KR20150069446A - Method and apparatus for call setup and mobile telecommunication system for the same - Google Patents

Abstract

The present invention relates to a method and apparatus for performing paging with another MME when a user equipment (UE) moves to an area covered by another MME (Mobility Management Entity) in an EPC (Evolved Packet Core) network. The call setup apparatus of the present invention is characterized in that after the radio resources used between the user equipment and the MME (Mobility Management Entity) managing the user terminal are released, the reception data for the user terminal is transmitted to the Serving GateWay If it is determined that the MME has changed, the MME transmits a message indicating that the received data for the user terminal exists in the S-GW in the changed MME.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a call setup method and apparatus, and a mobile communication system therefor.

The present invention relates to a mobile communication system, and more particularly, to a method of performing paging with another MME when a user equipment (UE) moves to an area covered by another MME (Mobility Management Entity) in an EPC (Evolved Packet Core) And apparatus.

Recently, due to the rapid development of communication, computer network and semiconductor technology, not only various services using wireless communication networks have been provided, but the demand of users has been increasing day by day, and the global wireless Internet service market has been exploding Trend. Accordingly, a service provided by a mobile communication system using a wireless communication network is being developed not only as a voice service, but also as a multimedia communication service for transmitting various data.

Recently, with the increase of smart phones and the demand for data traffic, mobile operators are investing equipment and technology considering the system part and the influence to accommodate the increased data traffic in various ways.

Wireless data services of CDMA (Code Division Multiple Access) 2000, EV-DO (Evolution Data Only), WCDMA (Wideband CDMA), and WLAN (Wireless Local Area Network) have been commercialized. Recently, There has been a proposal for providing a mobile communication service by installing an ultra-small base station indoors or outdoors to access a mobile communication core network through an indoor broadband network. In particular, in a next generation network system, a method of arranging a plurality of small-sized multi-cells (femtocells) as an alternative to satisfy a demand for a high data rate and stably providing various services is suggested. An ultra-small base station that manages such a femtocell is called an indoor base station or a femto base station. By reducing the size of the cell, the efficiency of a next generation network system using a high frequency band can be increased. In addition, the use of a plurality of small-sized cells is advantageous in terms of increasing the frequency reuse frequency. In addition, it is possible to improve the problem of deterioration of the channel condition due to the radio wave attenuation which occurred when one base station covers the entire cell area and the problem of inability to service the users in the shadow area, This has the advantage. Based on these advantages, a method of combining a macro cell (a cell area managed by an outdoor base station) and a femtocell (a cell area managed by an ultra-small base station such as an indoor base station or a femto base station) Is emerging.

Long Term Evolution (LTE) is a network for realizing requirements of high data rate, low-latency, and packet optimized radio access for an access network , And is designed to accommodate high-speed rich media while ensuring backward compatibility with existing 3GPP / non-3GPP access networks. LTE is an All-IP-based network that excludes existing circuit-switched based communications and enhances quality of service (OoS) management functions to provide real-time services (eg, voice communications, video communications) By providing differentiated QoS for real-time services (eg, web browsing, Store and Forward data transfer), we have increased the efficiency of network resources. In addition, by introducing smart antenna technology (ie, MIMO), the bandwidth for wireless communications has been extended.

In the Evolved Packet Core (EPC) network, which is an LTE core network, eNodeB <-> MME (Mobility Management Entity), MME <-> S-GW (Serving Gateway), and S-GW < Data Network Gateway) to perform call processing for voice and data processing.

In the EPC network, a control message such as call setup and release is recognized as an IP packet and transmitted to the P-GW or received from the P-GW and transmitted to the user equipment (UE). If there is no data to be transmitted to the user terminal, the mobile terminal releases the occupied resources for the efficiency of the radio resource. When the radio resources are released, if the incoming data occurs, the released radio resources are reassigned so that the received data can be processed. When there is data received from the S-GW / P-GW, the MME carries out a procedure called paging, and there is data received at the user terminal via the eNodeB, so that a series of processes for reconnecting via the existing radio resource information . However, if the user terminal moves to an adjacent eNodeB that is not managed by the same MME before receiving the paging, the received packet is discarded. Due to such a problem, the quality of the incoming call is degraded and the incoming call can not be received from the subscriber.

