The Rearch And Implementation Of Multi-carrier DS-CDMA In Underwater Acoustic Communication Technology

underwater communication system has been rapidly developped, with the application of underwater acoustic communications were becoming increasingly wide. The underwater acoustic channel was a random non-ideal channel, with non-stationary and frequency-selective fast fading characteristics. Due to the influence of water conditions, the effective bandwidth of the channel was severely restricted and have the Doppler instability. It brought great challenges in underwater communications data transmission. So in this paper, direct sequence spread spectrum systems and multi-carrier DS-CDMA system were designed to improve information transfer and bandwidth utilization rate and used under the conditions of low SNR, the long-distance communication. This research work has the following aspects:1,First, multi-carrier spread spectrum technology was led conceptually in the underwater acoustic communication. Combined with its development process, systematically, the subject of this paper was expounded and located.2,Direct sequence spread spectrum systems was empoldered with key technologies such as QPSKmodulated emission, RLS received equilibriume and M sequence generation by the traditional DS-SS theory and principles of the spread spectrum analysis. Comparison of simulation results validate the performance feasibility of a complex transmission environment.3,Designed and developed two kinds of multi-carrier spread spectrum system which based on non-coherent modulation mode of Matched Filter-related principles and coherent modulation mode of Single carrier DS-SS technology. As the environment of underwater acoustic channel was Simulated, the two systems were compared under different conditions of communication in the transmission performance. 4,Participated in the design of the hardware system platform on which the ADI-561DSP was the core processing chip and developed to achieve the software system functions of direct sequence spread spectrum and multi-carrier DS-CDMA technology. Completed debugging software and hardware of the acoustic communication system platform.5,The pool and the lake communication system experiments have proved the capacity of the two systems'date transmission in real complex underwater acoustic channel and certain robustness to the harsh interference of acoustic environment.