SYSTEMS, METHODS AND TRANSCEIVERS FOR WIRELESS COMMUNICATIONS OVER DISCONTIGUOUS SPECTRUM SEGMENTS

• US 20070202816A1
• Filed: 02/27/2007
• Published: 08/30/2007
• Est. Priority Date: 02/28/2006
• Status: Active Grant

• Current Assignee: ATC Technology Corporation (FedEx Corporation)
• Original Assignee: ATC Technology Corporation (FedEx Corporation)
• Inventors: Zheng, Dunmin
• Granted Patent: US 7,974,176 B2
• Time in Patent Office: Days
• US Class Current: 455/91
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

Methods of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band include defining a plurality (N_FFT) of orthogonal subcarriers across the frequency band, defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers. The available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments. The methods further include multiplexing the plurality of communications signals onto the plurality of available physical subcarriers. Multiplexing the plurality of communications signals onto the plurality of available physical subcarriers may include assigning the communications signals to respective ones of a plurality (N) of logical subcarriers, and mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers. Related transmitters, receivers and communications systems are also disclosed.

Claims

1. A method of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band, comprising:

defining a plurality (N_FFT) of orthogonal subcarriers across the frequency band;

defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers, wherein N<

N_FFT, and wherein the available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments; and

multiplexing the plurality of communications signals onto the plurality of available physical subcarriers.

2. The method of claim 1, wherein multiplexing the plurality of communications signals onto the plurality of available physical subcarriers comprises:

assigning the communications signals to respective ones of a plurality (N) of logical subcarriers; and

mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers.

3. The method of claim 2, wherein multiplexing the communications signals onto the plurality of available physical subcarriers comprises:

assigning at least one pilot signal to at least one of the plurality of logical subcarriers; and

modulating each of the available physical subcarriers with data from a corresponding logical subcarrier.

4. The method of claim 3, further comprising:

defining a plurality (N_FFT-N) of unavailable physical subcarriers within the frequency band; and

setting an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero;

wherein the communications signals and the at least one pilot signal comprise N information signals corresponding to the available physical subcarriers; and

wherein modulating each of the available physical subcarriers with data from a corresponding logical subcarrier comprises performing an N_FFT-point inverse fourier transform of the N information signals corresponding to the available physical subcarriers and the N_FFT-N input data signals corresponding to each of the plurality of unavailable physical subcarriers.

6. The method of claim 4, further comprising

converting an output of the N_FFT-point inverse fourier transform to a serial data stream;

and

transmitting the serial data stream.

7. The method of claim 4, further comprising:

defining a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality contiguous subcarriers;

defining an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols;

allocating a first plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel; and

allocating a second plurality of subcarriers within the AMC subchannel as data subcarriers.

8. The method of claim 7, wherein defining the AMC subchannel comprises

defining a subchannel comprising two clusters over three symbols.

9. The method of claim 7, wherein defining the AMC subchannel comprises

defining a subchannel comprising one cluster over six symbols.

10. The method of claim 7, wherein the pilot subcarriers for an AMC subchannel are allocated at locations determined by the indices of logical subcarriers.

11. The method of claim 10, wherein pilot subcarriers in an AMC channel are offset by two subcarriers in adjacent symbols.

12. The method of claim 10, wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation:

13. The method of claim 7, further comprising:

assigning a plurality of data symbols to data subcarriers in the AMC subchannel according to a scrambling sequence.

14. The method of claim 13, wherein the scrambling sequence is defined by a Galois field and an offset.

15. The method of claim 13, wherein the scrambling sequence is unique to a particular cell and/or sector of a wireless communications system.

16. The method of claim 1, wherein multiplexing the plurality of communications signals onto the plurality of available physical subcarriers comprises:

spreading the plurality of communications signals using a plurality of corresponding spreading codes;

combining the plurality of spread communications signals to form a combined communications signal; and

converting the combined communications signal to parallel communications signals.

17. The method of claim 16, wherein combining the plurality of communications signals to form a combined communications signal comprises combining the plurality of communications signals with a pilot signal.

18. The method of claim 16, wherein multiplexing the plurality of communications signals onto the plurality of available physical subcarriers comprises:

assigning the parallel communications signals to respective ones of a plurality (N) of logical subcarriers; and

mapping the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers.

