KR102339947B1 - Method and Apparatus for Performing Evolved Packet System Fallback - Google Patents

Abstract

A method for performing a base station fallback in a terminal is provided. The method includes transmitting a SIP message carrying a voice call invitation message to a base station of a first type to which the terminal is connected, and receiving measurement configuration information from the base station of the first type in response to the transmission of the SIP message. Step, performing measurements on base stations of a second type based on the measurement configuration information and transmitting a measurement report message to the base station of the first type, from the base station of the first type to a target of a second type ) receiving a handover command message designating a base station, and attempting inter-RAT HO to the second type target base station in response to the reception of the handover command message and attempting to connect to another base station of the second type in response to confirming that a voice service indicator is included in the handover command message when the handover between heterogeneous networks fails. .

Description

Method and apparatus for performing EPS fallback {Method and Apparatus for Performing Evolved Packet System Fallback}

The present invention relates to mobile communication technology, and more particularly, to a technology for performing EPS fallback (Evolved Packet System Fallback) in a terminal.

One of the main services in a mobile communication system is a voice service. In Long Term Evolution (LTE), VoIP (Voice over IP) technology interworking with IMS (IP Multimedia Subsystem) is used to provide a high-quality voice service. In LTE, the service is sometimes referred to as VoLTE (Voice over LTE). In an LTE (or E-UTRAN) system, virtual between a UE and a P-GW by a Serving Gateway (S-GW) and/or a Packet Data Network Gateway (P-GW) of an Evolved Packet Core (EPC) to use VoLTE technology An EPS bearer (Evolved Packet System Bearer) providing a virtual connection is connected to an IMS PDN (Packet Data Network).

The 5G (5th Generation) mobile communication system based on the 3GPP standard will first apply NSA (Non-standalone) network operation to shorten the commercialization time, and then gradually expand to SA (Standalone) network operation. The SA network refers to a 5G network that operates independently without the help of a previous-generation network, just like the existing 3G/4G network. The NSA network refers to a network operated with the help of a 4G network (E-UTRAN) due to the reason that independent operation of the 5G network is unstable. In the NSA network, the control plane for network access is the LTE base station (eNB) and the data transmission area (User Plane) is in charge of the 5G base station (gNB). This network structure is called EN-DC (E-UTRA-NR Dual Connectivity).

The SA network may have a structure in which it is connected and operated independently of the EPC to a 5th generation core network (5GC). The SA network may not support interworking with IMS depending on the degree of development of the 5G core network. In this case, a terminal connected to the SA network can receive VoLTE service through connection to the EPC supporting interworking with IMS. EPS describes the process in which the terminal accessing the SA network disconnects the connection to the 5G base station (gNB) bound to the 5G core network and attempts to connect to the LTE base station (eNB) bound to the EPC in order to receive VoLTE service. This is referred to as an Evolved Packet System Fallback.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technology capable of preventing service delay that may occur while a terminal performs EPS fallback to receive a voice call service.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In one aspect, a method for performing base station fallback in a terminal is provided. The method includes transmitting a Session Initiation Protocol (SIP) message carrying a Voice Call Invite message to a base station of a first type to which the terminal is connected, and in response to the transmission of the SIP message, the first Receiving measurement configuration information from a base station of a type, performing measurements on base stations of a second type based on the measurement configuration information and sending a Measurement Report Message to the base station of the first type Transmitting to, receiving an RRC release message from the base station of the first type, and disconnecting the connection with the base station of the first type in response to the reception of the RRC release message and performing redirection performing and attempting to access the second type of candidate base station, and if the access to the second type of candidate base station fails, confirming that the RRC release message includes a Voice Service Indicator and attempting to connect to another base station of the second type in response to

In one embodiment, the terminal is a standalone (SA) terminal.

In an embodiment, the step of receiving measurement configuration information from the base station of the first type in response to the transmission of the SIP message comprises: an RRC connection reconfiguration message from the base station of the first type (radio resource control connection reconfiguration) and receiving the measurement configuration information through a message).

In an embodiment, in response to the reception of the RRC release message, disconnecting from the first type of base station and performing redirection to attempt access to a second type of candidate base station includes: and performing an RRC connection reestablishment procedure with a type candidate base station.

In an embodiment, the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies.

In one embodiment, when the connection to the second type candidate base station fails, in response to confirming that a voice service indicator is included in the RRC release message, to another base station of the second type The attempting access includes attempting to access a second type of base station serving the base station service frequency having the highest priority in the frequency priority list.

In an embodiment, the RRC release message further includes a cell priority list specifying priorities for cell IDs (Identifications).

In one embodiment, when the connection to the second type candidate base station fails, in response to confirming that a voice service indicator is included in the RRC release message, to another base station of the second type The attempting access includes attempting access to a second type of base station having a cell ID having the highest priority in the cell priority list.

In an embodiment, the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs.

In one embodiment, when the connection to the second type candidate base station fails, in response to confirming that a voice service indicator is included in the RRC release message, to another base station of the second type The attempting access includes trying to access the second type of base station selected by referring to the frequency priority list and the cell priority list.

In one embodiment, the base station of the first type is a 5th generation (5G) base station, the candidate base station of the second type is a candidate LTE base station, and the other base station of the second type is another LTE base station.

In one embodiment, the base station fallback is an Evolved Packet System Fallback (EPS).

In another aspect, a method for performing a base station fallback in a terminal is provided. The method includes transmitting a SIP message carrying a voice call invitation message to a base station of a first type to which the terminal is connected, and receiving measurement configuration information from the base station of the first type in response to the transmission of the SIP message. Step, performing measurements on base stations of a second type based on the measurement configuration information and transmitting a measurement report message to the base station of the first type, from the base station of the first type to a target of a second type ) receiving a handover command message designating a base station, and attempting inter-RAT HO to the second type target base station in response to the reception of the handover command message and attempting to connect to another base station of the second type in response to confirming that a voice service indicator is included in the handover command message when the handover between heterogeneous networks fails. .

In an embodiment, the step of receiving the measurement configuration information from the base station of the first type in response to the transmission of the SIP message includes: receiving the measurement configuration information through an RRC connection reconfiguration message from the base station of the first type; includes

In an embodiment, the step of receiving a handover command message specifying a target base station of a second type from the base station of the first type includes: mobility control information ( and receiving an RRC connection reconfiguration message including mobility control information).

In an embodiment, when the handover between heterogeneous networks fails, the step of trying to access another base station of the second type in response to confirming that a voice service indicator is included in the handover command message comprises: and retrying the connection to the two types of target base stations.

In an embodiment, retrying access to the second type target base station includes performing an RRC connection reconfiguration procedure with the second type target base station.

In an embodiment, the handover command message further includes a frequency priority list specifying priorities for base station service frequencies.

In an embodiment, when the handover between heterogeneous networks fails, the step of trying to access another base station of the second type in response to confirming that a voice service indicator is included in the handover command message comprises: The method further includes the step of attempting to access the second type of base station serving the base station service frequency having the highest priority in the frequency priority list when the access to the two-type target base station fails.

