Wideband Telephony On Mobile Phones

Over at VoIP Supply’s VoIP Insider Cory Andrews poses a good question, ” When Will HD Audio Come to Mobile Phones?” He frames it up in the context of having first hand experience with enterprise class wideband hardware like the new Polycom VVX-1500 Media Phone, but then recasts the question in the mobile space.

With 3G here and 4G coming, the bandwidth is certainly there to support HD calling on mobile devices. Seems all that is currently lacking is a traditional carrier or mobile VoIP provider and a handset manufacturer with a wireless device that supports G.722 or alternative wideband codecs. I wonder if there are existing mobile phone devices with a large deployed base that could be made “HD capable” via firmware update?

I’m certainly not  an expert in all facets of the technology involved, but I have been investigating wideband for some time, and tapping many sources along the way. After a while all the little pieces of information start to form a more complete picture of what’s involved.

There are a number of areas of concern, here are a few to be considered;

• Codecs
• Handsets
• Back-end network infrastructure

From the HDComms Summit on May 21st I learned that the mobile technology folks like Qualcomm and 3GPP have well evolved wideband capable codecs. In the case of 3GPP they have selected AMR-WB, whereas Qualcomm is pushing EVRC-WB. Of course 3GPP is a trade group behind the GSM sphere of influence, while Qualcomm is the dominant player in the CDMA realm.

However, cellular networks are an animal of a different color. It appears that none of the handsets presently available are ever likely to support G.722 natively. By natively, I mean in the handsets core operation as a phone. Some creative souls will no doubt deploy soft phones on smart phones using the data capability to backhaul the voice traffic. That is, if the carriers don’t stop this through some technical means. There’s already been some talk about Clear not allowing Skype on their 4G network in Seattle, as a means of protecting their  own VoIP offering.

The simple fact is that cellular networks are profoundly different from carrier or enterprise networks. They are completely different architecture built around a range of concerns that are unique to mobile services. Some of greatest insight I’ve been able to glean about this space comes from when David Burgess of the OpenBTS project has appeared on recent VUC calls. David’s depth of experience in the mobile space is extremely impressive, and he also speaks about it very well. You can hear the podcasts of those calls here and here.

My impression from the HDComms Summit is that mobile is going to have its own codec standards. Their networks are so bandwidth constrained that they simply will not adopt “fat” legacy codecs like G.722. The technical constraints of their operating environments are best served by dedicated codecs. So just as they don’t presently use G.711 or G.729 over the air, they will stick to codecs designed specifically for mobile networks, namely AMR-WB and EVRC-WB.

The result is that we can expect to have to live with transcoding between codecs, at least where calls traverse the chasm between wireless and wireline/VoIP carriers. Audio Codes, amongst others, has been developing the silicon forming the basis of IP-to-IP gateways to handle this transcoding task.

Yet wasn’t part of the promise of 3G and even 4G wireless networks increased bandwidth? Should we not be able to leverage that for the voice channel? The answer appears to be a definite maybe.

At the HDComms Summit it was noted that the 4G standards build upon the existing ones to the extent that the voice layer is not particularly more capable than present 3G networks. There was a slide series from one of the presentations (Broadcom?) that indicated this quite clearly. (These slide sets have not been posted online yet. When they are available I’ll post a link.) What has been dramatically enhanced is the data handling capacity. But as already noted, carriers are taking steps to ensure that this data bandwidth is not used to compete with their own voice offerings.

The physical reality of mobile handsets don’t generally support great audio quality. The microphones, earpieces and even the case designs are very often substandard. Even that most beloved of smart phones, Apple’s iPhone, is in fact a pretty poor sounding phone. We’ll need physically better handsets to deliver the promise of wideband.

The very fact that Orange supports wideband mobile calls in Europe implies that there are at least a few wideband capable cell phones available. The fashion in mobile handsets is very quick to change. If there was to be some demand for wideband capable handsets then they could become available in a relatively short period of time. I for one am hoping that Nokia’s N97, scheduled for release in a few weeks, is up to the task.

Wideband calling will only be delivered when calls can traverse are routed over IP end-to-end. Thus the back-end networks will also need to evolve beyond their present TDM-based foundation. Many carriers are already transitioning portions of their backhaul infrastructure to IP networks, that’s a trend that will need to be accelerated.

There are other issues as well, but those I’ll leave for another time, and people who can present in greater depth.

None of this speaks to Cory’s question which was fundamentally “when” will we have wideband via mobile carriers. That’s a much easier answer than the technical issues. You’ll see it when the mobile carriers are forced to implement it as a means of increasing or sustaining market share. That is, when there is a competitive advantage to be gained.

It’s all about the business case.