Abstract:
There is provided a method for processing Multimedia Broadcast/Multicast Service MBMS session update in M3 and M2 interfaces in a wireless communication system, the wireless communication system comprising a Mobility Management Entity MME, a Multi-cell/Multicast Coordination Entity MCE and an eNB, the method comprising: sending, by the MME, a first MBMS session update request message to the MCE; processing, by the MCE, the first MBMS session update request message, and sending, a second MBMS session update request message to the eNB and sending a first feedback message to the MME; processing, by the eNB, the second MBMS session update request message, and sending a second feedback message to the MCE. 
     The present invention enables a RAN and an EPC to consistently process the MBMS session update procedure. Thus, the present invention may avoid misunderstanding caused by signaling processing from the EPC to EUTRAN in a radio access network.

Description:
FIELD OF THE INVENTION 
     The present invention relates to wireless communications, and specifically relates to a method for updating a Multimedia Broadcast/Multicast Service (MBMS) session. 
     BACKGROUND OF THE INVENTION 
     At present, according to the conclusion of Service and System Aspects 2 (SA2) Workgroup, an ongoing MBMS session may change some service characteristics, for example, Service Area. An Evolved Packet Core (EPC) network defines an MBMS Session Update procedure. However, in a radio access network (RAN), there is no corresponding procedure definition especially in M3 (an interface between a Mobility Management Entity MME and a Multi-cell/Multicast Coordination Entity MCE) and M2 (an interface between the MCE and an eNB) interfaces. Upon receiving an MBMS Session Update Request message from a Broadcast/Multicast Service Center (BMSC), an MBMS gateway sends different messages to the MME based on different results of comparison between an updated control node list included in itself and the updated control node list included in the MBMS Session Update Request message, wherein the different messages may be MBMS Session Start Request, MBMS Session Stop request, and MBMS Session Update Request. The MME needs to send these messages to its corresponding MCE. Therefore, in the M3 and M2 interfaces, processing of the MBMS Session Update procedure needs to be defined. The processing comprises a new M3 application protocol (M3AP) and M2 application protocol (M2AP) signaling flow definition for the MBMS Session Update procedure, and a relevant processing mechanism for MBMS Session Update signaling of the M3AP and M2AP in the MCE and eNB. 
     SUMMARY OF THE INVENTION 
     Therefore, in order to solve the above problem, the present invention provides a method for processing MBMS session update. 
     According to one aspect of the present invention, there is provided a method for processing Multimedia Broadcast/Multicast Service MBMS session update, comprising: sending, by a Mobility Management Entity MME, a first MBMS session update request message to a Multi-cell/Multicast Coordination Entity MCE; processing, by the MCE, the first MBMS session update request message, and sending, a second MBMS session update request message to an eNB and sending a first feedback message to the MME; and processing, by the eNB, the second MBMS session update request message, and sending a second feedback message to the MCE. 
     Preferably, the processing, by the MCE, the first MBMS session update request message comprises: decoding the first MBMS session update request message, and storing session attribute update obtained by the decoding in an MBMS bearer context. 
     Preferably, the processing, by the eNB, the second MBMS session update request message comprises: decoding the second MBMS session update request message, comparing a service area already stored in an MBMS bearer context with a new service area, and performing corresponding update. 
     Preferably, after the MCE correctly processes the first MBMS session update request message, the MCE immediately sends a first MBMS session update response message to the MME. 
     Preferably, after the MCE receives a second MBMS session update response message from the eNB, the MCE sends a first MBMS session update response message to the MME. 
     Preferably, if the MCE fails to correctly process the received first MBMS session update request message, the MCE sends a first MBMS session update failure message to the MME. Further preferably, if the MCE sends the first MBMS session update failure message to the MME, the MME re-sends the first MBMS session update request message to the MCE. 
     Preferably, after the eNB correctly processes the second MBMS session update request message, the eNB sends a second MBMS session update response message to the MCE. 
     Preferably, if the eNB fails to correctly process the second MBMS session update request message, the eNB sends a second MBMS session update failure message to the MCE. Further preferably, if the eNB sends the second MBMS session update failure message to the MCE, the MCE re-sends the second MBMS session update request message to the eNB. 
     The present invention enables the RAN and EPC to consistently process the MBMS session update procedure. Thus, the present invention may avoid misunderstanding caused by signaling processing (i.e., MBMS session update request message) from the EPC to EUTRAN in the radio access network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention will become more apparent through the following detailed description with reference to the drawings, wherein, 
         FIG. 1  illustrates a flow chart of a method for processing MBMS Session Update on the M3 and M2 interfaces according to one embodiment of the present invention; 
         FIG. 2  illustrates a schematic diagram of an MBMS Session Update procedure between an MME and an MCE according to one embodiment of the present invention; and 
         FIG. 3  illustrates a schematic diagram of an MBMS Session Update procedure between an eNB and an MCE according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, through the description of specific embodiments of the present invention with reference to the drawings, the principle and implementation of the present invention will become more apparent. It should be noted that the present invention is not limited to the following specific embodiments. It should be further noted that for the sake of simplicity, those known components directly related to the present invention are not illustrated in the drawings. 
     In TS23.246, a MBMS Session Update procedure is defined for updating the Service Area for an ongoing MBMS broadcast service session by a BMSC. In section 8.8.4 of TS23.246, a detailed MBMS Session Update signaling procedure is described. This procedure is initiated by the BMSC, for modifying Service Area attributes and notifying related eNBs to join or leave the Service Area. Considering the existence of such possibility as changing the service area during the ongoing session, it is reasonable for SA2 to define such a procedure. However, it does not involve an interface signaling definition inside a radio access network and a processing procedure of related network elements. 
     There are three cases in which MBMS control plane nodes are changed due to change of Service Area (SA), which are:
     Case 1: some new MMEs are added into a MBMS control plane node list due to the change of SA;   Case 2: it is required to remove some MMEs from the MBMS control plane node list due to the change of SA;   Case 3: the MMEs in the MBMS control plane node list do not change, but the cells under these MMEs may change due to the change of SA.   

