AERONAUTICAL COMMUNICATIONS PANEL (ACP)

FIRST MEETING OF THE WORKING GROUP OF THE WHOLE

Montreal, Canada 21 – 29 JUNE 2005

International Civil Aviation Organization

WORKING PAPER

ACP-WGW01/WP41

21/06/05

Universal Access Transceiver (UAT):History, Description, Operational Experience and Implementation Status

(Presented by Rapporteur of WG-C)

Agenda Item 1: Development of SARPs and Guidance Materials for the Universal Access Transceiver (UAT)

SUMMARY: This Working Paper summarizes the history, description, operational experience and implementation status of the Universal Access Transceiver (UAT).

ACTION: The ACP WGW is invited to review this Working Paper as an introduction to UAT and as background for the consideration of the draft UAT SARPs and Guidance Materials.

2

Outline

• History• UAT Description

– System Overview– Some Details

• Operational Experience and Implementation Status

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A Brief History of UAT

• 1995 part of an independent research project on a broadcast data link for surveillance

– 6 prototype systems were flown on small aircraft– ADS-B, TIS-B, and Weather uplink was demonstrated

• 1997 U.S. Cargo Airlines incorporate UAT in their evaluation of ADS-B—United Parcel Service – Aviation Technologies (now part of Garmin International) developed prototype UAT equipment

• 1998 UAT is evaluated as part of RTCA ADS-B Link Evaluation Team study (later evaluated by FAA/Eurocontrol Technical Link Assessment Team)

• 1999 UAT part of winning bid for U.S. FAA’s Alaska Capstone ADS-B implementation 3-phase program

• 2001 First operational use of UAT for Air Traffic Services in AlaskaCapstone Program, Phase 1

• 2002 RTCA MOPS (DO-282) approved and ICAO UAT SARPs development was begun

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UAT Overview

• UAT was designed specifically for ADS-B and Broadcast Uplink Surveillance-Related Services

• Simplicity and robustness were paramount design objectives

• UAT operates on a single common wideband channel at 978 MHz

• 1 Mbps channel rate• UAT is capable of supporting multiple uplink

broadcast applications e.g., FIS-B, TIS-B

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UAT Ground

Transceiver

TrackerATC

Surveillance Radar

ADS-B

TIS-B(non-ADStargets)ATC System

Tracks

Observations WX Radar Forecasts Graphics Special Use Airspace

Weather Server

FIS-B

UAT Applications and Connectivity

ADS-Bair-ground

ADS-B

air-air

FIS-BTIS- B

UAT Airborne

Transceiver

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UAT Waveform Selection

• Requirements– Good capture effect– Relatively efficient and low cost power

amplifier– Simple/robust decoder

• Binary FM with high modulation index chosen

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UAT Frequency Band Selection

• Aeronautical band alternatives:– VHF: 108-118 MHz– L-band: 960-1215 MHz– C-band: 5000-5250 MHz

• Extremely difficult to assemble enough contiguous channels at VHF

• Propagation loss too high at C band• 960-1215 MHz has best combination of:

– channelization (1 MHz)– compatible current usage (pulsed systems)– and propagation characteristics

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UAT Media Access Approach

Ground Broadcast (32 time slots)

UAT Frame = 1 sec.

Aircraft Reports (random)

Ground Message (432 bytes) ADS-B Message (18/34 bytes )

• Requirement: Simple and Robust logic for aircraft media access

• ADS-B transmissions occur based on pseudorandom selection of one of 3200 Message Start Opportunities (MSO)

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UAT ADS-B Message Format

• Each aircraft transmits exactly one message each second

• Standard Forward Error Correction (FEC):– increases message robustness to pulsed interference and noise– provides an extremely low undetected message error rate ~10-9

SYN

C

Message Data Block FECPARITY

4 36 144/272 96/112 4Bit Intervals

UAT Operational Experience: UAT in FAA’s Alaska Capstone Program

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JZZ

IIK

5S8

4Z4SCM

AK85

PTU

KLGRSH

MOU

Bethel

Alaska Capstone Phase I:2001 – 2004 Yukon - Kuskokwim Delta

• Region is nearly 100% dependent upon aviation

• High accident rates• No surveillance radar coverage

below 5000 ft• Bethel is the “hub” for 50+ villages

• 200 single and twin engine aircraft equipped (air taxi)

– All costs incurred by the FAA• 10 UAT ground stations established

for this region• Connectivity with Anchorage ACC

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Capstone Services

• ADS-B (air-to-air)– Provides “enhanced see and avoid”

• ADS-B (air-to-ground)– Enables ATC services via Anchorage ACC

• TIS-B (ground-to-air radar targets) – Completes see and avoid

• FIS-B (weather uplink)– Provides weather awareness

• Flight Dispatch Services– Provides flight following and asset management services

• Controlled Flight Into Terrain (onboard avionics)– Provides terrain awareness

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Avionics Selection

• FAA solicited avionics proposals for integrated system of GPS, terrain data base, cockpit display, and broadcast data link.

