Abstract:
Provided is a method for generating a preamble sequence group. The method includes creating a preamble sequence, calculating a cross-correlation value between sequences using the created preamble sequence, determining a limit cross-correlation value using the cross-correlation value to construct a preamble set used in the communication system, calculating a preamble set that satisfies the determined limit cross-correlation value, and terminating construction of the preamble set.

Description:
This application claims priority under 35 U.S.C. § 119 to an application entitled “Method for Generating Preamble Sequence Group” filed in the Korean Intellectual Property Office on Oct. 27, 2003 and assigned Serial No. 2003-75271, the contents of which are incorporated herein by reference. This application is a divisional of and claims priority under 35 U.S.C. § 121 to U.S. application Ser. No. 10/889,276 filed in the U.S. Patent and Trademark Office on Jul. 12, 2004, now U.S. Pat. No. 7,366,229 the contents of which are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a method for generating a preamble set or group in a communication system and an apparatus adopting the method, and in particular, to a method for generating an optimal preamble set using a plurality of sequences used to increase the limited number of channels, and an apparatus adopting the method. 
   2. Description of the Related Art 
   Generally, communication systems support communication services and include transmitters and receivers. 
     FIG. 1  is a block diagram of a general communication system. Referring to  FIG. 1 , a transmitter  10  and a receiver  20  provide communication services using frames. The transmitter  10  and the receiver  20  need to acquire synchronization information for accurate transmission and reception of the frames. 
   In order to acquire the synchronization information of the receiver  20 , the transmitter  10  transmits to the receiver  20  a synchronization signal indicating the start position of a frame transmitted to the receiver  20 . Upon receiving the synchronization signal and the frame transmitted from the transmitter  10 , the receiver  20  detects the start position of the received frame, i.e. frame timing, using the received synchronization signal. The receiver  20  demodulates the received frame using the detected frame timing. A specific preamble sequence, which has been previously agreed upon between the transmitter  10  and the receiver  20 , is used as the synchronization signal. 
   Various methods such as the use of a preamble or a pilot signal are used to acquire synchronization with transmitted frames in communication systems. In the case of acquiring synchronization using a preamble as mentioned above, it is a general practice to use a single preamble. 
     FIG. 2  illustrates a frame structure used in the general communication system. As shown in  FIG. 2 , a frame is composed of a preamble  30  and data  40 . The preamble  30  is used for frame synchronization and channel estimation. The data  40  includes data selected and requested by a user for transmission and/or control information of the communication system. 
   The frame structure may have a fixed format according to the communication system as shown in  FIG. 2 , but in other communication systems, the preamble  30  may be positioned in the middle of or at the end of the data  40 . In other words, a preamble in a frame may be positioned differently according to communication systems. 
   The preamble  30  shown in  FIG. 2  is comprised of a first signal  32  and a second signal  34 . The first signal  32  is used for frame synchronization and the second signal  34  is used for channel estimation. The structure of the preamble  30  shown in  FIG. 2  can be formed by divided into two parts, i.e. the first signal  32  and the second signal  34 , but may also be formed repetitively using a single signal or using several concatenated signals without dividing into two parts. In some communication systems, the first signal  32  is divided into two parts: one for frame synchronization and the other for packet synchronization. 
     FIG. 3  is a block diagram of a transmitter for the general communication system. 
   A data creator  51  receives data, creates transmission data, and transmits the created transmission data to a first multiplexer  54 . A media access control (MAC) header creator  52  creates a MAC header suitable for frames and transmits the created MAC header to the first multiplexer  54 . A physical (PHY) header creator  53  creates a PHY header suitable for the communication system and transmits the created PHY header to the first multiplexer  54 . The first multiplexer  54  multiplexes, i.e. mixes signals transmitted from the data creator  51 , the MAC header creator  52 , and the PHY header creator  53 , and transmits a resultant signal to a second multiplexer  57 . The resultant signal is referred to as transmission data. 
   A preamble creator  56  creates a preamble suitable for the communication system and transmits the created preamble to the second multiplexer  57 . The transmission data multiplexed by the first multiplexer  54  and the preamble created by the preamble creator  56  are input to the second multiplexer  57 . The second multiplexer  57  combines the transmission data from the first multiplexer  54  with the preamble from the preamble creator  56  to convert them into a transmission frame, and transmits the transmission frame to a receiver side through a transmission antenna  58 . 
     FIG. 4  is a block diagram of a receiver for the general communication system. Referring to  FIG. 4 , the frame transmitted from the transmitter of  FIG. 3  is received through a reception antenna  61 . The frame received through the reception antenna  61  is sent to a preamble analyzer  62  and a demultiplexer  63 . The preamble analyzer  62  analyzes the preamble in the received frame and detects synchronization information and channel estimation information. The preamble analyzer  62  determines the start position of the received frame using the synchronization information and the channel estimation information. 
   When the start point of the received frame is detected, the demultiplexer  63  separates the PHY header, the MAC header, and the data from the transmission data of the received frame with reference to the start position of the received frame. The separated signals are input to a PHY header analyzer  64 , an MAC header analyzer  65 , and a data restorer  66 . 
   The PHY header analyzer  64  analyzes the PHY header transmitted from the demultiplexer  63  and transmits the result of the header analysis to the data restorer  66 . The MAC header analyzer  65  analyzes the MAC header transmitted from the demultiplexer  63  and transmits the result of the header analysis to the data restorer  66 . The data restorer  66  restores the data transmitted from the demultiplexer  63  using the results of the header analysis transmitted from the PHY header analyzer  64  and the MAC header analyzer  65 . 
   The preamble sequence, which is agreed upon between the transmitter and the receiver of the communication system, may vary from system to system, but an aperiodic recursive multiplex (ARM) sequence will be used as the preamble sequence herein as an example. The preamble sequence that can be applied to the present invention is not limited to the ARM sequence, and may include any possible sequences that can be used as preambles. The ARM sequence exhibits superior auto-correlation in an aperiodic environment where sequences are not periodically transmitted. 
   Superior auto-correlation indicates that auto-correlation is high when the sequences are synchronized and auto-correlation is relatively low in other cases. 
     FIG. 5  is a block diagram of an ARM sequence generation apparatus that can generate an ARM sequence of a length  128 . As shown in  FIG. 5 , when one of the possible 2-bit combinations of real numbers (‘00’, ‘01’, ‘10’, or ‘11’) is input as an input signal, the input signal is also input to a first multiplexer  81 . The input signal is input to a first XOR operator  71 . 
   At the same time, a first signal generator  91  generates a signal ‘01’ or ‘10’ and outputs the generated signal to the first XOR operator  71 . The first XOR operator  71  performs an exclusive or operation on the signal output from the first signal generator  91  and the input signal, and outputs a result of the XOR operation to the first multiplexer  81 . The first multiplexer  81  alternatively multiplexes the input signal and a signal output from the first XOR operator  71  and creates an ARM sequence of 4 bits. The first multiplexer  81  outputs the created 4-bit ARM sequence to a second multiplexer  82  and a second XOR operator  72 . 
   A second signal generator  92  generates a signal ‘0101’ or ‘1010’ and outputs the generated signal to the second XOR operator  72  at the same time that the 4-bit ARM sequence is input to the second multiplexer  82  from the first multiplexer  81 . The second XOR operator  72  performs an XOR operation on the signal output from the second signal generator  92  and the 4-bit ARM sequence output from the first multiplexer  81 , and outputs a result of the XOR operation to the second multiplexer  82 . The second multiplexer  82  alternatively multiplexes the signal output from the first multiplexer  81  and the signal output from the second XOR operator  72  to create an ARM sequence of 8 bits and outputs the created 8-bit ARM sequence to a third multiplexer  83  and a third XOR operator  73 . 
   A third signal generator  93  generates a signal ‘01010101’ or ‘10101010’ and outputs the generated signal to the third XOR operator  73  at the same time that the 8-bit ARM sequence is input to the third multiplexer  83  from the second multiplexer  82 . The third XOR operator  73  performs an XOR operation on the signal output from the third signal generator  93  and the 8-bit ARM sequence output from the second multiplexer  82 , and outputs a result of the XOR operation to the third multiplexer  83 . The third multiplexer  83  alternatively multiplexes the signal output from the second multiplexer  82  and the signal output from the third XOR operator  73  to create an ARM sequence of 16 bits and outputs the created 16-bit ARM sequence to a fourth multiplexer  84  and a fourth XOR operator  74 . 
   A fourth signal generator  94  generates a signal ‘0101010101010101’ or ‘1010101010101010’ and outputs the created signal to the fourth XOR operator  74  at the same time that the 16-bit ARM sequence is input to the fourth multiplexer  84  from the third multiplexer  83 . The fourth XOR operator  74  performs an XOR operation on the signal output from the fourth signal generator  94  and the 16-bit ARM sequence output from the third multiplexer  83 , and outputs a result of the XOR operation to the fourth multiplexer  84 . The fourth multiplexer  84  alternatively multiplexes the signal output from the third multiplexer  83  and the signal output from the fourth XOR operator  74  to create an ARM sequence of 32 bits, and outputs the created 32-bit ARM sequence to a fifth multiplexer  85  and a fifth XOR operator  75 . 
   A fifth signal generator  95  generates a signal ‘01010101010101010101010101010101’ or ‘10101010101010101010101010101010’ and outputs the created signal to the fifth XOR operator  75  at the same time that the 32-bit ARM sequence is input to the fifth multiplexer  85  from the fourth multiplexer  84 . The fifth XOR operator  75  performs an XOR operation on the signal output from the fifth signal generator  95  and the 32-bit ARM sequence output from the fourth multiplexer  84  and outputs a result of the XOR operation to the fifth multiplexer  85 . The fifth multiplexer  85  alternatively multiplexes the signal output from the fourth multiplexer  84  and the signal output from the fifth XOR operator  75  to create an ARM sequence of 64 bits and outputs the created 64-bit ARM sequence to a sixth multiplexer  86  and a sixth XOR operator  76 . 
   A sixth signal generator  96  generates a signal ‘01010101010101010101010101010101010101010101010101010101010101’ or ‘1010101010101010101010101010101010101010101010101010101010101010’ and outputs the created signal to the sixth XOR operator  76  at the same time that the 64-bit ARM sequence is input to the sixth multiplexer  86  from the fifth multiplexer  85 . The sixth XOR operator  76  performs an XOR operation on the signal output from the sixth signal generator  96  and the 64-bit ARM sequence output from the fifth multiplexer  85 , and outputs a result of the XOR operation to the sixth multiplexer  86 . The sixth multiplexer  86  alternatively multiplexes the signal output from the fifth multiplexer  85  and the signal output from the sixth XOR operator  76  to create an ARM sequence of 128 bits. 
   The created 128-bit ARM sequence is used for detecting frame synchronization in the preamble analyzer  62  of  FIG. 4 . The length of the ARM sequence is extendable by powers of 2 such as 64, 128, 256, 512, and the like. Since the ARM sequence is produced from a plurality of inputs, the number of sequences of the ARM sequence is equal to two times the length of the ARM sequence. For example, the 128-bit ARM sequence shown in  FIG. 5  has a total of 256 (=128* 2) sequences. 
   Conventional preamble signals are only used for detection of frame synchronization and channel estimation in receivers of communication systems. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide a method for generating a superior sequence set from a sequence candidate group that can be used as preambles, and an apparatus adopting the method. 
   To achieve the above and other objects, there is provided a method for generating a preamble sequence group in a communication system having a transmitter and a receiver. The method comprises creating a preamble sequence, calculating a cross-correlation value between sequences using the created preamble sequence, determining a limit cross-correlation value using the cross-correlation value to construct a preamble set used in the communication system, calculating a preamble set that satisfies the determined limit cross-correlation value, and terminating construction of the preamble set. 
   According to the present invention, a preamble set useful for user or channel discrimination is provided using a plurality of preambles, thereby stabilizing user or channel discrimination. 

