preferred embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings . in the following description of the present invention , a detailed description of known functions and configuration incorporated herein will be omitted when it may obscure the subject matter of the present invention . the present invention provides a method for transmitting a start of an mbms , a session start of the mbms , and mbms - related control information to ues having joined the mbms in a 3g asynchronous mobile communication system supporting the mbms . that is , the present invention proposes a method for reducing a false alarm , which causes a ue having joined a random mbms to start a second notification checking , because of a primary notification for another mbms when a primary notification procedure is performed in order to report the existence of the control information . further , the present invention proposes a method in which a ue can recognize a primary notification for an mbms that the ue has joined in a preset ue specific drx cycle , and proposes a method of ensuring reliability when a cn or utran ( upper system ) transmits nis for the primary notification for the mbms . in the present invention , an ni representing existence or absence of an alarm message ( i . e ., a notification message ) corresponding to an mbms requested by a ue is confirmed using an mich that reports the existence or absence of an alarm of control information for an mbms . herein , the ue receives at least one ni and confirms if a primary notification for a corresponding mbms exists , instead of receiving one ni in the mich and confirming a primary notification for an mbms for which the ue has joined . fig4 is a diagram illustrating a method for confirming existence of a primary notification for transmission of a start of an mbms that a ue has joined , a session start of the corresponding mbms , or control information , using a method for the primary notification , which is proposed by the present invention . referring to fig4 , an mich 420 transmits an ni for the mbms . accordingly , a plurality of nis may be transmitted . for example , it is assumed that one mich transmits 18 nis and there are 300 mbmss available that ues have joined . herein , it is assumed that the mbmss are distinguished from each other using service identifiers . accordingly , an mbms notification group for the mbms exists in accordance with the 18 nis and about 17 mbmss are included in each one notification group . that is , in an example for a method of constructing the mbms notification group , a modulo calculation is performed for identifiers of the mbmss by 18 , i . e ., he number of ni , such that the identifiers correspond to 18 mbms notification groups according to the remainder values obtained through the modulo calculation . herein , when a random ue joins an mbms and receives an ni corresponding to an mbms notification group to which the mbms belongs , the ue receives an ni sixteen times because of another service , i . e ., for a service different from the mbms for which the ue has joined . accordingly , the ue unnecessarily receives an mcch , which includes a notification message , i . e ., final information , about sixteen times for the corresponding mbms . table 1 shows an mbms notification group that is distinguishable through an mich of 10 ms when a ue recognizes an existence of a notification message or control information through a plurality of nis proposed by the present invention . that is , table 1 shows the mbms notification group according to selected values of the ni . in table 1 , the total number of nis of the first column represents the number of nis allocated to one mich . that is , the total number of nis is the total number of nis for each mich . the number of ni to be selected in the second column represents the number of nis used for recognizing existence of notification or control information . the combination value of the third column represents the available number of mbms notification groups according to a change in the number of the nis used for recognizing the existence of notification or control information for a random mbms with respect to the total number of the nis . referring to table 1 , when 18 nis exist and the notification groups are distinguished using only one ni , 18 mbms notification groups may exist . further , when the notification groups are distinguished using two nis , 153 mbms notification groups may exist . accordingly , when it is assumed that 300 mbmss exist and one of the total 18 nis is used , the ue must unnecessarily receive the mcch , sixteen times , because of primary notifications for other services in order to confirm a second notification . further , when two of the total 18 nis are used , the number of times by which the ue must unnecessarily receive the mcch in order to confirm the second notification is approximately once . in addition , when three of the total 18 nis are used , the number of times by which the ue must unnecessarily receive the mcch is zero . herein , a calculation result of the third column can be defined by equation ( 1 ). number of notification group = a c b , wherein a = n ni , b = n nis ( 1 ) in equation ( 1 ), c is a combination operator used in the mathematics , n ni is the total number of nis existing in one mich , and n nis is the number of nis used for recognizing existence of the notification or the control information . as shown in table 1 , when the total number of nis used for a primary notification increases to a predetermined number , the number of mbms notification groups in one mich also increases . for example , the cases of 9 c 2 and 18 c 1 are considered as follows . for 9 c 2 , 36 bits correspond to each ni . for 18 c 1 , 18 bits correspond to each ni . herein , when it is assumed that the transmit powers of all of the transmitted