KR102354644B1 - Method and apparatus for reducing voice call setup time in mobile communication network - Google Patents

Abstract

The present invention relates to a method and apparatus for shortening a voice call setup time in a mobile communication system, and the method for supporting a security procedure for a terminal of a core network node in a mobile communication system of the present invention is a method for supporting a security procedure for a terminal in a mobile communication system. Back, CSFB) generating CS security key related information to be used in the procedure, and transmitting the generated CS security key related information to a control node of a CS domain.

Description

Method and apparatus for reducing voice call setup time in mobile communication network

The present invention relates to connection control in a mobile communication network, and more particularly, to a method and apparatus for improving voice service quality by reducing a time required for setting up a voice call in a mobile communication system.

In general, a mobile communication system has been developed to provide a voice service while ensuring user activity. However, the mobile communication system is gradually expanding its scope not only to voice but also to data services, and has now developed to the extent that it can provide high-speed data services. However, in a mobile communication system in which a service is currently provided, a more advanced mobile communication system is required because there is a shortage of resources and users demand a higher speed service.

In response to this demand, as one of the systems being developed as a next-generation mobile communication system, the 3rd Generation Partnership Project (3GPP) is currently working on a standard for Long Term Evolution (LTE). LTE is a technology that implements high-speed packet-based communication with a transmission speed of up to 100 Mbps. To this end, various methods are being discussed, for example, a method of reducing the number of nodes located on a communication path by simplifying the network structure, or a method of bringing wireless protocols as close to a wireless channel as possible.

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

1, as shown, the radio access network of the LTE mobile communication system includes a next-generation base station (Evolved Node B, EUTRAN, hereinafter referred to as ENB or Node B) 110 and MME (Mobility Management Entity, 120) and It may include a Serving Gateway (S-GW) 130 .

A user equipment (User Equipment, hereinafter referred to as UE) 100 accesses an external network through ENB, S-GW, and P-GW (PDN Gateway; Packet Data Network Gateway).

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

In LTE, all user traffic, including real-time services such as VoIP (Voice over IP) through the Internet protocol, is serviced through a shared channel, so a device for scheduling by collecting situation information of UEs is required. in charge

The MME 120 is a device in charge of various control functions, and one MME may be connected to a plurality of base stations.

The S-GW 130 is a device that provides a data bearer, and creates or removes a data bearer under the control of the MME 120 .

Meanwhile, the core network of the LTE mobile communication system may further include a node (not shown in the drawing) such as an application function, PCRF, and P-GW in addition to the MME 120 and the S-GW 130 .

An application function (AF) is a device for exchanging application-related information with a user at an application level.

PCRF (Policy Charging and Rules Function) is a device that controls a policy related to the user's Quality of Service (QoS), and the PCC (Policy and Charging Control) rule corresponding to the policy is P- It is transmitted to the GW and applied. The PCRF (Policy Charging and Rules Function) is an entity that collectively controls QoS and charging for traffic.

On the other hand, in general, UP refers to the UE 100 and the RAN node 110 through which user data is transmitted and received, the S-GW 130 in the RAN node 110, and the P-GW ( 160). However, a part of this path using a radio channel with severe resource limitation is a path between the UE 100 and the RAN node 110 .

Meanwhile, a unit to which QoS can be applied in a wireless communication system such as LTE is an Evolved Packet System (EPS) bearer. One EPS bearer is used to transmit IP flows having the same QoS requirements. The EPS bearer can be assigned parameters related to QoS, including QoS Class Identifier (QCI) and Allocation and Retention Priority (ARP). The QCI is a parameter in which QoS priority is defined as an integer value, and the ARP is a parameter that determines 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 GPRS (General Packet Radio Service) 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 for an IMS (IP Multimedia Subsystem) service such as Voice over LTE (VoLTE) is created, the corresponding PDN connection must be created using a well-known IMS APN.

Meanwhile, in LTE networks, IMS-based Voice over LTE (VoLTE) technology is used in the PS (Packet Switched) method to support voice calls, or CSFB (CS) that recycles the CS (Circuit Switched) method of the 2G/3G system. fall back) technique can be used. In the LTE network, VoLTE is a term that can be used in the same concept as VoIMS (Voice over IMS).

In such a wireless communication system, in particular, when an incoming or outgoing voice call occurs while the terminal is using the LTE network in the LTE system, the CSFB (Circuit Switched Fall Back) process for switching to the CS (Circuit Switched) network for the voice service is performed. . In this case, since a separate authentication procedure for the terminal is required, there may be a delay in providing the voice service. In general, a 2G/3G system is a CS network that can provide a CS service, and an entity in charge of control related to the CS service is called an MSC (or VLR). CSFB, which provides a switching function for CS service in LTE, is made by utilizing the SGs interface between MSC/VLR and MME.

The present invention has been devised to solve the above problems, and an object of the present invention is to provide a method and apparatus for shortening a voice call setup time in a mobile communication system.

Specifically, an object of the present invention is to provide a method and apparatus for reducing service delay caused by an authentication or security information exchange process required when a terminal moves to another service while receiving a specific service.

The method of supporting the security procedure for the terminal of the core network node in the mobile communication system of the present invention for solving the above problems is the CS security key related information to be used by the terminal in the Circuit Switched Fall Back (CSFB) procedure. generating, and transmitting the generated CS security key related information to a control node of a CS domain.

In addition, the core network node supporting the security procedure for the terminal in the mobile communication system of the present invention includes a terminal or a transceiver for transmitting and receiving signals with arbitrary nodes of the mobile communication system, and the terminal is circuit switched fallback (Circuit). It is characterized in that it comprises a control unit for generating CS security key related information to be used in the Switched Fall Back (CSFB) procedure and controlling to transmit the generated CS security key related information to a control node of a CS domain.

In addition, the method of performing a circuit switched fall back (CSFB) procedure of the terminal in the mobile communication system of the present invention includes the steps of detecting the CSFB triggering, checking the CS security key related information, and the CS security key and performing a call setup process for a circuit switched domain based on the related information.

And in the mobile communication system of the present invention, a terminal performing a circuit switched fall back (CSFB) procedure detects a transceiver that transmits and receives a signal with a base station, and the CSFB triggering, and confirms CS security key related information and a control unit controlling to perform a call setup process for a circuit switched domain based on the CS security key related information.

According to the present invention, since the CS security key that can be used after the user terminal switches to the legacy network is transmitted to the CS CN node in advance, the CS CN node stores the CS security key related information, so that the user When CSFB occurs in the terminal, the stored CS security key-related information can be used, so there is no need for separate authentication or security-related signaling, thereby shortening the call connection time.

1 is a diagram showing the structure of a general LTE mobile communication system.
2 is a flowchart illustrating an operation sequence of a user terminal and a network (network) in a process of registering a user terminal for a PS domain according to an embodiment of the present invention.
3 is a flowchart illustrating an operation sequence of a user terminal and a network when CSFB is triggered in the user terminal according to another embodiment of the present invention.
4 is a flowchart illustrating an operation sequence of a user terminal and a network when CSFB is triggered in the user terminal according to another embodiment of the present invention.
5 is a flowchart illustrating a process of delivering CS security key related information according to the present invention when the MCS managing the terminal is changed.
6 is a flowchart illustrating an operation sequence of a user terminal when a CS-based service is required for a user terminal in an idle mode when SRDS is used.
7 is a flowchart illustrating an operation sequence of a user terminal and an LTE system according to another embodiment of the present invention when a CS-based service is required for a user terminal in an idle mode when using SRDS.
8 is a flowchart illustrating an operation sequence of a user terminal and an LTE system according to another embodiment of the present invention when a CS-based service is required for a user terminal in an idle mode when using SRDS.
9 is a diagram illustrating a method of activating ULI reporting for a user terminal existing in a specific RAN according to an embodiment of the present invention.
10 is a diagram illustrating a method of activating ULI reporting for a user terminal existing in a specific RAN according to another embodiment of the present invention.
11 is a diagram illustrating a method of activating RCI reporting for a user terminal existing in a specific RAN according to another embodiment of the present invention.
12 is a flowchart illustrating an operation of exchanging messages between two network nodes in order to identify user terminals located in a congested cell (or base station) according to an embodiment of the present invention.
13 is a flowchart illustrating an operation of exchanging messages between two network nodes in order to grasp information on PDN connection between user terminals located in a congested cell (or base station) and each terminal.
14 is a flowchart illustrating a message exchange process for activating a notification to periodically receive user terminal information;
15 is a block diagram illustrating an internal structure of a user terminal according to an embodiment of the present invention.
16 is a block diagram illustrating an internal structure of a core network node according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that in the accompanying drawings, the same components are denoted by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted.

