Whitepaper: Voice over LTE via Generic Access (VoLGA)

Martin Sauter has published a whitepaper on VoLGA. I havent read it as of yet but I am sure it will be an interesting read for people who are interested in learning more about Voice options in LTE.

The whitepaper can be found here.

Feel free to post comments regarding the whitepaper on Martin's blog here.

Stage 2 Specification For Voice Over LTE from VOLGA Forum now available

From our friend Martin Sauter's blog:

Regular readers of this blog probably remember that I'm a fan of Voice over LTE via GAN (VOLGA). For those who don't, have a look here on more details on why I think it has a good chance of becoming THE voice solution for LTE. It's amazing how fast the Volga-Forum is pushing out the specifications. In May, they published the stage 1 specification document, which contains a high level architecture and the requirements. Now only a month later, a first version of the stage 2 specification is available. Stage 2 specifications as per 3GPP contain a detailed architecture description and all procedures required from connecting to the network, originating and terminating calls, doing handovers, etc.

While their speed is incredible, maybe it should not be that surprising, because VOLGA is based on the already existing 3GPP GAN (Generic Access Network, i.e. GSM over Wi-Fi) specification. That's a good thing because that means that VOLGA could thus be developed quite quickly as it's likely that existing products can be modified instead of being designed from scratch. In addition, this should also mean that the first version of the standard is already quite mature as many areas were already verified during implementation and rollout of GAN in current networks.

I did a quick comparison between the two stage 2 specs and as I expected, many parts are very similar. While the GAN stage 2 specification has 126 pages, the current VOLGA stage 2 specification has 87 pages. This is probably because VOLGA is simpler than GAN. There are fewer handover procedures and most of the handover details are part of the 3GPP Single Radio Voice Call Continuity (SR-VCC) specification (for IMS) so they don't have to be included in the VOLGA spec. In addition to fewer handover scenarios, handovers are a bit more simple with LTE from a VOLGA perspective, as the network takes care of it unlike with GAN, where the mobile has to force the network into a handover. Also, there's no need to support the packet switched part of the network which also significantly lowers the complexity.

Well done, I am looking forward to the stage 3 specification which will contain the details on all messages and information elements used.

I blogged about VoLGA last month here.

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

• See http://www.volga-forum.com/ for more information about joining

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:

• VoLGA Forum
• VoLGA Specifications
• Voice - Bearer Aware, Bearer Adaptive or Bearer Agnostic?
• The Volga-Forum: Taking the Quest For Voice over LTE out of 3GPP
• VoLGA - reinventing UMA for Voice-over-LTE
• LTE, mobile broadband & SMS - VoLGA vs. IMS

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

Solving the LTE voice dilemma

Continuing the discussion from LTE World Summit, this is something that has been discussed in the past by myself and other blogs as well. We know that there is no out of the box solution for voice calls in Release 8 but there are some solutions that are being standardised for this problem. Dr. Howard Benn, Director of Cellular Standards, Motorola Mobile Devices gave an interesting presentation on this topic titled, "Voice –how to talk over LTE". Here is the summary of his presentation along with some more information:
As we know, IMS was introduced in Rel 5 but even till today, there has been no major IMS rollouts. There are some operators working on deploying the IMS solution but in reality its not been as successful as it should have been. If IMS is available then the problem of voice call on LTE goes away. The problem can be solved using Voice Call Continuity or VCC. Infact there is a bunch of specifications on IMS Centralized Services (ICS) and network Centric VCC for solving this and other similar problems.

So with IMS not being available, the first alternative for this problem is Circuit Switched Fallack (CSFB). In this, as can be seen from the MSC above, the user is attached to an LTE network. MSC can send Paging to the UE and if the user accepts the voice call then he is handed over to 2G/3G network. The big problem with this approach is additional time required to establish the voice call and the PS services might get disrupted, depending on how its handled.

The second solution is to have a Generic Access Network (GAN... previously known as UMA) based solution. This is similar solution to the ones used by some Femtocells. This would mean that the UE's would require GAN chipsets and GAN is known to be power hungry so it can impact the battery life significantly.

China Mobile's, Bill Huang in a recent interview mentioned that “We could carry voice over UMA” and “We will have an LTE network that supports voice…”. He was referring to this approach mentioned above.

Finally there are always proprietary options like Skype that can be used along with the data services to solve the voice problem.

Infact a service like Vonage, modified for mobiles, can solve this problem easily. You can connect a VoIP client from your phone or device to Vonage and you are given a landline number that you can pass to others. When calls are received on this number, the client in the mobile rings and you answer the call normally.

