Performance comparison of Different Pilot Aided Channel Estimation Techniques for OFDM IEEE 802. 11e (Mobile Wimax) Systems

Orthogonal frequency-division multiplexing (OFDM) modulation is a promising technique for achieving the high bit rates required for a wireless multimedia service. In this paper we present differentchannel estimation algorithms for OFDM mobile communication systems based on the use of pilot subcarriers. Specifically we present LS (Least Square),MMSE(Minimum Mean Square Error) and LMS iterative channel estimation techniques to show the performance comparison of channel estimation techniques supported by n IFFT-based time channel estimation. The channel estimation is based on the principle of pilot-symbol aided channel estimation (PACE), and it has been implemented using block-type pilot subcarrier arrangements. The low complexity of LMS algorithm, has a higher efficiency than conventional methods(without channel estimation,LS& LMMSE ) and it can work in lower amount of SNRs. We have compared the performances of all schemes by measuring bit error rate with 16QAM as modulation scheme, and multi-path Rayleigh fading channel as channel model. Simulation results validate that the LMS Iterative channel estimation scheme can achieve tremendous performance as the existing channel estimation methods.