1 Summary of Alternative Navigation Architectures for meeting of October 22-23, 2009 Sherman Lo Stanford University

2 Purpose Summarize basic alternate navigation architectures –Common terms of reference –Set up later talks Discuss technical evaluation roadmap

3 Two way aircraft based (ping-pong) Each measurement yields a “true” range –Minimum 2 meas. needed for 2-D position Terminology/Use: Traditional DME (DME/N or DME/P), GBT query & response Little change to avionics if DME, if GBT, need change to ADS-B OUT & IN and needs position output from ADS-B in to go to nav system 1. Aircraft sends query (analog (DME) or digital) 2. DME or GBT responds after fixed delay 3. Aircraft calculates range from reception of response (2 different ranges min for horizontal position)

4 One way aircraft based Each measurement yields a pseudorange since aircraft clock offset with ground is unknown –Minimum 3 meas. for 2-D position Terminology/Use: DME or GBT based heartbeat (pseudolite) Ground needs to be synchronized ADS-B IN or DME IN need to changed to recognize “heartbeat” 1. DME or GBT sends signal at known instances in time or synchronized at same time 2. Aircraft calculates range from reception of response. Range measurement contains aircraft clock offset error (3 different ranges min for horizontal position since need to solve for offset)

5 Hybrid aircraft based The 2 way measurement yields a “true” range –Clock ground offset can be solved –Other measurements are pseudoranges –Minimum 2 meas. needed for 2-D position Terminology/Use: None Ground needs to be synchronized, data channel? ADS-B OUT/IN or DME IN need to changed to utilize two way & recognize one way 1. Aircraft sends query (analog (DME) or digital) 2. DME or GBT responds after fixed delay (with time sync info) 3. Aircraft calculates range from reception of response and solves own clock offset Since clock offset determined, can use one way positioning

6 Two way ground based (ping-pong) Each measurement yields a “true” range –Minimum 2 meas. needed for 2-D position Terminology/Use: Active MLAT, secondary surveillance radars use this technique (without step 4) Ground needs to initiate and calculate range/position on receipt of reply Avionics need to recognize ground query and respond with fixed delay (preferably with data). ADS-B IN or DME IN need to changed to recognize position report sent from ground Data channel - authentication 2. Aircraft responds after fixed delay 1. DME or GBT sends query (likely directed at specific aircraft) 3. Ground calculates range from reception of response (2 different ranges min for horizontal position) 4. Ground sends calculated position (as traffic broadcast or directed transmission to aircraft)

7 One way ground based Each measurement yields a pseudorange since aircraft clock offset with ground is unknown –Minimum 3 meas. for 2-D position Terminology/Use: Passive MLAT (reverse heartbeat) Ground needs to be synchronized, need to calculate pseudorange/position on receipt of aircraft broadcast ADS-B IN or DME IN need to changed to recognize position report sent from ground 1. Aircraft sends broadcast 2. Ground calculates range from reception of response (3 different ranges min for horizontal position) Must solve for aircraft clock or time of transmission 3. Ground sends calculated position (as traffic broadcast or directed transmission to aircraft)

8 Hybrid ground based The 2 way measurement yields a “true” range –Clock ground offset can be solved –Other measurements are pseudoranges –Minimum 2 meas. needed for 2-D position Terminology/Use: None Ground needs to be synchronized, needs to initiate and calculate range/pseudorange/position on receipt of reply Avionics need to recognize ground query and respond with fixed delay (preferably with data). ADS-B IN or DME IN need to changed to recognize position report sent from ground 2. Aircraft responds after fixed delay 1. One DME or GBT sends query (likely directed at specific aircraft) 3. Multiple ground stations receives response Ground calculates range from reception of response (2 different ranges min for horizontal position) 4. Ground sends calculated position (as traffic broadcast or directed transmission to aircraft)

9 Summary of architecture alternatives TechniqueCharacteristicTx for horiz. Position Add’l Req. Two way, aircraft basedDME DME-P/enhanced DME 2222 One way, aircraft basedPseudolite/heartbeat, DME/TDOA (DME-Loran) 3333 Gnd clock sync Hybrid, aircraft basedPseudolite/heartbeat, DME/TDOA (DME-Loran) 2222 Gnd clock sync Two way, ground basedActive MLAT (reverse DME)2 One way, ground basedPassive MLAT (reverse heartbeat) 3Gnd clock sync Hybrid, ground basedActive/Passive MLAT2Gnd clock sync

10 First Steps (Technical) Preliminary performance analysis –Narrow down choices to investigate and required infrastructure (cost, integrity study) Determine high level feasibility –Data capability & requirements (equipment & to support mission) –Security protocols & time synchronization (common to many architectures) –Integrity –Design (is it feasible & how)

Performance Analysis Major unknown is DME/GBT accuracy –DME (existing, upgraded), GBT performance, architecture –May contain a mixture of accuracy levels Can generalize other factors –2-3 basic ground infrastructure scenarios (DME, GBT, DME & GBT –2 navigation solution types (need/don’t need additional station to solve for time) 11

12 Work Areas Threats to NAS Integrity study Alternatives Data Capacity Performance User Acceptance Cost Technical Risk Requirements Security Protocols User Equipment Provider Equipment

13 Technical Summary Results TechniqueCoverage (Requirement) Integrity (Not level but ability to prove) Accuracy (best RNP or operation) Airborne equipment & requirements Ground equipment & requirements DME … Passive MLAT

14 Institutional Summary Results TechniqueCost (User) (Hi, Med, Low) Acceptance Risk (Hi, Med, Low) Schedule Risk DME … Passive MLAT