VDL 2 Capacity Planning through Advanced Simulations Patrick Delhaise Communications Domain, Eurocontrol Brussels ATN2005 conference -Sept 2005 European 1 Organisation for the Safety of Air Navigation
Agenda Objectives of VDL 2 Capacity project Reasons for developing simulations Simulations strategy for first channel/ multi-channels deployment Capacity results for the first VDL 2-channel Airborne co-site interference : it is now quantified and fixed. Objectives and options in planning multi-channels VDL 2 operation Planning for further VDL 2 deployment Current conclusions from VDL 2 capacity project 2
Reasons for VDL 2-capacity project VDL 2 deployment became a fact since 99, for AOC and then for data-link (Link2000+ framework for Europe) In support for Link2000+, since 2002 we felt several needs : Evaluate accurately the first VDL 2 channel capacity Optimize VDL 2 parameters and capacity/channel Predict total spectrum requirements for Link2000+ deployment (along AOC migration from ACARS, along air and data traffics growth ) Monitor traffic growth through crucial parameters and optimise multichannels deployment steps and planning 3
Reasons for advanced simulations: Requirements were : Inputs to be accurate and tunable flows (Air traffic, AOC and ATS traffic patterns ) Using realistic (or live) Air Traffic records Using realistic (or real) Ground-Stations deployment Accurate standards-compliant VDL 2 simulations with access to parameters Options for realistic propagation models (multipath, fading,..), for inclusion of airborne co-site integration, for hand-off algorithm refinement, for multichannels simulations through different options Extended list of simulator outputs An open simulation tool : view what how - how is it validated 4
Example : crucial or negligible? A same channel is perceived differently by each station. This has a significant impact on large sectors AC 2 AC 3 AC 1 Crucial! Level 1 2 3 τ 1/2 τ 1/3 Absolute time τ 1/2 τ 2/3 t(ac 1) τ 1/3 τ 2/3 t(ac 2) 5 t(ac 3)
Example : crucial or negligible? VGS1 and VGS2 can not see each other. Aircraft see both VGS RH AC1 Hidden terminals may create collisions on the uplink GS 2 GS 1 RH GS1 Area of interest is impacted by a larger area when a common frequency is used Exposed terminal may be delayed in downlink messages transmission RH AC1 Crucial! Interfering Area 6
First target : To assess total capacity for a single VDL 2 channel Using peak days-peak hour air traffic records in 600 NM radius busiest part of Europe Accurate simulation of Ground-station deployment, of VHF propagation and VDL 2 in all details Heavy validation through several independent sources (live data; mathem. models, second 100% independent simulator,..) AOC traffic profiles coming from live- ACARS statistics in Europe ( 2004 peak traffic) 7
In search for total capacity for a single VDL 2 channel(2/2) ATS traffic reproducing heavy Link2000+ usage (in ENR phase of flight) Applying different % of aircraft equipment with AOC and ATS applications Increasing % equipped as long as QoS is OK (95% of Round Trip Tx within 8sec, as required for ACL ) 8
Total Capacity for a single VDL 2 channel: results Up to 1220 flights operating AOC + 730 flights of them operating Link2000+, can be connected on a single VDL2 channel (1 hour) Equivalent to 100% migration of 2004-ACARS traffic + 35% of flights in UA during peak hour already running Link2000+. 9
Comparison with Link2000 capacity requirements (1/2) 10 Link2000+ running on ~ 35-40% of UA traffic : forecasted within 2008-2009 At that time, full AOC migration (nearly) completed from ACARS to VDL 2?? Air traffic increase for coming years =?? Our best guess : 1rst Channel saturated (earliest) within 2007-2010 in busiest areas Forward fit Retro fit Mandate 75% Incentives Pioneers 25% 2012