     In view of the above three cases caused by the change of SA, once the MBMS gateway receives Session Update Request signaling from the BMSC, it compares a new MBMS control plane node list with the MBMS control plane node list already stored in an MBMS bearer context, and decides which case occurs. According to the description in TS23.246, the MBMS gateway sends different signaling to corresponding MMEs based on different cases caused by the change of SA, that is, for case 1, the MBMS gateway sends an MBMS Session Start Request message to any added MME in the new list;
     for case 2, the MBMS gateway sends an MBS Session Stop Request message to any MME removed from the new list;   for case 3, the MBMS gateway sends an MBMS Session Update Request (Temporary Mobile Group Identity (TMGI), flow identifier, QoS, MBMS Service Area, session identifier, estimated session duration, transport network IP Multicast Address, IP address of a multicast source, and Common Tunnel End Identifier (C-TEID), etc.) to the remaining MMEs in the new list.   

     The MME receives the Session Start Request message and the Session Stop Request message, and operates as usual, such as, creates or updates the MBMS bearer context and session attributes. Then, the MME notifies the related MCE by sending M3AP Session Start Request and Session Stop Request signaling. In this procedure, all processing on related network nodes are consistent with the existing processing mechanisms for the MBMS Session Start Request and the MBMS Session Stop Request. 
     Hereinafter, the processing of a MBMS Session Update Request within a radio access network (RAN) will be described in detail with reference to  FIGS. 1-3 . 
       FIG. 1  illustrates a flow chart of a method for performing a MBMS Session Update procedure on the M3 and M2 interfaces according to one embodiment of the present invention. Method 10 starts at step S 100 . In the M3 interface, firstly, it is required to define a Class 1 elementary procedure MBMS Session Update Request message for the MBMS session, as specified in the following table: 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Class 1 Procedure for MBMS Session Update for M3 interface 
               
