On Wed, Jun 11, 2008 at 4:01 PM, thomasg <[EMAIL PROTECTED]> wrote: ...extra removed...
> 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. Mike _______________________________________________ Openmoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
