Cellular Phone

Cellular phones, more commonly referred to as cell phones, or mobile phones, are entirely portable phones that not require a wire connection to a network, but connect using a wireless radio waves through a cellular network which are linked to the conventional telephone network. This site will explain how cell phones work and trace their evolution.

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Cell Phone - Introduction
A mobile phone, also known as a cellular or cell phone, is an electronic telecommunications device with the same basic capability as a conventional fixed-line telephone, but which is entirely portable and does not require a wire connection to a network. Most mobile phones connect to a network using a wireless radio wave transmission technology rather than a wired system. The mobile phone communicates via a cellular network of base stations, also known as cell sites, which are in turn linked to the conventional telephone network.

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, Fujitsu, Kyocera (formerly the handset division of Qualcomm), LG, Motorola, NEC, Nokia, Panasonic (Matsushita Electric), Philips, Sagem, Samsung, Sanyo, Sharp, Siemens, SK Teletech, Sony Ericsson, and Toshiba.

There are also specialist communication systems related to, but distinct from, mobile phones. These include satellite phones and Professional Mobile Radio. Mobile phones are also distinct from cordless telephones, which generally operate only within limited range of a specific base station.

Worldwide deployment

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 and Latin America, Australia, Canada, and the US, mobile phones are now widely used, with the majority of the adult, teenage, and even child population using them. 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, in which the subscriber does not 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 all working to the same standard, particularly the GSM standard which was designed for Europe-wide interoperability. All European nations and some Asian nations use the GSM as their sole standard, while Japan and South Korea opt for the CDMA standard.

The Mobile Culture
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 using mobile phones as their primary means of communication. It is not uncommon for young adults to own a mobile phone instead of a land-line for their residence. In some developing countries, where there is little to no existing fixed-line infrastructure, the mobile phone has become widespread.

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 to keep in touch with their friends. Many people keep in touch using SMS, resulting in the development of a “texting” culture. The commercial market in SMS is growing. Many phones offer Instant Messenger services to increase the simplicity and ease of texting on phones and some phones even offer an emailing service to their subscribers.

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 phone customization has emerged as its own industry. For instance, the sale of commercial ringtones, a tool used by the youth to personalize their phone, exceeded $2.5 billion dollars in 2004.

Mobile phone etiquette has become an important issue with mobiles ringing at funerals, weddings, movies, plays, and other times of questionable appropriateness. Users often speak at increased volume, with little regard for other people nearby. It has become common practice for places like bookshops, libraries, movie theatres, and houses of worship to post signs prohibiting the use of cell phones, even installing jamming equipment to prevent them. The US intercity passenger system Amtrak offers a "quiet car" where cell phone use is prohibited, much like the designated non-smoking cars created as a courtesy to non-smokers. Mobile phone use on aircraft is also prohibited.

Camera phones 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 camera phone users on news sites like NowPublic and photo sharing 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 cellular phones; an interactive menu accessible through the phone's internet browser notifies the company if the user is safe or in distress.

Phone Features
There are many mobile phone features today that offer a range of capabilities beyong voicemail or text messaging.

General Features

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"), access WAP services, and provide full Internet access using technologies such as GPRS. Most mobile phones have a clock, calculator, and often some assortment of games on them as well.

Before a phone can be used, a subscription to a mobile phone operator (a.k.a. carrier) is required. For phones on GSM networks, the operator will issue a SIM card which contains the unique subscription and authentication parameters for that customer; alternatively, the carrier will put the customer's handset identifier into its subscriber database so that the handset is able to calls on the network. Once the SIM card is inserted into the phone, services can be accessed. Many mobile phones support 'auto-roaming', which permits the same phone to be used in multiple countries. For this to work, the operators of both countries must have a roaming agreement.

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.

Most models also allow for the sending and receiving of pictures via a built-in digital camera. Sound and video recording is often also possible. This prevalence of recording capability has given rise to some concern about privacy, in view of possible voyeurism. For this reason, Saudi Arabia has entirely banned the sale of camera phones (although the country allows pilgrims on the Hajj to bring in camera phones) and South Korea requires manufacturers to ensure that all new handsets emit a beep whenever a picture is taken.

