KR20220143441A - Method and apparatus for conditional reconfiguration in wireless communication system - Google Patents

Abstract

A method for conditional reconfiguration performed in a first communication node of a wireless communication system according to an embodiment of the present invention includes the steps of: performing cell monitoring in a predetermined communication coverage area; transmitting a cell monitoring result report signal to a serving base station, which includes information on one or more target cells identified based on the cell monitoring; receiving a reconfiguration instruction signal from the serving base station, which includes information on one or more candidate cells for which conditional handover is approved among the one or more target cells; if multiple cells having an average reception quality equal to or greater than a first threshold are identified in monitoring the one or more candidate cells, selecting one first final cell from the multiple identified cells based on each beam reception quality; and performing handover to the selected first final cell. According to the present invention, the communication node may efficiently perform a conditional reconfiguration procedure through monitoring of communication environments.

Description

CONDITIONAL RECONFIGURATION IN WIRELESS COMMUNICATION SYSTEM

The present invention relates to a method and apparatus for conditional reconfiguration in a wireless communication system, and more particularly, to a method and apparatus for conditional reconfiguration for efficiently performing a conditional reconfiguration procedure through monitoring a communication environment in a communication node.

With the development of information and communication technology, various wireless communication technologies are being developed. Representative wireless communication technologies include long term evolution (LTE) and new radio (NR) defined in 3rd generation partnership project (3GPP) standards. LTE may be one of 4G (4th Generation) wireless communication technologies, and NR may be one of 5G (5th Generation) wireless communication technologies.

For the processing of wireless data rapidly increasing after the commercialization of a 4G communication system (eg, a communication system supporting LTE), a frequency band of a 4G communication system (eg, a frequency band of 6 GHz or less) as well as a 4G communication system A 5G communication system (eg, a communication system supporting NR) using a frequency band higher than the frequency band of (eg, a frequency band of 6 GHz or more) is being considered. The 5G communication system may support enhanced Mobile BroadBand (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC).

In an embodiment of the communication system, a handover (HO) may be performed from a serving base station to which a communication node such as a terminal is currently connected to another base station. The handover may be conditionally performed based on a preset specific condition. The serving base station may support or control the conditional reconfiguration procedure including such conditional handover operation. A technique for efficiently performing a conditional reconfiguration procedure based on a control signal exchange between a communication node and a serving base station may be required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a conditional reconfiguration method and apparatus for efficiently performing a conditional reconfiguration procedure through monitoring of a communication environment in a communication node.

Conditional reconfiguration method performed in a first communication node of a wireless communication system according to an embodiment of the present invention for achieving the above object, performing cell monitoring in a predetermined communicable area, check according to the cell monitoring Transmitting a cell monitoring result report signal including information of one or more target cells to a serving base station, a reconfiguration indication signal including information on one or more candidate cells for which conditional handover is approved among the one or more target cells Receiving from a serving base station, when a plurality of cells having an average reception quality equal to or greater than the first threshold are identified in monitoring the one or more candidate cells, one of the identified plurality of cells is selected based on each beam reception quality. It may include selecting a first last cell, and performing handover to the selected first last cell.

According to an embodiment of the present invention, a communication node such as a terminal and/or a base station may perform a conditional reconfiguration procedure through monitoring a communication environment. As a result of monitoring the communication environment, when a plurality of candidate cells satisfying the conditional reconfiguration condition are identified, one cell may be selected based on the beam reception quality. Accordingly, the conditional reconstruction operation can be performed more efficiently.

1 is a conceptual diagram illustrating an embodiment of a communication system.
2 is a block diagram illustrating an embodiment of a communication node constituting a communication system.
3 is a flowchart illustrating a first embodiment of a conditional reconfiguration procedure in a communication system.
4 is a flowchart illustrating a second embodiment of a conditional reconfiguration procedure in a communication system.
5 is a conceptual diagram for explaining an embodiment of a method of monitoring one or more candidate cells in a communication system.
6A and 6B are graphs for explaining an embodiment of a method of measuring beam reception strength and cell reception strength while monitoring one or more candidate cells in a communication system.
7 is a flowchart illustrating a third embodiment of a conditional reconfiguration procedure in a communication system.
8 is a graph for explaining an embodiment of a method for measuring a base station signal in a communication system.
9A and 9B are graphs for explaining an embodiment of a method of selecting one cell from among a plurality of cells satisfying a reconfiguration condition in a communication system.

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

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

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

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

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

Throughout the specification, a network is, for example, a wireless Internet such as WiFi (wireless fidelity), a wireless broadband internet (WiBro) or a portable Internet such as a world interoperability for microwave access (WiMax), a global system for mobile communication (GSM). ) or 2G mobile communication networks such as code division multiple access (CDMA), wideband code division multiple access (WCDMA) or 3G mobile networks such as CDMA2000, high speed downlink packet access (HSDPA) or high speed uplink packet access (HSUPA) such as It may include a 3.5G mobile communication network, a 4G mobile communication network such as a long term evolution (LTE) network or an LTE-Advanced network, and a 5G mobile communication network.

Throughout the specification, a terminal is a mobile station, a mobile terminal, a subscriber station, a portable subscriber station, a user equipment, and an access terminal. and the like, and may include all or some functions of a terminal, a mobile station, a mobile terminal, a subscriber station, a portable subscriber station, a user equipment, an access terminal, and the like.

