# US 7,609,771 B2 · Maximum ratio transmission

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- Number: US 7,609,771 B2
- Document ID: US7609771B2
- Status: Granted
- Kind: B2
- Application number: 12/034,771
- Filed: 2008-02-21
- Published: 2008-06-19
- Granted: 2009-10-27
- Earliest claimed: 1998-09-17
- Assignees: AT&T Mobility II LLC
- Inventors: Titus Lo
- Web page: https://patentgrep.com/patent/US7609771B2

## CPC

- H04B 7/0615: {of weighted versions of same signal}
- H04B 7/0617: {for beam forming}
- H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]}
- H04B 7/0857: {using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]}
- H04L 1/06: using space diversity
- H04L 25/03343: {Arrangements at the transmitter end}
- H04B 7/0842: {Weighted combining}
- H04L 25/0204: {of multiple channels}
- H04L 2025/03426: {transmission using multiple-input and multiple-output channels}
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

An arrangement where a transmitter has a plurality of transmitting antennas that concurrently transmit the same symbol, and where the signal delivered to each transmitting antenna is weighted by a factor that is related to the channel transmission coefficients found between the transmitting antenna and receiving antennas. In the case of a plurality of transmit antennas and one receive antenna, where the channel coefficient between the receive antenna and a transmit antenna i is hi, the weighting factor is hi* divided by a normalizing factor, a, which is ( ∑ k = 1 K ⁢  h k  2 ) 1 / 2 , where K is the number of transmitting antennas. When more than one receiving antenna is employed, the weighting factor is 1 a ⁢ ( gH ) H , where g=[g1 . . . gL), H is a matrix of channel coefficients, and α is a normalizing factor ( ∑ p = l L ⁢ ∑ q = l L ⁢  ∑ k = l K ⁢ h p ⁢ ⁢ k ⁢ h qk *  ) 1 / 2 .

## Claims

### Claim 1

A system comprising:
K transmit antennas;
a transmitter configured to weight a symbol c by a vector of K weighting factors, to thereby generate K weighted versions of the symbol c and configured to transmit respective weighted versions of the symbol c on corresponding antennas of the K transmit antennas,
wherein the vector of K weighting factors is proportional to [gH]H, where g is a vector having L components and the superscript H is the Hermitian operator,
wherein at least one of K and L is greater than one.

### Claim 2 (depends on 1)

The system, as recited in claim 1, further comprising:
L receive antennas; and
a receiver configured to receive from the L receive antennas, L received versions of the symbol c transmitted by the K transmit antennas and configured to weight the L received versions of the symbol c by the vector g to generate L weighted, received versions of the symbol c.

### Claim 3 (depends on 2)

The system, as recited in claim 2, wherein K is greater than one and L is greater than one.

### Claim 4 (depends on 2)

The system, as recited in claim 2, wherein the vector of K weighting factors is normalized by a normalization factor, a, equal to
(
∑
p
=
1
L
⁢
⁢
∑
q
=
1
L
⁢
⁢
g
p
⁢
g
q
*
⁢
∑
k
=
1
K
⁢
⁢
h
p
⁢
⁢
k
⁢
h
qk
*
)
1
/
2
,
wherein hpq is a matrix of coefficients for the channel between the K transmit antennas and the L receive antennas.

### Claim 5 (depends on 4)

The system as recited in claim 4, wherein the normalization factor, a, is
(
∑
p
=
1
L
⁢
⁢
∑
q
=
1
L
⁢
⁢

∑
k
=
1
K
⁢
⁢
h
p
⁢
⁢
k
⁢
h
qk
*

)
1
/
2
.

### Claim 6 (depends on 2)

The system as recited in claim 2, wherein the elements of vector g satisfy
(
g
p
⁢
g
q
*
)
=
∑
k
=
1
K
⁢
h
p
⁢
⁢
k
⁢
h
qk
*
⁢

∑
k
=
1
K
⁢
⁢
h
p
⁢
⁢
k
⁢
h
qk
*

,
where
p
=
1
,
2
,
…
⁢
,
⁢
K
⁢
⁢
and
⁢
⁢
q
=
1
,
2
,
…
⁢
,
⁢
L
.

### Claim 7 (depends on 2)

The system as recited in claim 2, wherein the receiver is configured to sum the L weighted, received versions of the symbol c to thereby form an estimated version, ĉ, of the symbol c.

### Claim 8 (depends on 7)

The system, as recited in claim 7, wherein an overall signal-to-noise ratio of the estimated version ĉ is set to a maximum value.

### Claim 9 (depends on 7)

The system, as recited in claim 7, wherein an overall signal-to-noise ratio (SNR) of the estimated version ĉ is
γ
=
a
2
L
⁢
γ
o
,
where
⁢
⁢
a
=
(
∑
p
=
1
L
⁢
⁢
∑
q
=
1
L
⁢
⁢

∑
k
=
1
K
⁢
⁢
h
p
⁢
⁢
k
⁢
h
qk
*

)
1
/
2
and γo is the average SNR for the case of a single transmitting antenna.

### Claim 10

A system comprising:
K transmit antennas;
L receive antennas;
a transmitter configured to weight a symbol c and configured to transmit respective weighted versions of the symbol c on corresponding antennas of the K transmit antennas; and
a receiver configured to receive from the L receive antennas, L received versions of the symbol c transmitted by the K transmit antennas and configured to weight the L received versions of the symbol and configured to sum the L weighted, received versions of the symbol to thereby form an estimated version, ĉ, of the symbol c,
wherein K is greater than one and L is greater than one and the overall signal-to-noise ratio (SNR) of the estimated version ĉ is
γ
=
a
2
L
⁢
γ
o
,
where
⁢
⁢
a
=
(
∑
p
=
1
L
⁢
⁢
∑
q
=
1
L
⁢
⁢

∑
k
=
1
K
⁢
⁢
h
p
⁢
⁢
k
⁢
h
qk
*

)
1
/
2
,
γo is the average SNR for the case of a single transmitting antenna, and
hpq is the element indexed by p and q of a channel estimate matrix H having K×L elements.

### Claim 11 (depends on 10)

The system, as recited in claim 10, wherein the transmitter weights the symbol c by a vector of K weighting factors, the vector of K weighting factors being proportional to [gH]H, where g is a vector having L components and the superscript H is the Hermitian operator.

### Claim 12 (depends on 10)

The system, as recited in claim 10, wherein the receiver weights L received versions of the symbol by the vector g the elements of vector g satisfying
(
g
p
⁢
g
q
*
)
=
∑
k
=
1
K
⁢
h
p
⁢
⁢
k
⁢
h
qk
*
⁢

∑
k
=
1
K
⁢
⁢
h
p
⁢
⁢
k
⁢
h
qk
*

,
where
p
=
1
,
2
,
…
⁢
,
⁢
K
⁢
⁢
and
⁢
⁢
q
=
1
,
2
,
…
⁢
,
⁢
L
,
and
hpq is an element indexed by p and q of a channel estimate matrix H having K×L elements.