments may also be implemented in AR glass types shown in  FIG. 23 . 
     Referring to  FIG. 23 , the AR glasses may include a frame, a control unit  200 , and an optical display unit  300 . 
     Although the frame may be formed in a shape of glasses worn on the face of the user  10  as shown in  FIG. 23 , the scope or spirit of the present disclosure is not limited thereto, and it should be noted that the frame may also be formed in a shape of goggles worn in close contact with the face of the user  10 . 
     The frame may include a front frame  110  and first and second side frames. 
     The front frame  110  may include at least one opening, and may extend in a first horizontal direction (i.e., an X-axis direction). The first and second side frames may extend in the second horizontal direction (i.e., a Y-axis direction) perpendicular to the front frame  110 , and may extend in parallel to each other. 
     The control unit  200  may generate an image to be viewed by the user  10  or may generate the resultant image formed by successive images. The control unit  200  may include an image source configured to create and generate images, a plurality of lenses configured to diffuse and converge light generated from the image source, and the like. The images generated by the control unit  200  may be transferred to the optical display unit  300  through a guide lens P 200  disposed between the control unit  200  and the optical display unit  300 . 
     The controller  200  may be fixed to any one of the first and second side frames. For example, the control unit  200  may be fixed to the inside or outside of any one of the side frames, or may be embedded in and integrated with any one of the side frames. 
     The optical display unit  300  may be formed of a translucent material, so that the optical display unit  300  can display images created by the control unit  200  for recognition of the user  10  and can allow the user to view the external environment through the opening. 
     The optical display unit  300  may be inserted into and fixed to the opening contained in the front frame  110 , or may be located at the rear surface (interposed between the opening and the user  10 ) of the opening so that the optical display unit  300  may be fixed to the front frame  110 . For example, the optical display unit  300  may be located at the rear surface of the opening, and may be fixed to the front frame  110  as an example. 
     Referring to the XR device shown in  FIG. 23 , when images are incident upon an incident region S 1  of the optical display unit  300  by the control unit  200 , image light may be transmitted to an emission region S 2  of the optical display unit  300  through the optical display unit  300 , images created by the controller  200  can be displayed for recognition of the user  10 . 
     Accordingly, the user  10  may view the external environment through the opening of the frame  100 , and at the same time may view the images created by the control unit  200 . 
     As described above, although methods described herein can be applied to all the 5G communication technology, robot technology, autonomous driving technology, and Artificial Intelligence (AI) technology, following figures illustrate various examples of the present disclosure applicable to multimedia devices such as XR devices, digital signage, and TVs for convenience of description. However, it should be understood that other embodiments implemented by those skilled in the art by combining the examples of the following figures with each other by referring to the examples of the previous figures are also within the scope of the present disclosure. 
     In some embodiments, the multimedia device (or a device) described in the following figures can be implemented as any of devices each having a display function without departing from the scope or spirit of the present disclosure, so that the multimedia device is not limited to the XR device and corresponds to the user equipment (UE) described with respect to  FIGS. 1 to 9  and the multimedia device shown in the following figures can additionally perform 5G communication. 
     The XR device (or a device) for providing XR content may provide a virtual fitting service (or AR fitting service). In some embodiments, the virtual fitting service refers to an XR service provided to minimize the inconvenience of a user who wears a plurality of clothes when purchasing clothes. However, using excessive user selection signals are required in process for using the XR service may cause significant burden on the user. In addition, less user interaction with the device may make the XR environment tedious and less user-friendly XR content. Accordingly, the device for providing XR content may provide information on styling corresponding to a combination of one or more items in accordance with a user selection so as to provide user-friendly XR content and enhance user experience at the same time. 
     In some embodiments, the device for providing XR content provides an XR image such as an avatar generated based on an image representing the user&#39;s appearance, and one or more virtual clothing items (e.g., a T-shirt, jeans, etc.) so that the device can provide XR content including the avatar wearing one or more items in accordance with the user&#39;s selection signal. For example, in response to a user input signal for representing (or selecting) a T-shirt and jeans, the device provides the XR content including the avatar wearing the selected T-shirts and jeans. In addition, in some embodiments, the device for providing XR content may present a plurality of fashion styles (or styling) by changing such a shape of the selected item for the same time or changing the pre-selected time to another item in accordance with the user input signal. Moreover, the device provides information regarding various stylings that correspond to one or more items selected in accordance with the user selection and provide information on recommendation items suitable for respective styling. 
     In some embodiments, since the XR content include an avatar generated based on the exact body size of the user, it may provide more realistic user experience. In addition, the device may provide XR content representing various stylings in accordance with a combination of one or more items selected by the user, and thus may provide more various XR content environments. 
     The XR device may provide XR content in which the styling of each item is changed in accordance with a user input signal, thereby providing more user-friendly XR content. 
     The XR device may recommend additional items suitable for styling generated by a combination of one or more items for high user convenience. 
       FIG. 24  illustrates an example of a user using an application that provides XR content. 
