Application of a pseudo-randomly shuffled Hadamard function in a wireless CDMA system

• US 20050047482A1
• Filed: 09/16/2004
• Published: 03/03/2005
• Est. Priority Date: 12/05/2000
• Status: Abandoned Application

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Gossett And Gunter, Inc.
• Inventors: Gossett, Carroll Philip, Gunter, Michial Allen
• Application Number:
  US10/943,677
• Publication Number:
  US 20050047482A1
• Time in Patent Office: Days
• US Class Current: 375/146
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04J 13/004 Orthogonal

Abstract

A method of improving bandwidth of wireless CDMA systems by shuffling the rows of a Hadamard function in a pseudo-random manner. A Hadamard function is used to provide orthogonality between users. The orthogonal waveforms are used to prevent interference from different users sharing the same cell as well as multiple channels from the same user. The rows of the Hadamard function are shuffled in a pseudo-random manner. This effectively maximally spreads the spectral density of the transmitted signal out across the available spectrum. These codes are pre-computed and stored in lookup tables of mobile wireless devices. The data signals are modulated by one set of codes. Thereby, one data bit can be transmitted per chip.

Claims

1. In a wireless spread-spectrum system, a method of modulating a signal comprising the steps of:

generating a plurality of columns of code in an orthogonal matrix;

arranging rows of the code in a pseudo-random manner to achieve maximal spread spectral density independent of chip replication;

modulating a data signal according to the columns of codes;

transmitting the modulated data signal on a carrier.

2. The method of claim 1 further comprising the steps of:

storing columns of codes in a receiver which match the columns of codes stored on a transmitter;

demodulating a received signal according to a same code which was used to modulate the received signal.

3. The method of claim 1, wherein pre-shuffled rows of codes correspond to a Walsh function.

4. The method of claim 3 further comprising the step of shuffling rows of the Walsh function to arrange the columns of codes in the pseudo-random manner.

5. The method of claim 4, wherein the rows of codes are shuffled to maximally spread the data signal in an RF spectrum

6. The method of claim 1 further comprising the step transmitting signals according to a Code Division Multiple Access (CDMA) technique.

7. The method of claim 1, wherein the data signal comprises digitized speech.

8. The method of claim 1, wherein the data signal comprises packetized data.

9. The method of claim 1 further comprising the step of storing the plurality of columns of codes in a lookup table.

10. The method of claim 1 further comprising the steps of:

compressing the columns of codes;

storing compressed matrix codes in a lookup table.

11. The method of claim 10, wherein the codes is compressed by storing only the power-of-two numbered columns of a pseudo-randomly shuffled Hadamard matrix.

12. The method of claim 1 further comprising the step of transmitting one data bit per chip.

13. The method of claim 1 further comprising the step of aggregating more than 64 channels.

14. The method of claim 1 further comprising the step of aggregating more than 128 channels.

15. The method of claim 1 further comprising the step of aggregating more than 256 channels.

16. The method of claim 1 further comprising the step of aggregating more than 512 channels.

17. The method of claim 1 further comprising the step of aggregating more than 1024 channels.

18. The method of claim 1 further comprising the step of aggregating more than 2048 channels.

19. The method of claim 1 further comprising the step of aggregating more than 4096 channels.

20. The method of claim 1 further comprising the step of aggregating more than 8192 channels.

21. The method of claim 1 further comprising the step of aggregating more than 16384 channels.

22. A spread-spectrum system comprising:

a memory having a set of rows of codes corresponding to an orthogonal function which has been arranged in a pseudo-random manner to achieve maximal spread spectral density;

a modulator coupled to the memory which modulates an information signal according to one of the columns of codes stored in the memory;

an RF transmitter which transmits the modulated signal on a carrier over the air.

23. The spread-spectrum system of claim 22, wherein the same set of columns of codes are stored on a plurality of wireless devices.

24. The spread-spectrum system of claim 22, wherein unshuffled rows of codes correspond to a Hadamard function.

25. The spread-spectrum system of claim 24, wherein the rows of the Hadamard function are shuffled in a pseudo-random manner.

26. The spread-spectrum system of claim 25, wherein the rows of codes are shuffled to maximally spread the spectral density of the transmitted signal across the spectrum.

27. The spread-spectrum system of claim 22 further comprising the implementation of a Code Division Multiple Access (CDMA) technique.

28. The spread-spectrum system of claim 22, wherein the information signal comprises digitized speech.

29. The spread-spectrum system of claim 22, wherein the information signal comprises packetized data.

30. The spread-spectrum system of claim 22, wherein the memory stores the set of codes in a lookup table.

31. The spread-spectrum system of claim 30, wherein the codes comprise N by 2 memory of compressed codes.

32. The spread-spectrum system of claim 22, wherein the codes are compressed by storing only the power-of-two columns of a pseudo-randomly shuffled Hadamard matrix.

33. The spread-spectrum system of claim 22 further comprising a counter which is incremented to select which of the rows of codes stored in the memory is used to modulate the information signal.

34. The spread-spectrum system of claim 22, wherein modulation of the information signal by the column is DC free.

35. The spread-spectrum system of claim 22, wherein one data bit is transmitted per chip.

36. The spread-spectrum system of claim 22, wherein the RF transmitter transmits to a receiver on a peer-to-peer basis.

37. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 64 channels.

38. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 128 channels.

39. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 256 channels.

40. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 512 channels.

41. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 1024 channels.

42. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 2048 channels.

43. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 4096 channels.

44. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 8192 channels.

45. The spread-spectrum system of claim 22 further comprising the step of aggregating more than 16384 channels.

46. In a wireless spread-spectrum system, a method of transmitting aggregated channels comprising the steps of:

generating a plurality of columns of codes which are orthogonal to achieve maximal spread spectral density;

modulating a data signal according to the columns of codes;

aggregating more than 64 channels;

transmitting the modulated data signal on a carrier.

47. The method of claim 46 further comprising the step of aggregating more than 128 channels.

48. The method of claim 46 further comprising the step of aggregating more than 256 channels.

49. The method of claim 46 further comprising the step of aggregating more than 512 channels.

50. The method of claim 46 further comprising the step of aggregating more than 1024 channels.

51. The method of claim 46 further comprising the step of aggregating more than 2048 channels.

52. The method of claim 46 further comprising the step of aggregating more than 4096 channels.

53. The method of claim 46 further comprising the step of aggregating more than 8192 channels.

54. The method of claim 46 further comprising the step of aggregating more than 16384 channels.

55. The method of claim 46 further comprising the step of pseudo-randomly shuffling rows of the orthogonal codes.

56. A system for transmitting aggregated channels, comprising:

a memory having a matrix corresponding to an orthogonal function with maximally spread spectral density;

a modulator coupled to the memory which modulates an information signal according to one of the columns of the matrix stored in the memory;

an aggregator coupled to the memory which aggregates more than 64 channels for transmission;

an RF transmitter which transmits the modulated signal on a carrier over the air.

57. The system of claim 56, wherein more than 128 channels are aggregated.

58. The system of claim 56, wherein more than 256 channels are aggregated.

59. The system of claim 56, wherein more than 512 channels are aggregated.

60. The system of claim 56, wherein more than 1024 channels are aggregated.

61. The system of claim 56, wherein more than 2048 channels are aggregated.

62. The system of claim 56, wherein more than 4096 channels are aggregated.

63. The system of claim 56, wherein more than 8192 channels are aggregated.

64. The system of claim 56, wherein more than 16384 channels are aggregated.

65. The system of claim 56, wherein rows of the orthogonal function are pseudo-randomly shuffled.