Complementary beamforming methods and apparatuses
View Patent ↗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.
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
W
c
=
k
0
C
0
N
[
u
K
+
1
u
K
+
2
…
u
N
]
wherein C 0 =Nc 0 is the level of the main lobe, k 0 is the scaling factor and u l is the l-th column vector of U; otherwise using a complementary beamforming matrix of
W
c
=
k
0
C
0
N
[
u
_
1
u
_
2
…
u
_
N
-
K
]
wherein ū 1 is the l-th left singular vector of the matrix
(
∑
l
=
K
+
1
N
u
~
1
u
~
1
H
)
U
Λ
c
=
U
Λ
_
V
_
H
,
where A*=Ũ{tilde over (Λ)}{tilde over (V)} H is assumed and a scattering channel
H*=Ũ{tilde over (Λ)}{tilde over (V)} H is assumed.
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=UΛV H .
4. A method as recited in claim 1 , wherein it is assumed that 2K<N,
W
a
=
(
W
A
*
)
=
U
a
Λ
a
V
a
H
,
and
W
c
=
k
0
C
0
N
[
u
a
,
r
+
1
u
a
,
r
+
2
…
u
a
,
N
]
;
and
wherein r is rank of W a .
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)}=└w 1 . . . w k−1 {tilde over (w)} k w k+1 . . . w k ┘, where {tilde over (w)} k =p 0 w k +W c p and p is complex conjugate transpose of the l-th row of W c ,
p
0
=
w
k
,
l
*
w
k
,
l
is normalized complex conjugate of the l-th element of w k ,
where W c =√{square root over (c 0 [u K+1 , u K+2 , . . . u N ])},
C 0 is a scalar, K=the number of users, N=the number of antennas and u l is the l-th vector of U.
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*) −1 A T , and in scattering channel P s =H*(H T A*) −1 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 −Δθ 1 ) a (θ k ) a (θ k +Δθ 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)}=[w 1 w 2 . . . w k W c p]
wherein:
p is complex conjugate transpose of the l-th row of W c ,
W c =√{square root over ( c 0 [u K+1 , u K+2 , . . . , u N ])},
c 0 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*) −1 A T , and in scattering channel P s =H*(H T A*) −1 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 −Δθ 1 ) a (θ k ) a (θ k +Δθ 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)}=└w 1 . . . w k−1 {tilde over (w)} k w k+1 . . . w k ┘, where {tilde over (w)} k =p 0 w k +W c p and p is complex conjugate transpose of the l-th row of W c ,
p
0
=
w
k
,
l
*
w
k
,
l
is normalized complex conjugate of the l-th element of w k ,
where W c =√{square root over (c 0 [u a,r+1 , u a,r+2 , . . . , u a,N ])},
c 0 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.
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*) −1 A T , and in scattering channel P s =H*(H T A*) −1 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 −Δθ 1 ) a (θ k ) a (θ k +Δθ 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)}=[w 1 w 2 . . . w k W c p]
wherein:
p is complex conjugate transpose of the l-th row of W c ,
W c =√{square root over ( c 0 [u a,r+1 , e a,r+2 , . . . , u a,N ])},
c 0 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*) −1 A T , and in scattering channel P s =H*(H T A*) −1 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 −Δθ 1 ) a (θ k ) a (θ k +Δθ 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.