Method and apparatus for reducing peak-to-average power ratio in a discrete multi-tone signal
Assignee3Com Corporation
InventorYaqi Cheng
Life of this patent
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Abstract
A method and apparatus for reducing peak-to-average power ratio in a discrete multi-tone signal. A shaping signal is generated and added to a discrete multi-tone signal to be transmitted. The shaping signal includes tones that are outside a transmission band assigned to the discrete multi-tone signal to be transmitted. One or more filters may be used to suppress the shaping function after digital-to-analog conversion has been performed. Alternatively, echo cancellation may be performed to cancel feedback tones associated with the transmit signal and shaping signal that may occur on the receive path of a discrete multi-tone transceiver. The peak-to-average power ratio reduction method and apparatus may be used in an ADSL modem in one embodiment.
Claims14
In a discrete multi-tone transceiver, a method for reducing peak-to-average power ratio in a transmit signal, comprising the steps of:
- interpolating a discrete multi-tone signal to produce an interpolated discrete multi-tone signal;
- determining whether a peak magnitude exceeds a pre-determined magnitude parameter, wherein the peak magnitude is associated with either of the discrete multi-tone signal or the interpolated discrete multi-tone signal;
- adding a shaping signal to the interpolated discrete multi-tone signal to produce a modified signal, in response to determining that the peak magnitude exceeds the pre-determined magnitude parameter, wherein the shaping signal consists entirely of tones located outside a transmission band allocated to the discrete multi-tone signal;
- converting the modified signal to an analog transmit signal;
- and
- canceling feedback tones introduced to a receive signal within the discrete multi-tone transceiver, wherein the feedback tones are associated with the shaping signal.
A discrete multi-tone transmitter, comprising in combination:
- an Inverse Fast Fourier Transform that transforms transmit signals from a frequency domain to a time domain;
- an interpolation unit that interpolates the transmit signals to produce tones located outside a transmission band allocated to the transmit signals;
- a shaping signal generator that generates a shaping signal from tones located outside the transmission band allocated to the transmit signals in response to a transmit signal exceeding a pre-determined magnitude parameter;
- an adder that adds the shaping signal to the transmit signal exceeding the pre-determined magnitude parameter;
- a digital-to-analog converter that converts the transmit signals in the time domain to analog transmit signals;
- a filter that suppresses a shaping component from one or more of the analog transmit signals, wherein the shaping component is associated with the shaping signal;
- and
- an interface for interfacing the transmitter to a communications medium.
Dependencies are inferred from the claim text.