Mitigating radio frequency interference in multi-carrier transmission systems
First Claim
1. In a data transmission system that facilitates communications between a pair of modems using a multi-carrier transmission scheme that has a multiplicity of discrete subchannels within a designated transmission bandwidth, a method of transmitting multi-carrier signals in a manner that reduces the power spectral density of radio frequency emissions in a designated restricted frequency band within the designated transmission bandwidth, the method comprising the steps of:
- (a) transmitting data signals over a plurality of selected data subchannels within the designated transmission bandwidth; and
(b) transmitting a dummy tone over a selected dummy subchannel, wherein the magnitude and phase of the dummy tone is chosen to suppress the transmission power in the restricted frequency band due to sidelobe transmissions from at least one of the data subchannels outside of the restricted frequency band.
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Abstract
Methods and mechanisms for reducing the impact of radio frequency interference in multi-carrier data transmission systems are disclosed. In one aspect of the invention, dummy tones are used to suppress emissions within restricted frequency bands. In another aspect of the invention, signals received on designated quiet tones are detected and used to facilitate canceling of RF interference on adjacent active tones.
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Citations
23 Claims
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1. In a data transmission system that facilitates communications between a pair of modems using a multi-carrier transmission scheme that has a multiplicity of discrete subchannels within a designated transmission bandwidth, a method of transmitting multi-carrier signals in a manner that reduces the power spectral density of radio frequency emissions in a designated restricted frequency band within the designated transmission bandwidth, the method comprising the steps of:
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(a) transmitting data signals over a plurality of selected data subchannels within the designated transmission bandwidth; and (b) transmitting a dummy tone over a selected dummy subchannel, wherein the magnitude and phase of the dummy tone is chosen to suppress the transmission power in the restricted frequency band due to sidelobe transmissions from at least one of the data subchannels outside of the restricted frequency band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In a data transmission system that facilitates communications between a pair of modems using a multi-carrier transmission scheme that has a multiplicity of discrete subchannels within a designated transmission bandwidth, a method of suppressing radio frequency noise that is likely to occur in a designated frequency band within the designated transmission bandwidth, the method comprising the steps of:
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(a) receiving data signals over a plurality of selected data subchannels within the designated transmission bandwidth; (b) detecting noise received on a selected dummy subchannel, wherein it is assumed that no data has been transmitted over the dummy subchannel; and (c) canceling RF interference imposed on the data signals received over a first plurality of the selected data subchannels based at least in part on the detected magnitude and phase of the signal received on the selected dummy subchannel. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. In a data transmission system that facilitates communications between a pair of modems using a multi-carrier transmission scheme that has a multiplicity of discrete subchannels within a designated transmission bandwidth, a method suppressing radio frequency interference in a designated restricted frequency band within the designated transmission bandwidth, the method comprising the steps of:
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(a) transmitting data signals over a plurality of selected data subchannels within the designated transmission bandwidth, wherein the selected data subchannels do not include any subchannels within the restricted frequency band and no transmissions are made on any subchannels within the restricted frequency band and no transmissions are made on a dedicated quiet subchannel; (b) transmitting a dummy tone over a selected dummy subchannel, wherein the magnitude and phase of the dummy tone is chosen to suppress the transmission power in the restricted frequency band due to sidelobe transmissions from at least one of the data subchannels (c) receiving the transmitted signals and passing the received signals through a notch filter that is tuned to a frequency within the restricted frequency band; (d) detecting the magnitude and phase of the signal received on a the dedicated quiet subchannel, wherein it is assumed that no data has been transmitted over the dedicated quiet subchannel; and (e) canceling RF interference imposed on data signals received over a first plurality of the selected data subchannels based at least in part on the detected magnitude and phase of the signal received on the dedicated quiet subchannel.
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20. A multi-carrier transmitter comprising:
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an encoder for encoding digital information; a modulator for modulating the encoded digital information onto a multiplicity of subcarriers to form a multi-carrier signal having a transmission bandwidth, each subcarrier corresponding to an associated tone and an associated subchannel, wherein the modulator is arranged to transmit data signals over a selected plurality of the data subchannels and to transmit a dummy tone over a selected dummy subchannel, wherein the magnitude and phase of the dummy tone is chosen to suppress the transmission power in a restricted frequency band portion of the transmission bandwidth due to sidelobe transmissions from at least one of the data subchannels outside of the restricted frequency band. - View Dependent Claims (21, 22, 23)
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Specification