Digital communication systems and methods for differential and/or amplitude encoding and decoding secondary symbols

• US 6,426,978 B1
• Filed: 10/01/1998
• Issued: 07/30/2002
• Est. Priority Date: 10/01/1998
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Bottomley, Gregory E., Ramesh, Rajaram
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Bayard, Emmanuel
• Application Number:
  US09/164,600
• Time in Patent Office: 1,398 Days
• Field of Search: 375/251, 375/265, 375/261, 375/262, 375/296, 375/308, 375/316, 375/329, 375/341, 375/343, 375/141, 375/219, 375/240.24, 375/240.25, 375/240.27, 714/752, 714/755, 714/781, 714/780, 714/786, 714/790, 714/791, 714/792, 714/793, 714/794, 714/795, 341/143, 348/410.1
• US Class Current: 375/265
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04L 23/02 adapted for orthogonal signalling

Abstract

Digital communication systems and methods combine block encoding and differential and/or amplitude modulation. For every codeword period, one or more additional bits can be transmitted by applying differential modulation and/or amplitude modulation to the codewords. In differential modulation, additional information may be sent by flipping or not flipping the sign of a codeword. In amplitude modulation, additional information may be sent by changing the amplitude of successive codewords. A combination of differential and amplitude encoding may also be used. Thus, the data rate can be increased without increasing the symbol transmission rate.

Claims

1. A transmitter that transmits a first bit stream and a second bit stream, the transmitter comprising:

a block encoder that encodes the first bit stream to produce codewords based on the first bit stream;

a differential and/or amplitude encoder that produces secondary symbols based on the second bit stream;

a first modulator that modulates the codewords according to the secondary symbols to produce modified codewords; and

a second modulator that modulates a carrier wave according to the modified codewords.

2. A transmitter according to claim 1 wherein the block encoder comprises a block encoder that encodes the first bit stream using an orthogonal code.

3. A transmitter according to claim 1 wherein the block encoder comprises a block encoder that encodes the first bit stream using at least one of Nordstrom-Robinson, Reed Muller and Kerdock codes.

4. A transmitter according to claim 1 wherein the differential and/or amplitude encoder is a differential encoder.

5. A transmitter according to claim 1 wherein the second modulator modulates a carrier wave according to the modified codewords using at least one of direct-sequence spreading and offset QPSK modulation.

6. A transmitter that transmits a first bit stream and a second bit stream, the transmitter comprising:

means for block encoding the first bit stream to produce codewords;

means for differential and/or amplitude encoding the second bit stream to produce secondary symbols;

means for modulating the codewords according to the secondary symbols to produce modified codewords; and

means for modulating a carrier wave according to the modified codewords.

7. A transmitter according to claim 6 wherein the means for block encoding comprises means for block encoding the first bit stream using an orthogonal code.

8. A transmitter according to claim 6 wherein the means for block encoding comprises means for block encoding the first bit stream using at least one of Nordstrom-Robinson, Reed Muller and Kerdock codes.

9. A transmitter according to claim 6 wherein the means for differential and/or amplitude encoding is a differential encoder.

10. A transmitter according to claim 6 wherein the means for modulating a carrier wave comprises means for modulating a carrier wave according to the modified codewords using at least one of direct-sequence spreading and offset QPSK modulation.

11. A method of transmitting a first bit stream and a second bit stream comprising the steps of:

block encoding the first bit stream to produce codewords;

differential and/or amplitude encoding the second bit stream to produce secondary symbols;

modulating the codewords according to the secondary symbols to produce modified codewords; and

modulating a carrier wave according to the modified codewords.

12. A method according to claim 11 wherein the step of block encoding comprises the step of block encoding the first bit stream using an orthogonal code.

13. A method according to claim 11 wherein the step of block encoding comprises the step of block encoding the first bit stream using at least one of Nordstrom-Robinson, Reed Muller and Kerdock codes.

14. A method according to claim 11 wherein the differential and/or amplitude encoding step comprises the step of differential encoding.

15. A method according to claim 11 wherein the step of modulating a carrier wave comprises the step of modulating a carrier wave according to the modified codewords using at least one of direct-sequence spreading and offset QPSK modulation.

16. A data signal embodied in a carrier wave comprising:

a plurality of codewords that are modulated on the carrier wave, the codewords comprising a block encoding of a first bit stream with differential and/or amplitude encoding of a second bit stream modulated thereon.