Korean Patent Publication No. 10-2013-0083505 (published on July 23, 2013)

The present invention provides a method and apparatus for performing paging to another MME when a user equipment (UE) moves to an area covered by another MME (Mobility Management Entity) in an EPC (Evolved Packet Core) network.

A method of establishing a call according to the present invention comprises the steps of: a) after a radio resource used between a user equipment and an MME (Mobility Management Entity) associated with the user terminal is released, Serving GateWay, if the MME has been changed; And b) transmitting a message indicating that the received data for the user terminal is present in the S-GW to the changed MME if the MME controlling the user terminal is changed.

Further, the call setup apparatus of the present invention is characterized in that after the radio resources used between the user equipment and the MME (Mobility Management Entity) that manages the user terminal are released, the reception data for the user terminal is transmitted to the S- A gateway for determining whether or not the Mobility Management Entity (MME) of the user terminal is changed; And a call processing unit for transmitting a message that the received data for the user terminal is present in the S-GW to the changed MME when the MME managing the user terminal is changed.

Also, the mobile communication system of the present invention is characterized in that after the radio resources used between the user equipment and the MME (Mobility Management Entity) that manages the user terminal are released, the reception data for the user terminal is transmitted to the S- GateWay), it is determined whether or not the MME of the user terminal is changed. If the MME is changed, the received data for the user terminal is changed to the changed MME in the S-GW And a call setup device that sends a message to the user.

According to the present invention, when a user terminal moves to an adjacent eNodeB that the same MME does not control before receiving paging, it is possible to prevent a received packet from being discarded. Thus, the quality of the incoming call can be improved, and the possibility that the subscriber does not receive the incoming call can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a configuration of a mobile communication network according to an embodiment of the present invention; Fig.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]
3 is a diagram illustrating a call processing procedure for packet and voice service support in an EPC network according to an embodiment of the present invention.
4 is a diagram illustrating an example of a call processing procedure for releasing a wireless zone and receiving data according to an embodiment of the present invention.
5 is a diagram illustrating an example of a configuration of a call setup apparatus according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a call processing procedure for preventing packet discarding according to an embodiment of the present invention; FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions will not be described in detail if they obscure the subject matter of the present invention.

1 is a diagram illustrating a configuration of a mobile communication network according to an embodiment of the present invention.

In one embodiment, the mobile communication network includes a wireless network such as a Global System for Mobile communication (GSM), a 2G wireless communication network such as CDMA, an LTE network, a wireless Internet such as WiFi, a Wireless Broadband Internet (WiBro), and a World Interoperability for Microwave Access (For example, 3G mobile communication network such as WCDMA or CDMA2000, High Speed Downlink Packet Access (HSDPA) or 3.5G mobile communication network such as High Speed Uplink Packet Access (HSUPA), or the like) A 4G mobile communication network currently in service, and any other mobile communication network including a macro base station (macro eNodeB), a micro base station (Pico eNodeB, Home eNodeB), and a user terminal (UE: User Equipment) However, the present invention is not limited thereto. Hereinafter, an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) as a radio access network of LTE will be mainly described.

As shown in FIG. 1, the mobile communication network may include one or more network cells, and may include a Heterogeneous Network (HET) environment in which different kinds of network cells may be mixed in a mobile communication network. The mobile communication network includes miniature base stations (Pico eNodeB, Home-eNodeB, relay, etc.) 11 to 15, 21 to 23, and the like, which manage small-sized network cells (e.g., 'small cells' such as picocells, femtocells, (Macro eNodeBs) 10, 20 and 30 for managing a wide range of cells (e.g., 'macro cells'), a user equipment (UE) 40, A SON (Self Organizing / Optimizing Networks) server 50, an MME (Mobility Management Entity) 60, an S-GW (Serving Gateway) 80, a P-GW (Packet Data Network) And a Home Subscriber Server (HSS) 100. The number of each component shown in FIG. 1 is illustrative, and the number of each component of the mobile communication network in which the present invention can be implemented is not limited to the number shown in the drawings.

For example, the macro base stations 10, 20 and 30 can be used in an LTE network, a WiFi network, a WiBro network, a WiMax network, a WCDMA network, a CDMA network, a UMTS network, But is not limited to, the characteristics of the macro cell base station that manages the base station.

