Suppression of synchronization errors in OFDM based carrier aggregation system

Abstract

OFDM (Orthogonal Frequency Division Multiplexing) has been chosen as the air interface technique for LTE (Long Term Evolution) standard. Furthermore, CA (Carrier Aggregation) is defined by 3GPP (the 3rd Generation Partnership Project) to support wide-bandwidth transmission. However, OFDM system is sensitive to synchronization errors generated by multipath delay, Doppler shift and oscillator instability. In this paper, we address the synchronization problem in non-continuous CA scenario and propose a block type pilot based synchronization algorithm to suppress the STO (Sampling Timing Offset) and CFO (Carrier Frequency Offset). The pilot pattern used here is CAZAC (Constant Amplitude Zero Autocorrelation) sequence, which is also exploited in LTE-Advanced standard. Since the proposed method is a parallel processing, different bands could experience different synchronization errors. Simulation results show the proposed method can significantly improve system performance and has smooth performance when synchronization errors vary.