Abstract:
The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. 
     Methods and apparatuses provide a service to user equipment through a dedicated core network. In one method, a base station, also referred to as eNB, receives a non-access stratum (NAS) message from user equipment (UE), and transmits a first initial UE message having the NAS message to a first mobility management entity (MME). Also, the base station receives a redirection request message having the NAS message from the first MME, and transmits a second initial UE message having the NAS message to a second MME. In another method, the MME receives the first initial UE message having the NAS message from the base station, and transmits the redirection request message having the NAS message when the MME fails to support a dedicated core network according to UE usage type information. If the redirection request message is transmitted, a second initial UE message having the NAS message is transmitted to a dedicated MME.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional application No. 62/126,917 filed on Mar. 2, 2015, 62/202,406 filed on Aug. 7, 2015 and 62/232,100 filed on Sep. 24, 2015 in the U.S. patent and trademark office, the entire disclosure of which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a wireless communication system and, more particularly, to a method and apparatus for providing a service to user equipment through a dedicated core network. 
       BACKGROUND 
       [0003]    To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’. The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed. 
         [0004]    The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications. 
         [0005]    In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology. 
         [0006]    Meanwhile, a terminal (also referred to as user equipment (UE) or the like) should be offered a service through a suitable core network (CN) for providing that service. This suitable core network may be referred to as a dedicated core network (DCN). Therefore, when a non-access stratum (NAS) message is received from a terminal, a base station (also referred to as evolved node B (eNodeB or eNB) or the like) should transmit the NAS message to a mobility management entity (MME) contained in the DCN so that the terminal can be offered a service through the DCN. However, if any MME selected by the base station is not a dedicated MME which is contained in the DCN, the base station is required to select an MME again. 
       SUMMARY 
       [0007]    In order to meet the above-mentioned need or the like, the present invention provides a method and apparatus for allowing a base station to transmit an NAS message to a dedicated MME through rerouting of the NAS message when an MME receiving the NAS message is not the dedicated MME. 
         [0008]    According to various embodiments of the present invention, a method implemented at a base station in a wireless communication system includes steps of receiving a non-access stratum (NAS) message from user equipment (UE); transmitting a first initial UE message having the NAS message to a first mobility management entity (MME); receiving a redirection request message having the NAS message from the first MME; and transmitting a second initial UE message having the NAS message to a second MME. 
         [0009]    According to various embodiments of the present invention, a base station in a wireless communication system includes a communication unit configured to perform communication with other network entity; and a control unit configured to control the communication unit to receive a non-access stratum (NAS) message from user equipment (UE), to transmit a first initial UE message having the NAS message to a first mobility management entity (MME), to receive a redirection request message having the NAS message from the first MME, and to transmit a second initial UE message having the NAS message to a second MME. 
         [0010]    According to various embodiments of the present invention, a method implemented at a mobility management entity (MME) in a wireless communication system includes steps of receiving a first initial user equipment (UE) message having a non-access stratum (NAS) message from a base station; and transmitting a redirection request message having the NAS message when the MME fails to support a dedicated core network according to UE usage type information, wherein if the redirection request message is transmitted, a second initial UE message having the NAS message is transmitted to a dedicated MME. 
         [0011]    According to various embodiments of the present invention, a mobility management entity (MME) in a wireless communication system includes a communication unit configured to perform communication with other network entity; and a control unit configured to control the communication unit to receive a first initial user equipment (UE) message having a non-access stratum (NAS) message from a base station, and to transmit a redirection request message having the NAS message when the MME fails to support a dedicated core network according to UE usage type information, wherein if the redirection request message is transmitted, a second initial UE message having the NAS message is transmitted to a dedicated MME. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a diagram illustrating the structure of a communication system according to an embodiment of the present invention. 
           [0013]      FIGS. 2A and 2B  are flow diagrams illustrating a procedure in which UE registers with a network. 
           [0014]      FIG. 3A  is a flow diagram illustrating an attach process of UE according to the first embodiment of the present invention. 
           [0015]      FIG. 3B  is a flow diagram illustrating an NAS message reroute process according to the first embodiment of the present invention. 
           [0016]      FIG. 3C  is a flow diagram illustrating a process of registering UE in a network through MME/SGSN according to the first embodiment of the present invention. 
           [0017]      FIG. 4  is a flow diagram illustrating another NAS message reroute process according to the first embodiment of the present invention. 
           [0018]      FIG. 5  is a flow diagram illustrating a process in which the first MME registers UE in a network according to the first embodiment of the present invention. 
           [0019]      FIG. 6  is a flow diagram illustrating a process in which eNodeB registers UE in a network according to the first embodiment of the present invention. 
           [0020]      FIG. 7  is a flow diagram illustrating a process in which HeNB GW registers UE in a network according to the first embodiment of the present invention. 
           [0021]      FIG. 8  is a block diagram illustrating a configuration of the first MME according to the first embodiment of the present invention. 
           [0022]      FIG. 9  is a block diagram illustrating a configuration of eNodeB according to the first embodiment of the present invention. 
           [0023]      FIG. 10  is a block diagram illustrating a configuration of UE according to the first embodiment of the present invention. 
           [0024]      FIG. 11  is a flow diagram illustrating a process in which UE applies ACDC in a TAU procedure according to the second embodiment of the present invention. 
           [0025]      FIG. 12  is a flow diagram illustrating a process of applying ACDC in a TAU procedure according to the second embodiment of the present invention. 
           [0026]      FIG. 13  is a flow diagram illustrating another process in which UE applies ACDC in a TAU procedure according to the second embodiment of the present invention. 
           [0027]      FIG. 14  is a flow diagram illustrating another process of applying ACDC in a TAU procedure according to the second embodiment of the present invention. 
           [0028]      FIG. 15  is a block diagram illustrating a configuration of UE according to the second embodiment of the present invention. 
           [0029]      FIG. 16A  and  FIG. 16B  are flow diagrams illustrating a method for providing an MBMS service according to the third embodiment of the present invention. 
           [0030]      FIG. 17  is another flow diagram illustrating a method for providing an MBMS service according to the third embodiment of the present invention. 
           [0031]      FIG. 18  is a block diagram illustrating a configuration of MME according to the third embodiment of the present invention. 
           [0032]      FIG. 19  is a block diagram illustrating a configuration of MCE according to the third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Through the drawings, the same or similar reference numerals denote corresponding features consistently. Additionally, well known functions and configurations may not be described or illustrated in detail to avoid obscuring the subject matter of the present invention. 
         [0034]    Also, embodiments of the present invention will be described hereinafter by mainly targeting Long-Term Evolution (LTE) and Evolved Packet Core (EPC), which are a Radio Access Network (RAN) and a Core Network (CN) defined as standards by the 3rd Generation Partnership Project (3GPP), the essential concept of this invention may be favorably applied to any other communication system having a similar technical background without departing from the scope of this invention as will be apparent to those skilled in the art. 
         [0035]    The present invention may be embodied in many different forms without changing technical subject matters and essential features as will be understood by those skilled in the art. Therefore, embodiments set forth herein are exemplary only and not to be construed as a limitation. 
         [0036]    In embodiments, all steps and messages are not a target for selective implementation or omission. Additionally, in each embodiment, steps may not be always performed in the order described and may be changed in order. Similarly, delivery of messages may not be always performed in the order described and may be changed in order. Each step and messaging may be performed independently. 
         [0037]    The whole or parts of exemplary contents in embodiments are provided to promote understanding by showing a detailed embodiment of this invention. Therefore, the detailed contents may be regarded as expressing a part of method and apparatus proposed by this invention. Namely, with regard to such contents, a syntax-based approach may be more desirable than a semantics-based approach. While this disclosure has been particularly shown and described with reference to an exemplary embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of this disclosure as defined by the appended claims. 
         [0038]    The present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, the disclosed embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this invention to those skilled in the art. The principles and features of the present invention may be employed in varied and numerous embodiments without departing from the scope of the invention. 
         [0039]    The terms used in the present disclosure are only used to describe specific various embodiments, and are not intended to limit the present disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
         [0040]    It will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which are executed via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block or blocks. These computer program instructions may also be stored in a computer usable or computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. 
         [0041]    And each block of the flowchart illustrations may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. 
         [0042]    The term “unit”, as used herein, may refer to a software or hardware component or device, such as a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks. A unit may be configured to reside on an addressable storage medium and configured to execute on one or more processors. Thus, a module or unit may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided for in the components and modules/units may be combined into fewer components and modules/units or further separated into additional components and modules. 
       First Embodiment 
       [0043]      FIG. 1  is a diagram illustrating the structure of a communication system according to an embodiment of the present invention. According to this embodiment, the communication system may be an LTE-based mobile communication system. 
         [0044]    Referring to  FIG. 1 , as shown, a wireless access network of the LTE mobile communication system may be formed of an evolved Node B (also referred to as eNB, a base station, E-UTRAN, etc.)  130 , a mobility management entity (MME) 150, and a serving gateway (S-GW)  140 . 
         [0045]    User equipment (also referred to as UE, a terminal, etc.)  100  may access an external network through the eNB  130 , the S-GW  140 , and a PDN gateway (P-GW)  160 . In order to transmit or receive data through the P-GW, the UE should create a PDN connection, which may include at least one EPS bearer. 
         [0046]    An application function (AF)  110  is an apparatus that exchanges application-related information with a user at the level of application. 
         [0047]    A policy charging and rules function (PCRF)  120  is an apparatus that controls a policy associated with user&#39;s quality of service (QoS). A policy and charging control (PCC) rule corresponding to the above policy is delivered and applied to the P-GW  160 . 
         [0048]    The eNB  130  is a radio access network (RAN) node and corresponds to RNC of a UTRAN system and to BSC of a GERAN system. The eNB  130  is connected to the UE  100  in a radio channel and performs a role similar to that of the existing RNC/BSC. 
         [0049]    Since all user traffics including real-time services such as a voice over internet protocol (VoIP) are offered through a shared channel in LTE, an apparatus for collecting status information of UEs  100  and performing scheduling is needed. The eNB  130  is in charge of this. 
         [0050]    The S-GW  140  is an apparatus that offers a data bearer, and creates or removes the data bearer under the control of the MME  150 . 
         [0051]    The MME  150  is an apparatus that performs various control functions, and a single MME  150  may be connected with a plurality of eNBs. In this invention, a certain MME newly accessed by the UE  100  is referred to as a new MME  150 . Also, an MME accessed before attachment and a corresponding network entity are referred to as old MME/SGSN  152 . And also, an MME accessed by the UE  100  to access a dedicated core network is referred to as a dedicated MME  154 . 
         [0052]    The PCRF  120  is an entity that controls QoS of traffic and charging. 
         [0053]    Meanwhile, as mentioned above, the LTE system supports interworking with any access network other than 3GPP as well as E-UTRAN. If any non-3GPP access network is interworked, the non-3GPP access network may be connected to the PGW  160  directly or through an additional ePDG. For processing subscriber information or authentication with regard to the non-3GPP access network, a home subscriber server (HSS)  170  and an authentication, authorization and accounting (AAA) server may exchange information with each other and may also be realized as a signal entity. The term ePDG is exemplarily used for convenience. Even in case the non-3GPP access network is connected to the PGW directly or connected through any node, e.g., the S-GW, other than ePDG, an embodiment disclosed herein may be applied without any considerable modification. 
         [0054]      FIGS. 2A and 2B  are flow diagrams illustrating a procedure in which UE registers with a network. 
         [0055]    This registration procedure is also referred to as a network attachment. During this procedure, a default EPS bearer is created for always-on IP connectivity. 
         [0056]    Referring to  FIG. 2A , at step  201 , the UE  100  may transmit an attach request message to the eNB  130 . At step  202 , the eNB  130  that receives the attach request message may transmit the attach request message to a new MME  150 . 
