Final Report 

of the 

Working Group 

on 

Oceanic and Sparse Area Communications 

Air Traffic Services Subcommittee 

FAA Research, Engineering, and Development Advisory Committee 

8 June 2004
ii

(This page left blank)
i

Table of Contents

I Introduction and Summary 1

 Study Process 1

 Structure of Report 2

 Findings 3

 Recommendations 5

II Oceanic Operations 7

 Growth Forecasts 7

 Present Oceanic ATM 8

 Near-Future Oceanic ATM 10

 Future Oceanic ATM 11

III Requirements to Support Reduced Separation 15

 Separation Assurance 15

 New CNS Capabilities to Improve Oceanic Separation 22

IV Communication Requirements to Support Oceanic Weather 

Data Exchange 

25

V Oceanic Communication Alternatives – Present and Near 

Future 

27

 HF Voice 27

 HF Data Link 27

 INMARSAT 28

 FANS 33

 Enhanced TDMA Over INMARSAT 37

 Iridium 38

 Globalstar 43

 NexSAT 46

Appendices 

 A. Terms of Reference 51

 B. Study Participants 53

 C. List of Presentations 55

 D. Bibliography 57
ii
1

I - Introduction and Summary 

The efficiency of aircraft operations in oceanic and sparse area airspace and the capacity 

of oceanic air routes are limited in part by the absence of rapid, highly reliable means of 

communication between the pilot and controller (or, more generally, between the aircraft 

and the controlling facility). While general communications capability has rapidly 

advanced in recent decades, oceanic operations1 still depend, in most areas, on relayed 

voice radios operating in the high frequency band, unchanged for the past 50 years or 

more except for equipment improvements. 

In oceanic airspace large inter-aircraft spacings are maintained, and aircraft deviations 

from preset flight plans are constrained, because of uncertainties in aircraft position and 

the reliability of air/ground communications. This limits both the efficiency and capacity 

of oceanic operations. Air traffic in oceanic and remote areas has lessened with the 

economic decline and the terrorist attack of September 11, 2001, and this has provided a 

respite from the aggressive growth rates in the late 1990s. However, the recent 2003 

FAA Forecast predicts a return to more normal growth rates beginning in 2005. Even 

with the introduction of RVSM and improved navigational accuracy (better INS, GNSS), 

access to best weather routes and the ability to change flight paths once en route is still 

limited due to the lack of real-time surveillance and rapid, reliable communication. 

A variety of new communication technologies are available to enhance communication 

between aircraft and control facilities. As a follow-on to an earlier study2, the Air Traffic 

Services (ATS) Subcommittee of the FAA Research, Engineering, and Development 

Advisory Committee (REDAC) recommended that an additional study address, in more 

detail, the issues of oceanic and remote area communication. The FAA concurred in this 

recommendation, following which the REDAC ATS Subcommittee formed a Working 

Group to assess the need for improved communication and the technical options 

available, and to develop recommendations for actions, if any, which the FAA should 

undertake. 

Study Process

The Working Group solicited inputs from all segments of the aviation community with a 

stake in oceanic operations. These included ATM service providers, communication 

service providers, aircraft operators, and R&D organizations with relevant activities: 

 

1

 In this report, the term “oceanic operations” will be used to refer to aircraft operations in airspace beyond line-of-sight 

of ground-based communication and surveillance facilities, both over oceans and over sparsely populated and/or 

underdeveloped areas, e.g. much of Asia and Africa and polar regions. In some oceanic airspace both capacity and 

efficiency are issues; in the remainder safety and operating efficiency are the primary concerns. 

2 Kern, et al; Recommendations For Aviation Communications Research Investments; report of the Air Traffic 

Services Subcommittee Aviation Communication Research and Technology Subgroup; March 2003 
2

ATM Service providers 

 FAA 

 Air Services Australia (via written communications) 

 Nav Canada (via written communications) 

 Eurocontrol 

Communication Service Providers 

 ARINC – Satellite and HF 

 INMARSAT 

 Iridium 

 Boeing - CONNEXION 

Aircraft Operators 

 Air Transport Association – for scheduled airlines 

 National Business Aircraft Association – for business aviation 

 FedEx – for cargo airlines 

 DoD 

R&D Organizations 

 Mitre/CAASD 

 MIT Lincoln Laboratory 

 NASA Glenn Research Center 

 DoD 

To the extent available, copies of the presentations by these organizations are included in 

the “Appendices” section of the enclosed CDROM. 

In addition to these inputs, Working Group members contributed substantially from their 

own knowledge and experience. 

Structure of the Report

This initial section of the report concludes with summaries of the principal findings and 

conclusions of the Working Group. It is followed by several sections that discuss in more 

detail oceanic operations and communication alternatives. Appendices include the 

Working Group Terms of Reference, its membership and meeting participants, meeting 

agendas, and a bibliography. The enclosed CDROM contains an electronic copy of this 

report, plus copies of all available presentations to the working group and copies of 

available reference material. These are included as an aid to readers who wish to 

understand in depth the basis for the Working Group conclusions and recommendations 

and to make readily available reference material to assist in subsequent studies in this 

area. 
3

Findings

1. The efficiency and capacity of aircraft operations in oceanic and sparse area airspace 

are limited by a number of factors, one of which is the lack of a rapid, reliable means of 

communication between aircraft and control facilities. This results in significant 

economic penalties to aircraft operators by forcing many flights to use non-optimum 

routes, a situation that will worsen as traffic levels increase in the future. 

2. The introduction of RVSM (reduced vertical separation minima) on oceanic routes has 

significantly alleviated the near-term capacity problem, allowing more aircraft to operate 

on optimum or nearly-optimum flight paths. However, in many regions aircraft are still 

limited in their ability to make non-preplanned changes in flight paths once en route, e.g. 

to perform en route climb or to avoid unforecast adverse winds or hazardous weather. In 

addition, as oceanic traffic grows, there will be increasing pressure to allow operation at 

reduced interaircraft spacings. 

3. Most providers of oceanic ATS services are deploying new oceanic ATS automation 

systems that support ADS-A and CPDLC FANS-1/A satellite data link applications. 

These include: 

 Australia - TAAATS 

 New Zealand - OCS 

 Fiji - EASY 

 Canada – GAATS 

 UK - GAATS 

 US – ATOP 

4. Using these new oceanic automation systems and based on new ICAO oceanic 

separation standards, aircraft equipped with approved ADS (automatic dependent 

surveillance), controller/pilot data link communication capability, and the appropriate 

RNP capability will be able to operate at reduced interaircraft spacing and to change 

flight paths to respond to varying flight conditions. To achieve maximum benefits, all 

users of the airspace must be equipped. The FAA/RTCA CONOPS3

 envisions that such 

equipage will be required in the mid- to far-term. To foster universal equipage, it is 

desirable that the cost of equipage to the aircraft operator be commensurate with the 

economic benefit resulting from more efficient operation. 

5. Existing means of oceanic communication are either expensive or do not meet the 

requirements to support improved ATS services. These include: 

 HF voice – does not meet requirements for improved ATS services 

 FANS/INMARSAT – expensive to install and operate 

(Current) HFDL (high frequency data link) – does not meet requirements for 

improved ATS services 

 

3

 RTCA document DO-244 – Government/Industry Guidelines and Concept for National Airspace Analysis and 

Redesign 
4

 

6. There are both existing and proposed communication systems that could provide part 

or all of the requisite communication capability if they can meet US and international 

requirements. These include4

: 

 Enhanced TDMA over INMARSAT 

 Improved HFDL 

 Iridium 

 NexSAT 

The principal attributes of the systems in Findings 5&6 are summarized in Table 1. 

Meets rqmts 

for ( ) sep Comm 

Alternative Coverage Cost to 

Users 

Cost to 

ATC Voice Data

Meets 

current 

rqmts. 50/50 30/30 

Comments 

HF voice Global Low Low Y N Y N N Moderate 

reliability 

FANS/ 

INMARSAT 

All 

longitudes, 

no polar 

High Low Y Y Y Y Y 

Commercial; only 

2.5% income from 

aviation 

Current 

HFDL Global Low Low N Y N N N Commercial; not designed for ATC

Enhanced 

TDMA over 

INMARSAT 

All 

longitudes, 

no polar 

Low Low N Y ? ? N* R&D concept; not 

yet realized 

Improved 

HFDL Global Low Low N Y ? ? N* Under development 

Iridium Global Low ? Y Y ? ? ? 

Commercial; longterm viability 

uncertain 

NexSAT Europe +?; 

no polar ? High Y Y Y Y Y R&D program; not 

yet realized 

* By itself, only provides data link, not voice 

Table 1 

7. A major element of the cost of equipping an aircraft for ADS and CPDLC is 

interfacing the communication system with the aircraft’s navigation and flight control 

system, and providing the pilot interface. This problem is most severe on the older 

(legacy, classic) aircraft without modern flight control systems and CMU’s 

(communication management units). To increase the economic viability of equipping 

such older aircraft, consideration should be given ways to reduce the cost of this 

interface. 

8. While its long-term economic viability is uncertain, Iridium appears to be an attractive 

candidate for communication to support global ATM. (It is possible that the adoption of 

Iridium as an element of international ATS communications would itself enhance its 

economic viability.) 

4

 Because of its limited coverage in oceanic regions, Globalstar is not considered to be a viable candidate. 
5

9. It is likely that the required communication performance will be met not by a single 

very high reliability system but by a combination of subsystems that together meet the 

communication requirements. 

Recommendations

The FAA should initiate an activity to develop standards for an oceanic communication 

system that can meet the needs of advanced oceanic operations. The system should 

initially meet the requirements for 30/30 separation (30 miles lateral, 30 miles 

longitudinal), but should have the potential for closer spacings when and if indicated by 

demand. The standards should be realizable by a system that is economical to install and 

operate for a broad class of aircraft. 

The performance standards should be expressed as Required Communication 

Performance (RCP). 

Specific activities should include: 

1. Designate organizational responsibility within the FAA for the development of 

oceanic communication standards and systems 

2. Assess the performance of Iridium, especially its short-message service, as a means of 

supporting ADS and CPDLC. 

3. Assess the ability of upgraded HFDL to serve as a primary means of communications 

for oceanic operations. 

4. Examine new approaches5, e.g. TDMA over INMARSAT 

5. Reexamine the minimum communication performance required to support reduced 

oceanic separation standards (initially 30/30, but ultimately lower) 

6. Request RTCA to form a Special Committee on oceanic data link to encourage and 

provide a forum for industry involvement. An early task for this Special Committee 

would be defining a standard interface among aircraft flight control systems, CMU 

and pilots (see Finding 7 above). 

7. Conduct a trade study that examines the user implementation costs and benefits for 

each of the proposed links and for a broad class of aircraft including cargo, business 

and military, over the next several decades. 

8. Participate actively in the Eurocontrol NexSAT program. 

9. Continue to work with ICAO and other relevant groups to ensure that new 

international standards for minimum communication performance are developed and 

adopted. 

10. Investigate means of reducing FANS installation and/or message traffic costs. 

11. If a potential new communication system emerges from these activities, identify a 

“lead carrier” oceanic airspace user to initiate the avionics certification process. 

 

5

 In addition to the approaches discussed here, two additional approaches should be considered. The first is the Boeing 

Connexion system. While Connexion is primarily focused on large-aircraft passenger communication, it will be carried 

by many airline aircraft and could potentially be useful for ATC communication. The second is the 

Boeing/INMARSAT proposal for Aero-BGAN (Broadband Global Aero Network), which appears to have many of the 

desired attributes. Unfortunately the Working Group did not become aware of the details of this proposed system until 

after the completion of its data-gathering activities. 
6

(This page left blank)
7

II – Oceanic Operations 

Growth Forecasts

The air traffic in oceanic and remote areas has lessened with the economic decline and 

the terrorist attack of September 11, 2001. While this has provided a respite from the 

aggressive growth rates in the late 1990s, the recent 2003 FAA Forecast predicts a return 

to higher rates beginning in 2005. 

The FAA 2003 Forecast asserts the following key points: 

• There will be a return to positive economic growth by 2005 

o Most growth expected in Latin America and Asia/Pacific 

o The U.S. economy will slightly lag the rest of the world 

o International passenger markets will grow faster than domestic U.S. 

• Forecast passenger annual growth rates for 2005-2014 

o Domestic U.S. - 4.6% 

o All International - 4.2% 

o Latin America - 5% 

o Pacific - 4.9% 

• Forecast cargo annual growth rates for 2005-2014 

o Domestic RTM - 4.4% 

o International RTM - 6.3% 

o One carrier expects a 12% growth rate 

• The key forecast risks are 

o Overly optimistic Asian economic forecasts 

o Impact of terrorism and heightened security measures 

o Impact of increasing fuel costs 

A recent AIAA paper6 by Jiang, Ren, and Hansman noted that China’s soaring economy 

– growing at 9.4% during 1978-2002 - was accompanied in 2002 by an international air 

cargo increase of 19.3%. It also suggests air cargo – domestic and international - growth 

rates will continue to be high through 2020. 

The potential impact on oceanic air traffic will be an increased demand for the best, most 

economic routes that avoid bad weather. Since airlines have been recently emphasizing 

profitability over market share, they will have increased interest in the most economical 

flight paths in most oceanic/remote airspace. A recent study indicated time savings 

ranging between 4.9 minutes to 29 minutes for aircraft flying between LAX and Sidney, 

when flex tracks (user preferred) tracks were used. 

 

6 H. Jiang, L. Ren and R. Hansman; Market and Infrastructure Analysis of Future Air Cargo Demand in China; AIAA's 

3rd Annual Aviation Technology, Integration, & Operations (ATIO) Forum; AIAA Paper 2003-6770; 2003 
Present Oceanic ATM

The current oceanic ATC automation system differs significantly from the domestic ATC 

automation system because much of oceanic flight is beyond the range of radars and Very 

High Frequency (VHF) communications. Oceanic ATC operations are performed 

manually or with limited automation, and most air/ground voice communication is 

through a third party communications service provider via High Frequency (HF) radio. 

These system limitations force large separation standards and impact the ability of the 

controller to grant aircraft requests for changes to flight profiles. In the early 1990s, 

these problems were exacerbated by the explosive growth in oceanic traffic. In 1994, the 

Federal Aviation Administration (FAA) made a commitment to the international aviation 

community that the FAA would implement “the use of a global navigation satellite 

system, digital data communications, and advanced automation” to address inefficiencies 

and projected traffic growth in oceanic airspace. 

Figure 1 depicts the worldwide allocation of airspace into Flight Information Regions 

(FIRs). The FAA has a requirement for an ATC modernization system for the oceanic 

Flight Information Regions (FIRs) assigned to the United States. 

Figure 1. ICAO FIRs 

8
The system also will be required to support radar services in transition sectors. The 

airlines that operate in this airspace have urged the FAA to provide automation that can 

reduce delays, support fuel-efficient routes, and manage growing international traffic 

loads, while maintaining current safety levels. In response, the FAA is acquiring 

automation capabilities to support requirements for modernized oceanic and transition 

operations at the Oakland, Anchorage, and New York Air Route Traffic Control Centers 

(ARTCCs). See Figure 2. 

