Abstract:
Provided is a method for performing handover between a communication network and a broadcast network by a handover controller of a first network corresponding to either the communication network or the broadcast network. The method for performing handover includes: searching for a second network capable of providing the same broadcast content broadcasted over the first network; performing a handover preparation procedure between the communication network and the broadcast network with a handover controller of the second network; delivering the broadcast content broadcasted over the first network to the handover controller of the second network; and sending a message requesting a terminal to watch, over the second network, the broadcast content broadcasted over the first network.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0085933 and 10-2010-0086691 filed in the Korean Intellectual Property Office on Sep. 11, 2009 and Sep. 3, 2010, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to providing broadcast content, and more particularly, to a method of handover between a communication network and a broadcast network for providing broadcast content. 
     (b) Description of the Related Art 
     With the development of IT technologies, terminals each including both a communication network receiver and a broadcast network receiver are coming into use. Broadcast content can be provided through a communication network or a broadcast network. 
     A user terminal can receive paid broadcast content (e.g., a soccer match) through a communication network. At this point, if the number of users receiving the broadcast content through the communication network increases, the load on the communication network becomes heavier. A user terminal also can receive broadcast content (e.g., a baseball match) through a communication network. When the broadcast content is forcibly ended according to a regular broadcasting schedule, a user may want to continue watching the broadcast content. In these cases, a handover procedure between the broadcast network and the communication network is required. 
     A general handover procedure between the broadcast network and the communication network begins with a request from a terminal. That is, the terminal continues to measure radio signals in the vicinity, and reports measurement results to the currently connected network. The network having received the report on the measurement results makes a decision to perform a handover operation according to predetermined criteria, and the terminal submits a resource reservation request to a network (i.e., target network) for handover. Thereby, the terminal can continuously receive particular broadcast content by performing the handover operation between the communication network and the broadcast network and resuming the broadcast service. 
     However, such a general handover operation between a communication network and a broadcast network only applies to a specific terminal that has requested the handover. Accordingly, in the case that a group handover for multiple terminals is required, it is difficult to perform an appropriate handover operation due to changes in the network states. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a method of handover between a communication network and a broadcast network. 
     One exemplary embodiment the present invention provides a method for performing handover between a communication network and a broadcast network by a handover controller of a first network corresponding to either the communication network or the broadcast network, the method including: searching for a second network capable of providing the same broadcast content broadcasted over the first network; performing a handover preparation procedure between the communication network and the broadcast network with a handover controller of the second network; delivering the broadcast content broadcasted over the first network to the handover controller of the second network; and sending a message requesting a terminal to watch, over the second network, the broadcast content broadcasted over the first network. 
     Another exemplary embodiment the present invention provides a method for performing handover between a communication network and a broadcast network by a handover controller of a first network corresponding to either the communication network or the broadcast network, the method including: receiving, from a handover controller of a second network, a first message inquiring whether the same broadcast content broadcasted over the second network can be provided and whether there are available resources in the first network; sending, in response to the first message, a second message including information on whether the broadcast content can be provided and whether there are available resources; receiving, from the handover controller of the second network, a third message requesting preparation for provision of the broadcast content; sending, in response to the third message, a fourth message including information required for a terminal to receive the broadcast content; receiving the broadcast content delivered from the handover controller of the second network; and providing the broadcast content to the terminal. 
