A subspace-based blind method is proposed for estimating

the channel responses of a multiuser and multiantenna orthogonal

frequency division multiplexing (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 the 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. Equalization

methods are discussed based on the estimated channels. By using

partial knowledge of the channels, a multipath subspace method is

proposed that reduces the computational complexity. Simulations

show that the methods are effective and robust.