Htydjtk

documentclass{article}

usepackage{tabularx}

usepackage{multirow}

usepackage{rotating}

usepackage{ragged2e}

usepackage{longtable}            

usepackage{rotating}

newcolumntype{R}{>{RaggedRightletnewline\arraybackslashhspace{0pt}}X}

usepackage{pdflscape}

begin{document}



begin{landscape}

  centering





begin{longtable}{textwidth}{|R|R|R|R|R|R|R|R|}

hline

textbf{Mobility  Model} &   multicolumn{7}{c|}{textbf{Parameter}}  \

        cline{2-8}

        & textbf{Basic Description} 

        & textbf{Adaptability for AANETs} 

        & textbf{Support to higher node mobility and Frequent topology updates} 

        & textbf{Safety parameters} 

        & textbf{Mechanical and aerodynamic constraint} 

        & textbf{Degree of Randomness} & textbf{Applications} \

hline



end{longtable}%



end{landscape}%

end{document}

Here is a possible solution using the ltablex package that combines the features of tabularx with longtable.

documentclass{article}

usepackage{tabularx}

usepackage{ragged2e}

usepackage{longtable}            

newcolumntype{R}{>{RaggedRightletnewline\arraybackslashhspace{0pt}}X}

usepackage{pdflscape}

usepackage{ltablex}



begin{document}



begin{landscape}

  centering



begin{tabularx}{linewidth}{|R|R|R|R|R|R|R|R|}

hline

textbf{Mobility  Model} &   multicolumn{7}{c|}{textbf{Parameter}}  \

        cline{2-8}

        & textbf{Basic Description} 

        & textbf{Adaptability for AANETs} 

        & textbf{Support to higher node mobility and Frequent topology updates} 

        & textbf{Safety parameters} 

        & textbf{Mechanical and aerodynamic constraint} 

        & textbf{Degree of Randomness} & textbf{Applications} \

hline

endhead

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end{tabularx}%



end{landscape}%

end{document}

Please note that all the 1\1\1\ are just added to show the page breaking behaviour of the table. I have also added endhead in order to repeat the column headers on all following pages.

I propose to load the xltabular package and use its eponymous environment, which combines the possibilities of longtable and tabularx. Also, note that in the landscape environment, for a full width table, you have to use linewidth or textheight, but not textwidth. Last, you can gain some space in cells loading geometry, which has more sensible margins if you don't use margin notes, setting tabcolsep to a lower value (6 pt by default, I set it to 3) and using a smaller fontsize.

documentclass{article}

usepackage{geometry}

usepackage{tabularx}

usepackage{xltabular}

usepackage{multirow}

usepackage{rotating}

usepackage{ragged2e}

usepackage{longtable}

usepackage{rotating}

renewcommand{tabularxcolumn}[1]{>{RaggedRightarraybackslash}m{#1}}

usepackage{pdflscape}



begin{document}



begin{landscape}

setlength{tabcolsep}{3pt}

setlength{extrarowheight}{3pt}

 centering

begin{xltabular}{linewidth}{|*{8}{X|}}

hline

multirow{8.45}{=}{textbf{Mobility Model} }& multicolumn{7}{c|}{textbf{Parameter}} \

        cline{2-8}

        & textbf{Basic Description}

        & textbf{Adaptability for AANETs}

        & textbf{Support to higher node mobility and Frequent topology updatessmallskip}

        & textbf{Safety parameters}

        & textbf{Mechanical and aerodynamic constraint}

        & textbf{Degree of Randomness} & textbf{Applications} \

hline

end{xltabular}%

end{landscape}%



end{document}