There’s a few different ways to access the internet on your device (smartphone, tablet, or laptop) when you’re travelling – you can find out about them, here. The two most common ways are Wi-Fi and mobile data. Both of these methods use radio waves to carry the information to your device.
Just in case you think that Wi-Fi networks and mobile data sound like the same thing, I’ll detail the difference for you, because while both network connections are supplied using radio waves, they are implemented very differently.
For a start, Wi-Fi and mobile data are technically different, with different radio frequency bands and different power levels. The components of your device that receive and transmit the radio waves for Wi-Fi and the components that receive and transmit the radio waves for mobile data are completely separate from each other and function independently and concurrently.
The equipment at the other end of the radio waves for each connection are wildly different from each other – for Wi-Fi, it’s a small low-powered box called a modem Wi-Fi router sitting on a shelf or screwed to a wall; for mobile data, it’s multiple powerful large antenna arrays on huge towers or on the roofs of tall buildings all around you, nearly wherever you are.
But none of that gives you the essence of the difference between Wi-Fi and mobile data.
Wi-Fi is a small-scale, local system, commonly owned by a private person or a small business, and even when it’s part of a much bigger business it’s usually a relatively simple setup. The radio waves usually comes from a single or small number of small devices, Wi-Fi routers, placed at a low level within a building; although, it may be provided from an external wall or an outdoor post for outdoor use. It only works over a limited area, and if you move out of that area, which may be a move of just a few metres, you’ll lose your connection – it’s a very local thing.
A Wi-Fi router has to get the internet access that it shares from an internet service provider (ISP). That internet access may be in a form such as an ADSL (copper wire phone line), optical fibre, mobile data, or a co-axial cable connection.
Mobile data is a large-scale national or even international system, usually owned by a large telecommunications company. The radio waves come from large antenna arrays on huge towers, or on the roofs of tall buildings. The antenna arrays are spread broadly across the land, but are especially evident in urban areas and along major transport routes so that devices can connect to the system from virtually anywhere. As a connected device is moved around its connection is swapped from antenna to antenna automatically to ensure that it is always connected.
In any country there are likely to be several competing mobile phone/mobile data systems running independently beside one another, each owned by a different telecommunications company and connecting to a separate set of customers.
Just to complicate things and disturb my nice clear separation between Wi-Fi and mobile data, there is a type of device, a mobile Wi-Fi hotspot (amongst other names), which receives mobile data from a mobile network and retransmits it as a Wi-Fi signal to be received by nearby laptops, tablets, and other devices to give them access to the internet. Most smartphones are able to act as a mobile Wi-Fi hotspot.