Comparison with Link2000 capacity requirements (2/2) Final Link2000+ target: equipping 75% of UA traffic, forecasted in 2014 At that time, assume full AOC migration from ACARS to VDL 2 Peak hour ( 2004 traffic): 75% of UA flights ~ = 1600 flights for Link +, along [1220 to 1600] flights equipped with AOC Final Link2000+ (2014) deployment requires : 2 3(*) VDL 2 channels for busiest areas (*) Need revisiting/ simulating ENR sectors, H.O. algorithm and round-trip delay requ ts. 11
Target VDL deployment plan for ICAO FMG EUR status Sept05 Since 1999, coordination with FMG EUR for stepwise provision of 4 VDL-2 ch. 136.575 136.600 136.700 136.800 136..900 136.975 Ac Ac 2002 A A A A A A A A A O O O O M4 M2 Si Ar 131.825 Step 1 Pln d 9/04 Ac A A A A A - - - - O - O - O - O - - M4 - M2 Si Step 2 Pln d 06 Ac A A A A A - - - - M? - - M2 - M4 - M2 Si Step 4 Pl d 08 A A A A A - M2 - - M2 - M? - M2 - M4 - M2 * * * 12 * : Protected : Specific measures on ground : some services could stay
Example of VDL 2 channel characteristics (at simulated saturation level see above) (with defaults VDL 2 - parameters) UP DW Total Offered Channel Load (G) (kbit/s) Physical-layer Net Throughput (S) 11.7 kbit/s 9.9kbit/s 5.6 kbit/s 6.0 kbit/s 21.6 kbit/s 11.6 kbit/s Tx Requests (in 1 hour traffic) Tx Success Collisions Lost by collisions Average Tx Delay (1 way) Successful Tx (2 ways) within 8 sec 128292 115099 74% 93.8% 28.4 % 2.2% 24.7 % 1.7% 1443 ms 230 ms 95.2 % 97.3 % 243391 83.4% 16 % 13.8% 810 ms 96.3% 13
Potential improvements to capacity/channel Tailoring VGS-set to ENR or to airports service (better S/N >reduced losses>higher capacity) Hand-Off algorithm and SQP- threshold need refinements Discussion on truly required performance for VDL2 segments (..8..10.. Sec for Rnd trip?) T1 improvement: typically 3/6 repetead frames would be of no-value for CPDLC p-(persistence) has been revisited (recommendation for maximising traffic : p-ac unchanged, p-gs at 60/256) remark: Industrial partners (through AEEC DLK Sc) willing to accept recommandations into VDL 2 standards for medium-term implementation in products 14
The airborne co-site interference : it s clear now! In-depth analysis of interference between VHF voice and VDL 2 VDL 2 Tx AM-DSB voice Rx Case A Conclusions supported by AM-DSB voice Tx AM-DSB voice Tx 15 VDL 2 Rx Case B VDL 2 Tx Case C VDL 2 and ACARS users feedback Lab aircraft tests Audio interference samples presented to ICAO ACP WG-B Voice traffic gathered on 700+ flights Detailed VDL 2 traffic simulation used for quantifying impact of co-site on the total capacity/channel VDL 2 channels deployment plan were revisited and confirmed after co-site analysis conclusions
Case A AM-DSB VDL 2 Tx voice Rx Case A : aircraft VDL 2 Tx producing noise in VHF-voice reception chain * Lab aircraft exploited to identify required combinations of parameters (antenna coupling, frequency separation and aircraft distance to voice ground-station). Worst cases were analysed and recorded. * It has been compared to similar ACARS-interference : In worst case, ACARS interference is affecting intelligibility of voice reception, it produces strong beep noises in pilot ears * In worst case, VDL 2 is producing light pulse noise, a kind of pchhtt not affecting intelligibility. *Even under the heaviest CPDLC and AOC data-traffic, the audio samples demonstrating worst case interference in the second adjacent channel have clearly been considered tolerable by ICAO ACP WG B experts. This conclusion is valid independently of the CPDLC traffic volume. The second VHF channel adjacent to VDL 2 is thus confirmed adequate for protected ATC-voice service, all interference scenarios being considered. 16
