©2005, The Aerospace Corporation, All Rights Reserved 1Electronic_Systems_Division@aero.org

Satellite TT&C Denial, Electronic Counter Measure and Mitigation

By

Don Olsen

For Presentation at

Security Working Group

Of CCSDS

April 11-15, 2005

Athens Greece

©2005, The Aerospace Corporation, All Rights Reserved 2Electronic_Systems_Division@aero.org

Background

• Satellite TT&C links are susceptible to electronic counter measures (ECM).– Spoofing

– Eavesdropping

– Denial/Jamming

• Satellite TT&C links can be protected against ECM by– Encryption,

– Authentication, and

– Spread spectrum

• This presentation will focus on AJ performance with spread spectrum.

©2005, The Aerospace Corporation, All Rights Reserved 3Electronic_Systems_Division@aero.org

Waveform Security and Jamming Mitigation

• Some systems provide anti-jam capability through spread spectrum.– This could include frequency hopping or pseudo-noise (PN)

spreading.

– The measure of the improvement achieved is called processing gain.

– Frequency hopping anti-jam waveforms:– Provide greater processing gain for same complexity than PN,

– But has disadvantage of susceptibility to partial band and smart jamming,

– Secure TRANSEC can protect against frequency agile, smart, narrow band jamming.

– Presentation will restrict discussion to frequency hopping.

• Power efficient modulation minimizes Eb/No in AWGN as well as jamming.

©2005, The Aerospace Corporation, All Rights Reserved 4Electronic_Systems_Division@aero.org

Waveform Security and Jamming Mitigation (Cont.)

• Coding needs to maximize the required channel BER (Pcbe) so that partial band jamming is a disadvantage.– BER is inversely proportional to Eb/Nj , for partial band noise jammed

(PBNJ) single diversity signals as shown next. – Nj is avg. jammer density.

– Curve is tangent to the AWGN curve. (p. 11)– The slope is equal to the diversity symbol repetition combining.– Error correction coding must permit operation with the Pcbe at or

above the tangent point,– For no Eb/Nj degradation from the Eb/No performance and– Forces jammer to jam entire hopping bandwidth.

• Interleaving is needed to protect the decoder from burst channel errors.– The graphs in the backup charts show the Pbe with both ideal and

non-ideal interleaving.

©2005, The Aerospace Corporation, All Rights Reserved 5Electronic_Systems_Division@aero.org

Scope and Limitations

• Spectral allocation limits S band electronic counter counter measures (ECCM) processing gain.

• X Band and Ka Band (21 GHz) would improve the processing gain over S band and are included herein as typical but not as exhaustive examples.

• C and Ku are not Government bands and not included.

• Since the uplink EIRP advantage is only bandwidth dependent Q band is included with its 3 dB bandwidth advantage.

©2005, The Aerospace Corporation, All Rights Reserved 6Electronic_Systems_Division@aero.org

Assumptions

• Satellites are at synchronous altitude.

• Secure TRANSEC will mitigate certain smart jammer attacks.

• The choice of modulation, coding and interleaving will greatly influence the performance in smart partial band jamming.

• Hop diversity count has a significant effect on the performance of a frequency hopped waveform in the presence of partial band jammers.– The interleaver needs to preserve a hop diversity of ~700.

– To keep diversity related performance losses to 0.3 dB.

©2005, The Aerospace Corporation, All Rights Reserved 7Electronic_Systems_Division@aero.org

Link Parameters

Link Up DownBand S X Q S X 21 GHzFrequency MHz 2000 8000 44000 2200 8000 20000RF Allocation Bandwdith MHz 80 500 2000 80 500 1000Data Rate kbps 2 2 2 100 100 100Satellite Range Nmi 22760 22760 22760 22760 22760 22760Jammer Range Nmi 22760 22760 22760 20 20 20Range Ratio 1 1 1 0.000879 0.000879 0.000879Rx Antenna Sidelobe Level dB 0 0 0 20 30 40Required Rx Eb/No dB 10 10 10 10 10 10

J/S Available with No Spreading dB -10 -10 -10 -51.12 -41.12 -31.12

©2005, The Aerospace Corporation, All Rights Reserved 8Electronic_Systems_Division@aero.org

AJ Performance Versus Spread Bandwidth for Various Frequencies and Link Options

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

1 10 100 1000 10000 100000 1000000 10000000

Spread Bandwidth (kHz)

Req

uire

d Ja

mm

er t

o U

plin

k U

ser

Ter

min

al o

r S

atel

lite

Dow

nlin

k E

IRP

Rat

io

Up

S

X

21 GHz

©2005, The Aerospace Corporation, All Rights Reserved 9Electronic_Systems_Division@aero.org

Conclusions for Above Scenarios

• Uplink jammer EIRP needed to degrade a 60 dBW uplink is:

– 50 dBW with no frequency spreading

– 96 dBW with 80 MHz frequency spreading

– 130 dBW with 2 GHz frequency spreading

• The Jammer EIRP needed to degrade a 30 dBW EIRP synchronous altitude satellite downlink is:

– -38 dBW at S Band with no frequency spreading.

