Cellular radio has other popular names as cellular mobile or mobile phone. Radio is basically a device, which uses receiver and transmitter. Wireless communication can also be carried out without using radio. The interference caused by high power line to radio transmission is also an example of wireless communication though it is termed as noise. Inductive and conductive circuits and devices can communicate wirelessly for limited distance with less reliability and implementation problem. Therefore, these techniques cannot be termed as radio transmission.
The term radio may be defined as consisting of modulation and radiation of the signal.. Therefore, a transmitter and an antenna are used to modulate and radiate the modulated signal within radio spectrum. On the hand at the receiving end, an antenna and a receiver is required to demodulate the signal. If the transmitting and receiving end are receiving and transmitting, a transceiver (consisting of transmitter and receiver operation) is employed. In telephone system as we know that a voice with bandwidth of approximately 4 kHz modulates the current of a telephone line. Wireless can be defined as the radio transmission and reception of signals by means of high frequency electrical waves without a connecting wire.
A cellular system is the communication system that divides a geographic region into sections, called cells, each having its own dedicated frequency. The frequency of a cell may be reused after the interfere once zone. Now, we can define cellular radio or cellular mobile or mobile phone as a communication system that consists of a combination of radio transmission and Public Switched Telephone Network (PSTN) to permit telephone communication to and from mobile subscribers within a specified area. This requires a cellular architecture, which has been described in the subsequent sections. For digital communications, several competing cellular systems exist. These are Global System for Mobile Communication (GSM), CDMA etc.
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