So, what is 4G? Fourth-generation, or 4G, technology is the moniker the nation's cell-phone providers are using to promote the latest upgrades to their network infrastructures. The main advantage of 4G is improved performance: Sprint says that its WiMax 4G network is up to ten times faster than its 3G service, with average download speeds of 3 to 6 megabits per second.

Translated, that means quicker file downloads and the ability to stream movies and TV shows in high definition. A peppy 4G connection opens the door to new capabilities, too. For instance, the Samsung Epic 4G smart phone ($250 with a two-year Sprint contract) can act as a hot spot, allowing up to five Wi-Fi devices to connect to the Web via the handset's 4G link.

Who else offers it? AT&T, MetroPCS and Verizon Wireless are ramping up their 4G networks. Verizon boasts that its 4G network, with average download speeds of 5 to 12 megabits per second, is faster than Sprint's network (real-world performance, of course, will vary). Verizon currently offers 4G in at least 38 U.S. markets, and its 4G network will be available across its entire 3G coverage area by 2013. AT&T expects to launch its 4G in mid 2011 and reach 70 million to 75 million people by the end of the year. T-Mobile claims that its enhanced 3G HSPA+ network will deliver 4G-like speeds. MetroPCS plans to extend 4G to its full, 14-market region early in 2011.

How much will I have to pay for service? As with most cutting-edge technologies, you'll pay a premium to upgrade. MetroPCS's service plans range from $55 to $60 a month, comparable to the carrier's priciest 3G offerings. AT&T and Verizon hadn't announced 4G pricing at press time. Sprint charges Epic and Evo users an extra $10 per month, even if they don't live in a 4G coverage area. Plus, current phones (3G or older) aren't 4G-compatible, so you'll have to buy a 4G-ready handset. Selection is limited and prices are high, but that should change as more 4G models arrive on the market. In addition to the Epic 4G, Sprint sells the HTC Evo 4G, which is $200 with a two-year contract. (A 4G phone will work on a 3G network, but at 3G speeds.) MetroPCS offers one 4G phone, the Samsung Craft ($350, with no contract).

Is 4G worth it? If you watch a lot of HD movies or transfer massive files – such as videos you shoot with your phone's camera – a speedy 4G connection is a boon. Sprint's 4G customers get another perk: They can send and receive an unlimited amount of data each month. Sprint's 3G users are capped at 5 gigabytes, even with an "unlimited" plan. (Metro-PCS's unlimited 4G plans also have no cap.) If you plan to set up a 4G hot spot at home or work, a truly unlimited data plan has its advantages.

Can I get 4G where I live? The 4G rollout will take time. If you live in an urban area, your chances of getting 4G coverage are better than if you live out in the country.

Reprinted with permission. All Contents ©2011 The Kiplinger Washington Editors. www.kiplinger.com.