Abstract:
Disclosed is a method for efficiently transmitting and receiving control information messages necessary for a Multimedia Broadcast/Multicast Service (MBMS) provided in a mobile communication system. The method includes setting information elements for the control information messages to reduce unnecessary signaling overhead during the transmission of the control information. The method prevents a user equipment (UE) from performing duplicate reception on the control information, thereby reducing power consumption of a battery.

Description:
PRIORITY  
       [0001]     This application claims priority under 35 U.S.C. § 119 to an application entitled “Method for Transmitting and Receiving Control Information in a Mobile Communication System Supporting Multimedia Broadcast/Multicast Service” filed in the Korean Intellectual Property Office on Apr. 16, 2004 and assigned Serial No. 2004-26266, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to a mobile communication system supporting a Multimedia Broadcast/Multicast Service (MBMS), and in particular, to a method for efficiently transmitting control information for an MBMS service.  
         [0004]     2. Description of the Related Art  
         [0005]     As the communication technology develops, a service provided in a mobile communication system is evolving into a multimedia broadcast/communication service capable of supporting not only the conventional voice service but also a packet service and a multimedia service to enable the transmission of large amounts bulk data such as packet data and circuit data. In order to support the multicast broadcast/communication, there has been proposed a Multimedia Broadcast/Multicast Service (hereinafter referred to as an “MBMS service”) in which one or more multimedia data sources provide a service to a plurality of user equipments (UEs).  
         [0006]     The MBMS service can transmit the same multimedia data to a plurality of recipients through a wireless network. The MBMS service can save wireless transmission resources by allowing a plurality of recipients to share one radio channel. The MBMS service supports the transmission of such multimedia data as real-time image and voice, still image, text, etc., and can simultaneously transmit voice data and image data based on a transfer mode of the multimedia data. This requires a large amount of transmission resources. In the MBMS service, because the same data should transmitted to a plurality of cells where users are located, point-to-point (PtP) connection or point-to-multipoint (PtM) connection is achieved according to the number of users located in each cell. The PtP connection allocates a dedicated channel to each UE and provides a desired MBMS service to the UE through the dedicated channel on an individual basis. However, the PtM connection allocates a common channel to multiple UEs requesting the same MBMS service and provides the MBMS service to the UEs through the common channel.  
         [0007]     The following description will be made with reference to a 3 rd  Generation Partnership Project (3GPP) mobile communication network, which is a typical 3 rd  generation asynchronous mobile communication network.  
         [0008]      FIG. 1  is a diagram illustrating an MBMS service in a 3GPP mobile communication network. Referring to  FIG. 1 , a core network (CN)  100  provides the MBMS service, the MBMS data transmission, to a UMTS Terrestrial Radio Access Network (UTRAN)  110 , and authenticates the UEs  120 ,  121  and  122 . The UTRAN  110  connects the CN  100  to the UEs  120 ,  121  and  122 , and performs wire/wireless resource allocation and management to enable the transmission of the MBMS service. The UTRAN  110  is comprised of at least one radio network controller (RNC)  111  and at least one Node B  112 . The RNC  111  can control a plurality of Node Bs. Node B  112  can represent a plurality of Node Bs. The plurality of Node Bs including the Node B  112  each comprise of a plurality of cells. The cell refers to a basic communication unit are in a wireless communication network, and the cells can be identified by their unique frequencies or locations.  
         [0009]     The UE# 1   120 , the UE# 2   121  and the UE#n  122  are UEs capable of receiving the MBMS service, and a plurality of UEs can be located in each cell. A basic service unit for the MBMS service is the cell, and the MBMS service is provided through a PtP channel or a PtM channel based on the radio environment of the cell and the number of UEs desiring to receive the MBMS service located in the cell. A counting process to determine the number of UEs is performed to determine which type of MBMS service is preferred.  
         [0010]     In order to provide the MBMS service, a plurality of control information messages are transmitted, which include not only data for the MBMS service, but also information on the MBMS service, information on a channel over which the MBMS data is transmitted, information indicating a start time of the MBMS service, information on a change in transfer mode during transmission of the MBMS data, information on neighbor cells, if any, where the MBMS service is provided, and information on an MBMS service provided in the current cell.  
         [0011]      FIG. 2  is a diagram illustrating a detailed structure of upper layers of a UTRAN and channels between the respective layers, defined in the current 3GPP, to which the present invention is applied. Referring to  FIG. 2 , upper layer messages processed in the UTRAN can be roughly divided into signaling and user data.  
         [0012]     Disclosed herein are control plain (C-Plain) signaling  201  and User plain (U-Plain) information  202 . The C-Plain signaling  201  and the U-Plain information  202  are Non-Access Stratum (NAS) messages, which the UTRAN is not required to know because they are not used for wireless connection between a UE and the UTRAN. Unlike the NAS messages, messages directly used for the wireless connection between the UTRAN and the UE are called Access Stratum (AS) messages, and the AS messages indicate signaling used under a radio resource controller (RRC)  203 .  
         [0013]     The RRC  203  controls a physical layer (L 1 )  210 , and a Medium Access Control (L 2 /MAC)  208 , a Radio Link Control (L 2 /RLC)  206 , a Packet Data Convergency Protocol (L 2 /PDCP)  204 , and a Broadcast/Multicast Control (L 2 /BMC)  205  for Layer  2  (L 2 ), all of which are related to an access to a UE and a UTRAN, to control all of the events related to a connection between the UE and the UTRAN. These include physical call setup, logical call setup, control information transmission/reception, and measurement data transmission/reception between the UE and the UTRAN.  
         [0014]     The L 2 /PDCP  204  receives the U-Plain information  202  of a NAS layer, processes the received U-Plain information  202  using an appropriate protocol, and transmits the processing result to the L 2 /RLC  206 . The L 2 /BMC  205  receives the data needed for the broadcast/multicast, processes the received data using an appropriate protocol, and transmits the processing result to the L 2 /RLC  206 .  
         [0015]     The L 2 /RLC  206  receives a control message output from the RRC  203 , processes the received control message in an appropriate format in an RLC# 1   261  and an RLC# 2   262  taking a feature of the control message into consideration, and transmits the processing result to the L 2 /MAC  208  using logical channels  207 . Further, the L 2 /RLC  206  receives data from the L 2 /PDCP  204  and the L 2 /BMC  205 , processes the received data in an appropriate format in an RLC# 1   263  and an RLC#n  264 , and transmits the processing result to the L 2 /MAC  208  using the logical channels  207 . The number of RLC entities ( 261  to  264 ) included in the L 2 /RLC  206  is determined according to the number of types of the logical channels  207  and the number of radio links.  
         [0016]     The logical channels  207  are roughly divided into a dedicated type and a common type according to whether they are for a specified UE(s) or for a plurality of UEs, and into a control type and a traffic type according to a feature of a message transmitted therethrough.  
         [0017]     Table 1 illustrates types and functions of the logical channels  207  used in the 3GPP standard.  
