Reliable multicarrier communication in the presence of timing phase error

• US 7,433,395 B2
• Filed: 02/04/2004
• Issued: 10/07/2008
• Est. Priority Date: 02/04/2004
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: 2Wire, Inc. (CommScope Holding Company, Inc.)
• Inventors: Sedarat, Hossein
• Primary Examiner(s): Fan; Chieh M.
• Assistant Examiner(s): PUENTE, EVA YI ZHENG
• Application Number:
  US10/773,054
• Publication Number:
  US 20050169357A1
• Time in Patent Office: 1,707 Days
• Field of Search: 375/222, 375/227, 375/130, 375/260, 375/355, 375/343, 375/346, 370/208, 370/432, 370/337, 370/229, 370/345, 370/350, 455/255, 455/67.16
• US Class Current: 375/222
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols

Abstract

A method, system and apparatus for reliable multicarrier communication in the presence of timing phase error is disclosed. Phase noise due to a sampling-time phase mismatch between a transmitter device and a receiver device is measured in a signal. A Gaussian noise power level in the signal is determined, and a gain factor associated with the phase noise is calculated. The gain factor is applied to the Gaussian noise power level to calculate an equivalent noise power. In one aspect, the equivalent noise power is used to determine a signal-to-noise ratio. In another aspect, the signal is a multicarrier signal including a plurality of sub-carriers.

Claims

1. A method comprising:

measuring phase noise in a signal, the phase noise due to a sampling-time phase mismatch between a transmitter device and a receiver device, wherein said signal is a multicarrier signal including a plurality of sub-carriers;

determining a Gaussian noise power level in the signal, wherein determining the Gaussian noise power level in the signal comprises;

determining a total noise power level in the signal;

determining a phase noise power level in the signal; and

subtracting the phase noise power level from the total noise power level to determine the Gaussian noise power level in the signal;

calculating a gain factor associated with the phase noise; and

applying the gain factor to the Gaussian noise power level to calculate an equivalent noise power.

2. The method of claim 1, wherein the phase noise power level of a first sub-carrier is based on an average power of a timing phase error in a phase error measurement sub-carrier and a ratio of a frequency of the first sub-carrier and a frequency of the phase error measurement sub-carrier.

3. The method of claim 2, wherein the phase error measurement sub-carrier is a pilot-tone.

4. The method of claim 2, wherein the phase noise power level of the first sub-carrier is calculated as

$\stackrel{}{{\theta }^{}}$

2 _ ⁢

f 2 f p 2 ⁢

r 2 _ ,

where θ

² is the average power of the timing phase error in the phase error measurement sub-carrier, f is a frequency of the first sub-carrier, f_P is a frequency of the phase error measurement sub-carrier, and r² is the average signal power of the first sub-carrier.

5. The method of claim 4, wherein the gain factor, G_P, is calculated as

$G_P=1+\frac{2}{\alpha }$

⁢

⁢

σ

⁢

r max ⁢

f f p ⁢

θ

max ,

where α

is a constant factor based on an error rate and a sub-carrier coding scheme, σ

² is the Gaussian noise power level of the signal, r_max is a maximum distance of an error constellation point from an origin, and θ

_max is a maximum phase error.

6. The method of claim 5, wherein the equivalent noise power, σ

_e², for the first sub-carrier is calculated as

σ

_e²=σ

²G_P².

7. A method comprising:

measuring phase noise in a signal, the phase noise due to a sampling-time phase mismatch between a transmitter device and a receiver device;

determining a Gaussian noise power level in the signal;

calculating a gain factor associated with the phase noise;

activating phase noise compensation based on whether the gain factor is above a first threshold;

deactivating phase noise compensation based on whether the gain factor is below a second threshold; and

applying a gain factor to the Gaussian noise power level to calculate an equivalent noise power when phase noise compensation is activated.

8. A computer readable medium storing executable instructions, which when executed, to cause a device to perform operations comprising:

measuring phase noise in a signal, the phase noise due to a sampling-time phase mismatch between a transmitter device and a receiver device, wherein said signal is a multicarrier signal including a plurality of sub-carriers;

calculating a gain factor associated with the phase noise;

applying the gain factor to the Gaussian noise power level to calculate an equivalent noise power;

determining a Gaussian noise power level in the signal, wherein determining the Gaussian noise power level in the signal comprises;

determining a total noise power level in the signal;

determining a phase noise power level in the signal; and

subtracting the phase noise power level from the total noise power level to determine the Gaussian noise power level in the signal.

9. The computer readable medium of claim 8, wherein the phase noise power level of a first sub-carrier is based on an average power of a timing phase error in a phase error measurement sub-carrier and a ratio of a frequency of the first sub-carrier and a frequency of the phase error measurement sub-carrier.

10. The computer readable medium of claim 9, wherein the phase error measurement sub-carrier is a pilot-tone.

11. The computer readable medium of claim 9, wherein the phase noise power level of the first sub-carrier is calculated as

$\stackrel{}{{\theta }^{}}$

2 _ ⁢

f 2 f p 2 ⁢

r 2 _ ,

where θ

² is the average power of the timing phase error in the phase error measurement sub-carrier, f is a frequency of the first sub-carrier, f_P is a frequency of the phase error measurement sub-carrier, and r² is the average signal power of the first sub-carrier.

