| OFDM underwater acoustic communication technology has high spectrum efficiency and outstanding abilities of anti-inter-symbol interference. The advantages of OFDM including anti-frequency selective fading, anti-inter-symbol interference, anti-ICI, high spectrum efficiency, and these advantages largely overcome the problems caused by the characteristics of underwater channel. OFDM communication technology has wide range of applications both in military and civilian fields. Be a multi-carrier communication technology, OFDM communication system has its specific shortcomings-Peak to Average Power Ratio, thus reducing the urgent need for the OFDM underwater acoustic communication system-solve the PAPR problem.In this thesis, we introduce the architecture of the OFDM underwater acoustic communication systems, analysis the basic principles of OFDM technology. Based on the study of existing methods about reducing PAPR, we improved those methods in two ways. Clipping way: the original method just think about the reducing of PAPR, and don't care much about the inconvenience of the system, we improved the method by correcting the clipping function, considering both the BER performance and PAPR problem; Probability way: the original method simply reduces the probability of high PAPR, without increasing the computational complexity of the system, we introduce the new method: SLM-Clipping. Simulation results show that: the two improved methods reduce the PAPR and improve the system's bit error rate performance.In the acoustic tests, we require the spectrum of the acoustic transducer flat as far as possible. This thesis presents a pre-distortion technology to overcome the uneven problem of the acoustic transducer caused by human factors. The simulation results show the pre-distortion technology has no effect on PAPR. In the end of this thesis, we give the solutions of transmitter about PAPR reducing and pre-distortion technology of the acoustic transducer. |
PDF Full Text Request