KR20110064407A - Method for providing service in mobile communication system and system thereof - Google Patents

Abstract

PURPOSE: A method for providing a service in a mobile communication system and a system for the same are provided to maintain the service even an error occurred in a specific MME(Mobility Management Entity). CONSTITUTION: Each mobile terminal of an active MME(Mobility Management Entity) transfers IMSI(International Mobile Subscriber Identity) information of a terminal to a backup MME(301,303). The backup MME confirms the failure of the active MME(311). The backup MME transmits the paging request message to the terminal(313). The terminal transfers the connection information to the eNB(evolved-NodeB)(315). The eNB transmits the access request message to the active MME(317).

Description

METHOD FOR PROVIDING SERVICE IN MOBILE COMMUNICATION SYSTEM AND SYSTEM THEREOF}

The present invention relates to a mobile communication system, and more particularly, to a method and system for providing a service using a mobility management entity (MME) in a mobile communication system.

 In general, a mobile communication system is a system developed to perform communication without restriction of location to a user. Such a mobile communication system has been developed from a simple form of providing only a simple voice communication service to providing a high speed data service and a voice service using a packet.

Users using these mobile communication systems want to be provided with higher speed data service, so there is a need for a system that is more advanced than the 2nd and 3rd generation systems, and the development of a long term evolution (LTE) system is now made. ought.

The LTE system provides a bearer service for delivering a service data packet of a user terminal to a service, an MME that is responsible for authentication and registration of the terminal when the terminal accesses a network, and guarantees mobility when moving between base stations, and a user. Serving Gateway (S-GW), a Packet Data Network Gateway (PDN-GW) that assigns an IP address to a terminal connected to the network and provides IP connectivity, and the current location and registration status of the terminal. And a Home Subscriber Server (HSS) that stores and provides information such as: Here, the MME, S-GW, and PDN-GW are referred to as Evolved Packet Core Newwork (EPC).

In this case, when the terminal is in an idle mode, unless a location information (Tracking Area TA) is changed until a periodic location registration time, a special operation is not performed. In this situation, the S-GW and the PDN-GW of the EPC maintain a bearer context of the terminal, and since the bearer is also reserved, the packet can be transmitted from the external network to the terminal.

However, if a service is disabled due to a failure in the MME in which the location of the terminal in the idle mode is registered, the terminal does not recognize that the failure occurs in the MME until the periodic location registration time. At this time, when the S-GW receives a packet to be transmitted to the terminal from the PDN-GW, the terminal knows that the terminal is in an idle state and notifies the MME that the packet to be transmitted to the terminal has arrived. However, since a failure occurs in the MME managing the terminal, the MME does not respond to the S-GW. Here, the S-GW sends a GTP-C echo message for managing the GTP-C (GPRS Tunneling Protocol-Control) path to the MME several times, and recognizes the MME as a failure state if there is no response. When the S-GW recognizes the MME as a failure state, all bearer contexts related to the MME are deleted, and the PDN-GW is notified that the MME is in a failure state so that all bearer contexts related to the MME are deleted from the PDN-GW. do. As a result, bearers of all terminals belonging to the MME in a faulty state are deleted from the network, and downlink packets are not delivered to all terminals registered in the MME. Therefore, all terminals registered in the MME in a faulty state may not be aware of the faulty state of the corresponding MME when periodic location registration occurs or the TA is not changed, thereby causing a service free time for a long time.

Accordingly, there is a need for a method for providing a continuous service to a corresponding terminal even when a failure occurs in the MME in the mobile communication system.

The present invention provides a method for providing a service through an MME in a mobile communication system and a system therefor.

The present invention also provides a method and system for providing a service to a corresponding terminal even when a failure occurs in the MME in the mobile communication system.

A method for providing a service in a mobile communication system including a plurality of mobility management entities (MMEs) according to the present invention includes a method of providing an IMSI of a terminal from at least one active MME of the plurality of MMEs in a backup MME of the plurality of MMEs. International Mobile System Identifier) information, and if the backup MME detects that a failure occurs in the first active MME of the at least one active MME, a paging request message including the backed up IMSI information to the terminal Transmitting and receiving the paging request message from the terminal and accessing an active MME other than the first active MME.

