1. Assisted GPS Tian Qiao

2. What is AGPS Assisted GPS, generally abbreviated as A-GPS, is a system which can improve the startup performance of a GPS satellite-based positioning system. It is used extensively with GPS-capable mobile phones. Its development is accelerated by the requirement to quickly determine the location when in emergency. (Enhanced 911)

3. What is AGPS

4. Using information known to the assistance server but not the GPS receiver It can supply orbital data or almanac for the GPS satellites to the GPS receiver, enabling the GPS receiver to lock to the satellites more rapidly in some cases. The network can provide precise time. The device captures a snapshot of the GPS signal, with approximate time, for the server to later process into a position. Accurate, surveyed coordinates for the cell site towers allow better knowledge of local ionospheric conditions and other conditions affecting the GPS signal than the GPS receiver alone, enabling more precise calculation of position.

5. Calculation of position by the server using information from the GPS receiver The assistance server has a good satellite signal, and plentiful computation power, so it can compare fragmentary signals relayed to it by GPS receivers, with the satellite signal it receives directly, and then inform the GPS receiver or emergency services of the GPS receiver's position.

6. Options Standalone - No connection to the network, uses only the GPS satellite signals currently received to try and establish a location. MS(Mobile Station) Based - Connected to the network, uses the GPS signals + a location signal from the network. MS Assisted - Connected to the network, uses GPS signals + a location signal then relays its 'fix' to the server. You can still maintain voice communication in this scenario, but not 'Internet/Network service' ie Web Browser, IM, streaming TV etc.. MS Assisted/Hybrid - Same as above, but network functionality remains. Normally only in areas with exceptional coverage.

7. AGPS VS. GPS GPS Only use GPS satellite signal; Requiring a fine signal condition; Recall:At least 4 satellites to precisely locating A initial state: 30seconds to few minutes for TTFF(Time to First Fix) Don not need any other infrastructure except GPS infrastructure: they are already their!

8. AGPS VS. GPS AGPS Use GPS satellite signal (+ a location signal); Relatively do NOT need a fine signal condition; A quick start; Need a network to transfer satellite signal & location signal as well as responding location info. Need GPS stations + computers to compute locations.

9. Advantages Faster startup Lower signal requirement. ← It is important when considering the original purpose. Less processing power is required by the device. Q: Is this meaningful? Location acquisition indoors or in non-optimal environmental settings Potentially higher precision

10. Drawback Privacy: They know where I am Extra infrastructure Hardware & Software Locked down or limited AGPS (such as AT&T) some are not accessible for end users, only for emergency So how about normal GPS function? Redundancy

11. Summary Works when less than 4 satllites. Safe people in emergency.