Maximum ratio transmission

• US 7,609,771 B2
• Filed: 02/21/2008
• Issued: 10/27/2009
• Est. Priority Date: 09/17/1998
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: Lo, Titus
• Primary Examiner(s): Corrielus; Jean B
• Application Number:
  US12/034,771
• Publication Number:
  US 20080144739A1
• Time in Patent Office: 614 Days
• Field of Search: 375/299, 375/267, 375259-260, 375/347
• US Class Current: 375/259
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0842 Weighted combining
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

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 h_i, the weighting factor is h_i* divided by a normalizing factor, a, which is

${\left(\sum _{k=1}^K{h_k}^2\right)}^{1/2},$
where K is the number of transmitting antennas. When more than one receiving antenna is employed, the weighting factor is

$\frac{1}{a}{\left(\mathrm{gH}\right)}^H,$
where g=[g₁ . . . g_L), H is a matrix of channel coefficients, and α is a normalizing factor

${\left(\sum _{p=l}^L\sum _{q=l}^L\stackrel{K}{\sum _{k=l}}{h}_{pk}{h}_{\mathrm{qk}}^{*}\right)}^{1/2}.$

Claims

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.

2. 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.

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

4. The system, as recited in claim 2, wherein the vector of K weighting factors is normalized by a normalization factor, a, equal to

${(\sum _{}^{}}^{}$

p = 1 L ⁢

⁢

∑

q = 1 L ⁢

⁢

g p ⁢

g q * ⁢

∑

k = 1 K ⁢

⁢

h p ⁢

⁢

k ⁢

h qk * ) 1 / 2 ,

wherein h_pq is a matrix of coefficients for the channel between the K transmit antennas and the L receive antennas.

5. The system as recited in claim 4, wherein the normalization factor, a, is

${(\sum _{}^{}}^{}$

p = 1 L ⁢

⁢

∑

q = 1 L ⁢

⁢



∑

k = 1 K ⁢

⁢

h p ⁢

⁢

k ⁢

h qk * 

) 1 / 2 .

6. 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 .

7. 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.

8. 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.

9. The system, as recited in claim 7, wherein an overall signal-to-noise ratio (SNR) of the estimated version ĉ

is

$\mathrm{\gamma <br><br>}=\frac{a^2}{L}<br><br>{\mathrm{\gamma <br><br>}}_o,\text{where}<br><br><br><br>a={\left(\underset{p=1}{\overset{L}{\sum <br><br>}}<br><br><br><br>\underset{q=1}{\overset{L}{\sum <br><br>}}<br><br><br><br><br><br>\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br><br><br>h_{p<br><br><br><br>k}<br><br>h_{\mathrm{qk}}^{*}<br><br>\right)}^{1/2}$

and γ

_o is the average SNR for the case of a single transmitting antenna.

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

$\mathrm{\gamma <br><br>}=\frac{a^2}{L}<br><br>{\mathrm{\gamma <br><br>}}_o,\text{where}<br><br><br><br>a={\left(\underset{p=1}{\overset{L}{\sum <br><br>}}<br><br><br><br>\underset{q=1}{\overset{L}{\sum <br><br>}}<br><br><br><br><br><br>\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br><br><br>h_{p<br><br><br><br>k}<br><br>h_{\mathrm{qk}}^{*}<br><br>\right)}^{1/2},$

γ

_o is the average SNR for the case of a single transmitting antenna, and

h_pq is the element indexed by p and q of a channel estimate matrix H having K×

L elements.

11. 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.

12. 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

$\left(g_p\; <li></li>g_q^{*}\right)=\frac{\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br>h_{p<br><br><br><br>k}<br><br>h_{\mathrm{qk}}^{*}}{<br><br><br><br>\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br><br><br>h_{p<br><br><br><br>k}<br><br>h_{\mathrm{qk}}^{*}<br><br>},\text{where}\text{p}=1,2,\mathrm{\dots <br><br>}<br><br>,<br><br>K<br><br><br><br>\text{and}<br><br><br><br>q=1,2,\mathrm{\dots <br><br>}<br><br>,<br><br>L,\text{and}$

h_pq is an element indexed by p and q of a channel estimate matrix H having K×

L elements.