Describing the optimum pilot symbol interval via curve fitting methods in OFDM system

Abstract

Increasing demand on higher data rates, makes multi carrier systems popular. Orthogonal frequency division multiplexing (OFDM), a form of multicarrier modulation, has been widely applied in wireless communication systems for major advantages. In order to obtain channel state information, and overcome multipath fading channel estimation must be performed in these systems. The channel estimation quality significantly depends on the pilot pattern. In this study, the relationship between the optimum pilot symbol interval that yields the minimum channel estimation mean squared error and coherence bandwidth, coherence time at 0,9 correlation is investigated in OFDM systems for different time and frequency selective channels. Different curve fitting methods are applied to data and performances are compared in terms of normalized root mean squared errors (NRMSE). Considering both simplicity and NRMSE; the optimum pilot symbol interval is calculated by cubic polynomial in frequency direction, and by quadratic polynomial in time direction.