PRIORITY  
         [0001]    This application claims priority under 35 U.S.C. § 119 to an application entitled “Method for Providing Broadcast Service in a CDMA Mobile Communication System” filed in the Korean Intellectual Property Office on May 13, 2002 and assigned Serial No. 2002-26290, 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 broadcast services, and in particular, to a method for more efficiently providing broadcast services in a mobile communication system using code division multiple access (hereinafter referred to as “CDMA”) technology.  
           [0004]    2. Description of the Related Art  
           [0005]    In the future, communications environments will undergo rapid changes regardless of wired/wireless region or country. In particular, the communications environment, such as IMT-2000 (International Mobile Telecommunication-2000), tends to synthetically provide users with various information needs including image and voice information on a real-time basis. With the development of mobile communication technology, even in a cellular wireless communication system or PCS (Personal Communications System) mobile communication system, a mobile station (MS) has the ability to not only simply perform voice communication but also to transmit text information and to receive broadcast services.  
           [0006]    At present, 3GPP2 (3 rd  Generation Partnership Project 2) considers the efficient utilization of various service media and resources for a broadcast service in a mobile communication system. Such a broadcast service is performed by unidirectionally transmitting high-speed forward data without receiving reverse feedback information from a mobile station. A broadcast service in a mobile communication system is characterized in that a plurality of base stations (BSs) simultaneously transmit the same data stream. This is conceptually similar to a general television broadcasting service.  
           [0007]    If a common channel is designed so as to guarantee the same performance even at a cell boundary, cell capacity is excessively wasted. Therefore, in a 3 rd  generation mobile communication system, a structure of a supplemental channel proposed as a dedicated channel for a packet data service is partially modified to realize high-speed transmission for a broadcast service. The supplemental channel uses a common long code mask instead of a long code mask dedicated to a user, for a broadcast service. During a broadcast service, autonomous handoff not requiring feedback information from a mobile station and outer coding are performed to guarantee performance higher than or equal to that of an existing common channel.  
           [0008]    In an existing wireless broadcast service under discussion, a broadcast service provider is limited to a specific broadcast server or a contents server designated by a common carrier, so mobile stations can only passively receive the broadcast service. Therefore, the service provider cannot charge for the broadcast service according to its service time or quantity. In addition, because the same data stream is simultaneously transmitted from several base stations as stated above, network resources for a broadcast service must be assigned to all the base stations, preventing efficient utilization of resources.  
         SUMMARY OF THE INVENTION  
         [0009]    It is, therefore, an object of the present invention to provide a broadcast service method for simultaneously transmitting and receiving voice, text and image data between mobile stations in a mobile communication system.  
           [0010]    It is another object of the present invention to provide a broadcast service method for forming a group of mobile stations in a network, and simultaneously transmitting and receiving voice, text or image data between the mobile stations in the group.  
           [0011]    It is further another object of the present invention to provide a broadcast service method capable of efficiently using wired/wireless resources of a base station and a network.  
           [0012]    It is still another object of the present invention to provide a broadcast service method capable of controlling a transmission time of a base station and assignment of network resources.  
           [0013]    According to one aspect of the present invention, there is provided a method for receiving a broadcast service by a mobile station in a wireless broadcast service system including the mobile station existing in a service area, a base station capable of connecting a wireless channel, a packet data serving node for connecting the base station to a packet communication network, a broadcast server connected to the packet communication network, and an authentication server connected to the packet communication network. The method comprises the steps of: performing user authentication by setting up a connection with the authentication server, and receiving, if the user authentication is passed, information on available broadcast services from the broadcasting server; registering a desired broadcast service in the packet data serving node based on the received information so that the packet data serving node assigns a network resource for the desired broadcast service; if the desired broadcast service is authorized by the packet data serving node, registering the desired broadcast service in the base station so that the base station assigns a wireless broadcast supplemental channel and a network resource for the desired broadcast service; and receiving broadcast data for the desired broadcast service over the broadcast supplemental channel assigned to the base station.  
