Patent ID: 7916797
Filing Date: 2011-03-29
Classification: H04L

Abstract:
1. An error tracking apparatus for tracking a residual frequency error, a phase error, a time offset, and a signal amplitude variation in an orthogonal frequency division multiplexing (OFDM) system, comprising: a frequency error corrector for correcting a frequency in a time domain by adding a tracking carrier error estimating value to an initial carrier frequency error estimating value; a signal amplitude tracking corrector for controlling a signal amplitude by multiplying a fast Fourier transform (FFT) of an input signal by an output value corresponding to a power calculating amount of a receive pilot signal, wherein the signal amplitude tracking corrector operates after the frequency error corrector; a Fourier Transform unit for extracting only the receive pilot signal; a channel corrector for outputting a channel corrected pilot by multiplying the receive pilot signal by a complex conjugate of a frequency channel response of the receive pilot signal; a carrier frequency error estimator for estimating a carrier frequency error parameter using the channel-corrected pilot and providing the tracking carrier frequency error estimating value; a time offset estimator for estimating a time offset parameter using the channel-corrected pilot; and a carrier phase error estimator for estimating a carrier phase error parameter using the channel-corrected pilot, wherein at least one of the carrier frequency error parameter, the time offset parameter and the carrier phase error parameter is estimated by the receive pilot signal allocated for a present symbol and is applied to a data signal of a present symbol, wherein the carrier phase error estimator employs a feedforward scheme in which the present symbol is tracked and the carrier phase error is directly corrected at the present symbol.