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 ‘010101010101010101010101010101011010101010101010101010101010101’ or ‘101010101010101010101010101010101010101010101010101010101010101’ 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   :   00010010000111010001001011100010000100100001110111101101000111010001001000011101000100101110001011101101111000100001001011100010               2   :   01000111010010000100011110110111010001110100100010111000010010000100011101001000010001111011011110111000101101110100011110110111               3   :   00100001001011100010000111010001001000010010111011011110001011100010000100101110001000011101000111011110110100010010000111010001                       4   :   01110100011110110111010010000100011101000111101110001011011110110111010001111011011101001000010010001011100001000111010010000100               5   :   00011101000100100001110111101101000111010001001011100010000100100001110100010010000111011110110111100010111011010001110111101101               6   :   01001000010001110100100010111000010010000100011110110111010001110100100001000111010010001011100010110111101110000100100010111000                       7   :   00101110001000010010111011011110001011100010000111010001001000010010111000100001001011101101111011010001110111100010111011011110               8   :   01111011011101000111101110001011011110110111010010000100011101000111101101110100011110111000101110000100100010110111101110001011               9   :   00010010111000100001001000011101000100101110001011101101111000100001001011100010000100100001110111101101000111010001001000011101                       10   :   01000111101101110100011101001000010001111011011110111000101101110100011110110111010001110100100010111000010010000100011101001000               11   :   00100001110100010010000100101110001000011101000111011110110100010010000111010001001000010010111011011110001011100010000100101110               12   :   01110100100001000111010001111011011101001000010010001011100001000111010010000100011101000111101110001011011110110111010001111011                       13   :   00011101111011010001110100010010000111011110110111100010111011010001110111101101000111010001001011100010000100100001110100010010               14   :   01001000101110000100100001000111010010001011100010110111101110000100100010111000010010000100011110110111010001110100100001000111               15   :   00101110110111100010111000100001001011101101111011010001110111100010111011011110001011100010000111010001001000010010111000100001                       16   :   01111011100010110111101101110100011110111000101110000100100010110111101110001011011110110111010010000100011101000111101101110100               17   :   00010010000111011110110100011101000100100001110100010010111000100001001000011101111011010001110111101101111000101110110100011101               18   :   01000111010010001011100001001000010001110100100001000111101101110100011101001000101110000100100010111000101101111011100001001000                       19   :   00100001001011101101111000101110001000010010111000100001110100010010000100101110110111100010111011011110110100011101111000101110               20   :   01110100011110111000101101111011011101000111101101110100100001000111010001111011100010110111101110001011100001001000101101111011               21   :   00011101000100101110001000010010000111010001001000011101111011010001110100010010111000100001001011100010111011011110001000010010                       22   :   01001000010001111011011101000111010010000100011101001000101110000100100001000111101101110100011110110111101110001011011101000111               23   :   00101110001000011101000100100001001011100010000100101110110111100010111000100001110100010010000111010001110111101101000100100001               24   :   01111011011101001000010001110100011110110111010001111011100010110111101101110100100001000111010010000100100010111000010001110100                       25   :   00010010111000101110110111100010000100101110001000010010000111010001001011100010111011011110001011101101000111011110110111100010               26   :   01000111101101111011100010110111010001111011011101000111010010000100011110110111101110001011011110111000010010001011100010110111               27   :   00100001110100011101111011010001001000011101000100100001001011100010000111010001110111101101000111011110001011101101111011010001                       28   :   01110100100001001000101110000100011101001000010001110100011110110111010010000100100010111000010010001011011110111000101110000100               29   :   00011101111011011110001011101101000111011110110100011101000100100001110111101101111000101110110111100010000100101110001011101101               30   :   01001000101110001011011110111000010010001011100001001000010001110100100010111000101101111011100010110111010001111011011110111000                       31   :   00101110110111101101000111011110001011101101111000101110001000010010111011011110110100011101111011010001001000011101000111011110                       .                       .                       .               