Patent Publication Number: US-8112081-B2

Title: Broadcast/multicast service system and method providing inter-network roaming

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of pending U.S. application Ser. No. 11/196,344 filed on Aug. 4, 2005, which claims priority of U.S. Provisional Application No. 60/598,447 filed on Aug. 4, 2004, U.S. Provisional Application No. 60/661,409 filed on Mar. 14, 2005, U.S. Provisional Application No. 60/648,139 filed on Jan. 27, 2005, Korean Patent Application No. 10-2005-0017041 filed in Republic of Korea on Feb. 28, 2005, and Korean Patent Application No. 10-2005-0059809 filed in Republic of Korea on Jul. 4, 2005. The entire contents of each of these applications are hereby fully incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mobile communication system and, more particularly, to a broadcast/multicast service system and method supporting inter-network roaming in order to provide a broadcast/multicast service to a user when the user roams in a visiting network which may or may not be a broadcast type network. 
     2. Description of the Related Art 
     A broadcast/multicast service (referred to hereinafter as ‘BCAST service’) is a new type of service that provides a sky wave broadcast or supplementary information to a mobile terminal. The BCAST service includes both a broadcast service and a multicast service. A broadcast service, offered by a service provider, transmits usable information to every user who has subscribed to the services of the service provider. A multicast service, also offered by a service provider, transmits information only to a certain group of users who have subscribed for a specific subject or contents. 
     Currently, in the mobile communication network, a simple service is provided to provide simple information to users, but the BCAST service providing a multimedia type broadcast or various contents to users roaming in the mobile communication network is not provided yet. 
     Further, in a situation where the BCAST service is independently operated by each BCAST service provider, if a user who has subscribed to a specific service provider is moved to an area of a different service provider, continuity of the BCAST service for the user is not provided. 
     In addition, when the user who has subscribed for a specific BCAST service with the ussr&#39;s home network roams to a visiting network, there is no procedure, system or mechanism by which the BCAST service contents of the home network are provided to the user roaming in the visiting network. If the visiting network is a non-broadcast type network or is a broadcast type network which may be the same type as or different from the home network, there is no defined procedure by which the user roaming in the visiting network can obtain the BCAST service of the home network or the BCAST service of the visiting network. This inconveniences the user greatly. 
     SUMMARY OF THE INVENTION 
     Therefore, one object of the present invention is to provide a broadcast/multicast service (BCAST) system and method supporting inter-network roaming, which are capable of guaranteeing continuity of a broadcast/multicast service even when a user roams in the same service network or in a different service network. 
     Another object of the present invention is to provide a broadcast/multicast service system and method supporting inter-network roaming, which are capable of allowing a user who has roamed from a home network to a visiting network to receive a broadcast/multicast service by using a service supported in the visiting network. 
     Still another object of the present invention is to provide a broadcast/multicast service system and method capable of allowing a mobile terminal to use a service provided in a home network when the terminal roams among broadcast type networks. 
     Yet another object of the present invention is to provide a broadcast/multicast service system and method capable of allowing a mobile terminal to use a broadcast/multicast service through a non-broadcast type network when the terminal roams from a broadcast type network into a non-broadcast type network. 
     Another object of the present invention is to provide a mobile terminal, a system, a method, and computer software embodied on at least one computer-readable medium for implementing the method, for providing a BCAST service to an end user/terminal roaming in a visiting network, which overcome limitations and disadvantages associated with the background art. 
     According to an aspect of the present invention, there is provided a method of providing a broadcast/multicast (BCAST) service to a terminal, the method comprising: obtaining, by the terminal, at least one BCAST service from a visiting network when the terminal roams in the visiting network. 
     According to an aspect of the present invention, there is provided a method of obtaining a broadcast/multicast (BCAST) service when a terminal moves from a home network, the method comprising: receiving, by the terminal BCAST service guide information from the visiting network; transmitting, by the terminal, a request to access at least one BCAST service provided in the BCAST service guide information; and obtaining the at least one BCAST service from the visiting network. 
     According to an aspect of the present invention, there is provided a mobile terminal device for obtaining a broadcast/multicast (BCAST) service while roaming in a visiting network, the device comprising: a controller to receive BCAST service guide information from the visiting network, to transmit a request to access at least one BCAST service provided in the BCAST service guide information to the visiting network, and to obtain the at least one BCAST service from the visiting network. 
