Sounding reference signal based timing advance adjustment for LTE-satellite mobile communication systems

LTE-satellite mobile communication system integrates satellite communication technology and LTE standard, and possesses special superiorities in providing mobile communication services. In consideration of the particularities of the satellite communication, traditional correlation based timing estimation schemes are not competent for rapid and effective adjustment of timing advance in LTE uplink. In this paper, a novel segment-based correlation approach that utilizes the excellent property of sounding reference signal (SRS) is proposed to resist large carrier frequency offsets (CFOs) caused by high Doppler shifts and accumulated frequency uncertainties. This method is derived by partitioning the local SRS into several parts and performing multiple cross-correlations with the received signal, and the timing metric is obtained through the differential multiplications of the symmetric correlation results. Due to the flexible choice of correlation length, the proposed method is capable of having an adjustable CFO-allowed range. To achieve reliable timing estimation, a peak-joint detection approach is further presented to eliminate the adverse influence of the mirror peaks caused by the correlation of repeated preamble. Moreover, the computational complexity of the proposed estimator is evaluated, and a complexity-reduced estimation based on numerical representation is also proposed for improving the run-time efficiency of system. Simulation results under a typical Line-Of-Sight (LOS) satellite channel demonstrate that the proposed methods achieve a remarkably improved timing estimation performance in terms of the mean squared error compared to the previous methods.