In addition, a mobile communication system including a plurality of mobility management entities (MME) according to the present invention, at least one active MME for managing the International Mobile System Identifier (IMSI) information of the terminal, and the at least one active MME from the Paging request including the backed up IMSI information when the IMSI information of the terminal is backed up, and the operating state of the at least one active MME is detected to detect a failure of a first active MME among the at least one active MME. A backup MME for transmitting a message to the terminal, and the terminal receiving the paging request message and accessing an active MME other than the first active MME.

In addition, the method for providing a service in a mobile communication system including a plurality of mobility management entities (MME) according to the present invention, the EMS (Element Management System) detects that the failure of the first MME of the plurality of MME In the case of transmitting a cell broadcast message transmission request message including an IP address of the second MME, an identifier of the first MME, and failure information, to transmit a cell broadcast message among the plurality of MMEs, to a CBC (Cell Broadcast Center). And generating, by the CBC, a cell broadcast message including the identifier of the first MME and the failure information and transmitting the cell broadcast message to an IP address of the second MME, and receiving the cell broadcast message at the second MME. And broadcasting the received cell broadcast message to terminals through base stations, and receiving the cell broadcast at the terminals. Receiving a loadcast message, comparing the identifier of the first MME included in the received cell broadcast message with an identifier of a pre-stored MME, and accessing an MME except for the first MME when the same is the same;

In addition, the mobile communication system including a plurality of mobility management entities (MME) according to the present invention, when detecting that a failure occurs in the first MME of the plurality of MME, to transmit a cell broadcast message of the plurality of MME An element management system (EMS) for transmitting a cell broadcast message transmission request message including an IP address of a second MME, an identifier of the first MME, and fault information; and the first message included in the cell broadcast message transmission request message; 1 generates a cell broadcast message including an identifier of the MME and the failure information and transmits the cell broadcast message to the IP address of the second MME; and receives the cell broadcast message through the second MME. Compares an identifier of the first MME and an identifier of a pre-stored MME included in the received cell broadcast message to the same value. It includes the terminal to be connected to the MME, except for claim 1 wherein the MME.

According to the present invention, even when a failure occurs in a specific MME, the terminal may be provided with a service. According to the present invention, all the terminals can be restored to the normal service state by using the minimum information. Therefore, the present invention can minimize the cost of backing up information in the mobile communication system and can be driven without changing the operation of the MME interworking system.

In addition, the present invention can check whether a failure occurs in the MME to which the terminal is registered in the mobile communication system can be restored to the normal service state when a failure occurs.

On the other hand various other effects will be disclosed directly or implicitly in the detailed description of the embodiments of the present invention to be described later.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The main aspect of the present invention, in order to provide a continuous service to the terminal even in the event of a failure in the MME in the mobile communication system, IMSI (International Mobile System Identifier) information of the terminal managed by the active MME in the first embodiment The backup MME uses a backup MME for backing up, and a second embodiment uses a cell broadcast message for notifying that a faulty MME is detected.

To this end, in the first and second embodiments of the present invention to be described below, a method and a system for providing a service through an MME in a mobile communication system will be described in detail.

First, the first embodiment of the present invention defines a backup MME among a plurality of MMEs included in an MME pool, and manages the backup MME by receiving IMSI information of the UE from an active MME. The backup MME manages the active MME state by exchanging a bit (that is, heart beat) for managing the state of the active MME with the active MME. If the active MME fails to service due to a failure, the backup MME enables the corresponding terminals to reconnect to the network using the IMSI information of the backed up terminal.

1 briefly illustrates a configuration of a mobile communication system according to a first embodiment of the present invention.

Referring to FIG. 1, a mobile communication system includes an MME pool 110 including a plurality of MMEs 101 to 109, a plurality of enhanced Node Bs (eNBs) 130, an HSS 151, a router 153, and an S. A GW 155 and a terminal 170.

The MME pool 110 includes at least one active MME 101 to 105 and one backup MME 109. Each of the active MMEs 101 to 105 provides a mobility management and session management function of the terminal. When the terminal accesses, the active MME 101 to 105 generates IMSI information of the terminal and generates a default bearer. In particular, each of the active MMEs 101 to 105 according to the first embodiment of the present invention delivers the IMSI information of the terminal managed by the backup MME 109 to the backup MME 109 during normal operation (that is, when no failure occurs). . Each of the active MMEs 101 to 105 exchanges a heart beat with the backup MME 109 to support state management of the active MMEs 101 to 105. Here, the IMSI information of the terminal is minimum information for paging by the terminal.

