Underwater acoustic communication channels have various characteristics including attenuation, distortion, multipath, and Doppler frequency shifts that degrade communication reliability. To overcome these challenges, among various communication techniques, direct sequence spread spectrum (DSSS) has been studied recently. DSSS compensates for signal distortion caused by multipath effects and is robust against frequency-selective fading due to its wide frequency spectrum. For compensating DSSS signals, a RAKE receiver was employed which is a matched filter that correlates received the signal with the spreading code on each tap. When configuring spread data format in designing packet structure for various spreading factors and source data rates, it is essential to consider channel state information (CSI) such as coherent time and coherent bandwidth, which are influenced by multipath and Doppler frequency shifts. Through simulations, we propose an optimal DSSS packet design model that satisfies CSI both in the time domain and frequency domain by evaluating performance for these channel conditions. This research is supportedby a KRIT grant funded by the Korean government (DAPA) (KRIT-CT-23-035-01, Multi AUV operation Technology for Mine Detection ('23–'28))
Hong et al. (Tue,) studied this question.