Abstract:
An apparatus and method for receiving a multimedia broadcasting service in a mobile communication system including a satellite digital multimedia broadcasting (DMB) reception system and a terrestrial DMB reception system. In the apparatus, a satellite DMB modem block demodulates a satellite broadcast signal received from the satellite DMB system. A terrestrial DMB modem block, sharing at least one function block with the satellite DMB modem block, demodulates a terrestrial broadcast signal received from the terrestrial DMB system. A Motion Picture Experts Group (MPEG) decoder separately decodes MPEG transport streams (TSs) for the satellite broadcast signal and the terrestrial broadcast signal.

Description:
PRIORITY  
       [0001]     This application claims priority under 35 U.S.C. § 119 to an application entitled “Apparatus and Method for Receiving Digital Multimedia Broadcasting Signals” filed in the Korean Intellectual Property Office on Sep. 6, 2004 and assigned Serial No. 2004-70711, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to a broadcasting reception apparatus and method in a mobile communication system, and in particular, to a Digital Multimedia Broadcasting (DMB) reception apparatus and method capable of receiving both satellite broadcast signals and terrestrial broadcast signals, transmitted through a digital broadcasting system.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, mobile terminals are mobile communication devices that can be carried by individuals for performing voice communications regardless of time and location. Moreover, with recent developments of mobile communication technologies, mobile terminals have begun to serve as information terminals capable of transmitting/receiving voice data and/or packet data. Mobile terminals capable of serving as information terminals include mobile phones, Work Analysis Program (WAP) phones, Personal Digital Assistants (PDAs), and a Web Pads. Improvements of mobile terminals in terms of mobility and personal service have resulted in an increase in number of the mobile terminals users.  
         [0006]     The rapid progress of multimedia technologies has enabled additional services in which mobile terminals can transmit and/or receive high-quality still and/or moving image data in addition to voice data. Recently, attention has been directed to additional services provided by service providers. These additional services include broadcasting services in which the user can receive moving picture information such as movies, news, sports, stocks and weather. Moreover, attention has also been directed to call success rate and call quality of mobile terminals.  
         [0007]     Broadcasting services are classified into analog broadcasting services and digital broadcasting services. Compared with conventional analog broadcasting services, digital broadcasting services can provide users with an advanced, high-image quality, high-voice quality services. In order to provide high-image quality, high-voice quality services, the digital broadcasting services compress broadcast traffic at a high compression rate before transmission, using a Motion Picture Experts Group-2 (MPEG-2) scheme or a Motion Picture Experts Group-4 (MPEG-4) scheme.  
         [0008]     Digital broadcasting services use a high compression rate because of the requisite amount of data information. Currently, a digital multimedia broadcast (DMB) service is the most common type of digital broadcasting service.  
         [0009]     The DMB service can broadcast various multimedia signals such as audio and video signals on a digital basis. For example, the DMB service can extend the concept of radio broadcasting from voice-only (e.g., audio) broadcasting to multimedia (e.g. audio and video) broadcasting, and can transmit various multimedia information such as traffic information, news information, etc., in textual, graphical and real-time moving image form in addition to the audio broadcasting. Further, the DMB service can link moving image broadcasting to the existing digital broadcasting networks such as terrestrial broadcasting, satellite broadcasting and cable TV, to provide various multimedia services. In addition, the DMB service can interwork with Intelligent Transportation System (ITS) and Global Positioning System (GPS), to provide a telematics service.  
         [0010]     In particular, because the DMB service provides high-image quality, high-voice quality broadcasting not only to fixed terminals but also to mobile terminals such as mobile phones, PDAs and in-vehicle terminals, it is envisioned that the use of the DMB service will dramatically increase. The DMB service can be classified into terrestrial DMB service and satellite DMB service. The terrestrial DMB service refers to technology of providing a broadcasting service via a terrestrial repeater, also known as a gap filler. The satellite DMB service refers to technology of providing a broadcasting service via the terrestrial repeater and/or a satellite repeater.  
         [0011]     A brief description will now be made of a broadcasting system that provides both the satellite DMB service and the terrestrial DMB service.  
         [0012]      FIG. 1  is a block diagram illustrating a configuration of a system for providing a general satellite DMB service.  
         [0013]     Referring to  FIG. 1 , a satellite DMB broadcasting center  100  on the ground transmits broadcast signals to a DMB satellite  106  through a Ku-band of 12 GHz through 13 GHz using Time Division Multiplexing (TDM) signals  102  or Code Division Multiplexing (CDM)  104  signals. Then the DMB satellite  106  receives the broadcast signals  102  and  104 , and transmits the received broadcast signals  102  and  104  to mobile terminals  116  on the ground either directly or by using a gap filler  108  or a terrestrial repeater (not shown).  