9 Increased Sector

Capacity and Traffic

Throughput

9 Reduced Delays and

Restrictions

9 Increased Predictability

Comm, Nav and

Surveillance

Infrastructure

and

Workload Reductions Target System

Provides

Enables ...which result in...

Vertical

9

Figure 2. Oceanic Modernization Needs 

Separation 

Separation standards in a given airspace are a function of the communication, navigation, 

and surveillance capabilities available in a specific operating environment. Safety 

analysis and operational judgment consider factors such as: timeliness and reliability of 

controller-pilot communications, accuracy of aircraft navigation, the controller’s ability 

to determine potential separation loss, aircraft traffic density, and procedures for 

contingencies such as engine failure and weather deviations. 

The Required Navigation Performance (RNP) concept has been introduced into ATC 

operations to standardize navigation. For example, RNP-10 approved aircraft are 

equipped with navigation systems that can navigate within 10 nautical miles of desired 

position with 95% probability. 

Currently in oceanic airspace, the minimum lateral separation applied by the FAA is 120 

nm in Atlantic and Caribbean/South American airspace; 60 nm in North Atlantic 

minimum navigation performance specification airspace; 50 nm between RNP-10 

approved aircraft in Pacific airspace except in the Central Pacific where, due to 

convective weather, 100 nm lateral is applied south of 30N. 

Lateral Longitudinal

New York Center ZNY

Oakland Center ZOA

Separation Reductionsand Increased Controller Efficiency

What’s Needed

Anchorage Center ZAN
10

The FAA standard for longitudinal separation is 10 minutes (approximately 80 nm). 

Air Traffic Service Providers in New Zealand, Australia, Tahiti, and Fiji use FANS 1/A 

Automatic Dependent Surveillance-Address (ADS-A) systems in Pacific oceanic 

airspace. A 50 nm longitudinal separation standard is currently applied by South Pacific 

air traffic service providers having enhanced CNS/ATM systems to aircraft certified for 

RNP-10 and approved for direct controller-pilot communication via voice or data link. 

The FAA and other civil aviation authorities have certified ADS-A, CPDLC7, and RNP 

capabilities on aircraft such as the B-747-400, B-777 and the A-340. 

Controller-pilot data link communication (CPDLC) allows digital communication 

between air traffic controllers and Future Air Navigation Systems (FANS-1) equipped 

aircraft. The system reduces voice communications by allowing pilots and controllers to 

transmit digital data messages directly between computers on the ground and on-board 

flight computers. Information such as altitude changes and altimeter settings can now be 

transmitted electronically, freeing up the voice communications bandwidth for urgent 

voice messages. Unlike ADS, CPDLC requires flight crew interaction. Pilots remain 

constantly aware of which air traffic service unit (ATSU) has the active connection, and 

they are also aware of the transfer of control taking place from one ATSU to another. 

CPDLC has been a significant step in the FAA’s modernization plans. The first use of 

FANS 1/A CPDLC was implemented at Oakland Center in 1995 and New York Center in 

2003. CPDLC has been the primary means of communication over the Pacific for 

suitably equipped aircraft since early 1999. The system greatly reduces pilot and air 

traffic controller workloads, allowing for greater flexibility. One of the most significant 

aspects of this system is its reduction of crew-input errors. The crew can downlink a 

route clearance request, which the controller can review and return to the crew. This 

eliminates the errors that occur during manual input of data. 

ICAO, FAA and other civil aviation authorities have also approved RVSM (Reduced 

Vertical Separation Minima) operations that permit a 1000-foot vertical separation 

standard to be applied to certified aircraft over the ocean. This has greatly alleviated the 

capacity constraints in the North Atlantic Oceanic FIRs. 

Near-Future Oceanic ATM

ATOP (Advanced Technologies & Oceanic Procedures) 

ATOP is FAA’s advanced ATC automation system that is replacing oceanic ATC 

automation systems currently in use at the Oakland, New York, and Anchorage ARTCCs. 

Anchorage will retain its current automation platforms to support domestic operations. 

ATOP will be delivered in two increments, ATOP Builds 1 and 2. Build 1 replaces the 

current systems at Oakland and New York, providing ATC automation for non-radar 

procedural airspace. Build 2 adds a radar data and ADS-B processing capabilities for use 

 

7

 When used in this report, the term CPDLC refers to generic controller-pilot data link, not the specific implementation 

using VDL-2. 
11

in Anchorage, as well as the radar transition sectors in Oakland and New York currently 

utilizing Host/DSR equipment. 

ATOP will provide a Flight Data Processing (FDP) capability fully integrated with 

Surveillance Data Processing (SDP). The SDP will be capable of processing primary and 

secondary radar, Automatic Dependent Surveillance (ADS), both Addressable (ADS-A) 

and Broadcast (ADS-B), Controller Pilot Data Link Communications (CPDLC) position 

reports, and relayed HF radio voice pilot position reports from an HF radio operator 

employed by a communications service provider under contract to the FAA. 

ATOP will support radar and non-radar procedural separation, tracking clearances issued 

via CPDLC or messages through the HF radio service provider, conflict 

detection/prediction capabilities through the use of controller tools (Conflict Alert and 

Minimum Safe Altitude Warning for radar airspace and Conflict Probe for non-radar 

procedural separation applications), and fully automated coordination via Air Traffic 

Services Inter-facility Data Communications System (AIDCS) with adjacent AIDCSequipped Flight Information Regions (FIRs). 

 

The ATOP system is scheduled to become operational at Oakland in June 2004, in New 

York in March 2005, and in Anchorage in March 2006. 

Separation 

The ICAO Separation and Airspace Safety Panel has established standards for the 

implementation of 30 nm lateral and longitudinal separation that call for: direct 

controller-pilot communication via voice or data link, aircraft navigation accuracy to 

RNP-4 (4 nm/95% probability) and ADS-A capability in the aircraft and at the oceanic 

control center. The ATOP system will enable the application (to such suitably-equipped 

aircraft) of 30 nm lateral and longitudinal separation. These reduced separation standards 

will increase oceanic airspace capacity and aircraft time/fuel burn efficiency. ATOP will 

also improve the safety of oceanic operations by giving controllers enhanced tools to 

track aircraft progress and identify potential aircraft conflicts and problems. Initial FAA 

goals are to implement 30 nm lateral and longitudinal (30/30) separation in Oakland 

controlled South Pacific airspace by 2005. As ADS-A deployment progresses and as 

more aircraft become RNP-4 capable and approved, use of 30/30 separation will be 

expanded beyond the South Pacific. In the period 2006-2013 it is expected that 30/30 will 

be utilized throughout the Pacific and potentially in the North Atlantic airspace controlled 

by New York ARTCC. (Note that most North Atlantic airspace is controlled by Canada 

and the U.K., each of which are implementing similar oceanic automation systems.) 

Future Oceanic ATM8

There are expanded capabilities available to all aircraft and in all airspace. Userpreferred routes replace the track system. Increased airspace capacity is achieved 

through further reductions in separation minima. 

 

8

 The following is adapted from the description of the operational improvements derived from the RTCA Concept of 

Operations and documented in the NAS Architecture as the Target System Description for Oceanic Operations. 
12

 

The positions of all controlled aircraft are determined through automated means and are 

displayed to the service provider. Separation assurance is accomplished with the aid of 

Decision Support Systems (DSSs) and a visual display system similar to that used in 

domestic en route. Communications are seamless as data-link services become common 

in both environments. ATM services (including TFM planning and agreements), DSSs, 

and automation in assigned international oceanic airspace are harmonized with those of 

the domestic en route environment. User-preferred routings are available throughout the 

airspace. Advanced CNS and automation capabilities enable achievement of domesticlike separation services in the international oceanic environment. 

 

Intelligent agents operating on behalf of the user and service provider monitor changes in 

the flight environment, and propose adjustments to the profile in response to changes in 

ATM system constraints. The proposed changes reflect the removal of constraints and 

permit the as-flown profile to more closely align with either the user’s original preferred 

profile or a profile constructed based on known user preferences. Different users may 

have different operational responses and preferences to the same changes in ATM system 

conditions. These responses are similar to those experienced by flights operating in the 

domestic en route environment, with some adjustment for the differences in response 

times and traffic volume. 

There will be increasing reliance on satellite technology for data communication and 

surveillance with a higher reporting rate, potentially enabling separation reduction 

beyond 30 lat/30 long. Situational awareness in the cockpit (CDTI) will allow for shared 

separation responsibility and enhanced safety during contingency events. User preferred 

trajectories will be utilized, rather than fixed or flexed tracks; improved sharing of 

information with AOCs, collaborative decision making, will allow for more efficient 

route/altitude profiles. 

Automation 

The use of ATOP is expanded to support conflict free 4-D flight profiles. Periodic 

position reports using either ADS or other means (Satellite or HF radio) are automatically 

processed by ATOP to ensure that the aircraft are adhering to their cleared 4-D profiles. 

Non-conformance to the cleared 4-D profile is noted to the controller for resolution. 

Clearances are issued to effect changes to an aircraft’s profile and these are ensured to be 

conflict free before they are sent. The aircraft’s cleared 4-D flight profile is automatically 

updated upon the acceptance of the clearance by the aircraft. The goal is to ensure that 

the 4-D cleared profile held by the ATOP system and that being executed by the aircraft 

is the same. 

Communications 

VDL Mode 3 voice along with DSB AM voice will be used for Air-Air communications 

in domestic US airspace. Satellite communication will be available for oceanic airspace, 

utilizing both voice and data capabilities, but data communication will be the primary 

capability. Both HF voice and HFDL data capabilities will be used as backup to the 

satellite capabilities. ATN will be the networking technology to provide data link 

interoperability across the various technologies. ATN will likely be enhanced with IP 
13

protocols due to user demand. Data security will be increased with all links being 

modified as necessary to minimize the risks and probabilities of deliberate interference. 

Navigation 

Satellite based navigation systems will become more accurate and will be available from 

a number of service providers. The availability of WAAS in oceanic transition areas will 

reduce the occurrence and duration of “holes” in GPS coverage. RNP capability (beyond 

RNP-10 which is currently required in Pacific oceanic airspace) will be required to use 

certain routes and gain the most efficiency. 

Weather 

Various products tailored for transoceanic flights such as convection, volcanic ash, inflight icing, clear air turbulence (CAT), and convection-induced turbulence (CIT) will 

emerge from FAA-sponsored R&D. Better data link technology using ground- and 

satellite-based dissemination architectures speed delivery enabling common situation 

awareness (oceanic control, AOC dispatcher & flight deck) of the hazard along the flight 

path. 
14

(This page left blank)
15

III - Requirements to Support Reduced Separation 

Given global improvements in the capabilities of CNS, ATM controllers can provide 

improved oceanic separation assurance (SA) by: 

1) monitoring the progress of aircraft under their control, 

2) estimating the future “trajectory “ of each aircraft 

3) intervening in a timely manner whenever any pair of aircraft are predicted to 

be “encountering” each other. 

An “Intervention” is a controller instruction communicated to one or both pilots that 

changes the future trajectories such as to increase the minimum separation during the 

encounter. It must be understood and executed by pilots before the time of passage for 

the encounter, and controllers will monitor its execution, and also the remainder of the 

encounter until passage, to ensure the desired separation at passage is maintained. 

As the quality of both the surveillance and communication is improved, the procedures 

for SA can be improved and the separation criteria used to define an “encounter” and a 

“safe separation at passage” can be reduced. It is necessary to understand the relationship 

between the degree of improvement in surveillance and communication and the 

corresponding improvements in SA if we are to make the tradeoffs necessary to find cost 

efficient improvements in oceanic ATM for all classes of users. This section discusses 

the particular qualities of surveillance and communication that are needed to allow 

improvements in oceanic procedures. 

Separation Assurance

Separation assurance is the primary service provided by ATM. The procedures used for 

separation assurance in various operational situations (along with their corresponding 

minimum separation criteria) are strongly dependent on the performance of all of the 

redundant systems that are available for CNS (communications, and navigation, and

surveillance). Through ICAO, using guidance manuals such as Reference X, ATM 

managers from many countries will develop safe new oceanic SA procedures. 

We will briefly provide a common understanding of separation assurance and its issues 

before discussing how improved CNS capabilities lead to SA improvements and reduced 

aircraft separations. 

Measuring the Quality of CNS Performance 

Measures for the quality of operational performance for communication systems (both 

voice and data) are transfer-delay, availability, reliability, continuity, integrity, priority, 

preemption, and precedence. 

Measures for quality of operational performance for surveillance systems are position 

accuracy, position data rate, independence/dependence from aircraft navcom systems, 

availability, reliability, continuity, and integrity. 
16

Measures for the quality of operational performance for navigation systems are position 

accuracy, position update rate, availability, reliability, continuity, and integrity. 

In determining safe separations, average values for these measures of performance are 

not as important as the 95 or 99% level of performance. An acceptable operational 

procedure to provide separation assurance must have a probability of failure of the order 

of one in a million. 

Dealing with Uncertainty in SAS Information 

In providing SA, controllers use information about the actual, intended, and the probable 

future 4-D trajectories that extend ahead of each aircraft. A trajectory consists of the 

projected horizontal and vertical paths, and the rates of progress along those paths – e.g., 

intended and future ground speeds and vertical rates, and consequently the expected, or 

estimated, times of arrival at various waypoints/altitudes. This is uncertain information, 

and the degree of uncertainty in future positions (and the increase in levels of uncertainty 

with the projected time until an encounter) strongly influences the procedures and criteria 

used to provide SAS. 

Types of ATC Separation 

There are three types of separation provided by ATC: vertical, lateral, and longitudinal. 

1) Vertical Separation - When using vertical separation, controllers assign 

aircraft to different pressure altitudes that differ by 1000 or 2000 feet, and 

then rely on pilots/autopilots to maintain “conformance” to their assigned 

levels. Because of the accuracy of height measurement, and also the quality 

of manual and automatic height-keeping systems onboard current aircraft, the 

average quality of vertical conformance is exceptionally good (average 

deviations are 100 feet or less), so that these small separations are 

operationally acceptable as being “safe”). 

Controllers monitor for “Gross Altitude Deviations” by manually (in the case 

of voice position reports) or automatically (in the case of data-linked position 

reports) comparing reported altitude with assigned altitude. Monitoring 

altitude separation and handling gross altitude deviations requires good 

performance from both surveillance and communication systems. 