             
          
           
               
                   
                   
                 Successful 
                 Unsuccessful 
               
               
                 Elementary 
                 Initial 
                 Outcome 
                 Outcome 
               
               
                 Procedure 
                 Message 
                 Response Message 
                 Response Message 
               
               
                   
               
               
                 MBMS 
                 MBMS 
                 MBMS 
                 MBMS 
               
               
                 Session 
                 Session 
                 Session 
                 Session 
               
               
                 Update 
                 Update Request 
                 Update Response 
                 Update Failure 
               
               
                   
               
             
          
         
       
     
     In step S 102 , the MME sends a first MBMS Session Update Request message to the MCE on the M3 interface. This message is used for notifying the MCE of the changed characteristics (for example, the service area) of the ongoing service session, and requests the MCE to update its parameters. The first MBMS Session Update Request is specifically defined below: 
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Detailed Definition of MBMS Session Update 
               
               
                 Request Message for M3 Interface 
               
             
          
           
               
                   
                   
                   
                 IE Type 
                 Semantics 
                   
                   
               
               
                 IE/Group 
                 Pres- 
                   
                 and 
                 Descrip- 
                 Criti- 
                 Assigned 
               
               
                 Name 
                 ence 
                 Range 
                 Reference 
                 tion 
                 cality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.1.1 
                   
                 Yes 
                 Reject 
               
               
                 type 
               
               
                 MME 
                 M 
                   
                 9.2.3.2 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
               
               
                 M3AP ID 
               
               
                 TMGI 
                 M 
                   
                 9.2.3.3 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
                 0 
                   
                 9.2.3.4 
                   
                 Yes 
                 Ignore 
               
               
                 Session 
               
               
                 Identity 
               
               
                 MBMS 
                 M 
                   
                 9.2.1.3 
                   
                 Yes 
                 Reject 
               
               
                 E-RAB 
               
               
                 QoS 
               
               
                 Parameters 
               
               
                 MBMS 
                 M 
                   
                 9.2.3.5 
                   
                 Yes 
                 Reject 
               
               
                 Session 
               
               
                 Duration 
               
               
                 MBMS 
                 0 
                   
                 9.2.3.6 
                   
                 Yes 
                 Ignore 
               
               
                 Service 
               
               
                 Area 
               
               
                 Minimum 
                 M 
                   
                 9.2.3.8 
                   
                 Yes 
                 Reject 
               
               
                 Waiting 
               
               
                 Time for 
               
               
                 MBMS Data 
               
               
                 Transfer 
               
               
                 TNL 
                 M 
                   
                   
                   
                 Yes 
                 Reject 
               
               
                 Information 
               
               
                 &gt;IP 
                 M 
                   
                 9.2.2.1 
                   
                 — 
               
               
                 Multicast 
               
               
                 Address 
               
               
                 &gt;GTP DL 
                 M 
                   
                 GTP 
                   
                 — 
               
               
                 TEID 
                   
                   
                 TEID 
               
               
                   
                   
                   
                 9.2.2.2 
               
               
                   
               
               
                 Note: 
               
               
                 the content in the row of “IE Type and Reference” in the table corresponds to TS36.444 V.9.0.0. 
               
             
          
         
       
     
     In step  104 , the MCE processes the first MBMS Session Update Request message, sends a first feedback message to the MME, and sends a second MBMS Session Update Request message to the eNB on the M2 interface. Specifically, the MCE updates its own parameters in the session by utilizing the information in the first MBMS Session Update Request message, for example, the QoS parameter, the Service Area parameter, etc., stores new session attribute update in the MBMS bearer context, and compares the original Service Area with new Service Area. Thereafter, the MCE sends the first feedback message to the MME on the M3 interface and sends the second MBMS Session Update Request message including the new session attributes to each eNB connected thereto on the M2 interface. 
     Depending on the processing result of the MCE, the first feedback message may be a first MBMS Session Update Response message or a first MBMS Session Update Failure message. The first MBMS Session Update Response message is used for reporting the successful outcome of the first MBMS Session Update Request message, while the first MBMS Session Update Failure message is used for reporting the unsuccessful outcome of the first MBMS Session Update Request message. Definitions for both messages are provided below: 
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Detailed Definition of MBMS Session Update 
               
