Method and apparatus for initial connection using noma in a communication network

Abstract

A method and apparatus for initial connection using NOMA in a communication network are disclosed. A method performed by a base station comprises the steps of: receiving a signal including a first message from a first terminal and a first message from a second terminal in a single RO; determining the first terminal as a nearby terminal based on a preset standard; determining a second terminal as a remote terminal based on the preset standard; transmitting, to the first terminal and the second terminal, one or more pieces of DCI including a NOMA indicator indicating that a second message, which is a response to a first message from the first terminal and the second terminal, is transmitted on the basis of a NOMA scheme, respectively; and transmitting a second message to the first terminal and the second terminal based on the one or more pieces of DCI.

Description

Technical Field

[0001] Exemplary embodiments of the present disclosure relate to an initial access technology, and more particularly, to an initial access technology based on non-orthogonal multiple access (NOMA). Background Art

[0002] Communication systems (e.g., New Radio (NR) communication systems) using frequency bands higher than those of Long-Term Evolution (LTE) communication systems (or LTE-Advanced (LTE-A) communication systems) (e.g., frequency bands of 6 GHz or higher) are being considered for handling soaring wireless data. The NR system can support not only frequency bands of 6 GHz or below, but also frequency bands of 6 GHz or higher, and can support various communication services and scenarios compared to the LTE system. In addition, requirements of the NR system may include enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC).

[0003] Communication networks (e.g., NR networks) can be classified into terrestrial networks and non-terrestrial networks. Non-terrestrial networks can be referred to as NTN. In terrestrial networks, communication services for terminals can be provided by base stations located on the ground. In non-terrestrial networks, communication services for terminals can be provided by communication nodes located in non-terrestrial positions (e.g., satellites, base stations, unmanned aerial vehicles (UAVs), drones, etc.). Communication in terrestrial networks and non-terrestrial networks can be performed based on NR communication technology.

[0004] In addition, a terminal can perform an initial access process to connect to a base station. In the initial access process, the terminal can send a first message (e.g., Message 1 (Msg1) or Message A (MsgA)) to the base station in a random access channel (RACH) occasion (RO). When multiple terminals send the same first message to the base station in the same RO, the base station may not be able to decode the first messages of the multiple terminals. In other words, the base station may not be able to distinguish each first message of the multiple terminals. In this case, the initial access process may fail, and the establishment of a connection between the terminal and the base station may be delayed. Summary of the Invention

[0005] Technical Problem Exemplary embodiments of the present disclosure aim to provide a method and apparatus for initial access using non-orthogonal multiple access (NOMA) in a communication network.

[0006] Technical Solution According to a first exemplary embodiment of the present disclosure, a method for a base station may include: receiving, in a random access channel (RACH) occasion (RO), a signal including a first message of a first terminal and a first message of a second terminal; determining the first terminal as a near terminal based on a preconfigured criterion; determining the second terminal as a far terminal based on the preconfigured criterion; sending, to the first terminal and the second terminal, one or more downlink control information (DCI) including a non-orthogonal multiple access (NOMA) indicator, the NOMA indicator indicating that a second message as a response to the first messages of the first terminal and the second terminal will be sent respectively in a NOMA scheme; and sending the second message to the first terminal and the second terminal based on the one or more DCI.

[0007] When a first received power of the first message of the first terminal is equal to a target received power, the first terminal may be determined as the near terminal, and when a second received power of the first message of the second terminal is less than the target received power, the second terminal may be determined as the far terminal.

[0008] When the same transmission power is configured for the first messages of the first terminal and the second terminal, and the first received power of the first message of the first terminal is greater than the second received power of the first message of the second terminal, the first terminal may be determined as the near terminal, and the second terminal may be determined as the far terminal.

[0009] The number of the one or more DCI may be 1, and one DCI belonging to the one or more DCI may further include resource allocation information and a power allocation coefficient for sending the second message based on the NOMA scheme.

[0010] The step of sending the second message to the first terminal and the second terminal based on the one or more DCI may include: sending the second message to the first terminal, on a physical downlink shared channel (PDSCH) indicated by the resource allocation information included in the one DCI, using a first transmission power determined based on a value indicated by the power allocation coefficient; and sending the second message to the second terminal, on the PDSCH indicated by the resource allocation information included in the one DCI, using a second transmission power determined based on (1 - the value indicated by the power allocation coefficient).

[0011] The number of the one or more DCI may be 2, a first DCI among the one or more DCI may further include first resource allocation information and a terminal indicator indicating the near terminal, and a second DCI among the one or more DCI may further include second resource allocation information and a terminal indicator indicating the far terminal.

[0012] The step of sending a second message to the first terminal and the second terminal based on the one or more DCIs may include: sending the second message to the first terminal on a first PDSCH indicated by first resource allocation information included in a first DCI; and sending the second message to the second terminal on a second PDSCH indicated by second resource allocation information included in a second DCI.

[0013] The number of the one or more DCIs may be 1, and one DCI belonging to the one or more DCIs may further include common resource allocation information for the near terminal and the far terminal and additional resource allocation information for the far terminal.

[0014] The one DCI may further include first modulation and coding scheme (MCS) information for the near terminal and second MCS information for the far terminal.

[0015] The step of sending a second message to the first terminal and the second terminal based on the one or more DCIs may include: sending the second message to the first terminal on a first PDSCH indicated by the common resource allocation information included in the one DCI; and sending the second message to the second terminal on a second PDSCH indicated by the common resource allocation information and the additional resource allocation information included in the one DCI.

[0016] The first message of each of the first terminal and the second terminal may be Msg1 or MsgA, and the second message may be Msg2 or MsgB.

[0017] According to a second exemplary embodiment of the present disclosure, a method for a terminal may include: sending a first message to a base station in a random access channel (RACH) occasion (RO); receiving, from the base station, one or more downlink control information (DCIs) for scheduling a second message as a response to the first message; in response to the one or more DCIs including a non-orthogonal multiple access (NOMA) indicator indicating that the second message will be sent based on a NOMA scheme, determining the type of the terminal as a near terminal or a far terminal based on a preconfigured criterion; and receiving the second message from the base station based on the determined type.

[0018] When the first message is sent using a transmission power less than the maximum transmission power, the terminal may be determined as the near terminal, and when the first message is sent using a transmission power equal to the maximum transmission power, the terminal may be determined as the far terminal.

[0019] When the path loss between the terminal and the base station is less than or equal to a reference path loss, the terminal can be determined as the near terminal, and when the path loss between the terminal and the base station is greater than the reference path loss, the terminal can be determined as the far terminal.

[0020] The number of the one or more DCIs may be 1. A DCI belonging to the one or more DCIs may further include resource allocation information and a power allocation coefficient for transmitting a second message based on the NOMA scheme. The second message may be received on a physical downlink shared channel (PDSCH) indicated by the resource allocation information, and the second message may be decoded considering the power allocation coefficient.

[0021] The number of the one or more DCIs may be 2. The first DCI among the one or more DCIs may further include first resource allocation information and a terminal indicator indicating the near terminal. The second DCI among the one or more DCIs may further include second resource allocation information and a terminal indicator indicating the far terminal. And the second message may be received based on the DCI corresponding to the determined type among the first DCI and the second DCI.

[0022] The number of the one or more DCIs may be 1. A DCI belonging to the one or more DCIs may further include common resource allocation information for the near terminal and the far terminal and additional resource allocation information for the far terminal. When the terminal is the near terminal, the second message may be received on a first PDSCH indicated by the common resource allocation information, and when the terminal is the far terminal, the second message may be received on a second PDSCH indicated by the common resource allocation information and the additional resource allocation information.

[0023] According to a third exemplary embodiment of the present disclosure, a terminal may include at least one processor, and the at least one processor may cause the terminal to perform the following operations: sending a first message to a base station in a random access channel (RACH) opportunity (RO); receiving from the base station one or more downlink control information (DCIs) for scheduling a second message as a response to the first message; in response to the one or more DCIs including a non-orthogonal multiple access (NOMA) indicator, determining the type of the terminal as a near terminal or a far terminal based on a pre-configured criterion, the NOMA indicator indicating that the second message will be sent based on the NOMA scheme; and receiving the second message from the base station based on the determined type.

[0024] When the first message is transmitted using a transmission power less than the maximum transmission power, the terminal can be determined as the near terminal, and when the first message is transmitted using a transmission power equal to the maximum transmission power, the terminal can be determined as the far terminal.

[0025] The number of the one or more DCIs may be 1, and one DCI belonging to the one or more DCIs may further include resource allocation information and a power allocation coefficient for transmitting a second message based on the NOMA scheme. The second message may be received on a physical downlink shared channel (PDSCH) indicated by the resource allocation information, and the second message may be decoded considering the power allocation coefficient.

