Subspace Blind Channel Estimation Methods in OFDM Systems under Multi-path Channels

In this paper, we compare two methods of subspace blind channel estimation in orthogonal frequency division multiplexing (OFDM) systems using different guard intervals under a multi-path channel with an exponentially decaying power profile. In both methods, we propose the same solution to solve the scalar ambiguity problem, which is a common problem in subspace blind estimation methods, by using a single pilot signal. The bit error rate (BER) and the normalized mean square error (NMSE) of the estimated channel vector were compared under various signal-to-noise ratio (SNR) and different numbers of transmitted OFDM symbols. The impact of using different positions of the pilot signal is also demonstrated. The results of channel estimation, data detection, and system complexity show that the zero padding (ZP) model is superior to the model with a cyclic prefix (CP).