GPS receivers are beginning to appear in cell phones as well, either through direction integreation or connected using Bluetooth. This development has occurred primarily to aid in dispatching emergency responders and road tow truck services.

There are also many features aimed toward personalization, such as user defined and downloadable ring tones and logos, and interchangeable covers, which have helped in the uptake by the teenage market. Mobile phone content advertising has become massively popular but has also drawn a great deal of criticism. Usually one can choose between a ring tone, a vibrating alert, or a combination of both.

As users become more focused on greater capability and decreased size, mobile phones have been increasingly criticized for their poor ergonomics. Their small size, plethora of features and modes, and attempts at stylish design often make them difficult and confusing to use.

Multi-mode cell phones

A multi-mode (also known more specifically as dual, tri or quad band) mobile phone is a phone which is designed to work on more than one GSM radio frequency. GSM was originally specified in the 900 MHz band, but expanded to the 1800 MHz band, then added 1900 MHz and finally 850 MHz in the Americas. Some multi-mode phones can operate on analog networks as well (for example, dual band, and tri-mode: AMPS 800 / CDMA 800 / CDMA 1900).

For a GSM phone, dual-band usually means 850 / 1900 MHz in the United States and Canada, 900 / 1800 MHz in Europe and most other countries. Tri-band means 850 / 1800 / 1900 MHz or 900 / 1800 / 1900 MHz. Quad-band means 850 / 900 / 1800 / 1900 MHz, and is also called a world phone, because it can work on any GSM network.

For CDMA or TDMA phones, multiple bands usually indicates both an analog and a digital capability.

Multi-mode phones have been useful in enabling 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 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 a way to share the components between the different standards. A phone’s keypad and display must obviously should be shared in order for a single phone to be multi-mode. Beyond that, 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, as a side effect, to larger phones.

An interesting case of multi-mode phones is the WCDMA/GSM phone. The radio interfaces in each of these systems are very different from each other, but mobile to core network messaging has strong similarities, meaning that software sharing is quite easy. More importantly, the WCDMA air interface has been designed with GSM compatibility in mind. A special mode of operation, known as punctured mode, allows the phone to take brief breaks from transmission and search for GSM carries in the area, rather than transmitting continuously. This mode allows for safe inter-frequency handovers with channel measurements which can only be approximated using "pilot signals" in other CDMA based systems.

Another interesting case is that of mobiles covering the DS-WCDMA and MC-CDMA 3G variants of the CDMA-2000 protocol. Initially, the chip rate of these phones was incompatible with others. As part of negotiations relating to patents, it was agreed to use compatible chip rates. This should mean that much of the hardware for each system within a phone should be common, despite differences in air and system interfaces. This hardware compatibility does not negate software differences.

The majority of mobile phone networks now use one of two standards, GSM or CDMA. A third standard, iDEN, is found exclusively in North America and is confined to the Nextel network. It is believed that this network will eventually disappear as Nextel merges with Sprint PCS, a CDMA carrier. Similarly, AT&T Wireless's TDMA network in North America is slowly being phased out as a result of its merger with Cingular, a GSM carrier.

Data Communications

Mobile phones are now heavily used for data communications such as SMS messages, browsing mobile websites, and even streaming audio and video files. The main limiting factors are the size of the screen, lack of a keyboard, processing power, and connection speed.
With newer smartphones, screen resolution and processing power has become bigger and better. Some new phone CPUs run at over 400 MHz. Many complex programs are now available for the various smartphones, such as Symbian and Windows Mobile.

With newer smartphones, screen resolution and processing power has become bigger and better. Some new phone CPUs run at over 400 MHz. Many complex programs are now available for the various smartphones, such as Symbian and Windows Mobile.

Connection speed is based on network support. The data section of the GSM protocol is called GPRS. Many recent GSM phones also support EDGE, a high speed version of GPRS. Some phones also feature real keyboards, such as the Nokia 6820.

