WO2015069076A1

WO2015069076A1 - Method for continuously providing emergency call service through packet network

Info

Publication number: WO2015069076A1
Application number: PCT/KR2014/010738
Authority: WO
Inventors: 백영교; 정상수; 조성연
Original assignee: 삼성전자 주식회사
Priority date: 2013-11-08
Filing date: 2014-11-10
Publication date: 2015-05-14

Abstract

Disclosed are a method and a device for maintaining an emergency call service through a packet network in a mobile communication network. A terminal using VoLTE receives identification information for indicating whether an IMS voice over PS (IMS VoPS) is supported from a network to determine whether the IMS VoPS of the network is supported, and processes paging for a CS voice call according to the determination result if the emergency call service continues through the packet network.

Description

Method for continuously providing emergency call service through packet network

The present specification is a method for continuously providing an emergency call service through a packet network in a mobile communication network. Specifically, an emergency call is stopped due to an incoming call while providing an emergency call service through a packet network. A method and apparatus for solving the problem.

In general, mobile communication systems have been developed to provide voice services while guaranteeing user activity. However, mobile communication systems are gradually expanding not only voice but also data services, and now they have developed to the extent that they can provide high-speed data services.

In today's mobile communication system, there is a need to solve the shortage of resources due to the provision of various services, and the need for developing a more advanced mobile communication system is in line with the needs of users who want to provide higher speed services. .

In response to these demands, one of the systems being developed as a next-generation mobile communication system, a specification work for Long Term Evolution (LTE) is underway in the 3GPP (The 3rd Generation Partnership Project). LTE is a technology that implements high-speed packet-based communication with a transmission rate of up to 100 Mbps. To this end, various methods are discussed. For example, the network structure can be simplified to reduce the number of nodes located on the communication path, or the wireless protocols can be as close to the wireless channel as possible.

Meanwhile, in the LTE network, CSFB (CS fall) using IMS-based Voice over LTE (VOLTE) technology as a packet switched method (PS) to support voice calls or recycling a CS (circuit switched) method of 2G / 3G systems back) technology. VoLTE in LTE network is a term that can be used in the same concept as Voice over IMS (VoIMS). In addition, an LTE network may serve an emergency call through VoLTE.

The current LTE system may be configured to allow emergency call service or VoLTE service in some areas of the network and disallow emergency call service or VoLTE service in the remaining areas. In this case, when the VoLTE voice call is connected to the terminal in the VoLTE service allowance area, and the terminal moves to the VoLTE service disallowed area, even when the VoLTE voice call continues, it is in progress when a new voice call arrives in the CS domain. The VoLTE voice call is dropped. Similarly, when an emergency call is connected to a terminal in an emergency call service allowance area, and the terminal moves to an emergency call service disallowed area, even if the emergency call continues, the emergency call in progress when the voice call arrives in the CS domain is disconnected. Since the disconnection of voice calls can cause serious problems, it is necessary to study how to solve them.

According to the network configuration and load control method, the present specification allows certain network areas and some network areas to be allowed to be started when certain network areas are allowed to be started in some network areas, but not in the other network areas. Provided are a method and an apparatus for maintaining an emergency call service in a situation where a terminal moves between remaining network areas which are not yet available.

In a communication method of a network device supporting a packet-based voice service in a mobile communication system according to an embodiment of the present invention, a TA in which a terminal does not support a packet-based voice service based on a message received from a home subscriber server (HSS) Recognizing a location in a tracking area; determining whether a VoLTE call or an emergency call is in progress for the terminal when receiving a call request message for the terminal; and VoLTE for the terminal. If a call or emergency call is in progress, selecting a packet switched domain as the domain for the received call request message.

In a mobile communication system according to an embodiment of the present invention, a network device supporting a packet-based voice service may include a terminal that transmits and receives data to and from another device based on a message received from a home subscriber server (HSS). Recognizing that the packet is located in a TA (Tracking Area) that does not support the packet-based voice service, and receives a call request message for the terminal determines whether the VoLTE call or emergency call is in progress (ongoing) for the terminal And a controller for selecting a packet switched domain as a domain for the received call request message when a VoLTE call or an emergency call is in progress for the terminal.

According to various embodiments of the present disclosure, emergency call and VoLTE call services may be seamlessly provided when an emergency call or VoLTE supported region and an emergency call or VoLTE supported region are mixed.

1 is a diagram illustrating the structure of a general LTE mobile communication system;

2 is a flowchart illustrating a communication method according to a first embodiment of the present invention;

3 is a flowchart illustrating a communication method according to a second embodiment of the present invention;

4 is a flowchart illustrating a communication method according to a third embodiment of the present invention;

5 is a diagram illustrating interworking between a 3GPP modem layer and an IMS / connection manager layer inside a user terminal;

6 is a view showing a configuration of a terminal operating according to a preferred embodiment of the present specification;

7 is a flowchart illustrating a communication method according to a fourth embodiment of the present invention.

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this case, it should be noted that like elements are denoted by like reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may blur the gist of the present specification will be omitted.

In describing the embodiments of the present specification in detail, an OFDM-based wireless communication system, in particular, the 3GPP EUTRA standard will be the main target, and as a kind of specific service, the main target will be VoLTE or emergency call. The subject matter is applicable to other communication systems and services having a similar technical background and a channel form with slight modifications without departing from the scope of the present disclosure, which is obvious to those skilled in the art. It will be possible to judge. In addition, the technology described for VoLTE herein may be applied to other voice providing services (eg, Voice over Wi-Fi) based on IMS without major changes.

