Frequency estimation for the downlink of the TD-SCDMA system over frequency flat Rician fast fading channels

In this paper, a new frequency estimation scheme is proposed for the downlink of Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system over frequency flat Rician fast fading channels. The proposed algorithm exploits the synchronous downlink sequence of the downlink pilot time slot in the sub-frame, and takes account of the case where the carrier frequency offset (CFO) and the Doppler shift coexist. The new approach first presents the second-order and fourth-order statistics of the signals which contain unknown CFO, unknown Rician fading coefficients with the Doppler shift, and additive white Gaussian noise. Then, by flexible parameters setting and concrete mathematical operations for above statistics, a new closed-form expression for frequency estimation (the CFO and the Doppler shift) is derived. The simulation results are finally provided to illustrate the accuracy and reliability of the proposed method within the expectative frequency estimation range.