KR20230115065A - Pre measurement method and apparatus for accelerating epx fallback in communication system - Google Patents

Abstract

This disclosure relates to a 5th generation (5G) or 6th generation (6G) communication system for supporting a higher data rate after a long term evolution (LTE) communication system. The present disclosure relates to a method performed by an electronic device in a wireless communication system, a process of determining whether a base station supports voice over new radio (VoNR), and if it is confirmed that the base station does not support VoNR, the base station A process of obtaining information on a cell list from the cell list, a process of checking whether the measurement of the cell list is triggered, and if it is confirmed that the measurement is triggered, measurement of a plurality of cells included in the cell list. The process of performing, based on the result of the measurement, the process of identifying one or more candidate cells among the plurality of cells, the process of transmitting information on the one or more candidate cells to the base station, and a handover command from the base station. It may include a process of receiving.

Description

Pre-measurement method and apparatus for accelerating EPS fallback in communication system

The present disclosure relates to a pre-measurement method and apparatus for accelerating fallback from a communication system to an evolved packet system (EPS).

With the spread of various electronic devices such as smart phones, tablet PCs, portable multimedia players (PMPs), personal digital assistants (PDAs), laptop personal computers (laptop PCs), and wearable devices, , Various wireless communication technologies are being developed in which various electronic devices are used to perform communication.

Efforts are being made to develop an improved 5G communication system or pre-5G communication system to meet the growing demand for wireless data traffic after the commercialization of the 4G communication system. For this reason, the 5G communication system or pre-5G communication system is being called a system after a 4G network (Beyond 4G Network) communication system or an LTE system (Post LTE). In order to achieve a high data rate, the 5G communication system is also considering implementation in a mmWave band (eg, a 60 GHz band) in addition to a band of 6G or less.

However, since the 5G communication system uses a high frequency band, cell coverage may not be perfect. Therefore, in standalone (SA), which is one of the deployment scenarios of the 5G communication system, it is necessary to provide smooth voice service to users by falling back to evolved packet system (EPS) during call setup. .

Based on the above discussion, the present disclosure provides a method and apparatus for reducing call setup time.

In addition, the present disclosure provides a method and apparatus for performing measurement on evolved-universal terrestrial radio access (E-UTRA) cells before an evolved packet system fallback (EPS fallback) trigger of a 5th generation (5G) base station.

A method performed by an electronic device in a wireless communication system according to the present disclosure includes a process of checking whether a base station supports voice over new radio (VoNR), if it is confirmed that the base station does not support VoNR, The process of acquiring information on the cell list from the base station, the process of checking whether the measurement of the cell list is triggered, and if it is confirmed that the measurement is triggered, a plurality of cells included in the cell list A process of performing a measurement for the measurement, a process of identifying one or more candidate cells among the plurality of cells based on a result of the measurement, a process of transmitting information about the one or more candidate cells to the base station, and a process of transmitting the information on the one or more candidate cells to the base station, and a hand from the base station. It may include a process of receiving an over command.

In addition, an electronic device of a wireless communication system according to the present disclosure includes at least one processor and at least one transceiver operably connected to the at least one processor, wherein the at least one processor includes a voice over new (VoNR) base station. radio), and if it is confirmed that the base station does not support VoNR, obtain information about a cell list from the base station, check whether measurement of the cell list is triggered, , If it is confirmed that the measurement is triggered, it performs measurement on a plurality of cells included in the cell list, identifies one or more candidate cells among the plurality of cells based on the result of the measurement, and identifies the one or more candidate cells. It may be configured to transmit information on candidate cells to the base station and receive a handover command from the base station.

Apparatus and method according to embodiments of the present disclosure can reduce call setup time.

In addition, the apparatus and method according to the embodiments of the present disclosure may perform measurements on E-UTRA cells before an EPS fallback (evolved packet system fallback) trigger of a 5th generation (5G) base station.

1 illustrates an evolved packet system (EPS) fallback procedure according to embodiments of the present disclosure.
2 illustrates a conditional handover (CHO) procedure according to embodiments of the present disclosure.
3 illustrates an operation of a terminal for EPS fallback according to embodiments of the present disclosure.
4 illustrates a signal flow of a terminal registration procedure according to embodiments of the present disclosure.
5 illustrates an operational flow of a terminal managing an evolved-universal terrestrial radio access (E-UTRA) cell list according to embodiments of the present disclosure.
6a illustrates an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure.
6B illustrates an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure.
6C illustrates an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure.
7 illustrates an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure.
8 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
9 illustrates an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure.
10 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
11 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
12 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
13 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
14 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
15 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
16 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure.
17 illustrates a configuration of a terminal according to embodiments of the present disclosure.
18 illustrates a configuration of a base station according to embodiments of the present disclosure.
19 is a block diagram of an electronic device in a network environment according to embodiments of the present disclosure.

Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the accompanying drawings. Terms used in this disclosure are only used to describe a specific embodiment, and are not intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly dictates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art described in this disclosure. Among the terms used in the present disclosure, terms defined in general dictionaries may be interpreted as having the same or similar meanings as those in the context of the related art, and unless explicitly defined in the present disclosure, ideal or excessively formal meanings. not be interpreted as In some cases, even terms defined in the present disclosure cannot be interpreted to exclude embodiments of the present disclosure.

In addition, in the present disclosure, the expression of more than or less than is used to determine whether a specific condition is satisfied or fulfilled, but this is only a description for expressing an example and excludes more or less description. It is not. Conditions described as ‘above’ may be replaced with ‘exceeds’, conditions described as ‘below’ may be replaced with ‘less than’, and conditions described as ‘above and below’ may be replaced with ‘exceed and below’.

In addition, in the present disclosure, embodiments are described using terms used in some communication standards (eg, long term evolution (LTE) and new radio (NR) defined in 3rd generation partnership project (3GPP)), but this description is just an example for Embodiments of the present disclosure can be easily modified and applied to other communication systems.

1 illustrates an evolved packet system (EPS) fallback procedure according to embodiments of the present disclosure. 1 describes an EPS fallback procedure for internet protocol multimedia subsystem (IMS) voice. 1 illustrates a user equipment (UE), a new generation radio access network (NG RAN), an E-UTRAN, AMF, MME, SGW, PGW-C, SMF, PCF, and IMS as components of a wireless communication system. do. Here, the NG RAN may correspond to a 5G base station and the E-UTRAN may correspond to a 4G base station.

First, when a terminal camps on an NG RAN of a 5th generation system (5GS), a mobile originated (MO) or mobile terminated (MT) voice session establishment procedure may be started. Then, a PDU session modification procedure for setting up a quality of service (QoS) flow for IMS voice may be initiated by the network (NW). NG RAN configured to support EPS fallback for IMS voice includes UE capability, indication received from AMF (e.g., redirection for EPS fallback for voice is possible), It is possible to determine whether to trigger EPS fallback in consideration of network configuration and radio conditions. In this case, if the NG RAN determines not to trigger the EPS fallback, the following process may not be performed. If it is determined that EPS fallback is triggered, the NG RAN responds with a rejection of PDU session modification for establishing a flow for IMS voice by sending a PDU session modification response message to SMF+PGW+C through AMF. can do. In this case, the PDU session modification response message may include an indication indicating that mobility due to fallback to IMS voice is in progress. After that, the NG RAN may start an access network (AN) release or handover through inter-system redirection to the EPS in consideration of the UE capability. When redirection or handover is performed between systems having an N26 interface, the terminal may initiate a tracking area update (TAU) procedure. In the case of redirection between systems with an N26 interface, an active flag may be included in the TAU request. On the other hand, in case of system-to-system redirection without an N26 interface, the terminal may initiate an attach with a PDN connection request having a request type of "handover". Upon completion of the mobility procedure to the EPS or as part of the handover procedure, PDN connection modification to establish a dedicated bearer for voice may be initiated by the NW.

Referring to the above description, after the NG RAN (ie, 5G base station) triggers the EPS fallback, a handover procedure may be performed to access the EUTRAN (ie, 4G base station). In this case, a conditional handover (CHO) procedure among handover procedures that can be performed is described in FIG. 2 .

2 illustrates a conditional handover (CHO) procedure according to embodiments of the present disclosure. A legacy handover is triggered when a radio condition deteriorates in a handover preparation procedure. On the other hand, CHO is a handover performed by the terminal when one or more handover execution conditions are satisfied, and can be started even in a good radio condition. In addition, since CHO can be performed targeting one or more candidate target cells instead of one target cell as in the prior art, mobility robustness of the UE can be improved. Hereinafter, in FIG. 2, the CHO procedure is described on the premise that the terminal 210 is in a radio resource control (RRC) connected state with the source base station 220.