     The left part of  FIG. 24  illustrates an example  2400  of a scanning operation by which a user recognizes a space (e.g., a physical space, a real space) to use an application for providing XR content (e.g., VR content, AR content, MR content, etc.). The scanning operation in accordance with some embodiments is intended to recognize a space to secure information about a space represented by a real image and/or video (for example, whether a real object is present in the space) obtained by analyzing the obtained real image and/or video. The device in accordance with some embodiments may provide XR content generated by combining the real image representing a space based on the scanning operation with an image representing one or more virtual objects that may be located in the space. In accordance with some embodiments, the XR content (or content) may be provided to a user through an application. In accordance with some embodiments, the application (or app) is application software, which represents a program or a set of programs designed for a user. In accordance with some embodiments, an application may be installed on the device, executed, stopped, or terminated by a user input signal (e.g., a touch gesture, an input signal of a remote controller, an input signal of a mouse, etc.). Accordingly, the user may execute one or more apps to generate and provide XR content representing a space in which one or more real objects and one or more virtual objects are located. For example, in accordance with some embodiments, the device may provide the user with content representing a real space in which a virtual floor stand (virtual object) and a chair (real object) are located. In this case, the device may determine whether sufficient space is required to place a virtual object in the space shown in the real image. If the virtual object is placed without determining whether sufficient space for placing the virtual object is required, the image representing the virtual object and the image representing the real object may overlap with each other and be displayed. Such content may hinder a user&#39;s realistic XR experience. Even when the image representing the virtual object and the image representing the real object do not overlap with each other, XR content having a virtual object placed without taking into consideration an area in the space occupied by the real object (e.g., the size of the virtual object, the location and/or orientation of the virtual object, etc.) may hinder immersion of the user in the content. 
     The right part of  FIG. 24  illustrates an example  2410  in which a device in accordance with some embodiments provides a message  2420  to a user. As shown in the example  2410 , when content representing a space in which a virtual object is located according to execution of a user application cannot be provided, the device  2410  may provide the user with a message indicating that the device has not found a space for locating the object. That is, the user may check whether a virtual object can be located in the space after the scanning operation is performed. The scanning operation generally takes a long time of about 10 minutes, and accordingly the user may recognize the possibility of the virtual object being located or executability of an application for providing content representing a space where a virtual object is located after waiting for a long time. Such a configuration may increase user inconvenience and provide only a low-quality user experience. 
     Therefore, in some embodiments, the device may use one or more algorithms to quickly identify a space in which one or more real objects are located to determine whether one or more virtual objects can be correctly located. In addition, in some embodiments, the device may preferentially provide the user with information about whether an application for providing the content representing the space in which the one or more virtual objects are located is executable. That is, the device in accordance with the embodiments may provide more realistic XR content. In addition, the device in accordance with the embodiments may enhance user convenience and provide various user experiences. 
       FIG. 25  is a block diagram illustrating a device in accordance with some embodiments. 
     The device  2500  illustrated in  FIG. 25  may perform the functions/operations described with reference to  FIGS. 1 to 24 . In addition, although not illustrated in the figure, the device  2500  in  FIG. 25  may further include a module configured to perform the functions/operations described with reference to  FIGS. 1 to 24 . 
     The device  2500  may include an image/video receiver  2510 , an image/video processor  2520 , a display  2530 , and a controller  2540 . Although not shown in  FIG. 25 , the device  2500  in accordance with some embodiments of the present disclosure may include one or more modules (elements) configured to perform one or more of the functions/operations described with reference to  FIGS. 1 to 24 . 
     In accordance with some embodiments, the image/video receiver  2510  may obtain one or more real images and/or videos to recognize a space. The real image/or video in accordance with the embodiments may represent a space in which one or more real objects are located. The space in accordance with the embodiments may include an outdoor space as well as an indoor space such as an indoor space of a house, a building, or the like, and an indoor space of an autonomous vehicle. The image/video receiver  2510  in accordance with the embodiments may include one or more sensors. In addition, the image/video receiver  2510  may obtain a real image and/or video according to a user input signal. For example, when a user signal (e.g., a touch gesture, etc.) obtained through the display  2530  indicates an operation of the image/video receiver  2510 , the image/video receiver  2510  may obtain one or more real images and/or videos. The image/video receiver  2510  may transmit the obtained real images and/or videos to the image/video processor  2520 . 
     The image/video processor  2520  in accordance with the embodiments may analyze the obtained real image and/or video. The image/video processor  2520  may quickly analyze the real image and/or video using one or more algorithms for the scanning operation. The image/video processor  2520  may also obtain information about the space (e.g., presence or absence of one or more real objects in the space, an area occupied by the one or more real objects located in the space, or a region in which the real objects are located in the space, and the like) through the scanning operation. In accordance with some embodiments, the one or more algorithms may include a Simultaneous Localization and Mapping (SLAM) algorithm and a semantic segmentation algorithm. The image/video processor  2520  in accordance with the embodiments may determine whether one or more virtual objects may be located in the space, based on the obtained information. In accordance with some embodiments, the image/video processor  2520  may determine whether the application is executable based information about the one or more real objects (e.g., the number of the one or more real objects, the type of an area occupied by the one or more real objects in the space, the size of the area, etc.) and information about the virtual object (e.g., a type and size of an area required for locating the virtual object in the space, etc.). For example, when two chairs (real objects) are located in the space, and an application for locating a floor stand which is a virtual object is executed, the image/video processor  2520  may obtain information about the chairs (e.g., the number of chairs, the size (area) of the region where the chair occupies the floor, etc.). Based on the obtained information, the image/video processor  2520  may identify the type of an area (e.g., floor) required for locating the floor stand in the space and calculate the size (or area) of the area required for locating the floor stand. In addition, the image/video processor  2520  may determine whether the floor stand is allowed to be located in the space based on the pre-stored information on the type and size of the minimum area required for locating the floor stand in the space. 
     Based on the result of the determination, In addition, the image/video processor  2520  in accordance with the embodiments may generate information about whether an application for providing content representing the space in which one or more virtual objects are located is executable. In accordance with some embodiments, the information representing whether the application is executable may include a type of an area (e.g., wall, floor, table, etc.) required for locating the virtual object in the space, and the type of the area required for locating the virtual object in the space. When the image/video processor  2520  determines that the application is not executable, the image/video processor  2520  may learn information about an area in the space occupied by one or more real objects located in the space represented by the obtained real image, and generate, based on the result of the learning, information for obtaining an additional area of which size is required for executing the application. The information representing whether the application is executable is not limited to this embodiment and may include more information. 
     In accordance with some embodiments, the display  2530  may display an image (e.g., an application icon) representing one or more applications together with information about whether each application is executable. The information about whether each application is executable may be represented by an image (e.g., a graphic image including a figure representing a table, an icon for representing an area size, and an indicator). In accordance with some embodiments, the image may represent the size of an area required for locating each of one or more virtual objects associated with one application in the space, or may represent the size of the entire area required for locating the one or more virtual objects associated with one application in the space (e.g., a value representing the size of the entire area required for locating the one or more objects in the space compared to the size of the remaining space except the area occupied by the real object). In accordance with some embodiments, the size of the image may be determined according to the size of the area required for locating the virtual object in the space. In addition, the size of the image may range from a minimum value to a maximum value. In addition, in accordance with some embodiments, the image may be color-processed with one or more colors representing whether the application is executable. In accordance with some embodiments, the one or more colors may include a first color (e.g., white) representing that the application is not executable, a second color (e.g., orange) representing that execution of the application is not decided, and a third color (e.g., green) representing that the application is executable. The first color, the second color, and the third color are different from each other. 
     The controller  2540  in accordance with the embodiments may control the overall operation of the device. The controller  2540  may be communicatively connected to the image/video receiver  2510 , the image/video analyzer  2520 , and the display  2530 . The controller  2540  may control the image/video receiver  2510  to obtain one or more real images and/or videos, control the image/video analyzer  2530  to analyze the obtained real images and/or videos, determine whether an application is executable, and generate information representing a result of the determination. In addition, the controller  2540  may control the display  2530  to display information representing whether the application is executable together with an image representing the application. 
     In some embodiments, one or more elements of the device  2500  depicted in  FIG. 25  (e.g., the image/video receiver  2510 , the image/video processor  2520 , the display  2530 , and the controller  2540 , etc.), can be implemented in hardware, software or firmware or a combination thereof, including one or more processors and/or integrated circuits that are communicable with a memory (not shown) of the device  2500 . The one or more processors run or execute various software programs and/or sets of instructions stored in the memory to perform various functions for the device  2500  for providing content and to process data. In some embodiments, the memory optionally includes high-speed random access memory and optionally also includes non-volatile memory, such as one or more magnetic disk storage devices, flash memory devices, or other non-volatile solid-state memory devices. The memory may include one or more programs including instructions in order to control operation of the image/video receiver  2510 , the image/video processor  2520 , the display  2530 , and the controller  2540 . In accordance with some embodiments, the program includes instructions to execute one or more algorithms. In some embodiments, the device  2500  further includes one or more elements not illustrated in  FIG. 25  for analogous functions/operations to functions/operations described with respect to  FIGS. 1-23 . 
     Accordingly, the device in accordance with the embodiments may provide the user with information about whether the application is executable together with the image of the application. In other words, the device may provide intuitive information to the user to maximize user convenience. 
       FIG. 26  illustrates an example of a space recognition method in accordance with some embodiments. 
     As described with reference to  FIG. 25 , the device (e.g., the image/video receiver  2510 ) in accordance with the embodiments may obtain a real image and/or video to recognize a space. 
