Orthogonal frequency division multiplexing/modulation communication system for improving ability of data transmission and method thereof

A system for transmitting sub-channels having a minimum PAPR (Peak-to-Average Power Ratio) in on OFDM communication system, comprising:

• a pilot scrambling code generator for generating a predetermined number of pilot scrambling codes for identifying pilot sub-channel data blocks among input sub-channel data blocks;
• a scrambling code generator for generating a predetermined number of scrambling codes for scrambling the input sub-channel data blocks;
• a plurality of first multipliers for multiplying the input pilot sub-channel data blocks by a first pilot scrambling code among the pilot scrambling codes, for scrambling;
• a plurality of second multipliers for multiplying the sub-channel data blocks excluding the pilot sub-channel data blocks from the input sub-channel data blocks and data blocks output from the first multipliers by a first scrambling code among the scrambling codes, for scrambling;
• a first inverse fast Fourier transformer (IFFT) for IFFT-transforming the signals output from the second multipliers;
• a plurality of third multipliers for multiplying the input pilot sub-channel data blocks by a second pilot scrambling code among the pilot scrambling codes, for scrambling;
• a plurality of fourth multipliers for multiplying the sub-channel data blocks excluding the pilot sub-channel data blocks from the input sub-channel data blocks and data blocks output from the third multipliers by a second scrambling code among the scrambling codes, for scrambling;
• a second IFFT for IFFT-transforming the signals output from the fourth multipliers;
• first and second PAPR calculators for calculating PAPRs of the sub-channel data blocks output from the first IFFT and the second IFFT, respectively;
• and
• a selector for selecting sub-channel data blocks output from the first and second IFFTs having a minimum PAPR among the calculated PAPRs, and transmitting the selected sub-channel data blocks over a sub-channel of the OFDM communication system.

A system for receiving sub-channels having a minimum PAPR in an OFDM communication system, comprising:

• a pilot extractor for extracting pilot sub-channel data blocks among input sub-channel data blocks;
• a scrambling code generator for generating a plurality of scrambling codes for scrambling the input sub-channel data blocks;
• a pilot scrambling code extractor for extracting received pilot scrambling codes by descrambling the input sub-channel data blocks with the scrambling codes;
• a plurality of first multipliers for multiplying the extracted pilot sub-channel data blocks by complex-conjugated values of the extracted pilot scrambling codes;
• a pilot scrambling code generator for generating a predetermined number of pilot scrambling codes, the number of generated pilot scrambling codes being equal to the number of pilot scrambling codes transmitted by a transmitting system;
• a plurality of second multipliers for multiplying conjugated values of the generated pilot scrambling codes by the values output from the first multipliers;
• a scrambling code extractor for extracting scrambling codes by multiplying the data blocks output from the second multipliers by the pilot sub-channel data blocks transmitted by the transmission system;
• and
• a demodulator for demodulating the received sub-channel data blocks by scrambling the received sub-channel data blocks with the extracted scrambling codes.

A method for transmitting sub-channels having a minimum PAPR (Peak-to-Average Power Ratio) in on OFDM communication system, comprising the steps of:

• (a) generating a predetermined number of pilot scrambling codes for identifying pilot sub-channel data blocks among input sub-channel data blocks, and generating a predetermined number of scrambling codes for scrambling the input sub-channel data blocks;
• (b) multiplying the input pilot sub-channel data blocks by a first pilot scrambling code among the pilot scrambling codes, for scrambling;
• (c) multiplying the sub-channel data blocks excluding the pilot sub-channel data blocks from the input sub-channel data blocks and pilot sub-channel data blocks scrambled with the first pilot scrambling code by a first scrambling code among the scrambling codes, for scrambling;
• (d) IFFT-transforming the signals generated in the step (c);
• (e) multiplying the input pilot sub-channel data blocks by a second pilot scrambling code among the pilot scrambling codes, for scrambling;
• (f) multiplying the sub-channel data blocks excluding the pilot sub-channel data blocks from the input sub-channel data blocks and data blocks output in the step (b) by a second scrambling code among the scrambling codes, for scrambling;
• (g) IFFT-transforming the signals generated in the step (f);
• and
• (h) calculating PAPRs of the sub-channel data blocks generated in the steps (d) and (g), respectively, selecting sub-channel data blocks having a minimum PAPR among the calculated PAPRs, and transmitting the selected sub-channel data blocks over a sub-channel of the OFDM communication system.

A method for receiving sub-channels having a minimum PAPR in an OFDM communication system, comprising the steps of:

• (a) extracting pilot sub-channel data blocks among input sub-channel data blocks;
• (b) generating a plurality of scrambling codes for scrambling the input sub-channel data blocks, and extracting received pilot scrambling codes by descrambling the input sub-channel data blocks with the scrambling codes;
• (c) multiplying the extracted pilot sub-channel data blocks by complex-conjugated values of the extracted pilot scrambling codes;
• (d) generating a predetermined number of pilot scrambling codes, the number of generated pilot scrambling codes being equal to the number of pilot scrambling codes transmitted by a transmitting system, and multiplying conjugated values of the generated pilot scrambling codes by the values generated in the step (c);
• and
• (e) extracting scrambling codes by multiplying the data blocks generated in the step (d) by the pilot sub-channel data blocks transmitted by the transmission system, and demodulating the received sub-channel data blocks by scrambling the received sub-channel data blocks with the extracted scrambling codes.

An OFDM communication system comprising:

• a Reed-Solomon interleaver for dispersing Reed-Solomon symbol elements existing in the same positions, obtained by Reed-Solomon coding input information data blocks, to sub-channels of the OFDM symbols, for interleaving;
• a sub-channel repeater for converting the interleaved singles to parallel data blocks, repeating the parallel data blocks a predetermined number of times, and transmitting the repeated data blocks over corresponding sub-channels;
• a sub-channel assignor for adding the sub-channel data blocks and the pilot sub-channel data blocks, and dynamically assigning sub-channels for transmitting the sub-channel data blocks each time the added sub-channel data blocks are received, according to input time points;
• a sub-channel scrambler for mapping the assigned sub-channel signals according to a predetermined modulation mode, scrambling pilot sub-channel data blocks among the mapped sub-channel data blocks with a pilot scrambling code, and scrambling the scrambled pilot sub-channel data blocks and the remaining mapped sub-channel data blocks with the scrambling code;
• a selector for IFFT-transforming a signal output from the sub-channel scrambler, and selecting sub-channel data blocks having a minimum PAPR among the IFFT-transformed sub-channel data blocks;
• and
• antennas for transmitting the sub-channel data blocks output from the selector as an in-phase signal having no phase offset, and alternately transmitting the sub-channel data blocks output from the selector as an in-phase signal having no phase offset and a phase-inversed signal having a 180°-phase offset in a training symbol period.