Low overhead cell selection

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A method performed by a user equipment (UE) in a communication system includes receiving a synchronization signal associated with a cell group identifier; identifying a physical random access channel (PRACH) resource based on the cell group identifier; and transmitting, to a plurality of cells, PRACH transmissions via the PRACH resource, wherein the plurality of cells are included in a cell group corresponding to the cell group identifier.

Description

LOW OVERHEAD CELL SELECTION

[0001] This disclosure generally relates to a wireless communication system, more particularly, to a method / device for a terminal to perform a network access operation in a wireless communication system, and a network operation method and device supporting the same.

[0002] 5thgeneration (5G) mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] The above information is presented as background information only to assist with an understanding of the disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure.

[0009] The disclosure proposes a new initial access process (initial access procedure) that reduces the energy consumed by a base station when performing and supporting initial access based on cell broadcasting information and a device that supports the same.

[0010] The disclosure proposes a signal structure, operation procedure, and device to support a new initial access process.

[0011] According to an embodiment of the disclosure, a method for transmitting cell information required for initial access of a terminal through separate scheduling to specific terminals requesting initial access rather than transmitting the cell information through broadcast may be provided.

[0012] According to an embodiment of the disclosure, an initial access process may be provided by transmitting cell information required for initial access of a terminal through separate scheduling to specific terminals requesting initial access rather than transmitting the cell information through broadcast. .

[0013] The technical objects to be achieved by the disclosure are not limited to the technical objects mentioned above, and other technical objects not mentioned may be clearly understood by those skilled in the art from the following descriptions.

[0014] According to an embodiment, a method performed by a user equipment (UE) in a communication system is provided.

[0015] According to an embodiment, the method may include receiving a synchronization signal associated with a cell group identifier; identifying a physical random access channel (PRACH) resource based on the cell group identifier; and transmitting, to a plurality of cells, PRACH transmissions via the PRACH resource.

[0016] According to an embodiment, wherein the plurality of cells are included in a cell group corresponding to the cell group identifier.

[0017] According to an embodiment, wherein the PRACH resource is identified among a plurality of PRACH resources associated with a plurality of cell group identifiers.

[0018] According to an embodiment, wherein the plurality of PRACH resources are configured at least n slots after a slot in which the synchronization signal is received.

[0019] According to an embodiment, wherein the plurality of PRACH resources are included in one slot after n slots from the slot in which the synchronization signal is received.

[0020] According to an embodiment, wherein starting symbols of the plurality of PRACH resources are different from each other in the one slot.

[0021] According to an embodiment, wherein the plurality of PRACH resources are slot-level time division multiplexed or frequency division multiplexed.

[0022] According to an embodiment, wherein one cell group identifier corresponds to a plurality of PRACH resources.

[0023] According to an embodiment, wherein the PRACH resource is randomly selected among a plurality of PRACH resources corresponding to the cell group identifier.

[0024] According to an embodiment, the method may include: receiving at least one random access response (RAR) from at least one of the plurality of cells, respectively, wherein at least one physical downlink control channel (PDCCH) for the at least one RAR is identified based on the cell group identifier and the at least one RAR respectively includes at least one cell specific configuration or cell specific system information; and transmitting an acknowledgement (ACK) message.

[0025] According to an embodiment, wherein in case that the at least one RAR is one RAR received from one of the plurality of cells, the ACK message is transmitted to the one of the plurality of cells.

[0026] According to an embodiment, wherein in case that the at least one RAR is a plurality of RARs received from at least some of the plurality of cells, the ACK message is transmitted to one of the at least some of the plurality of cells identified by the UE.

[0027] According to an embodiment, wherein the at least one of the plurality of cells are based on uplink reference signal received power (RSRP) associated with the PRACH transmissions.

[0028] According to an embodiment, wherein a resource for the ACK message is identified based on: the cell group identifier among at least one candidate resource; or down-selection by a PDCCH for the one RAR including a corresponding cell specific configuration.

[0029] According to an embodiment, a user equipment (UE) in a communication system is provided.

[0030] According to an embodiment, the UE may include a transceiver; and a processor coupled with the transceiver and configured to: receive a synchronization signal associated with a cell group identifier; identify a physical random access channel (PRACH) resource based on the cell group identifier; and transmit, to a plurality of cells, PRACH transmissions via the PRACH resource.

[0031] According to an embodiment, wherein the plurality of cells are included in a cell group corresponding to the cell group identifier.

[0032] According to an embodiment, wherein the PRACH resource is identified among a plurality of PRACH resources associated with a plurality of cell group identifiers.

[0033] According to an embodiment, wherein the plurality of PRACH resources are configured at least n slots after a slot in which the synchronization signal is received.

[0034] According to an embodiment, wherein the plurality of PRACH resources are included in one slot after n slots from the slot in which the synchronization signal is received.

[0035] According to an embodiment, wherein starting symbols of the plurality of PRACH resources are different from each other in the one slot.

[0036] According to an embodiment, wherein the plurality of PRACH resources are slot-level time division multiplexed or frequency division multiplexed.

[0037] According to an embodiment, wherein one cell group identifier corresponds to a plurality of PRACH resources.

[0038] According to an embodiment, wherein the PRACH resource is randomly selected among a plurality of PRACH resources corresponding to the cell group identifier.

[0039] According to an embodiment, wherein the processor is further configured to: receive at least one random access response (RAR) from at least one of the plurality of cells, respectively, wherein at least one physical downlink control channel (PDCCH) for the at least one RAR is identified based on the cell group identifier and the at least one RAR respectively includes at least one cell specific configuration or cell specific system information; and transmit an acknowledgement (ACK) message.

[0040] According to an embodiment, wherein in case that the at least one RAR is one RAR received from one of the plurality of cells, the ACK message is transmitted to the one of the plurality of cells.

[0041] According to an embodiment, wherein in case that the at least one RAR is a plurality of RARs received from at least some of the plurality of cells, the ACK message is transmitted to one of the at least some of the plurality of cells identified by the UE.

[0042] According to an embodiment, wherein the at least one of the plurality of cells are based on uplink reference signal received power (RSRP) associated with the PRACH transmissions.

[0043] According to an embodiment, wherein a resource for the ACK message is identified based on: the cell group identifier among at least one candidate resource; or down-selection by a PDCCH for the one RAR including a corresponding cell specific configuration.

[0044] According to an embodiment, a method performed by a base station in a communication system is provided.

[0045] According to an embodiment, the method may include: transmitting a synchronization signal associated with a cell group identifier; and receiving, on a plurality of cells, physical random access channel (PRACH) transmissions via a PRACH resource.

[0046] According to an embodiment, wherein the PRACH resource is based on the cell group identifier.

[0047] According to an embodiment, wherein the plurality of cells are included in a cell group corresponding to the cell group identifier.

[0048] According to an embodiment, the method may include: identifying at least one of the plurality of cells based on uplink reference signal received power (RSRP) associated with the PRACH transmissions; transmitting at least one random access response (RAR) on the at least one of plurality of cells, respectively, wherein at least one physical downlink control channel (PDCCH) for the at least one RAR is based on the cell group identifier; and receiving an acknowledgement (ACK) message, wherein a PDCCH for the ACK message is based on the cell group identifier.

[0049] According to an embodiment, a base station in a communication system is provided.

[0050] According to an embodiment, the base station may include a transceiver; and a processor coupled with the transceiver and configured to: transmit a synchronization signal associated with a cell group identifier; and receive, on a plurality of cells, physical random access channel (PRACH) transmissions via a PRACH resource.

[0051] According to an embodiment, wherein the PRACH resource is based on the cell group identifier.

[0052] According to an embodiment, wherein the plurality of cells are included in a cell group corresponding to the cell group identifier.

[0053] The various embodiments of the disclosure described above are only some of the preferred embodiments of the disclosure, and those skilled in the art may derive and understand many embodiments in which technical features of the various embodiments of the disclosure are reflected based on the following detailed description.

[0054] According to an embodiment of the disclosure, a base station or network can minimize the broadcasting load that must be performed to support initial access of a terminal, which has the effect of reducing energy consumed by the network.

[0055] The effects that can be obtained from the disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0056] FIG. 1　is a diagram illustrating a basic structure of a time-frequency domain, which is a radio resource domain in which data or a control channel is transmitted in a wireless communication system to which an embodiment of the disclosure is applicable.

[0057] FIG. 2　is a diagram illustrating a frame, subframe, slot structure in a wireless communication system to which an embodiment of the disclosure is applicable.

[0058] FIG. 3　is a diagram illustrating the structures of a synchronization signal and a PBCH transmitted in LTE and NR, which are considered in the disclosure.

[0059] FIG. 4 is a diagram　illustrating an example in which a plurality of SS blocks are transmitted using different beams.

[0060] FIG. 5 is a diagram illustrating a procedure in which a base station encodes an MIB to transmit the MIB to a PBCH.

[0061] FIG.　6 is a diagram　illustrating a time domain mapping structure and a beam sweeping operation for a synchronization signal according to an embodiment of the disclosure.

[0062] FIG.　7 is a diagram illustrating a random access procedure according to an embodiment of the disclosure.

[0063] FIG.　8 is a diagram　illustrating a procedure in which a UE reports UE capability information to a BS according to an embodiment of the disclosure.

[0064] FIG. 9 is a diagram illustrating an example of a cell access procedure (or initial access procedure) of a UE defined by 3GPP new radio (NR) to which an embodiment of the disclosure is applicable.

[0065] FIG. 10 is a diagram illustrating an example of an initial access procedure according to an embodiment of the disclosure.

[0066] FIG. 11 is a diagram illustrating an example of an initial access procedure according to an embodiment of the disclosure.

[0067] FIG. 12 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure.