Cases B & C Aircraft voice transmission interfering or blocking VDL 2 up-link reception and/or down-link transmission AM-DSB voice Tx *Also here, it depends on antenna coupling, frequency separation and aircraft distance to VDL 2- ground-station. VDL 2 Rx Worst cases have been analysed assuming use of the second adjcacent VHF channel for voice. *Focus was on the possible impact on data-link (VDL 2 frame losses and repetitions) and resulting quality-of-service *Performance have been checked against highest CPDLC requirements (ED120): AM-DSB voice Tx VDL 2 Tx The highest CPDLC- performance requirements are respected even with 20x more CPDLC and 20x more VHF voice traffic than typical flights not equipped with data-link. Conclusion: effects B and C put in practise no limit to VHF voice nor VDL 2 volumes, even when operating voice in the second adjacent channel to VDL 2. 17
Cases B& C impacts on total capacity per VDL 2 channel Simulation results : (recall ) 1220 flights operating AOC + 730 flights operating Link2000+ (One hour traffic spread within 600 NM radius) Equivalent to 100% ACARS traffic + 35% of flights in UA running Link2000+. Impact of co-site on total channel capacity is accounted: it is ~= 1.8% of ATS traffic (along an unchanged AOC traffic) 18
VDL 2 Capacity From single to multi-channels.. Starting in March 05, Eurocontrol investigated with ARINC and SITA actions required (standards, on-board, on-ground) for multi-channels operation in VDL 2. The standards contain autotune, but for short term and for the use of the 2nd channel, this was not the single technical possiblity In that meeting, 7 theoritical scenarios have been defined with criterias : Limitation to max. 2 channels vs any # of channels Shared channels versus Dedicated ones (Service Providers X, Y,..) Channel selection by avionics (trigger using WoW, or policy,..) or more complex cases, including Autotune 19
VDL 2 Multi-channels scenarios definition Examples : Case 1: Two shared channels; F1= CSC used by default. F2= terminal used where available, triggered by WoW onboard signal Case 6: Multiple shared alternate channels selected by DSP F1= shared CSC, used by default. F2,F3,..are additional TERM or ENR shared- channels selected by Autotune (DSP) Case 7: Multiple dedicated alternate channels selected by DSP F1= shared CSC, used by default. F2,F3,..are additional TERM or ENR dedicated- channels selected by Autotune (DSP) 20
Case 1 -Sharing F1(ENR)+ F2(TERM) Simulation of Freq 1: whole peah hour-traffic in 600 NM volume excepting red volumes (WoW) Simulation Freq 2 (TERM) = com during preflight,taxiing, taking off + taxiing + postflight F2 600 NM radius Is it spectrum efficient, how long does it extend Link2000+ and AOA deployments? 21
From single channel to Case 1 Scenario Multi-channels 1 : TERM - traffic is separated (F2), the max. CPDLC- flights (on F1) increases of ~ 10% : Use of a second channel allows to go in total from 1220 AOC-equipped + 730 CPDCL-equipped flights to 1220 AOC + (800..840) CPDLC flights Large spare capacity remaining on Freq 2 (Terminal) At least double # aircraft and double AOC traffic/aircraft possible (more simulations being achieved) Deduction: in our case the single channel saturation is mainly linked to ENR traffic. 22
First findings on Multi-channels : Two Shared vs two dedicated (1/2) Two shared delivering apparently (much) less than two dedicated?.. But.. Current simulations assume heavy CPDLC usage/aircraft and target final Link2000+ stage, while 2004- AOC traffic figures/aircraft are used. AOC is expected to grow a lot (Air France, Lufthansa,.. ; A380 traffic,..). Uncertainty : which portion of traffic (TERM vs ENR )will actually grow the quickest?? 23