The backup MME 109 manages IMSI information of the terminal received from each of the active MMEs 101 to 105 for each active MME 101 to 105. The backup MME 109 manages the states of the plurality of active MMEs 101 to 105 through a heart beat to check whether a failure occurs in a specific active MME. When a failure occurs in the specific active MME, the backup MME 109 eNB transmits a paging request message including the IMSI information of the terminal 170 so that reconnection may be performed in the terminal 170 belonging to the failed active MME. Send to 130.

The enhanced Node B (eNB) 130 receives the paging request message from the backup MME 109 and provides the received paging request message to the terminal 170 located in the corresponding area. The eNB 130 distributes the load so that the terminal 170 does not send the access information to the backup MME 109. In addition, when a specific active MME is unable to operate normally due to a failure, the eNB 130 identifies the corresponding active MME as a failure through an element management system (EMS) or a connection management function and does not transmit the connection information to the active MME. .

When the terminal 170 receives the paging request message from the eNB 130, the terminal 170 performs a reconnection procedure by confirming that it is a reconnection request, and supports interworking with an external server for supporting an existing service after reconnection.

The HSS 151 stores and provides information such as a current location and a registration state of the terminal 170, and the router 153 includes a plurality of MMEs 101 to 109 and an eNB 130 included in the MME pool 110. ) Relays data transmission and reception, and the S-GW 155 provides a bearer service for delivering a user's service data packet to the access network.

2 illustrates an operation of providing a service to a terminal even when a failure occurs in a specific MME in the mobile communication system according to the first embodiment of the present invention.

2, when all of the plurality of active MMEs 101 to 105 included in the MME pool 110 are in a normal state, each of the plurality of active MMEs 101 to 105 backs up IMSI information of the UE. To). In addition, the backup MME 190 manages the IMSI information of the terminal received from each of the active MMEs 101 to 105 for each active MME 101 to 105. The backup MME 109 exchanges hear beats with each active MME 101 to 105 for state management of each active MME 101 to 105. In addition, the backup MME 109 may be provided with the status information of each of the active MME (101 to 105) through the EMS. In addition, IMSI information of the terminal managed by each of the active MMEs 101 to 105 may be distributed and backed up to an independent backup MME system or another MME system in operation.

In the normal state, the backup MME 109 manages the active MME 105 as a failure state when it is confirmed that a failure occurs in the active MME 105 through the heart beat exchange with each of the active MMEs 101 to 105.

In the failure state, the backup MME 109 reconnects to the terminal 170 belonging to the active MME 105 by using the IMSI information of the terminal 170 managed for the active MME 105 in the failure state. Delivering what to do That is, the backup MME 109 transmits a paging request message including IMSI information, that is, paging information, to the terminal 170 through the eNB 130. Upon receiving the paging request message, the terminal 170 attempts to access a number of times using the IMSI information included in the paging request message. When the terminal 170 attempts to connect, the eNB 130 receives the access information of the terminal 170 from the terminal 170, and the active MME (except for the backup MME 109 and the active MME 103 in a failed state) ( 101, 102 to distribute the connection request message. In addition, the eNB 130 performs the first paging using the TA list of the UE backed up to prevent the paging overload, and if there is no response, the eNB 130 performs paging to a large area according to the second paging operation criteria of the MME pool 110. do.

Here, since the backup MME 109 that has transmitted the paging request message cannot receive the response message for the paging request message, the backup MME 109 may repeatedly transmit the paging request message to the terminal 170 through the eNB 130. . At this time, in order to prevent the terminal 170 from receiving a repetitive paging request message and attempting to reconnect, the backup MME 109 includes the number of paging requests in the paging request message so that the terminal 170 receives the first paging request message. Make sure you know whether or not. In response to the paging request message, the terminal 170 attempts to reconnect if the received paging request message is the first paging request message. On the other hand, if the received paging request message is not the first paging message, the terminal 170 checks whether there is a previous access attempt history and attempts to access if there is no previous access attempt history, and if there is a previous access attempt history, the reception is performed. Ignored paging request messages

3 illustrates a flow of a mobile communication system for providing a service according to the first embodiment of the present invention.

