KR20230017733A - Communication method utilizing multiple wireless acess points and apparatus therefor - Google Patents

Abstract

A method of operating a terminal in a mobile communication system comprises the steps of: receiving setting information for supporting an mTRP function from a first base station through a first TRP belonging to the first base station; detecting and selecting a second TRP supporting the mTRP function based on the setting information; transmitting a measurement report for the second TRP or a first control message requesting the support of the mTRP function in which the second TRP participates to the first base station through the first TRP; and receiving a second control message indicating the start of the mTRP function in which the first TRP and the second TRP participate from the base station through the first TRP or the second TRP. According to embodiments of the present invention, the mTRP function in which a plurality of wireless access points provide services to a user terminal can be efficiently established.

Description

Communication method utilizing multiple wireless access points and apparatus therefor

The present invention relates to a mobile communication system, and more particularly, achieves performance improvement by utilizing multiple wireless access points (TRP, RRH, relay, repeater, etc.) in a mobile communication system using a high frequency band of millimeter wave or higher. It relates to a communication method and an apparatus therefor.

In order to cope with the explosive increase in wireless data, the mobile communication system considers a transmission frequency of 6 GHz to 90 GHz band for a wide system bandwidth. In such a high-frequency region, methods using wireless access points (TRP, RRH, relay, repeater, etc.) are used to improve terminal performance at the base station (or cell) boundary due to degradation of received signal performance due to path attenuation and reflection of radio waves. is being considered

In order to deploy a mobile communication system based on a small base station with a small service area considering the millimeter frequency band of the 6 GHz to 90 GHz band, all wireless protocol functions of the mobile communication system must be implemented and a plurality of remote radios rather than deploying all small base stations. Apply a functional split method that divides the functions of a base station into a transmit/receive block and one concentrated baseband processing function block, or carrier aggregation, dual connectivity, and duplication transmission A method of constructing a mobile communication system by utilizing a plurality of wireless access points (TRP, RRH, relay, or repeater, etc.)

In a mobile communication system to which such function separation, bi-casting function or duplication transmission function is applied, a plurality of wireless access points (TRPs) belonging to network nodes (eNB, gNB, Cell, etc.) classified by different identifiers , RRH, relay, or repeater, etc.) for providing services to terminals, radio resource management procedures, control signaling methods, and operation procedures.

An object of the present invention to solve the above problems is to provide a communication method that achieves performance improvement by utilizing multiple wireless access points (TRP, RRH, relay, repeater, etc.).

Another object of the present invention to solve the above problems is to provide a configuration of a device (eg, a terminal or a base station) that performs the communication method.

An embodiment of the present invention for achieving the above object is a method of operating a terminal, and supports a multi-TRP (mTRP) function from a first base station through a first transmission and reception point (TRP) belonging to the first base station. Receiving setting information for; Based on the setting information, detecting and selecting a second TRP supporting the mTRP function; Transmitting a measurement report for the second TRP or a first control message requesting support of the mTRP function in which the second TRP participates to the first base station through the first TRP; And receiving a second control message indicating a start of the mTRP function in which the first TRP and the second TRP participate from the first base station through the first TRP or the second TRP. .

The configuration information includes information on neighboring TRP(s) and/or candidate TRP(s), and the terminal determines the second based on the information on the neighboring TRP(s) and/or candidate TRP(s). TRP can be detected and selected.

The second TRP is selected based on whether the second TRP satisfies an mTRP function support condition, and the mTRP function support condition is: the quality of a radio channel between the terminal and the first base station or the first TRP is a reference value if less than; When the terminal is located at the boundary of the service area of the first base station or the first TRP; When the transmission frequency, frequency band, and/or BWP of the second TRP satisfies the priority for supporting the mTRP function; When the quality of the radio channel between the terminal and the second TRP is equal to or greater than a preset reference value; When the quality of the radio channel between the terminal and the second TRP is maintained above a preset reference value until a predefined timer expires; or at least one of a combination thereof.

The second TRP may belong to the first base station or may belong to a second base station different from the first base station.

The mTRP function may be controlled by an mTRP L2/L3 entity executed in a medium access control (MAC) layer and/or a radio resource control (RRC) layer of the first base station or the second base station.

The operating method further includes receiving a service by the mTRP function in which the first TRP and the second TRP participate, and when the second TRP belongs to the second base station, the first base station and When one of the second base stations is determined as an mTRP function controlling base station for controlling the mTRP function, and the first TRP and the second TRP belong to the first base station, the first base station controls the mTRP function It may be determined as an mTRP function control base station.

When the second TRP belongs to the second base station, control information for supporting the mTRP function may be exchanged between the first TRP and the second TRP.

The operating method further includes determining whether the first TRP or the second TRP satisfies an mTRP function release condition, wherein the mTRP function release condition is: until a predefined timer expires. When the quality of the radio channel between the 1 TRP or the second TRP and the terminal is less than or equal to the reference value; When the random access procedure for the first TRP or the second TRP fails; When beam failure recovery (BFR) for the first TRP or the second TRP fails; When the mTRP function controlling base station and/or the mTRP L2/L3 entity belonging to the mTRP function controlling base station determines to release the mTRP function for the first TRP or the second TRP; When the terminal requests release of the mTRP function or requests to change the first TRP or the second TRP to another TRP; or any combination thereof.

The operating method: When it is determined that the first TRP or the second TRP satisfies the mTRP function release condition, the first TRP function satisfying the mTRP function release condition through the first TRP or the second TRP. The method may further include transmitting a third control message requesting release of the mTRP function for the TRP or the second TRP to the mTRP function control base station.

The operating method: When it is determined that the first TRP or the second TRP satisfies the mTRP function release condition, the first TRP or the second TRP that satisfies the mTRP function release condition is newly detected. It may further include performing a procedure for replacing with TRP.

The first message or the second message may be at least one of an RRC control message, a MAC control element (CE), a physical layer control message, or a combination thereof.

Another embodiment of the present invention for achieving the above object is an operation method of a first base station, for supporting a multi-TRP (mTRP) function through a first transmission and reception point (TRP) belonging to the first base station. Transmitting setting information to a terminal; Receiving a measurement report for a second TRP detected and selected based on the configuration information or a first control message requesting support of the mTRP function in which the second TRP participates, from the terminal through the first TRP; and transmitting a second control message indicating a start of the mTRP function in which the first TRP and the second TRP participate to the terminal through the first TRP or the second TRP.

The setting information includes information on neighboring TRP(s) and/or candidate TRP(s), and the second TRP is configured to configure the second TRP based on the information on the neighboring TRP(s) and/or candidate TRP(s). It can be detected and selected by the terminal.

The second TRP is selected based on whether the second TRP satisfies an mTRP function support condition, and the mTRP function support condition is: the quality of a radio channel between the terminal and the first base station or the first TRP is a reference value if less than; When the terminal is located at the boundary of the service area of the first base station or the first TRP; When the transmission frequency, frequency band, and/or BWP of the second TRP satisfies the priority for supporting the mTRP function; When the quality of the radio channel between the terminal and the second TRP is equal to or greater than a preset reference value; When the quality of the radio channel between the terminal and the second TRP is maintained above a preset reference value until a predefined timer expires; or at least one of a combination thereof.

The second TRP may belong to the first base station or may belong to a second base station different from the first base station.

The operating method further includes providing a service to the terminal based on the mTRP function in which the first TRP and the second TRP participate, and when the second TRP belongs to the second base station. When one of the first base station and the second base station is determined as an mTRP function controlling base station that controls the mTRP function, and the first TRP and the second TRP belong to the first base station, the first base station It may be determined as an mTRP function control base station that controls the mTRP function.

The operating method further includes: determining whether the first TRP or the second TRP satisfies an mTRP function release condition, wherein the mTRP function release condition: until a predefined timer expires; When the quality of the radio channel between the first TRP or the second TRP and the terminal is equal to or less than a reference value; When the random access procedure for the first TRP or the second TRP fails; When beam failure recovery (BFR) for the first TRP or the second TRP fails; When the mTRP function controlling base station and/or the mTRP L2/L3 entity belonging to the mTRP function controlling base station determines to release the mTRP function for the first TRP or the second TRP; When the terminal requests release of the mTRP function or requests to change the first TRP or the second TRP to another TRP; or at least one of a combination thereof.

An embodiment of the present invention for achieving the other object is a terminal of a mobile communication system, comprising: at least one processor, a memory storing instructions executed by the at least one processor; And a transceiver, wherein when executed by the at least one processor, the instructions cause the terminal to: from a first base station through a first transmission and reception point (TRP) belonging to the first base station (mTRP) - Receiving setting information for supporting a TRP) function; Based on the setting information, detecting and selecting a second TRP supporting the mTRP function; Transmitting a measurement report for the second TRP or a first control message requesting support of the mTRP function in which the second TRP participates to the first base station through the first TRP; and receiving a second control message indicating a start of the mTRP function in which the first TRP and the second TRP participate from the base station through the first TRP or the second TRP.

The second TRP may belong to the first base station or may belong to a second base station different from the first base station.

The instructions cause the terminal to further perform a step of receiving a service by the mTRP function in which the first TRP and the second TRP participate, and when the second TRP belongs to the second base station, the second TRP If one of the first base station and the second base station is determined as an mTRP function controlling base station that controls the mTRP function, and the first TRP and the second TRP belong to the first base station, the first base station determines the mTRP function It may be determined as an mTRP function control base station that controls.

According to embodiments of the present invention, an mTRP function in which a plurality of wireless access points provide a service to a user terminal can be efficiently set. In particular, the conditions for supporting the mTRP function and the conditions for releasing the mTRP function are defined, and a procedure for adding a new TRP to support the mTRP function and a procedure for releasing the mTRP function for a TRP performing the mTRP function are provided. can be defined

1 is a conceptual diagram illustrating an embodiment of a communication system.
2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.
3 is a conceptual diagram illustrating an embodiment of an operating state of a terminal in a communication system.
4 is a conceptual diagram illustrating an embodiment of a method for setting a bandwidth part (BWP) in a communication system.
5 is a conceptual diagram illustrating an example of a connection method between a base station and a core network in a mobile communication network to which functional separation is applied.
6 is a conceptual diagram illustrating an example of a connection method for supporting a multi-wireless access point function in a mobile communication system.
7 is a flowchart for explaining an embodiment of an operation procedure by supporting the mTRP function in a mobile communication system.

Since the present invention can make various changes and have various embodiments, specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, they should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate overall understanding in the description of the present invention, the same reference numerals are used for the same components in the drawings, and redundant descriptions of the same components are omitted.

A communication system to which embodiments according to the present invention are applied will be described. A communication system to which embodiments according to the present invention are applied is not limited to the contents described below, and embodiments according to the present invention can be applied to various communication systems. Here, the communication system may be used in the same sense as a communication network.

1 is a conceptual diagram illustrating an embodiment of a communication system.

Referring to FIG. 1, a communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). A plurality of communication nodes are 4G communication (eg, long term evolution (LTE), advanced (LTE-A)), 5G communication (eg, new radio (NR)) specified in the 3rd generation partnership project (3GPP) standard ), etc. can be supported. 4G communication may be performed in a frequency band of 6 GHz or less, and 5G communication may be performed in a frequency band of 6 GHz or more as well as a frequency band of 6 GHz or less.

For example, for 4G communication and 5G communication, a plurality of communication nodes may use a code division multiple access (CDMA)-based communication protocol, a wideband CDMA (WCDMA)-based communication protocol, a time division multiple access (TDMA)-based communication protocol, FDMA (frequency division multiple access)-based communication protocol, OFDM (orthogonal frequency division multiplexing)-based communication protocol, Filtered OFDM-based communication protocol, CP (cyclic prefix)-OFDM-based communication protocol, DFT-s-OFDM (discrete Fourier transform-spread-OFDM) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (Non-orthogonal multiple access), GFDM (generalized frequency) division multiplexing)-based communication protocol, FBMC (filter bank multi-carrier)-based communication protocol, UFMC (universal filtered multi-carrier)-based communication protocol, SDMA (Space Division Multiple Access)-based communication protocol, etc. can be supported. .

