MEASUREMENT REPORT METHOD AND APPARATUS FOR PATH SWITCHING IN A WIRELESS COMMUNICATION SYSTEM

The disclosure relates to a 5th generation (5G) or 6th generation (6G) communication system for supporting a higher data transmission rate. A method performed by a base station (BS) in a wireless communication system is provided. The method includes transmitting, to a user equipment (UE), a radio resource control (RRC) message including measurement configuration information through a direct path or an indirect path via a relay UE, and receiving, from the UE, a MeasurementReport message including measurement result through the direct path or the indirect path via the relay UE. Further, the measurement result includes a first measurement result for direction communications (PC5) link and a second measurement result for Uu link.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. § 119(a) of a Korean patent application number 10-2022-0128724, filed on Oct. 7, 2022, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

The disclosure relates to a wireless communication system (or a mobile communication system). More particularly, the disclosure relates to an enhanced measurement reporting method and apparatus for path switching in a wireless communication system.

2. Description of Related Art

SUMMARY

Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide a method and apparatus for transmitting a measurement report message for a path switch in a wireless communication system, so as to efficiently provide a path switching procedure between different base stations.

In accordance with an aspect of the disclosure, a method performed by a base station (BS) in a wireless communication system is provided. The method includes transmitting, to a user equipment (UE), a radio resource control (RRC) message including measurement configuration information through a direct path or an indirect path via a relay UE, and receiving, from the UE, a MeasurementReport message including measurement result through the direct path or the indirect path via the relay UE. Further, the measurement result includes a first measurement result for direction communications (PC5) link and a second measurement result for Uu link.

Another aspect of the disclosure is to provide an enhanced measurement reporting method and apparatus for a path switch in a wireless communication system.

DETAILED DESCRIPTION

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

The following description of embodiments of the disclosure is mainly directed to new radio (NR) as a radio access network and packet core 5G system or 5G core network or next generation core (NG Core) as a core network in the 5G mobile communication standards specified by the 3rdgeneration partnership project (3GPP) that is a mobile communication standardization group, but based on determinations by those skilled in the art, the main idea of the disclosure may be applied to other communication systems having similar backgrounds through some modifications without significantly departing from the scope of the disclosure.

In the following description, some of terms and names defined in the 3GPP standards (standards for 5G, NR, LTE, or similar systems) may be used for the sake of descriptive convenience. However, the disclosure is not limited by these terms and names, and may be applied in the same way to systems that conform other standards.

In the following description, terms for identifying access nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, and the like are illustratively used for the sake of descriptive convenience. Therefore, the disclosure is not limited by the terms as used below, and other terms referring to subjects having equivalent technical meanings may be used.

In the following description, a base station is an entity that allocates resources to terminals, and may be at least one of a gNode B, an eNode B, a Node B, a base station (BS), a wireless access unit, a base station controller, and a node on a network. A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing communication functions. In the disclosure, a “downlink (DL)” refers to a radio link via which a base station transmits a signal to a terminal, and an “uplink (UL)” refers to a radio link via which a terminal transmits a signal to a base station.

Various embodiments of the disclosure describe a method in which, in a sidelink user equipment (UE)-to-network relay structure, a UE-to-network remote UE simultaneously transmits a signal intensity measurement result associated with a UE-to-network relay UE, which may be an object to which the path is switchable, and a signal intensity measurement result associated with another base station, which may be an object to which the path is switchable. In addition, a description is provided in association with a method in which a base station that receives a signal intensity measurement result determines path switching for direct communication or path switching for indirect communication via a UE-to-network relay UE, or a method in which a base station that receives a signal intensity measurement result transmits the signal intensity measurement result to another base station that may be an object to which the path is switchable via an inter-base station message.

According to various embodiments of the disclosure, a description is provided in association with a method in which a base station that receives a signal intensity measurement result effectively determines path switching for direct communication via an inter-base station message or path switching for indirect communication via a UE-to-network relay UE.

According to various embodiments of the disclosure, a UE may simultaneously transmit a signal intensity measurement result associated with a UE-to-network relay UE, which may be an object to which the path is switchable, and a signal intensity measurement result associated with another base station, which may be an object to which the path is switchable, and may effectively determine path switching for direct communication with a base station via inter-base station message transmission or path switching for indirect communication via a UE-to-network relay UE.

In the disclosure, the operation of a base station and the operation of a UE according to various embodiments will be described.

FIG.1is a diagram illustrating a user equipment (UE)-to-network relay in a wireless communication system according to an embodiment of the disclosure.

Referring toFIG.1, a UE-to-network (U2N) Relay UE120and130is illustrated, which is capable of supporting the operation of a U2N Relay UE. The U2N Relay UE120and130may be located in an coverage area111of a base station110, which corresponds to an in-coverage (IC) case. In addition,FIG.1illustrates a U2N Remote UE140and150that is capable of supporting the operation of a U2N Remote UE. In the case of in-coverage (IC), the U2N Remote UE140and150is located in the coverage area111of the base station110. In the case of out-of-coverage (OOC), the U2N Remote UE140and150is not located in the coverage area111of the base station110. The U2N Remote UEs140and150may be sidelink UEs.

