LMMSE channel estimation for block - pilot insertion in OFDM systems under time varying conditions

In this paper, we propose a new use of LMMSE and Lr-LMMSE algorithms for channel estimation in OFDM (Orthogonal Frequency Division Multiplexing) system which, as known suffers from the time variation of the channel under high mobility conditions using block pilot insertion. The loss of sub channel orthogonality leads to inter-carrier interference (ICI). Using many algorithms for channel estimation, we will show that, for a 16- QAM modulation, the LMMSE algorithm performs well to achieve this estimation but when the SNR (Signal Noise Rate) is high, the three algorithms (LS, LMMSE and Lr-LMMSE) performs similarly. The challenge in this paper is that we will demonstrate that the LMMSE algorithm performs well with the block pilot insertion and is not suitable just with comb pilot insertion.