TVGPS Enhancing Global Positioning Systems Using Television Signals

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

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

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

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

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

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

Positioning u Components required: • Mobile device equipped with TV tuner • Location server • Regional monitor u Steps to finding position: • Pseudo-range calculation

Positioning

Positioning u Message flow diagram

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

Positioning u Position signal error sources: • Multi-path • Transmitter clock instability u Multi-path • Line-of-sight is not the strongest signal u Transmitter clock instability • Fluctuations in oscillator

Applications/Advances u Applications • People tracking • Mobile resource management • Public/Personal safety • National security/Warfare • Asset tracking u Advances • 3 D positioning (TV-GPS Plus)

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

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

Resources u A New Positioning System Using Television Synchronization Signals. Matthew Rabinowitz, James Spilker. ROSUM u http: //www. gpsworld. com/gpsworld/article/article. Detail. jsp? id =180165 u http: //www. pcworld. com/news/article/0, aid, 118031, 00. asp u http: //www. directionsmag. com/press. releases/index. php? duty =Show&id=11394&trv=1 u http: //www. dailywireless. org/modules. php? name =News&file=article&sid=782 u http: //www. fcw. com/article 88942 -05 -23 -05 -Print u http: //fleetowner. com/information_technology/patentpending/fleet_tvgps/ u http: //www. rosum. com/rosum_tv-gps_plus_indoor_location_technology. html u http: //www. popsci. com/popsci/computerselec/7 a 924 c 3 ee 4 d 05010 vgnvcm 1000004 eecbccdrcrd. html u http: //www. wipo. int/cgi-pct/guest/getbykey 5? KEY=01/43428. 010614&ELEMENT_SET=DECL u http: //www. embeddedstar. com/press/content/2003/2/embedded 7435. html u http: //en. wikipedia. org/wiki/Pseudorange Questions?