Reconfigurable Intelligent Surfaces (RISS) have emerged as a promising technology for improving wireless communication performance by intelligently controlling the propagation of electromagnetic signals. This search investigates the impact of RIS-SISO wireless communication system under four small-scale fading models: Rayleigh, Rician, Nakagami-m, and Two-Wave with Diffuse Power (TWDP). The system performance is first evaluated without RIS to establish a baseline for the four fading models. The effect of introducing a RIS is then investigated under the considered fading conditions. Then, the study also examines the effect of the number of RIS elements.

The results demonstrate that the four fading models exhibit different baseline BER characteristics, while maintaining consistent performance trends with increasing SNR. After introducing a 50-element RIS with phase control and its ability to enhance the effective channel. A substantial improvement in BER is achieved across all considered channels. At 10 dB SNR, the BER reduction reaches approximately 94.9% for Rayleigh, 96.6% for Rician, 96.2% for Nakagami-m, and 98.8% for TWDP, based on the adopted baseline comparison. Also, the capacity achieves (4) times compared without RIS configuration and showing that increasing the number of reflecting elements strengthens the RIS-assisted channel contribution. The power analysis further shows that increasing the number of RIS elements enhances both the reflected-channel power and the effective channel power across the considered fading models. The Rician channel exhibits the highest power levels, while Nakagami-m and TWDP show closely related behavior, followed by the Rayleigh channel.

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