Communication System Model


BGP Congig

Components are the building blocks for creating virtual network models. Just as live networks are constructed out of individual pieces of equipment and software, virtual network models are created out of previously defined component models of network protocols, radio waveforms, equipment, and other characteristics that influence network behavior.

The QualNet and EXata platforms and the Network Defense Trainer system come with a GUI-driven virtual network model building facility that includes a set of standard communication system component libraries for creating typical network models. Optional component libraries are available which add more specialized functionality and network protocols.

Communication systems model libraries contain high fidelity programmatic definitions of the protocols and waveforms used in communications equipment. SCALABLE offers a range of libraries, which can be combined with custom libraries as necessary, to represent every element in a communications network and add increased, specialized functionality. These various libraries enable the inclusion of required hardware components, live software or hardware to interact with the network protocols and waveforms allowing the equipment to communicate the potential effects on wireless communication.  The virtual network models can leverage both the included and any optionally licensed component libraries for protocols, waveforms and propagation effects. Design Mode is also used to create custom communication system models which can then be used in specialized virtual network models.

lt is also possible to modify communication systems models and develop custom models, add them to a system, and then use them in virtual network model configuration. Communication system models are written in C/C++, and source code is available for most SCALABLE-developed component models.

The "classes" of component libraries include:

  • Cyber  (attacks against the network)
  • Equipment  (the various hardware components)
  • Human-in-the-Loop (HITL)  (commands that control various elements during scenario execution)
  • Images  (icons and other components that graphically depict elements and behavior)
  • Integration Interfaces  (protocols and mechanisms that enable interaction between a SCALABLE system and other simulators or external systems)
  • Protocols  (the network protocols and waveforms that enable equipment to communicate)
  • Terrain  (the physical terrain over which the communications takes place)
  • Weather  (descriptions of different weather behavior and its impact on communications)


Standard Component Libraries  Click on the [+] for details

The following component model libraries are included with the QualNet and EXata platforms.  They cover a wide range of models for equipment, protocols, terrain and weather.

Developer Library

The Developer Library includes a very long list of standard communications protocols and mechanisms.

The library supports:

MAC Layer

  • 802.3 LAN/Ethernet
  • Abstract Link MAC
  • Abstract Satellite Model
  • Address Resolution Protocol (ARP)
  • Logical Link Control (LLC) Protocol

Network Layer

  • Domain Name System (DNS)
  • Dynamic Host Configuration Protocol (DHCP)
  • Fixed Communications Model
  • Internet Control Message Protocol (ICMP)
  • Internet Control Message Protocol version 6 (ICMPv6)
  • Internet Group Management Protocol (IGMP)
  • Internet Protocol - Dual IP
  • Internet Protocol version 4 (IPv4)
  • Internet Protocol version 6 (IPv6)
  • IPv6 Autoconfiguration Model
  • Neighbor Discovery Protocol

Unicast Routing

  • Bellman-Ford Routing Protocol
  • Routing Information Protocol next generation (RIPng)
  • Routing Information Protocol/Routing Information Protocol version 2 (RIP/RIPv2)
  • Static and Default Routes

Multicast Routing

  • Static Multicast Routes

Queues and Schedulers

  • First-In First-Out (FIFO) Queue
  • Random Early Detection (RED) Queue
  • Random Early Detection with In/Out (RIO) Queue
  • Round Robin Scheduler
  • Self-Clocked Fair Queueing (SCFQ) Scheduler
  • Strict Priority Scheduler
  • Weighted Fair Queuing (WFQ) Scheduler
  • Weighted RED (WRED) Queue
  • Weighted Round Robin (WRR) Scheduler

Transport Layer

  • Abstract Transmission Control Protocol (Abstract TCP)
  • Multicast Dissemination Protocol (MDP)
  • Transmission Control Protocol (TCP)
  • User Datagram Protocol (UDP)

Application Layer

  • Background Traffic Model
  • Constant Bit Rate (CBR) Traffic Generator
  • File Transfer Protocol (FTP)
  • File Transfer Protocol/Generic (FTP/Generic)
  • HyperText Transfer Protocol (HTTP)
  • Lookup Traffic Generator
  • Multicast Constant Bit Rate (MCBR) Traffic Generator
  • Super Application Traffic Generator
  • Telecommunications Network (TELNET)
  • Traffic Generator (Traffic-Gen)
  • Trace File-based Traffic Generator (Traffic-Trace)
  • Variable Bit Rate (VBR) Traffic Generator


  • Asynchronous Transfer Mode (ATM)

Vendor Interfaces

  • AGI System Toolkit (STK) Interface


  • Faults
  • File-based Node Placement Model
  • Grid Node Placement Model
  • Random Node Placement Model
  • Uniform Node Placement Model

Wireless Library

The standard Wireless Library includes many typical wireless protocols and mechanisms.

