Patent Publication Number: US-8976899-B2

Title: Apparatus and method for transmitting/receiving data in mobile communication system

Description:
PRIORITY 
     This application claims priority under 35 U.S.C. 119(a) to an application filed in the Korean Intellectual Property Office on Nov. 11, 2010, and assigned Serial No. 10-2010-0111902, the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a method and apparatus for transmitting/receiving data in a mobile communication system, and more particularly, to a method and apparatus for transmitting/receiving data in consideration of carrier frequency in the mobile communication system using multiple transmission antennas for increasing data rate and system throughput. 
     2. Description of the Related Art 
     Orthogonal Frequency Division Multiplexing (Multiple Access) (OFDM(A)) has been adopted as a multi-carrier multiple access scheme for most evolved 3 rd  generation wireless communication technologies including, for example, 3 rd  Generation Partnership Project (3GPP) Long Term Evolution (LTE), 3GPP LTE-Advanced (LTE-A), and Institute of Electrical and Electronics Engineers (IEEE). 
     In a downlink portion of a wireless communication system that adopts multi-carrier multiple access, a base station (e.g., evolved Node B (eNB)) allocates resources to the terminal (e.g., User Equipment (UE) or Mobile Station (MS)) for data transmission in units of Resource Blocks (RBs), which are composed of a plurality of subcarriers and a plurality of OFDM symbols. 
     A Space Frequency Block Code (SFBC) technique has been considered as a transmit diversity scheme in present 3GPP LTE downlinks for a base station with two antennas. When there is a base station with 4 antennas, SFBC and Frequency Switched Transmit Diversity (FSTD) can be used. This technique is advantageous with respect to transmission spatial correlation and simplification of receiver implementation of a terminal. 
     This transmit diversity technique is implemented based on Orthogonal Frequency Division Multiplexing (OFDM). For a base station having two or four antennas, the symbols are transmitted on corresponding subcarriers, and two antennas and 2 subcarriers are added when operating in a combination of SFBC and FSTD. 
     However, general communication systems, including, for example, 3GPP GSM EDGE Radio Access Network (GERAN), are designed without taking OFDM into account. For 3GPP GERAN, dual carrier transmission is included as an optional technique in release  7  or later. Although SFBC can be considered, it is not possible to adopt the combination of SFBC and FSTD schemes. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention to provides a method and apparatus for transmitting/receiving data using transmit diversity technique. 
     In accordance with an aspect of the present invention, a method is provided for data transmission in a transmitter having at least two antennas. A number of antennas and a plurality of symbols are determined via an in-phase domain and a quadrature-phase domain. The symbols are mapped according to the number of antennas and the in-phase domain and the quadrature-phase domain. The mapped symbols are transmitted through the at least two antennas. 
     In accordance with another aspect of the present invention, a method is provided for data reception in a receiver. When symbols are received, a number of antennas and a number of carriers that are used to transmit the symbols are determined. The symbols are demodulated according to the number of antennas and the number of carriers. 
     In accordance with an additional aspect of the present invention, a data transmission apparatus is provided. The apparatus includes a modulator that determines a number of antennas and a plurality of symbols via an in-phase domain and a quadrature-phase domain. The apparatus also includes a symbol mapper that maps the plurality of symbols according to the number of antennas and the in-phase domain and the quadrature-phase domain. The apparatus further includes at least two antennas that transmit the mapped symbols. 
     In accordance with a further aspect of the present invention, a data reception apparatus includes a decoder that determines, when symbols are received, a number of antennas and a number of carriers that are used to transmit the symbols. The apparatus also includes a demodulator that demodulates the symbols according to the number of antennas and the number of carriers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic block diagram illustrating a mobile communication system, according to an embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating a configuration of an encoder, according to an embodiment of the present invention; 
         FIG. 3  is a diagram illustrating a Phase Shift Keying (PSK) signal constellation for transmitting symbols, according to an embodiment of the present invention; 
         FIG. 4  is a diagram illustrating a Quadrature Amplitude Modulation (QAM) signal constellation for transmitting symbols, according to an embodiment of the present invention; 
         FIG. 5  is a flowchart illustrating a data transmission method, according to an embodiment of the present invention; 
         FIG. 6  is a flowchart illustrating a symbol mapping procedure of the data transmission method of  FIG. 5 , according to an embodiment of the present invention; 
         FIG. 7  is a block diagram illustrating a configuration of a decoder of the receiver, according to an embodiment of the present invention; and 
         FIG. 8  is a flowchart illustrating a method for receiving symbols, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION 
     Embodiments of the present invention are described in detail with reference to the accompanying drawings in detail. The same or similar components may be designated by the same or similar reference numerals although they are illustrated in different drawings. Detailed descriptions of constructions or processes known in the art may be omitted to avoid obscuring the subject matter of the present invention. 
     The present invention provides a method for transmitting and receiving data using transmit diversity based on SFBC and FSTD in a various communication systems. 
     SFBC is a frequency domain channel coding technique applicable to a base station having two antennas. SFBC can be expressed as shown in Equation (1) below. Here, s0 and s1 denote symbols. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
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                               ⁢ 
                               