Referring to FIG. 2 , in operation 201, the source base station 220 may transmit a handover request message to the target base station 230. In this case, the handover request message may include a CHO indication. In operation 203, the target base station 230 may receive the handover request message, perform admission control, and transmit a handover request response message to the source base station 220. In this case, the handover request response message may include information about CHO. Here, the CHO information includes information on CHO execution conditions of the target base station 230, identification information of the target base station 230 (eg, physical cell identifier (PCI), cell global identifier (CGI), node ID), target In relation to the base station 230, it may include at least one of radio resource configuration information to be used after CHO and information on a timer (eg, CHO execution timer) for determining whether CHO fails. In operation 205, the source base station 220 may transmit the CHO information received from the target base station 230 to the terminal 210. In this case, the CHO information may be transmitted through an RRC reconfiguration message or a CHO command. Meanwhile, in FIG. 2, it is shown that the source base station 220 transmits a handover request message to one target base station 230 and receives a handover request response message from the corresponding target base station 230, but this is an example. only one For example, the source base station 220 may transmit a handover request message to other candidate target base stations in addition to the target base station 230 and include a handover request response message from the candidate target base stations. Accordingly, in operation 205, the source base station 220 may transmit CHO information about a plurality of candidate base stations to the terminal 210. In operation 207, the terminal 210 may measure the CHO execution condition included in the received CHO information and monitor whether an event given as the CHO execution condition occurs. In operation 209, the terminal 210 may transmit and receive data with the source base station 220 while performing measurement and monitoring. In operation 211, when the CHO execution condition is satisfied, the terminal 210 may perform CHO. Here, performing the CHO may correspond to a process in which the terminal 210 disconnects from the source base station 220 and performs synchronization with the target base station 230 . In this case, the process of performing synchronization may correspond to a random access channel (RACH) procedure as illustrated in operation 213 of FIG. 2 . Meanwhile, when the CHO execution condition of a plurality of base stations is satisfied among one or more base stations for which CHO information is set, the terminal may select one of the plurality of base stations. For example, the terminal 210 may select a base station having the strongest signal strength among base stations satisfying the CHO execution condition as a base station to perform CHO. 2 illustrates the selected base station as the target base station 230 . In operation 215, when synchronization is completed, the terminal 210 may transmit a handover complete message to the target base station. In operation 217, the target base station 230 may transmit a use equipment context release message to the source base station 220. In operation 219 , the source base station 220 receiving the terminal context release message may release the terminal context of the terminal 210 .

Referring to the EPS fallback procedure described in FIGS. 1 and 2, the UE may receive the E-UTRA cell list to perform measurement through the RRC reset message in the CHO procedure after the EPS fallback trigger of the 5G base station. However, even when EPS fallback is expected because the terminal or network (NW) does not support voice over new radio (VoNR), waiting for the EPS fallback trigger by the terminal may cause delay. Similarly, receiving the E-UTRA cell list after the EPS fallback trigger by the UE may also cause a delay. As a result, these delays may negatively affect user experience for a voice over long term evolution (VoLTE) service to be performed in a 4G base station after handover by increasing call setup time. Therefore, if EPS fallback is expected, it is necessary to reduce the delay by allowing the UE to perform measurement on the E-UTRA cell list in advance.

3 illustrates an operation of a terminal for EPS fallback according to embodiments of the present disclosure. In FIG. 3, a method for reducing call setup time by performing prior measurement by the terminal will be described.

Referring to FIG. 3 , in operation 310, the terminal may determine capabilities for voice over new radio (VoNR) and pre-measurement of the terminal and the network. Here, the network may include a radio access network (RAN) node (ie, a base station). In addition, the network may include at least one of network functions (NFs) of a core network (CN) as well as a RAN node. Since the UE already acquires VoNR capability information of the UE and capability information for pre-measurement, it is necessary to acquire VoNR capability information and capability information for pre-measurement of the network.

In one embodiment, the terminal may obtain capability information for VoNR of the network based on a local database. For example, the UE may obtain VoNR capability information of the network based on at least one of public land mobile network (PLMN), operation support information, and location coverage information. In another embodiment, the terminal may obtain capability information for VoNR of the network based on the NR cell list. Here, the NR cell list may include NR cells that the UE previously camped on. That is, by managing NR cells that do not support VoNR among NR cells camped on as a cell list, the terminal can check whether the corresponding network supports VoNR during reconnection. In the above-described embodiments, it has been described that the terminal obtains capability information for VoNR of the network based on a local database or a NR cell list, but this is only an example, and in embodiments according to the present disclosure, the above-described embodiments can be combined there is. For example, in the case of a reconnected cell, the terminal checks the VoNR capability information of the network based on the NR cell list, and in the case of the first cell accessed, the UE may check the network VoNR capability information based on the local database. .

In one embodiment, in order for the UE to check capability information for pre-measurement of the network, a new flag is added to the UE capability information and registration accept message of the UE registration procedure. may be included. Here, for example, pre-measurement bits included in the UE capability information and the registration approval message may be defined as follows.

- Pre-measurement bit = 1: If the pre-measurement bit included in the UE capability information reported by the UE to the network is 1, it may mean that the UE supports the pre-measurement. Similarly, when the pre-measurement bit included in the registration approval message transmitted from the network to the terminal is 1, it may mean that the network supports the pre-measurement.

- Pre-measurement bit = 0: If the pre-measurement bit included in the UE capability information reported by the UE to the network is 0, it may mean that the UE does not support the pre-measurement. Similarly, when the pre-measurement bit included in the registration approval message transmitted from the network to the terminal is 0, it may mean that the network does not support pre-measurement.

However, the above definition is only an example, and if the pre-measurement bit is 0, it may mean that the terminal and the network support the pre-measurement, and if the pre-measurement bit is 1, the terminal and the network do not support the pre-measurement. may mean

In operation 320, the UE may receive the E-UTRA cell list from the NW. Here, the E-UTRA cell list may include E-UTRA neighbor cells that can be detected by a serving base station. In order for the UE to perform prior measurement on E-UTRA neighboring cells without waiting for the EPS fallback of the serving base station, it is necessary to receive information on the E-UTRA cell list from the base station. In this case, an example of signaling for receiving information on the E-UTRA cell list may be as follows.

- System information block (SIB): E-UTRA cell list may be included in system information. System information (SI) may be a message for the base station to deliver network configuration information to the terminal. SI can be divided into minimum system information (MSI) and other system information (OSI). MSI may include a master information block (MIB) and SIB1, and OSI may include system information excluding the MIB and SIB1. Here, OSI may be periodically broadcast through DL-SCH. In addition, OSI may be broadcast based on an on-demand (eg, SIB5 may be transmitted based on a request of a terminal in an RRC connection, RRC inactive, or RRC idle state). In addition, the OSI may be transmitted to a terminal in an RRC connected state through a DL-SCH in a dedicated manner (e.g., when there is a request from a terminal in an RRC connected state or to an active bandwidth part (BWP) of the terminal) If a common search space (CSS) is not set, the OSI may be transmitted to the terminal through the DL-SCH in a dedicated manner). SIB5 is designated to carry information about E-UTRA frequencies and E-UTRA neighboring cells. Accordingly, information on the E-UTRA cell list may be included in SIB5 and transmitted to the UE. However, this is only an example, and information on the E-UTRA cell list may also be included in other system information.

- RRC release message: The network may request the UE to measure the E-UTRA carrier to the UE in the RRC inactive or RRC idle state through the RRC release message. Accordingly, information on the E-UTRA cell list may also be included in the RRC release message.

In operation 330, the terminal may store and update information about the received E-UTRA cell list. The UE may obtain information on the E-UTRA cell list through the above-described system information or RRC release message. In this case, the terminal may store information about the E-UTRA cell list and update the E-UTRA cell list based on the information.

In operation 340, the terminal may perform prior measurement. The UE may perform preliminary measurement on cells included in the E-UTRA cell list. In this case, the terminal may start pre-measurement based on a specific trigger condition. For example, the trigger condition may be configured as follows.

- Based on INVITE message: When the UE transmits or receives the INVITE message, the UE may perform preliminary measurement on cells included in the E-UTRA cell list. In this case, the INVITE message may be a message for requesting a call.

- Event-based: The UE may perform preliminary measurement on cells included in the E-UTRA cell list based on user input. For example, when a user inputs a phone number, the terminal may perform preliminary measurement on cells included in the E-UTRA cell list. For another example, when a user inputs a short message service (SMS) message, the terminal may perform preliminary measurement on cells included in the E-UTRA cell list.

The UE may identify candidate cells from among cells included in the E-UTRA cell list based on prior measurement. For example, the UE may compare the intensities of signals received from cells included in the E-UTRA cell list with a predetermined threshold value. In this case, the terminal can identify cells whose signal strength exceeds a predetermined threshold as candidate cells. The terminal may transmit information about the identified candidate cells to the network.

In operation 350, the terminal may perform handover to EPS. The base station may identify one cell as a target cell for EPS fallback based on the received information on candidate cells. In this case, the base station may transmit a handover command to the terminal after going through a handover preparation procedure. After receiving the handover command, the UE can access the corresponding cell by performing a random access channel (RACH) procedure with a cell that is an EPS fallback target.

Meanwhile, it has been described that general handover is performed in the above-described operations 340 and 350, but this is only an example. For example, the terminal may perform a synchronization process by disconnecting from the base station and selecting one of the candidate cells without transmitting information on the identified candidate cells to the network, as in the CHO procedure. .

4 illustrates a signal flow of a terminal registration procedure according to embodiments of the present disclosure. 4 describes a procedure in which a UE obtains capability information for VoNR of a base station and capability information for pre-measurement.

Embodiments of the present disclosure aim to reduce call setup time by allowing a UE to perform pre-measurement without waiting for an EPS fallback trigger from a base station. Therefore, the terminal must be able to predict that the base station will trigger EPS fallback later. That is, if at least one of the terminal and the base station does not support VoNR, the terminal can predict that the base station will trigger the EPS fallback. In addition, since measurement must be performed in advance to shorten the EPS fallback setup, the terminal must be able to know whether both the terminal and the base station support preliminary measurement.

