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Print 15 comment(s) - last by anoldnewb.. on Apr 3 at 1:33 PM

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 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.


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