     According to an aspect of the present invention, there is provided a broadcast/multicast (BCAST) system comprising: a terminal, a home network of the terminal and configured to communicate with the terminal, and a visiting network configured to communicate with the home network and the terminal, wherein the terminal obtains at least one BCAST service from the visiting network when the terminal roams in the visiting network. 
     According to an aspect of the present invention, there is provided a method of providing a broadcast/multicast (BCAST) service when a terminal roams to a visiting network, the method comprising: providing, by a BCAST service distribution/adaptation (BSDA) unit of the visiting network, a service guide to the terminal; transmitting, by the terminal, a request to access at least one BCAST service to a BCAST subscription management (BSM) unit of the visiting network; transmitting, by the BSM unit of the visiting network, a service authorization request to a BSM unit of a home network of the terminal; receiving, by the BSM of the visiting network, a service authorization response form the BSM unit of the home network in response to the service authorization request; transmitting, by the BSM unit of the visiting network, at least one right object for accessing the at least one BCAST service to the terminal; and providing, by the BSDA unit of the visiting network, the at least one BCAST service to the terminal. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG. 1  is a block diagram showing the construction of a BCAST service system according to an embodiment of the present invention; 
         FIG. 2  illustrates three examples in which a terminal roams from a home network to a visiting network and receives a BCAST service in the visiting network according to embodiments of the present invention; 
         FIG. 3  is a signal flow chart of a BCAST service method wherein a terminal roams from a home network to a visiting network in accordance with a first embodiment of the present invention; 
         FIG. 4  is a signal flow chart of a BCAST service method wherein a terminal roams from a home network to a visiting network in accordance with a second embodiment of the present invention; 
         FIG. 5  is signal flow chart of a BCAST service method wherein a terminal roams from a home network to a visiting network in accordance with a third embodiment of the present invention; and 
         FIG. 6  is signal flow chart of a BCAST service method wherein a terminal roams from a home network to a visiting network in accordance with a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A broadcast/multicast (BCAST) service system and method that provide inter-network roaming in accordance with preferred embodiments of the present invention will now be described with reference to the accompanying drawings. 
     In the present invention, when a user (having a mobile terminal) who has subscribed to a BCAST service offered by a home network of the terminal roams from the home network to a visiting network, the user can receive, in the visiting network, the same BCAST service that is provided in the home network. In this case, the visiting network may transmit a service guide of the home network to the user in the visiting network, or incorporate the service guide of the home network with the visiting network&#39;s service guide and transmits it to the user in the visiting network. 
     In the present invention, when a user who has subscribed to a specific BCAST service roams from the user&#39;s home network to a visiting network, the visiting network checks service authentication of the user from the home network and provides a public key (right object) used to view contents of the BCAST service in the visiting network, to the terminal of the user. 
     In the present invention, when a user who has subscribed to a specific BCAST service roams from a broadcast type network to another same broadcast type network, or to a different broadcast type network, or to a non-broadcast type network, the user can still receive the BCAST service through the roamed network. 
       FIG. 1  is a block diagram showing the construction of a BCAST service system according to an embodiment of the present invention. All the components of the BCAST service system are operatively coupled. 
     As shown in  FIG. 1 , the BCAST service system includes a contents provider (content creation)  10  for providing contents to distribute in the BCAST service, a broadcast/multicast (BCAST) server  17  for providing a BCAST service to a user or performing protection of the contents or maintaining/managing the BCAST service, and a terminal  30  for receiving a BCAST service selected by the user from the BCAST server  17 . The terminal  30  is a mobile terminal such as a mobile phone, a PDA, etc. and includes known elements including an input unit (e.g., a keypad, buttons, etc.), a controller, a memory, etc. 
     The BCAST service system additionally includes a broadcast distribution system (BDS)  20  or an interaction network (IN)  22  for distributing the BCAST service and performing an interaction function for bi-directional communication, and/or a BDS service distribution (BDS-SD) unit  18  for applying the interaction network according to a bearer. The units  18 ,  20  and  22  are involved in distributing the BCAST service contents provided by the server  17  to an appropriate device such as the terminal  30  or a home or visiting network. 
     The BDS  20  or the interaction network  22  is a bearer providing a BCAST service such as a DVB-H (Digital Video Broadcasting-Handled), an MBMS (Multimedia Broadcast Multicast Service), a BCMCS (Broadcast Multicast Service), an ISDB-T (Integrated Service Digital Broadcasting-Terrestrial), or a T/S DMB (Terrestrial/Satellite-Digital Multimedia Broadcasting). Thus the BDS  20  and the interaction network  22  support the broadcasting mechanism. 
