Also do you know why mobile phones are called cellular phones? Read on to find out…
A cellular phone is similar to a radio. However cell phones allow you to speak and listen at the same time because two separate frequencies are used to transmit and receive signals.
Cellular phones are also similar to cordless phones, which use a pair of frequencies for communication between the base unit and the handset. In the case of cellular phones, the base unit is located a much greater distance away from the mobile phone and is also capable of handling communications with several mobile units at a time.
Within a city, the phone company divides the area into small units called cells. It is for this reason that mobile phones are called cellular phones. In each cell, a tower is installed which has a radio transmitter and receiver, which is capable of communicating with several phones at a time. Each of these cells has a radius of about a couple of kilometres.
When one starts a telephone conversation, the mobile unit will communicate with the base unit in the cell that is nearest. This is similar to the operation of a cordless phone. If you are close to the base unit within a cell, the signal strength will be sufficient to carry on a conversation comfortably. However as one moves away from the base unit, the signal strength will reduce. The base unit senses this reduction in signal strength. Simultaneously, the adjoining cell detects that the signal strength from your phone is increasing and therefore you are moving closer to it. When the signal to the second cell becomes greater than that from the first cell, the conversation automatically switches to the second cell.
In addition every cell phone company will have one central office, which handles communication between the cell phones and ordinary landlines.
For good communication over an entire city, it is important to have a large number of cells, which overlap slightly. This will ensure that there is coverage at all points of the city and also that the communication is uniform. A larger number of cells allow the use of lower power transmitters, and results in less interference.
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