In addition, uplinks and downlinks112and113between the base station110and the UEs120and130may be referred to as Uu interfaces, and the transmission links or reception links121and131with the sidelink UEs140and150may be referred to as PC5 interfaces. Hereinafter, the uplinks or downlinks112and113may be interchangeably used with Uu interfaces, and the transmission links or reception links121and131between the sidelink UEs may be interchangeably used with PC5 interfaces. In case that data transmitted from the base station110to the U2N Relay UE120and130via a Uu link112and113according to the configuration of the base station110is data to be relayed to the U2N Remote UE140and150, the U2N Relay UE120and130may transmit the data to the U2N Remote UE140and150via the PC5 link121and131. In addition, the data transmitted from the U2N Remote UE140and150to the U2N Relay UE120and130via the PC5 link121and131is data to be relayed to the base station110, the U2N Relay UE120and130may transmit the data transmitted from the U2N Remote UE140and150to the base station110via the Uu link112and113.

FIG.2is a diagram illustrating a discovery message transmission or reception configuration in UE-to-network relay in a wireless communication system according to an embodiment of the disclosure.

Referring toFIG.2, a base station may transmit a dedicated configuration for sidelink communication and a dedicated configuration for L2 U2N relay, to an L2 U2N Relay UE220via an RRC (e.g., RRCReconfiguration) message in operation231. In addition, a base station230may broadcast an SIB (SystemInformationBlock) message in operation232, or may receive an SIB transmission request from a UE and transmit, to the L2 U2N Relay UE220, information whether the base station230supports layer 2 (L2) U2N relay, a common configuration for sidelink communication, and a common configuration for L2 U2N relay. The common and dedicated configurations for sidelink communication may include a Tx pool and an Rx pool indicating resources for transmission and reception of sidelink data, and a discovery Tx pool and a discovery Rx pool indicating resources for transmission and reception of a sidelink discovery message. The common and dedicated configurations for L2 U2N relay may include a configuration (sl-relayUE-config) that designates the conditions for transmission and reception of a discovery message for the UE220that supports the operation of an L2 U2N Relay UE. In case that the discovery Tx pool and the discovery Rx pool are configured, transmission or reception of a discovery message of operation240by using the corresponding resource pools. Otherwise, transmission or reception may be performed by using a Tx pool and an Rx pool. The transmission and reception of a discovery message of operation240may be performed by using a described predetermined resource pool or by using a resource not mentioned in the disclosure. Hereinafter, it is assumed that a UE that transmits a discovery message and a UE that receives a discovery message have the same transmission and reception resource pool.

In operation221, depending on a reference signal received power (RSRP) measurement result associated with a serving base station, the L2 U2N Relay UE220may determine discovery message transmission or reception of operation240for transferring information to the neighboring L2 U2N Remote UE210that desires to receive a U2N relay service. In addition, the RSRP reference may be determined based on an RRC (e.g., RRCReconfiguration) message231or SIB message232received from the base station230. Specifically, in case that a value obtained based on an RSRP measurement result associated with the base station230and hysteresis is less than a threshold, information associated with at least one of threshHighRelay and hystMaxRelay may be included so that a discovery message is transmitted or received in operation240. In addition, in case that a value obtained based on an RSRP measurement result associated with the base station230and hysteresis is more than a threshold, information associated with at least one of threshLowRelay and hystMinRelay may be included so that a discovery message is not transmitted or received in operation240.

The base station230may transmit a dedicated configuration for sidelink communication and a dedicated configuration for L2 U2N relay to the L2 U2N Remote UE210via an RRC (e.g., RRCReconfiguration) message in operation233. The base station230may broadcast an SIB (SystemInformationBlock) message in operation234, or may transmit, to the L2 U2N Remote UE210in response to an SIB transmission request from a UE, information whether the base station230supports layer 2 (L2) U2N relay, a common configuration for sidelink communication, and a common configuration for L2 U2N relay. In addition, in the state of out-of-coverage (OOC) state, the L2 U2N Remote UE210may use a configuration for sidelink communication and a configuration for L2 U2N relay which may be included in Pre-configuration211configured in advance. The common and dedicated configurations for sidelink communication and the Pre-configuration211may include a Tx pool and an RX pool indicating resources for transmission and reception of sidelink data, and a discovery TX pool and a discovery Rx pool indicating resources for transmission and reception of a sidelink discovery. The common and dedicated configurations for L2 U2N relay may include a configuration (sl-RemoteUE-Config) indicating the conditions for transmission and reception of a discovery message of operation240for the UE210that supports the operation of a U2N Remote UE. In operation212, an RSRP reference for the serving base station230with which the U2N Remote UE210performs transmission or reception of a discovery message of operation240may be configured for the L2 U2N Remote UE210via an RRC (e.g., RRCReconfiguration) message or SIB message received from the base station230. Specifically, in case that a value obtained based on an RSRP measurement result associated with the base station230and hysteresis is less than a threshold, threshHighRemote and hystMaxRemote may be included so that a discovery message is transmitted or received in operation240. In the case of OOC, the L2 U2N Remote UE210may always transmit and receive a discovery message in operation240. In a measurement report transmitted to the base station230, the L2 U2N Remote UE210may include a result of measurement of a discovery message transmitted from the L2 U2N Relay UE220as an SD-RSRP, and may include a result of measurement of sidelink data transmitted from the L2 U2N Relay UE220as an SL-RSRP.

FIG.3is a diagram illustrating configuring a direct-path and an indirect-path of a UE-network relay according to an embodiment of the disclosure.

