We address the challenge of developing an orthogonal time-frequency space (OTFS)-based non-orthogonal multiple access (NOMA) system where each user is modulated using orthogonal pulses in the delay Doppler domain. Building upon the concept of the sufficient (bi)orthogonality train-pulse [1], we extend this idea by introducing Hermite functions, known for their orthogonality properties. Simulation results demonstrate that our proposed Hermite functions outperform the traditional OTFS-NOMA schemes, including power-domain (PDM) NOMA and code-domain (CDM) NOMA, in terms of bit error rate (BER) over a high-mobility channel. The algorithm's complexity is minimal, primarily involving the demodulation of OTFS. The spectrum efficiency of Hermite-based OTFS-NOMA is K times that of OTFS-CDM-NOMA scheme, where K is the spreading length of the NOMA waveform.

翻译：本文致力于解决基于正交时频空间（OTFS）的非正交多址接入（NOMA）系统设计中的挑战，在该系统中，每个用户通过延迟多普勒域中的正交脉冲进行调制。基于充分（双）正交训练脉冲的概念[1]，我们通过引入以正交性著称的Hermite函数来拓展这一思路。仿真结果表明，在高移动性信道下，我们提出的Hermite函数在误码率（BER）方面优于传统的OTFS-NOMA方案，包括功率域（PDM）NOMA和码域（CDM）NOMA。该算法的复杂度极低，主要涉及OTFS解调过程。基于Hermite的OTFS-NOMA方案的频谱效率是OTFS-CDM-NOMA方案的K倍，其中K为NOMA波形的扩频长度。