KR20060133429A - Apparatus and method for deleting session in mobile communication system - Google Patents

Abstract

An apparatus and a method for deleting sessions in a mobile communication system are provided to prevent a waste of system resources by deleting a ghost session left in a previous subnet in case an AT(Access Terminal) moves between subnets after losing a connection with an AN(Access Network). An AN transmits an OldUATIRequest message to request an AT to transmit the prior UATI(Unicast Access Terminal Identifier) to the present UATI(401). The AT transmits an OldUATIResponse message containing the prior UATI to the AN(402). The AN, receiving the OldUATIResponse message, transmits an A14-Delete Prior Session message to an SC/MM(Session Control/Mobility Management) in a target PCF/RNC(403). The SC/MM acquires previous subnet information using some information of the prior UATI contained in the A14-Delete Prior Session message. The SC/MM transmits an A13-Delete Session message to the SC/MM of a source PCF/RNC(404).

Description

Apparatus and method for deleting a session in a mobile communication system {APPARATUS AND METHOD FOR DELETING SESSION IN MOBILE COMMUNICATION SYSTEM}

1 is a structural diagram of a general mobile communication system,

2 is a flowchart illustrating a control between a terminal and a base station in establishing a general session;

3 is a structural diagram of a mobile communication system for deleting a session according to an embodiment of the present invention;

4 is a view showing a session deletion method in a mobile communication system according to an embodiment of the present invention;

5A and 5B illustrate an example of an A14-Delete Prior Session message in which an eNB instructs SC / MM to delete a previous session in an embodiment of the present invention.

6A and 6B illustrate an example of an A14-Delete Prior Session Ack message transmitted by an SC / MM to inform a base station that deletion of a previous session is completed in an embodiment of the present invention;

7A and 7B illustrate an example of an A13-Delete Session message in which the current SC / MM instructs a previous SC / MM to delete a specific session in an embodiment of the present invention.

8A and 8B illustrate an A13-Delete Session Ack message transmitted by an SC / MM that receives an A13-Delete Session message to inform the current SC / MM that a session of the UE has been deleted. Figure showing an example,

9 is a diagram illustrating a session deletion method in a mobile communication system according to another embodiment of the present invention.

The present invention relates to an apparatus and method for deleting a session in a mobile communication system, and more particularly, to an apparatus and method for deleting an unnecessary session left in a previous subnet due to a high speed movement of a terminal.

In general, a mobile communication system for providing a line-based voice service divides a frequency band determined according to the communication method into a plurality of channels and uses a frequency channel allocated to each subscriber (Frequency Division Multiple Access). FDMA), Time Division Multiple Access (TDMA), in which multiple subscribers share time on one frequency channel, and multiple subscribers use the same frequency band in the same time frame. Code Division Multiple Access (hereinafter referred to as " CDMA ") for assigning and communicating.

According to the rapid development of communication technology, the mobile communication system represented by the CDMA has reached the stage of providing a high-speed packet data service capable of transmitting a large amount of digital data such as an e-mail, a still image, a video, and a mobile terminal as well as a general voice service. have.

The so-called third generation mobile communication system for providing the high-speed packet data service generally adopts the CDMA scheme, which is divided into a synchronous scheme adopted in the United States and the asynchronous scheme adopted in Europe and Japan. For example, the asynchronous scheme may include General Packet Radio Service (GPRS), and the synchronous scheme may include CDMA 2000 1x, 1x Evolution Data Only (EV-DO), and 1x EV-DV ( Evolution of Data and Voice). In addition, the mobile communication systems are being rapidly developed for the next generation of mobile communication systems aiming for synchronous IMT-2000 (International Mobile Telecommunication 2000) and asynchronous UMTS (Universal Mobile Telecommunication Systems). The UMTS is also called W-CDMA.

