Methods and apparatuses for canceling correlated noise in a multi-carrier communication system

• US 20060193390A1
• Filed: 02/25/2005
• Published: 08/31/2006
• Est. Priority Date: 02/25/2005
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Sedarat, Hossein
• Granted Patent: US 7,852,950 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H03D 1/04 Modifications of demodulators to reduce interference by undesired signals
• CPC Class Codes: H03D 3/002 Modifications of demodulators to reduce interference by undesired signals H03D3/248 takes precedence
• CPC Class Codes: H04L 25/03828 Arrangements for spectral shaping; Arrangements for providing signals with specified spectral properties partial response systems H04L25/497
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

Embodiments of an apparatus, system, and method are described for a multi-carrier communication system that cancels at least some correlated noise estimated to be present in a channel in the multi-carrier communication system. Values of noise present on at least on reference channel in a multi-channel communication system may be measured. Correlated noise on a second target channel using the noise measurement on the reference channel may be estimated. A residual noise on the second target channel may be determined by canceling the estimated correlated noise on the second target channel.

Claims

1. A method, comprising:

measuring noise present on at least one reference channel in a multi-channel communication system;

estimating noise present on a second target channel correlated to the noise on the reference channel; and

determining a residual noise on the second target channel based on the estimated noise.

2. The method of claim 1, further comprising:

determining a signal to noise ratio for the second target channel based on the residual noise.

3. The method of claim 2, further comprising:

determining a bit loading rate for the second target channel based on the channel'"'"'s signal to noise ratio.

4. The method of claim 1, wherein estimating noise on the second target channel, further comprises:

weighting the noise measured on the reference channel using a weighting factor.

5. The method of claim 4, wherein estimating noise on the second target channel, further comprises:

adding the weighted noise measurements for two or more reference channels for the second target channel.

6. The method of claim 4, wherein the noise measured on the reference channel is weighed using a factor representing the effect of the reference channel noise on the second target channel noise.

7. The method of claim 4, wherein estimating correlated noise on the second target channel, further comprises the equation:

8. The method of claim 6, wherein the weighting factor is initially determined during a training session of the multi-channel communication system and updated during data transmission periods of the communication system.

9. The method of claim 6, wherein the weighting factor is refined using an adaptive algorithm.

10. The method of claim 9, wherein the adaptive algorithm is a Least Mean Square algorithm.

11. The method of claim 10, wherein the Least Mean Square algorithm further comprises updating the weighting factor after an nth measurement using the equation:

a_n+1(t,t₀)=a_n(t,t₀)+μ

Xe_c,n(t₀)Xe_n*(t),

where μ

is an adaptation rate;

e_n* (t) is the conjugate complex of the n^th error measurement and e_c,n(t₀) is error at t₀.

12. The method of claim 1, wherein determining the residual noise on the second target channel, further comprises subtracting the estimated correlated noise on the second target channel from the noise on the second target channel.

13. The method of claim 12, wherein determining a residual noise on the second target channel further comprises the operation:

e_c(t₀)=e(t₀)−

Σ

a(t,t₀)e(t),

t≠

t₀, where e_c(t₀) represents residual noise on second target channel t₀, e(t₀) represents noise on t₀, and Σ

a(t,t₀)e(t) represents estimated correlated noise on t₀.

14. The method of claim 12, wherein generating a residual noise on the second target channel further comprises the operation:

x_c(t₀)=x(t₀)−

Σ

a(t,t₀)e(t),

t≠

t₀, where x_c(t₀) represents Fast Fourier Transform value of residual noise on the second target channel t₀, x(t₀) represents a Fast Fourier Transform value of noise on t₀, and Σ

a(t,t₀)e(t) represents estimated correlated noise on t₀.

15. A computer readable medium containing instructions to cause a machine to perform the method of claim 1.

16. A computer readable medium containing instructions to cause a machine to perform the following operations, comprising:

measuring noise present on at least one reference channel;

estimating noise on at least one second target channel correlated to the noise on the reference channel using the measurement of noise on the reference channel;

generating a residual noise on the second target channel; and

determining a Signal to Noise Ratio in a multi-channel communication system for the second target channel based on the residual noise.

17. The article of manufacture of claim 16, wherein estimating noise on a second target channel correlated to the noise on the reference channel further comprises:

calculating a weighted noise factor using the measurement of noise on the reference channel and a weighting factor.

18. The article of manufacture of claim 17, wherein the weighted noise factor is a factor representing contribution of noise from the reference channel to the second target channel.

19. The article of manufacture of claim 16, wherein generating the residual noise on the second target channel, further comprises:

subtracting the estimated correlated noise on the second target channel from the noise on the second target channel.

20. A method of determining bit loading rate for a channel in a multi-channel communication system, comprising:

selecting at least one channel as a reference channel;

selecting at least a second channel as a target channel;

measuring the noise on the reference channel;

predicting the noise on the target channel correlated to the noise on the reference channel using the noise measurement on the reference channel; and

generating a residual noise on the target channel by canceling the predicted correlated noise on the target channel.

21. An apparatus, comprising:

a transmitter-receiver configured to receive multi-tone signals in a multi-channel communication system, wherein the receiver portion generates a residual noise in a selected channel by canceling an estimated value of noise correlated to noise on neighboring channels to determine a Signal to Noise Ratio (SNR) based on the residual noise.

22. An apparatus, comprising:

means for measuring noise present on at least one reference channel;

means for estimating noise on a second target channel correlated to the noise on the reference channel using the noise measurement on the reference channel; and

means for generating a residual noise on the second target channel by canceling the estimated correlated noise on the second target channel.

23. The apparatus of claim 22, further comprising:

means for selecting at least one channel as a reference channel; and

means for selecting at least a second channel as a target channel.

24. The apparatus of claim 22, further comprising means for measuring the contribution of noise from the reference channel to the target channel.