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UAS Control and Non Payload Communications (CNPC) Link Availability

UAS Control and Non Payload Communications (CNPC) Link Availability. ICAO ACP-WG-F Meeting #24 Paris, March 2011 Michael Neale and Brooks Cressman. Overview. What levels of UAS Control and Non-Payload Communications (CNPC) Link Availability will be required?

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UAS Control and Non Payload Communications (CNPC) Link Availability

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  1. UAS Control and Non Payload Communications (CNPC) Link Availability ICAO ACP-WG-F Meeting #24 Paris, March 2011Michael Neale and Brooks Cressman

  2. Overview • What levels of UAS Control and Non-Payload Communications (CNPC) Link Availability will be required? • Safety driven analysis of Collision Avoidance Scenario. • Dependent on Aircraft type, Class of Airspace, Operation. • ICAO AMS(R)S Manual. • What levels of Availability can be achieved? • LOS and BLOS (satellite). • Using frequencies likely to be approved at ITU WRC-12. • An overall system view. • A candidate UAS CNPC design solution

  3. Safety Analysis • Analysis of a Collision Avoidance Scenario • Conflict Avoidance Period 5-10 seconds. • Collision Avoidance Period 5-10 seconds. • CNPC Link temporary outage must last for less than 1-2 seconds during this 10-20 second period.

  4. Safety Analysis • Target UAS Midair Collision Rates per flight hour to be the same as manned aircraft • AOPA NALL Report shows about 10 Part 91 (GA) manned aircraft midair collisions per year during approximately 25 million flight hours = 4x10^-7 per flight hour. • NTSB and FAA data shows for manned Part 121 (airline and large cargo) aircraft no midair collisions during over 400 million flight hours = 2.5x10^-9 per flight hour. • Collision Likelihood • Current estimates of the likelihood of an intruder, on a collision course with a UA, entering the UA's self conflict avoidance volume (self separation volume) is once every 10,000hrs. Collision Likelihood = 1x10^-4 per flight hour. • Sense and Avoid and CNPC systems must reduce this Collision Likelihood to the target Midair Collision rates achieved by manned aircraft

  5. Safety Analysis • Assuming no autonomous UA operation • Collision Likelihood x SA & CNPC Unavailability < Manned Aircraft Midair Collision Rate • Part 91 Type UA Unavailability Case • 4x10^-7/1x10^-4 = 4x10-3 • Assume SA and CNPC systems share equal Unavailabilities. • CC link Unavailability 1/2 x 4x10^3 = 2x10-3 = 0.2% • 99.8% CNPC Link Availability = Total outage of 2.88min per day. • Part 121 Type UA Unavailability Case • 2.5x10^-9/1x10^-4 = 2.5x10-5 • Assume SA and CNPC systems share equal Unavailabilities. • CNPC Link Unavailability 1/2 x 2.5x10-5 = 1.25x10-5 = 0.00125% • 99.99875% CNPC Link Availability = Total outage of 1.08 seconds per day.

  6. Safety Analysis • Part 91 Type UA Unavailability Case • Required CNPC Link Availability approximately 99.8% • Part 121 Type UA Unavailability Case • Required CNPC Link Availability approximately 99.99875% • ICAO Manual on Required Communications Performance Doc 9869 AN/462, 2008 prescribes a similar level of availability based on supporting ATC separation service.

  7. LOS CNPC Link Availability • LOS Availability impairments compared to free space • Multipath and Diffraction – low altitude e.g. takeoff and landing as well as earth curvature obstruction near maximum range. • Airframe antenna obstruction - maneuvering during takeoff and landing as well as when flying straight and level en-route. • LOS Multipath • Using ITU-R P.530 Propagation data and prediction methods required for the design of terrestrial line of sight systems – Section 2.3.2. • Additional propagation loss of 11-19dB (depending on frequency and aircraft altitude) added for 99.8% availability.

