2 OVERVIEW (i.e physical and data-link layers in OSI model) Simulating the air/ground sub-network(i.e physical and data-link layers in OSI model)A modular architecture for re-using partsFirst development for VDL mode 2Multi platform supported (currently PC under windows)Adaptation and validation of key air/ground sub-networkPrediction of system performance and capacity limits.Optimisation of parameters, standards function, and implementation aspects respecting operational requirements
3 Capacity/ Reliability Analyser PrincipleMSG INPUT-Random-DeterministicArea to be studiedAIR TRAFFICINPUTGS3CommunicationChannelsGS1FrequencyStation 1Station 2GS2Capacity/ Reliability AnalyserStation 3TimeStation NSYSTEM PARAMETERS
4 Each station perceives differently the common channel at a given time Relative channelsEach station perceives differently the common channel at a given timeAC 3t 1/33AC 2t 1/22AC 11t(AC 3)Absolute timet(AC 2)t(AC 1)Levelt 1/2t 1/3t 2/3t 2/3
5 Relative channel information Generic ArchitectureUpper layersMessagesChannelSTATION (AC or GS)Relative channel informationCHANNEL FILTERSYSTEMAir trafficSystem parameters
6 Relative position calculator Generic ArchitectureAnalyseCapacityreliabilityAverage delay ...Upper layersMessagesChannelSTATION (AC or GS)CHANNEL FILTERPropagationmodelPowerReceiverData LinkRxRelative position calculatorDelayChannel MonitorDataTransmitterSYSTEMAir trafficSystem parameters
7 Propagation model (several accuracy levels) InputsAir trafficFor 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 recordMessages profilesMessages transmission rate distributionMessage length distributionMessages exchange based on eventsSystem parametersPropagation model (several accuracy levels)Physical layerMedium access control layerData-link layer
8 Other ACTS application areas Validation achievedApplication of Certification tests for single stationTheoretical models-comparison for the whole sub-network (Mathematical checks for simple cases)Field trialsCross check with other simulatorsInitial operation feedbackOther ACTS application areasOther VDL modes (3,4)1090 E.S.UAT3G systemsSatellites systems……………………..
10 ACARS network ATN ACARS, VDL 2, AOA, ATN, ... Unchanged ACARS ACARS applications in a Management Unit, CMU or ATSUAnalogic VHF radio or VDR running in ACARS modeCurrent ACARS configurationACARSGround-StationsACARSapplicationsACARS networkAOA data pathUnchangedNew CNS/ATM applicationsATN Router8208ATN phaseUnchangedACARSapplicationsAVLCVDR running VDL mode2CMU/ ATSUD8PSK Tx/RxCSMAAOA phaseVDL 2VDL 2Ground-StationsATNNew CNS/ATM applications
11 VDL2 Simulation Objectives Accurate evaluation of capacity and performance of any VDL2 channel:Net Throughput Vs Channel loadCollisions rate, retransmission rateTransmission delaysIdentifying the critical aspects:The impact of the “hidden and the exposed stations”The ground-station density as providers currently planCritical capacity environment (airport or en-route domains...? )Best frequency scenarios for current and future ( ) air traffic demands both supporting ATS and AOC needs
12 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 ofDifferent 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 ofTransmission delaysLost messages
13 ACTS VDL2 Capabilities Standards: Accurate Propagation delay (1m- precision)VHF propagation model including large scale fadingD8PSK behaviour => BER calculationReed Solomon FEC-function, and related Frame error rateVDL2 specific p-persistent CSMA Mac layer mechanismHidden/Exposed terminal effectsAVLC Data link layer aspects including hand-offDynamic Air traffic and tuneable Ground stations locationAOC and ATS Traffic Messages distribution in timeAOC and ATS message sizes distributionStandards:SARPS - VDL2 Technical ManualMOPSARINC 618-5, 631-3MASPS RTCA/DO-224 A
14 Main Milestones Sept 02 High Level Simulation Requirements Oct/Nov 02 ArchitectureJan 03 First Software release including VDL2 physical and MAC layerFeb 03 AVLC implementationMarch 03 First Simulation Inputs Scenarios definitionMarch-December 03 Theoretical and cross check validationJune 03 Discussion of initial results with AEEC, SITA and ARINCNov 03 Definition of second set of simulationsJan- June 04 Presentation of results and contributions (in AEEC, ICAO WGM, with manufacturers, airlines, standard bodies…)
16 The simulator is not real time => Time has to be sampled. Time samplingThe simulator is not real time => Time has to be sampled.However, the simulator is triggered on eventsTime sampling frequency is critical for the simulation accuracy:eg : with Fs = 300 MHz (period of 33 ns) => Position accuracy = 1m
