© 2011 the mitre corporation. all rights reserved. unclassified a frequency assignment strategy for...

© 2011 The MITRE Corporation. All rights reserved.

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A Frequency Assignment Strategy for Common Data Link (CDL) Users

An Inspection of USCENTCOM Operations in Afghanistan

Rob Moser, The MITRE CorporationJeff Bench, L-3 Communications

16 March 2011


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Provide a Frequency Allocation Strategy for CDL Links supporting ISR Operations in Afghan Theater

■ Problem Statement

■ USCENTCOM Study Guidance

■ CDL Background Information

■ Approach to Problem

■ Study Limitations

■ Options Availability

■ Option 1: Limited Airspace Management

■ Option 2: Managing Airspace, More CDL Links

■ Further Study

■ Summary

■ RecommendationsPage

2

Purpose and Agenda (U)


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■ Demand for Ku-band CDL assignments exceeds allocation by 300% – 700% in “hot spot” regions of Combined Joint Operations Area

Afghanistan (CJOA-A)

■ New Wide Area Surveillance (WAS) aircraft consume 75% of allocation by themselves

■ Aircraft using overlapping frequency assignments will interfere with one another without a solid deconfliction plan– Interference causes loss of data or loss of UAV control

■ No pre-mission or real-time spectrum deconfliction tools are currently available for frequency managers or ISR planners in the CJOA-A– Current approach to frequency assignment is best effort

■ A frequency plan is needed that can mitigate interference and still support ISR operations

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Problem Statement (U)


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■ Many studies produce “academic” recommendations– Current situation is a growing problem; need actionable results now

■ Operational Guidance– Use no formulas!

– Allow operators/planners to apply guidance within 5 seconds (from question to answer)

– Be based on situational data already available to the operators/planners

– Rely on tools, maps, software, etc. already available to the operators/planners

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USCENTCOM Study Guidance (U)


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■ Common Data Link (CDL) operates in Ku-band– 14.4 – 14.83 GHz Air to Ground Downlink (430 MHz bandwidth)– 15.15 – 15.35 GHz Ground to Air Uplink (200 MHz bandwidth)

■ OSD Policy & Public Law require CDL to be incorporated in all manned & unmanned ISR platforms (circa 2005)– Affects the acquisition pipeline for every UAV Program of Record– Influences QRC development activities– OSD Waiver (Feb 2011) authorizes 15.7 – 17.3 GHz for CDL in AOR

■ 14 unique models of CDL-enabled ISR aircraft were deployed to CJOA-A as of Jan 2011– Does not include Recce pods on fighter/bomber aircraft

■ Data throughput requirements for aerial downlinks has steadily increased due to advances in sensor technology (i.e. WAS, HD FMV, etc.)– Constant Hawk: 21Mbps– Blue Devil / Gorgon Stare / Yellow Jacket / AAA: 274Mbps

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Background (U)


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■ USCENTCOM J2/J6 tasked MITRE to …– Study the problem

– Propose frequency mgt/deconfliction guidance for specific geographic areas of interest in the CJOA-A

■ MITRE collaborated with L-3 Communications– Used “FlyPlan” Modeling & Simulation (M&S) software

■ Created by L-3 specifically to solve CDL management problems

■ Developed under contract to CDL PMO, Hanscom AFB (ESC)

– Analyzed CDL equipped platforms operating in CJOA-A■ Platform data provided by the Services via USCENTCOM data call

■ Performed RF analysis of inputs/outputs/results

– Developed recommended operational guidelines■ Identified deconfliction procedures applicable across the CJOA-A

■ Provided focused examples for Regional Command South (RC-S)

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Approaching the Problem (U)


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■ 90% solution delivered

■ Analysis is limited to aircraft in USCENTCOM data call– Omits Ku-band microwave towers; ground-based interferers

■ Data call is not complete– Not all platform program offices responded

■ PTDS / Canadian King Air

– New systems arriving since data call;■ Inbound systems not included : Yellow Jacket / Fire Scout

■ Operating locations for inbound platforms are still TBD (AAA aircraft)

■ Engineering data not available (platform not included in data call)

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Study Limitations (U)


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■ Minimum frequency separation between 10Mbps channels is 15MHz for currently deployed aircraft– Key factor is the spectral emission mask

