Deloitte Telecom SIG: Word of the Day: GPS and A-GPS

Now that we’ve seen the network solutions for location services:

- Angle of Arrival (AOA)
- Uplink Time Difference of Arrival (U-TDOA)
- Wireless Location Signatures
- Location Pattern Matching (LPM)
- Multi-path Fingerprinting (MP)
- Enhanced Cell Identity (E-CID)

We can begin to focus on various handset solutions for location services.

GPS: GPS techniques use handsets equipped with GPS receivers. The GPS receiver determines the caller’s latitude and longitude which is sent to the provider’s receivers and relayed to the PSAP (Public Safety Access Point).

Assisted GPS: A-GPS uses techniques and advanced chipsets designed to allow reception of GPS signals indoors. Assisted GPS can be supplemented with an advanced forward link trilateration (A-FLT) system. A-FLT is a network-based location technology that takes measurements of signals from nearby base stations and reports time and distance readings back to the network, which uses them to triangulate an approximate location of the handset.

The benefits of A-GPS over standard GPS include but are not limited to:
· Faster location acquisition
· Less processing power is required by the device
· Saves battery life on your phone
· Location acquisition indoors or in non-optimal environmental settings

Source: http://www.wmexperts.com/articles/gps_vs_agps_a_quick_tutorial.html

*Note: In the picture below, you can see that the AGPS server actually offloads work from the phone/satellites so that most of the CPU and programming required for location identification is performed on the server itself.