Referring to FIG. 3, when both of the active MMEs 101 and 105 are in a normal state, each of the active MMEs 101 and 105 delivers IMSI information of the terminal to the backup MME 190 in steps 301 and 303. Here, the backup MME 109 manages IMSI information of the terminal received from each of the active MMEs 101 and 105 for each active MME 101 and 105.

In step 305, the backup MME 109 transmits a heart beat to the active MME 101. In step 307, the backup MME 109 receives a heart beat from the active MME 101 to confirm that the active MME 101 is in a normal state.

However, when the backup MME 109 transmits a heart beat to the active MME 105 in step 309, but does not receive a heart beat from the active MME 105, the MME 105 determines that the active MME 105 is in a failure state in step 311. do. In step 313, the backup MME 109 transmits a paging request message including the IMSI information of the terminal 170 managed by the active MME 105 and the number of paging requests of the terminal 170 through the eNB 130. To send). In step 315, the terminal 170 receives the paging request message, and transmits the access information to the eNB 130 in step 315 when the received paging request message is the first paging request message or there is no previous connection attempt history. In step 317, the eNB 130 receives the access information and transmits an access request message to the active MME 101 in the normal state. When the eNB 130 receives the access response message for the access request message from the active MME 101 in step 319, it notifies the terminal 170 of the access completion in step 321.

Accordingly, in the first embodiment of the present invention, even when a failure occurs in a specific MME, the terminal may be restored to a normal service state using only IMSI information for paging in the terminal, and the minimum information is used to minimize the cost of backup. can do.

Next, according to the second embodiment of the present invention, when the EMS monitors the states of a plurality of MMEs and detects that a failure has occurred in a specific MME, information on the failed MME is transmitted to a CBC (Cell Broadcast Center). The CBC generates a cell broadcast message including information on the MME received from the EMS, and transmits the generated cell broadcast message to all UEs registered in the MME included in the MME pool to which the MME in the fault state belongs. do. Accordingly, the terminal receiving the cell broadcast message may attempt to reconnect.

4 briefly illustrates a configuration of a mobile communication system according to a second embodiment of the present invention.

Referring to FIG. 4, the mobile communication system includes an MME pool 410 including a plurality of MMEs 401 to 405, a plurality of base stations 430, an HSS 451, a router 453, and an S-GW 455. , An EMS 457, a terminal 470, and a CBC 490.

Each of the plurality of MMEs 401 to 405 is an active MME and provides a mobility management and session management function of a subscriber in a mobile communication system. Each MME 401 to 405 generates IMSI information of the terminal and generates a default bearer when the terminal accesses. In particular, a specific MME of all MMEs 401 to 405 according to the second embodiment of the present invention transmits a cell broadcast message to all eNBs 430 in association with the CBC 490.

The EMS 457 monitors the states of the plurality of MMEs 401 to 405 and detects an IP address of a specific MME to which a cell broadcast message is to be transmitted when an MME with a failure state is detected in the MME pool 410. The identifier and failure information are transmitted to the CBC 490 to request transmission of a cell broadcast message. In this case, the specific MME is characterized in that the MME is not a failure of the MME (401 to 405) included in the MME pool 410.

When the CBC 490 is requested to transmit a cell broadcast message from the EMS 457, the CBC 490 generates a cell broadcast message including an MME identifier and failure information of a failure state received from the EMS 457. The cell broadcast message is transmitted to the IP address of the specific MME received from the EMS 457.

Every eNB 430 receives a cell broadcast message from a specific MME, broadcasts the received cell broadcast message in a cell and transmits it to all terminals in a corresponding area.

The terminal 170 receives the cell broadcast message, and confirms that the MME corresponding to the MME identifier is in a failure state through the MME identifier and failure information included in the received cell broadcast message. The terminal 170 compares an MME identifier in a prestored Temporary Mobile Station Identity (S-TMSI) with an MME identifier of the fault state and performs a reconnection procedure. Support.

The HSS 451 stores and provides information such as a current location and a registration state of the terminal 470, and the router 453 includes a plurality of MMEs 401 to 405 and an eNB 430 included in the MME pool 410. Relays data transmission and reception between the S-GW 455 and provides the bearer service for delivering the service data packet of the user to the access network.

5 illustrates an operation of providing a service to a terminal even when a failure occurs in a specific MME in the mobile communication system according to the second embodiment of the present invention.

In FIG. 5, it is assumed that the MME 401 is an MME in a fault state, and the MME 405 is an MME to transmit a cell broadcast message.

