[ns] RE : Re: CBR Traffic ?
yes that fix it statically. but how to dynamically change this rate during simulation (dynamiquely). Thanks a lot Aditya [EMAIL PROTECTED] a écrit : Hii $cbr set interval_ 0.05 This is how u can specify interval between 2 packets. I hope this wll solve ur problem. Regards -- Aditya On 3/6/07, leticia bela wrote: Hi All, Could anyone please tell me how to change dynamiquely the rate of cbr trafic under NS2 your help is highly appreciated, Regards - Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions ! Profitez des connaissances, des opinions et des expériences des internautes sur Yahoo! Questions/Réponses.
[ns] call for suggestion of how to modify 802.11 module in ns2
Hi,all, I'm gonna make some change in the 802.11 module in ns2 to support my algorithm. I've finished the study of ns2 tutorial. Now I'm working into the code of mac802.11.cc, mac802.11.h,etc. with the help of http://linear.engmath.dal.ca/ns-2/doxygen/html/files.html and ke liu's Understanding the implementation of IEEE MAC 802.11 standard in ns2. But the complicated classes and their members still confused me,and i'm not familiar with TCL.So right now i don't know what the important things to do. Do i have to read and understand the whole structure of the 802.11 module before i have the abilitity to make some change on it. Any suggestion will be appreciated!
[ns] Help me the files for Dynamic Virtual BackBone Routing Protocl(A hybrid protocol for Adhoc Networks) NS2 code
Hi friends, Please help to get the NS2 code for Dynamic Virtual BackBone Routing Protocl(A hybrid protocol for Adhoc Networks) .The author name is Melvin John ,THE UNIVERISTY IF ADELAIDE,Australia. I didn't get his email id. Please if you have this NS2 code forward it to me. Thank you very much, Thank you, Regards, Tarakapraveen Uppalapati Goud __ Yahoo! India Answers: Share what you know. Learn something new http://in.answers.yahoo.com/
[ns] Installation problem in ns-allinone-2.26
hello sir, I m shyam. i want to install ns-2.26 on cygwin on windosxp. i copied ns-allinone-2.26.tar , nam-1.9-cygwin-configure and ns-allinone-2.26.cygwinn.patch in cygwin/usr/local/ then i use startx command at cygwin promt after that i typed following line at bash terminal gzip -d -c ns-allinone-2.26.tar.gz | tar xvf - this will work after that next when in nest line i type mv nam-1.9.configure ns-allinone-2.26/nam-1.9/configure this will not work and if i use command cd /usr/local/ns-allinone-2.26/ ./install the the following error comes . Build OTcl-1.0a8 No .configure file found in current directory Continuing with default options... checking build system type... i686-pc-cygwin checking host system type... i686-pc-cygwin checking target system type... i686-pc-cygwin checking for gcc... gcc checking for C compiler default output... a.exe checking whether the C compiler works... yes checking whether we are cross compiling... no checking for executable suffix... .exe checking for object suffix... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for g++... g++ checking whether we are using the GNU C++ compiler... yes checking whether g++ accepts -g... yes checking how to run the C preprocessor... gcc -E checking for ANSI C header files... yes checking for string.h... yes checking for main in -lXbsd... no checking for socket in -lsocket... no checking for gethostbyname in -lnsl... no checking for dcgettext in -lintl... yes checking for getnodebyname in -ldnet_stub... no checking that g++ can handle -O2... no checking standard STL is available... no checking for tcl.h... -I../include checking for libtcl8.3... -L../lib -ltcl8.3 checking for init.tcl... ../lib/tcl8.3 checking for tclsh8.3.2... no checking for tclsh8.3... ../bin/tclsh8.3 checking for tk.h... -I../include checking for libtk8.3... -L../lib -ltk8.3 checking for tk.tcl... ../lib/tk8.3 checking for X11 header files checking for X11 library archive checking for XOpenDisplay in -lX11... no can't find X library otcl-1.0a8 configuration failed! Exiting ... Please check http://www.isi.edu/nsnam/ns/ns-problems.html for common problems and bug fixes. please help me , How this probleb will solve shyam M.Tech student
[ns] Rate of CBR Traffic ?