   
     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 block diagram of a general communication system; 
       FIG. 2  illustrates a frame structure used in the general communication system; 
       FIG. 3  is a block diagram of a transmitter for the general communication system; 
       FIG. 4  is a block diagram of a receiver for the general communication system; 
       FIG. 5  is a block diagram of an aperiodic recursive multiplex (ARM) sequence generation apparatus; 
       FIG. 6  is a flowchart illustrating a method for acquiring a preamble set according to an embodiment of the present invention; 
       FIG. 7  is a block diagram of a transmitter of a communication system using a preamble set according to an embodiment of the present invention; 
       FIG. 8  is a block diagram of the preamble creator of  FIG. 7  according to an embodiment of the present invention; 
       FIG. 9  is a block diagram of a receiver of a communication system using a preamble set according to an embodiment of the present invention; and 
       FIG. 10  is a block diagram of the preamble analyzer of  FIG. 9  according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Several preferred embodiments of the present invention will now be described in detail with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness. 
   In the present invention, a plurality of preambles is used for user or channel discrimination. A plurality of preamble signals or sequences, instead of a single preamble signal, should be used simultaneously for a communication system. Preamble signals should satisfy two conditions. First, the preamble signals should have superior characteristics. Second, the preamble signals should not be alike, that is, correlation between different preamble signals should be sufficiently low. 
   When a plurality of preamble sequences is used, receivers should be able to discriminate from among the preambles. When the receivers check correlation with other preamble signals except for those used for the receivers, the correlation should be sufficiently low so as to reduce the possibility that other preamble signals are regarded as those used for the receivers. 
   A preamble set used for user or channel discrimination can be structured in different forms. However, in the present invention, an ARM sequence having superior auto-correlation will be described. An ARM sequence set has a variable structure that provides preambles whose number is two times the length of the ARM sequence set, as shown in  FIG. 5 . ARM sequences are created to calculate a cross-correlation value of each of the ARM sequences. A limit correlation value is determined in relation to the number of preambles to be used for a desired communication system. Then preambles that satisfy the determined correlation value are acquired, and a preamble set is comprised of the acquired preambles. 
     FIG. 6  is a flowchart illustrating a method for acquiring a preamble set according to an embodiment of the present invention. 
   In step S 110 , an ARM sequence is created to acquire preamble sequences. In step S 120 , cross-correlation values between the preamble sequences are calculated using the created ARM sequence. In step S 130 , a limit correlation value is determined to provide the optimal preamble set to the communication system using the calculated cross-correlation values. In step S 140 , a preamble set that satisfies the determined limit cross-correlation value is constructed. In step S 150 , it is determined if the generated preamble set is suitable for the communication system. If the generated preamble set is suitable for the communication system, construction of the preamble set is terminated in step S 160 . 
   However, if the generated preamble set is not suitable for the communication system, the limit cross-correlation value is adjusted in step S 170 , and steps S 140  and S 150  are performed again. The generated preamble set is applied to the communication system. 
     FIG. 7  is a block diagram of a transmitter in a communication system using the preamble set according to an embodiment of the present invention. Referring to  FIG. 7 , a preamble creator  100  creates preamble signals according to an embodiment of the present invention and transmits the created preamble signals to a multiplexer  300 . Transmission data  200  is transmission data to be transmitted to a receiver and includes an MAC header and a PHY header. The multiplexer  300  performs multiplexing, i.e. multiplexes the preamble signals created by the preamble creator  100  and the transmission data  200 , and transmits a resultant signal to the receiver through a transmission antenna  350 . 
     FIG. 8  is a block diagram of the preamble creator  100  of  FIG. 7 . Referring to  FIG. 7 , the preamble creator  100  includes a preamble selector  120  and a preamble generator  140 . The preamble selector  120  selects one of the preambles available in a preamble set that is agreed upon between the transmitter and the receiver in the communication system, and transmits the preamble information to the preamble generator  140 . The preamble generator  140  creates the selected preamble using the preamble information transmitted from the preamble selector  120  and outputs the created preamble to the multiplexer  300 . 
     FIG. 9  is a block diagram of a receiver of the communication system using the preamble set according to an embodiment of the present invention. A frame signal transmitted from the transmitter of  FIG. 7  is received through a reception antenna  410 , and input to a preamble analyzer  500  and a data restorer  420 . 
   The preamble analyzer  500  analyzes the received frame signal, detects the preamble information, synchronization information and channel estimation information, and transmits the detected information to the data restorer  420 . The data restorer  420  restores the received data based on the information transmitted from the preamble analyzer  500 , and outputs the restored data  430 . 
     FIG. 10  is a block diagram of the preamble analyzer  500  of  FIG. 9 . Referring to  FIG. 10 , the preamble analyzer  500  includes a preamble generator  510 , a correlation measurer  520 , and a synchronization acquisition/channel estimation unit  540 . 
   A received signal  600  received through the reception antenna  410  is a frame signal transmitted from the transmitter of  FIG. 7 , and is input into the correlation measurer  520 . The preamble generator  510  generates preambles that are agreed upon between the transmitter and the receiver of the communication system, and inputs the preambles to the correlation measurer  520 . 
   The correlation measurer  520  measures cross-correlation between the frame signal, i.e., the received signal  600 , and the preambles generated by the preamble generator  510 , and detects preambles included in the received frame signal. The correlation measurer  520  transmits information on the detected preambles to the synchronization acquisition/channel estimation unit  540 . The synchronization acquisition/channel estimation unit  540  acquires synchronization information of the frame signal, i.e. the received signal  600 , and estimates channels based on the information received from the correlation measurer  520 . Here, the acquired information is transmitted to the data restorer  420  of  FIG. 9 . 
   As described above, the present invention provides a preamble set useful for user or channel discrimination using a plurality of preambles, thus providing more stable user or channel discrimination. 
   A process of acquiring a preamble set in  FIG. 6  will now be described herein below. The process below is intended to acquire preamble sets each comprised of 4 preambles, using 128-bit ARM sequences. First, all of the ARM sequences are created in step S 110  of  FIG. 6 . 
   Table 1 tabulates the 128-bit ARM sequences created in step S 110  of  FIG. 6 . In Table 1, values at the left side are indices of created ARM sequences and values at the right side are the ARM sequences. The indices of the ARM sequences shown in Table 1 are used to facilitate understanding of the present invention and may be defined differently or may not be used according to the preambles. In step S 120  of  FIG. 6 , cross-correlation values between created preamble sequences are calculated. 
   