     The left part of  FIG. 26  illustrates a field of view (FOV)  2601 , which is a range in which the device is capable of recognizing a space at a time when a user  2600  recognizes the space through the device in accordance with some embodiments. The size of the FOV  2601  in accordance with the embodiments may be determined (as, for example, 60 degrees, 70 degrees, 90 degrees, etc.) in consideration of an FOV that a person may perceive at one time. The device may obtain a real image and/or video having a size corresponding to the size of the FOV  2601 . The right part of  FIG. 26  illustrates a method  2610  by which the device recognizes a space through a full scanning operation. The full scanning operation is intended to augment a space represented by a real image with a virtual object, considering spatial characteristics. In accordance with some embodiments, the device may use a three-dimensional (3D) map generation algorithm, such as a Simultaneous Localization and Mapping (SLAM) algorithm or a 3D reconstruction algorithm. In order to recognize the space through the full scanning operation in accordance with the embodiments, detailed 3D information about the space including data obtained by observing a target at the closest distance is needed. As described above, the size of an image and/or video that may be obtained at a time in the FOV  2601  of the device is limited, as much information representing all parts of the space as possible is required for the device to obtain detailed information about the space which is a target of observation. Accordingly, the device in accordance with the embodiments may recognize the space by full scanning of the entire space by collecting an image and/or video obtained while the user moves from a first position  2611  to a second position  2612 , an image and/or video obtained while the user moves from the second position  2612  to a third position  2613 , and an image and/or video obtained while the user moves from the third position  2613  to a fourth position  2614  ( 2610 ). The method  2610  of recognizing the space through the full scanning operation requires more user movements and thus may not secure high user convenience. Further, the method may require generation of information such as a 3D map, thereby increasing complexity of operation of the device. 
       FIG. 27  illustrates an example of a 3D map generated through a SLAM algorithm in accordance with some embodiments. 
     As described with reference to  FIGS. 25 to 26 , a device (e.g., the image/video analyzer  2510 ) in accordance with some embodiments may obtain information about an area occupied by one or more real objects located in a space represented by a real image and/or video obtained using one or more algorithms. The left part of  FIG. 27  shows an example  2700  of applying the SLAM algorithm to the real image obtained by the device in accordance with the embodiments. The right part of  FIG. 27  shows an example  2710  of a 3D map generated through the SLAM algorithm. 
       FIG. 28  illustrates an example of a space recognition method in accordance with some embodiments. 
     As described with reference to  FIG. 25 , a device (e.g., the image/video receiver  2510 ) in accordance with some embodiments may obtain a real image and/or video to recognize a space.  FIG. 28  is another example of the space recognition method described with reference to  FIG. 26 . 
       FIG. 28  shows a method  2800  by which the device recognizes a space through a compact scanning operation. The compact scanning operation is intended to augment a space represented by a real image with a virtual object by determining whether elements required to augment the space represented by the real image with the virtual object (e.g., an environmental element related to presence or absence of a real object, an area occupied by the real object, the size of the area required to augment the space with the virtual object, etc.) are present. The device in accordance with the embodiments may use the semantic segmentation algorithm for the compact scanning operation. The device in accordance with the embodiments may perform the compact scanning operation by estimating the environmental elements (e.g., the number and presence of real objects, etc.) in the space and the size of the area occupied by the environmental elements. Accordingly, unlike the full scanning operation, the compact scanning operation does not require detailed 3D information about the space. Accordingly, the device in accordance with the embodiments may recognize the space through the compact scanning operation by collecting an image and/or video obtained while the user moves from a first position  2810  to a second position  2820 , an image and/or video obtained while the user moves from the second position  2820  to a third position  2830 , and the like ( 2800 ). In particular, as shown in the figure, the method  2800  of recognizing a space through the compact scanning operation does not require information on every part of the space as illustrated in the example  2700  of  FIG. 27 . The device may sufficiently recognize the space with only the images and/or videos obtained according to the minimum user movements. That is, the method  2800  of recognizing a space through the compact scanning operation requires fewer user movements, therefore may secure high user convenience. Further, since the method does not require generation of information such as a 3D map, it may reduce complexity of operation of the device. 
       FIG. 29  illustrates an example of a real image to which a semantic segmentation algorithm is applied by a device in accordance with some embodiments. 
     As described with reference to  FIGS. 25 and 28 , a device (e.g., the image/video analyzer  2510 ) in accordance with some embodiments may obtain information about an area occupied by one or more real objects located in a space represented by a real image and/or video obtained using one or more algorithms (for example, the type of the real objects, the size of the area occupied by the real objects in the space, etc.). The left part of  FIG. 29  illustrates an example  2900  of applying the semantic segmentation algorithm to a real image obtained by the device in accordance with the embodiments (e.g., a real image obtained at a first location  2810  of a user). As shown in the figure, the device may distinguish the real objects shown in the real image by the types of the real objects (e.g., sofa, wall, etc.) or the like, and segment the real image based on the area occupied by each real object in the space (e.g., a first area  2901  occupied by the sofa in the space, a second area  2902  occupied by the wall in the space). The right part of  FIG. 29  illustrates an example  2910  of applying the semantic segmentation algorithm to a real image obtained by the device in accordance with the embodiments (e.g., a real image obtained at a second location  2820  of a user). As shown in the figure, the device may distinguish the real objects shown in the real image by the types of the real objects (e.g., sofa, floor, etc.) or the like, and segment the real image based on the area occupied by each real object in the space (e.g., a first area  2911  occupied by the sofa in the space, a second area  2912  occupied by the floor in the space). The device in accordance with the embodiments may determine whether an application is executable, based on the information about the areas in the space occupied by one or more real objects obtained through the algorithm. 
