Joint channel estimation and time-frequency synchronization for uplink TDS-OFDMA systems

As one of the key technologies of the Chinese national digital television terrestrial broadcasting (DTTB) standard, time domain synchronous OFDM (TDS-OFDM) is used in the downlink broadcasting transmission scenarios. Based on TDS-OFDM, the uplink multiple access scheme called TDS-OFDMA has been recently proposed. The TDSOFDMA system assumes perfect timing and frequency synchronization, both of which are difficult to be achieved in the uplink transmission where each user's signal is characterized by the user-specific timing and frequency errors. By utilizing the time-domain constant amplitude zero autocorrelation (CAZAC) training sequence and the "timespace two-dimensional frame structure", this paper proposes a joint channel estimation and time-frequency synchronization scheme for TDS-OFDMA. The channel estimation has the minimum mean square error (MSE), the timing synchronization is accurate and the frequency synchronization error can reach the Cramer-Rao lower bound (CRLB). The joint algorithm only relies on the time-domain circular correlation, thus low complexity is achieved. Simulation results demonstrate the performance of the proposed joint method under both additive white Gaussian noise (AWGN) and multi-path channels.