In addition, in describing the embodiments of the present invention in detail, OFDM-based wireless communication system, in particular, 3GPP EUTRA standard will be mainly targeted, but the main gist of the present invention is other communication systems having a similar technical background and channel type. Also, it can be applied with a slight modification within a range that does not significantly depart from the scope of the present invention, and this will be possible at the discretion of a person having technical knowledge skilled in the art of the present invention.

In addition, in describing the embodiments of the present invention in detail, the main target of the CSFB (Circuit Switched Fall Back) process in which a user terminal uses LTE and switches to a CS network for a voice service will be the main target of the present invention The gist is to shorten the authentication/security information exchange process required when switching from one system to another system for a specific service, which does not significantly depart from the scope of the present invention for other communication systems or services with similar technical backgrounds. It can be applied with some modifications within the scope of the present invention, which will be possible at the judgment of a person skilled in the art of the present invention.

Meanwhile, in this specification and drawings, the LTE network may be used in the same sense as E-UTRAN, and the CS network may be UTRAN, GERAN, CDMA2000, or similar networks capable of supporting CS services, and these networks are collectively referred to as legacy networks. can call In addition, in this specification and drawings, being in one network may cover both cases of being connected to one network or camping in an idle state. In addition, the term base station corresponds to the eNB in the case of E-UTRAN. In addition, in the specification and drawings of the present invention, CS security key (CS security key) may refer to the entire CS security context in a wide range, which is CK' (or CK), IK' (or IK) , KSI (Key Set Identifier), integrity protection algorithm (integrity protection algorithm), start value (start value), and may be information including at least one of a ciphering algorithm (ciphering algorithm). In other words, the CS security key may be referred to as CS security key related information according to an embodiment of the present invention, may mean the CS security key itself, or to generate a CS security key. It may include at least one necessary parameter. In addition, the supplement-related information includes all or part of a downlink NAS count value for the user terminal.

In addition, in the embodiments and drawings of the present invention, the HSS may be the same as the HRL or may be an entity physically attached to it.

When a user terminal exists in E-UTRAN and an incoming or outgoing voice call occurs, the CSFB process may be started. The user terminal transmits a request for CSFB to the MME through an extended service request message. Then, the MME receiving the message determines whether CSFB is possible, and if possible, an initial context setup request (Initial Context Setup Request) message to the eNB or an identifier indicating that CSFB is required in a UE context modification request message Communicate with a cause.

Upon receiving this, the eNB transmits a move command (Handover command or RRC connection release) for CSFB to the user terminal.

Upon receiving this, the user terminal switches to the legacy network supporting the CS service and attempts to access it.

The above-described CSFB process is for conceptually explaining the operation of 3GPP TS 23.272, and a more detailed process may be based on the 3GPP TS 23.272.

Meanwhile, after accessing the legacy network, the user terminal must transmit a location registration or service request message to the legacy network. Since the user terminal does not have security information (eg, CS security key) to be used in the CS network, security (integrity protection or ciphering) cannot be applied to the location registration or service request message.

Since the CN (Core Network) node (MSC or VLR) of the legacy network that has received the request message does not have authentication information (eg, CS security key) for the user terminal, a process for generating authentication information is additionally performed. After doing so, you can start setting up a CS call.

However, the security or authentication procedure of the CS network that occurs during the CSFB process results in an increase in the total time of CSFB call setup, which may be a factor of lowering the quality of service experienced by the user.

In order to solve the above-described problem, in the present invention, the CS security key, which can be used after the user terminal switches to the legacy network, is transmitted to the CS CN node in advance so that the CS CN node is related to the CS security key. Suggest ways to store information. That is, the present invention stores CS security key-related information in advance during the location registration process between the user terminal and the CS CN node, and then uses the stored CS security key-related information when CSFB occurs to separate A method and apparatus for reducing time without authentication or security related signaling are provided.

According to an embodiment of the present invention, when the user terminal performs a combined attach or combined TAU (combined TAU) process in the LTE network, the PS CN node, CS security key related information during the location registration process (CS security key) is generated and delivered to the CS CN node for storage. Then, when CSFB occurs, the user terminal uses a CS security key matching the CS security key when performing CS signaling so that the CSFB process can be performed without a separate security or authentication procedure. Hereinafter, the above process will be described in detail with reference to FIG. 2 .

2 is a flowchart illustrating an operation sequence of a user terminal and a network (network) according to an embodiment of the present invention.

The terminal 200 transmits a combined attach or TAU request message to the MME 210 by including a UE identity (eg, IMSI, GUTI, or S-TMSI) in step S205. . The combined access message may be, for example, a message requesting to be provided with a packet switched service and a circuit switched service at the same time.

Then, the MME 210 transmits a request message for subscription information and authentication information to the HSS 230 using the ID of the terminal 200 in step S210 . Then, in step S215 , the HSS 230 transmits subscription information and authentication information for the user terminal (parameters and key sets related to authentication and security, hereinafter referred to as an authentication vector) to the MME 210 in response thereto.

Then, in step S220 , the MME 210 may perform the remaining authentication/security-related processes with the user terminal by using the subscription information and the authentication vector information.

According to an embodiment of the present invention, during the remaining combined attach or TAU process, the MME 210 generates CS security key related information (CS security key) in step S225. In this case, the MME 210 uses the authentication vector received from the HSS 230, or security for the PS domain among the MM contexts that the MME 210 has decided to use with the user terminal. It can be created using a security context, for example, a Kasme key. Here, CS security key related information (CS security key) is CK' (CK for CSFB), IK' (IK for CSFB), KSI (Key Set Identifier), integrity protection algorithm, start value (start) value), and one or more of a ciphering algorithm.

In addition, the CS security key related information includes all or part of the downlink NAS count value for the user terminal. More specifically, the MME and the UE generate the CS security key using the stored Kasme key and parameters, and the selected NAS count value.

If CSFB or SMS over SGs can be applied to the user terminal 200, the MME 210 performs a location update process with the MSC/VLR 220 in step S230. The MME 210 may include the CS security key related information in the SGsAP-LOCATION-UPDATE-REQUEST message delivered to the MSC/VLR 220 .

Upon receiving this, the MSC/VLR 220 transmits the SGsAP-LOCATION-UPDATE-ACCEPT message to the MME 210 in step S240 after performing the location registration operation. In this case, if part or all of the CS security key transmitted by the MME 210 is changed, the MSC/VLR 220 changes or generated CS security key related information (CS security key) may be included. A case in which part or all of the CS security key related information is changed will be described as follows. As described above, the CS security key-related information may include parameters necessary for generating the CS security key, and even if the MME 210 transmits a specific parameter to the MSC 220 , the MSC 220 transmits the transmission. Some of the received parameters can be changed and used. In this case, the MSC 220 needs to inform the MME 210 of the changed CS security key related information.

On the other hand, the MSC / VLR (220), in step S235, the CS security key-related information (CS security key) received from the MME (210) or updated from the received information can be stored as part of the context for the terminal (200). have.

Thereafter, if the access request to the terminal 200 is accepted, the MME 210 in step S245, in the attach (Attach) or TAU accept (accept) message all of the information received from the MSC / VLR (220) or A part may be included and delivered to the terminal. In this case, in particular, when the MSC/VLR 220 changes or generates a CS security key and delivers it to the MME 210, the MME 210 transmits all or part of the related information to the terminal. can If the downlink NAS count value is used when generating the CS security key and the UE needs to generate the CS security key directly, the MME includes all or part of the downlink NAS count value in the information sent to the UE.

Thereafter, the terminal 200 may detect that the CSFB process has occurred in step S255 while performing a normal operation in step S250. Then, in step S260, the terminal 200 may generate and transmit a location area (LA) update request or a CM service request_ message after switching to the legacy network. Before that, the terminal 200 may determine if the MME 210 ), if the CS security key is included in the message, use it, or if the received message does not include the CS security key Integrity protection is applied to the previous request messages by generating related information (CS security key), or all or part of CS security key information used by the terminal in the message, for example, KSI When the user terminal directly generates the CS security key from the PS security context, it uses the received information, downlink NAS count information, and the stored EPS context (ie, Kaseme key).

