TV-GPS Enhancing Global Positioning Systems Using Television Signals By Chris Lehnert

Overview Introduction Introduction Dissecting the Signal Dissecting the Signal Positioning Positioning Conclusions Conclusions Resources Resources

Introduction What is TV-GPS? What is TV-GPS? Positioning using synchronization signals that are broadcast by VHF and UHF frequencies Positioning using synchronization signals that are broadcast by VHF and UHF frequencies Why use TV transmitters? Why use TV transmitters? Higher power transmitters Higher power transmitters Lower broadcast frequency Lower broadcast frequency Higher bandwidth Higher bandwidth

Introduction Benefits Benefits Compliments conventional GPSCompliments conventional GPS No modifications to current TV signalsNo modifications to current TV signals Works stand-alone or with regular GPSWorks stand-alone or with regular GPS Robust and jamming resistantRobust and jamming resistant Low Horizontal Dilution of Precision (HDOP)Low Horizontal Dilution of Precision (HDOP)

Dissecting the Signal TV signal bandwidth -> 6-8Mhz TV signal bandwidth -> 6-8Mhz Low frequency & high power signals Low frequency & high power signals Synchronization signals Synchronization signals VSYNC, HSYNCVSYNC, HSYNC Keeps receiver in step with senderKeeps receiver in step with sender

Dissecting the Signal Frame: 626 segments, 832 symbols eachFrame: 626 segments, 832 symbols each Segment: 4 symbols for synchronizationSegment: 4 symbols for synchronization Segment types: Field synchronization, DataSegment types: Field synchronization, Data

Positioning Components required: Components required: Mobile device equipped with TV tunerMobile device equipped with TV tuner Location serverLocation server Regional monitorRegional monitor Steps to finding position: Steps to finding position: Pseudo-range calculationPseudo-range calculation

Positioning

Positioning Message flow diagram Message flow diagram

Positioning Pseudo-range Calculation: Pseudo-range Calculation: A measure of apparent propagation time from transmitter to mobile unit expressed as a distance A measure of apparent propagation time from transmitter to mobile unit expressed as a distance Determined from difference between time received and time sent Determined from difference between time received and time sent Receive time is measured at mobile receiver Receive time is measured at mobile receiver Send time is included in frame header Send time is included in frame header Requirements:Requirements: Needs 3 transmitters to form accurate horizontal measurements Needs 3 transmitters to form accurate horizontal measurements

Positioning Position signal error sources: Position signal error sources: Multi-pathMulti-path Transmitter clock instabilityTransmitter clock instability Multi-path Multi-path Line-of-sight is not the strongest signalLine-of-sight is not the strongest signal Transmitter clock instability Transmitter clock instability Fluctuations in oscillatorFluctuations in oscillator

Applications/Advances Applications Applications People trackingPeople tracking Mobile resource managementMobile resource management Public/Personal safetyPublic/Personal safety National security/WarfareNational security/Warfare Asset trackingAsset tracking Advances Advances 3D positioning (TV-GPS Plus)3D positioning (TV-GPS Plus)

Applications / Advances TV-GPS Plus: TV-GPS Plus: Uses portable pseudo TV transmitters (PTTs) Uses portable pseudo TV transmitters (PTTs) Can be used with existing TV-GPS and GPS infrastructures Can be used with existing TV-GPS and GPS infrastructures Applications: Applications: Emergency first responders – Firefighters, Police, etc. Emergency first responders – Firefighters, Police, etc. Child safety Child safety

Conclusions Positive: Positive: Excellent positioning system when paired with conventional GPS Excellent positioning system when paired with conventional GPS Robust, high speed, large coverage Robust, high speed, large coverage Many practical uses Many practical uses Negative: Negative: Location privacy Location privacy

Resources A New Positioning System Using Television Synchronization Signals. Matthew Rabinowitz, James Spilker. ROSUM A New Positioning System Using Television Synchronization Signals. Matthew Rabinowitz, James Spilker. ROSUM Questions? Questions?