Aeronautical Communications Technologies Simulator

1
Aeronautical Communications
Technologies Simulator
Bertrand Desperier - EEC bertrand.desperier_at_euro
control.int Patrick Delhaise - Eurocontrol
DAS/CSM patrick.delhaise_at_eurocontrol.int
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OVERVIEW

• Simulating the air/ground sub-network
• (i.e physical and data-link layers in OSI model)
• A modular architecture for re-using parts
• First development for VDL mode 2
• Multi platform supported (currently PC under
  windows)

• Adaptation and validation of key air/ground
  sub-network
• Prediction of system performance and capacity
  limits.
• Optimisation of parameters, standards function,
  and implementation aspects respecting operational
  requirements

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Principle
MSG INPUT -Random -Deterministic
Area to be studied
AIR TRAFFIC INPUT
GS3
Communication Channels
GS1
Station 1
Frequency
Station 2
GS2
Capacity/ Reliability Analyser
Station 3
Time
Station N
SYSTEM PARAMETERS
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Relative channels
Each station perceives differently the common
channel at a given time
AC 3
AC 2
AC 1
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Generic Architecture
Channel
STATION (AC or GS)
Relative channel information
CHANNEL FILTER
SYSTEM
System parameters
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Generic Architecture
Analyse Capacity reliability Average delay ...
Channel
STATION (AC or GS)
CHANNEL FILTER
Propagation model
Power
Data Link
Receiver
Rx
Relative position calculator
Delay
Channel Monitor
Data
Transmitter
SYSTEM
System parameters
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Inputs

• Air traffic
• For each station (airborne and ground) 3-D
  positions in a given area
• ? Can be extracted from any air traffic simulator
  (RAMS, TAAM, SAAM) or radar plots record
• Messages profiles
• Messages transmission rate distribution
• Message length distribution
• Messages exchange based on events
• System parameters
• Propagation model (several accuracy levels)
• Physical layer
• Medium access control layer
• Data-link layer

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Validation achieved

• Application of Certification tests for single
  station
• Theoretical models-comparison for the whole
  sub-network (Mathematical checks for simple
  cases)
• Field trials
• Cross check with other simulators
• Initial operation feedback

Other ACTS application areas

• Other VDL modes (3,4)
• 1090 E.S.
• UAT
• 3G systems
• Satellites systems
• ..

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VDL Mode 2-ACTS
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ACARS, VDL 2, AOA, ATN, ...
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VDL2 Simulation Objectives

• Accurate evaluation of capacity and performance
  of any VDL2 channel
• Net Throughput Vs Channel load
• Collisions rate, retransmission rate
• Transmission delays

• Identifying the critical aspects
• The impact of the hidden and the exposed
  stations
• The ground-station density as providers currently
  plan
• Critical capacity environment (airport or
  en-route domains...? )
• Best frequency scenarios for current and future
  (2005-2010) air traffic demands both supporting
  ATS and AOC needs

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VDL2 Simulation Objectives

• Optimising the VDL Mode 2 MAC sub-layer (CSMA)
  and data-link layer (AVLC) parameters
• CSMA persistence (p)
• Different timers values (e.g M1, TM1, T1)

• Evaluating the possible benefit of improvements
  to VDL Mode 2 standard among others evaluating
  the impact of
• Different p-values given to avionics (static or
  dynamic value), ground-stations (en-route) and
  ground-stations (at airport).
• Hand-off mechanism (SQP scale, HO criteria)

• Giving input for future real time ATC
  simulations including data-link
• To evaluate impact on operations of
• Transmission delays
• Lost messages

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ACTS VDL2 Capabilities

• Accurate Propagation delay (1m- precision)
• VHF propagation model including large scale
  fading
• D8PSK behaviour gt BER calculation
• Reed Solomon FEC-function, and related Frame
  error rate
• VDL2 specific p-persistent CSMA Mac layer
  mechanism
• Hidden/Exposed terminal effects
• AVLC Data link layer aspects including hand-off
• Dynamic Air traffic and tuneable Ground stations
  location
• AOC and ATS Traffic Messages distribution in
  time
• AOC and ATS message sizes distribution

• Standards
• SARPS - VDL2 Technical Manual
• MOPS
• ARINC 618-5, 631-3
• MASPS RTCA/DO-224 A

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Main Milestones

• Sept 02 High Level Simulation Requirements
• Oct/Nov 02 Architecture
• Jan 03 First Software release including VDL2
  physical and MAC layer
• Feb 03 AVLC implementation
• March 03 First Simulation Inputs Scenarios
  definition
• March-December 03 Theoretical and cross check
  validation
• June 03 Discussion of initial results with
  AEEC, SITA and ARINC
• Nov 03 Definition of second set of
  simulations
• Jan- June 04 Presentation of results and
  contributions (in AEEC, ICAO WGM, with
  manufacturers, airlines, standard bodies)

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ACTS VDL Mode 2
Technical aspects
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Time sampling

• The simulator is not real time gt Time has to be
  sampled.
• However, the simulator is triggered on events
• Time sampling frequency is critical for the
  simulation accuracy
• eg with Fs 300 MHz (period of 33 ns)
  gt Position accuracy 1m

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Hidden and exposed terminal

• GS1 and GS2 can not see each other, Aircraft
  sees both GS

• Hidden terminal can create collisions on the
  uplink

• Exposed terminal can delay the downlink messages

GS 2
GS 1

• Cases to be considered

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VHF Propagation Models

• Free space propagation model commonly used by
  other simulators
• Large scale fading (2 rays model vertical
  polarisation) which have been validated by STNA

