A quick guide to… GSM

GLOBAL – Over the last twenty years, the ability to make clear and secure calls, browse the web and to do text messaging on your mobile phone has really taken off, and it’s all thanks to the Global System for Mobile communications (GSM). Want to know more but you’ve only got five minutes? Join us after the break for a crash course on the world’s favourite mobile communications system.

The GSM standard has done for mobile what the WWW protocol has done for the Web and what the Ethernet standard has done for networking. Because it’s a worldwide standard, it’s enabled consumers, to benefit from the ability to roam and switch carriers without replacing phones, and it’s enabled network operators to be able to pick and choose their mobile base station and network equipment from a number of different manufacturers.

GSM is essentially a digital standard for mobile phone communications and it was the second generation (2G) of mobile communication technology after analogue (effectively 1G). With GSM, information is passed over the network as a sequence of 1’s and 0’s. Your speech is converted from analogue to a digital signal, passed over the network and then translated at the other end back into an analogue. Before GSM, mobile phones were analogue, calls were prone to interference, they were unsecure, and the only way to send data was to use an external modem that converted the digital information to analogue and then back at the other end.

The first GSM network launched in 1991 in Finland, and it’s now a global standard that’s used in practically every country in the world, on billions of mobile phones, and hundreds of millions of mobile devices.

One of the key reasons why GSM is so important is the security built into the system. With the previous analogue mobile phones, anyone with the right sort of radio receiver could tap into a mobile call. With GSM, security is built in, and there are two levels to the security. Data is only passed across the system once the caller and the receiver have verified that they are who they say they are, using a sophisticated key-system, additionally the data is then encrypted as it’s sent across the network.

Another key reason why GSM has proved so popular is text messaging aka the short message service (SMS). Part of the GSM standard allows for short messages to be sent for minimal cost on parts of the system reserved for controlling the network. Initially, SMS was used by engineers on the mobile network to communicate with each other, and by networks to inform mobile users that there was a voice mail message waiting. It’s now used by both young and old to do everything from updating Twitter, to sending vouchers for free entry to the cinema, and growth continues to be spectacular, in 2007 56.9 billion text messages were sent in the UK, and by 2009 that number had risen to 96.8 billion text messages.