Referring to FIG. 5, the EMS 457 monitors the states of a plurality of MMEs 401 to 405 and transmits a cell broadcast message when a failure occurs in the MME 401 in the MME pool 410. IP address, identifier of MME 401 and failure information are transmitted to CBC 490 to request transmission of cell broadcast message. Accordingly, the CBC 490 generates a cell broadcast message including the identifier and failure information of the MME 401 received from the EMS 457, and transmits the generated cell broadcast message to the IP address of the MME 405. To send. The MME 405 transmits a cell broadcast message received from the CBC 490 to all eNBs 430 serviced by the MME pool 410 including the MME 405. All the eNBs 430 transmit the cell broadcast message to terminals in a cell.

Upon receiving the cell broadcast message, the terminal 170 confirms that the MME 401 is in a failure state by using the identifier and failure information of the MME 401 included in the received cell broadcast message, The identifiers of the MME 401 are compared to perform the reconnection procedure if they are the same, and if not, the reconnection procedure is not performed.

Since the CBC 490 transmitting the cell broadcast message cannot receive the response message for the cell broadcast message, the CBC 490 may repeatedly transmit the cell broadcast message to the terminal 470. In this case, in order to prevent the UE 470 from receiving a repeated cell broadcast message and attempting to reconnect a number of times, the CBC 490 includes the number of message transmissions in the cell broadcast message so that the UE 470 first. It can recognize whether it is the first cell broadcast message or not. Therefore, the terminal 470 receives the cell broadcast message, and attempts to access the cell broadcast message if it is the first cell broadcast message.

6 illustrates a flow of a mobile communication system for providing a service according to a second embodiment of the present invention.

Referring to FIG. 6, in step 601, the EMS 457 monitors the states of the plurality of MMEs 401 to 405, and when a failure state of the MME 401 in the MME pool 410 is detected, cell broadcast in step 603. The IP address of the MME 405 to transmit the message, the identifier of the MME 401 and the failure information are transmitted to the CBC 490 to request transmission of the cell broadcast message.

In step 605, the CBC 490 generates a cell broadcast message including an identifier and failure information of the MME 401 received from the EMS 457, and transmits the generated cell broadcast message to the MME in step 607. 405 is transmitted to the IP address.

In step 609, the third MME 405 transmits a cell broadcast message received from the CBC 490 to all eNBs 430 serviced by the MME pool 410 including the MME 405. In step 611, the eNB 430 transmits the cell broadcast message to the terminal 470 in a cell.

Upon receiving the cell broadcast message, the terminal 170 confirms that the MME 401 is in a fault state by using the identifier and fault information of the MME 401 included in the received cell broadcast message in step 613, and stores the fault in advance. The MME identifier is compared with the identifier of the MME 401, and if the same, the access information is transmitted to the eNB 430. In step 615, the eNB 430 receives the access information and transmits an access request message to the MME 405. In step 617, when the eNB 430 receives the access response message for the access request message from the MME 405, the eNB 430 notifies the terminal 170 of the access completion.

Therefore, according to the second embodiment of the present invention, if a failure occurs in the MME in which the UE is registered, the UE may return to the normal service state.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the appended claims, but also by the equivalents of the claims.

1 is a diagram schematically showing a configuration of a mobile communication system according to a first embodiment of the present invention;

2 is a diagram illustrating an operation of providing a service to a terminal even when a failure occurs in a specific MME in a mobile communication system according to the first embodiment of the present invention;

3 is a diagram illustrating a flow of a mobile communication system for providing a service according to a first embodiment of the present invention;

4 is a diagram briefly showing a configuration of a mobile communication system according to a second embodiment of the present invention;

5 is a diagram illustrating an operation of providing a service to a terminal even when a failure occurs in a specific MME in a mobile communication system according to a second embodiment of the present invention;

6 is a diagram illustrating a flow of a mobile communication system for providing a service according to a second embodiment of the present invention.