[0068] FIG. 13 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure.

[0069] FIG. 14 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure.

[0070] FIG. 15 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure.

[0071] FIG. 16 is a diagram illustrating an example of an initial access procedure according to an embodiment of the disclosure.

[0072] FIG. 17 is a diagram illustrating an example of a UE operation according to an embodiment of the disclosure.

[0073] FIG. 18 is a diagram illustrating an example of a BS operation according to an embodiment of the disclosure.

[0074] FIG.　19 is a diagram illustrating a structure of a UE in a wireless communication system according to an embodiment of the disclosure.

[0075] FIG.　20 is a diagram illustrating a structure of a BS in a wireless communication system according to an embodiment of the disclosure.

[0076] Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

[0077] In describing embodiments of the disclosure, descriptions related to technical contents well-known in the art and not associated directly with the disclosure will be omitted. Such an omission of unnecessary descriptions is intended to prevent obscuring of the main idea of the disclosure and more clearly transfer the main idea.

[0078] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted, or schematically illustrated. Further, the size of each element does not completely reflect the actual size. In the drawings, identical or corresponding elements are provided with identical reference numerals.

[0079] The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described below in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments set forth below, but may be implemented in various different forms. The following embodiments are provided only to completely disclose the disclosure and inform those skilled in the art of the scope of the disclosure, and the disclosure is defined only by the scope of the appended claims. Throughout the specification, the same or like reference numerals designate the same or like elements. Further, in describing the disclosure, a detailed description of known functions or constitutions incorporated herein will be omitted in case that it is determined that the description may make the subject matter of the disclosure unnecessarily unclear. The terms which will be described below are terms defined in consideration of the functions in the disclosure, and may be different according to users, intentions of the operators, or customs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

[0080] Hereinafter, a base station is an entity that allocates resources to terminals, and may be at least one of a gNode B, an eNode B, a Node B, a base station (BS), a wireless access unit, a base station controller, and a node on a network. A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing communication functions. In the disclosure, a "downlink (DL)" refers to a radio transmission path via which a base station transmits a signal to a terminal, and an "uplink (UL)" refers to a radio transmission path via which a terminal transmits a signal to a base station. Further, hereinafter, LTE or LTE-A systems may be described by way of example, but the embodiments of the disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. Examples of such communication systems may include 5th generation mobile communication technologies (5G, new radio, and NR) developed beyond LTE-A, and hereinafter, the "5G" may be the concept that covers the exiting LTE, LTE-A, or other similar services. In addition, based on determinations by those skilled in the art, the embodiments of the disclosure may also be applied to other communication systems through some modifications without significantly departing from the scope of the disclosure.

[0081] Herein, it will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, can be implemented by computer program instructions. Because these computer program instructions may be embedded in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatuses, the instructions executed through the processor of the computer or other programmable data processing apparatus generates means for performing the functions described in the flowchart block(s). Because these computer program instructions may also be stored in a computer usable or computer-readable memory that may direct the computer or other programmable data processing apparatus so as to implement functions in a particular manner, the instructions stored in the computer usable or computer-readable memory are also capable of producing an article of manufacture containing instruction modules for performing the functions described in the flowchart block(s). Because the computer program instructions may also be embedded into the computer or other programmable data processing apparatus, the instructions for executing the computer or other programmable data processing apparatuses by generating a computer-implemented process by performing a series of operations on the computer or other programmable data processing apparatuses may provide operations for executing the functions described in the flowchart block(s).

[0082] Further, each block of the flowchart illustrations may represent a module, segment, or portion of code, which includes one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the corresponding functionality involved.

[0083] As used herein, the "unit" refers to a software element or a hardware element, such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), which performs a predetermined function. However, the "unit" does not always have a meaning limited to software or hardware. The "unit" may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the "unit" includes, for example, components, such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided in the components and "units" may be combined into fewer components and "units" or may be further separated into additional components and "units". Further, the components and "units" may be implemented to operate one or more CPUs in a device or a secure multimedia card. In addition, in an embodiment, "units" may include one or more processors.

[0084] A wireless communication system has evolved from providing an initial voice-oriented service to a broadband wireless communication system that provides high-speed and high-quality packet data services, such as high speed packet access (HSPA) in 3rd Generation Partnership Project (3GPP), long term evolution (LTE) or evolved universal terrestrial radio access (E-UTRA), LTE-advanced (LTE-A), LTE-pro, high rate packet data (HRPD) in 3GPP2, ultra-mobile broadband (UMB), and communication standards such as IEEE's 802.16e.

[0085] In the LTE system, which is a representative example of the broadband wireless communication system, in downlink (DL), an orthogonal frequency division multiplexing (OFDM) scheme is adopted, and in uplink (UL), a single carrier frequency division multiple access (SC-FDMA) scheme is adopted. Uplink refers to a radio link in which a terminal (user equipment (UE) or mobile station (MS)) transmits data or control signals to a base station (eNode B or base station (BS)), and downlink refers to a radio link in which the BS transmits data or control signals to the UE. The above-described multiple access scheme allows the data or control information of each user to be distinguished by allocating and operating the time-frequency resources to which the data or control information for each user are to be transmitted do not overlap each other, that is, to establish orthogonality.

[0086] The 5G communication system, which is a communication system after LTE, must support services that simultaneously satisfy various requirements so that various requirements from users and service providers can be freely reflected. Services considered for the 5G communication system include enhanced mobile broadband (eMBB), massive machine type communication (mMTC), ultra-reliability low latency communication (URLLC), and the like.

[0087] The eMBB aims to provide more improved data transfer rates than those supported by existing LTE, LTE-A or LTE-Pro. For example, in the 5G communication system, the eMBB may be able to provide a peak data rate of 20 Gbps in the downlink and a peak data rate of 10 Gbps in the uplink from the viewpoint of one base station. In addition, the 5G communication system must provide the peak data rate and the increased user perceived data rate of the UE at the same time. In order to satisfy such a requirement, improved various transmission / reception technologies including a more advanced multi-antenna (multiple-input multiple-output, (MIMO)) transmission technology are required. In addition, in the LTE system, a signal is transmitted using a transmission bandwidth of up to 20 MHz in the 2 GHz band, whereas the 5G communication system can satisfy the data transmission rate required by the 5G communication system by using a frequency bandwidth wider than 20 MHz in a frequency band of 3 to 6 GHz or 6 GHz or more.

[0088] At the same time, mMTC is being considered to support application services such as the Internet of Things (IoT) in the 5G communication system. In order to efficiently provide the Internet of Things, mMTC requires access support for large-scale UEs within a cell, improvement of coverage of UEs, improved battery life, and reduction of costs of UEs. Because the Internet of Things is attached to various sensors and various devices to provide communication functions, the IoT must be able to support many UEs (e.g., 1,000,000 UEs / km2) within a cell. In addition, because a UE supporting mMTC is highly likely to be in a shaded area that a cell cannot cover, such as the basement of a building, due to the nature of the service, wider coverage compared to other services provided by the 5G communication system may be required. A UE supporting mMTC must be composed of a low-cost UE, and because it is difficult to frequently exchange the battery of the UE, a very long battery lifetime of 10 to 15 years may be required.

[0089] Lastly, URLLC is a cellular-based wireless communication service used for a specific purpose (mission-critical). For example, services used for remote control of a robot or machinery, industrial automation, an unmanned aerial vehicle, remote health care, an emergency alert, etc. may be considered. Therefore, the communication provided by URLLC must provide very low latency and very high reliability. For example, a service supporting URLLC must satisfy the air interface latency of less than 0.5 milliseconds and, at the same time, must satisfy the requirement of a packet error rate of 10-5or less. Therefore, for a service supporting URLLC, the 5G communication system must provide a transmit time interval (TTI) that is smaller than that of other services, and at the same time, design requirements for allocating wide resources in the frequency band to secure the reliability of the communication link may be required.

[0090] The three services of the 5G, i.e., eMBB, URLLC, and mMTC, may be multiplexed and transmitted in one system. In this case, different transmission / reception techniques and transmission / reception parameters may be used between services to satisfy different requirements of each service. It is apparent that 5G is not limited to the above-described three services.

[0091] Hereinafter, a / b may be understood as at least one of a and b.

[0092] Hereinafter, a frame structure of the 5G system will be described in more detail with reference to the drawings.

[0093] FIG. 1　is a diagram illustrating a basic structure of a time-frequency domain, which is a radio resource domain in which data or control channel is transmitted in a wireless communication system according to an embodiment of the disclosure is applicable.

[0094] In FIG. 1, the horizontal axis represents a time domain and the vertical axis represents a frequency domain. The basic unit of resource in the time domain and frequency domain is a resource element (RE)　101, which may be defined as one OFDM　symbol　102　in the time axis and may be defined as one　subcarrier　103　in the frequency axis. In the frequency domain, (e.g., 12) consecutive REs may configure one resource block (RB)　104. One subframe 110 in the time axis may include a plurality of OFDM symbols 102. For example, the length of one subframe may be 1 ms.

[0095] FIG.　2　is a diagram illustrating a frame, subframe, and slot structures in a wireless communication system to which an embodiment of the disclosure is applicable.

[0096] Examples of structures of a　frame　200, a　subframe　201, and a　slot　202　are illustrated in FIG. 2. The one　frame　200　may be defined to have a length of 10 ms. The one　subframe　201　may be defined to have a length of 1 ms, and thus a total of 10　subframes　201　may constitute the 1　frame　200. The one　slot　202　or　203　may be defined to have 14 OFDM symbols (i.e., the number of symbols per 1 slot . The one　subframe　201　may include one or　more slots　202　and　203, and the number of　slots　202　and　203　per 1 subframe 201 may vary depending on subcarrier spacing　configuration values p　204　and　205.　FIG.　2　illustrates a case where μ=0　204　and μ=1　205　for the subcarrier spacing configuration values. In the case of μ=0　204, the one　subframe　201　may include one　slot　202, and in the case of μ=1　205, the one　subframe　201　include two　slots　203. That is, depending on the subcarrier spacing configuration value μ, the number of slots per 1 subframe ( ) may vary and the number of slots per 1 frame ( ) may vary accordingly. and depending on the subcarrier spacing configuration value μ may be defined as in the following Table 1.

