This paper proposes two novel wireless transmission schemes, namely reconfigurable intelligent surface (RIS)-assisted received adaptive spatial modulation (RASM) scheme and RIS-assisted received adaptive space shift keying (RASSK) scheme, designed to enhance spectral efficiency (SE) and physical layer security (PLS). In both proposed schemes, transmitting bits are dynamically mapped at receive antennas by leveraging the characteristics of the RIS in each time slot, which enables the enhancement of signal-to-noise ratio (SNR) at specific selected antennas with nearly few power, thus leading to a reliable and green wireless communication. Unlike conventional fixed-antenna RIS-RSM/GSSK, the term ``adaptive'' indicates the number of active antennas dynamically changes per symbol, conveying extra spatial information to break existing spectral efficiency bottlenecks.This adaptive approach facilitates the conveyance of extra bits to the receiver, which means it needs less cost of radio-frequency chains at transmitter while improving SE. Besides, the proposed schemes offer an inherent PLS security advantage, as the eavesdropper is unable to completely detect signals reflected from the RIS. To comprehensively evaluate the performance of the proposed RASM and RASSK schemes, this paper presents a detailed analytical performance of their spectral efficiency, detection complexity, bit error rate, and secrecy rate, which are accompanied by insightful findings and conclusions. Simulation and analytical results demonstrate the superiority of the proposed schemes, showcasing their improved error performance and robustness against wiretapping, while also highlighting the potential of the RASM and RASSK schemes for future wireless applications.

翻译：本文提出了两种新颖的无线传输方案，即可重构智能表面（RIS）辅助的接收端自适应空间调制（RASM）方案与RIS辅助的接收端自适应空间移位键控（RASSK）方案，旨在提升频谱效率（SE）与物理层安全（PLS）。在所提出的两种方案中，通过利用RIS在每个时隙的特性，传输比特在接收天线处被动态映射，这使得能以极低的功率增强特定选定天线处的信噪比（SNR），从而实现可靠且绿色的无线通信。与传统的固定天线RIS-RSM/GSSK不同，“自适应”一词意味着活跃天线数量随符号动态变化，从而传递额外的空间信息以突破现有频谱效率瓶颈。这种自适应方法有助于向接收端传递额外比特，这意味着在提升频谱效率的同时，发射端所需的射频链成本更低。此外，所提方案具有固有的物理层安全优势，因为窃听者无法完全检测从RIS反射的信号。为全面评估所提出的RASM与RASSK方案的性能，本文详细分析了其频谱效率、检测复杂度、误比特率与保密速率，并给出了深入的发现与结论。仿真与分析结果证明了所提方案的优越性，展示了其改进的误码性能与抗窃听鲁棒性，同时凸显了RASM与RASSK方案在未来无线应用中的潜力。