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Acknowledgement
The following information was jointly developed by Tony Henley of BAE Systems
and Joe Barnard of Barnard Microsystems, and formed part of a contribution to
EuroCAE Working Group 73 on UAVs.
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The communications scenarios during the phases of an Unmanned Aircraft mission
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Meaning of acronyms used
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Air Traffic Control
A service provided for the purposes of: a) preventing collisions between
aircraft and in the manoeuvring area between aircraft and obstructions; and b)
expediting and maintaining an orderly flow of air traffic. - STANAG 4586
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Flight Information Service - Broadcast
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Ground Control System
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Line-Of-Sight: maximum seperation = 5 km
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Request
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Airport Control Tower
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Unmanned Aircraft
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Very High Frequency
FM analog radio communications in the 118 MHz to 132 MHz band
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payload communications requirements (such as
ground monitoring
video data) are considered to be a separate issue from the command and control
requirements
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the GPS navigation signals received from the US GPS satellites at 1,575.42 MHz
(the civilian L1 signal) and at 1,227.60 MHz (the civilian L2 signal) are
acknowledged, but are excluded from the following discussion
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for Beyond-Line-Of-Sight operation of the UA, we assume a Sense and Avoid system
is fitted and operational in the UA, and that this system operates autonomously
on the UA, with reports of what is sensed and being tracked included in the
status reports which are transmitted each second
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for video data transmission via a satellite link, we have suggested the use of
MPEG-2 video compression in which a 720 x 480 pixel frame at a rate of 30 frames
per second requires a bit rate of about 4 Mbps.
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EUROCONTROL, FAA and ICAO plan to equip high traffic densities areas with ATC
data links for man and unmanned aircrafts by 2020. The ATC data link will
require an availability of 99.999% and must meet the 95th percentile one-way
transit times shown in the following table (from Pelmoine):
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Domain
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Threshold
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Objective
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En Route
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3.0 sec
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1.5 sec
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Tower
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3.0 sec
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1.5 sec
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Terminal
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3.0 sec
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1.5 sec
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for US military systems, the proposed:
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Line-Of-Sight data link frequency = 14,500 to 15,350 MHz
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satellite communications uplink (satellite to Unmanned Aircraft) frequency = 30
GHz to 31 GHz
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satellite downlink (Unmanned Aircraft to satellite) frequency = 20.2 GHz to 21.2
GHz
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Communications systems requirements based on following scenarios
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Here are the communications requirements we derive from the following scenarios.
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communications requirements
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reason / use
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3 OFF COFDM video channels, each 8 MHz bandwidth, in an ISM band such as the 5.8
GHz ISM band
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continuous situation awareness and following while the UA is on the runway
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in an emergency landing, where the UA is remotely flown from the GCS
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3 OFF MPEG-2 video channels, each 4 Mbps bit rate, for video information, on a
SAT comms link
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9.6 kbps satellite links with backup
GSM 900 / 1800 modem links
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CHA = 4.8 kbps
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download status messages (typically one per second) and video line scan data
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upload flight plan changes / remote operation of UA
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CHB = 4.8 kbps for digitised, duplex, TWR VHF voice relay
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9.6 kbps satellite links with backup
GSM 900 / 1800 modem links
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CHA = 4.8 kbps for digitised (CELP) duplex, ATC1 VHF voice relay
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CHB = 4.8 kbps for digitised (CELP) duplex, ATC2 VHF voice relay
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this VHF channel is also used to pick up the weather FIS
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Notes
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The GSM 900 / 1800 link is used to reduce the latency in satellite communication
link, but the satellite link is also used to ensure back-up in the event of
failure, or, unavailability of the GSM link.
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The Sense and Avoid (S+A) system, if fitted, functions autonomously and no S+A
video information is relayed back to the GCS.
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COFDM can be used as a modulation scheme to transmit video information from the
UA at or near the airport to a GCS that is within LOS of the UA on an ISM band,
such as the 5.8 GHz ISM band. The 5.8 GHz ISM band has a contiguous 125 MHz
bandwidth that can be subdivided into 15 channels of 8 MHz each for the purposes
of video information transmission. This band is at present not as heavily used
as the 2.4 GHz ISM band, which is heavily used for WLAN communications link
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From gate to take-off
From landing to gate
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UA within local line-of-sight of Airport
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UA within line-of-sight of GCS
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Local weather FIS data picked up by GCS
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sensing of obstacles on the runway
sensing runway and runway number
reading signs beside the runway
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continuous for situation awareness and following
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data downlink UA to GCS
data uplink GCS to UA
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UA status monitoring
1 msg / second
UA control
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digitised (eg. using CELP) voice:
downlink UA to GCS
uplink GCS to UA
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ATC acknowledge
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voice relay: TWR, ATC to UA
voice relay: UA to TWR, ATC
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R engine start
R push back
R taxi clearance
R take off
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Notes
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latency in the satellite voice relay is an issue
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From gate to take-off
From landing to gate
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If a field is used rather than an airport, then Case 1B is as per Case 1A,
except that there will be no ATC communications.
