Mobile Teleohony
Inroduction
As we look around, in markets, on trains and buses, people crossing streets, we can see many individuals talking on cell phones or mobile phones. Mobile phones have changed the way we live and communicate. With advancement of technology, look and utility of mobile phone has also undergone change.In latest mobile phones, along with making and receiving phone calls one can also:
Store contact information
Make task or to-do lists
Keep track of appointments and set reminders
Use the built-in calculator for simple math
Send or receive e-mail
Get information (news, entertainment, stock quotes) from the
Internet
Play games
Listen radio/music and watch TV
Send text messages
Take photos and videos etc.
In a way, today’s mobile phone is a handy computer equipped with Internet. In ordinary landline phones, phone instruments are connected to a telephone exchange through electric wires, which in turn connect our phone calls to the other phones. However, wire connections limit the mobility of a landline phone. Mobile phone technology has successfully overcome this limitation.
Mobile phone is a low power operated device (transmitter), which can wirelessly send and receive radio frequency signals. Before this, walkie-talkie was also a wireless system of communication. You must have seen a policeman talking on his wireless set. After completing one sentence, he says “Over” and then listens. This was because the same radio frequency is used for both sending and receiving the audio signal. However, in a mobile phone, the outgoing and incoming signals use different frequencies, so the two individuals can talk and listen at the same time.
Working principle of Mobile phone
In a mobile phone, it is possible to talk while moving. This becomes possible because of a cellular radio network technology (a replacement of telephone exchange system). Under a cellular radio network a given physical area is divided into smaller parts call cells (or cell zones). To completely cover a given area use of hexagonal cells is a best possible way as shown in the figure.
In every hexagonal cell a radio antenna is installed to receive and send radio signals to and from mobile phones physically present within the cell. All cell antennas present within an area are connected to each other through a network (the way computers are connected in internet). All network related works including handling of all the incoming and outgoing calls are managed by a central control room called Mobile Telephone Switching Office (MTSO). i.e. MTSO is basically a telephone exchange for mobile phone calls. Every cell antenna has a working range of minimum 1.5 to 2 km and maximum up to 48 to 56 or more km area around it. When a mobile phone is switched on, MTSO records its location by identifying the cell in which it is present. When a mobile phone user moves from one cell zone to another cell zone, MTSO of its own switches mobile phone link to new cell antenna. This way, user gets an uninterrupted link to talk while on move. Also, mobile phones use high frequency radio waves for conversation. Audio signals of these waves are better. As mobile phones works on cell division of physical areas they are also referred as cell phones.
Scientific process of a mobile phone call
When we dial a mobile number from your mobile phone, an oscillator circuit (frequency generator) inside the mobile generates a particular frequency electromagnetic wave. This electromagnetic wave carrying called number’s information is transmitted through antenna of your mobile to the antenna of the cell in which we are present. The cell antenna in turn transfers this signal to MTSO. The MTSO computer system identifies the location (cell) of the mobile phone you have dialed and connects you to that phone. The caller mobile on receiving your signal generates again through an oscillator circuit your ID (mobile number) and displays it. This whole process happens with in a few seconds as all the signals are transferred through electromagnetic waves, which travel at the speed of light. Here, it is important to note that mobile phone call is transferred from dialer cell antenna to MTSO and MTSO to caller cell antenna only through cell antenna lying in between. That is why mobile phone network is also called terrestrial cellular network.
Mobile phone numbering system
Due to mobility of a mobile phone it is necessary to identify every mobile phone. For this, a SIM (Subscriber Identity Module) card in inserted in every mobile phone. SIM card is like an identity card of its user. It is a small IC (Integrated circuit) chip with a unique SIM number and a mobile phone number. A typical SIM card is shown in the figure. All SIM cards are issued by mobile operator companies and their information is provided to MTSO. After SIM verification, MTSO activates the mobile number of the user. This makes a mobile phone usable. Every mobile number in India is of 10 digits. All mobile numbers in India have the prefix 9,8 or 7. As per National Numbering Plan 2003, the way to split mobile numbers is as XXXX-NNNNNN where XXXX is Network operator digits and NNNNNN is\ the subscriber number digits. To regulate the use of mobile phones system in India a Telecom Regulatory Authority of India (TRAI) was established in 1997 by an act of Parliament.
Mobile network Generations (1G, 2G, 3G & 4G)
With increasing use of mobile phones and advancement of technology, it is pertinent to make the mobile phone networks more efficient. The efficiency of mobile networks is mentioned by word ‘Generation’ and abbreviation ‘G’. 1G were first generation of mobile networks, which were based on analogue radio signals. 2G were narrow band digital signal based networks with good quality of calls.
They provided world over connectivity. 3G networks increased the data transfer speed for efficient use of Internet on mobile phone. 4G networks are going to provide a high-speed internet facility on mobile phones for surfing net, chatting, viewing television, listening music etc.
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