         [0057]    The new MME  150  that receives the attach request message may transmit an identification request message for identifying UE to an old MME or serving GPRS support node (SGSN)  152  at step  203   a  and may receive an identification response message from the old MME/SGSN  152  at step  203   b . If the old MME/SGSN  152  and the new MME  150  fail to identify the UE  100 , the new MME  150  may transmit an identity request message to the UE  100  at step  204   a  and may receive an identity response message containing an international mobile subscriber identity (IMSI) from the UE  100  at step  204   b.    
         [0058]    If context of the UE  100  does not exist in the network, the UE  100 , the new MME  150  and the HSS  170  may perform an authentication/security procedure at step  205   a.    
         [0059]    After the authentication/security procedure, at step  205   b , the UE  100  may transmit a ciphered identity request message to the new MME  150  and may receive a ciphered identity response message from the new MME  150 . This step may be performed together with the authentication/security step  205   a.    
         [0060]    Thereafter, if the UE  100  sets a ciphered options transfer flag in the attach request message, the new MME  150  may transmit a ciphered options request message to the UE  100  at step  206   a  and may receive a ciphered options response message from the UE  100  at step  206   b.    
         [0061]    If there is activated bearer context for the UE  100  in the new MME  150 , the new MME  150  may transmit a delete session request message to the S-GW  140  at step  207   a . Then the S-GW  140 , the P-GW  160  and the PCRF  120  may terminate a session at step  207   b , and the S-GW  140  may transmit a delete session response message to the new MME  150  at step  207   c.    
         [0062]    If the MME is changed after the final detach, or if there is no valid subscriber context for the UE in the MME, the new MME  150  may transmit an update location request message to the HSS  170  at step  208 . Then the HSS  170  may transmit a cancel location message to the old MMS/SGSN  152  at step  209   a  and may receive a cancel location ACK message from the old MMS/SGSN  152  at step  209   b.    
         [0063]    If there is activated bearer context for the UE  100  in the old MME/SGSN  152 , the old MME/SGSN  152  may transmit a delete session request message to the S-GW  140  at step  210   a . Then the S-GW  140 , the P-GW  160  and the PCRF  120  may terminate a session at step  210   b , and the S-GW  140  may transmit a delete session response message to the old MME  150  at step  210   c . Thereafter, the HSS  170  may transmit an update location ACK message to the new MME  150  at step  211 . 
         [0064]      FIG. 2B  shows steps after the new MME  150  receives the update location ACK message in  FIG. 2A . 
         [0065]    Referring to  FIG. 2B , at step  212 , the new MME  150  may transmit a create session request message to the S-GW  140 . Then the S-GW  140  may create a session with the P-GW  160  and the PCRF  120  at steps  213 ,  214  and  215 , and may transmit a create session response message to the new MME  150  at step  216 . 
         [0066]    Thereafter, the new MME  150  may transmit an initial context setup request message, by inserting an attach accept message therein, to the eNB  130  at step  217 . 
         [0067]    The eNB  130  that receives this may transmit a radio resource control (RRC) connection reconfiguration message to the UE  100  at step  218 . If the UE  100  transmits an RRC connection reconfiguration complete message to the eNB  130  at step  219 , the eNB  130  may transmit an initial context setup response message to the new MME  150  at step  220 . 
         [0068]    Thereafter, the UE  100  may transmit a direct transfer message containing an attach complete message to the eNB  130  at step  221 , and the eNB  130  may deliver the attach complete message to the new MME  150  at step  222 . 
         [0069]    The new MME  150  that receives the initial context response message and the attach complete message may transmit a modify bearer request message to the S-GW  140  at step  223   a . The S-GW  140  and the P-GW  160  may perform a bearer modification at steps  223   b  and  223   c , and the S-GW  140  may transmit a modify bearer response message to the new MME  150  at step  224 . 
         [0070]    Thereafter, if a mobile equipment identity of the UE  100  is changed, the new MME  150  may transmit a notify request message to the HSS  170  at step  225  and may receive a notify response message from the HSS  170  at step  226 . 
         [0071]    Meanwhile, when the UE  100  transmits the attach request message to the eNB  130  at step  201 , this attach request message may be contained in an RRC connection setup complete message that is transmitted from the UE to the eNB. Also, at step  202 , the eNB may transmit an initial UE message, which is an S  1 -MME control message containing the attach request message, to the new MME  150 . 
         [0072]    At this time, a core network to which the new MME  150  receiving the attach request message from the UE  100  belongs may be not identical to a dedicated core network (DCN) of the UE. This dedicated core network may be used for allowing an operator to offer a particular function or for separating specific UE or subscriber. For example, the dedicated core network may be used for separating subscribers for machine-to-machine (M2M) communication or separating subscribers of a specific company. 
         [0073]    The UE needs to access the DCN corresponding to a usage type thereof and then be offered a suitable service. However, if the eNB  130  fails to select the DCN, it may be required to deliver a message, transmitted to the MME/SGSN  150 , to a dedicated MME/SGSN  154  contained in the DCN such that the UE can be serviced by the DCN. Therefore, described hereinafter is a method for allowing the UE to be offered a service from the DCN by rerouting an NAS message when the eNB fails to select the DCN. 
         [0074]      FIG. 3A  is a flow diagram illustrating an attach process of UE according to the first embodiment of the present invention. Steps which are not described herein may follow, partially or totally, a normal EPS attach procedure. 
         [0075]    Referring to  FIG. 3A , the new MME/SGSN  150  may receive an attach request message from the UE  100  through the eNB  130  at steps  201  and  202 . Although the attach request message is used exemplarily herein, an NAS message including a tracking area update (TAU) message, a routing area update (RAU) message, or the like may be used alternatively. The attach request message may be delivered to the eNB  130  from the UE  100  in the form of being contained in an RRC message and also delivered to the MME/SGSN  150  from the eNB  130  in the form of being contained in an initial UE message (an RAN message). 
         [0076]    The attach request message may contain a globally unique temporary UE identity (GUTI)/P-temporary mobile subscriber identity (P-TMSI) and/or additional GUTI/P-TMSI. In case a GUTI is created from a P-TMSI and a routing area identifier (RAI) (this GUTI may be referred to as a mapped GUTI), or in case a P-TMSI is created from a GUTI (this P-TMSI may be referred to as a mapped P-TMSI), the attach request message may contain additional GUTI/P-TMSI. If the DCN is not considered, the additional GUTI/P-TMSI may be used for checking whether there is context of UE identified using such additional GUTI/P-TMSI in the new MME/SGSI  150 . 
         [0077]    The new MME  150  that receives the attach request message may transmit an identification request message to the old MME/SGSN  152  at step  203   a  and may receive an identification response message having MM context from the old MME/SGSN  152  at step  203   b . The identification response message having MM context may contain UE usage type information. In embodiments disclosed herein, the UE usage type information may refer to information about UE. Specifically, the UE usage type information may be used for steering the UE to a suitable DCN. Namely, the UE usage type information may be information that indicates a usage character of the UE. A mobile communication network operator may deploy a suitable DCN for such a UE usage character. 
         [0078]    The UE usage type information may be delivered in the form of being contained in the MM context or as an information element which is independent of the MM context. As will be described below in detail, a suitable DCN for serving the UE  100  may be identified from this UE usage type information, and the MME  150  may transmit suitable information to the eNB  130  so that the eNB  130  can retransmit the attach request message to a suitable DCN. Alternatively, contrary to this, the UE usage type information and/or any helpful information to select a DCN may be contained in an RRC message having the attach request message and then sent to the eNB  130 . 
         [0079]    At step  303   a , the new MME/SGSN  150  that receives the identification response message may have already obtained the UE usage type information of the UE  100 , and thus can determine whether to support a DCN depending on the UE usage type information of the UE  100 . 
         [0080]    As a result, if it is determined that the new MME/SGSN  150  fails to support a DCN of the UE, the new MME/SGSN  150  may reroute (also referred to as redirect) the attach request message such that the UE can receive a service from a suitable dedicated MME/SGSN  154 . 
         [0081]    As discussed above, the UE usage type information may be delivered through the identification response message transmitted from the old MME/SGSN  152  to the new MME  150  at step  203   b  or through an update location acknowledgement message transmitted from the HSS  170  to the new MME  150  at step  211 . The update location acknowledgement message is a message delivered to the new MME  150  from the HSS  170  at step  211 , and the HSS  170  may deliver subscription data to the new MME  150 . At this time, the UE usage type information may be contained in the subscription data or delivered separately from the subscription data. Therefore, a redirection process of a non-access stratum (NAS) message to be described below may be performed after step  203   b  or after step  211 . Also, the HSS  170  may deliver the UE usage type information to the MME  150  at step  205   a.    
         [0082]    Although an example of rerouting the attach request message is described above, this is not considered as a limitation of the present invention. Namely, this invention relates to a process of rerouting the NAS message, and this rerouting process may be performed during the attach procedure, the TAU procedure, and the RAU procedure. 
         [0083]      FIG. 3B  is a flow diagram illustrating an NAS message reroute process according to the first embodiment of the present invention. 
         [0084]    Referring to  FIG. 3B , in case the new MME/SGSN  150  that becomes aware of the UE usage type applied to the UE  100  through step  203   b , step  205   a , and/or step  211  fails to support the DCN of the UE  100 , the new MME/SGSN  150  may deliver, at step  300 , a message for rerouting the NAS message to MME/SGSN corresponding to characteristics of UE. Herein, the MME/SGSN corresponding to characteristics of UE may refer to the dedicated MME/SGSN  154  located in the DCN corresponding to the UE usage type information of UE. In this case, a message (hereinafter, referred to as a redirection message) for rerouting the NAS message may be defined as a new RAN message named a reroute command message, reroute message, or a reroute NAS request message. 
         [0085]    The redirection message (i.e., the RAN message) may contain at least one of MME UE S1AP ID, eNB UE S1AP ID, (revised) NAS-PDU (Protocol Data Unit), GUTI, GUMMEI (Globally Unique MME Identity), MMEGI (MME Group Identifier) or Null NRI (Network Resource Identifier)/SGSN group ID, GUMMEI type, S-TMSI (SAE Temporary Mobile Subscriber Identity), TAI (Tracking Area Identity) and RRC establishment cause, additional GUTI/P-TMSI, and information delivered to the MME/SGSN  150  by the eNB  130 . 
         [0086]    MME UE S1AP ID is an identifier allocated by the new MME/SGSN  150  to identify the UE  100  on the S1 interface. Also, eNB UE S1AP ID is an identifier allocated by the eNB  130  to identify the UE  100  on the S1 interface. Using eNB UE S1AP ID, the eNB  130  may determine which UE needs redirection. This eNB UE S1AP ID contained in the redirection message by the new MME/SGSN  150  may be identical to eNB UE S1AP ID contained in an S1 message received through at least one of steps  202 ,  204   b ,  205   a ,  205   b  and  206   b.    
         [0087]    NAS-PDU contained in the redirection message may be an NAS message received from the eNB. For example, the NAS message may be an attach request message. This attach request message may be identical to the attach request message received by the new MME/SGSN  150  at step  202  or a slightly revised version thereof. For example, the EPS mobile identity field of the attach request message may be revised to GUTI allocated by the new MME/SGSN  150 . In another example, NAS-PDU may not be revised and GUTI may be delivered as an independent information element. In this case, the eNB  130  may deliver GUTI, received at step  300 , as an independent information element to the dedicated MME/SGSN  154  when an initial UE message or uplink NAS transport message is transmitted at step  310 . 
         [0088]    GUMMEI, MMEGI or Null-NRI/SGSN group ID, GUMMEI type, S-TMSI, and additional GUTI/P-TMSI are information that may be used for the eNB  130  to select the dedicated MME/SGSN  154 . The new MME/SGSN  150  may set at least one of GUMMEI, MMEGI or Null-NRI/SGSN group ID, GUMMEI type, and S-TMSI as a value associated with the dedicated MME/SGSN  154  and then transmit it to the eNB  130 . 
         [0089]    MMEGI or Null-NRI/SGSN group ID may be used to identify a DCN in a PLMN (Public Land Mobile Network). 
         [0090]    GUMMEI may directly indicate the dedicated MME  154 . GUMMEI may be formed of a PLMN identifier, MMEGI, and MMEC. The new MME may set a PLMN identifier as a serving PLMN of the UE  100  (namely, identical to a PLMN part of TAI), set MMEGI as a value corresponding to a dedicated MME group, and set MMEC (MME Code) as a value corresponding to MMEC of the new MME. The eNB  130  may select a dedicated MME group by using PLMN and MMEGI, and also select dedicated MME by referring to MMEC. In another example, GUMMEI may be a GUMMEI part of additional GUTI contained in the attach request message. MMEGI may be information corresponding to a dedicated MME group. This may be MMEGI included in MMEI (MME Identifier) contained in GUMMEI of additional GUTI contained in the attach request message. 
         [0091]    TAI and RRC establishment cause may be information received from the eNB  130  together with the attach request message by the new MME  150 . 
         [0092]    Additional GUTI/P-TMSI may be contained in the reroute NAS message request only in case the attach request message received by the MME/SGSN  150  contains the additional GUTI/P-TMSI. Namely, if additional GUTI/P-TMSI is contained in the attach request message received at step  202 , the MME/SGSN  150  may insert the additional GUTI/P-TMSI into the reroute NAS message request to be transmitted at step  300 . 
         [0093]    The eNB  130  that receives at least one kind of information mentioned above may insert the TAI and/or RRC establishment cause, received at step  300 , into a message to be transmitted to the dedicated MME  154  at step  310 . The new MME  150  may also transmit additional GUTI contained in the attach request message. This additional GUTI may be delivered only when the new MME  150  fails to find UE context by means of additional GUTI and when old GUTI denotes that GUTI is mapped with P-TMSI (P-temporary mobile subscriber identity) and RAI (routing area identifier). 
         [0094]    The information delivered to the new MME/SGSN  150  by the eNB  130 , which is contained in a message delivered by the eNB  130  at step  300 , may mean information contained in the first initial UE message delivered by the eNB  130  at step  202 . The information may include all or part of information delivered at step  202 . According to 3GPP Release 13, the first initial UE message is formed as shown in Table 1. 
         [0000]    
       