In an embodiment, the handover command message further includes a cell priority list specifying priorities for cell IDs.

In an embodiment, when the handover between heterogeneous networks fails, the step of trying to access another base station of the second type in response to confirming that a voice service indicator is included in the handover command message comprises: The method further includes the step of trying to access the second type of base station having the highest priority cell ID in the cell priority list when the access to the two-type target base station fails.

In an embodiment, the handover command message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs.

In an embodiment, when the handover between heterogeneous networks fails, the step of trying to access another base station of the second type in response to confirming that a voice service indicator is included in the handover command message comprises: The method further includes the step of attempting access to the selected second type of base station by referring to the frequency priority list and the cell priority list when the access to the two types of target base stations fails.

In one embodiment, the base station of the first type is a 5G base station, the target base station of the second type is a target LTE base station, and the other base station of the second type is another LTE base station.

In one embodiment, the base station fallback is an EPS fallback.

In another aspect, a method for supporting a terminal to perform a base station fallback in a first type of base station is provided. The method includes the steps of receiving a SIP message carrying a voice call invitation message from the terminal, transmitting the SIP message to a first type of communication network, and a PDU session change message (Protocol Data) from the first type of communication network. Receiving a Unit Session Modification Message, transmitting a PDU session modification response message to the first type of communication network in response to the reception of the PDU Session Modification message, measuring configuration to the terminal Transmitting information, receiving a measurement report message including measurement results for the second type of base stations from the terminal, and an RRC release message or a second type target to the terminal based on the measurement report message Transmitting a handover command message designating a base station, wherein the RRC release message and the handover command message include a voice service indicator.

In an embodiment, transmitting the measurement configuration information to the terminal includes transmitting the measurement configuration information to the terminal through an RRC connection reconfiguration message.

In an embodiment, transmitting an RRC release message or a handover command message designating a second type target base station to the terminal based on the measurement report message - The RRC release message and the handover command message are voice service including an indicator - includes transmitting the RRC release message or the handover command message to the terminal further based on UE capability information and network capability information.

In one embodiment, the RRC release message is a message instructing the terminal to disconnect from the first type of base station and perform redirection to attempt access to the second type of candidate base station.

In an embodiment, the voice service indicator is information instructing the terminal to attempt access to another base station of the second type when the terminal fails to access the candidate base station of the second type.

In an embodiment, the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs. The frequency priority list and the cell priority list are for enabling the terminal to select a base station of a second type to which the terminal attempts to access when the terminal fails to access the candidate base station of the second type. will be.

In an embodiment, the handover command message is a message instructing the terminal to attempt an inter-heterogeneous handover to the second type target base station.

In an embodiment, the voice service indicator is information instructing the terminal to retry access to the second type target base station when the handover between the heterogeneous networks fails.

In an embodiment, the handover command message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs. The frequency priority list and the cell priority list are such that, when the terminal fails to access the second type target base station, the terminal can refer to and select another base station of the second type to attempt access it is for

In an embodiment, the first type of base station is a 5G base station, the first type of communication network is a 5th generation core network (5GC), and the second type of target base station is a target LTE base station.

In one embodiment, the base station fallback is an EPS fallback.

In another aspect, an apparatus for performing a base station fallback in a terminal is provided. The device may include a communication unit and a control unit supporting LTE communication and NR (New Radio) communication. The control unit transmits a SIP message carrying a voice call invitation message to the base station of the first type to which the terminal is connected through the communication unit, and in response to the transmission of the SIP message, measurement configuration information from the base station of the first type is received through the communication unit, performs measurement on base stations of a second type based on the measurement configuration information, and transmits a measurement report message to the first type base station through the communication unit, and It may be configured to receive an RRC release message from the base station through the communication unit. The control unit, in response to the reception of the RRC release message, disconnects from the base station of the first type and performs redirection to attempt access to the candidate base station of the second type, and connects to the candidate base station of the second type. When the connection fails, in response to confirming that the voice service indicator is included in the RRC release message, it may be further configured to control access to another base station of the second type.

In an embodiment, the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies, and the control unit, when the connection to the second type candidate base station fails, the RRC and in response to confirming that the voice service indicator is included in the release message, control to attempt access to a second type of base station serving on a base station service frequency having the highest priority in the frequency priority list .

In an embodiment, the RRC release message further includes a cell priority list specifying priorities for cell IDs, and the controller is configured to release the RRC when the connection to the second type candidate base station fails. and in response to confirming that the voice service indicator is included in the message, control to attempt access to a base station of a second type having the highest priority cell ID in the cell priority list.

In an embodiment, the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs, wherein the control unit includes: In response to confirming that the voice service indicator is included in the RRC release message when the connection to the two-type candidate base station fails, the second type selected by referring to the frequency priority list and the cell priority list and control to attempt access to the base station.

In an embodiment, the base station of the first type is a 5G base station, the candidate base station of the second type is a candidate LTE base station, and the other base station of the second type is another LTE base station.

In one embodiment, the base station fallback is an EPS fallback.

In another aspect, an apparatus for performing a base station fallback in a terminal is provided. The device may include a communication unit and a control unit supporting LTE communication and NR communication. The control unit transmits a SIP message carrying a voice call invitation message to the base station of the first type to which the terminal is connected through the communication unit, and in response to the transmission of the SIP message, measurement configuration information from the base station of the first type is received through the communication unit, performs measurement on base stations of a second type based on the measurement configuration information, and transmits a measurement report message to the first type base station through the communication unit, and It may be configured to receive a handover command message specifying the second type of target base station from the base station through the communication unit. The control unit, in response to the reception of the handover command message, attempts an inter-heterogeneous handover to the target base station of the second type, and when the inter-heterogeneous handover fails, a voice service indicator is included in the handover command message. and control to attempt access to another base station of the second type in response to confirming that it is included.

In one embodiment, when the handover between the heterogeneous networks fails, the controller reconnects to the second type target base station in response to confirming that the voice service indicator is included in the handover command message is further configured to attempt to control.

In an embodiment, the handover command message further includes a frequency priority list specifying priorities for base station service frequencies, and the controller is configured to: and control to attempt access to a base station of a second type that is serving at a base station service frequency having the highest priority in the frequency priority list.

In an embodiment, the handover command message further includes a cell priority list specifying priorities for cell IDs, and the control unit is, when the access to the second type of target base station fails, the cell and control to attempt access to the second type of base station having the highest priority cell ID in the priority list.

In an embodiment, the handover command message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs, the control unit comprising: and control to attempt access to the second type of base station selected by referring to the frequency priority list and the cell priority list when the access to the second type of target base station fails.

In one embodiment, the base station of the first type is a 5G base station, the target base station of the second type is a target LTE base station, and the other base station of the second type is another LTE base station.

In one embodiment, the base station fallback is an EPS fallback.