                   TABLE 1                       Type   Function                   BCCH   It stands for a Broadcast Control Channel, and is used for           downlink transmission from a UTRAN to a UE and for           transmission of UTRAN system control information.       PCCH   It stands for a Paging Control Channel, and is used for downlink           transmission from a UTRAN to a UE, and for transmission of           control information to the UE when a position of a cell to which           the UE belongs is unknown.       CCCH   It stands for a Common Control Channel, and is used for           transmission of control information between a UE and a           network.       DCCH   It stands for a Dedicated Control Channel, and is used for           transmission of control information between a UE and a network           on a one-to-one basis. Also, it is used when the UE has a           channel connected to an RRC layer.       CTCH   It stands for a Common Traffic Channel, and is used for data           transmission between a network and UEs. Also, it is used when           data that should be transmitted by all of the UEs is transmitted           or when information needed by several UEs is transmitted on a           time-division basis.       DTCH   It stands for a Dedicated Traffic Channel, and is used for data           transmission between a network and a UE on a one-to-one basis.                  
 
         [0018]     The L 2 /MAC  208 , under the control of the RRC  203 , manages radio resources between a UE and a UTRAN, manages a connection between the UE and the UTRAN, or maps data received from the L 2 /RLC  206  through logical channels to transport channels  209 , and transmits the mapping result to the L 1  layer  210 .  
         [0019]     Table 2 illustrates types and functions of the transport channels  209  used in the 3GPP standard and a mapping relation with the logical channels  207 .  
                   TABLE 2                       Type   Function                   BCH   It stands for a Broadcast Channel, and is mapped to BCCH           to transmit data on the BCCH.       PCH   It stands for a Paging Channel, and is mapped to PCCH to           transmit data on the PCCH.       RACH   It stands for a Random Access Channel, and is used for           transmission from a UE to a network and for           transmission of network access, a control message           and short-length data. It can be accessed at a predetermined           acquisition probability, and DCCH, CCCH and DTCH           can be mapped to this channel.       FACH   It stands for a Forward Access Channel, and is used for control           message and data transmission from a network to a particular           UE or particular UEs. BCCH, CTCH, CCCH, DTCH           and DCCH can be mapped to this channel.       DCH   It stands for a Dedicated Channel, and is used for transmission           of data and control signaling between a network and a UE.       DSCH   It stands for a Downlink Shared Channel, and is a downlink           channel from a network to a UE, used for high-capacity           data transmission. DTCH and DCCH are mapped to this           channel.       HS-   It stands for a High Speed DSCH (Dedicated Shared Channel),       DSCH   and is a downlink channel from a network to a UE,           obtained by improving transmission capacity of the DSCH.           DTCH and DCCH are mapped to this channel.                  
 
         [0020]     Aside from the transport channels described in Table 2, such transport channels as an uplink shared channel (USCH) and a common packet channel (CPCH) are defined in the current 3GPP.  
         [0021]     As illustrated, data on the transport channels transmitted to the L 1  layer  210  is mapped to physical channels through an appropriate process, and then transmitted to a UE or a UTRAN.  
         [0022]     The physical channels include a Primary Common Control Physical Channel (P-CCPCH) for the transmission of a BCH, a Secondary Common Control Physical Channel (S-CCPCH) for the transmission of a PCH and a FACH, a Dedicated Physical Channel (DCH) for the transmission of a DCH, a Physical Downlink Shared Channel (PDSCH) for the transmission of a DSCH, a High Speed Physical Downlink Shared Channel (HS-PDSCH) for the transmission of a HS-DSCH, and a Physical Random Access Channel (PRACH) for the transmission of a RACH. In addition, the physical channels include a Pilot Channel, a Primary Synchronization Channel, a Secondary Synchronization Channel, a Paging Indicator Channel, an Acquisition Indicator Channel, and a Physical Common Packet Channel.  
         [0023]     Aside from the foregoing logical channels, logical channels for supporting an MBMS service are defined in the 3GPP. The newly defined logical channels include an MBMS Traffic Channel (MTCH) over which MBMS data is transmitted for the MBMS service, and an MBMS Control Channel (MCCH) over which control information needed for reception of the MBMS service is transmitted. The two logical channels are mapped to the FACH which is a transport channel, and then transmitted to UEs scheduled to receive the MBMS service, through the S-CCPCH which is a physical channel.  
         [0024]     The “control information” refers to (i) information on a transmission start and a transmission end of MBMS data, and a logical channel, a transport channel and a physical channel, over all of which MBMS data is transmitted, (ii) information on neighbor cells in which the same MBMS is provided, and (iii) information on MBMS services provided in the current cell. Information elements (IEs) needed for the control information messages can be separately defined for each individual message. The messages may overlap each other in terms of the IEs defined for each individual message.  
       SUMMARY OF THE INVENTION  
       [0025]     In order to prevent the unnecessary overlapping of the IEs, there is a demand for a method to precisely define the IEs needed for each control information message and appropriately arrange the IEs according to a use of the control information messages. In addition, the number of the control information messages increases the amount of control information that a UE should receive for reception of an MBMS service and causes generation of periodically repeated control information messages to support mobility of the UE, a demand for preventing the duplicate reception of the IEs of the control information messages is required. Furthermore, there is a demand for a method that is capable of minimizing a reception time for which the UE receives the control information messages.  
         [0026]     It is, therefore, an object of the present invention to provide a method for transmitting and receiving control information messages needed for an MBMS service.  
         [0027]     It is another object of the present invention to provide a method for minimizing the signaling overhead in the process of transmitting control information messages for an MBMS service.  
         [0028]     It is another object of the present invention to provide an efficient scheduling method for the transmission of control information messages for an MBMS service.  
         [0029]     It is further another object of the present invention to provide a method for preventing the duplicate reception of control IEs having the same contents in the process of receiving control information messages for an MBMS service.  
         [0030]     It is still another object of the present invention to provide a method for minimizing the power consumption of a UE in the process of receiving control information messages for an MBMS service.  
         [0031]     According to one aspect of the present invention, there is provided a method for transmitting control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of generating an MBMS notification information message indicating a significant change in an MBMS service; and transmitting the MBMS notification information message to at least one user equipment (UE) located in a cell capable of providing the MBMS service; wherein the MBMS notification information message includes an MBMS service identifier (ID), a cause value indicating the cause for the notification, frequency information for the MBMS service, and continue reading information indicating whether to continuously receive control information messages transmitted after the MBMS notification information message.  
         [0032]     According to another aspect of the present invention, there is provided a method for receiving control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of receiving a notification indicator (NI) for an MBMS service; if the received notification indicator is affirmative, determining if a current frame corresponds to a start time of a predetermined modification period (MP); if the current frame arrives at the start time of the modification period, receiving an MBMS notification information message for indicating a significant change in the MBMS service, the MBMS notification information message includes an MBMS service identifier (ID), a cause value indicating the cause for the notification, frequency information for the MBMS service, and continue reading information indicating whether to continuously receive control information messages transmitted after the MBMS notification information message; and checking the cause value of the MBMS notification information message, and performing an operation according to the cause value.  
         [0033]     According to further another aspect of the present invention, there is provided a method for transmitting control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of generating an MBMS service list message including control information for at least one MBMS service of a current cell; and transmitting the MBMS service list message to at least one user equipment (UE) located in the current cell, wherein the MBMS service list message includes an MBMS service identifier (ID), information indicating a transfer mode of a corresponding MBMS service, and frequency information for the corresponding MBMS service.  