Here, a desktop computer that can communicate with a terminal, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, a smart watch (smart watch), smart glass, e-book reader, PMP (portable multimedia player), portable game console, navigation device, digital camera, DMB (digital multimedia broadcasting) player, digital voice Digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player ) can be used.

Throughout the specification, a base station is an access point, a radio access station, a Node B, an advanced nodeB, a base transceiver station, MMR ( It may refer to mobile multihop relay)-BS, and the like, and may include all or some functions of a base station, an access point, a wireless access station, a Node B, an eNodeB, a transceiver base station, and an MMR-BS.

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

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

1, the communication system 100 is 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 is a core network (core network) (eg, S-GW (serving-gateway), P-GW (packet data network (PDN)-gateway), MME (mobility management entity)) may include more.

The plurality of communication nodes may support 4G communication (eg, long term evolution (LTE), advanced (LTE-A)), 5G communication, etc. defined in a 3rd generation partnership project (3GPP) standard. 4G communication may be performed in a frequency band of 6 GHz or less, and 5G communication may be performed in a frequency band of 6 GHz or more as well as a frequency band of 6 GHz or less. For example, a plurality of communication nodes for 4G communication and 5G communication is a CDMA (code division multiple access) based communication protocol, WCDMA (wideband CDMA) based communication protocol, TDMA (time division multiple access) based communication protocol, FDMA (frequency division multiple access) based communication protocol, OFDM (orthogonal frequency division multiplexing) based communication protocol, Filtered OFDM based communication protocol, CP (cyclic prefix)-OFDM based communication protocol, DFT-s-OFDM (discrete) Fourier transform-spread-OFDM) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (Non-orthogonal multiple access), GFDM (generalized frequency) Division multiplexing)-based communication protocol, FBMC (filter bank multi-carrier)-based communication protocol, UFMC (universal filtered multi-carrier)-based communication protocol, SDMA (Space Division Multiple Access)-based communication protocol, etc. can be supported. . Each of the plurality of communication nodes may have the following structure.

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

Referring to FIG. 2 , the communication node 200 may include at least one processor 210 , a memory 220 , and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240 , an output interface device 250 , a storage device 260 , and the like. Each of the components included in the communication node 200 may be connected by a bus 270 to communicate with each other. However, each of the components included in the communication node 200 may not be connected to the common bus 270 but to the processor 210 through an individual interface or an individual bus. For example, the processor 210 may be connected to at least one of the memory 220 , the transceiver 230 , the input interface device 240 , the output interface device 250 , and the storage device 260 through a dedicated interface. .

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

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

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 is a NodeB, an evolved NodeB, gNB, ng-eNB, BTS. (base transceiver station), radio base station (radio base station), radio transceiver (radio transceiver), access point (access point), access node (node), RSU (road side unit), RRH (radio remote head), TP ( It may be referred to as a transmission point), a transmission and reception point (TRP), a flexible (f)-TRP, and the like. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 includes a user equipment (UE), a terminal, an access terminal, and a mobile terminal. Terminal (mobile terminal), station (station), subscriber station (subscriber station), mobile station (mobile station), portable subscriber station (portable subscriber station), node (node), device (device), Internet of things (IoT) It may be referred to as a device supporting a function, a mounted module/device/terminal, an on board unit (OBU), or the like.

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, and 120-2 transmits a signal received from the core network to the corresponding terminals 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 transmitted to the core network can be sent to

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits MIMO (eg, 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)), and the like. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 is the base station 110-1, 110-2, 110-3, and 120-1. , 120-2) and operations supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be performed. For example, the second base station 110-2 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 based on the SU-MIMO method. A signal may be received from the second base station 110 - 2 . Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO scheme, and the fourth terminal 130-4. and each of the fifth terminals 130 - 5 may receive a signal from the second base station 110 - 2 by the MU-MIMO method.

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on the CoMP method, and the fourth The terminal 130-4 may receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 by the CoMP method. A plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) each of the terminals (130-1, 130-2, 130-3, 130-4) belonging to its own cell coverage , 130-5, 130-6) and the CA method can transmit and receive signals. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 controls D2D between the fourth terminal 130-4 and the fifth terminal 130-5. and each of the fourth terminal 130-4 and the fifth terminal 130-5 may perform D2D under the control of the second base station 110-2 and the third base station 110-3, respectively. .

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may emit a single beam or a multi-beam to form cell coverage. For example, a base station operating a relatively low frequency band (eg, 2.8 GHz band, etc.) may form and provide coverage of a relatively wide area by forming one beam. Meanwhile, a base station operating a relatively high frequency band (eg, a 28 GHz band, etc.) may form a plurality of beams to secure cell coverage.

Meanwhile, in a communication system, a base station may perform all functions of a communication protocol (eg, a remote radio transmission/reception function, a baseband processing function). Alternatively, a remote radio transmission/reception function among all functions of a communication protocol may be performed by a transmission reception point (TRP) (eg, f(flexible)-TRP), and a baseband processing function among all functions of a communication protocol may be performed by a baseband unit (BBU) block. The TRP may be a remote radio head (RRH), a radio unit (RU), or a transmission point (TP). The BBU block may include at least one BBU or at least one digital unit (DU). A BBU block may be referred to as a “BBU pool”, “centralized BBU”, or the like. The TRP may be connected to the BBU block through a wired fronthaul link or a wireless fronthaul link. A communication system composed of a backhaul link and a fronthaul link may be as follows. When the function split technique of the communication protocol is applied, the TRP may selectively perform some functions of the BBU or some functions of the MAC/RLC.