         [0014]     The DMB satellite  106  converts the broadcast signals  102  and  104  received from the satellite DMB broadcasting center  100  into an S-band (2 GHz through 3 GHz) CDM signal  112  and a Ku-band TDM signal  110 . The S-band CDM signal  112  is transmitted directly to the mobile terminals  116  and the Ku-band TDM signal  110  is transmitted to the gap filler  108 . The DMB satellite  106  transmits the broadcast signal to the gap filler  108  in order to provide the broadcast signals transmitted by the DMB satellite  106  to unserviceable areas, (i.e., areas in which satellite broadcast signals are insufficient for reception), which are also known as the “gap”, and can typically include areas such as basements, tunnels and other areas in which a satellite signal is not provided, or is attenuated, polluted by noise, reflected, etc. The gap filler  108  converts the received broadcast signals into S-band signals  114  and transmits the S-band signals  114  to the mobile terminals  116  in the unserviceable area.  
         [0015]     In contrast with a satellite DMB broadcasting system, a terrestrial DMB system uses a broadcasting transmission tower (not shown) for transmission of terrestrial broadcasting, instead of using a DMB satellite transmitter (as is used in the satellite DMB system), transmitting broadcast signals to mobile terminals, and uses a gap filler, of an individual service provider, for providing service to an unserviceable area. The digital terrestrial DMB system is based on the European Digital Audio Broadcasting (DAB) system. Herein, the term “digital broadcasting system” refers to both the satellite DMB system and the terrestrial DMB system.  
         [0016]     The terrestrial DMB system uses Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme, and configures a single frequency network (SFN) using a plurality of broadcasting transmitters. In the SFN transmitters synchronously transmit the same data signals using the same frequency. Because the broadcast signals transmitted by the transmitters,, the signals do not serve as interference components to each other and provide a multipath channel effect. The multipath channel effect improves the quality of reception signals at a receiving mobile terminal.  
         [0017]     DMB reception apparatuses for mobile terminals in the general satellite DMB system and terrestrial DMB system will now be described with reference to  FIGS. 2 and 3 , respectively.  
         [0018]      FIG. 2  is a block diagram illustrating a structure of a general satellite DMB reception apparatus.  
         [0019]     The satellite DMB system is provided such that it generally requires a channel for transmission of Conditional Access System (CAS) information, a channel for transmission of Electronic Program Guide (EPG) information, a channel for transmission of broadcast traffic and a channel for transmission of pilot information. Conventionally, broadcast traffic is transmitted over two channels. Therefore, as illustrated in  FIG. 2 , a bit deinterleaver  220 , a convolutional decoder  230 , a byte deinterleaver  240  and a Reed-Solomon (R-S) decoder  250  must be provided for each channel path.  
         [0020]     The DMB reception apparatus for receiving satellite DMB service, as illustrated in  FIG. 2 , receives a satellite broadcast signal transmitted from the DMB satellite  106  or the gap filler  108  (i.e., a satellite repeater) at a CDM demodulator  210 . The CDM demodulator  210  demodulates (despreads) the received satellite broadcast signal using a Walsh code for a corresponding reception channel, and outputs the demodulated satellite broadcast signal to the bit deinterleaver  220 . To be specific, the outputs of the CDM demodulator  210  are separately provided to the bit deinterleavers  220  according to Walsh codes for reception channels. The bit deinterleaver  220  deinterleaves the received satellite broadcast signal bit-by-bit in order to disperse a possible per-bit burst error.  
         [0021]     The deinterleaved satellite broadcast signal is input to the convolutional decoder  230 . The convolutional decoder  230  performs error correction on the convolutional-coded signal output from the bit deinterleaver  220 , and outputs the error-corrected satellite broadcast signal to the byte deinterleaver  240 . The byte deinterleaver  240  deinterleaves the satellite broadcast signal output from the convolutional decoder  230  byte-by-byte in order to disperse a possible per-byte burst error. That is, the byte deinterleaver  240  corrects a burst error which occurs when the convolutional decoder  230  fails to perform adequate error correction.  