           [0014]    According to another aspect of the present invention, there is provided a method for providing a broadcast service to a mobile station by a base station in a wireless broadcast service system including the mobile station existing in a service area, the base station capable of connecting a wireless channel, a packet data serving node for connecting the base station to a packet communication network, a broadcast server connected to the packet communication network, and an authentication server connected to the packet communication network. The method comprises the steps of: upon receiving a broadcast service registration request from the mobile station, determining whether the requested broadcast service is already being provided; if the requested broadcast service is not being provided, registering the requested broadcast service in the packet data serving node so that the packet data serving node assigns a network resource for the requested broadcast service; and if the requested broadcast service is authorized by the packet data serving node, assigning a wireless broadcast supplemental channel for the broadcast service and transmitting broadcast data for the requested broadcast service received from the packet data serving node to the mobile station over the assigned broadcast supplemental channel.  
           [0015]    According to another aspect of the present invention, there is provided a method for providing a broadcast service to a mobile station by a packet data serving node in a wireless broadcast service system including the mobile station existing in a service area, a base station capable of connecting a wireless channel, the packet data serving node for connecting the base station to a packet communication network, a broadcast server connected to the packet communication network, and an authentication server connected to the packet data communication network. The method comprising the steps of: receiving information on broadcast services available for the mobile station from the authentication server; upon receiving a registration request for a broadcast service desired by the mobile station, assigning a network resource for the requested broadcast service based on the received information on the available broadcast services; and upon receiving a registration request for the requested broadcast service from the base station, transmitting broadcast data for the requested broadcast service received from the broadcast server to the mobile station through the base station, using the assigned network resource. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    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:  
         [0017]    [0017]FIG. 1 illustrates the entire configuration of a common broadcast service system;  
         [0018]    [0018]FIG. 2 illustrates the configuration of a broadcast service system in which an authenticated mobile station serves as a source of a broadcast service according to an embodiment of the present invention;  
         [0019]    [0019]FIG. 3 illustrates configuration of a broadcast service system in which an authenticated broadcast server serves as a source of a broadcast service according to another embodiment of the present invention;  
         [0020]    [0020]FIG. 4 is a message flow diagram illustrating a procedure for registering a broadcast service desired by a mobile station in a packet data serving node (PDSN) via a base station to thereby assign system and network resources according to an embodiment of the present invention;  
         [0021]    [0021]FIG. 5 is a flowchart illustrating an operation performed by a mobile station to initiate a broadcast service as illustrated in FIG. 4;  
         [0022]    [0022]FIG. 6 is a flowchart illustrating an operation performed by a base station to initiate a broadcast service as illustrated in FIG. 4;  
         [0023]    [0023]FIG. 7 is a flowchart illustrating an operation performed by a packet data serving node to initiate a broadcast service as illustrated in FIG. 4;  
         [0024]    [0024]FIG. 8 is a message flow diagram illustrating a procedure for returning system resources by a mobile station after leaving (or terminating) a broadcast service according to an embodiment of the present invention;  
         [0025]    [0025]FIG. 9 is a flowchart illustrating an operation of leaving a broadcast service by a base station as shown in FIG. 8;  
         [0026]    [0026]FIG. 10 is a message flow diagram illustrating a procedure for performing accounting on a broadcast service of a mobile station according to an embodiment of the present invention;  
         [0027]    [0027]FIG. 11 is a flowchart illustrating an operation of performing accounting on a broadcast service by a base station and a packet data serving node as shown in FIG. 10;  
         [0028]    [0028]FIG. 12 is a message flow diagram illustrating a procedure for assigning broadcast service resources using a registration message according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]    Several preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. In the drawings, it should be noted that the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness.  