3 is a flowchart illustrating a first embodiment of a conditional reconfiguration procedure in a communication system.

Referring to FIG. 3 , the communication system 300 may include a first communication node 310 and a second communication node 320 . The first and second communication nodes 310 and 320 of the communication system 300 may be the same as or similar to the communication node, base station, and/or terminal described with reference to FIGS. 1 and/or 2 . For example, the first communication node 310 may correspond to a terminal or user equipment (UE), and the second communication node 320 may correspond to a base station.

In an embodiment, the second communication node 320 may correspond to a serving base station to which the first communication node 310 is connected. The first communication node 310 may perform communication by accessing the second communication node 320 , or may perform handover (HO) to another communication node (eg, a base station). The handover may be conditionally performed based on a preset specific condition. This may be referred to as 'conditional handover' (CHO). Alternatively, the first communication node 310 may perform reconfiguration or reconfiguration of a connection with a higher node including the second communication node 320 . Here, reconfiguration may include the same or similar operations to handover, or a series of operations for performing procedures such as handover. Reconfiguration may be conditionally performed based on a preset specific condition. This can be called 'conditional reconstruction'.

The second communication node 320 may support or control the conditional reconfiguration procedure of the first communication node 310 . The second communication node 320 may transmit a first monitoring instruction signal to the first communication node 310 (S340). The first monitoring indication signal may correspond to, for example, a signal for instructing the first communication node 310 to perform monitoring for searching for a target base station to perform conditional reconfiguration. For example, the first monitoring indication signal may be referred to as a 'measurement configuration' signal. The first monitoring indication signal may include information for operations such as channel measurement, cell measurement, and cell monitoring, or information on a measurement event. For example, the first monitoring indication signal may include information on a first discovery threshold, which is a reference for searching a target base station.

The first communication node 310 may receive the first monitoring instruction signal (S340). The first communication node 310 may perform cell monitoring within a predetermined communication area based on the received first monitoring indication signal (S345). This may be referred to as 'neighbor cell monitoring'. In neighboring cell monitoring, signal reception quality or strength of neighboring base stations (eg, RSRP, RSRQ, RSSI, etc.) may be monitored. The first communication node 310 may compare the monitored reception quality information with the first discovery threshold. A cell whose reception quality is equal to or greater than the first search threshold may be classified as a target cell. 3 illustrates a situation in which one target cell is identified as a result of one monitoring.

The first communication node 310 may transmit the first result report signal including the monitoring result to the second communication node 320 ( S350 ). The first result report signal may be referred to as a 'measurement report'. The first result report signal may include information on the target cell or information on the first target node 330 corresponding to the base station of the target cell.

The second communication node 320 may check information of the first target node 330 based on the first result report signal. The second communication node 320 may transmit a conditional handover request signal to the first target node 330 (S355). The first target node 330 may determine whether to approve (or accept) the conditional handover based on the received conditional handover request signal (S360). In order to determine whether to grant conditional handover permission, an admission control operation, a congestion control operation, and the like may be performed.

After determining whether to approve the conditional handover, the first target node 330 may transmit the determined item to the second communication node 320 indicating the decision (S365). The first target node 330 may transmit a 'conditional handover response signal' indicating whether to approve the conditional handover to the second communication node 320 . For example, when the first target node 330 determines to approve the conditional handover, information indicating that the conditional handover is approved may be included in the conditional handover response signal to transmit the conditional handover response signal to the second communication node 320 . Meanwhile, when the first target node 330 determines not to approve the conditional handover, information indicating that the conditional handover is rejected may be included in the conditional handover response signal and transmitted to the second communication node 320 . The conditional handover response signal may be referred to as a 'conditional handover request ack' signal. When the conditional handover is approved, the conditional handover response signal may further include information related to the first target node 330 or the first target cell. For example, the conditional handover response signal may further include an RRC container containing first target cell configuration information such as new C-RNTI, security information, SIB information, and/or a dedicated RACH preamble.

The second communication node 320 may check whether the conditional handover is approved in the first target node 330 based on the conditional handover response signal. When the conditional handover is rejected, the conditional handover procedure may be terminated. Meanwhile, when the conditional handover is approved, the second communication node 320 may transmit a 'conditional reconfiguration indication signal' instructing to perform the conditional reconfiguration to the first communication node 310 (S370). The 'conditional reconfiguration indication signal' may also be referred to as a 'conditional HO command'. The conditional reconfiguration indication signal may include information on one or more conditions for executing a handover and/or reconfiguration operation (hereinafter, 'first execution condition'). The first execution condition may be based on a received signal quality, such as from the first target node 330 or the second communication node 320 , or the like (eg, compared to a first execution threshold), or a time elapsed. It may also be based on a degree (eg, a time-to-trigger (TTT) parameter, etc.). The first execution condition may also be referred to as a 'CHO execution condition'. The conditional reconfiguration indication signal may include information in the same or similar format as the first monitoring indication signal or the measurement configuration signal transmitted in step S340.

The conditional reconfiguration indication signal may include specific configuration information required for the first communication node 310 to perform reconfiguration when the first execution condition is satisfied. For example, the conditional reconfiguration indication signal may further include information (eg, first target cell related information, etc.) included in the conditional handover response signal transmitted from the first target node 330 .