17 Hidden and exposed terminal GS1 and GS2 can not see each other, Aircraft sees both GSHidden terminal can create collisions on the uplinkExposed terminal can delay the downlink messagesGS 1GS 2RH AC1Interfering AreaRH GS1Area to be studiedRH AC1Cases to be considered
18 VHF Propagation Models Free space propagation model commonly used by other simulatorsLarge scale fading (2 rays model vertical polarisation) which have been validated by STNAFree SpaceLarge scale
19 Receiving processRelativeTx/Rx positionsOut of LOS ?SNRprocessReceiverN0CollidedFrames powerRx filter widthModulationSchemeBERTx and Rx filter lossCorrectingCodeFrame lengthFERPropagationmodelPReceived powerNoSuccess/FailureRandomReception success rate can be derived from the transmitter/ receiver relative position
20 Message collision process For collision, worst cases are always considered:Frames involved in collision are considered as additional WGN=> BER and FER are then computed as previously with the specific noise level
21 List of system parameters Propagation modelModel in useground typePhysical parametersTransmission powerAntenna gainCable lossVSWR Possibility to define range for these valuesNoise figureFilter widthChannel frequencyMac sub-layer (CSMA)Station’s persistenceTM1 : timer between two attemptsM1TM2AVLCAVLC (VME, DLS) timersNumber of retransmissionHands off algorithm
22 INPUTS Collection Process High- Level ARINCSITAECTL Analysis and StatisticsLINK 2000+ACTSTrafficSimulatorReplayECTL CFMU Flight DB
23 Air Traffic inputThe first step shall consist in using an Air traffic simulator log file.Time ID Lat Long Alt Status04:40:18 TYR413D ON TAXI TO GATE04:40:18 TYR531L ON APPROACH04:40:18 TYR541G ON TAXI TO GATE04:40:21 TYR413D ON TAXI TO GATE04:40:21 TYR531L ON APPROACH04:40:21 TYR541G ON TAXI TO GATE04:40:24 TYR413D ON TAXI TOThe 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.
24 AOC Message profilesFormal 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-linkClass S SmallClass M MediumClass L LargeBoth deterministic and stochastic message distribution : The number of exchanged messages depends on :The airlineThe flight phase (random distribution into the Flight Phase)
25 AOC Messages profile 4 classes of data-link users : Class 0 No data-linkClass S SmallClass M MediumClass L LargeA message size distribution is also implemented for uplink and downlink, it depends on the airline class.
26 ATS- Link 2000+ Applications CM Application ServiceDLIC (Datalink initiation Capability)CPDLC Application ServiceACM (ATC communication management)ACL (ATC clearance)AMC (ATC Microphone check)DCL (Departure clearance)DSC (Downstream clearance)DFIS Application ServiceD-ATISADS Application ServiceFLIPCY (Flight plan consistency)Transactions per flight1 DLIC / FIR (ATSU)1 FLIPCY / FIR (ATSU)1 D-ATIS / Departure airport1 D-ATIS / Departure TMA1 D-ATIS / Arrival TMA1 D-ATIS / Arrival airport1 DCL / Departure airport1 ACM / ATSU sector5 ACL (3U,2D) / Departure TMA16 ACL (1-2 per ATSU) in En-Route10 ACL (6U,4D) / Arrival TMA1DSC / En-Route1 AMC / Sector
27 Simulator Output (per station) TransmitterNumber of INF transmission requestNumber of INF transmitted% Re-transmission 0, 1, 2 …N2Average and maximum CSMA delay% of TM2 occurrenceReceiverNumber of received INFTransmission delay (Average, maximum) (CSMA, propagation) in sRound trip delay in s% of msg out of delay (depending on the application)% of successfully acknowledged transmitted messagesApplication related statistics:%CPDLC within allowed round trip delay% CAP within allowed one way delayOthers statistics:% of lost frames : % collision + % low SNRHands off successes and failureLog on delay
28 Simulator Output (common to all stations) Average and maximum uplink and downlink transmission delayAverage and maximum uplink, downlink round trip delayReal 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 rateHands off success rate
29 Scenarios2 main scenarios based on a critical sector : CDG-airport, ParisThe air traffic will be the peak hour of the peak day of 2002 (30 August)2005Single VDL 2 channel across EuropeGS deployment as shown on mapAll AOC traffic assumed migrated to VDL22010Stepwise, from 2 possibly up to 4 frequenciesGS configuration as shown on mapIncreased AOC traffic, all ATS/Link2000 applications consideredAircraft equipment rate according to EUROCONTROL STATFOR inputs
30 Sita VDL2 Ground stations in 2005 Area to be studiedInterfering area
31 For further information please contact : Patrick DELHAISEEUROCONTROL DAS/CSMTelFaxBertrand DESPERIEREEC / Brétigny CNSTelFax
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