On Comparison of DFT-Based and DCT-Based Channel Estimation for OFDM System

For high data rate communication with the required Quality of Service (QoS) in 3G and 4G systems, Orthogonal Frequency Division Multiplexing (OFDM) is proposed, which is capable to resist the channel impairments caused by high mobility conditions, by dividing the frequencyselective fading channel into narrowband flat fading channels. In this paper two time-domain channel estimation techniques, Discrete Fourier Transform (DFT) and Discrete Cosine Transform (DCT), are compared based on the timedomain channel impulse response (CIR) energy characteristics and they have less complexity and efficient performance than Linear Minimum Mean Square Error (LMMSE) and Least Square Error (LSE). The effect of power limitation in terms of SNR and the number of multipaths for a wireless channel is determined to compare these transform approaches. Two well known performance criteria: Mean Square Error (MSE) and Symbol Error Rate (SER) are used for comparison by using Monte Carlo Simulations for Quadrature Phase Shift Keying (QPSK) modulation.