Method of multiple-antenna communication having improved utilization of channel correlations
View Patent ↗A MIMO transmission scheme is provided which provides some advantages of the Alamouti code but which can be adapted so as to provide enhanced performance for a given amount of antenna correlation. A block of complex scalar input symbols is mapped to a block-code matrix which is transmitted as a spacetime signal matrix from an array of two or more antennas. The block-code matrix is assembled by combining input data with specified dispersion matrices. Each of the dispersion matrices is determined, in part, by an adjustable parameter which relates to a degree of beam-forming behavior by the transmission antenna array.
1. A communication method in which two complex-valued input symbols s 1 and s 2 having respective real and imaginary parts Re(s 1 ), Im(s 1 ), Re(s 2 ) and Im(s 2 ) are mapped to a block-code matrix S for subsequent transmission, the communication method comprising:
constructing the block-code matrix S as a weighed sum of dispersion matrices A 1 , B 1 , A 2 , and B 2 , wherein the weights of A 1 and B 1 are respectively derived from Re(s 1 ) and Im(s 1 ) and the weights of A 2 and B 2 are respectively derived from Re(s 2 ) and Im(s 2 ); and
transmitting the block-code matrix S as a space-time signal matrix from an array of two or more antennas during two transmit symbol intervals;
wherein the dispersion matrices are defined by
A
1
=
[
1
ⅇ
jφ
α
0
ⅇ
jφ
1
-
α
]
A
2
=
[
α
ⅇ
jφ
-
1
-
α
0
]
B
1
=
[
1
-
α
0
-
α
-
ⅇ
jφ
]
B
2
=
[
0
ⅇ
jφ
1
-
α
1
ⅇ
jφ
α
]
;
and wherein the constructing of the block-code matrix S comprises selecting a value for α such that 0<α<1 to control a degree of beam-forming behavior by the antenna array, and further comprises selecting a value for φ based on an angular position of one of a user and a base station relative to the user to control a phase shift between two or more antennas of the array.
2. The method of claim 1 , further comprising obtaining values for α and φ and using the values to construct the dispersion matrices.
3. The method of claim 2 , wherein at least one value for φ is obtained by identifying a relative angular position between the base station and the user.
4. The method of claim 2 , wherein the obtaining values for α and φ comprises:
obtaining an initial value of φ and an initial estimate of α, and then refining the value of α.
5. The method of claim 4 , wherein the value of α is refined by an iterative estimation procedure that uses feedback information provided by a receiver.
6. The method of claim 2 , further comprising signaling a value for α to a receiver.