19. The method of claim 18, wherein multiplexing the communications signals onto the plurality of available physical subcarriers comprises:

assigning at least one pilot signal to at least one of the plurality of logical subcarriers; and

modulating each of the available physical subcarriers with data from a corresponding logical subcarrier.

20. The method of claim 19, further comprising:

defining a plurality (N_FFT-N) of unavailable physical subcarriers within the frequency band; and

setting an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero;

wherein the parallel communications signals and the at least one pilot signal comprise N information signals corresponding to the available physical subcarriers; and

wherein modulating each of the available physical subcarriers with data from a corresponding logical subcarrier comprises performing an N_FFT-point inverse fourier transform of the N information signals corresponding to the available physical subcarriers and the N_FFT-N input data signals corresponding to each of the plurality of unavailable physical subcarriers.

21. The method of claim 20, further comprising

converting an output of the N_FFT-point inverse fourier transform to a serial data stream;

and

transmitting the serial data stream.

22. The method of claim 20, further comprising:

defining a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality contiguous subcarriers;

defining an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols; and

allocating a plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel.

23. The method of claim 22, wherein the pilot subcarriers for an AMC subchannel are allocated at locations determined by the indices of logical subcarriers.

24. The method of claim 23, wherein pilot subcarriers in adjacent symbols of an AMC channel are offset by two subcarriers.

25. The method of claim 23, wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation:

44. The transmitter of claim 18, wherein the subcarrier mapper is further configured to assign at least one pilot signal to at least one of the plurality of logical subcarriers, and wherein the IFFT processor is further configured to modulate each of the available physical subcarriers with data from a corresponding logical subcarrier.

45. The transmitter of claim 44, wherein the subcarrier mapper is further configured to set an input data signal corresponding to each of a plurality (N_FFT-N) of unavailable physical subcarriers to zero, wherein the parallel communications signals and the at least one pilot signal comprise N information signals corresponding to the available physical subcarriers;

and

wherein the IFFT processor is further configured to perform an N_FFT-point inverse fourier transform of the N information signals corresponding to the available physical subcarriers and the N_FFT-N input data signals corresponding to each of the plurality of unavailable physical subcarriers.

46. The transmitter of claim 45, further comprising a parallel to serial converter configured to convert an output of the N_FFT-point inverse fourier transform to a serial data stream.

26. A method of transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band, comprising:

defining a plurality (N_FFT) of orthogonal subcarriers across the frequency band;

defining a plurality (N) of available physical subcarriers from among the orthogonal subcarriers, wherein the available physical subcarriers are distributed among the plurality of discontiguous bandwidth segments;

receiving M data symbols for each of K users;

spreading the data symbols of each user by an L-bit spreading code associated with the user to provide M spread data symbols for each of the K users;

combining m^th data symbols associated with each of the K users to provide M composite data signals;

converting the M composite data signals to parallel input signals having a length L;

interleaving the M parallel input signals to provide Q interleaved input signals having a length N;

assigning the Q interleaved input signals to the N available physical subcarriers; and

transmitting the Q interleaved input signals on the N available physical subcarriers.

27. The method of claim 26, wherein transmitting the Q interleaved input signals on the N available physical subcarriers comprises assigning zeros to N_FFT-N unavailable physical subcarriers to provide N_FFT input signals and performing an N_FFT point inverse fourier transform on the N_FFT input signals.

28. A transmitter for a wireless communications system, comprising:

a subcarrier mapper configured to receive a plurality of input symbols, configured to assign the plurality of input symbols to N logical subcarriers, configured to map the N logical subcarriers to N available physical subcarriers out of N_FFT physical subcarriers, and configured to generate N_FFT transmit symbols corresponding to the N_FFT physical subcarriers;

an inverse fast fourier transform (IFFT) processor configured to perform an inverse fourier transform on the N_FFT transmit symbols output by the subcarrier mapper; and

a parallel to serial converter configured to convert an output of the IFFT processor to a serial output stream.

29. The transmitter of claim 28, wherein the N_FFT available physical subcarriers comprise orthogonal subcarriers defined across a frequency band including a plurality of discontiguous available bandwidth segments, and wherein the N available physical subcarriers are distributed among the plurality of discontiguous available bandwidth segments.

