In its Monday announcement the Apple iPhone's exclusive US carrier AT&T said that it has completed its upgrades of 3G network in New York; and claimed that the upgrade project, over the last six months, has resulted in a steady improvement of service in Manhattan, Brooklyn, Queens and the Bronx.

AT&T customers in New York had been frequently complaining about the evidently deplorable quality of the carrier's 3G service, which has been marred by high dropped calls rates and sluggish downloads, ever since the iPhone launch three years back.

In fact, wireless coverage has been noticeably problematic in a number of metropolitan areas across the US, largely because of a lethal combination of data-hungry iPhone users, high population density, and tall buildings that adversely affect that high frequencies used by 3G communications.

With the 3G coverage upgrades in place, AT&T's cellular infrastructure now boasts towers capable of transmitting in the 850MHz frequency spectrum, in most of Manhattan and a few locations in the Bronx, Brooklyn and Queens.

Along with the upgrades, which also apparently take the stress off of the 3G frequencies in areas with high concentration of mobile users, the connections of the smartphones to AT&T's central offices - called backhauls - have also been replaced such that they now allow faster data transmission rates, to up to 7.2Mbps on compatible devices.