I'm sure you are all familiar with 4G cellular technologies which are being deployed by Sprint and soon by Verizon and AT&T... Here is a little insight on how each is developing their network--
Sprint first launched their 4G service in Baltimore in December 2008, promising speeds of up to 12 Mbps (In reality, that means 2-3 Mbps average). CDMA carriers are using WiMAX technology; an old technology that broadcasts using microwave links over a wide area. Networks like these have been deployed as early as 2004.
So why did Sprint decide to go with it? Less work and faster deployment, obviously. It's old technology!
Verizon has their eyes set on LTE, or Long Term Evolution networks, which entail plans to expand and enhance current cellular technology. Deployment involves upgrading and replacing existing cells, erecting new sites, and launching new equipment to support the network (all that was involved in 3G too). LTE promises inexpensive opportunity for expansion and speed increase. A wiser choice over WiMAX. While Sprint is currently at an advantage for taking advantage of old technology as a quick way to market 4G and make some extra money, they plan to invest in the development of an entirely new network in the future and claim that WiMAX is just a shortcut.
Now onto AT&T... They are also taking advantage of LTE technology on their GSM network; however unlike Verizon, they have no plans on turning their back on 3G and even 2G. AT&T understands that launching an entirely 4G network is very time consuming, so they plan on taking advantage of the expansion opportunities that their 2G EDGE (which compares to Verizon's 3G network and its true speed is misconceived in their advertising campaign based on the way AT&T markets the technology) and 3G HSPDA network. They see opportunity to expand their 3G network to speeds up to and exceeding 7 Mbps. Through HSPDA+, their network has the ability to support speeds of up to 21 Mbps using technology that they already have their hands on and is on the market! Additionally, they are also able to merge both 2G and 3G technologies to offer customers increased speed and reliability. This is their short term focus, and I'd say that this approach is the smartest and will benefit them in the end, when competing with other carriers and also financially because they're able to save money in the deployment process.
More information about AT&T's plans can be found here--
http://www.engadget.com/2010/03/12/atandts...tain-locations/