Research on Direct Spread Spectrum Sequence Synchronization Technology for Underwater Acoustic Multi-User Positioning Systems

The underwater acoustic positioning system faces challenges in the complex and dynamic underwater environment and limited frequency band resources. Expanding the frequency band range through hardware enhancement is costly and challenging. In contrast, spread spectrum technology enables multiple users to communicate within the same frequency bandwidth. This study addresses these challenges by employing direct sequence spread spectrum (DSSS) signals for multi-user underwater positioning. Experimental trials in pools and canals are conducted using the AM5708 platform. The received signal is correlated with the local spread spectrum signal using the overlap retention method for real-time detection and positioning. Upon detecting correlation peaks, the cosine function fitting interpolation method is applied to enhance the accuracy of correlation peaks and peak points, facilitating precise delay measurement and overall system positioning accuracy improvement. Experimental results demonstrate that the direct sequence spread spectrum's favorable autocorrelation and cross-correlation properties enable signal differentiation among multiple users utilizing distinct spread-spectrum sequences, thereby supporting concurrent multi-target positioning.