         [0022]     The satellite broadcast signal output from the byte deinterleaver  240  is input to the R-S decoder  250 . The R-S decoder  250  corrects an error signal in the received deinterleaved signal using parity data, and outputs the error-corrected signal to a CAS  260 . The CAS  260  performs reception authentication on a CAS channel signal received from the R-S decoder  250 . After the satellite broadcast signal undergoes reception authentication by the CAS  260 , the satellite broadcast signal of the traffic channel is transmitted to an MPEG decoder  280  via an output interface  270 . The MPEG decoder  280  decodes the satellite broadcast service signal and provides the decoded signal to the user.  
         [0023]     With reference to  FIG. 3 , a description will now be made of a mobile terminal for receiving terrestrial DMB broadcast service.  
         [0024]      FIG. 3  is a block diagram illustrating a structure of a general terrestrial DMB reception apparatus.  
         [0025]     A mobile terminal for receiving terrestrial DMB broadcast service receives a terrestrial DMB-based radio signal (hereinafter referred to as a terrestrial broadcast signal) transmitted over the air via an antenna (not shown). The terrestrial broadcast signal is received in the form of an OFDM symbol, and input to an OFDM demodulator  311 . The OFDM demodulator  311  removes a guard interval from the received OFDM symbol and performs fast Fourier transform (FFT) on the guard interval-removed OFDM symbol for demodulation. The demodulated terrestrial broadcast signal is input to a bit deinterleaver  312 . The bit deinterleaver  312  deinterleaves the terrestrial broadcast signal received from the OFDM demodulator  311  bit-by-bit in order to disperse a possible per-bit burst error.  
         [0026]     The deinterleaved terrestrial broadcast signal, which is a convolutional-coded signal, is input to a convolutional decoder  313 . The convolutional decoder  313  performs error correction on the deinterleaved terrestrial broadcast signal received from the bit deinterleaver  312 , and outputs the error-corrected terrestrial broadcast signal to a demultiplexer (DEMUX)  315 . The demultiplexer  315  demultiplexes the error-corrected terrestrial broadcast signal received from the convolutional decoder  313  into audio/data information and an MPEG signal. The audio/data information is input to an audio/data decoder  321  via an output interface  320  and then is input into an audio/data decoder  321  which decodes a DAB-based terrestrial broadcast service signal and provides the decoded signal to the user.  
         [0027]     The MPEG signal is input from the demultiplexer  315  to an MPEG transport stream (TS) synchronizer  314 . The MPEG TS synchronizer  314  acquires synchronization by detecting predetermined code information “0x47” periodically included in header information of an MPEG TS. An output of the MPEG TS synchronizer  314  is input into a byte deinterleaver  316 . The byte deinterleaver  316  deinterleaves the convolutional-decoded MPEG signal byte-by-byte, and outputs the deinterleaved MPEG signal to an R-S decoder  317 . The R-S decoder  317  decodes an error signal in the deinterleaved MPEG signal using parity data, and outputs the decoded signal to an MPEG decoder  319  via an output interface  318 . The MPEG decoder  319  decodes a terrestrial broadcast service signal from the MPEG signal and provides the decoded signal to the user.  
         [0028]     As described above, the satellite DMB reception apparatus and the terrestrial DMB reception apparatus have different structures and receive broadcast signals according to their own standards. Therefore, in order to receive both satellite and terrestrial DMB service, conventional mobile terminals may require a terrestrial DMB reception apparatus and a satellite DMB reception apparatus, which the mobile terminal&#39;s hardware complexity. Alternatively, when a mobile terminal includes a satellite DMB reception apparatus and a terrestrial DMB reception apparatus that share the same functions to reduce the hardware complexity, the mobile terminal cannot receive a satellite broadcast signal and a terrestrial broadcast signal at the same time. Therefore, there is a need for a DMB reception apparatus capable of receiving a satellite broadcast signal and a terrestrial broadcast signal with low hardware complexity. Additionally, there is a need for a DMB reception apparatus with low hardware complexity which is capable of simultaneously receiving a satellite broadcast signal and a terrestrial broadcast signal.  
       SUMMARY OF THE INVENTION  
       [0029]     It is, therefore, an object of the present invention to provide a DMB reception apparatus and method capable of receiving both terrestrial broadcast signals and satellite broadcast signals in a digital broadcasting system.  
         [0030]     It is another object of the present invention to provide a DMB reception apparatus and method for receiving both terrestrial broadcast signals and satellite broadcast signals with low hardware complexity in a digital broadcasting system.  
