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Wednesday, 10 June 2009

VoLGA: Bringing Voice to LTE

Voice is becoming an Important issue for seamless introduction of LTE services. Even though most people think that LTE will start with the Broadband Dongles, it is important to resolve the issue sooner rather than later.



VoLGA Forum is one such body proposing a solution and its backed by quite a few well known industry players.



In the LTE World Summit, Franz Seiser of T-Mobile Germany spoke about VoLGA. Here is a summary from his presentation:

In order to ensure LTE will be used as much as possible, voice-and messaging services need to be supported on LTE networks in high quality asearly as possible.

The main Drivers being:
  • Ensure acceptance of LTE as an possible next generation PLMN
  • Shift traffic to new network as fast as possible
  • Avoid price competition with DSL
The industry needs a stable, scalable voice and SMS solution forLTE:
  • delivering a seamless user experience (voice hand-over to existing 2G/3G networks)
  • with proven, commercial quality
  • availability in 2010 (SMS) /2011 (voice) latest

In a post earlier, I discussed about the possible voice options for LTE and that generated quite a discussion relating to GAN. Recently Dean Bubley and Martin Sauter have covered this VoLGA issue and in general Voice over LTE in far more detail than I have earlier or even in this post. Please see the links at the bottom to read their post details.

Specified 3GPP solutions for Voice/SMS in LTE do not meet all requirements because:

CS Fallback ruled out due to customer experience and non-LTE usage

  • issues with customer experience (call set-up time increase >1.5sec., no parallel voice/data if legacy network is 2G w/o DTM)
  • not using LTE radio for voice
  • requires changes to Rel-4 architecture MSC-Servers
  • has much more impacts than originally envisaged

IMS based solution has very high complexity; availability and stability notfeasible in time, roaming eco-system is not yet existent

  • solution would consist of IMS platform, various application servers and a major upgrade/change to Rel-4 architecture MSC-Servers
  • no eco-system in place yet for IMS voice/SMS roaming and interconnect (only GPRS data or CS eco-systems are available today)
  • solution requires updates/changes to quite many IT systems and processes as well

Key Objectives for Voice/SMS over LTE Solution is to Re-use as much as possible of existing systems, mechanism and eco-system while avoiding proprietary extensions to 3GPP nodes

  • build upon existing Rel-4 CS network and investments
  • “do not touch the MSC”
  • build upon fully 3GPP compliant Rel-8 EPC/LTE network
  • re-use existing CS roaming/inter-connect regime
  • minimise impact on UE, especially on user-interface

As a result, the simplest solution is “Voice over LTE Generic Access” or VoLGA



What is VoLGA?
  • A technological approach for delivering voice and SMS services over LTE access networks
  • Leverages a mobile operator’s existing core voice network
  • Derived from the existing 3GPP GAN standard

What is the VoLGA Forum?

A group of companies working to…

  • Leverage collective technical skills to define VoLGA specifications
  • Publish proposed specifications via the VoLGA Forum web site (coming soon)
  • Facilitate the easy adoption of VoLGA technology by other vendors and operators

The group is open to interested parties in the mobile community

The main Highlights of VoLGA are:

  • Full service transparency
  • Supports all circuit services over LTE
  • Supports IMS RCS and combinational services (CS+IMS) over LTE
  • Supports handover of active calls between LTE and GSM/UMTS
  • Supports expected LTE femtocell deployments
    • Low risk, low investment
    • Based on well proven 3GPP GAN standard
    • Requires no change to existing MSCs and operational systems
    • Conserves existing, extensive voice interconnection regime


    To keep things simple, VoLGA is the best option available at the moment.

    Further Reading:

    You can search multiple blogs (including mine) in a single search via the 3G4G search here. (Search at the bottom of the page).

    2 comments:

    Ulf Nilsson said...

    Where are all the operators? I just wonder how many of these vendors will continue to support T-Mobile when they announce their chosen LTE vendors.

    Steve said...

    Zahid,

    First, nice post on VoLGA. I'm covering voice over LTE issues on my blog.

    You point out that “…most people think that LTE will start with broadband dongles." This is why SMS over LTE support is so critical. It lets operators reuse the SMS-based operational, provisioning and customer care systems used for 3G dongles on an LTE network. This is an area where VoLGA really shines.

    As for the previous commentator, I would turn the question around. How many operators really believe CS Fallback is the right way to do voice over LTE?

    There is a real problem in the industry and the current proposed solution is DOA. T-Mobile and the VoLGA Forum are stepping up to solve a problem many operators don't even know they have yet.