         [0030]    The disclosed embodiments of the present invention are characterized in that in a mobile communication system supporting a broadcast service, a broadcast server or a specific mobile station provides a broadcast service to registered mobile stations constituting a logical group. A packet data serving node (PDSN) authenticates mobile stations registered in a broadcast service receiving group, and controls base stations servicing corresponding mobile stations to assign a forward broadcast supplemental channel (hereinafter referred to as “F-BSCH”). Herein, reference will be made to a structure of a mobile communication system and a wireless channel based on 3GPP2 in order to describe an operating principal of the present invention. However, it should be readily understood by those of skill in the art that the present invention is not limited to 3GPP2 implementations.  
         [0031]    [0031]FIG. 1 illustrates a common broadcast service system. Referring to FIG. 1, a broadcast server or contents server (CS)  14  generates an IP packet by compressing image and/or voice data for a broadcast service, i.e., broadcast data, according to an Internet protocol (IP), and delivers the IP packet to base stations (BS)  12   a ,  12   b  and  12   c  via packet data serving nodes (PDSNs)  13   a  and  13   b  over a packet communication network such as the Internet. Each of the base stations  12   a ,  12   b  and  12   c  are comprised of a base transceiver subsystem (BTS), a base station controller (BSC), and a packet control function unit (PCF), and thus, they are represented by BS/PCF.  
         [0032]    In order to deliver the broadcast data generated by the broadcast server  14  to the base stations  12   a ,  12   b  and  12   c , IP multicast technology is used. The base stations  12   a ,  12   b  and  12   c  form a multicast group which is provided with IP multicast data from the broadcast server  14 . Membership information of the multicast group is retained by an undepicted multicast router (MR) connected to each of the base stations  12   a ,  12   b  and  12   c . That is, IP multicast data including the image and/or voice data generated by the broadcast server  14  is broadcasted to the base stations  12   a ,  12   b  and  12   c  forming the multicast group, and the base stations  12   a ,  12   b  and  12   c  convert the IP multicast data into a radio frequency (RF) signal, and then transmit the RF signal in their service areas.  
         [0033]    In FIG. 1, however, the base stations  12   a ,  12   b  and  12   c  always transmit the broadcast data regardless of whether a mobile station exists in their service areas. Thus, the base stations  12   a ,  12   b  and  12   c  may unnecessarily waste wired and wireless resources, and mobile stations  11   a,    11   b  and  11   c  located in the service areas of the base stations  12   a ,  12   b  and  12   c  must passively receive the broadcast data.  
         [0034]    [0034]FIG. 2 illustrates the configuration of a broadcast service system in which an authenticated mobile station serves as a source of a broadcast service according to an embodiment of the present invention. Referring to FIG. 2, a mobile station  21   a , serving as a broadcast service source authenticated by an authentication server (or an Authentication, Authorization and Accounting (AAA) server)  24 , has been registered in a packet data serving node (PDSN)  23   a  to provide a broadcast service. Broadcast data transmitted over a reverse fundamental channel (hereinafter referred to as “R-FCH”) established between the mobile station  21   a  and its associated base station  22   a  is provided to base stations  22   b  and  22   c  by packet data serving nodes  23   a  and  23   b . The base stations  22   b  and  22   c  provide the broadcast data to mobile stations  21   b  and  21   c  in their service areas over forward broadcast supplemental channels (F-BSCHs). The broadcast data is transmitted in the form of IP multicast data. The mobile stations  21   b  and  21   c  provided with the broadcast data have been registered in the corresponding packet data serving nodes  23   a  and  23   b  for broadcast reception, forming a logical group. The authenticated mobile station  21   a  can transmit broadcast data to the registered mobile stations  21   b  and  21   c.    
