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

A timing recovery system, comprising:

• a sampler capable of sampling a signal at a sampling rate, the signal having a data rate;
• a timing error estimator which estimates a phase error between the data rate and the sampling rate;
• a frequency offset estimator which estimates a frequency error between the data rate and the sampling rate during a first phase, the frequency offset estimator comprising an accumulator which accumulates the estimated phase error a number of times, and a multiplier which scales the accumulated estimated phase error by a constant inversely proportional to the number of times the estimated phase error is accumulated to generate the estimated frequency error;
• a combiner which combines the estimated phase error and the estimated frequency error during a second phase;
• and
• a clock adjuster which adjusts the sampling rate of the sampler as a function of the combined estimated frequency error and estimated phase error.

A data transmission system, comprising:

• a telephony device which outputs a signal having a data rate;
• and
• a data exchange coupled to the telephony device, the data exchange having,
• a sampler capable of sampling the signal at a sampling rate,
• a timing error estimator which estimates a phase error between the data rate and the sampling rate,
• a frequency offset estimator which estimates a frequency error between the data rate and the sampling rate during a first phase, the frequency offset estimator comprising an accumulator which accumulates the estimated phase error a number of times, and a multiplier which scales the accumulated estimated phase error by a constant inversely proportional to the number of times the estimated phase error is accumulated to generate the estimated frequency error,
• a combiner which combines the estimated phase error and the estimated frequency error during a second phase, and
• a clock adjuster which adjusts the sampling rate of the sampler as a function of the combined estimated frequency error and estimated phase error.

A timing recovery system, comprising:

• sampling means for sampling a signal at a sampling rate, the signal having a data rate;
• phase error estimation means for estimating a phase error between the data rate and the sampling rate;
• frequency error estimation means for estimating a frequency error between the data rate and the sampling rate during a first phase, the frequency error estimation means comprising an accumulation means for accumulating the estimated phase error a number of times, and scaling means for scaling the accumulated estimated phase error by a constant inversely proportional to the number of times the estimated phase error is accumulated to generate the estimated frequency error;
• combining means for combining the estimated phase error and the estimated frequency error during a second phase;
• and
• clock adjusting means for adjusting the sampling rate of the sampling means as a function of the combined estimated frequency error and estimated phase error.

The computer-readable media embodying a program of instructions executable by a computer to perform a method of timing recovery, the method comprising:

• receiving a signal at a data rate;
• sampling the signal at a sampling rate;
• measuring a phase error between the data rate and the sampling rate;
• estimating a frequency error between the data rate and the sampling rate during a first phase by accumulating the measured phase error a number of times, and scaling the accumulated measured phase error by a constant inversely proportional to the number of times the measured phase error is accumulated;
• combining the phase error and the frequency error during a second phase;
• and
• adjusting the sampling rate as a function of the combined frequency error and phase error.

A timing recovery system, comprising:

• a sampler configured to sample a signal at a sampling rate, the signal having a data rate;
• a timing error estimator configured to estimate a phase error between the data rate and the sampling rate;
• a frequency offset estimator configured to compute a frequency error between the data rate and the sampling rate during a first time period;
• a combiner configured to combine the estimated phase error and the computed frequency error over a second time period;
• switch control logic configured to couple the timing error estimator to, and decouple the combiner from, the frequency offset estimator during the first time period, and couple the combiner to, and decouple the timing error estimator, from the frequency offset estimator during the second time period;
• and
• a clock adjuster configured to adjust the sampling rate of the sampler as a function of the combined phase and frequency error.

A timing recovery system, comprising:

• sampling means for sampling a signal at a sampling rate, the signal having a data rate;
• phase error estimation means for estimating a phase error between the data rate and the sampling rate;
• frequency error estimation means for computing a frequency error between the data rate and the sampling rate during a first time period;
• combining means for combining the estimated phase error with the computed frequency error during a second time period;
• switching means for coupling the phase error estimation means to, and decoupling the combining means from, the frequency error estimation means during the first time period, and coupling the combining means to, and decoupling the phase error estimation means from, the frequency error estimation means during the second time period;
• and
• clock adjusting means for adjusting the sampling rate of the sampler as a function of the combined phase and frequency error.