Fourth generation wireless technology (4G) offers faster data transmission speeds which is critical to smartphones or computers using tethering to access the internet.

This week Sprint, the third largest carrier in the U.S., announced that three more cities are covered by its 4G network.  The additions to the official coverage list are Boston, MA; Daytona Beach, FL; and Providence, RI.  With the additions, Sprint now covers over 40 million people in approximately 40 large U.S. cities.

Sprint is betting on the 4G tech WiMAX.  Verizon, AT&T, and T-Mobile have all pledged to support a rival technology -- LTE -- though only Verizon has begun to implement an LTE test network.  Sprint says it won't rule out developing an LTE network at some point, but for now thinks WiMAX is the superior tech. 

Sprint has finally got its act together and released a pair of 4G-capable phones.  Its HTC EVO 4Gwas the first 4G phone to hit.  Now the Epic 4G is offered as well, giving buyers yet another option.  And Sprint also offers a 4G ready USB modem and wireless hotspot, via a partnership with Sierra wireless.

T-Mobile, the fourth largest carrier in the U.S. is opting for a different approach.  Instead of a direct leap to a 4G tech like LTE, its rolling out a "3.5G" technology HSPA+ technology.  HSPA stands for High-Speed Packet Access, and HSPA+ combines the advances of HSDPA (faster packet downloads) and HSUPA (faster uploads).

The company claims HSPA+ offers "4G-like" speeds.  While some (namely AT&T) take issue with these claims, the tech is much faster than 3G and T-Mobile is rolling it out at a more rapid speed than Sprint or Verizon's 4G rollout.

Of course there's one minor problem -- the company currently has no HSPA+ phones.  The first to land will be the Android G2.

But for those with T-Mobile wireless modems, they can now get HSPA+ speeds in nine new cities -- Boston, MA; Erie, PA; Fresno, CA; Palm Springs, CA; San Diego, CA; Miami, FL; Richmond, VA; Spokane, WA; or Topeka, KS.

Neville Ray, chief network officer for T-Mobile USA comments, "Our new network offers today’s available 4G speeds to more people than any other wireless network in the country and we’re not done yet.  We are now on pace to more than double our HSPA+ footprint – reaching more than 200 million people by this year – with plans to offer 42Mbps theoretical speeds in 2011."

Its obvious there is demand for 3.5G and 4G technologies.  What's frustrating is that while Sprint, T-Mobile and others charge ahead with their deployment, there still are relatively few compatible handsets (or none in T-Mobile's case).