Inter-carrier interference reduction in Broadband Wireless Access technology using extended Kalman Filter

OFDM technology in Broadband Wireless Access has some disadvantages, one of which is Intercarrier Interference (ICI) caused by carrier frequency offset (CFO). Moreover, in high-mobility communication, Doppler effect from user shift causes CFO that affects the impairment of orthogonality among subcarriers, and obviously degrades OFDM performance. This research used Extended Kalman Filter (EKF) as scheme of ICI reduction by deploying CFO estimation and making CFO correction using estimation value in earlier iteration. This method requires preamble in every beginning of frame for estimation purpose prior to the delivery of the information. This method works optimally in slow time varying channel. Differing from other researches, this research sets CFO dynamically using certain stretches of CFO value in order to approach real condition. The result of the research shows that OFDM with EKF is able to improve OFDM system performance significantly by reducing ICI coefficient value in the system and maintain the stability of system, even under dynamic CFO condition. For instance, in condition CFO = 15% with QPSK mapper, the system gain improves as high as 2 dB for BER performance 10⁻⁵. Whereas, under worse condition (i.e. CFO = 30%) and with similar parameters, OFDM system is able to produce almost 6 dB gain. Besides, EKF scheme can deliver reliable performance in different mappers.