Carrier Frequency Offset Estimator for OFDMA Mode of WMAN

Orthogonal Frequency Division Multiple Access (OFDMA) is proposed in IEEE 802.16e standards for broadband, high data rate fixed/mobile communications. As the basic modulation technique in OFDMA is orthogonal frequency division multiplexing (OFDM), it is severely affected by carrier frequency offset (CFO). The CFO causes loss of orthogonality among the subcarriers. In this paper, we propose a method for estimation of CFO. The proposed method is based on the preamble suggested for OFDMA mode of WMAN where the preamble is loaded on every third subcarrier. The proposed method is an extension of Schimdl and Cox’s method. Simulations are conducted for AWGN and frequency selective channels to demonstrate the performance of the proposed method. CRLB for the proposed fractional CFO is derived and is shown that the variance of proposed CFO closely follows CRLB.