Only in San Jose did the Atrix score an average download speed of more than 2 mbps--our dividing point between 3G and 4G speeds. The phone didn't break the 2-mbps barrier even once in our Las Vegas and Los Angeles tests; in San Francisco it passed the barrier four times, and in Seattle it did so only twice. In the majority of our tests, the Atrix clocked download speeds of between 1 and 2 mbps.
While we were conducting our tests, news surfaced that AT&T had admitted to intentionally throttling back the upload speeds of the Atrix. This certainly bore out in the test results we were seeing at street level. Our measured average upload speed of just 0.19 mbps on the Atrix is the kind of performance that would seriously hinder bidirectional apps like VoIP or video chat. In our 13-city tests earlier this year, the iPhone 4 achieved far faster uploads (0.97 mbps on average) on the very same AT&T network.
Nor would the Atrix's latency scores help the performance of the above-mentioned apps: AT&T's network registered an average 247 milliseconds of latency time across our five testing cities, well above the 100-millisecond breaking point between smooth, responsive performance and delayed, choppy results.
Sprint: Where Art Thou, WiMax?
Our January speed tests demonstrated that Sprint's 4G WiMax service is indeed fast, but that it isn't available in enough places in Sprint's markets. The same theme was evident in our recent five-city testing of Sprint's EVO Shift 4G phone. (The Shift was the first new 4G phone to hit the shelves this year; the company announced it at CES on January 4, and put it on sale January 9.) The Shift averaged 1.65 mbps for downloads and 0.50 mbps for uploads--pretty good in 3G terms, but poor in 4G terms.
Sprint and its WiMax partner Clearwire simply don't have sufficient density of WiMax base stations on the ground to ensure that Sprint 4G customers can pick up the WiMax signal consistently across cities. We found that when the EVO Shift 4G was close to a WiMax base station, it could connect at between 2 mbps and 4 mbps--but we spent much of our time outside the reach of a base station.