1 is a diagram illustrating a structure of a general LTE mobile communication system.

Referring to FIG. 1, a radio access network of an LTE mobile communication system includes a next-generation base station (evolved Node B, EUTRAN, hereinafter referred to as ENB or Node B) 110, a mobility management entity (MME) 120, and an S-GW. (Serving Gateway) 130.

The user equipment (hereinafter referred to as UE) 100 is connected to an external network through the ENB 110, the S-GW 130, and the P-GW (PDN Gateway; Packet Data Network Gateway) 160.

The ENB 110 is a Radio Access Network (RAN) node and corresponds to a Radio Network Controller (RNC) of a Universal Terrestrial Radio Access Network (UTRAN) system and a Base Station Controller (BSC) of a GSM EDGE Radio Access Network (GERAN) system. . The ENB 110 is connected to the UE 100 through a radio channel and plays a role similar to that of the existing RNC / BSC. The ENB 110 may use several cells at the same time.

In LTE, all user traffic including a real-time service such as Voice over IP (VoIP) using the Internet protocol is serviced through a shared channel, and therefore, an apparatus for collecting and scheduling situation information of UEs 100 is required. This is handled by the ENB 110.

The MME 120 is a device that is in charge of various control functions. One MME 120 may be connected to a plurality of base stations 110.

The S-GW 130 is a device for providing a data bearer, and generates or removes a data bearer under the control of the MME 120.

An application function (AF) 140 is a device that exchanges information related to a user and an application at an application level. The AF 140 may be, for example, a Service Centralization and Continuity Application Server (SCC AS) for supporting a voice service through a packet network. The SCC AS may perform a function of indicating a pageable domain of a terminal to be called through T-ADS (Terminating Access Domain Selection).

The Policy Charging and Rules Function (PCRF) 150 is a device that controls a policy related to a quality of service (QoS) of a user, and corresponds to a policy and charging control (PCC) rule corresponding to the policy. Is transmitted to and applied to the P-GW 160. Policy Charging and Rules Function (PCRF) 150 is an entity that collectively controls QoS and billing for traffic.

In general, UP (User Plane) refers to the UE 100 and RAN node ENB 110, the RAN node ENB 110 and the S-GW 130, and the S-GW 130 to which user data is transmitted and received. ) Refers to a path connecting the P-GW 160. The portion of the path that uses a resource-limited radio channel is a path between the UE 100 and the ENB 110 which is a RAN node.

In a wireless communication system such as LTE, a unit to which QoS is applicable is an EPS (Evolved Packet System) bearer. One EPS bearer is used to transmit IP flows having the same QoS requirements. EPS bearers can be assigned parameters related to QoS, which include a QoS Class Identifier (QCI) and Allocation and Retention Priority (ARP). The QCI is a parameter defining QoS priority as an integer value, and the ARP is a parameter used to determine whether to allow or reject the creation of a new EPS bearer.

The EPS bearer corresponds to a Packet Data Protocol (PDP) context of a General Packet Radio Service (GPRS) system. One EPS bearer belongs to a PDN connection, and the PDN connection may have an access point name (APN) as an attribute. If a PDN connection is created for an IP Multimedia Subsystem (IMS) service such as Voice over LTE (VoLTE), the PDN connection should be created using a well-known IMS APN.

According to various embodiments of the present disclosure, the mobile communication network may be configured such that an LTE system and a legacy system coexist. That is, some network operators of a mobile communication system may install a network in which emergency call service or VoLTE is supported and a network in which emergency call service or VoLTE is not supported. More specifically, based on Voice over LTE (VoLTE), a type of voice service, a mobile communication network allows the use of an emergency call service or a VoLTE service in some areas (TA) and an emergency in the other areas. Instead of disallowing call service or VoLTE service, it may be configured to allow CS (Circuit Switched) emergency call or CS voice call using legacy network. VoLTE is a method of providing voice services using a packet switched (PS) network and an IMS network.

Here, whether the emergency call service or the VoLTE service is supported may be different for each network configuration area, for example, for each cell or base station, and for larger units, for each tracking area (TA) or MME pool area. can be different.

The core network node (for example, MME) is available for emergency call service when the user terminal performs an emergency call service or a location registration (attach or tracking area update (TAU)) procedure in the VoLTE support area. An identifier indicating) or an identifier indicating that an IMS-based voice service is available is provided to the terminal. On the contrary, when the user terminal performs location registration in the emergency call service or the VoLTE unsupported area, the core network node may designate an identifier indicating that the emergency call service is unavailable or an identifier indicating that the IMS-based voice service is unavailable. Provided to the terminal. In such a network configuration, when an actual user terminal moves between two areas, a domain for providing a voice service (PS for VoLTE, CS for the remaining areas) may be changed. In the case of a terminal registered in the IMS, the I-CSCF / S-CSCF determines which domain (PS or CS) to page the voice call to the T-ADS in the procedure of processing the voice call request to the terminal. Ask. When the T-ADS informs the I-CSCF / S-CSCF of the domain to process the voice call by referring to the result collected from the entities of the network, the I-CSCF / S-CSCF refers to the domain information and requests the voice call. Perform the procedure in accordance with

Emergency call service or VoLTE provides emergency call service or VoLTE service for the voice call currently in progress for the voice call user's sensibility when the user crosses the two areas as above while the user has the active voice call. You can keep it going. Accordingly, the user terminal may maintain the ongoing emergency call or VoLTE voice call as it is even after moving to the emergency call or VoLTE non-allowed area after starting the emergency call or VoLTE voice call in the emergency call or VoLTE allowed area.

According to the above-described method, when an emergency call or voice call via VoLTE is being performed in an area where emergency call or VoLTE is not allowed, when another user calls the terminal performing the voice call, the MSC / The request is received by the Mobile Switching Center / Visitor Location Register (VLR). Upon receiving the request, the MSC / VLR sends a CS paging request to the MME. At this time, since the terminal is performing an emergency call or a voice call through VoLTE, the terminal is in the connected mode (EMM-CONNECTED mode). Accordingly, the MME sends a CS SERVICE NOTIFICATION message to the terminal and sends voice call paging through the CS domain. In this case, the terminal moves to another network from which the emergency call or voice call via VoLTE is being used while performing CSFB for processing voice call paging, and as a result, the emergency call may be disconnected.

Therefore, there is a need for a method of continuously receiving voice services for emergency calls.

In the present specification, a voice call is started in a TA supporting an IMS-based emergency call or VoLTE voice service, and a method of continuously maintaining an ongoing voice call even when a terminal moves to an unsupported TA and performs location registration is considered. do.

According to the first embodiment of the present disclosure, when a terminal in an emergency call or a TA in which a VoLTE is not supported receives a CS SERVICE NOTIFICATION message from the MME while maintaining an emergency call or VoLTE call, the CSFB is rejected to the VoLTE to the MME. Be sure to let them know that an emergency call is in progress. Accordingly, the terminal informs the MSC / VLR that the MME requested CS paging is in progress so that the terminal rejects the received call. As a result, an embodiment of the present disclosure may allow a voice call to be continuously performed even in the above case, and notify the other party that has called the terminal that the terminal is currently performing a call.

The above-described embodiment of the present invention specifies that the VoLTE emergency call is applicable not only to the VoLTE emergency call but also to the ongoing VoLTE general call.

Alternatively, according to the second embodiment of the present specification, when the MSC / VLR requests CS paging for a UE in a TA in which an emergency call or a VoLTE is not supported, the MME is assigned to a bearer of the UE. The terminal is called an emergency call or VoLET by referring to all or a part of whether the access point name (APN) is emergency, whether the QCI (QoS Class Identifier) # 1, and whether the Allocation and Retention Priority (ARP) is emergency. Determine if the call is in progress. When the UE is in an emergency call or VoLTE call, the MME notifies the MSC / VLR that the CS paging request is in progress. In this case, the MSC / VLR may perform a procedure such as rejecting an incoming call so that a voice call may be continuously performed and may notify the other party calling the terminal that the call is in progress.

Or, according to the third embodiment of the present specification, the Home Subscriber Server (HSS) requests the MME for information on whether an emergency call or VoLTE call is in progress for a UE that is Combined and HMS registered with the HSS. Update the received information. The T-ADS requests the HSS whether the emergency call or the VoLTE call proceeds to the terminal, and updates the received information. Subsequently, when a call comes to the terminal and the S-CSCF / I-CSCF requests domain selection information from the T-ADS, if the terminal is in an emergency call or a VoLTE call, the S-CSCF / I-CSCF Send a response to select the PS domain. In this way, S-CSCF / I-CSCF prevents paging to the CS domain so that voice calls can continue.

Or, according to the fourth embodiment of the present disclosure, the terminal that initiated the emergency call or VoLTE call informs the MME that the corresponding service is started to the MME, and the HSS determines whether the terminal is in an emergency call or VoLTE call from the MME. Update the information. The T-ADS requests the HSS for information on whether an emergency call or a VoLTE call is in progress and updates the received information. Subsequently, when a call is received by the terminal and the S-CSCF / I-CSCF requests domain selection information from the T-ADS, if the terminal is in an emergency call or a VoLTE call, the T-ADS may display the S-CSCF / The I-CSCF sends a response to select the PS domain. In this way, the S-CSCF / I-CSCF prevents paging of the terminal to the CS domain so that the voice call can continuously proceed.

Hereinafter, the embodiments of the present invention described above will be described in more detail. The following embodiments may be applied to emergency calls, VoLTE calls, VoLTE emergency calls, and VoLTE general calls without departing from the spirit of the present invention, and in the following embodiments, emergency calls, VoLTE, VoLTE calls, voice The terms call, VoLTE emergency call, etc. may be used interchangeably, but are not limited to any one technology.

2 is a flowchart illustrating a communication method according to a first embodiment of the present invention. In detail, FIG. 2 is a flowchart illustrating a communication method in which a terminal rejects a CS voice call by recognizing an emergency call or a VoLTE call.

Referring to FIG. 2, when the terminal 200 coupled to the CS and the PS moves to a TA that does not exist in the TA list while the emergency call or the VoLTE call is in progress, the terminal 200 performs the combined TAU. 201. Specifically, the terminal 200 determines whether the EMC BS flag = 0 or the IMS VoPS flag = 0 is set from the TAU accept message sent by the MME 220. If the EMC BS flag is set to 0, the terminal 200 recognizes that emergency call service is not supported in the TA. If the IMS VoPS flag is set to 0, the terminal 200 recognizes that VoLTE is not supported in the TA. Even if the emergency call service or the VoLTE service is not supported as described above, the ongoing voice call is maintained until the end of the service (202).

Meanwhile, since the terminal 200 is combined attached to the CS and the PS, when another user calls the terminal 200, an IAM message is received by the MSC / VLR 240 in which the terminal 200 is registered. In operation 241, the MSC / VLR 240 recognizes that a CS voice call for the terminal 200 has occurred. Thereafter, the MSC / VLR 240 transmits a CS paging request to the MME 220 (242). Since the MME 240 is in the EMM-CONNECTED mode, the MME 240 sends a CS SERVICE NOTIFICATION message to the terminal 200 to notify that there is a CS voice call (221).

