\usetikzlibrary{arrows,matrix}
% \usepackage{amssymb, amsmath, mathptmx}

\begin{tikzpicture}[font=\scriptsize,node distance=1.5cm,scale=0.9]


\tikzstyle{simpleBlock}=[centered, text centered]
\tikzstyle{block}=[simpleBlock, draw, minimum size=1cm, minimum width=2.4cm, thick]
\tikzstyle{arrow}=[draw,-latex,thick]
\tikzstyle{point} = [draw, fill=black, circle,inner sep=1pt]



\node[block] (PreProc) {Pre-processing};
\node[block,right=of PreProc] (Encoding) {Encoding};
\node[block,right=of Encoding, yshift=-1cm, text width=2cm] (Transmission) {Transmission or Storage};
\node[block,left=of Transmission, yshift=-1cm] (Decoding) {Decoding};
\node[block,left=of Decoding] (PostProc) {Post-processing};

\node[simpleBlock,left=of PreProc, text width=1.5cm] (Input) {\textbf{Input}};
\node[simpleBlock,left=of PostProc, text width=1.5cm] (Output) {\textbf{Output}};

\path[arrow] (Input) -- (PreProc);
\path[arrow] (PreProc) -- (Encoding);
\path[arrow] (Encoding) -| (Transmission);
\path[arrow] (Transmission) |- (Decoding);
\path[arrow] (Decoding) -- (PostProc);
\path[arrow] (PostProc) -- (Output);

\end{tikzpicture}