KR20230151898A - Method and apparatus of cell switching and beam management for supporting multi-transmission and reception point function - Google Patents

Abstract

A method and apparatus for cell switching and beam management to support multi-TRP function are disclosed. The method of the terminal includes performing a measurement operation on a wireless channel, transmitting the result of the measurement operation to a serving cell, receiving a cell switching instruction message from the serving cell, and based on the cell switching instruction message. It includes the step of performing communication with the target cell.

Description

Method and apparatus for cell switching and beam management for support of multi-TRP function {METHOD AND APPARATUS OF CELL SWITCHING AND BEAM MANAGEMENT FOR SUPPORTING MULTI-TRANSMISSION AND RECEPTION POINT FUNCTION}

This disclosure relates to communication technology using a high frequency band of millimeter wave or higher, and more specifically, to technology for supporting terminal-centric mobility functions using a wireless access point.

In order to respond to the explosive increase in wireless data, mobile communication systems can support wide system bandwidth. To support a wide system bandwidth, the 6GHz to 90GHz band can be considered as the transmission frequency band in mobile communication systems. In high frequency bands, performance deterioration of the received signal may occur due to path attenuation and reflection of radio waves. In the above situation, a method of utilizing a wireless access point to improve terminal performance at the base station (or cell) border may be considered. A wireless access point may mean a transmission and reception point (TRP), remote radio head (RRH), relay, or repeater.

In a mobile communication system supporting millimeter frequency bands (e.g., 6GHz to 90GHz band), functional split method and carrier aggregation method are used rather than deploying a small base station that implements all wireless protocol functions. , dual connectivity method, and/or duplication transmission method may be considered. In other words, a method of configuring a mobile communication system using a plurality of wireless access points instead of a small base station can be considered. When a function separation method is used, the base station's functions (e.g., wireless protocol functions) may be processed separately in a plurality of remote wireless transmit/receive blocks and in one centralized baseband processing function block.

In a mobile communication system that supports functional separation, bi-casting, and/or redundant transmission, belonging to network nodes (e.g., base station, eNB, gNB, cell, etc.) are distinguished by different identifiers. Methods are needed for a terminal to proactively perform support operations for mobility functions at a plurality of wireless access points.

The purpose of the present disclosure to solve the above problems is to provide a method and device for cell switching and beam management in a mobile communication system.

The method of the terminal according to the first embodiment of the present disclosure for achieving the above purpose includes performing a measurement operation on a wireless channel, transmitting the result of the measurement operation to a serving cell, and cell switching from the serving cell. It includes receiving an indication message, and performing communication with a target cell based on the cell switching indication message, wherein the cell switching operation according to the cell switching indication message is a MAC-based cell switching operation without RRC reset. .

Each of the serving cell and the target cell may include one or more TRPs, and the serving cell and the target cell may belong to the same base station or different base stations.

The cell switching operation may mean a TRP switching operation or a beam switching operation.

The method of the terminal may further include receiving a cell switching list from a base station to which the serving cell belongs, and the measurement operation may be performed on one or more cells indicated by the cell switching list.

The cell switching list may include at least one of a cell identifier, TRP identifier, beam identifier, or TCI state ID.

The method of the terminal may further include transmitting a cell switching request message to the target cell after performing the measurement operation, and the cell switching request message is transmitted together with the result of the measurement operation or the measurement operation. may be transmitted after transmission of the result, and the cell switching request message may be an L1 message or an L2 message.

The L1 message may be an RA preamble, scheduling request, or uplink reference signal.

The L2 message may be Msg3 payload in the 4-step RA procedure or MsgA payload in the 2-step RA procedure.

Radio resources for transmission of the cell switching request message may be allocated in advance in an RRC connection establishment procedure or an RRC connection re-establishment procedure between the terminal and the base station to which the serving cell belongs.

The cell switching indication message may be MAC CE or DCI.

The cell switching indication message includes information instructing the performance of an operation for acquiring uplink timing, information on the uplink timing, scheduling information, an identifier of the target cell, an identifier of a target TRP associated with the target cell, and information on the uplink timing. It may include at least one of the identifier of the target beam or the identifier of the serving beam associated with the serving cell.

The method of the terminal may further include performing an operation to obtain uplink timing for the target cell when the cell switching indication message is received.

A method of a base station according to a second embodiment of the present disclosure for achieving the above object includes receiving a result of a measurement operation for a wireless channel from a terminal, and whether to perform a cell switching operation based on the result of the measurement operation. determining, and if it is determined that the cell switching operation is performed, transmitting a cell switching indication message to the terminal, wherein the result of the measurement operation is received in a serving cell belonging to the base station, and A cell switching indication message is transmitted by the serving cell, the serving cell includes one or more TRPs, and the cell switching operation is a MAC-based cell switching operation without RRC reset.

The method of the base station may further include transmitting a cell switching list to the terminal, and the measurement operation of the terminal may be performed on one or more cells indicated by the cell switching list.

The cell switching list may include at least one of a cell identifier, TRP identifier, beam identifier, or TCI state ID.

The method of the base station may further include receiving a cell switching request message from the terminal, and the cell switching request message may be an L1 message or an L2 message.

The L1 message may be an RA preamble, scheduling request, or uplink reference signal, and the L2 message may be Msg3 in the 4-step RA procedure or MsgA payload in the 2-step RA procedure.

Radio resources for transmission of the cell switching request message may be pre-allocated in an RRC connection establishment procedure or an RRC connection re-establishment procedure between the base station and the terminal.

The cell switching indication message may be MAC CE or DCI.

The cell switching indication message includes information instructing the performance of an operation for acquiring uplink timing, information on the uplink timing, scheduling information, an identifier of the target cell, an identifier of a target TRP associated with the target cell, and information on the uplink timing. It may include at least one of the identifier of the target beam or the identifier of the serving beam associated with the serving cell.

According to the present disclosure, in a mobile communication system supporting functional separation, considering the state of the terminal in the access link between the terminal and one or more wireless access points, a wireless link management and recovery procedure, and a setting and change procedure of a plurality of wireless access points etc. can be performed efficiently. The terminal may be mounted on a moving vehicle (e.g., unmanned aerial vehicle, train, self-driving car, car using navigation, etc.). According to the above procedure, the performance of downlink and/or uplink communication in a mobile communication system can be improved.

1 is a conceptual diagram showing a first embodiment of a communication system.
Figure 2 is a block diagram showing a first embodiment of the device.
Figure 3 is a conceptual diagram showing a first embodiment of the operating state of a terminal in a communication system.
Figure 4 is a conceptual diagram showing a first embodiment of a method for setting a bandwidth portion in a communication system.
Figure 5 is a conceptual diagram showing a second embodiment of a communication system.
FIG. 6 is a conceptual diagram illustrating a first embodiment of a method of providing a service using a plurality of wireless access points in a communication system.
FIG. 7A is a conceptual diagram illustrating a first embodiment of a method in which a wireless access point controlled by a base station provides a service.
FIG. 7B is a conceptual diagram illustrating a second embodiment of a method in which a wireless access point controlled by a base station provides a service.
FIG. 7C is a conceptual diagram illustrating a first embodiment of a method in which a wireless access point controlled by a DU included in a base station to which functional separation is applied provides a service.
FIG. 7D is a conceptual diagram illustrating a second embodiment of a method in which a wireless access point controlled by a DU included in a base station to which functional separation is applied provides a service.
Figure 8 is a flowchart showing a first embodiment of a cell/TRP/beam switching procedure in a communication system.
Figure 9 is a flowchart showing a second embodiment of a cell/TRP/beam switching procedure in a communication system.
Figure 10 is a flowchart showing a third embodiment of a cell/TRP/beam switching procedure in a communication system.

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

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be referred to as a second component, and similarly, the second component may be referred to as a first component without departing from the scope of the present disclosure. The term “and/or” includes any of a plurality of related stated items or a combination of a plurality of related stated items.

In embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Additionally, in embodiments of the present disclosure, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B.” A and/or B may mean at least one of A or B. A/B may mean at least one of A or B.

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

The terms used in this disclosure are only used to describe specific embodiments and are not intended to limit the disclosure. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present disclosure, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which this disclosure pertains. 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 technology, and unless clearly defined in the present disclosure, should not be interpreted in an idealized or excessively formal sense. No.

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

A communication system to which embodiments according to the present disclosure are applied will be described. The communication system may be a 4G communication system (e.g., long-term evolution (LTE) communication system, LTE-A communication system), a 5G communication system (e.g., new radio (NR) communication system), a 6G communication system, etc. there is. The 4G communication system can support communication in frequency bands below 6GHz, and the 5G communication system can support communication in frequency bands above 6GHz as well as frequency bands below 6GHz. Communication systems to which embodiments according to the present disclosure are applied are not limited to those described below, and embodiments according to the present disclosure can be applied to various communication systems. Here, communication system may be used in the same sense as communication network, “LTE” may indicate “4G communication system”, “LTE communication system” or “LTE-A communication system”, and “NR” may refer to may indicate “5G communication system” or “NR communication system”.

In an embodiment, “setting an operation (e.g., a transmission operation)” means “setting information (e.g., information element, parameter) for the operation” and/or “performing the operation.” This may mean that “indicating information” is signaled. “An information element (eg, parameter) is set” may mean that the information element is signaled. Signaling may include system information (SI) signaling (e.g., transmission of a system information block (SIB) and/or master information block (MIB)), radio resource control (RRC) signaling (e.g., RRC parameters and/or higher transmission of layer parameters), medium access control (MAC) control element (CE) signaling, or PHY signaling (e.g., downlink control information (DCI), uplink control information (UCI), and/or sidelink control information (SCI) transmission) may be at least one of the following.

1 is a conceptual diagram showing a first embodiment of a communication system.

Referring to FIG. 1, the 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). In addition, the communication system 100 includes a core network (e.g., serving-gateway (S-GW), packet data network (PDN)-gateway (P-GW), mobility management entity (MME)). More may be included. If the communication system 100 is a 5G communication system (e.g., a new radio (NR) system), the core network includes an access and mobility management function (AMF), a user plane function (UPF), a session management function (SMF), etc. may include.

A plurality of communication nodes 110 to 130 may support communication protocols (eg, LTE communication protocol, LTE-A communication protocol, NR communication protocol, etc.) specified in the 3rd generation partnership project (3GPP) standard. The plurality of communication nodes 110 to 130 may use code division multiple access (CDMA) technology, wideband CDMA (WCDMA) technology, time division multiple access (TDMA) technology, frequency division multiple access (FDMA) technology, orthogonal frequency division (OFDM) technology. multiplexing) technology, Filtered OFDM technology, CP (cyclic prefix)-OFDM technology, DFT-s-OFDM (discrete Fourier transform-spread-OFDM) technology, OFDMA (orthogonal frequency division multiple access) technology, SC (single carrier)-FDMA technology, NOMA (Non-orthogonal Multiple Access) technology, GFDM (generalized frequency division multiplexing) technology, FBMC (filter bank multi-carrier) technology, UFMC (universal filtered multi-carrier) technology, SDMA (Space Division Multiple Access) technology, etc. can support. Each of the plurality of communication nodes may mean an apparatus or a device. Embodiments may be performed by an apparatus or device. The structure of the device (eg, device) may be as follows.

Figure 2 is a block diagram showing a first embodiment of the device.

Referring to FIG. 2, the device 200 may include at least one processor 210, a memory 220, and a transmitting and receiving device 230 that is connected to a network and performs communication. Additionally, the device 200 may further include an input interface device 240, an output interface device 250, a storage device 260, etc. Each component included in the device 200 is connected by a bus 270 and can communicate with each other.

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 disclosure are performed. Each of the memory 220 and the storage device 260 may be comprised of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be comprised of at least one of read only memory (ROM) and random access memory (RAM).

