UAS Control and Non Payload Communications (CNPC) Link Availability

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 lt
  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 4x103 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 (lt0.5dB).
• 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_at_uav.com
• Brooks Cressman brooks.cressman_at_itt.com