In another aspect, an apparatus for supporting a terminal to perform a base station fallback in a first type of base station is provided. The apparatus may include a communication unit and a control unit supporting NR communication. The control unit receives a SIP message carrying a voice call invitation message from the terminal through the communication unit, transmits the SIP message to a first type communication network through the communication unit, and receives a PDU from the first type communication network Receives a session change message through the communication unit, transmits a PDU session change response message to the first type of communication network through the communication unit in response to receiving the PDU session change message, and transmits measurement configuration information to the terminal Transmitted through a communication unit, and receives a measurement report message including measurement results for the second type of base stations from the terminal through the communication unit, and based on the measurement report message, an RRC release message or a second type of RRC release message to the terminal It may be configured to transmit a handover command message designating a target base station of , through the communication unit. The RRC release message and the handover command message may include a voice service indicator.

In an embodiment, the control unit is further configured to transmit the RRC release message or the handover command message to the terminal further based on the terminal capability information and the network capability information.

In one embodiment, the RRC release message is a message instructing the terminal to disconnect from the first type of base station and perform redirection to attempt access to the second type of candidate base station.

In an embodiment, the voice service indicator is information instructing the terminal to attempt access to another base station of the second type when the terminal fails to access the candidate base station of the second type.

In an embodiment, the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs. The frequency priority list and the cell priority list are for enabling the terminal to select a base station of a second type to which the terminal attempts to access when the terminal fails to access the candidate base station of the second type. will be.

In an embodiment, the handover command message is a message instructing the terminal to attempt an inter-heterogeneous handover to the second type target base station.

In an embodiment, the voice service indicator is information instructing the terminal to retry access to the second type target base station when the handover between the heterogeneous networks fails.

In an embodiment, the handover command message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs. The frequency priority list and the cell priority list are such that, when the terminal fails to access the second type target base station, the terminal can refer to and select another base station of the second type to attempt access it is for

In an embodiment, the first type of base station is a 5G base station, the first type of communication network is a 5G core network, and the second type of target base station is a target LTE base station.

In one embodiment, the base station fallback is an EPS fallback.

In another aspect, a method for performing a base station fallback in a terminal is provided. The method comprises the steps of: the terminal exchanging messages with a base station of a first type to which the terminal is connected to receive a voice call service - The messages include an RRC release message received by the terminal from the base station of the first type including - in response to receiving the RRC release message, disconnecting from the first type of base station and performing redirection to attempt access to a second type of candidate base station, and the second type of candidate base station It may include the step of trying to connect to another base station of the second type when the access to the BS fails.

In an embodiment, the step of attempting access to another base station of the second type when the access to the second type candidate base station fails may include: When the access to the second type candidate base station fails, the RRC and attempting to connect to another base station of the second type in response to confirming that the voice service indicator is included in the release message.

In another aspect, a method for performing a base station fallback in a terminal is provided. The method includes the steps of: the terminal exchanging messages with a base station of a first type to which the terminal is connected to receive a voice call service, wherein the messages are a handover command message received by the terminal from the base station of the first type including, wherein the handover command message specifies a target base station of a second type; attempting an inter-heterogeneous handover to the target base station of the second type in response to receiving the handover command message; and The method may include attempting to access another base station of the second type when the handover between the heterogeneous networks fails.

In an embodiment, the step of attempting to access another base station of the second type when the inter-heterogeneous handover fails includes a voice service indicator included in the handover command message when the inter-heterogeneous network handover fails. and attempting to connect to another base station of the second type in response to confirming that there is.

In another aspect, a method for supporting a terminal to perform a base station fallback in a first type of base station is provided. The method includes transmitting measurement configuration information to the terminal in response to receiving a voice call service request from the terminal, and receiving a measurement report message including measurement results for base stations of a second type from the terminal and transmitting an RRC release message or a handover command message to the terminal based on the measurement report message.

In one embodiment, the RRC release message includes a voice service indicator instructing to attempt access to another base station of the second type when the terminal fails to access the base station of the second type, and the handover The command message includes a voice service indicator instructing the terminal to attempt access to another base station of the second type when the handover to the second type of base station fails.

According to the embodiments of the present invention, there is a technical effect that can prevent service delay that may occur while the terminal performs EPS fallback to receive a voice call service.

1 is a diagram illustrating an embodiment of a simplified network configuration diagram for explaining a concept in which a terminal accessing a 5G base station performs EPS fallback.
FIG. 2 is a diagram illustrating an embodiment of a block diagram of an apparatus in the 5G base station of FIG. 1 for supporting the UE to perform EPS fallback.
3 is a diagram illustrating an embodiment of a block diagram of an apparatus in the terminal of FIG. 1 for performing EPS fallback.
FIG. 4 is a diagram illustrating an embodiment of a flowchart for explaining a method for supporting a UE to perform EPS fallback in the 5G base station of FIG. 1 .
FIG. 5 is a diagram illustrating an embodiment of a flowchart for explaining a method of performing EPS fallback in the terminal of FIG. 1 .
FIG. 6 is a diagram illustrating an embodiment of a flowchart for explaining a method of performing EPS fallback in the terminal of FIG. 1 .

Advantages and features of the present invention and a method of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and these embodiments merely allow the disclosure of the present invention to be complete and those of ordinary skill in the art to which the present invention pertains. It is provided to fully inform the person of the scope of the invention, and the present invention is only defined by the scope of the claims.

The terms used herein are used only to describe specific embodiments and are not intended to limit the present invention. For example, a component expressed in a singular should be understood as a concept including a plurality of components unless the context clearly means only the singular. In addition, in the specification of the present invention, terms such as 'include' or 'have' are only intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, and such The use of the term does not exclude the presence or addition of one or more other features or numbers, steps, operations, components, parts, or combinations thereof. In addition, in the embodiments described in this specification, a 'module' or 'unit' may mean a functional part that performs at least one function or operation.

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

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, in the following description, if there is a risk of unnecessarily obscuring the gist of the present invention, detailed descriptions of well-known functions or configurations will be omitted.

1 is a diagram illustrating an embodiment of a simplified network configuration diagram for explaining a concept in which a terminal connected to a 5G base station performs EPS fallback.

Referring to FIG. 1 , the 5G base station 125 is connected to the 5G core network 127 that does not support interworking with the IMS 149 , and the terminal 110 is connected to the 5G base station 125 and receives a service therefrom. have. The terminal 110 performs a base station fallback (hereinafter referred to as 'EPS fallback') under the control of the 5G base station 125 for connection to the EPC 147 supporting interworking with the IMS 149 to receive a voice service. There is a need. In order to perform EPS fallback, the terminal 110 performs a redirection procedure to attempt access to the candidate LTE base station 145 or a heterogeneous network (Inter-RAT) hand to the target LTE base station 145 . try over In this case, the terminal 110 may fail to access the candidate or target LTE base station 145 . The connection failure may have various reasons, such as insufficient signal strength of the candidate or target LTE base station 145 or overloading of traffic of the candidate or target LTE base station 145 . When the terminal 110 fails to access the candidate or target LTE base station 145, the terminal 110 performs reconnection to the source cell, that is, the 5G base station 125 that was previously being serviced. do. However, since the terminal 110 is in a state to receive VoLTE service, it will attempt EPS fallback again after reconnection to the source base station 125 is completed. Due to this, the terminal 110 is subjected to a serious deterioration in service quality. According to the disclosed technology, even if the terminal 110 fails to access the candidate or target LTE base station 145, it does not return to the source base station 125 and retryes access to the target LTE base station 145 or Controlled to attempt access to possible LTE base stations. Therefore, according to the disclosed technology, it is possible to prevent deterioration of service quality due to regression when the terminal 110 receives VoLTE service.