     One exemplary embodiment the present invention provides a handover controller of a first network corresponding to either a communication network or a broadcast network, which performs handover between the communication network and the broadcast network, including: a broadcast content detector for detecting broadcast content to be handed over to a second network; a second network selector for selecting at least one second network capable of providing the broadcast content with reference to information on whether the broadcast content received from a second network in the vicinity can be provided and information on whether there are available resources; and a transceiver for transmitting a preparation request message for handover to the at least one second network and transmitting a message requesting a terminal to receive the broadcast content from the at least one second network. 
     As a handover procedure begins at a network end, a ground handover for a plurality of terminals is possible. 
     If the number of users receiving broadcast content over a communication network increases, the reception of the corresponding broadcast content can be switched to a broadcast. Hereupon, the communication network operator can reduce the load on the communication network, and the users can receive the same broadcast content at a low price. 
     If specific broadcast content transmitted over a broadcast network is forcibly ended, the reception of the corresponding broadcast content can be switched to a communication network. Hereupon, the users can continue to receive the corresponding broadcast content. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing a broadcast content providing system according to one exemplary embodiment of the present invention. 
         FIG. 2  is a block diagram showing a handover controller according to one exemplary embodiment of the present invention. 
         FIG. 3  is a flowchart showing a method of handover from a communication network to a broadcast network according to one exemplary embodiment of the present invention. 
         FIG. 4  is a flowchart showing a method of handover from a broadcast network to a communication network according to one exemplary embodiment of the present invention. 
         FIG. 5  is a view showing in detail a broadcast content providing system according to one exemplary embodiment of the present invention. 
         FIG. 6  is a flowchart showing a method of handover from a communication network to a broadcast network according to one exemplary embodiment of the present invention when a system supporting 3GPP MBMS (Multimedia Broadcast/Multicast Service) is used as the communication network, a DVB-IPDC (IP Datacasting) system is used as the broadcast network, and the communication network and the broadcast network support the IEEE 802.21 MIH (Media Independent Handover) function. 
         FIG. 7  is a flowchart showing a method of handover from a broadcast network to a communication network according to one exemplary embodiment of the present invention when a system supporting 3GPP MBMS (Multimedia Broadcast/Multicast Service) is used as the communication network, a DVB-IPDC (IP Datacasting) system is used as the broadcast network, and the communication network and the broadcast network support the IEEE 802.21 MIH (Media Independent Handover) function. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, to clarify the present invention, parts that are not related to description are omitted, and the same parts have the same reference numerals through the specification. 
     Throughout the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
     In the specification, a terminal may designate a mobile station (MS), a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), user equipment (UE), an access terminal (AT), etc., and may include the entire or partial functions of the mobile station, the mobile terminal, the subscriber station, the portable subscriber station, the user equipment, the access terminal, etc. 
     In the specification, an access point (AP) may designate a base station (BS), a radio access station (RAS), a node B, an evolved node-B (eNB), a base transceiver station (BTS), a mobile multihop relay (MMR)-BS, etc., and may include the entire or partial functions of the base station, the radio access station, the node B, the eNB, the base transceiver station, the MMR-BS, etc. 
       FIG. 1  is a view showing a broadcast content providing system according to one exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , the broadcasting content providing system  100  includes a content providing server  110 , a communication network handover controller  120 , a broadcast network handover controller  130 , a communication network  140 , a broadcast network  150 , and a terminal  160 . 
     The content providing server  110  provides broadcast content to the communication network handover controller  120  and the broadcast network handover controller  130  over the internet. The broadcast content refers to media content such as real-time TV broadcast and on-demand video. The broadcast content may refer to general data files. 