         
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 IE type and 
                 Semantics 
                   
                 Assigned 
               
               
                 IE/Group Name 
                 Presence 
                 reference 
                 description 
                 Criticality 
                 Criticality 
               
               
                   
               
             
             
               
                 Message Type 
                 M 
                   
                   
                 YES 
                 ignore 
               
               
                 eNB UE S1AP ID 
                 M 
                   
                   
                 YES 
                 reject 
               
               
                 NAS-PDU 
                 M 
                   
                   
                 YES 
                 reject 
               
               
                 TAI 
                 M 
                   
                 Indicating the 
                 YES 
                 reject 
               
               
                   
                   
                   
                 Tracking Area from 
               
               
                   
                   
                   
                 which the UE has 
               
               
                   
                   
                   
                 sent the NAS 
               
               
                   
                   
                   
                 message. 
               
               
                 E-UTRAN CGI 
                 M 
                   
                 Indicating the E- 
                 YES 
                 ignore 
               
               
                   
                   
                   
                 UTRAN CGI from 
               
               
                   
                   
                   
                 which the UE has 
               
               
                   
                   
                   
                 sent the NAS 
               
               
                   
                   
                   
                 message. 
               
               
                 RRC 
                 M 
                   
                   
                 YES 
                 Ignore 
               
               
                 Establishment 
               
               
                 Cause 
               
               
                 S-TMSI 
                 O 
                   
                   
                 YES 
                 reject 
               
               
                 CSG Id 
                 O 
                   
                   
                 YES 
                 reject 
               
               
                 GUMMEI 
                 O 
                   
                   
                 YES 
                 reject 
               
               
                 Cell Access Mode 
                 O 
                   
                   
                 YES 
                 reject 
               
               
                 GW Transport 
                 O 
                 Transport 
                 Indicating GW 
                 YES 
                 ignore 
               
               
                 Layer Address 
                   
                 Layer 
                 Transport Layer 
               
               
                   
                   
                 Address 
                 Address if the GW 
               
               
                   
                   
                   
                 is collocated with 
               
               
                   
                   
                   
                 eNB. 
               
               
                 Relay Node 
                 O 
                   
                 Indicating a relay 
                 YES 
                 reject 
               
               
                 Indicator 
                   
                   
                 node. 
               
               
                 GUMMEI Type 
                 O 
                 ENUMERATED 
                   
                 YES 
                 ignore 
               
               
                   
                   
                 (native, 
               
               
                   
                   
                 mapped, . . . ) 
               
               
                 Tunnel 
                 O 
                 Tunnel 
                 Indicating HeNB&#39;s 
                 YES 
                 ignore 
               
               
                 Information for 
                   
                 Information 
                 Local IP Address 
               
               
                 BBF 
                   
                   
                 assigned by the 
               
               
                   
                   
                   
                 broadband access 
               
               
                   
                   
                   
                 provider, UDP port 
               
               
                   
                   
                   
                 Number. 
               
               
                 SIPTO L-GW 
                 O 
                 Transport 
                 Indicating SIPTO 
                 YES 
                 ignore 
               
               
                 Transport Layer 
                   
                 Layer 
                 L-GW Transport 
               
               
                 Address 
                   
                 Address 
                 Layer Address if 
               
               
                   
                   
                   
                 the SIPTO L-GW is 
               
               
                   
                   
                   
                 collocated with 
               
               
                   
                   
                   
                 eNB. 
               
               
                 LHN ID 
                 O 
                   
                   
                 YES 
                 ignore 
               
               
                 MME Group ID 
                 O 
                   
                   
                 YES 
                 ignore 
               
               
                   
               
             
          
         
       
     
         [0095]    Among various kinds of information shown in Table 1, certain information may be known semipermanently to the eNB  130  and certain information may need to be received again since the eNB  130  has already received it from the UE  100  and then stores it. For example, GW Transport Layer Address is inherent information of the eNB  130  and thus known to the eNB  130 . Also, RRC Establishment Cause is information received from the UE  100  at step  201 . 
         [0096]    However, since backhaul is not very congested in general, the redirection message delivered at step  300  may contain the first initial UE message completely for simplification of the operation of the MME/SGSN  150 . 
         [0097]    Additionally, the redirection message may contain other S1 message, e.g., an uplink NAS transport message. This is for encompassing various cases in which the UE delivers the NAS message. For example, the UE may register a new location in the MME/SGSN  150  after handover. In this case, since the NAS message for location registration is not the initial S1 message for the UE, the NAS message may be delivered through the uplink NAS transport message rather than through the initial UE message. In this case, the redirection message delivered at step  300  may contain the uplink NAS transport message. 
         [0098]    For selecting the dedicated MME/SGSN  154 , the eNB  130  may use at least one of MMEGI or Null-NRI/SGSN group ID and additional GUTI/P-TMSI which are received at step  300 . Specifically, the eNB  130  may select MME/SGSN in a DCN indicated by MMEGI or Null-NRI/SGSN group ID. If additional GUTI/P-TMSI identifies MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN group ID, MME/SGSN identified by additional GUTI/P-TMSI may be selected. 
         [0099]    The eNB  130  that selects the dedicated MME/SGSN  154  may transmit the second initial UE message or uplink NAS transport message to the dedicated MME/SGSN  154  at step  310 . Herein, while an initial UE message transmitted to the new MME by the eNB at step  202  is referred to as the first initial UE message, an initial UE message transmitted to the dedicated MME by the eNB at step  310  is referred to as the second initial UE message. If it is not possible to find selectable MME/SGSN in a DCN identified by means of MMEGI or Null-NRI/SGSN group ID, the eNB  130  may select MME/SGSN in the default DCN or select again the MME/SGSN  150 . 
         [0100]    The above discussion may be applied to only a network which is not shared by several PLMNs. In a network shared by several PLMNs, a DCN may be selected using the following method. 
         [0101]    The eNB  130  may select the dedicated MME/SGSN  154  by using a PLMN (CN operator) selected by the UE  100  and at least one of MMEGI or Null-NRI/SGSN group ID and additional GUTI/P-TMSI which are received at step  300 . Specifically, the eNB  130  may select MME/SGSN in a DCN indicated by MMEGI or Null-NRI/SGSN group ID within the PLMN selected by the UE  100 . If additional GUTI/P-TMSI identifies MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN group ID within the PLMN selected by the UE  100 , the eNB  130  may select MME/SGSN identified by additional GUTI/P-TMSI. In this case, the PLMN in the additional GUTI/P-TMSI may be ignored. 
         [0102]    Namely, in case the eNB  130  receives additional GUTI/P-TMSI in the network shared by several PLMNs, the eNB  130  may select (if possible) a core network indicated by a combination of the following information:
       PLMN selected by the UE  100 ;   MMEGI or Null-NRI/SGSN group ID; and   Most significant 8 bits of MMEC or NRI in additional GUTI/P-TMSI.       
 
