Artificial channel aided LMMSE estimation for time–frequency selective channels in OFDM context

This paper proposes a linear minimum mean square error-based (LMMSE) channel estimation method, which allows avoiding the necessary knowledge of the channel covariance matrix or its estimation. To do so, a perfectly tunable filter acting like an artificial channel is added at the receiver side. We show that an LMMSE estimation of the sum of this artificial channel and the physical channel only needs the covariance matrix of the artificial channel, and the channel estimation is finally obtained by subtracting the frequency coefficients of the added filter. We call this method artificial channel aided-LMMSE (ACA-LMMSE). Theoretical developments and simulations prove that its performance is close to theoretical LMMSE, and we show that this method reduces the computational complexity, compared to usual LMMSE, due to the covariance matrix used for ACA-LMMSE is computed only once throughout the transmission duration. We put the conditions on the artificial channel parameters to get the expected mask effect. Simulations display the performance of the proposed method, in terms of MMSE and bit error rate (BER). Indeed, the difference of BER between our method and the theoretical LMMSE is less than 2 dB.

•
• We propose an LMMSE-based channel estimation.
•
• We avoid the a priori need of the channel covariance matrix by adding a mask.
•
• We give rules on the added filter parameters in order to get the mask effect.
•
• We show that the performance of estimation is close to the theoretical LMMSE one.
•
• We give a practical application of the method by using a simple constant filter.