     
       
             
             
           
             
           
             
             
           
         
             
               TABLE 1 
             
             
                 
             
           
           
             
               1 
               000100100001110100010010111000100001001000011101111011010001110100010010 
             
             
                 
               00011101000100101110001011101101111000100001001011100010 
             
             
               2 
               010001110100100001000111101101110100011101001000101110000100100001000111 
             
             
                 
               01001000010001111011011110111000101101110100011110110111 
             
             
               3 
               0010000100101110001000011101000100100001001011101101111000101110001000010 
             
             
                 
               0101110001000011101000111011110110100010010000111010001 
             
             
               4 
               0111010001111011011101001000010001110100011110111000101101111011011101000 
             
             
                 
               1111011011101001000010010001011100001000111010010000100 
             
             
               5 
               0001110100010010000111011110110100011101000100101110001000010010000111010 
             
             
                 
               0010010000111011110110111100010111011010001110111101101 
             
             
               6 
               0100100001000111010010001011100001001000010001111011011101000111010010000 
             
             
                 
               1000111010010001011100010110111101110000100100010111000 
             
             
               7 
               0010111000100001001011101101111000101110001000011101000100100001001011100 
             
             
                 
               0100001001011101101111011010001110111100010111011011110 
             
             
               8 
               0111101101110100011110111000101101111011011101001000010001110100011110110 
             
             
                 
               1110100011110111000101110000100100010110111101110001011 
             
             
               9 
               0001001011100010000100100001110100010010111000101110110111100010000100101 
             
             
                 
               1100010000100100001110111101101000111010001001000011101 
             
             
               10 
               010001111011011101000111010010000100011110110111101110001011011101000111 
             
             
                 
               10110111010001110100100010111000010010000100011101001000 
             
             
               11 
               001000011101000100100001001011100010000111010001110111101101000100100001 
             
             
                 
               11010001001000010010111011011110001011100010000100101110 
             
             
               12 
               011101001000010001110100011110110111010010000100100010111000010001110100 
             
             
                 
               10000100011101000111101110001011011110110111010001111011 
             
             
               13 
               000111011110110100011101000100100001110111101101111000101110110100011101 
             
             
                 
               11101101000111010001001011100010000100100001110100010010 
             
             
               14 
               010010001011100001001000010001110100100010111000101101111011100001001000 
             
             
                 
               10111000010010000100011110110111010001110100100001000111 
             
             
               15 
               001011101101111000101110001000010010111011011110110100011101111000101110 
             
             
                 
               11011110001011100010000111010001001000010010111000100001 
             
             
               16 
               011110111000101101111011011101000111101110001011100001001000101101111011 
             
             
                 
               10001011011110110111010010000100011101000111101101110100 
             
             
               17 
               000100100001110111101101000111010001001000011101000100101110001000010010 
             
             
                 
               00011101111011010001110111101101111000101110110100011101 
             
             
               18 
               010001110100100010111000010010000100011101001000010001111011011101000111 
             
             
                 
               01001000101110000100100010111000101101111011100001001000 
             
             
               19 
               001000010010111011011110001011100010000100101110001000011101000100100001 
             
             
                 
               00101110110111100010111011011110110100011101111000101110 
             
             
               20 
               011101000111101110001011011110110111010001111011011101001000010001110100 
             
             
                 
               01111011100010110111101110001011100001001000101101111011 
             
             
               21 
               000111010001001011100010000100100001110100010010000111011110110100011101 
             
             
                 
               00010010111000100001001011100010111011011110001000010010 
             
             
               22 
               010010000100011110110111010001110100100001000111010010001011100001001000 
             
             
                 
               01000111101101110100011110110111101110001011011101000111 
             
             
               23 
               001011100010000111010001001000010010111000100001001011101101111000101110 
             
             
                 
               00100001110100010010000111010001110111101101000100100001 
             
             
               24 
               011110110111010010000100011101000111101101110100011110111000101101111011 
             
             
                 
               0111010010000100011101001000010010001011100001000:110100 
             
             
               25 
               000100101110001011101101111000100001001011100010000100100001110100010010 
             
             
                 
               11100010111011011110001011101101000111011110110111100010 
             
             
               26 
               010001111011011110111000101101110100011110110111010001110100100001000111 
             
             
                 
               10110111101110001011011110111000010010001011100010110111 
             
             
               27 
               001000011101000111011110110100010010000111010001001000010010111000100001 
             
             
                 
               11010001110111101101000111011110001011101101111011010001 
             
             
               28 
               011101001000010010001011100001000111010010000100011101000111101101110100 
             
             
                 
               10000100100010111000010010001011011110111000101110000100 
             
             
               29 
               000111011110110111100010111011010001110111101101000111010001001000011101 
             
             
                 
               11101101111000101110110111100010000100101110001011101101 
             
             
               30 
               010010001011100010110111101110000100100010111000010010000100011101001000 
             
             
                 
               10111000101101111011100010110111010001111011011110111000 
             
             
               31 
               001011101101111011010001110111100010111011011110001011100010000100101110 
             
             
                 
               11011110110100011101111011010001001000011101000111011110 
             
           
        
         
             
               . 
             
