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NewsGlobe: Interviews
Operator considerations for supporting voice over LTE
A Q&A with Steve Shaw, VP of corporate marketing at Kineto Wireless
by TelecomEngine Newsdesk
In this interview, Steve Shaw, vice president of corporate marketing for Kineto Wireless talks about Long Term Evolution, (LTE) and the problems with voice and SMS over LTE. He also discusses the competing solutions currently in the market -- CS Fallback, VoLGA and IMS Telephony and offers a comprehensive pro and con list for each.
1. What do you see as the status of current LTE deployments and timelines?
Long Term Evolution (LTE) is certainly leading in the U.S., where spectrum auctions have concluded. Both Verizon and AT&T have publicly stated plans for LTE services. In Europe, there has been harmonization around the 2.6 gHz spectrum band, and quite a bit of promise for the ‘digital dividend’ band, typically in the 800 mHz range. Many countries have yet to auction off the spectrum, yet some operators are currently laying the foundation for LTE service availability in 2011.
2. What is the problem with voice and SMS over LTE?
Today’s mobile voice network is based on circuit technology. Billions of subscribers place trillions of minutes of calls across a vast interconnected web of circuit voice infrastructure. This network includes interconnections between operators in-country as well as across the globe, and has the ability to support roaming, billing and a host of other features (voice mail, SMS, pre-paid, etc.). Today, it is estimated that voice and SMS accounts for approximately 86 percent of the mobile industry’s $884 billion dollar services market (Pyramid Research, June 2009).
In Global System for Mobile communication (GSM), the network relies solely on circuit connectivity. In 3G, a handset has both a circuit connection (for voice and SMS) and a packet connection for IP-based services/applications. But in LTE, the circuit connection has been dropped and the connection to the handset is purely packet. Thus, there is no native circuit voice or SMS capability built into LTE. Operators must develop some type of overlay technology to provide voice calling.
The ‘conventional’ wisdom is that operators will invest in new packet voice infrastructure, specifically IP Multimedia Subsystem (IMS). However, there is a fairly significant cost to investing in a new IMS telephony system, so for many mobile operators, IMS telephony is still many years away.
The VoLGA Forum was created to develop an opportunity for operators that leverages their existing circuit voice networks and can provide a smooth transition to IMS when it arrives.
3. What are the competing solutions in the market?
There are three specific options available today for operators -- CS Fallback, VoLGA and IMS Telephony. Nokia Siemens Networks also announce an approach called “Fast Track” voice over LTE; however, currently without operator or vendor support, its success as a viable solution in the market remains unclear.
4. What are the pros and cons of these approaches and how do they meet real operator demands?
Both CS Fallback (CSFB) and VoLGA rely on the existing circuit voice network, whereas IMS is the longer term evolution. Let’s compare CSFB and VoLGA to begin.
It might be helpful to have a short overview of how each technology works.
In a VoLGA solution, there is a controller (VAN-C) which connects to the operator’s existing mobile voice switch. The controller scales up as traffic increases. The VoLGA controller takes all the standard circuit voice and SMS messages, puts them into IP packets, and routes them over LTE to the phone. On the phone, the ‘dialer’ sends and receives the exact same messages it would over GSM or 3G. Therefore the user gets the exact same set of services and user experience when on all three networks (GSM, 3G, LTE). Providing a common and consistent user experience across networks is a key requirement for mobile operators.
In a CSFB solution, the idea is that the handset ‘falls back’ to GSM when it needs to make (or receive) a call. To do this, the operator’s entire circuit voice network must be upgraded to add a new feature to ‘page’ the handset when it’s on LTE and tell it to ‘fall back’. Clearly this is *not* a voice over LTE solution as the voice isn’t being carried over LTE; it’s still carried over the GSM network. There are severe implications for the user experience because the handset needs to constantly switch between LTE and GSM networks.
The table below highlights these issues:
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CS Fallback |
VoLGA |
| Path to IMS |
- No support for combinational IMS/RCS + voice over LTE
- No validating LTE network QoS capabilities
- No verification of IMS telephony plumbing features
|
- Supports combinational IMS/ RCS + voice over LTE
- Delivering voice over LTE validates LTE QoS capabilities
- VoLGA uses IMS Telephony plumbing features RFC 4867, RoHC
|
| User Experience |
- Minimum 30% increase* in call setup times (requires a ‘blind fallback’ to achieve 30%, delay is higher if handset must do network scan before fallback)
- No support for simultaneous voice/ data over LTE
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- Call setup times as good as 3G
- Supports simultaneous voice/ data over LTE
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| Deployment cost/ complexity |
- Requires upgrade to MSC network
- Dependent on MSC vendors to implement (home and visited networks)
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- External controller minimizes impact to core network
- Controllers available from variety of TEMs
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| Support for LTE femtocells |
- “Falling back” to GSM network negates value of LTE femtocell
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- Voice services delivered natively through LTE femtocell
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As shown in the table, an ‘evolution to IMS’ is considered a key advantage for VoLGA. Thus comparing IMS to VoLGA doesn’t make a lot of sense. Plenty of operators will get to IMS when it’s ready; the ‘problem’ is that there is no solution for the next several years.
5. If LTE is still a ways off, why must operators address the voice over LTE problem today?
Well, depending on your perspective, either LTE will be here in 2011 or it’s still a ways off. Either way, everything in the mobile world takes time and deploying LTE will be a gradual process. Companies are already in the planning stages for handsets to be delivered at the end of 2011; therefore, having code and specifications available today is critical for products that will be available in the beginning of 2012.
More holistically, why would an operator charge into LTE without knowing *exactly* what their voice strategy is? After all, voice accounts for 86 percent of operator revenues. That’s like changing jobs without knowing what the salary will be. Operators are preparing to make massive investments in LTE and developing a voice strategy is imperative.
Steve Shaw is vice president of corporate marketing for Kineto Wireless and is responsible for the market development and corporate communication strategies of Kineto's product lines. A frequent speaker, blogger and general evangelist for the fixed-mobile convergence and UMA/GAN industries, Steve has nearly 20 years experience in product, marketing, and business development roles with telecommunications companies. He holds a bachelor's degree in computer science from University of Southern California.
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