The Challenge of Finding Your Position in a World Hostile to Radio Navigation

Durk van Willigen

1reelektronika

The Challenge of Finding Your Position in a World Hostile

to Radio Navigation

Prof.dr. Durk van Willigen

Reelektronika, Netherlands

ILA 2003Boulder, Colorado, USA, 3-7 November 2003

Durk van Willigen

2reelektronika

Overwhelming GPS Success

• GPS revolutionised navigation

• GPS is embraced by its users

• GPS never fails • Emerging worries on GPS • Concern PCCIP Volpe Report

• US leads rethinking on vulnerability GPS

• From sole-means dissimilar systems

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Vulnerability a today’s Issue?

• Yes, because society never relied so strongly on a single source of navigation and time before the GPS era

• Yes, because never before the bad guys were able to disable our core navigation and time sources so easily and untraceably, and over such large areas

• Yes, because many do not recognize this flaw and do not take timely precautions

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User’s Attitude

• We have GPS, it performs excellent, it is extremely cost-effective, so why worry?

• Question: Imagine living without fire fighters, vaccination, life-boats, police, dikes, …

• We have them all, we generously pay for it, but we are convinced that we will never need them

• Fortunately, we don’t need such precautions for GPS or GLONASS or Galileo because these systems are perfect !!

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Why Galileo next to GPS?

• Because Europe is an industrial high-tech world player

• Europe aims to be successful in GNSS technology just as it is with Airbus, ESA, Concorde, TGV, GSM, Bach, Rembrandt, ….

• But like the US, Europe prefers to be auto-nomous in respect of navigation and timing

• Europe is keen to make profit with its own Galileo business

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US-European Navigation Co-operation?

• Users will like Galileo as it doubles the number of navigation satellites improving availability in city areas

• Professional navigators think Galileo may reduce the single-point-failure effects in the technical and control segments

• US military highly dislikes Galileo’s PRS as it makes GPS’ M-code less effective

• PRS = Public Restricted Services

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PRS versus M-code• The US officially and repeatedly stated that it will

deny all non-US satellite navigation services if US national security requires so

• Europe would like to prevent that• Europe might also deny GPS to many other

countries if needed• Question from a simple not involved observer:

– Does the US rule GNSS like the UK ruled the waves?– Are the US and Europe each others hostages?

• In all public statements these issues are not mentioned of course (ION-GPS 2003)

• What is the discussion all about?

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L1 spectrum (USA at ease)

P(Y) / -160 dBW M-code / -158 dBW(Earth Coverage Mode)

C/A / -157 dBW

1565 15801575 1585 159015701560

GPS IIF

1565 15801575 1585 159015701555 15951560

Galileo

OS / -152 dBW PRS / -152 dBW ?

PRS / -152 dBW ?

US-Europe Conflict

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Denial Dilemma

• Imagine that the US would ever like to deny GPS to non-US countries by jamming civil parts of GNSS bands

• Then GPS CA and Galileo OS will stop – OS = Open Service

• So, the US continues with M-code and Europe with its PRS

• But if US would like to deny PRS also then it will harm its own M-code as well, or the other way around with identical effect

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L1 spectrum (USA in action)

Spot Beam Mode-138 dBW (+20

dB)

1565 15801575 1585 159015701555 15951560

All non M-code signals on L1, L2,

and L5 can be denied

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Solution?

• Increase GPS M-code signal power levels by e.g. 20 dB in selected areas so that jamming PRS will not kill M-code signals as a collateral damage

• But what will happen if Europe would take identical initiatives?

• Challenging issue for American and European politicians

• Or, is it a technical challenge only?

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Who Might Endanger GNSS?