[0026] Advantageous Effects According to the present disclosure, an initial access procedure based on non-orthogonal multiple access (NOMA) can be performed. In this case, the base station can distinguish the same first message (e.g., Msg1 or MsgA) received from the terminal, and transmit a second message (e.g., Msg2 or MsgB) for the same first message to each terminal. Through the above operations, the conflict problem between terminals during the initial access procedure can be solved, thereby reducing the delay during the access procedure (e.g., connection establishment) between the terminal and the base station. In other words, multiple terminals can support low-latency access operations. The method (e.g., exemplary embodiment) proposed in the present disclosure can be particularly effective in cases where conflicts between terminals are frequent during the initial access procedure performed in an environment with a large number of terminals. Brief Description of the Drawings

[0027] Figure 1 is a block diagram showing a first exemplary embodiment of a communication node in a communication network.

[0028] Figure 2 is a conceptual diagram showing a first exemplary embodiment of a communication network.

[0029] Figure 3 is a conceptual diagram showing a second exemplary embodiment of a communication network.

[0030] Figure 4 is a conceptual diagram showing a third exemplary embodiment of a communication network.

[0031] Figure 5 is a sequence diagram showing a first exemplary embodiment of an initial access procedure.

[0032] Figure 6 is a conceptual diagram showing PDSCH regions for a near terminal and a far terminal. Detailed Description of the Embodiments

[0033] This disclosure presents exemplary embodiments of the present disclosure. However, for the purpose of describing the embodiments of the present disclosure, the specific structural and functional details disclosed herein are merely representative. Accordingly, the embodiments of the present disclosure may be implemented in many alternative forms and should not be construed as limited to the embodiments of the present disclosure set forth herein.

[0034] Accordingly, while the present disclosure is capable of various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the intention is not to limit the present disclosure to the particular forms disclosed, but on the contrary, the present disclosure will cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure. Throughout the description of the drawings, like reference numerals refer to like elements.

[0035] It should be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] In an exemplary embodiment of the present disclosure, "at least one of A and B" may mean "at least one of A or B" or "at least one of a combination of one or more of A and B". Further, in an exemplary embodiment of the present disclosure, "one or more of A and B" may mean "one or more of A or B" or "one or more of a combination of one or more of A and B".

[0037] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, no intervening elements are present. Other words used to describe the relationship between elements should be interpreted in a similar manner (i.e., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.).

[0038] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and / or "including" when used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0039] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0040] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. For the sake of general understanding in describing the present disclosure, the same components in the drawings are denoted by the same reference numerals, and their repeated description will be omitted.

[0041] A communication system to which an exemplary embodiment of the present disclosure is applied will be described. The communication system may be a 4G communication system (e.g., a Long Term Evolution (LTE) communication system or an LTE-Advanced (LTE-A) communication system), a 5G communication system (e.g., a New Radio (NR) communication system), a sixth generation (6G) communication system, etc. The 4G communication system may support communication in a frequency band of 6 GHz or lower, and the 5G communication system may support communication in a frequency band of 6 GHz or higher and a frequency band of 6 GHz or lower. The communication network may include a terrestrial network and a non-terrestrial network. The communication system to which an exemplary embodiment of the present disclosure is applied is not limited to the content described below, and an exemplary embodiment of the present disclosure may be applied to various communication systems. Here, the communication system may be used in the same sense as the communication network, "LTE" may refer to "4G communication system", "LTE communication system" or "LTE-A communication system", and "NR" may refer to "5G communication system" or "NR communication system".

[0042] In an exemplary embodiment, "configuring an operation (e.g., a transmission operation)" may mean "signaling configuration information for an operation (e.g., an information element or a parameter) and / or information indicating the execution of the operation". "Configuring an information element (e.g., a parameter)" may mean "signaling the corresponding information element". In other words, "configuring an operation (e.g., a transmission operation) in a communication node" may mean that the communication node receives "configuration information for an operation (e.g., an information element, a parameter)" and / or "information indicating the execution of the operation". "Configuring an information element (e.g., a parameter) in a communication node" may mean "signaling an information element to the communication node (e.g., the communication node receives the information element)".

[0043] The signaling may be at least one of system information (SI) signaling (e.g., transmission of a system information block (SIB) and / or a master information block (MIB)), RRC signaling (e.g., transmission of RRC parameters and / or higher layer parameters), MAC control element (CE) signaling, or PHY signaling (e.g., transmission of downlink control information (DCI), uplink control information (UCI), and / or sidelink control information (SCI)). The signaling message may be at least one of an SI signaling message (e.g., an SI message), an RRC signaling message (e.g., an RRC message), a MAC CE signaling message (e.g., a MAC CE message or a MAC message), or a PHY signaling message (e.g., a PHY message).

[0044] Hereinafter, even when describing a method (e.g., transmission or reception of a signal) performed at a first communication node in a communication network, a corresponding second communication node may perform a method corresponding to the method performed at the first communication node (e.g., reception or transmission of a signal). That is, when describing the operation of a terminal, a base station corresponding to the terminal may perform an operation corresponding to the operation of the terminal. Conversely, when describing the operation of a base station, a terminal corresponding to the base station may perform an operation corresponding to the operation of the base station. Additionally, when describing the operation of a first terminal, a second terminal corresponding to the first terminal may perform an operation corresponding to the operation of the first terminal. Conversely, when describing the operation of a second terminal, a first terminal corresponding to the second terminal may perform an operation corresponding to the operation of the second terminal.

[0045] Figure 1 is a block diagram showing a first exemplary embodiment of a communication node in a communication network.

[0046] Referring to Figure 1, Communication 100 can perform communication in a communication network. The communication node 100 may include: at least one processor 110; a memory 120; and a transceiver 130, which is connected to the network for performing communication. In addition, the communication node 100 may further include an input interface device 140, an output interface device 150, a storage device 160, etc. Each component included in the communication node 100 can communicate with each other when connected via a bus 170.

[0047] However, each component included in the communication node 100 may not be connected to the common bus 170, but may be connected to the processor 110 via a separate interface or a separate bus. For example, the processor 110 may be connected to at least one of the memory 120, the transceiver 130, the input interface device 140, the output interface device 150, and the storage device 160 via a dedicated interface.

[0048] The processor 110 may execute a program stored in at least one of the memory 120 and the storage device 160. The processor 110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which a method according to an embodiment of the present disclosure is executed. Each of the memory 120 and the storage device 160 may be constituted by at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 120 may include at least one of a read-only memory (ROM) and a random access memory (RAM).

[0049] Figure 2 It is a conceptual diagram showing a first exemplary embodiment of a communication network.

[0050] Referring to Figure 2 , the communication network 200 may be a terrestrial network. The communication system 200 may include a plurality of communication nodes 210-1, 210-2, 210-3, 220-1, 220-2, 230-1, 230-2, 230-3, 230-4, 230-5, and 230-6. In addition, the communication system 200 may further include a core network (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), and a mobility management entity (MME)). When the communication system 200 is a 5G communication system (e.g., a new radio (NR) system), the core network may include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc.

[0051] Multiple communication nodes 210 to 230 may support communication protocols defined by the 3rd Generation Partnership Project (3GPP) specifications (e.g., LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.). Multiple communication nodes 210 to 230 may support Code Division Multiple Access (CDMA) technology, Wideband CDMA (WCDMA) technology, Time Division Multiple Access (TDMA) technology, Frequency Division Multiple Access (FDMA) technology, Orthogonal Frequency Division Multiplexing (OFDM) technology, Filtered OFDM technology, Cyclic Prefix OFDM (CP-OFDM) technology, Discrete Fourier Transform Spread OFDM (DFT-s-OFDM) technology, Orthogonal Frequency Division Multiple Access (OFDMA) technology, Single Carrier FDMA (SC-FDMA) technology, Non-Orthogonal Multiple Access (NOMA) technology, Generalized Frequency Division Multiplexing (GFDM) technology, Filter Bank Multicarrier (FBMC) technology, Universal Filtered Multicarrier (UFMC) technology, Space Division Multiple Access (SDMA) technology, etc. Each of the multiple communication nodes may have the following structure.

