Breaking down 4G vs. 3G cellular networks

What is 4G?

With Sprint and Verizon Wireless launching fourth-generation high-speed networks in the Denver area this month, the term has dominated cellphone marketing recently and will continue to do so next year, when Apple is expected to release a 4G-capable iPhone.

The differences between 4G and predecessor 3G, which surfaced commercially nearly a decade ago, are fairly substantial. Sprint and network partner Clearwire have both generations of wireless technology atop a luxury high-rise near Washington Park in Denver.

The 3G cell site is the equivalent of an 8-foot- high storage cabinet filled with computer equipment. The 4G site is about half the size and consumes about five times less power.

3G networks

Clearwire operations manager Mark Severseike displays a 4G cell, with a much bulkier 3G cell in the background. Clearwire is majority-owned by Sprint. (John Prieto, The Denver Post)

carry voice and Internet traffic. 4G networks are built specifically for Internet content, so cell sites don't include equipment to route phone calls, reducing their footprint and creating energy efficiencies. That also positions 4G networks to better handle high-bandwidth activities.

"These are really key differentiators in the next generation of wireless networks," said Mark Loarie, director of technical operations in the Rockies for Clearwire.

Sprint is the majority owner of Clearwire, which is building the WiMax network that Sprint uses for its mobile broadband service.

When a user makes a call with Sprint's 4G cellphones, that traffic travels through 3G cell sites. The device uses 4G connections for Web browsing, video streaming and other Internet-related services. Clearwire has nearly 200 4G sites along the Front Range.

Of course, the most significant difference between 4G and 3G for consumers is speed. Sprint 4G offers Internet download speeds that are up to 10 times faster than 3G service, generally ranging from 3 megabits per second to 6 Mbps. Speeds can reach 12 Mbps, comparable to standard residential broadband service, depending on network congestion and how far a user is from a 4G cell site.

There are also differences between 4G technologies. Verizon's Long Term Evolution 4G service has faster average download speeds, advertised at 5 Mbps to 12 Mbps, and uses spectrum that can better penetrate buildings. Sprint and Clearwire's WiMax service uses a frequency with more capacity, allowing them to offer unlimited data plans.

Until recently, Sprint's and Verizon's networks didn't officially qualify for 4G classification, previously reserved for technology not yet commercially available.

But the International Telecommunication Union, which handles such designations for the industry, said this month that WiMax and LTE could both be recognized as 4G. The agency also said upgraded 3G networks could use the designation.