LTE is great, but will not be rolled out for years to come.
WiMax chipsets are ready, and the Hardware is in a very advanced stage of testing.
i predict that in under a year we will see vast WiMax networks, particularly in Asia. 
obviously, US providers don't feel like spending hundreds of millions of dollars to upgrade their huge networks. WiMax will first be deployed in areas where traditional cell networks are absent or under-developed.
perhaps LTE will be ready in 4 years. but seeing as how WiMax was delayed by problems, LTE will probably also be.

Isn't that a way to prevent mobile VOIP ?.

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