Abstract:
Disclosed is a method for using an identifier for an MBMS in a CDMA mobile communication system providing the MBMS. The method assigns by a radio network controller a cell identifier related to the MBMS available in a cell that includes the user equipment. The cell identifier is different from an identifier used in an upper layer. The method also transmits to the user equipment a control message that includes the cell identifier.

Description:
PRIORITY  
       [0001]     This application claims priority to an application entitled “Method Of Using Service Identifier For Transmitting Control Information In Mobile Communication System Providing Multimedia Broadcast/Multicast Service” filed with the Korean Intellectual Property Office on Aug. 14, 2003 and assigned Serial No. 2003-56628, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a multimedia broadcast/multicast service (“MBMS”) for a mobile communication system, and more particularly to a method for effectively using an identifier used for the MBMS.  
         [0004]     2. Description of the Related Art  
         [0005]     Recently, as communication technologies have developed, a CDMA (code division multiple access) mobile communication system provides not only a voice service, but also a packet service for transmitting mass storage data, such as packet data or circuit data. In addition, the CDMA mobile communication system has been developed into a multimedia broadcast/communication system capable of providing multimedia services. Thus, in order to support the multimedia broadcast/communication system, there has been suggested an MBMS that provides services from one or more multimedia data sources to user equipment (“UE”).  
         [0006]     The MBMS uses a multimedia transmission mode for transmitting data, such as real time images, voice data, still images, and characters. The MBMS can simultaneously transmit voice data and image data in the multimedia transmission mode and may require extensive transmission resources. Since a plurality of UEs may join in the same service, the MBMS is provided through a broadcasting channel.  
         [0007]     The MBMS includes a point to point (“PtP”) service for providing services required by each subscriber and a point to multi-point (“PtM”) service for providing services required by a plurality of subscribers. According to the MBMS, the PtP service can be replaced with the PtM service, while the PtP service is being provided to each cell, based on the number of UEs requesting the MBMS and the transmission power of a network supporting the MBMS. Of course, the PtM service can be replaced with the PtP service while the PtM service is being provided to each cell.  
         [0008]     Hereinafter, a structure of an asynchronous mobile communication system for providing an MBMS will be described with reference to  FIG. 1 .  
         [0009]      FIG. 1  is a block diagram illustrating a structure of a conventional asynchronous mobile communication system for providing the MBMS.  
         [0010]     Referring to  FIG. 1 , the conventional asynchronous mobile communication system includes a UE  101 , a UMTS terrestrial radio access network (“UTRAN”)  102 , a serving general packet radio service support node (“SGSN”)  103  included in a core network (“CN”), a home location register (“HLR”)  104 , a gateway general packet radio service support node (“GGSN”)  105 , a broadcast/multicast service center (“BM-SC”)  106 , and a contents provider (“CP”)  107 .  
         [0011]     The functions of the above elements shown in  FIG. 1  are shown in Table 1. Although the functions of the above elements shown in  FIG. 1  may vary slightly depending on the network administrators, the basic functions thereof will not be changed. In addition, although it is not illustrated in  FIG. 1 , a cell broadcast center (“CBC”) can be added to the above structure in order to provide information to the UE  101 .  
                           TABLE 1                                   Elements   Functions                           UE   Receives MBMS data so as to provide               the MBMS data to users           UTRAN   Transfers MBMS data to the UE               and transfers a MBMS request               message from the UE to the CN           SGSN   Receives data related to the UE requesting               the MBMS from the HLR               and authorizes the UE               Receives MBMS right requested by the               UE from the HLR and               authorizes the MBMS right               Sets an RAB for the MBMS requested by the UE               Supports the UE such that the UE can               receive the MBMS when the               UE moves from a corresponding cell               Makes connection with an MBMS               provider through the GGSN               Collects charge information for the               MBMS used by the UE           HLR   Manages authorization information               for each UE and the sort of               MBMS to be provided to the UE           GGSN   Receives the MBMS data to be               provided to the UE from the BM-SC               and transmits the MBMS data to the SGSN               Collects charge information for the UE               Manages mobility of each UE, a                movement state of each UE, and               quality of the MBMS provided to each UE           BM-SC   Manages authorization and               charge information for the contents               provider               Determines the quality of the MBMS               Corrects error for the MBMS data loss               Transfers the MBMS data provided from               the contents provider to the               GGSN               Notifies the UE of the available MBMS           CP   Provides the MBMS contents to the BM-SC                      
 
         [0012]     The BM-SC  106  is a source for providing an MBMS data stream. The BM-SC  106  transfers the MBMS data stream to the GGSN  105  after scheduling the MBMS data stream. The GGSN  105  transfers the MBMS data stream to the SGSN  103 . Herein, the SGSN  103  belongs to the CN and connects the CN to the UTRAN  102 . For instance, if there are a plurality of UEs which are to receive the MBMS at a predetermined time, the SGSN  103  receiving the MBMS data stream from the GSN  105  may control the MBMS-related services for the users, that is, control the MBMS-related services for the UEs.  
         [0013]     For example, the SGSN  103  manages the MBMS-related charge data for each subscriber and selectively transmits the MBMS data to a predetermined radio network controller (“RNC”), thereby controlling the MBMS. In addition, the SGSN  103  forms and manages a SGSN service context (“service context”) with respect to a predetermined MBMS “X”, and transfers the MBMS stream data to the RNC. A MBMS context is a set of control information required for providing the predetermined MBMS.  