• Hackers• Feels good to get large user groups on a string• Compare with virus creators

• Road users• Attempt to cheat the system to get a free ride

• Thieves• Disable car-theft protection systems• Disable GNSS-based tracking and tracing of valuable cargo

• Terrorists• Use your own imagination and, please, don’t tell anybody the

results

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Very Annoying L1 Dinky Toy

• Low GNSS power levels makes jamming relatively easy– Just 100 Watts to

illuminate 38% of earth’s surface

• Much progress observed today in jamming rejection technology– Outside military world

not yet available– Complex– Fail safe?

• 1 mW L1 jammer• 100 meters range• 30 mm on a side• 4 hours on single battery• Not for sale !!

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A Powerful Solution

• Avoid Single-Point-Failure Structure through integration of highly dissimilar sub-systems

• Which systems are dissimilar to GPS?

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Integrated Navigation Concept

Sensor 1

Sensor 1

Sensor l

Sensor k

Sensor 1

D ata link 1

Traffic C ontro l C hannel Input

Traffic C ontro l C hannel O utput

D ata link n

Increm enta l R awPosition ing D ata

Absolute R awPosition ing D ata

R elative R awPosition ing D ata

Augm entation D ata B roadcast

Traffic C ontro l and R oute G uidance

Sensor m

IntegratedPosition,Velocity,A ttitude,

H eading &Integrity

D eterm ination

Sensor System &Terra in /R oadm ap

D atabase

N avigation P lan &N avigation D atabase

N avigationInform ation &

G uidance/ D isp layS ignal

G eneration

Selection, Acquisition, Track a id ing

Inputs OutputsPositionDetermination

Navigation &Guidance

Pilot Input

P ilo t O utputN av D isp lays

Autopilo t

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Galileo backing up GPS?

• Yes, because– Galileo has higher power level– Galileo uses some un-modulated carriers– More satellites yield better availability– If one control link fails the other one may survive

• No, because– Low dissimilarity in frequency and power levels– Denial requirement of the other party

• Conclusion: Other very dissimilar systems needed

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Strengths/Weaknesses Navigation

Galileo/GPS/GLONASS Loran-C/Chayka

(Un-)intentional long-range interference robustness

Low Very high

Unintentional short-range interference robustness

High Low*

Accuracy High / Very high Medium / High**

Availability in urban areas Medium High

Reliability High High

Initial provider costs High Medium

Recurring provider costs Medium Low

* Interference from e.g. car generators, computer monitors, etc** Medium accuracy with accurate ASF tables, high accuracy with DLoran-C or SLA technology

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GNSS versus Loran

GNSS Loran-CPhenomenon Risk Effect Solution Risk Effect Solution

Long-range interference robustness

Low High BSA + DSP Low Low DSP

Short-range interference robustness

Low HighNone

(non-linearity)Medium High BSA + DSP

Spoofing Low Very high RA(S)IM Very low Low RA(S)IM

Shadowing Medium Medium Many SVs Low Low n.a.

Multipath Medium MediumBSA + MEDLL

Low Medium BSA + DSP

BSA = Beam Steering Antenna

DSP = Digital Signal Processing

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Questions

• If Loran is that good why are there no GPS-like receivers available?

• Why are there no integrated GPS-Loran receivers?

• How to integrate GPS and Loran-C?• Integrate or mutually calibrate?• What is the real error budget chain under

adverse signal conditions?• Why are inertial sensors not integrated with

Loran to increase dynamic response?

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Frankfurt Down-Town

Tall buildings and narrow streets

in Financial Center of Europe

GPS suffers from shadowing and multipath

New Loran-C receiver not yet available at time of

test

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GPS only in Frankfurt

111 m/div

71 m/div

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GPS-INS Integrated

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Unaided Versus Aided GPS

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TOA Tracking Accuracy @ Boston: 5m 95%

Calibrated LoranIntegrated NavNovAtel POSA

Longitude Error (m)420-2-4-6-8-10

Latit

ude

Err

or (

m)

10

8

6

4

2

0

-2

-4

-6

Measurements in Boston harbor

Integrate and dump every 5 seconds

FAA LORAPP program

(LORAPP =LORan Accuracy Performance Panel)

