UK mobile network O2 is launching a 4G mobile data trial in London giving much faster downloading and streaming speeds.
The system is called Long Term Evolution (LTE). It's hoped the system will give data speeds up to 15 times faster than the current 3G.
O2 are planning more than 1,000 testers in London. They'll be given special data dongles to use with laptops.
Everything Everywhere, which runs Orange and T-Mobile - is also carrying out tests in Cornwall involving 200 people.
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