Efficient Carrier Frequency Offset Estimation Method in Uplink OFDMA for Mobile WiMax

摘要

Mobile WiMax uses Orthogonal Frequency Division Multiple Access (OFDMA) in uplink where frequency synchronization is a crucial task as each user presents different Carrier Frequency Offsets (CFOs). The process of Synchronization begins with the estimation of CFO and followed by compensating its effect on the received signal. The CFO estimation methods use pilot subcarriers that are included in the data frame. Data Aided Phase Incremental technique (DA-PIT) compares the phase shift of pilot subcarriers from first and last of M OFDMA symbols. The problem in DA-PIT is that CFO is estimated once for M OFDMA symbols and not suitable for fast varying channels. Data Aided phase pilot technique (DA-PPT) is used for fast varying channels. In DA-PPT, the phase shift between the received pilots and transmitted pilots is used to estimate the CFO. There will be more number of computations in DA-PPT compared to DA-PIT. In this paper, Modified Data Aided Phase Incremental technique (MDA-PIT) is proposed for CFO estimation that uses pilot subcarriers of the 802.16e frame. In MDA-PIT, the CFO estimation is performed after FFT to use the received frequency domain pilot subcarrier information. Simulation results show that the performance of the proposed MDA-PIT technique has better Mean Square Error (MSE) than DA-PIT and DA-PPT with reduced computations.