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gsmserver.com/articles/articles.php
Posted by crouse
www.endruntechnologies.com/gps-cdma3.htm
Posted by crouse
Sagitaraz is right:
GPS plays an important role in providing a good time-base reference for those applications that need good frequency; all CDMA base-stations are GPS-equipped in order to synchronize their clocks to a common time reference. GPS also plays an important role in locating mobile handsets.
Working of GPS:
Here's how GPS works in five logical steps:
1. The basis of GPS is "triangulation" from satellites.
We're using the word "triangulation" very loosely here because it's a word most people can understand, but purists would not call what GPS does "triangulation" because no angles are involved. It's really "trilateration."
Trilateration is a method of determining the relative positions of objects using the geometry of triangles.
2. To "triangulate," a GPS receiver measures distance using the travel time of radio signals.
3. To measure travel time, GPS needs very accurate timing which it achieves with some tricks.
4. Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret.
5. Finally you must correct for any delays the signal experiences as it travels through the atmosphere.
Posted by crouse
All CDMA base-stations are GPS-equipped in order to synchronize their clocks to a common time reference.
Posted by waqqas1
In the case of time dispersion,equalization schemes are employed to overcome the ISI effects introduced by the channel.Equalization circuitry can be power hungry and today,advanced modulation schemes are employed to mitigate the effects of time dispersion.In IS-95 and other CDMA systems,Direct Sequence Spear Spectrum(DSSS) is employed for multiple access.In DSSS,a symbol is split up into "chips" thereby spreading the spectrum and providing processing gain.A by-product of DSSS is that it can resolve or suppress multipath components with delays larger than a chip duration thereby mitigating ISI.At the same time DSSS is also employed in GPS for accurate positioning.
Posted by gsmxprt
GPS plays an important role in providing a good time-base reference for those applications that need good frequency; all CDMA base-stations are GPS-equipped in order to synchronize their clocks to a common time reference. GPS also plays an important role in locating mobile handsets.
Working of GPS:
Here's how GPS works in five logical steps:
1. The basis of GPS is "triangulation" from satellites.
We're using the word "triangulation" very loosely here because it's a word most people can understand, but purists would not call what GPS does "triangulation" because no angles are involved. It's really "trilateration."
Trilateration is a method of determining the relative positions of objects using the geometry of triangles.
2. To "triangulate," a GPS receiver measures distance using the travel time of radio signals.
3. To measure travel time, GPS needs very accurate timing which it achieves with some tricks.
4. Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret.
5. Finally you must correct for any delays the signal experiences as it travels through the atmosphere.
Posted by sagitraz
cdma200 system uses GPS clock to synchronize BTS system clock.
Posted by ykkim
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