By Daniel Eran Dilger

Published: 05:00 PM EST (02:00 PM PST)

Apple now sells iPhones that work on three of the top four national US mobile carriers. Here's a look at how well you can expect Apple's latest smartphones to work on each of these mobile data networks, based on real world testing of each carrier's data throughput.

Evaluating how well a mobile device works across different mobile networks is difficult. First, there's the characteristics of the phone itself, added to the technology type of the carrier, whether a GSM/UMTS network like AT&T or the CDMA EV-DO 3G mobile networks of Verizon and Sprint.

On top of that, each carrier's network strength, usability and reliability depends upon tower placements and the backhaul networks that connect them, making some spots or even regions better on one carrier than another, independent of the conditions of another nearby spot or region across the country.

We didn't test the strength of radio connectivity between phones and towers, which is reflected in the "bars" of service reported by a phone. Instead, we measured actual data throughput, providing a better indication of how well the iPhone will actually work on each carrier when you look up maps, browse the web or make Siri requests.

Evaluating carrier claims

Carriers are often very secretive about their networks, hoping to avoid disclosure of any competitive disadvantages. On the other hand, they're very open about any competitive advantages they hold. AT&T advertises the nation's fastest 3G network, while Verizon claims the best coverage and Sprint trumpets its status as the last US iPhone carrier offering an all you can eat data plan.

AppleInsider has been evaluating the three carrier's networks in a series of West Coast tests that seem to have provided fairly conclusive results on what users can expect from each network. The tests of three iPhones on each carrier were performed in parallel across urban areas of San Francisco, Los Angeles, Sacramento and Reno, Nevada, with some rural testing performed between those locations.

The tests we performed won't tell you what level of data service you can expect in any specific region across the US on each of the three carriers. Each provider has strong and weak spots related to their national build outs. Each also has technical pros and cons, divergent plans for the future of their networks, and differing policies for supporting data throughput.

However, while our tests were confined to a limited area of the US, the tests do provide pretty clear results that seem to represent the findings of other users and the reports of other mobile data tests, indicating they are representative of the carriers' own policies that have influenced how their nationwide networks are configured and operated.



On page 2 of 3: AT&T is indeed the fastest phone network, Verizon coverage is indeed more widely available.