Apple Inc. has released an iPhone software update it says improves communication between the smart phone and wireless networks.

The iPhone 3G, which went on sale July 11, connects to cellular providers' speedier third-generation networks and was meant to deliver snappier Web surfing and online video viewing than the year-old original model.

But some customers who shelled out $199 for Apple's newest gizmo flocked to message boards in recent weeks, posting complaints about dropped calls and spotty wireless broadband connectivity.

Cupertino, Calif.-based Apple did not acknowledge a problem until Tuesday, and then provided few specifics about what, exactly, Monday evening's software update was designed to fix.

The iPhone 2.0.2 software update "improved communication with 3G networks," said Apple spokeswoman Jennifer Bowcock.

Bowcock would not say which of the many possible parts _ from the iPhone's antenna and amplifier and the radio frequency transceiver, to the baseband that processes the digital signal and sends it to the speaker or screen _ were targeted with the software update.

She also declined to describe the sort of improvements users might expect after installing the update.

No definitive information has been released about the source of the problem, which seemed to affect some iPhone users and not others. Last week, Sweden's foremost engineering weekly published a report indicating a problem between the iPhone's antenna and an amplifier meant to improve performance in areas with a weak signal.

Apple declined to comment on the report.