bits are identical , the transmit power of an ni transmitted for 9 c 2 , is twice as large as that of an ni transmitted for 18 c 1 . accordingly , a ue for each ni has the most improved reception ability for 9 c 2 . further , the number of mbms notification groups for 9 c 2 is also twice as many as that of 18 c 1 . that is , when the method proposed by the present invention is used , even though the same transmit power is used for each bit of an mich , the reception error probability of an ni for each primary notification can be reduced . further , the number of notification groups increases , such that the probability that the ue unnecessarily receives the mcch for secondary notification is reduced . as described in conjunction with fig4 , the present invention using table 1 and equation ( 1 ) has the following characteristics : 3 ) the le receives an mich of 10 ms and may simultaneously have the advantages of 1 ) and 2 ) above , such that battery consumption of the ue can be reduced ; and 4 ) even when it is assumed that the same mich transmit power is used , it is possible to decrease the reception error probability of the ni and increase the number of notification groups . additionally , it is necessary to provide a method for corresponding positions of the nis to the increased notification groups as described above . table 2 shows an example for the method for corresponding the positions of the nis to the notification groups , i . e ., 9 c 2 . that is , table 2 shows a correspondence relation between the mbms notification group and the ni for 9 c 2 according to an embodiment of the present invention . for 9 c 2 , n ni is 9 and nms is 2 . accordingly , the number of notification groups is 36 . herein , the first column represents notification groups from 0 to 35 according to a combination of 9 c 2 , and the columns from 0 to 8 are the positions of each ni . that is , 0 in the first row is the position of the first ni and 8 is the position of the 9 th ni . herein , each allocated ni ( shadow portion ) indicates that a corresponding ni is set and transmitted as a positive response (+). that is , when a primary notification for an mbms belonging to an mbms notification group 0 is required , a first ni and a second ni are set to 1 and then transmitted . in table 2 , two factors representing a position of an ni are required in order to indicate a correspondence relation between the mbms notification group and the two nis . when a position of the first ni is called a p ni1 ( i ) and a position of the second ni is called a p ni2 ( j ), the i and the j may have a value of 0 or a positive integer meeting the following equations . in equation ( 3 ), i is a maximum positive integer meeting equation ( 2 ). as described above , p ni1 ( i ) and p ni2 ( j ), i . e ., the positions of the nis are determined using the equations above . for example , when there is a primary notification for an mbms belonging to an mbms notification group 10 , i has a value of 4 and j has a value of 0 through equations ( 2 ) and ( 3 ). further , the position of the first ni , which is calculated using equations ( 4 ) and ( 5 ), is the fifth ni of 9 nis , and the position of the second ni is the first ni of 9 nis . this result can be confirmed in table 2 . equations ( 2 ) to ( 5 ) are true for all values when nni is larger than 2 and n nis is 2 . as described above , a correspondence relation of the nis indicating existence of notification or control information of an mbms corresponding to the mbms notification group can be transferred to ues , which receive the mbms , through various methods . fig5 is a diagram illustrating a process for confirming a position of an ni according to an embodiment of the present invention . that is , fig5 illustrates a method in which a ue can recognize a primary notification for an mbms that the ue has joined after receiving required information from a utran and a cn . referring to fig5 , in step 501 , when an mbms requested by the ue 500 exists among mbmss already recognized through an mbms announcement , the ue 500 transmits a joining request message to a cn 520 . the joining request message may include an identifier of the ue 500 and an identifier of the mbms requested by the ue 500 , and may include other parameters other than the identifiers . in step 521 , the cn 520 performs a subscriber authentication procedure after receiving the joining request message . the subscriber authentication authenticates the ue 500 and confirms if the ue 500 is qualified to receive the mbms that the ue 500 has joined . further , the subscriber authentication may include a procedure for determining if it is possible to provide the mbms requested by the ue 500 . herein , the authentication procedure performed by the cn 520 may also be performed through an entity belonging to the cn 520 or through a plurality entities . in step 522 , the cn 520 transmits a joining response message indicating if the requested mbms may be received to the ue 500 . in step 511 , the ue 500 having received the joining response message in step 522 receives a bch transmitted from a utran 510 . for an easier description of the present invention , fig5 illustrates that the ue 500 receives the bch after receiving the joining response message . however , the ue 500 can receive system information of a cell including the ue 500 at any time . herein , the bch is a broadcasting channel for transmitting system information of a cell including a ue , which transmits information of the cn 520 and the utran 510 , etc . in addition , the bch also transmits information for a common channel capable of being received in the ue 500 . step 511 represents that the ue 500 receives required information from the bch in order to perform a primary notification work for the mbms . that is , in step 511 , the ue 500 receives mich