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 process for equalizing stream weights in a system having a plurality n of received signal streams, each said signal stream having a plurality m of subcarriers, the process having the steps:
a first step of measuring a noise variance σ j 2 for each signal stream j of said signal streams 1 through n;
a second step of computing a channel weighting for each j stream of:
s
j
=
n
(
σ
1
*
…
*
σ
n
)
/
σ
j
∑
k
=
1
n
(
σ
1
2
*
…
*
σ
n
2
)
/
σ
k
2
a third step of multiplying each of said m subcarriers of said signal stream j by said s j .
2. A process for equalizing stream weights in a system having two received signal streams, each stream having a plurality m of subcarriers, the process having the steps:
a first step of measuring a noise variance σ j 2 for each stream j of said two streams;
a second step of computing a channel weighting to said first stream of
s
1
=
2
σ
2
σ
1
2
+
σ
2
2
and a channel weighting to said second stream of
s
2
=
2
σ
1
σ
1
2
+
σ
2
2
a third step of multiplying said first stream by said s 1 and said second stream by said s 2 .
3. A process for equalizing stream weights in a system having three received signal streams, each stream having a plurality m of subcarriers, the process having the steps:
a first step of measuring a noise variance σ j 2 for each stream j of said three streams;
a second step of computing a channel weighting for said first stream of
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
for said second stream of
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
and for said third stream of
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
a third step of forming a channel equalized first stream by multiplying the subcarriers of said first stream by said s 1 , forming a channel equalized second stream by multiplying the subcarriers of said second stream by said s 2 , and forming a channel equalized third stream by multiplying the subcarriers of said third stream by said s 3 .