Undulating transmit patterns to support signal separation at a receiver

• US 7,362,269 B2
• Filed: 12/19/2006
• Issued: 04/22/2008
• Est. Priority Date: 09/23/2004
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Goldberg, Steven J., Shah, Yogendra
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Mull, Fred H.
• Application Number:
  US11/612,797
• Publication Number:
  US 20070176825A1
• Time in Patent Office: 490 Days
• Field of Search: 342/373, 342377-378, 342/380, 342382-383, 455/103, 455/105, 455137-138, 702190-197, 702/FOR.164
• US Class Current: 342/378
• CPC Class Codes: H04B 7/02 Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas RAKE receivers H04B1/7115
• CPC Class Codes: H04B 7/08 at the receiving station
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A communications system includes a fixed transmitter and a mobile wireless communications device. The fixed transmitter transmits a source signal defined by a character set made up of symbols. At least one of the symbols in the character set is transmitted at a different power level so that the transmitted source signal appears with linearly independent power level time periods. The linearly independent power level time periods are used by the mobile wireless communications device to populate a mixing matrix for signal separation processing.

Claims

1. A communications system comprising:

at least one fixed transmitter for transmitting a source signal defined by a character set comprising a plurality of symbols, and at least one of the symbols in the character set being transmitted at a different power level so that the transmitted source signal appears with L linearly independent power level time periods, where L≧

2; and

a mobile wireless communications device for separating source signals provided by M signal sources, where M≧

2, and with said at least one transmitter providing one of the M source signals with the L linearly independent power level time periods, said wireless communications device comprising

an antenna array comprising N antenna elements for receiving at least N different summations of the M source signals, where N≧

1,

a receiver coupled to said antenna array for receiving the at least N different summations of the M source signals, and

a signal separation processor coupled to said receiver for forming a mixing matrix comprising the at least N different summations of the M source signals, the mixing matrix having a rank equal to at least L*N, said signal separation processor for separating desired source signals from the mixing matrix.

2. A communications system according to claim 1 wherein the amplitude of each symbol in the character set is constant, with at least two of the symbols being at different power levels.

3. A communications system according to claim 1 wherein said at least one fixed transmitter is part of a base station so that the communications system is configured as a cellular network.

4. A communications system according to claim 3 wherein said at least one fixed transmitter comprises a plurality of fixed transmitters, wherein a coverage area associated with the base station is divided into sectors, with a respective fixed transmitter associated with each sector and transmitting at least one of the symbols in the respective character sets at a different power level.

5. A communications system according to claim 1 further comprising at least one fixed receiver associated with said at least one fixed transmitter;

and wherein said wireless communications device further comprises a mobile transmitter for providing feedback to said at least one fixed transmitter via said at least one fixed receiver on transmission of the at least one symbol in the character set at the different power level.

6. A communications system according to claim 5 wherein the feedback comprises at least one of adjustment of the power level, and a sequence of the symbols within character sets being transmitted at the different power level.

7. A communications system according to claim 1 wherein said N antenna elements comprise N correlated antenna elements.

8. A communications system according to claim 7 wherein said N correlated antenna elements comprise N active antenna elements so that said antenna array forms a phased array.

9. A communications system according to claim 7 wherein said N correlated antenna elements comprise at least one active antenna element, and up to N-1 passive antenna elements so that said antenna array forms independent sums of incident signals.

10. A communications system according to claim 1 wherein at least two of said N antenna elements are correlated and have different polarizations for receiving at least two of the N different summations of the M source signals.

11. A communications system according to claim 1 wherein said wireless communications device further comprises a respective in-phase and quadrature module coupled between each antenna element and said receiver for separating each one of the N different summations of the M source signals received thereby into an in-phase and quadrature component set;

said receiver receiving the at least N in-phase and quadrature component sets for the at least N different summations of the M source signals; and

said signal separation processor forming the mixing matrix comprising at least 2*L*N different summations of the M source signals, with each in-phase and quadrature component set providing 2 inputs into the mixing matrix for each of the L linearly independent power level time periods, and with the mixing matrix having a rank equal to at least 2*L*N.

