Complementary beamforming methods and apparatuses

• US 7,925,303 B2
• Filed: 05/12/2006
• Issued: 04/12/2011
• Est. Priority Date: 11/04/2002
• Status: Active Grant

• Current Assignee: XR Communications, LLC
• Original Assignee: XR Communications, LLC
• Inventors: Alamouti, Siavash, Choi, Yang-Seok, Tarokh, Vahid
• Primary Examiner(s): Chang; Kent
• Assistant Examiner(s): Lam; Dung
• Application Number:
  US11/383,167
• Publication Number:
  US 20060234789A1
• Time in Patent Office: 1,796 Days
• Field of Search: 455/562.1, 455/63.4, 455/575.7, 455/25, 455/271, 342/351, 342/354, 342/367, 342/369, 342/67, 342/368
• US Class Current: 455/562.1
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Improved methods and apparatuses are provided to address a potential “hidden beam problem” in wireless communication systems employing smart antennas. The improved methods and apparatuses utilize complementary beamforming (CBF) techniques, such as, for example, Subspace Complementary Beamforming (SCBF), Complementary Superposition Beamforming (CSBF) and/or Single Beam Complementary Beamforming (SBCBF) techniques.

Claims

1. A method, comprising:

determining at least one signal operatively configured for subspace complementary beamforming (SCBF) in a wireless communication system;

generating the at least one signal such that the signal is operatively configured to cause a smart antenna to perform said SCBF and transmit at least one complementary beam; and

determining the at least one signal using a Steering Matrix;

A=[a(θ

₁) a(θ

₂) . . . a(θ

_k)], wherein a(θ

_k) represents a steering vector of user k;

wherein;

if W=A*B, where B is a non-singular K-by-K matrix, then using a complementary beamforming matrix of

2. A method as recited in claim 1, further comprising determining the at least one signal by at least one of:

modifying a weight matrix to operatively support said SCBF;

expanding a size of the weight matrix to operatively support said SCBF.

3. A method as recited in claim 1, further comprising determining the at least one signal using a Downlink Beamforming Matrix:

W=UΛ

V^H.

4. A method as recited in claim 1, wherein it is assumed that 2K<

N,

5. A method, comprising:

determining at least one signal operatively configured for complementary superposition beamforming (CSBF) in a wireless communication system;

generating the at least one signal such that the signal is operatively configured to cause a smart antenna to perform said CSBF and to transmit at least one complementary beam, and

determining the at least one signal using a downlink beamforming matrix;

{tilde over (W)}=└

w₁ . . . w<sub>k−

1</sub> {tilde over (w)}_k w_k+1 . . . w_k┘

, where {tilde over (w)}_k=p₀w_k+W^cp and p is complex conjugate transpose of the l-th row of W^c,

6. A method as recited in claim 5, further comprising determining the at least one signal using a null-generation technique that is configured to generate L nulls at angles θ

₁, θ

₂, . . . θ

_L at a beam.

7. A method as recited in claim 5, further comprising determining said at least one signal using:

A=[a(θ

₁) a(θ

₂) . . . a(θ

_L)].

8. A method as recited in claim 5, further comprising determining the at least one signal using a vector:

w=(I−

P_s)w where P_s=A*(A^T A*)<sup>−

1</sup> A^T, and in scattering channel P_s=H*(H^T A*)<sup>−

1</sup> H^T.

9. A method as recited in claim 5, further comprising determining the at least one signal using a null-widening technique that is configured to produce at least one null at a vicinity of selected angles.

10. A method as recited in claim 5, further comprising determining the at least one signal by selectively modifying a steering matrix to:

A=└

ã

(θ

₁){tilde over (a)}(θ

₂) . . . ã

(θ

_K)┘

, wherein {tilde over (a)}(θ

_K)=└

a(θ

_k−

Δ

θ

₁)a(θ

_k)a(θ

_k+Δ

θ

_r)┘

.

