Emulation Experimentation Using the Extendable Mobile Ad-hoc ...

Abstract
The current deployment and continuing evolution
of wireless technology within commercial and military
applications places an increased importance
on providing researchers and evaluators with a scalable,
practical, and realistic experimentation framework.
The experimentation framework must provide
researchers with the ability to examine any
and all aspects of complex wireless networks and
their corresponding interactions at all points within
the network stack with a certain level of confidence.
Emulation is a viable option providing researchers
with the ability to bridge the gap between simulation
and field testing in a practical and realistic
manner.
In this paper we describe the Extendable Mobile
Ad-hoc Network Emulator (EMANE) with its open,
flexible, and modular architecture. EMANE’s flexible
design provides the ability to operate in various
hardware configurations (centralized, decentralized,
and virtualized). EMANE’s modularity provides
the ability to utilize plugins with the appropriate
fidelity and realism to support diverse experiment
objectives. The open EMANE architecture leverages
the user community to develop and contribute
models, tools, and applications.
1 Introduction
As wireless technology becomes more prevalent
in every day commercial and military applications,
there is a growing demand within research and test
communities to evaluate existing and evolving technologies
in a scalable, practical, and realistic environment.
Within recent years, network emulation
has gained favor within these communities to complement
traditional approaches such as simulation
and field testing. However, significant challenges
must be overcome to fully realize the benefits of
wireless network emulation.
This paper describes the open source 1 Extend-
Emulation Experimentation
Using the Extendable Mobile Ad-hoc Emulator
1 EMANE is release under the BSD license. EMANE plu-
Kaushik B. Patel and Steven M. Galgano
CenGen, Inc.
Columbia, MD 21045
{kbpatel, sgalgano}@cengen.com
1
able Mobile Ad-hoc Network Emulator (EMANE)
developed by CenGen, Inc., sponsored by the OSD
Network Communication Capabilities (NCC) Tactical
Edge Experimentation Testbed Initiative, to
address many of the challenges with wireless network
emulation.
EMANE supports the emulation of both simple
and complex wireless network architectures consisting
of heterogeneous networking technologies and
their interactions. For example, the Army Future
Combat System’s (FCS) vision of a highly mobile
digital battlefield consists of heterogeneous platforms
(sensors, dismounts, vehicles, UAVs, etc.) all
interconnected with varying MANET wireless technologies.
EMANE provides the ability to replicate
such networks in a realistic manner to provide the
necessary insight into overall system performance.
EMANE provides a flexible and modular architecture
to support realistic emulation of current and
future networking technologies. By implementing
an open and modular emulation architecture, the
cost associated with the integration of new features
and technologies can be significantly reduced. In
addition, the open and modular approach promotes
independent development of tools, models and applications
by respective experts which can be leveraged
by the emulation community at large.
EMANE uses a generic mechanism for distribution
of events, control, and logging information to
and from emulation components. This generic distribution
mechanism allows EMANE developers to
focus on component functionality, eliminates the
need for pre-computed scenarios, and allows emulation
components to report errors and alerts in
real-time minimizing experimentation cycles.
EMANE supports configuration of large scale experiments
comprised of physical and virtual nodes
with the same ease as small scale experiments containing
a hand full of nodes.
gin components are the property of their author and may be
distributed under any license.

EMANE was developed using cross platform tool
kits to support Linux, OS X and MS Windows experiment
testbed environments 2 .
The remainder of this paper is organized as follows:
Section 2 describes the modular EMANE software
architecture and component types. Section 3
describes the rationale for realistic wireless models
and identifies existing wireless models, as well
as models under development within EMANE. Section
4 lists some of the current programs utilizing
EMANE. Section 5 provides a near term road map
for EMANE and planned future work.
2 Architecture
EMANE implements a highly flexible modular architecture
capable of accommodating a wide range
of experiment testbeds. The flexibility of EMANE
centers around its ability to centralize or distribute
some or all of an experiment’s emulation processing
across any number of testbed nodes. XML inputs
to the emulator control the types of processing
deployments and their respective locations, as
well as the types of emulation modules to instantiate.
