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

• US 20020172184A1
• Filed: 03/26/2002
• Published: 11/21/2002
• Est. Priority Date: 03/27/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: TeleCIS Wireless, Inc.
• Inventors: Kim, Je-Woo, Park, Jong-Hyeon, Bae, Si-Hyun, Shim, Bok-Tae, Han, Kyung-Sup
• Granted Patent: US 7,028,246 B2
• Time in Patent Office: Days
• US Class Current: 370/344
• CPC Class Codes: H03M 13/2703 the interleaver involving at least two directions
• CPC Class Codes: H03M 13/31 combining coding for error detection or correction and efficient use of the spectrum without error detection or correction H03M5/14 , H03M5/145
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/04 using frequency diversity
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/262 Reduction thereof by selection of pilot symbols
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

Disclosed is an OFDM communication system and method for improving frequency utilization efficiency. In the system, a Reed-Solomon encoder codes input information data, and outputs a Reed-Solomon block comprised of a second number of Reed-Solomon symbols each comprised of a first number of Reed-Solomon symbol elements. An interleaver receives the Reed-Solomon block, and disperses 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.

Claims

1. A system for improving error correction capability in an OFDM (Orthogonal Frequency Division Multiplexing) communication system, comprising:

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.

2. The system as claimed in claim 1, wherein the first number and the fourth number are equal to each other, and the second number and the third number are equal to each other.

3. The system as claimed in claim 1, wherein the interleaver performs interleaving such that 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.

4. A system for repeatedly transmitting sub-channels in an OFDM communication system, comprising:

a sub-channel repeater for repeating input data blocks so as to transmit each of the input data blocks over a predetermined number of sub-channels; and

a plurality of mappers for mapping the sub-channels output from the sub-channel repeater according to a predetermined modulation mode.

5. The system as claimed in claim 4, 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 selectors for selecting a specific input data block among the input data blocks under the control of the sub-channel repetition controller, and transmitting the selected data block over a corresponding sub-channel.

6. The system as claimed in claim 5, 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.

7. The system as claimed in claim 4, 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.

8. The system as claimed in claim 4, 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.

9. A system for performing sub-channel assignment in an OFDM communication system, comprising:

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 such that 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.

10. The system as claimed in claim 9, 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.

11. 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.

12. The system as claimed in claim 11, wherein the number of the pilot scrambling codes is equal to the number of the scrambling codes.

13. The system as claimed in claim 12, wherein the number of the scrambling codes is equal to the number of IFFTs included in the OFDM communication system.

14. The system as claimed in claim 11, wherein when the number of the pilot scrambling codes is 4, the 4 pilot scrambling codes have a 90°

-phase difference from one another.

15. The system as claimed in claim 11, 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].

19. The method as claimed in claim 18, wherein the first number and the fourth number are equal to each other, and the second number and the third number are equal to each other.

20. The method as claimed in claim 18, wherein the interleaving step comprises the step of performing interleaving such that 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.

16. 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.

17. A transmission system employing transmission antenna diversity in an OFDM communication system, comprising:

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.

18. A method for improving error correction capability in an OFDM (Orthogonal Frequency Division Multiplexing) communication system, comprising 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. A method for repeatedly transmitting sub-channels in an OFDM communication system, comprising the steps of:

repeating input data blocks so as to transmit each of the input data blocks over a predetermined number of sub-channels; and

mapping the sub-channels over which the input data blocks are repeated, according to a predetermined modulation mode.

22. The method as claimed in claim 21, 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.

23. The method as claimed in claim 22, wherein the sub-channels over which the input data blocks are to be repeated, are determined depending on channel information of the sub-channels.

25. The method as claimed in claim 24, wherein the input sub-channel data blocks are connected to the sub-channels according to channel information and channel condition of the sub-channels.

27. The method as claimed in claim 26, wherein the number of the pilot scrambling codes is equal to the number of the scrambling codes.

28. The method as claimed in claim 27, wherein when the number of the pilot scrambling codes is 4, the 4 pilot scrambling codes have a 90°

-phase difference from one another.

29. The method as claimed in claim 27, 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].

24. A method for performing sub-channel assignment in an OFDM communication system, comprising 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.

26. 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.

30. 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.

31. A transmission method employing transmission antenna diversity in an OFDM communication system, comprising 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.

32. 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.