Synchronization of a pilot assisted channel estimation orthogonal frequency division multiplexing system
First Claim
1. Apparatus for use in a pilot assisted channel estimation orthogonal frequency multiplexing system comprising:
- an initial time and frequency synchronizer for setting time and frequency parameters of the apparatus as a function of a received signal containing pilot symbols;
a fast Fourier transformer;
a pilot extractor and channel estimator;
a controller that controls first and second phase rotators according to an output of the pilot extractor and channel estimator, wherein the first phase rotator phase rotates an output of the initial time and frequency synchronizer for output to the fast Fourier transformer; and
wherein the second phase rotator phase rotates an output of the fast Fourier transformer for output to the pilot extractor and channel estimator and a receiver.
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Abstract
A synchronization of a pilot assisted channel estimation orthogonal frequency division multiplexing can be achieved by receiving a signal containing pilot symbols, providing an initial time and frequency synchronization to the signal, phase rotating the signal across time, transforming the signal with a fast Fourier transformation, phase rotating the signal across frequency, extracting the pilot symbols and generating a channel estimator. The phase rotating across time and the phase rotating across frequency are controlled by a phase rotation controller in accordance with the channel estimator. The initial time and frequency synchronization synchronizes the signal such that intercarrier interference effects and intersymbol interference effects are negligible. The signal may include plural carrier frequencies each having an arrival timing offset and a frequency offset. The signal may also include delay spread or Doppler spread. The phase rotation controller measures a phase different between the channel estimator at times k and k+Δk, where k is time and Δk is a symbol period and measures a phase difference between the channel estimator at frequencies n and n+Δn, where n is tone frequency and Δn is a frequency spacing between adjacent tones.
51 Citations
30 Claims
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1. Apparatus for use in a pilot assisted channel estimation orthogonal frequency multiplexing system comprising:
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an initial time and frequency synchronizer for setting time and frequency parameters of the apparatus as a function of a received signal containing pilot symbols;
a fast Fourier transformer;
a pilot extractor and channel estimator;
a controller that controls first and second phase rotators according to an output of the pilot extractor and channel estimator, wherein the first phase rotator phase rotates an output of the initial time and frequency synchronizer for output to the fast Fourier transformer; and
wherein the second phase rotator phase rotates an output of the fast Fourier transformer for output to the pilot extractor and channel estimator and a receiver. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of synchronization for use in a pilot assisted channel estimation orthogonal frequency multiplexing system, the method comprising the steps of:
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receiving a signal containing pilot symbols;
setting time and frequency parameters as a function of the signal so as to provide an initial time and frequency synchronization;
phase rotating the signal across time;
transforming the signal with a fast Fourier transformation;
phase rotating the signal across frequency; and
extracting the pilot symbols and generating a channel estimate from the signal after the signal has been phase rotated across frequency, wherein the phase rotating across time and the phase rotating across frequency are controlled as a function of the channel estimate. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A pilot assisted channel estimation orthogonal frequency multiplexing system comprising:
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initial synchronization means for initial time and frequency setting time and frequency parameters of the system as a function of a received signal containing pilot symbols;
fast Fourier transform means for fast Fourier transforming the received signal;
extracting and estimating means for extracting pilots and providing a channel estimate;
controlling means for controlling a first and second phase rotations according to the channel estimate, wherein the first phase rotation rotates an output of the initial synchronization means for output to the fast Fourier transform means; and
the second phase rotation rotates an output of the fast Fourier transform means for output to the extracting and estimating means and a receiver means for receiving the received signal. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A computer program in computer readable form for causing a processor executing the program to synchronize the sub-components of a received signal to each other, the program comprising:
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a module for initially synchronizing a pilot containing signal so as to provide an initial time and frequency synchronization;
a module for phase rotating the signal across time;
a module for transforming the signal with a fast Fourier transformation;
a module for phase rotating the signal across frequency; and
a module for extracting the pilot symbols and generating a channel estimate from the signal after the signal has been phase rotated across frequency, wherein the module for phase rotating across time and the module for phase rotating across frequency are responsive to the channel module for extracting and estimating. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification