Adaptive channel estimation for high Doppler channel

This paper considered about how the channel estimation effectively done for high-speed mobility system. Here the transmission rate greatly varied depending on speed of the mobile moving far away or close to the base station. The impulse swings are frequency shifts and delay spread various for each symbol called multipath fading is because of this OFDM signals losses the orthogonality because of Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI). Therefore, accuracy of estimating the signal is necessary. To estimate the frequency selective fading signal an iterative estimation scheme designed with less complexity, which makes use of information about pilot symbols, Doppler spread (f_D) value and previously detected symbols to increase overall performance. The channel estimation algorithms like Maximum Likelihood (ML), Minimum Mean Square (MMSE) and Zero Forcing (ZF) is taken in to account with the consideration of color noise. In addition to that, MIMO-OFDM techniques utilized to produce better efficiency. If the channel condition is very poor because of the multipath fading then the estimation technique is swifts adaptively to estimate the signal variance. Therefore, computation complexity reduced considerably for low Doppler spread similarly for high Doppler bester estimation technique used to estimate. The simulation results show the performance under high mobility the performance increased significantly with ML at low SNR.