OPNET wireless models
Professor: Andrew Yang
Student: Tuan Anh Nguyen
School of Science and Computer Engineering
University of Houston – Clear Lake
Purpose of the report: to learn the existing wireless models in OPNET.
Table of Contents
1. Introduction to wireless models in OPNET: ............................................................... 3
2. OPNET modeler 11.0 modeling hierarchy: ................................................................ 3
3. OPNET wireless standard models: ............................................................................. 4
4. MANET routing models: ............................................................................................ 6
5. References: .................................................................................................................. 9
1. Introduction to wireless models in OPNET:
Wireless models are implemented in Wireless Module. Wireless module is an extended
module to OPNET modeler.
Wireless Module features:
- Moving sites: Wireless module supports both type of moving sites as mobile and
satellite nodes/sub-networks. Mobile sites can be assigned pre-defined
trajectories. Similarly, satellite sites can be assigned orbits that describe their
- Radio links: Fixed, mobile and satellite sites communicate with each other via
radio links. Unlike bus or point to point links, radio links vary with time as the
movement of communication sites, modification of transmitter and receiver
2. OPNET modeler 11.0 modeling hierarchy:
Wireless sub-networks: Wireless module models two types of sub-networks: mobile sub-
network and satellite sub-network.
- Mobile sub-network: typically simulate networks whose position change with the
time such as ship, airplane. Mobile sub-networks can change their position via
one of three ways: pre-defined trajectory, vector trajectory, or change the sub-
- Satellite sub-network: satellite sub-networks change their positions via assigned
orbit. Objects within sub-network cannot connect to object outside via point-to-
point or bus link.
OPNET standard library has two types of node for wireless simulation: mobile and
satellite nodes. These nodes in general are similar to fixed nodes, but they change their
position during simulation time.
- Mobile nodes: The same as sub-network, their positions vary from time to time.
However, mobile nodes are often placed within sub-network. Once again, the
position of mobile nodes change according to one of three mechanisms:
trajectory segment, vector trajectory or direct changes to the node’s attribute
- Satellite nodes: Satellite nodes are contained within satellite sub-network. Its
orbital path is independent from its parent sub-network.
Wireless Communication Links
In wireless communication, the information or signals are transmitted via air medium. In
OPNET, the communication links are not presented by object but by dynamic evaluation.
Because the wireless communication is based on broadcast technology so the simulation
kernel must calculate the connectivity whenever a node wants to sends a packet to other
nodes. In wireless communication, the distance between nodes is the vital factor to affect
the propagation delay and path loss of radio signal. OPNET also model the weakening of
radio signal as it propagates from the source. If terrain modeling is used, the surface
terrain also affects the propagation and path loss.
The antenna also affect the signal level. In some direction, the power is higher than some
others. On the receiving node, the receiver pipeline will calculate the incoming direction
of signal and compare with receiver’s antenna and then the antenna will increase or
decrease the power level.
The propagation delay and signal strength will determine the acceptability of a packet. A
ratio of signal to noise is calculated and then the bit error rate and bit error count.
Modeling the movement of node and sub-network:
Because the position of nodes and sub-network affect the performance of wireless
communication. Thus, the good models of movement are critical to the quality of
wireless communication simulation. As we know before, there are three mechanisms of
movements in OPNET: pre-defined (segment based) trajectories, vector based trajectories
and position attributes.
- Segment based trajectories: define the movement using a series of pre-defined
points. Movement points are stored in ASCII text file with an extension of .trj.
This file contains time values and three corresponding coordinates (x, y and z-
altitude). During simulation course, the system will move nodes from one position
to the next position. If the simulation tile is longer than the highest time in the file
then nodes will stay in the last position for the rest of duration.
Segment based trajectories come in two varieties fixed interval and variable
interval. With fixed interval trajectory, one time value determines the traversal
time for all segment. That means nodes will traverse all segments in the same
duration. In contrast, each node has its own traversal time, delay, altitude in
- Vector based trajectories: define the movement according to bearing, velocity and
ascend rate. Typically, the vector-based trajectory does not change during the
simulation. But in Modeler sometimes, the path can change in this case the re
computation of longitude and latitude is triggered.
