The Enhanced Network Simulator(Release Version 1.2)
(Developed at Department of Computer Science & Engineering, Indian Institute of
Technology, Kanpur, India)
The Changes in TENS fro NS-2 and in subsequent versions in TENS1.1 and TENS 1.2 are given below. These may serve as a starting point for anyone wishing to learn about the code level changes made to NS-2 and further extend NS-2
ChangeLog for TENS1.0 - A file wise description of the changes made to NS-2 code
ChangeLog for TENS1.1 - A file wise decsription of bug fixes and feature additions to TENS1.0
ChangeLog for TENS1.2 - A file wise decsription of bug fixes and feature additions to TENS1.1
Multiple interface support added
Static Routing implemented for wireless nodes
Co Channel interference added
Adaptive data rate support for 802.11
BPSK Modulation Scheme Added
Directional Antenna support added (More radiation pattern added in TENS1.2)
Channel Number made configurable
Addition of ARP entries through script
2-p protocol for point to point link added
Several MAC parameters like RTS Threshold, Capture threshold made configurable. See the tutorial for full details.
In this section we provide a quick tutorial on the new feature
additions and their usage. Please note that this tutorial assumes that the
reader is fairly acquainted with NS-2. Extensive NS-2 tutorials can be found at
the following links:
Marc Greis's
tutorial
NS for Beginners
NS Manual
4.1 Configuring Network Components
4.3.1 Setting up Multiple interfaces
4.3.2 Attaching a directional antenna
4.3.3 Setting the Transmit Power
4.3.5 Capture Threshold Setting
4.3.6 Carrier Sense Threshold Setting
4.3.8 Modulation Scheme Settings
4.3.9 Frequency settings and Loss factor
4.5 Setting up parameters for MAC
4.7 Using the 2P Iimplementation
4.7.1 Link Layer Configurations
4.7.2 MAC Layer
Configurations
4.1 Configuring Network
Components
A mobilenode consists of network components like Link Layer (LL), Interface
Queue (IfQ), MAC layer, the wireless channel nodes transmit and receive signals
from etc. At the beginning of a wireless simulation, we need to define the type
for each of these network components. Additionally, we need to define other
parameters like the type of antenna, the radio-propagation model, the type of
ad-hoc routing protocol used by mobilenodes etc. The following snippet of code
will usually be there. Look at the comments for a decsription of the variable
and changes from NS-2.
|
set val(chan)
Channel/Channel_802_11
;# channel type, NS-2 used Channel/WirelessChannel |
4.2 Main Program
The main programme can be started in the same manner as NS-2, when a new
simulator is started, trace files are opened, creation of GOD object and
creation of topology. All these remain unchanged in NS-2. So, the following code
will start the script. Also, higher layers implementation remain
unchanged. So, one could attach a CBR, FTP or a TCP connection with a node.
4.3. Configuration of
Nodes.
4.3.1 Setting up Multiple
Interfaces
Nodes in TENS may be configured to have multiple interfaces. This may be done by
the following line in your tcl script.
| $ns node-config -numif 1 |
Subsequent parameter additions for different interfaces can be done by using the following format:
| $node set netif_(<interface number>) set <parameter> <value> |
4.3.2 Attaching a directional
antenna
Directional Antenna may be created and setup as follows:
| set a [Antenna/DirAntenna] $a setType 0 # types can vary upto 2 currently $a setAngle 85 # Angle from horizon of antennas axis $a setWidth 10 # width of the antenna |
Width is needed only for type 0. For type 0, the antenna returns a gain of 1
multiplied by the solid angle, if the node falls inside the cone of coverage
formed.
The following antenna types are also present:
Type 1 HG2424G See data sheet over
here.
Type 2 HG2414P See data sheet over
here.
Type 3 HG2418P See data sheet over here
Type 4 HG2417P-090 See data sheet over here
Type 5 HG2417P-120
See data sheet over here
Only radiation pattern and gain
values are relevant in the data sheet. If you add a new antenna radiation
pattern, please mail in your antenna file to
abagri@cse.iitk.ac.in along with a
radiation pattern graph image or data sheet of the antenna.
An antenna can then be attached to a nodes interface in the following manner:
| [$node_(0) set netif_(0)] dir-antenna $a |
The directional antenna module takes its input from a antenna file which is
expected to be in the NS_ANTENNA_FILE enviroment variable. the default exists in
...../ns-allinone-2.1b9a/ns-2.1b9a/mobile/antenna.txt. The format of this file
is lines of antenna gains for differnet angles and antenna types. This can be
replaced by ones own antennas file where each line has the following format
|
<type> <angle> <gain> |
4.3.3 Setting the
Transmit Power
The transmit power of an interface may be set by using the following:
| [$node set netif_(<interface number>)] set Pt_ <transmit power in W> |
4.3.4 Channel Number Setting
Channel Number for a node/interface may be set up by the following:
| [$node set netif_(<interface number>)] set channel_number_ <channel number> |
TENS implements co-channel interference and this should be noted while setting
up channels for interfaces. The co channel interference is implemented as
follows:
If a node is receiving and sending simultaeously on two different channels,
difference of their frequency is calculated and normalized by dividing the
difference by 5e+6. If the normalized value is greater than 5 then Tx power is
reduced to 0, For 4, it is reduced to 20%, 40% for 3, 60% for 4, 80% for 4.
