Abstract:
A signal transmission apparatus in a communication system, includes: a first IFFT unit for generating a first signal by performing inverse fast Fourier transform on a first communication service signal corresponding to a first communication scheme; a first CP inserter for generating a second signal by inserting a first cyclic prefix having a length corresponding to the first communication scheme into the first signal; a second IFFT unit for generating a third signal by performing inverse fast Fourier transform on a second communication service signal corresponding to a second communication scheme; a second cyclic prefix inserter for generating a fourth signal by inserting a second cyclic prefix having a length corresponding to the second communication scheme into the third signal; and a transmission unit for multiplexing the second signal and the fourth signal and transmitting the multiplexed signals.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
       [0001]    This application claims the priority under 35 U.S.C. §119(a) of an application entitled “Apparatus And Method For Transmitting and Receiving A Signal In A Communication System” filed in the Korean Industrial Property Office on Jan. 31, 2007 and assigned Serial No. 2007-10275, the contents of which are hereby incorporated by reference. 
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to an apparatus and a method for transmitting and receiving a signal in a communication system, and more particularly to an apparatus and a method for transmitting and receiving a signal in a communication system (OFDM and OFDMA communication system) using an Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Frequency Division Multiple Access (OFDMA) scheme. 
       BACKGROUND OF THE INVENTION 
       [0003]    Next generation communication systems are being developed in order to provide various high-speed large-capacity services to Mobile Stations (MSs), and are making use of the OFDM or OFDMA scheme into consideration. Hereinafter, structures of a signal transmission apparatus and a signal reception apparatus of a conventional OFDM or OFDMA communication system will be described with reference to  FIGS. 1 and 2 . 
         [0004]      FIG. 1  is a block diagram illustrating a structure of a signal transmission apparatus of a conventional OFDM/OFDMA communication system. 
         [0005]    Referring to  FIG. 1 , the signal transmission apparatus includes an encoder  101 , a modulator  103 , a serial-to-parallel (S/P) converter  105 , an Inverse Fast Fourier Transform (IFFT) unit  107 , a parallel-to-serial converter  108 , a Cyclic Prefix (CP) inserter  109 , and a Radio Frequency (RF) processor  111 . 
         [0006]    First, when a signal to be transmitted occurs in the signal transmission apparatus, the signal is input to the encoder  101 . The encoder  101  encodes the input signal according to a preset encoding scheme and then outputs the encoded signal to the modulator  103 . The preset encoding scheme may be, for example, a turbo encoding scheme or a convolutional encoding scheme. The modulator  103  receives the signal output from the encoder  101 , modulates the signal according to a preset modulation scheme, and then outputs the modulated signal to the S/P converter  105 . The preset modulation scheme may be, for example, a Quadrature Amplitude Modulation (QAM) scheme, a Binary Phase Shift Key (BPSK) scheme, or a Quadrature Phase Shift Keying (QPSK) scheme. 
         [0007]    The S/P converter  105  receives the serial signal output from the modulator  103 , converts the serial signal to parallel signals, and then outputs the converted parallel signals to the IFFT unit  107 . The IFFT unit  107  receives the parallel signals output from the S/P converter  105 , performs IFFT on the parallel signals, and then outputs the IFFTed signals to the P/S converter  108 . The P/S converter  108  converts the parallel signals output from the IFFT unit  107  to a serial signal, and then outputs the converted serial signal to the CP inserter  109 . The CP inserter  109  inserts a CP to the serial signal output from the P/S converter  108  and then outputs the CP-inserted signal to the RF processor  111 . The RF processor  111  receives the signal output from the CP inserter  109 , performs RF processing of the signal, and then transmits the RF-processed signal through an antenna. 
         [0008]      FIG. 2  is a block diagram illustrating a structure of a signal reception apparatus of a conventional OFDM and OFDMA communication system. 
         [0009]    Referring to  FIG. 2 , the signal reception apparatus includes an RF processor  201 , a CP remover  203 , an S/P converter  204 , a Fast Fourier Transform (FFT) unit  205 , a P/S converter  207 , a demodulator  209 , and a decoder  211 . 