The first communication node 310 may receive a conditional reconfiguration indication signal from the second communication node 320 (S370). The first communication node 310 may check the first execution condition included in the received conditional reconfiguration indication signal. The first communication node 310 may perform candidate cell monitoring based on the checked first execution condition (S375). In an embodiment, when the target base station approves the conditional handover, the target base station may be regarded as a candidate base station and the target cell may be regarded as a candidate cell. The first communication node 310 may monitor whether the first execution condition is satisfied (or satisfied) with respect to the first candidate cell corresponding to the existing first target cell. When it is confirmed that the first execution condition is satisfied during monitoring, the first communication node 310 may perform a handover (S380). When it is confirmed that the first execution condition is satisfied during monitoring, the first communication node 310 performs a handover immediately without transmitting a report on the measurement result to the second communication node 320 or the first candidate node. can

The first communication node 310 may attempt handover to the first candidate cell (S385). That is, the first communication node 310 may perform operations for accessing the first candidate base station instead of the second communication node 320 . The first communication node 310 may acquire synchronization with the first candidate base station to perform handover and attempt a random access (RA) connection.

When the access to the first candidate base station is successful, the first communication node 310 may transmit a reconfiguration completion report signal to the first candidate base station (S390). The reconfiguration completion report signal may also be referred to as an 'RRCReconfigurationComplete' signal (or message). Upon receiving the reconfiguration completion report signal, the first candidate node may execute a path switch and a terminal context release procedure (S395). Accordingly, a series of procedures for conditional reconfiguration of the first communication node 310 may be completed.

4 is a flowchart illustrating a second embodiment of a conditional reconfiguration procedure in a communication system.

Referring to FIG. 4 , the communication system 400 may include a first communication node 410 and a second communication node 420 . The first and second communication nodes 410 and 420 of the communication system 400 may be the same as or similar to the communication node, base station, and/or terminal described with reference to FIGS. 1 and/or 2 . The first and second communication nodes 410 and 420 of the communication system 400 may be the same as or similar to the first and second communication nodes 310 and 320 described with reference to FIG. 3 , respectively. For example, the first communication node 410 may correspond to a terminal or user equipment (UE), the second communication node 420 may correspond to a base station, and in particular, the second communication node 420 may It may correspond to a serving base station to which the first communication node 410 is connected. Hereinafter, in describing a second embodiment of a conditional reconfiguration procedure in a communication system with reference to FIG. 4 , the content overlapping with that previously described with reference to FIG. 3 may be omitted.

The first communication node 410 may receive a first monitoring instruction signal from the second communication node 420 (S440), and perform cell monitoring within a predetermined communication area based on the received first monitoring instruction signal. There is (S445). The first communication node 410 may compare the reception quality information confirmed in cell monitoring with a preset first discovery threshold. A cell whose reception quality is equal to or greater than the first search threshold may be classified as a target cell. 4 illustrates a situation in which a plurality of target cells are identified as a result of monitoring. A plurality of identified target cells may be referred to as a first target cell, ... , and an nth target cell. Base stations such as the first target cell, ..., and the nth target cell may be referred to as the first target base station 430-1, ..., and the nth target base station. The first target base station 430-1, ..., and the n-th target base station 430-n with the first target node 430-1, ..., and the n-th target node 430-n can be called together.

The first communication node 410 may transmit the first result report signal including the monitoring result to the second communication node 420 (S450). The first result report signal may include information on one or more target cells whose reception quality is equal to or greater than the first discovery threshold. Alternatively, the first result report signal may include information on one or more target nodes 430 - 1 , ... 430 - n corresponding to a base station of each of one or more target cells. Here, the one or more target nodes 430-1, ... 430-n may include first to n-th target nodes 430-1, ... 430-n. The second communication node 420 may check information of one or more target nodes 430 - 1 , ... 430 - n based on the first result report signal. The second communication node 420 may transmit a conditional handover request signal to one or more target nodes 430-1, ... 430-n (S455-1, ... S455). -n). One or more target nodes 430-1, ... 430-n may determine whether to approve (or accept) conditional handover based on the received conditional handover request signal (S460-1 ... S460- n). In order to determine whether to approve conditional handover, admission control operation and congestion control operation may be performed. After determining whether to approve the conditional handover, one or more target nodes 430-1, ... 430-n may transmit the determined item to the second communication node 420 indicating the decision (S465-1, ... 430-n). S465-n). One or more target nodes 430 - 1 , ... 430 - n may transmit a 'conditional handover response signal' indicating whether to approve the conditional handover to the second communication node 420 . For example, when the one or more target nodes 430 - 1 , ... 430 - n decide to approve the conditional handover, the conditional handover response signal includes information indicating that the conditional handover is approved in the second communication can be transmitted to node 420 . On the other hand, if one or more target nodes 430-1, ... 430-n decide not to approve the conditional handover, the conditional handover response signal includes information indicating that the conditional handover is rejected in the second communication can be transmitted to node 420 . The conditional handover response signal may be referred to as a 'conditional handover request ack' signal. The conditional handover response signal transmitted from the target node that has approved the conditional handover among the one or more target nodes 430-1, ... 430-n includes information on the target node that has approved the conditional handover or conditional handover. It may further include information related to the target cell corresponding to the cell of the target node that has approved . For example, the conditional handover response signal may further include an RRC container containing configuration information for a target cell for which conditional handover is approved, such as new C-RNTI, security information, SIB information, and/or dedicated RACH preamble. .

