Receiver for discrete multitone modulated signals having window function
AssigneeNEC USA, Inc.
InventorsSamir Kapoor, Slobodan Nedic
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Abstract
A receiver for improving the performance of conventional Discrete Multitone Modulation (DMT) based Asymmetric Digital Subscriber Line (ADSL) modems, in the presence of noise and/or interference. A demodulator having an FFT followed by a single-tap-per-bin frequency-domain equalizer is augmented by an additional data-path utilizing windowing or pulse shaping. Windowing is done independently for each symbol over the orthogonality interval and efficiently in the time domain or frequency domain. A decision feedback equalizer at the output of the windowed data-path cancels inter-bin-interference created by windowing.
Claims46
A receiver providing a demodulated output including a demodulated digital bit stream from a received discrete multi-tone modulated input signal, the input signal received from a communication channel having noise thereon, the input signal having modulated thereon a digital bit stream, the receiver comprising:
- first and second data paths coupled to receive the input signal;
- the first of the two data paths comprising a first stage having a frequency response for applying a discrete Fourier Transform to the input signal and further comprising a frequency domain equalizer having an input coupled to an output of the first stage;
- the second of the two data paths comprising a window stage for suppressing side lobes of the frequency response of the first stage;
- and
- a logic stage for selecting an output from the first data path or the second data path based on a predefined test and for providing a selected output representing the demodulated digital bit stream.
A receiver providing a demodulated including a demodulated digital bit stream output from a received discrete multi-tone modulated input signal, the input signal received from a communication channel having noise thereon, the input signal having modulated thereon a digital bit stream, the receiver comprising:
- first and second data paths coupled to receive the input signal:
- the first of the two data paths comprising a first stage having a frequency response for applying a discrete Fourier Transform to the input signal and further comprising a frequency domain equalizer having an input coupled to an output of the first stage;
- the second of the two data paths comprising a window stage for suppressing side lobes of the input signal;
- and
- a logic stage for selecting an output from the first data path or the second data path based on a predefined test and for providing a selected output representing the demodulated digital bit stream;
- wherein the window stage in said second path comprises a time domain window stage.
A method of providing a demodulated output including a demodulated digital bit stream from a received discrete multi-tone modulated input signal, the input signal received from a communication channel having noise therein, the input signal having modulated thereon a digital bit stream, the method comprising the steps of:
- providing the input signal to first and second data paths;
- applying a discrete Fourier Transform to the input signal in the first data path to generate a first transformed signal and frequency domain equalizing the first transformed signal to provide a frequency domain equalized signal;
- suppressing side lobes of the frequency response of the first transformed signal by applying a window function in the second data path to provide a pulse shaped signal;
- and
- selecting an output from the first data path or the second data path based on a predefined test and providing a selected output representing the demodulated digital bit stream.
A method of providing a demodulated output including a demodulated digital bit stream from a received discrete multi-tone modulated input signal, the input signal received from a communication channel having noise therein, the input signal having modulated thereon a digital bit stream, the method comprising the steps of:
- providing the input signal to first and second data paths;
- applying a discrete Fourier Transform to the input signal in the first data path to generate a first transformed signal and frequency domain equalizing the first transformed signal to provide a frequency domain equalized signal;
- suppressing side lobes of the input signal by applying a window function in the second data path to provide a pulse shaped signal;
- and
- selecting an output from the first data path or the second data path based on a predefined test and providing a selected output representing the demodulated digital bit stream;
- wherein the step of suppressing side lobes by applying a window function in said second path further comprises the step of applying a time domain window function.
Dependencies are inferred from the claim text.