     In a situation where terminals  160  are watching broadcast content over a communication network, when it is necessary to service the terminals through a broadcast network, the communication network handover controller  120  performs a handover procedure to the broadcast network. That is, the communication network handover controller  120  selects an appropriate broadcast network capable of providing the broadcast content, and allows the selected broadcast network to provide the broadcast content to the terminals. 
     In a situation where terminals  160  are watching broadcast content over a broadcast network, when it is necessary to service the terminals through a communication network, the broadcast network handover controller  130  performs a handover procedure to the communication network. That is, the broadcast network handover controller  130  selects an appropriate communication network capable of providing the broadcast content, and allows the selected communication network to provide the broadcast content to the terminals. 
     The communication network  140  is a mobile communication network or wireless communication network that provides a bidirectional data communication service and a broadcast service. For example, the communication network includes mobile communication networks such as 3GPP (3 rd  Generation Partnership Project) and 3GPP2 and wireless networks such as WiMAX and WLAN (Wireless Local Access Network). 
     The broadcast network  150  is a cable TV network, a satellite TV network, or a mobile digital broadcasting network that provides an unidirectional broadcast service. For example, the broadcast network includes DVB-H (Digital Video Broadcasting-Handheld), MediaFLO, ATSC-M/H (Advanced Television Systems Committee-Mobile/Handheld), and so on. 
     While the communication network handover controller  120  and the broadcast network handover controller  130  are illustrated as being separate from the communication network  140  and the broadcast network  150 , respectively, the communication network handover controller  120  may be part of the components included in the communication network  140  or part of the components included in the broadcast network  150 . 
     The terminal  160  receives broadcast content over the communication network  140  and the broadcast network  150 . To this end, the terminal  160  includes both a communication network receiver  161  and a broadcast network receiver  162 . The terminal  160  may be a portable mobile terminal. 
       FIG. 2  is a block diagram showing a handover controller according to one exemplary embodiment of the present invention. The handover controller refers to a communication network handover controller  120  or a broadcast network handover controller  130 . Here, a network currently providing broadcast content to a terminal is referred to as a serving network, and a network to which the terminal is to perform handover is referred to as a target network. 
     Referring to  FIG. 2 , the handover controller  200  includes a broadcast content detector  210 , a network searching unit  220 , a network selector  230 , a message configuration unit  240 , and a transceiver  250 . 
     If the handover controller  200  is a handover controller of a serving network, the broadcast content detector  210  detects, among the broadcast content currently provided by the serving network, broadcast content that needs to be switched to a target network. 
     The network searching unit  220  searches for a target network capable of providing the detected broadcast content. The number of searched target networks may be one or more. 
     The network selector  230  selects an appropriate target network capable of detected broadcast content among the searched target networks. 
     The message configurator  240  configures a message to be sent to and received from the handover controller of the target network and the terminal  160  to perform a handover procedure from the serving network to the target network. 
     The transceiver  250  sends and receives the message configured by the message configurator  240  to and from the handover controller of the target network and the terminal  160 . 
     On the other hand, if the handover controller  200  is a handover controller of a target network, the message configurator  240  configures a message to be sent to and received from the handover controller of the serving network and the terminal  160  to perform a handover procedure, and the transceiver  250  sends and receives the message configured by the message configurator  240  to and from the handover controller of the serving network and the terminal  160 . 
     Hereinafter, a handover procedure from a communication network to a broadcast network will be described. If a number of terminals watch the same broadcast content over the communication network, a communication network handover controller is able to allow the broadcast network to provide the broadcast content. 
       FIG. 3  is a flowchart showing a method of handover from a communication network to a broadcast network according to one exemplary embodiment of the present invention. 
     Referring to  FIG. 3 , the communication network handover controller  120  determines whether there is any broadcast content that increases the load on the communication network (S 300 ). For example, if the number of terminals watching the same broadcast content exceeds a predetermined range, it is determined that the broadcast content is increasing the load on the communication network. The step S 300  may be periodically or non-periodically performed. 