         [0035]    [0035]FIG. 3 illustrates configuration of a broadcast service system in which an authenticated broadcast server serves as a source of a broadcast service according to another embodiment of the present invention. Referring to FIG. 3, a broadcast server  36  serves as a broadcast service source authenticated by an authentication server (or an AAA server)  34 , and broadcast data transmitted in the form of IP multicast data by the broadcast server  36  is directly delivered to an adjacent packet data serving node  33   b  and also delivered to a packet data serving node  33   a  of another network via a multicast router (MR)  35 . The packet data serving nodes  33   a  and  33   b  transmit the broadcast data to base stations  32   a ,  32   b  and  32   c  that service mobile stations  31   a,    31   b  and  31   c  registered for a broadcast service. The base stations  32   a ,  32   b  and  32   c  provide the broadcast data to the mobile stations  31   a ,  31   b  and  31   c  over forward broadcast supplemental channels (F-BSCHs). The mobile stations  31   a ,  31   b  and  31   c  provided with the broadcast data have been registered in the corresponding packet data serving nodes  33   a  and  33   b  for broadcast reception, forming a logical group. As a result, the authenticated broadcast server  36  can transmit broadcast data to the registered mobile stations  31   a ,  31   b  and  31   c.    
         [0036]    With reference to FIGS.  4  to  12 , a description will now be made of an operation of providing a broadcast service in a mobile communication system according to an embodiment of the present invention.  
         [0037]    [0037]FIG. 4 is a message flow diagram illustrating a procedure for registering a broadcast service desired by a mobile station in a packet data serving node (PDSN) via a base station to thereby assign system and network resources according to an embodiment of the present invention. As shown in FIG. 4, a packet data serving node and a base station start providing a broadcast service only at the request of a mobile station, rather than always providing the broadcast service.  
         [0038]    Referring to FIG. 4, in step  100 , a mobile station (MS) sets up a connection to an authentication server (AAA) according to a point-to-point protocol (hereinafter referred to as “PPP”), and then sends a user authentication request to the authentication server (AAA) through the set connection in order to request a broadcast service. If the authentication is passed, the authentication server delivers information on broadcast services that the mobile station can receive to a corresponding packet data serving node (PDSN) in step  102 , the information being stored in its database through a service authorization procedure.  
         [0039]    The delivered information includes broadcast multicast service identifiers (hereinafter referred to as “BCMCS_IDs”) for identifying broadcast services, multicast IP addresses and source IP addresses for identifying sources that provide a broadcast service, or includes a table identifier by which the above parameters can be searched from a database of the packet data serving node (PDSN).  
         [0040]    In step  104 , the mobile station connects a call to a broadcast server (or a contents server (CS)) using a hypertext transfer protocol (HTTP) or a session description protocol (SDP), and receives session information related to broadcast services from the broadcast server. This is achieved through a dedicated channel by using a call based on Service Option 33 (hereinafter referred to as “SO33”) designating a packet data service. In step  106 , the mobile station sends an IGMP (Internet Group Management Protocol) message to the packet data serving node along with a multicast IP address corresponding to a desired broadcast service. The packet data serving node analyzes the requested multicast IP address included in the IGMP message.  
         [0041]    In the case where the packet data serving node is already servicing the corresponding broadcast contents while the multicast IP address requested in step  104  by the mobile station is identical to a multicast IP address authorized in step  102  by the authentication server, the packet data serving node does not require new management such as system and network resource assignment for providing a broadcast service. On the other hand, in the case where the requested multicast IP address is identical to the authorized multicast IP address but the packet data serving node is not performing the service, the packet data serving node registers the requested multicast IP address in a multicast IP routing table of its internal database.  
         [0042]    If the requested multicast IP address is not identical to the authorized multicast IP address, the packet data serving node inquires of the authentication server about whether the requested multicast IP address is available, through an optional service authentication procedure, in step  108 . If it is determined that the requested multicast IP address is available, the packet data serving node registers the requested multicast IP address in the multicast IP routing table, and builds a multicast IP spanning tree by communicating a routing message indicating the particulars registered in the routing table with neighboring routers.  
         [0043]    After the requested multicast IP address is analyzed, the packet data serving node transmits an IGMP message to the mobile station in response to the IGMP message in step  110 . In step  112 , the broadcast server starts transmitting broadcast data for the corresponding broadcast service to the packet data serving node.  