In addition, the communication system 100 may further include a core network. When the communication system 100 supports 4G communication, the core network may include a serving-gateway (S-GW), a packet data network (PDN)-gateway (P-GW), a mobility management entity (MME), and the like. there is. When the communication system 100 supports 5G communication, the core network may include a user plane function (UPF), a session management function (SMF), an access and mobility management function (AMF), and the like.

Meanwhile, a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-1 constituting the communication system 100 4, 130-5, 130-6) may each have the following structure.

2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.

Referring to FIG. 2 , a communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each component included in the communication node 200 may be connected by a bus 270 to communicate with each other.

However, each component included in the communication node 200 may be connected through an individual interface or an individual bus centered on the processor 210 instead of the common bus 270 . For example, the processor 210 may be connected to at least one of the memory 220, the transmission/reception device 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260 . The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may include at least one of a read only memory (ROM) and a random access memory (RAM).

Referring back to FIG. 1, the communication system 100 includes a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2), a plurality of terminals 130- 1, 130-2, 130-3, 130-4, 130-5, 130-6). Base stations 110-1, 110-2, 110-3, 120-1, and 120-2 and terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 The inclusive communication system 100 may be referred to as an “access network”. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the cell coverage of the third base station 110-3. there is. The first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 is a NodeB, an evolved NodeB, a base transceiver station (BTS), Radio base station, radio transceiver, access point, access node, RSU (road side unit), RRH (radio remote head), TP (transmission point), TRP ( transmission and reception point), eNB, gNB, etc.

Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a UE (user equipment), terminal, access terminal, mobile Mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, IoT (Internet of Thing) It may be referred to as a device, a mounted device (mounted module/device/terminal or on board device/terminal, etc.), and the like.

A plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6) Each is cellular (cellular) communication (eg, long term evolution (LTE), LTE-A (advanced), etc. specified in the 3rd generation partnership project (3GPP) standard), or mmWave (eg, 6GHz to 80GHz band )-based radio access technology can support the radio protocol standard. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through ideal backhaul or non-ideal backhaul, and ideal backhaul Alternatively, information can be exchanged with each other through non-ideal backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network (not shown) through an ideal backhaul or a non-ideal backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits a signal received from the core network to a corresponding UE 130-1, 130-2, 130-3, and 130. -4, 130-5, 130-6), and the signal received from the corresponding UE (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) to the core network can be sent to

3 is a conceptual diagram illustrating an embodiment of an operating state of a terminal in a communication system.

Referring to FIG. 3, in the radio protocol RRC (Radio Resource Control) layer of the mobile communication system, the operating state of the terminal is classified into an RRC connected state 301, an RRC inactive state 302, and an RRC idle state 303. can When the terminal operates in the RRC connected state 301 or the RRC inactive state 302, a radio access network (RAN) (eg, a control function block of the RAN) and a base station transmit RRC connection configuration information and / Alternatively, context information (eg, RRC context information, AS context information) may be stored/managed (310).

A terminal operating in the RRC connected state 301 may receive configuration information of a physical layer control channel and/or a reference signal necessary for maintaining connection establishment and transmitting/receiving data from the base station. The reference signal may be a reference signal for demodulating data. Alternatively, the reference signal may be a reference signal for channel quality measurement or beamforming. Therefore, a terminal operating in an RRC connected state can transmit and receive data without delay.

In the RRC inactive state 302, the base station and the terminal of the radio access network store and manage the RRC connection configuration information or RRC (or AS) context information of the corresponding terminal, but perform only the mobility management function corresponding to the idle state 303 means the state of When the terminal operates in the RRC inactive state, the same or similar mobility management function/operation to the mobility management function/operation supported in the RRC idle state may be supported for the corresponding terminal. That is, when the terminal operates in an RRC inactive state, a data bearer for transmitting and receiving data may not be established, and the function of the MAC layer may be deactivated. Accordingly, the terminal operating in the RRC inactive state may transition the operating state of the terminal from the RRC inactive state to the RRC connected state by performing the non-initial access procedure 306 to transmit data. Alternatively, a terminal operating in an RRC inactive state may transmit data having a limited size, data having a limited quality of service, and/or data related to a limited service.

The RRC idle state 303 means a state in which there is no connection established between the base station and the terminal in terms of the radio access network, or the connection setting information or context information of the corresponding terminal is not stored in the base station or control function block of the radio access network. When the terminal operates in the RRC idle state, there may not be a connection setting between the terminal and the base station, and the RRC connection setting information and / or context information (eg, RRC context information, AS context information) of the corresponding terminal It may not be stored in the RAN (eg, the control function block of the RAN) and the base station. In order to transition the operating state of the UE from the RRC idle state to the RRC connected state, the UE may perform an initial access procedure (304). Alternatively, when the initial access procedure is performed, the operating state of the terminal may transition from the RRC idle state to the RRC inactive state according to the determination of the base station.

The terminal may transition from the RRC idle state to the RRC inactive state by performing an initial access procedure or a separate access procedure 308 defined for the RRC inactive state. When a limited service is provided to the terminal, the operating state of the terminal may transition from the RRC idle state to the RRC inactive state. Alternatively, the operating state of the UE may transition from the RRC idle state to the RRC inactive state according to the capability of the UE. In this way, when the terminal in the idle state 303 transitions to the inactive state 302, only limited services are provided or allowed according to the capability level of the terminal.

The control function block of the base station and / or RAN considers one or more of the type of terminal, capability, and service (eg, service currently being provided, service to be provided) to allow transition to the RRC inactive state (condition ( s) may be set, and the transition operation to the RRC inactive state may be controlled based on the set condition(s). "If the base station allows transition to the RRC inactive state" or "if it is configured to be able to transition to the RRC inactive state", the operating state of the terminal may transition from the RRC connected state or the RRC idle state to the RRC inactive state. can

4 is a conceptual diagram illustrating an embodiment of a method for setting a bandwidth part (BWP) in a communication system.

A bandwidth part (BWP) is a bandwidth set for transmission and reception of a terminal. Referring to FIG. 4 , a plurality of bandwidth parts (BWP #1-4) may be set within a system bandwidth of a base station. BWP #1-4 may be set to be larger than the system bandwidth of the base station. Bandwidths of BWP #1-4 may be different from each other, and different subcarrier intervals may be applied to BWP #1-4. For example, the bandwidth of BWP #1 may be 10 MHz, and BWP #1 may have a 15 kHz subcarrier spacing. The bandwidth of BWP #2 may be 40 MHz, and BWP #2 may have a 15 kHz subcarrier spacing. The bandwidth of BWP #3 may be 10 MHz, and BWP #3 may have a 30 kHz subcarrier spacing. The bandwidth of BWP #4 may be 20 MHz, and BWP #4 may have a 60 kHz subcarrier spacing.

BWP may be classified into initial BWP (eg, initial BWP), active BWP (eg, active BWP), and default BWP. The terminal may perform an initial access procedure (eg, access procedure) with the base station in the initial BWP. One or more BWPs may be configured by the RRC connection setup message, and one BWP among the one or more BWPs may be configured as an active BWP. Each of the terminal and the base station may transmit and receive packets in an active BWP among configured BWPs. Therefore, the terminal can perform monitoring operation of the control channel for transmitting and receiving packets in the active BWP.

The terminal may change the operating BWP from the initial BWP to the active BWP or the default BWP. Alternatively, the terminal may change the operation BWP from active BWP to initial BWP or default BWP. The BWP change operation may be performed based on an instruction from the base station or a timer. The base station may transmit information indicating BWP change to the terminal using one or more of an RRC message, a MAC message (eg, MAC control element (CE)), and a PHY message (eg, DCI). The terminal may receive information indicating BWP change from the base station, and may change the operating BWP of the terminal to a BWP indicated by the received information.

5 is a conceptual diagram illustrating an example of a connection method between a base station and a core network in a mobile communication network to which functional separation is applied.

Referring to FIG. 5, in a wireless communication network, a base station 510 (or a macro base station) or a small base station 530 is connected to an end node of a core network through a backhaul 540 or 560. Here, the end node of the core network may be a Serving Gateway (SGW), a User Plane Function (UPF), a Mobility Management Entity (MME), or an Access and Mobility Function (AMF).

In addition, the base stations 510 and 530 to which functional separation is applied (eg, an eNB of a 3GPP LTE/LTE-A system or a gNB of a 3GPP NR system) may be composed of a central unit (CU) and a distributed unit (DU). The CU of the base station is a logical node that performs RRC, SDAP, and PDCP layer functions of the radio access protocol, and can control the operation of one or more DUs. The CU of the base station is connected to an end node of the core network using a backhaul 540 or 560 based on an S1 interface (in the case of a 3GPP LTE/LTE-A system) or an NG interface (in the case of a 3GPP NR system).

A DU of a base station is a logical node that performs functions of the base station RLC, MAC, and PDCP layers, and supports one or more cells. In addition, the base station CU and DU may be connected in a wired or wireless (eg, integrated access and backhaul (IAB)) method using the F1 interface of the 3GPP system.

The base station (or cell, DU, etc.) 510 or 530 of FIG. 5 may be connected to the wireless access point 520 through a wired or wireless Fx interface 570 (or fronthaul). The wireless access point 520 may be configured in the form of a transmit/receive point (TRP), a remote radio head (RRH), a relay, or a repeater in a 3GPP system. Here, the TRP may be configured to perform both a transmission function and an uplink reception function, only a downlink transmission function, or only an uplink reception function from a downlink perspective of a terminal direction from a base station. In addition, the wireless access point 520 may be configured to perform only an RF function or to perform some functions (eg, a physical layer and/or a MAC layer) of a base station DU together with an RF function. When the functions performed by the wireless access point 520 include some functions of the DU, the lower functions of the physical layer, physical layer functions, and/or lower functions of the MAC layer may be performed by the DU.

Therefore, the Fx interface 570 between the base station (or cell, DU, etc.) 510, 530 and the wireless access point 520 differs depending on which function of the physical layer and/or MAC layer is performed by the wireless access point. can be defined

The wireless access point 320 of FIG. 5 and the base stations 110-1, 110-2, 110-3, 120-1, 120-2, 510, and 530 shown in FIGS. 1 and 5 are OFDM, OFDMA, and SC, respectively. -FDMA or NOMA-based downlink transmission and uplink reception may be supported. In addition, when the wireless access point of FIG. 5 and a plurality of base stations shown in FIGS. 1 and 5 apply a mmWave band transmission carrier and support a beamforming function using an antenna array, each base station performs beamforming. It is possible to provide a service without interference between beams within a beam, and to provide a service for a plurality of terminals (or UEs) within one beam.

In addition, the wireless access point 520 and the plurality of base stations 110-1, 110-2, 110-3, 120-1, 120-2, 510, and 530 each perform MIMO transmission (eg, single user SU (SU)). )-MIMO, MU (multi user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, CA (carrier aggregation) transmission, transmission in an unlicensed band, direct communication between devices (device to device communication, D2D) (or proximity services (ProSe)), etc. may be supported. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is a base station 110-1, 110-2, 110-3, 120-1 , 120-2) and operations supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be performed. For example, the second base station 110-2 can transmit a signal to the fourth terminal 130-4 based on the SU-MIMO scheme, and the fourth terminal 130-4 uses the SU-MIMO scheme. A signal may be received from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, and the fourth terminal 130-4 And each of the fifth terminal 130-5 may receive a signal from the second base station 110-2 by the MU-MIMO method. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on the CoMP scheme, and The terminal 130-4 may receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by CoMP. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 includes a terminal 130-1, 130-2, 130-3, and 130-4 belonging to its own cell coverage. , 130-5, 130-6) and a CA method. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 controls D2D between the fourth terminal 130-4 and the fifth terminal 130-5. and each of the fourth terminal 130-4 and the fifth terminal 130-5 may perform D2D under the control of the second base station 110-2 and the third base station 110-3, respectively. .