- Direct manipulation of position attribute: if no trajectory is applied to the
movement of a mobile node, the node position can be updated by any process
during simulation. There are two techniques to change the node position by
updating the position attributes. One is by centralized process, which is
responsible to update the position of all nodes; the other is de-centralized that
each node updates its own position by its own process.
Statistics in a wireless Network:
Wireless Module in OPNET enhances the modes for statistics collection by adding
one more mode, which is to remove the glitch. In this mode, only the last values at
any given time of simulation are collected.
Besides, several probes help users to capture the information that they want to
monitor such as Coupled Node Statistics Probes, Automatic Animation Probes and
Customer Automation Probes.
3. OPNET wireless standard models:
OPNET provides variety of models to use with wireless network.
- Standard models:
o Wireless LAN: WLAN shipped in OPNET as standard model release.
Wireless LAN model feature Access mechanism of CSMA/CA, roaming,
mobile IP, frame exchange sequence, deference and back off, data rate of
1, 2, 5,5 or 11 Mbps, recovery mechanism, fragmentation and reassembly,
duplicate packet detection, physical layer, communication distance and
spatial reuse, access point functionality, radio IP auto-addressing and
o Jammer models: There are three basic jamming sources in OPNET: pulsed
jammer, a frequency swept jammer and a fixed frequency single band
jammer. These allow models to be constructed to take into account self-
interference and jamming. Interference signals undergo the same
processing as normal signals. But it is not forwarded to higher level for
Single band jammer: This model can be a mobile, fixed or satellite
mode in Project Editor. It continuously sends packets through radio
transmitter at the rate of one packet per second on a fixed
Pulsed Jammer: This model can also be deployed as fix, mobile or
satellite node. It provides transmission on single fixed frequency
band, which is masked by a periodic pulse train in time. In addition
to the built node object attribute, the attributes that can be
controlled for a pulse jammer are:
Jamming band base frequency
Jamming transmitter power,
Duration of jamming pulses.
Duration separating jamming pulses
Frequency Swept Jammer: It can be deployed as a fixed, mobile or
a satellite node in the Project Editor. It provides continuous
transmission over a range of frequency at a specified rate. The
swept through the frequencies is modeled by sampling the
bandwidth into a number or frequency intervals and continuously
cycling through these intervals. The attributes can be controlled for
a frequency jammer are:
Jamming band base frequency
Encompassing jamming sweep bandwidth
Jamming transmitter power
Time to complete a single sweep
Number of frequency intervals (implicitly specifies interval
- Antenna Models: OPNET provides pattern for selected models from several
vendors. Documentation about these antennas is contributed under OPNET
- Specialized Models:
Universal Mobile Telecommunications System (UMTS): This is a third generation
(3G) wireless protocol …
4. MANET routing models:
- DSR - Dynamic Source Routing protocol model:
It is simple and efficient routing protocol and as its name implies it is a source
routing protocol. It is particular useful for routing across multi-hop wireless ad-
hoc network. This model captures the following features:
o Route Discovery: implement a complete set of route discovery
mechanisms including broadcast route request to find a route and receive
route replies with route to destination.
o Route Maintenance: The complete set of route maintenance mechanism
comprising of sending acknowledgment request and receiving
o Route Cache: Each node maintains a list of route to each destination. The
node will choose a route to a destination with the least number of hops to
o Replying to Route Requests using Cached Routes: A node reply to a Route
Request by searching its cache for a route to a destination
o Non-propagating route request:
o Packet Salvaging: When an intermediate detects a link to a neighbor is
broken and it has an alternate route, It will salvage the packet by using the
o Automatic Route Shortening: An intermediate node will automatic
removes one or more nodes that are no longer needed.
o Mobility in DSR: mobility can be modeled using pre-defined trajectories.
o Simulation statistics: Several statistics can be collected on a per node or
global basis. The picture below is per-node statistics for raw application
packet statistics. In addition, statistics for the routing protocol such as
maintenance buffer size, route discovery time and many more.