Referring toFIG.3, an L2 U2N Remote UE320may perform direct communication with a base station310via a Uu link311, and in this instance, the Uu link311that communicates with the base station310may be referred to as a direct-path. In addition, the L2 U2N Remote UE320may communicate with the base station310via an L2 U2N Relay UE330. A PC5 link331between the L2 U2N Remote UE320and the L2 U2N Relay UE330or a Uu link, an indirect-path312, between the L2 U2N Relay UE330and the base station310may be referred to as an indirect-path. The base station310may configure a measurement configuration with respect to the L2 U2N Remote UE320in order to receive a wireless measurement result associated with a neighboring NR cell of the L2 U2N Remote UE320or a wireless measurement result associated with the neighboring U2N Relay UE340via a measurement report transmitted from the L2 U2N Remote UE320. The base station310may receive a measurement report transmitted from the L2 U2N Remote UE320, and, based on the measurement result, may proceed with a direct-to-indirect-path switch procedure that changes the L2 U2N Remote UE320from the direct-path, the Uu link311, to the indirect-path312and331or may proceed with an indirect-to-direct-path switch procedure that changes the indirect-path312and331to the direct-path, the Uu link311. In addition, the base station310may proceed with an indirect-to-indirect-path switch procedure that changes the indirect-path312and331to another indirect-path313and341.

In the OOC situation in which the L2 U2N Remote UE320happens to move to a coverage edge of a base station or beyond the coverage area of the base station, the L2 U2N Remote UE320may receive a service via an indirect path without disconnection of the service by performing a direct-to-indirect-path switch procedure that changes to an indirect path via the L2 U2N Relay UE330and340. In addition, in case that the L2 U2N Remote UE320moves close to the center of the coverage area of a serving base station or another base station, the L2 U2N Remote UE320may receive a service via an indirect-to-direct-path switch procedure that changes to a direct path again. In addition, a service may be continuously provided (service continuity) via an indirect-to-indirect-path switch procedure that changes to an indirect path of another L2 U2N Relay UE340while the L2 U2N Remote UE320is receiving a service via an indirect path via the serving L2 U2N Relay UE330.

Although path switching in the single base station310has been described as an example, indirect-to-direct-path switching to another base station, direct-to-indirect-path switching to an L2 U2N Relay UE served by another base station, and indirect-to-indirect-path switching to an L2 U2N Relay UE served by another base station may also be supported for service continuity of UE-to-network relay. A measurement report procedure for determining path switching and a path switch procedure will be described below with reference to other drawings.

FIGS.4A,4B, and4Care diagrams illustrating a measurement reporting for inter-base station path switching in UE-to-network relay according to various embodiments of the disclosure.

FIG.4Ais a diagram illustrating a base station configuring a measurement configuration with respect to a U2N Remote UE and receives a measurement report according to an embodiment of the disclosure.

Referring toFIG.4A, a base station430may transmit an RRC (e.g., RRCReconfiguration) message in operation431to an L2 U2N Remote UE410via a direct link432, or may transmit the same via an indirect link433by using an L2 U2N Relay UE420. In addition, the base station430may configure a measurement configuration in order to receive a measurement result of the L2 U2N Remote UE410. The base station430according to various embodiments of the disclosure may be a serving base station, and the serving base station430may be a base station including a primary cell (PCell), a primary secondary cell (PSCell), or a special cell (SpCell) that performs transmission and reception of the RRCReconfiguration message in operation431with the L2 U2N Remote UE410via the direct link432or the indirect link433. A neighboring base station and a target base station may be other base stations different from a serving base station. In addition, the serving L2 U2N Relay UE420may be an L2 U2N Relay UE that constitutes the indirect link433used when the L2 U2N Remote UE410communicates with the serving base station430, and a neighboring L2 U2N Relay UE and a target L2 U2N Relay UE may be other L2 U2N Relay UEs different from a serving L2 U2N Relay UE. Hereinafter, NR and a sidelink will be described, however, a method described in the disclosure is not limited to the above-mentioned combination and the embodiment may be applicable to other communication systems that have similar technical backgrounds or channel forms.

A measurement configuration may include at least one of a measurement object, a report configuration, and a measurement identity.

The measurement object may include information for measuring an object including at least one of NR, EUTRA, UTRA-FDD, and a sidelink. An NR measurement object may include at least one of a frequency for measuring an NR cell, a subcarrier spacing (SCS), a reference signal configuration (RSS), an allowed/excluded cell list, an object specific offset, and a cell specific offset, and may be configured in the form of measObjectNR. In addition, a sidelink measurement object may include SL-MeasObject including a frequency for measuring a sidelink UE and a sidelink measurement object identity (SL-MeasObjectId) that is in one-to-one correspondence with the frequency and is unique for each UE, and may be configured in the form of measObjectRelay. measObjectNR or measObjectRelay may be in one-to-one correspondence with a measurement object identity, and the measurement object identity may be configured in the form of measObjectId that is unique for each UE and thus, different measurement objects may be distinguished.

A report configuration may be configured by including an event trigger configuration in a report type. An event trigger configuration may include a parameter for determining an entering condition and a leaving condition for an event defined in 3GPP TS 38.331, and may include at least one threshold, an offset, time to trigger (TTT), and hysteresis. In addition, a report interval, a report amount, a cell report measurement unit (report quantity cell), and a relay report measurement unit (report quantity relay) may be included in the event trigger configuration. A report configuration may be in one-to-one correspondence with a report configuration identity, and the report configuration identity may be configured in the form of reportConfigId that is unique for each UE and thus, different report configurations may be distinguished.