Next, operating methods of a communication node in a wireless communication network will be described. Even when a method (for example, transmission or reception of a signal) performed in a first communication node among communication nodes is described, a second communication node corresponding thereto is described as a method performed in the first communication node and a method (eg, signal transmission or reception) For example, receiving or transmitting a signal) may be performed. That is, when the operation of the UE is described, the corresponding base station may perform an operation corresponding to the operation of the UE. Conversely, when the operation of the base station is described, the corresponding UE may perform an operation corresponding to that of the base station.

In the following description, UPF (or S-GW) may refer to an end communication node of a core network exchanging packets (eg, control information, data) with a base station, and AMF (or MME) may refer to a terminal It may refer to a communication node of a core network that performs a control function in a radio access interval (or interface) of . Here, each of the backhaul link, fronthaul link, Xhaul link, DU, CU, BBU block, S-GW, MME, AMF, and UPF functions of a communication protocol according to radio access technology (RAT) (eg, X It may be referred to as different terms depending on the function of the hole network and the function of the core network.

To perform a mobility support function and a radio resource management function, a base station may transmit a synchronization signal (eg, a synchronization signal/physical broadcast channel (SS/PBCH) block) and/or a reference signal. To support multiple numerologies, a frame format supporting symbols having different lengths may be set. In this case, the terminal may perform a monitoring operation of a synchronization signal and/or a reference signal in a frame according to initial numerology, default numerology, or default symbol length. Each of the initial numerology and the default numerology is a frame format applied to a radio resource for which a UE-common search space is set, and a radio resource for which a control resource set (CORESET) #0 of the NR communication system is set. It may be applied to an applied frame format and/or a frame format applied to a radio resource in which a synchronization symbol burst capable of identifying a cell in an NR communication system is transmitted.

The frame format is information on setting parameters for a subcarrier spacing, a control channel (eg, CORESET), a symbol, a slot, and/or a reference signal in a radio frame (or subframe) (eg, For example, it may mean a value of a setting parameter, an offset, an index, an identifier, a range, a period, an interval, and a duration. The base station may inform the terminal of the frame format using system information and/or a control message (eg, a dedicated control message).

A terminal connected to the base station may transmit a reference signal (eg, an uplink-only reference signal) to the base station using resources configured by the base station. For example, the uplink-only reference signal may include a sounding reference signal (SRS). In addition, a terminal connected to a base station may receive a reference signal (eg, a downlink-only reference signal) from the base station in resources configured by the base station. The downlink-only reference signal may be a channel state information-reference signal (CSI-RS), a phase tracking-reference signal (PT-RS), a demodulation-reference signal (DM-RS), and the like. Each of the base station and the terminal may perform a beam management operation through monitoring of a configured beam or an active beam based on a reference signal.

For example, the first base station 611 provides a synchronization signal and a synchronization signal so that the first terminal 621 located within a communication service area can search for itself and perform a downlink synchronization maintaining operation, a beam setting operation, or a link monitoring operation. / or a reference signal may be transmitted. The first terminal 621 connected to the first base station 611 (eg, serving base station) may receive radio resource configuration information of a physical layer for connection establishment and radio resource management from the first base station 611. . Radio resource configuration information of the physical layer may be configuration parameters included in an RRC control message in the LTE communication system and/or the NR communication system.

For example, radio resource configuration information is PhysicalConfigDedicated, PhysicalCellGroupConfig, PDCCH-Config(Common), PDSCH-Config(Common), PDCCH-ConfigSIB1, ConfigCommon, PUCCH-Config(Common), PUSCH-Config(Common), BWP-DownlinkCommon , BWP-UplinkCommon, ControlResourceSet, RACH-ConfigCommon, RACH-ConfigDedicated, RadioResourceConfigCommon, RadioResourceConfigDedicated, ServingCellConfig, ServingCellConfigCommon, and the like.

The radio resource configuration information includes a configuration period (or allocation period) of a signal (or radio resource) according to a frame format of a base station (or transmission frequency), time resource allocation information for transmission, frequency resource allocation information for transmission, It may include parameter values such as transmission time (or allocation time). To support multiple numerologies, a frame format of a base station (or transmission frequency) may mean a frame format having different symbol lengths according to a plurality of subcarrier intervals within one radio frame. For example, the number of symbols constituting each mini-slot, slot, and subframe within one radio frame (eg, a frame having a length of 10 ms) may be different from each other.

- Base station transmission frequency and frame format setting information

Transmission frequency setting information: all transmission carriers of the base station (eg, transmission frequency in units of cells), bandwidth part (BWP), transmission reference time or time difference information between transmission frequencies of the base station ( For example, a transmission period or offset parameter indicating a transmission reference time (or time difference) of a synchronization signal), etc.

Setting information of frame format: setting parameters of minislots, slots, and subframes having different symbol lengths according to subcarrier intervals

-Configuration information of downlink reference signals (eg, CSI-RS, common RS, etc.)

Configuration information of common RS: configuration parameters such as transmission period, transmission position, code sequence, masking sequence (or scrambling sequence) of a reference signal commonly applied in coverage of a base station (or beam)

-Setting information of uplink control signal

SRS, reference signal for uplink beam sweeping (or beam monitoring), radio resource (or preamble) for uplink grant-free, etc.

-Setting information of a downlink control channel (eg, PDCCH (physical downlink control channel))

A reference signal for PDCCH demodulation, a common beam reference signal (eg, a reference signal receivable by all terminals within beam coverage), a reference signal for beam sweeping (or beam monitoring), a reference signal for channel estimation, etc.

-Configuration information of an uplink control channel (eg, physical uplink control channel (PUCCH))

-Setting information of scheduling request signal

-Configuration information of a feedback (eg, acknowledgment (ACK) or negative ACK (NACK)) transmission resource in a hybrid automatic repeat request (HARQ) procedure

- Information on the number of antenna ports, antenna array, beam configuration and / or beam index mapping information for applying beamforming

-Configuration information of downlink signal and/or uplink signal (or uplink access channel resource) for beam sweeping (or beam monitoring)

Reception of a beam triggering a beam setting operation, a beam recovery operation, a beam reconfiguration operation, a radio link re-establishment operation, a beam change operation in the same base station, and a handover procedure to another base station Setting information such as signals and control timers of the above operations

In a radio frame format supporting different symbol lengths to support multiple numerologies, a setting period (or allocation period) of parameters constituting the above information, time resource allocation information, frequency resource allocation information, transmission time, and /or Allocation timing may be information set according to a corresponding symbol length (or subcarrier interval).

In the following embodiments, "Resource-Config information" may be a control message including one or more parameters among radio resource configuration information of a physical layer. Also, "Resource-Config information" may refer to an attribute and/or a set value (or range) of an information element (or parameter) delivered by a control message. The information element (or parameter) delivered by the control message is radio resource configuration information commonly applied throughout the coverage of the base station (or beam) or dedicated to a specific terminal (or specific terminal group) It may be radio resource configuration information allocated to . A terminal group may include one or more terminals.

Configuration information included in "Resource-Config information" may be transmitted through one control message or different control messages according to properties of the configuration information. Beam index information may not clearly distinguish between the index of a transmission beam and an index of a reception beam. For example, the beam index information may be expressed using an index (or identifier) of a reference signal mapped or associated with a corresponding beam index or a transmission configuration indicator (TCI) state for beam management.

Accordingly, a terminal operating in an RRC-connected state can receive a communication service through a beam (eg, a beam pair) set between itself and the base station. For example, when a communication service is provided using beam configuration (eg, beam pairing) between a base station and a terminal, the terminal sets a beam with the base station and a synchronization signal of a receivable beam (eg, SS/PBCH block) and/or a reference signal (eg, CSI-RS) to perform a radio channel search operation or monitoring operation. Here, "providing a communication service through a beam" may mean "transceiving a packet through an activation beam among one or more configuration beams". In the NR communication system, “activating a beam” may mean “activating a configured TCI state”.

The terminal may operate in an RRC idle state or an RRC inactive state. In this case, the terminal may perform a downlink channel search operation (eg, monitoring operation) using parameter(s) obtained from system information or common Resource-Config information. In addition, a terminal operating in an RRC idle state or an RRC inactive state may attempt access using an uplink channel (eg, a random access channel or a physical layer uplink control channel). Alternatively, the terminal may transmit control information using an uplink channel.

The terminal may detect or detect a radio link problem by performing a radio link monitoring (RLM) operation. Here, "detection of a problem in the wireless link" may mean "that there is an abnormality in setting or maintaining synchronization of the physical layer of the wireless link". For example, "detection of a radio link problem" may mean "detection of mismatch of physical layer synchronization between a base station and a terminal for a preset time period". When a radio link problem is detected, the terminal may perform a radio link recovery operation. If the radio link is not restored, the terminal may declare a radio link failure (RLF) and may perform a radio link re-establishment procedure.

The radio link physical layer problem detection procedure according to the RLM operation, the radio link recovery procedure, the radio link failure detection (or declaration) procedure, and the radio link re-establishment procedure are the layers of the radio protocol constituting the radio link ( May be performed by functions of layer) 1 (eg, physical layer), layer 2 (eg, MAC layer, RLC layer, PDCP layer, etc.) and/or layer 3 (eg, RRC layer) there is.

The physical layer of the UE may monitor the radio link by receiving a downlink synchronization signal (eg, a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and an SS/PBCH block) and/or a reference signal. can In this case, the reference signal is a base station common reference signal, a beam common reference signal, or a UE (or UE group) specific reference signal (eg, a dedicated (dedicated) allocated to a UE (or UE group) dedicated reference signal). Here, the common reference signal may be used for channel estimation of all terminals located within the coverage (or service area) of a corresponding base station or beam. The dedicated reference signal may be used for a channel estimation operation of a specific terminal or a specific group of terminals within the coverage of a base station or a beam.

Accordingly, when a base station or a beam (eg, a configuration beam between a base station and a terminal) is changed, a dedicated reference signal for beam management may be changed. The beam may be changed based on configuration parameter(s) between the base station and the terminal. A change procedure for the setting beam may be required. "Changing the beam in the NR communication system" means "changing a TCI state index (or identifier) to another TCI state index", "newly setting a TCI state", or "activating a TCI state" It can mean "to change to state". The base station may transmit system information including configuration information of the common reference signal to the terminal. The terminal may obtain a common reference signal based on system information. Alternatively, in a handover procedure (handover or reconfiguration with sync) or connection reconfiguration procedure in which a base station is changed, the base station may transmit a dedicated control message including configuration information of a common reference signal to the terminal. The set beam information includes a set beam index (or identifier), a set TCI state index (or identifier), set information of each beam (eg, transmit power, beam width, vertical angle, horizontal angle), transmission and / or one or more of reception timing information (eg, subframe index, slot index, mini-slot index, symbol index, offset), reference signal information corresponding to each beam, and reference signal identifier.

In embodiments, the base station may be a base station installed in the air. For example, the base station may be installed in an unmanned aerial vehicle (eg, a drone), a manned aircraft, or a satellite.

The terminal may receive configuration information (eg, identification information of the base station) of the base station from the base station through one or more of an RRC message, a MAC message, and a PHY message, and based on the configuration information, beam monitoring operation, wireless access ( A base station to perform an access) operation and/or a control (or data) packet transmission/reception operation may be identified.

