Abstract:
Apparatus and method for sending a multicast packet in a mobile digital broadcast system are provided. The mobile digital broadcast system includes a broadcaster for indicating the designated recipient in an Internet Protocol (IP) header of a multicast packet and including a temporary IP address of the recipient in the IP header when multicasting data of a designated recipient; a receiver for providing the received multicast packet to an application program for outputting a digital broadcasting when the receiver joins a group of the multicast packet and the recipient is designated to the receiver upon receiving the multicast packet; and an IP allocating server for allocating a temporary IP address when the receiver requests to allocate the temporary IP address, storing the allocated temporary IP address and ID information of the receiver, and sending the allocated temporary IP address and the ID information of the receiver to the broadcaster.

Description:
PRIORITY 
       [0001]    This application claims priority under 35 U.S.C. §119(a) to an application filed in the Korean Intellectual Property Office on Jan. 29, 2007 and assigned Serial No. 2007-8829, the contents of which are herein incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to an apparatus and method for sending a multicast packet in a mobile digital broadcast system, and in particular, to an apparatus and method for sending a multicast packet in a mobile digital broadcast system such that a broadcaster of the mobile digital broadcast sends the multicast packet and a receiver determines whether the multicast packet is a necessary packet by merely examining the header information. 
         [0004]    2. Description of the Related Art 
         [0005]    Digital Video Broadcasting-Handheld (DVB-H), which is a technology combining mobile and digital broadcastings, is rapidly spreading over Europe. The DVB-H broadcasts information to a user, such as Audio/Video (A/V) data, Entitlement Control Message (ECM), Entitlement Management Message (EMM), and Electronic Service Guide (ESG) data, by using an Internet Protocol Data Cast (IPDC) technique, which encapsulates the information in an IP packet. 
         [0006]    DVB-H broadcasting basically works in a multicast manner to reduce the load of an irrelevant host because of the surge in broadcasting. The multicast technology sends a packet only to a host joining the group. How a general multicast packet is generated, transmitted, and received is described by referring to  FIGS. 1 and 2 . 
         [0007]      FIG. 1  is a flowchart of a method for generating and sending a multicast packet at a general multicast transmitter in the prior art. When data to be multicast is generated in step  100 , the general multicast transmitter of  FIG. 1  inputs a multicast group address in a destination Internet Protocol (IP) address field of an IP header in step  102 , completes the IP header generation in step  104 , and multicasts a packet to a receiver by attaching data after the IP header in step  106 . 
         [0008]      FIG. 2  is a flowchart of a method for receiving and processing a multicast packet at a general multicast receiver in the prior art. Upon receiving a multicast packet in step  200 , the multicast receiver of  FIG. 2  determines whether the destination IP address of the IP header of the received packet matches a group address of the receiver in step  202 . 
         [0009]    When the two addresses match in step  202 , the multicast receiver forwards a received multicast packet to an application program in step  204 . By contrast, when the two addresses are different from each other in step  202 , the multicast receiver discards the received multicast packet in step  206 . 
         [0010]    While a DVB-H system alleviates the load of the irrelevant host by operating in the multicast manner, there still exists a problem. To control the viewing authority for a scrambler channel of digital broadcasting channels, the DVB-H system employs a Conditional Access System (CAS) module. When a user purchases a scrambler channel using CALL/HTTP, the DVB-H system sends a UDP packet, being Entitlement Management Message (EMM), which contains a unique address and the purchased access authority of the corresponding user, to every receiver joining the multicast group. The receiver receives the EMM through a socket and forwards the EMM to its CAS. Upon receiving the EMM, the CAS determines whether the received EMM is destined for itself based on the ID information. When the received EMM is correctly received, the receiver uses the EMM to access the scrambler channel. When the received EMM is incorrectly received, the receiver discards the received EMM. The broadcaster of the DVB-H system sends the same EMM over a certain time period in the case where the EMM is incorrectly received at the receiver. In other words, when receiving the multicast packet containing the EMM, the receiver of the DVB-H system needs to forward the packet to the CAS being the application program and the CAS needs to determine whether the packet is necessary by comparing the ID information of the EMM as in step  204  of  FIG. 2 . 
