智能反射面辅助索引调制（RIS-IM）系统作为智能电磁环境下的潜在传输方案，但目前相关研究仅考虑单用户直接发送M阶调制信号场景，若要面向未来无线通信连接海量用户，需结合多址技术对相同资源下更多用户接入场景进行讨论。非正交多址接入（NOMA）技术通过主动引入干扰，对时频资源块进行功率域复用以连接更多用户，实现资源高效利用。文中基于NOMA提出了一种智能反射面辅助索引调制（RIS-IM-NOMA）系统，以实现RIS-IM系统的多用户接入。该系统利用智能反射面提升接收信号质量，并选择最佳发送天线、传递索引信息，通过NOMA将相同时频资源分配给更多用户，以提高频谱效率。在接收端采用贪婪检测方法进行信号检测，并对误码率理论上界进行推导及分析，针对NOMA带来用户间干扰造成的误码率性能下降提出了改进方案。对系统频谱效率进行理论分析，针对用户间频谱效率公平性问题，提出了一种功率分配方式。仿真结果表明：增加反射元件个数可有效降低系统误码率，所提功率分配方式可有效保证系统公平性，从而验证所提方案的有效性。

Reconfigurable intelligent surface assisted index modulation (RIS-IM) scheme is a developed transmission technology in smart radio environment. However, the current relevant research only considers the direct transmission of M-ary modulation signal to a single user. It is necessary to use multiple access technology to make more users share time-frequency resources in the future scenario of wireless communication connecting massive users. Nonorthogonal multiple access (NOMA) technology uses power domain multiplexing of time-frequency blocks to connect more users and realizes efficient utilization of resources by actively introducing interference. Based on nonorthogonal multiple access, this paper proposed a reconfigurable intelligent surface assisted index modulation system (RIS-IM-NOMA) to realize multi-user access for RIS-IM. The system improves the quality of the received signal using the reconfigurable intelligent surface and at the same time selects the best transmitting antenna to transmit index information in this system. And time-frequency resources are allocated to more users through NOMA and the spectral efficiency is improved. The greedy detection method was used to detect the signal at the receiving end, and the upper bound of the bit error rate was derived and analyzed theoretically. Then an improvement scheme was proposed for the performance decline of bit error rate caused by interuser interference of NOMA. The spectral efficiency of the system was analyzed theoretically, and a power allocation method was proposed to solve the problem of fairness of spectral efficiency among users. The simulation results show that increasing the number of reflecting elements can effectively reduce the bit error rate of the system, and the proposed power allocation method can effectively ensure the fairness of the system. Thus, the effectiveness of the proposed schemes is verified.