According to the above-described embodiment of the present invention, since the terminal 200 and the CS CN node use the CS security key synchronized with each other, the rest of the CS call setup process can be performed without a separate authentication or security procedure. have.

According to another embodiment of the present invention, the CS security key related information for the user terminal (CS security key) may be transferred between CN nodes when the CSFB actually occurs, not during the attach/TAU process.

Specifically, when the CSFB process occurs and the operation between the user terminal, the MME, the eNB, and the legacy network base stations is in progress, the MME delivers the CS security key related information to the MSC/VLR. , the CS CN node may have CS security key information before the user terminal switches to the legacy network and transmits the message. That is, if the MME transfers the CS security key related information to the MSC/VLR in parallel with the existing operation of CSFB according to 3GPP TS 23.272, the necessary security/authentication process between the terminal and the CS CN node can be shortened. Hereinafter, the above-described process will be described in detail with reference to FIGS. 3 and 4 .

3 is a flowchart illustrating an operation sequence of a user terminal and a network according to another embodiment of the present invention.

In step S305, it is assumed that the user terminal 300 is attached to the LTE network according to 3GPP TS 23.401 and 23.272 (combined type) and is in a state in which CSFB can be used.

In addition, the user terminal 300 detects that the transmission or reception CSFB has occurred in step S310. Then, the user terminal 300 transmits an extended service request (Extended Service Request) message to the MME 320 to request the CSFB in step S310.

Then, if the CSFB is possible, the MME 320 generates CS security key related information (CS security key) in step S315. In this case, the MME 320 uses the stored authentication vector, or the MME 320 decides to use the user terminal 300 and the MM context for the PS domain among the MM contexts, e.g. For example, it can be generated using Kasme key_, where the CS security key is CK', IK', KSI (Key Set Identifier), and integrity protection algorithm. , a start value, and a ciphering algorithm.

In addition, the CS security key related information includes all or part of the downlink NAS count value for the user terminal. More specifically, the MME and the UE generate the CS security key using the stored Kasme key and parameters, and the selected NAS count value.

In step S320, the MME 320 sends the generated CS security key related information (CS security key) to the MSC/VLR 330. SGsAP-SERVICE-REQUEST (in case of reception) or SGsAP-MO-CSFB-INDICATION ( In the case of an outgoing call), it may be inserted into a message and transmitted to the MSC/VLR 330 .

Then, the MSC/VLR 330 stores the CS security key related information (CS security key) received from the MME 320 in step S325 as part of the context for the user terminal 340, or, if necessary, the MME Based on the information received from 320 , the CS security key may be updated and then stored. And when the CS security key is updated, the MSC/VLR 330 may deliver it to the MME 320 through a separate SGsAP message in step S330. Since the case in which the CS security key is updated has been described above, a detailed description thereof will be omitted.

The MME 320 sends a request to the eNB 310 to proceed with CSFB in step S335, an initial context setup request (idle mode) or a UE context modification request (UE context modification request) (connected mode) to It can be transmitted including an identifier or cause indicating that CSFB has occurred. In this case, the messages may optionally include CS security key information to be used by the user terminal in the future. In addition, the CS security key related information includes all or part of the downlink NAS count value for the user terminal. That is, if the downlink NAS count value is used when generating the CS security key and the UE needs to generate the CS security key directly, the MME includes all or part of the downlink NAS count value in the information sent to the eNB.

Then, the eNB 310 transmits a response thereto in step S340.

And, in step S345, the eNB 310 transmits a command (RRC connection release or handover command) message for moving the user terminal 300 to the legacy network in which the CS service can be provided. If, in the above process, the MME 320 transmits CS security key information to the eNB 310, the eNB 310 selectively receives CS security key information (CS security key) information. may be included in the message and transmitted to the user terminal 300 . In addition, the CS security key related information includes all or part of the downlink NAS count value for the user terminal.

Meanwhile, according to an embodiment of the present invention, among the above processes, the MME 320 sends a request to the eNB 310 to proceed with CSFB and receives a response, and the MSC/VLR 330 related to the CS security key. In the process of transferring information (CS security key), precedence is not important, and it may be performed in parallel regardless of order. This embodiment will be described in detail with reference to FIG. 4 .

Thereafter, the user terminal 345 may generate and transmit a Location Area (LA) update request or CM service request message after switching to the legacy network according to the command of the eNB 310 in step S355.

Before that, the user terminal 300 in step S350, if the message previously received from the eNB 310 includes the CS security key related information (CS security key) using it, or if it is not included, it directly A CS security key can be generated, and integrity protection can be applied to the previous request messages by using it, or CS security key related information used by the terminal in the message (CS security key) All or part of the information, for example, KSI may be included. When the user terminal directly generates the CS security key from the PS security context, it uses the received information, downlink NAS count information, and the stored EPS context (ie, Kaseme key).

According to the above embodiment, since the user terminal and the CS CN node use the CS security key synchronized with each other, the rest of the CS call setup process can be performed without a separate authentication or security procedure.

According to another embodiment of the present invention, the CS security key related information for the user terminal (CS security key) may be transmitted between CN nodes when CSFB actually occurs, not during the attach/TAU process. That is, while the CSFB process occurs and the operation between the user terminal, the MME, the eNB, and the legacy network base stations is in progress, the MME delivers the CS security key related information to the MSC/VLR, the user terminal Prior to transferring a message by switching to the legacy network, the CS CN node may have CS security key related information. That is, if the MME transfers the CS security key related information to the MSC/VLR in parallel with the existing operation of CSFB according to 3GPP TS 23.272, the necessary security/authentication process between the terminal and the CS CN node can be shortened.

4 is a flowchart illustrating an operation sequence of a user terminal and a network according to another embodiment of the present invention.

First, it is assumed that the user terminal 400 is attached (combined type) to the LTE network according to 3GPP TS 23.401 and 23.272 in step S405 and is in a state in which CSFB can be used. And it is assumed that the user terminal 400 has generated or received CSFB.

Then, the user terminal 400 transmits an extended service request (Extended Service Request) message to the MME 420 to request the CSFB in step S410. Then, if CSFB is possible, the MME 420 generates CS security key related information (CS security key) in step S415. In this case, the MME 420 uses the stored authentication vector, or the security context for the PS domain among the MM contexts that the MME 420 has decided to use with the user terminal 400, for example, a Kasme key. ) can be used to create Here, CS security key-related information (CS security key) includes CK', IK', Key Set Identifier (KSI), an integrity protection algorithm, a start value, and a ciphering algorithm among It may include at least one or more. In addition, the CS security key related information includes all or part of the downlink NAS count value for the user terminal. That is, if the downlink NAS count value is used when generating the CS security key and the UE needs to generate the CS security key directly, the MME includes all or part of the downlink NAS count value in the information sent to the eNB.

Thereafter, the MME 420 sends a request to the eNB 410 to proceed with CSFB in step S420, an initial context setup request (in idle mode) or a UE context modification request (UE context modification request) ( connected mode), including an identifier or cause indicating that CSFB has occurred, and may be transmitted. In this case, the messages may optionally include CS security key information to be used by the user terminal 400 in the future. In addition, the CS security key related information includes all or part of the downlink NAS count value for the user terminal.

The eNB 410 transmits a response thereto to the MME 420 in step S425. And, in step S430 , the eNB 410 transmits a command (RRC connection release or handover command) message for moving the user terminal 400 to a legacy network in which the CS service can be provided to the terminal 400 .

If, in the above process, the MME 420 transmits CS security key information to the eNB 410 , the eNB 410 selects the received CS security key information (CS security key) information. may be included in the message and transmitted to the user terminal 400. In addition, the CS security key related information includes all or part of the downlink NAS count value for the user terminal.

Subsequently, in step S435, the MME 420 adds the generated CS security key related information (CS security key) to the SGsAP-Service-Request (in the case of an incoming call) or SGsAP-MO-CSFB-Indication (in the case of an outgoing call) message. It may be included and delivered to the MSC/VLR 430 .

Then, the MSC/VLR 430 may store the received CS security key related information (CS security key) in step S440 . The MSC/VLR 430 may then use the stored information when CS security is required for the user terminal 400 .

