Improved Cell Search and Initial Synchronization Using PSS in LTE

Abstract

Cell search as well as synchronization in the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system is performed in each User Equipment (UE) by using both the Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS), and the overall synchronization performance is dominated heavily by a robust PSS detection. Conventional non-coherent detector can achieve a reliable PSS detection based on the near-perfect auto-correlation and crosscorrelation properties of Zadoff-Chu (ZC) sequences [1], but at the cost of a relatively high computational complexity. This paper proposes two improved PSS detectors, i.e., Almost Half-Complexity (AHC) and Central Self-Correlation (CSC) detectors, by exploiting the central-symmetric property of ZC sequences. The AHC detector has exactly the same detection accuracy as that of the conventional detector but with 50% complexity being saved, and the proposed CSC detector can further reduce its complexity to 50% that of the AHC detector, however, at a cost of a slight accurate degradation. In order to mitigate the potential failure risk due to a large frequency offset in the proposed algorithms while at the same time keep the PSS detection accuracy un-degraded, an improvement of CSC, i.e., CSCIns, is also proposed. The performance of CSCIns detector is independent of the frequency offset, and numerical results show that the 90% PSS acquisition time of CSCIns is well within a 55ms duration with Signal-to-Noise Ratio (SNR) of -10 dB.