The library supports:


  • Constant Shadowing Model
  • Fast Rayleigh Fading Model
  • Free-space Pathloss Model
  • Inter-channel Interference Model
  • Irregular Terrain Model (ITM)
  • Lognormal Shadowing Model
  • Pathloss Matrix Model
  • Rayleigh Fading Model
  • Ricean Fading Model
  • Two-ray Pathloss Model

Physical (PHY) Layer

  • 802.11a/g PHY Model
  • 802.11b PHY Model
  • 802.11n PHY Model
  • 802.11ac PHY Model  (NEW)
  • Abstract PHY Model
  • Antenna Models
  • Bit Error Rate-based (BER) Reception Model
  • Radio Energy Models
  • SNR-based Reception Model

Media Access Control (MAC) Layer

  • 802.11 MAC Protocol
  • 802.11e MAC Protocol
  • 802.11n MAC Protocol
  • 802.11ac MAC Model  (NEW)
  • 802.11s MAC Protocol
  • Aloha MAC Protocol
  • Carrier Sense Multiple Access (CSMA) MAC Protocol
  • Generic MAC Protocol
  • Microwave Links
  • Multiple Access Collision Avoidance (MACA) MAC Protocol
  • Time Division Multiple Access (TDMA) MAC Protocol

Unicast Routing

  • Ad-Hoc On Demand Distance Vector (AODV) Routing Protocol
  • Bordercast Resolution Protocol (BRP)
  • Dynamic MANET On-demand (DYMO) Routing Protocol
  • Dynamic Source Routing (DSR) Protocol
  • Fisheye State Routing Protocol
  • Intrazone Routing Protocol (IARP)
  • Interzone Routing Protocol (IERP)
  • Landmark Ad Hoc Routing (LANMAR) Protocol
  • Location-Aided Routing (LAR) Protocol
  • Optimized Link State Routing Protocol - INRIA (OLSR-INRIA)
  • Optimized Link State Routing Protocol version 2 (OLSRv2)
  • Source Tree Adaptive Routing (STAR) Protocol
  • Zone Routing Protocol (ZRP)

Multicast Routing

  • On-Demand Multicast Routing Protocol (ODMRP)


  • File-based Mobility Model
  • Group Node Placement and Mobility Models
  • Random Waypoint Mobility Model


  • Cartesian Terrain Format
  • Digital Elevation Model (DEM) Terrain Format
  • Digital Terrain Elevation (DTED) Terrain Format
  • ESRI Shapefile Terrain Format
  • Urban Terrain Data Format


  • Battery Models
  • Weather Pattern Model

Multimedia & Enterprise Library

The Multimedia and Enterprise Library covers an array of protocol and equipment elements.

The library supports:

Media Access Control (MAC) Layer

  • Detailed Switch Model
  • Switched Ethernet
  • Virtual LAN (VLAN)

Network Protocols

  • Mobile IPv4

Unicast Routing

  • Border Gateway Protocol version 4 (BGPv4)
  • Enhanced Interior Gateway Routing Protocol (EIGRP)
  • Interior Gateway Routing Protocol (IGRP)
  • Open Shortest Path First version 2 (OSPFv2) Routing Protocol
  • Open Shortest Path First version 3 (OSPFv3) Routing Protocol

Multicast Routing

  • Distance Vector Multicast Routing Protocol (DVMRP)
  • Multicast Extensions to OSPF (MOSPF)
  • Protocol Independent Multicast Protocol: Dense Mode (PIM-DM) and Sparse Mode (PIM-SM)
  • Multicast Source Discovery Protocol (MSDP)

Router Configuration

  • Hot Standby Router Protocol (HSRP)
  • Policy-based Routing Protocol (PBR)
  • Route Map
  • Route Redistribution
  • Router Access List
  • Router Model

Quality of Service (QoS)

  • Differentiated Services (DiffServ)
  • Multiprotocol Label Switching (MPLS)
  • Quality of Service Extensions to OSPF (QOSPF)

Multimedia Applications

  • H323 and H225 Protocols
  • Real-time Transfer Protocols
  • Session Initiation Protocol (SIP)
  • Voice over Internet Protocol (VoIP)

Network Management Library (EXata only)

The Network Management Library includes a model of the Simple Network Management Protocol (SNMP).

The SNMP is a UDP-based network protocol which runs over IP using Port 161 and 162. It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. SNMP makes management data available in the form of variables on the managed systems, which describe the system configuration. These variables can then be queried (and sometimes set) by managing applications.

The EXata platform offers the capability to manage nodes in a scenario by an SNMP manager. The SNMP managers can review the current network status, set the network properties, or assign traps to receive feedback from the managed nodes. EXata provides this feature by implementing SNMP agents on nodes in a scenario. SNMP agents can be enabled on all nodes and can be configured to handle the SNMP get and set commands. Additional configuration is required to handle the trap command.

Implemented features:

  • Command responder application
  • Notification originator
  • User-based Security Module (for SNMPv3)
  • Authentication (for SNMPv3)
  • Encryption (for SNMPv3)
  • Access Control


Currently available Optional Libraries   Click on the [+] for details

Advanced Wireless Library

The Advanced Wireless Library can be incorporated into QualNet, EXata and NDT models, adding support for fixed and mobile WiMAX communications, based on IEEE 802.16d and 802.16e standards.

The library supports:

  • 802.16 MAC and 802.16e MAC
  • 802.16 PHY

IEEE 802.16 specifies multiple physical specifications including SC, SCa, OFDM and OFDMA. QualNet PHY802.16 only implemented the OFDMA PHY. OFDMA is similar to OFDM using multiple subcarriers to transmit data. However, while OFDM uses all available subcarriers in each transmission, different subcarriers could be arranged to different subscribers in downlink and each transmission could use a subset of the available subcarriers in uplink in OFDMA.

The mandatory features are implemented in current implementation. It supports variable channel bandwidth, different FFT sizes, multiple cyclic prefix time, and different modulation schemes such as QPSK, 16QAM, and 64QAM with convolutional encoding at variety encoding rates.

The raw data rates of the OFDMA are functions of several parameters such as channel bandwidths, FFT size, sampling factor, cyclic prefix time, modulation scheme, encoding scheme and encoding rate. It can be up to 70 Mbps by using high grade modulation scheme with other suitable parameters.

Implemented Features

  • OFDMA physical model
  • Variety channel bandwidth support
  • Multiple FFT size support
  • Multiple cyclic prefix time support
  • Multiple data rates support
  • BER-based reception quality estimation
  • Subchannel SINR representation
  • Data rate and transmission range estimation

Cellular Library

The Cellular Library can be incorporated into QualNet, EXata and NDT models, adding support for GSM communications.

In the Abstract Cellular Model, a single base station serves a circular service area that is divided into multiple sectors, each of which is allocated with a certain amount of bandwidth. For each base station, several control channels are defined. A large number of base stations cover the simulated area and they are connected to a hub, the switch center, with wired links. The hub routes the control and data messages to/from the base stations. An aggregated node emulates the services originated or destined to nodes outside the simulated area. A gateway connects to all the BSs and the aggregated node. With help from HLR, the gateway routes the information flows between MSs or between MS and the aggregated node.

The GSM model in QualNet models the behavior of Mobile Stations (MSs), Base Stations (BSs), and Mobile Switching Centers (MSCs), and the “Um” (BS-to-MS) and “A” (BS-to-MSC) interfaces. The MSs can be located anywhere and can be mobile. The BSs and MSC are stationary. The GSM model allows multiple MSs, multiple BSs, and a single MSC in any scenario. Each BS is connected to the MSC by a wired point-to-point link.

Implemented Features

  • Configuration of MSC, multiple Base Stations, and multiple Mobile Stations
  • Standard band is supported (900 MHz Mobile Stations and Base Stations)
  • Cell selection and re-selection
  • Dynamic channel assignment and release
  • Location update
  • Call setup and tear-down
  • Handover (intra-MSC and inter-cell/Base Station)

UMTS Library

The UMTS Library can be incorporated into QualNet, EXata and NDT models, adding support for Universal Mobile Telecommunications System (UMTS) standards based on GSM technology.

The Universal Mobile Telecommunication System (UMTS) is a third generation (3G) mobile communication system that provides a range of broadband wireless and mobile communication services. UMTS maintains the global roaming capability of the second generation (2G) GSM system and its packet-switch mode enhancement (GPRS system) and provides enhanced capabilities. Compared with 2G telecommunication systems, UMTS is able to support multimedia services including graphics, pictures, and video communications, as well as voice and data at a higher data rate and with better quality of service.

There are three major categories of network elements:

GSM Core Network Elements: Mobile Service Center (MSC), Visitor Location Register (VLR), Home Location Register (HLR), Authentication Center (AuC), and Equipment Identity Register (EIR).

