Will VoLTE Be Open to All?

One of the big issues with Voice-over-LTE (VoLTE) goes beyond pure technology, because making IP voice communications work like today's standard cellphone or landline call will require that operators co-operate. That is, they will have to create SIP interconnects between their separate networks to make calls across the different U.S. operator networks. They will have to strike LTE roaming deals to allow international LTE calls. When you recall that AT&T Inc. and Verizon Wireless -- the two biggest LTE operators in the U.S. -- still haven't struck an LTE roaming agreement yet, you can see how things could get awkward. I would think that user expectations around how a phone call should work will mean operators will interconnect their networks sooner rather than later. When I asked about roaming on Tuesday, however, a spokesman for AT&T wouldn't say anything beyond the fact that the operator is launching VoLTE in 2013. We can already get a glimpse of what VoLTE networks might look like without interoperability. When Sprint launches its HD Voice service in the second quarter, users won't be able to place HD calls cross-country, nor will the technology work across different network suppliers' equipment. These technology and co-operative issues are probably part of the reason that VoLTE seems to be taking so long to arrive. There are a lot of moving parts to juggle. I would be mildly -- but not totally -- shocked if VoLTE didn't run across different networks ASAP after the major launches happen in 2013 and 2014. I say "not totally" because I remember how long it took carriers to open up text messaging between networks in the U.S. Of course, the technology challenges could still trip operators up, too. In this day and age though, keeping VoLTE shuttered would be like handing even more users over to the over-the-top messaging apps that already thrive on operators' networks. So, I've asked the GSMA for more information on VoLTE interconnects, and I'll keep an eye on how this all develops. — Dan Jones, Site Editor, Light Reading Mobile

Sandro Tavares 5/4/2013 | 2:45:34 AM
re: Will VoLTE Be Open to All? Exactly Ian. You nailed the point. And the feedback from people that experience "HD VoLTE" in Korea, where they have it commercially already, is extremely positive. In fact VoLTE will be an upgrade in terms of quality for the end user and efficiency for the operator, not a downgrade.
lanbrown 5/3/2013 | 1:54:47 AM
re: Will VoLTE Be Open to All? Based upon what? GSM, CDMA and VoIP all use codecs. You are making a blanket statement.

Originally GSM was 6.5 and 13kbps. Then came EFR at 12.2kbps followed by AMR-NB also at a peak of 12.2kbps. The sampling frequency is 8 kHz/13-bit.

VoLTE is G722.2 but can be AMR-NB.

So how is it going to be a downgrade when the minimum per the spec is what is currently used and an option of higher quality. Don't confuse the transport to that of the codec used. It is the codec that dictates the quality, not the transport!
Sandro Tavares 5/2/2013 | 9:21:57 PM
re: Will VoLTE Be Open to All? Well, in my point of view, interconnection is not really the thing holding up VoLTE for now. As most of the LTE networks are still being built we still need voice handover capabilities from LTE to 3G to guarantee a seamless experience to the subscribers. This will come with SRVCC, that is currently in trial phase. When it gets commercial more operators will decide to move ahead with VoLTE, the demand for terminals will grow and the "market machine" will start to run.

SIP interconnection, as mentioned in other comments is not really required for VoLTE to work. HD Voice is another story and might be really limited to intra-operator calls for the time being. But VoLTE would still work with transcoding towards a legacy voice protocol (even CS in some cases) at the edge of the network.

In what comes to roaming. Pure LTE roaming alone will not do the trick. For VoLTE, in addition to LTE roaming, the data sessions will have to be terminated at the visited P-GW, instead of the home P-GW as we see today. This is to avoid having a voice call to that pizza place right beside your hotel in Rome being routed all the way back to your provider in Texas before getting delivered to the local switch in Rome. Having your voice packets taking this trip around the world would increase costs and potentially jeopardize the quality of the call. This adjustment on the termination of the data sessions is being discussed in the standardization forums and will come as a necessary step to make VoLTE roaming work. In the meantime CS-Fallback is the official roaming solution, regardless of the existence of LTE roaming agreement. So, right now, even if you are roaming with your VoLTE terminal, your voice call will be delivered on 3G/2G over CSFB.
Tsahi Levent-Levi 5/2/2013 | 10:41:58 AM
re: Will VoLTE Be Open to All? VoIP runs on IP but isn't on-net for the telco - it is external and resides in the "internet".

Telco providers offer VoLTE as a tightly run operation, and to connect it externally to another telco, they need to solve interconnect issues - mainly business ones.

Think of it as Skype calling Google Talk. Telcos know how to do it between themselves by using the same specification (VoLTE in this case) and by having business agreements in place (which they need to add to make this an open service).
Himanshu 5/2/2013 | 9:43:40 AM
re: Will VoLTE Be Open to All? Why the same problem did not come for VOIP calls
Tsahi Levent-Levi 5/2/2013 | 5:27:37 AM
re: Will VoLTE Be Open to All? You make a very good point. It was the same case with 3G mobile video calling (a service that never took off, but was available in most 3G phones).

There were two main issues in the ubiquity front then:
1. Available phones and interoperability - the first Motorola devices couldn't make video calls with the Nokia ones - you'd see a black screen on one of them in calls due to an interoperability bug
2. Network roaming agreements weren't in place - you could dial a video ISDN call from Israel to a 3G phone in Japan, but not a 3G video call from Israel to a 3G phone in Japan for example

These things take time, and as you state - operators don't really have the luxury of time on this one.
San Sanco 5/1/2013 | 11:06:26 PM
re: Will VoLTE Be Open to All? The thing I think really needs to be addressed is the quality because out of the box its going to be a downgrade from GSM and CDMA quality no matter what they say. VOIP isnt even close in quality to a digital cellular network connection.
Sarah Thomas 5/1/2013 | 5:53:06 PM
re: Will VoLTE Be Open to All? I spoke with Genband and Ericsson about this and both thought it wouldn't be an issue right out the gate. Ericsson's North American CTO Dr. Vish Nandlall said there is a profound understanding amongst operators that they have to work it out right away.
DanJonesLRMobile 5/1/2013 | 1:13:30 PM
re: Will VoLTE Be Open to All? Yeah, there's also LTE roaming clearing houses like so:


My question is more when is this going to happen, then? We can't roam across LTE networks in the US at present. Will VoLTE cause operators to open that up?
lanbrown 4/30/2013 | 11:54:14 PM
re: Will VoLTE Be Open to All? "That is, they will have to create SIP interconnects between their separate networks to make calls across the different U.S. operator networks."

Not true at all. They can use gateways to take the VoLTE calls and put it over the existing interconnects. Someone making a VoIP call to someone that has an analog line is handled the same exact way. It does make more sense to make it end-to-end VoIP though and does allow for better use of the connections. I would also expect that HD voice service will be allowed even with SIP trunking between providers.
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