2) Lateral Separation – In applying Lateral Separation on well-defined parallel 

tracks for aircraft at the same altitude, in a manner similar to providing 

vertical separation, controllers will assign aircraft to tracks nominally 

separated by certain distances and then monitor their conformance to those 

tracks. The track separations used depends on the operational situation (for 

oceanic parallel tracks, the current separations are roughly 50 nm. i.e., 30,000 

feet). (Note that RNP-10 tracks are generated 1 degree apart which is 

approximately 60 miles. Applied separation is 50 nm). This increase of three 

hundred times over the vertical separation is due to the relatively poor quality 

of lateral conformance due to the historical quality of position information 

from aircraft navigation systems, and also the track-keeping performance of 
17

their manual or automatic guidance systems. The introduction thirty years ago 

of digital autopilots (now called Flight Management Systems) in larger 

aircraft and the newer availability of good position information from GPS 

create the potential for a significant reductions in lateral track separation 

whenever all (or most) aircraft flying the parallel tracks are using such 

systems. 

But the “Gross Lateral Deviation” problem must still be handled in some way. 

This requires recurrent position information (i.e., primary and backup modes 

of surveillance of some form) to monitor aircraft lateral deviations, and also 

requires the ability to communicate reliably and with little delay to provide 

aircraft with a resolution. 

3) Longitudinal Separation - For aircraft at the same altitude, when using 

longitudinal separation for aircraft on the same track (or lateral separation for 

aircraft on crossing tracks) ATC controllers will use time or distance 

separation. Typical time separations for oceanic operations are 10-15 

minutes, but it depends on the operational situations and the expected speeds 

of successive in-trail aircraft. At cruising speeds for jet subsonic transport 

aircraft of roughly 8 miles per minute, 15 minutes separation translates to 120 

nm, or 720 times the vertical separation used by ATC. The required initial 

longitudinal separation applied to successive aircraft on the same track 

depends on the expected speeds and the length of time between reporting 

waypoints. If the following aircraft adopts the same airspeed as the prior 

aircraft, initial separation may be reduced (e.g., 10 minutes on the North 

Atlantic Track System), and conversely, if the first aircraft is expected to be 

significantly faster, the initial longitudinal separation may be reduced to 5 

minutes.. 

Having assigned the track and altitude and an initial longitudinal separation, ATC does 

not currently assign and continuously monitor groundspeed, nor assign a RTA (Required 

Time of Arrival) at waypoints along the track. Instead, it assumes that constant airspeeds 

will be maintained, and monitors using ETAs (Estimated Time of Arrival) and ATAs 

(Actual Time of Arrival) at waypoints at specified intervals along the track. Today in the 

oceanic environment this information is usually provided rather infrequently by each 

aircraft via an occasionally unreliable HF voice communication system. Uncertainty is 

introduced into the ATA by short-term variations in the actual winds as well as the errors 

in expected average winds obtained from different forecast sources, using forecasts that 

are created and updated at different times. 

ATC performs conformance monitoring by examining the difference in ATAs reported 

by successive aircraft at each waypoint. If the difference violates longitudinal separation 

criteria, then oceanic ATC will intervene to change airspeeds or assign different altitudes. 

This “after–the-fact” conformance monitoring and resolution causes the use of larger 

longitudinal separations since there must be some extra margin to allow time for safe 

resolution. Alternatively, it may be possible to use the “closure trend” from successive 

and more frequent waypoints to intervene early - although uncertainties from wind 

variations might mean that such interventions were actually unnecessary. 
18

The ability to specify the frequency of position reports during a closure/crossing 

situation, and to communicate a resolution quickly and reliably, would allow longitudinal 

and lateral crossing separation criteria to be reduced in oceanic/remote regions. This 

would require future improvements in surveillance and communications in the 

oceanic/remote area environment. 

Component Sub-functions of SAS 

There are three sub-functions imbedded in separation assurance: Flight Plan Management 

(FPM), Conformance Management (CM), and Conflict/Encounter Management 

(CNM/ENM). 

1) Flight Plan Management - FPM provides information about the intended 

“flight path”, and while available before a flight starts, this information is 

continuously updated and revised during each flight using air/ground 

communications. There should be agreement at all times between the 

information existing on the ground and in the cockpit concerning intended 

flight paths. That information may be incomplete for some future portion of 

the path (e.g., altitude, ETAs), but it will be mutually understood by the pilot 

and controller that it will be extended/updated at an appropriate time to cover 

the future portions of the flight. This updating requires good air-ground 

communications. 

There are meteorological and aircraft state variables that limit the performance 

of each aircraft in terms of achievable groundspeeds and vertical rates, and 

these may be unknown to controllers, and uncertain in the minds of pilots and 

dispatchers. For example, long haul oceanic aircraft may not be able to climb 

initially to their desired cruising altitude because of their heavy fuel load and 

air temperatures at cruising altitudes affecting engine performance. While the 

pilot may have a general idea of where and when he is usually able to climb 

on this trip, it depends on the diminishing fuel load and the actual 

temperatures as they are encountered. It is possible to climb to a better 

cruising altitude earlier in the flight if ATC can accommodate the slower 

climb rates that result in longer and uncertain times to report being safely 

established at the new altitude. Otherwise, ATC normally prefers to wait until 

the step climb can be accomplished promptly and its completion reported 

promptly. As these uncertainties resolve themselves, better trajectory 

predictions can be made to improve the flight plan and support SAS. 

2) Conformance Management – As described above, CM consists of 

monitoring the actual progress of all aircraft along their intended trajectories, 

and resolution, where the controller may intervene from time to time to 

eliminate any undesirable deviations. 

Monitoring is accomplished using surveillance information on the recent 

position/altitude of each aircraft to compare it with the expected 

position/altitude at those times. There are conformance limits on the 

deviations that will be tolerated by a controller. These limits depend on the 
19

traffic situation, (e.g., an imminent encounter with another aircraft, an 

apparent failure to initiate an expected turn or level-off, or an expected change 

of altitude). As well as the accuracy of the position reported by surveillance, 

the time between surveillance position reports is important to monitoring. A 

number of consecutive reports are required to establish that the aircraft is truly 

deviating from its intended path/altitude, and will not be correcting the 

deviation on its own. Notice that when CM uses dependent surveillance, 

where communication of each aircraft's position derived from its onboard 

navigation systems is substituted for direct and "independent" ground 

surveillance, an error in navigation data onboard the aircraft denies redundant, 

independent conformance monitoring – both pilot and controller will think the 

aircraft is following the intended path/altitude. A second independent source 

of position/altitude data onboard the aircraft is required to allow the pilot to 

detect non-conformance. Such second, independent, backup CNS systems are 

very desirable in ATC to ensure safety. Loran C is being considered 

currently to provide such backup to GPS. During Oceanic operations, this is 

accomplished with redundant IRS systems and, recently, GNSS. 

Resolution of any altitude/path deviation requires good communications 

performance since an intervention will be initiated by the controller to advise 

the pilot of the deviation and suggest a correction. The pilot will not be 

expecting this communication, and may or may not be aware of the deviation, 

and may or may not agree that there is a deviation. It may take some longer 

period of time for the pilot to respond and understand the deviation, and to 

concur with a suggested resolution, or perhaps try to negotiate another 

correction, and then to report initiation of the agreed correction. These 

operational, not technical, time delays, and the reliability and continuity of 

expected communications needed to carry them out, affect the ability of ATC 

to introduce reduced separations dependent on real-time intervention and 

resolution. 

Conformance Management of the longitudinal progress along the trajectory is 

performed quite differently due to continuously varying winds. Progress 

along the path is monitored and expected times of arrival at varying waypoints 

are revised on the ground by ATC rather than intervening to change the 

airspeed (and hence the groundspeed) to try to maintain a desired time of 

arrival. Where independent surveillance is available, longitudinal 

conformance can be achieved with no requirement for air/ground 

communication by revising the future estimated time of arrival on the ground, 

i.e., the expected future flight path is modified, not the airspeed of the aircraft. 

With dependent surveillance, there will be frequent communication of the 

aircraft's position, and also, perhaps, its own estimated times of arrival at the 

next one or two waypoints, or at additional waypoints as requested by ATC. 

It may be possible to reduce oceanic separation criteria if such automated 

capabilities can be reliably introduced. It requires good communications 

performance – but it need not be voice communication. 
20

Conflict/Encounter Management – CNM/ENM 

There is a spectrum of methods that provide separation assurance to aircraft 

by intervening to modify future flight paths and trajectories. These can be 

classified as conflict management for longer-term path probes (say 15 to 60 

minutes), encounter management for intermediate terms (say 2 to 15 minutes), 

and collision avoidance for a very short term (less than 2 minutes) response to 

imminent, unexpected potential collisions. We are interested in the first two 

classes of methods in examining the possibilities for improving oceanic ATC. 

We are not limiting ourselves to incremental improvements of existing 

oceanic SA procedures. 

Conflict Management - The first class of methods predates the introduction of 

radar surveillance to ATC. It does not use surveillance, but depends strongly 

on communication performance. It must be accompanied by some degree of 

conformance management. The basic approach is to create and maintain 

longer term, conflict-free flight plans. It is still in use in oceanic areas, and 

consists of two sub-processes; conflict monitoring and conflict resolution. 

The conflict monitoring sub-process (whether human or automated) examines 

flight plans for all aircraft when they are introduced and also as they are 

continuously updated during the flight to detect a "conflict" between any pair 

of flight plans, i.e., a potential violation of the standards for required 

separation. Upon detection of a potential conflict, a conflict resolution subprocess then modifies one or both of the flight plans of the conflict pair 

appropriately to provide the required separation, transmits the desired changes 

to each pilot at an appropriate time, and awaits a report of their execution. 

CNM operates closely with conformance management since the update of 

flight plans and particularly the monitoring of longitudinal progress is a major 

input to conflict detection. 

Encounter Management – The second class of methods are relatively 

undeveloped at the present time. They use real-time, surveillance information 

about the current position, ground speed and direction, and vertical rate of 

each aircraft, plus good knowledge of its near-term planned path. The basic 

approach is to create and maintain for every aircraft, a set of continuously 

updated, shorter term (15 minutes or less), 4-D trajectories that are encounterfree. The prime example occurs in "radar control" where flight plans are not

modified, but instead, only the immediate trajectory of one or both aircraft is 

temporarily changed. These methods also have two sub-processes: encounter 

monitoring and encounter resolution. 

The encounter monitoring sub-process creates continuously updated 

predictions of the probable trajectory of every aircraft for some probe time 

like the next 15 minutes or less. These 4-D trajectories are then monitored to 

detect an "intrusion" event where the minimum separation between two 

trajectories is expected to violate some defined separation criteria. Encounter 

resolution then modifies either one or both trajectories to eliminate the 

Intrusion, and then to restore conformance to the original flight plans. 
21

ANALYSIS OF A CONTROLLER’S DECISION TO INTERVENE – EXAMPLE 

To illustrate the role of CNS in providing information to controllers when they are 

providing SA with intervention, consider an example of two aircraft approaching a 

crossing encounter in mid-ocean at the same altitude. We shall describe the elements of 

the controller’s problem of deciding whether, and when, to intervene. 

Although the original flight plans indicated that the aircraft should have sufficient 

separation at the crossing point, at some large “time-to-passage” the controller 

monitoring the progress of both aircraft becomes aware that there is some probability of 

violating the required “separation-at-passage”. But because the time-to-passage is large, 

there is still a high degree of uncertainty in both trajectory predictions and consequently 

the estimated separation-at-passage. Since the probability of an actual violation is not 

high at this point, and there is a desire to avoid intervening with an unnecessary change 

of altitude or direction, the controller may decide to defer the intervention. To defer, the 

CNS must have a high probability of allowing the controller to intervene later, and also 

must have good surveillance information over the period of the deferral. 

Upon deferral, the controller will decide to improve the quality of conformance 

monitoring and trajectory prediction by asking (via some communication link) for more 

frequent position reports. This will reduce the uncertainties in trajectory prediction and 

improve the estimated separation. The improvement in uncertainty avoids unnecessary 

interventions, and can also allow the use of smaller crossing separation. 

There is a minimum time-to-passage to allow the execution of an intervention. It is 

determined not by the speed to transmit a message, but rather by the time it takes to gain 

the pilot’s attention, get agreement on the execution of the intervention, and get it 

completed. The reliability of the communication link and in particular the continuity of 

maintaining “contact” is also important, but it is swamped by this longer time in setting 

the “critical time-to-go”. If there is any question about maintaining contact, a backup 

communication system will be required by ATC procedures, but this increases the critical 

time-to-passage, and thus the crossing separation criteria. 

The controller may decide to make the pilots aware of the potential crossing problem at 

some appropriate time before the critical time-to-passage just to test any voice link, and 

to improve the alertness and awareness of the pilots. The use of dependent surveillance 

in reporting aircraft position at specified times inherently provides a frequent test of its 

data link to the aircraft. Procedures for oceanic SA can be developed to rely on this data 

link as the primary means of intervening. The simple awareness by pilots of the location 

and time of a potential upcoming encounter enlists TCAS as a safety backup for such 

procedures in the event of a sudden and unexpected failure of communications. 

It is pertinent to note that the critical case in making the intervention decision occurs 

when the estimated actual separations have values near the required crossing separation, 

not when they are near zero. The controller is trying to avoid a “violation” of the 

crossing separation criteria, not trying to avoid a mid-air collision. If the estimated 

separations begin to indicate that the actual separation will be near zero, the probability 

that an intervention will be needed will much higher, and the decision to intervene 
22

becomes obvious much earlier. Since we are dealing with a possible violation, not a midair collision, if there is a sudden, unexpected failure of communications or surveillance as 

the critical time-to-passage is approached, it will lead to a violation that still has a very 

small probability of a mid-air collision, even without the backup of TCAS. It is this rare 

failure situation that determines the allowable reduction in separation. 

It will require further study to develop oceanic SA procedures based on various levels of 

expected performance of CNS systems in order to perform benefit–cost tradeoffs. But 

almost any CNS improvement can lead to some degree of ATC improvement. It is a 

mistake to insist on “gold-plated” requirements for excellent voice and data 

communications before examining what can be done with lesser performance - and cost -

CNS, since such systems might be much more acceptable to aircraft operators and lead to 

earlier and wider equipage, and thus earlier reductions in separation criteria. 

New CNS Capabilities To Improve Oceanic SAS

We now turn to examining characteristics of newer forms of CNS that would be valuable 

in creating new operating procedures for ATC (and particularly improved separation 

assurance) for low density traffic areas with a high proportion of level cruising flight such 

as typically found in oceanic/remote regions, but also at higher flight levels everywhere. 

Navigation 

We can assume that dual redundant and independent GPS/Galileo navigation systems 

will become available in all aircraft over the next 15 years. That means that there will be 

accurate digital data available from every aircraft for determination of position, ground 

speed, and direction, with global signal coverage and high continuity, reliability, and 

integrity. It is this digital data that we wish to make available to ATC using a global 

satellite data communication system to match the characteristics of GPS/Galileo. 

It is likely that there will also be an increasing equipage of most aircraft to make digital 

information available on many more items of flight data, such as next waypoints, 

airspeed, wind speed, vertical rates, aircraft weight, outside air temperature, guidance 

mode, etc. This has been called extended or enhanced surveillance. 