[0097] [Table 1]

[0098]

[0099] When a UE accesses a wireless communication system, a synchronization signal is used to acquire synchronization with a cell in a network. Specifically, the synchronization signal refers to a reference signal transmitted by a base station for time and frequency synchronization and cell search at the initial access of the UE. In the LTE system, the signals for synchronization such as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) may be transmitted. In addition, in order to access a cell after acquiring synchronization with a cell through a cell search procedure, cell system information must be obtained, and the following system information may be transmitted through PBCH and PDSCH.

[0100] Here, the synchronization signal and the PBCH may be transmitted at regular intervals in the time axis, and may be transmitted within a predetermined transmission bandwidth in the frequency axis. A special sequence may be mapped to a subcarrier within the transmission bandwidth in order for the synchronization signal to indicate a cell number (ID), and the cell number may be mapped using a combination of one or a plurality of sequences. Therefore, the UE may detect the cell number to which the UE desires to access by detecting the sequence used for the synchronization signal.

[0101] FIG. 3　is a diagram illustrating the structures of a synchronization signal and a PBCH transmitted in LTE and NR, which are considered in the disclosure. Table 2 below is a table comparing channel structures of SS / PBCH blocks of LTE and NR.

[0102] [Table 2]

[0103]

[0104] With reference to　FIG. 3, as shown in Table 2, in　LTE　300, a PSS, an SSS, and a PBCH are transmitted using the same frequency resource (6 PRBs)　310　on the frequency axis. However, in an　NR　350, the amount of resources occupied on the frequency is 12　PRBs　360　for the PSS and SSS and the amount thereof is 20　PRBs　370　for the PBCH, which are different from each other. In addition, a　TDD　330　and FDD　320　in　LTE　300　have different transmission positions, but the TDD and FDD in　NR　350　all have the same transmission position.

[0105] Table 3 below compares PSS sequences in LTE and NR.

[0106] [Table 3]

[0107]

[0108] As mentioned in the above Table 3, in LTE, the PSS uses a Zadoff-Chu sequence having a constant amplitude zero auto correlation (CAZAC) characteristic. However, in NR, an M-sequence which is a pseudo random sequence is used. LTE and NR are the same in that they support four sequences.

[0109] Table 4 below compares SSS sequences in LTE and NR.

[0110] [Table 4]

[0111]

[0112] As mentioned in the above Table 4, unlike LTE, which has used an M-sequence of length of 31, NR supports SSS through a gold sequence of length of 127. In LTE, a PSS is generated using three Zadoff-Chu sequences as described above, and an SSS is generated using an M-sequence. Here, the PSS of one cell may have three different values according to a physical layer cell ID of the cell, and the three cell IDs of one cell ID group correspond to different PSSs. Accordingly, the UE may detect the PSS of the cell to identify one cell ID group among the three cell ID groups supported by LTE. The UE additionally detects an SSS among 168 cell IDs, reduced from 504 cell IDs, through the cell ID group identified through the PSS, so as to finally determine the cell ID to which the corresponding cell belongs.

[0113] In NR, the UE identifies three cell ID groups through the PSS based on the M-sequence and detects 336 cell ID groups by using the SSS based on the gold sequence, thereby finally detecting one cell ID among 1008 cell IDs by detecting 1008 cell IDs.

[0114] Thereafter, as to PBCH transmission, the PBCH transmission in NR has many differences with LTE in the channel coding and the reference signal. Table 5 below compares a difference in the PBCH transmission between LTE and NR

[0115] [Table 5]

[0116]

[0117] As shown in the above Table 5, in LTE, the PBCH is transmitted every 40 ms based on TBCC, but in NR, the PBCH is transmitted every 80 ms using a polar code. Here, unlike in LTE where channel estimation is performed on PBCH by using CRS, NR estimates a channel for PBCH decoding by using PBCH DMRS.

[0118] In NR, the above-mentioned PSS, SSS and PBCH are combined and called SS blocks (which can be interchangeably used with SSB, SS / PBCH, SS / PBCH block, etc.). The NR system allows the SS and PBCH to be transmitted using different beams by allowing transmission of these multiple SS blocks.

[0119] FIG. 4　is a diagram illustrating an example in which a plurality of SS blocks are transmitted using different beams. As illustrated in FIG. 4, the SS block in NR includes PSS, SSS, and PBCH, and a plurality of SS blocks may be transmitted to a UE. Here, each of the SS blocks may be transmitted to the UE by using a different beam. For example, the SS blocks shown in　FIG. 4　are transmitted using　beams #　0, #1, #2, and #3, respectively

[0120] Information transmitted through the PBCH in the SS block is also changed in comparison with LTE. Table 6 below compares master information block (MIB) information transmitted through the PBCH in LTE and NR.

[0121] [Table 6]

[0122]

[0123] In order to transmit the above information, the base station encodes the MIB and transmits the encoded MIB on the PBCH.

[0124] As shown in Table 6, in the PBCH of NR, the channel bandwidth and PHICH configuration-related information supported by LTE are removed. However, various information such as a most significant bit (MSB) of an SS / PBCH block index, half frame timing, a subcarrier spacing for a common control channel, SS / PBCH subcarrier offset, and the like are added to the PBCH of NR. In particular, the MSB of the SS / PBCH block index provides MSB information of the SS block index for supporting a plurality of SS blocks, and thus transmission of a plurality of SS blocks is possible. The UE transmits beam-based physical random-access channel (PRACH) to the base station by using PRACH resources allocated for each SS block through the achievement of the SS block index, and thus a random access procedure required for initial access may be performed.

[0125] FIG. 5 illustrates a procedure in which a base station encodes an MIB to transmit the MIB to a PBCH. With reference to FIG. 5, a base station (gNode B) performs scrambling, channel coding, and rate matching based on a transport block 500 of a fixed size (510). Specifically, in operation 510, 2-bit system frame number (SFN), half frame timing information, and SS block index information are added to MIB information (511). Next, the MIB information is scrambled based on a cell ID and the 2-bit SFN (512), and the scrambled MIB information, 2-bit system frame number (SFN), half frame timing information, and SS block index information are generated (513). Next, 24-bit cyclic redundancy check (CRC) is generated based on the above information (514) and is added to the above information (515). Next, the above information is channel-coded (516), rate-matched (517), and re-scrambled based on 3-bit least significant bits (LSB) of the cell ID and SSB index (518). Next, the scrambled information is demodulated (520), mapped to resources and mapped to antennas and transmitted (520, 530).

[0126] In an initial access stage for the UE to access a system for the first time, the UE may first make synchronization in the downlink time and frequency from the synchronization signal transmitted by the base station through cell search and obtain a cell ID.

[0127] Then, the UE may receive a physical broadcast channel (PBCH) using the obtained cell ID, and obtain a master information block (MIB), which is essential system information, from the PBCH. The UE may additionally receive system information (System Information Block, SIB) transmitted by the base station to obtain control information related to cell common transmission / reception. The control information related to cell common transmission / reception may include random access-related control information, paging-related control information, common control information for various physical channels, and the like.

[0128] The synchronization signal may serve as a reference for cell search. Each frequency band employs subcarrier spacing that fits the channel condition such as phase noise. For the data channel or control channel to support various services as described above, different subcarrier spacing may be applied for each service type.

[0129] FIG. 6 is a diagram illustrating a time domain mapping structure and a beam sweeping operation for a synchronization signal according to an embodiment of the disclosure.

[0130] The following components may be defined for description.

[0131] - Primary synchronization signal (PSS): It is a signal used as a reference for DL time / frequency synchronization, and provides some information of cell ID.

[0132] - Secondary synchronization signal (SSS): It is used as a reference for DL time / frequency synchronization and provides some remaining information of cell ID. The SSS may also serve as a reference signal for demodulation of a PBCH,

[0133] - Physical broadcast channel (PBCH): It provides a master information block that is essential system information needed for the UE to transmit and receive a data channel and a control channel. The master information block (MIB) may include search space related control information indicating radio resource mapping information of a control channel, scheduling control information of a separate data channel for transmitting system information, information such as a system frame number (SEN) that is an index in a frame level that becomes a timing reference, and the like.

[0134] - Synchronization signal (SS) / PBCH block (or SSB): The SS / PBCH block consists of N OFDM symbols and is a combination of the PSS, SSS, and PBCH. For a system using a beam sweeping technique, an SS / PBCH block is the smallest unit for applying beam sweeping. In the 5G system, it may be N=4. The BS may transmit a maximum of L SS / PBCH blocks, and the L SS / PBCH blocks are mapped within a half frame (0.5 ms). In addition, the L SS / PBCH blocks are periodically repeated with a predetermined periodicity P unit. The BS may inform the UE of the periodicity P via signaling. In case that there is no separate signaling for the periodicity P, the UE applies a predetermined default value. Each SS / PBCH block has an SS / PBCH block index from 0 to a maximum of L-1, and the UE may know the SS / PBCH block index through SS / PBCH detection.