     The BCAST server  17  includes a BCAST service application (BSA) unit  12  for performing functions such as protecting BCAST service contents and/or maintaining/managing the BCAST service, a BCAST service distribution/adaptation (BSDA) unit  14  for performing and controlling broadcasting, interface and contents scheduling function by using a specific bearer (DVB-H, MBMS, BCMCS, etc.), and a BCAST subscription management (BSM) unit  16  for performing functions of protecting/managing service/contents and maintaining/managing user subscription information in order to manage users who have subscribed to the BCAST service. In this case, the BSA unit  12 , the BCAST service distribution/adaptation unit  14  and the BCAST subscription/management unit  16  of the BCAST server  17  transmit or exchange information and signals to each other or with each other through internal communication. Communications from the BSDA unit  14  and the BSM unit  16  may be communicated to a final destination device (e.g., the terminal  30 ) directly or through one or more of the BDS-SD unit  18 , the BDS  20 , and the interaction network  22 . 
     The terminal  30  includes an application/software for receiving the BCAST service and an application for storing and editing a portion of a BCAST service list provided by the BCAST service provider and storing information on a channel preferred by the user. A BCAST service preference list edited and generated by the user by reflecting the preferences of the user based on the BCAST service list provided by the service provider is called a wish list. The terminal  30  and its associated network (e.g., the home network) may include an application for managing the wish list, which is called a wish list management application. The terminal  30  can be a mobile phone, a PDA, etc., but is not limited thereto and can be any device that is configured to receive BCAST services. 
     The wish list management application manages the wish list separately, and when a user of a terminal who has subscribed to a service of a specific provider roams to a service area of a different provider and receives a different BCAST service list provided by the corresponding provider, the wish list management application stores and edits a portion of the wish list. When the service provider of the visiting network to which the user has roamed does not provide a service list with respect to the BCAST provided in the terminal&#39;s home network, the wish list management application receives the service list from the home network in advance and stores it, or stores a service selected by the user among the provided service list in the wish list in advance. 
     A service provider providing a specific service can transfer a list of services provided in a network of a different service provider with which the service provider has made a roaming contract as well as a list of services provided in its own network. In this case, the service provider should indicate that the service is a service provided by a different provider and not by the service provider itself. Namely, the BCAST server includes a wish list checking application which fetches a wish list of the user&#39;s terminal and checks whether the BCAST server can currently provide any service on the wish list, and if the BCAST service cannot provide the services on the wish list, it checks whether a different provider or a different server can provide it. 
     The wish list checking application may exist in every BCAST server, and when a roaming contact exists between service providers, wish list checking applications in the BCAST servers of different providers can interwork so that a service requested by the user can be provided among BCAST services provided by each BCAST server. It should be noted that ‘a wish list of the terminal’ and ‘a wish list of the user’ refer to the same and are used below interchangeably. 
     The BCAST server  17  periodically can check the wish list of the terminal  30  and store it as part of the server  17 &#39;s stored service broadcast list (server BCAST list) therein or in a separate storage unit outside the BCAST server. The BCAST server  17  can store therein (or in a separate storage unit) information on services which have been provided by different service providers to each requesting user. Thus, when a certain user requests a BCAST service thereafter, the BCAST server  17  searches its storage unit and obtains the current user&#39;s history of the BCAST service. And this information can be used by the BCAST server or others to provide the requested BCAST service to the current user more easily and quickly. In addition, even if the user does not provide the user&#39;s wish list to the BCAST server, since the BCAST server stores the corresponding information, the BCAST service can be provided to the user. 
       FIG. 2  illustrates three different examples in which a terminal may roam and still receive a BCAST service according to the embodiments of the present invention. 
     As shown in  FIG. 2 , a user of the terminal can roam between the same broadcast type networks (e.g., between MBMSs), can roam between different broadcast type networks (e.g., between the MBMS and the DVB-H), or can roam between a broadcast type network and a non-broadcast type network. In the third example, the broadcast type network is not limited to the MBMS or the DVB-H, but can be the BCMCS, ISDB-T, T/S-DMB, or others, and the non-broadcast type network can be the GSM or CDMA, which does not directly offer the BCAST service or does not support the broadcasting mechanism. 