         [0011]    Thus, if 100,000 users purchase the access authority in that situation, the CAS of the receiver is subject to the unnecessary load while processing at least 99,999 EMMs, excluding one EMM corresponding to itself. 
       SUMMARY OF THE INVENTION 
       [0012]    An aspect of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages below. Accordingly, an aspect of the present invention is to provide an apparatus and method for sending a multicast packet in a mobile digital broadcast system. 
         [0013]    Another aspect of the present invention is to provide an apparatus and method for sending a multicast packet destined for a certain receiver in a mobile digital broadcast system. 
         [0014]    Yet another aspect of the present invention is to provide an apparatus and method for sending a multicast packet in a mobile digital broadcast system such that a broadcaster of the mobile digital broadcast system sends the multicast packet and a receiver determines whether the received packet is necessary or not by merely examining the header information. 
         [0015]    Still another aspect of the present invention is to provide an apparatus and method for sending a multicast packet in a mobile digital broadcast system such that a transmitter of the mobile digital broadcast system sends an EMM as a multicast packet containing information relating to a designated receiver in a packet header and the receiver determines whether the received packet is necessary or not by merely examining the header information. 
         [0016]    The above aspects are achieved by providing a mobile digital broadcast system for sending a multicast packet with a designated recipient. The packet includes an IP allocating server, a receiver and a broadcaster when multicasting data to a designated recipient. The broadcaster indicates the designated recipient in an IP header of the multicast packet and includes a temporary IP address of the recipient in the IP header; upon receiving the multicast packet, the receiver provides the received multicast packet to an application program for outputting a digital broadcasting when the receiver joins a group of the multicast packet and the recipient is designated to the receiver; and the IP allocating server allocates a temporary IP address when the receiver requests the allocation of the temporary IP address, stores the allocated temporary IP address and ID information of the receiver, and sends the allocated temporary IP address and the ID information of the receiver to the broadcaster. 
         [0017]    According to one aspect of the present invention, a broadcaster of a mobile digital broadcast system for sending a multicast packet with a designated recipient, includes a Conditional Access System (CAS) for generating an Entitlement Management Message (EMM) including authority to view a scrambler broadcasting; an IP manager for receiving from an IP allocating server connected over a network and managing the temporary IP address of a receiver, which is a recipient; and when receiving the EMM data from the CAS, an IP packet encapsulator for, indicating a recipient in an IP header of a generated multicast packet, including a temporary IP address in the IP header by confirming the temporary IP address of the recipient through the IP manager, and generating the multicast packet with the IP header appended to the EMM data. 
         [0018]    According to another aspect of the present invention, a receiver of a mobile digital broadcast system for sending a multicast packet with a designated recipient, includes an IP manager and an IP layer. The IP manager requests the IP allocating server to allocate a temporary IP address over a network when a digital broadcast viewing is requested, receives and manages the temporary IP address from the IP allocating server; and upon receiving a multicast packet the IP layer provides the received multicast packet to an application program for outputting the digital broadcast when a group of the multicast group is joined by the receiver and the recipient of the multicast group is designated to the receiver. 
         [0019]    According to yet another aspect of the present invention, a method for sending a multicast packet with a designated recipient in a broadcaster of a mobile digital broadcast system, includes generating an Entitlement Management Message including authority to view a scrambled broadcasting; indicating a recipient in an IP header of a multicast packet including the EMM; confirming a temporary IP address of the recipient; inputting the temporary IP address in the IP header of the multicast packet; and outputting the multicast packet with the appended IP header. 
         [0020]    According to still another aspect of the present invention, a method for receiving a multicast packet with a designated recipient in a receiver of a mobile digital broadcast system, includes, determining whether a group of the received multicast packet is a group joined by the receiver upon receiving a multicast packet; determining whether a recipient of the multicast packet is designated or not by examining an IP header of the multicast packet when the receiver joins the group of the multicast packet; determining whether the receiver is the designated recipient of the multicast packet by examining the IP header of the multicast packet when the recipient of the multicast packet is designated; and providing the received multicast packet to an application program to view a digital broadcasting when the receiver is the designated recipient of the multicast packet. 