4.3.5 Capture Threshold Setting
Settings for Capture Threshold may be setup for a node/interface may be set up
by the following:
| [$node set netif_(<interface number>)] set CPThresh_ <value> |
4.3.6 Carrier Sense Threshold
Setting
Settings for Carrier Sense Threshold may be setup for a node/interface may be
set up by the following:
| [$node set netif_(<interface number>)] set CSThresh_ <value> |
4.3.7 Rx Threshold Setting
Threshold settings for receiving a packet may be setup different from the
capture packet threshold as follows. Unless, receiving power is less than this
value, packet will not be sent up the layers
| [$node set netif_(<interface number>)] set RXThresh_ <value> |
4.3.8 Modulation Scheme Settings
Modulation Scheme of an interface may be changed as follows:
| [$node set netif_(<interface number>)] set modulationscheme_<value> |
The value may be 1 for BPSK and 0 for no modulation. No other modulation scheme
is supported as of now.
4.3.9 Frequency settings
and Loss factor
The frequency of operation and Loss factor may be setup as follows:
| [$node set netif_(<interface number>)] set freq_ <value> ; #frequency settings [$node set netif_(<interface number>)] set L_ <value> ; #Loss factor |
4.4 Adding Static Routes
Static routes may be added by lines in the following format:
| [$node set ragent_] addstaticroute <number of hops> <next hop> <destination node> <interface> |
4.5 Setting up parameters for
MAC
MAC Parameters for 802.11 may be setup using following lines of code:
| Mac/802_11 set dataRate_ 11mb ;# Setting the data rate Mac/802_11 set basicRate_ 1mb ;# Setting the basic data rate Mac/802_11 set isAdaptive_ 1 ;# Uses an adaptive rate scheme Mac/802_11 MAC_RTSThreshold 3000 ;# Setting the RTS threhold |
Similarly, the following parameters may be configured for 802.11 by using the command:
| Mac/802_11 <parameter name> <value> |
Each of the parameters is self explanatory by its name:
|
MAC_ShortRetryLimit MAC_LongRetryLimit MAC_FragmentationThreshold MAC_MaxTransmitMSDULifetime MAC_MaxReceiveLifetime DSSS_CWMin DSSS_CWMax DSSS_CCATime DSSS_RxTxTurnaroundTime DSSS_PreambleLength DSSS_PLCPHeaderLength DSSS_PLCPDataRate DSSS_RxRFDelay DSSS_RxPLPCDelay DSSS_MACProcessingDelay |
4.6 Adding ARP entries
One could add ARP entries as follows:
| $ll add-arp-entry <node-address> <mac-address> |
4.7 Using the 2p
Implementation
For 2p implementation while configuring netwrok components, set Link Layer to 2P
link Layer and MAC to 2p Link Layer
| set val(mac)
Mac/WP2P_MAC ; set val(ll) LL/WP2P_LL ; |
After making link layer and mac layer configuration with each node, one may
attach either a tcp or ftp agent and send packets
4.7.1 Link Layer Configurations
The following settings may be made for a point to point link:
| $ll set-my-node-id <id>
;set the node's id $ll set-nbr-node-id <id> ;set the neighbouring node's id $ll set-my-mac-id <id> ;set the node's mac address $ll set-nbr-mac-id <id> ;set the neighbouring node's mac address $ll set-dummy-packet-size <size> ;set the size of the dummy packet $ll set-mac $mac ;set the mac as Mac/WP2P_MAC $ll set-limit <value> ;set the link layer buffer limit value |
4.7.2 MAC Layer configurations
| $mac link-up
; activate the link/interface $mac link-down ; deactivate the link/interface $mac set-ifa-nbr <value> ; set MAC of the neighbouring links of this node $mac set-ll $ll ; set link layer as LL/WP2P_LL, different configurations at different node is possible $mac set-delay <value> ; set delay value |
two-node.tcl: A sample script for two nodes interacting over a type 1 antenna. A good starting point to understand TENS
sample.tcl: A four node network with multiple interfaces and static routing.
topo.tcl : A more dense topology simulation.
2-p.tcl: A script using the 2-p protocol
sample_long.tcl This script shows how directional antennas can be used for simulating long distance links. It is same as four node network except that the last hop is 6 Kms
6 Credits
TENS was output of the thesis of Siddharth Saha in.. during his maters at
Indian institute of Technology, Kanpur. It was then extended by Sabyasachi Roy
and Ashwinias a part of their Bachelor's project at IIT Kanpur. Dr Bhaskaran
Raman of Computer science and Engineering Department and Dr Kameswari Chebrolu
of electrical Engineering Department have been involved in upgrade of TENS since
1.0 with a lot of bug fixes and feature addition, the most significant being the
2-p implementation.
For comments and further queries regarding TENS or this tutorial please feel
free to mail at abagri@cse.iitk.ac.in.