– May be different for systems not included in the data call

■ Minimum angular separation between 274Mbps aircraft– 30 Degrees if using the same frequency assignment

– 15 Degrees if frequencies spaced as far apart as possible■ 14.550 & 14.680 GHz (30 MHz separation – no further separation is possible)

■ May be different for systems not included in the data call

■ Minimum angular separation between 10Mbps aircraft is 10 Degrees (if using the same frequency)

■ 21Mbps users (e.g. Constant Hawk) consume equivalent of two 10Mbps channels

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FlyPlan Software Analysis Key Findings (U)

All determinations were made using FlyPlan software and data provided by the respective Program Managers


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-70

-60

-50

-40

-30

-20

-10

0

-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

Rela

tive

Am

plitu

de (d

B)

Frequency (MHz)

10Mbps Measured Spectral Emission

■ Signals are not “Lego Bricks”; they are complex functions– FlyPlan assesses interference as signals overlap; finds the breaking

point regardless of how bandwidth is defined (e.g. 3 dB, Necessary, etc)

■ 10Mbps links require 15MHz frequency separation to share the same airspace without interference

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Minimum Frequency Separation Explained (U)

3 dB BW (10.1MHz)

90% of the Power (11.5MHz)

Necessary BW (18.2MHz)

As used by:

• Vader

• MARSS

• Harvest Hawk

• Constant Hawk

• Hunter

• AAA


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■ All GCS antennas in the data call are highly directional (4 ft parabolic)– Example: 5 Degrees offset has a 31 dB drop in antenna gain

■ FlyPlan assesses interference at off-axis angles; finds breaking point– Takes into account GCS pointing stability and A/C power outputs

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Minimum Angle Separation Explained (U)

-15

-10

-5

0

5

10

15

20

25

30

35

40

45

50

-65 -60 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65

Ante

nna G

ain

(dBi

)

Off-Axis Antenna Angle (Degrees)

4 Ft Parabolic Ground Control Station Antenna Pattern Envelope


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■ 10Mbps Narrowband Aircraft fall into one of two categories– Narrowband aircraft using only Omni Antennas

– Narrowband aircraft using Directional Antennas

■ Omni-Only Narrowband Aircraft– Omni antennas broadcast everywhere, in all directions

– Broadcast reach GCS & Remote Video Terminals (RVT) simultaneously

■ Directional Narrowband Aircraft– Focuses a radio beam at the GCS with directional antenna

– Directional radio beam does not illuminate dismounted soldier RVT’s

– Most A/C in data call require support to dismounted soldiers; therefore

– Directional narrowband aircraft require a second CDL link ■ RVT links typically use an omni so as to reach all soldiers on the ground

■ The term “Links” is used throughout this briefing– If referring to omni-only aircraft, then # Aircraft = # Links

– If referring to directional aircraft, then # Aircraft = Half the # LinksPage

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Links vs. Aircraft (U)


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Data Call CDL-Platform Summary for Afghanistan (U)

TERMINAL ANTENNA TERMINAL ANTENNA

VADER Mini-T Bicone N/A N/A

SHADOW UNK Omni N/A N/A

HARVEST HAWK N/A N/A Mini-T Button Omni

MARSS Mini-T Thunder Omni N/A N/A

GREY EAGLE Rev F Term Comp Lens Rev F Term Button Omni

CONSTANT HAWK Mini-T Comp Lens N/A N/A

HUNTER Mini-T 1x8 Horn Array Mini-T Omni

AAA TARS Cir Horn Array Mini-T Button Omni

BLUE DEVIL TARS Comp Lens Mini-CDL 200 Button Omni

GORGON STARE TARS 9.5" Parabolic TARS Horn (CL Ped Mount)

CANADIAN KING AIR

PTDS

YELLOW JACKET

FIRE SCOUT

No Data Call Response

Not Included in Data Call

NARROW-BAND OMNI EMITTERS

GCS LINK RVT LINK

NARROW-BAND DIRECTIONAL

EMITTERS

WIDE-BAND EMITTERS

CATEGORY PLATFORM


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■ Develop frequency plans requiring little or no airspace management or tasking considerations– Aircraft can fly anywhere without regard to frequency considerations

■ Use airspace management to expand the number of CDL links– Requires disciplined airspace management