Briefly describing the mobile communication systems, the GPRS is developed to provide a packet data service in a circuit switched global system for mobile communication (GSM). The CDMA 2000 1x has a forward speed of 144kbps, which is faster than the IS-95A / IS-95B network, which provides a data transfer rate of 14.4kbps / 56kbps using the IS-95C network evolved from the existing IS-95A and IS-95B networks. Provides data service at the transmission rate. In addition, the 1x EV-DO (1x EVolution Data Only) is designed to provide a forward transmission rate of about 2.4 Mbps by evolving the CDMA 2000 1x one step to transmit a large amount of digital data. Simultaneous support of data services complements the problem of the 1x EV-DO, which cannot be simultaneously supported.

Meanwhile, the 1xEV-DO system is a representative mobile communication system having a channel structure for high-speed data transmission, and is a mobile communication system of a standard proposed by 3GPP2 (3rd Generation Partnership Project 2) to supplement data communication of an IS-2000 system. .

Looking at the configuration of the forward channel of the 1xEVDO system, the time division multiplexing of the pilot channel, the forward medium access control (MAC: MAC) channel, the forward traffic channel and the forward control channel, etc. do. In this case, a bundle of time division multiplexed signals is referred to as a burst.

User data packets are transmitted in the forward traffic channel, and control messages and user data packets are transmitted in the forward control channel. The forward MAC channel is used to transmit reverse rate control and power control information or a designated channel for forward data transmission.

Unlike the forward channel, the reverse channel of the 1xEV-DO system has a channel having a different identification code for each terminal, and the reverse channel for each terminal includes a pilot channel, a reverse traffic channel, and an access channel. Access Channel), Data Rate Control Channel (hereinafter referred to as "DRC Channel"), and Reverse Rate Indicator Channel (Reverse Rate Indicator Channel, RRI Channel). User data packets are also transmitted in the reverse traffic channel, and a data rate control (DRC) channel is used to indicate a forward rate that the terminal can support, and a reverse rate indication (RRI: Reverse). Rate Indicator) The channel is used to indicate the data rate of the data channel transmitted in the reverse direction. The access channel is used when the terminal transmits a message or traffic to the base station before the traffic channel is connected.

The structure of such a 1xEV-DO system will be described with reference to FIG. 1 as follows. The 1xEV-DO system is connected to the Internet network and transmits a packet data service node (hereinafter referred to as a PDSN) 40 to transmit high-speed packet data to the base station 20, and controls the base station 20. It consists of a Packet Control Function (PCF) or Base Station Controller (RNC) 30. The base station 20 wirelessly communicates with a plurality of terminals 10, and transmits the high speed packet data to a terminal having the best transmission rate (eg, 10a).

Unlike the IS-2000 system, the 1xEVDO system does not use a physical identifier of a terminal such as an electronic serial number (ESN) to distinguish the terminal. Instead, the terminal is identified by assigning an identifier called unicast access terminal identifier (UATI) to each terminal. The UATI is composed of an area under the control of the same controller (eg, PCF or RNC), that is, a subnet identifier portion and a terminal identifier portion defined for each subnet. Therefore, when a 1xEVDO terminal moves from one subnet to another subnet, a new UATI consisting of a new subnet identifier is allocated.

In order to exchange data with the base station 20, the terminal 10 must first be assigned an UATI which is an identifier of the terminal. The terminal 10 assigned with the UATI has a method of transmitting and receiving data through a physical layer channel between the terminal and the base station, a method of determining and transmitting a transmission type and format in the media layer, and a connection layer. It is necessary to exchange data with each other, such as how to maintain a call or send and receive data in an idle state, and how to separate, rearrange, and retransmit higher layer data such as TCP / IP packets at the application layer. Negotiate the system parameters of each layer protocol. The negotiation process is performed by exchanging predefined messages. For this purpose, the terminal 10 and the base station 20 establish a dedicated channel. Since this dedicated channel is set up before the exchange of parameters necessary for transmission, the terminal 10 and the base station 20 set up the dedicated traffic channel using a predetermined initial parameter and perform parameter negotiation. The set of negotiated system parameters and system variables is defined as "Session Configuration" or "Session Information" and the process of negotiating such session configuration is referred to as "session establishment procedure". The negotiated session establishment is maintained and updated for one session, that is, during a period in which data communication between the terminal 10 and the base station 20 is possible. The area of the packet controller that manages the session information is called a "subnet" and each subnet has an identifier of 128 bits.

