Multi-carrier transmission systems
First Claim
1. A receiver for use with a multi-carrier transmission system using orthogonal carriers with quadrature amplitude modulation (QAM) constellations, in which a receiver sampling clock is phase locked to a pilot carrier, the receiver comprising:
- selection means for selecting a frame from a stream of received time domain data;
a one-frequency discrete Fourier transform (DFT) means for performing a one-frequency DFT on the selected frame, to produce a complex number, representing the pilot carrier, having an argument which is the phase of the pilot carrier; and
processor means for generating the argument from the complex number.
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Accused Products
Abstract
A multi-carrier transmission system using orthogonal carriers with high order QAM constellations for the transmission of multiple bits per carrier and symbol. Such systems place high demands on the synchronization of the receiver with the transmitter. The maximum permitted deviation from exact synchronization is usually a small fraction of a sampling interval. A reserve carrier, the pilot carrier, which is given a fixed phase, is usually used as the reference to achieve this high accuracy. The receiver sampling clock oscillator is phase locked to the pilot carrier. It is therefore necessary to estimate the phase of the pilot carrier. Using a bandpass filter to recover the pilot carrier, regardless of the frame structure of the DMT signal, does not eliminate the influence of neighboring carriers on the pilot carrier.
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Citations
23 Claims
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1. A receiver for use with a multi-carrier transmission system using orthogonal carriers with quadrature amplitude modulation (QAM) constellations, in which a receiver sampling clock is phase locked to a pilot carrier, the receiver comprising:
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selection means for selecting a frame from a stream of received time domain data;
a one-frequency discrete Fourier transform (DFT) means for performing a one-frequency DFT on the selected frame, to produce a complex number, representing the pilot carrier, having an argument which is the phase of the pilot carrier; and
processor means for generating the argument from the complex number. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
a complex exponential table;
a complex accumulator; and
a complex multiplier having a first input receiving a stream of digitized input samples, a second input receiving an output from the complex exponential table, and an output connected to the complex accumulator;
wherein the complex accumulator outputs components of the pilot carrier.
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8. A receiver according to claim 7 further comprising frame timing logic means for providing control signals to the complex exponential table and the complex accumulator.
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9. A receiver according to claim 1, wherein the multi-carrier transmission system is a multi-tone based very-high bit-rate digital subscriber line (VDSL) system.
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10. A transceiver for use with a multi-carrier transmission system using orthogonal carriers with quadrature amplitude modulation (QAM) constellations, in which a receiver sampling clock is phase locked to a pilot carrier, the transceiver comprising:
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a transmitter; and
a receiver for selecting a frame from a stream of received time domain data, and for performing a one-frequency DFT on said selected frame, to produce a complex number, representing the pilot carrier, having an argument which is the phase of the pilot carrier, and a processor for generating the argument from the complex number. - View Dependent Claims (11, 12)
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13. A multi-carrier transmission system using orthogonal carriers with high order QAM constellations, in which a receiver sampling clock is phase locked to a pilot carrier, the multi-carrier transmission system comprising two transceivers each including:
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a transmitter; and
a receiver comprising selection means for selecting a frame from a stream of received time domain data, a one-frequency discrete Fourier transform (DFT) means for performing a one-frequency DFT on the selected frame, to produce a complex number, representing the pilot carrier, having an argument which is the phase of the pilot carrier, and processor means for generating the argument from the complex number. - View Dependent Claims (14, 15)
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16. A method of phase locking a receiver'"'"'s sampling clock to a received pilot carrier in a multi-carrier transmission system using orthogonal carriers with quadrature amplitude modulation (QAM) constellations, the method comprising:
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selecting a frame from a stream of received time domain data;
performing a one-frequency discrete Fourier transform (DFT) on the selected frame, to produce a complex number, representing the pilot carrier, and having an argument which is the phase of the pilot carrier; and
generating the argument from the complex number. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
multiplying a stream of digitized input samples by values derived from a table of complex exponential values; and
processing the results of said multiplication in a complex accumulator to yield components of the pilot carrier.
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23. A method according to claim 16 wherein the multi-carrier transmission system is a multi-tone based very-high bit-rate digital subscriber line (VDSL) system.
Specification