The terminal 110 to which the disclosed technology is applied may be a standalone (SA) terminal. The terminal 110 is a portable terminal such as a desktop or laptop PC, a tablet PC, a notebook computer, and a note pad that supports various RAT (Radio Access Technology) such as NR (new radio) and LTE/LTE-A. , and various types of handheld-based wireless communication devices such as smart phones, etc. may be included, but it should be recognized that the type of the terminal 110 is not limited thereto.

FIG. 2 is a diagram illustrating an embodiment of a block diagram of an apparatus in the 5G base station of FIG. 1 for supporting the UE to perform EPS fallback.

As shown in FIG. 2 , the EPS fallback performance support apparatus 200 includes a storage unit 220 , a communication unit 230 , and a control unit 210 communicatively connected to the storage unit 220 and the communication unit 230 . can do. The communication unit 230 includes a 2G wireless communication network such as a GSM network and a CDMA network, a wireless Internet network such as a WiFi network, a portable Internet network such as a WiBro network and a WiMax network, a wireless communication network supporting packet transmission, an LTE (4G) network, and / or may implement RATs and communication protocols adopted in the 5G network and may include functions/features of a communication unit of a communication device used in such a wireless communication network, but the function of the communication unit 230 is not limited thereto. In this case, the RATs and communication protocols may be implemented in suitable hardware and/or firmware.

The control unit 210 receives a SIP (Session Initiation Protocol) message carrying a Voice Call Invite message from the terminal 110 through the communication unit 230, and sends the SIP message to the 5G core network 127 through the communication unit ( 230), and receives a PDU session modification message from the 5G core network 127 through the communication unit 230, and in response to the reception of the PDU session modification message, a PDU session change response message (PDU session modification response message) to the 5G core network 127 through the communication unit 230 may be configured to perform a series of message transmission and reception procedures. The controller 210 can recognize that the VoLTE service is requested by receiving the PDU session change message from the 5G core network 127 . The control unit 210 may be further configured to transmit measurement configuration information to the terminal 110 through the communication unit 230 . In one embodiment, the control unit 210 transmits the measurement configuration information to the terminal 110 by loading the RRC connection reconfiguration message (radio resource control connection reconfiguration message). The control unit 210 receives a measurement report message including measurement results for LTE base stations from the terminal 110 through the communication unit 230, and RRC to the terminal 110 based on the measurement report message. It may be further configured to transmit a release message (RRC release message) or a handover command message designating a target LTE base station through the communication unit 230 . In an embodiment, the control unit 210 further refers to UE Capability information and Network Capability information to determine whether to transmit an RRC release message or a handover command message to the UE 110 . do. In an embodiment, the RRC release message and the handover command message may include a voice service indicator (hereinafter, referred to as an 'LTE voice service indicator'). The RRC release message may be a message instructing the terminal 110 to disconnect the 5G base station 125 and perform redirection to attempt access to the candidate LTE base station 145 . The handover command message may be a message instructing the terminal 110 to attempt an inter-heterogeneous handover (Inter-RAT) to the target LTE base station 145 . The LTE voice service indicator does not return to the source base station 125 when the terminal 110 fails to access the candidate LTE base station or fails in handover between heterogeneous networks, but retry access to the target LTE base station 145 or It may be information instructing to try access to another possible LTE base station nearby. In one embodiment, the LTE voice service indicator may not be included in the RRC release message and the handover command message. In this embodiment, when the connection to the candidate LTE base station fails or the handover between heterogeneous networks fails, the LTE voice service indicator is displayed. It is possible to design the terminal 110 to retry access to the target LTE base station 145 without confirmation or to attempt access to another possible nearby LTE base station.

In an embodiment, the RRC release message may further include a frequency priority list specifying priorities for base station service frequencies. For example, in the frequency priority list, 800 MHz, which is known as a frequency having the widest coverage, may be designated as the highest priority. For another example, in the frequency priority list, 2.1 GHz may be designated as having a low priority. The frequency priority list is to reduce the probability of access failure by allowing the terminal 110 to select another LTE base station to preferentially attempt access when the terminal 110 fails to access the candidate LTE base station. When the access to the candidate LTE base station 145 fails, the terminal 110 may select an LTE base station using the highest 800 MHz as a service frequency from the frequency priority list and attempt access. In this case, since the corresponding LTE base station has a wide coverage, the possibility that the terminal 110 succeeds in access is increased. If the terminal 110 selects and attempts to access an LTE base station using 2.1 GHz, which has a low priority, as a service frequency, if there are many users receiving services from the LTE base station, the attempt to access the LTE base station is resource allocation problems may be more likely to fail. In an embodiment, the RRC release message may further include a cell priority list specifying priorities for cell IDs (Cell Identifications). For example, in the cell priority list, a cell ID with low traffic may be designated as a high priority. The cell priority list is to reduce the probability of access failure by allowing the terminal 110 to select another LTE base station to preferentially attempt access when the terminal 110 fails to access the candidate LTE base station. The terminal 110 can increase the access success rate by preferentially selecting an LTE base station having a cell ID having a higher priority from the cell priority list and attempting access. In one embodiment, the RRC release message may include both a frequency priority list and a cell priority list. In this embodiment, the terminal 110 refers to both the frequency priority list and the cell priority list and selects another LTE base station to preferentially try to access, thereby further increasing the access success rate.

In an embodiment, the handover command message may further include a frequency priority list specifying priorities for base station service frequencies. In an embodiment, the handover command message may further include a cell priority list specifying priorities for cell IDs. In one embodiment, the handover command message may further include a frequency priority list and a cell priority list. In the above embodiments, when the terminal 110 fails to retry access to the target LTE base station 145, it refers to the frequency priority list and/or the cell priority list to select another LTE base station to preferentially access. By selecting it, the success rate of the connection can be increased.

The controller 210 described above is, in terms of hardware, ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), It may be implemented using at least one of processors, controllers, micro-controllers, and microprocessors, and embodiments including procedures, steps, or functions include at least one It may be implemented as firmware/software modules executable on a hardware platform to perform functions or operations The software code may be implemented by a software application written in a suitable programming language.

The storage unit 220 may store a program and/or data for the operation of the control unit 210 , and may also store input/output data and the like. Storage unit 220 is a flash memory type (flash memory type), hard disk type (hard disk type), multimedia card micro type (multimedia card micro type), card type memory (for example, SD or XD memory, etc.), Random Access Memory (RAM), Static Random Access Memory (SRAM), Read-Only Memory (ROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Programmable Read-Only Memory (PROM) Magnetic Memory, Magnetic It may include at least one type of storage medium among a disk and an optical disk.

3 is a diagram illustrating an embodiment of a block diagram of an apparatus in the terminal of FIG. 1 for performing EPS fallback.

