AI 中文总结
该研究针对混合移动用户的OTFS-NOMA HetNets，分析分数多普勒效应的影响，表明优化NOMA功率分配可缓解多普勒间干扰，提升系统性能。
AI 中文摘要
异构网络（HetNets）被认为是满足6G车载网络日益增长的吞吐量需求的有前景方案。正交时频空间（OTFS）调制与非正交多址（NOMA）的结合，已在混合移动场景下显著提升无线网络的可靠性。将该组合应用于HetNets，可同时适配高移动性（HM）和低移动性（LM）用户，且能有效应对大多普勒频移。然而，实际场景中，分数多普勒源于实际多普勒频率与DD网格上离散表示的不匹配，该效应会引发多普勒间干扰（IDI），大幅降低检测性能。本研究探讨混合移动条件下分数多普勒对OTFS-NOMA系统的影响，分析如何优化NOMA功率分配以缓解由此产生的性能下降。OTFS调制用于HM用户，LM用户的符号嵌入时频（TF）域。在对IDI参数知识的多种假设下，采用最小均方误差（MMSE）检测，研究优化NOMA功率分配对整体系统性能的影响。本研究旨在分析HetNets中OTFS-NOMA系统内分数多普勒的影响，而非提出新的OTFS调制检测算法。结果验证了分数多普勒对系统的显著性能影响，并证明功率分配在缓解IDI效应（频谱效率和服务用户数方面）的作用。
英文摘要
Heterogeneous networks (HetNets) are considered a promising approach to meet the increasing throughput requirements of 6G vehicular networks. The integration of orthogonal time frequency space (OTFS) modulation and non-orthogonal multiple access (NOMA) has demonstrated significant improvements in the reliability of wireless networks under mixed-mobility. Applying this combination in HetNets helps accommodate high-mobility (HM) and low-mobility (LM) users while effectively addressing high Doppler shifts. However, in practical scenarios, fractional Doppler arises from the mismatch between the actual Doppler frequency and its discrete representation on the DD grid. This effect leads to inter-Doppler interference (IDI) that can significantly degrade detection performance. In our work, we investigate the effect of fractional Doppler on OTFS-NOMA systems under mixed-mobility conditions and analyze how NOMA power allocation can be optimized to mitigate the resulting performance degradation. OTFS modulation is used for the HM user, while the LM users' symbols are embedded in the time-frequency (TF) domain. Minimum mean square error (MMSE) detection is utilized under multiple assumptions regarding the knowledge of the IDI parameters. We investigate the impact of optimizing NOMA power allocation on the overall system performance. The purpose of this work is to analyze the impact of fractional Doppler in OTFS-NOMA systems in HetNets rather than proposing new detection algorithms for OTFS modulation. The results validate the significant performance impact of fractional Doppler on the system and demonstrate the role of power allocation in mitigating IDI effects in terms of spectral efficiency and number of users served.
DOI：10.1109/ACCESS.2026.3716420
