Initial Synchronization Exploiting Inherent Diversity for the LTE Sector Search Process

Abstract

This paper proposes an initial synchronization architecture for the sector search process in third-generation partnership project (3GPP) long-term evolution (LTE) communications. The proposed system, consisting of three techniques, takes intercell interference, intercarrier interference and multipath fading into consideration with assistance from inherent diversity. The outage and detection probabilities are derived by taking multisector diversity into account in the coarse timing alignment. The long-lag differential correlator can achieve approximately 4.7-dB signal-to-noise ratio (SNR) gain in primary synchronization sequence (PSS) acquisition probability. Joint estimation of the residual timing error and the fractional frequency offset is achieved by evaluating the short-lag autocorrelation at an orthogonal frequency division multiplexing (OFDM) symbol duration. Mean-square errors obtained via simulations are compared with the modified Cramér-Rao lower bounds derived here. The proposed technique can achieve approximately 6.9-dB SNR gain when it is compared with that assisted from the synchronization signalling. Joint detection of the integral frequency offset (IFO) and the sector identification (SID) is achieved by exploiting a frequency-domain (FD) matched filter (MF) to deal with frequency selectivity. Differential detection on a segmental FD MF is considered in frequency-selective environments. Computer simulations are conducted to verify that the proposed technique can achieve high IFO and SID detection probabilities.