Hi aditya, when an event arrives suddenly for example the load of network is important, I will need to reduce the rate. at the beginning I do not have idea of the time of arrival of this event. thanks a lot Aditya [EMAIL PROTECTED] a écrit : Hii $ns at 1.0 $cbr set interval_ 0.05 This will change the rate at 1.0 time instance. You can change it any number of times. Bye. On 3/6/07, leticia bela wrote: yes that fix it statically. but how to dynamically change this rate during simulation (dynamiquely). Thanks a lot Aditya a écrit : Hii $cbr set interval_ 0.05 This is how u can specify interval between 2 packets. I hope this wll solve ur problem. Regards -- Aditya On 3/6/07, leticia bela wrote: Hi All, Could anyone please tell me how to change dynamiquely the rate of cbr trafic under NS2 your help is highly appreciated, Regards Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions ! Profitez des connaissances, des opinions et des expériences des internautes sur Yahoo! Questions/Réponses. - Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions ! Profitez des connaissances, des opinions et des expériences des internautes sur Yahoo! Questions/Réponses.
[ns] help of executing wireless1.tcl in example of tutorial needed!
from the terminal...go to the example folder, then type ns example1.tcl enter. that's it!!
[ns] simulating new protocol under ns2
Hi,
I am a new user for Ns and i have a same problem like [EMAIL PROTECTED]
I well studied document Implementing a new MANET protocol in ns-2. I wrote
the same code in ns-2. that was compiled without error. I made all indicated
changes in ns-2 .
After wich i recompile ns-2 by typing make at ns-2.29 directory
it got compiled well. But when i try to use this protocol in my simulation
script, it produces the following errors.
num_nodes is set 2
warning: Please use -channel as shown in tcl/ex/wireless-mitf.tcl
(_o14 cmd line 1)
invoked from within
_o14 cmd addr
invoked from within
catch $self cmd $args ret
invoked from within
if [catch $self cmd $args ret] {
set cls [$self info class]
global errorInfo
set savedInfo $errorInfo
error error when calling class $cls: $args $...
(procedure _o14 line 2)
(SplitObject unknown line 2)
invoked from within
_o14 addr
(eval body line 1)
invoked from within
eval $node addr $args
(default arm line 2)
invoked from within
switch -exact $routingAgent_ {
DSDV {
set ragent [$self create-dsdv-agent $node]
}
DSR {
$self at 0.0 $node start-dsr
}
AODV {
set ragent [$self cre...
(procedure _o3 line 11)
(Simulator create-wireless-node line 11)
invoked from within
_o3 create-wireless-node
(eval body line 1)
invoked from within
eval $self create-wireless-node $args
(procedure _o3 line 23)
(Simulator node line 23)
invoked from within
$ns_ node
(for body line 2)
invoked from within
for {set i 0} {$i $val(nn) } {incr i} {
set node_($i) [$ns_ node]
$node_($i) random-motion 1 ;# disable random
motion
}
(file protoname.tcl line 65)
**
my script for simulate this protocol is:
# ==
# Define options
# ==
set val(chan) Channel/WirelessChannel;# channel type
set val(prop) Propagation/TwoRayGround ;# radio-propagation model
set val(netif) Phy/WirelessPhy;# network interface type
set val(mac)Mac/802_11 ;# MAC type
set val(ifq)Queue/DropTail/PriQueue;# interface queue type
set val(ll) LL ;# link layer type
set val(ant)Antenna/OmniAntenna;# antenna model
set val(ifqlen) 50 ;# max packet in ifq
set val(nn) 2 ;# number of mobilenodes
set val(rp) protoname ;# routing protocol
# ==
# Main Program
# ==
#
# Initialize Global Variables
#
set ns_[new Simulator]
set tracefd [open out.tr w]
$ns_ trace-all $tracefd
# pour avoir la nouvelle trace new trace format
$ns_ use-newtrace
# set up topography object
set topo [new Topography]
$topo load_flatgrid 500 500
#
# Create God
#
create-god $val(nn)
