Effects of imperfect channel information on adaptive loading gain of OFDM

Abstract

The performance of OFDM system in mobile wireless channels can be enhanced by introducing adaptive loading schemes: information bits are distributed unequally in subchannels according to the channel frequency response. Under the assumption of perfect channel estimation, considerable gain can be achieved over the non-adaptive loading scheme for typical channels. If there are channel estimation errors in the system, the adaptive loading gain will be adversely affected in proportion to the MSE of the errors. The effect of channel mismatch due to Doppler spread is also studied. The results show that adaptive loading can preserve most of its gain even with imperfect channel information.