         [0106]    In this case, a method for identifying the PLMN selected by the UE  100  at the eNB  130  may include at least one of the followings. 
         [0107]    The eNB  130  may store and use information about the PLMN selected by the UE  100  by receiving it from the UE  100  at step  201 . Also, the eNB  130  may identify the PLMN selected by the UE  100  from information contained in the redirection message (S1 message) received at step  300 . In the latter case, the eNB  130  may extract a PLMN ID part of TAI information in the redirection message (S1 message) and thereby identify the PLMN selected by the UE. 
         [0108]    The eNB  130  that selects the dedicated MME/SGSN  154  may transmit the second initial UE message or uplink NAS transport message to the dedicated MME/SGSN  154  at step  310 . If it is not possible to find selectable MME/SGSN in a DCN identified by means of MMEGI or Null-NRI/SGSN group ID, the eNB  130  may select MME/SGSN in the default DCN or select again the MME/SGSN  150 . Herein, the second initial UE message (S1 message) delivered at step  310  may be the S1 message contained in the redirection message received at step  300 . 
         [0109]    The second initial UE message of step  310  may include information contained in the first initial UE message transmitted at step  202  and further include at least one of MME UE S1AP ID, NAS-PDU, GUTI, S-TMSI, and additional GUTI. Namely, the second initial UE message delivered at step  310  may include the NAS message (e.g., the attach request message) delivered to the MME/SGSN  150  at step  202 . The dedicated MME  154  that receives this may check, using at least one of additional GUTI and S-TMSI, whether there is context of the UE therein. If there is context of the UE, the existing UE context may be reused without obtaining context from any other node (the new MME  150  and/or the HSS  170 ). For example, context of the UE may be used for mobility management of the UE. At least one of NAS-PDU, GUTI, MME UE S1AP ID, and S-TMSI delivered at step  300  may be also delivered at step  320  through step  310 . 
         [0110]    Thereafter, at step  320 , the new MME  150  may receive an MM context request message from the dedicated MME  154 . At this time, the MM context request message may be an identification request message. The dedicated MME  154  may transmit the attach request message received from the new MME  150  through the eNB  130 . Then, the new MME  150  may verify the attach request message and adjust an uplink NAS count in MME at step  303   a  in order to prevent errors at verification step. For example, even in case verification is made, the uplink NAS count may be not increased. The operation related to step  303   a  may be performed after step  205   a.    
         [0111]    When the MME that sends the identification request at step  320  is the dedicated MME  154 , and/or when the reroute command message has been already sent for the UE identified by means of information contained in the identification request message, the new MME  150  may skip verification through NAS-PDU. In another example, when an indicator for indicating a verification skip is delivered at step  320 , the new MME  150  may skip the verification step. As discussed above, verification is performed in case the NAS count is adjusted at step  303   a . The new MME  150  may identify the UE  100  by using at least one of GUTI, MME UE S1AP ID, and S-TMSI contained in the identification request message for requesting MM context, and then deliver MM context corresponding to the UE by using an identification response message at step  340 . 
         [0112]    Thereafter, steps  204  to  211  shown in  FIG. 2  may be performed. The difference is that the dedicated MME  154  is involved instead of the new MME  150 . 
         [0113]      FIG. 3C  is a flow diagram illustrating a process of registering UE in a network through MME/SGSN according to the first embodiment of the present invention. 
         [0114]    Referring to  FIG. 3C , steps  312  to  326  shown in  FIG. 3C  may be identical to steps  212  to  226  previously discussed in  FIG. 2B . However, contrary to  FIG. 2B , the process of  FIG. 3C  involves the dedicated MME/SGSN  154  instead of the new MME  150  in the registration procedure. Details will be omitted herein since the same is discussed in  FIG. 2B . Using the process discussed in  FIGS. 3A to 3C , the UE can be offered a service through the DCN. In this case, the UE  100  may transit a message to a core network through two or more eNBs rather than through a single eNB only. For example, this message may be transmitted to the core network through HeNB, HeNB GW, MME or UE, relay node, donor eNB, and MME. 
         [0115]      FIG. 4  is a flow diagram illustrating another NAS message reroute process according to the first embodiment of the present invention. 
         [0116]    Referring to  FIG. 4 , the NAS message reroute process in case HeNB (home eNB)/DeNB (donor eNB) and HeNB GW (HeNB gateway)/RN (relay node) are included is shown. 
         [0117]    The new MME may transmit the redirection message to the HeNB GW/DeNB at step  400 . The redirection message may mean a message for rerouting the NAS message and may include a reroute command or a reroute NAS request message. 
         [0118]    Considering that a UE-associated message is not terminated at the HeNB GW/DeNB except for unusual circumstance, steps  410  and  420  may be performed in spite of inefficiency in signaling. Also, in case an initial UE message needs revision, steps  410  and  420  may be performed. 
         [0119]    Specifically, the HeNB GW/DeNB may transmit a reroute command to the HeNB/RN at step  410  and receive a response message (S1 (NAS EMM)) at step  420 . 
         [0120]    However, if the message delivered at step  400  contains the entire information of the attach request message delivered at step  202  (e.g., in case the first initial UE message delivered at step  202  is completely contained in the redirection message delivered at step  400 ), the HeNB GW and/or DeNB may perform a message redirection without performing steps  410  and  420  even though not storing information received from the HeNB and/or relay node. Therefore, in this case, the HeNB GW/DeNB may not transmit the reroute command message to the HeNB. 
         [0121]    Additionally, step  400  may correspond to step  300  in  FIG. 3 . Specifically, information contained in the redirection message may be identical to information contained in the redirection message transmitted at step  300 . 
         [0122]    Thereafter, the HeNB GW may select a DCN at step  430 . This step  430  may correspond to a process of selecting a core network node performed by the eNB  300  after step  300  in  FIG. 3 . 
         [0123]    The HeNB GW that selects the DCN may transmit the S1 message to the dedicated MME at step  440 . The step  440  (and step  420 ) may correspond to step  310  in  FIG. 3 , and detailed description thereof will be omitted. 
         [0124]      FIG. 5  is a flow diagram illustrating a process in which the first MME registers UE in a network according to the first embodiment of the present invention. 
         [0125]    Referring to  FIG. 5 , the first MME may receive an initial UE message from the eNB at step  510 . The initial UE message may contain an NAS message received from the UE by the eNB. The NAS message may be transmitted to the eNB from the UE in the form of being contained in an RRC message, and then transmitted to the first MME in the form of being contained in the initial UE message. 
         [0126]    The first MME that receives the first message may transmit an identification request message to the second MME at step  520 . Also, the first MME may receive an identification response message for the identification request message at step  530 . 
         [0127]    The identification response message may contain UE usage type information. The UE usage type information is information for indicating a usage type of UE and may be included in the MM context contained in the identification response message or may be transmitted as an information element which is independent of the MM context. 
         [0128]    Additionally, the UE usage type information may be contained in an update location ACK message received from the HSS, and the following steps may be performed after the eNB receives the update location ACK message. This embodiment will be discussed regarding an example in which the UE usage type information is contained in the identification response message. 
         [0129]    At step  540 , the first MME that receives the identification response message may identify a DCN corresponding to the UE usage type information and then may check whether the first MME can support the DCN. 
         [0130]    As the result of check, if it is determined that the first MME can support the DCN, the first MME may perform a subsequent network registration process of UE at step  550 . 
         [0131]    As the result of check, if it is determined that the first MME cannot support the DCN, the first MME may enable the UE to be serviced from a suitable dedicated MME through redirection of the attach request message. 
         [0132]    Therefore, at step  560 , the first MME may transmit a redirection message to the eNB so as to reroute the attach request message. At this time, the redirection message may include a reroute command message or a reroute NAS request message. 
         [0133]    The redirection message may have at least one of MME UE S1AP ID, eNB UE S1AP ID, (revised) NAS-PDU (Protocol Data Unit), GUTI, GUMMEI (Globally Unique MME Identity), MMEGI (MME Group Identifier) or Null NRI (Network Resource Identifier)/SGSN group ID, GUMMEI type, S-TMSI (SAE Temporary Mobile Subscriber Identity), TAI (Tracking Area Identity) and RRC establishment cause, additional GUTI/P-TMSI, and information delivered to the MME/SGSN by the eNB. 
         [0134]    NAS-PDU contained in the redirection message may include an NAS message. This embodiment uses an attach request message as the NAS message. Namely, the first MME may insert the received attach request message in the redirection message and then transmit it to the eNB. Also, the first MME may insert the attach request message with partially revised information in the redirection message and then transmit it to the eNB. 
         [0135]    Additionally, the redirection message may contain totally the initial UE message received from the eNB. 
         [0136]    Details of information contained in the redirection message are discussed earlier in  FIG. 3B , so the repetition is omitted herein. 
         [0137]    The first MME that transmits the redirection message may receive an identification request message from the dedicated MME at step  570 . The identification request message may have the attach request message. 
         [0138]    The first MME that receives the identification request message may check or verify the attach request message at step  580  and then adjust an NAS count in the first MME in order to prevent errors at the check or verification step. For example, even in case the attach request message is checked or verified, the uplink NAS count may be not increased. 
         [0139]    Additionally, the first MME may identify the UE by using at least one of GUTI, MME UE S1AP ID, and S-TMSI which are contained in the identification request message. Then, at step  590 , using an identification response message, the first MME may transmit MM context corresponding to the identified UE to the dedicated MME. 
         [0140]      FIG. 6  is a flow diagram illustrating a process in which eNodeB registers UE in a network according to the first embodiment of the present invention. 
         [0141]    Referring to  FIG. 6 , the eNB may receive an NAS message contained in an RRC message at step  610 . Since the NAS message may include an attach request message, a TAU message, an RAU message, etc., this process may be performed during an attach procedure, a TAU procedure, or an RAU procedure. 
         [0142]    The eNB that receives the NAS message may transmit the first initial UE message having the NAS message to the first MME at step  620 . In this case, since information contained in the first initial UE message is discussed earlier in  FIG. 3B , the repetition is omitted herein. 
         [0143]    If the first MME is not MME contained in the DCN, the first MME may transmit a redirection message for rerouting the NAS message to the eNB. 
         [0144]    Therefore, at step  630 , the eNB may receive the redirection message for rerouting the NAS message. 
         [0145]    The redirection message may have at least one of MME UE S1AP ID, eNB UE S1AP ID, (revised) NAS-PDU (Protocol Data Unit), GUTI, GUMMEI (Globally Unique MME Identity), MMEGI (MME Group Identifier) or Null NRI (Network Resource Identifier)/SGSN group ID, GUMMEI type, S-TMSI (SAE Temporary Mobile Subscriber Identity), TAI (Tracking Area Identity) and RRC establishment cause, additional GUTI/P-TMSI, and information delivered to the MME/SGSN by the eNB. 
         [0146]    The eNB that receives the redirection message may select the second MME by using information contained in the redirection message at step  640 . In this case, the second MME may refer to a dedicated MME located in the DCN. 
         [0147]    A method for selecting the second MME by using information contained in the redirection message is as follows. 
         [0148]    The first MME may set, as a value associated with the dedicated MME/SGSN  154 , at least one of GUMMEI, MMEGI or Null-NRI/SGSN Group ID, GUMMEI Type, and S-TMSI and transmit it to the eNB. Then the eNB may select the dedicated MME by using information set as the value associated with the dedicated MME. MMEGI or Null-NRI/SGSN Group ID may be used to identify a DCN in a PLMN. GUMMEI may directly indicate the dedicated MME. Specifically, GUMMEI may be formed of a PLMN identifier, MMEGI, and MMEC. In this case, a PLMN identifier may be set as a serving PLMN of the UE  100  (namely, identical to a PLMN part of TAI at step  102 ), MMEGI may be set as a value corresponding to a dedicated MME group, and MMEC (MME Code) may be set as a value corresponding to MMEC of the first MME. Therefore, the eNB may select a dedicated MME group by using a PLMN identifier and MMEGI, and then select a dedicated MME by referring to MMEC. 
         [0149]    Additionally, the eNB may select MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID. If additional GUTI/P-TMSI identifies MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID, the eNB may select MME/SGSN identified by additional GUTI/P-TMSI. 
         [0150]    Meanwhile, in a network shared by several PLMNs, a DCN may be selected using the following method. 
         [0151]    The eNB may select a dedicated MME by using at least one of PLMN, MMEGI or Null-NRI/SGSN Group ID, and additional GUTI/P-TMSI which are selected by the UE. The eNB may select MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID in PLMN selected by the UE. If additional GUTI/P-TMSI identifies MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID, the eNB may select MME/SGSN identified by additional GUTI/P-TMSI. Namely, in case the eNB receives additional GUTI/P-TMSI, the eNB may select a core network by considering PLMN, MMEGI or Null-NRI/SGSN Group ID, and most significant 8 bits of MMEC or NRI in additional GUTI/P-TMSI which are selected by the UE. In this case, PLMN in additional GUTI/P-TSMI may be ignored. 
