And AT&T's speed gains didn't translate well to our smartphone-based tests: The average download speeds we measured on our Apple iPhone 4 (1.4 mbps) increased only 15% over the speeds we measured on the same device in early 2010. However, AT&T intends to launch its own 4G LTE network later this year, a move that might tip the balance of the 4G speed race in its favor once again.
Sprint needs more 4G: In the cities where Sprint offers its 4G WiMax service, customers saw large speed increases over the past year. Sprint's average download speeds grew 170% to 2.1 mbps in our tests this year; the result would have been even better had the WiMax service been more consistently available throughout our test locations. But in cities such as New Orleans, Phoenix, and San Diego, where Sprint still relies on its 3G CDMA network for data service, download speeds have fallen, and remain well below the 1 mbps mark.
4G Speed-Test Results: Reading the Charts
In our study we tested both with representative smartphones and with a laptop employing a USB modem recommended by the carrier. The laptop-based testing, which uses the Ixia industry-standard testing software, provides more precise metrics than smartphone testing does. The laptop results are a good measure of the maximum performance possible on a network and are a satisfactory predictor of the speeds that the network will likely deliver to smartphones in a year or so.
We use Ookla, an FCC-approved Web-based speed test, to measure data rates on smartphones. Those results aren't as precise for a number of reasons: we must use different smartphones on different networks, and the results necessarily reflect the limitations of the smartphone's radio chipset, processor, and battery, and the test itself comes with a somewhat higher margin of error.
The charts below (click to see enlarged versions) list the cities in the leftmost column; moving rightward across the chart, you can see the speed averages and network latency times for each of the four wireless networks. Speeds are expressed in megabits per second (mbps). Latency (or the time it takes a single small packet of data to travel to a network server and back) is represented in milliseconds. We recorded download and upload speeds and latency times during our laptop-modem tests, and download and upload speeds in our smartphone tests. (For more details, see "How We Test.")
Speed-Test Methodology in a Nutshell