The user terminal 400 may generate a location area (LA) update request or CM service request message after switching to the legacy network according to the command of the eNB 410 in step S450 and transmit it to the MSC/VLR 430 .

On the other hand, before performing the step S450, the user terminal 400 uses the CS security key if it is included in the message previously received from the eNB 410, or if it is not included, it A CS security key can be directly generated. And, the user terminal 400 applies integrity protection to the previous request messages using the generated CS security key related information, or CS security key related information used by the terminal in the message. All or part, for example, KSI may be included. When the user terminal directly generates the CS security key from the PS security context, it uses the received information, downlink NAS count information, and the stored EPS context (ie, Kaseme key).

According to the embodiment of the present invention, since the user terminal 400 and the CS CN node use CS security key related information synchronized with each other, the rest of the CS call setup process is performed without a separate authentication or security procedure. can proceed.

On the other hand, a situation may occur in which the user terminal moves during the CSFB process and has to establish a call through an MSC/VLR (hereinafter referred to as MSC2) different from the MSC/VLR (hereinafter referred to as MSC 1) to which it has been previously registered. If, according to another embodiment of the present invention, CS security key-related information for a user terminal is set in MSC1, when a situation in which the MSC is changed during the CSFB process occurs as described above, MSC1 provides its own information to MSC2. By delivering the CS security key it has, it is possible to prevent a separate security/authentication information exchange process from occurring between the user terminal and MSC2. The above will be described with reference to FIG. 5 .

5 is a flowchart illustrating an operation sequence between CN nodes according to another embodiment of the present invention.

First, in step S505, it is assumed that a combined attach process is performed with the MSC1 510 so that CSFB has occurred for the user terminal 500 that can use the CSFB. At the same time, it is assumed that the MSC1 510 has delivered CS security key related information to the user terminal 500 in the S510 process.

Thereafter, as in step S515, it is assumed that call setup is required in the area managed by the MSC2 520 due to the movement of the user terminal 500 during the CSFB process.

In this case, the user terminal 500 transmits an LA update request message to the MSC2 520 in step S520 because the area managed by the MSC has changed. In this case, when the user terminal 500 has the CS security key according to the previous embodiment of the present invention, the CS security key related information (CS) in the location area update request (LA update request) message security key) including a part (eg, KSI), or integrity protection can be applied to the LA update request message based on CS security key-related information (CS security key). have.

MSC2 520 that has received this is not a user terminal registered to the MSC2 520, so it requests an update location from the HLR 530 in step S525. In this case, the location update request message may include the number of the original MSC (MSC1 in this embodiment) for the user terminal 500 .

Then, the HLR 530 transmits a cancel location request to the MSC1 510 in step S530 using the MSC number. In this case, the message may include a new MSC number (MSC2 in this embodiment) for the user terminal 500 .

Upon receiving this, the MSC1 510 includes the CS security key-related information it has stored while transmitting the PRN message to the MSC2 520 in step S535 to proceed with the call. Thereafter, MSC2 520 and MSC1 510 exchange PRN responses and IAM messages in steps S545 and S550, respectively.

When the MSC2 520 collects all the information related to the user terminal 500 , the MSC2 520 uses the CS security key received from the MSC1 510 , and in step S555 , the user terminal 500 and the location area Complete the LA update process. And MSC2 (520) further proceeds with the remaining CSFB process in step S560.

Meanwhile, from now on, a method of delivering CS security information (a CS security key generated by the MME or a parameter used to generate a security key, for example, downlink NAS count) to the terminal when CSFB occurs will be described in more detail.

The purpose of delivering the downlink NAS count to the terminal is as follows. The user terminal stores the uplink NAS count value, the MME stores the downlink NAS count value, and the counterpart's count value has no choice but to estimate each other. In the case of generating a CS key from an EPS security context in order to shorten the CSFB time, a method is needed to ensure that the UE and the MME generate the same key. If the downlink NAS count is used when generating the CS key, in order to increase the accuracy of the downlink NAS count estimated by the terminal, information that can estimate the entire downlink NAS count value to the terminal or an accurate estimate (e.g., downlink NAS It is necessary to pass some bits of count).

The first method is a method in which the MME delivers CS security information to the base station, and the base station receives it and transmits it back to the terminal. That is, the MME that has received the Extended Service Request for CSFB from the terminal sends CS security information (the generated CS key or the CS to be used when the terminal performs CSFB) in the S1 message (Initial UE context setup or UE context modification request) sent to the base station. Passes parameters to be used when generating a key, including downlink NAS count). The base station transmits the received CS security information in an RRC message sent to the terminal. If CSFB is performed simultaneously with PSHO (Packet Switched Handover), the base station generates the CS security information (the generated CS key or the CS key to be used when the terminal performs CSFB) in the HO command RRC message (MobilityFromEUTRA Command) sent to the terminal. parameters to be used, including downlink NAS count). If CSFB is performed without PSHO, the base station includes the CS security information in an RRC message such as an RRC connection release message or an RRC connection reconfiguration message sent to the terminal. If the CS security information is included in the RRC message received from the base station, the terminal performs the CSFB process using the CS security information received from the base station. If the CS key is included, the terminal uses the received CS key. If all or a part of a parameter for generating a CS key instead of a CS key, for example, a downlink NAS count value is included, the UE generates a CS key using it and performs the CSFB process using it. If only a part of the downlink NAS count is included in the received message, the terminal estimates the entire downlink NAS count value from the received value and then proceeds with the rest of the process.

The second method is that the MME directly informs the UE of CS security information through a NAS message. That is, the MME that has received the Extended Service Request for CSFB from the terminal is a NAS message including CS security information (including a generated CS key or a parameter to be used when generating a CS key to be used when the terminal performs CSFB, downlink NAS count) is generated and transmitted using the S1 message (Initial UE context setup, UE context release, or UE context modification request) sent to the base station. Meanwhile, in order to transmit the NAS message including the CS security information to the terminal, the MME may perform a downlink NAS transport process with the base station before the interworking process with the base station for the general process of CSFB. The base station transmits the received NAS message by including it in the RRC message. If the NAS message is included in the RRC message received by the terminal from the base station, the terminal extracts CS security information from the NAS message, and the terminal performs a CSFB process using the received CS security information. If the CS key is included, the terminal uses the received CS key. If a parameter for CS key generation instead of CS key, for example, all or part of the downlink NAS count value is included, the UE generates a CS key using it, and performs the CSFB process using it. If only a part of the downlink NAS count is included in the received message, the terminal estimates the total downlink NAS count value from the received value and then proceeds with the rest of the process.

On the other hand, since the LTE network cannot support the CS service by itself, it has been mentioned earlier that a technology such as CSFB that uses the CS network of 2G/3G can be used when a specific service is required.

However, CSFB uses an interface called SGs for information exchange between MME and MSC, but it is difficult for some MSCs in the operator network to add SGs interface. In this case, a method that operators having both LTE and 2G/3G networks can use to support specific services that are difficult to provide directly in LTE networks, such as voice, are as follows: the LTE network moves to the CS network for user terminals, such as CSFB. Instead of using a method that helps the user, a method in which the user terminal directly monitors the control signals of the LTE network and the 2G/3G CS network is used.

That is, the user terminal generally transmits data through the LTE network and exchanges control signals with the 2G/3G network at regular intervals to perform an MM (Mobility Management) operation in the CS network. Hereinafter, such a method will be referred to as SGLTE (simultaneous GSM and LTE), and in particular, a method using only one radio (radio module) among these SGLTEs will be referred to as SRDS (Single Radio Dual System).

6 shows an operation of a user terminal when a CS-based service is required for a user terminal in an idle mode when the SRDS is used.

6 is a flowchart illustrating an operation sequence of a user terminal when a CS-based service is required for a user terminal in an idle mode when SRDS is used.

When a CS-based service is required for the user terminal 600, the user terminal 600 does not exchange special control information with the LTE system as in step S605, but switches directly to the 2G/3G network to receive the service. do.

In this situation, the LTE system (ie, the Evolved Packet System, EPS) cannot explicitly know whether the user terminal 600 has switched to the 2G/3G network. That is, as in step S610, the LTE system assumes that the user terminal 600 is still connected to the eNB 610 of the LTE system.