         [0034]     According to further another aspect of the present invention, there is provided a method for receiving control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of determining if a current frame corresponds to a start time of a predetermined repetition period (RP), if there is a need for receiving an MBMS service list message including control information for at least one MBMS service of a current cell; if the current frame arrives the start time of the repetition period, receiving the MBMS service list message, the MBMS service list message includes an MBMS service identifier (ID), information indicating a transfer mode for a corresponding MBMS service, and frequency information for the corresponding MBMS service; determining if there is an ID of a joined MBMS service in the MBMS service list message; checking a transfer mode of the joined MBMS service, if there is an ID of the joined MBMS service in the MBMS service list message; and receiving the joined MBMS service according to whether the transfer mode of the joined MBMS service corresponds to point-to-multipoint (PtM), point-to-point (PtP), or no-RB (radio bearer).  
         [0035]     According to further another aspect of the present invention, there is provided a method for transmitting control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of generating an MBMS common radio bearer (RB) information message including common control information for RBs, physical channels and transport channels used for MBMS services provided in a current cell; and transmitting the MBMS common RB information message to at least one user equipment (UE) located in the current cell, wherein the MBMS common RB information message includes an RB information list for RBs commonly used by the MBMS services, transport channel information and physical channel information.  
         [0036]     According to further another aspect of the present invention, there is provided a method for receiving control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of receiving an MBMS common radio bearer (RB) information message, if there is a need for receiving the MBMS common RB information message including common control information for RBs, physical channels and transport channels used for MBMS services provided in a current cell, the MBMS common RB information message includes an RB information list for RBs commonly used by the MBMS services, transport channel information and physical channel information; and acquiring the RB information list, the transport channel information and the physical channel information, all of which are included in the MBMS common RB information message.  
         [0037]     According to further another aspect of the present invention, there is provided a method for transmitting control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of generating an MBMS service point-to-multipoint (PtM) radio bearer (RB) information message including control information for MBMS services provided in a current cell and neighbor cells; and transmitting the MBMS service PtM RB information message to at least one user equipment (UE) located in the current cell, wherein the MBMS service PtM RB information message includes current cell RB information including an RB information list for RBs used by MBMS services provided in the current cell, transport channel information and physical channel information, and neighbor cell RB information including an RB information list for RBs used by MBMS services provided in the neighbor cells, transport channel information and physical channel information.  
         [0038]     According to further another aspect of the present invention, there is provided a method for receiving control information for supporting a Multimedia Broadcast/Multicast Service (MBMS) service in a mobile communication system providing the MBMS service, the method including the steps of receiving an MBMS notification information message for indicating a significant change in an MBMS service, and receiving an MBMS service point-to-multipoint (PtM) radio bearer (RB) information message including control information for MBMS services provided in a current cell and neighbor cells according to the MBMS notification information message; determining if there is RB information for a joined MBMS service in the MBMS service PtM RB information message; and if there is RB information for the joined MBMS service, acquiring control information for the current cell and the neighbor cells for the joined MBMS service from the MBMS service PtM RB information message. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0039]     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:  
         [0040]      FIG. 1  is a diagram illustrating a network configuration of a 3 rd  generation asynchronous mobile communication system supporting a Multimedia Broadcast/Multicast Service (MBMS) service;  
         [0041]      FIG. 2  is a diagram illustrating a protocol structure of a wireless access network in a 3 rd  generation mobile communication network;  
         [0042]      FIG. 3  is a diagram illustrating an example of control information transmitted over an MCCH in a 3 generation mobile communication network;  
         [0043]      FIG. 4  is a diagram illustrating an example for transmission and scheduling of control information messages proposed in the present invention;  
         [0044]      FIG. 5  is a flowchart illustrating a UTRAN operation of transmitting control information messages proposed in the present invention;  
         [0045]      FIG. 6  is a flowchart illustrating a UE operation of receiving an MBMS Notification Info message according to an embodiment of the present invention;  
         [0046]      FIG. 7  is a flowchart illustrating a UE operation of receiving an MBMS Service List message proposed in the present invention;  
         [0047]      FIG. 8  is a flowchart a UE operation of receiving an MBMS Service PtM RB Info message proposed in the present invention; and  
         [0048]      FIG. 9  is a flowchart illustrating a UE operation of receiving an MBMS Common RB Info message proposed in the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0049]     Several preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness.  
         [0050]     Control information necessary for an MBMS service includes: 
        1. system information for all of the MBMS services,     2. a transmission start time and a repetition period of the control information transmitted over an MBMS Control Channel (MCCH),     3. channel information (logical channel information, transport channel information and physical channel information) for an MBMS Traffic Channel (MTCH) that transmits MBMS data on a PtM basis,     4. information (e.g., an MBMS service ID) on an MBMS service transmitted over the MTCH,     5. a list of MBMS services of the current cell, provided for mobility of UEs,     6. neighbor cell MBMS information for supporting selective combining (SC) used to increase the MBMS data reception performance of a UE,     7. transmission scheduling information for the MBMS data, for supporting discontinuous transmission (DTX) of the MBMS data transmitted over an MTCH, and     8. information indicating a frequency band in which MBMS service can be received.        
 
         [0059]     Aside from the foregoing information, other control information can be additionally defined. Herein, there are two possible paths through which the control information can be provided to UEs scheduled to receive an MBMS service, and a path used is changed according to a feature of the control information.  
         [0060]     A first method transmits the control information through a BCH, and control information that can be transmitted over the BCH can include system information for all of the MBMS services. The system information can include repetition periods of Notification Indicator Channel (NICH) information indicating the presence of the control information for the transmission and a start of an MBMS service, information on a FACH and an S-CCPCH, over both of which an MCCH is transmitted, and control information transmitted over the MCCH. There are 3 possible repetition periods defined: Modification Period (MP), Repetition Period (RP) and Access Info Period (AIP). A detailed description of the periods will be made later with reference to  FIG. 4 .  
         [0061]     A second method transmits the control information through an MCCH used for the transmission of the control information for an MBMS service. The control information that can be transmitted over the MCCH can include the information described in items 3 to 8 from among the forgoing necessary control information items. That is, a UE receives the control information of items 3 to 8 through an MCCH depending on the control information of items 1 and 2 received over a BCH. In this case, the control information items transmitted over the MCCH overlap each other in several information details. For example, in order to provide information indicating that a particular MBMS service is effective in a cell, it is necessary to transmit an identifier (ID) for the MBMS service. Also, the ID for the MBMS service is required in order to provide information on a channel type for the MBMS service and a channel over which the MBMS service is transmitted.  
         [0062]     Embodiments of the present invention described below define the control information messages necessary for an MBMS service, and propose the following control information message formats to prevent the information elements (IEs) of the control information messages from undergoing a duplicate transmission. Control information messages transmitted over an MCCH, proposed in preferred embodiments of the present invention, include: 
        1. MBMS Notification Info message: This is a control signaling message indicating a start and an end of a session which is a basic transmission unit for an MBMS service. It is used to indicate a significant change in MBMS service, and is also known as an MBMS Modified Service Info message. Also, this can be used for a counting operation to determine the number of UEs in a cell to determine a transfer mode of MBMS data.     2. MBMS Service List message: This is a control signaling message providing a list of MBMS services currently provided in or available in the current cell. It serves to inform a UE powered on in the current cell or UEs entering from another cell of the available MBMS services, and is also known as an MBMS Unmodified Service Info message as it is used for notification on unmodified control information for an MBMS service.     3. MBMS Common RB Info message: This is a control information message used for informing a UE of common information details for radio bearers (RBs), physical channels and transport channels used by MBMS services provided in the current cell, and is also known as an MBMS Common PtM RB Info message. The MBMS Common RB Info message can include RB information for an MBMS service selectively transmitted from neighbor cells. Information on the neighbor cells can be used for selective combining (SC).     4. MBMS Service PtM RB Info message: This is a control information message used for informing a UE of all of the information details for a particular MBMS service which is provided in the current cell on a PtM basis. During new MBMS data transmission, if the MBMS service is performed in neighbor cells, the MBMS Service PtM RB Info message can include neighbor cell information as well. An information part for the current cell is referred to as an MBMS Current Cell PtM RB Info message, and an information part for the neighbor cell is referred to as an MBMS Neighboring Cell PtM RB Info message. A UTRAN preferentially transmits an MBMS Service PtM RB Info message that should be first received, from among several MBMS Service PtM RB Info messages.        