Claims (18)

In the method for providing a service in a mobile communication system comprising a plurality of mobility management entities (MME), Backing up International Mobile System Identifier (IMSI) information of a terminal from at least one active MME of the plurality of MMEs in a backup MME of the plurality of MMEs; Transmitting a paging request message including the backed up IMSI information to the terminal when the backup MME detects that a failure occurs in a first active MME among the at least one active MME; Receiving the paging request message from the terminal and accessing an active MME other than the first active MME. The method of claim 1, wherein the connecting process comprises: Requesting access from the terminal to the base station; Transmitting, at the base station, a connection request message to at least one active MME except for the first active MME, and receiving a connection response message; And providing a connection completion from the base station to the terminal. The method of claim 1 or 2, wherein the paging request message, And providing a paging request count. The method of claim 3, wherein The terminal checks the number of paging requests included in the paging request message, and accesses the active MME except for the first active MME only when the paging request message is the first paging request message. The method of claim 1, The service providing method characterized in that the backup MME manages the backup IMSI information for each active MME. In a mobile communication system comprising a plurality of mobility management entities (MME), At least one active MME for managing International Mobile System Identifier (IMSI) information of the terminal; When the IMSI information of the terminal is backed up from the at least one active MME, the operation state of the at least one active MME is managed to detect that a failure occurs in a first active MME among the at least one active MME. A backup MME for transmitting a paging request message including the IMSI information to the terminal; And the terminal receiving the paging request message and accessing an active MME other than the first active MME. The method of claim 6, And a base station transmitting a connection request message to at least one active MME except for the first active MME according to a connection request from the terminal, receiving a connection response message, and transmitting a connection completion to the terminal. Mobile communication system. The method of claim 6 or 7, wherein the paging request message, And a number of paging requests. The method of claim 8, wherein the terminal, And checking the number of paging requests included in the paging request message and accessing an active MME other than the first active MME only when the paging request message is a first paging request message. The method of claim 6, wherein the backup MME, A mobile communication system characterized by managing the backup IMSI information for each active MME. In the method for providing a service in a mobile communication system comprising a plurality of mobility management entities (MME), When an EMS (Element Management System) detects that a failure has occurred in a first MME of the plurality of MMEs, an IP address of the second MME to transmit a cell broadcast message among the plurality of MMEs, an identifier and a failure of the first MME. Transmitting a cell broadcast message transmission request message including information to a cell broadcast center (CBC); Generating, by the CBC, a cell broadcast message including the identifier of the first MME and the failure information and transmitting the cell broadcast message to the IP address of the second MME; Receiving the cell broadcast message at the second MME, and broadcasting the received cell broadcast message to terminals through base stations; The terminal receives the cell broadcast message and compares an identifier of the first MME included in the received cell broadcast message with an identifier of a pre-stored MME to access an MME except the first MME when the same is the same. Service providing method comprising a process. The method of claim 11, wherein the connecting process comprises: Requesting an access from a terminal having the same identifier of the first MME and an identifier of a pre-stored MME among the terminals to the corresponding base station; Transmitting, by the corresponding base station, an access request message to at least one MME other than the first MME, and receiving an access response message; And providing a connection completion from the corresponding base station to the terminal. The method of claim 11 or 12, wherein the cell broadcast message, The service providing method characterized in that it further comprises the number of message transmission. The method of claim 13, The terminal checks the number of message transmissions included in the cell broadcast message, and accesses to the MME except the first MME only when the cell broadcast message is the first cell broadcast message. . In a mobile communication system comprising a plurality of mobility management entities (MME), When detecting that a failure has occurred in a first MME of the plurality of MMEs, a cell broadcast including an IP address of a second MME to which a cell broadcast message is to be transmitted, an identifier of the first MME, and failure information among the plurality of MMEs An element management system (EMS) for transmitting a message transmission request message; A Cell Broadcast Center (CBC) for generating a cell broadcast message including an identifier of the first MME and the failure information included in the cell broadcast message transmission request message and transmitting the cell broadcast message to an IP address of the second MME; Receiving the cell broadcast message through the second MME, and compares the identifier of the first MME and the identifier of the pre-stored MME included in the received cell broadcast message to the MME except the first MME A mobile communication system comprising the terminals to access. The method of claim 15, wherein the identifier of the first MME and the identifier of the pre-stored MME of the terminal according to the connection request from the same terminal And a base station for transmitting an access request message to at least one MME except for the first MME, receiving an access response message, and transmitting an access completion to the terminal. The method of claim 15 or 16, wherein the cell broadcast message, A mobile communication system, characterized in that it further comprises a message transmission number. The method of claim 17, wherein the terminal, Checking the number of message transmissions included in the cell broadcast message, and accessing to the MME other than the first MME only when the cell broadcast message is the first cell broadcast message.

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