AT&T and Apple have apparently been working together to improve cellular network performance ahead of the next iPhone launch, which will most likely hit some time between June and August. Sources close to the matter say that AT&T kicked off a “100-day plan” in December to improve coverage and reduce dropped calls, according to the Wall Street Journal.

AT&T has been working with Apple to improve how the iPhone uses cell network resources, so now the combination iPod and smartphone uses fewer network resources when performing tasks like downloading text messages and locating nearby cell towers. Apple is “well past networking 101, 201 or 301 now” said John Donovan, AT&T’s chief technology officer. Apple is now “in a Master’s class.”

Mr. Donovan also said that AT&T plans to continue improving coverage in big-city markets over the next few months. That’s good news for subscribers, because one of the biggest complaints coming from iPhone owners has been dropped calls and limited signal availability.

The company hopes to address those issues by continuing to build out its wireless network, reposition antennas for improved signal strength, and add new wireless spectrum to deal with increasing usage. At&T plans to spend some US$2 billion this year to improve its network, too.

Whether or not AT&T’s network will be able to hold up under the strain, however, remains to be seen. Apple’s 3G-compatible iPad will be available at the end of April, and new iPhone models are expected later this spring, and both will likely add even more strain to the cell carrier’s network. AT&T is working to meet the demand, but if the company’s network upgrades aren’t in place in time, it could lose customers to competitors — and that’s a scenario AT&T is hoping to avoid.