The session establishment procedure is divided into an AT initiated state in which the terminal 10 requests desired parameters and an AN initiated state in which the base station 20 proposes parameters to be used. The terminal 10 and the base station 20 include a list of parameter values to be used for one parameter in a configuration request message and transmit the same. If the other party has a desired value in the list, the corresponding value is transmitted. Send a Configuration Response Message including a. If the user does not have a desired value in the list, he repeats the process of writing a list of setting values he wants to support and use for the parameter in a setting response message, and finally, the terminal 10 and the base station ( The parameter is set to the setting value supported by 20).

When the terminal 10 and the base station 20 complete parameter negotiation for all protocols to be used, the terminal 10 and the base station 20 transmit a configuration complete message to complete the session setup process. When the session setup is completed, the terminal 10 and the base station 20 release the traffic channel set as a predetermined initial parameter and apply the newly negotiated parameters.

2 shows an example of a session establishment procedure. In step 201, the terminal 10 sends a UATI request message (UATIRequest) to the base station 20 to request UATI. Then, the base station 20 transmits a UATI assignment message (UATIAssignment) to the terminal 10 in step 202 to allocate a new UATI, and the terminal 10 sends a UATI completion message (UATIComplete) as a response message in step 203. Complete the UATI assignment process by sending. In step 204, a traffic channel between the terminal 10 and the base station 20 is set using the initial parameter value.

The base station 20 transmits a configuration start message through a traffic channel established to the terminal 10 in step 205 to perform negotiation with the terminal, and establishes a session of the AT initiated state. To start. In step 206, the terminal 10 exchanges a configuration request message and a configuration response message in step 207 with the base station 20 several times to set a desired value for a specific parameter. After completing the setting of the desired parameter value, the terminal 10 transmits a configuration complete message in step 208 to notify the end of the terminal start state and the start of the AN initiated state. On the other hand, the base station 20 is encrypted and transmitted to the user data and signaling messages exchanged between the terminal and the base station to provide a higher confidentiality. Accordingly, in step 209, the base station 20 assigns encryption key values to the terminal 10, and in step 210 and 211, the base station 20 transmits a configuration request message and a configuration response message ( The configuration response message) is exchanged with the terminal 10 several times to set a desired value for a specific parameter. After completing the setting of the desired parameter value, the base station 20 transmits a configuration complete message to the terminal 10 in step 212 to indicate that the entire session setup process is completed.

In the 1x-EVDO system, a data structure in the form of configuration attribute is used to describe each parameter. This configuration property consists of the identifier of the parameter and the parameter value you want to use for that parameter. When the base station 20 and the terminal 10 negotiate each parameter, the base station 20 and the terminal 10 propose a value to be used by using the corresponding configuration characteristic and negotiate the result, and store the negotiation result in the form of the configuration characteristic.

In a mobile communication system such as 1x-EVDO, when a terminal moves, an area of the same controller, that is, a subnet is moved, session information of a terminal managed by a session control and mobility management unit (not shown) of the corresponding subnet is moved. Performs the transfer to the subnet. The operation is performed by transmitting some bits of the identifier of the previous subnet and the terminal identifier in the process of requesting a new terminal identifier to the controller of the corresponding subnet after the terminal detects the new subnet. Upon receiving some bits of the previous subnet identifier, the packet controller determines the previous subnet to which the terminal has moved based on the corresponding information, and requests session information of the terminal from the previous subnet. The previous controller, which has received a request for session transfer from the controller in which the terminal is present, transfers session information through a process of delivering session information corresponding to the requested terminal identifier to the requested controller.