 
         [0067]     Table 3, Table 4, Table 5 and Table 6 below illustrate information elements (IEs) necessary for a description of the present invention for the foregoing control information messages, in which IEs newly defined in the present invention are underlined and expressed in bold. In the following tables, ‘Information Element/Group name’ indicates the names of IEs and the names of groups to which the IEs belong, ‘Need’ indicates whether a corresponding IE is mandatory (MP) or optional (OP), and ‘Multi’ indicates whether the number of IEs is one or several. In addition, ‘Type and reference’ indicates a type in which IEs are expressed, and for example, possible bit expressions include bit-string expression, octet expression, and integer expression. ‘Semantics description’ is a field in which a description is made of the meaning of a corresponding IE, a function of the IE, and which event will happen if the IE is not used. Although many of the possible IEs according to embodiments of the present invention are illustrated herein, particular IEs selected by a system designer can be omitted or unremunerated IEs can be added.  
         [0068]     Table 3 illustrates a format of an MBMS Notification Info message and a description of respective IEs.  
                                   TABLE 3                       Information                           Element/Group           Type and   Semantics       name   Need   Multi   reference   description   Comments                   Message Type   MP       Message       Used to indicate MBMS Notification                   Type       Info message.           XX               information               elements           Service list   OP   maxMBMSservNotif       Providing   Used in the present of control                       details about   information for a particular MBMS                       the changed   service, and this IE includes as many                       services. May   services as maxMBMSservNotif                       be absent in                       case of a                       Common RB                       Info                       modification.       &gt;Service ID   MP       Bit string       an ID used to identify an MBMS                   (32)       service for which notification is made       &gt;CHOICE   MP               IE used to indicate a cause for       Notification                   notification       cause       &gt;&gt;Counting                   Indicating that a cause for notification                           is counting for determining the                           number of users for the MBMS data                           transfer mode       &gt;&gt;&gt;RACH   OP       Integer   Absence   Used to control transmission of       access           (1 . . . 8)   indicates end   uplink RACK for UEs such that       probability               of counting   collision between different UEs       factor                   should not occur in the process of                           RRC connection for counting in case                           there are four UEs. Absence of this IE                           indicates inactivation of counting.       &gt;&gt;PTM RB               Used in case   IE used to indicate that a cause for       change               further details   notification is transfer mode of an RB                       are provided in   that transmits the MBMS data.                       the PTM RB   Transfer mode of the MBMS data                       info eg. PTM   includes two modes of PtP and PtM.                       RB                       establishment,                       PTM RB re-                       configuration           &gt;&gt;&gt;Short       MP       Integer       Identity used to indicate the MBMS           MBMS               (1 . . . 32)       service with the transfer mode           service                       changed. Because of excessive long           identity                       length of IE SERVICE ID, it can                           indicate MBMS service in a cell with                           a length of about 5 bits.       &gt;&gt;PTM RB               (no data)   Used to indicate that a cause for       release                   notification is to release the RB used                           by the MBMS service due to end of                           data transmission for a particular                           MBMS service.       &gt;&gt;Other               (no data)   IE used in case there are additionally                       Covering   needed causes except the foregoing                       cases like   causes for notification.                       frequency                       redirection,                       counting                       decision&lt;PTP,                       no RB&gt; and                       mode change                       to PTP           &gt;Preferred       OP       30 b   DL ARFCN   MBMS service can be performed           frequency                   (14b) and UL   only at a particular frequency in case                       ARFCN   several frequencies coexist spatially.                       unless default   In this case, this IE is used to indicate                       duplex   the frequency at which the MBMS                       distance is   service is performed, and UE can                       used. It seems   reselect cells having the frequency at                       better to   which the MBMS service is                       reference a list   performed, using this IE.                       on BCCH           &gt;Continue       MP       BOOLEAN   Indicates that   This IE is used to indicate that the UE           MCCH                   the UE shall   should continue to receive control           reading                   continue   information transmitted after the                       reading   Notification Info message. Control                       MCCH in the   information messages that the UE                       next   should receive after Notification Info                       modification   message include MBMS SERVICE                       period (since   PTM RB INFO, or MBMS                       more changes   COMMON RB INFO.                       are                       forthcoming)           Common RB       OP           Included in   IE used in case there is a change in           value tag                   case of   contents of COMMON RB INFO. In                       common RB   the case there is a change in contents                       info   of COMMON RB INFO, release of                       modification   PTM RB or reconfiguration of                       and if the   existing RBs are available. The UE                       notification   compares this IE with a value tag of                       includes a   MBMS COMMON RB INFO                       PTM RB   received before this message, and if                       establishment   the two values are different, receives                       or re-   MBMS COMMON RB INFO to                       configuration   acquire new information.                       for one or                       more services       Scheduling   OP       Integer   Indicates the   When receiving control messages       info           (1 . . . 256)   final TTI   transmitted over the MCCH, the UE                       containing   can determine the transmission start                       MBMS   time of each message through the MP,                       SERVICE   RP and AIP on the BCH, but cannot                       INFO for   determine an end time of each                       changed   message, because a length of each                       services or the   message is variable. This IE allows                       final TTI   the UE to exactly determine an end of                       containing the   each message, preventing the UE                       changed   from unnecessarily receiving the                       MBMS   MCCH, thereby saving reception                       COMMON   power of the UE.                       RB INFO                       included in                       case of PTM                       RB                       establishment                       &amp; re-                       configuration                       and/or change                       of common                       RB                       configuration                  
 
         [0069]     Table 4 illustrates a format of an MBMS Service List message.  