The micro base stations 11 to 15 and 21 to 23 and 31 to 33 may be used in an LTE network, a WiFi network, a WiBro network, a WiMax network, a WCDMA network, a CDMA network, a UMTS network, but is not limited to, the features of a pico base station, an indoor base station or a femto base station, or a relay that manages a cell having a radius of about m to several tens of meters.

The micro base stations 11 to 15, 21 to 23, and 31 to 33 and the macro base stations 10, 20, and 30 can independently have connectivity with the core network.

The user terminal 40 may be a mobile Internet network such as a GSM network, a 2G wireless communication network such as a CDMA network, a wireless Internet network such as an LTE network and a WiFi network, a WiBro network, and a WiMax network, But are not limited to, the characteristics of the terminal.

The management server (O & M server) 70, which is a network management apparatus of the micro-base station, is responsible for configuration information and management of the micro base stations 11 to 15, 21 to 23, and 31 to 33 and the macro base stations 10, . The management server 70 can perform all the functions of the SON server 50, the MME 60, and the HSS 100. [ SON server 50 may include any server that performs macro / micro base station installation and optimization and functions to provide basic parameters or data necessary for each base station. The MME 60 may include any entity used to manage the mobility of the user terminal 40 and the like. In addition, the MME 60 performs a function of a base station controller (BSC) and performs resource allocation, call control, handover control, voice and packet processing, and the like on the base stations (pico eNodeB, home eNodeB, macro eNodeB, Control and so on. The HSS 100 is a kind of database for service / authentication of the subscriber.

In one embodiment, one management server 70 can perform all the functions of the SON server 50, the MME 60 and the HSS 100, but the SON server 70 50, MME 60 and HSS 100 may directly manage one or more macro base stations 10, 20, 30 and one or more micro base stations 11 to 15, 21 to 23, 31 to 33.

Although it is assumed that a macro cell, a pico cell, and a femtocell are mixed in the mobile communication network, the network cell may be composed of a macro cell, a pico cell, and a macro cell.

When the mobile communication network is assumed to be an LTE network, the LTE network is interworked with an inter-RAT network (WiFi network, WiBro network, WiMax network, WCDMA network, CDMA network, UMTS network, GSM network, etc.). (LTE network, WiFi network, WiMax network, WCDMA network, CDMA network, UMTS network, GSM network, etc.) when one of the inter-RAT networks (e.g., WiBro network) is the mobile communication network. (WiFi network, WiMax network, WCDMA network, CDMA network, UMTS network, GSM network, etc.) are shown apart from one another in the drawing, it is assumed that it is overlaid.

When the micro base stations 11 to 15, 21 to 23 and 31 to 33 and / or the macro base stations 10, 20 and 30 are collectively referred to as a 'base station device', the base station device (eNB 25 in FIG. The E-UTRAN having a flat structure based on IP processes data traffic between the user terminal 40 and the core network. The signal control between them is performed by the MME 60. The MME 60 takes charge of signal control between the base station device 25 and the S-GW 80 and determines where to route incoming data from the user terminal 40. [ The S-GW 80 is responsible for an anchor function between the base station device 25 and the base station device 25 for movement of a user terminal between the 3GPP network and the E-UTRAN, Connect to the network. The MME 60 / S-GW 80, which is a core network equipment, manages a plurality of base station devices 25, and each base station device 25 is composed of a plurality of cells. The S1 interface is used between the base station apparatus 25 and the MME 60 / S-GW 80 and the X2 interface is used for handover and SON functions between the base station apparatus 25 and the MME 60 /

The setup of the network interface is accomplished by setting up the S1 interface connecting with the MME 60 at the center of the system and the X2 interface, which is a network line for direct communication with the base station device 25 of other cells present on the current system. The S1 interface exchanges operation and management (OAM) information to support the movement of the user terminal 40 by exchanging signals with the MME 60. [ In addition, the X2 interface exchanges signals for fast handover, load indicator information, and information for self-optimization among the base station apparatuses 25.