12. The computer readable medium of claim 11, wherein the gain factor, G_P, is calculated as

$G_P=1+\frac{2}{\alpha }$

⁢

⁢

σ

⁢

r max ⁢

f f p ⁢

θ

max ,

where α

is a constant factor based on an error rate and a sub-carrier coding scheme, σ

² is the Gaussian noise power level of the signal, r_max is a maximum distance of an error constellation point from an origin, and θ

_max is a maximum phase error.

13. The computer readable medium of claim 12, wherein the equivalent noise power, σ

_e², for the first sub-carrier is calculated as

σ

_e²=σ

²G_P².

14. The computer readable medium storing executable instructions, which when executed, to cause a device to perform operations comprising:

measuring phase noise in a signal, the phase noise due to a sampling-time phase mismatch between a transmitter device and a receiver device;

determining a Gaussian noise power level in the signal;

calculating a gain factor associated with the phase noise;

activating phase noise compensation based on whether the gain factor is above a first threshold;

deactivating phase noise compensation based on whether the gain factor is below a second threshold; and

applying the gain factor to the Gaussian noise power level to calculate an equivalent noise power when phase noise compensation is activated.

15. An apparatus comprising:

means for measuring phase noise in a signal, the phase noise due to a sampling-time phase mismatch between a transmitter device and a receiver device, wherein said signal is a multicarrier signal including a plurality of sub-carriers;

means for determining a Gaussian noise power level in the signal, wherein the means for determining the Gaussian noise power level in the signal comprises;

means for determining a total noise power level in the signal;

means for determining a phase noise power level in the signal; and

means for subtracting the phase noise power level from the total noise power level to determine the Gaussian noise power level in the signal;

means for calculating a gain factor associated with the phase noise; and

means for applying the gain factor to the Gaussian noise power level to calculate an equivalent noise power.

16. The apparatus of claim 15, wherein the phase noise power level of a first sub-carrier is based on an average power of a timing phase error in a phase error measurement sub-carrier and a ratio of a frequency of the first sub-carrier and a frequency of the phase error measurement sub-carrier.

17. The apparatus of claim 16, wherein the phase error measurement sub-carrier is a pilot-tone.

18. The apparatus of claim 16, wherein the gain factor, G_P, associated with a first sub-carrier is calculated as

$G_P=1+\frac{2}{\alpha }$

σ

⁢

r max ⁢

f f p ⁢

θ

max ,

where α

is a constant factor based on an error rate and a sub-carrier coding scheme, σ

² is the Gaussian noise power level of the signal, r_max is a maximum distance of an error constellation point from an origin, f is a frequency of the first sub-carrier, f_P is a frequency of a phase error measurement sub-carrier, and θ

_max is a maximum phase error.

19. An apparatus comprising:

means for measuring phase noise in a signal, the phase noise due to a sampling-time phase mismatch between a transmitter device and a receiver device, wherein said signal is a multicarrier signal including a plurality of sub-carriers;

means for determining a Gaussian noise power level in the signal;

means for calculating a gain factor associated with the phase noise;

activating phase noise compensation based on whether the gain factor is above a first threshold;

deactivating phase noise compensation based on whether the gain factor is below a second threshold; and

means for applying the gain factor to the Gaussian noise power level to calculate an equivalent noise power when phase noise compensation is activated.

20. A Digital Subscriber Line (DSL) modem comprising:

a timing recovery module to measure a timing phase error within a signal, the timing phase error due to a sampling-time phase mismatch between a transmitter device and the DSL modem;

a phase noise power module to determine a phase noise power level of the signal, the phase noise power level based on the timing phase error;

a total noise power measurement module to measure a total noise power level of the signal, wherein a Gaussian noise power level of the signal is represented as the difference between the phase noise power level and the total noise power level; and

a gain factor module to calculate a gain factor associated with the timing phase error and to apply the gain factor to the Gaussian noise power level in the signal to calculate an equivalent noise power.

21. The DSL modem of claim 20, further comprising:

a signal power measurement module to measure a signal power level of the signal; and

a signal-to-noise power module to determine a signal-to-noise ratio (SNR) based on the signal power level and the calculated equivalent noise power.

22. The DSL modem of claim 21, further comprising:

a bit-loading module to determine bit-loading based on the signal-to-noise ratio.

23. The DSL modem of claim 22, wherein the signal is a multicarrier signal including a plurality of sub-carriers.

24. The DSL modem of claim 23, wherein the timing phase error is measured from a pilot-tone of the multicarrier signal.

25. The DSL modem of claim 23, wherein the gain factor, G_P, associated with a first sub-carrier is calculated as

$G_P=1+\frac{2}{\alpha }$

σ

⁢

r max ⁢

f f p ⁢

θ

max ,

where α

is a constant factor based on an error rate and a sub-carrier coding scheme, σ

² is the Gaussian noise power level of Gaussian noise power level of the signal, r_max is a maximum distance of an error constellation point from an origin, f is a frequency of the first sub-carrier, f_P is a frequency of a phase error measurement sub-carrier, and θ

_max is a maximum phase error.

26. The DSL modem of claim 20, wherein the gain factor module is further to activate phase noise compensation based on a first threshold and deactivate phase noise compensation based on a second threshold, wherein the first threshold is greater than the second threshold.