Abstract:
A channel spreading method in a CDMA communication system which spreads a pair of symbols obtained by repeating one symbol with a quasi-orthogonal code having a given length to transmit the spread symbols through a first antenna and spreads said symbol and an inverted symbol of said symbol with said quasi-orthogonal code to transmit the spread symbols through a second antenna. The method comprises spreading one of said pair of symbols with a portion of said quasi-orthogonal code and spreading another symbol of said pair of symbols with a remaining portion of said quasi-orthogonal code; and spreading said symbol with a portion of said quasi-orthogonal code and spreading said inverted symbol with the remaining portion of said quasi-orthogonal code.

Description:
PRIORITY 
   This application claims priority to an application entitled “Apparatus and Method for Spreading Channel Data in CDMA Communication System Using Orthogonal Transmit Diversity” filed in the Korean Industrial Property Office on Feb. 4, 1999 and assigned Serial No. 99-4899, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to an apparatus and method for spreading channel data in a CDMA communication system, and in particular, to an apparatus and method for spreading channel data in a CDMA communication system using orthogonal transmit diversity (OTD). 
   2. Description of the Related Art 
   In order to increase channel capacity, a CDMA (Code Division Multiple Access) communication system spreads channels using orthogonal codes. For example, the forward link of an IMT-2000 system performs channel spreading using orthogonal codes. A reverse link can also perform channel spreading using orthogonal codes through time alignment. An example of an orthogonal code that is typically used is a Walsh code. 
   The number of available orthogonal codes is determined depending upon a modulation method and a minimum data rate. However, in the proposed IMT-2000 CDMA system, the channels assigned to the users will increase in number in order to improve system performance. To this end, the future CDMA system includes a plurality of common channels and dedicated channels, and assigns the channels to the mobile stations, thereby increasing channel capacity. 
   However, even in the proposed IMT-2000 CDMA system, an increase in the utilization of the channels limits the number of available orthogonal codes. Further, the reduced number of available Walsh orthogonal codes limits the increase in channel capacity. In an effort to solve this problem, a method has been proposed for using quasi-orthogonal codes for channel spreading codes which have a minimum interference with the orthogonal codes and have a variable data rate. 
   In the IMT-2000 system, a 1× system uses a spreading code group having a spreading code rate  1 , and a 3× system uses a spreading code group having a spreading code rate  3 . In the 1× system, the spreading code generator stores spreading codes with a maximum length of  128  and generates a spreading code corresponding to a designated spreading code index to spread code symbols with the generated spreading code. Further, in the 3× system, the spreading code generator stores spreading codes with a maximum length of  256  and generates a spreading code corresponding to a designated spreading code index to spread code symbols with the generated spreading code. 
   The IMT-2000 system supports a transmit diversity, for which an orthogonal transmit diversity (ODT) scheme is typically used. Further, the IMT-2000 system can support a multicarrier system. Therefore, the IMT-2000 system can either employ or not employ orthogonal transmit diversity for the 1× direct spreading (DS) system according to circumstances. Further, for the 3× system, the IMT-2000 system can support both the multicarrier system and the direct spreading system, wherein orthogonal transmit diversity can be either used or not used for the direct spreading system. 
   The orthogonal transmit diversity scheme inputs the coded symbols to first and second antennas by dividing, and then divides again the signals input to the first and second antennas into two components respectively by demultiplexing to transmit them via the different antennas. At this point, the symbol rate decreases by half, because the signals input to the first and second antennas are divided into two components by the demultiplexer. Therefore, in order to match the halved symbol rate to the total symbol rate, the divided input symbols are repeated and the pair of symbols (both the original and the repeated symbol) are orthogonally spread. One of the divided components goes to the first antenna, and the second divided component goes to the second antenna. The signal input to the first and second antennas is divided again into two components by demultiplexing, which results in a total of 4 components from the original signal. Then, the 4 components are orthogonally spread with independent orthogonal codes. 
   In the orthogonal transmit diversity scheme, the respective component symbols undergo repetition before orthogonal spreading. Spreading the repeated symbols with the respective spreading factors is equivalent to spreading one symbol with twice the spreading factors. The receiver then accumulates the chips for two times the spreading factor duration during spreading and multiplexes the accumulated chips. Since spreading the chips using the quasi-orthogonal codes is equivalent to spreading each component chip with twice the spreading factor in the orthogonal transmit diversity scheme, the correlation property of the quasi-orthogonal codes may vary. Actually, when using orthogonal codes of length  256 , the correlation for 256 chip duration is ±16 and ±16j. Therefore, any orthogonal transmit diversity scheme should consider the effect of spreading the chips with twice the spreading factor, when selecting the quasi-orthogonal codes for use in the spreading scheme using the quasi-orthogonal codes. 
     FIG. 1  shows a transmitter using an orthogonal transmit diversity scheme. Referring to  FIG. 1 , a channel encoder  110  encodes input data into coded symbols, and an interleaver  130  interleaves the coded symbols and provides the interleaved symbols to an adder  120 . At this point, a long code generator  100  generates a long code and a decimator  105  decimates the generated long code and provides the decimated long code to the adder  120 . The adder  120  adds the decimated long code and the interleaved code symbols, and a demultiplexer  140  demultiplexes the signals input from the adder  120  to the first and second antennas. 
   The signals demultiplexed to the first and second antennas are input to demultiplexers  150  and  155 . The demultiplexer  150  demultiplexes the I-component input signal for the first antenna into I 1  and Q 1  components, and provides the I 1  and Q 1  components to symbol repeaters  160  and  162 , respectively. Similarly, the demultiplexer  155  demultiplexes the Q-component input signal for the second antenna into I 2  and Q 2  components, and provides the I 2  and Q 2  components to symbol repeaters  164  and  166 , respectively. The symbol repeaters  160  and  162  repeat their input signal I 1  and Q 1  two times, respectively. The symbol repeater  164  outputs the I 2  signal once and then outputs an inverted input signal. Similarly, the symbol repeater  166  outputs the Q 2  signal once and then outputs an inverted input signal. In order to maintain the orthogonality between the first and second antenna signals demultiplexed by the demultiplexer  140 , the symbol repeaters  160  and  162  repeat the input symbols in the different manner from the symbol repeaters  164  and  166 . Although the symbol repeaters  160  and  162  have a similar operation to the existing symbol repetition, the symbol repeaters  164  and  166  repeat the input symbols in different manner. For example, upon receipt of an input signal ‘1’, the repeaters  164  and  166  output a symbol ‘1’ and an inverted symbol ‘−1’. 
