On 2007-11-08, David W Studeman <eat_your_own_spam@hormel.com> wrote:
> planetx wrote:
>> I am a verizon user and honestly I love it. But all my friends and
>> family are on ATT so I am most likely going to switch. About 6months
>> ago I tried a 30day trial with ATT but the voice quality was terrible.
>> I live in a 3g market, but I did not have a 3g phone. So is the voice
>> quality better on 3g(if you have the phone) than gsm?
>
> 3G has absolutely nothing to do with voice. While it is true with Verizon
> and Sprint that CDMA is also used for voice, for the rest of the planet,
> GSM is used for voice. Data can be GPRS/EDGE or in the case of 3G and
> better, UMTS/HSDPA.

That's not right. Both GSM and 3G UMTS provide both voice and data
service. Right now my phone is getting service from a 2100 MHz UMTS
operator in Hong Kong, and it makes voice calls just fine. The phone
also works fine for voice service in Japan where there is UMTS service
but no GSM service.

It may be that AT&T always uses GSM, and never UMTS, for voice, but
this isn't how it works most other places on the planet.

I'd note that there is a general difference between GSM and CDMA
codecs, though. GSM codecs send a fixed bit rate, since a fixed
bandwidth is assigned to the phone when a call is connected. For
CDMA, however, variable rate codecs (i.e. that send more bits per
second when you are talking than when you are not) make sense since
when you send fewer bits everyone else sharing the bandwidth gets
less noise. In principle there should be no way to tell the difference
between the sounds to these two types of codecs, but no never know.

Dennis Ferguson