A Novel Timing Synchronization Method for Localized OFDMA Uplink System

This paper proposes a novel symbol timing synchronization method for localized OFDMA uplink system. Two neighboring pilot symbols are designed for timing synchronization utilizing the property of successive subcarrier assignment. For OFDMA separation, there is almost no inter-user interference, which is very beneficial for timing synchronization. At receiver, the position of the pilot symbols can be found by correlating the received signal with the local pilot replica. For better correlation result, Zadoff-Chu sequence is employed as the pilot data for its ideal autocorrelation property, which can well suppress the inter-multipath interferences. Furthermore, a novel timing metric is constructed according to the obtained correlation profile by using the special pilot structure. The timing metric is proportional to the received SNR and has a plateau since the CP length is designed larger than the maximum channel delay. The timing estimator is dedicated to locate in the middle position of the ISI-free CP part for this timing offset will not degrade system BER performance. Simulations results demonstrate that the proposed timing estimator can work well in localized OFDMA uplink system. As long as the maximum channel delay is shorter than the CP length, it can reach the same BER performance with that of ideal synchronization.