         [0044]    At this moment, the mobile station has already received all information necessary for reception of a broadcast service, and in particular session information, BCMCS_ID, and multicast IP address. Therefore, in step  114 , the mobile station sends a registration request for the desired broadcast service corresponding to the BCMCS_ID and the multicast IP address to a base station (BS) over an access channel, using the session information. The base station then analyzes the BCMCS_ID and the multicast IP address, registration of which was requested by the mobile station.  
         [0045]    If a broadcast service corresponding to the BCMCS_ID and the multicast IP address is not currently being provided by the base station, the base station must newly assign wired and wireless resources for the broadcast service. Thus, in step  116 , the base station sends a packet control function unit (PCF) a call setup message (A 9 -Setup-A 8 ) carrying the BCMCS_ID and the multicast IP address. In step  118 , the packet control function unit sends the packet data serving node a registration request message (A 11 -Registration Request) carrying the BCMCS_ID and the multicast IP address, in response to the call setup message.  
         [0046]    In step  120 , the packet data serving node transmits to the packet control function unit a registration response message (A 11 -Registration Reply) indicating that a broadcast service corresponding to the BCMCS_ID and the multicast IP address was authorized, in response to the registration request message. In step  122 , the packet control function unit (PCF) determines from the registration response message that the broadcast service was authorized, and then delivers a connection message (A 9 -Connect-A 8 ) for notifying this situation, to the base station. The base station then assigns wired and wireless resources as well as a forward broadcast supplemental channel (F-BSCH) for the broadcast service, and starts the broadcast service. That is, the base station receives broadcast data from the broadcast server via the packet data serving node, and starts transmitting the received broadcast data over the forward broadcast supplemental channel (F-BSCH).  
         [0047]    In step  124 , the mobile station receives the broadcast data by tuning to the forward broadcast supplemental channel corresponding to the BCMCS_ID. A plurality of mobile stations desiring to receive the same broadcast service are registered as a broadcast service receiving group, and the broadcast service in the packet data serving node and the base station continues until a predetermined broadcast timer expires or all mobile stations terminate (or leave) their broadcast services.  
         [0048]    [0048]FIG. 5 is a flowchart illustrating an operation performed by a mobile station to initiate a broadcast service as shown in FIG. 4. Referring to FIG. 5, a mobile station desiring to receive a broadcast service sends a user authentication request to an authentication server through PPP connection in step S 100 , and receives service authorization information for the user in response to the user authentication request in step S 102 . If the user is not authorized in step S 102 , the flow ends. In step S 104 , if session information for broadcast services is received from a broadcast server, the mobile station requests, in step S 106 , the desired broadcast service by transmitting information related to the desired broadcast service, i.e., BCMCS_ID and multicast IP address, to a packet data serving node.  
         [0049]    If a broadcast service authorization response is received in step S 108  in response to the broadcast service request, the mobile station transmits in step S 110  a registration request for the desired broadcast service corresponding to the BCMCS_ID and the multicast IP address to a base station in order to register the desired broadcast service. If the service is not authorized in step S 108 , the flow ends. The base station then transmits broadcast data for the broadcast service in response to the registration request. In step S 112 , the mobile station receives the broadcast data for the desired broadcast service.  
         [0050]    [0050]FIG. 6 is a flowchart illustrating an operation performed by a base station to initiate a broadcast service as shown in FIG. 4. Referring to FIG. 6, if a registration request for a broadcast service that a mobile station desires to receive is received in step S 200 , a base station determines in step, S 202  whether the broadcast service is already being provided. If the broadcast service is currently in operation, the base station proceeds to step S 210  where it continues to transmit broadcast data for the broadcast service. However, if the broadcast service is not being provided, the base station sends a broadcast service request to a packet data serving node in step S 204 . If it is determined in step S 206  that the broadcast service was authorized, the base station assigns a wireless broadcast supplemental channel and a network resource for the broadcast service in step S 208 , and then transmits broadcast data for the broadcast service over the assigned broadcast supplemental channel in step S 210 .  
