• 1
• 2
• 3

LTE’s strength is also its weakness: It’s all IP. There is no baked-in support for voice. In order to make LTE voice work, there are essentially four choices at this time (summed up nicely on the Teknocrat blog):

• Circuit switched fallback (CSFB), which is a temporary solution based on 3GPP standards.
• Voice over LTE via Generic Access (VoLGA), which is also a temporary solution and offers little promise of developing into a full multimedia service.
• OTT applications like Skype, which raise access/permissions issues for many carriers And,
• IMS

This is an issue that was addressed by the One Voice initiative orchestrated through the GSMA in 2009- 2010. This initiative, composed of AT&T, Orange, Telefónica, TeliaSonera, Verizon Wireless, Vodafone, Alcatel-Lucent, Ericsson, Nokia Siemens Networks, Nokia, Samsung and Sony Ericsson, used current open standards to define the minimum mandatory set of functionality for interoperable IMS-based voice and SMS over LTE. The recommendations of the members of this initiative were folded into the broader VoLTE program in early 2010.



In VoLTE, IMS has found, if not its rebirth, definitely its ride into the future:

“Our 2011 survey results show that fixed-line VoIP continues to be the primary service deployed over IMS,” said Diane Myers, Directing Analyst for VoIP and IMS at Infonetics Research in a statement released alongside that firm’s IMS global provider survey. “However, there also is a notable continuing shift toward IMS in the mobile world, evidenced by the rising number of mobile services planned over IMS by 2013: 78% of our respondents will have a mobile-specific service such as mobile messaging, VoLTE (voice over LTE), RCS (Rich Communication Service), and/or VoIP over 3G by 2013, up from 35% today.”

According to that survey, the leading factors driving IMS deployments are the desire to possess the ability to offer converged services and LTE deployment. This may be partly driven by pressure from the GSMA VoLTE initiative to avoid the aforementioned temporary solutions whenever possible (solutions like CSFB and VoLGA, which could prove difficult and costly to remove).