     If it is determined that there is broadcast content that increases the load on the communication network, the communication network handover controller  120  searches for a broadcast network capable of providing the broadcast content (S 310 ). The broadcast network capable of providing the broadcast content may be a broadcast network currently providing the broadcast content or a broadcast network planning to provide the broadcast content later. The number of searched broadcast networks may be one or more. 
     The communication network handover controller  120  sends an inquiry message to the broadcast network handover controller  130  of the searched broadcast network (S 320 ). When there are a plurality of searched broadcast networks, the communication network handover controller  120  can send an inquiry message to the plurality of broadcast network handover controllers  130 . The inquiry message is a message that inquires whether the broadcast network can provide the broadcast content detected as increasing the load on the communication network and whether there are available network resources in the broadcast network for this service. The inquiry message may include information on the broadcast content detected as increasing the load on the communication network. For example, the information on the broadcast content may include media information and session information. The media information may include audio encoding information, video encoding information, etc., and the session information may include channel information, service identification information, address information, transmission time information, etc. 
     The broadcast network handover controller  130  sends a response message to the inquiry message received from the communication network handover controller  120  (S 330 ). The response message indicates whether the broadcast network can provide the broadcast content detected as increasing the load on the communication network and whether there are available network resources. 
     The communication network handover controller  120  determines, with reference to the response message received from the broadcast network handover controller  130 , whether the corresponding broadcast network can provide the broadcast content detected as increasing the load on the communication network to the terminal  160 . When a plurality of response messages are received from a plurality of broadcast network handover controllers  130 , an appropriate broadcast network is selected with reference to the received plurality of response messages (S 340 ). At this point, at least one broadcast network can be selected. 
     The communication network handover controller  120  sends a preparation request message for the corresponding broadcast content to the broadcast network handover controller  130  of the selected broadcast network (S 350 ). The preparation request message includes information on the content providing server  110  that provides the broadcast content detected as increasing the load on the communication network. 
     The broadcast network handover controller  130  sends a response message to the preparation request (S 360 ), and prepares to provide the broadcast content detected as increasing the load on the communication network. The response message to the preparation request includes information required for the terminal  160  to receive the corresponding broadcast content over the broadcast network. For example, the response message to the preparation request may include information on a time at which the broadcast network provides the corresponding broadcast content and information on network resources (e.g., channels) allocated such that the broadcast network provides the corresponding broadcast content. If the corresponding broadcast content is paid content, the response message to the preparation request may include encryption information, i.e., an encryption key. 
     Meanwhile, when there are network resources established by prior agreement between the broadcast network operator and the communication network operator, the network resources allocated such that the broadcast network provides the corresponding broadcast content detected as increasing the load on the communication network may be network resources established by prior agreement. On the contrary, when there are no network resources established by prior agreement, the broadcast network allocates part of the network resources currently in use to provide the corresponding broadcast content. For example, the broadcast network can allocate network resources for providing broadcast content with a small number of viewers or network resources for providing broadcast content scheduled to end soonest in order to provide the broadcast content detected as increasing the load on the communication network. When the broadcast network allocates network resources currently in use, the response message to the preparation request may further include information on an expected end time of the broadcast content being provided by the allocated network resources. Therefore, the communication network provides the corresponding broadcast content to the terminal until the expected end time, and requests the broadcast network to provide the corresponding broadcast content after the expected end time. Accordingly, the problem of interruption of broadcast content provided by network resources currently in use can be avoided. 
