AT&T's New Network May Not Help Your Old iPhone

main-rightApple (s aapl) unveiled the new iPhone today, and once again the device is inspiring lust while the network inspires loathing. While a lot of sites are hacked off that AT&T (s T) will not support tethering (using your phone as a modem) and MMS picture messaging on the iPhone 3G right away, owners of older 3G iPhones in the U.S. may have a bigger beef. Sources are telling me — and AT&T doesn’t deny — that the network upgrades AT&T announced two weeks ago won’t boost the old 3G iPhone’s data connections to the promised 7.2 Mbps speeds.

AT&T said today that the latest iPhone, which will be in stores on June 19, will be able to use the soon-to-be-launched HSPA networks, which could theoretically reach speeds of 7.2 Mbps down. From its release:

iPhone 3G S will be compatible with High Speed Packet Access (HSPA) 7.2 technology, which offers theoretical peak download speeds of up to 7.2 Mbps, though actual speeds will vary as these capabilities become available. AT&T plans to begin deploying HSPA 7.2 later this year, with completion expected in 2011.

What it doesn’t say, however, is whether or not the existing 3G iPhone will be compatible with the network upgrades. I asked AT&T about this last month, and was sent a link to the AT&T web site noting that the original iPhone is HSPA compatible in the 850 MHz spectrum band that AT&T is using to augment its 3G coverage. When I specifically asked if this meant the device could reach HSPA 7.2 speeds, however, I was not given an answer. I asked the question again today and was again pointed to the aforementioned link on the web site.

The original iPhone 3G won’t, according to various people I’ve spoken with, be able to zip along at the fastest speeds offered by the network upgrade because of its hardware limitations. The Infineon chip inside the phone has the capability to offer HSPA in three bands, including the ones AT&T is using, but the antennas and power amplifiers inside the phone may not give it the boost it needs to offer those speeds without consuming too much power, or even at all.  Apple has so far not responded to my requests for comment. Readers may be able to help us by letting us know if they can run the iPhone 3G at speeds close to 7.2 Mbps on other HSPA networks around the world.

As for the complaints about the new iPhone, AT&T spokesman Seth Bloom says AT&T plans to offer tethering, but “has no announcement at this time,” and notes that MMS support will come later this summer. “We absolutely will offer MMS on iPhone 3G S in the late summer once we complete some system upgrades that will ensure our customers have the best experience with MMS. These upgrades are unrelated to our 3G network.”