Everyone knows that the popularity of the iPhone has put a strain on AT&T's network over the years. The #1 reason people give me for not buying an iPhone is that they prefer the Verizon network. AT&T is well aware of this and has several initiatives underway to improve performance on the iPhone and other cell phon... oh, who are we kidding. We all know that this is all about the iPhone.
One initiative was to unveil a faster 7.2 Mbps HSDPA 3G network, which both the iPhone 3GS and iPhone 4 can take advantage of. You can learn more about HSDPA in this article written last year by Glenn Fleishman.
Another initiative by AT&T has been to add 3G support at its cell towers for the 850 MHz spectrum. I am certainly no expert in cell phone spectrum, but here is my understanding of what this means. 850 MHz is the original frequency that was used in the U.S. for cell phone service, originally for analog cell phone service in the 1980s. The 1900 MHz frequency (also called PCS) was added about 15 years ago and is only digital. AT&T debuted its GSM network on the 1900 spectrum, and then more recently used 1900 for 3G. The higher frequency means that the signal does not travel as far, which can result in problems when you are trying to use the phone inside of a building with thick walls. As analog and other uses of 850 MHz have gone away, AT&T started to support GSM on both 850 and 1900 MHz.
The iPhone, like most other current generation phones on AT&T, supports both 850 and 1900. In the past, however, 3G was only available on the 1900 MHz band, and thus an iPhone could only use the 850 MHz band for slower Edge service. To improve coverage, AT&T has been working for over a year to bring 3G to the 850 MHz spectrum across the country. This helps users in two ways. First, by moving some of the 1900 traffic over to the 850 band, there is room for more traffic on 1900 MHz and hopefully fewer dropped calls for everyone on both bands. Second, as noted, the 850 band can work better inside of buildings. In New York City — a city famous for both lots of buildings and poor AT&T coverage — AT&T worked hard to add 850 MHz support throughout the country, and the company announced this past June that it had finished upgrading all of the Big Apple. To be clear, New York is not unique; AT&T supports 3G over 850 MHz in areas across the country. However, I'm not aware of AT&T previously announcing which cities have 3G over 850 MHz, except for New York where AT&T is now bragging about it quite a bit.
In the following video from AT&T's Seth the Blogger Guy, Seth explains what the 850 MHz upgrade means in New York, and of course most of what he says will also benefit you in your city when the 3G 850 MHz rollout is complete. I'd love to hear from New Yorkers on whether they have seen improvements now the that the new band is rolled out.
[UPDATE 9/16/2010: See also this post from Nilay Patel at Engadget on additional announcements from AT&T on upgrades.]