Sprint is not only working on a nationwide 4G mobile network for continental US, it’s also bringing a new toy to run it on.

Sprint Nextel has been planning to build its 4G mobile network via WiMAX for at least a year. It seems right after delivering its 3G network, EVDO (Evolution Data Optimized), the company almost immediately started development in the next frontier. Sprint hopes to have it available to 100 million Americans sometime in 2008.

The WiMAX 4G (IEEE 802.16e) network will start in Chicago, Baltimore and Washington, DC. By the end of 2008 it hopes to have hit 19 more markets in the US with help from partners in the 4G rollout including Motorola, Samsung and Nokia.

The new network will support peak download speeds of 20 Mbps (megabits per second) and average data rates between 1 and 4 Mbps. This is a significant step up from current 3G technologies which give us average download speeds of 400 to 700 Kbps. 4G mobile networks will give North Americans a whole new set of wireless capabilities like mobile TV.

Sprint will also bring a WiMAX enabled version of the Nokia N800 Internet Tablet to the US. We can’t have an awesome, cool 4G WiMAX mobile network and nothing to play it on. Despite my previous grumblings about the troubles with the Tablet form factor, Sprint’s new version of the N800 will probably set itself apart with voice communications and high speed mobile capabilities previous tablets have lacked.