Nick Yamasaki from KDDI mentioned that KDDI will roll out LTE with CS fallback option for voice initially but then SRVCC (Single Radio VCC) solution will be adopted in future.

Which way: Femtocells or UMA?

Discussions are again resurfacing about which technology should be used to improve coverage; Femtocells or UMA. Honestly, I have not been a big supporter of UMA (and you dont have to agree with me) and earlier this year when Nokia raised doubts about the technology, i stopped following it completely. Kineto has been the biggest supporter of UMA and is still carrying the torch.

Kineto recently received over $15 million in investment from Motorola that it plans to use to increase its reach in UMA. Last month it had received investment from NEC. One of the reasons for the resurgence could be because the UMA technology has matured since being used for some time. T-Mobile has already rolled Hotspot @ Home using UMA. Also more phones are now available supporting UMA.

One of the drawbacks that will always be present in case of UMA is that special handsets will be required that would support WiFi as UMA is based on 802.11. This means more expensive phones and higher consumption of power leading to smaller battery lives. One more problem with UMA is the interference due to other ISM band devices and there are many technologies like Bluetooth, etc that are competing for the band.

The drawback in case of Femtocells could be that their price is still quite high as complete Node B + RNC functionality is generally available in a Femtocell and at the same time all the aspects have not yet been standardised. Along with these, Femtocells that use the same spectrum as that of the operator can cause interference with the Macro cell. This would in turn require very clever management of spectrum frequencies, etc.

A possible long term solution could be (but I dont see anyone agreeing to it right now) that phones with UMA technology become more common and a combined UMA + Femtocell equipment is rolled out by the operator. At the end user premises, depending on the strength of rf reception, the equipment can either use UMA or normal Femtocell functionality. If this idea is agreed upon, then there would still be couple of years before all interworking and other technological problems are ironed out.

T-Mobile USA Hotspot@Home goes National

T-Mobile's Hotspot@Home can be labelled as pre-femtocell service. Its based on UMA and needs UMA based phones for this service to work.

The following is from a report in C-net:

Subscribers will be able to connect any regular home telephone to a T-Mobile router that will send calls over the Internet much the same way as services like Vonage operate. The service costs $10 a month plus taxes and fees for unlimited domestic local and long-distance calls.

Only T-Mobile wireless customers who subscribe to at least a $39.99 individual calling plan or families subscribing to at least the $49.99 monthly T-Mobile calling plan can get the service. The @Home service also requires that users subscribe to a separate broadband service from a cable operator or telecom provider. And they are required to use a special T-Mobile router, which also provides Wi-Fi Internet access throughout the home.

This router can also be used to provide T-Mobile's HotSpot @Home phone service. This service, launched last year, allows T-Mobile subscribers to use dual-mode cellular and Wi-Fi phones that switch between both networks. When subscribers are near their home Wi-Fi hot spot, they use the broadband network to make unlimited domestic calls. And when they are outside the home, the phone seamlessly switches to T-Mobile's cellular network.

The service, which also costs $10 extra per month, serves two purposes. It helps provide better in-home cell phone coverage and also helps reduce the number of minutes used on the T-Mobile cellular network.

Via: Dailywireless

UMA is not Dead

I did not hear about UMA for long time and i was starting to think that this would be one of the dead technologies that never saw the light of the day. I was wrong. It was pointed out to me by a colleague that T-Mobile (U.S.) recently announced Hotspot @ home that will allow UMA access to the Mobile while within a WiFi coverage area.

Note: UMA or Unlicensed Mobile Access is no longer called UMA but by its new name GAN or Generic Access Network

T-Mobiles GAN service lets users make phone calls over their in-home WiFi networks or over T-Mobile's national cellular network, depending on whether the customer is inside a T-Mobile HotSpot or not. The big problem with UMA, though, is that users must use dual-mode phones. T-Mobile's HotSpot@Home plan currently costs $10 a month after the purchase of a dual-mode phone and WiFi router, if one isn't owned already.

AT&T (again U.S) is also planning a similar move but its going the FemtoCell Way. Industry sources have revealed that AT&T has filed a request for proposal (RFP) to suppliers that may be interested in participating in AT&T's in-home femtocell service, according to wireless trade publication Unstrung. Femtocells are access points that act as repeaters to strengthen cellular communication signals inside homes, offices, and underground areas like subways. T-Mobile is trying to accomplish a similar task with its HotSpot@Home service, which brings better call quality to subscribers through the use of WiFi routers.

