Re: [ns] how do i transfrom Bit Error Rate to Packet Error Rate?
As far as I know, the relationship between BER and PER , assuming that bit errors are independent and uniformly distributed is, PER=1-(1-BER)^N where N is the number of bits. However, the above formula is only approximate because in real life scenarios, the bit errors are not completely independent but may occur in bursts. Further, the error distribution is also not exactly uniform. Hope it helps Cheers, Abdul. 林泰邑 wrote: Hi all, how can I transform “Bit error Rate” to “packet error rate”? Is there any formulas for this ? Can any body help me?
Re: [ns] how do i transfrom Bit Error Rate to Packet Error Rate?
If you plug the values in the formula PER=1-(1-0.001)^8000 = 0.9996658 The above result implies that 99.96% of you packets will have errors and if there are no additional error correction mechanisms, they will be dropped/lost. A BER of 10^-3 is too high and is not practical. For example, in most wireless scenarios, the BER is assumed to be 10^-6. By the way, why are you posting this in ns-users list? Abdul. 林泰邑 wrote: for example : when I give ber=10^-3, packet size=1000bytes, what is PER? -Original Message- From: Abdul Jabbar [mailto:[EMAIL PROTECTED] Sent: Monday, October 02, 2006 6:24 PM To: 林泰邑 Cc: ns-users@isi.edu Subject: Re: [ns] how do i transfrom Bit Error Rate to Packet Error Rate? As far as I know, the relationship between BER and PER , assuming that bit errors are independent and uniformly distributed is, PER=1-(1-BER)^N where N is the number of bits. However, the above formula is only approximate because in real life scenarios, the bit errors are not completely independent but may occur in bursts. Further, the error distribution is also not exactly uniform. Hope it helps Cheers, Abdul. 林泰邑 wrote: Hi all, how can I transform “Bit error Rate” to “packet error rate”? Is there any formulas for this ? Can any body help me?
Re: [ns] trouble with error model over wired links
I was able to solve this problem. I would like to thank both Pedro and
Alam for their response. The solution provided by Pedro: that is to
apply the error to just one link does work. However, my intention was to
simulate a network where every link has a certain error rate. The
solution provided by Alam: that is to use a separate errorModel object
for each link works exactly as I intended.
The mistake on my part was that after attaching the errorModel object to
one link, I was trying to attach the same object to a second link.
However, the response of ns was very confusing.
Thanks,
Abdul.
Abdul Jabbar wrote:
Hello,
I am having unusual trouble getting a simple error model to work over
wired links in ns2.29. I have checked the mailing list archives and
could not find a similar problem/solution. Below is my tcl script
which represents a simple network topology of 3 nodes connected in a
chain using duplex-links. I have a CBR/UDP flow between the nodes 0
and 3. The flow path is 0-1-2-3.
If I don't use any error on the links, everything works fine as is
confirmed by the trace file and the nam visualization.
However, if I include a simple error model and attach it to each of
the three links, the whole simulation goes awry. In the trace file I
see packets going from node 0 to node 1. There is no data flow between
node 2 and node 3 and there is a data flow between nodes 2 and 3.
Basically the packets disappear on node 1 and magically reappear at
node 2. In nam visualization, it is even worse...there is just one
flow between nodes 0 and 1thats it.no other data flows.
Changing the error rate does not help.
When I have a more complex topology ( like a mesh topology of 8x8
nodes) the whole simulation goes so bizarre, that it is even hard to
trace what is going wrong. That's why I am using this simple 3 node
topology to illustrate the problem.
I am hoping that there is some fundamental mistake on my part. Please
point in the right direction.
Thanks,
Abdul.
Here's the TCL script
--
set ns [new Simulator]
set tf [open simout.tr w]
$ns trace-all $tf
set nf [open simout.nam w]
$ns namtrace-all $nf
proc finish {} {
global ns nf tf
$ns flush-trace
close $nf
close $tf
exec nam simout.nam
exit 0
}
for {set i 0} {$i 4} {incr i} {
set n($i) [$ns node]
}
$ns duplex-link $n(0) $n(1) 500Mb 10ms DropTail
$ns duplex-link $n(1) $n(2) 500Mb 10ms DropTail
$ns duplex-link $n(2) $n(3) 500Mb 10ms DropTail
set em [new ErrorModel]
$em unit pkt
$em set rate_ 0.01
$em ranvar [new RandomVariable/Uniform]
$em drop-target [new Agent/Null]
$ns link-lossmodel $em $n(0) $n(1)
$ns link-lossmodel $em $n(1) $n(2)
$ns link-lossmodel $em $n(2) $n(3)
set udp0 [new Agent/UDP]
$ns attach-agent $n(0) $udp0
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 1000
$cbr0 set interval_ 0.005
$cbr0 attach-agent $udp0
set null0 [new Agent/Null]
$ns attach-agent $n(3) $null0
$ns connect $udp0 $null0
$ns at 0.5 $cbr0 start
$ns at 4.5 $cbr0 stop
$ns at 5.0 finish
$ns run
Re: [ns] urgent about setdest : node movement file
I see the same problem. However, if you use the make-scen.csh script the directory ~/ns2.29/indep-utils/cmu-scen-gen/setdest, it works just fine. Also you could use the bonnmotion tool to generate node movement files. It is has more features than setdest utility. Hope it helps. Cheers. Abdul. Muhammad Azam Akram wrote: Hi I want to create node movement file by setdest. but when i run this command for example, ./setdest -n 20 -p 2.0 -s 10.0 -t 200 -x 500 -y 500 scen-20-test it gives error as assertion spped != 0.0 failed: file setdest.cc, line 595 Aborted core dumped please help me to solve this problem. Thank you. - Do you Yahoo!? Everyone is raving about the all-new Yahoo! Mail.
