Choosing the voice technology within 4G radio access is a decision of which path to take, and it is generally not the same path for every operator.
Although there is no unique recipe for the short-term path, it is possible to design a solution based on an IP Multimedia Subsystem (IMS) as a long-term target architecture for the delivery of voice services and that's what David Eror, CCNP and CCSI at NIL Data Communications is talking about in March IP corner article.