Although AT&T's femtocells would likely require a broadband internet connection, femtocells don't use the WiFi routers that most people already have in their homes. Instead, users would need to buy a new plug-and-play unit that could cost in the area of $200. Companies like picoChip currently develop reference designs for units that could be used by AT&T or its suppliers.

Because femtocells do not use WiFi signals, they don't require dual-mode handsets, which opens up the market to customers that don't want to ditch their current phones just to get the benefits of a stronger in-home signal. Meanwhile, potential T-mobile HotSpot@Home customers can only choose between two phones (the Nokia 6086 and Samsung T409), which means existing customers have to ditch their current mobile phones for a dual-mode device. Blackberry 8820 will soon be available in U.S. which has support of UMA.

Meanwhile Kineto Wireless, the innovator and pioneer of UMA, recently joined femtoforum. In addition to the promotion of femtocell deployment, the forum is focused on addressing several key technical issues, including radio planning and control, provisioning and management, and device-to-core network connectivity. As the core network technology behind a growing number of large-scale, dual-mode handset deployments, the 3GPP UMA standard is now being recognized as the de-facto standard for device-to-core network connectivity in the femtocell market as well. Recently, Kineto initiated interoperability testing between femtocell access points and its industry leading UMA Network Controller (UNC), and has already completed testing with Ubiquisys, the number one femtocell access point vendor.

"The femtocell industry is starting to appreciate the three year head start
UMA has over proprietary approaches being proposed for device-to-core network connectivity," said Patrick Tao, Kineto's vice president of technology. "As the
technology behind successful l dual-mode handset services, such as unik from
FT/Orange and T-Mobile's Hotspot @Home, the 3GPP UMA standard has already identified and addressed the real-world deployment issues operators face in
bringing femtocells to market. These issues include security, device
authentication, access controls, handover, regulatory compliance, as well as
scalability to support millions of endpoints."

One thing to remember here is that not all mobiles supporting WiFi will support UMA. On the other hand all phones that support UMA will support WiFi.

An Introduction on UMA can be found here or here.

FMC: IMS and UMA (15/05/07)

One of the topics that came up during a discussion with a client is how would IMS replace UMA. My opinion is that UMA is something for present while IMS would be something for future. Doing some digging up afterwards turned up some interesting results.



An article in TMCNet confirmed my opinion. The following is a snippet of discussion with Steve Shaw, marketing director of Kineto wireless, it can be seen that UMA:

Shaw explained that carriers first started building IMS in order to standardize the process for wirelessly delivering the types of data services that IP enables—including push-to-talk, videoconferencing, and mapping.

As development of IMS got underway, Shaw told TMCnet, carriers realized that it could have applications for traditional voice services as well, and the specifications grew to become a potential enabler of FMS.

Today, IMS is generally viewed as the way in which all networks—both fixed and mobile—will evolve to become completely IP-based.

The problem is that, although IMS has lots of promise for many applications (including FMS), it is not yet fully developed and the number of specifications involved is still growing.

“IMS isn’t a specification, it’s a journey,” Shaw said

He added that IMS eventually will solidify and deliver on its promise, but that probably will take another decade or more.

Although beginning the transition to IMS-based systems now may theoretically be a good long-term investment, for many carriers the cost simply cannot yet be justified. That leaves them looking for a non-IMS way to cost-effectively deliver FMS now.

UMA, For Now

As a fully-developed specification capable of delivering low-cost FMS service today, UMA is the no-brainer choice for most operators, Shaw told TMCnet.

“UMA is unbelievably inexpensive and low-impact. There is really nothing else that has the same approach,” he said.

UMA isn’t perfect, of course, and cannot provide all the functionality that IMS promises to someday deliver.

Shaw noted that some companies who build IMS-based applications have positioned UMA as being a temporary solution, and one that operators will regret investing in because new specifications will come along and render UMA obsolete.

That could end up being true, but operators still need a way to cost-effectively deliver FMS now, and for the time being UMA is the only specification available to do that.

Shaw added that 3GPP has started work on a second-generation version of UMA—dubbed eUMA—that will add more functionality including the ability to natively connect into high-speed data portions of 3G networks.

There are couple of white papers from Kineto wireless which are an interesting reading. The first is "How UMA Enables Broadband IMS" and the other is "The Complementary Roles of UMA and IMS in Fixed-Mobile
Convergence"

I found another old article from last year talking about the same thing.