Upon receiving the CS SERVICE NOTIFICATION message, the UE may determine that the emergency call or VoLTE is still in progress when the UE does not receive a notification from the IMS layer that the emergency call or VoLTE service is no longer needed (203). Alternatively, the terminal 200 may determine whether an emergency call or VoLTE is in progress by asking the IMS layer whether an emergency call or VoLTE is in progress.

If it is determined that an emergency call or VoLTE is in progress, the terminal 200 may perform a procedure of rejecting a CS voice call.

In an embodiment, the terminal 200 receiving the CS SERVICE NOTIFICATION message displays the user's phone number and the like delivered through the CS SERVICE NOTIFICATION message to reject the CS voice call when the user wants to reject the CS voice call. The procedure can be performed.

In order to reject the CS voice call, the terminal 200 may include the CSFB response IE in the EXTENDED SERVICE REQUEST message, and set the CSFB response value to 000 to transmit to the MME 220 (204). As a result, the terminal 200 may inform the MME 220 that an emergency call or VoLTE call is in progress. For example, the EXTENDED SERVICE REQUEST message may be expressed as shown in Table 1. The CSFB failure cause IE may be expressed to indicate that the CSFB failure cause value = 0001 indicates that a VoLTE call is in progress as shown in Table 2.

Table 1

IEI	Information Element	Type / Reference	Presence	Format	Length
	Protocol discriminator	Protocol discriminator9.2	M	V	1/2
	Security header type	Security header type 9.3.1	M	V	1/2
	Extended service request message identity	Message type9.8	M	V	One
	Service type	Service type9.9.3.27	M	V	1/2
	NAS key set identifier	NAS key set identifier	M	V	1/2
	M-TMSI	Mobile identity9.9.2.3	M	LV	6
B-	CSFB response	CSFB response9.9.3.5	C	TV	One
B-	CSFB failure cause	CSFB failure cause 9.9.3.x	C	TV	One
57	EPS bearer context status	EPS bearer context status	O	TLV	4
D-	Device properties	Device properties9.9.2.0A	O	TV	One

TABLE 2

8	7	6	5	4	3	2	One
CSFB failure causeIEI				CSFB failure cause value				octet 1

In one embodiment, the terminal 200 may indicate that an emergency call or VoLTE call is in progress by determining a value not used previously among the CSFB response values of the existing CSFB response IE. For example, the terminal 200 may set the CSFB response value to 100 as shown in Table 3 to reject the CS voice call, and may indicate that the reason for rejection is an emergency call or a VoLTE call in progress.

TABLE 3

8	7	6	5	4	3	2	One
CSFB responseIEI				0spare	CSFB response value000 = CSFB failure001 = CSFB accept 100 = CSFB failure due to busy line			octet 1

Upon receiving the EXTENDED SERVICE REQUEST message, the MME 220 transmits a CS paging rejection message to the MSC / VLR 240 in response to the paging request 242 (222). At this time, the CS paging rejection message includes a value indicating that the VoLTE call is in progress for the reason of rejection. For example, the CS paging rejection message may be expressed as shown in Table 4, and the rejection reason (i.e SGs Cause) may be expressed as shown in Table 5.

Table 4

Information element	Type / Reference	Presence	Format	Length
Message type	Message type9.2	M	V	One
IMSI	IMSI9.4.6	M	TLV	6-10
SGs Cause	SGs Cause9.4.18	M	TLV	3

Table 5

Upon receiving the CS paging rejection message, the MSC / VLR 240 may reject the received CS voice call. In this case, the MSC / VLR 240 may indicate that the terminal that has sent the CS voice call is busy.

The method is applicable not only to VoLTE emergency calls but also to situations where VoLTE general calls are in progress.

3 is a flowchart illustrating a communication method according to a second embodiment of the present invention. Specifically, FIG. 3 is a flowchart illustrating a communication method in which an MME rejects a CS voice call by recognizing a VoLTE emergency call service.

Referring to FIG. 3, when the terminal 300 coupled to the CS and the PS moves to a TA that does not exist in the TA list while the emergency call or the VoLTE call is in progress, the terminal 300 performs the combined TAU. 301. In more detail, the terminal 300 determines whether the EMC BS flag = 0 or the IMS VoPS flag = 0 is set from the TAU accept message sent by the MME 320. If the EMC BS flag is set to 0, the terminal 300 recognizes that the emergency call is not supported in the TA. If the IMS VoPS flag is set to 0, the terminal 300 recognizes that VoLTE is not supported in the TA. Even if the emergency call or the VoLTE is moved to the TA which is not supported as described above, the ongoing VoLTE call or emergency call is maintained until the end of the service (302).

Meanwhile, since the terminal 300 is combined attached to the CS and the PS, when another user calls the terminal 300, an IAM message is received by the MSC / VLR 340 in which the terminal 300 is registered. The MSC / VLR 340 learns that a CS voice call has occurred for the terminal 300 (341). Thereafter, the MSC / VLR 340 transmits a CS paging request to the MME 320 (342).

Thereafter, the MME 320 determines the emergency call or VoLTE call progress of the terminal 300 (321).

In one embodiment, when the terminal 300 is in the EMM-CONNECTED mode, the MME 340 determines whether the APN assigned to the bearer is an emergency call, whether the assigned ARP is an emergency call, or an assignment. The VoLTE emergency call progress of the terminal 300 may be determined by referring to all or a part of information regarding whether the QCI is # 1 or the like.