In this case, in step S615 , a downlink packet for the user terminal 600 may arrive at the PGW 640 . Then, the PGW (640) generates the charging information in step S620, and forwards the packet to the SGW (630). Then, the SGW 630 transmits a downlink data notification (Downlink Data Notification) message to the MME (620).

Upon receiving the downlink data notification message, the MME 620 requests paging from the eNBs 610 .

However, since the user terminal 600 has already switched to the 2G/3G network in step S605, the user terminal 600 cannot receive or respond to the paging.

Therefore, the user data packet charged by the PGW (640) cannot be transmitted to the user terminal (600).

When the user terminal switches to the 2G/3G network for the CS-based service in the connected mode, the PGW 640 that receives the downlink packet generates charging information, and then the SGW Through 630, the downlink packet is transferred to the eNB 610 directly. However, since the eNB 610 cannot deliver the downlink packet to the user terminal 600, it is difficult to avoid a situation similar to the above.

The present invention proposes a method to solve the above problems. That is, the user terminal using the SRDS technology can inform the LTE system that it will switch to the 2G/3G network just before switching to the 2G/3G network for the CS-based service. In addition, the LTE system receiving this may give information to the GW to stop charging for the user terminal so that erroneous charging does not occur, or may additionally request that the downlink packet transmission itself be stopped.

The stopped charging for the user terminal and the transmission stop for the additional optional downlink packet, after the user terminal finishes the CS-based service, returns to the LTE system and transmits a TAU request (TAU request) or a service request (Service Request) it can be restarted.

7 is a flowchart illustrating an operation sequence of a user terminal and an LTE system according to an embodiment of the present invention.

For the user terminal 700 that was camping in the E-UTRAN, a case in which a CS-based service is required as in step S705 (ie, an outgoing call is required or a paging for an incoming call is received) may occur. have.

In this case, the user terminal switches to the 2G/3G network for the CS-based service to the LTE system before switching to the 2G/3G network in steps S720 and S725, and in the meantime, the PS data is transferred to the E-UTRAN It can inform you that it cannot be received. This may be delivered to the MME 720 through the eNB 710 using a specific NAS message (eg, EMM status), and this NAS message is a situation, that is, the terminal temporarily switches to a 2G/3G network for a CS-based service. IE or Cause notifying that In the present invention, the NAS message is delivered to the MME through the eNB means that the NAS message generated by the user terminal is delivered to the eNB in the form included in the RRC message, and the receiving eNB puts the NAS message in the S1_AP message to the MME. to be transmitted until

If the user terminal 700 is in the idle mode, as shown in steps S710 and S715, an RRC connection setup process must be performed. If the user terminal 700 is already in a connected mode, the user terminal 700 may directly transmit the NAS message using an RRC message.

Upon receiving the message, the MME 720 can determine that the user terminal 700 switches to the 2G/3G network to receive the CS-based service, and that the PS data packet should not be charged or data transmitted temporarily. .

Based on this, if the MME 720 has a GBR (Guaranteed Bit Rate) bearer for the user terminal 700, the process for deactivating/deleting the GBR bearers is performed in the SGW 730 in steps below S725, Performs with the PGW (740). At this time, in the MME 720 to the SGW 730 in step S730, and the SGW 730 to the PGW 740 in the step S735, in the Delete Bearer Command message, the user terminal 700 is IE or Cause to inform that the switch is temporarily switched to 2G/3G network for CS-based service may be included.

In addition, the MME 720 may perform a Suspend process to suspend non-GBR bearers. To this end, in the MME 720 to the SGW 730 in step S730, and the SGW 730 to the PGW 740 in the step S735, in a Suspend Notification message, the user terminal 700 temporarily CS IE or Cause notifying switching to 2G/3G network for base service may be included.

Through these processes, the PGW 740 deletes the GBR bearer and suspends the non-GBR bearer.

The MME 720 may repeatedly perform this operation for each PDN connection. The MME 720 commands the base station 710 to release the ECM connection to the user terminal 700 in step S760, that is, the S1 terminal context release command (S1), in parallel with the operation with these GWs. UE context release command) may be transmitted.

Then, the base station 710 receiving the command may transmit an RRC connection release message to the user terminal 700 in step S765 .

According to the above-described embodiment of the present invention, the user terminal 700 may then switch to a 2G/3G network to perform a CS-based service.

On the other hand, as another modification of an embodiment of the present invention, the user terminal notifies the MME of switching to the 2G/3G network through the NAS message, but informs the base station through the RRC message (that is, not the NAS message), It is also possible for the base station to transmit it to the MME.

More specifically, the user terminal notifies that it switches to the 2G/3G network for the CS-based service through an RRC message (eg, RRC connection request or RRC connection setup complete), and after receiving the response, 2G/3G You can switch to the network. Then, when the base station receives the information from the user terminal, the base station delivers the information to the MME through an S1 AP message. Subsequent MME and SGW/PGW operations are the same as in the embodiment shown in FIG. 7 .

8 is a flowchart illustrating an operation sequence of a user terminal and an LTE system according to another embodiment of the present invention.

First, as shown in step S805, when a CS-based service is required for the user terminal 800 camping in E-UTRAN (ie, an outgoing call is required or a paging for an incoming call is received) ) may occur.

In this case, the user terminal (800) in step S820, before switching to the 2G/3G network, it immediately switches to the 2G/3G network for the CS-based service to the LTE system, and in the meantime, the PS data is transmitted through the E-UTRAN It can indicate that it cannot be received. As in step S825, it may be delivered to the MME 820 using a specific NAS message (eg, EMM status), and this NAS message is a situation, that is, the user terminal 800 temporarily 2G / for a CS-based service. An IE or Cause indicating switching to the 3G network may be included.

If the user terminal 800 is in the idle mode, it must go through an RRC connection setup process as in steps S810 and S815. If the user terminal 800 is already in a connected mode, the user terminal 800 may directly transmit the NAS message using an RRC message.

Upon receiving the message, the MME 820 may determine that the user terminal 800 switches to the 2G/3G network to receive the CS-based service, and that charging or data transmission of PS data packets should not be temporarily performed. . Accordingly, the MME 820 may transmit a Release Access Bearers Request message to the S-GW 830 in step S830 to stop charging for the user terminal 800 . The message may include an IE or Cause notifying that the user terminal 800 temporarily switches to a 2G/3G network for a CS-based service.

Upon receiving the message, the SGW 830 may transmit a Modify Bearer Request message to the PGWs 840 having a PDN connection with the user terminal 800 in step S835 . The message may include a PDN pause ON flag, and additionally, an IE or Cause notifying that the user terminal 800 temporarily switches to a 2G/3G network for a CS-based service may be included. Then, the PGW 840 transmits a bearer modification response message to the SGW 830 in step S840. Then, the SGW 830 transmits an access bearer release response message to the MME 820 in step S845, and receives a bearer deletion response message from the MME 820 in step S850. Then, the SGW 830 transmits a bearer deletion response message to the PGW 840 in step S855.

On the other hand, the MME 820 commands the base station 810 to release the ECM connection to the user terminal 800 as in step S860, that is, release the S1 terminal context, in parallel with the operation with these GWs. A command (S1 UE context release command) may be transmitted.

Upon receiving this, the base station 810 may transmit an RRC connection release message to the user terminal 800 in step S865. The user terminal 800 may then switch to a 2G/3G network to perform a CS-based service.

On the other hand, as another modification of one embodiment of the present invention, the user terminal 800 through an RRC message (that is, not a NAS message) instead of informing the MME of switching to the 2G/3G network through a NAS message. It is also possible for the base station to transmit it to the MME.

More specifically, the user terminal notifies that it switches to the 2G/3G network for the CS-based service through an RRC message (eg, RRC connection request or RRC connection setup complete), and after receiving the response, 2G/3G You can switch to the network. Then, when the base station receives the information from the user terminal, the base station delivers the information to the MME through an S1 AP message. Thereafter, MME and SGW/PGW operations are the same as in the embodiment shown in FIG. 8 .

On the other hand, if congestion occurs in the RAN (Radio Access Network) (hereinafter, RAN congestion refers to the congestion situation of the RAN or a specific cell controlled by the base station), this is transmitted to the CN (Core Network) for more optimized traffic It may be desirable to treat. If the traffic control according to the congestion situation is to be applied for each user terminal or each bearer or service, the CN must be able to identify which user terminals are located in the RAN where the congestion has occurred.

