In MS-assisted mode,
When a request for position location is issued, available network information is provided to the location server and assistance is requested from the location server. The location server sends the assistance information to the handset. The handset/mobile unit measures the GPS observables and provides the GPS measurements along with available network data (that is appropriate for the given air interface technology) to the location server. The location server then calculates the position location and returns results to the requesting entity.
In MS-based mode,
The assistant data provided by the location server encompasses not only the information required to assist the handset in measuring the satellite signals, but also the information required to calculate the handset’s position. Therefore, rather than provide the GPS measurements and available network data back to the location server, the mobile calculates the location on the handset and passes the result to the requesting entity.
| MS Assisted | Server | Module |
| Location server sends aiding data that is valid for the current fix | Send aiding data | |
| Module sends code phases | Code phases | |
| Server calculates position | Calculate position | |
| MS based | Server | Module |
| Location server sends aiding data that is valid for the current fix | Send aiding data | |
| Module calculates position | Calculate position |
GPSoneXTRA introduction (Qualcomm modules)
gpsOneXTRA assistance – Provides enhanced standalone performance. Eliminates the need to demodulate the GPS signal for ephemeris, almanac, iono, UTC, or health. Normally requires -144 dBm or stronger for all SVs in viewTTF can be reduced by 18 to 30 sec (or more in harsh signal environments).
The propriety binary file (approximately 40 kB, depending on number of active satellites), contains current assistance data (ephemeris, almanac, iono, UTC, health) predicted satellite coordinates and clock biases valid for up to 7 days