       FIG. 30  illustrates an example of information in accordance with some embodiments representing whether an application is executable. 
     The left part of  FIG. 30  shows an example  3000  of information representing whether an application in accordance with some embodiments is executable. A device in accordance with some embodiments may generate information representing whether the application is executable based on the information about areas occupied by one or more real objects located in a space represented by the real image obtained by the method/operation described with reference to  FIGS. 26 to 29 . However, virtual objects of the same type may require different sizes of areas depending on the sizes, designs, and the like of the virtual objects (e.g., a single chair and a double chair). Virtual objects of different types may require different types or sizes of areas where the virtual objects are to be located (e.g., a wall area is required to locate a frame and a floor area is required to locate a chair). Therefore, the information representing whether the application is executable in accordance with the embodiments may be represented as the type of area (e.g., wall, floor, table, etc.) required for locating a virtual object in the space and an image representing the size of the area required for locating the virtual object in the space (e.g., a graphic image including a figure representing a table, an icon representing the size of an area, and an indicator). In accordance with some embodiments, the size of the image may be set in proportion to the size of an area required for locating the virtual object in the space. In addition, the size of the image may be determined within a range having a minimum value  3005  and a maximum value  3006  as shown in the figure. Information included in the information representing whether the application is executable is not limited to the above embodiment (for example, the information representing whether the application is executable may include information about the type of the virtual object). In addition, a method of expressing the information representing whether an application is executable is not limited to the example described (for example, the method may include a character for describing the area). 
     The example  3000  of  FIG. 30  shows a first image  3001 , a second image  3002 , a third image  3003 , and a fourth image  3004  which represent information representing whether an application is executable. As shown in the figure, the first image  3001 , the second image  3002 , the third image  3003 , and the fourth image  3004  may each include an image representing the type of an area where a virtual object (e.g., a frame, etc.) is to be located as the application is executed. The device in accordance with the embodiments may determine the sizes of the first image  3001 , the second image  3002 , the third image  3003 , and the fourth image  3004  based on information about the areas occupied by one or more real objects located in the space represented by a real image obtained by the method/operation described with reference to  FIGS. 26 to 29 . The first image  3001  illustrated in the figure represents a case where the size of the wall area in which the virtual object is to be located is the smallest, and the fourth image  3004  represents a case where the size of the wall area in which the virtual object is to be located is the largest. In addition, the sizes of the first image  3001 , the second image  3002 , the third image  3003 , and the fourth image  3004  are included in a range having a minimum value  3005  and a maximum value  3006 . Accordingly, the device in accordance with the embodiments may provide higher user convenience by enabling the user to intuitively recognize information on an area required for locating a virtual object without executing the application. 
     The right part of  FIG. 30  illustrates an example  3010  of displaying the information representing whether an application is executable together with the application. As described with reference to  FIGS. 25 to 29 , a device in accordance with some embodiments (e.g., the device  2500  or the display  2530  of  FIG. 25 ) may display images representing respective applications (e.g., a graphic image of a figure, a menu, and the like). The example  3010  of  FIG. 30  shows images representing one or more applications displayed by the device (e.g., the device  2500  or display  2530  of  FIG. 25 ). In accordance with some embodiments, the images representing the applications may be represented as part of a graphical user interface. The device in accordance with the embodiments may selectively or completely execute the one or more applications, or selectively or completely stop or terminate one or more applications which are running, according to a user input signal (e.g., a touch gesture or the like). As shown in the figure, the device in accordance with the embodiments may display images representing the applications together with images representing whether the application is executable. The example  3010  of  FIG. 30  represents a case where four applications among a plurality of applications are applications for providing content representing the space in which one or more virtual objects are located. In this example, each image representing each application (an image  3020  of a first application, an image  3030  of a second application, an image  3040  of a third application, and an image  3050  of a fourth application are displayed together with information representing whether each application is executable (a first image  3025 , second images  3035 - 1  and  3035 - 2 , a third image  3045 , and a fourth image  3055 ). In some embodiments, each image representing an application and the image representing whether the application is executable may be displayed in an overlapping manner or displayed side by side without overlapping with each other. When an image representing an application and the image representing whether the application is executable overlap with each other, the device in accordance with the embodiments may change the transparency of at least one of the two images and display the images. 
     In accordance with some embodiments, the first image  3025  represents the size of an area (wall) required for locating a virtual object (e.g., a frame, etc.) in a space according to execution of the first app. The first second image  3035 - 1  represents the size of an area (wall) required for locating a virtual object (e.g., a frame, etc.) in the space according to execution of the second application. The second image  3035 - 2  represents the size of an area (floor) required for locating a virtual object (e.g., a chair, etc.) in the space according to execution of the second application. That is, the second images  3035 - 1  and  3035 - 2  may provide size information about a required area for different objects that may be located in the space according to execution of the second application. The third image  3045  represents the size of an area (table) required for locating a virtual object (e.g., a vase, etc.) in the space according to execution of the third application. The fourth image  3055  represents the size of an area (wall) required for locating a virtual object (e.g., a frame, etc.) in the space according to execution of the fourth application. 