The operation of requesting the transmission of the session information by using the upper part bits of the previous subnet identifier in the new subnet in the new subnet may be caused by the terminal losing connection with the base station due to the fast movement of the terminal in the session transfer process or the operation of the terminal or the base station. Problems arise when you lose control of the. That is, in the above example, when only some information of the subnet identifier is transmitted, a situation in which a plurality of subnets corresponding to the information exist may occur. For example, when the terminal transmits the upper 8 bits of the subnet identifier, the two subnets having '11111111 ....... 000' and '11111111 ....... 001' as identifiers can be distinguished. No problem occurs. Since the identifiers of the adjacent subnets are given enough to be distinguishable even if some information is used, the above problem does not occur in a normal session transfer process. However, when the connection with the base station is lost due to a high speed movement, the conventional session transfer process cannot be used because the mobile station can move a long distance where some information of the subnet identifier is duplicated.

In order to prevent such a problem, when the connection with the base station is reset and the subnet is changed, the terminal does not request the transfer of the session information to the previous subnet and establishes the current subnet and the new session information. In this case, session information negotiated with the UE remains in the previous subnet without being erased. Such a session is called a "ghost session". The ghost session unnecessarily wastes system resources because it is maintained in the system for a long time (54 hours) even if there is no response from the terminal. In addition, there is a problem in that a large amount of storage space is consumed and related operations must be continuously performed in the system.

In addition, if the terminal moves at a high speed and loses connection with the base station, the previous information, that is, the ghost session may be deleted because only a portion of the 8-bit subnet identifier (originally 128 bits) delivered when the current subnet is moved cannot be accurately determined. There was no.

Accordingly, an object of the present invention is to provide an apparatus and method for deleting a ghost session that remains undeleted in a previous subnet when a movement between subnets occurs while a terminal loses connection with a base station.

Another object of the present invention is to provide an apparatus and method for reducing resource waste of a system by finding and deleting a ghost session overlapping several subnets due to frequent movement of a terminal.

In a mobile communication system according to an embodiment of the present invention, a method for deleting a session includes a mobile terminal, a base station transmitting packet data to the mobile terminal through a wireless channel, a packet controller controlling the base station, and a packet through the packet controller. A method for deleting a session in a mobile communication system including a packet data service node for transmitting data to a base station, the method comprising: transmitting a first message including terminal identifier information used in a previous subnet received from the terminal to a current packet controller; And the current packet controller acquires previous subnet information by using some information of the terminal identifier used in the previous subnet through the first message, and then includes the terminal identifier using the A13 interface as the acquired previous subnet. Send the second message to the previous packet controller Process, and the previous packet controller characterized in that it comprises a step of deleting the session information corresponding to the terminal identifier of the first session that is stored upon receipt of the second message information.

In the mobile communication system according to an embodiment of the present invention, the apparatus for deleting a session identifies a mobile terminal, a base station for identifying a mobile terminal by assigning a terminal identifier to the mobile terminal, and transmitting packet data through a wireless channel, and controlling the base station. In the mobile communication system including a packet controller for transmitting the packet data to the base station through the packet controller, and when the mobile terminal moves from one subnet to another subnet, session information in the session deletion device, A session control and mobility management unit, a session control and mobility management unit, and a session control and mobility management unit to transmit and store corresponding session information and delete previous subnet session information when the terminal moves to another subnet, and the data received from the packet data service node. By selecting the base station where the terminal is located Song, and characterized in that it comprises a selector, and a controller for transmitting the data received from the terminal to the packet data service node.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention relates to an apparatus and method for deleting unnecessary ghost sessions left in a previous subnet due to movement of a terminal in a mobile communication system.

As shown in FIG. 3, the mobile communication system includes a terminal 300, a base station 310, a packet controller or a base station controller 320, and a packet data service node (PDSN) 330. Consists of

The terminal 300 performs overall control and stores the negotiated session information or user data to be transmitted and received with the controller 301 for negotiating session information to be used during communication with the packet controller or the base station controller 320. An encoder 303 for encoding the user data or the generated message, a modulator 304 for modulating the encoded user data or message, and a transmitter / receiver 305 for transmitting and receiving to a base station via a wireless channel. And a demodulator 306 for demodulating user data or messages received through the transmitter / receiver 305 and a decoder 307 for decoding demodulated user data or messages.