         [0152]    A method in which the eNB identifies PLMN selected by the UE may be a method of storing PLMN selected by and received from the UE and then using stored information, or a method of using PLMN contained in the redirection message and selected by the UE. 
         [0153]    In case of using information contained in the redirection message, the eNB may identify PLMN selected by the UE by extracting PLMN ID of TAI information contained in the redirection message. 
         [0154]    Selection of DCN and dedicated MME by the eNB may be similar to that discussed in  FIG. 3B . 
         [0155]    The eNB that selects the dedicated MME may transmit the second initial UE message containing an NAS message to the dedicated MME at step  650 . In this case, the second initial UE message may include the entire information contained in the redirection message. Also, the eNB may transmit an uplink NAS transport message to the dedicated MME. If it is not possible to find selectable MME in a DCN, the eNB may select MME in the default DCN or select again the MME. 
         [0156]    Using the above-discussed process, the eNB may enable the UE to be offered service through a DCN. 
         [0157]      FIG. 7  is a flow diagram illustrating a process in which HeNB GW registers UE in a network according to the first embodiment of the present invention. 
         [0158]    Referring to  FIG. 7 , the first MME that identifies a UE usage type may transmit a redirection message to HeNB GW in case of failing to support a DCN corresponding to the UE usage type. Details are similar to discussed above, so the repetition is omitted herein. 
         [0159]    Therefore, the HeNB GW may receive the redirection message at step  710 . The redirection message may include a reroute command or a reroute NAS request message. 
         [0160]    In this case, the redirection message may include an NAS message received from the UE and delivered to the first MME. 
         [0161]    Since a UE-associated message is not terminated at the HeNB GW/DeNB except for unusual circumstance, the HeNB GW may transmit the redirection message to the HeNB at step  720  in spite of inefficiency in signaling. Also, the HeNB GW may receive a response message (an initial UE message) at step  730 . Also, in case the initial UE message needs revision, the HeNB GW may transmit the redirection message to the HeNB and then receive the response message. 
         [0162]    However, if the redirection message has the entire information contained in the attach request message, the HeNB GW may perform step  740  without performing steps  720  and  730 . 
         [0163]    At step  740 , the HeNB GW may select the DCN and dedicated MME. The HeNB GW may select the dedicated MME by using information contained in the redirection message. Details are similar to those discussed above, so the repetition is omitted herein. 
         [0164]    The HeNB GW that selects the dedicated MME may transmit the initial UE message having the redirection message to the dedicated MME at step  750 . Using the above-discussed process, the HeNB GW may enable the UE to be offered service through a DCN. 
         [0165]      FIG. 8  is a block diagram illustrating a configuration of the first MME according to the first embodiment of the present invention. 
         [0166]    Referring to  FIG. 8 , the first MME may be formed of a communication unit  810 , a control unit  820 , and a storage unit  830 . 
         [0167]    The communication unit  810  may perform communication with other network entities such as the eNB, the second MME, or the like. 
         [0168]    The control unit  820  may control the reception of an initial UE message from the eNB. The initial UE message may contain an NAS message transmitted from the UE. 
         [0169]    Additionally, the control unit  820  may control the transmission and reception of an identification request message and an identification response message to and from the second MME, and may check UE usage type information contained in the received identification response message. Also, the control unit  820  may control the reception of an update location ACK message from the HSS, and may check UE usage type information contained in the update location ACK message. The control unit  820  may determine whether to support a DCN according to the UE usage type information. 
         [0170]    In case of failing to support the DCN as the result of determination, the control unit  820  may create a redirection message for rerouting the NAS message so as to allow the UE to be serviced from a dedicated MME, and then may transmit the redirection message to the eNB. The redirection message may include all or part of information contained in the NAS message. Additionally or alternatively, the redirection message may include all or part of information contained in the initial UE message. 
         [0171]    Namely, the control unit  820  may deliver the received NAS message, as it is, to the eNB so that the eNB can forward the NAS message to the dedicated MME. Therefore, the UE can be offered a service from the DCN. 
         [0172]    Additionally, the control unit  820  may insert, in the redirection message, at least one of MME UE S1AP ID, eNB UE S1AP ID, (revised) NAS-PDU (Protocol Data Unit), GUTI, GUMMEI (Globally Unique MME Identity), MMEGI (MME Group Identifier) or Null NRI (Network Resource Identifier)/SGSN group ID, GUMMEI type, S-TMSI (SAE Temporary Mobile Subscriber Identity), TAI (Tracking Area Identity) and RRC establishment cause, additional GUTI/P-TMSI, and information delivered to the MME/SGSN by the eNB. Therefore, using such information, the eNB may determine the dedicated MME. 
         [0173]    Further, the control unit  820  may control the reception of an identification request message from the dedicated MME. After this reception, the control unit  820  may check or verify the NAS message contained in the identification request message. 
         [0174]    Further, the control unit  820  may identify the UE by using at least one of GUTI, MME UE S1AP ID, and S-TMSI which are contained in the received identification request message. Therefore, using an identification response message, the control unit  820  may transmit MM context corresponding to the identified UE to the dedicated MME. 
         [0175]    The storage unit  830  may store information contained in the initial UE message received from the eNB. Also, the storage unit  830  may store information contained in the identification response message received from the second MME and information contained in the update location ACK message received from the HSS. Therefore, information stored in the storage unit  830  may be used when the control unit  820  checks whether the DCN corresponding to the UE usage type information can be supported. Also, such information may be used when the control unit  820  creates the direction message. 
         [0176]      FIG. 9  is a block diagram illustrating a configuration of eNodeB according to the first embodiment of the present invention. 
         [0177]    Referring to  FIG. 9 , the eNB may be formed of a communication unit  910 , a control unit  920 , and a storage unit  930 . 
         [0178]    The communication unit  910  may perform communication with other network entities such as the first MME, the UE, the dedicated MME, or the like. 
         [0179]    The control unit  920  may control the reception of an NAS message contained in an RRC message from the UE. The control unit  920  may create the first initial UE message including the received NAS message and then transmit it to the first MME. Information contained in the first initial UE message is discussed earlier in  FIG. 3B , so the repetition is omitted herein. 
         [0180]    In case the first MME that receives the first initial UE message from the eNB is not a dedicated MME, the control unit  920  may receive a direction message from the first MME. The redirection message may include all or part of information contained in the NAS message. Additionally or alternatively, the redirection message may include all or part of information contained in the first initial UE message. 
         [0181]    When the redirection message having the NAS message or the first initial UE message is received, the control unit  920  may forward the received message to the dedicated MME. Alternatively, the control unit  920  may create the second initial UE message having the NAS message contained in the redirection message and then transmit it to the dedicated MME. 
         [0182]    Therefore, the control unit  920  should determine the dedicated MME. A method for determining the dedicated MME is as follows. 
         [0183]    The redirection message may contain at least one of MME UE S1AP ID, eNB UE S1AP ID, (revised) NAS-PDU (Protocol Data Unit), GUTI, GUMMEI (Globally Unique MME Identity), MMEGI (MME Group Identifier) or Null NRI (Network Resource Identifier)/SGSN group ID, GUMMEI type, S-TMSI (SAE Temporary Mobile Subscriber Identity), TAI (Tracking Area Identity) and RRC establishment cause, additional GUTI/P-TMSI, and information delivered to the MME/SGSN by the eNB. 
         [0184]    The first MME may set, as a value associated with the dedicated MME/SGSN  154 , at least one of GUMMEI, MMEGI or Null-NRI/SGSN Group ID, GUMMEI Type, and S-TMSI and transmit it to the eNB. Then the control unit  920  may select the dedicated MME by using information which is set as the value associated with the dedicated MME. 
         [0185]    MMEGI or Null-NRI/SGSN Group ID may be used to identify a DCN in a PLMN. 
         [0186]    GUMMEI may directly indicate the dedicated MME. Specifically, GUMMEI may be formed of a PLMN identifier, MMEGI, and MMEC. In this case, a PLMN identifier may be set as a serving PLMN of the UE  100  (namely, identical to a PLMN part of TAI at step  102 ), MMEGI may be set as a value corresponding to a dedicated MME group, and MMEC (MME Code) may be set as a value corresponding to MMEC of the first MME. Therefore, the control unit  920  may select a dedicated MME group by using a PLMN identifier and MMEGI, and then select a dedicated MME by referring to MMEC. 
         [0187]    Additionally, the control unit  920  may select MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID. If additional GUTI/P-TMSI identifies MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID, MME/SGSN identified by additional GUTI/P-TMSI may be selected. 
         [0188]    Meanwhile, in a network shared by several PLMNs, the control unit  920  may select a DCN by using the following method. 
         [0189]    The control unit  920  may select a dedicated MME by using at least one of PLMN, MMEGI or Null-NRI/SGSN Group ID, and additional GUTI/P-TMSI which are selected by the UE. The control unit  920  may select MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID in PLMN selected by the UE. If additional GUTI/P-TMSI identifies MME/SGSN in the DCN indicated by MMEGI or Null-NRI/SGSN Group ID, MME/SGSN identified by additional GUTI/P-TMSI may be selected. Namely, in case additional GUTI/P-TMSI is received, the control unit  920  may select a core network by considering PLMN, MMEGI or Null-NRI/SGSN Group ID, and most significant 8 bits of MMEC or NRI in additional GUTI/P-TMSI which are selected by the UE. In this case, PLMN in additional GUTI/P-TSMI may be ignored. 
         [0190]    In this case, the control unit  920  may control the storage unit  930  to store PLMN selected by and received from the UE, and may use stored information. Alternatively or additionally, the control unit  920  may identify PLMN selected by the UE through PLMN contained in the redirection message. 
         [0191]    If it is not possible to find selectable MME in a DCN, the eNB may select MME in the default DCN or select again the MME. 
         [0192]    Using the above-discussed process, the control unit  920  may enable the UE to be offered service through a DCN. 
         [0193]    The storage unit  930  may store information contained in the RRC message received from the eNB. Also, the storage unit  930  may store information contained in the identification response message received from the first MME. Such information stored in the storage unit  930  may be used for creating the first initial UE message or the second initial UE message. 
         [0194]      FIG. 10  is a block diagram illustrating a configuration of UE according to the first embodiment of the present invention. 
         [0195]    Referring to  FIG. 10 , the UE may be formed of a communication unit  1010 , a control unit  1020 , and a storage unit  1030 . 
         [0196]    The communication unit  1010  may perform communication with other network entities such as the eNB, the first MME, or the like. 
         [0197]    The control unit  1020  may create an RRC message having an NAS message and transmit the created RRC message to the eNB through the RRC layer. The NAS message may include at least one of an attach request message, a TAU message, and an RAU message. 
         [0198]    The NAS message may be contained in the first initial UE message transmitted to the first MME by the eNB. Also, the NAS message may be contained in the redirection message transmitted by the first MME. The eNB that receives the redirection message having the NAS message may create the second initial UE message having the NAS message and then transmit it to the dedicated MME. 
         [0199]    The storage unit  1030  may store the created NAS message. Also, the storage unit  1030  may store ID information for response to an ID request. Also, the storage unit  1030  may store authentication information. 
       Second Embodiment 
       [0200]    Hereinafter, a congestion control method and apparatus for an application according to the second embodiment of the present invention will be described. 
         [0201]    According as the number of transmission packets is increased in a network, the performance of the network is degraded. A phenomenon of rapid degradation in network performance is referred to as congestion. 
         [0202]    Typically, when congestion occurs, ACM, SSAC, EAB, SCM, etc. are used as access control technique for UE. However, the UE fails to support an application-specific congestion control for data communication (ACDC). 
         [0203]    If there is pending uplink data in the UE when the UE sends a tracking area update (TAU) request message, the UE sets an active flag of the TAU request message to 1 and performs transmission. As a result, a user plane connection is established between the UE and the network. 
         [0204]    Therefore, ACDC may be applied even when an active flag of the TAU request message is 1. The present invention proposes a method for applying ACDC in case of TAU. 
         [0205]    Additionally, in case the UE uses a power saving mode (PSM), the UE inserts an active timer in the TAU request message and transmits it to the network. In this case as well, since the active flag may be set to 1 when there is pending uplink data, ACDC should be applied. Also, the UE that has the active timer and intends to enter PSM may be allowed to send a service request regardless of ACDC with regard to the service request sent during the period of time. 
