Abstract:
An apparatus for receiving MPEG-2 A/V data by using a cable MODE is disclosed. The apparatus includes: a cable MODEM for separating broadcasting data and broadcasting supplementary data by demodulating an input signal; and a multiplexer for multiplexing the separated broadcasting data from the cable MODEM with broadcasting data inputted from other input source, and outputting the multiplexed broadcasting data to an external cable card.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an apparatus for receiving MPEG-2 audio/video (A/V) data by using a cable MODEM in a digital cable broadcasting system; and, more particularly, to a MPEG-2 A/V data receiving apparatus using a cable MODEM for processing A/V data transmitted through a cable MODEM according to a conditional access by using a cable card and providing the processed A/V data to a subscriber in a set-top box of a digital cable broadcasting system.  
       Description of Related Arts  
       [0002]      FIG. 1  is a block diagram illustrating a digital cable broadcasting system in accordance with a prior art.  
         [0003]     As shown in  FIG. 1 , the digital cable broadcasting system includes a digital cable head end  100  that is a transmitting system and a subscriber terminal  200  connected to the digital cable head end  100  through a hybrid fiber coaxial (HFC) network  10 .  
         [0004]     The digital cable head end  100  includes an in-band network processing unit  110  and an output-of-band network processing unit  120 .  
         [0005]     The in-band network processing unit  110  transmits encoding motion picture experts group-2 (MPEG-2) audio/video (A/V) data based on a quadrature amplitude modulation (QAM) scheme through a digital video broadcasting-asynchronous serial interface (DVB-ASI). In order to transmit the data, the in-band network processing unit  110  includes: a MPEG-2 A/V unit  111  as an encoding unit for encoding MPEG-2 A/V data and a quadrature amplitude (QAM) modulator  112 .  
         [0006]     The output-of-band network processing unit  120  transmits supplementary data related to broadcasting based on a digital video subcommittee (DVS)-167 (ATM) or DVS-178(MPEG-2 TS) by including an application server  121  providing a conditional-receiving and an electronic program guide (EPG) service. Or, the output-of band processing unit  120  transmits supplementary data related to broadcasting and Internet protocol (IP) data based on a data over cable service interface specifications (DOCSIS) set-top gateway (DSG).  
         [0007]     The out-of-band network processing unit  120  includes an out-of-band (OOB) modulator/demodulator (MODEM)  122  and a set-top controller  123  for transmitting the supplementary data related to broadcasting based on DVS-167 (ATM) or DVS-18 (MPEG-2 TS), where ATM denotes an asynchronous transfer mode and TS denote a transport stream. The out-of-band network processing unit  120  also includes a cable MODEM termination system (CMTS)  142  and a management system  125  for transmitting the supplementary data related to broadcasting and the IP data based on DOCSIS set-top gateway.  
         [0008]     The subscriber terminal  200  includes a set-top box  230  and a cable card  250 . The subscriber terminal  200  is connected to a television set (TV) or connected to a personal computer (PC) through a cable MODEM  240 . The subscriber terminal  200  may be commonly connected to TV and PC through a cable MODEM built-in set-top box  210  and the cable card  250 .  
         [0009]     The subscriber terminal  200  receives signals transmitted from the digital cable head end  100  through the HFC network  10 . That is, the set-top box  230  or the cable MODEM built-in set-top box  210  receives A/V data and supplementary data related to broadcasting, and outputs the A/V data and the supplementary data to a display unit such as TV after authenticating a subscriber&#39;s authority and processing the A/V data and the supplementary data according to a conditional access. Also, the cable MODEM built-in set-top box  210  or the cable MODEM  240  receives data related to Internet protocol (IP), and outputs the IP data to a computing system, such as a personal computer (PC).  
         [0010]      FIG. 2  is a detailed diagram showing a open-cable based cable modem built-in set-top box and a cable card in accordance with a prior art.  
         [0011]     In the OpenCable standard, a cable card is defined by separating a conditional access system from a conventional cable set-top box as an independent module, and a standard interface between a set-top box and the cable card is defined. Therefore, a set-top box may be manufactured by anyone who follows the interface standard of the OpenCable standard.  
