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Pilot-assisted channel estimation method for OFDMA systems over time-varying channels

Conventional time-varying (TV) channel estimation (CE) methods for OFDM systems need optimal evenly spaced pilots to track channel time variations in one symbol period and the inter-carrier interference (ICI) on pilots caused by Doppler spread are regarded as noise. For practical OFDMA systems, the required evenly spaced pilots are unsatisfied and the ICI on pilots increase estimation errors. In this letter, a TV CE method for practical OFDMA systems is proposed. The time variations of the frequency domain transmission function in one symbol period are approximated by a linear model in time-frequency blocks for each user. Time domain transformations are avoided and evenly spaced pilots are not required. Furthermore, the ICI on pilots are mitigated by correlative coding. Simulation results demonstrate the Symbol-error-rate (SER) and mean-square- error (MSE) performances of the proposed OFDMA CE method over TV channels.