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

1. An OFDM (Orthogonal Frequency Division Multiplexing) 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 signals to parallel data blocks, repeating the parallel data blocks with 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 minimum PAPR (Peak-to-Average Power Ratio) selector for IFFT (Inverse Fast Fourier Transformer)-transforming a signal output from the sub-channel scrambler, and selecting sub-channel data blocks having a minimum PAPR among the LEFT-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.

2. The OFDM communication system in accordance with claim 1 , wherein the Reed-Solomon interleaver comprises

a Reed-Solomon encoder for coding input information data, and outputting a Reed-Solomon block comprised of a second number of Reed-Solomon symbols each comprised of a first number of Reed-Solomon symbol elements; and

an interleaver for receiving the Reed-Solomon block, and dispersing the Reed-Solomon symbol elements existing in a specified one Reed-Solomon symbol within the received Reed-Solomon block in the same sub-channel positions in a fourth number of sub-channels of each of a third number of consecutive OFDM symbols.

3. The OFDM communication system in accordance with claim 2 , wherein the first number and the fourth number are equal to each other, and said second number and said third number are equal to each other.

4. The OFDM communication system in accordance with claim 2 , wherein the interleaver performs interleaving so a last Reed-Solomon symbol element among the Reed-Solomon symbol elements of each of the Reed-Solomon symbols are arranged in sub-channels of a last OFDM symbol by sequentially arranging from a first Reed-Solomon symbol element among Reed-Solomon symbol elements of the Reed-Solomon symbols from sub-channels of a first symbol among consecutive OFDM symbols.

5. The OFDM communication system in accordance with claim 1 , wherein the OFDM communication system further comprises a plurality of mappers for mapping the sub-channels output from the sub-channel repeater according to a predetermined modulation mode.

6. The OFDM communication system in accordance with claim 5 , wherein the number of the mappers are equal in number to the number of output sub-channels, and the mappers map the sub-channels on a one-to-one basis according to the predetermined modulation mode.

7. The OFDM communication system in accordance with claim 5 , wherein the number of the mappers is less than the number of output sub-channels, and each of the mappers receives a predetermined number of sub-channels as an input signal and maps the predetermined number of sub-channels according to the predetermined modulation mode.

8. The OFDM communication system in accordance with claim 1 , wherein the sub-channel repeater comprises

a sub-channel repetition controller for determining a sub-channel over which a specific input data block among the input data blocks is to be repeated, and performing the sub-channel repetition according to the determined sub-channel; and

a plurality of selector for selecting a specific input data block among the input data blocks under the control of the sub-channel repetition controller, end transmitting the selected data block over a corresponding sub-channel.

9. The OFDM communication system in accordance with claim 8 , wherein the sub-channel repetition controller determines a sub-channel, over which the input data blocks are to be repeated, depending on channel information of the sub-channels.

10. The OFDM communication system in accordance with claim 1 , wherein the sub-channel assignor comprises

a plurality of selectors for selecting a specific sub-channel data block among input sub-channel data blocks according to a control signal, and transmitting the selected sub-channel data block over a corresponding sub-channel; and

a sub-channel assignment controller for controlling sub-channel assignment so each of the selectors converts a sub-channel data block to be selected from the sub-channel data blocks in a predetermined period of time.

11. The OFDM communication system in accordance with claim 10 , wherein the sub-channel assignment controller determines a sub-channel data block to be selected among the input sub-channel data blocks by the selectors according to channel information and channel condition of the sub-channels.

12. The OFDM communication system in accordance with claim 1 , wherein the sub-channel scrambler comprises

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; and

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.

13. The OFDM communication system in accordance with claim 12 , wherein the number of the pilot scrambling codes is equal to the number of the scrambling codes.

14. The OFDM communication system in accordance with claim 13 , wherein the number of the scrambling codes is equal to the number of IFFTs included in the OFDM communication system.

15. The OFDM communication system in accordance with claim 12 , wherein when the number of the pilot scrambling codes is 4, the 4 pilot scrambling codes have a 90°-phase difference from one another.

16. The OFDM communication system in accordance with claim 12 , wherein when the number of the pilot scrambling codes is 4, the 4 pilot scrambling codes include a first pilot scrambling code [1, 1, 1, 1], a second pilot scrambling code [−1, −1, −1, −1], a third pilot scrambling code [j, j, j, j], and a fourth pilot scrambling code [−j, −j, −j, −j].

17. The OFDM communication system in accordance with claim 1 , wherein the minimum PAPR selector comprises

a first 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 sub-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.

18. The OFDM communication system in accordance with claim 1 , wherein the antennas comprise

a first antenna for transmitting an in-phase signal having no phase offset with output data, upon receiving the output data; and

a second antenna for alternately transmitting the received output data as an in-phase signal having no phase offset with the output data and as a phase-inversed signal having a 180°-phase offset with the output data in a training symbol period.

19. A method of OFDM communication comprising the steps of:

Reed-Solomon interleaving 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;

sub-channel repeating for converting the interleaved singles to parallel data blocks, repeating the parallel data blocks with a predetermined number of times, and transmitting the repeated data blocks over corresponding sub-channels;

sub-channel assigning 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;

sub-channel scrambling 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;

minimum PAPR selecting 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

transmitting 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 via antennas.

20. The method of OFDM communication in accordance with claim 19 , wherein the Reed-Solomon interleaving step comprises the steps of:

coding input information data, and outputting a Reed-Solomon block comprised of a second number of Reed-Solomon symbols each comprised of a first number of Reed-Solomon symbol elements; and

performing interleaving by dispersing the Reed-Solomon symbol elements existing in a specified one Reed-Solomon symbol within the received Reed-Solomon block in the same sub-channel positions in a fourth number of sub-channels of each of a third number of consecutive OFDM symbols.

21. The method of OFDM communication in accordance with claim 19 , wherein the sub-channel repeating step comprises the steps of:

determining sub-channels over which a specific input data block among the input data blocks is to be repeated; and

repeatedly transmitting the input data blocks over the determined sub-channels.

22. The method of OFDM communication in accordance with claim 19 , wherein the sub-channel assigning step comprises the steps of:

transmitting input sub-channel data blocks over corresponding sub-channels connected at an initial input point; and

transmitting input sub-channel data blocks received after a lapse of a predetermined time from the initial input point, over sub-channels different from the sub-channels connected at the initial input point.

23. The method of OFDM communication in accordance with claim 19 , wherein the sub-channel scrambling step comprises the steps of:

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;

multiplying the input pilot sub-channel data blocks by a first pilot scrambling code among the pilot scrambling codes, for scrambling;

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.

24. The method of OFDM communication in accordance with claim 19 , wherein the minimum PAPR selecting step comprises the steps of:

IFFT-transforming the signals generated in the sub-channel scrambling step;

multiplying the input pilot sub-channel data blocks by a second pilot scrambling code among the pilot scrambling codes, for scrambling;

multiplying the sub-channel data blocks excluding the pilot sub-channel data blocks from the input sub-channel data blocks and data blocks output by a second scrambling code among the scrambling codes, for scrambling;

IFFT-transforming the signals generated in the multiplying step; and

calculating PAPRs of the sub-channel data blocks, 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.

25. The method of OFDM communication in accordance with claim 19 , wherein the transmitting step comprises the steps of:

transmitting an in-phase signal having no phase offset with output data, upon receiving the output data of the OFDM communication system; and

alternately transmitting the received output data as an in-phase signal having no phase offset with the output data and as a phase-inversed signal having a 180°-phase offset with the output data in a training symbol period.