Voice and data exchange over a packet based network with timing recovery

• US 20050018798A1
• Filed: 08/13/2004
• Published: 01/27/2005
• Est. Priority Date: 09/20/1999
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Li, Henry
• Granted Patent: US 7,529,325 B2
• Time in Patent Office: Days
• US Class Current: 375/355
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers
• CPC Class Codes: H04B 3/234 using double talk detection
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/66 Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
• CPC Class Codes: H04L 65/1026 at the edge
• CPC Class Codes: H04L 65/1036 at the edge
• CPC Class Codes: H04L 65/1069 Session establishment or de-establishment
• CPC Class Codes: H04L 65/1095 Inter-network session transfer or sharing
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/752 adapting media to network capabilities
• CPC Class Codes: H04L 65/80 Responding to QoS
• CPC Class Codes: H04L 7/0278 Band edge detection
• CPC Class Codes: H04M 7/125 Details of gateway equipment

Abstract

A signal processing system which discriminates between voice signals and data signals modulated by a voiceband carrier. The signal processing system includes a voice exchange, a data exchange and a call discriminator. The voice exchange is capable of exchanging voice signals between a switched circuit network and a packet based network. The signal processing system also includes a data exchange capable of exchanging data signals modulated by a voiceband carrier on the switched circuit network with unmodulated data signal packets on the packet based network. The data exchange is performed by demodulating data signals from the switched circuit network for transmission on the packet based network, and modulating data signal packets from the packet based network for transmission on the switched circuit network. The call discriminator is used to selectively enable the voice exchange and data exchange.

Claims

1. A method for timing recovery of a signal having a data rate, the method comprising:

sampling the signal at a sampling rate to produce a plurality of samples;

estimating a phase error between the data rate and the sampling rate;

estimating a frequency error between the data rate and the sampling rate, during an estimation phase;

combining the estimated phase error with the estimated frequency error; and

adjusting the sampling rate as a function of the combined phase and frequency error during an application phase, wherein the estimation phase and the application phase are non-overlapping in time.

2. The method of claim 1 wherein the frequency error is estimated from a first portion of the samples.

3. The method of claim 2 wherein the phase error is estimated from a second portion of the samples different from the first portion.

4. The method of claim 1 further comprising scaling the estimated phase error before combining it with the computed frequency error.

5. The method of claims 1 wherein the combining of the computed frequency error with the estimated phase error is performed incrementally.

6. The method of claim 5 wherein the combining of the estimated frequency error with the estimated phase error is performed in incremental linear steps over a second portion of the samples.

12. The system of claim 5 wherein the frequency offset estimator estimates the frequency error from a first portion of the samples.

13. The system of claim 12 wherein the timing error estimator estimates the phase error from a second portion of the samples different from the first portion.

7. A system for timing recovery of a signal having a data rate, the method comprising:

a sampler configured to sample the signal at a sampling rate to produce a plurality of samples;

a timing error estimator configured to estimate a phase error between the data rate and the sampling rate;

a frequency offset estimator configured to estimate a frequency error between the data rate and the sampling rate, during an estimation phase;

a combiner configured to combine the estimated phase error with the estimated frequency error; and

a clock adjuster which adjusts the sampling rate of the sampler as a function of the combined phase and frequency error, wherein the estimation phase and the application phase are non-overlapping in time.

8. The system of claim 7 further comprising a multiplier which scales the estimated phase error before the estimated phase error is combined with the estimated frequency error by the combiner.

9. The timing recovery system of claim 7 wherein the frequency offset estimator comprises an accumulator which accumulates the estimated phase error for the samples, and a multiplier which scales the accumulated estimated phase error to compute the frequency error.

10. The timing recovery system of claim 7 wherein the combiner incrementally combines the estimated frequency error with the estimated phase error over the samples.

11. The timing recovery system of claim 10 wherein the combiner combines the estimated frequency error with the estimated phase error in incremental linear steps over a second portion of the samples.

14. A data transmission system, comprising:

a telephony device for outputting a signal having a data rate; and

a data exchange coupled to the telephony device, the data exchange having,

a sampler configured to sample the signal at a sampling rate to produce a plurality of samples,

a timing error estimator configured to estimate a phase error between the data rate and the sampling rate,

a frequency offset estimator configured to estimate a frequency error between the data rate and the sampling rate, during an estimation phase,

a combiner configured to combine the estimated phase error with the estimated frequency error, and

a clock adjuster which adjusts the sampling rate of the sampler as a function of the combined phase and frequency error, wherein the estimation phase and the application phase are non-overlapping in time.

15. The data transmission system of claim 14 further comprising a multiplier for scaling the estimated phase error before the combiner combines the estimated phase error with the estimated frequency error.

16. The data transmission system of claim 14 wherein the frequency offset estimator comprises an accumulator for accumulating the estimated phase error for the samples, and a multiplier for scaling the accumulated estimated phase error to estimate the frequency error.

17. The data transmission system of claim 14 wherein the combiner incrementally combines the estimated frequency error with the estimated phase error over a second portion of the samples.

18. The data transmission system of claim 17 wherein the combiner combines the estimated frequency error with the estimated phase error in incremental linear steps over the second portion of the samples.