         [0014]     The RNC controls a plurality of nodes B and transmits the MBMS data to a node B having a UE that is requesting the MBMS from among the node Bs managed by the RNC. In addition, the RNC controls a radio channel providing the MBMS, forms an RNC service context with respect to the predetermined MBMS “X”, and manages the RNC service context based on the MBMS stream data transmitted thereto from the SGSN  103 . At this time, the HLR  104  connected to the SGSN  103  performs a subscriber authorization for the MBMS.  
         [0015]     In addition, as mentioned above, the RNC and the SGSN manage information related to the MBMS based on the type of MBMS. The information stored in the MBMS context includes a list of UEs requesting the MBMS, that is, the identifiers of the UEs requesting the MBMS, the service areas in which the UEs are positioned, and the quality of service (“QoS”) required for providing the MBMS.  
         [0016]     Hereinafter, the structure of the UTRAN shown in  FIG. 1  will be described in detail with reference to  FIG. 2 .  
         [0017]      FIG. 2  is a diagram illustrating the structure of the UTRAN in a mobile communication system providing the MBMS.  
         [0018]     Referring to  FIG. 2 , a UE  230  is a user equipment for receiving the MBMS and has hardware or software for supporting the MBMS. The UTRAN is a radio communication network for connecting the UE  230  to a CN  200 . The UTRAN includes a plurality of radio network systems (“RNS”)  210  and  220 , and the RNS includes a plurality of radio network controllers (“RNC”)  211  and  212 , base station apparatuses (“Node Bs”) controlled by the RNCs  211  and  212 , and a plurality of cells included in the Node Bs  115 ,  113 ,  114 , and  116 .  
         [0019]     The RNS  210  includes Node Bs  215  and  213  controlled by the RNC  211 , a plurality of cells controlled by the Node B  215 , and a plurality of cells controlled by the Node B  213 . In addition, the RNS  220  includes Node Bs  214  and  216  controlled by the RNC  212 , a plurality of cells controlled by the Node B  214 , and a plurality of cells controlled by the Node B  216 . The total number of Node Bs controlled by the RNCs  211  and  212 , and the total number of cells included in each Node B are determined according to a service provider and the performance of the RNCs  211  and  212  and Node Bs.  
         [0020]     The UE  230  is connected to the RNSs  210  and  220  through a Uu interface  221 . Each of RNSs  210  and  220  is connected to the CN  200  through an Iu interface  222 . Table 2 shows interfaces for connecting nodes to each other.  
                           TABLE 2                                   Interface Name   Function                           Uu   Interface between UE and UTRAN           Iu   Interface between UTRAN and CN           Gr   Interface between SGSN and HLR           Gn/Gp   Interface between SGSN and GGSN           Gi   Interface between GGSN and BM-SC           Gn/Gp   Interface between BM-SC and CP                      
 
         [0021]     The interface name shown in Table 2 is defined in the 3GPP (3 rd  Generation Partnership Project) standards, and it is possible to change the interface name. A structure of an upper layer of the UTRAN defined in the 3GPP and the channels between the layers will be described with reference to  FIG. 3 .  
         [0022]      FIG. 3  is a diagram illustrating a structure of a UTRAN protocol.  
         [0023]     Referring to  FIG. 3 , the messages of the upper layer processed in the UTRAN are divided into a control signaling group and a user data group.  
         [0024]     In  FIG. 3 , the messages of the upper layer of the UTRAN are represented as a control plane (“C-Plane”) signaling  301  and user plane (“U-Plane”) data  302 . The C-plane signaling  301  and the U-plane data  302  are messages of a non access stratum (“NAS”). The NAS messages are messages which are not used for a radio connection between the UE and the UTRAN, and it is not necessary for the UTRAN to know the contents of the NAS messages. Differently from the NAS messages, the messages used for the radio connection between the UE and the UTRAN are called “access stratum (“AS”) messages”, which are data or control signals used at an area below a radio resource control (“RRC”)  303  shown in  FIG. 3 .  
         [0025]     The RRC  303  controls a physical layer (“L 1 ”) relating to a connection between the UE and the UTRAN, a medium access control of L 2  (“L 2 /MAC”), a radio link control of L 2  (“L 2 /RLC”), a packet data convergency protocol of L 2  (“L 2 /PDCP”), and a broadcast/multicast control of L 2 (“L 2 /BMC”). In addition, the RRC  303  controls the connection between the UE and the UTRAN, such as a physical call setting, a logical call setting, the control information reception/transmission, and the data reception/transmission between the UE and the UTRAN.  
         [0026]     The L 2 /PDCP  304  receives the data to be transmitted from an NAS layer and transmits the data to the L 2 /RLC  306  by using a predetermined protocol. The L 2 /BMC  305  receives the data required for the broadcast and multi-broadcast from the NAS layer and transmits the data to the L 2 /RLC  306  by using a predetermined protocol.  
