[pak]

If you want to know the real reason for this, it's because normal cell calls still have to go over POTS (https://en.wikipedia.org/wiki/Plain_old_telephone_service) on the backend, which typically uses 8-bit mu-law companding of audio at 8kHz. This compresses the typical frequency range for phone calls to 300-3000Hz, which is a lot smaller than the real range of human hearing, although it covers the range used by human speech so it was considered totally acceptable before unreliable wireless packeting became the typical last leg.

VoIP, FaceTime, Skype and other IP-only technologies can use much better audio codecs, going all the way up to CD quality audio (44kHz, 16bit). This makes a huge difference when there is background noise and clipping and less than optimal transmission conditions.

(Source: I used to work for an IVR company.)

[Aloha]

I'd argue that 64 kbit PCM performs significantly better than most compressed codecs in high noise situations, I don't consider it a benefit to include audio up to CD quality for a conversation on the phone, because much of what you do include is unwanted/unneeded noise.

[rcthompson]

That doesn't really explain why smartphones (and cell phones in general) sound so much worse than landlines, does it?

[pak]

It's the combination of wireless packets dropping and the audio having to be degraded to 8bit/8kHz to pass between carriers that really brings on the terrible. It's kind of like TCP over TCP [1] -- works well enough a lot of the time, but when it fails, it fails badly because of how the two layers aren't really built for each other.

[1]: http://sites.inka.de/bigred/devel/tcp-tcp.html

[Aloha]

POTS lines do not carry more audio bandwidth than a cell phone. All of them are 64kbit PCM uncompressed audio.

[rcthompson]

Ah, ok, that makes more sense.

[Aloha]

Compression largely, EVRC and GSM (CDMA and GSM respectively) are pretty heavily compressed, while I prefer the sound of EVRC, both are compressed - another thing to point out is most smartphones are pretty lousy telephones, bad earpieces, poor microphones, and so on. If you want to see how cellular handset can perform, use a good communications grade handset.

[tumba]

Any recommendations or examples of "good communications grade" handsets?

[thaumasiotes]

> This compresses the typical frequency range for phone calls to 300-3000Hz, which is a lot smaller than the real range of human hearing, although it covers the range used by human speech so it was considered totally acceptable before unreliable wireless packeting became the typical last leg.

But... landline telephones have always mangled human speech. They're awful.

[solotronics]

I deal with a ton of cell towers interconnected with Ethernet over fiber [ Ethernet point to point built on MPLS ]. I am not sure about cell towers over POTS but I dont think thats how its done now.

Thats not to say there arent legacy towers out there on POTS, but all new towers are on Ethernet via fiber as far as I can tell.

[pak]

Sure, you can connect the towers to the carrier however you want, and this is why certain carriers can sometimes hack in better quality protocols within-network (see the discussion on voLTE further down the page). Carrier-to-carrier connections, however, still have to use POTS/PSTN (since, if you send a voice call to another carrier's network, you can't a priori know it's a smartphone vs. a landline vs. something else right now, and PSTN is the only standard they all agree on). I agree, it's dumb.

Also see https://en.wikipedia.org/wiki/Public_switched_telephone_netw... regarding the 64kbit/s limitation.

[superuser2]

I've usually found POTS-to-POTS calls to sound much better than latest-iPhone to latest-iPhone telephone calls. Why can't cells at least get to that level?