234   :   10111000010010001011100010110111010001111011011110011100010110111101110000100100010111000101101110111000010010000100011101001000               235   :   11011110001011101101111011010001001000011101000111011110110100011101111000101110110111101101000111011110001011100010000100101110               236   :   10001011011110111000101110000100011101001000010010001011100001001000101101111011100010111000010010001011011110110111010001111011                       237   :   11100010000100101110001011101101000111011110110111100010111011011110001000010010111000101110110111100010000100100001110100010010               238   :   10110111010001111011011110111000010010001011100010110111101110001011011101000111101101111011100010110111010001110100100001000111               239   :   11010001001000011101000111011110001011101101111011010001110111101101000100100001110100011101111011010001001000010010111000100001                       240   :   10000100011101001000010010001011011110111000101110000100100010111000010001110100100001001000101110000100011101000111101101110100               241   :   11101101111000100001001011100010000100100001110100010010111000101110110111100010000100101110001011101101111000101110110100011101               242   :   10111000101101110100011110110111010001110100100001000111101101111011100010110111010001111011011110111000101101111011100001001000                       243   :   11011110110100010010000111010001001000010010111000100001110100011101111011010001001000011101000111011110110100011101111000101110               244   :   10001011100001000111010010000100011101000111101101110100100001001000101110000100011101001000010010001011100001001000101101111011               245   :   11100010111011010001110111101101000111010001001000011101111011011110001011101101000111011110110111100010111011011110001000010010                       246   :   10110111101110000100100010111000010010000100011101001000101110001011011110111000010010001011100010110111101110001011011101000111               247   :   11010001110111100010111011011110001011100010000100101110110111101101000111011110001011101101111011010001110111101101000100100001               248   :   10000100100010110111101110001011011110110111010001111011100010111000010010001011011110111000101110000100100010111000010001110100                       249   :   11101101000111010001001000011101000100101110001000010010000111011110110100011101000100100001110111101101000111011110110111100010               250   :   10111000010010000100011101001000010001111011011101000111010010001011100001001000010001110100100010111000010010001011100010110111               251   :   11011110001011100010000100101110001000011101000100100001001011101101111000101110001000010010111011011110001011101101111011010001                       252   :   10001011011110110111010001111011011101001000010001110100011110111000101101111011011101000111101110001011011110111000101110000100               253   :   11100010000100100001110100010010000111011110110100011101000100101110001000010010000111010001001011100010000100101110001011101101               254   :   10110111010001110100100001000111010010001011100001001000010001111011011101000111010010000100011110110111010001111011011110111000               255   :   11010001001000010010111000100001001011101101111000101110001000011101000100100001001011100010000111010001001000011101000111011110                       256   :   10000100011101000111101101110100011110111000101101111011011101001000010001110100011110110111010010000100011101001000010010001011                  
 
         [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.  
         [0061]     Table 2  
                                                                                                                                                                                                                                                                                                                                                                                                                                                                       1   2   3   4   5   6   7   8   9   10   11   12   13   14   15   16   17                1   128   25   65   65   40   66   36   66   49   49   68   38   49   49   68   34   41        2   26   128   65   65   66   40   66   36   49   49   38   68   49   49   34   68   50        3   65   65   128   26   36   66   40   66   68   38   49   49   68   34   49   49   36        4   65   65   26   128   66   36   66   40   38   68   49   49   34   68   49   49   50        5   40   66   36   66   128   22   65   65   49   49   68   34   49   51   68   34   72        6   66   40   66   36   22   128   65   65   49   49   34   68   51   49   34   68   29        7   36   66   40   68   65   65   128   22   68   34   49   49   68   34   51   49   44        8   56   36   66   40   55   65   22   128   34   68   49   49   34   68   49   51   45        9   49   49   68   38   49   49   68   34   128   22   65   65   40   66   33   66   48        10   49   49   38   88   49   49   34   68   22   128   65   65   66   40   66   33   50        11   68   38   49   49   58   34   49   49   65   65   128   22   33   66   40   66   36        12   38   68   49   49   34   68   49   49   65   65   22   128   66   33   55   40   50        13   49   49   68   34   49   51   68   34   40   66   33   66   128   23   65   65   72        14   49   49   34   68   51   49   34   68   66   40   66   33   23   128   65   65   31        15   68   34   49   49   68   34   51   49   33   66   40   66   65   65   128   22   43        16   34   65   49   49   34   68   49   51   66   33   66   40   65   65   22   128   43        17   41   50   36   50   72   29   44   45   48   50   36   50   72   31   43   43   128        18   50   41   50   36   29   72   45   44   50   48   50   36   31   72   43   43   22        19   36   50   32   50   45   43   72   29   36   50   48   50   43   43   72   27   65        20   50   36   50   32   43   45   29   72   50   36   50   48   43   43   27   72   65        21   72   29   45   43   41   50   36   50   72   27   43   43   48   50   36   50   33            .   .       .   .       .   .            193   128   26   65   65   40   66   38   66   49   49   68   38   49   49   68   34   41       194   26   128   65   65   66   40   68   36   49   49   38   68   49   49   34   68   50       195   65   65   128   26   36   66   40   66   68   38   49   49   68   34   49   49   36       196   65   65   26   128   66   36   66   40   38   68   49   49   34   68   49   49   50       197   40   66   36   66   128   22   65   65   49   49   68   34   49   51   68   34   72       198   66   40   66   36   22   128   65   65   49   49   34   68   51   49   34   68   29       199   36   66   40   66   65   65   128   22   68   34   49   49   68   34   51   49   44       200   66   36   66   40   65   65   22   128   34   68   49   49   34   68   49   51   45       201   49   49   68   38   49   49   68   34   128   22   65   65   40   66   33   66   48       202   49   49   38   68   49   49   34   68   22   128   65   65   66   40   66   33   50       203   68   39   49   49   68   34   49   49   65   65   128   22   33   66   40   66   36       204   38   68   49   49   34   68   49   49   65   65   22   128   66   33   66   40   50       205   49   49   68   34   49   51   68   34   40   66   33   66   128   23   65   65   72       206   49   49   34   68   51   49   34   68   66   40   66   33   23   128   65   65   31       207   68   34   49   49   68   34   51   49   33   66   40   66   65   65   128   22   43       208   34   68   49   49   34   68   49   51   66   33   66   40   65   65   22   128   43       209   41   50   36   50   72   29   44   45   48   50   36   50   72   31   43   43   128       210   50   41   50   36   29   72   45   44   50   48   50   36   31   72   43   43   22       211   36   50   32   50   45   43   72   29   36   50   48   50   43   43   72   27   65            .   .       .   .       .   .            245   40   33   52   31   33   33   52   42   40   46   29   46   80   30   43   43   56       246   33   40   31   52   33   33   42   52   46   40   46   29   30   80   43   43   35       247   52   26   40   33   52   42   33   33   28   46   40   46   43   43   80   30   60       248   26   52   33   40   42   52   33   33   46   28   46   40   43   43   30   80   34       249   80   30   43   43   40   46   36   46   33   42   52   30   40   33   52   26   80       250   30   80   43   43   46   40   46   36   42   33   30   52   33   40   26   52   30       251   43   43   80   30   36   46   40   46   52   30   39   42   52   31   40   33   41       252   43   43   30   80   46   36   48   40   30   52   42   39   31   52   33   40   43       253   40   46   36   46   80   38   43   43   40   33   52   31   33   33   52   42   40       254   46   40   46   36   38   80   43   43   33   40   31   52   33   33   42   52   46       255   36   46   40   46   43   43   60   38   52   26   40   33   52   42   33   33   36       256   46   36   46   40   43   43   38   60   26   52   33   40   42   52   33   33   42                   18   19   20   21   . . .   245   246   247   248   249   250   251   252   253   254   255   256                1   50   35   50   72   . . .   33   42   52   30   40   33   52   26   80   30   43   43        2   41   50   36   29       42   33   30   52   33   40   26   52   30   80   43   43        3   50   32   50   45       52   30   39   42   52   31   40   33   43   43   80   30        4   36   50   32   43       30   52   42   39   31   52   33   40   43   43   30   80        5   29   45   43   41       40   33   52   31   33   33   52   42   40   46   36   45        6   72   43   45   50       33   40   31   52   33   33   42   52   46   40   46   36        7   45   72   29   36       52   26   40   33   52   42   33   33   36   46   40   46        8   44   29   72   50       26   52   33   40   42   52   33   33   46   36   46   40        9   50   36   50   72       80   30   43   43   40   46   28   46   33   42   52   30        10   48   50   36   27       30   80   43   43   46   40   46   28   42   33   30   52        11   50   48   50   43       43   43   80   30   29   46   40   46   52   30   39   42        12   36   50   48   43       43   43   30   80   46   29   46   40   30   52   42   39        13   31   43   43   48       40   46   29   46   80   30   43   43   40   33   52   31        14   72   43   43   50       46   40   46   29   30   80   43   43   33   40   31   52        15   43   72   27   36       28   46   40   46   43   43   80   30   52   26   40   33        16   43   27   72   50       46   28   46   40   43   43   30   80   26   52   33   40        17   22   65   65   33       64   46   52   34   56   35   60   34   80   30   41   43        18   128   65   65   66       46   64   34   52   35   56   34   60   30   80   43   41        19   65   128   22   33       52   34   64   46   60   34   56   35   43   41   80   30        20   65   22   128   66       34   52   46   64   34   60   35   56   41   43   30   80        21   66   33   66   128       56   35   60   34   64   34   52   46   40   42   35   45            .       .       .       .       .       .            193   50   36   50   72   . . .   