Adaptive channel estimation and interference cancellation in space-time coded OFDM systems

The paper presents an LSE-RLS interference suppression scheme for space-time block coded orthogonal frequency division multiplexing (ST-OFDM) systems over frequency selective fading channels. We consider a multi-user environment with K synchronous cochannel users, each equipped with n transmit antennas. The receiver is equipped with m(≥K) receive antennas. The proposed scheme utilizes OFDM to transform frequency selective fading channels into multiple flat fading subchannels on which space-time coding is applied. It is shown that by applying the LSE-RLS algorithm over each subchannel at the receiver, the proposed scheme is capable of suppressing the interference from the K cochannel users without any explicit knowledge of the channel or the interference. The proposed scheme is computationally less intensive than the MMSE scheme, which assumes perfect channel knowledge, and retains the simple linear decoding property of space-time block codes with acceptable performance degradation due to imperfect channel estimation.