#
# Create the specified number of mobilenodes [$val(nn)] and attach them
# to the channel.
# Here two nodes are created : node(0) and node(1)
# configure node
$ns_ node-config -adhocRouting $val(rp) \
-llType $val(ll) \
-macType $val(mac) \
-ifqType $val(ifq) \
-ifqLen $val(ifqlen) \
-antType $val(ant) \
-propType $val(prop) \
-phyType $val(netif) \
-channelType $val(chan) \
-topoInstance $topo \
-agentTrace ON \
-routerTrace ON \
-macTrace OFF \
-movementTrace OFF
for {set i 0} {$i $val(nn) } {incr i} {
set node_($i) [$ns_ node]
$node_($i) random-motion 1;# disable random motion
}
#
# Provide initial (X,Y, for now Z=0) co-ordinates for mobilenodes
#
$node_(0) set X_ 5.0
$node_(0) set Y_ 2.0
$node_(0) set Z_ 0.0
$node_(1) set X_ 390.0
$node_(1) set Y_ 385.0
$node_(1) set Z_ 0.0
#
# Now produce some simple node movements
# Node_(1) starts to move towards node_(0)
#
$ns_ at 50.0 $node_(1) setdest 25.0 20.0 15.0
$ns_ at 10.0 $node_(0) setdest 20.0 18.0 1.0
# Setup traffic flow between nodes
# TCP connections between node_(0) and node_(1)
set tcp [new Agent/TCP]
$tcp set fid_ 2 # donne un identifiant au flux
set sink [new Agent/TCPSink]
$ns_ attach-agent $node_(0) $tcp
$ns_ attach-agent $node_(1) $sink
$ns_ connect $tcp $sink
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ns_ at 1.0 $ftp start
#Agent/Protoname set
[ns] Problem regarding make.
maybe you run it from different folder. check from where you run it.. eg: [EMAIL PROTECTED] ~]# or [EMAIL PROTECTED] ns-allinone-2.30]# etc...
[ns] Multi-interface support howto
Hi there, Is the coding working for 802_15_4 (LR-WPAN)?
Re: [ns] Rate of CBR Traffic ?
Hi leticia, My knowledge of ns2 is very limited so you need to specify abit more... where is your code that checks the load of the network for example. When it reaches a set threshold, can't you just call $cbr set interval_ 0.05? If you need to set the rate from cc code then you could do like this: char out[100]; sprintf(out, $cbr set interval_ 0.05); Tcl tcl = Tcl::instance(); tcl.eval(out); $cbr set interval_ 0.05 is sent as a tcl commando to the interpreter and the interval is changed. This is very similar to the ns2 Tutorial for creating a Ping agent: http://www.isi.edu/nsnam/ns/tutorial/nsnew.html#fourth Hi aditya, when an event arrives suddenly for example the load of network is important, I will need to reduce the rate. at the beginning I do not have idea of the time of arrival of this event. thanks a lot Aditya [EMAIL PROTECTED] a ??rit : Hii $ns at 1.0 $cbr set interval_ 0.05 This will change the rate at 1.0 time instance. You can change it any number of times. Bye.
Re: [ns] simulating new protocol under ns2
Hi,
Please note that the agent's name is case sensitive, so if you wrote
'Protoname' in ns-lib.tcl (as indicated in
http://masimum.inf.um.es/nsrt-howto/html/node20.html), you mustn't write
'protoname' in your TCL simulation script.
Hope this solves the problem.
Regards,
fran
On Tuesday 06 March 2007 10:29, leticia bela wrote:
Hi,
I am a new user for Ns and i have a same problem like
[EMAIL PROTECTED] I well studied document Implementing a new MANET
protocol in ns-2. I wrote the same code in ns-2. that was compiled without
error. I made all indicated changes in ns-2 .
After wich i recompile ns-2 by typing make at ns-2.29 directory
it got compiled well. But when i try to use this protocol in my simulation
script, it produces the following errors.
num_nodes is set 2
warning: Please use -channel as shown in tcl/ex/wireless-mitf.tcl
(_o14 cmd line 1)
invoked from within
_o14 cmd addr
invoked from within
catch $self cmd $args ret
invoked from within
if [catch $self cmd $args ret] {
set cls [$self info class]
global errorInfo
set savedInfo $errorInfo
error error when calling class $cls: $args $...
(procedure _o14 line 2)
(SplitObject unknown line 2)
invoked from within
_o14 addr
(eval body line 1)
invoked from within
eval $node addr $args
(default arm line 2)
invoked from within
switch -exact $routingAgent_ {
DSDV {
set ragent [$self create-dsdv-agent $node]
}
DSR {
$self at 0.0 $node start-dsr
}
AODV {
set ragent [$self cre...
