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Member
Reputation: 63
why is GPS required in CDMA but not in WCDMA ?
In ZTE based systems, GPS is mandatory for CDMA but isn't required for WCDMA based UMtS networks ...Can anyone explain in detail regarding this ?
thanks in advance..
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2010-09-20 10:06 PM
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Re: why is GPS required in CDMA but not in WCDMA ?
Originally Posted by
coursekec
In ZTE based systems, GPS is mandatory for CDMA but isn't required for WCDMA based UMtS networks ...Can anyone explain in detail regarding this ?
thanks in advance..
Hi!
It is all about timing. In CDMA (IS-95) all cells have to know exact time,
so bit 0 TS 0 frame 0 is transmitted at the same moment from every site.
As a side effect, accurate TX frequency is obtained (Remeber, T1 can not be used).
W-CDMA is designed differently, so there is no need for coordination between cells.
Thus, bit 0, TS 0, frame 0, multiframe 0 depends on last Node-B restart.
For frequency, E1 is used (or IP based methods).
GPS might be nigtmare for some indoor installation: even on macro sites, sometimes
it is not as easy as IS-95 designers felt 15 years ago.
Thus, W-CDMA managed to avoid it.
BR
s52d
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Member
Reputation: 63
Re: why is GPS required in CDMA but not in WCDMA ?
thanks for the reply...
But i have one query still ...
why in CDMA (IS-95) all cells have to know exact time ? Is it because of decoding or other reasons ?
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Re: why is GPS required in CDMA but not in WCDMA ?
Originally Posted by
coursekec
thanks for the reply...
But i have one query still ...
why in CDMA (IS-95) all cells have to know exact time ? Is it because of decoding or other reasons ?
Quick guess (Never really looked into IS-95 details):
- ortogonality of codes.
- easy sync, remember this is 15 years old system (eh, W-CDMA is over 10...)
Maybe some IS-95 expert here could enlight us?
BR
s52d
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VIP Member
Reputation: 1849
Re: why is GPS required in CDMA but not in WCDMA ?
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