The modularity of EMANE comes from a
set of well defined component APIs that allow independent
development of emulation module plugins,
while retaining the ability to deploy and control
these components in a consistent generic manner.
There are three main types of EMANE components:
Network Emulation Modules, Emulation
Boundaries and Emulation Event Components.
All EMANE components are implemented as
Dynamic-Link Libraries and referred to as plugins.
All plugins, regardless of type, implement a set of
common interfaces to allow generic creation, configuration,
and control. In addition, plugins implement
a set of specialized interfaces which vary
based on their respective type. EMANE uses a layered
XML approach to instantiate any number of
plugins and configure each plugin with any number
of input parameters. The XML configuration
is designed to minimize the amount of redundant
information necessary to create an EMANE deployment.
This is done by building a hierarchical series
of emulation element groups. Each level in the hierarchy
encapsulates the previous level(s) while still
allowing tailoring of parameters from the level(s)
below.
2 EMANE is developed using The ADAPTIVE Communication
Environment (ACE TM )[1] and The XML C parser
and toolkit of Gnome (libxml2)[2].
2
2.1 Network Emulation Modules
A Network Emulation Module (NEM) is a logical
component that encapsulates all the functionality
necessary to emulate a particular type of network
technology. Each NEM is composed of two types
of plugins: a Medium Access Control (MAC) Layer
plugin and a Physical (PHY) Layer plugin. Instantiated
NEM component layers are configured and
then connected to the layer immediately above and
below. NEM layers communicate with each other
using a generic message passing interface. Each
layer is capable of communicating cross-layer control
messages and Over-The-Air (OTA) messages
with their neighboring layers (See Figure 1). Examples
of cross-layer messages include: per packet
RSSI, carrier sense, and transmission control messages.
Each layer has the capability to generate
OTA messages for communication with respective
layer counterparts contained in different NEMs.
Layers may also append and strip layer specific
headers to OTA messages.
Figure 1: NEM Stack with Boundary and OTA connections
(Left). NEM Stack showing physical and
logical communication paths (Right).
NEMs are created and managed by a NEM Platform
Server. NEMs managed by the same NEM
Platform Server are referred to as being part of the
same platform (See Figure 2). The determination
as to how many NEM platforms are required to support
a given emulation experiment is a function of
the number of NEMs, the complexity of the emulation
modules, and the processing and memory
resources available. Inter-NEM communication is
manged by the NEM Platform Server. NEMs belonging
to the same platform use in memory message
passing. NEMs belonging to different platforms
communicate using a multicast channel.
The EMANE infrastructure delivers all OTA mes-

Figure 2: NEM Platform Server hosting 4 NEMs.
sages to every NEM participating in the emulation.
This provides the opportunity to model more
complex PHY phenomena such as RF interference.
PHY layer modules use a common header to allow
cooperation between heterogeneous modules in
the same experiment. The common header includes
the following information: PHY type, NEM source,
NEM destination, time, message duration, center
frequency, bandwidth, data rate, antenna gain, antenna
beam width, antenna elevation, antenna azimuth
and transmission power. This information is
used to support high fidelity RF models which may
compute noise floors, detect frequency interference,
and support directional antennas.
2.2 Emulation Boundaries
Emulation boundary components are responsible
for transferring data between the emulation and application
domain 3 . The top of every NEM layer
stack is connected to one side of its associated emulation
boundary instance (See Figure 1). The
other side of the emulation boundary instance interfaces
with the application domain. Data received
from the application domain is transmitted
opaquely to the boundary’s respective NEM for
OTA message processing. The emulation boundary
is the only EMANE component aware of the exact
format of the application domain data. Along
with the opaque data, the boundary component
supplies the destination address, either a unicast or
broadcast NEM identifier, to the NEM stack. This
decoupling of application domain data knowledge
from the emulation functionality allows NEMs to
be used in conjunction with various types of net-
3 The application domain refers to entities running during
the experiment which are not part of EMANE. The application
domain includes, but is not limited to, user space
processes, kernel space processes, network appliances or any
other device, system, or component that is not operating on
behalf of or as part of EMANE.
3
works, for example, IP and non-IP based networks.
EMANE boundary components may or may not
be designed to inter-operate with other dissimilar
boundary components in the same experiment.