30. The transmitter of claim 29, wherein the subcarrier mapper is further configured to assign at least one pilot signal to at least one of the plurality of logical subcarriers;

and

wherein the IFFT processor is further configured to modulate each of the available physical subcarriers with data from a corresponding logical subcarrier.

31. The transmitter of claim 30, wherein the subcarrier mapper is further configured to set an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero.

32. The transmitter of claim 31, wherein the subcarrier mapper is further configured to define a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality contiguous subcarriers, configured to define an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols, configured to allocate a first plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel, and configured to allocate a second plurality of subcarriers within the AMC subchannel as data subcarriers.

33. The transmitter of claim 32, wherein the AMC subchannel comprises two clusters over three symbols.

34. The transmitter of claim 32, wherein the AMC subchannel comprises one cluster over six symbols.

35. The transmitter of claim 32, wherein the subcarrier mapper is configured to allocate the pilot subcarriers for an AMC subchannel at locations determined by the indices of logical subcarriers.

36. The transmitter of claim 32, wherein pilot subcarriers in an AMC channel are offset by two subcarriers in adjacent symbols.

37. The transmitter of claim 36, wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation:

38. The transmitter of claim 32, wherein the subcarrier mapper is further configured to assign a plurality of data symbols to data subcarriers in the AMC subchannel according to a scrambling sequence.

39. The transmitter of claim 38, wherein the scrambling sequence is defined by a Galois field and an offset.

40. The transmitter of claim 38, wherein the scrambling sequence is unique to a particular cell and/or sector of a wireless communications system.

41. The transmitter of claim 29, further comprising:

a plurality of spreaders configured to spread the communications signals using a plurality of corresponding spreading codes;

a combiner configured to combine the plurality of spread communications signals to form a combined communications signal; and

a serial to parallel converter configured to convert the combined communications signal to parallel communications signals.

42. The transmitter of claim 41, wherein the combiner is further configured to combine the plurality of communications signals with a pilot signal.

43. The transmitter of claim 41, wherein the subcarrier mapper is further configured to assign the parallel communications signals to respective ones of a plurality (N) of logical subcarriers, and configured to map the plurality of logical subcarriers to corresponding ones of the plurality of available physical subcarriers.

59. The receiver of claim 29, further comprising:

a parallel to serial converter configured to convert the reconstructed transmit data stream to a parallel communications signal; and

a despreader configured to despread the parallel communications signals using a spreading code associated with the receiver.

47. A transmitter for transmitting a plurality of communications signals over a plurality of discontiguous bandwidth segments in a frequency band, comprising:

a plurality of spreaders configured to spread M data symbols for each of K users according to a corresponding spreading code having length L;

a plurality of combiners configured to combine the m^th data symbols for each of the K users to provide M composite spread signals;

a plurality of serial to parallel converters configured to convert the M composite spread signals to M parallel input signals;

a frequency interleaver configured to interleave the M parallel input signals to provide Q interleaved input signals having a length N;

a subcarrier mapper configured to assign the Q interleaved input signals to the N available physical subcarriers; and

an inverse fast fourier transform (IFFT) processor configured to modulate N available physical subcarriers with the Q interleaved input signals.

48. The transmitter of claim 47, wherein the subcarrier mapper is configured to assign zeros to N_FFT-N unavailable physical subcarriers to provide N_FFT input signals, and wherein the IFFT processor is configured to perform an N_FFT point inverse fourier transform on the N_FFT input signals.

49. A receiver for a wireless communications system, comprising:

a serial to parallel converter configured to convert a received symbol stream to an N_FFT symbol wide parallel received symbol stream;

a fast fourier transform (FFT) processor configured to perform an N_FFT-point fourier transform on the parallel received symbol stream and to generate received symbols corresponding to N_FFT subcarriers; and

a subchannel demapper configured to select N symbols of the received symbols corresponding to the N_FFT subcarriers, wherein the N selected symbols correspond to N available physical subcarriers out of the N_FFT subcarriers, and configured to reconstruct a transmit data stream associated with the receiver from the N selected symbols.

50. The receiver of claim 49, wherein the N_FFT available physical subcarriers comprise orthogonal subcarriers defined across a frequency band including a plurality of discontiguous available bandwidth segments, and wherein the N available physical subcarriers are distributed among the plurality of discontiguous available bandwidth segments.

51. The receiver of claim 50, wherein the subcarrier demapper is further configured to receive at least one pilot signal from at least one of the plurality of available physical subcarriers.