■ Airspace management tied directly to aircraft tasking in support of ISR collection requirements

– Aircraft cannot fly “anywhere”

– Coordination must occur before an A/C can change from one geographical sector to another

– Frequencies may need to be centrally or regionally assigned (perhaps daily) to manage channels

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Two Frequency Mgt Option Approaches Available (U)


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Option 1: Little to No Airspace Management (U)

0

1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840

10Mbps CDL Downlink Frequency Plan

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1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840

Provision for 274Mbps Downlinks

■ Max number of CDL links that fit into Ku-band (each base)– 27 Links @ 10Mbps (15 MHz separation)

– 1 Link @ 274Mbps + 12 Links @ 10Mbps (15 MHz separation)

■ Aircraft can fly anywhere within LOS range of base (200NM)– Useful if you do not want to manage airspace & frequencies


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■ There is not enough spectrum to separate two wideband A/C that share the same airspace

■ Minimum angular separation between two wideband A/C measured from operating location is 30°– A/C use same frequency

■ Depending on orbit size, airspace can handle upwards of 9 wideband A/C– Each separated by 30°

– Spread out around the base

■ Twelve 10Mbps CDL links can operate simultaneously anywhere within range of base Page

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274Mbps Wideband Considerations (U)

12 Links @ 10Mbps can fly anywhere

Co-located GCS on same base


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■ There is insufficient spectrum available for use to separate two wideband A/C to share the same airspace; but,

■ Spacing two wideband A/C channels as far as possible reduces the minimum angular separation– From 30° to 15°

■ Channel assignments of 14.550 & 14.680 GHz

■ 30 MHz max separation possible

– Huge cost; Number of 10Mbps links drops from 12 to 4

■ The 4 Links @ 10Mbps can be anywhere in the airspace

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Bringing Wideband A/C Closer Together (U)

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1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840



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■ Minimum separation angle between 10Mbps platforms is 10°

■ Result– Wedge containing wideband

A/C can support 4 links @ 10Mbps (shown in green)

– Larger wedge (shown in red) can reuse frequencies with normal 10Mbps pattern (below) supporting 27 links

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Overcoming Cost of 2 Wideband A/C Close Together (U)

27 Links

4 Links

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1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840



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■ Divide airspace into 4 sectors

■ Alternate frequency patterns

■ Results– 13 Links (10Mbps) in “A”

– 14 Links (10Mbps) in “B”

– 54 TOTAL @ 10Mbps)

■ Freedom of Movement: – A/C in “B” can move into “A” & vice versa

– Provides 270° of freedom

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Option 2: Managing Airspace to Increase CDL Links (U)

A

B

B

A

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3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840


A

B


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■ Dividing airspace into more sectors yields more links– 4 Sectors: 54 Links @ 10Mbps

– 6 Sectors: 81 Links @ 10Mbps



■ Alternate Even/Odd frequencies– A/C have freedom to move into adjacent

sector

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Further Link Increases => More Sectors (U)

1

2

3

4

56

8

7

10

9

1112

1

2

34

5

6

1

2

345

6

8

7

0

1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840


ODD

EVEN


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■ Conclusions in this study based exclusively on data for aircraft currently operating in CJOA-A– Future A/C may have different transmitter/receive characteristics

– Conclusions contained herein may not apply

■ Urge all future deployments provide USCENTCOM with completed Data Call worksheet– Can assess impact (if any) fairly quickly (two weeks)

– Importance is amplified for wide band assets or narrow band assets operating out of a FOB that supports a wide band asset

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Caution (U)


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■ Due to operational urgency, this study focused exclusively on the here and now

■ Mitigation steps for the long term are likely– 9 Months estimated to complete a long term study

■ Long term study areas: – Waveform improvements

■ Modulation, Coding, Tunability, Power Control

– Antenna improvements (Aircraft & Ground Stations)

– Diplexer improvements

– Cross-Polarization benefits

– Improvements to FlyPlan M&S software

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Recommended Further Study (U)


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■ Ku-band spectrum supports…– 27 Links @ 10Mbps, or

– 1 Link @ 274Mbps + 12 Links @ 10Mbps

■ 274Mbps A/C require 30° separation if using same channel– 12 Links @ 10Mbps can overlap same area of operations

■ 274Mbps A/C can operate within 15° w/staggered frequencies– 4 Links @ 10Mbps can overlap same area of operations