         [0027]     The L 2 /RLC  306  receives a control message, which is transmitted to the UE from the RRC  303 , processes the control message in an RLC #1  361  and an RLC #n  362  by considering the characteristics of the control message, and transmits the processed control message to the LC/MAC  308  through a logical channel  307 . In addition, the L 2 /RLC  306  receives DATA from the L 2 /PDCP  304  and the L 2 /BMC  305 , processes the data in an RLC #1′  363  and an RLC #n′  364  and transmits the processed data to the LC/MAC  308  through the logical channel  307 . The number of RLCs formed in the L 2 /RLC  306  may depend on the number of radio links between the UE and the UTRAN.  
         [0028]     The logical channel  307  is divided into a dedicated type logical channel for a predetermined UE and a common type logical channel for a plurality of UEs. In addition, the logical channel  307  can be divided into a control type logical channel used for transmitting messages including data related to the control information and a traffic type logical channel used for transmitting messages including data related to the traffic information.  
         [0029]     The types and functions of the logical channels  307  used in the 3GPP are shown in Table 3.  
                           TABLE 3                                   Channel Name   Function                           BCCH (broadcast   Used for the downlink transmission           control channel)   from the UTRAN to the               UE and for transmitting control               information of a UTRAN               system           PCCH (paging   Used for the downlink           control channel)   transmission from the UTRAN to the               UE and for transmitting control               information to the UE when               a position of a cell including               the UE is not known           CCCH (common   Used for the PtM control           control channel)   information transmission between               the UE and a network and               used when the UE has no               connection channel for the RRC           DCCH (dedicated   Used for the PtP control           control channel)   information transmission between               the UE and a network and               used when the UE has a               connection channel for the RRC           CTCH (common   Used for the PtM control           transport channel)   information transmission between a               plurality of the UEs and a network           DTCH (dedicated   Used for the PtP control            transport channel)   information transmission between               the UE and a network                      
 
         [0030]     The L 2 /MAC  308  manages radio resources and a connection between the UE and the UTRAN under the control of the RRC  303 . Thus, the L 2 /MAC  308  receives corresponding logical channels as shown in Table 3 from the L 2 /RLC  306  and transmits the corresponding logical channels to the L 1   310  by mapping the corresponding logical channels with transport channels  309  represented in Table 4.  
                   TABLE 4                       Channel name   Function                   BCH (broadcast   Mapped with the BCCH       channel)   to transmit the data of the BCCH       PCH (paging   Mapped with the PCCH       channel)   to transmit the data of the PCCH       RACH (random   Used for the network access and for transmitting the       access channel)   control messages and the short data from the UE to a           network           Mapped with the DCCH, the CCCH, or the DTCH       FACH (forward   Used for transmitting the       access channel)   control information messages or           the data from a network           to the UE or predetermined the UEs           Mapped with the BCCH, the CTCH, the CCCH, the           DCTH, or the DTCH       DCH (dedicated   Used for transmitting       channel)   the data and the control information           messages between a network and the UE           Mapped with the BCCH or the DCTH       DSCH (down-link   Downlink channel used       shared channel)   for transmitting the mass storage           data from a network to the UE           Mapped with the DCTH or the DCCH       HS-DSCH (high   Downlink channel from       speed DSCH)   a network to the UE and having           improved transmission efficiency as compared with the           DSCH           Mapped with the DCTH or the DCCH                  
 
         [0031]     Although it is not illustrated in Table 4, other transport channels, such as an up-link shared channel and a common packet channel, can be used.  
         [0032]     The transport channels  309  transmitted to the L 1   310  shown in  FIG. 3  are processed through a procedure corresponding to real physical channels and transmitted to the UE or the UTRAN. The physical channels include a primary common control physical channel (“P-CCPCH”) for transmitting the BCH, a secondary common control synchronization channel for transmitting the PCH and FACH, a paging indicator channel (“PICH”), an acquisition indicator channel, and a physical common packet channel.  
         [0033]     An example of the MBMS in the 3GPP mobile communication system has been described with reference to  FIG. 1 , and the structure of the UTRAN and structures of L 1 , L 2  and L 3  of the UTRAN shown in  FIG. 1  have been described with reference to  FIGS. 2 and 3 . Hereinafter, a procedure of providing the MBMS will be described with reference to FIGS.  1  to  3 .  
         [0034]     The CN  200  transmits the basic information and the service guide information of the MBMS to a plurality of UEs including the UE  230  through the UTRAN  210  in order to provide a predetermined MBMS. If the UE  230  receiving the basic information and the service guide information of the MBMS is to receive MBMS, the UE  230  is joined in the CN  200 , which is called “joining”. A list of the UEs including the UE  230  requesting the MBMS is transferred to the BM-SC  106 , the SGSN  103  and the UTRAN  210  shown in  FIG. 1 .  
         [0035]     At this time, when the MBMS starts, the CN  200  receiving the list of the UEs requesting the predetermined MBMS and the UTRANs  210  and  220  connected to the CN  200  transmit a paging message to the UEs including the UE  230 . After that, a radio bearer (“RB”) is set in order to provide the MBMS to the corresponding UEs. When the MBMS ends, it must be transferred to the all UEs that the MBMS ends. Thus, the CN  200  and the UTRAN  220  release the radio resources assigned to the UEs for the MBMS, so that the predetermined MBMS ends.  
