A Doppler shift estimation algorithm with low computational complexity for underwater acoustic communication

In underwater acoustic communication system, carrier synchronization and symbol synchronization are adversely affected by Doppler Effect, due to relative motion of the transmitter and receiver. This paper presents a novel Doppler shift factor estimation algorithm. That is the joint estimation of frequency spectrum using FFT and technique of ambiguity function. First the search range of ambiguity function is determined in a small range by using FFT spectrum analysis of the continuous wave (CW) signal. Then Doppler shift factors estimated by using ambiguity function for linear frequency modulated (LFM) signal. Simulation results show that a small number of corrugators can achieve the required Doppler shift accuracy when SNR is greater than -5dB. Therefore the hardware complexity is dramatically reduced.