To clarify a tad bit more. Sprints 4G is actually a completely seperate network using WiMax as the source. So technically its not 4G at all due to it not being an upgrade to an existing network. However it is a faster thru put of data speeds and can be considered 4G.
This page will explain a lot of the technical jargon to most people.
3GPP Long Term Evolution - Wikipedia, the free encyclopedia
The good news is WiMax is covered under the LTE conversion. "Part of the LTE standard is the
System Architecture Evolution, a flat
IP-based
network architecture designed to replace the
GPRS Core Network and ensure support for, and mobility between, some legacy or non-
3GPP systems, for example
GPRS and
WiMax respectively"
So that is what allows Sprint to call it a 4G network.
Verizon and MetroPCS have launced the begining of LTE which is the first of many upgrades to bring their system to a true LTE system. LTE Advanced will actually be considered 4G. Thats covered here,
"The main advantages with LTE are high throughput, low latency, plug and play,
FDD and
TDD in the same platform, an improved end-user experience and a simple architecture resulting in low operating costs. LTE will also support seamless passing to cell towers with older network technology such as
GSM,
cdmaOne,
UMTS, and
CDMA2000. The next step for LTE evolution is LTE Advanced and is currently being standardized in 3GPP Release 10."
Eventually all the carriers in the US will be on the same page.
Right now its CDMA2000 or GSM / UMTS