         [0021]    According to a further aspect of the present invention, a method for allocating a temporary IP address for sending and receiving a multicast packet with a designated recipient in an IP allocating server of a mobile digital broadcast system, includes allocating and sending a temporary IP address to the receiver when a receiver requests the allocation of a temporary IP address, storing the allocated temporary IP address and ID information of the receiver; and sending the allocated temporary IP address and the ID information of the receiver to a broadcaster. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
           [0023]      FIG. 1  is a flowchart of a method for generating and sending a multicast packet at a general multicast transmitter in the prior art; 
           [0024]      FIG. 2  is a flowchart of a method for receiving and processing a multicast packet at a general multicast receiver in the prior art; 
           [0025]      FIG. 3  is a block diagram of a mobile digital broadcast system, which sends a multicast packet containing receiver information according to the present invention; 
           [0026]      FIG. 4  is a diagram of the multicast packet transmitted by a broadcaster of the mobile digital broadcast system according to the present invention; 
           [0027]    FIG. S is a flowchart of a method for generating and sending the multicast packet at the broadcaster of the mobile digital broadcast system according to the present invention; 
           [0028]      FIG. 6  is a flowchart of a method for receiving and processing the multicast packet at the receiver of the mobile digital broadcast system according to the present invention; and 
           [0029]      FIG. 7  is a flowchart of a method for allocating and canceling a temporary IP address at an IP allocating server of the mobile digital broadcast system according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]    Preferred embodiments of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. 
         [0031]    The present invention provides an apparatus and method for sending a multicast packet in a mobile digital broadcast system such that a broadcaster of the mobile digital broadcast system sends an Entitlement Management Message (EMM) as a multicast packet containing information relating to a destined receiver in a packet header and the receiver determines whether the received packet is necessary by examining only header information. 
         [0032]    Note that the multicast packet sending method of the present invention is applicable not only to the mobile digital broadcast system but also a single recipient for which the multicast packet is destined for. Hereafter, the general structure of a Digital Video Broadcasting-Handheld (DVB-H) mobile digital broadcast system is illustrated. 
         [0033]    The mobile digital broadcast system of  FIG. 3  includes a DVB-H broadcaster  300 , a receiver  350 , and an Internet Protocol (IP) allocating server  371  positioned in a Universal Mobile Telecommunications System (UMTS)/General Packet Radio Service (GPRS) network  370 . 
         [0034]    DVB-H broadcaster  300  includes a content provider  301 , an Electronic Service Guide (ESG) provider  302 , a scrambler  303 , a Real-time Transport Protocol (RTP) streamer  304 , an IP packet encapsulator  305 , a Conditional Access System (CAS)  306 , an IP manager  307 , and a multiplexer (MUX)  308 . 
         [0035]    Content provider  301  selects and outputs broadcast channels and contents. ESG provider  302  generates and outputs information relating to the channels to provide the channel information to a user. The channel information output from ESG provider  302  includes information relating to channel titles, IP address/UDP port of a server for receiving AN stream of the corresponding channel, IP address/port of ECM/EMM server, and contents broadcast by time zone. 
         [0036]    Scrambler  303  receives the output AN data when the channel output from content provider  301  is a scrambler channel, encrypts the AN data using a time-variant key (TEK). When the channel output from content provider  301  is a free channel, scrambler  303  receives and outputs the AN data without the encryption. 
         [0037]    RTP streamer  304  controls real-time data transfer to reproduce the A/V data received from scrambler  303  in real time. 
         [0038]    IP packet encapsulator  305  generates and outputs an IP packet by adding a UDP header and an IP header to the RTP-packetized A/V data fed from streamer  304  and the ECM data and the EMM data fed from CAS  306 . When receiving the EMM data from CAS  306 , IP packet encapsulator  305  includes a designated recipient into the IP header, examines a temporary IP address according to ID information of the recipient through IP manager  307 , and includes the temporary IP address in the header. The structure of the IP packet carrying the EMM data is explained by referring to  FIG. 4 . 
