By Kevin Purdy

Whether to Tether: What You Should Know About Phone-to-Laptop Connections

Pumping your smartphone's 3G/4G data into your laptop, or "tethering," seems like a convenient and money-saving productivity hack. But is tethering as fast or reliable as a dedicated wireless modem or MyFi? Here's what you should know before you tether.

Image via preetamrai.

Tethering is a service you can purchase from your cellular carrier—a basic kind of on/off switch, with a little extra software, to allow you to connect your phone by USB, Wi-Fi, or Bluetooth to your laptop and utilize the phone's cellular internet through your normal browser, email client, and other net-needing apps. Most carriers charge for the privilege of using the web they're serving up to your phone on something other than your phone. But, then again, some mobile apps can do the job for free, on Androids, iPhones, and other platforms.

Free? Yep, free—beyond the cost of your phone's data plan, that is. So why would any sucker pay their carrier for tethering, or a 3G card, or a "MyFi"? A free, occasional tethering solution may, indeed, be the most practical solution for some users, and some tight situations. But here's what you should know.

Phone Tethering Might Not Be Quite as Fast as a Stand-Alone Device

Tethering apps are small in size and fairly quick to start up, once you've set up both ends of the connection—the app on your phone, and the software needed on your PC. And they are, basically, pulling down the same 3G, 4G, CDMA, or whatever signal your carrier would give you on a dedicated USB card or portable device. So shouldn't they be just as efficient as those dedicated devices?

In theory, maybe. In real life, not so much.

I'm a T-Mobile subscriber with a data plan in Buffalo—no high-speed HSPA+ for us yet, and not quite the country's fastest 3G. I'm toting a Nexus One, which still has the built-in USB and Wi-Fi Hotspot tethering options built in. Measuring my phone's connection through the SpeedTest.net app, and then tethering my laptop to run the same test, I found that my phone averaged about 3.0 Megabits per second, while USB tethering options came in at around 2.3. That's not to say that, in some bandwidth tests, that tethering didn't approach that speed. But all things being equal, tethering apps like PDAnet and Tether didn't seem to consistently deliver the same speeds to my laptop that I could get on the phone alone.

Want proof? Here are my test results, using built-in Android tethering (Nexus One/Froyo only, at this point), PDAnet, and Tether:

Carriers (Generally) Won't Catch You Tethering, But They Will Profit From Your Overages

I know two different people who told me, after obtaining a Droid X on Verizon Wireless and an EVO 4G on Sprint, that they would be dropping their home internet connections. "With tethering," their pitch went, "and only using email and the web, really, I'll save at least $30 a month."

Neither person was able to actually box up the cable modem and return it. That's because no cellular data plan, in the U.S. at least, is really "unlimited," despite whatever naming scheme they use. Once you go over a "soft" limit of 2 or 5 GB of data usage—or 200 MB, if you're on a discount plan—your connection will be throttled to something like a 2G crawl, and/or you bill starts growing exponentially. And if you start using your phone like a primary modem, you will inevitably meet the money-minded folks on the other end of that pipeline.

Having dug around the web in as many geeky corners and forums I could think of—iPhone forums, XDA Android developers' boards, and elsewhere—and obsessive web searching, I found that the answer seems to be somewhere between "They don't know that you're tethering" and "They might know, but it only matters if you're over your limit or hurting their network." For our purposes, a request from your phone for a web address looks the same, because once your phone's antenna and hardware makes the data exchange, it could go to your phone's browser, your laptop's browser through PDAnet, or anywhere.

Update: Reader Pete Gaines tells us that T-Mobile caught him tethering and asked him to upgrade, though we're not sure whether it was a raw data-usage issue, or if they actually detected a desktop-oriented connection.

When I first moved into my house, I lacked cable internet for a week. I used my G1 and its Cyanogen-powered tethering to get my Lifehacker work done, but that was it—no YouTube, no leisure browsing, just straight HTML posts and image editing. If I needed evening internet beyond email, I went to a coffee shop. I managed to avoid T-Mobile's wrath and stay under 5 GB. Both acquaintances received stern letters from Verizon and Sprint about their overages, and both argued the confusion of "unlimited data plans." In the end, they might have escaped some overage fees, but dropped the freedom-from-cable idea.

Note: Want to monitor exactly how much you're using over your tether connection? Check out our guide to the best tools for monitoring your cellphone data usage.

Tethering Burns Out Batteries—Even Over Self-Charging USB

If you're going to rely on tethering to save your butt on a long-distance train ride, or for more than an hour without a plugged-in laptop, you'd better bring an extra battery—or two.

Using the built-in tethering on my Nexus One, and toting a spare battery, I wanted to see how long I could last on an Amtrak train, heading West-to-East, when I recently found myself doing just that. Starting from Buffalo's Exchange Street station, I made it to just past Utica before my phone shut down to save itself, and felt as hot as a griddle cake. And that was with the phone connected via USB, so therefore drawing a low level of charge from the plugged-in laptop. Image via Kai Hendry.

It's not just the continuous data pulling that chugs down battery juice—it's going in and out of service, switching between service levels (GPRS to EDGE to 3G and back), and laptop apps that draw on a steady stream of data. Most smartphone apps are written to respect the platform they're on, while standard computer applications generally assume you're plugged in and connected to some kind of decent Wi-Fi.

It's not an issue if you have smartphone battery backups galore, but most of us don't. And when you run out of tethering power, you're also without a phone until you can charge back up.

With an Unofficial Tether, You Can't Get Righteously Ticked at Bad Service

Obvious, perhaps, but when you're paying for your tethered connection, or a dedicated USB device or MyFi-style portable hotspot, it's your prerogative to get righteously angry at the drop-offs in coverage where coverage is expected, to measure your speeds and report just how sad they are, and get credits for data usage that wasn't really warranted. If you're make-shifting your phone into a 3G/4G modem, you're just another phone customer—and as long as you have basic voice coverage, your carrier won't care quite so much that your Gmail SSL connection is taking forever.

Bottom Line: Use Unofficial Tether as a Make-Due Email and Data Sync Tool

From personal testing, anecdotes from web users and acquaintances, and some research into the nature of "unlimited" data plans, we can draw a few conclusions:

Tethering is not a long-term mobile data solution
The Thought Police won't mace and handcuff you for hooking up your laptop through unofficial means, but your natural inclination to open just One More Tab could easily lead to a bigger bill and stern carrier letter.
You need extra phone batteries to reliably tether for more than 30 minutes at a time.
You won't get top speeds while tethering, so make accommodations: sync simple text files through Dropbox rather than open Google Docs sessions, and batch together your online actions through apps like the very Gmail-friendly Thunderbird.

Have you made tethering, official or unofficial, into a regular part of your work routine? Got a better tip on getting the most from a phone-to-laptop connection? Tell us your take in the comments.