Check this code that I'm using to set the power based on the circular
distance in meters:
Usage:
set coverage [CellCoverage 1 1 $MAX_X $MAX_Y $OVERLAP]
set power [SetPt $coverage]
Phy/WirelessPhy set Pt_ $power
$ns node-config -rxPower $power -txPower $power
-------------
###################################################################
###################################################################
### generic POWER functions
#
# Given overlaping area, calculate the desired coverage
# expects a BOUNDING BOX for the cell, with the mobile in the center
#
proc CellCoverage { x1 y1 x2 y2 overlap} {
set d2 [expr ($x2-$x1)*($x2-$x1) + ($y2-$y1)*($y2-$y1)]
set d [expr sqrt($d2)] ;#
Hipotenusa
set ret [expr ($overlap + $d) / 2]
puts "D2: $d2 D: $d RET: $ret"
return $ret
}
#
# Given overlaping area, calculate the desired coverage
# expects a QUARTER BOUNDING BOX for the cell, with the mobile in the 0,0
position (lower left corner)
#
proc HalfCellCoverage { x1 y1 x2 y2 overlap } {
return [expr [CellCoverage $x1 $y1 $x2 $y2 $overlap] * 2]
}
#
# Calculate Necessary Transmission Power Pt for given coverage
#
# See /mobile/tworayground.cc
#
proc SetPt { coverage } {
set Gt [Antenna/OmniAntenna set Gt_]
set Gr [Antenna/OmniAntenna set Gr_]
set ht [Antenna/OmniAntenna set Z_]
set hr [Antenna/OmniAntenna set Z_]
set RXThresh [Phy/WirelessPhy set RXThresh_]
set L [Phy/WirelessPhy set L_]
set Pt_ [Phy/WirelessPhy set Pt_]
set freq_ [Phy/WirelessPhy set freq_]
set lambda [expr 300000000 / $freq_]
set crossover_dist [expr (4 * 3.1415926535897 * $ht * $hr) / $lambda
];
puts "old pt: $Pt_ RXThresh: $RXThresh lambda: $lambda \t\t
crosshover: $crossover_dist coverage: $coverage"
if { [expr $coverage < $crossover_dist] } {
puts ">>> Using Friis formula <<<"
set M [expr $lambda / (4.0 * 3.1415926535897 * $coverage)]
set Pt [expr $RXThresh * ($L / ($Gt*$Gr*$M*$M))]
puts " RET: $Pt"
} else {
puts ">>> Using TwoRay formula <<<"
#Calculate input power necessary to have, at dist $coverage,
output power = $RXThresh
set d4 [expr pow($coverage,4)]
set Pt [expr $RXThresh * (($L*$d4) /
($Gt*$Gr*$ht*$ht*$hr*$hr))]
puts "D4: $d4 RET: $Pt"
}
#debug 1
return $Pt
}
# /*
# * Friis free space equation:
# *
# * Pt * Gt * Gr * (lambda^2)
# * P = --------------------------
# * (4 * pi * d)^2 * L
# */
# from /mobile/tworayground.cc:
#
# TwoRayGround formula
# power = Pt * Gt * Gr * (hr * hr * ht * ht) / (d * d * d * d * L);
#
#
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
> Of Ashish Sangwan
> Sent: quinta-feira, 13 de Julho de 2006 14:59
> To: Q. R. Iqbal
> Cc: ns-users@ISI.EDU
> Subject: Re: [ns] Transmission and Interference Range
>
>
> Hi ,
>
> I didnot know about these three transmit power levels. Thanks Iqbal for
> that.
> I wanted to have Interference Range(Carrier Sense Range) to be twice the
> Communication Range. So I achieved by calculating CSThresh_ value by
> following formula
> Pt * Gt * Gr * (hr * hr * ht * ht) / {(Required interference range) ^ 4}
>
> --Ashish
>
> On 7/13/06, Q.R.Iqbal <[EMAIL PROTECTED]> wrote:
> >
> > Hi there
> >
> > I think there is no other cleaner or easiar way to do that unless you
> > modify the code.
> >
> > One thing you have to be aware of is that by modifying the transmission
> > range, you are only changing the receiver threshold, A distance from
> > which a receiver can receive.
> >
> > Again there are three different transmit power levels that are given for
> > the wavelan Modem
> >
> > 40m 8.5872e-4
> > 100m 7.214e-3
> > 250m 02818
> >
> > Maybe you need to use one of these parameters, the closest to your
> > required transmission range and then calculate the RXthreshold values,
> to
> > get a better result.
> > Also you need to be aware of CSthreshold,. If you are limiting the
> node's
> > transmission range to 40m or 100m or any value, the CSthreshold value,
> > will still be very large, about 550m by default, you might also want to
> > tweak that parameter to see if this improves your results
> >
> > I hope this helps
> >
> > > Hi,
> > >
> > > Can you tell me a clean way to change transmission and interference
> > ranges
> > > in ns-2?
> > > I tried the threshold program given ~ns/indep-utils/propagation/ but
> > that
> > > somehow is not giving correct values.
> > >
> > > Regards,
> > > --
> > > Ashish Sangwan
> > > B.Tech, Computer Science & Engineering
> > > IIT Delhi
> > >
> > > --
> > > I do know everything, just not all at once. It's a virtual memory
> > problem.
> > >
> >
> >
> > Kind regards
> >
> > Qasim Raza Iqbal
> > PhD Candidate,
> > ACNRG Lab N504, Office N505
> > Adaptive Communications Networks Research Group,
> > School of Engineering And Applied Science
> > Aston University
> > Birmingham B4 7ET
> > United Kingdom
> > http://www.ee.aston.ac.uk/research/acrg/index.html
> >
> >
> >