         [0012]     Accordingly, a use can receives a cable broadcasting service from a cable service operator (SO) according to a conditional access contract by directly purchasing an OpenCable standard based set-top box as like as buying a general electric household appliance and using a cable card provided from the cable service operator with the purchased set-top box.  
         [0013]     As shown in  FIG. 2 , the OpenCable based cable MODEM built-in set-top box  210  includes a tuner  211 , a QAM demodulator  212 , an OOB transmitter/receiver  213 , a cable MODEM  214 , a de-multiplexer  215 , a MPEG-2 A/V decoder  216 , and a set-top box CPU  217 . The cable card  250  includes an OOB processor  251 , a conditional access (CA) processor  252  and a cable card CPU  253 .  
         [0014]     The tuner  211  and the QAM demodulator  212  tunes and demodulates MPEG-2 A/V TS transmitted through an In-band network, and the QAM demodulator  212  outputs the demodulated MPEG-2 A/V TS to the CA processor  252  through an In-band channel. Also, the tuner  211  tunes and outputs data related to a program guide and a conditional access transmitted through an out-of-band network to the OOB processor  251  of the cable card  250  through an out-of-band channel based on an out-of-band transmitting scheme. Otherwise, the tuner  211  tunes and outputs the data related to the program guide and the conditional access to the cable card CPU  253  through the set-top box CPU  217  and a CPU interface channel. The CPU interface channel includes a data channel and an extended channel, logically.  
         [0015]     The OpenCable standard defines an In-band channel, an out-of-band channel and a CPU interface channel (Data channel, Extended channel) as a standard interface between a set-top box and a cable card. According to the OpenCable standard, the MPEG-2 A/V data is transmitted through the In-band channel, broadcasting receiving and supplementary data are transmitted through the out-of-band channel, and the data between the set-top box and the cable card is transmitted through the data channel that is a logical channel of the CPU interface channel.  
         [0016]     Broadcasting signal inputted to the cable card, i.e., MPEG-2 A/V TS, is processed according to the conditional access, and is outputted to a display device of a subscriber such as TV through the de-multiplexer  205  and the MPEG-2 A/V decoder  206  in the set-top box.  
         [0017]     Meanwhile, an Ethernet interface is recently introduced to a digital cable head end transmitting/receiving system for providing a smooth link between elements, managing and sharing resources within a system, and increasing extendibility.  
         [0018]     Also, the In-band network transmitting the MPEG-2 A/V is developed from a single-channel broadcasting using a conventional QAM scheme to a multi-channel broadcasting using a plurality of QAM modulators for providing improved supplementary services to support a picture-in-picture (PIP) and a digital video recorder (DVR).  
         [0019]     In case of the out-of-band network, a DOCSIS based cable MODEM transmitting scheme is selected to support high transmission rate. Conventionally, an OOB transmitting scheme based on DVS-167 or DVS-178 was selected for the out-of-band network. The DOCSIS based cable MODEM transmitting scheme supports high transmission rate of 27 Mbps or 38 Mbps and the OOB transmitting scheme based on DVS-167 or DVS-178 supports comparatively low data transmission rate of maximum 3 Mbps.  
         [0020]     Furthermore, the DOCSIS based transmitting scheme can simultaneously transmit a supplementary data related to broadcasting and an IP service. That is, the DOCSIS based transmitting scheme is advantageous scheme to provide advanced supplementary services such as VOIP and VOD. Accordingly, both of A/V data transmitted as MPEG-2 TS and general IP data can be simultaneously transmitted by using a same head-end network infra. Therefore, the DOCSIS based out-of-band network transmitting system will be used in a next generation digital cable head end transmitting/receiving system to simultaneously provide not only an IP data service and a supplementary service such as VoIP, VOD, but also MPEG-2 TS A/V broadcasting data transmitted based on a conventional QAM scheme by using the DOCSIS based cable MODEM.  
         [0021]     Meanwhile, a transmitting/receiving system using a DOCSIS based out-of-band network transmits broadcasting receiving and supplementary information, i.e., a conditional access information or an electronic program guide (EPG) information, through the extended channel of the CPU interface channel according to DOCSIS Set-Top Gateway (DSG) standard which is a transmission standard for transmitting/receiving data related to broadcasting through a cable MODEM.  
