【摘要】 针对传统OFDM系统在应对深度频率选择性衰落信道时性能下降和多普勒频偏造成子载波相互干扰的问题,提出采用正交的线性调频(LFM)信号作为载波,基于分数阶Fourier变换(FRFT)的正交多载波水声通信方案。该方案选用相同调频斜率,不同中心频率,频带相互重叠的正交LFM作为子载波进行信息调制,以分数阶Fourier变换作为调制解调方法来传输信息。为应对水声信道的多途效应,采用在数据帧与帧之间插入保护间隔(GI)来减小码间干扰。提出结合QDPSK和分数阶域载波位置修正抑制多普勒效应,简化系统复杂度。该方案最高通信速率可达3.6kbit/s,通过仿真研究和湖试实验验证了该方案的有效性与可行性。更多还原

【Abstract】 Aimed at the traditional OFDM communication system fails when the channel was frequency-selective,rap-idly fading and had the Doppler effects,resulting in inter-carrier interference,a orthogonal multi-carrier system for un-derwater acoustic communication was proposed,which employed orthogonal signal basis of the chirp type corresponding to the fractional Fourier transform(FRFT) signal basis.The scheme used the orthogonal LFM signal as sub-carrier to modulate,which had same chirp rate but different center frequency with overlapped bandwidth,and used fractional Fou-rier transform for modulation and demodulation method to transmit information.For suppression of the multi-paths channel effect,the guard interval(GI) was used between signal data frame.And the position correction in fractional do-main method combining with QDPSK was proposed to suppress the Doppler effects,which simplified the system com-plexity.The communication scheme had the characteristic of high communication rate,and the maximum rate was up to 3 600bit/s.The effectiveness and reliability of this system was verified through a large number of simulation and lake ex-periments.更多还原