• UPS-AT (now Garmin AT) was awarded the avionics contract in 1999 -- with UAT as the surveillance data link – judged to have the best overall system cost– the avionics package was judged to have the best probability of

implementation within the aggressive Capstone schedule• Phase I Capstone avionics was “pre-MOPS/SARPs” with the

intent to replace units when the standards were completed. • Phase II Capstone avionics have been certified to FAA TSO C-

154, are draft SARPs compliant, and have been fielded in 2005

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UAT Ground Station

• Known as Ground Broadcast Transceiver (GBT)• Contract awarded to Sensis Corporation in July

2003 and the first draft SARPs compliant (with one exception) production GBT system was commissioned in Juneau Alaska on 9 May 2005

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Capstone AvionicsUniversal Access Transceiver (UAT) GPS Receiver Multi-function

Display

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Capstone Avionics Install Kit

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Fielded UAT Ground Broadcast Transceiver (GBT)

Redundant GBT Units

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UAT GBT Site: Juneau, Alaska

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Typical Capstone Aircraft

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Capstone Avionics Installation: Cessna 206

UAT data link unit Mounted in aft fuselage

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Capstone Traffic and Terrain Display

C182R+11

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FIS Weather – Graphics on Capstone Display

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FIS Weather – Text on Capstone Display

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First Operational use of Radar-Like Services -- January 2001 / 0018Z

• Controller vectoring Capstone-equipped aircraft to Bethel, Alaska ILS Runway 18, below radar coverage

• Maintaining separation from a second Capstone-equipped aircraft using UAT ADS-B

• System certified as part of U.S. National Airspace for routine use

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FAA Air Traffic Control Perspective on the Capstone Program

• UAT ADS-B source target is displayed only if radar is unavailable for a given target

• UAT ADS-B target positions are updated at a 6 second rate (adaptable)– 1 sec update of velocity vector provides rapid indication of any

maneuver for ADS-B targets• 5 NM separation standard: ADS-B or Radar• Track “bonding” logic ensures that a single target is depicted

in cases where radar/ADS-B coverage overlaps• ADS-B targets “auto-acquire” via a “Mode A” (4096) code

that is broadcast by ADS-B

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Capstone Operational Observations (1)

• UAT ADS-B accuracy has been found to be consistently superior to radar for ranges greater than 5 NM from the radar site

• UAT ADS-B at 1 second transmission rate:– is robust to any single message loss– provides rapid turn indications to ATC– aids track bonding– BUT, increases communications/processing load for ATC

automation (Local Area Network upgrade was completed to accommodate additional UAT ADS-B sites)

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Cape Newenham Long Range Radar/ADS-B Comparison: Turning Track

585

586

587

588

589

590

591

592

593

594

595

1615 1617 1619 1621 1623 1625 1627 1629

System Plane 1 nmi E/W units

Syst

em P

lane

1 n

mi N

/S u

nits

ADS-B reports (1 second transmission interval)Radar returns (12 second scan interval)

Cape Newenham radar 130 nmi range

Flight of FAA’s N40 with Capstone avionics in vicinityof Bethel AK, 21 Aug 2000

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Capstone Operational Observations (2)

• Provided Important Operational Feedback to MOPS/SARPs and avionics installation activities

• Replicate SSR transponder indicators (IDENT, 4096 code)• Adjustments to the way GPS integrity is reported in ADS-B (NIC

vs NUC)• Integrity of 24 bit address (installer discipline, pilot access)• Desirable for GPS sensor that is “tightly coupled” to ADS-B

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UAT Status in Alaska: June 2005

• 230 aircraft equipped with UAT as part of Capstone program

• 12 GBT sites in Alaska are currently providing services; others in various stages of installation

• ATC separation service using UAT ADS-B has been provided since January 2001. Using new standards-conforming UAT equipment since 9 May 2005– Air-to-air surveillance as advisory service– TIS-B, FIS-B as advisory service

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UAT Status in Alaska: Safety

• In the Y-K Delta, Phase 1 population, Capstone-equipped aircraft has had a consistently lower accident rate than all aircraft prior to Capstone, and non-equipped aircraft during Capstone.

• From 2000 through the end of 2004 the rate of accidents for Capstone-equipped aircraft was lower by 47%.

• In Y-K Delta villages where Capstone has created instrument approaches, the fraction of time that weather makes air travel unavailable has been reduced by 50%.

• See Information Paper ACP-WGW01-IP07 for a summary of the Final Report of the “Safety Impact of Capstone Phase 1”

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Further U.S. UAT Implementation

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Additional UAT Avionics Installations

• Embry Riddle University equipped their training fleets in Daytona Beach Florida and Prescott Arizona: ~100 shipsets

• Training and law enforcement aircraft in the Washington DC area: 6 shipsets

• Several Research and State Aviation Agencies have funded installations in North Carolina, Virginia and North Dakota

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June 2005 UAT Ground Station Coverage additional to that in Alaska

Mid-Atlantic

Florida

Arizona

North Dakota

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Summary

• FAA certified, draft UAT SARPs compliant, production avionics is currently commercially available for UAT– Over 300 installations to date

• FAA has specified, procured and commissioned a UAT ground station for use in the U.S. National Airspace

• ATC separation services are being provided in Alaska based on UAT ADS-B surveillance

• FAA is expanding UAT ground station coverage both in Alaska and in the remainder of the U.S. to encourage further equipage as part of implementation of 2002 U.S. FAA ADS-B link decision

• See FAA-maintained web site http://www.flyadsb.com for current status on ADS-B deployment in the U.S.