20 years ago we would have never thought about a device revolutionising the way of our communication. But all of a sudden the Cellphones became one of the great technological innovations that changed in fact, improved the way we connect with people. In a matter of seconds, we could speak to a person who is on the other side of the globe. Today to live a day without mobile phones are very hard. More than that, what makes everyone annoying is having a mobile phone without a proper network. Have you ever imagined why sometimes your call never connected though you had a good network? How come all your calls are recorded somewhere? Do you know how mobile network works? Read further to know in detail.

What happens while making a call?

When you speak your voice is picked up by your phone’s microphone and it is converted into a digital signal that consists of 0 and 1 which is further received by an antenna and it transmits in form of electromagnetic waves. When this electromagnetic wave reaches the other persons mobile phone they are able to hear from you. But the electromagnetic waves cannot travel on their own and hence the cellular towers are constructed. A geographical land is divided into a hexagonal cell with each cell having an own tower and a frequency slot. All these towers are connected with wires or optical fibre cables.

The electromagnetic waves are picked up by the tower and converted into high-frequency light pulses which are transferred to the base transfer box for further signal processing. This is sent to the destination tower and the destination tower radiates the high-frequency light pulses into electromagnetic waves and reaches the phone of the receiver and undergoes a reverse process to hear your voice. You might have a question that, “In spite of so many towers how frequency go and reach the right tower where the receiver is?”

How the tower of the receiver is identified?

Here comes the central point of the group of cell towers called the Mobile Switching Centre (MSC). There is a home MSC where all the information is registered when you buy a SIM card. When you move away a new MSC serves the signal to you is called a Foreign MSC. When someone calls you the frequency is directed to your Home MSC and from there it is further connected to the current foreign MSC. As in detail,

  • The control channel is a special frequency that the phone and base station use to talk to one another. When the mobile phone is switched on, it tries for a System Identification Number (SID) on the control channel. When the mobile phone could not get the link with the control channel, it displays a “no service” message.
  • When the mobile phone gets the SID, it compares with the SID programmed in the phone. When both the SID match, the phone identifies that the cell it is communicating is the part of its home system.
  • The Mobile Switching Centre (MSC) keeps track of your phone’s location in a database. It knows in which cell you are when it wants to ring the phone.
  • The MTSO gets the signal and tries to find the phone. The MSC looks in its database to find the cell in which the phone is present and then picks a frequency pair to take the call.
  • MSC communicates with the mobile phone over the control channel to tell it what frequencies to use. Once the Mobile phone and the tower switch on those frequencies, the call is connected.
  • While travelling, when the mobile phone moves toward the edge of the cell, the cell’s base station will note that the signal strength is diminishing. At the same time, the base station in the cell in which the phone is moving will be able to see the phone’s signal strength increasing.

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