Universidad Politécnica de Madrid

Escuela Técnica Superior de Ingenieros de Telecomunicación

Máster Universitario en

Ingeniería de Redes y Servicios Telemáticos

PROPUESTA DE TRABAJO FIN DE MÁSTER

CHARACTERIZATION OF THE SATELLITE DATA

LINK FOR AIR TRAFFIC SURVEILLANCE

Author

Gustavo Ambrosio Vicente

i

Change Control

Document Purpose Propuesta de Trabajo Fin de Máster

(TFM)

Document Title Characterization of the Satellite Data

Link for Air Traffic Surveillance

Author Gustavo Ambrosio Vicente

Director Carlos Miguel Nieto

Departamento Ingeniería Sistemas

Telemáticos

Version 27th October 2013

ii

Contents

Change Control ...................................................................................................................... i

Contents .................................................................................................................................. ii

List of Figures ....................................................................................................................... iii

List of Tables ......................................................................................................................... iii

Acronyms .............................................................................................................................. iii

1 Introduction .................................................................................................................... 5

2 Objectives ........................................................................................................................ 8

2.1 Datalink characterization and capacity assessment .......................................... 8

2.2 Statistical models for datalink characterization ................................................. 9

3 TFM Organization ........................................................................................................ 10

3.1 Introduction to Air Traffic Surveillance ............................................................ 10

3.2 Datalink characterization .................................................................................... 11

3.3 Statistical models .................................................................................................. 11

3.4 Conclusions and Future Work ............................................................................ 12

4 References ...................................................................................................................... 13

About the Author ................................................................................................................ 15

iii

List of Figures

Figure 1. ADS-B System Architecture ................................................................................ 7

List of Tables

Table 1. Acronyms................................................................................................................ iv

Table 2. CNS Systems with Terrestrial and Satellite technologies ................................. 5

Acronyms

Acronym Description

ADS-B Automatic Dependent Surveillance Broadcast

ATC Air Traffic Control

APT Airport Area

ATM Air Traffic Management

CNS Communication, Navigation and Surveillance

CPDLC Controller-Pilot Data Link Communication

DME Distance Measuring Equipment

ENR En-Route Area

ESA European Space Agency

GEO Geo Stationary Orbit

GNSS Global Navigation Satellite System

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GPS Global Positioning System

HF High Frequency

ILS Instrument Landing System

ISL Inter Satellite Link

LEO Low Earth Orbit

ORP Oceanic Remote and Polar Areas

PIAC Peak Instantaneous Aircraft Count

PSR Primary Surveillance Radar

R&D Research and Development

SSR Secondary Surveillance Radar

TMA Terminal Maneuvering Area

VDL VHF Data Link

VHF Very High Frequency

VOR VHF Omni directional Range

Table 1. Acronyms

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1 Introduction

The Aeronautical community expects a notable increase of Air Traffic demand on

European skies within the next decade. In order to address such expected increase, the

European aeronautical stakeholders are investing a lot of R&D effort towards the

modernization of the current Air Traffic Management (ATM) system. In this context,

the core R&D Programme at European level is SESAR, the Single European Sky ATM

Research initiative [9], with the participation of Eurocontrol, Air Traffic Regulators and

Aeronautical industry at European level.

The Space community is also committed to the modernization of the ATM system

with the involvement in several R&D projects such as the ESA Iris Programme [10],

which aims to develop a new satellite-based communication system for the future

SESAR ATM infrastructure.

In order to achieve this modernization, it is necessary to address the three main

pillars of the ATM infrastructure: Communication, Navigation and Surveillance (CNS).

Traditionally, the operation of CNS aeronautical systems rely on terrestrial based

technologies: radio navigation aids, radar, voice communications, etc. The satellite

technology has been recently introduced and it will play a very important role in the

modernization of the CNS/ATM infrastructure: GPS will replace radio navigation aids,

air-ground communications will rely on a satellite datalink, etc. Table 2 includes an

overview of terrestrial and satellite-based technologies used in CNS systems.

Terrestrial-based

Technologies

Satellite-based

Technologies

Communications VHF, HF (Voice)

VDL (Data)

CPDLC

Iris Satcom (future)

Navigation Radio Navigation Aids

(VOR, DME, ILS)

GPS, GNSS

Surveillance Primary and Secondary Radar

(PSR, SSR)

ADS-B and Multilateration

Space-based ADS-B

(future)

Table 2. CNS Systems with Terrestrial and Satellite technologies

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In the scope of this thesis, we will focus on the Surveillance branch of the ATM

infrastructure. Besides the traditional radar systems for surveillance (PSR, SSR), the

aim of the current work is to study a more recent technology which is referred to as

ADS-B (Automatic Dependent Surveillance Broadcast). The ADS-B technology is

defined according to the following:

Automatic: Periodically transmits information with no pilot or operator input

required.

