Discussion of various aspects of mobile app development surrounding location-based services, including intelligent use of GPS to conserve battery life and reducing network data transfer.

1. 2009 Sprint Open
Developer Conference
Rodney Nelson
Mike McMullen
Sean Barbeau
October 27
Location Based Services

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2009 Sprint Open Developer Conference
Agenda
• Location Privacy
• Service Enablers
• Open and LBS
• GPS and LBS 101
• Device OS LBS specifics
• Research on LBS enabled apps, battery life, data
optimization

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2009 Sprint Open Developer Conference
Privacy
3 General Types of LBS Applications
1. Concierge
– End User Consent
2. Business Solutions – Corporate Liable Devices
– Account Holder Consent
– Employee Notification
3. Other
– End User Consent
– Account Holder Notification

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2009 Sprint Open Developer Conference
Who can help me get access to location?
See http://developer.sprint.com/site/global/working_with_us/p_p2e/p_p2e.jsp

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2009 Sprint Open Developer Conference
Service Enablers and Open APIs
• Enhance your web based application with location
Web
Application
Service
Enabler
Sprint
Location GW
opt-in
• Open APIs enable native OS apps with location
Sprint
Location GW
Assistance request
Assistance
response

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2009 Sprint Open Developer Conference
Device Type verses Location Type
• Many GPS capabilities are Open
Android Blackberry Palm Web OS Windows CDMA Java iDEN Java
Autonomous GPS Open Open Open Open
Instinct - Open
Others -Restricted
Open
MS-Based GPS N/A Open Open Open
Instinct - Open
Others -Restricted
Open
MS-Assisted via Network API
via Network API
(CDMA Only)
Once per hour
OR
via Network API
via Network API
Restricted
or
via Network API
N/A
Cell Tower Open Open N/A N/A Restricted Open

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2009 Sprint Open Developer Conference
CDMA Location Method
Controlled by application & environment
Network PDE
Autonomous Operation
High fix rate
No network support
Must “see” satellites
MS-Based Operation
High fix rate
Req’s network support
(approx. 1 / hour)
Must “see satellites”
Improved acquisition time &
sensitivity over autonomous
MS-Assisted Operation
Low fix rate
Network support each fix
Indoor fix capable
Hybrid
Fix
AFLT
Fix
Cell Sector
Fix
Cell Tower Operation
High fix rate
No LBS network support
Serving Cell Tower Loc.
(poorest accuracy)
GPS
Fix
Declining Accuracy

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2009 Sprint Open Developer Conference
AGPS fix hierarchy (CDMA)
Cell/Sector Fix … indoors, edge coverageCell/Sector Fix … indoors, edge coverage
Cell/Sector location reports the center of the cell/sector
as the handset position.
AFLT Fix … indoorsAFLT Fix … indoors
AFLT Fix requires a minimum of three
CDMA pilot Phase measurements to fix
position in accordance with TDOA (Time
Difference of Arrival) theory. If less than
three are available, use Cell/Sector.
Hybrid Fix … partial view of skyHybrid Fix … partial view of sky
CDMA pilot phase measurements can be
used as a virtual GPS measurement in
fixing position. If no GPS measurements
are possible, attempt AFLT fix.
AGPS Fix ... open skyAGPS Fix ... open sky
AGPS Fix requires a minimum of three GPS measurements.
“Assisted” because network resources still required. Fewer
than three, attempt Hybrid Fix.

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2009 Sprint Open Developer Conference
Non-AGPS Capabilities (iDEN & CDMA)
Cell Tower Fix … No GPS, indoorsCell Tower Fix … No GPS, indoors
Cell Tower (Cell Site) location reports the Longitude/Latitude
the serving Cell Tower as the current position.
Autonomous GPS Fix ... open skyAutonomous GPS Fix ... open sky
“View” of a minimum of three GPS
satellites is required. No network
assistance required.

