The Design And Simulation Of High-speed Underwater Acoustic Communication Systems

Underwater acoustic (UWA) communication technolog originally has been used in the military field ,and it's of great strategic significance in national defense. And it's also demonstrated broad prospects in civilian areas and commercial areas while human beings has been incessantly exploiting and using the marine resources in recently ten yeas. High-speed data transmission has always been one of the hot research topics for the UWA communication researchers.Early studies showed that sound transmission loss and water absorption are the main factors caused the UWA channels to be limited bandwidth and signal transmission distance greatly restricted , at the same time,UWA channel is a typical time-varying and muti-path fading channel ,so UWA communication system just to use lower symbol transmission rate, non-coherent demodulation, frequency modulation to achieve reliable communication in the past.As orthogonal frequency division multiplexing(OFDM)technology with high spectrum efficiency,strong ability of overcome multi-path interference,and also as a Multi-carrier modulation technique,it can reach high-speed data communications ,in view of the above reasons ,we put OFDM in UWA communication system.The paper mainly studies and discusses the OFDM's IFFT/FFT implementation and the key technologies with OFDM while it been applied in UWA communication system.The main content of this paper are as follows: introduces the principle of OFDM in detail;analyzes how does the guard interval(GI) to overcome multi-path interferences , gives two forms of GI and compares their performances; discusses four OFDM system models based on IFFT/FFT, compares their complexity level and the transmission efficiency ;mainly investigates the channel estimation technology ,firstly pulls in several pilot pattern , secondly estimates pilot sub-carriers'channel response value by estimation criterions of LS and MMSE , compares the algorithms both on mean-squared error(MSE) and symbol error rate(SER) , then discusses several interpolation algorithms to estimate the data sub-carriers'channel response ,simulates and analyzes the results ;finally , gives the UWA OFDM communication system's whole simulation and analyzes the results.