– Spectrum reuse begins 10° later, provide 27 Links @ 10Mbps

■ Airspace can be divided into sectors to further increase # of Links– Requires airspace management

– A/C are restricted to their assigned sector + adjacent sectors (each side)

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Summary (U)


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■ Assign Blue Devil and Gorgon Stare a “shared” wideband channel (14.550 GHz center frequency) and assign narrowband users remaining channel assignments per below

■ IJC and RC-S CM&D need to be cognizant that tasking Blue Devil and Gorgon Stare within 30o of angular separation will result in signal interference (i.e. imagery degradation to PED cell)

■ COA supports the minimum number of assets but requires the least day-to-day deconfliction measures by RC-S CM&D.

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COA #1: Assign Frequencies Independent of Airspace

0

1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840



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■ Same as COA#1, but with two pre-planned 10° keep out zones on either side of the wideband aircraft

■ Enables 12 narrowband links as with COA#1 co-located with wideband aircraft

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COA#2: Include two “Keep-Out” zones Around Wideband Aircraft

27 Links

12 Links

10° Keep-Out Zone■ Complete frequency re-use beyond the keep-out zones

– Enables 27 additional narrowband links to be assigned as needed

■ IJC and RC-S CM&D need to be aware that …

– A/C in green zone are confined to green sector

– A/C in red zone are confined to red sector


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■ Same as COA #2, but change frequency plan for the Green Zone– Enables IJC and RC-S CM&D

to bring wideband A/C within 15° of each other

– Reduces narrowband assignments from 12 to 4

– Red zone is unaffected

■ Wideband center frequencies will be 14.550 & 14.680 GHz

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25

COA#3: Operate Wideband A/C in Close Proximity

27 Links

4 Links

10° Keep-Out Zone

0

1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840



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■ Use a 4/6/8/10/12-sector approach to divide airspace around the designated RC-S FOB– Permits the frequency re-use of both wideband and narrowband users

– Alternate Red/Blue channel assignments with sectors

■ Minimizes and/or prevents “accidental” blue-on-blue frequency interference

■ Aerial assets communicating with GCS at FOB locations other than the sectors radius but in the general Area of Operations may require dedicated channels

■ COA supports the highest number of possible assets (and channel assignments) although requires the RC-S CM&D (or appropriate authority) to have an intimate hand in spectrum coordination based on aircraft tasking requirements

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COA#4: Assign Frequencies by Sector

0

1

2

3

4

14.390 14.405 14.420 14.435 14.450 14.465 14.480 14.495 14.510 14.525 14.540 14.555 14.570 14.585 14.600 14.615 14.630 14.645 14.660 14.675 14.690 14.705 14.720 14.735 14.750 14.765 14.780 14.795 14.810 14.825 14.840


ODD

EVEN


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27

Backup

BACKUP


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■ This briefing (slide 8) showed that…– Min separation angle = 30° for 274Mbps wideband links

– Min separation angle = 10° for 10Mbps narrowband links

■ In reality, min separation angle is a function of range– CCJ6 guidance (slide 4) was “no formulas”, “5 second decision time”

– Therefore, this briefing took worst case separation angle (max range)

■ Planners probably need to know that they have options, particularly for the 274Mbps wideband aircraft– See Slide 29 – 31 for examples

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28

Minimum Separation Angles for Frequency Reuse

274Mbps 10Mbps

120 NM 5° 2.5°

130 NM 10° 2.5°

140 NM 30° 2.5°

150 NM 360° 10°

160 NM BLOS 30°

170 NM BLOS BLOS

SEPARATION ANGLE (Deg)RANGE(NM)


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29

274Mbps (STD-CDL) Wideband Aircraft(Blue Devil & Gorgon Stare, both with Directional Antennas)

150NM

10 Deg Separation out to 130NM



140NM

130NM

120NM


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30

274Mbps (STD-CDL)(Blue Devil [Omni Antenna] & Gorgon Stare [Directional Antenna])



50NM

40NM


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31

10 Mbps (STD-CDL)(25,000 Feet Altitude, Directional Antennas)



2.5 Deg Separation out to 140NM

160NM

150NM

140NM

© 2011 the mitre corporation. all rights reserved. unclassified a frequency assignment strategy for...

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