Two emulation boundary implementations are
supplied with the core EMANE distribution: Virtual
Transport and Raw Transport. Both of
these emulation boundaries were designed to interoperate
and interface with the application domain
using Ethernet Frames. The Virtual Transport uses
a virtual network interface as the emulation stack
entry and exit point. All traffic routed to the virtual
interface is transmitted to the boundary’s respective
NEM stack for processing. All messages
received from the boundary’s respective NEM stack
are written back to the virtual interface for delivery
to the application domain via the operating system
kernel. The Raw Transport promiscuously opens
a dedicated network interface and transmits all inbound
traffic to the boundary’s respective NEM
stack and conversely writes received traffic from its
NEM stack out the network interface.
Emulation boundary components are created and
managed by a Transport Daemon. Boundaries managed
by the same Transport Daemon are referred to
as being part of that Transport Daemon. The Virtual
Transport and Raw Transport support two different
types of emulation experiment configurations.
The Virtual transport is ideal when you are able to
run some or all of the EMANE components on the
experiment test node. This lightweight transport
simply packs and unpacks Ethernet frames moving
them between the NEM stack and the application
domain. The Raw transport is ideal when you are
unable to run any EMANE components on the experiment
test node. For instance, if you are using
EMANE as a black box emulator and connecting
network appliances to the emulator using multiple
physical interfaces. Multichannel gateway emulation
is supported by configuring the Transport Daemon
to instantiate one boundary for each gateway
channel and then configuring an application domain
routing protocol to gateway the corresponding interfaces.
2.3 Emulation Event Components
An emulation event is an opaquely distributed
message which is delivered in real-time to one
or more targeted EMANE components. Every
EMANE component is capable of transmitting and
receiving events. Components which create events
based on experiment scenarios are called Event Generators.
Event Generators are instantiated and
managed by the EMANE Event Service, which pro-

vides the interface used to publish events.
No restriction is placed on how generators create
events. Some generators may read precomputed
state information from input files and publish
events on time boundaries. Others may create
event data algorithmically in real-time and publish
the events based on update threshold logic. When
new EMANE event types are introduced, no modifications
are necessary to existing EMANE components,
provided those components are not required
to process the new events. Only the Event Generator
and the destination EMANE components need
to know the more specialized form of the generically
transmitted event. Events are addressable using a
three field tuple: NEM Platform Server identifier,
NEM identifier, and component identifier.
An Event Agent is an EMANE component that
translates events from their emulation domain representation
to a format usable by application domain
entities. They facilitate the reuse of any experiment
scenario information propagated via an
event that is of interest outside of the emulation domain.
For example, position information contained
in the EMANE Location Event which is used by
some PHY layers to compute path loss may also be
of interest to application domain entities that require
GPS location.
2.4 NEM Advanced Topics
A Shim Layer plugin provides a mechanism to interact
with the OTA messages and cross-layer messages
exchanged between contiguous layers. Shims
may generate their own OTA messages for communication
with their respective Shim layer contained
in a different NEM, and can append and strip layer
specific headers to OTA messages.
It is possible to insert one or more Shims between
the layers of a NEM stack or at the top and bottom
of the layer stack. A Shim plugin implements the
same generic interface as a MAC and PHY plugin.
This generic interface allows Shims to be inserted
between components without requiring those components
to have knowledge of their presence. Figure
3 shows what a NEM layer stack looks like after
inserting Shim layers and the resulting physical and
logical connections.
A NEM containing a MAC and PHY layer is formally
known as a structured NEM. A NEM may
also be unstructured. An unstructured NEM relaxes
NEM layer stack constraints to allow for the
creation of NEMs that may or may not contain
MAC, PHY or Shim layers. Unstructured NEMs
are useful when porting legacy emulation models
that do not support a separation of MAC and PHY
4
Figure 3: NEM Layer stack as it appears without
Shims and with three Shims inserted. Two Shims
reside between the MAC and PHY layers and one
Shim resides between the PHY Layer and the OTA
message interface.
layer functionally.
