低轨卫星通信的信道存在快变和多径问题，正交时频空间(Orthogonal Time Frequency Space，OTFS)调制技术是解决该问题的候选技术。结合广义索引调制(Index Modulation，IM)，提出正交时频空间与广义索引调制(Orthogonal Time Frequency Space and Generalized Index Modulation，OTFS-GIM)的方案。与固定激活数据点的基于正交时频空间与索引调制(Orthogonal Time Frequency Space and Index Modulation，OTFS-IM)不同的是，所提方案引入改进的 IM块，增加了激活数据点选择模式，为不同数量的激活数据点分配额外信息，实现更高的频率效率。同时改进了信息传递检测(Message Passing Detection，MPD)算法、检测激活数据点携带的索引信息、恢复传输的星座信息。仿真结果表明在高速移动场景下，相较于OTFS和 OTFS-IM，所提OTFS-GIM以较小的性能损失为代价，获得了更高的频谱效率。
Orthogonal Time-frequency Generalized Index Modulation in High-speed Mobile Scenarios
To improve the spectral efficiency of communication systems,this paper proposes a modulation scheme combining Or-thogonal Time Frequency Space(OTFS)and Generalized Index Modulation(OTFS-GIM).Unlike traditional Orthogonal Time Frequen-cy Space and Index Modulation(OTFS-IM)scheme with fixed activation data points,the proposed scheme introduces an improved index modulation block,increases the selection process of activation data points,which can carry additional information for different numbers of activation data points,and achieves higher frequency efficiency.Meanwhile,this scheme improves the Information Transfer Detection(MPD)algorithm to detect the index information carried by activated data points and recover transmitted constellation infor-mation.Simulation results show that in high-speed mobile scenarios,the proposed OTFS-GIM in this paper outperforms traditional OTFS and OTFS-IM schemes in terms of spectral efficiency at the cost of small performance loss.
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