The ICAO Surveillance and Conflict Resolution Systems Panel (SCRSP) has defined 

several levels of enhanced surveillance reporting in response to states concerns about 

altitude violations and the need for conflict detection. For example, the UK has 

mandated the reporting of selected altitude by Mode S in the 2005-6 time frame; France 

and Germany are taking similar actions in the future, to insure that flight crews select the 

correct assigned altitude and to monitor their compliance. It is likely that similar 

requirements will exist in oceanic and remote areas. However, because of the cost of 

installing the required systems (usually called FMS on the larger aircraft), we cannot 

assume a single common type of equipage, nor can we assume that at some future time 

civil aviation authorities will mandate a minimal performance of such digital flight 

systems for all aircraft operations in all areas. 
23

Surveillance 

Using the onboard position/groundspeed/direction data from each aircraft means that 

ATC becomes dependent on each aircraft's navigation and data communication 

capabilities. If we are to rely on this data for separation assurance at reduced separations, 

then as well as dual independent onboard navigation systems, we also need dual 

independent onboard data communication systems, and perhaps an alternate means of 

communication to advise the aircraft that surveillance data is no longer arriving at the 

ground. These alternate means may also necessary to be able to intervene quickly and 

reliably to apply larger reversionary separations (e.g., altitude change) to resolve any 

imminent encounter if both aircraft have lost data contact due to satcom system failure. 

The probability of loss of continuity (i.e., loss of data over the next period of time given 

that it is working now) must be kept small, especially as ATC separations become 

smaller, and consequently ATC intervention times must get smaller. ATC procedures for 

handling an encounter will confirm communication contact with both aircraft at some 

point before passage, and it is desirable that the probability of losing contact between that 

point and commitment to passage at reduced separation be very small. 

Communication 

The following briefly summarizes desirable characteristics of a new satellite-based 

oceanic communication system 

 1) Efficiently handle frequent transmission of short position data messages from 

multiple aircraft to one or more ground facilities. 

2) Capability of the ground to vary the reporting intervals of the short position 

messages for each airborne aircraft, i.e., re-arrange contracts for position reporting as a 

function of the traffic situation. 

3) Availability of reliable longer-message data links between controller/pilot for 

requesting revisions of trajectories and flight plans (due to weather or desired altitude 

change), accepting revisions, confirming completion of a revision, transmitting weather 

and traffic advisories by the controller, performing handoffs of each aircraft to the next 

oceanic facility, and announcing emergencies ( e.g., engine failures or loss of 

pressurization that require rapid and unexpected descents, or cargo fires or passenger 

sickness requiring diversion to nearest airport 

 4) Provision of independent, backup voice or data communication in case of 

failure of the primary data link. 

With the exception of (1), these capabilities are all provided by FANS-1/A; FANS-1/A is 

not efficient (in terms of channel usage) in transmitting short data messages such as 

position reports.
24

(This page left blank)
25

 

IV - Communication Requirements to Support Oceanic 

Weather Data Exchange

Flights in oceanic and remote areas must contend with the risks of bad weather and 

volcanic dust. Accordingly, the FAA Aviation Weather Research Program has formed an 

Oceanic Weather Product Development Team (OWPDT). The OWPDT is tasked to 

develop near-term, 0-6 hour forecasts of convection, turbulence, high-resolution winds, 

volcanic ash, and in-flight icing, and to develop data dissemination methods. 

A major challenge to this effort is the lack of meteorological data in oceanic and remote 

areas. Presently meteorological data is sent each 15 minutes from equipped aircraft, but 

there is interest in higher update rates. The OWPDT is addressing this issue, by seeking 

additional data and by developing better methods to use existing data to provide more 

accurate and timely forecasts. As the value of additional data is understood, it is likely 

that additional communications bandwidth will be sought to enable this capability. This 

relatively modest need should be accounted for as improved oceanic and remote 

communications links are developed. 

In considering the potential burden of weather reporting on a future oceanic/remote area 

data link, the Tropospheric Airborne Meteorological Data Reporting (system), 

TAMDAR, being developed by the NASA Aviation Safety Program, may be a useful 

design example9

. TAMDAR is addressing the current lack of atmospheric data in the 

lower atmosphere. It will sense and report moisture, temperature, winds, turbulence, and 

ice for use by forecast modelers, weather breifers, controllers, and other aircraft 

The TAMDAR 250 bit message consists of the 208 data bits shown in Table 2 below, 

plus a 20% overhead added to account for framing, error detection, and reserve. NASA 

has estimated the frequency of message transmissions for TAMDAR, using DO-237, 

which provides different rates of transmission for different phases of flight. The lower 

portion of the atmosphere is of greatest interest, requiring more frequent transmissions 

for flights in that domain. 

9

 TAMDAR information received from Tom Tanger, courtesy of Konstantinos Martzaklis at NASA Glen Research 

Center, via email on 26 August 2003. 
26

Table 2. TAMDAR Data Message 

Element Bits 

I.D. 16 

A/C Type 8 

Date/Time 

Date 

Time 

16 

20 

Location 

Latitude 

Longitude 

Pressure Altitude 

20 

20 

16 

Weather Elements 

Wind 

Speed 

Direction 

Temperature 

Moisture 

Humidity 

Water Vapor Mixing Ratio 

Peak Liquid Water 

Content 

Average Liquid Water 

Content 

Super Cooled Large 

Droplet 

Turbulence 

Average 

Peak 

Icing 

Roll Angle 

Phase of Flight 

8 

8 

12 

8 

8 

8 

8 

4 

8 

8 

4 

4 

4 

Total 208 

The proposed message transmission rates are as follows: 

Takeoff and landing 1 report per 6 seconds 

Climb and descent 1 report per 20 seconds 

Cruise 1 report per 15 minutes 

NASA also states that the maximum latency for these transmissions should be less than 1 

minute, where latency is defined as the time from message creation at the source until 

receipt at the destination. 

As the FAA oceanic research activity advances its understanding of weather in the 

oceanic domain, and TAMDAR is field tested, these proposed requirements will be 

refined. Additionally, trade studies will be conducted to determine the how safety and 

efficiency are improved through better oceanic meteorological sensing and forecasting. In 

any case, it is clear that oceanic and remote area operations will need to consider 

metrological data reporting in the coming years. 
27

V - Oceanic Communication Alternatives 

Present and (Near) Future 

HF Voice

Single-sideband voice communication operating in the high frequency band (3 – 30 

MHz) is the primary means of communication for aircraft operating beyond line-of-sight 

of VHF ground facilities. The performance capability of HF voice communication is a 

primary limiting factor in oceanic procedures and separation standards. 

In most oceanic airspace HF voice communication is not directly between pilot and 

controller; rather it is between the pilot and a radio operator of a communication service 

provider (ARINC, SITA). The radio operator in turn relays the content of the 

communication to/from the controller, generally as a text message. 

Except for some hardware improvements, this is basically the same technology/system 

used for long-range communication since the 1940’s. The major change has been the 

switch from Morse code to voice, with the concomitant elimination of an aircraft radio 

operator, and the later change from DSB (double-sideband) to SSB (single-sideband) 

modulation. 

HF voice communication is subject to disruption by interference and ionospheric 

disturbances. Both effects can reduce intelligibility or completely preclude 

communication. Therefore oceanic procedures and separation standards have been 

designed to accommodate long periods of communication outage (possibly as long as the 

entire beyond line-of-sight part of the flight) without compromising safety. 

Typically aircraft report position roughly every hour or 10 degrees of longitude on North 

Atlantic tracks. The length of time it takes to make a report, especially under degraded 

communication conditions, limits the number of aircraft which can be accommodated on 

the available frequencies 

HF Data Link 

The use of digital communication on HF overcomes many of the problems of HF voice, 

while retaining its long-range, over-the-horizon capability. As part of its GLOBALink 

service, ARINC provides HFDL air-ground service from a worldwide network of 13 

ground stations (with one more planned). To make use of this service, the aircraft must 

be fitted with a data-link-capable HF radio. Most modern HF aircraft radios have this 

capability built-in. Many older radios can be retrofit. For aircraft already fitted with HF 

radios (required for all aircraft used on oceanic routes), the addition of HFDL capability 

is significantly less expensive than installing current satellite communications systems. 

Although data transmission on HF frequencies has a long history (the earliest HF 

communication using Morse code was a form of data link, and the military services 

developed and tested sophisticated HFDL systems in the 1950’s), modern HFDL for civil 

aviation is a recently introduced and still evolving service. 
28

As of the beginning of 2003, more than 300 aircraft were HFDL-equipped, with 

that number increasing by approximately 8 per month 

HFDL message traffic has grown from approximately 50K messages per month at 

the beginning of 2000 to over 300K messages per month in December 2002. 

Overall message success rate has increased to over 97% 

On the North Atlantic, 95% of position reports were received in 2 minutes or less 

(the goal was 95% in 5 minutes or less) 

For aircraft equipped with SATCOM data link, HFDL is a useful backup in the event of a 

SATCOM outage. For other aircraft, especially cargo and military, it is a relatively lowcost means of providing long range, over-the-horizon data communication. However, 

HFDL is currently certified only for AOC communications, not for ATC. It has not yet 

been established whether HFDL alone can meet the communication requirements to 

support 30/30 oceanic separation. 

INMARSAT

INMARSAT was formed as a maritime-focused intergovernmental organization over 20 

years ago. It has been a limited company since 1999, serving a broad range of markets. 

Starting with a user base of 900 ships in the early 1980s, it now supports links for phone, 

fax and data communications at up to 64kbit/s to more than 250,000 ship, vehicle, aircraft 

and portable terminals. That number is growing at several thousand a month. 

 

INMARSAT operates a constellation of geostationary satellites designed to extend 

phone, fax and data communications all over the world. The constellation comprises five 

third-generation satellites backed up by four earlier spacecraft10. INMARSAT also 

operates a worldwide network of ground stations to deliver its services. 

The overall architecture of the INMARSAT system, as seen by the user, is shown in 

Figure 3.. 

The satellites are controlled from the Satellite Control Centre (SCC) at the INMARSAT 

HQ in London. The control teams there are responsible for keeping the satellites in 

position above the Equator, and for ensuring that the onboard systems are fully functional 

at all times. Data on the status of the nine INMARSAT satellites is supplied to the SCC 

by four tracking, telemetry and control (TT&C) stations located at Fucino, Italy; Beijing 

in China; Lake Cowichan, western Canada; and Pennant Point, eastern Canada. There is 

also a back-up station at Eik in Norway. 

The flow of communications traffic through the INMARSAT network is monitored and 

managed by the Network Operations Centre (NOC) at INMARSAT HQ. The NOC is 

supported by network co-ordination stations (NCSs). Their primary role is to help set up 

 

10 www.INMARSAT.com 
Inmarsat

Satellite Owner

& Operator

Inmarsat

Satellite Owner

& Operator

Land Earth Stations

Owner&Operator

Land Earth Stations

Owner&Operator

Aeronautical

 Earth Stations

(User)

Aeronautical

 Earth Stations

(User)

End User End User Aeronautical

Service Provider

Aeronautical

Service Provider

Figure 3. INMARSAT System Architecture 

each call by assigning a channel to the Aeronautical Earth Station (AES) and the 

appropriate Land Earth Station (LES). There is one NCS for each ocean region and for 

each INMARSAT system (INMARSAT A, B, C, etc). Each NCS communicates with all 

the land earth station operators in its ocean region, the other NCS and the NOC, making it 

possible to distribute operational information throughout the system. 

Traffic from a user terminal passes via a satellite and then down to a land earth station 

(LES), which acts as a gateway into the terrestrial telecom networks and to applications 

providers. There are about 40 LESs, located in 30 countries. The LESs are owned and 

operated by LES Operators (LESOs), who contract with INMARSAT to provide the 

transmission capabilities. Eight of the LESs are equipped to support the current 

aeronautical services offered by INMARSAT. 

The aeronautical service provider (e.g., ARINC, SITA) contracts with the LES Operators 

for transmission access, and to provide transmission services out to the end users. 

The data and voice communications architecture for the INMARSAT system is shown in 

Figure 4.. 

INMARSAT aeronautical services require one of six available airborne terminal 

configurations (known as Aeronautical or Aircraft Earth Stations (AESs)) to be installed 

in the aircraft. These configurations currently provide different maximum data rates 

under different coverage areas, as summarized in Table 3. 

29
Avinet

ARINC

Comm Centre

PSTN

AOC

Voice

Datalink

(AOC,ATC,

CNS/ATM)

Datalink

(AOC,ATC,

CNS/ATM)

AOC Voice

AOC and 

Passenger Voice

IFE

IFE

Passenger

Voice

Aircraft

Earth Station

Space Segment

Ground

Earth Station

CPS

Terminal/Service Aero H Aero H+ Aero I Aero L Aero M Aero C

General Description

Global Beam 

Voice & 

Data

Global & 

Spot Beam 

Voice & Data

Spot beam 

voice. Global 

Beam data.

Packet Mode 

Data

Spot Beam 

Voice & Data

Store & 

Forward 

Packet Mode

Global Beam

Voice (bps) 9600 9600

Packet Data (bps) Š 10,500 Š 10,500 Š 4800 600/1200 600

Circuit Data (bps) 4800/9600 4800/9600 2400/4800

Spot Beam

Voice (bps) 4800 4800 4800

Packet Data (bps) Š 10500

Circuit Data (bps) 4800/9600 2400/4800

High Speed Data (kbps) 64/128 64/128

Channels 1 to 11 1 to 11 1 to 7 1 1 1

Services

ICAO SARPS Safety Yes Yes Yes Yes No No

Passenger Yes Yes Yes No Yes No

Antenna

Gain 12 dBiC 12 dBiC 6 dBiC 0 dBiC 6 dBiC 0 dBiC

Typical Size (inches) 18x18x8 18x18x8 18x9x8 10x8x5 18x9x8 10x8x5

Weight (typ) with Antenna 220 lbs 220 lbs 40 lbs 11 lbs 20 lbs 11 lbs

Figure 4. General User Communications Architecture of INMARSAT 

Table 3. INMARSAT Aeronautical Terminals/Services

30
31

Figure 5. INMARSAT Coverage Areas for Aeronautical Services 

rd packets worldwide 

uires 12 dB Gant

 beams 

he next generation of satellites, known as INMARSAT-4, will expand the High Speed 

he estimated equipage for 2004 is: 

 and government aircraft 

Aero-C) 

 

The associated coverages, determined by the satellite resources and the installed GES 

equipment, are shown in Figure 5. 

The Aeronautical Services include: 

– Aero C - store and forwa

– Aero H/H+ - up to 10 kbps in Global Beam, req

– Aero I11 - up to 4.8 kbps in Global Beam, requires 6 dB Gant

– Aero L12 - 600bps/1200bps Airline ATC 

– Aero Mini-M - upgradeable to Aero I 

– Aero HSD – up to 128 kbps under spot

T

Data (HDS) to global beam coverage, and enable data rates greater than the 64/128 kbps 

in the spot beams. The INMARSAT-4 satellites are scheduled to enter service in 2005. 