   Thereafter, a spreader  170  receives the signals output from the symbol repeaters  160  and  162 , and at the same time, a spreading code generator  180  generates a spreading code corresponding to an input spreading code index k 1  and provides the generated spreading code to the spreader  170 . The spreader  170  then spreads the signals output from the symbol repeaters  160  and  162  with the spreading code. Further, a spreader  175  receives the signals output from the symbol repeaters  164  and  166 , and at the same time, a spreading code generator  185  generates a spreading code corresponding to an input spreading code index k 2  and provides the generated spreading code to the spreader  175 . The spreader  175  then spreads the signals output from the symbol repeaters  164  and  166  with the spreading code. 
     FIG. 2  shows a receiver using orthogonal transmit diversity. Referring to  FIG. 2 , a despreader  270  receives input data rI 1  and rQ 1 , and at the same time, a spreading code generator  280  generates the spreading code corresponding to an input spreading code index k 1  and provides the generated spreading code to the despreader  270 . The despreader  270  then despreads the input data rI 1  and rQ 1  using the spreading code provided from the spreading code generator  280  and provides the despread signals to a multiplexer  250 . Similarly, a despreader  275  receives input data rI 2  and rQ 2 , and at the same time, a spreading code generator  285  generates the spreading code corresponding to an input spreading code index k 2  and provides the generated spreading code to the despreader  275 . The despreader  275  then despreads the input data rI 2  and rQ 2  using the spreading code provided from the spreading code generator  285  and provides the despread signals to a multiplexer  255 . 
   The multiplexer  250  multiplexes the signals output from the despreader  270  to output a first antenna component, and the multiplexer  255  multiplexes the signals output from the despreader  275  to output a second antenna component. A multiplexer  240  multiplexes the first and second antenna components and provides the multiplexed signals to an adder  220 . At the same time, a long code generator  200  generates a long code and a decimator  205  decimates the long code and provides the decimated long code to the adder  220 . The adder  220  then adds the decimated long code and the codes output from the multiplexer  240 , and a deinterleaver  230  deinterleaves the signals output from the adder  220 . A channel decoder  210  decodes the signals output from the deinterleaver  230 . 
     FIG. 3  shows a direct spreading scheme which does not use orthogonal transmit diversity. Referring to  FIG. 3 , a channel encoder  310  encodes input data into coded symbols, and an interleaver  330  interleaves the coded symbols and provides the interleaved symbols to an adder  320 . At the same time, a long code generator  300  generates a long code and a decimator  305  decimates the long code and provides the decimated long code to the adder  320 . The adder  320  then adds the decimated long code and the interleaved code symbols, and provides its outputs to a demultiplexer  340 . The demultiplexer  340  demultiplexes the input signals into an I-component signal and a Q-component signal. A spreader  370  receives the I-component and Q-component signals, and at the same time, a spreading code generator  380  generates a spreading code corresponding to an input spreading code index k and provides the generated spreading code to the spreader  370 . The spreader  370  then spreads the I-component and Q-component signals output from the demultiplexer  340  with the spreading code. 
     FIG. 4  shows a receiver which does not use orthogonal transmit diversity. Referring to  FIG. 4 , a despreader  470  receives input data I and Q, and at the same time, a spreading code generator  480  provides the despreader  470  with a spreading code corresponding to an input spreading code index k. The despreader  470  despreads the input data I and Q using the spreading code provided from the spreading code generator  480 , and provides the despread signals to a multiplexer  440 . The multiplexer  440  multiplexes the despread I and Q components, and provides the multiplexed signals to an adder  420 . At this point, a long code generator  400  generates a long code, and a decimator  405  decimates the long code and provides the decimated long code to the adder  420 . The adder  420  adds the decimated long code and the codes output from the multiplexer  440 , and provides its output signals to a deinterleaver  430 . The deinterleaver  430  deinterleaves the input signals and a channel decoder  410  decodes the deinterleaved signals. 
   The IMT-2000 system having the above spreading scheme supports a multicarrier system. The multicarrier mobile communication system transmits signals at one carrier of a 1.25 MHz band for the 1× system, and transmits the signals at three carriers for 3× system. The respective carriers are assigned independent orthogonal codes. When the 1× system is overlaid with the 3× system, using orthogonal codes of different lengths will cause interference between the systems. Herein, it will be assumed that the 1× system generates a quasi-orthogonal code using a mask function of length  128 , and the 3× system generates a quasi-orthogonal code using a mask function of length  256 . In this case, since a good correlation property is not guaranteed between a spreading code of length  128  which uses a mask function at a spreading rate  1  and a spreading code of length  128  which uses a mask function at a spreading rate  3  at each 1.25 MHz band, increased interference may occur between a user using a mask function at the spreading rate  1  and a user using a mask function at the spreading rate  3 . 
   When the 1× system uses the quasi-orthogonal code and the 3× system uses the orthogonal code, interference that the quasi-orthogonal code (QOF m +W k ) user of the 1×system, experiences from the orthogonal code (W j ) user of the 3× system can be given by the equation: 
                 ∑   i     T   i       ⁢     [       (       QOF     m   ,   i       +     W     k   ,   i         )     +     W     j   ,   i         ]       =         ∑   i     T   i       ⁢     [       QOF     m   ,   i       +     (       W     k   ,   i       +     W     j   ,   i         )       ]       =         ∑   i     T   i       ⁢     [       QOF     m   ,   i       +     W     s   ,   i         ]       &lt;     Θ   min                 (   1   )             
 