Referring again to FIG. 1, the communication system 100 includes a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) and a plurality of terminals (130- 1, 130-2, 130-3, 130-4, 130-5, 130-6). 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 NB (NodeB), eNB (evolved NodeB), gNB, ABS (advanced base station), and HR. -High reliability-base station (BS), base transceiver station (BTS), radio base station, radio transceiver, access point, access node, radio access station (RAS) ), MMR-BS (mobile multihop relay-base station), RS (relay station), ARS (advanced relay station), HR-RS (high reliability-relay station), HNB (home NodeB), HeNB (home eNodeB), It may be referred to as a road side unit (RSU), radio remote head (RRH), transmission point (TP), transmission and reception point (TRP), etc.

Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 includes a user equipment (UE), a terminal equipment (TE), an advanced mobile station (AMS), HR-MS (high reliability-mobile station), terminal, access terminal, mobile terminal, station, subscriber station, mobile station, mobile It may be referred to as a portable subscriber station, a node, a device, an on board unit (OBU), etc.

Meanwhile, 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 an ideal backhaul link or a non-ideal backhaul link. , information can be exchanged with each other through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) transmits the signal received from the core network to the corresponding terminal (130-1, 130-2, 130-3, 130). -4, 130-5, 130-6), and the signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) is sent to the core network. can be transmitted to.

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 performs MIMO transmission (e.g., single user (SU)-MIMO, multi user (MU)- MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, device to device communication (D2D) (or , ProSe (proximity services), IoT (Internet of Things) communication, dual connectivity (DC), etc. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is connected to a base station 110-1, 110-2, 110-3, and 120-1. , 120-2) and operations corresponding to those supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2. For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method, and the fourth terminal 130-4 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method. A signal can 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 method, and the fourth terminal 130-4 and the fifth terminal 130-5 can each 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 method, and the fourth terminal 130-4 may transmit a signal to the fourth terminal 130-4. The terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 using the CoMP method. Each of a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) has a terminal (130-1, 130-2, 130-3, 130-4) within its cell coverage. , 130-5, 130-6), and signals can be transmitted and received based on the CA method. The first base station 110-1, the second base station 110-2, and the third base station 110-3 each control 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 can perform D2D under the control of each of the second base station 110-2 and the third base station 110-3. .

Figure 3 is a conceptual diagram showing a first embodiment of the operating state of a terminal in a communication system.

Referring to FIG. 3, the state (e.g., operating state) of the terminal in the RRC layer of the communication system can be classified into RRC connected state, RRC inactive state, and RRC idle state. there is. When the terminal operates in the RRC connected state or the RRC inactive state, the base station of a radio access network (RAN) and the terminal transmit RRC connection configuration information, RRC context information, or access stratum (AS) of the terminal. ) At least one of the context information may be stored and/or managed.

A terminal in an RRC connection state may receive allocation information of a physical layer control channel and/or reference signal necessary for maintaining RRC connection settings and/or transmitting and receiving packets (eg, data). The reference signal may be a reference signal for demodulating data, a reference signal for measuring channel quality, and/or a reference signal for beamforming. A terminal in an RRC connection state may be able to transmit and receive packets (e.g., data) without additional delay. In this disclosure, packet may mean data.

A terminal in the RRC inactive state can perform mobility management functions corresponding to the RRC dormant state. The terminal in the RRC inactive state is connected to the base station, but the data bearer for transmitting and receiving packets may not be set in the terminal in the RRC inactive state, and functions such as the MAC layer may be disabled in the terminal in the RRC inactive state. there is. A terminal in the RRC inactive state may transition to the RRC connected state by performing a non-initial access procedure to transmit data. Alternatively, a terminal in the RRC inactive state may transmit limited data allowed in the RRC inactive state. Restricted data may be data with a limited size, data with limited quality of service, and/or data belonging to a limited type of service.

From the perspective of the wireless access network, there may not be a connection established between the terminal in the RRC idle state and the base station. Connection setup information and/or context information (eg, RRC context information, AS context information) for a terminal in the RRC idle state may not be stored in the base station and/or control function block of the wireless access network. A terminal in the RRC idle state may perform an initial connection procedure to transition to the RRC connected state. Although the terminal in the RRC dormant state attempted to transition to the RRC connected state by performing an initial connection procedure, the state of the terminal may transition from the RRC dormant state to the RRC inactive state according to the decision of the base station.

A terminal in the RRC dormant state can transition to the RRC inactive state by performing an initial connection procedure or a separate connection procedure defined for transition to the RRC inactive state. When limited services are provided to the terminal, the operating state of the terminal may transition from the RRC idle state to the RRC inactive state. Alternatively, depending on the capability of the terminal, the operating state of the terminal may transition from the RRC idle state to the RRC inactive state.

The control function block of the base station and/or wireless access network is a condition in which transition to the RRC inactive state is possible considering one or more of the type, capability, and service of the terminal (e.g., service currently being provided, service to be provided). (s) can be set, and the transition operation to the RRC inactive state can be controlled based on the set condition (s). “If the base station allows transition to the RRC inactive state” or “if transition to the RRC inactive state is set to be possible”, the operation state of the terminal may transition from the RRC connected state or the RRC idle state to the RRC inactive state. You can.

Figure 4 is a conceptual diagram showing a first embodiment of a method for setting a bandwidth part (BWP) in a communication system.

Referring to FIG. 4, a plurality of bandwidth portions (BWP #1-4) may be set within the system bandwidth of the base station. A plurality of bandwidth portions may be configured for transmission and/or reception operations of the terminal. BWP #1-4 can be set to be no larger than the base station's system bandwidth. The bandwidth of BWP #1-4 may be different, and different subcarrier spacing (SCS) may be applied to BWP #1-4. For example, the bandwidth of BWP #1 may be 10 MHz, and BWP #1 may have an SCS of 15 kHz. The bandwidth of BWP #2 may be 40 MHz, and BWP #2 may have an SCS of 15 kHz. The bandwidth of BWP #3 may be 10 MHz, and BWP #3 may have an SCS of 30 kHz. The bandwidth of BWP #4 may be 20 MHz, and BWP #4 may have an SCS of 60 kHz.

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

The terminal can change the operating BWP from Initial BWP to Active BWP or Default BWP. Alternatively, the terminal may change the operating BWP from Active BWP to Initial BWP or Default BWP. The BWP change operation may be performed based on instructions from the base station or a timer. The base station may transmit information indicating BWP change to the terminal using at least one of an RRC message, a MAC message (eg, MAC CE (control element)), or a PHY message (eg, DCI). The terminal can receive information indicating BWP change from the base station and change the operating BWP to the BWP indicated by the received information.

In an NR communication system, if RA (random access) resources are not set in the active UL (uplink) BWP, the terminal can change the operation BWP of the terminal from the active UL BWP to the initial UL BWP in order to perform a random access procedure. there is. The operation BWP may be a BWP through which the terminal performs communication (eg, transmission and reception operations of signals and/or channels).

Figure 5 is a conceptual diagram showing a second embodiment of a communication system.

Referring to Figure 5, the communication system may include a core network and an access network. Core networks supporting 4G communications may include MME, S-GW, P-GW, etc. Functional blocks supporting S-GW and MME can be expressed as S-GW/MME 540. Core networks supporting 5G communications may include AMF, UPF, PDN-GW, etc. Functional blocks supporting UPF and AMF can be expressed as UPF/AMF 540. The access network may include a base station 510, a wireless access point 520, a small base station 530, and terminals 550-1, 550-2, and 550-3. Base station 510 may refer to a macro base station. The base station 510 and/or the small base station 530 may be connected to an end node of the core network through a backhaul. The end node may be S-GW, UPF, MME, AMF, etc.

Functional separation may be applied to base station 510 and small base station 530. In this case, each of the base station 510 and the small base station 530 may include one central unit (CU) and one or more distributed units (DU). A CU may be a logical node that performs the functions of the RRC layer, service data application protocol (SDAP) layer, and/or packet data convergence protocol (PDCP) layer. A CU can control the operation of one or more DUs. The CU can be connected to the end nodes of the core network using backhaul based on the S1 interface or backhaul based on the NG interface. Backhaul based on the S1 interface can refer to backhaul in a 4G communication system. NG interface-based backhaul can refer to backhaul in a 5G communication system.

A DU may be a logical node that performs the functions of the radio link control (RLC) layer, MAC layer, and/or PDCP layer. A DU can support one or more cells. DU can be connected to the CU in a wired or wireless manner using the F1 interface. When a wireless method is used, the connection between the DU and CU can be established in the integrated access and backhaul (IAB) method.

Each of the base station 510 and the small base station 530 may be connected to the wireless access point 520 in a wired or wireless manner using an Fx interface (or fronthaul). In the present disclosure, a base station (eg, macro base station, small base station) may mean a cell, DU, etc. A wireless access point may mean a transmission and reception point (TRP), remote radio head (RRH), relay, or repeater. The TRP may perform at least one of a downlink transmission function or an uplink reception function. The wireless access point 520 may only perform radio frequency (RF) functions.

Alternatively, the wireless access point 520 may perform RF functions and some functions of the DU (eg, some functions of the physical (PHY) layer and/or MAC layer). Some functions of the DU supported at wireless access point 520 may include PHY layer sub-functions, PHY layer functions, and/or MAC layer sub-functions. The Fx interface between the base stations 510 and 530 and the wireless access point 520 may be defined differently depending on the function(s) supported by the wireless access point 520.

“Wireless access point 520 in FIG. 5” and “base station 110-1, 110-2, 110-3, 120-1, 120-2, 510, 530 in FIGS. 1 and 5” each use OFDM and OFDMA , SC-FDMA, or NOMA-based downlink communication and/or uplink communication may be supported. The wireless access point 520 and the base stations 110-1, 110-2, 110-3, 120-1, 120-2, 510, and 530 each perform a beamforming function using an antenna array in the transmission carrier of the millimeter wave band. Support is available. In this case, services through each beam can be provided without interference between beams within the base station. One beam can provide services to multiple terminals.

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 (e.g., single user (SU)- MIMO, MU (multi user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, CA (carrier aggregation) transmission, transmission in unlicensed band, direct communication between devices (device to device communication) , D2D) (or ProSe (proximity services), sidelink communication), etc. may be supported. Here, each of the plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6, 550-1, 550-2, 550-3) has a "wireless access point (520) ) and/or operations corresponding to a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2, 510, 530)" and/or "wireless access point 520 and/or “Operations supported by a plurality of base stations 110-1, 110-2, 110-3, 120-1, 120-2, 510, and 530” can be performed. For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method, and the fourth terminal 130-4 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method. A signal can 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 method, and the fourth terminal 130-4 and the fifth terminal 130-5 can each 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 method, and the fourth terminal 130-4 may transmit a signal to the fourth terminal 130-4. The terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 using the CoMP method. Each of a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) has a terminal (130-1, 130-2, 130-3, 130-4) within its cell coverage. , 130-5, 130-6), and signals can be transmitted and received based on the CA method. The first base station 110-1, the second base station 110-2, and the third base station 110-3 each coordinate D2D between the fourth terminal 130-4 and the fifth terminal 130-5 ( coordination), and each of the fourth terminal 130-4 and the fifth terminal 130-5 performs D2D through coordination with the second base station 110-2 and the third base station 110-3, respectively. can do.

Next, operating methods of a communication node in a communication system will be described. Even when a method (e.g., transmission or reception of a signal) performed in a first communication node among communication nodes is described, the corresponding second communication node is described as a method (e.g., transmitting or receiving a signal) corresponding to the method performed in the first communication node. For example, reception or transmission of a signal) can be performed. That is, when the operation of the terminal is described, the corresponding base station can perform the operation corresponding to the operation of the terminal. Conversely, when the operation of the base station is described, the corresponding terminal can perform the operation corresponding to the operation of the base station.

In a communication system, UPF (or S-GW) may refer to an end communication node of the core network that exchanges packets (eg, control information, data) with a base station that provides services to the terminal. In a communication system, AMF (or MME) may refer to a communication node of the core network that performs a control function in the wireless access section (or interface) of the terminal. Here, each of the backhaul link, fronthaul link, It may be referred to by different terms depending on the condition.