T

– 1700 airliners 

– 1200 corporate

– 1200 helicopters and military transports (

11 Complies with SARPS for AMSS, can be used as part of CNS/ATM 

12 Complies with SARPS for AMSS, can be used as part of CNS/ATM
32

he underlying access of the satellite channel is by demand assignment. That is, an AES 

 back 

his 

he satellite link supports several types of channels: 

P-channel: A Packet-mode time division multiplex (TDM) channel, used in the 

hannels. 

-channel: A Random access (slotted Aloha) channel, used in the return 

 An Rile 

els. 

-channel: A Reservation Time Division Multiple Access (TDMA) channel, 

smits 

-channel: A Circuit-mode single channel per carrier (SCPC) channel, used in 

he modulation for the 600 bps to 2400bps modes is A-BPSK, a form of BPSK with 

0 

l 

he aeronautical services provide relatively little revenue to INMARSAT: $12M out of 

s so 

small that negligible investment in increased capability is anticipated in the near term. 

 

T

sends a request for service to the NCS via the associated LES in a random access 

channel, and a TDMA slot assignment for subsequent communications is provided

to the requesting LES. This general service paradigm is analogous to circuit switching in

the Plain Old Telephone System. Digital voice and data can be transmitted over the 

assigned channel(s). Short data messages can be sent in the random access channel. T

set of protocols is well suited to low-density traffic such as individual telephone-like 

calls, but is not efficient for large numbers of users such as aeronautical who need to 

communicate with the same ground node. 

 T

forward direction (ground-to-air) to carry signaling and packet-mode data. The 

transmission is continuous from each GES in the satellite network. A P-channel 

being used for System Management functions is designated Psmc, while a Pchannel being used for other functions is designated Pd. The functional 

designations Psmc and Pd do not necessarily apply to separate physical c

R

direction (aircraft-to-ground) to carry signaling and packet-mode data, 

specifically the initial signals of a transaction, typically request signals.

channel being used for System Management functions is designated Rsmc, wh

an R-channel being used for other functions is designated Rd. The functional 

designations Rsmc and Rd do not necessarily apply to separate physical chann

T

used in the return direction only. The receiving GES reserves time slots for 

transmissions requested by AESs, according to length. The sending AES tran

the messages in the reserved time slots according to priority. 

C

both forward and return directions to carry digital voice or data/facsimile traffic.

The use of the channel is controlled by assignment and release signaling at the 

start and end of each call. 

T

particular pulse shaping for spectral containment. The modulation for rates above 240

bps is A-QPSK, a form of QPSK with particular pulse shaping for spectral containment.

Offset QPSK is used for some of the higher rates. Interleaving and standard convolutiona

coding with Viterbi decoding is specified for the P and R channels described above. 

T

total revenue of $442M in 200113. INMARSAT does not anticipate saturation of the 

aeronautical capability for the foreseeable future. As capacity demand increases, the 

NCS just assigns more channels until the total system begins to saturate. The market i

13 INMARSAT Annual Report for 2001. 
The Defense Information Services Agency14 has entered into a series of contracts for 

INMARSAT services that could extend until 2012. Under that set of bulk contracts, 

budgetary pricing for some services is given in Table 4. 

Cost Units

Inmarsat C

Service

33

der DISA Contract 

From

peater is to lease the bandwidth (and power) over the desired coverage area, and to 

y 8 

 for 

ANS

Table 4. Budgetary Pricing for INMARSAT Services un

 a continuing cost standpoint, usually the most economic way to utilize a satellite

re

lease space in the associated GES to provide tailored processing. In the specific case of 

INMARSAT, suppose only 100 kHz were leased, and the bandwidth were utilized onl

hours/day. With a total of 14,400 minutes in a 30-day month, the cost of the lease 

averaged over the 8 hours/day would be under $2/minute. While this is not a design, it 

seems likely that the 100 kHz bandwidth would provide more than enough capacity

Oceanic CNS. 

F

f FANS and FMS Development 

Study conducted by ICAO during the 1980’s 

cused on the possible use of satellites for global air navigation/ATC. As the FANS 

t). 

 introduction of FANS and CNS/ATM, 

ommitted to introducing a first version of the necessary aircraft equipment (called 

th 

tened 

 

History o

The Future Air Navigation System (FANS) 

fo

concept was further developed for new forms of management of ATC, it became known 

as CNS/ATM (Communication, Navigation, and Surveillance/Air Traffic Managemen

There is now an ICAO Global Plan for ATM Development based on CNS/ATM that 

contains a Global Concept for Future ATM. 

Boeing and Honeywell, hoping to stimulate the

c

FANS-1) for the new B747-400, and certified it in 1995. A similar FANS-1 system, wi

a different pilot interface, has been built later for the B-777, and another version is 

apparently available for the Boeing Business Jet (BBJ). Airbus started a similar project 

that was initially called AIM-FANS (Airbus Interoperable Modular-FANS, but shor

X.25, Polled, FAX, Telex $0.13 to $0.30 per 256 bits

Small Data Report $0.03 up to 8 bytes

Medium Data Report $0.06 up to 20 bytes

Large Data Report $0.09 up to 32 bytes

Aero H+, Aero I

AES <-> AES $10.26 per minute

AES -> PSTN $5.39 per minute

PSTN -> AES $7.35 per minute

Bandwidth Lease

100 kHz $29,692 per month

14 http://www.disa.mil/acq/contracts/INMARSAT/contract/pdf/INMARSAT_pricing.pdf 
34

ft 

ew global system for ATM, both these initial 

versions claim to have been designed in a modular fashion as the first steps of an 

he 

ill 

aft, such 

as Canadian Marconi, Universal Avionics, and Rockwell Collins are capable of 

emand 

Cor the FMS 

ght management system that automates and 

tegrates some of the various cockpit functions involved in managing the flight 

ions it 

ntrol; 4) 

ht 

f 

as. 

The FMS provides optimal area navigation (RNAV) by selective use of the 

avigation sensors available onboard the aircraft (e.g., INS, 

if it is 

t’s 

he 

to FANS-A in its first implementation) that provided equipment that became available 

after 1997 for the later production of the Airbus 330/340 fleets. Approximately 1500 

aircraft have these two initial versions of FANS equipment, but very few of other aircra

currently used on oceanic routes have been retrofitted (e.g., DC-10, MD-11, older B-747, 

B-767, B757, B-737Adv, older A300/340) 

Because of the uncertainties in adopting a n

evolution towards the ultimate CNS/ATM system, particularly with regard to 

accommodating various future forms of data link communication. That explains t

original descriptive name given by Airbus to emphasize its interoperability and

modularity. They can accommodate any form of future satcom or data link. There w

be many future implementations of FMS equipment for all types of aircraft, and 

hopefully most will be based on newer and cheaper forms of satellite data link. 

Today, other manufacturers of FMS systems for business aviation and other aircr

modifying their installed (and new installations) of their FMS on various different aircraft 

to provide some (or all) of the CNS/ATM functionalities. They need sufficient d

from prospective and current customers to commit to certification costs. Canadian 

Marconi is teaming with Boeing to retrofit the older B-747s of Japan Airlines. The 

USAF is considering modifying the current FMS to retrofit some of its fleets (e.g., K

10, C-17, C-5, and perhaps the leased tanker versions of B-767) to gain certain 

CNS/ATM functions. 

CNS/ATM Functions f

FMS is the name used for a digital fli

in

operation of a modern aircraft in an air traffic environment. The CNS/ATM funct

handles can be organized as: 1) navigation management; 2) guidance; 3) flight co

flight planning/aircraft performance; 5) dependent surveillance management; and 6) 

communications management. These functions will be briefly described below to 

provide an idea of what the current FANS implementations can do, but also what mig

be done in the future. As yet, there is no requirement that some of the CNS/ATM 

functions be implemented to fly in any airspace, but there have been some introduction o

use of the initial versions of FANS for Oceanic ATM in very low traffic density are

1. Navigation Management 

multiple redundant n

GPS, and in the future - Galileo, WAAS, LAAS, and perhaps even Loran-C 

adopted as the backup for GPS). It estimates and monitors the continuous 

operation and accuracy of each of the various navigation systems onboard the 

aircraft during the flight, and provides an ongoing assessment of the aircraf

actual overall navigation performance. If a value is inserted into the FMS for 

Required Navigation Performance ( RNP), it will provide alerts to the pilots if t

current aircraft navigation performance falls below the desired value. 
35

2. Guid

maintaining vertical and lateral conformance to any flight-planned route (or ATC 

nce). The route is usually described by a series of waypoints with desired 

 with 

e. 

) 

nformance is 

entical to that currently being used by ATC. FANS originally specified data 

ation 

3. Fligh

pilot capable of smooth, stable automatic maneuvering 

required to capture and maintain the dynamic values of heading, or track over the 

altitude that are specified by the Guidance function. It is this function 

4. Fligh

ation about future winds and temperatures at various altitudes, and 

knowing the current aircraft weight as fuel burn makes it lighter, and using a 

ine performance, the FMS can provide the 

or 

 for 

ance 

The FMS is a full digital autopilot capable of automatically flying and 

cleara

altitudes. It can monitor its own conformance to this inserted flight plan

automatic alerts of non-conformance to the pilots for either lateral or vertical 

deviations beyond some specified value. Some FMS installations provide RTA 

(Required Time of Arrival) capability, changing the airspeed as winds vary, to

maintain groundspeed and try to arrive at some future waypoint at a desired tim

It will then provide alerts to the pilots if the aircraft is not going to be capable of 

conforming to this RTA due to airspeed limitations of the aircraft. 

There should be a means for ATC to check that the flight plan (or ATC clearance

that the aircraft’s Guidance function is currently using to maintain co

id

link waypoint reports that provide next (and next+1) waypoints from the FMS. If 

there is not agreement, then ATC needs time to communicate and confirm a 

mutual understanding of the intended flight path. If the Guidance function is 

working correctly, it is difficult to see why there should be any deviation unless 

the pilots have accidentally or deliberately disengaged it for a temporary devi

from the intended path. 

t Control 

The FMS is a digital auto

ground, or 

that makes the FMS software “flight critical” in safety certification terms, and 

seems to cause the expensive need that FMS software, and any changes, be fully 

tested for correct and reliable operation. It should be possible to create modular 

FMS software and/or separate hardware to isolate the inevitable evolutionary 

changes in non-flight critical functions of the FMS after it is installed, and thereby

avoid rigorous re-certification for every minor revision of FMS software as it 

evolves. 

t Planning/Aircraft Performance 

Given inform

idealized model of aircraft and eng

pilots with a variety of estimates for current and future aircraft performance that 

may enable onboard flight planning in the event of an emergency diversion. F

example, it can estimate desired future or current en route speeds and altitudes

best time and fuel burn, current and future altitude and airspeed capabilities (with

an engine failure), time required to climb to some altitude, the future position of 

Top of Climb and Top of Descent, landing and takeoff airspeeds and distances, 

onboard fuel at arrival, landing weight, etc. If good digital communications exist 

with the current ATC facility, the pilots may create a new flight plan and send it 

as a request to ATC directly from the FMS. 
36

ce used by other oceanic traffic), a 

ispatcher may initiate and perform this re-planning and can send one or more 

ay 

ay 

P 

(Dynam c Airborne Reroute Procedure) by the Oakland Oceanic Center on the 

h 

rne via 

ic 

ent types 

 the 

5. Depe

imes about the current and intended 

position of the aircraft, it plays a key role in providing Automatic Dependent 

tudy called for ATC controllers, using their 

ell 

een 

If there is also good data link communication with the AOC (Airline Operations 

Center, or a commercial Flight Planning Servi

d

flight plans (named as A, B, C, etc.) in digital form directly to the FMS. Upon 

acceptance of one new plan by the pilots (digital or voice), the pilot or dispatcher 

may then send the requested new flight plan directly to the appropriate ATC 

facility. If it is not acceptable to ATC because of other traffic, the dispatcher m

negotiate directly with ATC to find the best acceptable flight plan, and then send 

this negotiated plan to the FMS for pilot concurrence. Remember that there m

be more than one ATC facility interested in the revision to the flight plan. It may 

take some while to negotiate, and a good communication link between ATC 

facilities on different continents may also be necessary to gain acceptance of the 

proposed revision. AIDC (Automatic Inter-facility Data link Communications) 

may be available in the future to speed up this negotiation across oceans and 

between countries. The pilots may prefer to negotiate their own updated flight 

plan if they have satellite data links with pertinent ATC facilities, especially if 

ATC has current reports of turbulence at various altitudes along the route. 

There will be various forms of this dynamic re-planning in the future as good 

oceanic data links and AIDC become available. The current example is DAR

i

South Pacific routes where given new weather and their calculation of better 

routes (using their model of B747-400 performance and their definition of 

“better”). If there is a significant improvement, Oakland facility informs (or 

initiates negotiations) with other Oceanic facilities, and then updates the Sout

Pacific track system for all B747-400 aircraft, including those already airbo

data link. A second proposal under study by Oakland is called DUPR (Dynam

User-Preferred Rerouting) where each airline’s dispatcher calculates a revised 

flight plan and initiates negotiations with ATC to gain its acceptance in 

competition with other revisions (either already submitted or about to be resubmitted). It will not be easy to find a larger set of compatible revisions for 

oceanic areas when there is a higher traffic density and a variety of differ

of aircraft requesting changes. It requires good data communications to gain

benefits of dynamic re-planning of flights. 

ndent Surveillance Management 

Since the FMS has digital information at all t

s

Surveillance (ADS). The FANS S

automation and the aircraft’s FMS, to be able to establish and modify Periodic, 

Event-based, and On-Demand Contracts for position reporting with aircraft. 

Periodic reports confirm that data link communication is being maintained as w

as monitoring longitudinal progress. Event reports provide a timely alert to ATC

that certain events have now occurred (e.g., a waypoint or crossing point has b

reached, or a non-conformance has occurred), and may also provide a check on 

the current value of the next two intended waypoints. On-Demand reports will be 

needed when unexpected non-conformance events are occurring in the area, or 

revised flight plans have been requested. These ADS contracts are automatically

managed by the FMS with oversight and agreement of pilots and controllers. 
37

ta 

6. Com

ber of ways to communicate by voice (VHF, 

HF, SATCOM, HF), and all aircraft will be adopting data link or CPDL in 

t media (SATCOM, HFDL, Mode S, VDL-X, ATN). 

ous 

pilots 

Summ

The current implementations of FANS (FANS-1, FANS-A) have adopted INMARSAT 

ince it was available at the time and simultaneously provided voice, fax, and 

data communications to meet the needs of both passengers and AOCs. This multiple 

nd 

eir 

terim 

S 

physical size of the 

antenna system limit the class of aircraft on which FANS can be used. This in turn will 

There may be a coordinated contract to report simultaneously certain weather da

to support and improve weather forecasting and planning activities of ATC and 

AOCs. They create a random occurrence of short data messages from many 

aircraft to one (or more) ATC/AOC facilities. There is a growing set of 

developments by the GPS industry for the “tracking” of terrestrial vehicles using

satellite data communications. 

munication Management 

Modern aircraft now have a num

U

future years using differen

The FMS usually provides some degree of Communications Management 

(isolated to some degree from the flight-critical FMS functions) for these vari

means of communication, particularly for data messages that need integration 

with the FMS and should have similarity in their handling/management by 

that is independent of the media used for communication. 

ary 

Service H s

requirement led to the use of steerable satellite antennas with their large size and 

expensive installation, and costly message fees (e.g., $7.50/minute). To get FANS 

working in the 1995 period, the existing ACARS ground network was used as the grou

link, necessitating in an inefficient conversion of bit-oriented messages to allow th

transmission over the ACARS character-oriented format. This was considered an in

implementation since it was expected that ATN and other aviation data link media would 

eventually appear to allow more efficient communications. This evolution has been 

delayed, and FANS continues to use this “temporary” system. 