52. The receiver of claim 51, wherein the subcarrier demapper is further configured to receive a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality contiguous subcarriers, and configured to extract the at least one pilot signal from an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols.

53. The receiver of claim 52, wherein the AMC subchannel comprises two clusters over three symbols.

54. The receiver of claim 52, wherein the AMC subchannel comprises one cluster over six symbols.

55. The receiver of claim 52, wherein the subcarrier demapper is configured to locate pilot subcarriers in an AMC channel including nine subcarriers per cluster according to the equation:

56. The receiver of claim 52, wherein the subcarrier demapper is further configured to extract a plurality of data symbols from data subcarriers in the AMC subchannel according to a scrambling sequence.

57. The receiver of claim 56, wherein the scrambling sequence is defined by a Galois field and an offset.

58. The receiver of claim 56, wherein the scrambling sequence is unique to a particular cell and/or sector of a wireless communications system.

60. A communications system, comprising:

a transmitter comprising;

a subcarrier mapper configured to receive a plurality of input symbols, configured to assign the plurality of input symbols to N logical subcarriers, configured to map the N logical subcarriers to N available physical subcarriers out of N_FFT physical subcarriers, and configured to generate N_FFT transmit symbols corresponding to the N_FFT physical subcarriers;

an inverse fast fourier transform (IFFT) processor configured to perform an inverse fourier transform on the N_FFT transmit symbols output by the subcarrier mapper; and

a parallel to serial converter configured to convert an output of the IFFT processor to a serial output stream; and

a receiver comprising;

a serial to parallel converter configured to convert a received symbol stream to an N_FFT symbol wide parallel received symbol stream;

a fast fourier transform (FFT) processor configured to perform an N_FFT-point fourier transform on the parallel received symbol stream and to generate received symbols corresponding to N_FFT subcarriers; and

a subchannel demapper configured to select N symbols of the received symbols corresponding to the N_FFT subcarriers, wherein the N selected symbols correspond to N available physical subcarriers out of the N_FFT subcarriers, and configured to reconstruct a transmit data stream associated with the receiver from the N selected symbols.

61. The communications system of claim 60, wherein the N_FFT available physical subcarriers comprise orthogonal subcarriers defined across a frequency band including a plurality of discontiguous available bandwidth segments, and wherein the N available physical subcarriers are distributed among the plurality of discontiguous available bandwidth segments.

62. The communications system of claim 61, wherein the subcarrier mapper is further configured to assign at least one pilot signal to at least one of the plurality of logical subcarriers;

and

wherein the IFFT processor is further configured to modulate each of the available physical subcarriers with data from a corresponding logical subcarrier.

63. The communications system of claim 62, wherein the subcarrier mapper is further configured to set an input data signal corresponding to each of the plurality of unavailable physical subcarriers to zero.

64. The communications system of claim 63, wherein the subcarrier mapper is further configured to define a plurality of clusters in the discontiguous bandwidth segments, each of the clusters comprising a plurality contiguous subcarriers, configured to define an adaptive modulation and coding (AMC) subchannel comprising a plurality of contiguous clusters extending over a plurality of contiguous symbols, configured to allocate a first plurality of subcarriers within the AMC subchannel as pilot subcarriers, such that the pilot subcarriers are distributed uniformly across the AMC subchannel, and configured to allocate a second plurality of subcarriers within the AMC subchannel as data subcarriers.

65. The communications system of claim 64, wherein the AMC subchannel comprises two clusters over three symbols.

66. The communications system of claim 64, wherein the AMC subchannel comprises one cluster over six symbols.

67. The communications system of claim 64, wherein the subcarrier mapper is configured to allocate the pilot subcarriers for an AMC subchannel at locations determined by the indices of logical subcarriers.

68. The communications system of claim 64, wherein pilot subcarriers in an AMC channel are offset by two subcarriers in adjacent symbols.

69. The communications system of claim 68, wherein the pilot subcarriers for an AMC channel including nine subcarriers per cluster are determined according to the equation:

70. The communications system of claim 64, wherein the subcarrier mapper is further configured to assign a plurality of data symbols to data subcarriers in the AMC subchannel according to a scrambling sequence.

71. The communications system of claim 70, wherein the scrambling sequence is defined by a Galois field and an offset.