Based on the conditional handover response signal, the second communication node 420 may identify a target node to which the conditional handover is approved among one or more target nodes 430 - 1 , ... 430 - n . When the conditional handover is rejected by all of the one or more target nodes 430-1, ... 430-n, the conditional handover procedure may be terminated. On the other hand, when conditional handover is approved in some or all of the one or more target nodes 430-1, ... 430-n, the second communication node 420 performs a 'conditional reconfiguration' instructing to perform conditional reconfiguration. An indication signal' may be transmitted to the first communication node 410 (S470). The 'conditional reconfiguration indication signal' may also be referred to as a 'conditional HO command'. The conditional reconfiguration indication signal may include information on one or more conditions for executing a handover and/or reconfiguration operation (hereinafter, 'first execution condition'). The first execution condition may be based, for example, on a received signal quality from one or more target nodes 430 - 1 , ... 430 - n or the second communication node 420 , etc. (eg, a first execution threshold). value), or the degree of time elapsed (eg, a time-to-trigger (TTT) parameter, etc.). The first execution condition may also be referred to as a 'CHO execution condition'.

The conditional reconfiguration indication signal may include specific configuration information for performing reconfiguration when the first execution condition is satisfied. For example, the conditional reconfiguration indication signal may further include information (eg, information related to the first target cell, etc.) included in the conditional handover response signal transmitted from one or more target nodes that have approved the conditional handover.

The first communication node 410 may receive a conditional reconfiguration indication signal from the second communication node 420 (S470). The first communication node 410 may check one or more execution conditions for one or more target nodes that have approved the conditional handover, included in the received conditional reconfiguration indication signal. For example, in an embodiment, the conditional reconfiguration indication signal may include a first execution condition for a first target node that has approved the conditional handover, an nth execution condition for an nth target node, and the like. Here, one or more execution conditions may be set identically or may be set differently. The first communication node 410 may perform candidate cell monitoring for one or more candidate cells based on one or more confirmed execution conditions (S475). In this case, one or more target base stations that have approved the conditional handover may be regarded as candidate base stations, and one or more target cells corresponding to cells of the one or more target base stations that have approved the conditional handover may be considered candidate cells. The first communication node 410 may monitor whether one or more execution conditions corresponding to each candidate cell are satisfied (or satisfied) by performing monitoring on each of one or more candidate cells for which conditional handover is approved. . When it is confirmed that a specific execution condition is satisfied during monitoring, the first communication node 410 may perform a handover (S480). For example, if it is confirmed that the first execution condition is satisfied during monitoring, the first communication node 410 does not transmit a report on the measurement result to the second communication node 420 but immediately the first target node 430 - 1 ) to perform handover. Alternatively, when it is confirmed that the n-th execution condition is satisfied during monitoring, the first communication node 410 does not transmit a report on the measurement result to the second communication node 420 but immediately the n-th target node 430-n ) to perform handover. Hereinafter, a second embodiment of a conditional reconfiguration procedure in a communication system will be described with an example in which it is confirmed that the n-th execution condition is satisfied. However, the embodiment of the present invention is not limited thereto and may be equally or similarly applied to various situations depending on whether each execution condition is satisfied.

When it is confirmed that the n-th execution condition is satisfied during monitoring, the first communication node 410 may attempt handover to the n-th target cell ( S485 ). For example, the first communication node 410 may perform operations for accessing the n-th target base station 430 - n instead of the second communication node 420 . The first communication node 410 may acquire synchronization with the n-th target node 430 - n to perform handover and attempt a random access (RA) connection.

When the connection to the n-th target node 430-n is successful, the first communication node 410 may transmit a reconfiguration completion report signal to the n-th target node 430-n ( S490 ). The reconfiguration completion report signal may also be referred to as an 'RRCReconfigurationComplete' signal (or message). Upon receiving the reconfiguration completion report signal, the n-th target node 430-n may execute a path switch and a terminal context release procedure (S495). Accordingly, a series of procedures for conditional reconfiguration of the first communication node 410 may be completed.

5 is a conceptual diagram for explaining an embodiment of a method of monitoring one or more candidate cells in a communication system.

Referring to FIG. 5 , in an embodiment of a mobile communication system, a terminal may be located within cell coverage of one or more base stations corresponding to one or more candidate cells. Here, one or more base stations may form a single beam or multiple beams (or multi-beams) to form cell coverage. The terminal may be configured the same as or similar to the first communication node 310 described with reference to FIG. 3 and/or the first communication node 410 described with reference to FIG. 4 . The one or more base stations include the second communication node 320, the first target node 330 described with reference to FIG. 3, the second communication node 420 described with reference to FIG. 4, and one or more target nodes 430-1, . .., 430-n) may be configured the same as or similarly to some of them. The UE may identify one or more candidate cells according to the method described with reference to FIG. 4 . Hereinafter, a case in which the terminal performs monitoring of two candidate cells between two candidate cells (ie, a first cell and a second cell) through which a multi-beam is transmitted as an example, performing monitoring of the candidate cell One embodiment of the method is described. However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto.

