Does АТ&T use AMR-WB (Adaptive Multi-Rate Wideband)

[zephxiii]

Yep ya nailed it, I've heard HR sound decent on GSM before (and crappy if the network is stressed) but the handoffs is what kills it.

In my city the handoffs even screw up FR...seems like they have been bad ever since 3G has come along. But it doesn't matter since we are always on 3G and the quality is great.

The nice thing though is that GSM in the city seems to be mostly running on FR...probably because of all the GSM capacity there is lost acquisition and how most people are on 3G anyways.

Ironically though GSM sounds great w/o handoff problems in the non 3G areas in my market.

[dctmpeg]

That reminds me...

One of the things I noticed with my now-gone Motorola Razr2v9x, was that once I disabled HR on it, and was on GSM, the network would actually make the call quality worse than HR because it could never decide which cell site to keep me on... And while the handoffs were less problematic on FR, it still resulted in a gap in the audio. Call me crazy, but I sware T-Mobile's handoffs sound different than AT&T. An accurate description might be "very quick digital farting noise" but the audio is mostly intact. AT&T, on the other hand, usually has chunks of words missing, even in full-rate... Again, what is going on network wide, and why could they never make things work as good as T-Mobile?!

A similar thing would happen with such phones as my old Nokia 6010 when I would use that old *3370# code to turn off AMR and use EFR. (In the case of mobile networks like Immix Wireless which were using FR, not EFR, well into 2010... well, it would probably use FR. I kid you not - that small carrier in PA still has sites on FR... And no AMR Full-Rate at all... Works great for their customers at the edge-of-cell... *Laughs.*)

Anyway, the Nokia, while on EFR, would hand off a whole lot more than AMR.

Of course, this was a few years ago. I would imagine that the GSM networks are not quite as bombarded as they used to be with traffic. But who knows... AT&T still insists on selling GSM-only prepaid devices...

[zephxiii]

Yep, I know that farting sound on tmobile, I have noticed it before. I have a girlfriend on tmobile now so I get to check out how their calls as going. Last night's long call was solid but not the clearest, but I think most of it is her phone's fault.

I live in a major cell overlap area, there are 4 cell site locations I could bounce off of so it makes GSM bounce around all over the place.

I remember a few years back using GSM in the DC area and even at home and hearing the handoffs via a quick "click" with zero audio drop out, it was very nice.

I could swear when 3g came to town, GSM just seemsd to work different.

[Guest 214]

Yep, I know that farting sound on tmobile, I have noticed it before. I have a girlfriend on tmobile now so I get to check out how their calls as going. Last night's long call was solid but not the clearest, but I think most of it is her phone's fault.

I live in a major cell overlap area, there are 4 cell site locations I could bounce off of so it makes GSM bounce around all over the place.

I remember a few years back using GSM in the DC area and even at home and hearing the handoffs via a quick "click" with zero audio drop out, it was very nice.

I could swear when 3g came to town, GSM just seemsd to work different.

If you have any sensitive audio equipment or crappy speakers, you can put both a GSM T-Mobile phone and a GSM AT&T phone and make a call, and you can hear the way the system sets up the call is quite different just by the buzzing sound. Makes me wonder if they are running a different revision or spec of GSM.

[zephxiii]

If you have any sensitive audio equipment or crappy speakers, you can put both a GSM T-Mobile phone and a GSM AT&T phone and make a call, and you can hear the way the system sets up the call is quite different just by the buzzing sound. Makes me wonder if they are running a different revision or spec of GSM.

That's interesting, might have to score a t-mobile sim now

[dctmpeg]

I am fairly sure that T-Mobile is frequently on the full-rate channel, thus a higher-pitched buzz than half-rate, which is what AT&T is typically on a lot of the time. Though, having had used several T-Mobile SIM cards, Half-rate kicks in as well... Just when your signal is very good, then you are put back on AMR Full Rate if the signal gets bad... as opposed to the vast majority of AT&T's network, which treats AMR as half-rate only unless the network has very little traffic - Then you might get AMR Full Rate, and better quality of service at the edge of the cell! Otherwise, you just need more bars...!

As a side note... I wonder if T-Mobile is using 8PSK AMR half-rate. That is, full-rate voice bit-rates on a half-rate connection. This PDF is one example I found that explains it... http://www2.rohde-schwarz.com/file_9...200_codecs.pdf