         [0039]      FIG. 4  shows the structure of the IP packet of the multicast type for carrying the EMM data. IP packet encapsulator  305  indicates the designated recipient in the multicast packet by setting the first bit of the IP header to ‘1’, and inputs the temporary IP address confirmed through IP manager  307  in a source IP address field of the IP header. The other fields, excluding those two fields, conform to RFC 791 Internet Protocol. 
         [0040]    CAS  306  grants the user access to the scrambled broadcast contents and allows only the authorized user to view the broadcasting. When receiving the encrypted key from scrambler  303 , CAS  306  re-encrypts the decryption key with the encrypted key so that the authorized user can view the encrypted broadcasting, and outputs the generated ECM data to IP packet encapsulator  305 . Also, CAS  306  generates EMM data for decrypting the ECM data in order to acquire the decryption key, which is the broadcast access right, and outputs the generated EMM data to IP packet encapsulator  305 . The EMM data is data destined for the user having the broadcasting access authority. 
         [0041]    IP manager  307  receives the temporary IP addresses assigned to the users who request to view the digital broadcasting by IP allocating server  371 , together with the ID information of the recipients who are assigned the temporary IP addresses by communicating with IP allocating server  371  over the UMTS/GPRS network, and provides the received data to IP packet encapsulator  305 . Next, when the receiver assigned the temporary IP address requests to cancel the temporary IP address, IP manager  307  informs IP packet encapsulator  305  of the cancellation request and cancels the assigned temporary IP address. 
         [0042]    MUX  308  transmits the IP packets respectively containing the EMM, the ECM, and the A/V data fed from IP packet encapsulator  305  at the same time. 
         [0043]    Receiver  350  includes an IP layer  351 , a broadcast processor  352 , and an IP manager  353 . 
         [0044]    When the received multicast packet belongs to the group of receiver  350  and its recipient is not designated, IP layer  351  processes the multicast packet as in  FIG. 2  of the prior art. By contrast, when the received multicast packet belongs to the group of receiver  350  and its recipient is designated, IP layer  351  determines whether receiver  350  is the designated recipient by examining the source IP address of the IP header of the multicast packet. When the source IP address is the temporary IP address assigned to receiver  350 , which is fed from IP manager  535 , IP layer  351  provides the multicast packet to broadcast processor  352 . When the source IP address is different from the assigned temporary IP address, IP layer  351  discards the received multicast packet because receiver  350  is not the destined recipient. Since IP layer  351  discards the incorrectly received multicast packet, the load of broadcast processor  352  can be reduced in the subsequent procedures. 
         [0045]    Broadcast processor  352  controls to output the A/V data received according to the DVB-H broadcast specification through a display (not shown) and a speaker (not shown). In doing so, when the received broadcast channel is the scrambled channel, broadcast processor  352  controls to decrypt the scrambled channel with the decryption key contained in the ECM by decrypting the ECM with the received EMM and then to output the scrambled channel. 
         [0046]    When broadcast processor  352  detects the broadcast view request, IP manager  353  requests the allocation of the temporary IP address and acquires the allocated temporary IP address by communicating with IP allocating server  371  over the UMTS/GPRS network. When broadcast processor  352  terminates the broadcast viewing, IP manager  353  requests IP allocating server  371  to cancel the assigned temporary IP address. 
         [0047]    IP allocating server  371 , which communicates with receiver  350  over the UMTS or GPRS network  370 , allocates the temporary IP address when receiver  350  requests the allocation of the temporary IP address, stores the allocated temporary IP address and the ID information of receiver  350 , which assigned the temporary IP address, and sends the allocated temporary IP address and ID information of receiver  350  to DVB-H broadcaster  300 . Next, when receiver  350  requests to cancel the allocated temporary IP address, IP allocating server  371  sends the temporary IP address to be canceled and the ID information of receiver  350  requesting the cancellation to DVB-H broadcaster  300 , and cancels the assigned temporary IP address. 