3 Network Emulation Modules
Within the EMANE architecture, NEMs address
the “hard problem” in wireless network emulation
associated with representing the behavior of the underlying
wireless technology at both the Media Access
and Physical Layers. Physical and MAC layer
phenomena such as frequency interference, multipath/fading,
collisions, channel access protocols,
adaptive power and data rate controls, quality of
service, and others vary significantly based on the
underlying wireless commercial or tactical technology.
Depending on the research/test objective, failure
to account for these or any corresponding cross
layer interactions can provide misleading and outright
false results. Conversely, the ability to account
for some of these complex phenomena within
a real-time emulation environment can impose requirements
(hardware, timing, scale, etc.) which
may not be critical to the research/test objective.
As such, the modular EMANE architecture is designed
specifically to support independent development
of NEMs to emulate current and evolving wireless
technology of varying fidelity under a single emulation
framework. These independently developed
modules can be contributed to the EMANE project
as add-ons for use by the community at large or
can be maintained as proprietary/sensitive modules

with restricted access by the developing organization.
3.1 PHY and MAC Phenomena
Although the details on the methodology and
techniques for NEM development to account for
PHY and MAC phenomena is beyond the scope
of this paper, we will highlight two specific areas,
frequency interference and channel access scheme,
where the development of novel techniques and advanced
algorithms within the EMANE framework
can significantly improve the utility and effectiveness
of wireless network emulation.
3.1.1 Frequency Interference
The impact of RF interference from either intentional
or unintentional (fratricide) sources can be
significant compared to effects on propagation from
phenomena such as ducting, weather, foliage, and
others. As networks/systems become more complex
and RF resource remain scarce, RF interference is
a common occurrence rather than an anomaly and
as such needs to be accounted for within the emulation
environment to properly assess the effectiveness
of current and evolving communication technologies.
Many simulators and emulators today utilize
the notion of Signal to Interference and Noise Ratio
(SINR) as defined in Equation 1 along with Bit Error
Rate (BER) or Packet Error Rate (PER) curves
as the basis for the receive packet treatment logic.
The SINR equation although accurate in definition,
loses significance as the interference term,
n�
i=0
Rxpoweri
is approximated by accounting only for “in-band” 4
traffic and ignores traffic from all “out-of-band”
sources. Simplifying assumptions like network homogeneity
and static spectral environment limit the
ability to effectively research and evaluate advanced
wireless research topics within an emulation framework
such as: heterogeneous networks, directional
antennas, frequency hopping, interference mitigation
techniques against wide and narrow band jammers,
and dynamic spectral allocation algorithms.
EMANE, with its implementation of the common
PHY header along with the OTA distribution mechanism,
provides the framework for developing NEMs
in support of the more advanced research topics
4 In-Band traffic is all traffic that is associated with a single/homogeneous
wireless technology.
5
identified above.
⎡
⎢
SINR = 10 log ⎢
⎣
Noise + n�
Rxpower
n�
Rxpower
Rxpoweri
i=0
⎤
⎥
⎦
Receive power of the packet/frame to
be evaluated accounting for transmit
power, antenna gains and propagation
effects
Rxpoweri Receive power of all other pack-
i=0
ets/frames received during the packet
interval (i.e. collisions)
Noise Thermal and platform noise of the receiver
taking into account bandwidth,
noise figure, etc.
3.1.2 Channel Access Scheme
(1)
Packet mode channel access schemes, also commonly
referred to as Media Access Protocol (MAC),
for wireless communications have been and continue
to be heavily researched due to their significant impact
on network performance associated with scale,
throughput, and latency. The MAC protocol defines
the mechanisms used to control access to a
wireless medium shared by multiple nodes and can
also include other controls (acknowledgments, retries,
fragmentation, etc.) in support of quality
of service (QoS) requirements. The MAC protocol,
based on the given wireless technology can vary
from very simple, such as static Time Division Multiple
Access (TDMA) where nodes are statically assigned
one or more time slots for transmissions, to
very complex, such as a hybrid protocol that dynamically
leverages the benefits of contention based
access via Carrier Sense Multiple Access/Collision
Avoidance (CSMA/CA) in conjunction with contention
free dynamic TDMA reservations on top
of advanced channelization techniques using Frequency
Division Multiple Access (FDMA) or Code
Division Multiple Access (CDMA).
