Stream weight estimation and compensation in SIMO/MIMO OFDM receivers
A process for equalizing streams of OFDM subcarrier data computes the noise variance for each stream, and forms a stream weighting coefficient by equalizing the noise variance, such that for a first stream having a noise variance σ 1 and a second stream having a noise variance of σ 2 , the first stream is scaled by k 1 = 2 σ 2 σ 1 2 + σ 2 2 and the second stream is scaled by k 2 = 2 σ 1 σ 1 2 + σ 2 2 .
1. A noise equalizer for a plurality n of data streams, each stream j of said n streams coupled to a receive antenna and baseband converted, each said stream j accompanied by a channel characterization matrix and a noise measurement σ j , each said j data stream and each said j channel characterization matrix scaled by a value
s
j
=
n
(
σ
1
*
…
*
σ
n
)
/
σ
j
∑
k
=
1
n
(
σ
1
2
*
…
*
σ
n
2
)
/
σ
k
2
.
2. The noise equalizer of claim 1 where said data stream is from an FFT output.
3. The noise equalizer of claim 1 where said data stream contains OFDM data modulated into subcarriers.
4. The noise equalizer of claim 1 where said data stream contains OFDM data modulated by subcarriers, and each said subcarrier is scaled by said S j value.
5. The noise equalizer of claim 1 where said data stream contains a plurality m of spatial streams of data, said plurality being equal to or less than said n.
6. The noise equalizer of claim 1 where said n is two, and said first data stream and said first channel characterization matrix is scaled by
s
1
=
2
σ
2
σ
1
2
+
σ
2
2
and said second data stream and said second channel characterization matrix is scaled by
s
2
=
2
σ
1
σ
1
2
+
σ
2
2
.
7. The noise equalizer of claim 1 where said n is three, and said first data stream and said first channel characterization matrix is scaled by s 1 , said second data stream and said second channel characterization matrix is scaled by s 2 , and said third data stream and said third channel characterization matrix is scaled by s 3 , where:
s
1
=
3
σ
2
σ
3
σ
1
2
σ
2
2
+
σ
2
2
σ
3
2
+
σ
3
2
σ
1
2
s
2
=
3
σ
3
σ
1
σ
1
2
σ
2
2
+
σ
2
2
σ
3
2
+
σ
3
2
σ
1
2
s
3
=
3
σ
1
σ
2
σ
1
2
σ
2
2
+
σ
2
2
σ
3
2
+
σ
3
2
σ
1
2
.
8. A noise equalizer for a plurality n of data streams, each stream j of said n streams coupled to a receive antenna, baseband converted, and transformed into a subcarrier frequency, each said stream j accompanied by a channel characterization matrix and a noise measurement σ j , whereby for a particular data stream and associated channel characterization matrix, if said particular data stream is associated with a larger σ j than a different data stream with a comparatively smaller σ j , said particular data stream is multiplied by a scaling factor which is smaller than the scaling factor for said different data stream.
9. The noise equalizer of claim 8 where said scaling factor for a channel j is
s
j
=
n
(
σ
1
*
…
*
σ
n
)
/
σ
j
∑
k
=
1
n
(
σ
1
2
*
…
*
σ
n
2
)
/
σ
k
2
.
10. The noise equalizer of claim 8 where said data stream is from an FFT output.
11. The noise equalizer of claim 8 where said data stream contains OFDM data modulated into subcarriers.
12. The noise equalizer of claim 8 where said data stream contains OFDM data modulated by subcarriers, and each said subcarrier is scaled by said S j value.
13. The noise equalizer of claim 8 where said data stream contains a plurality m of spatial streams of data, said plurality being equal to or less than said n.
14. The noise equalizer of claim 8 where said n is two, and said first data stream and said first channel characterization matrix is scaled by
s
1
=
2
σ
2
σ
1
2
+
σ
2
2
and said second data stream and said second channel characterization matrix is scaled by
s
2
=
2
σ
1
σ
1
2
+
σ
2
2
.
15. The noise equalizer of claim 8 where said n is three, and said first data stream and said first channel characterization matrix is scaled by s 1 , said second data stream and said second channel characterization matrix is scaled by s 2 , and said third data stream and said third channel characterization matrix is scaled by s 3 , where:
s
1
=
3
σ
2
σ
3
σ
1
2
σ
2
2
+
σ
2
2
σ
3
2
+
σ
3
2
σ
1
2
s
2
=
3
σ
3
σ
1
σ
1
2
σ
2
2
+
σ
2
2
σ
3
2
+
σ
3
2
σ
1
2
s
3
=
3
σ
1
σ
2
σ
1
2
σ
2
2
+
σ
2
2
σ
3
2
+
σ
3
2
σ
1
2
.