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Re: [ns] Satellite Problems



On Mon, 26 Jun 2000, Andrea Detti wrote:

> I have to simulate a earth gateway for LEO satellites. Can the
> sat-terminal object (used to simulate the gateway) link more than
> one satellite?

I'd have thought, after a glance at section 16.4 of nsdoc, that after
you've done 

set $satnode [$ns satnode-terminal lat long]

you should be able to just do:

$satnode add-gsl blah as usual.
$satnode add-gsl blah for the second gsl link.

...but I consistently get:

phy.cc:82: failed assertion `channel_ == 0'

even when adding an (unnecessary, if you see ns-sat.tcl)
add-interface between the two add-gsl commands. At a guess, this seems
to be due to an assumption about the relationship between channel and
linkhead made in phy.cc. Anyone?

Using a slightly modified 2.1b6-SNAPSHOT-20000220 here, with a current
(i.e. hasn't been touched in six months) phy.cc.


In any case, if that did work, note that both gsls will follow the
same handover rules because there's only one linkhandoff manager per
node rather than per link, which might get in your way. (Some
per-link restructuring needed).

A better approach might be to create two satellite nodes with the same
latitude and longitude, and use them in parallel.


> If it can, where I can find some example ?

try adding an extra add-gsl line to the supplied iridium-ish and
teledesic-ish scripts in ~ns/tcl/ex and see what happens.

btw, users of the satellite code may find recent changes to
http://www.isi.edu/nsnam/ns/CHANGES.html
of interest.

L.

<[email protected]>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>