               
                 Response Message for M3 Interface 
               
             
          
           
               
                   
                   
                   
                 IE Type 
                 Semantics 
                   
                   
               
               
                 IE/Group 
                 Pres- 
                   
                 and 
                 Descrip- 
                 Criti- 
                 Assigned 
               
               
                 Name 
                 ence 
                 Range 
                 Reference 
                 tion 
                 cality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.1.1 
                   
                 Yes 
                 Reject 
               
               
                 Type 
               
               
                 MME 
                 M 
                   
                 9.2.3.2 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
               
               
                 M3AP ID 
               
               
                 MCE 
                 M 
                   
                 9.2.3.1 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
               
               
                 M3AP ID 
               
               
                 Criticality 
                 0 
                   
                 9.2.1.7 
                   
                 Yes 
                 Ignore 
               
               
                 Diagnostics 
               
               
                   
               
               
                 Note: 
               
               
                 the content in the row of “IE Type and Reference” in the table corresponds to TS36.444 V.9.0.0. 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Detailed Definition of MBMS Session Update 
               
               
                 Failure Message for M3 Interface 
               
             
          
           
               
                   
                   
                   
                 IE Type 
                 Semantics 
                   
                   
               
               
                 IE/Group 
                 Pres- 
                   
                 and 
                 Descrip- 
                 Criti- 
                 Assigned 
               
               
                 Name 
                 ence 
                 Range 
                 Reference 
                 tion 
                 cality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.1.1 
                   
                 Yes 
                 Reject 
               
               
                 Type 
               
               
                 MME 
                 M 
                   
                 9.2.3.2 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
               
               
                 M3AP ID 
               
               
                 Cause 
                 M 
                   
                 9.2.1.2 
                   
                 Yes 
                 Ignore 
               
               
                 Criticality 
                 0 
                   
                 9.2.1.7 
                   
                 Yes 
                 Ignore 
               
               
                 Diagnostics 
               
               
                   
               
               
                 Note: 
               
               
                 the content in the row of “IE Type and Reference” in the table corresponds to TS36.444 V.9.0.0. 
               
             
          
         
       
     
     Likewise, the Class 1 elementary procedure MBMS Session Update Request message is also defined for MBMS session update in the M2 interface, as specified in the following table: 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Class 1 Procedure defined for MBMS 
               
               
                 Session Update for M2 interface 
               
             
          
           
               
                   
                   
                 Successful 
                 Unsuccessful 
               
               
                 Elementary 
                 Initial 
                 Outcome 
                 Outcome 
               
               
                 Procedure 
                 Message 
                 Response Message 
                 Response Message 
               
               
                   
               
               
                 MBMS 
                 MBMS 
                 MBMS 
                 MBMS 
               
               
                 Session 
                 Session 
                 Session 
                 Session 
               
               
                 Update 
                 Update Request 
                 Update Response 
                 Update Failure 
               
               
                   
               
             
          
         
       
     
     The second MBMS Session Update Request is specifically defined as follows: 
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Detailed Definition of MBMS Session Update 
               
               
                 Request Message for M2 Interface 
               
             
          
           
               
                   
                   
                   
                 IE Type 
                 Semantics 
                   
                   
               
               
                 IE/Group 
                 Pres- 
                   
                 and 
                 Descrip- 
                 Criti- 
                 Assigned 
               
               
                 Name 
                 ence 
                 Range 
                 Reference 
                 tion 
                 cality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.1.1 
                   