         [0010]    The RF processor  201  receives an RF signal from a signal transmission apparatus, restores an original signal before the RF processing from the received RF signal, and outputs the restored signal to the CP remover  203 . The CP remover  203  receives the signal output from the RF processor  201 , removes the CP from the signal, and then outputs the CP-removed signal to the S/P converter  204 . The S/P converter  204  receives the serial signal output from the CP remover  203 , converts the serial signal to parallel signals, and outputs the parallel signals to the FFT unit  205 . The FFT unit  205  receives the parallel signals output from the S/P converter  204 , performs FFT on the signals, and then outputs the FFTed signals to the P/S converter  207 . The P/S converter  207  receives the parallel signals output from the FFT unit  205 , converts them into a serial signal, and then outputs the converted serial signal to the demodulator  209 . The demodulator  209  demodulates the signal output from the P/S converter  207  according to a demodulation scheme corresponding to a modulation scheme used in a signal transmission apparatus corresponding to the signal reception apparatus, and outputs the demodulated signal to the decoder  211 . The decoder  211  decodes the signal output from the demodulator  209  according to a decoding scheme corresponding to an encoding scheme used in the signal transmission apparatus corresponding to the signal reception apparatus, and outputs the decoded signal. 
         [0011]    Meanwhile, in order to provide various types of services, next generation communication systems are being developed in pursuit of broadband communication systems capable of providing a broadband service. Current broadband communication systems that have been proposed up to now are systems designed based on a basic assumption that broadband communication systems are allocated different frequency bands for providing the broadband service, respectively. In order to provide the broadband service through different frequency bands, each frequency band requires a signal transmission apparatus as shown in  FIG. 1  and a signal reception apparatus as shown in  FIG. 2 , that is, as many signal transmission apparatuses of  FIG. 1  and as many signal reception apparatuses of  FIG. 2  as the number of used frequency bands are required, respectively. However, such multiple signal transmission apparatuses and signal reception apparatuses increase complexity in the hardware configuration. 
       SUMMARY OF THE INVENTION 
       [0012]    To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide an apparatus and a method for transmitting and receiving a signal in a communication system. 
         [0013]    Also, the present invention provides an apparatus and a method for transmitting and receiving a signal by using multiple frequency bands together. 
         [0014]    In accordance with an aspect of the present invention, there is provided a signal transmission apparatus in a communication system, including: a first Inverse Fast Fourier Transform (IFFT) unit for generating a first signal by performing IFFT on a first communication service signal corresponding to a first communication scheme; a first Cyclic Prefix (CP) inserter for generating a second signal by inserting a first CP having a length corresponding to the first communication scheme into the first signal; a second IFFT unit for generating a third signal by performing IFFT on a second communication service signal corresponding to a second communication scheme; a second CP inserter for generating a fourth signal by inserting a second CP having a length corresponding to the second communication scheme into the third signal; and a transmission unit for multiplexing the second signal and the fourth signal and transmitting the multiplexed signals. 
         [0015]    In accordance with another aspect of the present invention, there is provided a signal reception apparatus in a communication system, including: a reception unit for receiving an incoming signal and dividing the incoming signal into a first communication service signal corresponding to a first communication scheme and a second communication service signal corresponding to a second communication scheme; a first CP remover for generating a first signal by removing a first CP corresponding to the first communication scheme from the first communication service signal; a first Fast Fourier Transform (FFT) unit for performing FFT on the first signal; a second CP remover for generating a second signal by removing a second CP corresponding to the second communication scheme from the second communication service signal; and a second FFT unit for performing FFT on the second signal. 
         [0016]    In accordance with another aspect of the present invention, there is provided a signal reception apparatus in a communication system, including: a reception unit for receiving an incoming signal and dividing the incoming signal into a first communication service signal corresponding to a first communication scheme and a second communication service signal corresponding to a second communication scheme; a first CP remover for generating a first signal by removing a first CP corresponding to the first communication scheme from the first communication service signal; a second CP remover for generating a second signal by removing a second CP corresponding to the second communication scheme from the second communication service signal; and an FFT unit for performing FFT on the first signal and the second signal. 