In one embodiment, the terminal may obtain capability information on VoNR of the base station. For example, the terminal may obtain VoNR capability information of the base station based on at least one of public land mobile network (PLMN), operation support information, and location coverage information. In another embodiment, the UE may obtain VoNR capability information of the base station based on the NR cell list. Here, the NR cell list may include NR cells that the UE previously camped on. That is, by managing NR cells that do not support VoNR among NR cells camped on as a cell list, the terminal can check whether the corresponding network supports VoNR during reconnection. In the above-described embodiments, it has been described that the terminal obtains capability information for VoNR of the network based on a local database or a NR cell list, but this is only an example, and in embodiments according to the present disclosure, the above-described embodiments can be combined there is. For example, in the case of a reconnected cell, the terminal checks the VoNR capability information of the network based on the NR cell list, and in the case of the first cell accessed, the UE may check the network VoNR capability information based on the local database. .

In one embodiment, the terminal may obtain capability information for pre-measurement of the base station through a non-access stratum (NAS) registration procedure. The NAS registration procedure may be configured as follows. In operation 410, the terminal may transmit a registration request message to a 5th generation core network (5GC). Here, 5GC may mean AMF. In operation 420, the 5GC may transmit a UE radio capability check request message to the base station. In operations 430 and 440, the base station may transmit a UE radio capability inquiry message to the UE and receive UE capability information from the UE. In operation 550, the base station may transmit a UE radio capability check response message to the 5GC. At operation 460, the 5GC may send an initial context setup request to the base station. In operation 470, the 5GC may transmit a registration accept message to the terminal. In this NAS registration procedure, a new flag may be included in the UE capability information and the registration approval message in order for the UE to check the capability information for the preliminary measurement of the base station. Here, for example, pre-measurement bits included in the UE capability information and the registration approval message may be defined as follows.

- Pre-measurement bit = 1: When the pre-measurement bit included in the UE capability information reported by the UE to the base station is 1, it may mean that the UE supports the pre-measurement. Similarly, when the pre-measurement bit included in the registration approval message transmitted from the network to the terminal is 1, it may mean that the base station supports the pre-measurement.

- Pre-measurement bit = 0: If the pre-measurement bit included in the UE capability information reported by the UE to the base station is 0, it may mean that the UE does not support the pre-measurement. Similarly, when the pre-measurement bit included in the registration approval message transmitted from the network to the terminal is 0, it may mean that the base station does not support pre-measurement.

However, the above definition is only an example, and when the pre-measurement bit is 0, it may mean that the terminal and the base station support pre-measurement, and when the pre-measurement bit is 1, the terminal and the base station do not support pre-measurement. may mean

The terminal can obtain capability information on VoNR of the base station and capability information on pre-measurement through the process described in FIG. 4 . In this case, the terminal can identify whether the terminal and the base station support pre-measurement when at least one of the terminal and the base station does not support VoNR. If the terminal and the base station are identified as supporting pre-measurement, the terminal can expect that EPS fallback will be triggered.

5 illustrates an operational flow of a terminal managing an E-UTRA cell list according to embodiments of the present disclosure. In FIG. 5, the operation of the terminal in which the terminal stores and updates the E-UTRA cell list will be described.

In the legacy procedure, the UE may receive the E-UTRA cell list in the CHO procedure after the EPS fallback is triggered by the base station. In this case, the call setup time is delayed by the difference between the EPS fallback triggered time and the E-UTRA cell list received time. Therefore, in embodiments according to the present disclosure, regardless of whether EPS fallback is triggered, the UE needs to receive the E-UTRA cell list in advance.

Referring to FIG. 5 , in operation 510, a UE may receive information about an E-UTRA cell list from a base station. As described in FIG. 4, when it is expected that EPS fallback will be triggered, the UE can receive information on the E-UTRA cell list by requesting system information (SI) from the base station. In addition, when it is expected that the EPS fallback will be triggered based on the received UE capability information, the base station may include information on the E-UTRA cell list in the RRC release message and transmit it. An example of the aforementioned signaling may be as follows.

- System information block (SIB): E-UTRA cell list may be included in system information. System information (SI) may be a message for the base station to deliver network configuration information to the terminal. SI can be divided into minimum system information (MSI) and other system information (OSI). MSI may include a master information block (MIB) and SIB1, and OSI may include system information excluding the MIB and SIB1. Here, OSI may be periodically broadcast through DL-SCH. In addition, OSI may be broadcast based on an on-demand (eg, SIB5 may be transmitted based on a request of a terminal in an RRC connection, RRC inactive, or RRC idle state). In addition, the OSI may be transmitted to a terminal in an RRC connected state through a DL-SCH in a dedicated manner (e.g., when there is a request from a terminal in an RRC connected state or to an active bandwidth part (BWP) of the terminal) If a common search space (CSS) is not set, the OSI may be transmitted to the terminal through the DL-SCH in a dedicated manner). SIB5 is designated to carry information about E-UTRA frequencies and E-UTRA neighboring cells. Accordingly, information on the E-UTRA cell list may be included in SIB5 and transmitted to the UE. However, this is only an example, and information on the E-UTRA cell list may also be included in other system information.

- RRC release message: The network may request the UE to measure the E-UTRA carrier to the UE in the RRC inactive or RRC idle state through the RRC release message. Accordingly, information on the E-UTRA cell list may also be included in the RRC release message.

The terminal may receive and store information on the E-UTRA cell list through the above-described system information or RRC message.

In operation 520, the terminal may identify whether a serving cell has changed. That is, the terminal may update the E-UTRA cell list when the serving cell is changed due to movement or changes in the radio environment. For example, when it is confirmed that the serving cell is changed, the terminal may receive a new E-UTRA cell list from the changed serving cell through the signaling illustrated in operation 510. In operation 530, the UE may update the E-UTRA cell list based on the new E-UTRA cell list received from the new serving cell.

6a to 6c illustrate an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure. 6A to 6C describe a result of comparing a difference between a legacy call setup time and a call setup time according to an EPS fallback procedure according to embodiments of the present disclosure.

Meanwhile, prior to description, the times shown in FIGS. 6A to 6C may be defined as follows.

- t0: Time required to measure one cell included in the E-UTRA cell list.

- t1: Difference between the time when EPS fallback is triggered by the base station and the time when the UE receives the E-UTRA cell list (eg 50 ms).

- t2: Time required until the HO procedure after reporting candidate cells (eg, 100 ms).

- t3: Time required to perform pre-measurement after a measurement event (eg, INVITE transmission or reception) occurs (eg, 0 ms) or time required to report candidate cells after a measurement event occurs (eg, 0 ms).

- A: The number of cells included in the E-UTRA cell list.

6A is a diagram for explaining a call setup time according to a conventional EPS fallback procedure. Referring to FIG. 6A, even if the UE transmits or receives the INVITE message, it takes time t1 because it can receive the E-UTRA cell list after EPS fallback is triggered by the network. In addition, the UE performs measurement on A cells and reports candidate cells. It takes time t0. In addition, after reporting the candidate cells, it takes time t2 to complete the handover. Therefore, according to FIG. 6a, the call setup time according to the conventional EPS fallback procedure is A It is t0+t1+t2.

6B is a diagram for explaining a call setup time according to an EPS fallback procedure of embodiments according to the present disclosure. Referring to FIG. 6C, through operations 611 and 613, the UE can expect EPS fallback to be triggered. Accordingly, in operation 615, the UE may receive, store, and update the E-UTRA cell list in advance. After all, when the UE transmits or receives the INVITE message, it can immediately start measuring the E-UTRA cell list without waiting for EPS fallback to be triggered by the network (ie, t3 = 0ms). After all, the time A required for the UE to measure A number of cells and report candidate cells After t0 and the terminal reports the candidate cells, it takes time t2 to complete the handover, so the call setup time is A It is t0+t2. Therefore, the call setup time is reduced by t1 compared to the conventional EPS fallback procedure.

6C is a diagram for explaining a call setup time according to an EPS fallback procedure of embodiments according to the present disclosure. Referring to FIG. 6C, through operations 625 and 627, the UE can expect EPS fallback to be triggered. Accordingly, in operation 629, the UE may receive, store, and update the E-UTRA cell list in advance. In operation 631, the terminal may identify the occurrence of a measurement event. Here, the measurement event may be based on user input. For example, the measurement event may include at least one of a user inputting a phone number or a short message service (SMS) message. In this case, the measurement event may be pre-configured in the terminal or set by the base station. In operation 633, the UE may perform measurement on cells included in the E-UTRA cell list in response to the identification of the measurement event, and at time A It may take t0. In addition, since the time t3 (=0 ms) required for reporting the candidate cells after the terminal transmits or receives the INVITE message and the time t2 required for the terminal to complete the handover after reporting the candidate cells, the call The setup time is t2. Therefore, compared to the conventional EPS fallback procedure, the call setup time is t1+ A It is reduced by t0.

As described in FIGS. 6A to 6C , call setup time may be reduced according to the present disclosure. Therefore, since the terminal can perform a VoLTE call more quickly, user experience can be improved.

7 illustrates an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure. 7 is a diagram for explaining an embodiment in which a terminal is in an RRC connected state and transmission and reception of an INVITE message is used as a trigger condition for prior measurement.

In operation 710, the terminal may identify whether the terminal and the network (network, NW) support voice over new radio (VoNR). The terminal can identify whether the network supports VoNR based on a local database. For example, the terminal based on capability information for VoNR of the network obtained based on at least one of a public land mobile network (PLMN), operation support information, or location coverage information, It can identify whether the network supports VoNR or not. In addition, the terminal can identify whether the network supports VoNR based on the NR cell list. Here, the NR cell list may include NR cells that the UE previously camped on. That is, the terminal can identify whether a corresponding network supports VoNR during reconnection by managing cells that do not support VoNR among NR cells camped on as a cell list. The terminal may perform VoNR-based communication with the network when both the terminal and the network support VoNR. On the other hand, the terminal may perform operation 720 when at least one of the terminal or the network does not support VoNR.

