Of course, Clearwire's WiMax network is far from built out--it's currently only in --but Sprint could earn bragging rights and maybe lure early adopters by introducing the first 4G handset. There are risks in being too early, however, particularly if spotty 4G coverage disappoints Sprint's customers.

Benefits of 4G

The Clearwire WiMax network is theoretically up to 10 times faster than today's 3G systems, according to Sprint. For example, on Sprint's 4G network are 3 to 6 megabits per second versus a relatively poky 600 Kbps to 1.4 Mbps via 3G. Only a few devices currently work on the Sprint 4G network, including the .

Sprint's 4G window of opportunity is small. Verizon Wireless has announced plans to roll out LTE service in 25 to 30 U.S. markets by the end of the year, and will likely debut its 4G service in 2011.

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