– 8 dBW at S Band with 80 MHz frequency spreading.

– 39 dBW at 21 GHz with 1GHz frequency spreading.

©2005, The Aerospace Corporation, All Rights Reserved 10Electronic_Systems_Division@aero.org

Backup Slides on AJ Performance with Imperfect Interleaving

©2005, The Aerospace Corporation, All Rights Reserved 11Electronic_Systems_Division@aero.org

BPSK Channel Bit Error Rate in AWGN and Optimized Partial Band Jamming (Eb/Nj)

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

-5.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00Eb/Nx Assuming Rate 1/2 Coding (dB)

Pcb

e

Pcbe AWGN

Pcbe PBNJ

©2005, The Aerospace Corporation, All Rights Reserved 12Electronic_Systems_Division@aero.org

Waveform Background

• Non-ideal interleaving will allow smart jammers to degrade performance.

– Slow hopping (many bits per hop) and partial band jamming creates burst errors.

– Convolutional and turbo codes are very susceptible to degradation from burst errors.

– Ideal interleaving will distribute bursts uniformly to mitigate the loss.

• Hop diversity is the number of hops across which the code block is spread.

– Or the number of hops across which the content of a convolutional code’s path memory is spread

– However, the interleaver may not provide enough depth or effective use of the hopping diversity.

– This limitation can degrade both processing gain and anti-jam capability.

• The analysis and graphs later in this briefing show the effect of limited hop diversity.

©2005, The Aerospace Corporation, All Rights Reserved 13Electronic_Systems_Division@aero.org

Hop Diversity Analysis Approach• The analysis calculates and plots the BER curve for various

Eb/Nj.

– and partial band fraction for various numbers of diversity hops, Nh

– with Eb/No set to 0.

• The envelope of Pbe for worst case jammer fraction at each Eb/Nj was determined.

– The set of envelope curves for various values of diversity were plotted.

• The model sums the binomial weighted probabilities of error for each number of jammed hops out of a set of Nh hops.

• This was repeated for several modulation and coding options.• The waviness of some of the lines is due to the size of the

step in the partial band fraction.

©2005, The Aerospace Corporation, All Rights Reserved 14Electronic_Systems_Division@aero.org

Definitions of Parameters• The partial band Gaussian noise jammer fraction is r .

• The code is either – Convolutional with rate, rc of ½ and constraint length 7

– Or convolutional turbo with rc of ½, constraint length 5 and 5120 bit block size.

• The decoder transfer model was obtained– By fitting a judicious curve to the Pbe versus Pcbe relationship,

– Where Pcej is the channel probability of error,

– Pbe is the decoder output probability of error,

– Given j of Nh diversity hops are jammed.

• Code parameters definitions:– The linear scale factor for the code probability of error transfer model is a.

– The exponential factor for the code probability of error transfer model is b.– It is closely related to half the minimum free distance of the code.

– The curve corner fitting tightness factor for the code transfer model is n.

• Pbe is the sum over j of the decoded binomial distribution weighted Pcej.

©2005, The Aerospace Corporation, All Rights Reserved 15Electronic_Systems_Division@aero.org

Analysis for DPSK Modulation Case

cbenNjN

cbejNcej PPPh

h

h

j )(

jo

cbcbej NN

REP

exp

o

cbcben N

REP exp

hN

j cejPjjhNhN

beP0

!!

!/1

11

©2005, The Aerospace Corporation, All Rights Reserved 16Electronic_Systems_Division@aero.org

Modulation Performance for Coherent DPSK and BPSK Cases Is Respectively

jo

cb

NNRE

cebj QP 2

o

cb

NRE

cben QP 2

o

cb

o

cbcben N

REQ

N

REQP 12

jo

cb

jo

cbcbej NN

REQ

NN

REQP

12

©2005, The Aerospace Corporation, All Rights Reserved 17Electronic_Systems_Division@aero.org

Where the complementary error function is given by Sklar in “Digital Communications” 2nd ed., p. 210 as:

duxQx

u

22

1 2

exp

©2005, The Aerospace Corporation, All Rights Reserved 18Electronic_Systems_Division@aero.org

Coding Parameters

Alpha Beta Nu RcSoft Decision Convolutional Coding 6.23 9.6 0.50605 0.5Hard Decision Convolutional Coding 6.60 4.9 0.60006 0.5Soft Decision Turbo Coding 7.89 89.0 0.145 0.5Hard Decision Turbo Coding 12.00 43.2 0.145 0.5