Dependent: Position and velocity are derived from Global Positioning System

(GPS) or a Flight Management System (FMS).

Surveillance: A method of determining position of aircraft, vehicles or other

assets.

Broadcast: Transmitted information available to anyone with the appropriate

receiving equipment.

The ADS-B conventional system consists of two main elements: (1) a ground based

receiver and (2) an aircraft transponder/transceiver. The aircraft is able to determine

its position based on GPS (Dependent definition), and then use the ADS-B transponder to

send the corresponding surveillance report to a Ground Station. The Ground Station

has an ADS-B receiver that decodes the information and forwards the surveillance

reports to the Air Traffic Control (ATC) centre.

The ADS-B conventional system relies on a terrestrial data link to enable the

communication between the aircraft transponder and the ground-based receiver using

the 1090 Mhz frequency band. This system is operational in Airport areas (APT) and in

Continental areas, including Terminal Maneuvering areas (TMA) and En-route areas

(ENR). However, the system is not operational in Oceanic, Remote and Polar areas

(ORP).

In order to cover the gap of the ORP areas, it is necessary to introduce a satellite

communications system that will enable worldwide coverage complementing the

existing ADS-B infrastructure. The introduction of the satellite technology in the ADS-

B system is a very innovative solution that is currently under development in the scope

of several initiatives in Europe [4][11] and the USA [13].

Figure 1 depicts the ADS-B system architecture including (a) the terrestrial-based

solution which is operational today in the APT/TMA/ENR areas and (b) the satellite-

based solution which is planned for the future in order to cover the ORP areas.

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Figure 1. ADS-B System Architecture

From the Air Traffic Management point of view, the capability of global coverage

provided by the future ADS-B system, will enable the optimization of dense oceanic

routes, resulting in aircraft fuel savings, a reduction in greenhouse gas emissions, and

enhanced safety in airspace when ADS-B reporting aircraft can be displayed on a radar

screen at an Air Traffic Control Centre.

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2 Objectives

This master thesis belongs in general to the area of Networks Design and in

particular to the area of Satellite Networks.

The thesis is conceived in the scope of the R&D work that is currently ongoing for

the modernization of the Air Traffic Surveillance ADS-B infrastructure using a Satellite

Communications System.

In the context described in Section 1, this thesis aims to study the characterization of

the satellite datalink that will enable the download of ADS-B surveillance data to the

Air Traffic Control centre in the Ground Segment. Figure 1 depicts in “yellow” the

satellite downlink which is intended to be characterized in this study.

The characterization will address the analysis of the ADS-B data communication

traffic profile and will derive a bandwidth estimation for the satellite datalink,

according to a capacity assessment which depends on the amount of air traffic.

The characterization of the satellite datalink is an important contribution to the

global design of the future satellite system that is planned in order to enable global

surveillance coverage using ADS-B.

Hereinafter we describe in more detail the objectives of this master thesis.

2.1 Datalink characterization and capacity assessment

Although the primary objective is to cover the gap of ORP areas, the current design

of the future satellite-based ADS-B system aims to achieve full coverage, i.e. to be able

to monitor the air traffic worldwide including every airspace (APT, ENR, TMA, ORP).

In order to fulfill this requirement, it is planned to design a full constellation of

satellites in Low Earth Orbit (LEO).

The LEO constellation has to be designed according to the mission requirements in

order to enable (1) the acquisition of the ADS-B signals from the aircrafts and (2) the

delivery in real-time of the ADS-B surveillance reports to the Ground Stations.

As it is stated above, this thesis aims to characterize the satellite downlink of the

future ADS-B system. So the first goal of the characterization will be to study the

different design alternatives for the datalink, fulfilling the requirement of data delivery

in real-time from space to ground. Several possibilities will be considered for the

design, including:

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1. Use a wide network of ground stations that are able to keep a permanent

communication link with the satellites

2. Use Inter-Satellite Links (ISL) and limited number of ground stations

3. Use a GEO Satellite Relay

Besides the study about the downlink architecture, the characterization of the

satellite datalink will include an analysis regarding the ADS-B data communication

traffic profile and the estimation of the required bandwidth in the satellite downlink,

i.e which is the information transfer rate (in bits per second) that is required in order to

enable the download of the ADS-B data collected by the satellites in the LEO

constellation.