Referring to FIG. 2, a configuration of an EPC (Evolved Packet Core) network to which the present invention can be applied will be described. A call processing process for supporting packet and voice services in an EPC network will be described with reference to FIG.

2 is a diagram illustrating an exemplary configuration of an EPC network according to an embodiment of the present invention.

The E-UTRAN is an LTE radio access network composed of a base station apparatus (eNB) 25, is IP-based, and is located between the UE 40 and a wireless communication core network to transmit data and control information. In addition, when a terminal using the LTE system moves to an existing 2G / 3G mobile communication network using a voice service, a paging request for a circuit switch (Fallback) to receive voice service, an SMS message to the UE 40 ) And a direct connection to a target cell capable of a CS service.

2, "LTE-Uu" denotes an air interface between the E-UTRAN (base station apparatus 25) and the UE 40, S5 / S8 "is an interface between the S-GW 80 and the E-UTRAN (base station device 25) and the S- GW 90. [0033] FIG. And "SGi" is an interface between the P-GW 90 and the IP network.

The UE 40 and the eNB 25 of the E-UTRAN communicate via a radio resource control (RRC) protocol and a broadcasting message to the cell area controlled by the eNB 25 RRC message. The RRC message may include control messages from the Non-Access Stratum (NAS) protocol, which are transparently transmitted to the UE 40 or the core network without being read in the E-UTRAN.

The eNB 25 is an end point for the radio signal of the E-UTRAN and the control signal is interlocked with the MME 60 via the S1-MME interface and the data traffic is interworked with the S-GW 80 via the S1- do. The S-GW 80 performs a buffering function for anchor and downlink traffic for mobility in the E-UTRAN. The P-GW 90 is an external IP network connection point, and performs IP allocation and billing for a mobile subscriber and traffic control functions for user data.

The IP network provides an IMS (IP Multimedia Subsystem) service for the UE 40 in the EPC network, and includes Policy & Charging Rule Function (PCRF), IMS nodes (for example, Proxy Call Session Control Function (P-CSCF) (Interrogating Call Session Control Function (CSCF), Serving Call Session Control Function (S-CSCF), Application Function (AF)), and the like.

UE 40 sends and receives a call control message for multimedia services using IMS nodes and the Gm interface through an EPC bearer (provided by E-UTRAN / S-GW / P-GW).

The E-UTRAN 25 provides a radio communication function to the UE 40 and performs a function of managing radio resources for the radio communication function.

The MME 60 may receive authentication information for authenticating the UE 40 from the HSS 100 and perform authentication of the UE 40. [ In addition, the MME 60 manages the mobility of the UE 40 and the base station apparatus 25 in the upper layer of the base station apparatus 25, and can perform a call control function such as bearer setup / release. In addition, the MME 60 can be directly connected to the IP network through the S-GW 80 and the P-GW 90. The call processing control signal of the base station apparatus 25 is transmitted to the S-GW 80 via the MME 60 and is transmitted to the P-GW 90 in response to the call processing control signal, Lt; / RTI &gt;

The S-GW 80 acts as a gateway between the 3GPP network and the E-UTRAN 25 and performs handover between the base station apparatus and the base station apparatus (inter-eNodeB) and between the 3GPP network and the 3GPP network (inter-3GPP) 40 to provide a mobility anchor function. The S-GW 80 can transmit to the P-GW 90 a job necessary for call processing in accordance with the control signal of the base station device 25. [

The P-GW 90 may allocate an IP address to the UE 40 and apply different QoS policies to the UE 40. [ In addition, the P-GW 90 acts as a gateway to a PDN (Packet Data Network), allowing the UE 40 to access a data network such as the Internet or the Internet to receive services.

The S-GW 80 and the P-GW 90 are separated and communicate with each other via the S5 / S8 interface. However, the S-GW 80 and the P-GW 90 may be implemented as a single gateway .

The HSS 100 may manage authentication information for authenticating the UE 40, location information of the UE 40, and the profile of the UE 40. [ The profile of the UE 40 may include QoS rating information (e.g., priority, maximum available bandwidth, etc.) for each service item to which each UE 40 subscribes. In one embodiment, the authentication information for authenticating the UE 40 and the profile of the UE 40 may be transferred from the HSS 100 to the MME 60 when the UE 40 connects to the network.