In the embodiment shown in FIG. 5 , the terminal may be viewed as being located in the center of beam No. 1 of the first cell. Therefore, when the terminal measures the signal strength of all beams of the first cell, the signal strength of the beam 1 of the first cell may be measured as the strongest. On the other hand, the terminal can be viewed as being located between beam 4 and beam 5 of the second cell. Accordingly, if the terminal measures the reception strengths of all beams of the second cell, the beam reception strengths of beams 4 and 5 may be measured as the strongest.

The UE may calculate beam reception strength and/or cell reception strength for the first and second cells. For example, in the example shown in FIG. 5, when the terminal calculates the cell reception strength for the first and second cells, the beam reception strengths measured for beams 1 to 8 of each of the first and second cells are all combined. Or it can be calculated by averaging. Alternatively, in calculating the cell reception strength for the first and second cells, the terminal selects only a beam having a beam reception strength equal to or greater than a preset threshold from among beams 1 to 8 of each of the first and second cells, and selects a beam of the selected beam. It can be calculated by summing or averaging only the received strengths. A method for the UE to measure the beam reception strength and the cell reception strength will be described in more detail below with reference to FIGS. 6A and 6B .

6A and 6B are graphs for explaining an embodiment of a method of measuring beam reception strength and cell reception strength while monitoring one or more candidate cells in a communication system.

Referring to FIGS. 6A and 6B , in an embodiment of a mobile communication system, a terminal may be located within cell coverage of one or more base stations corresponding to one or more candidate cells to perform monitoring. Here, FIG. 6a can be viewed as a graph showing the result of the terminal performing monitoring on the first cell in the embodiment shown in FIG. 5 , and FIG. 6b is the first cell of the terminal in the embodiment shown in FIG. 5 . It can be seen as a graph showing the results of monitoring for Hereinafter, an embodiment of a method of measuring beam reception strength and cell reception strength will be described with reference to FIGS. 6A and 6B . However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto.

Here, the 'beam reception strength' (or reception signal quality) referred to in this specification may mean the reception strength of an individual beam measured by the terminal by the terminal, and the cell reception strength is the multi-beam intensity of each of the multi-beams of a specific cell measured by the terminal. It may mean summing or averaging all beam reception intensities. In calculating the cell reception strength, the UE may calculate by summing or averaging the reception strengths of all beams emitted from a specific cell regardless of the reception strength of each beam. Alternatively, in calculating the cell reception strength, the terminal may select a beam having a beam reception strength equal to or greater than a predetermined threshold and calculate by summing or averaging the beam reception strengths of the selected beams.

Referring to FIG. 6A , in calculating the cell reception strength for the first cell, the UE may calculate by summing or averaging the beam reception strengths measured for each of beams 1 to 8 of the first cell. Alternatively, in calculating the cell reception strength for the first cell, the terminal selects only beams having a beam reception strength equal to or greater than a preset threshold among beams 1 to 8 of the first cell, and sums or averages only the beam reception strengths of the selected beams. can be calculated For example, in the embodiment shown in FIG. 6A , the terminal selects beam 1, beam 2, and beam 8 having a beam reception intensity equal to or greater than a preset first threshold value from among beams 1 to 8 of the first cell, and selects the selected beams 1, 2 and By summing or averaging only the beam reception strengths of 8, the cell reception strength of the first cell may be measured or calculated.

Referring to FIG. 6B , when calculating the cell reception strength for the second cell, the UE may calculate by summing or averaging the beam reception strengths measured for each of beams 1 to 8 of the second cell. Alternatively, in calculating the cell reception strength for the second cell, the terminal selects only beams having a beam reception strength equal to or greater than a preset threshold among beams 1 to 8 of the second cell, and sums or averages only the beam reception strengths of the selected beams. can be calculated For example, in the embodiment shown in FIG. 6B , the terminal selects beams 4 and 5 in which the beam reception intensity is greater than or equal to a preset first threshold value among beams 1 to 8 of the second cell, and the selected beam reception intensity of beams 4 and 5 The cell reception strength of the second cell may be measured or calculated by summing or averaging only .

If the UE recognizes the first cell and the second cell as a candidate cell, monitoring the first cell and the second cell is performed in the same or similar manner as described with reference to FIGS. 6A and 6B, and beam reception strength and/or Cell reception strength may be measured or calculated. The terminal determines each of the beam reception strength and/or cell reception strength confirmed for the first cell and the second cell, the conditional handover execution condition (ie, the first execution condition and the second cell) set for each of the first cell and the second cell. 2 execution conditions, etc.) to finally select a cell to be handed over.

When a conditional handover command for a plurality of candidate target base stations is set, there may be more than one candidate target cell that satisfies the handover execution condition. If a plurality of candidate target cells satisfy the conditional handover execution condition, a criterion for determining which cell to select and perform handover may be required. When a plurality of candidate target cells satisfy the conditional handover execution condition, the UE may select one cell by comparing beam reception strength and/or cell reception strength measured for each cell. An embodiment of the operation of the terminal selecting a cell to be handed over is the same as the operation of the first communication node selecting a cell to be handed over in the third embodiment of the conditional reconfiguration procedure described below with reference to FIG. 7 , or may be similar.

7 is a flowchart illustrating a third embodiment of a conditional reconfiguration procedure in a communication system.

