No 3G for GTA03, 2G/EDGE only?
mystica at gmail.com
Thu Jun 12 23:31:58 CEST 2008
On Wed, Jun 11, 2008 at 4:01 PM, thomasg <thomas at gstaedtner.net> wrote:
> The battery problem is a bit odd, too - especially because technically umts
> takes less power - in use and even less in standby. It powers up on higher
> data rates what of course will take some power.
> So why is this? First I think it's because if the relatively bad 3G-coverage
> that causes a weaker signal. The other point is that GSM is a pretty old
> (for techies :) and more than just widely used and mature technique.
Actually, the battery issue is due to one main concept, the difference
between air interfaces: Time Division Duplex, or Code Division Duplex.
GSM/TDMA uses timeslots, vs CDMA/UMTS using a special code to spread
its constant output to a wide 1.25mhz (CDMA2000) or 5mhz
(3G/UMTS)spectrum. GSM has 8 timeslots per channel. Therefore, with
GSM you end up only having to power up the recieve hardware (and god
knows what else, amplifiers, supporting hardware, codecs?) only 1/8 of
the time. I would presume even less when in AMR half-rate, being only
1/2 of the original timeslot is used for carrying the voice payload.
CDMA/UMTS and GSM all stop/limit transmitting when you aren't talking,
but again, when you ARE talking, 1/8 of the time transmitting vs 1/1
of the time transmitting = a lot more power used for code-division
spread spectrum style air interfaces.
Standby times also are affected by this, but are IMHO more to do with
the manufacturers skill at power reduction versus the transmission of
(re-)registration data to the network on an occasional basis.
My 2 cents.
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