Mobile Wi-Fi and femtocells: All your questions answered

Losing your mobile phone signal or your Internet connection is like having the plug pulled on life support. Happily, boffins have come up with a couple of ways to keep you connected by merging broadband and the mobile network, even when it goes against physics, logic and nature.

But what the heck are all these little black boxes -- known variously as mobile hotspots, mobile Wi-Fi, MiFi, access gateways and femtocells -- and how do they get us online? All will be revealed.

Two sides of the connectivity coin

There are two techno-plans for combining broadband and the mobile network to keep us connected everywhere.

First, you can hook your laptop up to the Internet where there's no broadband by using the 3G network that was intended for mobile phones. This is the tweak that gets you broadband on the train, and there's a whole heap of options to get connected.

Second, you can receive calls where there's no phone coverage by routing them over a broadband Internet connection. This solution turns your mobile into a not-so-mobile, since you've got to stay close to your own personal phone mast, but at least it's got a cool name: femtocell.

Femtocells

Mobile phone signals aren't that great indoors, between high buildings or in valleys. It's a wonder they work at all without phone masts being installed in our faces. The networks can't wrangle that, but they can sell a signal booster, which in geekspeak is called a femtocell.

Where it got this groovy name is a mystery to us, because it's not so teeny tiny that you need to measure it in protons. It's about the size of a modem, and it plugs into your home Internet connection and puts out a 3G signal.

Vodafone is the first network to offer the box in Europe, calling it the Vodafone Access Gateway. You can connect to that signal using your normal mobile, as long as it supports 3G and it has a Vodafone SIM in it. Vodafone's box supports up to four simultaneous calls, so your family doesn't have to take turns. You'll also have to register the mobile numbers that are allowed to connect, to prevent cheeky neighbours from piggybacking your signal. And of course, you need an Internet connection to hook up to, and you pay for and maintain that yourself.

You can rent an Access Gateway from £5 per month, or make a one-off purchase for £160. It's also available as part of a phone contract, starting at £15 per month.

It's something of a kick in the satchel to pay three times to use your mobile -- once for a normal contract, once for the femtocell contract, and again for broadband. But trust us -- nothing's worse than having no phone coverage in your evil lair deep underground, so it might be worth the extra spend.Of course, you could just use a landline, but where's the fun in that?

Mobile Wi-Fi

The flipside is when you've got a good 3G mobile signal but there's no broadband to be had. You could just check your email and do some browsing on your phone, but for documents in the cloud, for example, you need to use your laptop.

You could surf over the mobile network by using a 3G dongle, which is definitely the cheapest option. You could also try tethering -- connecting your phones to your laptop -- but that's only possible on some smart phones, and it usually involves a USB cable connection. Either way, you can only connect one laptop at a time -- for multiple computers and wireless-enabled devices such as cameras, you need a proper Wi-Fi signal.

For this, you need a mobile hotspot, which connects to the 3G network and spits out Wi-Fi. The Novatel MiFi is such a box, and it's only about the size of a deck of cards.

Just pop a SIM card inside and fire it up to create your own Wi-Fi mini-cloud for up to five devices within 10m. The 3 network is planning to sell the MiFi with a 3 SIM card this winter, although it's not spilling the beans on prices yet. You can also pick up the MiFi for £210 from distributers such as eXpansys and pop in your own SIM from any network.

We haven't seen 3's version of the MiFi, but the one we tested offered four hours of battery life, HSDPA for speedy surfing, optional WPA security, and a microSD card slot so you can share files over Wi-Fi. It supported up to five devices, which have to stay within about 10m of the box.

Beware of going over your data allowance or going nuts with downloads -- even if you have an unlimited data package. Although the MiFi will take any SIM card, and there's no way for your network operator to know you're using it, every network has a fair-use policy, and if you're using huge amounts you could receive a stern call from customer services telling you to lay off or face a massive bill.