Re: [ns] Satnode Queries !!

[Lloyd Wood <l.wood@eim.surrey.ac.uk>]

On Mon, 4 Sep 2000, Martin Koyabe wrote:

> 1) Suppose I have a scenario where the forward path is 2 Mb/s and a return path of 64Kb/s.
> i.e. scenario 1: terminal----2Mb/s---->satellite-----2Mb/s------>terminal and
>      scenario 2: terminal<---64Kb/s----satellite<----64Kb/s------terminal
> 
>  How does one go about setting these parameters ? The only examples available show 
> 
>    set opt(bw_up)   2Mb  (terminal - sat)
>    set opt(bw_down) 2Mb  (sat - terminal)
> 
> which I presume is scenario 1 !!!      

Yes - but the opt() is just a shorthand Tom uses in his scripts. Note
that $opt() forms a parameter passed to the add-gsl method. It's just
a placeholder variable.


> 2) In ~/tcl/ex/sat-aloha.tcl lines 67 - 76 below
> 
> -----
> # GEO satellite at 0 degrees longitude 
> set n1 [$ns satnode-geo-repeater 0 $opt(chan)]
> 
> # Place 100 nodes at 100 different locations
> set num_nodes		100
> for {set a 1} {$a <= $num_nodes} {incr a} {
> 	set n($a) [$ns satnode-terminal [expr -15 + $a * 0.3] [expr 15 - $a * 0.3] ]
> 	$n($a) add-gsl geo $opt(ll) $opt(ifq) $opt(qlim) $opt(mac) $opt(bw_up) \
>   		$opt(phy) [$n1 set downlink_] [$n1 set uplink_]
> }
> ------
> 
> Q) Why is node n1 set to [$ns satnode-terminal ...] in the for-loop while it has already 
> been assigned to satnode-geo-repeater

$n1 and $n(1) are two different nodes with different names.


> Q) If wrong, should the for-loop then look like this
> 
>    for {set a 2} {$a <= $num_nodes} {incr a} { ... }

no.

L. 

<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>