In another embodiment, the terminal 300 transmits an ESM NOTIFICATION message or the like to the MME 320 when the emergency call or VoLTE call is started or terminated as shown in Table 6, indicating that the emergency call or VoLTE call has been started or terminated. You can inform. The MME 320 may determine the emergency call or VoTEL call progress of the terminal 300 through the ESM NOTIFICATION message received from the terminal 300.

Table 6

IEI	Information Element	Type / Reference	Presence	Format	Length
	Protocol discriminator	Protocol discriminator9.2	M	V	1/2
	EPS bearer identity	EPS bearer identity9.3.2	M	V	1/2
	Procedure transaction identity	Procedure transaction identity9.4	M	V	One
	Notification message identity	Message type9.8	M	V	One
	Notification indicator	Notification indicator9.9.4.7A	M	LV	2

The value of the notification indicator included in the ESM NOTIFICATION message may include information for notifying the MME 320 that an emergency call session is created or terminated as shown in Table 7.

TABLE 7

When the terminal 300 finds that the emergency call service is not available through the TAU process, the terminal 300 may inform the MME 320 whether the emergency call or the VoLTE call proceeds using the ESM NOTIFICATION message. In addition, the terminal 300 transmits an ESM NOTIFICATION message to the MME 320 when the emergency call or VoLTE call starts or ends, and the MME 320 continuously proceeds with the emergency call or VoLTE call of the terminal 300. You can tell. This will be described in more detail in the fourth embodiment.

In one embodiment, when the MME 320 is changed, the terminal 300 may transmit whether the terminal proceeds with an emergency call or a VoLTE call to the target MME.

If it is determined that the VoLTE emergency call is in progress, the MME 320 transmits a CS paging rejection message to the MSC / VLR 340 in response to the paging request (322). The CS paging rejection message includes a value indicating that an emergency call or a VoLTE call is in progress for the rejection reason. For example, the CS paging rejection message may be expressed as shown in Table 4, and the reason for rejection (i.e. SGs Cause) may be expressed as shown in Table 5.

Upon receiving the CS paging rejection message, the MSC / VLR 340 may reject the received CS voice call. In this case, the MSC / VLR 340 may indicate that the terminal that has sent the CS voice call is busy (343). .

The method specifies that the VoLTE emergency call is applicable not only for VoLTE emergency calls but also for ongoing situations.

4 is a flowchart illustrating a communication method according to a third embodiment of the present invention. Specifically, FIG. 4 is a flowchart illustrating a method for recognizing VoLTE emergency call service in T-ADS so that CS paging does not occur.

Referring to FIG. 4, the terminal 400 completes registration with the IMS (401), and is attached to the CS and the PS that are serving the emergency call or VoLTE call. If the terminal 400 moves to a TA that does not exist in the TA list, the terminal 400 performs a combined TAU. In detail, the terminal 400 transmits a TAU request message to the MME 420 (402), and the MME 420 receiving the TAU request message requests a location update from the HSS 440 (421).

At this time, the MME 420 determines whether an emergency call or a VoLTE call is currently in progress in the terminal 400. 4 illustrates that the MME 420 determines whether an emergency call or a VoLTE call is currently in progress in the terminal 400, but is not limited thereto. Other network devices (e.g., SCC AS / T-ADS 460) may be implemented to determine this.)

In one embodiment, the MME 420 may send all of the information indicating whether the APN assigned to the bearer is an emergency call, whether the assigned ARP is an emergency call, whether the assigned QCI is # 1, etc. Alternatively, the terminal 400 determines whether an emergency call or a VoLTE call is currently in progress.

In another embodiment, the terminal 300 transmits an ESM NOTIFICATION message or the like to the MME 420 at the start or end of an emergency call or VoLTE call to the MME 420 that the emergency call or VoLTE call is started or terminated. The value of the notification indicator included in the ESM NOTIFICATION message is for notifying the MME 420 that an emergency call session is created or terminated (a packet-based voice service for a terminal is started or terminated), as shown in Table 7. May contain information.

When the terminal 400 finds that the emergency call service is not available through the TAU process, the terminal 400 may inform the MME 320 whether the emergency call or the VoLTE call proceeds using the ESM NOTIFICATION message. In addition, the terminal 400 transmits an ESM NOTIFICATION message to the MME 420 when the emergency call or VoLTE call starts or ends, and the MME 420 continuously proceeds with the emergency call or VoLTE call of the terminal 400. You can tell. This will be described in detail later in the fourth embodiment.

In an embodiment, when the MME 420 is changed, the terminal 400 may transmit whether the terminal proceeds with an emergency call or a VoLTE call to the target MME.

If the emergency call service or VoLTE is not supported in the corresponding TA, but the VoLTE emergency call is currently in progress at the terminal 400, the MME 420 may use the VoLTE in the TA in which the emergency call service or VoLTE is not supported in the location update request message. It may include an indicator (VoLTE emergency call status) for indicating that the emergency call is in service.

The HSS 440 receiving the location update request message maintains the VoLTE emergency call status and then updates whether the VoLTE emergency call proceeds through

steps

442 and 443 or

steps

423 and 444.

The HSS 440 sends an acknowledgment message for the location update request message to the MME 420 (441), and the MME 420 sets the EMC BS flag = 0 or the IMS VoPS flag = 0 in the TAU accept message. The TA notifies the terminal that the emergency call is not supported or VoLTE is not supported (422). However, in case of VoLTE emergency call, the call is maintained until the end of service (403).