(procedure _o3 line 11)
(Simulator create-wireless-node line 11)
invoked from within
_o3 create-wireless-node
(eval body line 1)
invoked from within
eval $self create-wireless-node $args
(procedure _o3 line 23)
(Simulator node line 23)
invoked from within
$ns_ node
(for body line 2)
invoked from within
for {set i 0} {$i $val(nn) } {incr i} {
set node_($i) [$ns_ node]
$node_($i) random-motion 1 ;# disable random
motion }
(file protoname.tcl line 65)
**
my script for simulate this protocol is:
# ==
# Define options
# ==
set val(chan) Channel/WirelessChannel;# channel type
set val(prop) Propagation/TwoRayGround ;# radio-propagation
model set val(netif) Phy/WirelessPhy;# network
interface type set val(mac)Mac/802_11 ;# MAC
type
set val(ifq)Queue/DropTail/PriQueue;# interface queue type
set val(ll) LL ;# link layer type
set val(ant)Antenna/OmniAntenna;# antenna model
set val(ifqlen) 50 ;# max packet in ifq
set val(nn) 2 ;# number of mobilenodes
set val(rp) protoname ;# routing protocol
# ==
# Main Program
# ==
#
# Initialize Global Variables
#
set ns_[new Simulator]
set tracefd [open out.tr w]
$ns_ trace-all $tracefd
# pour avoir la nouvelle trace new trace format
$ns_ use-newtrace
# set up topography object
set topo [new Topography]
$topo load_flatgrid 500 500
#
# Create God
#
create-god $val(nn)
#
# Create the specified number of mobilenodes [$val(nn)] and attach them
# to the channel.
# Here two nodes are created : node(0) and node(1)
# configure node
$ns_ node-config -adhocRouting $val(rp) \
-llType $val(ll) \
-macType $val(mac) \
-ifqType $val(ifq) \
-ifqLen $val(ifqlen) \
-antType $val(ant) \
-propType $val(prop) \
-phyType $val(netif) \
-channelType $val(chan) \
-topoInstance $topo \
-agentTrace ON \
-routerTrace ON \
-macTrace OFF \
-movementTrace OFF
for {set i 0} {$i $val(nn) } {incr i} {
set node_($i) [$ns_ node]
$node_($i) random-motion 1;# disable random motion
}
#
# Provide initial (X,Y, for now Z=0) co-ordinates for mobilenodes
#
$node_(0) set X_ 5.0
$node_(0) set Y_ 2.0
$node_(0) set Z_ 0.0
$node_(1) set X_ 390.0
$node_(1) set Y_ 385.0
$node_(1) set Z_ 0.0
#
# Now produce some simple node movements
# Node_(1) starts to move towards node_(0)
#
$ns_ at 50.0 $node_(1) setdest 25.0 20.0 15.0
$ns_ at 10.0 $node_(0) setdest 20.0 18.0 1.0
#
[ns] ns-2 hierarchical routing
Hi all, Could someone tell me how routes are computed inside a same hierarchical cluster as defined in NS-2 ? What is the algorithm used for that ? is it Dijkstra? or should the routes be set statically? Could the hierarchical routing react to topological changes? Your help is highly appreciated best regards, Ramzi
[ns] Problem NOAH with wired cum wireless scenario
Hi all !,
I have ns-2 2.30 and I've installed recently NOAH protocol. After succesful
test in wireless simple scenario, I add a couple of wired nodes, resulting a
topology of two wired nodes, one base station node, and 4 wireless nodes (one
of them acts as a repeater that connects the rest of the wireless nodes and
base-station node). Problem comes when I send traffic form a wired node to a
wireless one, appearing this error:
--- Classfier::no-slot{} default handler (tcl/lib/ns-lib.tcl) ---
_o18: no target for slot -1
_o18 type: Classifier/Hash/Dest
content dump:
classifier _o18
0 offset
0 shift
2147483647 mask
1 slots
slot 1: _o152 (Classifier/Port)
-1 default
-- Finished standard no-slot{} default handler --
I am using cygwin in its latest release, but I think there is no problem
with that. If anyone could help me, I ould be very pleased. Thanks in advance!!