                                   
                               
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                               1 
                             
                           
                           
                             2 
                           
                         
                       
                     
                   
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     When the base station has 4 antennas, a transmit diversity technique, which is based on the combination of SFBC and FSTD, can be adopted. FSTD is a transmit diversity technique transmitting symbols as switched between antennas. The base station assigns the symbols as shown in Equation (2) below. Here, s0, s1, s2, and s3 denote symbols. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                             
                         
                       
                       
                         
                           
                             
                               
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     SFBC and FSTD are diversity techniques that are based on an OFDM scheme. Embodiments of the present invention propose a transmit diversity technique for use in a communication system designed without consideration of OFDM. 
     In a communication system such as 3GPP GERAN, the symbols carrying the data to be transmitted are divided between two bands and then modulated into In-phase (I) and Quadrature-phase (Q) signals with a phase difference of φ/2. The modulated data is transmitted to the terminal in a combined manner. The phases at which the data is modulated is referred to as an I domain and a Q domain, respectively. Assuming that the symbols modulated on the same carrier are transmitted, the symbols are transmitted on the subcarriers in OFDM-based communication system, while the symbols are transmitted on the I domain and the Q domain in the non-OFDM communication system. 
     Space Quadrature Block Code (SQBC) is a transmit diversity technique for transmitting symbols in the I domain and the Q domain. Unlike SFBC, in which the symbols are mapped to antennas and subcarriers, SQBC maps the symbols to antennas and domains depending on the number of symbols. 
       FIG. 1  is a schematic block diagram illustrating a mobile communication system, according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the mobile communication system includes a transmitter  110  and a receiver  150 . 
     The transmitter  110  maps the symbols according to the transmit diversity scheme proposed in embodiments of the present invention. The transmitter  110  is provided with a plurality of antennas. The transmitter  110  modulates the 2 or 4 symbols carrying the data to be transmitted into transmit symbols by means of an SQBC encoder  115 . 
     The SQBC encoder  115  determines spaces to transmit individual symbols, i.e. antennas. The SQBC encoder  115  determines the domain to which the symbols are mapped. The domains to which the symbols are mapped can be categorized into the I domain and the Q domain. The transmitter  110  can check the numbers of antennas and carriers through which the symbols carry the data using the I domain and the Q domain. The transmitter  110  can map the symbols according to the numbers of antennas and carriers. The transmitter  110  can transmit the symbols mapped to the individual antennas among symbols mapped to at least two antennas. 
     The receiver  150  estimates channels using symbols transmitted by the transmitter  110  by means of an SQBC decoder  153 . The channel-estimated symbols are processed by a demodulator  155  so as to output the transmitted data. The receiver  150  determines whether the channel-estimated symbols are transmitted through the same antenna or the same carrier such that the demodulator  155  process the data based on the determination result. Specifically, the I domain and the Q domain carrying the symbols are orthogonal with each other, resulting in no inter-domain interference. 
     When the symbols are transmitted through the same antenna and the same carrier, the orthogonality is not guaranteed due to channel estimation error and channel interference. In order to avoid inter-symbol interference, the receiver  150  can be provided with an interference canceller. When the symbols are transmitted through different antennas and different carriers, the receiver  150  demodulates the channel-estimated symbols according to the mapping conditions without needing the interference canceller. 
       FIG. 2  is a block diagram illustrating a configuration of an encoder, according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the SQBC encoder  115  includes a modulator  210  and a symbol mapper  220 . 
     The modulator  210  is responsible for modulating transmission symbols carrying data. The symbol mapper  220  maps the symbols according to the numbers of the antennas and carriers to be used for transmitting the symbols. The symbol mapper  220  checks whether the number of antennas to be used for transmitting symbols is 2 or 4, and maps the symbols according to whether the number of carriers to be used for transmitting the symbols is 1 or 2. 
     Embodiments of the present invention provide a method for transmitting symbols in an SQBC scheme in the communication system using the I domain and the Q domain. A description of a method for modulating symbols in the I domain and the Q domain is set forth in greater detail below. 
       FIG. 3  is a diagram illustrating a PSK signal constellation for transmitting symbols, according to an embodiment of the present invention. 
     Referring to  FIG. 3 , the symbols are mapped in PSK. PSK is a modulation scheme in which the data is carried in the phase of a sine wave, which is used as a carrier. In PSK, the carrier having a predetermined amplitude is divided into 2 sections (having a phase difference of 180 degrees), 4 sections (having phase difference of 90 degrees), or  8  sections (having a phase difference of 45 degrees) to transmit the symbols differentiated by phase.  FIG. 3  shows the symbols mapped to 8 different phases of the carrier wave 
       FIG. 4  is a diagram illustrating a QAM signal constellation for transmitting symbols, according to an embodiment of the present invention. 
     Referring to  FIG. 4 , the symbols can be mapped in a QAM scheme. QAM is a modulation scheme in which a predetermined quantity of digital signals is conveyed by changing a carrier signal and phase. QAM can use the size as a variable as well as the phase, unlike PSK. As shown in  FIG. 4 , the symbols quantized into 16 levels are mapped to the distributed 16 coordinates in the I domain and the Q domain. 
     The transmitter  110  transmits the symbols modulated in the above-described modulation scheme in SQBC. SQBC is a transmit diversity scheme transmitting the symbols mapped using the I domain and the Q domain. When using SQBC for symbol transmission, the transmitter  110  checks the numbers of antennas and carriers for symbol transmission and the number of symbols to be transmitted, and transmits the symbols according to formulas described in greater detail below. The embodiments of the present invention described herein are directed to situations in which the number of transmit antennas is 2 or 4, the number of carrier is 1 or 2, and the number of symbols to be transmitted is 2 or 4. 
     When the first condition of two transmit antennas, one carrier, and two transmission symbols s0 and s2 is fulfilled, the symbols are mapped as set forth in Equation (3) or (4) below. The transmitter  110  maps the symbols using one of Equations (3) and (4) as first condition formula. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                             
                         
