How 4G Works
Offering cell phone data speeds several times faster than you're used to, 4G is expected to start heating up the airwaves in the next year or so.
As for what 4G is — basically, there's nothing simple about 4G expect for the name, which refers to fourth generation cell phones. First-generation cell phones were basic analog units, based on a scheme that Alexander Graham Bell would recognize. Second-generation cell phones were digital units; third-generation (3G) were faster digital units; while fourth generation (4G) opens the door to broadband speeds.
What that means: You could, in theory, watch the Superbowl in HD on a 4G phone while downloading email and talking to a like-minded fan on the phone. In theory.
As for how 4G works, the simple answer is OFDM (orthogonal frequency-division multiplexing.) Translation: the signal is divided into parallel data streams carried over closely-spaced radio sub-channels, to be reassembled at the far end. The approach is already used in certain kinds of WiMAX and Wi-Fi systems, which let you get on-line at Starbucks at a reasonable speed.
How fast is 4G? The maximum speed is usually given as 100 megabits per second downstream (from the network to you) and 50 megabits per second upstream (back to the network). By comparison, an HDTV signal consumes about 25 megabits per second.
But 100 megabits down and 50 megabits up are purely theoretical numbers, cautions Fred Campbell, president of the Wireless Communications Association International (WCAI) in Washington, DC. "In the real world you don’t reach maximum speeds, because in the real world you have trees and buildings and distance attenuation and moving receivers and bandwidth limitations," he told TechNewsDaily.
Campbell pointed to a network test several months ago by a cell phone carrier whose technicians drove around in cars, averaging 35 mph, to see what data speeds they could get. Their 4G gear saw average download speeds of 6 megabits, while their 3G gear was averaging 1.5 megabits.
However, steady enhancements can be expected to gradually drive real-world speeds towards the maximum, Campbell added.
The first 4G networks were unveiled last month in Stockholm, Sweden, and Oslo, Norway. Campbell expects to see 4G rollouts in the U.S. to start this year, with most of the activity in 2011.