A Coarse Time Offset Estimation in TD-SCDMA Downlink with Low SNRs

The time offset estimation (TOE) is an important issue in TD-SCDMA downlink, which conventionally is realized together with downlink synchronization code acquisition, and therefore the correlation detection is prefered. However, the resulting complexity is very high due to the start search within a full frame. In order to tackle this problem, this paper presents a coarse TOE scheme independent of the synchronization code acquisition, where the intrinsic power transition property of the TD-SCDMA frame is exploited and a power ratio detection (PRD) method is proposed for coarse TOE, then, if a subsequent coherent detction is employed, its start search can be confined to a very small range. Monte Carlo simulations are exploited to test the proposed scheme and the result shows a good performance at low signal-to-noise ratios (SNR).