The PCRF (not shown) manages policies and rules for charging and allows the P-GW 90 and the S-GW 80 to provide appropriate QoS to the UE 40 and use Allows you to perform the billing function for the bearer.

The IMS node (not shown) is made up of nodes such as P-CSCF, I-CSCF, S-CSCF, AF and the like and the UE 40 provides multimedia services such as Voice over IP (VoIP) give.

3 is a diagram illustrating call processing procedures for packet and voice service support in an EPC network according to an embodiment of the present invention.

When the UE 40 requests the MME 60 to perform call processing through the E-UTRAN, the MME 60 receives the subscriber information for the UE 40 from the HSS 100. The bearer for packet transmission is established by the S-PW 80 / P-GW 90 by constructing various information necessary for the call processing, and the UE 40 responds.

Specifically, in order to receive the packet service and the voice service, the UE 40 first transmits a call setup request message to the radio section (S301).

The eNB 25 of the E-UTRAN forwards the call processing request message received from the UE 40 to the MME 60 (S302), and the MME 60 transmits the call processing request message The HSS 100 requests information for preparation of call setup with the UE 40 and receives information for preparation of call setup from the HSS 100 in step S303. The MME 60 selects one of the plurality of S-GWs 80 / P-GWs 90 using the information received from the HSS 100 and requests a bearer setup. When the bearer setup is completed (S304), a packet service and a voice service for the UE 40 are possible. At this time, upon completion of the bearer setup with the S-GW 80 / P-GW 90, the MME 60 transmits a completion message (attach complete) for the attach request of the UE 40 to the user And informs that the resource allocation for the network has been granted and assigned in the network.

4 is a diagram illustrating an example of a call processing procedure for releasing a wireless zone and receiving data according to an embodiment of the present invention.

When the bearer setting is completed (S401) and the predetermined time has elapsed, the MME 60 releases the radio resources occupied by the UE 40 (S402). The MME 60 transmits a paging message to the UE 40 in order to receive the data (step S403). If the UE 40 receives the paging message from the UE 40, S404), the radio section can be established again for the released radio resource (S405). In step S406, a channel for transmitting data to the UE 40 may be formed using the released radio resources through the above-described procedure.

The configuration of the call setup apparatus according to the present invention may include a control unit 501, a call processing unit 502, and a communication unit 503 with reference to FIG. In one embodiment, the call setup apparatus 500 of the present invention may be included in the S-GW 80, but may be provided separately from the S-GW 80.

The control unit 501 determines whether the corresponding UE 40 is connected to the MME 60 when the IP address of the MME 60 is changed with respect to the UE 40 having the released radio resource. And controls the call processing unit 502 to retransmit the Downlink Data Notification message.

When it is determined that the UE 40 has moved to the changed MME 60 with respect to the UE 40 having radio resources released through the communication unit 503 through the communication unit 503, The UE 40 can retransmit the Downlink Data Notification message that has been previously transmitted to the previous MME (not shown) to the new MME 60 that the UE 40 has moved. Further, when the call processing unit 502 retransmits the Downlink Data Notification message, the call processing unit 502 can notify that the present message is a message that has already been transmitted to the previous MME (not shown) by using a specific field called Private Extension IE.

The communication unit 503 can receive the Modify Bearer Req message twice from the MME 60 and transmit the Downlink Data Notification message to the MME 60. [ The Modify Bearer Req message received from the MME 60 can be used to notify that the MME 60 has been changed and the UE 40 can receive the Modify Bearer Req message from the eNodeB 25 (Tunnel Endpoint IDentifier), which is information on a port number to receive a tunnel endpoint identifier (TEID).

6 is a diagram illustrating call processing procedures for preventing packet discarding according to an embodiment of the present invention.