                 Yes 
                 Reject 
               
               
                 Type 
               
               
                 MCE 
                 M 
                   
                 9.2.3.1 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
               
               
                 M2AP ID 
               
               
                 TMGI 
                 M 
                   
                 9.2.3.3 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
                 0 
                   
                 9.2.3.4 
                   
                 Yes 
                 Ignore 
               
               
                 Session 
               
               
                 Identity 
               
               
                 MBMS 
                 M 
                   
                 9.2.3.5 
                   
                 Yes 
                 Reject 
               
               
                 Session 
               
               
                 Duration 
               
               
                 MBMS 
                 0 
                   
                 9.2.3.6 
                   
                 Yes 
                 Ignore 
               
               
                 Service Area 
               
               
                 TNL 
                 M 
                   
                   
                   
                 Yes 
                 Reject 
               
               
                 Information 
               
               
                 &gt;IP 
                 M 
                   
                 9.2.2.1 
                   
                 — 
               
               
                 Multicast 
               
               
                 Address 
               
               
                 &gt;GTP DL 
                 M 
                   
                 GTP 
                   
                 — 
               
               
                 TEID 
                   
                   
                 TEID 
               
               
                   
                   
                   
                 9.2.2.2 
               
               
                   
               
               
                 Note: 
               
               
                 the content in the row of “IE Type and Reference” in the table corresponds to TS36.443 V.9.0.0. 
               
             
          
         
       
     
     In step S 106 , the eNB processes the second MBMS Session Update Request message and sends a second feedback message to the MCE. Specifically, the eNB processes the second MBMS Session Update Request message, compares the Service Area stored in the MBMS bearer context with new Service Area, and performs corresponding update. In addition, the eNB sends the second feedback message to the MCE on the M2 interface. 
     Likewise, depending on the processing result of the eNB, the second feedback message may be a second MBMS Session Update Response message or a second MBMS Session Update Failure message. The second MBMS Session Update Response message is used for reporting the successful outcome of the second MBMS Session Update Request message, while the second MBMS Session Update Failure message is used for reporting the unsuccessful outcome of the second MBMS Session Update Request message. Definitions for both messages are specified below: 
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Detailed Definition of MBMS Session Update 
               
               
                 Response Message for M2 Interface 
               
             
          
           
               
                   
                   
                   
                 IE Type 
                 Semantics 
                   
                   
               
               
                 IE/Group 
                 Pres- 
                   
                 and 
                 Descrip- 
                 Criti- 
                 Assigned 
               
               
                 Name 
                 ence 
                 Range 
                 Reference 
                 tion 
                 cality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.1.1 
                   
                 Yes 
                 Reject 
               
               
                 Type 
               
               
                 MCE 
                 M 
                   
                 9.2.3.1 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
               
               
                 M2AP ID 
               
               
                 eNB MBMS 
                 M 
                   
                 9.2.3.2 
                   
                 Yes 
                 Reject 
               
               
                 M2AP ID 
               
               
                 Criticality 
                 0 
                   
                 9.2.1.7 
                   
                 Yes 
                 Ignore 
               
               
                 Diagnostics 
               
               
                   
               
               
                 Note: 
               
               
                 the content in the row of “IE Type and Reference” in the table corresponds to TS36.443 V.9.0.0. 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Detailed Definition of MBMS Session Update 
               
               
                 Failure Message for M2 Interface 
               
             
          
           
               
                   
                   
                   
                 IE Type 
                 Semantics 
                   
                   
               
               
                 IE/Group 
                 Pres- 
                   
                 and 
                 Descrip- 
                 Criti- 
                 Assigned 
               
               
                 Name 
                 ence 
                 Range 
                 Reference 
                 tion 
                 cality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.1.1 
                   
                 Yes 
                 Reject 
               
               
                 Type 
               
               
                 MCE 
                 M 
                   
                 9.2.3.1 
                   
                 Yes 
                 Reject 
               
               
                 MBMS 
               
               
                 M2AP ID 
               
               
                 Cause 
                 M 
                   
                 9.2.1.2 
                   
                 Yes 
                 Ignore 
               
               
                 Criticality 
                 0 
                   
                 9.2.1.7 
                   
                 Yes 
                 Ignore 
               
               
                 Diagnostics 
               
               
                   
               
               
                 Note: 
               
               
                 the content in the row of “IE Type and Reference” in the table corresponds to TS36.443 V.9.0.0. 
               