     The communication network handover controller  120  delivers the broadcast content detected as increasing the load on the communication network to the broadcast network handover controller  130  (S 370 ). If the response message to the preparation request includes an expected end time of the broadcast content currently being provided by allocated network resources, the communication network handover controller  120  can deliver the corresponding broadcast content after the expected end time. 
     Further, the communication network handover controller  120  sends a request message to the terminal  160  using the corresponding broadcast content over the communication network to connect to the selected broadcast network and continue to watch the corresponding broadcast content (S 380 ). The request message includes information on the selected broadcast network. When there is one or more selected broadcast networks, the request message may include information on the one or more broadcast networks. The request message is transmitted to a plurality of terminals in a multicast or broadcast format, and requires no response message from the terminals. 
     The terminal  160  connects to the broadcast network selected by the communication network handover controller  120 , and then requests the broadcast network handover controller to provide the corresponding broadcast content (S 390 ). When there are a plurality of selected broadcast networks, the terminal  160  can select and connect to one of the plurality of broadcast networks. 
     Hereinafter, a handover procedure from a broadcast network to a communication network will be described. When it is necessary to forcibly end particular broadcast content broadcasting according to a broadcast schedule, the broadcast network handover controller enables the terminal to continue to watch the broadcast content over a communication network. 
       FIG. 4  is a flowchart showing a method of handover from a broadcast network to a communication network according to one exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , the broadcast network handover controller  130  determines whether there is any broadcast content to be continuously provided over a communication network (S 400 ). The broadcast content to be continuously provided over the communication network may be broadcast content currently being provided over a broadcast network but expected to be forcibly ended or broadcast content that has already been forcibly ended. For example, this applies to a case where a baseball game takes longer than the broadcast schedule and the broadcast of the baseball game has to be ended before the game is over. The step S 400  can be periodically or non-periodically performed. At this point, the broadcast network handover controller  130  can collect information on the corresponding broadcast content. For example, the information on the corresponding broadcast content may include media information and session information. The media information may include audio encoding information, video encoding information, etc., and the session information may include channel information, service identification information, address information, transmission time information, etc. 
     If it is determined that there is any broadcast content to be continuously provided over the communication network, the broadcast network handover controller  130  searches for a communication network capable of providing the broadcast content (S 410 ). The communication network capable of providing the broadcast content may be a communication network currently providing the broadcast content or a communication network planning to provide the broadcast content later. The number of searched communication networks may be one or more. 
     The broadcast network handover controller  130  sends an inquiry message to the communication network handover controller  120  of the searched communication network (S 420 ). When there are a plurality of searched communication networks, the broadcast network handover controller  130  can send an inquiry message to the plurality of communication network handover controllers  120 . The inquiry message is a message that inquires whether the communication network can provide the broadcast content that has been forcibly ended in the broadcast network and needs to be continuously provided over a communication network and whether there are available network resources in the communication network for this service. The inquiry message may include information on the broadcast content that needs to be continuously provided over the communication network. 
     The communication network handover controller  120  sends a response message to the inquiry message received from the broadcast network handover controller  130  (S 430 ). The response message indicates whether the communication network can provide the corresponding broadcast content and whether there are available network resources. 