         [0031]     According to one aspect of the present invention, there is provided an apparatus for receiving a multimedia broadcasting service in a mobile communication system in which a satellite digital multimedia broadcasting (DMB) system and a terrestrial DMB system coexist. The apparatus includes a satellite DMB modem block for demodulating a satellite broadcast signal received from the satellite DMB system, a terrestrial DMB modem block sharing at least one function block with the satellite DMB modem block, the terrestrial DMB modem block for demodulating a terrestrial broadcast signal received from the terrestrial DMB system, and a Motion Picture Experts Group (MPEG) decoder for separately decoding MPEG transport streams (TSs) for the satellite broadcast signal and the terrestrial broadcast signal.  
         [0032]     According to another aspect of the present invention, there is provided a method for receiving a multimedia broadcasting service in a mobile communication system in which a satellite digital multimedia broadcasting (DMB) system and a terrestrial DMB system coexist. The method includes simultaneously receiving a satellite broadcast signal of the satellite DMB system and a terrestrial broadcast signal of the terrestrial DMB system, from a wireless network; modifying a header of a first Motion Picture Experts Group (MPEG) transport stream (TS) for the terrestrial broadcast signal with a predetermined value being different from that of a header of a second MPEG TS for the satellite broadcast signal, and separately MPEG-decoding the first MPEG TS for the terrestrial broadcast signal and the second MPEG TS for the satellite broadcast signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]     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:  
         [0034]      FIG. 1  is a block diagram illustrating a configuration of a general satellite DMB system;  
         [0035]      FIG. 2  is a block diagram illustrating a structure of a general satellite DMB reception service;  
         [0036]      FIG. 3  is a block diagram illustrating a structure of a general terrestrial DMB reception apparatus;  
         [0037]      FIG. 4  is a block diagram illustrating a structure of a DMB reception apparatus according to an embodiment of the present invention;  
         [0038]      FIG. 5  is a block diagram illustrating a structure of a DMB reception apparatus according to another embodiment of the present invention;  
         [0039]      FIG. 6  is a block diagram illustrating a structure of a DMB reception apparatus according to further another embodiment of the present invention;  
         [0040]      FIGS. 7A and 7B  are flowcharts illustrating a terrestrial DMB reception process in a simultaneous reception mode according to an embodiment of the present invention; and  
         [0041]      FIG. 8  is a flowchart illustrating a process of replacing a reception channel for satellite broadcast signals with a spare channel according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0042]     Several preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness.  
         [0043]     The present invention will be described herein below with reference to the following three embodiments.  
         [0044]     A first embodiment simultaneously receives satellite broadcast signals and terrestrial broadcast signals using a single DMB reception apparatus, wherein the DMB reception apparatus receives the satellite broadcast signals using a satellite DMB modem and receives the terrestrial broadcast signals using spare channels in the satellite DMB modem. A second embodiment increases the number of channels available for reception of the terrestrial broadcast signals. A third embodiment receives the terrestrial broadcast signals using a predetermined channel in the satellite DMB modem, wherein when the satellite DMB modem desires to use the particular channel to receive satellite broadcast signals, the satellite DMB modem receives the corresponding satellite broadcast signals using spare channels.  
         [0045]     With reference to the accompanying drawings, a detailed description will now be made of the embodiments of the present invention.  
         [0046]      FIG. 4  is a block diagram illustrating a structure of a DMB reception apparatus according to an embodiment of the present invention. A detailed description of the elements being identical in structure to those in  FIGS. 2 and 3  will be omitted herein for the sake of clarity.  
         [0047]     In  FIG. 4 , a satellite DMB modem block for receiving satellite broadcast signals includes a plurality of channels for receiving Conditional Access System (CAS) information, Electronic Program Guide (EPG) information, broadcast traffic, and pilot information, etc. Herein, the channels for receiving the broadcast traffic include at least two channels for receiving at least one satellite broadcast signal, and at least one channel for receiving at least one terrestrial broadcast signal. Therefore, as illustrated in  FIG. 4 , bit deinterleavers  411 , convolutional decoders  412 , multiplexers  413 , byte deinterleavers  414  and R-S decoders  415  included in the satellite DMB modem block are equal in number to required channels.  
         [0048]     Referring to  FIG. 4 , the DMB reception apparatus is designed such that the bit deinterleavers  411  and the convolutional decoders  412  of the satellite DMB modem block and a bit deinterleaver  420  and a convolutional decoder  421  of a terrestrial DMB modem block, respectively, are separate units the byte deinterleavers  414  and the R-S decoders  415  of the satellite DMB modem block are shared with the terrestrial DMB modem block. This is because the bit deinterleavers  411  and  420  and the convolutional decoders  412  and  421  use different signal processing methods for processing the satellite DMB signals and the terrestrial DMB signals while the byte deinterleavers  414  and the RS-decoders  415  are used for receiving both the satellite DMB scheme and the terrestrial DMB signals because signal processing required by these units to receive both the satellite DMB signals and the terrestrial DMB signals is identical. Therefore, the present invention can simplify the DMB reception apparatus capable of simultaneously receiving the satellite DMB service and the terrestrial DMB servicesharing components which have identical functions in both the satellite DMB modem block and the terrestrial DMB modem block.  
