A Low-Complexity Joint Time Synchronization and Channel Estimation Scheme for Orthogonal Frequency Division Multiplexing Systems

Abstract

In this paper, a novel training sequence structure along with a joint time synchronization and channel estimation scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed. The proposed training sequence structure is composed of an orthogonal sequence attached by cyclic prefix and cyclic postfix. Both the lengths of the cyclic extensions attached are chosen to be longer than the maximum delay spread of the wireless channel. Based on the unique structure of the training sequence, we present a low-complexity joint time synchronization and channel estimation scheme. Unlike conventional methods, which require either discrete Fourier transform (DFT) operations or matrix inversions to acquire channel impulse response (CIR) information, the proposed scheme requires only a correlator and a comparator. At the expense of the same training sequence overheads, computer simulation results show that the proposed joint scheme outperforms conventional time synchronization methods by orders. Furthermore, the overall bit error rate (BER) performance of the proposed joint scheme is shown to be close to the ultimate bound characterized by perfect synchronization and channel estimation. The proposed joint scheme also provides significant BER performance gain as compared to a scheme that properly combines a conventional synchronization method with a DFT-based channel estimation method.