     In some embodiments of the present invention, when the terminal (user) has subscribed to one or more BCAST services of a home network and roams to another network (visiting network) which may be the same type of broadcast network or a different type of broadcast network, the visiting network is configured to provide the BCAST service of the home network to the terminal by obtaining the BCAST service of the home network and broadcasting the BCAST service (contents) to the terminal in the visiting network. In another embodiment, the BCAST service of the visiting network may be provided to the terminal roaming in the visiting network, once the visiting network performs a service authorization check of the terminal through the home network of the terminal. Further, even if the visiting network is a non-broadcast type network, which does not support the broadcasting mechanism, the visiting network can still provide the BCAST service of the home network to the terminal roaming in the visiting network using a unitcast method. For example, even if the visiting network is a non-broadcast type network and only provides a general mobile communication service, the visiting network can still provide an MBMS service or a DVB-H service to the terminal. 
       FIG. 3  is a signal flow chart of a BCAST service method according to an embodiment of the present invention. It is assumed that a user of a terminal  300  has a subscription to one or more BCAST services offered by a home network  100  of the terminal  300  before the user roams to a visiting network  200 . The home network  100  may include a BSA unit  110 , a BSM unit  120 , a BSDA unit  130 , and a BDS-SD unit or BDS or IN  140 . The visiting network  200  may include a BSA unit  210 , a BSM unit  220 , a BSDA unit  230 , and a BDS-SD unit or BDS or IN  240 . The terminal  300  has the same configuration as the terminal  30  in  FIG. 1 . These components of the system have been discussed in connection with  FIG. 1 . The home network  100  and the visiting network  200  can be the same broadcast type networks or different broadcast type networks. All the components of  FIG. 3  are operatively coupled. 
     Now, referring to  FIG. 3 , when the user of the terminal  300 , which has roamed from the home network  100  to the visiting network  200 , wants to receive a BCAST service at a current position (in the visiting network), the user operates a BCAST application of the terminal  300 , and then, the terminal  300  transmits a BCAST service guide request message or a BCAST service request message to the BSM unit  220  of the visiting network  200  (step S 11 ). This request message may include identification information of the user/terminal, etc. 
     The BSM unit  220  informs the BSDA unit  230  of the visiting network about the reception of the BCAST service guide request message or the BCAST service request message through internal communication (step S 13 ), and checks the service authentication of the user of the terminal (step S 15 ). For instance, a service authorization request message is sent from the BSM unit  220  to the BSM  120  of the home network. In this case, because the BCAST service subscription information of the terminal user (e.g., information on which service or which service bundle the user has subscribed to) exists in the home network  100 , the BSM unit  220  of the visiting network requests the subscription information of the user from the BSM unit  120  of the home network (e.g., by transmitting the user/terminal ID, etc.) and performs the service authentication. The service authentication may involve verifying that the current user/terminal is a subscriber to the BCAST service(s) offered by the home network  100 . In the alternative, the home network  100  may perform the actual service authentication and the visiting network  200  may just receive the result of the service authentication from the home network  100 . In this regard, a service authorization response message from the BSM unit  120  to the BSM unit  220  may include the result of the service authentication check and/or other information needed for the subsequent procedures of the visiting network  200 . 
     Upon checking the service authentication of the terminal  300 , the BSM unit  220  of the visiting network informs the BSDA unit  230  that the service authentication has been completed and the current user/terminal is authorized, through internal communication (step S 17 ). At this time, the BSDA unit  230  checks whether there is a wish list for the current user in a server BCAST list stored in the visiting network  200 . The server BCAST list is stored in the BCAST server of the visiting network  200 , and can exist in the BSA unit  210 , in the BSM unit  220  or in the BSDA unit  230 , or can be stored in a separate storage unit. The server BCAST list can be managed by the wish list checking application. The server BCAST list includes wish lists of a plurality of different users. A wish list of a user/terminal is the user&#39;s preferred BCAST service(s), which can be selected by the user from a list of all the BCAST services offered by the user&#39;s home network or from a list of all the BCAST services that the user has subscribed to from the user&#39;s home network. The wish list of the terminal may also include other information such as user information, which may be used to generate a service guide. 
     The wish list of the current user may be stored as part of the server BCAST list stored in the visiting network  200 . For instance, before the user roams to the visiting network, the visiting network may obtain the wish list of the user in advance through communication with the home network. This can be accomplished in many different ways. For instance, once the user subscribes to the BCAST service(s) of the home network  100  and compiles the user&#39;s wish list based on the BCAST service list offered by the home network  100 , the home network  100  can be configured to transmit the wish list to the visiting network  200  so that it can be prestored in the visiting network  200 . The system can also be configured such that any updated wish list of the user, which is stored in the home network  100  and/or the terminal  300 , is communicated to the visiting network  200  from the home network  100  or the terminal  300 . 