         [0017]    In accordance with another aspect of the present invention, there is provided a signal reception apparatus in a communication system, including: a reception unit for receiving an incoming signal and dividing the incoming signal into a first communication service signal corresponding to a first communication scheme and a second communication service signal corresponding to a second communication scheme; a first band delay filter for generating a first signal by delaying the first communication service signal during a first time interval; a second band delay filter for generating a second signal by delaying the second communication service signal during a second time interval; a CP remover for generating a third signal by removing a first CP corresponding to the first communication scheme from the first signal and generating a fourth signal by removing a second CP corresponding to the second communication scheme from the second signal; and an FFT unit for performing FFT on the third signal and the fourth signal. 
         [0018]    In accordance with another aspect of the present invention, there is provided a signal transmission method in a communication system, including the steps of: generating a first signal by performing IFFT on a first communication service signal corresponding to a first communication scheme by a first IFFT unit; generating a second signal by inserting a first CP having a length corresponding to the first communication scheme into the first signal by a first CP inserter; generating a third signal by performing IFFT on a second communication service signal corresponding to a second communication scheme by a second IFFT unit; generating a fourth signal by inserting a second CP having a length corresponding to the second communication scheme into the third signal by a second CP inserter; and multiplexing and transmitting the second signal and the fourth signal by a transmission unit. 
         [0019]    In accordance with another aspect of the present invention, there is provided a signal reception method in a communication system, including the steps of: receiving an incoming signal and dividing the incoming signal into a first communication service signal corresponding to a first communication scheme and a second communication service signal corresponding to a second communication scheme by a reception unit; generating a first signal by removing a first CP corresponding to the first communication scheme from the first communication service signal by a first CP remover; performing FFT on the first signal by a first FFT unit; generating a second signal by removing a second CP corresponding to the second communication scheme from the second communication service signal by a second CP remover; and performing FFT on the second signal by a second FFT unit. 
         [0020]    In accordance with another aspect of the present invention, there is provided a signal reception method in a communication system, including the steps of: receiving an incoming signal and dividing the incoming signal into a first communication service signal corresponding to a first communication scheme and a second communication service signal corresponding to a second communication scheme by a reception unit; generating a first signal by removing a first CP corresponding to the first communication scheme from the first communication service signal by a first CP remover; generating a second signal by removing a second CP corresponding to the second communication scheme from the second communication service signal by a second CP remover; and performing FFT on the first signal and the second signal by an FFT unit. 
         [0021]    In accordance with another aspect of the present invention, there is provided a signal reception method in a communication system, including the steps of: receiving an incoming signal and dividing the incoming signal into a first communication service signal corresponding to a first communication scheme and a second communication service signal corresponding to a second communication scheme by a reception unit; generating a first signal by delaying the first communication service signal during a first time interval by a first band delay filter; generating a second signal by delaying the second communication service signal during a second time interval by a second band delay filter; generating a third signal by removing a first CP corresponding to the first communication scheme from the first signal and generating a fourth signal by removing a second CP corresponding to the second communication scheme from the second signal by a CP remover; and performing FFT on the third signal and the fourth signal by an FFT unit. 
         [0022]    Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
           [0024]      FIG. 1  is a block diagram illustrating a structure of a signal transmission apparatus of a conventional OFDM and OFDMA communication system; 
           [0025]      FIG. 2  is a block diagram illustrating a structure of a signal reception apparatus of a conventional OFDM and OFDMA communication system; 
           [0026]      FIG. 3  illustrates a structure of an OFDM signal of an LBC communication system according to an embodiment of the present invention; 
           [0027]      FIG. 4  is a block diagram illustrating a structure of a signal transmission apparatus in an LBC communication system according to an embodiment of the present invention; 
           [0028]      FIG. 5  is a block diagram illustrating a structure of a signal reception apparatus in an LBC communication system according to a first embodiment of the present invention; 
           [0029]      FIG. 6  is a block diagram illustrating a structure of a signal reception apparatus in an LBC communication system according to a second embodiment of the present invention; and 
           [0030]      FIG. 7  is a block diagram illustrating a structure of a signal reception apparatus in an LBC communication system according to a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]      FIGS. 3 through 7 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication systems. 
