Cyclic prefix-based time and frequency synchronization for TD-LTE downlink transmission

For Long Term Evolution (LTE) time division duplex (TDD) system, time and frequency synchronization play an important role in downlink transmission. Different from previous existing schemes, in this paper, cyclic prefix (CP)-based time and frequency synchronization is presented. By considering two types of CP in TD-LTE, there are two steps for estimating CP type and time-frequency synchronization respectively. Firstly, the estimation of CP-type is adopted here through the metric of maximum likelihood, which appears flat when CP is the short-type. This phenomenon is used here to distinguish CP types, while all previous existing papers assume the CP type is known. Then, a joint time and fractional frequency offset coarse synchronization is presented through cross-correlation between primary synchronization signal and local reference sequence. Simulation results demonstrate that, compared to previous existing schemes, the proposed algorithm is an effective and feasible scheme.