In this paper, we investigate the performance of reconfigurable intelligent surface (RIS)-aided spatial shift keying (SSK) wireless communication systems in the presence of imperfect channel state information (CSI). Specifically, we analyze the average bit error probability (ABEP) of two RIS-SSK systems respectively based on intelligent reflection and blind reflection of RIS. For the intelligent RIS-SSK scheme, we first derive the conditional pairwise error probability of the composite channel through maximum likelihood (ML) detection. Subsequently, we derive the probability density function of the combined channel. Due to the intricacies of the composite channel formulation, an exact closed-form ABEP expression is unattainable through direct derivation. To this end, we resort to employing the Gaussian-Chebyshev quadrature method to estimate the results. In addition, we employ the Q-function approximation to derive the non-exact closed-form expression when CSI imperfections are present. For the blind RIS-SSK scheme, we derive both closed-form ABEP expression and asymptotic ABEP expression with imperfect CSI by adopting the ML detector. To offer deeper insights, we explore the impact of discrete reflection phase shifts on the performance of the RIS-SSK system. Lastly, we extensively validate all the analytical derivations using Monte Carlo simulations.

翻译：本文研究了在非理想信道状态信息条件下，智能超表面辅助空间移位键控无线通信系统的性能。具体而言，我们分析了分别基于RIS智能反射和盲反射的两种RIS-SSK系统的平均误比特率。针对智能RIS-SSK方案，首先通过最大似然检测推导了复合信道的条件成对错误概率，进而推导了组合信道的概率密度函数。由于复合信道公式的复杂性，无法直接推导出精确的闭式ABEP表达式，因此我们采用高斯-切比雪夫求积法进行结果估计。此外，在存在CSI非理想性时，采用Q函数近似方法推导了非精确闭式表达式。对于盲RIS-SSK方案，我们基于ML检测器推导了非理想CSI条件下的闭式ABEP表达式和渐近ABEP表达式。为深入分析，我们探讨了离散反射相位偏移对RIS-SSK系统性能的影响。最后，通过蒙特卡洛仿真全面验证了所有解析推导结果。