To perform mobility support functions and radio resource management functions, the base station may transmit synchronization signals (e.g., synchronization signal/physical broadcast channel (SS/PBCH) blocks, synchronization signal blocks (SSB)) and/or reference signals. there is. To support multiple numerologies, a frame format that supports symbols with different lengths can be set. In this case, the terminal may perform a monitoring operation of the synchronization signal and/or reference signal in a frame according to the initial numerology, default numerology, or default symbol length. The initial numerology and default numerology are each a frame format applied to radio resources for which the UE-common search space is set, and are applied to radio resources for which CORESET (control resource set) 0 of the NR communication system is set. A frame format, and/or a synchronization symbol burst capable of identifying a cell in an NR communication system may be applied to the frame format applied to the transmitted radio resource.

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

A terminal connected to a base station may transmit a reference signal (eg, an uplink-only reference signal) to the base station using resources set by the base station. For example, the uplink-only reference signal may include a sounding reference signal (SRS). Additionally, a terminal connected to a base station can receive a reference signal (eg, a downlink-only reference signal) from the resources set 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), etc. Each of the base station and the terminal can perform beam management operations through monitoring of a configured beam or an active beam based on the reference signal.

For example, the base station 510 provides a synchronization signal and/or reference so that a terminal located within the communication service area can search for the base station 510 and perform a downlink synchronization maintenance operation, beam setting operation, or link monitoring operation. Signals can be transmitted. The terminal 550-1 connected to the base station 510 (eg, a serving base station) may receive physical layer radio resource configuration information for connection establishment and radio resource management from the base station 510.

Radio resource configuration information of the physical layer may be configuration parameters included in an RRC control message in an LTE communication system and/or NR communication system. For example, wireless resource configuration information includes 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, etc.

Radio resource setting information includes the setting period (or allocation period) of signals (or radio resources) according to the frame format of the 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 numerology, the frame format of the 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, within one wireless frame (eg, a frame with a length of 10 ms), the number of symbols constituting each of the mini slot, slot, and subframe may be different.

● Setting information of the base station’s transmission frequency and frame format

■ Transmission frequency setting information: All transmission carriers of the base station (e.g., cell-level transmission frequency), bandwidth part (BWP), and transmission reference time or time difference information between the base station's transmission frequencies (e.g. For example, a transmission period or offset parameter indicating the transmission reference time (or time difference) of the synchronization signal), etc.

■ Setting information of frame format: Setting parameters of mini slot, slot, and subframe with different symbol lengths according to subcarrier spacing

● Setting information of downlink reference signals (e.g., CSI-RS, common RS, etc.)

■ Common RS setting information includes setting parameters such as transmission period, transmission position, code sequence, masking sequence (or scrambling sequence) of the reference signal commonly applied in the coverage of the base station (or beam), etc.

● Setting information of uplink control signal

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

● Setting information of downlink control channel (e.g., physical downlink control channel (PDCCH))

■ Reference signal for demodulation, beam common reference signal (e.g., a reference signal that can be received by all terminals within beam coverage), reference signal for beam sweeping (or beam monitoring), reference signal for channel estimation, etc.

● Setting information of uplink control channel (e.g., PUCCH (physical uplink control channel))

● Setting information of scheduling request signal

● Setting information of feedback (e.g., acknowledgment (ACK) or negative ACK (NACK)) transmission resources in the HARQ (hybrid automatic repeat request) procedure

● Number of antenna ports, information on antenna array, beam configuration and/or beam index mapping information for beamforming application

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

● Reception of a beam that triggers a beam establishment operation, a beam recovery operation, a beam reconfiguration operation, a wireless link re-establishment operation, a beam change operation at the same base station, and a handover procedure to another base station. Setting information such as signals, control timers of the above-mentioned operations, etc.

In a wireless frame format that supports different symbol lengths to support multiple numerology, the setting cycle (or allocation cycle) of parameters constituting the above-described information, time resource allocation information, frequency resource allocation information, transmission time, and /Or, the allocation timing may be information set according to the corresponding symbol length (or subcarrier interval).

In this disclosure, “Resource-Config information” may be a control message including one or more parameters among physical layer radio resource configuration information. Additionally, “Resource-Config information” may mean the properties and/or setting value (or range) of an information element (or parameter) transmitted by a control message. The information elements (or parameters) delivered by the control message are radio resource setting information that is commonly applied throughout the coverage of the base station (or beam) or dedicated to a specific terminal (or a specific terminal group). It may be wireless resource setting information allocated as . A terminal group may include one or more terminals.

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

Therefore, a terminal operating in the RRC connection state can receive communication services through a beam (eg, beam pair) established between the terminal and the base station. For example, when a communication service is provided using a beam setting (e.g., beam pairing) between a base station and a terminal, the terminal has a set beam with the base station and a synchronization signal of a receivable beam (e.g., SS/PBCH A wireless channel discovery or monitoring operation may be performed using a block) and/or a reference signal (e.g., CSI-RS). Here, “communication service being provided through a beam” may mean “packets are transmitted and received through an activation beam among one or more set beams.” In an NR communication system, “a beam is activated” may mean “a configured TCI state is activated.”

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

The terminal can detect or detect a problem in the radio link by performing a radio link monitoring (RLM) operation. Here, “a problem with the wireless link has been detected” may mean “there is an error in setting or maintaining physical layer synchronization for the wireless link.” For example, “a wireless link problem has been detected” may mean “a lack of physical layer synchronization between the base station and the terminal has been detected during a preset time.” If a wireless link problem is detected, the terminal can perform a wireless link recovery operation. If the radio link is not restored, the terminal may declare radio link failure (RLF) and perform a re-establishment procedure for the radio link.

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

The physical layer of the terminal establishes a wireless link by receiving a downlink synchronization signal (e.g., primary synchronization signal (PSS), secondary synchronization signal (SSS), SS/PBCH block, SSB) and/or a reference signal. It can be monitored. In this case, the reference signal is a base station common reference signal, a beam common reference signal, or a terminal (or terminal group) specific reference signal (e.g., a dedicated (or, terminal group) assigned to the terminal (or group). It may be a dedicated reference signal). Here, the common reference signal can be used for channel estimation operations of all terminals located within the coverage (or service area) of the corresponding base station or beam. The dedicated reference signal can be used for channel estimation operations of a specific UE or specific UE group within the coverage of the base station or beam.

Accordingly, when the base station or beam (eg, the beam set between the base station and the terminal) changes, the dedicated reference signal for beam management may change. The beam may be changed based on the parameter(s) set between the base station and the terminal. A change procedure for the setup beam may be required. “Change of beam in NR communication system” means “changing the index (or identifier) of a TCI state to the index of another TCI state”, “setting a new TCI state”, or “activating a TCI state”. It can mean “changing to a state.” The base station may transmit system information including configuration information of a common reference signal to the terminal. The terminal can acquire a common reference signal based on system information. In a handover procedure, synchronization reconfiguration procedure, or connection reconfiguration procedure, the base station may transmit a dedicated control message including configuration information of a common reference signal to the terminal.

Configuration beam information includes configuration beam index (or identifier), configuration TCI status index (or identifier), configuration information of each beam (e.g., transmission power, beam width, vertical angle, horizontal angle), transmission of each beam, and /or may include one or more of reception timing information (e.g., subframe index, slot index, mini slot index, symbol index, offset), reference signal information corresponding to each beam, and reference signal identifier.

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

The terminal may receive base station configuration information (e.g., base station identification information) from the base station through one or more of the RRC message, MAC message, and PHY message, and perform beam monitoring operations and wireless access based on the configuration information ( The base station that will perform the access) operation and/or the transmission and reception operation of the control (or data) packet can be confirmed.

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

The base station may obtain the results of the beam measurement operation or beam monitoring operation from the terminal, and may change the properties of the beam or the properties of the TCI state based on the results of the beam measurement operation or beam monitoring operation. Beams can be classified into primary beams, secondary beams, preliminary (or candidate) beams, active beams, and inactive beams depending on their properties. The TCI state can be classified into primary TCI state, secondary TCI state, spare (or candidate) TCI state, serving TCI state, established TCI state, active TCI state, and inactive TCI state depending on its properties. The primary TCI state and secondary TCI state may be assumed to be an active TCI state and a serving TCI state, respectively. The reserve (or candidate) TCI state may be assumed to be an inactive TCI state or an established TCI state.

The procedure for changing beam (or TCI state) properties may be controlled by the RRC layer and/or MAC layer. If the change procedure of the beam (or TCI state) properties is controlled by the MAC layer, the MAC layer can inform the upper layer of information about the change of the beam (or TCI state) properties. Information about changes in beam (or TCI state) properties may be transmitted to the terminal through a MAC message and/or a physical layer control channel (eg, PDCCH). Information about changes in beam (or TCI state) properties may be included in downlink control information (DCI) or uplink control information (UCI). Information about changes in beam (or TCI state) properties may be expressed as a separate indicator or field.

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

A change in the properties of a beam (or TCI state) can be defined as “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 spare (or candidate) beam,” or “change from spare (or candidate) beam to primary beam.” The attribute change procedure of the beam (or TCI state) may be controlled by the RRC layer and/or MAC layer. The attribute change procedure of the 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 beams among the plurality of beams may be set as beam(s) transmitting a physical layer control channel. For example, the primary beam and/or 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 (e.g., radio resource allocation information, modulation and coding scheme (MCS) information), feedback information (e.g., channel quality indication (CQI), precoding matrix indicator (PMI), HARQ ACK , HARQ NACK), resource request information (e.g., SR (scheduling request)), results of beam monitoring operation to support beamforming function, TCI status ID, and measurement information for active beam (or inactive beam). Can be used for more than one transmission.

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

In the allocation procedure of a plurality of beams (or, the setting procedure of the TCI state), the assigned (or set) beam index, information indicating the spacing between beams, and/or information indicating whether consecutive beams are allocated are provided to the 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 terminal's status information (eg, movement speed, movement direction, location information) and/or the quality of the wireless channel. The base station can obtain status information of the terminal from the terminal. Alternatively, the base station may obtain the status information of the terminal through another method.

Radio resource information includes parameter(s) indicating frequency domain resources (e.g., center frequency, system bandwidth, PRB index, number of PBRs, CRB index, number of CRBs, subcarrier index, frequency offset) and time domain resources. (For example, radio frame index, subframe index, TTI (transmission time interval), slot index, mini slot index, symbol index, time offset, period, length of transmission section (or reception section), It may include parameter(s) indicating a window). In addition, radio resource information is occupied according to the hopping pattern of radio resources, information for beamforming operation (e.g., beam configuration information, beam index), and characteristics of the code sequence (or bit string, signal sequence). Additional resource information may be included.

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

A reference signal for beam (or TCI state) or wireless link management may be a synchronization signal (e.g., PSS, SSS, SS/PBCH block), CSI-RS, PT-RS, SRS, DM-RS, etc. The reference parameter(s) for the reception quality of a beam (or TCI state) or reference signal for wireless link management include a measurement time unit, a measurement time interval, a reference value (or threshold) indicating the degree of improvement in reception quality, It may be a condition (for example, a reference value) indicating the degree of deterioration in reception quality. Each measurement time unit and measurement time interval can be set in absolute time (e.g., millisecond, second), TTI, symbol, slot, frame, subframe, scheduling cycle, base station operation cycle, or terminal operation cycle unit. there is.

A condition (eg, reference value) indicating 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 reference signals for beam (or TCI status) or wireless link management includes reference signal received power (RSRP), reference signal received quality (RSRQ), received signal strength indicator (RSSI), and signal-to-signal (SNR). -noise ratio), signal-to-interference ratio (SIR), and/or signal-to-interference and noise ratio (SINR).

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

Measurement operations (e.g., monitoring operations) for beam (or TCI status) or wireless link management may be performed at the base station and/or 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 terminal can report measurement results according to the setting parameter(s) for measurement reporting.

