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Unmanned Aircraft communication scenarios
from 1033_paparazzi.pdf
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 |
Meaning of acronyms used
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ATC |
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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FIS-B |
Flight Information Service - Broadcast |
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GCS |
Ground Control System |
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LOS |
Line-Of-Sight: maximum seperation = 5 km |
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R |
Request |
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TWR |
Airport Control Tower |
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UA |
Unmanned Aircraft |
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VHF |
Very High Frequency FM analog radio communications in the 118 MHz to 132 MHz band |
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Notes |
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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
- 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.
- 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 |
Threshold |
Objective |
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En Route |
3.0 sec |
1.5 sec |
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Tower |
3.0 sec |
1.5 sec |
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Terminal |
3.0 sec |
1.5 sec |
- for US military systems, the proposed:
- Line-Of-Sight data link frequency = 14,500 to 15,350 MHz
- satellite communications uplink (satellite to Unmanned Aircraft) frequency = 30 GHz to 31 GHz
- 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 |
Here are the communications requirements we derive from the following scenarios.
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communications requirements |
scenario |
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 |
UA is in LOS of GCS |
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3 OFF MPEG-2 video channels, each 4 Mbps bit rate, for video information, on a SAT comms link |
UA is BLOS of GCS |
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9.6 kbps satellite links with backup GSM 900 / 1800 modem links |
all |
CHA = 4.8 kbps
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|
primarily when close to, or at, an airport |
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 |
primarily when climb out and cruise + when cruise / mission |
CHA = 4.8 kbps for digitised (CELP) duplex, ATC1 VHF voice relay |
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primarily when on cruise / mission and passing from one ATC centre to another |
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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 links. It must be noted that COFDM is sensitive to Doppler shift, and is degraded in situations where the difference in speed between the transmitter on the UA and the receiver at the static ground station exceeds 185 kph.
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Case 1A |
From gate to take-off From landing to gate |
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sensing of obstacles on the runway sensing runway and runway number reading signs beside the runway |
3 OFF video cameras each COFDM BW = 8 MHz 5.8 GHz ISM band |
continuous for situation awareness and following |
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data downlink UA to GCS data uplink GCS to UA |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
UA status monitoring 1 msg / second UA control |
|
|
digitised (eg. using CELP) voice: downlink UA to GCS uplink GCS to UA |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
ATC acknowledge |
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voice relay: TWR, ATC to UA voice relay: UA to TWR, ATC |
VHF channel x (TWR - UA) VHF channel y (ATC - UA) VHF FM 118 - 132 MHz |
R engine start R push back R taxi clearance R take off |
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Notes
- latency in the satellite voice relay is an issue
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Case 1B |
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
- latency in the satellite voice relay is an issue
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Case 1C |
From gate to take-off From landing to gate |
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sensing of obstacles on the runway sensing runway and runway number reading signs beside the runway |
3 OFF video cameras each MPEG-2 at 4 Mbps via SAT COMMS link |
continuous for situation awareness and following |
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data downlink UA to GCS data uplink GCS to UA |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
UA status monitoring 1 msg / second UA control |
|
|
digitised (eg. using CELP) voice: downlink UA to GCS uplink GCS to UA |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
ATC acknowledge
|
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voice relay: TWR, ATC to UA voice relay: UA to TWR, ATC |
VHF CH x (TWR - UA) VHF CH y (ATC - UA) VHF FM 118 - 132 MHz |
R engine start R push back R taxi clearance R take off |
|
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weather FIS information |
picked up on VHF CH z relayed via GSM 900/1800 back-up is 4.8 kbps SAT comms voice relay link |
not time critical |
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Notes
- latency in the satellite voice relay is an issue
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Case 1D |
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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Case 2A |
Climb out and cruise |
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|||
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sensing of other aircraft |
3 OFF video cameras data processed on-board status reported each sec |
continuous for situation awareness |
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data downlink GCS to UA data uplink GCS to UA |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
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 |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
ATC acknowledge |
|
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voice relay: ATC1, ATC2 to UA voice relay: UA to ATC1, ATC2 |
VHF channel x (ATC1 - UA) VHF channel y (ATC2 - UA) VHF FM 118 - 132 MHz |
R flight level / bearing R enter / leave sector Freq change instr ALT ref QNH transition Mode S transponder setting |
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Notes
-
latency in the satellite voice relay is an issue
Emergency management
-
In case of emergency, ATC and GCS notified, UA identified
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Case 2B |
Climb out and cruise |
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sensing of other aircraft |
3 OFF video cameras data processed on-board status reported each sec |
continuous for situation awareness and following |
|
|
data downlink UA to GCS data uplink GCS to UA |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
UA status monitoring 1 msg / second UA control |
|
|
digitised (eg. using CELP) voice: downlink UA to GCS uplink GCS to UA |
(1) GSM 900 / 1800 modem (2) satellite phone modem 4.8 kbps of a 9.6 kbps link |
ATC acknowledge
|
|
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voice relay: TWR, ATC to UA voice relay: UA to TWR, ATC |
VHF CH x (TWR - UA) VHF CH y (ATC - UA) VHF FM 118 - 132 MHz |
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 |
picked up on VHF CH z relayed via GSM 900/1800 back-up is 4.8 kbps SAT comms voice relay link |
not time critical |
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Notes
-
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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Case 3A |
Cruise / mission |
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sensing of other aircraft |
3 OFF video cameras data processed on-board status reported each sec |
continuous for situation awareness |
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data downlink UA to SAT to GCS data uplink GCS to SAT to UA |
satellite phone modem 4.8 kbps of a 9.6 kbps link |
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 |
satellite phone modem 4.8 kbps of a 9.6 kbps link |
ATC acknowledge |
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voice relay: ATC to UA voice relay: UA to ATC |
VHF channel x (ATC1 - UA) VHF channel y (ATC2 - UA) VHF FM 118 - 132 MHz |
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UA-to-UA WLAN data link |
802.11g or 802.11n (draft) WLAN link operating in the 2.4 GHz ISM band |
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
-
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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Case 3B |
Cruise / mission |
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sensing of other aircraft |
3 OFF video cameras data processed on-board status reported each sec |
continuous for situation awareness |
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data downlink UA to SAT to GCS data uplink GCS to SAT to UA |
satellite phone modem 4.8 kbps of a 9.6 kbps link |
UA status monitoring 1 msg / second UA control |
|
|
digitised (eg. using CELP) voice: downlink UA to SAT to GCS uplink GCS to SAT to UA |
satellite phone modem 4.8 kbps of a 9.6 kbps link |
ATC acknowledge |
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voice relay: ATC to UA voice relay: UA to ATC |
VHF channel x (ATC1 - UA) VHF channel y (ATC2 - UA) VHF FM 118 - 132 MHz |
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|
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UA-to-UA WLAN data link |
802.11g or 802.11n (draft) WLAN link operating in the 2.4 GHz ISM band |
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
- GSM 900 / 1800 coverage unreliable or unavailable
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 and / or perform emergency landing
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S+A system failure: not detected and / or not reported: SERIOUS SITUATION in a REMOTE arena
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