The base station 310 includes an RF unit 311 for transmitting and receiving user data or messages, a data queue 312 for storing received user data or messages, the amount of data for each queue, and channels of terminals. The scheduler and the controller 313 select and transmit data of a specific user and a specific queue in consideration of a situation, service characteristics, fairness, and the like.

The packet controller or base station controller (PCF / RNC) 320 is a Session Control / Mobility Management (SC / MM) 321 and a PDSN (Negotiated) to negotiate session information to be used during communication with the terminal 300. The selector and the controller 322 transmit data received from the terminal 330 by selecting the base station 310 in which the corresponding terminal 300 exists and transmitting the data received from the terminal 300 to the PDSN 330.

The SC / MM 321 stores session information. When the terminal 300 moves to another subnet, the SC / MM 321 plays a role of delivering a corresponding session and maintains mobility information of the terminal.

4 illustrates a method for deleting a session in a mobile communication system according to an embodiment of the present invention.

In step 401, the base station 310 transmits an OldUATIRequest message to the terminal 300 to request the terminal identifier used before the currently used terminal identifier UATI.

Table 1 below shows an example of an OldUATIRequest message for requesting the terminal identifier used by the base station 310 before the terminal identifier UATI currently being used by the terminal 300. In Table 1 below, the OldUATIRequest message includes an 8-bit message identifier (MessageID) field for identifying the message from another message and an 8-bit transaction identifier (TransactionID) field for distinguishing the OldUATIRequest message from a previous or subsequent OldUATIRequest message. It consists of.

Field Length (bits) MessageID 8 TransactionID 8

 Upon receiving the OldUATIRequest message, the terminal 300 transmits an OldUATIResponse including the previous terminal identifier to the base station 310 in step 402.

Table 2 below shows an example of an OldUATIResponse that the terminal 300 receiving the OldUATIRequest message uses to transmit a previous terminal identifier to the base station 310. In Table 2 below, the OldUATIResponse message includes an 8-bit message identifier (MessageID) field for identifying the message from another message and an 8-bit processing identifier corresponding to the OldUATIRequest message to distinguish which OldUATIRequest message is a response. TransactionID) field, and an Old Identifier (OldUATI) field that specifies an identifier previously assigned to the terminal.

Field Length (bits) MessageID 8 TransactionID 8 Olduati 128

Upon receiving the OldUATIResponse message, the base station 310 uses the A14, which is an interface between the SC / MMs 321 in the target PCF / RNC 320b, to the A14-Delete Prior Session message including the previous UE identifier in step 403. To the SC / MM 321.

5A and 5B illustrate an example of an A14-Delete Prior Session message in which an eNB instructs SC / MM to remove a previous session in an embodiment of the present invention. The A14-Delete Prior Session message is an A14 Message Type element representing a message type, an ATI element representing a newly allocated identifier of the UE, and a Correlation ID element for distinguishing different A14-EncryptionInfo Request messages as shown in FIG. 5A. , Sector ID element identifying the base station transmitting the A14-EncryptionInfo Request, Security Layer Packet element including the received encryption layer packet, the previous terminal identifier used in the previous subnet, etc. Each element is a packet in the base station 310 It includes information passed to the controller 320. 5B is a message bitmap that further refines the message structure.

The SC / MM 321 of the target PCF / RNC 320b that has received the A14-Delete Prior Session message uses the partial information of the previous terminal identifier included in the A14-Delete Prior Session message in step 404 to transmit the previous subnet information. Acquire. Subsequently, in step 404, the SC / MM 321 of the target PCF / RNC 320b receives an A13-Delete Session message including an A13-Delete Session message including a terminal identifier using A13, which is an interface between SC / MMs, to the acquired previous subnet. Source) SC / MM 321 of PCF / RNC 320a is transmitted.

6A and 6B illustrate an A13-Delete Session message in which the current SC / MM instructs the previous SC / MM to delete a specific session in an embodiment of the present invention. The A13-Delete Session message is an A13 Message Type element representing a message type, a UATI128 element representing a previous identifier of a terminal, a Security Layer Packet element including a received encryption layer packet, and an A13-Delete Session as illustrated in FIG. 6A. A Sector ID element for identifying a PCF / RNC transmitting the same, and each element includes information transmitted from the current PCF / RNC 320b to the previous packet controller (or base station controller) 320a. 6B shows a message bitmap that further refines the message structure.