The bandwidth estimation implies a Capacity Assessment concerning which is the

amount of data that needs to be downloaded to the Ground Segment in real-time. The

Capacity Assessment depends on several factors including:

a) The Aircraft Count: number of aircrafts that are detected by the LEO satellite

constellation in the different airspaces (APT, TMA, ENR, ORP)

b) The ADS-B message distribution per aircraft, including the message size (in

bytes) and the message update rate (i.e. rate of messages per second)

2.2 Statistical models for datalink characterization

The second objective of this master thesis is to apply statistical methods in order to

complete the satellite datalink characterization that is introduced in Section 2.1.

As it is stated above, the characterization of the satellite datalink includes a capacity

assessment regarding the amount of ADS-B data that needs to be exchanged with the

Ground Segment in real-time. From now on, we can refer to this amount of data as a

variable named “ADS-B traffic quantity”. The capacity assessment based on the “ADS-

B traffic quantity” determines the required bandwidth for the satellite downlink.

This work aims to model the “ADS-B traffic quantity” variable using statistical

methods. The “ADS-B traffic quantity” is understood as a function of two basic

variables: the number of aircrafts (Aircraft Count) and the frequency of message

exchange between an aircraft and the Ground ATC System (ADS-B message update rate).

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In the scope of the statistical analysis, both of the latter variables can be considered

as “random”, and so it is the “ADS-B traffic quantity”. Hence, the network design

should take into account uncertainty conditions and a therefore a probability

distribution is required to deal with this uncertainty.

Relative little work has been done on the analysis of the “ADS-B traffic quantity”,

taken into account its uncertainty. A recent study of the University of Salzburg [2]

deals with scenarios of future communication air traffic volumes, but they do not

associate a probability to each scenario and, as a result, it is not possible to deal with

the underlying uncertainty. Here in the current thesis, a probability function will be

considered to model the air traffic variability, in such a way that it is possible to assess

the uncertainty surrounding the global network design.

3 TFM Organization

This chapter introduces the preliminary organization of the master thesis with the

different chapters and expected contents per chapter.

3.1 Introduction to Air Traffic Surveillance

Air Traffic Surveillance Technologies: Radar (PSR, SSR), ADS-B,

Multilateration, etc

Airspace Domains: APT, TMA, ENR, ORP

Architecture of the ADS-B terrestrial system

Architecture of the ADS-B satellite based system

R&D initiatives in the scope of ADS-B satellite-based systems

o USA: Aireon Iridium Next [5] [6] [12] [13]

o European Projects [4][11][14]

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3.2 Datalink characterization

Analysis of the design alternatives for the satellite downlink architecture

o Wide network of Ground Stations

o Inter-Satellite Links (ISL)

o GEO Satellite Relay

Review of state-of-the-art studies for datalink characterization and capacity

assessment

o Characterization of the Air Traffic Model and ATM/CNS services.

Eurocontrol study [1]

o Datalink characterization performed by the University of Salzburg in

the scope of the ESA Iris project [2]

o Analysis performed by CNES and ESA in the scope of the “Satcom

for ATM” project [15]

Capacity assessment for the satellite downlink

o ADS-B data communication traffic profiles

o Analysis of the required information transfer rate (bps) and

bandwidth estimation

o Use cases for different communication air traffic profiles considering:

Several airspaces in terms of density: High-Density, Medium-

Density, Low-density

Several airspace domains: APT, TMA, ENR, ORP

3.3 Statistical models

Statistical model of the Aircraft Count for different airspaces

o Estimation of the number of aircrafts in a specific region of the

global airspace

o Usage of the Poisson distribution for the Probability Distribution

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Statistical model of the ADS-B message distribution per aircraft

o Estimation of the update message rate

o Usage of the Poisson distribution for the Probability Distribution

Simulations of the statistical models

o Evaluation of the Probability Distributions (Aircraft Count, Update

Rate) for several uses cases

o Usage of the tool “Octave” for the simulations

3.4 Conclusions and Future Work

This chapter will include the conclusions of the master thesis and the analysis of

the future work to be done in the scope of the research area of the thesis.

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4 References

[1] Eurocontrol / FAA. “Communications Operating Concept and Requirements for the Future Radio System (COCR)”. Version 2.0, May 2007.