12. A communications system according to claim 1 wherein said wireless communications device further comprises a code despreader coupled between said N antenna elements and said receiver for decoding the at least N different summations of the M source signals, each one of the N different summations including k codes for providing k different summations of the M source signals with L linearly independent power level time periods associated therewith;

said receiver receiving at least k*L*N different summations of the M source signals; and

said signal separation processor forming the mixing matrix comprising the at least k*L*N different summations of the M source signals, the mixing matrix having a rank equal to at least k*L*N.

13. A communications system according to claim 1 wherein said antenna array generates N initial antenna patterns, said antenna array comprising an elevation controller for selectively changing an elevation of at least one of the N initial antenna patterns for generating at least one additional antenna pattern so that at least one additional different summation of the M source signals is received thereby;

said receiver receiving the N different summations of the M source signals using the N initial antenna patterns, and receiving the at least one additional different summation of the M source signals using the at least one additional antenna pattern;

said signal separation processor forming the mixing matrix comprising the N different summations of the M source signals and the at least one additional different summation of the M source signals, for each of the L linearly independent power level time periods, the mixing matrix having the rank equal up to at least L*N plus the number of additional different summations of the M source signals times the L linearly independent power level time periods using the additional antenna patterns.

14. A communications system according to claim 1 wherein said at least one fixed transmitter comprises J spaced apart fixed transmitters, where J≧

2, each fixed transmitter for transmitting the at least one source signal defined by the character set comprising a plurality of symbols, with at least one of the symbols in the character set being transmitted at a different power level so that the J source signals from the J transmitters appear with at least L₁ to L_J linearly independent power level time periods, where L_j≧

1 with at least one L_j>

1; and

the power levels at each fixed transmitter being coordinated to maximize the different relative linearly independent power level time periods from said J fixed transmitters; and

wherein said signal separation processor forms the mixing matrix comprising the at least N different summations of the M source signals, the mixing matrix having a rank equal to at least (L₁* . . . *L_J)*N.

15. A communications system according to claim 14 wherein coordination of said J spaced apart fixed transmitters is based upon at least one of pattern usage, orientation, power levels and timing of said J transmitters.

16. A communications system according to claim 14 wherein a number of combinations for populating the mixing matrix is based upon the number of different power levels being used, the time periods being used and the coordination between said J transmitters.

17. A communications system according to claim 1 wherein said signal separation processor comprises a blind signal separation processor, and separates the desired source signals from the mixing matrix based on at least one of principal component analysis (PCA), independent component analysis (ICA), and single value decomposition (SVD).

18. A communications system according to claim 1 wherein said signal separation processor separates the desired source signals from the mixing matrix based on a knowledge based processing signal extraction process.

19. A communications system according to claim 1 wherein said signal separation processor separates the desired source signals from the mixing matrix based on a combination of a knowledge based signal extraction process and a blind signal separation process.

20. A communications system comprising;

at least one transmitter for transmitting a spread spectrum source signal defined by symbols, each symbol comprising a plurality of chips based upon a spreading code, and a portion of the chips within each symbol being transmitted at different power levels so that the transmitted source signal appears with L linearly independent power level time periods, where L≧

2; and

a mobile wireless communications device for separating source signals provided by M signal sources, where M≧

2, and with said at least one transmitter providing one of the M source signals with the L linearly independent power level time periods, said wireless communications device comprising

an antenna array comprising N antenna elements for receiving at least N different summations of the M source signals, where N≧

1,

a receiver coupled to said antenna array for receiving the at least N different summations of the M source signals, and

a signal separation processor coupled to said receiver for forming a mixing matrix comprising the at least N different summations of the M source signals, the mixing matrix having a rank equal to at least L*N, said signal separation processor for separating desired source signals from the mixing matrix.

21. A communications system according to claim 20 where a number of the portions of chips being transmitted at different power levels within each symbol is equal to the rank of the mixing matrix.

22. A communications system according to claim 20 wherein the chips in each portion of chips being transmitted at different power levels within each symbol comprises a set of contiguous chips.

23. A communications system according to claim 20 wherein an amplitude of each chip within a symbol is constant.

24. A communications system according to claim 20 wherein said at least one transmitter is part of a base station so that the communications system is configured as a cellular network.

