Multistage Enhancement of Channel Quality using Channel Estimation Techniques for effective BER/SNR using 16 QAM for Mobile Communication

---In this paper we present an improved and robustchannel estimation algorithm for OFDM mobile communication systems based on the use of pilot subcarriers.Specifically we present an iterative channel estimation technique to improve the performance of channel estimators.In iterative receiver structures,soft information becomes available after the decoding stage.This information is used to enhance the quality of the channel estimates for the nextiteration.The low complexity proposed receiver including LMS algorithm, has a higher efficiency than conventional methods(without channel estimation,LS& LMMSE ) and it can work in lower amount of SNRs.We derive a generalized estimator based on the linear minimum mean square error (LMMSE) principle for deterministic pilot information combined with soft information. The performance is presented in terms of Bit-error rate (BER) for a system using 16-quadrature amplitude modulation (QAM).Simulation results validate that the proposed channel estimation scheme can achieve tremendous performance as the existing channel estimation methods. Keywords—Channel estimation(CE),OFDM(Orthogonal Frequency Division Multiplexing).