                                   TABLE 4                       Information                           Element/Group           Type and   Semantics       name   Need   Multi   reference   description   Comments                   Message Type   MP       Message       This IE is used to indicate an MBMS                   Type       SERVICE LIST message.       XX information       elements       Service list   MP   maxMBMSservCell           This IE can include as many services as                           maxMBMSservCell indicating the                           number of the MBMS services                           provided in the current cell.       &gt;Service ID   MP       Bit string       This IE is an ID for an MBMS service                   (32)       provided in the current cell.       &gt;CHOICE   MP               IE used to indicate transfer mode of the       Transfer mode                   MBMS service indicated by the IE                           SERVICE ID       &gt;&gt;PTM                   IE indicating that the MBMS service                           indicated by the IE SERVICE ID is                           transmitted in PtM mode.           &gt;&gt;&gt;Short       MP       Integer       IE indicating short identity used by the           MBMS service               (1 . . . 32)       MBMS service indicated by the IE           identity                       SERVICE ID. The short identity is                           used for identifying the MBMS service                           in another message through which                           control information for the MBMS                           service is transmitted.       &gt;&gt;PTP               (no data)   IE indicating that the MBMS service                           indicated by the IE SERVICE ID is                           transmitted in Ptp mode.       &gt;&gt;No RB               (no data)   IE indicating that the MBMS service                           indicated by the IE SERVICE ID can                           be provided but is not currently                           transmitted.           &gt;Preferred       OP       30b   DL ARFCN   IE used to indicate a frequency at           frequency                   (14b) and   which the MBMS service is transmitted                       UL ARFCN                       unless                       default                       duplex                       distance is                       used. It                       seems better                       to reference                       a list on the                       BCCH.           &gt;Continue       MP       BOOLEAN   Indicates that   This IE is used to indicate that the UE           MCCH                   the UE shall   should continue to receive control           reading                   continue   information transmitted after the                       reading the   MBMS Service List message. Control                       MCCH in   information messages that UE should                       the next   continuously receive after the MBMS                       modification   Service List message include MBMS                       period (since   SERVICE PTM RB INFO or MBMS                       changes are   COMMON RB INFO.                       forthcoming)           Common RB       MP           Included   This IE is used in case there is a change           value tag                   even if none   in contents of COMMON RB INFO. In                       of the   the case where there is a change in                       services is   contents of COMMON RB INFO,                       provided via   release of the PTM RB or the                       the PTM RB   reconfiguration of existing the RBs are                           available. UE compares this IE with a                           value tag of MBMS COMMON RB                           INFO received before this message,                           and if the two values are different,                           receives MBMS COMMON RB INFO                           to acquire new information.                  
 
         [0070]     Table 5 illustrates a format of an MBMS Common RB Info message.  
                                   TABLE 5                       Information                           Element/Group           Type and   Semantics       name   Need   Multi   reference   description   Comments                   Message Type   MP       Message       This IE is used to indicate the MBMS                   Type       Common RB Info message.           RB                       Group name indicating the IEs related           information                       to the RB           elements               Common RB       MP           Valid within   This IE is used to indicate a change in           info value tag                   the scope of a   the IEs currently included in the                       cell group   COMMON RB INFO message. In the                           case there is a change in the IEs                           contained in the COMMON RB                           INFO message, a value of this IE is                           different from a value tag common                           RB info value in the COMMON RB                           INFO message transmitted before this                           message. When the SC used to                           increase the throughput of the MBMS                           data is introduced, the same MBMS                           service can be serviced with the same                           RB in neighbor cells. Thus, this IE                           can also be used to indicate a change                           in MBMS RB Info of the neighbor                           cells in the case where the MBMS RB                           change information of neighbor cells                           is transmitted within Common RB                           Info.       PTM RB info   MP   maxMBMS-           This IE indicates a list of the RBs that       list       RB           transmit the MBMS data in the PTM                           mode, and can include as many RBs                           as maxMBMS-RB.       &gt;RB identity   MP       Integer   Beneficial to   This IE is an identity indicating the                   (1 . . . 32)   the facilitate   RB that transmits the PtM MBMS                       removal of the   data.                       configurations       &gt;PDCP info   MP               Packet Data Convergence Protocol                           (PDCP) is a part of L2, which                           compress a part unnecessary for the                           transmission of the packet data before                           the transmission, and this IE indicates                           the information used in the PDCP.       &gt;RLC info   MP               Radio Link Control (RLC) is a part of                           the L2, used to transmit/receive the                           data in the retransmission mode or the                           ordered mode, and this IE indicates                           information used in the RLC.           PhyCh and                       Group name indicating the IEs used           TrCh                       for the physical channels and the           information                       transport channels           elements           SCCPCH list   MP   MaxMBMS-       S-CCPCH on   IE capable of indicating a list of S-               SCCPCH       to which both   CCPCHs on which the MCCH or the                       MCCH and   MTCH is transmitted. This IE can                       MTCH are   have as many S-CCPCHs as                       mapped are   maxMBMS-SCCPCH.                       specified on                       BCCH       &gt;S-CCPCH   MP       Integer   Beneficial to   Identity capable of indicating S-       identity           (1 . . . 16)   facilitate   CCPCH over which the MCCH or the                       removal of   MTCH is transmitted                       configuration       &gt;TFCS   MP               This IE indicates a transport format of                           the transport channels which are                           mapped to the S-CCPCH before                           being transmitted. Transport Format                           Combination Set (TFCS) indicates a                           transport format combination for the                           FACHs mapped to the S-CCPCH                           corresponding to the S-CCPCH                           identity IE.       &gt;FACH list   MP   maxFACHPCH           IE capable of indicating a list of the                           FACHs mapped to the S-CCPCH                           corresponding to the S-CCPCH                           identity IE. This IE can have as many                           FACHs as maxFACHPCH.       &gt;&gt;FACH   MP       Integer   Beneficial to   This IE indicates the identity capable       identity           (1 . . . 16)   facilitate   of the identifying FACHs mapped to                       removal of   the S-CCPCH corresponding to the S-                       configurations   CCPCH identity IE.       &gt;&gt;TFS   MP               This IE indicates Transmit Format Set                           of FACHs mapped to S-CCPCH                           corresponding to the S-CCPCH                           identity IE.       &gt;Secondary   MP               Physical channel information of S-       CCPCH info                   CCPCH corresponding to the S-                           CCPCH identity IE                  
 
         [0071]     Table 6 illustrates a format of an MBMS Service PtM RB Info message.  
