Transcript Shuttle Tracking using GPS Enable

GPS Technology
Tech Talk
April, 2008
Chad Halvarson
Agenda
 Current GPS and Assisted GPS (AGPS)
Overview
 CDMA GPS Service
 Conclusion
 Q&A
GPS Review
 A GPS receiver determines the travel time of a signal from a satellite –
Synchronization
A Travel Time x c (Speed of Light ~ 3 x 109m/s) = Total Distance
GPS Requirements
 GPS is good for open field.
 Less accurate for blocked or indoor areas (urban
locations).
 Requires line of sight to at least 3 satellites.
 GPS Receiver requires high processing power.
 Expensive GPS hardware and Pre-loaded
software.
AGPS Overview
 Affordable solution
 Uses an assistance server to calculate locations
via Wireless Carrier Backbone
 Commonly associated with Location Based
Services (LBS) over cellular networks.
– E911 – Mandated by FCC to provide emergency service
– Mobile Tracking
– Navigation
 Ability to download specific information
dynamically in real-time
Assisted GPS Overview
WEB for
Operator
or
Customer
Wireless
Carrier
Internet
Assistance Server
Data
Communication to
cellular IP
CDMA GPS Service
 Replaces expensive typical GPS receivers
with inexpensive Handset
 Provides various mobile services
– Location Base Service (i.e. E911, Weather, POI
etc.)
– Tracking
– Navigation
CDMA Location Hierarchy
AGPS Fix ... open sky
AGPS Fix requires a minimum of three GPS measurements.
“Assisted” because network resources are still required.
Hybrid Fix … partial view of sky
CDMA pilot phase measurements
can be used as a virtual GPS to
determine position.
Advanced Forward Link Tri-lateration
AFLT Fix … indoors
AFLT is a “triangulation type” fix that
requires contact with a minimum of
three towers to establish a position.
Cell Sector Fix … indoors, edge coverage
Cell Sector location reports the center of
the cell sector as the current position.
CDMA
CDMA
Strength
Weakness
 System delivers best fix
available
 Mid-level quality indoor fixes
possible
 Cell Sector fix, worst case
 Network utilized for every initial fix
 Network fixes take more time
(non-GPS)
 No off network capability
CDMA - Network Initiated
Features:
Satellite
R1
R1
R1
Satellite Data
No Ranging
Raw GPS data
collected & passed
Mobile Station
Base Station
Satellite Acquisition and Sensitivity
Assistance Data requested & passed
Location Application
Network HW
Network does the math to calculate position
• First fix in tens of seconds
• Very high accuracy
• Available during a voice call
• Fallback modes available
Limitations:
• Each additional fix requires
same time as initial fix
• Limited to specific devices
• Network resources needed
for every location request
CDMA
CDMA  Assigns dynamic IP address for each
phone
 Java not supported – Network dependent
 Tracking is not supported directly by phone
Conclusion
 Current GPS technology Overview
– GPS vs. AGPS
 CDMA GPS Service Offerings