Patent Publication Number: US-2022240337-A1

Title: Method for processing exceptional case of establishing default bearer in mobile communication system and device therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. application Ser. No. 13/058,719 filed Feb. 11, 2011, and claims the benefit under 35 U.S.C. Section 371, of PCT International Application No. PCT/KR2009/004471, filed Aug. 11, 2009, which claimed priority to Korean Application No. 10-2008-0078446, filed Aug. 11, 2008 and Korean Application No. 10-2009-0068532, filed Jul. 27, 2009 in the Korean Patent Office, the disclosures of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     An exemplary embodiment of the present invention relates to a method for processing an exceptional case of establishing a default bearer and a device therefor. 
     BACKGROUND ART 
     An advanced third generation mobile communication system has introduced a concept of a default bearer in order to rapidly control various packet services and facilitate management of a service duality. Upper layer service context information for the default bearer is generated when a user equipment is firstly registered in a packet network and is always present in a terminal and a network regardless of signaling connection between the user equipment and the packet network when the user equipment is registered in the packet network. 
     A resource is allocated to the default bearer while the signaling connection between the user equipment and the packet network is established. When the signaling connection is cancelled, the corresponding resource is also cancelled. Since an Internet protocol (IP) signaling packet (i.e., ICMP), an IP application signaling packet (i.e., SIP) or an IP packet (i.e., E-mail) having a service quality of a ‘best-effort’ type are transmitted through the default bearer, the default bearer is the basis of the advanced third generation mobile communication system. 
     A procedure of establishing the default bearer is performed by being included in an attachment procedure to be executed for the user equipment to firstly access the packet network. An exceptional case may occur in which only the attachment procedure is completed while the default bearer may not normally established due to various reasons. 
     At this time, even if the user equipment accesses the packet network, the user equipment cannot receive an IP service, a procedure for processing the exceptional case is required. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     The present invention has been made in an effort to provide a method for processing an exceptional case of establishing a default bearer in failing in establishing the default bearer and a device therefor. 
     Solution to Problem 
     An exemplary embodiment of the present invention provides a method for processing an exceptional case of establishing a default bearer in a mobility management entity of a mobile communication system includes: receiving a network attachment request from a user equipment; transmitting a network attachment acceptance including an activation request of the default bearer to the user equipment in response to the network attachment request; and cancelling a network attachment procedure when a completion response to the activation request of the default bearer is not received from the user equipment within a predetermined time. 
     Herein, cancelling the network attachment procedure includes determining whether or not the predetermined time elapses by using a timer and further includes retransmitting the network attachment acceptance to the user equipment when the timer is expired while the completion response to the activation request of the default bearer is not received. 
     Another embodiment of the present invention provides a device for processing an exceptional case of establishing a default bearer in a mobile communication system includes: a communication unit that supports a communication protocol for transmitting and receiving a request and a response depending on a network attachment procedure to and from a user equipment; and a control unit that transmits a network attachment acceptance including an activation request of the default bearer in response to the network attachment request of the user equipment to the user equipment and cancels the network attachment procedure when a complete response to the activation request of the default bearer is not received from the user equipment within a predetermined time and further includes a timer for determining whether or not the predetermined time elapses. 
     Herein, the control unit retransmits a message of the network attachment acceptance to the user equipment when the timer is expired while the complete response to the activation request of the default bearer is not received within the predetermined time. 
     Yet another embodiment of the present invention provides a method for processing an exceptional case of establishing a default bearer in a mobility management entity of a mobile communication system includes: receiving a network attachment request from a user equipment; transmitting a network attachment acceptance including an activation request of the default bearer to the user equipment in response to the network attachment request; and cancelling a network attachment procedure when a complete response to the activation request of the default bearer is not received from the user equipment until a timer is expired at the predetermined times. 
     Herein, cancelling the network attachment procedure includes: retransmitting the network attachment acceptance to the user equipment whenever the timer is expired; and reactuating the timer after retransmitting the network attachment acceptance. 
     There is provided a reliable IP service by providing an operational procedure for an exceptional case in which only an attachment procedure is completed while a default bearer is not normally established. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic block diagram illustrating a configuration of an advanced third generation mobile communication system. 
         FIG. 2  illustrates a protocol stack of a control plane of an advanced third generation mobile communication system according to an exemplary embodiment of the present invention, 
         FIGS. 3 and 4  are flowcharts illustrating a method of establishing a default bearer for each step according to an exemplary embodiment of the present invention. 
         FIG. 5  is a block diagram illustrating a configuration of a mobility management entity that processes an exceptional case of establishing a default bearer according to an exemplary embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. In the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
     In the specification, a user equipment (UE) may designate a mobile terminal (MT), a mobile station (MS), a terminal, a subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), etc. or and may include the entire or partial functions of the mobile terminal, the terminal, the mobile station, the subscriber station, the portable subscriber station, the access terminal, etc. 
