Extremes of Reflecting Gaussian Processes on Discrete Grid

Abstract

For $\{X(t), t \in G_\delta\}$ a centered Gaussian process with stationary increments and a.s. sample paths on a discrete grid $G_\delta=\{0,\delta,2\delta, ...\}$, where $\delta>0$, we investigate the stationary reflected process $$Q_{\delta,X}(t) = \sup\limits_{s\in [t,\infty)\cap G_\delta}\big( X(s)-X(t)-c(s-t)\big), \ t \in G_\delta $$ with $c>0$. We derive the exact asymptotics of $$\mathbb P\{\sup\limits_{t\in [0,T]\cap G_\delta} Q_{\delta,X}(t)>u\} \quad \text{and} \quad \mathbb P\{\inf\limits_{t\in [0,T]\cap G_\delta} Q_{\delta,X}(t)>u\},$$ as $u\to\infty$, with $T>0$. It appears that $\varphi=\lim_{u\to\infty} \frac{\sigma^2(u)}{u}$ determines the asymptotics, leading to three qualitatively different scenarios: $\varphi=0$, $\varphi\in(0,\infty)$ and $\varphi=\infty$.