In addition, for the case that the MME 420 does not know the emergency call progress of the terminal 400, the terminal 400 after receiving the TAU accept message, to the MME 420 in Table 6 and Table 7 The ESM NOTIFICATION message as disclosed may be transmitted to the MME 420 to inform the MME 420 that the emergency call has been started or ended. That is, although IMS VoPS or EMC BS is set to 0 in the TAU accept message, it is recognized that emergency call or VoLTE is not supported in the current TA. However, when an emergency call or VoLTE call is still in progress, the UE returns to the MME 420. An ESM NOTIFICATION message can be sent to indicate that an emergency or VoLTE call has started. Receiving the ESM NOTIFICATION message, the MME 420 may transmit information about whether an emergency call or a VoLTE call is progressed to the HSS 440.

Meanwhile, since the HSS 440 receives the VoLTE emergency call status in step 421, the HSS 440 may transmit a PS emergency status request message to the MME 420 periodically or aperiodically to update the VoLTE emergency call status (442). The MME 420 receives a PS emergency status request message from the HSS 440 or transmits information on whether VoLTE emergency call is progressed periodically or aperiod to the HSS 440 through a PS emergency status report message (423). . When the HSS 440 requests information from the MME 420, the HSS 440 may transmit a confirmation message 444 for the PS emergency status report message 423 to the MME 420.

Therefore, when another user calls the terminal 400, when the SCC AS / T-ADS 460 requests the HSS 440 for information about the terminal 400 (461), the HSS 440 A message including information on whether the VoLTE call or emergency call is in progress may be delivered to the SCC AS / T-ADS 460 (443).

As an example, when an INVITE message including information about the terminal 400 arrives to call the S-CSCF / I-CSCF 480 to the terminal 400 (481), the S-CSCF / I The CSCF 480 sends the INVITE back to the SCC-AS / T-ADS 460 (482). The SCC-AS / T-ADS 460 sends a message Sh-Pull request to the HSS 440 in order to request not only the subscription information but also information on the location information of the terminal and information on whether VoLTE emergency call is in progress in order to service the voice call. Can send (461). Upon receiving the request message Sh-Pull request, the HSS 440 requests the necessary information from another network entity such as the information stored therein or the MME 420, if necessary, and collects the collected information through the SCC-AS / T-ADS 460. ) Is sent in the message Sh-Pull response (433). In particular, when receiving the VoLTE emergency call status in step 421 from the MME 420, in the case of a terminal that is combined attached and registered in the IMS at the same time or in the public land mobile network (PLMN), the same VoLTE service or emergency call service (Homogeneous) If the service is not, the HSS 440 may collect information on whether the emergency call or VoLTE call progress for the terminal from the MME 420 through the

step

442, 423 or step 423, 444.

Meanwhile, the SCC-AS / T-ADS 460 that receives the information message Sh-Pull response 443 for the terminal determines whether a VoLTE call or an emergency call is in progress for the terminal, A domain for serving a voice call to the terminal is selected. For example, when the terminal 400 is recognized as a combined attached terminal in which a VoLTE emergency call is in progress (462), the SCC-AS / T-ADS 460 may be able to page a voice call through the PS domain. The INVITE message may be sent to the / I-CSCF 480 (463). Alternatively, the SCC-AS / T-ADS 460 sends a SIP 486 (User Busy) message such as S-CSCF / I-CSCF (User Busy) message so that a voice call connection attempt does not occur in the VoLTE call or the emergency call terminal 400. By sending to 480, the terminal 400 may be operable to reject the voice call attempt.

The S-CSCF / I-CSCF 480 receiving the INVITE message performs a VoLTE voice call setup process according to an existing procedure.

On the other hand, when the ongoing VoLTE emergency call service is terminated (405), the MME 420 notifies the HSS 440 that the VoLTE call or emergency call is completed through a PS emergency status report message (424). In addition, the HSS 440 may transmit a confirmation message for the PS emergency status report message to the MME 420 (445).

5 is a diagram illustrating interworking between a 3GPP modem layer and an IMS / connection manager layer inside a user terminal. Specifically, FIG. 5 is a diagram illustrating interworking between a 3GPP modem layer 520 that is in charge of a 3GPP access network and an IMS / connection manager layer 500 that manages IMS and overall communication functions within a user terminal. .

The two layers may be directly connected or may have a RIL (Radio Interface Layer) in between. If the 3GPP modem receives a TAU accept message with IMS VoPS = 0 (VoLTE is not supported) or EMC BS = 0 (Emergency bearer service is not supported) (521), the 3GPP modem Notifies the IMS / Connection Manager that the emergency call service or IMS VoPS is no longer supported via the RIL layer or using the Application Programmable Interface (API) (522). Upon receiving this, the IMS / Connection Manager sends a SIP message requesting IMS deregistration when the current voice call is terminated (501), and sends an emergency call service to the 3GPP modem when the emergency call or VoLTE call ends. Or it notifies that the VoLTE service is terminated (503). The IMS / Connection Manager can also inform the 3GPP modem that the voice domain should be changed to CS. Upon receipt of the notification, the 3GPP modem layer changes the voice domain to CS (523) and, if necessary (when the preceding TAU procedure is not a combined type), performs a combined TAU procedure (524).

In FIG. 5, the interworking between the IMS / connection management layer and the 3GPP modem layer is described as a request / command and an operation thereof. However, this is only an embodiment. Receiving that IMS VoPS is not supported, and based on this, changing the domain of the IMS deregistration process and subsequent voice service to CS (or CSFB) may also apply to operations with minor variations. Say.

