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:
PRIORITY  
       [0001]     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.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     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.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, communication systems support communication services and include transmitters and receivers.  
         [0006]      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.  
         [0007]     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.  
         [0008]     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.  
         [0009]      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.  
         [0010]     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.  
         [0011]     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.  
         [0012]      FIG. 3  is a block diagram of a transmitter for the general communication system.  
         [0013]     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.  
         [0014]     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 .  
         [0015]      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.  
         [0016]     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 .  
         [0017]     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 .  
         [0018]     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.  
         [0019]     Superior auto-correlation indicates that auto-correlation is high when the sequences are synchronized and auto-correlation is relatively low in other cases.  
         [0020]      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 .  
         [0021]     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 .  
         [0022]     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 .  
         [0023]     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 .  
         [0024]     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 .  
         [0025]     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 .  
         [0026]     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.  
         [0027]     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.  
         [0028]     Conventional preamble signals are only used for detection of frame synchronization and channel estimation in receivers of communication systems.  
       SUMMARY OF THE INVENTION  
       [0029]     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.  
         [0030]     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.  
         [0031]     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  
       [0032]     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:  
         [0033]      FIG. 1  is a block diagram of a general communication system;  
         [0034]      FIG. 2  illustrates a frame structure used in the general communication system;  
         [0035]      FIG. 3  is a block diagram of a transmitter for the general communication system;  
         [0036]      FIG. 4  is a block diagram of a receiver for the general communication system;  
         [0037]      FIG. 5  is a block diagram of an aperiodic recursive multiplex (ARM) sequence generation apparatus;  
         [0038]      FIG. 6  is a flowchart illustrating a method for acquiring a preamble set according to an embodiment of the present invention;  
         [0039]      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;  
         [0040]      FIG. 8  is a block diagram of the preamble creator of  FIG. 7  according to an embodiment of the present invention;  
         [0041]      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  
         [0042]      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  
       [0043]     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.  
         [0044]     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.  
         [0045]     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.  
         [0046]     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.  
         [0047]      FIG. 6  is a flowchart illustrating a method for acquiring a preamble set according to an embodiment of the present invention.  
         [0048]     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 .  
         [0049]     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.  
         [0050]      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 .  
         [0051]      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 .  
         [0052]      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 .  
         [0053]     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 .  
         [0054]      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 .  
         [0055]     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 .  
         [0056]     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 .  
         [0057]     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.  
         [0058]     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 .  
         [0059]     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                  
 
         [0060]     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   30        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   38   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   20       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                      
 
         [0061]     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.  
         [0062]     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.  
         [0063]     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                  
 
         [0064]     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.  
         [0065]     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.  
         [0066]     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 .  
         [0067]     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.  
         [0068]     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.  
         [0069]     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.  
         [0070]     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.