what is VoLGA and how it is works in lte to serve voice requirement ?

Question

How does it work actually and why it is introduced in lte network ?

Answer 1

VoLGA stands for "Voice over LTE via generic access". It is used to provide voice call via LTE network. There is a node VANC (VoLGA access network controller) , which has SGi interface with PGW of LTE network. VANC is a gateway. It is responsible to make connection with circuit switch network and lte session network.
whenever a voice call is coming. it reaches at VANC. VANC contact to some other network nodes to check the user's subscription and it prepares an IP packet send to PGW. This ip packet has ipsec. so PGW just passes this IPsec packet to SGW. SGW passes this packet to eNB and it reaches to UE. In this way voice call is supported. VANC has capability to convert circuit switch to packet switch and vice a versa.

Answer 2

VoLGA (Voice over LTE via Generic Access) is, or rather was, an approach to use GSM and WCDMA circuit-switched services over LTE. Depending on the speaker, VoLGA was proposed as an in interim solution before IMS VoLTE, or as an alternative to IMS VoLTE. Since then industry, and most importantly operators, have clearly indicated their support for IMS VoLTE, as defined by GSMA.

Perhaps the main drawback in the VoLGA approach was to tie LTE/EPC into GSM/WCDMA circuit core for years to come. This would have been strategically difficult choice, considering that LTE/EPC was specifically designed to be PS-only, allowing both voice and data to be served over packet core.