The service area is allotted a radio frequency (RF) transmitter, whereas adjacent cells operate on different frequencies to avoid interference.Ĭellular telephones began as a simple two-way analogue communication system using frequency modulation for voice and frequency-shift keying for transporting control and signalling information. The discrete channels are capable of being reused in different cells with diameters ranging from 2 to 50 km. The cellular system works as follows: An available frequency spectrum is divided into discrete channels, which are assigned in groups to geographic cells covering a service area. Advances in wireless access, digital signal processing, integrated circuits, increased battery life, etc led to exponential growth of personal communication services. The advent of cellular operation brought frequency reuse capabilities. The most important breakthrough was the cellular concept. Since the commercial introduction of the advanced mobile phone system (AMPS) service in 1983, mobile communication systems have witnessed explosive growth. Present and past of mobile communicationsīefore I narrate the journey from 1G to 4G, let me explain the important technologies behind the phenomenal growth of mobile communication systems. These include continuous wave (CW), AM, FM, radio teleprinter, HF slow-scan still picture TV, VHF or UHF slow-scan or fast-scan TV, facsimile, frequency-shift keying and amplitude-shift keying. For privacy, each mobile unit carries a unique telephone number.Īmateur (HAM) radios cover a broad frequency band from 1.8 MHz to above 30 MHz. These are one-to-one systems that permit two simultaneous transmissions.
Mobile telephones offer full-duplex transmission. It is limited to small geographical areas. Public land mobile radio is a two way FM radio system, used in police, fire and municipal agencies. It can be amplitude modulated having double-sideband suppressed carrier or single-sideband suppressed carrier. It is a non-commercial service that uses a press-to-talk switch. It operates in the frequency range of 26-27.1 MHz having 40 channels of 10 kHz. The most common among this type is citizen band (CB) radio, which uses amplitude modulation (AM). Mobile two-way radios are one-to-many communication systems that operate in half-duplex mode, i.e., push to talk. The different types of mobile communication systems are a mobile two-way radio, public land radio, mobile telephone and amateur ( HAM) radio. These communication systems may have different facilities. Read this article to understand the evolution from 1G to 4G with technologies behind this phenomenal growth and important developments along the way.Īny radiotelephone capable of operating while moving at any speed, battery operated and small enough to be carried by a person comes under the mobile communication systems. Mobile communications technology has come a long way since the initial analogue phones.
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