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Главная » 2010 » Июнь » 17 » Mobile phones
13:49
Mobile phones
     A mobile phone or cell(ular) phone is an electronic telecommunications device. Most current mobile phones connect to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN)(the exception are satellite phones). Cellular networks were first introduced in the early to mid 1980s (the 1G generation). Prior mobile phones operating without a cellular network (the so-called 0G generation), such as Mobile Telephone Service, date back to 1946. Until the mid to late 1980s, most mobile phones were sufficiently large that they were often permanently installed in vehicles as car phones. With the advance of miniaturization, currently the vast majority of mobile phones are handheld. In addition to the standard voice function of a telephone, a mobile phone can support many additional services such as SMS for text messaging, packet switching for access to the Internet, and MMS for sending and receiving photos and video.
     Some of the world's largest mobile phone manufacturers include Alcatel, Audiovox, BenQ-Siemens, Dopod, Fujitsu, Kyocera, LG, Motorola, NEC, Nokia, Panasonic (Matsushita Electric), Philips, Sagem, Samsung, Sanyo, Sharp, SK Teletech, Sony Ericsson, and Toshiba.
      There are also specialist communication systems related to, but distinct from mobile phones, such as Professional Mobile Radio. Mobile phones are also distinct from cordless telephones, which generally operate only within a limited range of a specific base station. Technically, the term mobile phone includes such devices as satellite phones and pre-cellular mobile phones such as those operating via MTS which do not have a cellular network, whereas the related term cell(ular) phone does not. In practice, the two terms are used nearly interchangeably, with the preferred term varying by location.
      Mock-up of the "portable phone of the future", from a mid-60s Bell System advertisement, shows a device not too different from today's mobile telephones.
      Radio phones have a long and varied history that stretches back to the 1950s, with hand-held cellular radio devices being available since 1983. Due to their low establishment costs and rapid deployment, mobile phone networks have since spread rapidly throughout the world, outstripping the growth of fixed telephony.
     In most of Europe, wealthier parts of Asia, Africa, the Caribbean, Latin America, Australia, Canada, and the United States, mobile phones are now widely used, with the majority of the adult, teenage, and even child population owning one. At present India and China have the largest growth rates of cellular subscribers in the world. The availability of Prepaid or pay as you go services, where the subscriber does not have to commit to a long term contract, has helped fuel this growth.
      The mobile phone has become ubiquitous because of the interoperability of mobile phones across different networks and countries. This is due to the equipment manufacturers working to meet one of a few standards, particularly the GSM standard which was designed for Europe-wide interoperability. All European nations and most Asian and African nations adopted it as their sole standard. In other countries, such as the United States, Japan, and South Korea, legislation does not require any particular standard, and GSM coexists with other standards, such as CDMA and iDen
     In less than twenty years, mobile phones have gone from being rare and expensive pieces of equipment used by businesses to a pervasive low-cost personal item. In many countries, mobile phones now outnumber land-line telephones, with most adults and many children now owning mobile phones. It is not uncommon for young adults to simply own a mobile phone instead of a land-line for their residence. In some developing countries, where there is little existing fixed-line infrastructure, the mobile phone has become widespread. According to the CIA World Factbook the UK now has more mobile phones than people.
      With high levels of mobile telephone penetration, a mobile culture has evolved, where the phone becomes a key social tool, and people rely on their mobile phone addressbook to keep in touch with their friends. Many people keep in touch using SMS, and a whole culture of "texting" has developed from this. The commercial market in SMS's is growing. Many phones even offer Instant Messenger services to increase the simplicity and ease of texting on phones. Cellular phones in Japan, offering Internet capabilities such as NTT DoCoMo's i-mode, offer text messaging via standard e-mail.
     The mobile phone itself has also become a totemic and fashion object, with users decorating, customizing, and accessorizing their mobile phones to reflect their personality. This has emerged as its own industry. The sale of commercial ringtones exceeded $2.5 billion in 2004.
      The use of a mobile phone is prohibited in some rail carriages
      Mobile phone etiquette has become an important issue with mobiles ringing at funerals, weddings, movies, and plays. Users often speak at increased volume which has led to places like bookshops, libraries, movie theatres, doctor's offices, and houses of worship posting signs prohibiting the use of mobile phones, sometimes even installing illegal jamming equipment to prevent them. Many rail companies, particularly those providing long-distance services, offer a "quiet car" where phone use is prohibited, much like the designated non-smoking cars in the past. Mobile phone use on aircraft is also prohibited, but because of concerns of possible interference with aircraft radio communications.