         [0036]     When providing the MBMS, the CN and the UTRAN may provide the corresponding MBMS to the UEs requesting the MBMS through a plurality of identifiers. In addition, the UEs may use a plurality of identifiers in such a manner that the MBMS data and the control information requested by the UEs can be distinguished from the MBMS data and the control information of other MBMSs.  
         [0037]     Table 5 shows the identifiers used for the MBMS. The MBMS identifiers shown in Table 5 are distinguished from each other based on assigned areas thereof and effective ranges.  
                           TABLE 5                                   Type of               identifiers   Function                           MBMS service   Used for identifying a predetermined           identifier   MBMS from the other               MBMSs               Including IP address           MBMS CN   Used for identifying a predetermined           identifier   MBMS from the other               MBMSs in the CN               Effective range of an MBMS identifier               is defined according to               a master assigning the MBMS CN identifier           MBMS   Used for identifying a predetermined           UTRAN   MBMS from the other           identifier   MBMSs in the UTRAN                      
 
         [0038]     As shown in Table 5, the identifiers used for providing the MBMS may include the MBMS service identifier (“MBMS service ID”) for identifying the predetermined MBMS from the other MBMSs, the MBMS CN identifier for identifying the predetermined MBMS from other MBMSs in the CN, and the MBMS UTRAN identifier for identifying the predetermined MBMS from other MBMSs in the UTRAN. Herein, the MBMS service ID is used for identifying the predetermined MBMS in the upper layer of the CN. In addition, in the CN and the UTRAN, a temporary MBMS group indicator (TMGI) is set in relation to the MBMS service ID so as to identify the predetermined MBMS. As mentioned above, the applications of the identifiers can be defined in the corresponding nodes forming the MBMS. That is, if the BM-SC sets an identifier with respect to the predetermined MBMS, the identifier is effective in the BM-SC. In addition, if the SGSN sets an identifier according to the MBMS, the identifier is effective in the SGSN.  
         [0039]     In other words, as shown in Table 5, an effective range for supporting the MBMS is determined in the corresponding node and a length of the corresponding identifier is determined according to the effective range. That is, the identifiers have lengths different from each other according to the effective ranges thereof. For instance, the MBMS CN identifier has a length of about 128 bits. In contrast, the TMGI has a length of about 4-5 bytes.  
         [0040]     The MBMS identifiers are used for identifying the MBMS from the other MBMS in the 3GPP mobile communication network and for transferring the data and the control information in order to provide the MBMS. At this time, the data and control information pertaining to the MBMS are transmitted by using the MBMS identifier in relation to the predetermined MBMS requested by the corresponding UE.  
         [0041]     In addition, the MBMS control information pertaining to the corresponding MBMS must be transmitted together with a proper identifier according to the effective range thereof. That is, the MBMS control information of the CN must be transmitted together with the MBMS identifier used in the CN and the MBMS control information of the UTRAN must be transmitted together with the MBMS identifier used in the UTRAN.  
         [0042]     However, according to the conventional mobile communication network, the identifier used in the UTRAN is identical to the identifier used in the cell including the UE. That is, the conventional mobile communication network uses an identifier used in the RNC, so the effective MBMS control information is transmitted from the cell, causing an unnecessary overhead.  
         [0043]     For instance, the MBMS service identifier may have a length of about 128 bits if the Internet protocol version 6 is used as a standard. Thus, whenever the control information pertaining to the MBMS is transferred from the RNC to the UE, the MBMS service identifier having the long length must be used to transfer the control information, causing an unnecessary overhead. In addition, it is difficult to effectively use limited radio resources.  
       SUMMARY OF THE INVENTION  
       [0044]     Accordingly, the present invention has been made to solve at least the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a method of using an identifier suitable for transmitting the MBMS data or the control information in a mobile communication system providing an MBMS.  
         [0045]     Another object of the present invention is to provide a method of allowing a UE to effectively receive the control information pertaining to an MBMS in a mobile communication system providing the MBMS.  
         [0046]     Still another object of the present invention is to provide a method of allowing a cell controller to transmit to a UE the control information regarding an MBMS in a mobile communication system providing the MBMS.  
         [0047]     Still another object of the present invention is to provide a method of allowing a UE to receive the control information regarding an MBMS in a cell by using a proper identifier in a mobile communication system providing the MBMS.  
         [0048]     In order to accomplish these objects, according to one aspect of the present invention, there is provided a method for transmitting control information to a user equipment to provide a multimedia broadcast/multimedia service (MBMS) in a mobile communication system, the method includes the steps of assigning by means of a radio network controller a cell identifier pertaining to the MBMS and available in a cell that includes the user equipment, the cell identifier being differentiated from an identifier used in an upper layer; and transmitting a control message including the cell identifier to the user equipment for receiving the MBMS.  
         [0049]     In order to accomplish these objects, according to another aspect of the present invention, there is provided a method for transmitting control information to a user equipment by using a cell controller to provide a multimedia broadcast/multimedia service (MBMS) in a mobile communication system, the method including the steps of transmitting a first control message including an MBMS service identifier for identifying a first MBMS from other MBMSs, a Cell 13 specific 13 ID identifying a cell that includes the user equipment, and radio bearer information pertaining to a predetermined MBMS to a predetermined user equipment when the predetermined user equipment requests the predetermined MBMS; and transmitting a second control message including the Cell 13 specific 13 ID and the control information to the user equipment when the control information pertaining to the MBMS is generated.  
