Closed loop precoding over a set of parallel channels
View Patent ↗Methods and apparatus are disclosed for applying successive multi-rank beamforming strategies (e.g., successive precoding strategies) for the design of precoders over a set of parallel channels. Successive beamforming is applied to a narrow band channel model and is also applied for finer quantization of a single beamforming vector (e.g., recursive beamforming). A first embodiment provides the optimal approach with high complexity. An alternative embodiment provides successive beamforming for near optimal precoding selection with medium complexity. A low complexity method for precoder selection is also provided wherein a channel representative matrix for the set of parallel channels is determined and successive beamforming on the calculated channel representative is applied.
1. A method of precoding for data transmission over set of parallel channels, the method comprising:
a. determining representative channels {H rep } for the set of parallel channels;
b. determining transmission rank; and
c. determining a precoding matrix of the transmission rank, based on {H rep }
wherein a representative channel for a subset of the set of parallel channels {H i } from a first index, T 1 , to a second index, T 2 , is determined as
H
rep
=
{
∑
i
=
T
1
T
2
H
i
*
H
i
}
1
2
wherein H i , is a channel of an i th tone.
2. The method of claim 1 , wherein the precoding is over wideband.
3. The method of claim 1 , wherein the precoder matrix selection is based on a capacity measure and the representative channels are defined for the capacity measure.
4. The method of claim 3 , wherein the capacity measure is based on Minimum Mean Square Error (MMSE).
5. The method of claim 3 , wherein the capacity measure is given by
C
MRBF
=
∑
i
=
T
1
T
2
∑
p
=
1
k
log
(
1
+
(
i
)
SINR
p
)
summed from the first index T 1 to the second index T 2 and over all streams where (i) SINR p , is a signal to noise ratio of a p th stream for an i th tone.
6. The method of claim 3 , wherein the capacity measure is based on successive interference cancellation (SIC).
7. The method of claim 3 , wherein the capacity measure is given by
C
MRBF
=
∑
i
=
T
1
T
2
log
(
det
(
I
+
ρ
H
i
*
H
i
*
)
)
summed from the first index T 1 to the second index T 2 where Q is the precoding matrix.
8. The method of claim 3 , wherein the capacity measure is based on maximum likelihood (ML) or quasi-ML detection.
9. The method of claim 1 , wherein the set of parallel channels is a set of OFDM tones.
10. A method of precoding for data transmission over set of parallel channels, the method comprising:
choosing a capacity measure C MRBF for the set of parallel channels;
determining transmission rank; and
determining a precoding matrix of the transmission rank, based on the capacity measure,
wherein the capacity measure is given by
C
MRBF
=
∑
i
=
T
1
T
2
∑
p
=
1
k
log
(
1
+
(
i
)
SINR
p
)
summed from a first index T 1 to a second index T 2 and over all streams where (i) SINR p , is a signal to noise ratio of a p th stream for an i th tone.
11. A method of precoding for data transmission over set of parallel channels, the method comprising:
choosing a capacity measure C MRBF for the set of parallel channels;
determining transmission rank; and
determining a precoding matrix of the transmission rank, based on the capacity measure,
wherein the capacity measure is given by
C
MRBF
=
∑
i
=
T
1
T
2
log
(
det
(
I
+
ρ
H
i
*
H
i
*
)
)
summed from a first index T 1 to a second index T 2 where H i is a channel of an i th tone, and Q is the precoding matrix.