Apparatus and method for transmitting a preamble and searching a cell in an OFDMA system
First Claim
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1. A method for transmitting a preamble in an orthogonal frequency division multiple access (OFDMA) system using N subcarriers, the method comprising the steps of:
- generating an allocated pseudo-random noise (PN) code of PCODE PN codes from each cell such that all NCODE cells are identified, where PCODE is less than NCODE;
transforming the PN code into N orthogonal frequency division multiplexing (OFDM) samples according to N-point inverse fast Fourier transform (IFFT);
cyclically shifting the OFDM samples by an allocated value of QCODE cyclic shift values, where NCODE is PCODE*QCODE;
inserting a cyclic prefix (CP) for preventing inter-symbol interference into a head end of the cyclically shifted OFDM samples, and generating a first OFDM symbol to be used for a preamble; and
transmitting the first OFDM symbol at a beginning of a data frame through a radio frequency (RF) band.
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Abstract
An apparatus and method for generating a preamble and searching a cell using the generated preamble in an orthogonal frequency division multiple access (OFDMA) system. Q cyclic shift values and P pseudo-random noise (PN) codes are used to distinguish N cells. One of the P PN codes is cyclically shifted according to one of the Q cyclic shift values and therefore a preamble is generated. Because a relatively small number of PN codes are used, the memory capacity of a mobile terminal for storing the PN codes is saved and a cell search error is reduced.
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Citations
27 Claims
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1. A method for transmitting a preamble in an orthogonal frequency division multiple access (OFDMA) system using N subcarriers, the method comprising the steps of:
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generating an allocated pseudo-random noise (PN) code of PCODE PN codes from each cell such that all NCODE cells are identified, where PCODE is less than NCODE;
transforming the PN code into N orthogonal frequency division multiplexing (OFDM) samples according to N-point inverse fast Fourier transform (IFFT);
cyclically shifting the OFDM samples by an allocated value of QCODE cyclic shift values, where NCODE is PCODE*QCODE;
inserting a cyclic prefix (CP) for preventing inter-symbol interference into a head end of the cyclically shifted OFDM samples, and generating a first OFDM symbol to be used for a preamble; and
transmitting the first OFDM symbol at a beginning of a data frame through a radio frequency (RF) band. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for transmitting a preamble in an orthogonal frequency division multiple access (OFDMA) system using N subcarriers, the apparatus comprising:
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a pseudo-random noise (PN) code generator for generating an allocated PN code of PCODE PN codes from each cell such that all NCODE cells are identified, where PCODE is less than NCODE;
an inverse fast Fourier transform (IFFT) unit for transforming the PN code into N orthogonal frequency division multiplexing (OFDM) samples according to N-point IFFT;
a cyclic shifter for cyclically shifting the OFDM samples by an allocated value of QCODE cyclic shift values, where NCODE is PCODE*QCODE;
a cyclic prefix (CP) inserter for inserting a CP for preventing inter-symbol interference into a head end of the cyclically shifted OFDM samples, and generating a first OFDM symbol to be used for a preamble; and
a radio frequency (RF) unit for transmitting the first OFDM symbol at a beginning of a data frame through an RF band. - View Dependent Claims (7, 8, 9, 10)
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11. A method for receiving a preamble in an orthogonal frequency division multiple access (OFDMA) system using N subcarriers, the method comprising the steps of:
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receiving an orthogonal frequency division multiplexing (OFDM) signal comprising at least one OFDM symbol used for a preamble through the subcarriers;
removing a cyclic prefix (CP) for preventing inter-symbol interference from the received OFDM signal, and detecting N OFDM samples;
transforming the N OFDM samples into a frequency domain signal according to N-point fast Fourier transform (FFT);
multiplying the frequency domain signal by PCODE pseudo-random noise (PN) codes for identifying all NCODE cells, determining a time domain in which energy of each of multiplied signals is concentrated, and detecting a cyclic shift value of a PN code applied to each OFDM symbol, wherein the cyclic shift value is one of QCODE cyclic shift values and NCODE is PCODE*QCODE; and
searching a cell mapped to the detected cyclic shift value of the PN code. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. An apparatus for receiving a preamble in an orthogonal frequency division multiple access (OFDMA) system using N subcarriers, the apparatus comprising:
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a radio frequency (RF) unit for receiving an orthogonal frequency division multiplexing (OFDM) signal comprising at least one OFDM symbol used for a preamble through the subcarriers;
a cyclic prefix (CP) remover for removing a CP for preventing inter-symbol interference from the received OFDM signal, and detecting N OFDM samples;
a fast Fourier transform (FFT) processor for transforming the N OFDM samples into a frequency domain signal according to N-point FFT;
a preamble detector for multiplying the frequency domain signal by PCODE pseudo-random noise (PN) codes for identifying all NCODE cells, determining a time domain in which energy of each of multiplied signals is concentrated, and detecting a cyclic shift value of a PN code applied to each OFDM symbol, wherein the cyclic shift value is one of QCODE cyclic shift values and NCODE is PCODE *QCODE; and
a cell detector for searching a cell mapped to the detected cyclic shift value of the PN code. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification