Presentation on theme: "A Frequency Assignment Strategy for Common Data Link (CDL) Users"— Presentation transcript:
1 A Frequency Assignment Strategy for Common Data Link (CDL) Users An Inspection of USCENTCOM Operations in AfghanistanRob Moser, The MITRE CorporationJeff Bench, L-3 Communications16 March 2011
2 Purpose and Agenda (U)Provide a Frequency Allocation Strategy for CDL Links supporting ISR Operations in Afghan TheaterProblem StatementUSCENTCOM Study GuidanceCDL Background InformationApproach to ProblemStudy LimitationsOptions AvailabilityOption 1: Limited Airspace ManagementOption 2: Managing Airspace, More CDL LinksFurther StudySummaryRecommendations
3 Problem Statement (U)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 themselvesAircraft using overlapping frequency assignments will interfere with one another without a solid deconfliction planInterference causes loss of data or loss of UAV controlNo pre-mission or real-time spectrum deconfliction tools are currently available for frequency managers or ISR planners in the CJOA-ACurrent approach to frequency assignment is best effortA frequency plan is needed that can mitigate interference and still support ISR operationsEach operating location (e.g. Kandahar) has requests for 1 to 3 GHz worth of downlink spectrum. The frequency band only supports 0.43 GHz. Clever ways to re-use spectrum must be achieved.Most aircraft require 30MHz for a downlink. Half of the deployed aircraft require 2 downlinks, half require only one downlink.Some wide area surveillance systems (e.g. Blue Devil, Gorgon Stare, AAA) require extremely wideband links that consume 300MHz by themselves.Some operating locations have more than one of these wide area surveillance aircraft
4 USCENTCOM Study Guidance (U) Many studies produce “academic” recommendationsCurrent situation is a growing problem; need actionable results nowOperational GuidanceUse 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/plannersRely on tools, maps, software, etc. already available to the operators/plannersCCJ6 described two distinct types of guidance requiredGuidance for mission planners to assign daily frequencies for CDL aircraft. This has been described as a “thoughtful exercise with meticulous care.”Guidance for J3 operations personnel to rapidly respond to ad hoc requests for coverage. The 5-second rule applies here. Examples:Can I move aircraft “A” from where it is now to where I need it to be without causing frequency interference/fratricide?We need to launch another aircraft. Can the coverage area handle another aircraft? Can I quickly determine what frequency to use?
5 Background (U) Common Data Link (CDL) operates in Ku-band 14.4 – GHz Air to Ground Downlink (430 MHz bandwidth)15.15 – 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 RecordInfluences QRC development activitiesOSD Waiver (Feb 2011) authorizes 15.7 – 17.3 GHz for CDL in AOR14 unique models of CDL-enabled ISR aircraft were deployed to CJOA-A as of Jan 2011Does not include Recce pods on fighter/bomber aircraftData throughput requirements for aerial downlinks has steadily increased due to advances in sensor technology (i.e. WAS, HD FMV, etc.)Constant Hawk: 21MbpsBlue Devil / Gorgon Stare / Yellow Jacket / AAA: 274MbpsOASD Policy Memorandum, “Department of Defense Common Data Link Policy”, Dated 30 DEC 2005 mandates CDL for ISR Dissemination other than Tactical UAVs (under 30 lbs)OSD Policy Memorandum, “UAS Spectrum Regulatory Policy Guidance”, Dated 14 APR 2006 reinforces earlier 30 DEC 2005 policy and quotes Public LawPublic Law , Dated 6 Jan 2006, withholds acquisition funding for UAS (other than tactical) that do not include CDL capability for ISR dissemination
6 Approaching the Problem (U) USCENTCOM J2/J6 tasked MITRE to …Study the problemPropose frequency mgt/deconfliction guidance for specific geographic areas of interest in the CJOA-AMITRE collaborated with L-3 CommunicationsUsed “FlyPlan” Modeling & Simulation (M&S) softwareCreated by L-3 specifically to solve CDL management problemsDeveloped under contract to CDL PMO, Hanscom AFB (ESC)Analyzed CDL equipped platforms operating in CJOA-APlatform data provided by the Services via USCENTCOM data callPerformed RF analysis of inputs/outputs/resultsDeveloped recommended operational guidelinesIdentified deconfliction procedures applicable across the CJOA-AProvided focused examples for Regional Command South (RC-S)All analysis for this USCENTCOM study performed collaboratively by Mr. Jeff Bench (L-3 Communications) and Mr. Rob Moser (MITRE)Platform data was provided by US Gov’t program offices within the Services in response to USCENTCOM data call (CCJ2/OR , 21 Oct 2010)Prime Integrators and/or datalink subcontractors provided additional engineering fidelity with approval from their respective Gov’t acquisition officesL-3 Communications developed an enhanced version of FlyPlan for this effort (funded out of pocket). Enhanced version addresses critical comments from the Joint Spectrum CenterPlatform data includes substantial amounts of proprietary vendor information; therefore, copies of the vendor-provided platform data will not be available for dissemination
7 Study Limitations (U) 90% solution delivered Analysis is limited to aircraft in USCENTCOM data callOmits Ku-band microwave towers; ground-based interferersData call is not completeNot all platform program offices respondedPTDS / Canadian King AirNew systems arriving since data call;Inbound systems not included : Yellow Jacket / Fire ScoutOperating locations for inbound platforms are still TBD (AAA aircraft)Engineering data not available (platform not included in data call)The FlyPlan analysis tool can, and has, successfully modeled the aircraft in the data call and verifies the correctness of the Downlink & Uplink frequency plan proposals in this briefing. If the data call were 100% correct and inclusive, then guarantees could be offered. We know that not all contributors of RF interference were modeled (e.g. microwave towers, commercial Ku-band satellite terminals, Persistent Threat Detection System [PTDS] teathered blimps, etc.). We also know that additional platforms are projected to be in the theater this year (or may already be in place), but were not included in the data call (e.g. Yellow Jacket, Shadow WAAS, Fire Scout, MARSS, etc.). There is therefore some level of risk that interference may still occur even when the recommended frequency plans in this briefing are followed.One means of mitigating interference is to have USCENTCOM require that each platform, US and coalition, that operates CDL provide USCENTCOM/CCJ6 with the engineering data outlined in the data call template. Systems may then be modeled in FlyPlan on a continuing basis to help ensure that problems do not arise, or that problems may be anticipated and mitigated with changes to the frequency plan.
8 FlyPlan Software Analysis Key Findings (U) Minimum frequency separation between 10Mbps channels is 15MHz for currently deployed aircraftKey factor is the spectral emission maskMay be different for systems not included in the data callMinimum angular separation between 274Mbps aircraft30 Degrees if using the same frequency assignment15 Degrees if frequencies spaced as far apart as possible& GHz (30 MHz separation – no further separation is possible)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 channelsThese key findings will be applied to formulate frequency plans for varying scenarios, presented in the following slides.All determinations were made using FlyPlan software and data provided by the respective Program Managers
9 Minimum Frequency Separation Explained (U) Signals are not “Lego Bricks”; they are complex functionsFlyPlan 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 interference3 dB BW (10.1MHz)90% of the Power (11.5MHz)Necessary BW (18.2MHz)As used by:VaderMARSSHarvest HawkConstant HawkHunterAAAA signal in space has energy dispersed across a nearly infinite bandwidth; therefore, the term “bandwidth” has no meaning without an associated qualifier.Typical qualifiers are bandwidths at 3 dB down from peak, some specified percentage of power (e.g. 90%), and Necessary BandwidthThe Joint Spectrum Center prefers to use 3 dB Bandwidth definitions when describing signalsThe SPECTRUM-XXI GMF database typically identifies Necessary BandwidthsBOTTOM LINE: FlyPlan software does not care how we choose to define bandwidth. FlyPlan uses the actual spectral response curve to find the breaking point on minimum frequency separation.LESSON LEARNED: This type of analysis clearly points to the continued need for USCENTCOM to request spectral emission plots for each aircraft heading into the theater. Without this detailed data, it is impossible for FlyPlan (or any other software) to make an accurate determination on interference assessments.
