Comparison of Three Interpolation Techniques in Comb-Type Pilot-Assisted Channel Coded OFDM System

Doppler shifts and channel induced fading effects are more likely to induce inter carrier interference (ICI), which is the challenging research area in the orthogonal frequency division multiplexing (OFDM). This paper uses channel estimation for canceling the effect of ICI from the received signal. One dimensional frequency domain comb-type channel estimation is considered because of its low computational complexity and effective tracking ability of the fast fading channel. The channel at pilot subcarriers is estimated by using zero forcing (ZF) estimator. In this paper an improved and computationally efficient interpolation technique is proposed for the estimation of channel impulse response at the data subcarriers. Simulation results reveal that the proposed interpolation technique outperforms other one dimensional interpolation techniques. Errors induced by the channel results in degradation of the BER performance. Turbo codes have been used in addition to ZF estimator for further improving BER performance of the OFDM system. Log maximum a posteriori (Log-MAP) decoding algorithm is used for the component decoders in the iterative turbo decoder. Rayleigh fading channel in the presence of AWGN is used to evaluate the performance of the proposed OFDM system.