   That is, the interference satisfies an upper limit formula of the correlation for the quasi-orthogonal code. Therefore, in this case, this is not a serious matter. However, when the 1× system and 3× system both use the quasi-orthogonal code, interference that the quasi-orthogonal code (QOF m +W k ) user of the 1× system experiences from the quasi-orthogonal code (QOF n +W j ) user of the 3× system does not satisfy the upper limit formula, as shown in Equation (2) below: 
                 ∑   i     T   i       ⁢     [       (       QOF     m   ,   i       +     W     k   ,   i         )     +     (       QOF     n   ,   i       +     W     j   ,   i         )       ]       =         ∑   i     T   i       ⁢     [       (       QOF     m   ,   i       +     W     k   ,   i         )     +     (       QOF     n   ,   i       +     W     j   ,   i         )       ]       =       ∑   i     T   i       ⁢     [       (       QOF     m   ,   i       +     QOF     n   ,   i         )     +     W     s   ,   i         ]                 (   2   )             
 
   In this case, the mutual interference between the channels increases. 
   Therefore, when using the quasi-orthogonal codes of spreading code groups having different lengths, the mobile communication system stores the spreading codes of different lengths, and thus increases the hardware complexity. Further, using the spreading codes having different spreading rates in the overlay scheme deteriorates the interference property between two users thereby causing performance degradation. 
     FIG. 5  shows a transmitter for a 3× multicarrier system. Referring to  FIG. 5 , a channel encoder  500  encodes an input signal into coded symbols, and an interleaver  505  interleaves the coded symbols. A long code spreader  510  spreads the interleaved symbols with a long code output from a long code generator  515 . A demultiplexer  580  demultiplexes the spread signals into three components, each of which is divided again into I component and Q component, and provides the I and Q components to spreaders  520 ,  522  and  524 . 
   When the spreader  520  receives the signals from the demultiplexer  580 , a spreading code generator  540  generates a spreading code of length  256  corresponding to an input spreading code index k indicating a channel assigned to the user, and provides the generated spreading code to the spreader  520 . The spreader  520  spreads the long code spread signals at a chip rate of 1.2288 Mcps by operating each symbol of the input signal with a specified number of chips (256/2 n , 0≦n≦6) of the spreading code. When the spread signals are input to a PN spreader  530 , a short PN code generator  550  generates a short PN code and outputs the generated short PN code at a chip rate of 1.2288 Mcps. The PN spreader  530  PN spreads the input signals with the PN codes output from the short PN code generator  550 . Since the other spreaders and spreading code generators have the same operation, a detailed description will not be given in order to avoid duplication. 
     FIG. 6  shows a receiver for the 3× multicarrier system. Referring to  FIG. 6 , when the spread signals are input to a PN despreader  630 , a short PN code generator  650  generates a short PN code and outputs the generated short PN code at a chip rate of 1.2288 Mcps. The PN despreader  630  operates the input signals and the short PN code on a chip unit basis to output PN despread signals. 
   When the PN despread signals are input to a despreader  620 , a spreading code generator  640  generates a spreading code of a maximum length  256  corresponding to an input spreading code index k indicating a channel assigned to the user, and provides the generated spreading code to the despreader  620 . The despreader  620  then operates on each symbol of the PN despread signal with a specified number of chips (256/2 n , 0≦n≦6) of the spreading code, and accumulates the signals. The despread signals from the despreader  620  are provided to a multiplexer  680 . In the same manner, the signals input to PN despreaders  632  and  634  are provided to the multiplexer  680  after despreading. The multiplexer  680  then multiplexes the input signals despread through three different paths in the reverse order of signal demultiplexing performed in the transmitter. When the multiplexed signals are input to a long code despreader  610 , a long code generator  615  generates a long code. The long code despreader  610  despreads the multiplexed signals with the long code output from the long code generator  615 . A deinterleaver  605  deinterleaves the long code despread signals and a channel decoder  600  decodes the deinterleaved signals. 
   In the CDMA communication system using orthogonal transmit diversity, even though the same symbol is repeated two times when spreading the signals transmitted to the respective antennas, it is undesirably necessary to spread the symbols using the orthogonal codes according to the spreading rates of the respective symbols. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide a device and method for spreading a transmission signal with a spreading code having at least two times a spreading factor in a chip spreading rate in a CDMA communication system using orthogonal transmit diversity. 
   It is another object of the present invention to provide a device and method for enabling two users having different spreading rates to spread transmission signals using spreading codes of the same length in a CDMA communication system. 
   To achieve the above objects, there is provided a channel spreading method in a CDMA communication system which spreads a pair of symbols obtained by repeating one symbol with a quasi-orthogonal code having a given length to transmit the spread symbols through a first antenna and spreads said symbol and an inverted symbol of said symbol with said quasi-orthogonal code to transmit the spread symbols through a second antenna. The method comprises spreading one of said pair of symbols with a portion of said quasi-orthogonal code and spreading another symbol of said pair of symbols with a remaining portion of said quasi-orthogonal code; and spreading said symbol with a portion of said quasi-orthogonal code and spreading said inverted symbol with the remaining portion of said quasi-orthogonal code. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a diagram illustrating a transmitter using an orthogonal transmit diversity in a mobile communication system; 
       FIG. 2  is a diagram illustrating a receiver using orthogonal transmit diversity in a mobile communication system; 
       FIG. 3  is a diagram illustrating a transmitter not using orthogonal transmit diversity in a mobile communication system; 
       FIG. 4  is a diagram illustrating a receiver not using orthogonal transmit diversity in a mobile communication system; 
       FIG. 5  is a diagram illustrating a transmitter in a 3× multicarrier mobile communication system; 
       FIG. 6  is a diagram illustrating a receiver in a 3× multicarrier mobile communication system; 
       FIG. 7  is a diagram illustrating a spreading scheme for the transmitter and receiver in a mobile communication system according to an embodiment of the present invention; 
       FIG. 8  is a diagram illustrating a rotator in the spreading scheme of  FIG. 7  for the transmitter according to an embodiment of the present invention; 
       FIG. 9  is a diagram illustrating a rotator in the despreading scheme of  FIG. 7  for the receiver according to an embodiment of the present invention; 
       FIG. 10A  is a timing diagram explaining the operation of a spreader in a 1× direct spreading system not using orthogonal transmit diversity according to a first embodiment of the present invention; 
       FIG. 10B  is a timing diagram explaining the operation of a spreader at a first antenna in a 1× direct spreading system using orthogonal transmit diversity according to a first embodiment of the present invention; 
       FIG. 10C  is a timing diagram explaining the operation of a spreader at a second antenna in the 1× direct spreading system using orthogonal transmit diversity according to a first embodiment of the present invention; 
       FIG. 10D  is a timing diagram explaining the operation of a spreader in a 3× direct spreading system not using orthogonal transmit diversity according to a first embodiment of a present invention; 
       FIG. 10E  is a timing diagram explaining the operation of a spreader at a first antenna in the 3× direct spreading system using orthogonal transmit diversity according to a first embodiment of the present invention; 
       FIG. 10F  is a timing diagram explaining the operation of a spreader at a second antenna in the 3× direct spreading system using orthogonal transmit diversity according to a first embodiment of the present invention; 
       FIG. 10G  is a timing diagram explaining the operation of a spreader in a 3× multicarrier system using orthogonal transmit diversity according to a first embodiment of the present invention; 
       FIG. 11A  is a timing diagram explaining the operation of a spreader in the 1× direct spreading system not using orthogonal transmit diversity according to a second embodiment of the present invention; 
       FIG. 11B  is a timing diagram explaining the operation of a spreader at a first antenna in the 1× direct spreading system using orthogonal transmit diversity according to a second embodiment of the present invention; 
       FIG. 11C  is a timing diagram explaining the operation of a spreader at a second antenna in the 1× direct spreading system using orthogonal transmit diversity according to a second embodiment of the present invention; 
       FIG. 11D  is a timing diagram explaining the operation of a spreader in the 3× direct spreading system not using orthogonal transmit diversity according to a second embodiment of the present invention; 
       FIG. 11E  is a timing diagram explaining the operation of a spreader at a first antenna in the 3× direct spreading system using orthogonal transmit diversity according to a second embodiment of the present invention; 
       FIG. 11F  is a timing diagram explaining the operation of a spreader at a second antenna in the 3× direct spreading system using orthogonal transmit diversity according to a second embodiment of the present invention; 
       FIG. 11G  is a timing diagram explaining the operation of a spreader in the 3× multicarrier system using orthogonal transmit diversity according to a second embodiment of the present invention; 
       FIG. 12A  is a timing diagram explaining the operation of a spreader in the 1× direct spreading system not using orthogonal transmit diversity according to a third embodiment of the present invention; 
       FIG. 12B  is a timing diagram explaining the operation of a spreader at a first antenna in the 1× direct spreading system using orthogonal transmit diversity according to a third embodiment of the present invention; 
       FIG. 12C  is a timing diagram explaining the operation of a spreader at a second antenna in the 1× direct spreading system using orthogonal transmit diversity according to a third embodiment of the present invention; 