             
               . 
             
             
               . 
             
           
        
         
             
               234 
               101110000100100010111000101101110100011110110111101110001011011110111000 
             
             
                 
               01001000101110001011011110111000010010000100011101001000 
             
             
               235 
               110111100010111011011110110100010010000111010001110111101101000111011110 
             
             
                 
               00101110110111101101000111011110001011100010000100101110 
             
             
               236 
               100010110111101110001011100001000111010010000100100010111000010010001011 
             
             
                 
               01111011100010111000010010001011011110110111010001111011 
             
             
               237 
               111000100001001011100010111011010001110111101101111000101110110111100010 
             
             
                 
               00010010111000101110110111100010000100100001110100010010 
             
             
               238 
               1011011101000111101101111011100001001000101110001011011110111000101101110 
             
             
                 
               1000111101101111011100010110111010001110100100001000111 
             
             
               239 
               1101000100100001110100011101111000101110110111101101000111011110110100010 
             
             
                 
               0100001110100011101111011010001001000010010111000100001 
             
             
               240 
               1000010001110100100001001000101101111011100010111000010010001011100001000 
             
             
                 
               1110100100001001000101110000100011101000111101101110100 
             
             
               241 
               1110110111100010000100101110001000010010000111010001001011100010111011011 
             
             
                 
               1100010000100101110001011101101111000101110110100011101 
             
             
               242 
               10111000101101110100011110110111010001110100100001000111101101111011100010 
             
             
                 
               110111010001111011011110111000101101111011100001001000 
             
             
               243 
               11011110110100010010000111010001001000010010111000100001110100011101111011 
             
             
                 
               010001001000011101000111011110110100011101111000101110 
             
             
               244 
               10001011100001000111010010000100011101000111101101110100100001001000101110 
             
             
                 
               000100011101001000010010001011100001001000101101111011 
             
             
               245 
               11100010111011010001110111101101000111010001001000011101111011011110001011 
             
             
                 
               101101000111011110110111100010111011011110001000010010 
             
             
               246 
               10110111101110000100100010111000010010000100011101001000101110001011011110 
             
             
                 
               111000010010001011100010110111101110001011011101000111 
             
             
               247 
               11010001110111100010111011011110001011100010000100101110110111101101000111 
             
             
                 
               011110001011101101111011010001110111101101000100100001 
             
             
               248 
               10001100100010110111101110001011011110110111010001111011100010111000010010 
             
             
                 
               001011011110111000101110000100100010111000010001110100 
             
             
               249 
               11101101000111010001001000011101000100101110001000010010000111011110110100 
             
             
                 
               011101000100100001110111101101000111011110110111100010 
             
             
               250 
               10111000010010000100011101001000010001111011011101000111010010001011100001 
             
             
                 
               001000010001110100100010111000010010001011100010110111 
             
             
               251 
               11011110001011100010000100101110001000011101000100100001001011101101111000 
             
             
                 
               101110001000010010111011011110001011101101111011010001 
             
             
               252 
               100010110111101101110100011110110111010010000100011101000111101110001011011 
             
             
                 
               11011011101000111101110001011011110111000101110000100 
             
             
               253 
               111000100001001000011101000100100001110111101101000111010001001011100010000 
             
             
                 
               10010000111010001001011100010000100101110001011101101 
             
             
               254 
               101101110100011101001000010001110100100010111000010010000100011110110111010 
             
             
                 
               00111010010000100011110110111010001111011011110111000 
             
             
               255 
               110100010010000100101110001000010010111011011110001011100010000111010001001 
             
             
                 
               00001001011100010000111010001001000011101000111011110 
             
             
               256 
               100001000111010001111011011101000111101110001011011110110111010010000100011 
             
             
                 
               10100011110110111010010000100011101001000010010001011 
             
             
                 
             
           
        
       
     
   
   Table 2 tabulates the largest cross-correlation values among the calculated cross-correlation values in Table 1. Here, a larger cross-correlation value implies that similarity between two signals is high. Such high similarity is likely to cause generation of an error during analyzing of preambles and searching of synchronization in the preamble analyzer  62  of the receiver of  FIG. 4 . Thus, the largest cross-correlation value among cross-correlation values between corresponding sequences is used as a representative value. 
   
     
       
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
             
           
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
             
           
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
             
             
             
           
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
             
             
             
             
           
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
         
             
               TABLE 2 
             
             
                 
             
           
           
             
                 
               1 
               2 
               3 
               4 
               5 
               6 
               7 
               8 
               9 
               10 
               11 
               12 
               13 
               14 
               15 
               16 
               17 
               18 
               19 
               20 
             
             
                 
             
             
                1 
               128 
               26 
               65 
               65 
               40 
               56 
               36 
               66 
               49 
               49 
               68 
               38 
               49 
               49 
               68 
               34 
               41 
               50 
               36 
               50 
             
             
                2 
               26 
               128 
               65 
               65 
               68 
               40 
               68 
               36 
               49 
               49 
               38 
               68 
               49 
               49 
               34 
               68 
               50 
               41 
               50 
               36 
             
             
                3 
               65 
               65 
               128 
               26 
               38 
               66 
               40 
               56 
               53 
               38 
               49 
               49 
               68 
               34 
               49 
               49 
               36 
               50 
               32 
               50 
             
             
                4 
               65 
               65 
               26 
               128 
               68 
               36 
               66 
               40 
               38 
               68 
               49 
               49 
               34 
               68 
               40 
               49 
               50 
               36 
               50 
               32 
             
             
                5 
               40 
               66 
               36 
               66 
               128 
               22 
               65 
               65 
               49 
               49 
               68 
               34 
               49 
               51 
               68 
               34 
               72 
               29 
               45 
               43 
             
             
                6 
               66 
               40 
               66 
               36 
               22 
               128 
               65 
               65 
               49 
               49 
               34 
               68 
               51 
               49 
               34 
               68 
               29 
               72 
               43 
               45 
             
             
                7 
               36 
               66 
               40 
               66 
               65 
               65 
               128 
               22 
               68 
               34 
               49 
               49 
               68 
               34 
               51 
               49 
               44 
               45 
               72 
               29 
             
             
                8 
               66 
               38 
               56 
               40 
               65 
               65 
               22 
               128 
               34 
               68 
               49 
               49 
               34 
               68 
               49 
               51 
               45 
               44 
               29 
               72 
             
             
                9 
               49 
               49 
               68 
               38 
               49 
               49 
               68 
               34 
               128 
               22 
               65 
               65 
               40 
               66 
               33 
               66 
               48 
               50 
               36 
               50 
             
             
                10 
               49 
               49 
               38 
               68 
               49 
               49 
               34 
               68 
               22 
               128 
               65 
               65 
               66 
               40 
               68 
               33 
               50 
               48 
               50 
               36 
             
             
                11 
               68 
               38 
               49 
               49 
               68 
               34 
               49 
               49 
               65 
               65 
               128 
               22 
               33 
               66 
               40 
               66 
               36 
               50 
               48 
               50 
             
             
                12 
               38 
               68 
               49 
               49 
               34 
               68 
               49 
               49 
               65 
               65 
               22 
               128 
               86 
               33 
               66 
               40 
               50 
               36 
               50 
               48 
             
             
                13 
               49 
               49 
               68 
               34 
               49 
               51 
               68 
               34 
               40 
               68 
               33 
               66 
               128 
               23 
               65 
               65 
               72 
               31 
               43 
               43 
             