[0135] With reference to FIG. 6, in FIG. 6, beam sweeping is applied in units of an SS / PBCH block over time. In the example of FIG. 6, a UE1 605 may receive an SS / PBCH block via a beam radiated in direction #d0 603 due to beamforming applied to SS / PBCH block #0 at a time point t1 601. Also, a UE2 606 may receive an SS / PBCH block via a beam radiated in direction #d4 604 due to beamforming applied to SS / PBCH block #4 at a time point t2 602. The UE may obtain an optimal synchronization signal via a beam radiated from the BS in a direction toward a location of the UE. For example, it may be difficult for the UE1 605 to obtain time / frequency synchronization and essential system information from an SS / PBCH block via the beam radiated in the direction #d4 that is far away from the location of the UE1.

[0136] In addition to the initial access procedure, the UE may receive an SS / PBCH block to determine whether a radio link quality of a current cell is maintained above a predetermined threshold level. Furthermore, in a procedure for performing handover of a UE from the current cell to a neighboring cell, the UE may receive an SS / PBCH block from the neighboring cell in order to determine a radio link quality of the neighboring cell and obtain time / frequency synchronization of the neighboring cell.

[0137] After the UE obtains MIB and system information from the BS through the initial access procedure, the UE may perform a random access procedure to switch a link with the BS to a connected state (or RRC CONNECTED state). Upon completion of the random access procedure, the UE transitions to a connected state, and one-to-one communication is enabled between the BS and the UE. Hereinafter, a random access procedure will be described in detail with reference to FIG. 3.

[0138] FIG. 7 is a diagram illustrating a random access procedure according to an embodiment of the disclosure.

[0139] The disclosure is not limited to the 4-step random access procedure illustrated in FIG. 7, and may be applied to a 2-step random access procedure (message A (message including information corresponding to message 1 and message 3) transmission / reception and message B (message including information corresponding to message 2 and message 4) transmission / reception).

[0140] With reference to FIG. 7, in a first operation 710 of the random access procedure, a UE transmits a random access preamble to a BS. In the random access procedure, the random access preamble, which is a first message transmitted by the UE, may be referred to as Message 1. The BS may measure a propagation delay value between the UE and the BS from the random access preamble and achieve UL synchronization. In this case, the UE may randomly select a random access preamble to use from a set of random access preambles given by system information in advance. In addition, an initial transmission power for the random access preamble may be determined according to a pathloss between the BS and the UE, which is measured by the UE. Also, the UE may transmit the random access preamble by determining a direction of a transmit beam for the random access preamble based on a synchronization signal received from the BS.

[0141] In a second operation 720, the BS transmits a UL transmission timing control command to the UE based on the propagation delay value measured from the random access preamble received in the first operation 710. The BS may also transmit, to the UE, a UL resource to be used by the UE and a power control command as scheduling information. Control information regarding a UL transmit beam of the UE may be included in the scheduling information.

[0142] If the UE does not successfully receive, from the BS, a random access response (RAR) (or Message 2) that is scheduling information for Message 3 within a predetermined time period in the second operation 720, the UE may perform the first operation 710 again. In case that the UE performs the first operation 710 again, the UE may transmit the random access preamble with transmission power increased by a predetermined step (power ramping), thereby increasing the probability of reception of the random access preamble at the BS.

[0143] In a third operation 730, the UE transmits UL data (message 3) including its UE ID to the BS through a UL data channel (a physical UL shared channel (PUSCH)) by using the UL resource allocated in the second operation 720. A transmission timing of the UL data channel for transmitting the Message 3 may be controlled according to the timing control command received from the BS in the second operation 720. In addition, a transmission power for the UL data channel for transmitting the Message 3 may be determined by taking into account the power control / adjustment command received from the BS in the second operation 720 and a power ramping value of the random access preamble. The UL data channel for transmitting the Message 3 may mean a first UL data signal transmitted by the UE to the BS after the UE transmits the random access preamble.

[0144] In a fourth operation 740, when the BS determines that the UE has performed the random access procedure without colliding with another UE, the BS transmits data (Message 4) including an ID of the UE that has transmitted the UL data in the third operation 730 to the corresponding UE. Upon receiving a signal transmitted by the BS in the fourth operation 740, the UE may determine that the random access procedure is successful. In addition, the UE may transmit, to the BS, HARQ-ACK information indicating whether the Message 4 has been successfully received through a UL control channel (a physical UL control channel (PUCCH)).

[0145] If the data transmitted by the UE in the third operation 730 collides with data transmitted by another UE and thus the BS fails to receive a data signal from the UE, the BS may no longer transmit data to the UE. Accordingly, if the UE fails to receive the data transmitted by the BS in the fourth operation 740 within a predetermined time period, the UE may determine that the random access procedure has failed and restart the random access procedure from the first operation 710.

[0146] Upon successful completion of the random access procedure, the UE may transition to a connected state, and one-to-one communication between the BS and UE is enabled. The BS may receive UE capability information from the UE in the connected state and adjust scheduling based on the UE capability information of the corresponding UE. The UE may inform, via the UE capability information, the BS of whether the UE itself supports a certain functionality, a maximum allowable value of the functionality supported by the UE, etc. Accordingly, the UE capability information reported by each UE to the BS may have a different value for each UE.

[0147] As an example, the UE may report, to the BS, UE capability information including at least some of the following control information as the UE capability information.

[0148] - Control information related to a frequency band supported by the UE

[0149] - Control information related to a channel bandwidth supported by the UE

[0150] - Control information related to a highest modulation scheme supported by the UE

[0151] - Control Information related to a maximum number of beams supported by the UE

[0152] - Control information related to a maximum number of layers supported by the UE

[0153] - Control information related to CSI reporting supported by the UE

[0154] - Control information about whether the UE supports frequency hopping

[0155] - Control information related to a bandwidth when carrier aggregation (CA) is supported

[0156] - Control information about whether cross carrier scheduling is supported when CA is supported

[0157] FIG. 8 is a diagram illustrating a procedure in which the UE reports UE capability information to the BS according to an embodiment of the disclosure.

[0158] With reference to FIG. 8, in operation 810, a BS 802 may transmit a UE capability information request message to a UE 801. In response to a request for UE capability information from the BS, the UE transmits UE capability information to the BS in operation 820.

[0159] Hereinafter, an embodiment of the disclosure will be described in detail with the accompanying drawings. Hereinafter, a base station, which is a subject for allocating resources to terminals, may be at least one of gNode B, gNB, eNode B, Node B, base station (BS), a wireless connection unit, a base station controller, and a node on a network. A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. Hereinafter, the embodiment of the disclosure is described using the 5G system as an example, the embodiment of the disclosure may also be applied to other communication systems with similar technical background or channel type. For example, such communication systems may include LTE or LTE-A mobile communication and mobile communication technologies developed after 5G. Accordingly, based on determinations by those skilled in the art, the embodiments of the disclosure may also be applied to other communication systems through some modifications without significantly departing from the scope of the disclosure. For example, the content in the disclosure is applicable to a frequency division duplex (FDD) system, a time division duplex (TDD) system, a cross division duplex (XDD) system, and a subband full duplex (SBFD) system.

[0160] Also, in the following descriptions of the disclosure, related known functions or constitutions are not described in detail when it is deemed that they would unnecessarily obscure the essence of the disclosure. Furthermore, the terms to be described later are defined by taking functions described in the disclosure into account and may be changed according to a user's or operator's intent or customs. Therefore, definition of the terms should be made based on the overall descriptions in the specification.

[0161] In describing the disclosure, higher layer signaling may be signaling corresponding to at least one of the signalings below or a combination of one or more thereof.

[0162] - MIB (Master Information Block)

[0163] - SIB (System Information Block) or SIB X (X=1, 2, ...)

[0164] - RRC (Radio Resource Control)

[0165] - MAC (Medium Access Control) CE (Control Element)

[0166] In addition, L1 signaling may be signaling corresponding to at least one of signaling methods using the physical layer channels or signalings below or a combination of one or more of the methods.

[0167] - PDCCH (Physical Downlink Control Channel)

[0168] - DCI (Downlink Control Information)

[0169] - UE-specific DCI

[0170] - Group common DCI

[0171] - Common DCI

[0172] - Scheduling DCI (e.g., DCI used for scheduling downlink or uplink data)

[0173] - Non-scheduling DCI (e.g., DCI not for scheduling downlink or uplink data)

[0174] - PUCCH (Physical Uplink Control Channel)

[0175] - UCI (Uplink Control Information)

[0176] Hereinafter, the above examples are described through plural embodiments of the disclosure, but these are not independent and one or more embodiments may be applied simultaneously or in combination. In the description of an embodiment of the disclosure, SSB may be replaced with a synchronization signal.

[0177] In the description of an embodiment of the disclosure, PRACH resource may be replaced with PRACH opportunity.

[0178] In the description of an embodiment of the disclosure, transmission and reception for PRACH may be replaced with transmission and reception for message A, and transmission and reception for RAR may be replaced with transmission and reception for message B.

[0179] In the description of an embodiment of the disclosure, the synchronization signal received by the UE may be replaced with a best synchronization signal among a plurality of synchronization signals received by the UE. For example, among a plurality of synchronization signals, a measured value (e.g., reference signal received power (RSRP)) may be the largest synchronization signal.

[0180] In the description of an embodiment of the disclosure, unless specifically stated otherwise, a synchronization signal, synchronization reference signal, reference signal, cell synchronization signal, cell reference signal, cell synchronization reference signal, cell target synchronization signal, cell target synchronization signal, etc. may be substituted for each other and may be understood to have the same meaning.

[0181] In a cellular network, each cell is responsible for communication in a specific area. In case that the UE desires to access the network, the UE obtains the access information transmitted by each cell and then performs an access request based on the obtained access information. In the disclosure, an access request may correspond to a PRACH transmission.

[0182] In the existing communication method, in order to transmit access information to the UE, each cell uses transmits, to the UE, various information such as information corresponding to master information such as synchronization signal, physical cell identifier (ID) (PCID), cell barred info, and other system information in various formats such as MIB and SIB through various channels and reference signals such as PBCH and PDSCH.

