Abstract
Wireless communication at sea is an essential way to establish a smart ocean. In the communication system, however, signals are affected by the carrier frequency offset (CFO), which results from the Doppler effect and crystal frequency offset. The offset deteriorates the demodulation performance of the communication system. The conventional Gardner bit-synchronization algorithm performs timing synchronization on the baseband, but it fails to solve the problem of carrier frequency offset. In this paper, a carrier-based timing-synchronization Gardner algorithm was proposed. The algorithm performed error detection in the carrier signal to estimate the synchronization error in real time and the time-domain expansion in the passband signal. Based on the estimated expansion factor, the algorithm located the sampling points of the ideal signal and re-interpolated all the sampling points on the passband to recover the passband signal without Doppler. This algorithm can solve both the frequency shift and time-domain expansion caused by the Doppler effect without further CFO estimation and compensation, thus reducing the overall computational complexity of the system. The simulations showed that the proposed algorithm greatly improves the ability of the communication system to combat Doppler compared to the conventional Gardner algorithm. The algorithm is primarily designed for binary phase-shift keying (BPSK)-modulated signals under the additive white Gaussian noise (AWGN) channel and can be applied to various maritime communication scenarios.