[2] C.Morlet, M.Ehammer, T.Gräupl, C.- H.Rokitansky, "Characterisation of the datalink communication air traffic for the European Airspace." In Proc. 29th DASC, 2010.

[3] “Minimum Operational Performance Standards for 1090 MHz Extended Squitter Automatic Dependent Surveillance Broadcast (ADS-B) and Traffic Information Services Broadcast (TIS-B)” (RTCA DO-260B) RTCA, December 2009.

[4] Blomenhofer, H.; Rosenthal, P.; Pawlitzki, A.; Escudero, L., "Space-based Automatic Dependent Surveillance Broadcast (ADS-B) payload for In-Orbit Demonstration," Advanced Satellite Multimedia Systems Conference (ASMS) and 12th Signal Processing for Space Communications Workshop (SPSC), 2012 6th , vol., no., pp.160,165, 5-7 Sept. 2012

[5] Noschese, P.; Porfili, S.; Di Girolamo, S., "ADS-B via Iridium NEXT satellites," Digital Communications - Enhanced Surveillance of Aircraft and Vehicles (TIWDC/ESAV), 2011 Tyrrhenian International Workshop on , vol., no., pp.213,218, 12-14 Sept. 2011 [6] Gupta, O.P. “Revolutionizing air travel through Aireon's global space-based ADS-B surveillance”. Integrated Communications, Navigation and Surveillance Conference (ICNS), 2013

[7] Li, Tianyuan; Sun, Qibo; Li, Jinglin, "A Research on the Applicability of ADS-B Data Links in Near Space Environment," Connected Vehicles and Expo (ICCVE), 2012 International Conference on , vol., no., pp.1,5, 12-16 Dec. 2012

[8] Coya, José Luis. “Sistemas Satélite en Aeronaves. Análisis del escenario actual y futuros caminos de investigación e innovación.” Trabajo Fin de Master (TFM) presentado en Junio 2012. Máster en Ingeniería de Redes y Servicios Telemáticos, DIT-UPM.

[9] SESAR. ”Single European Sky ATM Research”. [Online]. Retrieved 22/09/2013 from: http://www.sesarju.eu/

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[10] ESA. “Iris Programme. ATM communications via satellite”. [Online]. Retrieved 22/09/2013 from: http://telecom.esa.int/telecom/www/area/index.cfm?fareaid=56

[11] DLR Press Release. “ADS-B over satellite – first aircraft tracking from space” [Online]. Retrieved 22/09/2013 from: http://www.dlr.de/dlr/presse/en/desktopdefault.aspx/tabid-

10308/471_read-7318/year-all/#gallery/11231

[12] IRIDIUM. “Iridium Next Constellation”. [Online]. Retrieved 22/09/2013 from http://www.iridium.com/About/IridiumNEXT.aspx

[13] AIREON. [Online]. Retrieved 22/09/2013 from http://www.aireon.com/Home

[14] Press Release WSJ. “DLR, Thales Alenia Space and SES Develop Innovative Space-Based Air Traffic Control Monitoring System”. [Online] Retrieved 19/10/2013 from: http://online.wsj.com/article/PR-CO-20131017-910112.html

[15] ESA, CNES. “SATCOM for ATM Programme”. [Online] Retrieved 19/10/2013 from: http://telecom.esa.int/telecom/www/object/index.cfm?fobjectid=27783

[16] Eurocontrol. “CASCADE Programme”. [Online] Retrieved 19/10/2013 from: http://www.eurocontrol.int/surveillance/cascade

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About the Author

Academic Background

Gustavo Ambrosio holds a MSc degree in Telecommunication Engineering (2007)

and a postgraduate Master in Space Technology (2009) by Universidad Politécnica de

Madrid (UPM). He is currently studying the “Master Universitario en Ingeniería de

Redes y Servicios Telemáticos” at Universidad Politécnica de Madrid (UPM).

Professional Background

He has expertise in R&D with involvement in several projects within the aerospace

sector both at national level (CENIT, Avanza) and European level (ESA, FP7, Artemis).

He has worked at the company Integrasys from 2007 to 2012 as a R&D Software

Engineer, participating in several research projects in the scope of Air Traffic

Management (ATM) and leading the development of the “System Wide Information

Management” (SWIM) system.

Since 2012 he is working in Thales Alenia Space (Deutschland) as a Space Software

Engineer, being involved in a research project in the scope of space-based Air Traffic

Surveillance with ADS-B technology.