The term does not comprise the so-called portable phone or cordless phone, which is associated with a fixed telephone landline and can only be operated close to (less than 100 metres of) its base station, such as in and around the house (see telephone for more). The term cell phone applies specifically to mobile phones which use a cellular network; satellite phones are also mobile phones, but not cellular.
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2 Cellular telephony 3 Satellite telephony (INMARSAT) 4 Related articles |
Mobile phones have existed at least since the 1950s, though the distinction becomes blurry when special systems are used to "patch" conventional Radiotelephones (2-way radio) into a phone network with the assistance of human operators. Modern mobile phones can make and receive calls automatically, operating as would a normal phone (though most have a superset of the ability of fixed-line phones).
Mobile phones began to proliferate through the 1980s with the introduction of "cellular" phones, with multiple base stations located relatively close to each other, and protocols for the automated "hand-off" between two cells when a phone moved from one cell to the other. In this era, mobile phones were somewhat larger than current ones, and many were designed for permanent installation in cars, or as "transportable" phones the size of a briefcase.
As technology improved through the 1990s, the larger "bricks" disappeared and tiny hand-held phones became the norm.
In most of Europe, wealthy parts of Asia, and Australasia, mobile phones are now virtually universal, with the majority of the adult, teenage, and even child population owning one. They are less common in the United States — while widely available, market penetration is lower than elsewhere in the developed world (around 66 percent of the U.S. population as of 2003). Reasons advanced for this include incomplete coverage, fragmented networks making roaming difficult, inferior network technology, relatively high minimum monthly service charges, relatively low-cost fixed-line networks, and the car-centric nature of US society.
The effects of antitrust legislation in the United States breaking up the nationwide Bell network may also have had an effect. In other parts of the world the competing mobile phone companies have offered a wide range of service plans from pre-paid cards to high flat rate subscriptions. They have also resorted to cut-throat discounting, normally selling handsets at high discounts (including wholly subsidised units) in return for long term (usually 1-year) contracts with high disconnection costs and handsets locked to single networks (SIMLOCKS). Such practices allowed many consumers to obtain a mobile phone and caused spectacular market penetration. The experience of the American telephone companies with antitrust cases in the 1980s and 1990s meant that they would be reluctant to engage in these practices to build their customer base.
Due to their low establishment costs and rapid deployment, mobile phone networks are rapidly spreading throughout the developing world, outstripping the growth of fixed telephony. Such networks can often be economic, even with a small customer base, as mobile network costs are mostly call volume related, while fixed-line telephony has a much higher subscriber related cost component.
A cell phone is a portable telephone which receives or sends messages through a Cell site, or transmitting tower. Radio waves are used to transfer signals to and from the cell phone. Each cell site has a range of 3-5 miles and overlaps other cell sites. All of the cell sites are connected to one or more cellular switching exchanges which can detect the strength of the signal received from the telephone. As the telephone user moves or roams from one cell area to another, the exchange automatically commands the handset and a cell site with a stronger signal (from the handset) to go to a new radio channel. When the handset responds through the new cell-site, the exchange switches the connection to the new cell-site.
Modern mobile phones use cells because radio frequencies are a limited, shared resource. Cell-sites and handsets change frequency under computer control and use low power transmitters so that a limited number of radio frequencies can be reused by many callers with less interference. An incidental benefit is that the batteries in the handsets need less power.
The term "cell phone" is uncommon outside of the US and Japan. However, almost all mobile phones use cellular technology, including GSM, CDMA and the old analog mobile phone systems. Hence, many people use the term "cell phone" to mean any mobile telephone system. The exception to mobile phones using cellular technology are satellite phones.
The Iridium phone system is very like a cell phone system except the cell sites are in orbit.
The marine radio telephone satellites administered by INMARSAT have a completely different system (see below).
Old systems pre-dating the cellular principle may still be in use in places.
The most notable real hold-out is that many amateur radio operators maintain phone patches in their clubs' VHF repeaters.
Early mobiles were analog; newer ones are digital.
There are a number of different digital cellular technologies; these include: GSM, CDMA, DECT.
Mobile phone technology is often divided into generations: 1G, 2G, 2.5G,2.7G, 3G:
Major mobile phone manufacturers include Nokia, Sony Ericsson, Motorola, and Samsung.
Many mobile phones support 'auto-roaming', which permits the same phone to be used in multiple countries. However, both countries must use the same mobile system and the same frequencies (this is an important issue for GSM users traveling between North America and the rest of the world), and there must be an agreement between the two countries' telephone operators.
In the UK and Australia, mobile phones are often called simply mobiles. In Germany, they are called Handys. In Sweden they are sometimes called nalle, or "teddy bear", referring to the fact that many people always carry them around and feel insecure if they misplace them.
Mobile phones must be distinguished from portable phones (called cordless phones in the US); with a portable phone the user purchases their own base station, which they connect to a landline, the range of the phone is generally restricted to under 50 m, and the phones operate on a different frequency and protocol (e.g. DCTS in North America; DECT in Europe).
Mobile phones do not only support voice calls; they can also send and receive data and faxes (if a computer is attached), sending short messages (or "text messages"; see Short Message Service), access WAP services, and provide full Internet access using technologies such as GPRS. Mobile phones often have a clock and a calculator and often one can play some games on them.
Newer models also allow for sending pictures and have a built-in digital camera. This gives rise to some concern about privacy, in view of possible voyeurism, for example in swimming pools. For this reason, Saudi Arabia has banned camera phones entirely; South Korea has ordered manufacturers to ensure that all new handsets emit a beep whenever a picture is taken. On the other hand, cameras can be used by crime victims or witnesses to help identify the criminals.
GPS receivers are starting to appear in cell phones, primarily to aid in dispatching emergency responders.
Newer models have included many features aimed towards personalisation, such as user defined ring tones and operator logos, and interchangeable covers, which have helped in the uptake by the teenage market.
Usually one can choose between a ring tone and a vibrating alert.
Inmarsats use a completely different system. Basically, the satellite simply retransmits whatever signals it receives. The mobile stations actually log into a ground station. More information is available at INMARSAT.
Note: In cellular mobile systems, large geographical areas are segmented into many smaller areas, i.e., cells, each of which has its own radio transmitters and receivers and a single controller interconnected with the public switched telephone network. Synonyms cellular phone, mobile phone, cellular radio, cellular telephone.
Source: from Federal Standard 1037CHistory
Cellular telephony
Satellite telephony (INMARSAT)