[0183] Therefore, the UE performing an access request may first receive a signal broadcast from a target cell to obtain synchronization and MIB. Thereafter, the UE performs SIB reception through the PDCCH transmitted through a cell common search space. The UE performs the access request to the target cell through PRACH transmission based on information obtained through SIB reception. The BS may transmit additional information necessary for access through RAR transmission to the UE that has performed the access request. When the UE reports that it has received the above information, the initial access operation may be completed by assigning a cell radio network temporary identifier (C-RNTI) value to the UE.

[0184] In performing the above operation, most of the information transmitted by the cell is transmitted to the UE in the form of broadcasting, and therefore the cell has a burden of continuously broadcasting the corresponding information regardless of the presence or absence of the UE performing the access request.

[0185] The disclosure proposes a scheme to reduce the energy consumed by the network in a situation where there is no UE requesting the access request or only a small number of UEs can request the access request by reducing the burden of cell broadcasting.

[0186] An embodiment of the disclosure may provide a method for transmitting cell information necessary for initial access of the UE through separate scheduling to specific UEs requesting initial access rather than transmitting the cell information through broadcast.

[0187] An embodiment of the disclosure may provide an initial access process in which cell information necessary for initial access of the UE is provided for specific UEs requesting initial access through separate scheduling rather than transmitting the cell information through broadcast.

[0188] FIG. 9 is a diagram illustrating an example of a cell access procedure (or initial access procedure) of a UE defined by 3GPP new radio (NR) to which an embodiment of the disclosure is applicable.

[0189] With reference to FIG. 9, gNB corresponds to network equipment and / or base stations that are used or involved in transmitting and receiving radio signals from a base station, such as a radio unit (RU) and distributed unit (DU).

[0190] The BS performs transmission of a broadcasting channel composed of synchronization signal block (SSB), that is, PSS / SSS / PBCH, to transmit access information to the UE. The corresponding channel transmits, to the UE, synchronization information for the BS, PCID information for the cell defined by or belonging to the corresponding BS, control resource set (CORESET) #0 information, which is information on radio resources of the physical downlink control channel (PDCCH) used to transmit SIB (e.g., SIB1) information, cell barring information, which is information about whether the corresponding cell allows access to a new UE, and the like. Based on the above information, the UE obtains information about reception of SIB transmitted by the same BS or a BS sharing the same PCID. The UE then obtains information necessary for the initial access request, such as cell selection information, cell access information, PRACH radio resource information (RACH parameters), and cell common system information through SIB reception.

[0191] The UE may determine / select a PRACH radio resource to use for the initial access request based on the above information and the SSB resource used for cell search. The UE performs PRACH transmission through the radio PRACH resource.

[0192] After receiving the PRACH transmission, the BS may perform PDCCH transmission through cell specific common search space. The BS schedules PRACH response information (random access response (RAR)) to the UE through the PDCCH and transmits the corresponding information (PRACH response information) through a physical downlink shared channel (PDSCH) channel. The PRACH response information may include timing advance (TA) information, scheduling information for msg3 (UL grant), and temporary cell (TC)-RNTI information. Thereafter, the initial access operation of the UE is completed through the transmission of the UE's msg3 information and allocation of the C-RNTI value by the BS.

[0193] In the above initial access operation, the BS may perform PCID broadcasting for each cell, different PRACH radio resources and transmission methods for each cell, and different RAR transmission schemes and radio resource allocation for each cell. Through this, it is possible to secure initial access capacity.

[0194] However, there is a disadvantage in that a lot of information / signals, such as MIB and SIB, must be continuously and periodically broadcasted. For example, in areas with low demand for wireless communication, such as office areas after business hours, guaranteeing initial access capacity through the above scheme may not be an essential element. Therefore, the scheme of continuously broadcasting a large amount of information / signals for each cell as described above may cause unnecessary use of radio resources and decrease the energy efficiency of the network.

[0195] According to an embodiment of the disclosure, a method for transmitting cell information necessary for initial access of a UE to specific UEs requesting initial access through separate scheduling rather than transmitting the cell information through broadcast may be provided. The disclosure proposes an initial access process that reduces energy consumed by a BS and / or network in situations where large capacity for initial access is not required.

[0196] According to the disclosure, the BS may minimize the performance of cell specific broadcasting. Through this, the disclosure may increase the energy efficiency of a BS transmission end.

[0197] FIG. 10 is a diagram illustrating an example of an initial access procedure according to an embodiment of the disclosure.

[0198] The initial access process according to an embodiment of the disclosure proposes a scheme for managing radio resources for each cell group or cell set, instead of a technique for managing radio resources used for initial access according to existing cell-specific characteristics. The initial access process according to an embodiment of the disclosure may be cell group specific or cell set specific. A cell group (group of cell) or cell set (set of cell) may include one or more cells or a plurality of cells. Unless specifically stated otherwise, in the disclosure, cell group (group of cell) may be replaced with cell set (set of cell), and cell set (set of cell) may be replaced with cell group (group of cell).

[0199] According to an embodiment of the disclosure, since there is no need to transmit cell-specific information, broadcasting of information corresponding to cell-specific information such as existing MIB and SIB or system information may not be required. In addition, according to an embodiment of the disclosure, since there is no need to distinguish the ID of the cell that is the target of the initial access request, broadcasting of the PCID is also not required. Comparing this with the existing initial access process, among the respective operations required by the existing initial access process, transmission of SSS and PBCH, transmission of SIB information, etc. may be omitted. That is, at least one operation of the operations of the existing initial access process may be omitted. For example, at least one operation among transmission of SSS and PBCH and transmission of SIB information may be omitted.

[0200] In FIG. 10, it is schematized that PSS is transmitted among existing SSBs, but the technique proposed by the disclosure is not limited thereto.

[0201] For example, according to an embodiment of the disclosure, the PSS-based UE operation may be understood as an operation in which the UE performs a synchronization operation based on a synchronization signal that does not include information about the cell ID. According to an embodiment of the disclosure, a synchronization signal different from the existing PSS may be proposed.

[0202] For example, the above synchronization signal may be understood as a synchronization signal shared by a cell group or set of cells including a plurality of cells, for example, a synchronization signal in which a different sequence is used for each cell group. For example, in sequence generation of the corresponding synchronization signal, cell group ID (or cell set ID) (or a value corresponding thereto) may be used as a seed value. That is, the cell group ID (or cell set ID) (or a value corresponding thereto) may be used to initialize the sequence generator used to generate the corresponding sequence. That is, the formula used to initialize the corresponding sequence generator may include cell group ID (or cell set ID) (or a value corresponding thereto) as a variable. In the following description of the disclosure, the synchronization signals, etc., including / indicating cell group ID, etc. may be understood and / or replaced as such. However, this is an example of a synchronization signal in which a different sequence is used for each cell group, and the disclosure is not limited thereto.

[0203] FIG. 11 is a diagram illustrating an example of an initial access procedure according to an embodiment of the disclosure. With reference to FIG. 11, the initial access process proposed by the disclosure will be described in more detail.

[0204] As a first operation (sharing least info.), the BS performs broadcasting of a synchronization reference signal (synchronization signal) to support synchronization of the UE. In this case, a plurality of BSs may transmit synchronization signals of the same structure, for example, the same sequence. As a scheme for transmitting the synchronization signal of the same structure, a scheme in which a plurality of cells belonging to each cell group determine the generation and transmission of the synchronization signal according to the cell group ID may be used. In addition, the synchronization signal of the same structure as above may be transmitted simultaneously through the same radio resource. To this end, the transmission location of the synchronization signal may be determined according to the cell group ID, or the transmission timing of the synchronization signal may be adjusted equally through prior cooperation between the plurality of cells. Alternatively, the plurality of cells belonging to the same cell group may share a synchronization signal. In this case, only some cells within the cell group may transmit the synchronization signal. The UE may receive the same synchronization reference signal from different BSs responsible for the plurality of cells. That is, each BS operates one or more cells, and the UE may receive the same synchronization reference signal from the corresponding BSs. The UE may secure downlink synchronization with the network through the synchronization reference signal.

[0205] In addition, the UE obtains information about PRACH radio resources to perform PRACH transmission with respect to the BS that has transmitted the reference signal according to predefined conditions. This will be described in more detail with reference to FIGS. 12 to 15. Hereinafter, the examples of PRACH radio resource selection in FIGS. 12 to 15 are not separate embodiments, and at least some of them may be applied in combination. For example, one or more of the examples of PRACH radio resource selection shown in FIGS. 12 to 15 may be predefined / configured to be used.

[0206] FIG. 12 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure.

[0207] With reference to FIG. 12, after the UE receives a synchronization signal for each cell group or a synchronization signal for a random cell for which a PCID for each cell is not specified, a PRACH radio resource selection rule may be configured / defined as the UE performing PRACH transmission after a delay of ‘n’ slots from the reception of the signal used for synchronization (synchronization signal). For example, the PRACH resource may be selected after n slots from the slot (e.g., SSB dedicated slot) in which the synchronization signal is received. For example, a specific PRACH resource may be selected among PRACH resources in a slot (PRACH slot) after n slots from the slot in which the synchronization signal is received. A specific PRACH resource may be determined based on association or correspondence with a resource (for example, the resource may include one or more symbols) where the synchronization signal is actually received within the slot in which the synchronization signal is received. The PRACH resources may be PRACH resources with different starting points (for example, starting symbols) within one slot. Detailed information about the radio resources used for PRACH transmission may be determined according to the PRACH radio resource selection rules. For example, radio resource information on the frequency axis, information about the PRACH sequence (e.g., information about one or more parameters for generating the PRACH sequence), etc. may be determined.