         [0032]    The present invention proposes an apparatus and a method for transmitting and receiving a signal in a communication system (OFDM and OFDMA communication system) using an Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA) scheme. For convenience of description, the following description employs a communication system (LBC communication system) using a Loosely Backward Compatibility (LBC) scheme as an example of the OFDM/OFDMA communication system. The LBC communication system refers to a communication system for either providing a communication system according to a legacy scheme and a new scheme or providing a communication system according to a Strictly Backward Compatibility (SBC) scheme and a new scheme. Further, the LBC communication system uses the same frequency band when providing a communication system according to the legacy scheme and when providing a communication system according to the SBC scheme. In the present invention, for convenience of description, it is assumed that the LBC communication system is a system providing a communication service according to the SBC scheme and the new scheme, a communication service according to the SBC scheme is called an “SBC communication service,” and a communication service according to the new scheme is called an “new communication service.” 
         [0033]    Further, the SBC frequency band, which is used in providing the SBC communication service, is named “band # 1 ,” and the new frequency band, which is used in providing the new communication service, is named “band # 2 .” Moreover, a Mobile Station (MS) providing only the SBC communication service is called an “SBC MS,” and an MS providing the LBC communication service is called an “LBC MS.” The SBC MS can transmit and receive a signal through only band # 1 , and the LBC MS can transmit and receive a signal through both band # 1  and band # 2 . 
         [0034]    Further, it is assumed that a Cyclic Prefix (CP) used in the SBC scheme has a length different from that of a CP used in the LBC scheme. Moreover, it is assumed that a guard band between band # 1  and band # 2  has a size that corresponds to a multiple of an OFDM sub-carrier interval. 
         [0035]      FIG. 3  illustrates a structure of an OFDM signal of an LBC communication system according to an embodiment of the present invention. 
         [0036]    Referring to  FIG. 3 , the Fc1 band corresponds to the SBC frequency band, i.e. band # 1 , and the Fc2 band corresponds to the new frequency band, i.e. band # 2  (note that the SBC frequency band is marked “SBC” and the new frequency band is marked “NEW” in  FIG. 3 ). Further, the Fc band refers to the entire frequency band including the Fc1 band, the Fc2 band, and the guard band between the Fc1 band and the Fc2 band. In addition, the length of the CP for the SBC communication service and the length of the CP for the new communication service are different from each other.  FIG. 3  shows an example in which the length of the CP for the SBC communication service is longer than the length of the CP for the new communication service. 
         [0037]    Next, structures of a signal transmission apparatus and a signal reception apparatus of an LBC communication system according to an embodiment of the present invention will be described with reference to  FIGS. 4 to 7 . 
         [0038]      FIG. 4  is a block diagram illustrating a structure of a signal transmission apparatus in an LBC communication system according to an embodiment of the present invention. 
         [0039]    Referring to  FIG. 4 , the signal transmission apparatus includes a new modulator  401 , a new IFFT unit  403 , a new CP inserter  405 , an Fc2 Intermediate Frequency (IF) processor  407 , an SBC modulator  409 , an SBC IFFT unit  411 , an SBC CP inserter  413 , an Fc1 IF processor  415 , a multiplexer  417 , and an Fc RF processor  419 . 
         [0040]    First, a new communication service signal generated in the signal transmission apparatus is input to the new modulator  401 . The new modulator  401  modulates the new communication service signal according to a preset modulation scheme and outputs the modulated signal to the new IFFT unit  403 . The preset modulation scheme may be, for example, a QAM scheme, a BPSK scheme, or a QPSK scheme. 
         [0041]    The new IFFT unit  403  receives the signal output from the new modulator  401 , performs IFFT on the signal, and then outputs the IFFTed signal to the new CP inserter  405 . The new CP inserter  405  inserts a CP in the signal output from the new IFFT unit  403  and then outputs the CP-inserted signal to the Fc2 IF processor  407 . The Fc2 IF processor  407  receives the signal output from the new CP inserter  405 , IF-processes the signal for the Fc2 band, and then outputs the IF-processed signal to the multiplexer  417 . 