         [0206]    In this disclosure, ACDC may be determined according to operator&#39;s policy or regional regulations, providing a service in a disaster state and also controlling congestion for a commercial service. Additionally, ACDC may be used as a similar concept with other functions capable of a congestion control for each application. An embodiment of the present invention may be similarly used generally in wireless communication such as WLAN, Bluetooth, Zigbee, and the like in addition to the communication system discussed herein. Additionally, a mobile communication operator may provide UE with information for ACDC. This may be implemented using OMA standard called Management Object (MO) and thus referred to as ACDC MO. In order to deliver ACDC MO, a network operator may use other method such as presetting in the UE or SIM rather than using OMA standard. 
         [0207]      FIG. 11  is a flow diagram illustrating a process in which UE applies ACDC in a TAU procedure according to the second embodiment of the present invention. 
         [0208]    Referring to  FIG. 11 , the UE may decide to initiate the TAU procedure at step  1110  according as a tracking area is changed. When initiating TAU, the UE may have uplink data to be transmitted through a network. 
         [0209]    At step  1120 , the UE may determine whether to set the active flag of the TAU message to 1 by determining whether there is uplink data in the UE. If there is no uplink data in the UE, the UE may not set the active flag to 1 and perform a normal TAU procedure at step  1130 . Namely, the UE may transmit a TAU message contained in an RRC message to the eNB without checking application information. 
         [0210]    If there is uplink data in the UE, the UE may set the active flag of the TAU message to 1. Then, at step  1140 , the UE may determine information about an application that generates the uplink data. 
         [0211]    In this case, the application information may be a criterion of determination for applying ACDC, depending on an application from which pending uplink data in the UE is generated. The application information may include an application category. 
         [0212]    For example, if an application that generates uplink data belongs to an application category having lower priority, access may be disallowed (hereinafter, the term barring may be also used) as the result of applying ACDC and thus data may be not transmitted. 
         [0213]    If an application that generate uplink data belongs to an application category having higher priority, a UE access process may be performed again even in case of barring access by an application contained in an application category having lower priority. 
         [0214]    Therefore, the UE may identify an application generating transmission-ready uplink data and check an application category by using an identifier of the application and setting information thereof. Herein, this setting information may be contained in ACDC MO. Namely, the UE may map the application to an application category received with ACDC MO. Through this procedure, the UE finds application information. 
         [0215]    In this case, an application category contained in application information may be formed of bit information. For example, in case information is formed of 3 bits, category #1 may be represented as  001  and category #4 may be represented as  011 . A value from 2 bits to 8 bits may be used. 
         [0216]    The UE that finds application information may determine, at step  1150 , whether to control access. Namely, the UE may determine whether to perform access barring. 
         [0217]    Specifically, the UE may extracts, from system information block (SIB) information received from the eNB, a barring factor corresponding to an application category contained in application information. The UE may determine, based on a value specified or created through random number generation using the barring factor, whether to perform access barring or not (i.e., pass). 
         [0218]    At this time, access barring of UE may mean, for example, that the TAU procedure of UE is not initiated. Namely, it may mean that the UE does not transmit the TAU message to the eNB. 
         [0219]    However, as discussed above, even in case of access barring due to lower priority of a specific application category, the access procedure may be performed if the UE supports ACDC in case radio resources of a user plane is requested for an application category having higher priority. 
         [0220]    If the access of UE is passed, the UE may transmit the RRC message containing the TAU message to the eNB at step  1260 . 
         [0221]      FIG. 12  is a flow diagram illustrating a process of applying ACDC in a TAU procedure according to the second embodiment of the present invention. 
         [0222]    Referring to  FIG. 12 , the first upper layer unit of the UE may receive a data transmission request from the third upper layer unit at step  1210 . Then the first upper layer unit may decide to initiate a TAU procedure at step  1220 . Although an example in which the first upper layer unit initiates the TAU procedure after receiving the data transmission request is shown, the first upper layer unit may decide to initiate the TAU procedure and then receive the data transmission request from the third upper layer unit. 
         [0223]    Herein, the first upper layer unit may mean an apparatus for controlling operations on an NAS layer. Also, the third upper layer unit may mean an apparatus for controlling operations on an application layer. 
         [0224]    Meanwhile, when the UE initiates the TAU procedure, the UE may have uplink data to be transmitted through a network. 
         [0225]    If the UE supports ACDC, if user plane radio resource allocation according to uplink data is requested, and if it is possible to apply ACDC to this request, the UE may set the active flag of the TAU message to 1 at step  1230 . Additionally, at step  1240 , the UE may determine information about an application that generates the uplink data. This application information may contain an application category, which is discussed for example hereinafter. However, the application information is not limited to application category information. 
         [0226]    In this case, an application from which uplink data pending in the UE is generated may be a criterion for applying ACDC. For example, if an application that generates uplink data belongs to an application category having lower priority, access barring is determined as the result of applying ACDC and thus data may be not transmitted. 
         [0227]    Therefore, the UE may find an application category by identifying an application generating transmission-ready uplink data and by using an identifier of the application and setting information thereof. Herein, this setting information may include category determination information for finding the category of an application, and may be contained in ACDC MO. Namely, the UE may map the application to an application category received with ACDC MO. This ACDC MO may be received through the application that generates transmission-ready uplink data. Through this procedure, the UE finds application information. 
         [0228]    The UE that finds application information may transmit the application information to the second upper layer unit of the UE at step  1250 . Herein, the second upper layer unit may mean an apparatus for controlling operations on a radio resource control (RRC) layer of the UE. 
         [0229]    At this time, the first upper layer unit of the UE may form a call type, based on application category information for applying ACDC, the TAU message, and RRC establishment cause, and then may deliver this information to the second upper layer unit. 
         [0230]    In this case, application category information for applying ACDC may be formed of bit information for indicating an application category. For example, in case information is formed of 3 bits, category #1 may be represented as  001  and category #4 may be represented as  011 . A value from 2 bits to 8 bits may be used. 
         [0231]    At step  1260 , the second upper layer unit that receives the TAU message, the application category information for applying ACDC, and the RRC establishment cause from the first upper layer unit may determine UE access or not. In order to determine transmission of uplink data, the UE may compare the application category information for applying ACDC with ACDC information of SIB information received from the eNB. 
         [0232]    Specifically, the UE may extracts, from SIB information, a barring factor corresponding to the application category information received from the first upper layer unit. Then, based on the barring factor, the UE performs an access control, i.e., UE access barring or passing, depending on a value specified or created through random number generation. 
         [0233]    At this time, barring UE access may mean, for example, that the TAU procedure of UE is not initiated. Namely, it may mean that the UE does not transmit the TAU message to the eNB. 
         [0234]    However, even in case of access barring due to lower priority of a specific application category, the access procedure may be performed if the UE supports ACDC when radio resources of a user plane is requested for an application category having higher priority. 
         [0235]    If the access of UE is passed, the UE may transmit the RRC message to the eNB at step  1270 . This RRC message contains the TAU message received from the first upper layer unit of the UE. 
         [0236]    Meanwhile, if the UE does not set the active flag to 1 at step  1230 , the UE does not perform application category mapping for ACDC. Instead, the UE sets a call type complying with TAU initiation conditions, based on the TAU message and the establishment cause, and then deliver this information to the second upper layer unit. Thereafter, the second upper layer unit transmits the TAU message contained in the RRC message to the eNB. 
         [0237]      FIG. 13  is a flow diagram illustrating another process in which UE applies ACDC in a TAU procedure according to the second embodiment of the present invention. 
         [0238]    Referring to  FIG. 13 , the UE may decide to initiate the TAU procedure at step  1310  according as a tracking area is changed. When initiating the TAU procedure, the UE may have uplink data to be transmitted through a network. 
         [0239]    If there is uplink data in the UE, the UE may set the active flag of the TAU message to 1 at step  1320 . 
         [0240]    In this case, an application from which uplink data pending in the UE is generated may be a criterion for applying ACDC. For example, if an application that generates uplink data belongs to an application category having lower priority, access barring is determined as the result of applying ACDC and thus data may be not transmitted. 
         [0241]    If an application that generate uplink data belongs to an application category having higher priority, a UE access process may be performed again even in case of barring access by an application contained in an application category having lower priority. 
         [0242]    If the UE desires to use a power saving mode (PSM), the UE may set an active timer value of the TAU message and, based on this, determine whether to apply ACDC. 
         [0243]    The term PSM may refer to a mode in which the UE sends data for a short time and then enters an idle state. Therefore, the UE that enters PSM may contribute to reduction in network congestion. 
         [0244]    Therefore, in case the UE sets the active flag of the TAU message to 1 at step  1320 , the UE may determine whether to set the active timer value of the TAU message for using PSM at step  1330 . 
         [0245]    If the active timer value is set, the UE may skip a congestion control through ACDC at step  1340 . Therefore, at step  1350 , the UE may transmit the TAU request message to the network according to a normal TAU procedure. 
         [0246]    Namely, in case both the active flag and the active timer value are set, the UE may determine a call type corresponding to RRC establishment cause corresponding to the TAU message, form the RRC message including this information, and transmit the RRC message to the eNB. 
         [0247]    In another example, if the TAU procedure is completed in a state where both the active flag and the active timer value are set (i.e., in case of transmitting the TAU request message to the eNB and then receiving the TAU accept message from the eNB), the UE may skip ACDC for other service request message until entering a PSM state after the expiration of an active timer. 
         [0248]    Meanwhile, if the UE fails to set the active timer value of TAU at step  1330 , the UE may apply ACDC to uplink data. Namely, the UE may find application information (e.g., application category) associated with the generation of uplink data at step  1370  and then determine access or not of UE according to the application information at step  1380 . Details are discussed above in  FIG. 11 , so the repetition is omitted herein. 
         [0249]    Meanwhile, if the UE does not set the active flag to 1 at step  1320 , the UE may perform a normal TAU procedure at step  1390 . 
         [0250]    Namely, the UE may select a call type for the TAU message and RRC establishment cause without application category mapping, form the RRC message having such information, and transmit the RRC message to the eNB. 
         [0251]      FIG. 14  is a flow diagram illustrating another process of applying ACDC in a TAU procedure according to the second embodiment of the present invention. 
         [0252]    While  FIG. 12  shows a case in which an active timer is not set,  FIG. 14  shows a case in which the active timer is set. 
         [0253]    Referring to  FIG. 14 , the first upper layer unit of the UE may receive a data transmission request from the third upper layer unit at step  1410 . Then the first upper layer unit may decide to initiate a TAU procedure at step  1420 . Alternatively, the first upper layer unit may decide to initiate the TAU procedure and then receive the data transmission request from the third upper layer unit. 
         [0254]    Herein, the first upper layer unit may mean an apparatus for controlling operations on an NAS layer. Also, the third upper layer unit may mean an apparatus for controlling operations on an application layer. 
         [0255]    When the UE initiates the TAU procedure, the UE may have uplink data to be transmitted through a network. 
         [0256]    If the UE supports ACDC, if user plane radio resource allocation according to uplink data is requested, and if it is possible to apply ACDC to this request, the UE may set the active flag of the TAU message to 1 at step  1430 . Additionally, at step  1440 , the UE may set the active timer of the TAU message. 
         [0257]    The case where the UE sets the active timer of the TAU message may mean a case in which the UE uses PSM. The term PSM may refer to a mode in which the UE sends data for a short time and then enters an idle state. Therefore, the UE that enters PSM may contribute to reduction in network congestion. 