     In the example of  FIG. 3 , it is assumed that the wish list of the current terminal  300  does not exist on the visiting network&#39;s server. However, the scenario in which the wish list of the current terminal  300  does exist on the visiting network&#39;s server, is discussed later in connection with  FIG. 4 . 
     If the wish list of the terminal  300  does not exist in the server BCAST list at step S 17 , the BSDA unit  230  of the visiting network transmits a service guide request message to the BSDA unit  130  of the home network  100  (step S 19 ). Then the BSDA unit  130  of the home network collects various information (e.g., subscription information, user&#39;s wish list, etc.) for generating a service guide for the current terminal  300 , from the BSM unit  120  and the BSA unit  110  of the home network  100  via internal communication (step S 21 ). Thereafter, the BSDA unit  130  generates the service guide (BCAST service guide) based on the wish list of the current terminal. 
     The BSDA unit  130  of the home network transmits the generated service guide to the BSDA unit  230  of the visiting network (step S 23 ), and the BSDA unit  230  of the visiting network transmits the service guide to the terminal  300  (step S 25 ). In this case, the BSDA unit  230  of the visiting network can transmit the service guide received from the BSDA unit  130  of the home network to the terminal  300 , or can transmit a new service guide obtained by incorporating a service guide of the visiting network  200  into the service guide received from the BSDA unit  130  of the home network. Namely, the service guide transmitted to the BSDA unit  230  of the visiting network from the BSDA unit  130  of the home network and the service guide transmitted from the BSDA unit  230  of the visiting network to the terminal  300  can be same service guides or different service guides. In step S 31 , the visiting network  200  broadcasts the service guide to the terminal  300  by using its broadcasting mechanism, e.g., through a broadcast distribution system (e.g., BDS  20  in  FIG. 1 ) or an interaction network (e.g., IT  22  in  FIG. 1 ). 
     When the user checks the BCAST service guide received by the terminal  300  and selects contents (BCAST service) desired to be received among the programs or services identified in the BCAST service guide, the terminal  300  transmits a BCAST contents request message to the BSDA unit  230  of the visiting network (step S 27 ). In this case, the desired contents are a BCAST service provided in the home network. Thus the BSDA unit  230  of the visiting network transmits the BCAST contents request message to the BSDA unit  130  of the home network (step S 27 ). 
     Upon receiving the BCAST contents request message, the BSDA unit  130  receives contents requested by the user from a contents provider  50  through internal communication with the BSA unit  110  (step S 29 ), and transmits the received contents (BCAST service) to the terminal  300  through the BSDA unit  230  of the visiting network (step S 31 ). The visiting network  200  transmits the contents to the terminal  300  by using its broadcasting mechanism. Accordingly, the user roaming in the visiting network receives the BCAST service of the user&#39;s home network. 
       FIG. 4  is a signal flow chart of a BCAST service method according to another embodiment of the present invention, wherein a current terminal  300  roams to a visiting network  200 . The system components discussed in the embodiment of  FIG. 3  are also provided in the embodiment of  FIG. 4 . In  FIG. 4 , there is a wish list of the current terminal  300  in the server BCAST list of the BCAST server of the visiting network  200 , which differs from the embodiment of  FIG. 3 . The home network  100  and the visiting network  200  can be the same broadcast type networks or different broadcast type networks. It is assumed that the user of the terminal  300  has a subscription to one or more BCAST services offered by the home network  100  of the terminal  300  before the user roams to the visiting network  200 . All the components of  FIG. 4  are operatively coupled. 
     Referring to  FIG. 4 , when the user of the terminal  300  which has roamed from the home network  100  to the visiting network  200  wants to receive a BCAST service at a current location in the visiting network  200 , the user operates a BCAST application of the terminal  300  and transmits a BCAST service guide request message or a BCAST service request message to the BSM unit  220  of the visiting network (step S 41 ). 
     The BSM unit  220  informs the BSDA unit  230  of the visiting network about the reception of the BCAST service guide request message or the BCAST service request message through internal communication (step S 43 ), and checks the service authentication of the terminal/user through the BSM unit  120  of the home network (step S 45 ). Steps S 41 , S 43  and S 45  correspond respectively to steps S 11 , S 13  and S 15  of  FIG. 3 . 