         [0042]    Meanwhile, when an SBC communication service signal to be transmitted is generated in the signal transmission apparatus, the SBC communication service signal is input to the SBC modulator  409 . The SBC modulator  409  modulates the SBC communication service signal according to a modulation scheme corresponding to the modulation scheme used by the new modulator  401  and then outputs the modulated signal to the SBC IFFT unit  411 . The SBC IFFT unit  411  receives the signal output from the SBC modulator  409 , performs IFFT on the signal, and then outputs the IFFTed signal to the SBC CP inserter  413 . The SBC CP inserter  413  inserts a CP in the signal output from the SBC IFFT unit  411  and then outputs the CP-inserted signal to the Fc1 IF processor  415 . The Fc1 IF processor  415  receives the signal output from the SBC CP inserter  413 , IF-processes the signal for the Fc1 band, and then outputs the IF-processed signal to the multiplexer  417 . 
         [0043]    The multiplexer  417  receives the signals output from the Fc2 IF processor  407  and the Fc1 IF processor  415 , multiplexes the two input signals, and then outputs the multiplexed signal to the Fc RF processor  419 . The Fc RF processor  419  receives the signal output from the multiplexer  417 , RF-processes the signal for the Fc band, and then transmits the RF-processed signal to a signal reception apparatus through an antenna. 
         [0044]    In the signal transmission apparatus according to an embodiment of the present invention as shown in  FIG. 4 , the CP inserted by the new CP inserter  405  and the CP inserted by the SBC CP inserter  413  have different lengths, in order to improve the efficiency and performance of the system. 
         [0045]      FIG. 5  is a block diagram illustrating a structure of a signal reception apparatus in an LBC communication system according to a first embodiment of the present invention. 
         [0046]    Referring to  FIG. 5 , the signal reception apparatus includes an Fc RF processor  501 , an Fc2 IF processor  503 , a new CP remover  505 , a new FFT unit  507 , a new demodulator  509 , an Fc1 IF processor  511 , an SBC CP remover  513 , an SBC FFT unit  515 , and an SBC demodulator  517 . 
         [0047]    The Fc RF processor  501  receives a signal from a signal transmission apparatus, RF-processes the signal for an Fc band, and then outputs the RF-processed signal to the Fc2 IF processor  503  and the Fc1 IF processor  511 . The Fc2 IF processor  503  receives the Fc2 band signal output from the Fc RF processor  501 , IF-processes the Fc2 band signal, separates a new communication service signal from the Fc2 band signal, and then outputs the separated new communication service signal to the new CP remover  505 . The new CP remover  505  removes the CP from the signal output from the Fc2 IF processor  503  and then outputs the CP-removed signal to the new FFT unit  507 . The new FFT unit  507  receives the signal output from the new CP remover  505 , performs FFT on the signal, and then outputs the FFTed signal to the new demodulator  509 . 
         [0048]    In the meantime, the Fc1 IF processor  511  receives the Fc1 band signal output from the Fc RF processor  501 , IF-processes the Fc1 band signal, separates an SBC communication service signal from the Fc1 band signal, and then outputs the separated SBC communication service signal to the SBC CP remover  513 . The SBC CP remover  513  removes the CP from the signal output from the Fc1 IF processor  511  and then outputs the CP-removed signal to the SBC FFT unit  515 . The SBC FFT unit  515  receives the signal output from the SBC CP remover  513 , performs FFT on the signal, and then outputs the FFTed signal to the SBC demodulator  517 . 
         [0049]    In the signal reception apparatus as shown in  FIG. 5 , the SBC communication service signal and the new communication service signal are separately processed as described above. Therefore, even though the two signals have CPs of different lengths, there is no inter-channel interference (ICI) between the two signals. 
         [0050]      FIG. 6  is a block diagram illustrating a structure of a signal reception apparatus in an LBC communication system according to a second embodiment of the present invention. 
         [0051]    Referring to  FIG. 6 , the signal reception apparatus includes an Fc RF processor  601 , an Fc IF processor  603 , a new CP remover  605 , an LBC FFT unit  607 , a new demodulator  609 , an SBC CP remover  611 , and an SBC demodulator  613 . 
