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AT&T also plans to embrace over-the-top services

About a week ago, T-Mobile announced that it would finally be brining the iPhone 5 to its wireless network. The company also made plans to bring HD Voice service to its LTE network.

Not to be outdone, AT&T has now announced that it will also add HD Voice service later this year. HD Voice provides users with higher quality (High Definition) audio, and requires support from the calling network and the devices making the call. That means that the network, your device, and the device of the person you're calling all have to support HD Voice capability.

AT&T senior VP Kris Rinne said, "HD Voice is part of our voice over LTE strategy."

Rinne also said that AT&T would be working on LTE Advanced service as well. LTE Advanced is designed to reduce interference and bond traffic from multiple frequencies together.

Source: AllThingsD



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RE: HD Voice is What?
By drycrust3 on 4/2/2013 3:41:50 PM , Rating: 2
quote:
A gimmick, really.

No, not a gimmick, a change brought on by competition from companies like Skype, who offer high quality 20 Hz - 20 kHz long distance voice communication (with video as well).
The reason for the 300 Hz to 3.4 kHz bandwidth was, originally, the cost of all the stuff necessary to get a phone call over long distances was so high that to help keep the prices charged down the bandwidth was limited to 4kHz, but fibre optic cables have changed all this.
When digital switching systems and digital transmission systems became popular, they were designed around the same 4kHz bandwidth as the previous generation analogue equipment, mainly to make interfacing with everyone else in the industry easy.
When Skype (and others) came along, they didn't care about the 4 kHz interfacing (other than how it restricted them when a user was connected to the internet via a dial up modem), they cared about attracting customers and staying in business while fighting the phone companies.
Now, with Skype being the top supplier of international phone calls in the whole world (they have about 10% of the market and are growing), the rest of the telecommunications industry sees they need to upgrade their product or disappear down the same path as analogue mobile phones, telegrams, telex, smoke signals, semaphore, etc.
At first glance this isn't a simple change because the whole of the digital switching system your phone is attached to is built around sampling audio 8000 times per second. For example, your phone is attached to a line card that samples your voice (and gets the other person's voice) at 8000 times per second, that information is fed into the strange digital switching world that thinks and behaves and does a ton of things on the basis of 8000 times per second.
It may well be the changes aren't too complex, but they would require both hardware and software changes.
It could well be the number of changes necessary are so many as to make it cheaper and easier for AT&T to connect those customers wanting this service onto a whole new platform built from the ground up for 20 Hz to 20 kHz.


RE: HD Voice is What?
By aliasfox on 4/2/2013 3:53:49 PM , Rating: 2
Thank you for that - I knew the frequency response was much more restrictive than other audio devices, but 300Hz on the low end seems awfully restrictive. I can't imagine too many people having voices that go above 3000Hz, but 300Hz would seem to cut off the bottom octave of James Earl Jones' voice.

Also, an 8000Hz sampling rate (minimum required for 4000Hz audio) seems awfully low when there are people who claim they can hear the difference between 44.1Khz (CD quality) and whatever SACD or DVD audio are.


RE: HD Voice is What?
By anoldnewb on 4/3/2013 1:33:52 PM , Rating: 2
Actually the current state of cell phone audio fidelity is quite poor.
For the Public Switched Telephone Network (PSTN), audio is filtered with a 300 Hz to 3.4 kHz bandwidth and sampled at 8 kHz and then encoded into an 8 bit logarithmic resolution to yield a 64 kbit/sec data stream. (http://en.wikipedia.org/wiki/PSTN). and http://en.wikipedia.org/wiki/G.711)

This filtering excludes the fundamental frequency of most adult voices: "The voiced speech of a typical adult male will have a fundamental frequency from 85 to 180 Hz, and that of a typical adult female from 165 to 255 Hz. Thus, the fundamental frequency of most speech falls below the bottom of the "voice frequency" band as defined above. However, enough of the harmonic series will be present for the missing fundamental to create the impression of hearing the fundamental tone." (http://en.wikipedia.org/wiki/Voiceband)

Cell phones make things much worse by reducing the G.711 data rate approximately 4 times. They use lossy compression to yield more compressed formats: "GSM has used a variety of voice codecs to squeeze 3.1 kHz audio into between 6.5 and 13 kbit/s" (http://en.wikipedia.org/wiki/GSM) and CDMA compresses similarly allowing up to 14.4 Kbit/s, (http://en.wikipedia.org/wiki/CdmaOne.).

I'm ready for HD cellphone voice quality and I hope it leads to some overdue emphasis on voice quality in the phones themselves.


RE: HD Voice is What?
By bug77 on 4/2/2013 7:13:11 PM , Rating: 2
Yeah, well, if your friends are used to singing to you on the phone, I guess you need all the quality you can get. Me, I just need to understand the other guy while he's not sounding like a robot.

Oh, and the joke's on us, when the same carrier limits out Internet access due to bandwidth being limited :D


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