Real-time Signal Acquisition Algorithm and Optimization for DSSS Broadband Underwater Acoustic Positioning

Traditional underwater acoustic positioning signals are difficult to achieve both high accuracy and long effective measurement distance. Therefore, a wideband underwater positioning software receiver based on Direct Sequence Spread Spectrum (DSSS) technique was designed in this paper. However, the DSSS signal has the disadvantages of requiring transmission periodic extension and Doppler sensitivity for real-time acquisition. Thus, the overlap-save cyclic correlation method was adopted in order to avoid DSSS signal transmitting periodic extension and minimize the signal width. Meanwhile, a sample frequency-shift Doppler search method was proposed to reduce the acquisition algorithm complexity caused by the Doppler sensitivity of DSSS signal. Using the two optimized methods above, the designed software receiver could be applied to various low-power processors within an acceptable processing gain loss for real-time DSSS signal acquisition. The sea experiment was conducted using the optimized software receiver, which verified the effectiveness of the optimized real-time acquisition algorithm.