         [0050]     In order to accomplish these objects, according to still another aspect of the present invention, there is provided a method for receiving a multimedia broadcast/multimedia service (MBMS) in a mobile communication system providing the MBMS by using a user equipment, the method including the steps of receiving by means of the user equipment a paging message pertaining the MBMS from a cell controller in such a manner that the user equipment recognizes an existence of control information regarding the MBMS; receiving a control message including a mapping relationship between an identifier used for an upper layer of the MBMS and a cell identifier for identifying the MBMS in a cell that includes the user equipment from the cell controller; and receiving the MBMS by using the cell identifier after the MBMS starts.  
         [0051]     In order to accomplish these objects, according to still another aspect of the present invention, there is provided a method for receiving control information by means of a user equipment in a mobile communication system providing multimedia broadcast/multimedia service (MBMS), the method including the steps of receiving a first control message including an MBMS service identifier for identifying a first MBMS from other MBMSs, a Cell 13 specific 13 ID identifying a cell that includes the user equipment from other cells, and radio bearer information pertaining to a predetermined MBMS after joining in the MBMS; and receiving a second control message including the Cell 13 specific 13 ID and the control information in order to receive the MBMS while the MBMS is being provided. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0052]     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0053]      FIG. 1  is a block diagram illustrating a structure of a mobile communication system providing an MBMS;  
         [0054]      FIG. 2  is a diagram illustrating a UTRAN used in a mobile communication system providing an MBMS;  
         [0055]      FIG. 3  is a diagram illustrating a structure of a UTRAN protocol in a 3GPP mobile communication network;  
         [0056]      FIG. 4  is a diagram illustrating a method of using an identifier identifying an MBMS in a cell according to one embodiment of the present invention;  
         [0057]      FIG. 5  is a diagram illustrating the MBMS control channels for transmitting an identifier identifying an MBMS in a cell according to one embodiment of the present invention;  
         [0058]      FIG. 6  is a flowchart showing an operation of a UTRAN according to one embodiment of the present invention; and  
         [0059]      FIG. 7  is a flowchart showing an operation of a UE according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0060]     Hereinafter, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following detailed description, representative embodiments of the present invention will be described.  
         [0061]     For the purpose of explanation, it is noted that a mobile communication used in the following description is a mobile communication system for the 3 rd  generation partnership project (“3GPP”), which provides the standards for an asynchronous mobile communication system.  
         [0062]     The preferred embodiments of the present invention will be described in detail with reference to accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.  
         [0063]     The present invention provides a method of effectively using a plurality of identifiers used for identifying the MBMS in a corresponding service node supporting the MBMS in a mobile communication system providing the MBMS.  
         [0064]     The present invention provides an MBMS service ID for identifying a predetermined MBMS requested by a UE from other MBMSs, an MBMS CN identifier for identifying the MBMS in a CN, an MBMS UTRAN identifier for identifying the MBMS in the UTRAN to provide the MBMS, and an MBMS cell specific identifier (“MBMS Cell 13 specific 13 ID”) for identifying the MBMS in the cell that includes the UE. The MBMS Cell 13 specific 13 ID identifies a predetermined MBMS in the cell that includes the UE according to the present invention and can be defined as an MBMS radio bearer (“MBMS RB”) ID.  
         [0065]     Although the MBMS RB ID is represented as an identifier for identifying the MBMS in the cell in the present invention, it is also possible to use other identifiers for identifying the MBMS in the cell without departing from the present invention.  
         [0066]     The data pertaining to the MBMS is transmitted to an MBMS RB. The MBMS RB is a connection path for the signals or the data from the UTRAN to the UE. About thirty-two MBMS RBs can be provided for one UE and the MBMS RB has thirty-two values for one cell in the MBMS.  
         [0067]      FIG. 4  is a diagram illustrating a method of using the identifier identifying the MBMS in the cell according to one embodiment of the present invention.  
         [0068]     An RNC and the UE sequentially perform a service announcement, a subscription, a joining, a notification, and an RB setup processes such that the MBMS can be transmitted to the corresponding UEs. Although the above service announcement, subscription, and the joining processes are omitted in  FIG. 4 , the service announcement, subscription, and the joining processes are carried out prior to the notification process. In addition, after performing the service announcement and the joining processes, the RNC receives a session start message that includes information related to the MBMS service ID and the MBMS QoS parameters from a CN, thereby recognizing that the MBMS may soon start.  
         [0069]     Referring to  FIG. 4 , the RNC  410  that receives the session start message from the CN transmits a control message pertaining to the MBMS to the UE  401 . The UE  401  receives an initial MBMS control message  402  transmitted from the RNC  410 . The initial MBMS control message  402  includes the RB parameters that represent information for determining the radio. channels through which the MBMS is to be transmitted, and represent information related to the radio resources in the cell that includes the UE  401 , an MBMS IUD for discriminating the MBMS requested by the UE  401  in the RNC  410 , and an MBMS Cell 13 specific 13 ID for discriminating the MBMS in the cell that includes the UE  401  in relation to the MBMS ID.  