The result of the measurement operation (eg, beam monitoring operation) on the beam may be reported through a physical layer control channel (eg, PUCCH) and/or a MAC message (eg, MAC CE, control PDU). . Here, the result of the beam monitoring operation may be a measurement result of one or more beams (or beam groups). For example, a result of the beam monitoring operation may be a measurement result of beams (or beam groups) according to a beam sweeping operation of the base station.

The base station may obtain a result of the beam measurement operation or the beam monitoring operation from the terminal, and may change the beam property or the TCI state property based on the result of the beam measurement operation or the beam monitoring operation. Beams may be classified into primary beams, secondary beams, preliminary (or candidate) beams, active beams, and inactive beams according to properties. The TCI state may be classified into a primary TCI state, a secondary TCI state, a reserve (or candidate) TCI state, a serving TCI state, a set TCI state, an active TCI state, and an inactive TCI state according to attributes.

Each of the primary TCI state and the secondary TCI state may be assumed to be an active TCI state or a serving TCI state in which data packets or control signaling may be transmitted or received even in a limited manner. In addition, the preliminary (or candidate) TCI state may be assumed to be a deactivated TCI state or a configured TCI state in which data packets or control signaling cannot be transmitted or received while being subject to measurement or management.

A procedure for changing beam (or TCI state) attributes may be controlled by the RRC layer and/or the MAC layer. When a procedure for changing a beam (or TCI state) attribute is controlled by the MAC layer, the MAC layer may inform an upper layer of information about a change in a beam (or TCI state) attribute. Information on the change of beam (or TCI state) attributes may be transmitted to the UE through a MAC message and/or a physical layer control channel (eg, PDCCH). Information on the change of beam (or TCI state) attributes may be included in downlink control information (DCI) or uplink control information (UCI). Information on the change of beam (or TCI state) attributes may be expressed as a separate indicator or field.

The terminal may request a property change of the TCI state based on a result of a beam measurement operation or a beam monitoring operation. The terminal may transmit control information (or feedback information) requesting a change in TCI state properties to the base station using one or more of a PHY message, a MAC message, and an RRC message. Control information (or feedback information, control message, control channel) requesting a property change of the TCI state may be configured using one or more of the above configuration beam information.

A change in the properties of a beam (or TCI state) is "change from active beam to inactive beam", "change from inactive beam to active beam", "change from primary beam to secondary beam", "change from secondary beam to primary beam" It may mean "change to head beam", "change from primary beam to preliminary (or candidate) beam", or "change from preliminary (or candidate) beam to primary beam". An attribute change procedure of a beam (or TCI state) may be controlled by the RRC layer and/or the MAC layer. A procedure for changing a property of a beam (or TCI state) may be performed through partial cooperation between the RRC layer and the MAC layer.

When a plurality of beams are allocated, one or more of the plurality of beams may be configured as beam(s) transmitting a physical layer control channel. For example, a primary beam and/or a secondary beam may be used for transmission and reception of a physical layer control channel (eg, PHY message). Here, the physical layer control channel may be PDCCH or PUCCH. The physical layer control channel includes scheduling information (eg, radio resource allocation information, modulation and coding scheme (MCS) information), feedback information (eg, channel quality indication (CQI), precoding matrix indicator (PMI), HARQ ACK , HARQ NACK), resource request information (eg, scheduling request (SR)), a result of a beam monitoring operation for beamforming function support, a TCI state ID, and active beam (or inactive beam) Among the measurement information Can be used for more than one transmission.

The physical layer control channel may be configured to be transmitted as a downlink primary beam. In this case, feedback information may be transmitted and received through the primary beam, and data scheduled by control information may be transmitted and received through the secondary beam. Alternatively, the physical layer control channel may be configured to be transmitted as an uplink primary beam. In this case, resource request information (eg, SR) and/or feedback information may be transmitted and received through the primary beam.

In a procedure for allocating a plurality of beams (or a procedure for setting a TCI state), an assigned (or set) beam index, information indicating an interval between beams, and/or information indicating whether to allocate consecutive beams is a base station It can be transmitted and received through a signaling procedure between the terminal and the terminal. The signaling procedure of beam allocation information may be performed differently depending on the state information (eg, movement speed, movement direction, location information) of the UE and/or the quality of the radio channel. The base station may obtain state information of the terminal from the terminal. Alternatively, the base station may obtain state information of the terminal through another method.

The radio resource information includes parameter(s) indicating frequency domain resources (eg, center frequency, system bandwidth, PRB index, number of PBRs, CRB index, number of CRBs, subcarrier index, frequency offset) and time domain resources (eg, radio frame index, subframe index, transmission time interval (TTI), slot index, mini-slot index, symbol index, time offset, period of transmission interval (or reception interval), length, window). In addition, the radio resource information includes a hopping pattern of radio resources, information for beamforming (eg, beamforming) operation (eg, beam configuration information, beam index), and code sequences (or bit strings). , signal sequence) may further include resource information occupied according to characteristics.

The name of the physical layer channel and/or the name of the transport channel are the data type (or attribute), the control information type (or attribute), and the transmission direction (eg, uplink, downlink, sidelink). ), etc. may vary.

A reference signal for beam (or TCI state) or radio link management may be a synchronization signal (eg, PSS, SSS, SS/PBCH block), CSI-RS, PT-RS, SRS, DM-RS, and the like. The reference parameter (s) for the reception quality of a beam (or TCI state) or a reference signal for radio link management includes a measurement time unit, a measurement time interval, a reference value representing the degree of improvement in reception quality, and a degree of degradation in reception quality. It may be a reference value, etc. Each measurement time unit and measurement time interval may be set in units of absolute time (eg, millisecond, second), TTI, symbol, slot, frame, subframe, scheduling period, operation period of the base station, or operation period of the terminal. there is.

The reference value representing the degree of change in reception quality may be set as an absolute value (dBm) or a relative value (dB). In addition, the reception quality of a reference signal for beam (or TCI state) or radio link management is RSRP (reference signal received power), RSRQ (reference signal received quality), RSSI (received signal strength indicator), SNR (signal-to -noise ratio), signal-to-interference ratio (SIR), and the like.

Meanwhile, in an NR communication system using a millimeter frequency band, flexibility in channel bandwidth management for packet transmission can be secured based on a bandwidth part (BWP) concept. The base station can configure up to four BWPs having different bandwidths in the terminal. BWP can be set independently in downlink and uplink. That is, downlink BWP can be distinguished from uplink BWP. Each of the BWPs may have a different subcarrier spacing as well as a different bandwidth.

A measurement operation (eg, monitoring operation) for beam (or TCI state) or radio link management may be performed by a base station and/or a terminal. The base station and/or terminal may perform a measurement operation (eg, monitoring operation) according to parameter(s) set for the measurement operation (eg, monitoring operation). The UE may report measurement results according to configuration parameter(s) for measurement reporting.

When the reception quality of the reference signal according to the measurement result meets a preset reference value and/or a preset timer condition, the base station performs a beam (or radio link) management operation, a beam switching operation, or a beam blockage situation. It is possible to determine whether to perform a beam deactivation operation (or beam activation operation) according to . When it is determined to perform a specific operation, the base station may transmit a message triggering the execution of the specific operation to the terminal. For example, the base station may transmit a control message instructing the performance of a specific operation to the terminal. The control message may include setting information of a specific operation.

When the reception quality of the reference signal according to the measurement result meets a preset reference value and/or a preset timer condition, the terminal may report the measurement result to the base station. Alternatively, the terminal performs a beam (or radio link) management operation, a beam switching operation (or a TCI state ID change operation, an attribute change operation), or a beam deactivation operation (or beam activation operation) according to a beam blocking situation. A triggering control message may be transmitted to the base station. A control message may request the performance of a specific action.

A basic procedure for beam (or TCI state) management through radio link monitoring may include a beam failure detection (BFD) procedure for a radio link, a beam recovery (BR) request procedure, and the like. . "Operation of determining whether to perform a beam failure detection procedure and/or beam recovery request procedure", "operation of triggering execution of a beam failure detection procedure and/or beam recovery request procedure", and "beam failure detection procedure and/or Each of the "control signaling operations for the beam recovery request procedure" may be performed by one or more of the PHY layer, the MAC layer, and the RRC layer.

6 is a conceptual diagram illustrating an example of a connection method for supporting a multi-wireless access point function in a mobile communication system.

Referring to FIG. 6, base stations 611 and 612 communicate with wireless access points (hereinafter referred to as transmission and reception points (TRPs)) 621-1, 621-2, and 622-1 in their respective service areas in a wired or wireless manner. It is connected through an interface 670 (eg, Fx interface or fronthaul) of the terminal, and can provide service to terminals. The base stations 611 and 612 and the TRPs 621-1, 621-2, and 622-1 are connected to the terminals 650, 651-1, 651-2, 651-3, 652-1, and 652 within their respective service areas. -2) may be provided with a service through a wireless link (eg, Uu interface of the 3GPP system). The TRPs 621-1 and 621-2 in the base station 611 for supporting a multi-radio access point function (hereinafter, a multi-transmission and reception point (mTRP) function) use the same frequency band or use different frequency bands. Available. Also, the TRPs 621-1 and 621-2 in the base station 611 may operate the same cell having the same physical cell ID (PCI) or different cells having different physical layer IDs. When the TRP 621-1 and the TRP 621-2 operate in the same frequency band, the terminal 651-3 can receive service in a single frequency network (SFN) scheme. Here, the SFN scheme refers to a scheme in which two or more TRPs providing services on the same frequency simultaneously transmit the same data to the terminal. In addition, two or more TRPs (621-2 and 622-1 in FIG. 6) belonging to different base stations 611 and 612 may provide service to one terminal (650 in FIG. 6) to support the mTRP function. there is.

7 is a flowchart for explaining an embodiment of an operation procedure by supporting the mTRP function in a mobile communication system.

A serving base station (or cell, mTRP L2/L3 entity) 704 supporting the mTRP function may provide a service to the terminal 703 using one or more TRPs (hereinafter TRPs). The base station may perform operations and procedures for supporting the mTRP function in an entity that controls configuration/operation of the physical layer (or part of the physical layer) of the TRP (hereinafter referred to as mTRP L2/3 entity). Here, the function of the mTRP L2/3 entity may be performed by the MAC layer and/or the RRC layer.

The serving base station (or cell, mTRP L2 / L3 entity) 704 transfers the parameter (s) for mTRP function support to the terminal 703 using an RRC and / or MAC layer control message and transmits the TRP1 belonging to the base station ( 701) can be used to provide a service to the terminal 703 (S701). That is, step S701 is a step in which a service is provided using a single TRP (ie, TRP1). In step S701, the serving base station 704 may transmit cell or TRP selection conditions for supporting the mTRP function to the terminal via the TRP1 701 using an RRC message. In step S701, the serving base station (or cell) may transmit information about neighboring TRP(s) and/or candidate TRP(s) for supporting the mTRP function to the terminal. Here, the neighboring TRP(s) and/or candidate TRP(s) (eg, TRP2 702) may be a TRP belonging to the same base station (or cell) as the serving base station 704 or a TRP belonging to another base station (or cell). can Information on neighboring TRP(s) and/or candidate TRP(s) transmitted by the base station to the terminal through a dedicated control message and/or system information includes the identifier(s) of the corresponding TRP(s), the cell of the TRP(s) Identifier(s), and/or beam configuration information (eg, SSB, downlink reference signal identifier information) of each TRP, C-RNTI-based scheduling identifier of LTE/NR system (hereinafter referred to as scheduling identifier or C-RNTI), or It can be configured including a combination.

