Maximum ratio transmission

• US 7,274,752 B2
• Filed: 10/12/2004
• Issued: 09/25/2007
• Est. Priority Date: 09/17/1998
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Cingular Wireless II LLC (AT&T, Inc.)
• Inventors: Lo, Titus
• Primary Examiner(s): Corrielus; Jean B.
• Application Number:
  US10/963,838
• Publication Number:
  US 20050078769A1
• Time in Patent Office: 1,078 Days
• Field of Search: 375/299, 375/267, 375/347, 375/349, 455/101
• US Class Current: 375/299
• 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, α, 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

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

Claims

1. A wireless communication system for transmitting a signal to a receiver, the system comprising:

means for multiplying two or more symbols, to be transmitted, by a distinct weighting factor; and

means, coupled to the means for multiplying, for transmitting the two or more multiplied symbols over two or more separate channels from the system for transmitting to the receiver; and

wherein each weighting factor is proportional to a complex conjugate of a particular one channel transfer coefficient for one of the two or more channels between the system for transmitting to the receiver.

2. The wireless communication system of claim 1 wherein the weighting factor is divided by a normalizing factor, and wherein the normalizing factor depends in part upon a number of transmitting antennas.

3. The wireless communication system of claim 1 wherein the receiver includes two or more antennas, and the weighting factor is a linear transformation of a channel condition between each one of two or more transmitting antennas and one of the two or more receiving antennas of the receiver.

4. The wireless communication system of claim 1, wherein the weighting factor is a vector according to the equation

$v={\frac{1}{a}}^{}$

[ h ⁢

1 ⁢

…

⁢

⁢

h ] H ,

wherein

$a={\left(\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br><br><br>{<br><br>h_k<br><br>}^2\right)}^{\frac{1}{2}};<br><br>\mathrm{and}$

wherein each of h₁ . . . h_k represents the particular one channel transfer coefficient for one of two or more channels between the system for transmitting to the receiver and H is a Hermitian operator.

5. A wireless communication method for a transmitter to a receiver, the method comprising:

multiplying two or more symbols, to be transmitted, by a distinct weighting factor; and

transmitting the two or more multiplied symbols over two or more separate channels from the transmitter to the receiver; and

wherein each weighting factor is proportional to a complex conjugate of a particular one channel transfer coefficient for one of the two or more channels between the transmitter to the receiver.

6. The method of claim 5 wherein the weighting factor is divided by a normalizing factor, and wherein the normalizing factor depends in part upon a number of transmitting antennas.

7. The method of claim 5 wherein the transmitter and the receiver each include two or more antennas, and the weighting factor is a linear transformation of a channel condition between each one of two or more transmitting antennas and one of the two or more receiving antennas.

8. The method of claim 5, wherein the weighting factor is a vector according to the equation

$v={\frac{1}{a}}^{}$

[ h 1 ⁢

…

⁢

⁢

h K ] H ,

wherein

$a={\left(\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br><br><br>{<br><br>h_k<br><br>}^2\right)}^{\frac{1}{2}};<br><br>\mathrm{and}$

wherein each of h₁ . . . h_k represents the particular one channel transfer coefficient for one of the two or more channels between the transmitter to the receiver and H is a Hermitian operator.

9. In a closed loop system for wireless communication, the system comprising in part a transmitter apparatus and a receiver apparatus, a method of receiving a wirelessly transmitted signal, the method comprising:

receiving a signal at one or more receiver antennas;

multiplying the received signal using one or more multipliers, wherein for each one of the receiver antennas, the multiplying includes multiplying a received signal by multiple weighting factors; and

wherein the weighting factors are vectors associated with multiple channel transfer coefficients, wherein each channel transfer coefficient is associated with one of multiple transmit antennas and each of the one or more receiver antennas, and wherein each vector also represents a correlation vector between multiple channels associated with the one or more channel transfer coefficients.

10. The method of claim 9 wherein the weighting factors are divided by a normalizing factor, and wherein the normalizing factor depends in part upon a number of transmitting antennas.

11. The method of claim 9 wherein the weighting factors are complex conjugates of corresponding channel coefficients.

12. The method according to claim 9, wherein the weighting factor is a vector determined according to the equation

$v={\frac{1}{a}}^{}$

[ h 1 ⁢

…

⁢

⁢

h K ] H ,

wherein

$a={\left(\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br><br><br>{<br><br>h_k<br><br>}^2\right)}^{\frac{1}{2}};<br><br>\mathrm{and}$

wherein each of h₁ . . . h_k represents the particular one channel transfer coefficient for one of the two or more channels between the transmitter to the receiver and H is a Hermitian operator.