To achieve a table such as this, you need to adjust the following:
- Background colour of the top row. Packages:
xcolor + colortbl
- The double horizontal line at the top. Package:
hhline
- The format of the caption. Package:
caption
You define a light grey colour with \definecolor{mygrey}{rgb}{211,211,211} and in the table you then use \rowcolor{mygrey}. The double horizontal lines are achieved by using \hhline{==}. The caption is formatted through two commands:
\captionsetup{justification=centering,singlelinecheck=false,labelfont=sc,labelsep = newline} It centers the caption, turns font into small-caps, and provides a new line after the name
\renewcommand*\thetable{\Roman{table}} This changes the table numbering to Roman numerals.
This code will work:
\documentclass{article}
\usepackage{xcolor,colortbl,hhline,caption}
\definecolor{mg}{RGB}{211,211,211}
\captionsetup{justification=centering,singlelinecheck=false,labelfont=sc,labelsep = newline}
\renewcommand*\thetable{\Roman{table}}
\begin{document}
\begin{table}
\begin{center}
\caption{\label{tab:tab1}
\scshape{{Security modes in the IEEE802.15.4e Standard.}}}
\begin{tabular}{l|c}
\hhline{==}
\rowcolor{mg}
Security mode & Security provided \\\hline
\hhline{==}
No Security & Data is not encrypted \\\hline
AES-CBC-MAC-32 & Data is not encrypted\\\hline
AES-CBC-MAC-64 & Data is not encrypted\\\hline
AES-CBC-MAC-128 & Data is not encrypted\\\hline
AES-CTR & Data is encrypted\\\hline
AES-CCM-32 & Data is encrypted\\\hline
AES-CCM-64 & Data is encrypted\\\hline
AES-CCM-128 & Data is encrypted\\\hline
\end{tabular}
\end{center}
\end{table}
\end{document}
Output:

\captioncommand before the\begin{tabular}– LonLon Nov 09 '18 at 09:05