Applied research on RA codes in underwater acoustic ofDM communication system

正交频分复用(OrTHOgOnAl frEQuEnCy dIVISIOn MulTIPlEXIng,OfdM)技术由于具有频谱利用率高、抗多径能力强等优点,成为当前水声通信的研究重点和热点,但较高的峰均功率比(PEAk-TO-AVErAgE POWEr rATIO,PAPr)严重影响了水声OfdM通信系统的性能。采用重复累积码(rEPEAT ACCuMulATE,rA)作为信道编码方案,并用线性反馈移位寄存器(lInEAr fEEdbACk SHIfT rEgISTErS,lfSr)代替原rA码结构中的累加器,再通过选择映射(SElECTIVE MAPPIng,SlM)方法降低系统的峰均功率比。计算机仿真和水池实验结果表明,采用改进结构的rA码结合SlM技术能有效降低水声OfdM系统的PAPr,提高系统的性能,具有很好的应用前景。Orthogonal frequency division multiplexing(ofDM) technology has become the research focus and hotspot of underwater acoustic communications owing to its advantages such as high spectrum efficiency and robustness to multipath fading,but it possesses high peak-to-average power ratio(PAPR) which severely degrades the performance of Underwater Acoustic ofDM Communication System.In this paper,repeat accumulate(RA) code is adopted as the channel coding scheme,and linear feedback shift registers(LFSR) is used to replace the accumulator of original RA code structure,then selective mapping(SLM) method is also adopted to reduce the PAPR of system.Computer simulation and experimental results show that modified RA code and SLM can effectively reduce the PAPR and improve the per-formance of underwater acoustic ofDM communication system,which have a very good application prospect.研究基金访问学者项目(2011631504); 中央高校基础研究基金项目(201112G020和201212G012); 国家自然科学基金项目(41176032

Studies on the Mechanism of Heterophase Reaction in Preparation of Nanometer-sized Nickel Powders by Hydrothermal Hydrogen Reduction

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台灣與大陸地區藝術教育師資培育之教學信念研究

計畫執行年代:2005/8-2006/