[0052] The communication system 200 may include multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2, and multiple terminals 230-1, 230-2, 230-3, 230-4, 230-5, and 230-6. Each of the first base station 210-1, the second base station 210-2, and the third base station 210-3 may form a macro cell, and each of the fourth base station 220-1 and the fifth base station 220-2 may form a small cell. The fourth base station 220-1, the third terminal 230-3, and the fourth terminal 230-4 may belong to the cell coverage area of the first base station 210-1. In addition, the second terminal 230-2, the fourth terminal 230-4, and the fifth terminal 230-5 may belong to the cell coverage area of the second base station 210-2. In addition, the fifth base station 220-2, the fourth terminal 230-4, the fifth terminal 230-5, and the sixth terminal 230-6 may belong to the cell coverage area of the third base station 210-3. In addition, the first terminal 230-1 may belong to the cell coverage area of the fourth base station 220-1, and the sixth terminal 230-6 may belong to the cell coverage area of the fifth base station 220-2.

[0053] Here, each of the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 may refer to a NodeB (NB), an evolved NodeB (eNB), a gNB, an advanced base station (ABS), a high-reliability base station (HR-BS), a base transceiver station (BTS), a radio base station, a radio transceiver, an access point, an access node, a radio access station (RAS), a mobile multi-hop relay base station (MMR-BS), a relay station (RS), an advanced relay station (ARS), a high-reliability relay station (HR-RS), a home NodeB (HNB), a home eNodeB (HeNB), a roadside unit (RSU), a radio remote head (RRH), a transmission point (TP), a transmission and reception point (TRP), etc.

[0054] Each of the multiple terminals 230-1, 230-2, 230-3, 230-4, 230-5, and 230-6 may refer to a user equipment (UE), a terminal device (TE), an advanced mobile station (AMS), a high-reliability mobile station (HR-MS), a terminal, an access terminal, a mobile terminal, a station, a user station, a mobile station, a portable user station, a node, a device, an on-board unit (OBU), etc.

[0055] Each of the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 may operate in the same frequency band or different frequency bands. The multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 may be connected to each other via an ideal backhaul or a non-ideal backhaul and exchange information with each other via the ideal backhaul or the non-ideal backhaul. In addition, each of the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 may be connected to the core network via the ideal backhaul or the non-ideal backhaul. Each of the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 may send the signals received from the core network to the corresponding terminals 230-1, 230-2, 230-3, 230-4, 230-5, or 230-6, and send the signals received from the corresponding terminals 230-1, 230-2, 230-3, 230-4, 230-5, or 230-6 to the core network.

[0056] In addition, each of the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 may support multiple-input multiple-output (MIMO) transmission (e.g., single-user MIMO (SU-MIMO), multi-user MIMO (MU-MIMO), massive MIMO, etc.), coordinated multi-point (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, device-to-device (D2D) communication (or proximity service (ProSe)), Internet of Things (IoT) communication, dual connectivity (DC), etc. Here, each of the multiple terminals 230-1, 230-2, 230-3, 230-4, 230-5, and 230-6 may perform operations corresponding to the operations of the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 (i.e., the operations supported by the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2). For example, the second base station 210-2 may send a signal to the fourth terminal 230-4 in an SU-MIMO manner, and the fourth terminal 230-4 may receive the signal from the second base station 210-2 in an SU-MIMO manner. Optionally, the second base station 210-2 may send signals to the fourth terminal 230-4 and the fifth terminal 230-5 in an MU-MIMO manner, and the fourth terminal 230-4 and the fifth terminal 230-5 may receive the signals from the second base station 210-2 in an MU-MIMO manner.

[0057] The first base station 210-1, the second base station 210-2, and the third base station 210-3 may send signals to the fourth terminal 230-4 in a CoMP transmission manner, and the fourth terminal 230-4 may receive the signals from the first base station 210-1, the second base station 210-2, and the third base station 210-3 in a CoMP manner. In addition, each of the multiple base stations 210-1, 210-2, 210-3, 220-1, and 220-2 may exchange signals with the corresponding terminals 230-1, 230-2, 230-3, 230-4, 230-5, or 230-6 belonging to its cell coverage area in a CA manner. Each of the base stations 210-1, 210-2, and 210-3 may control the D2D communication between the fourth terminal 230-4 and the fifth terminal 230-5, so that the fourth terminal 230-4 and the fifth terminal 230-5 may perform D2D communication under the control of the second base station 210-2 and the third base station 210-3.

[0058] Figure 3 is a conceptual diagram showing a second exemplary embodiment of a communication network.

[0059] Refer to Figure 3, the communication network can be a non-terrestrial network (NTN). The NTN can include a satellite 310, a communication node 320, a gateway 330, a data network 340, etc. Figure 3 The illustrated NTN can be a transparent payload-based NTN. The satellite 310 can be a low Earth orbit (LEO) satellite, a medium Earth orbit (MEO) satellite, a geostationary orbit (GEO) satellite, a highly elliptical orbit (HEO) satellite, or an unmanned aerial vehicle system (UAS) platform. The UAS platform can include a high altitude platform station (HAPS).

[0060] The communication node 320 can include a communication node located on a ground site (e.g., a user equipment (UE) or a terminal) and a communication node located in non-terrestrial space (e.g., an aircraft, a drone). A service link can be established between the satellite 310 and the communication node 320, and the service link can be a radio link. The satellite 310 can use one or more beams to provide communication services to the communication node 320. The shape of the coverage area of the beam of the satellite 310 can be elliptical.

[0061] The communication node 320 can perform communication (e.g., downlink communication and uplink communication) with the satellite 310 using LTE technology and / or NR technology. The communication between the satellite 310 and the communication node 320 can be performed using the NR-Uu interface. When dual connectivity (DC) is supported, the communication node 320 can be connected to other base stations (e.g., base stations supporting LTE and / or NR functions) as well as the satellite 310, and perform DC operations based on the technologies defined in the LTE and / or NR specifications.

[0062] The gateway 330 can be located on a ground site, and a feeder link can be established between the satellite 310 and the gateway 330. The feeder link can be a radio link. The gateway 330 can be referred to as a "non-terrestrial network (NTN) gateway". The communication between the satellite 310 and the gateway 330 can be performed based on the NR-Uu interface or the satellite radio interface (SRI). The gateway 330 can be connected to the data network 340. There can be a "core network" between the gateway 330 and the data network 340. In this case, the gateway 330 can be connected to the core network, and the core network can be connected to the data network 340. The core network can support NR technology. For example, the core network can include an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc. The communication between the gateway 330 and the core network can be performed based on the NG-C / U interface.

[0063] Optionally, the base station and the core network may exist between the gateway 330 and the data network 340. In this case, the gateway 330 may be connected to the base station, the base station may be connected to the core network, and the core network may be connected to the data network 340. The base station and the core network may support NR technology. The communication between the gateway 330 and the base station may be performed based on the NR-Uu interface, and the communication between the base station and the core network (e.g., AMF, UPF, SMF, etc.) may be performed based on the NG-C / U interface.

[0064] Figure 4 is a conceptual diagram showing a third exemplary embodiment of a communication network.

[0065] Referring to Figure 4 , the communication network may be an NTN. The NTN may include a first satellite 411, a second satellite 412, a communication node 420, a gateway 430, a data network 440, etc. Figure 4 The NTN shown may be a regenerative payload-based NTN. For example, each of the satellites 411 and 412 may perform a regeneration operation (e.g., demodulation, decoding, re-encoding, re-modulation, and / or filtering operations) on the payload received from other entities (e.g., the communication node 420 or the gateway 430), and transmit the regenerated payload.

[0066] Each of the satellites 411 and 412 may be a LEO satellite, a MEO satellite, a GEO satellite, a HEO satellite, or a UAS platform. The UAS platform may include a HAPS. The satellite 411 may be connected to the satellite 412, and an inter-satellite link (ISL) may be established between the satellite 411 and the satellite 412. The ISL may operate in the RF band or the optical waveband. The ISL may be established optionally. The communication node 420 may include a terrestrial communication node (e.g., a UE or a terminal) and a non-terrestrial communication node (e.g., an aircraft or a drone). A service link (e.g., a radio link) may be established between the satellite 411 and the communication node 420. The satellite 411 may use one or more beams to provide communication services to the communication node 420.

[0067] The communication node 420 may perform communication (e.g., downlink communication or uplink communication) with the satellite 411 using LTE technology and / or NR technology. The communication between the satellite 411 and the communication node 420 may be performed using the NR-Uu interface. When DC is supported, the communication node 420 may be connected to other base stations (e.g., base stations supporting LTE and / or NR functions) as well as the satellite 411, and may perform DC operations based on the technologies defined in the LTE and / or NR specifications.

[0068] The gateway 430 can be located at a ground station, a feeder link can be established between the satellite 411 and the gateway 430, and a feeder link can be established between the satellite 412 and the gateway 430. The feeder link can be a radio link. When no ISL is established between the satellite 411 and the satellite 412, the feeder link between the satellite 411 and the gateway 430 can be forced to be established.