                       
                       
                         
                           
                             
                               
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                   | 
                 
               
               
                 
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                   4 
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     Equations (3) and (4) are identical in symbol mapping, with the exception that symbol transmission order in the I domain and the Q domain is changed. Accordingly, the transmitter  110  can transmit the symbols as mapped to the antennas according to the I domain and the Q domain. 
     When the second condition of two transmit antennas, one carrier, and four transmission symbols s0, s1, s2, and s3 is fulfilled, four symbols are transmitted on the same carrier using the I domain and the Q domain and the QAM scheme. The transmitter  110  can map the symbols using one of Equations (5) and (6) as a second condition formula. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
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                               2 
                             
                           
                           
                             
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                               1 
                             
                           
                           
                             
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                               2 
                             
                           
                         
                       
                     
                   
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                   6 
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     Equations (5) and (6) are identical in symbol mapping, with the exception being the order of the I domain and the Q domain. Using Equations (5) or (6), the transmitter  110  maps four symbols in the I domain and the Q domain and transmits the symbols through two antennas. 
     When the third condition of two transmit antennas and two carriers is fulfilled, each carrier can have a predetermined bandwidth. The transmitter can map the symbols using Equation (7) as a third condition formula. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
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                               carrier 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             2 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
     Equation (7) is identical with the formula of the SFBC scheme. 
     When the fourth condition of four transmit antennas, two carriers, and four transmit symbols s0, s1, s2, and s3 is fulfilled, the transmitter multiplexes the symbols on the carriers dividing between the I domain and the Q domain. The transmitter  110  can map the symbols using one of Equations (8), (9), (10), and (11) as a fourth condition formula. 
                             antenna   ⁢             ⁢             ⁢   0               antenna   ⁢           ⁢   1           ⁢       [           s   ⁢           ⁢   0           s   ⁢           ⁢   1                 -   s     ⁢           ⁢   1   *           s   ⁢           ⁢   0   *           ]             carrier   ⁢           ⁢   1         2             |           (   8   )                       antenna   ⁢             ⁢             ⁢   0                           antenna   ⁢           ⁢   1               antenna   ⁢           ⁢   2                     antenna   ⁢           ⁢   3                 ⁢       [           s   ⁢           ⁢   0           s   ⁢           ⁢   1         0       0           0       0         s   ⁢           ⁢   2           s   ⁢           ⁢   3                 -   s     ⁢           ⁢   1   *           s   ⁢           ⁢   0   *         0       0           0       0           -   s     ⁢           ⁢   3   *           s   ⁢           ⁢   2   *           ]             carrier   ⁢           ⁢     1   /   Q             1   /   I                       2   /   Q                       2   /   I                     (   9   )                       antenna   ⁢             ⁢             ⁢   0                           antenna   ⁢           ⁢   1               antenna   ⁢           ⁢   2                     antenna   ⁢           ⁢   3                 ⁢       [           s   ⁢           ⁢   0           s   ⁢           ⁢   1         0       0           0       0         s   ⁢           ⁢   2           s   ⁢           ⁢   3                 -   s     ⁢           ⁢   1   *           s   ⁢           ⁢   0   *         0       0           0       0           -   s     ⁢           ⁢   3   *           s   ⁢           ⁢   2   *           ]             carrier   ⁢           ⁢     1   /   Q             1   /   I                       2   /   Q                       2   /   I                     (   10   )                         antenna   ⁢             ⁢             ⁢   0                           antenna   ⁢           ⁢   1               antenna   ⁢           ⁢   2                     antenna   ⁢           ⁢   3                 ⁢       [           s   ⁢           ⁢   0           s   ⁢           ⁢   1         0       0           0       0         s   ⁢           ⁢   2           s   ⁢           ⁢   3                 -   s     ⁢           ⁢   1   *           s   ⁢           ⁢   0   *         0       0           0       0           -   s     ⁢           ⁢   3   *           s   ⁢           ⁢   2   *           ]             carrier   ⁢           ⁢     1   /   I             2   /   Q                       1   /   Q                       2   /   I               |           (   11   )               
Using one of the formulas, the transmitter  110  can transmit the symbols as mapped in the I domain and the Q domain. The rows and columns of each formula can be changed from each other, and the symbols corresponding to individual antennas and carriers can be expressed differently from the definition.
 
       FIG. 5  is a flowchart illustrating a data transmission method, according to an embodiment of the present invention. 
     Referring to  FIG. 5 , the transmitter  110  performs encoding and modulating on the signal to be transmitted to the receiver, in step  510 . The transmitter  110  checks the numbers of antennas and carriers for transmitting the modulation signal, in step  520 . The transmitter  110  maps the symbols corresponding to the modulation signals using the formula selected, according to the numbers of antennas and carriers, in step  530 . Step  530  is described in greater detail below with reference to  FIG. 6 . The transmitter  110  transmits the mapped symbols through corresponding antennas, in step  540 . The transmitter  110  transmits symbol allocation information indicating a symbol allocation scheme to the receiver  150 . 
       FIG. 6  is a flowchart illustrating a symbol mapping procedure of the data transmission method of  FIG. 5 , according to an embodiment of the present invention. 
     Referring to  FIG. 6 , the transmitter determines whether the number of antennas to be used for transmitting symbols is 2, in step  610 . If the number of antennas for symbol transmission is 2, the transmitter  110  checks the number of carriers for transmitting the symbols, in step  615 . 
     The transmitter  110  determines whether the number of carriers is 1, in step  620 . If the number of carriers is 1, the transmitter  110  checks the number of symbols to be transmitted, in step  630 . The transmitter  110  determines whether the number of symbols is 2, in step  635 . If the number of symbols is 2, the transmitter  110  maps the symbols according to the first condition formula, in step  640 . The first condition formula is a symbol mapping for two antennas, one carrier, and two symbols s0 and s2. The first condition formula can be one of Equations (12) and (13) below. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               antenna 
                               ⁢ 
                               
                                 
                                     
                                 
                                 ⁢ 
                                 
                                     
                                 
                               
                               ⁢ 
                               0 
                             
                           
                         
                         
                           
                             
                               antenna 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                         
                       
                       ⁡ 
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                     
                     
                       
                         
                           
                             in 
                             - 
                             
                               phase 
                               ( 
                               I 
                               ) 
                             
                           
                         
                         
                           
                             quadrature 
                             ( 
                             Q 
                             ) 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   12 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       
                         
                           
                             