             
                14 
               49 
               49 
               34 
               68 
               51 
               49 
               34 
               68 
               66 
               40 
               66 
               33 
               23 
               128 
               65 
               65 
               31 
               72 
               43 
               43 
             
             
                15 
               68 
               34 
               49 
               49 
               68 
               34 
               51 
               49 
               33 
               66 
               40 
               66 
               65 
               65 
               128 
               22 
               43 
               43 
               72 
               27 
             
             
                16 
               34 
               68 
               49 
               49 
               34 
               68 
               49 
               51 
               66 
               33 
               66 
               40 
               65 
               65 
               22 
               128 
               43 
               43 
               27 
               72 
             
             
                17 
               41 
               50 
               36 
               50 
               72 
               20 
               44 
               45 
               48 
               50 
               36 
               50 
               72 
               31 
               43 
               43 
               128 
               22 
               65 
               65 
             
             
                18 
               50 
               41 
               50 
               36 
               29 
               72 
               45 
               44 
               50 
               48 
               50 
               36 
               31 
               72 
               43 
               43 
               22 
               128 
               65 
               66 
             
             
                19 
               36 
               50 
               32 
               50 
               45 
               43 
               72 
               29 
               36 
               50 
               48 
               50 
               43 
               43 
               72 
               27 
               65 
               65 
               128 
               22 
             
             
                20 
               50 
               36 
               50 
               32 
               43 
               45 
               29 
               72 
               50 
               38 
               50 
               48 
               43 
               43 
               27 
               72 
               66 
               65 
               22 
               128 
             
             
                21 
               72 
               29 
               45 
               43 
               41 
               50 
               36 
               50 
               72 
               27 
               43 
               43 
               48 
               50 
               36 
               50 
               33 
               66 
               33 
               66 
             
           
        
         
             
               . 
               . 
             
             
               . 
               . 
             
             
               . 
               . 
             
           
        
         
             
               193 
               128 
               26 
               65 
               65 
               40 
               68 
               38 
               68 
               49 
               49 
               68 
               38 
               49 
               49 
               68 
               34 
               41 
               50 
               36 
               50 
             
             
               194 
               26 
               128 
               65 
               65 
               66 
               40 
               66 
               36 
               49 
               49 
               38 
               68 
               49 
               49 
               34 
               68 
               50 
               41 
               50 
               36 
             
             
               195 
               65 
               65 
               128 
               26 
               36 
               68 
               40 
               66 
               68 
               38 
               40 
               49 
               68 
               34 
               49 
               49 
               36 
               50 
               32 
               50 
             
             
               196 
               65 
               65 
               26 
               128 
               66 
               36 
               66 
               40 
               38 
               68 
               49 
               49 
               34 
               68 
               49 
               49 
               50 
               36 
               50 
               32 
             
             
               197 
               40 
               66 
               36 
               66 
               128 
               22 
               65 
               65 
               49 
               49 
               68 
               34 
               49 
               51 
               68 
               34 
               72 
               29 
               45 
               43 
             
             
               198 
               60 
               40 
               66 
               36 
               22 
               128 
               65 
               65 
               49 
               49 
               34 
               68 
               51 
               49 
               34 
               68 
               20 
               72 
               43 
               45 
             
             
               199 
               36 
               66 
               40 
               66 
               65 
               65 
               128 
               22 
               68 
               34 
               49 
               49 
               68 
               34 
               51 
               49 
               44 
               45 
               72 
               29 
             
             
               200 
               68 
               36 
               66 
               40 
               65 
               65 
               22 
               128 
               34 
               68 
               49 
               49 
               34 
               68 
               49 
               51 
               45 
               44 
               29 
               72 
             
             
               201 
               49 
               49 
               68 
               38 
               49 
               49 
               68 
               34 
               128 
               22 
               65 
               65 
               40 
               66 
               33 
               68 
               48 
               50 
               36 
               50 
             
             
               202 
               49 
               40 
               38 
               68 
               49 
               49 
               34 
               68 
               22 
               128 
               65 
               65 
               66 
               40 
               68 
               33 
               50 
               48 
               50 
               36 
             
             
               203 
               68 
               38 
               49 
               49 
               68 
               34 
               49 
               40 
               65 
               65 
               128 
               22 
               33 
               66 
               40 
               66 
               30 
               50 
               48 
               50 
             
             
               204 
               38 
               68 
               49 
               49 
               34 
               68 
               49 
               40 
               65 
               65 
               22 
               128 
               66 
               33 
               56 
               40 
               50 
               36 
               50 
               48 
             
             
               205 
               49 
               49 
               68 
               34 
               49 
               51 
               68 
               34 
               40 
               66 
               33 
               66 
               126 
               23 
               65 
               65 
               72 
               31 
               43 
               43 
             
             
               206 
               49 
               49 
               34 
               68 
               51 
               49 
               34 
               68 
               66 
               40 
               66 
               33 
               23 
               128 
               66 
               65 
               31 
               72 
               43 
               43 
             
             
               207 
               68 
               34 
               49 
               49 
               68 
               34 
               51 
               49 
               33 
               66 
               40 
               66 
               65 
               65 
               128 
               22 
               43 
               43 
               72 
               27 
             
             
               208 
               34 
               68 
               49 
               49 
               34 
               66 
               49 
               51 
               66 
               33 
               66 
               40 
               05 
               65 
               22 
               128 
               43 
               43 
               27 
               72 
             
             
               209 
               41 
               50 
               36 
               50 
               72 
               29 
               44 
               45 
               48 
               50 
               36 
               50 
               72 
               31 
               43 
               43 
               128 
               22 
               65 
               65 
             
             
               210 
               50 
               41 
               50 
               36 
               29 
               72 
               45 
               44 
               50 
               48 
               50 
               36 
               31 
               72 
               43 
               43 
               22 
               128 
               65 
               65 
             
             
               211 
               36 
               50 
               32 
               50 
               45 
               43 
               72 
               29 
               36 
               50 
               48 
               50 
               43 
               43 
               72 
               27 
               65 
               65 
               128 
               22 
             
           
        
         
             
               . 
               . 
             
             
               . 
               . 
             
             
               . 
               . 
             
           
        
         
             
               245 
               40 
               33 
               52 
               31 
               33 
               33 
               52 
               42 
               40 
               46 
               29 
               46 
               80 
               30 
               43 
               43 
               56 
               35 
               60 
               34 
             
             
               246 
               33 
               40 
               31 
               52 
               33 
               33 
               42 
               52 
               46 
               40 
               46 
               29 
               30 
               80 
               43 
               43 
               36 
               56 
               34 
               60 
             
             
               247 
               52 
               26 
               40 
               33 
               52 
               42 
               33 
               33 
               28 
               46 
               40 
               45 
               43 
               43 
               80 
               30 
               60 
               34 
               56 
               35 
             
             
               248 
               26 
               52 
               33 
               40 
               42 
               52 
               33 
               33 
               46 
               28 
               46 
               40 
               43 
               43 
               30 
               60 
               34 
               60 
               35 
               56 
             
             
               249 
               80 
               30 
               43 
               43 
               40 
               46 
               36 
               46 
               33 
               42 
               52 
               30 
               40 
               33 
               52 
               26 
               60 
               30 
               43 
               41 
             
             
               250 
               30 
               80 
               43 
               43 
               46 
               40 
               46 
               36 
               42 
               33 
               30 
               52 
               33 
               40 
               26 
               52 
               30 
               60 
               41 
               43 
             
             
               251 
               43 
               43 
               80 
               30 
               36 
               46 
               40 
               46 
               52 
               30 
               39 
               42 
               52 
               31 
               40 
               33 
               41 
               43 
               80 
               30 
             