25. A communications system according to claim 20 further comprising at least one receiver associated with said at least one transmitter;

and wherein said wireless communications device further comprises a mobile transmitter for providing feedback to said at least one transmitter via said at least one receiver on transmission of the portion of chips within each symbol at the different power level.

26. A communications system according to claim 25 wherein the feedback comprises at least one of adjustment of the power level, and a sequence of the chips being transmitted at the different power level.

27. A communications system according to claim 20 wherein said N antenna elements comprise N correlated antenna elements.

28. A communications system according to claim 27 wherein said N correlated antenna elements comprise N active antenna elements so that said antenna array forms a phased array.

29. A communications system according to claim 27 wherein said N correlated antenna elements comprise at least one active antenna element, and up to N-1passive antenna elements so that said antenna array forms independent sums of incident signals.

30. A communications system according to claim 20 wherein at least two of said N antenna elements are correlated and have different polarizations for receiving at least two of the N different summations of the M source signals.

31. A communications system according to claim 20 wherein said wireless communications device further comprises a respective in-phase and quadrature module coupled between each antenna element and said receiver for separating each one of the N different summations of the M source signals received thereby into an in-phase and quadrature component set;

said receiver receiving the at least N in-phase and quadrature component sets for the at least N different summations of the M source signals; and

said signal separation processor forming the mixing matrix comprising at least 2*L*N different summations of the M source signals, with each in-phase and quadrature component set providing 2 inputs into the mixing matrix for each of the L linearly independent power level time periods, and with the mixing matrix having a rank equal to at least 2*L*N.

32. A communications system according to claim 20 wherein said wireless communications device further comprises a code despreader coupled between said N antenna elements and said receiver for decoding the at least N different summations of the M source signals, each one of the N different summations including k codes for providing k different summations of the M source signals with L linearly independent power level time periods associated therewith;

said receiver receiving at least k*L*N different summations of the M source signals; and

said signal separation processor forming the mixing matrix comprising the at least k*L*N different summations of the M source signals, the mixing matrix having a rank equal to at least k*L*N.

33. A communications system according to claim 20 wherein said antenna array generates N initial antenna patterns, said antenna array comprising an elevation controller for selectively changing an elevation of at least one of the N initial antenna patterns for generating at least one additional antenna pattern so that at least one additional different summation of the M source signals is received thereby;

said receiver receiving the N different summations of the M source signals using the N initial antenna patterns, and receiving the at least one additional different summation of the M source signals using the at least one additional antenna pattern;

said signal separation processor forming the mixing matrix comprising the N different summations of the M source signals and the at least one additional different summation of the M source signals, for each of the L linearly independent power level time periods, the mixing matrix having the rank equal up to at least L*N plus the number of additional different summations of the M source signals times the L linearly independent power level time periods using the additional antenna patterns.

34. A communications system according to claim 20 wherein said at least one fixed transmitter comprises J spaced apart fixed transmitters, where J≧

2, each fixed transmitter for transmitting the at least one source signal defined by the character set comprising a plurality of symbols, with at least one of the symbols in the character set being transmitted at a different power level so that the J transmitted source signals from the J transmitters appear with at least L₁ to L_J linearly independent power level time periods, where L_J≧

1 with at least one L_j>

1; and

the power levels at each fixed transmitter being coordinated to maximize the different relative linearly independent power level time periods from said J fixed transmitters; and

wherein said signal separation processor forms the mixing matrix comprising the at least N different summations of the M source signals, the mixing matrix having a rank equal to at least (L₁* . . . *L_J)*N.

35. A communications system according to claim 33 wherein coordination of said J spaced apart fixed transmitters is based upon at least one of pattern usage, orientation, power levels and timing of said J transmitters.

36. A communications system according to claim 33 wherein a number of combinations for populating the mixing matrix is based upon the number of different power levels being used, the time periods being used and the coordination between said J transmitters.

37. A communications system according to claim 20 wherein said signal separation processor comprises a blind signal separation processor, and separates the desired source signals from the mixing matrix based on at least one of principal component analysis (PCA), independent component analysis (ICA), and single value decomposition (SVD).

38. A communications system according to claim 20 wherein said signal separation processor separates the desired source signals from the mixing matrix based on a knowledge based processing signal extraction process.