A mobile or cellular telephone is a long-range, portable electronic device for personal telecommunications over long distances.

Most current mobile phones connect to a cellular network of base stations, which is in turn interconnected to the public switched telephone network (PSTN). The public switched telephone network (PSTN) is the network of the world's public circuit-switched telephone networks, in much the same way that the Internet is the network of the world's public IP-based packet-switched networks. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital, and now includes mobile as well as fixed telephones.

Fully automatic cellular networks were first introduced in the early to mid 80s (1G generation). The first fully automatic cell phone system was the Nordic Mobile Telephone (NMT) system, introduced in 1981. Nordic Mobile Telephone in English) is the first fully-automatic cellular phone system. It was specified by Nordic telecommunications administrations (PTTs) starting in 1970, and opened for service in 1981 as a response to the increasing congestion and heavy requirements of manual mobile phone networks:

Prior mobile telephones (the 0G generation), such as Mobile Telephone Service, date back to 1945. These were not categorized as cellular phones, since they did not support handover, i.e. automatic change of channel frequency in the middle of a call, when the user moved from one cell to another.

Until the mid to late 80s, most mobile phones were were 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 additional services such as SMS for text messaging, email, packet switching for access to the Internet, and MMS for sending and receiving photos and video.

There are 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 terms are used interchangeably, with the preferred term varying by location. There are different networks on mobile phones. Some are pay as you go, where top ups can be purchased and added to a phone unit, so there is no monthly bill. Many are pay monthly, where a bill is issued every month for the amount of calls and texts made.

The concept of using hexagonal cells for mobile phone base stations was invented in 1947 by Bell Labs engineers at AT&T and was further developed by Bell Labs during the 1960s. In 1970 Amos Joel of Bell Labs invented call handoff that allowed a mobile phone user to travel through several cells during the same conversation. Martin Cooper of Motorola is widely considered to be the inventor of the first practical cell phone for handheld use in a non-vehicle setting. Using a modern, if somewhat heavy portable handset, Cooper made the first call on a handheld cell phone on April 3, 1973. At the time he made his call, Cooper was working as Motorola's General Manager of its Communications Division.

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.Radiophones have a long and varied history that stretches back to the 50s, 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.

Luxembourg has the highest mobile phone penetration rate in the world, at 164% in December 2005. In Hong Kong the penetration rate reached 117% of population in September 2004. The total number of mobile phone subscribers in the world was estimated at 2.14 billion in 2005.Around 80% of world's population have mobile phone coverage as of 2006. This figure is expected to increase to 90% by the year 2010.

At present, Africa has the largest growth rate of cellular subscribers. African markets are expanding twice as fast as Asian markets. 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 on a monumental scale, not only in Africa but on other continents as well.

All European nations and most Asian and African nations have adopted GSM. In other nations , such as the US, Australia, Japan, and South Korea, legislation does not require any particular standard, and GSM coexists with other standards, such as CDMA and iDEN.

Pay As You Go, often shortened to PAYG, is used as al term for the concept of a prepay mobile phone. In many countries this is referrred to as prepaid mobile service.

The concept was initially developed by Eircell in the Republic of Ireland in the 1990s, as a method of letting different types of people (those under the age of 18, those without bank accounts and those without proof of identity) obtain a mobile phone. Originally limited to one TACS handset, costing £99 upfront, the system was an amazing success, despite the high price of calls and a 7p service charge on every operation. The system was branded as Ready To Go, a name still used by Vodafone, who now own Eircell.

Mobile phone culture and customs
In fewer than twenty years, mobile phones have gone from being rare and expensive pieces of equipment used primarily by the business elite, to a pervasive low-cost personal item. In many nations , mobile phones now outnumber land-line telephones, with most adults and many children now owning mobile phones. In the US, 70% of children own 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 nations , where there is little 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 address book 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.

Use in disaster response
Camera phones and videophones that can capture video and take photographs are increasingly being used by companies like Scoopt 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 photo sharing sites like Flickr. In Japan, 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.

Use by drivers

It is been argued the distraction caused by using mobile phones while driving is responsible for many 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.
Mobile-phone use while driving is common but controversial. While few jurisdictions have banned motorists from using cell phones while driving outright, some, including the US states of New York, Connecticut, and California, have banned or restricted drivers from using hand-held cell phones while exempting phones used by a hand-free method. It is generally agreed that using a mobile phone while driving is a distraction that brings risk of road traffic accidents. However, some studies have found similarly elevated accident rates among drivers using hand-held and hand-free phones, suggesting that the distraction of a telephone conversation itself is the main safety problem.

Mobile phone features
Invented in 1997, the camera phone is now 85% of the market. Mobile phones also often have features beyond sending text messages and making 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, video call and serve as a wireless modem for a PC. A camera phone is a mobile phone which has a camera built-in and usually has an implementation of a server-based infrastructure that allows the user to share pictures with anyone instantly

In most nations, including Europe, Japan, India, the person receiving a cellular phone call pays nothing. However, in Hong Kong, Canada, and the US, one can be charged per minute. In the US, a few carriers are beginning to offer unlimited received phone calls. For example as of December 2006, Sprint now has 4 plans under "Sprint Free Incoming Plans" section of their website, although the restriction is the receiving phone must be on the Sprint PCS network. For the Chinese mainland, it was reported that both of its two operators will adopt the caller-pays approach as early as January 2007.

Mobile phone forensics and evidence
The UK appears to be leading the world when in comes to mobile telephone forensics and evidence. Law enforcement globally, though, relies heavily upon mobile telephone evidence. The concerns over terrorism and the use by terrorist to use technology promoted an enquiry by the UK House of Commons Home Affairs Select Committee into the use of evidence from mobile telephone devices, prompting leading mobile telephone forensic specialists to identify forensic techniques available in this area.

Technology

Mobile phone towerMobile phones and the network they operate under vary significantly from provider to provider, and nation to nation. However, all of them communicate through electromagnetic microwaves with a cell site base station, the antennas of which are usually mounted on a tower, pole, or building.

A Mobile Switching Center (MSC) is a component of a wireless/mobile telephone/data network. With GSM, this is called a Network Switching Subsystem. With CDMA, this is called a Mobile Switching Center.

The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, usually 5 to 8 miles (approximately 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 various cell sites during calls, or while waiting (idle) between calls it will reselect cell sites.

Cell sites have relatively low-power 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. The technology that achieves this depends on the system which the mobile phone operator has adopted. Some technologies include AMPS for analog, and D-AMPS, CDMA2000, GSM, GPRS, EV-DO, and UMTS for digital communications. Each network operator has a unique radio frequency band.

Terminology
Cordless 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. Increasingly, with wireless local loop technologies, namely DECT, the distinction is blurred.
Professional Mobile Radio
Advanced professional mobile radio systems can be very similar to cell phone systems. Notably, the IDEN standard has been used as both a private trunked radio system as well as the technology for several large public providers. Similar attempts have even been made to use TETRA, the European digital PMR standard, to implement public mobile networks.
Radio phone
This is a term which covers radios which could connect into the telephone network. These phones may not be mobile; for example, they may require a mains power supply. Also, they may require the assistance of a human operator to set up a PSTN phone call.