         [0051]    [0051]FIG. 7 is a flowchart illustrating an operation performed by a packet data serving node to initiate a broadcast service as shown in FIG. 4. Referring to FIG. 7, if information on broadcast services available for a mobile station is received from a broadcast server in step S 300 , and BCMCS_ID and a multicast IP address for a broadcast service desired by the mobile station is received in step S 302 , a packet data serving node determines in step S 304  whether the multicast IP address is identical to a multicast IP address for the broadcast services available for the mobile station. Here, the multicast IP address for the broadcast services available for the mobile station is included in the information received from the broadcast server.  
         [0052]    If the multicast IP addresses are not identical to each other, the packet data serving node inquires, in step S 316 , of an authentication server about whether the multicast IP address for the desired broadcast service is available. If it is determined in step S 318  that the multicast IP address for the desired broadcast service is not available, the packet data serving node ends the operation, and otherwise, proceeds to step S 308 .  
         [0053]    If the multicast IP addresses are identical to each other in step S 304 , the packet data serving node determines in step S 306  whether the desired broadcast service corresponding to the multicast IP address is currently being provided. If the desired broadcast service corresponding to the multicast IP address is currently not in operation, the packet data serving node registers in step S 308  the multicast IP address for the desired broadcast service in a multicast IP routing table. However, if the desired broadcast service corresponding to the multicast IP address is currently in operation, the packet data serving node proceeds to step S 310 . In step S 310 , the packet data serving node starts receiving broadcast data for the registered broadcast service from the broadcast server.  
         [0054]    If a registration request for the broadcast service corresponding to the multicast IP address registered in the multicast IP routing table is received from a base station in step S 312 , the packet data serving node delivers the corresponding broadcast data received from the broadcast server to the base station in step S 314 .  
         [0055]    [0055]FIG. 8 is a message flow diagram illustrating a procedure for returning resources by a mobile station after leaving (or terminating) a broadcast service according to an embodiment of the present invention. Referring to FIG. 8, in step  200 , a plurality of mobile stations (MSs) registered as a broadcast service receiving group receives broadcast data for a broadcast service from a broadcast server (or a contents server (CS)). In step  202 , one of the mobile stations sends a broadcast service leave request to a packet data serving node (PDSN) through a leave procedure based on IGMP. In step  204 , the mobile station sends a BCMCS de-registration message to a base station (BS). The base station determines whether each of the mobile stations registered as the broadcast service receiving group has left its broadcast service, depending on whether the BCMCS deregistration message was received or whether a broadcast timer has expired.  
         [0056]    If the mobile station that transmitted the BCMCS de-registration message is the last mobile station that was using a corresponding broadcast supplemental channel in its service area, the base station stops in step  206  the use of resources (i.e., broadcast supplemental channel and network resource), and then transmits in step  208  a release message (A 9 -Release-A 8 ) to a packet control function unit (PCF) in order to return the resources. In this case, the packet control function unit does not send a response for the release message. This is because when a plurality of base stations are connected to one packet control function unit, there may exist other base stations, which are providing a corresponding broadcast service.  
         [0057]    If all of the base stations connected to the packet control function unit determine that all mobile stations that were receiving the broadcast supplemental channel have left the broadcast service, the packet control function unit transmits in step  210  a release complete message (Complete A 9 -Release-A 8 ) to all the base stations connected thereto. Then, the packet control function unit and the packet data serving node release all network resources related to the broadcast service.  
         [0058]    [0058]FIG. 9 is a flowchart illustrating an operation of leaving a broadcast service by a base station as illustrated in FIG. 8. Referring to FIG. 9, in step S 400 , broadcast data for a broadcast service desired by a mobile station is transmitted from a base station to the mobile station. If a broadcast service leave request is received in step S 402 , or a broadcast service of a particular mobile station is left as a broadcast timer expires, the base station determines in step S 404  whether the particular mobile station is the last mobile station that uses the corresponding broadcast supplemental channel. If the particular mobile station is the last mobile station, the base station releases the broadcast channel and withdraws the network resource in step S 406 . Otherwise, if the particular mobile station is not the last mobile station, the base station maintains the broadcast supplemental channel.  