       FIG. 31  illustrates an example of information in accordance with some embodiments representing whether an application is executable. 
       FIG. 31  illustrates an example of information representing whether the applications described with reference to  FIG. 30  are executable. As described above, a device in accordance with the embodiments (e.g., the device  2500  or the image/video processor  2520 ) determine whether one or more virtual objects can be located in the space according to execution of the applications based on any one of the methods/operations described with reference to  FIGS. 25 to 28 . The device in accordance with the embodiments may generate information about whether an application is executable based on the result of the determination. As described with reference to  FIG. 30 , the information representing whether the application is executable may include information about a type of area (e.g., a wall, a floor, a table, etc.) required for locating a virtual object in the space, and an image representing the size of the area (e.g., a graphic image including a figure representing a table, an icon representing the size of the area, and an indicator). 
     The left part of  FIG. 31  shows an example  3100  of processing such an image in one or more colors depending on whether the application is executable. As described with reference to  FIG. 25 , the one or more colors may include a first color representing that the application is not executable, a second color representing that execution of the application is not decided, and a third color representing that the application is executable. The left part of  FIG. 31  shows the example  3100  of a first image  3101  color-processed in the first color representing that the application is not executable, and a second image  3102  color-processed in the second color representing execution of the application is not decided, and a third image  3103  color-processed in the third color representing that the application is executable. As shown in the figure, the first image  3101 , the second image  3102 , and the third image  3103  may each include an image representing a type (e.g., a figure representing a wall) of an area where a virtual object (e.g., a frame, etc.) is to be located as in the example  3000  of  FIG. 30 . In addition, as described with reference to  FIG. 30 , the device in accordance with the embodiments may determine the sizes of the first image  3101 , the second image  3102  and the third image  3103  based on the information about the areas occupied by one or more real objects located in the space represented by a real image obtaining by the method/operation described with reference to  FIGS. 26 to 29 . In the example  3100  of  FIG. 31 , the first color is white, the second color is orange, and the third color is green. The first color, the second color, and the third color are not limited to the embodiments, may have any colors as long as the first color, the second color, and the third color are different from each other. Accordingly, the device in accordance with the embodiments may provide higher user convenience by enabling the user to intuitively recognize whether an application is executable. 
     The right part of  FIG. 31  illustrates an example  3110  of displaying information representing whether an application is executable together with the application. As described with reference to  FIGS. 25 to 29 , a device in accordance with the embodiments (e.g., the device  2500  or the display  2540  of  FIG. 25 ) may display an image representing each application (e.g., a graphic image such as a figure or a menu). The example  3100  of  FIG. 31  is an example in which the device (e.g., the device  2500  or the display  2540  of  FIG. 25 ) displays an image representing an application and an image representing whether the application is executable together. The example  3110  of  FIG. 31 , which is an example of the example  3010  of  FIG. 30 , represents a case where four applications among a plurality of applications are applications for providing content representing the space in which one or more virtual objects are located. In the example  3110  of  FIG. 31 , each image representing each application (an image  3120  of the first application, an image  3130  of the second application, an image  3140  of the third application, and an image  3150  of a fourth application are displayed together with information representing whether each application is executable (a first image  3125 , second images  3135 - 1  and  3135 - 2 , a third image  3145 , and a fourth image  3155 . The method of displaying the image representing the application and the image representing whether the application is executable is the same as described with reference to  FIG. 30 , and thus a detailed description thereof will be omitted. 
     In some embodiments, the first image  3125  is an image processed according to the second color. The first image  3125  represents the size of an area (wall) required for locating a virtual object (e.g., a frame, etc.) in a space, and represents that execution of the first application is not decided. That is, the user may recognize, based on the first image  3125 , that there is a high possibility that there is no area for locating a virtual object in the space even if the first application is executed. The first second image  3135 - 1  is an image processed according to the second color. The first second image  3135 - 1  represents the size of an area (wall) required for locating a virtual object (e.g., a frame, etc.) in the space, and represents that execution of the second application is not decided. That is, the user may recognize, based on the first second image  3135 - 1 , that there is a high possibility that there is no area for locating a virtual object in the space even if the second application is executed. The second image  3135 - 2  is an image processed according to the third color. The second image  3135 - 2  represents the size of an area (floor) required for locating a virtual object (e.g., a frame, etc.) in the space according to execution of the second application, and represents that the second application is executable. That is, the second image  3135 - 2  shows that there is a sufficient area for locating a virtual object in the space. The second images  3135 - 1  and  3135 - 2  may provide information about the possibility of locating each of different objects that may be located in a space according to execution of the second application, thereby providing high user experience and enabling efficient device operation. The third image  3145  is an image processed according to the first color. The third image  3145  represents the size of an area (table) required for locating a virtual object (e.g., a vase) in the space according to execution of the third application, and represents that the third application is not executable. That is, the user may recognize, based on the third image  3145 , that there is no area for locating the virtual object in the space even if the third application is executed. The fourth image  3155  is an image processed according to the first color. The fourth image  3155  represents the size of an area (wall) required for locating a virtual object (e.g., a frame, etc.) in the space according to execution of the fourth application, and represents that the fourth application is not executable. That is, the user may recognize, based on the fourth image  3155 , that there is no area for locating the virtual object in the space even if the fourth application is executed. 