         [0258]    Therefore, if the UE sets the active flag to 1 because of the presence of uplink data to be transmitted, and if the UE sets the active timer value for the use of PSM, the UE may not require a congestion control through ACDC. 
         [0259]    Therefore, at step  1450 , the first upper layer unit may determine a call type corresponding to RRC establishment cause corresponding to the TAU message, and transmit this information to the second upper layer unit. At this time, the second upper layer unit may mean, but not limited to, an apparatus for controlling operations on the RRC layer. 
         [0260]    Thereafter, the second upper layer unit may form the RRC message having the above information at step  1460 , and transmit the RRC message to the eNB at step  1470 . 
         [0261]    Meanwhile, if the TAU procedure is completed in a state where both the active flag and the active timer value are set (i.e., in case of transmitting the TAU request message to the eNB and then receiving the TAU accept message from the eNB), the UE may skip ACDC for other service request message until entering a PSM state after the expiration of an active timer. If the first upper layer unit of the UE does not set the active flag to 1, the first upper layer unit may determine a call type corresponding to the TAU message and RRC establishment cause without application category mapping for using ACDC according to a normal TAU procedure, and transmit this to the second upper layer unit. Then the second upper layer unit may form the RRC message having the above information and transmit the RRC message to the eNB. 
         [0262]      FIG. 15  is a block diagram illustrating a configuration of UE according to the second embodiment of the present invention. 
         [0263]    Referring to  FIG. 15 , the UE according to the second embodiment includes a transceiver unit  1505 , a control unit  1510 , a multiplexing and demultiplexing unit  1520 , a control message processing unit  1545 , and various upper layer processing units  1525 ,  1530  and  1535 . Although three upper layer processing units  1525 ,  1530  and  1535  are shown, this is exemplary only and not to be considered as a limitation of this invention. 
         [0264]    The transceiver unit  1505  may perform communication with other network entities. The transceiver unit  1505  may receive data and control signals through a downlink channel of a serving cell and also transmit data and control signals through an uplink channel. 
         [0265]    The multiplexing and demultiplexing unit  1520  may multiplex data generated at the upper layer processing units  1525 ,  1530  and  1535  or the control message processing unit  1545 . Also, the multiplexing and demultiplexing unit  1520  may demultiplex data received from the transceiver unit  1505  and then deliver it to the upper layer processing units  1525 ,  1530  and  1535  or the control message processing unit  1545 . 
         [0266]    The control message processing unit  1545  is a kind of RRC layer apparatus and may process a control message received from the eNB. 
         [0267]    The upper layer processing units  1525 ,  1530  and  1535  may be formed of the first upper layer processing unit  1525 , the second upper layer processing unit  1530 , and the third upper layer processing unit  1535 . The UE may further include a plurality of upper layer processing units. 
         [0268]    The first upper layer processing unit  1525  may control operations on the NAS layer, and the second upper layer processing unit  1530  may control operations on the RRC layer. Also, the third upper layer processing unit  1535  may control operations on the application layer. Such upper layer processing units may be formed for each service. The upper layer processing units may process data created in a user service such as FTP (File Transfer Protocol) or VoIP (Voice over Internet Protocol) and then deliver it to the multiplexing and demultiplexing unit  1520 , or may process data delivered from the multiplexing and demultiplexing unit  1520  and then deliver it to a service application on the upper layer. 
         [0269]    The control unit  1510  may check scheduling commands, e.g., reverse grants, received through the transceiver unit  1505  and then control the transceiver unit  1505  and the multiplexing and demultiplexing unit  1520  so that reverse transmission can be performed with suitable transmission resources at a suitable time point. Also, the control unit  1510  controls all procedures applying ACDC in the TAU procedure. Namely, the control unit  1510  performs control operations associated with the operation of UE as shown in  FIGS. 11 to 14 . 
         [0270]    Specifically, the control unit  1510  may control the first upper layer processing unit to determine whether to initiate the TAU procedure. At this time, if uplink data transmission is requested through the third upper layer processing unit, the control unit  1510  may control the first upper layer processing unit to determine whether to initiate the TAU procedure. Alternatively or additionally, the control unit  1510  may control the reception of a data transmission request from the third upper layer processing unit after the first upper layer processing unit determines the initiation of the TAU procedure. Also, the control unit  1510  may control a value of the active flag to be set to 1, depending on whether there is transmission-ready uplink data. If the value of the active flag is not set to 1, the control unit  1510  may control performing a normal TAU procedure. If the value of the active flag is set to 1, the control unit  1510  may control determining application information of an application from which transmission-ready uplink data is generated. This application information may include an application category. Additionally, the control unit  1510  may control delivering the application information from the first upper layer processing unit to the second upper layer processing unit. Also, the control unit  1510  may determine whether to allow the access of UE, using the application information through the second upper layer processing unit. The control unit  1510  may extract a barring factor corresponding to an application category from SIB information received from the eNB. The control unit  1510  may determine UE access barring or passing, depending on a value specified or created through random number generation using the barring factor. 
         [0271]    However, even in case of access barring due to lower priority of a specific application category, the control unit  1510  may perform the access procedure if the UE supports ACDC when radio resources of a user plane is requested for an application category having higher priority. 
         [0272]    If the access of UE is passed, the control unit  1510  may control transmitting the RRC message having the TAU message to the eNB through the second upper layer processing unit. 
         [0273]    Meanwhile, with regard to UE that uses PSM, the control unit  1510  may control determining whether to apply ACDC. The term PSM may refer to a mode in which the UE sends data for a short time and then enters an idle state. Therefore, the UE that enters PSM may contribute to reduction in network congestion. 
         [0274]    Therefore, in case of setting the active flag to 1 (i.e., transmission-ready uplink data exists) and in case of setting the active timer value so as to operate in PSM, the control unit  1510  may control performing no congestion control through ACDC. Therefore, the control unit  1510  may control performing a normal TAU procedure. Specifically, the control unit  1510  may control the first upper layer processing unit to determine a call type corresponding to RRC establishment cause corresponding to the TAU message, and transmit this information to the second upper layer processing unit. Further, the control unit  1510  may control the second upper layer processing unit to form the RRC message having the above information and transmit the RRC message to the eNB. 
         [0275]    Meanwhile, if the TAU procedure is completed in a state where both the active flag and the active timer value are set (i.e., in case of transmitting the TAU request message to the eNB and then receiving the TAU accept message from the eNB), the control unit  1510  may skip ACDC for other service request message until entering a PSM state after the expiration of an active timer. 
       Third Embodiment 
       [0276]    Hereinafter, a method and apparatus for providing a multimedia broadcast multicast service (MBMS) according to the third embodiment of the present invention will be described. 
         [0277]    In case of providing data to UE through MBMS, a group communication service application server (GCS AS) and/or a broadcast/multicast service center (BM-SC) may transmit information associated with MBMS service area, and the UE may receive MBMS data based on the MBMS service area. However, since the MBMS service area covers a wide range, MME may change the MBMS service area even when considerable traffic is generated due to numerous users in a specific area. Therefore, in case there are many users in a specific area, the MME may transmit a message for instructing a setup or modification of MBMS session to a multi cell/multicast coordination entity (MCE) contained in the MBMS service area so that the MBMS session can be created or changed and finally MBMS data can be transmitted to the UE. However, this method for creating or changing the MBMS session may invite necessary signaling. Therefore, this invention proposes a method for transmitting and receiving data in a smaller MBMS area than the MBMS service area. 
         [0278]      FIGS. 16A and 16B  are flow diagrams illustrating a method for providing an MBMS service according to the third embodiment of the present invention. 
         [0279]    In this embodiment, an MBMS applicable area may be a smaller area than the MBMS service area. 
         [0280]    Referring to  FIG. 16A , the GCS AS may transmit an activate MBMS bearer request message to the BM-SC at step  1601 . Alternatively, the GCS AS may transmit a modify MBMS bearer request message for modifying an activated MBMS bearer to the BM-SC at step  1604 . The activate MBMS bearer request message and the modify MBMS bearer request message may contain information about an MBMS broadcast area. The GCS AS may determine the MBMS broadcast area information, based on information (e.g., a UE location which may be represented as a cell identifier, an MBSFN area identifier, an MBMS service area, etc.) obtained from the UE through application signaling and/or setting information. The MBMS broadcast area information may include an MBMS service area, an MBSFN area identifier list, and/or a cell list (i.e., an ECGI (E-UTRAN cell global identifier) list). 
         [0281]    At step  1602 , the BM-SC that receives the activate MBMS bearer request message may allocate resources in an MBMS system so as to support a data flow. Alternatively, at step  1605 , the BM-SC that receives the modify MBMS bearer request message may determine whether to modify the MBMS bearer. 
         [0282]    If a cell list is contained in the MBMS broadcast area information received by the BM-SC, the BM-SC may induce the MBMS service area from the cell list information. For this, the BM-SC may have mapping information between the cell list information and the MBMS service area. In this case, if the MBMS service area is received from the GCS AS, the BM-SC may overwrite the received MBMS service area with the induced MBMS service area. Thereafter, the BM-SC may insert mapped MBMS service area and/or cell list in a message sent to MBMS GW for requesting MBMS bearer activation and/or MBMS bearer modification. Of course, even though a cell list is contained in the MBMS broadcast area information received by the BM-SC, the MBMS service area information received from the GCS AS may be used as it is. In case the GCS AS sends the cell list and the MBMS service area, whether the BM-SC will use them as received or use a new MBMS service area induced from the cell list may depend on an operator&#39;s policy and/or setting. 
         [0283]    If the BM-SC induces the MBMS service area from the cell list, the BM-SC may deliver, to the GCS AS, the induced MBMS service area (i.e., the MBMS service area contained in a message sent to the MBMS GW for requesting MBMS bearer activation and/or MBMS bearer modification) through a response message for the request of MBMS bearer activation and/or MBMS bearer modification at step  1603  or  1606 . If the BM-SC does not induce the MBMS service area from the cell list, or if the received MBMS broadcast area information does not contain the cell list, the BM-SC may not insert the MBMS service area in the response message for the request of MBMS bearer activation and/or MBMS bearer modification. 
         [0284]    The GCS AS may transmit, to the UE, the MBMS service area received at step  1603  or  1606 . If the GCS AS fails to receive the MBMS service area at step  1603  or  1606 , the GCS AS may transmit, to the UE, the MBMS service area transmitted to the BM-SC at step  1601  or  1604 . Although any cell is located in the MBMS service area, MBMS may not be applied if the MBMS bearer is activated using the cell list. Therefore, in case the MBMS service area received from the GCS AS is not contained in the MBMS service area information broadcasted by the cell, the UE can know that MBMS is not applied to a service in that cell. However, in case the MBMS service area received from the GCS AS is contained in the MBMS service area information broadcasted by the cell, the UE may not know whether MBMS is applied or not to a service in that cell. 
         [0285]    Referring to  FIG. 16B , the MME may receive, from MBMS-GW, a message that contains the MBMS service area and the cell list (i.e., the ECGI list). Also, a message transmitted to the MCE by the MME may contain parameters received through the BM-SC by the MBMS-GW. In this case, these parameters may include a temporary mobile group identity (TMGI), FlowID, QoS, MBMS broadcast area information, a start time, and the like. The MBMS broadcasts area information may include the MBMS service area or the cell list information. If the cell list information is contained in the MBMS broadcast area information, this information may be mapped to the MBMS service area by the BM-SC. The BM-SC may deliver, to the GCS AS, information (MBMS service area) created from the cell list information. 
         [0286]    The MME that receives the message including the MBMS service area and the cell list from the MBMS GW may transmit a message (hereinafter, referred to as an MBMS session setup or modify message) for a setup or modification of MBMS session to the MCE. At this time, the MME may send the MBMS session setup or modify message to only the MCE that controls the received cell list. 
         [0287]    For this, at step  1610  for M3 setup with the MME, the MCE may deliver, to the MME, an M3 setup request message having a cell identifier list and/or an identifier list of the eNB connected to the MCE. 
         [0288]    The M3 setup request message may be defined as shown in Table 2 and Table 3. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 IE/Group 
                   