                               antenna 
                               ⁢ 
                               
                                 
                                     
                                 
                                 ⁢ 
                                 
                                     
                                 
                               
                               ⁢ 
                               0 
                             
                           
                         
                         
                           
                             
                               antenna 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                         
                       
                       ⁡ 
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                     
                     
                       
                         
                           
                             in 
                             - 
                             
                               phase 
                               ( 
                               I 
                               ) 
                             
                           
                         
                         
                           
                             quadrature 
                             ( 
                             Q 
                             ) 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   13 
                   ) 
                 
               
             
           
         
       
     
     If, in step  635 , it is determined that the number of symbols is not 2, and is 4, for example, the transmitter  110  maps the symbols according to the second condition formula, in step  645 . The second condition formula is a symbol mapping for two antennas, one carrier, and four symbols s0, s1, s2, and s3. The second condition formula can be one of Equations (14) and (15) below. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             
                               antenna 
                               ⁢ 
                               
                                 
                                     
                                 
                                 ⁢ 
                                 
                                     
                                 
                               
                               ⁢ 
                               0 
                             
                           
                         
                         
                           
                             
                               antenna 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                         
                       
                       ⁡ 
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                     
                     
                       
                         
                           
                             in 
                             - 
                             
                               phase 
                               ( 
                               I 
                               ) 
                             
                           
                         
                         
                           
                             quadrature 
                             ( 
                             Q 
                             ) 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   14 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                               
                                   
                               
                               ⁢ 
                               
                                   
                               
                             
                             ⁢ 
                             0 
                           
                         
                       
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                       
                     
                     ⁢ 
                     
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 3 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 2 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 2 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 3 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                       
                         
                           
                             
                               Q 
                               - 
                               1 
                             
                           
                           
                             
                               Q 
                               - 
                               2 
                             
                           
                           
                             
                               I 
                               - 
                               1 
                             
                           
                           
                             
                               I 
                               - 
                               2 
                             
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   15 
                   ) 
                 
               
             
           
         
       
     
     Returning to step  620 , if the number of carriers is not 1, and is 2, for example, the transmitter  110  maps the symbols according to the third condition formula, in step  650 . The third condition formula is a symbol mapping for two antennas and two carriers. Each carrier can have a predetermined bandwidth. The third condition formula is set forth below in Equation (16). 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                               
                                   
                               
                               ⁢ 
                               
                                   
                               
                             
                             ⁢ 
                             0 
                           
                         
                       
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                       
                     
                     ⁢ 
                     
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                       
                         
                           
                             
                               carrier 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             2 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   16 
                   ) 
                 
               
             
           
         
       
     
     If, at step  610 , the number of antennas for symbol transmission is not 2, and is 4, for example, the transmitter  110  maps the symbols according to the fourth condition formula, in step  660 . The fourth condition formula is a symbol mapping for four antennas, two carriers, and four symbols s0, s1, s2, and s3. The transmitter  110  divides the carriers between the I domain and the Q domain and multiplexes the symbols to be transmitted. The fourth condition formula can be one of Equations (17), (18), (19), and (20), according to the domains divided among the carriers. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                               
                                   
                               
                               ⁢ 
                               
                                   
                               
                             
                             ⁢ 
                             0 
                           
                         
                       
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                       
                     
                     ⁢ 
                     
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                       
                         
                           
                             
                               carrier 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             2 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   17 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                               
                                   
                               
                               ⁢ 
                               
                                   
                               
                             
                             ⁢ 
                             0 
                           
                         
                       
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                       
                     
                     ⁢ 
                     
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                       
                         
                           
                             
                               carrier 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             2 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   18 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                               
                                   
                               
                               ⁢ 
                               
                                   
                               
                             
                             ⁢ 
                             0 
                           
                         
                       
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                       
                     
                     ⁢ 
                     
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                       
                         
                           
                             
                               carrier 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             2 
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   19 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       
                         
                           
                             antenna 
                             ⁢ 
                             
                               
                                   
                               
                               ⁢ 
                               
                                   
                               
                             
                             ⁢ 
                             0 
                           
                         
                       
                       
                         
                           
                             
                               
                                 
                                   
                                     
                                       
                                         antenna 
                                         ⁢ 
                                         
                                             
                                         
                                         ⁢ 
                                         1 
                                       
                                     
                                   
                                   
                                     
                                       
                                         antenna 
                                         ⁢ 
                                         
                                             
                                         
