There's something in the air in the Apple community, and this time it's not the same old buzz about a next-gen iPod, Steve Jobs's health or a Mac tablet: It's the sour topic of the iPhone 3G's poor data reception.

Specifically, people aren't happy about how fast the iPhone downloads data over AT&T's wireless network. Many have reported that the phone frequently switches from the faster 3-G network to the older, slower EDGE network without warning -- or drops the data signal altogether. And even on 3-G, some users are disappointed by the performance, which seems far short of Apple's promise that it would be twice as fast as the old iPhone.

Apple and AT&T remain stoic about the issue, but there's no denying that these complaints have become more prominent since Wired.com last explored user reports of spotty iPhone 3G reception. Apple and AT&T have been either mum or have offered bland, "everything's fine here, nothing to see" statements (see below). That's led some bloggers and journalists to crowdsource the issue: CNET has been collecting user comments in an attempt to find patterns and an iPhone 3G user started a blog to collect comments, too.

But what's the source of the problem? Is it a bad 3G chipset in the iPhone? Problems in AT&T's network? Or something else altogether? We contacted several wireless network experts, as well as Apple and AT&T, to see if they could shed any light on the problem. Here's a rundown of theories about the iPhone's problematic 3G reception:

• In an e-mail interview, David Nowicki, president of femtocell developer Airvana, laid the blame at the network's feet. He pointed out that AT&T's 3-G network is new and will take several years to optimize, which is normal -- problems crop up in new networks all the time. Also, when AT&T deployed its 3-G equipment, the company put it on its existing transmission towers. Those towers were spaced based on the requirements of earlier, 2-G technology, which has a longer effective range than 3-G. That means that on the edges of any given cell, 3-G reception is going to be much worse than comparable 2-G or 2.5-G (EDGE) reception. In short, EDGE has an edge over 3-G in reaching your phone (pardon the pun).
• Nowicki added that capacity constraints could be an issue: The network towers provide both data and voice services and they communicate with devices even when those devices are not in active use. That creates strain on the network. When a 3-G tower gets overloaded with requests it dumps out data packets; some users' phones get no signal at all while others' default to the EDGE network on a less overloaded cell tower.
• Sam Greenholtz, founder of Telecom Pragmatics, echoed Nowicki's explanation and added that AT&T and Apple simply were not prepared for this tremendous growth in the number of users. Apple was not even able to keep up with demand for iPhone 3G handsets, leaving many stores tapped dry. "AT&T may have had 10,000 users in downtown, and the cell site may have been engineered to handle that many calls, but with this phenomenal buying there are now 20,000 people out there that have AT&T service on the 3-G iPhone," Greenholtz said in a phone interview. Greenholtz stressed that data traffic is the main cause of spotty reception -- especially in major metropolitan areas where 3-G is being used the most, thus straining the network.
• The inconsistent 3-G connection is due to an "immature" 3-G chip inside the iPhone, presumably manufactured by Infineon, says analyst Richard Windsor. This would point fingers at iPhone's hardware -- not the AT&T network.
• FixMy3GiPhone.com blogger Matt Wakeling's report is essentially a combination of the above theories: He reports that Portland AT&T employees said Apple "went cheap on their chips," and that AT&T's 1900MHz towers are not communicating well with the handset. AT&T told Wakeling it would be switching network towers to 850MHz to improve reception for iPhone users.   
• AT&T spokesperson Brad Mays told Wired.com, "The new iPhone is performing very well on our network." He explained that reception issues must be examined on a case-by-case basis: "Customer experience on the iPhone 3G or any device can vary based on a number of factors, including the proximity to the cell site, buildings, trees, terrain and the number of people on the network at any given time."

Whatever the case may be, the widespread concern over 3-G performance on the iPhone signifies a disconnect between Apple and AT&T, which doesn't come as a surprise: Each company already has a lot on its plate in addition to the iPhone. But considering how huge of a device the iPhone has become, that's not an excuse.

If you've got an iPhone 3G, what's your experience been? Is it faster, slower, more intermittent, or more consistent than with the previous iPhone or other phones?

by Brian X. Chen for Wired.com

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