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% Table generated by Excel2LaTeX from sheet 'Sheet1'
documentclassarticle
usepackagetabularx,booktabs
usepackagemultirow

begindocument

begintable[htbp]
 centering
 captionAdd caption
 begintabular
 hline
 multirow2*textbfMobility Model
 & multicolumn7ctextbfParameter \
 cmidrule2-8& textbfBasic Description & textbfAdaptability for AANETs & textbfSupport to higher node mobility and Frequent topology updates & textbfSafety parameters & textbfMechanical and aerodynamic constraint & textbfDegree of Randomness & textbfApplications \
 hline

 endtabular%
 labeltab:addlabel%
endtable%
enddocument

One of the issues you're encountering is that pdfLaTeX never hyphenates the first word of a paragraph. The contents of a cell in a p column form a paragraph, in the TeX-specific sense of the term.

The way to enable hyphenation of the first words in some of the cells -- "Adaptability" and "Mechanical" are prime candidates -- is to slip in a somewhat artificial-looking hspace0pt. In the code below, this is done by setting up new column type, called P, which is a p column that sets its contents ragged-right rather than fully justified, while still allowing hyphenation, even of the first word in the cell.

documentclassarticle
usepackage[letterpaper,margin=1in]geometry % set suitable page parameters
usepackage[english]babel

usepackagearray,ragged2e
newcolumntypeP[1]>RaggedRightarraybackslashhspace0ptp#1

begindocument

begintable[htbp]
centering
captionAdd caption
labeltab:addlabel
begintabular
hline
textbfMobility Model
& multicolumn7textbfParameter \
cline2-8
& textbfBasic Description 
& textbfAdaptability for AANETs 
& textbfSupport to higher node mobility and Frequent topology updates 
& textbfSafety parameters 
& textbfMechanical and aerodynamic constraint 
& textbfDegree of Randomness 
& textbfApplications \
hline
endtabular
endtable
enddocument

Here are two (three) more possible solutions. In all of them I have used the tabularx package to make the tables as wide as the textwidth. I have also replaced the cmidrule comand by cline as booktabs' rules don't cooperate well with vertical lines. For an alternative, see the third example.

In the first one, I have used abbreviations for the column headers that are explained below the table:

documentclassarticle
usepackagetabularx
usepackagemultirow

begindocument

begintable[htbp]
 centering
 captionAdd caption
 begintabularxtextwidthX
 cline1-8
 textbfMobility Model & multicolumn7textbfParameter \
 cline2-8
 & textbfBD & textbfAA & textbfSF & textbfSP & textbfMC & textbfDR & textbfAP \
 cline1-8
multicolumn8ptextwidthsmall BD: Basic Description, AA: Adaptability for AANETs, SF: Support to higher node mobility and Frequent topology updates, SP: Safety parameters, MC: Mechanical and aerodynamic constraint, DR: Degree of Randomness, AP: Applications
 endtabularx%
 labeltab:addlabel%
endtable%
enddocument

In the second example, I have used sidewaystable from the rotating package in order to rotate the table:

documentclassarticle
usepackagetabularx
usepackagemultirow
usepackagerotating
usepackageragged2e
newcolumntypeR>RaggedRightletnewline\arraybackslashhspace0ptX

begindocument

beginsidewaystable[htbp]
 centering
 captionAdd caption
 begintabularxtextwidth
 hline
 textbfMobility Model & multicolumn7textbfParameter \
 cline2-8
 & textbfBasic Description 
 & textbfAdaptability for AANETs 
 & textbfSupport to higher node mobility and Frequent topology updates 
 & textbfSafety parameters 
 & textbfMechanical and aerodynamic constraint 
 & textbfDegree of Randomness & textbfApplications \
 hline

 endtabularx%
 labeltab:addlabel%
endsidewaystable%
enddocument

In this last example I have removed all vertical lines and replaced the horizontal lines by the rules from booktabs. I have also removed the bold from the column headers as it might distract:

documentclassarticle
usepackagetabularx
usepackagemultirow
usepackagebooktabs

begindocument

begintable[htbp]
 centering
 captionAdd caption
 begintabularxtextwidthp1.5cmXXXXXXX
 toprule
 Mobility Model & multicolumn7cParameter \
 cmidrule2-8
 & BD & AA & SF & SP & MC & DR & AP \
 bottomrule
multicolumn8ptextwidthsmall BD: Basic Description, AA: Adaptability for AANETs, SF: Support to higher node mobility and Frequent topology updates, SP: Safety parameters, MC: Mechanical and aerodynamic constraint, DR: Degree of Randomness, AP: Applications
 endtabularx%
 labeltab:addlabel%
endtable%
enddocument

(adding this answer separately from the first, as the solution method is quite different)

Your table doesn't seem to be set up to fully span the available width of the text block. If this were my table, I would switch to a tabularx environment (with overall width set to textwidth) and drop the unnecessary bold-facing of the contents of the header cells. The seven data columns employ a column type called C, which is simply a modified, centered version of the X column type. A feature is that it's straightforward to allow for varying column widths; the only constraint is that the 7 C arguments must sum to 7, which is the number of columns of this type. A principal formatting goal that guided the width choices was to have no more than four rows in any header cell.

documentclassarticle
usepackage[letterpaper,margin=1in]geometry % set suitable page parameters
usepackage[english]babel
usepackagetabularx,ragged2e,booktabs
newcolumntypeL>RaggedRightarraybackslashhspace0ptX
newcolumntypeC[1]>Centeringarraybackslashhspace0pthsize=#1hsizeX
usepackage[skip=0.333baselineskip]caption % optional

newcommandmytab[1]smash%
 begintabular[t]@l@ #1 endtabular

begindocument

begintable[htbp]
setlengthtabcolsep3pt % default value: 6pt
captionAdd caption
labeltab:addlabel
small
begintabularxtextwidth@ L 
 C0.8C1C1.5C0.8C1C0.9C1 @ % 7 args sum to 7
toprule
mytabMobility\Model & multicolumn7c@Parameters \
cmidrule(l)2-8
& Basic Description 
& Adaptability for AANETs 
& Support for higher node mobility and frequent topology updates
& Safety parameters
& Mechanical and aero-dynamic constraint
& Degree of randomness
& Applications \
midrule
blabla & blabla & blabla & blabla & blabla & blabla & blabla & blabla \
blabla & blabla & blabla & blabla & blabla & blabla & blabla & blabla \
blabla & blabla & blabla & blabla & blabla & blabla & blabla & blabla \
bottomrule
endtabularx
endtable

enddocument