         [0048]    Now, the method for sending the multicast packet with the designated recipient in the mobile digital broadcast system is explained by referring to the drawing. 
         [0049]    In  FIG. 5 , when EMM data to be sent is generated in step  500 , the broadcaster of the mobile digital broadcast system indicates a multicast packet with the designated recipient by setting the first bit of the flags of the IP header in step  502 , confirms the temporary IP address of the destined receiver in step  504 , inputs the confirmed temporary IP address in the source IP address field of the IP header in step  506 , inputs the multicast group address in the destination IP address field of the IP header in step  508 , completes the IP header generation by generating other fields of the IP header according to the standard specification in step  510 , and broadcasts the multicast packet containing the EMM data with the IP header appended to the receivers of the multicast group in step  512 . 
         [0050]    In  FIG. 6 , when detecting the viewing request of the digital broadcasting from the user in step  600 , the receiver requests the IP allocating server to allocate a temporary IP address over the UMTS/GPRS network in step  602  and is assigned the temporary IP address from the IP allocating server in step  604 . 
         [0051]    In step  606 , the receiver examines whether a multicast packet is received or not. When receiving the multicast packet, the receiver determines whether the destination IP address of the IP header is the address of the multicast group of the receiver based on the IP header of the multicast packet in step  608 . When the destination IP address is different from the multicast group address, the receiver discards the received multicast packet in step  614 . 
         [0052]    When the destination IP address is the multicast group address in step  608 , the receiver examines whether the multicast packet has the designated recipient based on the first bit of the flags of the IP header in step  610 . When the first bit of the flags is ‘0’ signifying no designated recipient, the receiver performs the subsequent processes as in the related art. 
         [0053]    By contrast, when the first bit of the flags is ‘1’ signifying the designated recipient in step  608 , the receiver determines whether the receiver is the recipient of the multicast packet by examining whether the source IP address of the IP header matches the temporary IP address assigned from the IP allocating server in step  612 . When the two addresses are different from each other, the receiver is not the correct recipient of the multicast packet and thus discards the received multicast packet in step  614 . 
         [0054]    When the source IP address matches the temporary IP address in step  612 , the receiver is the destined recipient of the multicast packet and thus provides the received multicast packet to the application program to view the digital broadcasting in step  616 . 
         [0055]    In step  618 , the receiver determines whether the digital broadcast viewing is finished or not. When the digital broadcast viewing is not finished, the receiver goes back to step  606  and repeats steps  606  through  616 . 
         [0056]    When the digital broadcast viewing is finished in step  618 , the receiver requests the IP allocating server to cancel the temporary IP address in step  620  and erases the allocated temporary IP address in step  622 . 
         [0057]    Referring to  FIG. 7 , The IP allocating server communicates with the broadcaster and the receiver of the digital broadcast system over the UMTS/GPRS network. When the receiver requests the allocation of a temporary IP address in step  700 , the IP allocating server allocates and sends the temporary IP address to the receiver in step  702 , stores the temporary IP address and ID information of the receiver in step  704 , and sends the allocated temporary IP address and the ID information of the receiver to the broadcaster in step  706 . 
         [0058]    When the receiver requests to cancel the allocated temporary IP address in step  708 , the IP allocating server confirms the requested temporary IP address of the receiver in step  710 , sends the temporary IP address to be canceled and the ID information of the receiver to the broadcaster in step  712 , and erases the stored ID information and the allocated temporary IP address of the receiver in step  714 . 
         [0059]    As set forth above, the transmitter of the mobile digital broadcast system sends the EMM as the multicast packet containing the information relating to the receiver in the packet header. Hence, the receiver, upon receiving the multicast packet, can determine whether the received multicast packet is necessary merely based on the header information. Therefore, the load and the processing rate latency of the receiver can be reduced without having to check the unnecessary EMMs. 
         [0060]    While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as further defined by the appended claims.