In operation 720, the UE may identify whether the UE and the network support pre-measurement for EPS fallback (FB). The terminal may identify whether the network supports preliminary measurement based on capability information for preliminary measurement of the network obtained through a non-access stratum (NAS) registration procedure. In order for the UE to obtain capability information for pre-measurement of the network, a new flag may be included in the UE capability information and registration accept message of the NAS UE registration procedure. Here, for example, pre-measurement bits included in the UE capability information and the registration approval message may be defined as follows.

- Pre-measurement bit = 1: If the pre-measurement bit included in the UE capability information reported by the UE to the network is 1, it may mean that the UE supports the pre-measurement. Similarly, when the pre-measurement bit included in the registration approval message transmitted from the network to the terminal is 1, it may mean that the network supports the pre-measurement.

- Pre-measurement bit = 0: If the pre-measurement bit included in the UE capability information reported by the UE to the network is 0, it may mean that the UE does not support the pre-measurement. Similarly, when the pre-measurement bit included in the registration approval message transmitted from the network to the terminal is 0, it may mean that the network does not support pre-measurement.

However, the above definition is only an example, and if the pre-measurement bit is 0, it may mean that the terminal and the network support the pre-measurement, and if the pre-measurement bit is 1, the terminal and the network do not support the pre-measurement. may mean When at least one of the UE or the network does not support pre-measurement, the UE may wait for EPS fallback triggered by the network as in the case of legacy. On the other hand, the terminal may perform operation 730 when the terminal and the network support pre-measurement.

In operation 730, the terminal may receive the E-UTRA cell list from the base station. Here, the E-UTRA cell list may include E-UTRA neighbor cells that can be detected by a serving base station. The UE may obtain information on the E-UTRA cell list through system information (SI) or an RRC release message.

In operation 740, the terminal may transmit or receive an INVITE message. For example, the terminal may transmit an INVITE message requesting a call to the IMS. A case where the terminal transmits INVITE may be referred to as mobile originated (MO). For another example, the terminal may receive an INVITE message requesting a call from the IMS. When the terminal receives the INVITE message, it may be referred to as mobile terminated (MT). When the INVITE message is not transmitted and received and the serving base station is changed, the terminal may perform operation 730 again. On the other hand, the terminal may perform operation 750 when the INVITE message is transmitted or received.

In operation 750, the UE may perform prior measurement on cells included in the E-UTRA cell list. In operation 760, the UE may identify candidate cells from among cells included in the E-UTRA cell list based on prior measurement. After that, the terminal may report the identified candidate cells to the base station. In operation 770, the terminal may perform handover to the EPS according to a handover command received from the base station and perform a VoLTE call.

8 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 8 is a diagram for explaining an embodiment in which a terminal is in an RRC connected state and an INVITE message is used as a trigger condition for prior measurement.

Operations 801 to 813 of FIG. 8 are processes in which the terminal acquires capability information for VoNR and pre-measurement of the network through a non-access stratum (NAS) registration procedure, and is illustrated in FIG. 4, so description is omitted.

In operation 815, the terminal may receive system information (SI) from the base station. In this case, the system information may include information about the E-UTRA cell list. Here, the system information may correspond to a system information block (SIB) 5 .

In operation 819, the terminal 817 in an RRC connected state may transmit and receive an INVITE message. Here, transmission and reception of the INVITE message may be a trigger for starting prior measurement. In operation 819, when the UE transmits or receives the INVITE message, the UE may perform preliminary measurement on cells included in the E-UTRA cell list. The UE may identify candidate cells among cells included in the E-UTRA cell list based on a result of performing preliminary measurement. Then, in operation 823, the terminal may report the candidate cells to the base station. In operation 827, the base station may trigger an EPS fallback. In operation 829, the base station may transmit a handover command to the terminal. In this case, the UE may perform handover to the target cell indicated by the EPS. As a result, the IMS voice session 825 of the 5th generation system (5GS) can be delivered to the EPS.

9 illustrates an operation flow of a terminal for EPS fallback according to embodiments of the present disclosure. 9 is a diagram for explaining an embodiment in which a UE is in an RRC connected state and a measurement event is used as a trigger condition for prior measurement.

Operations 910 to 930 of FIG. 9 are operations of the terminal illustrated in operations 710 to 730 of FIG. 7 and are illustrated in FIG. 7 , so descriptions thereof are omitted.

In operation 940, the terminal may identify a measurement event. A measurement event may be a trigger to initiate prior measurement. This measurement event may be identified by a communication processor (CP) of the terminal based on a user input. For example, the terminal may identify that a measurement event has occurred when a user inputs a phone number. As another example, when a user inputs a short message service (SMS) message, the terminal may identify that a measurement event has occurred.

In operation 950, when a measurement event occurs, the UE may perform prior measurement on cells included in the E-UTRA cell list.

In operation 960, the terminal may identify whether a call has started. In this case, the terminal may identify whether a call has started based on the user input. For example, the terminal may identify that a call has started when the user inputs making a call. For another example, when the user inputs SMS message transmission, the terminal may identify that a call has started. The terminal may perform operation 930 again if the serving base station is changed without being identified as having started a call. On the other hand, when the terminal identifies that the call has started, operation 970 may be performed.

In operation 970, the terminal may report candidate cells to the base station. In this case, candidate cells may be identified based on a result of performing preliminary measurement among E-UTRA cells. Meanwhile, in FIG. 9 , although operation 960 precedes operation 970 , this is only an example. If preliminary measurement is completed before user input (eg, making a call or sending an SMS message), operation 970 may precede operation 960 .

In operation 980, the terminal may perform handover to the EPS according to a handover command received from the base station and perform a VoLTE call.

10 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 10 is a diagram for explaining an embodiment in which a UE is in an RRC connected state and a measurement event is used as a trigger condition for prior measurement.

Operations 1001 to 1013 of FIG. 10 are processes in which the terminal acquires capability information on VoNR and pre-measurement of the network through a non-access stratum (NAS) registration procedure, and is illustrated in FIG. 4, so description is omitted.

In operation 1015, the terminal may receive system information (SI) from the base station. In this case, the system information may include information about the E-UTRA cell list. Here, the system information may correspond to a system information block (SIB) 5 .

In operation 1019, the terminal 1017 in an RRC connected state may identify a measurement event. A measurement event may be a trigger to initiate prior measurement. These measurement events may be identified based on user input. For example, the terminal may identify that a measurement event has occurred when a user inputs a phone number. As another example, when a user inputs a short message service (SMS) message, the terminal may identify that a measurement event has occurred.

In operation 1021, when a measurement event occurs, the UE may perform prior measurement on cells included in the E-UTRA cell list.

In operation 1023, the terminal may identify whether a call has started. In this case, the terminal may identify whether a call has started based on the user input. For example, the terminal may identify that a call has started when the user inputs making a call. For another example, when the user inputs SMS message transmission, the terminal may identify that a call has started.

In operation 1025, the terminal may report candidate cells to the base station. In this case, candidate cells may be identified based on a result of performing preliminary measurement among E-UTRA cells. In operation 1029, the base station may trigger an EPS fallback. In operation 1031, the base station may transmit a handover command to the terminal. In this case, the UE may perform handover to the target cell indicated by the EPS. As a result, the mobile originated (MO) voice session 1027 of the 5th generation system (5GS) may be delivered to the EPS.

11 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 11 is a diagram for explaining an embodiment in which a UE is in an RRC inactive state and transmission of an INVITE message is used as a trigger condition for prior measurement.

Operations 1101 to 1113 of FIG. 11 are processes in which the terminal acquires capability information on VoNR and pre-measurement of the network through a non-access stratum (NAS) registration procedure, and is illustrated in FIG. 4, so description is omitted.

In operation 1115, the terminal may receive an RRC release message from the base station. In this case, the RRC release message may include dedicated measurement configuration information. The dedicated measurement configuration information may include at least one of information requesting measurement of an E-UTRA carrier in an RRC inactive state or information about an E-UTRA cell list.

In operation 1117, the UE may transition to an RRC inactive state based on the received RRC release message. In operation 1119, the terminal may identify whether a call has started. In this case, when the terminal transmits the INVITE message to the IMS, it can identify that the call has started. When the terminal transmits the INVITE message, it may be referred to as mobile originated (MO). In operation 1121, when it is identified that the call has started, the terminal may perform prior measurement on cells included in the E-UTRA cell list. The UE may identify candidate cells among cells included in the E-UTRA cell list based on the result of performing the preliminary measurement. In operation 1123, the terminal may transmit an RRC resume complete message to the base station. Here, the RRC resume complete message may include information on the identified candidate cells. In operation 1127, the base station may trigger an EPS fallback. In operation 1129, the terminal may receive a handover command from the base station. In this case, the UE may perform handover to the target cell indicated by the EPS. As a result, the mobile originated (MO) IMS voice session 1125 of the 5th generation system (5GS) can be delivered to the EPS.

12 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 11 is a diagram for explaining an embodiment in which a terminal is in an RRC inactive state and reception of an INVITE message is used as a trigger condition for prior measurement.

Operations 1201 to 1213 of FIG. 12 are processes in which the terminal obtains capability information on VoNR and pre-measurement of the network through a non-access stratum (NAS) registration procedure, and is illustrated in FIG. 4, so description is omitted.