  8. LOS CNPC Link Availability • LOS Installed antenna performance analysis • Using a single antenna yields 20-25dB nulls. • Using two diversity controlled antennas gives 12dB nulls. • Additional loss (12dB) added to link budgets to account for airframe obstruction

  9. LOS CNPC Link Availability • Assuming • Control - Telecommand and telemetry data rates 10kbps • Pilot Voice Communication data rates 5kbps • SA/TCAS support data rates 10kbps • Weather radar and nose camera video 270kbps • L Band (circa 1GHz) and C Band (circa 5GHz) ITU preferred AM(R)S LOS frequencies. • 10 Watt transmitters • 2dB Noise Figure receivers • Realistic system losses • Two Omnidirectional antennas on the aircraft • High gain antenna(s) at Control Station • Include 6dB safety margin • Approximately 150km (80nm) range • Single Link Availability of 99.8% can be achieved

  10. BLOS CNPC Link Availability • BLOS Satellite Availability impairments compared to free space • L and C Band scintillation loss (<0.5dB). • Ku and Ka Band. • Rain and scintillation fading. • Use ITU-R P.618 - Propagation data and prediction methods required for the design of Earth-space telecommunication systems - Section 2.2.1.1. • Additional propagation loss of 1.6-14dB depending on rain rate and altitude for 99.8% availability. • Other Ku and Ka Band limitations • Aircraft size and power capability, limits antenna size and transmit amplifier power output which limits EIRP and G/T and link margin.

  11. BLOS CNPC Link Availability • Rain at lower altitudes causes additional propagation loss on Ku/Ka satellite links • UA can only use Ku/Ka Band satellites at aircraft altitudes where rain loss is not excessive. This limits the lowest altitude the UA can fly. UA will switch to LOS for takeoff and landing. • Manned Aircraft avoid weather radar level 3 (red) and above regions where rain is higher than an R 0.01 of approximately 20mm/hr.

  12. BLOS CNPC Link Availability • Assuming • Control - Telecommand and telemetry data rates 10kbps • Pilot Voice Communication data rates 5kbps • SA/TCAS support data rates 10kbps • Weather radar and nose camera video 270kbps • L Band (circa 1.6GHz), C Band (circa 5GHz), Ku (12/14GHz) and Ka Band (20/30GHz) frequencies • 10 Watt transmitters • Realistic system losses • Omnidirectional antennas on the aircraft at L and C Band • 0.8m and 0.5m dish antennas on aircraft at Ku and Ka Band • EIRP limited by uplink power flux density regulations • Single Link Availability 99.8% can be achieved

  13. Candidate Design • A single CNPC link is probably adequate for Part 91 Type UA operating in class E or G airspace • A very effective way to achieve the availability needed for a Part 121 Type UA operating in class A, B or C airspace is to use two non-correlated CNPC systems • 1- 0.998 x 1-0.998 = 1-0.999996 or 99.9996% Availability • Also mitigates against hardware and software failures. • Use the multiple frequency bands that are being considered by ITU to provide the diversity. • Dual links for larger UA already assumed in ITU-R M.2171 spectrum analysis. • Allows some margin for other parts of the CNPC link.

  14. Candidate Design • Part 91 Type UA • Operation in Class E or G airspace. • LOS - Use Single L (1GHz) or C (5GHz) Band LOS link. • BLOS - Use Single L (1.6GHz) or C (5GHz) BLOS link – only required for operation outside Visual LOS. • If desiring to operate in class A, B or C airspace may be treated as a Part 121 Type UA if suitably equipped. • Part 121 Type UA • Operation in Class A, B, C or D airspace. • LOS - Use Dual L (1GHz) and C (5GHz) Band LOS Links. • BLOS – Use Dual L(1.6GHz) or C (5GHz) Band link and Ku (12/14GHz) or Ka (20/30GHz) Band Link. • If desiring to operate in Class E, or G airspace may do so.

  15. Conclusions • A flexible dual band approach can deliver the levels of safety anticipated while affording a number of advantages: • Redundancy • Using two non-correlated frequencies offers protection against equipment failure as well as improvements in availability. • Scalability • A smaller UA only requires a simple single AM(R)S L (1GHz) or C (5GHz) Band system for Visual LOS or Radio LOS operation. • A larger UA, that can support more equipment, can achieve higher levels of availability. • Interference Protection • Combining an L(1.6GHz) or C (5GHz) Band AMS(R)S BLOS system with a Ku or Ka Band FSS system provides the interference protection of AMS(R)S with the ubiquity and payload data rate capability of FSS.

  16. Future Liaison • RTCA SC203 Control and Communications Work Group has developed a number of papers on: • UAS CNPC Spectrum • UAS CNPC Security • UAS CNPC messaging and data requirements • UAS Candidate CNPC Architectures • UAS CNPC Required Communications Performance • Latency, Availability Continuity, Integrity etc. • Contact Michael Neale for copies of SC203 papers or to participate in RTCA UAS MASPS and MOPS development • Michael Neale – michael.neale@uav.com • Brooks Cressman – brooks.cressman@itt.com

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