     The broadcast network handover controller  130  determines, with reference to the response message received from the communication network handover controller  120 , whether the corresponding communication network can provide the broadcast content that has been forcibly ended in the broadcast network and needs to be continuously provided over the communication network to the terminal  160 . When a plurality of response messages are received from a plurality of communication network handover controllers  120 , an appropriate communication network is selected with reference to the received plurality of response messages (S 440 ). At this point, at least one communication network can be selected. 
     The broadcast network handover controller  130  sends a preparation request message for the corresponding broadcast content to the communication network handover controller  120  of the selected communication network (S 450 ). The preparation request message includes information on the content providing server  110  that provides the broadcast content that has been forcibly ended in the broadcast network and needs to be continuously provided over the communication network. 
     The communication network handover controller  120  sends a response message to the preparation request (S 460 ), and prepares to provide the broadcast content that has been forcibly ended in the broadcast network and needs to be continuously provided over the communication network. The response message to the preparation request includes information required for the terminal  160  to receive the corresponding broadcast content over the communication network. For example, the response message to the preparation request may include information on a time at which the communication network provides the corresponding broadcast content and information on allocated network resources (e.g., channels) such that the communication network provides the corresponding broadcast content. 
     The broadcast network handover controller  130  delivers, to the communication network handover controller  120 , the broadcast content that has been forcibly ended in the broadcast network and needs to be continuously provided over the communication network (S 470 ). If the response message to the preparation request includes an expected end time of the broadcast content currently being provided by allocated network resources, the broadcast network handover controller  130  can deliver the corresponding broadcast content after the expected end time. 
     Further, the broadcast network handover controller  130  sends a request message to the terminal  160  using the corresponding broadcast content over the broadcast network to connect to the selected communication network and continue to watch the corresponding broadcast content (S 480 ). The request message includes information on the selected communication network. When there are one or more selected communication networks, the request message may include information on the one or more communication networks. The request message is transmitted to a plurality of terminals in a multicast or broadcast format, and requires no response message from the terminals. 
     The terminal  160  connects to the communication network selected by the broadcast network handover controller  130 , and then requests the communication network handover controller to provide the corresponding broadcast content (S 490 ). When there are a plurality of selected communication networks, the terminal  160  can select and connect to one of the plurality of communication networks. If the terminal  160  has already has been connected to the selected communication network, a separate connection procedure may not be needed. 
     Hereinafter, a method of handover between a communication network and a broadcast network will be described by way of example, in which a 3GPP MBMS (Multimedia Broadcast/Multicast Service) system is used as the communication network and a DVB-IPDC (IP Datacasting) system is used as the broadcast network. 
       FIG. 5  is a view showing a broadcast content providing system according to one exemplary embodiment of the present invention in detail. 
     Referring to  FIG. 5 , a Broadcast Multicast Service Centre (BM-SC)  520 , which is a communication network handover controller, receives broadcast content from a broadcast content providing server  510 , and transmits the received broadcast content to terminals  560  in a broadcast or multicast transmission format. The BM-SC  520  is connected to a radio access network via a core network  521 . The core network may include an SGSN (Serving GPRS Support Node) and a GGSN (Gateway GPRS Support Node). 
     A service application (SA)  530 , which is a broadcast network handover controller, receives broadcast content from the broadcast content providing server  510 , and transmits the received broadcast content to the terminals  560  in a broadcast transmission format. The SA  530  may be directly connected to a broadcast access network  550 , or may be connected to the broadcast access network  550  via a service management unit  531 . 
     A radio access network  540  of a communication network may be, for example, one of a GERAN (GSM EDGE Radio Access Network), a UTRAN (Universal Terrestrial Radio Access Network), an E-UTRAN (Evolved Universal Terrestrial Radio Access Network), and radio access networks to be developed in the future. 
     The broadcast access network  550  of a broadcast network may be, for example, one of a DVB-H, a T-DMB, a MediaFLO, an ATSC-M/H, and broadcast access networks to be developed in the future. 
