If you've seen the new(ish) mobile broadband dongles you might be wondering how they work. They are small devices which fit in the USB slot of a laptop computer (or desktop if you want!) and offer you moderately high-speed internet access on the move.

The way they work is actually pretty straightforward, but if you don't know much about how ordinary mobile phones work, or how the internet or broadband works it does become slightly trickier to explain. In this guide we will try to keep things as simple as possible.

Changes Mean Faster Broadband

Several recent changes to the way that phone lines (both landlines and mobiles) work have meant that we can now have fast mobile broadband on the move.

Originally, mobile phone lines and landlines created one unbroken, single circuit between themselves and another phone or server, which means that once a call (or connection) was in progress you couldn't use the line for anything else because it was effectively blocked until the call ended.

That is called circuit switching because it involves one simple circuit. However, if broadband is enabled on a telephone line it works differently, the line is split in to two separate parts; a voice channel so you can chat to friends and a data channel so that you can access data from the internet. Because this type of line constantly exchanges data packets, this is called packet switching.

So, in short; more and more lines have converted to packet switching methods over time and now it is common enough for some plug-in mobile phone technology to utilise this.

Back when mobile phones only used circuit-switching, they could only access the internet at very slow speeds, but now that networks are using packet switching technology we can achieve broadband speeds of 350kbps-2Mbps which is typically the same as low-speed landline broadband.

However, there is an even faster method available right now, which is called HSDPA (High-Speed Downlink Packet Access) and it's up to 5 times faster!

HSPDA and Mobile Technology

You might already use HSPDA without realising it. Some new models of mobile phone handset (such as Apple iPhones) have the capability built-in. They allow you to download music and videos to your phone at high broadband speeds and access websites quickly on the go.

Most mobile broadband dongles also use HSDPA and all you need to do is buy a dongle from a mobile phone provider such as 3, Orange or Vodafone, plug it in to your laptop and you're online in no time. These dongles have integrated software which installs on your laptop or PC automatically and that means you can often get online the first time you use your dongle, within 5 minutes!

Sim Cards and Mobile Broadband

A mobile broadband dongle from any given network will also contain a Sim card so that it can access the phone network for the HSDPA access we've just described. The Sim card in a broadband dongle is just the same as a Sim card for a mobile phone (in fact, they're actually interchangeable.)

The only drawback to mobile broadband is that, just as a mobile phone signal will strengthen and weaken when travelling on a train (for example) your broadband signal will also be challenged in certain situations.