Notes
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latency in the satellite voice relay is an issue
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From gate to take-off
From landing to gate
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UA within local line-of-sight of Airport
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UA beyond line-of-sight of GCS
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sensing of obstacles on the runway
sensing runway and runway number
reading signs beside the runway
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3 OFF video cameras
each MPEG-2 at 4 Mbps
via SAT COMMS link
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continuous for situation awareness and following
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data downlink UA to GCS
data uplink GCS to UA
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(1) GSM 900 / 1800 modem
(2) satellite phone modem
4.8 kbps of a 9.6 kbps link
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UA status monitoring
1 msg / second
UA control
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digitised (eg. using CELP) voice:
downlink UA to GCS
uplink GCS to UA
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(1) GSM 900 / 1800 modem
(2) satellite phone modem
4.8 kbps of a 9.6 kbps link
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ATC acknowledge
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latency of SatComms link could be a problem
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need live link through take-off sequence
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availability / integrity is safety critical
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voice relay: TWR, ATC to UA
voice relay: UA to TWR, ATC
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VHF CH x (TWR - UA)
VHF CH y (ATC - UA)
VHF FM 118 - 132 MHz
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R engine start
R push back
R taxi clearance
R take off
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weather FIS information
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picked up on VHF CH z
relayed via GSM 900/1800
back-up is 4.8 kbps SAT comms voice relay link
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not time critical
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Notes
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latency in the satellite voice relay is an issue
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From gate to take-off
From landing to gate
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If a field is used rather than an airport, then Case 1D is as per Case 1C,
except that there will be no ATC communications.
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This case could also apply to an emergency landing situation.
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Climb out and cruise
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UA within local line-of-sight of Airport
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UA within line-of-sight of GCS
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Local weather FIS data picked up by GCS
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sensing of other aircraft
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continuous for situation awareness
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data downlink GCS to UA
data uplink GCS to UA
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UA status monitoring
1 msg / second
UA control
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digitised (eg. using CELP) voice:
downlink UA to GCS
uplink GCS to UA
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ATC acknowledge
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voice relay: ATC1, ATC2 to UA
voice relay: UA to ATC1, ATC2
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R flight level / bearing
R enter / leave sector
Freq change instr
ALT ref QNH transition
Mode S transponder setting
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Notes
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latency in the satellite voice relay is an issue
Emergency management
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Climb out and cruise
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UA within local line-of-sight of Airport
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UA beyond line-of-sight of GCS
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sensing of other aircraft
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3 OFF video cameras
data processed on-board
status reported each sec
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continuous for situation awareness and following
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data downlink UA to GCS
data uplink GCS to UA
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(1) GSM 900 / 1800 modem
(2) satellite phone modem
4.8 kbps of a 9.6 kbps link
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UA status monitoring
1 msg / second
UA control
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digitised (eg. using CELP) voice:
downlink UA to GCS
uplink GCS to UA
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(1) GSM 900 / 1800 modem
(2) satellite phone modem
4.8 kbps of a 9.6 kbps link
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ATC acknowledge
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latency of SatComms link could be a problem
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need live link through take-off sequence
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availability / integrity is safety critical
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voice relay: TWR, ATC to UA
voice relay: UA to TWR, ATC
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VHF CH x (TWR - UA)
VHF CH y (ATC - UA)
VHF FM 118 - 132 MHz
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R flight level / bearing
R enter / leave sector
Freq change instr
ALT ref QNH transition
Mode S transponder setting
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weather FIS information
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picked up on VHF CH z
relayed via GSM 900/1800
back-up is 4.8 kbps SAT comms voice relay link
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not time critical
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Notes
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latency in the satellite voice relay is an issue
Emergency management
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In case of emergency, ATC and GCS are notified, the UA is identified
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If the Sense and Avoid system fails, and is reported, the emergency situation is
flagged to ATC
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A major safety problem arises if a failure of the on-board Sense and Avoid
system is not detected, or, if a failure of the S+A system is detected, but not
then reported (two failures).
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Cruise / mission
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UA beyond line-of-sight of Airport
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UA beyond line-of-sight of GCS
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No local weather FIS data available
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OCEANIC with ATC seperation service
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sensing of other aircraft
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continuous for situation awareness
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data downlink UA to SAT to GCS
data uplink GCS to SAT to UA
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UA status monitoring
1 msg / second
UA control
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digitised (eg. using CELP) voice:
downlink UA to SAT to GCS
uplink GCS to SAT to UA
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ATC acknowledge
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voice relay: ATC to UA
voice relay: UA to ATC
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infrequent: 1 or 2 msg every 10 minutes
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ATC clearances
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UA-to-UA WLAN data link
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for a formation (swarm) of Unmanned Aircraft, in which only one UA maintains a
SAT comms link (although all carry the equiment for this link)
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Notes
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latency in a satellite communication link is considered tolerable
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no GSM 900 / 1800 service available
Emergency management
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ATC identified
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UA identified
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S+A system failure: detected and reported: flag emergency to ATC
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S+A system failure: not detected and / or not reported: not serious in oceanic
arena: serious if UA then processed into more crowded air space on land.
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Cruise / mission
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UA beyond line-of-sight of Airport
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UA beyond line-of-sight of GCS
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No local weather FIS data available
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Flying over REMOTE area with no ATC seperation service
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sensing of other aircraft
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continuous for situation awareness
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data downlink UA to SAT to GCS
data uplink GCS to SAT to UA
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UA status monitoring
1 msg / second
UA control
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digitised (eg. using CELP) voice:
downlink UA to SAT to GCS
uplink GCS to SAT to UA
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ATC acknowledge
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voice relay: ATC to UA
voice relay: UA to ATC
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UA-to-UA WLAN data link
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for a formation (swarm) of Unmanned Aircraft, in which only one UA maintains a
SAT comms link (although all carry the equiment for this link)
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Notes
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latency in a satellite communication link is considered tolerable
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GSM 900 / 1800 coverage unreliable or unavailable
Emergency management
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