Beginning of Mobile or Wireless Communication

The very first mobile phones were referred to as ‘radiotelephones’ and were first used in the early part of the last century for ship to shore or ship to ship communications.

 

Guglielmo Marconi was the person who developed the first successful wireless telegraph, but this system could only transmit the dots and dashes of Morse Code. We might say, without stretching theanalogy too far, that Marconi pioneered the first wireless data system. In 1901,Marconi placed a radio aboard a steam-powered truck, in effect creating the first land based wireless mobile data network.

The first successful wireless transmission of human speech, however, had to wait until Christmas Eve in 1906, when Reginald Fessenden used a radio totransmit music and spoken word to ships at sea in the Atlantic Ocean.

Experimental service began on coastal steamers between Boston and Baltimore in the United States in 1919; commercial service using AM technology at 4.2 and 8.7 MHz began in 1929. This was period DURING which AM radio broadcasting began to capture the public’s attention.  

By 1932, tests were being conducted at a number of other frequencies over a variety of transmission paths with varying distances, and with effects due to such phenomena as signal reflection, refraction, and diffraction noted. (Such tests are still being conducted today by various investigators for different signal propagation environments, both indoor and outdoor, and at different frequency bands.

In 1935, further propagation tests were carried out in Boston at frequencies of 35 MHz and 150 MHz. Multipath effects were particularly noted at this time. The tests also demonstrated that reliable transmission was possible using FM rather than the earlier AM technology

In 1946, the Federal Communications Commission, FCC, in the USA, granted a license for the operation of the first commercial land-mobile telephone system in St Louis. By the end of the year, 25 US cities had such systems in operation. The basic system used FM transmission in the 150 MHz band of frequencies, with carrier frequencies or channels spaced 120 kHz apart. In the 1950s the channel spacing was reduced to 60 kHz, but, because of the inability of receivers to discriminate sufficiently well between adjacent channels, neighboring cities could only use alternate channels spaced 120 kHz apart. A 50-mile separation between systems was required. High towers covering a range of 20–30 miles were erected to provide the radio connections to and from mobile users. Forty channels or simultaneous calls were made available using this system

In 1949 the Bell System had requested permission from the FCC to move mobile telephone operations to the 470–890 MHz band to attain more channels and, hence, greater mobile capacity. This band was, at that time, intended for TV use however, and permission was denied. In 1958 the Bell System requested the use of the 764–840 MHz band for mobile communications, but the FCC declined to take action. By this time, the introduction of the cellular concept into mobile systems was under full discussion at Bell Laboratories.

Federal Communications Commission (FCC) had decided to allocate spectral capacity in the vicinity of 840 MHz for mobile telephony in 1968. In 1971, Bell System responded by submitting a proposal for a “High-Capacity Mobile Telephone System,” which included the introduction of cellular technology. (This proposed system was to evolve later into AMPS, the Advanced Mobile Phone Service, the first-generation analog cellular system mentioned earlier.)

The AMPS system is generally called a 1st (1G) first-generation cellular mobile system, as noted above, and is still used, as noted earlier, for cell-system backup. It currently covers two 25 MHz-wide bands: the range of frequencies 824–849 MHz in the uplink or reverse-channel direction of radio transmission, from mobile unit to the base station; 869–894 MHz in the downlink or forward-channel direction, from base station to the mobile units. The system uses analog-FM transmission, as already noted, with 30 kHz 6 Mobile Wireless Communications allocated to each channel, i.e. user connection, in each direction. The maximum frequency deviation per channel is 12 kHz. Such a communication system, with the full 25 MHz of bandwidth in each direction of transmission split into 30 kHz-wide channels, is called a frequency-division multiple access (FDMA) system.

Despite the mobile capacity improvements made possible by the introduction of the cellular-based AMPS in 1983, the Cellular Telecommunications Industry Association began to evaluate various alternatives, studying the problem from 1985 to 1988 and a decision was made to move to a digital time-division multiple access, TDMA, technology. This system would use the same 30 kHz channels over the same bands in the 800–900 MHz range as AMPS, to allow some backward compatibility. Each frequency channel would, however, be made available to three users, increasing the corresponding capacity by a factor of three.

In 1986, QUALCOMM, a San Diego communications company that had been developing a code-division multiple access, CDMA, mobile system, got a number of the RBOCs, such as NYNEX and Pacific Bell, to test out its system, which, by the FCC rules, had to cover the same range of frequencies in the 800–900 MHz band as did AMPS and D-AMPS.

                In 1982 the Telecommunications Commission of the European Conference of Postal and Telecommunication Administrations (CEPT) established a study group called the Groupe Speciale Mobile (GSM) to develop the specifications for a European-wide second-generation digital cellular system in the 900 MHz band. By 1986 the decision had been reached to use TDMA technology.

 In 1987 the European Economic Community adopted the initial recommendations and the frequency allocations proposed, covering the 25 MHz bands of 890–915 MHz for uplink, mobile to base station, communications, and 935–960 MHz for downlink, base station to mobile, communications which is the beginning of 2nd Generation (2G) of Mobile communication also called GSM (for either Global System for Mobile Communications or the GSM System for Mobile Communications). The first GSM systems were running by 1991 and commercial operations began in 1992. GSM has since been deployed throughout Europe, allowing smooth roaming from country to country. As of now 2G or second generation mobile communication is the successful communication system with the service of voice call, message service and also internet service which is adopted by millions people throughout the world.

In 1998, 3rd Generation (3G) mobile communication system commercially launched in JAPAN by NTT DoCoMo which uses the W-CDMA (Wideband CDMA) technology. But its research and development was carried out International Telecommunication Union (ITU) in the early 1980s.

3G technology offers wide range of services compared to 2G which are mobile TV, Global positioning sytem(GPS), Video conferencing, Video on demand. Most enhanced features include HIGH data speed upto 3.5 Mbps and video call

 

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