         [0049]     In addition, the present invention interposes the multiplexers  413  between the convolutional decoders  412  of the satellite DMB modem block and the byte deinterleavers  414  so that the DMB reception apparatus can simultaneously receive the satellite broadcast signals and the terrestrial broadcast signals. Although the multiplexers  413  are equal in number to the channels of the satellite DMB modem in  FIG. 4 , the DMB reception apparatus can also be designed such that at least one multiplexer is arranged in a particular channel path for which a spare channel can be allocated.  
         [0050]     Preferably, the present invention arranges the multiplexers  413  in the front of the byte deinterleavers  414  to simplify the DMB reception apparatus. However, if the terrestrial DMB modem block does not share the byte deinterleavers  414  or all of the byte deinterleavers  414  and the R-S decoders  415  with the satellite DMB modem block, the present invention can arrange the multiplexers  413  immediately before or after the R-S decoders  415 .  
         [0051]     In the structure of  FIG. 4 , acontroller (not shown) controls the multiplexers  413  to connect the terrestrial DMB modem block to the satellite DMB modem block such that the DMB reception apparatus receives the next terrestrial broadcast signals using spare channels of the satellite DMB modem block, after detecting setting of a predetermined mode for simultaneously receiving satellite broadcast signals and terrestrial broadcast signals. The setting of the simultaneous reception mode can be implemented with the well-known picture-in-picture (PIP) function of outputting a plurality of screens with a display (not shown). A detailed description of the PIP function will be omitted herein for the sake of clarity.  
         [0052]     When the simultaneous reception mode is set, the terrestrial broadcast signals are input to all of the multiplexers  413 , but a controller (not shown) selects the terrestrial broadcast signals output through the multiplexer  413  located in a path for the spare channel and blocks terrestrial broadcast signals output through the remaining multiplexers  413 . That is, because the satellite DMB modem block performs channel decoding using a corresponding Walsh code, the controller determines a Walsh code used for reception of the satellite broadcast signals and its channel route using a CDM demodulator  410 , and controls the multiplexers  413  to set a channel unused for reception of the satellite broadcast signals as a spare channel and receives the terrestrial broadcast signals using the spare channel.  
         [0053]     However, if the broadcast signals of the two different types (i.e., the satellite broadcast and the terrestrial broadcast signals) are input to an MPEG decoder  418 , the MPEG decoder  418  cannot distinguish between transport streams (TSs) of the two different types. This is because both of the satellite broadcast signals and the terrestrial broadcast signals are transmitted with MPEG TSs in which predetermined header information “0x47” (where “0x47” means a start code of a MPEG TS having a size of 188 bytes) is periodically included.  
         [0054]     A description will now be made of a novel method for separately receiving an MPEG TS corresponding to the satellite broadcast signals and an MPEG TS corresponding to the terrestrial broadcast signals  
         [0055]     A demultiplexer  422  of the terrestrial DMB modem block classifies a terrestrial broadcast signal received from the convolutional decoder  421  into audio/data and an MPEG signal. The audio/data is input to an audio/data decoder  424  via an output interface  423  according to conventional methods. The MPEG signal is input from the demultiplexer  422  to an MPEG TS synchronizer  425 . The MPEG TS synchronizer  425  acquires synchronization by detecting periodic header information “0x47” of the MPEG TS. An output of the MPEG TS synchronizer  425  is delivered to a TS header modifier  426 , and the TS header modifier  426  modifies an MPEG TS header in the terrestrial broadcast signals using a predetermined value.  
         [0056]     Modifying the MPEG TS header using a predetermined value (e.g., “0x47”) which is different from a value for a MPEG TS header for a satellite service allows the signals to be distinguished from each other by the R-S decoders as will be described below means that in the terrestrial and satellite DMB services,  
         [0057]     Terrestrial broadcast signals including the modified MPEG TS header value are input to the multiplexers  413 . The controller (not shown) of the mobile terminal selects an output of a terrestrial broadcast signal by controlling the multiplexer  413  connected to a spare channel, blocks the terrestrial broadcast signals output through the remaining multiplexers  413  and outputs the satellite broadcast signals through the remaining multiplexer  413 .  