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

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

The basic procedure for beam (or TCI status) management through wireless link monitoring may include a beam failure detection (BFD) procedure for the wireless link, a beam recovery (BR) request procedure, etc. . “An operation of determining whether to perform a beam failure detection procedure and/or a beam recovery request procedure,” “An operation of triggering the performance of a beam failure detection procedure and/or a beam recovery request procedure,” and “A beam failure detection procedure and/or Each “control signaling operation for beam recovery request procedure” may be performed by one or more of the PHY layer, MAC layer, and RRC layer.

FIG. 6 is a conceptual diagram illustrating a first embodiment of a method of providing a service using a plurality of wireless access points in a communication system.

Referring to FIG. 6, base stations 611 and 612 may provide services to wireless access points 621-1, 621-2, and 622-1 within the service area through a wired interface or a wireless interface. The interface between the base station 611 and the wireless access points 621-1 and 621-2 within the service area of the base station 611 may be provided in a wired or wireless manner. The interface between the base station 612 and the wireless access point 622-1 within the service area of the base station 612 may be provided in a wired or wireless manner. Functional separation may be applied to base stations 611 and 612. In this case, the base stations 611 and 612 may be composed of two or more nodes (eg, CU, DU) that perform the wireless protocol functions of the base stations 611 and 612.

Base stations (611, 612) and wireless access points (621-1, 621-2, 622-1) are connected to terminals (650, 651-1, 651-2, 651-3, 652-1, 652-2) within each service area. ) can provide services through a wireless link (e.g., Uu interface). The transmission frequencies (or frequency bands) of the wireless access points 621-1 and 621-2 within the base station 611 may be the same or different. When the wireless access points 621-1 and 621-2 use the same frequency, the wireless access points 621-1 and 621-2 are connected to the same cell with the same PCI (physical cell ID) or different PCIs. It can operate with different cells.

When the wireless access points 621-1 and 621-2 operate at the same frequency, the wireless access points 621-1 and 621-2 provide services to the terminal 651-3 in a single frequency network (SFN) method. can be provided. The SFN method may mean "a method in which one or more wireless access points simultaneously transmit the same data to the terminal using the same frequency." To provide SFN-type service, each of the wireless access points 621-1 and 621-2 uses the same resource (e.g., physical resource block (PRB)) in the frequency and time domains to connect to the terminal 651-3. A downlink channel and/or signal may be transmitted. The terminal 653-1 uses a beam (or radio resource) corresponding to the beam identifier (e.g., TCI state identifier) of each of the wireless access points 621-1 and 621-2 ( 621-1, 621-2) A downlink channel and/or signal can be received from each. The downlink channel and/or signal may mean at least one of a downlink channel or a downlink signal. The TCI state identifier may be a TCI state ID or TCI state index.

Wireless access points 621-1 and 621-2 operating at the same frequency may not use the SFN method. In this case, each of the wireless access points 621-1 and 621-2 provides a downlink channel and/or signal to the terminal 651-3 using different resources (e.g., PRB) in the frequency and time domains. Can be transmitted. The terminal 653-1 uses a beam (or radio resource) corresponding to the beam identifier (e.g., TCI state identifier) of each of the wireless access points 621-1 and 621-2 ( 621-1, 621-2) A downlink channel and/or signal can be received from each.

Wireless access points 621-1 and 621-2 may have different PCIs. In other words, the wireless access points 621-1 and 621-2 may operate as different cells. “Wireless access points 621-1 and 621-2 operating as different cells” means “the base station 611 includes two or more cells with different PCIs, and the wireless access points 621-1 and 621-2 operate as different cells.” 621-2) This may mean that each is a lower node (or wireless access point) of a cell. Alternatively, “wireless access points 621-1 and 621-2 operating as different cells” means “two or more cells with different PCIs within one DU included in the base station 611 to which functional separation is applied. This may mean that “there exist, and each of the wireless access points 621-1 and 621-2 is a lower node (or wireless access point) of the cell.”

When the wireless access points (621-1, 621-2) belong to different cells within the base station or the DU of the base station, the service for a terminal that does not support the carrier aggregation function (e.g., a terminal in RRC connection state) is It can be provided from one wireless access point.

A base station may provide services to a terminal using one or more cells or one or more wireless access points. A base station to which functional separation is applied may include one CU and a plurality of DUs, and each of the plurality of DUs may provide a service to a terminal using one or more cells or one or more wireless access points.

FIG. 7A is a conceptual diagram showing a first embodiment of a method in which a wireless access point controlled by a base station provides a service, and FIG. 7B shows a second embodiment of a method in which a wireless access point controlled by a base station provides a service. It is a conceptual diagram, and FIG. 7C is a conceptual diagram illustrating a first embodiment of a method in which a wireless access point controlled by a DU included in a base station to which functional separation is applied provides a service, and FIG. 7D is a conceptual diagram illustrating a method for providing a service to a base station to which functional separation is applied. This is a conceptual diagram showing a second embodiment of a method in which a wireless access point controlled by an included DU provides a service.

7A to 7D, the wireless access point may be referred to as a TRP. In the embodiments of FIGS. 7A and 7B , the base stations 701 and 711 to which functional separation is not applied may include one or more cells 705 and 715 and/or one or more TRPs 703 and 713. The base stations (701, 711) use cells (705-2, 715-1) to which TRP (703, 713) is not applied and/or cells (705-1, 705-n, 715-) to which TRP (703, 713) is applied. 2, 715-n). One cell may consist of one or more TRPs.

In the embodiments of FIGS. 7C and 7D , the base stations 721 and 731 to which functional separation is applied may include one CU (722 and 732) and one or more DUs (726 and 736). Cells 725, 735 and TRPs 723, 733 are shown as belonging within DUs 726, 736, however, this means that all functions of cells 725, 735 and TRPs 723, 733 are within DUs 726, 736. It may not mean that it is performed or implemented by. From the perspective of the structure of the communication system, DUs 726, 736 and cells 725, 735 may belong to different layers, and DUs 726, 736 and TRPs 723, 733 may belong to different layers. You can. Cells 725 and 735 within the DUs 726 and 736 may perform functions of layers below the RLC layer (eg, RLC layer, MAC layer, and/or PHY layer) among the wireless protocol layers.

The base station (721, 731) to which functional separation is applied is a cell (725-2, 735-1) to which TRP (723, 733) is not applied and/or a cell to which TRP is applied (725-1, 725-n, 735-2) , 735-3, 735-n). One DU (726, 736) may include one or more cells (725, 735) and/or one or more TRPs (723, 733).

The same PCI can be applied to multiple TRPs constituting one cell. Each of a plurality of TRPs within a cell can be distinguished by a TRP index (or TRP ID, TRP identifier). Different PCIs may be applied to TRPs belonging to different cells.

The base station may provide services to the terminal 704 within the coverage of the cell and/or TRP using a wireless link (eg, RL1, RL2). The base station (701, 711, 721, 731) may not set the CA (carrier aggregation) function to the terminal 704 in the RRC connection state. In this case, the service for the terminal 704 may be provided through one cell (or primary cell (PCell)) and RL1. When the CA function is set to the terminal 704 in the RRC connection state, services for the terminal 704 can be provided through RL1 for the PCell and RL2 for the secondary cell (SCell).

The functional blocks of the TRP may belong to the same cell or different cells. The same cell may mean cell(s) having the same PCI. Different cells may mean cells having different PCIs. The same PCI can be applied to TRPs 703-1 and 703-2 belonging to the same cell. The same PCI can be applied to TRPs 723-1 and 723-2 belonging to the same cell. Different PCIs may be applied to TRPs (703-m, 713-2, 713-m, 723-m, 733-1, 733-2) belonging to different cells. TRPs belonging to different cells may operate at the same frequency or different frequencies. If TRPs operate at different frequencies, the TRPs may have different PCIs. In other words, TRPs with different PCIs may belong to different cells.

When the DC (dual connectivity) function is not set in a terminal in an RRC connection state, the terminal can establish an RRC connection with one base station, and services for the terminal can be provided by one base station. If the CA function is not set in the terminal, services for the terminal may be provided by one cell (eg, PCell) through RL1. If the DC function is not configured in the terminal in the RRC connection state, the terminal can perform the MAC layer function using only one MAC entity.

Figure 8 is a flowchart showing a first embodiment of a cell/TRP/beam switching procedure in a communication system.

Referring to FIG. 8, TRPs belonging to one cell with the same PCI can provide services to the terminal. The base station 801 to which functional separation is applied may include the CU 801-1 and the DU 805. The base station 801 to which functional separation is not applied may include one or more cells. The DU 805 of the base station 801 to which functional separation is applied may include one or more cells. The cell may provide services to the terminal 804 using one or more TRPs 802 and 803. TRP3 (803) may belong to the same cell 1 as “TRP1 (802-1) and/or TRP2 (802-2)”. Alternatively, TRP3 803 may belong to a cell different from Cell 1 within the base station 801 or DU 805. The base station to which TRP3 (803) belongs may be the same or different from the base station to which “TRP1 (802-1) and TRP2 (802-2)” belong. In the present disclosure, cell/TRP/beam may mean at least one of a cell, TRP, or beam.

In S801, the terminal 804 in the RRC idle state or RRC inactive state can perform a wireless access procedure with the base station 801. The wireless access procedure may include a random access procedure and/or a resume procedure. In S801, the terminal 804 may transition to the RRC connection state by performing an RRC connection establishment procedure or an RRC connection (re)establishment procedure with the base station 801 (or CU 801-1). In S801, the terminal 804 may monitor and/or measure the wireless channel for the downlink of the cell (or TRP) 802, 803, and select the best cell (or , the best TRP) and/or the best downlink beam can be selected, and a wireless access procedure (e.g., random access procedure, resumption procedure) can be performed using the radio resources of the uplink channel corresponding to the selected beam. You can. Best cell may mean the optimal cell, best TRP may mean the optimal TRP, and best downlink beam may mean the optimal downlink beam.

In the present disclosure, a beam, beam identifier, or beam ID refers to a downlink channel (e.g., PDCCH, PDSCH), a downlink signal (e.g., SSB, CSI-RS, tracking reference signal (TRS), or positioning reference signal (PRS). signa), DM-RS), an index (or identifier) that distinguishes beams for uplink channels (e.g., PUCCH, PUSCH), and/or uplink signals (e.g., DM-RS, SRS) It can mean. “Index for distinguishing beams” may mean a TCI state index (eg, TCI state ID) for setting or distinguishing beams. The TCI state index may be set by the RRC layer and may be controlled or indicated by the MAC CE of the MAC layer and/or the DCI of the PHY layer.

In a wireless access procedure, the terminal 804 sends downlink channel measurement results, service requests, and/or capability information (e.g., terminal capability information) to the base station 801 (or CU 801-1). )). The channel measurement results are the channel quality (e.g., RSRP, RSRQ) for the signal (e.g., SSB, reference signal (RS)) transmitted by the base station (or cell, TRP) requiring radio link and/or beam selection. , RSSI, SNR, SIR, Eb/No, etc.), SSB index, and/or RS index.

The base station 801 (or CU 801-1) may receive channel measurement results, service requests, and/or capability information for cells (or TRPs) 802 and 803 from the terminal 804, , RRC configuration information necessary to provide the service requested by the terminal 804 may be generated based on the channel measurement result, service request, and/or capability information. The base station 801 (or CU 801-1) sends an RRC connection control message (e.g., RRC reset message, RRC release message, RRC resume message, etc.) containing RRC configuration information. It can be transmitted to the terminal 804. The RRC connection control message may include configuration parameter information for each layer of the wireless protocol. The RRC connection control message may be transmitted using the cell (or TRP) and/or beam (or TCI state ID) selected by the terminal 804. The terminal 804 may receive an RRC connection control message from the base station 801 (or CU 801-1), and use the information included in the RRC connection control message to configure each layer of the wireless protocol necessary for service provision. Parameter values can be set.