[0069] The communication between each of the satellites 411 and 412 and the gateway 430 can be performed based on the NR-Uu interface or SRI. The gateway 430 can be connected to the data network 440. A core network can exist between the gateway 430 and the data network 440. In this case, the gateway 430 can be connected to the core network, and the core network can be connected to the data network 440. The core network can support NR technology. For example, the core network can include AMF, UPF, SMF, etc. The communication between the gateway 430 and the core network can be performed based on the NG-C / U interface.

[0070] Optionally, a base station and a core network can exist between the gateway 430 and the data network 440. In this case, the gateway 430 can be connected to the base station, the base station can be connected to the core network, and the core network can be connected to the data network 440. The base station and the core network can support NR technology. The communication between the gateway 430 and the base station can be performed based on the NR-Uu interface, and the communication between the base station and the core network (such as AMF, UPF, SMF, etc.) can be performed based on the NG-C / U interface.

[0071] The NTN reference scenario can be defined as shown in Table 1 below.

[0072] [Table 1]

[0073] When Figure 3 the satellite 310 in the NTN shown in Figure 4 is a GEO satellite (for example, a GEO satellite supporting the transparent function), this can be called "Scenario A". When

[0074] When Figure 3 the satellites 411 and 412 in the NTN shown in Figure 3 are GEO satellites (for example, GEOs supporting the regeneration function), this can be called "Scenario B". Figure 4When satellites 411 and 412 in the NTN shown are LEO satellites with steerable beams, this can be referred to as "Scenario D1". When Figure 4 satellites 411 and 412 in the NTN shown are LEO satellites with beams that move with the satellites, this can be referred to as "Scenario D2".

[0075] The parameters of the scenarios defined in Table 1 can be defined as shown in Table 2 below.

[0076] [Table 2]

[0077] In addition, in the scenarios defined in Table 1, delay constraints can be defined as shown in Table 3 below.

[0078] [Table 3]

[0079] In addition, the terminal can perform an initial access procedure with the base station. The initial access procedure can be classified into a 4-step random access (RA) procedure and a 2-step RA procedure. In the present disclosure, the exemplary embodiments will focus on the 4-step RA procedure for description, but the exemplary embodiments of the present disclosure can be applied to the 2-step RA procedure as well as the 4-step RA procedure. In addition, the exemplary embodiments in the present disclosure will focus on the operations of two terminals performing the initial access procedure simultaneously for description, but the exemplary embodiments of the present disclosure can also be applied to the operations of three or more terminals performing the initial access procedure simultaneously.

[0080] When the terminal is turned on, the terminal can perform a cell search process. For example, the terminal can receive a Synchronization Signal / Physical Broadcast Channel (SS / PBCH) block from the base station and obtain time synchronization and / or frequency synchronization of the cell based on the SS / PBCH block. In addition, the terminal can obtain a Physical Cell Identifier (PCI) and / or a Master Information Block (MIB) from the SS / PBCH block. The SS / PBCH block can be referred to as a Synchronization Signal Block (SSB).

[0081] The terminal can receive a Physical Downlink Control Channel (PDCCH) in a Control Resource Set (CORESET) and a search space indicated by PDCCH - ConfigSIB1 included in the MIB. Depending on the context, the PDCCH can be interpreted as Downlink Control Information (DCI) or a channel (e.g., a resource) through which the DCI is transmitted and received. The terminal can receive a Physical Downlink Shared Channel (PDSCH) indicated (e.g., scheduled) by the PDCCH and obtain a System Information Block 1 (SIB1) from the PDSCH. Depending on the context, the PDSCH can be interpreted as data (e.g., a data unit) or a channel (e.g., a resource) through which the data is transmitted and received.

[0082] The terminal can perform an initial access procedure (e.g., a random access (RA) procedure) based on information elements included in SIB1 (e.g., RACH-ConfigCommon, RACH-ConfigCommonTwoPRA, RACH-ConfigGeneric, RACH-ConfigGenericTwoPRA). The MIB can include information about the subcarrier spacing (SCS) of SIB1 (e.g., subCarrierSpacingCommon) and PDCCH configuration information of SIB1 (e.g., PDCCH-ConfigSIB1). SIB1 can include a public land mobile network (PLMN) identifier, cell selection parameters, and / or RACH parameters. In the present disclosure, a parameter can refer to an information element, configuration information, etc.

[0083] Figure 5 is a sequence diagram showing a first exemplary embodiment of the initial access procedure.

[0084] Referring to Figure 5 , the terminal can receive SIB1 from the base station and identify the RACH configuration information included in SIB1. The terminal can identify the RACH resources (e.g., RACH opportunity (RO)) based on the RACH configuration information. The terminal can send Message 1 (Msg1) (or Message A (MsgA)) in the RO (S510). Step S510 can be the first step of the initial access procedure. Msg1 and / or MsgA can be referred to as the first message. In other words, the first message can refer to Msg1 and / or MsgA. The first message can include a RA preamble. The RA preamble can be referred to as a PRACH preamble. The terminal can calculate a radio network temporary identifier (RA-RNTI) using information about the resource (e.g., time resource information of the RO, frequency resource information of the RO), through which the first message is sent.

[0085] The base station may receive a first message (e.g., Msg1 or MsgA) from the terminal and, in response to the first message, send a second message (e.g., Message 2 (Msg2) or Message B (MsgB)) to the terminal (S520). Step S520 may be the second step of the initial access procedure. The second message may be referred to as a random access response (RAR). Msg2 and / or MsgB may be referred to as the second message (e.g., RAR). The base station may use the PDCCH and PDSCH to send the second message to the terminal. For example, the base station may send DCI with a cyclic redundancy check (CRC) scrambled by the RA-RNTI on the PDCCH to the terminal and send the second message to the terminal on the PDSCH scheduled by the DCI. Here, the base station may calculate the RA-RNTI based on the information about the resources of the RO in which the first message from the terminal is received. The terminal may use the RA-RNTI to detect the DCI sent from the base station, receive the second message from the base station on the PDSCH scheduled by the DCI, and identify the information elements included in the second message. The second message may include a random access preamble index (RAPID), a timing advance (TA) command, an uplink (UL) grant, and / or a temporary cell (TC)-RNTI.

[0086] When the RAPID included in the second message is the same as the RAPID of the first message sent in step S510, the terminal may send Message 3 (Msg3) to the base station by using the resources indicated by the UL grant included in the second message (e.g., the physical uplink shared channel (PUSCH)) (S530). Step S530 may be the third step of the initial access procedure. Msg3 may be referred to as the third message. The third message may be a radio resource control (RRC) connection request message. In other words, the third message may include the information elements for the RRC connection request.

[0087] The base station can receive a third message from the terminal via the resources indicated by the UL grant included in the second message. The base station can generate Message 4 (Msg4) in response to the third message and send Msg4 to the terminal (S540). Step S540 can be the fourth step of the initial access procedure. Msg4 can be referred to as the fourth message. The fourth message can be an RRC connection establishment message. In other words, the fourth message can include information elements for RRC connection establishment. The base station can use the PDCCH and PDSCH to send the fourth message to the terminal. For example, the base station can send DCI with a CRC scrambled by the TC-RNTI (e.g., the TC-RNTI included in Msg2) to the terminal on the PDCCH, and send the fourth message to the terminal on the PDSCH scheduled by the DCI. The terminal can detect the DCI sent from the base station using the TC-RNTI, receive the fourth message from the base station on the PDSCH scheduled by the DCI, and identify the information elements included in the fourth message.

[0088] When the decoding of the fourth message is successful, the terminal can set the TC-RNTI to the cell (C)-RNTI and complete the access procedure for the base station (e.g., the initial access procedure, the RA procedure, the connection procedure). Additionally, the terminal can send a hybrid automatic repeat request (HARQ)-acknowledgment (ACK) for the fourth message to the base station. When receiving the HARQ-ACK for the fourth message from the terminal, the base station can determine that the initial access procedure for the terminal has been completed. On the other hand, when the decoding of the fourth message fails and the contention resolution timer expires, the terminal can consider the reception of the fourth message to have failed. In this case, the terminal can perform the RA procedure again.

[0089] Furthermore, in the cell selection process (e.g., the cell search process), in order to send SIB1, the base station can send DCI (e.g., DCI format 1_0) with a CRC scrambled by the system information (SI)-RNTI to the terminal on the PDCCH, and send SIB1 to the terminal on the PDSCH scheduled by the DCI. The terminal can detect the DCI sent from the base station by using the SI-RNTI, receive SIB1 from the base station on the PDSCH scheduled by the DCI, and identify the information elements included in SIB1. The DCI format 1_0 with a CRC scrambled by the SI-RNTI can include one or more information elements (e.g., one or more fields) defined in Table 4 below.

