正交啁啾复用框架下低复杂度扫频−扩频水声通信方法
A low complexity underwater sweep-spread communication method within OCDM framework
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摘要: 基于扫频−扩频载波(SSC)在多径信道下接收信号与正交啁啾复用(OCDM)符号的关联性, 通过引入离散菲涅尔变换(DFnT), 提出了一种低复杂度的SSC解调器。在该方法下, SSC的大部分多径分量被视作OCDM系统的子载波, 并通过离散菲涅尔变换滤除。进而使用训练符号记录残余邻近多径造成的相位偏移, 并采用偏转的星座图解调数据符号。相较于常规的解调与均衡方法, 所提方法在基带使用DFnT变换直接提取SSC主径信息的策略, 使得多径分离、信道均衡与符号解调的复杂度降低至接近O(1)水平, 大大减少了系统计算负担。仿真与实验表明, 该解调器在降低复杂度的同时, 其性能依旧与常规均衡解调方案相当。Abstract: Leveraging the correlation between the received signal of sweep-spread carrier (SSC) in a multipath channel and the orthogonal chirp division multiplexing (OCDM) symbol, this paper introduces the discrete fractional Fourier transform (DFnT) and proposes a low-complexity SSC demodulator. Within this framework, most multipath components in SSC are treated as subcarriers within the OCDM system and are filtered out using the DFnT. Training symbols are then employed to record the phase shifts caused by residual nearby multipath, and a deflected constellation diagram is utilized for the direct demodulation of data symbols. Compared to the traditional demodulation and equalization methods, the strategy of using DFnT transform in the baseband in this paper reduces the complexity of multipath filtering and channel equalization to near O(1). Simulations and experiments indicate that the proposed demodulator maintains performance comparable to conventional demodulation methods, while significantly reducing complexity.