As a new candidate waveform for the next generation wireless communications, orthogonal chirp division multiplexing (OCDM) has attracted growing attention for its ability to achieve full diversity in uncoded transmission, and its robustness to narrow-band interference or impulsive noise. Under high mobility channels with multiple lags and multiple Doppler-shifts (MLMD), the signal suffers doubly selective (DS) fadings in time and frequency domain, and data symbols modulated on orthogonal chirps are interfered by each other. To address the problem of symbol detection of OCDM over MLMD channel, under the assumption that path attenuation factors, delays, and Doppler shifts of the channel are available, we first derive the closed-form channel matrix in Fresnel domain, and then propose a low-complexity method to approximate it as a sparse matrix. Based on the approximated Fresnel-domain channel, we propose a message passing (MP) based detector to estimate the transmit symbols iteratively. Finally, under two MLMD channels (an underspread channel for terrestrial vehicular communication, and an overspread channel for narrow-band underwater acoustic communications), Monte Carlo simulation results and analysis are provided to validate its advantages as a promising detector for OCDM.

翻译：作为下一代无线通信的新型候选波形，正交啁啾复用（OCDM）因其在非编码传输中实现全分集能力以及对窄带干扰或脉冲噪声的鲁棒性而日益受到关注。在多时延多普勒（MLMD）高移动性信道下，信号在时域和频域遭受双选衰落，且调制在正交啁啾上的数据符号相互干扰。为解决MLMD信道下OCDM符号检测问题，本文在假设信道路径衰减因子、时延和多普勒频移已知的条件下，首先推导了菲涅耳域的闭合信道矩阵，并提出一种低复杂度方法将其近似为稀疏矩阵。基于该近似菲涅耳域信道，提出了一种基于消息传递（MP）的检测器，通过迭代方式估计发射符号。最后，在两种MLMD信道（用于地面车辆通信的欠扩展信道和用于窄带水声通信的过扩展信道）下，通过蒙特卡洛仿真结果与分析验证了该检测器作为OCDM候选检测方案的优势。