Figure 1: Raw application packet statistics for DSR
- AODV - Ad hoc On demand Distance Vector routing protocol model:
It is a reactive routing protocol used in Mobile Ad-hoc Networks. Below listed
main features of the model.
o Route Discovery: OPNET ADV implements complete set of route
discovery mechanisms: broadcasting route requests, creating a reverse
path while forwarding route reply by destination or intermediate nodes.
Other procedures such as rate limit, maximum number of retries and
exponential back off after each retry are also implemented.
o Maintaining Sequence Numbers: AODV maintains a sequence number to
avoid loops when searching for a route and updating route.
o Hello Messages: Nodes maintain connectivity by sending local hello
o Maintaining local connectivity: If a node doesn’t receive any packet from
a neighbor ALLOWED_HELLO_LOSS*HELLO_INTERVAL it will
declare the link is lost.
o Route maintenance: Each node has a routing table. Each entry in the table
has a time out value that is set whenever the entry is used. If a route is not
used after ACTIVE_ROUTE_TIME, it is marked invalid. Or when a
broken link is detected a the route will be invalid.
o Route reply by intermediate node: An intermediate node can answer route
requests by sending its route to the destination. This feature can be turned
off by DESTINATION ONLY flag. In this case only destination can send
the route reply packet.
o Gratuitous route reply:
o Expanding ring search: to avoid route request packet flood entire network.
A time to live TTL value is set. After a RING_TRAVERSAL_TIME
seconds, if no reply packet received, TTL value will be increased by
TTL_INCREMENT value. When TTL_THRESHOLD is reached, TTL is
set to NET_DIAMETER that means a request will be broadcasted over
o Local repair: When a broken link occurs, upstream node will try to repair
the link locally if the feature is enabled. During the recovery time, the
packets will be buffered in the node and this node will start a route
discovery procedure. This process is often invisible to the originating
o IP v6 support: Besides IP v4, IPv6 addressing is also supported by AODV
o Simulation statistics: On MANET station node model, raw application
packet statistics are also collected on a per-node or global basis.
AODV is implemented at IP layer. IP dispatch is the root process of IP layer
and has a child process manet_mgr. This process acts as common interface to
MANET routing protocols (TORA, AODV, DSR) as in the figure 2 below.
Figure 2: Node Model Struture
A node contains two route table, one is IP common route table the other is
AODV routing table. Route added and deleted affects both table. When a node
forwards a packet, it bases on IP route table. AODV table is used for
maintaining the normal operation of the protocol.
- TORA - Temporally-Ordered Routing Algorithm model:
TORA uses IMEP (internet MANET encapsulation protocol) for link status and
neighbor connectivity sensing.
o Creating routes: model supports route discovery to other TORA node in a
network by using QRY and UPD packet.
o Erasing routes: The model erases route to neighbor that it loses the
o Routing mode of operation: The model supports on-demand and proactive
modes of operation for route discovery.
o IMEP neighbor discovery: The model support full exchange of Beacon,
Echo, ACK and NewColor objects.
o IMEP route injection: The model supports route injection for one-hop
neighbors into common route table of the node.
o IMEP upper layer packet segmentation and reassembly: The segmentation
and reassembly of upper layer packets
o Global statistic:
Dropped un-routable IP packet
IMEP control traffic sent and received
IMEP Upper Layer Protocol sent/received.
o Node statistic:
IMEP number of neighbor: Number of neighbors that a node can
discover at the moment. This number is updated whenever the
node detects or loses a neighbor.
IMEP retransmission: indicating the number of retransmission
sent by IMEP process on the node.
Route Discovery Delay: Time spent on searching a valid route to a
Un-routable Packet Queue Size:
The full list of statistics can be seen in the figure 3
Figure 3: Node Statistics
- OPNET modeler 11.0: Wireless Module User Guide.
- OPNET : DSR Model User Guide
- OPNET : AODV Model User Guide
- OPNET : TORA Model User Guide