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Modeling and testing data link technologies in a highly realistic environment.

DREAM is the most advanced solution on the market for data link communications testing and modeling. It is a versatile, fully automated platform that immerses data link communications technologies or equipment into a highly realistic environment for test purposes. DREAM is used by the FAA and by SESAR JU in Europe – as well as by major aircraft manufacturers – to accompany the deployment of datalink.
How does it work?

DREAM is able to model vast portions of airspace – as well as vast ground communications networks – all in a fully-controlled lab environment. DREAM’s simulated airspace portions involve hundreds and even thousands of moving aircraft, each exchanging data with simulated ATC or airline systems through widely-deployed emulated ground infrastructures.

The DREAM model may be connected with actual data link implementations – either ground-based or airborne system components – to put them to the test. This System Under Test (SUT) connects to DREAM either via the VHF link or via an A429 bus connection. Test runs can last anywhere from hours to several days, and involve hundreds of thousands of datalink messages exchanged.

ALTYS’s datalink experts have perfected the DREAM model through years of experience in testing activities – allowing us to reproduce the real, observed scenarios that make the VHF data link environment so complex. Testing your data link technologies and equipment with the DREAM model is the only way to ensure they are mature prior to industrialization and large-scale deployment.
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Unlimited configuration options. Unlimited test possibilities.

DREAM provides infinite possibilities for testing through sophisticated configuration options. DREAM users have full control over simulated behavior through a number of different input criteria, including:
✓ Aircraft configuration and traffic scenario: (VDL Mode 0/A or VDL Mode 2 aircraft; available applications; flight volumes …)
✓ Ground network topology and station deployment (geographical position of VGS; network infrastructures; service providers; airports; ATC centers…)
✓ ATC and airline application profiles (level of data link equipage per airline; aircraft type…)
Powerful reporting and analysis capabilities

DREAM integrates ALTYS’s powerful reporting and statistics engines, allowing users to deeply analyze simulation and test results. During the test runs, DREAM users can access a real-time monitoring interface that displays the simulation status. Following the simulation, users access Key Performance Indicators, maps, and a number of test reports that can be generated automatically.

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A proven propagation model

DREAM implements the RF propagation model developed and perfected by ALTYS for over a decade. This propagation model has been used as the model of reference for all European and U.S. VHF data link capacity studies since 2004.
It has been validated against theoretical models, real measures recorded during flight test campaigns, and against other models during cross-check simulations in a continuous and iterative calibration process.
It realistically simulates all RF physical behaviors and finely restitutes all phenomena that may be experienced at aircraft or ground-station antenna level.

These phenomena include:

  • Free-space / multipath propagation, large-scale fading (two-ray model), Doppler effect

  • Channel sensing per emulated entity (CSMA, TDMA)

  • Antenna equipment behavior (radiation pattern), antenna gain, signal strength levels, noise estimation, Signal-to-Noise Ratio (SNR)

  • Frame collision: co-channel, co-site interferences

  • Bit Error Rate (BER), Frame Error Rate (FER), Reed-Solomon correction effects

How is DREAM used?


DREAM is used for evaluating the performance of new data communications technologies in their targeted operational environment. Our customers use the DREAM model for the following purposes: - System design and capacity studies - Frequency planning - Ground station deployment surveys - Protocol evolution assessment


DREAM is used for immersing new data communications equipment and systems into a wholly virtualized test environment. Our customers rely on DREAM for the following tests: - Airborne and ground system components testing - Dynamic, stochastic, and robustness testing - Certification of equipment or systems - Achieve the “Best In Class” avionics label

Contact Us
If you are interested in learning more about DREAM, please
send us an e-mail.
Case Studies

SESAR Joint Undertaking, ELSA project

The ELSA Study, or the VDL Mode 2 Measurement, Analysis, and Simulation Campaign, was launched by SESAR JU in 2014 in order to evaluate VDL Mode 2’s capacity to support SESAR concepts. ALTYS was named one of the project’s Work Area leaders, and was in charge of large-scale simulations and airport equipment testing in realistic RF conditions using the DREAM platform.

Given the growing number of aircraft communicating via the VDL Mode 2 link in Europe, one of the project’s objectives was to evaluate the potential performance and capacity gains – as well as the potential issues – from VDL Mode 2 multifrequency deployment.

DREAM enabled this aspect of the study, since it is able to simulate a multifrequency environment, while varying test criteria such as ground network deployment and configuration, number and configuration of aircraft, and factors such as frequency switching methods (ground-initiated or aircraft-initiated).

DREAM also enabled the in-depth analysis of the effects of the current geographical deployment of VHF Ground Stations (VGS). As part of the ELSA project, DREAM also served as a fully representative RF environment in which to inject avionics systems in order to assess their performance. This allowed interoperability tests to be performed on the avionics systems in question, including physical layer tests (VDR RF tests), VDL Mode 2 multifrequency tests, virtual flight tests, and end-to-end CPDLC tests.

DREAM enabled the ELSA consortium to identify a list of “best in class” avionics systems. Tests were performed against many main CMUs and VDRs available to the industry, in order to determine their performance and robustness. Avionics systems identified as “best in class” were determined to comply with EASA’s ATN and VDL Mode 2 performance specifications.
FAA Data Comm Program, AC-SIM

A version of the DREAM platform was provided to Harris Corporation to provide key large-scale testing support to the FAA on the initial phase of the FAA Data Comm Program. ALTYS played a critical role in Integration and Testing activities performed on the Data Comm Network Services Test Bed at the FAA’s William J Hughes Technical Center in Atlantic City, NJ. AC-SIM, a derivative of DREAM, is a distributed and automated aircraft simulation platform.

Starting in June 2013, ALTYS was involved in the requirement and scenario definition phase with Harris and the FAA, working on a test solution capable of modeling entire portions of US airspace. ALTYS was uniquely positioned to provide high-quality ready-to-use test solutions meeting the FAA’s requirements, allowing for rapid implementation to maintain a tight schedule.

AC-SIM is used extensively on the Data Comm Program to validate and stress test all segments of Data Comm’ services integrated together in a lab environment. AC-SIM runs aircraft in a total of up to 8,000 flights for test runs lasting several days, in which hundreds of thousands of CPDLC messages are exchanged.

Managing such high volumes of traffic requires great performance and stability. The platform includes powerful scripting capabilities and can accommodate multiple simultaneous user sessions.