The ability to accurately model the various channel
access schemes within the framework of a realtime
emulation environment faces significant challenges.
One of the major challenges associated with
accurate real-time emulation of MAC protocols is
timing. To highlight this, we examine CSMA/CA, a
contention based access protocol which is utilized in
both commercial and tactical products and as such
provides a good basis for discussion. CSMA/CA
utilizes two basic principles: carrier sensing and collision
avoidance. Here we look a little deeper into
the timing associated with collision avoidance for
802.11. In 802.11, collisions are minimized by requiring
all nodes with a packet for transmit to se-

lect a random slot within a given contention window
once the channel becomes idle. The size of a
slot is on the order of tens of microseconds, sufficiently
long enough in real systems to ensure multiple
nodes selecting different slots will not step on
one another. Within an emulated system, however,
the time it takes for a packet to get from one emulated
node to another can be significantly larger
than the contention delay implying that actual implementation
of the protocol will not provide an
accurate representation of the collision and backoff
phenomena associated with CSMA/CA. Advanced
statistical models or simplistic approximations can
be utilized to account for such a phenomena, but the
determination of which model is appropriate should
be based on the research/test objective.
3.2 Models
The EMANE project currently contains three
models each having varying features and complexity
supporting research and evaluation of wireless
technologies within DoD, Academia, and Industry:
RF-Pipe, Comm Effects, and IEEE 80211abg. In
addition, there are two high-fidelity tactical models
(SRW and HNW) currently under development
with controlled/restricted access.
3.2.1 RF-Pipe
The RF-Pipe model is a simplistic yet feature rich
model which can be configured to provide capabilities
similar to existing emulators, such as NRL’s
MANE[3] and Boeing’s Core[4], to emulate throughput
and loss of various wireless technologies such
as satellite comms, 802.11, and tactical waveforms.
In addition, the model also serves as a template to
guide independent NEM developers of more complex
models. The majority of the functionality of
the RF-Pipe model is contained within the PHY
layer and can be summarized as follows:
• Filters out-of-band packets.
• Adds transmission delay based on data rate,
propagation delay, and jitter.
• Computes propagation effects based on runtime
Path Loss or Location events. Path Loss
Event values are computed off-line with events
dispatched in real-time during the emulation
experiment. Location Event based path loss is
computed in real-time using one of two configured
propagation models (Free Space or 2-Ray
Flat Earth).
• Performs packet treatment based on Receive
Power (Rxpower) and configured min/max
6
thresholds as depicted in Figure 4.
Rxpower = T xpower+T xgain+Rxgain−P athloss
(2)
The model utilizes the common EMANE PHY
header to provide the Txpower and Txgain in
each over-the-air packet transmission providing
the ability to emulate different types of
platforms such as base stations, vehicles, dismounts,
and sensors.
Figure 4: RF-Pipe Packet Treatment.
3.2.2 Comm Effects
The Comm Effect model provides the ability to
control network impairments commonly provided
via traditional COTS network emulators on a per
link basis asymmetrically. The Comm Effect model
is a Shim-only implementation utilizing unstructured
EMANE NEMs as described in Section 2.4.
The Comm Effects model provides the ability to
define the following network impairments:
• Loss: The percentage of packets that are
dropped based on a uniform loss distribution
model.
• Delay: Defines the delay for a packet to traverse
a specific link. The delay is composed of
a fixed and variable (jitter) component. Delay
is computed at the receiver and the packet is
delivered up the stack once the delay expires
providing the ability to emulate out of order
packet reception.
• Duplicates: Defines the percentage of packets
to be duplicated at the receiver.
The network impairments defined above are controlled
based on time and/or predefined filters.
Time based impairments are controlled via the
use of Comm Effect events dispatched in real-time
during the emulation experiment. The events provide
each node with the effects/impairments to every
other node within the scenario.

Filter based impairments provide the ability to
define static impairments at start up. A filter consists
of one or more rules based on IPv4/IPv6 packet
header fields. All packets matching the defined set
of rules are effected with the appropriate network
impairments. The model provides the ability to define
more than one filter and as such each received
packet is evaluated against the defined filters in the
order they are defined, with the first match determining
the impairment to be applied. When filters
are used in conjunction with time based impairments,
the event driven impairments serves as
the default effect for all packets that do not match
any defined filters.