         [0059]    [0059]FIG. 10 is a message flow diagram illustrating a procedure for performing accounting on a broadcast service of a mobile station according to an embodiment of the present invention. Referring to FIG. 10, in step  300 , a mobile station (MS) desiring to receive a broadcast service connects a call based on Service Option 33 (hereinafter referred to as “SO33”) through a dedicated channel assigned between the mobile station and a base station (BS), establishes PPP connection with a packet data serving node (PDSN), and then receives information for the broadcast service from a broadcast server (or a contents server (CS)) through the PPP connection. Thereafter, if the broadcast service is registered, the dedicated channel is released and the SO33-based call transitions to a dormant state, in step  302 .  
         [0060]    In the dormant state, a broadcaster service parameter message (BSPM) is transmitted from the base station to the mobile station through an overhead message. The overhead message includes a physical channel parameter, a logical parameter and mapping information for a broadcast service.  
         [0061]    In step  304 , the mobile station registers the desired broadcast service in the base station through an access channel. In step  306 , the base station transmits a call setup message (A 9 -Setup-A 8 ) to a packet control function unit (PCF) in response to a broadcast service registration request from the mobile station. In this case, the call setup message includes information on a time when the mobile station registered the broadcast service, i.e., information on a service start time.  
         [0062]    In step  308 , the packet control function unit receives the call setup message, searches a packet data serving node that can provide the desired broadcast service, based on IMSI (International Mobile System Identifier) of the mobile station, and then transmits a registration message (All Registration) with service start time information to the packet data serving node. The packet data serving node then assigns system and network resources for the broadcast service in response to the registration message, and generates accounting information based on the IMSI and the service start time information.  
         [0063]    If the mobile station transmits a de-registration message to the base station in step  310  or the broadcast service of the mobile station is left as a broadcast timer expires, the base station transmits in step  312  a release message (A 9 -Release-A 8 ) including IMSI of the mobile station and service leave time information (i.e., information on a time when the mobile station deregistered the broadcast service) to the packet control function unit. In step  314 , the packet control function unit searches corresponding connection information of the mobile station according to the IMSI in response to the release message, and transmits a registration message (A 11  Registration) with service leave time information to the packet data serving node according to the searched connection information. In this case, the connection information means connection information based on an interface set during S 033  setup in step  300 , rather than an interface set for broadcasting.  
         [0064]    [0064]FIG. 11 is a flowchart illustrating an operation of performing accounting on a broadcast service by a base station and a packet data serving node as shown in FIG. 10. Referring to FIG. 11, if a base station receives in step S 500  a broadcast service registration request from a mobile station, the base station generates in step S 502  broadcast service registration time information (i.e., service start time information) and transmits the generated broadcast service registration time information to a packet data serving node. In step S 504 , the packet data serving node starts generating accounting information, using the broadcast service registration time information. In step S 506 , the broadcast service is performed. If the broadcast service is left in step S 508 , the base station generates information on a time when the broadcast service is left in step S 510 , and transmits the generated broadcast service leave time information to the packet data serving node. In step S 512 , the packet data serving node generates accounting information related to the broadcast service, using the broadcast service registration time information and the broadcast service leave time information.  
         [0065]    [0065]FIG. 12 is a message flow diagram illustrating a procedure for assigning broadcast service resources using a registration message according to another embodiment of the present invention. In FIG. 12 compared with FIG. 4, a mobile station registers a broadcast service using a registration message instead of using an IGMP message.  
         [0066]    Referring to FIG. 12, in step  400 , a mobile station (MS) sends a user authentication request to an authentication server (AAA) through PPP connection in order to request a broadcast service. If the user authentication is completed, the authentication server delivers in step  402  to a corresponding packet data serving node (PDSN) information on broadcast services that the user can receive, the information being stored in a database of the authentication server.  
