MAXIMUM RATIO TRANSMISSION

• US 20080144739A1
• Filed: 02/21/2008
• Published: 06/19/2008
• Est. Priority Date: 09/17/1998
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: Lo, Titus
• Granted Patent: US 7,609,771 B2
• Time in Patent Office: Days
• 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, 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

$\left(\sum _{p=i}^L\sum _{q=l}^L\stackrel{K}{\sum _{k=l}}h_{pk}h_{\mathrm{qk}}^{*}\right).$

Claims

1. In a wireless communication system comprising a transmitter, the transmitter having a plurality of antennae for concurrently transmitting the same symbol to a receiver by said plurality of antennae, a method of estimating a value of a transmitted symbol c received at said receiver comprising:

weighting the transmitted symbol c with a transmit weighting vector v, a weighting factor of the transmit weighting vector v being equal to the conjugate, h_i*, of a channel coefficient, h_i, for a given transmission channel divided by a normalization factor, a quality of an estimate of the value of a transmitted symbol being improved by said weighting, where i is the number of transmit antennae between 2 and K where K is an integer greater than or equal to 2.

2. A method as recited in claim 1 comprising:

initially transmitting a sequence of pilot symbols from said transmitter to said receiver.

3. A method as recited in claim 1 where the normalization factor is given by the equation:

${\left(\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br>{<br><br>h_k<br><br>}^2\right)}^{1/2}.$

4. A method as recited in claim 1 wherein the weighting factor is a vector determined according to the equation

$v={\frac{1}{a}}^{}$

[ h 1 



…





h K ] H ,

where a is the normalization factor, K is the number of transmit antennae and H is the Hermitian operator.

5. A method as recited in claim 1 further comprising, at a receiver, weighting and summing received signals to produce an estimate of the transmitted symbol, c.

6. A method as recited in claim 1, when more than one receiving antenna is employed at said receiver, a weighting factor is proportional a receive channel coefficient and to the inverse of the normalization factor.

7. A method as recited in claim 6 wherein the normalization factor is given by the equation:

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

where L is the number of receive antennae.

8. A method as recited in claim 5, when more than one receiving antenna is employed at said receiver, a gain in signal-to-noise ratio of a channel between a transmit antenna and a receive antenna being proportional to the square of the normalization factor divided by the number of receive antennae.

22. A method as recited in claim 1 comprising:

initially transmitting a sequence of pilot symbols from said transmitter to said receiver.

9. A wireless communication transmitter, the transmitter having a plurality of antennae for concurrently transmitting the same symbol to a receiver by said plurality of antennae, the transmitter for transmitting a transmitted symbol c for receipt at a receiver, the transmitter comprising:

a plurality of multipliers, each multiplier associated with a respective transmit antenna, a given multiplier for weighting the transmitted symbol c with a transmit weighting vector v, a weighting factor of the transmit weighting vector v being equal to the conjugate, h_i*, of a channel coefficient, h_i, for a given transmission channel divided by a normalization factor, a quality of an estimate of the value of a transmitted symbol being improved by said weighting, where i is the number of transmit antennae between 2 and K where K is an integer greater than or equal to 2.

10. A wireless communication transmitter as recited in claim 9, each antenna for initially transmitting a sequence of pilot symbols from said transmitter to said receiver.

11. A wireless communication transmitter as recited in claim 9 where the normalization factor is given by the equation:

${\left(\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br>{<br><br>h_k<br><br>}^2\right)}^{1/2}.$

12. A wireless communication transmitter as recited in claim 9 wherein the weighting factor is a vector determined according to the equation

$v={\frac{1}{a}}^{}$

[ h 1 



…





h K ] H ,

where a is the normalization factor, K is the number of transmit antennae and H is the Hermitian operator.

13. A wireless communication transmitter as recited in claim 9 for use in a wireless communication system further comprising a receiver comprising a multiplier circuit for weighting received signals and a summation circuit for summing the weighted signals to produce an estimate of the transmitted symbol, c.

14. A wireless communication transmitter as recited in claim 13, when more than one receiving antenna is employed at said receiver, a weighting factor of said multiplier circuit being proportional to a receive channel coefficient and to the inverse of the normalization factor.

15. A wireless communication transmitter as recited in claim 14 wherein the normalization factor is given by the equation:

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

where L is the number of receive antennae.

16. A wireless communication transmitter as recited in claim 13, when more than one receiving antenna is employed at said receiver, a gain in signal-to-noise ratio of a channel between a transmit antenna and a receive antenna being proportional to the square of the normalization factor divided by the number of receive antennae.

19. A wireless communication system as recited in claim 16 wherein the receiver further comprises a multiplier circuit for weighting received signals and a summation circuit for summing the weighted signals to produce an estimate of the transmitted symbol, c.

20. A wireless communication system as recited in claim 16 wherein the receiver comprises more than one receive antenna, a gain in signal-to-noise ratio of a channel between a transmit antenna and a receive antenna being proportional to the square of the normalization factor divided by the number of receive antennae.

17. A wireless communication system comprising a transmitter and a receiver, the transmitter having a plurality of antennae for concurrently transmitting the same symbol to a receiver by said plurality of antennae, the transmitter for transmitting a transmitted symbol c for receipt at the receiver, the transmitter comprising:

a plurality of multipliers, each multiplier associated with a respective transmit antenna, a given multiplier for weighting the transmitted symbol c with a transmit weighting vector v, a weighting factor of the transmit weighting vector v being equal to the conjugate, h_i*, of a channel coefficient, h_i, for a given transmission channel divided by a normalization factor, a quality of an estimate of the value of a transmitted symbol being improved by said weighting, where i is the number of transmit antennae between 2 and K where K is an integer greater than or equal to 2;

and the receiver comprising a receive antenna.

18. A wireless communication system as recited in claim 17, each transmit antenna for initially transmitting a sequence of pilot symbols from said transmitter to said receiver.

21. A method of estimating a value of a transmitted symbol c received at a receiver for receiving the same symbol c transmitted to the receiver by a plurality of antennae, the method for use in a wireless communication system comprising:

receiving a weighted symbol c, weighted with a weighting vector v, a weighting factor of the transmit weighting vector v being equal to the conjugate, h_i*, of a channel coefficient, h_i, for a given transmission channel to the receiver divided by a normalization factor, a quality of an estimate of the value of a transmitted symbol being improved by said weighting, where i is the number of transmit antennae between 2 and K where K is an integer greater than or equal to 2.

23. A receiver for use in a wireless communication system, the receiver for processing a weighted symbol c, weighted with a weighting vector v, a weighting factor of the transmit weighting vector v being equal to the conjugate, h_i*, of a channel coefficient, h_i, for a given transmission channel to the receiver divided by a normalization factor, a quality of an estimate of the value of a transmitted symbol being improved by said weighting, where i is the number of transmit antennae between 2 and K where K is an integer greater than or equal to 2.

24. A receiver as recited in claim 23, the receiver comprising a summation circuit for summing received signals and a weighting circuit, responsive to the summation circuit, for applying a weighting factor to obtain an estimate of a transmitted signal.