     In the specification, an evolved Node-B may designate a base station (BS), an access point (AP), a radio access station (RAS), a node-B, a base transceiver station (BTS), a mobile multihop relay (MMR)-BS, etc. and may include the entire or partial functions of the BS, the AP, the RAS, the node-B, the BTS, the MMR-BS, etc. 
       FIG. 1  is a schematic block diagram illustrating a configuration of an advanced third generation mobile communication system. 
     In the embodiment, the mobile communication system includes a user equipment (UE)  110 , an evolved Node-B (eNB)  120 , an access gateway (aGW)  130 , and a mobility management entity (MME)  140 . 
     The user equipment  110  accesses the eNB  120  through a wireless interface and the eNB  120  accesses the access gateway  130  through a wired interface. Further, the access gateway  130  is connected to an external packet data network (PDN)  150  through an Internet protocol (IP) interface. The mobility management entity  140  supports a control protocol of the third generation mobile communication system, and controls a packet service and a bearer through a signaling procedure with the user equipment  110 . 
     The user equipment  110  performs IP-based packet transmission and reception with a server (not shown) located on the packet data network  150  or a corresponding node (not shown), The bearer needs to be established among the user equipment  110 , the eNB  120 , and the access gateway  130  in order to transmit and receive IP packets. 
     The user equipment  110  can establish one or more bearers for one packet data network  150 . The bearer includes a default bearer that is basically established with address allocation at the time of accessing each packet data network and a dedicated bearer that is additionally established by a request of quality of service (QoS) at the time of performing a service. The embodiment of the present invention relates to a processing procedure when the default bearer of two bearers is not normally established, 
       FIG. 2  illustrates a protocol stack of a control plane of an advanced third generation mobile communication system according to an exemplary embodiment of the present invention. 
     In  FIG. 2 , the protocol stack of the control plane for the user equipment includes an evolved session management (ESM) layer  201  that manages a session including the default bearer, an evolved mobility management (EMM) layer  202  that manages mobility, a radio resource control (RRC) layer that manages a radio resource, a radio link control layer (RLC) layer that controls a radio link, a media access control (MAC) layer that controls access of media, and a physical (PHY) layer which is a physical layer. 
     Further, In  FIG. 2 , the protocol stack of the control plane for the mobility management entity includes an evolved session management (ESM) layer  203  that manages a session including the default bearer and an evolved mobility management (EMM) layer  204  that manages mobility, and in addition, includes an SI application (SIAP) layer, a user datagram protocol (UDP) layer, an Internet protocol (IP) layer, layer  2  (L 2 ) layer, and a layer  1  (LI) layer. 
     Hereinafter, a method of establishing the default bearer according to an exemplary embodiment of the present invention will be described with reference to the protocol stack of the control plane of  FIG. 2 . 
       FIGS. 3 and 4  are flowcharts illustrating a method of establishing a default bearer for each step according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 3 , when the user equipment  110  firstly accesses the packet data network  150 , the ESM layer  201  of the user equipment  110  requests the EMM layer  202  to perform an attachment procedure in the packet data network (S 301 ). The EMM layer  202  that receives the attachment request transmits an attachment request message (i.e., ATTACH_REQUEST) to the mobility management entity  140  through the eNB120 (S 302 ). 
     The mobility management entity  140  that receives the attachment request message establishes an RRC connection to allocate the resource to the user equipment  110  (S 303 ) and performs an authentication procedure of the user equipment  110  (S 304 ). When authentication is successively performed, the EMM layer  204  of the mobility management entity  140  transmits an attachment acceptance message (i.e., ATTACH_ACCEPT) to the user equipment  110  (S 305 ). The attachment acceptance message includes a message (i.e., Active_Default_EPS_Bearer_Context_Request) of requesting the user equipment  110  to activate the default bearer. 
     Thereafter, the ESM layer  203  of the mobility management entity  140  drives a predetermined timer (i.e., T3485 timer or T3450 timer) for supervising whether or not the default bearer is activated in the user equipment  110  (S 306 ). If a response message (i.e., Active_Default_EPS_Bearer_Context_Complete or ATTACH_COMPLETE) to the activation request of the default bearer is not received from the user equipment  110  (S 308 ) until the timer is expired (S 307 ), the ESM layer  203  cancels the resource allocated for establishing the default bearer at step S 303  (S 309 ) and notifies a failure in establishing the default bearer to the EMM layer  204  of the mobility management entity  140  (S 310 ). 
     The EMM layer  204  that receives the notification of the failure in establishing the default bearer initializes all establishments for the user equipment  110  and waits to receive the attachment acceptance message again (S 311 ). 
     If the response message (i.e., Active_Default_EPS_Bearer_Context_Complete or ATTACH_COMPLETE) to the activation request of the default bearer from the user equipment  110  before the timer is expired at step S 307  (S 308 ), attachment of the user equipment  110  to the network is normally completed, (S 312 ). 