     The terminal  560  includes both an MBMS receiver  561  serving as a communication network receiver and a DVB-IPDC receiver  562  serving as a broadcast network receiver, and receives broadcast content over the radio access network  540  or the broadcast access network  550 . 
     The BM-SC  520  and the SA  530  are connected to a data interface and a control interface. In order to provide the broadcast content that has been provided to the terminal  560  over the radio access network  540  of the 3GPP MBMS system to the terminal  560  over the broadcast access network  550  of the DVB-IPDC system, the BM-SC  520  and the SA  530  perform preparation through the control interface and the BM-SC  520  delivers the corresponding broadcast content to the SA  530  through the data interface. The SA  530  provides the broadcast content delivered from the BM-SC  520  to the terminal  560  over the broadcast access network  550 . 
     On the contrary, in order to provide the broadcast content that has been provided to the terminal  560  over the broadcast access network  550  of the DVP-IPDC system to the terminal  560  over the radio access network  540  of the MBMS system, the BM-SC  520  and the SA  530  perform preparation through the control interface and the SA  530  delivers the corresponding broadcast content to the BM-SC  520  through the data interface. The BM-SC  520  provides the broadcast content delivered from the SA  530  to the terminal  560  over the radio access network  540 . 
       FIG. 6  is a flowchart showing a method of handover from a communication network to a broadcast network according to one exemplary embodiment of the present invention when a system supporting 3GPP MBMS (Multimedia Broadcast/Multicast Service) is used as the communication network, a DVB-IPDC (IP Datacasting) system is used as the broadcast network, and the communication network and the broadcast network support the IEEE 802.21 MIH (Media Independent Handover) function. 
     Referring to  FIG. 6 , the BM-SC  520  determines whether there is any broadcast content that increases the load on the communication network (S 600 ). For example, using the multicast-mode of the MBMS, a plurality of terminals connected to the communication network can join a specific multicast session and watch the same broadcast content via multicast transmission. If both the number of terminals joining a specific multicast session and the number of base stations (e.g. RNCs (Radio Network Controllers) in a WCDMA network) servicing the terminals exceed a predetermined range, the number of branches of the multicast tree increases, and thus it can be determined that there is broadcast content that increases the load on the communication network. If the number of terminals joining a specific multicast session exceeds a predetermined range while the number of base stations servicing the terminals does not exceed a predetermined range the broadcast content may be detected as not increasing the load on the communication network because the terminals watching the corresponding broadcast content are gathered in the range of a specific base station. In the case that the IEEE 802.21 MIH (Media Independent Handover) protocol is used as one example of the method for notifying the communication network handover controller of the result that the broadcast content is detected as increasing the load on the communication network, the broadcast content can be delivered to the communication network handover controller via an MHI function entity. 
     When it is found that there is broadcast content that increases the load on the communication network, the BM-SC  520  searches for a broadcast network capable of providing the corresponding broadcast content (S 610 ). In one example, the BM-SC  520  can obtain information about surrounding broadcast networks from a 3GPP ANDSF (Access Network Discovery Support Functions) server. In another example, the BM-SC  520  can obtain information about surrounding broadcast networks from an MIH information server. The information about the surrounding broadcast networks includes a list of broadcast networks that are providing the corresponding broadcast content or planning to transmit it later. 
     The BM-SC  520  selects an appropriate broadcast network to provide the corresponding broadcast content from a received list of surrounding broadcast networks (S 620 ). The BM-SC  520  can send an inquiry message for handover to the SA  530 , and select an appropriate broadcast network with reference to a response message received from the SA  530 . 
     The BM-SC  520  performs a preparation procedure for handover, together with the SA  530  of the selected broadcast network, through the control interface (S 630 ), and then delivers the corresponding broadcast content through the data interface (S 640 ). 
     Then, the BM-SC  520  requests the terminals  160  using the corresponding broadcast content over the communication network to connect to the selected broadcast network and continue to watch the corresponding broadcast content (S 650 ). An example of a request message includes using an MIH protocol message, and the following Table 1 or the following Table 2 shows an MIH_SAP (Service Access Point) Primitive. 
     
