In spite of the fact that Apple and AT&T promoted the iPhone 3G as being "twice as fast" as its predecessor, some users don't seem to be experiencing the near Wi-Fi like performance they had been promised to.

Therefore the guys from Wired made a global survey of 4,200 iPhone 3G owners, to investigate the problem. They found that the 3G speeds do oscillate broadly, and that these differences seem to be because of the carriers, not the iPhone itself.

The study invited users to measure their local 3G speeds and enter the data on an interactive map. However the most striking differences in 3G reception occurred between the United States and Europe.

The most “no signal” results came from the users in the United States. Moreover, users in Germany and the Netherlands reported the world’s fastest average 3G download speed - about 2,000 Kbps while participants in Australia had the slowest average 3G download speeds at 759 Kbps.

Results established for individual carriers showed that European T-Mobile had the fastest speeds at 1,822 Kbps, followed by Canada (both Rogers and Fido) at 1,330 Kbps. U.S. AT&T customers found themselves in 3rd place, tied with Telstra, Telia and Softbank at an average speed of 990 Kbps.

Wired also found that metropolitan areas that usually have the highest 3G saturation are often slow due to overloaded towers, explained Dave Nowicki, expert in the technology that extends the reach of wireless networks.

Therefore Apple hasn’t got much power where this matter is concerned as it directly depends on all of its carriers to optimize 3G network behavior.