More specifically, the situation under consideration in the embodiment of the present invention is as follows.

When the RAN node detects that RAN congestion has occurred and reports that congestion has occurred to the RAN Congestion Awareness Function (RCAF), the RCAF collects it and includes the ID of the RAN where the congestion has occurred (eg, cell ID). Congestion information may be delivered to the PCRF. If PCRF intends to apply traffic control or policy control for each user terminal, each user's service, or each bearer, the PCRF needs to identify which user terminals are located in the RAN where congestion occurs. In order to solve the above problem, in an embodiment of the present invention, the PCRF transfers the identifier of the RAN in which the congestion has occurred to the PCEF (a function inside the PGW, which is later used interchangeably with the PGW). Then, the PCEF requests ULI (User Location Information) reporting to the MME along with the identifier of the RAN, and the MME may start ULI reporting of user terminals included in the requested RAN.

The LI reporting may occur immediately after receiving a request or whenever the location of the user terminal is changed.

9 is a diagram illustrating a method of activating ULI reporting for a user terminal existing in a specific RAN according to an embodiment of the present invention.

First, it is assumed that the RAN node (which may be the eNB 900 in the drawing) has identified that RAN congestion has occurred. Then, the eNB 900 may report indication information indicating that congestion has occurred to the RCAF 910 together with an identifier (eg, Cell ID) of the RAN where the congestion has occurred.

Then, the RCAF 910 may collect it and transmit the congestion information to the PCRF 920 together with the identifier (eg, cell ID) of the RAN where the congestion has occurred.

If the PCRF 920 intends to apply traffic control or policy control for each user terminal, each user's service, or each bearer, the PCRF 920 determines which user terminals are located in the RAN where the congestion has occurred. There is a need. To this end, the PCRF 920 may transmit a request message requesting to activate ULI reporting for a user terminal located in a specific RAN to the PCEF 930 .

* The message may include an identifier of the RAN (eg, Cell ID) and time information (eg, a time value) at which the request is valid.

Upon receiving the request, the PCEF 930 may transmit a request message to the S-GWs 940 to activate ULI reporting. The request message may also include an identifier of the RAN and time information (eg, a time value) during which the request is valid.

Upon receiving this, the S-GW 940 may transmit the information to the MMEs 950 . Upon receiving this, the MME 950 identifies the user terminals located in the requested RAN, and starts ULI reporting for them.

If time information is included in the request message, ULI reporting may be applied only during the time period, and may be deactivated after sending ULI reporting the moment a specific user terminal leaves the requested RAN.

According to another embodiment of the present invention, the problem situation is that the PCRF transfers the identifier of the RAN in which congestion has occurred to the PCEF, and after the PCEF obtains a list of user terminals belonging to the RAN, ULI reporting is activated for the user terminal. It may be solved by ULI reporting may occur immediately after receiving a request or whenever the location of the user terminal is changed.

10 is a diagram illustrating a method of activating ULI reporting for a user terminal existing in a specific RAN according to another embodiment of the present invention.

It is assumed that the RAN node (which may be the eNB 1000 in the drawing) has identified that RAN congestion has occurred. Then, the eNB 1000 may report indication information indicating that congestion has occurred to the RCAF 941010 together with an identifier (eg, Cell ID) of the RAN where the congestion has occurred.

Then, the RCAF 1010 may collect it and transmit the congestion information to the PCRF 1020 together with the identifier (eg, cell ID) of the RAN where the congestion has occurred.

If the PCRF 1020 intends to apply traffic control or policy control for each user terminal, each user's service, or each bearer, the PCRF 1020 determines which user terminals are located in the RAN where the congestion is currently occurring. There is a need. To this end, the PCRF 1020 may transmit a request message requesting to activate ULI reporting for a user terminal located in a specific RAN to the PCEF 1030 . The request message may include an identifier of the RAN (eg, Cell ID) and time information (eg, a time value) at which the request is valid.

Upon receiving the request, the PCEF 1030 may transmit a message requesting a list of user terminals belonging to the RAN including the RAN identifier to the S-GWs 1040 . The request message may include a period for reporting a list of terminals and time information (eg, a time value) during which the request is valid.

* Upon receiving the request message, the S-GW 1040 may transmit the information to the MMEs 1050 . Upon receiving this, the MME 1050 may identify user terminals located in the requested RAN, and create a list of their identifiers. In addition, the MME 1050 may include the created list in a message sent to the S-GW 1040 and deliver it to the S-GW 1040 .

The report of the user terminal list may occur every set period when the period is included in the request message transmitted through the S-GW 10440 previously. In addition, if an effective time is included, it may be applied until the effective time expires.

The list of user terminals written and reported by the MME 1050 is finally delivered to the P-GW (PCEF) 1030 through the S-GW 1040 . The PCEF 1030 may know which user terminals are included in the RAN where congestion has occurred based on the information, and based on this, may also activate ULI reporting to dynamically know the location information of the user terminals.

According to another embodiment of the present invention, the problem situation may be solved by another method. More specifically, the PCRF requests a RAN Congestion Information (RCI) report through GTP (GPRS Tunneling Protocol-C/GTP-U) while delivering the identifier of the RAN in which congestion has occurred to the PCEF, and the PCEF is the user terminals belonging to the RAN It can be solved by requesting the RCI reporting to the RAN node.

Activated RCI reporting may occur immediately after receiving a request or whenever the location of the user terminal is changed, and may be terminated when a specific user terminal moves to an uncongested RAN.

11 is a diagram illustrating a method of activating RCI reporting for a user terminal existing in a specific RAN according to another embodiment of the present invention.

The RAN node (which may be the eNB 1100 in the drawing) detects that RAN congestion has occurred, and provides information indicating that congestion has occurred along with the identifier (eg, Cell ID) of the RAN where the congestion has occurred, RCAF 1110 report to

Then, the RCAF 1110 may collect it and transmit the congestion information to the PCRF 1120 together with the identifier (eg, cell ID) of the RAN where the congestion has occurred. If the PCRF 1120 intends to apply traffic control or policy control for each user terminal, each user's service, or each bearer, the PCRF 1120 identifies which user terminals are located in the RAN where the congestion is currently occurring. In addition, more specific congestion information for each user/bearer/service may need to be identified.

To this end, the PCRF 1120 may transmit a request message requesting to activate RCI reporting for a user terminal located in a specific RAN to the PCEF 1130 . The message may include an identifier of the RAN (eg, Cell ID) and time information (eg, a time value) at which the request is valid. The RCI may include an identifier of a user terminal, a RAN identifier, and congestion state information (congestion level, congestion status, etc.).

Upon receiving the request, the PCEF 1130 may transmit a message requesting activation of RCI reporting for user terminals existing in the RAN using a GTP-C message. This request may include the aforementioned validity time information and reporting period.

The request is transmitted from the PCEF 1130 to the S-GW 1140 through a GTP-C message, and then from the SGW 1140 to the MME 1150 again. Then, the MME 1150 may transmit the information by inserting the information into the S1AP message transmitted to the RAN node. In particular, the MME 1150 may transmit a request to start RCI reporting only to the matching RAN using the received RAN identifier.

Upon receiving this, the RAN node may identify user terminals located in the requested RAN and start RCI reporting for them. If time information is included in the request message, RCI reporting may be applied only during the time period, and may be deactivated after the last RCI reporting is transmitted the moment a specific user terminal leaves the requested RAN.

Such RCI uses a user data packet (eg, using a GTP-U header or an IP header) transmitted through the uplink, or separate S1-AP (when the base station delivers it to the MME) and GTP-C ( When the MME forwards the S-GW and the S-GW to the P-GW) may be included in the message.

In the above embodiment, one network node (eg, RAN Congestion Awareness Function, RCAF) requests information for determining whether the user terminals located in the congested cell are other network nodes (eg, MME) and It includes the process of receiving.

In addition, in the above embodiment, when one network node requests and responds to information with another network, messages are transmitted via (via) intermediate nodes (eg, PCRF, PGW, or SGW). heard and explained.

In this case, it should be noted that the main gist of the above embodiments can be applied even when one network node has a direct connection (reference point or interface) with another network node and directly transmits and receives messages without intermediate nodes.

The above-described other embodiment of the present invention, that is, an embodiment in which one network node has a direct connection with another network node and directly transmits and receives a message will be described in detail with reference to the following drawings.

