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
Our testing method is designed to approximate the experience of a real laptop-modem or smartphone user on any given day in their city. PCWorld's testing partner, Novarum, tested in each of our 13 cities during the first six weeks of 2011. At each of our 20 testing locations in each city, we took a "snapshot" of the performance of each wireless service, testing for upload speed, download speed, and network latency.
We looked for the fastest signal available for each carrier, searching first for 4G service and then, failing that, defaulting to the carrier's 3G service. In all, we ran 177,000 timed performance measurements from 260 testing locations in both urban and suburban environments. (See "How We Test" for additional information.)
Because we couldn't test every city in the country, we chose 13 cities that are broadly representative of midsize and large wireless markets in terms of size and topography: Baltimore, Boston, Chicago, Denver, New Orleans, New York, Orlando, Phoenix, Portland, San Diego, San Francisco, San Jose, and Seattle. Because wireless signal quality depends to a large extent on variables such as network load, distance from the nearest cell tower, weather, and time of day, our results can't be used to predict exact performance in a specific area. Rather, they illustrate the relative performance of wireless service in a given city on a given day. Each speed number has a margin of error of plus or minus 5 percent.
Next page: Verizon's new 4G network impresses, but its 3G network stagnates