GPRS Network Elements: Serving GPRS Support Node (SGSN), and Gateway GPRS Support Node (GGSN).

UMTS-specific Network Elements: User equipment (UE), and UMTS Terrestrial Radio Access Network (UTRAN) elements. UMTS targets to build an all-IP network by extending the second generation GSM/GPRS system and using complex technologies including Code Division Multiple Access (CDMA), Asynchronous Transfer Mode (ATM), and Internet Protocol (IP). GPRS is the convergence point between the 2G technologies and the packet-switch domain of UMTS.

LTE Library

The SCALABLE LTE Library can be incorporated into QualNet, EXata and NDT models, adding support for LTE-based communications.

The Long Term Evolution (LTE) Model Library provides high fidelity simulation of 4G cellular networks based on the 3GPP Release 9 standards. It is built on the SCALABLE network simulator to provide system-level scalability, fast execution speeds and detailed MAC and PHY modeling. It includes models of nodes called eNodeB (Base Station) and UE (Mobile Station).

Implemented Features

  • LTE Evolved Packet Core (EPC)
  • LTE Layer 2

The LTE PHY model is based on the 3GPP 36.3XX architecture, and specifies E-UTRAN physical layer models. The main functions of the E-UTRAN PHY module are:

  • Downlink transmission/reception using OFDMA
  • Uplink transmission/reception using SC-FDMA
  • Coding/decoding, modulation/demodulation
  • Multi antenna operation (MIMO)
  • CQI/RI/PMI reporting
  • Power Control
  • Cell Selection
  • Random Access
  • Measurements

The LTE models now support Hybrid Automatic Repeat Request (HARQ)  (NEW)

Federation Interfaces Library

The Federation Interfaces Library can be incorporated into QualNet and EXata models, adding support for multi-simulator integration.

Multiple simulators can be used to simulate different aspects of the same scenario. The results of such a co-operative simulation can be more realistic and meaningful than those obtained by using any single simulator. The simulators interoperate with each other via data sharing to achieve a consistent representation of the simulation environment. Several standards, such as Distributed Interactive Simulation (DIS) and High Level Architecture (HLA), have been developed to facilitate data sharing among simulators.

High Level Architecture

High Level Architecture (HLA) is a specification that enables two or more software programs (usually simulation software) to interoperate. The software programs communicate with each other through a Run-Time Infrastructure (RTI) module, which implements the HLA interface specification.

Distributed Interactive Simulation

Distributed Interactive Simulation (DIS) is an IEEE standard for interfacing multiple simulation tools into a single, real-time simulation. The transport of information between simulators is performed using UDP and broadcast and/or multicast IP. Although superseded by HLA and IEEE 1516, DIS still remains popular for its simplicity of operation and the ease of creating a DIS interface. In HLA terminology, the collection of communicating simulations is called a federation and each simulation is called a federate. The object and interaction classes used in the federation are defined in a module called Federation Object Model (FOM). Information is exchanged between simulations using this FOM.

Socket Interface

Communication between a SCALABLE application and the external program is implemented over a TCP socket, with the SCALABLE application acting as the server and the external program as the client. Several types of messages can be sent between the two processes.

Cyber Library for EXata

TIREM Propagation Library (1)

The Terrain Integrated Rough Earth Model (TIREM) Library can be incorporated into QualNet and EXata virtual network models, adding support for terrain propagation effects.

TIREM is a propagation model which predicts the pathloss along the propagation path over irregular terrain at frequencies between 1 MHz and 40 GHz. Based on the geometry of the terrain profile, the appropriate propagation behavior is used to calculate the pathloss.

The core technology for TIREM was developed by Alion Science & Technology Corporation under contract to the US Defense Information Systems Agency.  Alion licenses this core technology directly to customers for a fee.  The SCALABLE TIREM Library is a connector and a "wrapper" for the Alion code providing tight integration into QualNet and EXata virtual network models.  Customers who want TIREM functionality would purchase our TIREM Library and then contact Alion directly to purchase the core code. These two elements are then compiled together and linked into your QualNet or EXata simulation platform implementation.

Contact information for the TIREM core technology at Alion can be found HERE.

SCALABLE supports terrain data for both Cartesian and latitude/longitude coordinate systems. DTED and DEM, which both require latitude/ longitude coordinates, are the most commonly used.

Urban Propagation Library

The Urban Propagation Library can be incorporated into QualNet, EXata and NDT models.

