Methods and device for estimating and correcting clipping in a discrete multi-tone communications system
First Claim
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1. A method of communicating data over a Discrete Multi-Tone (“
- DMT”
) communications system between a first modem and a second modem, each modem including a receiver and a transmitter, comprising the steps of;
in the receiver of said first modem measuring a signal to noise ratio (“
SNR”
) in all operating subchannels of the system;
transmitting SNR measurements for the operating subchannels to said second modem; and
transmitting data, using the transmitter of said second modem, over each of the operating subchannels using the SNR measurements to affect a throughput of data transmitted on the system.
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Abstract
A method for obtaining a reliable estimate of the transmitter clipping error compliant with T1.413 ADSL standard is disclosed. An architecture is disclosed that uses the clipping error estimate at the receiver to reconstruct a frequency-domain compensation signal. The method for computing the compensation signal is disclosed along with an asymmetric digital subscriber line modem supporting T1.413 standard transmission/reception functions over a discrete multi-tone communications system capable of estimating clipping errors and computing clipping compensation signals.
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Citations
11 Claims
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1. A method of communicating data over a Discrete Multi-Tone (“
- DMT”
) communications system between a first modem and a second modem, each modem including a receiver and a transmitter, comprising the steps of;in the receiver of said first modem measuring a signal to noise ratio (“
SNR”
) in all operating subchannels of the system;
transmitting SNR measurements for the operating subchannels to said second modem; and
transmitting data, using the transmitter of said second modem, over each of the operating subchannels using the SNR measurements to affect a throughput of data transmitted on the system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
measuring the thoughput of transmitted data over the operating subchannels;
using throughput measurements to compute an estimate of clipping that occurred in the transmitter;
applying the estimate of clipping to construct a compensation signal; and
adding the compensation signal at the receiver to correct for clipping that occurred at the transmitter.
- DMT”
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3. The method according to claim 1 wherein the step of transmitting data over each of said operating subchannels is performed by adjusting the amount of data transmitted over individual operating subchannels to get a better estimate of clipping parameters.
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4. The method according to claim 1 wherein the step of transmitting data over each of said operating subchannels is performed by transmitting more data in subchannels with a high SNR.
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5. The method according to claim 1 further comprising the step of designating operating subchannels with a low SNR.
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6. The method according to claim 5 further comprising the step of using said operating subchannels with a low SNR to compute an error signal representative of the amount of distortion likely to occur in each of said operating subchannels.
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7. The method according to claim 5 further comprising the step of limiting the amount of data transmitted over said operating subchannels with a low SNR to two bits each.
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8. The method according to claim 1 further comprising the step of designating operating subchannels with a high SNR.
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9. The method according to claim 1 further comprising the step of estimating the amount of transmission error that is likely to occur in each of said operating subchannels.
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10. The method according to claim 1 further comprising the step of constructing an error compensation signal to compensate for transmission errors that are likely to occur in each of said operating subchannels.
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11. The method according to claim 1 wherein the step of communicating data over each of said operating subchannels comprises the further steps of:
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separating said data into a plurality of transmission bits; and
adjusting the allocation of said plurality of transmission bits over said operating subchannels so that more transmission bits are transmitted in subchannels having a high SNR.
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Specification