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Mobile phone
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Mobile phone

A mobile phone is a portable device which acts as a normal telephone whilst being able to move over a wide area. Mobile phones allow connections to be made to the telephone network, normally by directly dialling the other party's number on an inbuilt keypad. Most current mobile phones use a combination of radio wave transmission and conventional telephone circuit switching, though packet switching is already in use for some parts of the mobile phone network, especially for services such as push to talk.

There are also specialist communication systems related to, but distinct from mobile phones, such as satellite phones and Professional Mobile Radio.

Table of contents
1 History
2 Worldwide Deployment
3 Terminology
4 Mobile Phone Features
5 Cellular telephony
6 Spectrum Allocation
7 International roaming
8 Multi mode mobile phones
9 Terms in other Languages
10 Using Mobile phones on aircraft
11 Health controversy
12 Future prospects
13 See also
14 External links

History

What was possibly the first real mobile phone, in the sense that it was connected to the telephone network, was tested by the Swedish police in 1946. A half dozen calls could be made before the (car's) battery ran out. Radiophones began to be publicly available, in the US, at the end of the 1940s[1] though the distinction between such phones and a two way radio becomes blurry since special systems are required to "patch" into the phone network with the assistance of human operators. Recognisable mobile phones with direct dialling have existed at least since the 1950s

Modern mobile telephony is often considered to have started on April 3rd, 1973, when Martin Cooper – then an employee of Motorola – placed the first call to the company's rival AT&T;'s Bell Labs, while walking the streets of New York City.

Mobile phones began to proliferate through the 1980s with the introduction of "cellular" phones based on cellular networks 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. At this time analog transmission was in use in all systems. Mobile phones were somewhat larger than current ones, and many were designed for permanent installation in cars (hence the term car phone), or as "transportable" phones the size of a briefcase. These systems (NMT, AMPS, TACS) later became known as first generation mobile phones.

In October 1981 the first cell phone network with automatic roaming between countries was started in the Nordic countries, it was a NMT system. It became the start of the cell phone boom and became much more successful then ever anticipated.

In the 1990s, second generation (2G) mobile phone systems such as GSM, IS-136 ("TDMA"), iDEN and IS-95 ("CDMA") began to be introduced. The first digital cellular phone call was made in the United States in 1990, in 1991 the first GSM network opened in Europe. 2G phone systems characterised by digital circuit switched transmission and the introduction of advanced and fast phone to network signalling. In general the frequencies used by 2G systems were higher though with some overlap, for example the 900MHz frequency range was used for both 1G and 2G systems in Europe and so such 1G systems were rapidly closed down to make space for 2G systems.

Coinciding with the introduction of 2G systems were trends which meant that the larger "bricks" disappeared and tiny 100–200g hand-held devices became the norm. These trends included technology improvements such as better battery technologies and lower power electronics, but also are largely related to the higher density of cellular sites caused by increasing usage levels.

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, relatively high minimum monthly service charges (around $30), and the availability of relatively low-cost fixed-line networks (around $30 for unlimited local calling).

Not long after the introduction of 2G networks, projects began to develop 3G systems. Inevitably there were many different standards with different contenders pushing their own technologies. Quite differently from 2G systems, however, the meaning of 3G has been standardised in the IMT-2000 standardisation process. This process did not standardise on a technology, but rather on a set of requirements (2Mb/s maximum data rate indoors, 384Kb/s outdoors, for example). At that point, the vision of a single unified worldwide standard broke down and several different standards have been introduced.

During the development of 3G systems, 2.5G systems such as CDMA-2000 1X and GPRS were developed as extensions to existing 2G networks. These provide some of the features of 3G without fulfilling the promised high data rates or full range of multimedia services. E.g. CDMA2000-1X delivers theoretical maximum data speeds of up to 307 Kbps. Just beyond these is the EDGE system which in theory covers the requirements for a 3G system, but is so narrowly above these that any practical system would be sure to fall short.

At the beginning of the 21st century, 3G mobile phone systems such as UMTS and CDMA-2000 1xEV-DO have now begun to be publicly available. The final success of these systems is still to be determined.

Worldwide Deployment

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.

Terminology

Mobile Phone Terms

; Cell Phone or Cellular telephone : Term used currently in America and during the 80s to refer to most mobile phones. This term applies specifically to mobile phones which use a cellular network. ; Mobile phone : A term covering cellular phones, satellite phones and any phones giving wide ranging mobility. ; Satellite Phone : A mobile phone which communicates with a satellite rather than a land-based tower. ; Wireless Phone : This is a term which is generally used to refer to a mobile phone although it could legitimately cover almost any phone which does not use a wire. ; 3G Phone : A mobile phone which uses a 3G network.

