Straight talk about cellphone ‘Gs’

How much faster is 3G than 2G? Where can you get 4G? And what is 2.5G?

China issued long-awaited third-generation mobile phone licenses in January, a move that will pour billions of dollars into new networks as consumers buy video- and Internet-enabled handsets.

Speedy 3G cellphone service, the kind that smart phones crave, can feel a bit sluggish if you live in Baltimore. Sprint picked the city to test out its “4G” network. To explain the difference between the many Gs that litter cellphone marketing, let’s start with the baseline.

2G: Nearly all cellphones in America run off at least 2G – or “second generation.” But the term encompasses two different technologies. Verizon and Sprint Nextel use CDMA service. T-Mobile and AT&T prefer GSM, which can be identified easily by the SIM card hidden underneath each phone’s battery. The two services are very similar but not compatible. This can make life frustrating for travelers, since most of the world relies on GSM, while the US offers better CDMA coverage, especially in rural areas.

2.5G: As America transitions to 3G service, phone companies have invented ways to amp up their regular connections, creating what many call a “half” generation. Basic 2G tops out at 144 kilobits per second – fast enough to download songs in a matter of minutes – but 2.5G EDGE nearly triples that speed. Not bad. However, true 3G surpasses 2,000 kilobits per second.

It should be noted that these numbers are under “ideal conditions,” something that only those in lab coats get to enjoy. The rest of us need to deal with hills and valleys, everyone else hogging the system’s attention, and the cell tower trying to follow you while you’re on the go.

3G: Today’s smart-phone features weren’t really practical until mobile speed limits reached “third generation.” Now, songs and streaming video download in seconds. AT&T is ratcheting up its 3G network from 3,600 kilobits per second to 7,200 – and will tiptoe toward 20,000-kilobit speeds this year.

4G: Technology companies like to label things long before they actually come out. Better to brand an emerging standard quickly, than to wait for others to get their hands on it. That’s the case with 4G. Right now, the term doesn’t really mean anything other than “faster than 3G.”

Sprint calls itself “the first 4G network.” Its Baltimore service uses WiMAX, which acts like Wi-Fi but covers much broader distances.

While its speed rivals that of home Internet connections, we may look back on WiMAX as 3.5G. For one thing, very few phones recognize WiMAX. And engineers in Europe and Asia are hard at work planning a 4G mobile service that will blaze past Sprint’s current service.

Their list of “next generation” objectives has some impressive bullet points, such as speeds 10 to 50 times faster than 3G (think 100,000 kilobits per second – and perhaps even zippier if you’re standing still.

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