A measurement identity may be associated with one measObjectId and one reportConfigId, and may be in one-to-one correspondence. For example, in the case of a single measurement identity, a combination of one measObjectId and one reportConfigId may be expressed in the form of measId that is unique for each UE and thus, different measurement identities may be distinguished.

The L2 U2N Remote UE410may obtain an layer-1 measurement result and layer-1 filtering result associated with a Uu link or a PC5 link of another sidelink UE or an NR cell according to requirements of 3GPP TS 38.133 and a procedure of 3GPP TS 38.300, by using a reference signal configured in the measurement configuration. In the case of the layer-1 filtering result, layer-3 filtering may be performed during beam consolidation/selection and TTT to obtain quality of a Uu link or a PC5 link according to the procedure of 3GPP TS 38.331. Subsequently, the L2 U2N Remote UE410may evaluate the quality of the Uu link or PC5 link in order to transmit a measurement result based on a report configuration. The layer-1 measurement method and layer-1 filtering associated with a PC5 link and a Uu link are performed according to implementation by a UE and the requirements of 3GPP TS 38.133. The beam consolidation/selection and layer-3 filtering procedure for obtaining a Uu link or PC5 link measurement result for evaluation may be performed according to 3GPP TS 38.331. In addition, a cell quality or PC5 quality after layer-3 filtering may be interchangeably used with a term, such as a Uu link measurement result, a PC5 link measurement result, and or the like. In addition, via a discovery message or a PC5-RRC message, the L2 U2N Remote UE may receive a Uu link measurement unit and measurement result associated with a serving cell of the L2 U2N Relay UE that is measured by the L2 U2N Relay UE.

The measurement result may be expressed as an absolute value or a relative value, and the measurement result may be rounded off or may be expressed to be different from an actually measured value according to an index based on a range.

In case that evaluation in operation411indicates that the Uu link or PC5 link measurement result satisfies a measurement report triggering evaluation condition and an entering or leaving condition based on a report configuration, the L2 U2N Remote UE410may transmit a measurement report message412to the serving base station430via a direct link413or an indirect link414. In the case of the Uu link or PC5 link measurement result, RSRP, RSRQ, SINR, SD-RSRP, SL-RSRP, or CBR configured in a report quantity cell or report quantity relay or report quantity sidelink may be used, and a measurement result obtained for each cell, in a unit of a sidelink UE, in a unit of an SSB, in a unit of a CSI-RS may be used. In addition, the distance between a measured UE and a reference location and an interference value of a measured UE may be used. Measurement for each quantity may be performed according to the requirements of 3GPP TS 38.133 and the definitions in 3GPP TS 38.331. The measurement report triggering condition may be based on the definitions and procedures in 3GPP TS 38.331, and at least one condition among a condition that a Uu link or PC5 link measurement result of a measured UE be greater than or less than a threshold, a condition that a difference in Uu link measurement results between a Uu link and another Uu link be greater than or less than an offset, a condition that a difference in PC5 link measurement results between a PC5 link and another PC5 link be greater than or less than an offset, a condition that a difference between the location of a measured UE and a reference location be greater than or less than a threshold according to a Uu link measurement result associated with a serving cell that is measured in association with a discovery message by a UE having a PC5 link measurement result, and a condition that an interference of a measurement UE be greater than or less than a threshold may be combined and configured as the entering or leaving condition. Furthermore, in association with a Uu link measurement result, configuration may be performed so that a measurement result associated with a serving cell, a PSCell, an SpCell, an SCell, or other cells may be used for evaluation. In association with a PC5 link measurement result, configuration may be performed so that a measurement result associated with the serving L2 U2N Relay UE420or another L2 U2N Relay UE may be combined and used for evaluation. In this instance, a serving cell, PSCell, SpCell, SCell, and serving L2 U2N Relay UE with which the measured UE performs communication via a Uu link or a PC5 link may be included in the measurement report triggering condition even without designation by a measurement object. Each measurement result may be evaluated by increasing or decreasing a result value according to an object specific offset and a cell specific offset included in the measurement configuration, and evaluation may be performed based on the entering or leaving condition based on an additional value based on hysteresis. The measurement report triggering evaluation condition may be expressed in the form of a report triggering event.

The measurement report message412may include a measurement identity of a measurement configuration that triggers the measurement report, one or more Uu link measurement results that satisfy a report condition evaluation, and one or more PC5 link measurement results that satisfy a report condition evaluation. Specifically, a Uu link measurement result may include one or more pieces of information among a serving cell index of a measured cell, a cell identity of a measured cell, a physical cell identity of a measured cell, a unit of measurement used for evaluating a report condition, and a measurement result used for evaluating a report condition. A PC5 link measurement result may include one or more pieces of information among a serving cell identity of a measured L2 U2N Relay UE, a serving cell PLMN identity of a measured L2 U2N Relay UE, a source identity of a measured L2 U2N Relay UE, a unit of measurement used for evaluating a report condition, a measurement result used for evaluating a report condition, a unit of Uu link measurement associated with a serving cell of a L2 U2N Relay UE measured by the L2 U2N Relay UE, and a Uu link measurement result associated with a serving cell of a L2 U2N Relay UE measured by the L2 U2N Relay UE.