channel information , the total number of nis transmitted through an mich of 10 ms , i . e ., n ni and n nis used for recognizing a primary notification , etc . herein , the mich channel information may be transmitted through existing system information blocks , etc ., of the bch , and may also be transmitted through other system information blocks of the bch , which are newly defined for the mbms . accordingly , in step 502 , the ue 500 receives an mich based on the information received in step 511 and continuously determines an existence or absence of a session start or control information of the mbms that the ue 500 has joined . herein , when a start point or a session start point of the mbms that the ue 500 has joined in an upper layer arrives , the cn 520 transmits a session start message to the utran 510 in step 523 . the session start message may include an identifier of the mbms , control information for transmitting the mbms , etc . the utran 510 having received the session start message in step 523 recognizes the start of the mbms , and sets nis of an mich to have proper values in step 512 . that is , the utran 510 sets values of the nis so that ues have joined the mbms can recognize the start or the session start of the mbms , and transmits the ni values through the mich in step 513 . in step 503 , the ue 500 receives the mich and determines if nis corresponding to the primary notification for the mbms that the ue 500 has joined are being transmitted through the mich while the nis have positive values . as a result of the determination , when the nis are transmitted while having the positive values , the ue 500 receives a second notification for receiving a control message transmitted through an mcch . that is , when the ue 500 checks positions of the nis for a corresponding mbms and the nis have the positive values for the corresponding mbms transmitted through the mich , the ue 500 confirms the mcch , thereby confirming control information for the corresponding mbms . fig6 is a diagram illustrating a process for confirming a position of an ni according to another embodiment of the present invention . that is , fig6 illustrates a method in which a ue can recognize a primary notification for an mbms that the ue has joined after receiving required information from a cn . referring to fig6 , in step 601 , when an mbms requested by the ue 600 exists among mbmss already recognized through an mbms announcement , the ue 600 transmits a joining request message to a cn 620 for the mbms that the ue 600 has joined . the joining request message may include an identifier of the ue 600 and an identifier of the mbms requested by the ue 600 , and may include other parameters other than the identifiers . in step 621 , the cn 620 having received the joining request message performs a subscriber authentication procedure . the subscriber authentication authenticates the ue 600 and confirms if the ue 600 is qualified to receive the mbms . further , the subscriber authentication may include a procedure for determining if it is possible to provide the mbms requested by the ue 600 . in step 622 , the cn 620 transmits a joining response message indicating if the mbms requested by the ue 600 may be received to the ue 600 . herein , the joining response message includes supplementary information used for recognizing a primary notification for the mbms . the supplementary information including nis that must be confirmed by the ue 600 in order to recognize the primary notification . for example , a bitmap such as “ 000100001 ” may be used as the supplementary information . that is , the cn 620 determines a position of an ni for the mbms and informs the ue 600 of the determined position . according to the bitmap of this example , it can be understood that 9 nis exist in an mich and the fourth ni and the ninth ni of the 9 nis are used for the primary notification of the mbms requested by the ue 600 . in step 611 , the ue 600 having received the joining response message receives a bch transmitted from a utran 610 . this represents that the ue 600 receives required information from the bch in order to perform a primary notification procedure . that is , in step 611 , the ue 600 receives mich channel information , etc . herein , the mich channel information may be transmitted through existing system information blocks , etc ., of the bch , and may also be transmitted through other system information blocks of the bch , which are newly defined for the mbms . accordingly , the ue 600 receives an mich based on the information received in step 611 and continuously determines an existence or absence of a session start or control information of the mbms . in step 623 , when a start point or a session start point of the mbms occurs , the cn 620 transmits a session start message to the utran 610 . the session start message may include an identifier of the mbms , additional control information for transmitting the mbms , etc . the utran 610 recognizes a start of the mbms corresponding to the session start message after receiving the session start message , and sets nis of an mich to have proper values in step 612 . herein , the utran 610 may also recognize ni values through reception of the session start message from the cn 620 , or may also recognize the ni values through a separate message from the cn 620 . further , the utran 610 may directly set the ni values . when the separate message is received from the cn 620 , the utran 610 may receive an entire correspondence relation between mbms notification groups and the nis of the mich . accordingly , after receiving the session start message , the utran 610 may set and transmit proper ni values . in step 613 , after the utran 610 sets the ni values so that ues have joined the mbms can recognize the start or the session start of the mbms , it transmits the