Blind Channel and Frequency Offset Estimation for OFDM via Frequency-Domain Oversampling

With only second-order statistical information, subspace based blind channel estimation has received considerable attention. To make subspace based blind channel estimation methods feasible, signal redundancy is necessary, which is usually acquired by time-domain oversampling or using multiple receive antennas. In this paper, a new perspective, frequency-domain oversampling, is taken to develop a subspace based blind channel estimation scheme for OFDM in quasi-static fading channels. We consider a practical situation, in which the channel order/length is unknown and there is nonzero frequency offset between the transmit and receive carriers. It turns out that the proposed blind channel estimation scheme is not only robust against frequency offset but also leads to a straightforward blind channel order estimate. Then, given the channel, frequency offset is blindly estimated by using a nonlinear least square approach. Simulation results demonstrate good performance of the proposed scheme with blindly estimated channel order, channel impulse response, and frequency offset.