World Of Mobile & Telecommunication.

A Mobile Telephone is defined as a 'portable electronic device for the purpose of telecommunications over long distances'. Which boils down to 'a telephone you can roam freely with'. Most current mobile phones actaully connect to a cellular networi of base stations (the cell sites themselves) which overlap to yield coverage and which also link to the standard landline public switched telephone network. It should be noted that mobile phones are distinct from household cordless telephones which generally operate only within range of a dedicated base station (though the distinction is blurring with mobile phones that can link via bluetooth to a home internet base station).
It should be noted, however, that the term mobile phone can refer to any type of mobile telephony device and also includes satellite phones and radio phones. In contrast cell(ular) phones refers only to those mobile phones that function via cellular base stations. Despite these distinctions, in common parlance the terms are used almost interchangeably.
t is generally accepted that the first truly portable 'modern' mobile phone was invented by Martin Cooper of Motorola Corp in 1973 and he made the first call on this handheld device on April 3rd and thus changed our world forever. However, it wasn't for a further eight years that NMT (Nordisk MobilTelefoni or Nordiska MobilTelefoni-gruppen, Nordic Mobile Telephone in English) introduced the first fully-automatic cellular telephone system.
Most current mobile phones work on what's termed 2.5G (sedcond and a halfth generation) which includes technologeis such as packet-switched connection and enhanced data rates and these networks support WAP, MMS (Multimedia Messaging Service), SMS mobile games, and search and directory but they exclude EDGE (Enhanced Data GSM Environment) and GPRS (General Packet Radio Service) technologies. The reality is that most non-3G telephones sold today adhere to 2.5G standards and technologies rather than 2G and texting services such as SMS, MMS and picture messaging have become standard features of mobile telephones.
Though electronically complex, how a mobile phone works can be defined in fairly simple terms: In effect, the phone is simply a means of converting the owner’s voice into a digital signal that can be transmitted via the phone’s antenna to a receiving station. At the same time the telephone receives an incoming signal from the receiving station via its antenna which the phone converts into the voice of the person on the other end of the call.
Most phones today have a SIM (Subscriber Identity Module) card that is a specialized form of flash memory. This card stores information such as address books, contacts, calendars. But it also holds other very important data that the user cannot normally access. Indeed, the first time a new mobile phone is used (actually, to be precise, the first time a new SIM card is used in a phone) a number held on the SIM card called the International Mobile Subscriber Identifier (IMSI) number is transmitted to the network. The network then looks this number up in a database to ensure the SIM card is registered there. If this is the case then a number called the Temporary Mobile Subscriber Identity (TMSI) is encrypted and sent back to the phone where it is stored in the SIM card. In all subsequent calls the phone uses this TMSI number to identify itself by broadcasting the number to the network.
Each time a call is made the TMSI is transmitted to the network. The transmission of this number is followed by a complex series of events — each designed to verify that the phone and the phone’s owner are who they actually claim to be. Once this is verified a mobile telephone call can be made. The usual thing to do at this point is to dial a call using the telephone’s keypad. This is modelled on the numeric keypad of landline telephones for the sake of familiarity. Though, as phones are increasingly used for data and message transmission the keypads can access a wide range of characters and some phones now come with full computer keypads. There is also a move away from the traditional numeric keypad, such as in Apple’s iPhone which uses a touch sensitive bezel that is similar to the one found on Apple’s iPod range of music players.
In terms of being able to make and receive mobile telephone calls then the control channel of the mobile telephone network is all important as it's this that infroms the network where your phone is so that you can connect to the appropriate cell. This is a signal broadcast by mobile telephone transmitter towers and it's this which tells the system which cell you are in, so that this information can be stored in the system's database. It is entirely because of this that an incoming call can be routed to your phone.