         [0022]     In order to transmit MPEG-2 A/V TS through a cable MODEM by applying the DSG to the above described conventional OpenCable based set-top box, MPEG-2 A/V TS transmitted through a cable MODEM must be transmitted to the cable card through the extended channel to process the MPEG-2 A/V TS for the conditional access. That is, the MPEG-2 A/V TS is transmitted to the cable card through the extended channel guaranteeing a transmission rate of only  7 Mbps, and the processed MPEG-2 A/V TS is transmitted back to the set-top box from the cable card through the extended channel after processing the MPEG-2 A/V TS for the conditional access.  
         [0023]     If MPEG-2 A/V TS transmitted from DOCSIS based cable MODEM providing a transmission rate of maximum 27 Mbps or 38 Mbps is transmitted through the extended channel guaranteeing a transmission rate of 7 Mbps, significant amount of data would be lost and long delay would be generated. Therefore, it is impossible to provide a service for the condition access.  
       SUMMARY OF THE INVENTION  
       [0024]     It is, therefore, an object of the present invention to provide an apparatus for receiving MPEG-2 A/V data using a cable MODEM for processing MPEG-2 A/V data transmitted through a cable MODEM according to a conditional access while maintaining comparability to interface specifications defined in an OpenCable standard by multiplexing the MPEG-2 A/V data with data received through a QAM modulator and inputting/outputting the multiplexed data through an In-band channel.  
         [0025]     In accordance with an aspect of the present invention, there is provided an apparatus for receiving broadcasting data using a cable MODEM in a digital cable broadcasting system, the apparatus including: a cable MODEM for separating broadcasting data and broadcasting supplementary data by demodulating an input signal; and a multiplexer for multiplexing the separated broadcasting data from the cable MODEM with broadcasting data inputted from other input source, and outputting the multiplexed broadcasting data to an external cable card.  
         [0026]     In accordance with another aspect of the present invention, there is provided a cable MODEM in a digital cable broadcasting receiving system for processing broadcasting data received through a cable MODEM according to a conditional access in a cable card, the cable MODEM including: a demodulating unit for demodulating an inputted signal; and a data separating unit for receiving the demodulated signal from the demodulating unit and separating broadcasting data and broadcasting supplementary data from the demodulated signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The above and other objects and features of the present invention will become better understood with regard to the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which:  
         [0028]      FIG. 1  is a block diagram illustrating a digital cable broadcasting system in accordance with a prior art;  
         [0029]      FIG. 2  is a detailed diagram showing a open-cable based cable modem built-in set-top bock and a cable card in accordance with a prior art;  
         [0030]      FIG. 3  is a block diagram depicting an apparatus for receiving MPEG-2 A/V data by using a cable modem in accordance with a preferred embodiment of the present invention;  
         [0031]      FIG. 4  is a detailed diagram illustrating a cable modem in accordance with a preferred embodiment of the present invention; and  
         [0032]      FIG. 5  is a flowchart of a method for processing MPEG-2 TS in a cable modem in accordance with a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]     Hereinafter, a system and a method for providing an anti-virus program by using a wireless communication terminal in accordance with a preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings.  
         [0034]      FIG. 3  is a block diagram depicting an apparatus for receiving MPEG-2 A/V data by using a cable modem in accordance with a preferred embodiment of the present invention.  
         [0035]     As shown in  FIG. 3 , the apparatus for receiving MPEG-2 A/V data using a cable MODEM according to the present embodiment includes a tuner  310 , a QAM demodulator  320 , a multiplexer  330 , a cable MODEM  340 , a de-multiplexer  350 , a MPEG-2 A/V decoder  370  and a CPU  360 . Hereinafter, function of each element will be explained.  
         [0036]     The tuner  310  receives a radio frequency (RF) signal transmitted from an external digital cable head end, and tunes data transmitted through an In-band network and data transmitted through an Out-of-band network. After tuning, the tuner  310  separates the data transmitted through an In-band network and the data transmitted through the Out-of-band network, and output the data transmitted through the In-band network to the QAM demodulator  320  and the data transmitted through the Out-of-band network to the cable MODEM  340 .  