         [0058]     The byte deinterleavers  414  deinterleave MPEG TSs for the convolutional-decoded satellite broadcast signals and terrestrial broadcast signals byte-by-byte, and output the deinterleaved MPEG TSs to the R-S decoders  415 . The R-S decoders  415  correct error signals in the deinterleaved MPEG TSs, and output the error-corrected MPEG TSs for both the satellite broadcast signals and the terrestrial broadcast signals to the MPEG decoder  418  via an output interface  417 .  
         [0059]     The R-S decoders  415  perform a 0x47-header calculation regardless of whether the MPEG TS headers include 0x47 or another pattern. The R-S decoders  415  can recognize MPEG TS headers for the terrestrial broadcast signals, modified with a pattern other than 0x47, as a defective header, and correct the defective header. Therefore, the R-S decoders  415  must be set such that when the terrestrial DMB signals and the satellite DMB signals are simultaneously received, the R-S decoders  415  should not correct the value modified by the TS header modifier  426 . This is to maintain the error correction capability of the R-S decoders  415 .  
         [0060]     A CAS  416  performs reception authentication on CAS information, and delivers the MPEG TSs error-corrected through the R-S decoders  415  to the MPEG decoder  418 , if the reception authentication is successful or a conditional access is not set. A conditional access function is used to control various access channels provided in the satellite DMB service and to prevent unauthorized channels from being displayed. In other words, the controlled access function prevents users from watching unauthorized channels (e.g., pay-per-view channels, etc.) which they have not subscribed to. The MPEG decoder  418  recognizes an MPEG TS starting with a different header pattern as a terrestrial broadcast signal and distinguishes the terrestrial broadcast signal from the satellite broadcast signal in the decoding process.  
         [0061]      FIG. 5  is a block diagram illustrating a structure of a DMB reception apparatus according to another embodiment of the present invention, wherein the number of channels simultaneously available for reception of terrestrial broadcast signals is increased.  
         [0062]     The terrestrial DMB service can transmit broadcast signals on a plurality of channels through one frequency band on a time division basis. If two terrestrial channels are simultaneously received, the DMB reception apparatus further includes MPEG TS synchronizers  525  and  527  and TS header modifiers  526  and  528  as illustrated in  FIG. 5 . The embodiment of  FIG. 5 , similarly to the embodiment shown in  FIG. 4 , receives terrestrial broadcast signals using spare channels in the satellite DMB modem block, and forms MPEG TSs having different header patterns for distinguishing broadcast signals at an MPEG decoder  518 .  
         [0063]     Both of the embodiments of  FIGS. 4 and 5  are implemented such that byte deinterleavers  414  and  514  selectively receive either the satellite broadcast signals or the terrestrial broadcast signals through multiplexers  413  and  513 , and receive the terrestrial broadcast signals using spare channels (i.e., channels unused for reception of  10  the satellite broadcast signals). Referring to  FIG. 5 , bit deinterleavers  511  and convolutional decoders  512  of a satellite DMB modem block and a bit deinterleaver  520  and a convolutional decoder  521  of a terrestrial DMB modem block are separately provided, and byte deinterleavers  514  and R-S decoders  515  of the satellite DMB modem block are shared with the terrestrial DMB modem block.  
         [0064]     In the structure of  FIG. 5 , if terrestrial broadcast signals on two channels are simultaneously received, a demultiplexer  522  of the terrestrial DMB modem block classifies the terrestrial broadcast signals on the two channels received from the convolutional decoder  521  into audio/data and MPEG TSs. The demultiplexer  522  delivers a terrestrial broadcast signal (first DMB data) on one channel among the MPEG TSs to the first MPEG TS synchronizer  525 , and delivers a terrestrial broadcast signal (second DMB data) on another channel to the second MPEG TS synchronizer  527 .  
         [0065]     The first and second MPEG TS synchronizers  525  and  527  acquire synchronization by detecting periodic header information ‘0x47’ from the MPEG TSs for the corresponding channels. The MPEG TS for the channel of which synchronization is detected through the first MPEG TS synchronizer  525  is delivered to the first TS header modifier  526  where its MPEG TS header is modified with a predetermined value other than 0x47. Similarly, an MPEG TS for another channel of which synchronization is detected through the second MPEG TS synchronizer  527  is delivered to the second TS header modifier  528  where its MPEG TS header is modified with a predetermined value.  
