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History of mobile phones

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					     History of mobile phones

The history of mobile phones records the development of interconnection
between the public switched telephone systems to radio transceivers. From
the earliest days of transmitting speech by radio, connection of the
radio system to the telephone network had obvious benefits of eliminating
the wires. Early systems used bulky, high power consuming equipment and
supported only a few conversations at a time, with required manual set-up
of the interconnection. Today cellular technology and microprocessor
control systems allow automatic and pervasive use of mobile phones for
voice and data.

The transmission of speech by radio has a long and varied history going
back to Reginald Fessenden's invention and shore-to-ship demonstration of
radio telephony, through the Second World War with military use of radio
telephony links. Mobile telephones for automobiles became available from
some telephone companies in the 1950s. Hand-held radio transceivers have
been available since the Second World War. Mobile phone history is often
divided into generations (first, second, third and so on) to mark
significant step changes in capabilities as the technology improved over
the years.

Pioneers of radio telephony

By 1930, telephone customers in the United States could place a call to a
passenger on a liner in the Atlantic Ocean. Air time charges were quite
high, at $7(1930)/minute (about $92.50/minute in 2011 dollars). In areas
with Marine VHF radio and a shore station, it is still possible to
arrange a call from the public telephone network to a ship, still using
manual call set-up and the services of a human marine radio operator.

However it was the 1940s onwards that saw the seeds of technological
development which would eventually produce the mobile phone that we know
today. Motorola developed a backpacked two-way radio, the Walkie-Talkie
and a large hand-held two-way radio for the US military. This battery
powered "Handie-Talkie" (HT) was about the size of a man's forearm.

In 1946 in St. Louis, the Mobile Telephone Service was introduced. Only
three radio channels were available, and call set-up required manual
operation by a mobile operator. Although very popular and commercially
successful, the service was limited by having only a few voice channels
per district.

In 1964 Improved Mobile Telephone Service was introduced with additional
channels and more automatic handling of calls to the public switched
telephone network. Even the addition of radio channels in three bands was
insufficient to meet demand for vehicle-mounted mobile radio systems.

In 1969, a patent for a wireless phone using an acoustic coupler for
incoming calls was issued in US Patent Number 3,449,750 to George
Sweigert of Euclid, Ohio on June 10, 1969, but did not include dialing a
number for outgoing calls.

Cellular concepts:
In December 1947, Douglas H. Ring and W. Rae Young, Bell Labs engineers,
proposed hexagonal cells for mobile phones in vehicles. Philip T. Porter,
also of Bell Labs, proposed that the cell towers be at the corners of the
hexagons rather than the centers and have directional antennas that would
transmit/receive in three directions (see picture at right) into three
adjacent hexagon cells. At this stage, the technology to implement these
ideas did not exist, nor had the frequencies been allocated. Several
years would pass before Richard H. Frenkiel and Joel S. Engel of Bell
Labs developed the electronics to achieve this in the 1960s.

In all these early examples, a mobile phone had to stay within the
coverage area serviced by one base station throughout the phone call,
i.e. there was no continuity of service as the phones moved through
several cell areas. The concepts of frequency reuse and handoff, as well
as a number of other concepts that formed the basis of modern cell phone
technology, were described in the 1970s. In 1970 Amos E. Joel, Jr., a
Bell Labs engineer, invented an automatic "call handoff" system to allow
mobile phones to move through several cell areas during a single
conversation without interruption.

In 1969 Amtrak equipped commuter trains along the 225-mile New York-
Washington route with special pay phones that allowed passengers to place
telephone calls while the train was moving. The system re-used six
frequencies in the 450 MHZ band in nine sites, a precursor of the concept
later applied in cellular telephones.

In December 1971, AT&T submitted a proposal for cellular service to the
Federal Communications Commission (FCC). After years of hearings, the FCC
approved the proposal in 1982 for Advanced Mobile Phone System (AMPS) and
allocated frequencies in the 824–894 MHz band. Analog AMPS was eventually
superseded by Digital AMPS in 1990.

A cellular telephone switching plan was described by Fluhr and Nussbaum
in 1973, and a cellular telephone data signaling system was described in
1977 by Hachenburg et al. In 1979 a U.S. Patent 4,152,647 was issued to
Charles A. Gladden and Martin H. Parelman, of Las Vegas for an emergency
cellular system for rapid deployment in areas where there was no cellular
service.

				
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Description: all info about mobiles