         [0037]     The QAM demodulator  320  receives the data transmitted through the In-band network from the tuner  310 . After receiving, the QAM demodulator  320  demodulates the received data, which was modulated based on a quadrature amplitude modulation (QAM) scheme, and extracts MPEG-2 A/V TS from the demodulated data. After extracting, the QAM demodulator  320  outputs the MPEG-2 A/V TS to the multiplexer  330 .  
         [0038]     The cable MODEM  340  is a DOCSIS based cable MODEM, where DOCSIS denotes a data over cable service interface specifications. The cable MODEM  340  receives the data transmitted through the Out-of-band network from the tuner  310 , and extracts MPEG-2 A/V transport stream (TS) and broadcasting supplementary data from the received data by demodulating the received data. The broadcasting supplementary data includes information about a conditional access and an electronic program guide (EPG). After extracting, the cable MODEM  430  transmits the MPEG-2 A/V TS to the multiplexer  330  in order to multiplex the MPEG-2 A/V TS with the data transmitted through the In-band network. The cable MODEM  430  also transmits the broadcasting supplementary data to the CPU  360  in order to process the broadcasting supplementary data according to a conventional DOCSIS Set-Top Gateway (DSG) standard. The cable MODEM  340  is a major element of the present embodiment. The cable MODEM  340  will be explained in detail with reference to related drawings in later.  
         [0039]     The multiplexer  330  receives the MPEG-2 A/V TS from the QAM demodulator  320  and the cable MODEM  340 , and multiplexes the received MPEG-2 A/V TS as single TS. After multiplexing, the multiplexer  330  outputs the multiplexed TS to an external cable card  250  through an In-band channel to process the multiplexed TS for the conditional access in the external cable card  250 . The de-multiplexer  350  receives MPEG-2 A/V TS from the external cable card  250  through the In-band channel, and de-multiplexes the received MPEG-2 A/V TS.  
         [0040]     The MPEG-2 A/V decoder  370  receives the de-multiplexed MPEG-2 A/V TS, and decodes the de-multiplexed MPEG-2 A/V TS. The decoded MPEG-2 A/V TS is outputted to a display unit to be reproduced.  
         [0041]     The CPU  360  provides the broadcasting supplementary data outputted from the cable MODEM  340  to a CPU interface channel of the external cable card to process a conditional access, and generally controls the above described elements.  
         [0042]     As described above, the apparatus for receiving MPEG-2 A/V data using the cable MODEM according to the present embodiment separates MPEG-2 A/V broadcasting data inputted through the cable MODEM  340  from other data, i.e., the broadcasting supplementary data, and multiplexes the separated MPEG-2 A/V data with MPEG-2 A/V broadcasting data inputted to the QAM demodulator  320  through the In-band Network. After multiplexing, the apparatus according to the present embodiment transmits the multiplexed MPEG-2 A/V broadcasting data to the cable card through an In-band channel of a card interface based on a conventional OpenCable standard, which guarantees a transmission rate of maximum 200 Mbps. Therefore, the apparatus for receiving MPEG-2 A/V data using a cable MODEM completely overcomes the conventional problems, i.e., data loss and delay, caused by transmitting MPEG-2 A/V broadcasting data from an OpenCable based set-top box to a cable card through an extended channel having a transmission rate of below 7 Mbps.  
         [0043]      FIG. 4  is a detailed diagram illustrating a cable modem in accordance with a preferred embodiment of the present invention.  
         [0044]     As shown in  FIG. 4 , the cable MODEM  340  according to the present embodiment includes a demodulator  341 , a TS de-multiplexer  342 , a MPEG-2 A/V TS processor  342  and a DS MAC frame processor  344 .  
