Abstract: For OFDM systems, necessary and sufficient conditions for blind channel identifiability based on the finite alphabet property of information symbols are established. Under these conditions, a novel frequencydomain minimum distance (FMD) algorithm is proposed for blind channel estimation. By polyphase decomposition, the channel frequency response sequence is divided into several subsequences, and phase ambiguities of each subcarrier can be resolved by exhaustive searching only (L+1) elements in one subsequence, where L is the channel order. Simulation results show that the channel estimation accuracy of the FMD algorithm is better than the modified minimum distance (MMD) algorithm, both having the same computation complexity.

Key words: OFDM, blind channel estimation, finite alphabet property, polyphase decomposition