         [0070]     Herein, the MBMS ID includes the MBMS service ID for identifying the predetermined MBMS requested by the UE  401  from the other MBMSs, the MBMS CN identifier for identifying the MBMS in the CN, and the MBMS UTRAN identifier for identifying the MBMS in the UTRAN (RNC  410 ) to provide the MBMS. In addition, the initial MBMS control message  402  includes the MBMS Cell 13 specific 13 ID for identifying the MBMS in the cell and including the MBMS RB ID  
         [0071]     Therefore, the UE that receives the initial MBMS control message  402  may receive corresponding MBMS data by using the MBMS RB information and recognizes the mapping relationship between the MBMS identifiers through the MBMS ID and the MBMS RM ID. When providing the predetermined MBMS, the RNC  410  assigns the MBMS service ID or the Temporary MBMS Group Indicator(TMGI) used in the upper layer including the CN to the MBMS RB ID and transmits the MBMS service ID or the TMGI to the UE  401  through the control message, which is referred to as an “initial MBMS control message”.  
         [0072]     In step  403  shown in  FIG. 4 , the UE  401  receives the MBMS control message to check for an MBMS service K in the cell and transmits a response message for the MBMS control message to the RNC  410 . That is, in step  402 , the UE  401  receiving the MBMS control message recognizes a mapping relationship between the MBMS identifiers through the MBMS ID and the MBMS RB ID. In other words, the UB  401  recognizes the mapping relationship between the MBMS service identifier (TMGI), to which the MBMS is being provided or will be provided, and an identifier for identifying the MBMS service in the cell that includes the UE  401  and transmits the mapping relationship to the RNC  410  through the response message.  
         [0073]     At this time, in step  404 , if it is required to transmit the control information due to a variation of radio the environment or other causes while providing the MBMS service K, the RNC  410  transmits a control message including the MBMS RB ID and the parameters. For instance, the control message includes a message requesting the change of the information related to the MBMS RB or requesting a measurement of the radio environment.  
         [0074]     In step  405 , the RNC  410  transmits the control message including the MBMS RB ID and the parameters. The control message includes a message that the MBMS service K has finished or that the session, which is a transmission unit of the MBMS, has finished.  
         [0075]     The RNC  410  transmits a relationship between the service identifier for identifying the MBMS in the upper layer and the service identifier for identifying the MBMS in the cell through the initial MBMS control message  402  and transmits the MBMS control message by adding the MBMS RB ID, which is the identifier for identifying the MBMS in the cell, to the MBMS control message. The RNC  410  transmits the control information related to the MBMS service K through the MBMS control message and a last MBMS control message by using only the MBMS RB ID.  
         [0076]      FIG. 5  is a diagram illustrating the MBMS control channels (“MCCH”) for transmitting an identifier identifying the MBMS in the cell according to one embodiment of the present invention.  
         [0077]     The diagrams (a) through (d) of  FIG. 5  show the contents and structures of the control messages to be transmitted as control information regarding the MBMS through the MCCH.  
         [0078]     Diagram (a) of  FIG. 5  represents a structure of the MCCH for transmitting the control information pertaining to the MBMS service K (“MBMS K”) when the MBMS K is provided. Herein, it is assumed that the MCCH is mapped with the FACH included in the transport channels and transmitted through the S-CCPCH.  
         [0079]     In diagram (a) of  FIG. 5 , a control message  501  is a notification message representing that the MBMS K requested by the UE  401  may soon start. Upon receiving the notification message, the UEs provided in a predetermined cell perform a response to the notification. At this time, the RNC  410  of the UTRAN receives the response messages from the UEs and determines a transmission mode for the MBMS K, that is, determines whether to use the PtP service or the PtM service.  
         [0080]     The RNC  410  then transmits the RB information related to the MBMS K to the UE  401  through a control message  502  (MCCH) based on the selected transmission mode. The UE  401  that receives the control message  502  may receive the predetermined MBMS K by using the RB information. A structure of the control message  502  is shown in diagram (b) of  FIG. 5 .  
         [0081]     In diagram (b) of  FIG. 5 , reference numeral  511  represents a service identifier for the MBMS K. The service identifier  511  includes an MBMS CN identifier for identifying the MBMS in the CN related to the MBMS K and an MBMS UTRAN identifier for identifying the MBMS in the UTRAN in order to provide the MBMS. That is, the service identifier  511  is an MBMS service ID for identifying the MBMS K from other MBMSs in the CN or RNC  410 . Reference numeral  512  represents an MBMS Cell 13 specific 13 ID used for identifying the MBMS K in the cell that includes the UE  401 , that is, MBMS RB ID. Reference numeral  513  is MBMS RB information.  
         [0082]     A message  503  is a control message for transmitting a mapping relationship between a service identifier for the MBMS K and an identifier for a related to the MBMS K to a UE newly introduced into the cell related to the MBMS K from a predetermined cell or UEs for receiving the MBMS K. That is, the control message  503  transmits the mapping relationship between the service identifier for the MBMS K and the service identifier for the cell to the UE  401  by taking into consideration the mobility of the UEs. A structure of the control message  503  is shown in diagram (c) of  FIG. 5 .  