3.2.3 IEEE 802.11abg
The 802.11abg model is a high-fidelity NEM
to emulate the IEEE 802.11 MAC layers Distributed
Coordination Function (DCF) channel access
scheme on top of the IEEE 802.11 Direct
Spread Spectrum Sequence (DSS) and Orthogonal
Frequency Division Multiplexing (OFDM) signals in
space. The key features of this high fidelity model
are as follows:
• Distributed Coordination Function (DCF)
channel access protocol.
• Support for 802.11b (DSS), 802.11a/g (OFDM)
and 802.11b/g (DSS and OFDM) modes with
the corresponding rates and waveform timing.
• Support for unicast and broadcast messaging.
• Half duplex operations where all packets received
while transmitting are silently discarded.
• Receive power calculation based on transmit
power, antenna gain, and externally computed
propagation model (path loss) with real-time
dissemination via EMANE events.
• Bit Error Rate (BER) curves as a function of
SINR and data rate specified via XML providing
the ability to represent different communication
channel models. Default curves provided
for an Additive White Gaussian Noise (AWGN)
channel.
• Probability of Reception (PoR) computed
based on BER and packet size.
P oR = (1 − BER) L
BER Bit Error Rate for the corresponding
data rate and SINR.
L Length of the received packet in bits.
(3)
7
3.2.4 Tactical Models
There are currently two high-fidelity tactical
EMANE models under development. The two models
are the Highband Networking Waveform (HNW)
being developed by Harris Corporation and the
Solider Radio Waveform (SRW) being developed by
CenGen, Inc. HNW is designed to serve as a tactical
backbone network (i.e. wireless Wide Area
Network) that can bridge multiple wireless Local
Area Networks at the tactical edge being serviced by
waveforms such as SRW. The two waveforms were
chosen based on their maturity and their diverse set
of capabilities and services in support of the DoD’s
research and testing of wireless technologies associated
with tactical networks. Both models have restricted
access and all inquiries should be directed
to the Naval Research Laboratory.
4 EMANE User Community
EMANE falls under the umbrella of the OSD Network
Communication Capabilities (NCC) Tactical
Edge Experimentation Testbed Initiatives with an
objective on the development and collaboration of
common testbed and experimentation capabilities
that proliferate to DoD, Academia, and Industry.
Since EMANE’s initial release in late 2008, the user
community has steadily begun to embrace EMANE
as an emulation suite to support research and evaluation
of various wireless networking technologies.
5 Summary and Future Direction
EMANE, with its open, flexible, and modular architecture
provides the framework for practical and
realistic emulation of current and evolving wireless
networking technologies. EMANE’s flexible design
provides the ability to operate in various hardware
configurations (centralized, decentralized, and virtualized).
EMANE’s modularity provides the ability
to utilize plugins with the appropriate fidelity
to support diverse experiment objectives. The open
EMANE architecture leverages the user community
to develop and contribute models, tools, and applications.
Future work in this area will focus on the following:
• EMANE framework enhancements to further
optimize performance and provide additional
mechanisms to monitor and analyze emulator
operation.
• Characterize requirements (hardware, timing,
scale, etc.), for high-fidelity emulation based on
complex MAC and PHY implementations.

• Development of additional high-fidelity NEMs
of both commercial (WiMAX) and tactical
waveforms.
• Investigate feasibility and techniques of using
EMANE with simulation in the loop to leverage
existing simulation models.
References
[1] ACE TM , The ADAPTIVE Communication
Environment (ACE TM ). [Online], URL: http:
//www.cs.wustl.edu/~schmidt/ACE.html.
[2] libxml2, The XML C parser and toolkit of
Gnome. [Online], URL: http://www.xmlsoft.
org.
[3] MANE, Mobile Ad-hoc Network Emulator
(MANE). [Online], URL: http://cs.itd.
nrl.navy.mil/work/mane/index.php.
[4] CORE, The Common Open Research Emulator
(CORE). [Online], URL: http://cs.itd.nrl.
navy.mil/work/core.
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