New Features

There are also new means of digital communications, such as text messaging and e-mail. As of 2004, even basic phones were able to send and receive text messages making them vulnerable to attack by worms and viruses. More advanced phones, capable of e-mail, can be susceptible to viruses that can multiply by sending messages through a phone's address book. Of more concern, a virus has been developed that may allow unauthorized users to access a phone in order to find passwords or corporate data stored on the device. Moreover, they can be used to commandeer the phone to make calls or send messages at the owner's expense. Unlike computers that are restricted to a few widespread operating systems, cellular phones use a variety of systems that require separate programs to be designed in order to disable each one. While reducing overall compatibility from an application design standpoint, this has the beneficial effect of making it harder to design a mass attack. However, the rise of cellular phone operating system programming platforms shared by many manufacturers such as Java, Microsoft operating systems, Linux, or Symbian OS, may change this in the future.

Bluetooth is a wireless communication feature now found in many higher-end phones. Recently, the virus Cabir hijacked this function, sending Bluetooth phones on a search-and-destroy mission to infect other Bluetooth phones. In early November 2004, several websites began offering a specific piece of software promising ringtones and screensavers for certain phones. Those who downloaded the software found that it turned each icon on the phone's screen into a skull-and-crossbones and disabled their phones, disabling their ability to access text messaging capabilities, contact lists or calendars. The virus has since been dubbed "Skulls" by security experts. The Commwarrior.A virus, which attempts to replicate itself through MMS to others on a phone’s contact list, was identified in March 2005. Like Cabir, Commwarrior.A also tries to communicate via Bluetooth wireless connections with other devices, which can eventually lead to depletion of the phone’s battery. However, the virus requires user intervention for propagation. Bluetooth telephones are also subject to bluejacking, which is the generally benign transmission of messages from anonymous Bluetooth users. In 2004, rumors spread of using Bluetooth to arrange casual sexual encouters; this activity, widely publicized in both print and online media as toothing, was revealed to be a hoax in 2005.

Technology
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 over the air (through electromagnetic radio waves) with a base station (a special radio mast or tower designed for the purpose). These phones have a low power transceiver that is typically designed to transmit voice and data up to a few kilometers from where the tower is located. The handset constantly listens for the nearest tower with the strongest signal. Once found, the handset informs the tower of its unique identifier, and alerts the mobile phone network that it is ready and standing-by to receive telephone calls. This cycle is repeated as the phone roams around the network and new towers appear in the handset's range.

Towers have high power radio transmitters which broadcast their presence and relay communications to and from mobile handsets. The tower is connected to the telephone network by a high-capacity link. The base station connects to the operator's backbone network and the wider public telephone network as well as the networks of other mobile phone operators.

The dialogue between the handset and the tower is a stream of digitized audio. The technology that achieves this depends on the system adopted by mobile phone operator. Some technologies include AMPS for analogue, and TDMA, CDMA, GSM, GPRS and UMTS for digital communications. Each network operator also has a unique radio frequency chosen from a small number of standard frequencies allocated to each technology.

Controversial Issues

Health Controversy

As with many new technologies, concerns have arisen about the effects on health from using a mobile telephone. Originally, there was 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 report that the mobile phone industry has interfered with further research on health risks, making it difficult to discern the actual affects of continuous use. To date, however, the World Health Organization Task Force on EMF effects on health has no definitive conclusion on the veracity of these allegations. It is generally thought, that RF is incapable of producing any effect other than heat, as it is considered non-ionizing radiation; in other words, it lacks the energy to disrupt molecular bonds such as occurs in genetic mutations.

Driving Controversy

Another controversial but perhaps more lethal health concern is the correlation of mobile phone use and automobile accidents. Several studies have shown that motorists have a much higher risk of collision when using a mobile telephone while driving. These studies have shown that losing control of one’s vehicle is also much more common amongst users employing a “hands-free” system. One such study conducted by the 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. In some jurisdictions, such as Ireland, Japan, Singapore, Brazil, Australia, Austria, the United Kingdom and France, as well as several states in the United States, driving while using a mobile phone is illegal, though an exception is often made if the phone is equipped with a hands free system. In Canada it is banned in Newfoundland (Dec 2002) with fines up to US$180.