       FIG. 32  illustrates an example of information in accordance with some embodiments representing whether an application is executable. 
     When a device (e.g., the device  2500  or the image/video processor  2520 ) in accordance with the embodiments determines that an application is not executable, the device may learn information about areas occupied by one or more real objects located in the space represented by the obtained real image, and generate information for obtaining an additional area of a size required to execute the application, based on the result of the learning. In some embodiments, the device may use one or more algorithms (e.g., an AI learning algorithm) to learn information about the areas occupied by the one or more real objects in the space. Based on the learning information obtained using the one or more algorithms, the device may determine whether there is another area in the space corresponding to the area of the size required when the virtual object is located in the space according to execution of the application. For example, when the space between two chairs (real objects) located in the room is narrower than the space required for locating a floor stand (virtual object), the device may determine whether there is another space for locating the floor stand (e.g., a space other than the space between the two chairs). When there is an area of the size required for locating the virtual object in the space as a result of the determination, the device may generate information for securing the area (e.g., information about the direction and distance of movement when movement is required within the space, information about movement of a real object located in the space when an area can be secured by moving the real object, etc. In addition, a device in accordance with the embodiments (or the display  2540 ) may express information for obtaining the corresponding area as an image (e.g., a graphic image such as an arrow, an arrow key, or a character) such as an image for the information representing whether an application is executable. When there are one or more methods of obtaining the corresponding area, the device in accordance with the embodiments may determine the priorities of the one or more methods, select the information on the most optimal method and express the selected information as an image. The image expressing the information representing whether an application is executable may be displayed including an image representing information for obtaining the corresponding area. In accordance with some embodiments, the image expressing the information representing whether the application is executable and the image representing information for obtaining the corresponding region may be displayed simultaneously as different images. 
     As described with reference to  FIGS. 25 to 31 , a device in accordance with the embodiments (e.g., the device  2500  or the display  2540  of  FIG. 25 ) may display an image (e.g., a graphic image such as a figure or a menu) representing each application.  FIG. 32  illustrates an example  3200  in which the device (e.g., the device  2500  or display  2540  of  FIG. 25 ) displays an image representing an application and an image  3225  representing whether the application is executable together. The example  3200  of  FIG. 32 , which is an example of the example  3010  of  FIG. 30  and the example  3110  of  FIG. 31 , illustrates a case where one of the plurality of applications is an application for providing content representing the space where a virtual object is located. The method of displaying the image representing the application and the image representing whether the application is executable together is the same as described with reference to  FIGS. 30 and 31 , and thus a detailed description thereof will be omitted. 
     The image  3225  in accordance with the embodiments is an image processed according to the second color described with reference to  FIG. 31 . The image  3225  represents the size of an area (wall) required for locating a virtual object (e.g., a frame, etc.) in a space, and represents that execution of an application (e.g., the first application described with reference to  FIGS. 30 and 31 ) associated with the image  3225  is not decided. When an area of the size required for locating a virtual object in the space is located on the right side of a current position, the device according to the embodiments may display an arrow image  3230  representing the rightward direction together with the image  3225  to further represent information for obtaining the area (e.g., information representing that the area may be obtained by moving to the right. In accordance with some embodiments, the arrow image  3230  may be color-processed in the second color representing execution of the application is not decided and the third color representing that the application is executable. Examples of the information representing whether the application is executable are not limited to the above-described embodiments. 
       FIG. 33  illustrates an example in which a device in accordance with some embodiments displays information to control the operation of a remote robot. 
     The device described with reference to  FIGS. 24 to 32  may control the operation of a robot cleaner  3310  by remotely communicating with the robot. The device in accordance with embodiments (e.g., the device  2500  of  FIG. 25 ) may receive a real image and/or the video from the robot cleaner  3310 . In accordance with some embodiments, the device may analyze the space based on the real image and/or video, and display information about an area that needs to be cleaned (e.g., the size of the area, the location of the area, etc.) together with one or more images representing operation of the robot cleaner.  FIG. 33  illustrates an example  3300  of displaying an image  3320  representing an operation of the robot cleaner and information about the space to which the operation needs to be applied (e.g., a size (area), location, and the like of the space that needs to be cleaned). When there is a foreign substance that needs to be cleaned by wet mopping in a floor area of the space represented by the real image and/or video, the device in accordance with the embodiments may display an image  3320  representing a wet mopping operation and an image  3325  representing the floor area and the size of the area to be cleaned. 