As shown in FIG. 6, when the bearer setting is completed and a predetermined time has elapsed, the eNodeB 25b releases the radio resources occupied by the UE 40 (S601). If there is received data for the UE 40 having the released radio resource (S602), a Downlink Data Notification message may be transmitted to the MME 60b managing the corresponding UE 40 to inform it (S603). The MME 60b receiving the Downlink Data Notification message can confirm the Downlink Data Notification Ack message by sending a Downlink Data Notification Ack message to the call setup device 500 in operation S604 and transmit the paging message to the eNodeB 25b in operation S605. The eNodeB 25b receiving the paging message from the MME 60b may broadcast a paging message to the network (S606). On the other hand, when the UE 40 that has not received the page message broadcasted to the network moves to the eNodeB 25a managed by the other MME 60a, it transmits a TAU (Tracking Area Update) Request message to inform it ), the eNodeB 25a may transmit the TAU Request message to the MME 60a which is in charge of the eNodeB 25a (S608). In one embodiment, the TAU Request message may set up a radio resource that was released during the TAU so that the TAU Request message can perform call processing using the released radio resource including the Active Flag. The MME 60a having received the TAU Request message may transmit the MME 60a including the MME IP address of the UE 40 moved to the call setup apparatus 500 to the Modify Bearer Req message in step S609. The call setup apparatus 500 having received the Modify Bearer Req message can reply by sending a Modify Bearer Rsp message to the MME 60a (S610). The MME 60a having received the Modify Bearer RSP message can transmit a TAU Accept message including an Initial Context Setup Req message for setting the released radio resource to the eNodeB 25a at step S611, The MME 60a may transmit the TAU Accept message to the MME 60a in step S612 and may transmit the Initial Context Setup Rsp message in response to the Initial Context Setup Req message in step S614. The MME 60a having received the Initial Context Setup Rsp message transmits a Modify Bearer Req message including a TEIN (Tunnel Endpoint Identifier), which is information on a port number from which the UE 40 receives a signal from the eNodeB 25a To the call setup apparatus 500 (S615). The call setup apparatus 500 receiving the Modify Bearer Req message can respond to the Modify Bearer Rsp message with the MME 60a (S616).

Although the method has been described through particular embodiments, the method may also be implemented as computer readable code on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission over the Internet) . In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the above embodiments can be easily deduced by programmers of the present invention.

Although the present invention has been described in connection with some embodiments thereof, it should be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention as understood by those skilled in the art. something to do. It is also contemplated that such variations and modifications are within the scope of the claims appended hereto.

11 to 15, 21 to 23, and 31 to 33: micro base stations 10, 20, and 30:
40: User terminal 50: SON server
60: MME 80: S-GW
90: P-GW 100: HSS
500: call setting device 501:
502: call processing unit 503:

Claims (9)

As a call setup method,
a) when the received data for the user terminal exists in the Serving GateWay (S-GW) after the release of the radio resources used between the user equipment and the MME (Mobility Management Entity) Determining whether the MME that is in charge of the UE has been changed; And
b) transmitting a message indicating that the received data for the user terminal is present in the S-GW to the changed MME if the MME managing the user terminal is changed. The method according to claim 1,
The step a)
And determining whether the MME for which the user terminal is controlled has been changed using the IP address information of the MME. The method according to claim 1,
The step b)
Using the Private Extension IE field to notify the modified MME that the message has already been sent to the MME. As a call setup device,
After the release of the radio resources used between the user equipment and the MME (Mobility Management Entity) that manages the user terminal, if the received data for the user terminal exists in the S-GW (Serving GateWay) A control unit for determining whether the Mobility Management Entity (MME) under control is changed; And
And a call processing unit for sending a message that the received data for the user terminal is present in the S-GW to the changed MME when the MME managing the user terminal is changed. 5. The method of claim 4,
Wherein,
And determines whether or not the MME for the user terminal is changed using the IP address information of the MME. 5. The method of claim 4,
The call processing unit,
And uses the Private Extension IE field to notify the changed MME that the message is a message already sent to the MME. 5. The method of claim 4,
The call setting device comprises:
And an S-GW that performs an anchor function for the movement of the user terminal. A mobile communication system,
After the release of the radio resources used between the user equipment and the MME (Mobility Management Entity) that manages the user terminal, if the received data for the user terminal exists in the S-GW (Serving GateWay) Determines whether or not the MME has been changed, and transmits a message that the received data for the user terminal is present in the S-GW to the changed MME when the MME managing the user terminal is changed / RTI &gt; 9. The method of claim 8,
Whether or not the Mobility Management Entity (MME)
And the IP address information of the MME transmitted to the call setup device is used.

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