I enclose my whole script, if it helps:
set val(chan) Channel/WirelessChannel ;# channel type
set val(prop) Propagation/TwoRayGround ;# radio-propagation model
set val(netif) Phy/WirelessPhy ;# network interface type
set val(mac) Mac/802_11 ;# MAC type
set val(ifq) Queue/DropTail/PriQueue ;# interface queue type
set val(ll) LL ;# link layer type
set val(ant) Antenna/OmniAntenna ;# antenna model
set val(ifqlen) 50 ;# max packet in ifq
set val(nn) 4 ;# number of mobilenodes
set val(bs) 1 ;# number of base station nodes
set val(wired) 2 ;# number of wired nodes
set val(rp) NOAH ;# routing protocol
set val(x) 3000
set val(y) 3000
set timefin 5.0
set pi 3.141592654
set incrfase [expr ($pi/($val(nn)-2))]
# ==
# ==
# Programa Principal
# ==
# ==
#===
# Inicializacion de las variables globales y trazas
#===
set ns_ [new Simulator]
$ns_ use-newtrace
set tracefd [open prueba.tr w]
$ns_ trace-all $tracefd
set tracenam [open prueba.nam w]
$ns_ namtrace-all-wireless $tracenam $val(x) $val(y)
set perdidos0 [open perdidos0.tr w]
set recibidos0 [open recibidos0.tr w]
#===
# Declaracion de la topografia
#===
set topo [new Topography]
$topo load_flatgrid $val(x) $val(y)
#===
# Creacion del objeto God
#===
set god_ [create-god [expr $val(nn)+$val(bs)]]
#===
# Creacion del canal
#===
set canal [new $val(chan)]
#===
# Configuracion y creacion de nodos
#===
# Definimos los nodos cableados (puesto de mando y core network)
set mando [$ns_ node]
$mando set X_ 0
$mando set Y_ 1500
$mando set Z_ 0
set core [$ns_ node]
$core set X_ 50
$core set Y_ 1500
$core set Z_ 0
$ns_ node-config -adhocRouting $val(rp) \
-llType $val(ll) \
-macType $val(mac) \
-ifqType $val(ifq) \
-ifqLen $val(ifqlen) \
-antType $val(ant) \
-propType $val(prop) \
-phyType $val(netif) \
-topoInstance $topo \
-wiredRouting ON \
-agentTrace ON \
-routerTrace ON \
-macTrace OFF \
-movementTrace OFF \
-channel $canal
# Definimos los parametros de la antena para el puesto avanzado,
# asi como su cobertura (2.933km), potencia...
Antenna/OmniAntenna set X_ 0
Antenna/OmniAntenna set Y_ 0
Antenna/OmniAntenna set Z_ 8
Antenna/OmniAntenna set Gt_ 21
Antenna/OmniAntenna set Gr_ 21
Phy/WirelessPhy set CPThresh_ 10.0
Phy/WirelessPhy set CSThresh_ 8.40163e-21
Phy/WirelessPhy set Pt_ 0.281838
Phy/WirelessPhy set freq_ 2.4e+9
Phy/WirelessPhy set L_ 1.0
Phy/WirelessPhy set RXThresh_ 8.40163e-18
$ns_ node-config -antType $val(ant) \
-phyType $val(netif)
set base [$ns_ node]
$base random-motion 0
$base set X_ 100
$base set Y_ 1500
$base set Z_ 0
$ns_ initial_node_pos $base 10
# Definimos los parametros de la antena para la unidad movil,
# asi como su cobertura (1.466km), potencia...
Antenna/OmniAntenna set X_ 0
Antenna/OmniAntenna set Y_ 0
Antenna/OmniAntenna set Z_ 4
Antenna/OmniAntenna set Gt_ 9.5
Antenna/OmniAntenna set Gr_ 9.5
Phy/WirelessPhy set CPThresh_ 10.0
[ns] accessing via tcl?
Hi, I wrote a code for sending broadcast packets on a wireless network. Now I want to count how many mac-802_11 collisions occur during the simulation. I have been created a new variable in the mac-802_11.* files and I need to access this variable via tcl after the end of the simulation. How can I do it? I wroted only this references to Mac 802.11 in my tcl code set val(mac)Mac/802_11 $ns_ node-config -macType $val(mac) May be something like set coll [Mac/802_11 set collisions_] ? collisions_ is the variable on the tcl code, I have already binded this variable with the variable on c collision adding on mac-802_11.cc the line bind (collisions_, collisions) -- ciao, Gianpaolo
[ns] problem with DSR in ns-2.30
*HI all,*
i have ns-allinone-2.30, when i used *DSR* protocol,i got this error:
num_nodes is set 10
syntax error in expression 2147483647 0: unexpected operator
while executing
expr $addrstr [AddrParams NodeMask 1] [AddrParams NodeShift 1]
invoked from within
if [Simulator hier-addr?] {
set addressObj [[[Simulator instance] get-AllocAddrBits ] get-Address]
return [$addressObj str2addr $addrstr]
} else {
...