The SC / MM of the previous subnet that receives the A13-Delete Session message, that is, the SC / MM 321 of the source PCF / RNC 320a, stores the session information corresponding to the corresponding terminal identifier among the session information stored in step 405. Delete it. Subsequently, in step 405, the SC / MM 321 of the source PCF / RNC 320 sends an A13-Delete Session Ack message indicating that the deletion of the session information is completed, that is, the SC / MM in which the current UE exists, that is, the target PCF / RNC 320b. Transmits to the SC / MM 321.

7A and 7B illustrate an example of an A13-Delete Session Ack message transmitted by an SC / MM that receives an A13-Delete Session message to notify the current SC / MM that a session of the UE has been deleted. The figure shows. The A13-Delete Session Ack message is composed of an A13 Message Type element indicating a message type, a UATI128 element indicating a previous identifier of the UE, a Cause element indicating a response type, and the like, as shown in FIG. 7A. It includes information passed from the controller (or base station controller) 320a to the current packet controller (or base station controller) 320b. 8B is a message bitmap that further refines the message structure.

The current SC / MM, that is, the SC / MM 321 of the target PCF / RNC 320 that has received the A13-Delete Session Ack message, informs the base station 310 where the UE is located in step 406 that the session has been deleted. Delete Deletes the ghost session by sending a Prior Session Ack message.

8A and 8B illustrate an example of an A14-Delete Prior Session Ack message transmitted by an SC / MM to inform a base station that deletion of a previous session is completed in an embodiment of the present invention. The A14-Delete Prior Session Ack message is an A14 Message Type element representing a message type, an ATI element representing an address of a terminal, and an A14-EncryptionInfo Response message to which A14-EncryptionInfo Request message, as shown in FIG. 8A. Correlation ID element (set to the same value as the Correlation ID sent by the target A14-EncryptionInfo Request message), Cause element indicating the type of response, etc., each element of the base station 310 in the packet controller 320b. Contains information passed to. 8B is a message bitmap that further refines the message structure.

9 illustrates a method for deleting a session in a mobile communication system according to another embodiment of the present invention. The present invention proposes a method for transmitting a terminal identifier information necessary for deleting a ghost session, not based on a request from the base station, but under a condition determined by the terminal. This determination can be made by combining whether the connection with the system has been lost or not, or whether the subnet has been changed.

In step 901, the terminal 300 determines whether or not the connection with the base station is reset, whether the control of the base station or the terminal is lost, or if the subnet is changed or instructed to move to another system or frequency. If it is determined that the generation of the ghost session in accordance with the condition of the deleteOldSession message including the previous terminal identifier information is transmitted to the base station (310).

Table 3 below is an example of DeleteOldSession transmitted to delete the ghost session of the previous subnet at the terminal's discretion. In Table 3 below, the DeleteOldSession message includes a message identifier field for identifying the message from another message, and a previous identifier field for specifying an identifier previously assigned to the terminal.

