Q. How do 3G (third generation) data networks of the cell phone companies compare when it comes to Internet speed?
A. The 3G cell speeds can vary because of distance from a cell tower or how many other people are using the network. But they're usually less than the advertised maximum speed.
Last spring, a Computerworld magazine study of cellular broadband speeds for laptops found AT&T was the fastest. But it also found average 3G network speeds were less than half the "peak" speeds.
In the test, AT&T's average download speed was 755,000 bits per second (47 percent of its peak speed), Verizon Wireless' average download speed was 592,000 bits per second (46 percent of peak speed) and Sprint's average download speed was 494,000 bits per second (41 percent of peak speed). That put all three below the definition of broadband used by research firm Gartner, which is a download speed of more than 1.5 million bits per second.
Another 2008 comparison (www.mobile-broadband-reviews.com/wireless-broadband-reviews.html) shows AT&T, Verizon and Sprint in a dead heat for average download speeds. (T-Mobile lagged behind.) But Verizon was given the edge for "bigger bursts of speed nationwide."
As recently as last month, Gartner said average cellular broadband speeds are often 300,000 to 700,000 bits per second slower than advertised top speeds.
Bear in mind that these speeds are constantly being increased, so who's faster is a moving target.
Q. Recent news reports talked about a computer worm that could affect 30 percent of Windows-based computers. How can I tell if my Windows XP system has been protected?
A. If you have antivirus software, it should be protecting you against the Conficker or Downadup computer worm. (A worm is a self-copying program that works without you taking any action.)
Most antivirus software is updated online frequently, so the chances are that you've been protected since late November, the month the worm was discovered. To make sure, click the antivirus icon on your PC's toolbar to see if the software is up to date.
Even though you're probably safe, the worm still infects an estimated 3 million computers worldwide. Microsoft, whose Windows software was affected, is offering a $250,000 reward for information leading to the arrest and conviction of the worm's creators.
(Steve Alexander covers technology for the Star Tribune. E-mail your technology questions to steve.j.alexander(at)gmail.com or write Tech Q&A, 425 Portland Ave. S., Minneapolis, MN 55488-0002. Please include a full name, city and phone number.)
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