Referring to FIG. 7 , the first communication node may perform conditional reconfiguration by monitoring one or more candidate cells in a situation in which the first communication node is connected to the second communication node. Here, the first communication node is the first communication node 310 described with reference to FIG. 3 , the first communication node 410 described with reference to FIG. 4 , the terminal described with reference to FIG. 5 , and/or FIGS. 6A and 6B . It may be configured the same or similar to some of the terminals described with reference to. The second communication node is configured the same or similar to some of the second communication node 320 , the first target node 330 described with reference to FIG. 3 and/or the second communication node 420 described with reference to FIG. 4 . can be The one or more candidate cells include the first candidate cell described with reference to FIG. 3 , the one or more candidate cells described with reference to FIG. 4 , the first and second cells described with reference to FIG. 5 , and/or see FIGS. 6A and 6B . It may be configured the same or similar to some of the first and second cells described above.

The first communication node may check one or more reconfiguration execution conditions set for each of one or more candidate cells. Here, the one or more reconfiguration execution conditions may be set to be the same as or similar to the one or more execution conditions described with reference to FIG. 4 . The first communication node may perform monitoring on one or more candidate cells based on the confirmed one or more reconfiguration execution conditions (S710). The first communication node may check whether there is a cell satisfying the reconfiguration execution condition through monitoring of one or more candidate cells (S720). If a cell satisfying the reconfiguration execution condition is not identified (S720), the first communication node may continuously monitor one or more candidate cells (S710).

Meanwhile, if a cell satisfying the reconfiguration execution condition is checked (S720), the first communication node may check whether there is one or a plurality of cells satisfying the reconfiguration execution condition (S730). If only one cell satisfying the reconfiguration execution condition is identified (S730), the first communication node may perform conditional reconfiguration (S750). For example, the first communication node may perform conditional reconfiguration, such as performing handover to one cell that satisfies the identified reconfiguration execution condition.

On the other hand, if a plurality of cells satisfying the reconfiguration execution condition are identified (S730), the first communication node selects one cell based on the beam reception quality measured for a plurality of cells satisfying the checked reconfiguration execution condition. A selection operation may be performed (S740). For example, the first communication node may select one cell based on the beam reception quality and/or the size and/or change pattern of the cell reception quality measured for a plurality of cells that satisfy the identified reconfiguration execution condition. When one cell is selected in the first communication node in step S740, the first communication node may perform conditional reconfiguration (S750). For example, the first communication node may perform conditional reconfiguration, such as performing handover to one cell selected in step S740.

In operation S740 , the first communication node may select one cell based on the beam reception quality measured for a plurality of cells satisfying the reconfiguration execution condition. The first communication node may check the beam reception strength for each beam and/or the cell reception strength for each cell by monitoring the beams of each of the plurality of cells that satisfy the reconfiguration execution condition.

In steps S710 to S740 of FIG. 7 , operations based on reception quality or reception strength measured by the first communication node with respect to a beam or signal received from the second communication node or one or more base station cells may be performed. Meanwhile, even in the embodiment described with reference to FIGS. 3 and 4 , the first communication node 310 , 410 includes the second communication node 320 , 420 and one or more target nodes 330 , 430 - 1 , 430 - 2, ... 430-n), the conditional reset procedure may be performed by performing monitoring and/or measurement on a beam or signal received from some or all. Here, the operation in which the first communication node measures the strength or quality of a beam or signal received from the second communication node and/or one or more target nodes or target cell is the same as the embodiment described with reference to FIG. 8 below. may be performed identically or similarly.

8 is a graph for explaining an embodiment of a method for measuring a base station signal in a communication system.

In an embodiment of the communication system, the terminal may measure the signal of the base station based on the same or similar measurement model as shown in FIG. 8 . Here, the terminal may correspond to the first communication node 310 described with reference to FIG. 3 , the first communication node 410 described with reference to FIG. 4 , the first communication node described with reference to FIG. 7 , and the like. The base station includes the second communication node 320 , the first target node 330 described with reference to FIG. 3 , the second communication node 420 described with reference to FIG. 4 , the first to nth target nodes 430 - 1 , ..., 430-n), the second communication node described with reference to FIG. 7, and the like.

Referring to FIG. 8 , the UE may measure the strength, quality, power value, etc. of each of one or more beams or signals received from the base station or cell in the RRC connection state or RRC_CONNECTED. In order to calculate the cell quality, the UE may calculate an average value of measurement results for each beam. The terminal may be configured to select or consider some of the detected beams, for example, one or more beams having a measurement value greater than or equal to a preset threshold. Filtering may be done at the physical layer to derive the beam quality, and/or at the RRC level to derive the cell quality from one or more beams. The operation of acquiring cell quality through beam measurement may be performed in the same manner for a serving cell and/or one or more non-serving cells (eg, a target cell or a candidate cell). A measurement report including information confirmed or obtained through measurement may include measurement results for X selected beams (or best beams).

Specifically, the terminal may receive one or more beams (beams 1 to K) from a base station (eg, gNB) or a cell of the base station (A). In layer 1 (layer 1, L1) of the terminal, for one or more beams received from the base station, reception quality information or reception strength information (eg, RSRP, RSRQ, RSSI, etc.) measurement may be performed in units of each beam. In L1 of the terminal, L1 filtering may be performed in units of beams. Reception quality information measured in units of beams may be periodically reported as layer 3 (layer 3, L3) or RRC (A ¹ ). In L3 of the terminal, a beam satisfying a preset condition may be identified based on reception quality information measured and reported in units of beams. Here, the cell quality may be calculated by averaging the reception quality information of the beams confirmed to satisfy a preset condition (B). L3 filtering may be performed on the information of cell quality calculated in L3. Based on the result (C) of the L3 filtering performed on the cell quality information, it may be determined whether the measurement report condition is satisfied. Meanwhile, the terminal may calculate and report the reception strength in units of beams for one or more beams received from the base station. The terminal may identify a beam that meets a preset condition from the base station among one or more beams. The terminal may calculate the reception quality of each beam by performing an L3 beam filtering function on a beam determined to meet a preset condition from the base station (F).

