\begin{center}
\begin{texdraw}
\centering 
\drawdim in \linewd 0.015 \setunitscale 0.5
\arrowheadsize l:0.25 w:0.13 \arrowheadtype t:F
\move(0 0)
\rmove(-5 0) \ravec(+1 0) \bulbox{$\bullet$} 
\rlvec(0 +0.75) 
\sysbox{0}
\rmove(-3.75 -0.75) 
\rlvec(0 -0.75) \sysbox{1}
\rmove(0 1.5)
\rlvec(0 -0.6)
\rmove(0 +0.6)
\rmove(0 -1.5)
\rlvec(0 +0.6)
\move(0 0)
\switchbox{$y(t_i)$} \rmove(-0.03 0)\bulbox{$\bullet$}
\rlvec(0 -2.2) 
\ravec(-0.855 0) \rmove(-1.26 0)  \lbox{$\mathscr{F}_{0}$}
\rmove(-1.25 0) \ravec(-1.25 0) \rmove(-1.254 0)  
\lbox{$f_{\mathrm{R}}(\cdot)$}
\rmove(-1.25 0) \ravec(-0.995 0) \rlvec(0 +2.2) \rmove(-0.75 0)
\forbox{$u(t_i)$} \rmove(4.127 -2.5)   \ravec(0 -0.5)
\rmove(-0.625 -0.3) \lbox{$\mathscr{DG}$} \rmove(-0.625 -0.3)  
\ravec(0 -0.5)
\rmove(+0.05 +0.15) \forbox{$d_{0}(t_k)$} \rmove(-0.7 +1.2)
\forbox{$\nu(t_{1}^{k})$} \rmove(-2.45 +0.8) \forbox{$\hat x_{0}(t_{i}^{+})$}
\rmove(-3.265 +0.5) \bulbox{$\bullet$} \ravec(+2.5 0) \tbox{$q^{-1}$}
\rlvec(+1.9 0) \rlvec(0 -0.5) \ravec(-0.4 0) \rmove(-0.3 +0.75)
\forbox{$u(t_{i-1})$} 

\end{texdraw}
\end{center}

\noindent