FANS is the only existing system that meets the oceanic system requirements for AD

and CPDLC. However, installation and operating costs, and the 

, 

limit access to airspace in which these capabilities are required. We encourage the FAA

and the aviation industry to build on the operationally useful portions of FANS, and 

develop a newer-technology, less expensive implementation in order to encourage 

increased equipage and open the airspace to all users. 

Enhanced TDMA over INMARSAT

As noted above, the set of TDMA protocols used in INMA

density traffic such as individual telephone-lik

RSAT is well suited to low 

e calls, but is not efficient for large 

umbers of users who need to communicate with the same ground node. The amount of 

e 

der 

n

satellite transponder power and bandwidth utilized for a given service strongly drives th

cost of INMARSAT transmission. Thus, more efficient use of the satellite transpon

bandwidth and power has the potential to reduce the cost of a service. 
In a previous study15, representative cost for reporting a 150-bit aircraft position report 

message every 30 seconds using offered services (and the existing protocols) was 

stimated to be $45 for a 5-hour flight based on $0.50/kbit service charge. Supporting 

 a 

n the 

e

500 such aircraft over a single 100 kHz leased INMARSAT channel could be done with

more efficient slotted TDMA scheme. Leasing the channel at $30k/month (based o

DISA lease rates given above) would cost an average $2 per aircraft per day. Total 

service costs might be twice this. In any event, the potential economic advantage for 

using an efficient TDMA protocol is substantial and worth further investigation. 

Iridium16

The Iridium System is a satellite-based, wireless communications network providing a 

robust suite of voice and data services to virtually any destination anywhere on earth. The 

Iridium system comprises three principal components: the satellite network, the ground 

network and the Iridium subscriber products including phones and pagers. The design of 

the Iridium network allows voice and data to be routed virtually anywhere in the world. 

Calls are relayed from one satellite to another until they reach the satellite above the 

Iridium Subscriber Unit and the signal is relayed back to Earth. 

The on-orbit Iridium constellation 

consists of 66 operational satellites 

and 14 spares in a constellation of 

six polar planes. Each plane has 11 

mission satellites performing as 

nodes in the telephony network. The 

14 additional satellites orbit as 

spares ready to replace any 

unserviceable satellite. This 

constellation ensures that every 

region on the globe is covered by at 

least one satellite at all times. The 

satellites are in a near-polar orbit at 

an altitude of 485 miles (780 km). 

They circle the earth once every 100 

minutes traveling at a rate of 16,832 

miles per hour. Each satellite is 

cross-linked to four other satellites; 

two satellites in the same orbital plane and two in an adjacent plane. The satellite 

constellation is expected to provide continuous global coverage until 2014. 

The ground network is comprised of the System Control Segment and gateways used to 

connect into the terrestrial voice and data networks. The System Control Segment is the 

central management for the Iridium system. It provides global operational support and 

control services for the satellite constellation and delivers satellite-tracking data to the 

38

 

15 Goblick, “Advanced Satellite Communication Technology for Oceanic Air Traffic Control,” MIT Lincoln 

Laboratory Advanced Concepts Committee Project #262 Final Report, September 1998 16 Adapted from: www.iridium.com 
gateways. The System Control Segment consists of three main components: Four 

Telemetry Tracking and Control sites, the Operational Support Network, and the Satellite

Network Operation Center. The primary linkage between the System Control Segment,

the satellites, and the gateways is via K-Band feeder links and cross-links throughout th

satellite constellation. 

Gateways are the terrestrial infrastructure that provides interconnection to the terrestrial 

voice and data networks. Gateways also provide network management functions for their 

own network elements 

39

e 

and links. 

 for around $1400 retail . Calls are set up 

ery much like a cellphone: dialing a number results in a transmission to the 

teway 

d 

property and intellectual capital. Headed by aviation industry 

eteran Dan Colussy, and funded by a group of private investors, Iridium Satellite LLC 

e cost of the 

f Defense 

ther U.S. 

, 

nd 

us on industrial clients 

hose operations require reliable communications to and from remote areas of the globe 

 the 

t the 2003 Paris Air Show, Iridium announced four new aviation-based efforts firmly 

s 

dministration's fleet of aircraft; a contract with the U.S. State Department to equip an 

t of Wild 

 

The Iridium system was designed to provide cellular-like voice services 

anywhere on earth. The common subscriber equipment is a cellphone-like 

handset with a data port, available 17

v

cognizant gateway (generally via crosslink) requesting a channel. The ga

assigns the channel and sets up the communications path, and manages 

handovers among satellites as individual satellites rise and set. (Individual 

satellites will only remain within view of a given location for less than 15 

minutes.) 

In December 2000, Iridium Satellite LLC acquired the operating assets of 

Iridium LLC including the satellite constellation, the terrestrial network, an

Iridium real 

v

has essentially no debt and monthly operating charges that are one-tenth th

previous Iridium. Through its own gateway in Hawaii, the U.S. Department o

(DoD) utilizes Iridium for global communications capabilities. Services to o

government entities are available through the DoD contract. 

Iridium Satellite began service to the U.S. Government in December 2000. On March 28

2001, commercial satellite communications services were launched to heavy industry a

other government customers. The marketing strategy is to foc

w

where terrestrial systems are not available. Specifically, the company will pursue 

industrial segments including aviation, maritime, oil & gas, mining, heavy construction, 

forestry, emergency services, and the leisure market. 

Iridium Satellite has contracted with the Boeing Company to operate and maintain

satellite constellation, and Motorola has agreed to provide subscriber equipment. 

A

establishing Iridium's ever-growing reach into the aviation sector. Those announcement

included; a contract to supply Iridium communications on the Federal Aviation 

A

initial 80 aircraft in support of drug enforcement programs in South America; a contract

with the U.S. Department of Agriculture, Forest Services to provide tracking capabilities 

for their large fleet of aircraft and ground support equipment for mission suppor

land Fire Suppression and an additional announcement of Iridium communication 

17 Web posting by SatPhoneStore at http://www.satphonestore.com/servprod/iridium/AirTime.htm 
services being utilized by the Russian space firm, Space Flight Operations Company to 

provide ground, recovery aircraft and spacecraft communications. Iridium is currently 

working on trial applications with several commercial airlines and foresees a strong 

continual growth for its voice and data capabilities within this industry. 

The projected lifetime of the satellites has been evaluated based on on-orbit experience

and the initial constellation is estimated to provide service into 2014. Nonetheless, th

bankruptcy of the original Iridium naturally raises questions about the lo

40

, 

e 

ng-term 

conomic viability of Iridium Satellite LLC. The DoD contract, at $36M/year for up to 

t 

itting 

e another. 

eneral Dynamics suggested that this Netted Voice method might be extended to provide 

s 

ations. The Motorola Satellite 

eries 9522 L-Band Transceiver (LBT) is intended for incorporation into an data solution 

 is 

Honeywell and Icarus are offering 

example, the Icarus Satphone II rec

Of the available Iridium data servic

idium Short Burst Data (SBD) Service is an efficient network protocol designed for 

shorter sized data messages than can be economically sent via Iridium Circuit Switched 

ork protocol to transfer data messages to and 

 

e

20,000 users, provides a substantial initial business base. The new Iridium, unlike the 

original one that needed 1 million subscribers to break even, only needs 60,000 

subscribers to cover costs18. However, Iridium will need a larger business base to

finance a follow-on generation of satellites. Assuming a seven-year lead-time for the nex

generation, Iridium has until about 2007 to achieve the larger business base. 

General Dynamics is presently developing a method to support a “party-line” perm

multiple voice users to share a single channel. This system is to be demonstrated in 2004 

for the USMC, where all the terminals are within the order of 100 miles of on

G

Aviation Netted Voice. The estimated capacity, assuming each aircraft generates 3 voice 

messages of 10 seconds duration, and 5 data messages of 100 bytes each, every hour, is 

about 120 aircraft per Iridium channel with 40% loading. 

In addition to voice services, Iridium has developed a large number of data services19

with different characteristics, as summarized in Table 5. Also, Iridium developed and ha

made available a data transceiver for embedding into applic

S

or product. The LBT is simply the core modem that

required in order to communicate over the Iridium 

network. Additional components are required such as 

power supply, antenna, environmental protection and 

the serial based interface between the LBT and the 

customer’s application. At least AirCell, Blue Sky, 

Iridium Terminals to the aviation community. For 

ently listed at $4495.20 

es, the Short Burst Data (SBD) Service and Short 

Messaging Service (SMS) seem of most interest for Oceanic CNS. 

Iridium Short Burst Data (SBD) Service 

Ir

Data Services. SBD uses a proprietary netw

18 Quote attributed to Dan Colussy in 2001, see: http://uk.gsmbox.com/news/mobile_news/all/35771.gsmbox 19 Iridium Satellite Data Services White Paper, Version 1.0, June 2nd, 2003. 20 E.g., see SatPhoneStore web site at http://www.satphonestore.com 
41

d 

BD messages from the subscriber is between 1 and 1960 bytes. (0 byte 

essages are referred to as “mailbox checks.”) Message size for outbound messages to 

rs. Iridium 

self does not provide complete end-to end solutions. However, it looks to selectively 

e, 

from the remote terminal. Example applications include flight following for aircraft an

helicopters. 

It is possible to originate and receive messages at the subscriber terminal. Message size 

for inbound S

m

the subscriber is between 1 and 1890 bytes. All messages are acknowledged. 

The target vertical markets for SBD are Oil, Gas, Rail, Maritime, Aeronautical, and 

Utility industries as well as applications in the Government and Military secto

it

partner with skilled Value Added Resellers (VARs) to integrate the required hardwar

software, and SBD service that ultimately forms the complete packaged solution for the 

end customer. 

Table 5. Iridium Data Services 

Remote Applications send data messages via an Iridium 9522 L-Band Transceiver 

(“LBT”). The application microcontroller or microprocessor communicates with the LBT 

using AT commands over an RS232 serial port. The application loads the data message 

into the LBT and instructs it to send the data message. The data message is transmitted 

across the Iridium satellite network utilizing inter-satellite links to reach the Iridium 
42

ansmit 

es 

 approximately 20 seconds for maximum length messages. This latency is the elapsed 

 in 

) 

ility designed for both mobile origination and reception of short text 

essages. There are numerous GSM-SMS applications developed for terrestrial GSM 

isting terrestrial based applications and also to 

evelop new applications using the Iridium SMS service. 

ibers are able to receive SMS 

essages via <MSISDN>@msg.iridium.com, where <MSISDN> is the Iridium phone 

subscribers (when available.) 

ssages can be entered into the phone in one of two ways: 

ort, using standard AT commands 

n send 

pecific applications 

may inc & alerts, schedule information, personal messaging, 

basic e

tive 

act with General Dynamics, the FAA currently experimenting with the use of 

idium for air-ground communications in support of the Capstone program in Alaska. 

Gateway. From there the data message is transferred via e-mail to the VARs host 

computer system. Here the message is stored in a database for further data processing. 

Outbound messages to the remote terminal are sent to the Iridium Gateway via e-mail 

from the VAR’s host computer system. Data messages are delivered to the LBT 

following a “mailbox check” initiated by the remote application. Global network tr

latency for delivery of messages ranges from approximately 5 seconds for short messag

to

time before the Iridium SBD system sends the SBD message to its email destination. 

Additional latency introduced by the Internet or the customer’s host system is not

Iridium’s control. 

Iridium Short Message Service (SMS) 

Short Message Service (SMS) is a Global System for Mobile Communications (GSM

based system capab

m

networks. It should be possible to adapt ex

d

The Iridium SMS service offers the following capabilities: 

• Two-way global text messaging. 

• Send to and receive from other Iridium SMS subscribers. 

• Send to and receive from email addresses. Iridium subscr

m

number. 

• Send to and receive from cellular 

• 160 characters per message. 

• Messages will be stored until delivered (up to 8 days.) 

• Supported on 9505 handsets and 9522 LBTs with SMS capable firmware. 

• SMS me

• via the phone’s keypad 

• via the phone’s data p

The Iridium SMS Service can be used to serve a range of applications that ca

useful information within the 160-character limit of each message. S

lude: weather information

mail messaging, and monitoring of remote applications. 

A major advantage of Iridium is that its current cost structure is very low. An illustra

cost comparison provided by an Iridium aviation service and equipment supplier is given 

in Table 6. 

Current Aviation Usage of Iridium 

Under contr

Ir
43

e services to regions that do not have conventional 

HF air-ground communication coverage. 

o 

Globalstar21

Iridium will be used to extend Capston

V

In addition, several service providers, including ARINC, are providing Iridium service t

aircraft. To date, this service is for personal and company communications, not for air 

traffic control. 

Table 6. Example Cost Comparison between Iridium and INMARSAT 

lobalstar currently offers service from virtually anywhere across over 100 countries, as 

ell as from m st territorial waters and several mid-ocean regions. Signals from a 

e or modem are received by the company's constellation of 48 Low Earth 

rbiting (LEO) satellites and relayed to ground-based gateways, which then pass the call 

logy 

 

G

w o

Globalstar phon

O

on to the terrestrial telephone network. The satellites act as “bent-pipe” relays to the 

gateways. 

Gateways process calls, then distribute them to existing fixed and cellular local networks. 

Terrestrial gateways are an important part of Globalstar's strategy to keep key techno

21 Adapted in part from www.globalstar.com
44

ent easily accessible and to integrate services as closely as possible with 

xisting local telephony networks. This makes the Globalstar system and its services 

anic 

and equipm

e

simple to manage, expand and improve. Since only satellites within view of gateways 

provide service, coverage is correspondingly limited by the gateway deployments. From 

the above figure, it appears that Globalstar primary coverage is not sufficient for Oce

CNS. 

 Primary Globalstar Service Area 

 Extended Globalstar Service Area (Customers may occasionally experience lower 

Fringe Globalstar Service Area (Customers may experience intermittent signals) 

 

signal availability) 

 

Figure 6. Current GLOBALSTAR coverage 

In addition to normal voice communications, Globalstar services include: Internet and 

private data network connectivity, position location, SMS (short messaging service), and 

call forwarding. These services are supported by a growing range of products and 

accessories designed to make Globalstar service productive and easy-to-use in almost any 

situation or environment, including aviation and maritime applications. The company's 

data modem products can also be used for asset tracking and environmental telemetry 

applications. 