The terminal may determine whether TRP(s) satisfying the mTRP function support condition (or event) exist while performing measurement and/or reporting operations according to measurement/report settings (S702). Based on the measured value of the quality of the radio channel of the serving cell currently providing service (or active TRP, serving TRP) and the detected TRP (or added TRP) (hereinafter, the detected TRP), the UE It may be determined whether each TRP satisfies the mTRP function support condition. The parameter (s) for determining whether the mTRP function support condition is satisfied may be configured based on one or more of the following conditions, and the corresponding condition parameter (s) is determined by using the control message and / or system information of step S701. It can be delivered to the terminal.

● When the radio channel quality between the terminal and the serving cell (or active TRP, serving TRP) is below the reference value

● When the terminal is located at the boundary of the service area of the serving cell (or active TRP, serving TRP)

● If the transmission frequency, frequency band, and/or BWP of the detected TRP satisfies the priority for supporting the mTRP function

● When the quality of the radio channel between the terminal and the detected TRP is higher than the preset reference value

● When the quality of the radio channel between the terminal and the detected TRP is maintained at a preset reference value or higher until a predefined timer expires

Here, whether the terminal is located at the boundary of the service area of the serving cell (or active TRP, serving TRP) is determined by the quality of the radio channel and/or the additional information (eg, GNSS/GPS information, Alternatively, geographic location information according to a location estimation method using PRS, etc.) may be used.

When a TRP (e.g., TRP2 702) satisfying the above condition(s) is detected and selected, the terminal 703 transmits the measurement result for TRP2 702 via TRP1 701 to the serving base station (or cell, mTRP L2/L3 entity) (704) (S703). In step S703, the terminal 703 transmits only the measurement result to the serving base station (or cell, mTRP L2/L3 entity) 704 or includes the measurement result in a control message requesting mTRP function support to serve base station (or cell, mTRP L2/L3 entity) 704 (S703). Even when a TRP that is not included in the list information of neighboring TRP(s) and/or candidate TRP(s) received in step S701 but satisfies the mTRP function support condition is detected in step S702, the terminal performs step S703 for the corresponding TRP. can be done In step S703, the UE identifies one or more detected TRP(s) identifier(s), cell identifier(s) (eg, PCI) of the TRP(s), and/or one or more beam identifier(s) for each TRP (eg, SSB and/or downlink reference signal (RS) identifier) information may be transmitted together with the measurement result. The control message for requesting or triggering support for the mTRP function in step S703 may be an RRC message or a MAC layer control message (eg, a MAC control element (CE)). When MAC CE is used, the corresponding MAC CE includes a logical channel identifier (LCID) indicating that it is a MAC CE requesting mTRP function support, and the TRP identifier (s) and / or TRP (s) transmitted in step S701 Cell identifier(s) may be included. Here, the MAC CE may include a MAC subheader, a MAC header, a MAC PDU, and/or a MAC subPDU.

The base station 704 receiving the measurement result and/or triggering message for supporting the mTRP function from the terminal 703 receives the corresponding base station (or cell, mTRP L2/L3 entity) when the TRP2 702 belongs to another base station (or cell). ) 705 and control information for supporting the mTRP function may be exchanged (S704). In step S704, the mTRP L2/3 entity (mTRP L2/L3 entity) 705 of the added TRP (TRP2 702 in FIG. 7) controls the TRP1 and the mTRP L2/3 entity 704 may be performed in other cases. In addition, when the mTRP L2/L3 entities are different from each other, in step S704, the related base stations (704 and 705 in FIG. 7) will actively support the mTRP function for the corresponding terminal (703 in FIG. 7). A base station (eg, 704) to operate the entity may be determined. A base station that will operate an mTRP L2/3 entity that will actively support the mTRP function for the corresponding terminal (703 in FIG. 7) can be expressed as an 'mTRP function control base station'.

When the mTRP L2/3 entities 704 and 705 of the TRPs 701 and 702 that provide the mTRP function for one terminal (703 in FIG. 7) are different from each other, the mTRP L2/3 entities 704 and 705 ) determines downlink radio resources (eg, PDSCH, PDCCH (or CORESET)) and uplink radio resources (eg, PUCCH, PUSCH) for mTRP function support through consultation, and mTRP L2/3 entity of active TRP is detected Downlink and/or uplink radio resources of the added TRP (or added TRP) 702 may be allocated. Hereinafter, 'active TRP' refers to a TRP that performs downlink transmission and/or uplink reception operations to support the mTRP function. To this end, in step S704, the mTRP L2/3 entity 704 of the active TRP (TRP1 701 in FIG. 7) measures the measurement result for one or more detected TRPs received from the terminal and information about the corresponding terminal (e.g., corresponding terminal). The movement speed of the terminal, the capability of the terminal, and the service being provided) may be transmitted to the mTRP L2/3 entity 705 of the TRP (TRP2 702 in FIG. 7) additionally participating in the mTRP function.

When TRP2 and TRP1 belong to the same cell or when TRP2 and TRP1 are operated by the same mTRP L2/3 entity, step S704 can be omitted. In addition, even when TRP2 belongs to other cells belonging to the same base station as TRP1, step S704 may be omitted. Alternatively, in step S704, reference signal settings such as related physical layer parameters for providing the mTRP function (e.g., downlink radio resource configuration information including CORESET, uplink radio resource configuration information including PUCCH, CRS, TRS, DMRS, and SRS) It can be replaced by transmitting setting information such as information, beam setting (or TCI state setting) information, etc.).

When preparation for supporting the mTRP function is completed, the base station (or cell) may transmit a control message notifying the start (or permission) of supporting the mTRP function using TRP1 and TRP2 to the terminal through TRP1 or TRP2 (S705). In step S705, the base station may transmit a message (or primitive information) notifying that the terminal 703 is ready to support the mTRP function or instructing or informing the start of supporting the mTRP function (or primitive information) to TRP1 and TRP2. The control message generated by the base station 704 and delivered to the terminal 703 in step S705 may be an RRC layer, MAC CE, physical layer control message, or a combination thereof. If the control message of step S705 is an RRC message, the mTRP L2/L2 entity of the active TRP may generate and transmit configuration information for supporting the mTRP function, including related physical layer parameters for providing the above-described mTRP function, to the terminal. If the control message of step S705 is configured as MAC CE, the mTRP L2/L2 entity of the active TRP activates the TRP performing the mTRP operation based on the setting parameter(s) of step S701 and/or the beam (or TCI state) may be generated and transmitted. In this case, the MAC CE identifies the TRP/beam (or TCI) to be activated using the bitmap in the sub-header or configures the identifier of the TRP/beam (or TCI) to be activated as field information of the MAC CE and transmits the corresponding TRP. / Can indicate the activation of the beam (or TCI). In addition, as described above, step S705 may be performed without explicit transmission of an RRC layer/MAC layer control message notifying support start (or permission) of the mTRP function. That is, when the terminal receives a physical layer control message instructing downlink reception from a plurality of TRPs according to the mTRP function and/or a physical layer control message instructing uplink transmission from a plurality of TRPs, the terminal supports the mTRP function. You can recognize that this has started. If the control message corresponding to step S705 is not received before the preset related timer (eg, mTRP_Timer) expires, the terminal may determine that the mTRP function support procedure described with reference to FIG. 7 has failed. mTRP_Timer can be (re)started when the terminal performs step S703 and stopped when the terminal receives the control message of step S705. If the procedure of FIG. 7, once started, fails, the terminal and the base station (or cell) may perform the corresponding procedure again from step S702.

When TRP1 and TRP2 supporting the mTRP function perform not only the RF function but also some functions of the physical layer, the base station 704 generates scheduling information and downlink data and/or control information according to the performance level of the TRP1 and TRP2. and can be delivered to TRP1 and TRP2 (S706). TRPs supporting the mTRP function can perform limited functions such as physical layer code block generation, channel coding, rate matching, scrambling, modulation, and/or layer mapping. . In this case, according to the function level performed by the TRPs, the base station transfers the MAC PDU (or transport block) and scheduling information generated in the MAC layer to the TRPs, or before performing channel coding (or encoding). The bit stream is delivered to the TRPs, or the bit stream (or code block) for which channel coding and/or rate matching has been completed, scheduling information (eg, time/frequency domain resource allocation, MCS information, etc.), DCI for PDCCH and/or Alternatively, a control channel element (CCE) for UCI or PDCCH may be generated and transmitted.

In addition, the physical layer of the TRP supporting the mTRP function may be configured to include only the HARQ function. In this case, the TRP may perform HARQ buffer management for HARQ retransmission, HARQ process management, HARQ feedback information processing, and/or HARQ retransmission.

In addition, when the TRP supporting the mTRP function is configured to perform only a radio frequency (RF) function without performing the physical layer function, the base station 704 passes through the TRP1 and TRP2 supporting the mTRP function without performing the above-described step S706. to transmit downlink packets (data/control information) (S707).

Through step S705, the terminal can recognize the start of mTRP function support using TRP1 and TRP2. Therefore, based on the parameter(s) for supporting the mTRP function transmitted through the control message before step S705 and/or step S705, the terminal can receive downlink (data/control information) from TRP1 and TRP2.

In step S707 in which the UE performs downlink reception, transmission of TRP1 and TRP2 may be simultaneously performed in the same time domain and/or frequency domain or may be performed in different time/frequency domains. Here, the same time domain may mean the same scheduling timing, and the same frequency domain may mean the same transmission frequency, frequency band, and/or BWP.

A terminal to be supported for the mTRP function may transmit uplink packets (data/control information) to TRP1 and TRP2 (S708). In step S708, transmission from the terminal to TRP1 and TRP2 may be simultaneously performed in the same time domain and/or frequency domain, or may be performed in different time/frequency domains. As described in step S706, each TRP may perform the function of the receiving end corresponding to the operation of step S706 according to the radio protocol functional configuration of TRP1 and TRP2. For example, each TRP performs descrambling, de-rate matching, channel decoding (or decoding), and/or MAC PDU extraction of received uplink packets according to its radio protocol function configuration. etc. can be performed. TRP1 and TRP2 may deliver bit streams (or signal sequences) or MAC PDUs generated through processing of uplink packets from the terminal to the base station according to the performance level of the physical layer function (S709).

When TRPs for mTRP operation operate different cells, scheduling identifier (eg, C-RNTI) information for transmitting scheduling information may be delivered to the terminal in the form of an RRC message or MAC CE in step S705. Alternatively, the C-RNTI may be pre-allocated to the UE together with parameter setting information of neighboring TRP(s) and/or candidate TRP(s) in step S701. In particular, when the scheduling identifier is transmitted to the MAC CE, the corresponding MAC CE may be identified using a logical channel ID (LCID) indicating that the MAC CE is a MAC CE for allocating a scheduling identifier for supporting the mTRP function. In addition, the corresponding MAC CE may include cell identifier(s) and/or TRP identifier(s). In allocating a scheduling identifier for supporting the mTRP function, the same C-RNTI may be applied to TRPs belonging to the same base station. That is, in the above-described method, the same C-RNTI may be predefined to be applied to support the mTRP function by TRPs belonging to the same base station. However, in the case of a UE supporting the mTRP function from two or more TRPs (621-2 and 622-1 in FIG. 6) belonging to different base stations 611 and 612, different scheduling identifiers are assigned to one UE (FIG. 6). 650 of) can be assigned to.

If necessary to support the mTRP function, TRP1 (701) and TRP2 (702) can forward downlink data to the terminal or uplink data from the terminal to the counterpart TRP, and provide downlink scheduling information and/or Uplink control information (or feedback information) may be transmitted to the counterpart TRP. Depending on the configuration of the radio protocol for supporting the mTRP function, data forwarding and/or transfer of control information between TRPs may not be necessary. That is, the corresponding data and/or control information may be delivered to a node in which an upper protocol layer (eg, MAC layer) corresponding to each TRP exists without being delivered to the counterpart TRP.