      Cameraphones and videophones that can capture video and take photographs are increasingly being used to cover breaking news. Stories like the London Bombings, the Indian Ocean Tsunami and Hurricane Katrina have been reported on by cameraphone users on news sites like NowPublic and photosharing sites like Flickr.
      In Japan, cellular phone companies provide immediate notification of earthquakes and other natural disasters to their customers free of charge. In the event of an emergency, disaster response crews can locate trapped or injured people using the signals from their mobile phones; an interactive menu accessible through the phone's Internet browser notifies the company if the user is safe or in distress.
      Mobile phones often have features beyond sending text messages and make voice calls—including Internet browsing, music (MP3) playback, personal organizers, e-mail, built-in cameras and camcorders, ringtones, games, radio, Push-to-Talk (PTT), infrared and bluetooth connectivity, call registers, ability to watch streaming video or download video for later viewing, and serving as a wireless modem for a PC.
      Mobile phones and the network they operate under vary significantly from provider to provider, and even from nation to nation. However, all of them communicate through electromagnetic radio waves with a cell site base station, the antennas of which are usually mounted on a tower, pole, or building.
      The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, usually 5 to 8 miles (0.8 to 13 kilometres) away. When the cellular phone or data device is turned on, it registers with the mobile telephone exchange, or switch, with its unique identifiers, and will then be alerted by the mobile switch when there is an incoming telephone call. The handset constantly listens for the strongest signal being received from the surrounding base stations. As the user moves around the network, the mobile device will "handoff" to new cell sites.
      Cell sites have relatively low-power (often only one or two Watts) radio transmitters which broadcast their presence and relay communications between the mobile handsets and the switch. The switch in turn connects the call to another subscriber of the same wireless service provider or to the public telephone network, which includes the networks of other wireless carriers.
      The dialogue between the handset and the cell site is a stream of digital data that includes digitized audio (except for the first generation analog networks). The technology that achieves this depends on the system which the mobile phone operator has adopted. Some technologies include AMPS for analog, and TDMA, CDMA, GSM, GPRS, EV-DO, and UMTS for digital communications. Each network operator has a unique radio frequency band.
      As with many new technologies, concerns have arisen about the effects on health from using a mobile telephone. There is a small amount of scientific evidence for an increase in certain types of rare tumors (cancer) in long-time, heavy users. More recently a pan-European study provided significant evidence of genetic damage under certain conditions. Some researchers also report the mobile phone industry has interfered with further research on health risks. So far, however, the World Health Organization Task Force on EMF effects on health has no definitive conclusion on the veracity of these allegations. (See also electromagnetic radiation hazard.) It is generally thought, however, that RF is incapable of producing any more than heating effects, as it is considered non-ionizing radiation; in other words, it lacks the energy to disrupt molecular bonds such as occurs in genetic mutations.
      Another controversial but more lethal health concern is the correlation with road traffic accidents. Several studies have shown that motorists have a much higher risk of collisions and losing control of the vehicle while talking on the mobile telephone simultaneously with driving, even when using "hands-free" systems. A study in The New England Journal of Medicine reports that drivers who used mobile phones while driving were four times more likely to crash than those who don't, a rate equal to that for drunken driving at the .01 blood alcohol concentration (BAC) level. An experiment conducted by the American television show MythBusters concluded that use of mobile phones while driving poses the same risk as someone operating a vehicle while under the influence of alcohol.
      Accidents involving a driver being distracted by talking on a mobile phone have begun to be prosecuted as negligence similar to driving while intoxicated. At least 25 countries restrict or prohibit cell and other wireless technology: India, Israel, Japan, Portugal and Singapore all prohibit mobile phone use while driving. Australia, Brazil, Chile, Croatia, Denmark, Germany, Greece, Hungary, Iran, Italy, the Netherlands, Poland, the Philippines, Romania, Slovenia, South Africa, Spain, Switzerland, Turkey, the United Kingdom, and the United Arab Emirates prohibit the use of hand-held cell phones while driving. Drivers in the Czech Republic and France may use cell phones but can be fined if they are involved in crashes while using such a device.
      Restrictive legislation has been proposed in 40 states in the US, but only New York State, Connecticut, and New Jersey, and Washington, D.C. have passed laws regarding cell phone use and driving.