[0208] FIG. 13 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure.

[0209] With reference to FIG. 13, the resource allocation rule may be configured / defined so that PRACH is transmitted through different radio resources according to the cell group identity or ID value indicated by the synchronization reference signal. For example, the resource allocation rule may be configured or defined so that PRACH is transmitted through different slots. For example, PRACH resources may be time division duplex (TDM) at a slot level.

[0210] For example, a first resource in a slot in which a synchronization signal is received (e.g., the first resource includes one or more symbols) and / or a synchronization signal received in the first resource may correspond to group identity #0.

[0211] For example, a second resource in a slot in which a synchronization signal is received (e.g., the second resource includes one or more symbols) and / or a synchronization signal received in the second resource may correspond to group identity #1.

[0212] For example, a third resource within a slot in which a synchronization signal is received (e.g., the third resource includes one or more symbols) and / or a synchronization signal received from the third resource may correspond to group identity #2.

[0213] For example, group identity #0 may correspond to a slot (PRACH slot) after n slots from a slot in which a synchronization signal is received.

[0214] For example, group identity #1 may correspond to a slot (PRACH slot) after n+1 slots from a slot in which a synchronization signal is received.

[0215] For example, group identity #2 may correspond to a slot (PRACH slot) after n+2 slots from a slot in which a synchronization signal is received.

[0216] For example, in case that a synchronization signal is received in group identity #0, the UE may transmit PRACH on a PRACH resource in a slot (PRACH slot) after n slots from a slot in which the synchronization signal is received.

[0217] For example, in case that a synchronization signal is received in group identity #1, the UE may transmit PRACH on the PRACH resource in a slot (PRACH slot) after n+1 slots from a slot in which the synchronization signal is received.

[0218] For example, in case that a synchronization signal is received in group identity #2, the UE may transmit PRACH on a PRACH resource in a slot (PRACH slot) after n+2 slots from a slot in which the synchronization signal is received.

[0219] FIG. 14 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure. More specifically, FIG. 14 is an example of a case where the location of a radio resource is determined on the frequency used for PRACH transmission based on the cell group identity or ID indicated by the reference signal used for cell target synchronization.

[0220] With reference to FIG. 14, the resource allocation rule may be configured / defined so that PRACH is transmitted through different radio resources according to the cell group identity or ID value indicated by a synchronization reference signal. For example, within one slot, a plurality of PRACH resources may be configured on different frequency resources. For example, the plurality of PRACH resources may be frequency division multiplexed (FDMed). In addition, the resource allocation rule may be configured or defined so that PRACH is transmitted through a specific PRACH resource among the plurality of PRACH resources.

[0221] For example, the first resource in the slot in which the synchronization signal is received (e.g., the first resource includes one or more symbols) and / or the synchronization signal received in the first resource may correspond to group identity #0.

[0222] For example, the second resource in the slot in which the synchronization signal is received (e.g., the second resource includes one or more symbols) and / or the synchronization signal received in the second resource may correspond to group identity #1.

[0223] For example, the third resource within the slot in which the synchronization signal is received (e.g., the third resource includes one or more symbols) and / or the synchronization signal received in the third resource may correspond to group identity #2.

[0224] For example, group identity #0 may correspond to the first PRACH resource among PRACH resources in a slot (PRACH slot) after n slots from the slot in which the synchronization signal is received.

[0225] For example, group identity #1 may correspond to the second PRACH resource among PRACH resources in a slot (PRACH slot) after n slots from the slot in which the synchronization signal is received.

[0226] For example, group identity #2 may correspond to the third PRACH resource among PRACH resources in a slot (PRACH slot) after n slots from the slot in which the synchronization signal is received.

[0227] For example, in case that the synchronization signal is received in group identity #0, the UE may transmit PRACH on the first PRACH resource in the slot (PRACH slot) after n slots from the slot in which the synchronization signal is received.

[0228] For example, in case that the synchronization signal is received in group identity #1, the UE may transmit PRACH on the second PRACH resource in the slot (PRACH slot) after n slots from the slot in which the synchronization signal is received.

[0229] For example, in case that the synchronization signal is received in group identity #2, the UE may transmit PRACH on the third PRACH resource in the slot (PRACH slot) after n slots from the slot in which the synchronization signal is received.

[0230] According to an embodiment of the disclosure, in addition to determining the PRACH radio resources on the time and / or frequency axis, such as the PRACH sequence being determined according to the cell group identity of the synchronization signal, various parameters defining PRACH transmission may be determined by the reception location of the synchronization signal and the cell group ID indicated by the synchronization signal. In addition, a plurality of parameters defining PRACH transmission may be determined simultaneously or sequentially by the reception location and / or cell group ID of the synchronization signal.

[0231] FIG. 15 is a diagram illustrating an example of PRACH radio resource selection according to a synchronization signal according to an embodiment of the disclosure.

[0232] With reference to FIG. 15, each synchronization reference signal may be defined or configured to receive allocation of a number of corresponding PRACH radio resources. In this case, the UE may select a radio resource to use for PRACH transmission through random selection.

[0233] For example, candidates for PRACH resources in one or more slots after n slots from the slot (e.g., SSB dedicated slot) in which the synchronization signal is received may be defined / configured. Although FIG. 15 illustrates that within three slots, a candidate for PRACH resource in each slot is defined / configured, the disclosure is not limited thereto. The UE may randomly select a resource to transmit PRACH among the PRACH resource candidates. The candidates of PRACH resources corresponding to each synchronization reference signal may be configured in a plurality of slots, and the PRACH resources corresponding to different synchronization reference signals may be PRACH resources with different starting points (e.g., starting symbols) within one slot.

[0234] According to an embodiment of the disclosure, the amount of radio resources used for PRACH transmission, such as PRACH length (e.g., PRACH sequence length) / radio resource size / whether to be repeated, may be determined according to a cell synchronization reference signal.

[0235] For example, the cell synchronization reference signal may transmit an index for PRACH radio resources. Depending on the index, the length of PRACH transmission, such as short, mid, or long, may be determined. In the above PRACH transmission length, the short may be the PRACH transmission using a length shorter than a slot, the mid may be the PRACH transmission using the same as a slot or one or more slots, and the long may be the PRACH transmission using a plurality of slots. The PRACH transmission length may be determined by the difference in sequence length used for PRACH transmission and / or whether the PRACH sequence is repeatedly transmitted.

[0236] The synchronization signal or synchronization reference signal according to an embodiment of the disclosure may be named a low overhead cell reference signal. The transmission of the low overhead cell reference signal according to an embodiment of the disclosure does not have to be performed by all cells, and may be performed only by a network node or cell that requires energy saving operations. The UE may receive both the low overhead cell reference signal and the general cell reference signal proposed by the disclosure from different cells. In this case, it may be defined or configured such that the PRACH transmission targeting the cell transmitting the general cell reference signal is given priority (high priority on PRACH transmission). That is, initial access to a network node or cell that does not require an energy saving operation may be given priority over a network node or cell that requires an energy saving operation.

[0237] For the low overhead cell reference signal proposed by the disclosure, in the case of a cell that does not allow the access by a new UE, that is, a cell configured to cell barring = on, transmission of the reference signal may be stopped. That is, in the case of a cell configured to cell barring = on, the low overhead cell reference signal may not be transmitted. In other words, receiving a synchronization signal may mean that the cell is not barred.

[0238] FIG. 16 is a diagram illustrating an example of an initial access procedure according to an embodiment of the disclosure. FIG. 16 is a more detailed example of an initial access procedure according to an embodiment of the disclosure illustrated in FIG. 11 , and detailed descriptions of content that overlaps with the content described in FIG. 11 will be omitted. The following description refers to FIGS. 16 and 11. As a second operation (cell selection by network), the UE transmits an initial access request signal to a cell whose PCID is unknown through the selected PRACH radio resource or to a plurality of cells sharing the cell group ID measured by the synchronization signal. The radio resource used for the PRACH transmission may be a radio resource shared by a plurality of cells, as described above in the first operation, and therefore the UE PRACH transmission may be received by the plurality of cells. However, this is an example, and one cell may receive PRACH.

[0239] For example, in case that there is no PCID (a case where the synchronization signal does not correspond to the PCID), the synchronization signal may correspond to a cell-group ID (PCID group (PCIDG)). For example, the synchronization signal may correspond to a cell-group identification sequence.

[0240] For example, in case that there is no specific PRACH resource configuration, the PRACH resource may be identified according to the cell-group ID.

[0241] In case that the PRACH transmission is received by the plurality of cells, the network may select a cell to perform access permission among the plurality of cells. For example, the network may select a cell that will perform access permission through RAR among the cells that have received the PRACH transmission through coordination between network nodes (and / or cells) that have received the PRACH transmission, such as coordination between cells, coordination between RUs in charge of cells, and / or coordination between DUs managing RUs. Through the above operation, one cell may be selected or a plurality of cells may be selected. For example, the network may select a cell to permit access by comparing parameters indicating the channel states between each cell and the UE that has performed PRACH transmission, such as the uplink reference signal received power (UL RSRP) of the PRACH received by each cell. For example, there may be one or plurality of cells to perform access permission.

[0242] As a third step operation (UL grant with cell specific config.), when transmitting access permission and information for performing the next operation to the UE that has performed the PRACH transmission, the cell may inform the UE whether access is permitted and the information for performing the next operation through the PDCCH. For example, a response to an initial access request having been received through the PDSCH and control information necessary for receiving the corresponding PDSCH may be transmitted through the PDCCH. Alternatively, the information necessary for receiving the PDSCH, including the contents corresponding to the response, may be transmitted through the PDCCH.