(procedure AddrParams line 2)
(AddrParams addr2id line 2)
invoked from within
AddrParams addr2id [$node node-addr]
(procedure _o4 line 9)
(Simulator create-wireless-node line 9)
invoked from within
_o4 create-wireless-node
(eval body line 1)
invoked from within
eval $self create-wireless-node $args
(procedure _o4 line 23)
(Simulator node line 23)
invoked from within
$ns node
invoked from within
set post(0) [$ns node]
(file deuxpfe.tcl line 2106)
can any one help me plz.
*Regards.*
[ns] How to run sample script for AODV, DSDV, DSR
Hello..
I'm new user for ns2 and I've ns2 2.30.. I want to run the sample of the
script in few ad hoc routing protocols such as AODV, DSR and DSDV that is in
the directory ../ns-allinone-2.30/ns-2.30/aodv or dsr or dsdv. I run this
script by typing ' ns aodv.tcl ' but seems like it's not working and I got an
error like this.
invalid command name Agent/rtProto/AODV
while executing
Agent/rtProto/AODV instproc init args {
$self next $args
}
(file aodv.tcl line 19)
Is it possible to me to run this script? (aodv.tcl, aodv.cc, aodv.h). What is
the command I should use for?
How can I run the script for dsdv directory that contain dsdv.cc and dsdv.h
file?
[ns] ns configure problem
Dear all, Now I meet a tough problem that I can not configure ns . when I run ns in command line prompt. It gives me that information : When configured, ns found the right version of tclsh in /home/wjw101/ns-allinon e-2.30/bin/tclsh8.4BRbut it doesn't seem to be there anymore, so ns will fall back on running the fir st tclsh in your path. The wrong version of tclsh may break the test suites. Rec onfigure and rebuild ns if this is a problem.BR% I can also run TCL script, but when i modified the *.cc and *.h file and run make make depend make command, I find that modification does not work , I do not konw why it is. my system configuration is that: intel cpu , fedora core 5 linux, ns-2.30 . I install ns-2.30 in wjw100,wjw101,wjw103 user. any advice and help will be appreciated! So I am appreciate you a lot for that I have a lot experiment to do in it. yours sincerely Wang Junwei 2007/03/05
[ns] How to run sample script for AODV, DSDV, DSR
Hello..
I'm new user for ns2 and I've ns2 2.30.. I want to run the sample of the
script in few ad hoc routing protocols such as AODV, DSR and DSDV that is in
the directory ../ns-allinone-2.30/ns-2.30/aodv or dsr or dsdv. I run this
script by typing ' ns aodv.tcl ' but seems like it's not working and I got an
error like this.
invalid command name Agent/rtProto/AODV
while executing
Agent/rtProto/AODV instproc init args {
$self next $args
}
(file aodv.tcl line 19)
Is it possible to me to run this script? (aodv.tcl, aodv.cc, aodv.h). What is
the command I should use for?
How can I run the script for dsdv directory that contain dsdv.cc and dsdv.h
file?
-
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[ns] link bandwidth and delay link in ad hoc networks
Hi all, I have read articles speaking about the band-width of a wireless link and delay of this link in the ad hoc networks. but I have not find any explanation on the way of calculating them under NS. Please If anyone has an idea of this topic to help me . It is very important I am very grateful for you. Thanks in advance - Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions ! Profitez des connaissances, des opinions et des expériences des internautes sur Yahoo! Questions/Réponses.
[ns] Bug in 802.15.4 implementation
Hi all,
I've found a possible bug / unhandled scenario in the 802.15.4 code included
in version 2.28 and subsequent.
It is due to a change introduced in the CCA and may cause the csma status to
get locked to 1, with various disastrous consequences.
I think that this may help someone who is working with 802.15.4.
Understanding what follows requires the reader to be very familiar with the
802.15.4 implementation on ns, both for my english ;) and for the
complicated subject.