In S801, the base station 801 (or CU 801-1) may provide information on the cell/TRP/beam providing the service to the terminal 804. In S801, DC and CA functions may not be set in the terminal 804 in the RRC connection state. In this case, the service for the terminal 804 is one TRP (802-1, 802-2, 803) or two TRPs (802-1, 802-) belonging to the same cell (e.g., cell 1). 2) can be provided by. The terminal 804 can check the configuration parameters for the two TRPs 802-1 and 802-2 included in the RRC connection control message. In this case, in S802, the terminal 804 receives a PDCCH (e.g., DCI) and/or PDSCH (e.g., DL (downlink) packet) from two TRPs (802-1, 802-2). You can. Scheduling information of DL packets may be included in DCI.

In single-DCI mode, the terminal 804 can receive the same DCI from two TRPs 802-1 and 802-2. In this case, DL packets can be scheduled by the same two DCIs. In multi-DCI mode, the terminal 804 can receive independent DCI from each of the two TRPs 802-1 and 802-2. In this case, DL packets can be scheduled by an independent DCI. To improve DCI reception performance, the terminal can repeatedly receive the same DCI through search spaces associated with different CORESETs of TRPs. As another way to improve DCI reception performance, DCI can be transmitted in one search space (or CORESET) using different beams. Alternatively, the terminal may receive the same DCI from scheduled radio resources using different TCI status IDs. At this time, the terminal can receive the same DCI based on the SFN method.

In S803, the terminal 804 in an RRC connection state in which DC and CA functions are not configured sends PUCCH (e.g., UCI) and/or PUSCH (e.g., UL (uplink) packet) to two TRPs belonging to the same cell. It can be transmitted to fields 802-1 and 802-2. To improve the performance of uplink communication, the terminal 804 repeats the same PUCCH and/or the same PUSCH using uplink radio resources configured for another beam or uplink radio resources scheduled for a different TCI state ID. It can be transmitted to TRP (802-1, 802-2).

In S804 (e.g., S804-1 and S804-2), the terminal 804 periodically or aperiodically reports measurement results for a cell (e.g., another cell) and/or a TRP (e.g., another TRP). It can be reported as S804 may be performed based on the RRC control message of the base station 801 (or CU 801-1) and/or the MAC CE of the DU 805. The MAC CE of the DU 805 may be control information of the MAC layer of the DU 805. In S804, the terminal 804 may determine whether the wireless channel quality of the cell/TRP/beam meets a preset standard, and based on the determination result, change, restore, or modify the current cell/current TRP/current beam. Alternatively, a control message requesting reset (e.g., RRC control message, MAC CE, DCI, PDCCH field, PDCCH parameter) may be transmitted. Current cell may mean a serving cell, current TRP may mean a serving TRP, and current beam may mean a serving beam. A serving TRP may be associated with a serving cell. In other words, the serving TRP may belong to the serving cell. A serving beam may be associated with a serving cell and/or serving TRP. In other words, the serving beam may belong to a serving cell and/or a serving TRP. In the present disclosure, changing may be used with the same or similar meaning as switching. For example, a cell change operation and a cell switching operation may be the same operation.

In S804-1, the UE 804 may report the L1 and/or L2 measurement results to the MAC layer (eg, MAC entity) of the DU 805. In S804-2, the L3 measurement result may be reported to the RRC layer of the base station 801 (or CU 801-1). The L1 and/or L2 measurement results reported by the terminal 804 may include one or more information elements listed in Table 1 below.

The performance measurement results of L2 are PER (packet error rate), BLER (block error rate), ARQ (automatic repeat request) retransmission rate, ARQ (re)transmission failure rate, HARQ retransmission rate, HARQ (re)transmission failure rate, and BFD (beam) It may include at least one of the number of occurrences of failure detection, the number of failures (or failure rate) of beam failure recovery (BFR), or the number of occurrences of radio link failure (RLF). The number of occurrences of a BFD may refer to the number of occurrences of the BFD within a unit time. The number of BLF failures may mean the number of failures of the BLF within a unit time. The number of occurrences of the BLF may refer to the number of occurrences of the BLF within a unit time. Each of the L1 measurement operation, L1 measurement result reporting, L2 measurement operation, and L2 measurement result reporting can be performed in units of cell/TRP/beam.

The DU 805 may request (or instruct) the UE 804 to report L1 and/or L2 measurement results for the serving TRP, active TRP, and/or specific TRP (or target TRP). At this time, the DU 805 contains an identifier of a specific TRP (e.g., target TRP) that is a measurement target, a beam identifier, a measurement object identifier, and/or a type (or measurement result format) of the measurement result parameter. (format)) can be indicated to the terminal 804. The target TRP may be associated with the target cell. In other words, the target TRP may belong to the target cell. The target beam may be associated with a target cell and/or a target TRP. In other words, the target beam may belong to the target cell and/or target TRP.

To report measurement operations and measurement results for L1 and/or L2 in S804, the base station 801 (or CU 801-1) uses a signaling message (e.g., RRC control message) as shown in Table 2 below. You may establish measurement criteria(s) and/or measurement reporting criteria(s) described in . Measurement standard(s) may refer to measurement condition(s). Measurement reporting standard(s) may refer to measurement reporting condition(s). The reference value may mean a threshold.

If one or more conditions listed in Table 2 are satisfied, the terminal 804 may perform an L1 measurement operation, L1 measurement result reporting, L2 measurement operation, and/or L2 measurement result reporting. “If one or more conditions listed in Table 2 are satisfied,” “If preset TRP change conditions (or standards) are satisfied,” or “If the terminal determines that a change to the serving TRP (or active TRP) is necessary.” ", In S804, the terminal 804 may request to disable the function of the serving TRP (or active TRP) and/or change the TRP.

In S804, the DU 805 may receive a control message requesting a TRP change, an L1 measurement result, and/or an L2 measurement result from the UE 804. At S805, the DU 805 determines whether to change the cell/TRP/beam belonging to the cell having the same PCI based on the control message requesting cell/TRP/beam switching, the L1 measurement result, and/or the L2 measurement result. You can.

At S805, the DU 805 (e.g., a MAC entity within the DU 805) may decide to switch the cell/TRP/beam providing service to the UE 804. In this case, in S806, the DU 805 may transmit cell/TRP/beam switching information to the base station 801 (or CU 801-1). S806 can be performed optionally. For example, S806 may be omitted depending on the policy (or decision) of the communication system (or communication network). In S807, the DU 805 may transmit a control message instructing cell/TRP/beam switching to the UE 804.

In S807, the message instructing switching of cell/TRP/beam transmitted from the DU 805 to the UE 804 may be DCI and/or MAC CE. The message may include a TRP identifier and/or beam identifier. The UE 804 may receive a message indicating switching of cell/TRP/beam from the DU 805. When switching from “TRP1 (802-1) and TRP2 (802-2)” to “TRP2 (802-2) and TRP3 (803)”, in S808, the terminal (804) switches to “TRP2 (802-2) and TRP3”. (803)" and communication (e.g., downlink communication and/or uplink communication) may be performed. In other words, “TRP2 (802-2) and TRP3 (803)” can provide services to the terminal (804). TRP2 (802-2) and TRP3 (803) may operate as serving TRPs for the terminal 804 in S808.

The above-described cell/TRP/beam switching procedure is used when TRP3 (803) belongs to the same cell (e.g., one cell with the same PCI) as “TRP1 (802-1) and TRP2 (802-2)”. It can be done.

In the embodiment of Figure 8, the terminal 804 and the DU (805) for cell/TRP/beam measurement indication, cell/TRP/beam measurement report, cell/TRP/beam switching request, and/or cell/TRP/beam switching indication. ) may be fields (e.g., parameters) of a control channel (e.g., PDCCH, PUCCH, DCI, UCI) and/or MAC CE. MAC CE may be configured in the form of a MAC PDU (protocol data unit) along with a MAC (sub) header. If separate MAC CE parameters are not needed, a control message containing only a MAC subheader and/or a logical channel ID (LCID) indicating or directing a specific operation may be used.

Figure 9 is a flowchart showing a second embodiment of a cell/TRP/beam switching procedure in a communication system.

Referring to FIG. 9, the base station 901 to which functional separation is applied may include a CU (901-1) and a DU (905). The base station 901 to which functional separation is not applied may include one or more cells. The DU 905 of the base station 901 to which functional separation is applied may include one or more cells. The cell may provide services to the terminal 904 using one or more TRPs 902 and 903. TRP1 (902-1) and TRP2 (902-2) may belong to Cell 1, and TRP3 (903) may belong to Cell 2. Cell 1 and Cell 2 may have different PCIs. Cell 1 and Cell 2 may belong to the same base station or different base stations.

In S901, the terminal 904 in the RRC idle state or RRC inactive state may perform a wireless access procedure with the base station 901. The wireless access procedure may include a random access procedure and/or a resumption procedure. In S901, the terminal 904 may transition to the RRC connection state by performing an RRC connection establishment procedure or an RRC connection (re)establishment procedure with the base station 901 (or CU 901-1). In S901, the terminal 904 may monitor and/or measure the wireless channel for the downlink of the cell (or TRP) 902, 903, and select the best cell (or , TRP) and/or the best downlink beam can be selected, and a wireless access procedure (e.g., random access procedure, resumption procedure) can be performed using the radio resources of the uplink channel corresponding to the selected beam. . Best cell may mean the optimal cell, best TRP may mean the optimal TRP, and best downlink beam may mean the optimal downlink beam.

In a wireless access procedure, the terminal 904 sends downlink channel measurement results, service requests, and/or capability information (e.g., terminal capability information) to the base station 901 (or CU 901-1). Can be transmitted. Channel measurement results are the channel quality (e.g., RSRP, RSRQ, RSSI, SNR) for signals (e.g., SSB, RS) transmitted by the base station (or cell, TRP) requiring radio link and/or beam selection. , SIR, Eb/No, etc.), SSB index, and/or RS index.

The base station 901 (or CU 901-1) may receive channel measurement results, service requests, and/or capability information for cells (or TRPs) 902 and 903 from the terminal 904, , RRC setting information necessary to provide the service requested by the terminal 904 may be generated based on the channel measurement result, service request, and/or capability information. The base station 901 (or CU 901-1) transmits an RRC connection control message (e.g., RRC reset message, RRC release message, RRC resume message, etc.) containing RRC configuration information to the terminal 904. You can. The RRC connection control message may include configuration parameter information for each layer of the wireless protocol. The RRC connection control message may be transmitted using the cell (or TRP) and/or beam (or TCI state ID) selected by the terminal 904. The terminal 904 may receive an RRC connection control message from the base station 901 (or CU 901-1), and use the information included in the RRC connection control message to configure each layer of the wireless protocol necessary for service provision. Parameter values can be set.

In S901, the base station 901 (or CU 901-1) provides “information on cells and/or TRPs providing services” and/or “cell/TRP/beam switching list” to the terminal 904. You can. The cell/TRP/beam switching list includes “information on cell(s) capable of cell switching based on L1 measurement results and/or L2 measurement results,” “information on cells capable of TRP switching based on L1 measurement results and/or L2 measurement results.” It may include at least one of “information on TRP(s)” or “information on beam(s) capable of beam switching based on L1 measurement results and/or L2 measurement results.” Cell/TRP/beam switching can be L1-based cell/TRP/beam switching, L2-based cell/TRP/beam switching, L1 and L2-based cell/TRP/beam switching, or MAC-based cell/TRP/beam switching. It can mean.

DU 905 may independently perform cell switching operations, TRP switching operations, and/or beam switching operations. Cell switching may mean switching between cells belonging to the same DU or different DUs. TRP switching may mean switching between TRPs belonging to the same cell and/or switching between TRPs belonging to different cells (eg, different cells within the same DU or different DUs). Beam switching may mean switching between beams for the same cell, switching between beams for different cells, switching between beams for the same TRP, and/or switching between beams for different TRPs. The base station 901 transmits a cell/TRP/beam switching list to allow the terminal 904 and/or DU 905 to switch on cells, TRPs, and/or beams belonging to the cell/TRP/beam switching list. can do. The cell/TRP/beam switching list may include at least one of a cell identifier (eg, PCI), a TRP identifier, a beam identifier, or a TCI status ID.

