Adaptive equalizer and compensation of ICI in the wireless repeater system

In this paper, we propose adaptive equalizer and compensation of ICI (Inter carrier interference) in the wireless repeater system based on OFDM in order to effectively cancel feedback channel and phase noise. When the gain of a wireless repeater is larger than the isolation between transmit and receive antennas of the repeater, the feedback signal that comes into the receive antenna from the transmit antenna of the repeater causes the repeater to go into feedback oscillation regardless of the input signal. And the phase noise effect can exist on up and down converter of wireless repeater. Thus, in order to cancel feedback channel and phase noise, we suggest an adaptive equalizer such as NLMS (Normalizer least mean square), RLS (Recursive least square) and a phase noise compensator. In case of phase noise compensator, because phase noise has random characteristic, comb type pilot is used for estimation and compensation phase noise in wireless communication systems. First, we remove CPE (Common phase error) by received pilot symbol. After that, we use the obtained error power as a MMSE (Minimum mean square error) detection criterion factor and a forgetting factor to compensate ICI caused by phase noise. BER performance of proposed method is satisfied with 13.5dB at 10^-4.