       FIG. 12D  is a timing diagram explaining the operation of a spreader in the 3× direct spreading system not using orthogonal transmit diversity according to a third embodiment of the present invention; 
       FIG. 12E  is a timing diagram explaining the operation of a spreader at a first antenna in the 3× direct spreading system using orthogonal transmit diversity according to a third embodiment of the present invention; 
       FIG. 12F  is a timing diagram explaining the operation of a spreader at a second antenna in the 3× direct spreading system using orthogonal transmit diversity according to a third embodiment of the present invention; and 
       FIG. 12G  is a timing diagram explaining the operation of a spreader in the 3× multicarrier system using orthogonal transmit diversity according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. 
   The term “orthogonal spreading” as used herein has the same meaning as the term “channel spreading”. Further, the term “spreading codes of the same length” means quasi-orthogonal code sets having the same length. 
   In an exemplary embodiment of the present invention, a description will be made of spreading and despreading operation of the IMT-2000 base station and mobile station, wherein the 1× system and the 3× system use spreading codes of the same length. It is also possible to apply the invention to the systems using the spreading codes of different lengths. 
   A description has already been made of the spreader in the transmitter and receiver of  FIGS. 1 to 6 . The spreaders for the transmitter and the receiver are identical except for the operation of a rotator therein. 
     FIG. 7  shows a spreader for a CDMA communication system according to an embodiment of the present invention. Herein, the quasi-orthogonal code is a code generated by mixing a Walsh orthogonal code and a QOF mask, wherein the QOF mask is comprised of a sign code QOF sign  and phase code QOF rot . Further, the phase code has the same value as a specific Walsh orthogonal code. 
   Referring to  FIG. 7 , when adders  710  and  715  receive I and Q signals, an adder  700  adds a first Walsh code Walsh1 and a sign component QOF sign  and provides its output to the adders  710  and  715 . Here, the first Walsh code Walsh1 is a Walsh code for generating the quasi-orthogonal code. The adder  710  adds the input signal I and the output signal of the adder  700  and provides its output to a rotator  720 , and the adder  715  adds the input signal Q and the output signal of the adder  700  and provides its output to the rotator  720 . The rotator  720  then rotates the signals input from the adders  710  and  715  according to QOF rot . Here, QOF rot  is used to control a phase of the spread signal. 
     FIG. 8  shows the rotator  720  in the spreader of  FIG. 7  for the transmitter. Referring to  FIG. 8 , the signal output from the adder  710  is input to a D 1  node of a selector  800  and a D 2  node of a selector  810 , and the signal output from the adder  715  is input to an inverter  820  and a D 1  node of the selector  810 . The inverter  820  inverts the input signal by multiplying it by ‘−1’ and provides the inverted signal to a D 2  node of the selector  800 . The selectors  800  and  810  output the signals received at their D 1  nodes when the QOF rot  is ‘0’, and otherwise, output the signals received at their D 2  nodes. 
     FIG. 9  shows the rotator  720  in the despreader of  FIG. 7  for the receiver. Referring to  FIG. 9 , the signal output from the adder  710  is input to a D 1  node of a selector  900  and an inverter  920 . The inverter  920  inverts the input signal by multiplying it by ‘−1’ and provides the inverted signal to a D 2  node of a selector  910 . The signal output from the adder  715  is input to a D 2  node of the selector  900  and a D 1  node of the selector  910 . The selectors  900  and  910  output the signals received at their D 1  nodes when QOF rot  is ‘0’, and otherwise, output the signals received at their D 2  nodes. 
   In the embodiments of the present invention, the quasi-orthogonal sequence mask function of length  128  and the quasi-orthogonal sequence of length  256  are used, which are disclosed in Korean patent application Nos. 99-888 and 99-1339. The quasi-orthogonal sequence mask function of length  128  and the quasi-orthogonal sequence of length  256  should have (1) a good full correlation property with the Walsh orthogonal code, (2) a good full correlation property between quasi-orthogonal codes, and (3) a good full partial correlation property with the Walsh orthogonal code. In addition, they should have a good partial correlation property between the quasi-orthogonal codes. The invention also provides quasi-orthogonal codes of length  128  and quasi-orthogonal codes of length  256  that satisfy the above conditions. 
   In the embodiments below, the orthogonal transmit diversity scheme uses the quasi-orthogonal sequences. Further, the multicarrier system also uses the quasi-orthogonal sequences. In the various embodiments below, the overall system operation is similar except the spreader. Further, since only the process for processing the spreading codes of different lengths is varied, the description of the invention will be made with reference to the timing diagrams for the symbols in the rotator  720  of  FIG. 7 . 
   A. First Embodiment 
   In the first embodiment, the 1× direct spreading system uses quasi-orthogonal sequences of length  128 , the 3× direct spreading system uses quasi-orthogonal sequences of length  256 , and the 3× multicarrier system uses quasi-orthogonal sequences of length  256 . 
   A description will be made of spreading operation in the 1× direct spreading system not using orthogonal transmit diversity (or 1× non-OTD direct spreading system), with reference to  FIGS. 7 and 10A . The 1× direct spreading system not using orthogonal transmit diversity uses the spreading codes of length  128 , shown in  FIG. 10A , output from the rotator  720  of  FIG. 7 . In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds a Walsh code of length  128  and a sign component QOF sign  of a quasi-orthogonal sequence of length  128  as shown in  FIG. 10A , and provides its output to the adders  710  and  715 . The adders  710  and  715  add the I and Q component input symbols, respectively, and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  rotates the 128-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  128 . Referring to  FIG. 10A , one input symbol is added to the Walsh orthogonal code of length  128  and the sign component QOF sign  of the quasi-orthogonal code of length  128 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  128 . 
   Next, a description will be made of spreading operation in the 1× direct spreading system using orthogonal transmit diversity (or  1 × OTD direct spreading system), with reference to  FIGS. 7 ,  10 B and  10 C, wherein  FIGS. 10B and 10C  show the timing diagrams for the first and second antennas, respectively. 
   In the first embodiment, the 1× direct spreading system using orthogonal transmit diversity uses the spreading code of length  128 , and with regard to the first antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 10B . When the first I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  128  and a sign component QOF sign  of a quasi-orthogonal sequence of length  128  as shown in  FIG. 10B , and provides its output to the adders  710  and  715 . The adders  710  and  715  add the I and Q component input symbols, respectively, and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  128 . 
   When the second I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  128  and a sign component QOF sign  of a quasi-orthogonal sequence of length  128  as shown in  FIG. 10B , and provides its output to the adders  710  and  715 . The adders  710  and  715  add the I and Q component input symbols, respectively, and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  128 . Referring to  FIG. 10B , the first input symbol is added to the Walsh orthogonal code of length  128  and the sign component QOF sign  of the quasi-orthogonal code of length  128 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  128 . Subsequently, in the same manner, the second input symbol is added to the Walsh orthogonal code of length  128  and the sign component QOF sign  of the quasi-orthogonal code of length  128 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  128 . 
   With regard to the second antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 10C . When the first I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  128  and a sign component QOF sign  of a quasi-orthogonal sequence of length  128  as shown in  FIG. 10C , and provides its output to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component input symbols, respectively, and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  128 . 
   The second I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  are the inverted symbols obtained by multiplying the first symbols by ‘−1’. When inverted symbols are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  128  and a sign component QOF sign  of a quasi-orthogonal sequence of length  128  as shown in  FIG. 10C , and provides its output to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component input symbols, respectively, and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  128 . 
   Referring to  FIG. 10C , the first input symbol out of the symbols repeated by the symbol repeaters  160  and  162  is added to the Walsh orthogonal code of length  128  and the sign component QOF sign  of the quasi-orthogonal code of length  128 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  128 . Subsequently, in the same manner, the second input symbol obtained by inverting the first symbol is added to the Walsh orthogonal code of length  128  and the sign component QOF sign  of the quasi-orthogonal code of length  128 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  128 . 
   A description will now be made of spreading operation in the 3× direct spreading system not using orthogonal transmit diversity, with reference to  FIGS. 7 and 10D . The 3× direct spreading system not using orthogonal transmit diversity uses spreading codes of length  256 , shown in  FIG. 10D , output from the rotator  720  of  FIG. 7 . In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds a Walsh code of length  256  and a sign component QOF sign  of a quasi-orthogonal sequence of length  256  as shown in  FIG. 10D , and provides its output to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component input symbols, respectively, and the output of the adder  700 , and provide its output signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . Referring to  FIG. 10D , one input symbol is added to the Walsh orthogonal code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Next, a description will be made of spreading operation in the 3× direct spreading system using orthogonal transmit diversity, with reference to  FIGS. 7 ,  10 E and  10 F, wherein  FIGS. 10E and 10F  show the timing diagrams for the first and second antennas, respectively. 