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Generic IS-801 Call Flow (CDMA)
MS
Handset searches for identified
Satellites and collects raw data
PDE
WARN
Obtain AFLT data for Pre-
Fix
Initiate IS-801 Session via
Network or Handset
PDE calculates position using
available information
Satellites over N. America
are continually monitored
Detailed Satellite info
maintained at PDE
Send raw AFLT Data to PDE.
PDE calculates approx. position
PDE returns Satellite Acquisition
& Sensitivity Assistance Data
Handset returns satellite data
and current AFLT data
Return Long/Lat and Uncertainty
(Accuracy) to MS or requesting entity
Raw AFLT data is collected as well

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2009 Sprint Open Developer Conference
CDMA Feature Phone Location
• MS-Assisted
– GPS/Hybrid/AFLT/Cell Sector
– Indoor Capable
• MS-Based GPS
– Very fast update rate
– Outdoor only
• Cell Tower Longitude / Latitude (CLM)

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2009 Sprint Open Developer Conference
Android Location
• GPS Provider
– Autonomous GPS (with gpsOneXTRA)
• High precision GPS accuracy
• Very fast update rate
• Network Provider
– Long / Lat of the serving cell tower
(Note: not accurate when roaming)

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Blackberry Location (CDMA & iDEN)
• MS-Based GPS
– High precision GPS accuracy
– Very fast update rate
– Outdoor only (higher sensitivity than autonomous)
• Long / Lat of the serving cell tower

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Palm Web OS Location
• MS-Based GPS
– Very fast update rate
– Outdoor only
• MS-Assisted
– GPS/Hybrid/AFLT/Cell Sector
– Indoor Capable
– Once per hour

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2009 Sprint Open Developer Conference
Windows Mobile Location
• MS-Based GPS
– High precision GPS accuracy
– Very fast update rate
– Outdoor only (higher sensitivity than autonomous)

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2009 Sprint Open Developer Conference
16
Location-Aware Info. Systems Lab
• Research
– Improve efficiency of location-based services through
intelligent software
– Create innovative location-aware applications
• Education
– Train future workforce in mobile information systems software
development through:
• Research assistantships
• Classroom education
• Commercialization
– Indentify commercial partners
– License relevant technology
– Ongoing partnership for research and career track for students

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17
Challenges Facing Real-time LBS
• Battery Life
– GPS chip
• Uses energy for every position calculation
• Tracking can generate data every few seconds
– Wireless communication
• Radio is biggest consumer of battery energy
– Hidden during emulator development
• Overwhelming amount of data
– Limited capacity of mobile phones
– Transfer of data to server requires wireless
transmission
– Post-processing – Servers crunches all numbers
– Server storage capacity – Large databases

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18
GPS Interval Changes Can Save Energy!
Sanyo Pro 200
Sprint CDMA
EV-DO Rev. A
network

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19
• Transition GPS from “awake” to “asleep” based
on user’s movement
Solution: GPS-Auto Sleep
“ASLEEP”“AWAKE”

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Solution: GPS-Auto Sleep
Sanyo Pro 200
Sprint CDMA
EV-DO Rev. A
network
“Asleep”
“Awake”

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Potential Savings – GPS Auto-Sleep
With
GPS Auto-
Sleep
Without
GPS Auto-Sleep
~Total # Assisted GPS Fixes
(Over 13 hrs)
1,035 11,700
21
• Also reduces cost for using assisted GPS, since
fewer fixes are calculated
*Sleep time of 120 seconds between GPS fixes while user is not moving,
and 4 seconds between GPS fixes while user is moving

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Wireless Transmissions Use Energy!
Sanyo 7050
Sprint CDMA
1xRTT network
UDP

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Solution: Critical Point Algorithm
• Pre-filters real-time GPS data on mobile device before
it is wireless transmitted
• Preserves representation of path while eliminating
redundant, or “non-critical,” data

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Solution: Critical Point Algorithm
All GPS Points Critical Points Only

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Potential Savings – Critical Point Algorithm

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Distributed Systems Use Web Services
• Mobile phone must communicate with server
• Web Services are useful for request-response model
• Two common ways to implement web services:
– SOAP
• XML-based messaging protocol
• Encapsulates data in XML tags
• Normally on top of HTTP
– HTTP (e.g. REST-ful Web Service)
• Directly uses HTTP methods
– (e.g.POST)
• State-less model
• No additional tags required for data
26
Layered Networking Model

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Extra overhead (e.g. XML) costs energy!
27
Motorola i580
Nextel iDEN
network
• Using REST-ful web services instead of XML-based
(e.g. JAX-RPC) can save energy

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Implications – Need Smarter Mobile Apps!
• LAISYC Framework handles energy, privacy,
security, authenticity, scalability for real-time apps

29. Question and Answer

30. 2009 Sprint Open
Developer Conference
Thank you