AT&T Wireless last week anticlimactically launched Universal Mobile Telecommunications Service in four markets here in the U.S.

I say "anticlimactically" because while UMTS uses 3G technology sanctioned by the International Telecommunications Union (ITU), AT&T Wireless' service runs at relatively low speeds and is not yet backward-compatible with the carrier's fairly ubiquitous Enhanced Data for GSM Evolution (EDGE) offering. (See my second newsletter from last week.)

However, if you require service only in Detroit, Phoenix, San Francisco or Seattle, and are willing to invest in a new $150 modem or $300 handset, plus pay $79.99 per month for an unlimited data service (standard for such business plans), you can get twice the data rates of AT&T Wireless' existing service.

The carrier says its UMTS service runs at 220K to 320K bit/sec with bursts to 384K bit/sec. But should you roam beyond the metro areas mentioned, you won't fall back to the 100K- to 130K-bit/sec EDGE service; you will fall back to the carrier's older 20K- to 40K-bit/sec General Packet Radio Service (GPRS) data service instead.

Weston Henderek, a senior analyst at Current Analysis, puts it adroitly: "The main candidates for 3G networks are road warriors with extreme connectivity needs. AT&T Wireless' main advantage for them is its EDGE network, because it has decent connectivity - in all its top markets - that Verizon and Sprint have yet to match. The UMTS network doesn't capitalize on the EDGE network."

AT&T Wireless did say it will roll out UMTS in Dallas and San Diego by year-end for a total of six markets. But, gosh, EDGE is available in 7,500 U.S. cities and towns plus other countries now. And it reportedly bursts to 200K bit/sec, which is getting close to the low-end speed of the UMTS service. All this is, well, a real edge.

Consumers can use the new network for mMode, the U.S. version of the popular Japanese i-Mode voice, messaging and gaming service offered by NTT DoCoMo. They can add unlimited UMTS-based mMode to a monthly voice plan for $24.99 and pay another 5 bucks for streaming content services provided by RealNetworks.

AT&T Wireless seemed to be rushing to fulfill a commitment to DoCoMo, a shareholder, to launch UMTS-based service in four cities this year before its merger with Cingular Wireless goes through. Cingular has said it will begin UMTS trials in Atlanta this summer.

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.