One of the most interesting things about a cell phone is that it is actually a radio, an extremely sophisticated radio.
The telephone was invented by Alexander Graham Bell in 1876, and In the 1880’s Nikolai Tesla invented the radio which is the basis of wireless communication (formally presented in 1894 by a young Italian named Guglielmo Marconi).
Before the birth of cell phones, people who really needed mobile-communications ability installed radio telephones in their cars. In the radio-telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower. This central antenna meant that the phone in your car needed a powerful transmitter - big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use radio telephones - there just were not enough channels.
The genius of the cellular system is the division of a city into small cells. This allows extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously. In a typical analog cell-phone system in the United States, the cell-phone carrier receives about 800 frequencies to use across the city. Each cell is typically sized at about 10 square miles (26 square kilometers). Cells are normally thought of as hexagons on a big hexagonal grid.
Now, the cell phone has change the way
we access the world and everything in it, and that is
why it has made such an impact on the people in the world, and has become such
a necessity. If cell phones were to
disappear after having them for so long people wouldn’t know what to do or how
to contact people, because we are so used to it. Cell phones are used all around the world,
and it has become a common thread that connects every single country whether
you live in the United States, Australia, London, or China. Being able to be connected with one another
by a small piece of technology makes the cell phone very unique and further
more makes it all the more important in our world.
The telephone was invented by Alexander Graham Bell in 1876, and In the 1880’s Nikolai Tesla invented the radio which is the basis of wireless communication (formally presented in 1894 by a young Italian named Guglielmo Marconi).
Before the birth of cell phones, people who really needed mobile-communications ability installed radio telephones in their cars. In the radio-telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower. This central antenna meant that the phone in your car needed a powerful transmitter - big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use radio telephones - there just were not enough channels.
The genius of the cellular system is the division of a city into small cells. This allows extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously. In a typical analog cell-phone system in the United States, the cell-phone carrier receives about 800 frequencies to use across the city. Each cell is typically sized at about 10 square miles (26 square kilometers). Cells are normally thought of as hexagons on a big hexagonal grid.
Cell phones that used analog
signals used to have 7 channels per cell. That system was called 1G and only
allowed 7 simultaneous calls at once. Currently, there are about 168 channels
available with the digital system. This system is called 2G. Cell phones are
low powered transmitters. What this means is that the towers can reuse the
frequencies because the signal does not travel very far. This also means that
the battery can be small enough to fit in your pocket.
Because cell phones and base stations use low-power transmitters, the same frequencies can be reused in non-adjacent cells. The two purple cells can reuse the same frequencies.