Referring back to FIG. 7 , in step S740 , the first communication node may select one cell based on beam reception quality measured for a plurality of cells satisfying the reconfiguration execution condition. The first communication node may check the beam reception strength for each beam and/or the cell reception strength for each cell by monitoring the beams of each of the plurality of cells that satisfy the reconfiguration execution condition.

For example, the first communication node may select a cell emitting a beam having the largest beam reception intensity among each beam. Alternatively, the first communication node may select a cell having the greatest cell reception strength. If two or more cells having the best result of performing comparison based on beam reception strength and/or cell reception strength are identified (that is, one cell is selected through comparison based on beam reception strength and/or cell reception strength) if not possible), one cell may be selected by comparing the beam reception strength and/or the cell reception strength measured in the last n measurement operations. For example, when two or more cells having the best result of performing comparison based on the beam reception strength and/or the cell reception strength are identified, the first communication node receives the beam reception strength and/or the cell reception measured in the latest n measurement operations. One cell with the highest intensity may be selected.

Alternatively, the first communication node may select one cell from among a plurality of cells based on a change rate of the cell reception strength. Hereinafter, with reference to FIGS. 9A and 9B , an embodiment of a method in which the first communication node selects one cell from among a plurality of cells based on a change in beam reception strength and/or cell reception strength will be described.

9A and 9B are graphs for explaining an embodiment of a method of selecting one cell from among a plurality of cells satisfying a reconfiguration condition in a communication system.

9A and 9B , the first communication node may check the beam reception strength for each beam and/or the cell reception strength for each cell through monitoring the beams of each of a plurality of cells that satisfy the reconfiguration execution condition. . The first communication node may check the checked beam reception strength and/or the change aspect of the cell reception strength. Hereinafter, a plurality of cells (corresponding to one or more cells described with reference to FIG. 7) satisfying the reconfiguration execution condition from the serving base station (corresponding to the second communication node described with reference to FIG. 7) to which the first communication node is currently connected. ), an embodiment of a method of selecting one cell among a plurality of cells will be described by taking as an example a situation in which one base station or cell is selected by performing measurements on candidate base stations A and B forming the plurality of cells. However, this is only an example for convenience of description, and the embodiment of the present invention is not limited thereto.

As shown in FIG. 9A , the beam reception strength and/or the cell reception strength that the first communication node receives from the candidate base station A may gradually increase over time. This may mean that the distance between the first communication node and the candidate base station A is getting closer or that the channel condition between the first communication node and the candidate base station A is getting better.

Meanwhile, as shown in FIG. 9B , the beam reception strength and/or the cell reception strength that the first communication node receives from the candidate base station B may gradually decrease over time. This may mean that the distance between the first communication node and the candidate base station A increases, or the channel condition between the first communication node and the candidate base station A is getting worse.

In this case, the first communication node may select the candidate base station A having a better change aspect of the beam reception strength and/or the cell reception strength from among the candidate base stations A and B. The first communication node may perform conditional reconfiguration or conditional handover to the cell of the selected candidate base station A.

According to the above-described embodiments of the present invention, a cell selection method for a case in which one or a plurality of cells satisfy an execution condition for performing conditional reconfiguration may be provided. Accordingly, from among a plurality of cells satisfying the conditional reconfiguration execution condition, one cell having a higher received signal strength or an aspect may be selected and reconfiguration or handover may be performed. Accordingly, a failure rate of reconfiguration or handover may be reduced, and communication quality may be better as a result of reconfiguration or handover.

According to the above-described embodiments of the present invention, a communication node such as a terminal and/or a base station may perform a conditional reconfiguration procedure through monitoring a communication environment. As a result of monitoring the communication environment, when a plurality of candidate cells satisfying the conditional reconfiguration condition are identified, one cell may be selected based on the beam reception quality. Accordingly, the conditional reconstruction operation can be performed more efficiently.

However, effects that can be achieved by the conditional reconfiguration method and apparatus in the wireless communication system according to the above embodiments are not limited to those mentioned above, and other effects not mentioned are described in the specification of the present application. From the configurations, it will be clearly understood by those of ordinary skill in the art to which the present invention pertains.

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

Examples of computer-readable media include hardware devices specially configured to store and carry out program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as at least one software module to perform the operations of the present invention, and vice versa.

Although it has been described with reference to the above embodiments, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. will be able

Claims (1)

A method for conditional reconfiguration performed in a first communication node of a wireless communication system, the method comprising:
performing cell monitoring in a predetermined communicable area;
transmitting a cell monitoring result report signal including information on one or more target cells identified according to the cell monitoring to a serving base station;
receiving, from the serving base station, a reconfiguration indication signal including information on one or more candidate cells for which conditional handover is approved among the one or more target cells;
When a plurality of cells having an average reception quality equal to or greater than a first threshold are identified in the monitoring of the one or more candidate cells, a first final cell of one of the identified plurality of cells is selected based on each beam reception quality step; and
and performing a handover to the selected first last cell.

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