In S901, DC and CA functions may not be set in the terminal 904 in the RRC connection state. In this case, the service for the terminal 904 is one TRP (902-1, 902-2, or 903) or two TRPs (902-1, 902) belonging to the same cell (e.g., cell 1). It can be provided by -2). The terminal 904 can check the configuration parameters for the two TRPs 902-1 and 902-2 included in the RRC connection control message. In this case, in S902, the terminal 904 may receive a PDCCH (eg, DCI) and/or PDSCH (eg, DL packet) from two TRPs 902-1 and 902-2. Scheduling information of DL packets may be included in DCI.

In S902, the terminal 904 may receive DCI from two TRPs 902-1 and 902-2 based on single-DCI mode or multi-DCI mode. To improve DCI reception performance, repeated transmission of DCI can be performed. At S903, the terminal 904 may transmit PUCCH and/or PUSCH, and the base station 901 may receive the PUCCH and/or PUSCH from the terminal 904. S903 may be performed identically or similarly to S803 in the embodiment of FIG. 8.

At S904, the DU 905 (e.g., MAC layer or MAC entity) may determine a specific cell/specific TRP/specific beam for cell/TRP/beam switching, and determine the specific cell/specific TRP/specific beam for the specific cell/specific TRP/specific beam. The terminal 904 may be instructed to perform L1 measurement, L1 measurement result reporting, L2 measurement, and/or L2 measurement result reporting. The DU 905 performs L1 measurement, L1 measurement result reporting, L2 measurement, and /Or, the terminal 904 may be instructed to report the L2 measurement results. The cell/TRP/beam switching list may be indicated in the RRC connection setup procedure between the terminal and the base station in S901. Alternatively, the cell/TRP/beam switching list may be indicated in the re-establishment procedure of the RRC connection between the terminal and the base station after S901. In other words, the cell/TRP/beam that can be indicated by the DU (905) in S904 is “a cell/TRP/beam belonging to the cell/TRP/beam switching list” and/or “a cell that can be independently switched by the DU (905).” It may be limited to "/TRP/beam". The control message transmitted by the DU 905 to the terminal 904 in S904 includes the identifier of a specific TRP (or target TRP) that is the measurement target, the beam identifier, the measurement object identifier, or the type (type) of the measurement result parameter. Measurement result format) may be included.

At S904, the terminal 904 may receive a control message (e.g., measurement report indication of cell/TRP/beam) from the DU 905 and check the information element(s) included in the control message. . Based on the RRC control message of the base station 901 (or CU 901-1) and/or the control message of the DU 905 received at S904, the terminal 904 is connected to the cell, TRP, and/or beam. A measurement operation (eg, an L1 measurement operation and/or an L2 measurement operation) may be performed. In S905, the terminal 904 may report measurement results (eg, L1 measurement results and/or L2 measurement results) periodically or aperiodically. The measurement results of the terminal 904 may be transmitted to the CU 901-1 through the serving cell/serving TRP 902-1 and 902-2.

At S905, the terminal 905 may determine whether the wireless channel quality of the cell, TRP, and/or beam meets a preset standard, and based on the determination result, the terminal 905 may determine whether the current cell, current TRP, and/or current beam A control message requesting change, recovery, or reset (e.g., RRC control message, MAC CE, DCI, PDCCH field, PDCCH parameter) may be transmitted. Current cell may mean a serving cell, current TRP may mean a serving TRP, and current beam may mean a serving beam.

In S905-1, the L1 measurement result and/or the L2 measurement result may be reported to the MAC layer (e.g., MAC entity) of the DU 905. In S905-2, the L3 measurement result may be reported to the RRC layer of the base station 901 (or CU 901-1). The L1 measurement result and/or L2 measurement result reported by the terminal 904 may include one or more information elements listed in Table 1 above. In S905, the terminal 904 may transmit an L1/L2-based cell/TRP/beam switching request message (e.g., MAC-based cell/TRP/beam switching request message) to the DU 905. The L1/L2-based cell/TRP/beam switching request message may be transmitted through the serving cell/serving TRP (902-1, 902-2). The L1/L2-based cell/TRP/beam switching request message includes at least one of a target cell identifier, a target TRP identifier, a beam identifier, a measurement result for the target cell, a measurement result for the target TRP, or a measurement result for the beam. may include.

In S905-1, the DU 905 may receive an L1/L2 based cell/TRP/beam switching request message from the UE 904. In S905-2, the DU 905 sends some or all information elements included in the L1/L2-based cell/TRP/beam switching request message of the UE 904 to the base station 901 (or CU 901- 1)) can be sent or notified to. Among the information elements included in the L1/L2-based cell/TRP/beam switching request message, the information element(s) transmitted to the base station 901 may be selected by the DU 905.

8 and 9, the L1 measurement operation, L1 measurement result reporting, L2 measurement operation, and L2 measurement result reporting may each be performed in units of cells, TRPs, and/or beams. In order to report measurement operations and measurement results for L1 and/or L2 in S905, the base station 901 (or CU 901-1) uses a signaling message (e.g., RRC control message) as shown in Table 2 above. You may establish measurement criteria(s) and/or measurement reporting criteria(s) described in .

If one or more conditions listed in Table 2 are satisfied, the terminal 904 may perform an L1 measurement operation, L1 measurement result reporting, L2 measurement operation, and/or L2 measurement result reporting. “If one or more conditions listed in Table 2 are satisfied,” “If preset TRP change conditions (or standards) are satisfied,” or “If the terminal determines that a change to the serving TRP (or active TRP) is necessary.” ", In S905, the UE 904 transmits a control message to the DU 905 that triggers or requests MAC-based cell/TRP/beam switching, deactivation of the serving TRP (or active TRP), and/or TRP change. You can.

In S905, the DU 905 may receive a control message requesting MAC-based cell/TRP/beam switching, a control message requesting TRP switching, an L1 measurement result, and/or an L2 measurement result from the UE 904. . At S906, the DU 905 determines “to a cell with the same PCI” based on a control message requesting MAC-based cell/TRP/beam switching, a control message requesting TRP switching, an L1 measurement result, and/or an L2 measurement result. It can be determined whether “whether TRPs and/or beams belonging to cells are switched,” “whether TRPs and/or beams belonging to cells with different PCIs are switched,” or “whether cells are switched based on MAC.” MAC-based cell/TRP/beam switching operation (e.g., L1-based cell/TRP/beam switching operation, L2-based cell/TRP/beam switching operation) is cell/TRP/beam switching without re-establishment of RRC connection. It could be a movement. MAC-based cell/TRP/beam switching operation may mean a cell switching operation including L1-based cell/TRP/beam switching operation and/or L2-based cell/TRP/beam switching operation.

In S906, the DU 905 may decide to perform a MAC-based cell/TRP/beam switching operation. In this case, in S907, the DU 905 may transmit a control message indicating performance of a MAC-based cell/TRP/beam switching operation to the base station 901 (or CU 901-1). In S908, the DU 905 may transmit a control message (e.g., scheduling information) to the UE 904 instructing performance of a MAC-based cell/TRP/beam switching operation.

The control message transmitted by the DU 905 in S908 may be MAC CE and/or DCI. A control message notifying performance of a MAC-based cell/TRP/beam switching operation may include information element(s) for the target cell (or target TRP). The control message may include one or more information elements listed in Table 3 below.

“If the control message received in S908 indicates acquisition of uplink timing” or “If the control message received in S908 includes scheduling information for uplink access,” the terminal 904 determines the target cell/target TRP. A procedure to obtain the uplink timing (eg, uplink transmission timing) of the physical layer for (903) may be performed (S909). “If the control message received in S908 does not indicate acquisition of uplink timing” or “If the control message received in S908 includes adjustment information of the uplink timing of the physical layer for the target cell/target TRP (903) case", the terminal 904 may omit S909.

After S908 or S909, the terminal 904 may perform communication (e.g., downlink communication and/or uplink communication) with the target cell/target TRP 903 (S910). In other words, Cell/TRP3 (903) can provide services to the terminal (904). The target cell/target TRP 903 may operate as a serving cell/serving TRP for the terminal 904 in S910.

In the MAC-based cell/TRP/beam switching procedure, radio resources and/or parameters set (or allocated) between the source cell/source TRP (e.g., serving cell/serving TRP) and the terminal 904 are controlled by S908. The message (or scheduling information) may be released at the time it is received by the terminal 904. S909 may be performed based on RRC configuration by the base station 901 (or CU 901-1) and/or control of the DU 905. S909 may be a synchronization acquisition procedure for the target cell/target TRP. “After synchronization for the target cell/target TRP is obtained in S909” or “after downlink communication is successfully completed in S910,” the source cell/source TRP (e.g., serving cell/serving TRP) and the terminal Radio resources and/or parameters set (or allocated) may be released (or deleted) in S904. In S910, downlink communication may include a PDCCH transmission and reception operation and/or a PDSCH transmission and reception operation. .

In the embodiment of FIG. 9, the terminal (904) provides measurement instructions for target cell/target TRP/target beam, reports measurement results for target cell/target TRP/target beam, and/or instructions for MAC-based cell/TRP/beam switching. ) and the DU 905 may be fields (e.g., parameters) and/or MAC CE of a control channel (e.g., PDCCH, PUCCH, DCI, UCI). MAC CE may be configured in the form of a MAC PDU along with a MAC (sub)header. If separate MAC CE parameters are not needed, a control message containing a MAC subheader and/or LCID indicating or directing a specific operation may be used.

Figure 10 is a flowchart showing a third embodiment of a cell/TRP/beam switching procedure in a communication system.

Referring to FIG. 10, the base station 1001 to which functional separation is applied may include a CU 1001-1 and a DU 1005. The base station 1001 to which functional separation is not applied may include one or more cells. The DU 1005 of the base station 1001 to which functional separation is applied may include one or more cells. The cell may provide services to the terminal 1004 using one or more TRPs 1002 and 1003. TRP1 (1002-1) and TRP2 (1002-2) may belong to Cell 1, and TRP3 (1003) may belong to Cell 2. Cell 1 and Cell 2 may have different PCIs. Cell 1 and Cell 2 may belong to the same base station or different base stations.

In S1001, the terminal 1004 in the RRC idle state or RRC inactive state can perform a wireless access procedure with the base station 1001. The wireless access procedure may include a random access procedure and/or a resumption procedure. In S1001, the terminal 1004 may transition to the RRC connection state by performing an RRC connection establishment procedure or an RRC connection (re)establishment procedure with the base station 1001 (or CU 1001-1). In S1001, the terminal 1004 may monitor and/or measure the wireless channel for the downlink of the cell (or TRP) 1002, 1003, and select the best cell (or , TRP) and/or the best downlink beam can be selected, and a wireless access procedure (e.g., random access procedure, resumption procedure) can be performed using the radio resources of the uplink channel corresponding to the selected beam. .

In a wireless access procedure, the terminal 1004 sends downlink channel measurement results, service requests, and/or capability information (e.g., terminal capability information) to the base station 1001 (or CU 1001-1). Can be transmitted. Channel measurement results are the channel quality (e.g., RSRP, RSRQ, RSSI, SNR) for signals (e.g., SSB, RS) transmitted by the base station (or cell, TRP) requiring radio link and/or beam selection. , SIR, Eb/No, etc.), SSB index, and/or RS index.

