For a few years now, you’ve heard the term “3G” used to describe data services on cellular networks. Now, all of a sudden, there is a new term showing up. Ads on TV, in magazines and newspapers, web sites, billboards, and anywhere else you can imagine are starting to feature new “4G” service from Sprint.

You may find yourself wondering “Do we really need an additional G? What is ‘G’ and why do I need four of them? Are the other carriers going to roll out an extra G for their customers too?”

First and foremost, “G” stands for “Generation”. The first generation cellular technology was the original analog cell phone system that became popular in the 80’s and early 90’s. The second generation transitioned us from analog to digital cell phone service in the late 90’s. The third generation, or “3G” technology added support for higher data speeds that have enabled the rich mobile experience we have grown accustomed to on our smart phones.

Quite simply, “4G” refers to the fourth generation cellular network technology that is optimized for high speed internet traffic. I know, this is an extreme simplification, but I don’t want to get hung up on the formal technical definition of 4G as set forth by the ITU. For the overwhelming majority of cell phone users, this is a good enough working definition to understand what the carriers are talking about.

Sprint is rolling out a 4G technology called WiMax on their network. This network upgrade will allow new devices to connect to the internet at speeds up to 20 Mbps. What this really means is that WiMax will allow mobile connections at speeds comparable to, or faster than many people’s home internet connections.

Sprint won’t be the only wireless carrier in the US to offer 4G service. AT&T, Verizon Wireless, and Tmobile are also planning to roll their own 4G network upgrades. The catch though, is that AT&T, Verizon, and Tmobile are planning to roll out a different 4G technology called LTE. LTE offers theoretical speeds of 56 Mbps, but real world connections will probably not reach this limit.

At this time, Sprint has a head start. They have already rolled out WiMax in a handful of markets around the US, and will expand their service throughout 2010. Verizon Wireless will be rolling out LTE starting this year, and plan to finish upgrading their network bo 2013. AT&T plans to start rolling out LTE on their network in 2011. Tmobile plans to launch their LTE network in 2011.