www.DLR.de • Chart 1 Current Status of LDACS Development Michael Schnell German Aerospace Center (DLR) ICAO Communications Panel 1-5 December 2014 Presentation of IP01
www.DLR.de • Chart 2 Motivation The Future Communications Infrastructure (FCI)
www.DLR.de • Chart 3 Motivation Air/Ground Communications VDL2: Kind of SMS LDACS: Connectivity DSB-AM: Analog Voice From Voice to Data … … to Internet and SWIM
www.DLR.de • Chart 4 Outline Achievements and Current Status of LDACS LDACS1 Extension Towards Navigation Conclusions Open Issues
www.DLR.de • Chart 5 Achievements and Current Status of LDACS Brief Review of LDACS - L-band Digital Aeronautical Communications System (LDACS) is the future ground-based communications link within the FCI - Two proposals: LDACS1 and LDACS2 - Deployment in L-band (960-1164 MHz) - L-band already heavily used by - Aeronautical navigation services - Aeronautical military communications systems - Different deployment options - Use only lower part of L-band, 960-978 MHz (LDACS2) - Use lower and upper part of L-band, 960-978 MHz / 1150-1157 MHz - Slight rearrangement of L-band assignments for radar navigation - Inlay scenario (preferred approach for LDACS1)
www.DLR.de • Chart 6 Achievements and Current Status of LDACS Brief Comparison Between LDACS1 and LDACS2 - LDACS1 can utilize more spectrum in L-band due to inlay approach; no reorganization of spectrum assignments required - LDACS1 is the broadband LDACS proposal (fivefold bandwidth) making available considerably more capacity - LDACS1 applies modern communications concepts (OFDM) - LDACS1 considerably more mature than LDACS2 - Continuous development since 2007 - Detailed evaluations of PHY and MAC layer - Receiver concept with strong robustness against interference - Numerous publications (> 30 since 2007) - Several demonstrators/prototypes available - Europe: DLR, Frequentis AG, Rohde & Schwarz - Japan: ENRI, GNU radio implementation - China: BUAA, hardware implementation, flight testing
www.DLR.de • Chart 7 Achievements and Current Status of LDACS Potentials of LDACS1 - LDACS1 enables high-capacity aeronautical communications - Min. net data rate (FL+RL=overall): 291+270 = 561 kbit/s - Max. net data rate (FL+RL=overall): 1.32+1.27 = 2.59 Mbit/s - Well suited to serve modern ATM application and future needs - Comparison with LDACS2 (overall): 70-115 kbit/s - LDACS1 is highly flexible and scalable, enables long-term evolution - OFDM based physical layer - Scalability towards higher data rates - LDACS1 foresees quality-of-service - Fast access to resources and low delays for application - Different priorities for different applications - LDACS1 enables integration of navigation functionality
www.DLR.de • Chart 8 Achievements and Current Status of LDACS LDACS1 Work in Europe SESAR 2020? Mature Technology, Update Specification SESAR JU Project P15.2.4 ATM Research in Europe Compatibility Testing at DFS labs LDACS1 Demonstrator Developed by FRQ
www.DLR.de • Chart 9 Achievements and Current Status of LDACS LDACS1 Work in Germany Demonstrator Complete Transmitter Software Receiver DLR Internal Projects Receiver Optimization Interference Mitigation Receiver Concept
www.DLR.de • Chart 10 Achievements and Current Status of LDACS LDACS1 Work in Germany MICONAV Follow-on Project LDACS-NAV DLR Internal Project ICONAV German National Project with R&S as Industry Lead LDACS-COM Hardware Implementation Including Security
www.DLR.de • Chart 11 Achievements and Current Status of LDACS LDACS1 Work Outside Europe Japan ENRI (Electronic Navigation Research Institute) LDACS1 Demonstrator Based on GNU Radio Hardware Implementation China Beihang University (aka BUAA) National Key Laboratory of CNS/ATM Theoretical Studies and Simulation on LDACS1 Demonstrator Implementation Preliminary Flight Tests in (May 2014)
www.DLR.de • Chart 12 LDACS1 Extension Towards Navigation Navigation Functionality for APNT - What is APNT? Alternative Positioning Navigation and Timing - Why APNT? For the GNSS failure case! Navigation services require high performance Large distance for all phases of flight SAT-aircraft, GPS easily jammed Newark Liberty Int’l Airport “GPS Jammer” GNSS becomes Personal Privacy Device primary navigation means
www.DLR.de • Chart 13 LDACS1 Extension Towards Navigation LDACS1 as Pseudolite System Aircraft performs pseudo-range measurements towards LDACS1 ground station Continuously transmitting LDACS1 ground stations act as pseudolites: “GPS on Ground”
www.DLR.de • Chart 14 LDACS1 Extension Towards Navigation Performance Bounds on Ranging With LDACS1 Reality: Schmidl-Cox Synchronization 4 10 Freq. Domain: Synchronization Symbols • Performance in real environment? Time Domain: Synchronization Symbols • Flight measurement campaign! CRLB: Synchronization Symbols 3 10 Mean Range Error [m] ~230 m Simulations: 2 10 • Slight adjustments to sync. ~4.1 m • Theoretical bound achievable 1 @ reasonable C/N 10 Theory: • Cramer Rao Lower Bound (CRLB) • Mean range error several meters 0 10 ~4.1 m 0 5 10 15 20 25 Carrier to Noise Ratio [dB]
www.DLR.de • Chart 15 LDACS – L-band Digital Aeronautical Communications System > Michael Schnell > October 2014 LDACS1 Extension Towards Navigation Flight Measurement Campaign Three flight levels: • FL100 • FL280 30 km • FL380 LDACS D LDACS C LDACS B LDACS A TACAN GSM 960 962 965 970 975 f/MHz
www.DLR.de • Chart 16 LDACS1 Extension Towards Navigation Range Estimation Results – Whole Flight 0.08 µ = 6.7 m µ = 6.7 m RMSE = 15.2 m RMSE = 15.2 m 0.06 Probability Raw range estimates, 0.04 averaged over 1 s time intervals 0.02 0 -60 -40 -20 0 20 40 60 Estimation Error [m]
www.DLR.de • Chart 17 LDACS1 Extension Towards Navigation Range Estimation Results – Whole Flight 0.08 µ = 6.7 m µ = 6.7 m RMSE = 15.2 m RMSE = 15.2 m Main error source: Main error source: 0.06 Troposphere Probability Multipath propagation Tropospheric models Second campaign for available 0.04 channel sounding Significant reduction Channel modeling of bias possible 0.02 Ranging algorithms: Maximum Likelihood Doppler Smoothing Particle Filtering 0 -60 -40 -20 0 20 40 60 Estimation Error [m]
www.DLR.de • Chart 18 Conclusions - LDACS1 is well-suited to serve modern ATM applications - High-capacity data link - Highly flexible and scalable - LDACS1 has been considerably matured within the last years - First compatibility investigations (LDACS1 DME) have been performed - LDACS1 offers an excellent opportunity for extension towards navigation - APNT service on top of communications infrastructure - Theoretical ranging performance in the order of meters - Measurement campaign validates navigation performance for APNT
www.DLR.de • Chart 19 Open Issues - Further L-band compatibility evaluations for LDACS1 - DME/TACAN, UAT, SSR Mode S - Military communications systems (JTIDS) - Development of deployment concept for LDACS1 - Development of a migration strategy from VDL2 to LDACS1 - Development of final LDACS1 specification including technology amendments as required and initiation of standardization - Development of fully functional LDACS1 prototype and flight testing
www.DLR.de • Chart 20 Thank You! More about LDACS1 www.ldacs.com
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