FIG.4Bis a diagram illustrating additional information in a measurement report and transmitting the same according to an embodiment of the disclosure.

As described inFIG.4A, referring toFIG.4B, in case of a single measurement identity, a combination of one measObjectId and one reportConfigId is expressed in the form of measId that is unique for each UE and thus, different measurement identities may be distinguished. In addition, a measurement report may include a measurement identity of a measurement configuration that triggers the measurement report. Therefore, a single measurement report may include a value that is evaluated based on one measObjectId and one reportConfigId, and is reported. In case that there are two or more frequencies that need to be measured by a UE that performs reporting or two or more evaluation conditions, to receive merely a single measurement report may provide insufficient information for a serving base station to determine various operations including path switch, handover, secondary cell group addition and modification, and secondary cell addition and modification. To receive various measurement reports required for making such decisions, an additional configuration and a delay time may be incurred until the measurement reports are received. Therefore, a method of including various pieces of information requested by a base station in a single measurement report may reduce a delay time and a signaling overhead.

Referring toFIG.4B, via the direct link432or the indirect link433, the base station430may transmit an RRC (e.g., RRCReconfiguration) message in operation434including a configuration for including additional information (an additional report) in a measurement report that a UE transmits. In case that evaluation in operation411indicates that the Uu link or PC5 link measurement result satisfies a measurement report triggering evaluation condition and an entering or leaving condition based on a report configuration, the L2 U2N Remote UE410may transmit the measurement report message412to the serving base station430via the direct link413or the indirect link414.

Hereinafter, the report condition and the report result associated with a measurement identity described inFIG.4Aare described as terms, main report condition and main report result, respectively, and a report condition and a report result based on an additional configuration are described as terms, additional report condition and additional report result, respectively.

Configuration method 1: For an additional report, a base station may configure, for a measurement identity, one or more pieces of information among the following.An additional report configuration: a configuration to include a Uu link measurement result in an additional report result or to include a PC5 link measurement result to an additional report result, which may be provided in a form indicating application or non-application, or in the form of a list or a single value including one or more among an additional report object or an additional report condition.An additional report object, measObjectId, i.e., in the form of a list or a single value of measObjectId.An object of additionally report, SL-measObjectId, i.e., in the form of a list or a single value of SL-measObjectId.An additional report condition, reportConfigId, i.e., in the form of a list or a single value of reportConfigId.A main report condition for including an additional report, reportConfigId, i.e., in the form of a list or a single value of reportConfigId.

Configuration method 2: to configure a measurement object for an additional report, a base station may configure, for a measurement object, one or more pieces of information for a main report among the following.An additional report configuration: a configuration to include a Uu link measurement result in an additional report result or to include a PC5 link measurement result to an additional report result, which may be provided in a form indicating application or non-application, or in the form of a list or a single value including an additional report object.An additional report object: an NR measurement object identity, i.e., in the form of a list or a single value of measObjectid.An additional report object: a sidelink measurement object identity, i.e., in the form of a list or a single value of SL-MeasObjectId.An additional report object: a parameter included in an NR measurement object, i.e., in the form of a list or a single value of at least one parameter among a frequency for measuring an NR cell, a subcarrier spacing, a reference signal configuration, an allowed/excluded cell list, an object specific offset, and a cell specific offset.An additional report object: a parameter included in a sidelink measurement object, i.e., in the form of a list or a single value of at least one parameter among sl-MeasObject including a frequency for measuring a sidelink UE, a sidelink measurement object identity that is in one-to-one correspondence with the frequency and is unique for each UE.

Configuration method 3: to configure a report configuration for an additional report, a base station may configure, for a report configuration for a main report, one or more pieces of information among the following.Additional report configuration: a configuration to include a Uu link measurement result in an additional report result or to include a PC5 link measurement result to an additional report result, which may be provided in a form indicating application or non-application, or in the form of a single value or a list including one or more among an additional report object or an additional report condition.An additional report object: an NR measurement object identity, i.e., in the form of a list or a single value of measObjectid.An additional report object: a sidelink measurement object identity, i.e., in the form of a list or a single value of SL-MeasObjectId.An additional report object: an NR measurement object, i.e., in the form of a list or a single value of measObject.An additional report object: a sidelink measurement object, i.e., in the form of a list or a single value of SL-MeasObject.An additional report condition: one or more report configuration identities, i.e., in the form of list or a single value of reportConfigId.An additional report condition: provided in the form of a report triggering event, or includes at least one piece of information among one or more thresholds, an offset, a TTT, a hysteresis, a report quantity cell, and a report quantity relay, and an evaluation condition may be configured as an evaluation condition described inFIG.2.Main report condition for including an additional report: provided in the form of a report triggering event, or includes at least one piece of information among one or more thresholds, an offset, a TTT, a hysteresis, a report quantity cell, and a report quantity relay, and an evaluation condition may be configured as an evaluation condition described inFIG.2B.

A base station may transmit, to a UE, at least one of an additional report configuration, an additional report object, an additional report condition, and a main report condition for including an additional report via the RRC (e.g., RRCReconfiguration) message in operation434by using at least one of methods 1, 2, and 3. In case that at least one of an additional report object, an additional report condition, and a main report condition for including an additional report is configured, the U2N Remote UE410that receives the RRCReconfiguration message in operation434may implicitly recognize that an additional report is configured. In operation415, a measurement report triggering event is performed by the U2N remote UE410.