In operation 1215, the terminal may receive an RRC release message from the base station. In this case, the RRC release message may include dedicated measurement configuration information. Dedicated measurement configuration information may include at least one of information requesting measurement of an E-TURA carrier in an RRC inactive state or information about an E-UTRA cell list.

In operation 1217, the UE may transition to an RRC inactive state based on the received RRC release message.

In operation 1219, the terminal may receive a paging message and perform an RRC resume procedure. For example, it may be configured as follows. The terminal may receive a paging message from the base station. The paging message may refer to calling the terminal through a base station in the area where the terminal is located when an incoming call occurs in the terminal. In this case, the terminal may transmit an RRC resume request message to the base station in order to transition to the RRC connected state. The terminal may receive an RRC resume message from the base station and transition to an RRC connected state. After transitioning to the RRC connected state, the terminal may transmit an RRC resume complete message to the base station.

In operation 1221, the terminal may receive an INVITE message for mobile terminated (MT) voice from the IMS. In operation 1223, the terminal may transmit information on candidate cells to the base station. In this case, information on candidate cells may be included in the aforementioned RRC resume complete message. In operation 1227, the base station may trigger an EPS fallback. In operation 1229, the terminal may receive a handover command from the base station. In this case, the UE may perform handover to the target cell of the EPS indicated by the handover command. As a result, the MT IMS voice session 1225 of the 5th generation system (5GS) can be delivered to the EPS.

13 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 13 is a diagram for explaining an embodiment in which a UE is in an RRC inactive state and a measurement event is used as a trigger condition for prior measurement.

Operations 1301 to 1313 of FIG. 13 are processes in which the terminal obtains capability information on VoNR and pre-measurement of the network through a non-access stratum (NAS) registration procedure, and is illustrated in FIG. 4, so description is omitted.

In operation 1315, the terminal may receive an RRC release message from the base station. In this case, the RRC release message may include dedicated measurement configuration information. The dedicated measurement configuration information may include at least one of information requesting measurement of an E-UTRA carrier in an RRC inactive state or information about an E-UTRA cell list.

In operation 1317, the UE may transition to an RRC inactive state based on the received RRC release message.

In operation 1319, the terminal may identify the occurrence of a measurement event. A measurement event may be a trigger to initiate prior measurement. These measurement events may be identified based on user input. For example, the terminal may identify that a measurement event has occurred when a user inputs a phone number. As another example, when a user inputs a short message service (SMS) message, the terminal may identify that a measurement event has occurred.

In operation 1321, when a measurement event occurs, the UE may perform prior measurement on cells included in the E-UTRA cell list.

In operation 1323, the terminal may identify whether a call has started. In this case, the terminal may identify whether or not a call has started based on the user input. For example, the terminal may identify that a call has started when the user inputs making a call. For another example, when the user inputs SMS message transmission, the terminal may identify that a call has started.

In operation 1325, the terminal may perform an RRC resume procedure when it is identified that the call has started. For example, it may be configured as follows. The terminal may transmit an RRC resume request message to the base station in order to transition to the RRC connected state. The terminal may receive an RRC resume message from the base station and transition to an RRC connected state. After transitioning to the RRC connected state, the terminal may transmit an RRC resume complete message to the base station. In this case, the RRC resume complete message may include information about candidate cells identified based on a preliminary measurement result. In operation 1329, the base station may trigger an EPS fallback. In operation 1331, the terminal may receive a handover command from the base station. In this case, the handover command may include information on a target cell selected from among candidate cells. The UE may perform handover to the target cell of the EPS indicated by the handover command. As a result, the MO IMS voice session 1327 of the 5th generation system (5GS) can be delivered to the EPS.

14 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 14 is a diagram for explaining an embodiment in which a UE is in an RRC inactive state and transmission of an INVITE message is used as a trigger condition for prior measurement.

Operations 1401 to 1413 of FIG. 14 are processes in which the terminal acquires capability information on VoNR and pre-measurement of the network through a non-access stratum (NAS) registration procedure, and is illustrated in FIG. 4, so description is omitted.

In operation 1415, the terminal may receive an RRC release message from the base station. In this case, the RRC release message may include dedicated measurement configuration information. The dedicated measurement configuration information may include at least one of information requesting measurement of an E-UTRA carrier in an RRC idle state or information about an E-TURA cell list.

In operation 1417, the UE may transition to the RRC idle state based on the received RRC release message.

In operation 1419, the terminal may identify whether a call has started. In this case, the terminal may identify whether or not a call has started based on the user input. For example, the terminal may identify that a call has started when the user inputs making a call.

In operation 1421, the terminal may perform an RRC setup procedure when it is identified that the call has started. The terminal may transmit an RRC setup request message to the base station. The terminal may receive an RRC setup message from the base station. After transitioning to the RRC connected state, the terminal may transmit an RRC setup complete message to the base station.

In operation 1425, the terminal may transmit an INVITE message for mobile originated (MO) voice to the IMS to request a call. In operation 1427, the terminal may transmit information on candidate cells to the base station after transmitting the INVITE message. In operation 1431, the base station may trigger an EPS fallback. In operation 1433, the terminal may receive a handover command from the base station. In this case, the handover command may include information on a target cell selected from among candidate cells. The UE may perform handover to the target cell of the EPS indicated by the handover command. As a result, the MO IMS voice session 1429 in 5GS can be carried over to the EPS.

15 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 15 is a diagram for explaining an embodiment in which a UE is in an RRC idle state and a measurement event is used as a trigger condition for prior measurement.

Operations 1501 to 1513 of FIG. 15 are processes in which the terminal acquires capability information on VoNR and pre-measurement of the network through a non-access stratum (NAS) registration procedure, and is illustrated in FIG. 4, so description is omitted.

In operation 1515, the terminal may receive an RRC release message from the base station. In this case, the RRC release message may include dedicated measurement configuration information. The dedicated measurement configuration information may include at least one of information requesting measurement of an E-UTRA carrier in an RRC idle state or information about an E-UTRA cell list.

In operation 1517, the UE may transition to the RRC idle state based on the received RRC release message.

In operation 1519, the terminal may identify whether a measurement event has occurred. A measurement event may be a trigger to initiate prior measurement. These measurement events may be identified based on user input. For example, the terminal may identify that a measurement event has occurred when a user inputs a phone number. As another example, when a user inputs a short message service (SMS) message, the terminal may identify that a measurement event has occurred.

In operation 1521, when a measurement event occurs, the UE may perform prior measurement on cells included in the E-TURA cell list.

In operation 1523, the terminal may identify whether a call has started. In this case, the terminal may identify whether a call has started based on the user input. For example, the terminal may identify that a call has started when the user inputs making a call. For another example, when the user inputs SMS message transmission, the terminal may identify that a call has started.

In operation 1525, when it is identified that the call has started, the terminal may perform an RRC setup procedure. The terminal may transmit an RRC setup request message to the base station. The terminal may receive an RRC setup message from the base station. After transitioning to the RRC connected state, the terminal may transmit an RRC setup complete message to the base station.

In operation 1527, the terminal may transmit an INVITE message for mobile originated (MO) voice to the IMS to request a call. In operation 1529, the terminal may transmit information on candidate cells to the base station after transmitting the INVITE message. In operation 1533, the base station may trigger an EPS fallback. In operation 1535, the terminal may receive a handover command from the base station. In this case, the handover command may include information on a target cell selected from among candidate cells. The UE may perform handover to the target cell of the EPS indicated by the handover command. As a result, the MO IMS voice session 1531 in 5GS can be delivered to the EPS.

16 illustrates a signal flow of an EPS fallback procedure according to embodiments of the present disclosure. 16 describes an embodiment in which a terminal performs preliminary measurement when a 5th generation core network (5GC) does not support short message service over internet protocol multimedia system (SMSoIMS) and SMS over non-access stratum (SMSoNAS). . Here, SMSoIMS may refer to transmitting and receiving SMS through IMS. Also, SMSoNAS may refer to transmitting and receiving SMS through a NAS.

If 5GC does not support SMSoIMS and SMSoNAS, it can be easily expected that EPS fallback will be triggered when the terminal transmits SMS. Therefore, if 5GC does not support SMSoIMS and SMSoNAS, the UE needs to reduce call setup time by performing prior measurement on the E-UTRA cell list in advance. First, the terminal needs to check whether 5GC supports SMSoIMS and SMSoNAS.

Referring to FIG. 16, in operation 1601, the terminal may transmit a registration request message to the 5GC. Here, 5GC may mean AMF. In operation 1603, the base station may transmit a UE radio capability check request message from the 5GC to the base station. In operations 1605 and 1607, the base station may transmit a UE radio capability inquiry message to the UE and receive UE capability information from the UE. Here, the terminal capability information may include information on whether the terminal supports SMSoIMS and information on whether the terminal supports SMSoNAS. In operation 1609, the base station may transmit a UE radio capability check response message to the 5GC. In operation 1611, the 5GC may send an initial context setup request to the base station. In operation 1613, 5GC may transmit a registration request message to the terminal. Here, the registration approval message may include information on whether 5GC supports SMSoIMS and information on whether 5GC supports SMSoNAS. Based on the received registration approval message, the terminal can check whether 5GC supports SMSoIMS and whether 5GC supports SMSoNAS. If it is confirmed that 5GC does not support SMSoIMS and SMSoNAS, the terminal may request transmission of system information from the base station. Here, the system information (eg system information block (SIB) 5) may include information about the E-UTRA cell list. In operation 1615, the terminal may receive the requested system information from the base station.