The base station 1001 (or CU 1001-1) may receive channel measurement results, service requests, and/or capability information for cells (or TRPs) 1002 and 1003 from the terminal 1004, , RRC configuration information necessary to provide the service requested by the terminal 1004 may be generated based on the channel measurement result, service request, and/or capability information. The base station 1001 (or CU 1001-1) transmits an RRC connection control message (e.g., RRC reset message, RRC release message, RRC resume message, etc.) containing RRC configuration information to the terminal 1004. You can. The RRC connection control message may include configuration parameter information for each layer of the wireless protocol. The RRC connection control message may be transmitted using the cell (or TRP) and/or beam (or TCI state ID) selected by the terminal 1004. The terminal 1004 may receive an RRC connection control message from the base station 1001 (or CU 1001-1), and use the information included in the RRC connection control message to configure each layer of the wireless protocol necessary for service provision. Parameter values can be set.

In S1001, the base station 901 (or CU 1001-1) provides “information on cells and/or TRPs providing services” and/or “cell/TRP/beam switching list” to the terminal 1004. You can. The cell/TRP/beam switching list includes “information on cell(s) capable of cell switching based on L1 measurement results and/or L2 measurement results,” “information on cells capable of TRP switching based on L1 measurement results and/or L2 measurement results.” It may include at least one of “information on TRP(s)” or “information on beam(s) capable of beam switching based on L1 measurement results and/or L2 measurement results.” Cell/TRP/beam switching may mean “cell/TRP/beam switching based on L1/L2” or “cell/TRP/beam switching based on MAC.”

DU 1005 may independently perform cell switching operations, TRP switching operations, and/or beam switching operations. Cell switching may mean switching between cells belonging to the same DU or different DUs. TRP switching may mean switching between TRPs belonging to the same cell and/or switching between TRPs belonging to different cells (eg, different cells within the same DU or different DUs). Beam switching may mean switching between beams for the same cell, switching between beams for different cells, switching between beams for the same TRP, and/or switching between beams for different TRPs. When a cell is switched, not only the cell but also the TRP and/or beam may be switched. Therefore, cell switching operation may mean TRP switching operation and/or beam switching operation.

The base station 1001 performs switching on the cell(s), TRP(s), and/or beam(s) belonging to the cell/TRP/beam switching list by transmitting a cell/TRP/beam switching list to the terminal 1004. and/or DU 1005. The cell/TRP/beam switching list may include at least one of a cell identifier (eg, PCI), a TRP identifier, a beam identifier, or a TCI status ID. The terminal 1004 may perform a measurement operation (eg, a channel measurement operation) for a cell/TRP/beam for which switching is permitted by the base station 1001.

In S1001, DC and CA functions may not be set in the terminal 1004 in the RRC connection state. In this case, the service for the terminal 1004 is one TRP (1002-1, 1002-2, or 1003) or two TRPs (1002-1, 1002) belonging to the same cell (e.g., cell 1). It can be provided by -2). The terminal 1004 can check the configuration parameters for the two TRPs 1002-1 and 1002-2 included in the RRC connection control message. In this case, in S1002, the terminal 1004 may receive a PDCCH (eg, DCI) and/or PDSCH (eg, DL packet) from two TRPs 1002-1 and 1002-2. Scheduling information of DL packets may be included in DCI.

In S1002, the terminal 1004 may receive DCI from two TRPs 1002-1 and 1002-2 based on single-DCI mode or multi-DCI mode. To improve DCI reception performance, repeated transmission of DCI can be performed. At S1003, the terminal 904 may transmit PUCCH and/or PUSCH, and the base station 1001 may receive the PUCCH and/or PUSCH from the terminal 1004. S1003 may be performed identically or similarly to S803 in the embodiment of FIG. 8.

At S1004, the DU 1005 (e.g., MAC layer or MAC entity) may determine a specific cell/specific TRP/specific beam for cell/TRP/beam switching, and determine the specific cell/specific TRP/specific beam for the specific cell/specific TRP/specific beam. L1 measurement, L1 measurement result reporting, L2 measurement, and/or L2 measurement result reporting may be instructed to the terminal 1004. The DU (1005) performs L1 measurement, L1 measurement result reporting, L2 measurement, and /Or, the terminal 1004 may be instructed to report the L2 measurement results. The cell/TRP/beam switching list may be indicated in the RRC connection setup procedure between the terminal and the base station in S1001. Alternatively, the cell/TRP/beam switching list may be indicated in the re-establishment procedure of the RRC connection between the terminal and the base station after S1001. In other words, the cell/TRP that can be indicated by the DU (1005) in S1004 is “a cell/TRP/beam belonging to the cell/TRP/beam switching list” and/or “a cell/TRP that can be independently switched by the DU (1005).” It may be limited to "/beam". The control message transmitted by the DU 1005 to the UE 1004 in S1004 includes the identifier, beam identifier, measurement object identifier, or type of measurement result parameter (or measurement result format) of a specific TRP (or target TRP) that is the measurement target. ) may include at least one of

At S1004, the terminal 1004 may receive a control message (e.g., measurement report indication of cell/TRP/beam) from the DU 1005 and check the information element(s) included in the control message. . Based on the RRC control message of the base station 1001 (or CU 1001-1) and/or the control message of the DU 1005 received at S1004, the terminal 9104 is connected to the cell, TRP, and/or beam. A measurement operation (eg, an L1 measurement operation and/or an L2 measurement operation) may be performed. In S1005, the terminal 1004 may report measurement results (eg, L1 measurement results and/or L2 measurement results) periodically or aperiodically. The measurement results of the terminal 1004 may be transmitted to the CU 1001-1 through the serving cell/serving TRP 1002-1 and 1002-2.

In S1005-1, the L1 measurement result and/or the L2 measurement result may be reported to the MAC layer (eg, MAC entity) of the DU 1005. In S1005-2, the L3 measurement result may be reported to the RRC layer of the base station 1001 (or CU 1001-1). The L1 measurement result and/or L2 measurement result reported by the terminal 1004 may include one or more information elements listed in Table 1 above.

In S1006, the terminal 1004 sends a MAC-based cell/TRP/beam switching request message to the DU (1005) through the target cell/target TRP (1003) instead of the serving cell/serving TRP (1002-1, 1002-2). Can be transmitted. In the embodiment of FIG. 9, the MAC-based cell/TRP/beam switching request message was transmitted to the DU 905 through the serving cell/serving TRP (902-1, 902-2), but in the embodiment of FIG. 10, the MAC-based The cell/TRP/beam switching request message may be transmitted to the DU (1005) through the target cell/target TRP (1003). If it is determined that MAC-based cell/TRP/beam switching is performed, the DU 1005 switches to the MAC-based cell through the serving cell/serving TRP (1002-1, 1002-2) or target cell/target TRP (1003). A /TRP/beam switching response message can be transmitted to the terminal 1004. The MAC-based cell/TRP/beam switching response message may be a MAC-based cell/TRP/beam switching indication message or a MAC-based cell/TRP/beam switching allow message. The MAC-based cell/TRP/beam switching response message may indicate performance of MAC-based cell/TRP/beam switching.

The MAC-based cell/TRP/beam switching request message transmitted by the terminal 1004 in S1006 may be a physical layer signal and/or MAC CE (eg, L2 (layer2) message, MAC message). A physical layer signal (e.g., layer1 (L1) message, PHY message) may be at least one of an RA preamble, a scheduling request, or an uplink reference signal (e.g., SRS). The RA preamble may be an RA preamble in a 4-step RA procedure and/or an RA preamble in a 2-step RA procedure. The scheduling request may be a separately set scheduling request to request MAC-based cell/TRP/beam switching. MAC CE may be an L2 message in the RA procedure. The L2 message may be Msg3 in a 4-step RA procedure or MsgA payload (e.g., MsgA-PUSCH) in a 2-step RA procedure. Alternatively, the MAC CE may be a MAC CE set separately to request MAC-based cell/TRP/beam switching.

Radio resources for transmission of MAC-based cell/TRP/beam switching request messages (e.g., physical layer signals and/or MAC CE) are provided to the terminal (1004) after the RRC connection (re)establishment procedure of S1001 and/or S1001. ) can be pre-allocated in the RRC connection re-establishment procedure. When transmission of the MAC-based cell/TRP/beam switching request message is performed based on the RA procedure, the terminal 1004 sends the MAC-based cell/TRP/beam switching request message according to the CFRA (contention free random access) method. To enable transmission, the base station 1001 may transmit RACH configuration information to the terminal 1004. The transmission operation of RACH configuration information may be performed in S1001. RACH configuration information may include RO (RA occasion) resource information, and RA resource information may include an RA preamble index. For MAC-based cell/TRP/beam switching procedures, the base station 1001 can allocate and deliver CFRA-type RACH configuration information for multiple cells to the terminal 1004.

If the MAC-based cell/TRP/beam switching request message is a physical layer signal, the base station 1001 may allocate radio resources for transmission of the physical layer signal to the terminal 1004. An allocation operation of radio resources for transmission of physical layer signals may be performed in S1001. Allocation information of radio resources for transmission of physical layer signals includes an index for identifying physical layer signals, time resource allocation information for transmission of physical layer signals, and/or frequency resource allocation information for transmission of physical layer signals. can do.

If CFRA resources and/or physical layer signal resources for transmission of the MAC-based cell/TRP/beam switching request message are not allocated, the terminal 1004 performs S1006 using a content-based random access (CBRA) procedure. It can be done. In this case, the MAC-based cell/TRP/beam switching request message may be at least one of Msg3 in the 4-step RA procedure, MsgA-payload (e.g., MsgA-PUSCH) in the 2-step RA procedure, or MAC CE. . The MAC CE may be a MAC CE set separately for MAC-based cell/TRP/beam switching requests. In S1006, the MAC-based cell/TRP/beam switching request message may include a scheduling identifier (eg, cell-radio network temporary identifier (C-RNTI)) assigned to the terminal 1004. If the preset conditions are satisfied, the terminal 1004 may transmit a MAC-based cell/TRP/beam switching request message in S1006. Conditions for transmission of the MAC-based cell/TRP/beam switching request message may be transmitted to the terminal 1004 through system information and/or RRC connection (re)establishment message. The RRC connection (re)establishment message may be transmitted in S1001. Conditions for transmission of the MAC-based cell/TRP/beam switching request message may include one or more conditions listed in Table 2 above.

DU 1005 may receive a MAC-based cell/TRP/beam switching request message from UE 1004. The DU 1005 may determine whether to perform MAC-based cell/TRP/beam switching at the request of the UE 1004 (S1007). If it is determined in S1007 that MAC-based cell/TRP/beam switching is performed, the DU 1005 sends a control message (e.g., control information) indicating that MAC-based cell/TRP/beam switching is performed to the base station ( 1001) (or, CU (1001-1)) (S1008). The control message transmitted in S1008 may include information about the terminal 1004 and/or cell/TRP/beam change information.

If it is determined in S1007 that MAC-based cell/TRP/beam switching is performed, the DU 1005 may transmit a response message indicating performance of MAC-based cell/TRP/beam switching to the UE 1004 (S1009) ). If S1006 is performed based on the CFRA procedure or CBRA procedure, the MAC-based cell/TRP/beam switching response message in S1009 may be an RA response message. The MAC-based cell/TRP/beam switching response message may include information indicating whether MAC-based cell switching is permitted. If it is determined in S1007 that MAC-based cell/TRP/beam switching is not performed, the DU 1005 sends a MAC-based cell/TRP/beam switching response message indicating rejection of the MAC-based cell/TRP/beam switching request. It can be transmitted to the terminal 1004 (S1009).

In S1009, the MAC-based cell/TRP/beam switching response message may be transmitted to the terminal 1004 through the serving cell/serving TRP (1002-1, 1002-2) or the target cell/target TRP (1003). In S1009, when the MAC-based cell/TRP/beam switching response message is transmitted to the terminal 1004 through the serving cell/serving TRP (1002-1, 1002-2), the MAC-based cell/TRP/beam switching response The message may be transmitted to the terminal 1004 using the scheduling identifier assigned in the serving cell 1002-1 and 1002-2. The MAC-based cell/TRP/beam switching response message may be DCI.

