Summary of Alternative Navigation Architectures for meeting of October 22-23, 2009

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) 1. Aircraft sends query (analog (DME) or digital) 3. Aircraft calculates range from reception of response (2 different ranges min for horizontal position) 2. DME or GBT responds after fixed delay • 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

4. One way aircraft based 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) • 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”

5. Hybrid aircraft based 1. Aircraft sends query (analog (DME) or digital) 3. Aircraft calculates range from reception of response and solves own clock offset 2. DME or GBT responds after fixed delay (with time sync info) Since clock offset determined, can use one way positioning • 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

6. Two way ground based (ping-pong) 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) 2. Aircraft responds after fixed delay 4. Ground sends calculated position (as traffic broadcast or directed transmission to aircraft) • 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

7. One way ground based 2. Ground calculates range from reception of response (3 different ranges min for horizontal position) Must solve for aircraft clock or time of transmission 1. Aircraft sends broadcast 3. Ground sends calculated position (as traffic broadcast or directed transmission to aircraft) • 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

8. Hybrid ground based 3. Multiple ground stations receives response Ground calculates range from reception of response (2 different ranges min for horizontal position) 1. One DME or GBT sends query (likely directed at specific aircraft) 2. Aircraft responds after fixed delay 4. Ground sends calculated position (as traffic broadcast or directed transmission to aircraft) • 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

9. Summary of architecture alternatives

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)

11. 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)

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

13. Technical Summary Results

14. Institutional Summary Results