In operation 1617, the terminal may identify the user's SMS input. Here, the user's SMS input may be a trigger for starting prior measurement. In operation 1619, the UE may perform preliminary measurement on cells included in the E-UTRA cell list. In operation 1621, the terminal may transmit SMS in 5GS. Since 5GC does not support SMSoIMS and SMSoNAS, the terminal can expect E-UTRA fallback to be triggered soon. In operation 1623, the terminal may transmit information about candidate cells to the base station. At operation 1625, the base station may trigger an E-UTRA fallback. In operation 1627, the terminal may receive a handover command from the base station. In this case, the handover command may include information on a target cell selected from among candidate cells. The terminal may perform handover to the EPS target cell indicated by the handover command and transmit/receive SMS through LTE.

17 illustrates a configuration of a terminal according to embodiments of the present disclosure. Referring to FIG. 17 , a terminal may include a processor 1710, a memory 1720, and a transceiver 1730.

The processor 1710 may control the overall operation of the terminal. For example, the processor 1710 may transmit and receive signals through the transceiver 1730 . Also, the processor 1710 may perform protocol stack functions required by communication standards. To this end, the processor 1710 may include at least one processor. Also, the processor 1710 may control the terminal to perform operations according to the above-described embodiments.

The memory 1720 may store data such as a basic program for operating a terminal, an application program, and setting information. The memory 1720 may be comprised of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. The memory 1720 may provide stored data according to a request of the processor 1710 .

The transceiver 1730 may perform functions for transmitting and receiving signals through a wired channel or a wireless channel. For example, the transceiver 1730 may perform a conversion function between a baseband signal and a bit string according to the physical layer standard of the system. For example, during data transmission, the transceiver 1730 may generate complex symbols by encoding and modulating a transmission bit stream. Also, upon receiving data, the transceiver 1730 may restore the baseband signal to a received bit stream through demodulation and decoding. In addition, the transceiver 1730 may up-convert a baseband signal into a radio frequency (RF) band signal, transmit the signal through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal. To this end, the transceiver 1730 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and the like. Also, the transceiver 1730 may include an antenna unit. The transceiver 1730 may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the transceiver 1730 may be composed of digital and analog circuits (eg, a radio frequency integrated circuit (RFIC)). Here, digital and analog circuits may be implemented in one package. Also, the transceiver 1730 may include multiple RF chains. Also, the transceiver 1730 may transmit and receive signals. To this end, the transceiver 1730 may include at least one transceiver.

18 illustrates a configuration of a base station according to embodiments of the present disclosure. Referring to FIG. 18 , a base station may include a processor 1810, a memory 1820, and a transceiver 1830.

The processor 1810 may control overall operations of the base station. For example, the processor 1810 may transmit and receive signals through the transceiver 1830 . Also, the processor 1810 may perform protocol stack functions required by communication standards. To this end, the processor 1810 may include at least one processor. Also, the processor 1810 may control the base station to perform operations according to the above-described embodiments.

The memory 1820 may store data such as a basic program for operation of the base station, an application program, and setting information. The memory 1820 may be comprised of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. The memory 1820 may provide stored data according to a request of the processor 1810 .

The transceiver 1830 may perform functions for transmitting and receiving signals through a wired channel or a wireless channel. For example, the transceiver 1830 may perform a conversion function between a baseband signal and a bit string according to the physical layer standard of the system. For example, during data transmission, the transceiver 1830 may generate complex symbols by encoding and modulating a transmission bit stream. Also, upon receiving data, the transceiver 1830 may restore the baseband signal to a received bit stream through demodulation and decoding. In addition, the transceiver 1830 may up-convert a baseband signal into a radio frequency (RF) band signal, transmit the signal through an antenna, and down-convert an RF band signal received through the antenna into a baseband signal. To this end, the transceiver 1830 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), and an analog-to-digital converter (ADC). Also, the transceiver 1830 may include an antenna unit. The transceiver 1830 may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the transceiver 1830 may be composed of digital and analog circuits (eg, a radio frequency integrated circuit (RFIC)). Here, digital and analog circuits may be implemented in one package. Also, the transceiver 1830 may include multiple RF chains. Also, the transceiver 1830 may transmit and receive signals. To this end, the transceiver 1830 may include at least one transceiver.

19 is a block diagram of an electronic device in a network environment according to embodiments of the present disclosure. The electronic device of FIG. 19 may correspond to the terminal of FIG. 16 . Referring to FIG. 19 , in a network environment 1900, an electronic device 1901 communicates with an electronic device 1902 through a first network 1998 (eg, a short-range wireless communication network) or through a second network 1999. It may communicate with at least one of the electronic device 1904 or the server 1908 through (eg, a long-distance wireless communication network). According to an embodiment, the electronic device 1901 may communicate with the electronic device 1904 through the server 1908. According to an embodiment, the electronic device 1901 includes a processor 1920, a memory 1930, an input module 1950, a sound output module 1955, a display module 1960, an audio module 1970, a sensor module ( 1976), interface (1977), connection terminal (1978), haptic module (1979), camera module (1980), power management module (1988), battery (1989), communication module (1990), subscriber identification module (1996) , or an antenna module 1997. In some embodiments, in the electronic device 1901, at least one of these components (eg, the connection terminal 1978) may be omitted or one or more other components may be added. In some embodiments, some of these components (eg, sensor module 1976, camera module 1980, or antenna module 1997) are integrated into a single component (eg, display module 1960). It can be.

The processor 1920, for example, executes software (eg, the program 1940) to cause at least one other component (eg, hardware or software component) of the electronic device 1901 connected to the processor 1920. It can control and perform various data processing or calculations. According to one embodiment, as at least part of data processing or operation, the processor 1920 transfers instructions or data received from other components (e.g., sensor module 1976 or communication module 1990) to volatile memory 1932. , process commands or data stored in the volatile memory 1932, and store resultant data in the non-volatile memory 1934. According to one embodiment, the processor 1920 may include a main processor 1921 (eg, a central processing unit or an application processor) or an auxiliary processor 1923 (eg, a graphic processing unit, a neural network processing unit ( NPU: neural processing unit (NPU), image signal processor, sensor hub processor, or communication processor). For example, when the electronic device 1901 includes a main processor 1921 and an auxiliary processor 1923, the auxiliary processor 1923 may use less power than the main processor 1921 or be set to be specialized for a designated function. can The auxiliary processor 1923 may be implemented separately from or as part of the main processor 1921 .

The auxiliary processor 1923 may, for example, take the place of the main processor 1921 while the main processor 1921 is inactive (eg, sleep), or when the main processor 1921 is active (eg, running an application). ) state, together with the main processor 1921, at least one of the components of the electronic device 1901 (eg, the display module 1960, the sensor module 1976, or the communication module 1990) It is possible to control at least some of the related functions or states. According to one embodiment, the co-processor 1923 (eg, image signal processor or communication processor) may be implemented as part of other functionally related components (eg, camera module 1980 or communication module 1990). there is. According to an embodiment, the auxiliary processor 1923 (eg, a neural network processing device) may include a hardware structure specialized for processing an artificial intelligence model. AI models can be created through machine learning. Such learning may be performed, for example, in the electronic device 1901 itself where the artificial intelligence model is executed, or may be performed through a separate server (eg, the server 1908). The learning algorithm may include, for example, supervised learning, unsupervised learning, semi-supervised learning or reinforcement learning, but in the above example Not limited. The artificial intelligence model may include a plurality of artificial neural network layers. Artificial neural networks include deep neural networks (DNNs), convolutional neural networks (CNNs), recurrent neural networks (RNNs), restricted boltzmann machines (RBMs), deep belief networks (DBNs), bidirectional recurrent deep neural networks (BRDNNs), It may be one of deep Q-networks or a combination of two or more of the foregoing, but is not limited to the foregoing examples. The artificial intelligence model may include, in addition or alternatively, software structures in addition to hardware structures.

The memory 1930 may store various data used by at least one component (eg, the processor 1920 or the sensor module 1976) of the electronic device 1901 . The data may include, for example, input data or output data for software (eg, the program 1940) and commands related thereto. The memory 1930 may include a volatile memory 1932 or a non-volatile memory 1934 .

The program 1940 may be stored as software in the memory 1930, and may include, for example, an operating system 1942, middleware 1944, or an application 1946.

The input module 1950 may receive a command or data to be used by a component (eg, the processor 1920) of the electronic device 1901 from an outside of the electronic device 1901 (eg, a user). The input module 1950 may include, for example, a microphone, a mouse, a keyboard, a key (eg, a button), or a digital pen (eg, a stylus pen).

The sound output module 1955 may output sound signals to the outside of the electronic device 1901 . The sound output module 1955 may include, for example, a speaker or receiver. The speaker can be used for general purposes such as multimedia playback or recording playback. A receiver may be used to receive an incoming call. According to one embodiment, the receiver may be implemented separately from the speaker or as part of it.

The display module 1960 may visually provide information to the outside of the electronic device 1901 (eg, a user). The display module 1960 may include, for example, a display, a hologram device, or a projector and a control circuit for controlling the device. According to one embodiment, the display module 1960 may include a touch sensor configured to detect a touch or a pressure sensor configured to measure the intensity of force generated by the touch.

The audio module 1970 may convert sound into an electrical signal or vice versa. According to an embodiment, the audio module 1970 acquires sound through the input module 1950, the sound output module 1955, or an external electronic device connected directly or wirelessly to the electronic device 1901 (eg: Sound may be output through the electronic device 1902 (eg, a speaker or a headphone).

