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

Durk van Willigen

3reelektronika

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

Durk van Willigen

4reelektronika

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 !!

Durk van Willigen

5reelektronika

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

Durk van Willigen

6reelektronika

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

Durk van Willigen

7reelektronika

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?

Durk van Willigen

8reelektronika

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

Durk van Willigen

9reelektronika

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

Durk van Willigen

10reelektronika

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

Durk van Willigen

11reelektronika

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?

Durk van Willigen

12reelektronika

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

Durk van Willigen

13reelektronika

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 !!

Durk van Willigen

14reelektronika

A Powerful Solution

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

• Which systems are dissimilar to GPS?

Durk van Willigen

15reelektronika

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

Durk van Willigen

16reelektronika

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

Durk van Willigen

17reelektronika

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

Durk van Willigen

18reelektronika

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

Durk van Willigen

19reelektronika

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?

Durk van Willigen

20reelektronika

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

Durk van Willigen

21reelektronika

GPS only in Frankfurt

111 m/div

71 m/div

Durk van Willigen

22reelektronika

GPS-INS Integrated

Durk van Willigen

23reelektronika

Unaided Versus Aided GPS

Durk van Willigen

24reelektronika

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)

Durk van Willigen

25reelektronika

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

Durk van Willigen

26reelektronika

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

Durk van Willigen

27reelektronika

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

Durk van Willigen

28reelektronika

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

Durk van Willigen

30reelektronika

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

Durk van Willigen

31reelektronika

Integrated GPS/Loran/Eurofix Receiver

Credit Card 85 x

54 mmFront End &

ADC77 x 47 mm

Signal Processor77 x 51 mm

Durk van Willigen

32reelektronika

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

Durk van Willigen

33reelektronika

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!!