Mobile phone (telefone celular) is a wireless, portable,
long-range, electronic telephone, which during travel can seamlessly
change antenna connections, from one radio reception cell to another
radio reception cell, without dropping or losing the ongoing call.
Besides the standard voice function of a telephone, latest Mobile
phones (telefone celular) have features such as SMS for text
messages, MMS for multimedia messages, radio, games, internet
connectivity for email, browsing, blogging, music (MP3) playback,
memo recording, built-in cameras and camcorders, ringtones, personal
organizers, Push-to-Talk (PTT), Bluetooth and infrared connectivity,
call registers, streaming video, downloading video, video call, and
also serve as wireless modems for PCs that can be connected to the
Internet.
The power in a mobile phone (telefone celular) is obtained from
rechargeable batteries, which can be recharged from the mains, a USB
port or a cigarette lighter port in an automobile. Nickel Metal
Hydride were the most common types of batteries, which due to the
"memory effect" (the user can recharge only when the entire battery
is drained off) were replaced by Lithium-Ion batteries, which did
not suffer from any memory effect.
Mobile phones (telefone celular) came into existence because of the
invention of hexagonal cells in 1947, for the base stations by Bell
Labs engineers at AT&T. This was further developed during the 1960s
by Bell Labs. During a call, the channel frequency could not be
changed automatically from one cell (base station coverage area) to
another cell (base station coverage area) as the person traveled
from the area of one cell to the area of another cell. Amos Joel of
Bell Labs invented a breakthrough invention and called it as the
`call handoff` by which the channel frequency could be changed
automatically from one cell to another cell, during the same call,
as the mobile user traveled from one cell to another cell. Due to
their heavy construction, these phones were used mainly in
automobiles.
The first practical mobile phone in a non-vehicle setting, and which
could be handheld, was invented by Martin Cooper, the General
Manager (Communications Division) of Motorola, who made the world`s
first handheld mobile phone (telefone celular) call on April 3,
1973.
The technology by which the mobile phone (telefone celular) works
depends on the mobile phone operator; however, all of them use
electromagnetic radio waves, which are in touch with a cell site
(base station). The base station is composed of several antennas
which are mounted on a pole, tower, or building. Cell sites are
spread at a distance of 5 to 8 miles (approx. 8 to 13 km) from each
other. The low power transceiver from the mobile phone transmits the
voice and data to the nearest cell site. During movement, the mobile
phone will "handoff" the information to other cell site. Mobile
phone operators use many technologies to maintain the smooth stream
of digitized data from the mobile phone to the cell site and vice
versa.
The wireless telephone technologies are grouped under heads known as
generations, starting from zero generation or 0G. The current
generation going on is 4G; however, there are old mobile phones (telefone
celular) that still operate on 1G, 2G, and 3G technologies. The
wireless telephone technologies used in each generation are as given
below:
0G: PTT, MTS, IMTS, AMTS, OLT, MTD, Autotel/PALM, ARP
1G: NMT, AMPS/TACS/ETACS, Hicap, CDPD, Mobitex, DataTac
2G: GSM, iDEN, D-AMPS, IS-95/cdmaOne, PDC, CSD, PHS, GPRS, HSCSD,
WiDEN, CDMA2000 1xRTT/IS-2000, EDGE (EGPRS)
3G: W-CDMA, UMTS (3GSM), FOMA, TD-CDMA/UMTS-TDD, 1xEV-DO/IS-856, TD-SCDMA,
GAN (UMA), HSPA, HSDPA, HSUPA, HSPA+, HSOPA
4G : UMB, UMTS Revision 8 (LTE), WiMAX
Frequency bands: SMR, Cellular, PCS
The impact of mobile phone (telefone celular) usage on human health
has been of considerable worldwide concern. Research studies in
Copenhagen, from the Danish Institute of Cancer Epidemiology, the
National Cancer Institute, and the Institute of Cancer Research, do
not establish any link between cancer and mobile phone usage.
However, an intergovernmental agency IARC (International Agency for
Research on Cancer) forming part of the World Health Organization of
the United Nations, undertook a study of 4,500 users and found a
statistically significant link between mobile phone usage and tumor
frequency. Further research is going on.
Mobile phone (telefone celular) usage and driving is a common
worldwide phenomenon. Some jurisdictions have banned usage of
hand-held phones during driving, but allowed the hands-free fashion
of mobile phone usage while driving. However, studies have found out
that the distraction is caused by the conversation itself; hence,
both hand-held and hands-free mobile phones contribute towards road
traffic accidents. Further studies on mobile phone usage and driving
are going on.
Nokia Corporation is currently the world`s largest manufacturer of
mobile phones (telefone celular). Other notable mobile phone
manufacturers, in alphabetical order, are 3G, Audiovox (now UT
Starcom), Benefon, BenQ-Siemens, Fujitsu, High Tech Computer
Corporation (HTC), Kyocera, LG Mobile, Motorola, NEC, Panasonic
(Matsushita Electric), Pantech Curitel, Philips, Research In Motion,
Sagem, Samsung, Sanyo, Sharp, Siemens, Sierra Wireless, SK Teletech,
Sony Ericsson, T&A Alcatel, Toshiba, and Verizon.