The sensor module 1976 detects an operating state (eg, power or temperature) of the electronic device 1901 or an external environmental state (eg, a user state), and generates an electrical signal or data value corresponding to the detected state. can do. According to one embodiment, the sensor module 1976 may include, for example, a gesture sensor, a gyro sensor, an air pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an IR (infrared) sensor, a bio sensor, It may include a temperature sensor, humidity sensor, or light sensor.

The interface 1977 may support one or more specified protocols that may be used to directly or wirelessly connect the electronic device 1901 to an external electronic device (eg, the electronic device 1902). According to one embodiment, the interface 1977 may include, for example, a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, an SD card interface, or an audio interface.

The connection terminal 1978 may include a connector through which the electronic device 1901 may be physically connected to an external electronic device (eg, the electronic device 1902). According to one embodiment, the connection terminal 1978 may include, for example, an HDMI connector, a USB connector, an SD card connector, or an audio connector (eg, a headphone connector).

The haptic module 1979 may convert electrical signals into mechanical stimuli (eg, vibration or movement) or electrical stimuli that a user can perceive through tactile or kinesthetic senses. According to one embodiment, the haptic module 1979 may include, for example, a motor, a piezoelectric element, or an electrical stimulation device.

The camera module 1980 may capture still images and moving images. According to one embodiment, the camera module 1980 may include one or more lenses, image sensors, image signal processors, or flashes.

The power management module 1988 may manage power supplied to the electronic device 1901 . According to one embodiment, power management module 1988 may be implemented as at least part of a power management integrated circuit (PMIC), for example.

The battery 1989 may supply power to at least one component of the electronic device 1901 . According to one embodiment, the battery 1989 may include, for example, a non-rechargeable primary cell, a rechargeable secondary cell, or a fuel cell.

The communication module 1990 is a direct (eg, wired) communication channel or a wireless communication channel between the electronic device 1901 and an external electronic device (eg, the electronic device 1902, the electronic device 1904, or the server 1908). Establishment and communication through the established communication channel may be supported. The communication module 1990 may include one or more communication processors that operate independently of the processor 1920 (eg, an application processor) and support direct (eg, wired) communication or wireless communication. According to one embodiment, the communication module 1990 may be a wireless communication module 1992 (eg, a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module) or a wired communication module 1994 (eg, a cellular communication module). : a local area network (LAN) communication module or a power line communication module). Among these communication modules, the corresponding communication module is a first network 1998 (eg, a short-range communication network such as Bluetooth, wireless fidelity (WiFi) direct, or infrared data association (IrDA)) or a second network 1999 (eg, legacy It may communicate with the external electronic device 1904 through a cellular network, a 5G network, a next-generation communication network, the Internet, or a telecommunications network such as a computer network (eg, LAN or WAN). These various types of communication modules may be integrated as one component (eg, a single chip) or implemented as a plurality of separate components (eg, multiple chips). The wireless communication module 1992 uses subscriber information (eg, International Mobile Subscriber Identifier (IMSI)) stored in the subscriber identification module 1996 within a communication network such as the first network 1998 or the second network 1999. The electronic device 1901 may be identified or authenticated.

The wireless communication module 1992 may support a 5G network after a 4G network and a next-generation communication technology, for example, NR access technology (new radio access technology). NR access technologies include high-speed transmission of high-capacity data (enhanced mobile broadband (eMBB)), minimization of terminal power and access of multiple terminals (massive machine type communications (mMTC)), or high reliability and low latency (ultra-reliable and low latency (URLLC)). -latency communications)) can be supported. The wireless communication module 1992 may support a high frequency band (eg, mmWave band) to achieve a high data rate, for example. The wireless communication module 1992 uses various technologies for securing performance in a high frequency band, such as beamforming, massive multiple-input and multiple-output (MIMO), and full-dimensional multiplexing. Technologies such as input/output (FD-MIMO: full dimensional MIMO), array antenna, analog beam-forming, or large scale antenna may be supported. The wireless communication module 1992 may support various requirements specified in the electronic device 1901, an external electronic device (eg, the electronic device 1904), or a network system (eg, the second network 1999). According to one embodiment, the wireless communication module 1992 is a peak data rate for eMBB realization (eg, 20 Gbps or more), a loss coverage for mMTC realization (eg, 164 dB or less), or a U-plane latency for URLLC realization (eg, Example: downlink (DL) and uplink (UL) each of 0.5 ms or less, or round trip 1 ms or less) may be supported.

The antenna module 1997 may transmit or receive signals or power to the outside (eg, an external electronic device). According to one embodiment, the antenna module 1997 may include an antenna including a radiator formed of a conductor or a conductive pattern formed on a substrate (eg, PCB). According to one embodiment, the antenna module 1997 may include a plurality of antennas (eg, an array antenna). In this case, at least one antenna suitable for a communication method used in a communication network such as the first network 1998 or the second network 1999 is selected from the plurality of antennas by, for example, the communication module 1990. can be chosen A signal or power may be transmitted or received between the communication module 1990 and an external electronic device through the selected at least one antenna. According to some embodiments, other components (eg, a radio frequency integrated circuit (RFIC)) may be additionally formed as a part of the antenna module 1997 in addition to the radiator.

According to various embodiments, the antenna module 1997 may form a mmWave antenna module. According to one embodiment, the mmWave antenna module includes a printed circuit board, an RFIC disposed on or adjacent to a first surface (eg, a lower surface) of the printed circuit board and capable of supporting a designated high frequency band (eg, mmWave band); and a plurality of antennas (eg, array antennas) disposed on or adjacent to a second surface (eg, a top surface or a side surface) of the printed circuit board and capable of transmitting or receiving signals of the designated high frequency band. can do.

At least some of the components are connected to each other through a communication method between peripheral devices (eg, a bus, general purpose input and output (GPIO), serial peripheral interface (SPI), or mobile industry processor interface (MIPI)) and signal ( e.g. commands or data) can be exchanged with each other.

According to an embodiment, commands or data may be transmitted or received between the electronic device 1901 and the external electronic device 1904 through the server 1908 connected to the second network 1999. Each of the external electronic devices 1902 or 1904 may be the same as or different from the electronic device 1901 . According to an embodiment, all or part of operations executed in the electronic device 1901 may be executed in one or more external electronic devices among the external electronic devices 1902 , 1904 , or 1908 . For example, when the electronic device 1901 needs to perform a certain function or service automatically or in response to a request from a user or another device, the electronic device 1901 instead of executing the function or service by itself. Alternatively or additionally, one or more external electronic devices may be requested to perform the function or at least part of the service. One or more external electronic devices receiving the request may execute at least a part of the requested function or service or an additional function or service related to the request, and deliver the execution result to the electronic device 1901 . The electronic device 1901 may provide the result as at least a part of a response to the request as it is or additionally processed. To this end, for example, cloud computing, distributed computing, mobile edge computing (MEC), or client-server computing technology may be used. The electronic device 1901 may provide an ultra-low latency service using, for example, distributed computing or mobile edge computing. In another embodiment, the external electronic device 1904 may include an internet of things (IoT) device. Server 1908 may be an intelligent server using machine learning and/or neural networks. According to an embodiment, the external electronic device 1904 or server 1908 may be included in the second network 1999. The electronic device 1901 may be applied to intelligent services (eg, smart home, smart city, smart car, or health care) based on 5G communication technology and IoT-related technology.

Electronic devices according to various embodiments disclosed in this document may be devices of various types. The electronic device may include, for example, a portable communication device (eg, a smart phone), a computer device, a portable multimedia device, a portable medical device, a camera, a wearable device, or a home appliance. An electronic device according to an embodiment of the present document is not limited to the aforementioned devices.

Various embodiments of this document and terms used therein are not intended to limit the technical features described in this document to specific embodiments, but should be understood to include various modifications, equivalents, or substitutes of the embodiments. In connection with the description of the drawings, like reference numbers may be used for like or related elements. The singular form of a noun corresponding to an item may include one item or a plurality of items, unless the relevant context clearly dictates otherwise. In this document, "A or B", "at least one of A and B", "at least one of A or B", "A, B or C", "at least one of A, B and C", and "A Each of the phrases such as "at least one of , B, or C" may include any one of the items listed together in that phrase, or all possible combinations thereof. Terms such as "first", "second", or "first" or "secondary" may simply be used to distinguish a given component from other corresponding components, and may be used to refer to a given component in another aspect (eg, importance or order) is not limited. A (e.g., first) component is said to be "coupled" or "connected" to another (e.g., second) component, with or without the terms "functionally" or "communicatively." When mentioned, it means that the certain component may be connected to the other component directly (eg by wire), wirelessly, or through a third component.

The term "module" used in various embodiments of this document may include a unit implemented in hardware, software, or firmware, and is interchangeable with terms such as, for example, logic, logical blocks, parts, or circuits. can be used as A module may be an integrally constructed component or a minimal unit of components or a portion thereof that performs one or more functions. For example, according to one embodiment, the module may be implemented in the form of an application-specific integrated circuit (ASIC).

Various embodiments of this document provide one or more instructions stored in a storage medium (eg, internal memory 1936 or external memory 1938) readable by a machine (eg, electronic device 1901). It may be implemented as software (eg, the program 1940) including them. For example, a processor (eg, the processor 1920) of a device (eg, the electronic device 1901) may call at least one command among one or more instructions stored from a storage medium and execute it. This enables the device to be operated to perform at least one function according to the at least one command invoked. The one or more instructions may include code generated by a compiler or code executable by an interpreter. The device-readable storage medium may be provided in the form of a non-transitory storage medium. Here, 'non-temporary' only means that the storage medium is a tangible device and does not contain a signal (e.g. electromagnetic wave), and this term refers to the case where data is stored semi-permanently in the storage medium. It does not discriminate when it is temporarily stored.