First findings on Multi-channels : Two Shared vs two dedicated (2/2) It seems likely that a common TERM frequency will be spectrum efficient from a certain deployment status. (discarding ground traffic and avoiding many hidden stations on ground for 3 or 4.. ENR channels) Should TERM frequency preferably be implemented as second frequency or not? Choice for implementing Autotune gives flexibility: The second channel can be allocated in future where/when required : -saturation in ENR due to growing CPDLC traffic? -saturation at large airports due to AOC traffic growth? 24
At AEEC DLK Sc, May 2005 : Objectives in selection Eurocontrol was invited to co-ordinate DLK discussion and proposed as objectives : Solution to be ready on time for 2 channels (..2008..), but open to more than 2 channels Preferably only 1 change in avionics,.. Spectrum efficient for each channel Flexibility for allocation of 3rd, 4th channel,..(enr, or TERM,..) Open to new DSP Stepwise DSP implementation, only where/when required 25
AEEC DLK Sc decisions and workprogram Case 6&7 (autotune for shared/dedicated channels resp.) were selected for implementation Review of AEEC 631 required: Refinement of Autotune description for avionics; for groundequipment Target planning : consolidated 631 : spring 2006. Products by 2007. The F2 operation possible by 2008. Allocation of F2 can be based on local traffic growth (monitoring from today on) Simulations of 1 and 2 frequencies to be redone with increased -AOC traffic figures 26
Next steps in VDL traffic simulations Multi-channels VDL 2 simulation, with Autotune With revisited AOC traffic plans A look at Cascade program : Which air and data-link traffic growth? Which addit l spectrum requirements In the mission of Eurocontrol, simulations of VDL 4 in a similar way to position VDL 4 option for data-link (Any justification in spectrum or performance, for VDL 4 as addition or replacement to VDL Mode 2?) 27
VDL 2 Capacity Planning -Conclusions Since end 2004, advanced VDL 2 simulations have assessed capacity available with the first operational channel. ICAO FMG deployment plans for datalink are confirmed compatible with Link2000+ and AOC deployment Capacity for 2 and more channels will be further simulated for optimisation and planning AEEC DLK Sc has setup a workplan for delivering through Autotune implementation, the F2, F3,.. from 2008 on. EUROCONTROL will further support at AEEC DLK Sc level and at ICAO FMG EUR the next VDL deployment steps 28
VDL 2 project - contacts Patrick DELHAISE, Eurocontrol DAS/CSM, Coordinator, patrick.delhaise@eurocontrol.int, Massimiliano ESPOSITO, Eurocontrol DAS/CSM, VDL 2 engineer, massimiliano.esposito@eurocontrol.int, Bertrand DESPERIER, ISA TELECOMS, ACTS simulation design, VDL 2/4 Lab bertrand.desperier@isa-telecoms.com, Yannick MONTULET, ISA TELECOMS, ACTS development, yannick.montulet@isa-telecoms.com, 29
VDL 2 capacity and cosite studies: Documentation and contacts The complete studies including technical annexes are available on Eurocontrol web site. http://www.eurocontrol.int/vdl2 For VDL 2 airborne cosite interference, the document «Assessment of VDL 2 airborne co-site interference in Link2000+ framework» is available with some audio-samples supporting the analysis achieved with ICAO and AEEC. 30
Annex : ACTS features and validation (1/2) 31 Air traffic model in 4D-positions based on real flights records in European area VDL 2 ground-stations topology in 3D according to commercial deployments AOC data traffic model based on service providers traffic statistics in Europe. ATS data-link traffic tuneable per flight phase, based on Link2000+ requirements Multi-path VHF propagation model validated by flight trials
Annex :ACTS features (2/2) Accurate and SARPS compliant simulations of VDL 2 physical layer, CSMA and AVLC, each one validated per specific programs with independent developments ATN overhead and signalling inserted according to live records of service providers. Airborne co-site interference simulated with interfering voice traffic model based on live statistical records. 32