Reconfigurable intelligent surfaces (RIS) and index modulation (IM) represent key technologies for enabling reliable wireless communication with high energy efficiency. However, to fully take advantage of these technologies in practical deployments, comprehending the impact of the non-ideal nature of the underlying transceivers is paramount. In this context, this paper introduces two RIS-assisted IM communication models, in which the RIS is part of the transmitter and space-shift keying (SSK) is employed for IM, and assesses their performance in the presence of hardware impairments. In the first model, the RIS acts as a passive reflector only, reflecting the oncoming SSK modulated signal intelligently towards the desired receive diversity branch/antenna. The second model employs RIS as a transmitter, employing M-ary phase-shift keying for reflection phase modulation (RPM), and as a reflector for the incoming SSK modulated signal. Considering transmissions subjected to Nakagami-m fading, and a greedy detection rule at the receiver, the performance of both the system configurations is evaluated. Specifically, the pairwise probability of erroneous index detection and the probability of erroneous index detection are adopted as performance metrics, and their closed-form expressions are derived for the RIS-assisted SSK and RIS-assisted SSK-RPM system models. Monte-Carlo simulation studies are carried out to verify the analytical framework, and numerical results are presented to study the dependency of the error performance on the system parameters. The findings highlight the effect of hardware impairment on the performance of the communication system under study.

翻译：可重构智能表面（RIS）与索引调制（IM）是实现高能效可靠无线通信的关键技术。然而，要在实际部署中充分利用这些技术，理解底层收发器非理想特性的影响至关重要。在此背景下，本文提出了两种RIS辅助的IM通信模型，其中RIS作为发射机的一部分，并采用空间移位键控（SSK）进行索引调制，评估了它们在硬件损伤存在下的性能。在第一种模型中，RIS仅作为无源反射器，将接收到的SSK调制信号智能地反射至期望的接收分集支路/天线。第二种模型将RIS用作发射器，采用M进制相移键控进行反射相位调制（RPM），同时作为入射SSK调制信号的反射器。考虑传输经历Nakagami-m衰落，并在接收端采用贪婪检测准则，评估了两种系统配置的性能。具体而言，采用错误索引检测的成对概率和错误索引检测概率作为性能指标，并针对RIS辅助SSK和RIS辅助SSK-RPM系统模型推导了其闭式表达式。通过蒙特卡洛仿真研究验证了分析框架，并给出数值结果以研究误码性能对系统参数的依赖性。研究结果突显了硬件损伤对所研究通信系统性能的影响。