AT&T late yesterday answered questions by confirming that it had completed its 850MHz 3G upgrade in New York City. Company representative Mark Siegel told PCMag that the area should now have access to the lower frequency for HSPA service and see much better performance as a result. He also acknowledged that San Francisco upgrades were underway but didn't estimate how soon the area would get the extra bandwidth.

Subscribers in both cities, as well as some other major cities, have previously complained of dropped calls, slow or non-existent data and delayed text messages due to the oversaturation of the 1,900MHz band, which in those areas was the only frequency AT&T was using for 3G service. The older spectrum by itself has left little room for the heavy traffic that reached the network after the iPhone 3G's launch last year. Its density also makes it more susceptible to interference from buildings and thus limited AT&T's reach.

Siegel argues that the late arrival of 850MHz 3G in these key areas stemmed in part from having to previously reserve it for TDMA, the old analog cellular format that was finally discontinued last year.

Updates to 850MHz in most if not all of AT&T's service area should continue over coming months but will also be supplemented by a 7.2Mbps rollout starting late this year that should double the theoretical speeds of the provider's 3G service on devices that support it, like the iPhone 3GS. It plans to complete this update in 2011 but should also add 21Mbps HSPA+ and, in 2011 or later, 4G service through LTE.