         [0067]    The delivered information includes broadcast multicast service identifiers (BCMCS_IDs) for identifying broadcast services, multicast IP addresses and source IP addresses for identifying sources that provide a broadcast service, or includes a table identifier by which the above parameters can be searched from a database of the packet data serving node (PDSN).  
         [0068]    In step  404 , the mobile station sets up a call based on Service Option 33 (SO33) designating a packet data service through a dedicated channel, and receives session information related to broadcast services from a broadcast server (or a contents server (CS)), using HTTP or SDP. In step  406 , the mobile station transmits a registration message with BCMCS_ID and multicast IP address corresponding to a desired broadcast service, to a base station (BS) over an access channel.  
         [0069]    In step  408 , the base station sends a packet control function unit (PCF) a call setup message (A 9 -Setup-A 8 ) carrying the BCMCS_ID and the multicast IP address. In step  410 , the packet control function unit sends the packet data serving node a registration request message (A 11 -Registration Request) carrying the BCMCS_ID and the multicast IP address in response to the call setup message. The packet data serving node then analyzes the requested multicast IP address in response to the registration request message.  
         [0070]    In the case where the packet data serving node is already servicing the corresponding broadcasting contents while the multicast IP address requested by the mobile station is identical to the multicast IP address authorized in step  402  by the authentication server, the packet data serving node does not require new management such as system and network resource assignment for providing a broadcast service. On the other hand, in the case where the requested multicast IP address is identical to the authorized multicast IP address but the packet data serving node is not performing the service, the packet data serving node registers the requested multicast IP address in a multicast IP routing table.  
         [0071]    If the requested multicast IP address is not identical to the authorized multicast IP address, the packet data serving node inquires of the authentication server about whether the requested multicast IP address is available, through an optional service authentication procedure, in step  412 . If it is determined that the requested multicast IP address is available, the packet data serving node registers the requested multicast IP address in the multicast IP routing table, and builds a multicast IP spanning tree by communication a routing message indicating the particulars registered in the routing table with neighboring routers.  
         [0072]    After the requested multicast IP address is analyzed, the broadcast server starts transmitting broadcast data for the corresponding broadcast service to the packet data serving node, in step  414 . Subsequently, in step  416 , the packet data serving node transmits to the packet control function unit a registration response message (A 11 -Registration Reply) indicating that a broadcast service corresponding to the BCMCS_ID and the multicast IP address was authorized, in response to the registration request message. In step  418 , the packet control function, unit determines from the registration response message that the broadcast service was authorized, and then delivers a connection message (A 9 -Connect-A 8 ) for notifying this situation, to the base station. In step  420 , the mobile station receives the broadcast data by tuning to the forward broadcast supplemental channel corresponding to the BCMCS_ID.  
         [0073]    The disclosed embodiments of the present invention control transmission of a broadcast service data stream according to base station areas through registration of a broadcast service of a mobile station, thereby minimizing a waste of wired/wireless resources. Therefore, embodiments of the present invention can efficiently use base station resources by controlling broadcast service times of base stations, and efficiently use resources of the base stations and a network when a plurality of mobile stations simultaneously request broadcast services.  
         [0074]    While the invention has been shown and described herein 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.
Disclosed is a method for providing a broadcast service in a mobile communication system using code division multiple access (CDMA) technology. The novel method controls transmission of broadcast service data according to base station areas by registering a mobile station with a broadcast service. For that purpose, the mobile station requests an authentication server to authenticate a desired broadcast service, and registers the authenticated broadcast service in a packet data serving node via a base station so that the base station and the packet data serving node can set up a transmission path for the broadcast service. The method increases the efficiency of base station resources by controlling transmission times of base stations, and the packet data serving node can perform accounting on the broadcast service of the mobile station. Further, a plurality of registered mobile stations constitute a group, and broadcast service data is transmitted from one mobile station to other mobile stations within the group.