In case that an additional report result is included in the measurement report of operation416that the U2N Remote UE410reports to the base station430, a measurement identity of a measurement configuration in which an additional report is configured, one or more Uu link measurement results that satisfy an additional report condition evaluation, and one or more PC5 link measurement results that satisfy an additional report condition evaluation may be included. Specifically, a Uu link measurement result may include one or more pieces of information among a serving cell index of a measured cell, a cell identity, a physical cell identity, a unit of measurement used for evaluating an additional report condition, and a measurement result used for evaluating an additional report condition, and a PC5 result link measurement result may include one or more pieces of information among a serving cell identity of a measured UE, a serving cell PLMN identity, a source identity, a unit of measurement used for evaluating an additional report condition, a measurement result used for evaluating an additional report condition, a unit of Uu link measurement associated with a serving cell of an L2 U2N Relay UE measured by the L2 U2N Relay UE, and a Uu link measurement result associated with a serving cell of an L2 U2N Relay UE measured by the L2 U2N Relay UE.

FIG.4Cis a diagram illustrating a measurement reporting operation by an L2 U2N Remote UE according to an embodiment of the disclosure. Specifically, there is provided an example in which an L2 U2N Remote UE evaluates, based on a main report condition, a Uu link measurement result or a PC5 link measurement result, and includes, based on an evaluation result of an additional report condition, an additional report result in a measurement result when transmitting the measurement result.

Referring toFIG.4C, the L2 U2N Remote UE may determine whether a Uu link or PC5 link measurement result satisfies a main report condition in operation441. In case that the Uu link or PC5 link measurement result satisfies an evaluation based on the main report condition, the L2 U2N Remote UE proceeds with operation442so as to determine whether an additional report is configured.

The L2 U2N Remote UE may determine whether an additional report is configured in operation442. In case that an additional report is not configured, the L2 U2N Remote UE may proceed with operation450and may transmit a measurement result excluding an additional report result to a serving base station. In case that an additional report is configured, the L2 U2N Remote UE may proceed with operation443, and may determine whether a main report condition for including an additional report is configured.

The L2 U2N Remote UE may determine whether a main report condition for including an additional report is configured in operation443. In case that a main report condition for including an additional report is not configured, the L2 U2N Remote UE may proceed with operation445and may evaluate an additional report condition. In case that a main report condition for including an additional report is configured, the L2 U2N Remote UE may proceed with operation444and may evaluate the main report condition for including an additional report.

The L2 U2N Remote UE may evaluate whether a measurement result satisfies the main report condition for including the additional report is satisfied in operation444. In case that the main report condition for including the additional report is not satisfied, the L2 U2N Remote UE may proceed with operation450and may transmit a measurement result that excludes an additional report result to the serving base station. In case that the main report condition for including the additional report is satisfied, the L2 U2N Remote UE may proceed with operation445and may evaluate the additional report condition.

The L2 U2N Remote UE may evaluate an additional report condition in operation445. In case that the additional report condition is not satisfied, the L2 U2N Remote UE may proceed with operation450and may transmit a measurement result that excludes the additional report result to the serving base station. In case that the additional report condition is satisfied, the L2 U2N Remote UE may proceed with operation460and may transmit a measurement result that includes the additional report result to the serving base station.

FIGS.5A and5Bare diagrams illustrating an inter-base station path switching operation in UE-to-network relay according to various embodiments of the disclosure.

As illustrated inFIGS.4A to4C, referring toFIGS.5A and5B, a serving base station of an L2 U2N Remote UE may receive measurement results associated with one or more L2 U2N Relay UEs or measurement results associated with one or more neighboring base stations respectively or parallelly via one or more measurement reports that the L2 U2N Remote UE transmits via a direct-path or an indirect-path.

Referring toFIG.5A, based on a measurement report511received via a direct or indirect path, a serving base station530of the L2 U2N Remote UE510may determine path switching of L2 U2N Remote UE510in operation531, and may determine direct-path switching or indirect-path switching in operation532. In operation533, by using a measurement result of the L2 U2N Remote UE510in association with another base station and information associated with the other base station, that is, at least one piece of information among load information associated with the other base station, information associated with whether XnAP connection with the other base station is present, a success rate of path switching or handover previously performed with the other base station, the serving base station530may determine a target base station540that is an object to which the path is to be switched for direct-path switching. In addition, by using the measurement result of the L2 U2N Remote UE510in association with the L2 U2N Relay UE and at least one piece of information among reported information associated with a serving base station of the L2 U2N Relay UE, the serving base station530may determine a target L2 U2N Relay UE520that is an object to which the path is to be switched for indirect-path switching in operation533, and may determine the serving base station of the target L2 U2N Relay UE520as the target base station540. Hereinafter, the target L2 U2N Relay UE520may be an L2 U2N Relay UE that is an object to which the path is to be switched for indirect-path switching among one or more L2 U2N Relay UEs reported by the L2 U2N Remote UE510. The target base station540may be a base station that is an object to which the path is to be switched for direct-path switching among one or more neighboring base stations reported by the L2 U2N Remote UE510or may be the serving base station of the target L2 U2N Relay UE520that is an object to which the path is to be switched for indirect-path switching.