                   
                 IE type and 
                 Semantics 
                   
                 Assigned 
               
               
                 Name 
                 Presence 
                 Range 
                 reference 
                 description 
                 Criticality 
                 Criticality 
               
               
                   
               
             
             
               
                 Message Type 
                 M 
                   
                 9.2.1.1 
                   
                 YES 
                 reject 
               
               
                 Global MCE ID 
                 M 
                   
                 9.2.1.10 
                   
                 YES 
                 reject 
               
               
                 MCE Name 
                 O 
                   
                 PrintableString(1 . . . 150, 
                   
                 YES 
                 ignore 
               
               
                   
                   
                   
                 . . . ) 
               
               
                 MBMS Service 
                   
                 1 
                   
                   
                 YES 
                 reject 
               
               
                 Area List 
               
               
                 &gt;MBMS 
                   
                 1 to 
                   
                 Supported 
                 GLOBAL 
                 reject 
               
               
                 Service Area 
                   
                 &lt;maxnoofMBMSServiceAreaIdentitiesPerMCE&gt; 
                   
                 MBMS 
               
               
                 List Item 
                   
                   
                   
                 Service Area 
               
               
                   
                   
                   
                   
                 Identities in 
               
               
                   
                   
                   
                   
                 the MCE 
               
               
                 &gt;&gt;MBMS 
                 M 
                   
                 OCTET 
                 MBMS 
               
               
                 Service Area 1 
                   
                   
                 STRING(2) 
                 Service Area 
               
               
                   
                   
                   
                   
                 Identities as 
               
               
                   
                   
                   
                   
                 defined in TS 
               
               
                   
                   
                   
                   
                 23.003 [13]. 
               
               
                 eNB list or cell 
                   
                 1 to n 
               
               
                 list 
               
               
                 &gt; Global eNB 
               
               
                 ID or ECGI 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Range bound 
                 Explanation 
               
               
                   
                   
               
             
             
               
                   
                 maxnoofMBMSServiceArea- 
                 Maximum no. of Service Area 
               
               
                   
                 IdentitiesPerMCE 
                 Identities per MCE. The value for 
               
               
                   
                   
                 maxnoofMBMSServiceArea- 
               
               
                   
                   
                 Identities is 65536. 
               
               
                   
                   
               
             
          
         
       
     
         [0289]    At step  1620 , the MME that receives the above-message may transmit an M3 setup response message for the setup request message. 
         [0290]    At this time, the MME may identify the eNB by using a global eNB ID part of the cell list information (ECGI) and also check serving MCE information for each eNB contained in the setup request message. Therefore, the MME can determine the MCE to which the MBMS session setup or modify message will be transmitted. In this manner, the MME may send the MBMS session setup or modify message to a few of MCEs, thus effecting a reduction in signaling. 
         [0291]    Meanwhile, the MME may receive, from the eNB, an S1 setup request message or eNB configuration update request message which contains an identifier of MCE connected to the eNB or a cell in the eNB. Therefore, in similar manner using similar information as discussed above, the MME may determine the MCE to which the MBMS configuration message will be transmitted. 
         [0292]      FIG. 17  is another flow diagram illustrating a method for providing an MBMS service according to the third embodiment of the present invention. 
         [0293]    Referring to  FIG. 17 , the MME may receive, from MBMS-GW, a message that contains the MBMS service area and the cell list (i.e., the ECGI list). Details are discussed earlier in  FIG. 16B , so the repetition is omitted herein. 
         [0294]    The MME that receives the message including the MBMS service area and the cell list from the MBMS GW may transmit the MBMS session setup or modify message to the MCE. At this time, the MME may send the MBMS session setup or modify message to only the MCE that controls the received cell list. 
         [0295]    For this, at step  1710 , the MCE may deliver, to the MME, an MCE configuration update message having a cell identifier list and/or an identifier list of the eNB connected to the MCE. 
         [0296]    The MCE configuration update message may be defined as shown in Table 4 and Table 5. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                 IE type and 
                 Semantics 
                   
                 Assigned 
               
               
                 IE/Group Name 
                 Presence 
                 Range 
                 reference 
                 description 
                 Criticality 
                 Criticality 
               
               
                   
               
             
             
               
                 Message Type 
                 M 
                   
                 9.2.1.1 
                   
                 YES 
                 reject 
               
               
                 Global MCE ID 
                 O 
                   
                 9.2.1.10 
                   
                 YES 
                 reject 
               
               
                 MCE Name 
                 O 
                   
                 PrintableString(1 . . . 150, 
                   
                 YES 
                 ignore 
               
               
                   
                   
                   
                 . . . ) 
               
               
                 MBMS Service 
                   
                 0 . . . 1 
                   
                   
                 YES 
                 reject 
               
               
                 Area List 
               
               
                 &gt;MBMS Service 
                   
                 1 to 
                   
                 Supported 
                 GLOBAL 
                 reject 
               
               
                 Area List Item 
                   
                 &lt;maxnoofMBMSServiceAreaIdentitiesPerMCE&gt; 
                   
                 MBMS 
               
               
                   
                   
                   
                   
                 Service 
               
               
                   
                   
                   
                   
                 Area 
               
               
                   
                   
                   
                   
                 Identities in 
               
               
                   
                   
                   
                   
                 the MCE 
               
               
                 &gt;&gt;MBMS Service 
                 M 
                   
                 OCTET 
                 MBMS 
               
               
                 Area 1 
                   
                   
                 STRING(2) 
                 Service 
               
               
                   
                   
                   
                   
                 Area 
               
               
                   
                   
                   
                   
                 Identities as 
               
               
                   
                   
                   
                   
                 defined in 
               
               
                   
                   
                   
                   
                 TS 23.003 
               
               
                   
                   
                   
                   
                 [13]. 
               
               
                 eNB list or cell 
                   
                 1 to n 
               
               
                 list 
               
               
                 &gt; Global eNB ID 
               
               
                 or ECGI 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 Range bound 
                 Explanation 
               
               
                   
                   
               
             
             
               
                   
                 maxnoofMBMSServiceArea- 
                 Maximum no. of Service Area 
               
               
                   
                 IdentitiesPerMCE 
                 Identities per MCE. The value for 
               
               
                   
                   
                 maxnoofMBMSServiceArea- 
               
               
                   
                   
                 Identities is 65536. 
               
               
                   
                   
               
             
          
         
       
     
         [0297]    At step  1720 , the MME that receives the above-message may transmit an MCE configuration update acknowledge message. 
         [0298]    At this time, the MME may identify the eNB by using a global eNB ID part of the cell list information (ECGI) and also check serving MCE information for each eNB contained in the MCE configuration update message. In this manner, the MME may send the MBMS session setup or modify message to a few of MCEs, thus effecting a reduction in signaling. 
         [0299]      FIG. 18  is a block diagram illustrating a configuration of MME according to the third embodiment of the present invention. 
         [0300]    Referring to  FIG. 18 , the MME may be formed of a communication unit  1810 , a control unit  1820 , and a storage unit  1830 . 
         [0301]    The communication unit  1810  may perform communication with other network entities such as the MBMS GW, the MCE, the eNB, or the like. 
         [0302]    The control unit  1820  may control the reception of a message having the MBMS service area and the cell list from the MBMS GW. This message may contain parameters received through the BM-SC by the MBMS-GW. In this case, these parameters may include TMGI, FlowID, QoS, MBMS broadcast area information, a start time, and the like. Details are discussed earlier in  FIG. 16 , so the repetition is omitted herein. 
         [0303]    The control unit  1820  may control the reception of an M3 setup request message from the MCE at M3 setup with the MCE. The M3 setup request message may have a cell identifier list and/or an identifier list of the eNB connected to the MCE. The control unit  1820  may control the transmission of a setup response message for the setup request message. 
         [0304]    Additionally, the control unit  1820  may identify the eNB by using a global eNB ID part of the cell list information (ECGI) and also check serving MCE information for each eNB contained in the setup request message. Therefore, the control unit  1820  can determine the MCE to which the MBMS session setup or modify message will be transmitted. 
         [0305]    Meanwhile, a cell identifier list and/or an identifier list of the eNB may be contained in the MCE configuration update message and transmitted to the MME from the MCE. 
         [0306]    Additionally, the control unit  1820  may control the reception, from the eNB, of the S1 setup request message or eNB configuration update request message having an identifier of MCE connected to the eNB or a cell in the eNB. Using the above information, the control unit  1820  may determine the MCE to which the MBMS session setup or modify message will be transmitted. This method is discussed above. 
         [0307]    The storage unit  1830  may store information received from the MBMS GW. Also, the storage unit  1830  may store information received from the MCE or the eNB. Therefore, such information stored in the storage unit  1830  may be used for determining the MCE to which the MBMS session setup or modify message will be transmitted. 
         [0308]    Further, the storage unit  1830  may store a list of MCE determined to transmit the MBMS session setup or modify message. 
         [0309]      FIG. 19  is a block diagram illustrating a configuration of MCE according to the third embodiment of the present invention. 
         [0310]    Referring to  FIG. 19 , the MCE may be formed of a communication unit  1910 , a control unit  1920 , and a storage unit  1930 . 
         [0311]    The communication unit  1910  may perform communication with other network entities such as the MME, the eNB, or the like. 
         [0312]    The control unit  1920  may control the transmission of the M3 setup request message to the MME for M3 setup with the MME. The control unit  1920  may insert, in the M3 setup request message, a cell identifier list and/or an identifier list of the eNB connected to the MCE. Also, the control unit  1930  may control the reception of the setup response message for the setup request message. 
         [0313]    Additionally, the control unit  1920  may control the transmission, to the MME, of the M3 setup request message having a cell identifier list and/or an identifier list of the eNB connected to the MCE, and also control the reception of the MCE configuration update acknowledge message. 
         [0314]    Further, the control unit  1920  may control the reception of the MBMS session setup or modify message from the MME in case the MCE is selected by the MME. 
         [0315]    The storage unit  1930  may store a cell identifier list and/or an identifier list of the eNB connected to the MCE. Therefore, such information stored in the storage unit  1930  may be used for creating the M3 setup request message or the MCE configuration update message. 
         [0316]    The present invention may be embodied in many different forms without changing technical subject matters and essential features as will be understood by those skilled in the art. Therefore, embodiments set forth herein are exemplary only and not to be construed as a limitation. 
         [0317]    In embodiments, all steps and messages are not a target for selective implementation or omission. Additionally, in each embodiment, steps may not be always performed in the order described and may be changed in order. Similarly, delivery of messages may not be always performed in the order described and may be changed in order. Each step and messaging may be performed independently. 
         [0318]    The whole or parts of exemplary contents in embodiments are provided to promote understanding by showing a detailed embodiment of this invention. Therefore, the detailed contents may be regarded as expressing a part of method and apparatus proposed by this invention. Namely, with regard to such contents, a syntax-based approach may be more desirable than a semantics-based approach. 
         [0319]    While the present invention has been particularly shown and described with reference to an exemplary embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.