In this paper, two novel spectrum resource allocation schemes, based on orthogonal frequency division multiplexing with index modulation (OFDM-IM) and dual-mode OFDM-IM, are proposed for a three-node cooperative non-orthogonal multiple access (C-NOMA) system. In the first scheme, we allocate IM bits to serve the cell-edge user, and save the transmit power to assist the delivery of constellation symbols. Alternatively, constrained by the spectral efficiency (SE), the rest information bits of the cell-edge user can be carried by the conventional signal constellation. In the second scheme, to further eliminate the interference between users and boost the SE, different modulation modes (Mode I and Mode II) are employed to distinguish the subcarriers of the cell-center and cell-edge users, and to encode the incoming bit stream from these users, respectively. Furthermore, we consider two different detectors for the cell-edge user, i.e., the optimal/suboptimal maximum-likelihood detectors. Asymptotically tight bounds on the bit error rate of the above-mentioned users are derived in closed-form. Finally, simulation results verify the theoretical analysis and show that the proposed schemes have the potential to outperform C-NOMA.

中文翻译：

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基于协同NOMA和索引调制的频谱资源分配

在本文中，针对三节点协作非正交多址（C-NOMA）提出了两种基于正交频分复用索引调制（OFDM-IM）和双模OFDM-IM的频谱资源分配方案。 ） 系统。在第一种方案中，我们分配IM比特为小区边缘用户服务，并节省发射功率以辅助星座符号的传递。或者，受限于频谱效率（SE），小区边缘用户的其余信息比特可以由传统的信号星座承载。在方案二中，为了进一步消除用户之间的干扰，提升SE，采用不同的调制方式（Mode I和Mode II）来区分小区中心和小区边缘用户的子载波，并对输入比特进行编码来自这些用户的流，分别。此外，我们为小区边缘用户考虑了两种不同的检测器，即最优/次优最大似然检测器。上述用户误码率的渐近紧界是以封闭形式导出的。最后，仿真结果验证了理论分析，并表明所提出的方案具有优于 C-NOMA 的潜力。