AT&T Wireless Services Tuesday launched a third-generation mobile data service in Detroit, Phoenix, San Francisco and Seattle, offering a claimed average of 220K bit\/sec to 320K bit\/sec of data throughput to two handset models and one type of modem.The Wideband Code Division Multiple Access (WCDMA) technology is also being rolled out in San Diego and Dallas for expected commercial launch by the end of the year, the Redmond, Wash.-based mobile operator said in a statement.Customers of AT&T's service will be able to use streaming audio and video services, create and share video clips and use business applications over the new high-speed service, the carrier said. The service costs $25 per month on top of a voice plan for consumers, and for business customers it costs $80 per month in addition to a voice plan.WCDMA, also known as\u00a0Universal Mobile Telecommunications System, is the 3G migration path from Global System for Mobile Communications (GSM), the 2G cellular technology used by AT&T Wireless as well as by Cingular Wireless, which agreed in February to acquire AT&T. That deal is expected to close by the end of this year. GSM is the most widely used cellular technology in the world, but in the U.S. and some other countries it faces competition from CDMA.The next-generation cellular technology for CDMA, called Evolution-Data Only (EV-DO), got a head start on WCDMA in the U.S. last year when Verizon Wireless launched services in San Diego and Washington, D.C. That service is still available only in those two markets, but Verizon expects to make it available to one-third of its customers by the end of this year. Sprint expects to begin rolling out EV-DO later this year and offer it nationwide by early 2006.The claimed speed of EV-DO is a bit higher than for AT&T's network, at an average 300K bit\/sec to 500K bit\/sec. The peak rate of EV-DO is 2.4M bit\/sec, compared with a peak rate of 384K bit\/sec for WCDMA. But AT&T's network could be upgraded "easily and cost-effectively" to High Speed Downlink Packet Access (HSDPA), with a peak data rate of 14.4M bit\/sec, according to the statement. The change would be primarily a software upgrade, according to AT&T spokesman Ritch Blasi. HSDPA is still in the testing stage, he said.