GPS A UTO -S LEEP FOR E NERGY -E FFICIENT L OCATION T RACKING Sean Barbeau, Phil Winters, Nevine Georggi Center for Urban Transportation Research Rafael Perez, Miguel Labrador Department of Computer Science & Engineering Portions of work funded by the Florida Department of Transportation and the National Center for Transit Research Protected under US Patent # 8,036,679

P ROBLEM Past vehicle-based GPS tracking give low- resolution view of daily travel behavior Are these GPS fixes: – Points-of-interest? – Stops in traffic? Difficult to extract info: – Distance traveled – Origin-Destination pairs Misses non-vehicle trips 2 Protected under US Patent # 8,036,679

I NNOVATION Our research team created TRAC-IT, a GPS- enabled mobile phone app TRAC-IT can capture high-definition view of travel behavior Much easier to determine: – Path, distance traveled – Origin-Destination pairs – Avg. speeds Can capture transit/bike/walk trips 3 Protected under US Patent # 8,036,679

N EW P ROBLEM We can record GPS fixes as frequently as once per second and send to our server However, frequent GPS fixes come at great cost to: – battery energy – data transfer over network Both battery life and cell network data transfer are very limited resources 4 Protected under US Patent # 8,036,679

5 Sprint CDMA EV-DO Rev. A network Sprint CDMA EV-DO Rev. A network One-day Requirement Protected under US Patent # 8,036,679

N EW I DEA What if we could dynamically change the GPS sampling interval on the phone? – Use four second sampling interval when moving – Use five minute interval when stopped Challenges: – Can we create mobile apps that do this? – Would this be enough to make a difference in battery life? – How do we handle GPS noise when trying to detect movement? 6 Protected under US Patent # 8,036,679

GPS D ATA N OISE C AUSES U NCERTAINTY IN M OVEMENT meters HTC Hero Sprint EV-DO Rev A network Protected under US Patent # 8,036,679

D ETECTING U SER M OVEMENT MovingStopped d 8 GPS noise causes uncertainty in states Many false transitions waste battery energy 4 second GPS sampling 5 minute GPS sampling Protected under US Patent # 8,036,679

D ETECTING U SER M OVEMENT MovingStopped 9 4 second GPS sampling 5 minute GPS sampling What if we represent this binary, or two-state, problem more like a continuum? Protected under US Patent # 8,036,679

10 Gradually change GPS interval from awake to asleep based on certainty in users movement With some data (e.g., very high speeds) snap back to awake ASLEEP AWAKE New invention – GPS Auto-Sleep Protected under US Patent # 8,036,679

11 Sanyo Pro 200 Sprint CDMA EV-DO Rev. A network Protected under US Patent # 8,036,679

12 Sanyo Pro 200 Sprint CDMA EV-DO Rev. A network Asleep Awake Protected under US Patent # 8,036,679

13 n = 30 Evaluation – Summary of 30 tests Protected under US Patent # 8,036,679

E VALUATION – D AILY T RACKING 14 Sanyo Pro 200 Sprint CDMA EV-DO Rev. A network Impact of GPS Auto-Sleep on Battery Life Protected under US Patent # 8,036,679

P OTENTIAL D ATA S AVINGS – GPS A UTO -S LEEP With GPS Auto-Sleep Without GPS Auto-Sleep # Assisted GPS Fixes Over 13 hrs 1,035 (~0.1 MB) 11,700 (~1.4 MB) 15 Assuming each GPS fix is transmitted to server, GPS Auto-Sleep saves ~1.3MB in data transfer PER PHONE in 13 hours *Sleep time of 120 seconds between GPS fixes while user is not moving, and 4 seconds between GPS fixes while user is moving Protected under US Patent # 8,036,679

P ATENT ISSUED ON O CT. 11, 2011 US Patent # 8,036,679 Optimizing Performance of Location-Aware Applications using State Machines 16 Protected under US Patent # 8,036,679

U TILITY & C OMMERCIALIZATION We have been tracking high-def travel behavior of over 30 participants over 9 months – Using TRAC-IT mobile app w/ GPS Auto-Sleep – USDOT-funded Value Pricing project DAJUTA, a Florida-based company, has non- exclusively licensed the technology from USF – Other companies are also expressing interest GPS Auto-Sleep is one module in Location-Aware Information Systems Client (LAISYC) framework – 15 patents pending on other modules 17 Protected under US Patent # 8,036,679

T HANK YOU Questions? Sean Barbeau, M.S. Research Associate (813) locationaware.usf.edu 18 Protected under US Patent # 8,036,679