     A time taken to activate the default bearer may be longer than a predetermined time set in the timer. For this, the ESM layer  203  of the mobility management entity  140  can determine the failure in establishing the default bearer or not through an expiration frequency of the timer.  FIG. 4  is a flowchart illustrating a processing procedure in this case. 
     In  FIG. 4 , steps S 401  to S 406  and steps S 409  to S 411  are the same as steps S 301  to  5306  and steps S 309  to S 311  of  FIG. 3 . Therefore, steps S 407  and S 408  will be described herein. 
     That is, the ESM layer  203  of the mobility management entity  140  reactuates the timer until the timer is expired at the n-1-th times (n is a natural number equal to or larger than 2), but if the response message (i.e., active_Default_EPS_Bearer_Context_Complete or ATTACH_COMPLETE) to the activation request of the default bearer is not received from the user equipment  110  ( 5408 ) until the timer is expired ( 5407 ) at the n-th times, the E5M layer  203  cancels the resource allocated for establishing the default bearer at step S 403  ( 5409 ) and notifies the failure in establishing the default bearer to the EMM layer  204  of the mobility management entity  140  ( 5410 ). 
     For example, the E5M layer  203  reactuates the timer until the timer is expired at the 4-th times, but if the response message to the activation request of the default bearer is not received from the user equipment  110  until the timer is expired at the 5-th times, the E5M layer  203  cancels the resource allocated for establishing the default bearer and notifies the failure in establishing the default bearer to the EMM layer  204 . 
     The EMM layer  204  that receives the notification of the failure in establishing the default bearer initializes all establishments for the user equipment  110  and waits to receive the attachment acceptance message again ( 5310 ). 
     Even when the default bearer is not established, an access to the corresponding packet data network is possible, but an actual IP service is impossible, such that an incomplete access is made. However, if the default bearer is not established up to a pre-determined time or a temporary identifier is not reallocated, an operation of the EMM layer is initialized through the notification of the failure to disable accessing the packet data network and allow the establishment procedure of the default bearer to be re-executed in the initialization state, 
       FIG. 5  is a block diagram illustrating a configuration of a mobility management entity  140  that processes an exceptional case of establishing a default bearer according to an exemplary embodiment of the present invention. The mobility management entity  140  of the embodiment includes a communication unit  141 , an ESM control unit  142 , an EMM control unit  143 , a timer  144 , and a memory  145 . 
     The communication unit  141  transmits and receives various message for a network connection and a mobility management to and from the user equipment  110  through the eNode-B  120  under the control of the EMM control unit  143 . 
     When the ESM control unit  142  receives the attachment request message of the user equipment  110  through the communication unit  141 , the ESM control unit  142  allocates the resource to the user equipment  110  by establishing the RRC connection and performs an authentication procedure of the user equipment  110 , The mobility management entity  140  includes the memory  145  that stores user authentication information. 
     When the authentication is successively performed, the ESM control unit  142  transmits to the EMM control unit  143  of the mobility management entity  140  a request message (i.e., Active_Default_EPS_Bearer_Context_Request) for activating the default bearer to the user equipment  110 . The EMM control unit  143  transmits the attachment acceptance message (i.e., ATTACH_ACCEPT) including the activation request of the default bearer to the user equipment  110 . 
     The ESM control unit  142  actuates the timer  144  (i.e., T3485 timer or T3450 timer) just after the ESM control unit  142  transmits the request message for activating the default bearer or just after the EMM control unit  143  transmits the attachment acceptance message. In addition, when the default bearer is not activated with respect to the activation request of the default bearer until the timer  144  is expired, the ESM control unit  142  cancels the resource allocated for establishing the default bearer and notifies the failure in establishing the default bearer to the EMM control unit  143 . When the failure in establishing the default bearer is notified from the ESM control unit  142 , the EMM control unit  143  initializes all establishments for the user equipment  110 . 
     The ESM control unit  142  can determine the failure in establishing the default bearer or not in accordance with an expiration frequency of the timer  144 . In other words, the ESM control unit  142  reactuates the timer until the timer  144  is expired at the n-1-th times (n is a natural number equal to or larger than 2), but when the default bearer is not activated until the timer is expired at the n-th times, the ESM control unit  142  cancels the resource allocated for establishing the default bearer and notifies the failure in establishing the default bearer to the EMM control unit  143 , As one example, the ESM control unit  142  reactuates the timer until the timer  144  is expired at the 4-th times, but when default bearer is not activated until the timer is expired at the 5-th times, the ESM control unit  142  cancels the resource allocated for establishing the default bearer and notifies the failure in establishing the default bearer to the EMM control unit  143   
     The above-mentioned exemplary embodiments of the present invention are not embodied only by a method and apparatus. Alternatively, the above-mentioned exemplary embodiments may be embodied by a program performing functions that correspond to the configuration of the exemplary embodiments of the present invention, or a recording medium on which the program is recorded. These embodiments can be easily devised from the description of the above-mentioned exemplary embodiments by those skilled in the art to which the present invention pertains. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.