         [0083]     Referring to diagram (c) of  FIG. 5 , the control message  503  transmits the mapping relationship between the MBMS ID for the MBMS K and the MBMS RB ID to the UE  401 . That is, if the UE  401  requests the MBMS K, the CN or the UTRAN may assign the MBMS ID with respect to the MBMS K, which is being provided or to be provided, from the first session to the last session of the MBMS K. At this time, the MBMS RB ID of the cell including the UE  401 is mapped with the MBMS ID and is transmitted to the UE  401 .  
         [0084]     In  FIG. 5 , reference numeral  521  represents the first MBMS service ID regarding the MBMS K, the MBMS CN identifier for identifying the MBMS service in the CN, or the MBMS UTRAN identifier for identifying the MBMS in the UTRAN. Reference numeral  522  represents the MBMS Cell 13 specific 13 ID provided in the cell that is related to the first MBMS service identifier. Reference numeral  523  represents the last MBMS service ID that is related to the MBMS K, the MBMS CN identifier for identifying the last MBMS in the CN, or the MBMS UTRAN identifier for identifying the last MBMS in the UTRAN. Reference numeral  524  represents the MBMS Cell 13 specific 13 ID provided in the cell that is related to the last MBMS service ID  523 .  
         [0085]     If the control information related to the MBMS K is generated some time later, the RNC transmits a message  504  or a message  505  including the MBMS RB ID by adding the control information related the MBMS K to the message  504  or the message  505 . That is, if it is necessary to transmit the control information due to a variation of the radio environment in the cell that includes the UE, the RNC may transmit the MBMS control message including the MBMS RB ID having a short length.  
         [0086]     At this time, a new UE, is wants to receive the MBMS K, or UEs that have moved into the cell to which the MBMS K is provided may receive the RB information related to the MBMS K, which is periodically transmitted from the RNC to the UEs. In addition, the new UE or the UEs may receive the control information related to the MBMS K by recognizing the mapping relationship between the MBMS ID and the MBMS RB ID of the MBMS K included in the MBMS RB information. The UE may receive the message  504  or the message  505  while recognizing the mapping relationship between the MBMS ID and MBMS RB ID, and then, receive the control information related to the MBMS K.  
         [0087]     The structure of the control information  504  and the message  505  regarding the MBMS K are shown in diagram (d) of  FIG. 5 .  
         [0088]     In diagram (d) of  FIG. 5 , reference numeral  531  represents the MBMS Cell 13 specific 13 ID, which is an identifier for identifying the MBMS in the cell, that is, the MBMS RB ID. Reference numeral  522  is the control information related to the MBMS K. The control information may include the RB change information related to the MBMS K or the measurement information related to the MBMS K.  
         [0089]     As mentioned above, if the control information related to the MBMS k is generated, the RNC  410  transmits only the MBMS Cell 13 Specific 13 ID for providing the MBMS K in the cell, that is, the RNC  410  transmits the control information to the UEs provided in the cell by using an identifier having a short length, thereby reducing an overhead caused by the excessive transmission of the identifier and efficiently using radio resources.  
         [0090]      FIG. 6  is a flowchart showing an operation of the UTRAN according to one embodiment of the present invention.  
         [0091]     Referring to  FIG. 6 , the RNC of the UTRAN transmits a notification message related to the MBMS service K to a predetermined cell that includes UEs requesting the MBMS K (step  601 ). Then, the RNC receives a response message in response to the notification message from the UEs of the cell, performs an RAB setup for the MBMS K based on the response message, and performs an RB setup such that the MBMS data related to the MBMS K are transmitted into the cell (step  602 ). The RAB setup is a transmission path setup from the CN to the UTRAN for transmitting the MBMS data related to the MBMS K and the RB setup is a transmission path setup from the RNC to the UE for transmitting the MBMS data related to the MBMS K.  
         [0092]     Based on the response message transmitted from the UEs, the RNC determines the transmission mode for the MBMS data related to the MBMS K, that is, selects either a PtP transmission mode or a PtM transmission mode. If the number of UEs transmitting the response message in response to the notification message exceeds a predetermined reference number, the PtM transmission mode is selected. In addition, if the number of UEs transmitting the response message in response to the notification message is less than the predetermined reference number, the PtP transmission mode is selected. Accordingly, if the RNC determines that the MBMS data must be transmitted through the PtM transmission mode in step  603 , the procedure goes to step  604 . If RNC determines that the MBMS data must be transmitted through the PtP transmission mode in step  603 , the procedure goes to step  620 .  
         [0093]     In step  604 , the RNC transmits the RB information related to the MBMS K through the MCCH by using the FACH of the S-CCPCH. That is, the RNC transmits the RB information to the UEs, which are provided in the predetermined cell in order to receive the MBMS K. After that, the RNC provides the MBMS K to the UEs of the cell by using the predetermined RB information (step  605 ).  
         [0094]     If the control information related to the MBMS K is generated at a predetermined point as shown in step  606 , the RNC transmits the MCCH including the Cell 13 specific 13 ID and the RB information related to the MBMS K to the UEs provided in the cell.  
         [0095]     If a UE moves into another cell from a predetermined cell, the RNC transmits the CN, the UTRAN MBMS ID, the MBMS Cell 13 specific 13 ID or MBMS RB information related to the MBMS K (step  607 ). This is because the UE cannot recognize the mapping relationship from among the CN, the UTRAN MBMS ID and the MBMS Cell 13 specific 13 ID as the UE moves to the other cell. That is, in step  607 , the RNC determines a state of the UE and transmits only the MBMS Cell 13 specific 13 ID, or transmits the CN, the UTRAN MBMS ID, the MBMS Cell 13 specific 13 ID regarding the MBMS K according to the state of the UE.  
