Tellabs Blog

What if you could get Internet or access applications on your mobile phone — but couldn’t make a voice call?

It seems silly. Yet as data and application usage (and subsequent “network chattiness”) increases, operators have been more focused on data in their networks — especially LTE networks. As LTE becomes a mainstream technology, it must quickly address the most basic, yet the most important, service required of a mobile phone: the voice call.

LTE offers scalability and cost advantages, but it doesn’t come without challenges. LTE’s data-centric design differs from service-centric 2G and 3G mobile networks. So, every mobile network operator (MNO) must choose between service delivery options because there is no well specified mechanism to deliver voice services over LTE networks.

Voice service options
The current “default option” for mobile network operators is the IP multimedia subsystem (IMS), which requires a network-wide investment in a new service core. MNOs choosing this option also face interoperability challenges. Additionally, the operator must have appropriate handsets and network equipment to support IMS.

Through the GSMA’s VoLTE initiative, a minimal set of requirements necessary to support voice and SMS has been defined. But not every MNO will be able to justify the investment in a new service core simply for voice and SMS. VoLTE is currently the leading contender for deploying voice over LTE networks.

Without ways to define, develop and monetize IMS-based services, operators may look for other options. These options include circuit switched fallback (CSFB), voice over LTE via generic access (VoLGA) or dual radio (a.k.a simultaneous radio). These are often referred to as “transient” options because they enable mobile operators to continue to provide voice services over their legacy 2G or 3G service core with some additional or upgraded equipment. Transient options are not a permanent fix. All the options have a key deficiency: they do not support rich communication such as video calling or instant messaging.  They also have deficiencies involving call setup, network complexity, and handset battery life.

The OTT wild card
A final option is to use voice over IP from an OTT service provider such as Skype, Google, or Yahoo. An OTT service provider can offer rich multimedia services over virtually any IP technology. However, many MNOs consider OTT VoIP to be a competitive threat, and may use its existence as a justification for investing in IMS.

Those MNOs actually may be able to justify the investment in IMS as a means of putting themselves in the strongest competitive position vis-à-vis the OTT VoIP providers. The question remains whether LTE network infrastructure can truly add value in delivering voice and other rich multimedia services, or if it will relegate itself to being a dump pipe.