Method and apparatus for frequency domain data frame transmission

• US 6,598,200 B1
• Filed: 06/02/2000
• Issued: 07/22/2003
• Est. Priority Date: 06/02/2000
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Greenwood, John Christopher, Carotti, David
• Primary Examiner(s): Decady, Albert
• Assistant Examiner(s): Torres, Joseph D.
• Application Number:
  US09/587,036
• Time in Patent Office: 1,145 Days
• Field of Search: 714/776,774 370/329,341
• US Class Current: 714/774
• CPC Class Codes: H03M 13/05 using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits H03M13/2906 takes precedence
• CPC Class Codes: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/156 Encoding or decoding using time-frequency transformations, e.g. fast Fourier transformation
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0078 Avoidance of errors by organising the transmitted data in a format specifically designed to deal with errors, e.g. location forward error control, e.g. FEC, CRC H04L1/004; adaptive formatting H04L1/0006; mappings H04L27/00
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

Within a transmission channel in a frequency domain transmission medium, a plurality of non-contiguous channel portions are selected for data transmission. The selected channel portions are separated in frequency by unused channel portions. A transmitter generates a data frame of predetermined length for transmission, comprising a payload and an error detection portion. The frame length is equal to the length which would map for transmission into a symbol in the transmission channel if the entire channel were selected for transmission. The payload contains a header and a data portion, into which the transmitter inserts data bytes and a number of padding bytes. Block coding error correction is performed on the padded payload to generate error detection bytes to fill the error detection portion. The frame is then mapped into the frequency domain for transmission such that the header, data and error detection bytes map into the selected channel portions and the padding bytes map into the unused channel portions and are not transmitted. At a receiver, the padding bytes are reinstated and error detection performed to correct transmission errors in the header and the data. The corrected data is then extracted from the frame.

Claims

1. A method of operating a frequency domain data transmission system to transmit a data frame from a transmitter to a receiver using a transmission frequency band from which one or more frequency band portions are selected, by adaptive or pre-emptive selection or by allocation, for data transmission such that the frequency band contains one or more unused frequency band portions, comprising the steps of;

inserting data bits into a payload portion of the data frame;

padding with a predetermined bit sequence a portion of the payload;

applying error correction to the data bits and the padding bits and inserting error detection bits into the frame to form a data frame of a predetermined length;

mapping the data frame-into the transmission frequency band such that the payload and the error detection bits are mapped to and transmitted in the one or more selected frequency band portions and the padding bits are mapped to the one or more unused frequency band portions and are not transmitted;

receiving the data bits and the error detection bits from the one or more selected frequency band portions;

reinserting the padding bit sequence to restore the predetermined length frame, subject to any transmission errors;

applying error correction using the error detection bits to correct the transmission errors in the data bits, where possible; and

extracting the data bits.

2. A method according to claim 1, in which the predetermined bit sequence is a sequence of zero bits.

3. A method according to claim 1, in which the error correction is performed by a block coding technique.

4. A method according to claim 1, in which the error correction is performed by Reed Solomon coding.

5. A method according to claim 1, in which the error correction has an error correction capability which increases as the length of the predetermined padding bit sequence increases.

6. A method according to claim 1, in which the selection of frequency band portions for data transmission is independent of the predetermined length of the padded data frame.

7. A method according to claim 1, in which the predetermined length of the padded data frame is equal to the length of a data frame transmittable if the entire transmission frequency band were selected for transmission.

8. A method according to claim 1, in which the error correction has an error correction capability which is maintained independent of the bandwidth of the selected frequency band portions by adaptively varying the ratio of the number of data bits to the number of error detection bits in a data frame in accordance with the bandwidth of the selected frequency band portions.

9. A method according to claim 1, further comprising the step of sounding or monitoring the frequency band, or the selected frequency band portions, and modifying the selection of frequency band-portions in response to channel fading-in order to prevent use of frequency band portions likely to give rise to high transmission error rates.

10. A data transmission and reception system for implementing a method for operating a frequency domain transmission system as defined in claim 1.

11. A reduced-length data frame as transmitted using the method defined in claim 1.

12. A method of transmitting data in the frequency domain on a transmission frequency band from which one or more frequency band portions are selected, by adaptive or pre-emptive selection or by allocation, for data transmission, comprising the steps of;

inserting data bits into part of a payload portion of a data frame, leaving an unfilled part of the payload portion;

inserting padding bits into the unfilled part of the payload portion;

performing an error correction procession the payload portion to generate error detection bits, and inserting the error detection bits into an error detection portion of the data frame; and

mapping the frame into the frequency domain for transmission such that the error detection portion and all contents of the payload portion other than the padding bits map into the selected channel portions.

13. A transmitter for transmitting data using the method defined in claim 12.

14. A method of receiving data in the frequency domain on a transmission frequency band from which one or more frequency band portions are selected, by adaptive or preemptive selection or by allocation, for data transmission, in which data frames of a predetermined length, comprising a header and data bytes in a payload portion and error detection bytes in an error detection portion, are transmittable if all of the frequency band were used for data transmission, comprising the steps of;

receiving from the transmission frequency band a data frame of a reduced length, less than the predetermined length, and mapping it from the frequency domain to the time domain;

padding the payload portion of the frame with a predetermined padding bit sequence to restore the reduced-length frame to the predetermined length;

performing error correction using the error detection bits to detect and correct any transmission errors in the data bits, where possible; and

extracting the corrected data bits from the data frame.

15. A receiver for receiving data using the method defined in claim 14.