Over the past two years I've written numerous posts about different proposed options on how to do voice calls over LTE and the lack of a simple and straight voice solution. This is, in my opinion, a serious threat to the success of LTE if not resolved soon. A number of alternative solutions to the IP Multimedia Subsystem (IMS) have been analyzed in 3GPP, which is envisaged to be the successor to the circuit switched MSC voice architecture. However, even after many years of standardization, it has still not seen the light of day and some fear that it's become to complex. Instead, only fallback to GSM or UMTS for an incoming voice call has made it into the 3GPP standards. Looks like some parties in the game are not happy and have started to push things forward by going off stream with the newly formed Volga-Forum (Voice over LTE via Generic Access).
It seems that other solutions, which have been examined in 3GPP for connecting the current MSC (Mobile Switching Center) architecture to LTE have so far not found the necessary approval by the necessary majority of 3GPP members to become a work item, a necessity for becoming an official feature. I've discussed one of the alternatives back in August 2008 here for those who would like to have a closer look. In summary, the two MSC options examined suggest to replace the lower layers of the current voice protocol stack by IP, while leaving the higher layers of the protocol stack untouched. With relatively little work, the existing voice service can be reused for LTE, including the seamless handover of an ongoing call between LTE, UMTS and GSM and international roaming.
Even simple things don't happen over night and each day waiting for 3GPP to finally start working on this topic drags out the day when LTE can really go beyond USB dongles or built in laptop modems and compete with HSPA where voice calls work like a charm. This is where the Volga-Forum comes in. With a strong list of supporters such as T-Mobile and Ericsson, just to name the two biggest (some more operators in the boat would be nice though), they have pledged to take the task of defining an interoperable voice solution for LTE outside of 3GPP.
I would guess the aim is to put some pressure on 3GPP to move forward and the intention is to fold their work back into the standards later on. But even if they stay separate, the solution selected is based on UMA/GAN, as described in option 2 in 3GPP TR 23.879, so the Volga-Forum does not depend on the support of 3GPP to drive their implementation. The main parts of the approach require no modifications in the LTE radio network, the LTE core network or the MSC. All enhancements suggested would be implemented on the mobile device and a new gateway controller between the LTE core network and the MSC. The situation is thus very similar to the days when Kineto and others privately developed UMA, which tunnels GSM and GPRS over Wi-Fi, before it officially became part of the 3GPP standards some years later after being renamed to GAN (Generic Access Network).
A very interesting move, and I think it's good to see that things are moving forward! If you would like to add anything on the political or technical side of this, please leave a comment below.
Thanks to LTE Watch for the first pointer!
3 thoughts on “The Volga-Forum: Taking the Quest For Voice over LTE out of 3GPP”
Thanks Martin for this blog. You raise an important issue and I have blogged and tracked back to it. keep up the good work! http://opengardensblog.futuretext.com/archives/2009/03/grand_central_a.html rgds Ajit
Perhaps it is worth mentioning that this solution was considered by 3GPP but thrown out due to lack of support (T-Mobile being basically the only company, not just operator that acfively supported it in the discussions) and complexity reasons.
Also, the solution has issues with the roaming of voice and VOLGA may in the end be just another home network-only voice solution.
Thanks for the comment. When I look at 3GPP TR 23.879, I see the roaming architecture for this solution quite well described.
From a complexity point of view, I think it is much simpler than others described in the same document, since most, if not all changes have to
be made on the gateway who’s vendors I imagine are quite flexible and willing to do it very quickly.
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