   In the first embodiment, the 3× direct spreading system using orthogonal transmit diversity uses the spreading code of length  256 , and, with regard to the first antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 10E . When the first I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  256  and a sign component QOF sign  of a quasi-orthogonal sequence of length  256  as shown in  FIG. 10E , and provides its output to the adders  710  and  715 . The adders  710  and  715  add the I and Q component input symbols and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   When the second I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  256  and a sign component QOF sign  of a quasi-orthogonal sequence of length  256  as shown in  FIG. 10E , and provides its output to the adders  710  and  715 . The adders  710  and  715  add the I and Q component input symbols and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . Referring to  FIG. 10E , the first input symbol is added to the Walsh orthogonal code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the second input symbol is added to the Walsh orthogonal code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   With regard to the second antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 10F . When the first I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  256  and a sign component QOF sign  of a quasi-orthogonal sequence of length  256  as shown in  FIG. 10F , and provides its output to the adders  710  and  715 . The adders  710  and  715  add the I and Q component input symbols and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   The second I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  are the inverted symbols obtained by multiplying the first symbols by ‘−1’. When inverted symbols are input to the adders  710  and  715  of  FIG. 7 , the adder  700  adds a Walsh code of length  256  and a sign component QOF sign  of a quasi-orthogonal sequence of length  256  as shown in  FIG. 10F , and provides its output to the adders  710  and  715 . The adders  710  and  715  add the I and Q component input symbols and the output of the adder  700 , and provide their output signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 10F , the first input symbol is added to the Walsh orthogonal code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the inverted symbol obtained by inverting the first symbol is added to the Walsh orthogonal code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   A description will now be made of spreading operation in the 3× multicarrier system with reference to  FIGS. 7 and 10G . In the 3× multicarrier system according to the first embodiment, the spreader uses the spreading codes of length  256  for all three carriers, and the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 10G . 
   In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , and provides its output to the adders  710  and  715 . Then, the adders  710  and  715  add the I and Q component symbols, respectively, and the output of the adder  700 , and provide their outputs to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . Referring to  FIG. 10G , one input symbol is added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   B. Second Embodiment 
   In the second embodiment, the 1× direct spreading system uses the quasi-orthogonal codes of length  256 , the 3× direct spreading system uses the quasi-orthogonal codes of length  256 , and the 3× multicarrier system uses the quasi-orthogonal codes of length  256 . 
   First, a description will be made of spreading operation in the 1× direct spreading system not using orthogonal transmit diversity, with reference to  FIGS. 7 and 11A . The 1× non-OTD direct spreading system according to the second embodiment uses quasi-orthogonal spreading codes of length  256 , and the spreading codes output from the rotator  720  of  FIG. 7  are shown in FIG  11 A. 
   In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11A , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the leading 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . After this process, when the next I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11A , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the following 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 11A , one input symbol is added to the leading 128-chip portion of the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the leading 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, the next input symbol is added to the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the following 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Next, a description will be made of spreading operation in the 1× OTD direct spreading system, with reference to  FIGS. 7 ,  11 B and  11 C, wherein  FIG. 11B  shows a timing diagram for the first antenna and  FIG. 11C  shows a timing diagram for the second antenna. The 1× OTD direct spreading system according to the second embodiment uses the quasi-orthogonal spreading codes of length  256 , and the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 11B . 
   In  FIG. 7 , when the first I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in FIG.  11 B, and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the leading 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . Thereafter, when the second I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11B , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the following 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 11B , the first input symbol out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  is added to the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the leading 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the second input symbol is added to the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the following 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   With regard to the second antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 11C . When the first I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11C , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the leading 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   The second I and. Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are inverted symbols obtained by inverting the first I and Q component symbols. When the inverted symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11C , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the following 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 11C , the first input symbol out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  is added to the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the leading 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the second input symbol obtained by inverting the first input symbol is added to the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the following 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Further, a description will be made of spreading operation in the 3× non-OTD direct spreading system, with reference to  FIGS. 7 and 11D . The 3× non-OTD direct spreading system according to the second embodiment uses the quasi-orthogonal spreading codes of length  256 , and the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 11D . 
   In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11D , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . Referring to  FIG. 11D , one input symbol is added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Next, a description will be made of spreading operation in the 3× OTD direct spreading system with reference to  FIGS. 7 ,  11 E and  11 F, wherein  FIG. 11E  shows a timing diagram of the first antenna and  FIG. 11F  shows a timing diagram of the second antenna. 
   The 3× OTD direct spreading system according to the second embodiment uses the spreading codes of length  256 , and with regard to the first antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 11E . When the I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 1E , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   When the second I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11E , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 11E , the first input symbol out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  is added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the second input symbol is added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   With regard to the second antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 11F . When the I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11F , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   The second I and Q symbols out of the symbols repeated by the symbol repeaters  164  and  166  are the inverted symbols obtained by inverting the first symbols. When the inverted symbols are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11F , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 11F , the first input symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the second input symbols obtained by inverting the first symbols are added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Next, a description will be made of spreading operation in the 3× multicarrier system, with reference to  FIGS. 7 and 11G . The 3× multicarrier system according to the second embodiment uses the spreading codes of length  256  for all the three carriers. The spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 11G . 
   When the I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 11G , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 11G , one input symbol is added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   C. Third Embodiment 
   In the third embodiment, the 1× direct spreading system uses the quasi-orthogonal codes of length  256 , the 3× direct spreading system uses the quasi-orthogonal codes of length  512 , and the 3× multicarrier system uses the quasi-orthogonal codes of length  256 . 
   The 3× direct spreading system according to the third embodiment requires a mask function of length  512 . In this context, the quasi-orthogonal sequences should have (1) a good full correlation property with the Walsh orthogonal codes, (2) a good full correlation property between the quasi-orthogonal codes, and (3) a good partial correlation property with the Walsh orthogonal codes, as disclosed in Korean patent application Nos. 99-888 and 99-1339, filed by the applicant. In addition, they should have a good partial correlation property between the quasi-orthogonal codes. The invention provides quasi-orthogonal codes that satisfy the above conditions. 
   Tables below show quasi-orthogonal sequence masks of length  512 . More specifically, Tables 1 and 3 show the quasi-orthogonal codes expressed in quaternary values, satisfying the above conditions, wherein ‘0’ indicates ‘1’, ‘1’ indicates ‘j’, ‘2’ indicates ‘−1’ and ‘3’ indicates ‘−j’. Further, Tables 2 and 4 show the quasi-orthogonal codes expressed in polar coordinates comprised of the sign component QOF sign  and the phase component QOF rot , wherein the phase component is equal to a specific Walsh code. Therefore, the respective signals are represented by W i . 
   
