Patent ID: 7336742
Filing Date: 2008-02-26
Classification: H04L

Abstract:
1. A frequency error correction device for an OFDM receiver which receives an OFDM signal with a preamble section and a payload section including pilot carriers, said device including a first frequency correction means for correcting a relative phase error in a predetermined period of time based upon a frequency error in the preamble section of said OFDM signal in time domain, and a second frequency correction means for correcting a remaining phase error in every predetermined period of time based upon the pilot carriers of said OFDM signal in frequency domain, said first frequency correction means comprising: a delay means for time-delaying an in-phase I component and an orthogonal Q component of said OFDM signal in time domain for a predetermined delay period of time; a first sign-inverting means for inverting the delayed orthogonal Q component of said OFDM signal; a first complex multiplying means for complex multiplying the received OFDM signal with the in-phase I component and the orthogonal Q component by a complex conjugated signal consisting of the delayed in-phase I component and the sign-inverted orthogonal Q component to derive phase-rotation amount ΔI and ΔQ for the delay time period; a correction signal memory for storing first frequency-correction signals with respect to the frequency error, a first frequency-correction signal depending upon said derived phase-rotation amount ΔI and ΔQ being generated from said correction signal memory; and multiplying means for multiplying the in-phase I component and the orthogonal Q component of the received OFDM signal by the first frequency correction signal, wherein said predetermined period of time corresponds to a predetermined number M (M is an integer more than zero) of OFDM symbols, said second frequency correction means comprises: a reference signal memory for storing reference pilot carriers; a second complex multiplying means for complex multiplying pilot carriers inserted in the received OFDM signal in frequency domain by the reference pilot carriers provided from said reference signal memory; a second sign-inverting means for inverting the complex-multiplied orthogonal Q component of said pilot carriers to provide complex conjugate signals; an averaging means for averaging the complex conjugate signals over said pilot carriers; a third complex multiplying means for complex multiplying all sub-carriers of the received OFDM signal in frequency domain by the averaged complex conjugate signals; and a third sign-inverting means for inverting the orthogonal Q component of the complex-multiplied OFDM signal from said third complex multiplying means to provide corrected OFDM complex conjugate signal.