As shown in FIG. 3 , the EPS fallback performing apparatus 300 may include a storage unit 320 , a communication unit 330 , and a control unit 310 communicatively connected to the storage unit 320 and the communication unit 330 . can The communication unit 330 includes a GSM network, a 2G wireless communication network such as a CDMA network, a wireless Internet network such as a WiFi network, a portable Internet network such as a WiBro network and a WiMax network, a wireless communication network supporting packet transmission, an LTE (4G) network, and / or may implement RATs and communication protocols adopted in the 5G network and may include functions/features of a communication unit of a communication device used in such a wireless communication network, but the function of the communication unit 330 is not limited thereto. In this case, the RATs and communication protocols may be implemented in suitable hardware and/or firmware.

The control unit 310 transmits the SIP message carrying the voice call invitation message to the 5G base station 125 to which the terminal 110 is connected through the communication unit 330, and in response to the transmission of the SIP message, from the 5G base station 125. It may be configured to receive measurement configuration information through the communication unit 330 . The measurement configuration information may be included in the RRC connection reconfiguration message transmitted by the 5G base station 125 . The control unit 310 may be further configured to perform measurement on LTE base stations based on the measurement configuration information and transmit a measurement report message carrying the measurement result to the 5G base station 125 through the communication unit 330 .

The control unit 310 may be further configured to receive an RRC release message from the 5G base station 125 through the communication unit 330 . The controller 330 may be further configured to disconnect the connection with the 5G base station 125 in response to the reception of the RRC release message and perform redirection to attempt access to the candidate LTE base station. The controller 310 may perform an RRC connection reestablishment procedure with a candidate LTE base station to perform redirection. The RRC connection reestablishment procedure may involve a procedure of exchanging an RRC connection reestablishment request message and an RRC connection reestablishment response message. In one embodiment, the control unit 310 attempts to access another possible LTE base station nearby in response to confirming that the RRC release message contains the LTE voice service indicator when the connection to the candidate LTE base station fails. It may be further configured to control. The LTE voice service indicator indicates that the RRC release message including the indicator is being used for the purpose of performing EPS fallback for the voice service, and when the terminal 110 fails to access the candidate LTE base station, the source base station 125 ) may be information instructing to try access to another possible LTE base station nearby without returning to. In an embodiment, when access to a candidate LTE base station fails, it is possible to configure the control unit 310 to control access to another possible LTE base station nearby without checking the LTE voice service indicator.

In an embodiment, the RRC release message may further include a frequency priority list specifying priorities for base station service frequencies. In an embodiment, the RRC release message may further include a cell priority list specifying priorities for cell IDs. In one embodiment, the RRC release message may further include a frequency priority list and a cell priority list. In the case of these embodiments, when the terminal 110 fails to access the candidate LTE base station 145, it refers to the frequency priority list and/or the cell priority list and selects another LTE base station to preferentially access. The connection success rate can be increased.

The control unit 310 may be configured to receive a handover command message designating a target LTE base station from the 5G base station 125 through the communication unit 330 . The handover command message may be included in an RRC connection reconfiguration message including mobility control information, transmitted from the 5G base station 125 . The controller 310 may be further configured to attempt an Inter-RAT handover to the target LTE base station in response to the reception of the handover command message. In one embodiment, the control unit 310 is further configured to control access to another LTE base station in response to confirming that the handover command message contains the LTE voice service indicator when the handover between heterogeneous networks fails can be In one embodiment, when the handover between heterogeneous networks fails, the controller 310 connects to the same target LTE base station that performed the handover in response to confirming that the LTE voice service indicator is included in the handover command message. can retry. Connection retry to the target LTE base station may be made by performing an RRC connection reconfiguration procedure with the target LTE base station. As described above, the LTE voice service indicator indicates that the handover command message including the indicator is being used for the purpose of performing EPS fallback for the voice service, and the terminal 110 fails to access the target LTE base station. In this case, it may be information instructing to retry access to the same target LTE base station without returning to the source base station 125 . In an embodiment, when handover between heterogeneous networks fails, it is possible to configure the controller 310 to control access to another LTE base station without checking the LTE voice service indicator.

In an embodiment, the handover command message may further include a frequency priority list specifying priorities for base station service frequencies. In an embodiment, the handover command message may further include a cell priority list specifying priorities for cell IDs. In one embodiment, the handover command message may further include a frequency priority list and a cell priority list. In the case of these embodiments, the terminal 110 refers to the frequency priority list and/or the cell priority list when the connection retry to the target LTE base station 145 fails, referring to the next LTE connection to be preferentially attempted. By selecting a base station, it is possible to increase the access success rate.

The controller 310 described above is, in terms of hardware, ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays, It may be implemented using at least one of processors, controllers, micro-controllers, and microprocessors, and embodiments including procedures, steps, or functions include at least one It may be implemented as firmware/software modules executable on a hardware platform to perform functions or operations The software code may be implemented by a software application written in a suitable programming language.

The storage unit 320 may store a program and/or data for the operation of the control unit 310 , and may also store input/output data and the like. Storage unit 320 is a flash memory type (flash memory type), hard disk type (hard disk type), multimedia card micro type (multimedia card micro type), card type memory (for example, SD or XD memory, etc.), Random Access Memory (RAM), Static Random Access Memory (SRAM), Read-Only Memory (ROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Programmable Read-Only Memory (PROM) Magnetic Memory, Magnetic It may include at least one type of storage medium among a disk and an optical disk.

FIG. 4 is a diagram illustrating an embodiment of a flowchart for explaining a method for supporting a UE to perform EPS fallback in the 5G base station of FIG. 1 .

As shown in FIG. 4 , the EPS fallback support method starts with receiving a SIP message carrying a voice call invitation message from the terminal 110 ( S405 ). In step S410, the SIP message is delivered to the 5G core network 127. In step S415, a PDU session change message for generating a QoS flow for a voice call is received from the 5G core network 127 (Quality of Service Flow). In step S420, the VoLTE service is selected through EPS fallback in response to the reception of the PDU session change message, and the PDU session change response message is transmitted to the 5G core network 127 accordingly. In step S425, the terminal 110 transmits measurement configuration information to the terminal 110 in order to measure the LTE base stations. In an embodiment, the measurement configuration information may be transmitted in an RRC connection reconfiguration message. In step S430 , a measurement report message including measurement results for LTE base stations is received from the terminal 110 . In step S435, an RRC release message or a handover command message for designating a target LTE base station is transmitted to the terminal 110 based on the measurement report message. The RRC release message and the handover command message include an LTE voice service indicator. In an embodiment, it may be determined whether to transmit the RRC release message or the handover command message to the terminal 110 with further reference to the terminal capability information and the network capability information. The RRC release message may be a message instructing the terminal 110 to disconnect from the 5G base station 125 and perform redirection to attempt access to the candidate LTE base station. The LTE voice service indicator included in the RRC release message may be information instructing to attempt access to another LTE base station when the terminal 110 fails to access the candidate LTE base station. The RRC release message may further include a frequency priority list and/or a cell priority list. As described above, the frequency priority list and the cell priority list are for the terminal 110 to select an LTE base station to which the terminal 110 attempts to access when the terminal 110 fails to access the candidate LTE base station. . The handover command message may be a message instructing the terminal 110 to attempt an inter-heterogeneous handover to the target LTE base station. The LTE voice service indicator included in the handover command message may be information instructing the terminal 110 to retry access to the same target LTE base station when the handover between heterogeneous networks to the target LTE base station fails. The handover command message may further include a frequency priority list and/or a cell priority list. As described above, the frequency priority list and the cell priority list are prioritized by referring to the terminal 110 when the terminal 110 retrys access to the failed target LTE base station and fails again. This is to enable you to select an LTE base station to attempt access to.

FIG. 5 is a diagram illustrating an embodiment of a flowchart for explaining a method of performing EPS fallback in the terminal of FIG. 1 .

As shown in FIG. 5 , in the EPS fallback method, in order to receive a voice call service in a state in which the terminal 110 is connected to the 5G system and receiving a service, the terminal 110 is connected to the 5G base station 125 to receive a voice call. It starts from the step S505 of transmitting the SIP message carrying the call invitation message. In step S510, measurement configuration information is received from the 5G base station 125 in response to the transmission of the SIP message. As described above, the measurement configuration information is information for allowing the terminal 110 to measure LTE base stations, and may be transmitted while being included in the RRC connection reconfiguration message. In step S515, measurements are performed on LTE base stations based on the measurement configuration information, and a measurement report message including the measurement result is transmitted to the 5G base station 125. In step S520 , an RRC release message is received from the 5G base station 125 . In step S525, in response to the reception of the RRC release message, the connection with the 5G base station 125 is disconnected and redirection is performed to attempt access to the candidate LTE base station. In an embodiment, an attempt to access the candidate LTE base station may be made by performing an RRC connection reconfiguration procedure with the candidate LTE base station. In step S530, it is checked whether access to the candidate LTE base station has been successful. If it is determined that the connection to the candidate LTE base station is successful as a result of the check in step S530, the process is terminated. On the other hand, if it is determined that the connection to the candidate LTE base station is not successful as a result of the check in step S530, the process proceeds to step S535 to check whether the LTE voice service indicator is included in the RRC release message. If it is determined that the LTE voice service indicator is not included in the RRC release message as a result of the check in step S535, the process proceeds to step S540 and performs a procedure of returning to the 5G base station 125, which is the source base station, and ends do. Meanwhile, if it is determined that the RRC release message includes the LTE voice service indicator as a result of the check in step S535, the process proceeds to step S545 and attempts to access another LTE base station. The LTE voice service indicator included in the RRC release message may be information instructing to attempt access to another LTE base station when the terminal 110 fails to access the candidate LTE base station. The RRC release message may further include a frequency priority list and/or a cell priority list. As described above, the frequency priority list and the cell priority list are for the terminal 110 to select an LTE base station to which the terminal 110 attempts to access when the terminal 110 fails to access the candidate LTE base station. . In step S550, it is checked whether access to another LTE base station is successful. As a result of the check in step S550, if it is determined that the access to another LTE base station has not been successful, the process returns to step S545 and attempts to connect to another LTE base station repeatedly. In this case, by referring to the frequency priority list and/or the cell priority list, an LTE base station to attempt access may be selected again. On the other hand, if it is determined that the connection to another LTE base station is successful as a result of the check in step S550, the process is terminated.

FIG. 6 is a diagram illustrating an embodiment of a flowchart for explaining a method of performing EPS fallback in the terminal of FIG. 1 .

As shown in FIG. 6 , in the method for performing EPS fallback, in order to receive a voice call service in a state in which the terminal 110 is connected to the 5G system and receiving the service, the terminal 110 is connected to the 5G base station 125 to receive a voice call. It starts from the step S605 of transmitting the SIP message carrying the call invitation message. In step S610, measurement configuration information is received from the 5G base station 125 in response to the transmission of the SIP message. As described above, the measurement configuration information is information for allowing the terminal 110 to measure LTE base stations, and may be transmitted while being included in the RRC connection reconfiguration message. In step S615, measurement is performed on the LTE base stations based on the measurement configuration information and a measurement report message including the measurement result is transmitted to the 5G base station 125. In step S620, a handover command message designating a target LTE base station is received from the 5G base station 125. In an embodiment, the handover command message may be transmitted while being included in an RRC connection reconfiguration message including mobility control information. In step S625, a heterogeneous network handover to the target LTE base station is attempted in response to the reception of the handover command message. In step S630, it is checked whether the handover between heterogeneous networks to the target LTE base station is successful. As a result of the check in step S630, if it is determined that the handover between heterogeneous networks to the target LTE base station is successful, the process ends. On the other hand, if it is determined that the handover between heterogeneous networks to the target LTE base station is not successful as a result of the check in step S630, the process proceeds to step S635 to determine whether the LTE voice service indicator is included in the handover command message. check the If it is determined that the LTE voice service indicator is not included in the handover command message as a result of the check in step S635, the process proceeds to step S640 and performs a procedure of returning to the 5G base station 125, which is the source base station, and It ends. Meanwhile, if it is determined that the handover command message includes the LTE voice service indicator as a result of the check in step S635, the process proceeds to step S645 to attempt access to another LTE base station. In an embodiment, the other LTE base station may be a target LTE base station that has already attempted a handover and has failed to access once. In an embodiment, the retry connection to the target LTE base station may be made by performing an RRC connection reconfiguration procedure with the target LTE base station. The LTE voice service indicator included in the handover command message may be information instructing the terminal 110 to attempt access to another LTE base station (target LTE base station) when the handover between heterogeneous networks to the target LTE base station fails. . In step S650, it is checked whether the connection to another LTE base station (target LTE base station) is successful. If it is determined that the connection to another LTE base station (target LTE base station) is successful as a result of the check in step S650, the process ends. On the other hand, if it is determined that the connection to another LTE base station (target LTE base station) is not successful as a result of the check in step S650, the process proceeds to step S655 to attempt access to another LTE base station. In this case, the terminal 110 may select another LTE base station to attempt access by referring to the frequency priority list and/or the cell priority list included in the handover command message. In step S660, it is checked whether access to another LTE base station is successful. If it is determined that the connection to another LTE base station has not been successful as a result of the check in step S660, the process returns to step S655 and attempts to connect to another LTE base station repeatedly. On the other hand, if it is determined that the connection to another LTE base station is successful as a result of the check in step S660, the process is terminated.

In the above description, embodiments related to the UE performing EPS fallback from the 5G core network to the EPC in order to receive the VoLTE service have been described. It will be appreciated that it can also be applied with respect to performing EPS fallback to the communication network of

In the above description, the meaning of the description that a component is connected to or coupled to another component does not only mean that the component is directly connected or coupled to the other component, but also means that one or more other components are interposed therebetween. It should be understood to include the meaning that may be connected or coupled via an element. In addition, terms for describing the relationship between the elements (eg, 'between', 'between', etc.) should also be interpreted with similar meanings.