When the condition for releasing the mTRP function preset during mTRP function support is satisfied, the terminal and / or the base station (or cell) transmits a control message requesting or instructing the release of mTRP function support to release the mTRP function. (S710). Conditions for releasing the mTRP function in step S710 may be delivered to the terminal using a control message in step S701 and/or step S705, and may be defined as one or more of the following conditions.

● When the quality of the radio channel between the TRP (s) and the terminal is below the reference value until a predefined timer (eg, mTRP_MaintainTimer) expires

● If the random access procedure for the TRP(s) performing the mTRP function fails

● When beam failure recovery (BFR) fails for the TRP(s) performing the mTRP function.

● When the base station (or cell) and/or the mTRP L2/L2 entity decides to release the mTRP function for that TRP.

● When the terminal requests release of the mTRP function or requests to change the TRP performing the mTRP function to another TRP

In step S710, when the TRPs belong to different base stations (or cells), if TRP1 (701 in FIG. 7) is the release target TRP, the base station leading the mTRP function (704 in FIG. 7) and the base station 705 to which TRP2 belongs Control messages for procedures such as release of mTRP function support, cell change for mTRP function support, or handover may be exchanged between the terminals. At this time, a control message or information for transferring the mTRP L2/L3 entity function for supporting the mTRP function may be exchanged. When the exchange of control messages for transferring the mTRP L2/L3 entity function between the base stations 704 and 705 is completed in step S710, the connection control management function for providing service to the corresponding terminal (703 in FIG. 702) may be transferred to the base station (705 in FIG. 7) to which it belongs. That is, the serving base station (or cell) 705 and the terminal that have released the mTRP function for TRP1 through step S710 can maintain service with only one TRP (eg, TRP2 in FIG. 7) (S711).

In addition to the method of stopping mTRP function support and using only one TRP as in step S711 according to the performance of step S710 and receiving the service, if there is a TRP that satisfies the mTRP function support condition of step S710, TRP change (or reset) Through this, mTRP function support can continue. That is, when the function of the mTRP L2/L3 entity for supporting the mTRP function is transferred to base station 705 in FIG. 7 with the release of the function of TRP1 in step S710, and another TRP (eg, TRP3) added with TRP2 provides the mTRP function. , the above-described mTRP function can be supported to the terminal using TRP2 and TRP3.

During the above-described mTRP operation, when an active TRP is a release target, a TRP change and/or selection (or switching) operation (hereinafter referred to as L2-based TRP selection) may be performed.

If the mTRP function using a plurality of TRPs in the same base station (or cell, mTRP L2/3 entity) is performed, L2-based TRP selection may be performed using MAC CE.

When the quality measurement value of the radio channel of the currently serving cell (or active TRP, serving TRP) and the newly detected TRP satisfy the mTRP function support condition, the UE sends a MAC CE requesting L2-based TRP selection. can transmit MAC CE requesting or triggering L2-based TRP selection (eg, L2basedTRP_Select MAC CE) may be configured with one or more of the following information.

● Identifier of the TRP to be released among the active TRP(s)

● Identifier of a newly detected TRP that satisfies the above-mentioned mTRP function support condition among the TRP(s) set for mTRP function support

● Target TRP indicator for mTRP function support

● Cell identifier of detected TRP or target TRP

● Target TRP activation request indicator

● Downlink transmission request for mTRP function support

● Uplink scheduling request for mTRP function support

● Terminal buffer status report (BSR: buffer status report) information

Here, the 'target TRP' is a TRP that satisfies the mTRP function support condition and means a TRP selected by the terminal for the purpose of supporting the mTRP function. In addition, the L2basedTRP_Select MAC CE may be transmitted together with beam (or TCI state) identifier information and/or L2 measurement result information for corresponding TRPs, or may be configured in the form of a separate MAC CE and transmitted.

When requesting L2-based TRP selection for TRP switching (or change) while mTRP function is supported, one of the following methods may be performed.

● Method 1: L2 TRP (or cell) selection method

● Method 2: L2 triggered TRP (or cell) change method

● Method 3: L2 TRP (or cell) request (or triggering) method

Here, method 1 is a method in which the terminal selects (or determines) the TRP while supporting the mTRP function. That is, the terminal transmits the above-described L2basedTRP_Select MAC CE to the source TRP or target TRP to notify the base station (or cell, mTRP L2/3 entity) of the change to the TRP indicated by the TRP identifier in the corresponding MAC CE. Here, 'source TRP' means a TRP currently performing the mTRP function.

According to method 1, the terminal transmits a control signal (e.g., MAC CE or physical layer control signal) instructing TRP selection while supporting a scheduling request (SR), buffer status report (BSR), or mTRP function to the target TRP. The base station (or cell, mTRP L2/3 entity) may be notified that a TRP (ie, target TRP) for this mTRP has been selected. According to method 1, the base station (or cell, mTRP L2/3 entity) recognizing the target TRP selected by the terminal releases (or stops) supporting the mTRP function of the previous TRP (or source TRP), and uses the target TRP selected by the terminal. Thus, the above-described mTRP function may be supported.

Method 2 is a method in which the terminal requests or triggers cell change (or handover) by transmitting L2basedTRP_Select MAC CE to the source TRP. The base station (or cell, mTRP L2/3 entity) that obtains the target TRP and/or release TRP information using the L2basedTRP_Select MAC CE received through the source TRP releases (or stops supporting) the source TRP (or release TRP) mTRP function. ), and activating the target TRP selected by the terminal to provide service to the corresponding terminal. At this time, the base station (or mTRP L2/3 entity, source TRP) transmits (eg, MAC CE or physical layer control signal) instructing the terminal to activate the target TRP, or transmits downlink/uplink scheduling information (or PDCCH, DCI) ) to activate the target TRP.

In scheme 3, the terminal transmits the above-described L2basedTRP_Select MAC CE to the source TRP or target TRP to request or trigger a change to the TRP indicated by the TRP identifier in the corresponding MAC CE to the base station (or cell, mTRP L2 / 3 entity) way. Upon receiving the L2basedTRP_Select MAC CE from the UE, the L2 layer of the base station transfers the control information to the L3 layer of the base station to perform cell change according to the existing handover procedure. That is, a procedure in which the mTRP L2/3 entity of the base station (or cell) performs a measurement result of the SRS received from the terminal, a measurement report from the terminal, and/or a procedure for switching to the TRP indicated by the L2basedTRP_Select MAC CE may be performed. there is. In addition, the mTRP L2/3 entity of the base station may deliver internal primitive information indicating TRP switching (or change) to the L3 layer of the base station while the mTRP function is supported.

To support L2-based TRP selection (or L1/L2 centric mobility) according to methods 1 to 3 described above, parameter settings for L2 measurement/reporting are required. Therefore, in the step of setting support for the mTRP function, the base station selects a measurement target (SSB, CSI-RS, TRS, PRS, etc.) for periodic and/or aperiodic L2 measurement, a measurement time, and a measurement timer for L2 filtering. , and/or SRS resource configuration information for uplink measurement and L2 event configuration information for L2-based TRP selection may be delivered.

Here, the SRS resource for uplink measurement may be configured in units of TRPs or for all TRPs supporting the mTRP function. However, when the above-described beamforming technique is applied, measurement targets (SSB, CSI-RS, TRS, PRS, etc.) and/or SRS resources for L2 measurement may be set in units of beams.

In addition, L2 event configuration information for L2-based TRP selection is based on an L2 event based on SSB, CSI-RS, TRS, and/or PRS initiated by the UE and SRS indicated (or triggered) by the base station. It can be set by distinguishing the L2 event of

In addition, before starting the L2-based TRP selection operation according to the above-described methods 1 to 3, the UE checks a cell identifier or TRP identifier such as a candidate TRP and a detected TRP that meets the mTRP function condition. If the cell identifier or TRP identifier of the detected TRP is different from the cell identifier or TRP identifier of the existing TRP performing the mTRP operation, the terminal may perform a random access (RA) procedure to transmit the above-described control information. Here, the above-described control information is an RRC layer control message, MAC CE, and/or physical layer control transmitted by the UE to the source TRP or target TRP for the L2-based TRP selection operation described in Method 1, Method 2, or Method 3. It means a signal and is expressed as 'TrpSW_L1/L2_Sig' below. If the UE is pre-allocated with non-contention based random access (RA) resources for the corresponding TRP (or cell or base station), the UE performs a non-contention based RA procedure using the corresponding RA resource, and In this case, the UE performs a contention based random access (RA) procedure. The UE may transmit the above-described TrpSW_L1/L2_Sig during the RA procedure execution step or after the RA procedure is completed. In the RA procedure, the UE may transmit the above-described TrpSW_L1/L2_Sig using RA MSG3 of 4-step RA procedure or MSG-A payload of 2-step RA procedure. If TrpSW_L1/L2_Sig cannot be transmitted (or cannot be transmitted) in the RA procedure progress step, the UE can transmit TrpSW_L1/L2_Sig using the first uplink radio resource transmitted after the RA procedure is completed.

If L2-based TRP selection to a TRP belonging to another cell within the same DU (or the same gNB / eNB or the same mTRP L2 / 3 entity) is requested, TRP switching according to the above-described method 1, method 2, or method 3 ( intra-DU TRP switching) may be applied.

However, in the case of switching between TRPs belonging to different DUs (inter-DU TRP switching) (or switching between TRPs belonging to different gNBs / eNBs or different mTRP L2 / 3 entities), the above-described method 1, If method 2 or method 3 is applied, the mTRP L2/3 entity of each base station (or cell) to which the TRP supporting the mTRP function belongs and/or the RRC layer must support the mobility function together.

When the above method 1 is applied for Inter-DU TRP switching, the UE may transmit TrpSW_L1/L2_Sig to the target TRP after the RA procedure step or the RA procedure according to the above method. The target base station (or cell, mTRP L2/3 entity) receiving the TRP selection information according to method 1 from the terminal may acquire the RRC context (or AS context) of the corresponding terminal from the source base station. The source base station and the target base station may determine a base station that will actively operate the mTRP L2/3 entity for the corresponding terminal. The primary base station determined through consultation with the target base station or the source base station may support the mTRP function to the corresponding terminal through the mTRP L2/3 entity. In addition, if necessary, the mTRP L2/3 entity may release (or stop) source TRP (or release TRP) mTRP function support.

In the case of applying the above-described method 2 or method 3 for inter-DU TRP switching, the UE may request or trigger cell change (or handover) by transmitting L2basedTRP_Select MAC CE to the source TRP. The base station (or cell, mTRP L2/3 entity) of the source TRP that has obtained the identifier of the target cell, the identifier of the target TRP, and/or beam information (or SSB ID, CSI-RS ID, etc.) from the UE is the target base station (or cell) can request mTRP function support. In a process in which the base station of the target TRP generates and transmits a response message to the request of the source base station, the source base station and the target base station may determine a base station that will actively operate the mTRP L2/3 entity for the corresponding terminal. Through the response message received from the target base station, the base station of the source TRP may receive radio resource configuration information for the target TRP for supporting the mTRP function from the target base station (or cell) and transmit it to the terminal. Here, the information on the target TRP is an RA procedure execution indicator for the target TRP, a non-contention RA radio resource, a CORESET resource for PDCCH (or DCI) reception, an uplink radio resource, a scheduling identifier (or C-RNTI), a beam (or TCI state), reference signals (CSI-RS, SRS, TRS, DMRS, etc.), and allocation or configuration information about parameters. Here, the RA procedure execution indicator information is information indicating whether the corresponding UE will perform the RA procedure to the target TRP in order to support the mTRP function.

When the RA procedure execution indicator information informs that the UE does not need to perform the RA procedure with the target TRP or instructs the omission of the RA procedure, the UE receives radio resource configuration (or allocation) information of the target TRP transmitted from the source base station The mTRP function can be supported from the target TRP by using.

