A few weeks ago, a Calix Solutions Director attended an industry event that included a session on HD Voice. He felt it was a topic worthy of discussion and further consideration and since I was intrigued by this, I started to do a little reading and a little thinking.
What is HD voice and how would it work? Let’s start with the facts.
Science of Telephony
HD voice is also generally known as wideband voice. The common codec used for wideband voice is G.722 or one of its variants. G.722 offers a frequency range from 50 Hz to 7 KHz and requires a sampling rate of 16 KHz. The additional frequency range greatly improves the clarity of speech and gives the listener the ability to follow conversations even in low SNR scenarios such as when high levels of background noise exist on the phone line.
HD Voice Applications
Teleconferencing is one of the best and most obvious applications for High Definition Voice but I have a few questions about HD Voice as a consumer offering.
- G.722 does not appear to be compatible with traditional analog POTS. Long copper runs affect the higher frequencies and distort the signal. Additionally, I suspect that analog telephone sets were optimized around G.711 voice frequencies and may have trouble with the expanded frequency range of wideband audio.
- G.722 is best for on-net to on-net calls. Off-net calls, especially ones that must interface to the telephone TDM network are less likely to be able to use G.722 codecs for the conversation. To benefit from the call quality, all endpoints must use the same codec or use a transcoder to adapt between different codecs being used.
Consumers have been willing to jettison voice quality in favor of mobility. Would the same consumers see an increase in quality for wireline voice service as necessary or desirable? Would they be willing to pay for the extra clarity? Does it create “stickiness?” or frustration?
I would greatly enjoy feedback and discussion of these items.
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About the Author Buck Graham Buck Graham has been with Calix for over eight years and currently holds the position of manager of technical marketing. Prior to Calix, Buck was a network consultant with Sweden’s Ericsson Communications and was an evangelist of all-packet converged IP networks in the wireless and wireline communication industries. His career up to that point was highlighted by architecting large wide-area networks for Wal*Mart and Western Auto to support point-of-sale applications. Buck holds an MSc Degree in telecommunications from the University Colorado at Boulder and a BSc from the United States Naval Academy, Annapolis, MD. He is author of a best-selling technical text on TCP/IP as well as a children’s book. Buck and his family live in Danville, a nice little town in Kentucky. |