     
       
             
           
             
             
           
         
             
               TABLE 1 
             
             
                 
             
           
           
             
               f(x) = 1 + x 1  + x 2  + x 4  + x 5  + x 7  + x 9   
             
             
               g(x) = 3 + 3x 1  + x 2  + x 4  + 3x 5  + 2x 6  + 3x 7  + 2x 8  + x 9   
             
           
        
         
             
               e1: 
               0211312222133302130002111120221300311120203313001120221313000211 
             
             
                 
               1322023311022231023331002231332011022231132202330013110220111322 
             
             
                 
               3122021111200031021113000031330233022213130020330031330202111300 
             
             
                 
               2011310022311102132220113320223122311102201131001102001331000233 
             
             
                 
               2213112002111300330222133122021102111300221311201300203311200031 
             
             
                 
               1102001313222011001333202011310031000233332022312011310000133320 
             
             
                 
               3302003113000211003111200211312213000211330200312033130022133302 
             
             
                 
               0013110202333100332000131322023320111322223133201322023333200013 
             
             
               e2: 
               0222333131112220202211311311002033310222222031113313020022023133 
             
             
                 
               0222333131112220202211311311002011132000000213331131202200201311 
             
             
                 
               1311220202001131133322200222111322021311113102000002311133312000 
             
             
                 
               3133002020223313311100022000333122021311113102000002311133312000 
             
             
                 
               0002311111130222002031331131020013332220200033313133002002001131 
             
             
                 
               2220133333312000220213113313202213332220200033313133002002001131 
             
             
                 
               3313020000201311111320002220311120221131313322022000111331112220 
             
             
                 
               3313020000201311111320002220311102003313131100200222333113330002 
             
             
               e3: 
               0130302323301223120101303001233010030332102103102110100321321021 
             
             
                 
               3203031032210332031010210332100301121223231230231223233030230130 
             
             
                 
               0332100303101021322103323203031012012312300101120130120123303001 
             
             
                 
               1223011230232312011230012312120121321021211010031021031010030332 
             
             
                 
               1003211032030310033210032132320301301201011212233023013030010112 
             
             
                 
               2330122323121201122301121201013010210310322121100310320321101003 
             
             
                 
               1201013012230112231212012330122303323221213210211003033232032132 
             
             
                 
               0310102121103221102121323221033230010112302301300112122301301201 
             
             
               e4: 
               0121301023211210303223211232012112100103123201210121301001033032 
             
             
                 
               1030210132300301212332300323103003011012032310301030210110122123 
             
             
                 
               0103303223031232301023031210010330102303303223212321121023031232 
             
             
                 
               3230030110302101032310302123323003231030030110121012212310302101 
             
             
                 
               2101103003013230323021231030032310120301103003232101103021231012 
             
             
                 
               3010012112102321232130320121123201031210012112323010012130320103 
             
             
                 
               2123101203233212321221011012030132122101323021230301323003233212 
             
             
                 
               1210232130100121012112322321303201211232010312103032010330100121 
             
             
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
           
         
             
               TABLE 2 
             
             
                 
             
           
           
             
               f(x) = 1 + x 1  + x 2  + x 4  + x 5  + x 7  + x 9   
             
             
               g(x) = 3 + 3x 1  + x 2  + x 4  + 3x 5  + 2x 6  + 3x 7  + 2x 8  + x 9   
             
           
        
         
             
               Sign: 
               0100101111011101010001000010110100100010101101000010110101000100 
             
             
                 
               0111011100011110011110001110111000011110011101110001000110000111 
             
             
                 
               1011010000100010010001000010110111011101010010110010110101000100 
             
             
                 
               1000100011100001011110001110111011100001100010000001000110000111 
             
             
                 
               1101001001000100110111011011010001000100110100100100101100100010 
             
             
                 
               0001000101111000000111101000100010000111111011101000100000011110 
             
             
                 
               1101001001000100001000100100101101000100110100101011010011011101 
             
             
                 
               0001000101111000111000010111011110000111111011100111011111100001 
             
             
               rot: 
               W214 
             
             
               Sign: 
               0111111010001110101100100100001011100111111010001101010011011011 
             
             
                 
               0111111010001110101100100100001000011000000101110010101100100100 
             
             
                 
               0100110101000010011111100111000111010100001001000001100011101000 
             
             
                 
               1011001010111101100000011000111011010100001001000001100011101000 
             
             
                 