17. A data signal embodied in a carrier wave according to claim 16 wherein the block encoding comprises an orthogonal block encoding.

18. A data signal embodied in a carrier wave according to claim 16 wherein the block encoding comprises at least one of Nordstrom-Robinson, Reed Muller and Kerdock block encoding.

19. A data signal embodied in a carrier wave according to claim 16 wherein the codewords are modulated on a carrier wave using at least one of direct-sequence spreading and offset QPSK modulation.

20. A receiver that receives a data stream, the receiver comprising:

a correlator that correlates the data stream to a set of codewords to produce correlations;

a block code detector that detects codewords that correspond to the data stream; and

a differential and/or amplitude detector that detects sign and/or amplitude changes in the correlations to thereby detect differential and/or amplitude encoded secondary symbols in the data stream.

21. A receiver according to claim 20 wherein the block code detector comprises a soft decision block code detector or a hard decision block code detector and wherein the differential and/or amplitude detector comprises a soft decision differential and/or amplitude detector or a hard decision differential and/or amplitude detector.

22. A receiver according to claim 20 wherein the block code detector detects the highest correlations to thereby detect the codewords that correspond to the data stream.

23. A receiver according to claim 20 wherein the differential and/or amplitude detector comprises:

a delay unit that delays a correlation corresponding to a detected codeword; and

a multiplier that multiplies the complex conjugate of the delayed correlation with a current correlation to detect differentially encoded secondary symbols in the data stream.

24. A receiver that receives a data stream, the receiver comprising:

means for correlating the data stream to a set of codewords to produce correlations;

first means for detecting codewords that correspond to the data stream; and

second means for detecting sign and/or amplitude changes in the correlations to thereby detect differential and/or amplitude encoded secondary symbols in the data stream.

25. A receiver according to claim 24 wherein the first means for detecting comprises a soft decision block code detector or a hard decision block code detector and wherein the second means for detecting comprises a soft decision differential and/or amplitude detector or a hard decision differential and/or amplitude detector.

26. A receiver according to claim 24 wherein the first means for detecting comprises means for detecting the highest correlations to thereby detect the codewords that correspond to the data stream.

27. A receiver according to claim 24 wherein the second means for detecting comprises:

means for delaying a correlation corresponding to a detected codeword; and

means for multiplying the complex conjugate of the delayed correlation with a current correlation to detect differentially encoded secondary symbols in the data stream.

28. A method of receiving a data stream comprising the steps of:

correlating the data stream to a set of codewords to produce correlations;

detecting codewords that correspond to the data stream; and

detecting sign and/or amplitude changes in the correlations to thereby detect differential and/or amplitude encoded secondary symbols in the data stream.

29. A method according to claim 28 wherein the step of detecting codewords comprises the step of soft decision or hard decision detecting the codewords and wherein the step of detecting sign and/or amplitude changes comprises the step of soft detecting or hard detecting sign and/or amplitude changes.

30. A method according to claim 28 wherein the step of detecting the codewords comprises the step of detecting the highest correlations to thereby detect codewords that correspond to the data stream.

31. A method according to claim 28 wherein the step of detecting sign and/or amplitude changes comprises the steps of:

delaying a correlation corresponding to a detected codeword; and

multiplying the complex conjugate of the delayed correlation with a current correlation to detect differentially encoded secondary symbols in the data stream.

32. A digital communication system comprising:

a block encoder that encodes a first bit stream to produce codewords based on the first bit stream;

a differential and/or amplitude encoder that produces secondary symbols based on a second bit stream;

a first modulator that modulates the secondary symbols onto the codewords to produce modified codewords;

a second modulator that modulates a carrier wave according to the modified codewords;

a processor that receives the modulated carrier wave and produces a data stream therefrom;

a correlator that correlates the data stream to a set of codewords to produce correlations;

a block code detector that detects the codewords from the set of codewords; and

a differential and/or amplitude detector that detects sign and/or amplitude changes in the correlations corresponding to the detected codewords to thereby detect the secondary symbols in the data stream.

33. A system according to claim 32 wherein the block code detector is a soft decision block code detector or a hard decision block code detector and wherein the differential and/or amplitude detector is a soft decision differential and/or amplitude detector or a hard decision differential and/or amplitude detector.

34. A system according to claim 32 wherein the block code detector detects the highest correlations to thereby detect the codewords from the set of codewords.