         [0066]     The terrestrial broadcast signals on the two channels output from the first and second TS header modifiers  526  and  528  are applied to all of the multiplexers  513 . A controller (not shown) selects outputs of the terrestrial broadcast signal on the two channels by controlling two multiplexers  513  connected to the spare channels, cuts off the terrestrial broadcast signals output through the remaining multiplexers  513 , and outputs the satellite broadcast signals. The R-S decoders  515  perform 0x47-header calculation regardless of whether the MPEG TS headers include 0x47 or another pattern to correct errors in the MPEG TSs, and deliver the error-corrected MPEG TSs for the satellite broadcast signals and/or the terrestrial broadcast signals to the MPEG decoder  518  via a CAS  516  and an output interface  517 .  
         [0067]     The MPEG decoder  518  separately decodes the satellite broadcast signals and the terrestrial broadcast signals by analyzing headers of the received MPEG TSs.  
         [0068]     With reference to  FIGS. 7A and 7B , a description will now be made of a novel DMB reception method using spare channels according to the embodiments of  FIGS. 4 and 5 .  FIGS. 7A and 7B  are flowcharts illustrating a detailed description of a terrestrial DMB reception process in a simultaneous reception mode. A satellite DMB reception process has been described above, so a detailed description thereof will be omitted herein for the sake of clarity.  
         [0069]     In step  701 , a controller (not shown) of a mobile terminal determines if a simultaneous reception mode for both a satellite DMB service and a terrestrial DMB service is set. Herein, the mobile terminal can selectively receive one of or simultaneously receive both of the satellite DMB service and the terrestrial DMB service because it includes a satellite DMB modem block for receiving satellite broadcast signals and a terrestrial DMB modem block for receiving terrestrial broadcast signals as illustrated in  FIGS. 4 and 5 . Setting of the simultaneous reception mode is performed by the controller, and it will be understood by those skilled in the art that a user interface for selecting a DMB reception mode can be simply provided to the structures of  FIGS. 4 and 5 .  
         [0070]     Therefore, a user of the mobile terminal can select one of a satellite DMB reception mode, a terrestrial DMB reception mode and a simultaneous reception mode using a predetermined screen interface provided by the controller.  
         [0071]     If it is determined in step  701  that the simultaneous reception mode is not set, the controller proceeds to step  703  where it receives satellite broadcast signals or terrestrial broadcast signals using the satellite DMB modem block or the terrestrial DMB model block according to a selected reception mode. In the terrestrial DMB reception mode, byte deinterleaving and R-S decoding in  FIGS. 4 and 5  are performed using corresponding elements in the satellite DMB modem block.  
         [0072]     However, if it is determined in step  701  that the simultaneous reception mode is set, an OFDM demodulator  419  or  519  removes a guard interval from terrestrial broadcast signals transmitted over an OFDM symbol, and perform an FFT process on the guard interval-removed terrestrial broadcast signals for demodulation in step  705 . Thereafter, in step  707 , a bit deinterleaver  420  or  520  deinterleaves the terrestrial broadcast signals received from the OFDM demodulator  419  or  519  bit-by-bit. In step  709 , a convolutional decoder  421  or  521  convolutional-codes the deinterleaved terrestrial broadcast signals for error correction. In step  711 , a demultiplexer  422  or  522  demultiplexes the error-corrected terrestrial broadcast signals received from the convolutional decoder  421  or  521  into audio/data and MPEG TS(s). The MPEG TS(s) is input from the demultiplexer  422  or  522  to the MPEG TS synchronizer(s).  
         [0073]     The MPEG TS(s) is applied to a single MPEG TS synchronizer  425  in the case of  FIG. 4  where one channel is received, and is applied to multiple MPEG TS synchronizers  525  and  527  in the case of  FIG. 5  where multiple channels are received. In step  713 , the MPEG TS synchronizer(s)  425  (or  525  and  527 ) acquires synchronization by detecting predetermined periodic code information “0x47” from a header of the MPEG TS. An output(s) of the MPEG TS synchronizer(s)  425  (or  525  and  527 ) is delivered to a TS header modifier(s)  426  (or  526  and  528 ).  
         [0074]     In step  715 , the TS header modifier(s)  426  (or  526  and  528 ) modifies a header of the MPEG TS with a predetermined value to distinguish between the terrestrial broadcast signals and the satellite broadcast signals. In step  717 , the terrestrial broadcast signals including the modified MPEG TS header value are delivered to multiplexers  413  or  513  on all of the channel paths of the satellite DMB modem. In step  719 , the controller determines if there one or more spare channel(s). If spare channels are unavailable, the controller proceeds to step  721  where it displays a message indicating the reception of the terrestrial DMB service on a display (not shown) is currently unavailable.  