Field Length (bits) MessageID 8 Olduati 128

Upon receiving the DeleteOldSession message, the base station 310 receives the A14-Delete Prior Session message including the previous terminal identifier using the A14 interface between the base station and the SC / MM in step 902 and the SC / MM of the target PCF / RNC 320b. To 321. The SC / MM 321 of the target PCF / RNC 320b that has received the A14-Delete Prior Session message obtains the previous subnet information using some information of the previous UE identifier included in the A14-Delete Prior Session message. Subsequently, the SC / MM 321 of the target PCF / RNC 320b receives the source PCF with an A13-Delete Session message including the terminal identifier using A13, which is an interface between SC / MMs, to the acquired previous subnet in step 903. It transmits to SC / MM 321 of / RNC 320a. The SC / MM 321 of the previous subnet that receives the A13-Delete Session message, that is, the SC / MM 321 of the source PCF / RNC 320a, stores session information corresponding to the corresponding terminal identifier among the stored session information. Delete it. Thereafter, the SC / MM 321 of the source PCF / RNC 320a receives an A13-Delete Session Ack message indicating that the deletion of the session information is completed in step 904, that is, the target SC / MM 321, that is, the target. The SCF is transmitted to the SC / MM 321 of the PCF / RNC 320b. Upon receiving the A13-Delete Session Ack message, the current SC / MM 321 transmits an A14-Delete Prior Session Ack message indicating that the corresponding session has been deleted to the base station 310 where the terminal 300 is located in step 905. Complete the process of deleting the ghost session.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention is effective in preventing system resource wastage by deleting a ghost session that remains undeleted in the previous subnet when movement between subnets occurs while the terminal loses connection with the base station.

Claims (12)

A mobile terminal, a base station for identifying a mobile terminal by assigning a terminal identifier to the mobile terminal, transmitting packet data through a wireless channel, a packet controller controlling the base station, and transmitting the packet data to the base station through the packet controller. In the mobile communication system including a packet data service node for transmitting, when the mobile terminal moves from one subnet to another subnet, in the session deletion method, Transmitting a first message including terminal identifier information used in a previous subnet received from the terminal to a current packet controller; After acquiring the previous subnet information using the partial information of the terminal identifier used in the previous subnet through the first message, the second packet including the terminal identifier using the A13 interface as the acquired previous subnet information, the previous packet Transmitting to the controller, And deleting session information corresponding to a corresponding terminal identifier among session information stored and received by the second message. The method of claim 1, The first message is a message indicating the deletion of a previous session (A14-Delete Prior Session). The method of claim 1, And the second message is an A13-Delete Session message indicating deletion of a previous session. The method of claim 1, And transmitting a third message to the current packet controller to inform the current packet controller that the session of the terminal has been deleted. The method of claim 4, wherein And transmitting, by the current packet controller to the base station where the terminal is located, a fourth message indicating that the session has been deleted. A mobile terminal, a base station for identifying a mobile terminal by assigning a terminal identifier to the mobile terminal, transmitting packet data through a wireless channel, a packet controller controlling the base station, and transmitting the packet data to the base station through the packet controller. In the mobile communication system including a packet data service node to transmit when the mobile terminal moves from one subnet to another subnet, in the session deletion method, When the connection with the base station is lost, transmitting a first message including previous terminal identifier information to the base station to the base station; Transmitting a second message including terminal identifier information used in a previous subnet received from the terminal to a current packet controller; After acquiring the previous subnet information using the partial information of the terminal identifier used in the previous subnet through the second message, the third packet including the terminal identifier using the A13 interface as the acquired previous subnet information is transferred to the previous packet. Transmitting to the controller, And deleting session information corresponding to a corresponding terminal identifier among session information stored and received by the third message. The method of claim 6, The first message is a message (DeleteOldSession) including the previous terminal identifier information. The method of claim 6, The second message is a message for instructing deletion of a previous session (A14-Delete Prior Session). The method of claim 6, And the third message is a message for instructing deletion of a previous session (A13-Delete Session). The method of claim 6, And transmitting a third message to the current packet controller to inform the current packet controller that the session of the terminal has been deleted. The method of claim 7, wherein And transmitting, by the current packet controller to the base station where the terminal is located, a fourth message indicating that the session has been deleted. A mobile terminal, a base station for identifying a mobile terminal by assigning a terminal identifier to the mobile terminal, transmitting packet data through a wireless channel, a packet controller controlling the base station, and transmitting the packet data to the base station through the packet controller. In the mobile communication system including a packet data service node to transmit when the mobile terminal moves from one subnet to another subnet, in the session deletion device, A session control and mobility management unit for storing and managing session information, transferring the corresponding session information and deleting previous subnet session information when the terminal moves to another subnet; And a selector and a controller for transmitting data received from the packet data service node to a base station in which the terminal is located, and transmitting data received from the mobile terminal to the packet data service node. .

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