Robust frequency offset estimation with a single symbol for FH-OFDMA

An initial carrier frequency offset estimation algorithm is proposed for a multi-user frequency hopping orthogonal frequency division modulation-frequency division multiple access (FH-OFDMA) system with a single preamble symbol. Since a multi-user OFDMA system is sensitive to carrier frequency offset which causes interferences among users, data loaded in subcarriers are easily damaged by the frequency offset. To mitigate the effect of the frequency offset, every mobile station needs to accurately and rapidly acquire synchronization. The proposed algorithm uses only one preamble symbol in which two kinds of subcarriers are designed for coarse and fine frequency offset estimation. The non-data aided estimation using the energy spectrum is exploited for fine offset estimation, and maximum likelihood estimation using correlation for coarse offset estimation. By combining the two estimation results, an accurate frequency offset can be estimated with a single symbol. Through simulations, the performance of the proposed algorithm is evaluated by comparing estimation error variance with a conventional method.