Channel estimation for MIMO-OFDM systems based on data nulling superimposed pilots

This paper proposes a new channel estimation algorithm based on data nulling superimposed pilots for the spatial multiplexing multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. In the proposed method each OFDM data symbol of each transmit antenna is spread over all subcarriers by using a spreading matrix then nulls are introduced at certain subcarriers to cancel the mutual interference between data symbols and superimposed pilots. At receiver accurate channel estimation can be easily acquired based on the superimposed pilots. Then the superimposed pilots are removed from the received signal and simple iterative data detection scheme is used to compensate the distortion which occurred in the data symbols. The simulation results of the proposed algorithm show improvement in the estimation accuracy, bit error rate (BER) and computational complexity compared to that of the conventional superimposed pilot technique. The simulation results also show that the performance of the proposed technique approaches that of the frequency division multiplexed pilots technique while having higher data rate and some excess in the receiver complexity