      Early mobile phones did not have much security designed in. Some problems with these models were "cloning", a variant of identity theft, and "scanning" whereby third parties in the local area could intercept and eavesdrop in on calls. Analogue phones could also be listened to on some radio scanners.
      Although more recent digital systems (such as GSM) have attempted to address these fundamental issues, security problems continue to persist. Vulnerabilities (such as SMS spoofing) have been found in many current protocols that continue to allow the possibility of eavesdropping or cloning.
       The Madrid Bombings were set off by mobile devices in 2004. During the 7/7/05 Bombing in London the mobile network was disabled by the authorities who tried to pre-empt the use of this type of threat.
       There is a great deal of active research and development into mobile phone technology that is currently underway. Some of the improvements that are being worked on are:
      Now that operators are upgrading their networks to advanced wireless and other third-generation (3G) services, many new entertainment and communications services are becoming available, including new broadcast-type operations on spectrum formerly occupied by Televison Channels 52-69. With downlink speeds comparable to that of wireline DSL, mobile service can now offer capabilities such as streaming video sharing and music downloads. Services such as MobiTV or Juice Caster are just some examples of applications that leverage these new networks.
       One difficulty in adapting mobile phones to new uses is 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.
       One function that would be useful in phones is a translation function. Currently it is only available in stand-alone devices, such as Ectaco translators.
       An important area of evolution relates to the Man Machine Interface. New solutions are being developed to create new MMI more easily and let manufacturers and operators experiment new concepts. Examples of companies that are currently developing this technology are Digital Airways with the Kaleido product, e-sim, mobile arsenal, and Qualcomm with UIOne for the BREW environment.
      Mobile phones will include various speech technologies as they are being developed. Many phones already have rudimentary speech recognition in a form of voice dialing. However, to support more natural speech recognition and translation, a drastic improvement in the state of technology in these devices is required.
      New technologies are being explored that will utilize the Extended Internet and enable mobile phones to treat a barcode as a URL tag. Phones equipped with barcode reader-enabled cameras will be able to snap photos of barcodes and direct the user to corresponding sites on the Internet. This technology can be extended to RFID tags, or even snapped pictures of company logos. Searches can also be personalized to local areas using a GPS system built in to cell phones. Examples of companies that are currently developing this technology are Neomedia (via Paperclick), Mobot and Scanbuy. Another approach (used by jumptag.com) is to map URLs to short text tags tailored for easy user entry on phone keypads.
      Developments in miniaturised hard disks and flash drives to solve the storage space issue are already surfacing, therefore opening a window for phones to become portable music libraries and players similar to the iPod.
      Developments in podcast software enables mobile phones to become podcast playback devices through existing channels like MMS Podcast, J2ME Podcast and AMR-NB Podcast.
The emergence of integration capabilities with other unlicensed access technologies such as a WiMAX and WLAN, as well as allowing handover between traditional operator networks supporting GSM, CDMA and UMTS to unlicensed mobile networks. The new standard (UMA) has been developed for this to move towards fixed mobile convergence.
      Further improvements in battery life will be required. 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, and 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.
       New technology in Japan has combined the RFID chip principle into the handset and hooked it up to a network of readers and interfaces. The system, pioneered by NTT DoCoMo and SonyEricsson, is called Felica and there are around 10,000 convenience stores where one can now use a phone to pay for goods just by 'swiping' it over a flat reader. By charging up a phone with pre-paid cash credits, it can act as a sophisticated mobile-phone wallet. The technology is proving popular and there are now even vending machines that accept this form of payment.
The delivery of multimedia and broadcast content including video to mobiles is beginning to become a reality with the rollout of Qualcomm's MediaFLO. In addition, there are two main competing standards DMB - Digital Multimedia Broadcasting - and DVB-H - a handset version of the Digital Video Broadcasting standard. These methods avoid swamping the network by using traditional broadcasting.
       Image scanning, as seen in existing research. With time, this may develop into full 3D texturing and modeling. It is unlikely that cell phones will have the processing power to construct models and textures. But it is likely that the bandwidth to communicate the video, and receive a processed model will exist.
       There are several cell phones that can perform GPS positioning. In the future, GPS positioning may be coupled with accelerometer positioning, for covering underground or indoor positioning. This would likely lead to maps and help finding where you are going, and supports social efforts, such as locating friends or group members nearby, and identifying some strangers. The GPS technology already available in some phones, while coupled with the camera phone, may also allow users in the future to not only take a picture, but snap the exact location and angle at which the picture was taken.
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