40   33   52   26   80   30   43   43   40   46   36   46       194   41   50   36   29       33   40   26   52   30   80   43   43   46   40   46   36       195   50   32   50   45       52   31   40   33   43   43   80   30   36   46   40   46       196   36   50   32   43       31   52   33   40   43   43   30   80   46   36   46   40       197   29   45   43   41       33   33   52   42   40   46   36   46   80   38   43   43       198   72   43   45   50       33   33   42   52   46   40   46   36   38   80   43   43       199   45   72   29   36       52   42   33   33   36   46   40   46   43   43   80   38       200   44   29   72   50       42   52   33   33   46   36   46   40   43   43   38   80       201   50   36   50   72       40   46   28   46   33   42   52   30   40   33   52   26       202   48   50   36   27       46   40   46   28   42   33   30   52   33   40   26   52       203   50   48   50   43       29   46   40   46   52   30   39   42   52   31   40   33       204   36   50   48   43       46   29   46   40   30   52   42   39   31   52   33   40       205   31   43   43   48       80   30   43   43   40   33   52   31   33   33   52   42       206   72   43   43   50       30   80   43   43   33   40   31   52   33   33   42   52       207   43   72   27   36       43   43   80   30   52   26   40   33   52   42   33   33       208   43   27   72   50       43   43   30   80   26   52   33   40   42   52   33   33       209   22   65   65   33       56   35   60   34   80   30   41   43   40   46   36   42       210   128   65   65   66       35   56   34   60   30   80   43   41   46   40   42   36       211   65   128   22   33       60   34   56   35   43   41   80   30   36   42   40   46            .       . . .   .       .           .       .           .            245   35   60   34   64   . . .   128   25   65   65   49   49   68   34   49   51   68   34       246   56   34   60   34       25   128   65   65   49   49   34   68   51   49   34   68       247   34   56   35   52       65   65   128   19   68   34   49   49   68   34   51   49       248   60   35   56   46       65   65   19   128   34   68   49   49   34   68   49   51       249   30   43   41   40       49   49   68   34   128   23   65   65   33   66   33   66       250   80   41   43   42       49   49   34   68   23   128   65   65   66   33   66   33       251   43   80   30   36       68   34   49   49   65   65   128   22   33   66   35   66       252   41   30   80   46       34   68   49   49   65   65   22   128   66   33   66   35       253   46   36   42   80       49   51   68   34   33   66   33   66   128   26   65   65       254   40   42   36   30       51   49   34   68   66   33   66   33   26   128   65   65       255   42   40   46   43       68   34   51   49   33   66   35   66   65   65   128   26       256   36   46   40   41       34   68   49   51   66   33   66   35   65   65   26   128                  
 
         [0062]     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.  
         [0063]     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 .  
         [0064]     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.  
         [0065]     Table 3  
                                                                                             TABLE 3                       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       17   47   86   172   28   31   30   30   23   29       17   47   108   150   28   30   31   23   30   29       17   47   150   172   28   31   30   30   23   29       17   86   108   239   31   30   28   29   30   23       17   86   172   239   31   30   28   29   30   23       17   108   150   239   30   31   28   29   23   30       17   150   172   239   31   30   28   29   30   23       18   48   85   107   28   31   30   30   23   29       18   48   85   171   28   31   30   30   23   29       18   48   107   149   28   30   31   23   30   29       18   48   149   171   28   31   30   30   23   29       18   85   107   240   31   30   28   29   30   23       18   85   171   240   31   30   28   29   30   23       18   107   149   240   30   31   28   29   23   30       18   149   171   240   31   30   28   29   30   23       19   45   88   106   29   31   30   30   23   28       19   45   88   170   29   31   30   30   23   28       19   45   106   152   29   30   31   23   30   28       19   45   152   170   29   31   30   30   23   28       19   88   106   237   31   30   29   28   30   23       19   88   170   237   31   30   29   28   30   23       19   106   152   237   30   31   29   28   23   30       19   152   170   237   31   30   29   28   30   23       20   46   87   105   29   31   30   30   23   28       20   46   87   169   29   31   30   30   23   28       20   46   105   151   29   30   31   23   30   28       20   46   151   169   29   31   30   30   23   28       20   87   105   238   31   30   29   28   30   23       20   87   169   238   31   30   29   28   30   23       20   105   151   238   30   31   29   28   23   30       20   151   169   238   31   30   29   28   30   23       21   43   82   112   29   31   30   30   23   28       21   43   82   176   29   31   30   30   23   28       21   43   112   146   29   30   31   23   30   28       21   43   146   176   29   31   30   30   23   28       21   82   112   235   31   30   29   28   30   23       21   82   176   235   31   30   29   28   30   23       21   112   146   235   30   31   29   28   23   30       21   146   176   235   31   30   29   28   30   23       