       FIG. 34  illustrates operation of a device in accordance with some embodiments. 
       FIG. 34  illustrates an example  3400  in which a device described above with reference to  FIGS. 24 to 32  (e.g., the device  2500  of  FIG. 25 ) obtains a real image and/or video representing the internal space of an autonomous vehicle (e.g., a vehicle performing the autonomous driving operation and function described with reference to  FIGS. 20 and 21 ), and shows information about whether an application for providing content representing the space in which one or more virtual objects are located is executable. The device in accordance with the embodiments may perform one or more of the one or more operations/methods described with reference to  FIGS. 24 to 32 . Detailed description of the operations/methods described with reference to  FIGS. 24 to 32  will be omitted. The device in accordance with the embodiments may display images of one or more applications for a user on the driver&#39;s seat and images representing whether each application is executable ( 3410 ), and may display images of one or more applications for a user on the front passenger seat and images representing whether each application is executable ( 3420 ). The device in accordance with the embodiments may display images of one or more applications for a user on the back seat and images representing whether each application is executable ( 3430 ). As shown in the figure, the device in accordance with the embodiments may select applications available to the user according to the location of the user and display the images of the selected applications. For example, the applications available to the user on the driver&#39;s seat may include an application related to driving, but the applications available to a user on the back seat may not include the application related to driving. The device in accordance with the embodiments may also display images representing applications set as a default regardless of the location of the user in the vehicle. 
       FIG. 35  illustrates a flow diagram showing a method for providing content in accordance with some embodiments. 
       FIG. 35  is a flow diagram  3500  illustrating a method for providing content by the device described with reference to  FIGS. 24 to 34 . 
     The device in accordance with embodiments (e.g., the device  2500 ) may obtain a real image ( 3510 ). The device in accordance with the embodiments may obtain a real image and/or video through the above-described scanning operation. In addition, the device in accordance with the embodiments may receive a real image and/or video from a remotely located sensor (e.g., a robot cleaner). The device in accordance with the embodiments may perform at least one of the one or more methods/operations described with reference to  FIGS. 24 to 34  to obtain a real image. Detailed description of the one or more methods/operations described with reference to  FIGS. 24 to 34  will be omitted. 
     The device in accordance with the embodiments (e.g., the device  2500  of  FIG. 25 ) may obtain information about a space represented by the obtained real image, and determine whether an application for providing content representing the space where one or more virtual objects are located is executable, based on the obtained information. The information about the space may include information about one or more real objects located in the space. The device may also obtain information about the space using one or more algorithms. In some embodiments, the one or more algorithms may include the algorithms described with reference to  FIGS. 26 to 29  (e.g., the semantic segmentation algorithm). The device in accordance with the embodiments may determine whether an application is executable based on information about the type of the real object, the size of an area occupied by the real object in the space, the type of an area in which the virtual object is to be located, and the size of an area required for locating the virtual object in the space. The device may obtain information about the space represented by the obtained real image, and perform at least one of the one or more methods/operations described with reference to  FIGS. 24 to 34  to determine whether an application for providing content representing the space in which one or more virtual objects are located is executable based on the obtained information. Detailed description of the one or more methods/operations described with reference to  FIGS. 24 to 34  will be omitted. 
     The device in accordance with the embodiments (e.g., the device  2500  of  FIG. 25 ) may display information representing whether the application is executable according to the result of the determination ( 3530 ). In some embodiments, the information representing whether the application is executable may be expressed as an image representing the type of an area for locating the virtual object and the size of the area required for locating the virtual object in the space. The size of the image may be determined according to the size of the area required for locating the virtual object in the space and may be included within a range having a minimum value to a maximum value. In accordance with some embodiments, the image may be processed in one or more colors. In accordance with some embodiments, the one or more colors may include a first color representing that the application is not executable, a second color representing that execution of the application is not decided, and a third color representing that the application is executable. In addition, the first color, the second color, and the third color may be different from each other. In some embodiments, the information representing whether the application is executable may further include information representing a method of obtaining an additional area of which size required for executing the application. The device in accordance with the embodiments may perform at least one of the one or more methods/operations described with reference to  FIGS. 24 to 34  to display the information representing whether the application is executable according to the result of the determination. Detailed description of the one or more methods/operations described with reference to  FIGS. 24 to 34  will be omitted. 
     The various elements of the XR device shown in  FIGS. 1 to 35  are implemented in hardware, software, firmware or a combination thereof. The various elements of the XR device are implemented on a single chip such as a hardware circuit. In some embodiments, they are, optionally, implemented on separate chips. In some embodiments, at least one of the elements of the XR device may be constructed in one or more processors capable of executing one or more programs including instructions of performing or causing performance of the operations of any of the methods described herein. 
     It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first image could be termed a second image, and, similarly, a second image could be termed a first image, without departing from the scope of the various described embodiments. The first image and the second image are both images, but they are not the same image, unless the context clearly indicates otherwise. 
     The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     As used herein, the term “if” is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context. Similarly, the phrase “when it is determined” or “when [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context.