               0001100000010111001010110010010001111110100011101011001001000010 
             
             
                 
               1110011111101000110101001101101101111110100011101011001001000010 
             
             
                 
               1101010000100100000110001110100010110010101111011000000110001110 
             
             
                 
               1101010000100100000110001110100001001101010000100111111001110001 
             
             
               rot: 
               W172 
             
             
               Sign: 
               0010101111100111010000101000111000010111001001001000000110110010 
             
             
                 
               1101010011100111010000100111000100010111110110110111111010110010 
             
             
                 
               0111000101000010111001111101010001001101100000010010010011101000 
             
             
                 
               0111000110111101000110001101010010110010100000010010010000010111 
             
             
                 
               0001100011010100011100011011110100100100000101111011001010000001 
             
             
                 
               1110011111010100011100010100001000100100111010000100110110000001 
             
             
                 
               0100001001110001110101001110011101111110101100100001011111011011 
             
             
                 
               0100001010001110001010111110011110000001101100100001011100100100 
             
             
               rot: 
               W375 
             
             
               Sign: 
               0010100011100100101111100111001001000001011100100010100000011011 
             
             
                 
               0010100011100100101111100111001001000001011100100010100000011011 
             
             
                 
               0001101111010111100011010100000110001101101111101110010011010111 
             
             
                 
               1110010000101000011100101011111001110010010000010001101100101000 
             
             
                 
               1000001001001110111010110010011100010100001001111000001010110001 
             
             
                 
               1000001001001110111010110010011100010100001001111000001010110001 
             
             
                 
               1011000101111101110110000001010011011000111010110100111001111101 
             
             
                 
               0100111010000010001001111110101100100111000101001011000110000010 
             
             
               Rot: 
               W117 
             
             
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
           
         
             
               TABLE 3 
             
             
                 
             
           
           
             
               f(x) = 1 + x 2  + x 3  + x 5  + x 6  + x 8  + x 9   
             
             
               g(x) = 3 + 2x 1  + 3x 2  + 3x 3  + 2x 4  + 3x 5  + x 6  + 3x 8  + x 9   
             
           
        
         
             
               e1: 
               0121103021231210210112322321323010120103123221013032030110300121 
             
             
                 
               1210030110302303101223213010210121013010010332302303103021233032 
             
             
                 
               3230232130100323121021233212230323033212030130320323301001031012 
             
             
                 
               2101301001033230230310302123303212100301103023031012232130102101 
             
             
                 
               1210030110302303101223213010210103231232232110120121321203011210 
             
             
                 
               0121103021231210210112322321323032302321301003231210212332122303 
             
             
                 
               0323123223211012012132120301121012100301103023031012232130102101 
             
             
                 
               1012010312322101303203011030012123033212030130320323301001031012 
             
             
               e2: 
               0222313311312220200013111131222031330222222011313133022200023313 
             
             
                 
               0020111313330200002011133111202233312202202231111113002020223111 
             
             
                 
               3111020022021113311102000020333102003111111322022022133311132202 
             
             
                 
               3313222020003133113100022000313300021131131102220002113131332000 
             
             
                 
               2000313333132220200031331131000213110222000211313133200000021131 
             
             
                 
               2202111331110200002033313111020011132202020031111113220220221333 
             
             
                 
               3111202222023331133302002202333102001333111300200200133333312202 
             
             
                 
               3313000220001311331300020222313300023313131120002220113113112000 
             
             
               e3: 
               0222313311312220200013111131222031330222222011313133022200023313 
             
             
                 
               3122110202332213201122131300110202332213312211023122332002330031 
             
             
                 
               0013203333021322330231000013021111203100223102110013021133023100 
             
             
                 
               1102312200312011221320113320312200312011110231221102130000310233 
             
             
                 
               3100330220332231021122311322330220332231310033023100112020330013 
             
             
                 
               2011221313001102130033202011003131223320023300312011003113003320 
             
             
                 
               3302310000130211223102111120310000130211330231003302132200132033 
             
             
                 
               0031023311021300110231220031201133203122221320110031201111023122 
             
             
               e4: 
               0130233030231223302330010130011203100332102110031021322103102110 
             
             
                 
               2312011230231223302330012312233003100332320332213203100303102110 
             
             
                 
               0130011212011223120130010130233003102110320310033203322103100332 
             
             
                 
               2312233012011223120130012312011203102110102132211021100303100332 
             
             
                 
               1021100321322110031021103203100330231223231201120130011212011223 
             
             
                 
               3203322121322110031021101021322130231223013023302312233012011223 
             
             
                 
               1021322103102110213221103203322130233001013001122312011212013001 
             
             
                 
               3203100303102110213221101021100330233001231223300130233012013001 
             
             
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
           
         
             
               TABLE 4 
             
             
                 
             
           
           
             
               f(x) = 1 + x 2  + x 3  + + x 5  + x 6  + x 8  + x 9   
             
             
               g(x) = 3 + 2x 1  + 3x 2  + 3x 3  + 2x 4  + 3x 5  + x 6  + 3x 8  + x 9   
             
           
        
         
             
               Sign: 
               0010001010110100100001111110111000010001011110001011010000100010 
             
             
                 
               0100010000101101000111101000100010001000000111101101001010111011 
             
             
                 
               1110111010000111010010111101110111011101010010110111100000010001 
             
             
                 
               1000100000011110110100101011101101000100001011010001111010001000 
             
             
                 
               0100010000101101000111101000100001110111111000010010110101000100 
             
             
                 
               0010001010110100100001111110111011101110100001110100101111011101 
             
             
                 
               0111011111100001001011010100010001000100001011010001111010001000 
             
             
                 
               0001000101111000101101000010001011011101010010110111100000010001 
             
             
               rot: 
               W485 
             
             
               Sign: 
               0111101100101110100001000010111010110111111000101011011100011101 
             
             
                 
               0010000101110100001000011000101111101101101110000001001010111000 
             
             
                 
               1000010011010001100001000010111001001000000111011011011100011101 
             
             
                 
               1101111010001011001000011000101100010010010001110001001010111000 
             
             
                 
               1000101111011110100010110010000101000111000100101011100000010010 
             
             
                 
               1101000110000100001011101000010000011101010010000001110110110111 
             
             
                 
               1000101111011110011101001101111001000111000100100100011111101101 
             
             
                 
               1101000110000100110100010111101100011101010010001110001001001000 
             
             
               rot: 
               W172 
             
             
               Sign: 
               0100111001111101011100100100000110000010101100010100000101110010 
             
             
                 
               1011000101111101100011010100000101111101101100011011111001110010 
             
             
                 
               0001101111010111110110000001010000101000111001000001010011011000 
             
             
                 
               0001101100101000110110001110101100101000000110110001010000100111 
             
             
                 
               1000110110111110010011100111110110111110100011011000001010110001 
             
             
                 
               1000110101000001010011101000001010111110011100101000001001001110 
             
             
                 