You can skip my explanation and just consider the following fix:
locate this method
void Phy802_15_4::PLME_CCA_request()
{
if (trx_state == p_RX_ON)
{
//perform CCA
//refer to sec 6.7.9 for CCA details
//we need to delay 8 symbols
CSH.start(1/getRate('s'));
CCAH.start(8/getRate('s'));
}
}
and change this line:
CSH.start(1/getRate('s'));
to
CSH.start(8/getRate('s'));
Stop.
For those who are interested here is all: consider a network entity willing to
send a data packet. It will issue a Mac802_15_4::mcps_data_request, which
through a series of calls makes the backoff timer start with a random time as
in the following scheme:
Mac802_15_4::mcps_data_request
[...]
printf(node %d: CSMA requested by MAC at %f \n,index_,NOW);
csmacaBegin('d');
\__
[...]
csmacaResume();
*** important: csmacaResume set the status of the csma to 99 ***
\__
[...]
csmaca-start
\__
[...]
backoffT-start(wtime);
When the backoff timer expires CsmaCA802_15_4::backoffHandler is invoked:
CsmaCA802_15_4::backoffHandler
[...]
mac-plme_set_trx_state_request(p_RX_ON);
[...]
The transceiver is requested to change its state to RX_ON
If the state is successfully changed to RX_ON
void Mac802_15_4::PLME_SET_TRX_STATE_confirm(PHYenum status)
invokes
csmaca-RX_ON_confirm(status);
which in turn launches the Clear Channel Assessment:
phy-PLME_CCA_request();
Now, with version 2.28 a variation in the Clear Channel Assessment mechanism
has been introduced:
the standard mandates that the channel has to be sensed for 8 symbols before
its status can be determined and in version 2.27 (or earlier) the status of
the channel was tested at the end of the 8th symbol. This way it could happen
that a busy channel in the first symbols but idle at the time of the test was
detected as IDLE instead of BUSY, as it should be in this situation.
Therefore two timers are used now: the first for testing the channel status
at the end of the first symbol and the second for giving the CCA response at
the end of the 8th symbol. A sample of the corrisponding code is reported
here:
void Phy802_15_4::PLME_CCA_request()
{
if (trx_state == p_RX_ON)
{
//perform CCA
//refer to sec 6.7.9 for CCA details
//we need to delay 8 symbols
CSH.start(1/getRate('s'));
CCAH.start(8/getRate('s'));
}
}
Consider if the channel is idle at the end of the 1st symbol and the reception
of a packet begins just after:
when CSH expires the channel is deermined to be IDLE, even if the response is
given when CCAH expires, as the channel is BUSY!
mac-PLME_CCA_confirm is invoked with a sensed_ch_state=IDLE and after a
series of calls...
mac-PLME_CCA_confirm(sensed_ch_state);
\__csmaca-CCA_confirm(status);
\__
mac-csmacaCallBack(p_IDLE);
*** important: csmacaCallBack set the status of the csma to 1 ***
\__
dispatch(status,__FUNCTION__);
\__
mcps_data_request(0,0,0,0,0,0,0,0,0,taskP.mcps_data_request_TxOptions,false,status);
\__
plme_set_trx_state_request(p_TX_ON);
...Phy802_15_4::PLME_SET_TRX_STATE_request(PHYenum state) is invoked but it
cannot change the transceiver state to TX_ON, since the transceiver is
receiving a packet!!!
It will answer with a status p_BUSY_RX;
When the reception of the packet ends the old request for changing the
transceiver status to TX_ON is overwritten by the MAC which requests that the
tranceiver passes to a RX_ON o TRX_OFF, and a PD_DATA.confirm is not invoked
for the previous PD_DATA.request.
As a result the status of the csma (which is reset by PD_DATA.confirm) remains
to the value 1.
The csma status set to 1 prevents for example any following attempt to start
the beaconing process, with START_request getting ignored!!! (the
corresponding confirm is not invoked).
For me this triggered a sequence of events which caused a task overflow error
and the simulation to abort.
So in my simulations I turned back the CCA behaviour to the previous version
by synchronizing the moment in which the channel is tested and that one in
which the response is given.
Bye.
--
Daniele Messina
Ph.D. Student, Dept. of Informatic Engineering (DINFO), University of Palermo
Research collaborator, Dept of
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Découvrez une nouvelle façon d'obtenir des réponses à toutes vos questions !
Profitez des connaissances, des opinions et des expériences des internautes sur
Yahoo! Questions/Réponses.
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