Alternatively, in S1009, the MAC-based cell/TRP/beam switching response message may be transmitted to the terminal 1004 through the target cell/target TRP 1003. When the MAC-based cell/TRP/beam switching response message is transmitted in the form of an RA response message, the MAC-based cell/TRP/beam switching response message is transmitted to the target cell/target TRP (1003) assigned to the terminal (1004). It may include a scheduling identifier. If the MAC-based cell/TRP/beam switching response message is transmitted to the terminal 1004 through the target cell/target TRP (1003) in a form different from the RA response message, the scheduling identifier of the target cell/target TRP (1003) is It may be pre-allocated to the terminal 1004 in “S1001” and/or “step in which it is determined to support the multi-TRP function for the terminal 1004.” If the scheduling identifier of the target cell/target TRP 1003 is pre-assigned to the UE 1004, the DU 1005 targets a MAC-based cell/TRP/beam switching response message using the pre-assigned scheduling identifier in S1009. It can be transmitted through cell/target TRP (1003).

In S1009, the UE 1004 may receive a MAC-based cell/TRP/beam switching response message (e.g., a message instructing performance of MAC-based cell/TRP/beam switching) from the DU 1005. In this case, the terminal 1004 may release resources (e.g., radio resources) set for the serving cell/serving TRP (1002-1, 1002-2) and for the target cell/target TRP (1003). Communication can be performed with the target cell/target TRP (1003) using set resources (or scheduled resources) (S1010). In other words, in S1010, the target cell/target TRP (1003) can provide a service to the terminal (1004). The target cell/target TRP 1003 may operate as a serving cell/serving TRP for the terminal 1004 in S1010.

8 to 10, the DU may perform at least one of a cell change operation, a TRP change operation, and a beam change operation based on a request from the terminal and/or a measurement result report from the terminal. In this case, the setting value(s) of MAC layer parameters and/or variables in the MAC entity for the terminal may be synchronized. Alternatively, the setting value(s) of MAC layer parameters and/or variables in the MAC entity for the terminal may have continuity. In other words, the setting value(s) of MAC layer parameters and/or variables in the MAC entity for the terminal may be maintained. Each of the cell change operation, TRP change operation, and beam change operation may be performed based on MAC.

The setting value(s) of parameters and/or variables set on a cell basis by the RRC layer may be reset. At S805, S906, or S1007, the DU may decide to change the cell, TRP, and/or beam. The cell, TRP, and/or beam change operation in S805, S906, or S1007 may be a MAC-based change operation (eg, switching operation). The DU may transmit information related to changes in cells, TRPs, and/or beams to a base station (eg, CU) (S806, S907, S1008).

When each of S806, S907, and S1008 is performed, cell-level configuration parameter(s), RRC layer parameter(s), and/or L1/L2 layer for the UE between the DU and the base station (e.g., CU) Parameters of (e.g., PHY layer, MAC layer, RLC layer) may be newly set. The DU may transmit a control message (e.g., a separate control message) containing newly set parameters to the terminal. The control message may direct switching of cells, TRPs, and/or beams. The switching operation indicated by the control message may be a MAC-based switching operation.

In the cell, TRP, and/or beam switching operation (eg, MAC-based switching operation) described in FIGS. 8 to 10, one MAC entity may be set in the terminal. The switching operation may be for supporting and operating the multi-TRP function.

While the terminal is performing a switching operation to a TRP (or beam) belonging to another base station and/or another cell, an improved TRP/beam switching method may be required to provide service without packet loss. For one terminal that does not have the DC function configured, a switching operation using two MAC entity configurations can be considered.

The two MAC entities set in a terminal that does not support the DC function are primary-MAC (or, active-MAC) and candidate-MAC (or, inactive-MAC). , may include configured (MAC). Primary-MAC may be referred to as P-MAC, and candidate-MAC may be referred to as c-MAC. P-MAC may be a MAC entity configured (or created) for serving cell/serving TRP/serving beam. c-MAC may be a MAC entity configured (or created) for target cell/target TRP/target beam.

P-MAC may be generated at the stage when an RRC connection is established or configured between a terminal and a base station (eg, CU). c-MAC can be created at the stage where multi-TRP function support and RRC connection re-establishment for the terminal are performed.

Simultaneous activation of P-MAC and c-MAC for one terminal may be restricted. In other words, simultaneous operation of P-MAC and c-MAC for one terminal may be restricted. In this case, a terminal supporting the multi-TRP function can perform the control function of the MAC layer based on one MAC entity among the two MAC entities.

Alternatively, a method in which P-MAC and c-MAC are activated (e.g., operated) together during a preset time period (e.g., a timer operation period) may be applied. For example, P-MAC for a serving cell/serving TRP/serving beam is “after completion of the cell/TRP/beam switching operation” or “when the resources of the serving cell/serving TRP/serving beam for the UE are released. “It can be lifted. c-MAC for target cell/target TRP/target beam can be activated at the point when the cell/TRP/beam switching operation to target cell/target TRP/target beam is triggered. In other words, c-MAC for target cell/target TRP/target beam can operate at the point when the cell/TRP/beam switching operation to target cell/target TRP/target beam is triggered. The point at which the cell/TRP/beam switching operation is triggered is “when the UE transmits a cell/TRP/beam switching request message,” and “when the base station (e.g., DU) receives a cell/TRP/beam switching request message from the UE.” It may be “a point in time at which a base station (e.g., DU) transmits a cell/TRP/beam switching response message (e.g., a message instructing cell/TRP/beam switching).”

To support multi-TRP functionality, the two MAC entities can be created and MAC-based cell/TRP/beam switching operations can be performed. In this case, the setting values of MAC layer parameters and/or variables between P-MAC and c-MAC may be synchronized. In other words, in setting MAC layer parameters and/or variables between P-MAC and c-MAC, scheduling identifier (e.g., RNTI-based identifier such as C-RNTI), HARQ identifier, logical channel identifier, and TCI state setting. The initial settings of c-MAC for parameter and variable settings of information, and/or PUCCH/CORESET (CORESET) setting parameter value(s), etc. may be copy-assigned from P-MAC or maintained at the same value without change. The setting value(s) of parameters and/or variables set on a cell basis by the RRC layer may be reset.

In this disclosure, the wireless channel quality may be CSI, RSSI, RSRP, RSRQ, and/or SINR. Measurement results can be defined or explained based on wireless channel quality. Starting, stopping, resetting, restarting, and/or expiring a timer may mean or include a counter operation for the timer. A terminal is a UE, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, and IoT (Internet of Thing). ) may be referred to as a device, and/or a mounted device (mounted module, mounted device, mounted terminal, on board device, on board terminal).

The operation of the method according to the embodiment of the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. Computer-readable recording media include all types of recording devices that store information that can be read by a computer system. Additionally, computer-readable recording media can be distributed across networked computer systems so that computer-readable programs or codes can be stored and executed in a distributed manner.

Additionally, computer-readable recording media may include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, or flash memory. Program instructions may include not only machine language code such as that created by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

Although some aspects of the disclosure have been described in the context of an apparatus, it may also refer to a corresponding method description, where a block or device corresponds to a method step or feature of a method step. Similarly, aspects described in the context of a method may also be represented by corresponding blocks or items or features of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, programmable computer, or electronic circuit. In some embodiments, at least one or more of the most important method steps may be performed by such an apparatus.

In embodiments, a programmable logic device (e.g., a field programmable gate array) may be used to perform some or all of the functionality of the methods described herein. In embodiments, a field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. In general, the methods are preferably performed by some hardware device.

Although the present disclosure has been described above with reference to preferred embodiments, those skilled in the art may modify and change the present disclosure in various ways without departing from the spirit and scope of the present disclosure as set forth in the claims below. You will understand that it is possible.

Claims (20)

As a terminal method,
performing a measurement operation on a wireless channel;
Transmitting the result of the measurement operation to a serving cell;
Receiving a cell switching indication message from the serving cell; and
Comprising communicating with a target cell based on the cell switching indication message,
The cell switching operation according to the cell switching instruction message is a medium access control (MAC)-based cell switching operation without radio resource control (RRC) reset.
Terminal method. In claim 1,
Each of the serving cell and the target cell includes one or more transmission and reception points (TRPs), and the serving cell and the target cell belong to the same base station or different base stations.
Terminal method. In claim 1,
The cell switching operation means a TRP switching operation or a beam switching operation,
Terminal method. In claim 1,
The method of the terminal is,
Further comprising receiving a cell switching list from the base station to which the serving cell belongs,
The measurement operation is performed on one or more cells indicated by the cell switching list,
Terminal method. In claim 4,
The cell switching list includes at least one of a cell identifier, a TRP identifier, a beam identifier, or a transmission configuration indicator (TCI) state identifier.
Terminal method. In claim 1,
The method of the terminal is,
Further comprising transmitting a cell switching request message to the target cell after performing the measurement operation,
The cell switching request message is transmitted together with the result of the measurement operation or is transmitted after transmission of the result of the measurement operation, and the cell switching request message is an L1 (layer1) message or an L2 (layer2) message,
Terminal method. In claim 6,
The L1 message is a random access (RA) preamble, scheduling request, or uplink reference signal,
Terminal method. In claim 6,
The L2 message is Msg3 in the 4-step RA procedure or MsgA payload in the 2-step RA procedure,
Terminal method. In claim 6,
Radio resources for transmission of the cell switching request message are pre-allocated in the RRC connection establishment procedure or RRC connection re-establishment procedure between the base station to which the serving cell belongs and the terminal.
Terminal method. In claim 1,
The cell switching indication message is a MAC control element (CE) or downlink control information (DCI),
Terminal method. In claim 1,
The cell switching indication message includes information instructing the performance of an operation for acquiring uplink timing, information on the uplink timing, scheduling information, an identifier of the target cell, an identifier of a target TRP associated with the target cell, and information on the uplink timing. Containing at least one of an identifier of a target beam or an identifier of a serving beam associated with the serving cell,
Terminal method. In claim 1,
The method of the terminal is,
When the cell switching indication message is received, further comprising performing an operation to obtain uplink timing for the target cell,
Terminal method. As a method of a base station,
Receiving a result of a measurement operation for a wireless channel from a terminal;
determining whether to perform a cell switching operation based on the result of the measurement operation; and
When it is determined that the cell switching operation is performed, transmitting a cell switching indication message to the terminal,
The result of the measurement operation is received in a serving cell belonging to the base station, the cell switching indication message is transmitted by the serving cell, the serving cell includes one or more transmission and reception points (TRPs), and the cell The switching operation is a medium access control (MAC)-based cell switching operation without radio resource control (RRC) reset.
Base station method. In claim 13,
The method of the base station is,
Further comprising transmitting a cell switching list to the terminal,
The measurement operation of the terminal is performed on one or more cells indicated by the cell switching list,
Base station method. In claim 14,
The cell switching list includes at least one of a cell identifier, a TRP identifier, a beam identifier, or a transmission configuration indicator (TCI) state identifier.
Base station method. In claim 13,
The method of the base station is,
Further comprising receiving a cell switching request message from the terminal,
The cell switching request message is an L1 (layer1) message or an L2 (layer2) message,
Base station method. In claim 16,
The L1 message is a random access (RA) preamble, scheduling request, or uplink reference signal, and the L2 message is Msg3 in the 4-step RA procedure or MsgA payload in the 2-step RA procedure,
Base station method. In claim 16,
Radio resources for transmission of the cell switching request message are pre-allocated in the RRC connection establishment procedure or RRC connection re-establishment procedure between the base station and the terminal.
Base station method. In claim 13,
The cell switching indication message is a MAC control element (CE) or downlink control information (DCI),
Base station method. In claim 13,
The cell switching indication message includes information instructing the performance of an operation for acquiring uplink timing, information on the uplink timing, scheduling information, an identifier of the target cell, an identifier of a target TRP associated with the target cell, and information on the uplink timing. Containing at least one of an identifier of a target beam or an identifier of a serving beam associated with the serving cell,
Base station method.

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