Surely, you often hear the expression “cell phone”. But have you ever wondered why a cell phone is called a cell phone? In this article we will talk about the history of the emergence of cellular communications and the principles of its operation.
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The history of the appearance of cell phones
American journalist Robert Sloss predicted the emergence of “cell phones” back in 1910. The police were the first to use the new technology – in 1921, Detroit law enforcement officers received information from radio dispatchers in the 2 MHz band, and by 1940, mobile phones were already operating in 10,000 police cars across the country. And in 1946, the first public mobile radiotelephone appeared in St. Louis. Communication was carried out in two ranges – 150 and 450 MHz.
In 1957, Moscow engineer Kupriyanovich introduced the LK-1 mobile phone. The prototype of the “mobile phone” weighed three kilograms and allowed you to call 25-30 km in the district.
The very next year, Kupriyanovich presented a noticeably more advanced model LK-1 – weighing only a pound and the size of a cigarette box.
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Around the same time, experts at the Voronezh Research Institute of Communications developed the world’s first Altai automatic (previously manually connected subscribers) mobile communication system. By 1970, she worked in 30 cities of the USSR at a frequency of 150 and 330 megahertz. Each city was served by one base station, the range was from 50 to 100 km, they called on the Altai phones, city and intercity / international numbers.
Modern cellular communication systems appeared in the USA in 1978, when tests of the first such system for 2 thousand subscribers in the 800 MHz band began in Chicago. The city’s first commercial cellular communication system was received in October 1983 from AT&T. And the first commercially successful cellular network was Finnish Autoradiopuhelin (ARP, “Car Radiotelephone”). By 1986, more than 30 thousand subscribers used it.
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How does cellular communication work?
A modern cellular network consists of base stations – multi-frequency VHF transceivers, evenly distributed throughout the coverage area. Outwardly, they look like huge towers of red or white color with special equipment.
The vertical parts of the antenna are responsible for mobile communications, round – provide communication with the controller. The range of the base station is 35 kilometers (but this is not the limit, see below). Each base station has six service sectors, one sector receives up to 70 phone calls simultaneously. Multiply 6 by 70 and you will understand why no one can get through to the New Year :).
Nearby stations never operate in the same band – otherwise interference interference cannot be avoided.
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Where did the name “cellular communication” come from
What about honeycombs? There are many basic networks used, circle-radii overlap each other and together form a network resembling a honeycomb. Hence the name of the technology – “cellular communications”. A group of seven hundred is called a cluster.
Such an approach gives a mobile subscriber several advantages at once. Firstly, the “dense” arrangement of hundreds of cells of mobile communications ensures uninterrupted communication – unlike landline communications, we are not tied to one line. Secondly, a mobile (aka cellular) telephone automatically leaves the station with the greatest signal attenuation to the smallest, i.e. provides the best call quality. For a “seamless” transition from the old station to the new one, the controller handover is responsible.
Now let’s look at how everything works on the part of the subscriber. A working cell phone always scans the air for the signal from the base station. When a signal is found, the cell sends its unique identification code to the station. Then begins the periodic exchange of radio packets through an analog or digital protocol (for example, CDMA, GSM, UMTS). The communication channel from the station to the subscriber is called DownLink (“downlink”), from the subscriber to the station is called UpLink (“uplink”). When you call someone, the phone contacts the station and asks you to select a voice channel. The station forwards the signal to the controller, the one to the switch. If the subscriber uses another mobile operator, the request goes to “his” switch, if he is on the same network as you, the switch will find the subscriber himself and direct the call to him.