The serving base station530may transmit an XnAP handover request message534to the target base station540so as to request direct-path switching or indirect-path switching. In case that path switching needs to be performed by using NGAP since an XnAP connection is not configured or for other reasons, the serving base station530may transmit an NGAP handover required message to an AMF so as to request direct-path switching to the target base station540or indirect-path switching to the target L2 U2N Relay UE520. In case that direct-path switching is performed, the procedure and the content of the XnAP handover request message534may be based on the definitions in 3GPP TS 38.300. In case that indirect-path switching is performed, the XnAP handover request message534used for direct-path switching may additionally include indirect-path switching indication information, the identity of the target L2 U2N Relay UE520, and a measurement result associated with the target L2 U2N Relay UE520reported by the L2 U2N Remote UE. Hereinafter, although only a path switching procedure using XnAP is described, the embodiment may be easily modified and applied to a path switching procedure using NGAP. The target base station540may distinguish direct-path switching or indirect-path switching via indication information included in the XnAP handover request message534received from the serving base station530, and may determine whether to allow direct or indirect-path switching via admission control in operation541based on information recognized by the target base station540, such as a success rate of path switching or handover previously performed with the serving base station530, load information of the target base station, quality of a Uu link with the target L2 U2N Relay UE520, an RRC state of the target L2 U2N Relay UE520, and the like. In case that path switching is allowed, the target base station540may transmit, to the serving base station530, an XnAP handover request acknowledge message543including an RRC transparent container to be transmitted to the L2 U2N Remote UE510. In the case of indirect-path switching, the target base station540may transmit U2N relay configuration information associated with the L2 U2N Remote UE510to the target L2 U2N Relay UE520via a RRCReconfiguration message542. In case that the serving base station530receives the XnAP handover request acknowledge message543from the target base station540, the serving base station may transmit an RRCReconfiguration message535including ReconfigurationWithSync in order to indicate, to the L2 U2N Remote UE510, direct or indirect-path switching. In case that direct-path switching is indicated to the L2 U2N Remote UE510, the L2 U2N Remote UE510may transmit an RRCReconfigurationComplete512to the target base station540via a direct-path513and may complete path switching. Alternatively, in case that indirect-path switching is indicated, the L2 U2N Remote UE510may transmit the RRCReconfigurationComplete message512to the target base station540via an indirect link514of the target L2 U2N Relay UE520indicated by the serving base station530.

FIG.5Bis a diagram illustrating an inter-base station path switching operation in UE-to-network relay according to an embodiment of the disclosure.

Referring toFIG.5B, based on the received measurement report511, the serving base station530of the L2 U2N Remote UE510may determine path switching of the L2 U2N Remote UE510in operation531, and may consider another base station or L2 U2N Relay UE as an object to which the path is switchable. In operation536, by using a measurement result of the L2 U2N Remote UE510in association with another base station and information associated with another base station, that is, at least one piece of information among load information associated with the other base station, information associated with whether an XnAP connection with the other base station is present, a success rate of path switching or handover previously performed with the other base station, and the like, the serving base station530may determine the target base station540that is an object to which the path is to be switched for direct-path switching. In addition, by using the measurement result of the L2 U2N Remote UE510in association with an L2 U2N Relay UE and at least one piece of information among reported information associated with a serving base station of the L2 U2N Relay UE, the serving base station530may determine, as the target base station540, a base station that serves one or more L2 U2N Relay UEs that may be objects to which the path is to be switched for indirect-path switching. In case that the serving base station530determines that the single target base station540is available for both direct-path switching and indirect-path switching, or determines that the single target base station540is available for indirect-path switching, the serving base station530may transmit an XnAP handover request message537to the target base station540so that the target base station540determines direct-path switching or indirect-path switching and the target L2 U2N Relay UE520in operation544. Via the XnAP handover request message537, the serving base station530may transfer a request for path switching and information needed for operation544for determining direct-path switching or indirect-path switching and the target L2 U2N Relay UE520. The XnAP handover request message537may include one or more pieces of information among measurement results associated with the target base station540and the L2 U2N Remote UE510, measurement results associated with one or more L2 U2N Relay UEs served by the target base station540and the L2 U2N Remote UE510, and identities of one or more L2 U2N Relay UEs served by the target base station540. Based on the information included in the XnAP handover request message537received from the serving base station530and one or more pieces of information among information that the target base station540recognizes, that is, a success rate of path switching and handover performed previously with the serving base station530, load information of the target base station540, the quality of a Uu link with an L2 U2N Relay UE, and radio resource control (RRC) state information of a L2 U2N Relay UE, the target base station540may determine, as the target L2 U2N Relay UE520, an L2 U2N Relay UE among the one or more L2 U2N Relay UEs included in the XnAP handover request message537in operation544. The target base station540may select one of direct-path switching or indirect-path switching with respect to the target L2 U2N Relay UE520in operation544. In case that direct or indirect-path switching is allowed by the admission control541, the target base station540may transmit, to the serving base station530, an XnAP handover request acknowledge message543including an RRC transparent container to be transmitted to the L2 U2N Remote UE510. In the case of indirect-path switching, the target base station540may include one or more pieces of information among information indicating that indirect-path switching is determined and the identity of the target L2 U2N Relay UE520in the XnAP handover request acknowledge message543, so as to inform the serving base station530that indirect-path switching is to be performed. The target base station540may transmit, to the target L2 U2N Relay UE520, the RRCReconfiguration message542including U2N relay configuration information associated with the L2 U2N Remote UE510. In case that the serving base station530receives the XnAP handover request acknowledge message543from the target base station540, the serving base station530may transmit, to the L2 U2N Remote UE510, the RRCReconfiguration message535including ReconfigurationWithSync for indicating direct or indirect path switching. In case that direct-path switching is indicated, the L2 U2N Remote UE510may transmit the RRCReconfigurationComplete message512to the target base station540via the direct path513and may complete path switching. In case that indirect-path switching is indicated, the L2 U2N Remote UE510may transmit the RRCReconfigurationComplete message512to the target base station540via the indirect link514of the target L2 U2N Relay UE520indicated by the serving base station530.