Related systems which are not mobile phones

; Cordless Phone (Portable Phone) : Cordless phones are standard telephones with radio handsets. Unlike mobile phones, cordless phones use private base stations that are not shared between subscribers. The base station is connected to a land-line. ; Radio Phone : This is an term which covers radios which could connect into the telephone network. These phones may not be mobile, e.g. they may require a mains power supply. ; Professional Mobile Radio : Professional mobile radio systems are very similar to mobile phone systems and attempts have even been made to use TETRA, the international digital PMR standard, to implement public mobile networks, but normally PMR systems are sufficiently separate from the phone network to not really be considered phones but rather radios.

Mobile Phone Features

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 do not only support voice calls; they can also send and receive data and faxes (if a computer is attached), send short messages (or "text messages"; see SMS), access WAP services, and provide full Internet access using technologies such as GPRS. Mobile phones usually 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 cameraphones entirely; South Korea has ordered manufacturers to ensure that all new handsets emit a beep whenever a picture is taken. Some swimming pools have banned camera mobile phones in their pools and changing rooms. Some companies and military agencies prohibit camera phones in certain locations for security reasons. 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 toward personalisation, such as user defined and downloadable ring tones and logoss, and interchangeable covers, which have helped in the uptake by the teenage market. Usually one can choose between a ring tone, a vibrating alert, or a combination of both.

Cellular telephony

A cell phone is a portable telephone which receives or makes calls through a Cell site, or transmitting tower. Radio waves are used to transfer signals to and from the cell phone. Large geographic areas (representing the coverage range of a service provider) are split up into smaller cells to deal with line-of-sight signal loss and the large number of active phones in an area. Each cell site has a range of 3-15 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 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 channels. When the handset responds through the new cell-site, the exchange switches the connection to the new cell-site.

With CDMA technology, the process is slightly different. Multiple CDMA handsets share a specific "channel"; the signals are separated by sending each bit using a pseudo-random code sequence specific to each phone. As the user moves from one cell to another, the handset actually connects to both sites simultaneously. This is known as a "soft handoff" because, unlike with traditional cellular technology, there is no one defined point where the phone switches to the new cell.

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. CDMA handsets, in particular, must have strict power controls to avoid interference with each other. An incidental benefit is that the batteries in the handsets need less power.

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.

Old systems predating 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.

There are a number of different digital cellular technologies; these include: GSM, CDMA (Code Division Multiple Access), DECT, IS-136, and iDEN.

Spectrum Allocation

PCS is often mistakenly referred to as a different 2G technology. It is not. PCS is an acronym for Personal Communications Service, which merely represents the 1900 MHz spectrum set aside by the FCC in America for additional wireless phone capacity. GSM-1900, IS-95, IS-136, and CDMA2000 operate on the 1900 MHz PCS band today.

The other spectrum used in North America (850 MHz) was the original spectrum licensed by the FCC in the 1980s, commonly referred to as Cellular spectrum. Today, AMPS, IS-95, CDMA2000, IS-136, and more recently GSM-850 all operate on the Cellular spectrum.

Mobile phone manufacturers include Motorola, Nokia, Samsung, Siemens, Sony Ericsson, Alcatel and Sagem.

International roaming

Many mobile phones support 'auto-roaming', which permits the same phone to be used in multiple countries. For this to work, the telephone operators of both countries must have a 'roaming agreement' which permits each other's subscribers to use each other's networks also required is a mobile phone which supports both networks. In the most common case (a GSM mobile roaming onto another compatible GSM network: a large proportion of the roaming which occurs) this is trivial.

In the case where there is a difference in the mobile phone systems used by the operators, the situation becomes more complex and a multi-band or multi-mode phone may be required. The multi-band case occurs mostly in GSM which originated in the 900MHz band, but expanded to other bands. See the GSM article for more details on this.

Multi-mode phones are a more complicated case case. They are phones which provide access to two systems such as IS-95 and GSM 900. Such phones could give an American subscriber, who would otherwise have limited access to international roaming, full access to all of the GSM countries in Europe and Asia. Multi-mode phones are becoming much more common with the introduction of WCDMA, but the reason here is slightly different. See the section on multi mode phones below.

Multi mode mobile phones

A multi-mode mobile phone is a phone which is designed to work on more than one mobile phone standard. Multimode phones have been valuable to enable roaming but are now becoming most important in allowing the introduction of WCDMA without customers having to give up the wide coverage of GSM. Almost every single true 3G phone sold is actually a WCDMA/GSM dual-mode mobile. This is also true of 2.75G phones such as those based on CDMA-2000 or Edge.

The special challenge involved in producing a multi-mode mobile is in finding ways to share the components between the different standards. Obviously, the phone keypad and display should be shared, otherwise it would be hard to treat as one phone. Beyond that, though, there are challenges at each level of integration. How difficult these challenges are depends on the differences between systems. The different variants of the GSM system have only different frequencies and so aren't even considered true multi-mode phones but rather are called multi-band phones. When talking about IS-95/GSM multi-mode phones, for example, or AMPS/IS-95 phones, the base band processing is very different from system to system. This leads to real difficulties in component integration and so to larger phones.