                                   TABLE 6                       Information                           Element/Group           Type and   Semantics       name   Need   Multi   reference   description   Comments                   Message Type   MP       Message       This IE is used to indicate the MBMS                   Type       Service PTM RB Info message.       XX       information       elements           Short MBMS       MP       Integer       This IE serves to indicate the           service               (1 . . . 32)       information on PtM RB through           identity                       which the MBMS service having the                           MBMS service ID corresponding to a                           short MBMS service identity IE                           acquired from the Notification Info is                           transmitted.       Current cell   MP           The exiting   This IE indicates information on the       RAB               model is re-   Radio Access Bearer (RAB) used in       information               used in which   the current cell by an MBMS service                       one service   corresponding to the short MBMS                       maps to a   service identity IE. The RAB refers to                       RAB which   a connection path between UE and                       may map to   CN, and is different from the RB in                       one or more   that the RB is a connection path                       RBs. See note 1   between the UE and the UTRAN.       &gt;RB   MP   maxRBperRAB           Several of the RBs can be used for       information                   one RAB, and this IE is used to       list                   indicate a list of several of the RBs                           used for one RAB and can have as                           many RBs as maxRBperRAB.       &gt;&gt;RB identity   MP       Integer   Identifies a RB   This IE can be used to indicate the                   (1 . . . 32)   configuration   RB identity.                       included in the                       MBMS                       COMMON                       RB INFO                       message       &gt;&gt;RB   MP           Note 2   This IE is used to indicate the       mapping info                   transport channels and the physical                           channels mapped to RB.       &gt;&gt;&gt;Logical   OP       Integer   Used to   This IE is used to indicate identities       channel           (1 . . . 16)   distinguish   for distinguishing MTCHs, being       identity               different   logical channels, mapped to the RB.                       MTCH within   The MTCHs have unique identities                       the MAC   within one FACH.                       header.                       Identifier is                       unique within                       the scope of                       the indicated                       FACH.       &gt;&gt;&gt;CHOICE   MP               This IE indicates whether the MBMS       Specification                   service indicated by the MBMS       mod                   Service PTM RB Info message can                           use RB Info used before this message.       &gt;&gt;&gt;&gt;Same as                   This IE indicates that MBMS service       previous                   indicated by the MBMS Service PTM                           RB Info message can use the same                           RB information as the previous RB of                           the RB corresponding to the RB                           identity IE.       &gt;&gt;&gt;&gt;Different                   This IE indicates the new RB                           mapping info to be used by the                           MBMS service indicated by the                           MBMS Service PTM RB Info                           message.       &gt;&gt;&gt;&gt;&gt;FACH   OP       Integer   Identifier is   This IE is used to indicate the IDs for       identity           (1 . . . 16)   unique within   the FACHs in the S-CCPCH to which                       the scope of   the FACHs corresponding to this IE is                       the indicated   mapped. This IE is unnecessary when                       S-CCPCH.   only one FACH is used.                       Absent if a                       single FACH                       is mapped on                       to the                       indicated S-                       CCPCH.       &gt;&gt;&gt;&gt;&gt;S-   MP       Integer   Identifies a   This IE indicates the S-CCPCH       CCPCH           (1 . . . 16)   PhyCh and   defined in the Common RB Info       identity               TrCh   message. The meaning of this IE                       configuration   indicates that the information on S-                       included in the   CCPCH of Common RB Info                       MBMS   message should be used.                       COMMON                       RB INFO                       message. The                       assumption is                       that UE is                       required to                       receive all of                       the FACHs                       (according to                       its capabilities                       on the S-                       CCPCH)           Neighboring       OP   MaxMBMSneighCell       Allowing for   This IE serves to allow the UE to           cell RAB                   up to 32   perform the SC by informing the UE           information                   neighboring   of information on neighbor cells for                       cells. Absent if   MBMS service the UE is receiving.                       selection   This IE can inform the UE of                       combining is   information on a maximum of                       not used for   maxMBMSneighCell of neighbor                       this service.   cells.       &gt;Cell identity   MP       Integer   Corresponds   This IE serves to indicate the MBMS                   (0 . . . &lt;max   with the inter-   data of neighbor cells that UE will                   CellMeas   frequency cell   use for the SC using identities of                   &gt;−1)   id as specified   neighbor cells, transmitted through                       within SIB   the BCH.                       11/12       &gt;RB   OP   maxRBperRAB       Absent for the   This IE serves to indicate the RB       information               first entity if   information of the neighbor cells for       list               the   the MBMS service that UE is                       configuration   currently receiving. Absence of this                       is exactly the   IE indicates that the UE can receive                       same as in the   signals from a neighbor cell,                       current cell,   corresponds to the Cell identity IE                       Absent for   using RB information used in the                       subsequent   current cell. In the absence of this IE                       cells if the   in information on neighbor cell                       configuration   having a cell identity different from                       is exactly the   the cell identity IE, it indicates that                       same as that   the same RB information as that of                       for the   the other cell is used. This IE can                       previous cell.   have as many RBs as                           maxRBperRAB.       &gt;&gt;Logical   OP       Integer   Used to   This IE is the identity for       channel           (1 . . . 32)   distinguish the   distinguishing MTCHs in the S-       identity               different   CCPCH.                       MTCH within                       the MAC                       header.                       Identifier is                       globally                       unique within                       the scope of                       the S-CCPCH                       carrying the                       MTCH           &gt;&gt;CHOICE       MP           RB identity is   This IE is used for indicating the RB           Neighbor RB                   not included   mapping info of neighbor cells.           mapping.                   since PDCP           mode                   and RLC                       configurations                       are the same                       when using                       selection                       combining           &gt;&gt;&gt;Same as                       This IE serves to indicate that the RB           previous                       mapping info of initially defined                           neighbor cell or the RB mapping info                           of previously defined neighbor cell is                           used as that of neighbor cell                           corresponding to the Cell identity IE.           &gt;&gt;&gt;Different                       This IE is used to indicate the RB                           mapping info corresponding to the                           Cell identity IE.       &gt;&gt;&gt;&gt;FACG   OP       Integer   Identifier is   This IE is used to indicate the       identity           (1 . . . 16)   unique within   identities for the FACHs in the S-                       the scope of   CCPCH to which the FACHs                       the indicated   corresponding to this IE are mapped.                       S-CCPCH.   This IE is unnecessary when only one                       Absent if a   FACH is used.                       single FACH                       is mapped on                       to the                       indicated S-                       CCPCH.           &gt;&gt;&gt;&gt;S-       MP       Integer   Identifies a   This IE indicates the S-CCPCH           CCPCH               (1 . . . 16)   PhyCh and   defined in the Common RB Info           identity                   TrCh   message. A meaning of this IE                       configuration   indicates that the S-CCPCH                       included in the   information in the Common RB Info                       MBMS   message should be used. S-CCPCH                       COMMON   defined in SIB 5 or 6 for current cell                       RB INFO   can be used.                       message or in                       SYSTEM                       INFORMATION                       BLOCK                       TYPE 5 or 6                  
 
         [0072]      FIG. 3  is a diagram illustrating a transmission start time and a transmission period for the control information transmitted over an MCCH, and  FIG. 4  is a diagram illustrating the transmission and scheduling for the messages presented in Table 3, Table 4, Table 5 and Table 6.  
         [0073]     Referring first to  FIG. 3 , an MCCH  301  transmits various control information messages for supporting an MBMS service. The control information messages include information transmitted to inform UEs of a start/end of the MBMS service and a significant change in the MBMS service, and can also include control information periodically repeated to guarantee the continuity of the MBMS service by taking into consideration the movement of the UE in the mobile communication system. A Modification Period (MP)  304  indicates a period for which the contents of the periodically repeated control information remain unmodified. That is, for the MP  304 , the contents of the control information are unmodified. A Repetition Period (RP)  303  represents a period for which the same control information is repeatedly transmitted. The MP  304  can include several RPs  303 . An Access Information Period (AIP)  302  is a period used when a counting operation for determining a transfer mode of an MBMS service is performed, and for each AIP  302 , a RACH acquisition probability at which the counting operation is to be performed is changed. The RACH acquisition probability is a value used to prevent many UEs from attempting a RACH acquisition at one time, causing a collision. The RACH acquisition probability can be transmitted through the MBMS Notification Info message described above, and if the same MBMS Notification Info message is repeated for several RPs  303 , the AIP  302  becomes equal to the RP  303  in length.  
         [0074]      FIG. 4  is a diagram illustrating an example in which messages transmitted through an MCCH proposed in the present invention are transmitted according to an RP and an MP described with reference to  FIG. 3 . Referring to  FIG. 4 , it is assumed that an MP, as represented by reference numeral  403 , has a length of 256, and an RP, as represented by reference numeral  402 , has a length of 64. The 256 means a length of 256 10-ms radio frames which are used as a basic unit for radio communication transmission in 3GPP, and the 64 means a length of 64 10-ms radio frames. In the 3GPP system, a system frame number (SFN) is used to distinguish a time by 10 ms, and the SFN can have a value of 0 to 4091.  