             
               252 
               43 
               43 
               30 
               80 
               46 
               36 
               46 
               40 
               30 
               52 
               42 
               39 
               31 
               52 
               33 
               40 
               43 
               41 
               30 
               80 
             
             
               253 
               40 
               46 
               36 
               48 
               80 
               38 
               43 
               43 
               40 
               33 
               52 
               31 
               33 
               33 
               52 
               42 
               40 
               46 
               36 
               42 
             
             
               254 
               46 
               40 
               46 
               36 
               38 
               80 
               43 
               43 
               33 
               40 
               31 
               52 
               33 
               33 
               42 
               52 
               46 
               40 
               42 
               36 
             
             
               255 
               36 
               46 
               40 
               46 
               43 
               43 
               80 
               38 
               52 
               26 
               40 
               33 
               52 
               42 
               33 
               33 
               36 
               42 
               40 
               46 
             
             
               256 
               46 
               36 
               46 
               40 
               43 
               43 
               38 
               60 
               26 
               52 
               33 
               40 
               42 
               52 
               33 
               33 
               42 
               36 
               46 
               40 
             
             
                 
             
           
        
         
             
                 
                 
               21 
               . . . 
               245 
               246 
               247 
               248 
               249 
               250 
               251 
               252 
               253 
               254 
               155 
               256 
             
             
                 
                 
             
             
                 
                1 
               72 
               . . . 
               33 
               42 
               52 
               30 
               40 
               33 
               52 
               26 
               80 
               30 
               43 
               43 
             
             
                 
                2 
               29 
                 
               42 
               33 
               30 
               52 
               33 
               40 
               26 
               52 
               30 
               80 
               43 
               43 
             
             
                 
                3 
               45 
                 
               52 
               30 
               39 
               42 
               52 
               31 
               40 
               33 
               43 
               43 
               80 
               30 
             
             
                 
                4 
               43 
                 
               30 
               52 
               42 
               39 
               31 
               52 
               33 
               40 
               43 
               43 
               30 
               80 
             
             
                 
                5 
               41 
                 
               40 
               33 
               52 
               31 
               33 
               33 
               52 
               42 
               40 
               46 
               36 
               46 
             
             
                 
                6 
               50 
                 
               33 
               40 
               31 
               52 
               33 
               33 
               42 
               52 
               46 
               40 
               46 
               36 
             
             
                 
                7 
               38 
                 
               52 
               26 
               40 
               33 
               52 
               42 
               33 
               33 
               38 
               46 
               40 
               46 
             
             
                 
                8 
               50 
                 
               26 
               52 
               33 
               40 
               42 
               52 
               33 
               33 
               48 
               36 
               46 
               40 
             
             
                 
                9 
               72 
                 
               60 
               30 
               43 
               43 
               40 
               46 
               28 
               46 
               33 
               42 
               52 
               30 
             
             
                 
                10 
               27 
                 
               30 
               80 
               43 
               43 
               46 
               40 
               46 
               28 
               42 
               33 
               30 
               52 
             
             
                 
                11 
               43 
                 
               43 
               43 
               80 
               30 
               20 
               46 
               40 
               46 
               52 
               30 
               39 
               42 
             
             
                 
                12 
               43 
                 
               43 
               43 
               30 
               80 
               46 
               29 
               46 
               40 
               30 
               52 
               42 
               39 
             
             
                 
                13 
               48 
                 
               40 
               46 
               29 
               46 
               80 
               30 
               43 
               43 
               40 
               33 
               52 
               31 
             
             
                 
                14 
               50 
                 
               48 
               40 
               46 
               29 
               30 
               80 
               43 
               43 
               33 
               40 
               31 
               52 
             
             
                 
                15 
               36 
                 
               28 
               46 
               40 
               46 
               43 
               43 
               80 
               30 
               52 
               26 
               40 
               33 
             
             
                 
                16 
               50 
                 
               46 
               28 
               48 
               40 
               43 
               43 
               30 
               80 
               26 
               52 
               33 
               40 
             
             
                 
                17 
               33 
                 
               04 
               46 
               52 
               34 
               56 
               35 
               60 
               34 
               80 
               30 
               41 
               43 
             
             
                 
                18 
               68 
                 
               46 
               64 
               34 
               52 
               35 
               56 
               34 
               00 
               30 
               80 
               43 
               41 
             
             
                 
                19 
               33 
                 
               52 
               34 
               64 
               46 
               60 
               34 
               56 
               35 
               43 
               41 
               80 
               30 
             
             
                 
                20 
               66 
                 
               34 
               52 
               46 
               84 
               34 
               60 
               35 
               56 
               41 
               43 
               30 
               80 
             
             
                 
                21 
               128 
                 
               56 
               35 
               60 
               34 
               64 
               34 
               52 
               46 
               40 
               42 
               36 
               46 
             
           
        
         
             
                 
               . 
                 
               . 
             
             
                 
               . 
                 
               . 
             
             
                 
               . 
                 
               . 
             
           
        
         
             
                 
               193 
               72 
               . . . 
               40 
               33 
               52 
               28 
               80 
               30 
               43 
               43 
               40 
               46 
               36 
               46 
             
             
                 
               194 
               29 
                 
               33 
               40 
               26 
               52 
               30 
               60 
               43 
               43 
               46 
               40 
               46 
               36 
             
             
                 
               195 
               45 
                 
               52 
               31 
               40 
               33 
               43 
               43 
               80 
               30 
               38 
               46 
               40 
               46 
             
             
                 
               196 
               43 
                 
               31 
               52 
               33 
               40 
               43 
               43 
               30 
               80 
               46 
               36 
               46 
               40 
             
             
                 
               197 
               41 
                 
               33 
               33 
               52 
               42 
               40 
               46 
               36 
               46 
               80 
               38 
               43 
               43 
             
             
                 
               198 
               50 
                 
               33 
               33 
               42 
               52 
               46 
               40 
               46 
               36 
               38 
               80 
               43 
               43 
             
             
                 
               199 
               36 
                 
               52 
               42 
               33 
               33 
               36 
               46 
               40 
               45 
               43 
               43 
               80 
               38 
             
             
                 
               200 
               50 
                 
               42 
               52 
               33 
               33 
               46 
               36 
               46 
               40 
               43 
               43 
               38 
               80 
             
             
                 
               201 
               72 
                 
               40 
               46 
               26 
               46 
               33 
               42 
               52 
               30 
               40 
               33 
               52 
               26 
             
             
                 
               202 
               27 
                 
               48 
               40 
               48 
               28 
               42 
               33 
               30 
               52 
               33 
               40 
               26 
               52 
             
             
                 
               203 
               43 
                 
               29 
               46 
               40 
               46 
               52 
               30 
               39 
               42 
               52 
               31 
               40 
               33 
             
             
                 
               204 
               43 
                 
               46 
               29 
               46 
               40 
               30 
               52 
               42 
               39 
               31 
               52 
               33 
               40 
             
             
                 
               205 
               48 
                 
               80 
               30 
               43 
               43 
               40 
               33 
               52 
               31 
               33 
               33 
               52 
               42 
             
             
                 
               206 
               50 
                 
               30 
               80 
               43 
               43 
               33 
               40 
               31 
               52 
               33 
               33 
               42 
               52 
             
             
                 
               207 
               36 
                 
               43 
               43 
               60 
               30 
               52 
               28 
               40 
               33 
               52 
               42 
               33 
               33 
             
             
                 
               208 
               50 
                 
               43 
               43 
               30 
               80 
               26 
               52 
               33 
               40 
               42 
               52 
               33 
               33 
             
             
                 
               209 
               33 
                 
               56 
               35 
               60 
               34 
               80 
               30 
               41 
               43 
               40 
               46 
               36 
               42 
             
             
                 
               210 
               66 
                 
               35 
               56 
               34 
               60 
               30 
               80 
               43 
               41 
               46 
               40 
               42 
               38 
             
             
                 
               211 
               33 
                 
               60 
               34 
               56 
               35 
               43 
               41 
               80 
               30 
               36 
               42 
               40 
               46 
             
           
        
         
             
                 
               . 
                 