         [0096]     In addition, the RNC determines whether or not it is necessary to transmit the Cell 13 Specific 13 ID and the RB information related to the MBMS K (step  608 ). This is because the RNC periodically transmits RB information related to MBMS K to the UE. If the RNC determines that it is necessary to transmit the Cell 13 Specific 13 ID and the RB information related to the MBMS K in step  608 , the procedure goes to step  609 . In step  609 , the RNC transmits the Cell 13 specific 13 ID and the RB information related to the MBMS K. The RNC may continuously transmit the MBMS K to the UE (step  610 ).  
         [0097]     Meanwhile, if the RNC determines that the MBMS data related to the MBMS K must be transmitted through the PtP transmission mode in step  603 , the RNC may transmit the MCCH including the RB information related to the MBMS K by using the DCH of the S-CCPCH (step  620 ). Accordingly, the RNC assigns the DCH with respect to each UE, which is provided in the predetermined cell to receive the MBMS K, so as to transmit the MCCH including the RB information related to the MBMS K to each UE. After that, the RNC provides the MBMS K to each UE formed in the predetermined cell (step  621 ).  
         [0098]     In addition, the RNC determines whether or not it is necessary to change the transmission mode for the MBMS K being transmitted to each UE through the DCH (step  622 ). That is, if the number of UEs requesting the MBMS K in the cell to which the MBMS K is provided increases and exceeds the reference number, the RNC changes the transmission mode for the MBMS K from the PtP transmission mode to the PtM transmission mode. In other words, if the RNC determines that the MBMS K must be transmitted through the PtM transmission mode based on the response message transmitted from the UEs in step  622 , the procedure goes to step  604 . However, if the RNC determines that the MBMS K must be transmitted through the PtP transmission mode, the procedure goes to step  623 . In step  623 , the RNC transmits the MBMS K through the predetermined DCH.  
         [0099]      FIG. 7  is a flowchart showing an operation of the UE according to one embodiment of the present invention.  
         [0100]     Referring to  FIG. 7 , the UE receives the notification message related to the MBMS K from the RNC (step  701 ). In step  702 , the UE transmits the response message to the RNC in response to a counting command of the RNC transmitting the notification message. The counting command is a procedure of the RNC for determining the transmission mode in order to allow the UEs provided in the predetermined cell to receive the MBMS K. Then, the UE transmitting the response message waits for a paging message for receiving the RB information related to the MBMS K.  
         [0101]     After that, if the UE receives a paging message related to the MBMS K from the RNC in step  703 , the procedure goes to step  704 . At this time, the UEs requesting the MBMS K may receive the paging message for the MBMS K and check the identifier for the MBMS K in order to determine whether or not there is the control information related to the MBMS K. If the UE recognizes that the control information exists in step  704 , the UE determines whether or not the control information related to the MBMS K is suitable for the UE. That is, the UE receives the MBMS service ID of the CN or the UTRAN transmitted to the PCH and determines whether or not the MBMS service ID is suitable for the MBMS K.  
         [0102]     If the UE determines that the control information is suitable for the MBMS K in step  704 , the UE receives the RB information related to the MBMS K through the MCCH (step  705 ). After that, the UE receives the MBMS K by using the received RB information.  
         [0103]     In addition, the UE that receives the MBMS K determines whether or not the control information related to the MBMS K is transmitted from the RNC (step  706 ). If there is control information related to the MBMS K, the UE receives the MBMS Cell 13 specific 13 ID and the MBMS RB information related to the control information of MBMS K from the RNC (step  707 ). In addition, the UE continuously receives the MBMS K transmitted from the RNC (step  708 ).  
         [0104]     If the UE does not receive the paging message related to the MBMS K, but receives the paging message for the UE in step  703 , the procedure goes to step  720 .  
         [0105]     In step  720 , the UE checks the PCH and receives the PtP RB information through the DCCH. In addition, the UE receives the MBMS K by using the RB information (step  721 ). If the UE recognizes that MBMS data related to the MBMS K will be transmitted from the RNC through the PtM transmission mode in step  722 , the procedure goes to step  705 . In step  705 , the UE receives the RB information related to the MBMS K through the MCCH. The UEs that receives the MBMS K through the PtP transmission mode by using the RB information of the MBMS K can previously receive the RB information related to the MBMS K through the PtM transmission mode in step  722 . In addition, the Ues that receives the MBMS K through the PtP transmission mode may continuously receive the MBMS K in step  723 .  
         [0106]     As described above, according to the present invention, an identifier is used when transmitting the MBMS data or the MBMS control information, and the identifier is selected by taking into consideration a usable range of the MBMS identifiers, thereby reducing the overhead of the radio resources.  
         [0107]     In addition, when providing the MBMS according to the present invention, the identifier is selectively used by taking into consideration an effective range thereof according to a master of the MBMS data or the MBMS control information. Accordingly, it is possible to efficiently use limited radio resources.  
         [0108]     While the invention has been shown and described with reference to certain preferred embodiments 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.