[T-Mobile Samsung Galaxy Note II] casperi:
Cell and data are basically the same as voice runs over the data lines pulled to the towers. It will be even more so as carriers upgrade to LTE-rev14 I think which is from my understanding is pure carrier level voice IP network vs switched network now.

Basically now voice is segmented out to a Nortel, Lucent, Alcatel gear to handle the phone side and then data is routed to their respective network gear. In a pure IP network both voice and data are run data only. Voice will be filtered out with QoS rules with along with virtual pbx box vs the circuit switched like we have now. The advantages of going pure IP are

1) Carriers are no longer tied to large circuit switched gear that runs into the millions and is proprietary to each manufacturer's specs. So the carriers try to buy just one type of pbx so not to run into compatibility issues. Just replacing a line card which typically hosts 129 lines at the "CO" known as central office is always same day aired if they don't have a replacement handy and those cards run 5 or so grand a piece. So downtime is a problem and cost vs ROI is as well.

2) In a pure voice IP setup the carriers can run a virtual PBX that is software bound vs hardware that the call is then routed via data to CO or datacenter to the last leg to terminate the call with say level 3 being your terminating host that then routes the call from there. If that call is cell phone to cell phone then it can stay data the entire way. This cost the carriers fare less as the hardware is agnostics, think vmware etc. Also audio codec on the BOX and towers can be adjusted in learning mode and then into dynamic mode as to give the callers the best overall call experience and if the tower gets loaded down with calls that gear can downgrade to a lower codec to handle more call volume. Think rush hour traffic where your stuck and everyone is on their cell. I could go into more details but you would fail asleep but this killer feature alone.

Bottom line is this cost the carriers far less, the audio codec used has much better call quality and can be setup to be dynamic to the load of individual towers vs switched which is hard coded. Downtime is dramatically reduced as there's no actual phone/linecards to go bad.

Many T-Mobile users "use" the Wi-Fi calling feature because it just sounds better. The reason that is because the audio codec "your call" runs around 96kbs. With voice over LTE "depending on tower config and load" can provide the same call quality. For example vzw cell call is 4.7kbs "data" which means that call is heavily compressed. You can tell if you listen, the bass and highs are gone. It's like talking to someone that speaks monotone. The reverse, GSM to GSM call uses a audio codec in the 14.8kbs range and sounds awesome. Even better is two T-Mobile callers using Wi-Fi calling. The problem the carriers have is CDMA to GSM or the other way around, all those calls sound like crap cause the voice gear has to downgrade or upscale to meet the setting of caller and vzw doesn't scale higher than 9.2kbs so the convo sounds mutilated with call echo, drop data packets which sounds like garbage like distorted audio. Think Sat radio when you go under a long bridge. Voice over LTE "voice over data" will allow all carriers gear to talk correctly and adjust audio codecs correctly on the fly giving the callers the best call possible.

I know I went WAY beyond and in depth but I love this stuff and its fun to share it with others.

Casperi