Mobile Phone: a brief history Over the last few decades the mobile phone has grown from being a YUPPY status symbol to the most used portable gadget in the word. The mobile phone is truly ubiquitous and is used for far more that making and receiving phone calls; in fact it is a sophisticated computer and universal communications device. The mobile phone was the progeny of a marriage between the ordinary telephone as invented in 1876 by Alexander Graham Bell and radio transmissions as invented in 1894 by Guglielmo Marconi. The first mobile phones were radio telephones installed in cars. These worked from one central radio station which had access to between twenty to thirty different radio frequencies. This limited the number of radio phones that could be used without interfering with each other. The limitations of this type of system were overcome by introducing cellular networks. The first type of cellular network was an analogue system that allowed around 800 frequencies to be used and the area of coverage was divided into cells, generally with a hexagonal geometry, covering around ten square miles. Each cell had a single base station and as the range was low, radio frequencies could be re-used. As a phone moved between adjacent cells, then the call was passed seamlessly between the cells. The base station of each cell communicates with six base stations in adjacent cells. Due to frequency limitations the maximum number of people that could communicate with a single base station was limited to 56. This limitation was increased with the move to digital networks and the maximum number of connections per cell increased to 168. Digital networks were termed 2G networks, meaning second generation networks, and this meant that 2G phones had to include far more processing power than their analogue forebears and their functionality is controlled by a microprocessor. Such is the sophistication of modern mobile phones that in order to produce so much computing power thirty years ago in the days when analogue phones were first appearing a computer the size of a building would be required. Now we have 3G networks and we will soon be enjoying 4G as progress moves inextricably onwards. Mobile phones are already what back in the 1970’s were seen only on Star Trek, so who knows what we might see in the future.
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