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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. [ABSTRACT FROM AUTHOR]

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