               . . . 
               . 
             
             
                 
               . 
                 
                 
               . 
             
             
                 
               . 
                 
                 
               . 
             
           
        
         
             
                 
               245 
               64 
               . . . 
               128 
               25 
               65 
               66 
               49 
               49 
               68 
               34 
               49 
               51 
               68 
               34 
             
             
                 
               246 
               34 
                 
               25 
               128 
               65 
               65 
               49 
               49 
               34 
               68 
               51 
               49 
               34 
               68 
             
             
                 
               247 
               52 
                 
               65 
               65 
               128 
               19 
               68 
               34 
               49 
               49 
               68 
               34 
               51 
               49 
             
             
                 
               248 
               46 
                 
               65 
               65 
               19 
               128 
               34 
               68 
               49 
               49 
               34 
               68 
               49 
               51 
             
             
                 
               249 
               40 
                 
               49 
               49 
               68 
               34 
               128 
               23 
               65 
               65 
               33 
               66 
               33 
               66 
             
             
                 
               250 
               42 
                 
               49 
               49 
               34 
               68 
               23 
               128 
               65 
               65 
               66 
               33 
               68 
               33 
             
             
                 
               251 
               36 
                 
               68 
               34 
               49 
               49 
               65 
               65 
               128 
               22 
               33 
               66 
               35 
               68 
             
             
                 
               252 
               48 
                 
               34 
               68 
               49 
               49 
               65 
               65 
               22 
               128 
               66 
               33 
               66 
               35 
             
             
                 
               253 
               80 
                 
               49 
               51 
               58 
               34 
               33 
               66 
               33 
               66 
               128 
               26 
               65 
               65 
             
             
                 
               254 
               30 
                 
               51 
               49 
               34 
               68 
               66 
               33 
               66 
               33 
               26 
               128 
               65 
               65 
             
             
                 
               255 
               43 
                 
               68 
               34 
               51 
               49 
               33 
               68 
               35 
               66 
               65 
               65 
               128 
               26 
             
             
                 
               256 
               41 
                 
               34 
               68 
               49 
               51 
               68 
               33 
               66 
               35 
               65 
               65 
               26 
               128 
             
             
                 
                 
             
           
        
       
     
   
   A preamble set having the minimum value among the representative values of Table 2 should be constructed. By acquiring a limit cross-correlation value that makes the cross-correlation value to be the smallest, it is possible to minimize the possibility of the generation of an error when the preamble analyzer  62  of  FIG. 4  analyzes the preambles. 
   To construct the preamble set of the smallest cross-correlation values in step S 130  of  FIG. 6 , one representative value that is largest or smallest is set as the limit cross-correlation value. An appropriate preamble set is searched for using the set representative value. According to the present invention, the representative value set in step S 310  of  FIG. 6  is set to 31. 
   Table 3 tabulates a preamble set calculated using the representative value ‘31’. As shown in Table 3, there are 128 preamble sets. Here, if the representative value is lowered to 30, there is no appropriate preamble set since when any 4 sequences are selected from among the 256 sequences, the lowest limit of all cross correlation values pertaining to the selected sequence group is 31. 
   
     
       
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
         
             
               TABLE 3 
             
             
                 
             
             
               s1 
               s2 
               s3 
               s4 
               s1:s2 
               s1:s3 
               s1:s4 
               s2:s3 
               s2:s4 
               s3:s4 
               s1 
               s2 
               s3 
               s4 
               s1:s2 
               s1:s3 
               s1:s4 
               s2:s3 
               s2:s4 
               s3:s4 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               17 
               47 
               86 
               108 
               28 
               31 
               30 
               30 
               23 
               29 
               41 
               84 
               110 
               215 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               17 
               47 
               86 
               172 
               28 
               31 
               30 
               30 
               23 
               29 
               41 
               84 
               174 
               215 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               17 
               47 
               108 
               150 
               28 
               30 
               31 
               23 
               30 
               29 
               41 
               110 
               148 
               215 
               23 
               30 
               28 
               29 
               30 
               31 
             
             
               17 
               47 
               150 
               172 
               28 
               31 
               30 
               30 
               23 
               29 
               41 
               148 
               174 
               215 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               17 
               86 
               108 
               239 
               31 
               30 
               28 
               29 
               30 
               23 
               42 
               83 
               109 
               216 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               17 
               86 
               172 
               239 
               31 
               30 
               28 
               29 
               30 
               23 
               42 
               83 
               173 
               216 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               17 
               108 
               150 
               239 
               30 
               31 
               28 
               29 
               23 
               30 
               42 
               109 
               147 
               216 
               23 
               30 
               28 
               29 
               30 
               31 
             
             
               17 
               150 
               172 
               239 
               31 
               30 
               28 
               29 
               30 
               23 
               42 
               147 
               173 
               216 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               18 
               48 
               85 
               107 
               28 
               31 
               30 
               30 
               23 
               29 
               43 
               82 
               112 
               213 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               18 
               48 
               85 
               171 
               28 
               31 
               30 
               30 
               23 
               29 
               43 
               82 
               176 
               213 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               18 
               48 
               107 
               149 
               28 
               30 
               31 
               23 
               30 
               29 
               43 
               112 
               146 
               213 
               23 
               30 
               29 
               28 
               30 
               31 
             
             
               18 
               48 
               149 
               171 
               28 
               31 
               30 
               30 
               23 
               29 
               43 
               146 
               176 
               213 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               18 
               85 
               107 
               240 
               31 
               30 
               28 
               29 
               30 
               23 
               44 
               81 
               111 
               214 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               18 
               85 
               171 
               240 
               31 
               30 
               28 
               29 
               30 
               23 
               44 
               81 
               175 
               214 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               18 
               107 
               149 
               240 
               30 
               31 
               28 
               29 
               23 
               30 
               44 
               111 
               145 
               214 
               23 
               30 
               29 
               28 
               30 
               31 
             
             
               18 
               149 
               171 
               240 
               31 
               30 
               28 
               29 
               30 
               23 
               44 
               145 
               175 
               214 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               19 
               45 
               88 
               106 
               29 
               31 
               30 
               30 
               23 
               28 
               45 
               88 
               106 
               211 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               19 
               45 
               88 
               170 
               29 
               31 
               30 
               30 
               23 
               28 
               45 
               88 
               170 
               211 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               19 
               45 
               106 
               152 
               29 
               30 
               31 
               23 
               30 
               28 
               45 
               106 
               152 
               211 
               23 
               30 
               29 
               28 
               30 
               31 
             
             
               19 
               45 
               152 
               170 
               29 
               31 
               30 
               30 
               23 
               28 
               45 
               152 
               170 
               211 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               19 
               88 
               106 
               237 
               31 
               30 
               29 
               28 
               30 
               23 
               46 
               87 
               105 
               212 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               19 
               88 
               170 
               237 
               31 
               30 
               29 
               28 
               30 
               23 
               46 
               87 
               169 
               212 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               19 
               106 
               152 
               237 
               30 
               31 
               29 
               28 
               23 
               30 
               46 
               105 
               151 
               212 
               23 
               30 
               29 
               28 
               30 
               31 
             
             
               19 
               152 
               170 
               237 
               31 
               30 
               29 
               28 
               30 
               23 
               46 
               151 
               169 
               212 
               30 
               23 
               29 
               28 
               31 
               30 
             
