Blind channel estimation with periodicity for OFDM systems without cyclic prefix

Generation of the signal and noise subspaces is a critical problem in subspace-based algorithms for orthogonal frequency division multiplexing (OFDM) systems. Some special characteristics, such as virtual carriers (VCs), real symbols, and/or cyclic prefix (CP), can be exploited to construct the required noise subspace in conventional subspace approaches. In this paper, a blind channel estimation algorithm with periodicity property is proposed for OFDM systems without CP. Using the time-domain periodicity, which can be obtained by inserting zeros at some positions of frequency-domain OFDM symbols, a method for constructing the noise subspace is developed based on the proposed signal model. Simulation results show that the proposed blind channel estimation method has better normalized mean-squared error (NMSE) performance than that of a conventional approach with VCs.