10 Minimum Angle Separation Explained (U) All GCS antennas in the data call are highly directional (4 ft parabolic)Example: 5 Degrees offset has a 31 dB drop in antenna gainFlyPlan assesses interference at off-axis angles; finds breaking pointTakes into account GCS pointing stability and A/C power outputsThe high directionality of the CGS antennas identified in the data call is the key determinant in permitting frequency re-use in the airspace surrounding any given operating location.One may observe an alarming trendThe original U-2 MIST ground antenna was 2 meters (78 Inches).Current antennas in the data call are 4 ft (48 Inches)There are antennas on the market that are only 3 feet (36 inches)As the ground antenna gets largerPeak gain increasesSide lobes decreaseOff-axis angle differences provide greater interference rejectionAllow faster frequency re-useFuture systems that arrive in theater may have large impacts on frequency reuse if their ground antennas are smaller than the 4 ft antennas analyzed for this current data callInvestigating the operational impact of ground antenna sizes is one of the long term study areas recommended at the end of this briefing
11 Links vs. Aircraft (U)10Mbps Narrowband Aircraft fall into one of two categoriesNarrowband aircraft using only Omni AntennasNarrowband aircraft using Directional AntennasOmni-Only Narrowband AircraftOmni antennas broadcast everywhere, in all directionsBroadcast reach GCS & Remote Video Terminals (RVT) simultaneouslyDirectional Narrowband AircraftFocuses a radio beam at the GCS with directional antennaDirectional radio beam does not illuminate dismounted soldier RVT’sMost A/C in data call require support to dismounted soldiers; thereforeDirectional narrowband aircraft require a second CDL linkRVT links typically use an omni so as to reach all soldiers on the groundThe term “Links” is used throughout this briefingIf referring to omni-only aircraft, then # Aircraft = # LinksIf referring to directional aircraft, then # Aircraft = Half the # Links
12 Data Call CDL-Platform Summary for Afghanistan (U) The above table contains a summary of the platforms whose program offices responded to USCENTCOM Data CallCanadian King Air and PTDS did not respondYellow Jacket and Fire Scout were not included in the Data Call because their deployments to Afghanistan were not certain at the time of the Data Call release (21 Oct 2010)
13 Two Frequency Mgt Option Approaches Available (U) Develop frequency plans requiring little or no airspace management or tasking considerationsAircraft can fly anywhere without regard to frequency considerationsUse airspace management to expand the number of CDL linksRequires disciplined airspace managementAirspace management tied directly to aircraft tasking in support of ISR collection requirementsAircraft cannot fly “anywhere”Coordination must occur before an A/C can change from one geographical sector to anotherFrequencies may need to be centrally or regionally assigned (perhaps daily) to manage channelsUSCENTCOM desires a frequency plan that will enable aircraft operating from a given location to fly anywhere within their line of sight range without changing frequencies or causing interference to other CDL usersThis is possible and is presented in this briefing; however, the quantity of CDL links that can be supported may be insufficient for large operating locationsThis presentation presents options to increase the number of CDL links, but the cost of doing this is disciplined airspace~frequency managementAircraft will not be able to fly “anywhere”Aircraft flight operations will have to be pre-planned and have frequencies assigned each day based on planned operating locationThis pre-planning with daily frequency assignments may have to be performed by a central authority that may or may not exist today.