Globalstar L. P. was established in 1991 and began commercial service in late 1999. In 

February 2002 it reached agreement with several of its major creditors to restructure the 

company’s debt and, in order to facilitate the timely completion of the restructuring, filed 

a voluntary petition under Chapter 11 of the U.S. Bankruptcy Code in the U.S. 
45

w 

ated 

 has entered 

e 

ooking ahead, Globalstar intends to continue expanding its operations to provide service 

. 

t for an individual gateway, and the relatively 

odest traffic opportunity afforded by the oceanic areas, it does not seem likely that 

eral 

RNAV RCOM-100 SatPhone and Accessories: A single line, multi-port Globalstar 

-Function Display. 

RNAV also offers a number of accessories for the RCOM-100, including cordless and 

e 

th Northern Airborne's PTA12 

ialer/Adapter, a full feature keypad that allows calls to be made through the aircraft's 

in 

e flightomnion satellite systems. Globalstar antennas require no aiming or 

alibration, and their small size results in extremely low aerodynamic drag. 

 

Bankruptcy Court in Delaware. The court approved transfer of substantially all of 

Globalstar L.P.’s assets to a newly created Delaware corporation in exchange for a 

minority interest in the new corporation. Under the agreement, ICO Global 

Communications (Holdings) Limited was to acquire a majority interest in the ne

corporation in exchange for an investment of $55 million. However, that contempl

restructuring did not occur. Instead, a new Globalstar company, 81.25% owned by 

Thermo Capital Partners LLC for an investment of up to $43 million in cash,

into an acquisition agreement for Globalstar’s business asset. The acquisition will b

completed upon receipt of U.S. regulatory approval, expected the first quarter of 200422. 

As of June 30, 2003, Globalstar had approximately 93,000 subscribers worldwide, an 

increase of 11% over the previous quarter. 

L

in the few remaining land areas not covered today, as well as across mid-ocean regions

Nonetheless, in view of the large investmen

m

gateways to provide primary coverage into the mid-Atlantic or mid-Pacific areas would 

be installed until the business base on the existing assets becomes a net cash generator. 

Globalstar has announced several products supporting voice and data services for gen

aviation fixed wing and helicopter aircraft. Examples include 

A

duplex transceiver, which uses a standard telephone interface for installation flexibility 

and easy connectivity to a phone handset, PC or cockpit Multi

A

retractor-reel handsets as well as a dialer/adapter that allows calls to be made through th

aircraft's audio panel for full headset operation. 

Northern Airborne STX100 Satcom System: An airborne communications system, 

certified by Transport Canada and the U.S. Federal Aviation Administration, that 

combines a Globalstar-compatible system unit wi

D

audio system for full headset operation. For cabin applications, a handset can be used 

parallel with the PTA12 to provided independent access to the system. Optional 

accessories include the LMC01 geo-location system, which can be used to provid

following capability. 

All Globalstar aviation products take advantage of Globalstar's very-low- profile, 

directional antenna technology, which eliminates the need for expensive, bulky antennas 

used in earlier-generati

c

Airtime for all Globalstar aviation products is available through three aircraft service 

pricing plans, specifically designed for low, medium and high minute-of-use 

requirements. Service plans start as low as $39.95 per month. 

22 “Thermo Capital Partners Complete Take Over of Globalstar”, Space Daily News, Dec 09, 2003. 
46

NexSAT23

n the VHF 

ed lack of capacity to 

ted communications traffic in the future. Therefore other technologies are 

eing considered in the timeframe of 2010-2015 to complement VHF systems and 

n 

world. 

The tim

commu

atellite communications could be a potential candidate technology but only with 

ation 

envisioned as a global system with the 

bility to complement terrestrial systems to meet regional needs. The basic NGSS would 

T 

ctivities. The first meeting of the NexSAT SG was in November 2002. 

lted 

d to a more 

omplex system design. Safety-related communications were only a small fraction of the 

, 

ift64, 

mmercial issues as AMSS. 

here was currently no system dedicated to support safety-related communications (i.e. 

 

In Europe air traffic growth is expected to outstrip communication resources i

band despite introduction of 8.33kHz spacing. There is a predict

handle expec

b

Eurocontrol is currently pursuing two options in line with its Communications Strategy - 

1. Terrestrial-based using UMTS-type technology 

2. Satellite-based using enhancement of existing AMSS as a Next Generatio

Satellite System (NGSS) that would be useable in Europe and the rest of the 

escale is for the system(s) to be operational by 2010 to 2015 to meet the 

nication shortfall predicted at that time. 

S

improved performance over current AMSS and at lower cost. Although consider

was being given to benefits in Europe, NGSS is 

a

have many benefits in other parts of the world particularly low-density areas. 

Accordingly, the EUROCONTROL Next Generation Satellite System Steering Group 

(NexSAT SG) was formed to address NGSS to meet future aeronautical communication 

requirements. EUROCONTROL has contracted with QinetQ to support NexSA

a

The point of departure for this community is that some of the limitations of the current 

Aeronautical Mobile Satellite Service (AMSS), as defined in ICAO standards, resu

from its design goal to support the full range of aeronautical users. This le

c

total communication traffic, and although they had priority over the use of the spectrum

the business case was mainly driven by the non-safety traffic. The cost of aircraft 

installation and avionics was high; large GESs were needed and quality of 

communication service not adequate for medium or high-density region usage. In 

addition the resulting shared use of spectrum between safety and non-safety services 

made it difficult to defend the need for exclusive spectrum. 

Although new satellite based communication systems are being considered (e.g. Sw

Connexion) these are primarily aimed at non-safety communications such as Internet 

access for passengers and they would be subject to similar co

T

AMS(R)S) 

23 This discussion is based primarily on presentations by Phil Platt and Philippe Renaud of NexSAT at the Working 

Group meeting on 26 November 2002. 
47

 had enabled a good infrastructure to be built up which could be re-used for a 

GSS. These elements include - 

rks 

ional arrangements 

Th infrastructure and on it overlay improved technology and 

tec tures - 

• Lower cost AESs by tailoring the system to meet safety and regularity of flight 

A, to improve multiple access and overall 

• service - global (low rate) and regional (higher rate) 

• igh levels of availability, reliability and continuity required for safety 

A 

infras strated using regional beam coverage to 

rovide enhanced capability. 

s of advanced ATM concepts emerging from Eurocontrol 

rategies, the communication requirements appear to require modest instantaneous 

. 

orted 

g at 

rcoming some of the limitations of the current 

MSS. 

ced 

CAO AMCP work programme. Some papers have already presented that have 

resented some high level considerations. The high level SARPS for a generic NGSS 

nly 

 

Despite limitations with existing AMSS its current use to support ATM in various parts 

of the world

N

• GEO Satellites 

• GESs 

• Spectrum in L-band 

• Terrestrial netwo

• Institut

e NGSS could reuse this

hniques with the following fea

communications only 

• Use of modern techniques, e.g. CDM

efficiency 

Providing two levels of

• Options to allow use of Ku-band feeder links enabling small GESs 

Design in h

and regularity of flight communications 

possible initial deployment in Europe was shown based on the existing AMSS 

tructure; an extension of this was also illu

p

The design of the NGSS would be requirements driven, based on supporting ATS and 

AOC applications. By analysi

st

throughputs - these can be met by a medium rate highly reliable communication system

Aggregated ATM data link based concepts seemed to be able to be supported by a 

throughput of around 1 kb/s per aircraft24. In addition, voice services would be supp

too for non-routine or emergency situations. Using a 4.8Kbps vocoder plus error 

detecting/correcting this requirement could be accommodated in a channel operatin

around 7 kb/s per aircraft. It may be possible to increase this basic rate to around 30kbps 

in a regional beam e.g. over Europe. 

Based on work undertaken by ESA it seems there is an opportunity to define a NGSS that

could meet these requirements by ove

A

The technical specification for such a NGSS would have to be refined and be introdu

into the I

p

already exist and the draft ICAO Communications Roadmap Document for presentation 

at the 11th Air Navigation Conference is expected to explicitly include NGSS. 

Eurocontrol has visited the Japanese Civil Aviation Bureau (JCAB). JCAB uses AMSS 

and is generally concerned about the quality of the communication service (mai

24 Eurocontrol Report ‘Operating Concept for the Future Mobile Communication Infrastructure - D2’
48

vailability). However it is about to launch its own satellite (MTSAT) for supporting the 

 the 

or 

cular. 

d pending on 

pporting services in the 1 - 6 priority levels (according to ITU definition) - ITU 

to 

 System. For many 

ears, ESA has been investigating the concept of new mobile satellite communication 

e 

as – 

 of accessing GESs and need for a Network Control System 

• Slow service recovery following a GES outage 

 following a satellite outage 

e Public Switched Telephone 

A of 

SDLS

• Illustrate the capacity of modern techniques in mobile communication systems to 

ng AMSS 

•

ES

definition, starting in December 2002. This would be complementary to the Eurocontrol 

NGSS activities. SDLS Full system development of SDLS may start in 2004. In the 

a

current AMS(R)S services. A second co-located satellite will follow this the following 

year and two hot redundant GESs have been built. JCAB are interested in enhancing

current system and are also interested in co-operating with activity underway in Europe 

and other parts of the world on the system definition for a NGSS, a common approach f

spectrum availability, and participating in technical tasks. 

A NexSAT priority is the development of a more descriptive document of the proposed 

NGSS as mentioned above that could become an ICAO Cir

Aviation lost its exclusive AMS(R)S spectrum at L-band as a result of WRC 97. 

However, the ITU recognizes aviation as “priority” users of the ban

su

footnote S5.357A. At Eurocontrol’s request, CEPT CPG has confirmed that, when

aviation is ready to operate the service, National Radio Administrations will have 

ensure access to the frequency in the former AMS(R)S sub-band. 

An Agreement for Co-operation has been signed between EUROCONTROL and ESA. 

One task is to progress the definition of a Next Generation Satellite

y

services with tailored applications in a private network environment. The Satellite Data 

Link System (SDLS) was conceived with a view to meeting the highly demanding 

requirements of safety and regularity of flight communications. The “MSBN” prototyp

system for Land Mobile Service application developed by ESA has served as a basis for 

the SDLS concept. 

The main design goals of SDLS are to improve on the major identified limitations of the 

existing AMSS such 

• AES complexity and cost 

• Limitation of number

• Very slow service recovery

• Large usage of capacity hungry random access transmissions 

• Voice service limited to a mobile extension of th

Network supported telephony service 

demonstrator had now been built with the aim of showing some of the key features

 to - 

efficiently support some important ATM applications beyond the capability of the 

existi

• Demonstrate the party line functionality in the voice service 

Prove that guaranteed transmission delay for time-critical aircraft data (e.g. ADS) 

can be achieved 

A intended to fund future industrial activities to develop an SDLS detailed system 
49

meantime ESA would help industry support to Demonstrations/Evaluations of SDLS in 

co-operation with EUROCONTROL It is hoped that the ‘tool-box’ of good ideas from 

the SDLS work would be a major contribution to the definition of the NGSS. 
50

(This page left blank) 
51

Appendix A

Terms of Reference 

Study of Cost-Effective Aircraft-Controller Communications to Support Enhanced 

Oceanic ATC 

Short title: Oceanic Comm Study 

Background and Objectives

Air traffic in oceanic areas, the Polar Regions, and the Gulf of Mexico has been growing 

steadily in recent years. The March 2002 FAA Forecast predicts that international 

passenger traffic will grow through 2013 at an annual rate of 4% in the Atlantic, 4.9% in 

the Pacific, and 6% in the Latin American and Pacific markets. In response, civil 

aviation authorities are introducing new technologies and procedures to increase capacity 

and improve efficiency and predictability. These include Reduced Vertical Separation 

Minima (RVSM), Required Navigation Performance (RNP), and new automation 

systems for the control of oceanic traffic. 

To achieve maximum benefit of the new automation systems requires that the aircraft 

make frequent GNSS-based position reports (ADS) and have a rapid, reliable data 

communication link between aircraft and controller (CPDLC). The FANS program has 

defined the requisite message formats and operational protocols. However, the high cost 

of current air-ground satellite communications, both in terms of avionics and training 

costs and communication link charges, may limit the rate of aircraft equipage. Only 

when these costs have been reduced to the point that they are affordable to essentially all 

oceanic operators will it be possible to require equipage for operation in “prime” oceanic 

airspace (as has been done in the case of RVSM)), and thereby achieve the full potential 

operational benefits. (In addition, these techniques can provide the basis for enhanced 

ATC in sparse-traffic areas where increased safety, rather than capacity and efficiency, is 

the principal driver.) 

This study will examine the various technical alternatives for providing a high integrity 

communication link between the aircraft and control facility which can support the 

FANS-defined ADS and CPDLC, make an assessment of their economic viability, and 

provide its conclusions and a recommended course of action to the FAA via the REDAC. 

Specific Study Tasks

1. Assess and summarize projections of the growth in demand for oceanic operations. 

2. Based on existing studies, summarize the economic benefits of enhancing the capacity 

and efficiency of oceanic ATC. Determine what level of equipage is needed to obtain 

benefits and what are the current plans for oceanic operators to equip. 
3. Examine technical alternatives for providing a high integrity communication link 

between the aircraft and control facility which can support the FANS-defined ADS and 

CPDLC. Estimate costs of viable alternatives. 

4. Examine plausible strategies for transition to a more affordable oceanic ATC 

communications architecture. 

5. Prepare conclusions and recommendations for forwarding to the FAA via the ATS 

Subcommittee and the REDAC. 

Study Structure

The study will be performed by an ad hoc working group of the REDAC ATS 

subcommittee. This working group will comprise 10-12 subject matter experts drawn 

from the ATS subcommittee and other organizations. 

The output of the working group will be a final report to the ATS subcommittee, with the 

recommendation that the report be forwarded in turn to the REDAC and, with REDAC 

endorsement, to the FAA. 

Study Schedule

It is expected that the study will be carried out over an approximately six-month period, 

with five to seven meetings of the working group during that period. 