11. A method as recited in claim 5, further comprising determining the at least one signal by establishing at least two nulls such that a rank of A is less than N.

12. A method as recited in claim 5, further comprising determining the at least one signal using adaptive control of a complementary beam level.

13. A method as recited in claim 5, further comprising determining the at least one signal, in a non-zero angular channel, by selectively reducing a complementary beam level.

14. A method as recited in claim 5, further comprising determining the at least one signal, for delay spread channels, by selectively reducing a complementary beam level.

15. A method as recited in claim 5, further comprising determining the at least one signal, in free space, by selectively increasing the complementary beam level.

16. A method, comprising:

determining at least one signal operatively configured for complementary superposition beamforming (CSBF) in a wireless communication system;

generating the at least one signal such that the signal is operatively configured to cause a smart antenna to perform said CSBF and to transmit at least one complementary beam, and

determining the at least one signal using;

{tilde over (W)}=[w₁ w₂ . . . w_k W^cp]

wherein;

p is complex conjugate transpose of the l-th row of W^c,

W^c=√

{square root over (c₀[u_K+1, u_K+2, . . . , u_N])},

c₀ is a scalar, K=the number of users, N=the number of antennas and u_l is the l-th column vector of U.

17. A method as recited in claim 16, further comprising determining the at least one signal using a null-generation technique that is configured to generate L nulls at angles θ

₁, θ

₂, . . . θ

_L at a beam.

18. A method as recited in claim 16, further comprising determining said at least one signal using:

A=[a(θ

₁) a(θ

₂) . . . a(θ

_L)].

19. A method as recited in claim 16, further comprising determining the at least one signal using a vector:

w=(I−

P_s)w where P_s=A*(A^T A*)<sup>−

1</sup> A^T, and in scattering channel P_s=H*(H^T A*)<sup>−

1</sup>H^T.

20. A method as recited in claim 16, further comprising determining the at least one signal using a null-widening technique that is configured to produce at least one null at a vicinity of selected angles.

21. A method as recited in claim 16, further comprising determining the at least one signal by selectively modifying a steering matrix to:

A=└

ã

(θ

₁)ã

(θ

₂) . . . {tilde over (a)}(θ

_K)┘

, wherein ã

(θ

_K)=└

a(θ

_k−

Δ

θ

₁)a(θ

_k)a(θ

_k+Δ

θ

_r)┘

.

22. A method as recited in claim 16, further comprising determining the at least one signal by establishing at least two nulls such that a rank of A is less than N.

23. A method as recited in claim 16, further comprising determining the at least one signal using adaptive control of a complementary beam level.

24. A method as recited in claim 16, further comprising determining the at least one signal, in a non-zero angular channel, by selectively reducing a complementary beam level.

25. A method as recited in claim 16, further comprising determining the at least one signal, for delay spread channels, by selectively reducing a complementary beam level.

26. A method as recited in claim 16, further comprising determining the at least one signal, in free space, by selectively increasing the complementary beam level.

27. A method, comprising:

determining at least one signal operatively configured for complementary superposition beamforming (CSBF) in a wireless communication system;

generating the at least one signal such that the signal is operatively configured to cause a smart antenna to perform said CSBF and to transmit at least one complementary beam, and

determining the at least one signal using a downlink beamforming matrix;

{tilde over (W)}=└

w₁ . . . w<sub>k−

1</sub> {tilde over (w)}_k w_k+1 . . . w_k┘

, where {tilde over (w)}_k=p₀w_k+W^cp and p is complex conjugate transpose of the l-th row of W^c,

28. A method as recited in claim 27, further comprising determining the at least one signal using a null-generation technique that is configured to generate L nulls at angles θ

₁, θ

₂, . . . θ

_L at a beam.

29. A method as recited in claim 27, further comprising determining said at least one signal using:

A=[a(θ

₁) a(θ

₂) . . . a(θ

_L)].