An interesting special case of multi-mode phones is the WCDMA/GSM phone. The radio interfaces are very different from eachother, but mobile to core network messaging has some quite strong similarities, meaning that software sharing is quite easy. Probably more importantly, the WCDMA air interface has been designed with GSM compatibility in mind. It has a special mode of operation, known as punctured mode, in which, instead of transmitting continuously, the mobile is able to stop sending for a short period and try searching for GSM carriers in the area. This mode allows for safe inter-frequency handovers with channel measurments which can only be approximated using "pilot signals" in other CDMA based systems.

A final interesting case is that of mobiles covering DS-WCDMA and MC-CDMA the 3G variant of CDMA-2000. Initially, the chip rate of these phones was incompatible. As part of the negociations related to patents, it was agreed to use compatible chip rates. This should mean that, despite the fact that the air and system interfaces are quite different, even on a philosophical level, much of the hardware for each system inside a phone should be common with differences being mostly contained to software.

Terms in other Languages

In the US the phones are called cell phones. In the UK, Australia and New Zealand, mobile phones are often called simply mobiles. In Germany, they are called Handys, in Switzerland Natel. In Sweden, they are sometimes called nalle, or teddy bear translated to English, originally referring to the term yuppie nalle since in the beginning only rich yuppies could afford them and they showed them off in a way that looked as they where carrying a yuppie teddy bear, nowadays only nalle is used representing that people always carry them around and feel insecure if they misplace them, like a kid missing his/her teddy bear. In Russia, they are often called trubka, or tube in Russian, because the receiver part of the stationary phones was called telephone tube and the mobile phone consists of receiver alone, in some sense. In many Asian countries they are called hand phones.

Using Mobile phones on aircraft

The use of mobile phones is generally disallowed on aircraft during flight. One reason given for this is that the mobile phone could interfere with the sensitive equipment on the aircraft. This could be restated as "during development these aircraft were not designed to accept signals from mobile phones and there has not been sufficient testing to be sure that they could" as can be seen from plans to improve certification [1]. It is clear, however, that there is some level interference of possible from active radio transmitters such as mobile phones on aircraft. Exactly how much and in what way is dependent on the particular phone system in use and which component of the plane we are discussing. Whether that level of interference should have any influence on electronic systems which should be designed to fly through lightning storms without falling out of the sky is an entirely different question.

One area in which interference is likely is in the radio based audio equipment used for communicating from the aeroplane to the ground. The mobile phone transmitter will be much closer to the receiver on the aircraft; this means that any cross talk from the mobile phone will have a strong effect.

Some mobile phone systems such as GSM may cause an irritating buzz (explained in the TDMA article) which would certainly disrupt communications from the pilot to ground. Unfortunately, the conditions on an aeroplane are exactly those which might cause this. The maximum speed of travel in a mobile phone system is limited by several factors, frequency changes, rate of change of timing offset, etc. The speed of an aeroplane often exceeds these (typically phones are designed for use in a fast car) which means the mobile will fail to register to the network and retry registration repeatedly.

Older analogue systems simply broadcast at a high power of up to several watts. This will cause more general interference, and since the voice signal is not encoded there may be direct cross talk into the communication systems of the plane.

Another factor is that from an altitude, distant cells are visible to the mobile with no line-of-sight attenuation from intervening obstacles. This means that the phone could try to establish contact with a far away cell where the signal will not be recognised. This transmission will probably be at maximum power due to the lack of prior response. The U.S. Federal Communications Commission prohibits the use of mobile phones in the air for this reason. This repeated sending of maximum power messages increases the risk of interference with electronic equipment on the aircraft.

Having said all the above, according to the BBC "most of the evidence is circumstantial and anecdotal. There is no absolute proof mobile phones are hazardous." [1] Some airlines do allow use of mobiles phones in flight, only restricting their use (and use of all other electronic devices) during take off and landing when communications with the ground are most critical. Meanwhile the passenger aircraft manufacturers, such as Boeing and Airbus, have begun to introduce wireless services on their planes (e.g. WLAN) and radio based satellite phones are a standard installation on aeroplanes. Clearly there is a direct airline industry advantage in having control over communication systems from within an aeroplane, with no clear way for potential competitors to certify their systems as safe for use on board. Some articles have even gone so far as to accuse the airline industry of pushing the ban on mobile phones in order to increase revenue from on board telephones [1].

Health controversy

As with many new technologies, concerns have arisen about the effects on health from using a mobile telephone. Part of the radio waves emitted by a mobile telephone are absorbed by the human head; the microwaves emitted by a GSM-900 handset can have a power of up to 2 watts. According to the scientific consensus, the only effect on the human body is that the temperature of the head increases by a harmless fraction of a degree during prolonged calling. However, some controversial studies claim that there exist other undesired effects on health as a direct result of the radiation.

