AT & T is upgrading its network and use the 850MHz spectrum of beef its wireless 3G, which should help alleviate the dropped calls and slow network connections for the iPhone 3G and iPhone 3G S users.

Apple said this week that it sold over a million iPhone 3G in the model around the world late last week after the phone went on sale on Friday. Exactly how many of these phones have been activated on AT & T network in the United States is not yet known, but in addition to more intensive data iPhones, likely to put additional strain on the network carrier.

Nonetheless, AT & T representative Mark Siegel said Gearlog blog on Tuesday that the company is ready for onslaught of new users of iPhone. One of the things he was doing to prepare upgrading their networks, so that it can offer wireless 3G services with the use of its 850MHz spectrum licenses. For the most part, AT & T has been using the spectrum in the range 1900 MHz to deliver its services to 3G, which have become saturated, Gearlog explains. This means that, as AT & T sells more 3G devices, such as the iPhone, has been cramming more users in an increasingly crowded spectrum band.

This could explain why some users complained about dropped calls and slow Net connection using iPhone 3G, one question that CNET News said almost a year after, iPhone 3G was launched. This problem is especially acute in large cities such as New York and San Francisco where the bases are concentrated and where the iPhone users 1900MHz spectrum is dominant.

Siegel said that the upgrading of equipment will allow AT & T using its 850MHz spectrum for 3G services should help alleviate some of the problems of congestion. Since the 850MHz spectrum is at the lower boundary of the frequency range, it is able to travel long distances and penetrate walls more easily than signals on the 1900MHz band.

When asked about problems with dropped calls on iPhone 3G users a year ago, Siegel CNET News reported that the company is working to expand its share of 3G network, which operates on 850MHz band. He downplayed the need to add 850MHz spectrum for 3G services, saying that it “does not mean that you can not get a good experience on 1900MHz.”

Now, Siegel believes that the addition of 850MHz make a big improvement, according to Gearlog stories.

“At 850, when he turned in some markets, people have noticed a great difference,” he was quoted as saying.

Apart from adding 850MHz 3G services, AT & T also other improvements in its network, such as an upgrade to the next iteration of technology, HSDPA, which is expected to double download speeds from AT & T network.