         [0075]     Reference numeral  410  represents an enlarged period of an MCCH denoted by reference numeral  401 . Reference numeral  412  indicates an MBMS Notification Info message and the MBMS Notification Info message is transmitted at a start time of the MP. Reference numeral  411  indicates an MBMS Service PtM RB Info message for a particular MBMS service, and when the MBMS Service PtM RB Info message is transmitted at a start time of the MP or transmitted immediately after the MBMS Notification Info message  412  or when a transfer rate of an MCCH is high, the MBMS Service PtM RB Info message  411  can be transmitted together with the MBMS Notification Info message  412 . Reference numeral  413  indicates an MBMS Service List message, and the MBMS Service List message  413  has a list of all of the MBMS services currently provided in or available in the current cell, guaranteeing the continuity of an MBMS service by taking the movement of a UE into consideration. A UE receiving or attempting to receive an MBMS service, receives a Common RB value tag through the MBMS Notification Info message  412  and the MBMS Service List message  413 , and if the received Common RB value tag is different from a Common RB value tag currently stored in the UE, the UE receives an MBMS Common RB Info message  415 . Reference numeral  414  indicates an MBMS Service PtM RB Info message having PtM RB information for another MBMS service.  
         [0076]     In  FIG. 4 , reference numerals  416 ,  417 ,  418 ,  419  and  420  represent the same control information messages denoted by reference numerals  411 ,  412 ,  413 ,  414  and  415 , respectively, and as illustrated, the control information messages are repeated every RP  402 . The control information messages can be transmitted at a selected time if the transfer rate of the MCCH is very high, and can be transmitted on a time-division basis if the transfer rate of the MCCH is low.  
         [0077]      FIG. 5  is a flowchart illustrating an operation of a UTRAN (particularly, an RNC) according to an embodiment of the present invention. Specifically,  FIG. 5  is a flowchart illustrating an operation of transmitting control information messages for an MCCH proposed in the present invention upon receiving from a CN a Session Start message indicating a start of data transmission for a particular MBMS service.  
         [0078]     Referring to  FIG. 5 , in step  501 , a UTRAN transmits an MBMS Common RB Info message and an MBMS Service List message in order to support UE mobility. If the UTRAN receives a Session Start message for an MBMS service from a CN in step  502 , it proceeds to step  503 . However, if the UTRAN receives no Session Start message for an MBMS service from the CN, the UTRAN does not return the step  501 . In step  503 , the UTRAN determines if a current frame corresponds to a start time of a new MP. If the current frame does not correspond to the start time of the new MP, the UTRAN waits until the start time of the new MP in step  504 . If the UTRAN recognizes the approach of the start time of the new MP in step  503 , it sets up an MBMS Notification Info message and an MBMS Service PtM RB Info message based on a Session Start message received for the MBMS service in step  505 . The contents of the MBMS Notification Info message and the MBMS Service PtM RB Info message are illustrated in Table 3 and Table 6 proposed in the present invention. Although step  505  can precede step  503 , step  505  is shown to follow step  503 .  
         [0079]     Upon arrival at the start time of the new MP, the UTRAN transmits in step  506  the MBMS Notification Info message, the MBMS Service PtM RB Info message, an MBMS Common RB Info message, and an MBMS Service List message. The MBMS Service List message and the MBMS Common RB Info message are illustrated in Table 4 and Table 5. The MBMS Common RB Info message does not include changes related to a new MBMS service indicated by the MBMS Notification Info message at the current transmission time, but corresponding changes can be transmitted at the time when the MBMS service is performed. The MBMS Service List message can indicate if an MBMS service indicated by the MBMS Notification Info message will be provided in the current cell. In step  507 , the UTRAN determines if a counting operation is needed to determine a transfer mode of MBMS data, and if the counting operation is not required, the UTRAN proceeds to step  509 . However, if the counting operation is needed, the UTRAN proceeds to step  508 . The UTRAN retransmits the MBMS Notification Info message at a start time of a new AIP or RP in step  508 , and then proceeds to step  509 . In the MBMS Notification Info message, a different RACH access probability value from the value transmitted in step  506  is set.  
         [0080]     In step  509 , the UTRAN retransmits the MBMS Notification Info message, the MBMS Service PtM RB Info message, the MBMS Common RB Info message, and the MBMS Service List message at a start time of a new RP. In step  510 , the UTRAN determines whether it is time to start a new MP. If it is time to start a new MP, the UTRAN proceeds to step  511 , and if it is not time to start the new MP, the UTRAN returns to step  509 .  
         [0081]     In step  511 , the UTRAN modifies IEs to be modified, if any, included in the MBMS Notification Info message, the MBMS Service PtM Info message, the MBMS Common RB Info message, and the MBMS Service List message. If the contents of the MBMS Common RB Info message are modified, the UTRAN modifies a corresponding Common RB value tag. An effective range of the Common RB value tag can be limited to the inside of a cell, or can be defined as several cells that transmit the same MBMS service. In the case where the effective range is limited to the inside of a cell, the Common RB value tag is modified only when MBMS-related RB information in the cell is modified. If the effective range is defined as several cells, the Common RB value tag can be modified when MBMS-related RB information of neighbor cells is modified. In step  512 , the UTRAN retransmits the control information messages at a start time of a new MP.  
         [0082]     FIGS.  6  to  9  are flowcharts illustrating operations of a UE upon receiving 4 control information messages transmitted over an MCCH, proposed in the present invention.  
         [0083]      FIG. 6  is a flowchart illustrating an operation of receiving an MBMS Notification Info message by a UE according to an embodiment of the present invention. Referring to  FIG. 6 , in step  601 , the UE checks a Notification Indicator (NI) indicating expected transmission of an MBMS Notification Info message through an MBMS notification Indication Channel (MICH). In step  602 , the UE determines if the NI is an affirmative NI indicating an expected transmission of an MBMS Notification Info message for an MBMS service joined by the UE itself. If the NI is an affirmative NI, the UE proceeds to step  603 , and if the NI is a negative NI, the UE returns to step  601 .  
         [0084]     In step  603 , the UE determines if the current frame is a start time of a new MP. The start time of the new MP can be can be determined through a BCH over which the MBMS system information can be transmitted. If it is determined in step  603  that the UE detects a start time of the new MP, the UE proceeds to step  605 , and otherwise, proceeds to step  604  where it waits for a start time of a new MP. In step  605 , the UE receives an MBMS Notification Info message through an MCCH, and determines in step  606  if the received MBMS Notification Info message is for an MBMS service joined by the UE or currently in service. During the “joining” process a UE informs the RNC/SGSN of an interest in a service, and the RNC/SGSN stores an ID of the UE and location information of the UE. When the service of interest starts, the UE begins to receive the service and is referred to as being currently in service.  
         [0085]     The UE performs step  606  using an IE MBMS service ID included in the MBMS Notification Info message. If the received MBMS Notification Info message is not for an MBMS service joined by the UE or currently in service, the UE returns to step  601 , and otherwise, proceeds to step  607  where it checks a cause value included in the MBMS Notification Info message. In  FIG. 6 , although operations on 3 cause values illustrated in Table 3, i.e. Counting, PtM RB change, and PtM RB release will be described, the UE performs the operations according to other cause values, if they are set. If the UE recognizes in step  608  that counting is performed, it performs a counting-related operation in step  609  and then proceeds to step  614 . The UE can immediately perform step  614  regardless of completion of the counting.  
         [0086]     However, if the UE determines in step  608  that counting is not performed, it recognizes in step  610  that PtM RB change is performed, and performs a PtM RB change-related operation in step  611 . If the UE recognizes in step  610  that the PtM RB change is not performed, it recognizes in step  612  that PtM RB release is performed, and then performs an operation necessary for the PtM RB release in step  613 .  
