Fast Cell Search Method Using PSS and SSS Based on Frequency Offset Estimation for Heterogeneous Networks with Separate Frequency Spectrum

This paper proposes a fast initial cell search method based on frequency offset estimation for Long Term Evolution (LTE) heterogeneous networks using separate frequency spectra between a macrocell and a small cell. When using the primary synchronization signal (PSS) and secondary synchronization signal (SSS) in the LTE radio interface, the initial cell search time for small cells with a high carrier frequency becomes very long due to the false detection of the PSS received timing due to the large frequency offset. In the proposed initial cell search method, we first measure the frequency error of a temperature compensated crystal oscillator (TCXO) of a set of user equipment for a macrocell with the carrier frequency of 2 GHz. Based on the estimated frequency offset, we detect the correct PSS received timing among the probable timing candidates for a small cell that are estimated from the correlation between the received signal with the 3.5-GHz carrier frequency and PSS sequence replica for small cells. System-level simulation results show that by using the proposed cell search method, the cell search time to achieve the cell ID detection probability of 99% is within approximately 100 ms even with the large frequency offset of 10.5 kHz.