6 is a diagram illustrating a configuration of a network device operating according to various embodiments of the present disclosure. Referring to FIG. 6, a network device according to various embodiments of the present disclosure may include a wireless transceiver 600, a controller 620, and a storage 640. The network device of FIG. 6 may correspond to any one of a UE, an MME, an HSS, an SCC AS / T-ADS, and an S-CSCF / I-CSCF, but is not limited thereto. Hereinafter, the functions of each unit will be described based on the terminal.

The wireless transceiver 600 receives information on whether IMS VoPS is supported or emergency call support from the network, and transmits and receives a registration related message under the control of the controller 620.

The controller 620 determines whether to perform an IMS deregistration process, performs a determination on whether a VoLTE voice call or a VoLTE emergency call is in progress according to the above-described embodiments, or determines a domain for a voice service. Perform the change operation.

The storage unit 640 may store various types of information necessary for the operation of the terminal according to an embodiment of the present disclosure. For example, whether TA supports IMS VoPS or whether VoLTE voice call or VoLTE emergency call is in progress may be stored for each TA.

6, the wireless transceiver 600 of FIG. 6 corresponds to the 3GPP modem layer 520 of FIG. 5, and the controller 620 of FIG. 6 corresponds to the IMS / connection management layer of FIG. 5. Can be.

In the above description, the functions of each unit have been described based on the terminal, but the network device other than the terminal may also include a wireless transceiver 600, a controller 620, and a storage unit 640, and the units may be implemented in various embodiments of the present invention. You can perform the function according to the example.

7 is a flowchart illustrating a communication method according to a fourth embodiment of the present invention. Specifically, FIG. 7 is a flowchart illustrating a method of recognizing an emergency call or VoLTE service in T-ADS so that CS paging does not occur. Hereinafter, a fourth embodiment of the present invention will be described by taking an emergency call as an example for convenience of explanation, but the following embodiments may be applied to not only an emergency call but also a VoLTE emergency call and a VoLTE general call.

Referring to FIG. 7, the terminal 700 completes IMS emergency call registration and starts an emergency call (701). The terminal 700 recognizes the start of an emergency call by receiving a SIP 200 OK message indicating that an emergency call has been started, and the ESM NOTIFICATION message as shown in Table 6 to notify the MME 720 that the emergency call service has been started. 720). The value of the notification indicator included in the ESM NOTIFICATION message may include information for notifying the MME 720 that an emergency call session is generated as shown in Table 7.

At this time, the MME 720 stores information indicating that an emergency call is in progress in the terminal 700. For example, the MME 720 stores VoLTE emergency call status = ON with respect to the terminal 700, and the VoLTE emergency call status information of the terminal 700 even when the MME is changed according to the movement of the terminal 700. It can be delivered along with the context information to the target MME to keep track of the status of the emergency call service. Alternatively, the terminal 700 may send the ESM NOTIFICATION message to the MME 720 after completing the TAU process in step 702 so that the target MME can continuously know the situation of the progress of the emergency call service.

When the MME 720 receives the VoPS status request message 741 from the HSS 740, the MME 720 transmits the VoLTE call to the HSS 740 through the VoPS status report message 722. To pass.

On the contrary, if the HSS 740 stores the information on whether or not the emergency call progresses along with whether the VoLTE call proceeds, the terminal 700 generates an emergency call session through an ESM NOTIFICATION message in step 702. Notify the MME 720, the MME 720 sends a notification message to inform the HSS 740 whether to create an emergency call session, the HSS 740 stores that the emergency call is in progress for the terminal 700. For example, the HSS 740 stores VoLTE emergency call status = ON.

Meanwhile, when another user calls the terminal 700, when the SCC AS / T-ADS 760 requests the HSS 740 for information about the terminal 700 (761), the HSS 740 is a VoLTE. Information on whether the call or emergency call is in progress may be transmitted to the SCC AS / T-ADS 760 (742).

As an example, when an INVITE message including information about the terminal 700 arrives at the S-CSCF / I-CSCF 780 to make a call to the terminal 700 (781), S-CSCF / I The CSCF 780 sends the INVITE back to the SCC-AS / T-ADS 760 (782). The SCC-AS / T-ADS 760 sends a message Sh-Pull request to the HSS 740 to request not only subscription information but also information on the location of the terminal and information on whether a VoLTE call or an emergency call is in progress in order to service a voice call. (761). Upon receiving the request message Sh-Pull request, the HSS 740 requests necessary information from another network entity such as the information stored therein or the MME 720 if necessary, and loads the collected information into the message Sh-Pull response. Send to AS / T-ADS 760 (733). For example, the HSS 740 may inform the SCC-AS / T-ADS 760 whether a VoLTE call or emergency call service is in progress through an IMSVoPS indication or an IMS emergency session indication.

In particular, in the case of a terminal 700 that is combined attached and registered at the same time as the IMS, or when the public land mobile network (PLMN) does not provide the same Homogeneous service for the VoLTE service or emergency call service, the HSS ( The 740 may collect information on whether the emergency call proceeds from the MME 720 through

steps

741 and 722.

Meanwhile, the SCC-AS / T-ADS 760 that receives the information message Sh-Pull response 742 for the terminal selects a domain for serving a voice call to the terminal using the information. For example, when the terminal 700 is recognized as a combined attached terminal in which a VoLTE emergency call is in progress (762), the SCC-AS / T-ADS 760 can be used to page a voice call through the PS domain. The INVITE message may be sent to the / I-CSCF 780 (763). Alternatively, the SCC-AS / T-ADS 760 sends a SIP 486 (User Busy) message to the S-CSCF / I-CSCF (User Busy) message to prevent the voice call connection attempt from occurring in the VoLTE or emergency call terminal 700. And 780 to reject the voice call attempt.