35. A system according to claim 32 wherein the differential and/or amplitude detector comprises:

a delay unit that delays a correlation corresponding to a detected codeword; and

a multiplier that multiplies components of the delayed correlation and the current correlation together to detect differentially encoded secondary symbols in the data stream.

36. A system according to claim 32 wherein the block encoder comprises a block encoder that encodes the first bit stream using an orthogonal code.

37. A system according to claim 32 wherein the block encoder comprises a block encoder that encodes the first bit stream using at least one of Nordstrom-Robinson, Reed Muller and Kerdock codes.

38. A system according to claim 32 wherein the differential and/or amplitude encoder is a differential encoder.

39. A system according to claim 32 wherein the second modulator modulates a carrier wave according to the modified codewords using at least one of direct-sequence spreading and offset QPSK modulation.

40. A digital communication system comprising:

means for block encoding a first bit stream to produce codewords;

means for differential and/or amplitude encoding a second bit stream to produce secondary symbols;

means for modulating the codewords according to the secondary symbols to produce modified codewords;

means for modulating a carrier wave according to the modified codewords;

means for receiving the modulated carrier wave and for producing a data stream therefrom;

means for correlating the data stream to a set of codewords to produce correlations;

first means for detecting codewords that correspond to the first bit stream; and

second means for detecting differential and/or amplitude encoded secondary symbols that correspond to the second bit stream.

41. A system according to claim 40 wherein the means for block encoding comprises means for block encoding the first bit stream using an orthogonal code.

42. A system according to claim 40 wherein the means for block encoding comprises means for block encoding the first bit stream using at least one of Nordstrom-Robinson, Reed Muller and Kerdock codes.

43. A system according to claim 40 wherein the means for differential and/or amplitude encoding is a differential encoder.

44. A system according to claim 40 wherein the means for modulating a carrier wave comprises means for modulating a carrier wave according to the modified codewords using at least one of direct-sequence spreading and offset QPSK modulation.

45. A system according to claim 40 wherein the first means for detecting comprises a soft decision block code detector or a hard decision block code detector and wherein the second means for detecting comprises a soft decision differential and/or amplitude detector or a hard decision differential and/or amplitude detector.

46. A system according to claim 40 wherein the first means for detecting comprises means detecting the highest correlations to thereby detect the codewords that correspond to the first bit stream.

47. A system according to claim 40 wherein the second means for detecting comprises:

means for delaying a correlation corresponding to a detected codeword; and

means for multiplying components of the delayed correlation and the current correlation together to detect differentially encoded secondary symbols in the data stream.

48. A digital communication method comprising the steps of:

block encoding the first bit stream to produce codewords;

differential and/or amplitude encoding the second bit stream to produce secondary symbols;

modulating the codewords according to the secondary symbols to produce modified codewords;

modulating a carrier wave according to the modified codewords;

receiving the modulated carrier wave;

producing a data stream from the received modulated carrier wave;

correlating the data stream to a set of codewords to produce correlations;

detecting codewords that correspond to the bit stream; and

detecting sign and/or amplitude changes in the correlations corresponding to the detected codewords to thereby detect differential and/or amplitude encoded secondary symbols in the bit stream.

49. A method according to claim 48 wherein the step of block encoding comprises the step of block encoding the first bit stream using an orthogonal code.

50. A method according to claim 48 wherein the step of block encoding comprises the step of block encoding the first bit stream using at least one of Nordstrom-Robinson, Reed Muller and Kerdock codes.

51. A method according to claim 48 wherein the differential and/or amplitude encoding step comprises the step of differential encoding.

52. A method according to claim 48 wherein the step of modulating a carrier wave comprises the step of modulating a carrier wave according to the modified codewords using at least one of direct-sequence spreading and offset QPSK modulation.

53. A method according to claim 51 wherein the step of detecting codewords comprises the step of soft decision or hard decision detecting the codewords and wherein the step of detecting sign and/or amplitude changes comprises the step of soft detecting or hard detecting sign and/or amplitude changes.

54. A method according to claim 51 wherein the step of detecting codewords comprises the step of detecting the highest correlations to thereby detect the codewords that correspond to the first bit stream.

55. A method according to claim 51 wherein the step of detecting sign and/or amplitude changes comprises the steps of:

delaying a correlation corresponding to a detected codeword; and

multiplying components of the delayed correlation and the current correlation together to detect differentially encoded secondary symbols in the bit stream.