[0090] [Table 4]

[0091] In the first step of the initial access procedure (e.g., Figure 5In S510), the terminal can determine the transmission power of the Physical Random Access Channel (PRACH) (e.g., the first message, Msg1, MsgA) based on Equation 1 below.

[0092] [Equation 1]

[0093] P_PRACH can be the transmission power of the PRACH in the terminal. _ can be the maximum transmission power of the PRACH. _ _ _ can be the target reception power of the PRACH expected by the base station. The path loss ( ) can be the path loss between the base station and the terminal. The terminal can estimate the path loss between the base station and the terminal based on the SS / PBCH block and / or the reference signal (e.g., the Channel State Information - Reference Signal (CSI-RS)). _ _ _ and / or _ can be configured for the terminal by signaling from the base station. Optionally, _ _ _ and / or _ can be predefined in the technical specification.

[0094] The terminal can calculate ( _ _ _ + ). When ( _ _ _ + ) is less than _ ), the terminal can set ( _ _ _ + ) to _ . When ( _ _ _ + ) is equal to or greater than _ When, the terminal can _ be set to _ . The terminal can use _ to send a first message (e.g., Msg1 or MsgA) to the base station.

[0095] In the second step of the initial access procedure (e.g., Figure 5 S520 in

[0096] [Table 5]

[0097] In the fourth step of the initial access procedure (e.g., Figure 5 S540 in

[0098] In addition, power domain (PD) non-orthogonal multiple access (NOMA) technology can be introduced during the initial access process. PD NOMA technology can be a technology for transmitting and receiving multiple signals (e.g., multiple data signals) using the same resources. In this case, multiple signals can overlap in the same resources. PD NOMA technology can be referred to as a PD NOMA scheme. In the present disclosure, the NOMA scheme can be interpreted as a PD NOMA scheme according to the context. PD NOMA technology can be applicable to massive machine type communication (MMTC) and / or ultra-reliable and low-latency communication (URLLC). When using PD NOMA technology, a receiving node can receive overlapping signals in the same resources and decode each of the overlapping signals using a successive interference cancellation (SIC) method. For example, two terminals can use PD NOMA technology to transmit signals (e.g., data signals) in uplink communication. In this case, the overlapping signals received at the base station can be defined as in Equation 2 below.

[0099] [Equation 2]

[0100] can be the received signal at the base station (e.g., the overlapping signal). can be the signal transmitted by the first terminal (e.g., data signal, data symbol). can be the signal transmitted by the second terminal (e.g., data signal, data symbol). can represent the radio channel coefficient between the first terminal and the base station. can represent the radio channel coefficient between the second terminal and the base station. can represent the noise at the base station. It can be assumed that the power of (e.g., | | 2 ) and the power of (e.g., | | 2 ) have a difference. When | | 2 >| | 2 , the base station can regard the first terminal as a near terminal (e.g., a near user), and can regard the second terminal as a far terminal (e.g., a far user). The base station can first decode the data of the first terminal in the received signal , and obtain Equation 3 below by removing from the received signal based on the decoding result of the data .

[0101] [Equation 3]

[0102] The base station can calculate the signal of the second terminal based on equation 3 Therefore, the base station can obtain the data of the first terminal and the data of the second terminal Each of the. When | | 2 < | 2 When the base station receives the signal, the second terminal can be regarded as a near terminal and the first terminal can be regarded as a far terminal. The data of the second terminal in Decode and based on the data The decoding result from the received signal Remove , so that the data of the first terminal If there is a radio channel power difference between the two terminals, a NOMA technique (eg, PDNOMA technique) may be applied.

[0103] In downlink communication, the base station may send signals for two terminals in the same resource (eg, overlapping signals). In this case, the received signal at the first terminal may be defined as in equation 4 below, and the received signal at the second terminal may be defined as in equation 5 below.

[0104] [Equation 4]

[0105] [Equation 5]

[0106] It can be a received signal at the first terminal. It can be a received signal at the second terminal. It may be a signal of the first terminal (for example, data sent from the base station to the first terminal). It may be a signal of the second terminal (for example, data sent from the base station to the second terminal). The power allocation coefficient of the first terminal can be represented. The power allocation coefficient of the second terminal can be represented. A radio channel coefficient between the first terminal and the base station may be represented. A radio channel coefficient between the second terminal and the base station may be represented. It may be noise in the first terminal. It can be the noise in the second terminal.

[0107] and The sum of can be 1. It can be assumed that The power of (e.g., | | 2 ) and The power of (e.g., | | 2 ) There is a difference between. When | | 2 >| | 2 , the first terminal as the near terminal can first decode the data of the second terminal as the far terminal from the received signal , and based on the decoding result of the data remove from the received signal to decode the data of the first terminal. The second terminal can immediately decode the data of the second terminal by treating the data of the first terminal as the noise in the received signal .

[0108] When | | 2 <| | 2 , the second terminal as the near terminal can first decode the data of the first terminal as the far terminal from the received signal , and based on the decoding result of the data remove from the received signal to decode the data of the second terminal. The first terminal can immediately decode the data of the first terminal by treating the data of the second terminal as the noise in the received signal .

[0109] In addition, in a communication network, multiple terminals can simultaneously attempt the initial access process. In this case, conflicts between uplink signals / channels may occur. The uplink signals / channels can represent uplink signals and / or uplink channels. In the above case, the initial access process may fail and the access of the terminal may be delayed. Therefore, when multiple terminals simultaneously attempt the initial access process, a method for minimizing the failure of the initial access process is required.

[0110] To solve the conflict problem between terminals during the initial access process (e.g., the conflict problem between signals / channels), an initial access process based on NOMA (e.g., PD NOMA) can be performed. If the initial access process based on NOMA is performed, the access delay of the terminals can be reduced.

[0111] In the present disclosure, it can be assumed that the base station has the ability to distinguish the same first message (e.g., Msg1 or MsgA) sent by multiple terminals. The same first message can represent the first message sent and received in the same RO. The RA-RNTI for the same first message can be the same. The same first message can have the same preamble sequence. The RAPID for the same first message can be the same.

[0112] Two terminals can send the same first message. For example, the first terminal can send the first message, the second terminal can send the first message, and the first message of the first terminal can be the same as the first message of the second terminal. If there is a difference between the reception time of the first message of the first terminal and the reception time of the first message of the second terminal at the base station, the base station can distinguish the same first messages of the two terminals based on the difference between the reception times.

[0113] To distinguish the same first messages of multiple terminals, the preamble sequence can be improved. When the improved preamble sequence is used, the base station can easily distinguish the same first messages received from multiple terminals.

[0114] [Method 1: Method for distinguishing a near terminal (e.g., near user) and a far terminal (e.g., far user) that send the same first message (e.g., Msg1 or MsgA) during the initial access process] In the first step of the initial access process (e.g., Figure 5 S510 in

[0115] <Embodiment 1-1> Method for distinguishing a near terminal and a far terminal based on the transmission power of the existing PRACH Each of the two terminals (e.g., the first terminal and the second terminal) can determine the PRACH transmission power based on Equation 1 above. The two terminals can send the same first message to the base station in the same RO. The base station can receive the first message (e.g., the same first message) from the two terminals in the same RO. In other words, the base station can receive a signal including the first messages of the two terminals in the same RO. The base station can measure the received power of the first message for each of the two terminals and compare the measured received power with a target received power (e.g., ). For example, the base station can identify whether the received power of the first message is equal to or less than the target received power. The fact that the received power of the first message is equal to the target received power can indicate that the received power of the first message falls within the range of the target received power.

[0116] If the difference between the received power of the first message of the first terminal and the received power of the first message of the second terminal is greater than or equal to a power threshold, the base station can determine that the first message with the target received power is sent by the near terminal and determine that the first message with a received power less than the target received power is sent by the far terminal. The specific threshold can be set differently for each communication service, communication network, or base station. The base station can know the specific threshold.

[0117] Based on Embodiment 1-1, the base station can distinguish the terminals that send the same first message in the same RO into near terminals and far terminals. In the second step of the initial access process (e.g., Figure 5 S520 in), the base station can generate a first RAR (e.g., a second message, Msg2, MsgB) for the near terminal and a second RAR (e.g., a second message, Msg2, MsgB) for the far terminal, send the first RAR to the near terminal, and send the second RAR to the far terminal. The two terminals can receive the RAR from the base station. In this case, each of the two terminals can receive (e.g., decode) the RAR (e.g., the first RAR or the second RAR) corresponding to its type (e.g., near terminal or far terminal) from the base station.