         [0087]     Herein, the “counting-related operation” refers to an operation of attempting an RRC connection or a PtM connection for counting. The “PtM RB change” means that PtM RB information for an MBMS service that the UE was receiving has been changed, and the UE performs an RB change operation by receiving Common RB Info or MBMS service PtM RB Info. The “PtM RB release operation” refers to an operation of releasing current RB information because it is not necessary to maintain the current RB due to an end of a session for the MBMS service that the UE was receiving.  
         [0088]     If none of the causes of steps  608 ,  610  and  612  is recognized, a session for an MBMS service joined by the UE starts without the counting operation. Therefore, the UE checks the IEs required for the MBMS Notification Info message in at least one of steps  614  to  616 .  
         [0089]     In step  614 , the UE checks an IE continue MCCH reading, and based on the check result, determines if it should receive control information messages transmitted over an MCCH successively after the MBMS Notification Info message. In step  615 , the UE checks an IE Common RB value tag to determine if it should receive again a Common RB Info. In step  616 , the UE checks IE Scheduling Info to determine an end time of an MBMS Service PtM RB Info message or an MBMS Common RB Info message. With the use of the IE Scheduling Info, the UE can correctly presume an end time of MBMS Service PtM RB Info message and the MBMS Common RB Info message without the necessity of continuously monitoring an MCCH. After checking all of the IEs of the MBMS Notification Info message, the UE performs a required operation in step  617 . Herein, the “required operation” refers to an operation of receiving succeeding control information messages or storing required information.  
         [0090]      FIG. 7  is a flowchart illustrating an operation of receiving an MBMS Service List message by a UE according to a preferred embodiment of the present invention. Referring to  FIG. 7 , if a UE moves to a new cell or there is an event to receive an MBMS Service List message in step  701 , the UE determines in step  702  if a current frame corresponds to a start time of a new RP. If the current frame corresponds to the start time of the new RP, the UE receives an MBMS Service List message through an MCCH in step  704 , and otherwise, waits for a start time of a new RP in step  703 .  
         [0091]     In step  705 , the UE determines if there is an ID for an MBMS service joined by the UE in the received MBMS Service List message, and ends the operation if there is no ID for the joined MBMS service. However, if there is an ID for the MBMS service joined by the UE in step  705 , the UE determines in step  706  if a transfer mode for an MBMS service corresponding to the MBMS service ID corresponds to PtM depending on an IE Transfer mode included in the MBMS Service List message. If the transfer mode is PtM, the UE proceeds to step  707 , and otherwise, proceeds to step  708 . In step  707 , the UE acquires an MBMS Short service ID, i.e. an MBMS Transmission Identity, corresponding to the ID of the MBMS service joined by the UE, and then proceeds to step  712 . In step  708 , the UE determines if the transfer mode of the MBMS service joined by the UE corresponds to PtP based on the IE Transfer mode. If the transfer mode corresponds to PtP, the UE proceeds to step  709 , and otherwise, proceeds to step  710 . In step  709 , the UE performs an operation of receiving the MBMS service joined by the UE on a PtP basis. If the UE determines in step  710  that the MBMS service joined by the UE is not provided based on the IE Transfer mode, it performs in step  711  an operation of receiving the MBMS service joined by the UE in the current cell in which the UE is located. If the IE Transfer mode does corresponds to none of PtM, PtP and no-RB, the UE proceeds to step  712 , determining that there is an error.  
         [0092]     In any one of steps  712  to  714 , the UE checks the IEs necessary for the MBMS Notification Info message. In step  712 , the UE checks the IE Preferred frequency included in the MBMS Service List message to acquire the information on a frequency at which the MBMS service joined by the UE is provided. In step  713 , the UE checks the IE continue MCCH reading to determine if it should continuously receive control information transmitted over an MCCH. In step  714 , the UE checks the IE Common RB value tag to determine if it is necessary to receive an MBMS Common RB Info message. In step  715 , the UE performs a required operation based on information acquired from the MBMS Service List message. Herein, the “required operation” refers to an operation of receiving succeeding control information messages or storing required information.  
         [0093]      FIG. 8  is a flowchart describing an operation of receiving an MBMS Service PtM RB Info message by a UE according to a preferred embodiment of the present invention. Referring to  FIG. 8 , after receiving an MBMS Notification Info message for an MBMS service joined by a UE, the UE receives an MBMS Service PtM RB Info message over an MCCH in step  801 . In step  802 , the UE determines if a Short MBMS ID acquired from the MBMS Notification Info message is equal to an IE Short MBMS ID included in the MBMS Service PtM RB Info message. If the MBMS IDs are not equal to each other, the UE proceeds to step  804  where it waits for another MBMS Service PtM RB Info message.  
         [0094]     However, if the IDs are equal to each other in step  802 , it means that there is RB information for the joined MBMS service in the MBMS Service PtM RB Info message. In step  803 , the UE acquires the current cell RB information for the joined MBMS service from the MBMS Service PtM RB Info message. In step  805 , the UE determines if there is information on a neighbor cell for the joined MBMS service. If there is information on a neighbor cell for the joined MBMS service, the UE acquires the information on a neighbor cell for the joined MBMS service in step  806 , and otherwise, performs an operation of receiving the MBMS service in step  807 . In step  806 , the UE can acquire the neighbor cell information by receiving a separate MBMS Neighboring Cell PtM RB Info message. In step  807 , the “operation of receiving the MBMS service” refers to an operation of setting up an RB and a physical channel used for receiving the MBMS service, based on the acquired RB information.  
         [0095]      FIG. 9  is a flowchart illustrating an operation of receiving an MBMS Common RB Info message by a UE according to a preferred embodiment of the present invention. Referring to  FIG. 9 , in step  901 , a UE determines if there is a cause to receive an MBMS Common RB Info message. An example of the cause to receive the MBMS Common RB Info message corresponds to a case where the UE shifts to a new cell or a new frequency. If there is any cause to receive the MBMS Common RB Info message in step  901 , the UE proceeds to step  903 . However, if there is no cause to receive the MBMS Common RB Info message in step  901 , the UE proceeds to step  902 .  
         [0096]     In step  902 , the UE determines if a value tag stored in the UE is equal to a value tag included in other control information messages that the UE has previously received. If the value tag values are equal to each other, the UE proceeds to step  904  where it ends the operation without receiving the MBMS Common RB Info message.  
         [0097]     However, if the value tag values are not equal to each other, the UE receives an MBMS Common RB Info message through an MCCH in step  903 , and stores a value tag included in the MBMS Common RB Info message in step  904 . In step  906 , the UE acquires RB information included in the MBMS Common RB Info message received in step  903 . In step  907 , the UE acquires the physical channel information and the transport channel information from the MBMS Common RB Info message. The received RB information and physical channel/transport channel information are stored, preparing for the case where the UE sets up an RB to receive a corresponding MBMS service therethrough.  
         [0098]     As described above, the present invention proposes a method for defining the control information messages transmitted over an MCCH, and minimizing a signaling overhead during the transmission of the defined control information messages. In addition, the present invention proposes a method for efficiently scheduling the control information messages before the transmission. In this manner, a UE receiving the control information messages can prevent duplicate reception of the same information elements and prevent an MCCH from being continuously received, thereby minimizing power consumption of the UE.  
         [0099]     While the invention has been shown and described with reference to a certain preferred 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.