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Orthogonal frequency-division multiplexing (OFDM) cellular radio systems are expected to provide ubiquitous, high-quality, and high-rate mobile transmission. However they are more sensitive to synchronization errors than the single-carrier systems. In such systems, the uplink transmission must deal with the multiuser synchronization which is more important and challenging than synchronization in a broadcast or downlink scenario. In this paper, based on the analysis of the SNR requirement of the uplink in cellular radio systems, we propose a multiuser synchronization scheme based on time-frequency block structure for tracking the mobile's uplink time and frequency offsets. It uses the redundant information contained within the cyclic prefix and the pilots for channel estimation. We show through simulations that by using this synchronization scheme, the error probabilities of the timing and frequency estimation can be no more than 20 percent for SNR values of -4dB both in AWGN and multipath fading channels. This scheme is suitable for wireless communication.