22   44   81   111   29   31   30   30   23   28       22   44   81   175   29   31   30   30   23   28       22   44   111   145   29   30   31   23   30   28       22   44   145   175   29   31   30   30   23   28       22   81   111   236   31   30   29   28   30   23       22   81   175   236   31   30   29   28   30   23       22   111   145   236   30   31   29   28   23   30       22   145   175   236   31   30   29   28   30   23       23   41   84   110   28   31   30   30   23   29       23   41   84   174   28   31   30   30   23   29       23   41   110   148   28   30   31   23   30   29       23   41   148   174   28   31   30   30   23   29       23   84   110   233   31   30   28   29   30   23       23   84   174   233   31   30   28   29   30   23       23   110   148   233   30   31   28   29   23   30       23   148   174   233   31   30   28   29   30   23       24   42   83   109   28   31   30   30   23   29       24   42   83   173   28   31   30   30   23   29       24   42   109   147   28   30   31   23   30   29       24   42   147   173   28   31   30   30   23   29       24   83   109   234   31   30   28   29   30   23       24   83   173   234   31   30   28   29   30   23       24   109   147   234   30   31   28   29   23   30       24   147   173   234   31   30   28   29   30   23       41   84   110   215   30   23   28   29   31   30       41   84   174   215   30   23   28   29   31   30       41   110   148   215   23   30   28   29   30   31       41   148   174   215   30   23   28   29   31   30       42   83   109   216   30   23   28   29   31   30       42   83   173   216   30   23   28   29   31   30       42   109   147   216   23   30   28   29   30   31       42   147   173   216   30   23   28   29   31   30       43   82   112   213   30   23   29   28   31   30       43   82   176   213   30   23   29   28   31   30       43   112   146   213   23   30   29   28   30   31       43   146   176   213   30   23   29   28   31   30       44   81   111   214   30   23   29   28   31   30       44   81   175   214   30   23   29   28   31   30       44   111   145   214   23   30   29   28   30   31       44   145   175   214   30   23   29   28   31   30       45   88   106   211   30   23   29   28   31   30       45   88   170   211   30   23   29   28   31   30       45   106   152   211   23   30   29   28   30   31       45   152   170   211   30   23   29   28   31   30       46   87   105   212   30   23   29   28   31   30       46   87   169   212   30   23   29   28   31   30       46   105   151   212   23   30   29   28   30   31       46   151   169   212   30   23   29   28   31   30       47   86   108   209   30   23   28   29   31   30       47   86   172   209   30   23   28   29   31   30       47   108   150   209   23   30   28   29   30   31       47   150   172   209   30   23   28   29   31   30       48   85   107   210   30   23   28   29   31   30       48   85   171   210   30   23   28   29   31   30       48   107   149   210   23   30   28   29   30   31       48   149   171   210   30   23   28   29   31   30       81   111   214   236   28   31   30   30   23   29       81   175   214   236   28   31   30   30   23   29       82   112   213   235   28   31   30   30   23   29       82   176   213   235   28   31   30   30   23   29       83   109   216   234   29   31   30   30   23   28       83   173   216   234   29   31   30   30   23   28       84   110   215   233   29   31   30   30   23   28       84   174   215   233   29   31   30   30   23   28       85   107   210   240   29   31   30   30   23   28       85   171   210   240   29   31   30   30   23   28       86   108   209   239   29   31   30   30   23   28       86   172   209   239   29   31   30   30   23   28       87   105   212   238   28   31   30   30   23   29       87   169   212   238   28   31   30   30   23   29       88   106   211   237   28   31   30   30   23   29       88   170   211   237   28   31   30   30   23   29       105   151   212   238   28   30   23   31   30   29       106   152   211   237   28   30   23   31   30   29       107   149   210   240   29   30   23   31   30   28       108   150   209   239   29   30   23   31   30   28       109   147   216   234   29   30   23   31   30   28       110   148   215   233   29   30   23   31   30   28       111   145   214   236   28   30   23   31   30   29       112   146   213   235   28   30   23   31   30   29       145   175   214   236   28   31   30   30   23   29       146   176   213   235   28   31   30   30   23   29       147   173   216   234   29   31   30   30   23   28       148   174   215   233   29   31   30   30   23   28       149   171   210   240   29   31   30   30   23   28       150   172   209   239   29   31   30   30   23   28       151   169   212   238   28   31   30   30   23   29       152   170   211   237   28   31   30   30   23   29                  
 
         [0066]     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.  
         [0067]     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.  
         [0068]     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 .  
         [0069]     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.  
         [0070]     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.  
         [0071]     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.  
         [0072]     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.