The S-CSCF / I-CSCF 780 receiving the INVITE message performs a VoLTE voice call setup process according to an existing procedure.

On the other hand, if the ongoing VoLTE emergency call service is terminated (704), the terminal 700 may inform the MME 720 that the emergency call has ended via SIP 200 OK or SIP BYE. Alternatively, when the terminal 700 sends an IMS Deregistration message to the MME 720 and recognizes that the emergency call service is no longer used, the ESM NOTIFICATION shown in Table 6 to notify the MME 720 that the emergency call service is terminated. Send a message or the like (705).

The value of the notification indicator included in the ESM NOTIFICATION message may include information for notifying the MME 720 that the emergency call session is terminated as shown in Table 7. At this time, the MME 720 stores that the emergency call has ended for the terminal 700. For example, the MME 720 stores VoLTE emergency call status = OFF for the terminal 700 (723).

On the other hand, if the HSS 740 stores the information on the progress of the emergency call with the progress of the VoLTE call, the MME 720 that the emergency call session is terminated through the ESM NOTIFICATION message in step 705 ) Sends a notification message notifying the end of the emergency call session to the HSS 740, the HSS 740 stores that the emergency call is terminated for the terminal 700. For example, the HSS 740 stores VoLTE emergency call status = OFF for the terminal 700.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. For example, some of the configurations of at least two embodiments of the first to fourth embodiments may be mixed. The scope of the invention should not be limited to the described embodiments, but should be determined not only by the claims that follow, but also by the equivalents of those claims.

Claims

A communication method of a network device supporting a packet-based voice service in a mobile communication system,

Recognizing that the terminal is located in a tracking area (TA) that does not support packet-based voice service based on a message received from a home subscriber server (HSS);

When receiving a call request message for the terminal, determining whether a VoLTE call or an emergency call is in progress for the terminal; And

Selecting a packet switched domain as a domain for the received call request message, if a VoLTE call or an emergency call is in progress for the terminal.
The method of claim 1,

Determining whether an emergency call is in progress for the terminal,

Requesting and receiving information on whether the emergency call proceeds to the terminal from the HSS; And

And determining whether an emergency call is in progress for the terminal based on the received information on whether the emergency call is in progress for the terminal.
The method of claim 2,

The information on whether the emergency call proceeds to the terminal, characterized in that included in the location update request message received by the HSS from the Mobility Management Entity (MME).
The method of claim 1,

The terminal, when the emergency call to the terminal is started or terminated, the communication method characterized in that for transmitting the ESM NOTIFICATION message including information on the start or end of the emergency call to the MME.
The method of claim 1, wherein the determining of whether the VoLTE call or the emergency call is in progress for the terminal comprises:

Whether a VoLTE call or an emergency call is in progress for the UE based on at least one of an access point name (APN) assigned to a bearer of the UE, information on QoS Class Identifier (QCI), and information on Allocation and Retention Priority (ARP) A communication method comprising determining whether or not.
The method of claim 1, wherein the network device is Terminating Access Domain Selection (T-ADS) or Service Centralization and Continuity Application Server (SCC AS).
The method of claim 1,

Receiving a call request message, transmitting a Sh-Pull request message to the HSS; And

And receiving information on an ongoing VoLTE call or emergency call from the HSS for the terminal.
The method of claim 1,

If the packet switched domain is selected as the domain for the received call request message, transmitting the call request message to an S-CSCF / I-CSCF.
A network device supporting a packet-based voice service in a mobile communication system,

A communication unit for communicating with another device; And

On the basis of the message received from the Home Subscriber Server (HSS), the UE recognizes that the UE is located in a tracking area (TA) that does not support packet-based voice service, and receives a call request message for the UE, thereby VoLTE to the UE. A control unit for determining whether a call or an emergency call is in progress and selecting a packet switched domain as a domain for the received call request message when a VoLTE or emergency call is in progress for the terminal; Network device comprising a.
The method of claim 9,

The control unit,

Requesting and receiving information on whether the emergency call proceeds with respect to the terminal, and determining whether an emergency call is in progress with respect to the terminal based on information on whether the emergency call progresses with respect to the terminal. Characterized by a network device.
The method of claim 10,

The information on whether the emergency call proceeds to the terminal is included in the location update request message received by the HSS from a mobility management entity (MME).
The method of claim 9,

The terminal, when the emergency call to the terminal is started or terminated, the network device, characterized in that for transmitting the ESM NOTIFICATION message including information on the start or end of the emergency call to the MME.
The method of claim 9, wherein the control unit,

Whether a VoLTE call or an emergency call is in progress for the UE based on at least one of an access point name (APN) assigned to a bearer of the UE, information on QoS Class Identifier (QCI), and information on Allocation and Retention Priority (ARP) Determining whether or not the network device.
10. The network device of claim 9, wherein the network device is Terminating Access Domain Selection (T-ADS) or Service Centralization and Continuity Application Server (SCC AS).
The method of claim 9, wherein the control unit,

Receiving the call request message, transmitting a Sh-Pull request message to the HSS, and receiving information on a VoLTE call or an emergency call in progress for the terminal from the HSS.
The method of claim 9, wherein the control unit,

Selecting a packet switched domain as a domain for the received call request message, and transmitting the call request message to an S-CSCF / I-CSCF.