Cell Search Techniques for Underwater Acoustic Cellular Systems

The concept of frequency reuse has been considered for underwater acoustic cellular (UAC) systems owing to the limited available bandwidth of acoustic channels. In a UAC system, the underwater equipment (UE) should detect the identity of the underwater base station (UBS) and synchronize to a serving UBS. In this paper, two different types of cell search techniques are proposed for the downlink of UAC systems based on orthogonal frequency-division multiplexing (OFDM): a Zadoff-Chu sequence-based cell search technique (ZCS-CST) and a linear frequency modulation-based cell search technique (LFM-CST), all at the physical layer. The performances (correlation property, detection probability, and false alarm probability) of the cell search techniques are analyzed and compared with the simulation results in the additive white Gaussian noise (AWGN) and multipath channels. The performances of the cell search techniques are evaluated using the Bellhop channel simulator and field experiment. It is shown that the ZCS-CST is applicable to UAC systems with a small Doppler shift, while the LFM-CST is suitable for UAC systems with a large Doppler shift.