Estimation of frequency offset, cell ID and CP length in OFDMA mode of WMAN

Orthogonal Frequency Division Multiple Access (OFDMA) gains increasing attention 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 joint estimation of CFO and cell ID. Cell ID represents the number of the preamble selected by the base station in the downlink. 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. We also propose a method for estimation of CP length. Van de Beek’s method is adapted for the estimation of CP length in OFDMA mode of WMAN. Simulations are conducted for AWGN and frequency selective channels to demonstrate the performance of the proposed methods.