ASSISTED GPS (A-GPS) 簡介

Conventional Standalone GPS Worked on 1575.42MHz and 1227.60MHz 27 satellites were separated into 6 orbits on

20200km height 24 satellites for use 3 satellites for spare

At least 4 satellites to calculate position, 3 to find out Lat/Long and height 1 to synchronize

GPS characteristics When first turned on

Searching satellite -> Establish relation -> Receiving data -> Calculation -> Result

Poor signal conditions Surrounded by tall buildings (resulting in multi-path) The satellite signals are weakened when a GPS device is

used indoors or under trees.

GLOBAL POSITIONING SYSTEM (GPS)

Mobile device receives the frame sent by satellite 30 sec per frame

GLOBAL POSITIONING SYSTEM (GPS)

Enhance the startup performance of a GPS satellite-based positioning system Abbreviate TTFF (Time to First Fix) Enhance GPS sensitivity Indoor coverage

A-GPS, using network elements such as either an assistance server or other data from a network, falls into two modes: MS based A-GPS MS Assisted A-GPS

ASSISTED GPS (A-GPS)

Can locate the phone roughly by which cell site it is connected to on the cellular network.

Has a good satellite signal, and lots of computation power, so it can compare fragmentary signals relayed to it by cell phones, with the satellite signal it receives directly, and then inform the cell phone or emergency services of the cell phone's position.

Can supply orbital data and almanac for the GPS satellites to the cell phone, enabling the cell phone to lock to the satellites faster.

By having accurate, surveyed coordinates for the cell site towers, it has better knowledge of ionospheric conditions and other errors affecting the GPS signal than the cell phone alone, enabling more precise calculation of position.

ASSISTANCE SERVER

A-GPS terminal device MS, A-GPS module

GMLC Conversation gateway

A-GPS server Web-based

management Calculation

GIS server Map information

Database server: Location data POI

ASSISTED GPS SYSTEM STRUCTURE

Coordinates of the TX antenna of the cell in WGS-84 format. Latitude: degrees (0, 90), minutes (0..59), seconds

(0..59), fractions (0..99), Latitude sign (0,1) Longitude: degrees (0, 180), minutes (0..59), seconds

(0..59), fractions (0..99), Longitude sign (0,1) Altitude: direction (height, depth), altitude measured

from the sea level to the TX antenna: meters (0..10000)

ACOS(COS(RADIANS(90-Lat1)) *COS(RADIANS(90-Lat2)) +SIN(RADIANS(90-Lat1)) *SIN(RADIANS(90-Lat2)) *COS(RADIANS(Long1-Long2))) *6371 The greatest radius on an ellipsoid as 6378.135km The smallest as 6356.752km.

ASSISTED GPS DISTANCE CALCULATION