Patent ID: 6198782
Filing Date: 2001-03-06
Classification: H04L

Abstract:
Apparatus for estimating carrier frequency offset and sampling frequency offset between transmitter circuitry and receiver circuitry which communicate over a channel of an OFDM system, the apparatus including in a receiver circuit;a local oscillator having a frequency fb for converting a received OFDM modulated signal s(t), representing information symbols S(k) having components Sm(k) sampled at a first sampling rate ft and modulated onto a carrier of frequency fc, to a base-band signal,an analogue to digital converter having a second sampling rate fr for sampling the baseband signal,a demodulator for performing a discrete Fourier transform on the sampled baseband signal to generate blocks of symbols R(k) having components Rm(k) representing the information symbols S(k) of components Sm(k), and characterised by;a first module for removing parasitic effects of the channel on R(k) to generate at least one block Y(k) of components Ym(k),a second module for removing modulation effects from Y(k) to generate at least one block Z(k) of components Zm(k) and to compute V of components Vm where Vm=/Ym/,and a third module for estimating terms A and B relating respectively to the carrier frequency offset /fc-fb/ and the sampling frequency offset /ft-fr/ by performing a joint maximun likelihood estimation (MLE) such that; ##EQU18##