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 MIH_Net_HO_Bcst_HO_Notify.request 
                 ( 
               
               
                   
                 DestinationIdentifier, 
               
               
                   
                 HandoverDirection, 
               
               
                   
                 TargetProgramDescription, 
               
               
                   
                 TargetNetworksInfoList, 
               
               
                   
                 LinkActionExecutionDelay, 
               
               
                   
                 LinkActionsList 
               
               
                   
                 ) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
             
             
               
                 MIH_Net_HO_Bcst_HO_Notify.indication ( 
               
             
          
           
               
                   
                  SourceIdentifier, 
               
               
                   
                  HandoverDirection, 
               
               
                   
                  TargetProgramDescription, 
               
               
                   
                  TargetNetworksInfoList, 
               
               
                   
                  LinkActionExecutionDelay, 
               
               
                   
                  LinkActionsList 
               
               
                   
                  ) 
               
               
                   
                   
               
             
          
         
       
     
     The MIH_SAP (Service Access Point) Primitives for sending and receiving an MIH protocol message in Tables 1 and 2 may include at least one of handover direction information (HandoverDirection), information on the corresponding broadcast content (TargetProgramDescription), selected broadcast network information (TargetNetwroksInfoList), link action execution time information (LinkActionExecutionDelay, see IEEE Std 802.21-2008), and link action list information (LinkActionList, see IEEE Std 802.21-2008). Here, the handover direction information (HandoverDirection) indicates whether a handover is a handover from a communication network to a broadcast network or a handover from a broadcast network to a communication network. The selected broadcast network information (TargetNetwroksInfoList) indicates a list of selected broadcast networks and service provision information. The MIH command message can be multicast to a plurality of terminals. The MIH protocol message transmitted through the MIH_SAP primitives of Tables 1 and 2 is transmitted via a multicast session to the MIH users of the terminals  560  joining the corresponding multicast session. 
     Hereupon, the terminals  560  connect to the broadcast network, and, upon receiving the corresponding broadcast content over the broadcast network, leave the multicast session of the communication network. If the terminals  560  are unable to connect to the broadcast network or unable to receive the corresponding broadcast content over the broadcast network, the terminals can continue to receive the corresponding broadcast content over the communication network. 
       FIG. 7  is a flowchart showing a method of handover from a broadcast network to a communication network according to one exemplary embodiment of the present invention when a system supporting 3GPP MBMS (Multimedia Broadcast/Multicast Service) is used as the communication network, a DVB-IPDC (IP Datacasting) system is used as the broadcast network, and the communication network and the broadcast network support the IEEE 802.21 MIH (Media Independent Handover) function. 
     Referring to  FIG. 7 , the SA  530  determines whether there is any broadcast content that has been forcibly ended in the broadcast network and needs to be continuously provided over the communication network (S 700 ), and searches for a communication network capable of providing the corresponding broadcast content (S 710 ). In one example, the SA  530  can obtain information about surrounding communication networks from a 3GPP ANDSF (Access Network Discovery Support Functions) server. In another example, the SA  530  can obtain information about surrounding communication networks from an MIH information server. The information about the surrounding communication networks includes a list of communication networks which are providing the corresponding broadcast content or planning to transmit it later. 
     The SA  530  selects an appropriate communication network to provide the corresponding broadcast content from a received list of surrounding communication networks (S 720 ). The SA  530  can send an inquiry message for handover to the BM-SC  520 , and select an appropriate communication network with reference to a response message received from the BM-SC  520 . 
     The SA  530  performs a preparation procedure for handover, together with the BM-SC  520  of the selected communication network, through the control interface (S 730 ). For example, information required for the terminal  560  to receive the corresponding broadcast content can be transmitted to the terminal  560  through a service announcement. Afterwards, the SA  530  delivers the corresponding broadcast content to the BM-SC  520  of the selected communication network through the data interface (S 740 ). 
     Then, the SA  530  requests the terminals  160  using the corresponding broadcast content over the broadcast network to connect to the selected communication network and continue to watch the corresponding broadcast content (S 750 ). An example of a request message includes using an MIH protocol message, and the following Table 1 or the following Table 2 shows an MIH_SAP (Service Access Point) Primitive. 
     The MIH_SAP (Service Access Point) Primitives for sending and receiving an MIH protocol message in Tables 1 and 2 may include at least one of handover direction information (HandoverDirection), information on the corresponding broadcast content (TargetProgramDescription), selected communication network information (TargetNetwroksInfoList), link action execution time information (LinkActionExecutionDelay, see IEEE Std 802.21-2008), and link action list information (LinkActionList, see IEEE Std 802.21-2008). Here, the handover direction information (HandoverDirection) indicates whether a handover is a handover from a communication network to a broadcast network or a handover from a broadcast network to a communication network. The selected communication network information (TargetNetwroksInfoList) indicates a list of selected communication networks and service provision information. The MIH command message can be multicast to a plurality of terminals. The MIH protocol message transmitted through the MIH_SAP primitives of Tables 1 and 2 is transmitted via a multicast session to the MIH users of the terminals  560  joining the corresponding multicast session. 
     Hereupon, the terminals  560  connect to the communication network, and receive the corresponding broadcast content over the communication network. If the terminals  560  have already been connected to the selected communication network, a separate connection procedure may not be needed. 
     The exemplary embodiments of the present invention are not only realized by the method and device, but are also realized by a program for realizing functions corresponding to the configurations of the exemplary embodiments of the present invention or a recording medium for recording the program. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.