Equalization Techniques for an OFDM System under Fading Conditions

Abstract

We have studied frequency-and time-domain equalization techniques under fading conditions for the European DVB-T OFDM system. We first describe a frequency-domain equalizer using simplified linear interpolation in the symbol direction that estimates the channel response of receiving-data carriers by using the pilot-carrier channel response. We calculated the signal-to-interference ratio (SIR) and the bit error rate (BER) over one-path and two-path Rayleigh-fading channels. We found that an SIR of about 20 dB and a BER of less than 1.5 × 10^-3 (QPSK and 16 QAM) are obtained even for a maximum doppler frequency of 50 Hz in a 2-k FFT system. We next describe a simplified time-domain equalizer using step interpolation over the OFDM useful period. A simulated BER of 2 × 10^-3 (QPSK) over one-path Rayleigh-fading channels (fd =50 Hz) was attained for an 8-k FFT system, when the new time-domain and frequency-domain equalizer techniques were applied.