©2005, The Aerospace Corporation, All Rights Reserved 19Electronic_Systems_Division@aero.org

Performance of BPSK and Turbo Versus Rate 1/2, k = 7 Convolutional Coding for Both Hard and Soft Decisions in AWGN or Jamming

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 2 4 6 8 10 12 14 16 18 20

Eb/No (dB)

Pb

e

AWGN Turbo SoftAWGN Turbo HardAWGN Convo SoftAWGN Convo HardJammed Turbo SoftJammed Turbo HardJammed Convo SoftJammed Convo Hard

©2005, The Aerospace Corporation, All Rights Reserved 20Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for BPSK Modulation, Soft Decision Turbo Coding and 768 Hop Block Diversity for Various

Partial Band Gaussian Noise Jammer Fractions

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 1 2 3

Eb/Nj (dB)

Pbe

1.0000

0.8660

0.7499

0.6494

0.5623

0.4870

0.4217

0.3652

©2005, The Aerospace Corporation, All Rights Reserved 21Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for BPSK Modulation, Soft Decision Turbo Coding and 24 Hop Block Diversity for Various Partial

Band Gaussian Noise Jammer Fractions

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 1 2 3 4 5 6 7 8

EbNj (dB)

Pbe

1.0000

0.5623

0.3162

0.1778

0.1000

0.0562

0.0316

0.0178

©2005, The Aerospace Corporation, All Rights Reserved 22Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for BPSK Modulation, Soft Decision Turbo Coding and 3 Hop Block Diversity for Various Partial

Band Gaussian Noise Jammer Fractions

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15 20 25 30 35 40 45 50 55 60

Eb/Nj (dB)

Pbe

1.0000

0.1000

0.0100

0.0010

0.0001

0.0000

0.0000

0.0000

©2005, The Aerospace Corporation, All Rights Reserved 23Electronic_Systems_Division@aero.org

Table of Graphs

Page Modulation Coding Decisions24 DPSK Convolutional Hard25 CDPSK Convolutional Hard26 BPSK Convolutional Hard27 CDPSK Convolutional Soft28 BPSK Convolutional Soft29 BPSK Turbo Hard30 BPSK Turbo Soft

©2005, The Aerospace Corporation, All Rights Reserved 24Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for DPSK Modulation, Hard Decision Convolutional Coding and

Optimized Partial Band Gaussian Noise Jammer Fractions for Various Values of Block Hop Diversity

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15Eb/Nj (dB)

Dec

oded

Pbe

768

384

192

96

48

24

12

6

3

2

1

©2005, The Aerospace Corporation, All Rights Reserved 25Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for CDPSK Modulation, Hard Decision Convolutional Coding and

Optimized Partial Band Gaussian Noise Jammer Fractions for Various Values of Block Hop Diversity

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15Eb/Nj (dB)

Dec

oded

Pbe

768

384

192

96

48

24

12

6

3

2

1

©2005, The Aerospace Corporation, All Rights Reserved 26Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for BPSK Modulation, Hard Decision Convolutional Coding and

Optimized Partial Band Gaussian Noise Jammer Fractions for Various Values of Block Hop Diversity

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15Eb/Nj (dB)

Dec

oded

Pbe

768

384

192

96

48

24

12

6

3

2

1

©2005, The Aerospace Corporation, All Rights Reserved 27Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for CDPSK Modulation, Soft Decision Convolutional Coding and Optimized

Partial Band Gaussian Noise Jammer Fractions for Various Values of Block Hop Diversity

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15Eb/Nj (dB)

Dec

oded

Pbe

768

384

192

96

48

24

12

6

3

2

1

©2005, The Aerospace Corporation, All Rights Reserved 28Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for BPSK Modulation, Soft Decision Convolutional Coding and Optimized

Partial Band Gaussian Noise Jammer Fractions for Various Values of Block Hop Diversity

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15Eb/Nj (dB)

Dec

oded

Pbe

768

384

192

96

48

24

12

6

3

2

1

©2005, The Aerospace Corporation, All Rights Reserved 29Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for BPSK Modulation, Hard Decision Turbo Coding and Optimized

Partial Band Gaussian Noise Jammer Fractions for Various Values of Block Hop Diversity

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15Eb/Nj (dB)

Dec

oded

Pbe

768

384

192

96

48

24

12

6

3

2

1

©2005, The Aerospace Corporation, All Rights Reserved 30Electronic_Systems_Division@aero.org

Theoretical Single Link Pbe Performance for BPSK Modulation, Soft Decision Turbo Coding and Optimized Partial Band Gaussian Noise Jammer Fractions for Various Values of

Block Hop Diversity

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 5 10 15Eb/Nj (dB)

Dec

oded

Pbe

768

384

192

96

48

24

12

6

3

2

1