Research on multi-user detection and delay estimation technology for underwater acoustic multi-user positioning system in mobile scenes

Underwater acoustic (UWA) communication (UWAC) and positioning technology plays an important role in the field of underwater resource utilization and development. UWA multi-user detection and positioning technology is the core issue in UWAC and positioning systems. The time-varying ocean environment provides UWA multi-user detection, Doppler estimation and compensation and time delay estimation pose great challenges. First of all, in response to the requirements of multi-user UWAC and positioning technology, this article proposes a multi-user detection and delay estimation scheme based on Direct Sequence Spread Spectrum technology, using a 7th-order sequence as the spread spectrum code; secondly, in order to overcome the Doppler problem caused by high-speed motion, this article proposes a Doppler estimation and compensation technology based on ambiguity functions; then, based on the actual FPGA hardware platform, joint multi-user detection and multi-user detection are implemented. Doppler estimation and compensation and high-precision delay estimation algorithm; finally, the simulation and experiment results show that the solution proposed in this article can realize multi-user detection, Doppler estimation and compensation and high-precision delay estimation under 4-user conditions in real time. The delay estimation accuracy is less than 12us when the signal-to-noise ratio is 3dB, and the multi-user detection probability is greater than 90%.