ni values through the mich . in step 603 , the ue 600 receives the mich and determines if nis corresponding to the primary notification for the mbms are being transmitted through the mich while the nis have positive values . when the nis are transmitted while having the positive values , the ue 600 performs a second notification for receiving a control message transmitted through an mcch . fig7 is a diagram illustrating a process for confirming a position of an ni according to another embodiment of the present invention . that is , fig7 illustrates a method in which a ue can recognize a primary notification for an mbms that the ue has joined , after receiving required information from a utran . referring to fig7 , in step 701 , when an mbms requested by the ue 700 exists among mbmss already recognized through an mbms announcement , the ue 700 transmits a joining request message to a cn 720 for the mbms that the ue 700 has joined . the joining request message may include an identifier of the ue 700 and an identifier of the mbms requested by the ue 700 , and may include other parameters other than the identifiers . in step 721 , the cn 620 performs a subscriber authentication procedure , after receiving the joining request message . the subscriber authentication authenticates the ue 700 and confirms if the ue 700 is qualified to receive the mbms . further , the subscriber authentication may include a procedure for determining if it is possible to provide the mbms requested by the ue 700 . in step 722 , the cn 720 transmits a joining response message for permitting the ue 700 to receive the requested mbms to the ue 700 . in step 711 , a utran 710 sets a correspondence relation between mbms notification groups and nis of an mich , using nni and n nis . this procedure may be performed even before the ue 700 transmits the joining request message . in step 712 , the utran 710 transmits the correspondence relation between the mbms notification groups and the nis of the mich to the ue 700 and all ues requesting the mbms through a bch . further , the correspondence relation between the mbms notification groups and the nis of the mich may also be transmitted to ues having joined the mbms through an mcch transmitting mbms control information . herein , in transmitting the correspondence relation between the mbms notification groups and the nis of the mich through the bch , the correspondence relation may be included in system blocks or other system blocks newly defined for the mbms and transmitted . further , in transmitting the correspondence relation through the mcch , the ue 700 and all ues having joined the mbms acquire information , which is used for receiving the mcch , from the bch . accordingly , the ue 700 and all ues may recognize the correspondence relation after receiving the mcch . that is , after the ue 700 receives the joining response message in step 722 , in step 712 , the ue 700 receives the bch transmitted from the utran 710 . the ue 700 receives required information from the bch in order to perform a primary notification procedure . the ue 700 receives mich channel information , the nni , the nnis , and the correspondence relation between the mbms notification groups and the nis values , which has been determined in step 711 . the above information may be transmitted through system information blocks of the bch or may also be transmitted through other system information blocks newly defined for the mbms . in step 702 , the ue 700 receives an mich based on the information received in step 712 and continuously determines an existence or absence of a session start or control information of the mbms . in step 723 , when a start point or a session start point of the mbms occurs , the cn 720 transmits a session start message to the utran 710 . the session start message may include an identifier of the mbms , additional control information for transmitting the mbms , etc . the utran 710 , having received the session start message recognizes the start of the corresponding mbms , and sets nis corresponding to the mbms of the mich to have proper values in step 712 . then , in step 713 , the utran 710 sets the ni values so that the ue 700 have joined the mbms and other ues can recognize the start or the session start of the mbms , and transmits the ni values through the mich . in step 703 , the ue 700 receives the mich and determines if nis corresponding to the primary notification for the mbms are being transmitted while the nis have positive values . when the nis are transmitted while having the positive values , the ue 700 performs a second notification for receiving a control message transmitted through an mcch . according to the present invention , as described above , when a primary notification procedure is performed to report an existence of control information , at least one ni is confirmed to prevent a false alarm causing a ue having joined a random mbms to start a second notification checking because of a primary notification for another mbms , such that it is possible to confirm if a primary notification for the mbms which the ue has joined exists . therefore , it is possible to reduce a probability that the ue unnecessarily confirms a second notification , i . e ., an mcch , such that battery consumption of the ue can be reduced and the number of primary notification groups corresponding to the mbms within one mich can increase . consequently , it is possible to provide the mbms more efficiently . although preferred embodiments of the present invention have been described for illustrative purposes , those skilled in the art will appreciate that various modifications , additions , and substitutions are possible , without departing from the scope and spirit of the present invention as disclosed in the accompanying claims , including their full scope of equivalents .