Free Space Large scale
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Receiving process
Reception success rate can be derived from the
transmitter/ receiver relative position
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Message collision process

• For collision, worst cases are always considered
• Frames involved in collision are considered as
  additional WGN
• gt BER and FER are then computed as previously
  with the specific noise level

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List of system parameters

• Propagation model
• Model in use
• ground type
• Physical parameters
• Transmission power
• Antenna gain
• Cable loss
• VSWR Possibility to define range for these
  values
• Noise figure
• Filter width
• Channel frequency
• Mac sub-layer (CSMA)
• Stations persistence
• TM1 timer between two attempts
• M1
• TM2
• AVLC
• AVLC (VME, DLS) timers
• Number of retransmission

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INPUTS Collection ProcessHigh- Level
ACTS
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Air Traffic input

• The first step shall consist in using an Air
  traffic simulator log file.

Time ID Lat Long Alt Status 044018 TYR413D
47.8003 13.0192 1411 ON TAXI TO
GATE 044018 TYR531L 47.9715 16.4778
3000 ON APPROACH 044018 TYR541G
48.0987 16.5806 586 ON TAXI TO
GATE 044021 TYR413D 47.8005 13.0194
1411 ON TAXI TO GATE 044021 TYR531L
47.9725 16.4809 3000 ON
APPROACH 044021 TYR541G 48.0985 16.5803
586 ON TAXI TO GATE 044024 TYR413D
47.8007 13.0196 1411 ON TAXI TO

• The second step shall be to run an external
  library using CFMU flight plan as an input and
  able to give at any time any flight information.
  RAMS will provide such tool.
• For more accurate simulations other information
  about aircraft behaviour, such as pitch, roll
  could be integrated to achieve a more realistic
  link budget.

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AOC Message profiles

• Formal co-operation with ARINC and SITA is setup
  to provide under NDA typical AOC traffic message
  profiles for airlines flying in Europe.
• 4 classes of airlines in terms of data-link
  usage
• Class 0 No data-link
• Class S Small
• Class M Medium
• Class L Large
• Both deterministic and stochastic message
  distribution The number of exchanged messages
  depends on
• The airline
• The flight phase (random distribution into the
  Flight Phase)

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AOC Messages profile

• 4 classes of data-link users
• Class 0 No data-link
• Class S Small
• Class M Medium
• Class L Large

• A message size distribution is also implemented
  for uplink and downlink, it depends on the
  airline class.

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ATS- Link 2000 Applications

• CM Application Service
• DLIC (Datalink initiation Capability)
• CPDLC Application Service
• ACM (ATC communication management)
• ACL (ATC clearance)
• AMC (ATC Microphone check)
• DCL (Departure clearance)
• DSC (Downstream clearance)
• DFIS Application Service
• D-ATIS
• ADS Application Service
• FLIPCY (Flight plan consistency)

• Transactions per flight
• 1 DLIC / FIR (ATSU)
• 1 FLIPCY / FIR (ATSU)
• 1 D-ATIS / Departure airport
• 1 D-ATIS / Departure TMA
• 1 D-ATIS / Arrival TMA
• 1 D-ATIS / Arrival airport
• 1 DCL / Departure airport
• 1 ACM / ATSU sector
• 5 ACL (3U,2D) / Departure TMA
• 16 ACL (1-2 per ATSU) in En-Route
• 10 ACL (6U,4D) / Arrival TMA
• 1DSC / En-Route
• 1 AMC / Sector

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Simulator Output (per station)

• Transmitter
• Number of INF transmission request
• Number of INF transmitted
• Re-transmission 0, 1, 2 N2
• Average and maximum CSMA delay
• of TM2 occurrence
• Receiver
• Number of received INF
• Transmission delay (Average, maximum) (CSMA,
  propagation) in s
• Round trip delay in s
• of msg out of delay (depending on the
  application)
• of successfully acknowledged transmitted
  messages
• Application related statistics
• CPDLC within allowed round trip delay
• CAP within allowed one way delay
• Others statistics
• of lost frames collision low SNR
• Hands off successes and failure

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Simulator Output (common to all stations)

• Average and maximum uplink and downlink
  transmission delay
• Average and maximum uplink, downlink round trip
  delay
• Real channel load (for each GS point of view)
  (in of time)
• Net Throughput with regards to INF0 frames (in
  kbits/s)
• User data rate (without layers overhead) (in
  kbit/s)
• Uplink and downlink success rate
• Hands off success rate

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Scenarios

• 2 main scenarios based on a critical sector
  CDG-airport, Paris
• The air traffic will be the peak hour of the peak
  day of 2002 (30 August)
• 2005
• Single VDL 2 channel across Europe
• GS deployment as shown on map
• All AOC traffic assumed migrated to VDL2
• 2010
• Stepwise, from 2 possibly up to 4 frequencies
• GS configuration as shown on map
• Increased AOC traffic, all ATS/Link2000
  applications considered
• Aircraft equipment rate according to EUROCONTROL
  STATFOR inputs

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Sita VDL2 Ground stations in 2005
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For further information please contact
Patrick DELHAISE EUROCONTROL DAS/CSM Tel 32 2
729 34 78 Fax [phone] patrick.delhaise_at_eu
rocontrol.int
Bertrand DESPERIER EEC / Brétigny CNS Tel 33 1
69 88 76 09 Fax [phone] bertrand.desperi
er_at_eurocontrol.int