In the embodiments disclosed herein, the arrangement of the illustrated components may vary depending on the environment or requirements in which the invention is implemented. For example, some components may be omitted or some components may be integrated and implemented as one. Also, the arrangement order and connection of some components may be changed.

In the above, various embodiments of the present invention have been shown and described, but the present invention is not limited to the specific embodiments described above, and the above-described embodiments depart from the gist of the present invention as claimed in the appended claims. Without this, various modifications may be made by those of ordinary skill in the art to which the present invention pertains, and these modified embodiments should not be understood separately from the technical spirit or scope of the present invention. Accordingly, the technical scope of the present invention should be defined only by the appended claims.

110: terminal
125: 5G base station
127: 5G core network
145: LTE base station
147: EPC
149: IMS
200: EPS fallback performance support device
210: control unit
220: storage
230: communication department
300: EPS fallback performing device
310: control unit
320: storage
330: communication unit

Claims (65)

A method of performing base station fallback in a terminal, comprising:
transmitting a Session Initiation Protocol (SIP) message carrying a Voice Call Invite message to a first type of base station to which the terminal is connected;
receiving measurement configuration information from the base station of the first type in response to the transmission of the SIP message;
performing measurements on base stations of a second type based on the measurement configuration information and transmitting a Measurement Report Message to the base stations of the first type;
Receiving an RRC release message from the base station of the first type;
Disconnecting from the first type of base station in response to the reception of the RRC release message and performing redirection to attempt access to a second type of candidate base station, and
If the access to the second type candidate base station fails, attempting access to another base station of the second type in response to confirming that a voice service indicator is included in the RRC release message; including,
The RRC release message includes priorities for base station service frequencies or priorities for cell IDs (Identifications) or priorities for base station service frequencies and priority information for cell IDs,
When the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies, a voice service indicator (Voice) is included in the RRC release message when the connection to the second type candidate base station fails. The step of attempting access to another base station of the second type in response to confirming that the service indicator) is included is a base station of the second type serving the service frequency of the base station having the highest priority in the frequency priority list. including the step of attempting to access the
When the RRC release message further includes a cell priority list specifying priorities for cell IDs (Identifications), when the connection to the second type of candidate base station fails, in the RRC release message The step of attempting access to another base station of the second type in response to confirming that a Voice Service Indicator is included includes a second cell ID having the highest priority in the cell priority list. Including the step of trying to connect to a base station of the type, or
When the RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs, access to the second type of candidate base station The step of trying to access another base station of the second type in response to confirming that a Voice Service Indicator is included in the RRC release message includes the frequency priority list and the cell. A method of performing a base station fallback, comprising the step of attempting to access the selected second type of base station by referring to a priority list.
According to claim 1,
The terminal is a standalone (SA) terminal, the base station fallback method.
According to claim 1,
Receiving the measurement configuration information from the base station of the first type in response to the transmission of the SIP message may include: RRC connection reconfiguration message from the base station of the first type through a radio resource control connection reconfiguration message A method of performing a base station fallback, comprising: receiving measurement configuration information.
According to claim 1,
In response to the reception of the RRC release message, disconnecting from the first type of base station and performing redirection to attempt access to the second type of candidate base station includes: A method of performing a base station fallback, comprising the step of performing an RRC connection reestablishment procedure of
delete delete delete delete delete delete According to claim 1,
The method of claim 1, wherein the first type of base station is a 5th generation (5G) base station, the second type of candidate base station is a candidate LTE base station, and the other base station of the second type is another LTE base station.
According to claim 1,
The base station fallback is EPS fallback (Evolved Packet System Fallback), the base station fallback performing method.
A method of performing a base station fallback in a terminal, comprising:
transmitting a SIP message carrying a voice call invitation message to a base station of a first type to which the terminal is connected;
receiving measurement configuration information from the base station of the first type in response to the transmission of the SIP message;
performing measurement on base stations of a second type based on the measurement configuration information and transmitting a measurement report message to the base station of the first type;
Receiving a handover command message specifying a target base station of a second type from the base station of the first type;
In response to receiving the handover command message, attempting an inter-heterogeneous handover (Inter-RAT HO) to the target base station of the second type; and
When the handover between heterogeneous networks fails, in response to confirming that a voice service indicator is included in the handover command message, attempting access to another base station of the second type;
The step of attempting to access another base station of the second type in response to confirming that a voice service indicator is included in the handover command message when the handover between the heterogeneous networks fails includes: the target base station of the second type retrying the connection to the
The step of retrying access to the second type of target base station includes performing an RRC connection reconfiguration procedure with the second type of target base station,
The handover command message includes priority information for base station service frequencies or priority for cell IDs or priority for base station service frequencies and priority information for cell IDs,
The handover command message further includes a frequency priority list specifying priorities for base station service frequencies, and when the handover between heterogeneous networks fails, it is confirmed that the handover command message includes a voice service indicator The step of attempting access to another base station of the second type in response to Further comprising the step of trying to access the base station of the second type, or
The handover command message further includes a cell priority list specifying priorities for cell IDs, and when the handover between heterogeneous networks fails, confirming that a voice service indicator is included in the handover command message In response to the step of attempting access to another base station of the second type, if the access to the second type target base station fails, the second type having the highest priority cell ID in the cell priority list Further comprising the step of trying to access the base station of, or
The handover command message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs, and when the handover between heterogeneous networks fails, the In the step of attempting to access another base station of the second type in response to confirming that the voice service indicator is included in the handover command message, if the access to the second type target base station fails, the frequency priority The method further comprising the step of attempting to access the selected second type of base station by referring to the priority list and the cell priority list, the base station fallback performing method.
14. The method of claim 13,
The step of receiving the measurement configuration information from the base station of the first type in response to the transmission of the SIP message includes receiving the measurement configuration information from the base station of the first type through an RRC connection reconfiguration message. How to do a fallback.
14. The method of claim 13,
Receiving a handover command message specifying a target base station of a second type from the base station of the first type includes: receiving mobility control information from the base station of the first type A method of performing a base station fallback, comprising the step of receiving an RRC connection reconfiguration message comprising a.
delete delete delete delete delete delete delete delete 14. The method of claim 13,
The method of claim 1, wherein the base station of the first type is a 5G base station, the target base station of the second type is a target LTE base station, and the other base station of the second type is another LTE base station.
14. The method of claim 13,
wherein the base station fallback is an EPS fallback.
A method for supporting a terminal to perform a base station fallback in a first type of base station, the method comprising:
Receiving a SIP message carrying a voice call invitation message from the terminal;
forwarding the SIP message to a first type of communication network;
Receiving a PDU session modification message (Protocol Data Unit Session Modification Message) from the first type of communication network;
transmitting a PDU session modification response message to the first type of communication network in response to receiving the PDU session modification message;
transmitting measurement configuration information to the terminal;
Receiving a measurement report message including measurement results for the second type of base stations from the terminal, and
Transmitting an RRC release message or a handover command message designating a second type target base station to the terminal based on the measurement report message - The RRC release message and the handover command message include a voice service indicator - including,
The RRC release message is a message instructing that the terminal disconnects from the first type of base station and performs redirection to attempt access to a second type of candidate base station, and the voice service indicator indicates that the terminal Information instructing to attempt access to another base station of the second type when access to the candidate base station of the second type fails,
The RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs - the frequency priority list and the cell priority list is to enable the terminal to select a base station of the second type to attempt access by referring to when the terminal fails to access the candidate base station of the second type;
The handover command message is a message instructing the terminal to attempt an inter-heterogeneous handover to the second type target base station, and the voice service indicator is, when the terminal fails the inter-heterogeneous handover, the Information instructing to retry access to the second type of target base station,
The handover command message further includes a frequency priority list specifying priority for base station service frequencies and a cell priority list specifying priority for cell IDs - the frequency priority list and the cell priority The list is for allowing the terminal to select another base station of the second type to which the terminal attempts to access by referring to when the terminal fails to access the second type of target base station -, a method for supporting base station fallback.
27. The method of claim 26,
The transmitting of the measurement configuration information to the terminal includes transmitting the measurement configuration information to the terminal through an RRC connection reconfiguration message.
27. The method of claim 26,
Transmitting an RRC release message or a handover command message designating a second type target base station to the terminal based on the measurement report message - The RRC release message and the handover command message include a voice service indicator - , comprising transmitting the RRC release message or the handover command message to the terminal further based on UE capability information and network capability information.
delete delete delete delete delete delete 27. The method of claim 26,
The base station of the first type is a 5G base station, the communication network of the first type is a 5th generation core network (5GC), and the target base station of the second type is a target LTE base station. .
27. The method of claim 26,
The base station fallback is an EPS fallback, a method for supporting performing base station fallback.
An apparatus for performing a base station fallback in a terminal, comprising:
A communication unit supporting LTE communication and NR (New Radio) communication, and
comprising a control unit;
The control unit transmits a SIP message carrying a voice call invitation message to the base station of the first type to which the terminal is connected through the communication unit, and in response to the transmission of the SIP message, measurement configuration information from the base station of the first type is received through the communication unit, performs measurement on base stations of a second type based on the measurement configuration information, and transmits a measurement report message to the first type base station through the communication unit, and configured to receive an RRC release message from the base station through the communication unit,
The control unit, in response to the reception of the RRC release message, disconnects from the base station of the first type and performs redirection to attempt access to the candidate base station of the second type, and connects to the candidate base station of the second type. Further configured to control access to another base station of the second type in response to confirming that a voice service indicator is included in the RRC release message when the access fails,
The RRC release message includes priority information for base station service frequencies or priority for cell IDs or priority for base station service frequencies and priority information for cell IDs,
The RRC release message further includes a frequency priority list specifying priorities for base station service frequencies,
The control unit, in response to confirming that the voice service indicator is included in the RRC release message when the access to the second type candidate base station fails, the base station service having the highest priority in the frequency priority list further configured to control an attempt to access a base station of a second type serving the frequency; or
The RRC release message further includes a cell priority list specifying priorities for cell IDs,
In response to confirming that the voice service indicator is included in the RRC release message when access to the second type candidate base station fails, the control unit has the highest priority cell ID in the cell priority list or further configured to control access to a second type of base station with
The RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs,
When the access to the second type candidate base station fails, the control unit refers to the frequency priority list and the cell priority list in response to confirming that the voice service indicator is included in the RRC release message. and control to attempt access to the selected second type of base station by performing a base station fallback.
delete delete delete delete delete An apparatus for performing a base station fallback in a terminal, comprising:
A communication unit supporting LTE communication and NR communication, and
comprising a control unit;
The control unit transmits a SIP message carrying a voice call invitation message to the base station of the first type to which the terminal is connected through the communication unit, and in response to the transmission of the SIP message, measurement configuration information from the base station of the first type is received through the communication unit, performs measurement on base stations of a second type based on the measurement configuration information, and transmits a measurement report message to the first type base station through the communication unit, and configured to receive a handover command message specifying a second type of target base station from the base station through the communication unit,
The control unit, in response to the reception of the handover command message, attempts an inter-heterogeneous handover to the target base station of the second type, and when the inter-heterogeneous handover fails, a voice service indicator is included in the handover command message. further configured to control to attempt access to another base station of the second type in response to confirming that it is included,
When the handover between heterogeneous networks fails, the controller performs an RRC connection reconfiguration procedure with the target base station of the second type in response to confirming that the voice service indicator is included in the handover command message. and control to retry access to a second type of target base station;
The handover command message includes priority information for base station service frequencies or priority for cell IDs or priority for base station service frequencies and priority information for cell IDs,
The handover command message further includes a frequency priority list specifying priorities for base station service frequencies,
The control unit is further configured to control to attempt access to a base station of a second type that is being serviced at a service frequency of a base station having the highest priority in the frequency priority list when the access to the target base station of the second type fails or
The handover command message further includes a cell priority list specifying priorities for cell IDs,
The control unit is further configured to control access to the second type of base station having the highest priority cell ID in the cell priority list when the access to the second type of target base station fails,
The handover command message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs,
The control unit is further configured to control access to the second type of base station selected with reference to the frequency priority list and the cell priority list when the access to the second type of target base station fails. Base station fallback performing device.
delete delete delete delete delete delete An apparatus for supporting a terminal to perform a base station fallback in a first type of base station, the apparatus comprising:
a communication unit supporting NR communication, and
comprising a control unit;
The control unit receives a SIP message carrying a voice call invitation message from the terminal through the communication unit, transmits the SIP message to a first type communication network through the communication unit, and receives a PDU from the first type communication network Receives a session change message through the communication unit, transmits a PDU session change response message to the first type of communication network through the communication unit in response to receiving the PDU session change message, and transmits measurement configuration information to the terminal Transmitted through a communication unit, and receives a measurement report message including measurement results for the second type of base stations from the terminal through the communication unit, and based on the measurement report message, an RRC release message or a second type of RRC release message to the terminal configured to transmit, through the communication unit, a handover command message designating a target base station of
The RRC release message is a message instructing that the terminal disconnects from the first type of base station and performs redirection to attempt access to a second type of candidate base station, and the voice service indicator indicates that the terminal Information instructing to attempt access to another base station of the second type when access to the candidate base station of the second type fails,
The RRC release message further includes a frequency priority list specifying priorities for base station service frequencies and a cell priority list specifying priorities for cell IDs - the frequency priority list and the cell priority list is to enable the terminal to select a base station of the second type to attempt access by referring to when the terminal fails to access the candidate base station of the second type;
The handover command message is a message instructing the terminal to attempt an inter-heterogeneous handover to the second type target base station, and the voice service indicator is, when the terminal fails the inter-heterogeneous handover, the Information instructing to retry access to the second type of target base station,
The handover command message further includes a frequency priority list specifying priority for base station service frequencies and a cell priority list specifying priority for cell IDs - the frequency priority list and the cell priority The list is for enabling the terminal to select another base station of the second type to which the terminal attempts to access by referring to when the terminal fails to access the second type target base station -, an apparatus for performing base station fallback. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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