             
               20 
               46 
               87 
               105 
               29 
               31 
               30 
               30 
               23 
               28 
               47 
               86 
               108 
               209 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               20 
               46 
               87 
               169 
               29 
               31 
               30 
               30 
               23 
               28 
               47 
               86 
               172 
               209 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               20 
               46 
               105 
               151 
               29 
               30 
               31 
               23 
               30 
               28 
               47 
               108 
               150 
               209 
               23 
               30 
               28 
               29 
               30 
               31 
             
             
               20 
               46 
               151 
               169 
               29 
               31 
               30 
               30 
               23 
               28 
               47 
               150 
               172 
               209 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               20 
               87 
               105 
               238 
               31 
               30 
               29 
               28 
               30 
               23 
               48 
               85 
               107 
               210 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               20 
               87 
               169 
               238 
               31 
               30 
               29 
               28 
               30 
               23 
               48 
               85 
               171 
               210 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               20 
               105 
               151 
               238 
               30 
               31 
               29 
               28 
               23 
               30 
               48 
               107 
               149 
               210 
               23 
               30 
               28 
               29 
               30 
               31 
             
             
               20 
               151 
               169 
               238 
               31 
               30 
               29 
               28 
               30 
               23 
               48 
               149 
               171 
               210 
               30 
               23 
               28 
               29 
               31 
               30 
             
             
               21 
               43 
               82 
               112 
               29 
               31 
               30 
               30 
               23 
               28 
               81 
               111 
               214 
               236 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               21 
               43 
               82 
               176 
               29 
               31 
               30 
               30 
               23 
               28 
               81 
               175 
               214 
               236 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               21 
               43 
               112 
               146 
               29 
               30 
               31 
               23 
               30 
               28 
               82 
               112 
               213 
               235 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               21 
               43 
               146 
               176 
               29 
               31 
               30 
               30 
               23 
               28 
               82 
               176 
               213 
               235 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               21 
               82 
               112 
               235 
               31 
               30 
               29 
               28 
               30 
               23 
               83 
               109 
               216 
               234 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               21 
               82 
               176 
               235 
               31 
               30 
               29 
               28 
               30 
               23 
               83 
               173 
               216 
               234 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               21 
               112 
               146 
               235 
               30 
               31 
               29 
               28 
               23 
               30 
               84 
               110 
               215 
               233 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               21 
               146 
               176 
               235 
               31 
               30 
               29 
               28 
               30 
               23 
               84 
               174 
               215 
               233 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               22 
               44 
               81 
               111 
               29 
               31 
               30 
               30 
               23 
               28 
               85 
               107 
               210 
               240 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               22 
               44 
               81 
               175 
               29 
               31 
               30 
               30 
               23 
               28 
               85 
               171 
               210 
               240 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               22 
               44 
               111 
               145 
               29 
               30 
               31 
               23 
               30 
               28 
               86 
               108 
               209 
               239 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               22 
               44 
               145 
               175 
               29 
               31 
               30 
               30 
               23 
               28 
               86 
               172 
               209 
               239 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               22 
               81 
               111 
               236 
               31 
               30 
               29 
               28 
               30 
               23 
               87 
               105 
               212 
               238 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               22 
               81 
               175 
               236 
               31 
               30 
               29 
               28 
               30 
               23 
               87 
               169 
               212 
               238 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               22 
               111 
               145 
               236 
               30 
               31 
               29 
               28 
               23 
               30 
               88 
               106 
               211 
               237 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               22 
               145 
               175 
               236 
               31 
               30 
               29 
               28 
               30 
               23 
               88 
               170 
               211 
               237 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               23 
               41 
               84 
               110 
               28 
               31 
               30 
               30 
               23 
               29 
               105 
               151 
               212 
               238 
               28 
               30 
               23 
               31 
               30 
               29 
             
             
               23 
               41 
               84 
               174 
               28 
               31 
               30 
               30 
               23 
               29 
               106 
               152 
               211 
               237 
               28 
               30 
               23 
               31 
               30 
               29 
             
             
               23 
               41 
               110 
               148 
               28 
               30 
               31 
               23 
               30 
               29 
               107 
               149 
               210 
               240 
               29 
               30 
               23 
               31 
               30 
               28 
             
             
               23 
               41 
               148 
               174 
               28 
               31 
               30 
               30 
               23 
               29 
               108 
               150 
               209 
               239 
               29 
               30 
               23 
               31 
               30 
               28 
             
             
               23 
               84 
               110 
               233 
               31 
               30 
               28 
               29 
               30 
               23 
               109 
               147 
               216 
               234 
               29 
               30 
               23 
               31 
               30 
               28 
             
             
               23 
               84 
               174 
               233 
               31 
               30 
               28 
               29 
               30 
               23 
               110 
               148 
               215 
               233 
               29 
               30 
               23 
               31 
               30 
               28 
             
             
               23 
               110 
               148 
               233 
               30 
               31 
               28 
               29 
               23 
               30 
               111 
               145 
               214 
               236 
               28 
               30 
               23 
               31 
               30 
               29 
             
             
               23 
               148 
               174 
               233 
               31 
               30 
               28 
               29 
               30 
               23 
               112 
               146 
               213 
               235 
               28 
               30 
               23 
               31 
               30 
               29 
             
             
               24 
               42 
               83 
               109 
               28 
               31 
               30 
               30 
               23 
               29 
               145 
               175 
               214 
               236 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               24 
               42 
               83 
               173 
               28 
               31 
               30 
               30 
               23 
               29 
               146 
               176 
               213 
               235 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               24 
               42 
               109 
               147 
               28 
               30 
               31 
               23 
               30 
               29 
               147 
               173 
               216 
               234 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               24 
               42 
               147 
               173 
               28 
               31 
               30 
               30 
               23 
               29 
               148 
               174 
               215 
               233 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               24 
               83 
               109 
               234 
               31 
               30 
               28 
               29 
               30 
               23 
               149 
               171 
               210 
               240 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               24 
               83 
               173 
               234 
               31 
               30 
               28 
               29 
               30 
               23 
               150 
               172 
               209 
               239 
               29 
               31 
               30 
               30 
               23 
               28 
             
             
               24 
               109 
               147 
               234 
               30 
               31 
               28 
               29 
               23 
               30 
               151 
               169 
               212 
               238 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
               24 
               147 
               173 
               234 
               31 
               30 
               28 
               29 
               30 
               23 
               152 
               170 
               211 
               237 
               28 
               31 
               30 
               30 
               23 
               29 
             
             
                 
             
           
        
       
     
   
   If one preamble set is selected from among the 128 preambles sets and is used to discriminate users or channels, a preamble set having a superior auto-correlation and cross-correlation that is less than 31 can be used. 
   Once a preamble set is determined in a communication system, the preamble selector  120  of  FIG. 8  selects one from among preambles of the preamble set and transmits the preamble information to the preamble generator  140  of  FIG. 8 . The preamble generator  140  generates preambles using the preamble information. 
   Once the preambles included in a frame are transmitted from the transmitter to the receiver, the preamble analyzer  500  of  FIG. 9  analyzes the preambles. At this time, the preamble analyzer  500  detects the preambles selected by the preamble selector  120  of  FIG. 8  and creates the preamble information through the correlation measurer  520  of  FIG. 10 . 
   By providing a preamble set to discriminate between users or channels using a plurality of preambles, it is possible to more stably discriminate users or channels. 
   According to an embodiment of the present invention, by providing a preamble set to discriminate between users or channels using a plurality of preambles, it is possible to more stably discriminate the users or channels. 
   By lowering cross-correlation to the smallest possible value, users or channels can be discriminated while the preambles are not affected in acquiring synchronization information. 
   While the invention has been shown and described with reference to certain preferred embodiments 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.