             
          
         
       
     
     Finally, the method 10 ends in step S 108 . 
     After receiving a response from the eNB, the MCE reports the result of the requested MBMS Session Update to the MME. In different scenarios, the first feedback message sent from the MCE to the MME may include a plurality of cases. The MCE may immediately reply the MME to confirm reception of the MBMS Session Request after correctly receiving and decoding the MBMS Session Update Request message of the M3AP, without waiting until all related eNBs have completed processing of the second MBMS Session Update Request message and then sending the first MBMS Update Request Response message to the MME. In addition, the MCE may also send the first MBMS Update Request Response message to the MME after receiving all of the second feedback messages indicating that all related eNBs have correctly processed the second MBMS Session Update Request message. However, if the MCE determines that the radio access network is not adapted to the requested session update, the MME should be notified via the first MBMS Update Request Failure message. Alternatively, due to some reasons (for example, incorrect decoding, hardware failure, etc.), the MCE cannot correctly process the received Session Update Request, and at this point, the MCE feeds back to the MME via the first MBMS Session Update Failure message. Alternatively, the MME may consider re-sending the first MBMS Session Update Request message to those MCEs that fail in the processing. 
     Depending on different cases due to the change of Service Area, the eNB may need to newly join a multicast address group of the MBMS service session and send configuration information relating to the MBMS in a corresponding cell to prepare for receiving the MBMS service session; the eNB may also need to exit from the original session multicast address group of the MBMS service and stop receiving the MBMS service session; it is also possible that the eNB only requires to adjust the transmission conditions of the MBMS service in the cells under its control, including the transmission of corresponding MBMS configuration control information. In these cases, the eNB takes the second MBMS Update Request Response message as the second feedback message to feed back to the MCE. Obviously, the eNB may not correctly process the received second MBMS Session Update Request message due to several reasons (for example, incorrect decoding, some hardware error, etc.). At this point, the related eNB would take the second MBMS Session Update Failure message as the second feedback message to respond to the MCE so as to notify the MCE of the incapability of successfully processing the Session Update Request in the corresponding eNB. Alternatively, the MCE may re-send the second MBMS Session Update Request message to those eNBs that fail in the processing. 
       FIG. 2  illustrates a schematic diagram of an MBMS Session Update procedure between an MME and an MCE according to one embodiment of the present invention, wherein the MME communicates with the MCE via the M3 interface.  FIG. 2( a )  represents the case in which the MCE successfully processes the first MBMS Session Update Request message, and  FIG. 2( b )  represents the case in which the MCE fails to process the first MBMS Session Update Request message. 
       FIG. 3  illustrates a schematic diagram of an MBMS Session Update procedure between an eNB and an MCE according to one embodiment of the present invention, wherein the eNB communicates with the MCE via the M2 interface.  FIG. 3( a )  represents the case in which the eNB successfully processes the second MBMS Session Update Request message, and  FIG. 3( b )  represents the case in which the eNB fails to process the second MBMS Session Update Request message. 
     It should be noted that, for the sake of simplicity,  FIG. 2  and  FIG. 3  merely illustrate one MME and one MCE, as well as one MCE and one eNB, respectively. However, the present invention is not limited thereto. One MME may have a plurality of associated MCEs, and each MCE may have a plurality of associated eNBs. Those skilled in the art would appreciate that the above described MBMS Session Update procedure may be applied to a radio communication system having a plurality of MMEs, MCEs, and eNBs associated with each other. 
     Although the present invention has been illustrated above with reference to preferred embodiments of the present invention, those skilled in the art would appreciate that without departing from the spirit and scope of the present invention, the present invention may be subjected to a variety of modifications, substitutions, and change. Thus, the present invention should not be limited by the above embodiments, but should be limited by the appended claims and the equivalents thereof.