A subspace method for channel estimation of multi-user multi-antenna OFDM system

A subspace based blind method is proposed for estimating the channel responses of a multi-user and multi-antenna OFDM uplink system. It gives estimations to all channel responses subject to a scalar matrix ambiguity, and does not need precise channel order information (only an upper bound for all orders is required). Furthermore, the scalar ambiguity matrix can be easily resolved by using only one pilot OFDM block given that the number of users is smaller than the number of symbols in the pilot symbol block. Simulations show that the method is effective and robust.