However, when the corresponding indicator information instructs the RA procedure to be performed, the UE must perform the RA procedure before performing downlink reception from the target TRP and/or uplink transmission to the target TRP. In addition, the target base station may implicitly instruct RA performance for the target TRP by transferring non-contention-based RA radio resource configuration information to the terminal through the source base station without an RA procedure execution indicator.

If it is necessary to perform the RA procedure, the UE performs a random access procedure for the target TRP using the RA radio resource in the radio resource configuration (or allocation) information received from the source base station or the RA radio resource obtained from the system information of the target base station can do. After completing the random access procedure for the target TRP, the terminal can receive support for the mTRP function from the target TRP.

In addition, if necessary, the mTRP L2/3 entity of the initiating base station or the target base station of the mTRP function may release (or stop) supporting the mTRP function of the source TRP (or the TRP to be released).

As another method to support Inter-DU TRP switching, a cell (or TRP) change procedure performed by the L3 RRC layer is required, such as a handover (or 'Reconfiguration with sync' in NR system) procedure of 3GPP LTE/LTE-A system. do. The cell change (or handover, 'Reconfiguration with sync') procedure performed by the L3 RRC layer is in charge of the RRC layer of the serving base station (or cell) that actively performs the mTRP function for the corresponding terminal. For example, a change to a TRP with a different cell identifier (or PCI) within the same DU may be performed according to a primary cell (PCell) change procedure when a carrier aggregation (CA) function is supported. In addition, a change to a TRP having a different cell identifier (or PCI) within different DUs may be performed according to a special cell (SpCell) change procedure when a dual connectivity (DC) function is supported. Here, SpCell means a PCell of a master cell group (MCG) or a primary SCG cell (PSCell) of a secondary cell group (SCG) for supporting a DC function.

Only downlink resources may be configured in the TRP (TRP2 702 in FIG. 7) added while supporting the mTRP function according to the above method. Alternatively, even if the PUSCH for uplink transmission is configured, the PUCCH may not be configured. In this case, the UE's PUCCH transmission for HARQ feedback information for downlink reception from the added TRP, CSI reporting, etc. may be transmitted only with an active TRP (TRP1 701 in FIG. 7). Quality of a radio channel for supporting the mTRP function, beam measurement information (eg, TCI state estimation information), etc. may be separately generated and transmitted in units of TRPs. In order to generate and transmit radio channel quality and beam measurement information for mTRP function support in TRP units, a TRP identifier is used or uplink for reporting radio channel quality and beam measurement information (eg, TCI state estimation information) Radio resources may be allocated in units of TRPs. When uplink radio resources are allocated in units of TRPs, field parameters of a physical layer downlink control channel (PDCCH or DCI) transmitting scheduling information of the corresponding uplink radio resources may include a TRP identifier.

In the mTRP function operation or TRP switching operation procedure according to the above method, beam (or TCI state) management (hereinafter referred to as TCI state management) is performed separately for downlink and uplink, and related information may be signaled. In particular, in the mTRP function support, when the TRP (hereinafter referred to as DL-TRP) in charge of downlink transmission is different from the TRP (hereinafter referred to as UL-TRP) in charge of uplink reception, the TCI state of downlink and the TCI state of uplink are separately can be managed To this end, the UE may monitor (or measure) a downlink reference signal (CSI-RS, SRS, TRS, DMRS, etc.) of the DL-TRP and transmit the result to the UL-TRP. Based on the measurement result of the downlink reference signal of the DL-TRP received through the UL-TRP, the mTRP L2/3 entity can manage the TCI state for the downlink channel. TCI state management may be performed by transmitting TCI state index information to the UE as DCI or transmitting information indicating activation/deactivation in TCI state index units using MAC CE. In addition, the mTRP L2/3 entity of the base station transmits TCI state information of the uplink estimated based on the uplink reference signal (eg, SRS or a reference signal defined for uplink TCI state management) of the terminal to the PDCCH (or DCI, UCI). ) and / or MAC CE may be used to transmit to the terminal. Here, the base station (or cell) transmits uplink TCI state index information to the UE through PDCCH (or DCI, UCI) or transmits information indicating activation/deactivation in units of uplink TCI state indexes using MAC CE. By doing so, it is possible to indicate the TCI state management operation of the uplink. A UE receiving uplink TCI state information from a base station (or cell, mTRP L2/3 entity) may perform uplink transmission using a beam corresponding to a corresponding TCI index.

The above-described TCI state information and/or TCI state indication information for supporting the mTRP function is configured to indicate or identify one or more cell identifiers, TRP identifiers, and/or TCI state indexes. For example, the TCI state information and/or the TCI state indication information may be configured in a bitmap form to identify a cell, TRP, and/or TCI state. Alternatively, the TCI state information and/or the TCI state indication information may include a corresponding cell identifier, a TRP identifier, and/or a TCI state index. When the TCI status information and/or the TCI status indication information is configured as a bitmap, the cell identifier, TRP identifier, and/or TCI status index may be configured to have a correspondence with bits of the bitmap. Correspondence between the bits of the bitmap and cell identifiers, TRP identifiers, and/or TCI state indices is the order (or order in the list) of cells and TRPs in the RRC control message that sets the parameters for the mTRP function, Alternatively, it may be determined according to the order of participating in mTRP function support (or the order of addition). Therefore, the terminal can recognize that the control signal for the cell or TRP corresponding to the corresponding sequence is determined according to whether each bit value constituting the corresponding bitmap is toggled or according to the set value of the corresponding bit. For example, if the bit value is '1', it may indicate that the cell, TRP, and/or TCI state corresponding to the bit is activated or that a related operation needs to be performed.

In order to manage the TCI state for supporting the mTRP function, the UE may transmit the TCI state index received from the DL-TRP through uplink. In addition, the terminal may transmit TCI state information (or preferred TCI state index information) for the downlink channel to the base station when one or more of the following conditions is satisfied.

● When there is a request from the base station (or cell, mTRP L2/3 entity)

● When the transmission time according to the period set by the base station arrives

● In case the TCI state is changed according to the result of monitoring/measuring the downlink channel of the UE

● In case of meeting preset aperiodic TCI status reporting conditions

In addition, the base station (or cell, mTRP L2/3 entity) uses uplink channel data and reference signals received by the UL-TRP to estimate uplink TCI state information or uplink TCI state index indication information selected by the base station can be delivered to the terminal. The terminal may select an uplink TCI state index using the uplink TCI state information received from the base station or select an uplink TCI state index according to the TCI state index indication information selected by the base station. Here, selecting the TCI state index means selecting an uplink beam.

On the other hand, when DL-TRP and UL-TRP are not set differently, the base station (or cell, mTRP L2/3 entity) corresponds to the uplink beam (or TCI state index) received from the terminal. Alternatively, downlink transmission for the corresponding UE may be performed using the TCI state index).

In the mTRP function operation or TRP switching operation according to the above-described method, the base station (or cell, mTRP L2/3 entity) and/or the terminal may generate preference information for the corresponding operation and transmit it to the other party. In addition, the base station (or cell, mTRP L2/3 entity) may transmit corresponding preference information to other base stations participating in the mTRP operation.

Preference information for the mTRP function generated by the base station or the terminal may consist of one or more parameter(s) of the following.

● monitoring/measurement results of the reference signal;

● TCI state index identifying the identifier of the detected TRP and/or the beam configured in the detected TRP

● Indicator information indicating whether the monitoring/measurement result of the reference signal for the detected TRP satisfies the conditions for supporting the mTRP function.

● Optimal (or preferred) TCI state index for each detected DL-TRP and/or UL-TRP

● Monitoring/measurement results of uplink reference signals (e.g., reference signals defined for SRS or uplink TCI status management)

In support of the above-described mTRP function, a method for maintaining uplink physical layer synchronization between a terminal and TRPs participating in the mTRP function is required. The mTRP L2/3 entity (or mTRP function control base station) performs the mTRP function operation based on the measurement result of the physical layer signal (eg, uplink signal such as SRS or RA preamble) received from the terminal. Transmission timing control information (eg, timing advance (TA) information) of the terminal for maintaining physical layer synchronization between the TRP and the terminal may be generated and transmitted to the terminal.

To generate and transmit TA information, the mTRP L2/3 entity may use one or a combination of one or more of the following methods.

● Method 1: TA information can be generated and transmitted based on a TRP in which the quality of a radio channel with the terminal satisfies a preset condition or a TRP indicated as having a radio channel quality equal to or higher than the condition value.

● Method 2: TA information can be independently generated and transmitted for each TRP.

● Method 3: After generating reference TA information for the selected TRP according to Method 1, TA information for other TRPs (ie, TA information for each TRP) is generated and transmitted as an offset value for the reference TA information value. It can be.

● Method 4: TA information can be generated and transmitted as a median value of TAs independently estimated for each TRP according to the method 2 above.

When TA information is generated according to the method 1 above, the mTRP L2/3 entity may select a TRP in which the quality of a radio channel with the terminal satisfies a preset condition or a TRP indicated to have a radio channel quality equal to or greater than the condition value. there is. The mTRP L2/3 entity estimates the transmission timing adjustment value of the physical layer uplink channel of the corresponding UE for the selected TRP, generates one TA information (eg, TA value), and participates in the mTRP function operation TA information to be applied to all TRPs is transmitted to the UE. The terminal may adjust the transmission timing of the uplink physical layer channel transmitted to each TRP using the received one TA information, and perform uplink transmission according to the adjusted transmission timing.

When TA information is generated according to the method 2, the mTRP L2/3 entity generates TA information (or TA value) for each TRP supporting the mTRP function. In addition, TA information composed of a plurality of TA values generated as many as the number of mTRPs participating in the mTRP function operation is transmitted to the terminal. The UE adjusts the transmission timing of the uplink physical layer channel for each TRP using the corresponding TA information value for each TRP based on the TA value (TA valuer per TRP) for each TRP in the received TA information, and adjusts the transmission timing Uplink transmission can be performed according to

When TA information is generated according to Method 3, the mTRP L2/3 entity estimates the transmission timing adjustment value of the physical layer uplink channel of the corresponding UE for the TRP selected according to Method 1, and converts the corresponding TA value to the reference TA value. set to In addition, the mTRP L2/3 entity generates TA information for the corresponding terminal for each TRP participating in the mTRP function operation, and the TA information for each TRP is a difference compared to the reference TA value (reference TA vlaue). TA information composed of a plurality of TA values set to an expressed offset value is generated and transmitted to the terminal. The UE adjusts the transmission timing of the uplink physical layer channel for each TRP using the received TA information (eg, reference TA value and offset value relative to the reference TA), and performs uplink transmission according to the adjusted transmission timing. can be done

When TA information is generated according to scheme 4, the mTRP L2/3 entity estimates a TA value for maintaining uplink physical layer synchronization for each TRP supporting the mTRP function. In addition, one TA information is generated as a representative value (eg, an average value, a median value, etc.) of TA values estimated for each TRP and transmitted to the terminal. The UE adjusts the transmission timing of the uplink physical layer channel transmitted through each TRP using the received one TA information (eg, TA information determined as a median value) and performs uplink transmission according to the adjusted transmission timing. can

When the mTRP L2/3 entity generates and transmits a plurality of TA information as in Method 2 or Method 3, the TA information is configured to include each TRP identifier, or the TCI state index for TCI state management described above, TA It can be configured in the form of a MAC CE or DCI parameter by configuring a control message to have a mapping (or association) relationship with a reference signal index for information generation and/or a reference signal index for TCI state management. there is. Here, mapping (or association) between the above-described index and TA information for each TRP (or TA value for each TRP) uses a mapping relationship between the above-described index and TRP identifier, or a control message constituting TCI state information. It is possible to configure TA information with TA values for each TRP according to the enumeration order (or entry order) of the TCI state index in Alternatively, the TRPs supporting the mTRP function are classified as primary TRPs or secondary TRPs, or the order of predetermined TRPs is determined, and the TA values for each TRP are listed according to the order of each TRP setting in the TRP control message for supporting the mTRP function. How to organize information is possible.

