中文摘要：

针对传统正交频分复用系统在具有复杂多途和深度频率选择性衰落特点的水声信道中性能下降的问题，提出了啁啾扩频正交频分复用水声通信方案．该方案对原信息码扩频，子载波变为相同调频斜率、不同中心频率、频带相互重叠的正交啁啾信号．经过水声相干多途信道后在接收端解扩，使多个途径信号在频域上拓展．多径信号彼此分离．结合虚拟时间反转镜技术，聚焦多途信道能量，完成信道多径分集接收，不仅可以抑制频率选择性衰落的影响，还充分利用信道多径分集增益提高系统性能．通过仿真研究和湖试验证，表明该方案具有较好的有效性和可靠性．

英文摘要：

Aiming at the problem of traditional orthogonal frequency division multiplexing （OFDM） communication system performance degradation when the channel is subjected to complex multi-path and frequency-selective deeply fading, a chirp spread spectrum （CSS） of OFDM underwater acoustic communication system called CSS-OFDM is proposed in this paper. The CSS-OFDM system spreads the spectrum of traditional OFDM signals, whose sub-carriers are modulated into the same chirp rate, different center frequency orthogonal chirp signals with overlapped bandwidth. Dispreading after underwater acoustic coherent multi-path channel, at the receiving end, the multi-path signals will be expanded from each other in the frequency domain. Applying virtual time reversal mirror technology, the energies of the multi-path signals are focused to complete the multi-path channel diversity receiving. The system performance is improved not only by suppressing the frequency selective fading, but also taking full advantage of multi-path energy of the channel. The effectiveness and reliability of this system are verified through a number of simulations and lake trials.