System and method for Huffman shaping in a data communication system

• US 8,000,387 B2
• Filed: 03/31/2010
• Issued: 08/16/2011
• Est. Priority Date: 08/11/2000
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Ungerboeck, Gottfried, Carlson, Arthur J.
• Primary Examiner(s): Ha; Dac V
• Application Number:
  US12/751,647
• Publication Number:
  US 20100246661A1
• Time in Patent Office: 503 Days
• Field of Search: 375261-265, 375/254, 375/285, 375296-298, 704/500, 704/501, 704/503, 704/504, 341/200, 341/384, 341/65
• US Class Current: 375/240
• CPC Class Codes: H03M 7/40 Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code
• CPC Class Codes: H04L 27/3405 Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power

Abstract

In a communication system, Huffman coding techniques are used to obtain shaping gains for an improvement in data transmission rates. More particularly, a novel method of Huffman shaping is described that achieves a shaping gain of greater than 1 dB. The shaping gain results in a higher data rate transmission in a communication system where transmitted power is constrained.

Claims

1. A communication system, comprising:

a transmitter that includes a scrambler, a shaper and a modulator,

wherein data is input into the transmitter,

wherein the scrambler scrambles the inputted data,

wherein the shaper accumulates the scrambled data,

wherein the accumulated data forms Huffman codewords,

wherein the shaper maps the formed Huffman codewords into channel symbols,

wherein the channel symbols are passed to the modulator, and

wherein the modulator transmits the channel symbols at a constant rate.

2. The communication system according to claim 1, wherein the scrambled data comprises pseudo-random data.

3. The communication system according to claim 1, wherein the transmitter performs channel coding operations to achieve coding gain in addition to gains attributable to the Huffman codewords.

4. The communication system according to claim 1, wherein the shaper parses the accumulated data into Huffman codewords.

5. The communication system according to claim 1, wherein the transmitter frames the channel symbols.

6. The communication system according to claim 5, wherein the framing of the channel symbols by the transmitter comprises establishing symbol frames, and wherein the symbol frames have a same symbol frame length and have a same number of modulation symbols.

7. The communication system according to claim 6, wherein the symbol frames comprise a synchronization and pointer field that comprises a synchronization subfield and a pointer subfield.

8. The communication system according to claim 7, wherein the symbol frame comprises a portion of a first data frame and a portion of a second data frame.

9. The communication system according to claim 8, wherein the pointer subfield provides an offset value indicating a location of the second portion of the second data frame.

10. The communication system according to claim 8, wherein the symbol frame does not comprises a portion of a third data frame.

11. The communication system according to claim 6, wherein the channel symbols comprise variable-length channel symbols.

12. The communication system according to claim 1, wherein the channel symbols comprise variable-length channel symbols.

13. The communication system according to claim 1, wherein the transmitting of the channel symbols by the transmitter comprises transmitting the channel symbols onto one or more communications channels.

14. The communication system according to claim 1, wherein the transmitter does not perform trellis shaping, and wherein the transmitter does not perform shell mapping.

15. The communication system according claim 1, wherein the channel symbols comprise PAM symbols.

16. The communication system according to claim 1, wherein the channel symbols comprise QAM symbols.

17. The communication system according to claim 1, wherein the channel symbols do not form a uniform distribution.

18. The communication system according to claim 1, wherein the channel symbols are not equiprobable.

19. The communication system according to claim 1, wherein the channel symbols are equally spaced in time.

20. The communication system according to claim 1, wherein the transmitter provides Huffman shaping gains.

21. The communication system according to claim 1, wherein the channel symbols form a symbol constellation with unequal symbol probabilities and provide a shaping gain of greater than 1 dB.

22. The communication system according to claim 21, wherein the channel symbols provide a shaping gain of approximately 1.35 dB.

23. The communication system according to claim 21, wherein the channel symbols provide a shaping gain of approximately 1.5 dB.

24. The communication system according to claim 1, wherein the transmitter provides variable-rate encoded voice or video streams over one or more constant rate channels.

25. The communication system according to claim 1, wherein the scrambler is part of a source encoder, wherein the shaper is part of a channel encoder.

26. The communication system according to claim 25, wherein the channel encoder comprises the shaper and the modulator, and wherein the shaper is operatively coupled to the modulator.

27. The communication system according to claim 26, wherein the shaper comprises a Huffman decoder and a mapper, wherein the Huffman decoder is operatively coupled to the mapper and wherein the mapper is operatively coupled to the modulator.

28. The communication system according to claim 1, wherein the shaper controls a rate at which the shaper accumulates the scrambled data from the scrambler.

29. The communication system according to claim 1, wherein the channel symbols form an approximately Gaussian distribution.

30. The communication system according to claim 1, wherein the shaper comprises a mapper that maps the formed Huffman codewords into the channel symbols, and wherein the modulator provides a modulator clock to the mapper.

31. The communication system according to claim 1, comprising a receiver, wherein the receiver is operatively coupled to the transmitter over one or more communication channels.

32. The communication system according to claim 31, wherein the receiver comprises a demodulator, a Huffman encoder and a descrambler, wherein the Huffman encoder is operatively disposed between the demodulator and the descrambler.

33. The communication system according to claim 32, wherein the receiver comprises a slicer/decision element, wherein the slicer/decision element is operatively disposed between the demodulator and the Huffman encoder.