Sprint 3G/4G MiFi: Great Potential, Erratic Performance

Although its credit-card-size footprint is roughly equal to that of earlier models, the MiFi 4082 is a bit thicker than the original MiFi--more like half a deck of cards than a couple of stacked credit cards. Still, at 3 ounces, it's no hardship to carry around and should fit into any pocket that can accommodate an iPhone.

Easy Setup

Charging the device using the included adapter (which connects via a Micro-USB port) takes a couple of hours, but setup is a breeze (assuming that you've activated your Sprint account). Simply connect a PC or Mac to the device via Wi-Fi (it's unsecured out of the box), and you're good to go. However, Sprint (and we at PCWorld) strongly recommend that you secure your network by running the first-time wizard, which appears when you initially access the device's browser interface by typing http://mifi.mlp into the address field after making the Wi-Fi connection.

The setup wizard guides you through the process of creating both network and administrative passwords (the latter keeps outsiders from changing the former as well as other network settings). If you fail to complete the first-time wizard, it will appear whenever you try to open mifi.mlp in your browser. Once you have completed the wizard, however, going to mifi.mlp brings up the MiFi interface landing page, which not only displays basic battery-life and connection info but also provides access to standard router settings and available MiFi widgets--applications that use the MiFi platform.

My review unit came with a weather widget preinstalled, for example. Since the MiFi has geolocation support, you can check for the forecast in your location by clicking a refresh button. The MiFi also has a slot for a MicroSD card (not provided); if you use a card, anyone connected to your MiFi hotspot can access files stored on the card via the MiFi browser interface (again, by going to mifi.mlp). This lets small workgroups easily share documents while on the road. For security reasons, people who use the browser interface are logged in as guests by default, so they can't fiddle with network settings; to access those, you must log in with the administrative password you created during initial setup.

Status Window

Status information is available on the MiFi itself; somewhat inconveniently, however, it isn't all in one place. On the front of the MiFi, a bar-shaped display window shows the network strength, as well as whether you are currently roaming, the remaining battery level, whether the device has a GPS fix, and how many devices are connecting via Wi-Fi (Sprint says it supports up to five). The device presents that last bit of info through dots, which is a bit harder to read than a simple number. Regardless, all of the information can be a little hard to read indoors, since the display uses the same E Ink technology found in Kindles and other e-book readers. Outdoors, under bright light, the contrast improves dramatically.

A multicolored LED on a side edge indicates the network type and speed. A blue LED indicates that you're in 4G country; green is for 3G, and amber means that you aren't within range of a supported data network. That's straightforward enough, but a solid colored light merely indicates the presence of a network: Only when the colored light flashes is the MiFi actually connected to the network--and even more confusingly, Sprint says the speed of the flashing denotes the speed of the network connection. Since you have no point of reference for judging whether the light is flashing quickly or slowly, it isn't easy to tell how good the network speed is.

Connection Speeds

My admittedly anecdotal speed tests, conducted in downtown San Francisco and Seattle as well as in several San Francisco Bay Area suburbs, backed up reports we've seen suggesting that WiMax performance tends to be better outdoors than indoors. I ran tests five times on a laptop PC and five times on an iPhone at each of four locations; in Seattle I conducted my indoor tests in a hotel room with a window overlooking Qwest stadium, and in San Francisco my indoor tests were in my loft near the Bay Bridge, about 40 feet from an unobstructed window. I conducted outdoor tests next to my car in a couple of mall parking lots.

With the MiFi lights indicating a 4G connection, download speed tests on Speedtest.net sometimes registered an impressive 8 megabits per second outdoors--but more often they were in the range of 2 to 3 mbps (the average was 5.6 mbps). Speeds sometimes varied widely within the same group of tests run within a minute or two: In one outdoor group of five tests, I registered a low of 2.8 mbps and a high of 8.5 mbps.

Indoors, download speeds also varied significantly. On one day, the MiFi 3G/4G averaged 6 mbps, with a high of 7.33 mbps and a low of 4.6 mbps. But during another set of tests conducted in the same location on a different day, download speeds averaged 1.2 mbps, with a high of 1.9 mbps and a low of 500 kbps.

Uploads were more consistent--but far slower--across the board. Outdoors, the speed averaged 750 kbps; indoors, the average was 730 kbps.

Performance isn't always just a numbers game, however. I had trouble trying to watch streaming Netflix movies using the MiFi 3G/4G. In three of four attempts, the film simply stopped streaming after about 60 to 90 minutes--the MiFi's Internet connection had either slowed to a crawl or halted completely, so I couldn't even browse the Web, let alone stream video. On the fourth try, however, I was able to watch a whole film. Clearly the MiFi is capable of good performance, but the inconsistency is troubling.

Latency was generally mediocre, with ping results ranging from 200 to 300 milliseconds. Results were fairly similar in tests using Ookla's Speedtest.net app on my iPhone. Because the 4G results varied so widely, I found it difficult to gauge how well the unit was doing in handing off 4G to 3G connections.

Battery Life

Sprint says the MiFi's battery should support 4 hours of use, but in my tests battery life appeared to be closer to 3 hours.The Wi-Fi on the unit supports 802.11b/g/n, which should make the MiFi fast for transfers between devices on the local network; for Web browsing and other Internet tasks, though, the speed of 802.11n is largely wasted since the mobile broadband connection is so much slower than 802.11n Wi-Fi.

Sprint charges $60 a month for unlimited 4G usage--a good deal if you're in an area with 4G coverage and you use a lot of bandwidth. However, the carrier imposes a 5GB cap on 3G (EVDO-Rev. A) data usage, and a 300MB cap on data consumed while roaming.

In general, I suspect that the erratic performance of the Sprint MiFi 3G/4G Mobile Hotspot reflects issues in Sprint's WiMax coverage more than it indicates problems with the Novatel Wireless hardware. But although the MiFi 3G/4G can be superfast, its inconsistency makes it difficult to recommend. (For more, read our look at the burgeoning mobile hotspot category.)