     Upon checking the service authentication of the terminal/user, the BSM unit  220  of the visiting network informs the BSDA unit  230  that the service authentication of the current terminal  300  has been completed and the current user is authorized to receive the BCAST service, through internal communication (step S 47 ). Then in step S 47 , the BSDA unit  220  of the visiting network checks whether there is a wish list of the terminal  300  in the server BCAST list. The server BCAST list exists in the BCAST server of the visiting network, and it can exist in the BSA unit  210 , in the BSM unit  220  or in the BSDA unit  230 , and can be managed by the wish list checking application. 
     If there is the wish list of the terminal  300  in the server BCAST list of the visiting network, the BSDA unit  230  transmits a BCAST service guide to the terminal  300  (step  49 ). In this case, the BSDA unit  230  of the visiting network can transmit the BCAST service guide of the home network  100  based on the wish list of the terminal  300  to the terminal  300 , or can transmit a new service guide obtained by incorporating the BCAST service guide of the visiting network  200  to the BCAST service guide of the home network  100 , to the terminal  300 . In addition, the BSDA unit  230  of the visiting network can collect various information (e.g., BCAST service attribute, etc.) from the BSM unit  220  of the visiting network and the BSA unit  210 , for generating a service guide of the terminal  300  based on the wish list of the terminal  300  and generate the BCAST service guide for the terminal  300 . The visiting network  200  can transmit the service guide to the terminal  300  by using its broadcasting mechanism, e.g., through a broadcast distribution system (e.g., BDS  20  in  FIG. 1 ) or an interaction network (e.g., IT  22  in  FIG. 1 ). 
     When the user checks the BCAST service guide received by the terminal  300  and selects contents desired to be received among programs or services described in the service guide, the terminal  300  transmits a BCAST contents request message to the BSDA unit  130  of the home network through the BSDA unit  230  of the visiting network (step S 51 ). 
     Upon receiving the BCAST contents request message, the BSDA unit  130  of the home network receives contents requested by the user from a contents provider  50  through internal communication with the BSA unit  110  (step S 53 ), and transmits the received contents (BCAST service) to the terminal  300  through the BSDA unit  230  of the visiting network (step S 55 ). The visiting network  200  transmits the BCAST service contents to the terminal  300  by using its broadcasting mechanism. Accordingly, the user roaming in the visiting network receives the BCAST service of the user&#39;s home network. 
       FIG. 5  is a signal flow chart of a BCAST service method according to another embodiment of the present invention. This embodiment differs from the embodiments of  FIGS. 3 and 4  in that the visiting network  400  is a non-broadcast type network. Although the visiting network  400  does not directly offer the BCAST service, the terminal user receives the BCAST service through a uni-cast method of the visiting network according to this embodiment. The user of the terminal  300  has subscribed to the BCAST service of the home network before the user roams to the visiting network  400 . All the components of  FIG. 5  are operatively coupled. 
     As shown in  FIG. 5 , since the non-broadcast type network (visiting network  400 ) indicated by a wireless network or a mobile communication network does not have an entity for providing the BCAST service, it transmits a service guide and/or contents transmitted from the home network  100  to the current terminal  300  through its packet switched network. That is, communications between the visiting network  400  and the terminal  300  occur using existing communication protocols between the visiting network  400  and the terminal  300 . 
     Referring to  FIG. 5 , when the user of the terminal  300  roams or moves from the user&#39;s home network  100  (namely, a broadcast type network) to another network (the visiting network  400 , namely a non-broadcast type network), the user operates the BCAST application of the user&#39;s terminal  300  and the terminal  300  transmits a BCAST service guide request message or a BCAST service request message to the non-broadcast type visiting network  400  (step S 61 ). 
     Upon receiving the request message, the non-broadcast type visiting network (e.g., a server therein)  400  requests the BSM unit  120  of the home network  100  to check the service authentication of the terminal user (step S 63 ), and the BSM unit  120  of the home network checks the service authentication of the terminal user and transmits a response message including the service authentication result to the non-broadcast type visiting network  400  (step S 65 ). In this case, because the BCAST service subscription information of the terminal user (e.g., information on which service or which service bundle the user has subscribed to) exists in the home network  100 , the visiting network  400  requests the subscription information of the user from the BSM unit  120  of the home network (e.g., by transmitting the user/terminal ID, etc.) and performs the service authentication. The service authentication may involve verifying that the current user/terminal is a subscriber to the BCAST service(s) offered by the home network  100 . In the alternative, the home network  100  may perform the actual service authentication and the visiting network  400  may just receive the result of the service authentication from the home network  100 . 
