Apparatus and method for acquiring a preamble in an orthogonal frequency division multiple access mobile terminal

Abstract

A preamble acquisition apparatus includes a first PN code generation unit for generating a first PN code having a bit string, a first correlation calculation unit for correlating a received frequency domain preamble signal with the first PN code within a first correlation range to generate a first correlation value, a first correlation value comparison unit for comparing the first correlation value with a first threshold value, a second PN code generation unit for generating a second PN code, a second correlation calculation unit for correlating the received frequency domain preamble signal with the second PN code within a second correlation range to generate a second correlation value, and a preamble acquisition determination unit for comparing the second correlation value with a second threshold value to determine whether to acquire the preamble. The bit values of the first PN code are located in the second PN code.

1 . An apparatus to acquire a preamble in an orthogonal frequency division multiple access (OFDMA) mobile terminal, the apparatus comprising:
 a first pseudo-noise (PN) code generation unit to generate a first PN code comprising a bit string including at least one bit;   a first correlation calculation unit to correlate a received preamble signal with the first PN code within a first correlation range to generate a first correlation value;   a first correlation value comparison unit to compare the first correlation value with a first threshold value and to determine whether to generate a second PN code;   a second PN code generation unit to generate a second PN code according to the determination result;   a second correlation calculation unit to correlate the preamble signal with the second PN code to generate a second correlation value; and   a preamble acquisition determination unit to compare the second correlation value with a second threshold value and to determine whether to acquire the preamble.   
     
     
         2 . The apparatus of  claim 1 , wherein the second correlation calculation unit correlates the preamble signal with the second PN code within a second correlation range. 
     
     
         3 . The apparatus of  claim 1 , wherein the second PN code generation unit comprises:
 an index table storage unit to store an index value of the second PN code corresponding to the first PN code; and   a code generator to generate the second PN code based on the index value of the second PN code.   
     
     
         4 . The apparatus of  claim 1 , wherein the second PN code generation unit comprises:
 a code table storage unit to store a stored PN code corresponding to the first PN code; and   a code generator to generate the second PN code by selecting the stored PN code from the code table storage unit.   
     
     
         5 . The apparatus of  claim 1 , wherein the first PN code generation unit comprises:
 a code table storage unit to store a plurality of PN codes; and   a code generator to generate the first PN code by selecting a stored PN code from the code table storage unit.   
     
     
         6 . The apparatus of  claim 1 , wherein a bit length of the first correlation range is less than a bit length of a second correlation range. 
     
     
         7 . The apparatus of  claim 1 , wherein a bit length of the first correlation range is four bits. 
     
     
         8 . The apparatus of  claim 1 , wherein a bit length of a second correlation range is no longer than a number of subcarriers transmitting the preamble. 
     
     
         9 . The apparatus of  claim 1 , wherein the first threshold value or the second threshold value is determined based on at least one of a number of subcarriers transmitting the preamble, a bit length of the first correlation range, a bit length of a second correlation range, a number of possible first PN codes, and a number of possible second PN codes. 
     
     
         10 . The apparatus of  claim 1 , further comprising:
 a parameter configuration unit to configure a parameter value associated with at least one of the first threshold value, the second threshold value, a bit length of the first correlation range, and a bit length of a second correlation range,   wherein the parameter configuration unit configures the parameter value based on an input from a user or a property of a wireless channel transmitting the preamble signal.   
     
     
         11 . An orthogonal frequency division multiple access (OFDMA) mobile terminal apparatus, comprising:
 a frequency domain transform unit to transform a time domain preamble signal into a frequency domain preamble signal;   a preamble acquisition unit to acquire a preamble by correlating the transformed frequency domain preamble signal with a PN code; and   a cell search unit to extract base station information of a cell where the mobile terminal apparatus is located from the acquired preamble,   wherein the preamble acquisition unit correlates the transformed frequency domain preamble signal with a first PN code within a first correlation range to generate a first correlation value, determines whether to generate a second PN code according to the first correlation value, and correlates the transformed frequency domain preamble signal with the second PN code to determine whether to acquire the preamble.   
     
     
         12 . The OFDMA mobile terminal apparatus of  claim 11 , wherein the preamble acquisition unit correlates the transformed frequency domain preamble signal with the second PN code within a second correlation range. 
     
     
         13 . A method for acquiring a preamble in an orthogonal frequency division multiple access (OFDMA) mobile terminal, comprising:
 correlating a received preamble signal with a first PN code within a first correlation range to generate a first correlation value;   comparing the first correlation value with a first threshold value, and determining whether to generate a second PN code according to the comparison result;   generating a second PN code according to the determination result;   correlating the preamble signal with the second PN code to generate a second correlation value; and   comparing the second correlation value with a second threshold value, and acquiring the second PN code as the preamble according to the comparison result.   
     
     
         14 . The method of  claim 13 , wherein correlating the preamble signal with the second PN code further comprises correlating the preamble signal with the second PN code within a second correlation range. 
     
     
         15 . The method of  claim 13 , wherein generating the second PN code further comprises:
 generating the second PN code if the first correlation value is greater than the first threshold value; and   correlating the preamble signal with a new first PN code within the first correlation range to generate a new first correlation value if the first correlation value is less than the first threshold value.   
     
     
         16 . The method of  claim 13 , wherein the acquiring the second PN code as the preamble further comprises:
 generating a new second PN code comprising bit values of the first PN code and correlating the preamble signal with the new second PN code within a second correlation range to generate a new second correlation value if the second correlation value is less than the second threshold value; and   acquiring the second PN code as the preamble if the second correlation value is greater than the second threshold value.   
     
     
         17 . The method of  claim 13 , wherein a bit length of the first correlation range is less than a bit length of a second correlation range. 
     
     
         18 . The method of  claim 13 , wherein a bit length of the first correlation range is four bits. 
     
     
         19 . The method of  claim 13 , wherein a bit length of a second correlation range is no longer than a number of subcarriers transmitting the preamble.