         [0052]    The Fc RF processor  601  receives a signal from a signal transmission apparatus, RF-processes the received signal for an Fc band, and then outputs the RF-processed signal to the Fc IF processor  603 . The Fc IF processor  603  receives the signal output from the Fc RF processor  601 , IF-processes the signal for the Fc band, divides the IF-processed signal into a new communication service signal and an SBC communication service signal, and outputs the new communication service signal to the new CP remover  605  and the SBC communication service signal to the SBC CP remover  611 . The new CP remover  605  removes the CP from the new communication service signal output from the Fc IF processor  603 , and outputs the CP-removed signal to the LBC FFT unit  607 . Meanwhile, the SBC CP remover  611  removes the CP from the SBC communication service signal output from the Fc IF processor  603 , and outputs the CP-removed signal to the LBC FFT unit  607 . The LBC FFT unit  607  receives the signals output from the new CP remover  605  and the SBC CP remover  611 , performs FFT on the signals, and then outputs the new communication service signal to the new demodulator  609  and the SBC communication service signal to the SBC demodulator  613 . The new demodulator  609  demodulates the new communication service signal output from the LBC FFT unit  607 . The SBC demodulator  613  demodulates the SBC communication service signal output from the LBC FFT unit  607 . 
         [0053]    The signal reception apparatus as described above employs a single LBC FFT unit  607  instead of employing multiple FFT units corresponding to different frequency bands. The LBC FFT unit  607  has a size corresponding to used frequency bands. Further, the LBC FFT unit  607  performs the FFT two times because the LBC FFT unit  607  should separately process the received signals, that is, the new communication service signal and the SBC communication service signal. 
         [0054]      FIG. 7  is a block diagram illustrating a structure of a signal reception apparatus in an LBC communication system according to a third embodiment of the present invention. 
         [0055]    Referring to  FIG. 7 , the signal reception apparatus includes an Fc RF processor  701 , an Fc IF processor  703 , a band delay filter  705 , an LBC CP remover  707 , an LBC FFT unit  709 , a new demodulator  711 , an SBC band delay filter  713 , and an SBC demodulator  715 . 
         [0056]    The Fc RF processor  701  receives a signal from a signal transmission apparatus, RF-processes the received signal for an Fc band, and then outputs the RF-processed signal to the Fc IF processor  703 . The Fc IF processor  703  receives the signal output from the Fc RF processor  701 , IF-processes the signal for the Fc band, divides the IF-processed signal into a new communication service signal and an SBC communication service signal, and outputs the new communication service signal to the new band delay filter  705  and the SBC communication service signal to the SBC band delay filter  713 . The new band delay filter  705  receives the new communication service signal output from the Fc IF processor  703 , delays the new communication service signal as much as the length of the CP of the new communication service signal, and outputs the delayed signal to the LBC CP remover  707 . 
         [0057]    In the meantime, the SBC band delay filter  713  receives the SBC communication service signal output from the Fc IF processor  703 , delays the SBC communication service signal as much as the length of the CP of the SBC communication service signal, and outputs the delayed signal to the LBC CP remover  707 . 
         [0058]    The LBC CP remover  707  receives the signals from the new band delay filter  705  and the SBC band delay filter  713 , removes CPs from the signals, and outputs the CP-removed signals to the LBC FFT unit  709 . The LBC FFT unit  709  receives the signals output from the LBC remover  707 , performs FFT on the signals, and then outputs the new communication service signal to the new demodulator  711  and the SBC communication service signal to the SBC demodulator  715 . The new demodulator  711  demodulates the new communication service signal output from the LBC FFT unit  709 . The SBC demodulator  715  demodulates the SBC communication service signal output from the LBC FFT unit  709 . 
         [0059]    Referring to  FIG. 3  again, the length of the CP of the SBC communication service signal is larger than the length of the CP of the new communication service signal. Therefore, the new band delay filter  705  of  FIG. 7  has a delay value corresponding to a difference between the length of the CP of the SBC communication service signal and the length of the CP of the new communication service signal, for each symbol. Further, the SBC band delay filter  713  has a delay value of “0.” Further, as described above, due to the delay by the new band delay filter  705  and the SBC band delay filter  713 , the new communication service signal and the SBC communication service signal have CPs of the same length. Therefore, the new communication service signal and the SBC communication service signal can be simultaneously subjected to the FFT operation, and thus only one-time FFT will be sufficient in the signal reception apparatus. 
         [0060]    In a communication system according to the present invention as described above, when multiple signals having different frequency bands are simultaneously transmitted, a signal transmission apparatus and a signal reception apparatus proposed by the present invention can reduce the hardware complexity and can improve system efficiency and performance. 
         [0061]    Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.