         [0075]     Alternatively, it is preferable that the spare channel detection process of step  719  can be performed along with the simultaneous reception mode setting process of step  701 .  
         [0076]     However, if it is determined in step  719  that there is a spare channel, the controller proceeds to step  723  where it selects an output of a terrestrial broadcast signal received through a spare channel path by controlling the multiplexers  413  or  513 , cuts off terrestrial broadcast signals output through the remaining multiplexers  413  and  513 , and outputs the terrestrial and satellite broadcast signals. Thereafter, in step  725 , the byte deinterleavers  414  or  514  deinterleave the MPEG TSs for the terrestrial broadcast signals and the satellite broadcast signals received through their associated channel paths byte-by-byte.  
         [0077]     In step  727 , R-S decoders  415  or  515  perform a 0x47-header calculation regardless of whether the MPEG TS headers include “0x47” or another pattern to correct errors in the MPEG TSs, and deliver the error-corrected MPEG TSs to a MPEG decoder  418  or  518  via a CAS  416  or  516  and an output interface  417  or  517 . In step  729 , the MPEG decoder  418  or  518  separately decodes the satellite broadcast signals and the terrestrial broadcast signals by analyzing headers of the received MPEG TSs.  
         [0078]      FIG. 6  is a block diagram illustrating a structure of a DMB reception apparatus according to further another embodiment of the present invention, wherein the DMB reception apparatus receives terrestrial broadcast signals using a predetermined channel of a satellite DMB modem instead of using the spare channels.  
         [0079]     It is noted in  FIG. 6  that a multiplexer  626  is not connected to all of the channel paths of a satellite DMB modem block, but connected only to a particular channel path used for receiving broadcast signals from a terrestrial DMB modem block. However, when there is a need to receive satellite broadcast signals through the particular channel of the satellite DMB modem, it is not possible to receive terrestrial broadcast signals. Therefore, the current embodiment receives the satellite broadcast signals through a spare channel of the satellite DMB modem, thereby simultaneously receiving the satellite broadcast signals and the terrestrial broadcast signals without data loss.  
         [0080]     To this end, an output controller  615  is designed such that it can prevent an output of a particular channel designated as a spare channel and change a setting of preventing a channel output at a boundary of an input packet of an MPEG TS. In this manner, the embodiment can change a reception path of the satellite broadcast signals to be received through the particular channel to a spare channel. The output controller  615  prevents an output of the spare channel until the boundary of an input packet in order to prevent packet collision/loss for the satellite broadcast signals whose reception channel is changed.  
         [0081]      FIG. 8  is a flowchart illustrating a process of replacing a reception channel for satellite broadcast signals with a spare channel. With reference to  FIG. 8 , a detailed description of the embodiment of  FIG. 6  will be given below.  
         [0082]     In step  801 , a controller of a mobile terminal designates a particular channel of a satellite DMB modem as a terrestrial DMB reception channel. It is assumed herein that terrestrial broadcast signals can be received only through the particular channel. If it is determined in step  803  that there is a need to receive satellite broadcast signals through the particular channel, the output controller  615  prevents output of a corresponding spare channel to prevent a data loss of the satellite broadcast signals in step  805 . Thereafter, in step  807 , the controller controls to the DMB reception apparatus to simultaneously receive the satellite broadcast signals bound for the particular channel through the spare channel. To this end, the controller allocates a Walsh code for the particular channel to the spare channel by controlling a CDM demodulator  610 . The output controller  615  can be either included in the controller of the mobile terminal or separately provided. In this state, although output of terrestrial broadcasts on the spare channel is prohibited, the controller receives the satellite broadcast signals through the spare channel in step  807 .  
         [0083]     In step  809 , the output controller  615  determines if a satellite broadcast signal has arrived. If the satellite broadcast signal has arrived at the output controller  615 , the output controller  615  determines in step  811  whether the current time is a packet boundary of an MPEG TS for transmitting the satellite broadcast signal. If the current time is a packet boundary, the output controller  615  transmits the satellite broadcast signal through the spare channel in step  813 , prohibiting transmission/reception of the satellite broadcast signal through the particular channel.  
         [0084]     As can be understood from the foregoing description, to simultaneously receive satellite broadcast signals and terrestrial broadcast signals, the novel DMB reception apparatus is designed such that a satellite DMB modem and a terrestrial DMB modem share some elements rather than using entirely separate elements, thereby contributing a reduction in hardware complexity. Therefore, the DMB reception apparatus can separately decode MPEG TSs for the satellite broadcast signals and the terrestrial broadcast signals using a simple structure.  
         [0085]     While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.