     Upon checking the service authentication of the terminal  300 , the non-broadcast type visiting network  400  transmits a service guide request message to the BSDA unit  130  of the home network (step S 67 ). Upon receiving the service guide request message, the BSDA unit  130  of the home network collects service guide information of the terminal  300  from the BSM unit  120  of the home network and the BSA unit  110  through internal communication (step S 69 ). In this case, since the visiting network  400  is a non-broadcast type and thus does not have an entity for providing the BCAST service (via a broadcasting mechanism), the visiting network  400  does not itself have a wish list of the terminal  300  or a service guide with respect to the BCAST service provided from the home network or any other network. Accordingly, the visiting network  400  must obtain the service guide of the terminal  300  from the BSDA unit  130  of the home network, and the BSDA unit  130  of the home network collects the service guide information for the current terminal  300  based on the wish list of the terminal  300  prestored in the home network or provided by the terminal  300 . 
     The BSDA unit  130  of the home network then generates a BCAST service guide for the current terminal  300  using the collected service guide information. The BSDA unit  130  then transmits the generated service guide to the visiting network  400  (step S 71 ), and the visiting network  400  transmits the service guide to the terminal  300  (step S 71 ). In this case, the service guide transmitted by the visiting network  400  to the terminal  300  is the same as the service guide received from the home network  100 . 
     When the user checks the BCAST service guide received by the terminal  300  and selects contents desired to be received among programs or services listed in the service guide, the terminal  300  transmits a BCAST contents request message to the BSDA unit  130  of the home network through the visiting network  400  (step S 73 ). 
     Upon receiving the BCAST contents request message, the BSDA unit  130  of the home network receives contents requested by the user from a contents provider  50  through internal communication with the BSA unit  110  (step S 75 ), and transmits the corresponding contents to the terminal  300  through the non-broadcast type visiting network  400  (step S 77 ). In this case, the visiting network  400 , which has received the contents (BCAST service) from the BSDA unit  130  of the home network, transmits the contents to the terminal  300  through its packet switched network/method since the visiting network  400  is a non-broadcast type network. Namely, the contents (BCAST service) are transferred by 1:1 through a uni-cast method only between the server of the non-broadcast type visiting network  400  and the terminal  300 , e.g., through a data service channel provided in a mobile communication network and not through a broadcast distribution system (BDS) or an interaction network. 
     In the embodiment of  FIG. 5 , if an audio/video codec supported in the network offering the BCAST service (broadcast type network) and an audio/video codec supported in a visiting mobile communication network (non-broadcast type network) do not correspond, a certain transformation process for making the codecs correspond to each other may be used. For example, if the broadcast type network for providing BCAST service contents supports MPEG4 while the mobile communication network (non-broadcast type visiting network) for receiving the BCAST service contents supports MPEG2, not MPEG4, then the mobile communication network is configured to decode the MPEG-4 contents received from the broadcast type network, encode them to MPEG2 and then transmit the MPEG-2 contents to the user terminal. In this case, a procedure for exchanging a contents coding method supported in the broadcast type network and a contents coding method supported in the mobile communication network (non-broadcasting type network) can be added before the contents are provided, and such a procedure is known. In addition, if the home network knows capabilities (for example, a supported codec, a data rate, resolution of a screen of the terminal) of the user&#39;s terminal, then corresponding information (e.g., terminal&#39;s capability information) can be transmitted to the visiting network so that the visiting network can use the information to suitably transform the contents received from the home network before transmitting it to the user&#39;s terminal. 
     In the embodiments of  FIGS. 3-5 , it has been described that the wish list of the current user is used to generate the service guide to be provided to the terminal roaming in the visiting network. However, the present invention is not limited thereto, and encompasses a situation where the wish list of the current user is not used to generate the service guide to the current user at the terminal. For instance, without regards to the user&#39;s wish list, the service guide, to be provided to the end user at the terminal  300 , may be a service guide generated based on the user&#39;s subscription policy, or can be a service guide that includes all the BCAST services offered by the home or visiting network. 
       FIG. 6  is a signal flow chart of a BCAST service method according to another embodiment of the present invention. In this embodiment, a BCAST service guide is transmitted from a visiting network  200  to a terminal  300  before the terminal requests it. That is, the visiting network, which is a broadcast type network, broadcasts its service guide repeatedly using its broadcasting mechanism (e.g., BDS or interaction network) to all terminals roamed into the visiting network. Each terminal then can request access (request right objects) to one or more BCAST services on the service guide, and thereby accesses the BCAST service. 
