Study On ICI Analysis And Suppression For OFDM Systems

This thesis mainly deals with the intercarrier interference (ICI) of the OFDM systems caused by time-variant multipath channels. In the first part of this thesis, a general wireless channel is introduced and a time-selective multipath WSSUS fading channel model is further characterized. At the same time, a time-variant multipath channel model with time-selectivity for simulation is given. Then the basic knowledge of OFDM systems is introduced. In the second part, we identify the cause of ICI and give the relationship between ICI power and channel characters, OFDM system parameters. The average ICI power is obtained based on the analysis above. To mitigate the ICI caused by the time-variant channel for OFDM systems, in the third part of this work, two efficient ICI suppression schemes are designed based on the ICI power analysis. We first propose a comb-type pilot-based estimation scheme, which can compensate for the ICI terms that significantly affect the bit-error rate (BER) performance. Then, an ICI suppression scheme based on the impulse-type pilot symbols using Wiener filtering is proposed and the simulations show that it can effectively reduce the effect of Doppler spread on OFDM systems under fast fading channels. The effect of OFDM signal parameters on the ICI suppression scheme is also derived. Finally we summarize our work and give a view on our future work.