14 Option 1: Little to No Airspace Management (U) Max number of CDL links that fit into Ku-band (each base)27 10Mbps (15 MHz separation)1 274Mbps Mbps (15 MHz separation)Aircraft can fly anywhere within LOS range of base (200NM)Useful if you do not want to manage airspace & frequenciesTwo downlink frequency plans are shown:One for 100% 10Mbps platformsOne to accommodate a wideband platform with 100% 10Mbps aircraftNot all aircraft use 10Mbps; a separate plan has been developed but not shown in this presentation for brevityEach downlink frequency plan requires an associated uplink frequency planUplink frequency plans are not shown in this presentation for brevityMany operating locations have 100% narrowband (10Mbps) aircraft27 Links probably sounds pretty goodNarrowband aircraft that employ directional antennas require a second, dedicated RVT broadcast to support dismounted soldiersIf all of the aircraft operating of a given base were directional type systems, then 27 links translates to 13 aircraftThis may not be enough to satisfy a given operating location
15 274Mbps Wideband Considerations (U) There is not enough spectrum to separate two wideband A/C that share the same airspaceMinimum angular separation between two wideband A/C measured from operating location is 30°A/C use same frequencyDepending on orbit size, airspace can handle upwards of 9 wideband A/CEach separated by 30°Spread out around the baseTwelve 10Mbps CDL links can operate simultaneously anywhere within range of base12 10Mbps can fly anywhereThis plan requires use of the CDL frequency downlink plan of the previous slide in which one wideband and twelve 10Mbps channels are definedSeparating the wideband A/C by 30 degrees as measured from the runway allows the wideband frequency assignment to be re-usedKey Point: The twelve additional 10Mbps links do not necessarily translate to twelve aircraftEach of wideband aircraft require a separate RVT broadcast which consumes one of the twelve channels. With two wideband A/C, that leaves only ten links.If each of the narrowband platforms use directional antennas (e.g. Grey Eagle), then they too will need two channels (one for the GCS link, and one for the RVT broadcast).This worst case scenario implies 5 narrowband aircraft operating from the same base as the two wideband aircraft.Co-located GCS on same base
16 Bringing Wideband A/C Closer Together (U) 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 separationFrom 30° to 15°Channel assignments of & GHz30 MHz max separation possibleHuge cost; Number of 10Mbps links drops from 12 to 4The 4 10Mbps can be anywhere in the airspaceThe above scenario was fully tested in the FlyPlan M&S software. No additional 10Mbps narrowband platforms can radiate in close proximity to the wideband aircraft without causing mutual interferenceAs with the previous slide, the four 10Mbps links does not translate to four narrowband aircraftEach of the two wideband aircraft require a dedicated 10Mbps link for RVT dissemination. That leaves two links leftIf narrowband platforms employing directional antennas are used, then they too require a separate, dedicated RVT broadcast linkThis worst case scenario implies only one narrowband aircraft can operate out of the same base as the two wideband aircraft
17 Overcoming Cost of 2 Wideband A/C Close Together (U) Minimum separation angle between 10Mbps platforms is 10°ResultWedge containing wideband A/C can support 4 10Mbps (shown in green)Larger wedge (shown in red) can reuse frequencies with normal 10Mbps pattern (below) supporting 27 links27 Links4 LinksThe green wedge shows two wideband aircraft separated by 15 degrees with four additional 10Mbps CDL linksThese four links can operate anywhere within the green wedge without causing interference to anybodySince the minimum separation angle for narrowband aircraft is 10 degrees, we may leave 10 degrees of “no-man’s land” on either side of the green wedge, and then re-use the entire Ku-band spectrum!The frequency plan for the red wedge is the original plan shown under Option 1.This assumes that all 27 links are 10Mbps users.
