基于联合频分复用的水下多载波调制技术

目前水声通信的OFDM调制是一种高效率的多载波调制技术，但严格要求子载波正交，对频偏敏感.水声通信中主要采用多普勒补偿或增加子载波滤波器的方法解决多普勒频移的问题，实现复杂.本文从新的角度，即增大子载波间间隔角度研究减小子载波间干扰(ICI)，提出一种联合频分复用(C-FDM)方法，将多个OFDM子载波模块联合形成一个C-FDM子载波模块，并将频率相同的子载波放在相邻位置.在C-FDM和OFDM符号长度相同情况下，C-FDM的子载波间隔更大，不需要增加复杂补偿算法，就能有效提高抗多普勒频移能力.仿真结果表明C-FDM技术在水声信道中有更优良的误码率性能.

Multicarrier Modulation of UWA Communication Based on Combined Frequency Division Multiplexing

The orthogonal frequency division multiplexing (OFDM)， widely applied in underwater acoustic (UWA) communication， is an efficiently multicarrier modulation technique. But OFDM requires the subcarriers to be orthogonal and is very sensitive to frequency offset. The Doppler compensation or adding the subcarrier filter is mainly used to combat Doppler shift in UWA communication， but the implementation is complicated. This paper investigates the method of reducing intercarrier interference (ICI) from a new perspective， that is， increasing the spacing between subcarriers. The combined frequency division multiplexing (C-FDM) is proposed and several OFDM subcarrier blocks are combined into one new C-FDM subcarrier block， and the same frequency subcarrier near each other to construct new C-FDM subcarriers is arranged. Assuming the symbol lengths of C-FDM and OFDM are equal and the subcarrier spacing of C-FDM is larger，the anti-Doppler shifting capability is effectively improved without complex compensation algorithms. The simulation results showed that C-FDM technology has better BER performance in UWA channel.