* FIG. 12 is a flowchart illustrating an operation of exchanging messages between two network nodes in order to identify user terminals located in a congested cell (or base station) according to an embodiment of the present invention.

An arbitrary network node (hereinafter, the RCAF 1220 will be described as an example) should identify terminals located in a specific cell (or base station). This may be triggered when it is recognized that congestion has occurred in a specific cell (or base station), or a specific condition (eg, identified in a predetermined time unit) is satisfied.

As shown in FIG. 12 , in step S1210 , the RCAF 1220 may transmit a request message for requesting user terminal information to another network node (hereinafter, the MME 1210 will be described as an example). The message may be a UE information request or an IMSI/APN information request message. The message includes an identifier for identifying a target region, and the region identifier may be a cell identifier (Cell ID) or a base station identifier (eNB ID). In addition, the message may include an identifier for additionally identifying a target operator, for example, a selected PLMN ID. The operator identifier (PLMN ID) may be used to receive information about a user terminal registered with a specific operator if the RAN is shared by a plurality of operators. The message may be a request message using the Diameter protocol, and in this case, an identifier capable of distinguishing the target area may be included as one of Attribute-Value-Pair (AVP).

In addition, the MME 1210 may transmit a response message to the RCAF 1220 in step S1220 . The message includes a list of identifiers of user terminals located in the target area (cell, base station) included in the request message. The identifier for identifying the user terminal may be an IMSI. If the target operator identifier is included in the request message received in the previous step, the MME includes only terminals registered with the target operator (ie, limited to the case where the selected PLMN or registered PLMN among terminals is the same as the requested PLMN) in the list can do it In addition, the user terminal information may include a PLMN identifier to which the user terminal is registered.

In this case, the MME 1210 may perform a location reporting process separate from the base station in order to identify user terminals located in a specific area. The message may be a response message using the Diameter protocol, for example, a UE information response or an IMSI/APN information response message, and the user identifier information may be included as one of AVPs.

The RCAF 1220 can identify which user terminals are located in an area where congestion occurs by using the received information, and, if necessary, delivers RAN congestion information about a certain terminal to other network nodes (eg, PCRF). It can be used when deciding whether to

Meanwhile, when congestion control is applied only to a specific service, exchanging congestion information of user terminals having other services may cause unnecessary signaling. In addition, it may be a factor to increase the processing load of the network nodes. For example, the main cause of congestion in the network is traffic transmitted and received through EPS bearer using QCI (QoS Class Identifier) 9 or 6, and when congestion control is applied to this, other EPS bearers, e.g. For example, there is no need to transmit congestion information to a user terminal having only an EPS bearer using QCI No. 5. That is, the RCAF 1220 determines whether to deliver the congestion information to the PCRF using one or more combinations of user terminal information (APN, QCI, ARP) received from the MME 1210, thereby reducing unnecessary signaling and processing load. .

13 is a flowchart illustrating an operation of exchanging messages between user terminals located in a congested cell (or base station) and two network nodes in order to grasp information on a PDN connection of each terminal.

An arbitrary network node (hereinafter, the RCAF 1320 will be described as an example, and a node that collects congestion information and transmits it to other nodes) must understand information of terminals located in a specific cell (or base station). This may be triggered when it is recognized that congestion has occurred in a specific cell (or base station), or a specific condition (eg, identified in a predetermined time unit) is satisfied.

The RCAF 1320 may transmit a request message for requesting user terminal information to another network node (hereinafter, the MME 1310 will be described as an example) in step S1310. The message may be a UE information request (information request) or an IMSI/APN information request (information request) message. The message includes an identifier for identifying a target region, and the region identifier may be a cell identifier (Cell ID) or a base station identifier (eNB ID). In addition, the message may include an identifier for additionally identifying a target operator, for example, a PLMN ID. The operator identifier (PLMN ID) may be used to receive information about a user terminal registered with a specific operator if the RAN is shared by a plurality of operators. This message may be a request message using the Diameter protocol, and in this case, an identifier capable of distinguishing the target area may be included as one of the AVPs.

In addition, the MME 1310 may transmit a response message to the RCAF 1320 in step S1320 . The message includes an identifier of a user terminal located in a target area (cell, base station) included in the request message and a list of terminal information. The identifier for identifying the user terminal may be an IMSI, and information on the user terminal may be included for each IMSI. If the target operator identifier is included in the request message received in the previous step, the MME includes only terminals registered with the target operator (ie, limited to the case where the selected PLMN or registered PLMN among terminals is the same as the requested PLMN) in the list can do it In addition, the user terminal information may include a PLMN identifier to which the user terminal is registered.

In particular, the user terminal information may be PDN connection or EPS bearer related information, and as the information, APN, QCI of EPS bearer, and ARP of EPS bearer may be used.

If EPS bearer information is used, the target EPS bearer may be a default bearer of a PDN connection, and if the user terminal has two or more PDN connections However, in the case of having two or more EPS bearers, the message may include all information per PDN connection or per EPS bearer.

Meanwhile, the MME 1310 may perform a location reporting process separate from the base station in order to identify user terminals located in a specific area. The message may be a response message using the Diameter protocol, for example, a UE information response or an IMSI/APN information response message. may be included.

The RCAF 1320 can identify which user terminals are located in the congestion area by using the identifier of the user terminal among the received information, and, if necessary, transmits the RAN congestion information about a certain terminal to other network nodes (e.g. , PCRF) can be used to determine whether to deliver.

The RCAF 1320 may select a suitable PCRF for each user by using the APN being used by the user terminal among the received information. The RCAF 1320 may control congestion information delivery by using EPS bearer information (QCI or ARP) being used by the user terminal among the received information. That is, the RCAF 1320 may determine whether or not to transmit the congestion information to another network node (eg, PCRF) using EPS bearer information (QCI or ARP) being used by the user terminal among the received information or the transmission period. .

For example, the RCAF 1320 may transmit congestion information to the PCRF if the QCI of the EPS bearer of the user terminal is a specific value (eg, QCI 9 or QCI 6), otherwise it may not be transmitted.

Alternatively, the RCAF 1320 may also use APN information when determining whether to transmit congestion information to the PCRF. For example, the RCAF 1320 may not transmit congestion information in the case of an APN for a well-known IMS service or VoLTE, or may transmit congestion information in the case of an APN for a general best effort or Internet service. Of course, the RCAF 1320 may determine whether to transmit congestion information to the PCRF by combining APN, QCI, and ARP information.

Meanwhile, the RCAF and the MME exchange messages with each other even though the user terminals located in the congested cell are not changed or the user terminal information is not changed, which may increase unnecessary signaling and processing load.

Therefore, in an embodiment of the present invention to be described below, if the RCAF subscribes the user terminal information report (or notification) to the MME together with the notification condition, the MME will satisfy the notification condition even if the RCAF does not request the user. A method for reducing unnecessary message exchange or RCAF processing load by reporting terminal information to the RCAF is proposed.

14 is a flowchart illustrating a message exchange process for activating a notification to periodically receive user terminal information.

An arbitrary network node (hereinafter, the RCAF 1420 will be described as an example, a node that collects congestion information and transmits it to another node) registers a notification for receiving information of terminals located in a specific cell (or base station) . This may be triggered when it is recognized that congestion has occurred in a specific cell (or base station), or a specific condition (eg, identified in a predetermined time unit) is satisfied.

The RCAF 1420 may transmit a request message for registering user terminal information notification to another network node (hereinafter, the MME 1410 will be described as an example) in step S1410. The message may be a Subscribe Notification Request message. The message includes an identifier for identifying a target region, and the region identifier may be a cell identifier (Cell ID) or a base station identifier (eNB ID). In addition, the message may include an identifier for additionally identifying a target operator, for example, a PLMN ID. The operator identifier (PLMN ID) may be used to receive information about a user terminal registered with a specific operator if the RAN is shared by a plurality of operators.

In addition, the message may include an identifier for identifying a target terminal, and in particular, IMSI may be used.

In addition, the message may include time information indicating a time when a notification request is valid or a time at which the requested notification operation expires.

In addition, the message includes a condition for performing a notification operation, for example, a time period for which a notification occurs when a periodic notification is required, or when the user terminal information located in the target area is changed (eg, when a new user terminal is When entering an area or when the existing user terminal exits to another area) may be included.

