At the VON conference last week I had an interesting conversation with Karine Lachapelle of VoiceAge. Beside her interest in the status of my ride-on model railroad :-), we discussed our mutual interest in wideband speech coding and Karine mentioned a trial of wideband audio on mobile phones in Germany last spring.
I had completely missed this, but luckily she sent me some references which I read on the plane flying back from CTIA.
Background (skip this if you’re already up on wideband audio)
From it’s 19th century beginnings, telephony has provided a very limited representation of human speech. For the first 80+ years, the main problem was affordable microphone technology. Today, relatively high quality microphones can be included in consumer products at little cost. Unfortunately, digital telephony standards (basic coding and 64 Kbps circuits), were frozen in the 1960s, based on the voice quality of 1920s microphones. As a result, traditional telephony doesn’t pass sounds above 3.2 KHz, making it hard to distinguish “s” or “z” sounds (which contain energy up to 6 KHz and beyond) or tell letters like “c”, “d”, “e”, “g” apart.
The advent of VoIP brought the potential for dramatic improvements in voice quality, and indeed, I spoke repeatedly about wideband audio at early VON conferences, but to no avail. Early VoIP companies tried to duplicate “toll quality” telephone speech, rather than leapfrogging the telecom industry. That finally changed with the advent of Skype, where PC-to-PC calls can sound like you’re in the same room. And, with Skype's growing adoption, more and more people are realizing how good voice communications can be.
Mobile Voice Quality
With the advent of mobile telephony, radio capacity was a bottleneck so mobile systems used aggressive speech compression, even at some sacrifice in voice quality. Consumers put up with this as mobility was such an advantage. With 3G, radio capacity is still an issue, however advertised data capacities significantly exceed what’s required for voice, so there is new flexibility to consider better quality speech coding. Further more, speech coding algorithms have improved to the point where wideband audio requires only a little more radio capacity than today’s narrowband coders.
But while mobile telephony uses (potentially variable rate) packet transmissions on the radio links, calls are still switched using 64 Kbps circuits. To the extent mobile operators are trialing, or even deploying, IMS technology, it’s for new applications. No mobile operator has converted their basic voice telephony to IMS yet.
Luckily there’s a kludge that’s been standardized for several years, is available and is at least partially deployed. It’s called TFO, tandem free operation. TFO provides a way to tunnel lower rate signals through traditional 64 Kbps circuit switches. Indeed, TFO provides a viable way to connect two mobile handsets anywhere in the world provided the handsets use the same speech coder and the networks support TFO.
Ericsson’s trial with T-Mobile in Germany
The most interesting article Karine pointed out is by Berkehammar et. al. in the Ericsson Review No. 3, 2006. The article describes a consumer trial (150 users) on the T-Mobile network in Germany in April and May 2006. The trial used AMR-WB (Adaptive Multi-Rate, WideBand) speech coding (versus the normal or “narrowband” AMR-NB used in most GSM networks today).
The short summary:
More than 70% of the users perceived a distinct improvement in voice quality — they found that they could more easily place and complete calls in noisy environments, and reported that the improved voice quality created a greater sense of privacy, discretion and comfort.
If you add in those that merely found it good or “nice to have,” approval ratings were over 90%.
When do we get it?
The limiting factor for deployment will be handsets. Wideband mobile connections only work if both parties have wideband handsets, otherwise the call reverts to traditional mobile performance. Ericsson claims their "terminal platform" will support AMR-WB in 1Q07, however that's Ericsson, not Sony-Ericsson — the people who actually make handsets commercially.
So the good news is Ericsson is promoting wideband telephony and T-Mobile Germany has seen it's positive impact on the subscriber experience. But there is no committed date for commercial handsets or commercial service. It seems service providers continue to rely on mobility to make up for marginal voice quality, at least for the immediate future.
Feel free to talk this up with anyone who'll listen. Voice may not be "sexy" but wideband would do more for most mobile subscribers than any of the new "data" services getting all the attention.