[0243] According to an embodiment, radio resources used for transmitting the PDCCH may be determined by the cell reference signal transmitted in the first operation. For example, among the methods for defining the PRACH radio resources of the UE described above in the first operation, such as the location of the radio resource where the cell reference signal has been received and the index indicated by the cell reference signal (e.g., cell group ID, etc.), one or plurality of methods may be used.

[0244] According to an embodiment, the radio resource used for transmitting the PDCCH may be determined by the PRACH radio resource used by the UE in the first operation. For example, in case that each cell reference signal radio resource is connected to two or more PRACH radio resources, for example, PRACH radio resource locations on the time or frequency axis and / or PRACH sequences, as described in the first operation, the UE may perform the PRACH transmission by selecting one of the radio resources. Additionally, the PDCCH that schedules the response to the PRACH reception may be determined according to the selection of the PRACH radio resource.

[0245] According to an embodiment, when selecting radio resources used for the PDCCH transmission, one or more PDCCH radio resources may be allocated for each cell reference signal radio resource or each PRACH radio resource. In this case, the cell may randomly select one or plurality of the corresponding PDCCH radio resources.

[0246] According to an embodiment, the information necessary for performing PDCCH reception for scheduling a response to an initial access request may be selected according to the cell reference signal radio resource or PRACH radio resource. For example, the location of the PDCCH radio resource, subcarrier spacing of the PDCCH, PDCCH demodulation reference signal (DMRS) configuration, and / or other information may be selected according to the cell reference signal radio resource or PRACH radio resource. Among the information necessary for PDCCH reception, information that is not configured according to the cell reference signal radio resources or PRACH radio resources may be determined by predefined rules (e.g., rules defined by standards).

[0247] According to an embodiment, determination by the cell reference signal and / or PRACH radio resource means determination according to the location of the corresponding radio resource, the index information transmitted by the corresponding reference signal and / or radio resource, and / or the size of the corresponding reference signal and / or radio resource, etc. Some of the information necessary for PDCCH reception may be determined by the cell reference signal radio resources, and some of the information may be determined by PRACH radio resources. And / or a combination of two or more methods, such as some of the resources necessary for PDCCH reception being determined by the location of the corresponding radio resource (PRACH radio resource), other portions of the resources necessary for PDCCH reception being determined by the index indicated by the corresponding radio resource (PRACH radio resource), and still other portions of the resources necessary for PDCCH reception being determined by the size of the corresponding radio resource (PRACH radio resource), is also possible.

[0248] According to an embodiment, as another method for performing a response to an initial access request, a method for directly transmitting response information to the UE without a PDCCH is also possible. In this case, response information may be transmitted to the UE through preconfigured radio resources and / or preconfigured data transmission scheme, for example, preconfigured PDSCH DM RS, preconfigured PDSCH coding & modulation (modulation and coding scheme (MCS)). The configuration for the data transmission scheme may follow predefined rules (e.g., rules defined by standards) or may be determined by cell synchronization radio resources, PRACH radio resources, the size of PRACH radio resources, or the like.

[0249] The response information transmitted by the above scheme according to an embodiment may include some or all of the information necessary for the UE to complete / end performing of initial access with the cell.

[0250] For example, the response information may be or include information about cell specific configuration that the UE must recognize for subsequent communication.

[0251] For example, the above information may be or include information necessary for receiving cell specific PDCCH radio resources (PDCCH common search space) or cell specific common PDCCH.

[0252] For example, the information may include general information applicable to data reception, for example, information about PDSCH DMRS configurations.

[0253] For example, the above information may include other general system information, for example, information defined by existing SIB.

[0254] For example, the response signal may include UE identity, for example, an RNTI value.

[0255] After receiving the response information, the UE may indicate to the cell that information by the response has been received. Alternatively, the UE may indicate to the cell that it has failed to receive the above information. The indication may be transmitted in the form of, for example, Ack (acknowledgement) (ACK / NACK (negative ACK)). For example, it is hybrid automatic repeat request acknowledgment (HARQ-ACK). The transmission of the indication may be reported to the corresponding cell through the PUCCH channel, for example, in the form of control information.

[0256] The radio resource used for the report or indication may be determined by a cell synchronization signal or PRACH radio resource, and the detailed scheme for determining this may be the same as one of the methods for configuring PRACH radio resources or PDCCH radio resources described in the first and second operations.

[0257] Alternatively, as the scheme for selecting the radio resources used for the reporting or indication, a scheme for selecting a plurality of candidate resources for each cell synchronized radio resource or PRACH radio resource and then selecting one of the candidate resources through the response information or response PDCCH is also possible. For example, a candidate for one or more ACK resources may be configured, and a candidate for transmitting ACK may be selected based on cell-group ID. As another example, a down-selection scheme based on PDCCH may be applied.

[0258] In the second operation, in case that a plurality of cells are determined to transmit a response to the initial access request, the UE may receive the RAR signal described above from one or more cells. In this case, the UE may fail to receive RAR due to inter-cell interference, or may receive RAR from one or more cells, including the cell showing the best downlink characteristics among the plurality of cells. In case that the UE succeeds in receiving the plurality of RARs, the UE may select one of the plurality of cells and proceed with the subsequent process. For example, the UE may transmit ACK for the RAR of one cell and omit transmission of ACK for other cells. A cell that has transmitted RAR but does not receive ACK or NACK reporting from the UE determines that the UE does not desire to proceed with initial access and does not proceed with the subsequent operations. Alternatively, the UE may transmit a ‘deny’ message indicating cancellation of the initial access request for the cell that has transmitted the RAR for the initial access request instead of ACK or NACK, so that the cell may more accurately recognize that the initial access request has been canceled. In case that the UE fails to receive RAR due to interference between multiple RARs is divided into two cases, a case where the UE fails to receive the PDCCH scheduling the PDSCH including the RAR, or a case where the UE succeeds in receiving the PDCCH but fails to receive the PDSCH including the RAR. In case that the UE fails to receive the PDCCH, the UE may re-perform the cell group search procedure of the first operation or the initial access request procedure of the second operation. Alternatively, in case that the UE succeeds in receiving the PDCCH but fails to receive the PDSCH, the UE may request that fewer cells retransmit the RAR by transmitting a NACK to the corresponding cell.

[0259] FIG. 17 is a diagram illustrating an example of a UE operation according to an embodiment of the disclosure. Various changes could be made to the method illustrated in the flowchart in FIG. 17. For example, while a series of operations is illustrated, various operations in each drawing could overlap, occur in parallel, occur in a different order, or occur multiple times. In another example, an operation may be omitted or replaced by other operations.

[0260] With reference to FIG. 17, in operation 1710 according to an embodiment, the UE may receive a synchronization signal. For example, the synchronization signal may correspond to a cell group ID. For example, the cell group ID may be the ID of a cell group including one or more cells.

[0261] In operation 1720 according to an embodiment, the UE may transmit PRACH. For example, PRACH may be related to the synchronization signal. For example, PPACH may be transmitted to at least some of one or more cells included in the cell group.

[0262] In operation 1730 according to an embodiment, the UE may receive RAR. For example, RAR may be related to PRACH.

[0263] For more detailed information about the operation of the UE illustrated in FIG. 17, the description of the above-described embodiment may be referred.

[0264] FIG. 18 is a diagram illustrating an example of a BS operation according to an embodiment of the disclosure. Various changes could be made to the method illustrated in the flowchart in FIG. 18. For example, while a series of operations is illustrated, various operations in each drawing could overlap, occur in parallel, occur in a different order, or occur multiple times. In another example, an operation may be omitted or replaced by other operations.

[0265] With reference to FIG. 18, in operation 1810 according to an embodiment, the BS may transmit a synchronization signal. For example, the synchronization signal may correspond to a cell group ID. For example, the cell group ID may be the ID of a cell group including one or more cells.

[0266] In operation 1820 according to an embodiment, the BS may receive PRACH. For example, PRACH may be related to the synchronization signal. For example, PPACH may be received in at least some of one or more cells included in the cell group.

[0267] In operation 1830 according to an embodiment, the BS may transmit RAR. For example, RAR may be related to PRACH.

[0268] For more detailed information about the operation of the BS illustrated in FIG. 18, the description of the above-described embodiment may be referred.

[0269] FIG. 19 is a diagram illustrating a structure of a UE in a wireless communication system according to an embodiment of the disclosure.

[0270] With reference to FIG. 19 , the UE may include a transceiver with reference to a UE receiver 1900 and a UE transmitter 1910, a memory (not shown), and a UE processor 1905 (a UE controller or processor). According to a communication scheme of the UE described above, the UE transceiver 1900 and 1910, the memory, and the UE processor 1905 may operate. However, elements of the UE are not limited to the above example. For example, the UE may include more elements than the afore-described elements or may include fewer elements than the afore-described elements. In addition, the transceiver, memory, and processor may be implemented as a single chip.

[0271] The transceiver may transmit or receive a signal to or from the BS. Here, the signal may include control information and data. To this end, the transceiver may include a RF transmitter that up-converts and amplifies a frequency of a signal to be transmitted, and a RF receiver that low-noise amplifies a received signal and down-converts a frequency thereof. However, this is only an example of the transceiver, and the elements of the transceiver are not limited to the RF transmitter and RF receiver.

[0272] In addition, the transceiver may receive a signal on a wireless channel and output the signal to the processor, or transmit a signal output from the processor on a wireless channel.

[0273] The memory may store programs and data necessary for the UE to operate. Also, the memory may store control information or data included in a signal transmitted or received by the UE. The memory may include a storage medium such as ROM, RAM, hard disk, CD-ROM, and DVD, or any combination thereof. Also, the memory may include a plurality of memories.

