Robust doubly-differential primary synchronization approach for 3GPP LTE systems

In 3GPP Long Term Evolution (LTE) system, cell search must be first performed to allow the connection between the user equipment and the serving cell. In this paper, we investigate sector search, which is a part of the cell identifier, as well as timing synchronization based on the standardized Primary Synchronization Signal (PSS) generated from known Zadoff-Chu sequences. To this aim, an initial reduced complexity metric is first calculated to provide a coarse PSS start estimate. Then, to determine the sector identifier and fine tune the PSS start estimate, the received signal is cross-correlated to the known PSS candidates. The fine metric, which exhibits high sharp peak, allows detecting the PSS start and the sector identification. Unlike the conventional methods that perform the cross-correlation over all demodulated OFDM symbols, the proposed one carries it over a short interval centered on the coarse estimate, which greatly reduces the complexity. Simulation results show that the proposed approach provides satisfactory performance in terms of time estimation accuracy and successful sector identification rate. For practical SNR values, it also outperforms the considered benchmarks in the frame of LTE systems primary synchronization.