[0118] In the first step of the initial access process, use less than the maximum transmission power The transmission power of the terminal that sends the first message can determine the type of the terminal as a near - terminal. For example, if the path loss between the terminal and the base station is small, the target reception power can be guaranteed at the base station. In this case, the terminal can use a transmission power less than the maximum transmission power P_CMAX to send the first message. In the first step of the initial access process, a terminal that uses the maximum transmission power P_CMAX to send the first message can determine the type of the terminal as a far - terminal. For example, if the path loss between the terminal and the base station is large, the target reception power may not be guaranteed at the base station. In this case, the terminal can use the maximum transmission power P_CMAX to send the first message. Here, the base station can determine that the near - terminal uses a transmission power less than the maximum transmission power P_CMAX to send the first message.

[0119] <Example 1 - 2> Method for distinguishing near - terminals and far - terminals based on path loss In the first step of the initial access process (e.g., Figure 5 S510 in ), the PRACH transmission power of all or some terminals can be set to be the same. The base station can receive the same first message from two terminals (e.g., the first terminal and the second terminal) in the same RO and measure the reception power of the same first message. The base station can determine the type (e.g., near - terminal or far - terminal) of each of the first terminal and the second terminal based on the difference between the reception power of the first message of the first terminal and the reception power of the first message of the second terminal. For example, if the reception power of the first message of the first terminal is greater than the reception power of the first message of the second terminal, the base station can determine the first terminal as a near - terminal and the second terminal as a far - terminal. For another example, when the reception power of the first message of the first terminal is less than the reception power of the first message of the second terminal, the base station can determine the first terminal as a far - terminal and the second terminal as a near - terminal.

[0120] In the second step of the initial access process (e.g., Figure 5 S520 in ), the base station can generate a first RAR (e.g., the second message, Msg2, MsgB) for the near - terminal and a second RAR (e.g., the second message, Msg2, MsgB) for the far - terminal, send the first RAR to the near - terminal, and send the second RAR to the far - terminal. The two terminals can receive the RAR from the base station. In this case, each of the two terminals can receive a RAR (e.g., the first RAR or the second RAR) corresponding to its type (e.g., near - terminal or far - terminal) from the base station.

[0121] Each of the two terminals may measure the path loss between the terminal and the base station, compare the measured path loss with a reference path loss, and determine its type (e.g., a near terminal or a far terminal) based on the comparison result. For example, if the measured path loss is less than or equal to the reference path loss, the terminal may determine its type as a near terminal. If the measured path loss is greater than the reference path loss, the terminal may determine its type as a far terminal. The path loss may be measured based on the SSB, reference signal, and / or first message received from the base station. Information about the reference path loss may be included in SIB1. SIB1 may include information about one reference path loss.

[0122] Optionally, SIB1 may include information about a first reference path loss for determining a near terminal and information about a second reference path loss for determining a far terminal. If the measured path loss is less than or equal to the first reference path loss, the terminal may determine its type as a near terminal. If the measured path loss is greater than the second reference path loss, the terminal may determine its type as a far terminal. The reference path loss (e.g., the first reference path loss, the second reference path loss) may be set differently for each communication service, communication system, or base station.

[0123] [Method 2: Method for sending and receiving a RAR (e.g., a second message, Msg2, MsgB) during an initial access procedure based on NOMA (e.g., PD NOMA)] In the first step of the initial access procedure (e.g., Figure 5 S510 in), the base station may receive the same first message (e.g., Msg1 or MsgA) from two terminals in the same RO. In this case, the base station may distinguish the two terminals as a near terminal and a far terminal, respectively. In the second step of the initial access procedure (e.g., Figure 5 S520 in), the base station may send a RAR (e.g., Msg2 or MsgB) to the near terminal and the far terminal.

[0124] <Embodiment 2-1>The base station may send one DCI supporting NOMA to two terminals (e.g., a near terminal and a far terminal), and send a RAR to the two terminals on the same PDSCH scheduled by the one DCI.

[0125] Based on <Embodiment 1-1> or <Embodiment 1-2>, the base station may distinguish two terminals that send the same first message in the same RO as a near terminal and a far terminal. Each of the two terminals may determine its type as a near terminal or a far terminal based on <Embodiment 1-1> or <Embodiment 1-2>.

[0126] In the second step of the initial access procedure, in order to notify the PDSCH-related information (e.g., scheduling information) for the reception of RAR (e.g., Msg2 or MsgB) for each of the near terminal and the far terminal, the base station may send DCI (e.g., DCI format 1_0) with CRC scrambled by RA-RNTI to the terminal (e.g., two terminals) on the PDCCH. To ensure that each of the near terminal and the far terminal can receive its RAR, the base station may generate DCI format 1_0 including one or more information elements defined in Table 6 below and send DCI format 1_0.

[0127] [Table 6]

[0128] In Table 6, the NOMA indicator may indicate whether the base station sends RAR for each of the near terminal and the far terminal. In other words, the NOMA indicator may indicate whether the second message is sent based on the NOMA scheme. When receiving DCI including the NOMA indicator (e.g., the NOMA indicator indicating that the second message is sent based on the NOMA scheme), the terminal may determine that multiple terminals have sent the same first message in the same RO. In this case (e.g., when receiving DCI including the NOMA indicator), the terminal may determine whether its type is a near terminal or a far terminal based on <Example 1-1> or <Example 1-2>.

[0129] The NOMA indicator set to the first value (e.g., 0) may indicate that the base station sends RAR for one terminal. In other words, when the NOMA indicator is set to the first value, the base station may send one RAR to one terminal without distinguishing between the near terminal and the far terminal. When the NOMA indicator is set to the first value, the terminal may determine that the RAR is sent without using the NOMA scheme.

[0130] The NOMA indicator set to the second value (e.g., 1) may indicate that the base station sends RAR for each of the near terminal and the far terminal. In other words, when the NOMA indicator is set to the second value, the base station may send the first RAR for the near terminal and the second RAR for the far terminal. The first RAR and the second RAR may be distinguishable. When the NOMA indicator is set to the second value, the terminal may determine that the RAR is sent based on the NOMA scheme.

[0131] When the NOMA indicator is set to the second value, the base station may transmit two RARs on one PDSCH (e.g., the same PDSCH) or partially overlapping PDSCHs based on NOMA technology (e.g., PD NOMA technology). In this case, the received signal at the first terminal may be represented as in Equation 4 above, and the first terminal may obtain the first RAR from the received signal based on the description related to Equation 4 (e.g., decoding operation). The received signal at the second terminal may be represented as in Equation 5 above, and the second terminal may obtain the second RAR from the received signal based on the description related to Equation 5 (e.g., decoding operation).

[0132] When the NOMA indicator is set to the second value (e.g., when performing NOMA-based RAR transmission operation), the power allocation coefficient in Table 6 may indicate the power allocation coefficient (e.g., the ratio of transmission power) for PDSCH transmission (e.g., RAR transmission) for the near terminal. The power allocation coefficient for the near terminal may be defined as in Table 7 below. The power allocation coefficient for PDSCH transmission (e.g., RAR transmission) for the far terminal may be (1 - the power allocation coefficient defined in Table 7 below). The number of bits representing the power allocation coefficient may be set in various ways, and various ratios of transmission power may be indicated.

[0133] [Table 7]

[0134] The near terminal may first decode the second RAR of the far terminal using the information elements in Table 6 and Table 7, and remove the decoding result of the second RAR from the received signal using the SCI method to obtain the first RAR. The far terminal may decode the second RAR using the information elements in Table 6 and Table 7.

[0135] <Example 2-2>The base station may transmit two DCIs supporting NOMA to two terminals (e.g., a near terminal and a far terminal), and transmit RARs to the two terminals on the PDSCH scheduled by the respective DCIs.

[0136] Based on <Example 1-1> or <Example 1-2>, the base station may distinguish two terminals that transmit the same first message (e.g., Msg1 or MsgA) in the same RO as a near terminal and a far terminal. Each of the two terminals may determine its type as a near terminal or a far terminal based on <Example 1-1> or <Example 1-2>.

[0137] In the second step of the initial access procedure, in order to notify the information related to the PDSCH (e.g., scheduling information) received for each of the near terminal and the far terminal for the RAR (e.g., the second message, Msg2, MsgB), the base station may send a DCI (e.g., DCI format 1_0) with a CRC scrambled by the RA-RNTI to the terminal on the PDCCH. The base station may send the first DCI to the near terminal and the second DCI to the far terminal. The first DCI and the second DCI may be distinguishable from each other. The first PDSCH scheduled by the first DCI may be used for the transmission of the first RAR for the near terminal. The second PDSCH scheduled by the second DCI may be used for the transmission of the second RAR for the far terminal. The first PDSCH and the second PDSCH may be distinguishable from each other. The first PDSCH and the second PDSCH may completely overlap or partially overlap. In <Embodiment 2-2>, the base station may generate a DCI format 1_0 (e.g., the first DCI and the second DCI) including one or more information elements defined in Table 8 below, and send the DCI format 1_0.

