This paper proposes a Time-Frequency Space Transformation (TFST) to derive non-orthogonal bases for modulation techniques over the delay-doppler plane. A family of Overloaded Delay-Doppler Modulation (ODDM) techniques is proposed based on the TFST, which enhances flexibility and efficiency by expressing modulated signals as a linear combination of basis signals. A Non-Orthogonal Time-Frequency Space (NOTFS) digital modulation is derived for the proposed ODDM techniques, and simulations show that they offer high-mobility communication systems with improved spectral efficiency and low latency, particularly in challenging scenarios such as high overloading factors and Additive White Gaussian Noise (AWGN) channels. A modified sphere decoding algorithm is also presented to efficiently decode the received signal. The proposed modulation and decoding techniques contribute to the advancement of non-orthogonal approaches in the next-generation of mobile communication systems, delivering superior spectral efficiency and low latency, and offering a promising solution towards the development of efficient high-mobility communication systems.

翻译：本文提出了一种时频空间变换（TFST），用于在延迟-多普勒平面上推导调制技术的非正交基。基于TFST，提出了一类过载延迟-多普勒调制（ODDM）技术，通过将调制信号表示为基信号的线性组合，增强了灵活性和效率。针对所提出的ODDM技术，推导出非正交时频空间（NOTFS）数字调制方法，仿真结果表明，该技术能够为高移动性通信系统提供更高的频谱效率和更低的延迟，特别是在高过载因子与加性高斯白噪声（AWGN）信道等具有挑战性的场景中表现优异。此外，还提出了一种改进的球形译码算法用于高效解码接收信号。所提出的调制与译码技术为非正交方法在下一代移动通信系统中的发展做出了贡献，在实现高频谱效率和低延迟的同时，为构建高效的高移动性通信系统提供了有前景的解决方案。