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Forums » iPhones Eating Less Bandwidth Than AT&T Expected » The 3g speeds on AT&T suck.
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« Then why 3G speed SUCKS SO BAD NOW?  
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en102
Canadian, eh?

join:2001-01-26
Valencia, CA
·RoadRunner Cable
·DSL EXTREME

reply to MarkyD
Re: The 3g speeds on AT&T suck.

Problem in many areas have been the spectrum allocations in many markets, and issues with capacity on voice+data.

3G requires at least 5MHz of spectrum (paired no less).
EVDO requires 1.25MHz of spectrum (paired)

3G runs both voice and data across 3G
EVDO runs data only.

Pushing both voice+data over a 5MHz chunk in many areas doesn't cut it (metro), and in many areas, coming up with an extra large chunk of spectrum requires taking it away from GSM. This is why T-Mobile has to deploy its 3G in 1700/2100 MHz space.

Eg. Los Angeles market has a decent amount of spectrum to begin with. 22.5MHz paired - spread over 850/1900MHz.
Currently AT&T runs:
850MHz GSM (cell A block = 12.5MHz paired)
1900MHz GSM (pcs D block = 5MHz paired)
1900MHz UMTS/WCDMA (pcs B3 block = 5MHz paired)

In theory, all 3G devices will hit that 5MHz of 3G spectrum for voice and data. With spectrum capacity being maxed, calls 'should' handoff to GSM (happens ~50% in my case). If this was set for data only, it would work much better right now.
--
Canada = Hollywood North
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Forums » iPhones Eating Less Bandwidth Than AT&T Expected« Then why 3G speed SUCKS SO BAD NOW?  


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