[0138] [Table 8]

[0139] In Table 8, the NOMA indicator may indicate whether the base station sends an RAR for each of the near terminal and the far terminal. The NOMA indicator set to the first value (e.g., 0) may indicate that the base station sends an RAR for one terminal. In other words, when the NOMA indicator is set to the first value, the base station may send one RAR without distinguishing between the near terminal and the far terminal. The NOMA indicator set to the second value (e.g., 1) may indicate that the base station sends an RAR for each of the near terminal and the far terminal. In other words, when the NOMA indicator is set to the second value, the base station may send the first RAR for the near terminal and the second RAR for the far terminal. The first RAR and the second RAR may be distinguishable.

[0140] In Table 8, the near / far user indicator can be used to distinguish between a near user (e.g., a near terminal) and a far user (e.g., a far terminal). The near / far user indicator may be referred to as a "user indicator" or a "terminal indicator". The near / far user indicator set to a first value (e.g., 0) may indicate a far terminal. The near / far user indicator set to a second value (e.g., 1) may indicate a near terminal. When the NOMA indicator is set to the second value and the near / far user indicator is set to the first value, the DCI including the NOMA indicator and the near / far user indicator may schedule the transmission of a second PDSCH for the transmission of a second RAR for the far terminal. Accordingly, the far terminal may determine the DCI including the NOMA indicator set to the second value and the near / far user indicator set to the first value as the DCI for scheduling the transmission of its second RAR, and may receive the second RAR on the second PDSCH scheduled by the DCI.

[0141] When the NOMA indicator is set to the second value and the near / far user indicator is set to the second value, the DCI including the NOMA indicator and the near / far user indicator may schedule the transmission of a first PDSCH for the transmission of a first RAR for the near terminal. Accordingly, the near terminal may determine the DCI including the NOMA indicator set to the second value and the near / far user indicator set to the second value as the DCI for scheduling the transmission of its first RAR, and may receive the first RAR on the first PDSCH scheduled by the DCI.

[0142] <Example 2-3>The base station may send one DCI supporting NOMA to two terminals (e.g., a near terminal and a far terminal), and send RARs to the terminals on the PDSCH and the extended PDSCH scheduled by the one DCI, respectively.

[0143] Based on <Example 1-1> or <Example 1-2>, the base station may distinguish two terminals that send the same first message (e.g., Msg1 or MsgA) in the same RO as a near terminal and a far terminal. Each of the two terminals may determine its type as a near terminal or a far terminal based on <Example 1-1> or <Example 1-2>.

[0144] In the second step of the initial access procedure, to notify the PDSCH-related information (e.g., scheduling information) for the reception of RAR (e.g., the second message, Msg2, MsgB) for each of the near terminal and the far terminal, the base station sends DCI (e.g., DCI format 1_0) with CRC scrambled by RA-RNTI on the PDCCH to the terminal (e.g., two terminals). To ensure that each of the near terminal and the far terminal can receive its RAR, the base station may generate DCI format 1_0 including one or more information elements defined in Table 9 below, and send DCI format 1_0.

[0145] [Table 9]

[0146] In Table 9, FDRA and TDRA may be common resource allocation information for the near terminal and the far terminal. In Table 9, additional FDRA may be additional resource allocation information for the far terminal. The near terminal may use the common resource allocation information included in the DCI to perform the reception operation of RAR (e.g., the second message). The far terminal may use the common resource allocation information and the additional resource allocation information included in the DCI to perform the reception operation of RAR (e.g., the second message).

[0147] In <Embodiment 2-1>, the base station may send one DCI format 1_0 (e.g., the same DCI format 1_0) to the near terminal and the far terminal, and send the RARs of the near terminal and the far terminal on the same PDSCH. In <Embodiment 2-2>, the base station may send two different DCI formats 1_0 to the near terminal and the far terminal, and send the RAR for the near terminal and the RAR for the far terminal on the PDSCHs (e.g., different PDSCHs, partially overlapping PDSCHs, completely overlapping PDSCHs) indicated by the two different DCI formats 1_0.

[0148] Different from <Embodiment 2-1> and <Embodiment 2-2>, in <Embodiment 2-3>, the base station may send one DCI format 1_0 (e.g., the same DCI format 1_0) for the near terminal and the far terminal, and send the RARs for the near terminal and the far terminal on different PDSCHs (e.g., PDSCH and extended PDSCH) indicated by the one DCI format 1_0 respectively. The PDSCH and the extended PDSCH may partially overlap. The extended PDSCH may be configured as follows.

[0149] Figure 6 is a conceptual diagram showing the PDSCH regions for the near terminal and the far terminal.

[0150] Refer to Figure 6, the base station can allocate frequency resources (e.g., RB#1 and RB#2) for the near - terminal and allocate frequency resources (e.g., RB#1, RB#2, and RB#3) for the far - terminal. The frequency resources for the near - terminal can be located within the frequency resources for the far - terminal. The frequency resources for the near - terminal can be indicated by the FDRA defined in Table 9. The frequency resources for the far - terminal can be indicated by the FDRA and additional FDRA defined in Table 9. The FDRA can indicate RB#1 and RB#2. The additional FDRA can indicate RB#3.

[0151] Optionally, the base station can allocate frequency resources (e.g., RB#1 and RB#2) for the far - terminal and allocate frequency resources (e.g., RB#1, RB#2, and RB#3) for the near - terminal. The frequency resources for the far - terminal can be located within the frequency resources for the near - terminal. The frequency resources for the far - terminal can be indicated by the FDRA defined in Table 9. The frequency resources for the near - terminal can be indicated by the FDRA and additional FDRA defined in Table 9.

[0152] In addition, the channel state (e.g., channel quality, channel condition) between the near - terminal and the base station can be different from the channel state between the far - terminal and the base station. In this case, the MCS for the near - terminal and the MCS for the far - terminal can be set independently (e.g., differently). The size of the PDSCH (e.g., PDSCH resource, PDSCH area) for the RAR transmission of the near - terminal can be different from the size of the PDSCH for the RAR transmission of the far - terminal. In this case, the MCS for the near - terminal and the MCS for the far - terminal can be set independently (e.g., differently). To support the above - mentioned situation, as shown in Table 9, the DCI can include the MCS for the near - user (e.g., near - terminal) and the MCS for the far - user (e.g., far - terminal).

[0153] In Table 9, the NOMA indicator can indicate whether the base station sends RAR for each of the near - terminal and the far - terminal. The NOMA indicator set to the first value (e.g., 0) can indicate that the base station sends one RAR. In other words, when the NOMA indicator is set to the first value, the base station can send one RAR without distinguishing between the near - terminal and the far - terminal. The NOMA indicator set to the second value (e.g., 1) can indicate that the base station sends RAR for each of the near - terminal and the far - terminal. In other words, when the NOMA indicator is set to the second value, the base station can send the first RAR for the near - terminal and send the second RAR for the far - terminal. The first RAR and the second RAR can be distinguished.

[0154] When the NOMA indicator is set to the second value, the near terminal can identify the PDSCH (e.g., PDSCH region, PDSCH resource) based on the FDRA and TDRA defined in Table 9, and can identify the MCS for the near user (e.g., near terminal) defined in Table 9. The near terminal can perform a decoding operation based on the obtained information element (e.g., the information element defined in Table 9) to obtain the RAR.

[0155] When the NOMA indicator is set to the second value, the far terminal can identify the PDSCH of the near terminal (e.g., PDSCH region, PDSCH resource) based on the FDRA and TDRA defined in Table 9, and can identify the additional frequency resources (e.g., RBs) added to the PDSCH (e.g., PDSCH region, PDSCH resource) of the far terminal based on the additional FDRA defined in Table 9. In other words, the far terminal can identify its extended PDSCH (e.g., PDSCH region, PDSCH resource) based on the FDRA, TDRA, and additional FDRA defined in Table 9. Additionally, the far terminal can identify the MCS for the far user (e.g., far terminal) defined in Table 9. The far terminal can perform a decoding operation based on the acquired information element (e.g., the information element defined in Table 9) to obtain the RAR.