               1101100000010100111001000010100000010100110110001101011100011011 
             
             
                 
               0010011100010100000110110010100011101011110110000010100000011011 
             
             
               rot: 
               W378 
             
             
               Sign: 
               0010111010110111101110000010000101000111001000010010111001001000 
             
             
                 
               1101000110110111101110001101111001000111110111101101000101001000 
             
             
                 
               0010000101000111010010000010111001001000110100011101111001000111 
             
             
                 
               1101111001000111010010001101000101001000001011100010000101000111 
             
             
                 
               0010000110111000010010001101000110110111110100010010000101000111 
             
             
                 
               1101111010111000010010000010111010110111001011101101111001000111 
             
             
                 
               0010111001001000101110001101111010111000001000011101000101001000 
             
             
                 
               1101000101001000101110000010000110111000110111100010111001001000 
             
             
               rot: 
               W283 
             
             
                 
             
           
        
       
     
   
   First, a description will be made of spreading operation in the 1× non-OTD direct sp reading system, with reference to  FIGS. 7 and 12A . The 1× non-OTD direct spreading system according to the third embodiment uses the quasi-orthogonal spreading codes of length  256 , and the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 12A . 
   In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 12A , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the leading 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . After this process, when the next I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 12A , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the following 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 12A , one input symbol is added to the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the leading 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the next input symbol is added to the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the following 128-portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Next, a description will be made of spreading operation in the 1× OTD direct spreading system, with reference to  FIGS. 7 ,  12 B and  12 C, wherein  FIG. 12B  shows a timing diagram for the first antenna and  FIG. 12C  shows a timing diagram for the second antenna. The 1× OTD direct spreading system according to the third embodiment uses the quasi-orthogonal spreading codes of length  256 , and with regard to the first antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 12B . 
   In  FIG. 7 , when the first I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 12B , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the leading 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . Thereafter, when the second I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 12B , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the following 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 12B , the first input symbol out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  is added to the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the leading 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the second input symbol is added to the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the following 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   With regard to the second antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 12C . When the first I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 12C , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the leading 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   The second I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are inverted symbols obtained by inverting the first I and Q component symbols. When the inverted symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 12C , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 128-chip input signals according to the following 128-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 12C , the first input symbol out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  is added to the Walsh code of length  128  and the leading 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the leading 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . Subsequently, in the same manner, the second input symbol obtained by inverting the first input symbol is added to the Walsh code of length  128  and the following 128-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the following 128-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Next, a description will be made of spreading operation in the 3× non-OTD direct spreading system, with reference to  FIGS. 7 and 12D . The 3× non-OTD direct spreading system according to the third embodiment uses the quasi-orthogonal spreading codes of length  512 , and the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 12D . 
   In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the leading 256-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  512 , as shown in  FIG. 12D , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the leading 256-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  512 . After this process, when the next I and Q component symbols are input to the adders  710  and  715 , the adder  700  adds the Walsh code of length  256  and the following 256-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  512 , as shown in  FIG. 12D , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the following 256-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  512 . 
   Referring to  FIG. 12D , one input symbol is added to the Walsh code of length  256  and the leading 256-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  512 , and then rotated according to the leading 256-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  512 . Subsequently, the next input symbol is added to the Walsh code of length  256  and the following 256-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  512 , and then rotated according to the following 256-portion of the phase component QOF rot  of the quasi-orthogonal code of length  512 . 
   Further, a description will be made of spreading operation in the 3× OTD direct spreading system, with reference to  FIGS. 7 ,  12 E and  12 F, wherein  FIG. 12E  shows the timing diagram for the first antenna and  FIG. 12F  shows the timing diagram for the second antenna. The 3× OTD direct spreading system according to the third embodiment uses the quasi-orthogonal spreading codes of length  512 . 
   With regard to the first antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 12E . In  FIG. 7 , when the I and Q component symbols are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the leading 256-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  512 , as shown in  FIG. 12E , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the leading 256-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  512 . When the second I and Q component symbols out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the following 256-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  512 , as shown in  FIG. 12E , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the following 256-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  512 . 
   Referring to  FIG. 12E , the first input symbol out of the symbols repeated by the symbol repeaters  160  and  162  of  FIG. 1  is added to the Walsh code of length  256  and the leading 256-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  512 , and then rotated according to the leading 256-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  512 . Subsequently, in the same manner, the second input symbol is added to the Walsh code of length  256  and the following 256-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  512 , and then rotated according to the following 256-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  512 . 
   With regard to the second antenna, the spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 12F . When the I and Q component symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the leading 256-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  512 , as shown in  FIG. 12F , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the leading 256-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  512 . 
   The second I and Q symbols out of the symbols repeated by the symbol repeaters  164  and  166  are the inverted symbols obtained by inverting the first symbols. When the inverted symbols are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the following 256-chip portion of the sign component QOF sign  of the quasi-orthogonal sequence of length  512 , as shown in  FIG. 12F , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the following 256-chip portion of the input phase component QOF rot  of the quasi-orthogonal code of length  512 . 
   Referring to  FIG. 12F , the first input symbols out of the symbols repeated by the symbol repeaters  164  and  166  of  FIG. 1  are added to the Walsh code of length  256  and the leading 256-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  512 , and then rotated according to the leading 256-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  512 . Subsequently, in the same manner, the second input symbols obtained by inverting the first symbols are added to the Walsh code of length  256  and the following 256-chip portion of the sign component QOF sign  of the quasi-orthogonal code of length  512 , and then rotated according to the following 256-chip portion of the phase component QOF rot  of the quasi-orthogonal code of length  512 . 
   Next, a description will be made of spreading operation in the 3× multicarrier system, with reference to  FIGS. 7 and 12G . The 3× multicarrier system according to the third embodiment uses the spreading codes of length  256  for all the three carriers. The spreading codes output from the rotator  720  of  FIG. 7  are shown in  FIG. 12G . 
   When the I and Q component symbols are input to the adders  710  and  715 , respectively, the adder  700  adds the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal sequence of length  256 , as shown in  FIG. 12G , and provides the added signals to the adders  710  and  715 . The adders  710  and  715  then add the I and Q component symbols, respectively, to the signals output from the adder  700 , and provide the added signals to the rotator  720 . The rotator  720  then rotates the 256-chip input signals according to the input phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   Referring to  FIG. 12G , one input symbol is added to the Walsh code of length  256  and the sign component QOF sign  of the quasi-orthogonal code of length  256 , and then rotated according to the phase component QOF rot  of the quasi-orthogonal code of length  256 . 
   As described above, the novel device and method can minimize interference between the spreading codes in the OTD direct spreading system and multicarrier system. Particularly, when overlay occurs at a certain carrier in the multicarrier system, it is possible to minimize the interference between 1× user and the 3× user. 
   While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.