The message may be a request message using the Diameter protocol, in which case the information or conditions are encoded in AVP.

Then, the MME 1410 may set a notification in step S1420 and transmit a response message to the RCAF 1430 in step S1430. In this case, the message indicating that the notification has been registered may be a Subscribe Notification Answer message using the Diameter protocol.

Thereafter, the MME 1410 determines whether to perform a notification operation according to the set notification information, and performs a notification process with the RCAF 1420 when a condition is satisfied.

If a notification action expiration condition is included from the RCAF 1420 during the previous notification setting process, the MME 1410 performs notification only until the notification action expiration time comes.

If a notification condition is included in the previous notification setting process, the MME 1410 performs notification only when the notification condition is satisfied.

The message used for notification may include a terminal identifier and a list of terminal information. The identifier for identifying the user terminal may be an IMSI, and information on the user terminal may be included for each IMSI. If the target operator identifier is included in the request message received in the previous step, the MME includes only terminals registered with the target operator (ie, limited to the case where the selected PLMN or registered PLMN among terminals is the same as the requested PLMN) in the list can do it In addition, the user terminal information may include a PLMN identifier to which the user terminal is registered.

At this time, the user terminal and terminal information transmitted by the MME 1410 to the RCAF 1420 includes only those changed since the most recently transmitted information to the RCAF, or information of all terminals located in the target area. may be

If the MME 1410 transmits only updated information to the RCAF 1420, the RCAF 1420 may use the updated information to update, delete, or add some of the information it has stored.

If the MME 1410 transmits information of all user terminals located in the target area to the RCAF 1420, the RCAF 1420 replaces the information stored therein with the received information.

Meanwhile, the message may be a response message using the Diameter protocol, for example, a Push Notification Answer message, and the user identifier information and terminal information may be encoded using AVP and included in the message.

15 is a block diagram illustrating an internal structure of a user terminal according to an embodiment of the present invention. As shown in FIG. 15 , the user terminal of the present invention may include a wireless transceiver 1510 , a storage 1520 , and a controller 1530 .

The wireless transceiver 1510 performs a transmission/reception function of corresponding data for wireless communication of the user terminal. The wireless transceiver 1510 may include an RF transmitter for up-converting and amplifying the frequency of a transmitted signal, and an RF receiver for low-noise amplifying a received signal and down-converting the frequency. In addition, the wireless transceiver 1510 may receive data through a wireless channel and output it to the controller 1530 , and transmit the data output from the controller 1530 through a wireless channel.

The storage unit 1520 stores programs and data necessary for the operation of the user terminal.

The controller 1530 controls the signal flow between blocks so that the user terminal can operate according to an embodiment of the present invention. For example, when detecting CSFB triggering, the controller 1530 may check CS security key related information. In addition, the controller 1530 may control to perform a call setup process for the CS domain based on the CS security key related information.

In addition, the controller 1530 may control a series of processes of confirming the CS security key related information transmitted from the core network node of the mobile communication system. Also, the controller 1530 may control the user terminal to generate the CS security key related information from the PS security key related information used in the security procedure for the packet switched domain.

In addition to the above-described embodiment, the controller 1530 may control the user terminal to operate according to another embodiment of the present invention.

16 is a block diagram illustrating an internal structure of a core network node according to an embodiment of the present invention. As shown in FIG. 16 , the core network node of the present invention may include an interface unit 1610 , a storage unit 1620 , and a control unit 1630 . In this case, the core network node may include an MME.

The interface unit 1610 may perform a signal processing function for wired communication of the core network node.

The storage unit 1620 stores programs and data necessary for the operation of the core network node.

The controller 1630 controls the signal flow between blocks so that the core network node can operate according to an embodiment of the present invention. For example, the controller 1630 may generate CS security key related information to be used by the user terminal in a Circuit Switched Fall Back (CSFB) procedure. In addition, the controller 1630 may control to transmit the generated CS security key related information to a control node (eg, MSC/VLR) of a CS domain. In this case, the control unit 1630 may control the user terminal to generate the CS security key-related information in the process of registering it in the packet switched domain, or CSFB is triggered in the user terminal and transmitted from the user terminal. It may be controlled to generate the CS security key related information at the time of receiving the service request message.

Also, the controller 1630 may transmit the CS security key related information to the user terminal. Also, when receiving the changed CS security key related information from the control node of the CS domain, the controller 1630 may control to transmit the received changed CS security key related information to the user terminal.

In the above-described embodiments, all steps may be selectively performed or omitted. Also, the steps in each embodiment do not necessarily occur in order and may be reversed.

On the other hand, the embodiments of the present invention disclosed in the present specification and drawings are merely presented as specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. That is, it is apparent to those of ordinary skill in the art to which the present invention pertains that other modified examples can be implemented based on the technical spirit of the present invention.

Claims (16)

A method performed by a first network entity associated with mobility management in a communication system, the method comprising:
Receiving a first message requesting subscription to event notification from a second network entity, wherein the first message includes identification information for a target device and information on event report;
sending a second message to the second network entity in response to the first message, the second message indicating that the subscription to the event notification is approved;
confirming that an event corresponding to the identification information and the event report information has occurred; and
sending a third message for the event notification to the second network entity based on the confirmation;
The information on the event report includes information on the target area,
When the target device moves to or out of the target area, the event occurs. According to claim 1,
The information on the event report comprises information on a period for the event notification. According to claim 1,
The method of claim 1, wherein the information on the target area includes at least one cell identifier or at least one base station identifier. According to claim 1,
The information on the event report includes information related to a timer,
The method of claim 1, wherein the sending of the event notification is performed until the timer expires based on the information related to the timer. A method performed by a second network entity in a communication system, comprising:
Receiving a first message for requesting a subscription for event notification from a first network entity related to mobility management, the first message including identification information for a target device and information on event reporting;
receiving a second message from the first network entity in response to the first message, the second message indicating that the subscription to the event notification is approved;
When an event corresponding to the identification information and the information on the event report occurs, receiving a third message for the event notification from the first network entity,
The information on the event report includes information on the target area,
When the target device moves to or out of the target area, the event occurs.
6. The method of claim 5,
The information on the event report comprises information on a period for the event notification. 6. The method of claim 5,
The method of claim 1, wherein the information on the target area includes at least one cell identifier or at least one base station identifier. 6. The method of claim 5,
The information on the event report includes information related to a timer,
The method of claim 1, wherein the sending of the event notification is performed until the timer expires based on the information related to the timer. A first network entity related to mobility management, comprising:
transceiver; and
connected to the transceiver,
Receives a first message requesting subscription for event notification from a second network entity, wherein the first message includes identification information for a target device and information on event report,
send a second message to the second network entity in response to the first message, the second message indicating that the subscription to the event notification is approved;
Confirming that an event corresponding to the identification information and the information on the event report has occurred,
A control unit for transmitting a third message for the event notification to the second network entity based on the confirmation,
The information on the event report includes information on the target area,
The first network entity, characterized in that the event occurs when the target device moves to or out of the target area. 10. The method of claim 9,
The first network entity, characterized in that the information on the event report includes information on a period for the event notification. 10. The method of claim 9,
The first network entity, characterized in that the information on the target area includes at least one cell identifier or at least one base station identifier. 10. The method of claim 9,
The information on the event report includes information related to a timer,
The first network entity of claim 1, wherein the sending of the event notification is performed until the timer expires based on the information related to the timer. A second network entity in a communication system, comprising:
transceiver; and
connected to the transceiver,
Receives a first message requesting a subscription for event notification to a first network entity related to mobility management, wherein the first message includes identification information for a target device and information on event reporting,
receive a second message from the first network entity in response to the first message, the second message indicating that the subscription to the event notification is approved;
When an event corresponding to the identification information and the information on the event report occurs, a control unit for receiving a third message for the event notification from the first network entity,
The information on the event report includes information on the target area,
The second network entity, characterized in that the event occurs when the target device moves to or out of the target area. 14. The method of claim 13,
The second network entity, characterized in that the information on the event report includes information on a period for the event notification. 14. The method of claim 13,
The second network entity, characterized in that the information on the target area includes at least one cell identifier or at least one base station identifier. 14. The method of claim 13,
The information on the event report includes information related to a timer,
The second network entity of claim 1, wherein the sending of the event notification is performed until the timer expires based on the information related to the timer.

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