[0156] Optionally, an additional TDRA can be used instead of the additional FDRA in Table 9. In other words, the DCI can include an information element (e.g., additional TDRA) indicating the time resources added to the PDSCH (e.g., PDSCH region, PDSCH resource) of the far terminal. The additional time resources indicated by the additional TDRA can be located before or after the PDSCH region of the near terminal.

[0157] In the above exemplary embodiments, the number of bits of the DCI (e.g., the information element included in the DCI) can vary according to the network environment (e.g., system environment). In the present disclosure, the initial access process (e.g., RA process) can be performed based on a combination of the above methods (e.g., a combination of the above exemplary embodiments), and the methods (e.g., embodiments) proposed in the present disclosure can be applied to various communication networks (e.g., various communication systems) that support the initial access process (e.g., RA process).

[0158] The operations of the method according to an exemplary embodiment of the present disclosure can be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium can include all kinds of recording devices for storing data readable by a computer system. In addition, the computer-readable recording medium can store and execute programs or codes that can be distributed in computer systems connected through a network and read by a computer in a distributed manner.

[0159] A computer-readable recording medium may include a hardware device specifically configured to store and execute program commands, such as ROM, RAM, or flash memory. The program commands may include not only machine language code created by a compiler, but also high-level language code that can be executed by a computer using an interpreter.

[0160] Although some aspects of the present disclosure have been described in the context of devices, these aspects may indicate corresponding descriptions according to methods, and blocks or devices may correspond to steps of the method or features of the steps. Similarly, aspects described in the context of a method may be expressed as features of the corresponding block or item or corresponding device. Some or all of the steps of the method may be performed by (or using) a hardware device such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important steps of the method may be performed by such a device.

[0161] In some exemplary embodiments, a programmable logic device such as a field-programmable gate array may be used to perform some or all of the functions of the methods described herein. In some exemplary embodiments, a field-programmable gate array may be operated with a microprocessor to perform one of the methods described herein. Generally, the methods are preferably performed by some hardware device.

[0162] The description of the present disclosure is merely exemplary in nature, and thus, variations that do not depart from the essence of the present disclosure are intended to fall within the scope of the present disclosure. These variations should not be regarded as departing from the spirit and scope of the present disclosure. Accordingly, those of ordinary skill in the art will understand that various changes may be made in form and detail without departing from the spirit and scope defined by the appended claims.

Claims

1. A method for a base station, comprising: Receiving a signal including a first message of a first terminal and a first message of a second terminal in a random access channel (RACH) occasion (RO); Determining the first terminal as a near terminal based on a pre-configured criterion; Determining the second terminal as a far terminal based on the pre-configured criterion; Sending one or more downlink control information (DCI) including a non-orthogonal multiple access (NOMA) indicator to the first terminal and the second terminal, the NOMA indicator indicating that a second message in response to the first messages of the first terminal and the second terminal will be sent respectively using the NOMA scheme; And Sending a second message to the first terminal and the second terminal based on the one or more DCI.

2. The method according to claim 1, wherein The first terminal is determined as the near terminal when a first received power of the first message of the first terminal is equal to a target received power, and the second terminal is determined as the far terminal when a second received power of the first message of the second terminal is less than the target received power.

3. The method according to claim 1, wherein, The first terminal is determined as the near terminal and the second terminal is determined as the far terminal when the same transmission power is configured for the first messages of the first terminal and the second terminal, and the first received power of the first message of the first terminal is greater than the second received power of the first message of the second terminal.

4. The method according to claim 1, wherein The number of the one or more DCI is 1, and one DCI belonging to the one or more DCI further includes resource allocation information and a power allocation coefficient for sending the second message based on the NOMA scheme.

5. The method according to claim 4, wherein, The step of sending the second message to the first terminal and the second terminal based on the one or more DCI includes: Sending the second message to the first terminal on a physical downlink shared channel (PDSCH) indicated by the resource allocation information included in the one DCI, using a first transmission power determined based on a value indicated by the power allocation coefficient; and Sending the second message to the second terminal on the PDSCH indicated by the resource allocation information included in the one DCI, using a second transmission power determined based on (1 - the value indicated by the power allocation coefficient).

6. The method according to claim 1, wherein, The number of the one or more DCI is 2, a first DCI among the one or more DCI further includes first resource allocation information and a terminal indicator indicating the near terminal, and a second DCI among the one or more DCI further includes second resource allocation information and a terminal indicator indicating the far terminal.

7. The method according to claim 6, wherein, The step of sending the second message to the first terminal and the second terminal based on the one or more DCI includes: Sending the second message to the first terminal on a first PDSCH indicated by the first resource allocation information included in the first DCI; and Sending the second message to the second terminal on a second PDSCH indicated by the second resource allocation information included in the second DCI.

8. The method according to claim 1, wherein The number of the one or more DCI is 1, and one DCI belonging to the one or more DCI further includes common resource allocation information for the near terminal and the far terminal and additional resource allocation information for the far terminal.

9. The method according to claim 8, wherein, The one DCI further includes first modulation and coding scheme (MCS) information for the near terminal and second MCS information for the far terminal.

10. The method according to claim 8, wherein, The step of sending a second message to the first terminal and the second terminal based on the one or more DCIs includes: sending the second message to the first terminal on a first physical downlink shared channel (PDSCH) indicated by the common resource allocation information included in the one DCI; and sending the second message to the second terminal on a second PDSCH indicated by the common resource allocation information and the additional resource allocation information included in the one DCI.

11. The method according to claim 1, wherein, The first message of each of the first terminal and the second terminal is Msg1 or MsgA, and the second message is Msg2 or MsgB.

12. A method for a terminal, comprising: sending a first message to a base station in a random access channel (RACH) opportunity (RO); receiving from the base station one or more downlink control information (DCI) for scheduling a second message as a response to the first message; responsive to the one or more DCIs including a non-orthogonal multiple access (NOMA) indicator indicating that the second message will be sent based on a NOMA scheme, determining the type of the terminal as a near terminal or a far terminal based on a pre-configured criterion; and receiving the second message from the base station based on the determined type.

13. The method according to claim 12, wherein, When the first message is sent using a transmit power less than the maximum transmit power, the terminal is determined to be the near terminal, and when the first message is sent using a transmit power equal to the maximum transmit power, the terminal is determined to be the far terminal.

14. The method according to claim 12, wherein, When the path loss between the terminal and the base station is less than or equal to a reference path loss, the terminal is determined to be the near terminal, and when the path loss between the terminal and the base station is greater than the reference path loss, the terminal is determined to be the far terminal.

15. The method according to claim 12, wherein, The number of the one or more DCIs is 1. One DCI belonging to the one or more DCIs further includes resource allocation information and a power allocation coefficient for sending the second message based on the NOMA scheme. The second message is received on a physical downlink shared channel (PDSCH) indicated by the resource allocation information, and the second message is decoded considering the power allocation coefficient.

16. The method according to claim 12, wherein, The number of the one or more DCIs is 2. The first DCI among the one or more DCIs further includes first resource allocation information and a terminal indicator indicating the near terminal. The second DCI among the one or more DCIs further includes second resource allocation information and a terminal indicator indicating the far terminal. And the second message is received based on the DCI corresponding to the determined type among the first DCI and the second DCI.

17. The method according to claim 12, wherein The number of the one or more DCIs is 1. A DCI belonging to the one or more DCIs further includes common resource allocation information for the near terminal and the far terminal and additional resource allocation information for the far terminal. When the terminal is the near terminal, the second message is received on a first PDSCH indicated by the common resource allocation information, and when the terminal is the far terminal, the second message is received on a second PDSCH indicated by the common resource allocation information and the additional resource allocation information.

18. A terminal, comprising: At least one processor, wherein the at least one processor causes the terminal to perform the following operations: Send a first message to a base station in a random access channel RACH opportunity RO; Receive from the base station one or more downlink control information DCIs for scheduling a second message as a response to the first message; In response to the one or more DCIs including a non-orthogonal multiple access NOMA indicator, determine the type of the terminal as a near terminal or a far terminal based on a preconfigured criterion, the NOMA indicator indicating that the second message will be sent based on a NOMA scheme; and Receive the second message from the base station based on the determined type.

19. The terminal according to claim 18, wherein, When the first message is sent using a transmit power less than the maximum transmit power, the terminal is determined to be the near terminal, and when the first message is sent using a transmit power equal to the maximum transmit power, the terminal is determined to be the far terminal.

20. The terminal according to claim 18, wherein, The number of the one or more DCIs is 1. A DCI belonging to the one or more DCIs further includes resource allocation information and a power allocation coefficient for sending the second message based on the NOMA scheme. The second message is received on a physical downlink shared channel PDSCH indicated by the resource allocation information, and the second message is decoded considering the power allocation coefficient.

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