In the mTRP function operation or TRP switching operation according to the above-described method, the control signal (or message) for the triggering or request of the terminal and the response signal of the base station (or mTRP L2/3 entity) for the corresponding control signal (or message) ( or message) can be exchanged using a control signal (or message) of the same level in the radio protocol layer. For example, when a control signal transmitted by a terminal uses a physical layer control signal, the base station may transmit a response to a corresponding request using a physical layer control signal. Here, the physical layer control signal for triggering or requesting the UE may be transmitted through PUCCH radio resources, PUCCH information transmitted through PUSCH radio resources, and/or uplink radio resources configured/allocated for mTRP function support. In addition, the response signal for this may be transmitted using a PDCCH (DCI inner field, or DCI defined for mTRP function support) or a CORESET resource defined for mTRP function support.

In addition, when a control signal for triggering or request of the terminal is transmitted using the MAC CE, the base station may transmit a response to the request using the MAC CE. Here, the MAC CE transmitted by the terminal or base station may be composed of an LCID, MAC (sub) header, MAC (sub) PDU, etc. defined to support the mTRP function, and the above-described MAC CE includes uplink information and downlink Information about links can be separately included.

In addition, when the control signal transmitted by the terminal uses an RRC control message, the base station may transmit a response to the request using an RRC control message. Here, the RRC control message transmitted by the terminal or the base station may be configured in the form of a lower information element (IE) in an existing RRC control message for connection control or as a separate RRC control message defined to support the mTRP function.

In the above-described physical layer, mTRP function operation or TRP switching operation, the MAC CE or RRC control message sequentially corresponds to one or more bit(s) of a plurality of TRPs configured for the mTRP function or cells to which the corresponding TRP belongs. It may be configured in the form of a bitmap, or may include an identifier of each TRP (or an identifier of a cell). When the information included in the MAC CE or RRC control message is configured as a bitmap, the bitmap may be configured such that a cell identifier or a TRP identifier has sequential correspondence with bits in the bitmap. Correspondence between bits in the bitmap and cell identifiers/TRP identifiers is the order of cells and TRPs in the RRC control message that sets the parameters for the mTRP function (or the order in the list), or the order of participating in the mTRP function support (or added order). Therefore, the base station and the terminal can recognize that each bit value constituting the bitmap is toggled or is a control signal for a cell or TRP corresponding to the corresponding order according to the set value of the corresponding bit. For example, if the bit value is '1', it may indicate that the cell, TRP, and/or TCI state corresponding to the bit is activated or that a related operation needs to be performed.

In the present invention, the quality of a radio channel is CSI (Channel Status Indicator), RSSI (Received Signal Strength Indicator), RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), SINR (Signal to Interference and Noise Ratio), etc. It means the signal quality of the radio channel interval expressed by . In addition, the measurement result of the present invention is defined or explained based on the quality of the radio channel described above.

Regarding the operation of the timer defined or described in the present invention, operations such as start, stop, reset, restart, and expire of the timer are the operation of the timer or the timer It may mean the operation of the counter for.

In the present invention, a base station (or cell) includes a NodeB, an evolved NodeB, a base transceiver station (BTS), a radio base station, a radio transceiver, and an access point. point), access node (node), road side unit (RSU), radio remote head (RRH), transmission point (TP), transmission & reception point (TRP), or gNB. In addition, a base station (or cell) may be a CU node or a DU node to which functional separation is applied.

In the present invention, a terminal includes a UE, a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, and a portable subscriber station. subscriber station), a node, a device, an Internet of Thing (IoT) device, or a mounted device (mounted module/device/terminal or on board device/terminal).

The methods according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded on a computer readable medium. Computer readable media may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on a computer readable medium may be specially designed and configured for the present invention or may be known and usable to those skilled in computer software.

Examples of computer readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes generated by a compiler. The hardware device described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the present invention described in the claims below. You will be able to.

Claims (20)

As a method of operating a terminal in a mobile communication system,
Receiving configuration information for support of a multi-TRP (mTRP) function from a first base station through a first transmission and reception point (TRP) belonging to the first base station;
Based on the setting information, detecting and selecting a second TRP supporting the mTRP function;
Transmitting a measurement report for the second TRP or a first control message requesting support of the mTRP function in which the second TRP participates to the first base station through the first TRP; and
Receiving a second control message from the first base station through the first TRP or the second TRP indicating the start of the mTRP function in which the first TRP and the second TRP participate,
How the terminal operates. The method of claim 1,
The configuration information includes information on neighboring TRP(s) and/or candidate TRP(s), and the terminal determines the second based on the information on the neighboring TRP(s) and/or candidate TRP(s). detecting and selecting TRP,
How the terminal operates. The method of claim 1,
The second TRP is selected based on whether the second TRP satisfies an mTRP function support condition, and the mTRP function support condition is:
When the quality of the radio channel between the terminal and the first base station or the first TRP is less than or equal to a reference value;
When the terminal is located at the boundary of the service area of the first base station or the first TRP;
When the transmission frequency, frequency band, and/or BWP of the second TRP satisfies the priority for supporting the mTRP function;
When the quality of the radio channel between the terminal and the second TRP is equal to or greater than a preset reference value;
When the quality of the radio channel between the terminal and the second TRP is maintained above a preset reference value until a predefined timer expires;
or at least one of their combinations,
How the terminal operates. The method of claim 1,
The second TRP belongs to the first base station or belongs to a second base station different from the first base station,
How the terminal operates. The method of claim 4,
The mTRP function is controlled by an mTRP L2 / L3 entity executed in a medium access control (MAC) layer and / or a radio resource control (RRC) layer of the first base station or the second base station,
How the terminal operates. The method of claim 4,
Further comprising receiving a service by the mTRP function in which the first TRP and the second TRP participate, and when the second TRP belongs to the second base station, the first base station and the second base station one of which is determined as an mTRP function controlling base station controlling the mTRP function, and when the first TRP and the second TRP belong to the first base station, the first base station controls the mTRP function of the mTRP function controlling base station determined by
How the terminal operates. The method of claim 6,
When the second TRP belongs to the second base station, control information for supporting the mTRP function is exchanged between the first TRP and the second TRP.
How the terminal operates. The method of claim 6,
Further comprising determining whether the first TRP or the second TRP satisfies an mTRP function release condition, wherein the mTRP function release condition is:
When the quality of the radio channel between the first TRP or the second TRP and the terminal is equal to or less than a reference value until a predefined timer expires;
When the random access procedure for the first TRP or the second TRP fails;
When beam failure recovery (BFR) for the first TRP or the second TRP fails;
When the mTRP function controlling base station and/or the mTRP L2/L3 entity belonging to the mTRP function controlling base station determines to release the mTRP function for the first TRP or the second TRP;
When the terminal requests release of the mTRP function or requests to change the first TRP or the second TRP to another TRP;
or at least one of their combinations,
How the terminal operates. The method of claim 8,
When it is determined that the first TRP or the second TRP satisfies the mTRP function release condition, the first TRP or the second TRP satisfying the mTRP function release condition through the first TRP or the second TRP. Further comprising transmitting a third control message requesting release of the mTRP function for TRP to the mTRP function control base station,
How the terminal operates. The method of claim 8,
When it is determined that the first TRP or the second TRP satisfies the mTRP function release condition, a procedure for replacing the first TRP or the second TRP that satisfies the mTRP function release condition with another newly detected TRP. Further comprising the step of performing
How the terminal operates. The method of claim 1,
The first message or the second message is one of an RRC control message, a MAC control element (CE), a physical layer control message, or a combination thereof,
How the terminal operates. As a method of operating a first base station in a mobile communication system,
Transmitting configuration information for support of a multi-TRP (mTRP) function to a terminal through a first transmission and reception point (TRP) belonging to the first base station;
Receiving a measurement report for a second TRP detected and selected based on the configuration information or a first control message requesting support of the mTRP function in which the second TRP participates, from the terminal through the first TRP; and
Transmitting a second control message indicating the start of the mTRP function in which the first TRP and the second TRP participate to the terminal through the first TRP or the second TRP,
A method of operating a base station. The method of claim 12,
The setting information includes information on neighboring TRP(s) and/or candidate TRP(s), and the second TRP is configured to configure the second TRP based on the information on the neighboring TRP(s) and/or candidate TRP(s). detected and selected by the terminal,
A method of operating a base station. The method of claim 12,
The second TRP is selected based on whether the second TRP satisfies an mTRP function support condition, and the mTRP function support condition is:
When the quality of the radio channel between the terminal and the first base station or the first TRP is less than or equal to a reference value;
When the terminal is located at the boundary of the service area of the first base station or the first TRP;
When the transmission frequency, frequency band, and/or BWP of the second TRP satisfies the priority for supporting the mTRP function;
When the quality of the radio channel between the terminal and the second TRP is equal to or greater than a preset reference value;
When the quality of the radio channel between the terminal and the second TRP is maintained above a preset reference value until a predefined timer expires;
or at least one of their combinations,
A method of operating a base station. The method of claim 12,
The second TRP belongs to the first base station or belongs to a second base station different from the first base station,
A method of operating a base station. The method of claim 15
Further comprising providing a service to the terminal based on the mTRP function in which the first TRP and the second TRP participate, and when the second TRP belongs to the second base station, the first base station and When one of the second base stations is determined as an mTRP function controlling base station for controlling the mTRP function, and the first TRP and the second TRP belong to the first base station, the first base station controls the mTRP function Determined by the mTRP function control base station,
A method of operating a base station. The method of claim 16
Further comprising determining whether the first TRP or the second TRP satisfies an mTRP function release condition, wherein the mTRP function release condition is:
When the quality of the radio channel between the first TRP or the second TRP and the terminal is equal to or less than a reference value until a predefined timer expires;
When the random access procedure for the first TRP or the second TRP fails;
When beam failure recovery (BFR) for the first TRP or the second TRP fails;
When the mTRP function controlling base station and/or the mTRP L2/L3 entity belonging to the mTRP function controlling base station determines to release the mTRP function for the first TRP or the second TRP;
When the terminal requests release of the mTRP function or requests to change the first TRP or the second TRP to another TRP;
or at least one of their combinations,
A method of operating a base station. As a terminal of a mobile communication system,
at least one processor;
a memory storing instructions executed by the at least one processor; and
Including a transceiver,
When executed by the at least one processor, the instructions cause the terminal to:
Receiving configuration information for support of a multi-TRP (mTRP) function from a first base station through a first transmission and reception point (TRP) belonging to the first base station;
Based on the setting information, detecting and selecting a second TRP supporting the mTRP function;
Transmitting a measurement report for the second TRP or a first control message requesting support of the mTRP function in which the second TRP participates to the first base station through the first TRP; and
Receiving, through the first TRP or the second TRP, a second control message indicating the start of the mTRP function in which the first TRP and the second TRP participate from the base station,
Terminal. The method of claim 8,
The second TRP belongs to the first base station or belongs to a second base station different from the first base station,
Terminal. The method of claim 19
The instructions cause the terminal to further perform a step of receiving a service by the mTRP function in which the first TRP and the second TRP participate, and when the second TRP belongs to the second base station, the second TRP If one of the first base station and the second base station is determined as an mTRP function controlling base station that controls the mTRP function, and the first TRP and the second TRP belong to the first base station, the first base station determines the mTRP function Determined as an mTRP function control base station that controls,
Terminal.

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