extrapolate to determine the signal strength at data symbol positions on the basis of the signal strength of pilot symbol positions the signal strength at data symbol positions will be used as reference qam threshold to better illustrate the present invention an example applied to an ofdm system that uses pilot and data structure shown in fig3 will now be presented in such an example the qam threshold estimator 106 of fig1 or 212 of fig2 operates as follows 1 a finite impulse response fir filter is used to smooth the equalised pilot symbols with appropriate boundary handling 2 next the smoothed pilot symbols from step 1 are converted from complex number values into real amplitudes 3 interpolate and or extrapolate between smoothed pilot symbol positions in each ofdm symbol that contains pilot symbols eg ofdm symbol 312 of fig3 using the amplitudes of smoothed pilot symbols from step 2 to determine amplitude at each non pilot symbol position in the ofdm symbol 4 calculate the qam reference threshold for each data symbol in the ofdm symbols that do not contain pilot symbols by interpolating and or extrapolating the amplitudes of the smoothed pilot and non pilot symbols from step 3 following this method each equalised data symbol in the t.