[0274] In addition, the processor may control a series of processes to allow the UE to operate according to the aforementioned embodiment. For example, the processor may control the elements of the UE to receive a plurality of PDSCHs simultaneously by receiving DCI including two layers. The processor may include a plurality of processors and may execute a program stored in the memory to perform an operation of controlling the elements of the UE.

[0275] FIG. 20 is a diagram illustrating a structure of a BS in a wireless communication system according to an embodiment of the disclosure.

[0276] With reference to FIG. 20 , the BS may include a transceiver with reference to a BS receiver 2000 and a BS transmitter 2010, a memory (not shown), and a BS processor 2005 (or a BS controller or processor). According to a communication method of the BS described above, the BS transceiver 2000 and 2001, memory, and BS processor 2005 may operate. However, elements of the BS are not limited to the above example. For example, the BS may include more or fewer elements than those described above. In addition, the transceiver, memory, and processor may be implemented as a single chip.

[0277] The transceiver may transmit or receive a signal to or from the UE. Here, the signal may include control information and data. To this end, the transceiver may include an RF transmitter that up-converts and amplifies a frequency of a signal to be transmitted, and a RF receiver that low-noise amplifies a received signal and down-converts a frequency thereof. However, this is only an example of the transceiver, and the elements of the transceiver are not limited to the RF transmitter and RF receiver.

[0278] In addition, the transceiver may receive a signal on a wireless channel and output the signal to the processor, or transmit a signal output from the processor on a wireless channel.

[0279] The memory may store programs and data necessary for the BS to operate. Also, the memory may store control information or data included in a signal transmitted or received by the BS. The memory may include a storage medium such as ROM, RAM, hard disk, CD-ROM, and DVD, or any combination thereof. Also, the memory may include a plurality of memories.

[0280] The processor may control a series of procedures to operate the BS according to the afore-described embodiments of the disclosure. For example, the processor may control each element of the BS to configure and transmit two layers of DCI including allocation information for a plurality of PDSCHs. The processor may include a plurality of processors and may execute a program stored in the memory to perform an operation of controlling the elements of the BS.

[0281] The methods according to embodiments as described in the specification or in the following claims of the disclosure may be implemented as hardware, software, or a combination of hardware and software.

[0282] In case of being implemented in software, a computer-readable storage medium having one or more programs (software modules) stored thereon may be provided. One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors in an electronic device. The one or more programs include instructions for causing the electronic device to execute the methods according to the embodiments of the disclosure described in the claims or the specification.

[0283] The programs (e.g., software modules or software) may be stored in random access memory (RAM), non-volatile memory including flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), a magnetic disc storage device, a compact disc-ROM (CD-ROM), a digital versatile disc (DVD), another type of optical storage device, or a magnetic cassette. Alternatively, the programs may be stored in a memory including a combination of some or all of the above-mentioned memory devices. Also, a plurality of such memories may be included.

[0284] Also, the programs may be stored in an attachable storage device which is accessible via a communication network constituted by, for example, the Internet, an intranet, a local area network (LAN), a wireless LAN (WLAN), or a storage area network (SAN), or a combination thereof. Such a storage device may access, via an external port, a device performing the embodiments of the disclosure. Furthermore, a separate storage device on the communication network may access the electronic device performing the embodiments of the disclosure.

[0285] In the specific embodiments of the disclosure described above, elements included in the embodiments are expressed in a singular or plural form according to the specific embodiments. However, the singular or plural form is appropriately selected for convenience of descriptions and the disclosure is not limited to the singular or plural elements. As such, an element expressed in a plural form may also be constituted as a single element, and an element expressed in a singular form may also be constituted as plural elements.

[0286] Meanwhile, the embodiments of the disclosure described with reference to the specification and the drawings are merely illustrative of specific examples to easily facilitate description and understanding of the disclosure, and are not intended to limit the scope of the disclosure. That is, it will be obvious to one of ordinary skill in the art that various modifications may be made based on the technical spirit of the disclosure. Also, the respective embodiments may be combined to be implemented, when required. For example, a BS and a UE may be operated in a manner that portions of an embodiment of the disclosure are combined with portions of another embodiment of the disclosure. For example, a BS and a UE may be operated in a manner that portions of a first embodiment of the disclosure are combined with portions of a second embodiment of the disclosure.

[0287] Meanwhile, the order of explanation in the drawings for explaining the method of the disclosure does not necessarily correspond to the order of execution, and the order of precedence may be changed or executed in parallel.

[0288] Alternatively, drawings describing the method of the disclosure may omit some of the elements and include only some of the elements within the scope of not impairing the essence of the disclosure.

[0289] In addition, the method of the disclosure may be executed by combining some or all of the contents included in each embodiment within a range that does not impair the essence of the disclosure.

[0290] Various embodiments of the disclosure have been described. The embodiments of the disclosure described above are merely examples, and the embodiments of the disclosure are not limited thereto. It will be understood by one of ordinary skill in the art that the embodiments of the disclosure may be easily modified in other specific forms without changing the technical spirit or the essential features of the disclosure. The scope of the disclosure is defined by the claims to be described rather than the detailed description, and all changes or modifications within the meaning and scope of the claims and their equivalents will be construed as being included in the scope of the disclosure.

Claims

1.A method performed by a user equipment (UE) in a communication system, the method comprising:receiving a synchronization signal associated with a cell group identifier;identifying a physical random access channel (PRACH) resource based on the cell group identifier; andtransmitting, to a plurality of cells, PRACH transmissions via the PRACH resource,wherein the plurality of cells are included in a cell group corresponding to the cell group identifier.2.The method of claim 1, wherein the PRACH resource is identified among a plurality of PRACH resources associated with a plurality of cell group identifiers, andwherein the plurality of PRACH resources are configured at least n slots after a slot in which the synchronization signal is received.3.The method of claim 2, wherein the plurality of PRACH resources are included in one slot after n slots from the slot in which the synchronization signal is received, andwherein starting symbols of the plurality of PRACH resources are different from each other in the one slot.4.The method of claim 2, wherein the plurality of PRACH resources are slot-level time division multiplexed or frequency division multiplexed.5.The method of claim 2, wherein one cell group identifier corresponds to a plurality of PRACH resources, andwherein the PRACH resource is randomly selected among a plurality of PRACH resources corresponding to the cell group identifier.6.The method of claim 1, further comprising:receiving at least one random access response (RAR) from at least one of the plurality of cells, respectively, wherein at least one physical downlink control channel (PDCCH) for the at least one RAR is identified based on the cell group identifier and the at least one RAR respectively includes at least one cell specific configuration or cell specific system information; andtransmitting an acknowledgement (ACK) message,wherein in case that the at least one RAR is one RAR received from one of the plurality of cells, the ACK message is transmitted to the one of the plurality of cells,wherein in case that the at least one RAR is a plurality of RARs received from at least some of the plurality of cells, the ACK message is transmitted to one of the at least some of the plurality of cells identified by the UE, andwherein the at least one of the plurality of cells are based on uplink reference signal received power (RSRP) associated with the PRACH transmissions.7.The method of claim 6, wherein a resource for the ACK message is identified based on:the cell group identifier among at least one candidate resource; ordown-selection by a PDCCH for the one RAR including a corresponding cell specific configuration.8.A user equipment (UE) in a communication system, the UE comprising:a transceiver; anda processor coupled with the transceiver and configured to:receive a synchronization signal associated with a cell group identifier;identify a physical random access channel (PRACH) resource based on the cell group identifier; andtransmit, to a plurality of cells, PRACH transmissions via the PRACH resource,wherein the plurality of cells are included in a cell group corresponding to the cell group identifier.9.The UE of claim 8, wherein the PRACH resource is identified among a plurality of PRACH resources associated with a plurality of cell group identifiers, andwherein the plurality of PRACH resources are configured at least n slots after a slot in which the synchronization signal is received.10.The UE of claim 9, wherein the plurality of PRACH resources are included in one slot after n slots from the slot in which the synchronization signal is received, andwherein starting symbols of the plurality of PRACH resources are different from each other in the one slot.11.The UE of claim 9, wherein the plurality of PRACH resources are slot-level time division multiplexed or frequency division multiplexed.12.The UE of claim 7, wherein the processor is further configured to:receive at least one random access response (RAR) from at least one of the plurality of cells, respectively, wherein at least one physical downlink control channel (PDCCH) for the at least one RAR is identified based on the cell group identifier and the at least one RAR respectively includes at least one cell specific configuration or cell specific system information; andtransmit an acknowledgement (ACK) message,wherein in case that the at least one RAR is one RAR received from one of the plurality of cells, the ACK message is transmitted to the one of the plurality of cells,wherein in case that the at least one RAR is a plurality of RARs received from at least some of the plurality of cells, the ACK message is transmitted to one of the at least some of the plurality of cells identified by the UE, andwherein the at least one of the plurality of cells are based on uplink reference signal received power (RSRP) associated with the PRACH transmissions.13.The UE of claim 12, wherein a resource for the ACK message is identified based on:the cell group identifier among at least one candidate resource; ordown-selection by a PDCCH for the one RAR including a corresponding cell specific configuration.14.A method performed by a base station in a communication system, the method comprising:transmitting a synchronization signal associated with a cell group identifier; andreceiving, on a plurality of cells, physical random access channel (PRACH) transmissions via a PRACH resource,wherein the PRACH resource is based on the cell group identifier, andwherein the plurality of cells are included in a cell group corresponding to the cell group identifier.15.A base station in a communication system, the base station comprising:a transceiver; anda processor coupled with the transceiver and configured to:transmit a synchronization signal associated with a cell group identifier; andreceive, on a plurality of cells, physical random access channel (PRACH) transmissions via a PRACH resource,wherein the PRACH resource is based on the cell group identifier, andwherein the plurality of cells are included in a cell group corresponding to the cell group identifier.

Images