The GSMA VoLTE (Voice over LTE) initiative was formally announced on 15th February 2010. In establishing the VoLTE initiative, GSMA has adopted the work of the One Voice Initiative* as the basis of the work to lead the global mobile industry towards a standard way of delivering voice and messaging services for Long-Term Evolution (LTE).
Using IP Multimedia Subsystem specifications developed by 3GPP as its basis, GSMA have expanded upon the original scope of One Voice work to address the entire end-to-end voice and SMS ecosystem by also focussing on Roaming and Interconnect interfaces, in addition the interface between customer and network.
Source: http://www.gsmworld.com/our-work/mobile_broadband/VoLTE.htm
Using IP Multimedia Subsystem specifications developed by 3GPP as its basis, GSMA have expanded upon the original scope of One Voice work to address the entire end-to-end voice and SMS ecosystem by also focussing on Roaming and Interconnect interfaces, in addition the interface between customer and network.
Source: http://www.gsmworld.com/our-work/mobile_broadband/VoLTE.htm