Dynamic CFO reduction in various mobilities based on extended Kalman filter for broadband wireless access technology

Abstract

Alteration of user's speed and direction to the base station cause Carrier Frequency Offset (CFO). CFO is able to damage orthogonality among subcarriers and decrease system performance significantly. There are several researches already focused on ICI mitigation, however most of them only employed restricted inputs for CFO in order to generate Inter Carrier Interference (ICI). This research proposes modified dynamic CFO resulted from Doppler shift and oscillator accuracy tolerance. The CFO value takes user's velocity and random user's direction as well as involving oscillator instability. The main purpose of this research is to reduce CFO in dynamic propagation nature in various users' velocities using Extended Kalman Filter (EKF) method. The result showed that those dynamic CFO values can be reduced using EKF method and thereby enhance OFDM system performance, in this case Mobile WiMAX 802.16e. Besides, this proposed system has the adaptability upon different CFO values by adjusting better improvement for higher speed and worse oscillator's quality.