Future prospects

In the future, phones will incorporate more features from other handheld devices. This is already happening to some extent, with MP3 players, PDAs, GPS receivers, digital cameras, etc. It has long been speculated by technology experts that the phone development will culminate in a device similar to the Star Trek communicator. The phone has proved the most popular handheld personal device, probably because communicating with other humans is the most important need among those fulfilled by personal electronic devices — certainly more important than listening to music, keeping track of appointments, navigating on roads, or taking pictures.

Because of that, it currently seems more likely that in the evolution of personal digital devices the phone will be the winner, appropriating more and more functions from competing devices as technologies develop. For example, the phone won the evolutionary battle with handheld computers, as all electronics inside both devices is similar and as phones now have displays as good and almost as large as those in PDAs. Another function that will be acquired by phones is that of the music player. The only difficulty in adapting mobile phones to new uses is that of form factor. For example, ebooks may well become a distinct device, because of conflicting form-factor requirements — ebooks require large screens, while phones need to be smaller. However, this may be solved using folding e-paper or built-in projectors. This may also prove useful when phone manufacturers will be adding video playback to their devices. Of course, using eyeglasses displays (from wearable computers) or direct output to the retina (e.g. a laser scanner as a retinal display) or visual cortex can easily solve these problems.

One function from the original Star Trek communicator that will almost certainly included in phones is translation function, because the application area is similar to that of the ordinary phone and no changes to the form factor will be necessary. Currently it is only available in stand-alone devices, such as Ectaco translators, but mobile phones will include various speech technologies as they are being developed. Many phones already have rudimentary speech recognition in a form of voice dialling. Of particular interest will be real-time voice translation (that must include speech recognition, machine translation and speech synthesis). However, more natural speech recognition and translation in these devices requires a drastic improvement in the state of technology: the phone's processor must be faster by several orders of magnitude with the phone requiring far more internal memory, or new ways of processing speech data must be found.

New developments in miniaturised hard disk drives may solve the storage space issue, therefore opening a window for phones to become portable music libraries and players similar to the iPod. However, the fact remains that natural language processing requires inordinately powerful hardware (given today's standards).

One of the drawback of all phone developments is reduced battery life. Colour screens and additional functions put increasing demands on the device's power source, and battery developments may not proceed sufficiently fast to compensate. However, different display technologies, such as OLED displays, e-paper or retinal displays, smarter communication hardware (directional antennae, multi-mode and peer-to-peer phones) may reduce power requirements, while new power technologies such as fuel cells may provide better energy capacity. It is also possible that mobile phones will, together with some other devices, be powered via the movement of clothing (or via microscopic solar cells embedded in clothing), or biochemical activity in human skin.

Traditionally, all functions of the mobile phone (microphone, speaker, radio communications, display, computer) were integrated in one single device. But some technologies already make it possible to break down the phone. The parts could then communicate via short-range wireless connection such as Bluetooth, by sending a current through the human skin or by wire. It is possible that in the future this opportunity will be used to further reduce the weight and footprint of the phone. A wearable display may be used by the phone (and by other personal devices), such as eyeglasses projector, retinal display or, in long-term, direct connection to the optical nerve or the brain. Sound can already be sent to a wireless headset or even to the ear directly via skull bones or a finger pressing on the ear.

In 2002, an English team led by James Auger and Jimmy Loizeau developed an implant designed to be inserted into a tooth during dental surgery. This device consists of a radio receiver and transducer, which transmits the sound via bone conduction through the jawbone into the ear. Sound is transmitted via radio waves from another device (ostensibly a mobile phone) and received by the implant. The implant is currently powered externally, given that no current power source is small enough to fit inside the tooth with it. In addition, the implant was only designed to receive signals, not transmit them.

Directly tapping into the inner ear or the auditory nerve is already technologically feasible and will become practical as surgical methods advance. In the far future it is likely to become practical to integrate most of the functions into the human body itself. By then the mobile phone will cease to be a distinct device.

Mobile communication systems are one of the most problematic areas for bandwidth use since unlike broadcast systems there are many different transmitters. As such many different ways of improving transmission have been considered, even those that might be considered surpising. Infrared transmission has already been used in experimental mobile phone systems, with the specific advantage that with strong atmospheric absorption very small cell size can be easily achieved. Beam forming is a strong design criteria in a number of modern systems and would also allow large increases in cell capacity. It is likely that future mobile phones will be able to switch between multiple communication protocols (satellite, cellular, WLAN, optical/infrared, others) depending on the required range, efficiency and service availability.

See also

External links

Parts of this page are from Federal Standard 1037C: Glossary of Telecommunication Terms.