     In  FIG. 6 , it is assumed that the user of the current terminal  300  has a subscription to one or more (BCAST) services offered by the home network  100  of the terminal  300  before the user roams to the visiting network  200 . The home network  100  may include a BSA unit  110 , a BSM unit  120 , a BSDA unit  130 , and a BDS-SD unit or BDS or IN  140 . The visiting network  200  may include a BSA unit  210 , a BSM unit  220 , a BSDA unit  230 , and a BDS-SD unit or BDS or IN  240 . These components have been discussed in connection with  FIG. 1 . The home network  100  and the visiting network  200  can be the same broadcast type networks or different broadcast type networks. All the components of  FIG. 6  are operatively coupled. 
     Now, referring to  FIG. 6 , the terminal  300 , which has roamed to the visiting network  200 , receives a BCAST service guide of the visiting network  200  from the BSDA unit  230  of the visiting network, without being connected with the home network  100  (step S 81 ). Namely, the visiting network  200  provides its service guide to the terminal  300  which has roamed to the visiting network  200 , without the user&#39;s request and without any contact with the home network  100 . This may be accomplished by the visiting network  200  by repeatedly broadcasting its service to all terminals that roamed into the visiting network  200 , e.g., using its broadcasting mechanism. 
     Upon checking the service guide, the user requests a use privilege (access information, e.g., right object(s) RO) in order to access a specific BCAST service identified in the service guide from the BSM unit  220  of the visiting network (step S 83 ). The use privilege is a right with respect to contents requested by the user or a right for accessing or using the BCAST service. The BSM unit  220  of the visiting network receives this request and also checks the service authentication of the corresponding terminal  300  from the BSM unit  120  of the home network. Namely, the BSM unit  220  of the visiting network transmits a service authentication request message to the BSM unit  120  of the home network (step S 85 ), and the BSM unit  120  of the home network checks the service authentication of the terminal and transmits a service authentication response message to the BSM unit  220  of the visiting network (step S 87 ). The service authentication response message includes the result of the service authentication. The service authentication may involve determining whether or not the current terminal  300  is a subscriber of the home network  100 , and examining in detail the subscription policy of the user of the terminal  300  so as to determine whether or not the user should receive the specific BCAST service requested by the user at step S 81 . The actual service authentication can be performed by the home network  100 , or the visiting network, or in part by the home network and in part by the visiting network. 
     If the service authentication result indicates that the terminal  300  is authorized to receive the BCAST service, the BSM unit  220  of the visiting network transmits the use privilege (access information such as RO) for allowing access and/or use of the specific BCAST service requested by the user, to the user (step S 89 ). RO can be a key or code to open or decrypt the BCAST service (contents). The BSDA unit  230  of the visiting network transmits the user-requested contents (BCAST service) to the terminal  300  through its broadcasting mechanism (step S 91 ). In this case, the BSDA unit  230  and the BSM unit  220  may transmit or exchange information and signals through internal communication. 
     Upon receiving the contents, the terminal  300  accesses or interprets the received contents by using the RO. The BSM unit  220  of the visiting network generates charging (billing) information (e.g., charges regarding the use of the contents, etc.) according to the use of the corresponding contents (S 93 ), and the visiting network  200  can send the generated charging information to the home network  100  so that the user can be billed appropriately by the home network. The visiting network  200  sends the charging information to the home network  100  for the services the visiting network provided since the user has a subscription contract with the home network  100 . The charging information may include any other service fee of the visiting network  200  for allowing the roaming user to receive a BCAST service. 
     According to the present invention, the step of generating the charging information in step S 93  may also be performed in other embodiments, e.g., in the embodiments of  FIGS. 3-5 . For instance, if the visiting network merely passes on the BCAST service contents provided by the home network, the charging information may include any service fee of the visiting network  200  for merely passing on the BCAST service contents. 
     As so far described, the broadcast/multicast service system and method for supporting inter-network roaming in accordance with the embodiments of the present invention have many advantages. 
     For example, after the terminal roams into a visiting network, it can now receive the same BCAST service as the BCAST service that the terminal has received in the home network, at a current location in the visiting network. 
     In addition, because the user can set and receive his/her preferred BCAST service with continuity regardless of its position (e.g., whether the user is currently located in the home network or visiting network), the user&#39;s convenience and satisfaction for receiving the BCAST service can be enhanced greatly. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses or systems. The description of the preferred embodiments of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structure described herein as performing the recited function and not only structural equivalents but also equivalent structures.