Channel Quality Improvement for BER using Different Channel Estimation Techniques for OFDM Systems

---In this paper we present an improved and robust channel 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 next iteration. 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 Biterror 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),LS(Least Square),LMMSE(Linear Minimum Mean Square Error),LMS(Least Mean Square),QAM(Qadrature Amplitude Modulation).