Iterative Channel Estimation Using Superimposed Pilot for BICM-OFDM

The conventional superimposed pilot applied in OFDM system has drawback of low accuracy. An iterative channel estimation algorithm based on superimposed pilot is proposed for the combination of orthogonal frequency division multiplexing (OFDM) and bit-interleaved coded modulation (BICM) system. This algorithm makes full use of the information provided by decoding, and has two steps. Firstly, pilots are added to the transmitted signals. The initial estimation employs the first-order statistics. Secondly, using the hard-decision feedback information provided by the decoding of BICM , the information between the channel estimator and the decoder could be exchanged. The accuracy could be improved by the feedback information provided by iterative decoding of BICM. Through the wideband HF channel, the simulation results show that, compared with conventional superimposed pilot algorithm, the proposed algorithm efficiently improves the accuracy of channel estimation and BER performance after two iterations.