February 10, 2003 

52
Appendix B 

Study Participants 

Working Group Members25

Drouilhet, Paul – Chairman MIT Lincoln Laboratory (Retired) 

Parra, Ricardo – Designated Federal Official FAA 

Dundermann, Gloria – FAA Logistics Support FAA 

Fielding, John Raytheon (Retired) 

Kerczewski, Robert NASA Glenn Research Center 

LaFrey, Raymond MIT Lincoln Laboratory 

Perie, Michael Air Traffic Control Association 

Poritzky, Siegbert Consultant 

Seay, Thomas Consultant 

Simpson, Robert MIT Flight Transportation 

 Laboratory (Retired) 

Other Study Participants 

Anderson, Teresa 

Anton, Terri ARINC 

Bonard, Michael 

Bradford, Steve FAA 

Brown, John Boeing 

Budinger, James NASA/FAA 

Burton, C. Ross CSSI 

Chamness, Kevin FAA AUA-600 

Colamosca, Brian FAA 

Dieudonne, James Mitre/CAASD 

Feldman, Ellis 

Flax, Bennett 

Ford, David FAA AUA-600 

Gelinas, Michel General Dynamics 

Grappel, Robert MIT Lincoln Laboratory 

Greenfeld, Israel 

Grimm, Kevin FAA 

Gross, Amy Mitre/CAASD 

Hassan-Miller, Angel Mitre/CAASD 

Heinke, Ann USAF 

Leftwich, Roberta FAA 

Lindholm, Tenny NCAR 

Livingston, Dave 

 

25 Mitre/CAASD was invited to have a member of its staff on the working group, but had to decline because of workload 

considerations. However, Mitre personnel made several presentations to the working group, and reviewed and made a number of 

useful suggestions to the final report. 
Manning, Robert USAF 

McCarron, John FAA AUA-600 

Mittelman, Jeff 

Moulton, Jim 

Oishi, Roy ARINC 

Platt, Phil Eurocontrol 

Renaud, Philippe Eurocontrol 

Sears, Bill Air Transport Association 

Stine, Bill National Business Aircraft Assn. 

Storm, Allan USAF 

Terri Anton, ARINC 

Thoma, Don 

Zelenka, Rick Boeing 

54
Appendix C

Presentations to the Working Group 

(* indicates presentation is included on CDROM) 

Date Subject Presenter(s)

11 Dec 02 

CNS/ATM initiatives in the oceanic 

environment 

Kevin Chamness, FAA/AUA-600 

Benefits of Enhanced Oceanic Ops Ellis Feldman, Ricardo Parra 

8/9 Jan 03 

Potential Benefits of More Efficient 

Oceanic Operations 

Amy Gross, Mitre/CAASD 

Cost/Benefit Analysis of Oceanic 

Operations 

Ross Burton, CSSI 

Australia ADS-B Initiative 

 *FANS Implementation in Australia 

 *CNS-ATM in the Australia FIR 

Michael Perie 

*FANS 1 John Brown, Patrick Harper, Rick Zelenka, Boeing 

*Globalink/HF Data Link Terri Anton, ARINC Inc. 

6/7 Feb 03 

ATOP 30/30 Implementation Kevin Chamness, FAA/AUA-600 

*Thoughts on Communication 

Requirements 

Tom Seay 

*On Satellite Communications for Oceanic 

CNS 

Tom Seay 

*TACC Mobility 2000 Allan Storm, Bob Manning, Anne Heinke, 

DoD/USAF Flight Standards 

*Globalink/Satellite Tutorial Roy Oishi, ARINC 

*Separation and Airspace Safety Panel 

(SASP) 30/30 Activities 

Robbie Leftwich 

*CNS-ATM Oceanic (Federal Express 

Perspective on Oceanic Operations) 

Steve Vail 

6 Mar 03 

ATOPS Update and Tour Angel Hassan-Miller, Mitre/CAASD 

Requirements for 30/30 Separation Brian Colamosca 

ATA Perspective on Oceanic Operations Bill Sears, ATA 

NBAA Perspective on Oceanic Operations Bill Stine, NBAA 

3/4 Apr 03 

FANS/AMSS Kevin Grimm, FAA 

Eurocontrol's Outlook on ATC Comm Philippe Renaud, Eurocontrol 

*NextSAT – Satellite communication 

services dedicated to ATM 

Phil Platt, Eurocontrol 

55
INMARSAT Michael Bonard, Telenor 

Oceanic Aviation Weather Tenny Lindholm, NCAR 

Iridium Don Thoma, Iridium 

*Capstone Satellite Feasibility Study Jeff Mittelman, Mitre/CAASD 

*Netted Radio – A Cost-Effective Iridium 

Communications Link for Oceanic CNS 

Michel Gelinas, General Dynamics, 

1/2 May 03 

FAA Target System Description Robbie Leftwich & Steve Bradford 

Oceanic Benefits Analysis Ellis Feldman, FAA 

*Open System Protocols for Aviation Data 

Link Applications 

Bob Grappel, Lincoln Laboratory 

Comparison of ATN and TCP/IP Jim Moulton 

5 Jun 03 

*GCNSS Demonstration and Simulations Jim Dieudonne, Mitre/CAASD 

56
Appendix D

Bibliography

(* indicates document included on CDROM) 

FANS

Esler, David, FANS: Where Is It for Business Aviation?, Business and Commercial Aviation, 

March 2003

Esler, David, Avionics OEMs Contemplate FANS for Business Aviation, Business and 

Commercial Aviation, May 2003

*FAA, Operator Benefits of Future Air Navigation Systems, Internal paper

General

*ARINC, ARINC to Offer Data Link Services Direct to Business Aviation, ARINC Press 

Release 79-02, September 10, 2002 

ATMS Inc., History and Evaluation of Separation Standards; extract from a report “Potential 

Operational Impacts of GPS with Advanced CNS and ATC Automation Technologies”, prepared 

by ATMS, Inc. for the FAA under Contract #DTFA01-94-C-00039, February 1996 

Boeing Air Traffic Management, Architecture Options in the Gulf of Mexico, Trade Study 

OP-15a Interim Report, Document No. D794-10048-1, June 17, 2003 

*Colledge, Gary, Next Generation SATCOM: INMARSAT Aero-BGAN for Air Transport, 

INMARSAT presentation to Datalink Users Forum, Feb 3-5, 2004 

FAA, Initial Regulatory Impact Analysis, Initial Regulatory Flexibility Determination, 

Unfunded Mandates and Trade Impact Assessment; Reduced Vertical Separation 

Minimum Operations in United States Domestic Airspace (NPRM, 14 CFR Part 91), Office 

of Aviation Policy, Plans, and Management Analysis, Operations Regulatory Analysis Branch, 

April 23, 2002 

FAA, National Airspace System Operational Evolution Plan; Federal Aviation 

Administration, Washington, DC 

*Goblick, T.J., Advanced Satellite Communication Technology for Oceanic Air Traffic 

Control, Final Report, Advanced Concepts Committee Project 262; MIT Lincoln Laboratory; 6 

October 1998 

Horton, Catherine P.; Solomos, George H., Assessment of the Potential Implementation of 

RVSM Phase I in the WATRS Region, Mitre Report No. MP 99W0000206, September 1999; 

Mitre/CAASD 

57
*ICAO, Air Traffic Services - Annex 11 to the Convention on International Civil Aviation - 

International Standards and Recommended Practices; Thirteenth Edition, July 2001; 

International Civil Aviation Organization, Montreal 

*ICAO, Air Traffic Management - Procedures for Air Navigation Services, Doc 4444, 

ATM/501; Fourteenth Edition, 2001; International Civil Aviation Organization, Montreal 

ICAO, Manual on Implementation of a 300 M (1000 Ft) Vertical Separation minimum 

Between FL 290 and FL 410 Inclusive, ICAO Doc 9574, AN/934; Second Edition - 2002; 

International Civil Aviation Organization, Montreal 

Jarrett, K., et al, Ad-Hoc Networking Results to Date, Boeing Global CNS Team, April 30, 

2003 

Jensen, David, Satcom for Your Citation, Avionics News and Highlights, October 2000 

*Jiang, H.; Ren. L.; and Hansman, R., Massachusetts Institute of Technology, Cambridge, MA; 

Market and Infrastructure Analysis of Future Air Cargo Demand in China; AIAA Paper 

2003-6770; AIAA 3rd Annual Aviation Technology, Integration, & Operations (ATIO) Forum; 

2003 

Joseph, Mark, ADS Performance Characteristics for Mid-Term Operational Concepts, 

Mitre Report MP 98W0000154, September 1998; Mitre/CAASD 

*Kern, et al, Recommendations For Aviation Communications Research Investments, report 

of the Air Traffic Services Subcommittee Aviation Communication Research and Technology 

Subgroup(ACRT), March 2003 

*Kong, Stephen, Next Generation SATCOM: INMARSAT Aero-BGAN for Air Transport, 

Boeing Commercial Airplanes presentation to Datalink Users Forum, Feb 3-5, 2004 

Maroney, David R.; Tittsworth, Jeffrey A.; Horton, Catherine P., Potential User Benefits for 

WATRS RVSM Phase II Implementation, Mitre Report No. MP 00W0000158, July 2000, 

Mitre/CAASD 

*Masuda, Shigeki, MTSAT. Japanese Civil Aviation Bureau presentation at Integrated CNS 

Conference and Workshop, Annapolis, MD, 20 May 2003 

Mitre, CPDLC Build 1A Benefits, Mitre Corp., January 11, 2002 

*Norrish, Lindsay, SATCOMs for CNS/ATM, GATM USERS’ CONFERENCE, Hanscom 

AFB, MA, September 2000 

58
Owens, S., Collision Risk Assessment of ADS-Based Operations and Reduced Lateral 

Separation in North Atlantic Airspace, NATS R&D Report 9747, National Air Traffic 

Services Ltd., London 

*Perie, Michael E., Oceanic Communication, presentation at ATCA meeting, Budapest, July 

2003 

Phone Facts, (Letter) Business and Commercial Aviation, December 2002 

Ramsey, James W., Corporate Connectivity, Avionics Magazine, September 2002 

*Singleton, Marissa, Evaluation of Benefits Resulting from Architecture Options in High 

Altitude Airspace within the Gulf of Mexico, Boeing ATM GCNSS Trade Study OP-15a, 

January 31, 2003 

*Wigger, Burkard, Mobile Internet Access Onboard - Project Lufthansa Flynet, Lufthansa 

German Airlines 

High Frequency Data Link (HFDL)

*Airbus, Technical Information About the Use of HFDL; presentation FIF/8-WP to the North 

Atlantic FANS Implementation Group, Eighth Meeting, Shannon, 3-7 March 2003 

*ARINC, ATS Messaging via HFDL, presentation FIG/8-WP/14 to the North Atlantic FANS 

Implementation Group, WP14, Eighth Meeting, Shannon, 3-7 March 2003 

*ARINC, HFDL Function and Performance, presentation FIG/6-IP to the Informal Pacific 

ATC Coordinating Group, FANS Interoperability Team, Sixth Meeting, Tokyo, 7-8 October 

2002 

*ARINC, HFDL System and Performance, presentation FIG/8-IP/3 to the North Atlantic 

FANS Implementation Group, Eighth Meeting, Shannon, 3-7 March 2003 

*NATS Further HFDL Analysis; presentation FIG/8-WP/7 to the North Atlantic FANS 

Implementation Group, Eighth Meeting, Shannon, 3-7 March 2003 

*Nav Canada, Consideration of HFDL for CPDLC Uplinks, presentation FIG/8-WP to the 

North Atlantic FANS Implementation Group, Eighth Meeting, Shannon, 3-7 March 2003 

*Nav Canada, Proposal for Operational HFDL FMC WPR Trial, presentation FIG/8-WP to 

the North Atlantic FANS Implementation Group, Eighth Meeting, Shannon, 3-7 March 2003 

59
Internet Protocols/ATN

*Blake-Wilson, Simon, (Certicom Corp.), Cryptography and the ATN Security Solution, 

PowerPoint presentation 

*Dhas,Chris; Wargo,Chris, Potential for the Use of Internet Protocols in Aviation, Aerospace 

Conference, IEEE Proceedings, Volume 3, March 2001

Dickinson, Gary W. (FAA); Minnix, Mary A. (The Mitre Corp.), Feasibility Study of ATN 

Baseline 1 Avionics Use For U.S. Oceanic Air Traffic Control Operations, 19th Annual 

Digital Avionics Systems Conference, Philadelphia, PA, Oct. 2000 

Iridium

FAA/ASD-140, Iridium and the FAA Gulf of Mexico Program and FAA Capstone Phase I 

ADS-B Demo Concept of Operations and Satellite Technology for Air Traffic Services - 

summary of presentations by Michael Gelinas and James M. Budinger, General Dynamics, 

November 22, 2002 

George, Fred, Satcom Revolution: Iridium Comes on Strong, Business and Commercial 

Aviation, September 2002

NexSAT

*Eurocontrol, Defending the AMS(R)S Spectrum Allocation at L-band (1.5/1.6 Ghz), 

NexSAT1/WP6, Eurocontrol Spectrum Protection Group Meeting, 24/26 October 2002 

*Eurocontrol, Eurocontrol and ESA sign agreement for cooperation on using space 

technology for Civil Aviation; Eurocontrol press release, 26 July 2002 

*Eurocontrol, Most Probable Satellite Communication Operations Concept for ECAC and 

Other Regions of the World, Working Draft, Edition No. 1, 22 May 2002 

*Eurocontrol, New Generation Satellite Communication System - ECAC Mission 

Requirements, Working Draft, 19 July 2003 

*Eurocontrol, NexSAT - Next Generation Satellite System (NGSS) - Initial Technical 

Description; Draft Version 0.E 

*Eurocontrol, Notes of the first meeting of the NGSS Steering Group, 26 November 2002; 

Eurocontrol, Brussels 

60
*Eurocontrol, Preliminary Study of Satellite Spectrum Requirements - Overview of Civil 

Aviation Satellite Communications & Spectrum Requirement Refinement, NexSAT1/WP4, 

12 April 2002 

*Eurocontrol, Welcome to the Launch of the Steering Group for the NGSS, presentation to 

the NGSS SG meeting, 26 Nov 2002 

*Loisy, Claude, Satellite Data Link System (SDLS), ESA presentation to the NexSAT Steering 

Group, 26 Nov 2002 

Thales Avionics, Comments and Trade-offs for Eurocontrol’s Proposed NexSAT Satellite 

System; Thales Avionics Limited Technical Note, 18 April 2003

Oceanic operations

ARINC Launches Waypoint Reporting Service for Transatlantic Traffic; ATC Market 

Report, p.11, January 10, 2003 

*FAA, ADS Enabled D-50 in ATOP Build One, Internal FAA paper 

FAA, Implementation Plan For Oceanic Airspace Enhancements and Separation 

Reductions, June 1999 

FAA, Strategic Plan For Oceanic Airspace Enhancements And Separation Reductions, 

Draft 1.0, January 2002

Giant Leap For Oceanic Comms as FAA, Nav Canada Test Data Links, ATC Market 

Report, p.7, September 5, 2002 

Koslow, Sid; Fekkes, John, Nav Canada’s GAATS: Effective Innovation for Oceanic 

Control, Journal of ATC, October-December 2002

*Ott, Robert, GCNSS Oceanic Operations and Transitions Analysis Study, Boeing GCNSS 

Trade Study OP-16, January 31, 2003 

Wu, Yueh-Shiou; Hamrick, Lynne Y.; and Mills, Michael J. (The Mitre Corp.), Impact of 

Controller-Pilot Data Link Communications on Oceanic ATC Service, 21st Digital 

Avionics Systems Conference, Irvine, CA., Oct 2002 

61