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Local Interference Cancellation-1

3340 3360 3380 3400 3420 3440 3460 3480 3500 3520 3540

-6000

-4000

-2000

0

2000

4000

6000

8000

3340 3360 3380 3400 3420 3440 3460 3480 3500 3520 3540

-6000

-4000

-2000

0

2000

4000

6000

8000

Time Domain

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Local Interference Cancellation-2

85 90 95 100 105 110

90

95

100

105

110

115

120

Frequency [kHz]

[dB

]

85 90 95 100 105 110

90

95

100

105

110

115

120

Frequency [kHz]

[dB

]

Frequency Domain

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0 50 100 150 200 250 300 350 400

-0.5

-0.4

-0.3

-0.2

-0.1

0

5930X

9960X

8970X

9960M

5930M

9960W

9960Y

time (minutes)

us

TOA, 30 sec integrated

TOA Tracking Stability @ Boston

Y-axis = 30 m/div

Time jumps due to transmitter time control steps of 20 ns, equivalent to 6 m

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Strengths/Weaknesses Augmentation

WAAS/EGNOS/MSAS EGNOS via Eurofix

Long-range interference robustness

High* Very low

Short-range interference robustness

Low Medium

Availability in urban areas Medium High

Availability in Polar Region None High**

Reliability High High

Initial provider costs High Very low

Recurring provider costs Medium Very low

* Not relevant as under jamming conditions GNSS will fail too

** To be confirmed by real-life tests in the Artic Region. Covering Polar Region requires US and Russian stations to broadcast DBAS data too

Durk van Willigen

29reelektronika

EGNOS/Eurofix Station at Sylt

EGNOS TRAN equipment

← Thales EGNOS Rx

← Modem & power supply

← EGNOS TRAN PC

Existing Eurofix installation

← Eurofix Rx & power supply

← 2x GPS Rx & Modem

← CPU switch

← Integrity Monitor PC

← Reference Station PC

← UPS

Equipment RackAntenna mounts

ThalesEGNOS

GPSAntenna

EurofixIntegrityMonitor

GPSAntenna

EurofixReference

StationGPS

Antenna

EurofixDatalinkMonitorLoran-CAntenna

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Polar Routes

• Restricted Russian polar routes: Polar 1 to 4

• Preferred random routing in Canada

• 2005: 9000+ commercial polar flights estimated

• Savings:– Flying time: 2+ hrs– Costs: US$ 16

k/flight– Time slots Atlantic

• ‘Polar Routes Feasibility Study’, Nav Canada and FAAR, October 2000

4970M+5960Z 1,200 kW

4970X+5960Y 250 kW

5960X 1,200 kW

7001Y 250 kW7270X+5930Z

800 kW

7960M 560 kW

9990Y+7960Z 1,000 kW

7001X+9007W 250 kW

9990Y+7960Z 1,000 kW

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Integrated GPS/Loran/Eurofix Receiver

Credit Card 85 x

54 mmFront End &

ADC77 x 47 mm

Signal Processor77 x 51 mm

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H-Field Antenna Testing

• Antenna testing requires many

skills and lots of enthusiasm

• High performance Loran

receivers need many aspects

to be verified

• Most Loran-C challenges are

known today, and are taken

care of

• Loran development is a multi-

disciplinary task

• Much progress observed in US,

Asia and Europe

Antenna under test

H-field generating

loop

PC-controlled turn table

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Conclusions

• Loran-C/Chayka is the only wide area multi-modal navigation life boat if GNSS fails

• Skywave and man-made interference largest challenge to Loran-C land applications

• Loran-C receivers without GPS chip set may have a too low market appeal

• With land applications low-cost rate gyros and odometers may be of good help to smooth tracking and to coast if both Loran and GPS fail

• Large advances in Loran-C technology must now be marketed at high speed to create critical mass to keep Loran-C/Chayka alive!!