18 Option 2: Managing Airspace to Increase CDL Links (U) BDivide airspace into 4 sectorsAlternate frequency patternsResults13 Links (10Mbps) in “A”14 Links (10Mbps) in “B”54 10Mbps)Freedom of Movement:A/C in “B” can move into “A” & vice versaProvides 270° of freedomBy staggering the original frequency of Option 1 into “A” and “B”, and assigning these two frequency patterns into alternating Sectors “A” and “B”, we can achieve 100% frequency re-use and double the number of CDL linksAircraft no longer can operate “anywhere within line of sight of their runway”, but they do have reasonable freedom of movement for ad hoc ISR coverage requestsAny aircraft may operate in its assigned sector or either adjacent sector under proper coordination
19 Further Link Increases => More Sectors (U) 123456Dividing airspace into more sectors yields more links4 Sectors: 54 10Mbps6 Sectors: 81 10Mbps8 Sectors: Mbps12 Sectors: MbpsAlternate Even/Odd frequenciesA/C have freedom to move into adjacent sector12345687109111212345687
20 Caution (U)Conclusions in this study based exclusively on data for aircraft currently operating in CJOA-AFuture A/C may have different transmitter/receive characteristicsConclusions contained herein may not applyUrge all future deployments provide USCENTCOM with completed Data Call worksheetCan 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
21 Recommended Further Study (U) Due to operational urgency, this study focused exclusively on the here and nowMitigation steps for the long term are likely9 Months estimated to complete a long term studyLong term study areas:Waveform improvementsModulation, Coding, Tunability, Power ControlAntenna improvements (Aircraft & Ground Stations)Diplexer improvementsCross-Polarization benefitsImprovements to FlyPlan M&S software
22 Summary (U) Ku-band spectrum supports… 27 10Mbps, or1 274Mbps Mbps274Mbps A/C require 30° separation if using same channel12 10Mbps can overlap same area of operations274Mbps A/C can operate within 15° w/staggered frequencies4 10Mbps can overlap same area of operationsSpectrum reuse begins 10° later, provide 27 10MbpsAirspace can be divided into sectors to further increase # of LinksRequires airspace managementA/C are restricted to their assigned sector + adjacent sectors (each side)
23 COA #1: Assign Frequencies Independent of Airspace Assign Blue Devil and Gorgon Stare a “shared” wideband channel ( GHz center frequency) and assign narrowband users remaining channel assignments per belowIJC 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.
24 COA#2: Include two “Keep-Out” zones Around Wideband Aircraft Same as COA#1, but with two pre-planned 10° keep out zones on either side of the wideband aircraftEnables 12 narrowband links as with COA#1 co-located with wideband aircraft27 Links12 Links10° Keep-Out ZoneComplete frequency re-use beyond the keep-out zonesEnables 27 additional narrowband links to be assigned as neededIJC and RC-S CM&D need to be aware that …A/C in green zone are confined to green sectorA/C in red zone are confined to red sector
25 COA#3: Operate Wideband A/C in Close Proximity Same as COA #2, but change frequency plan for the Green ZoneEnables IJC and RC-S CM&D to bring wideband A/C within 15° of each otherReduces narrowband assignments from 12 to 4Red zone is unaffectedWideband center frequencies will be & GHz10° Keep-Out Zone4 Links27 Links
26 COA#4: Assign Frequencies by Sector Use a 4/6/8/10/12-sector approach to divide airspace around the designated RC-S FOBPermits the frequency re-use of both wideband and narrowband usersAlternate Red/Blue channel assignments with sectorsMinimizes and/or prevents “accidental” blue-on-blue frequency interferenceAerial assets communicating with GCS at FOB locations other than the sectors radius but in the general Area of Operations may require dedicated channelsCOA 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
28 Minimum Separation Angles for Frequency Reuse This briefing (slide 8) showed that…Min separation angle = 30° for 274Mbps wideband linksMin separation angle = 10° for 10Mbps narrowband linksIn reality, min separation angle is a function of rangeCCJ6 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 aircraftSee Slide 29 – 31 for examples
29 274Mbps (STD-CDL) Wideband Aircraft (Blue Devil & Gorgon Stare, both with Directional Antennas) 150NM140NM130NM120NM30 Deg Separation out to 140NM10 Deg Separation out to 130NM5 Deg Separation out to 120NM
30 30 Deg Separation out to 50NM 10 Deg Separation out to 40NM 274Mbps (STD-CDL) (Blue Devil [Omni Antenna] & Gorgon Stare [Directional Antenna])50NM30 Deg Separation out to 50NM40NM10 Deg Separation out to 40NM
31 10 Mbps (STD-CDL) (25,000 Feet Altitude, Directional Antennas) 160NM150NM140NM30 Deg Separation out to 160NM10 Deg Separation out to 150NM2.5 Deg Separation out to 140NM