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In orthogonal frequency division multiple access (OFDMA) uplink system, estimations of time delay and carrier frequency offset (CFO) are both particularly challenging. In IEEE 802.16-based networks, such synchronization problem can be resolved in initial ranging process. In this paper, exploiting the unique scheme of interleaved OFDMA, a special ranging symbol which has repetitive scheme in time-domain is designed. Furthermore, a novel ranging method for OFDMA system is proposed by utilizing such repetitive characteristic. Compared with the existing methods, this algorithm just need one ranging symbol and can get more correct estimation of time delay, at the same time, it can estimate the integral CFO in OFDMA uplink. Simulations illustrate efficiency of the proposed algorithm over the existing method.