Security Concerns

Early mobile phones were designed with only a small amount of security included. Some problems with these models were "cloning", a variant of identity theft, and "scanning" whereby third parties in the local area could intercept and listen in on calls. Radio scanners also allowed the tapping in to phone calls made on analogue phones.

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 systems, allowing the possibility of eavesdropping or cloning.

Future Prospects of cell phones
There is a great deal of active research and development underway in regard to mobile phone technology. Some of the improvements that are being worked on are:

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.

A translation function is also underway in many phones, in the hopes of allowing users to use their phones while traveling. 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 with new concepts. Digital Airways with the Kaleido product, e-sim, mobile arsenal, and Qualcomm with UIOne for the BREW environment, are all companies currently investigating this technology.

Mobile phone technology is also increasingly based on new and more creative speech technologies. 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 the phone. Neomedia (via Paperclick), Mobot, and Scanbuy are currently developing this technology.

Developments are being made in miniaturized hard disks and flash drives to solve the storage space issue, 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.

A new standard (UMA) has been developed in order to integrate 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.

Further improvements in battery life are required by many users. Color screens and additional functions put increasing demands on a device's power source and battery developments have not kept up with demand. 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.

Speculative improvements in the future may be inspired by an English team led by James Auger and Jimmy Loizeau who in 2002 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 (presumably 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 a tooth. 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.

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 content including video to mobiles is beginning to become a reality with 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.

How practical is it to browse the internet via your cell phone?
If connected to your computer properly, digital (PCS) cell phones can function as a computer modem. (Analog cell phones sometimes can as well, with the right network adapter added.) Using your cell phone as a modem can allow portable Internet connectivity when all other options fail. However, a cell phone modem generally performs worse than alternative forms of Internet accesses.

A cell phone modem generally runs much slower than home broadband Internet access, Wi-Fi hotspot access, or even a traditional dialup Internet connection.

The theoretical maximum bandwidth supported by a cell phone modem varies depending on the communication standards your phone service supports. Below are example modem speed ratings for common cell phone data communication protocols. Compare these to dialup Internet modems that handle a theoretical maximum bandwidth of 56 Kbps:

GSM - 9.6 Kbps

CDMA - 9.6 Kbps to 14.4 Kbps

CDPD - 19.2 Kbps

GPRS - 9.6 Kbps to 115 Kbps

EDGE - 384 Kbps

EV-DO - 1.5 Mbps - 2.4 Mbps

As with many networking standards, users of cell phone modems should not expect to achieve this theoretical maximum in practice.
The actual bandwidth you will enjoy depends on several factors:

Quality of the phone's wireless signal (typically, the distance away from the nearest cell tower)

Competing network traffic on the cell phone provider network

Version of the network communication protocol employed by the provider, along with any technical limitations or extensions they implement

Mix of upstream and downstream traffic you generate (cell phone modems support less bandwidth for uploads than for downloads)

Finally, consider that the "speed" of any network depends not only on amount of supported bandwidth but also on its latency. A cell phone modem suffers from very high latency given the nature of its open-air communications. When using your cell phone as a modem, you should expect to see sluggish delays and bursts of data transmission, which lowers the perceived speed of your connection even further.

Major Carriers
In the U.S., the major cellular carriers by total subscribers at the end of 2004, starting with the largest, are Cingular Wireless (formerly Cellular One and including AT&T Wireless), Verizon Wireless (formerly Bell Atlantic Mobile), Sprint Nextel (merger of Sprint and Nextel) and T-Mobile. The largest cellular company in the world is UK-based Vodaphone with 2003 revenues exceeding $60 billion. As of 2004, Vodaphone had substantial ownership in Verizon Wireless.

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