                                         ⁢ 
                                         2 
                                       
                                     
                                   
                                 
                               
                             
                             
                               
                                 
                                   antenna 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   3 
                                 
                               
                             
                           
                         
                       
                     
                     ⁢ 
                     
                       
                         [ 
                         
                           
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             
                               0 
                             
                             
                               0 
                             
                           
                           
                             
                               0 
                             
                             
                               0 
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 2 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 3 
                               
                             
                           
                           
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 0 
                                 * 
                               
                             
                             
                               0 
                             
                             
                               0 
                             
                           
                           
                             
                               0 
                             
                             
                               0 
                             
                             
                               
                                 
                                   - 
                                   s 
                                 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 3 
                                 * 
                               
                             
                             
                               
                                 s 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 2 
                                 * 
                               
                             
                           
                         
                         ] 
                       
                       
                         
                           
                             
                               carrier 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 1 
                                 / 
                                 I 
                               
                             
                           
                           
                             
                               2 
                               / 
                               Q 
                             
                           
                           
                             
                                 
                             
                           
                           
                             
                               1 
                               / 
                               Q 
                             
                           
                           
                             
                                 
                             
                           
                           
                             
                               2 
                               / 
                               I 
                             
                           
                         
                       
                     
                   
                   | 
                 
               
               
                 
                   ( 
                   20 
                   ) 
                 
               
             
           
         
       
     
     In the above-described method, the transmitter  110  maps the transmission symbols in the I domain and the Q domain. 
       FIG. 7  is a block diagram illustrating a configuration of a decoder of the receiver, according to an embodiment of the present invention. 
     Referring to  FIG. 7 , the SQBC decoder  153  of the receiver  150  includes a channel estimator  710 , a combiner  720 , and a symbol demapper  730 . 
     The channel estimator  710  is capable of extracting channel estimation information for identifying the antennas and carriers used for transmitting the symbols. The combiner  720  combines the received symbols per antenna and per carrier based on the channel estimation information. The symbol demapper  730  estimates channels based on the symbols received per antenna and per carrier. The symbol demapper  730  can perform channel estimation based on the symbol mapping information transmitted by the transmitter  110 . 
       FIG. 8  is a flowchart illustrating a method for receiving symbols, according to an embodiment of the present invention. 
     Referring to  FIG. 8 , the receiver  150  receives symbol mapping information indicating the symbol mapping scheme transmitted by the transmitter  110  and stores the symbol mapping information. The symbol mapping information includes the information on the formula defined depending on a number of antennas transmitting symbols, a number of carriers on which symbols are transmitted, and a number of symbols transmitted. 
     The receiver receives signals, in step  810 , and checks the carriers on which the signals are transmitted, in step  820 . The receiver  150  determines whether the symbols are transmitted on the same carrier, in step  830 . If it is determined that the symbols are transmitted on the same carrier, the receiver  150  checks the antennas through which the symbols are transmitted, in step  840 . 
     The receiver  150  determines whether the received symbols are transmitted through the same antenna, in step  850 . If the symbols are transmitted through the same antenna, the receiver  150  performs interference cancellation, in step  860 . The methodology then proceeds to step  870 . 
     If it is determined that the symbols are not transmitted on the same carrier in step  830 , the methodology proceeds to step  870 . Further, if it is determined that the symbols are not transmitted through the same antenna in step  850 , the methodology proceeds to step  870 . The receiver  150  performs channel demodulation and decoding according to the number of antennas and the number of carriers, in step  870 . Specifically, the receiver  150  checks the number of antennas through which the symbols are transmitted and the number of carriers on which the symbols are transmitted, according to the symbol mapping information, and performs channel modulation and decoding based on the checking result. The symbol mapping information includes the information on the formula defined according to the number of transmit antennas, the number of carriers, and the number of symbol to be transmitted. The formulas for symbol mapping are described in detail above. 
     As described above, the data transmission/reception method and apparatus of the embodiments of the present invention is capable of adopting transmission diversity to various communication systems. Also, the data transmission/reception method and apparatus of the embodiments of the present invention is capable of improving the diversity gain of a diversity scheme such as FSTD while reducing number of carriers. Furthermore, the data transmission/reception method and apparatus of the present invention is capable of adopting a transmit diversity scheme robust to spatial correlation to various communication system with a small number of carriers, resulting in reduction of implementation complexity of the receiver. 
     While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention, as defined by the appended claims.