With the exception of EE, existing mobile networks have until recently been relying purely on 3G/UMTS technology, which is now 10 years old and struggling to cope with the needs of today's data hungry users.
4G/LTE (Fourth Generation / Long Term Evolution) is the next stage in mobile network development and provides users with much faster data speeds than 3G is able to.
EE has been testing the waters with 4G since October 2012, and until just a few months ago had the market to itself in the UK.
While EE were able to leverage some of its existing spectrum in the 1800MHz band, the other networks had to wait till a spectrum auction held by Ofcom in February 2013 before they could even start preparing for a 4G launch.
However both O2 and Vodafone have launched 4G networks of their own, so EE is finally starting to see some competition, while Three is set to launch its own 4G network in December too, and is set to aggressively undercut the competition in terms of price.
- What's the best 4G handset?
So here's what you need to know if you're thinking of getting your hands on one of those fancy-Dan superfast 4G handsets everyone keeps going on about these days.
What are the differences between 4G frequency bands?
4G can be a confusing beast, particularly when there are three different frequency bands in use in the UK alone.
The 2.6GHz band is one of the two frequencies that were auctioned off by Ofcom in February. It has a greater data capacity than the other two bands so it can deal with loads of people connecting at once, but it doesn't fare so well over long distances, making it ideal for cities and other compact, densely populated areas but not so good for rural locations.
The 800MHz band is the other spectrum that was sold off in February. It was used to provide analogue terrestrial TV, but has been freed up since the big Digital switchover.
While it doesn't provide the same data capacity as the 2.6GHz band, the 800MHz frequency can easily travel over long distances and will be used to provide broadband speeds to rural areas where telephone exchanges can't reach.
Being low frequency it's also better at penetrating walls than the 2.6GHz or 1800MHz bands, so it will provide an improved signal when indoors.
The 1800MHz band is used by EE and once Three launches a 4G network of its own in December it will be using it too, thanks to purchasing a chunk of it from EE.
However, as part of the deal to get the spectrum off the brand formed from the merger of T-Mobile and Orange, Three had to agree not to launch 4G on the spectrum before October 2013, which is the main reason for it delaying its deployment until later in the year.
The 1800MHz band strikes a balance between coverage and capacity (falling between the extremes of the 2.6GHz and 800MHz bands) which makes it a good 'middle-ground' for getting 4G around the country.
Ofcom's 4G spectrum auction
The 4G spectrum auction held by Ofcom at the beginning of the year saw winning bids from O2 (Telefónica UK), Vodafone, Three (Hutchison Whampoa) and of course EE. Interestingly BT also came away with a piece of the pie through its subsidiary Niche Spectrum Ventures.
Remember, more MHz means a better connection, so the more 'x GHz' of spectrum, the more widespread and robust a network can be.
Vodafone spent the most at the auction- a whopping £790,761,000 and came away with 2 x 10MHz of 800MHz spectrum, 1 x 20MHz of 2.6GHz spectrum and a further 1 x 25MHz of 2.6GHz spectrum.
EE spent £588,876,000 and secured 2 x 5MHz of 800MHz spectrum and 2 x 35MHz of 2.6GHz spectrum, which is less spectrum overall than Vodafone has.