The library supports propagation models for:

  • Automatic Model Selection
  • COST 231-Hata
  • COST 231-Walfish-Ikegami (COST-WI)
  • Okumura-Hata
  • Street Microcell
  • Street Mobile-to—Mobile
  • Suburban

When the Auto-select option for pathloss model is chosen, QualNet selects appropriate pathloss models based on the node location and urban terrain features. Different path-loss models are used according to their locations with respect to obstacles in the propagation path. QualNet allows selection of different model(s) for each source-destination pair and changes the models dynamically as the node positions change.

The COST 231-Hata propagation model is an empirical model that extends the Hata model to higher frequencies (1500-2000 MHz). It is a outdoor propagation model that is applicable to urban and suburban areas. The model is based on extensive measurement campaigns, and it is valid for flat terrain. The application of the COST-Hata-Model is restricted to situations where node's antenna height is above roof-top levels adjacent to the node.

  • Environment is urban, suburban, or open area
  • Frequency is in the range 150-2000 MHz (recommended)
  • Antenna height of the base station is in the range 30-200 meters (recommended)
  • Antenna height of the mobile station is in the range 1-10 meters (recommended)
  • Distance between the base station and mobile station is in the range 1-20 km (recommended)

The COST 231-Hata propagating model is accurate within 1 dB for distances ranging from 1 to 20 km.

The model is capable of distinguishing between man-made structures and provides different formulation for small, medium, or large cities and urban, suburban, or open areas.

The COST 231-WI propagation model is a combination of the Walfisch and Ikegami models. It is an empirical model that is based on different contributions from members of the "COST 231 Subgroup on Propagation Models". The model allows for improved path-loss estimation by consideration of more data to describe the character of the urban environment and it is applicable to metropolitan centres and urban areas. This model is statistical as no topographical data base of the buildings is considered.

Sensor Networks Library

The Sensor Networks Library can be incorporated into QualNet, EXata and NDT models, adding support for distributed sensor environments.

ZigBee is a specification for a suite of high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4 standard for Wireless Personal Area Networks (WPANs). ZigBee is targeted at RF applications that require a low data rate, long battery life, and secure networking. These networks are aimed at automation, remote control, and Wireless Sensor Network (WSN) applications. The IEEE 802.15.4 standard defines the physical layer (PHY) and Medium Access Control sublayer (MAC) specifications as the wireless communication standard for low-power consumption, Low-Rate WPAN (LR-WPANs).

Implemented Features

  • ZigBee Application
  • ZigBee (IEEE 802.15.4) MAC
  • ZigBee (IEEE 802.15.4) PHY

The SCALABLE ZigBee PHY is based on the IEEE 802.15.4-2006 standard. The PHY layer provides an interface between the MAC layer and the physical radio channel. It provides two services, accessed through two service access points (SAPs). These are the PHY data service and the PHY management service.

The PHY layer is responsible for the following tasks:

Activation and deactivation of the radio transceiver

Turn the radio transceiver into one of the three states,(i.e., transmitting, receiving, or off (sleeping)) according to the request from MAC sublayer. The turnaround time from transmitting to receiving, or vice versa, should be not more than 12 symbol periods.

Energy Detection (ED) within the current channel

It is an estimate of the received signal power within the bandwidth of an IEEE 802.15.4 channel. No attempt is made to identify or decode signals on the channel in this procedure. The energy detection time shall be equal to 8 symbol periods. The result from energy detection can be used by a network layer as part of a channel selection algorithm, or for the purpose of clear channel assessment (CCA) (alone or combined with carrier sense).

Link Quality Indication (LQI) for received packets

Link quality indication measurement is performed for each received packet. The PHY layer uses receiver energy detection (ED), a signal-to-noise ratio, or a combination of these to measure the strength and the quality of a link from which a packet is received. However, the use of LQI result by the network or application layers is not specified in the standard.

Clear Channel Assessment (CCA) for Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA)

The PHY layer is required to perform CCA using energy detection, carrier sense, or a combination of these two. In energy detection mode, the medium is considered busy if any energy above a predefined energy threshold is detected. In carrier sense mode, the medium is considered busy if a signal with the modulation and spreading characteristics of IEEE 802.15.4 is detected. And in the combined mode, both conditions aforementioned need to be met in order to conclude that the medium is busy.

Military Radios Library (2)

The Military Radios Library includes models for:

  • Link 11
  • Link 16
  • Multi-Generator (MGEN) Toolset
  • Threaded Application
  • Compact Terrain Database
  • FCSC Radio Prototype

Details on this library are available upon request.


(1) This library requires code from a third party.

(2) This library is subject to export restriction under the International Traffic in Arms Regulations (ITAR) 22 CFR 120-130. International sales of these modules require authorization from the US Department of State.