Long-Distance Underwater Acoustic Remote Control System (LDUWARC) has received much attention recently. With the distance of remote control increasing (> 100km), the acoustic channel that transmitting the control information becoming very complex. These demand to develop a more reliable remote control system.Based on the analysis of underwater acoustic (UWA) channel, this thesis designs an auto-replying LDUWARC system by means of Spread Spectrum technique. Spread Spectrum technique has been widely used in remote underwater acoustic communications recently. It is quite suitable to the LDUWARC system demanding for covert communications while the signal-to-noise ratio (SNR) is low. Spread Spectrum technique can fight against the intersymbol interferences caused by the multipaths propagation and fading, and it has the advantage of low probability of detection. These are the reasons for us to choose spread spectrum technique as the mode of communication in LDUWARC system. The two control modes of LDUWARC system are direct control and controlling with relay station. Considering both the power of transmitting and SNR in the receiver, we adopt auto-reply mode to control the remote objects.The thesis analyzes the transmitting characteristic of the UWA channel, derives the propagation losses, eigenrays and channel impulse responses of UWA channel by use of the Kraken normal wave mode and the ray trace algorithm based on velocity-depth curvilinear profile approximation. Based on the analysis, a scheme of auto-replying LDUWARC system by means of Spread Spectrum technique has been designed. Simulations on the key technique of Spread Spectrum Communications are studied here, according to the characteristic of LDUWARC system, issues concerning pseudo-noise codes, spread spectrum method, correlation receiving and synchronization. We also design an error correction code for the system. Finally, the transmission system principle is embodied with hardware and software design.It is expected the thesis will find its academic values and practical applications in Long-Distance Underwater Acoustic Remote Control System. |