         [0045]     The demodulator  340  receives the data from the tuner  210  and demodulates the received data to MPEG-2 TS. After demodulating, the demodulator  340  outputs the MPEG-2 TS to the TS de-multiplexer  342 . The TS de-multiplexer  342  extracts TS of broadcasting program and MAC frame from the MPEG-2 TS. The extracted TS is processed in the MPEG-2 A/V TS processor  343 , and transmitted to an In-band channel of the cable card through the multiplexer  330 . The extracted MAC frame is processed in the DS MAC frame processor  344 , and is transmitted to the CPU  370 . Hereinafter, each element of the cable MODEM  340  will be explained in detail.  
         [0046]     The TS de-multiplexer  342  checks a PID value of the inputted MPEG-2 TS from the demodulator  341 . If the PID value is 0xFFE, corresponding data is determined as TS transmitting DOCSIS MAC data and outputted to the DS MAC frame processor  344 . If the PID value of the inputted MPEG-2 TS is a value of A/V data of a program selected by a user, corresponding data is decided as a TS transmitting A/V data and transmitted to the MPEG-2 A/V TS processor  343 . Processing MPEG-2 TS in the TS de-multiplexer  342  will be explained with reference to related drawing in later.  
         [0047]     The MPEG-2 A/V TS processor  343  outputs the MPEG- 2  A/V TS received from the TS de-multiplexer  404  to the multiplexer  330  through a TS FIFO (First In First Out) memory prepared in the MPEG-2 A/V TS processor  343 .  
         [0048]     The DS MAC frame processor  344  transmits data related to the IP service and the broadcasting supplementary data to the CPU  370 . The broadcasting supplementary data is process by transmitting the supplementary data to the cable card through the extended channel as mentioned above.  
         [0049]      FIG. 5  is a flowchart of a method for processing MPEG-2 TS in a cable modem in accordance with a preferred embodiment of the present invention.  
         [0050]     As shown in  FIG. 5 , the demodulator receives MPEG-2 TS at step S 501 . Then, a PID value of the received MPEG-2 TS is checked and determined whether the PID value is 0x1ffe or not at step S 503 .  
         [0051]     If the PID value is 0x1ffe at step S 503 , corresponding packet is outputted to the DS MAC frame processor  344  at step S 504 .  
         [0052]     If the PID value is not 0x1ffe at step S 503 , it determines whether the corresponding packet is a program packet selected by a viewer at step S 505 .  
         [0053]     If the corresponding packet is the program packet selected by the viewer at step S 505 , the corresponding packet is outputted to the MPEG2 A/V TS processor at step S 506 , and if not, the corresponding packet is destroyed at step S 507 .  
         [0054]     The above described invention can also be embodied as computer-readable code on a computer-readable recording medium including a CD-ROM, a RAM, a ROM, a floppy disk, a hard disk and a magneto-optical disk.  
         [0055]     As described above, MPEG-2 A/V broadcasting data can be transmitted and processed through not only OpenCable based system, but also DOCSIS based cable MODEM while maintaining a physical interface defined in a conventional cable card according the present invention.  
         [0056]     Also, broadcasting data conventionally provided through a QAM scheme based In-band network can be transmitted through DOCSIS based cable MODEM according to the present invention if a transmission speed of a DOCSIS based data transmitting/receiving network is advanced to faster than 100 Mbps.  
         [0057]     Furthermore, the present invention completely overcomes the conventional problems, i.e., data loss and delay, caused by transmitting MPEG-2 A/V broadcasting data to a cable card through an extended channel having a transmission rate of below 7 Mbps, because the apparatus for receiving MPEG-2 A/V data using the cable MODEM according to the present invention separates MPEG-2 A/V broadcasting data inputted through the cable MODEM from the broadcasting receiving and supplementary data or IP communication related data, multiplexes the separated MPEG-2 A/V broadcasting data with MPEG-2 A/V broadcasting data inputted to the QAM demodulator through the In-band Network, and transmits the multiplexed MPEG-2 A/V broadcasting data to the cable card through an In-band channel guaranteeing a transmission rate of maximum 200 Mbps,  
         [0058]     The present invention contains subject matter related to Korean patent application Nos. 2004-0105092 and 2005-038704, filed in the Korean patent office on Dec. 13, 2004, and May 10, 2005, respectively, the entire contents of which being incorporated herein by reference.  
         [0059]     While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.