FIG.6is a diagram illustrating a structure of a base station according to an embodiment of the disclosure.

Referring toFIG.6, the base station may include a transceiver610, a controller (for example, a processor)620, and a storage630. According to the above-described communication method of the base station, the transceiver610, the controller620, and the storage630may operate. A network device may also correspond to the structure of a base station. However, the component elements of the base station are not limited to the above-descried example. For example, the base station may include more or fewer component elements than the above-described component elements. For example, the base station may include the transceiver610and the controller620. In addition, the transceiver610, the controller620, and the storage630may be configured as a single chip.

The transceiver610is the collective name for the receiver of the base station and the transmitter of the base station, and may be capable of performing signal transmission or reception with a UE, another base station, or other network devices. The signal transmitted or received by the base station may include control information and data. The transceiver610may transmit, for example, system information to a UE, and may transmit a synchronization signal or a reference signal. To this end, the transceiver610may include an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, an RF receiver that low-noise amplifies a received signal and down-converts a frequency of a received signal, and the like. This is merely an example of the transceiver610, and the component elements of the transceiver610are not limited to an RF transmitter and an RF receiver. In addition, the transceiver610may include a wired and wireless transceiver, and may include various configurations for transmitting or receiving a signal. In addition, the transceiver610may receive a signal via a communication channel (e.g., a wireless channel) and output the same to the controller620, and may transmit a signal output from the controller620via a communication channel. In addition, the transceiver610may receive a communication signal and may output the same to a processor, and may transmit a signal output from the processor to a UE, another base station, or other entities via a wired or wireless network.

The storage630may store a program and data needed when the base station operates. In addition, the storage630may store control information or data included in a signal obtained by the base station. The storage630may be embodied as a storage medium, such as read only memory (ROM), a random access memory (RAM), a hard disk, a compact disc-ROM (CD-ROM), a digital versatile discs (DVD), and the like, or a combination of storage media. The storage630may store at least one piece of information among information transmitted or received via the transceiver610and information produced by the controller620.

In the disclosure, the controller620may be defined as a circuit, an application-specific integrated circuit, or at least one processor. A processor may include a communication processor (CP) that performs control for communication, and an application processor (AP) that controls a higher layer, such as an application program or the like. The controller620may control overall operation of the base station according to the embodiments of the disclosure. For example, the controller620may control a signal flow among blocks so that operations based on the above-described flowcharts are performed.

FIG.7is a diagram illustrating a structure of a user equipment (UE) according to an embodiment of the disclosure.

Referring toFIG.7, the UE may include a transceiver710, a controller (for example, a processor)720, and a storage730. According to the above-described communication method of the UE, the transceiver710, the controller720, and the storage730may operate. However, the component elements of the UE are not limited to the above-descried example. For example, the UE may include more or fewer component elements than the above-described component elements. For example, the UE may include the transceiver710and the controller720. In addition, the transceiver710, the controller720, and the storage730may be configured as a single chip.

The transceiver710is the collective name for the receiver of the UE and the transmitter of the UE, and may be capable of performing signal transmission or reception with a UE, another UE, or a network entity. The signal transmitted or received by the base station may include control information and data. The transceiver710may receive, for example, system information from a base station, and may receive a synchronization signal or a reference signal. To this end, the transceiver710may include an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, an RF receiver that low-noise amplifies a received signal and down-converts a frequency of a received signal, and the like. This is merely an example of the transceiver710, and the component elements of the transceiver710are not limited to an RF transmitter and an RF receiver. In addition, the transceiver710may include a wired and wireless transceiver, and may include various configurations for transmitting or receiving a signal. In addition, the transceiver710may receive a signal via a wireless channel and output the same to the controller720, and may transmit a signal output from the controller720via a wireless channel. In addition, the transceiver710may receive a communication signal and may output the same to a processor, and may transmit a signal output from a processor to a network entity via a wired or wireless network.

The storage730may store a program and data needed when the UE operates. In addition, the storage730may store control information or data included in a signal obtained by the UE. The storage730may be embodied as a storage medium, such as ROM, RAM, a hard disk, a CD-ROM, a DVD, and the like, or a combination of storage media.

In the disclosure, the controller720may be defined as a circuit, an application-specific integrated circuit, or at least one processor. A processor may include a communication processor (CP) that performs control for communication, and an application processor (AP) that controls a higher layer, such as an application program or the like. The controller720may control overall operation of the UE according to the embodiments of the disclosure. For example, the controller720may control a signal flow among blocks so that operations based on the above-described flowcharts are performed.

The methods according to various embodiments described in the claims or the specification of the disclosure may be implemented by hardware, software, or a combination of hardware and software.