According to one embodiment, the method according to various embodiments disclosed in this document may be included and provided in a computer program product. Computer program products may be traded between sellers and buyers as commodities. A computer program product is distributed in the form of a device-readable storage medium (eg compact disc read only memory (CD-ROM)), or through an application store (eg Play Store ^TM ) or on two user devices ( It can be distributed (eg downloaded or uploaded) online, directly between smart phones. In the case of online distribution, at least part of the computer program product may be temporarily stored or temporarily created in a device-readable storage medium such as a manufacturer's server, an application store server, or a relay server's memory.

According to various embodiments, each component (eg, module or program) of the above-described components may include a single object or a plurality of entities, and some of the plurality of entities may be separately disposed in other components. there is. According to various embodiments, one or more components or operations among the aforementioned corresponding components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (eg modules or programs) may be integrated into a single component. In this case, the integrated component may perform one or more functions of each of the plurality of components identically or similarly to those performed by a corresponding component of the plurality of components prior to the integration. . According to various embodiments, the actions performed by a module, program, or other component are executed sequentially, in parallel, iteratively, or heuristically, or one or more of the actions are executed in a different order, or omitted. or one or more other actions may be added.

Various embodiments of the present disclosure and terms used therein are not intended to limit the technical features described in this document to specific embodiments, and should be understood to include various modifications, equivalents, or substitutes of the embodiments. In connection with the description of the drawings, like reference numbers may be used for like or related elements. The singular form of a noun corresponding to an item may include one item or a plurality of items, unless the relevant context clearly dictates otherwise. In the present disclosure, “A or B”, “at least one of A and B”, “at least one of A or B,” “A, B or C,” “at least one of A, B and C,” and “A Each of the phrases such as "at least one of , B, or C" may include any one of the items listed together in that phrase, or all possible combinations thereof. Terms such as "first", "second", or "first" or "secondary" may simply be used to distinguish a given component from other corresponding components, and may be used to refer to a given component in another aspect (eg, importance or order) is not limited. A (e.g., first) component is said to be "coupled" or "connected" to another (e.g., second) component, with or without the terms "functionally" or "communicatively." When mentioned, it means that the certain component may be connected to the other component directly (eg by wire), wirelessly, or through a third component.

The term “module” used in this disclosure may include a unit implemented in hardware, software, or firmware, and may be used interchangeably with terms such as, for example, logic, logical block, component, or circuit. A module may be an integrally constructed component or a minimal unit of components or a portion thereof that performs one or more functions. For example, according to one embodiment, the module may be implemented in the form of an application-specific integrated circuit (ASIC).

According to one embodiment, the method according to various embodiments disclosed in this document may be included and provided in a computer program product. Computer program products may be traded between sellers and buyers as commodities. A computer program product is distributed in the form of a device-readable storage medium (e.g. compact disc read only memory (CD-ROM)), or through an application store (e.g. Play Store™) or on two user devices (e.g. It can be distributed (eg downloaded or uploaded) online, directly between smartphones. In the case of online distribution, at least part of the computer program product may be temporarily stored or temporarily created in a device-readable storage medium such as a manufacturer's server, an application store server, or a relay server's memory.

According to various embodiments, each component (eg, module or program) of the components described above may include a singular object or a plurality of entities. According to various embodiments, one or more components or operations among the aforementioned components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (eg modules or programs) may be integrated into a single component. In this case, the integrated component may perform one or more functions of each of the plurality of components identically or similarly to those performed by a corresponding component of the plurality of components prior to the integration. . According to various embodiments, operations performed by modules, programs, or other components are executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations are executed in a different order, omitted, or , or one or more other operations may be added.

Claims (20)

A method performed by an electronic device in a wireless communication system,
Checking whether a base station supports voice over new radio (VoNR);
obtaining cell list information from the base station if it is determined that the base station does not support VoNR;
Checking whether measurement of the cell list is triggered;
performing measurements on a plurality of cells included in the cell list when it is determined that the measurement is triggered;
identifying one or more candidate cells from among the plurality of cells based on a result of the measurement;
transmitting information about the one or more candidate cells to the base station; and
and receiving a handover command from the base station.
According to claim 1,
transmitting a registration request message including information indicating whether the terminal can perform the measurement to the base station; and
Receiving, from the base station, a registration acknowledgment message including information indicating whether the base station can perform the measurement, from the base station;
The method characterized in that the measurement is performed when the terminal and the base station can perform the measurement.
The method of claim 1, wherein the obtaining of information on the cell list comprises:
transmitting a request message for information on the cell list to the base station; and
Further comprising the step of receiving system information including information on the cell list from the base station,
The method characterized in that the terminal is in a radio resource control (RRC) connected state.
The method of claim 1, wherein the obtaining of information on the cell list comprises:
Receiving a radio resource control (RRC) release message including information about the cell list from the base station;
Based on the RRC release message, further comprising the process of the terminal transitioning to an RRC inactive state or an RRC idle state,
The method characterized in that the measurement is performed in the RRC inactive state or the RRC idle state.
According to claim 1,
Whether the base station supports VoNR is checked based on a local database or NR cell list of the terminal,
The local database includes at least one of a public land mobile network (PLMN), operator assistance information, or location coverage information of the base station,
The method of claim 1, wherein the NR cell list includes information on cells in which the terminal camps.
According to claim 1,
Measurement of the cell list is triggered based on a user input,
The user input includes at least one of a case in which a phone number is input in a call application or an SMS is input in a short message service (SMS) application.
According to claim 1,
Information on the one or more candidate cells is transmitted to the base station when an INVITE message is transmitted and received,
The information on the one or more candidate cells is characterized in that included in a radio resource control (RRC) resume complete message or an RRC setup complete message.
According to claim 1,
The method of claim 1 , wherein the one or more candidate cells correspond to cells having received signal strength greater than or equal to a threshold value among the plurality of cells.
According to claim 1,
performing handover to a target cell; and
Further comprising performing voice over long term evolution (VoLTE) through the target cell,
Wherein the handover command includes information about the target cell selected from among the one or more candidate cells.
According to claim 2,
checking whether the base station supports short message service over internet protocol multimedia system (SMSoIMS) and short message service over non-stratum access (SMSoNAS); and
requesting system information from the base station based on a user input when it is determined that the base station does not support the SMSoIMS and the SMSoNAS;
receiving the system information including information on the cell list from the base station;
The method further comprising the step of performing the measurement based on the user's SMS input.
In the electronic device of the wireless communication system, the electronic device,
at least one processor; and
at least one transceiver operably coupled to the at least one processor, the at least one processor comprising:
Check whether the base station supports voice over new radio (VoNR);
If it is confirmed that the base station does not support VoNR, obtaining information on a cell list from the base station;
Checking whether the measurement of the cell list is triggered,
If it is confirmed that the measurement is triggered, performing measurement on a plurality of cells included in the cell list,
Based on the result of the measurement, identifying one or more candidate cells among the plurality of cells;
Transmitting information on the one or more candidate cells to the base station;
An electronic device, characterized in that configured to receive a handover command from the base station.
The method of claim 11, wherein the at least one processor,
Transmitting a registration request message including information indicating whether the terminal can perform the measurement to the base station;
Further configured to receive, from the base station, a registration acknowledgment message including information indicating whether the base station can perform the measurement, from the base station;
The electronic device, characterized in that the measurement is performed when the terminal and the base station can perform the measurement.
The method of claim 11, wherein the at least one processor,
Transmitting a request message for information on the cell list to the base station;
Further configured to receive, from the base station, system information including information about the cell list,
The electronic device, characterized in that the terminal is in a radio resource control (RRC) connected state.
The method of claim 11, wherein the at least one processor,
Receiving a radio resource control (RRC) release message including information about the cell list from the base station;
Based on the RRC release message, the terminal is further configured to transition to an RRC inactive state or an RRC idle state,
The electronic device, characterized in that the measurement is performed in the RRC inactive state or the RRC idle state.
According to claim 11,
Whether the base station supports VoNR is checked based on a local database or NR cell list of the terminal,
The local database includes at least one of a public land mobile network (PLMN), operator assistance information, or location coverage information of the base station,
The NR cell list includes information on cells in which the terminal camps on.
According to claim 11,
Measurement of the cell list is triggered based on a user input,
The electronic device characterized in that the user input includes at least one of a case where a phone number is input on a call application or an SMS is input on a short message service (SMS) application.
According to claim 11,
Information on the one or more candidate cells is transmitted to the base station when an INVITE message is transmitted and received,
The electronic device characterized in that the information on the one or more candidate cells is included in a radio resource control (RRC) resume complete message or an RRC setup complete message.
According to claim 11,
The electronic device of claim 1, wherein the one or more candidate cells correspond to cells having a received signal strength greater than or equal to a threshold value among the plurality of cells.
The method of claim 11, wherein the at least one processor,
Perform handover to the target cell;
Further configured to perform voice over long term evolution (VoLTE) through the target cell,
The handover command includes information on the target cell selected from among the one or more candidate cells.
The method of claim 12, wherein the at least one processor,
Checking whether the base station supports short message service over internet protocol multimedia system (SMSoIMS) and short message service over non-stratum access (SMSoNAS);
If it is confirmed that the base station does not support the SMSoIMS and the SMSoNAS, based on a user input, request system information from the base station,
Receiving the system information including information on the cell list from the base station;
and further configured to perform said measurement based on a user's SMS input.

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