30. A method as recited in claim 27, further comprising determining the at least one signal using a vector:

w=(I−

P_s)w where P_s=A*(A^T A*)<sup>−

1</sup> A^T, and in scattering channel P_s=H*(H^T A*)<sup>−

1</sup>H^T.

31. A method as recited in claim 27, further comprising determining the at least one signal using a null-widening technique that is configured to produce at least one null at a vicinity of selected angles.

32. A method as recited in claim 27, further comprising determining the at least one signal by selectively modifying a steering matrix to:

A=└

ã

(θ

₁)ã

(θ

₂) . . . ã

(θ

_K)┘

, wherein {tilde over (a)}(θ

_K)=└

a(θ

_k−

Δ

θ

₁)a(θ

_k)a(θ

_k+Δ

θ

_r)┘

.

33. A method as recited in claim 27, further comprising determining the at least one signal by establishing at least two nulls such that a rank of A is less than N.

34. A method as recited in claim 27, further comprising determining the at least one signal using adaptive control of a complementary beam level.

35. A method as recited in claim 27, further comprising determining the at least one signal, in a non-zero angular channel, by selectively reducing a complementary beam level.

36. A method as recited in claim 27, further comprising determining the at least one signal, for delay spread channels, by selectively reducing a complementary beam level.

37. A method as recited in claim 27, further comprising determining the at least one signal, in free space, by selectively increasing the complementary beam level.

38. A method, comprising:

determining at least one signal operatively configured for complementary superposition beamforming (CSBF) in a wireless communication system;

generating the at least one signal such that the signal is operatively configured to cause a smart antenna to perform said CSBF and to transmit at least one complementary beam, and

determining the at least one signal using;

{tilde over (W)}=[w₁ w₂ . . . w_k W^cp]

wherein;

p is complex conjugate transpose of the l-th row of W^c,

W^c=√

{square root over (c₀[u_a,r+1, e_a,r+2, . . . , u_a,N])},

c₀ is a scalar, K=the number of users, N=the number of antennas, r=rank of W and is in the range of K to 2K and u_a,l is the l-th left singular vector whose corresponding singular value is zero.

39. A method as recited in claim 38, further comprising determining the at least one signal using a null-generation technique that is configured to generate L nulls at angles θ

₁, θ

₂, . . . θ

_L at a beam.

40. A method as recited in claim 38, further comprising determining said at least one signal using:

A=[a(θ

₁) a(θ

₂) . . . a(θ

_L)].

41. A method as recited in claim 38, further comprising determining the at least one signal using a vector:

w=(I−

P_s)w where P_s=A*(A^T A*)<sup>−

1</sup> A^T, and in scattering channel P_s=H*(H^T A*)<sup>−

1</sup> H^T.

42. A method as recited in claim 38, further comprising determining the at least one signal using a null-widening technique that is configured to produce at least one null at a vicinity of selected angles.

43. A method as recited in claim 38, further comprising determining the at least one signal by selectively modifying a steering matrix to:

A=└

ã

(θ

₁)ã

(θ

₂) . . . {tilde over (a)}(θ

_K)┘

, wherein ã

(θ

_K)=└

a(θ

_k−

Δ

θ

₁)a(θ

_k)a(θ

_k+Δ

θ

_r)┘

.

44. A method as recited in claim 38, further comprising determining the at least one signal by establishing at least two nulls such that a rank of A is less than N.

45. A method as recited in claim 38, further comprising determining the at least one signal using adaptive control of a complementary beam level.

46. A method as recited in claim 38, further comprising determining the at least one signal, in a non-zero angular channel, by selectively reducing a complementary beam level.

47. A method as recited in claim 38, further comprising determining the at least one signal, for delay spread channels, by selectively reducing a complementary beam level.

48. A method as recited in claim 38, further comprising determining the at least one signal, in free space, by selectively increasing the complementary beam level.